Chromatographic methods for amylases

This review surveys recent developments in chromatographic methods for the separation of amylases from complex extracts, including the separation of isozymes. It contains two tables with the properties and molecular characteristics of α- and β-amylases from different sources as well as an updated review of methods for the determination of amylase activity. The main subject of this review is a detailed evaluation of the application of newly developed chromatographic methods for the purification of amylases.     

Circadian Changes in Anxiolysis-Related Behavior of Syrian Hamsters. Correlation with Hypothalamic GABA Release

The diurnal variations in anxiolysis and exploratory behavior were examined in a plus-maze paradigm in Syrian hamsters exposed to 14 h light: 10 h dark photoperiods or to constant darkness for 3 days. The percent of time spent in open arms and the percent of entries to open arms (both indexes of anxiety-related behavior) as well as the number of crosses to both arms (an index of locomotor behavior) showed significant daily variations under the two lighting conditions, maxima being found at night (2400-0400 h). Flumazenil (5 mg/kg) injected at the middle of the light (at 1600 h) or dark period (at 0400 h) decreased by 39-54 % anxiolysis-related behavior without affecting locomotor activity significantly. 3 H-?-aminobutyric acid (GABA) release from preoptic-medial basal hypothalamic explants obtained from hamsters exposed to 14 h light: 10 h dark photoperiods attained maximal values at 2400-0400 h. The results further supported the existence of circadian changes in anxiolysis-related behavior in Syrian hamsters that correlated with an increased hypothalamic GABA release.     

Melatonin administration prevents lipopolysaccharide-induced oxidative damage in phenobarbital-treated animals

The protective effect of melatonin on lipopolysaccharide (LPS)-induced oxidative damage in phenobarbital-treated rats was measured using the following parameters: changes in total glutathione (tGSH) concentration, levels of oxidized glutathione (GSSG), the activity of the antioxidant enzyme glutathione peroxidase (GSH-PX) in both brain and liver, and the content of cytochrome P450 reductase in liver. Melatonin was injected intraperitoneally (ip, 4mg/kg BW) every hour for 4 h after LPS administration; control animals received 4 injections of diluent. LPS was given (ip, 4 mg/kg) 6 h before the animals were killed. Prior to the LPS injection, animals were pretreated with phenobarbital (PB), a stimulator of cytochrome P450 reductase, at a dose 80 mg/kg BW ip for 3 consecutive days. One group of animals received LPS together with N^w-nitro-L-arginine methyl ester (L-NAME), a blocker of nitric oxide synthase (NOS) (for 4 days given in drinking water at a concentration of 50 mM). In liver, PB, in all groups, increased significantly both the concentration of tGSH and the activity of GSH-PX. When the animals were injected with LPS the levels of tGSH and GSSG were significantly higher compared with other groups while melatonin and L-NAME significantly enhanced tGSH when compared with that in the LPS-treated rats. Melatonin alone reduced GSSG levels and enhanced the activity of GSH-PX in LPS-treated animals. Additionally, LPS diminished the content of cytochrome P450 reductase with this effect being largely prevented by L-NAME administration. Melatonin did not change the content of P450 either in PB- or LPS-treated animals. In brain, melatonin and L-NAME increased both tGSH levels and the activity of GSH-PX in LPS-treated animals. The results suggest that melatonin protects against LPS-induced oxidative toxicity in PB-treated animals in both liver and brain, and the findings are consistent with previously published observations related to the antioxidant activity of the pineal hormone.     

A new protein factor functional in the ferredoxin-independent light activation of chloroplast fructose 1,6-bisphosphatase

A protein purified from chloroplasts (the “new protein factor”) activated Fru-P₂ase in a photochemical reaction that depended only on chloroplast membranes. The results suggest that chloroplasts utilize the newly found mechanism for the photoregulation of Fru-P₂ase in addition to the recently described ferredoxin/thioredoxin system.     

Ferralterin: An iron-sulfur protein functional in enzyme regulation in photosynthesis

The chloroplast new protein factor that was recently shown to link light to the activation of fructose 1,6-bisphosphatase was identified as a previously unrecognized iron-sulfur protein. This protein, given the name “ferralterin,” was purified to homogeneity from spinach leaves and from the blue-green alga (cyanobacterium) Nostoc muscorum. Ferralterin from both sources showed a visible absorption peak at 410nm, a molecular weight of about 30,000 and (provisionally) 4 g-atoms per mole each of nonheme iron and acid labile sulfide. The homogeneous ferralterin preparations catalyzed a light-dependent activation of chloroplast fructose 1,6-bisphosphatase that was dependent only on chlorophyll-containing membranes.     

Release of norepinephrine from the rat ovary: local modulation of gonadotropins.

Experiments were undertaken to define the role of gonadotropins in the release of norepinephrine and the relationship with beta-receptors of the ovary. Rat ovaries were removed at different stages of the estrous cycle and incubated in [3H]norepinephrine. Subsequently, ovaries were electrically stimulated and the release of [3H]norepinephrine was recorded. There were no changes in the norepinephrine content during the estrous cycle. The ovary exhibited cyclical variation in norepinephrine-induced release during the estrous cycle. The lowest release of norepinephrine was found during diestrus; there was an increase during proestrus and estrus followed by a decline during metestrus. The release of norepinephrine changed in the opposite way to the beta-receptor number, suggesting a process involving down-regulation between norepinephrine release and beta-receptors of the ovary. Norepinephrine released from the ovary was locally regulated by gonadotropins. The presence of FSH in the superfusion medium stimulated the norepinephrine-induced release from the ovaries of rats in diestrus (by 20%) and estrus (by 40%), but no effect was found during proestrus. In addition, the presence of hCG stimulated (by 40%) norepinephrine-induced release during proestrus, but no changes were apparent during the other stages of the estrous cycle. These results suggest that the local action of gonadotropins on nerve terminals of the ovary might be one of the factors governing the changes in norepinephrine release through the estrous cycle. The changes in the norepinephrine released to the synaptic cleft might exert down-regulation on the beta-adrenergic receptor content of the ovary and in this way control the ovarian steroid secretory activity.     

A neural model of the interaction of tectal columns in prey-catching behavior

Building on a simple model of a tectal column as the unit of processing in the amphibian tectum, we conduct a computer analysis of the interaction of a linear array of such columns. The model suggests that the inhibitory and excitatory activity in the tectum may have three functions: 1) spatiotemporal facilitation of column activity to a moving stimulus; 2) preference for the head of the stimulus, probably to avoid possible defensive reactions of the prey; and 3) modulating the state of excitation of the column once it has produced a response. The model also shows that the spatio-temporal effects of excitation and inhibition increases the acuity of the animal to the direction of the prey, through processes similar to lateral inhibition.The search reported in this paper was supported in part by NIH grant NS14971-02. Our thanks to Peter Ewert and David Ingle for valuable discussions of the experimental data; and to Andrew Cromarty and Donald House for their help with the computer implementation     

Chromosome polymorphism in populations of the grasshopper Trimerotropis pallidipennis from southern Argentina

Three populations of the grasshopper Trimerotropis pallidipennis from southern Argentina have been studied cytologically. A very characteristic B-chromosome was found in all three. They also showed geographical variability in respect of the presence of pericentric inversions, and the inversion system was found to influence chiasma frequency. The Laguna Blanca population, which is on the hypothetical pathway the species is believed to have followed during its migration from northern to southern latitudes, has the same karyotype composition as the N. American form, with fixed inversions in the 3 largest autosomes and the X-chromosome. Its members have a high total chiasma frequency and a great number of interstitial chiasmata. The Sierra de la Ventana population, situated at the absolute eastern border of the species distribution is highly polymorphic with respect to the presence of inversions in the medium chromosomes. Its members have the lowest total chiasma frequency and a greatly reduced number of interstitial chiasmata. Situated geographically between the other two, the Choele-Choel population has the highest frequency of inversions and many of them are homozygous. Its members have a higher total chiasma frequency than that observed in specimens from Sierra de la Ventana, and a greatly reduced number of interstitial chiasmata, similar to that observed in individuals from the latter population.