Forskolin and ethanol both perturb the structure of liver plasma membranes and activate adenylate cyclase activity

Both forskolin and ethanol elicit the activation of basal and ligand-stimulated adenylate cyclase activities in rat liver plasma membranes. Ethanol is most potent at activating the fluoride- and glucagon-stimulated activities whilst having little effect on basal activity. In contrast forskolin exerts its greatest effect on basal activity. Over the concentration range that ethanol activates adenylate cyclase, it also increases bilayer fluidity as indicated by a decrease in the values of the order parameters for an incorporated fatty acid spin probe. At high concentrations forskolin does increase bilayer fluidity. However, it only begins to do so at concentrations above those where forskolin has already exerted its maximal effect in activating adenylate cyclase. Forskolin can still activate, albeit to a reduced extent, detergent-solubilized adenylate cyclase whereas ethanol cannot. Forskolin elicits a pronounced rise in hepatocyte intracellular cyclic AMP concentrations, whereas ethanol does not. Both forskolin and ethanol reduce the temperature of onset of the lipid phase separation occurring in rat liver plasma membranes. This is detected in Arrhenius plots of both glucagon-stimulated adenylate cyclase activity and order parameters of an incorporated fatty acid spin probe, where we find that forskolin is particularly potent in decreasing the temperature at which this lipid phase separation occurs. Our results are consistent with the notion that forskolin exerts its effect on adenylate cyclase primarily by a direct action on the catalytic unit of the enzyme. However, as forskolin is a potent perturber of the organisation of the lipid bilayer it is possible that this could modulate its effect on adenylate cyclase and might be expected to affect the activity of other membrane enzymes.     

Effects of chirality in 9-(2-hydroxy-3-nonyl)adenine upon deoxyribonucleic acid synthesis in herpes simplex virus-infected cells

The antiherpes activities of erythro- and threo-9-(2-hydroxy-3-nonyl)adenines (EHNA and THNA) have been determined. All isomers inhibited the replication of herpes simplex virus (HSV) and inhibited DNA synthesis in HSV-infected cells. The two enantiomers of EHNA, (+)-EHNA and (?)-ENHA, displayed equal antiviral activities. This is in contrast to their activities as inhibitors of adenosine deaminase (ADA); (+)-EHNA is a 250-fold more potent inhibitor of ADA than (?)-EHNA [Bessodes et al. Biochem. Pharmac. 31, 879 (1982)]. The antiherpes activity of (+)-THNA was only slightly less than that of the EHNA isomers, whereas (?)-THNA was somewhat less active. The abilities of the four isomeres of EHNA and THNA to inhibit DNA synthesis in HSV-infected cells correlated with their abilities to inhibit virus multiplication. EHNA failed to inhibit HSV DNA polymerase activity in extracts from infected cells. Moreover, addition of EHNA to infected cells at 6 hr post-infection resulted in no inhibition of DNA synthesis. These results are inconsistent with a direct inhibition of macromolecular DNA synthesis by EHNA. Treatment of HSV-infected cells with EHNA produced a 2- to 4-fold decrease in levels of the four DNA precursors, deoxyribonucleoside 5'-triphosphates (dNTPs). This treatment had much less effect on dNTP levels in uninfected cells.     

Regulation of herpesvirus thymidine kinase activity in LM(TK) cells transformed by ultraviolet light-irradiated herpes simplex virus.

The content and composition of Semliki Forest virus polypeptides were not affected by a change of the host from BHK 21 cells to Aedes albopictus cells. Galactose and sialic acid were, however, lost from the viral oligosaccharides in the change; most of the cholesterol was also lost and the phospholipid composition was profoundly changed. The morphology of the virions was not changed.     

Variants of transketolase from human erythrocytes

Analytical isoelectric focusing and a stain for transketolase have been applied to partially purified samples of human erythrocyte hemolysates and have detected individual species of transketolase having pI values of 6.6, 7.3, 7.5, 7.8, 8.1, 8.2, 8.4 and 9.2. Six different patterns of these species were detected in 25 healthy subjects. The species of pI 7.5, 7.8 and 8.1 were common to all six patterns. Species isolated by electrofocusing could be rerun in the same system with identical pI value. The addition of thiamin diphosphate to the staining mixture darkened some but not all bands of transketolase activity. Thus human erythrocyte transketolase is heterogeneous and appears to share with human fibroblast transketolase heterogeneity for affinity of the cofactor. This heterogeneity might need recognition when thiamin nutritional sufficiency is assessed by the ‘ thiamin diphosphate effect’ on erythrocyte transketolase.     

Topographical variations in the morphology and biochemistry of adult canine tibial plateau articular cartilage

Topographically, there are both morphological and biochemical differences in the articular cartilage of the tibial plateau of normal adult dogs when the cartilage covered by the meniscus is compared with that more centrally placed and not covered by meniscus. Histologically, differences are present in the surface morphology, in intra- and extracellular lipid content, and in the morphology of the mineralization front. Electron microscopy shows, in the covered cartilage, variability in collagen fiber size, with evenly spaced fibers apparently randomly distributed and an orderly relationship between the proteoglycans and collagen, whereas in the uncovered area, the collagen is aggregated into bundles and appears to be dissociated in large part from the proteoglycans. The most striking feature in the biochemistry of the two regions is an increased water content in the uncovered cartilage, as compared with the covered. In addition, there is an increased amount of proteoglycans that can be extracted in the uncovered cartilage. The heterogeneity of the cartilage on the tibial plateau should be taken into account when considering both the histologic and biochemical variations found in osteoarthritic cartilage; and when reflecting on the pathogenesis of osteoarthritis.     

The effect of long-distance running on some biochemical variables.

Biochemical variables have been measured in a group of volunteers during and after a long-distance run. Plasma glucose levels remained relatively constant and a significant decrease in plasma bicarbonate was noted. Plasma sodium, chloride, total protein, albumin and calcium showed significant increased of an order compatible with water losses occurring during the run. Plasma potassium, urea, creatinine, uric acid, phosphate and bilirubin all show much more marked and variable increases. The plasma enzymes alkaline phosphatase, lactate dehydrogenase, aspartate aminotransferase and creatine kinase likewise increased significantly throughout the run. Whilst most constituents showed a tendency to return to normal at 20-30 hours after the run, gross increases were observed for aspartate aminotransferase and creatine kinase.     

Role of hypertension in atherosclerosis and cardiovascular disease.

Clinical, experimental and pathologic studies strongly indicate that hypertension is a major factor in coronary heart disease, sudden death, stroke congestive heart failure and renal insufficiency. The deleterious effect of the elevated blood pressure on the cardiovascular system appears to be due mainly to the mechanical stress placed on the heart and blood vessels. Humoral factors and vasoactive hormones such as angiotensin, catecholamines and prostaglandins may play a role in the pathogenesis of hypertensive cardiovascular disease but this role has not yet been defined and is probably secondary. Hypertension and the resulting increase in tangential tension on the myocardial and arterial walls, leads to the development of hypertensive heart disease and congestive heart failure as well as hypertensive vascular disease that affects not only the kidneys but also the heart and brain. Hypertensive vascular disease involves both large and small arteries as well as arterioles and is characterized by fibromuscular thickening of the intima and media with luminal narrowing of the small arteries and arterioles. The physical stress of hypertension on the arterial wall also results in the aggravation and acceleration of atherosclerosis, particularly of the coronary and cerebral vessels. Moreover, hypertension appears to increase the susceptibility of the small and large arteries to atherosclerosis. Thus the patient with hypertension is a candidate for both hypertensive and atherosclerotic vascular disease of the coronary and cerebral vessels leading to occlusive disease of both the large and small arteries and resulting in myocardial infarction and stroke. Other major complications of hypertensive vascular disease include rupture and thrombotic occlusion of blood vessels, especially in the brain. Disease of the arterial media, which begins in childhood with the deposition of calcium in the vessels, may be an important cause of arterial hypertension. This form of hypertension may manifest itself in adults as arteriosclerotic hypertension and lead to cardiovascular complications very similar to those of essential hypertension. The relation of arteriosclerotic hypertension to nutritional factors, including dietary salt intake, deserves study.     

实验前标本因素对生化检验结果的影响

在日常工作中常遇到一些检验结果波动较大，甚至超过病情变化，与临床诊断不符，会被认为是检验结果不准确。殊不知影响检验结果的因素很多，不仅有实验中、实验后的误差，如仪器、试剂、反应条件、操作员个体等；而且还有实验前误差，如患者个体、标本收集、处理、贮存和运输等。实验误差中实验前误差占70％，其中标本因素是最主要的原因之一。我们对在工作中经常遇到的几种不能反映患者真实指标的检验标本作了分析研究，结果报告如下。     

Studies on the activities and properties of lysosomal hydrolases in fractionated populations of human peripheral blood cells

Studies have been carried out on the activities and properties of the isozymes of alpha-mannosidase, alpha-glucosidase and beta-glucosidase in granulocytes, monocytes, lymphocytes and platelts from peripheral blood of heatlhy adult donors. The findings reveal the differences in activities as well as a characteristic distribution of the different molecular forms of these lysosomal hydrolases in specific cell types. Therefore, the results obtained with unfractionated total leukocyte smples from different subjects may vary according to the distribution of cell types in the circulation. Granulocytes and monocytes show only the acid alpha-mannosidase activity whereas lymphocytes and platelets show both acid and neutral activities. The specific activity of acid alpha-mannosidase in granulocytes and monocytes is higher than in lymphocytes and platelets. By DEAE-cellulose chromatography, the acid alpha-mannosidase in granulocyte and monocyte extracts elutes as two peaks, but only one peak is seen in lymphocytes. All cell types show both acid and neutral alpha-glucosidase activities. The specific activities of both isozymes are higher in granulocytes and monocytes than in lymphocytes and platelets. Monocytes show a higher acid than neutral activity. All other cell types show a higher neutral activity. Beta-Glucosidase in all cell types is mainly membrane-bound and it can be released by Triton X-100 and sodium taurocholate. Taurocholate also stimulates the beta-glucosidase activity of granulocytes, monocytes and lymphocytes whereas it inhibits the activity of this enzyme in platelets. These results indicate that variations in the total number of leukocytes and in the relative proportion of the various cell types in health and disease may yield inconsistent or unreliable values for enzyme activity in the diagnosis of lysosomal storage disease and in carrier detection.     

Lactate dehydrogenase (LDH) isoenzyme pattern in normal and inflamed human dental pulp

Messelt E. B., Skogedal, O. Erik sen, H.M. Lactate Dehydrogenase (LDH) Isoenzyme pattern in normal and Inflamed Human Dental Pulp.

Enzyme variants may serve an adaptive role in providing the correct vectorial properties for the metabolism of a tissue, or broadening its environmental tolerance range.

To determine if the LDH isoenzyme pattern of human dental pulp changes during inflammation, supernatants from normal and inflamed dental pulp homogenates were separated by polyacrylamide gel elec-trophoresis.

Inflamed pulps had a higher M subunit content and a markedly increased enzyme activity. These results might reflect adaptive changes at the enzyme level associated with a partial shiit towards anaerobic metabolism during inflammation of the pulp.