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Biomedical subjects

R M Nair

Publications and source records attributed to R M Nair.

At least 19 recordsLinked to original sources
PubMed2006

SSR analysis of the Medicago truncatula SARDI core collection reveals substantial diversity and unusual genotype dispersal throughout the Mediterranean basin.

The world's oldest and largest Medicago truncatula collection is housed at the South Australian Research and Development Institute (SARDI). We used six simple sequence repeat (SSR) loci to analyse the genetic diversity and relationships between randomly selected individuals from 192 accessions in the core collection. M. truncatula is composed of three subspecies (ssp.): ssp. truncatula, ssp. longeaculeata, and ssp. tricycla. Analysis at the level of six SSR loci supports the concept of ssp. tricycla, all the samples of which showed unique alleles at two loci. Contingency Chi-squared tests were significant between ssp. tricycla and ssp. truncatula at four loci, suggesting a barrier to gene flow between these subspecies. In accessions defined as ssp. longeaculeata, no unique allelic distribution or diagnostic sizes were observed, suggesting this apparent ssp. is a morphological variant of ssp. truncatula. The data also suggest M. truncatula that exhibits unusually wide genotype dispersal throughout its native Mediterranean region, possibly due to animal and trade-related movements. Our results showed the collection to be highly diverse, exhibiting an average of 25 SSR alleles per locus, with over 90% of individuals showing discrete genotypes. The rich diversity of the SARDI collection provides an invaluable resource for studying natural allelic variation of M. truncatula. To efficiently exploit the variation in the SARDI collection, we have defined a subset of accessions (n = 61) that maximises the diversity.

Alleles↗
PubMed1987

Studies on LHRH and physiological fluid amino acids in human colostrum and milk.

Various physiological fluid amino acids including essential, nonessential and neuroinhibitory as well as excitatory entities in human milk, colostrum, and infant formula were determined on a microcolumn ion-exchange analyzer equipped with ninhydrin detection system and integrator. The levels of 6 essential and 6 nonessential amino acids were significantly lower in infant formula than those in milk and colostrum. The neurotransmitter amino acids were also high in milk except taurine. Peptide hormones like LHRH were undetectable in infant formula, but were found in appreciable quantities in milk and colostrum by high pressure liquid chromatography. LHRH levels in milk were 6 to 7 fold higher than the corresponding plasma values as measured by radioimmunoassay. These and other several unique ingredients in human breast milk play a very prominent role in the development of the neonate. The presence of such complex components makes it impossible to humanize cow's milk or any other alternate formulation and to serve as a substitute for human milk. Further extensive work in defining the role of such essential components in milk on the development of the infant is indicated.

Amino Acids↗
PubMed1985

Globin proteins of the normal and anemic duck.

The red blood cells of normal adult ducks contain two main hemoglobins. The most abundant type, HbA, comprises approximately 80% of the total, with the remaining 20% being made up of HbD. An attempt was made to determine whether during hemolytic anemia a special alpha globin chain (alpha s) replaces the alpha chain of HbA found in normal animals. This special stress alpha globin, whose existence has been seriously questioned, was originally postulated to explain the sequence discrepancies obtained between alpha chains of normal and anemic chickens and ducks. Using gel electrophoresis, isoelectric focusing, and HPLC peptide mapping techniques no qualitative differences between the alpha A globins of normal and anemic animals were found. The nature of the beta globin chains present in adult ducks has also never been rigorously established. In this work, a variety of techniques, including HPLC, gel electrophoresis, and microcolumn amino acid analysis, were used to examine the beta chains from each hemoglobin. Using these methods, no differences were found between the beta globin chains of the two hemoglobins.

Amino Acids↗
PubMed1985

Lactate dehydrogenase isoenzymes in diabetic patients.

Lactate dehydrogenase (LDH) isoenzyme profiles in human platelets and the sera of patients with type I and II diabetes mellitus and vascular complications, as well as normal subjects were measured utilizing a recently established, modified micromethod. LDH-3 was the predominating species in platelets (37.5 +/- 3.0%), with LDH-2, 1, 4 and 5 following in decreasing order of concentration. The LDH-3/LDH-4 ratio in platelets varied from 6.2 to 1.38. Type I and type II diabetic patients with vascular complications showed a significantly higher ratio for LDH-3/LDH-4 (3.99 +/- 1.20 for DM I, 2.16 +/- 0.25 for DM II patients) than the mean ratio for normal subjects (1.14 +/- 0.08). This platelet-specific LDH isoenzyme pattern may be the result of frequent in vivo platelet-vessel wall interactions in the diabetic patients whose platelets are known to be hyperaggregable in in vitro test systems. Since non-diabetic patients patients with vascular complications also displayed a similarly elevated LDH-3/LDH-4 ratio, a wider classification is preferable, although the measurement of the LDH isoenzyme pattern will be helpful in assessing diabetic vascular complications.

Adult↗
PubMed1983

Elevated LHRH levels in human milk.

Anterior pituitary gonadotropins are regulated by the hypothalamic peptide hormone LHRH. However, the extrahypothalamic source(s) as well as extrapituitary action(s) of LHRH exist. We describe the discovery of relatively elevated levels of LHRH in human milk and its possible functions in the neonates. Blood and milk samples were obtained at the same time in post-partum period from lactating mothers. Special methods of extraction and concentration of milk as well as plasma LHRH were developed, and the hormone levels were determined by a sensitive double antibody radioimmunoassay using 125I-LHRH of high specific activity and immunoreactivity. Human milk contained 5 to 6 times more LHRH than plasma samples. The pure milk LHRH was fully biologically active when tested in vivo. Another hypothalamic hormone, TRH, is not found in such high concentrations in milk, only 5% that of LHRH. This excludes the possibility of an in vivo concentrating mechanism for the hypothalamic LHRH. Since LHRH neurons possess only minute amounts of the hormone, which is released in hypophyseal portal circulation, the large amounts present in the milk of lactating mothers may be of extrahypothalamic origin. Partial absorption of intact LHRH from intestine is known. The elevated levels of milk LHRH may have a profound influence in certain biological processes in the neonatal life, in continuation of the intrauterine exposure to high levels of LHRH of placental origin.

Antibody Specificity↗
PubMed1981

Inter-relationship between changing patterns of LHRH and gonadotrophins in the menstrual cycle.

Optimum conditions for a sensitive and highly precise radioimmunoassay of LHRH were established. Precipitation and removal of interfering substances and concentration of the resultant LHRH extracts from peripheral plasma were also achieved. Using these methods, daily plasma LHRH levels in females with normal menstrual cycles were measured and correlated with the corresponding LH and FSH levels. The levels of LHRH in the peripheral plasma of postmenopausal females, as well as eugonadal males, were also determined. The LHRH profile in normal cycling women was found to be cyclic but the peak LHRH levels were observed at the beginning of the rise in LH and FSH levels and preceded the midcycle surge of gonadotrophins. The LHRH levels in the luteal phase (19.8 +/- 1.1 pg/ml, mean +/- SEM) were significantly (P less than 0.01) higher than those in the follicular phase (16.5 +/- 0.5 pg/ml) of the menstrual cycle. A high degree of correlation (r = 0.91) was seen between the immunoreactivity and biological activity of the extracted LHRH.

Adult↗
PubMed1981

Elevated levels of LRH in human milk.

Measurement by doubled antibody radioimmunoassay indicates that the levels of LRH in human milk are five to six times higher than the corresponding plasma samples. Such high levels of the hormone in the maternal milk may have a profound influence on the developing reproductive and other related biological processes of the neonates.

Female↗
PubMed1981

Plasma factors and platelet aggregation in diabetes mellitus.

Plasma fron some diabetic patients, particularly those with advanced retinopathy and nephropathy, will potentiate ADP-induced platelet aggregation. Partial purification of plasma from a diabetic patient with nephropathy has yielded a fraction with this activity. A linea dose response curve relating plasma factor (6.25-50 ng protein) and platelet aggregation or ATP release at 4 minutes after adding ADP has been found. The effect is blocked by exposure of platelets to aspirin, prostaglandin or eicosapentaenoic acid. Soluble immune complexes are found in many diabetics and are known to be platelet-active. We have isolated immune complexes from sera of six diabetics and have shown enhancement of the second phase of platelet aggregation and of ATP release by these immune complexes from platelets sensitized to ADP. We conclude that plasma proteins from diabetics may accentuate ADP-induced platelet aggregation and ATP release, possibly by acting through prostaglandin pathways. Immune complexes appear to be one group of plasma proteins with such platelet active behavior. Further studies are indicated to characterize these plasma factors and to assess their in vivo significance regarding platelet function and vascular disease in diabetes mellitus.

Antigen-Antibody Complex↗
PubMed1980

Combined use of clomiphene and intranasal luteinizing hormone-releasing hormone for induction of ovulation in chronically anovulatory women.

Combined therapy with clomiphene and intranasal luteinizing hormone-releasing hormone (LHRH) was used to induce ovulation in eight chronically anovulatory patients under treatment for infertility. Clomiphene, 100 mg daily, was given from the 5th to the 9th day of the cycle. Synthetic LHRH was administered intranasally in different dosages from day 11 to day 14, in an attempt to induce late follicular development and ovulation. Five of the eight patients ovulated, and three conceived. The success achieved with combined clomiphene and intranasal LHRH administration suggests a therapeutic potential in the management of anovulatory infertility.

Administration, Intranasal↗
PubMed1980

125I-labeled gonadoliberin and high specific activity and immunoreactivity: method of iodination and rapid separation.

We describe optimum conditions for iodinating gonadoliberin with use of relatively large proportions of Na 125I. Products of the iodination are separated on an anion-exchange resin (Amberlite IRA-400). The 125I-labeled gonadoliberin thus obtained has a high specific activity (1400 to 1590 Ci/g); because of the conditions of iodination, we believe that the predominant species of the labeled decapeptide is the mono-iodinated one. Our separation and purification of the labeled substance on ion-exchange resin is rapid, economical, and less cumbersome than the use of a Biogel P-2 column. There is no adsorption of the labeled hormone onto the resin, as evidenced by analytical recovery studies with tritium-labeled gonadoliberin. Paper-strip chromatoelectrophoresis showed no free Na 125I or radiolabeled damaged peptide fragments after purification on the resin. When antiserum was used at a concentration 32-fold that used in the regular assay procedure, only 4% of the radioactivity remained in the free form, indicating the high immunoreactivity of the labeled hormone.

Anion Exchange Resins↗
PubMed1979

Platelet adhesion and aggregation in diabetes mellitus.

Platelets from diabetic patients show both increased platelet adhesiveness and sensitivity to aggregating agents. Plasma levels of the platelet-active von Willebrand Factor and the closely related factor-VIII antigen are significantly elevated, while factor VIII procoagulant activity is not. This may reflect either intravascular coagulation or disproportionate production or degradation. Plasma factors that enhance ADP-induced platelet aggregation are found in 50% of unselected male diabetics. Activity is clearly demonstrated only when plasma is added immediately prior to adding subthreshold doses of ADP to platelet-rich plasma obtained from control subjects. Systematic investigations of the molecular nature of such factors and their interactions with platelets are in progress. In platelets obtained from diabetic subjects, we have previously found increased sensitivity to the aggregating effects of arachidonic acid, and increased synthesis of immunoreactive prostaglandin E-like material. More recent studies have shown that platelets obtained from diabetic subjects are less sensitive to the antiaggregatory effects of imidazole, a thromboxane synthetase inhibitor. These observations suggest that increased synthesis of the labile aggregating substance thromboxane A2 also occurs in platelets obtained from diabetics. Collectively, these platelet and plasma abnormalities may contribute to accelerated vascular disease of diabetes. Prospective studies using antiplatelet agents are presently underway or in the planning stages in diabetics to explore their potential beneficial effects.

Adenosine Diphosphate↗
PubMed1979

Action of gonadotropin-releasing hormone and its superactive analogues on the anterior pituitary: the mechanism of release and synthesis of gonadotropins.

The role of prostaglandins (PG), their active intermediates or the adenylcyclase-cyclic AMP system for gonadotropin release and/or synthesis was evaluated by administering gonadotropin-releasing hormone (Gn-RH) and its superactive analog to normal and aspirin-treated rats. Serum LH levels, anterior pituitary malondialdehyde (MDA) content and cyclic AMP (cAMP) levels were followed. The pituitaries stimulated with Gn-RH or its superactive analog yielded more MDA and cAMP than the controls. Stimulation of the pituitary with the releasing hormones, after aspirin treatment, yielded 40--70% less MDA and lower LH values than the nontreated animals. The cAMP levels were not significantly lowered by the aspirin treatment. These studies suggest that the activation of the PG biosynthesis and the adenyl-cyclase-cyclic AMP system are not sequential but 2 separate physiological events. The active PG intermediates may only be responsible for the release of LH. It is not clear whether the activation of cAMP initiates also the processes preparatory to the synthesis of LH in the endoplasmic reticulum. In vivo studies in rats showed that the analogs (I and II) were 30 times more potent and had a more prolonged action on the pituitary (3 h) than Gn-RH. Ultrastructural studies on the anterior pituitary after hypophyseal stalk portal vessel infusion of Gn-RH and the analog (I and II) provided ample morphological evidence for both Gn-RH and analog induced gonadotropin-release and synthesis. The prolonged action of the superactive analog (I and II) on the gonadotrophs was also indicated by ultrastructural studies.

Animals↗
PubMed1978

Stimulation of gonadotrophs by pituitary portal vessel infusion of superactive LH-RH analogues: an ultrastructural study.

LH-RH or its superactive analogues were infused into pituitary portal vessels of adult male rats for 1 min; pituitaries were then fixed for routine electron microscopy 1 min, 30 min and 3 h after infusion. A maximal increase of granule release at 2 min. and a maximal increase in synthetic activity (i.e., dilated cisternae of rough endoplasmic reticulum (RER) and Golgi apparatus (GA)) at 30 min, occurred in gonadotrophs in response to both LH-RH and the superactive analogues, but not to saline infusion. Only gonadotrophs from analogue infused pituitaries showed a high level of exocytosis and protein synthesis at 3 h. In addition, the superactive analogues typically stimulated formation of large vacuoles of RER at 30 min and 3 h that resembled those seen in "signet ring" cells following castration. Radioimmunoassay (RIA) values of serum LH supported these observations. The results of this study provide morphological evidence for a prolonged action of the superactive analogues of LH-RH on both gonadotropin secretion and synthesis under physiological conditions.

Animals↗
PubMed1977

The effect of oral glucose on von Willebrand factor activity in normal and diabetic subjects.

We have previously noted increased platelet aggregation and high von Willebrand factor activity in patients with chemical diabetes. In this paper we have studied platelet aggregation, plasma glucose, insulin, free fatty acids, growth hormone, and von Willebrand factor activity during the glucose tolerance test in six normal and six chemical diabetic subjects. The results suggest that von Willebrand factor activity is suppressed coincident with the rise of glucose and insulin and provide further evidence of hormonal and metabolic control of levels of von Willebrand factor activity.

Aged↗
PubMed1977

Relation between growth hormone levels and Von Willebrand factor activity.

The relationship between growth hormone and von Willebrand factor activity was studied in fasting plasma samples, nocturnal samples, and after intramuscular injection of growth hormone. A significant correlation was seen between the two levels in fasting samples. During sleep, peaks of growth hormone were associated with peaks of von Willebrand factor activity. A subject with isolated growth hormone deficiency had no peaks of either. Intramuscular injection of growth hormone produced a rise of von Willebrand factor activity in all subjects studied. These results indicate that there is a relationship between growth hormone and von Willebrand factor activity.

Adult↗