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Biomedical subjects

A Alexander

Publications and source records attributed to A Alexander.

At least 55 records · Page 3Linked to original sources
PubMed1990

Net production of cerebrospinal fluid is decreased by SCH-23390.

A high density of binding sites for the ligands 3H-SCH-23390 and 3H-SKF-83566 has been found in the choroid plexus. Although these sites have similar pharmacology to D1 dopamine receptors, the high-affinity component of 3H-SCH-23390 binding in the choroid plexus has been identified as the 5-HT1c subtype of serotonin receptor. We investigated the possible role of these receptors in modulating the production of cerebrospinal fluid (CSF) in rats. (R) SCH-23390 produced up to a 50% decrease in net CSF production, compared to saline. This compound is a partial agonist at 5-HT1c serotonin receptors, and an antagonist at D1 dopamine receptors. The (S) enantiomer of SCH-23390 (SCH-23388) was ineffective. Drugs interacting with receptors for neurotransmitters in the choroid plexus may hold promise for the treatment of patients with increased intracranial pressure, including those with mass lesions, head trauma, acute or chronic hydrocephalus, or pseudotumor cerebri.

Animals↗
PubMed1989

Biotinylated RNA probes for the detection of potato spindle tuber viroid (PSTV) in plants.

Diseases caused by potato spindle tuber viroid (PSTV) are of significant agronomic importance, and early detection is vital. The objective of this paper was to synthesize biotinylated RNA probes in order to develop a specific, sensitive, and reliable assay system for detection of PSTV in infected plants. RNA probes were prepared by in vitro transcription of cloned PSTV, and were labelled with either biotin-11-UTP or [32P]UTP. Partially purified total RNAs from healthy and from PSTV-infected plants were spotted onto nitrocellulose filters and hybridized with either biotin-labelled or 32P-labelled probes. Our results showed that the sensitivity of biotinylated probes was similar to that for the 32P-labelled probes.

Biotin↗
PubMed1989

Role of glutamic acid 177 of the ricin toxin A chain in enzymatic inactivation of ribosomes.

The gene for the A chain of ricin toxin was fused to a beta-galactosidase marker cistron via a DNA sequence encoding a short collagen linker, and the tripartite fusion protein was expressed in Escherichia coli. Site-specific mutagenesis was used to change glutamic acid residue 177 to aspartic acid or alanine. When the mutant proteins were expressed, purified, and tested quantitatively for enzymatic activity, the carboxylate function at position 177 was found not to be absolutely essential for ricin toxin A-chain catalysis.

Blotting, Western↗
PubMed1988

Gamma heavy chain disease in man. Genomic sequence reveals two noncontiguous deletions in a single gene.

A genomic clone was isolated from a human lymphoid cell line which synthesized an NH2-terminally deleted gamma 3 heavy chain disease protein. Nucleotide sequence analysis revealed a normal sequence from 310 bp 5' to the initiator ATG through the codon for VH amino acid 14. Amino acid 15 was derived from the codon for the last J4 amino acid. Thus, the clone contained a deletion of the codons for the VH region beyond amino acid 14, as well as those for the entire D region and most of the J coding region. Some sequence abnormalities were observed in the 400 bp after the deletion. Beyond this, there was excellent homology to published J and intervening sequences, including those containing the enhancer elements. The 1,200-bp switch region was abruptly interrupted by a sequence corresponding to the 3' one-third of CH1. Thus, a second deletion eliminated the acceptor splice site at the 5' end of CH1. When splicing of the primary RNA transcript occurred, the truncated VH region was joined via the J4 donor splice site to the next available acceptor site 5' to the first hinge exon. Hence, the aberrant serum protein was the product of two deletions and a splice correction as well as postsynthetic NH2-terminal proteolysis.

Amino Acid Sequence↗
PubMed1987

Cyclotherapy in the treatment of symptomatic latent hyperopia.

Many practitioners have long been frustrated with traditional treatments of symptomatic latent hyperopia (fogging techniques, bifocals, etc.). A technique employing short-acting cycloplegia has been developed which provides rapid relief of symptoms by promoting full correction of latent refractive error. Fifteen symptomatic subjects ages 3-40 were diagnosed as latent hyperopes with the aid of 1% cyclopentolate, and subsequently recyclopleged utilizing full correction in constant wear spectacles. Acuity was maintained via slow diminution of cycloplegia. Short-term and long-term follow-up, with continued use of spectacles or contact lenses, revealed rapid and complete resolution of symptoms and restoration of visual efficiency in each case. Cyclotherapy offers both practitioners and patients an efficient, rapid-acting, and satisfying alternative treatment for this vexing accommodative anomaly.

Accommodation, Ocular↗
PubMed1984

The potentiation of ototoxicity when aminooxyacetic acid and kanamycin are co-administered.

Aminooxyacetic acid (AOAA) has been shown to confer protection against noise-induced cochlear trauma [3]. We, therefore, decided to study the possible protective effect of AOAA against kanamycin (KM) ototoxicity and found, instead, that AOAA potentiated the toxicity. To produce ototoxicity in guinea pigs, KM is usually given in 10-14 daily doses of 400 mg/kg s.c. However, when combined with a single dose of AOAA (8, 11, 15, or 25 mg/kg) a single 400 mg/kg dose of KM is sufficient to cause cochlear damage. Such animals show a negative Preyer's reflex between 1 to 3 days post injection. 21 days later hearing thresholds as detected electrocochleographically at 2, 4, 8, 12 and 16 kHz have changed drastically sometimes to the point of being undetectable. The damage seen histologically at this time is destruction of both inner and outer hair cells. A pharmacokinetic analysis of this potentiation revealed a slight prolongation of KM's sojourn in the inner ear. The possible mechanisms of this unexpected, marked potentiation are discussed but remain unknown.

Acetates↗
PubMed1982

gamma Heavy chain disease in man: cDNA sequence supports partial gene deletion model.

Human gamma heavy chain disease (HCD) is characterized by the presence in serum of a short monoclonal Ig gamma chain unattached to light chains. Although most HCD proteins have internal deletions, in some the defect is NH2-terminal. The OMM gamma 3 HCD serum protein is of the latter type, having undergone an extensive NH2-terminal deletion with a sequence starting within the hinge. A cell line synthesizing the OMM protein has enabled us to study the biogenesis of the abnormal molecule. In vitro translation of isolated mRNA yields a protein containing a hydrophobic NH2-terminal leader sequence. In the intact cell, the precursor molecule is processed normally to yield a protein with an NH2-terminal sequence homologous to the beginning of the variable (V) region. The nucleotide sequence of cDNA prepared from the OMM mRNA encodes a 19-amino acid leader followed by the first 15 residues of the V region. An extensive internal deletion encompasses the remainder of the V and the entire CH1 domain. Immediately following the short V region, there is information in the cDNA for the entire normal hinge. The primary synthetic product is thus an internally deleted molecule that undergoes postsynthetic degradation to yield the NH2-terminally deleted serum protein. The structure of the OMM mRNA suggests that the protein abnormality results from a partial gene deletion rather than defective splicing.

Amino Acid Sequence↗