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Biomedical subjects

R Kumar

Publications and source records attributed to R Kumar.

At least 235 records · Page 13Linked to original sources
PubMed1992

Human nutrition in cold and high terrestrial altitudes.

The calorie and nutritional requirements for a man working in an alien hostile environment of cold regions and high altitude are described and compared to those of normal requirements. Carbohydrates, fats and vitamins fulfilling the caloric and nutritional requirements are generally available in adequate amounts except under conditions of appetite loss. However, the proteins and amino acids should be provided in such a way as to meet the altered behavioral and metabolic requirements. Work in extreme cold requires fulfilling enhanced calorie needs. In high mountainous regions, cold combined with hypoxia produced loss of appetite and necessitated designing of special foods.

Altitude↗
PubMed1992

Intracardiac echocardiography during simulated aortic and mitral balloon valvuloplasty: in vivo experimental studies.

The feasibility of intracardiac echocardiography with a low-frequency transducer to assess catheter position and detect complications during experimental aortic and mitral balloon valvuloplasty was studied in 10 dogs. Intracardiac echocardiography was performed with a transesophageal echocardiographic probe placed in the right atrium. In all instances high-quality images of cardiac structures were obtained. The guide wire and balloon catheter were clearly seen as they crossed the valves. With inflation the balloon was seen as a hyperechoic structure. Doppler echocardiography documented aortic regurgitation after inflations. Acute pericardial effusion was instantly detected. It is concluded that intracardiac echocardiography is a potentially useful technique for cardiac imaging, assessing wire and balloon catheter position, evaluating valvular regurgitation, and instantly detecting acute pericardial effusion. Further research in humans with low-frequency, catheter-based transducers needs to be performed.

Animals↗
PubMed1992

Vitamin D and mineral deficiencies increase the plasma membrane calcium pump of chicken intestine.

The basolateral membrane of the enterocyte was previously shown to contain an adenosine triphosphate-dependent calcium pump. Using immunological procedures, the localization of the Ca2+ pump in chick intestine, and the effect of dietary variables on the concentration of the pump, were studied. A monoclonal antibody produced against the human erythrocyte calcium pump was shown to cross-react with a chick intestinal Ca2+ pump epitope. The most intense staining of intestinal tissue, as determined immunohistochemically, occurred at the basolateral membrane of the duodenum, jejunum, ileum, and colon, with minor staining elsewhere. By the Western blotting procedure, vitamin D repletion of vitamin D-deficient chicks was shown to significantly increase the concentration of the Ca2+ pump epitope of duodenal, jejunal, and ileal mucosa by a factor of 2-3. Chicks were also fed diets deficient in calcium or phosphorus, a situation known to result in the stimulation of the synthesis of calbindin-D28k and an enhancement of the efficiency of Ca2+ absorption. Adaptation of the chicks to these deficient diets was verified by an increase in intestinal levels of calbindin-D28k, and is now shown to increase the Ca2+ pump epitope. From these immunological studies, it seems apparent that dietary variables that enhance intestinal Ca2+ absorption also increase the amount of the intestinal basolateral Ca2+ pump.

Animals↗
PubMed1992

Contribution of psychological and social factors to psychotic and non-psychotic relapse after childbirth in women with previous histories of affective disorder.

Twenty-six women with a history of bipolar or schizoaffective disorder, 17 women with histories of major depressive disorder and 45 control women without any previous psychiatric history were assessed in the 9th month of pregnancy on selected psychosocial measures. No subject was a 'case' as defined by the Research Diagnostic Criteria (RDC) from this time until the delivery. Within 6 months postpartum, 22 (51%) of the women with histories of mental illness were categorised as having relapsed (RDC case). Twelve women developed a psychosis (mania, hypomania or schizomania) and these illnesses occurred only in women with histories of affective or schizoaffective psychosis whereas 10 other women who became depressed after delivery came equally from the women with histories of psychosis (N = 5) as from those with histories of major depression (N = 5). Three (7%) control women also developed postpartum non-psychotic depressive disorders. Multivariate analyses suggest that different psychosocial factors contribute to the recurrence of affective and schizoaffective psychosis after delivery as opposed to non-psychotic postpartum affective disorders. A non-psychotic illness was predicted by antenatal neuroticism and a severe life event before illness onset. A recurrence of psychosis postpartum was predicted by a history of mania, hypomania or schizomania, a more recent psychiatric admission and reported marital difficulties. In this sample of women, life stress led to postpartum depression irrespective of the subject's past history and the high rates of recurrence of affective or schizoaffective psychosis (47%) probably mainly reflected a pre-existing physiological or psychological vulnerability which may have been exacerbated by, or contributed to, marital difficulties.

Bipolar Disorder↗
PubMed1992

Pernicious anaemia as a risk factor for osteoporosis.

1. If gastric acid is necessary for the absorption of dietary calcium, the total absence of gastric acid secretion that occurs in pernicious anaemia could result in bone loss. To investigate this, we measured calcium absorption and bone density in 21 postmenopausal women (ages 51-76 years) with pernicious anaemia and in 24 normal postmenopausal women (ages 51-79 years). 2. Relative to the normal women, in the women with pernicious anaemia the bone mineral density of the lumbar spine was decreased by 16% (P less than 0.001). 3. After adjustment for age and body weight, lumbar spine bone mineral density correlated with the serum concentration of group 1 pepsinogens (a group of proteins produced by the gastric fundus) (r = 0.61, P less than 0.01). 4. Despite achlorhydria, the women with pernicious anaemia had normal true fractional calcium absorption and normal serum levels of parathyroid hormone and 1,25-dihydroxyvitamin D. 5. We conclude that gastric acid is not required for the absorption of dietary calcium. Thus, the loss of cancellous bone must be caused by some mechanism yet to be identified.

Achlorhydria↗
PubMed1992

Use of the computed tomographic scan in Japanese encephalitis.

Fourteen children with laboratory-confirmed Japanese encephalitis were given cranial computed tomographic (CT) scans six to 30 days after the onset of illness. The findings were variable; there was a generalized decrease in attenuation values, three patients showed features of cerebral atrophy, and four others had normal scans. The findings appeared to relate to both the severity and the stage of the illness at the time the scans were made. CT would appear to be of little use in making a specific diagnosis of Japanese encephalitis.

Brain↗
PubMed1992

Caffeine-derived N-nitroso compounds--I: Nitrosatable precursors from caffeine and their potential relevance in the etiology of oesophageal and gastric cancers in Kashmir, India.

Salted tea prepared in Kashmir by adding sodium bicarbonate shows high methylating activity (equivalent to 3 p.p.m. N-methylnitrosourea) upon in vitro nitrosation. Pure caffeine treated under conditions of the tea preparation formed caffeidine and caffeidine acid. We report here the formation of two new compounds, mononitrosocaffeidine, an asymmetric nitrosamine, and dinitrosocaffeidine, a N-nitrosamide, on in vitro nitrosation of caffeidine. Mononitrosocaffeidine is also found after nitrosation of the typical Kashmir tea. The nitrosation of caffeidine acid produced N,N'-dimethyl-parabanic acid, mononitrosocaffeidine and N,N'-dimethyl-N-nitrosourea. In view of the well-known structure-activity relationships of these N-nitroso compounds, their possible endogenous formation due to high consumption of salted tea may be a critical risk factor for the high occurrence of oesophageal and gastric cancers in Kashmir.

Bicarbonates↗
PubMed1992

Increased exposure to dietary amines and nitrate in a population at high risk of oesophageal and gastric cancer in Kashmir (India).

Analytical data on aliphatic amines and nitrate from the most commonly used fresh and sun-dried vegetables, red chillies and a widely consumed beverage, salted tea, are presented from a high risk area for oesophageal and gastric cancer in Kashmir. Exposure estimates for the adult population show that high consumption of boiled Brassica vegetables leads to a high nitrate intake of 237 mg/day. The frequent consumption of hot salted tea is shown to result in exceptionally high exposure to methylamine (1200 micrograms/day), ethylamine (14,320 micrograms/day), dimethylamine (150 micrograms/day) and diethylamine (400 micrograms/day). The indiscriminate use of red chillies in the area leads to exposure to dimethylamine (280 micrograms/day), pyrrolidine (517 micrograms/day) and methylbenzylamine (40 micrograms/day). This is to our knowledge the first report where a chronic exposure to methylbenzylamine has been shown in a population at high risk of oesophageal cancer.

Adult↗
PubMed1992

Cloning and expression of the murine gene and chromosomal location of the human gene encoding N-acetylglucosaminyltransferase I.

A mouse cDNA clone previously isolated from an F9 teratocarcinoma cell library and shown to confer N-acetylglucosaminyltransferase I (GlcNAc-TI) activity on Lec1 Chinese hamster ovary (CHO) cell transfectants [Kumar, R., Yang,J., Larsen,R.D. and Stanley,P. (1990) Proc. Natl. Acad Sci. USA, 87, 9948-9952] has been sequenced. The nucleotide and deduced amino acid sequences are highly homologous to previously described human and rabbit GlcNAc-TI cDNAs. A 1250 bp portion of the mouse cDNA encoding all but the first 34 amino acids of the deduced protein sequence was inducibly expressed in Escherichia coli and gave rise to a prominent fusion protein of mol. wt approximately 45 kDa whose presence correlated with high levels of GlcNAc-TI activity in cell lysates. Probes generated from the cDNA were used to show that the GlcNAc-TI gene is present in a single copy in mammals and that a homologous gene was not detectable (under low-stringency hybridization conditions) in DNA from yeast, sea urchin, Drosophila or Chaenorhaditis elegans. Genomic DNA clones that hybridized to probes generated from the GlcNAc-TI cDNA were isolated from a mouse liver library. Restriction analyses, Southern hybridization and DNA sequence analyses of subcloned genomic DNA fragments and a polymerase chain reaction (PCR) product provided evidence that the coding and 3' untranslated regions of the cDNA reside in a single exon. However, the mouse GlcNAc-TI gene (Mgat-1) includes at least one additional exon 5' of the coding region. Southern analyses of DNA from mouse-human somatic cell hybrids and in situ hybridization were used to locate the human GlcNAc-TI gene (MGAT-1) between positions q31.2 and q31.3 on chromosome 5, a region of chromosome 5 that is syntenic with a region of mouse chromosome 11. Northern analyses of adult mouse tissues revealed two GlcNAc-TI gene transcripts that are differentially expressed in different tissues.

Amino Acid Sequence↗
PubMed1992

Intestinal calcium transport and calcium extrusion processes at the basolateral membrane.

The intestinal absorption of calcium has been proposed to occur by the transcellular transfer of Ca2+ through the enterocyte proper and between the cells of the intestinal epithelium, i.e., the paracellular path. Attention in this report is given to the transcellular models of Ca2+ absorption and, more specifically, the Ca2+ extrusion events occurring at the basolateral membrane. These extrusion processes include the operation of an ATP-dependent Ca2+ pump and a Na+/Ca2+ exchanger, as well as exocytosis as the terminal event in a proposed vesicular transport mechanism. Evidence for the presence of an ATP-dependent Ca2+ pump at the basolateral membrane is documented and illustrated with biochemical and immunological data from studies on the avian intestinal basolateral membrane. As shown immunohistochemically, the Ca2+ pump was primarily localized on the enterocyte basolateral membrane. The ATP-dependency and vitamin D enhancement of Ca2+ uptake by isolated basolateral membrane vesicles are shown. Western blot analysis of intestinal mucosa, by using a monoclonal antibody produced against the erythrocyte Ca2+ pump, indicated that the number of pump units is increased by 1,25-dihydroxycholecalciferol. The possible involvement of calbindin-D28K as a direct stimulator of the Ca2+ pump is discussed, and the quantitative relationship between Ca2+ transport rates and Ca2+ pumping activity has been estimated. Information related to the basolateral membrane Na+/Ca2+ exchanger and the vesicular transport model of Ca2+ absorption is also briefly reviewed.

Animals↗
PubMed1992

Prenatal growth curves corrected for certain genetic and environmental factors.

Factor analysis for non-orthogonal data was done to assess the straight and interaction effects of certain genetic and environmental factors on birth weight. While the interaction effects did not assume any significance, straight effects of gestational age, parity, mother's weight, and sex were significant in influencing the birth weight. Mother's height and socio-economic status of the family had no significant effect on birth weight. Step-up multiple regression analysis showed that contribution to the total variance explained (R2 x 100 = 29.7 per cent) in birth weight was about 15, 7, 5, and 2 per cent, respectively, from gestational age, parity, mother's weight, and sex of the baby. Correction of the mean weight curve was done by successive graphic approximation method and residuals were further minimized.

Birth Weight↗
PubMed1992

Is small bowel bacterial overgrowth of pathogenic significance in persistent diarrhea?

Bacterial overgrowth in the upper small intestine is postulated to cause persistent diarrhea. We compared the fecal and upper intestinal flora in 82 patients with persistent diarrhea aged < or = 36 months and weight-for-length < or = 90% of National Center for Health Statistics standards (NCHS) and 39 non-diarrheal children with age < or = 36 months, nutritionally matched with the patients and residing in the same environment. In the age groups < or = 12 months and > 12 months the duodenal fluid bacterial counts > or = 10(5)/ml were found with similar frequency in patients and controls for aerobic (p = 0.33; p = 0.1) and anaerobic (p = 1.0; p = 1.0) bacteria. However, the duodenal isolation rates of any aerobic bacteria (p < 0.05) without regard to counts and Enterobacteriaceae (p = 0.06) were higher in patients than in controls. Colonization with Enterobacteriaceae was directly correlated with increased stool weight over a 7-day observation period (p < 0.05; p < 0.01). One or more pathogens were isolated in the feces of 58% of the patients and 43.8% of the controls. Enteroadherent E. coli of the localized [EAEC-L] (p < 0.01) and aggregative [EAggEC] (p = 0.22) phenotypes were isolated more commonly from the feces of patients. The duodenal fluid detection rates for Klebsiella were significantly greater (p < 0.01) in patients, while Giardia lamblia was detected more commonly in the duodenal fluid of controls (p < 0.01). The presence of specific pathogens in the feces did not seem to be related to the extent of small bowel colonization.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Chondrosarcoma: MR imaging with pathologic correlation.

Magnetic resonance (MR) images of 21 surgically confirmed chondrosarcomas were retrospectively reviewed in conjunction with plain radiographs and computed tomographic scans and correlated with pathologic findings. The tumors appeared lobulated, and signal intensity, as analyzed visually (intermediate on T1-weighted, high on T2-weighted images), was similar for all lesions, regardless of pathologic type. Size of lesion was not an indicator of grade. The appearances of mesenchymal and dedifferentiated chondrosarcomas mimicked that of conventional chondrosarcoma. Extraskeletal chondrosarcoma was visualized as a lobulated soft-tissue mass. In all cases, MR imaging accurately depicted intraosseous and soft-tissue extent of tumor noted at surgery and pathologic examination. Histologic type or grade of chondrosarcoma generally cannot be characterized on the basis of visual analysis of signal intensity noted on routine MR images. However, MR imaging is excellent for exact delineation of tumor extent.

Bone Neoplasms↗
PubMed1992

Women whose mental illnesses recur after childbirth and partners' levels of expressed emotion during late pregnancy.

Expressed emotion (EE) in the partners of 25 pregnant women with a history of psychosis or severe depression and in 13 pregnant control subjects without any previous psychiatric disorder was assessed in the ninth month of pregnancy. At this time, no patient presented as a case according to RDC. Eleven subjects with a history of psychiatric disorder experienced a further episode of illness in the six months following delivery. Partners of women who became ill had made fewer critical and positive comments about their wives during the pregnancy than the partners of women who remained well. Poor self-rated social adjustment in the partners was also predictive of recurrence of illness after delivery.

Adult↗
PubMed1992

Skeletal responsiveness to endogenous parathyroid hormone in postmenopausal osteoporosis.

To test the hypothesis that increased sensitivity of bone to PTH may be a major cause of bone loss in postmenopausal osteoporosis, we induced acute calcium deprivation and measured bone responsiveness to endogenous PTH under physiological conditions. Eighteen osteoporotic and 17 normal postmenopausal women with similar dietary calcium intakes were studied before and after 4 days of calcium deprivation (dietary calcium 230 mg/day and treatment with a calcium-binding agent). Despite decreased serum PTH values, the baseline indices of bone turnover (serum osteocalcin level and 24-h urinary excretions of total deoxypyridinoline/creatinine and pyridinoline/creatinine corrected for total body bone mineral content), were higher in the osteoporotic women. During calcium deprivation, the changes in bone markers from baseline were similar in both groups, except for serum osteocalcin and serum type I procollagen carboxy-terminal propeptide. Changes in the normal and the osteoporotic women were, respectively: serum ionized calcium concentration decreased 3.3% and 2.1%; serum intact PTH increased 65% and 56%; plasma 1,25-dihydroxyvitamin D3 increased 29% and 39%; pyridinoline/creatinine increased 12% and 11%; and deoxypyridinoline/creatinine increased 27% and 12%. Serum osteocalcin increased 2.3% and serum procollagen carboxy-terminal propeptide decreased 9.4% in the normal women but did not change in the osteoporotic women. We conclude that women with postmenopausal osteoporosis do not have increased skeletal responsiveness to PTH compared with age-comparable normal postmenopausal women. Therefore, the higher bone turnover in postmenopausal osteoporosis, despite lower serum intact PTH concentration, must be due to other factors. Assessment of acute changes in bone turnover during physiological alterations in endogenous PTH secretion is a useful test in metabolic bone diseases.

Bone Density↗
PubMed1992

MR imaging of clival and paraclival lesions.

A wide spectrum of diseases involve the clivus and paraclival structures. Primary neoplasms, metastatic tumors, and inflammatory, vascular, and hematopoietic disorders are the most common abnormalities to arise from or directly involve the clivus. MR imaging exquisitely shows and helps characterize the diseases that affect this area. Sagittal and coronal MR imaging allows precise localization and evaluation of the signal characteristics of a mass, enabling a more specific diagnosis. The multiplanar capabilities of MR imaging provide superb visualization of the adjacent cranial nerves and vascular structures, aiding in surgical planning and radiation therapy. In this pictorial essay, the MR imaging, CT, and conventional radiographic findings of various clival and paraclival lesions are illustrated.

Adult↗