Communications

Abstract It has been reported that sialic acid (N-acetylneuraminic acid, NANA) is an integral component of a group specific carbohydrate hapten (1) and a lipopolysaccharide (2) in Group C meningococci. Recent reports (3, 4) suggest the occurrence of sialic acid in carbohydrate antigens, presumably lipopolysaccharides (LPS), extracted from cells of serogroups A, B and C. Unpublished studies in this laboratory of LPS derived from Group B organisms have revealed that sialic acid, although present in whole cells, is not a component of their purified LPS. The positive reactions observed with hydrolysates of LPS in the thiobarbiturate (TBA) test (5) commonly used to estimate sialic acids could be attributed to the presence of keto-deoxyoctonic acid (KDO), which was identified by paper chromatography. To clarify this situation, 19 strains of meningococci were examined as to the distribution of sialic acid and KDO in them. Each was incubated on a shaker for 18 hr in liter volumes of Mueller-Hinton broth, treated with 0.5% formaldehyde, harvested by centrifugation, washed with saline and dried with acetone.</jats:p

A role for podocytes to counteract capillary wall distension

A role for podocytes to counteract capillary wall distension. In a previous study of the changes in glomerular structure in the isolated perfused kidney (IPK), perfusion at high pressures lead to an enlargement of the glomerular tuft and to the formation of giant capillaries. The present paper analyzes the morphological and dimensional changes of the peripheral glomerular capillary wall under these circumstances. The enlargement of glomerular capillaries at high pressure perfusion was accompanied by a considerable increase in the surface area of the glomerular basement membrane (GBM). The podocyte as well as the endothelial layer perfectly adapted to the acute challenge in covering increasing GBM area. The interdigitating foot process pattern showed up in an ideal arrangement. The capillary wall expansion was associated with a significant increase in total pericapillary slit area. Compared to the corresponding low pressure groups (65mm Hg, without and with the application of vasodilators) the slit area increased in the high pressure groups (105mm Hg, without and with vasodilator) by approximately 50 and 75%, respectively. This increase of the slit area was mainly due to an increase in slit length; the slit width remained fairly constant. These findings indicate that the pericapillary wall is distensible based on a distensibility of the GBM. We suggest that the contractile apparatus of podocyte foot processes regulates the expansion of the GBM

Changes in glomerular structure following acute mesangial failure in the isolated perfused kidney

The glomerular tuft is a complex network of tortuous anastomosing capillaries supported by an axial mesangial stalk and invested with a tough basement membrane “sack,” which is itself surrounded by a layer of visceral epithelial cells. Under normal conditions, the complex architecture of the capillary tuft is maintained despite a high transmural hydrostatic pressure gradient which should favor capillary expansion. Some of the mechanical details of the way in which mesangium and GBM function as an integrated unit to resist capillary expansion have recently been examined [1–3]