In vivo topoisomerase II cleavage of the Drosophila histone and satellite III repeats: DNA sequence and structural characteristics.

We have identified two classes of in vivo topoisomerase II cleavage sites in the Drosophila histone gene repeat. One class co-localizes with DNase I-hypersensitive regions and another novel class maps to a subset of consecutive nucleosome linker sites in the scaffold-associated region (SAR) of the histone gene loop. Prominent topoisomerase II cleavage is also observed in one of the linker regions of the two nucleosomes spanning satellite III, a centromeric SAR-like DNA sequence with a repeat length of 359 bp. At the sequence level, in vivo topoisomerase II cleavage is highly site specific. Comparison of 10 nucleosome linker sites defines an in vivo cleavage sequence whose major characteristic is a prominent GC-rich core. These GC-rich cleavage sites are flanked by extensive arrays of oligo(dA).oligo(dT) tracts characteristic of SAR sequences. Treatment of cells with distamycin selectively enhances cleavage at nucleosome linker sites of the SAR and satellite regions, suggesting that AT-rich sequences flanking cleavage sites may be involved in determining topoisomerase II activity in the cell. These observations provide evidence for the association of topoisomerase II with SARS in vivo.     

Amino acid metabolism in several tissues of the obese Zucker rat as indicated by the tissue accumulation of α-amino[1-14C]isobutyrate

Measurements of the tissue accumulation of α-amino[1-¹⁴C]isobutyrate [1-¹⁴C]AIB) in lean (+/?) and obese (fa/fa) Zucker rats showed an augmented tissue/plasma ratio in the liver of the obese animals. In contrast, brown adipose tissue AIB accumulation was lower in the fa/fa animals. In response to a 24h starvation period AIB accumulation was significantly elevated in the liver and plasma of the lean animals and was unchanged in the liver of the fa/fa animals. The circulating concentration of alanine and branched-chain amino acids was elevated in the fa/fa animals as compared to their lean counterparts. These observations suggest that amino acid uptake is not involved in the impaired muscle development observed in the obese Zucker rat and that the ability of brown adipose tissue for amino acid utilization is decreased in the obese animals suggesting that this may partially explain the impaired thermoregulatory capacity observed in brown adipose tissue of obese Zucker rats.     

Effects of tumour necrosis factor-α (cachectin) on glucose metabolism in the rat

Intravenous administration of a single dose (20 g) of recombinant tumour necrosis factor- (TNF, cachectin) to rats decreased the rate of intestinal glucose absorption. In vivo, the oxidation of [U-¹⁴C]glucose to ¹⁴CO₂ was significantly increased by the cytokine. In addition, [¹⁴C]lipid accumulation from [U-¹⁴C]glucose was increased both in liver and brown adipose tissue of the TNF-injected animals. The decrease observed in intestinal glucose absorption was not associated with changes in intestinal metabolism. There was no difference in glucose metabolism by isolated enterocytes from either control or TNF-injected rats whether in the absence or presence of different concentrations of the cytokine in the incubation medium. In contrast, tumour necrosis factor altered the rate of gastric emptying as measured by the gastrointestinal distribution of [³H]inulin following an intragastric glucose load. These results suggest that the cytokine profoundly alters glucose metabolism by increasing its whole-body oxidation rate and delaying intestinal absorption through a reduced gastric emptying.     

Molecular heterogeneity underlying the G6PD Mediterranean phenotype

Summary As part of a study aiming to define the molecular basis of glucose-6-phosphate dehydrogenase (G6PD) deficiency, we analysed a sample from a Portugese boy with a family history of favism. Although the biochemical properties of red-cell G6PD from this subject were similar to those of the common variant G6PD Mediterranean, the corresponding mutation (563 CT) was not present. Instead, polymerase chain reaction (PCR) amplification and sequencing of the entire gene detected a CT transition at nucleotide 592 in exon VI, changing an arginine residue to a cysteine residue only 10 amino acids downstream from the Mediterranean mutation. Single-strand conformation polymorphism analysis of a PCR-amplified DNA fragment spanning exons VI and VII of the G6PD gene has detected the same mutation, confirmed by sequencing, in a G6PD-deficient patient from Southern Italy. We name this new variant G6PD Coimbra.     

Effect of recombinant bovine somatotropin (somidobove) in a sustained release vehicle on plasma somatotropin level and lactational performance of dairy cows.

The effects of administration of recombinantly derived bovine somatotropin (somidobove) in a sustained-release vehicle on the profiles of concentrations of bovine somatotropin (bST) in the blood plasma and on the milk yield of dairy cows of three herds were examined. Cows (36-87 days post partum) were treated subcutaneously with recombinant bST at 28-day intervals. In control animals, basal concentrations of bST averaged 1.4 ng.ml-1 in first-calf heifers and 1.5 ng.ml-1 in multiparous cows. In somidobove treated first-calf heifers, the concentration of bST was increased to 10.7, 14.5, and 27.0 ng.ml-1 at 24 h postinjection and in multiparous cows to 6.6, 11.0, and 11.7 ng.ml-1 on day 2 postinjection of 320, 640, and 960 mg of somidobove, respectively. On day 8 postinjection the average plasma bST levels of both parity groups are similar (on the average 3.4, 8.6, and 12.5 ng.ml-1 for three doses of somidobove respectively) and for the two highest doses being still significantly increased. During the 2nd week postinjection plasma bST concentration declined returning to control levels on day 15 postinjection. Somidobove-treated first-calf heifers produced 10.9, 16.7 and 17.9% and multiparous animals 25.5, 24.2 and 32.5% more milk than the controls when given 320, 640 and 960 mg somidobove, respectively. The cyclic pattern in milk yield within each 28-day injection interval was observed consistently in all herds. The milk yield increased to a maximum between day 4 to 8 postinjection and then slowly declined. Milk composition was not affected by somidobove treatment.     

Ethylene and in vitro rooting of hazelnut (Corylus avellana) cotyledons

Ethylene may be one of the many factors that play a role in rooting. However, in some studies ethylene promoted rooting, while in others it was inhibitory or had no effect. Using cotyledons of hazelnut ( Corylus avellana L. cv. Casina) observations were made of the effect of ethylene precursors on adventitious root formation. l-methionine (Met) or 1-aminocyclopropane-1-carboxylic acid (ACC) added to a standard indole-3-butyric acid (IBA)-kinetin-containing medium did not enhance rooting, while 2-chloroethylphosphonic acid (CEPA) did. The ethylene inhibitor, aminoethoxyvinylglycine (AVG), inhibited root formation, but its effect was reversed by ACC when cotyledonary segments were transferred to rhizogenic medium plus ACC at day 10. Ethylene production by cotyledons cultured on rhizogenic medium or rhizogenic medium plus CEPA was high at the beginning of rooting. Thus, the wound-induced ethylene is a key stimulatory factor in the formation of root primordia. The data support the hypothesis that ethylene plays a positive role in root formation.     

Short-term effects of carbon dioxide on carnation callus cell respiration

The addition of potassium bicarbonate to the electrode cuvette immediately stimulated the rate of dark O₂ uptake of photomixotrophic and heterotrophic carnation (Dianthus caryophyllus L.) callus, of Elodea canadensis (Michx) leaves, and of other plant tissues. This phenomenon occurred at pH values lower than 7.2 to 7.8, and the stimulation depended on the concentration of gaseous CO₂ in the solution. These stimulatory responses lasted several minutes and then decreased, but additional bicarbonate or gaseous CO₂ again stimulated respiration, suggesting a reversible effect. Carbonic anhydrase in the solution increased the stimulatory effect of potassium bicarbonate. The CO₂/bicarbonate dependent stimulation of respiration did not occur in animal tissues such as rat diaphragm and isolated hepatocytes, and was inhibited by salicylhydroxamic acid in carnation callus cells and E. canadensis leaves. This suggested that the alternative oxidase was engaged during the stimulation in plant tissues. The cytochrome pathway was severely inhibited by CO₂/bicarbonate either in the absence or in the presence of the uncoupler carbonylcyanide m-chlorophenyl hydrazone. The activity of cytochrome c oxidase of callus tissue homogenates was also inhibited by CO₂/bicarbonate. The results suggested that high carbon dioxide levels (mainly free CO₂) partially inhibited the cytochrome pathway (apparently at the oxidase level), and this block in electron transport elicited a large transient engagement of the alternative oxidase when present uninhibited.     

Influence of blood proteins in the in vitro adhesion of Staphylococcus epidermidis to teflon, polycarbonate, polyethylene and bovine pericardium.

The influence of human plasma proteins (fibrinogen, albumin and fibronectin) on the adherence of Staphylococcus epidermis to teflon, polyethylene, polycarbonate and bovine pericardium was studied in an in vitro quantitative assay by scintillation counting. Bacterial adhesion was generally reduced by the presence of protein during the adherence assay except in the case of bovine pericardium, in which adherence remained almost unaffected. The effect of these plasma proteins on bacterial surface properties resulted in strong increases of surface charge as measured by ion-exchange chromatography and with no effect on hydrophobicity, estimated as contact angles. Adherence was not found to be correlated with these two properties, suggesting that bacteria-surface interactions must not be simplified to the influence of interfacial forces.     

Ovarian function and pregnancy rates in reindeer calves (Rangifer tarandus ) in Southern Norway

Reindeer calves (n = 632) were slaughtered in November/December (n = 476) or in January (n = 156). Dressed weights and amount of perirenal fat were recorded, and the reproductive organs were collected. A separate group of 130 reindeer calves were weighed at 7 months of age and were followed up with repeated weighings and pregnancy examinations up to 21 months. The onset of puberty and the pregnancy rate were significantly influenced by body weight and the amount of perirenal fat. Approximately 60 g of perirenal fat and 22 kg dressed weight were found at the lower limits for pregnancy. A total of 222 (35%) animals had reached puberty and 126 (20%) were pregnant when examined after slaughter. Animals which conceived during their first autumn showed only a moderate weight gain the following year, and the calf mortality rate in these animals was 47.4%. It was concluded that calf pregnancies are common among the reindeer of Southern Norway and that measures need to be taken to prevent them.     

Enzymatic hydrolysis of 2,2,2,-trifluoroethyl α-chloro-α-phenylacetate in organic media

Summary 2,2,2-Trifluoroethyl -chloro--phenylacetate is succesfully hydrolysed in organic solvent in the presence of aniline andCandida cylindracea orPseudomonas cepacia lipase as catalysts.