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.     

The learning skills of primates: The rhesus macaque in comparative perspective

Twenty-month-old rhesus monkeys were tested in a modified discrimination-reversal paradigm, which was designed to distinguish abstract learning from stimulus-response associational learning. Previous studies indicate that talapoin monkeys learn associationally and great apes via forming abstract concepts. Adult rhesus monkeys are apparently capable of forming simple abstractions, but learn primarily through associational process. The results of this study show the adolescent rhesus monkeys to be associational learners, with their response patterns indicating more complexity than the talapoins but less than the adult rhesus monkeys. The data suggest that rhesus monkeys develop their low-level capacity of abstract learning with maturation.     

Glucocorticoids inhibit the induction of nitric oxide synthase and the related cell damage in adenocarcinoma cells

Lipopolysaccharide (LPS) induced a time-dependent synthesis of nitric oxide (NO) in EMT6 adenocarcinoma cells, assayed by accumulation of NO-derived nitrite in the medium. The induction NO synthesis was inhibited in a concentration-dependent manner by the glucocorticoids dexamethasone (IC₅₀ = 5 nM) and hydrocortisone (IC₅₀ = 20 nM) and this effect was partially antagonized by progesterone and cortexolone. If addition of dexamethasone was delayed 6 h or more, inhibition of nitrite accumulation over 24 h was substantially reduced, indicating a lack of direct effect of glucocorticoids on the NO synthase. Nitrite accumulation was accompanied by cell damage, which was increased by L-arginine and inhibited by $\text{N}{}^{\mathrm{<mtext>G</mtext>}}\text{-}\text{monomethyl-}\text{L}\text{-arginine}$ (L-NMMA) and dexamethasone. These data show that NO is a primary cytotoxic mediator and that suppression of its formation by glucocorticoids explains some of their anti-inflammatory and cytoprotective effects.     

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.