University of Texas Health Science Center at Houston

About: University of Texas Health Science Center at Houston is a education organization based out in Houston, Texas, United States. It is known for research contribution in the topics: Population & Cancer. The organization has 27309 authors who have published 42520 publications receiving 2151596 citations. The organization is also known as: UTHealth & The UT Health Science Center at Houston.

Differential properties of two gap junctional pathways made by AII amacrine cells

Abstract: The retina is sensitive to light stimuli varying over more than 12 log units in intensity. It accomplishes this, in part, by switching between rod-dominated circuits designed for maximum utilization of scarce photons and cone circuits designed for greater acuity. Rod signals are integrated into the cone pathways through AII amacrine cells, which are connected by gap junctions both to other AII amacrine cells and to cone bipolar cells. To determine the relative permeabilities of the two junctional pathways, we have measured the distribution of biotinylated tracers across this heterologous cell assembly after injecting a single AII amacrine cell. We found that neurobiotin (relative molecular mass, 286) passed easily through both types of gap junctions, but that biotin-X cadaverine (relative molecular mass, 442) passed through AII/bipolar cell gap junctions poorly compared to AII/AII gap junctions. Thus, the AII/bipolar cell channel has a lower permeability to large molecules than does the AII/AII amacrine cell channel. The two pathways are also regulated differently. Dopamine and cyclic AMP agonists, known to diminish AII-AII coupling, did not change the relative labelling intensity of AII to bipolar cells. However, nitric oxide and cGMP agonists selectively reduced labelling in bipolar cells relative to AII amacrine cells, perhaps by acting at the bipolar side of this gap junction. This suggests that increased cGMP controls the network switching between rod and cone pathways associated with light adaptation.

Plant-Symbiotic Fungi as Chemical Engineers: Multi-Genome Analysis of the Clavicipitaceae Reveals Dynamics of Alkaloid Loci

Abstract: The fungal family Clavicipitaceae includes plant symbionts and parasites that produce several psychoactive and bioprotective alkaloids. The family includes grass symbionts in the epichloae clade (Epichloe and Neotyphodium species), which are extraordinarily diverse both in their host interactions and in their alkaloid profiles. Epichloae produce alkaloids of four distinct classes, all of which deter insects, and some—including the infamous ergot alkaloids—have potent effects on mammals. The exceptional chemotypic diversity of the epichloae may relate to their broad range of host interactions, whereby some are pathogenic and contagious, others are mutualistic and vertically transmitted (seed-borne), and still others vary in pathogenic or mutualistic behavior. We profiled the alkaloids and sequenced the genomes of 10 epichloae, three ergot fungi (Claviceps species), a morning-glory symbiont (Periglandula ipomoeae), and a bamboo pathogen (Aciculosporium take), and compared the gene clusters for four classes of alkaloids. Results indicated a strong tendency for alkaloid loci to have conserved cores that specify the skeleton structures and peripheral genes that determine chemical variations that are known to affect their pharmacological specificities. Generally, gene locations in cluster peripheries positioned them near to transposon-derived, AT-rich repeat blocks, which were probably involved in gene losses, duplications, and neofunctionalizations. The alkaloid loci in the epichloae had unusual structures riddled with large, complex, and dynamic repeat blocks. This feature was not reflective of overall differences in repeat contents in the genomes, nor was it characteristic of most other specialized metabolism loci. The organization and dynamics of alkaloid loci and abundant repeat blocks in the epichloae suggested that these fungi are under selection for alkaloid diversification. We suggest that such selection is related to the variable life histories of the epichloae, their protective roles as symbionts, and their associations with the highly speciose and ecologically diverse cool-season grasses.

MFN2 mutation distribution and genotype/phenotype correlation in Charcot-Marie-Tooth type 2.

Abstract: Mutations in mitofusin 2 (MFN2) have been reported in Charcot-Marie-Tooth type 2 (CMT2) families. To study the distribution of mutations in MFN2 we screened 323 families and isolated patients with distinct CMT phenotypes. In 29 probands, we identified 22 distinct MFN2 mutations, and 14 of these mutations have not been reported before. All mutations were located in the cytoplasmic domains of the MFN2 protein. Patients presented with a classical but rather severe CMT phenotype, since 28% of them were wheelchair-dependent. Some had additional features as optic atrophy. Most patients had an early onset and severe disease status, whereas a smaller group experienced a later onset and milder disease course. Electrophysiological data showed in the majority of patients normal to slightly reduced nerve conduction velocities with often severely reduced amplitudes of the compound motor and sensory nerve action potentials. Examination of sural nerve specimens showed loss of large myelinated fibres and degenerative mitochondrial changes. In patients with a documented family history of CMT2 the frequency of MFN2 mutations was 33% indicating that MFN2 mutations are a major cause in this population.

Double-blind, multicenter comparison of sertraline and amitriptyline in elderly depressed patients.

Abstract: Two hundred forty-one elderly depressed patients entered the 8-week, double-blind phase of this parallel-group, multicenter study; 161 patients were randomized to receive sertraline (50-200 mg/day) and 80 were randomized to receive amitriptyline (50-150 mg/day). Among evaluable patients, there were no statistically significant differences between treatments in any of the primary efficacy variables: change in total Hamilton Rating Scale for Depression (HAM-D) score (17 items), percentage change in HAM-D score, change in HAM-D Item 1, change in Clinical Global Impressions (CGI) Severity score, change in the Depression Factor of the 56-item Hopkins Symptom Checklist, and the CGI Improvement score at the last visit. Similar results were obtained using data from all patients (intention-to-treat analysis), except that amitriptyline was superior in HAM-D Total score (p = .044). The two drugs produced a similar degree of response: on the basis of the HAM-D criterion, 69.4% of sertraline patients and 62.5% of amitriptyline patients responded, and, on the basis of CGI criterion, 79.5% of sertraline and 73.4% of amitriptyline patients responded. Twenty-eight percent of the sertraline patients withdrew from the study because of a treatment-related side effect and 2.5% (4) because of a laboratory abnormality. In comparison, 35% of the amitriptyline patients withdrew because of treatment-related side effects. Sertraline was associated with a statistically lower frequency of somnolence, dry mouth, constipation, ataxia, and pain and a higher frequency of nausea, anorexia, diarrhea/loose stools, and insomnia; thus, anticholinergic effects were less common and gastrointestinal effects were more common with sertraline than with amitriptyline.(ABSTRACT TRUNCATED AT 250 WORDS)