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T N Pullman

Publications and source records attributed to T N Pullman.

At least 19 recordsLinked to original sources
PubMed1999

Erythropoietin is produced by tubular cells of the rat kidney.

The cellular site of erythropoietin (epo) production within the mammalian kidney is still not completely understood. In the present study, we examined the expression of epo mRNA in microdissected rat nephron segments by RT-PCR after induction of epo expression with cobalt chloride. Erythropoietin mRNA was not detected in nephron segments from saline injected rats. In cobalt chloride injected animals, epo mRNA was found in the majority of samples from the cortical region of the nephron, PCT, and CAL. Medullary tubule preparations (MCT and MAL) were mostly negative for epo mRNA, and glomeruli were uniformly negative. The induction of epo transcripts in tubular cells by cobalt chloride was paralleled by stimulation of the major transport enzyme in the kidney, namely, Na-K ATPase in a tubular profile similar to that of induction of epo transcripts. These results support some earlier findings that epo gene expression in response to cobalt salt stimulation of rat kidney occurs in transporting tubular epithelial cells.

Adenosine Triphosphatases↗
PubMed1995

Renal reserve: early work and personal reminiscences from the 1940s.

The circumstances under which the author entered the field dealing with the effects of dietary protein intake on renal functions are discussed. The general state of knowledge in this field is outlined as it was in the late 1940s. Personal reminiscences of day-to-day operations of the laboratory, interactions with colleagues, and other thoughts and experiences of the author are described.

Dietary Proteins↗
PubMed1990

Molecular basis for the properties of the thyroxine-binding globulin-slow variant in American blacks.

Thyroxine-binding globulin-slow (TBG-S), a variant found in 4-12% of Black and Pacific Island populations, is inherited as an X-chromosome linked trait. This variant is detected on isoelectric focusing by the characteristic cathodal shift of all its isoforms, suggesting that the difference resides in the core protein. In addition, TBG-S is slightly more thermolabile, which explains why subjects expressing TBG-S have on the average lower serum TBG, and thus reduced T4, concentrations. We now report the molecular basis for this TBG variant, deduced from sequencing the TBG-S gene of an American Black man. Sequencing of the four coding regions and all intron/exon junctions revealed a single nucleotide substitution in the codon for amino acid 171 of the mature protein. The resulting change of the codon GAC to AAC results in replacement of the normal aspartic acid by asparagine. Since the negative charge provided by the aspartic acid is lost when replaced by the neutral asparagine, this substitution seems responsible for the cathodal shift on isoelectric focusing and slower electrophoretic mobility of TBG-S. An identical nucleotide substitution was identified in an unrelated American Black man expressing TBG-S. Whether the TBG-S phenotype observed in populations from the Pacific Islands is caused by the same mutation remains to be determined.

Amino Acid Sequence↗
PubMed1979

Renal tubular transport and catabolism of proteins and peptides.

The kidney plays an important role in the metabolism of proteins and peptides. Current evidence indicates that only the proximal tubule possesses the mechanism for degradation or transport of these substances and reabsorption of metabolic products. Proteins and large polypeptides filtered at the glomerulus are absorbed from proximal tubular fluid by luminal endocytosis into apical vacuoles. These fuse with primary lysosomes, where hydrolysis occurs followed by diffusion of metabolites out of the cells and into the blood. Recent evidence indicates that small linear peptides are handled by a different mechanism. It is likely that small peptides are degraded at the luminal surface of the brush border of proximal tubules, which contains many hydrolytic enzymes, by the process of membrane or contact digestion with reabsorption of the breakdown products. The probable biological significance of proximal tubular mechanisms for handling of proteins and peptides are conservation of amino acids, inactivation of toxic substances, and participation in the regulation of the circulating level of protein and peptide hormones.

Animals↗
PubMed1978

Effects of constituent amino acids on tubular handling of microinfused angiotensin II.

[14C]angiotensin II ([14C]AII) was microinjected alone or with excess L-isoleucine (IIe) or L-aspartic acid (Asp) into renal tubules of anesthetized rats. Urinary excretion of 14C-labeled material was measured, and the intact peptide and its metabolites were identified and quantified. When isoleucine was administered with [14C]AII, urinary recovery of the 14C-labeled material increased directly with distance of infusion site from glomerulus, and most of the radioactivity in urine was [14C]Ile. The data suggest that isoleucine interfered with reabsorption of [14C]Ile derived from hydrolysis of [14C]AII and less so with the hydrolysis itself. When aspartic acid was administered with [14C]AII into the proximal 5/6 of the proximal convolution, total urinary recovery of the 14C-labeled material was unchanged, but percentage of recovery as [14C]AII increased; with infusion into the distal 1/6 of the proximal convolution, total urinary recovery of the 14C labele increased. The data suggest that aspartic acid interfered with the enzymatic hydrolysis of [14C]AII and reabsorption of isoleucine. In distal tubules the 14C label was almost completely recovered as intact [14C]AII in all protocols. The results show that free amino acids influence proximal tubular handling of small linear peptides in rats.

Angiotensin II↗
PubMed1976

Micropuncture evidence of rapid hydrolysis of bradykinin by rat proximal tubule.

3H-labeled bradykinin ([3H]BKN) and 14C-labeled inulin ([14C]In) were simultaneously microinfused into proximal or distal tubules in Inactin-anesthetized rats, and urinary excretion and tubular transit times were measured. In other experiments higher doses of [3H]BKN were microinfused and intact peptide and its metabolites identified and quantified by two-dimensional peptide mapping. The site of infusion was identified by neoprene injection and microdissection. Urinary recovery of 3H label was 24.1% when proximal tubules were infused and 98.0% when distal tubules were infused. For proximal tubules, 85% of 3H activity recovered from urine consisted of metabolites (81%[3H]Pro and 4% [3H]Arg1-Phe5) and 15% was intact BKN. Urinary recoveries of [3H]BKN and metabolites were unrelated to tubular length. With distal tubules all 3H activity appeared as intact BKN. Excretion curves of simultaneously infused [3H]BKN and [14C]In showed no marked differences in configuration for either proximal or distal or distal tubules. We suggested that removal of [3H]BKN by proximal tubular cells occurs by rapid enzymatic cleavage at the luminal surface with reabsorption of most of the products and excretion of the remainder.

Animals↗
PubMed1976

Inhibition of proximal tubular hydrolysis and reabsorption of bradykinin by peptides.

[3H] bradykinin ([3H] BKN) was microinfused alone or in the presence of a 390- or 780-fold excess of BKN or angiotensin I (AI) into proximal tubules in Inactin-anesthetized rats. Urinary excretion of 3H-labeled material was measured, and intact peptide and its metabolites were identified and quantified. When [3H] BKN was administered with BKN or AI, urinary recovery of 3H-labeled material was increased in a manner directly proportional to tubular length, suggesting that reabsorption of [3H] BKN is related to extent of tubular contact. BKN and AI were equally effective in inhibiting the reabosroption of [3H] BKN and its metabolites from proximal tubular fluid. In contrast, BKN but not AI effectively inhibited the enzymatic hydrolysis of [3H] BKN in the proximal tubule, The data suggest that the proximal tubular mechanism for reabsorbing BKN and its metabolites is of high capacity but not high specificity and that the mechanisms for enzymatic cleavage and reabsorption of BKN and its metabolites may had different specificites and capacities.

Angiotensin II↗
PubMed1975

Fate of labeled angiotensin II microinfused into individual nephrons in the rat.

14C-labeled angiotensin II ([14C]AII) and tritiated inulin ([3H]In) were infused into individual nephrons in Inactin-anesthetized rats and urinary excretion was measured. Site of infusion was identified by neoprene injection and microdissection. In other experiments with higher doses of [14C]AII, microperfused at 10-4-10-5 M (concentrations 10-5-10-6 higher than contained in plasma), [14C]AII and its urinary metabolites were identified and quantified by two-dimensional peptide mapping. Recovery of 14C was 10.9% when proximal tubules were infused and 94.8% when distal tubules were infused. There was no correlation with tubular length in either case. For proximal tubules, two-thirds of the 11% recovered from urine appeared as peptide fragments of AII. With distal tubules almost all 14C activity appeared as intact AII. The principal metabolic product recovered from urine after proximal injection was the chymotryptic peptide, and its recovery was inversely related to tubular length. It is suggested that rapid removal of [14C]AII by proximal tubular cells occurs by enzymatic cleavage at the luminal surface with reabsorption of most of the products and excretion of the remainder

Angiotensin II↗