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Fulltext Novel Bi-heterocycles as Potent Inhibitors of Urease and Less Cytotoxic Agents: 3-({5-((2-Amino-1,3-thiazol-4-yl)methyl)-1,3,4-oxadiazol-2-yl}sulfanyl)-N-(un/substituted-phenyl)propanamides

Abbasi MA, Ramzan MS, Ur-Rehman A, Siddiqui SZ, Hassan M, Ali Shah SA, et al.

Iran J Pharm Res, 2020;19(1):487-506.
PMID: 32922502 DOI: 10.22037/ijpr.2019.13084.11362

The synthesis of a novel series of bi-heterocyclic propanamides, 7a-l, was accomplished by S-substitution of 5-[(2-amino-1,3-thiazol-4-yl)methyl]-1,3,4-oxadiazol-2-thiol (3). The synthesis was initiated from ethyl 2-(2-amino-1,3-thiazol-4-yl)acetate (1) which was converted to corresponding hydrazide, 2, by hydrazine hydrate in methanol. The refluxing of hydrazide, 2, with carbon disulfide in basic medium, resulted in 5-[(2-amino-1,3-thiazol-4-yl)methyl]-1,3,4-oxadiazol-2-thiol (3). A series of electrophiles, 6a-l, was synthesized by stirring un/substituted anilines (4a-l) with 3-bromopropanoyl chloride (5) in a basic aqueous medium. Finally, the targeted compounds, 7a-l, were acquired by stirring 3 with newly synthesized electrophiles, 6a-l, in DMF using LiH as a base and an activator. The structures of these bi-heterocyclic propanamides were confirmed through spectroscopic techniques, such as IR, 1H-NMR, 13C-NMR, and EI-MS. These molecules were tested for their urease inhibitory potential, whereby, the whole series exhibited very promising activity against this enzyme. Their cytotoxic behavior was ascertained through hemolysis and it was observed that all these were less cytotoxic agents. The in-silico molecular docking analysis of these molecules was also in full agreement with their in-vitro enzyme inhibition data.
Fulltext Synthesis, Kinetics, Binding Conformations and Structure-activity Relationship of Potent Tyrosinase Inhibitors: Aralkylated 2-aminothiazole-ethyltriazole Hybrids

Sadiq Butt AR, Abbasi MA, Rehman AU, Siddiqui SZ, Raza H, Hassan M, et al.

Iran J Pharm Res, 2021;20(2):206-228.
PMID: 34567157 DOI: 10.22037/ijpr.2020.15521.13145

Considering the diversified pharmacological importance of thiazole and triazole heterocyclic moieties, a unique series of S-aralkylated bi-heterocyclic hybrids, 7a-l, was synthesized in a convergent manner. The structures of newly synthesized compounds were characterized by 1H-NMR, 13C-NMR, IR, and EI-MS spectral studies. The structure-activity relationship of these compounds was envisaged by analyzing their inhibitory effects against tyrosinase, whereby all these molecules exhibited potent inhibitory potentials relative to the standard used. The Kinetics mechanism was ascertained by Lineweaver-Burk plots, which revealed that 7g inhibited tyrosinase non-competitively by forming an enzyme-inhibitor complex. The inhibition constants Ki calculated from Dixon plots for this compound was 0.0057µM. These bi-heterocyclic molecules also disclosed good binding energy values (kcal /mol) when assessed computationally. So, these molecules can be considered promising medicinal scaffolds for the treatment of skin disorders.
Biological activity and molecular docking studies of curcumin-related α,β-unsaturated carbonyl-based synthetic compounds as anticancer agents and mushroom tyrosinase inhibitors

Bukhari SN, Jantan I, Unsal Tan O, Sher M, Naeem-Ul-Hassan M, Qin HL

J Agric Food Chem, 2014 Jun 18;62(24):5538-47.
PMID: 24901506 DOI: 10.1021/jf501145b

Hyperpigmentation in human skin and enzymatic browning in fruits, which are caused by tyrosinase enzyme, are not desirable. Investigations in the discovery of tyrosinase enzyme inhibitors and search for improved cytotoxic agents continue to be an important line in drug discovery and development. In present work, a new series of 30 compounds bearing α,β-unsaturated carbonyl moiety was designed and synthesized following curcumin as model. All compounds were evaluated for their effects on human cancer cell lines and mushroom tyrosinase enzyme. Moreover, the structure-activity relationships of these compounds are also explained. Molecular modeling studies of these new compounds were carried out to explore interactions with tyrosinase enzyme. Synthetic curcumin-like compounds (2a-b) were identified as potent anticancer agents with 81-82% cytotoxicity. Five of these newly synthesized compounds (1a, 8a-b, 10a-b) emerged to be the potent inhibitors of mushroom tyrosinase, providing further insight into designing compounds useful in fields of food, health, and agriculture.
Fulltext Surfactant modified/mediated thin-layer chromatographic systems for the analysis of amino acids

Bhawani SA, Albishri HM, Khan ZA, Mohamad Ibrahim MN, Mohammad A

J Anal Methods Chem, 2013;2013:973280.
PMID: 24455427 DOI: 10.1155/2013/973280

This review incorporates a large number of chromatographic systems modified by the surfactants. A large number of solvent systems and stationary phases are summarized in this paper. Three different kinds of surfactants (anionic, cationic, and nonionic) are used as modifiers for stationary phases as well as solvent systems. Surfactants are used at all the three different concentration levels (below, above, and at critical micelle concentration) where surfactants behave differently. Modifications of both stationary phases and solvent systems by surfactants produced a new generation of chromatographic systems. Microemulsion solvent systems are also incorporated in this paper. Microemulsion thin-layer chromatography is a new approach in the field of chromatography.
Fulltext Live recombinant Lactococcus lactis vaccine expressing aerolysin genes D1 and D4 for protection against Aeromonas hydrophila in tilapia (Oreochromis niloticus)

Anuradha K, Foo HL, Mariana NS, Loh TC, Yusoff K, Hassan MD, et al.

J Appl Microbiol, 2010 Nov;109(5):1632-42.
PMID: 20602654 DOI: 10.1111/j.1365-2672.2010.04789.x

To evaluate a live recombinant Lactococcus lactis vaccine expressing aerolysin genes D1 (Lac-D1ae) and/or D4 (Lac-D4ae) in protection against Aeromonas hydrophila in tilapia (Oreochromis niloticus).
Fulltext Antibiotics dispensing for URTIs by community pharmacists (CPs) and general medical practitioners in Penang, Malaysia: A comparative study using simulated patients (SPs)

Alabid AH, Ibrahim MI, Hassali MA

J Clin Diagn Res, 2014 Jan;8(1):119-23.
PMID: 24596741 DOI: 10.7860/JCDR/2014/6199.3923

BACKGROUND: In Malaysia, doctors in private clinics (often called dispensing doctors) are permitted to dispense medicines. This potentially may compromise rational dispensing of medicines in general and antibiotics in particular.
AIM: This study explored, assessed and compared dispensing of antibiotics between Community Pharmacist (CP) and General Practitioners (GPs) regarding symptomatic diagnosis, antibiotic categories, adherence to therapeutic doses and promotion of generic antibiotics.
METHOD: The study used trained Simulated Patients (SPs), who used a scenario of common cold symptoms at GP private clinics and community pharmacies to observe and explore the practice of antibiotics dispensing. The study was conducted within the period of May to September 2011 in Penang, Malaysia. The data was analysed using descriptive statistics, Chi-square and Fisher's Exact Tests at alpha level of 0.05.
RESULTS: GPs dispensed more antibiotics than CPs (p= 0.001) for common cold symptoms. They dispensed more Amoxicillin (n = 14, 35%) than CPs (n = 11, 11%) (p < 0.001) and more Tetracycline (n = 3, 7.5%) while no CP dispensed this category (p = 0.022). On the other hand, CPs (n = 11, 11%) suggested brand antibiotics where as GPs dispensed only generic antibiotics (p < 0.001). Generally GPs comply better with the symptomatic diagnosis standard e.g. when asking SPs about the symptoms they had, all GPs (n = 40, 100%) complied better with this standard. Despite that, they dispensed more antibiotics (n = 26, 65%) than CPs (n = 29, 29%) (p = 0.001). GPs (n = 22, 55%) also are better than CPs (n = 16, 16%) in adherence to therapeutic doses (p< 0.001).
CONCLUSION: Findings showed poor adherence to rational dispensing of antibiotics by both providers. Although, GPs adhere better to symptomatic diagnosis and therapeutic dosing of antibiotics than CPs, they unnecessarily prescribe and dispense more antibiotics for Upper respiratory tract infection (URTI) symptoms. Establishing prescription guidance and regulatory actions, especially for URTIs treatment, and separating of medication dispensing are seemed to be crucial steps for the reform.
KEYWORDS: Community pharmacists; Dispensing doctors; Dispensing separation; General practitioners; Simulated patients ligament
Fulltext Do Professional Practices among Malaysian Private Healthcare Providers Differ? A Comparative Study using Simulated Patients

Alabid AH, Ibrahim MI, Hassali MA

J Clin Diagn Res, 2013 Dec;7(12):2912-6.
PMID: 24551673 DOI: 10.7860/JCDR/2013/6198.3789

BACKGROUND: Malaysia, a South East Asian country, legally permits general medical practitioners in private clinics to dispense medicines. This possibly can dilute the pharmacist role in the provision of healthcare and pharmaceutical care and deprive patients to benefit from these services.
OBJECTIVE: This study explored, assessed and compared the current status of medicines labeling, patient's counseling, and symptomatic diagnosis by general practitioners and community pharmacists.
MATERIAL AND METHODS: This study used trained Simulated Patients (SP), who participated in a scenario of common cold symptoms at private clinics and community pharmacies. SPs explored medication labeling, patients counseling and symptomatic diagnosis undertaken by general practitioners and community pharmacists. Later, study authors assessed and compared these practices. The study was conducted during June 2011 in Penang, Malaysia.
RESULTS: The study used descriptive statistics and Fisher-exact test to analyze data. Regarding patients counseling standard, among 100 visits by simulated patients, 64 (64%) from community pharmacists provided information about the medicine name, its indication, dosage and route of administration versus 17 (42.5%) general practitioners during 40 visits (p=0.024). Concerning adherence to labeling standard, for instance, only in one pharmacy visit, (1%) the pharmacist wrote the name of the patient on the medication label versus in 32 (80%) of doctors' visits, the doctors adhered to this labeling standard (p<0.001). In all doctors' visits (n=40, 100%), SPs were asked about symptoms, whereas in 87 (87%) CPs' visits, pharmacists fulfilled this counseling standard (p=0.02).
CONCLUSION: Although pharmacists showed less compliance to medicine labeling and symptomatic diagnosis compared to doctors, their counseling of patients was better. Separation will definitely contribute to more concentration of each provider on his/her roles and improve and direct the experiences and skills towards being more patient oriented.
Fulltext Lipid lowering effect of antioxidant alpha-lipoic Acid in experimental atherosclerosis

Amom Z, Zakaria Z, Mohamed J, Azlan A, Bahari H, Taufik Hidayat Baharuldin M, et al.

J Clin Biochem Nutr, 2008 Sep;43(2):88-94.
PMID: 18818758 DOI: 10.3164/jcbn.2008051

Accumulating data demonstrated that hypercholesterolemia and oxidative stress play an important role in the development of atherosclerosis. In the present study, a protective activity of alpha-lipoic acid; a metabolic antioxidant in hypercholesterolemic-induced animals was investigated. Eighteen adult male New Zealand White (NZW) rabbit were segregated into three groups labelled as group N, HCD and ALA (n = 6). Group N (normal control) was fed with normal chow, the rest (HCD and ALA) were fed with 100 g/head/day of 1% cholesterol rich diet to induce hypercholesterolemia. Four point two mg/body weight of alpha lipoic acid was concomintantly supplemented to the ALA group. Drinking water was given ad-libitum. The study was designed for 10 weeks. Blood sampling was taken from the ear lobe vein at the beginning, week 5 and week 10. Plasma was prepared for lipid profile estimation and microsomal lipid peroxidation index indicated with malondialdehyde (MDA) formation. At the end of the experiment, the animals were sacrificed and the aorta were excised for intimal lesion analysis. The plasma total cholesterol (TC) and low density lipoprotein (LDL) levels were found to be significantly low in ALA group compared to that of the HCD group (p<0.05). Similarly, low level of MDA (p<0.05) in ALA group was observed compared to that of the HCD group showing a significant reduction of lipid peroxidation activity. Histomorphometric intimal lesion analysis of the aorta showing less of atheromatous plaque formation in alpha lipoic acid supplemented group (p<0.05) compared to HCD group. These findings suggested that alpha lipoic acid posses a dual lipid lowering and anti-atherosclerotic properties indicated with low plasma TC and LDL levels and reduction of athero-lesion formation in hypercholesterolemic-induced rabbits.
Psychometric Properties of a Theory of Planned Behavior Questionnaire for Assessing the Midwives' Intention to Provide Planned Home Birth Services in Nigeria

Muhammed A, Shariff-Ghazali S, Said SM, Hassan M, Lee K

J Community Health Nurs, 2020 4 3;37(2):77-88.
PMID: 32233947 DOI: 10.1080/07370016.2020.1736377

We developed and psychometrically tested a Theory of Planned Behavior (TPB) questionnaire which focused on assessing the midwives' intention to provide planned home birth (PHB) services. This is a quantitative, cross-sectional survey, conducted among 226 midwives working in ten participating health facilities. The reliability and validity of the theoretical constructs were assessed. The Cronbach's alpha values were >0.8 for all scales, suggesting satisfactory internal consistency. Confirmatory factor analysis revealed sufficient convergent validity (the average variance extracted was >0.5 for each construct) and discriminant validity. The study gathered an evidence of the usefulness of TPB in the specific context of PHB.
Assessing the competency of University of Malaya dental graduates: employers' and graduates' perceptions

Razak IA, Latifah RR, Jaafar N, Abu Hassan MI, Ab Murat N

J Dent Educ, 2008 Mar;72(3):364-9.
PMID: 18316541

A survey was conducted to assess competencies of dental graduates of the Faculty of Dentistry, University of Malaya, as perceived by the graduates and their employers, based on the five-year undergraduate curriculum introduced in 1995. All senior dental officers in the Ministry of Health (MOH), representing employers, and all 164 dental graduates of the years 2000, 2001, and 2002 were sent a self-administered questionnaire covering eight areas of competency. The respondents had to rate these areas on a scale of 1 (very poor) to 4 (very good). The responses for each area were then dichotomized into poor (1 and 2) and good (3 and 4). If less than 60 percent of the respondents rated an area as good, then it was categorized as needing attention; 60-69 percent as satisfactory; and 70 percent and above as excellent. One hundred and six graduates (64.6 percent) and twenty-nine employers (96.7 percent) responded; of the graduates, 73.6 percent were working in the MOH and 22.6 percent in private practice. About 57.1 percent of employers reported that at least five graduates have worked under them. Graduates (85.7 percent) and employers (83.3 percent) agreed that graduates have excellent skills in communication. Although all graduates perceived their competency to be excellent in the four areas (treatment planning; community-based skills; management, administrative skills, and personal management; and professional development skills), employers felt that these are the areas that are of concern and needed attention. In conclusion, whilst generally the graduates' level of competency in almost all areas is acceptable or good, there are areas of concern that need to be addressed to further improve the five-year curriculum at the University of Malaya.
Effects of pre-treatment technologies on dark fermentative biohydrogen production: A review

Bundhoo MA, Mohee R, Hassan MA

J Environ Manage, 2015 Jul 1;157:20-48.
PMID: 25881150 DOI: 10.1016/j.jenvman.2015.04.006

Biohydrogen production from dark fermentation of lignocellulosic materials represents a huge potential in terms of renewable energy exploitation. However, the low hydrogen yield is currently hindering its development on industrial scale. This study reviewed various technologies that have been investigated for enhancing dark fermentative biohydrogen production. The pre-treatment technologies can be classified based on their applications as inoculum or substrates pre-treatment or they can be categorised into physical, chemical, physicochemical and biological based on the techniques used. From the different technologies reviewed, heat and acid pre-treatments are the most commonly studied technologies for both substrates and inoculum pre-treatment. Nevertheless, these two technologies need not necessarily be the most suitable since across different studies, a wide array of other emerging techniques as well as combined technologies have yielded positive findings. To date, there exists no perfect technology for either inoculum or substrate pre-treatment. Although the aim of inoculum pre-treatment is to suppress H2-consumers and enrich H2-producers, many sporulating H2-consumers survive the pre-treatment while some non-spore H2-producers are inhibited. Besides, several inoculum pre-treatment techniques are not effective in the long run and repeated pre-treatment may be required for continuous suppression of H2-consumers and sustained biohydrogen production. Furthermore, many technologies employed for substrates pre-treatment may yield inhibitory compounds that can eventually decrease biohydrogen production. Consequently, much research needs to be done to find out the best technology for both substrates and inoculum pre-treatment while also taking into consideration the energetic, economic and technical feasibility of implementing such a process on an industrial scale.
Bactericidal role of epidermal mucus of freshwater fish treated with Aeromonas hydrophila

Ali S, Shah SAUR, Rauf M, Hassan M, Ullah W, Dawar FU

J Fish Dis, 2023 Nov;46(11):1225-1237.
PMID: 37501533 DOI: 10.1111/jfd.13841

This study explored the bactericidal role of the epidermal mucus (EM) of five freshwater Cyprinid fish species namely Ctenopharyngodon idella, Labeo rohita, Catla catla, Hypophthalmichthys molitrix, and Cirrhinus mrigala after treatment with Aeromonas hydrophila. Extracts of EM (crude and acidic) of each species showed bactericidal activity against various Gram -ve (Pseudomonas aeruginosa, Escherichia coli, Aeromonas hydrophila, Edwardsiella tarda, Salmonella enterica, Klebsiella pneumonia, Serratia marcescens, and Enterobacter cloacae) and Gram +ve (Bacillus wiedmannii and Staphylococcus aureus) bacteria compared with standard antibiotics (Fosfomycin). The zone of inhibition (ZOI) was measured in millimetres against antibiotics (Fosfomycin). Variations in bactericidal activity of EM were observed against bacteria from the same and different fish species. The acidic extract was more effective than the crude extract and showed significantly higher ZOI values against various bacteria and Fosfomycin antibiotics. This result shows that fish EM may perform an important role in fish defence against bacteria. Therefore, this study may hint towards the substitution of synthetic antibiotics with fish EM that may be used as a novel 'bactericidal' in aquaculture as well as in humans against bacterial infections.
Mapping the global research landscape on malnutrition for patients with chronic kidney disease: a visualization analysis

Shakhshir MH, Vanoh D, Hassan M, Zyoud SH

J Health Popul Nutr, 2023 Sep 23;42(1):101.
PMID: 37742012 DOI: 10.1186/s41043-023-00445-8

BACKGROUND: Chronic kidney disease (CKD) is seen as a diverse disease and a primary contributor to global mortality. Malnutrition arises within chronic illness, which involves protein energy depletion and inadequate levels of essential nutrients. These factors increase the likelihood of death and the overall impact of the disease on affected individuals. Consequently, this study aims to utilize bibliometric and visual analysis to assess the current state of research, the latest advances and emerging patterns in the fields of CKD and malnutrition.
METHODS: Extensive research was conducted using the Scopus database, which is the most authoritative database of research publications and citations, to focus on CKD research between 2003 and 2022, as indicated by title and author keywords. Then, within this vast collection of academic publications, a notable subset of articles was exclusively dedicated to investigating the relationship between CKD and malnutrition. Finally, we performed bibliometric analysis and visualization using VOSviewer 1.6.19 and Microsoft Excel 2013.
RESULTS: Large global research between 2003 and 2022 resulted in 50,588 documents focused on CKD, as indicated by title and author keywords. In this extensive collection of scientific publications, a staggering portion of 823 articles is devoted exclusively to investigating the link between CKD and malnutrition. Further analysis reveals that this body of work consists of 565 articles (68.65%), 221 reviews (26.85%), and 37 miscellaneous entries (4.50%), which encompass letters and editorials. The USA was found to be the most productive country (n = 173; 21.02%), followed by Italy (n = 83; 10.09%), Sweden (n = 56; 6.80%), Brazil (n = 54; 6.56%) and China (n = 51; 6.20%). The most common terms on the map include those related to the topic of (a) malnutrition in hemodialysis patients and predicting factors; terms associated with the (b) impact of malnutrition on cardiovascular risk and complications in CKD patients; and terms related to the (c) dietary protein intake and malnutrition in CKD.
CONCLUSIONS: This study is the first of its kind to analyze CKD and malnutrition research using data from Scopus for visualization and network mapping. Recent trends indicate an increasing focus on protein-energy wasting/malnutrition in hemodialysis patients and predicting factors, dietary protein intake, and malnutrition in CKD. These topics have gained significant attention and reflect the latest scientific advances. Intervention studies are crucial to examining diet therapy's impact on patients with stages 1 to 5 CKD. We hope this study will offer researchers, dietitians and nephrologists valuable information.
Fulltext Isolation of an obscure fungus, Parengyodontium album, from the blood of a severely neutropenic patient: The first reported case from Malaysia

Mohamed N, Ding CH, Wahab AA, Tzar MN, Hassan M

J Infect Dev Ctries, 2022 Oct 31;16(10):1668-1670.
PMID: 36332225 DOI: 10.3855/jidc.17016

Parengyodontium album is a very rarely encountered opportunistic fungal pathogen. A severely neutropenic 11-year-old boy with acute T-cell lymphoblastic leukemia/lymphoma was febrile and lethargic during his admission for elective chemotherapy. No cutaneous lesion or obvious source of infection was noted, and clinical examination was otherwise unremarkable. A blood specimen was sent for culture and fungal elements were visualized. Amphotericin B was administered empirically while awaiting fungal identification. Morphologically, a hyaline mould with thin septate hyphae plus smooth-walled conidiophores and conidiogenous cells arranged in whorls of up to four was cultured. Internal transcribed spacer region sequencing identified the fungus conclusively as P. album. Repeat blood culture was also positive for the same fungus. Following a two-week course of amphotericin B, fungemia clearance was attained.
Synthesis of α,β-Unsaturated Carbonyl-Based Compounds, Oxime and Oxime Ether Analogs as Potential Anticancer Agents for Overcoming Cancer Multidrug Resistance by Modulation of Efflux Pumps in Tumor Cells

Qin HL, Leng J, Zhang CP, Jantan I, Amjad MW, Sher M, et al.

J Med Chem, 2016 Apr 14;59(7):3549-61.
PMID: 27010345 DOI: 10.1021/acs.jmedchem.6b00276

Sixty-nine novel α,β-unsaturated carbonyl based compounds, including cyclohexanone, tetralone, oxime, and oxime ether analogs, were synthesized. The antiproliferative activity determined by using seven different human cancer cell lines provided a structure-activity relationship. Compound 8ag exhibited high antiproliferative activity against Panc-1, PaCa-2, A-549, and PC-3 cell lines, with IC50 value of 0.02 μM, comparable to the positive control Erlotinib. The ten most active antiproliferative compounds were assessed for mechanistic effects on BRAF(V600E), EGFR TK kinases, and tubulin polymerization, and were investigated in vitro to reverse efflux-mediated resistance developed by cancer cells. Compound 8af exhibited the most potent BRAF(V600E) inhibitory activity with an IC50 value of 0.9 μM. Oxime analog 7o displayed the most potent EGFR TK inhibitory activity with an IC50 of 0.07 μM, which was analogous to the positive control. Some analogs including 7f, 8af, and 8ag showed a dual role as anticancer and MDR reversal agents.
Some flexural properties of a nylon denture base polymer

Yunus N, Rashid AA, Azmi LL, Abu-Hassan MI

J Oral Rehabil, 2005 Jan;32(1):65-71.
PMID: 15634304

Nylon denture base material could be a useful alternative to poly (methyl methacrylate) (PMMA) in special circumstances such as patient allergy to the monomer. The aim of this study was to evaluate the flexural properties of a nylon denture base material (Lucitone FRS), a conventional compression-moulded heat-polymerized (Meliodent), a compression-moulded microwave-polymerized (Acron MC) and an injection-moulded microwave-polymerized (Lucitone 199) PMMA polymers. The effect of aldehyde-free, oxygen releasing disinfectant solution (Perform) on these properties was also investigated. The flexural modulus and the flexural strength were assessed with a three-point bending test. Specimens were stored in water at a temperature of 37 degrees C for 30 days. For each material, half of the prepared specimens were randomly selected and immersed in the disinfectant 24 h prior to testing. Results were compared statistically at a confidence level of 95%. The result showed that in both the control and disinfected groups, the flexural modulus of nylon was significantly lower than the three PMMA polymers. The flexural strength of nylon was significantly lower than those of Meliodent and Acron MC but was comparable with Lucitone 199. A 24-h immersion in the disinfecting solution increased the rigidity of nylon denture base material.
Evaluation of load at fracture of Procera AllCeram copings using different luting cements

Al-Makramani BMA, Razak AAA, Abu-Hassan MI

J Prosthodont, 2008 Feb;17(2):120-124.
PMID: 18047490 DOI: 10.1111/j.1532-849X.2007.00270.x

PURPOSE: The current study investigated the effect of different luting agents on the fracture resistance of Procera AllCeram copings.
METHODS: Six master dies were duplicated from the prepared maxillary first premolar tooth using nonprecious metal alloy (Wiron 99). Thirty copings (Procera AllCeram) of 0.6-mm thickness were manufactured. Three types of luting media were used: zinc phosphate cement (Elite), glass ionomer cement (Fuji I), and dual-cured composite resin cement (Panavia F). Ten copings were cemented with each type. Two master dies were used for each group, and each of them was used to lute five copings. All groups were cemented according to manufacturer's instructions and received a static load of 5 kg during cementation. After 24 hours of distilled water storage at 37 degrees C, the copings were vertically compressed using a universal testing machine at a crosshead speed of 1 mm/min.
RESULTS: ANOVA revealed significant differences in the load at fracture among the three groups (p < 0.001). The fracture strength results showed that the mean fracture strength of zinc phosphate cement (Elite), glass ionomer cement (Fuji I), and resin luting cement (Panavia F) were 1091.9 N, 784.8 N, and 1953.5 N, respectively.
CONCLUSION: Different luting agents have an influence on the fracture resistance of Procera AllCeram copings.
A review of hydroxyapatite-based coating techniques: Sol-gel and electrochemical depositions on biocompatible metals

Asri RI, Harun WS, Hassan MA, Ghani SA, Buyong Z

J Mech Behav Biomed Mater, 2016 Apr;57:95-108.
PMID: 26707027 DOI: 10.1016/j.jmbbm.2015.11.031

New promising techniques for depositing biocompatible hydroxyapatite-based coatings on biocompatible metal substrates for biomedical applications have continuously been exploited for more than two decades. Currently, various experimental deposition processes have been employed. In this review, the two most frequently used deposition processes will be discussed: a sol-gel dip coating and an electrochemical deposition. This study deliberates the surface morphologies and chemical composition, mechanical performance and biological responses of sol-gel dip coating as well as the electrochemical deposition for two different sample conditions, with and without coating. The review shows that sol-gel dip coatings and electrochemical deposition were able to obtain the uniform and homogeneous coating thickness and high adherent biocompatible coatings even in complex shapes. It has been accepted that both coating techniques improve bone strength and initial osseointegration rate. The main advantages and limitations of those techniques of hydroxyapatite-based coatings are presented. Furthermore, the most significant challenges and critical issues are also highlighted.
Nanocrystalline forsterite for biomedical applications: synthesis, microstructure and mechanical properties

Ramesh S, Yaghoubi A, Lee KY, Chin KM, Purbolaksono J, Hamdi M, et al.

J Mech Behav Biomed Mater, 2013 Sep;25:63-9.
PMID: 23726923 DOI: 10.1016/j.jmbbm.2013.05.008

Forsterite (Mg2SiO4) because of its exceptionally high fracture toughness which is close to that of cortical bones has been nominated as a possible successor to calcium phosphate bioceramics. Recent in vitro studies also suggest that forsterite possesses good bioactivity and promotes osteoblast proliferation as well as adhesion. However studies on preparation and sinterability of nanocrystalline forsterite remain scarce. In this work, we use a solid-state reaction with magnesium oxide (MgO) and talc (Mg3Si4(OH)2) as the starting precursors to synthesize forsterite. A systematic investigation was carried out to elucidate the effect of preparatory procedures including heat treatment, mixing methods and sintering temperature on development of microstructures as well as the mechanical properties of the sintered forsterite body.
The nonlinear elastic and viscoelastic passive properties of left ventricular papillary muscle of a guinea pig heart

Hassan MA, Hamdi M, Noma A

J Mech Behav Biomed Mater, 2012 Jan;5(1):99-109.
PMID: 22100084 DOI: 10.1016/j.jmbbm.2011.08.011

The mechanical behavior of the heart muscle tissues is the central problem in finite element simulation of the heart contraction, excitation propagation and development of an artificial heart. Nonlinear elastic and viscoelastic passive material properties of the left ventricular papillary muscle of a guinea pig heart were determined based on in-vitro precise uniaxial and relaxation tests. The nonlinear elastic behavior was modeled by a hypoelastic model and different hyperelastic strain energy functions such as Ogden and Mooney-Rivlin. Nonlinear least square fitting and constrained optimization were conducted under MATLAB and MSC.MARC in order to obtain the model material parameters. The experimental tensile data was used to get the nonlinear elastic mechanical behavior of the heart muscle. However, stress relaxation data was used to determine the relaxation behavior as well as viscosity of the tissues. Viscohyperelastic behavior was constructed by a multiplicative decomposition of a standard Ogden strain energy function, W, for instantaneous deformation and a relaxation function, R(t), in a Prony series form. The study reveals that hypoelastic and hyperelastic (Ogden) models fit the tissue mechanical behaviors well and can be safely used for heart mechanics simulation. Since the characteristic relaxation time (900 s) of heart muscle tissues is very large compared with the actual time of heart beating cycle (800 ms), the effect of viscosity can be reasonably ignored. The amount and type of experimental data has a strong effect on the Ogden parameters. The in vitro passive mechanical properties are good initial values to start running the biosimulation codes for heart mechanics. However, an optimization algorithm is developed, based on clinical intact heart measurements, to estimate and re-correct the material parameters in order to get the in vivo mechanical properties, needed for very accurate bio-simulation and for the development of new materials for the artificial heart.

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