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Biomedical subjects

D J Johnson

Publications and source records attributed to D J Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1983

Avian pancreatic polypeptide-like immunoreactivity in ground squirrel hypothalamus.

The distribution of avian pancreatic polypeptide-like immunoreactivity (APP-LI) within the hypothalamus of the golden-mantled ground squirrel (Spermophilus lateralis) was analyzed using the indirect peroxidase-antiperoxidase immunocytochemical technique. Avian pancreatic polypeptide-LI is widely distributed within the hypothalamus of the golden-mantled ground squirrel and in general, the distribution of APP-LI containing neuronal fibers in this species is qualitatively similar to the distribution found in the laboratory rat. This similarity in APP-LI distribution in two rodents from different taxonomic Families suggests that the distribution of APP-LI containing neurons is probably very conservative within the Order Rodentia.

Animals↗
PubMed1983

Measurement of the absolute synthesis of soluble and insoluble elastin by chick aortic tissue.

The rate of in vitro synthesis of soluble and insoluble elastin by thoracic aorta of 2-day-old chicks has been measured in absolute terms. In the absence of beta-aminopropionitrile (beta APN), the steady state level of soluble elastin was 120 pmol/100 mg of aortic tissue or 3.7 micrograms/whole aorta segment. The rate of synthesis of elastin in vitro was approximately 130 micrograms/day per whole aorta segment. This is three- to four-fold lower than the estimated rate of in vivo synthesis for a comparable segment of aortic tissue at the same stage of development. Pulse-chase experiments suggested that this difference was not due to in vitro proteolysis of a significant proportion of the newly synthesized soluble elastin, but rather that the conversion of soluble to insoluble elastin was both rapid and efficient. These experiments also indicated the presence in aortic tissue of a substantial pool of elastin of intermediate solubility. Although inclusion of beta APN in the incubation medium resulted in an increase in the amount of soluble elastin in aortic tissue, the rate of accumulation of newly synthesized soluble elastin in the presence of this inhibitor of cross-linking was not linear, but decreased with incubation time. Furthermore, although beta APN effectively suppressed the appearance of insoluble elastin for at least 2 h, some escape from the effect of this inhibitor was seen with further incubation. In general, beta APN significantly depressed elastin synthesis.

Amino Acids↗
PubMed1983

Metabolic effects of facial cooling in exercise.

Metabolic responses to facial cooling during prolonged exercise was investigated in five male subjects. Exercise on a bicycle ergometer at 50 rpm for 1 h at 60% maximal heart rate was performed twice, once with cold wind (10 degrees C, 6.5 m . s-1) and once without. Resting experiments were conducted under identical conditions. Facial cooling apparently had no effect on plasma FFA or glucose concentration during exercise but did, however, result in significantly (p less than 0.05) greater fat utilization, as indicated by lower respiratory exchange ratios at 60 min of exercise. The respiratory exchange ratio, blood lactate concentration, oxygen consumption, and estimated myocardial oxygen consumption at 5 min of exercise were higher with facial cooling. The results suggest that metabolic changes occur with facial cooling that are related to a general thermoregulatory response and that the stress of exercise is greater with facial cooling.

Adult↗
PubMed1982

Prediction of plasma amino acid concentration from diet amino acid content.

The level of each plasma amino acid in male weanling rats was examined in relation to their intake from gluten, casein, synthetic amino acid, or zein diets. Plasma levels of valine, leucine, and isoleucine were found to be linearly related to the intake per gram diet regardless of the dietary source. Although levels of most other amino acids were not linearly related to intake, they were predictable if both the concentration of the amino acid in the diet and chronic level of protein intake were known. That is, a relationship, which applied to all diets, was found between the concentration of amino acid in the plasma, the concentration in the diet, and the total protein or amino acid nitrogen in the diet.

Amino Acids↗
PubMed1981

Exercise heart rate response to facial cooling.

The heart rate responses of physically untrained men to exercise with and without facial cooling were determined. Cold wind (10 degrees C, 6.5 m x s-1, or 2 degrees C, 6.5 m x s-1) was directed at the faces of the subjects during a 16 min bout of progressively intense exercise. The 10 degrees C wind resulted in a significantly (p less than 0.05) lowering of heart rate that appeared to be associated with a decline in forehead temperature at 4, 6, and 8 min of exercise. No differences were observed for blood pressure or rectal temperature. The significant (p less than 0.05) reduction in heart rate with the 2 degrees C cold wind did not appear to be associated with changes in facial temperature. The 2 degrees C wind also resulted in a persistent peripheral vasoconstriction (p less than 0.05). The results suggest that the heart rate response to facial cooling during exercise is mediated not through a reflex associated with increased stroke volume but rather via a central thermoregulatory response.

Body Temperature↗
PubMed1980

Improved radiochemical method for measuring ferrochelatase activity.

We describe a radiochemical method for measuring ferrochelatase activity in the in vitro incorporation of iron into mesoporphyrin-IX to form mesoheme. 59Fe is used to quantify ferrochelatase activity in rat liver. The uptake of iron is linearly related to the time allowed for it to occur, and the reaction proceeds optimally under reducing and anerobic conditions, maintained in sealed lyophilization vials under a positive pressure of nitrogen.

Animals↗
PubMed1979

Effect of cold submersion on intramuscular temperature of the gastrocnemius muscle.

This study investigated the effect of a 30-minute, 10 degrees C water bath on the intramuscular temperature of a lower leg and the contralateral lower leg. Intramuscular temperature was measured in 10 subjects using hypodermic thermistor probes inserted 25.3 mm into the lateral head of the gastrocnemius muscles of both legs. One lower leg was submersed in a 10 degrees C cold bath with the water level maintained 5 cm above the patella and with the subject in a nonweight-bearing position. Intramuscular temperature significantly decreased in both lower legs during treatment, although the intramuscular temperature of the treatment lower leg was significantly lower than that of the contralateral lower leg. A temperature difference continued for four hours after treatment; however, the temperature of both lower legs was significantly lower after four hours than it was before the cold bath treatment.

Adipose Tissue↗
PubMed1979

Isometric muscle contraction response during recovery from reduced intramuscular temperature.

This study was done to determine the effects of a 30-minute cold water bath on intramuscular temperature and plantar flexion strength, immediately after treatment and during a 3-hour posttreatment recovery period. Twenty persons were tested twice, receiving treatment once and serving as controls once. Measurements were taken prior to the treatment period, immediately after treatment and then every 30 minutes for 3 hours. The dominant leg was submerged in water at 10 C for 30 minutes. Plantar flexion strength was measured with a cable tensiometer and intramuscular temperature was measured with a hypodermic thermistor probe. Intramuscular temperature significantly decreased immediately posttreatment on the experimental days and then increased significantly during the recovery period. Significant increases in strength were noted during the recovery period. A definite relationship exists between intramuscular temperature and plantar flexion strength.

Adult↗
PubMed1977

Influence of cold bath on maximum handgrip strength.

12 female college students participated in a repeated-measures experiment, receiving an experimental treatment and a control treatment. The former was a 30-min. cold bath to the forearm while the control was a simolar 30-min. period without the cold bath. Subjects' maximum handgrip strength was measured 11 times, immediately prior to treatment, immediately following treatment, and then every 20 min. for 3 hr. The subjects were tested at the same time of the day, on the same day of the week, for two consecutive weeks. Grip strength was significantly decreased immediately following the experimental treatment below pre-treatment measures and post-treatment measures for the control session. Grip strength during the experimental session significantly increased at 80 min. post-treatment when compared to the strength measures for the control at the same time interval or when compared to pre-treatment measures for either treatment. The strength measures for the two treatments remained significantly different over the rest of the testing occasions.

Baths↗
PubMed1977

Simultaneous spectrophotometry of Fe2+ and Cu2+ in serum denatured with guanidine hydrochloride.

We show how iron and copper ions may be simultaneously measured in 0.2 ml of serum after using guanidine hydrochloride to cause their release from protein. Sensitive reagents for iron (2,4,6-tripyridyl-s-triazine) and copper (disodium 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline disulfonate) facilitate such measurement. We eliminated spectral interference between the two metal-ion complexes by selective use of pH. Results compare well with those obtained by accepted methods in which the concentrations of these ions are measured independently.

Copper↗
PubMed1977

Improved colorimetric determination of serum zinc.

We show how zinc may easily be quantified in serum by first using an optimum concentration of guanidine hydrochloride to cause release of zinc from proteins, followed by complexation of released metals with cyanide. The cyanide complex of zinc is preferentially demasked with chloral hydrate, followed by a colorimetric reaction between zinc and 4-(2-pyridylazo)resorcinol. This is a sensitive water-soluble ligand; its complex with zinc has an absorption maximum at 497 nm. Values found by this technique compare favorably with those obtained by atomic absorption spectroscopy.

Bilirubin↗