Charlotte Cywiner-Golenzer

Definition and diagnosis of cytomegalovirus colitis in patients infected by human immunodeficiency virus

The definition and routine diagnosis of cytomegalovirus (CMV) colitis in patients infected by human immunodeficiency virus (HIV) are controversial. In 100 consecutive HIV-infected patients who underwent colonoscopy for the investigation of diarrhea, we compared the yields of routine diagnostic tools for CMV infection and assessed the risk of further CMV organ disease in subgroups of patients with the following features: full evidence of CMV colitis (group 1), colonic CMV infection but no endoscopic lesions (group 2), and no evidence of colonic CMV infection (group 3). All biopsies taken during colonoscopy were examined immediately by routine hematoxylin and eosin (H&E) staining and viral culture and then pooled for second-line H&E staining and immunohistology. Among the 15 diagnoses of CMV colitis (group 1), two were missed during initial H&E examination, and both patients developed further CMV organ disease during follow-up. Of the 12 group 2 patients 11 were not receiving anti-CMV drugs at the time of initial colonoscopy. CMV organ disease was not significantly more common in these patients than in group 3 during follow-up. We conclude that routine H&E staining of colonic biopsy specimens for CMV inclusions is not 100% sensitive for CMV colitis. The favorable outcome of colonic CMV infection without endoscopic lesions suggests that only patients with full evidence of CMV colitis warrant specific antiviral therapy.

Fibre‐type distribution and subcellular localisation of α and β enolase in mouse striated muscle

Enolase is a dimeric glycolytic enzyme exhibiting tissue specific isoforms. During ontogenesis, a transition occurs from the embryonic αα towards the specific αβ, and ββ isoforms in striated muscle. Immunocytochemical analyses on transverse sections of adult mouse gastrocnemius muscle, allowed us to compare the expression of α and β subunits to that of myosin heavy chain (MHC) isoforms. Levels of β immunoreactivity followed the order IIB > IIX > IIA > I. This gradient parallels the ATPase activity associated to MHC isoforms, indicating that the expression of β enolase in myofibres is finely regulated as a function of energetic requirements. By contrast, variations in α immunolabelling intensity appeared independent of fibre types.

The –700/–310 Fragment of the Apolipoprotein A-IV Gene Combined with the –890/–500 Apolipoprotein C-III Enhancer Is Sufficient to Direct a Pattern of Gene Expression Similar to That for the Endogenous Apolipoprotein A-IV Gene

Spatial gene expression in the intestine is mediated by specific regulatory sequences. The three genes of the apoA-I/C-III/A-IV cluster are expressed in the intestine following cephalocaudal and crypt-to-villus axes. Previous studies have shown that the –780/–520 enhancer region of the apoC-III gene directs the expression of the apoA-I gene in both small intestinal villi and crypts, implying that other unidentified elements are necessary for a normal intestinal pattern of apoA-I gene expression. In this study, we have characterized transgenic mice expressing the chloramphenicol acetyltransferase gene under the control of different regions of the apoC-III and apoA-IV promoters. We found that the –890/+24 apoC-III promoter directed the expression of the reporter gene in crypts and villi and did not follow a cephalocaudal gradient of expression. In contrast, the −700/+10 apoA-IV promoter linked to the −500/−890 apoC-III enhancer directed the expression of the reporter gene in enterocytes with a pattern of expression similar to that of the endogenous apoA-IV gene. Furthermore, linkage of the −700/−310 apoA-IV distal promoter region to the −890/+24 apoC-III promoter was sufficient to restore the appropriate pattern of intestinal expression of the reporter gene. These findings demonstrate that the −700/−310 distal region of the apoA-IV promoter contains regulatory elements that, in combination with proximal promoter elements and the −500/−890 enhancer, are necessary and sufficient to restrict apoC-III and apoA-IV gene expression to villus enterocytes of the small intestine along the cephalocaudal axis.

Apolipoprotein A-II is catabolized in the kidney as a function of its plasma concentration.

We investigated in vivo catabolism of apolipoprotein A-II (apo A-II), a major determinant of plasma HDL levels. Like apoA-I, murine apoA-II (mapoA-II) and human apoA-II (hapoA-II) were reabsorbed in the first segment of kidney proximal tubules of control and hapoA-II-transgenic mice, respectively. ApoA-II colocalized in brush border membranes with cubilin and megalin (the apoA-I receptor and coreceptor, respectively), with mapoA-I in intracellular vesicles of tubular epithelial cells, and was targeted to lysosomes, suggestive of degradation. By use of three transgenic lines with plasma hapoA-II concentrations ranging from normal to three times higher, we established an association between plasma concentration and renal catabolism of hapoA-II. HapoA-II was rapidly internalized in yolk sac epithelial cells expressing high levels of cubilin and megalin, colocalized with cubilin and megalin on the cell surface, and effectively competed with apoA-I for uptake, which was inhibitable by anti-cubilin antibodies. Kidney cortical cells that only express megalin internalized LDL but not apoA-II, apoA-I, or HDL, suggesting that megalin is not an apoA-II receptor. We show that apoA-II is efficiently reabsorbed in kidney proximal tubules in relation to its plasma concentration.