The effect of microsomal enzyme inducing drugs on reproductive function in the ewe.

A number of drugs cause marked increases in the steroid hydroxylase activity of hepatic microsomes. Beginning 2 days after estrus, 117 mature ewes were each given 14 injections over a 27-day period of phenobarbital sodium, diphenylhydantoin, chlorcyclizine HCl or phenylbutazone. Blood samples for luteinizing hormone (LH) and progesterone determination by radioimmunoassay (RIA) were taken on day 10 of the first estrous cycle (day 18 if no heat was observed) and on days 5 and 10 of the second cycle. On day 10 of the second cycle, the ewes were given an intravenous injection of 1 ml of 6% solution of pentobarbitol sodium anesthetic per 4.5 kg body weight, and the length of anesthetic sleep time was measured. The ewes were then killed and corpora lutea and liver were weighed.In 33 ewes treated with either phenobarbitol sodium or phenylbutazone, sleep time was shortened (18 min $\text{vs}$ 29 min in untreated controls, P<.01), indicating that enzyme induction had occurred. For 41 ewes treated with either chlorcyclizine HCl or diphenylhydantoin, sleep time was lengthened to 93 min (P<.01 $\text{vs}$ controls), indicating impaired liver function. Electron micrographs of liver cells verified that enzyme induction or hepatic degeneration had occurred.     

Muscarinic acetylcholine receptor activation causes inhibition of cyclic AMP accumulation, prolactin and growth hormone secretion in GH3 rat anterior pituitary tumour cells

Acetylcholine, oxotremorine and carbachol, compounds that exhibit muscarinic agonist activity, maximally inhibited basal prolactin secretion from GH3 cells by approx. 50% and intracellular cyclic AMP levels by approx. 20%. Both parameters were inhibited with similar potencies by each agonist. These inhibitory effects were blocked by a muscarinic but not by a nicotinic receptor antagonist. In the presence of VIP or IBMX, which raise intracellular cyclic AMP levels and stimulate hormone release, the degree of muscarinic inhibition was increased, but the potency remained unchanged. Similar changes in the secretory rate of prolactin and growth hormone occurred in these and in cell perifusion experiments. These results suggest that the inhibition of hormone secretion from GH3 cells by muscarinic agonists is mediated by a decrease in intracellular cyclic AMP levels.     

Morphometry and growth of sea pen species from dense habitats in the Gulf of St. Lawrence,eastern Canada

We examined four species of sea pen (Anthoptilum grandiflorum, Halipteris finmarchica, Pennatula aculeata and Pennatula grandis) collected from the Gulf of St. Lawrence and mouth of the Laurentian Channel, eastern Canada. An exponential length–weight relationship was found for all four species, where growth in weight was progressively greater than growth in length with increasing colony size. Halipteris finmarchica, P. grandis and P. aculeata presented the better allometric fits, explaining over 80% of the variance. In addition, a count of growth increments visible in transverse sections in 86 A. grandiflorum and 80 P. aculeata samples was made. Presumed ages ranged between 5 and 28 years for A. grandiflorum and 2 and 21 years for P. aculeata. Radiocarbon assays were inconclusive and could not be used to confirm these ages; further age validation is required. Radial growth of the rod is slow during the first years, increasing at intermediate sizes of the colony and slowing down again for large colonies. Similar results were obtained from the relationship between colony length and number of growth increments where a logistic model was the best fit to the data. On average Spearman’s rank correlations showed 11% of shared variance between sea pen length or weight and environmental variables. Bottom temperature and salinity, depth and summer primary production were significantly correlated to sea pen size for most species.     

The binding of 1,N6-ethenoNAD to bovine liver glutamate dehydrogenase: studies using the time-correlated single photon counting fluorescence technique

The time-correlated single photon counting (TCPC) fluorescence technique has been used as a novel approach to investigate ligand-protein interaction, for the case of the binding of the fluorescent coenzyme analogue 1,N6-ethenoNAD (epsilon NAD) to bovine liver glutamate dehydrogenase in the presence of glutarate, a substrate analogue which stabilizes the complex. System calibration was performed using solutions of epsilon ADP and carefully purified epsilon NAD mixed at variable molar ratios (pH 7.0, 0.05 M sodium phosphate buffer, 20 degrees C). The fluorescence lifetimes obtained after deconvolution were 2.4 ns (for epsilon NAD) and 23 ns (for epsilon ADP), in good agreement with literature values obtained under similar conditions. epsilon NAD binds to glutamate dehydrogenase in the presence of 50 mM glutarate, with a fluorescence quantum yield enhancement factor, Q, of about 17-fold, as previously reported (Favilla, R. and Mazzini, A. (1984) Biochim. Biophys. Acta 48-57). For this system, fluorescence lifetime values were obtained after deconvolution as 2.4 ns for free epsilon NAD and 21 ns for bound epsilon NAD. These values did not vary appreciably with enzyme concentration nor with degree of saturation, thus reflecting the existence of only one spectroscopically relevant type of complex. Addition of either GTP or ADP did not affect the lifetime of epsilon NAD bound to the enzyme, but only its affinity, thus allowing calculations of binding strengths. In the case of a simple binding (i.e., in the absence of GTP) the dissociation constant of the complex could be derived from a simple relationship, in which only the ratio between the pre-exponential factors and the parameter gamma, which represents the molar fraction of epsilon NAD molecules free in solution in the open conformation, are to be taken into account. The results are in good agreement with those reported by some of us (reference above) using a steady-state fluorescence technique, which by itself is, however, unable to resolve the number of relevant species present in the system.     

The effects of manipulation of sedimentary iron and organic matter on sediment biogeochemistry and seagrasses in a subtropical carbonate environment

The microbial metabolism of organic matter (OM) in seagrass beds can create sulfidic conditions detrimental to seagrass growth; iron (Fe) potentially has ameliorating effects through titration of the sulfides and the precipitation of iron-sulfide minerals into the sediment. In this study, the biogeochemical effects of Fe availability and its interplay with sulfur and OM on sulfide toxicity, phosphorous (P) availability, seagrass growth and community structure were tested. The availability of Fe and OM was manipulated in a 2 × 2 factorial experiment arranged in a Latin square, with four replicates per treatment. The treatments included the addition of Fe, the addition of OM, the addition of both Fe and OM as well as no addition. The experiment was conducted in an oligotrophic, iron-deficient seagrass bed. Fe had an 84.5% retention efficiency in the sediments with the concentration of Fe increasing in the seagrass leaves over the course of the experiment. Porewater chemistry was significantly altered with a dramatic decrease in sulfide levels in Fe addition plots while sulfide levels increased in the OM addition treatments. Phosphorus increased in seagrass leaves collected in the Fe addition plots. Decreased sulfide stress was evidenced by heavier δ³⁴S in leaves and rhizomes from plots to which Fe was added. The OM addition negatively affected seagrass growth but increased P availability; the reduced sulfide stress in Fe added plots resulted in elevated productivity. Fe availability may be an important determinant of the impact that OM has on seagrass vitality in carbonate sediments vegetated with seagrasses.     

Environmental needs and social justice

Despite the growth in awareness and practical action to maintain biodiversity, environmental degradation and ecosystem destruction has continued at a high rate over the last 20 years. The roots of this lie in the predominant international economic order, underpinned by lifestyle demands for increased material consumption. Net flow of wealth from South (less developed) to North (more developed) nations has exacerbated a spiral of increased poverty and environmental degradation in the former. Global environmental conservation depends upon a radical change of direction with the principle of equity as the starting point. Notwithstanding the importance of continuing to add to local and small-scale conservation achievements, the prospect of radical change happening seems small, despite it being in the long-term self-interest of the North. The concept of equity is, apparently, unacceptable to Northern electorates.     

Sugar‐feeding status alters biting midge photoattraction

The biting midge Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae) transmits pathogens to both livestock and wildlife. Biting midge surveillance relies heavily on light traps for collection; however, little is known about the light spectra preferences of C. sonorensis midges. A light assay arena was constructed and light‐emitting diodes (LEDs) of various light spectra were used as light sources to evaluate midge photoattraction. A comparison of responses to light spectra indicated the highest proportions of C. sonorensis were attracted to ultraviolet (UV) light and that midges differentiated 10‐nm differences in wavelength. Stronger intensities of UV light resulted in greater attraction. Midges exhibited both sugar‐seeking and escape behaviours under different conditions of sugar supplementation before and during the experiment. These behaviours occurred with lights of 355 nm and 365 nm in wavelength. Based on the results of this study, the attraction of C. sonorensis to light traps can be improved through the use of bright LEDs at 355 nm or 365 nm.     

Means for efficient electron beam generation in wide-aperture open-discharge light sources

The interaction of a plasma in the accelerating gap of an open discharge with a strong external electric field and with the cathode surface has been investigated theoretically and experimentally. In a pulsed nanosecond discharge, the ion inertia and plasma screening of the electric field cause a fast growth of the electric field E in the cathode region and a decrease in the length of the latter. Along with a reduction of the electron multiplication factor at high electric fields, this leads to a substantial decrease in the ion flux toward the cathode, which allows one to develop highly efficient open-discharge light sources with a long lifetime and low cathode sputtering. In this respect, continuous and quasi-continuous discharges are less advantageous because of the smaller increase in the electric field in the cathode region. The Townsend coefficients of charge multiplication and electron emission at high electric fields typical of open discharges have been measured for the first time. Fast ions and atoms extracted from the plasma of the accelerating gap significantly affect the cathode emission properties. In particular, photoemission is enhanced by more than one order of magnitude and becomes the main mechanism for electron generation. This also increases the efficiency and lifetime of open-discharge light sources.     

Evaluation of the antimicrobial activity of methylglyoxal bis(guanylhydrazone) analogues, the inhibitors for polyamine biosynthetic pathway

Metabolic and antiproliferative effects of methylglyoxal bis(butylamidinohydrazone) (MGBB) and methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP), inhibitors for polyamine biosynthetic pathway, on Escherichia coli, Shigella sonnei, Aeromonas sobria, Aeromonas hydrophila and Vibrio cholerae were investigated. MGBB at the concentration of 100 mumol/l depleted intracellular putrescine and spermidine concentrations of E. coli to 25 and 20% of the controls, respectively, while MGBCP depressed their concentrations to 38 and 24%, respectively. In these polyamine-depleted E. coli cells the syntheses of RNA, DNA and protein decreased to 13, 54 and 29% of the control, respectively, with MGBB and to 23, 71 and 55%, respectively, with MGBCP. The minimum inhibitory concentrations (MIC) of MGBB for the growth of A. sobria, E. coli, A. hydrophila, V. cholerae and Sh. sonnei were estimated to be 50, 160, 240, 285 and 320 mumol/l, respectively, whereas those of MGBCP were slightly higher for respective bacteria.