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K Meeran

Publications and source records attributed to K Meeran.

52 records · Page 3Linked to original sources
PubMed1996

A role for glucagon-like peptide-1 in the central regulation of feeding.

The sequence of glucagon-like peptide-1 (7-36) amide (GLP-1) is completely conserved in all mammalian species studied, implying that it plays a critical physiological role. We have shown that GLP-1 and its specific receptors are present in the hypothalamus. No physiological role for central GLP-1 has been established. We report here that intracerebroventricular (ICV) GLP-1 powerfully inhibits feeding in fasted rats. ICV injection of the specific GLP-1-receptor antagonist, exendin (9-39), blocked the inhibitory effect of GLP-1 on food intake. Exendin (9-39) alone had no influence on fast-induced feeding but more than doubled food intake in satiated rats, and augmented the feeding response to the appetite stimulant, neuropeptide Y. Induction of c-fos is a marker of neuronal activation. Following ICV GLP-1 injection, c-fos appeared exclusively in the paraventricular nucleus of the hypothalamus and central nucleus of the amygdala, and this was inhibited by prior administration of exendin (9-39). Both of these regions of the brain are of primary importance in the regulation of feeding. These findings suggest that central GLP-1 is a new physiological mediator of satiety.

Animals↗
PubMed1996

Adrenomedullin inhibits feeding in the rat by a mechanism involving calcitonin gene-related peptide receptors.

The central effect of adrenomedullin on feeding was investigated in fasted rats. After intracerebroventricular administration, adrenomedullin decreased 2-h food intake in a dose-dependent manner. A dose of 1.7 nmol adrenomedullin decreased 2-h food intake by 57%. Adrenomedullin shares sequence homology with calcitonin gene-related peptide (CGRP), a central anorectic agent, and binding sites for both are present in the hypothalamus. Adrenomedullin competed for [125I]adrenomedullin- and [125I]CGRP-binding sites in hypothalamic membranes. The Kd for the [125I]adrenomedullin-binding site was 0.54 +/- 0.07 nM, with a binding capacity of 214 +/- 27 fmol/mg membrane protein (n = 3). CGRP and the CGRP receptor antagonist CGRP-(8-37) at concentrations up to 1 microM did not compete at these sites. The Kd for the CGRP-binding site was 0.10 +/- 0.02 nM, with a binding capacity of 250 +/- 31 fmol/mg, and the Ki values for adrenomedullin and CGRP-(8-37) were 4.6 +/- 2.1 and 4.0 +/- 1.6 nM, respectively (n = 3). Thus, adrenomedullin showed high affinity binding at both adrenomedullin- and CGRP-binding sites. To establish whether adrenomedullin reduces feeding via CGRP receptors, we coadministered adrenomedullin (1.7 nmol) and CGRP-(8-37) (30 nmol). The reduction in 2-h food intake induced by adrenomedullin was 50% inhibited by CGRP-(8-37). These results show that adrenomedullin decreases food intake in the rat, and this effect is mediated at least in part via CGRP receptors.

Adrenomedullin↗
PubMed1995

A large volume spacer significantly reduces the effect of inhaled steroids on bone formation.

Inhaled steroids are increasingly advocated as first line treatment for mild asthma. Some studies suggest that inhaled steroids suppress bone formation as reflected by a fall in plasma osteocalcin. Spacers have been shown to increase the proportion of inhaled aerosol that is deposited in the lungs and to reduce the amount swallowed. We measured plasma osteocalcin levels to determine the effect on bone formation of inhaled beclomethasone dipropionate (BDP) with and without a 750 ml spacer in a double-blind, randomised, placebo-controlled, cross-over study. Twenty-six healthy male volunteers took BDP 500 micrograms (two puffs of Becloforte) together with two puffs of placebo, inhaled twice daily for seven days. One inhaler was taken directly while the other was inhaled through a 750 ml spacer. After a two week washout period, the inhalers were exchanged so that BDP was taken by the alternate route for a further seven days. Fasting plasma osteocalcin levels were measured at 09.00 h before and at the end of each week. After a week of BDP taken directly (without a spacer), osteocalcin levels fell from 11.8 (SEM 0.6) ng/ml to 9.5 (SEM 0.5) ng/ml (p < 0.001). After a week of BDP taken through a spacer, osteocalcin levels fell from 12.1 (SEM 0.5) ng/ml to 11.1 (SEM 0.5) ng/ml (p < 0.001). The fall in osteocalcin when a spacer was used was significantly less than when BDP was taken directly (p < 0.005). This is likely to be because the systemic effects on bone are caused by swallowed rather than inhaled BDP, and this is limited by the use of a spacer. Spacers should be more widely prescribed with inhaled steroids. Further prospective studies are indicated to evaluate whether spacers protect bone mass.

Administration, Inhalation↗
PubMed1995

Oral and inhaled corticosteroids reduce bone formation as shown by plasma osteocalcin levels.

Osteoporosis is a well-known, serious complication of long-term high-dose corticosteroid therapy. This study was performed to determine the effects of commonly used doses of oral and inhaled steroids on biochemical indices of bone formation. Initially we examined the long-term effects of oral steroids. Thirty-four outpatients with symptomatic asthma or chronic obstructive airways disease (COAD) receiving long-term oral prednisolone (mean 10.1 mg daily) were compared with 34 control subjects with asthma or COAD matched individually for age, sex, and menopausal status who were not taking oral steroids. Plasma osteocalcin concentrations were significantly lower (patients 6.3 +/- 0.1 ng/ml; control subjects 8.6 +/- 0.5 ng/ml, mean +/- SEM; p < 0.01) in patients on steroids with no difference in alkaline phosphatase. To examine the short-term effects of oral and inhaled corticosteroids, healthy male volunteers were given a 7-d course of either 15 mg oral prednisolone daily (n = 10) or 500 micrograms inhaled beclomethasone twice daily (n = 20). After 1 wk of oral prednisolone, mean plasma osteocalcin decreased from 11.8 +/- 1.1 ng/ml to 6.9 +/- 0.8 ng/ml (p < 0.001). With inhaled beclomethasone mean plasma osteocalcin decreased from 11.6 +/- 0.6 ng/ml to 9.6 +/- 0.6 ng/ml (p < 0.001) with no change in alkaline phosphatase. In doses routinely prescribed for the prophylaxis and treatment of asthma, oral and inhaled steroids suppress osteocalcin levels and may therefore inhibit bone formation. This effect is seen with short courses of steroids and also with chronic administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1994

The effect of long- and short-term corticosteroids on plasma calcitonin and parathyroid hormone levels.

The role of calcitonin and parathyroid hormone (PTH) in corticosteroid-induced osteoporosis is controversial. We therefore measured plasma calcitonin and PTH levels in 34 adults receiving chronic pharmacological corticosteroids for obstructive airways disease, and in controls matched for age, sex, menopause, and disease. In addition, the acute effect of a 7-day course of 15 mg prednisolone daily on fasting and calcium-stimulated calcitonin was studied in 10 normal male volunteers. There was no difference in calcitonin and PTH levels in the corticosteroid-treated patients when compared with controls. The corrected serum calcium was significantly higher in the steroid-treated patients (patients mean 2.40 (SEM 0.01) mmol/liter; controls mean 2.33 (SEM 0.01) mmol/liter; P < 0.001). The short course of corticosteroids in volunteers did not alter basal or stimulated calcitonin, PTH, or calcium levels. These results suggest that neither calcitonin deficiency nor PTH excess is a feature of corticosteroid-induced osteoporosis.

Adult↗
PubMed1994

Neonatal primary hyperparathyroidism masked by vitamin D deficiency.

Neonatal primary hyperparathyroidism is a life threatening disorder that is associated with severe hypercalcaemia, hypotonia, bone demineralization, fractures and respiratory distress. Treatment consists of total parathyroidectomy and without this affected infants will usually die by the age of three months. We report a patient with neonatal primary hyperparathyroidism who survived without fractures or parathyroidectomy to an age of nine months, and in whom the hypercalcaemia became masked by vitamin D deficiency. At surgery, four-gland hyperplasia was demonstrated and total parathyroidectomy followed by oral calcitriol treatment has restored well-being and normocalcaemia. An absence of skeletal complications, a survival beyond three months of age without parathyroidectomy and the masking of the hypercalcaemia by vitamin D deficiency represents a unique combination of metabolic abnormalities in a patient with neonatal primary hyperparathyroidism.

Humans↗
PubMed1987

Peptide-specific antibodies as probes of the orientation of the glucose transporter in the human erythrocyte membrane.

Antibodies were raised in rabbits against synthetic peptides corresponding to the N-terminal (residues 1-15) and the C-terminal (residues 477-492) regions of the human erythrocyte glucose transporter. The antisera recognized the intact transporter in enzyme-linked immunosorbent assays (ELISA) and Western blots. In addition, the anti-C-terminal peptide antibodies were demonstrated, by competitive ELISA and by immunoadsorption experiments, to bind to the native transporter. Competitive ELISA, using intact erythrocytes, unsealed erythrocyte membranes, or membrane vesicles of known sidedness as competing antigen, showed that these antibodies bound only to the cytoplasmic surface of the membrane, indicating that the C terminus of the protein is exposed to the cytoplasm. On Western blots, the anti-N-terminal peptide antiserum labeled the glycosylated tryptic fragment of the transporter, of apparent Mr = 23,000-42,000, showing that this originates from the N-terminal half of the protein. The anti-C-terminal peptide antiserum labeled higher Mr precursors of the Mr = 18,000 tryptic fragment, although not the fragment itself, indicating that the latter, with its associated cytochalasin B binding site, is derived from the C-terminal half of the protein. Antiserum against the intact transporter recognized the C-terminal peptide on ELISA, and the Mr = 18,000 fragment but not the glycosylated tryptic fragment on Western blots.

Animals↗
PubMed1985

Characterisation of monoclonal antibodies which specifically recognise the human erythrocyte glucose transport protein.

Two monoclonal antibodies (mabs) of subclass IgG1 have been raised against the human erythrocyte glucose transport protein. The mabs bound to the purified glucose transporter in both its membrane-bound and detergent-solubilised forms. However, they exhibited little or no binding to the detergent-solubilised nucleoside transport protein, which is present as a minor contaminant in the glucose transport protein preparation. Both mabs inhibited the binding of cytochalasin B to the glucose transport protein, reducing the affinity of this binding by greater than 2-fold. Each mab labelled the transporter polypeptide on Western blots both before and after treatment of the protein with endoglycosidase F, indicating that the epitopes recognised were located on the protein moiety of the glycoprotein. However, the mabs did not bind to the large fragments produced by tryptic or chymotryptic digestion of the native protein, although both mabs were shown to bind to sites on the cytoplasmic surface of the erythrocyte membrane.

Animals↗
PubMedDate not supplied

Venepuncture causes rapid rise in plasma ACTH.

Serum cortisol and adrenocorticotropin (ACTH) levels were measured on nine sleeping volunteers at midnight, before and after the stress of being woken and exposed to a single standard venepuncture. In six volunteers, plasma ACTH levels were raised within 90 seconds of venepuncture, while it remained undetectable in the other three. Cortisol levels began to rise within 4 minutes. ACTH and cortisol levels may be greatly altered by the stress of venesection. Plasma ACTH measured after a difficult venesection in a subject with poor venous access may be misleading.

Adrenocorticotropic Hormone↗