群养鸡谨防痢菌净中毒

痢菌净学名乙酰甲喹,是我国研制的具有自主知识产权的兽用抗菌药品.本品抗菌谱广,不易产生抗药性,价格低廉,在畜牧养殖业上应用广泛.但在使用过程中常因超剂量应用导致中毒现象发生,造成不应有的损失.本文从药品特性、中毒症状、剖检变化、治疗、中毒原因分析等五个方面对群养鸡痢菌净中毒做了详尽阐述,以期基层兽医临床工作者有所借签.     

Biotin deficiency and liver metabolism in relation to fatty liver and kidney syndrome

1. Varying degrees of biotin deficiency were induced by adding freeze‐dried, raw egg white to the diet of broiler chicks. Aspects of liver metabolism were studied with reference to fatty liver and kidney syndrome.

2. Mortality was low with 11 .8 g egg white/kg diet, or less, but with 17.7 g/kg or more, mortality was very high. High mortality was observed with less than 0.33 μg biotin/g liver.

3. Associated with low concentrations of liver biotin were substantial increases in liver weight and lipid content in starved birds. The increased liver lipid content was not observed in birds fed ad libitum.

4. The increased liver lipid content in biotin‐deficient, starved birds was not reflected in the specific activities of hepatic lipogenic enzymes or hepatic lipogenesis in vivo measured by the incorporation of tritium from ³H‐labelled water into liver lipid.

5. Biotin deficiency affected the specific activities of the biotin‐requiring enzymes, pyruvate carboxylase and acetyl CoA carboxylase, differently; the latter was unaffected whereas the former decreased concomitantly with liver biotin concentration.     

DDT residues in rainwater in New Brunswick and estimate of aerial transport of DDT into the Gulf of St. Lawrence, 1967-68

Residues of DDT were detected in 76 of 101 samples of rainwater collected during spring and summer at several sites in the Province of New Brunswick in 1967 and 1968, and at one site in the Magdalen Islands, Quebec, in 1968. The dominant residue was p,p'-DDT. Levels of DDT and metabolites combined ranged from less than 0.01 to 1.33 microgram/kg. Levels of DDT and metabolites in the pollen of four species of forest trees in New Brunswick ranged from 0.544 to 1.01 mg/kg; such contaminated pollen possibly contributed to residues in rainwater. Residue data for rainwater from two sites were used to estimate the amount of DDT aerially transported into the Gulf of St. Lawrence during July to October 1968.     

Shell thinning and residues of organochlorines and mercury in seabird eggs, Eastern Canada, 1970-76.

Organochlorine and mercury concentrations are reported for 252 eggs of Leach's storm-petrel (Oceanodroma leucorhoa), double-crested cormorant (Phalarocorax auritus), common eider (Somateria mollissima), common tern (Sterna hirundo), razorbill (Alca torda), common murre (Uria aalge) black guillemot (Cepphus grylle), and Atlantic puffin (Fratercula arctica) from the Bay of Fundy, the Gulf of St. Lawrence, and the open Atlantic shore of Canada during 1970-76. Concentrations of all organochlorines except DDE and polychlorinated biphenyls (PCBs) were low. DDE, PCBs, and mercury residues were highest in cormorant and petrel, intermediated in alcids, and lowest in eider and tern. Temporal and spatial aspects of contamination patterns are discussed. Authors conclude that only in cormorants were DDE residues high enough to cause, through eggshell thinning, local population declines.     

Identification of paramyosin as schistosome antigen recognized by intradermally vaccinated mice

Mice immunized intradermally with extracts of Schistosoma mansoni in combination with the adjuvant BCG are significantly protected against subsequent infection with living larval forms of the parasite. Remarkably, these vaccinated animals produce antibodies predominantly against a single parasite protein of molecular weight 97 kilodaltons (Sm-97). A complementary DNA that encodes about half of the Sm-97 molecule has now been cloned and sequenced. Analysis of the deduced amino acid sequence reveals a protein containing periodic repeats of hydrophobic amino acids characteristic of an alpha-helical coiled-coil structure. The deduced amino acid composition of the cloned gene and several properties of the native protein are similar to that of paramyosin, an alpha-helical protein that forms the core for myosin filaments in invertebrate muscle. Paramyosin was isolated from Schistosoma mansoni adult worms and antibodies to Sm-97 were shown to react with this molecule as well as with a known paramyosin from molluscan muscle.     

A common fold mediates vertebrate defense and bacterial attack

Proteins containing membrane attack complex/perforin (MACPF) domains play important roles in vertebrate immunity, embryonic development, and neural-cell migration. In vertebrates, the ninth component of complement and perforin form oligomeric pores that lyse bacteria and kill virus-infected cells, respectively. However, the mechanism of MACPF function is unknown. We determined the crystal structure of a bacterial MACPF protein, Plu-MACPF from Photorhabdus luminescens, to 2.0 angstrom resolution. The MACPF domain reveals structural similarity with poreforming cholesterol-dependent cytolysins (CDCs) from Gram-positive bacteria. This suggests that lytic MACPF proteins may use a CDC-like mechanism to form pores and disrupt cell membranes. Sequence similarity between bacterial and vertebrate MACPF domains suggests that the fold of the CDCs, a family of proteins important for bacterial pathogenesis, is probably used by vertebrates for defense against infection.