A vertically integrated GaAs bipolar dynamic RAM cell with storagetimes of 4.5 h at room temperature

The storage times of FET-accessed GaAs dynamic RAM cells are limited to less than 1 min at room temperature by gate leakage in the access transistor. These transistor leakage mechanisms have been eliminated by designing a vertically integrated DRAM cell in which an n-p-n bipolar access transistor is merged with a p-n-p storage capacitor. Storage times of 4.5 h are obtained at room temperature, a 1000-fold increase over the best FET-accessed cells     

Abnormal carnitine distribution in the muscles of patients with idiopathic inflammatory myopathy

OBJECTIVE: To analyze the levels of free carnitine and carnitine esters in the muscles of patients with inflammatory myopathies. METHODS: Six men and 7 women with inflammatory myopathy and 25 age-matched healthy controls were studied. Free carnitine and carnitine esters in muscle homogenates were measured by a radiochemical procedure. Muscle histochemical staining and measurement of respiratory chain enzyme activity were also performed. RESULTS: Eleven patients had muscle carnitine insufficiency. Five of them had subsarcolemmal oxidative accumulations, 5 had lipid droplets, and 4 had defects of the respiratory chain enzyme complexes. CONCLUSION: Abnormal distribution of muscle carnitine is present in patients with inflammatory myopathies and could impair muscle function. Coexistent mitochondrial dysfunction may contribute to carnitine insufficiency.     

Height, occupation and back pain in a national prospective study

Back pain is an important public health problem but there is a paucity of knowledge about risk factors and causal mechanisms. Previous studies have shown that tall men are more at risk of back pain, although observations in women have been less consistent. This paper presents findings from a national longitudinal study of 3262 men and women aged 43 yr. Standing height and sitting height were related to 18-month reported prevalence of 'sciatica, lumbago or severe backache' in both men and women. The paper investigates explanations for these findings using previously collected data on childhood growth and detailed lifetime occupational histories. Neither greater susceptibility of tall men to heavy lifting, nor the timing of growth, were able to account for these relationships. To assess further the association between height and back pain, information is needed on the relationship between stature and characteristics of spinal structure.     

Evidence for a catabolic role of glucagon during an amino acid load

Despite the strong association between protein catabolic conditions and hyperglucagonemia, and enhanced glucagon secretion by amino acids (AA), glucagon's effects on protein metabolism remain less clear than on glucose metabolism. To clearly define glucagon's catabolic effect on protein metabolism during AA load, we studied the effects of glucagon on circulating AA and protein dynamics in six healthy subjects. Five protocols were performed in each subject using somatostatin to inhibit the secretion of insulin, glucagon, and growth hormone (GH) and selectively replacing these hormones in different protocols. Total AA concentration was the highest when glucagon, insulin, and GH were low. Selective increase of glucagon levels prevented this increment in AA. Addition of high levels of insulin and GH to high glucagon had no effect on total AA levels, although branched chain AA levels declined. Glucagon mostly decreased glucogenic AA and enhanced glucose production. Endogenous leucine flux, reflecting proteolysis, decreased while leucine oxidation increased in protocols where AA were infused and these changes were unaffected by the hormones. Nonoxidative leucine flux reflecting protein synthesis was stimulated by AA, but high glucagon attenuated this effect. Addition of GH and insulin partially reversed the inhibitory effect of glucagon on protein synthesis. We conclude that glucagon is the pivotal hormone in amino acid disposal during an AA load and, by reducing the availability of AA, glucagon inhibits protein synthesis stimulated by AA. These data provide further support for a catabolic role of glucagon at physiological concentrations.     

Acquired autoimmune thrombocytopenia post-bone marrow transplantation for severe combined immunodeficiency

Children with severe combined immunodeficiency (SCID) have profoundly diminished humoral and cellular immunity resulting in death during infancy unless immune reconstitution occurs by bone marrow transplantation (BMT). Thrombocytopenia post-bone marrow transplantation can be seen in relation to infection, graft-versus-host disease (GVHD) and rarely, as an autoimmune phenomenon due to immune dysregulation. We report two cases of severe AITP following BMT for SCID. Both cases developed large intracerebral hemorrhages from which one died. Autoimmune thrombocytopenia in this setting can be life-threatening and we recommend early and active intervention.     

The effect of growth hormone replacement on cortisol metabolism and glucocorticoid sensitivity in hypopituitary adults

OBJECTIVE: Growth hormone (GH) replacement therapy in hypopituitary adults is associated with sodium and water retention. The underlying mechanisms are incompletely understood and a possible contribution of altered cortisol metabolism or action has not been evaluated. We have investigated the effect of GH replacement therapy on cortisol metabolism, cortisol binding globulin and in-vitro glucocorticoid sensitivity in a group of adult hypopituitary patients. DESIGN AND PATIENTS: We studied 19 adult hypopituitary patients (18 adult onset, M:F, 6:13), who were receiving conventional hydrocortisone (16 patients), thyroxine (14 patients), triiodothyronine (1 patient), sex steroid (9 patients), human chorionic gonadotrophin (1 patient) or desmopressin (6 patients) replacement during a 6-month, double blind controlled trial of GH therapy (active:placebo, 8:11) followed by a 6-month open phase of GH (mean dose: 0.2 IU/kg/week, range 0.051-0.27) and after a 6-week washout phase following discontinuation of GH therapy. MEASUREMENTS: Twenty-four-hour urine free cortisol, cortisol metabolites (CoM), ratio 11-hydroxy/11-oxo CoM (F/E) and ratio 5 alpha/beta tetrahydrocortisol were measured at 6 months, 12 months and after the 6 week washout phase. Serum cortisol binding globulin was measured basally, at 6 months, 12 months and after washout. Glucocorticoid sensitivity was determined in lymphocyte preparations from 8 patients, during GH therapy and after washout, using an in-vitro technique dependent on dexamethasone suppression of phytohaemagglutinin-stimulated thymidine incorporation into DNA. Plasma renin activity and aldosterone were measured after 6-12 months GH therapy and after washout. RESULTS: After 6 months of GH, in patients on hydrocortisone (n = 9), there were significant decreases in CoM (mean decrement 21%, P < 0.01), F/E (mean decreased from 1.27 to 1.0, P = 0.04; reference range 0.33-1.29) and 5 alpha/5 beta tetrahydrocortisol (mean decreased from 0.67 to 0.48, P = 0.01) and a subsequent increase after washout. Patients not on hydrocortisone (n = 2) demonstrated a normal basal F/E falling by 25% on GH therapy but no change in CoM. During 12 months of GH therapy, patients on hydrocortisone (n = 7) demonstrated a further trend to decrement in CoM (P = 0.09) which reversed after washout (P = 0.04). Urine free cortisol tended to fall during GH therapy and increased significantly following washout after 12 months treatment (P < 0.02). Serum cortisol binding globulin decreased by 20% (P < 0.05) during 12 months GH treatment but remained within the reference range. In-vitro studies demonstrated a trend to reduced glucocorticoid sensitivity on GH therapy; the maximum inhibition of phytohaemagglutinin by dexamethasone tended to be less on GH therapy (P = 0.052) and was also lower than in 29 normal volunteers (P < 0.05). There were no significant changes in plasma renin but there was a small increment in aldosterone in recumbent patients (P = 0.04) during the open phase of GH therapy in the placebo arm. CONCLUSIONS: GH therapy in hypopituitary adults is associated with an apparent reduction in availability of administered hydrocortisone as measured by urine cortisol metabolites and urine free cortisol. This effect is unlikely to be clinically significant except possibly in ACTH deficient subjects on suboptimal hydrocortisone replacement. The changes in F/E suggest that GH may directly or indirectly modulate the activity of 11 beta-hydroxysteroid dehydrogenase. The apparent decrease in glucocorticoid sensitivity during GH therapy, demonstrated in vitro, merits further investigation.     

Theoretical comparison of SiC PiN and Schottky diodes based on power dissipation considerations

In order to select the optimal device for a particular application, designers must carefully analyze the tradeoffs between competing devices. Recent progress in SiC power rectifiers has resulted in the demonstration of high-voltage PiN and Schottky barrier diodes (SBDs). With both technologies maturing, power electronics engineers will soon face the task of selecting between these two devices. Until recently, the choice was simple, since silicon SBDs are only available for relatively low voltage applications. The choice is not as clear when considering SiC diodes, and guidelines for determining the proper application of each are needed. The purpose of this paper is to provide such guidelines, based on an analysis of the most significant tradeoffs involved.     

Tay-Sachs disease in persons of French-Canadian heritage in northern New England

This study sought to determine whether persons of French-Canadian heritage in northern New England are at high risk for the lethal infantile form of Tay-Sachs disease. In order to accomplish this, death records and laboratory diagnostic records were surveyed to ascertain Tay-Sachs deaths in a cohort of 372,000 live births between 1977-1986. The proportion of the total population with French-Canadian or Jewish heritage was determined from census and birth records, and the ethnic background of Tay-Sachs cases was determined from the corresponding birth records. In 1,860 births, both parents were of Ashkenazi Jewish heritage. One of those children was diagnosed with Tay-Sachs disease. In 41,000 births, both parents were of French-Canadian heritage, and in an additional 93,000 births, one parent was of French-Canadian heritage. No cases of Tay-Sachs disease were identified in the offspring of those individuals. Approximately 14 cases (95% confidence interval 8-20) would be expected, if the gene frequency approximated that reported for individuals of Ashkenazi Jewish heritage. Based on the results of this study, routine testing for Tay-Sachs disease heterozygosity is not indicated for persons of French-Canadian heritage in northern New England. This conclusion may not necessarily be valid for persons of French-Canadian heritage residing in other states. Further studies of Tay-Sachs disease mutations and prevalence among persons of French-Canadian heritage will be important to determine possible regional variations in gene frequencies.     

Antipneumococcal activities of levofloxacin and clarithromycin as determined by agar dilution, microdilution, E-test, and disk diffusion methodologies

The activities of levofloxacin and clarithromycin against 199 penicillin- and macrolide-susceptible and -resistant pneumococci were tested by agar and microdilution methods in air and by disk diffusion and E-test methods in air and CO2. For levofloxacin, >/=99. 0% of strains were susceptible at /=17 mm, regardless of incubation in air or CO2. Although zone sizes were smaller and E-test MICs were higher for clarithromycin in CO2 than those in air, category differences were minor, and susceptibility rates for clarithromycin were similar to those obtained by agar and microdilution in air (range, 76.9 to 80.9% by all methods). For clarithromycin, adjustment of breakpoints based upon distribution of results resulted in susceptibility rates which were similar by all methods (75.8 to 76.9% susceptible, 0 to 1.5% intermediate, 22.6 to 23.1% resistant). Minor discrepancies were obtained with levofloxacin for one strain (0.5%) by microdilution and two strains (1.0%) by disk diffusion in CO2. For clarithromycin, minor discrepancies were found in three strains (1.5%) by microdilution, seven strains (3.5%) by agar dilution, four strains (2.0%) by E-test in air, six strains (3.0%) by disk diffusion in air, and five strains (2.5%) by disk diffusion in CO2. Major discrepancies occurred with levofloxacin in one strain (0.5%) by microdilution but were not found with clarithromycin. Very major discrepancies were not seen with levofloxacin, but occurred with clarithromycin in five strains (2.5%) by microdilution, three strains (1.5%) by agar dilution, two strains (1.0%) by E-test in air, eight strains (4.0%) by disk diffusion in air, and one strain (0.5%) by disk diffusion in CO2.