Ascorbate modulates glutamate-induced excitations of striatal neurons

To assess the role of ascorbate (AA), an antioxidant vitamin, in modulating striatal activity, single-unit recording was combined with iontophoresis in awake, unrestrained rats. Brief applications of AA (20 s, 5-80 nA) elicited few changes in either basal activity or activity evoked by continuous application of glutamate (GLU), but relatively high AA ejection currents (>40 nA) often inhibited fast-firing units. Comparable results were obtained with the antioxidant isomer, iso-AA, suggesting the AA-induced inhibition represents a high-dose, antioxidant effect. When applied for prolonged periods (2-4 min) at doses that failed to alter basal activity, AA either enhanced or attenuated the excitatory response to test pulses of GLU. The AA-induced enhancement occurred more frequently (16 vs. 6 applications) and was characterized by a more rapid (shorter onset and peak latencies) and more pronounced (greater peak magnitude) excitation to GLU without an evident change in offset latency. In most cases, further increases in AA ejection current attenuated the GLU response. Iso-AA, in contrast, had only inhibitory effects, which occurred at moderate- to high-dose applications. Collectively, these results suggest that AA, apart from its antioxidant effects, modulates phasic changes in striatal excitability induced by GLU. Because extracellular levels of striatal AA fluctuate in relation to behavioral activation, this neuromodulatory action of AA may contribute to behaviorally relevant changes in sensorimotor responsivity.     

Viral contamination of food products: a poorly understood public health problem

Throughout the world there have been several epidemics of food-borne diseases (FBD) about which there is lack of sufficient information for public health institutions to take appropriate measures. This study was conducted for the purpose of contributing to the dissemination of information on these diseases and their etiologic agents, epidemiology, and control. The study was based on data from 61 sources, including review articles, reports of outbreaks, and databases. Results reveal considerable underregistration and lack of data on FBD throughout the various countries, with viruses being the second most important cause of FBD in the United States of America. Two agents, Norwalk virus and hepatitis A virus, were the fifth and sixth most frequent causes, respectively, although the former was the single most frequent cause of FBD in 1982 and the second most frequent cause of water-borne diseases during the period from 1986 to 1988. Despite the scarcity of information on the problem, rotavirus, poliovirus, hepatitis E virus, astrovirus, and small gastroenteric viruses are also important causes of FBD. We also discuss the importance of viral zoonoses, especially hemorrhagic fevers transmitted by contact with rodent feces and tick-borne viral encephalitides (Lassa fever). There is discussion of the controversial mad cow disease and its potential transmission through food products, as well as of dietary aspects of the management of AIDS and other viral infections. Finally, measures for the prevention and control of FBD are described.     

Liver function following pregnancy complicated by the HELLP syndrome

Serum levels of aminotransferases, lactate dehydrogenase, gammaglutamyl transferase, alkaline phosphatase, albumin and conjugated bilirubin, measured in 54 women at a median of 31 months (range 3-101) after pregnancies complicated by the HELLP syndrome, were not elevated. Total bilirubin levels, however, were elevated in 20% of these women; this represents a significant difference from the prevalence in 151 women with a previous normal pregnancy (chi2 = 12.23, P < 0.001), or in the normal female population (chi2 = 22.34, P < 0.00001). This raises the possibility that a dysfunction of the bilirubin-conjugating mechanism represents a risk factor for the development of the HELLP syndrome.     

Effects of arterial versus venous sampling on analysis of glucose kinetics in man

A compartmental model is presented to account for transient and steady-state changes in blood glucose concentration which result from transit through the forearm and hand in man. This model permits the inter-conversion of arterial and venous data and the derivation of arterial equivalent total body glucose models from venous data. Data were obtained from subjects in the basal state following a pulse injection of [1-14C]glucose tracer. An artery, an antecubital vein, and a dorsal vein of a heated hand (68 degrees C environment) were sampled. Blood transit time is shorter 0.3 vs. 1.0 min) and irreversible glucose loss is reduced (1.9 vs. 2.9%) in the heated hand preparation when compared to the antecubital vein preparation. Because of the smaller correction required and the smaller variation among individuals when heated hand rather than antecubital vein data are obtained, we suggest that for analysis of whole-body kinetics such data should be used along with the compartmental model correction when arterial data cannot be obtained.     

Impact of Microwave Interference on Dynamic Operation and Power Dissipation of CMOS Inverters

The effects of electromagnetic interference (EMI) from high-power microwave signals on CMOS inverters are reported. In order to study these effects more effectively, a novel analytical parameter extraction method, which allows us to predict the dynamic operation of the inverters under interference from experimentally measured load-line characteristics, is developed. Based on the method, the output voltages, output short-circuit currents, propagation delays, and dynamic power dissipation during EMI were extracted. The results showed that the inverters suffer severely from compressed output voltage swing, bit errors, significant changes in the propagation delays, and substantially increased short-circuit currents, as well as a large increase in dynamic power dissipation during logic state transition from high to low and vice versa. Scaling down of the inverters showed that such operational parameters of the devices were more strongly affected by the interference, resulting in significantly more vulnerable CMOS inverters.