Glutamate metabotropic receptor agonists depress excitatory and inhibitory transmission on rat mesencephalic principal neurons

Intracellular and whole-cell patch-clamp recordings were used to evaluate the actions of different metabotropic glutamate receptor (mGluR) agonists on the synaptic inputs evoked on principal cells of the rat mesencephalon. Bath application of the group III mGluR agonists L-2-amino-4-phosphonobutyric acid (L-AP4) and L-serine-O-phosphonobutanoate (L-SOP) did not change the holding current of the cells held at resting potential (-60 mV) but produced a dose-dependent inhibition of the amplitude of the excitatory and inhibitory events. L-AP4 and L-SOP were more effective at inhibiting the excitatory postsynaptic currents (EPSCs) than the GABA(A) and GABA(B) inhibitory postsynaptic currents (IPSCs). The suppressing effects of L-AP4 and L-SOP were antagonized by (S)-2-amino-2-methyl-4-phosphonobutanoic acid (MAP-4) but not by +/- -alpha-methyl-4-carboxyphenylglycine (MCPG). Moreover, the group II agonist (2S,1'S,2'S)-(carboxycyclopropyl)glycine (L-CCG1) and the group I agonist (RS)-3,5-dihydrophenylglycine (3,5-DHPG) depressed in a dose-related manner the EPSC, the GABA(A) IPSC and the GABA(B) IPSC. The suppressing effect of the two mGluRs agonists was partially antagonized by MCPG but not by MAP-4. In addition, both L-CCG1 and 3,5-DHPG caused an inward shift of the holding current. To characterize the site of action of the metabotropic receptor agonists, experiments were performed to examine the amplitude and ratio of EPSC and GABA(A) IPSC pairs. The increase of the s2/s1 ratio caused by the agonists suggests that the location of the inhibitory mGluRs was presynaptic. These results indicate that the activation of presynaptic mGluRs controls the release of excitatory and inhibitory transmitters on presumed dopaminergic cells within the ventral mesencephalon.     

The effects of growth hormone in children with a GH deficiency: a report of 5 cases

The authors describe 5 cases, 3 boys and 2 girls, with idiopathic growth hormone deficiency in prepubertal age, treated with human growth hormone. In four of five cases the response to treatment with GH was relevant. Only in one case (F1) the response was negative. The results of this study confirm that rhGH is a safe and effective therapy in children with GHD.     

Evidence for two types of spatial representations: Hemispheric specialization for categorical and coordinate relations.

Analyses of human object recognition abilities led to the hypothesis that 2 kinds of spatial relation representations are used in human vision. Evidence for the distinction between abstract categorical spatial relation representations and specific coordinate spatial relation representations was provided in 4 experiments. These results indicate that Ss make categorical judgments—on/off, left/right, and above/below—faster when stimuli are initially presented to the left cerebral hemisphere, whereas they make evaluations of distance—in relation to 2 mm, 3 mm, or 1 in. (2.54 cm)—faster when stimuli are initially presented to the right cerebral hemisphere. In addition, there was evidence that categorical representations developed with practice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Compositional constraints in the extremely GC-poor genome of Plasmodium falciparum

We have analyzed the compositional properties of coding (protein encoding) and non-coding sequences of Plasmodium falciparum, a unicellular parasite characterized by an extremely AT-rich genome. GC% levels, base and dinucleotide frequencies were studied. We found that among the various factors that contribute to the properties of the sequences analyzed, the most relevant are the compositional constraints which operate on the whole genome.     

Transient response of a microstrip line circuit excited by anexternal electromagnetic source

The transient voltages and currents induced by an external electromagnetic field along a microstrip line interconnecting active and/or passive components are studied by using a distributed-source transmission-line model. The influence of the angle of incidence as well as that of the microstrip geometrical and electrical parameters on the line response is analyzed. The instantaneous voltage and power induced on the loads by various types of pulse excitations are computed. Numerical results are obtained both for dispersive and nondispersive lines. A line feeding a transistor microwave amplifier is also considered. The results show the effects of the multiple reflections of the field inside the dielectric substrate and of the signal at the ends of the line. Indications of how to reduce the coupling between the external field and the considered structure are given     

Magnetotransport of two-dimensional electron gas in Si/SiGe modulation doped structures grown by gas source molecular beam epitaxy

We have characterized two-dimensional electron gases (2DEGs) in Si/SiGe modulation doped structures grown by gas source molecular beam epitaxy. Hall bar structures were fabricated to characterize the structures and magnetotransport measurements were carried out at temperatures down to 0.4 K. Pronounced Shubnikov-de Haas oscillations were observed in the longitudinal magnetoresistance, indicative of high quality 2DEG in the channel. Electron mobilities up to 87,000 cm² V⁻¹ s⁻¹ with sheet densities about 7 × 10¹¹ cm⁻² were obtained at low temperature. Dingle plots of the magnetoresistance vs reciprocal magnetic field were utilized to determine the single-particle relaxation times in order to investigate scattering mechanisms in these structure. The ratio of the transport scattering time derived from electron mobility to the single-particle relaxation time is of the order of 10, indicating that remote impurity scattering is a dominant factor limiting the mobility of our structures. The behaviour of the magnetotransport data is discussed using a model for parallel conduction.     

High levels of serum allopregnanolone in women with premature ovarian failure

BACKGROUND: Blue-on-yellow (B/Y) perimetry can reveal visual field defects earlier and larger in extent than white-on-white (W/W) perimetry. The Heidelberg Retina Tomograph (HRT) produces a three-dimensional image of the optic disc. The aim of this study was to compare the strength of the association of the B/Y and W/W visual hemifield mean deviation (HMD) variables with the optic nerve head (ONH) morphological variables of the respective area. METHODS: We evaluated one randomly chosen eye of 40 normal subjects and 37 patients with ocular hypertension and different stages of glaucoma. The B/Y and W/W visual fields (program 30-2) were obtained with a Humphrey perimeter. Results of both visual fields were adjusted for the patient's age and lens transmission index measured with a lens fluorometer. HMD was calculated as the difference between the measured and expected hemifield mean sensitivity values, predicted by the regression model fitted in our nonglaucomatous subject data. The HRT with the software version 1.11 was used to acquire and evaluate the topographic measurements of the optic disc. RESULTS: The B/Y and W/W visual field HMDs showed statistically significant correlation with ONH parameters such as cup shape measure (CSM), rim volume, rim area, mean retinal nerve fiber layer (RNFL) thickness and RNFL cross-sectional area. With forward stepwise logistic regression analysis using B/Y hemifield data 38% of the glaucoma patient's normal W/W hemifields were classified abnormal. With the CSM alone in the model 52% of the cases were classified abnormal. CONCLUSIONS: B/Y visual field hemifield mean deviation values correlate well with ONH parameters examined with the HRT.     

The effect of physical exercise on the response to exertion in the elderly

BACKGROUND: A decrease in adaptation to exertion has been observed as age progresses. Although this decline may also be affected by factors such as health conditions and age, physical inactivity related to sedentary behaviour plays a dominant role. METHODS: In order to evaluate the influence of physical activity on cardiovascular response to exertion in the elderly, 4 groups of 22 subjects each were submitted to maximal electrocardiographic exercise test on a cycloergometer (multistage program with 30 Watts x 3 min. steps). All subjects were male. The composition of the groups was as follows: 1) veteran long distance runners (mean age: 71 +/- 5.4); 2) sedentary veterans (mean age: 69.8 +/- 3.9); 3) young long distance runners (mean age: 25.4 +/- 4.3); 4) sedentary young adults (mean age: 25.8 +/- 3.9). The endurance athletes, well fitted to competition, had been practicing sport activity for at least 3 years. RESULTS: Heart rate, arterial systolic and diastolic blood pressure were recorded; mean blood pressure and double product were calculated at baseline and at the climax of the stress test; furthermore, total and maximal watts were recorded. For each of the parameters, Student's t test for non-paired observations were used to evaluate statistical differences amongst the four groups. The most interesting result arises in the comparison between veteran long distance runners and sedentary young adults: between the two groups no statistically significant differences in workload, expressed as total watts (1649.55 +/- 296.32 vs 1650.00 +/- 446.32; p = NS) and maximal watts (175.91 +/- 19.19 vs 173.18 +/- 24.38; p = N.S.), were observed. On the contrary, highly significant differences in both total (p < 0.01) and maximal (p < 0.01) watts were noticed by comparing long distance runners and sedentary subjects of the same age. CONCLUSIONS: These data support the hypothesis that the progressive reduction in physical activity, which is usually observed in aging, is the major determinant of exercise deconditioning in the elderly.