Collagenase Production by Endotoxin-Activated Macrophages

Peritoneal exudate macrophages, when exposed to bacterial lipopolysaccharide in culture, were found to produce collagenase (EC 3.4.24.3). This enzyme was not detected in extracts of the macrophages or in media from nonstimulated macrophage cultures. Lipidcontaining fractions of the lipopolysaccharide, including a glycolipid from the rough mutant of Salmonella minnesota (R595) and lipid A, were potent stimulators of collagenase production. The lipid-free polysaccharide fraction had no effect. Cycloheximide prevented the production of collagenase by endotoxin-treated macrophages, suggesting that it was newly synthesized.     

Pathophysiology of hypotension in patients with fulminant hepatic failure

Studies on the incidence and pathophysiology of hypotension in fulminant hepatic failure showed that 82 out of 94 patients developed arterial hypotension with a systolic blood pressure of less than 80 mmHg. Such episodes accounted for 16% of the total time spent in grade IV coma. Factors such as haemorrhage, cardiac or respiratory abnormalities, extracorporeal perfusion, or hypotension which occurred during the terminal stages of the illness, could be implicated for only 40% of this time, leaving 60% as unexplained. Further investigation of these unexplained factors showed that peripheral vasodilatation rather than primary heart failure was responsible, and in all but three patients construction of ventricular function curves showed a normal ventricular response to volume expansion with a corresponding increase in blood pressure. A small, but significant, slowing of the heart rate occurred during these periods of unexplained hypotension. This, together with the association that was found between the occurrence of hypotension and cerebral oedema with coning, suggests that central vasomotor depression may be important in its pathogenesis.     

Within- and between-laboratory precision in the measurement of body volume using air displacement plethysmography and its effect on body composition assessment

OBJECTIVE: To determine and compare the extent of within- and between-laboratory precision in body volume (BV) measurements using air displacement plethysmography (ADP), the BOD POD body composition system, and to interpret any such variability in terms of body composition estimates. DESIGN: Repeated test procedures of BV assessment using the BOD POD ADP were reproduced at two laboratories for the estimation of precision, both within and between laboratories. SUBJECTS: In total, 30 healthy adult volunteers, 14 men (age, 19-48 y; body mass index (BMI), 19.7-30.3 kg/m2) and 16 women (age, 19-40 y; BMI, 16.3-35.7 kg/m2), were each subjected to two test procedures at both laboratories. Two additional volunteers were independently subjected to 10 repeated test procedures at both laboratories. MEASUREMENTS: Repeated measurements of BV, uncorrected for the effects of isothermal air in the lungs and the surface area artifact, were obtained using the BOD POD ADP, with the identical protocol being faithfully applied at both laboratories. Uncorrected BV measurements were adjusted to give estimates of actual BV that were used to calculate body density (body weight (BWt)/actual BV) from which estimates of body composition were derived. The differences between repeated BV measurements or body composition estimates were used to assess within-laboratory precision (repeatability), as standard deviation (SD) and coefficient of variation; the differences between measurements reproduced at each laboratory were used to determine between-laboratory precision (reproducibility), as bias and 95% limits of agreement (from SD of the differences between laboratories). RESULTS: The extent of within-laboratory methodological precision for BV (uncorrected and actual) was variable according to subject, sample group and laboratory conditions (range of SD, 0.04-0.13 l), and was mostly due to within-individual biological variability (typically 78-99%) rather than to technical imprecision. There was a significant (P<0.05) bias between laboratories for the 10 repeats on the two independent subjects (up to 0.29 l). Although no significant bias (P=0.077) was evident for the sample group of 30 volunteers (-0.05 l), the 95% limits of agreement were considerable (-0.68 to 0.58 l). The effects of this variability in BV on body composition were relatively greater: for example, within-laboratory precision (SD) for body fat as % BWt was between 0.56 and 1.34% depending on the subject and laboratory; the bias (-0.59%) was not significant between laboratories, but there were large 95% limits of agreement (-3.67 to 2.50%). CONCLUSION: Within-laboratory precision for each BOD POD instrument was reasonably good, but was variable according to the prevailing conditions. Although the bias between the two instruments was not significant for the BV measurements, implying that they can be used interchangeably for groups of similar subjects, the relatively large 95% limits of agreement indicate that greater consideration may be needed for assessing individuals with different ADP instruments. Therefore, use of a single ADP instrument is apparently preferable when assessing individuals on a longitudinal basis.     

Prospective study of bacterial infection in acute liver failure: an analysis of fifty patients

Fifty consecutive patients admitted with acute liver failure, minimal grade II encephalopathy, were studied prospectively to determine the incidence, timing and cause of bacterial infection, the relationship to clinical criteria for infection; and the influence of early microbiological diagnosis on clinical outcome. There were 53 proven bacterial infections in 40 patients, whereas in 5 of the remaining 10 patients infection was suspected on clinical grounds in the absence of significant cultures. Seven patients (14%) had more than one bacterial infection, and four patients had simultaneous infections caused by different organisms at each site. Fourteen infections (26.4%) were associated with bacteremia, and in six of these no source was found. Twenty-five infections (47.1%) arose from the respiratory tract, 12 (22.6%) from the urinary tract and 2 (3.7%) from central venous cannulas. Thirty-seven (69.8%) of the 53 infections were due to gram-positive bacteria; Staphylococcus aureus accounted for 19 (35.8%) of all the infections. Thirty patients died (60%), 28 of whom had bacterial infection at some time; in 24 of these the infection was diagnosed less than 24 hr before death. All nine deaths that occurred more than 7 days after admission were directly attributable to microbial infection. Clinical features such as elevated temperature and elevated peripheral white blood cell count were poor indicators of bacterial infection because these were absent in 30.2% of cases. These data show that there is a high incidence of bacterial infection early in the course of acute liver failure and suggest that prophylactic antimicrobial therapy, although unproven, might be justified.     

The design effect and cluster samples: optimising tuberculosis prevalence surveys

Cross-sectional surveys of disease prevalence, including for tuberculosis (TB), often use a two (or more) stage sampling procedure. By choosing clusters of people randomly from all possible clusters, the logistic costs of doing the survey can be reduced. However, this increases the statistical uncertainty in the estimate of prevalence, and we need to balance the reduction in cost against the increase in uncertainty. Here we describe cluster sampling and consider ways to determine the optimal survey design as well as the extent to which deviations from the optimal design matter. We illustrate the results using data from a recent survey in Cambodia in which TB was diagnosed using sputum smears, cultures and X-rays.     

Impaired survival of peripheral T cells, disrupted NK/NKT cell development, and liver failure in mice lacking Gimap5

The loss of Gimap5 (GTPase of the immune-associated protein 5) gene function is the underlying cause of lymphopenia and autoimmune diabetes in the BioBreeding (BB) rat. The in vivo function of murine gimap5 is largely unknown. We show that selective gene ablation of the mouse gimap5 gene impairs the final intrathymic maturation of CD8 and CD4 T cells and compromises the survival of postthymic CD4 and CD8 cells, replicating findings in the BB rat model. In addition, gimap5 deficiency imposes a block of natural killer (NK)- and NKT-cell differentiation. Development of NK/NKT cells is restored on transfer of gimap5(-/-) bone marrow into a wild-type environment. Mice lacking gimap5 have a median survival of 15 weeks, exhibit chronic hepatic hematopoiesis, and in later stages show pronounced hepatocyte apoptosis, leading to liver failure. This pathology persists in a Rag2-deficient background in the absence of mature B, T, or NK cells and cannot be adoptively transferred by transplanting gimap5(-/-) bone marrow into wild-type recipients. We conclude that mouse gimap5 is necessary for the survival of peripheral T cells, NK/NKT-cell development, and the maintenance of normal liver function. These functions involve cell-intrinsic as well as cell-extrinsic mechanisms.     

Dilation of forearm blood vessels after angiotensin-converting-enzyme inhibition by captopril in hypertensive patients

In eight hypertensive patients, forearm vascular tone was assessed by water plethysmography following inhibition of angiotensin II-converting-enzyme (ACE) activity with captopril. Acute captopril administration increased venous distensibility (VV30) and decreased forearm vascular resistance (FVR), while it lowered systemic blood pressure (BP). Alpha-one adrenergic receptor blockade by prazosin did not prevent captopril from decreasing vascular tone or lowering blood pressure (BP). Thus, captopril dilated both veins and arterioles. The primary mechanism of captopril's acute antihypertensive action did not involve inhibition of alpha1-adrenergic receptor activity. Moreover, captopril and prazosin together produced a greater reduction in BP and peripheral resistance than occurred with either agent alone.