Biomedical subjects

J R Potts

Publications and source records attributed to J R Potts.

At least 37 records · Page 2Linked to original sources

PubMed1992

Urea exchange across the human erythrocyte membrane measured using 13C NMR lineshape analysis.

The 13C NMR spectrum of 13C-urea in a suspension of human red cells of reduced mean cell volume was observed to contain partially resolved resonances arising from the intra- and extracellular populations of the compound. It was shown that at 25 degrees C and a magnetic field strength of 9.4 T, the rate of exchange of urea between the intra- and extracellular populations was such that the NMR lineshape was sensitive to a change in the rate of 13C-urea exchange, induced either by the addition of the urea transport inhibitor phloretin, or by the addition of 12C-urea. Total lineshape analysis of 13C NMR spectra of 13C-urea in red cell suspensions containing different concentrations of 12C-urea resulted in a weighted mean estimate for the Km and Vmax for urea equilibrium exchange from three experiments of 44 +/- 18 mM and 3.1 +/- 0.6 x 10(-8) mol cm-2 s-1, respectively (the errors denote the weighted mean standard deviations). These estimates of Km and Vmax were significantly lower than previous values reported in the literature and determined using other techniques.

Adult↗

PubMed1991

The phenomenon of separate intra- and extracellular resonances of difluorophosphate in 31P and 19F NMR spectra of erythrocytes.

Trifluoroacetate and trifluoroacetamide, when added to a suspension of human red blood cells, give rise to separate 19F NMR signals from the intra- and extracellular species. This phenomenon has recently been exploited for measuring the membrane potential of erythrocytes. However, the separation of the peaks was incorrectly ascribed to a difference in magnetic susceptibility between the intra- and extracellular environments. Previously, we have reported well-resolved resonances in 31P NMR spectra for the intra- and extracellular populations of some phosphoryl compounds; in these cases, however, the intracellular peak is shifted to low frequency which is the opposite to the situation with the fluorinated compounds. By using difluorophosphate, which rapidly equilibrates across the membrane of human erythrocytes and which has both the phosphoryl and fluorine functional groups, we observed the separate intra- and extracellular resonances. But, the intracellular resonance was shifted to high frequency of the extracellular resonance in the 19F spectra and to low frequency in the 31P spectra. The basis for the phenomenon in both cases is thought to be the reduced hydrogen bonding inside the cells between the solvent water and the phosphoryl oxygen or fluorine atoms.

Erythrocytes↗

PubMed1991

Indications for gastric bypass in palliative operations for pancreatic carcinoma.

This review was undertaken to determine whether there are specific factors which predict the development of gastric outlet obstruction (GOO) in patients with pancreatic carcinoma. One hundred forty-two patients with biopsy proven pancreatic carcinoma had palliative operations of whom 74 had gastric bypass (GB). Of the 68 who did not, four died after biliary bypass. The 64 patients who remained at risk for GOO are the subject of this report. Seven of those patients developed GOO in the postoperative period and were compared with the 57 who did not. No significant difference was found between the two groups when they were compared on the basis of 20 historic, laboratory, and operative finding criteria. These data indicate that accurate prediction of subsequent GOO is not possible based on available objective data. Because GB creation does not increase operative blood loss, operative time, postoperative stay, or postoperative morbidity, and because prediction of need is difficult, prophylactic GB should be applied very liberally.

Adenocarcinoma↗

PubMed1991

Pancreatic-portal vein fistula with disseminated fat necrosis treated by pancreaticoduodenectomy.

I have reported the case of a 62-year-old man with chronic alcoholic pancreatitis and a rare pseudocyst-portal vein fistula. Even though he experienced no abdominal symptoms, he had severe metastatic fat necrosis manifested as subcutaneous fat necrosis, polyarthritis, medullary bone necrosis, and mental status changes. Remote tissue destruction continued until relief was gained by pancreaticoduodenectomy and repair of the necrotic portal vein. Disseminated fat necrosis is a rare syndrome that can be the only presenting feature in patients with pancreatitis and pancreatic cancer. Early recognition and treatment of the underlying pancreatic disease may decrease the high morality rate associated with this syndrome.

Adult↗

PubMed1990

Exchange of fluorinated glucose across the red-cell membrane measured by 19F-n.m.r. magnetization transfer.

The 19F n.m.r. spectrum of 3-fluoro-3-deoxy-D-glucose (3FG) in a red-cell suspension was observed to contain separate resonances from the intra- and extra-cellular populations of both the alpha- and beta-anomers. This phenomenon was used with an n.m.r. spin-transfer procedure to measure the rate of exchange of the anomers across the human red-cell membrane under equilibrium-exchange conditions at 37 degrees C. The beta-anomer crossed the membrane significantly more quickly than the alpha-anomer. At a total 3FG concentration of 9.3 mM; the first-order rate constants for the efflux of the alpha- and beta-anomers were 0.41 +/- 0.15 and 0.88 +/- 0.20 s-1 respectively. The measurable 3FG exchange was inhibited by 75 and 100% respectively by the glucose-transport inhibitors cytochalasin B and phloretin. Glucose inhibited the exchange of 3FG, and the results were consistent with glucose and 3FG binding to the hexose-transport protein with similar affinity.

Deoxy Sugars↗

PubMed1990

Palliative operations for pancreatic carcinoma.

Controversies in palliation of pancreatic carcinoma include the best biliary bypass, the best gastric by-pass, and how routinely gastric bypass should be used. We reviewed the records of 142 patients who underwent palliative operations for pancreatic carcinoma at the Cleveland Clinic over a 5-year period. Direct choledochal-enteric anastomosis proved superior to cholecystojejunostomy because of the high incidence of postoperative biliary sepsis and obstruction with the latter. The lowest incidence of these complications was achieved with choledochoduodenostomy. Loop gastrojejunostomy and Roux-Y gastrojejunostomy resulted in similar complication rates and postoperative stays, but, because loop reconstruction was simpler, it was deemed superior. Blood loss, operative time, and hospital stay were similar in patients with loop gastrojejunostomy and patients with no gastric bypass. This finding, coupled with a 10% incidence of subsequent gastric outlet obstruction in those without gastric bypass, indicates that gastric bypass should be liberally applied in the palliation of pancreatic carcinoma.

Adenocarcinoma↗

PubMed1989

Characterization of the transport of the nonelectrolyte dimethyl methylphosphonate across the red cell membrane.

We have refined the method for measuring the equilibrium exchange of the neutral phosphoryl compound dimethyl methylphosphonate across the human red cell membrane using 31P NMR spectroscopy. Using this improved technique we measured a permeability coefficient of dimethyl methylphosphonate of 9.47 +/- 1.01 X 10(-5) cm s-1 at a concentration of 164 mM, at 25 degrees C. The transport at 25 degrees C was not saturable up to a concentration of 600 mM and was not inhibited by 4,4'-diisothiocyano-2,2'-disulfonic acid, p-chloromercuriphenyl sulfonic acid, copper ions or phloretin, or by thiourea or urea at 16 degrees C. The permeability was enhanced by butanol and phloretin.

Biological Transport↗

PubMed1989

Clearance of atrial natriuretic factor by lung, liver, and kidney in human subjects and the dog.

We determined human and canine plasma clearance of atrial natriuretic factor (ANF) by lung, liver, and kidney from arteriovenous differences in plasma ANF and measured organ plasma flow. Human subjects had lower plasma ANF concentrations in the pulmonary vein or the pulmonary capillary wedge position when compared with the pulmonary artery, and both sites yielded pulmonary ANF extraction ratios of 24%. Canine lung ANF extraction was 19 +/- 3% and pulmonary ANF clearance was 328 +/- 78 ml/min per m2 vs. 357 +/- 53 ml/min per m2 in man. Hepatic plasma ANF clearance was 216 +/- 26 ml/min with an extraction ratio of 30 +/- 3% in humans and 199 +/- 89 ml/min and 36 +/- 6% in the dog. Renal plasma ANF clearance in human subjects was 78 +/- 12 ml/min per kidney and correlated well with each kidney's creatinine clearance (r = 0.58, P less than 0.05). The mean renal ANF extraction ratio was 35 +/- 4% in human subjects and 42 +/- 6% in the dog. These data quantitate the specific organ ANF clearances by lung, liver, and kidney in human subjects and in dogs and provide a rationale for elevated plasma ANF levels in cirrhosis, renal failure, and diseases accompanied by reduced perfusion of these organs. These findings support the conclusion that plasma ANF concentrations are dependent upon both the stimuli for ANF secretion as well as the specific organ clearances of ANF.

Adolescent↗

PubMed1989

Recent experience with benign biliary strictures.

The management of benign biliary strictures continues to represent one of the most difficult problems in the practice of general surgery. Twenty-eight consecutive patients with benign strictures treated between 1972 and 1987 are reviewed in this report. Stricture etiology was iatrogenic in 13 patients, pancreatitic in 11, idiopathic in three, and traumatic in one. The authors performed 27 operations and three percutaneous transhepatic balloon dilatations in the treatment of these patients. Operative morbidity was 18 per cent; there were no operative deaths. Treatment was successful in 23 of 28 patients with a mean followup of four years, and four of the five patients with initially unsuccessful results have undergone successful remedial operations. Roux-en-Y biliary enteric diversion procedures have been most successful in these patients: seven patients with Roux-en-Y choledochojejunostomy without recurrence (mean followup of 62 months) and eight patients with Roux-en-Y hepaticojejunostomy with a success rate of 87.5 per cent (mean followup of 50 months). Two patients underwent three percutaneous transhepatic balloon dilatations; one has had a good result with short followup and the other failed on two occasions and has required a remedial operation. Benign biliary strictures have multiple etiologies. Therapeutic approaches, which now include nonoperative procedures, must be tailored to the needs of individual patients. The potential for recurrence is always present. Longterm followup remains essential in the management of patients with this disorder.

Adult↗

PubMed1988

Preoperative colonoscopic diagnosis of villous adenoma of the appendix. Report of a case and review of the literature.

This case of villous adenoma of the appendix reported is unique by virtue of its having been diagnosed preoperatively using colonoscopy. Only 45 such lesions have been described previously, and a review of those cases reveals that 93 percent were discovered at appendectomy performed either incidentally or for acute appendicitis. The malignant potential of this entity is unknown and its treatment is controversial. Because of a report association between adenomas of the appendix and other gastrointestinal neoplasms, long-term surveillance is recommended.

Adenoma↗

PubMed1988

Acute pancreatitis.

In order to recognize acute pancreatitis in the setting of the acute abdomen, the surgeon must be thoroughly familiar with the numerous etiologies of the disease. No specific test is available to diagnose acute pancreatitis. CT scanning is arguably the most useful single tool, but surgical judgment is critical. Most cases of acute pancreatitis resolve spontaneously without sequelae, but the spectrum of the disease also includes highly lethal forms associated with a variety of systemic complications. Operative intervention is indicated when other, more rapidly fatal, abdominal processes cannot be reliably excluded and when local complications develop.

Abdomen, Acute↗

PubMed1988

Is total pelvic exenteration reasonable primary treatment for rectal carcinoma?

Total pelvic exeneration (TPE) is reasonable primary surgical therapy in select patients with large bulky locally invasive rectal cancers that can be removed en bloc. Many do not have either nodal or distant metastasis. Furthermore, TPE can be curative and often is palliative for similar lesions that are recurrent or nonresponsive to radiation therapy. Operative mortality rates should be under 10% and can be under 5% for primary cases. Although improvement in preoperative management and operative technique, especially with urinary conduits and postoperative care is clear, both early and late complications are significant. Unfortunately, preoperative identification of those patients requiring TPE rather than abdominoperineal or low anterior resection remains poor. Furthermore, recent improvements in techniques for pelvic slings to prevent small bowel entrapment and protection from irradiation or myocutaneous flaps to obliterate the massive dead space are not yet clearly established as preventors of either early or later complications.

Carcinoma↗

PubMed1988

Splenorrhaphy for blunt trauma with a functioning distal splenorenal shunt: rationale and report of a case.

Splenorrhaphy was successfully performed following blunt abdominal trauma in a 42-year-old man with a functioning distal splenorenal shunt. The shunt had been created 16 months earlier for bleeding gastroesophageal varices (BGEV) secondary to alcoholic cirrhosis. Uniquely, this case brings into simultaneous focus the principles of selective shunting for BGEV and the technique and rationale of splenorrhaphy, while furthering the list of indications for the latter. Splenic preservation, including splenorrhaphy following trauma, is being increasingly advocated as the role of that organ in hematologic and immunologic homeostasis is further elucidated. Too, in that small segment of the population with portal hypertension, preservation of the spleen for use as a route of selective decompression for bleeding gastroesophageal varices has been emphasized. The following case illustrates splenic preservation toward accomplishment of both of these ends.

Abdominal Injuries↗

PubMed1988

Early experience with the selective splenocaval shunt for variceal bleeding.

Selective variceal decompression is the operative method of choice in the definitive management of recurrent hemorrhage from gastroesophageal varices. The distal splenorenal shunt is the recommended procedure for selective variceal decompression, but its use may be limited in patients who have undergone left nephrectomy, in patients with an anatomically aberrant relationship between the splenic and left renal veins and in patients with preoperative visceral angiographic findings suggesting that they are at risk for development of the postoperative syndrome of renal vein hypertension. In these clinical situations, selective variceal decompression can be obtained with a splenocaval shunt, constructed by directly anastomosing the splenic vein to the infrarenal vena cava. Seven patients who have undergone the selective splenocaval shunt are reviewed in this report. Early experience with these patients demonstrates the use of the selective splenocaval shunt when an alternative to the distal splenorenal shunt is needed.

Adult↗

PubMed1987

Glucose transport in human erythrocytes measured using 13C NMR spin transfer.

We present the results of a new NMR-based procedure for measuring the fast transmembrane exchange of D-[1-13C]glucose in human erythrocytes. The method relies on different rates of exchange between the alpha- and beta-anomers of glucose inside and outside the cells; the rate outside the cells is greatly increased by the addition of mutarotase to the suspension. Theory is developed to describe nuclear-spin transfer in the present system and is used to analyse the data to yield estimates of transmembrane-exchange rate constants and their statistical uncertainties. For a total glucose concentration of 25.5 mmol/l at 40 degrees C the first order efflux rate constants for the alpha- and beta-anomers were 1.20 +/- 0.40 s-1 and 0.71 +/- 0.30 s-1, respectively.

Biological Transport↗

PubMed1987

Preoperative evaluation of patients with inguinal hernia for colorectal disease.

In retrospective series, 17.0 to 25.5 per cent of those patients with carcinoma of the colon or rectum have been found to have concurrent inguinal herniation. This observation prompted the recommendation that patients with hernias be thoroughly screened for disease of the colon and rectum. That recommendation remains controversial in part because it has not previously been prospectively evaluated. In a one year period, 202 consecutive patients with inguinal hernias completed a preoperative protocol which included: 1, gastrointestinal history; 2, rectal examination; 3, testing of at least two stool specimens with the Hemoccult (Smith Kline Diagnostics) device; 4, sigmoidoscopy, and 5, barium enema. Malignant and premalignant diseases were discovered in five patients, only one of whom had gastrointestinal symptoms. Each malignant lesion was localized (Dukes' A or B) and, therefore, highly curable. Benign disease was found in 49 patients, including polyps in eight and one instance of tight sigmoid stricture. All of the malignant and 91 per cent of the benign lesions were in patients 50 years of age and older. The association between inguinal herniation and colorectal disease was previously attributed to luminal obstruction. In the present series, however, the sole obstructing lesion was a benign stricture. Another explanation for this association must, therefore, be sought. We conclude, on the basis of the results of this experience, however, that screening for pathologic factors of the colon and rectum is warranted in otherwise asymptomatic patients who are more than 50 years old and who present with inguinal hernias.

Adult↗

PubMed1987

Fast transmembrane exchange in red cells studied with NMR.

13C NMR, with two fundamentally different procedures, was used to measure the H13CO3- permeability coefficient (P) of human erythrocytes. The values of P (approximately 3 X 10(-4) cm s-1) were similar to those obtained by other, non-NMR methods. A third procedure was used with 31P NMR to measure the permeability coefficient of human erythrocytes for the non-electrolyte dimethyl methylphosphonate; the effects on transmembrane exchange of varying haematocrit and butanol were studied.

Bicarbonates↗

PubMed1987

Rapid diagnosis of Candida sepsis in surgical patients.

Systemic candidiasis, an increasingly common disease, is associated with an extremely high mortality. Because of toxicity associated with amphotericin B therapy, clinicians are reluctant to initiate therapy until the presence of candidiasis is conclusively demonstrated. Using culture methods, such proof may not be forthcoming or may be available only late in the course of the disease. During the last 17 months, a new antigen latex agglutination test for candidiasis has been evaluated. Results indicate that this new test allows early, accurate diagnosis of the disease. In 36 consecutive cases of culture-proven candidiasis in surgical patients, the test was found to be 94.4 per cent sensitive and 100 per cent specific. On the basis of these findings initiation of amphotericin B therapy in patients with a positive Candida antigen titer is recommended.

Adult↗