Journal of Laboratory and Clinical Medicine最新文献

The VX2 tumor is derived from a papilloma virus-induced rabbit epithelial cell line. If VX2 tumor cells (trapped in a plasma clot) are introduced intravenously into NZW rabbits, the cells lodge in the lung capillary bed and produce tumors. Independently of the tumor burden (ie, the total tumor weight per rabbit), approximately 15% of rabbits with VX2 lung tumors accumulate an effusion in the interpleural space and this pleural effusion contains products of hemostasis. We hypothesized that these products were of intra-tumoral origin and that they changed in concentration as tumor burden increased. Interrelationships among lung-, tumor-weights, and pleural effusion volumes, and the concentrations of fibrinolytic factors, their catabolic products, and other proteins of pleural effusions were measured in rabbits with a wide range of tumor burdens. Positive correlations between tumor burden and total lung weight and between pleural effusion volume and net lung weight suggested that interstitial fluid from the stroma of tumors passed directly into the extravascular space of the lung(s) and into the interpleural space(s). Analyses of pleural effusions indicated that plasminogen-, α₂-antiplasmin-, and plasminogen activator inhibitor-1-related proteins, urokinase-like- and tissue-plasminogen activator activities, and vascular endothelial growth factor increased in concentration up to a tumor burden of ∼20–25 g. Plasmin activity and intact fibrinogen were absent. The concentration of fibrin(ogen) degradation products did not change significantly up to a tumor burden of ∼25 g but increased substantially as tumor burdens exceeded 25 g. In conclusion, interstitial fluid from tumors enters the extravascular space of the host and may accumulate with fluid from non-tumor sources as a pleural effusion. The concentrations of fibrinolytic factors and their products in pleural effusions reflect the tumor burden of the rabbit. Conceivably, the components of a malignant effusion contain much information about the extent of tumor growth.

Objective: Since glycohemoglobin values are widely used clinically as a surrogate for average glucose concentration over an extended period of time, we decided to determine the actual relationship between 24-hour integrated glucose values and percent total glycohemoglobin (%tGHb) in cohorts of people with and without diabetes. Research Design and Methods: In 48 people without known diabetes with known stability of fasting glucose over a 1-year period of time, the calculated 24-hour integrated glucose concentration was compared with their %tGHb. In 15 normal young medical students, the glucose area response was determined from 46 venous blood samples obtained during a 24-hour period and compared with their %tGHb. In 18 people with type 2 diabetes, interstitial glucose concentrations were monitored using the Continuous Glucose Monitoring System (Medtronic MiniMed, Inc., Sylmar, Calif) for 3 days at 20-day intervals over 100 days. %tGHb was performed at 20-day intervals simultaneously. In 29 people with untreated type 2 diabetes, glucose area response was determined from 46 venous blood samples obtained during a 24-hour period and compared with their %tGHb after being on a standardized diet provided to the subjects for at least 5 weeks. The %tGHb and 24-hour profiles were stable. Results: There was an excellent correlation between the mean 24-hour glucose concentration and the %tGHb among subjects with diabetes. The correlation was poor among subjects without diabetes. The relationship was curvilinear when plotted as a single group. Alternatively when data from subjects with or without diabetes were plotted separately, the slopes were identical but the y-intercepts were different. Conclusion: The relationship between the mean glucose concentration integrated over an extended period of time and the %tGHb is not linear. The reason for this nonlinearity remains to be determined. This non-linearity needs to be considered in the clinical interpretation of %tGHb (and probably HbA_1c) in reference to glucose values.

This study examines the existence of the urinary albumin degradation pathway and the proposed role of receptor-mediated endocytosis in this process using the isolated perfused rat kidney (IPK) model. Albumin-derived peptides in IPK urine are analyzed in terms of their relative size distribution using radioactivity and absorbance at 214 nm, and their susceptibility to trypsin digestion. The effects of perfusing kidneys with concanamycin A and myristoyl trimethyl ammonium bromide (MTMAB), inhibitors of the receptor-mediated endocytosis regulators vacuolar-type H⁺ ATPase (v-ATPase) and dynamin GTPase, respectively, are examined. Normal IPK urine contains mildly degraded (defined as ∼10–40 kDa; 43.0 ± 8.3%) and heavily degraded (defined as <10 kDa; 22.6 ± 7.7%) albumin peptides as well as intact albumin (34.5 ± 4.1%). The relative size distribution of the peptides is similar by radioactivity and absorbance at 214 nm, and both profiles are reduced to very small peptides following trypsin digestion. Administration of concanamycin A or MTMAB causes a significant increase in the proportion of intact albumin (concanamycin A: 55.8 ± 11.6%; MTMAB: 50.0 ± 11.9%) excreted compared with normal IPK urine. This coincides with a reduction in the proportion of mildly (concanamycin A: 27.6 ± 9.8%; MTMAB: 39.9 ± 11.5%) and heavily degraded (concanamycin A: 16.6 ± 7.4%; MTMAB: 10.0 ± 2.5%) albumin present and is not associated with changes in glomerular permeability to albumin because no significant change is observed in the fractional clearance of Ficoll (radius range 20–60 Å) in the presence of concanamycin A. This study demonstrates the existence of albumin peptides in IPK urine and suggests that receptor-mediated endocytosis plays a role in urinary albumin degradation.

The general methodology, strengths and weaknesses, and political uses of meta-analysis are examined. As a systematic study of all studies that have been conducted to answer a specific question or hypothesis, meta-analysis is strong in revealing structural flaws and sources of bias in primary research and in posing promising research questions for future study. It cannot exceed, however, the limits of what is reported by primary researchers. Meta-analysis is particularly challenged to quantify the size of a common effect of treatment across reported trials because of (1) the clinical diversity of the trials and (2) the myriad of potential differences among patients with varying characteristics within the trials. Without access to the original data of reported trials, meta-analysis cannot overcome the bias of underpowered trials toward overstatement of the size of main treatment effects, nor the tendency for such trials to falsely conclude there were no statistically significant adverse events. Although severely compromised by ghost-written or honorary-authored reports of primary research, meta-analysis can make use of its methods to focus on the conflicts of interest and likely sources of bias of such research and make known what precautions should be taken by would-be consumers. Examples show how meta-analysis has clarified thinking about the off-label use of selective serotonin reuptake inhibitors for treating child and adolescent depression, use of low-tidal volume respirator assistance for acute lung injury and acute respiratory distress syndrome patients, and the long-term use of COX-2 inhibitors for relieving arthritic pain. Recommendations are made for Congressional action.

The outer medullary collecting duct (OMCD) plays an important role in acid-base homeostasis by two luminal proton ATPases, H⁺-ATPase and H⁺–K⁺-ATPase (HKA), both of which are in the intercalated cells (ICs) of OMCD. We showed previously that HKAα1 (gastric H⁺-K⁺-ATPase) activity is the essential H⁺-K⁺-ATPase activity under normal conditions, and that HKAα2 (colonic H⁺-K⁺-ATPase) is induced and mediates increased proton-secretion under K-depleted conditions.1, 2, 3 To better understand the role of H⁺-ATPase (potassium-independent) in acid secretion and the relationship between H⁺-ATPase and a specific HKA isoform, we examined H⁺-ATPase activity in the H⁺–K⁺-ATPaseα1 knockout (KO) mice under normal and K-depleted conditions. Mice were fed a potassium-free diet and studied after 7 days. Segments of the OMCD were perfused in vitro, and intracellular pH (pH_i) was measured by ratiometric fluorescence microscopy using the pH-sensitive indicator BCECF-AM. The isolated OMCD tubules obtained from mice fed a potassium-free diet were examined by fluorescent immunocytochemistry with an antibody to the 31-kDa subunit of H⁺-ATPase (E-11) and were compared with those obtained from a normal diet. In the absence of Na⁺ and K⁺, the H⁺-ATPase-mediate pH_i recovery rates were 6.7 ± 1.1 × 10⁻⁴ units/s (n = 7 ICs) in wild-type (WT) mice and increased to 8.7 ± 1.8 × 10⁻⁴ (P < 0.05; n = 6) in HKAα1 KO mice. K-independent proton transport activity was significantly inhibited by the H⁺-ATPase inhibitor bafilomycin A₁ (BAF, 10 nM) with luminal applied in both WT and KO mice. Comparison of the results indicated upregulation of BAF-sensitive H⁺-ATPase activity in KO mice. To determine the intracellular localization of H⁺-ATPase in the intercalated cells of OMCD, we dissected the OMCD and performed fluorescent immunocytochemistry with the H⁺-ATPase antibody in the WT and KO mice. In the WT mice, on normal diet, H⁺-ATPase staining distributed diffusely throughout the intercalated cells and was slightly polarized to the apical plasma membrane in the KO mice, consistent with increase in the H⁺-ATPase-mediate pH_i recovery in the KO mice. One week of a potassium-free diet resulted in a significant increase in the degree of H⁺-ATPase polarization at the apical plasma membrane in both WT and KO mice. Hypokalemia stimulates H⁺-ATPase in the intercalated cells of OMCD of both WT and KO mice. The enhanced activity of H⁺-ATPase plays an important role in compensatory proton secretion in the HKAα1 KO mice under normal conditions.