Thyroid Hormones affect the Level and Activity of Nitric Oxide Synthase in Rat Cerebral Cortex during Postnatal Development

The effects of thyroid hormones (TH) on the enzyme level and activity of neuronal nitric oxide synthase (nNOS) were studied in the rat cerebral cortex during postnatal life. As revealed by arginine/citrulline conversion assay and Western blot analysis of the homogenate of the parietal cortex T4 significantly increased nNOS activity and nNOS protein level to 153 ± 25% and to 178 ± 20%, respectively. In contrast, 6-n-propyl-2-thyouracil (PTU) decreased nNOS activity and nNOS level to 45 ± 10% and to 19 ± 4%, respectively. The number of nNOS-immunoreactive neurons did not change after either T4 or PTU treatment, however, following T4 administration the percentage of intensively immunoreactive neurons increased to 85 ± 3% compared to control (65 ± 6%), whereas it decreased to 49 ± 2% after PTU treatment. Our findings indicate that abnormal TH levels differentially regulate the activity and the level of nNOS and suggest a cross-talk between the TH and NO signaling pathway in the developing cerebral cortex of rats.     

Synthesis and structural characterization of bioactive peptide conjugates using thioether linkage approaches.

Applications of cysteine-insertion and thioether linkage approaches to the preparation of a number of bioactive peptide conjugates are reported. Peptides containing epitopes from (i) herpes simplex virus type 1 glycoprotein D, (ii) a specific N-terminal beta-amyloid epitope recognized by therapeutically active antibodies, and (iii) a GnRH-III peptide from sea lamprey with antitumour activity, were elongated with Cys residues and attached to a chloroacetylated tetratuftsin derivative carrier via a thioether linkage either directly, or by insertion of a spacer. The structures and molecular homogeneity of all the peptide conjugates were ascertained by HPLC, MALDI and electrospray mass spectrometry. The use of a spacer such as an oligoglycine or GFLG-tetrapeptide gave an increased yield in the conjugation reaction and enhanced reaction rates. In the formation of cysteinyl-thioether linkages, it was found that the position of flanking Cys residues markedly influenced the conjugation reaction and the formation of intermolecular epitope disulfide-dimers. C-terminal Cys residues gave thioether conjugates with significantly diminished epitope-dimerization, while Cys at the N-terminal caused rapid disulfide-dimerization, thereby preventing efficient conjugation.     

The effects of predation risk on the use of social foraging tactics

The effects of predation on the use of social foraging tactics, such as producing and scrounging, are poorly known in animals. On the one hand, recent theoretical models predict increased use of scrounging with increasing predation risk, when scroungers seeking feeding opportunities also have a higher chance of detecting predators. On the other hand, there may be no relation between tactic use and predation when antipredator vigilance is not compatible with scanning flockmates. We investigated experimentally the effects of predation risk on social foraging tactic use in tree sparrows, Passer montanus. We manipulated predation risk in the field by changing the distance between shelter and a feeder. Birds visited the feeder in smaller flocks, spent less time on it and were somewhat more vigilant far from shelter than close to it. Increased predation risk strongly affected the social foraging tactic used: birds used the scrounger tactic 30% more often far from cover than close to it. Between-flock variability in scrounging frequency was not related to the average vigilance level of the flock members, and within-flock variability in the use of scrounging was negatively related to the vigilance of birds. Our results suggest that in tree sparrows, the increased frequency of scrounging during high predation risk cannot simply be explained by an additional advantage of increasing antipredator vigilance. We propose alternative mechanisms (e.g. increased stochasticity in food supply, and that riskier places are used by individuals with lower reserves) that may explain increased scrounging when animals forage under high predation risk.     

Circadian Clock-Regulated Expression of Phytochrome and Cryptochrome Genes in Arabidopsis

Many physiological and biochemical processes in plants exhibit endogenous rhythms with a period of about 24 h. Endogenous oscillators called circadian clocks regulate these rhythms. The circadian clocks are synchronized to the periodic environmental changes (e.g. day/night cycles) by specific stimuli; among these, the most important is the light. Photoreceptors, phytochromes, and cryptochromes are involved in setting the clock by transducing the light signal to the central oscillator. In this work, we analyzed the spatial, temporal, and long-term light-regulated expression patterns of the Arabidopsis phytochrome (PHYA to PHYE) and cryptochrome (CRY1 and CRY2) promoters fused to the luciferase (LUC(+)) reporter gene. The results revealed new details of the tissue-specific expression and light regulation of the PHYC and CRY1 and 2 promoters. More importantly, the data obtained demonstrate that the activities of the promoter::LUC(+) constructs, with the exception of PHYC::LUC(+), display circadian oscillations under constant conditions. In addition, it is shown by measuring the mRNA abundance of PHY and CRY genes under constant light conditions that the circadian control is also maintained at the level of mRNA accumulation. These observations indicate that the plant circadian clock controls the expression of these photoreceptors, revealing the formation of a new regulatory loop that could modulate gating and resetting of the circadian clock.     

Foraging in agricultural fields: local ‘sit-and-move’ strategy scales up to risk-averse habitat use in a wolf spider

By making field observations on the movement pattern of the agrobiont wolf spider Pardosa agrestis at two spatiotemporal scales, we explored how fine-scale foraging movements scale up to medium-scale habitat use by the spiders. For fine-scale observations, we followed individuals for several metres and for up to 1-2 h. For medium-scale observations we used marking and recapture in live-trapping pitfall grids, which allowed us to detect movements up to 70 m and for 4 weeks. The analysis of fine-scale movement indicated that spiders followed a ‘sit-and-move’ foraging strategy, which consisted of variable periods of waiting (mean 2.5 min) and brief bouts of movements between the waiting sites. Spiders spent over 90% of the total observation time waiting. Prey capture (or capture attempts) was initiated only from waiting sites. Movement between consecutive waiting sites was more directional than predicted by the correlated random walk model. At medium (2-day) timescales the mean displacement of marked spiders was 7.4 m. Simulations suggested that such a displacement could be achieved if movement observed at the fine scale followed a random path for 2 days. We concluded that movement became less directional with increasing scale. Such a phenomenon might be related to avoidance of revisiting food patches locally and an efficient sampling of the habitat at higher scales. High movement activity in a species that is primarily adapted to ephemeral habitats might increase its likelihood of colonizing new habitat patches. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.     

Treatment of primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a presumed autoimmune disease of the liver, which predominantly affects middle age women. Most patients are diagnosed when asymptomatic. The disease is characterised by chronic, granulomatous inflammation of the small bile ducts, which leads to progressive ductopenia, cholestasis, fibrosis, cirrhosis and eventual liver failure. All PBC patients with abnormal liver biochemistry should be considered for therapy. Ursodeoxycholic acid (URSO) treatment reduces intracellular hydrophobic bile acid levels and thereby may have a cytoprotective effect on cell membranes. URSO may also act as an immunomodulating agent. Multicenter randomised controlled trials proved that the treatment is associated with a marked improvement in serum biochemical markers of cholestasis, i.e. bilirubin, ALP, GGT, including fall in serum cholesterol levels. Treatment does not seem to benefit the symptoms of fatigue, pruritus, and osteoporosis. UDCA has been shown when given in a dose of 15 mg/kg daily for up to 4 years to prolong the time to liver transplantation or death. Immunosuppressive therapy: based on the immunological abnormalities, several immunosuppressive drugs have been tested. Neither azathioprine nor cyclosporine was found in large enough trials to show beneficial effect on survival. D-penicillamine, cholchicin, methotrexát, prednisolone were found without significant long-term benefit. Combination therapy with URSO and budenoside appears to add some benefit to URSO monotherapy, but further studies are needed. Liver transplantation. The most crucial question is the timing. Serum bilirubin, Mayo risk score and some other factors such as uncontrollable pruritus and severe osteoporosis influence the decision. Recurrence of PBC in allograft is rare, the progress is slow, and is no reason for not recommending transplantation. Symptomatic treatment of pruritus, sicca syndrome and preventive treatment of osteoporosis, neuropathy and fat soluble vitamin deficiency is also important.     

Gastric mucosal endogenous prostacyclin levels are different in Brattleboro rats compared with Wistar strain

Homozygous Brattleboro rats were investigated and compared to normal (physiological) Wistar strain rats regarding their gastric mucosal endogenous prostacyclin (PG-I(2)) level. It seems that the Brattleboro animals have a significantly lower level of this important protective material. Wistar rats having an artificial pituitary stalk lesion (which is the artificial equivalent of homozygous Brattleboro animals) showed no differences in endogenous mucosal prostacyclin level compared to normal Wistar rats. Therefore, we concluded that this hitherto unknown property of the homozygous Brattleboro rats is genetically determined.     

Glycogenolysis - and not gluconeogenesis - is the source of UDP-glucuronic acid for glucuronidation

Differences in cofactor (NADPH and UDP-glucuronic acid) supply for various processes of biotransformation were studied by investigating the interrelations between glucose production (gluconeogenesis and glycogenolysis) and drug (p-nitrophenol, aminopyrine, phenolphthalein) biotransformation (hydroxylation and conjugation) in isolated murine hepatocytes. In glycogen-depleted hepatocytes prepared from animals fasted for 48 h (i) p-nitrophenol conjugation was decreased by 80% compared to the fed control, while aminopyrine oxidation was unaltered, (ii) addition of glucose or gluconeogenic substrates failed to increase the rate of p-nitrophenol conjugation, while the rate of p-nitrophenol and also aminopyrine oxidation was increased and (iii) gluconeogenesis was inhibited by 80% by aminopyrine oxidation: it was moderately decreased by p-nitrophenol oxidation and conjugation and remained unchanged by phenolphthalein conjugation. In hepatocytes prepared from fed mice (i) p-nitrophenol conjugation was independent of the extracellular glucose concentration, (ii) it was linked to the consumption of glycogen - addition of fructose inhibited p-nitrophenol glucuronidation only, while sulfation was unaltered and (iii) p-nitrophenol oxidation was not detectable: aminopyrine oxidation was not affected by fructose addition. It is suggested that UDP-glucuronic acid for glucuronidation derives predominantly from glycogen, while the NADPH generation for mixed function oxidation is linked to glucose uptake and / or gluconeogenesis in the liver.