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Biomedical subjects

A Katz

Publications and source records attributed to A Katz.

At least 307 records · Page 17Linked to original sources
PubMed1990

CD3-T cell receptor modulation is selectively induced in CD8 but not CD4 lymphocytes cultured in agar.

The CD3-T cell receptor (TcR) complex is central to the immune response. Upon binding by specific ligands, internalized CD3-TcR molecules increase, and either T cell response or unresponsiveness may ensue depending on the triggering conditions. Using semi-solid agar culture, we have shown previously that quiescent CD4 but not CD8 lymphocytes generate clonal colonies under phytohaemagglutinin stimulation. Here we have demonstrated that the agar induces selective CD3-TcR modulation in the CD8 and not in the CD4 subset. CD8 lymphocytes preactivated in liquid culture and recultured in agar with exogenous recombinant interleukin-2 generate colonies with a modulated CD3-TcR surface expression. The peptides composing the CD3-TcR complex are synthesized in CD8 colonies as well as in CD4; however, the CD3 gamma chain is phosphorylated at a higher level in CD8 colonies. A component of the agar polymer, absent in agarose, appears to be the ligand that induces differential CD3-TcR modulation in the CD8 subset. In contrast to agar culture, CD8 colonies can be derived from quiescent CD8 lymphocytes in agarose. These CD8 colonies express unmodulated CD-TcR. CD3-TcR modulation with anti-CD3 monoclonal antibody prior to culturing in agarose inhibits the colony formation. We conclude that given triggering conditions can result in both CD3-TcR modulation and inhibition of the proliferative response selectively in the CD8 lymphocyte subset and not in the CD4.

Agar↗
PubMed1990

Failure of glutamate dehydrogenase system to predict oxygenation state of human skeletal muscle.

In a recent study, the total tissue contents of glutamate (Glu), ammonium (NH+4), and 2-oxoglutarate (2-OG) were used to estimate changes in the mitochondrial redox state ([NAD+]/[NADH]) of contracting skeletal muscle with intact circulation [Am. J. Physiol. 253 (Cell Physiol. 22): C263-C268, 1987]. These metabolites participate in the glutamate dehydrogenase (GDH) reaction, which, based on a number of assumptions, theoretically enables calculation of the mitochondrial redox state as follows (brackets indicate concentrations): [NAD+]/[NADH] = ([NH+4] [2-OG])/[( Glu]Kapp), where Kapp is the apparent equilibrium constant for GDH. The purpose of this study was to determine whether changes in the total tissue contents of Glu, NH+4, and 2-OG could be used to predict a reduction of the mitochondrial redox state in anoxic skeletal muscle. Anoxia was induced in the quadriceps femoris muscle by 10 min of circulatory occlusion (low metabolic rate) and isometric contraction to fatigue (high metabolic rate). The mean (+/- SE) value for the metabolite ratio ([NH+4][2-OG]/[Glu]) at rest was 6 +/- 3 mmol/kg dry wt (x 10(-4]. No significant change occurred after circulatory occlusion (4 +/- 2 x 10(-4); P greater than 0.05), whereas an almost 60-fold increase was observed after isometric contraction (P less than 0.05). Because the muscle was anoxic under both conditions, a significant decrease in the metabolite ratio should have occurred. These data demonstrate that changes in total tissue contents of Glu, NH+4, and 2-OG cannot be used to estimate changes in the redox and oxygenation state of mitochondria in intact human skeletal muscle.

Adenosine Triphosphate↗
PubMed1990

Tricarboxylic acid cycle intermediates in human muscle during prolonged exercise.

Seven subjects cycled to fatigue [75 +/- 5 (SE) min] at a work load corresponding to approximately 75% of their maximal oxygen uptake. Biopsies were taken from the quadriceps femoris muscle at rest and during exercise. Muscle glycogen decreased from a preexercise level of 445 +/- 33 mmol glucosyl units/kg dry wt to 50 +/- 14 at fatigue. The sum of the measured tricarboxylic acid cycle intermediates (TCAI = malate + citrate + fumarate + oxaloacetate) was 0.49 +/- 0.05 mmol/kg dry wt at rest, increased to 4.41 +/- 0.23 after 5 min of exercise, and then decreased continuously to 3.33 +/- 0.29 and to 2.83 +/- 0.27 mmol/kg dry wt after 40 min of exercise and at fatigue (P less than 0.05 vs. 5 min), respectively. The point of fatigue was characterized by an enhanced deamination of AMP (judged by increase in IMP) and reduced contents (vs. 5 min of exercise) of lactate, pyruvate, and alanine. In contrast, acetylcarnitine (reflects the availability of acetylunits) increased threefold at the onset of exercise and was maintained approximately at this level until fatigue. It is concluded that prolonged exercise to fatigue at moderate work loads results in glycogen depletion, energy deficiency (increased AMP deamination), reduced levels of three-carbon compounds and TCAI (compared with the initial phase of exercise) but in maintained levels of acetylunits. The present data indicate that carbohydrate depletion may impair aerobic energy production by reducing the level of TCAI.

Adenine Nucleotides↗
PubMed1990

Fibrillary glomerulonephritis in a patient with metastatic carcinoma of the liver.

A 61-year-old women presented with nephrotic syndrome and progressive renal failure associated with metastatic adenocarcinoma of the liver. Renal biopsy revealed marked widening of the basement membrane and nonamyloidotic fibrillary deposits composed chiefly of polyclonal IgG. This is the first reported case of Congo-red-negative fibrillary glomerulopathy in association with adenocarcinoma of the liver.

Adenocarcinoma↗
PubMed1990

SPECT in patients with epilepsia partialis continua.

We report 2 patients with epilepsia partialis continua (EPC) in whom ictal single photon emission computed tomography (SPECT) showed focal increased signal while EEG failed to show epileptic changes. SPECT may clarify confusing situations when EPC is suspected.

Aged↗
PubMed1990

Comparison of non-collagenous type IV collagen subunits in human glomerular basement membrane, alveolar basement membrane, and placenta.

This study examines the similarities and differences in the noncollagenous domain (NC1) of type IV collagen from human glomerular basement membrane (hGBM), alveolar basement membrane (hABM), and placenta (hPBM). Following collagenase digestion, NC1 domain was isolated on Bio-Gel A-0.5m or by cation exchange chromatography on S-Sepharose. NC1 from each source was characterized by SDS PAGE, and two dimension NEPHGE/SDS PAGE. Immunoblotting and ELISA inhibition was performed using antibody probes specific for M28 , M28+, M26 and M24 monomer subunits of human NC1. It was observed that all NC1 subunits were present in hGBM and hABM derived material, however M28 and M28+ monomers were absent in hPBM NC1. These findings indicate that while alpha 1(IV) and alpha 2(IV) collagen chains are present in hGBM, hABM and hPBM, alpha 3(IV) and alpha 4(IV) collagen chains are only found in hGBM and hABM but are absent in hPBM. It can now be appreciated that heterogeneity of alpha (IV) chain composition exists in basement membranes from various organs.

Basement Membrane↗
PubMed1990

Diabetic glomerulopathy following unilateral nephrectomy in the dog.

To elucidate the important features of early renal disease in the diabetic dog, renal capillary permselectivity and fractional mesangial expansion with and without unilateral nephrectomy (NX) were examined. Pancreatectomized mongrel dogs (N = 9) received 10-20 U Regular and NPH insulin daily. Weekly blood glucose monitoring, 300 +/- 75 mg/dl (means +/- SD). Three dogs without NX had serial open needle biopsies 6-23 months post-pancreatectomy, revealing significant glomerular basement membrane widening and mesangial expansion. Without NX, inulin clearance increased from 2.55 +/- 0.89 (pre-diabetes) to 4.30 +/- 0.70 ml/min/kg body weight (N = 4, means +/- SD, p less than 0.05), whereas albuminuria, measured by radioimmunoassay, remained unchanged 2.57 +/- 1.03 (pre-diabetes) to 2.83 +/- 1.63 micrograms/min/kg body weight up to 23 months post-pancreatectomy. To determine whether altered renal capillary permselectivity occurred despite normal albuminuria, glomerular charge and size selectivity was analysed with serial fractional anionic dextran (20-44 A Stokes Einstein Radius) clearances. Furthermore, peritubular capillary permselectivity was probed with anionic and neutral 3H-dextran (26 A) using the multiple indicator dilution method. Fractional anionic dextran clearances remained unchanged up to 23 months, as did peritubular capillary permselectivity. Five diabetic dogs were compared to non-diabetic dogs with (N = 4) and without (N = 10) NX. To identify whether angiotensin II converting enzyme inhibition modified glomerular function or morphology, 3 diabetic + NX dogs received Captopril (5 mg/kg/day). At one year, diabetes + NX had an additive effect on renal hypertrophy, although fractional mesangial expansion was not enhanced by NX. Albuminuria was unaffected by NX or Captopril.(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed1990

A rat hybridoma model of Heymann nephritis: production of a monoclonal anti GP330 from a nephritic rat.

Autologous (Heymann) nephritis was induced by immunizing Sprague-Dawley rats with a crude membrane extract (Fx1A) prepared from renal cortical tubules. Urine protein excretion was monitored to determine the onset of nephritis and then the spleens of nephritic rats were fused with a non-secretor rat myeloma cell line. Supernatants from hybridoma cultures were first screened for production of anti-brush border membrane (BBM) antibody by immunodot blotting of highly purified rat BBM on nitrocellulose. Positive hybrids were then tested by indirect immunofluorescence for the presence of IgG, which binds to the brush border of rat renal proximal tubules. Those hybrids which were positive by both screening assays were subcloned twice. Two monoclonal antibodies (C5, D11) were studied in some detail. Both C5 and D11 immunoprecipitated a single polypeptide from BBM, labelled with 125I by the lactoperoxidase method. Radioautography of gradient 4-11% slab sodium dodecyl sulphate polyacrylamide gels revealed that the polypeptide against which C5 and D11 were directed co-migrated with the polypeptide immunoprecipitated by (i) IgG eluted from the renal cortex of nephritic rats, and by (ii) a mouse anti-rat monoclonal against gp 330 [a BBM constituent with proven pathogenicity [9]]. Supernatants which tested positive by immunodot blotting but negative by indirect immunofluorescence showed no detectable immunoprecipitate after reaction with BBM. Immunocytochemical staining by immunoperoxidase and immunogold methods localized C5 and D11 to the BBM of the renal proximal tubule and to the urine face of the glomerular epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Magnesium sulfate suppresses electroencephalographic manifestations of CNS oxygen toxicity.

We studied the effects of parenteral magnesium sulfate (MgSO4) administration on electroencephalographic seizures induced by hyperbaric oxygen (HBO) in awake rats. Sixteen rats chronically implanted with electrocorticographic electrodes were preinjected i.p. with either vehicle or 3 mmol/kg MgSO4 (the latter resulted in serum levels of 3.5-5.5 mmol/liter) and then exposed to 6 ATA O2 in a pressure chamber. The time to develop an electric ichtal seizure was measured and compared to that in the same animal receiving the alternate treatment 3 days later. Mean and median times after the magnesium treatment were almost double those of vehicle administration. A central anticonvulsive action of magnesium, which should be investigated over the entire HBO range, is indicated.

Animals↗
PubMed1989

Characterization and reconstitution of the Na+/H+ antiporter from the plasma membrane of the halotolerant alga Dunaliella.

Na+/H+ exchange activity in plasma membrane preparations isolated from the unicellular halotolerant alga, Dunaliella salina, is shown to be competitively inhibited by amiloride or Li+, with Ki values of 25 and 30 microM, respectively. The activity can be followed by either the sodium-dependent change in transvesicular delta pH, as monitored by absorbance changes of Acridine orange, or by the delta pH-dependent uptake of 22Na+ into the intravesicular space. The activity was solubilized, by extraction with Triton, and reconstituted into active proteoliposomes. The activity of the reconstituted proteoliposomes was strongly stimulated by the presence of valinomycin and KCl, suggesting that the exchanger is electrogenic, presumably exchanging more than one proton for each Na+ ion. Partial purification of the Triton-extracted exchanger was obtained by fractionation on a DEAE-cellulose column.

Amiloride↗
PubMed1989

[Cough associated with captopril and enalapril].

Persistent dry cough is not a known adverse reaction of captopril and enalapril. We present 5 patients with persistent dry cough severe enough to warrant withdrawal of the drug, which resulted in rapid and complete recovery. Challenge with the drugs induced recurrence of cough. The pathogenesis of the reaction is unknown, but possible mediators include bradykinin and prostaglandins.

Aged↗
PubMed1989

Contraction-mediated inactivation of glycogen synthase is accompanied by inactivation of glycogen synthase phosphatase in human skeletal muscle.

Activities of glycogen synthase (GS) and GS phosphatase were determined on human muscle biopsies before and after isometric contraction at 2/3 maximal voluntary force. Total GS activity did not change during contraction (4.92 +/- 0.70 at rest versus 5.00 +/- 0.42 mmol/min per kg dry wt.; mean +/- S.E.M.), whereas both the active form of GS and the ratio of active form to total GS decreased by approximately 35% (P less than 0.01). GS phosphatase was inactivated in all subjects by an average of 39%, from 5.95 +/- 1.30 to 3.63 +/- 0.97 mmol/min per kg dry wt. (P less than 0.01). It is suggested that at least part of the contraction-induced inactivation of GS is due to an inactivation of GS phosphatase.

Adult↗
PubMed1989

[Standard meal substitute for oral glucose tolerance test in pregnancy].

The oral glucose tolerance test (OGTT) has been the recommended method of screening for the diagnosis of gestational diabetes. Based on the glycemic index of common foods, a standard meal was designed as a substitute meal test (SMT). It consisted of 3 slices of toast (75 g) with 60 g of jam, 11 g of sugar in a cup of tea, and 150 g of canned puree sweetened with sugar (8%), for a total of 118 g of available carbohydrate and a total of 518 cal. Plasma glucose concentrations of 46 pregnant women in the 2nd and 3rd trimesters were determined at 20 minute intervals for 3 hours after ingestion of this SMT, and were compared with those after a 100 g OGTT meal. There was a high correlation (r = 0.96, p less than 0.001) between comparable glucose concentrations after the 2 tests. With the SMT there were significantly fewer side-effects (nausea and vomiting), a higher level on preference scoring and reduced interassay variability of glucose levels after 2 hours. 6 gestational diabetics were diagnosed by the OGTT. In these patients glucose concentrations were higher than 3 standard deviations above the mean 2 hours after ingestion of the SMT. We propose the SMT as a side-effect-free, reliable and convenient alternative to the OGTT in pregnancy.

Blood Glucose↗
PubMed1989

Glucose formation in human skeletal muscle. Influence of glycogen content.

Eight men exercised at 66% of their maximal isometric force to fatigue after prior decrease in the glycogen store in one leg (low-glycogen, LG). The exercise was repeated with the contralateral leg (control) at the same relative intensity and for the same duration. Muscle (quadriceps femoris) glycogen content decreased in the LG leg from 199 +/- 17 (mean +/- S.E.M.) to 163 +/- 16 mmol of glucosyl units/kg dry wt. (P less than 0.05), and in the control leg from 311 +/- 23 to 270 +/- 18 mmol/kg (P less than 0.05). The decrease in glycogen corresponded to a similar accumulation of glycolytic intermediates. Muscle glucose increased in the LG leg during the contraction, from 1.8 +/- 0.1 to 4.3 +/- 0.6 mmol/kg dry wt. (P less than 0.01), whereas no significant increase occurred in the control leg (P greater than 0.05). It is concluded that during exercise glucose is formed from glycogen through the debranching enzyme when muscle glycogen is decreased to values below about 200 mmol/kg dry wt.

Adult↗
PubMed1989

Transient increase in glucose 1,6-bisphosphate in human skeletal muscle during isometric contraction.

Changes in glucose 1,6-bisphosphate and regulators of glucose-1,6-bisphosphate synthase and phosphatase during isometric contraction have been determined. Biopsies were obtained from the quadriceps femoris muscle before and after 20 s of contraction and at fatigue. Glucose 1,6-bisphosphate increased by 35% after 20 s of contraction (P less than 0.001) with no further change at fatigue (P greater than 0.05 versus 20 s). Pi, fructose 1,6-bisphosphate and glycerate 3-phosphate, all inhibitors of the synthase, increased significantly during the first 20 s (P less than 0.05-0.001), whereas muscle pH (decrease in which inhibits synthase) decreased continuously. The decrease in the total adenine nucleotide pool, which is stoichiometric with the increase in IMP (an activator of phosphatase), was not significant after 20 s, but was 15% at fatigue (P less than 0.001). The rapid increase in glucose 1,6-bisphosphate, despite increases in the inhibitors of synthase, suggests that the synthase was activated, possibly by the substrate glycerate 1,3-bisphosphate and/or a yet unknown activator(s). The lack of any further change in glucose 1,6-bisphosphate during the latter part of contraction may be due to concomitant activation of the synthase and phosphatase.

Adult↗