Displaying publications 61 - 80 of 380 in total

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  1. Lim YK, Keng FS, Phang SM, Sturges WT, Malin G, Abd Rahman N
    PeerJ, 2019;7:e6758.
    PMID: 31041152 DOI: 10.7717/peerj.6758
    Marine algae have been reported as important sources of biogenic volatile halocarbons that are emitted into the atmosphere. These compounds are linked to destruction of the ozone layer, thus contributing to climate change. There may be mutual interactions between the halocarbon emission and the environment. In this study, the effect of irradiance on the emission of halocarbons from selected microalgae was investigated. Using controlled laboratory experiments, three tropical marine microalgae cultures, Synechococcus sp. UMACC 371 (cyanophyte), Parachlorella sp. UMACC 245 (chlorophyte) and Amphora sp. UMACC 370 (diatom) were exposed to irradiance of 0, 40 and 120 µmol photons m-2s-1. Stress in the microalgal cultures was indicated by the photosynthetic performance (Fv/Fm, maximum quantum yield). An increase in halocarbon emissions was observed at 120 µmol photons m-2s-1, together with a decrease in Fv/Fm. This was most evident in the release of CH3I by Amphora sp. Synechococcus sp. was observed to be the most affected by irradiance as shown by the increase in emissions of most halocarbons except for CHBr3 and CHBr2Cl. High positive correlation between Fv/Fm and halocarbon emission rates was observed in Synechococcus sp. for CH2Br2. No clear trends in correlation could be observed for the other halocarbons in the other two microalgal species. This suggests that other mechanisms like mitochondria respiration may contribute to halocarbon production, in addition to photosynthetic performance.
  2. Al-Saari N, Amada E, Matsumura Y, Tanaka M, Mino S, Sawabe T
    PeerJ, 2019;7:e6769.
    PMID: 31024772 DOI: 10.7717/peerj.6769
    Biohydrogen is one of the most suitable clean energy sources for sustaining a fossil fuel independent society. The use of both land and ocean bioresources as feedstocks show great potential in maximizing biohydrogen production, but sodium ion is one of the main obstacles in efficient bacterial biohydrogen production. Vibrio tritonius strain AM2 can perform efficient hydrogen production with a molar yield of 1.7 mol H2/mol mannitol, which corresponds to 85% theoretical molar yield of H2 production, under saline conditions. With a view to maximizing the hydrogen production using marine biomass, it is important to accumulate knowledge on the effects of salts on the hydrogen production kinetics. Here, we show the kinetics in batch hydrogen production of V. tritonius strain AM2 to investigate the response to various NaCl concentrations. The modified Han-Levenspiel model reveals that salt inhibition in hydrogen production using V. tritonius starts precisely at the point where 10.2 g/L of NaCl is added, and is critically inhibited at 46 g/L. NaCl concentration greatly affects the substrate consumption which in turn affects both growth and hydrogen production. The NaCl-dependent behavior of fermentative hydrogen production of V. tritonius compared to that of Escherichia coli JCM 1649 reveals the marine-adapted fermentative hydrogen production system in V. tritonius. V. tritonius AM2 is capable of producing hydrogen from seaweed carbohydrate under a wide range of NaCl concentrations (5 to 46 g/L). The optimal salt concentration producing the highest levels of hydrogen, optimal substrate consumption and highest molar hydrogen yield is at 10 g/L NaCl (1.0% (w/v)).
  3. Jones SU, Chua KH, Chew CH, Yeo CC, Abdullah FH, Othman N, et al.
    PeerJ, 2021;9:e11195.
    PMID: 33889447 DOI: 10.7717/peerj.11195
    Background: Staphylococcus aureus is one of the important pathogens causing nosocomial infection. spa typing allows identification of S. aureus clones in hospital isolates and is useful for epidemiological studies and nosocomial infection control. This study aims to investigate the spa types in Malaysian S. aureus isolates obtained from various clinical specimens.

    Method: A total of 89 methicillin-resistant S. aureus (MRSA) [pus (n = 55), blood (n = 27), respiratory (n = 5), eye (n = 2)] isolates and 109 methicillin-susceptible S. aureus (MSSA) [pus (n = 79), blood (n = 24), respiratory (n = 3), eye (n = 2) and urine (n = 1)] isolates were subjected to spa typing with sequences analysed using BioNumerics version 7.

    Results: The spa sequence was successfully amplified from 77.8% of the strains (154/198) and 47 known spa types were detected. The distribution of known spa types in MRSA (36.2%, 17/47) was less diverse than in MSSA (70.2%, 33/47). The most predominant spa types were t032 (50%) in MRSA, and t127 (19%) and t091 (16.7%) in MSSA, respectively. spa type t091 in MSSA was significantly associated with skin and soft tissue infections (p = 0.0199).

    Conclusion: The previously uncommon spa type t032 was detected in the Malaysian MRSA strains, which also corresponded to the most common spa type in Europe and Australia, and has replaced the dominant spa type t037 which was reported in Malaysia in 2010.

  4. Fazhan H, Waiho K, Fujaya Y, Rukminasari N, Ma H, Ikhwanuddin M
    PeerJ, 2021;9:e10936.
    PMID: 33954025 DOI: 10.7717/peerj.10936
    Sexual dimorphism is a common phenomenon in the animal kingdom. To test the consistency of sexual dimorphism patterns among sympatric species of the same genus, ten morphometric characteristics of mud crabs Scylla olivacea, S. tranquebarica and S. paramamosain were measured and compared using Discriminant Function Analysis (DFA). The descriptive analysis revealed that in all three species, body size dimensions and cheliped dimensions were significantly larger in males whereas the abdomen width was female-biased. Also, we described a morphological variation (carapace width, CW ≤ CW at spine 8, 8CW) that is unique to S. olivacea. Discriminant function analysis revealed that all nine morphometric characteristics were sexually dimorphic in S. olivacea, S. tranquebarica (except right cheliped's merus length, ML) and S. paramamosain (except 8CW). The obtained discriminant functions based on the morphometric ratios (with CW as divisor) correctly classified 100% of adults of known sex of all three species. Further, based on the selected body traits, DFA was able to almost completely distinguish males (94%), but not females (74%), among the three Scylla species. This study highlights that congeneric species of portunids (e.g., Scylla spp.) show similar sexually dimorphic characteristics (body size and secondary sexual characteristics).
  5. Teo MYM, Ng JJC, Fong JY, Hwang JS, Song AA, Lim RLH, et al.
    PeerJ, 2021;9:e11063.
    PMID: 33959410 DOI: 10.7717/peerj.11063
    Background: KRAS oncogenes harboring codon G12 and G13 substitutions are considered gatekeeper mutations which drive oncogenesis in many cancers. To date, there are still no target-specific vaccines or drugs available against this genotype, thus reinforcing the need towards the development of targeted therapies such as immunotoxins.

    Methods: This study aims to develop a recombinant anti-mKRAS scFv-fused mutant Hydra actinoporin-like-toxin-1 (mHALT-1) immunotoxin that is capable of recognizing and eradicating codon-12 mutated k-ras antigen abnormal cells. One G13D peptide mimotope (164-D) and one G12V peptide mimotope (68-V) were designed to elicit antigen specific IgG titres against mutated K-ras antigens in immunised Balb/c mice. The RNA was extracted from splenocytes following ELISA confirmation on post-immunized mice sera and was reverse transcribed into cDNA. The scFv combinatorial library was constructed from cDNA repertoire of variable regions of heavy chain (VH) and light chain (VL) fusions connected by a flexible glycine-serine linker, using splicing by overlap extension PCR (SOE-PCR). Anti-mKRAS G12V and G13D scFvs were cloned in pCANTAB5E phagemid and superinfected with helper phage. After few rounds of bio-panning, a specific mKRAS G12V and G13D scFv antibody against G12V and G13D control mimotope was identified and confirmed using ELISA without any cross-reactivity with other mimotopes or controls. Subsequently, the anti-mKRAS scFv was fused to mHALT-1 using SOE-PCR and cloned in pET22b vector. Expressed recombinant immunotoxins were analyzed for their effects on cell proliferation by the MTT assay and targeted specificity by cell-based ELISA on KRAS-positive and KRAS-negative cancer cells.

    Results: The VH and VL genes from spleen RNA of mice immunized with 164-D and 68-V were amplified and randomly linked together, using SOE-PCR producing band sizes about 750 bp. Anti-mKRAS G12V and G13D scFvs were constructed in phagemid pCANTAB5E vectors with a library containing 3.4 × 106 and 2.9 × 106 individual clones, respectively. After three rounds of bio-panning, the anti-mKRAS G12V-34 scFv antibody against G12V control mimotope was identified and confirmed without any cross-reactivity with other controls using ELISA. Anti-mKRAS G12V-34 scFv fragment was fused to mHALT-1 toxin and cloned in pET22b vector with expression as inclusion bodies in E. coli BL21(DE3) (molecular weight of ~46.8 kDa). After successful solubilization and refolding, the mHALT-1-scFv immunotoxin exhibited cytotoxic effects on SW-480 colorectal cancer cells with IC50 of 25.39 μg/mL, with minimal cytotoxicity effect on NHDF cells.

    Discussion: These results suggested that the development of such immunotoxins is potentially useful as an immunotherapeutic application against KRAS-positive malignancies.

  6. Liew TS, Marzuki ME, Schilthuizen M, Chen Y, Vermeulen JJ, Mohd-Azlan J
    PeerJ, 2020;8:e9416.
    PMID: 32714659 DOI: 10.7717/peerj.9416
    Borneo has gone through dramatic changes in geology and topography from the early Eocene until the early Pliocene and experienced climatic cycling during the Pleistocene. However, how these changes have shaped the present-day patterns of high diversity and complex distribution are still poorly understood. In this study, we use integrative approaches by estimating phylogenetic relationships, divergence time, and current and past niche suitability for the Bornean endemic land snail genus Everettia to provide additional insight into the evolutionary history of this genus in northern Borneo in the light of the geological vicariance events and climatic fluctuations in the Pleistocene. Our results show that northern Borneo Everettia species belong to two deeply divergent lineages: one contains the species that inhabit high elevation at the central mountain range, while the other contains lowland species. Species diversification in these lineages has taken place before the Pliocene. Climate changes during the Pleistocene did not play a significant role in species diversification but could have shaped contemporary species distribution patterns. Our results also show that the species-rich highland habitats have acted as interglacial refugia for highland species. This study of a relatively sedentary invertebrate supports and enhances the growing understanding of the evolutionary history of Borneo. Species diversification in Everettia is caused by geological vicariance events between the early Miocene and the Pliocene, and the distribution patterns were subsequently determined by climatic fluctuations in the Pleistocene.
  7. Fadli N, Mohd Nor SA, Othman AS, Sofyan H, Muchlisin ZA
    PeerJ, 2020;8:e9641.
    PMID: 32844060 DOI: 10.7717/peerj.9641
    Knowledge on the precise identification of fish resources is critical for sustainable fisheries management. This study employs the DNA barcoding approach to generate a molecular taxonomic catalogue of commercially important reef fishes in the waters of Weh Island (Aceh Province), the most northerly inhabited island in the biodiverse Indonesian Archipelago. The waters not only support artisanal fisheries but also a feeder for the industry in the greater island of Aceh. In total, 230 specimens from 72 species belonging to 32 genera and 17 families were DNA barcoded, representing a major segment of the captured reef fish taxa and a quarter of fish species diversity that had previously been recorded. The sequence read lengths were 639 bp revealing 359 conserved sites, 280 variable sites, 269 parsimony informative and 11 singletons. Our molecular findings paralleled the morphological identification with no evidence of cryptic species or new species discovery. This study is a significant contribution to the fisheries statistics of this area, which would facilitate assessment of species catch composition and hence for strategizing management plans. It is an important input to the DNA barcode library of Indonesian marine fishes and to the global DNA barcode entries in general.
  8. Kong BH, Teoh KH, Tan NH, Tan CS, Ng ST, Fung SY
    PeerJ, 2020;8:e9650.
    PMID: 32832273 DOI: 10.7717/peerj.9650
    Background: Lignosus tigris, a recently discovered species of the unique Lignosus family, has been traditionally used by the indigenous communities in Peninsular Malaysia to treat various ailments and as an alternative medicine for cancer treatment. The L. tigris cultivar sclerotia (Ligno TG-K) was found to contain numerous bioactive compounds with beneficial biomedicinal properties and the sclerotial extract exhibited potent antioxidant activity. However, the anticancer property of the Ligno TG-K including in vitro and in vivo antitumor effects as well as its anticancer active compounds and the mechanisms has yet to be investigated.

    Methods: The cytotoxicity of the Ligno TG-K against human breast (MCF7), prostate (PC3) and lung (A549) adenocarcinoma cell lines was evaluated using MTT cytotoxicity assay. The cytotoxic mechanisms of the active high molecular weight proteins (HMWp) fraction were investigated through detection of caspases activity and apoptotic-related proteins expression by Western blotting. The in vivo antitumor activity of the isolated HMWp was examined using MCF7 mouse xenograft model. Shotgun LC-MS/MS analysis was performed to identify the proteins in the HMWp.

    Results and Discussion: Cold water extract of the sclerotia inhibited proliferation of MCF7, A549 and PC3 cells with IC50 ranged from 28.9 to 95.0 µg/mL. Bioassay guided fractionation of the extract revealed that HMWp exhibited selective cytotoxicity against MCF7 cells via induction of cellular apoptosis by the activation of extrinsic and intrinsic signaling pathways. HMWp activated expression of caspase-8 and -9 enzymes, and pro-apoptotic Bax protein whilst inhibiting expression of tumor survivor protein, Bcl-2. HMWp induced tumor-cell apoptosis and suppressed growth of tumor in MCF-7 xenograft mice. Lectins, serine proteases, RNase Gf29 and a 230NA deoxyribonuclease are the major cytotoxic proteins that accounted for 55.93% of the HMWp.

    Conclusion: The findings from this study provided scientific evidences to support the traditional use of the L. tigris sclerotia for treatment of breast cancer. Several cytotoxic proteins with high abundance have been identified in the HMWp of the sclerotial extract and these proteins have potential to be developed into new anticancer agents or as adjunct cancer therapy.

  9. Freeman MA, Yanagida T, Kristmundsson À
    PeerJ, 2020;8:e9529.
    PMID: 32742799 DOI: 10.7717/peerj.9529
    Gastrointestinal myxosporean parasites from the genus Enteromyxum are known to cause severe disease, resulting in high mortalities in numerous species of cultured marine fishes globally. Originally described as Myxidium spp., they were transferred to a new genus, Enteromyxum, to emphasize their novel characteristics. Their retention in the family Myxidiidae at the time was warranted, but more comprehensive phylogenetic analyses have since demonstrated the need for a new family for these parasites. We discovered a novel Enteromyxum in wild fish from Malaysia and herein describe the fourth species in the genus and erect a new family, the Enteromyxidae n. fam., to accommodate them. Enteromyxum caesio n. sp. is described infecting the tissues of the stomach in the redbelly yellowtail fusilier, Caesio cuning, from Malaysia. The new species is distinct from all others in the genus, as the myxospores although morphologically similar, are significantly smaller in size. Furthermore, small subunit ribosomal DNA sequence data reveal that E. caesio is <84% similar to others in the genus, but collectively they form a robust and discrete clade, the Enteromyxidae n. fam., which is placed as a sister taxon to other histozoic marine myxosporeans. In addition, we describe, using transmission electron microscopy, the epicellular stages of Enteromyxum fugu and show a scanning electron micrograph of a mature myxospore of E. caesio detailing the otherwise indistinct sutural line, features of the polar capsules and spore valve ridges. The Enteromyxidae n. fam. is a commercially important group of parasites infecting the gastrointestinal tract of marine fishes and the histozoic species can cause the disease enteromyxosis in intensive finfish aquaculture facilities. Epicellular and sloughed histozoic stages are responsible for fish-to-fish transmission in net pen aquaculture systems but actinospores from an annelid host are thought to be necessary for transmission to fish in the wild.
  10. Emrizal R, Nor Muhammad NA
    PeerJ, 2020;8:e9019.
    PMID: 32617187 DOI: 10.7717/peerj.9019
    Porphyromonas gingivalis is one of the major bacteria that causes periodontitis. Chronic periodontitis is a severe form of periodontal disease that ultimately leads to tooth loss. Virulence factors that contribute to periodontitis are secreted by Type IX Secretion System (T9SS). There are aspects of T9SS protein components that have yet to be characterised. Thus, the aim of this study is to investigate the phylogenetic relationship between members of 20 T9SS component protein families. The Bayesian Inference (BI) trees for 19 T9SS protein components exhibit monophyletic clades for all major classes under Bacteroidetes with strong support for the monophyletic clades or its subclades that is consistent with phylogeny exhibited by the constructed BI tree of 16S rRNA. The BI tree of PorR is different from the 19 BI trees of T9SS protein components as it does not exhibit monophyletic clades for all major classes under Bacteroidetes. There is strong support for the phylogeny exhibited by the BI tree of PorR which deviates from the phylogeny based on 16S rRNA. Hence, it is possible that the porR gene is subjected to horizontal transfer as it is known that virulence factor genes could be horizontally transferred. Seven genes (porR included) that are involved in the biosynthesis of A-LPS are found to be flanked by insertion sequences (IS5 family transposons). Therefore, the intervening DNA segment that contains the porR gene might be transposed and subjected to conjugative transfer. Thus, the seven genes can be co-transferred via horizontal gene transfer. The BI tree of UgdA does not exhibit monophyletic clades for all major classes under Bacteroidetes which is similar to the BI tree of PorR (both are a part of the seven genes). Both BI trees also exhibit similar topology as the four identified clusters with strong support and have similar relative positions to each other in both BI trees. This reinforces the possibility that porR and the other six genes might be horizontally transferred. Other than the BI tree of PorR, the 19 other BI trees of T9SS protein components also exhibit evidence of horizontal gene transfer. However, their genes might undergo horizontal gene transfer less frequently compared to porR because the intervening DNA segment that contains porR is easily exchanged between bacteria under Bacteroidetes due to the presence of insertion sequences (IS5 family transposons) that flank it. In conclusion, this study can provide a better understanding about the phylogeny of T9SS protein components.
  11. Cai D, Xu Y, Zhao F, Zhang Y, Duan H, Guo X
    PeerJ, 2021;9:e10702.
    PMID: 33520465 DOI: 10.7717/peerj.10702
    Background: Plant-growth-promoting rhizobacteria (PGPR) can promote plant growth and enhance plant tolerance to salt stress. Pseudomonas sp. strain M30-35 might confer abiotic stress tolerance to its host plants. We evaluated the effects of M30-35 inoculation on the growth and metabolite accumulation of Chenopodium quinoa Willd. during salt stress growth conditions.

    Methods: The effects of M30-35 on the growth of C. quinoa seedlings were tested under salt stress. Seedling growth parameters measured included chlorophyll content, root activity, levels of plant- phosphorus (P), and saponin content.

    Results: M30-35 increased biomass production and root activity compared to non-inoculated plants fertilized with rhizobia and plants grown under severe salt stress conditions. The photosynthetic pigment content of chlorophyll a and b were higher in M30-35-inoculated C. quinoa seedlings under high salt stress conditions compared to non-inoculated seedlings. The stability of P content was also maintained. The content of saponin, an important secondary metabolite in C. quinoa, was increased by the inoculation of M30-35 under 300 mM NaCl conditions.

    Conclusion: Inoculation of M30-35 rescues the growth diminution of C. quinoa seedlings under salt stress.

  12. Mohd Rosli RR, Norhayati MN, Ismail SB
    PeerJ, 2021;9:e10527.
    PMID: 33520436 DOI: 10.7717/peerj.10527
    Background: Iron deficiency anemia (IDA) is commonly treated with iron formulations. Despite the expanding acceptance of iron polymaltose complex (IPC) among clinicians, there is sparse and contradictory evidence regarding its efficacy in the management of IDA in children. This systematic review and meta-analysis aimed to assess the effectiveness of IPC in the treatment and prevention of IDA in children.

    Methods: We searched the Cochrane Central Register of Controlled Trials, MEDLINE and Epistemonikos for all randomized control trials (RCTs) comparing oral IPC with standard oral iron supplementation for the treatment or prevention of IDA in children. We independently screened the titles and abstracts of identified trials before the full text of relevant trials was evaluated for eligibility. We then independently extracted data on the methods, interventions, outcomes, and risk of bias from the included trials. A random-effects model was used to estimate the risk ratios and mean differences with 95% confidence intervals.

    Results: Eight trials comprising 493 randomized patients were included and analyzed using three comparison groups. The comparison group of which was used to evaluate IPC and ferrous sulphate (FS) for treatment of IDA showed that IPC is less effective in increasing Hb (MD -0.81, 95% CI -1.08 to -0.53; I2 = 48%, P 

  13. Dorairaj D, Osman N
    PeerJ, 2021;9:e10477.
    PMID: 33520435 DOI: 10.7717/peerj.10477
    Population increase and the demand for infrastructure development such as construction of highways and road widening are intangible, leading up to mass land clearing. As flat terrains become scarce, infrastructure expansions have moved on to hilly terrains, cutting through slopes and forests. Unvegetated or bare slopes are prone to erosion due to the lack of or insufficient surface cover. The combination of exposed slope, uncontrolled slope management practices, poor slope planning and high rainfall as in Malaysia could steer towards slope failures which then results in landslides under acute situation. Moreover, due to the tropical weather, the soils undergo intense chemical weathering and leaching that elevates soil erosion and surface runoff. Mitigation measures are vital to address slope failures as they lead to economic loss and loss of lives. Since there is minimal or limited information and investigations on slope stabilization methods in Malaysia, this review deciphers into the current slope management practices such as geotextiles, brush layering, live poles, rock buttress and concrete structures. However, these methods have their drawbacks. Thus, as a way forward, we highlight the potential application of soil bioengineering methods especially on the use of whole plants. Here, we discuss the general attributions of a plant in slope stabilization including its mechanical, hydrological and hydraulic effects. Subsequently, we focus on species selection, and engineering properties of vegetation especially rooting structures and architecture. Finally, the review will dissect and assess the ecological principles for vegetation establishment with an emphasis on adopting the mix-culture approach as a slope failure mitigation measure. Nevertheless, the use of soil bioengineering is limited to low to moderate risk slopes only, while in high-risk slopes, the use of traditional engineering measure is deemed more appropriate and remain to be the solution for slope stabilization.
  14. Saba AO, Ismail A, Zulkifli SZ, Shohaimi S, Azmai MNA
    PeerJ, 2021;9:e10643.
    PMID: 33520451 DOI: 10.7717/peerj.10643
    Malaysia is one of the top ten countries in the world that produce freshwater ornamental fishes. This industry can offer better livelihood opportunities to many poor households. However, most of the produced ornamental fishes are alien to Malaysia. In this study, we explore the contribution of alien freshwater fishes to the income of ornamental fish store owners and their attitude towards alien freshwater fishes within Klang Valley, Malaysia. Using a structured questionnaire, we surveyed 70 pet stores out of which 54 (81.42%) store owners responded. Most of the pet store owners were male (72%), Chinese (83%), and the highest educational level was at the secondary level (79%). Most of the pet store owners reported a monthly income of RM 2001-RM 5000 (78%) and were married (73%). Using Chi-square (χ2) test, significant relationships (p < 0.05) existed between the attitude of store owners towards alien ornamental fish species versus educational level (χ2 = 16.424, p = 0.007) and contribution of alien ornamental fishes to the pet store owners' income (χ2 = 27.266, p = 0.003). Fish sales as the main income source also related significantly with the impact of fish selling business on income level (χ2 = 10.448, p = 0.007). This study showed that the ornamental fish sales contributed over half of the income (51-100%) from the businesses of store owners. Almost half of the respondents (42%) reported that alien ornamental fish was the highest contributor to their income from the ornamental fish sale. While the mismanagement of alien ornamental fishes could give various negative ecological impacts, the socio-economic benefits of these fishes cannot be denied.
  15. Hasan M, Hanafiah MM, Alhilfy IHH, Aeyad Taha Z
    PeerJ, 2021;9:e10614.
    PMID: 33520446 DOI: 10.7717/peerj.10614
    Background: Laser applications in agriculture have recently gained much interest due to improved plant characteristics following laser treatment before the sowing of seeds. In this study, maize seeds were exposed to different levels of laser treatment prior to sowing to improve their field performance. The aim of this study is to evaluate the impact of pre-sowing laser photobiomodulation on the field emergence and growth of treated maize seeds.

    Methods: The maize seeds were first photobiomodulated with two lasers: 1) a helium-neon (He-Ne) red laser (632.8 nm), and 2) a neodymium-doped yttrium aluminum garnet (Nd:YAG) green laser (532 nm). Following three replications of randomized complete block design (RCBD), four irradiation treatments were applied (45 s, 65 s, 85 s, and 105 s) at two power intensities (2 mW/cm2 and 4 mW/cm2).

    Results: Based on the results, maize seeds pretreated with a green laser and 2 mW/cm2 power intensity for 105 s exhibited the highest rate of seed emergence (96%) compared to the untreated control seeds with a lower seed emergence rate (62.5%). Furthermore, maize seeds treated with a red laser for 45 s showed an increased vigor index compared to the other treatment options and the control (P 

  16. Estudillo AJ, Wong HK
    PeerJ, 2021;9:e10629.
    PMID: 33510971 DOI: 10.7717/peerj.10629
    The 20-Item Prosopagnosia Items (PI-20) was recently introduced as a self-report measure of face recognition abilities and as an instrument to help the diagnosis of prosopagnosia. In general, studies using this questionnaire have shown that observers have moderate to strong insights into their face recognition abilities. However, it remains unknown whether these insights are equivalent for the whole range of face recognition abilities. The present study investigates this issue using the Mandarin version of the PI-20 and the Cambridge Face Memory Test Chinese (CFMT-Chinese). Our results showed a moderate negative association between the PI-20 and the CFMT-Chinese. However, this association was driven by people with low and high face recognition ability, but absent in people within the typical range of face recognition performance. The implications of these results for the study of individual differences and the diagnosis of prosopagnosia are discussed.
  17. Do TD, Gui MM, Ng KY
    PeerJ, 2021;9:e10806.
    PMID: 33604187 DOI: 10.7717/peerj.10806
    This article presents the assessment of time-dependent national-level restrictions and control actions and their effects in fighting the COVID-19 pandemic. By analysing the transmission dynamics during the first wave of COVID-19 in the country, the effectiveness of the various levels of control actions taken to flatten the curve can be better quantified and understood. This in turn can help the relevant authorities to better plan for and control the subsequent waves of the pandemic. To achieve this, a deterministic population model for the pandemic is firstly developed to take into consideration the time-dependent characteristics of the model parameters, especially on the ever-evolving value of the reproduction number, which is one of the critical measures used to describe the transmission dynamics of this pandemic. The reproduction number alongside other key parameters of the model can then be estimated by fitting the model to real-world data using numerical optimisation techniques or by inducing ad-hoc control actions as recorded in the news platforms. In this article, the model is verified using a case study based on the data from the first wave of COVID-19 in the Republic of Kazakhstan. The model is fitted to provide estimates for two settings in simulations; time-invariant and time-varying (with bounded constraints) parameters. Finally, some forecasts are made using four scenarios with time-dependent control measures so as to determine which would reflect on the actual situations better.
  18. Mohd Amnan MA, Pua TL, Lau SE, Tan BC, Yamaguchi H, Hitachi K, et al.
    PeerJ, 2021;9:e10879.
    PMID: 33614294 DOI: 10.7717/peerj.10879
    Drought is one of the severe environmental stresses threatening agriculture around the globe. Nitric oxide plays diverse roles in plant growth and defensive responses. Despite a few studies supporting the role of nitric oxide in plants under drought responses, little is known about its pivotal molecular amendment in the regulation of stress signaling. In this study, a label-free nano-liquid chromatography-mass spectrometry approach was used to determine the effects of sodium nitroprusside (SNP) on polyethylene glycol (PEG)-induced osmotic stress in banana roots. Plant treatment with SNP improved plant growth and reduced the percentage of yellow leaves. A total of 30 and 90 proteins were differentially identified in PEG+SNP against PEG and PEG+SNP against the control, respectively. The majority of proteins differing between them were related to carbohydrate and energy metabolisms. Antioxidant enzyme activities, such as superoxide dismutase and ascorbate peroxidase, decreased in SNP-treated banana roots compared to PEG-treated banana. These results suggest that the nitric oxide-induced osmotic stress tolerance could be associated with improved carbohydrate and energy metabolism capability in higher plants.
  19. Liew TS, Phung CC, Mat Said MA, Hoo PK
    PeerJ, 2021;9:e11886.
    PMID: 34395099 DOI: 10.7717/peerj.11886
    This study aimed to reveal the habitat variables that determine the distribution and abundance of the land snail Pollicaria elephas in limestone habitats in Perak, Malaysia. Seventeen plots were selected on a limestone hill to determine the effect of environmental variables on the abundance of this land snail. The environmental variables we considered included habitat (canopy cover and leaf litter thickness), topography (elevation, aspect, ruggedness, and slope), microclimate (soil temperature, air temperature, and humidity), and vegetation (abundance of respective vascular plant species). The correlation analyses suggested that the snails' abundance was positively correlated with the abundance of the four vascular plant species: Diospyros toposia var. toposoides, Croton cascarilloides, Kibatalia laurifolia, and Mallotus peltatus. Plots with lower soil temperatures had more snails than plots with higher soil temperatures. Our results show that plots in the southern part of the limestone hill, in which P. elephas were absent, were similar in habitat, topography, microclimate, and vegetation to the plots in the northern part of the limestone hill, where specimens were mostly present. The absence of this species in suitable habitats may be due to their low dispersal ability rather than adverse environmental conditions.
  20. Tan HY, Goh ZY, Loh KH, Then AY, Omar H, Chang SW
    PeerJ, 2021;9:e11825.
    PMID: 34434645 DOI: 10.7717/peerj.11825
    Background: Despite the high commercial fisheries value and ecological importance as prey item for higher marine predators, very limited taxonomic work has been done on cephalopods in Malaysia. Due to the soft-bodied nature of cephalopods, the identification of cephalopod species based on the beak hard parts can be more reliable and useful than conventional body morphology. Since the traditional method for species classification was time-consuming, this study aimed to develop an automated identification model that can identify cephalopod species based on beak images.

    Methods: A total of 174 samples of seven cephalopod species were collected from the west coast of Peninsular Malaysia. Both upper and lower beaks were extracted from the samples and the left lateral views of upper and lower beak images were acquired. Three types of traditional morphometric features were extracted namely grey histogram of oriented gradient (HOG), colour HOG, and morphological shape descriptor (MSD). In addition, deep features were extracted by using three pre-trained convolutional neural networks (CNN) models which are VGG19, InceptionV3, and Resnet50. Eight machine learning approaches were used in the classification step and compared for model performance.

    Results: The results showed that the Artificial Neural Network (ANN) model achieved the best testing accuracy of 91.14%, using the deep features extracted from the VGG19 model from lower beak images. The results indicated that the deep features were more accurate than the traditional features in highlighting morphometric differences from the beak images of cephalopod species. In addition, the use of lower beaks of cephalopod species provided better results compared to the upper beaks, suggesting that the lower beaks possess more significant morphological differences between the studied cephalopod species. Future works should include more cephalopod species and sample size to enhance the identification accuracy and comprehensiveness of the developed model.

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