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Biomedical subjects

O H Lowry

Publications and source records attributed to O H Lowry.

At least 91 records · Page 5Linked to original sources
PubMed1982

"Increased" sensory stimulation leads to changes in energy-related enzymes in the brain.

The facial whiskers of mice project through several synapses to anatomically distinct structures called barrels in the contralateral cerebral cortex. With appropriate illumination, individual barrels can be recognized and dissected from unfixed, freeze-dried tissue sections taken parallel to the plane of layer IV. The tissue then can be analyzed using quantitative microhistochemical techniques to determine the level of various substances of biological importance (W.D. Dietrich, D. Durham, O. H. Lowry, and T. A. Woolsey (1981) J. Neurosci. 1: 929-935). The present paper describes results obtained in this way from adult mice subjected to a chronic "sensory deprivation" by repeatedly clipping all of the whisker hairs on one side of the face and during the recovery from this deprivation in which the whisker hairs were allowed to grow back. Sensory deprivation for 60 days leads to significant changes in the levels of the three energy-related enzymes studied--citrate synthase, malate dehydrogenase, and glycogen phosphorylase. surprisingly, during clipping, the enzyme levels in the barrels of the contralateral cortex are essentially normal, whereas enzyme levels in the barrels of the ipsilateral cortex are increased significantly. Specifically, activities expressed as a percentage of levels in normal animals were: citrate synthase, 135%; malate dehydrogenase, 130%; and glycogen phosphorylase, 170%. Forty-five days after the deprivation is reversed, the levels return to normal. These significant changes occurred in adult mice several synapses away from the sensory periphery. The data are in contrast to our earlier results in which damage to the primary afferents reduced the levels of the enzymes citrate synthase and malate dehydrogenase contralateral to the manipulation. A possible explanation for the enzymatic changes observed in the cortex ipsilateral to the clipped whiskers is an increased utilization of the intact sensory periphery by the animals; this has some behavioral support.

Animals↗
PubMed1981

Uptake of exogenous glutamate and aspartate by circumventricular organs but not other regions of brain.

Glutamate (Glu) and aspartate (Asp) concentrations in blood and selected regions of brain were measured at sequential intervals over a 3-h period following subcutaneous administration of Glu, Asp, or Glu plus Asp (2 mg/g body wt) to 4-day old mouse or rat pups. Marked serum elevations of the administered amino acids (peak values exceeding 200 times control levels) were detected within 1 h. In circumventricular organ (CVO) regions of brain, which are thought to have no blood-brain barriers, a sharp and steady increase times higher than control levels) occurred during a 15-120 min interval, whereas no appreciable increase were detected in other brain regions. When 2 mg/g Glu plus 2 mg/g Asp were administered, CVO tissue concentrations of each amino acid rose to approximately the same level obtained when the individual amino acids were given. It is concluded that blood-brain barriers preventing net entry of Glu or Asp into brain proper are relatively well established by the 4th postnatal day in rodents, but that CVO brain regions lack such barriers; selective access of blood-borne Glu or Asp to CVO neurons explains why these neurons are selectively destroyed by systemic administration of these neurotoxic amino acids.

Animals↗
PubMed1981

Distribution of cyclic nucleotide phosphodiesterase in mouse brain.

Seventy-one regions of mouse brain, and many subdivisions of some of these, were analyzed for cyclic nucleotide phosphodiesterase. The samples were dissected from lyophilized frozen sections. Since the average sample weighed only 25 ng (20 X 75 X 75 mu3), regions as small as the locus ceruleus could be analyzed. Activities in gray areas ranged 40-fold from a high in the pars reticulata of the substantia nigra to a low in the deep cerebellar nuclei. The activity in fiber tracts also varied about 40-fold, and on a lipid-free dry weight basis was similar to the activity in the gray matter where the fibers originated. The rank order for gray regions was basal ganglia, amygdala, hippocampus, cerebral cortex, most of the diencephalic nuclei, nuclei of the pons, cerebellum, and nuclei of the medulla.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1980

Amplification by enzymatic cycling.

Enzymatic cycling provides a methodology for virtually unlimited amplification of analytical sensitivity. The most widely applicable cycling systems are those for NAD and NADP, since these can be used to increase the sensitivity of methods for a host of other substances. However, cycling systems for ATP plus ADP, GTP + GDP, glutathione and coenzyme A have also proven to be very useful. A total of 19 cycling procedures are described in greater or lesser detail. Some of these are capable of amplification rates in excess of 20,000 per hour in a single cycling step (20,000 x 20,000 with two one hour cycling steps). Advantages, disadvantages, limitations and other practical considerations are stressed, as well as the means for coupling the cycling systems to assays for other substances.

Alcohol Oxidoreductases↗
PubMed1980

Metabolic effects of large fructose loads in different parts of the rat nephron.

Rats were given large parenteral loads of fructose and the different segments of single nephrons then analyzed for fructose metabolites, fructose metabolizing enzymes, and nucleotide high energy phosphates. Fructokinase and fructose-1-P aldolase activities, and all the major metabolite and nucleotide effects, were confined to the proximal tubule. The proximal straight segment had the highest fructokinase and suffered the greatest changes. In this segment, fructose-1-P rose to 60 mmol/kg (dry weight basis) and glycerol-3-P and glucose-6-P reached 8 and 12 mmol/kg, respectively. ATP fell 80% and GTP (judging from the changes in GTP plus GDP) fell by the same percentage, but UTP was less affected. Total adenylate decreased 50%. In the proximal convoluted tubule, where fructokinase was lower and fructose-1-P aldolase higher than in the straight segment, fructose-1-P rose ony one-fourth as much and glucose-6-P was almost unchanged. In contrast, glycerol-3-P rose more, reaching 16 mmol/kg. Other substances measured along the nephron were glycerol-3-P dehydrogenase, fructose-1,6-bisphosphate aldolase, fructose, glucose, fructose bisphosphate, triose phosphate, and 6-P-gluconate. Control ATP levels were found to be highest in the distal tubule.

Adenine Nucleotides↗
PubMed1980

The distribution of the components of the cyclic GMP cycle in retina.

Frozen sections of retinas from rabbit (mostly rods), ground squirrel (mostly cones), and monkey (mixed rods and cones) were freeze dried, and samples from all the discrete layers analyzed for the enzymes which form cyclic GMP and subsequently convert it back to GTP. The distribution of cyclic GMP was also measured in monkey retina, and the retinal layers of both monkey and rabbit were analyzed for GTP, GTP plus GDP, ATP, ATP plus ADP, and UTP plus CTP. The ratio of guanylates to adenylates was found to be about 1:1 in photoreceptor cell layers, but only 1:4 or 5 in deeper layers. In all species, guanylate cyclase (EC 4.6.1.2) and cyclic GMP phosphodiesterase were highest in the outer segment layer. Other layers were lower by factors of 10 to 500. Guanylate kinase (EC 2.7.4.8) was extremely high in all photoreceptor cell layers except the outer segments, but was much lower elsewhere. Nucleoside diphosphokinase (EC 2.7.4.6) paralleled guanylate kinase throughout the photoreceptor cell layers, but did not fall to such low levels in the deeper layers of the retina. Although there were significant differences among the three species, they all displayed the same general enzyme pattern.

Adenosine Diphosphate↗
PubMed1980

Enzyme levels in individual rat muscle fibers.

Individual muscle fibers from the rat anterior tibialis and soleus muscles were each analyzed in duplicate for lactate dehydrogenase (LDH, EC 1.1.1.27), malate dehydrogenase (MDH, EC 1.1.1.37), 3-hydroxyacyl-CoA dehydrogenase (EC 1.1.1.35), fumarate hydrotase (EC 4.2.1.2), glycogen phosphorylase (EC 2.4.1.1), 6-phosphofructokinase (EC 2.7.1.11), pyruvate kinase (EC 2.7.1.40), fructose-bisphosphatase (EC 3.1.3.11), and creatine kinase (EC 2.7.3.2). A few fibers were also analyzed for adenylate kinase (EC 2.7.4.3). In general, there was a wide and almost continuous spectrum of coordinated enzyme activities. In the tibialis muscle, two fiber groups could be clearly distinguished on the basis of MDH activity. The high MDH group had on the average lower LDH activity, but there was a great deal of overlap in LDH between the two groups. Less overlap was observed for phosphorylase and fructose-bisphosphatase, both inversely related to MDH. Only one main group of fibers (presumably slow twitch) was found in the soleus muscle, although enzyme activities also covered a wide range. These soleus fibers were clearly distinguished from the high MDH tibialis group by much lower activities of LDH, pyruvate kinase, and fructose-bisphosphatase.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1980

Effect of intervening lesions on amino acid distributions in rat olfactory cortex and olfactory bulb.

Levels of the proposed neurotransmitter amino acids glutamate, aspartate, gamma-aminobutyric acid (GABA), and glycine were measured within the layered structures of the olfactory bulb and olfactory cortex following unilateral transections of the lateral olfactory tract or of virtually all fiber tracts of the olfactory peduncle. Distributions of the amino acids on both lesion and control sides were examined and compared by means of a mapping procedure. The results suggest: 1) Glutamate and aspartate are specifically associated with mitral (and presumably also tufted) cell axons and terminals in the piriform cortex. The distribution of aspartate in the olfactory bulb is further suggestive of a specific association of aspartate with mitral cell dendrites and somata. 2) Glutamate might be specifically associated with some centrifugal fibers traveling to the olfactory bulb in or near the anterior commissure. 3) GABA might be specifically related to some certrifugal fibers to the olfactory bulb in addition to its prominent association with granule cells of the bulb. 4) Glycine is unlikely to play a prominent neurotransmitter role in either the olfactory bulb or olfactory cortex.

Amino Acids↗
PubMed1979

Enzymatic identification of mannose 6-phosphate on the recognition marker for receptor-mediated pinocytosis of beta-glucuronidase by human fibroblasts.

Human beta-glucuronidase (beta-D-glucuronide glucuronosohydrolase, EC 3.2.1.31), like many other glycoprotein lysosomal hydrolases, is subject to receptor-mediated endocytosis by fibroblasts. Prior work demonstrated charge heterogeneity in beta-glucuronidase and showed that high-uptake forms are more acidic than slowly internalized forms. Considerable indirect evidence implicated mannose 6-phosphate as an essential part of the recognition marker on high-uptake enzyme forms. Here we report the purification of beta-glucuronidase from human spleen and demonstrate enzymatically that mannose 6-phosphate is released on acid hydrolysis of pure enzyme varies directly with its susceptibility to pinocytosis by fibroblasts. Enzyme forms resolved by CM-Sephadex chromatography differed over an 18-fold range in uptake rate and in mannose 6-phosphate content. The most acidic forms had 4.4 mol of mannose 6-phosphate per mol of enzyme. The mannose 6-phosphate was released from the enzyme by treatment with endoglycosidase H with concomitant loss of susceptibility to adsorptive endocytosis. Thus, these studies provide direct evidence that mannose 6-phosphate is present on high-uptake enzyme forms, that it is present in the recognition marker for uptake, and that it is present on oligosaccharide that is released by endoglycosidase H.

Biological Transport, Active↗
PubMed1979

Distribution of two aminotransferases and D-amino acid oxidase within the nephron of young and adult rats.

In the adult rat kidney, alanine aminotransferase (EC 2.6.1.2), aspartate aminotransferase (EC 2.6.1.1) and D-amino acid oxidase (EC 1.4.3.3) were measured in glomeruli, 4 parts of the proximal tubule, 2 parts of the distal tubule and in patches from the thin limb area and the papilla. These enzymes were measured in more limited parts of the nephron during postnatal development. Adult aspartate aminotransferase activities (percentage of the highest) ranged from 100 in the distal straight segment to 25 in the late part of the proximal straight segment to 10 in the thin limb and papillary area. Alanine aminotransferase (lower by a factor of 100 in absolute terms) was distributed as the mirror image of aspartate aminotransferase within proximal and distal tubules. D-Amino acid oxidase was 850-fold higher in proximal straight segments than in medullary structures. During development alanine aminotransferase increased 6-fold and D-amino acid oxidase, 4.5-fold in proximal straight tubules but aspartate aminotransferase increased in distal straight tubles 8-fold.

Aging↗