Regulation of CFTR chloride channels by syntaxin and Munc18 isoforms.

The cystic fibrosis gene encodes a cyclic AMP-gated chloride channel (CFTR) that mediates electrolyte transport across the luminal surfaces of a variety of epithelial cells. The molecular mechanisms that modulate CFTR activity in epithelial tissues are poorly understood. Here we show that CFTR is regulated by an epithelially expressed syntaxin (syntaxin 1A), a membrane protein that also modulates neurosecretion and calcium-channel gating in brain.

Neonatal tetanus in the United States: a sentinel event in the foreign-born.

Background: Neonatal tetanus occurred in a 7-day-old infant born to Mexican immigrant parents in Tennessee in February, 1995. This was the first patient with neonatal tetanus reported in the United States since 1989.

Methods: We interviewed the infant's mother and physicians and reviewed the medical record.

Influence of subunit composition on desensitization of neuronal acetylcholine receptors at low concentrations of nicotine.

The influence of alpha and beta subunits on the properties of nicotine-induced activation and desensitization of neuronal nicotinic acetylcholine receptors (nAChRs) expressed in Xenopus oocytes was examined. Receptors containing alpha4 subunits were more sensitive to activation by nicotine than alpha3-containing receptors. At low concentrations of nicotine, nAChRs containing beta2 subunits reached near-maximal desensitization more rapidly than beta4-containing receptors.

Second messengers, trafficking-related proteins, and amino acid residues that contribute to the functional regulation of the rat brain GABA transporter GAT1.

Recent evidence indicates that several members of the Na+-coupled transporter family are regulated, and this regulation in part occurs by redistribution of transporters between intracellular locations and the plasma membrane. We elucidate components of this process for both wild-type and mutant GABA transporters (GAT1) expressed in Xenopus oocytes using a combination of uptake assays, immunoblots, and electrophysiological measurements of membrane capacitance, transport-associated currents, and GAT1-specific charge movements. At low GAT1 expression levels, activators of protein kinase C (PKC) induce redistribution of GAT1 from intracellular vesicles to the plasma membrane; at higher GAT1 expression levels, activators of PKC fail to induce this redistribution.

Aspartate 55 in the Na+/proline permease of Escherichia coli is essential for Na+-coupled proline uptake.

Four acidic residues in the N-terminal domain of Na+/proline permease of Escherichia coli (Asp33, Asp34, and Asp55 in putative loop 2, Glu75 in putative transmembrane domain II) were individually replaced with neutral or charged amino acid residues. Replacement of Glu75, the only residue in the permease presumed to be in the middle of a transmembrane domain, Asp33, or Asp34 had little or no influence on the kinetics of Na+-coupled proline transport. In contrast, removal of the carboxylate at position 55 (Asp55 --> Asn or Asp55 --> Cys permease) impaired proline uptake completely while lengthening of the side chain at this position by one methylene group (Asp55 --> Glu permease) allowed transport at a reduced initial rate.

Desensitization of inositol 1,4,5-trisphosphate/Ca2+-induced Cl- currents by prolonged activation of G proteins in Xenopus oocytes.

Expression of G protein alpha subunits of the Gq family with various G protein-coupled receptors induces activation of an inositol 1,4, 5-trisphosphate (IP3)/Ca2+-mediated Cl- conductance in Xenopus oocytes. Our present data show that two members of this family, the human Galpha16 subunit and the murine homologue Galpha15, can induce both activation and inhibition of these agonist-induced currents. Although extremely low amounts (10-50 pg) of injected Galpha16 subunit cRNA cause modest ( approximately 2-fold) enhancement of ligand-induced Cl- currents in oocytes co-injected with thyrotropin-releasing hormone (TRH) receptor cRNA 48 h postinjection, larger Galpha16 and Galpha15 cRNA injections cause >10-fold inhibition of TRH or 5HT2c receptor responses.

Redox-sensitive homodimerization of Pex11p: a proposed mechanism to regulate peroxisomal division.

Pex11p (formerly Pmp27) has been implicated in peroxisomal proliferation (Erdmann, R., and G. Blobel.

Ser57 in the Na+/proline permease of Escherichia coli is critical for high-affinity proline uptake.

Ser57 in the Na+/proline permease of Escherichia coli has been replaced with alanine, cysteine, glycine, or threonine, and properties of the corresponding putP mutants have been analyzed. Although Ser57 is not essential for activity, the amino acid side chain at this position is critical for proline uptake. Thus, alanine, cysteine, glycine, or threonine in place of Ser57 reduces the initial rate of proline transport under standard conditions to less than 10% of the wild-type value.

Domain organization and a protease-sensitive loop in eukaryotic ornithine decarboxylase.

Trypanosoma brucei ornithine decarboxylase was reconstituted by coexpression of two polypeptides corresponding to residues 1-305 and residues 306-425 in Escherichia coli. The two peptides were coexpressed, at wild-type levels, from a single transcriptional unit that was separated by a 15-nucleotide untranslated region containing a ribosome binding site. The fragmented enzyme was purified and analyzed.

Regions of beta 2 and beta 4 responsible for differences between the steady state dose-response relationships of the alpha 3 beta 2 and alpha 3 beta 4 neuronal nicotinic receptors.

We constructed chimeras of the rat beta 2 and beta 4 neuronal nicotinic subunits to locate the regions that contribute to differences between the acetylcholine (ACh) dose-response relationships of the alpha 3 beta 2 and alpha 3 beta 4 receptors. Expressed in Xenopus oocytes, the alpha 3 beta 2 receptor displays an EC50 for ACh approximately 20-fold less than the EC50 of the alpha 3 beta 4 receptor. The apparent Hill slope (n(app)) of alpha 3 beta 2 is near one whereas the alpha 3 beta 4 receptor displays an n(app) near two.

Delayed neuropathy in pigs induced by isofenphos.

In 1990 an outbreak of ataxia occurred in over 700 pigs in the north of England. Epidemiological studies demonstrated that the disorder was associated with the consumption of feed from a particular supplier and that one component (wheat screenings) was common to the batch of feed with which the ataxia was associated. An analysis of the feed demonstrated the presence of an organophosphorus pesticide, later identified as isofenphos, a pesticide not approved for use in the United Kingdom.

Differential coupling of G protein alpha subunits to seven-helix receptors expressed in Xenopus oocytes.

Xenopus oocytes were used to examine the coupling of the serotonin 1c (5HT1c) and thyrotropin-releasing hormone (TRH) receptors to both endogenous and heterologously expressed G protein alpha subunits. Expression of either G protein-coupled receptor resulted in agonist-induced, Ca(2+)-activated Cl- currents that were measured using a two-electrode voltage clamp. 5HT-induced Cl- currents were reduced 80% by incubating the injected oocytes with pertussis toxin (PTX) and inhibited 50-65% by injection of antisense oligonucleotides to the PTX-sensitive Go alpha subunit.

Natural strabismus in monkeys: accommodative errors assessed by photorefraction and their relationship to convergence errors.

Purpose: To examine accommodation and accommodative convergence relationships in naturally strabismic monkeys.

Methods: Photorefraction was used to measure accommodative responses of each eye under monocular and binocular viewing conditions. These accommodative results were then compared to assessments of vergence state made under monocular viewing conditions using methods previously described.

Protein kinase C modulates the activity of a cloned gamma-aminobutyric acid transporter expressed in Xenopus oocytes via regulated subcellular redistribution of the transporter.

We report that activators and inhibitors of protein kinase C (PKC) and protein phosphatases regulate the activity of a cloned rat brain gamma-aminobutyric acid (GABA) transporter (GAT1) expressed in Xenopus oocytes. Four compounds known to activate PKC increased GABA uptake 2-3.5-fold over basal control levels.

A cocaine-sensitive Drosophila serotonin transporter: cloning, expression, and electrophysiological characterization.

A cocaine-sensitive, high-affinity Drosophila serotonin (5-hydroxytryptamine; 5HT) transporter cDNA, denoted dSERT1, was isolated and characterized in oocytes. dSERT1 shows little transport of other monoamines and is Na+ and Cl- dependent. Sequence analysis indicates 12 putative transmembrane domains and strong homologies (approximately 50%) among dSERT1 and mammalian 5HT, norepinephrine, and dopamine transporters.

Random mutagenesis of G protein alpha subunit G(o)alpha. Mutations altering nucleotide binding.

Nucleotide binding properties of the G protein alpha subunit G(o)alpha were probed by mutational analysis in recombinant Escherichia coli. Thousands of random mutations generated by polymerase chain reaction were screened by in situ [35S]GTP gamma S (guanosine 5'-(3-O-thio)-triphosphate) binding on the colony lifts following transformation of bacteria with modified G(o)alpha cDNA. Clones that did not bind the nucleotide under these conditions were characterized by DNA sequence analysis, and the nucleotide binding properties were further studied in crude bacterial extracts.

Steady states, charge movements, and rates for a cloned GABA transporter expressed in Xenopus oocytes.

Voltage-clamp analysis was applied to study the currents associated with the uptake of extracellular gamma-aminobutyric acid (GABA) by the cloned transporter GAT1 expressed at high efficiency in Xenopus oocytes. Steady-state GABA currents were increased at higher extracellular [GABA], [Na+], and [Cl-] and at more negative potentials. The Hill coefficient for Na+ exceeded unity, suggesting the involvement of two Na+ ions.

Receptors that couple to 2 classes of G proteins increase cAMP and activate CFTR expressed in Xenopus oocytes.

The cystic fibrosis transmembrane conductance regulator (CFTR), a Cl- channel activated by phosphorylation, was expressed in Xenopus oocytes along with various combinations of several other components of the cAMP signalling pathway. Activation of the coexpressed beta 2 adrenergic receptor increased cAMP and led to CFTR activation. The activation of CFTR (1) requires only short (15 s) exposure to isoproterenol, (2) occurs for agonist concentrations 100-1000 fold lower than those that produce cAMP increases detectable by a radioimmunoassay, (3) requires injection of only 5 pg of receptor cRNA per oocyte, and (4) can be increased further by coexpression of cRNA for adenylyl cyclase type II or III or for Gs alpha.

A collaborative health promotion effort: nursing students and Wendy's Team Up.

Community health nursing students, faculty, and Wendy's fast food restaurant conducted a 2-day health fair that provided health screening, counseling, and educational opportunities for the community, an exciting learning experience for the students, funds for the school of nursing, and good public relations for Wendy's. The authors describe the planning, implementation, and evaluation of this health fair as a student learning activity.

Suspected cases of bromocyclen poisoning.

This report summarizes the case histories and tabulates the analytical results from investigations of 8 incidents of suspected bromocyclen poisoning. Interpretation of the results and withdrawal of ALUGAN from the UK market are discussed.

Natural strabismus in monkeys. Convergence errors assessed by cover test and photographic methods.

A standard set of clinical prism and cover tests and a recently developed photographic method were used to assess binocular alignment in ten monkeys that previously were determined to have a naturally occurring infantile strabismus. Extensive measurements of the alignment state were made for fixation attempts throughout the field of gaze. Patterns of alignment errors were examined in an attempt to compared the strabismus found in individual monkeys with common syndromes of human infantile strabismus.

Regions of beta 4.beta 2 subunit chimeras that contribute to the agonist selectivity of neuronal nicotinic receptors.

Fifteen chimeric nicotinic receptor beta subunits were constructed consisting of N-terminal neuronal beta 4 sequences and C-terminal beta 2 sequences. Responses to cytisine, nicotine, or tetramethylammonium were compared to acetylcholine responses for these subunits expressed in Xenopus oocytes with alpha 3 subunits. The results show that (i) two residues in the extracellular domain of chimeric beta 4.