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Biomedical subjects

R T Smith

Publications and source records attributed to R T Smith.

At least 37 records · Page 2Linked to original sources
PubMed1991

Surgical division of posterior septal accessory pathways in the Wolff-Parkinson-White syndrome: a new modified approach.

A new modified surgical approach for the division of posterior septal accessory pathways is described. This method incorporates some of the desirable components of previously reported techniques, while eliminating difficult and unreliable aspects of those same techniques. Interestingly this procedure was initially illustrated by Sealy and Mikat in 1983, although it has not been used clinically until now. The recognized intent of this dissection is to totally separate atrial and ventricular structures within the posterior septal space so that all accessory pathways encountered are permanently interrupted.

Atrioventricular Node↗
PubMed1990

Glycyl-L-proline transport in rabbit enterocyte basolateral-membrane vesicles.

The properties of a peptide-transport system in rabbit enterocyte basolateral membrane were examined with glycyl-L-proline as the substrate. Basolateral-membrane vesicles prepared from rabbit proximal intestine were characterized in terms of both purity and orientation. Marker-enzyme assays show that the basolateral-membrane marker, ouabain-sensitive K(+)-activated phosphatase, is enriched 17-fold with respect to the initial homogenate. The activities of enzymes used as markers for other membranes and organelles are low, and contamination of the final membrane fraction with these is minimal. The use of immunoblotting techniques further confirms the absence of brush-border-membrane contamination. Proteins in the basolateral-membrane vesicle preparation gave no cross-reaction with antibodies against the 140 kDa antigen and the Na+/glucose-symport protein, markers specific to the brush-border membrane of the enterocyte. Conversely, antibodies raised against the classical basolateral-membrane marker, the RLA class I histocompatibility complex, reacted strongly with a 43 kDa basolateral-membrane protein. The orientation of the basolateral-membrane vesicles was shown to be predominantly inside-out on determination by two independent criteria. The uptake of [1-14C]glycyl-L-proline by these vesicles is stimulated by the presence of an inwardly directed pH gradient, and this stimulation can be abolished by the proton ionophores carbonyl cyanide p-trichloromethoxyphenylhydrazone (CCCP) and tetrachlorotrifluoromethylbenzimidazole (TTFB). Transport is also inhibited by HgCl2, thimerosal, Na+ and other glycyl dipeptides.

Amino Acids↗
PubMed1990

The barrier function in extracapsular cataract surgery.

The distribution of fluorescein between the anterior chamber and the anterior vitreous was measured in two groups of patients after oral administration: group I, extracapsular cataract extraction (ECCE) patients with intact capsule and posterior chamber intraocular lens (PC IOL) (n = 12); group II, intracapsular cataract extraction (ICCE) patients with anterior chamber IOL (AC IOL) (n = 13). The fluorescein concentrations were measured by fluorophotometry and the penetration ratios were calculated. The penetration of fluorescein into the anterior vitreous was significantly less in the ECCE group (group I, penetration ratio = 2.03 +/- 1.00 X 10(-3) min-1; group II, penetration ratio = 5.99 +/- 4.89, X 10(-3) min-1, P less than 0.01). The authors concluded that in ECCE versus ICCE a significantly smaller proportion of fluorescein is found in the anterior vitreous relative to the aqueous after passage through the blood-aqueous barrier. This suggests a barrier to posterior movement of other molecules that may initially gain access to the eye in the anterior segment (e.g., prostaglandins).

Aged↗
PubMed1989

Flecainide acetate for resistant arrhythmias in the young: efficacy and pharmacokinetics.

Drug efficacy and pharmacokinetics were assessed in 63 patients, aged 5 days to 30 years (mean 8 years), who received flecainide acetate for control of resistant arrhythmias. Doses of flecainide ranged from 59 to 225 mg/m2 body surface area per day (mean 141) in divided doses every 8 to 12 h and serum trough levels ranged from 0.10 to 0.99 micrograms/ml (mean 0.36). Flecainide controlled or partially controlled arrhythmia in 53 (84%) of the 63 patients: 7 of 7 patients who had the permanent form of junctional reciprocating tachycardia, 12 of 13 who had an atrial ectopic tachycardia, 10 of 10 who had ventricular tachycardia and 18 of 25 patients who had reentrant supraventricular tachycardia. Five of seven patients who had the latter arrhythmia were unsuccessfully treated with flecainide. They had Wolff-Parkinson-White syndrome and developed asymptomatic, incessant, slower orthodromic reciprocating tachycardia while receiving the drug. Transient blurred vision was reported in three patients and two patients had transient hyperactivity. No significant hemodynamic side effects were seen in any patient. Twenty-five patients underwent oral pharmacokinetic investigation. Young infants (less than 1 year of age) had a mean plasma elimination half-life (t 1/2) approximating that (11 to 12 h) found in older children and healthy adults; children aged 1 to 12 years had a shorter mean t 1/2 of 8 h. Dosing schedules based on milligrams per square meter body surface area correlated better with plasma flecainide levels than did dosing based on milligrams per kilogram body weight.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1989

Smithisms.

Explore the source record for details and available documents.

Anesthesiology↗
PubMed1988

Encainide for resistant supraventricular tachycardia in children: follow-up report.

Forty-one children (26 weeks gestational age to 20 years) with drug-resistant supraventricular tachycardia were treated with oral encainide, and 29 were followed for 3 to 34 months (mean 15). Diagnoses obtained by electrocardiographic criteria (23 patients) or electrophysiologic testing (18 patients) included permanent junctional reciprocating tachycardia in 15 children, paroxysmal atrioventricular reciprocating tachycardias (AVRT) in 13, atrial ectopic tachycardia in 4, atrial flutter in 1, chaotic atrial tachycardia in 5 and junctional ectopic tachycardia in 3. Encainide was completely effective in 54% (22 of 41 study patients) and partially effective in an additional 24% (10 of 41 patients), when combined with propranolol or verapamil. Within 1 month, 13 (32%) discontinued encainide for inefficacy or intolerance. Encainide was most effective in the treatment of permanent junctional reciprocating tachycardia (60% effective) and AVRT (69% effective). It controlled only 40% of primary atrial tachycardias. Encainide was well tolerated on a long-term basis in patients not experiencing symptoms during initiation. In study infants younger than age 6 months, encainide was associated with excessive QRS aberrancy during initiation in 4 of 13 (31%), compared with 3 of 28 (11%) in older children. Ventricular proarrhythmia occurred in 2 children and 1 died suddenly. Mean effective encainide dose was 3.5 mg/kg/day or 86 mg/m2/day. In 4 children who had nonextensive metabolism of encainide, the drug was ineffective. Encainide is effective in the treatment of some resistant forms of permanent junctional reciprocating tachycardia and AVRT in otherwise healthy children. Children younger than age 6 months and those with either previous proarrhythmic events or severe cardiac dysfunction appear to have a high incidence of adverse effects.

Administration, Oral↗
PubMed1988

Early expression of a T-cell receptor beta-chain transgene suppresses rearrangement of the V gamma 4 gene segment.

beta transgenic mice have a T-cell receptor beta-chain gene that is prematurely expressed on the surface of CD4- CD8- thymocytes and paired with an uncharacterized non-T-cell receptor alpha-chain polypeptide. The rearrangement of the T-cell receptor variable region gamma chain gene segment V gamma 4, a component of the gamma-chain gene that is rearranged and expressed preferentially on thymocytes of normal adult mice, is severely repressed in beta transgenic mice. Consequently no gamma delta T-cell receptor heterodimers are detectable on the surface of adult thymocytes or splenic T cells. These results indicate that cells expressing alpha beta or gamma (V gamma 4)-delta TCRs originate from a common precursor in which the first productive rearrangement of either the beta or gamma locus determines the further differentiation pathway into either alpha beta or gamma delta T cells. The repression of V gamma 4 rearrangement by a preexisting beta-chain gene may be indicative of one of several mechanisms which ensure that gamma delta and alpha beta receptors do not as a rule appear on the surface of the same cell.

Alleles↗
PubMed1988

Functional recovery and medical costs of trauma: an analysis by type and severity of injury.

This study was designed to delineate the factors that influence the extent and rate of recovery as related to the characteristics and duration of functional limitations resulting from trauma. The study population was 597 surviving trauma patients aged 16-45 years from two trauma centers in a single state system which follow similar care protocols, and included patients with extremity, abdomen, thorax, brain, and spinal cord injuries. Of 479 trauma patients (80% of the total) who were followed for a full year, 57% had no activity restrictions, 16% had some limitation with either a major or minor physical activity, but did not have any difficulty with mobility or self care, and 27% were limited in either mobility or one of the five basic self-care activities. Further analyses show that of the 262 individuals who were working full-time before the injury, 57% had actually returned to full-time employment within the year. Factors in addition to type and severity of trauma that influence return to work were higher educational level, white collar employment, higher preinjury income, and the presence of supportive individuals among family or friends. Recovery as defined by functional status and return to full-time work is analyzed by body region and severity of the principal injury sustained.

Activities of Daily Living↗
PubMed1987

Ethmozine (moricizine HCl): a promising drug for "automatic" atrial ectopic tachycardia.

Atrial ectopic tachycardia is an uncommon life-threatening supraventricular tachycardia in children and is resistant to usual antiarrhythmic drugs. Whereas the cellular mechanism of atrial ectopic tachycardia is unknown, atrial ectopic tachycardia may be due to a form of automaticity. Moricizine HCl has been used primarily for ventricular rhythm disturbances; the drug depresses abnormal automaticity and delayed after-depolarizations but has little effect on normal automaticity. Because of this property, we have used moricizine HCl in 4 patients with atrial ectopic tachycardia. As evidenced by continuous 24-hour Holter monitoring, moricizine HCl was successful in suppressing atrial ectopic tachycardia in each patient. During a limited follow-up (6 months) no side effects have occurred. Moricizine HCl is a promising primary drug for atrial ectopic tachycardia.

Adolescent↗
PubMed1987

Quantification of diabetic macular edema.

In a cross-sectional study, 34 diabetic patients with clinically significant macular edema underwent visual acuity testing, stereo fundus photography (graded for retinal thickening and hard exudates), fluorescein angiography (evaluated for macular leakage and the outline of the foveal avascular zone [FAZ]), and vitreous fluorophotometry (whereby posterior penetration ratios were calculated). This last ratio provided the highest single correlation with visual acuity; next highest were patient age and FAZ grading. Multivariate regression confirmed that these three variables together best predicted visual acuity. Lesser correlations with acuity were obtained with angiographic leakage and fundus photography grading. Cross-correlations among all gradings showed that indicators of breakdown of the blood-retinal barrier, ie, fluorophotometry, angiographic leakage, and retinal thickening, were significantly correlated with each other, whereas FAZ grading was independent of all these factors and correlated only with acuity. By performing vitreous fluorophotometry and fluorescein angiography, it is possible to quantitate two major components of diabetic maculopathy: breakdown of the blood-retinal barrier and macular ischemia, both of which are highly correlated with visual acuity.

Adult↗
PubMed1987

Electroretinographic findings in sickle cell retinopathy.

We obtained electroretinograms (ERGs) from normal subjects and from patients with sickle cell disease. The ERG components (a-wave, b-wave, and oscillatory potentials) obtained from normal subjects and patients without peripheral retinal neovascularization did not differ in either amplitude or implicit time. However, ERG components obtained from patients with peripheral retinal neovascularization were reduced in amplitude compared with those obtained from normal subjects or patients without neovascularization. The reduced a-wave, b-wave, and oscillatory potential amplitudes may have been due to photoreceptor dysfunction secondary to choroidal ischemia or possibly increased oxygen demands by the inner retina. Ischemia of the inner retina may also have contributed to the altered b-wave and oscillatory potentials. These results suggest that ERG provides a means of assessing the consequence of peripheral retinal ischemia to retinal cell function and could be of value in monitoring patients with sickle cell disease for the development of clinically significant peripheral retinal neovascularization.

Anemia, Sickle Cell↗
PubMed1987

Use of fluorosilicone to unfold a giant retinal tear.

We unfolded and attached a giant retinal tear with an inverted edge using fluorosilicone oil while the patient was in the supine position. The advantages of high viscosity (10,000 centistokes) and specific gravity (1.31) fluorosilicone are discussed in this paper.

Humans↗
PubMed1987

Newer antiarrhythmic drugs in children.

Our experience with the use of five new antiarrhythmic drugs for treating life-threatening arrhythmias in children will be briefly reviewed. Prevention of recurrent episodes of atrial flutter with digoxin and local anesthetic antiarrhythmic drugs often is only moderately successful, benefiting 65% of patients. Amiodarone is particularly useful for those patients who cannot be controlled on this regimen. We caution that the heart rate be monitored carefully when therapy with amiodarone is initiated in patients likely to have sick sinus syndrome. We have found mexiletine useful for controlling significant ventricular arrhythmias in patients with congenital heart disease. Likewise, 79% (11 of 14) of patients with ventricular tachycardia treated with amiodarone were well controlled. However, the range of disease categories (congenital heart disease, myocarditis, cardiomyopathy) in which amiodarone is effective is much broader than for mexiletine. Although other investigators have used amiodarone successfully for controlling supraventricular tachycardia in the Wolff-Parkinson-White syndrome or secondary to concealed accessory AV connections, we recommend surgical ablation. Propafenone has significantly improved our ability to control postoperative JET. Although JET is self-limited in duration and spontaneously remits, it frequently produces life-threatening hemodynamic compromise in the postoperative setting. Propafenone slows the ventricular rate into a range in which AV sequential pacing may be instituted. Generally, after 24 to 72 hours, the patient may be quickly weaned from propafenone. Chronic incessant supraventricular tachycardia (SVT) is frequently associated with a dilated cardiomyopathy. The two most common mechanisms of incessant SVT are PJRT and AET. We have found encainide and ethmozine extremely effective in suppressing tachycardia episodes in PJRT and AET, respectively. Medical therapy has been associated with few side effects.

Adolescent↗
PubMed1987

Bond strengths of lingual orthodontic brackets bonded with light-cured composite resins cured by transillumination.

A method of curing light-cured composite resins by transillumination to cement acid-etched fixed partial dentures was adapted to bond solid mesh-backed lingual orthodontic brackets. Results of this investigation showed that the bond strengths of the orthodontic brackets bonded with light-cured composite resins were significantly less (P less than 0.05) than the bond strengths of the orthodontic brackets cemented with traditional adhesives and orthodontic composite resins. Notwithstanding, the bond strengths achieved with the transilluminated light-cured composite resins should be adequate to withstand the forces of mastication and orthodontic movements. There was no correlation of bond strengths of the brackets cemented with the transilluminated light-cured composite resins when compared to the faciolingual widths of the teeth.

Acrylic Resins↗
PubMed1987

Cryoablative techniques in the treatment of cardiac tachyarrhythmias.

Of 175 patients treated surgically for potentially lethal or refractory cardiac tachyarrhythmias, 53 underwent mapping and definitive operation using cryoablative techniques as the primary or adjunctive method. Included were 16 patients with supraventricular tachycardia caused by accessory pathways (Kent bundle) in the right anterior or posterior paraseptal location. Cryoablation was successful in abolishing tachycardia in 93.7% (15 of 16). Six patients (100%) with permanent junctional reciprocating tachycardia were cured by cryoablation. Eighteen of 19 patients with atrial ectopic tachycardia were treated by cryoablation alone or in combination with excision of the atrial appendage, with success in 15 (83.3%). Five of these were left atrial foci cured by cryoablation. Fourteen right atrial foci were treated by excision of the appendage only (1 patient), excision of the appendage and local cryoablation (8 patients), and cryoablation alone (5 patients). Three of these underwent partial (2 patients) or complete (1 patient) atrial disconnection after excisional and cryoablative techniques failed to control the tachycardia. Multiple ectopic atrial foci were common (9 patients), and successful cryoablation was accomplished in 100% of the patients with a single atrial ectopic focus (10 patients) but in only 66% of those with multiple foci. Thirteen of 19 infants with critical ventricular tachycardia were treated by cryoablation at the site of the ectopic focus, either alone or in combination with excision of the area. Elimination of tachycardia was accomplished in 13 patients (100%). Myocardial hamartoma (Purkinje cell tumor) was the histological diagnosis in 11 of the infants with ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Incessant ventricular tachycardia in infants: myocardial hamartomas and surgical cure.

Infants with incessant ventricular tachycardia (occurring greater than 10% of the day) have generally been described in pathologic studies. This report describes 21 patients with incessant ventricular tachycardia present greater than 90% of the day and night; the age at diagnosis ranged from birth to 30 months (mean 10.5 months). The most common clinical presentation was cardiac arrest (11 patients, in 5 after digitalis for presumed supraventricular tachycardia); another 6 patients had congestive heart failure and 4 were asymptomatic. Three patients had coexisting Wolff-Parkinson-White syndrome. The rate of incessant ventricular tachycardia ranged from 167 to 440 (mean 260 beats/min) and the QRS duration from 0.06 to 0.11 second. The most common electrocardiographic (ECG) pattern (10 of 21) was right bundle branch block with left axis deviation, but other right and left bundle branch block patterns were observed. Conventional and investigational antiarrhythmic agents (nine patients received amiodarone) failed to eliminate incessant ventricular tachycardia in all. Electrophysiologic studies localized incessant ventricular tachycardia to the left ventricle in 17 (to the apex in 2, the free wall in 9 and the septum in 6) and to the right ventricular septum in 4. No structural abnormalities were found on the echocardiogram or angiocardiogram. All 21 patients had surgery at an age of 3.5 to 31 months (mean 16). In 15 a tumor was found: 13 myocardial hamartomas (9 discrete, 4 diffuse throughout both ventricles) and 2 rhabdomyomas (1 multiple). Myocarditis was found in one patient (the oldest). In four, only myocardial fibrosis was found; results of one biopsy were normal.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-Arrhythmia Agents↗