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L C Garg

Publications and source records attributed to L C Garg.

96 records · Page 6Linked to original sources
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Multiple functional enhancer motifs of rat ribosomal gene.

Previous studies from this laboratory have characterized a 174 bp enhancer element which is located 2 kb upstream of the initiation site. Half of the enhancer action is controlled by a 37 bp element at the 3' end of the 174 bp region. We now report that a 43 bp adjacent domain which is located upstream of the 37 bp element constitutes an additional motif of the rDNA enhancer. When the plasmid consisting of the 43 bp DNA upstream of the rDNA core promoter was transcribed in a fractionated rat tumor cell extract (fraction DE-B), transcription of rDNA was augmented 4 fold. Electrphoretic mobility shift and DNAase I footprinting analyses showed that the purified 37 bp enhancer (E1)-binding protein, (E1BF) not only interacted with the enhancer motif E1 but also interacted with the neighbouring 43 bp enhancer domain E2. The specificity of the binding was demonstrated by competition with unlabelled 37 bp and 43 bp fragment and lack of competition with nonspecific DNAs in the mobility shift assay. These studies have shown that a single pol I transcription factor can bind to multiple enhancer domains with no significant sequence homologies and such multiple interactions may result in maximal transcription of ribosomal gene from the core promoter.

Animals↗
PubMedDate not supplied

Differences in renal tubular Na-K-adenosine triphosphatase in spontaneously hypertensive and normotensive rats.

Na-K-adenosine triphosphatase (ATPase) activity in seven specific renal tubular segments of 8-week-old spontaneously hypertensive rats (SHR) was compared with age-matched normotensive Wistar-Kyoto rats (WKY). Systolic blood pressure in 8-week-old SHR were significantly higher than in age-matched WKY. Na-K-ATPase activity in proximal convoluted tubule and outer and inner medullary collecting ducts was significantly higher in SHR than in WKY. On the other hand, medullary thick ascending limbs had reduced Na-K-ATPase activity in SHR. The possible role of the abnormal pattern of renal tubular Na-K-ATPase in the development of hypertension in SHR remains to be determined.

Animals↗
PubMedDate not supplied

Suppression of ouabain-insensitive K-ATPase activity in rabbit nephron segments during chronic hyperkalemia.

Recently, we demonstrated that an ATPase stimulated by K (and not inhibited by ouabain, Na-K-ATPase inhibitor) is present in the connecting tubule (CNT) and collecting duct segments of the rabbit. In this study, we determined the effects of high- and low-K diet on K-ATPase activity in the CNT and collecting duct segments of rabbit. One group of animals was given a low-K diet (34 mEq/kg diet) and the other group was given a high-K diet (700 mEq/kg diet) for 1 week. K-ATPase activity was measured by a microfluorometric assay in which ATP hydrolysis is coupled to oxidation of NADH. Low-K animals had plasma K = 3.1 +/- 0.2 as compared with 5.5 +/- 0.5 mEq/l in high-K animals. Low-K animals had significant K-ATPase activity in CNT, CCD (cortical collecting duct) and MCD (medullary collecting duct). On the other hand, K-ATPase activity in all 3 segments from high-K animals was not significantly different from zero. These results support a hypothesis that chronic K loading suppresses the ouabain-insensitive K-ATPase in the distal nephron.

Adenosine Triphosphatases↗
PubMedDate not supplied

Effects of low-potassium diet on N-ethylmaleimide-sensitive ATPase in the distal nephron segments.

The present study was undertaken to investigate whether or not potassium deficiency influences N-ethylmaleimide (NEM)-sensitive ATPase in the distal nephron segments of the rat. One group of animals was fed a low-K diet, whereas the normal K-group was given the same diet after supplementation with KCl. The nephron segments examined were: the medullary and cortical thick ascending limbs, the distal convoluted tubule, and the cortical, outer and inner medullary collecting ducts. NEM-sensitive ATPase activity in microdissected segments was measured by a fluorometric microassay. The plasma K+ concentration in the low-K group was 3.1 +/- 0.3 mEq/l compared with 4.2 +/- 0.1 mEq/l in the normal-K group. NEM-sensitive ATPase activity in the outer medullary collecting duct of low-K diet animals was significantly greater than in normal-K animals. There was no significant difference in NEM-sensitive ATPase activity between the two groups of animals in the other nephron segments examined. It is suggested that NEM-sensitive H-ATPase activity in the outer medullary collecting duct is modulated by the potassium status of the animal.

Animals↗