Because the small bowel is a site of significant cholesterol synthesis, we determined the ileal distribution of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase), the rate-limiting enzyme of the cholesterol biosynthetic pathway. Immunofluorescence microscopy on unfixed snap-frozen sections of ileum and jejunum from untreated rats or dogs showed HMG-CoA reductase in the absorptive villus epithelial cells and this appeared to be strikingly localized in their apical cytoplasm. This pattern of HMG-CoA reductase staining approximated a gradient along the villus-crypt axis with the distal villi labeling most intensely. Treatment of rats with mevinolin and/or cholestyramine for 12 days induced a 5- to 11-fold increase in ileal HMG-CoA reductase activity, and yielded a higher intensity of immunostaining without altering the pattern of enzyme distribution observed in control intestines. Also, rats with maximal induction of ileal HMG-CoA reductase exhibited a twofold increase in the number of epithelial villus cells containing prominent stacks of smooth-surfaced membranes in their apical cytoplasm as seen with electron microscopy. These observations suggest that the distal villus absorptive epithelial cells of the ileum contain high concentrations of HMG-CoA reductase, and therefore might be capable of contributing significant quantities of cholesterol to the circulation.

Animals↗

PubMedDate not supplied

Autologous red blood cell and platelet engulfment in hairy cell leukemia.

Seven cases of hairy cell leukemia (leukemic reticulo-endotheliosis) are presented in which peripheral blood or splenic hairy cells or both were identified engulfing autologous red blood cells or platelets. In 3 patients, approximately 5-15% of their peripheral blood hairy cells were engulfing red cells and platelets. In 2 patients, intercellular junctions were present between processes of hairy cells and were similar to processes occasionally seen connecting Langerhans cells to each other. Also, parallel tubular arrays were identified in the cytoplasm of hairy cells from 2 other patients. We conclude that autologous red blood cell and platelet engulfment is a common finding in hairy cell leukemia.

Aged↗

PubMedDate not supplied

Pharmacological modification of rabbit corneal endothelial transport and permeability.

Either isolated normal or preswollen rabbit corneas were perfused across their endothelial surface with various drugs in the specular microscope. The deswelling rate of preswollen corneas was uninfluenced by calmodulin (1 and 10 micrograms/ml), phenylephrine (0.1 and 1 mM), DbcAMP (10(-4) M), theophylline (10(-3) and 10(-4) M), isoproterenol (2 x 10(-7) and 2 x 10(-6) M), or cyclic GMP (10(-4) and 10(-6) M). The swelling rate of normal thickness corneas was increased by furosemide (10(-5) and 10(-4) M) and thiocyanate (5 x 10(-2) and 5 x 10(-3) M) but not by SITS (10(-4) M), dipyridamole (5 x 10(-5) M) or NAP-taurine (10(-3) M). The results suggest that alteration of endothelial cyclic AMP or cyclic GMP levels has no influence on transendothelial fluid flow. Modulation of the metabolic processes underlying anion fluxes by furosemide and thiocyanate caused corneal swelling but none of the agents which affect passive anion exchange in other systems influenced transendothelial fluid movement. The furosemide and thiocyanate effects confirm that bicarbonate, or chloride, exchange may be important in part in the regulation of corneal dehydration by the endothelium.

Animals↗

PubMedDate not supplied

Evaluation of variation in oxygen transmission in rigid contact lens extended wear.

Variation in thickness is known to affect the Dk/L of rigid gas permeable contact lenses. Our study was designed to evaluate the variability of central and average thickness of Oxyflow EW lenses. In addition, the relationship between overnight swelling of the central cornea and Dk/L was examined to determine whether Dk/L calculated with central lens thickness correlated better with lens-induced edema than Dk/L calculated with average lens thickness. The results showed marked variation among lens center thicknesses for all powers (-6 D, -2 D, +2 D, +6 D) examined, and, as expected, more variation for centrally calculated Dk/L with high minus lenses. Average Dk/L did not vary significantly with power. Average and central Dk/L values had a near 1:1 relationship for -2 D lenses for the base curve (7.8 mm) ordered; but only when power was kept constant was a good correlation seen between central and average Dk/L. A one-patient study evaluating the overnight central swelling response to three +6 D and three -6 D (high, medium, and low center thickness) lenses showed that central Dk/L correlated better with lens-induced edema than average Dk/L. Thus, specifying central thickness on lens orders appears to be a primary variable influencing extended wear edema at night. Peripheral Dk/L, however, may influence corneal physiological variables other than central edema and warrants further study.

Adult↗