Development of an ELISA test for determination of the urinary trypsin inhibitor: analytical performance and applications

Increased urinary excretion of urinary trypsin inhibitor (UTI) has been reported in various inflammatory conditions and in Alzheimer's subjects, but its diagnostic potential remains to be elucidated. A reliable and specific enzyme-linked immunosorbent assay (ELISA) test for the determination of the UTI in human urine was developed. This assay was performed using 96-well microtiter plates. The plate surface is coated with an anti-UTI polyclonal antibody, the urine sample was added in a dilution range, and the detection was achieved using the enzyme-conjugated antibody. The assay was quantified by the build-up of colored product upon the addition of the substrate. Recoveries were 93%, and the intra- and inter-assay CVs were 4.25% and 21%, respectively. The ELISA showed parallelism of standard and urine samples and no significant interference by the biological matrix. The usefulness of the assay has been demonstrated by applying it to urine samples from Alzheimer's disease patients, and comparing with negative controls. UTI urinary levels are significantly increased in Alzheimer's subjects.     

Relationships between total plasma load of torquetenovirus (TTV) and TTV genogroups carried

In 239 torquetenovirus-positive people, multiple-genogroup infections were common and associated with higher viral loads than would be expected from simple additive effects. The latter observation was restricted to the infections which included both genogroups 1 and 3, pointing to the possible existence of some kind of infection facilitation between these genogroups.     

Cellular distribution of phosphofructokinase activity and implications to metabolic regulation in human breast cancer

Neoplastic cells generally present profound changes in glucose metabolism. The mechanisms underlying such process are numerous and all may involve altered cellular hormonal responses. Here we report the first evidence that cellular location of phosphofructokinase activity in human breast cancer tissues is different from the one observed in control tissues and that this phenomenon may be involved in the increased glycolytic flux observed in those cells. Through co-sedimentation techniques, we observed that 60% of phosphofructokinase activity in neoplastic tissues is located in an actin-enriched fraction, against 36% in control tissues. Additionally, metastatic tumor tissues presented a two fold increase in this particulate activity when compared to non-metastatic tumor samples. We propose that the alteration in cellular distribution of phosphofructokinase activity in human breast cancer tissues is a mechanism associated to the process of cell transformation and may be a consequence of the altered hormonal milieu observed in several types of cancer.     

Ultrastructural Features of Neuroendocrine Differentiated Carcinomas of the Breast

The ultrastructural patterns of neuroendocrine (NE) differentiated breast carcinomas are analyzed and discussed. Reports in the literature describe wide variations in the size of observed dense-core membrane-bound granules and discrepancies in their interpretation. In the present study 24 cases of breast carcinoma with recognized morphologic, histochemical, and immunocytochemical features of NE tumors were investigated. Five different types of dense-core granules of neurosecretory (NS) type (confirmed by the ultrastructural localization of chromogranin A) and five different cell types were recognized. Some amphicrine cells were found to contain both mucin and NS granules. Another notable ultrastructural feature of breast NE carcinomas was the presence of clear vesicles of presynaptic type, which correlated with expression of synaptophysin.     

Regulation of human erythrocyte metabolism by insulin: cellular distribution of 6-phosphofructo-1-kinase and its implication for red blood cell function

Human erythrocytes are highly specialized cells whose function is oxygen transport. These cells' sole metabolic source of energy is the fermentation of glucose via glycolysis. They contain an active insulin receptor and respond to insulin by increasing phosphorylation of tyrosine residues in several proteins. However, no metabolic effects have yet been associated with activation of this receptor in human erythrocytes. Here, we show that insulin increases the rate of glycolysis in human erythrocytes. Lactate production increased 56 and 173% in the presence of 10 and 100 nM insulin, respectively. A higher insulin concentration (1000 nM) partially reversed the stimulation of glycolysis. These effects occur through activation of the key glycolytic enzyme 6-phosphofructo-1-kinase, which exhibits the same pattern of modulation by insulin as seen for glycolytic flux. This modulation also occurs physiologically since ex vivo experiments revealed 50% stimulation of 6-phosphofructo-1-kinase (PFK) activity following a high carbohydrate meal. Insulin increases phosphorylation of PFK and redistributes the enzyme in red blood cells, causing it to detach from the erythrocyte membrane: upon insulin stimulation, the amount of enzyme associated with the plasma decreases by 86%. Detachment is a common mechanism of enzyme activation. As a consequence, insulin prevents up to 68% of red cells hemolysis. These results show that insulin regulates erythrocyte glycolysis and viability and suggest that this regulation is associated to other erythrocyte functions such as oxygen transport. Finally, we suggest that this regulatory mechanism might be compromised in patients with diabetes mellitus.     

Expression of human CD81 in transgenic mice does not confer susceptibility to hepatitis C virus infection

We previously demonstrated that hepatitis C virus (HCV) binds to human CD81 through the E2 glycoprotein. Therefore, expression of the human CD81 molecule in transgenic mice was expected to provide a new tool to study HCV infection in vivo, as the chimpanzee is the only species currently available as a laboratory animal model that can be infected with HCV. We produced transgenic mice expressing the human CD81 protein in a wide variety of tissues. We confirmed binding of recombinant E2 glycoprotein to the liver tissue as well as to thymocytes and splenic lymphocytes in the transgenic mice. We inoculated chimpanzee plasma infected with HCV into these animals. None of these transgenic animals showed evidence of viral replication. Furthermore, human CD81 transgenic mice that lack expression of endogenous mouse CD81 were also resistant to HCV infection. We conclude that expression of human CD81 alone is insufficient to confer susceptibility to HCV infection in the mouse. The presence of additional possible factors for HCV infection is discussed.     

Identifying recent HIV infections using the avidity index and an automated enzyme immunoassay

We evaluated a procedure for identifying recent HIV infections, using sequential serum samples from 47 HIV-positive persons for whom the seroconversion date could be accurately estimated. Each serum sample was divided into two aliquots: one diluted with phosphate-buffered saline and the other diluted with 1 M guanidine. We assayed the aliquots with the automated AxSYM HIV1/2gO test (Abbott Diagnostics Division), without modifying the manufacturer's protocol. We then calculated the avidity index (AI): the ratio of the sample/cutoff value for the guanidine aliquot to that of the phosphate-buffered saline aliquot. We analyzed 216 serum samples: 34 samples were collected within 6 months of seroconversion (recent seroconversions), and 182 were collected after 6 months. The mean AIs, by time from seroconversion, were 0.68 +/- 0.16 (within 6 months) and 0.98 +/- 0.10 (after 6 months) (P < 0.0001). AI of <0.90 correctly identified 88.2% of recent infections but misclassified as recent infections 13.2% of serum samples collected afterward. The probability of an infection being classified as recent and having AI of > or = 0.90 would be 0.7% in a population with 5% recent infections. AI can identify with a certain degree of accuracy recent HIV infections, and being a quantitative index, it provides different levels of sensitivity and specificity, depending on the selected cutoff value. The standard assay procedure is not modified. This test is simple and inexpensive and could be used for surveillance, decision-making in treatment, and prevention.