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Biomedical subjects

A Fine

Publications and source records attributed to A Fine.

At least 163 records · Page 9Linked to original sources
PubMed1989

A sensitive double-diffusion microassay suitable for the detection of idiotype-antiidiotype precipitates.

Using agarose gel coated on GelBond film sheets and using Coomassie blue stain followed by silver stain, a sensitive double-diffusion microassay has been developed for detecting small amounts of precipitate forming during idiotype-antiidiotype reactions. The sensitivity of the method is 10-100 times greater than classical immunodiffusion tests. Other advantages include the need for minimal amounts of unconcentrated sample, the absence of radioactive or toxic substrates, no interference due to a second or third antibody coat such as are used in immunoenzymatic techniques, and the possibility of a direct evaluation of qualitative data such as identity, cross-reactivity or non-identity. As little as 40 ng antibody could be detected, corresponding to an antibody concentration of 8 micrograms/ml, making the microassay useful for rapid screening of idiotype-antiidiotype precipitates during routine analysis of hybridoma supernatants.

ABO Blood-Group System↗
PubMed1989

Nerve growth factor receptor mRNA distribution in human brain: normal levels in basal forebrain in Alzheimer's disease.

Nerve growth factor (NGF) receptor mRNA was found to be widely distributed throughout the human central nervous system, with the highest levels in the basal forebrain; this suggests that NGF may function as a retrograde trophic messenger for basal forebrain magnocellular cholinergic nerve cells. The degeneration of the latter constitutes one of the main features of Alzheimer's disease and it may be responsible for some of the cognitive impairment that characterizes the disease. No evidence was obtained for an insufficient synthesis of NGF receptor mRNA in the basal forebrain in Alzheimer's disease, where NGF receptor-like immunoreactivity was confined to neuronal cell bodies. NGF could thus be therapeutically beneficial. It could be expected to induce basal forebrain cholinergic cells to hypertrophy, synthesize more choline acetyltransferase and extend neurites.

Alzheimer Disease↗
PubMed1989

Rapid method for the isolation of two purified subfractions of high density lipoproteins by differential dextran sulfate-magnesium chloride precipitation.

We describe a rapid and reliable three-step precipitation procedure for the isolation of large amounts of the two major components of high density lipoproteins (HDL) in human serum. Precipitation was accomplished by means of dextran sulfate (DS) of mol. wt. 500,000 and MgCl2. First, all apoB-associated lipoproteins of any density were selectively precipitated with critical concentrations of reagents. Secondly, a subfraction of HDL was differentially precipitated from the apoB-depleted serum by increasing the concentration of both reagents. Eventually, the bulk of the remainder of HDL was precipitated by lowering the pH to 5.4. According to the precipitation patterns and the density profiles, the DS-Mg procedure provides a clear differentiation between the two HDL components. According to the compositional criteria and the ultracentrifugal characteristics, the two polyanion-precipitated subclasses are very similar to, if not identical with, the two density subclasses, the lighter HDL2 and the heavier HDL3, isolated by preparative ultracentrifugation after apoB-containing lipoproteins had been removed.

Chemical Precipitation↗
PubMed1989

[Detection and quantification of weak concentrations of antigens using a sensitive and direct method of demonstrating immunoprecipitation reactions].

Using agarose gel coated on GelBond film sheets, and using Coomassie blue stain followed by silver stain, a sensitive microassay has been developed for detecting small amounts of antigen-antibody precipitates, and for quantitating low concentrations of antigen. In order to obtain a high sensitivity, antigen-antibody ratios were adjusted imperatively close to the equivalence in double-diffusion, and for quantitative estimation, single radial immunodiffusion was performed, according to Mancini, by measuring circles at the end point. The use of a double staining procedure allows to detect as little as 8 micrograms/ml antigen by Ouchterlony and 200 ng/ml by Mancini technique. The sensitivity of the method is 100 times greater than classical techniques and other advantages such as the need for minimal amounts of unconcentrated samples, the absence of radioactive labelling, and the absence of interference due to a second or a third antibody coat, make this assay useful for analyzing and quantitating monoclonal antibodies obtained by hybridoma or B-cell immortalization.

Antibodies, Monoclonal↗
PubMed1989

The effects of fluorocitrate on renal glutamine, lactate, alanine, and oxygen metabolism in the dog.

Acid-base status is considered the major factor controlling renal NH4+ production from glutamine, with maximal values found in chronic acidosis. However, metabolic inhibitors have been shown to increase NH4+ production without acid-base change; the mechanism for this increase is unclear. Fluorocitrate was administered to dogs with chronic metabolic alkalosis. Following fluorocitrate total renal NH4+ production rose from 32 +/- 5 to 104 +/- 15 mumol/(min.100 mL glomerular filtration rate (GFR] (p less than 0.01) and glutamine extraction rose from 26 +/- 8 to 65 +/- 8 mumol/(min.100 mL GFR) (p less than 0.01). These values approximate maximal values found in chronic acidosis. Lactate utilization fell from 165 +/- 19 to 99 +/- 7 mumol/(min.100 mL GFR) following fluorocitrate (p less than 0.01). Citrate extraction fell to zero and alanine production rose from 27 +/- 4 to 46 +/- 7 mumol/(min.100 mL GFR) (p less than 0.01). Oxygen consumption remained unchanged following fluorocitrate, 584 +/- 29 vs. 549 +/- 29 mumol/(min.100 mL GFR). These results demonstrate that in the presence of metabolic inhibition in the kidney, ATP production remains constant. This is achieved by increased utilization of one substrate, glutamine, when the ATP production from other substrates is reduced. Thus the necessity to maintain constant ATP production appears to modulate renal NH4+ production.

Adenosine Triphosphate↗
PubMed1989

Stimulation of collagen formation by insulin and insulin-like growth factor I in cultures of human lung fibroblasts.

We examined the effects of insulin and insulin-like growth factor I (IGF-I) on the production of collagen by cultures of human embryonic lung fibroblasts. Insulin at 20 ng/ml increased collagen accumulation by 58% and total protein formation by 18%. At 2 micrograms/ml, insulin increased collagen production by 2- to 3-fold and total protein production by 2-fold. The mRNA levels for alpha 1(I) and alpha 1(III) collagen chains were elevated by insulin compared with untreated control values. IGF-I at 10 ng/ml increased collagen production 2-fold. IGF-I at 100 ng/ml maximally increased collagen production 3-fold. A specific antibody to the IGF-I receptor (alpha IR-3) caused a concentration-related decline in insulin-induced collagen formation. The addition of antibody at 1 micrograms/ml, resulted in 80% inhibition of insulin-induced collagen accumulation. Higher levels of antibody were required to inhibit IGF-I mediated collagen formation. The presence of antibody (alpha IR-3) also blocked fibroblast proliferation stimulated by epidermal growth factor plus insulin. These data show that insulin-induced collagen formation is mediated primarily through an interaction with the IGF-I receptor. The modulation of extracellular matrix production by insulin may influence the repair of tissue injury and the development of the accelerated atherosclerosis that accompanies the diabetic state in humans.

Blotting, Northern↗
PubMed1989

Enter the director of managed care.

Given the tremendous impact of managed care on hospitals' bottom lines, responsibility for managed care activities must be a full-time job. By creating the position of director of managed care, hospitals not only are making a commitment to truly managing their managed care activities, but they are sending a message to managed care providers that they take their contractual relationships seriously.

Delivery of Health Care↗
PubMed1989

Metabolism of D-lactate in the dog and in man.

Peritoneal fluid contains equimolar amounts of D- and L-isomers of lactate. Controversy exists as to whether D-lactate is metabolized as effectively as the L- isomer. D- and L-lactate were infused into the portal circulation of dogs and net hepatic uptake of both isomers measured by A-V sampling, blood flows being measured by flow probes. Hepatic extractions of both isomers were not significantly different. In three patients on intermittent peritoneal dialysis (IPD), and three patients on continuous ambulatory peritoneal dialysis (CAPD), arterial D-lactate was less than 15% of the concentration of L-lactate at the end of treatment. In conclusion, D-lactate is metabolized as effectively as L-lactate.

Animals↗
PubMed1988

Susceptibility to pilocarpine-induced seizures in rats increases with age.

Systemic administration of high doses of the cholinergic agonist pilocarpine induces motor limbic seizures in rats. Susceptibility to the convulsant effects of pilocarpine increases during adult life: the threshold dose for generalized seizures is essentially constant from age 30 to 70 days, but decreases thereafter, particularly beyond age 100 days. The increase in seizure susceptibility continues up to at least age 200 days, (the oldest age studied).

Acetylcholine↗
PubMed1988

The effects of amino acid loading on glomerular filtration in dogs on different protein diets: a controlled study.

Considerable variation in both the magnitude and pattern of response of glomerular filtration rate (GFR) to protein loading in omnivores has been reported in the literature. These experiments were designed to examine, under carefully controlled conditions, the effects of different acute protein loads given to a group of dogs placed on a normal protein (NP) intake for 4 weeks and to the same dogs when on a low protein (LP) intake for the same duration. GFR did not change when the dogs were changed from NP to LP diets, 3.0 + 0.2 (NP) vs. 3.2 + 0.3 (LP) mL.min-1.kg-1. Intravenous amino acid was infused at 15, 25, and 40 mL/h on different days. Regardless of whether on a low or high protein diet, the GFR did not change. Another set of experiments was performed in another Canadian centre 2000 miles away. In these studies with dogs on a similar normal protein diet, a striking rise in GFR occurred following amino-acid infusion at 25 mL/h, 3.1 + 0.3 vs. 4.8 + 0.6 mL.min-1.kg-1 (p less than 0.001). These results demonstrate, at least in the dog, that contrary to previous reports, dietary protein changes do not affect the GFR. Furthermore, the GFR response to an acute intravenous protein load does not depend on the amount of protein given nor the previous protein diet but appears to be possibly dependent on other factors that may be environmental or congenital.

Amino Acids↗
PubMed1988

Evidence for an adrenal contribution to plasma digitalis-like factors.

Digitalis-like factors (DLF) were assayed on plasma collected serially using antibody to digoxin: (1) after intravenous ACTH (n = 3 patients) and (2) after 0.15 U/kg crystalline insulin, 50 micrograms gonadotropin-releasing hormone and 0.2 mg thyrotropin-releasing hormone (n = 7) as a combined pituitary function test. Patients had either hypothalamic-pituitary or ovarian problems. Mean values for DLF rose fourfold after ACTH, and by a factor of 2.3 with the combined pituitary function test. DLF rose at least 50% in all 10 subjects. In 3 dogs, adrenal vein values for DLF were on average more than double values in either adrenal artery or lower vena cava. These results suggest that certain DLFs have an adrenal origin.

Adrenal Glands↗
PubMed1987

Maintenance of cortical somatostatin and monoamine levels in the rat does not require intact cholinergic innervation.

Levels of somatostatin, noradrenaline, dopamine, 5-hydroxytryptamine and 5-hydroxyindoleacetic acid were unchanged in rat neocortex 3 or 6 months after ibotenic acid lesion of the ipsilateral nucleus basalis that reduced cortical choline acetyltransferase levels by over 60%. These results render unlikely the possibility that non-cholinergic neurotransmitter deficits in Alzheimer's disease cortex are the consequence of cholinergic degeneration.

Animals↗
PubMed1987

The effect of transforming growth factor-beta on cell proliferation and collagen formation by lung fibroblasts.

We examined the effects of transforming growth factor-beta (TGF-beta) on the production of collagen by cultures of human embryonic lung fibroblasts. TGF-beta at 0.1 ng/ml appeared to activate selectively extracellular collagen accumulation as compared with total protein production. A maximal effect inducing a 2-3-fold increase in collagen and total protein production occurred at a dose of 1.0 ng/ml in fibroblast cultures. TGF-beta had no effect on fibroblast proliferation after a 24- and 48-h exposure, including cultures that received a second dose after 24 h. Collagenase digestion of radiolabeled collagen derived from TGF-beta-treated and -untreated cultures revealed no differences in the extent of hydroxylation (37.3 versus 33.4%). TGF-beta increased the production of types I and III collagen without affecting the proportion of collagen types. Fibroblast cultures maintained in medium containing TGF-beta sustained an activated rate of collagen production of 5 nmol/ml/24 h over at least 72 h. We found that epidermal growth factor slightly enhanced TGF-beta-induced collagen formation, whereas TGF-beta increased the proliferative effect of epidermal growth factor. Taken together, these data indicate that collagen production and cell proliferation can be independently regulated and that TGF-beta may have a role in the resolution of tissue injury by stimulating fibroblast-derived collagen synthesis.

Cell Division↗
PubMed1987

The effect of PGE2 on the activation of quiescent lung fibroblasts.

The effect of prostaglandin E2 (PGE2) on fibroblast proliferation was examined. The presence of PGE2 for 24 h inhibited the growth of quiescent cells stimulated with serum, platelet-derived growth factor and macrophage-derived factors. Maximal inhibition of nuclear labeling with [3H]thymidine occurred at concentrations greater than 10(-7) M. The inhibitory effect of PGE2 was less potent in exponentially growing cells and was not the result of conversion of PGE2 to PGA2 during incubation in growth medium. The G1 phase was determined to be 12-14 h in untreated cultures. The extent of growth inhibition by PGE2 was similar with addition of PGE2 at 0, 3, 6, or 9 h following restimulation of quiescent cell cultures. Approximately 25% of the cells that enter S phase are refractory to PGE2-induced growth inhibition. Short-term exposure to PGE2 (5 min and 30 min) caused substantial growth inhibition. The serum-induced proliferation was also inhibited by the cAMP analogue, dibutyrl cAMP. Our results suggest that PGE2 affects a distinct subpopulation of cells. Restimulation of quiescent cells treated with PGE2 for 24 h, indicated that release from PGE2 exposure is associated with prolongation of the G1 phase of the cell cycle.

Blood↗