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Biomedical subjects

J G McCormack

Publications and source records attributed to J G McCormack.

160 records · Page 9Linked to original sources
PubMed1981

Amplified lymphokine production phenomenon confirmed by a macrophage 2-D-[3H]deoxyglucose transport assay.

The amplified lymphokine production phenomenon was confirmed by using an improved macrophage 2-d-[(3)H]deoxyglucose uptake assay as an indicator of lymphokine activity. Amplified lymphokine titers were determined in supernatants derived from tuberculin-sensitive, antigen (purified protein derivative)-stimulated, guinea pig peritoneal exudate and spleen cell suspensions after the cells were allowed to sediment into a pellicle in a conical culture tube. The deoxyglucose uptake assay, which probably measured an effect on the macrophage cell membrane, was easy to perform, and the prozone phenomenon observed with other lymphokine assay systems did not occur. The deoxyglucose uptake-enhancing moiety was stable at 56 degrees C for 1 h and had a molecular weight of between 50,000 and 100,000, as defined by Amicon ultrafiltration. Exposure of macrophages to the lymphokine-containing supernatants did not increase macrophage deoxyglucose uptake significantly until after 9 h of incubation had elapsed. The effect on deoxyglucose uptake was to increase the V(max) without changing the K(m) value. Deoxyglucose uptake also involved a stereospecific carrier-facilitated transport system both in the presence and in the absence of lymphokine. The increased deoxyglucose transport induced by the lymphokine-containing supernatants was reversible. A migration inhibitory factor activity of similar molecular weight and heat stability was also present in these supernatants, but in titers lower than the titers of the deoxyglucose uptake-enhancing activity. Consequently, in the absence of a complete biochemical characterization, the two effects cannot be ascribed to the same molecular species at this time. Such a characterization, along with studies of lymphokine production and action, should be facilitated greatly by the availability of very high-titer supernatants derived by this geometric culture method.

Animals↗
PubMed1981

A lymphokine resembling transfer factor that stimulates MIF production by nonsensitive lymphocytes.

High potency preparations of a new heat-labile, low m.w. (less than 5000) lymphokine (LMWL) were obtained by culturing tuberculin-sensitive guinea pig peritoneal exudate cells (PEC) with PPD in geometric conditions that promote amplified lymphokine production. This LMWL has the ability, in the presence of PPD, to stimulate nonsensitive PEC to produce a heat-stable molecule(s) resembling MIF with a m.w. in the range 50,000 to 100,000. The effects of the LMWL (less than 5000 daltons) and the MIF-like molecule(s) (50,000 to 100,000 daltons) were defined by the indirect macrophage migration assay and a macrophage deoxyglucose uptake assay. It is possible that LMWL represents a form of transfer factor with the ability to recruit unsensitized lymphocytes to produce MIF.

Animals↗
PubMed1980

Role of calcium ions in the regulation of intramitochondrial metabolism. Properties of the Ca2+-sensitive dehydrogenases within intact uncoupled mitochondria from the white and brown adipose tissue of the rat.

1. Increasing concentrations of both Ca2+ and Sr2+ (generated by using EGTA buffers) resulted in 4-fold increases in the initial activity of pyruvate dehydrogenase within intact uncoupled mitochondria from rat epididymal adipose tissue incubated in the presence of the ionophore A23187, ATP, Mg2+ and oligomycin. The k0.5 values (concentrations required for half-maximal effects) for Ca2+ and Sr2+ were 0.54 and 7.1 microM respectively. In extracts of the mitochondria, pyruvate dehydrogenase phosphate phosphatase activity was stimulated about 4-fold by Ca2+ and Sr2+, with k0.5 values of 1.08 and 6.4 microM respectively. 2. NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase appeared to be rate-limiting in the oxidation of threo-Ds-isocitrate and oxoglutarate by uncoupled mitochondria from brown adipose tissue of cold-adapted rats. Ca2+ (and Sr2+) diminished the Km for the oxidation of both threo-Ds-isocitrate and oxoglutarate. The kinetic constants for these oxidations were very similar to those obtained for the activities of NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase in extracts of the mitochondria. In particular, the k0.5 values for Ca2+ were all in the range 0.2--1.6 microM and Sr2+ was found to mimic Ca2+, but with k0.5 values about 10 times greater. 3. Overall, the results of this study demonstrate that the activities of pyruvate dehydrogenase, NAD+-isocitrate dehydrogenase and oxoglutarate dehydrogenase may all be increased by Ca2+ and Sr2+ within intact mitochondria. In all cases the k0.5 values are close to 1 and 10 microM respectively, as found for the separated enzymes. Experiments on brown-adipose-tissue mitochondria incubated in the presence of albumin suggest that it may be possible to use the sensitivity of the dehydrogenases to Ca2+ as a means of assessing the distribution of Ca2+ across the mitochondrial inner membrane.

Adenosine Triphosphate↗
PubMed1980

Role of calcium ions in the regulation of intramitochondrial metabolism. Effects of Na+, Mg2+ and ruthenium red on the Ca2+-stimulated oxidation of oxoglutarate and on pyruvate dehydrogenase activity in intact rat heart mitochondria.

1. In uncoupled rat heart mitochondria, the kinetic parameters for oxoglutarate oxidation were very close to those found for oxoglutarate dehydrogenase activity in extracts of the mitochondria. In particular, Ca2+ greatly diminished the Km for oxoglutarate and the k0.5 value (concentration required for half-maximal effect) for this effect of Ca2+ was close to 1 microM. 2. In coupled rat heart mitochondria incubated with ADP, increases in the extramitochondrial concentration of Ca2+ greatly stimulated oxoglutarate oxidation at low concentrations of oxoglutarate, but not at saturating concentrations of oxoglutarate. The k0.5 value for the activation by extramitochondrial Ca2+ was about 20 nM. In the presence of either Mg2+ or Na+ this value was increased to about 90 nM, and in the presence of both to about 325 nM. 3. In coupled rat heart mitochondria incubated without ADP, increases in the extramitochondrial concentration of Ca2+ resulted in increases in the proportion of pyruvate dehydrogenase in its active non-phosphorylated form. The sensitivity to Ca2+ closely matched that found to affect oxoglutarate oxidation, and Mg2+ and Na+ gave similar effects. 4. Studies of others have indicated that the distribution of Ca2+ across the inner membrane of heart mitochondria is determined by a Ca2+-transporting system which is composed of a separate uptake component (inhibited by Mg2+ and Ruthenium Red) and an efflux component (stimulated by Na+). The present studies are entirely consistent with this view. They also indicate that the intramitochondrial concentration of Ca2+ within heart cells is probably about 2--3 times that in the cytoplasm, and thus the regulation of these intramitochondrial enzymes by Ca2+ is of likely physiological significance. It is suggested that the Ca2+-transporting system in heart mitochondria may be primarily concerned with the regulation of mitochondrial Ca2+ rather than cytoplasmic Ca2+; the possible role of Ca2+ as a mediator of the effects of hormones and neurotransmitters on mammalian mitochondrial oxidative metabolism is discussed.

Animals↗
PubMed1979

The effects of calcium ions and adenine nucleotides on the activity of pig heart 2-oxoglutarate dehydrogenase complex.

1. The effects of Ca2+ (mainly by using EGTA buffers), pH, ATP and ADP on the activity of the 2-oxoglutarate dehydrogenase complex from pig heart were explored. 2. Ca2+ (about 30 micrometer) resulted in a decrease in the apparent Km for 2-oxoglutarate from 2.1 to 0.16 mM (at pH 7) without altering the maximal velocity. At 0.1 mM-oxoglutarate there was a 4--5-fold activation by Ca2+, with an apparent Km for Ca2+ of 1.2 micrometer. A similar activation was also observed with Sr2+ (Km 15.1 micrometer), but not wised markedly from pH 7.4 TO 6.6. The effects of Ca2+ remained evident over this pH range. 4. In the presence of Mg2+, ATP resulted in a marked increase in the apparent Km for oxoglutarate, whereas ADP greatly decreased thisp arameter. The concentrations of adenine nucleotide required for half-maximal effects were about 10 micrometer in each case. 5. The effects of the adenine nucleotides and Ca2+ on the apparent Km for oxoglutarate appeared to be essentially independent of each other, reversible, and demonstrable in the presence of end product inhibition by NADH and obtained. 6. Effects similar to those described above were also observed on the activity of 2-oxoglutarate dehydrogenase from rat heart and brown adipose tissue. 7. We discuss the mechanisms controlling this enzyme's activity and compare these regulatory features with those of NAD-isocitrate dehydrogenase and the pyruvate dehydrogenase system, which are also sensitive to Ca2+ and adenine nucleotides.

Adenosine Diphosphate↗
PubMed1977

Evidence that fatty acid synthesis in the interscapular brown adipose tissue of cold-adapted rats is increased in vivo by insulin by mechanisms involving parallel activation of pyruvate dehydrogenase and acetyl-coenzyme A carboxylase.

Plasma insulin concentrations in cold-adapted rats were altered acutely by administration of glucose or anti-insulin serum. Rates of fatty acid synthesis in interscapular brown adipose tissue were determined from the incorporation of 3H from 3H2O into tissue lipid. Rates of synthesis were greatly elevated after glucose administration and markedly decreased after injection with anti-insulin serum. Parallel changes in the initial activities of both acetyl-CoA carboxylase and pyruvate dehydrogenase were observed under these conditions, but no changes in total activities were evident. The results suggest that this tissue is an important site of fatty acid synthesis in the cold-adapted rat and that this feature of the tissue is sensitive to changes in plasma insulin concentrations.

Acetyl-CoA Carboxylase↗
PubMedDate not supplied

Nosocomial infections in a developing Middle East hospital.

The prevalence and pattern of nosocomial infections in a new hospital in the United Arab Emirates is presented. During an 18-month period in which there were 6,544 discharges, 379 nosocomial infections occurred in 310 patients, representing an attack rate of 4.7%. The commonest site of infection was the urinary tract which accounted for 42.2% of the total. This was followed by surgical wound infections, cutaneous infections, bloodstream infections, lower and upper respiratory infections, infected burns and gastrointestinal infections. The most common organisms were Escherichia coli (22.7% of isolates), Pseudomonas species (17.5%) and Staphylococcus aureus (16.7%). Escherichia coli was the most common cause of urinary tract infections and bacteremia; Staphylococcus aureus was the most common cause of surgical wound and cutaneous infections. There was only one Serratia marcescens infection. We observed a high incidence of Pseudomonas infections, particularly of the urinary tract, and Staphylococcal surgical wound and other cutaneous infections, but otherwise our data are similar to nosocomial infection data from US hospitals.

Anti-Bacterial Agents↗