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Biomedical subjects

P Layer

Publications and source records attributed to P Layer.

151 records · Page 9Linked to original sources
PubMed1983

Calcium secretion from the feline pancreas. Influence of hormonal and cholinergic secretagogues and of serum calcium.

The influences of secretagogues and of elevated serum calcium concentrations on the calcium secretion from the cat pancreas have been studied in vivo. During a high and constant fluid secretion rate evoked by a background infusion of secretin, additional infusions of both cholecystokinin-pancreozymin and urecholine led to a dose-dependent increase in calcium secretion in pancreatic juice parallel to the rise of protein. The amount of calcium in pancreatic juice associated to 1 mg protein (18.3 nmol/mg protein) calculated from regression analysis was independent of dose or kind of stimulus used. The protein-independent pancreatic juice calcium fraction was 0.184 mM in normocalcemia. During an episode of hypercalcemia produced by an intravenous calcium infusion, the protein-independent calcium fraction was increased and correlated linearly to the serum calcium concentration. We conclude that pancreatic juice calcium consists of two major fractions, one being associated with the enzyme protein and stimulated by secretagogues, and the other being protein independent and directly dependent on the extracellular calcium concentration.

Animals↗
PubMed1981

Nerve growth factor-induced differentiation of PC12 cells: evaluation of changes in RNA and DNA metabolism.

The relationship between both DNA and RNA metabolism and the nerve growth factor (betaNGF)-induced differentiation of PC12 cells was investigated. Cells remained in log phase growth for 4 days after exposure to betaNGF. DNA synthesis was similarly unaffected by betaNGF during this time. Thereafter, a gradual decrease in DNA synthesis was observed. In contrast, as many as 40% of the cells display neurites after 4 days exposure to betaNGF. The implication, that cells which have begun to differentiate morphologically may still synthesize DNA, was confirmed using autoradiography. The cellular RNA concentration was elevated significantly within 1 day of exposure to betaNGF and continued to increase for up to 6 days. Dose-response analysis revealed that this increase in cellular RNA, both rRNA and tRNA, closely correlates with the size and number of neurites per cell rather than with the cell's capacity to grow a neurite per se. A parallel rise in the cellular protein concentration was observed also. It was concluded, therefore, that (1) cessation of cell division is not a prerequisite for the initiation of the morphological differentiation of these cells and (2) the elevation of the cellular RNA content influences some quantitative aspects of neurite outgrowth.

Adrenal Gland Neoplasms↗
PubMed1976

Photoaffinity labeling and quaternary structure of the acetylcholine receptor from Torpedo californica.

Membrane fragments from electric tissue of Torpedo californica containing nicotinic acetylcholine receptor are composed of four different polypeptide chains with molecular weights of 40,000 (alpha), 48,000 (beta), 62,000 (gamma), and 66,000 (delta). The alpha and beta chains are still present in all and gamma and delta in some of the receptor preparations after Triton X-100 extraction and purification by affinity chromatography. All components of the receptor react covalently with the photoaffinity label 4-azido-2-nitrobenzyltrimethylammonium fluoroborate, the delta chain incorporating less of the reagent as compared to the alpha and beta chains. Agonists and antagonists containing a quaternary ammonium group protect all chains against the label; the principal neurotoxin from Naja naja siamensis protects the alpha chain only. We conclude that the alpha chain binds the neurotoxin from Naja naja, the alpha and beta chains are involved in the binding of ligands with quaternary ammonium groups, and the function of the gamma and delta chains remains to be determined.

Affinity Labels↗
PubMedDate not supplied

A new molecular form of PYY: structural characterization of human PYY(3-36) and PYY(1-36).

A radioimmunoassay was developed using an antibody raised in rabbits against synthetic porcine PYY. This radioimmunoassay was used to detect PYY immunoreactivity in human intestinal extracts. Human colonic mucosa was extracted with acid, centrifuged and the supernatant concentrated by low pressure preparative reverse phase chromatography. A subsequent C-18 reverse phase HPLC step separated two peaks of PYY immunoreactivity. Each peak was purified by sequential steps of ion-exchange FPLC and reverse phase HPLC. In the final purification step single absorbance peaks were associated with PYY immunoreactivity. Microsequence, amino acid, and mass spectral analysis of the intact and tryptic fragments of the two peptides were consistent with the structures: YPIKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY-amide [human PYY(1-36)] and--IKPEAPGEDASPEELNRYYASLRHYLNLVTRQRY-amide [human PYY(3-36)]. Human PYY(1-36) differs from porcine PYY only at position 3, with Ile instead of Ala, and position 18, with Asn instead of Ser. PYY(3-36) may differ in its biological activity from the intact peptide. Its high proportions in the colon suggest that it is released into the circulation where it could act as a partial antagonist of PYY(1-36).

Amino Acid Sequence↗