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M N Nanjee

Publications and source records attributed to M N Nanjee.

At least 37 records · Page 2Linked to original sources
PubMed1991

Enzymatic fluorometric procedure for phospholipid quantification with an automated microtiter plate fluorometer.

We describe a new enzymatic assay for phospholipids that is rapid, sensitive, convenient, and inexpensive. The method is based on the fluorometric detection of H2O2, generated by the choline oxidase-catalyzed oxidation of choline, after liberation of choline from phospholipids by phospholipase D. Significant advantages over existing methods are that the entire reaction sequence can take place in a single vessel, a 12 x 8 well microtiter plate, and that the fluorescence intensity can be measured automatically with a Fluoroskan II (Labsystems Oy) detector. Extracting samples with organic solvents is unnecessary, although the method can be applied to extracts in isopropanol. The assay is approximately 60-fold more sensitive and has a limit of detection eightfold lower than currently available enzymatic colorimetric methods. Including solvent blanks, eight standards, and three quality-control pools, 34 samples can be pipetted and assayed in duplicate in 60 min. Results obtained by this procedure for total phospholipid choline in lipoproteins in primate plasma agreed well with those obtained for inorganic phosphorus by the Bartlett acid-digestion procedure.

Animals↗
PubMed1990

Hormonal determinants of apolipoprotein B,E receptor expression in human liver. Positive association of receptor expression with plasma estrone concentration in middle-aged/elderly women.

The relationships of the expression of hepatic low-density lipoprotein (LDL) receptors (apo B,E receptors) to several plasma hormone concentrations were examined in 15 fasted women aged 37-75 years (mean, 57 years), who were undergoing laparotomy for non-neoplastic disease. No subject had clinical or biochemical evidence of familial hypercholesterolemia, renal disease, hepatic disease, or endocrine disease. Hepatic apo B,E receptor expression was quantified in vitro as the EDTA-suppressible binding of 125I-labeled human LDL (15 micrograms protein/ml) by liver homogenate at 37 degrees C; values were 23-75 ng LDL protein/mg cell protein (mean, 47 ng/mg). Receptor expression was strongly correlated with plasma estrone concentration (rs = +0.70, P = 0.035), but was unrelated to the concentrations of testosterone, thyroxine, free triiodothyronine, cortisol, sex hormone-binding globulin (SHBG) or cortisol-binding globulin. Insulin and estradiol concentrations were mostly very low. The correlation of receptor expression with plasma total estrone concentration reflected associations with both the albumin-bound (rs = +0.78, P = 0.014) and unbound (rs = +0.80, P = 0.009) fractions, but not with the SHBG-bound fraction (rs = -0.22, P = 0.574), of this hormone. As the non-SHBG-bound fractions of gonadal steroids are considered to be the biologically active components, these results are consistent with experimental evidence that the synthesis of apo B,E receptors in hepatocytes is stimulated by estrogens, and suggest that circulating estrone may be the major hormonal determinant of receptor expression in fasted middle-aged/elderly women.

Adult↗
PubMed1990

Criteria to indicate testosterone administration.

A detection method for testosterone administration was developed using radioimmunoassay to measure the urinary ratios of testosterone (T) to epitestosterone (E) and to luteinizing hormone (LH). A comparative study of the effect on these ratios of a single intramuscular injection of testosterone heptanoate followed by stimulation with human chorionic gonadotrophin (HCG) in three normal men was undertaken. To allow immediate investigation, a commercially supplied epitestosterone antiserum was used. This study showed that both T/E and T/LH ratios could be used to detect testosterone administration, the latter also being an indicator of HCG use due to cross-reactivity with the LH antiserum. Subsequently, an epitestosterone antiserum of superior specificity was raised and used in a study to demonstrate the insignificant effect of exercise on these ratios. Finally, an intramuscular injection of a combined preparation of testosterone/epitestosterone heptanoates resulted in raised ratios of T/LH but not of T/E. This demonstrated the importance of the T/LH ratio in circumstances where the T/E ratio can be easily circumvented.

Adult↗
PubMed1990

Variation at the apolipoprotein (apo) AI-CIII-AIV gene cluster and apo B gene loci is associated with lipoprotein and apolipoprotein levels in Italian children.

We have used RFLPs of the apolipoprotein (apo) B gene and apo AI-CIII-AIV gene cluster to estimate the genetic contribution of variation at these loci to the variability of plasmid lipid, lipoprotein, and apolipoprotein levels in 209 children from Sezze in central Italy. The sample was randomly divided into group I (107 children) and group II (102 children). Four site polymorphisms (PvuII, XbaI, MspI, and EcoRI) of the apo B gene and five site polymorphisms (XmnI, PstI, SstI, PvuII-CIII, and PvuII-AIV) of the apo AI-CIII-AIV gene cluster were examined in group I children. After adjustment for gender, age, and body-mass index, polymorphisms at both gene loci (PvuII-B, PvuII-CIII, and PvuII-AIV) were associated with significant effects on the levels of plasma apo AI, apo B, or high-density lipoprotein-cholesterol. RFLPs that showed significant effects in group I were genotyped in group II. All three polymorphisms were associated with similar effects on apolipoprotein levels, though for all RFLPs the magnitude of the effects was smaller in the group II children and only statistically significant for the effect of the PvuII-B genotype on apo AI levels. In the total sample of 209 children 7.4% of the sample variance in apo AI levels was explained by variation associated with the apo B PvuII-B RFLP. In addition, the PvuII-B RFLP was associated with significant effects on plasma apo B levels and explained 5.7% of the sample variance. The PvuII-CIII and PvuII-AIV polymorphisms were both associated with differences in apo AI levels, explaining 3.7%-5.7% of the sample variance. Taken together, the three PvuII polymorphisms explained 17.7% of the phenotypic variance in apo AI levels. There was significant evidence for an effect of nonlinearity of the PvuII-CIII genotypes on apo AI levels, with the individuals heterozygous for the polymorphism having the highest apo AI levels. No evidence of interaction between genotype and gender, age, and body-mass index was shown by covariance analysis. The molecular explanation of this effect is unclear. Our data show that variation at both the apo AI-CIII-AIV and apo B loci are associated with lipoprotein and apolipoprotein levels in this sample of Italian children.

Alleles↗
PubMed1990

Evaluation of long-term frozen storage of plasma for measurement of high-density lipoprotein and its subfractions by precipitation.

The concentration of high-density lipoprotein cholesterol (HDL-C) in plasma is now established as an independent risk factor for coronary heart disease, but more data are needed on the relative risk-predictive powers of different HDL subclasses. For epidemiologic and clinical purposes, isolation of HDL from other lipoproteins and separation of its two major subclasses, HDL2 and HDL3, are performed most conveniently by precipitation. Although storage of plasma is commonly necessary, little information is available on the long-term stability of HDL subclasses at different temperatures. Therefore, we quantified HDL-C, HDL2-C, and HDL3-C by dual precipitation with heparin-MnCl2/15-kDa dextran sulfate (H-M/DS) in samples of EDTA-plasma from 93 healthy subjects, after storage for one to 433 days at -20 degrees C, at -70 degrees C, or in liquid nitrogen (-196 degrees C). Fourteen samples (15%) were stored for a year or longer. At -20 degrees C, HDL-C decreased by 4.8% per year and HDL3-C decreased by 6.9% per year (P = 0.002 for both variables) relative to results obtained with samples stored in liquid nitrogen; total cholesterol, HDL2-C, and triglyceride did not change significantly at this temperature. When stored at -70 degrees C, none of the lipids showed any change relative to results obtained with liquid nitrogen. Thus, long-term storage of EDTA-plasma at -20 degrees C is unsuitable for subsequent quantification of HDL-C and its subclasses by H-M/DS dual precipitation. Storage at -70 degrees C is preferable, and is as reliable as storage in liquid nitrogen.

Analysis of Variance↗
PubMed1989

Human hepatic low-density lipoprotein receptors: associations of receptor activities in vitro with plasma lipid and apolipoprotein concentrations in vivo.

The relationships of plasma lipid and apolipoprotein (apo) concentrations to hepatic low-density lipoprotein (LDL) receptor activity were examined in 21 subjects (16 females, 5 males), who were undergoing laparotomy for non-neoplastic disease (cholecystectomy in 16). None had familial hypercholesterolemia, or renal, endocrine or hepatic disease. Ages were 37-77 years (mean, 58 years), plasma cholesterol concentrations 4.09-6.72 mmol/l (5.38) and plasma triacylglycerol concentrations 0.75-2.35 mmol/l (1.36). Receptor activity was quantified in vitro as the total saturable binding and EDTA-suppressible binding (representing apoB,E receptors) of 125I-labelled human LDL (15 micrograms protein/ml) by liver homogenate at 37 degrees C. There were no significant differences between men and women in 125I-labeled LDL binding. In the pooled data, EDTA-suppressible binding averaged 50 ng 125I-LDL protein/mg cell protein (S.D., 15). Total saturable binding averaged 2-fold greater (mean, 101 ng/mg; S.D., 32). Plasma cholesterol, LDL cholesterol and apoB concentrations were negative functions of both EDTA-suppressible binding and total saturable binding, but the correlations with EDTA-suppressible binding were stronger (cholesterol: r = -0.59, P less than 0.01; LDL cholesterol: r = -0.48, P less than 0.05; apoB: r = -0.61, P less than 0.01). Plasma triacylglycerol, high-density lipoprotein cholesterol and apoA-I concentrations were not related to either measure of receptor activity. These results provide evidence that the activity of apoB,E receptors in the liver is a major determinant of the plasma LDL concentration in middle-aged and elderly humans.

Adult↗
PubMed1989

Plasma lipoproteins and adrenocortical hormones in men--positive association of low density lipoprotein cholesterol with plasma cortisol concentration.

The associations of plasma lipoprotein lipids with the plasma concentrations of two adrenocortical hormones (sampled at 09.00-11.00 h) have been investigated in a random sample of 70 men aged 52-67 yr (mean, 59 yr). Plasma low density lipoprotein (LDL) cholesterol concentration was found to be positively correlated with plasma cortisol, independently of the concentrations of plasma triglyceride, high density lipoprotein cholesterol and androstenedione. After adjusting for covariates, plasma cortisol explained approximately twelve per cent of the variance in LDL cholesterol. These results suggest that plasma cortisol may significantly influence the metabolism of LDL in healthy humans.

Aged↗
PubMed1989

Plasma lipoprotein lipids in relation to the MspI polymorphism of the apolipoprotein AII gene in Caucasian men. Lack of association with plasma triglyceride concentration.

Digestion of the human apolipoprotein (apo) A-II gene with the endonuclease MspI produces fragments of 3.0 or 3.7 kb, reflecting the presence or absence of a polymorphic site within an Alu sequence 3' to the gene. Patients with hypertriglyceridemia have been shown to have an increased prevalence of the 3.0 kb allele. To explore this observation further, plasma lipoprotein lipids were studied in a random sample of fasted middle-aged Caucasian men, of which 59 were 3.0 kb homozygotes, 24 were heterozygotes, and 2 were 3.7 kb homozygotes. After adjusting for the effects of age, height, weight, alcohol intake and cigarette consumption by covariance analysis, no statistically significant associations were present between genotype and the concentrations of triglyceride in whole plasma or the d less than 1.019 g/ml fraction of plasma (i.e., VLDL + IDL). Nor were the cholesterol concentrations in VLDL + IDL, low density lipoprotein (LDL, d = 1.019-1.063 g/ml), high density lipoprotein (HDL), HDL2 or HDL3 related to genotype. In an independent comparison of eight 3.0 kb homozygotes and eight 3.7 kb homozygotes (all Caucasians) drawn from a different community, genotype was unrelated to the triglyceride or cholesterol concentrations in VLDL (d less than 1.006 g/ml), IDL + LDL (d = 1.006-1.063 g/ml) or HDL, after adjustment for the effects of covariates. These results suggest that the MspI polymorphism of the apo A-II gene is not associated with genetic variation that significantly affects triglyceride transport in the majority of men.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein A-II↗
PubMed1989

Hyposexuality and epilepsy: a community survey of hormonal and behavioural changes in male epileptics.

A survey of five group practices in South London identified 60 male patients currently undergoing treatment for epilepsy. Fifty-four agreed to participate in a detailed enquiry into aspects of their sexual activity and behaviour. Anterior pituitary and sex-hormone levels were measured. The epileptic patients were characterized by low levels of sexual activity and interest. Temporal-lobe and non-temporal-lobe epileptics were indistinguishable in these respects, but when the latter group was further subdivided into primary generalized epilepsy and focal non-temporal lobe epilepsy, the focal groups (both temporal lobe and non-temporal lobe) were more impaired. Hormonal analysis confirmed earlier hospital-clinic-based reports. In the epilepsy group, plasma free testosterone and percentage free testosterone values were decreased, sex hormone binding globulin, luteinizing hormone (LH) and follicle stimulating hormone (FSH) were increased compared to values in a normal healthy population. As association between the behavioural and hormonal indices of hyposexuality was shown, particularly for LH, but this was less apparent than in previous work.

Adolescent↗
PubMed1989

Relationships of plasma lipoprotein concentrations to unbound, albumin-bound and sex hormone-binding globulin-bound fractions of gonadal steroids in men.

Most epidemiologic studies of plasma lipoproteins and gonadal steroids have measured total hormone concentrations only. Gonadal steroids are transported in plasma in unbound, albumin-bound and sex hormone-binding globulin (SHBG)-bound forms, only the first two of which are biologically active. In the present study the associations of plasma lipoproteins with the different fractions of testosterone, oestradiol and 5 alpha-dihydrotestosterone (5 alpha DHT) were explored by multiple regression in 70 men aged 52-67 years (mean, 59 years). The principal finding was that the distribution of cholesterol between the two major subclasses of high density lipoprotein (HDL) was correlated with the concentrations of unbound and albumin-bound oestradiol, but not with SHBG-bound oestradiol or any fraction of testosterone or 5 alpha DHT. These associations were independent of plasma triglyceride. Apoproteins A-I and A-II were not correlated with any hormone fraction. Thus, in middle-aged/elderly men HDL subclasses appear to be influenced by circulating estrogenic activity, but not by androgenic activity, through a mechanism that is unrelated to triglyceride transport or HDL apoprotein metabolism.

Aged↗
PubMed1988

Sex difference in the saturable binding of low-density lipoprotein by liver membranes in ageing rats.

It is well documented that women of child-bearing age tend to have lower serum low-density lipoprotein (LDL) concentrations than men. In order to explore the metabolic basis of this sex difference, we have compared the saturable binding of 125I-labeled LDL (d 1.02-1.05 g/ml) at 37 degrees C by liver membranes from healthy male and female Wistar rats of different ages (15-213 days). Woolf plots of saturable binding curves over the concentration range 15-65 micrograms LDL protein/ml were linear and compatible with a single class of binding sites. Maximum binding capacity (Bmax) was not significantly different in male and female animals of 15-19 days of age (respectively, 0.331 +/- 0.018 vs. 0.427 +/- 0.044 micrograms LDL protein/mg membrane protein, mean +/- S.E.). Thereafter, Bmax increased in females, reaching a peak of 0.635 +/- 0.042 micrograms LDL protein/mg membrane protein at 60 days. As no increase in Bmax occurred in males, values were significantly higher (P less than 0.02) in females than in males (by a mean of 61-117%) at all ages after 30 days. During ageing, serum cholesterol concentration changed reciprocally with Bmax in females (Pearson's correlation coefficient, r = -0.761, P less than 0.01) and remained essentially constant in males. The equilibrium dissociation constant for 125I-labelled LDL binding to the hepatic membranes was unaffected by both age and sex. These results provide evidence that the sex difference in the plasma total and LDL cholesterol concentrations is related, at least in part, to a greater mean LDL receptor density in the livers of females.

Aging↗
PubMed1988

Relationship of high density lipoprotein composition to plasma lecithin:cholesterol acyltransferase concentration in men.

The epidemiological associations between the plasma concentrations of several components of high density lipoprotein (HDL) and plasma lecithin:cholesterol acyltransferase (LCAT) concentration have been studied in 101 men aged 52-67 years. Subjects were apparently healthy, and had been selected to provide a wide range of HDL-cholesterol levels. A weak positive correlation was observed between plasma total HDL-cholesterol concentration and LCAT concentration (r = 0.24, P less than 0.02). This reflected an association between HDL3-cholesterol (measured by precipitation) and enzyme concentration (r = 0.21, P less than 0.05). Apoprotein (apo) A-II concentration was also positively correlated with LCAT (r = 0.27, P less than 0.01). HDL2-cholesterol and apo A-I concentration were unrelated to LCAT concentration, as also were the HDL2/HDL3 and HDL-cholesterol/apo A-I ratios. The associations of HDL3 cholesterol and apo A-II with LCAT were strengthened when allowance was made by multiple regression for the effect of log plasma triglyceride; under these circumstances variation in LCAT explained statistically 8% of the variance in HDL3-cholesterol, and 10% of that in apo A-II.

Aged↗
PubMed1988

Variations in the apolipoprotein AI-CIII-AIV gene region and in lecithin:cholesterol acyltransferase concentration are determinants of plasma cholesterol concentrations.

We have examined the effects of variation in the region of the apolipoprotein (apo) AI-CII-AIV genes, and in plasma lecithin: cholesterol acyltransferase (LCAT) concentration, on plasma cholesterol concentration in 109 unrelated men aged 52-67 yrs. Restriction fragment length polymorphisms (RFLPs) were detected using the restriction enzymes XmnI, PstI and SstI and individuals were divided into groups using information from all three RFLPs in conjunction. Mean plasma concentrations of both total cholesterol and estimated low density lipoprotein-cholesterol differed significantly (P less than 0.0125) among groups of men with different genotypes. Thus, variation in this gene region may be one of the polygenetic factors involved in determining cholesterol levels in the normal population. In the same subjects, plasma cholesterol was also positively correlated with plasma LCAT concentration (r = 0.55, P less than 0.001), due mainly to an increase in the cholesteryl ester content of apo B-containing lipoproteins with increasing LCAT concentration. Since apolipoproteins AI, CIII and AIV have each been shown to modify the activity of LCAT in vitro, the associations of the RFLPs with plasma cholesterol concentration may reflect changes in LCAT activity secondary to qualitative or quantitative changes in one or more of these apolipoproteins.

Aged↗
PubMed1988

Biochemical and pathological features of a modified strain of Watanabe heritable hyperlipidaemic rabbits.

A modified strain of heritable hyperlipidaemic rabbit has been produced by crossing male albino rabbits homozygous for low density lipoprotein receptor deficiency into a coloured commercial colony with strong breeding characteristics. The genetic deficiency has been preserved in the resulting offspring through many generations. Litter numbers, live weight gains and energy intake are similar to normal rabbits. Free and esterified cholesterol in serum, and total cholesterol in very low density plus low density lipoproteins, are markedly increased in homozygote, but only slightly raised in heterozygote, animals. High density lipoprotein-cholesterols show an opposite trend but with less marked differences between the genetic strains. Liver total and esterified cholesterol levels were substantially increased in homozygotes, and the ability of liver membranes to bind human 125I-LDL was markedly reduced, owing to a reduction of the number of high-affinity binding sites. All animals with serum cholesterol values greater than 14 mmol/l at weaning developed extensive aortic atherosclerosis within 16 weeks. The early lesions had the histological appearances of fatty streaks and progressed to complicated disease at 6-12 months. A distinctive pattern of calcific arteriosclerosis, quite different from atherosclerosis, was observed in most aging heterozygote animals and was associated with extensive renal calcium deposition. Corneal arcus developed in some homozygotes but there was no evidence of cerebral atherosclerosis. We conclude that homozygotes of this modified strain can be used for macroscopic studies of the progression of aortic atherosclerosis in the first 4 months after weaning but after this period a combination of macroscopic and microscopic techniques are required. Heterozygotes are unsuitable for studies of this nature.

Animals↗
PubMed1988

Effects of cimetidine and ranitidine on plasma high-density lipoprotein subclasses in humans.

The effects of cimetidine (400 mg b.d.) and ranitidine (150 mg b.d.) on high-density lipoprotein (HDL) subclasses and other plasma lipoproteins were studied in 18 men and 15 women with reflux oesophagitis and/or duodenitis. Serum testosterone and sex hormone binding globulin (SHBG) concentrations were also measured. Treatment with either drug was continued for 12 weeks. Ranitidine had no significant effect on any measured variable in either men or women. Cimetidine had no effect in men, but in women it raised the cholesterol concentration in the HDL2 subclass by 15% after 8 weeks, and by 48% after 12 weeks. In females, cimetidine also reduced the concentrations of SHBG (by 24% at 12 weeks) and of total testosterone (by 25% at 12 weeks). The significance of these latter changes is uncertain, however, as estimates of the biologically active free testosterone concentration were unchanged.

Adult↗
PubMed1987

Double-blind trial of the long-term effects of acebutolol and propranolol on serum lipoproteins in patients with stable angina pectoris.

In order to evaluate the long-term effects of propranolol and acebutolol on serum lipoprotein lipids, a double-blind clinical trial was carried out. Fifteen patients with stable angina pectoris, aged 32 to 79 years (mean = 53), were randomized to propranolol (80 to 160 mg/day) or acebutolol (400 mg/day) treatment groups, and followed for approximately 1 year (mean = 371 days). Blood was collected on the day treatment was begun, after approximately 5 months (mean = 158 days), and on completion of the trial. Very low-density lipoproteins (VLDL) (alpha less than 1.006), low-density lipoproteins (LDL) (1.006 to 1.063), and high-density lipoproteins (HDL) (1.063 to 1.125 [HDL2] and 1.125 to 1.21 [HDL3]) were isolated by sequential preparative ultracentrifugation, and their cholesterol and triglyceride quantified by enzymic procedures. After 1 year propranolol had raised the mean VLDL triglyceride concentration by 79% (p less than 0.005) and had lowered total HDL cholesterol by 24% (p less than 0.005). As LDL cholesterol was unchanged, the LDL cholesterol/HDL cholesterol ratio was increased by 26% (p less than 0.005). Mean values at 5 months were intermediate between those at baseline and those at 1 year. In contrast to these changes, acebutolol had no significant effect on any measured lipoprotein lipid.

Acebutolol↗
PubMed1987

Studies with doxazosin on the saturable binding of 125I-LDL by liver in normocholesterolemic mice.

Tissue culture studies have provided evidence that alpha 1-adrenergic receptor inhibition with doxazosin increases the number of low-density lipoprotein (LDL) receptors in human fibroblasts. A similar effect occurring in vivo might explain the reduction of plasma LDL concentration observed in some clinical trials of prazosin. In order to examine this question further, mice were given doxazosin 100 or 400 micrograms/kg/day by i.p. injection for 4 days, after which they were killed, blood was collected and livers were excised. Binding of 125I-labelled human LDL to tissue homogenates, over the concentration range 30-120 micrograms LDL protein/ml, was measured at 37 degrees C in the absence and presence of excess unlabelled LDL. Woolf plots of the results for saturable binding were found to be compatible with a single class of binding site. In control animals Bmax for this receptor was 867 +/- 117 ng LDL protein/mg tissue protein, and the equilibrium dissociation constant was 32.7 +/- 6.6 micrograms LDL protein/ml (mean +/- SD, n = 5). Doxazosin treatment had no effect on either parameter of 125I-LDL binding. A trend towards a decrease in liver triglyceride concentration with increasing doses of doxazosin was recorded, but there was no evidence for effects on liver cholesterol or serum lipid concentrations.

Adrenergic alpha-Antagonists↗