A comparison of basal and insulin-stimulated glucose transport in rat adipocyte plasma membranes.

Specific D-glucose transport in plasma membranes prepared from control and insulin-treated rat adipocytes was measured using a recently developed dual isotope ([3H]-D-glucose and [14C]-L-glucose), rapid filtration assay which allowed measurements of initial rates at 1 s and 37 degrees. Plasma membranes from insulin-treated adipocytes showed an increase in glucose transport compared with control cells. Saturation kinetic data revealed that the plasma membranes from insulin-treated and control cells had the same Km (26 mM) for glucose transport, whereas insulin treatment increased the Vmax from 4433 pmol/mg protein/s to 9465 pmol/mg proteins/s. Arrhenius plots showed no difference in the energy of activation between control and insulin-stimulated glucose transport states. The optimum pH of both control and insulin-stimulated glucose transport was 7.4. Lower or higher pHs progressively decreased both control and insulin-stimulated glucose transport proportionately. Calcium in the transport assay media did not affect basal or insulin-stimulated glucose transport. However, omission of calcium from the adipocyte incubation media significantly lowered the insulin stimulation by 24% while basal levels were not significantly affected. Insulin specifically bound to the plasma membrane was carried through the fractionation procedure, but removal of this insulin did not alter the stimulated glucose transport. Glucose transport by plasma membranes from control or insulin-treated adipocytes was equally (percentage) inhibited by N-ethylmaleimide, dithiothreitol, reduced glutathione, or cytochalasin B. No inhibition of control or insulin-stimulated transport was seen with cytochalasin D or oxidized glutathione. The data presented are consistent with insulin causing the formation of new transport sites similar to the existing basal sites.

Standardization fo a digestion-filtration method for isolation of pancreatic islets.

Standardization of a technic for isolating large numbers of pancreatic islets is described. This procedure employed collagenase digestion of rat pancreatic tissue in a cylindrical wire screen in order to separate isolated islets from undigested pancreas. From this basic protocol the following conditions were established: (1) the duration of the initial digestion period was found to be optimal at six minutes; (2) three subsequent digestions of one minute each effected maximum islet yield; (3) the optimal initial collagenase concentration was found to be 1,000 U. (Worthington)/ml.; and (4) proper reductions of collagenase concentrations during the three subsequent digestions were found to be 50 per cent of each preceding incubation period. This method, combined with Ficoll gradient separation, yielded a mean of 800 islets per two rat pancreases. The isolated islets appeared morphologically intact, contained 0.36 +/- 0.05 mug. protein/islet, and demonstrated a normal biphasic release of insulin in response to stimulative levels of D-glucose. The present method provides a means for obtaining a large mass of viable islet cell tissue in a short time.

D-lactate encephalopathy.

Although D-lactate is not a product of human intermediary metabolism, absorption of D-lactate produced by abnormal intestinal bacteria can cause systemic acidosis in patients who have undergone gastrointestinal surgery, particularly jejunoileal bypass. In order to learn more about the prevalence of D-lactate encephalopathy, its occurrence in other disorders, and how well D-lactate concentration correlates with clinical symptoms, serum D-lactate levels were determined in several specific populations. D-lactate was undetectable (less than 0.5 mmol/liter) in 72 healthy volunteers and 57 obese persons. In 33 patients who had jejunoileal bypass, 16 reported symptoms consistent with D-lactate encephalopathy since surgery. Nine of these 16 had D-lactate levels greater than 0.5 mmol/liter (range 0.7 to 11.5 mmol/liter). Levels of D-lactate fluctuated over time, and in two patients, markedly elevated levels correlated with an encephalopathy accompanied by hyperchloremic metabolic acidosis and elevated anion gap. In 470 randomly chosen hospitalized patients, D-lactate level greater than 0.5 mmol/liter was found in 13 (2.8 percent), and 60 percent of these had a history of gastrointestinal surgery or disease. It is concluded that elevated serum D-lactate levels are relatively common in patients with jejunoileal bypass, and although more rare, occur in other gastrointestinal disorders as well. The symptoms of D-lactate encephalopathy are quite sensitive, but not necessarily specific for this disorder.

The failure of neonates to form red blood cell alloantibodies in response to multiple transfusions.

Red blood cell alloantibody production was studied in 90 neonates who received a mean of 14.1 transfusions (range 2-35) from an average of 8.9 donors during the first three months after birth. Standard antibody detection procedures were done with the use of a selected red blood cell panel. No unexpected alloantibodies were detected. These findings suggest, at a 99% confidence level, that neonates do not make red blood cell alloantibodies in response to transfusion, indicating that repeated compatibility testing is probably unnecessary. Thus, following initial antibody screening and compatibility tests, further compatibility testing can be eliminated.

Similarities between insulin, hydrogen peroxide, concanavalin A, and anti-insulin receptor antibody stimulated glucose transport: increase in the number of transport sites.

Plasma membranes from insulin or insulin mimicker (hydrogen peroxide, anti-insulin receptor antibody, and concanavalin A) treated adipocytes showed an increase in glucose transport compared to control cells due to an increase in Vmax and not due to alteration in Km. Arrhenius plots showed no difference in the energy of activation between control and insulin or insulin mimicker stimulated glucose transport states. Glucose transport by plasma membranes from control or treated adipocytes was equally (percentage) inhibited by N-ethylmaleimide, reduced glutathione, or cytochalasin B. The data indicate that the increased transport resulted from addition of new transport sites similar to the sites existing in the basal state.

A fluorometric high performance liquid chromatographic assay for vanillylmandelic acid (VMA) developed from a commercial kit method.

A fluorometric procedure based on the Bio-Rad Vanillylmandelic Acid (VMA) by High Performance Liquid Chromatography (HPLC) Test was developed. Detection by fluorescence provides better sensitivity and specificity than the Pisano spectrophotometric method. Use of a C18 mini-column extraction to extract VMA prior to HPLC analysis significantly reduced the late eluting peaks. A linear range was established up to 400 mumol/L of VMA. Within-run and between-run CV's were 3.0% and 3.7%, respectively. In a comparison of this fluorometric method with the Pisano spectrophotometric method, a linear regression of y = 0.807x + 2.185 was obtained with a correlation coefficient of 0.945. In the analysis of over 50 samples, no intereferences have been found.

Vitamin supplements and purported learning enhancement in mentally retarded children.

Dr. Ruth Harrell and her colleagues conducted a study in 1981 in which the administration of high dosages of vitamins were determined to dramatically improve the intellectual functioning of mentally retarded children. This paper documents the efforts of its authors to replicate the Harrell et al. research and, although no significant differences were found between active treatment groups and control groups at study's end, a thorough comparison is made between the two research efforts.

Variables affecting the use of prescriptive formulae to fit modern nonlinear hearing aids.

It is routine for audiologists to fit nonlinear hearing aids by using one of several current prescriptive formulae. While such an approach might result in acceptable fittings for single-channel analog compression hearing aids, its direct application to fitting current multichannel compression hearing aids may result in less than an optimal fit. In this paper, the effects of filter bandwidth, number of channels, detector type, compression threshold, attack and release times, and distortion on the final output of a nonlinear compression hearing aid are discussed. The subjective results of such effects and its implications on our clinical practice will be explored as well.

Enhancing nurse mobility in Europe: a case for language skills.

The recognition of professional qualifications in all European Union (EU) member states for nurses is covered by both sectoral and general systems directives, yet in reality, few nurses take up their rights as European citizens to live and work in another EU country. One of the main reasons for this is a lack of linguistic skills. This article argues that the nursing profession should be taking a more active role in enabling nurses to move freely around Europe by encouraging language acquisition. It is argued that there are political, social, economic, professional and individual reasons why this should be so. The author gives a brief account of a pilot project which is currently under way to help improve (albeit in a small way) this situation. The project, which has been granted financial support of 100,000 ECU from the European Commission's new training programme, Leonardo da Vinci, will create a multimedia language pack in four languages aimed specifically at nurses.

European healthcare. Foreign exchange.

The European Union offers sources of funding, skills and experience, so why are health organisations not tapping into them? Carol Ludvigsen and Janet Allen recount one trust's experiences.