Temperature-sensitive mutants of Neisseria gonorrhoeae.

Nine temperature-sensitive (Ts) mutants of Neisseria gonorrhoeae strain 49191 were isolated. They were proven to be different from each other by results of transformation experiments. None of the Ts mutations appeared to be linked to antibiotic resistance genes from strain 24392. However, Ts-9 demonstrated 8% linkage with a nalidixic acid resistance marker from strain RW-2.     

Anti-masculinizing action of estradiol and cyproterone acetate: Regulation of a protein fraction with phospholipase-A2 stimulatory and masculinizing activities

Recently we have identified a protein fraction (55–63 K) from male and testosterone-exposed female mouse genital tract, which stimulates phospholipase A₂ (PLA₂) and induces masculine differentiation in an undifferentiated mouse genital explant, suggesting a role of this protein in the action of testosterone. In the current study we have further investigated the role of this protein by determining whether anti-masculinizing agents, namely, estradiol and cyproterone acetate, have any effect on the production of this protein. The results described here indicate that a protein fraction containing PLA₂ stimulatory activity was present in both control male and estradiol- or cyproterone acetate-exposed male fetal genital tract. However the specific activity of the PLA₂-stimulatory protein was significantly higher in the control males than in the experimental males. We did not find any major difference in the behavior of this protein fraction in various chromatographic steps except that in CM-sepharose column; the PLA₂-stimulatory activity from the male preparation was eluted in two overlapping peaks with 0.3 and 0.25 M NaCl and that from the treated males was eluted only with 0.25 M NaCl. The SDS-gel analysis of this protein fraction revealed a doublet band (55 and 63 K) in control samples and primarily a 63 K band in experimental samples. The protein fraction from all these sources showed a significant difference in their biological activity. The control male preparation induced Wolffian duct whereas the estradiol sample was completely ineffective and the cyproterone acetate sample was partially effective in inducing Wolffian duct. Thus, it appears that the protein fraction has a role in the masculinizing action of testosterone.     

Kinetics of active and passive components of water exchange between the air and a mite, Dermatophagoides farinae

Female North American house dust mites were found to exchange water with the ambient air from two compartments. At humidities above the critical equilibrium activity (CEA), transpiration out of a single large compartment was observed using HTO as a tracer for water. Total sorption into this compartment was also observed by following changes in the specific radioactivity. The sorption data required that an active process or pump be present. The water in this pump is the second compartment above the CEA. Below the CEA the large compartment could be identified as a compartment characterized by a small transpiration rate constant. The pump below the CEA becomes a rapidly transpiring fast compartment. By separating the water pool into two compartments, it was possible to relate a_v to k and $\text{m}\text{?}{}_{\mathrm{<mtext>S</mtext>}}$. The major effect of a_v on k was related to its effect on the permeability of the cuticle. The influence of a_v on $\text{m}\text{?}{}_{\mathrm{<mtext>S</mtext>}}$ was different for active and passive sorption. Above the CEA the pump operated at full capacity and active $\text{m}\text{?}{}_{\mathrm{<mtext>S</mtext>}}$ was directly proportional to a_v. Passive sorption was influenced by a_v in two ways. The driving force for $\text{m}\text{?}{}_{\mathrm{<mtext>S</mtext>}}$ was further reduced below saturation by the effect of a_v on the permeability of the exchange surface.     

Triplet and ground state potential energy surfaces of 1,4-diphenyl-1,3-butadiene: theory and experiment.

Relative energies of the ground state isomers of 1,4-diphenyl-1,3-butadiene (DPB) are determined from the temperature dependence of equilibrium isomer compositions obtained with the use of diphenyl diselenide as catalyst. Temperature and concentration effects on photostationary states and isomerization quantum yields with biacetyl or fluorenone as triplet sensitizers with or without the presence of O(2), lead to significant modification of the proposed DPB triplet potential energy surface. Quantum yields for ct-DPB formation from tt-DPB increase with [tt-DPB] revealing a quantum chain process in the tt --> ct direction, as had been observed for the ct --> tt direction, and suggesting an energy minimum at the (3)ct* geometry. They confirm the presence of planar and twisted isomeric triplets in equilibrium (K), with energy transfer from planar or quasi-planar geometries (quantum chain events from tt and ct triplets) and unimolecular decay (k(d)) from twisted geometries. Starting from cc-DPB, varphi(cc-->tt) increases with increasing [cc-DPB] whereas varphi(cc-->ct) is relatively insensitive to concentration changes. The concentration and temperature dependencies of the decay rate constants of DPB triplets in cyclohexane are consistent with the mechanism deduced from the photoisomerization quantum yields. The experimental DeltaH between (3)tt-DPB* and (3)tp-DPB*, 2.7 kcal mol(-1), is compared with the calculated energy difference [DFT with B3LYP/6-31+G(d,p) basis set]. Use of the calculated DeltaS = 4.04 eu between the two triplets gives k(d) = (2.4-6.4) x 10(7) s(-1), close to 1.70 x 10(7) s(-1), the value for twisted stilbene triplet decay. Experimental and calculated relative energies of DPB isomers on the ground and triplet state surfaces agree and theory is relied upon to deduce structural characteristics of the equilibrated conformers in the DPB triplet state.     

Ice-active proteins and cryoprotectants from the New Zealand alpine cockroach, Celatoblatta quinquemaculata

Celatoblatta quinquemaculata is moderately freezing tolerant. We have investigated low and high molecular weight compounds that may be associated with its survival. Glycerol and trehalose were identified as potential cryoprotectants, with trehalose at the higher concentration. Trehalose was at its highest concentration in late autumn, during the periods sampled. Water contents declined with time and were significantly lower in late autumn than in late summer. No thermal hysteresis activity was detected in haemolymph or in extracts of the head, muscles and the fat body. Extracts of the Malpighian tubules showed an hexagonal crystal growth form, as did those of the gut tissue and gut contents. The gut tissue had high levels of thermal hysteresis (∼2 °C) and the gut contents somewhat lower levels (∼0.6 °C). Recrystallization inhibition activity mirrored that of thermal hysteresis, with activity absent in the haemolymph or fat body cells but present in the gut tissues and contents. Activity was reduced by heating and was associated with a molecule >14 kDa in size. These findings suggest an antifreeze protein is involved. In fed animals, ice nucleation is likely to start in the gut. Gut cells have a much greater resistance to freezing than do fat body or Malpighian tubule cells. The antifreeze protein may enable this tissue to survive freezing stress by inhibiting recrystallization.