Changes in mitochondrial enzyme activity of rat lung during the development of silicosis.

Significant changes occurred in the activities of enzymes in silicotic rat lung at 30, 90 and 150 days after intratracheal injection of quartz dust. The pattern of changes indicated that the mitochondrial metabolism in silicosis is altered significantly indicating disturbances in bioenergetics. Increase in activity of cytochrome-$\text{c}$-oxidase and NADH-cytochrome-$\text{c}$-reductase at the early stage and a significant decline at the advanced stage of the disease suggest that metabolic changes in silicosis during the initial and the advanced stage of the disease are distinctly different. Besides, enhanced rate of glycolysis is also observed at the early stages of silicosis.     

Changes in enzyme activity of germinating conidia of Neurospora crassa

The conidia of wild-type Neurospora crassa are shown to have a drastically lower activity for three enzymes of the isoleucine-valine pathway—acetohydroxy acid synthetase, dihydroxy acid dehydratase, and aminotransferase—than the actively growing mycelium. Lower activity was also found in the conidia for ornithine transcarbamylase and aspartate transcarbamylase. Lower activity (10- to 100-fold) was found for the overall synthesis of valine from pyruvate in the conidia as compared to the mycelium as expected.In addition it is also apparent that the distribution of the isoleucine-valine enzymes is different in conidia from the mycelium as regards activity in the mitochondria as compared to the cytosol. In conidia their activity in the mitochondria is lower than in the cytosol, but the opposite holds in the mycelium. These differences are also reflected in the overall activity.Cycloheximide inhibits the increase in total activity of the acetohydroxy acid synthetase and the dehydratase during germination of the conidia.     

Changes in protein composition and hydrolytic enzyme activity of Escherichia coli and Hafnia alvei grown in human fluids

Growing of Escherichia coli and Hafnia alvei cells in several cell-free human fluids, such as normal serum, serum from diabetic patients, pleural, ascitic and spinal fluid, revealed that various biochemical changes occurred. Protein profile on SDS-PAGE as well as acid and alkaline phosphohydrolytic enzymes on native gels of cell extracts were affected after culturing of bacteria in the above fluids. Gelatinolytic and hyaluronolytic activity was of interest because both of them are histolytic enzymes. Although there was a potential appearance of gelatinolytic bands on gelatin-SDS-PAGE in cells starved in seawater, none of these activities were expressed in cells grown in human fluids. A hyaluronolytic activity of approximately 45 KDa was present in cells cultured in Mueller Hinton broth. This enzyme was decreased either in cells starved in seawater or in cells grown in human fluids to an almost invisible band on hyaluronan-SDS-PAGE.     

Changes in enzyme activity during differentiation in Chlamydomonas reinhardtii

The patterns of alanine dehydrogenase, glutamate dehydrogenase and malate dehydrogenase activity were studied during the normal vegetative cell cycle and during the process of gametic differentiation and dedifferentiation in synchronized cultures of Chlamydomonas reinhardtii. During all three phases of growth and differentiation the synthesis of DNA was also measured. During gametic differentiation all three enzyme levels were suppressed compared to vegetative cells although DNA and cell number were comparable. During gametic dedifferentiation no DNA synthesis occurred during the first 24 h cycle and only a doubling during the second. It was not until the third cycle that a normal 4-fold increase in DNA was observed. Cell number followed a similar pattern. Athough the levels of alanine dehydrogenase and malate dehydrogenase were uniformly low during the first cycle when glutamate dehydrogenase increased 4-fold, during the second cycle the patterns of these enzymes changed markedly. The enzymes did not attain levels characteristic of vegetative cells until the third cycle.     

Changes in glycolytic enzyme levels and isozyme expression in human lymphocytes during blast transformation.

The levels of each of the glycolytic enzymes were observed to exhibit a parallel increase of 200 to 300% when human lymphocytes were stimulated to undergo blast transformation. A series of electrofocusing and electrophoretic studies was utilized to assess the isozyme distribution of the glycolytic enzymes during blastogenesis. Hexokinase (pI = 7.40), glucosephosphate isomerase (pI = 9.35), and enolase (pI = 8.30) existed as single electrophoretic components and were unchanged during blast transformation. Phosphoglycerate mutase was observed to exist as two isozymes (pI = 5.80 and 6.63), which were also unchanged by blastogenesis. Aldolase, which was present as two electrophoretic forms in lymphocytes (pI = 9.25 and 8.75), exhibited a shift in the relative content of each. In addition to the lactate dehydrogenase isozymes at pI 9.50 and 7.60 found in lymphocytes, lymphoblasts contained isozymes with pI values of 7.30, 7.05, and 5.85. Although glyceraldehyde 3-phosphate dehydrogenase was present as a single electrophoretic form (pI ? 8.0) in both lymphocytes and lymphoblasts, the association of the enzyme with actin produced electrophoretic artifacts with lower pI values. Phosphoglycerate kinase, which appeared as a single form in lymphocytes (pI = 9.00), was present as two isozymes (9.00 and 8.74) in lymphoblasts. Similarly, pyruvate kinase (pI = 8.73 and 8.50 in lymphocytes) exhibited additional isozymes (pyruvate kinase, pI = 7.60 and 5.85, and triosephosphate isomerase, pI = 5.20) as a result of cell transformation.     

Residual mannosidase activity in human mannosidosis: characterization of the mutant enzyme.

The prenatal diagnosis of affected fetuses in two families at risk for mannosidosis gave us the opportunity to study the residual alpha-mannosidase activity. We found an altered acidic alpha-mannosidase characterized by lowered affinity toward the substrate, displacement of maximal activity toward pH 4-5, thermal lability, different migration in electrophoresis, and apparent change in molecular weight at alkaline pHs. The immunological properties seem unchanged since the enzyme was precipitated by an antiacidic alpha-mannosidase antiserum. The mutant enzyme instability, provoked by dialysis, and its reactivation after addition of dialysis fluid, suggests an association-dissociation phenomenon. We propose a possible hypothesis that a low molecular weight ligand is necessary to maintain the activity of the mutant enzyme.     

Changes in bioenergetics of skeletal muscle mitochondria during experimental trichinosis in rats

Changes in bioenergetics were studied in mitochondria isolated from skeletal muscles of rats in the course of experimental trichinosis. In fortified media supporting oxidative phosphorylation, oxygen uptake with succinate was greatly enhanced, while the oxidation of glutamate and of malate plus pyruvate was manifold inhibited. The protective effect of BSA added was negligible in this case.     

Changes in enzyme activity of white yam tubers after prolonged storage

There is a substantial increase in the activities of phosphorylase, hexokinase, glucose-6-phosphate dehydrogenase and alcohol dehydrogenase in white yam tubers as they age. The high glucose-6-phosphate dehydrogenase activities suggest that the pentose phosphate pathway is important in yam tuber tissue.     

Lipoprotein lipase activity of rat cardiac muscle. Changes in the enzyme activity during incubations of isolated cardiac-muscle cells in vitro.

1. Isolated cardiac-muscle cells from the hearts of adult rats were shown to retain a high amount of viability during 4 h of incubation when viability was assessed by Trypan Bue stain exclusion and intracellular enzyme leakage. 2. The cells also retained their ability to take up O2 and utilize added substrates over the period of incubation at both 25 and 30 degrees C. 3. When cells from the hearts of fed rats were incubated in a buffered-salts solution at pH 7.4 in the presence of amino acids and heparin, lipoprotein lipase activity in the medium increased progressively. 4. During these incubations the intracellular activity of the enzyme remained constant and the total activity of lipoprotein lipase in the system (cells plus medium) increased by 80% over the 4 h of incubation at 25 degrees C. 5. In the absence of heparin only low amounts of enzyme activity were detectable in the medium and the total lipoprotein lipase activity in the system remained constant. 6. The measurement of lipoprotein lipase activity in either fresh homogenates of the cells or in homogenates of acetone/diethyl ether-dried powders of the cells had no effect on the overall pattern of activity change during the incubations, although as reported previously the total activity detected with acetone/diethyl either-dried preparations was approx. 3-fold higher than with fresh cell homogenates. 7. The observations were compared with published data on lipoprotein lipase activity changes in neonatal heart cell cultures maintained in vitro.     

Changes in enzyme activity and isoperoxidases in haploid tobacco callus during organogenesis

Haploid tobacco tissues cultured on Murashige and Skoog (MS) medium supplemented with 0.3 mg/l indole-3-acetic acid (IAA) and 1% sucrose remained undifferentiated. Increasing sucrose level (3%) at the same IAA concentration induced shoot differentiation in 9 days. Further increase in sucrose level (6%) resulted in root differentiation on day 12. Total specific activity of peroxidase, IAA oxidase, malate dehydrogenase (MDH) and phenylalanine ammonia-lyase (PAL) exhibited definite development variations among the three programmes. The number of the anodic and cathodic isoperoxidase bands changed in each case with time. Shoot formation was characterized by the synthesis of anodic peroxidases: AS₁ (Rm=0.41), AS₂ (Rm=0.44) and AS₃ (Rm=0.46), all three being synthesized prior to visual manifestation of shoots. Likewise, root differentiation was heralded in advance by synthesis of one anodic isoperoxidase AR (Rm=0.30). Cathodic isoperoxidases did not show any subtle correlation with shoot or root formation.     

Changes in lysosomal enzyme activity in the mitotic cycle of L cells

Activities of lysosomal enzymes (acid phosphatase, N-acetyl-beta-D-glucosaminidase, acid lipase and cathepsin D) have been examined in a synchronized culture of mouse L-fibroblasts. Cell synchronization was achieved by the double thymidine block with a subsequent mitotic selection after colcemid treatment. Specific activities of the enzymes studied were found to be higher in S-G2 that in G1. There is a linear increase (approximate doubling) in enzyme activities per cell from G1 to M. Activity of galactosyltransferase, a marker of the Golgi apparatus, declined in mitotic cells in comparison with the interphase cells. Ultrastructural examination of L-cells revealed a reduction of the intracellular membrane system including the Golgi apparatus during mitosis. Changes in the Golgi apparatus activity have been considered as a possible regulatory point of lysosome formation. The data presented are compared with the results of morphological studies of lysosomal system in L-cells.