Serum concentrations of melatonin in prepubertal or postpubertal gilts exposed to artificial lighting or sunlight

To determine if the type of environmental lighting or reproductive status influences secretory patterns of serum melatonin, gilts were exposed to artificial light or full sunlight during the summer months. In Experiment 1, eight prepubertal and eight postpubertal gilts (Hampshire x Yorkshire x Duroc) were exposed to light intensity of 700 lux in an environmentally controlled room from 0730 to 1900 h daily. An additional eight prepubertal and eight postpubertal gilts were reared outdoors in an open modified-front gestation building and fed on a concrete apron outdoors where light intensity approached 50,000 lux in full sunlight. After 2 mo of acclimating to these environmental conditions, blood samples were drawn from each gilt at 2-h intervals from 1000 to 0200 h. Serum concentrations of melatonin were assayed utilizing Guildhay antisera. The experiment was repeated during the same months of the following year utilizing different gilts (Experiment 2). During both replications, neither light intensity nor reproductive status affected the secretory patterns of melatonin during the sampling period (P >0.05). In both prepubertal and postpubertal gilts, serum concentrations of melatonin were not reduced (P >0.05) by exposure to direct sunlight. Since baseline concentrations of serum melatonin were not reduced by sunlight during the day, the incidence of nocturnal rises of melatonin was not increased (P >0.05) in either prepubertal or postpubertal gilts.     

Influence of larval feeding history on the body condition of Amphiprion melanopus

The cellular condition of liver hepatocytes and the height of gut epithelium cells of larval Amphiprion melanopus were sensitive indicators of feeding condition. Muscle fibres of the trunk showed marked separation in fish fed every third day just prior to settlement. Low feeding regimes also caused reductions in growth, increases in larval duration and reductions in size at metamorphosis. Gut epithelium cell height was also influenced by fish standard length and age. This study suggests that gut epithelium cell height is a useful index for an examination of the importance of starvation of larvae in tropical waters; however, size and age standardization is required prior to comparisons of wild caught fish through time or with laboratory samples.     

Mercuric chloride-induced spin or ligation state changes in ferric or ferrous human cystathionine beta-synthase inhibit enzyme activity.

Cystathionine beta-synthase is a key heme and pyridoxal phosphate-dependent enzyme involved in homocysteine metabolism in humans. The role of the recently discovered heme in this protein remains an important open question. The axial ligands to the heme in both the ferrous and ferric states have been assigned as cysteine and histidine residues, respectively. In this study, we have examined the effect of ligation and spin state changes in the heme on the activity of the enzyme. Treatment of the ferric enzyme with HgCl2 results in the conversion of six-coordinate low-spin heme to five-coordinate high-spin heme and is paralleled by a loss of activity. In contrast, treatment of the ferrous enzyme with HgCl2 results in replacement of the cysteine ligand by an unidentified sixth ligand and retention of the six-coordinate state, and is also accompanied by loss of enzyme activity. Treatment of the five-coordinate HgCl2-treated enzyme with thiols, such as homocysteine, results in reversion to a six-coordinate state. Resonance Raman spectroscopy with 34S-labeled enzyme reveals the return of the endogenous thiol ligand under these conditions and rules out direct coordination by the thiolate of homocysteine to the heme.     

Parasite strain coexistence in a heterogeneous host population

Heterogeneity in host susceptibility and transmissibility to parasite attack allows a lower transmission rate to sustain an epidemic than is required in homogeneous host populations. However, this heterogeneity can leave some hosts with little susceptibility to disease, and at high transmission rates, epidemic size can be smaller than for diseases where the host population is homogeneous. In a heterogeneous host population, we model natural selection in a parasite population where host heterogeneity is exploited by different strains to varying degrees. This partitioning of the host population allows coexistence of competing parasite strains, with the heterogeneity-exploiting strains infecting the more susceptible hosts, in the absence of physiological tradeoffs and spatial heterogeneity, and even for markedly different transmission rates. In our model, intermediate-strategy parasites were selected against: should coexistence occur, an equilibrium is reached where strains occupied only the extreme ends of trait space, under appropriate conditions selecting for lower R₀.     

Importance of Ribosomal Frameshifting for Human Immunodeficiency Virus Type 1 Particle Assembly and Replication

The recent development and use of protease inhibitors have demonstrated the essential role that combination therapy will play in the treatment of individuals infected with the human immunodeficiency virus type 1 (HIV-1). Past clinical experience suggests that due to the appearance of resistant HIV-1 variants, additional therapeutics will be required in the future. To identify new options for combination therapy, it is of paramount importance to pursue novel targets for drug development. Ribosomal frameshifting is one potential target that has not been fully explored. Data presented here demonstrate that small molecules can stimulate frameshifting, leading to an imbalance in the ratio of Gag to Gag-Pol and inhibiting HIV-1 replication at what appears to be the point of viral particle assembly. Thus, we propose that frameshifting represents a new target for the identification of novel anti-HIV-1 therapeutics.     

Inflammatory cytokines (IL-1alpha , TNF-alpha ) and LPS modulate the Ca2+ signaling pathway in osteoblasts

Locally derived growth factors and cytokines in bone play acrucial role in the regulation of bone remodeling, i.e., bone formationand bone resorption processes. We studied the effect of interleukin(IL)-1, tumor necrosis factor (TNF)-, andEscherichia coli lipopolysaccharide(LPS) on the hormone-activatedCa²⁺ message system in theosteoblastic cell line UMR-106 and in osteoblastic cultures derivedfrom neonatal rat calvariae. In both cell preparations, IL-1,TNF-, and LPS did not alter basal intracellularCa²⁺ concentration([Ca²⁺]_i)but attenuated Ca²⁺ transientsevoked by parathyroid hormone (PTH) andPGE₂ in a dose (1-100 ng/ml)-and time (8-24 h)-dependent fashion. The cytokines modulatedhormonally induced Ca²⁺ influx(estimated by using Mn²⁺ as asurrogate for Ca²⁺) as well asCa²⁺ mobilization fromintracellular stores. The latter was linked to suppressed production ofhormonally induced inositol 1,4,5-trisphosphate. The effect ofcytokines on[Ca²⁺]_iwas abolished by the tyrosine kinase inhibitor herbimycin A (50 ng/ml).The cytokine's effect was, however, independent of nitric oxide (NO)production, since NO donors (sodium nitroprusside) as well as permeablecGMP analogs augment, rather than attenuate, hormonally inducedCa²⁺ transients in osteoblasts.Given the stimulatory role of cytokines on NO production inosteoblasts, the disparate effects of cytokines and NO on theCa²⁺ signaling pathway may servean autocrine/paracrine mechanism for modulating the effect ofcalciotropic hormones on bone metabolism.

     

Recombination and transfection mapping of cistron 5 of bacteriophage sp82g

Following infection of E. coli B with ligase-deficient rII bacteriophage T4D recombination between linked markers is increased 4.2 fold and heterozygote frequency increased 2.3 fold. In such infection recombination occurs at a rapid rate for an extended period. This is in contrast to the time course of recombination observed in wild-type, lysis-inhibited, or lysis-defective (gene t defective) infection. In all of these cases recombination under standard cross conditions occurs early in the vegetative cycle. The increased recombination in ligase-deficient rII infection is reduced in a bacterial strain which produces greater than normal levels of host ligase. These results indicate that ligase has a crucial role not only in the replication of DNA but also in recombination. The level of ligase may determine whether DNA replication occurs with or without concomitant recombination.     

The measurement of nanogram amounts of acetylcholine in tissues by pyrolysis gas chromatography

Abstract— A method previously described for measuring ACh in biological effluents has been simplified and extended for use with tissues. The tissue is homogenized in acetonitrile containing propionylcholine as the internal standard and after centrifugation the acetonitrile is removed by shaking with toluene. To the aqueous solution is added a solution of KI-I₂ to precipitate the quaternary compounds. The precipitate is dissolved in aqueous acetonitrile and then drawn through a small column of ion-exchange resin to convert the periodides of the quaternary compounds to chlorides which are then simultaneously pyrolysed and gas chromatographed. On the column the pyrolytic product of choline has a slower retention time than that of acetylcholine; under these circumstances the choline present in tissues does not obscure the measurement of acetylcholine. Specificity was demonstrated by several procedures including mass spectroscopy. The method can measure 25 ng (171 pmoles) of acetylcholine in extracts of brain, simply, and with high reproducibility. With the usual gas chromatograph, 16 samples can be run in a working day. The content of acetylcholine in rat brain was 26.4 nmol/g or almost precisely the values found with other gas chromatographic methods. The pyrolytic method was shown to be applicable to the detection of biologically interesting substances other than choline esters, including betaine, carnitine and the non- quaternary compound, ?-aminobutyric acid, which is readily converted to a volatile compound (probably its methyl ester) when pyrolysed in the presence of tetramethylammonium hydroxide. Of additional general interest is the demonstration of the advantages of acetonitrile as a solvent for extracting water-soluble compounds from tissues.