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Biomedical subjects

I Chin

Publications and source records attributed to I Chin.

11 recordsLinked to original sources
PubMed1999

Stress induced changes in transmitter release from sympathetic varicosities of the mouse vas deferens.

Activation of the sympathetic nervous system is an important component of the response to stress, but the effects of prolonged stress on sympathetic neurotransmission have not been assessed. In the present study we have examined the effect of 3 to 10 days exposure to stress induced by frequent handling and sham injections on neurotransmitter release from sympathetic varicosities of the mouse vas deferens. DiOC2(5)-fluorescence was used to visualise the sympathetic varicosities so that extracellular electrodes could be placed over known numbers of varicosities to monitor transmitter release using electrophysiological techniques. The frequency of excitatory junction currents (EJCs) increased with increasing duration of exposure to stress. The mean and maximum EJC amplitude significantly increased by 107% and 43%, respectively after 10 days of exposure to stress. The density of sympathetic varicosities innervating smooth muscle of the mouse vas deferens was not changed throughout the duration of the exposure to stress. The findings from this study demonstrate that the efficacy of transmitter release from the sympathetic varicosities is altered by repeated exposure of mice to stressful stimuli, such as handling and sham injections. Since such procedures are routine in many pharmacological experiments, it is important that investigators are aware of these changes so that due consideration is given when interpreting the data obtained from animals treated in this way.

Animals↗
PubMed1995

Evaluation of periodontal treatments using controlled-release tetracycline fibers: microbiological response.

In a 12-month multi-center study of 116 adult periodontitis subjects, six putative periodontal pathogens were monitored by DNA probe methods in a subset of 31 subjects. Monitored species included Porphyromonas gingivalis (Pg), Prevotella intermedia (Pi), Fusobacterium nucleatum (Fn), Eikenella corrodens (Ec), Campylobacter rectus (Cr), and Actinobacillus actinomycetemcomitans (Aa) with an average detection limit of 1.8 x 10(4) bacterial colony forming units/sample. The microbiological response to four periodontal treatments was studied, one treatment in each quadrant; scaling and root planing (S), scaling and root planing with tetracycline (TC) fiber (SF), a single application of TC fiber (F) and two serial applications of TC fiber (FF). Generally two sites were sampled in each quadrant, however, in some quadrants only one site was selected. These treatments were evaluated at baseline; immediately following therapy; and post-treatment at 1, 3, 6, and 12 months. The study was conducted with a split-mouth design with no maintenance therapy over a 12-month period. At baseline, 70.8% of sites had detectable Fn; 42.9% Pg; 63.5% Pi; 29.7% Ec; 28.3% Cr; and 5.5% Aa. No significant differences were seen in baseline proportions of these species between centers. Numbers and proportions of detectable pathogens (with the exception of Pg) exhibited a triphasic temporal response: a precipitous initial decrease immediately following therapy; a rise in proportions in the 1- to 3-month post-therapy period; and a spontaneous decline in the absence of therapy over the 3- to 12-month period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Salivary nystatin concentrations after administration of an osmotic controlled release tablet and a pastille.

Mucosal oral therapeutic system (MOTS) is a controlled-release osmotic system for oral cavity therapy. MOTS (nystatin) is designed to deliver approximately 200,000 units of nystatin over several hours. A crossover study was conducted in five healthy volunteers to evaluate the amount of nystatin released (based on residual drug content) when the system is held in the mouth for 30 min, 1 h, and 2 h, and to compare these concentrations with those achieved with a Mycostatin (nystatin) pastille. An average of 37% of the nystatin content was released intra-orally from MOTS during 2 h in the mouth, which was very similar to the percentage delivered in vitro. Mean salivary drug concentrations were as follows: 279 micrograms.ml-1 at 30 min; 654 micrograms.ml-1 after 1 h; and 532 micrograms.ml-1 at 2 h. These concentrations consistently exceeded those produced by the pastille at the same time points. Fifteen minutes after placement of the pastille in the mouth (i.e., immediately after its dissolution) mean nystatin concentrations reached 746 micrograms.ml-1 but fell rapidly to 13.2 micrograms.ml-1 at 30 min, 7.2 micrograms.ml-1 at 1 h, and 5.6 micrograms.ml-1 at 2 h. The study demonstrates that MOTS maintains high salivary nystatin concentrations throughout a 2 h dosing interval.

Administration, Oral↗
PubMed1993

On-line determination of pulmonary blood flow using respiratory inert gas analysis.

An inert gas analysis method has been developed to perform on-line real time determination of pulmonary blood flow using a nonrebreathing approach. This technique is based on a mathematical model describing mass balance of two inert gases which are breathed using an open gas circuit. The measurements using this method are noninvasive, easy to peform, and do not disturb normal physiological processes. As well, since data are collected on a breath-by-breath basis, it is possible to estimate other respiratory, cardiopulmonary, and metabolic parameters simultaneously in a breath-by-breath manner. Special consideration was given to developing effective data processing algorithms to minimize the influence of measurement noise and respiratory variations. Experimental studies to compare this method with other accepted techniques were conducted to validate the present technique.

Acetylene↗
PubMed1992

Gutta percha removal utilizing GPX instrumentation.

Two studies were performed in order to test the efficiency of GPX rotary instrumentation in removing gutta percha from endodontically-treated extracted teeth. A pilot project compared GPX to gates glidden instrumentation, and then a GPX technique was performed on 60 obturated mesial canals of mandibular molars. Assessment of the technique included radiographic and microscopic analysis of remaining debris. Results indicated that the GPX is a useful adjunct in these retreatment procedures. The clinical technique and time involved in the use of the GPX are discussed.

Dental Cavity Preparation↗
PubMed1990

Sudden fatal cardiac arrest in a child with an unrecognized anterior mediastinal mass.

We report a case of sudden fatal cardiac arrest in a 3-year-old boy. The arrest occurred when he was placed in the supine position by force for a venipuncture. Autopsy revealed a large anterior mediastinal mass. The death was attributed to the airway obstruction and cardiac compression by the mass. Postural change to supine position by force was believed to have triggered compression of the cardiopulmonary system by an unrecognized anterior mediastinal mass, resulting in cardiac arrest.

Child, Preschool↗
PubMed1989

Syndrome of resistance to thyroid hormone in an infant with congenital cytomegalovirus infection.

We describe an infant with congenital cytomegalovirus infection who developed the syndrome of resistance to thyroid hormone at three weeks of age, presenting with elevated thyroxine levels and non-suppressible thyroid-hormone-stimulating hormone secretions without any features of thyrotoxicosis. The resistance was present at the peripheral and pituitary levels and resolved spontaneously by 18 months of age. Cytomegalovirus infection was confirmed by the positive urine culture of this virus. This case demonstrates for the first time a possible association of thyroid hormone resistance with congenital cytomegalovirus infection.

Child, Preschool↗
PubMed1988

A disinfectant delivery system for control of micro-organisms in urine collection bags.

We developed a formaldehyde delivery system for urine collection bags and evaluated its effectiveness in suppressing the growth of bacteria in simulated human urine. The system was composed of paraformaldehyde in a polymeric carrier. We determined that inoculation of small numbers of Escherichia coli and Pseudomonas aeruginosa in urinary bags with a continuous flow of synthetic urine (40-80 ml h-1) quickly gives rise to high levels of contamination. This single tablet delivery system, however, proved bacteriostatic or bactericidal for both organisms over the 10-day lifespan. The formaldehyde concentration in the synthetic urine was c. 90 micrograms ml-1 or more during tests.

Disinfection↗
PubMed1985

[Fundamental and clinical studies on fosfomycin sodium in the field of obstetrics and gynecology].

Fosfomycin sodium (FOM-Na) was studied both fundamentally and clinically in the field of obstetrics and gynecology with following results. It showed good transference into the uterine tissues when given intravenously. The peak concentrations achieved in the uterine tissues following intravenous administration of 2 g of FOM-Na were 26.56 to 53.48 micrograms/g when given as one shot injection and 20.16 to 39.47 micrograms/g as drip infusion. In the serum of vein and uterine artery, peak concentrations of 163.6 to 143.40 micrograms/ml and 120 to 113.12 micrograms/ml were reached following one shot injection and drip infusion, respectively. In general, FOM-Na concentrations in the uterine tissues showed similar changes as those observed for serum concentrations. Clinically, FOM-Na was used in the treatment of 17 cases of obstetrical and gynecological infections at 2 g per dose twice daily as intravenous drip infusions. In all of these cases, good clinical efficacy was obtained. No side effects were observed.

Adnexa Uteri↗