Recognition and treatment of venous malformations of the rectum.

Venous malformations of the rectum are uncommon lesions that present complex management problems (1-6). The vast majority of these lesions present with rectal bleeding in infancy or childhood. Many cases have been treated as colitis for years before the correct diagnosis was made. The correct diagnosis has generally been based on gross appearance, confirmed subsequently by plain radiographs and angiography. Heroic surgical intervention has been the only repeatedly reported "cure" in the literature. One patient has been reported who did well for 20 years with sclerosis of the hemorrhoidal vein at surgery followed by intermittent transrectal sclerotherapy (7,8). Another patient would appear to have had longterm success with radiation therapy (9-11). We report four new cases of venous malformations of the rectum and results to date of a new therapeutic option with transcutaneous ethanol sclerotherapy in two of these patients. A discussion of alternate methods of treatment is included.

Characterization of binding of simian rotavirus SA-11 to cultured epithelial cells.

Rotavirus causes enteritis in both man and animals. The identity of the rotavirus receptor is not known. The nature of the binding interaction and the relationship between virus binding and internalization have not previously been reported. We studied the binding of [5,6-3H]uridine-labeled rotavirus SA11 to confluent monolayers of MA104 cells. We found approximately 13,000 receptor units per cell. The binding was sodium-dependent, pH-insensitive between 5.5 and 8, independent of added calcium, and dependent on sialic acid residues in the membrane. It could be inhibited by mucin. These features may provide clues to the identity of the receptor. Virus was not internalized to significant extent at 4 degrees C. After warming to 37 degrees C, virus was internalized over about 60 min. All binding sites appeared to be equally internalizable. The techniques developed to distinguish between binding and internalization may help to elucidate the mechanism of internalization.

Acidification of endosomes is not important for the entry of rotavirus into the cell.

Rotavirus causes enteritis in both man and animals. The mechanism by which this protein-enveloped virus enters the cell to initiate infection is not known. Many viruses depend on the acidification of endosomes for entry into the cell. We studied the importance of the acidification of endosomes for the initiation of two early phases of rotavirus infection, virus RNA and peptide synthesis. Monensin, nigericin, chloroquine and ammonium chloride at a variety of concentrations caused no specific inhibition of virus RNA or peptide synthesis. We conclude that the acidification of endosomes is not important for the entry of rotavirus into the cell.

In vivo intestinal uptake of immunoreactive bovine albumin in piglet enteritis.

We examined the uptake of bovine serum albumin (BSA) from the intestine into the circulation of 3-week-old piglets infected with transmissible gastroenteritis virus. Transfer of immunoreactive bovine serum albumin (iBSA) from the intestinal lumen into the circulation was enhanced during both the early invasive phase of this viral enteritis (12-h postinoculation) and the diarrheal phase (84-h postinoculation). In some animals, enhanced uptake persisted into the recovery phase, 324 h after inoculation. Gel filtration studies suggested that iBSA had the molecular size characteristic of native BSA; no immunoreactive fragments of BSA were detected. Based on studies of two animals, the half-life of iBSA approximated that of porcine albumin. Further study is required to determine the immunological consequences of the enhanced uptake of protein occurring during viral infection of the intestine.

D-Glucose transport in piglet jejunal brush-border membranes: insights from a disease model.

We measured glucose transport in jejunal brush-border membrane vesicles isolated from piglets with acute viral diarrhea, comparing our results with those from control animals. Characterization of membranes from both study groups demonstrated comparable purity and integrity. In the presence of an inwardly directed Na SCN gradient, D-glucose accumulated in control vesicles to a concentration several times the 60-min equilibrium level. "Overshooting" uptake was much lower and more gradual in vesicles from 40-h transmissible gastroenteritis (TGE)-infected pigs compared with control pigs. Equilibrium kinetic studies, in which gramicidin was used to clamp membrane potential at zero, demonstrated a pattern of Na-dependent D-glucose transport in 40-h TGE-infected membranes that differed greatly from the control pattern. From an Eadie-Hofstee plot of stereospecific Na-dependent D-glucose uptake into control vesicles, a pattern suggesting two carrier populations emerged: one with a low-affinity, apparent Km equaling 52.63 +/- 13.81 mM and the other a high-affinity apparent Km equaling 3.92 +/- 0.24 mM for D-glucose. In 40-h TGE-infected membranes, the pattern conformed to a single line, suggesting a homogeneous population of low-affinity carriers, (Km = 37.03 +/- 1.92 mM), which did not differ from the low-affinity carriers seen in control animals. We conclude that the absence of the high-affinity D-glucose carriers in jejunal brush-border membrane is an important determinant of the defective glucose transport that characterizes viral diarrhea. Because previous studies have strongly suggested that in acute TGE diarrhea the epithelium is composed of relatively undifferentiated crypt-type cells, we speculate that high-affinity D-glucose carriers are lacking in normal crypt epithelial cells and that they are incorporated into brush-border membranes of jejunal enterocytes as the cells differentiate in the course of their migration from crypt to villus.

Altered jejunal permeability to macromolecules during viral enteritis in the piglet.

We studied the macromolecular permeability of segments of jejunum from 2-wk-old piglets after the animals had been experimentally infected with an invasive enteric virus, transmissible gastroenteritis virus. Jejunal segments were mounted in Ussing chambers at stages of the infection, and permeability was measured using three probe molecules of differing molecular weights. In control tissue, permeability to horseradish peroxidase was 2.6 times higher across segments with Peyer's patches than across segments without Peyer's patches, whereas polyethylene glycol 4000 and mannitol permeabilities were the same in patch and nonpatch segments. Twelve hours after infection, when virus had invaded the mucosa causing a structural lesion, and before diarrhea had begun, horseradish peroxidase permeability increased in non-patch-containing segments to equal that across patch-containing tissue. At this early 12-h stage, polyethylene glycol 4000 and mannitol permeation were unchanged in patch-containing segments compared with controls. Ninety-six hours after transmissible gastroenteritis infection, when diarrhea was severe, horseradish peroxidase permeability in patch-free segments had returned to normal and patch-containing tissue permeability was diminished below control levels. Increased macromolecular permeability appears to occur only in the very early invasive stage of this viral enteritis and only in patch-free segments. Any consideration of the immunologic relevance of these complex phenomena must take into account the specialized function of the Peyer's patch regions of the small intestine.

Quantitative determination of macromolecular transport rate across intestinal Peyer's patches.

We used horseradish peroxidase (HRP) (mol wt, 40,000) to compare in vitro, in Ussing chambers, the rates of protein transport across segments of piglet jejunum with and without Peyer's patches. The mean HRP transport rate across intestinal segments with a patch, 25.2 +/- 4.2 SE ng . min-1 . cm-2 (22 animals), was increased threefold (P less than 0.0005) compared with control (no patch) tissue, 7.9 +/- 1.0 ng . min-1 . cm-2 (n = 29). Neither rate showed saturation with increasing concentrations of HRP; both were inhibited 75-95% by a temperature drop from 37 to 15 degrees C. Transport across patch-containing tissue was inhibited 48 +/- 6% (n = 5, P less than 0.0025) by 1 mM NaF, but NaF had no consistent effect on the transport across tissue without Peyer's patches. We conclude that HRP transport is increased across Peyer's patches. This transport is dependent on metabolism and does not involve specific receptors. These findings support the concept that the Peyer's patch serves an antigen-sampling function in the gut.

Influence of pH on elastic deformability of the human erythrocyte membrane.

Fresh human blood was diluted 1:5000 in buffered saline-sucrose solution and titrated to a pH varying from 4.5 to 10.5 with 0.1 N HCl or 0.1 N NaOH. Circular regions of the membrane of individual cells were then deformed at 25 degrees C by aspiration into a micropipette having an internal tip diameter of 0.9-1.4 micron. A membrane surface elasticity modulus, mu (dyn/cm), was computed from the relationship between length of the aspirated membrane and the deforming pressure according to a two-dimensional membrane model. Surface elasticity increases with decreasing pH and with time after the cell suspension is acidified, rising several orders of magnitude with a t1/2 of 1--5 h as pH is lowered from 7.2 to 4.6. This increase in mu is only partially reversible. pH greater than 7.2 had little effect on mu. Membrane surface elasticity is not affected by variations in external [Ca2+] over the range of 0--50 mM, tonicity of the suspension medium from 275--400 mosM, or age of 0--50 h. Addition of 50 mM NaHCO3 to the medium increases the rate of change of mu at a given pH. These results suggest that the elastic properties of the red cell membrane are largely determined by interactions among structural proteins located on the cytoplasmic surface of the membrane and that these interactions are initiated by changes in intracellular pH.

Is hexokinase present in the basal lateral membranes of rat kidney proximal tubular epithelial cells?

The possible presence of hexokinase in basal lateral membranes from rat kidney proximal tubules was investigated. Basal lateral membranes were obtained from homogenates of rat kidney cortex by differential centrifugation and free flow electrophoresis. They were further purified by density gradient centrifugation. Hexokinase activity was measured as the phosphorylation of D-[U14C]glucose. Throughout the purification of the membranes, the specific activity of hexokinase decreased while that of (Na+ + K+)-ATPase increased. Hexokinase activity in all fractions could be quantitatively accounted for in terms of cytosolic and mitochondrial enzyme contributions. It is concluded that there is no hexokinase activity in basal lateral membranes from rat kidney.