Search PubMed⌕ Search

Biomedical subjects

J C Collins

Publications and source records attributed to J C Collins.

At least 19 recordsLinked to original sources
PubMed1995

Managing choledocholithiasis in the laparoscopic era.

BACKGROUND: Management options for common bile duct stones have explained in the era of laparoscopic cholecystectomy (LC), and selecting the most appropriate method for each patient can be problematic due to the difficulty of predicting accurately which patients have choledocholithiasis (CDL). In order to improve selection of appropriate treatment for CDL, treatment options were analyzed for outcome retrospectively during a 25-month period beginning June 1, 1992. PATIENTS AND METHODS: Four hundred four patients underwent LC; 48 (12%) had CDL identified at preoperative endoscopic retrograde cholangiopancreatography (ERCP) or intraoperative cholangiogram (IOCG). Forty-seven patients were referred for preoperative ERCP for suspected CDL, 23 (49%) of whom had proven duct stones and underwent endoscopic sphincterotomy and stone retrieval with an 87% success rate. RESULTS: Of 357 patients scheduled for LC without preoperative ERCP, 236 had IOCG, of which 25 (11%) demonstrated CDL. Seven patients had open common bile duct exploration (CBDE). Sixteen patients had postoperative ERCP after positive IOCG, 7 (44%) of which were positive for CDL and whose stones were removed with 100% success. Two patients were observed, anticipating spontaneous passage of a small stone. CONCLUSIONS: Preoperative ERCP should be applied selectively. For the large majority of patients without preoperative evidence of CDL, we recommend routine IOCG; if CDL is demonstrated, an intraoperative decision can be made to proceed to postoperative ERCP in the usual case or to open CBDE for very large or multiple stones. Observation in anticipation of spontaneous passage may be appropriate for small, solitary common duct stones. Continuing advances in laparoscopic CBDE are likely to reduce further the need to rely on ERCP in managing CDL.

Cholangiography↗
PubMed1995

Surgical management of portal hypertension.

Portal hypertension is frequently complicated by upper gastrointestinal tract bleeding and ascites. Hemorrhage from esophageal varices is the most common cause of death from portal hypertension. Medical treatment, including resuscitation, vasoactive drugs, and endoscopic sclerosis, is the preferred initial therapy. Patients with refractory hemorrhage frequently are referred for immediate surgical intervention (usually emergency portacaval shunt). An additional cohort of patients with a history of at least 1 episode of variceal hemorrhage is likely to benefit from elective shunt operations. Shunt operations are classified as total, partial, or selective shunts based on their hemodynamic characteristics. Angiographically created shunts have been introduced recently as an alternative to operative shunts in certain circumstances. Devascularization of the esophagus or splenectomy is done for specific indications. Medically intractable ascites is a separate indication for surgical intervention. Liver transplantation has been advocated for patients whose portal hypertension is a consequence of end-stage liver disease. In the context of an increasingly complex set of treatment options, we present an overview of surgical therapy for complications of portal hypertension.

Ascites↗
PubMed1995

Collateral ablation improves portal perfusion after partial portacaval shunt.

Small-diameter portacaval H-grafts (partial shunts) effectively abolish bleeding from esophageal varices. Goals are 1) to prevent variceal hemorrhage by subtotal portal decompression, and 2) to minimize postshunt encephalopathy by maintaining substantial residual pressure and prograde flow in the portal vein. To reduce spontaneous shunting of portal blood away from the liver, we advocate ablation of collateral vessels after partial shunts. Others have performed partial shunts without collateral ablation. We postulated that ablation of collateral vessels would augment portal perfusion pressure and preserve prograde portal flow after partial shunts. In 15 patients undergoing 8 or 10 mm portacaval H-grafts, portal pressure was measured intraoperatively before and after ligation of principal venous collaterals. In another 13 patients, collateral embolization was performed during postoperative portography. The degree of portal perfusion was scored. Pressure measurements demonstrated a mean rise in portal pressure of 2.8 cm saline after ligation (P = 0.025). Angiographic perfusion scores after embolization improved by a mean of 0.57 points on a 4 point scale (P = 0.032). We conclude that intraoperative collateral ligation augments residual portal pressures and that postoperative collateral embolization improves portal flow patterns. Since both observed effects have been associated with decreased postshunt encephalopathy rates, ablation of collateral vessels must be an integral component of the partial portacaval shunt.

Constriction↗
PubMed1993

Effects of physical stress on peroxide scavengers in normal and sickle cell trait erythrocytes.

Sickle cell trait subjects are potentially at risk with microvascular complications frequently associated with high altitude and extreme exertion. Studies conducted in our laboratory suggest that exposure of sickle cell trait subjects to treadmill exercise resulted in an increase not only in the susceptibility of red blood cells to oxidation but also in the density of RBC membrane. The trend of increased susceptibility of red cells to oxidation as a consequence of exercise was associated with relatively excessive production of H2O2, inefficient breakdown of H2O2 by GSH-Px- and catalase-catalyzed reactions, and inability/failure to show a transitory increase in the activity of reduced nicotinamide adenine dinucleotide phosphate (NADPH)-generating enzymes.

Adult↗
PubMed1993

Admission serum albumin level as a predictor of outcome among geriatric patients.

This retrospective study consisted of 148 patients who were consecutively discharged during 1991 from a geriatric VA Hospital population. Seventy-six were 65 years of age or older, and all were male. Data included admission serum albumin level, age, length of stay, diagnosis, and disposition. Albumin level was negatively associated with length of stay and with outcome disposition. Albumin level was not associated with diagnosis. Age alone was not associated with albumin level, length of stay, diagnosis, or disposition. We conclude that a low albumin level is an independent predictor of a worse disposition. Age did not predict nutritional status, length of stay, diagnosis, or disposition.

Aged↗
PubMed1992

Metabolic studies in a mouse model of hepatorenal tyrosinemia: absence of perinatal abnormalities.

Radiation induced chromosomal deletions at the albino locus in the mouse, lethal when homozygous, cause abnormalities of expression of several unlinked liver specific genes. Recently, the gene encoding FAH was shown to be included in the deletions. Since in humans FAH mutations cause tyrosinemia type I, deletion homozygous mice were suspected of having tyrosinemia. Studies of plasma amino acids did not confirm this suspicion. Also, succinylacetone levels were normal in fetal and newborn livers of deletion homozygotes. The present evidence, therefore, does not support the assumption that the earlier described ultrastructural and enzyme abnormalities in deletion homozygotes are secondary effects of tyrosinemia caused by the deletion of FAH.

Amino Acid Metabolism, Inborn Errors↗
PubMed1992

Resources for getting started in modeling.

Modeling is a useful component of scientific investigation in nutrition. Nutrition scientists who would like to incorporate modeling into their studies frequently do not know where or how to begin. This paper describes a selected assortment of books, journals and articles, resource groups and individuals and computer software that may be of help to the beginning modeler and to those more experienced in modeling as well.

Computer Simulation↗
PubMed1992

Effects of physical stress on complete blood count and venous blood gas profile of individuals with sickle cell trait.

The association between sickle cell trait (SCT) and adverse effects of exercise has been controversial. While individuals with SCT are at higher risk of sudden death, the mechanism for this outcome remains to be elucidated. In order to shed light on this controversy, we have monitored venous blood count and blood gas parameter values in normal and SCT subjects during treadmill exercise. White and red blood cell counts and hemoglobin changed significantly over time in both the SCT and normal groups, with peak exercise values different from pre-exercise or post-exercise values. Red blood cell counts showed significant group-time interaction; increase in count during exercise was accentuated in SCT subjects. All blood gas parameters showed significant changes over time in both groups. O2 content was significantly higher in SCT than AA at all time intervals. O2 saturation, pO2 and CO binding to hemoglobin showed significant group-time interaction. Furthermore, O2 saturation for the combined groups was significantly greater at peak exercise and at rest than before exercise. It is possible that treadmill exercise causes microvascular shunting in SCT subjects, leading to a decrease in the peripheral utilization of oxygen.

Adult↗
PubMed1992

Occult traumatic pneumothorax: immediate tube thoracostomy versus expectant management.

Occult pneumothorax is pneumothorax identified by computed tomography but not seen on conventional chest radiographs. Twenty-seven occult traumatic pneumothoraces in 26 patients were identified retrospectively at the authors' level I trauma center. Of these, 24 patients survived to discharge or transfer; 2 died of brain injury. Eleven patients were treated immediately with tube thoracostomy (TT) and 13 were observed with interval chest radiography. The authors' data support the conclusion that it is safe to withhold immediate TT in patients who are hemodynamically stable. Close clinical observation and interval chest radiography can identify those patients who require subsequent TT. Prospective study of larger numbers of patients is needed to confirm the safety and cost efficacy of this approach.

Adolescent↗
PubMed1991

Indistinguishability and identifiability analysis of linear compartmental models.

Two compartmental model structures are said to be indistinguishable if they have the same input-output properties. In cases in which available a priori information is not sufficient to specify a unique compartmental model structure, indistinguishable model structures may have to be generated and their attributes examined for relevance. An algorithm is developed that, for a given compartmental model, investigates the complete set of models with the same number of compartments and the same input-output structure as the original model, applies geometrical rules necessary for indistinguishable models, and test models meeting the geometrical criteria for equality of transfer functions. Identifiability is also checked in the algorithm. The software consists of three programs. Program 1 determines the number of locally identifiable parameters. Program 2 applies several geometrical rules that eliminate many (generally most) of the candidate models. Program 3 checks the equality between system transfer functions of the original model and models being tested. Ranks of Jacobian matrices and submatrices and other criteria are used to check patterns of moment invariants and local identifiability. Structural controllability and structural observability are checked throughout the programs. The approach was successfully used to corroborate results from examples investigated by others.

Computer Simulation↗
PubMed1991

Erythropoietin response to anemia as a function of age.

The erythropoietin (EPO) response to anemia was assessed for 244 subjects aged 1-64 years (mean 45.2 years) and 121 subjects aged 65-94 years (mean 68.3 years). Subjects included non-anemic individuals as well as those with anemia of various etiologies, excluding renal disease and pregnancy. Significant inverse correlations between serum immunoreactive EPO and hematocrit were noted for both groups. Regression lines failed to show a significantly lower slope or y-intercept for older compared to younger subjects. EPO levels were not significantly lower for older compared to younger subjects when controlled for hematocrit level. These results suggest that the EPO response to anemia in older subjects is similar to that of younger subjects.

Adolescent↗
PubMed1989

Isolation and characterization of lactose permease mutants with an enhanced recognition of maltose and diminished recognition of cellobiose.

In the present study, lactose permease mutants were isolated which have an enhanced recognition toward maltose (an alpha-glucoside) and diminished recognition for cellobiose (a beta-glucoside). Nine mutants were isolated from a strain encoding a wild-type permease (pTE18) and nine from a strain encoding a mutant permease which recognizes maltose (pB15). All 18 mutants were subjected to DNA sequencing, and it was found that all mutations are single base substitutions within the lac Y gene effecting single amino acid substitutions within the protein. From the pTE18 parent, substitutions involved Tyr-236 to Phe or His; Ser-306 to Thr; and six independent mutants in which Ala-389 was changed to Pro. From pB15, Tyr-236 was changed to Phe or Asn, Ser-306 to Thr or Leu, Lys-319 to Asn, and His-322 to Tyr, Asn, or Gln. All 18 mutants exhibited enhanced recognition for maltose (compared with the pTE18 strain) and a diminished recognition for cellobiose. In addition, all mutants showed a diminished recognition toward beta-galactosides as well. The Phe-236, His-236, Leu-306, Asn-319, Tyr-322, Asn-322, and Gln-322 mutants were completely defective in the uphill accumulation of methyl-beta-D-thiogalactopyranoside whereas the Asn-236, Thr-306, and Pro-389 mutants could effectively accumulate methyl-beta-D-thiogalactopyranoside against a concentration gradient. The mutants obtained in this study, together with previous lactose permease mutants, tend to be found on transmembrane segments, and those which are on the same transmembrane segment are often found three or four amino acids away from each other. This pattern is consistent with a protein structure in which important amino acid side chains project from several transmembrane segments in such a way as to form a hydrophilic channel for the recognition and transport of H+ and galactosides. It is proposed that the mechanism for H+/lactose cotransport is consistent with a "flanking gate" model in which the protein contains a single recognition site for galactosides within the channel which is flanked on either side by gates.

Base Sequence↗
PubMed1989

Hepatic peroxisomal abnormalities in abetalipoproteinemia.

Spinocerebellar degeneration in a 17-yr-old boy with abetalipoproteinemia was associated with vitamin E deficiency and hepatic steatosis. In liver biopsy samples before and after 15 mo of vitamin E treatment, hepatocellular peroxisomes were morphologically abnormal; pleomorphic, with a broadened range of sizes; often larger than normal; and with marginal bars in some. In the first sample, peroxisomes exhibited matrical heterogeneity and dense nucleoids. Peroxisomes in the second biopsy sample lacked nucleoids and contained more homogeneous matrices. The mean peroxisomal diameter increased from 0.77 +/- 0.33 to 0.86 +/- 0.32 microM (normal, 0.62 +/- 0.14). These observations raise the possibility that peroxisomes may be involved in the metabolism of apolipoprotein B or may be affected by the disturbances of hepatocellular lipid metabolism caused by this disease.

Abetalipoproteinemia↗