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Biomedical subjects

L P Sullivan

Publications and source records attributed to L P Sullivan.

At least 37 records · Page 2Linked to original sources
PubMed1990

Small-bowel obstruction caused by a long-term indwelling urinary catheter.

The first known case report of a small-bowel obstruction caused by a long-term indwelling Foley catheter is presented. The balloon of the catheter passed into and obstructed the lumen of the distal ileum through a vesicoenteric fistula created by chronic irritation. With the exception of recurrent urinary-tract infections, complications of urinary catheters are rare. The patient presented a diagnostic dilemma that was solved with a preoperative computed tomographic scan.

Aged↗
PubMed1989

Volume regulation determinants in isolated proximal tubules in hypertonic medium.

Isolated nonperfused proximal tubules maintained their cell volume at a constant level [isovolumetric regulation (IVR)] when extracellular osmolality was gradually increased above 295 mosmol at 1.5 mosmol/min. Cell volume remained constant between 295 and 361 +/- 7 mosmol in medium containing HCO3- -CO2 as the major buffer. In N-2-hydroxyethyl piperazine-N'-2-ethanesulfonic acid-buffered medium, IVR maintained cell size constant between 295 and 370 +/- 11 mosmol; thus, the volume regulatory process did not require the presence of external HCO3- -CO2. Omission of medium phosphate and sulfate from defined bathing medium had no effect on the volume regulatory process, whereas acetate (5 mM) was required to maintain cell volume constant. Hypertonic IVR was inhibited by acetazolamide (10(-6) M), 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (2.5 x 10(-5) M), and, in medium in which choline replaced all but 25 mM of Na+, amiloride (1 mM). These results suggest the involvement of carbonic anhydrase, Cl-, and HCO3- transport, and Na-H exchange in IVR; and provide indirect support for the view that IVR in hyperosmotic medium depends on the intracellular accumulation of electrolytes resulting from altered rates of membrane ionic exchange mechanisms.

Animals↗
PubMed1989

Disruption of the proximal anastomosis of axillobifemoral grafts: two case reports.

The use of axillobifemoral grafting in the treatment of infected aortic prostheses or in the treatment of patients at high risk for aortoiliac occlusive disease has become a widely accepted treatment modality. Few complications involving the proximal anastomosis have been reported. The present report describes two patients who suffered proximal anastomotic dehiscence several weeks after surgery when they fully extended and raised the affected arm.

Aged↗
PubMed1988

Intracranial lesions shown by CT scans in 259 cases of first alcohol-related seizures.

We obtained CTs in 259 patients with a first alcohol-related convulsion. Each subject had generalized convulsions, recent abstinence from alcohol abuse, and no obvious etiology for seizures other than alcohol withdrawal. Patients with only focal seizures, major head injury, coma, or a severe toxic-metabolic disorder were excluded. We recorded history and signs of minor head injury, presence of headache, level of consciousness, neurologic signs, routine medical examination findings, and subsequent clinical course. Sixteen patients (6.2%) had intracranial lesions on CT. Eight had subdural hematomas or hygromas, two had vascular malformations, two had neurocysticercosis, and one each showed a Berry aneurysm, possible tumor, skull fracture with subarachnoid hemorrhage, and probable cerebral infarction. In ten cases (3.9%), clinical management was altered because of the CT result. History or signs of minor head trauma, headache, level of consciousness, or focal neurologic signs did not significantly correlate with CT abnormality.

Adult↗
PubMed1988

Resolution of syringomyelia and Chiari I malformation by ventriculoatrial shunting in a patient with pseudotumor cerebri and a lumboperitoneal shunt.

A sneeze caused acute left arm pain in a 36-year-old woman with a lumboperitoneal (LP) shunt that had been placed 3 years earlier for relief of headaches caused by pseudotumor cerebri. Numbness progressed up the left arm, neck, and back of the head and finally into the left face along with weakness of the hand and arm. Magnetic resonance imaging (MRI) and computed tomography revealed new tonsillar herniation and a large eccentric syrinx extending from C2 to T6. The functioning LP shunt was clamped, and a ventriculoatrial shunt was placed. Pain lessened and motor function improved slightly. MRI revealed complete resolution of the syrinx and resolution of the tonsillar herniation. Theories of syringomyelia formation, the relationship to Chiari I malformation, and the implications of this case are discussed.

Adult↗
PubMed1986

Renal compensation of hypercapnia in prolonged hypoxia.

We previously showed that rats made hypoxic for three weeks were able to regulate their plasma pH better than normoxic rats during acute hypercapnia. This improved pH regulation was abolished by nephrectomy, suggesting that it was due, at least in part, to a more effective renal compensation of hypercapnia in hypoxic rats. To test this possibility renal acid excretion was measured in conscious rats that had been kept at PB 370-380 Torr for three weeks. The rats were studied in a chamber where PIO2 was kept at 68-70 Torr at ambient PB (740-750 Torr). Controls were pair-fed normoxic rats. After a 2 h control period, inspired PCO2 was increased for 4 h. The apparent non-bicarbonate buffer value of arterial blood plasma was twice as high in the hypoxic than in the normoxic rats. Renal excretion of ammonium increased to a similar extent during hypercapnia in both normoxic and hypoxic rats. Titratable acid excretion of normoxic rats did not change significantly during hypercapnia. In the hypoxic rats, on the other hand, total excretion of titratable acid in the 2 h control period was 90.9 +/- 16.4 mumol/rat; and increased to 150.0 +/- 13.4 mumol/rat in the first 2 h and to 232.9 +/- 26.0 mumol/rat in the last 2 h of hypercapnia. In spite of this large increase in acid excretion, urine pH of hypoxic rats did not change significantly, indicating a higher buffer value of the urine of hypoxic rats. These results confirm our previous observations and support the idea that the improved pH regulation of hypoxic rats is due in part to a more effective renal compensation of hypercapnia.

Animals↗
PubMed1986

Effect of barium on potassium transport in amphibian kidney.

We have examined the effect of barium on K excretion and transport in the perfused frog kidney. The transepithelial secretory flux of K was calculated from the rate of excretion of 42K from the portal circulation. Barium was applied to the basolateral surfaces of the tubules via the portal circulation. Barium (0.1 mM) increased fractional K excretion from 55 to 178% by stimulating the K secretory flux; 0.5 mM Ba increased fractional K excretion from 39 to 386% primarily by increasing the secretory flux greater than 10-fold. Tissue content increased 10%. When Ba was applied to both the apical and basolateral surfaces by perfusion of the arterial circulation, K excretion and secretion also increased. This same result was obtained when K secretion was first stimulated by acetazolamide. In another series of experiments, tubular cells were loaded with 42K via a pulse injection into the portal circulation, and simultaneous washout of the isotope into the urine and the venous effluent was measured. Analysis of the washout curves revealed that basolateral (portal) application of Ba inhibited efflux of K from the cells into the circulation, reduced the influx from the circulation, and stimulated efflux into the urine. We suggest that blockade of K channels in the basolateral membrane indirectly depolarizes the apical membrane and thereby increases the electrochemical gradient favoring K movement from cells to tubular fluid. When Ba is applied simultaneously to both tubular surfaces, the effect on the basolateral surface apparently overrides any direct effect it may have on K movement across the apical surface. Using 133Ba, we measured a very small transepithelial perfusate-to-tubular fluid flux. However, fractional Ba reabsorption averaged 19% when 0.5 mM Ba was present in the arterial perfusate.

Animals↗
PubMed1985

Effect of barium on cell volume regulation in rabbit proximal straight tubules.

Rabbit proximal straight tubules swell abruptly when exposed to hypotonic medium but then shrink in a few minutes as they approach their base-line volume following loss of solute and water. Potassium, the major intracellular cation, as well as sodium, is lost during this process. In the present experiments, we studied hypotonic cell volume regulation in the presence of barium, an agent reported to decrease potassium permeability. Exposure to BaCl2 significantly prolonged hypotonic volume recovery in a dose-dependent manner. Tubules depleted of potassium and loaded with sodium chloride by exposure to 10(-4) M ouabain for 1 h swelled osmometrically and subsequently volume regulated in dilute medium. Volume regulation in such tubules is a consequence of transbasement membrane hydrostatic forces. By contrast, tubules similarly loaded with sodium, but also exposed to 10(-3) M BaCl2, volume regulated only minimally in dilute medium, suggesting BaCl2 might also affect sodium movement. However, hypotonic volume regulation was restored in sodium-loaded BaCl2-treated tubules when cells were more effectively depleted of potassium by incubation in 0-mM potassium medium. We conclude that barium retards hypotonic volume regulation primarily because of its effect on potassium movement.

Animals↗
PubMed1984

Ion transport by rabbit descending colon: mechanisms of transepithelial potassium transport.

In vitro preparations of rabbit descending colon were studied under steady-state short-circuit conditions to determine 1) the K concentration dependence of unidirectional K fluxes; 2) the effects of the K channel blocker barium and the diuretic agent furosemide; and 3) the steady-state tissue specific activity of 42K when added to the luminal bathing solution. Results from these studies reveal that 1) labeling of cellular K from the mucosal solution is less than 25% of that from the serosal solution; 2) both unidirectional K fluxes are composed of saturable and nonsaturable components; 3) the serosal-to-mucosal saturable component is abolished by ouabain, and subsequent addition of 2,4-dinitrophenol abolishes the saturable component of the mucosal-to-serosal K flux; 4) luminal or serosal barium alters K transport in a manner consistent with the presence of barium-sensitive K conductances at both membranes; 5) luminal furosemide did not alter K transport; and 6) there is no shunt selectivity for K. We conclude that the majority of both unidirectional K fluxes follow a transcellular pathway and that both the apical and basolateral membranes possess active K uptake mechanisms and barium-sensitive K exit mechanisms.

2,4-Dinitrophenol↗
PubMed1983

Localization of tissue potassium pools in the amphibian kidney.

Techniques were developed to determine the location of exchangeable K pools that had been identified previously in kinetic studies of the intact perfused bullfrog kidney. Following perfusion of the kidneys with 42K, a washout of the isotope was begun and interrupted at various times; the kidneys were removed, frozen, dried at low pressure and temperature, and then microdissected. Glomerular capillary tufts, small segments of tissue containing early distal tubules (diluting segment), and other segments containing proximal tubular convolutions were removed and analyzed for total content of K and 42K. In the intact kidney 77% of tissue K exchanged in 60 min. The exchangeable K concentration was 95 mu eq/ml cell water. Correction for the K activity coefficient in Ringer solution yielded an activity of 72 mu eq/ml. Thirty-two percent of glomerular capillary K exchanged in 60 min; 7% exchanged with a half time of 3.5 min; and the remainder exchanged at a rate too slow to measure. The data from tissue containing proximal tubular segments were too scattered to permit analysis. In segments containing early distal tubules, 67% of tissue K was contained in two exchangeable pools: one pool exchanged at a rate 10-fold greater than did the other. The data for these two distal pools were analyzed in terms of a parallel model (two cell types?) and a nested model (cytoplasm and subcellular organelles?). Pool size and exchange rates were calculated for both models. Electron microscopic analysis revealed that early distal tubular segments contain only one cell type which has a large population of mitochondria. This suggests that the nested model is more plausible. The fast distal pool exchanged at the same rate as the fast-exchanging pool identified in kinetic studies of the intact functioning kidney and is considered to be the K secretory pool.

Animals↗
PubMed1982

Potassium transport by rabbit descending colon.

Unidirectional mucosal-to-serosal (Jm leads to s) and serosal-to-mucosal (Js leads to m) fluxes of potassium and sodium were determined simultaneously on paired sections of descending colon from the same rabbit under short-circuit conditions. In 13-16 pairs of tissues, net potassium secretion and sodium absorption averaged 0.49 +/- 0.08 and 4.0 +/- 0.8 mueq.cm-2.h-1, respectively. Short-circuit current (Jsc) averaged 3.7 +/- 0.4 mueq.cm-2.h-1 and was approximately equal to the algebraic sum of net potassium and sodium fluxes. Treatment of both sides of the colon with 10(-4) M ouabain reduced the Jsc and transmural potential difference to near zero. Ouabain abolished net potassium secretion by reducing JKs leads to m and abolished net sodium absorption by inhibiting JNam leads to s. In the presence of ouabain, net potassium absorption averaging 0.15 +/- 0.07 mueq.cm-2.h-1 (n = 11) was observed. In the presence of 10(-3) M 2,4-dinitrophenol, both net potassium and net sodium fluxes were abolished, primarily as a result of a reduction in JKs leads to m and JNam leads to s without altering JKm leads to s and JNas leads to m. These results suggest that the rabbit descending colon has the capacity to secrete and possibly to absorb potassium by active mechanisms requiring metabolic energy. Comparison of potassium and sodium fluxes suggest that the paracellular pathway in the rabbit colon is not potassium selective.

Animals↗
PubMed1981

Effects of sodium and chloride on potassium transport by the bullfrog kidney.

We have studied the effect on K transport of reductions in the Na and Cl concentrations of solutions perfusing the isolated bullfrog kidney. We used recently developed techniques for estimating the unidirectional reabsorptive and secretory K fluxes. Reduction of Na and Cl concentrations in the arterial perfusate from 112 and 100 mM to 22 and 10 mM, respectively, inhibited K secretion 82% and K reabsorption 97%. Reduction of only the Na concentration inhibited K secretion 42% but did not affect K reabsorption. Arterial and portal perfusion with 37 mM Na, 23 mM Cl reduced urine Na concentration to 6 mM and Na reabsorption by 59%. However, K secretion rose 88% and reabsorption fell 76%. Arterial and portal perfusates with 37 mM Na, 100 mM Cl reduced urine Na concentration to 2 mM and Na reabsorption by 46%. Still, K secretion was elevated 57% by an increase in urine flow rate. K reabsorption was not reduced. Arterial and portal perfusates with 112 mM Na, 23 mM Cl, and containing SO4 also stimulated K secretion 26% and inhibited K reabsorption 91%. Thus, reduction of perfusate Na concentration to 22 mM inhibited secretion but 37 mM was sufficient to permit stimulation of secretion by low Cl concentrations and by increased tubular fluid flow rate. Reduction of the perfusate Cl concentration stimulated secretion and inhibited reabsorption. We conclude that a minimum level of Na reabsorption is required to maintain K secretion, but above that minimum level changes in the rate of Na reabsorption do not affect the rate of K secretion. The tubular fluid Cl concentration or the rate of Cl reabsorption affects both reabsorption and secretion of K and, therefore, may be an important regulator of the rate of K excretion.

Absorption↗
PubMed1979

Effects of ouabain on potassium transport in the perfused bullfrog kidney.

We studied the effect of ouabain on transepithelial and cellular potassium transport in the isolated perfused bullfrog kidney. We used recently developed techniques for estimating the unidirectional reabsorptive and secretory K fluxes (Jr and Js) and measuring the kinetics of cellular K transport. Two hours of perfusion with 1 X 10(-6) M ouabain did not affect GFR, reduced fractional Na reabsorption 57%, increased K excretion 41%, and inhibited Jr 34%. Js rose 68% at 60 min and then returned to the control level. Ninety minutes of perfusion with 5 X 10(-6) M ouabain reduced GFR 28% and fractional Na reabsorption 76%. K excretion rapidly increased 71% within 30 min and then fell to 60% of the control level, while Jr fell 64%. Js rose 42% in 30 min and then fell to 23% of the control level. Both doses reduced K uptake into cellular pools from the circulation and increased the rate coefficients for efflux into tubular fluid. The data indicate that ouabain inhibited reabsorption and transiently accelerated the rate of loss of K from the cells into the tubular fluid. This initially masked the ultimate inhibition of K secretion from the circulation into the tubular fluid.

Animals↗
PubMed1978

Potassium reabsorption and secretion in the perfused bullfrog kidney.

Techniques have been developed for obtaining comparative estimates of the rates of K secretion and reabsorption in the artificially perfused bullfrog kidney and the use of 42K infused into the portal circulation. In control experiments in which Kexc/Kfilt averaged 0.65, approximately 30% of filtered K escaped reabsorption and excreted K was composed of roughly equal parts of filtered K and secreted K. Fractional reabsorption of K was constant at 70% over a wide range of filtration rates. The rate of K secretion correlated significantly with the rate of Na reabsorption and with the urine flow rate. Acetazolamide stimulated secretion and inhibited reabsorption.

Acetazolamide↗
PubMed1977

Kinetic analysis of potassium transport in bullfrog kidney.

Techniques have been developed for studying the distribution and the rates of exchange of K among urine, the tubular cells, and the circulation in the isolated, pump-perfused, bullfrog kidney. Tubular cells were loaded with 42K via the portal circulation, and the subsequent washout of the tracer into the vena cava and into urine was measured. Analysis of the data indicated the existence of at least three cellular pools of K. Pools a and b have half times of exchange of 1.1 and 4.1 min and contain about 25 and 40% of tissue K, respectively. The remainder of cellular K is contained in one or more very slowly exchanging pools. The rate of exchange of K at the basolateral surface of tubular cells is 50-fold greater than at the luminal surface. A pulse-washout method was also devised to permit control and experimental measurements to be made in the same kidney. With this technique, we found that portal perfusion with 10 mM K increased the rate of uptake into pools a and b from the circulation and the rate constants for efflux into the urine from both pools, Acetazolamide increased uptake into pool a and the rate constants for efflux into the urine from both pools.

Acetazolamide↗