The clinical features of long QT syndrome result from episodic life-threatening cardiac arrhythmias, specifically the polymorphic ventricular tachycardia torsades de pointes. KVLQT1 has been established as the human chromosome 11-linked gene responsible for more than 50% of inherited long QT syndrome. Here we describe the cloning of a full-length KVLQT1 cDNA and its functional expression. KVLQT1 encodes a 676-amino acid polypeptide with structural characteristics similar to voltage-gated potassium channels. Expression of KvLQT1 in Xenopus oocytes and in human embryonic kidney cells elicits a rapidly activating, K ؉ -selective outward current. The I Kr -specific blockers, E-4031 and dofetilide, do not inhibit KvLQT1, whereas clofilium, a class III antiarrhythmic agent with the propensity to induce torsades de pointes, substantially inhibits the current. Elevation of cAMP levels in oocytes nearly doubles the amplitude of KvLQT1 currents. Coexpression of minK with KvLQT1 results in a conductance with pharmacological and biophysical properties more similar to I Ks than other known delayed rectifier K ؉ currents in the heart.

Benign familial neonatal convulsions (BFNC), a class of idiopathic generalized epilepsy, is an autosomal dominantly inherited disorder of newborns. BFNC has been linked to mutations in two putative K ؉ channel genes, KCNQ2 and KCNQ3. Amino acid sequence comparison reveals that both genes share strong homology to Kv-LQT1, the potassium channel encoded by KCNQ1, which is responsible for over 50% of inherited long QT syndrome. Here we describe the cloning, functional expression, and characterization of K ؉ channels encoded by KCNQ2 and KCNQ3 cDNAs. Individually, expression of KCNQ2 or KCNQ3 in Xenopus oocytes elicits voltagegated, rapidly activating K ؉ -selective currents similar to KCNQ1. However, unlike KCNQ1, KCNQ2 and KCNQ3 currents are not augmented by coexpression with the KCNQ1 ␤ subunit, KCNE1 (minK, IsK). Northern blot analyses reveal that KCNQ2 and KCNQ3 exhibit similar expression patterns in different regions within the brain. Interestingly, coexpression of KCNQ2 and KCNQ3 results in a substantial synergistic increase in current amplitude. Coexpression of KCNE1 with the two channels strongly suppressed current amplitude and slowed kinetics of activation. The pharmacological and biophysical properties of the K ؉ currents observed in the coinjected oocytes differ somewhat from those observed after injecting either KCNQ2 or KCNQ3 by itself. The functional interaction between KCNQ2 and KCNQ3 provides a framework for understanding how mutations in either channel can cause a form of idiopathic generalized epilepsy.Potassium channels are the largest and most diverse group of ion channels. They are primary regulators of resting membrane potential and action potential configuration and, therefore, modulate excitability of neurons, cardiac myocytes, and other electrically active cells. Recent identification of KCNQ1 (KvLQT1), the gene responsible for more than 50% of inherited cardiac long QT syndrome (LQTS), 1 established a new family of six-transmembrane domain K ϩ channels (1). KCNQ1, in combination with the KCNE1 subunit, encodes the slow component of the cardiac delayed rectifier K ϩ current (2-4), and mutations in KCNQ1, which occur in LQTS patients, partially or completely inhibit the channel in a dominant-negative fashion (5, 6). In an attempt to identify additional members of the KCNQ1 K ϩ channel gene family, the KCNQ1 sequence was used to search DNA and protein sequence data banks. Two additional KCNQ1-related genes, KCNQ2 and KCNQ3, were identified.Recent publications indicate that mutations in KCNQ2 or KCNQ3 are associated with BFNC, an autosomal dominantly inherited epilepsy in newborns (7-9). Preliminary functional characterization of KCNQ2 confirmed that this gene encodes a voltage-activated K ϩ channel (9). Here we describe the cloning, tissue distribution, and functional expression of both KCNQ2 and KCNQ3. More importantly, we demonstrate that these two channels interact functionally with each other and with KCNE1. EXPERIMENTAL PROCEDURES Molecular Cloning and Expression of KCNQ2 and KCNQ3-5ЈRap...

In LQTS-affected individuals these mutations would be predicted to result in a diminution of the cardiac I(Ks) current, subsequent prolongation of cardiac repolarization, and an increased risk of arrhythmias.

Dental caries exams and saliva samples were obtained from 541 adolescents, aged 10-15, initially and after 17 months as part of a 3-yr longitudinal study investigating the relationships of dietary intakes, specific microorganisms in saliva, and the prevalence and incidence of dental caries. The mean DMFS score detected in these subjects initially was 4.61, and they developed an average of 1.38 new DMFS during the first 17-month period. Initially, S. mutans and lactobacilli were detected in 64% and 56% of these subjects, respectively. Subjects with low levels of S. mutans and lactobacilli had significantly lower initial DMFS scores and developed significantly fewer new DMFS than subjects with high counts. The predictive values of a positive result for S. mutans or lactobacilli assays were low (31% and 39%), but those for a negative result were high (81% and 84%).

Selected microbial components in dental plaque were determined for children in Biddeford, Maine and Colombia, South America. Using cultural methods, Streptococcus mutans was detected in 51.4% of the Colombian children and 63.3% of the Maine children. Serotype c was predominant in both populations. The greatest difference between the two groups occurred with serotypes d and g which were present in 25% of the Colombian children with S. mutans and were not detected in the Maine children. In the specimens examined with specific FA conjugates. Actinomyces was the predominant genus, present in all individuals and comprising an average of 52% of all cells.

Direct FA staining for S mutans serotypes may be performed on smears made from plaque or strain isolates and on colonies attached to agar plates of black membrane filters. Staining with single conjugates directed to S mutans serotypes (a to e) as well as with polyvalent a-, b-, d-, f-fluorescein label and c-, e-rhodamine label conjugates indicate that serotype c is the most common. This is in agreement with many reports by other investigators. Cross-reactions with many S mutans conjugates occurred with organisms resembling Lancefield groups C and G streptococci.

A total of 82 strains of Streptococcus mutans representing serotypes a through g were tested for susceptibility to erythromycin, penicillin, methicillin, lincomycin, tetracycline, vancomycin, gentamicin, streptomycin, neomycin, kanamycin, bacitracin, and polymyxin B. Strains included stock cultures and isolates from human and animal dental plaque. Minimal inhibitory concentrations were determined by a broth-microdilution procedure. The major differences in antibiotic susceptibility observed among the serotypes resulted with antibiotics which act on the cell surface. Bacitracin was most active against serotype a strains and polymyxin B against serotype b strains. Serotypes a, d, and g were less susceptible than the other serotypes to methicillin.The involvement of Streptococcus mutans in dental caries and bacterial endocarditis has prompted interest in the susceptibility of this organism to antimicrobial agents. Furthermore, the inclusion of agents such as bacitracin and sulfonamide into selective media has produced preliminary evidence that there may be differences in antimicrobial susceptibility among the different serotypes of S. mutans (3,10,15). Baker and Thornsberry (1) and Ferretti and Ward (6) have examined the antibiotic susceptibility of S. mutans isolated from dental plaque and from patients with endocarditis. In the present study, we examine the antibiotic susceptibility of strains representing serotypes a-g (2, 13). MATERIALS AND METHODSBacterial cultures. The 82 strains examined included stock strains and isolates from human and animal dental plaque (

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