Influence of the Salmonella typhimurium pathogenicity island 2 type III secretion system on bacterial growth in the mouse.

We have investigated the in vivo growth kinetics of a Salmonella typhimurium strain (P11D10) carrying a mutation in ssaJ, a Salmonella pathogenicity island 2 (SPI2) gene encoding a component of a type III secretion system required for systemic growth in mice. Similar numbers of mutant and wild-type cells were recovered from the spleens and livers of BALB/c mice up to 8 h after inoculation by the intraperitoneal route. Thereafter, the numbers of wild-type cells continued to increase logarithmically in these organs, whereas those of P11D10 remained relatively static for several days before being cleared. Gentamicin protection experiments on spleen cell suspensions recovered from infected mice showed that viable intracellular wild-type bacteria accumulated over time but that intracellular P11D10 cells did not. Infection experiments were also performed with wild-type and P11D10 cells carrying the temperature-sensitive plasmid pHSG422 to distinguish between bacterial growth rates and killing in vivo. At 16 h postinoculation there were 10-fold more wild-type cells than mutant cells in the spleens of infected mice, but the numbers of cells of both strains carrying the nonreplicating plasmid were very similar, showing that there was little difference in the degree of killing sustained by the two strains and that the SPI2 secretion system must be required for bacterial replication, rather than survival, in vivo. The SPI2 mutant phenotype in mice is similar to that of strains carrying mutations in the Salmonella virulence plasmid spv genes. To determine if these two sets of genes interact together, a double mutant strain carrying SPI2 and spv mutations was constructed and compared with strains carrying single mutations in terms of virulence attenuation. These experiments failed to provide any evidence showing that the SPI2 and spv gene products interact together as part of the same virulence mechanism.

Genes encoding putative effector proteins of the type III secretion system of Salmonella pathogenicity island 2 are required for bacterial virulence and proliferation in macrophages.

The type III secretion system of Salmonella pathogenicity island 2 (SPI-2) is required for systemic infection of this pathogen in mice. Cloning and sequencing of a central region of SPI-2 revealed the presence of genes encoding putative chaperones and effector proteins of the secretion system. The predicted products of the sseB, sseC and sseD genes display weak but significant similarity to amino acid sequences of EspA, EspD and EspB, which are secreted by the type III secretion system encoded by the locus of enterocyte effacement of enteropathogenic Escherichia coli. The transcriptional activity of an sseA::luc fusion gene was shown to be dependent on ssrA, which is required for the expression of genes encoding components of the secretion system apparatus. Strains carrying nonpolar mutations in sseA, sseB or sseC were severely attenuated in virulence, strains carrying mutations in sseF or sseG were weakly attenuated, and a strain with a mutation in sseE had no detectable virulence defect. These phenotypes were reflected in the ability of mutant strains to grow within a variety of macrophage cell types: strains carrying mutations in sseA, sseB or sseC failed to accumulate, whereas the growth rates of strains carrying mutations in sseE, sseF or sseG were only modestly reduced. These data suggest that, in vivo, one of the functions of the SPI-2 secretion system is to enable intracellular bacterial proliferation.

Heterogeneity of human intestinal spirochaetes demonstrated by one-dimensional polyacrylamide gel electrophoresis of proteins visualised by (35)S-methionine labelling and Coomassie blue staining.

The relatedness of strains of a human intestinal spirochaete was investigated by comparison of electrophoretic protein profiles produced by Coomassie Blue staining of proteins separated by polyacrylamide gel electrophoresis (PAGE) of lysed organisms and by examination of autoradiographs following PAGE of lysed (35)S-methionine-labelled organisms. A wide diversity of strains was revealed by both techniques but clustering of strains was different by the two methods. These findings support the view that the human intestinal spirochaetes comprise a group of bacteria of considerable heterogeneity.

Disability syndrome: the effects of early vs delayed rehabilitation intervention.

1. Disability syndrome occurs when an individual with a work related injury or other disability chooses not to work when it has been medically determined that they are capable of doing so. 2. A possible contributor to the development of disability syndrome includes systems reinforcers or rules that discourage return to work. For example, many attorneys discourage early return to work or modified duty. 3. Early intervention by rehabilitation counselors at the time of injury can facilitate a positive attitude and empower the worker to resist the negative effect of systems reinforcers that discourage early return to work.

Vitamin D deficiency in a Manitoba community.

OBJECTIVE: Using a cross-sectional survey, to investigate the vitamin D status of a random sample of 80 mother-child pairs (child age 3-24 months) in a Manitoba community with a high incidence of rickets. METHOD: A questionnaire on feeding habits, gestational history, maternal diet and vitamin supplements was administered to mothers in their homes with the assistance of a local interpreter. Venous blood was collected from both mother and child for serum 25-hydroxyvitamin D levels. RESULTS: Of 91% babies initially breastfed, 36% received no formula or milk after weaning and 40% received no vitamin supplements. 24% of mothers took no vitamin supplements during pregnancy and lactation. Knowledge about rickets was poor. In 43% of children and 76% of mothers, serum 25-hydroxyvitamin D levels were below normal range. CONCLUSIONS: Vitamin D levels are low in this population due to lack of fortified dairy products and vitamin D supplements. A public health program should include counseling on rickets and vitamin D supplementation for all infants and pregnant or lactating women.

PIP: In the isolated Island Lake area of northern Manitoba, which has a high incidence of rickets, interviews were conducted with 80 mothers, each with a child at least 2 years old, living in St. Theresa Point and Garden Hill in their homes during June-July 1987 to determine their knowledge and attitudes towards rickets. Nurses obtained blood samples from the women and their young children so the researchers could determine the vitamin D status of both. The mother-child pairs were native Canadians from the Ojibway linguistic group that speaks its own dialect of Ojibway-Cree. Mothers initially breast fed 91% of the children. After weaning, 1/3 of infants received neither infant formula nor milk. No vitamin supplements were given to 40%. Many of the children who did receive vitamin supplements did not receive them regularly. 70% of the mothers did not drink any milk. 24% were milk-intolerant. 24% took no vitamin supplements during pregnancy and lactation. Mothers who did take supplements did not do so regularly. 17% claimed that their skin was sensitive to sunlight. 84% of mothers in one community had never heard of rickets. Most did not know its cause. Neither mothers nor the children were exposed to the sunlight in the summer. When outside, almost all small infants were completely covered to protect them from the elements. The mean 25-hydroxy-vitamin D level was 26.2 nmol/l for the children and 19.8 nmol/l for the mothers. 43% of children and 76% of mothers had a 25-hydroxy-vitamin D level below the normal range. These high levels of vitamin D insufficiency were even more troublesome given that the blood was taken in late June and July when vitamin D levels would be likely to be at their highest. The dearth of vitamin D fortified dairy products and vitamin supplements greatly contributed to the low level of vitamin D status in this area. The findings show a need for public health officials to include education on rickets and vitamin D supplementation for all infants and pregnant or lactating women.

Non-insulin-dependent diabetes mellitus in Indian children in Manitoba.

OBJECTIVE: To report on our 7-year experience with non-insulin-dependent diabetes mellitus (NIDDM) in native Indian children in Manitoba and to raise the awareness of physicians about the difficulties in the classification and management of hyperglycemia in Indian children. DESIGN: Case series. PATIENTS: All Indian children under 15 years of age referred for evaluation and management of diabetes to the diabetes clinic at the Children's Hospital of Winnipeg between 1984 and 1990 who did not have a history of diabetic ketoacidosis. MAIN RESULTS: Sixteen girls and four boys aged 7 to 14 years at the time of diagnosis were identified as having NIDDM. All 16 children whose family history could be confirmed had at least one parent with NIDDM. Five of the 20 complained of polyuria or nocturia; the remainder presented with asymptomatic glycosuria. At the time of diagnosis the random serum glucose level varied from 15.0 to 30.8 mmol/L, the fasting serum insulin level from 45 to 300 pmol/L and the total glycated hemoglobin level from 7.1% to 23.3%. Twelve of the children had been followed for at least 4 years. Six of the 12 had received insulin therapy at some time, including during pregnancy. At the time of writing, none was receiving therapy with insulin or orally given hypoglycemic drugs. All were encouraged to follow a weight-reduction diet and exercise regimen. During follow-up the mean total glycated hemoglobin level for each patient varied from 9.1% to 20.9%; none maintained a glycated hemoglobin level in the normal range. CONCLUSIONS: NIDDM occurs in Indian children under 15 years of age. The clinical features at presentation occasionally mimic those of insulin-dependent diabetes. A strong family history of NIDDM and lack of diabetic ketoacidosis during follow-up support the diagnosis of NIDDM. Adherence to a diet and exercise regimen has been poor. The conventional diabetes education approach may not be appropriate for this population.

Complex expression of the genes coding for plasminogen activators and their inhibitors in HeLa-smooth muscle cell hybrids.

As cells progress through the multistep process of neoplastic transformation, they eventually acquire the property of invasive behavior. Although both plasminogen activators (PA) and their inhibitors (PAI) contribute to this process, their regulation in normal and transformed cells remains poorly defined. Because somatic cell hybrids provide useful tools for examining the transformation pathway, tumorigenic and invasive HeLa cells were fused with human normal vascular smooth muscle cells and tested for invasion-related parameters, including the expression of PA and PAI genes, and matrix degradation. Both parental cell lines produced large amounts of PAI activities with no detectable PA in either cellular or secreted form. Opposite findings were obtained with the hybrid cell lines, which demonstrated the presence of receptor-bound and secreted PA but absence of enzymatically measurable PAI activities. Both urokinase-type and tissue-type PA were found in cell-associated and secreted form in the hybrid cells. In addition, expression of the urokinase-type PA receptor gene was found in the three hybrid cells and the vascular smooth muscle cells but not in the HeLa cells. Expression of active, receptor-bound and secreted PA provided the nontumorigenic hybrid cells with the enzymatic tools to degrade extracellular proteins in a plasminogen-dependent manner. Thus, the hybrid cells lost tumorigenicity while retaining the tissue-degrading capability of HeLa cells. These hybrid cell lines should prove to be important reagents for investigating the complex regulatory control of PA and PAI gene expression.

Central and peripheral actions of salicylate in altering nonpyrogenic thermoregulation of rats.

The effects on body temperature of intracerebroventricular and intraperitoneal sodium salicylate were evaluated in anesthetized and nonanesthetized, nonrestrained rats. Also, the effects of various neurotransmitter receptor blocking drugs were evaluated on salicylate-induced hypothermia of nonanesthetized animals. Sodium salicylate, 150-350 mg/kg induced a dose-related hypothermia of unanesthetized animals. However, in anesthetized animals, marked hyperthermia was observed. In unanesthetized, unrestrained rats, intracerebroventricular administration of 1.0 mg/h salicylate caused greater hypothermia than peripheral administration of salicylate, 350 mg/kg. Salicylate hypothermia was unaffected by para-chlorophenylalanine, cyproheptadine, or naloxone, and was only partially inhibited by pimozide. These results strongly suggest a potent direct action of salicylate within the central nervous system to induce hypothermia, and suggest possible involvement of dopaminergic neurons in this process.