Effects of different perfusates on functional parameters of isolated perfused dog kidneys.

BACKGROUND: The isolated perfused canine kidney has been established as a valid model for conducting both renal physiology and transplantation research. This model is of particular importance for developing new strategies to improve graft function after renal transplantation. In the present study, a newly developed method using isolated haemoperfused porcine kidneys was adapted for use in canine kidneys. In contrast to haemoperfusion, synthetic perfusion media can be standardized and can prevent the initiation of blood-mediated reperfusion reactions. Thus, an additional aim was to determine whether blood could be replaced by synthetic cell-free perfusion solutions. METHODS: Canine kidneys (n = 30) were harvested from donors euthanized in veterinary practices for causes unrelated to the present study. The kidneys were isolated and perfused with autologous blood or cell-free synthetic electrolyte buffer (Tyrode solution). During perfusion, we monitored renal perfusate flow (RPF), glomerular filtration rate (GFR), electrolyte and glucose reabsorption, oxygen consumption and urine concentration. RESULTS: Changes in perfusion medium did not affect the RPF. In contrast, GFR, urine concentration and oxygen consumption were significantly higher, whereas fractional excretion of sodium and glucose were significantly lower in blood- than in Tyrode-perfused kidneys. CONCLUSIONS: This system offers a simple model for studying whole-organ functional alterations after acute renal ischaemia. Renal function indicators were below values reported during in vivo physiological conditions. These functions were better conserved when kidneys were perfused with autologous blood than with Tyrode.     

Nitroblue-tetrazolium test for the functional evaluation of phagocytic cells: A critical analysis of the methodology

The reduction of NBT to formazan has been suggested as an indicator of the reduction potential of biological systems. An increase in the amount of reduced formazan reflects the activation of the hexose monophosphate shunt of phagocytes cultivated in vitro, as a result of cellular stimulation by chemical or biological factors, or during phagocytosis. This phenomenon has been widely used for the determination of activated phagocytes by different methods. However, the technical limitations of these methods have not been evaluated carefully. In the investigations presented here threesolvents for formazan, pyridine, dioxane and dimethylformamide, have been tested for their suitability as extraction agents. For each solvent the optimal wavelength for photometric evaluation has been determined and dose relation curves between dissolved formazan and OD have been established. Several factors (time, temperature, pH, contamination with water or acid) affecting the dissolving properties and stability of formazan in different solvents have been investigated. With the solvents tested, dioxane proved to be the most suitable agent for extracting NBF. Thus, a methodology for the quantitative evaluation of NBT has been established. This method can be used for the identification of activators as well as of inhibitors of the phagocyte system.     

Microalbuminuria and nerve conduction velocity in type-I diabetics during conventional therapy and during continuous I.V. insulin infusion

Summary The objective of this study was to follow the development of microalbuminuria and nerve conduction velocity under continuous i.v. insulin therapy over a limited period of 4 months. For this purpose, 8 labile type I diabetics were selected (age 33±8 years, duration of diabetes 16±9 years) and treated conventionally with two insulin injections daily over 4 months. Afterwards, the same patients were treated with continuous i.v. insulin infusion and finally again with two injections daily over 4 months each. This procedure allowed each diabetic to serve as his own control. HbA₁, microalbuminuria, nerve conduction velocity and relative refractory period of the ulnar nerve were checked at montly intervals. During the continuous i.v. infusion over 4 months, blood sugar values were significantly lower, glucosuria had disappeared almost completely and the glycosylated hemoglobin had fallen to near normal values. The mean rate of albumin excretion was 16±5 μg/min at rest and 76±26 μg/min during exercise (normal: 3.9±0.4 and 4.8±1.2 μg/min, respectively) and did not change significantly. Nerve conduction velocity in the ulnar nerve rose significantly under i.v. insulin therapy from 47.9±0.6 m/sec to 52±0.6 m/sec. Similarly, the relative refractory period of the same nerve fell significantly from 3.7±0.2 to 1.9±0.1 msec (i.e. to within normal range). It is concluded that functional disturbances of peripheral nerve can regress by improved blood sugar control with continuous i.v. insulin infusion over 4 months. On the other hand, incipient microangiopathy measured as microalbuminuria remains unchanged over the same period of time. If an improvement is at all possible, considerably longer periods of euglycemia are likely to be necessary. Supported by Grant No. 3.964-0.80 from the Swiss National Science Foundation.     

One-year results: palatal implants for the treatment of obstructive sleep apnea.

OBJECTIVE: To evaluate long-term effectiveness of palatal implants for treatment of mild to moderate obstructive sleep apnea (OSA). STUDY DESIGN: A prospective study of 26 referred patients with a pretreatment apnea-hypopnea index (AHI) of 10 to 30 and a body mass index of < or =30, representing an extended follow-up of a subset of 41 patients enrolled in previous short-term trials. RESULTS: Twenty-one of 26 patients (80.8%) experienced a decrease in AHI. Fifteen of 26 patients (57.7%) had a follow-up AHI <10 at 1 year, whereas 13 patients (50%) had a 50% or greater reduction to an AHI <10 at 1 year. Mean AHI was reduced from 16.5 +/- 4.5 at baseline to 12.5 +/- 10.5 at 3 months (P < 0.014) and to 12.3 +/- 12.7 at 1 year (P < 0.019). CONCLUSIONS: Patients initially responding to palatal implants with improved AHI maintained improvement through long-term follow-up at 1 year.     

Cyto- and genotoxic effects of coordination complexes of platinum,palladium and rhodium in vitro

The growing industrial use of platinum group elements as catalysts, especially in automobile exhaust detoxification (trimetal catalytic converters), is causing increasing occupational and environmental pollution. The cytotoxic and mutagenic properties of industrially used coordination complexes of platinum, palladium and rhodium were investigated using the neutral red cytotoxicity assay on two established cell lines and theSalmonella typhimurium/microsome test system (Ames test). Cytotoxic effects of the platinum complexes, measured as ED₅₀, occurred at test concentrations of 0.2 mM. The analogous palladium salts tested were 3 times less toxic with ED₅₀ being 0.6 mM, while the rhodium salts proved to be 30 times less toxic (ED₅₀=6 mM). Levels of toxicity of the different complexes of a particular metal did not differ significantly from each other, which indicates that the metal itself is responsible for the toxic effects. In the Ames test, the spontaneous mutation rates increased by factors of 3 to 20 when the four tester strains were exposed to the platinum complexes. The analogous rhodium compounds proved to be considerably less mutagenic, and palladium demonstrated no mutagenic potential. As all of the four tester strains contain different mutations, the mutagenic potential of platinum and rhodium complexes appears to be based on a variety of mechanisms that damage DNA. From these in vitro experiments, it can be concluded that water-soluble complex salts of rhodium are less toxic and have a smaller mutagenic potential than the analogous platinum complexes. For palladium there is no evidence of any mutagenic property. From this point of view, the development of a catalytic converter containing predominantly palladium may be a possible means of minimizing potential health risks from this exhaust detoxification technique.     

Rapid chemical kinetic techniques for investigations of neurotransmitter receptors expressed in Xenopus oocytes

Xenopus laevis oocytes have been used extensively during the past decade to express and study neurotransmitter receptors of various origins and subunit composition and also to express and study receptors altered by site-specific mutations. Interpretations of the effects of structural differences on receptor mechanisms were, however, hampered by a lack of rapid chemical reaction techniques suitable for use with oocytes. Here we describe flow and photolysis techniques, with 2-ms and 100-μs time resolution, respectively, for studying neurotransmitter receptors in giant (≈20-μm diameter) patches of oocyte membranes, using muscle and neuronal acetylcholine receptors as examples. With these techniques, we find that the muscle receptor in BC₃H1 cells and the same receptor expressed in oocytes have comparable kinetic properties. This finding is in contrast to previous studies and raises questions regarding the interpretations of the many studies of receptors expressed in oocytes in which an insufficient time resolution was available. The results obtained indicate that the rapid reaction techniques described here, in conjunction with the oocyte expression system, will be useful in answering many outstanding questions regarding the structure and function of diverse neurotransmitter receptors.     

Quantitative thallium-201 scintigraphy after dipyridamole infusion combined with low level exercise in healthy volunteers

To establish test specific normal limits for quantitative analysis of uptake and washout of ²⁰¹Tl after dipyridamole infusion combined with low level exercise, 20 healthy volunteers were studied with low likelihood of coronary artery disease (CAD) assessed by a stepwise probability analysis based on age, sex, symptoms, resting electrocardiogram, and exercise electrocardiography. Likelihood of CAD in these volunteers was calculated as 1%. After dipyridamole infusion combined with low level exercise, one volunteer complained of headache; no other side effects were observed. There were no chest pain complaints. Maximal hemodynamic changes were achieved during the 6th and 7th min of the test. No ST segment depression was recorded. Visual analysis of the ²⁰¹Tl scintigrams was normal in all volunteers. Mean regional washout at 4 h was 44.37%±2.11%. The regional washout in the 70° LAO view (46.65%±1.10%) was significantly higher than in the anterior and 30° LAO views (43.44%±1.50% and 43.02%±1.45%, respectively). Profiles of uptake and washout of ²⁰¹Tl were different after dipyridamole infusion combined with low level exercise as compared to maximal exercise. Thus, in quantitative analysis of ²⁰¹Tl scintigraphy after dipyridamole infusion in conjunction with low level exercise as applied in the present study, it is mandatory to use normal limits of uptake and washout of ²⁰¹Tl derived from healthy volunteers who underwent the same combined protocol.     

Radioreceptor Assay of Metoprolol in Human Plasma: Comparison with an Enantiospecific High-Performance Liquid Chromatographic (HPLC) Procedure

Plasma concentrations of metoprolol after acute and repetitive administration of R/S-metoprolol to healthy volunteers were measured by a -adrenoceptor subtype-specific radioreceptor assay (RRA) and by an enantiospecific high-performance liquid chromatographic (HPLC) method. In the RRA, R/S-metoprolol showed a 20-fold ₁-subtype selectivity: the S-( – )-enantiomer was 35-fold more potent than the R-( + )-enantiomer. A comparison between S-( – )-metoprolol concentrations detected in the plasma samples by HPLC and those detected by RRA yielded a 1/1 relationship, indicating that active metabolites are not present to a significant extent. These results were independent of the widely scattering metabolic clearance of metoprolol (with the potential of differences in the rate and extent of formation of active metabolites) in the volunteers. In general, HPLC methods can be validated by comparison with RRA in order to clarify whether active metabolites are present and—on the basis of the K_i value from RRA—whether the detection limit of the physicochemical procedure is sufficient to cover the therapeutically relevant range.