Outgassing behavior and composition of comet C/1999 S4 (LINEAR) during its disruption

The gas activity of comet C/1999 S4 (LINEAR) was monitored at radio wavelengths during its disruption. A runaway fragmentation of the nucleus may have begun around 18 July 2000 and proceeded until 23 July. The mass in small icy debris (相似文献   

Evidence of estrogen receptors in normal human osteoblast-like cells

In seven strains of cultured normal human osteoblast-like cells, a mean of 1615 molecules of tritium-labeled 17 beta-estradiol per cell nucleus could be bound to specific nuclear sites. The nuclear binding of the labeled steroid was temperature-dependent, steroid-specific, saturable, and cell type-specific. These are characteristics of biologically active estrogen receptors. Pretreatment with 10 nanomolar estradiol in vitro increased the specific nuclear binding of progesterone in four of six cell strains, indicating an induction of functional progesterone receptors. RNA blot analysis demonstrated the presence of messenger RNA for the human estrogen receptor. The data suggest that estrogen acts directly on human bone cells through a classical estrogen receptor-mediated mechanism.     

Structure of a legume lectin with an ordered N-linked carbohydrate in complex with lactose

The three-dimensional structure of the lactose complex of the Erythrina corallodendron lectin (EcorL), a dimer of N-glycosylated subunits, was determined crystallographically and refined at 2.0 angstrom resolution to an R value of 0.19. The tertiary structure of the subunit is similar to that of other legume lectins, but interference by the bulky N-linked heptasaccharide, which is exceptionally well ordered in the crystal, forces the EcorL dimer into a drastically different quaternary structure. Only the galactose moiety of the lactose ligand resides within the combining site. The galactose moiety is oriented differently from ligands in the mannose-glucose specific legume lectins and is held by hydrophobic interactions with Ala88, Tyr106, Phe131, and Ala218 and by seven hydrogen bonds, four of which are to the conserved Asp89, Asn133, and NH of Gly107. The specificity of legume lectins toward the different C-4 epimers appears to be associated with extensive variations in the outline of the variable parts of the binding sites.     

Transcription regulation through promoter-proximal pausing of RNA polymerase II

Recent work has shown that the RNA polymerase II enzyme pauses at a promoter-proximal site of many genes in Drosophila and mammals. This rate-limiting step occurs after recruitment and initiation of RNA polymerase II at a gene promoter. This stage in early elongation appears to be an important and broadly used target of gene regulation.     

The effect of diets supplemented with fish broth and fish oil on the health of weaners

The aim of this study was to determine the effect of fish-based feed materials, as a source of readily available protein contained in fish broth and essential polyunsaturated fatty acids (PUFAs) found in fish oil, on the health of piglets and rearing results. The experiment was conducted on a commercial pig fattening farm. The study involved a total of 80 weaners with an approximate body weight of 15 kg. The experiment was carried out over a period of 40 days. Feed samples were subjected to laboratory analyses. Blood samples were collected from experimental group animals to determine serum biochemical and immunological parameters. The body weight gains of weaners, mortality rates and average feed intake per animal were calculated for the entire experimental period. The addition of fish broth and fish oil significantly improved the n3:n6 fatty acid ratio in diets. The presence of EPA and DHA in the experimental diet could have had a positive health effect on piglets, comparable with that exerted by therapeutic doses of zinc often administered to pigs of this age group. During the experiment, feed conversion ratio (FCR) gain was considerably reduced in the experimental group, with similar daily gains in the control and experimental group.     

Embryonation and infectivity of Ascaris suum eggs. A comparison of eggs collected from worm uteri with eggs isolated from pig faeces

Ascaris suum eggs were collected from pig faeces or dissected from worms obtained from the same pigs. Eggs from the two sources were allowed to embryonate in 0.1 N H2SO4, in 1% buffered formalin or in tap water. The embryonation of the sulphuric acid and water cultures occurred at the same speed, while the formalin cultures developed slightly more slowly. By experimental inoculation of helminth-free pigs and subsequent counting of white spots in the livers and larvae in the lungs day 7 p.i., the infectivity of eggs dissected from worm uteri and embryonated in sulphuric acid (a normal laboratory procedure) was compared with that of eggs collected from faeces and embryonated in water (i.e. more naturally developed eggs). The results suggest that the two types of eggs were equally infective. For this reason the common practice of using Ascaris eggs dissected from worms for experimental infections might be acceptable.     

Coxiella burnetii and Chlamydia psittaci infection in dogs]

The prevalence of Coxiella burnetii and Chlamydia psittaci antibodies was investigated in 530 dog specimens divided into six groups, i. e. A = private watch dogs, B1 = service dogs from Bratislava, B2 = service dogs from other localities of Slovakia and Moravia, C = watch dogs from farms, I = household dogs, T = stray dogs. The dogs demonstrated the higher seropositivity to C. burnetii (11.7%) than to Ch. psittaci (5.5%). The highest percentage of antibodies to C. burnetii was found in stray dogs (23.7%), less prevalence of antibodies was observed in the animals in group C (13.6%), almost the same positivity was proved in the dogs of group B1 and B2 (10.5 and 10.6%). The highest positivity to Ch. psittaci was demonstrated in the dogs of group A (8.7%), less in group B2 (6.6%) and the least number in group B1 (1.9%). The stray dogs occupied the intermediate position in this data (Tab. I). Ninety four localities were tested, from which 38 were seropositive. Neither acute coxiellosis nor chlamydiosis were proved in any animals examined. Ninety per cent of dogs were found healthy, but 10% of dogs demonstrated hepatopathia and gastroenteritis. Two of them (category A and I) were seropositive to C. burnetii (titer 1:8 to 1:16) and one to Ch. psittaci (titer 1:16). Both C. burnetii and Ch. psittaci attack dogs parallely with the agents of other zoonoses, of which the most common is Toxoplasma gondii (Tab. II). Several dogs demonstrated seropositivity to three up to five zoonotic agents (Tab. III).     

An outbreak of meningo-encephalitis in fallow deer caused by Listeria monocytogenes

An outbreak of listeric meningo-encephalitis occurred in a population of 1800 fallow deer (Dama dama) in a park during the winter and early spring of 1985 to 1986. Listeriosis was diagnosed in 41 of 42 fallow deer that showed the typical central nervous system signs of circling disease or were found dead. The diagnosis was verified by bacteriological examination of the brains of 35 animals. In five of the seven remaining cases listeriosis was diagnosed by histological examination, and in one animal by clinical signs alone. Listeria monocytogenes was isolated in three of 23 soil samples taken from the park. In addition, L monocytogenes was isolated from the intestinal contents of apparently normal fallow deer. Fifty isolates from animals and soil were serotyped and all of them belonged to serovar 4b except one from brain (serovar 1/2b) and three from intestinal contents (serovar 1/2a). In phage typing of 54 isolates, the 35 isolates from the brain and spleen of diseased animals belonged to the same lysovar, as did most isolates from other sources, but strains from intestinal contents belonged to three other phage types. No external source of L monocytogenes was demonstrated in the outbreak and stress due to the poor beech-mast crop, an increased stocking rate and a sudden change in the weather are suspected as predisposing factors.