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Biomedical subjects

G Capasso

Publications and source records attributed to G Capasso.

At least 163 records · Page 9Linked to original sources
PubMed1977

Coupling between proximal tubular transport processes. Studies with ouabain, SITS and HCO3-free solutions.

The rate of active transport by the proximal renal tubule of amino acid (L-histidine), sugar (alpha-methyl-D-glycoside), H+ ions (glycodiazine), phosphate and para-aminohippurate was evaluated by measuring the zero net flux concentration difference (deltac) of these substances. In the case of calcium the electrochemical potential difference (delta + zF-CIdeltaphi/RT) was the criterion employed. The rate of isotonic Na+-absorption (JNa) was measured with the shrinking droplet method. The effect of ouabain on the transport of these substances was tested in the golden hamster and the effect of SITS (4-acetamido-4'isothiocyanatostilbene 2,2'-disulfonic acid) was observed in rats. Ouabain (1 mM) applied peritubularly incompletely inhibited JNa (80%), but in combination with acetazolamide (0.2 mM) the inhibition was almost complete (93%). In addition, ouabain inhibited the sodium coupled (secondary active) transport processes of L-histidine, alpha-methyl-D-glycoside, calcium and phosphate by more than 75%. It did not affect H+ (glycodiazine) transport and PAH transport was only slightly affected. When SITS (1 mM) was applied from both sides of the cell it inhibited H+ (glycodiazine) transport by 72% and reduced JNa by 38% when given from only the peritubular cell side. SITS (1 MM), however, had no significant affect on H+ secretion and sodium reabsorption if it was applied from only the luminal side. Furthermore it had no affect on the other transport processes tested, regardless of the cell side to which it was applied. When the HCO-3 buffer or physically related buffers were omitted from the perfusate the absorption of Na+ was reduced by 66%, phosphate by 44%, and L-histidine by 15%. All the other transport processes tested were not significantly affected. The data are consistent with the hypothesis that the active transport processes of histidine, alpha-methyl-D-glycoside and phosphate, which are located in the brush border, are driven by a sodium gradient which is abolished by ouabain. This may also apply to the Na+-Ca2+ countertransport located at the contraluminal cell side. The residual Na+ transport remaining in the presence of ouabain is likely to be passively driven by the continuing H+ transport which probably is driven directly by ATP. SITS seems to inhibit the exit step of HCO-3 from the cell and secondary to that, the luminal H+-Na+ exchange and consequently the Na+ reabsorption. In the absence of HCO-3 buffer in the perfusates the luminal H+-Na+ exchange seems to be affected and the pattern of inhibition of the other transport processes is almost the same as with SITS. The different effects on Pi reabsorption observed under these conditions might be explained by possible variations in intracellular pH.

Animals↗
PubMedDate not supplied

Glove perforation in pediatric orthopaedic surgery.

Three hundred eighty-three pairs of gloves were tested for punctures after 100 consecutive pediatric orthopaedic operations to assess the rate, site, procedure, and maneuver during which glove puncture accidents took place. Evidence of perforation was found in 14% of the gloves used. Surgeons appear to be significantly more at risk for glove perforation than do other members of the operating team.

Child↗
PubMedDate not supplied

Conventional and confocal epi-reflection and fluorescence microscopy of the rat kidney in vivo.

To visualize superficial and accessible renal tubule cells functioning in situ and to relate what we can 'see' to what we know of their function from more invasive in vivo or less direct in vitro studies means applying and adapting recent advances in epifluorescence and confocal microscopy to improve image resolution and to combine this with the use of fluorescent labels to monitor the handling of specific molecules by the proximal and distal renal tubule cells in vivo. Doing this in living tissue is novel, especially in the kidney. Application of confocal microscopy to the imaging of living tissue, as opposed to isolated cells, has not been widely reported. The kidney surface has been imaged before using the confocal microscope and in preliminary studies we have extended this by using a different confocal system with and without fluorescence. While the studies published up to now have been morphological, comparing standard renal (structural) histology of surface glomeruli and renal tubules with the corresponding in vivo confocal images, more dynamic, real-time studies have been limited. Individual red blood cells can be seen flowing around the peritubule capillary network and nucleated white blood cells can also be distinguished. Tubule cells, endothelial cells, the proximal tubule cell brush border and cell mitochondria can be visualized. Filtration and secretion can be observed, and the early and late parts of the proximal tubule distinguished, and the distal tubule recognized. Localization of fluorescently labeled insulin to the luminal brush border and progressive uptake of label and distribution within proximal tubule cells toward the basolateral (blood side) membrane can be demonstrated. The possibility of monitoring hemodynamic changes and tracking the filtration, uptake, secretion and absorption of fluorescently tagged molecules, as well as intracellular fluorescence, e.g. calcium or pH, is an exciting prospect and is ripe for detailed exploration.

Animals↗
PubMedDate not supplied

Effects of thyroid hormones on heart and kidney functions.

Thyroid hormones affect the functions of several organs including the heart and kidney. Using isolated left papillary muscles we have investigated the action of thyroid hormones on the mechanical and electrical properties of the heart. We found that pure hypothyroidism causes a depression in contractile and electrical parameters, but we noticed that superimposed hypoparathyroidism accounts for the marked prolongation in contractile kinetics and action potential duration. At kidney level we have shown that thyroid hormones affect proximal tubular sodium transport and this effect is only partially mediated by the action of thyroid hormones on Na-K-ATPase activity. Using the micropuncture technique, we hypothesized that the early effect of thyroid hormone action is on the potassium permeability of proximal tubular cell membrane. This latter effect would explain the increase in isotonic fluid reabsorption through an increase in the driving force for sodium. Finally, hypothyroid patients have a decrease in glomerular filtration rate and renal plasma flow that are completely reversed by thyroxine administration. On the other hand, hyperthyroid subjects exhibit a significant increase in both parameters.

Animals↗
PubMedDate not supplied

Renal handling of sodium after an oral protein load in adult humans.

This investigation was designed to study (1) renal sodium handling after an oral protein load and (2) its relationship to some known determinants of the hemodynamic response (glucagon, insulin, growth hormone, renin, aldosterone, and plasma amino acid concentration). To this end of group of 8 adult subjects was studied before (three 30-min clearances) and after a meat meal (MM; five 30-min clearances at 30, 60, 90, 120 and 180 min). The MM provided 2 g/kg BW of protein. Within 30 min from the MM an hyperfiltration response was seen, which was paralleled by a 2-fold increase in plasma alanine concentration while total plasma amino acid concentration was not different from the baseline values. The hemodynamic response was associated with a normally operating tubuloglomerular feedback mechanism independent of renin-aldosterone activity, but possibly associated with an early increase in plasma glucagon concentration and later on with a modest increase in postmeal plasma insuling concentration.

Adult↗
PubMedDate not supplied

Brain-gut peptides and the renal hemodynamic response to an oral protein load: a study of gastrin, bombesin, and glucagon in man.

With the aim of disclosing a possibility for gastrin and bombesin to participate in the postprandial regulation of the renal hemodynamic response, 10 healthy males were studied before and after a meat meal (2 g/kg BW of proteins as cooked red meat). We evaluated the time course changes of glomerular filtration rate (GFR) renal plasma flow (RPF), and the plasma concentrations of gastrin, bombesin, glucagon, and total amino acids. After the meat meal a significant increase in GFR and RPF was seen, within 30 min, along with an increase in plasma gastrin and glucagon. Bombesin and amino acid concentrations increased at a later time. The data suggest but cannot demonstrate a causal role for gastrin and glucagon in the genesis of the hyperfiltration response to acute protein administration.

Adult↗
PubMedDate not supplied

Results of percutaneous longitudinal tenotomy for Achilles tendinopathy in middle- and long-distance runners.

From August 1989 to January 1995 we performed multiple percutaneous longitudinal tenotomies under local anesthetic on 52 middle- and long-distance runners with unilateral Achilles tendinitis or peritendinitis that had failed conservative treatment. Forty-eight patients were reviewed at an average of 22.1 months (SD, 6.5) after surgery. Results were rated as excellent in 25 patients, good in 12, fair in 7, and poor in 4. Four patients developed subcutaneous hematomas. One patient developed a superficial infection at one of the incision sites, which was managed by oral antibiotics with full recovery. Three patients complained of over-sensitivity to the incisions; this was resolved by rubbing hand cream over the incisions several times a day. One patient developed hypertrophic painful scars on three of the five incisions, but corticosteroid injections yielded good functional and cosmetic results. Isometric strength and endurance of the gastrocsoleus complex was measured just before the procedure, and at 6 weeks and 6 months later. Both were within 10% of the normal contralateral limb by the 6th postoperative month. Percutaneous longitudinal tenotomy is simple, can be performed on an outpatient basis, requires minimal follow-up care, and, in our experience, has produced no significant complications. We use this procedure as the operative treatment of choice for cases of chronic tendinitis that have failed conservative treatment.

Achilles Tendon↗
PubMedDate not supplied

The use of micropuncture, isolated tubule, and vesicle technique in the study of the action of thyroid hormones on the proximal tubule function.

In hypothyroid rats (TX), the isotonic fluid reabsorption (Jv), that is closely linked to the transepithelial sodium transport (JNa), is impaired. The administration of physiological doses (10 micrograms/kg body weight per day) of tri-iodothyronine (T3) doubles Jv in three days (TX+T3). This phenomenon could be explained by several mechanisms: a direct stimulation of Na-K-ATPase, an increase in the Na+ entry step, changes in the permeability properties of the luminal and/or basal lateral membranes. Using a kinetic microassay, Na-K-ATPase activity was measured in early (S1) and late (S2) proximal tubules segments isolated from control, TX, and TX+3T3 animals. In TX rats the enzyme activity was lower (70%) in both segments versus control rats, it remained unchanged after 3 days, and it increased after 7 days of T3 substitution. The Na+ permeability of brush border membrane (BBM) vesicles isolated from TX and TX+T3 rats was identical. However the valuation of the K+ membrane permeability by in vivo perfusion of the lumen and peritubular space of proximal tubules of TX rats, with perfusate containing the K+ ionophore valinomycin (1 microgram/ml), induced a significant increase in Jv that accounted for 40% of that elicited by T3. Taken together, the in vivo and in vitro experiments suggest that the early effect on Jv of physiological doses of T3 cannot be explained by a direct action of T3 either on the Na+ entry step across the BBM or on the Na+ exit step (i.e., the Na-K-ATPase), but rather by an increase in K+ permeability of proximal tubular cell membranes.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMedDate not supplied

Cell volume regulatory mechanisms in progression of renal disease.

One of the striking morphological features of renal failure is an increase of cell volume. This review explores the role of cell volume regulatory mechanisms in the pathophysiology of progressive renal disease. The case is made that TGF-beta, a major cytokine involved in the development of progressive renal failure, upregulates the transcription of the serum and glucocorticoid-dependent kinase hSGK1, involved in cell volume regulation. Excessive extracellular glucose concentrations stimulate TGF-beta1 expression and thus similarly enhance hSGK1-transcription. The kinase stimulates two mechanisms important for cell volume regulation, i.e. the renal epithelial Na+ channel ENaC and the thick ascending limb Na+,K+,2Cl- cotransporter BSC1. On the one hand, stimulation of renal tubular transport leads to renal retention of Na+, which favours the development of hypertension. On the other, the increase of cell volume stimulates protein synthesis and inhibits protein degradation, contributing to the enhanced net formation and deposition of matrix proteins. At later stages, the increase of cell volume may be reversed to atrophy, and cell death may lead to loss of functional tissue. In conclusion, progressive renal disease is paralleled by deranged cell volume regulatory mechanisms.

Activin Receptors, Type I↗
PubMedDate not supplied

Achilles tendon rupture in athletes: histochemistry of the triceps surae muscle.

Bilateral percutaneous muscle biopsies of the triceps surae were analyzed in 12 athletes who had sustained a one-sided subcutaneous rupture of the Achilles tendon while practicing their main sport. No necrosis, atrophy, or significant fiber grouping or regeneration was evident. The soleus muscle in these athletes was composed of approximately 70% of type I fibers in both the noninjured and injured sides, and no significant differences were detected in their histochemical composition. Fiber areas were within described values and not significantly different between the two sides. The noninjured side revealed an insignificant trend to greater average capillary density and average capillary/fiber ratio. Muscle abnormalities do not appear to be a significant factor in determining Achilles tendon rupture in healthy athletes.

Achilles Tendon↗
PubMedDate not supplied

Clearance studies on the renal action of porins extracted from Salmonella typhimurium.

The effects of porins on renal hemodynamics and on the renal handling of salt and water were studied in rats. The animals injected with 100 micrograms/kg of porins showed an important change in renal potassium handling. In fact the total potassium excretion decreased significantly (p less than 0.02) from 1.11 +/- 0.13 to 0.495 +/- 0.069 muEq/min/100 g and was significantly associated to a reduction of fractional potassium excretion from 21.6 +/- 4.1% to 12.53 +/- 0.95% (p less than 0.001). It is speculated that porins have the capability to close the potassium channels.

Animals↗
PubMedDate not supplied

IgA glomerulonephritis in Wiskott-Aldrich syndrome.

Renal morphology was evaluated in 2 siblings with Wiskott-Aldrich syndrome (WAS) aged 12 and 4 years. They gave a typical history of recurrent episodes of respiratory infection and presented with microhematuria of glomerular origin and proteinuria. The study disclosed a membranoproliferative glomerulonephritis with IgA mesangial deposition in the elder child, while immunofluorescence was negative in the younger. The data indicate that (1) a specific nephropathy does not exist in WAS and (2) the IgA nephropathy is the result of recurrent infections and of related formation of IgA immune complexes scarcely removed by a deficient reticuloendothelial system. This view is consistent with presenting features in WAS (microhematuria, episodes of macrohematuria, proteinuria, Henoch-Schönlein syndrome) and with the fact that it takes years to develop as indicated by the negativity of immunofluorescence in the younger patient.

Child↗