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Biomedical subjects

R L Ney

Publications and source records attributed to R L Ney.

At least 19 recordsLinked to original sources
PubMed1986

Pedigree analysis of the 5' flanking region of the insulin gene in familial diabetes mellitus.

Non-insulin-dependent diabetes mellitus (NIDDM) has been reported to be associated with an insertion polymorphism in the 5' flanking region of the human insulin gene. We have attempted to examine linkage of this polymorphism to the phenotype of NIDDM by studying multiple pedigrees. We evaluated 142 individuals (120 white, 22 black), 80 of whom were from 7 pedigrees (5 white, 2 black) ranging in size from 4 to 37 members. Of these, 52 subjects had NIDDM, 10 had insulin-dependent diabetes mellitus (IDDM), and 80 were nondiabetics (ND). DNA was extracted from leukocytes and after digestion with Sst 1, and electrophoresis, the DNA was blotted to nitrocellulose filters and hybridized to a alpha 32P-labeled insulin gene probe. Two alleles of 6.0 and 7.6 kb in size were detected, the latter corresponding to the common previously described insertion polymorphism. In these families, the 7.6 kb allele occurred in 32 of 57 ND, 3 of 5 IDDM, and 10 of 18 NIDDM (P = 0.98). When sibships were analyzed the 7.6 kb allele occurred in 6 of 13 ND, 3 of 5 IDDM, and 8 of 12 NIDDM (P = 0.58). In examining 72 unrelated subjects, including 12 spouses from the pedigrees, the 7.6 kb allele was documented in 16 of 36 ND, 1 of 5 IDDM, and 16 of 31 NIDDM (P = 0.59). In these individuals and in the multiple families studied the insertion polymorphism flanking the insulin gene showed Mendelian inheritance and assorted independently of the phenotype of diabetes mellitus.

Adolescent↗
PubMed1985

Characterization of a peptide alpha-amidation activity in human plasma and tissues.

Peptidyl glycine alpha-amidation activity has been detected in human plasma and in several human tissues known to synthesize biologically active alpha-amidated peptides. Activity was monitored by measuring conversion of mono-[125I]-D-Tyr-Val-Gly into mono-[125I]-D-Tyr-Val-NH2. The plasma alpha-amidation activity is dependent on molecular oxygen, copper, and ascorbic acid and appears to recognize a variety of peptide substrates which contain carboxyl terminal glycine residues. Kinetic analyses demonstrated Michaelis-Menten kinetics with a Km of 14 mumol/L for D-Tyr-Val-Gly. Based on gel filtration, the apparent molecular weight of the peptidyl glycine alpha-amidation activity in human serum is 60,000. The level of peptidyl glycine alpha-amidation activity in adult plasma (N = 17) was 106 +/- 3 pmol/mL/h (Mean +/- SEM) with no difference between male and female subjects (range 84 to 126 pmol/mL/h). In subjects under 15 years old (N = 10), mean plasma activity was 128 +/- 10 pmol/mL/h, higher than values for adult control plasma (P less than .05). In serum from hypothyroid adults (N = 13), mean serum activity was 141 +/- 11 pmol/mL/hr, higher than euthyroid controls (P less than .025). The most striking elevations in alpha-amidation activity occurred in plasma from patients with peptide-secreting tumors. Patients with medullary thyroid carcinoma (N = 19) had a mean plasma peptidyl glycine alpha-amidation activity of 142 +/- 52 pmol/mL/h (range 84 to 435 pmol/mL/h). The level of plasma alpha-amidation activity in one patient with metastatic carcinoid tumor was 560 pmol/mL/h.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Characterization of peptide alpha-amidation activity in human cerebrospinal fluid and central nervous system tissue.

Peptidyl-glycine alpha-amidation activity has been detected in human cerebrospinal fluid (CSF) and in several regions of the central nervous system. Activity was monitored by measuring conversion of mono-125I-D-Tyr-Val-Gly into mono-125I-D-Tyr-Val-NH2. The alpha-amidation activity in CSF is dependent on molecular oxygen, copper ions and ascorbic acid and appears to recognize a variety of peptide substrates which contain carboxyl terminal glycine residues. Kinetic analyses demonstrated Michaelis-Menten kinetics with a Km of 4.6 microM for D-Tyr-Val-Gly. The level of peptidyl-glycine alpha-amidation activity in 14 samples of CSF averaged 43 +/- 5 pmol/ml/h (mean +/- SEM; range 11-85 pmol/ml/h) or 1.9 +/- 0.2 pmol/Mg protein/h. No difference was noted between samples from male and female subjects. Extracts of central nervous system tissue contained alpha-amidation activity. The highest levels of enzyme activity were found in the hypothalamus with lower levels in the neurohypophysis and the cerebral cortex. Still lower but detectable activity was found in the cerebellum and pons. Human peptidyl-glycine alph-amidation activity is found in central nervous system tissues known to synthesize alpha-amidated neuropeptides and may be secreted from these tissues along with alpha-amidated peptides into CSF.

Amides↗
PubMed1976

Adrenal cholesterol uptake from plasma lipoproteins: regulation by corticotropin.

The transfer of lipoprotein-bound cholesterol into adrenal cells was examined. Adrenal glands from unstimulated or corticotropin stimulated hypophysectomized rats were incubated with high density lipoprotein (HDL) or low density lipoprotein LDL containing radiolabeled cholesterol. The rate of transfer of labeled cholesterol from HDL into the glands was two to three times greater than from LDL. Corticotropin stimulation increased the transfer of cholesterol from HDL but not LDL. The effects of corticotropin were not dependent on subsequent cholesterol utilization for steroidogenesis. The process of cholesterol transfer from HDL was linear with time over 2 hr at 37 degrees and greatly reduced at 4 degrees. In addition, the transfer process became saturated above an HDL cholesterol concentration of 900 mug/ml. About 25% of the labeled adrenal cholesterol arising from HDL was recovered within the mitochondria. The labeled cholesterol within isolated mitochondria could undergo mitochondrial conversion to pregnenolone. Finally, the delipidated HDL apolipoproteins, apoA-I and apoA-II, when added to incubations containing less than saturating concentrations of HDL, stimulated transfer of labeled cholesterol from HDL to adrenal cells. These studies suggest that rat adrenal tissue possesses an HDL specific hormonally-responsive mechanism for accumulating extracellular cholesterol and that apoA-I and apoA-II have a significant function in the uptake process.

Adrenal Glands↗
PubMed1973

Regulation of adrenal ornithine decarboxylase by adrenocorticotropic hormone and cyclic AMP.

Adrenal ornithine decarboxylase activity was stimulated in a dose-related manner after administration of ACTH or dibutyryl ((6)N-2'-O-dibutyryl) cyclic AMP to hypophysectomized rats. Little effect was observed for 2 h, but striking increases in enzyme activity were observed 4 h after administration of these substances. Effects of ACTH and dibutyryl cyclic AMP were not secondary to stimulation of steroidogenesis, since hydrocortisone had no effect on adrenal ornithine decarboxylase although it did stimulate activity of the enzyme in the liver and kidney.ACTH, given subcutaneously to hypophysectomized rats, induced striking increases in adrenal cyclic AMP levels within 15-30 min with a fall towards the base line in 1 h. Increases in ornithine decarboxylase activity lag several hours after this endogenous cyclic AMP peak, in contrast to the stimulatin of steroidogenesis by the nucleotide that requires only 2-3 min. After graded doses of ACTH, increases in adrenal cyclic AMP levels at 30 min were paralleled by proportional increases in adrenal ornithine decarboxylase activity 4 h after hormone treatment. Whereas maximal levels of adrenal steroidogenesis have been observed at tissue cyclic AMP levels of 6 nmol/g. ACTH is capable of inducing increases in nucleotide levels up to 200 nmol/g or more. These high tissue levels of cyclic AMP, although unneccessary for maximal steroidogenesis, appear to stimulate adrenal ornithine decarboxylase activity. Several results in addition to the time lag in the stimulation of ornithine decarboxylase activity suggest a mechanism involving accumulation of the enzyme or some factor needed for its activity rather than direct activation of the enzyme by cyclic AMP. Thus, the addition of cyclic AMP directly to the ornithine decarboxylase assay mixture in vitro was without stimulatory effect. In addition, actinomycin D or cycloheximide in doses sufficient to block adrenal RNA and protein synthesis, respectively inhibited the stimulation of ornithine decarboxylase activity by ACTH in vivo. An adrenocortical cancer was found to maintain ornithine decarboxylase activity at very high levels, but did so at much lower cyclic AMP levels than those of ACTH-stimulated adrenals. It is concluded that ACTH stimulates adrenal ornithine decarboxylase activity and that this effect may be mediated by cyclic AMP. However, cyclic AMP be mediated by appear to be a determinant of the high level of enzyme activity found in adrenocortical cancer.

Adrenal Gland Neoplasms↗
PubMed1971

Abnormal hormone responses of an adrenocortical cancer adenyl cyclase.

Properties of adenyl cyclase of normal adrenals and of a corticosterone-producing adrenal cancer of the rat have been compared. Enzyme activity was found in all particulate fractions of both tissues. The cyclase of the tumor as well as of the adrenals was stimulated by adrenocorticotropic hormone (ACTH) over similar concentration ranges. Unexpectedly, the tumor enzyme was also stimulated by epinephrine, norepinephrine, and thyroid-stimulating hormone (TSH). These hormones produced a dose-related effect over a concentration span that was comparable with that for ACTH. The tumor cyclase was not responsive to angiotensin Il, vasopressin, glucagon, insulin, growth hormone, parathyroid hormone, and thyrocalcitonin. ACTH was the only hormonal preparation that stimulated normal adrenal cyclase. These findings are compatible either with the possibility that the adenyl cyclase receptor of the tumor has undergone structural alteration with a consequent loss of specificity for ACTH or with the possibility that the tumor possesses several cyclase regulatory receptors.

Adenine Nucleotides↗