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Biomedical subjects

R Kumar

Publications and source records attributed to R Kumar.

At least 1,351 records · Page 75Linked to original sources
PubMed1983

Differential susceptibility of mono- and di-O-alkyl ether phosphoglycerides to acetolysis.

The effectiveness of acetolysis as a tool in structural characterization of mono- and di-O-alkyl phosphoglycerides was investigated. Surprisingly, it was found that the di-O-alkyl phosphoglycerides were resistant to attack during acetolysis, whereas the mono-ether types, with a free hydroxyl function or an ester on carbon-2, were easily attacked at the glycerol-phosphate bond. On the other hand, Vitride reduction occurred readily with the mono-ether or di-ether phosphoglycerides. The implications of these findings as they relate to identification of ether phospholipids in tissues are discussed.

Acetates↗
PubMed1982

Evidence for a monoglucuronide of 1,25-dihydroxyvitamin D3 in rat bile.

We have isolated and characterized a monoglucuronide fraction of 9,10-secocholesta-5,7,10(19)triene-1 alpha, 3 beta, 25-triol, 5,6-cis isomer (1,25-dihydroxyvitamin D3) from rat bile. Polar radioactive metabolites of 1,25-dihydroxyvitamin D3 were purified by a sequence of chromatographic procedures which utilized Amberlite XAD-2, diethylaminohydroxypropyl Sephadex LH-20, liquid-liquid partition on paper, and reverse phase chromatography on C-18 microparticulate columns. A purified radioactive substance showed maximal absorbance at 264 nm, indicating the presence of a triene in the 5,6-cis configuration. Mass spectrometry by fast atom bombardment of the product demonstrated an ion at m/z 637 atomic mass units that is consistent with a natriated sodium salt of a monoglucuronide of 1,25-dihydroxyvitamin D3 ([MNa]Na+). Following methylation of the carboxylic acid group and formation of trimethylsilyl ethers of the hydroxyl groups, the fragmentation pattern of the product was compatible with that of a monoglucuronide of 1,25-dihydroxyvitamin D3. The intact metabolite was treated with beta-glucuronidase and the aglycon was isolated by chromatography on microparticulate silica. The aglycon co-migrated with authentic 1,25-dihydroxyvitamin D3 during chromatography and it gave a mass fragmentation pattern consistent with 1,25-dihydroxyvitamin D3. The aglycon was bound by an intestinal cytosol receptor with essentially the same affinity as 1,25-dihydroxyvitamin D3. These findings indicate that bile contains a monoglucuronide of 1,25-dihydroxyvitamin D3.

Animals↗
PubMed1982

Modified excretory urography in prehysterectomy patients.

A retrospective (520 patients) and prospective study (100 patients) of prehysterectomy patients was done to determine the role of preoperative excretory urography. Potentially useful information was provided by the urogram in only a small number of patients (7.4%). It is arguable whether or not preoperative intravenous urography should be done in these patients. However, since most of these patients routinely undergo this study, we suggest that a curtailed urogram consisting of a KUB film, a postinjection 15-minute prone film, and a supine film of the contrast-filled urinary bladder is adequate for preoperative screening, thereby minimizing cost and radiation to the patient.

Female↗
PubMed1982

Synthesis and biological activity of vitamin D2 3 beta-glucosiduronate and vitamin D2 3 beta-sulfate: role of vitamin D2 conjugates in calcium homeostasis.

To ascertain the physiologic function of vitamin D2 conjugates in calcium homeostasis, we synthesized vitamin D2 3 beta-glucosiduronate and vitamin D2 3 beta-sulfate in pure form and tested their biological activity in vitamin D deficient rats fed a low calcium diet. Vitamin D2 3 beta-glucosiduronate was active in promoting calcium transport in the intestine at a dose of 100 pmol per rat. It increased calcium mobilization from bone and soft tissue at a dose of 1000 pmol per rat. This conjugate was less active than equimolar doses of vitamin D2. These results demonstrate that vitamin D2 3 beta-glucosiduronate can be utilized by the rat as a source of vitamin D. In contrast, vitamin D2 3 beta-sulfate was biologically inert. It failed to increase calcium transport in the duodenum of vitamin D deficient rats except at the highest doses tested (greater than 100,000 pmol/rat). It was similarly ineffective in increasing calcium mobilization from bone and soft tissue. Our results lead us to conclude that vitamin D2 3 beta-glucosiduronate is probably utilized by the rat after hydrolysis to the free sterol; on the contrary, the sulfate is not biologically active except at the highest doses tested.

Animals↗
PubMed1982

Synthesis and biological activity of 3 beta-hydroxy-9,10-secopregna-5,7,10[19]-triene-20-one: a side chain analogue of vitamin D3.

The synthesis, biological and antagonistic activity of 3 beta-hydroxy-9,10-secopregna-5,7,10[19]-triene-20-one (20-oxopregnacalciferol, 7) a shortened side chain analogue of vitamin D3, are described. At the highest dose tested the analogue was found to have small though significant bone and soft tissue mobilization activity; no significant increase in intestinal calcium transport was noted. The compound was found to possess no antagonistic activity against vitamin D3.

Animals↗
PubMed1982

Decreased intestinal calcium absorption in vivo and normal brush border membrane vesicle calcium uptake in cortisol-treated chickens: evidence for dissociation of calcium absorption from brush border vesicle uptake.

The influence of cortisol on intestinal calcium transport was studied in isolated duodenal loops and brush border membrane (BBM) vesicles of vitamin D-deficient or replete chickens. Four- to five-week-old vitamin D-deficient cockerels were dosed intraperitoneally with 1 microgram of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] alone 15 hr before sacrifice or in combination with 1, 3, or 5 mg of cortisol 24 and 48 hr before sacrifice. After a 1-microgram dose of 1,25-)OH)2D3 the in situ intestinal ligated loop technique revealed a 60% increase in calcium absorption compared to control birds (P less than or equal to 0.001). However, the administration of cortisol in various doses (3 and 5 mg) to chickens given 1,25-(OH)2D3 resulted in significant decreases in intestinal calcium transport in vivo (P less than or equal to 0.05; P less than or equal to 0.05). When intestinal BBM vesicles were prepared from birds treated in a manner identical with that described above, there was no observable difference between calcium uptake in BBM vesicles of the 1,25-(OH)2D3-treated birds and that of the cortisol plus 1,25-(OH)2D3-treated birds. 1,25-(OH)2D3-treated and 1,25-(OH)2D3 plus cortisol-treated chicks had intestinal BBM vesicle uptakes that were significantly greater than those of vitamin D-deficient controls (P less than or equal to 0.02; P less than or equal to 0.025). These data show that in vivo intestinal calcium transport may be markedly reduced in the presence of normal intestinal BBM vesicle calcium uptake. This suggest that factors other than BBM calcium uptake (e.g., protein synthesis or contraluminal membrane events) play an important role in the movement of calcium from the intestinal lumen into the bloodstream and extracellular fluid of the organism.

Animals↗
PubMed1982

Modulation of adenosine 3', 5'-cyclic monophosphate-dependent protein kinase in skin.

Incubation in vitro of full-thickness guinea-pig skin with epinephrine or histamine resulted in the formation of adenosine 3', 5'-cyclic monophosphate (cyclic AMP) and increase in the cyclic AMP-dependent protein kinase activity ratio. The effect was dose-dependent between 10(-5) and 10(-3) M concentration of the agents. Histamine antagonists, diphenhydramine (H1) and cimetidine (H2) prevented stimulation by histamine in a dose-dependent manner suggesting the presence of both types of receptors in full-thickness skin. Cyclic AMP accumulation with a concomitant increase in protein kinase activity denotes that phosphoproteins may have an important role in skin biology.

Animals↗
PubMed1982

Time passes slowly for patients with depressive state.

Twenty-three depressive inpatients and the same number of matched non-psychiatric controls were examined on three occasions - following admission, 14 days after, and 28 days after the admission - by administering a self-rating questionnaire of time awareness and Hamilton's Rating Scale for Depression (HRS). The patients were found to feel time passing slowly. This was correlated with the severity of depression expressed as the total HRS score. No significant differences emerged between diagnostic groups, namely endogenous depression, neurotic depression, and schizophrenia or paranoid state with depressive symptoms. Correlations of the time awareness with symptoms listed in the HRS also denied a specific relationship of time awareness to specific diagnoses. The subjective feeling of slow time flow reflects, therefore, the depth of depressive state in general, which is nevertheless not specific to any diagnostic subcategory.

Adult↗
PubMed1982

Physiology of 24,25-dihydroxyvitamin D3 in normal human subjects.

We determined the metabolic clearance and production rates of 24,25-dihydroxyvitamin D3 in four normal healthy adults. We also examined the excretion of radioactivity in stool, urine, and bile after the intravenous administration of 24,25-[3H]dihydroxyvitamin D3 to human subjects. 24,25-Dihydroxyvitamin D3 is rapidly cleared from the plasma with a half-life of approximately 390 +/- 25 min (mean +/- SE). The metabolic clearance rate of 24,25-dihydroxyvitamin D3 was 9.2 +/- 1.5 liters/day with a production rate of 26.4 +/- 7.2 micrograms/day (mean +/- SE). Within 1 day 13.0 +/- 4.2% (mean +/- SE) of the administered dose had appeared in the stool; by day 7, 48.8 +/- 2.7% of the dose had appeared in the feces. Within 24 hr, 6.4 +/- 0.8% of the administered dose appeared in the urine; 7.4 +/- 1.8% of the dose had appeared in the urine within 2 days. The biliary excretion of 24,25-dihydroxyvitamin D3 was studied in two subjects. By 8 h, 15.3 +/- 1.3% of the administered dose had appeared in the bile. The metabolites present in bile, feces, and urine were much more polar than 24,25-dihydroxyvitamin D3. These results demonstrate that 24,25-dihydroxyvitamin D3 is rapidly cleared from plasma and is excreted in the feces (probably via the bile) and urine of normal human subjects.

24,25-Dihydroxyvitamin D 3↗
PubMed1982

Differential effects of endocrine dysfunction on the axial and the appendicular skeleton.

In 100 patients with various types of endocrine dysfunction, we measured bone mineral density (BMD) at the midradius (greater than 95% cortical bone) and distal radius (75% cortical and 25% trabecular bone) by single photon absorptiometry and at the lumbar spine (greater than 66% trabecular bone) using the new technique of dual photon absorptiometry. BMD in each endocrine disorder deviated in at least one site from the sex-specific age regression of 187 normal subjects. For patients with primary hyperparathyroidism, hypercortisolism, and hyperthyroidism this deviation was negative (suggesting bone loss), whereas for patients with secondary hyperparathyroidism due to chronic renal failure, acromegaly, and postsurgical hypoparathyroidism it was positive (suggesting bone gain). When all six states of endocrine dysfunction were compared concomitantly by multivariate analysis of variance, the profile of the changes in BMD differed significantly (P less than 0.001), indicating a nonuniform response of bone to the various hormonal alterations. When values for BMD at each of the three scanning sites were compared the midradius and distal radius did not differ significantly; either of the radius measurements, however, differed significantly (P less than 0.001) from the lumbar spine. Thus, the BMD of the axial skeleton cannot be reliably predicted from measurements made in the appendicular skeleton. We conclude that the effects of endocrine dysfunction on bone density are complex and are both disease and site specific.

Absorptiometry, Photon↗