Antidiuretic hormone (ADH) promotes fusion of cytoplasmic tubules with the luminal membrane and delivery of particles from the tubules to the membrane. The particles are believed to be the water-conducting elements in the membrane. We have employed several scanning (SEM) and transmission electron-microscopic (TEM) techniques to study the relationship of the cytoplasmic tubules to the luminal membrane and to the apical cytoskeleton of the toad bladder epithelial cell. This paper reports the results of freeze-crack SEM and tannic acid-fixed TEM studies, as well as studies with a resinless method of embedding. Freeze-cracked epithelial cells reveal that the tubules are anchored in a matrix of cytoskeleton and granules just below the luminal membrane, and many, if not all, retain their anchorage to the matrix after ADH-induced fusion. Tannic acid-fixed specimens show that the tubules in unstimulated cells lie horizontally. Fusion appears to involve an angulation of the tubules, and this may be the major mode of ADH-induced tubule movement. There are suggestions in the tannic acid sections of filamentous attachments of tubules to the surrounding cytoskeleton. In addition there are prominent microfilament bundles running down the microvilli and a dense concentration of filaments just below the luminal membrane. The presence of these filaments is confirmed in the resinless sections, and their possible role in ADH action is discussed.

Animals↗

PubMed1984

Examination of transepithelial exchange of water and solute in the rat renal pelvis.

Severance of the ureter beyond the renal papilla causes a fall in urinary osmolality, which suggests that exchange of water or solute between urine and renal parenchyma normally occurs in the intact renal pelvis. We examined water and solute flux in the renal pelvis with micropuncture and microcatheterization techniques. Four groups of antidiuretic rats were studied. Group I (n = 17) underwent micropuncture through the intact contracting ureter. Urine samples were obtained at the papillary tip, and in the pelvis beside the base of the extrarenal papilla. Urinary osmolality at the base, 880 +/- 97 mosmol/kg H2O (mean +/- SE), was less than that at the tip, 1,425 +/- 104 mosmol/kg H2O (P less than 0.005). In group II (n = 24), samples were analyzed for inulin and osmolality. In 15 rats (group IIA), comparison was made between base and tip samples. In the other nine animals (group IIB), comparisons were made among base, tip, and bladder samples and urea was also measured. In group II (A and B combined) urine-to-plasma (U/P) osmolality was lower at the base, 4.31 +/- 0.27, than at the tip, 6.08 +/- 0.23 (P less than 0.001), and U/P inulin was lower at the base, 192 +/- 25, than at the tip, 306 +/- 16 (P less than 0.001). In group IIB, the bladder urine had a lower U/P osmolality, 5.27 +/- 0.25, than the tip, 6.01 +/- 0.31 (P less than 0.02). The U/P urea was 59 +/- 10.6 (base), 98 +/- 9.4 (tip) (base vs. tip, P less than 0.05), and 81 +/- 6.5 (bladder, P less than 0.005, compared with tip). In group III (n = 8), samples were obtained by microcatheter from the fornices, the deepest intrarenal extensions of the pelvis, and compared with samples at the tip. Urinary osmolality was lower in the fornix, 646 +/- 106 mosmol/kg H2O, than at the tip, 1,296 +/- 99 mosmol/kg H2O (P less than 0.001). Similarly, U/P inulin was lower in the fornix, 48 +/- 14, than at the tip, 128 +/- 12 (P less than 0.001). The lower U/P inulin in the pelvic urine is the result of either the addition of fluid to the pelvis, or the backleak of inulin across the epithelium lining the pelvis. To verify that the pelvic epithelium was impermeable to inulin, in group IVA (n = 4) the left renal pelvis was superfused with a solution of chemical inulin. Cumulative absorption of inulin from the left kidney was 0.15 +/- 0.08% of that superfused. Using [14C]inulin in group IVB (n= 3), similar results were obtained (0.05 +/- 0.02%). These findings indicate that in the renal pelvis, fluid is added to urine after it emerges from the collecting ducts. We suggest that reflux of hyperosmotic urine over the renal papilla creates a transepithelial gradient for the flux of water into the pelvis. A model that incorporates diffusive and convective forces for water and solute transport is proposed to account for these findings.

Animals↗

PubMed1984

Neurological outcome correlated with spinal evoked potentials in a spinal cord ischemia model.

Occlusion of the abdominal aorta of the rabbit by inflating the balloon of a Swan-Ganz catheter positioned in the aorta is a simple and reliable method of producing spinal cord ischemia. The electrophysiological, neurological, and neuropathological correlates of ischemia with progressively longer durations and of ischemia after drug interventions were studied with the goal of developing an easily monitored, reproducible model for central nervous system ischemia. The percentage of animals developing paraplegia after varying periods of ischemia was zero after 15 minutes, 30% after 17 minutes, 33% after 20 minutes, 38% after 25 minutes, and 100% after 60 minutes of ischemia. After 25 minutes of ischemia the percentage of animals developing paraplegia was 87% when they were awake and not ventilated during ischemia and reperfusion, but dropped to 38% in animals that were paralyzed, sedated with ketamine, and ventilated, and when the metabolic acidosis that follows aortic occlusion was corrected during reperfusion. Pretreatment with thiopental, hypothermia, naloxone, methylprednisolone, and verapamil changed the percentage of animals developing paraplegia after 25 minutes of ischemia to 0%, 0%, 25%, 40%, and 100%, respectively. The component waves of the spinal somatosensory evoked potential (SSEP) disappeared sequentially during ischemia in the following order: P2, N4, N3, N2, and N1. After reperfusion, the SSEP components returned in reverse order of their disappearance. In the untreated animals, absence of the N3 wave for more than 10 minutes during ischemia was always followed by a neurological deficit. Pretreatment with thiopental or hypothermia permitted longer periods of electrophysiological silence without permanent neurological deficit. The ratio of the amplitude of N3 to N1 (N3/N1) was at least 70% of the control level, and N4 and P2 amplitudes were at least 30% of the control level at 120 minutes after reperfusion in all animals that had a normal outcome. Return of the N3/N1 amplitude to at least 90% of the control level or return of N3/N1 to 70% to 89% of control and P2 to at least 60% of control at 120 minutes after reperfusion reliably correlated with a normal 48-hour motor examination in animals with and without drug interventions.

Animals↗

PubMed1984

Clear the exercise hurdles for your diabetic patient.

Explore the source record for details and available documents.

Blood Glucose↗

PubMed1984

Collagen implant: an early assessment.

Injectable collagen has been used successfully to improve skin contour defects. This paper will briefly review the biosynthesis, the preparation, and the clinical application of this new material. Collagen is the major structural protein of the extracellular matrix and provides a scaffolding for the support cells. Skin collagen is composed of short fibriles grouped in bundles which are randomly orientated to provide strength and resiliency in all directions of the skin place.

Cicatrix↗

PubMed1983

Attachment and extracellular matrix differences between tendon and synovial fibroblastic cells.

Fibroblasts of the synovium of sheathed tendons were isolated, and their biochemical properties were compared with those of the fibroblasts of the remaining tendon. The synovial cells had a lower attachment efficiency than did the tendon cells. On the day of cell isolation the synovial cells synthesized collagen as 10% of their total protein, whereas the tendon cells synthesized 30% collagen. After growth in fetal bovine serum (FBS), the percentage of collagen synthesized by both populations decreased; however, the synovial cells still made less collagen than did the tendon cells (5 versus 11%). On the basis of cyanogen bromide peptide analysis, the synovial cells were found to synthesize Types I and III collagen in primary culture, whereas the tendon cells synthesized only Type I. The synovial cells also synthesized two to three times less sulfated glycosaminoglycans in culture than did the tendon cells. Thus, the two cell populations differed in attachment efficiency and in their biosynthesis of collagen and sulfated glycosaminoglycans. These differences reflect extracellular matrix differences that have been observed in the tendon in vivo. In addition, the results augment existing data showing that not all fibroblasts have identical phenotypes.

Animals↗

PubMed1983