Comparison of acute endotoxin-induced lesions in A/J and C57BL/6J mice.

Resistance to the action of endotoxin varies among inbred strains of mice, indicating that a component of this resistance has a genetic basis. Different responses to endotoxin that are characteristic of individual inbred strains represent phenotypes that can be used to genetically map the response modifier genes. This study compares the acute histologic lesions in 8-week-old male A/J and C57BL/6J (B6) mice injected intraperitoneally with endotoxin of E. coli O265:B6 (15 mg/kg). Animals of both strains exhibited splenitis, splenic lymphoid hyperplasia, splenic lymphoid necrosis, and sequestration of neutrophils in the pulmonary alveoli. The B6 mice showed increased margination of white blood cells to the pulmonary vascular endothelium relative to A/J mice. A large number of degenerating neutrophils was observed in the liver sinusoids of most B6 animals, while this lesion was much less severe in A/J mice. This difference was quantified, demonstrating a highly significant difference in neutrophil infiltration in B6 mice relative to A/J mice. Analysis of this phenotype in F1 mice demonstrates that major genes encoding the trait are not X-linked, imprinted, or maternally inherited and do not show the codominant inheritance expected if Lps(d) were primarily responsible. The distinctive, quantitative nature of these differences provides a useful assay for mapping genes that modify endotoxin responsiveness using the AXB and BXA recombinant inbred (RI) strains derived from A/J and B6 mice.

Genetic component in the inflammatory response induced by bacterial lipopolysaccharide.

Multiple organ dysfunction syndrome (MODS) appears to be the result of a complex program influenced by multiple factors, including environmental, physiological, and immunological conditions. Thus, an uncontrolled inflammatory response following a stochastic event, the initial injury, is believed to be the cause for the development of this syndrome. Several lines of evidence suggest that a genetic component could contribute to the regulation of the inflammatory response, as well, but no direct evidence demonstrates a heritable predisposition to MODS. In the present study, a genetic contribution was demonstrated for the inflammatory response induced by the administration of bacterial lipopolysaccharide (LPS) in different, genetically distinct strains of inbred mice. A survey of five inbred strains showed that mortality following administration of Escherichia coli LPS (20 mg/kg) was highest in C57BL/6J (B6) mice, while A/J mice were the most resistant. Accordingly, B6 and A/J mice were examined further for differences in the inflammatory response elicited by LPS. B6 mice showed higher levels of circulating interleukin-1beta and interleukin-6, as well as higher mRNA levels of hepatic beta-fibrinogen (an acute-phase gene) and metallothionein. Surprisingly, the circulating levels of tumor necrosis factor-alpha were significantly higher in A/J than in B6 mice after LPS administration. Since B6 and A/J mice were bred and raised in identical environments and received the same LPS challenge, the contrasting inflammatory response that was observed is largely attributable to genetic differences between these two strains. These data illustrate that the response to injury could be modulated by the genetic background of the individual. This information may be pertinent for the care of critically ill patients.

Presence of the stress-inducible form of hsp-70 (hsp-72) in normal rat colon.

The expression of heat shock proteins (hsp) is probably one of the most primitive mechanisms of cellular protection from stress. Pathogens such as viruses and bacteria have recently been found to induce the heat shock gene expression. In the present study hsp-72, the stress-inducible form of hsp-70, was detected by Western blotting in samples from rat distal colon (DC), proximal colon (PC), and terminal ileum (TI), but was not found in proximal small bowel (PSB) or other organs (liver, kidney, spleen, heart, and brain) of unstressed animals. The signal intensity of hsp-72 in colon (DC > PC > TI > PSB) correlates qualitatively with the presence of normal gut microflora. hsp-72 was also observed in DC, to a lesser extent in PC, but not in TI or PSB of bacteria-free or antibiotic-treated rats. Inflammatory states induced by the intravenous administration of endotoxin (1 mg/kg), the subcutaneous injection of zymosan (1 g/kg) or by cecal ligation and puncture (sepsis) failed to increase the hsp-72 levels in rat colon or other organs. These results demonstrate that hsp-72 is expressed in normal rat colon. However, the induction of hsp-72 expression may not be due solely to the presence of resident bacteria in the gut, but instead, may be the result of a more complex process.

A prospective study of the clinical utility of lymphocyte monitoring in the cardiac transplant recipient.

Monitoring peripheral lymphocytes for changes in antigen expression or subpopulations was performed by flow cytometry in an attempt to identify infection or rejection in cardiac transplantation recipients (CTRs). In this study, 32 cardiac transplantation recipients were followed prospectively, and the results of 274 lymphocyte analyses for transferrin receptor expression, an indicator of lymphocyte activation, and CD4/CD8 lymphocyte ratios were correlated with the patient's clinical status, e.g., infection (early or late), rejection (mild, moderate, or severe), or quiescence. The percentage of lymphocytes expressing the transferrin receptor (%TR+) increased significantly during all stages of infection (2.9%, P = 0.02), or stratified into early (2.7%, P = 0.03) or late stage infection (2.6%, P = 0.03). The increase in %TR+ lymphocytes was also noted during mild (2.8%, P = 0.01) and moderate (3.0%, P = 0.008) rejection. The specificity and positive predictive value of an increased %TR+ lymphocyte was 97% and 93%, respectively, during early infection; 92 and 71%, respectively, during mild rejection; and 85 and 80%, respectively, during moderate rejection. The CD4/CD8 lymphocyte ratio did not correlate with either infection or rejection (P greater than 0.05). In conclusion, an increase in the %TR+ lymphocytes indicates the presence of infection, especially acute infection, or, less likely, rejection in the cardiac transplant recipient, but its clinical utility may be as a screening test for the presence of infection, especially early infection in CTRs during the posttransplantation period. The CD4/CD8 lymphocyte ratio does not correlate with the presence of infection or rejection in the CTR.

Interaction between oral ciprofloxacin and caffeine in normal volunteers.

The influence of multiple doses of ciprofloxacin on the disposition of caffeine and its major metabolite, paraxanthine, was investigated in healthy volunteers. Ten xanthine-free, fasting males were given 100 mg of caffeine orally 24 h before being given ciprofloxacin and again with the third dose of ciprofloxacin (750 mg administered every 12 h). Blood samples were serially collected after both doses of caffeine and after the first and last doses of ciprofloxacin. Ciprofloxacin significantly increased the half-life of caffeine (from 5.2 +/- 1.2 to 8.2 +/- 2.5 h) and the area under the caffeine concentration-time curve (from 16.3 +/- 6.6 to 25.9 +/- 7.8 micrograms.h/ml) while decreasing the total body clearance (from 106 +/- 41.6 to 58.2 +/- 28.8 ml/min per 1.73 m2). In addition, the rate of conversion of caffeine to paraxanthine was significantly delayed. There was no significant linear correlation between the urinary recovery of oxociprofloxacin at 0 to 12 h and the change in the area under the caffeine concentration-time curve. There was also a small but statistically significant increase in the area under the ciprofloxacin concentration-time curve during simultaneous administration of caffeine. We concluded that ciprofloxacin causes a significant increase in the half-life of caffeine and in the area under the caffeine concentration-time curve by reducing total body clearance. This interaction is due at least in part to a delay in the conversion of caffeine to paraxanthine. The clinical significance of these observations remains to be determined. Lastly, caffeine may alter the kinetics of ciprofloxacin, a possibility which should be more fully explored.