Difference limens for formant patterns of vowel sounds

Studies of thresholds for discrimination of formant frequency variation in synthetic vowel sounds have been predominantly limited to variations in a single formant. Here, differences limens (DLs) are presented for multiformant variations expressed in measures of delta F and as distances in the auditory-perceptual space (APS) proposed by J. D. Miller [J. Acoust. Soc. Am. 85, 2114-2134 (1989)]. DLs for four subjects were estimated along 102 synthetic vowel continua representing five patterns of formant variation [(1) single variation in F1; (2) single variation in F2; (3) parallel simultaneous variation in F1 and F2; (4) opposing simultaneous variation in F1 and F2; and parallel simultaneous variation in F1, F2, and F3] and 17 within- or between-category vowel sounds. Minimal uncertainty methodology was employed utilizing an adaptive up-down procedure with a cued, two-interval forced-choice (2IFC) task. The results of this experiment reflect smaller DLs for both single- and multiple-formant changes than have been found in the past and also suggest that discrimination of parallel multiformant variation is significantly better than opposing multiformant or single-formant variation.     

Establishment and neurite outgrowth properties of neonatal and adult rat olfactory bulb glial cell lines

Two glial cell types surround olfactory axons and glomeruli in the olfactory bulb (OB) and may influence synapse development and regeneration. OB astrocytes resemble type-1 astrocytes, and OB ensheathing cells resemble non-myelinating Schwann cells. We have produced clonal OB astrocyte and ensheathing cell lines from rat neonatal and adult OB cultures by SV40 large T antigen transduction. These cell lines have been characterized by morphology, growth characteristics, immunophenotype, and ability to promote neurite outgrowth in vitro. Neonatal and adult ensheathing cell lines were found to support higher neurite outgrowth than OB astrocyte lines. Neonatal OB astrocyte lines were of two types, high and low outgrowth support. The low support astrocyte lines express J1 and a chondroitin sulfate-containing proteoglycan as do astrocytes encircling the neonatal glomeruli in vivo. The adult OB astrocyte cell lines supported lower levels of outgrowth than adult ensheathing cell lines. These results are consistent with a positive role for ensheathing cells in OB synapse regeneration, in vivo. Further, based on our results, we hypothesize that ensheathing cells and high-outgrowth astrocytes facilitate axon growth in vivo, while low outgrowth astrocytes inhibit axon growth and may facilitate glomerulus formation.     

Effects of fatty acid oxidation on glucose utilization by isolated hepatocytes

We have studied the inhibitory action of long- and short-chain fatty acids on hepatic glucose utilization in hepatocytes isolated from fasted rats. The rates of hepatic glucose phosphorylation and glycolysis were determined from the tritiated products of [2-3H] and [6-3H]glucose metabolism, respectively. The difference between these was taken as an estimate of the 'cycling' between glucose and glucose-6-phosphate. In the presence of 40 mM glucose this cycling was estimated at 0.68 mumol/min/g wet wt. Glucose phosphorylation was unaffected during palmitate and hexanoate oxidation to ketone bodies but glycolysis was inhibited. The rate of glucose cycling was increased during this phase to 1.25 mumol/min/g. Following the complete metabolism of the fatty acids, glycolysis was reinstated and cycling rates returned to control levels. Hepatic glucose cycling appears to be an important component of the glucose/fatty acid cycle.     

Desensitization of mutant acetylcholine receptors in transgenic mice reduces the amplitude of neuromuscular synaptic currents

While the slow onset of desensitization of nicotinic acetylcholine receptors (AChRs), relative to the rate of acetylcholine removal, excludes this kinetic state from shaping synaptic responses in normal neuromuscular transmission, its role in neuromuscular disorders has not been examined. The slow-channel congenital myasthenic syndrome (SCCMS) is a disorder caused by point mutations in the AChR subunit-encoding genes leading to kinetically abnormal (slow) channels, reduced miniature endplate current amplitudes (MEPCs), and degeneration of the postsynaptic membrane. Because of this complicated picture of kinetic and structural change in the neuromuscular junction, it is difficult to assess the importance of the multiple factors that may be responsible for the reduced endplate current amplitudes, and ultimately the clinical syndrome. In order to address this we have used a transgenic mouse model for the SCCMS that has slow AChR ion channels and reduced endplate responsiveness in the absence of any of the degenerative changes. We found that the reduction in MEPC amplitudes in these mice could not be explained by either reduced AChR number or by reduced AChR channel conductance. Rather, we found that the mutant AChRs in situ manifested an activity-dependent reduction in sensitivity that caused diminished MEPC and endplate current amplitude with nerve stimulation. This observation demonstrates that the basis for the reduction in MEPC amplitudes in the SCCMS may be multifactorial. Moreover, these findings demonstrate that, under conditions that alter their rate of desensitization, the kinetic properties of nicotinic AChRs can control the strength of synaptic responses.     

Chances of cure are not compromised with sphincter-saving procedures for cancer of the lower third of the rectum

BACKGROUND: The goal of this study was to compare patterns of recurrence and long-term outcome after sphincter-saving procedures (SSPs) and abdominoperineal resection (APR) in patients with tumors located in the lower third of the rectum. METHODS: We reviewed the charts of 1001 patients operated on for primary rectal adenocarcinoma between 1980 and 1991. All patients with tumors located between 5 and 7 cm from the anal verge and treated with curative intent were included. RESULTS: Of the 261 patients who met our criteria, 162 had undergone SSP and 99 had undergone APR. The local recurrence rates for SSP and APR were 8% and 11%, respectively (p = 0.41), and the distant metastases rates were 23% and 28%, respectively (p = 0.35). Recurrence and distant metastases rates for SSP and APR, respectively, did not differ by TNM classification: state I, 10% versus 9% (p = 0.9); stage II, 25% versus 43% (p = 0.13); and stage III, 56% versus 57% (p = 0.92). Five-year disease-free survival rates for SSP and APR patients were 70.5% and 62.3%, respectively (p = 0.2). CONCLUSIONS: Tumors in the lower third of the rectum can be treated with sphincter-saving procedures without compromising the chance of cure.     

Acute and chronic fetal hypoxia in monochorionic and dichorionic twins

OBJECTIVE: To assess the risk for acute and chronic fetal hypoxia in twin pregnancies. METHODS: We investigated 50 sets of twins (24-38 weeks' gestation, 660-3200 g birth weight) admitted consecutively to our neonatal intensive care unit. Seventy-six infants were appropriate for gestational age (AGA; tenth to 90th percentile), 20 were small for gestational age (SGA; below the tenth percentile), and four were large for gestational age (above the 90th percentile). Twenty-six singleton AGA term newborns served as controls. Umbilical arterial pH was used as a marker for acute and umbilical venous erythropoietin concentration for chronic fetal hypoxia. The results are given as median followed by quartiles. RESULTS: We identified 40 sets of diamniotic-dichorionic twins and ten sets of diamniotic-monochorionic twins with transplacental vascular shunts. In the second-born twin, umbilical arterial pH was lower (7.29, 7.23-7.33) than in the firstborn (7.31, 7.25-7.34) (P = .03), and the incidence of a low pH (less than 7.20) was higher (19 versus 11%). Two second-born twins and none of the firstborn twins had an umbilical arterial pH less than 7.05. In SGA twins, the erythropoietin concentration was elevated (34.8, 22.8-325 mU/mL) compared with that in AGA twins (16.2, 8.2-26.6 mU/mL) (P < .01). In AGA twins, erythropoietin concentration did not differ from that in AGA singleton newborns (19.6, 14.7-31.6 mU/mL). In 12 of 17 twin sets with weight discordancy greater than 15% and in all five twin sets with weight difference greater than 25%, erythropoietin concentration was higher in the smaller twin. The proportion of infants and of complete sets with elevated erythropoietin levels was higher (P < .01) in monochorionic than in dichorionic pregnancies. CONCLUSION: The second-born twin is at increased risk for acute birth asphyxia. Fetal growth restriction in twin pregnancies is associated with chronic fetal hypoxia. Monochorionic twins are at higher risk for chronic fetal hypoxia than are dichorionic twins.     

Development of an animal model for across-herd genetic evaluation of number born alive in swine

An animal model and computer software were developed to conduct across-herd genetic evaluations using data from producers participating in the Sow Productivity Index program of the American Yorkshire Club. The final data set consisted of 61,596 litter records from 1986 to early 1990. The animal model included fixed contemporary group effects and random additive direct, service sire, permanent environmental, and residual effects. Additive genetic relationships among animals were included. A separate relationship matrix for service sires and their sires was also included. A data set similar to the Yorkshire field data was simulated to use in testing the animal model. The simulated data set consisted of 40 herds, each with 120 reproducing dams and either four or five sires. Six generations of simulated data were produced, resulting in 20,605 litter records. These records were then evaluated using the animal model for number of pigs born alive. Finally, correlations between the true breeding values from the simulation and the predicted breeding values were computed. The correlation between the 918 true and predicted sire breeding values was considerably lower for the animal model without a service sire effect than when it was included (.53 vs .74, respectively). However, the difference was cut in half (.66 vs .77) when only sires with greater than five daughter records were included. The high accuracy of the animal model with a random service sire effect indicates that the proposed model adequately accounts for the variation found in records for number of pigs born alive.     

Diffusion bonding of an aluminium-lithium alloy (AA8090) using aluminium-copper alloy interlayers

Diffusion bonds have been produced between sheets of an Al-Li-Cu-Mg-Zr alloy using aluminium-4% copper vapour deposited metallic interlayers. Microstructural changes occurred both in the parent alloy and in the bond interface after diffusion bonding cycles and post-bonding heat treatments were analysed. Different metallographic techniques (light microscopy, scanning and transmission electron microscopy) have been used. Diffusion bonding trials were carried out using the same alloy (AA8090), both in non-superplastic (T6) and superplastic conditions. Differences in their behaviours in relation to diffusion bonding were observed.     

Model Driven Architecture

Bei der Model Driven Architecture (MDA) bilden Modelle die zentralen Elemente des Softwareentwicklungsprozesses. Ziel ist es, plattformspezifische Modelle möglichst automatisiert aus plattformunabhängigen Modellen abzuleiten. Dadurch soll der Aufwand der Softwareentwicklung verringert und die Adaptierung an neue Technologien erleichtert werden.*Vorschläge an Prof. Dr. Frank Puppe oder Dieter Steinbauer Alle „Aktuellen Schlagwörter“ seit 1988 finden Sie unter: www.ai-wuerzburg.de/as