Search PubMed⌕ Search

Biomedical subjects

B Sommer

Publications and source records attributed to B Sommer.

At least 127 records · Page 7Linked to original sources
PubMed1991

RNA editing in brain controls a determinant of ion flow in glutamate-gated channels.

L-glutamate, the principal excitatory transmitter in the brain, gates ion channels mediating fast neurotransmission. Subunit components of two related classes of glutamate receptor channels have been characterized by cDNA cloning and shown to carry either an arginine or a glutamine residue in a defined position of their putative channel-forming segment. The arginine residue in this segment profoundly alters, and dominates, the properties of ion flow, as demonstrated for one channel class. We now show that the genomic DNA sequences encoding the particular channel segment of all subunits harbor a glutamine codon (CAG), even though an arginine codon (CGG) is found in mRNAs of three subunits. Multiple genes and alternative exons were excluded as sources for the arginine codon; hence, we propose that transcripts for three subunits are altered by RNA editing. This process apparently edits subunit transcripts of the two glutamate receptor classes with different efficiency and selectivity.

Amino Acid Sequence↗
PubMed1991

[GM2 gangliosidosis, O variant (Sandhoff disease): suspected diagnosis of a storage disease by ultrasound].

We report on a 3.6 year old boy who suffers from Sandhoff disease. The diagnosis was suspected because of striking ultrasound findings: Parts of the thalamus were more echogenic, the cortical gyri were sharp and accentuated. The CT- and MRI features were similar to the US-findings. The diagnosis was confirmed by demonstrating the typical enzyme deficiency in leucocytes.

Brain Diseases, Metabolic↗
PubMed1990

Flip and flop: a cell-specific functional switch in glutamate-operated channels of the CNS.

In the central nervous system (CNS), the principal mediators of fast synaptic excitatory neurotransmission are L-glutamate-gated ion channels that are responsive to the glutamate agonist alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA). In each member of a family of four abundant AMPA receptors, a small segment preceding the predicted fourth transmembrane region has been shown to exist in two versions with different amino acid sequences. These modules, designated "flip" and "flop," are encoded by adjacent exons of the receptor genes and impart different pharmacological and kinetic properties on currents evoked by L-glutamate or AMPA, but not those evoked by kainate. For each receptor, the alternatively spliced messenger RNAs show distinct expression patterns in rat brain, particularly in the CA1 and CA3 fields of the hippocampus. These results identify a switch in the molecular and functional properties of glutamate receptors operated by alternative splicing.

Amino Acid Sequence↗
PubMed1990

A family of AMPA-selective glutamate receptors.

Four cloned cDNAs encoding 900-amino acid putative glutamate receptors with approximately 70 percent sequence identity were isolated from a rat brain cDNA library. In situ hybridization revealed differential expression patterns of the cognate mRNAs throughout the brain. Functional expression of the cDNAs in cultured mammalian cells generated receptors displaying alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-selective binding pharmacology (AMPA = quisqualate greater than glutamate greater than kainate) as well as cation channels gated by glutamate, AMPA, and kainate and blocked by 6,7-dinitroquinoxaline-2,3-dione (CNQX).

Amino Acid Sequence↗
PubMed1990

Pulmonary arteriovenous fistula: ultrasonographic approach.

Report of a pediatric case with pulmonary arteriovenous fistula (PAVF) in hereditary hemorrhagic teleangiectasia (HHT), primary suspected by ultrasound. There is a characteristic sonographic feature of the complex type of PAVF revealing septations in contrast of the simple type. The diagnosis was established by angiography.

Arteriovenous Fistula↗
PubMed1990

The murine GABAA receptor delta-subunit gene: structure and assignment to human chromosome 1.

The murine chromosomal gene for the GABAA receptor delta subunit was isolated and characterized by high-resolution mapping and DNA sequencing. Spanning 13 kb, it comprises nine exons and displays an intron pattern comparable, but not identical, to that seen in members of the nicotinic acetylcholine receptor family. Notably, the second transmembrane domain thought to line the ion channel and conserved among different GABAA receptor subunits, is interrupted by an intron. The 5'-flanking region of the delta gene displays features characteristic of a CpG island and lacks canonical promoter elements such as TATA and CCAAT consensus sequences in proximity to the transcriptional initiation site. The human delta subunit gene was localized on the short arm of chromosome 1.

Amino Acid Sequence↗
PubMed1989

The dopamine D2 receptor: two molecular forms generated by alternative splicing.

Cloned human dopamine D2 receptor cDNA was isolated from a pituitary cDNA library and found to encode an additional 29 amino acid residues in the predicted intracellular domain between transmembrane regions 5 and 6 relative to a previously described rat brain D2 receptor. Results from polymerase chain reactions as well as in situ hybridization revealed that mRNA encoding both receptor forms is present in pituitary and brain of both rat and man. The larger form was predominant in these tissues and, as shown in the rat, expressed by dopaminergic and dopaminoceptive neurons. Analysis of the human gene showed that the additional peptide sequence is encoded by a separate exon. Hence, the two receptor forms are generated by differential splicing possibly to permit coupling to different G proteins. Both receptors expressed in cultured mammalian cells bind [3H]spiperone with high affinity and inhibit adenylyl cyclase, as expected of the D2 receptor subtype.

Amino Acid Sequence↗
PubMed1988

Binding of nuclear proteins to promoter elements of the mouse alpha A-crystallin gene.

We have investigated the binding of nuclear proteins from the embryonic chicken lens to synthetic oligonucleotides derived from sequence -111/-55 of the murine alpha A-crystallin gene. These sequences were shown previously to consist of a distal (-111/-88) and a proximal (-88/-60) region which are required for expression of this gene (Chepelinsky, A. B., Sommer, B., and Piatigorsky, J. (1987) Mol. Cell. Biol. 7, 1807-1814). Here we use gel retardation and methylation interference experiments to provide evidence for selective binding of different nuclear proteins to oligonucleotides containing sequences -111/-84, -83/-55, and -111/-55. Similar (although not necessarily identical) proteins were found in nuclear extracts of chicken erythrocytes and HeLa cells. Despite this fact, the alpha A-crystallin promoter (-111/+46) did not function in transfected HeLa cells; moreover, deletion experiments showed that only the TATA box is required for activity of this promoter in a HeLa whole cell extract, the distal (-111/84) and proximal (-83/-55) elements having no positive effect on transcription in the HeLa cell extract. These experiments support the idea that the same or related nuclear proteins found in many tissues are necessary but not sufficient for expression of the murine alpha A-crystallin gene.

Animals↗
PubMed1987

[AIDS in Africa].

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Interaction between two different regulatory elements activates the murine alpha A-crystallin gene promoter in explanted lens epithelia.

Previous experiments have indicated that 5' flanking DNA sequences (nucleotides-366 to +46) are capable of regulating the lens-specific transcription of the murine alpha A-crystallin gene. Here we have analyzed these 5' regulatory sequences by transfecting explanted embryonic chicken lens epithelia with different alpha A-crystallin-CAT (chloramphenicol acetyltransferase) hybrid genes (alpha A-crystallin promoter sequences fused to the bacterial CAT gene in the pSVO-CAT expression vector). The results indicated the presence of a proximal (-88 to +46) and a distal (-111 to -88) domain which must interact for promoter function. Deletion experiments showed that the sequence between -88 and -60 was essential for function of the proximal domain in the explanted epithelia. A synthetic oligonucleotide containing the sequence between -111 and -84 activated the proximal domain when placed in either orientation 57 base pairs upstream from position -88 of the alpha A-crystallin-CAT hybrid gene.

Acetyltransferases↗
PubMed1986

A survey of the California Alliance for the Mentally Ill.

Family groups are becoming increasingly active in providing support to family members and in mental health advocacy. The authors report the results of a survey that assessed the concerns of members of the California Alliance for the Mentally Ill and the treatment history of disabled family members. The 199 respondents were typically the parents of a schizophrenic son between the ages of 24 and 34 whose illness was first noticed in the late teens and for whom assistance had been sought for at least a decade. The respondents indicated that medication, family support, socialization centers, community residential treatment, and locked facilities had most helped the family member to improve. The most important additional needs were housing, vocational, and social opportunities and research.

Adult↗