Effects of an Open Jaw Posture on Vowel Perception in the Aging Voice.

Purpose: This study aimed to verify through an auditory-perceptual approach, whether an "open jaw" posture would result in improved speech quality for older adults.

Methods: Forty normal-hearing listeners (20 males; 20 females) aged between 18 and 47 listened to vowel segments and performed two separate tasks: identifying vowels and comparing vowel clarity. Stimuli included vowels segmented from a sentence ("We saw two cars.

An Acoustic and Electroglottographic Study of the Aging Voice With and Without an Open Jaw Posture.

Objectives: This study aimed to determine if the use of an "open jaw" posture in healthy aging adults would result in voice improvement detectable through acoustic and electroglottographic measurements.

Study Design: A convenience sampling strategy was used to recruit 85 participants, with at least five females and five males in each of four age groups, between age 35 and 50 years (35+), above 50 (50+), 60+, and 70+ years.

Methods: Participants sustained the vowel /a/ at three pitch levels (normal, low, and high) and repeated the test sentence "We saw two cars" in both a normal and an open jaw postures.

Silent myocardial ischemia as a potential link between lack of premonitoring symptoms and increased risk of cardiac arrest during physical stress.

The risk of cardiac arrest is increased during strenuous physical exercise in patients with stable coronary artery disease (CAD). Because premonitoring symptoms are rarely observed, silent myocardial ischemia may represent the pathophysiological basis for the induction of malignant ventricular arrhythmias. Holter monitoring was, therefore, performed in 40 consecutive patients entering a randomized intervention trial on progression of CAD.

Low-fat diet and regular, supervised physical exercise in patients with symptomatic coronary artery disease: reduction of stress-induced myocardial ischemia.

The effects of physical exercise and normalization of serum lipoproteins on stress-induced myocardial ischemia were studied in 18 patients with coronary artery disease, stable angina pectoris, and mild hypercholesterolemia (total serum cholesterol 242 +/- 32 mg/dl). These patients underwent a combined regimen of low-fat/low-cholesterol diet and regular, supervised physical exercise at high intensity for 12 months. At 1 year serum lipoproteins has been lowered to ideal levels (serum cholesterol 202 +/- 31 mg/dl, low-density lipoproteins 130 +/- 30 mg/dl, very low-density lipoproteins 22 +/- 15 mg/dl, serum triglycerides 105 [69 to 304] mg/dl) and physical work capacity was improved by 21% (p less than .

Single potassium channels with delayed rectifier behavior from lobster axon membranes.

Single-channel potassium currents from lobster axon membranes were studied in planar bilayers made from monolayers. Channel-opening events are grouped by time, forming bursts with an average duration of 4.5 ms.

The labelling of an axonal membrane component with 4-(N-maleimido) benzyltrimethylammonium, a reagent capable of affinity-labelling the alpha-subunit of the nicotinic acetylcholine receptor.

Membrane vesicles, isolated from crustacean axons, were treated, following disulfide reduction, with 3H-NEM or with 3H-MBTA. SDS polyacrylamide gel electrophoresis showed that exposure to NEM (a nonspecific thiol reagent) resulted in the labelling of several peptide bands, while with MBTA only a single band with a molecular weight of 50,000 was labelled. Reaction with MBTA (believed to be a specific label for the nicotinic acetylcholine receptor) could be largely prevented by preincubation with d-tubocurarine or bromacetylcholine.

Local anesthetics noncompetitively inhibit terbium binding to the exterior surface of nerve membrane vesicles.

It has previously been shown that terbium binds to membrane vesicles prepared from the walking leg nerve of the lobster (Homarus americanus) with a high affinity Kd of 2.2 microM. Fluorescence of bound Tb3+ occurs via energy transfer from the aromatic residues of proteins (gamma ex = 280 nm; gamma em = 546 nm), and calcium inhibits Tb3+ binding competitively with a Ki of 1.

Interaction of aromatic dyes with the coenzyme A binding site of choline acetyltransferase.

The interaction of a series of aromatic dyes with the coenzyme A binding site of choline acetyltransferase was studied. Several of the dyes were very potent inhibitors of the enzyme. With few exceptions, inhibition was competitive with respect to acetylcoenzyme A and noncompetitive with respect to choline.

Evidence for presence of an arginine residue in the coenzyme A binding site of choline acetyltransferase.

Choline acetyltransferase (acetyl-CoA:choline O-acetyltransferase, EC 2.3.1.

On the specificity of 125-I-alpha-bungarotoxin binding to axonal membranes.

125I-alpha-Bungarotoxin (alpha-BGT) was used to characterize the binding sites for cholinergic ligands in lobster walking leg nerve membranes. The toxin binding component has been visualized histochemically on the external surfaces of intact axons and isolated axonal membrane fragments. Binding of alpha-BGT to nerve membrane preparations was demonstrated to be saturable and highly reversible (KappD congruent to 1.

Terbium binding to axonal membrane vesicles from lobster (Homarus americanus) peripheral nerve. A probe of calcium binding sites.

Tb3+, a fluorescent trivalent cation with physicochemical properties similar to Ca2+, binds to peripheral nerve membrane vesicles prepared from the walking leg nerve bundle of the lobster (Homarus americanus). Saturable binding is measured for at least two classes of binding site. Bound Tb3+ can be displaced by other cations in the order: Ca2+ greater than Mg2+ = Zn2+ greater than NH4+.

Synthesis and study of conformationally defined enantiomers of local anesthetics and conformationally defined enantiomers of fluorescent dyes designed to label electrically excitable membranes.

Conformationally defined enantiomeric local anesthetics and fluorescent dyes were synthesized. Neither the local anesthetics nor the fluorescent probes showed stereospecificity in interacting with nerve membranes. The fluorescence signals generated by the dyes showed excellent correlation with the time course and shape of the nerve action potential.

Acetylcholine and choline acetyltransferase.

The thermodynamics and kinetics of the alcoholysis of thiolesters are discussed and related to choline acetyltransferase. The conformation and rotational barriers of acetylcholine are described as is the specific inability of choline to induce depolarization. Evidence is presented for the involvement of imidazole and the non-involvement of thiol groups in the active site of choline acetyltransferase.

Ligand interactions of crustacean axonal membranes.

The relative abilities of a series of local anesthetics in which either or both the ester oxygens had been replaced with sulfur or selenium to block axonal or synaptic preparations are compared with their abilities to displace (3)H-nicotine from lobster axon plasma membrane fragments. The relative affinities of a series of cholinergic agonists and antagonists for synaptic and axonal membranes are discussed as is the salt sensitivity and reversibility of their interactions. The utility of a conjugate of ?-bungarotoxin and horse-radish peroxidase for the histochemical visualization of binding sites of intact axons or axonal vesicles is discussed.

Localization of horseradish peroxidase-alpha-bungarotoxin binding in crustacean axonal membrane vesicles and intact axons.

A conjugate of alpha-bungarotoxin with horseradish peroxidase was used to visualize alpha-bungarotoxin binding sites at the fine structural level in isolated axonal membrane vesicles from lobster walking leg nerve. These plasma membrane vesicles have previously been shown to exhibit saturable binding of [3H]nicotine and [3H]acetylcholine. Binding of the toxin was identified in the axon plasma membrane and could be blocked by pretreatment with excess free alpha-bungaratoxin or d-tubocurarine.

Choline acetyltransferase.

Acetylcholine is essential to neural function. It synthesis is catalyzed by choline acetyltransferase, the enzyme responsible for the acetylation of choline by acetyl coenzye A, a reaction favored slightly thermodymodynamically and not at all kinetically. An analytically pure enzyme still has not been obtained; however, method of purification have been greatly improved recently.

Interaction of cholinergic ligands and local anesthetics with plasma membrane fragments from lobster axon.

Isologous local anesthetics containing the ester, thiolester, or selenolester grouping and their quaternary ammonium analogs were studied for their ability to displace [3H]nicotine from plasma membrane fragments of lobster nerve. Tertiary and quaternary analogs were equiactive. The relative ability of oxo, thio, and seleno analogs to displace nicotine was the same as their relative ability to block axonal conduction and synaptic transmission.

Interaction of analogues of coenzyme A with choline acetyltransferase.

The finding that methyl methanethiolsulfonate appears to inhibit choline acetyltransferase from squid ganglia not by reacting with a thiol group of the enzyme but by reacting with the thiol group of coenzyme A to form a competitive inhibitor of acetyl coenzyme A led to the synthesis of the ethyl, propyl, and 3-carboxy-4-nitrophenyl disulfides of CoA. The methyl disulfide of 1,N6-etheno-C0A, a fluorescent ligand, was also prepared. All the disulfides are powerful inhibitors of ChA, their Ki values being very similar.