A mutant of Bacillus thuringiensis var. israelensis (B.t.i.) resistant to antibiotics

Summary PST, a spontaneous mutant of Bacillus thuringiensis var. israelensis (B.t.i.) resistant to penicillin, streptomycin and tetracycline was isolated by serial selections. In the absence of antibiotics it showed genetic stability for 16 generations. Mosquito larvicidal activity of PST was similar to that of B.t.i., its parental strain. It also maintained the specific antigenicity of B.t.i. although its rate of growth was somewhat lower, a generation time of 55 min for PST vs. 38 min for B.t.i. Cell concentration plays a major role in the phenomenon of PST resistance to penicillin.This antibiotic resistant mutant of b.t.i. provides us with an efficient tool to trace B.t.i. among the indigenous bacteria present in septic habitats in the field as well as inside the larval gut.     

Primary structure of the two variants of a sperm-specific histone H1 from the annelid Platynereis dumerilii

The amino acid sequences of the two variants (H1a 121 residues and H1b 119 residues) of the sperm-specific histone H1 from the polychaete annelid Platynereis dumerilii have been completely established. Comparison of the sequences of these two variants shows one deletion of two residues in histone H1b and 22 substitents, of which most occur in the globular domain. The two variants differ highly in a sequence of nine residues adjacent to the conservative phenylalanine residue of histone H1 (64-72 in H1a, 62-70 in H1b) which makes H1a less hydrophobic than H1b. The small molecular size of Platynereis H1a and H1b is a unique feature among the histones H1 of which the size ranges between 189 residues (chicken erythrocyte H5) and 248 residues (sea urchin sperm H1). H1a and H1b have short N- and C-terminal basic domains but the size of the globular domain (approximately equal to 80 residues) is similar to that of other H1s. In the globular region the variant H1a exhibits a close relationship with somatic or sperm H1s whereas the variant H1b is more related to H5 histones.     

Antigen-binding receptors on T cells from long-term MLR. Evidence of binding sites for allogeneic and self-MHC products

Antibody inhibition of radiolabelled stimulator membrane vesicle binding by T blasts activated in the mixed lymphocyte reaction (MLR) was used to identify responder-cell determinants involved in the binding phenomenon. Antisera or monoclonal antibodies against Thy-1, Lyt-1, Lyt-2 and Ly-6 antigens were not inhibitory. However, antibodies against heavy-chain V region (V_H) determinants strongly inhibited vesicle binding by both primary and longterm MLR blasts. Anti-Ia (both alloantisera and monoclonal reagents) caused inhibition of antigen binding by primary MLR blasts only. T blasts from long-term MLR lines were neither Ia-positive, nor susceptible to blocking of antigen binding with anti-Ia. However, these cells were capable of specifically absorbing soluble syngeneic Ia material, with the concomitant appearance of vesiclebinding inhibition with anti-Ia sera. Acquisition of syngeneic Ia by T blasts was effectively blocked with the anti-V_H reagent. Passively bound self-Ia did not interfere with vesicle binding in the absence of anti-Ia. These results strongly suggest the existance of specific self-Ia acceptor sites closely linked to the receptors for stimulator alloantigens on T cells proliferating in MLR. A receptor model based on these findings is briefly discussed.Abbreviations used in this paper B10 C57BL/10 - Con A concanavalin A - FcR Fc receptor - FCS fetal calf serum - H heavy chain - Ia I-region associated antigen - Ig immunoglobulin - LPS lipopolysaccharide - Lyt T-lymphocyte differentiation antigen - MHC major histocompatibility complex - MLR mixed lymphocyte reaction - PM plasma membrane - T thymus derived - Tcr T-cell receptor - V variable region of Ig     

Restriction endonuclease analysis of the transducing bacteriophage lambda rif d18

The rif d18 bacteriophage carries essential parts of the E. coli genome which can not be mapped by conventional methods. The phage DNA was analysed with four restriction endonucleases (endo R. BamHI, Sall, HpaI and EcoRI) and a physical map was constructed.     

The role of N-acyl groups in the inhibitory activity of LH-RH analogues

Inhibitory analogues of luteinizing hormone-releasing hormone (LH-RH) were prepared with formyl-D-Trp¹, acetyl-D-Trp¹, valeryl-D-Trp¹, tartaryl-D-Trp¹, diacetyl-tartaryl-D-Trp¹, acetyl-Gly¹, and acetyl-Sar¹ successively replacing the position one in the analogue [D-Trp¹, D-p-Cl-Phe², D-Trp³, D-Phe⁶, D-Ala¹⁰]-LH-RH. The formyl-D-Trp¹ and acetyl-D-Trp¹ analogues yielded 100% blockade of ovulation at the 10 μg dose; the others were less potent and inhibited ovulation at the 50 μg dose. The inhibitory potency seems to correlate with the polarity of the acyl group.     

In. vitro evaluation of corpus luteum function of cycling and pregnant rhesus monkeys: Progesterone production by dispersed luteal cells

Corpus luteum function in the cycling and the pregnant rhesus monkey (Macaca mulatta) was evaluated through short term $\text{in vitro}$ studies of progesterone production by suspensions of collagenase-dispersed luteal cells in the presence and absence of exogenous gonadotropin (human chortonic gonadotropin, HCG). Cells from mid-luteal phase of the menstrual cycle secreted progesterone, as measured by accumulation of this hormone in the incubation medium, and responded to the addition of 100 ng HCG/ml with a marked increase in progesterone secretion above basal level ($\text{63.7 ± 13.1}\text{versus}\text{24.7 ± 5.5}\text{ng progesterone}\text{/}\text{ml}\text{/5 × 10}{}^4\text{cells}\text{/ 3}\text{hr}\text{,}\text{X}\text{± S.E.,}\text{n}\text{= 6;}\text{p}\text{< 0.05}$). However, luteal cells from early pregnancy (23–26 days after fertilization) secreted significantly less progesterone than cells of the non-fertile menstrual cycle (3.6 ± 2.4 versus 24.7 ± 5.5 ng/ml/5 × 10⁴ cells/3 hr, n = 3; p < 0.05) and did not respond to HCG with enhanced secretion. By mid-pregnancy (108–118 days gestation) luteal cells exhibited partially renewed function, and near the time of parturition (163–166 days gestation) basal and HCG-stimulated progesterone secretion (30.2 ± 5.6 and 63.0 ± 13.0 ng/ml/5 × 10⁴ cells/3 hr, respectively; n = 3) was equivalent to that of cells from the luteal phase of the non-fertile menstrual cycle. The data suggest that following a period around the fourth week of gestation, when steroidogenic activity is markedly diminished, the corpus luteum of pregnancy progressively reacquires its functional capacity and at term exhibits gonadotropin-sensitive steroidogenesis similar to that of the corpus luteum of the menstrual cycle.     

Larval feeding status regulates the transcript levels of genes encoding PTTH and allatoregulatory peptides in silkworm Bombyx mori

In Bombyx mori, two dorsolateral neurosecretory cells (NSCs) in each of the two brain lobes have been identified as prothoracicotropic hormone (PTTH) producing cells. This neuropeptide in insects stimulates the prothoracic gland for the synthesis and release of ecdysone, responsible for the molting events. Allatotropin (AT) and allatostatin (AST) are allatoregulatory neuropeptides that regulate juvenile hormone biosynthesis. Here, by using RT-qPCR, we showed that in B. mori, nutritional stress modulates the mRNA expression of AT and AST-C (allatostain type C) in the central nervous system consisting of the brain lobes and all the associated ganglia. Using whole-mount in situ hybridization, we showed that the feeding status of Bombyx larvae also influences the expression of PTTH in the NSCs of the brain. Food deprivation significantly decreased the mRNA expression levels of PTTH in larvae at active or terminal growth period. Further, we showed that insulin modulates the expression level of PTTH. However, its action was dependent on the feeding status of the larvae. At feeding, the insulin decreased the PTTH expression level, while at food deprivation, the insulin increased the PTTH expression level. The data thus indicates that larval feeding status plays an important role in altering the mRNA expression levels of allatoregulatory peptide genes and PTTH.     

Molecular mechanisms creating bistable switches at cell cycle transitions

Progression through the eukaryotic cell cycle is characterized by specific transitions, where cells move irreversibly from stage i−1 of the cycle into stage i. These irreversible cell cycle transitions are regulated by underlying bistable switches, which share some common features. An inhibitory protein stalls progression, and an activatory protein promotes progression. The inhibitor and activator are locked in a double-negative feedback loop, creating a one-way toggle switch that guarantees an irreversible commitment to move forward through the cell cycle, and it opposes regression from stage i to stage i−1. In many cases, the activator is an enzyme that modifies the inhibitor in multiple steps, whereas the hypo-modified inhibitor binds strongly to the activator and resists its enzymatic activity. These interactions are the basis of a reaction motif that provides a simple and generic account of many characteristic properties of cell cycle transitions. To demonstrate this assertion, we apply the motif in detail to the G1/S transition in budding yeast and to the mitotic checkpoint in mammalian cells. Variations of the motif might support irreversible cellular decision-making in other contexts.     

Reconstructing Roma History from Genome-Wide Data

The Roma people, living throughout Europe and West Asia, are a diverse population linked by the Romani language and culture. Previous linguistic and genetic studies have suggested that the Roma migrated into Europe from South Asia about 1,000–1,500 years ago. Genetic inferences about Roma history have mostly focused on the Y chromosome and mitochondrial DNA. To explore what additional information can be learned from genome-wide data, we analyzed data from six Roma groups that we genotyped at hundreds of thousands of single nucleotide polymorphisms (SNPs). We estimate that the Roma harbor about 80% West Eurasian ancestry–derived from a combination of European and South Asian sources–and that the date of admixture of South Asian and European ancestry was about 850 years before present. We provide evidence for Eastern Europe being a major source of European ancestry, and North-west India being a major source of the South Asian ancestry in the Roma. By computing allele sharing as a measure of linkage disequilibrium, we estimate that the migration of Roma out of the Indian subcontinent was accompanied by a severe founder event, which appears to have been followed by a major demographic expansion after the arrival in Europe.