Alterations by peroxisome proliferators of acyl composition of hepatic phosphatidylcholine in rats, mice and guinea-pigs. Role of stearoyl-CoA desaturase.

Rats, mice and guinea-pigs were administered p-chlorophenoxyisobutyric acid (clofibric acid) or 2,2'-(decamethylenedithio)diethanol (tiadenol). The treatments of rats and mice with either clofibric acid or tiadenol increased markedly the activities of stearoyl-CoA desaturase, palmitoyl-CoA chain elongation, 1-acylglycerophosphate (1-acyl-GP) acyltransferase and 1-acylglycerophosphocholine (1-acyl-GPC) acyltransferase, but not 2-acylglycerophosphocholine (2-acyl-GPC) acyltransferase in liver microsomes. The treatment of guinea-pigs with clofibric acid did not cause any change in the activities of these enzymes. The treatment of guinea-pigs with tiadenol caused a slight, but significant, increase in the activities of 1-acyl-GP acyltransferase and 1-acyl-GPC acyltransferase. The treatment of rats and mice with either clofibric acid or tiadenol increased markedly the proportion of 18:1 and decreased greatly the proportion of 18:0 in liver microsomal phosphatidylcholine. However, there is a considerable difference in the effects of the two peroxisome proliferators on the composition of polyunsaturated fatty acids in phosphatidylcholine between rats and mice. The treatment of guinea-pigs with either of the two peroxisome proliferators caused no change in acyl composition of phosphatidylcholine. The possible role of stearoyl-CoA desaturation in the regulation of acyl composition of phosphatidylcholine was discussed.     

Clinical Use of a New Mitral Disc Valve

A disc valve of new design was used successfully for the replacement of the mitral valve in patients with rheumatic mitral valve disease. This valve would appear to have the following advantages over the mitral ball valve prosthesis:• Lower left atrial pressure after replacement.• Elimination of the hazard of left ventricular outflow tract obstruction with mitral valve replacement.• Decreased incidence of thromboembolization.• Abolition of possibility of ventricular septal irritation.Despite the better outlook for this valve compared with the ball valve for mitral valve substitution, the mitral valve should always be repaired whenever feasible. Repair is possible in the majority of patients.     

Selective inhibition by lasalocid of hydrolysis of the ADP-insensitive phosphoenzyme in the catalytic cycle of sarcoplasmic reticulum Ca2(+)-ATPase

The effect of a carboxylic ionophore (lasalocid) on the sarcoplasmic reticulum Ca2(+)-ATPase was investigated. The purified enzyme was preincubated with lasalocid in the presence of Ca2+ and the absence of K+ at pH 7.0 and 0 degrees C for 2 h. The Ca2(+)-dependent ATPase activity was strongly inhibited by this preincubation, whereas the activity of the contaminant Mg2(+)-ATPase was unaffected. The steady-state level of the phosphoenzyme (EP) intermediate remained constant over the wide range of lasalocid concentrations. The Ca2(+)-induced enzyme activation was unaffected. The kinetics of phosphorylation of the Ca2(+)-activated enzyme by ATP as well as the rate of conversion of ADP-sensitive EP to ADP-insensitive EP were also unaffected. Accumulation of ADP-insensitive EP was greatly enhanced, and almost all of the EP accumulating at steady state was ADP-insensitive. Hydrolysis of ADP-insensitive EP was strongly inhibited. A similar strong inhibition of the Ca2(+)-dependent ATPase activity by lasalocid was found with sarcoplasmic reticulum vesicles. To examine the effect of lasalocid on the conformational change in each reaction step, the Ca2(+)-ATPase of sarcoplasmic reticulum vesicles was labeled with a fluorescent probe (N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylenediamine) without a loss of catalytic activity and then preincubated with lasalocid as described above. The conformational changes involved in hydrolysis of ADP-insensitive EP and in the reversal of this hydrolysis were appreciably retarded by lasalocid. The conformational changes involved in other reaction steps were unaffected. These results demonstrate that hydrolysis of ADP-insensitive EP in the catalytic cycle of this enzyme is selectively inhibited by lasalocid.     

Increased choline acetyltransferase activity by Chinese herbal medicine Sho-saiko-to-go-keishi-ka-shakuyaku-to in aged rat brain

The effect of a Chinese herbal medicine Sho-saiko-to-go-keishi-ka-shakuyaku-to (TJ-960) on the brain choline acetyltransferase (CAT) activity was studied in adult (3.5 months of age) and aged (24 months of age) rats. After oral administration of 5% TJ-960 solution for 3 months, CAT activity in the hippocampus, pons-medulla oblongata and striatum of aged rats was significantly lower than that of adult rats. CAT activity in the cerebellum, however, was significantly higher in the aged rats, as compared to the adult rats. TJ-960 significantly increased CAT activity in the hippocampus and striatum of aged rats, but did not affect the activity of the enzyme in the adult rat brain.     

Involvement of Ca2+ release and activation of phospholipase A2 in mitochondrial dysfunction during anoxia

During anoxic incubation, depletion of mitochondrial ATP was followed by release of Ca2+ with concomitant increase in the rate of state 4 respiration due to disruption of the diffusion barrier against protons. The external addition of ATP and its non-metabolizable analog, beta,gamma-methylene adenosine 5'-triphosphate, prevented both the release of Ca2+ and increase in the rate of state 4 respiration. Addition of EGTA, which did not prevent release of the ion, resulted in little increase in the respiration rate. Addition of an inhibitor of mitochondrial phospholipase A2, such as quinacrine, dibucaine, or chlorpromazine, also prevented increase in the respiration rate without affecting Ca2+ release from mitochondria during anoxic incubation. Non-esterified polyunsaturated fatty acids were also found to be liberated from anoxic mitochondria. External addition of the ATP-analog, EGTA, and inhibitors of phospholipase A2 suppressed the liberation of non-esterified polyunsaturated fatty acids. Melittin and Ca2+, which activate phospholipase A2, increased the rate of state 4 respiration and the liberation of fatty acids. These findings support the hypothesis proposed previously that the following sequence changes occurs in mitochondria during anoxia; depletion of ATP, liberation of free calcium from mitochondria, and disruption of the diffusion barrier against H+ of the inner membrane. The results also indicate another event; activation of phospholipase A2 by release Ca2+ which results in H+ leakiness of the inner membrane.     

Production of Dihomo-γ-Linolenic Acid by a Δ5-Desaturase-Defective Mutant of Mortierella alpina 1S-4

A mutant, which has low Δ5-desaturase activity, of an arachidonic acid-producing fungus, Mortierella alpina 1S-4, was shown to be a novel potent producer of dihomo-γ-linolenic acid (DHGA). On submerged culture under optimal conditions for 6 days at 28°C in a 10-liter fermentor, the mutant produced 3.2 g of DHGA per liter of culture broth (123 mg/g of dry mycelia), which accounted for 23.4% of the total mycelial fatty acids. Mycelial arachidonic acid amounted to only 19 mg/g of dry mycelia (0.5 g/liter of culture broth), which accounted for 3.7% of the total mycelial fatty acids. The other major mycelial fatty acids were palmitic acid (11.0%), stearic acid (12.8%), oleic acid (22.7%), linoleic acid (8.9%), γ-linolenic acid (6.5%), and lignoceric acid (7.8%). More than 97 mol% of the DHGA produced was found in the triglyceride fraction irrespective of the growth temperature employed (12 to 28°C).     

Calpain activation is essential for membrane fusion of erythrocytes in the presence of exogenous Ca2+.

The membrane mobility agent, 2-(methoxyethoxy)ethyl-cis-8-(2-octylcyclopropyl)octanoate (A2C) promotes the fusion of rat, rabbit, and human erythrocytes in the presence of exogenous Ca2+. Under these conditions, the high sensitivity form of calcium-activated neutral protease (mu-calpain) in erythrocytes is activated autolytically. mu-Calpain is activated in accordance with fusion; that is, both erythrocyte fusion and autolytic activation of mu-calpain are induced in rat erythrocytes at 30 min, in rabbit erythrocytes at 150 min, and in human erythrocytes at 240 min after the addition of A2C and Ca2+. When erythrocytes are preincubated with the Ca2+ ionophore A23187, both fusion and autolytic activation start earlier. A leupeptin analogue, Cbz-Leu-Leu-Leu-aldehyde (ZLLLal), inhibits both the autolytic activation of mu-calpain and fusion induced by A2C and Ca2+. These results indicate that treatment of erythrocytes with A2C and Ca2+, results in first an influx of Ca2+ into the cells, followed by autolytic activation of mu-calpain, proteolysis of membrane proteins, exposure of fusion-sites, and, finally, fusion of erythrocytes.     

Preparation and characterization of human interleukin-5 expressed in recombinant Escherichia coli.

The gene coding for human interleukin-5 was synthesized and expressed in Escherichia coli under control of a heat-inducible promoter. High-level expression, 10-15% of total cellular protein, was achieved in E. coli. The protein was produced in an insoluble state. A simple extraction, renaturation and purification scheme is described. The recombinant protein was found to be a homodimer, similar to the natural murine-derived protein. Despite the lack of glycosylation, high specific activities were obtained in three 'in vitro' biological assays. Physical characterization of the protein showed it to be mostly alpha-helical, supporting the hypothesis that a conformational similarity exists among certain cytokines.     

Effect of season and photoperiod on the follicle-stimulating hormone receptors in a subtropical bird

Annual changes in and photoperiodic influence oh the weight of gonads, a parameter of gonadal activity, are much smaller in female birds than in males. Effect of season and photoperiod on the follicle-stimulating hormone receptors in the testis or ovary was studied using a subtropical weaver finch. The number of follicle-stimulating hormone binding sites per unit testicular weight showed a peak in the non-breeding phase; while the total number of binding sites per two testes was maximal in the breeding phase and minimal in the regressive phase. In contrast, seasonal changes in follicle-stimulating hormone binding sites in the ovary were less marked. Exposure to short-day during the breeding phase induced marked decreases in the numbers of binding sites per unit testicular weight and per two testes. These numbers markedly increased after transfer to long-day during the non-breeding phase. However, there was no significant effect of short-day or long-day exposure on follicle-stimulating hormone binding sites in the ovary. These results suggest that photoperiod is an effective environmental factor in the regulation of follicle-stimulating hormone receptors in the testis and the effect is manifested by pronounced changes in the testicular weight during annual breeding cycle.