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Biomedical subjects

E M Janle

Publications and source records attributed to E M Janle.

9 recordsLinked to original sources

Use of ultrafiltration probes in sheep to collect interstitial fluid for measurement of calcium and magnesium.

Studies of calcium and magnesium changes in living animals usually involve blood, urine, and fecal samples. These samples provide only information on whole-body averages and give no indication of differences between tissues. Ultrafiltration probes were developed to sample interstitial fluid from muscle, bone, and subcutaneous tissue of sheep to provide a tool for investigating tissue differences in calcium and magnesium concentrations. The potential of the probes for mineral distribution studies was demonstrated in sheep by using infusion of a calcium gluconate solution.

Animals↗

Microdialysis and ultrafiltration.

Microdialysis and ultrafiltration are complementary sampling techniques that facilitate acquisition of data in awake, freely moving animals. Because the necessity of blood removal is eliminated, sampling frequency is not limited by animal size. The samples obtained by these techniques usually require no processing for analysis.

Animals↗

Decreased rhodopsin regeneration in diabetic mouse eyes.

PURPOSE: To evaluate the effect of diabetes on rhodopsin regeneration in the excised mouse eye. METHODS: A superfused excised mouse eye preparation that exhibits rhodopsin regeneration after moderate bleaches and that is responsive to the composition of the perfusate was used. Diabetes was induced in albino mice (BALB/c) with the diabetogenic agent streptozotocin. Absorption spectrophotometry of the excised eye was used to monitor rhodopsin concentrations. RESULTS: Significant reductions in rhodopsin regeneration were observed in diabetic mice. Severely diabetic mice exhibited only 64% and 55% regeneration (at perfusate glucose levels of 5.1 mM and 10 mM, respectively), and moderately diabetic mice exhibited 74% and 73% regeneration, compared to the greater than 100% regeneration observed in nondiabetic mice. Glucose perfusate concentration has a major effect on rhodopsin regeneration. Lower concentrations of perfusate glucose (3 mM) reduced the amount of rhodopsin regeneration in both nondiabetic mice and diabetic mice. The diabetic mice seemed to tolerate higher concentrations of perfusate glucose (20 mM) better than the nondiabetic mice. Neither correction for osmolarity nor substitution with a nonglycolytic substrate increased the amount of rhodopsin regeneration in the diabetic mice. CONCLUSIONS: Diabetes reduced the amount of rhodopsin regeneration that followed moderate bleaches in excised mouse eyes. The data suggest that some process or processes associated with rhodopsin regeneration have been affected in the diabetic.

Animals↗

T-fluted peritoneal dialysis catheter.

While the current Tenckhoff catheter is generally successful, outflow failure due to omental obstruction, pericatheter hernias, pericatheter leaks, and exit infections remains a major cause for dropout from peritoneal dialysis therapy. Further, the irregular outflow characteristics of the catheter make highflow automated dialysis problematic. We have developed a catheter with a thin transabdominal tube connecting in a T-shape to a transverse cylinder resting against the parietal peritoneum, with flutes (grooves) as ports. The catheter can be inserted through the 3-mm diameter Quill guide of the Y-TEC peritoneoscopic system. Studies in normal dogs indicated that the T-fluted catheter allowed daily exchanges with 2 L of peritoneal dialysate without outflow obstruction, and peritoneoscopic inspection 2-4 weeks later showed no omental attachment to the grooved ports. By comparison, curled Tenckhoff catheters uniformly developed omental obstruction within 2-4 days, and all such catheters had firm omental attachment to the side holes. Five T-fluted catheters have been placed in continuous ambulatory peritoneal dialysis (CAPD) patients who had prior complications with Tenckhoff catheters (infections, leaks, and outflow failure). One patient with multiple intraperitoneal adhesions developed outflow failure of the T-fluted catheter, similar to a prior Tenckhoff catheter. All other T-fluted catheters had consistent outflow rates and no complications. In long-term use the T-fluted catheter should prevent omental attachment, deep cuff extrusion, pericatheter hernias, subcutaneous cuff erosion, and exit-site infection, although this is not yet proven.

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A comparison of peritoneal dialysance (D) during CAPD, intermittent peritoneal dialysis (IPD) and tidal PD (TPD) in awake normal dogs.

The important variables which determine peritoneal clearances include: residual volume, cycle volume, and cycle frequency. Various combinations of these variables result in CAPD, IPD, and TPD schedules. We decided to develop an animal model in which the clearances of these modes could be compared, performing dialysis on awake dogs with normal kidney function. In five successive experiments, two silicone catheters were placed in the abdomen of anesthetized dogs, one in the lower abdomen and one between the liver and diaphragm. On successive days, with the dogs awake but lying down, CAPD, IPD, and TPD schedules were performed for 4 hours, using 1.5% Inpersol (Abbott Laboratories, IL.). For CAPD the infused volume was 2 liters, drained at 4 hours. For IPD, 2 liters were infused and drained each hour. For TPD, one liter residual was infused, and another liter infused and drained each 20 minutes, to result in a 3 liter/hour flow-through-rate. The dialysance of glucose (Dglu) was calculated from changes in dialysate and blood glucose concentration. Dglu reproducibly predicted the Durea, with Dglu = 0.6 Durea. Our experiments demonstrated that without efforts to optimize TPD, its dialysance is similar to that of standard TPD. The higher average TP volume of TPD offsets the higher fluid flow rate of TPD schedules. Both IPD and TPD have higher dialysance than CAPD.

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Monitoring physiological variables with membrane probes.

Membrane probes are implantable devices, which can be used to sample from the interstitial fluid of the tissues in which they are implanted. Two types of membrane probes, one based on microdialysis and the other on ultrafiltration, were developed and tested in vitro for the following analytes: sodium, potassium, chloride, glucose and lactate. These membrane probes were then implanted subcutaneously in rats and used to monitor changes in interstitial analytes during the head-down tilt model of microgravity.

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A subcutaneous capillary filtrate collector for measurement of blood chemistries.

The capillary filtrate collector (CFC) contains 30,000 molecular weight cut-off, hollow fiber ultrafiltration membranes that are placed below the skin. A transcutaneous tube leads to an evacuated glass tube that provides a vacuum to pull ultrafiltrate at 40-60 microliters/hr from blood, through the fibers, and past a sampling port to the glass tube. Long-term (1-6 months) animal and clinical studies have shown that the ultrafiltrate concentration of chemicals such as glucose and a variety of drugs is exactly the same as that of the blood plasma water when the ultrafiltrate is created. In this study, the device was placed in six home monitored diabetics and four in-center hemodialysis diabetic patients. Over the following month, blood glucose concentrations were compared to CFC glucose concentrations. In spite of difficulties in diluting and assaying small samples of filtrate, there was a good correlation between blood and CFC glucose levels. A flow-through enzymatic glucose sensor has been tested and shown to accurately measure glucose in CFC filtrate. When placed in the transcutaneous tubing near the skin, this should allow a small external device to continuously monitor glucose levels in brittle or out of control diabetes with high accuracy and little risk, discomfort, or cost.

Blood Chemical Analysis↗

Continuous flow-through peritoneal dialysis (CFPD): comparison of efficiency to IPD, TPD, and CAPD in an animal model.

OBJECTIVE: To determine whether continuous flow-through peritoneal dialysis (CFPD), a treatment schedule in which peritoneal dialysate is infused continuously into one part of the abdomen (over the liver) and is drained from a distant part of the abdomen (the pelvis), can provide greater clearance than continuous ambulatory peritoneal dialysis (CAPD), tidal peritoneal dialysis (TPD), or intermittent peritoneal dialysis (IPD). DESIGN: A prospective study comparing four schedules of peritoneal dialysis in the awake, normal dog, using glucose clearance as a substitute for urea clearance. METHODS: We placed two chronic dialysis catheters into the abdomen of anesthetized dogs (with intraperitoneal portions of fluted or miniature column-disc design). On successive days, with the dogs awake and prone, we performed peritoneal dialysis for 4 hours with 1.5% dialysate according to one of four schedules, each with 2 L maximum intraperitoneal volume: CFPD (unidirectional flow at an average of 3.6 L/hr), IPD (2 L/hr), TPD (average of 3.6 L/hr, 1 L residual volume), and CAPD (2 L/4 hr). Glucose and urea clearances were calculated from blood and peritoneal concentrations and dialysate flow rates. RESULTS: Stabilized glucose clearances (from 60 to 240 minutes) averaged 11 +/- 5 mL/min for IPD, TPD, and CFPD, and 5 +/- 2 mL/min for CAPD. However, glucose clearances of CFPD were 13 +/- 6 mL/min when the intraperitoneal volume was maintained at 800-100 mL, and 16.5 +/- 6 mL/min when flow rate was 6 L/hr. Urea clearances were twice the measured glucose clearances. CONCLUSION: When CFPD is performed with an appropriate intraperitoneal volume and flow, it is the most chemically effective method of peritoneal dialysis in removing small molecules like urea.

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