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Biomedical subjects

R N Kulkarni

Publications and source records attributed to R N Kulkarni.

At least 37 records · Page 2Linked to original sources
PubMed1996

Investigation of the effects of antisense oligodeoxynucleotides to islet amyloid polypeptide mRNA on insulin release, content and expression.

We have investigated the effects of antisense oligodeoxynucleotides (oligos) to islet amyloid polypeptide (IAPP) mRNA on the expression and secretion of IAPP and insulin, in the clonal beta-cell line HIT-T15. Phosphorothioate-modified oligos were cytotoxic compared with phosphodiester (D)-oligos. Of the nine oligos tested using a lipofection reagent, O3, a 30-mer D-oligo complementary to a sequence downstream of the IAPP initiation codon, showed a significant dose-dependent suppression of IAPP mRNA, with a 42% decrease at 7.5 microM, compared with a scrambled (MSO3) control oligo (n = 3, P < 0.01). A subsequent 89% suppression of IAPP release was observed in the 4-h period following antisense treatment (1.78 +/- 0.13 (MSO3) vs 0.19 +/- 0.14 (O3) pmol/10(6) cells per 240 min, n = 7, P < 0.01). A significant increase in insulin mRNA (100 +/- 10% (MSO3) vs 124 +/- 8% (O3), n = 3, P < 0.05) and insulin content (13.0 +/- 0.9 (MSO3) vs 17.4 +/- 1.4 (O3) pmol/10(6) cells, n = 7, P = 0.028) was observed following treatment with O3 at 7.5 microM. O8, a 20-mer D-oligo directed to a region of IAPP mRNA further downstream than O3, also showed a decrease in IAPP mRNA and peptide release and an increase in insulin content. No significant changes were observed in the expression and release of the unrelated beta-cell peptide, neuropeptide Y. We thus show a suppression of synthesis and release of IAPP in HIT-T15 cells using antisense oligos. The associated increase in insulin mRNA and content in these cells after treatment with IAPP antisense oligos is in accord with an inhibitor action of IAPP on insulin availability.

Amyloid↗
PubMed1995

Pyroglutamyl-phenylalanyl-proline amide attenuates thyrotropin-releasing hormone-stimulated insulin secretion in perifused rat islets and insulin-secreting clonal beta-cell lines.

TRH immunoreactivity has been detected in the pancreas of man and rat and localized to the islets of Langerhans. We studied the effect of synthetic TRH and the related tripeptide pyroglutamyl-phenylalanyl-proline amide (EFP) on isolated perifused rat islets and the glucose-responsive clonal cell lines HIT-T15 and RIN5AH. TRH at 10 nM potentiated [0.5 +/- 0.1 (control) vs. 0.8 +/- 0.1 (TRH) pmol/10(6) cells per 120 min; mean +/- SEM; n = 6; P < 0.001; n = 15], whereas EFP from 1 nM upwards suppressed glucose-stimulated insulin secretion [0.8 +/- 0.1 (control) vs. 0.5 +/- 0.1 (EFP) pmol/10(6) cells per 120 min; P < 0.001; n = 12) in the cell lines. Further, EFP reversed TRH-stimulated insulin release. Similar responses were observed in perifused isolated rat islets at the tested dose of 1 microM. Gel permeation chromatography of rat adult and neonatal whole pancreas, isolated islets, and HIT cell extracts demonstrated the elution of total TRH-like immunoreactivity (t-TRH-LI) in the same position as synthetic TRH. Cation exchange analysis of the t-TRH-LI from rat adult pancreas and HIT cell extracts showed that neutral TRH-like peptides corresponding to synthetic EFP were also present. Reverse-phase fast protein liquid chromatographic analysis of t-TRH-LI in the unbound fraction of these extracts subjected to anion exchange columns, also demonstrated peaks corresponding to synthetic EFP. We conclude that TRH potentiates, whereas EFP inhibits, glucose-stimulated insulin release in isolated perifused islets and the cell lines. In addition, EFP reversed the stimulatory effect of TRH. The presence of EFP-LI in rat adult and neonatal pancreas and HIT cell extracts suggests it may contribute in the modulation of pancreatic endocrine function.

Amino Acid Sequence↗
PubMed1995

A 67 kDa protein mediates pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal peptide-stimulated insulin secretion in a hamster clonal beta-cell line.

Insulin secretion is regulated by neural and neurohormonal factors. The report of nerves releasing pituitary adenylate cyclase-activating polypeptide (PACAP)--a 38 amino acid peptide--in the endocrine pancreas, suggests it may be important in modulating insulin release. We therefore carried out receptor-binding studies on membranes prepared from the glucose-responsive clonal beta-cell line HIT-T15, and also examined the effects of PACAP38, PACAP27--a C-terminal truncated form of the peptide--and vasoactive intestinal peptide (VIP) on insulin and islet amyloid polypeptide (IAPP) release. We showed by chemical cross-linking that PACAP and VIP stimulate secretion from the clonal cells by binding to a receptor with a molecular weight of 67 kDa (n = 4). Binding was saturable when membranes were incubated with 125I-PACAP27 (Kd 1.2 +/- 0.2 nM; Bmax 415.7 +/- 35.3 fmol/mg; n = 4) or 125I-VIP (Kd 1.3 +/- 0.3 nM; Bmax 354.8 +/- 42.8 fmol/mg; n = 4). We also demonstrated an increase in glucose-stimulated insulin (PACAP27, 366.6 +/- 25.8%; PACAP38, 389.9 +/- 13.4%; VIP, 342.6 +/- 16.1% of control; all at 1 microM, P < 0.01 vs control) and IAPP release (PACAP27, 236.9 +/- 26.2%; PACAP38, 226.5 +/- 10.9%; VIP, 242.9 +/- 15.8% of control; all at 1 microM, P < 0.01 vs control). Incubation of the cells with these peptides, for a duration of 12 h, in the presence of 5.5 mM glucose, did not alter the expression of insulin or IAPP. These findings suggest that PACAP and VIP stimulate secretion of insulin and IAPP by binding to a 67 kDa protein on clonal beta-cells and do not alter the transcription of insulin and IAPP under the conditions tested.

Amyloid↗
PubMed1994

Imidazolines stimulate release of insulin from RIN-5AH cells independently from imidazoline I1 and I2 receptors.

The effect on insulin release of efaroxan, an alpha 2-adrenoceptor antagonist and a highly potent drug at imidazoline I1 receptors, and the effects of seven other imidazoline compounds selective for the imidazoline I1 or I2 receptors, were studied in the rat insulinoma cell line RIN-5AH. The cells released insulin in response to glucose (0.3-10 mM), and efaroxan (100 microM) potentiated glucose-induced insulin release. (-)-Adrenaline completely displaced the binding of [125I]p-iodoclonidine to membranes of RIN-5AH cells, indicating that these cells do not express imidazoline I1 receptors. Cirazoline and idazoxan (100 microM), both highly potent drugs at imidazoline I2 receptors, and the guanidines guanoxan and amiloride (200 microM), also promoted insulin release from RIN-5AH cells. Irreversible blockade of imidazoline I2 receptors with 10 microM clorgyline did not prevent the stimulatory effects of cirazoline or idazoxan; however, these compounds completely reversed the inhibition by diazoxide (250 microM), an opener of ATP-dependent K+ channels (K+ATP channels), of glucose-induced insulin release. These data indicate that the imidazoline/guanidine compounds promote insulin release from RIN-5AH cells, by interacting with a novel binding site related to K+ATP channels that does not represent any of the known imidazoline I1 or I2 receptors.

Adrenergic alpha-Agonists↗
PubMed1994

Plasma norepinephrine kinetics are unaltered in chronically undernourished adult subjects.

Twelve healthy adults divided into a well-nourished (WN; n = 6) and a chronically energy deficient (CED; n = 6) groups underwent a single 30 min infusion of norepinephrine (NE) administered at the rate of 0.15 micrograms/kg fat-free mass/min. Measured parameters in the basal state and during the infusion included heart rate (by electrocardiograph), stroke volume, cardiac output and other cardiac indices (by impedance cardiography) and blood pressure recordings. The data are suggestive of fairly similar cardiovascular responses in the CED and WN subjects, with the exception of cardiac inotropy (i.e. strength of cardiac muscle contractility) and changes in total peripheral resistance, both of which were enhanced in the CED. Peak NE levels of both groups during the infusion were similar and so was the clearance rate for NE corrected for fat-free mass differences. Although plasma half-life of NE tended to be higher in the CED group, plasma appearance rates of NE were comparable between the groups, suggesting that plasma NE kinetics were not altered in CED adults.

Adolescent↗
PubMed1993

Reduced postexercise recovery oxygen consumptions: an adaptive response in chronic energy deficiency?

Maximal aerobic capacity (VO2max) and oxygen consumption during recovery were measured in well-nourished control subjects (C) and compared with results from chronically energy-deficient (CED) subjects in the same age range. The absolute VO2max was lower in undernourished subjects (2.5 +/- 0.1 L/min [C] v 1.8 +/- 0.1 L/min [CED]; mean +/- SEM, P < .001); however, when expressed per kilogram fat-free mass (FFM), the values were comparable. The total O2 debt was higher in the well-nourished group even when corrected for FFM differences (249.1 +/- 17.1 v 147.3 +/- 9.2 mL/kg FFM; P < .001). O2 consumption in the recovery period returned to baseline values rapidly and in a single phase in undernourished subjects. In contrast, a slow biphasic decline was observed in well-nourished control subjects. The postexercise recovery phase may be an important period during which energy-saving may occur in chronically undernourished human subjects.

Adult↗
PubMed1993

Variability of cardiovascular and plasma noradrenaline responses to sustained isometric contraction in normal human subjects.

1. Eight healthy adult males underwent three sustained isometric contractions at 30% of maximal voluntary contraction for 3 min, within a 9 day period. 2. The study focuses on the inter-individual and day-to-day intra-individual variability of cardiovascular and plasma noradrenaline responses to sustained isometric contraction. 3. The results of this study indicate that inter-individual variability is generally greater than intra-individual variability. Diastolic blood pressure was the most sensitive as well as the least variable cardiovascular parameter measured. 4. The variability of plasma noradrenaline levels in both the basal and the stimulated state was high. The present study suggests that it is preferable to determine the 'true' noradrenaline peak after the release of handgrip, as this is associated with a lower variability than the plasma noradrenaline peak taken at the time of the release of handgrip.

Adult↗
PubMed1993

Immediate heart rate responses to head-up tilt in healthy human subjects: response characteristics and variability.

Eight healthy adult males underwent three 70* head-up tilts within a nine day period. Immediate heart rate responses were monitored for 30 beats following completion of change to upright posture. The pooled data demonstrates a clearly demarcated bimodal heart rate response with a rise in heart rate by the 20th beat and a subsequent fall by the 30th beat. There is a secondary rise in heart rate with continuation of the tilted position. The bimodal response is at variance with several earlier reports. There is a large variability in the immediate heart rate responses, both between subjects of a homogeneous group and within subjects with repeated measurements. The large variability precludes the use of the immediate heart rate responses to passive tilting in autonomic testing.

Adult↗
PubMed1992

Composition of the Essential Oil of Cymbopogon travancorensis.

The chemical composition of the essential oil of CYMBOPOGON TRAVANCORENSIS Bor. (Poaceae) was investigated by capillary GC and GC-MS. Thirty-five compounds were identified. The oil contains mono- and sesquiterpene hydrocarbons (39.60%), oxygenated terpenes (30.45%), and phenyl propanoids (22.04%). The main constituents of the oil are camphene (11.86%), limonene (18.07%), borneol (9.71%), elemicin (17.22%), and elemol (11.21%).

Journal Article↗
PubMed1992

Thermic effect of a meal. 3. Effect of dietary supplementation in chronically undernourished human subjects.

Five apparently healthy, chronically undernourished (UN) male volunteers aged between 18 and 30 years were studied before and after 12 weeks of dietary supplementation. The thermic effect of a meal (TEM) was measured over a period of 6 h using a ventilated-hood system. Results indicated a significant increase in body-weight after supplementation due to increases in body fat and fat-free mass (FFM) in the proportion of 69% and 31% respectively. The basal metabolic rates (BMR) measured post supplementation were significantly higher in absolute terms, with a trend towards higher values when adjusted for the changes in FFM. TEM responses measured after 12 weeks of supplementation were significantly lower when expressed either in absolute terms (presupplementation 227.0 kJ v. post supplementation 193.5 kJ), or as a percentage of the energy density of the meal (9.1% v. 7.7%). This lower TEM was reciprocal to the changes in the BMR (r -0.86). The post-meal total energy output (PMTEO) was, however, not significantly different after 12 weeks of dietary supplementation. The unchanged PMTEO would indicate an unaltered 'thermogenic capacity', following supplementation, in these chronically undernourished subjects. These results confirm our earlier conclusion that, in chronic undernutrition, the thermic response to a meal may not contribute to any energy saving.

Adolescent↗
PubMed1992

Energy supplementation reverses changes in the basal metabolic rates of chronically undernourished individuals.

The objective of the present study was to examine the influence of energy supplementation and its cessation thereafter on the basal metabolic rates (BMR) of chronically undernourished individuals. Seven apparently healthy males were supplemented daily with 3.35 MJ (15 g protein, 35 g fat, 105 g carbohydrate) for 12 weeks. The average gain in body-weight was 1.9 kg (body fat, 58%; fat-free mass (FFM), 42%). The rise in BMR exceeded that accounted for by the increases in FFM during the 12 weeks of supplementation and was attributed to increases in the amount and activity of the visceral tissue as well as to an added cost of lipogenesis. At 12 weeks after cessation of the supplement, body-weights and FFM had decreased to presupplementation levels. BMR at this stage were significantly lower than at the 12th week of supplementation, when expressed per kg FFM or when adjusted for FFM using an analysis of covariance. These results suggest an increase in the metabolic efficiency during this negative energy balance period. The study demonstrates that, in the chronically undernourished, the changes in BMR are reversible and, hence, physiologically important to the process of adaptation to low-energy intakes.

Adaptation, Physiological↗
PubMed1991

Variability in cardiovascular and plasma norepinephrine responses to head-up tilt in healthy human subjects.

Eight healthy, young adult males underwent three separate, 10-min 70 degrees head-up tilts (HUT) over a period of nine days, in order to assess the intra- and inter-individual variability of cardiovascular and plasma norepinephrine (NE) responses to the manoeuvre. Cardiovascular parameters and plasma NE were measured in the basal state and at 2-min intervals during the HUT. The results indicate that: (1) the intra-individual variability is a smaller component of the total variability of both cardiovascular and plasma NE responses to HUT; (2) the variability in cardiovascular parameters is smaller than that in plasma NE levels, both basal and in response to postural stress; (3) there does not appear to be any difference in variability when expressed either as the maximal or the mean response to HUT; and (4) there does not appear to be an increase in the variability of the measured parameters over the duration of the HUT.

Adult↗
PubMed1991

Thermogenic responses to noradrenaline are unaltered following energy supplementation in chronically energy-deficient human subjects.

A group of chronically undernourished labourers underwent a period of controlled supplementary feeding (3.35 MJ per day) over a period of 12 weeks. Thermogenic responses to Noradrenaline (NA) (0.15 microgram kg-1 fat-free mass per min) were assessed (1) before supplementation (2) during the 12th week of supplementation and (3) 12-16 weeks following the cessation of supplementation. There were significant changes in anthropometric indices and basal metabolic rates (BMR) during the three stages of the study; however, these were not accompanied by significant changes in the thermogenic responses to NA.

Adult↗
PubMed1991

The scalene tubercle.

One hundred and thirty right and 114 left first ribs from a random collection have been studied for the characters of the scalene tubercle and the related structures. The tubercle is not always present but the muscular impression for the insertion of the scalenus anterior muscle on the superior surface of the first rib is almost constant and it generally extends upto the medial third of this surface. The arterial groove, generally shallow, lies behind the tubercle or the muscular impression and generally extends only upto the medial 2/3 of the superior surface. Likewise, the venous groove, mostly shallow, lies in front of the tubercle or the muscular impression and extends, generally, only upto the medial 2/3 of the surface. Normally, there is no separate groove for the lower trunk of the brachial plexus.

Humans↗
PubMed1989

Repeated infusions of identical doses of norepinephrine show potentiation of metabolic responses in human subjects.

Thermogenic responses to similar doses of norepinephrine appear to be different when repeatedly administered. This hypothesis was tested by three consecutive 30-minute infusions of a fixed dose of norepinephrine separated by a rest period of one hour between infusions. There was a significant increase or potentiation of the metabolic response as measured by oxygen consumption to the third dose of norepinephrine, while the cardiovascular responses showed no change. It is therefore important to make allowances for this phenomenon when assessing intergroup differences in regulatory thermogenesis using dose-response protocols for norepinephrine administration.

Adult↗
PubMed1989

Thermogenic responses to graded doses of noradrenaline in undernourished Indian male subjects.

1. Seventeen male subjects with an energy intake of 10.6 (SD 1.7) MJ/d and ten male undernourished labourers with an energy intake of 8.0 (SD 1.2) MJ/d were studied. The controls were subdivided into ten underweight controls with a body mass index (weight/height2; BMI) less than 18 (17.2 (SD 0.9)) and seven normal-weight controls with a BMI greater than 20 (21.3 (SD 1.6)), while the undernourished labourers had a BMI less than 18 (16.8 (SD 1.2)). 2. Comparison of thermogenic responses to increasing doses of noradrenaline showed no overall significant inter-group differences when subjected to a nested analysis of variance (ANOVA). For the initial doses of 0.05 and 0.1 micrograms noradrenaline, significantly lower responses were seen in the undernourished subjects, while the highest dose showed comparable responses in all three groups. Thermogenic responses to the initial two doses, when corrected for fat-free mass (FFM) differences, were 40% lower in the undernourished group when compared with the underweight group with similar BMI and FFM values. However, this finding was not statistically significant. 3. The basal oxygen consumption of the undernourished group, expressed per unit FFM, was significantly higher than that of the controls.

Adult↗