Immunohistochemical localization of substance P and enkephalin in the nucleus tractus solitarii of the rhesus monkey, Macaca mulatta.

The nucleus tractus solitarii in the monkey Macaca mulatta was found to have several subdivisions based upon cytoarchitectonics and immunohistochemistry. Subdivisions that could be identified included commissural, medial, parvicellular, dorsolateral, ventrolateral, intermediate, and interstitial. Substance P and enkephalin immunoreactivity was localized within discrete regions of the nucleus tractus solitarii, by means of the peroxidase-antiperoxidase technique. Substance P immunoreactivity occurred most frequently in the interstitial subdivision of the nucleus tractus solitarii. Moderate accumulations of substance P immunoreactivity were present in the commissural, medial, parvicellular, dorsolateral, and intermediate subdivisions, but very little was present in the ventrolateral subdivision. Enkephalin immunoreactivity followed the staining patterns of substance P; however, the amounts of enkephalin immunoreactivity were less than amounts for substance P. Following colchicine treatment, large numbers of enkephalin-immunoreactive neurons were distributed throughout all subdivisions, many being located in the parvicellular and medial subdivisions. The few substance P-immunoreactive neurons found were restricted to the parvicellular subdivision. The distribution of substance P and enkephalin immunoreactivity in M. mulatta is very similar to that described in the cat and rat. In addition, the extensive overlap of the distribution of these two putative neurotransmitters provides morphological evidence for their possible participation in the autonomic regulation within the nucleus tractus solitarii.

Automation of a fluorometric method for the determination of 2-deoxy-D-glucose.

A continuous-flow fluorometric procedure for the determination of 2-deoxy-D-glucose (2DG) is described. The method utilizes Technicon Autoanalyzer equipment and modules, and is based on the acid-catalyzed condensation of 3,5-diaminobenzoic acid with 2DG. The procedure permits analysis of 20 samples/h, is sensitive to concentrations of 2DG as low as 0.2 mg/100 ml, and requires sample volumes of only 0.25 ml. 2DG can be quantitatively measured in serum samples or tissue extracts without requiring deproteinization. Glucose does not interfere with the assay while 2-deoxy-D-ribose develops a fluorescence which is about 15% of that produced by the same amount of 2DG and is additive when both deoxy sugars are present together. The procedure is accurate, reproducible, and fast, and can be run continuously.

Correlates of maximal oxygen consumption during treadmill exercise.

According to the Balke treadmill protocol, 39 healthy male USAF volunteers were subjected to maximal exercise. The subjects as a group passed the anaerobic threshold by the end of exercise since average venous lactate concentrations increased from 11.2 +/- 1.6 mg% (95% confidence limits) to 93.0 +/- 8.5 mg% (95% confidence limits), and the average gas exchange ratio (R) at the end of the exercise was greater than unity (p less than 0.0005). Tests for correlations showed weak but statistically significant (p less than 0.05) relationships between change in venous lactic acid concentrations and R (r = 0.44) and maximal heart rate (r = 0.34). Maximal oxygen consumption was correlated with time of exercise (r = 0.70) and subject weight (r = 0.33). Subject age and initial plasma lactate concentrations were not significantly correlated with any other variables. Multiple linear regression yielded an equation for prediction of maximal oxygen consumption which included terms for time of exercise and subject weight. Although the multiple correlation coefficent (r = 0.75) was statistically significant (p less than 0.05), it was considered insufficient for accurate prediction of maximal oxygen consumption.

Serum myocardial enzymes after +Gz acceleration.

Circulating levels of lactate dehydrogenase, glutamate-oxaloacetate, glutamate-pyruvate transaminase, and creatine phosphokinase, as well as its isoenzymes, were measured to investigate the possibility of myocardial damage during acceleration to high +Gz. Serum samples were analyzed in 12 human volunteers before, 6 h after, and 24 h after several bouts of accleration to 6, 8, 9, and 10 G. No substantial elevations of enzyme activities were observed. However, multivariate analysis of variance and multiple comparisons of the data indicated a small but statistically significant (p less than 0.01) increase in creatine phosphokinase. The results were consistent with enhanced skeletal muscle cell permeability consequent to muscular exercise.