Synthase-dependent exopolysaccharide secretion in Gram-negative bacteria.

The biosynthesis and export of bacterial cell-surface polysaccharides is known to occur through several distinct mechanisms. Recent advances in the biochemistry and structural biology of several proteins in synthase-dependent polysaccharide secretion systems have identified key conserved components of this pathway in Gram-negative bacteria. These components include an inner-membrane-embedded polysaccharide synthase, a periplasmic tetratricopeptide repeat (TPR)-containing scaffold protein, and an outer-membrane ß-barrel porin. There is also increasing evidence that many synthase-dependent systems are post-translationally regulated by the bacterial second messenger bis-(3'-5')-cyclic dimeric guanosine monophosphate (c-di-GMP). Here, we compare these core proteins in the context of the alginate, cellulose, and poly-ß-D-N-acetylglucosamine (PNAG) secretion systems.

Feeding of partially hydrogenated fish oils to rats in comparison with partially hydrogenated soybean oil and refined rapeseed oil: a combined chronic oral toxicity and carcinogenicity study with in utero phase.

Partially hydrogenated fish oils (PHFO) have been widely used in human food products for many years, particularly in Europe, North and South America and in South Africa. Animal studies, mainly with rapeseed oil, suggested that erucic acid might be responsible for morphological changes in the myocardium. It was suggested that other members of the docosenoic (22:1) family of fatty acids might produce similar effects to those ascribed to erucic acid. Certain PHFO can contain relatively high levels of these other isomers. Thus it was decided to evaluate PHFO of differing 22:1 levels in comparison with partially hydrogenated soybean oil (PHSBO) and refined rapeseed oil (LEAR) in a rat life span study, preceded by a breeding period in which the experimental lipids were fed to male and female parents. Two commercially produced PHFO were selected to represent the lower (PHFO-L) and upper (PHFO-U) range of 22:1 contents, 4.3 and 13.8%, respectively. A third test oil was prepared from a 50:50 blend of these (PHFO-M) to provide and intermediary 22:1 level. The control PHSBO and LEAR contained 0 and 1.0% 22:1, respectively. These experimental oils were included in semi-purified diets at 8 and 16%, respectively, in the breeding and life span periods of the study, together with 4% of oil mixtures providing essential fatty acids (EFA). Specific pathogen free (SPF). Wistar weanling rats, 200 of each sex, provided the subjects for the breeding period. Sufficient numbers of offspring were obtained in suitable condition from each treatment group to allow selection of a total of 555 weanlings for allocation to the five dietary treatments of the life span period of the study. For the life span period of the study, which was terminated after 107 to 110 weeks of treatment, 50 subjects were allocated to each of the PHSBO, PHFO-L and PHFO-U dietary groups, and 50 males to each of the LEAR and PHFO-M groups. The remaining subjects were allocated to sub-groups for sacrifice four days or 26 weeks after introduction of the life span period diets. All life span group subjects were weighed and had their food intakes recorded, and were subjected to clinical examination, routinely. At designated stages, ophthalmoscopic examination of all subjects was carried out, and samples of blood and urine were obtained from sub-groups for laboratory analysis. All decedent and terminated life span group subjects were subjected to post mortem examination, with weighing of 16 organs.(ABSTRACT TRUNCATED AT 400 WORDS)

Rabbit mortality survey.

In a survey of mortality in 2224 rabbits of up to 12 weeks of age, drawn from 10 production units, neonatal mortality was important with 111 stillbirths and 175 deaths in the 1st week of life out of a total of 457 deaths in the whole survey. There was a low overall incidence of death from respiratory and enteric disease during the period of study.

The cost of premature death in young rabbits.

The costs of death in a model 100-doe commerical rabbit unit were calculated on the basis of two levels of breeding (7.5 and 10.0 litters per doe per year) and two levels of feeding, (ad lib and controlled). Although the cost of individual deaths from stillbirth and other perinatal and neonatal deaths was half or two-thirds the cost of an individual death later in the rabbit's life, the total cost of these early deaths was three times the total cost of the later deaths. Early death thus plays a major part in the profitability of a commercial rabbitry.

Comparative studies of atherosclerosis in swine.

A survey of spontaneously occurring fatty streaks and fibrous plaques, considered as atherosclerosis, in 1637 swine in different European countries and the USA, using a standardized procedure, was undertaken to determine whether significant differences exist in the occurrence and extent of the disease in various groups of animals. At the same time a preliminary study on the possible relation of any differences observed in atherosclerosis to certain environmental and constitutional factors was carried out with the ultimate goal of contributing to the understanding of analogous problems in man.STATISTICALLY SIGNIFICANT INCREASES OF FATTY STREAKS AND FIBROUS PLAQUES WERE NOTED IN RELATION TO: (a) increasing age, starting at 6 to 7 months, the earliest age period studied; (b) geographical locality; and (c) considerable as compared with moderate or slight physical activity at 1 year of age. Although not statistically significant, there was also a suggestive trend towards more atherosclerosis in pigs consuming soft water as compared with those consuming hard water.While these correlations may represent contributory factors to the increases of the changes noted in the abdominal aortas, it is not possible to pinpoint the importance of individual components because of the limited data and the large number of variables involved in this preliminary study. Studies in swine and other animals are being encouraged in which all variables but one are being kept constant to determine their possible role in the development of atherosclerotic lesions.