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A Negro

Publications and source records attributed to A Negro.

69 records · Page 4Linked to original sources
PubMed1991

Differences in induction of c-fos transcription by cholera toxin-derived cyclic AMP and Ca2+ signals in astrocytes and 3T3 fibroblasts.

The B subunit of cholera toxin, a protein which binds specifically to membrane ganglioside GM1, is known to affect cell growth and differentiation. To investigate the mechanism of these cellular responses at the nuclear level, we used the induction of c-fos in astrocytes and 3T3 fibroblasts as a model. Northern blot analysis showed that treatment with B subunit provokes a rapid and transient expression of c-fos mRNA, independent of a measurable increase in cyclic AMP. The B subunit signal, which is mediated by Ca2+, was compared to cholera toxin and other agents which increase intracellular cyclic AMP levels. In transient transfection assays of astrocytes and fibroblasts, functional analysis of c-fos promoter deletions was used to identify the elements involved in transcriptional activation by B subunit. In astrocytes, the DNA region including the serum response element and the cyclic AMP response element (CRE) are equally required, whereas 3T3 cells require only the CRE for maximal induction. A synergistic effect of signal transduction was mediated by calcium and cyclic AMP on the CRE, being positive in 3T3 cells and negative in astrocytes. Diverse regulatory elements may be thus involved in responses of different cell types to the same extracellular signal. Furthermore, a single regulatory element (CRE) can integrate both calcium and cyclic AMP signals in the control of gene expression.

Animals↗
PubMed1991

Inhibition of diamine oxidase from porcine kidney by pentamidine and other aminoguanidine compounds.

1. Three bisguanidine compounds (those of pentamidine, streptidine and phenformin) were compared for their in vitro inhibitory capacity on diamine oxidase activity (EC 1.4.3.6), the first enzyme of putrescine degradation. 2. Pentamidine was the most potent inhibitor, and phenformine the weaker. Two and a half micromoles of pentamidine was enough to reduce the enzyme activity by 50%, while streptidine and phenformin produced the same effect at concentrations greater than 0.90 and 4 mM, respectively. 3. Pentamidine, streptidine and phenformin appeared to be non-competitive inhibitors, and the Ki values calculated by a Dixon plot were 3 microM, 0.95 mM and 4 mM, respectively.

Amine Oxidase (Copper-Containing)↗
PubMed1990

Protein-induced changes in kidney function depend on the time of administration but not on the dietary source.

Two separate experiments were carried out to study the effects of the same acute protein load given at different hours of the day and to assess the ability of proteins from different sources to induce hyperfiltration. In the first experiment, 9 healthy volunteers were kept at strict bedrest for 48 h, during which both a meat high-protein meal (protein load, PL) and a vegetable low-protein meal (control load, CL) were given either at lunch or at suppertime. As compared to a CL, PL determined a significant increase in GFR, total proteinuria (uTP), albuminuria (uA), and urinary retinol-binding protein (uRBP). These effects were much more significant after lunch PL than after supper PL, thus indicating an interaction between the PL and the time of the day. The existence of a circadian rhythm for GFR, uTP, uA, and uRBP was corroborated by spontaneous changes over baseline levels, which also were prominent after lunch CL as compared to those following supper CL. In the second experiment, 7 healthy volunteers ingested at lunch three protein-rich meals at 1-week intervals. The three protein loads consisted of about 80 g protein in the form of cooked red meat, cheese, and soya, respectively. The only significant differences between groups were urea appearance and urea clearance, lower and higher, respectively after soya load. These findings suggest that when evaluating the renal functional reserve after acute protein load both the spontaneous changes and the time-dependent sensitivity of kidney functions to acute challenges should be considered. Finally, the amount rather than quality of dietary proteins seems to be the determinant factor for protein-induced glomerular hyperfiltration.

Administration, Oral↗
PubMed1989

Circadian rhythm of proteinuria: effects of an evening meat meal.

Ten healthy volunteers were studied to test the effect of a meat meal on the circadian rhythm of urinary proteins. All subjects were kept at bed-rest during the whole 24-h evaluation period. An oral protein load (0.6 g/kg bodyweight) was given at supper-time (19.00 hours). Urinary and serum samples were collected every 3 h and examined for total protein, albumin, retinol-binding protein, and creatinine. All these variables and glomerular filtration rate (GFR), as measured by creatinine clearance, showed circadian rhythms. Acrophases were located at 14.21 hours (range 11.11-16.25) for urinary total protein, at 17.27 hours (13.14-22.31) for serum total protein, at 15.13 hours (13.01-18.04) for urinary albumin, at 14.18 hours (11.13-19.20) for serum albumin, at 21.22 hours (18.42-02.41) for urinary retinol-binding protein, at 14.51 hours (08.52-19.57) for serum retinol-binding protein, and at 16.17 hours (13.38-19.25) for creatinine clearance. Thus, the acrophases of urinary total protein and urinary albumin excretion rates occurred before the supper protein load, in a time span common to the acrophases of their serum levels and maximal GFR, whereas the acrophase of urinary retinol-binding protein occurred after the supper meat meal, concomitantly with the lowest value of serum retinol-binding protein. These findings suggest that circadian rhythms of urinary total protein and urinary albumin are influenced by changes in GFR, which occur also independently from an oral protein load. In fact, the latter did not modify creatinine clearance when administered at supper time.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Time-dependent increase of glomerular filtration rate after oral protein load: evidence for diurnal variations in renal response.

Seven healthy male volunteers were studied to test the effect of timing of an oral protein load on renal function. Creatinine clearance (Ccr) was measured during the 4-h period after administration of 72 g of protein in the form of cooked red meat at 1200 hours (lunch protein load, PL) and at 2000 hours (supper PL) the next evening. A low-protein meal in the form of vegetables was given as a control load at 2000 hours on the first day (supper control load, CL) and at 1200 hours on the second day (lunch CL). The 12-h night-time Ccr at fasting was used as the baseline reference value. After the lunch PL, Ccr (mean 127 +/- 6.8 ml/min) was 45% (p less than 0.001) higher than the baseline value (mean 87.9 +/- 5.3 ml/min) and 33% (p less than 0.001) higher than lunch CL (mean 95.8 +/- 5.6 ml/min). After the supper PL, Ccr (mean 106.2 +/- 8.7 ml/min) was 20% (p less than 0.01) higher than the baseline value and 15% (p less than 0.01) higher than the supper CL (mean 93.0 +/- 9.3 ml/min). The differences between baseline and control load values were not statistically significant. In all seven patients, the protein load induced a maximum Ccr value at lunchtime, and Ccr after the lunch PL was 22% higher than Ccr after the supper PL (p less than 0.01). We conclude that in healthy individuals, the Ccr after an oral protein load is correlated to the hour of the day when the study is performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

The use of reverse-phase high-performance liquid chromatography and precolumn derivatization with dansyl chloride for quantitation of specific amino acids in collagen and elastin.

A rapid and accurate reverse-phase high-performance liquid chromatography procedure for amino acid analysis of connective tissue proteins has been optimized. The method is based on quantitative dansyl chloride precolumn derivatization of protein hydrolyzates and chromatographic separation of the dansyl derivatives on Ultrasphere ODS C18 column. High molar uv absorption of Pro and Hyp derivatives, quantitation of low Des and Ide amounts (60 pmol), and good separation of all the amino acid derivatives (CV mostly less than 0.1%) including Hyl overcome the difficulties of other methods in producing reliable single run amino acid analysis of collagen and elastin. The use of fluorescence detector and the possibility of concentrating derivatized samples would give even higher sensitivity to the system. The procedure appeared to be suitable for single run analysis of other proteins, particularly those having an unbalanced amino acid composition.

Amino Acids↗
PubMed1986

Transient expression of type IV collagenolytic metalloproteinase by human mononuclear phagocytes.

A type IV collagenolytic metalloproteinase secreted by human monocytes/macrophages has been isolated and characterized. Monocytes isolated from peripheral blood and cultured in vitro exhibited a high type IV collagenolytic activity during the first and second day, but such activity declined markedly over subsequent days. Type IV collagenolytic activity was also transiently elaborated by macrophages isolated from (a) bronchioalveolar lavage of patients with pulmonary sarcoidosis, (b) primary human colostrum, and (c) peritoneal lavage of a patient with peritonitis. In contrast, macrophages isolated from the bronchioalveolar lavage of normal individuals, or from noninflammatory peritoneal fluids, failed to exhibit type IV collagenolytic activity. A type IV collagenolytic neutral proteinase was purified from macrophages isolated from inflammatory peritoneal fluid. The proteinase has a mass of 67 kDa on gel electrophoresis and is not altered in its migration under reducing conditions. It produces a characteristic 1/4-3/4 cleavage of type IV collagen, and its activity is abolished by treatment with EDTA but not phenylmethanesulfonyl fluoride. The isoelectric pH of the proteinase is 5.2 as judged by two-dimensional gel electrophoresis. The amino acid composition of the proteinase was notable for a high content of serine, glutamic acid, glycine, and alanine and no detectable hydroxyproline, cysteine, or methionine residues. The carbohydrate content of the proteinase was 11.2%, and galactose was the most abundant monosaccharide (8.7%) released following acid hydrolysis, followed by glucose (1.3%), mannose (1.2%), and trace amounts of fucose and galactosamine. Such a type IV collagenolytic protease may play an important role during the traversal of the vascular basement membrane by extravasating monocytes. The biochemical characteristics and biologic function of the macrophage proteinase may be similar or identical to the type IV collagenolytic proteinase identified in metastatic tumor cells.

Adult↗
PubMed1984

Macromolecular organization and functional architecture of basement membranes.

Basement membranes (BMs) are extracellular laminar matrices produced by endothelial and epithelial cells. They are composed by three major intrinsic macromolecules: type IV collagen, laminin and heparan sulfate proteoglycan (HSP), and by two major extrinsic ones: fibronectin and type V collagen. The intrinsic components are assembled in a three-dimensional network (type IV collagen) to which cells stick (by laminin) and through which (HSP) they interact with the stromal compartment. The BM is a barrier to be crossed by any cell that leaves the stroma to enter into the circulation or vice versa. Metastatic tumor cells secrete a protease which specifically degrades the BM collagen and some evidence suggests that the same enzyme is used also by normal monocytes.

Animals↗
PubMedDate not supplied

Liquorice-induced sodium retention. Merely an acquired condition of apparent mineralocorticoid excess? A case report.

Excessive ingestion of liquorice may result in sodium retention, hypertension, hypokalemia, and suppression of renin and aldosterone. Similarities between liquorice-induced effects and congenital apparent mineralocorticoid excess have recently been emphasized, as in both conditions, reduced activity of the enzyme 11 beta-hydroxysteroid dehydrogenase type 2 allows cortisol to act as a potent mineralocorticoid. We report a case of generalized edema without any increase in blood pressure, with biochemical and hormonal features of apparent mineralocorticoid excess, in a young woman who had been ingesting substantial amounts of liquorice for several years. Liquorice-induced wide-spread edema without hypertension in our patient, as well as in a few other cases previously reported, and the more common occurrence of edema associated with hypertension challenge the current explanation of liquorice syndrome as a purely acquired apparent mineralocorticoid excess. Indeed, in both congenital apparent and true mineralocorticoid excess, edema is typically absent, as a result of the sodium escape phenomenon. As pressure-natriuresis may be an essential mechanism accounting for the sodium escape phenomenon, some component of liquorice could partially or completely oppose the circulatory response that converts liquorice-induced sodium retention into blood pressure elevation. In patients with unexplained generalized edema and hypokalemia without hypertension, liquorice ingestion should be carefully investigated and the renin-aldosterone system should be assayed.

Adult↗
PubMedDate not supplied

Human parvovirus B19 infection mimicking systemic lupus erythematosus in an adult patient.

We report a case of widespread immune activation with moderate cytopenia during acute infection with human parvovirus B19 in an adult female patient, in whom five criteria for the diagnosis of systemic lupus erythematosus were present at disease onset. Our case is unusual due to the presence of a cutaneous rash mimicking leukocytoclastic vasculitis at presentation, moderate leukopenia with thrombocytopenia and the presence of a broad array of autoantibodies. Diagnosis was established on the grounds of serological tests confirming recent infection with human parvovirus B19; spontaneous regression of clinical and laboratory abnormalities was observed within 16 weeks, ruling out classic systemic lupus erythematosus. We conclude by proposing that human parvovirus B19 infection should be included in the differential diagnosis of lupus-like syndromes in adult patients.

Adult↗