Displaying publications 1 - 20 of 49 in total

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  1. Singh HJ
    Med J Malaysia, 1995 Mar;50(1):93-100.
    PMID: 7752984
    Serum concentrations and urinary output of calcium, magnesium, sodium and potassium were analysed in normotensive pregnant women and in women with pregnancy-induced hypertension during the third trimester. In addition, plasma renin activity (PRA) was also determined. Significantly lower serum total calcium, urinary calcium and magnesium excretions and plasma renin activity were evident in women with PIH. Urine output and creatinine clearance were not significantly different between the two groups. No significant correlation was evident between serum calcium, magnesium and PRA. The relationship between these parameters and high blood pressure is not immediately apparent. They nevertheless suggest of a disturbance in electrolyte metabolism in women with PIH, that may underly the pathogenesis of this disorder.
  2. Singh HJ
    Jpn. J. Physiol., 1995;45(2):327-36.
    PMID: 7563967
    Standard renal clearance techniques were used to compare the effects of intravenous infusions of L-arginine, D-lysine and glycine on urinary calcium excretion in the rat. A significant calciuric response was evident following the infusion of all three amino acids in all the animals. The maximal effect was evident in rats receiving L-arginine. The mechanism for the increased urinary calcium excretion in rats infused with L-arginine and D-lysine appeared more due to a decreased fractional reabsorption of this cation as no significant changes in the glomerular filtration rate (GFR) were evident in these two groups. The calciuria in rats receiving glycine appears due to increased filtered load secondary to the increased GFR, suggesting that the mechanism for calciuria evident following protein ingestion or amino acid infusion may vary and may be dependent upon the amino acid ingested or infused.
  3. Singh HJ
    Malays J Med Sci, 2009 Jan;16(1):7-15.
    PMID: 22589643 MyJurnal
    Hypertensive disorders of pregnancy complicate almost 7 - 10 % of all pregnancies. The dyad of hypertension and proteinuria after 20 weeks of gestation is referred to as pre-eclampsia. It is a major cause of maternal morbidity and mortality and is also associated with increased perinatal problems. Despite intensive research over the years the exact cause of pre-eclampsia remains unknown. Nevertheless, information gleaned from published studies point to the placenta as the probable pathogenetic focus of pre-eclampsia, as the disease usually resolves within 24 - 48 hours after delivery of the placenta. Although the precise involvement of the placenta in pre-eclampsia remains unclear there are indications that the trophoblastic invasion of the uterine spiral arteries is abnormal in women who develop pre-eclampsia. This impaired invasion leads to decreased placental perfusion and ultimately to placental hypoxia. The distressed or ischaemic placenta then secretes a factor(s) into the maternal circulation, which cause/s widespread endothelial cell dysfunction characterized by vasospasm, activation of coagulation system and organ ischaemia. The cause of the defective cytotrophoblastic invasion of the spiral arteries and the link between placental ischaemia and generalized maternal endothelial dysfunction remain unknown. Although the placenta appears to have a major role in the pathogenesis of pre-eclampsia, evidence also suggests that factors like maternal genetic predisposition, dietary, environmental and behaviour, which surface during the stress of pregnancy might also be involved in the development of pre-eclampsia. It is known that not all women with poor cytotrophoblast invasion develop pre-eclampsia and not all women with preeclampsia show poor cytotrophoblast invasion. Over the years, a number of potential risk factors associated with the development of pre-eclampsia are being recognized and it might be appropriate now to develop some preventative strategies based upon the available information.
  4. Singh R, Singh HJ
    J Sports Med Phys Fitness, 1993 Dec;33(4):378-82.
    PMID: 8035586
    Cardiopulmonary capacities of twelve adults (aged between 14 to 44 years) with varying degrees of blindness engaged in regular recreational activities were compared with twelve age-matched normal sighted healthy males (control group) who were also involved in regular recreational activities. Maximum oxygen consumption (VO2max) was measured directly during exhaustive exercise test on a cycle ergometer. Forced vital capacity, leg strength and power were determined by spirometry, standing long jump and vertical jump respectively. No significant differences in VO2max, forced vital capacity and leg strength and power were observed between the blind and the control groups. No anthropometric differences were evident between the two groups. The results show therefore that the visually handicapped who are active can have a similar level of physical fitness, lung function and explosive leg strength as those of their active sighted counterparts.
  5. Almabhouh FA, Singh HJ
    Andrologia, 2018 Feb;50(1).
    PMID: 28497500 DOI: 10.1111/and.12814
    This study examines the effect of melatonin on leptin-induced changes in transition of histone to protamine in adult rats during spermatogenesis. Twelve-week-old Sprague-Dawley rats were randomised into control, leptin-, leptin-melatonin-10-, leptin-melatonin-20- and melatonin-10-treated groups with six rats per group. Leptin was given via intraperitoneal injections (i.p.) daily for 42 days (60 μg/kg body weight). Rats in the leptin- and melatonin-treated groups were given either 10 or 20 mg day-1  kg-1 body weight of leptin in drinking water. Melatonin-10-treated group received only 10 mg of melatonin day-1  kg-1 body weight in drinking water for 42 days. Control rats received 0.1 ml of 0.9% saline. Upon completion of the treatment, sperm count, morphology and histone-to-protamine ratio were estimated. Gene expression of HAT, HDAC1, HDAC2, H2B, H2A, H1, PRM1, PRM2, TNP1 and TNP2 was determined. Data were analysed using ANOVA. Sperm count was significantly lower, whereas the fraction of spermatozoa with abnormal morphology, the ratio of histone-to-protamine transition and the expressions of HAT, HDAC1, HDAC2, H2B, H2A, H1, PRM1 were significantly higher in leptin-treated rats than those in controls or melatonin-treated rats. It appears that exogenous leptin administration adversely affects histone-to-protamine transition, which is prevented by concurrent administration of melatonin.
  6. Almabhouh FA, Singh HJ
    Reprod Fertil Dev, 2023 May;35(8):459-468.
    PMID: 37196661 DOI: 10.1071/RD22222
    Despite its important role in numerous physiological functions, including regulation of appetite and body weight, immune function and normal sexual maturation, raised leptin levels could result in significant damaging effects on sperm. The adverse effects of leptin on the male reproductive system result from its direct actions on the reproductive organs and cells instead of the hypothalamus-pituitary-gonadal axis. Binding of leptin to the receptors in the seminiferous tubular cells of the testes increases free radical production and decreases the gene expression and activity of endogenous enzymatic antioxidants. These effects are mediated via the PI3K pathway. The resultant oxidative stress causes significant damage to the seminiferous tubular cells, germ cells and sperm DNA leading to apoptosis, increased sperm DNA fragmentation, decreased sperm count, increased fraction of sperm with abnormal morphology, and decreased seminiferous tubular height and diameter. This review summarises the evidence in the literature on the adverse effects of leptin on sperm, which could underlie the often-reported sperm abnormalities in obese hyperleptinaemic infertile males. Although leptin is necessary for normal reproductive function, its raised levels could be pathologic. There is, therefore, a need to identify the cut-off level in the serum and seminal fluid above which leptin becomes pathological for better management of leptin associated adverse effects on male reproductive function.
  7. Ooi FK, Singh R, Singh HJ, Umemura Y
    Osteoporos Int, 2009 Jun;20(6):963-72.
    PMID: 18839049 DOI: 10.1007/s00198-008-0760-6
    SUMMARY: This study determines the minimum level of exercise required to maintain 8 weeks of jumping exercise-induced bone gains in rats. It was found that the minimum level of exercise required for maintaining the different exercise-induced bone gains varied between 11% and 18% of the initial exercise intensity.

    INTRODUCTION: This study ascertains the minimum level of follow-up exercise required to maintain bone gains induced by an 8-week jumping exercise in rats.

    METHODS: Twelve groups of 12-week old rats (n = 10 rats per group) were given either no exercise for 8 (8S) or 32 weeks (32S), or received 8 weeks of standard training program (8STP) that consisted of 200 jumps per week, given at 40 jumps per day for 5 days per week, followed by 24 weeks of exercise at loads of either 40 or 20 or 10 jumps per day, for either 5, or 3, or 1 day/week. Bone mass, strength, and morphometric properties were measured in the right tibia. Data were analyzed using one-way analyses of variance.

    RESULTS: Bone mass, strength, mid-shaft periosteal perimeter and cortical area were significantly (p < 0.05) higher in the rats given 8STP than that in the 8S group. The minimal level of exercise required to maintain the bone gains was 31, 36, 25, and 21 jumps per week for mass, strength, periosteal perimeter and cortical area, respectively.

    CONCLUSIONS: Eight weeks of jumping exercise-induced bone gains could be maintained for a period of 24 weeks with follow-up exercise consisting of 11% to 18% of the initial exercise load.

  8. Keong CC, Singh HJ, Singh R
    J Sports Sci Med, 2006;5(4):629-39.
    PMID: 24357959
    This study investigates the effects of tocotrienol-rich palm vitamin E supplementation on exercise-induced lipid peroxidation and endurance performance in the heat. In a double blind, cross-over study, eighteen healthy, male recreational athletes completed two endurance running trials, until exhaustion, on a motorized treadmill at 70% VO2max on two separate occasions following a 6-week supplementation regimen of either tocotrienol-rich palm vitamin E (E) or placebo (P). Both trials were conducted in the heat (31°C, 70% relative humidity). During the trials, rectal temperature (Trec), ratings of perceived exertion (RPE) and oxygen uptake (VO2) were recorded. Blood samples were collected for the determination of plasma volume changes (PVC), malondialdehyde (MDA), creatine kinase (CK), total antioxidant status (TAS) and vitamin E. After the supplementation regimen, serum alpha-tocopherol increased ~33% but serum concentrations of tocotrienols were negligible. No significant differences were evident in mean Trec, RPE, VO2 or in the time to exhaustion between the E-supplemented and the placebo- supplemented groups. Similarly, mean PVC, CK and TAS were also not different between the two groups. Resting plasma mean MDA concentration in the E-supplemented group was significantly lower than that in the placebo-supplemented group. At exhaustion, plasma mean MDA was higher than the resting values in both groups. Although tocotrienol-rich palm vitamin E supplementation decreased lipid peroxidation at rest and, to some extent, during exercise in the heat, as evident from the lower MDA levels, it however did not enhance endurance running performance or prevent exercise-induced muscle damage or influenced body core temperature or plasma volume changes during exercise in the heat. Key Pointsreduced lipid peroxidation at rest.did not enhance endurance running performance in the heat.did not prevent exercise-induced muscle damage as indicated by CK activity.
  9. Ooi FK, Singh R, Singh HJ
    Asian J Sports Med, 2012 Dec;3(4):225-32.
    PMID: 23342220
    To date, little is known about the effects of a reduced level of jumping exercise regimens on bone turnover markers and mass. This study investigates the effects of different jumping exercise regimens with varying exercise loads on serum bone turnover markers and bone mass in female rats.
  10. bin Long I, Singh HJ, Rao GJ
    J. Pharmacol. Sci., 2005 Nov;99(3):272-6.
    PMID: 16293937
    The effects of indomethacin and nabumetone on urine and electrolyte excretion in conscious rats were examined. Male Sprague-Dawley rats were housed individually for a five-week duration, consisting of acclimatization, control, experimental, and recovery phases. During the experimental phase, rats were given either indomethacin (1.5 mg . kg(-1) body weight . day(-1) in 0.5 ml saline, n = 10), nabumetone (15 mg . kg(-1) body weight . day(-1) 0.5 ml saline, n = 10), or 0.5 ml saline alone (n = 10) for a period of two weeks. Water and food intake, body weight, urine output, and electrolyte excretions were estimated. Data were analyzed using two-way ANOVA. Urine output in the indomethacin- and nabumetone-treated groups was not different from the controls, but was significantly different between the drug-treated groups (P<0.01). Sodium, potassium, calcium, and magnesium excretions were not different between nabumetone-treated and control rats. However, sodium and potassium excretion was significantly lower in rats receiving indomethacin when compared to the control rats. Calcium and magnesium outputs, although did not differ from the controls, nevertheless decreased significantly with indomethacin (P<0.01). It appears that indomethacin and nabumetone when given at maximum human therapeutic doses may affect urine and electrolyte output in conscious rats.
  11. Jawis MN, Singh R, Singh HJ, Yassin MN
    Br J Sports Med, 2005 Nov;39(11):825-9; discussion 825-9.
    PMID: 16244191
    OBJECTIVES: Anthropometric and physiological profiles of national sepak takraw players were determined.
    METHODS: Thirty nine players, specialising in the three playing positions (tekong/server, feeder, and killer/spiker) were divided into three age categories of under 15 (U15), under 18 (U18), and under 23 (U23) years of age. Height, weight, percent body fat (%bf), maximum oxygen consumption (Vo(2max)), range of motion (ROM), back and leg strength, and heart rate, for the estimation of oxygen consumption during matches, were recorded. Statistical analysis was performed using one way ANOVA for independent measurements and data are presented as mean+/-standard deviation.
    RESULTS: The U23 players were significantly taller and heavier with significantly better ROM of the neck, trunk, and ankle joints and back and leg strength than the U15 players. No significant difference was found in %bf between the three age categories. Mean maximum heart rate during exercise was significantly higher in the U15 group when compared to the U18 and U23 groups (p<0.05). Mean Vo2max was similar between the three groups. Estimated oxygen consumption during matches was 69.1%, 68.5%, and 56.4% of Vo2max in the killer, tekong, and the feeder groups, respectively.
    CONCLUSIONS: The mean height, body weight, and cardiopulmonary capacities of the players were within the Malaysian population norms, but were somewhat lower than those of players of other court games from other countries. %bf was also lower in these players. This study provides the much needed anthropometric and physiological data of sepak takraw players for further development of this sport.
  12. Singh HJ, Mohammad NH, Nila A
    J Matern Fetal Med, 1999 May-Jun;8(3):95-100.
    PMID: 10338062
    To ascertain the calcium status in normal pregnant Malay women.
  13. Singh R, Singh HJ, Sirisinghe RG
    Med J Malaysia, 1993 Jun;48(2):175-84.
    PMID: 8350793
    Spirometry was performed on 1,999 subjects (1,385 males and 614 females) ranging in age from 13 to 69 years and comprising of all the main races in Malaysia. They were divided into 6 age groups. Mean forced vital capacity (FVC) in the males and females was 3.49 +/- 0.02 L and 2.51 +/- 0.02 L respectively. Both FVC and FEV1 correlated negatively with age. Regression analysis on data between the ages of 20 to 69 years revealed an age-related decline in FVC of about 30 ml per year of life in the males and 22 ml per year in the females. Multiple stepwise regression of the data for the prediction of an individual's FVC above the age of 20 years gave an equation for the males: FVC = 0.0407 (height)-0.0296 (age)-2.343 L and for the females: FVC = 0.031 (height)-0.022 (age)-1.64 L. Predicted FVC values derived from equations based on other populations were considerably higher than the observed mean in this study, re-emphasizing the need to be cautious when applying formulae derived from one population to another. Grossly erroneous conclusions may be reached unless predicted equations for lung-function tests for a given population group are derived from studies based upon the same population group.
  14. Singh R, Singh HJ, Sirisinghe RG
    Br J Sports Med, 1995 Mar;29(1):13-5.
    PMID: 7788209
    Maximal oxygen consumption (VO2max) and maximal workload attained (WLmax) were determined in 28 Malaysian dragon boat rowers who were exercised to exhaustion on an arm ergometer. Mean VO2max was 2.75 l min-1 at a mean WLmax of 195.5 W. Anaerobic endurance power of the arms, determined by cranking at 100 RPM at a workload of 400 W and the time taken to maintain the cadence until it fell to 75 RPM, was 34.9(+/- 2.3) s. Leg performance, as determined by standing long jump and vertical jump, was 140.0(+/- 4.5) kg m and 100.3(+/- 3.1) kg m s-1 respectively. Right hand grip strength was significantly (p < 0.001) greater than the left hand. Percentage body fat of the rowers was 11.8(+/- 0.6)%. These values represent the first measurements of their kind performed on dragon boat rowers in Malaysia.
  15. Singh R, Singh HJ, Sirisinghe RG
    PMID: 7855654
    Spirometry was performed on 1,485 male subjects ranging in age from 13 years to 78 years and comprising of all the main ethnic groups in Malaysia. They were divided into six age categories. Mean forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1) were 3.45 +/- 0.02 and 3.10 +/- 0.02, respectively. Both FVC and FEV1 correlated negatively with age. Regression analysis revealed an age-related decline in FVC of 295 ml per decade of life. Multiple stepwise regression of the data for the prediction of an individual's FVC above the age of 20 years gave the equation FVC (1) = 0.0404 (height in cm)-0.0295 (age in years)-2.2892. Predicted FVC values derived from equations based on other populations were considerably higher than the observed mean in this study. This study therefore, reemphasises the need to be cautions when applying formulae derived from one population to another. Grossly erroneous conclusions may be reached unless predicted equations for lung-function tests for a given population group are derived from studies based upon the same population group.
  16. Singh R, Singh HJ, Sirisinghe RG
    Jpn. J. Physiol., 1989;39(4):475-85.
    PMID: 2601189
    Lung capacity and maximum oxygen uptake (VO2max) were measured directly in 167 healthy males, from all the main races in Malaysia. Their ages ranged from 13 to 59 years. They were divided into five age groups (A to E), ranging from the second to the sixth decade. Lung capacities were determined using a dry spirometer and VO2max was taken as the maximum rate of oxygen consumption during exhaustive exercise on a cycle ergometer. Mean forced vital capacity (FVC) was 3.3 +/- 0.5 l and it correlated negatively with age. Mean VO2max was 3.2 +/- 0.2 l.min-1 (56.8 +/- 3.5 ml.kg-1.min-1) in Group A (13-19 years) compared to 1.7 +/- 0.2 l.min-1 (28.9 +/- 2.9 ml.kg-1.min-1) in Group E (50-59 years). Regression analysis revealed an age-related decline in VO2max of 0.77 ml.kg-1.min-1.year-1. Multiple regression of the data gave the following equations for the prediction of an individual's VO2max: VO2max (l.min-1) = 1.99 + 0.035 (weight)-0.04 (age), VO2max (ml.kg-1.min-1) = 67.7-0.77 (age), where age is in years, weight in kg. In terms of VO2max as an index of cardiopulmonary performance. Malaysians have a relatively lower capacity when related to the Swedish norms or even to those of some Chilean workers. Malaysians were, however, within the average norms of the American Heart Association's recommendations. Age-related decline in VO2max was also somewhat higher in the Malaysians.
  17. Singh R, Singh HJ, Sirisinghe RG
    Jpn. J. Physiol., 1992;42(3):407-14.
    PMID: 1434102
    Spirometry was performed on 614 female subjects ranging in age from 13 to 69 years and comprising all the main races in Malaysia. They were divided into six age categories. Mean forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) were 2.51 +/- 0.02 and 2.31 +/- 0.02l, respectively. Both FVC and FEV1 correlated negatively with age. Regression analysis revealed an age-related decline in FVC of 220 ml per decade of life. Multiple stepwise regression of the data for the prediction of an individual's FVC above the age of 20 years gave an equation: FVC(l) = 0.0312 (height)-0.022 (age)-1.64. Predicted FVC values derived from equations based on other populations were considerably higher than the observed mean in this study. Our study, therefore, reemphasizes the need to be cautious when applying formulae derived from one population to another. Grossly erroneous conclusions may be reached unless predicted equations for lung-function tests for a given population group are derived from studies based on the same population group.
  18. Singh HJ, Singh R, Sirisinghe RG, Upadaya S
    Med J Malaysia, 1991 Dec;46(4):356-62.
    PMID: 1840445
    Two series of Blood Pressure (BP) measurements were carried out to assess the variability in BP following repeated measurements in normotensive individuals. In one series, measurement of BP on three occasions three and seven days apart revealed a significant drop in BP in unaccustomed subjects ('untrained'). In a second series assessing the significance of time-interval between measurements or the number of measurements, it was found that a significant fall in BP occurred over the first four days in 'untrained' individuals, whose blood pressure was measured repeatedly for five consecutive days. A significant positive correlation was evident between the falls in systolic and diastolic pressures and the pressure at first screening. Assessment of the anxiety status revealed a significantly lower state anxiety in 'trained' subjects. It therefore appears that (a) BP in normotensive individuals previously unaccustomed to BP measurements, drops significantly with repeated measurements, (b) the number of measurements seem more important than the time-interval between measurements, (c) the largest falls occur in individuals with high initial pressures and (d) the fall upon repeated measurements may be due to reduced anxiety as familiarity with the procedure makes the subjects comparatively relaxed and less state anxious.
  19. Malik IA, Durairajanayagam D, Singh HJ
    Asian J Androl, 2018 12 13;21(3):296-299.
    PMID: 30539926 DOI: 10.4103/aja.aja_98_18
    Leptin, an adipocyte-derived hormone, serves numerous physiological functions in the body, particularly during puberty and reproduction. The exact mechanism by which leptin activates the gonadotropin-releasing hormone (GnRH) neurons to trigger puberty and reproduction remains unclear. Given the widespread distribution of leptin receptors in the body, both central and peripheral mechanisms involving the hypothalamic-pituitary-gonadal axis have been hypothesized. Leptin is necessary for normal reproductive function, but when present in excess, it can have detrimental effects on the male reproductive system. Human and animal studies point to leptin as a link between infertility and obesity, a suggestion that is corroborated by findings of low sperm count, increased sperm abnormalities, oxidative stress, and increased leptin levels in obese men. In addition, daily leptin administration to normal-weight rats has been shown to result in similar abnormalities in sperm parameters. The major pathways causing these abnormalities remain unidentified; however, these adverse effects have been attributed to leptin-induced increased oxidative stress because they are prevented by concurrently administering melatonin. Studies on leptin and its impact on sperm function are highly relevant in understanding and managing male infertility, particularly in overweight and obese men.
  20. Singh HJ, Rahman A, Larmie ET, Nila A
    Acta Obstet Gynecol Scand, 2001 Feb;80(2):99-103.
    PMID: 11167202
    AIMS: The pathogenesis of pre-eclampsia is still unclear. Placental hypoperfusion, which precedes the maternal manifestations of pre-eclampsia, could be due to some vasoconstrictor factor/s like endothelin-1. The aim of the study therefore was to estimate the levels of endothelin-1 in feto-placental tissue homogenates from normotensive pregnant women and women with pre-eclampsia.

    METHOD AND MATERIAL: Fresh, vaginally delivered placentae from ten normotensive pregnant women and nine women with pre-eclampsia were carefully dissected and 4 gm each of amnion, chorion laeve, placental plate chorion, fetal placenta (fetal surface of the placenta) and maternal placenta (surface of the placenta attached to the uterine wall) were obtained. These tissues were then thoroughly washed in a 0.5 M phosphate buffer, pH 7.5, at room temperature and then individually homogenized for one minute in 4 ml of the same buffer. After centrifugation the supernatant was removed. The pellet was re-suspended in buffer, re-homogenized and then centrifuged. The supernatant was removed and the procedure was repeated once again and the three supernatants of each tissue were pooled. Endothelin-1 was estimated by RIA. All results are presented as mean+/-SEM. Statistical analysis was performed using students 't' test for unpaired samples and a 'p' value of <0.05 was considered significant.

    RESULTS: In tissues from normotensive pregnant women, no significant differences were evident in endothelin-1 concentrations in the chorion laeve, fetal placenta and maternal placenta but were significantly higher than those in the amnion and placental plate chorion (p<0.01). In tissues from pre-eclamptic women, no significant differences were evident between endothelin-1 concentrations in the chorion laeve, placental plate chorion and fetal placenta. Mean endothelin-1 concentration in the amnion and maternal placenta were significantly lower than those in chorion laeve, placental plate chorion and fetal placenta (p<0.01). Endothelin-1 concentrations were significantly higher in the amnion, chorion laeve, placental plate chorion and fetal placenta from women with pre-eclampsia when compared to tissues from normotensive pregnant women (p<0.01).

    CONCLUSIONS: Endothelin-1 levels were significantly higher in the placental tissues from women with pre-eclampsia. Endothelin-1, being a powerful vasoconstrictor, could cause significant vasoconstriction in the placental vasculature, and alterations in endothelin-1 levels in placental vasculature may therefore have a role in the pathogenesis of pre-eclampsia.

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