Comparative effects of trichothecene mycotoxins on bovine platelet function: Acetyl T-2 toxin,a more potent inhibitor than T-2 toxin

The effects of the trichothecene mycotoxins (acetyl T-2 toxin, T-2 toxin, HT-2 toxin, palmityl T-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON), and T-2 tetraol) on bovine platelet function were examined in homologous plasma stimulated with platelet activating factor (PAF). The mycotoxins inhibited platelet function with the following order of potency: acetyl T-2 toxin > palmityl T-2 toxin = DAS > HT-2 toxin = T-2 toxin. While T-2 tetraol was completely ineffective as an inhibitor, DON exhibited minimal inhibitory activity at concentrations above 10×10^?4M. The stability of the platelet aggregates formed was significantly reduced in all mycotoxin treated platelets compared to that of the untreated PAF controls. It is suggested that the increased sensitivity of PAF stimulated bovine platelets to the more lipophilic mycotoxins may be related to their more efficient partitioning into the platelet membrane compared to the more hydrophilic compounds.     

Centromere-Linkage Analysis and Consolidation of the Zebrafish Genetic Map

The ease of isolating mutations in zebrafish will contribute to an understanding of a variety of processes common to all vertebrates. To facilitate genetic analysis of such mutations, we have identified DNA polymorphisms closely linked to each of the 25 centromeres of zebrafish, placed centromeres on the linkage map, increased the number of mapped PCR-based markers to 652, and consolidated the number of linkage groups to the number of chromosomes. This work makes possible centromere-linkage analysis, a novel, rapid method to assign mutations to a specific linkage group using half-tetrads.     

Territorial Pheromones of Female Red-backed Salamanders

Pheromones provide an important source of communication during social interactions of caudate amphibians. To further examine their use in territorial defense, we performed a laboratory experiment to test the hypothesis that non-courting female red-backed salamanders (Plethodon cinereus) deposit pheromones in or on fecal pellets, as males are known to do during territorial advertisement. Four conditions were tested: (1) a burrow marked with a female's own pellet vs. a burrow marked by a conspecific female's pellet, (2) own vs. unmarked burrows, (3) conspecific vs. unmarked burrows, and (4) paired unmarked burrows as a control. Females nose-tapped (for olfactory cues) their own and conspecific pellets about equally. However, they spent significantly more time in both threat and submissive behavior toward the conspecific pellets and spent significantly more time in their own marked burrows. We infer that female P. cinereus do deposit pheromones in or on fecal pellets and that these pellets may be used to advertise territories. The behavioral responses of females toward pellets of other females were more aggressive than those of males (in a previous study) toward pellets of other males.     

Behaviour of the female beaugregory damselfish (Stegastes leucostictus)

Much less is known about the behaviour of female beaugregory damselfish than about males of the species. This study was initiated to determine behavioural patterns and interactions of female beaugregories on the back reef of Discovery Bay Marine Laboratory, North shore of Jamaica. Females fed, patrolled, and chased intruders in a significantly larger area and ate significantly more per 15-min observation period than did males. Males spent significantly more time patrolling their territories and chased significantly more total intruders than did females. However, this difference in total chases comes from the fact that males chased the bluehead wrasse, an egg predator, significantly more often than did females while all other species of intruder were chased the same by both sexes. The distance that females travelled from their homesite to court was significantly positively correlated to female body length. This increased distance travelled may relate to mate assessment. Female beaugregory damselfish may be able to be more selective in their choice of mate with increased size and distance travelled.     

Physiological Studies of Oxygen Protection Mechanisms in the Heterocysts of Anabaena cylindrica

The mechanism of O₂ protection of nitrogenase in the heterocysts of Anabaena cylindrica was studied in vivo. Resistance to O₂ inhibition of nitrogenase activity correlated with the O₂ tension of the medium in which heterocyst formation was induced. O₂ resistance also correlated with the apparent K_m for acetylene, indicating that O₂ tension may influence the development of a gas diffusion barrier in the heterocysts. The role of respiratory activity in protecting nitrogenase from O₂ that diffuses into the heterocyst was studied using inhibitors of carbon metabolism. Reductant limitation induced by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea increased the O₂ sensitivity of in vivo acetylene reduction. Azide, at concentrations (30 mM) sufficient to completely inhibit dark nitrogenase activity (a process dependent on oxidative phosphorylation for its ATP supply), severely inhibited short-term light-dependent acetylene reduction in the presence of O₂ but not in its absence. After 3 h of aerobic incubation in the presence of 20 mM azide, 75% of cross-reactive component I (Fe-Mo protein) in nitrogenase was lost; less than 35% was lost under microaerophilic conditions. Sodium malonate and monofluoroacetate, inhibitors of Krebs cycle activity, had only small inhibitory effects on nitrogenase activity in the light and on cross-reactive material. The results suggest that oxygen protection is dependent on both an O₂ diffusion barrier and active respiration by the heterocyst.     

Secretion of lipids induced by inhibition of peptidoglycan synthesis in streptococci.

Inhibition of peptidoglycan synthesis causes an immediate and massive secretion of both newly synthesized and "old" lipids from several species of bacteria, including streptococci, Staphylococcus epidermidis, and Bacillus subtilis. Lipid secretion occurs in the absence of detectable bacterial lysis. This novel phenomenon was examined in more detail in three strains of streptococci: S. sanguis (group H), S. pyogenes (group A), And S. pneumoniae. The secretion of lipids is specifically induced by inhibitors of peptidoglycan synthesis; it is not caused by inhibitors of protein, ribonucleic acid, or deoxyribonucleic acid synthesis. The occurrence appears to be reversible since penicillin-induced secretion comes to a halt upon the timely addition of penicillinase, correlating with resumption of culture growth. All cellular lipids are secreted in essentially the same proportions as those found in the drug treated bacteria. It is suggested that continued peptidoglycan synthesis may be essential for the integration and retention of lipid material in the plasma membrane.     

The peracid cleavage of 5-methyltetrahydrofolic acid at the C9-N10 bridge.

5-Methyltetrahydrofolate cannot be cleaved at the C⁹N¹⁰ bond by the zinc/HCl reductive or the permanganate oxidative cleavage methods. A new method has been developed to perform this cleavage, using peracetic acid in 50% trifluoroacetic acid; the cleavage is quantitative and nondestructive of γ-glutamyl peptide bonds.     

Studies on the transport mechanism of 5-methyltetrahydrofolic acid in freshly isolated hepatocytes: effect of ethanol.

The effect of ethanol on the transport of 5-methyltetrahydrofolate in freshly isolated hepatocytes in vitro resulted in about a 30% increase in accumulation of substrate. It was shown that this was not due to differences in metabolism, nor to an inhibition of efflux. Preincubation with 40 mm ethanol for 45 min resulted in a significantly increased rate of entry of 5-methyltetrahydrofolate into the cells. The stimulatory effect was specific to 5-methyltetrahydrofolate since ethanol inhibited uptake of folate and methotrexate. The increased uptake was due to metabolism of ethanol as shown by studies with pyrazole. Also, the n-alkanols, propanol through pentanol, and sorbitol but not methanol were stimulatory. Anaerobiosis and sodium azide stimulated uptake of 5-methyl-tetrahydrofolate but were inhibitory to methotrexate uptake. These data, taken together, suggest that the ethanol effect is due to increased entry of 5-CH₃-H₄PteGlu into the cells possibly as the result of an increased cellular $\text{NADH}\text{NAD}$ ratio.     

The effects of temperature and host density on the development and survival of Copidosoma koehleri

Developmental rates for Copidosoma koehleri Blanchard (Hymenoptera: Encyrtidae) and its host, Phthorimaea operculella (Zeller), were determined at 10, 15, 23, 27, 29, 32, 34 and 35°C from host egg to adult. The developmental rates determined for both species showed good fit to mathematical models of insect development. At 15°C mean emergence of adult C. koehleri was 15 days after P. operculella adults emerged. At 29°C mean emergence of C. koehleri was only 5 days after that of P. operculella. P. operculella developed at 35°C, but parasitized larvae, and therefore C. koehleri, did not tolerate temperatures above 32°C. In the presence of C. koehleri, host survival was low (3%) at low host egg densities, but greater (20%) at higher host densities. Parasitized larvae of P. operculella were less able to compete for food resources, as measured by adult emergence.