Flunitrazepam binding sites in rat diaphragm. Receptors for direct neuromuscular effects of benzodiazepines?

The evidence for direct muscle relaxant effects of benzodiazepines is controversial. We now show that a crude membrane preparation of rat diaphragm possesses binding sites for [3H]flunitrazepam (FNZ). Scatchard analysis gave a binding site density of 1689 +/- 143 fmol/mg protein (Kd = 25.6 +/- 2.6 nM). These sites are of the "peripheral" type since clonazepam fails to displace [3H]FNZ as effectively as R05-4864 (IC50 values: 7.5 x 10(-6) M and 8 x 10(-9) M, respectively). Diazepam is almost as effective as R05-4864 and potently displaces [3H]FNZ binding (IC50 = 3 x 10(-8) M). We propose that the previously described effects of diazepam on rat diaphragm are mediated through high-affinity binding sites.     

The chromosomal component of reproductive isolation in the grasshopper Caledia captiva

An analysis of the relative viabilities of recombinant and nonrecombinant chromosomes among the surviving embryos from back-crosses involving the Moreton (M) and Torresian (T) taxa has revealed that these embryos do not contain a representative sample of gametes derived from the F₁ hybrid parent. The significant deviations in the hybrid gametic population arise entirely from intrachromosomal effects with no evidence of any between-chromosome interactions. This is interpreted as clear evidence to show that recombinational repatterning within heterozygous bivalents in the F₁ parent is a significant factor in inducing the observed deviant segregation ratios. Furthermore, by using a population which is chromosomally equivalent to the Torresian but genically similar to the Moreton, it has been shown that over 46% of the F₂ embryonic breakdown arises solely from the effects of chromosomal heterozygosity upon recombination repatterning among (Moreton × Torresian) F₁ hybrids. From these data it is proposed that each chromosome is internally coadapted in the sense that it contains balanced blocks of cis-acting acting loci which can be disrupted by recombinational change. Disruption of the linear association of the genes on structurally different chromosomes by recombination repatterning results in novel intrachromosomal associations which may be functionally inadequate and so lead to arrested embryonic development. It is speculated that an important factor in arresting development may involve interactions between the novel recombinant chromosomes of the gamete and maternal factors laid down in the egg during oogenesis which are responsible for the sequential activation of the genomes of the progeny during development. Thus coadaptation is interpreted in terms of the functional intergration of a chromosome with the products of the genome of the previous generation. The assessment of the relative viabilities of recombinant and nonrecombinant chromosomes has shown that the Torresian nonrecombinant chromosomes possess the highest viabilities in the sequence T^N>M^NT^R = M^R where N and R represent nonrecombinant and recombinant classes. This sequence is relevant to the structure of the hybrid zone between the Torresian and Moreton taxa and explains both its asymmetry and the basis of the observed introgression of Torresian chromosomes into the Moreton taxon and the absence of the reverse movement.     

Dilatometric studies of the subtransition in dipalmitoylphosphatidylcholine

The phase transition between the newly discovered low-temperature subgel phase and the gel phase of dipalmitoylphosphatidylcholine has been studied by using dilatometry. Equilibrium measurements show that the subtransition upon heating is centered at 13.5 degrees C, has a dilatometric half-width of 0.6 degree C, and comprises a specific volume change of 0.009 mL/g (about one-fourth the size of the main transition). When the gel phase is cooled, the subtransition does not occur until below 5 degrees C. The rate of formation as a function of incubation temperature for 1 degree C less than TI less than 6 degrees C was determined; it is not well fit by quantitative theories based upon homogeneous nucleation. However, some form of nucleation is present since temperature-jump studies show that once the subgel phase has started to form, it continues to grow in the range 6 degrees C less than TJ less than 12.8 degrees C. Thus, the true transition temperature lies between 12.8 and 13.5 degrees C, but nucleation of the subgel phase is severely retarded above 6 degrees C, leading to the large hysteresis observed upon cooling.     

Enantiospecific quantification of hexobarbital and its metabolites in biological fluids by gas chromatography/electron capture negative ion chemical ionization mass spectrometry.

A highly sensitive and specific assay based on gas chromatography/electron capture negative ion chemical ionization mass spectrometry has been developed for the analysis of the enantiomers of hexobarbital and its major metabolites in human urine and plasma. S-(+)-(5-2H3)hexobarbital and R-(-)-(5-2H3)hexobarbital were synthesized for clinical studies along with (+/-)-(1,5-2H6)hexobarbital and the deuterated major metabolites for use as internal and reference standards. Hexobarbital enantiomers and their metabolites were analyzed after pentafluorobenzyl and trimethylsilyl derivatization, following solid-phase extraction from plasma and urine. Intense negative ion spectra were observed for all of the derivatives. The base peak in the spectra corresponded to the M-pentafluorobenzyl anion [M-PFB]- except for 1,5-dimethylbarbituric acid, where M-. was the most abundant ion. The applicability of the method was demonstrated by following the plasma concentration-time profiles and urinary excretion in a male extensive metabolizer of mephenytoin who was given a pseudoracemic oral dose of hexobarbital containing equal 50 mg amounts of S-(+)-2(H0)hexobarbital and R-(-)-(2H3)hexobarbital. Marked stereoselective disposition was observed, with the R-(-)-enantiomer being more efficiently metabolized, primarily by alicyclic oxidation and ring cleavage.     

Synergism within polyhexamethylene biguanide biocide formulations

Polyhexamethylene biguanides (PHMB) are mixtures of polymeric biguanides with an average polymer length (n) of 5, but containing high (n greater than 15, mol. wt 3300) and low molecular weight material (n = 2, mol. wt 400). Studies involving discrete molecular weight fractions of PHMB have shown that antimicrobial activity of PHMB increases with increasing polymer length. Cell suspensions which had not been subjected to centrifugation and/or washing during their preparation were employed. Whilst activity was still observed to increase with n, the trend was much reduced as n exceeded six. Centrifugation and washing of cells markedly increased the activity of high but not low molecular weight materials and corresponded to losses upon centrifugation of envelope lipopolysaccharide (LPS). Such envelope LPS represented high affinity binding sites on the surfaces of the cells. Combinations of various molecular weight fractions of PHMB were evaluated against filter-washed cells and revealed a profound synergy between extremes of polymer length.     

Occurrence,localization, and possible significance of an ornithine-containing lipid in Paracoccus denitrificans

A ninhydrin-positive, phosphorus-negative lipid from Paracoccus denitrificans ATCC 13543 has been isolated and purified by mild alkaline methanolysis followed by silicic acid column chromatography and preparative thin-layer chromatography. The lipid was identified as an ornithine-containing lipid. The major ester-linked fatty acid was cis vaccenic acid. Major amide-linked fatty acids were 3-OH-20:1 and 3-OH-18:0. Ornithine-containing lipid was a major lipid component of P. denitrificans. Phospholipids made up about 57% and ornithine-containing lipid about 14% of the weight of the total lipid of the organism. The ratios of lipid ornithine: lipid phosphorus were 0.23, 0.65 and 0.58 in cytoplasmic membrane, outer membrane, and an NaCl extract, which is thought to represent chiefly outer membrane, respectively. Thus ornithine-containing lipid appears to be present in larger amounts in outer membrane than cytoplasmic membrane. No substantial variations in lipid ornithine levels were noted in stationary phase versus exposnential phase organisms, organisms grown in complex medium versus organisms grown in minimal medium with and without amino acid supplements, or in organisms grown in low phosphate-containing medium.Non standard abbreviations TLC thin-layer chromatography - Tris-HCl tris(hydroxymethyl)aminomethane hydrochloride - TMS trimethylsilyl - TFA triluoroacetyl - NPPN ninhydrin-positive, phosphorus-negative - ECL equivalent chain length     

Investigation into the hypogonadism of the obese mouse (genotype ob/ob)

Features of the reproductive axis in the genetically hypogonadal, obese mouse (genotype, ob/ob) were examined at 5-8 months of age and compared with those of wild-type litter mates. Hypothalamic concentrations of dopamine and 5-hydroxytryptamine were normal. Those of 5-hydroxyindoleacetic acid, noradrenaline and LH-RH were raised. LH-RH was biologically active. Pituitary concentration of LH was normal, but that of FSH was raised. Serum concentrations of LH and FSH, compared with those of wild-type animals, were normal and low, respectively. Gonad and accessory sex organs weights were reduced. These findings suggest that the release of FSH but not LH is defective in the ob/ob mouse. Preliminary in-vitro experiments indicated that the pituitary gland responded normally or even supernormally towards LH-RH in its release of LH. The defect in the reproductive axis of the obese mouse may be due to inadequate release of LH-RH although an insensitivity of the pituitary gland towards LH-RH in its release of FSH cannot be excluded.     

Dissimilar effects of transglutaminase inhibitors on peptide hormone-indiced secretion from testis and pituitary

Inhibitors of transglutaminase (monodansylcadaverine and bacitracin) reduced luteinizing hormone stimulated androgen and adenosine - 3′: 5′ - monophosphate production by testicular tissue but had no inhibitory effect on gonadotropin releasing hormone-stimulated luteinizing hormone secretion by the pituitary. These results indicate that there are differences in the mechanisms by which these polypeptide hormones stimulate hormone secretion and suggest a role for protein cross-linking in the mechanism of luteinizing hormone action in the testis.     

Effect of the Nematode Contortylenchus brevicomi on Gallery Construction and Fecundity of the Southern Pine Beetle

Field-collected Dendroctonus frontalis were reared in a controlled environment. Male-female beetle pairs retrieved from galleries 1, 2, or 5 wk after introduction into pine bolts were examined for nematode parasites. Data were obtained for each pair on gallery length, egg niche construction, egg viability, and progeny survival. In a separate study, beetle pairs were reared under laboratory conditions for 10 wk. The number of emerged adult progeny of each pair was recorded. Contortylenchus brevicomi, a nematode parasite, was found in 25% of all beetles that established galleries. After 2 and 3 wk, female beetles infected with the nematode had produced fewer eggs and shorter galleries than did uninfected females. Uninfected females mated with nematode-infected males showed similar trends, although the differences in the 2- and 3-wk tests were not significant. Progeny survival or egg viability was not affected by nematode parasitism of either parent beetle. Unikaryon minutum, a microsporidian parasite found in 65% of all colonizing beetles, had no effect on measured variables. The lower fecundity of beetles parasitized by C. brevicomi continued throughout the insect''s reproductive cycle. After 10 wk, nematode-infected beetle pairs produced fewer emerged adult progeny than did uninfected pairs.     

Effect of light and temperature on epicuticular fatty acid and fatty alcohol of tobacco

Genetically uniform burley tobacco (Nicotiana tabacum) was grown under field and various controlled-environment conditions to determine whether environment influenced epicuticular alkane, fatty acid, and fatty-alcohol composition of the leaves. Quantity and quality of alkanes, fatty acids, and fatty alcohols were greatly influenced by environmental conditions. Highest light intensity did not result in the largest total long aliphatic carbon-chain production. Generally, long photoperiod and cool temperature were associated with highest long aliphatic carbon-chain production on a leaf area basis. Quantity of the individual alkane, fatty acid, or fatty alcohol classes present under the different growth conditions varied in relation to the leaf metabolic status and not leaf size.