Neonatal thyrotropin levels and auditory neural maturation in full-term newborns

Objective This study aimed to look for a possible relationship between thyrotropin (TSH) values from neonatal bloodspot screening testing and newborn lower auditory pathway myelinization evaluated using the brainstem evoked response audiometry (ABR) test. Methods Sixty-two healthy full-term newborns without perinatal problems were enrolled in the study. TSH results were collected from neonatal bloodspot screening data and were below the test cut-off level (15μUI/mL). The TSH test was performed between three and seven days, and the ABR test was performed in the first 28 days of life. The newborns were divided into two groups: Group 1 (n = 35), TSH between 0 and 5μUI/mL, and group 2 (n = 27), TSH between 5 and 15μUI/mL. Data are presented as mean ± SD, median, or percentage, depending on the variable. Results Wave latency and interpeak interval values for Groups 1 and 2 were as follows: Wave I: 1.8 ± 0.1 and 1.7 ± 0.1; Wave III: 4.4 ± 0.1 and 4.4 ± 0.1; Wave V: 6.9 ± 0.1 and 6.9 ± 0.1; interval I–III: 2.6 ± 0.1 and 2.6 ± 0.1; interval I–V: 5.1 ± 0.1 and 5.1 ± 0.1; interval III–V: 2.4 ± 0.1 and 2.4 ± 0.1. There were no significant differences in ABR parameters between groups 1 and 2 (p > 0.05). Multiple regression analysis showed a slight significant negative correlation between TSH and wave I values (standardized β = −0.267; p = 0.036), without observing any relationship with the other ABR waves recorded. Conclusions This study investigated the relationship of TSH and auditory myelinization evaluated by ABR. It did not show a significant change in lower auditory pathway myelinization according to TSH levels in newborns with TSH screening levels lower than 15 μUI/mL.

Glucose Induces Glucagon Release Pulses Antisynchronous with Insulin and Sensitive to Purinoceptor Inhibition

Both increase of the glucose concentration and activation of purinoceptors are known to affect pancreatic α-cells. Effects obtained with various purino derivatives at 2.8 and 8.3 mmol/liter glucose have been taken to indicate that external ATP is less potent than adenosine as a stimulator of glucagon release. However, when making a corresponding comparison at 20 mmol/liter glucose, we observed marked stimulation of glucagon release from isolated rat islets with 100 μmol/liter adenosine-5-O-2-thiodiphosphate but inhibition with 10 μmol/liter adenosine. Analyses of 30-sec samples of perfusate from rat pancreas indicated that a rise of the glucose concentration from 3 to 20 mmol/liter rapidly induces a glucagon peak followed by regular 4- to 5-min pulses. The glucagon pulses preceded those of insulin with a phase shift (1.8 ± 0.1 min) near half the interpeak interval. Because of the antisynchrony, the maximal glucagon effect on liver cells will be manifested during periods with low concentrations of insulin. In support for the idea that neural P2Y1 receptors are important for coordinating the secretory activity of the islets, both the insulin and glucagon pulses disappeared in the presence of the purinoceptor inhibitor MRS 2179 (10 μmol/liter). However, in contrast to what was observed for insulin, MRS 2179 lowered average glucagon release to the level of the oscillatory nadirs.

Auditory Brain Stem Response Throughout the Menstrual Cycle

A prospective study was performed to evaluate the changes in the auditory brain stem response (ABR) that occur in healthy premenopausal women throughout the menstrual cycle. Ninety-four women with ovulatory menstrual cycles underwent ABR testing by auditory evoked potentials for wave I, III, and V latencies and for interpeak I-III, I-V, and III-V intervals during the follicular, periovular, and luteal phases of the menstrual cycle. The wave latencies and the interpeak intervals showed shorter values during the periovular phase than during the luteal phase (p < .05) and shorter values during the follicular phase for wave I (p < .05) and interpeak interval I-V (p < .05). The ABR seems to be influenced by the variations of ovarian steroids that occur during the menstrual cycle.

Generated potentials of brain in patients with intermittent torticollis

For finding out a role of different afferent systems in processing a sensory signal it was performed an investigation of brain generated potentials in patients with intermittent torticollis. There had been studied acoustic truncus cerebri generated potentials and somato-sensory generated potentials. The acoustic truncus cerebri generated potentials were characterized by amplitude decrease, peak flatenning and by interpeak interval assymetry, while somato-sensory generated potentials - by amplitude increase of main peaks, peak latency assymetry. The obtained results give an opportunity to determine a functional activity of different sensory systems of brain in the structure of hyperkinesis.

ABR Indices

ABR absolute latencies and interpeak intervals were reviewed for 684 non-tumor ears and 75 eighth-nerve tumor ears having various degrees of high frequency hearing loss. For non-tumor ears, the percentage of abnormal absolute latencies for waves I, III, and V increased rather systematically as hearing loss increased, whereas absolute latencies for eighth-nerve tumor ears were largely abnormal regardless of hearing loss. Interpeak intervals were normal for most of the non-tumor ears, but the I–III and I–V intervals were abnormal for most of the tumor ears. The most sensitive index for otoneurologic assessment was a combination of abnormal wave V interaural latency differences or I–V interpeak interval, and the most specific criterion was the I–V interpeak interval. Tumor size influenced sensitivity of most ABR indices.

SPECTRAL STUDIES OF MARINE GEOPHYSICAL PROFILES

Gravity, magnetic, and echo‐sounding data profiles from widely separated single‐track surveys in the Atlantic and Indian Oceans were subjected to spectral studies. A two‐dimensional sea floor with a recurring structural pattern seemed a model able to explain the computed results. In testing the model, the most important quantity to be determined from the spectra was the “ripple frequency” or interpeak interval. During the course of this work, a number of practical problems connected with the computation of spectra were considered. In addition, the spectral methods were also shown to be tools capable of investigating more complex geophysical theories. The experience and techniques of this investigation can be of value in treating analogous problems which arise in geophysical exploration.