Regulation of eicosanoid synthesis in microvessel endothelium: glucocorticoids do not affect arachidonyl CoA synthetase activity

The properties of acyl coenzyme A (CoA) synthetase activity were characterized in cultured rabbit coronary microvessel endothelial cells. We report here that microvessel endothelial cells contain two long-chain acyl CoA synthetases. One shows activity with a variety of fatty acids, similar to long-chain non-selective fatty acyl CoA synthetases described previously. The other activity was selective for arachidonic acid and other structurally related substrates. Both activities required ATP, Mg2+ and CoA for optimal activity. The arachidonyl CoA and the non-selective acyl CoA synthetases showed different thermolabilities. Arachidonyl CoA formation was inhibited by greater than 50% after 1 min at 45 degrees C, whereas a 15 min heating treatment was necessary to produce the same relative inhibition of oleoyl CoA synthesis. Glucocorticoid pretreatment (10(-7) M dexamethasone) of the RCME cells did not affect the apparent Km or Vmax, nor the fatty acid selectivity for either acyl CoA synthetase. Therefore, although fatty acyl CoA synthetases may be involved in limiting eicosanoid formation, these activities do not appear to be glucocorticoid-responsive.     

Rats chronically injected with urine from Huntington's chorea patients do not striatal damage

Rats were injected subcutaneously for 147 consecutive days with large volumes of urine from control subjects and from patients with Huntington's chorea (HC) in an effort to test for presence of a possible neurotoxic substance in HC. No evidence of illness was observed in animals treated with HC urine, and their behavior did not differ from animals treated with control urine. After rats were sacrificed, striatum was examined for the biochemical and neuropathological changes seen in human striatum in HC. No deficiency of γ-aminobutyric acid content, nor reduction in activities of glutamic acid decarboxylase and choline acetyltransferase, was found in striatum of rats chronically treated with HC urine. Also, no significant differences were found between striatum of control and experimental rats by light or electron microscopy. These results neither support for exclude the possibility of a neurotoxic mechanism for the neuronal loss characteristic of HC.     

The effect of histone hyperacetylation on the nuclease sensitivity and the solubility of chromatin

We have examined the effects of histone hyperacetylation upon nuclease digestion of nuclei and subsequent fractionation of chromosomal material in the presence of MgCl2. DNase I shows a maximum sensitivity towards hyperacetylated nuclei at somewhat elevated ionic strengths (150-200 mM NaCl), whereas micrococcal nuclease exhibits no specificity for acetylated nuclei over a broad range of ionic strengths. Fractionation in the presence of MgCl2 of hyperacetylated nuclei digested with micrococcal nuclease results in a substantial increase in the amount of soluble chromatin relative to that obtained with control nuclei. This increased yield of Mg2+-soluble chromatin results from the recruitment into this fraction of oligonucleosomes containing extremely hyperacetylated histones. These results suggest that contiguous nucleosomes containing highly acetylated histones may be altered in their ability to interact with themselves and with other nucleosomes.     

Cytochalasin B blocks sperm incorporation but allows activation of the sea urchin egg

Cytochalasin B (CB) (2 × 10⁻⁶ M) prevents the incorporation of sperm into the eggs of Lytechinus pictus and Strongylocentrotus purpuratus as judged by light and transmission electron microscopy (TEM). At lower concentrations of CB (2 × 10⁻⁷ M), sperm are successfully incorporated into the egg, but their migration in the area of the egg cortex is impaired. The site of action of CB on the sperm may be on the initial rotation of the sperm nucleus in the cortex; the subsequent migration is not affected by CB. Although sperm incorporation is prevented at the higher CB concentrations, the eggs become activated—as judged by cortical reaction, increased protein synthesis and increased respiration. These findings raise the concept that egg activation by sperm could result from some pre-fusion event and hence that sperm-egg fusion would not be a prerequisite for the triggering of development. An alternative hypothesis is that fusion occurs between the acrosome process membrane and egg membrane, but since CB has destroyed the integrity of the cortex actin, the fusion bridge is so weak that it cannot be maintained without some contractile or cytoskeletal support by the cortex. The sperm may activate the CB-treated egg in the same manner as pricking with a microelectrode sometimes does.     

Regulation of the immune response to tumor antigen. VIII. The effects of host specific anti-I-J antibodies on the immune response to tumors of different origin

The efficiency of in vivo therapy using alloantisera produced to interact specifically with I-J subregion encoded determinants has been investigated in two etiologically distinct syngeneic tumor systems, both of which have been shown to evoke suppressor T-cell host responses. Administration of 2 μl/day of anti-I-J^k alloantisera caused a significant reduction in the growth of the P815 methylcholanthrene (MCA)-induced mastocytoma or the 1316 ultraviolet (uv) radiation-induced fibrosarcoma in the syngeneic host. Inhibition of tumor growth with anti-I-J antibody treatment occurred in normal as well as in subcarcinogenically uv-treated hosts given the uv-induced 1316 fibrosarcoma, even though the normal host is capable of spontaneously rejecting the tumor graft in the absence of external manipulation. Evidence is also provided that the effects of anti-I-J antibody treatment are not due to direct interactions with the tumor cells, or to contaminating antiviral antibody activity within the antiserum. We have previously demonstrated the reduction of tumor growth in two antigenically distinct MCA-induced tumor systems (S1509a, SAI) using similar treatments. The data presented herein thus reinforce the possibility that such means of therapy may be beneficial to the treatment of a wide variety to tumor types where suppression represents a detrimental component of the host response, and may also provide some insight into the mechanisms underlying the effects of uv radiation on the immune response to tumor antigen.     

The inhibition of peroxidase and indole-3-acetic acid oxidase activity by British Anti-Lewisite

British Anti-Lewisite (BAL) binds to horseradish peroxidase in a manner which results in inhibition of both peroxidatic and oxidative functions of the enzyme. BAL competes with hydrogen peroxide for binding on peroxidase, and the inhibition of peroxidatic activity is irreversible. Solutions of purified horseradish peroxidase and individually resolved peroxidase isozymes show a gradual loss of peroxidatic activity with time when incubated with BAL. In these same treatments, however, the inhibition of indole-3-acetic acid (IAA) oxidase activity is immediate. With increasing amounts of enzyme in the incubation mixture, IAA oxidase activity is not completely inhibited and is observed following a lag period in the assay which shortens with longer incubation times. Peroxidase activity during this same time interval shows a lag period which increases with longer incubation times. Lowering the pH removed the lag period for oxidase activity, but did not change the pattern of peroxidase activity. These results suggest that the sites for the oxidation of indole-3-acetic acid and for peroxidatic activity may not be identical in horseradish peroxidase isozymes.