Micromolar calcium stimulates proteolysis and glutamate binding in rat brain synaptic membranes.

Incubation of cortical synaptic membranes with low concentrations of calcium resulted in a decrease in the amount of a high-molecular-weight doublet protein and an increase in the sodium-independent binding of glutamate. Both effects were blocked by the thiol protease inhibitor leupeptin. These results suggest that calcium-induced proteolysis of membrane components regulates the number of glutamate receptors in neuronal membranes.

Myocardial tissue concentrations of magnesium and potassium in men dying suddenly from ischemic heart disease.

Optimum tissue levels of magnesium and potassium ions are essential to the structure and function of the myocardium. We hypothesized that an inapparent deficiency of one or both of these elements might contribute to sudden cardiac death in a susceptible person, and in this study investigated levels of these elements in the myocardium of men experiencing sudden death to determine if there was such an association. Subjects dying suddenly with ischemic heart disease had significantly lower levels of myocardial tissue magnesium and potassium than the controls (men dying of acute trauma). The four lowest potassium values were obtained for the only men in the group with a history of angina (P less than 0.0005). Three of the men with angina also had the lowest tissue magnesium levels (P less than 0.005). The intriguing finding gives support to the hypothesis.

Early function as the principal correlate of graft survival. A multivariate analysis of 200 cadaveric renal transplants treated with a protocol incorporating antilymphocyte globulin and cyclosporine.

We examined the factors determining graft survival in 200 consecutive cadaveric renal transplants managed on a quadruple-therapy protocol: Minnesota antilymphoblast globulin, cyclosporine, azathioprine, and low-dose prednisone. Perioperative central venous pressure monitoring and volume expansion were emphasized. To avoid CsA nephrotoxicity in the early posttransplant period, patients were treated with ALG until renal function was established (a mean of 7 days). Therapeutic CsA levels were achieved before ALG was discontinued. Azathioprine was used to supplement CsA in patients with nephrotoxicity or rejection. Twelve-month graft survival was 85% (first transplants 86%, retransplants 79%), with patient survival of 95%. ALG was not associated with excessive clinical cytomegalovirus infections, which occurred in 5% of patients, or with malignancy. When 3 technical failures were excluded, an analysis of numerous factors in the pretransplant and peritransplant period revealed that the strongest correlate of one-year graft survival was early renal function. Grafts with delayed function (DF) had 75% survival, compared with 91% for grafts with good early function (EF). A multivariate analysis confirmed this association: the relative risk of graft loss was increased 2.86 times for DF compared with EF. The mechanism of the deleterious effect of DF was apparently multifactorial: the DF group, by definition, contained all the kidneys that never functioned, but some risk also persisted in kidneys that achieved function. One reason for this may be that DF kidneys that achieved function had higher mean serum creatinine values at 1 month: elevated serum creatinine values at 1 month were strongly associated with increased risk of graft loss regardless of initial function. There was also a higher number of rejection episodes diagnosed in the DF group. These observations suggest that early renal function is a major determinant of graft outcome and should be a target for efforts to further improve renal graft survival.

Longevity of cold-exposed rats: a reevaluation of the "rate-of-living theory".

It has been postulated that increased energy expenditure results in shortened survival. To test this "rate-of-living theory" we examined the effect of raising energy expenditure by means of cold exposure on the longevity of rats. Male 6-mo-old SPF Long-Evans rats were gradually accustomed to immersion in cool water (23 degrees C). After 3 mo they were standing in the cool water for 4 h/day, 5 days/wk. They were maintained on this program until age 32 mo. The cold exposure resulted in a 44% increase in food intake (P less than 0.001). Despite their greater food intake, the cold-exposed rats' body weights were significantly lower than those of control animals from age 11 to 32 mo. The average age at death of the cold-exposed rats was 968 +/- 141 days compared with 923 +/- 159 days for the controls. The cold exposure appeared to protect against neoplasia, particularly sarcomas; only 24% of the necropsied cold-exposed rats had malignancies compared with 57% for the controls. The results of this study provide no support for the concept that increased energy expenditure decreases longevity.

Effect of voluntary exercise on longevity of rats.

The purpose of this study was to obtain information regarding the effects of exercise on longevity in rats. The exercise used was voluntary activity wheel running. The runners gradually decreased their running from approximately 4 to approximately 1 mile/day as they aged from 9 to 30 mo. The runners lived slightly but significantly longer than sedentary freely eating controls and sedentary pair-fed controls (1,012 +/- 138 vs. 923 +/- 160 and 928 +/- 186 days) but significantly less long than food-restricted paired-weight sedentary controls (1,113 +/- 150 days). Although the exercise improved survival, it did not result in an extension of life-span. In contrast, the food-restricted paired-weight sedentary rats showed a true increase in life-span. The paired-weight rats also had a significantly reduced incidence of malignancies compared with the other three groups. However, there was no significant difference between the runners and the freely eating or pair-fed sedentary controls in the cause of death. These results provide evidence that exercise improves survival but does not result in an extension of life-span in rats.

Hypertension and unilateral vascular occlusion. Diagnosis and surgical intervention.

Four hypertensive patients with unilateral atheromatous renal arterial occlusion have been studied. Each showed elevation of renal venous activity on the side of the vascular occlusion relative to the opposite side. Three of the patients underwent nephrectomy with amelioration of their hypertension. It is concluded that surgical treatment is valid therapy in patients with atheromatous unilateral renal vascular occlusion and ipsilateral elevation of renal venous renin activity.

Terminal loop cutaneous ureterostomy in renal transplantation.

Patients presenting for renal transplantation with urinary diversion abnormalities pose serious problems. The use of a terminal loop cutaneous ureterostomy (TLCU) in patients whose outcome was satisfactory was first described in 1977. Primary urinary drainage was achieved in 3 recipients of cadaver renal allografts by creating a TLCU. This method of drainage has been satisfactory in these patients with follow-up between four and thirty months. We suggest that this simple technique should be considered more frequently for selected patients who require supravesical urinary diversion.

Regulation by calcium ions of glutamate receptor binding in hippocampal slices.

Hippocampal slices were incubated in a Krebs-bicarbonate buffer with various concentrations of calcium and [3H]glutamate receptor binding was measured in crude synaptic membranes derived from these slices. Increasing the calcium concentration from 0 to 2.5 mM resulted in a 2.2-fold increase in the maximal number of the Na-independent [3H]glutamate binding sites without changes in their affinity for [3H]glutamate. This effect was totally blocked by the addition of the protease inhibitor leupeptin (50 microM) to the slice incubation medium. No effect was observed on the Na-dependent [3H]glutamate binding nor on the Na-independent [ 3H ]glutamate binding measured in the presence of a concentration of calcium of 250 microM. Increasing the calcium concentration also resulted in an increased proteolytic activity which was inhibited by about 70% by the addition of leupeptin. Finally, increasing the calcium concentration induced the degradation of high-molecular weight proteins, the microtubule-associated proteins (MAPs) and the 220 000 dalton doublet protein corresponding to fodrin. Both effects were partially prevented by the addition of leupeptin in the slice incubation medium. These results indicate that the same calcium-dependent processes which were previously shown to regulate [ 3H ]glutamate receptor binding to hippocampal membranes occur in the hippocampal slice preparation, and they suggest a mechanism by which fluctuations in calcium levels can activate a calcium-dependent proteinase, the degradation of cytoskeletal-associated proteins and the unmasking of additional glutamate receptors. The participation of such processes in various forms of plasticity is discussed.

The regulation of pyruvate dehydrogenase activity in rat hippocampal slices: effect of dichloroacetate.

The effects of dichloroacetate (DCA), an inhibitor of pyruvate dehydrogenase kinase, on the phosphorylation of the alpha-subunit of pyruvate dehydrogenase and on the activity of pyruvate dehydrogenase (pyruvate:lipoamide oxidoreductase (decarboxylating and acceptor-acetylating), EC 1.2.4.1, PDH) were investigated in rat hippocampal slices. Incubating hippocampal slices with increasing concentrations of DCA resulted in an increase in the active portion of PDH, without changes in the total PDH activity, as well as an increase in the in vitro phosphorylation of alpha-PDH. The effect of DCA on PDH activity was very rapid, being almost maximal after 5 min. These results indicate that DCA in the hippocampal slice preparation inhibits PDH kinase and consequently stimulates PDH activity by decreasing its endogenous state of phosphorylation. Moreover the time-course of the effect of DCA suggests that the turnover rate of the phosphate group carried by alpha-PDH is very rapid and can be manipulated by altering PDH kinase activity.

Ethylene oxide allergy in a dialysis center: prevalence in hemodialysis and peritoneal dialysis populations.

Chronic hemodialysis (HD) and peritoneal dialysis (PD) patients in one dialysis center were examined for (EO)-related sensitization. Five of 56 (8.9%) HD patients and 0 of 30 PD patients skin tested with a conjugate of human serum albumin (HSA) and EO had positive skin prick tests. The sera of 13 of 107 (12.1%) HD patients including sera from 5 patients with negative skin tests were positive in an EO-HSA radioallergosorbent test (RAST). Sensitized patients in this population did not experience allergic-type reactions during hemodialysis. There were no positive EO-HSA RAST results which could be ascribed to PD. Non-specific cutaneous responsiveness of the renal failure patients was compared with that of normal adult subjects by the use of skin prick tests with codeine phosphate and histamine phosphate. A significantly reduced responsiveness is present in chronic renal failure patients which would be expected to lower the sensitivity of the diagnostic skin test by comparison with the RAST.

Tuberculosis in dialysis patients.

In a retrospective study over a 13-year period, data from one of the largest dialysis units in Canada were reviewed. Seven cases of active tuberculosis were identified among a dialysis population of 433 patients. Although this was not a controlled study the data suggests a greater than 10 fold increase in incidence of tuberculosis among patients with end stage renal disease compared to the total population. The majority of patients were over 40 years of age; race and immigrant status appeared to be risk factors, and tuberculin skin tests in the main were unhelpful diagnostically. Symptoms and signs mimicked that of underlying chronic renal disease in most instances, and extrapulmonary disease occurred in 3 of 7 patients. Therapy proved safe and effective in all cases. In terms of the epidemiological and clinical indices the present study tends to support the observations of investigators in other countries.

Polyclonal B cell hyperplasia associated with Epstein-Barr virus causing acute renal allograft failure.

Six weeks post cadaver renal transplantation, a patient developed a flu-like illness. Acute renal failure unresponsive to anti-rejection therapy occurred and he died four days later from Pneumocystis carinii pneumonia and Streptococcus viridans septicemia. Autopsy revealed a diffuse polymorphic polyclonal B cell infiltrate occupying most organs, including the allograft. Primary Epstein-Barr Virus (EBV) infection was established by 1) rising anti-EBV antibody titres; 2) the demonstration of EBV nuclear antigen in the infiltrate and 3) the presence of EBV specific DNA sequences in affected tissues. EBV associated polymorphic B cell hyperplasia can mimic rejection and result in acute allograft failure.

Simultaneous determination of delta9-tetrahydrocannabinol and 11-nor-9-carboxy-delta9-tetrahydrocannabinol in human plasma by solid-phase extraction and gas chromatography-negative ion chemical ionization-mass spectrometry.

Delta9-tetrahydrocannabinol (THC) and 11-nor-9-carboxy-delta9-tetrahydrocannabinol (THCA) in human plasma can be simultaneously detected using solid-phase extraction with gas chromatography and negative ion chemical ionization mass spectrometry. THC-d3 and THCA-d3 are added as internal standards; protein is precipitated with acetonitrile and the resulting supernatants diluted with 0.1 M sodium acetate (pH 7.0) prior to application to the solid-phase extraction columns. THC and THCA were eluted separately and then pooled, dried under air, and derivatized with trifluoroacetic anhydride and hexafluoroisopropanol. The derivatized THC-d0 gives abundant molecular anions (m/z 410), and the derivatized THCA-d0 gives abundant fragment ions (m/z 422) formed by loss of (CF3)2CHOH from its molecular anion. The recoveries of THC and THCA were 74% and 17%, respectively. The lower and upper limits of quantitation were 0.5 and 100 ng/mL for THC and 2.5 ng/mL and 100 ng/mL for THCA. The within-run accuracy and precision for THC (measured at 0.5, 1, 10 and 75 ng/mL) ranged from 98 to 106% (% target) and 4.1 to 9.5 (%CV), respectively. For THCA, the within-run accuracy and precision (measured at 2.5, 5, 10, and 75 ng/mL) ranged from 89 to 101% and 4.3 to 7.5%, respectively. The between-run accuracy and precision for THC ranged from 92 to 110% and 0.4 to 12.4%, respectively. The between-run accuracy and precision for THCA ranged from 97 to 103% and 6.5 to 12.3%, respectively. In processed samples stored in reconstituted form at -20 degrees C, THC and THCA were stable for at least three days. THC and THCA stored in plasma were stable following three freeze/thaw cycles. THC and THCA in whole blood at room temperature for 6 h, or in plasma stored at room temperature for 24 h, did not show significant change. Storage in polypropylene containers for 7 days at -20 degrees C and the presence of 1% sodium fluoride or the cannabinoid receptor antagonist, SR141716, at 1 microg/mL did not interfere with the quantitation of THC and THCA. In three individuals who smoked marijuana under controlled dosing conditions, peak THC concentrations of 151, 266, and 99 ng/mL were seen in the first plasma samples drawn immediately after the end of smoking, and corresponding peak THCA concentrations of 41, 52, and 17 ng/mL occurred at 0.33 to 1 h after cessation of smoking.

Propionibacterium acnes immunotherapy in chronic recurrent canine pyoderma. An adjunct to antibiotic therapy.

In a randomized, double-blind, placebo-controlled study, dogs with chronic recurrent pyoderma were treated with antibiotics plus intravenous injections of either Propionibacterium acnes or placebo. Responses (an increase, decrease, or clearing of lesions) were measured and evaluated statistically. Eighty percent (12 of 15) of the dogs treated with antibiotics and P acnes compared with 38% (five of 13) of the dogs treated with antibiotics and placebo responded with significant improvement or complete remission of lesions at the end of the 12-week treatment schedule (P less than 0.05).