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Biomedical subjects

J C Collins

Publications and source records attributed to J C Collins.

87 records · Page 5Linked to original sources
PubMed1971

A model of respiratory heat transfer in a small mammal.

A steady-state model of the heat and water transfer occurring in the upper respiratory tract of the kangaroo rat, Dipodomys spectabilis, is developed and tested. The model is described by a steady-state energy balance equation in which the rate of energy transfer from a liquid stream (representing the flow of heat and blood from the body core to the nasal region) is equated with the rate of energy transfer by thermal conduction from the nose tip to the environment. All of the variables in the equation except the flow rate of the liquid stream can be either measured directly or estimated from physiological measurements, permitting the solution of the equation for the liquid stream flow rate. After solving for the liquid stream flow rate by using data from three animals, the energy balance equation is used to compute values of energy transfer, expired air temperature, rates of water loss, and efficiency of vapor recovery for a variety of ambient conditions. These computed values are compared with values measured or estimated from physiological measurements on the same three animals, and the equation is thus shown to be internally consistent. To evaluate the model's predictive value, calculated expired air temperatures are compared with measured expired air temperatures of eight additional animals. Finally, the model is used to examine the general dependence of expired air temperature, of rates of water loss, and of efficiency of vapor recovery on ambient conditions.

Animals↗
PubMedDate not supplied

Asialoglycoprotein receptor expression in murine pregnancy and development.

Hepatic asialoglycoprotein receptor activity of pregnant mice increased from the tenth day of gestation, reaching 3-fold the normal adult level just prior to parturition and returning to normal within 1 week postpartum. Increases in activity involved both intracellular and cell-surface associated receptors and were associated with enhanced endocytosis of asialoorosomucoid by isolated hepatocytes. Modulation of hepatic binding protein expression during murine pregnancy represents the first situation in which this receptor's concentration has been shown to exceed normal levels in response to a physiologic change. In the fetus, receptor activity was barely detectable throughout gestation, steadily increased in the neonatal period, and reached adult levels by the fifth postpartum day.

Animals↗
PubMedDate not supplied

Selective regulation of intrinsic membrane proteins in HepG2.

Expression of three hepatocellular membrane proteins--the asialoglycoprotein receptor (hepatic binding protein) the insulin receptor and organic anion binding protein--have been studied in the HepG2 cell line. HepG2 grown in minimal essential medium supplemented with 10% fetal bovine serum maximally expressed hepatic binding protein and insulin receptor only at confluence while organic anion binding protein appeared independent of the state of cellular proliferation. When cells were grown in medium supplemented with dialyzed fetal bovine serum, adult bovine serum or in chemically defined medium, expression of hepatic binding protein and insulin receptor but not organic anion binding protein was reduced by 60 to 80%. Immunoblotting techniques revealed that cells grown in dialyzed fetal bovine serum contained virtually no mature, glycosylated 45 kD hepatic binding protein, but a small amount of 36 kD protein. Metabolic labeling of cells grown in dialyzed fetal bovine serum with [35S] methionine indicated reduced synthesis of the 45 kD hepatic binding protein and the absence of the 36 kD protein. Restoration of normal expression of hepatic binding protein and insulin receptor was achieved by addition to dialyzed fetal bovine serum of: fetal bovine serum; 2,000 dalton ultrafiltrate of fetal bovine serum, or 300 to 350 dalton fraction of the ultrafiltrate. The normal concentration of organic anion binding protein demonstrable in cells grown in dialyzed fetal bovine serum indicates that the low molecular weight factor(s) is not a generalized modulator of plasma membrane biogenesis. However, its effect on the steady-state level of the hepatic binding protein and insulin receptor, characteristic of mature hepatocytes, suggests a role for this fetal serum factor in hepatocellular differentiation.

Anion Transport Proteins↗
PubMedDate not supplied

Narrow-diameter portacaval shunts for management of variceal bleeding.

Over the past decade, we have developed and refined a method for partial portosystemic shunting for the control of bleeding esophageal varices in alcoholic cirrhotic patients. The narrow-diameter interposition portacaval H-graft using 8 mm polytetrafluoroethylene has been performed in 32 patients at our institution with low operative mortality (6.3%) and nearly complete cessation of variceal bleeding (96.7%) over a mean follow-up period of 43 months. In comparison with total shunts, diminished rates of postshunt encephalopathy (13% versus 40%) have been observed. Prograde portal blood flow has been preserved in 90% of 30 patients studied by perioperative portography. Shunt patency with continued prograde flow has been demonstrated at up to 9 years of follow-up. Investigators at three other centers have studied partial shunting using substantially similar techniques, with similar findings. Based on these results, we conclude that narrow-diameter shunts provide effective, long-lasting treatment for variceal hemorrhage due to portal hypertension in the alcoholic.

Blood Vessel Prosthesis↗
PubMedDate not supplied

Common bile duct stone characteristics: correlation with treatment choice during laparoscopic cholecystectomy.

Determining the most appropriate management approach for patients with unsuspected choledocholithiasis may be difficult because of the subjective nature of this decision in the absence of clinical data. Treatment of incidental choledocholithiasis during laparoscopic cholecystectomy was reviewed during a 25-month period. Operative cholangiograms were analyzed retrospectively to determine if associations exist between common bile duct stone characteristics and the intraoperative treatment selected by the operating surgeon. Cholangiographic data included quantification of common bile duct stones, stone dimension, position, and presence of radiopaque contrast flow into the duodenum. Two hundred thirty-six laparoscopic cholecystectomy patients underwent operative cholangiography; 25 (11%) demonstrated choledocholithiasis. Seven patients were converted to open common bile duct exploration (group I), 16 patients were referred for postoperative endoscopic retrograde cholangiopancreatography (group II), and two patients were observed (group III). Evaluation of the operative cholangiograms revealed multiple common bile duct stones (>1) in 86% (6 of 7) in group I, 25% (4 of 16) in group II, and none in group III. All patients in group I had at least one stone larger than 5 ml in greatest diameter, whereas only 33% (6 of 18) in groups II and III combined had stones larger than 5 ml. Group I had significantly (P = 0.027) more representation of delayed or no contrast flow during operative cholangiography compared to groups II and III. The intraoperative decision to proceed with laparoscopic cholecystectomy and rely on postoperative endoscopic retrograde cholangiopancreatography for stone retrieval rather than open common bile duct exploration was associated with (1) a single common bile duct stone, less than or equal to 5 ml in size on operative cholangiogram and (2) normal contrast flow into the duodenum. Open common bile duct exploration was more frequently associated with the demonstration of multiple or large (>5 ml) stones. A periampullary stone did not discriminate among treatment choices.

Case-Control Studies↗
PubMedDate not supplied

Patient monitoring systems: criteria for evaluation & selection.

Patient monitoring is more than just the acquisition and accumulation of physiological data. In order for it to be efficacious in patient diagnosis and treatment, the professional staff must be continuously involved in protocol development, evaluation, and modification. Given the constraints of these tasks, of cost limitations, and of staff interest and expertise, the clinical engineer should develop a rationale for making judgments about patient monitoring systems at his particular site. This rationale should include: evaluation of design criteria from medical, nursing, and engineering standpoints; consideration of the considerable and increasing effect of computers on monitoring; and the intelligent appraisal of technique and system development performed at other sites.

Bibliographies as Topic↗
PubMedDate not supplied

Protein-losing enteropathy detected by 99mTc-labeled human serum albumin abdominal scintigraphy.

99mTc-labeled human serum albumin (HSA) abdominal imaging is a new way of demonstrating gastrointestinal protein loss. We present two children with hypoalbuminemia of obscure etiology in whom albumin loss was localized in the gastrointestinal tract with 99mTc-HSA scintigraphy and the loss correlated with abnormal fecal alpha 1-antitrypsin excretion. In the absence of gastrointestinal blood loss or contamination of the 99mTc-HSA with free pertechnetate, significant activity accumulating in the gastrointestinal tract and moving with its contents is thought to represent 99mTc-HSA leakage into bowel lumen. Abdominal imaging with 99mTc-HSA has a low radiation burden to the patient and is readily available, relatively inexpensive, and easily performed. It can be used as a screening test for the detection of protein-losing enteropathy. It also offers the potential of being able to localize the site of protein loss visually within the gastrointestinal tract.

Child↗
PubMedDate not supplied

Direct assay of vitamins B1, B2, and B6 in hospitalized patients: relationship to level of intake.

High-performance liquid chromatography assays for vitamins B1 by erythrocyte thiamine pyrophosphate, B2 by plasma and urinary riboflavin, and B6 by plasma pyridoxal phosphate and urinary pyridoxic acid were used to evaluate the B vitamin status of hospitalized patients. Over an intake range of up to 3.4 mg of thiamine per day and up to 4.1 mg of riboflavin per day, erythrocyte thiamine pyrophosphate and urine and plasma riboflavin increased proportionately with intake. There was no relationship between B6 intake and blood levels. Rather, a constant blood level was maintained with an intake range of 0.5 to 4 mg/d, and urinary pyridoxic acid showed a linear increase proportionate to intake. There were extremely variable blood and urine concentrations of B vitamins noted in our patient population.

Adult↗
PubMedDate not supplied

Direct, real time measurement of meniscal blood flow. An experimental investigation in sheep.

The functional microcirculatory system of the meniscus was investigated in nine sheep using laser Doppler flowmetry (LDF). The highest blood flows recorded were found at the periphery and at the anterior and posterior horns, and this finding was confirmed by india ink injections in five sheep and by meniscal autoradiographs following intraatrial injection of 20 million Cs46 microspheres in four sheep. LDF provides accurate and reproducible assessment of meniscal blood flow. If adequate probes can be developed, this method offers great promise in the clinical assessment of blood flow within the substance of meniscal tears, thus offering the surgeon initial information in the decision to repair or resect a meniscal tear.

Animals↗