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Production of embryos that are free of tough outer coats facilitates studies that are not possible with embryos surrounded by impenetrable envelopes. This report describes a new procedure for preventing formation of fertilisation membranes in the sea urchin (Lytechinus pictus) model. This procedure involves treating unfertilised eggs with the enzyme alpha-amylase, which cleaves alpha-1,4 glucosidic bonds in the vitelline layer. A major advantage of this method is that it is very well defined and completely controllable with alpha-amylase inhibitor. The results suggest that intact alpha-1,4 glucosidic bonds are essential for vitelline layer integrity required for formation of the fertilisation membrane. Eggs treated with alpha-amylase possessed the same surface lectin receptors as untreated eggs and, as shown by light and transmission electron microscopy, produced healthy, cleaving embryos that were free of fertilisation envelopes.

There are an estimated 2 million cases of salmonellosis in the United States every year. Unlike the incidence of many infectious diseases, the incidence of salmonellosis in the United States and other developed countries has been rising steadily over the past 30 years, and the disease now accounts for 10 to 15% of all cases of acute gastroenteritis in the United States. The infecting organism is ingested and must traverse the intestinal epithelium to reach its preferred site for multiplication, the reticuloendothelial system. Despite several recent studies, the genetic basis of the invasion process is poorly understood. An emerging theme from these studies is that wild-type Salmonella organisms probably have several chromosomal loci that are required for the most efficient level of invasion. In this study, we have identified and characterized 13 TnphoA insertion mutants of Salmonella enteritidis CDC5 that exhibit altered invasion phenotypes. The mutants were identified by screening a bank of TnphoA insertions in S. enteritidis CDC5str for their invasion phenotype in three tissue culture cell lines (HEp-2, CHO, and MDCK). These 13 mutants were separated into six classes based on their invasive phenotypes in the tissue culture cell lines. Several mutants were defective for entry of some cell lines but not for others, while two mutants (SM6 and SM7) were defective for entry into all three tissue culture cell lines. This suggests that Salmonella spp. may express more than one invasion pathway. Southern analysis and chromosomal mapping indicated that as many as nine chromosomal loci may contribute to the invasion phenotype. It is becoming clear that the invasive phenotype of Salmonella spp. is multifactorial and more complex than that of some other invasive members of the family Enterobacteriaceae.

Treatment of rats with monocrotaline (MCT) or its reactive pyrrole metabolite, dehydromonocrotaline (MCTP), injures pulmonary capillary endothelium and other lung cell types. The mechanism by which pulmonary damage occurs is unknown. To investigate the possibility that the metabolites of MCT can injure lung cells directly, slices of lung from male Sprague-Dawley rats were incubated with chemically synthesized MCTP (0.1-1.0 mM). The ability of the slices to accumulate 5-hydroxytryptamine (5HT) was then examined. After 5 hours exposure to MCTP in vitro, there was no change in either 5HT or PQ uptake at any of the MCTP concentrations tested. Similar results were obtained when lung slices were incubated with liver slices and MCT to generate MCT metabolites in vitro. In contrast, treatment in vivo with MCTP resulted in a 35% decrease in the uptake of 5HT and a 15% decrease in the uptake of PQ by lung slices 14 days after treatment. These results suggest that damage does not occur by direct interaction of MCTP with the lung tissue or that functional injury is slow to develop. Alternatively, the damage in vivo may be mediated by factors not present in the sliced tissue.