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J M Barrett

Publications and source records attributed to J M Barrett.

47 records · Page 3Linked to original sources
PubMed1979

The ultrastructural localization of membrane ATPase in rat thin limbs of the loop of Henle.

The cytochemical distribution of nonspecific membrane ATPase activity in the epithelial membranes of the thin limbs of the loops of Henle of rat nephrons was studied at the ultrastructural level. Membrane ATPase activity was localized in the luminal, lateral, and (to a lesser extent) basal membranes of only the outer medullary segment of the thin descending limbs of long nephrons (Type II epithelium). The reaction product was lacking in the thin limb of short nephrons (Type I epithelium) as well as in the inner medullary descending (Type III epithelium) and ascending (Type IV epithelium) segments of the thin limbs of long nephrons. These data reinforce the concept of thin limb heterogeneity and may indicate a specialized role for the outer medullary segment of thin descending limbs of long nephrons in the concentrating mechanism.

Adenosine Triphosphatases↗
PubMed1975

The structural organization of the kidney of the desert rodent Psammomys obesus.

The architecture of the desert rodent Psammomys obesus has been studied by means of standard histologic procedures and by single nephron injections. As other rodent kidneys (rat, mouse), the Psammomys kidney consists of two types of nephrons, 66% short looped and 34% long looped nephrons. The cortex is composed of 4 to 5 layers of glomeruli, which lie closely put together, the glomeruli often touch each other. The superficial and the midcortical glomeruli give rise to short looped neophrons, the juxtamedullary to long looped nephrons. In the strongly developed medulla the inner stripe shows the most striking pattern. It consists of two distinct compartments, that of the giant vascular bundles and that of the interbundle regions. The giant vascular bundles consist of about 8 to 14% arterial vasa recta and 39 to 47% venous vasa recta; furthermore they include the thin descending limbs of the short loops of Henle which amount to 44 to 51% of the bundle structures. The tubules of the interbundle regions surround the bundles in a regular pattern. The inner zone is almost completely surrounded by the renal pelvis; the long broad papilla protrudes into the ureter. The thin descending limbs of short looped nephrons traverse the inner stripe inside the giant vascular bundles. Leaving the bundles they turn back within the inner stripe; their ascending limbs lie in the interbundle region. Both limbs of the long loops of Henle run in the interbundle region, together with the ascending limbs of the short loops and the collecting ducts. The long loops penetrate deeply the inner zone. Many bends are found near the tip of the papilla. The renal pelvis has a very specialized form. It penetrates the inner stripe with many complexely shaped extensions, which surround the giant vascular bundles. Large parts of the bundles with their thin walled structures are thus separated from the pelvic urine only by a single layer of cuboidal epithelium. The possible functional importance of the described specializations of the Psammomys kidney (giant vascular bundles, large inner zone, special shape of the renal pelvis) for the urine concentrating and urea recyclng mechanisms is discussed.

Animals↗
PubMed1975

The ultrastructure of the thin loop limbs of the mouse kidney.

The thin limbs of the loops of Henle in the mouse kidney have been investigated by conventional electron microscopy. Resulting from light microscopic investigations, a distinction in the epithelia of short and long loops can be demonstrated. Ultrastructurally, the thin limbs (descending) of short loops are composed of a uniformly thin and simple epithelium. In contrast, long loops (thin descending and ascending) are composed of three different epithelial types which are representative of a distinctly more complex epithelial system. Two epithelial types were observed in the thin descending limbs of long loops and the third type was observed in the ascending thin limbs. Based upon these findings it is suggested that the thin descending limbs of short and long loops of Henle in the mouse kidney cannot perform the same functions in the renal concentrating mechanism.

Animals↗
PubMed1975

Microbodies of the rat renal proximal tubule: ultrastructural and cytochemical investigations.

The present study was undertaken to provide a detailed morphological and cytochemical characterization of the microbodies of the rat renal proximal tubule following perfusion fixation. The following observations were made: 1) Two basic types of microbodies (Mb-I and Mb-II) can be identified. Mb-I have both circular and tubular profiles which are located peripherally within the granular matrix of these microbodies. Mb-II have marginal plates and crystalloid inclusion in addition to circular and tubular profiles. 2) Circular and tubular profiles, 100 nm in diameter, described by previous investigators as being infrequent in occurrence, are the most consistent morphological characteristic of rat renal microbodies after perfusion fixation. These profiles have a homogeneous center surrounded by a double or single ring of granules. The uniform size and spacing of these granules within profiles establish a basic 100 A periodicity found in both types of microbodies. 3) Evidence is presented which suggests that both "nucleoids" and "tubular protrusion rods" as described by other investigators of the rat renal microbodies may result from poor fixation and/or osmotic stress. 4) The density of the matrix of Mb-I is, in contrast to previous reports, greater than the density of adjacent mitochondria. 5) Marginal plates or crystalloid inclusions were demonstrated in some microbodies (Mb-II) of all the rats studied; periodicities of 100, 200, and 300 A were identified within these structures. 6) Both types of microbodies were positive for catalase activity, but were negative for acid phosphatase activity. On the basis of both morphological and cytochemical criteria, it seems plausible that these two populations of renal microbodies (Mb-I and Mb-II) represent a morphological and functional continuum.

Acid Phosphatase↗