Gas-phase ionic reactions: dynamics and mechanism of nucleophilic displacements

Nucleophilic displacement reactions (the SN2 reaction) of ions in the gas phase are a prototypical reaction system that allows a study of dynamics, mechanisms, and structure-energy relations. This article reviews aspects of the kinetics (especially the applicability of statistical reaction rate theory), the relation of structure and reactivity, and the effects of small numbers of solvent molecules on the reaction and compares the behavior of the ionic reaction in the gas phase with that in solution.     

戊型肝炎病毒研究新进展

戊型肝炎病毒(hepatitis Evirus,HEV)是非甲非乙型急性肝炎的病原体,主要经粪-口途径传播,也有报道可以通过血液传播。戊型肝炎在亚洲、非洲及美洲的墨西哥等发展中国家常呈爆发流行,我国1986-1988年在新疆曾经发生戊型肝炎暴发流行[1],而在包括发达国家在内的世界各地呈散在传     

Comparative study of the lipid composition of the liver and bile from broiler birds during growth and egg laying

A comparative study was made of biliary and liver lipid compositions during the growth and egg laying periods of the broiler bird. The liver lipids showed high concentrations of triacylglycerols at seven weeks old which increased when egg laying proceeded. At seven weeks old the lipids of the bile also showed high levels of triacylglycerols which decreased with the onset of egg laying but increased slightly as egg laying proceeded. At seven weeks old the fatty acid composition of the bile triacylglycerols differed from that of the liver which in turn was different from that of the liver at the onset of egg laying. In particular the bile triacylglycerols had lower levels of oleic but higher levels of arachidonic and docosahexaenoic acids. By the late egg laying period, the fatty acid compositions of the bile and liver triacylglycerols were similar. The unique bile lipid composition and its changes are discussed in relationship to the major features of liver lipid metabolism in the broiler bird and the mechanism of lipid deposition during egg laying.     

Influence of dietary calcium and phosphorus on metabolism and production in laying hens

1. The effects of different dietary concentrations of calcium (24 to 56.9 g/kg) and phosphorus (4.5 to 14.2 g/kg) on production and some aspects of metabolism were studied in laying hens.

2. Treatments did not affect egg numbers, food consumption, conversion efficiency of food to egg, bodyweight gain or mortality.

3. Increasing dietary calcium (Ca) significantly increased plasma Ca and inorganic phosphorus (P), breaking strength at the radius and egg specific gravity and significantly decreased plasma alkaline phosphatase and egg weight.

4. Increasing dietary phosphorus increased plasma P and decreased egg specific gravity significantly.

5. Plasma Ca, P and alkaline phosphatase and radius breaking strength were suitable indices of the Ca status of the hens.     

Intussusception following methiocarb toxicity in three dogs

Objective: To report intussusception as a complication of methiocarb toxicity in dogs and discuss possible risk factors. Series summary: Intestinal intussusception was diagnosed from 24 hours to 18 days following symptomatic treatment of methiocarb toxicity in three dogs. All cases had persistent clinical signs of methiocarb toxicity despite initial treatment and attempts to eliminate residual toxin. Cases 1 and 3 recovered uneventfully following supportive care, enterectomy of the affected bowel and end‐to‐end anastamosis. All dogs were <8 months of age. New information provided: Details of three cases of methiocarb toxicity that later developed intussusception and possible risk factors in these cases.     

Feeding management practices and feed characteristics associated with Salmonella prevalence in live and slaughtered market-weight finisher swine: A systematic review and summation of evidence from 1950 to 2005

This review summarizes evidence for associations between Salmonella prevalence in market-weight swine and changes in feeding management practices or feed characteristics. A systematic review of the topic was conducted with the goal of minimizing the impact of bias on the review conclusions. Potential interventions included feed withdrawal from swine prior to slaughter, feed acidification, heat treatment of feed, pelletized feed versus mash, course versus fine grind, and wet versus dry feeds. In the reviewed literature, Salmonella prevalence was measured either by culture or by the presence of antibodies to Salmonella. The evidentiary value of studies was assessed, and studies that failed to meet predetermined standards were excluded. 7694 potentially relevant references were identified by an extensive literature search; however, 2623 references that were not published in English were excluded, because funds for translation were not available. Of the remaining references, only 277 were considered relevant to the review topic by two independent reviewers, and assessed for methodological quality. During quality assessment, 233 references were excluded because they failed to report design features that limit the introduction of bias or were conducted in a non-target population such as gnotobiotic, neonatal, nursery, or recently weaned pigs and sows. Forty-four publications passed the quality assessment conducted by 2 independent reviewers, but only 15 of the 44 publications reported studies that tested hypotheses associated with feeding management practices and feed characteristics and Salmonella prevalence in market-weight swine. The most common study design was cross-sectional (7/15). The included studies failed to provide strong evidence of an association between any of the potential interventions and Salmonella prevalence, due to the potential for confounding, and the failure to document temporal association between the intervention and Salmonella prevalence. The strongest evidence of an association was found for feed form, i.e. the use of non-pelleted may be potential interventions associated with reduced Salmonella prevalence. The uncertainty is primarily based on studies containing moderate to low evidentiary value or insufficient numbers of tested individuals, resulting in a low degree of confidence that results could be extrapolated to the target population. Therefore, the conclusion of the review is that there should be a low level of comfort among qualified scientists that the claimed association between non-pelleted feed and reduced Salmonella prevalence is scientifically valid. There is no strong evidence regarding associations between presence of Salmonella and the other feed characteristics examined.     

Notes on the routine intravenous use of isometamidium in the control of bovine trypanosomiasis on the Kenya coast

Summary Various chemotherapeutic regimes were used to control trypanosomiasis in 3,000 Boran cattle on an estate on the Kenya coast. Recently the therapeutic use of isometamidium by the intravenous route was adopted to treat individual trypanosome-infected cattle. This was in order to overcome tissue reactions encountered after intramuscular injection and also to control a thin cow syndrome attributed to chronic trypanosomiasis. Toxic side effects were eliminated by careful attention to the intravenous technique which was safely used in calves, pregnant cattle and bulls. Weekly blood sampling and treatments of infected individuals resulted in a reduction of cases from 2,187 to 208 out of 46,495 and 46,329 samples examined in 1985 and 1986 respectively. The standard of management was very high and although this routine successfully controlled bovine trypanosomiasis on this estate its application elsewhere is likely to be limited.

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Notas Sobre El Uso Intravenoso Rutinario De Isometamidio En El Control De Tripanosomiasis Bovina En La Costa De Kenia

Resumen Se usaron varios regímenes quimioterapéuticos, para controlar tripanosomiasis, en 3,000 bovinos Boran en un estado de Kenia localizado en las costa. El uso terapéutico de isometamidio vía intravenoso, se adoptó recientemente para tratar individualmente animales con tripanosomiasis. Esta práctica se instituyó para evitar las reacciones tisulares resultantes de la inyección intramuscular y para controlar también el síndrome de la vaca flaca atribuido a la tripanosomiasis crónica. Los efectos tóxicos colaterales fueron eliminados, mediante las atención cuidadosa a la técnica de la inyección intravenosa usada en terneras, hembras preñadas y toros. El muestreo semanal de sangre y el tratamiento de los animales infectados, resultó en la reducción de casos de 2,187 a 208, a partir de 46,495 y 46,329 muestras examinadas en 1985 y 1986 respectivamente. El estandar de manejo fue alto y aunque esta rutina controló exitosamente la tripanosomiasis bovina en ese estado, la aplicación de la misma en otros lugares podría ser limitada.

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Note Sur l'Utilisation Intraveineuse En Routine De l'Isometamidium Pour Le Controle De La Trypanosomose Bovine Sur La Cote Kenyane

Résumé Plusieurs regimes chimiothérapeutiques ont été mis en oeuvre pour contrôler la trypanosomose chez 3.000 bovins Boran d'une propriété de la côte du Kenya. On a adopté récemment l'utilisation de l'isométamidium par voie intraveineuse pour traiter individuellement des bovins infectés de trypanosomes. Cette pratique a été institutionalisée dans le but de surmonter les réactions tissulaires rencontrées à la suite des injections intramusculaires et aussi de contrôler le syndrôme vache maigre attribué à une trypanosomose chronique. Les effets toxiques secondaires ont été éliminés par une attention particulière à la technique intraveineuse; on a pu innoculer sans accident des veaux, des vaches pleines et des taureaux. Des prises de sang et des traitements hebdomadaires des animaux infectés ont amené une réduction des cas de 2.187 à 208 sur 46.495 et 46.329 échantillons examinés respectivmeent en 1985 et 1986. Le standard de l'élevage était excellent; bien que cette pratique de routine ait permis avec succès un contrôle de la trypanosomose bovine dans cette propriété, il est probable que son application ailleurs soit limitée.