A sensitive,versatile microfluidic assay for bacterial chemotaxis

We have developed a microfluidic assay for bacterial chemotaxis in which a gradient of chemoeffectors is established inside a microchannel via diffusion between parallel streams of liquid in laminar flow. The random motility and chemotactic responses to L-aspartate, L-serine, L-leucine, and Ni(2+) of WT and chemotactic-mutant strains of Escherichia coli were measured. Migration of the cells was quantified by counting the cells accumulating in each of 22 outlet ports. The sensitivity of the assay is attested to by the significant response of WT cells to 3.2 nM L-aspartate, a concentration three orders of magnitude lower than the detection limit in the standard capillary assay. The response to repellents was as robust and easily recorded as the attractant response. A surprising discovery was that L-leucine is sensed by Tar as an attractant at low concentrations and by Tsr as a repellent at higher concentrations. This assay offers superior performance and convenience relative to the existing assays to measure bacterial tactic responses, and it is flexible enough to be used in a wide range of different applications.     

Chronic pancreatitis: evaluation of pancreatic exocrine function with MR pancreatography after secretin stimulation

PURPOSE: To compare duodenal filling seen at magnetic resonance (MR) pancreatography after secretin stimulation and biochemical parameters determined with the intraductal secretin test (IDST) for evaluation of pancreatic exocrine function. MATERIALS AND METHODS: MR pancreatography after secretin stimulation and IDST were performed in 41 patients with chronic pancreatitis (group 1) and eight patients with other pancreatic disease (group 2). A control group (group 3, n = 28) underwent MR pancreatography after secretin stimulation only. MR pancreatograms were acquired before and every 30 seconds for 10 minutes after secretin injection. Duodenal filling was graded from least amount of filling (grade 1) to normal filling (grade 3) on the last MR pancreatogram. Pancreatic exocrine function was determined at IDST. Main pancreatic ductal diameter was compared between groups 1 and 3. RESULTS: All ductal diameters were significantly larger in group 1 (P <.001). The maximal diameter variation after secretin stimulation was significantly higher in the control group (P =.001). Pancreatic exocrine function parameters determined at IDST were significantly lower in patients with grade 1 duodenal filling than in those with grade 2 or 3 (P <.05). Maximal bicarbonate concentration alone was independently associated with all grades of duodenal filling (P =.007). The sensitivity and specificity of reduced duodenal filling for assessment of reduced pancreatic exocrine function were 72% and 87%, respectively. CONCLUSION: Duodenal filling grade determined at MR pancreatography after secretin stimulation allows specific estimation of pancreatic exocrine function.     

Long-term propofol infusion and cardiac failure in adult head-injured patients

Five adult patients with head injuries inexplicably had fatal cardiac arrests In our neurosurgical intensive-care unit after the introduction of a sedation formulation containing an increased concentration of propofol. To examine the possible relation further, we did a retrospective cohort analysis of head-injured adults admitted to our unit between 1996 and 1999 who were sedated and mechanically ventilated. 67 patients met the inclusion criteria, of whom seven were judged to have died from propofol-infusion syndrome. The odds ratio for the occurrence of the syndrome was 1.93 (95% CI 1.12-3.32, p=0.018) for every mg/kg per h increase in mean propofol dose above 5 mg/kg per h. We suggest that propofol infusion at rates higher than 5 mg/kg per h should be discouraged for long-term sedation in the intensive-care unit.     

Farber's disease as a ceramidosis: clinical, radiological and biochemical aspects

A case of Farber's disease associated with athyreosis is reported in a Belgian infant born from consanguineous parents. A detailed clinical observation made from the early onset of symptoms until death of the patient at age of 22 months, together with radiological, morphological and biochemical data confirmed the diagnosis of Farber's disease and its specific storage process. Cultured fibroblast studies disclosed an abnormal catabolism of ceramides, presumably related to the deficiency in lysosomal ceramidase. Family history confirms that the disease is inherited as an autosomal recessive trait.