Labidocera aestiva and L. scotti in Tamiahua Lagoon,Veracruz, Mexico

Labidocera aestiva and L. scotti were found in the Tamiahua Lagoon, Veracruz, Mexico. Fleminger (1957) found that the populations of these species may overlap geographically, although L. aestiva has affinity to the Carolinian province and L. scotti to the Caribbean province. This study describes the seasonal behavior and succession of this species in the Tamiahua Lagoon, a brackish water system with a high marine influence. A qualitative and quantitative analysis of samples was made in March, July, and September 1985 and January 1986. L. aestiva was found in temperatures below 26 °C in a wide salinity range. At temperatures above 26 °C and up to 32 °C, L. aestiva was present also with euryhaline character. In the Tamiahua Lagoon these two species did not overlap during this study. Both species are considered temporary inhabitants of this estuarine system in the Western Gulf of Mexico.     

Testicular main ducts and spermatic ducts in some cyprinid fishes I. Morphology, fine structure and histochemistry

Alburnus alburnus, Leuciscus cephalus and Vimba vimba efferent duct systems of the male gonads consist of testicular main ducts and spermatic ducts. These have similar histological, fine structural and (enzyme–) histochemical characteristics and function in (1) storage and (2) nutrition of spermatozoa, (3) synthesis of steroid glucuronides, (4) secretion of proteins and enzymes (5) formation of an ionic gradient in the seminal fluid and (6) they have auto– and heterophagocytotic activities. Therefore testicular main ducts and spermatic ducts are important in the formation of the seminal fluid.     

Hydrolysis of triglyceride by the whole cell of Pseudomonas putida 3SK in two-phase batch and continuous reactors systems

Batch and continuous hydrolysis of olive oil in an organic-aqueous two-phase system using the live whole cell of Pseudomonas putida 3SK as a source of a lipase is investigated. The strain was not only fully viable and grown well, but also produced extracellular lipase simultaneously. The degree of hydrolysis, depending on olive oil concentration in the solvents, was maximal at 13.5% (w/v) and decreased with the increase of the substrate concentration. At the optimal condition, a degree of hydrolysis higher than 95% was achieved with 24 h at 30 degrees C when the reaction was carried out in a two-phase batch stirred reactor. For long-term operation a continuous stirred reactor was designed. When the reaction was carried out in a continuous stirred reactor, the degree was hydrolysis reached 86% at a dilution rate of 0.2 h(-1). Satisfactory performance of a two-phase bioreactor was obtained in a long-term continous operation, which lasted for at least 30 days by feeding organic solvent containing olive oil and aqueous media separately. (c) 1994 John Wiley & Sons, Inc.     

Stimulatory Effect of Histamine on Cyclic AMP Formation in Chick Pineal Gland

Abstract: Histamine (HA) potently stimulated cyclic AMP accumulation in intact pineal glands taken from light-exposed chicks. The action of HA was stronger in the presence of forskolin and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). The effect of HA was mimicked by HA H₁- and H₂-receptor-selective agonists in the following order of potency: HA > 4-methylhistamine (H₂) > 2-methylhistamine (H₁) > 2-thiazolylethylamine (H₁) ≫ dimaprit (H₂). The HA H₃-receptor-selective agonist (R)α-methylhistamine was poorly active. The effect of HA was antagonized by selective H₂-receptor blockers (tiotidine > oxmetidine > cimetidine = ranitidine) and was not significantly affected by the selective H₁- and H₃-receptor blockers mepyramine and thioperamide. A detailed analysis of an antagonistic action of ranitidine (versus HA) revealed a noncompetitive mode of action of the H₂ blocker. The stimulatory action of the H₁ agonist 2-thiazolylethylamine (both under basal conditions and in the presence of forskolin or IBMX) was not significantly influenced by three H₁-receptor-selective blockers (mepyramine, triprolidine, and diphenhydramine), but it was totally counteracted by ranitidine. Using accepted selective agonists and antagonists of the HA H₁, H₂, and H₃ receptor we were unable to identify clearly the receptor subtype mediating the HA action on the cyclic AMP-generating system of the chick pineal. It is suggested that the receptor under consideration may represent either an H₂-like (in terms of mammalian criteria) or avian-specific HA receptor. The data suggest that HA may be considered a modulator of the pineal activity in chicks.     

Thyrotropin-Releasing Hormone Release Is Enhanced in Hippocampal Slices After Electroconvulsive Shock

Abstract: Hippocampal thyrotropin-releasing hormone (TRH) release was examined after seizures were induced by electroconvulsive shock (ECS). Rat hippocampal slices taken 12, 24, or 48 h after 3 days of alternate-day ECS treatment or sham-ECS treatment were stimulated with potassium with or without calcium in a superfusion system containing in-line charcoal adsorbent to concentrate TRH. Released TRH and tissue TRH were measured by radioimmunoassay. The TRH content of hippocampal slices was increased fivefold over sham-ECS levels 12, 24, and 48 h after ECS, but this was not associated with an increase in basal TRH release. Potassium-stimulated TRH release was significantly elevated over basal release 12, 24, and 48 h after ECS. Potassium-stimulated calcium-dependent TRH release increased linearly after ECS, reaching its highest level 48 h after seizure. Thus, although enhanced calcium-dependent TRH release was associated with elevated tissue levels, this relationship was not proportional in that tissue TRH was elevated to the same extent at all times after ECS, whereas potassium-evoked calcium-dependent TRH release increased gradually over time after seizure. These results suggest that postictal elevations in TRH are associated with an enhanced capacity for release that develops as a result of a time-dependent shift of TRH from a storage compartment to a readily releasable pool. The observed elevation in stimulated TRH release may be relevant to seizure-induced modulation of TRH receptors in vivo.     

New killing system controlled by two genes located immediately upstream of the mukB gene in Escherichia coli

The nucleotide sequence was determined of the region upstream of the mukB gene of Escherichia coli. Two new genes were found, designated kicA and kicB (killing of cell); the gene order is kicB-kicA-mukB. Promoter activities were detected in the regions immediately upstream of kicB and kicA, but not in front of mukB. Gene disruption experiments revealed that the kicA disruptant was nonviable, but the kicB-disrupted mutant and the mutant lacking both the kicB and kicA genes were able to grow. When kicA disruptant cells bearing a temperature-sensitive replication plasmid carrying the kicA ⁺ gene were grown at 30° C and then transferred to 42° C, the mutant cells gradually lost colony-forming ability, even in the presence of a mukB ⁺ plasmid. Rates of protein synthesis, but not of RNA or DNA synthesis, fell dramatically during incubation at 42° C. These results suggested that the kicB gene encodes a killing factor and the kicA gene codes for a protein that suppresses the killing function of the kicB gene product. It was also demonstrated that KicA and KicB can function as a post-segregational killing system, when the genes are transferred from the E. coli chromosome onto a plasmid.     

Mutations in somePolycomb group genes ofDrosophila interfere with regulation of segmentation genes

Mutations in severalPolycomb (Pc) group genes cause maternal-effect or zygotic segmentation defects, suggesting thatPc group genes may regulate the segmentation genes ofDrosophila. We show that individuals doubly heterozygous for mutations inpolyhomeotic and six otherPc group genes show gap, pair rule, and segment polarity segmentation defects. We examined double heterozygous combinations ofPc group and segmentation mutations for enhancement of adult and embryonic segmentation defects.Posterior sex combs andpolyhomeotic interact withKrüppel ² and enhance embryonic phenotypes ofhunchback andknirps, andpolyhomeotic enhanceseven-skipped. Surprisingly, flies carrying duplications ofextra sex combs (esc), that were heterozygous for mutations ofeven-skipped (eve), were extremely subvital. Embryos and surviving adults of this genotype showed strong segmentation defects in even-numbered segments. Antibody studies confirm that expression ofeve is suppressed by duplications ofesc. However,esc duplications have no effect on other gap or pair rule genes tested. To our knowledge, this is only the second triplo-abnormal phenotype associated withPc group genes. Duplications of nine otherPc group genes have no detectable effect oneve. Expression ofengrailed (en) was abnormal in the central nervous systems of mostPc group mutants. These results support a role forPc genes in regulation of some segmentation genes, and suggest thatesc may act differently from otherPc group genes.     

Damage and mutagenesis of E. coli and bacteriophage λ induced by oxathiolane and aziridinyl steroids

λ-Escherichia coli complexes exhibited remarkable sensitivity to the treatment with test steroidal derivatives in the presence of Cu(II). The decline in plaque-forming units after steroid treatment was more pronounced in complexes with some of the irradiation repair-defective mutants of E. coli K-12, i.e., recA, lexA and polA, as compared to uvrA and wild-type strains. The red gene of λ phage and recA gene of E. coli seem to have a complementary effect on the steroid-induced lesions. An enhanced level of mutagenesis was observed when steroid-treated E. coli cells were transformed with steroid-treated pBR322 plasmid DNA. A remarkable degree of c mutation was also observed when steroid I-treated phage particles were allowed to adsorb on steroid-treated wild-type bacteria. Moreover, the oxathione steroid treatment of λcI857-E. coli lysogen resulted in prophage induction in nutrient broth even at 32°C. Thus on the basis of these results, the role of SOS repair system in steroid-induced mutagenesis and repair of DNA lesions in E. coli and bacteriophage λ has been suggested.     

Enzyme IIBcellobiose of the phosphoenol-pyruvate-dependent phosphotransferase system of Escherichia coli: backbone assignment and secondary structure determined by three-dimensional NMR spectroscopy.

The assignment of backbone resonances and the secondary structure determination of the Cys 10 Ser mutant of enzyme IIBcellobiose of the Escherichia coli cellobiose-specific phosphoenol-pyruvate-dependent phosphotransferase system are presented. The backbone resonances were assigned using 4 triple resonance experiments, the HNCA and HN(CO)CA experiments, correlating backbone 1H, 15N, and 13C alpha resonances, and the HN(CA)CO and HNCO experiments, correlating backbone 1H,15N and 13CO resonances. Heteronuclear 1H-NOE 1H-15N single quantum coherence (15N-NOESY-HSQC) spectroscopy and heteronuclear 1H total correlation 1H-15N single quantum coherence (15N-TOCSY-HSQC) spectroscopy were used to resolve ambiguities arising from overlapping 13C alpha and 13CO frequencies and to check the assignments from the triple resonance experiments. This procedure, together with a 3-dimensional 1H alpha-13C alpha-13CO experiment (COCAH), yielded the assignment for all observed backbone resonances. The secondary structure was determined using information both from the deviation of observed 1H alpha and 13C alpha chemical shifts from their random coil values and 1H-NOE information from the 15N-NOESY-HSQC. These data show that enzyme IIBcellobiose consists of a 4-stranded parallel beta-sheet and 5 alpha-helices. In the wild-type enzyme IIBcellobiose, the catalytic residue appears to be located at the end of a beta-strand.     

Monte Carlo study of the effect of β2-microglobulin on the binding cleft of the HLA-A2 complex

Peptide recognition by class I products of the major histocompatibility complex requires association of the class I heavy chain with β₂-microglobulin. We present results of Monte Carlo simulations of the β-pleated sheet floor of the human class I MHC molecule, HLA-A2, with and without β₂-microglobulin. We find a significant effect of β₂-microglobulin on the side chains of residues near a region that would accommodate the C-terminus of a bound peptide. By modeling simultaneously each loop and its neighboring strand at either end of the class I cleft, we find that β₂-microglobulin restricts the conformational space of residues that are central to binding peptides. The effect is most pronounced for R97 and H114 and somewhat less important for Y99 and Y116, the latter forming strong hydrogen bonds with neighboring residues in the heavy chain itself.