The use of endoscopic biopsy in evaluation of polypoid lesions of the colon

Use of flexible endoscopes affords biopsy sampling of polypoid lesions of the colon, especially within the rectum and sigmoid colon by flexible fiberoptic sigmoidoscopes. Histologic examination of colonic biopsies usually allows division of polyps into neoplastic and non-neoplastic categories. There are significant limitations to such biopsies, however, due to sampling error and inability to reach deep submucosal cores of polyps where malignant invasion may occur. When properly aware of its limitations, the endoscopist will find the endoscopic biopsy a valuable aid in planning the therapeutic approach to a polypoid lesion of the colon.     

Control of protein synthesis by amino acid supply. The effect of asparagine deprivation on the translation of messenger RNA in reticulocyte lysates

The enzyme asparaginase, which hydrolyses asparagine to aspartic acid, inhibited cell-free protein synthesis by reticulocyte lysates. The inhibition was rapid and complete when sufficient enzyme was added but could be prevented or reversed by the addition of asparagine. The initial effect of asparaginase appears to be a block in polypeptide chain elongation due to asparagine deprivation, but there are some indications that prolonged incubation under these conditions may give rise to a secondary decrease in initiation of protein synthesis.     

Induction of cytochrome P-450 by glucocorticoids in rat liver. I. Evidence that glucocorticoids and pregnenolone 16 alpha-carbonitrile regulate de novo synthesis of a common form of cytochrome P-450 in cultures of adult rat hepatocytes and in the liver in vivo

We administered a series of steroid hormones to primary nonproliferating cultures of adult rat hepatocytes and found that dexamethasone and other glucocorticoids but not sex steroid hormones, mineralocorticoids, or derivatives of pregnenolone other than pregnenolone 16 alpha-carbonitrile (PCN) stimulated de novo synthesis of an immunoreactive protein, indistinguishable from the form of cytochrome P-450 (P450PCN) induced by PCN in rat liver. No difference were discerned among purified liver cytochromes from rats treated with dexamethasone, PCN or dexamethasone plus PCN, among proteolytic digests of these proteins, or among the immunoprecipitated cytochromes prepared from cultured hepatocytes treated with these steroids as judged by electrophoresis on polyacrylamide gels containing sodium dodecyl sulfate followed by immunoblot analysis. Of the steroids tested, dexamethasone proved to be the most efficacious inducer increasing the rate of synthesis of P450PCN from 0.05% of total cellular protein synthesis in incubated control cultures (measured as incorporation of [3H]leucine into immunoprecipitable P450PCN) to as much as 9.4% in cultures incubated for 5 days in medium containing dexamethasone (10(-5) M). As with traditional glucocorticoid-responsive liver functions, induction of immunoreactive P450PCN was dependent on the concentration of dexamethasone (10(-8) to 10(-5) M) and was promptly reversed upon withdrawal of the steroid. However, during the 24-h interval between 24 to 48 h of culture age the hepatocytes were refractory to either induction or de-induction of immunoreactive P450PCN even though continuous exposure of the cells to dexamethasone (including this interval) was mandatory for maximal induction of P450PCN at 120 h in culture. Unlike cultured rat hepatocytes, HTC hepatoma cultures failed to exhibit dexamethasone-responsive expression of immunoreactive P450PCN. We conclude that glucocorticoids and PCN constitute a specific "class" of synthetic and endogenous inducers of a single form of cytochrome P-450.     

Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi

Borrelia burgdorferi is a spirochete pathogen transmitted among warm- blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.      

Hyperplasia of adrenal rest tissue causing a retroperitoneal mass in a child with 11 beta-hydroxylase deficiency

We report the case of a child with congenital adrenal hyperplasia due to 11 beta-hydroxylase deficiency, with hyperplasia of adrenal rest tissue presenting as a retroperitoneal mass. Complete resolution of the mass was noted after 18 months of hydrocortisone replacement therapy.