Extracellular potassium ion dynamics and ventricular arrhythmias in the canine heart.

The relation between extracellular potassium ion activity [( K+]o) and ventricular tachyarrhythmias was studied in an open chest canine model with the use of two protocols. In Protocol I, potassium chloride was administered into the proximal left anterior descending coronary artery at a rate of 0.125 mEq/min for either 20 min or until [K+]o = 20 mEq/liter, whichever came first. In Protocol II, the proximal left anterior descending coronary artery was occluded in one step and was reperfused 20 min later. Fifteen dogs were subjected to Protocol I, nine of which were also subjected to Protocol II. In the latter group, a recovery period of greater than or equal to 1 h separated the two protocols. Local K+ and intramyocardial activities were recorded with use of bifunctional ion-sensitive plunge electrodes at multiple sites located in the region of the left ventricle perfused by the left anterior descending artery and at one site outside of this region. The following variables were recorded and analyzed: Lead II electrocardiogram, heart rate, systemic arterial blood pressure, local [K+]o and its time derivative (dK+/dt), local electrograms and ventricular arrhythmias. Maximal [K+]o and dK+/dt were 23 +/- 3 mEq/liter and 9 +/- 1 mEq/liter per min in Protocol I and 14 +/- 1 mEq/liter and 3 +/- 1 mEq/liter per min in Protocol II, respectively. In both protocols, the occurrence of ventricular arrhythmias correlated with [K+]o (p less than 0.02) as well as with dK+/dt (p less than 0.05). Ventricular arrhythmias were more frequent and more severe in Protocol II than in Protocol I (p less than 0.05). Therefore, whereas K+ dynamics were more pronounced in Protocol I, ventricular arrhythmias were more severe in Protocol II. This occurrence was apparently due, at least in part, to less heterogeneous changes in K+ gradients during constant K+ infusion. It was concluded that, in addition to the magnitude of [K+]o, the rate of change of this variable (that is, dK+/dt) apparently plays an important role in the genesis of ischemic ventricular arrhythmias.

Medical management of congenital nasolacrimal duct obstruction.

A consecutive series of 113 infants seen with congenital nasolacrimal duct obstruction were treated with local massage and topical antibiotic ointment. In 107 of the infants the obstruction was resolved within 8 months of initiation of this form of management. Nearly all of the infants were spared a surgical procedure that probably would have been performed if early probing of the nasolacrimal system had been advocated.

Early intrauterine development: I. The rate of growth of Caucasian embryos and fetuses between the 6th and 20th weeks of gestation.

Liberalization of abortion laws in various countries and states of Europe and America has offered an opportunity for the study of the correlations between menstrual age and the rate of bodily development of human embryos and fetuses. In several institutions where local bylaws mandated the consent of the patients requesting therapeutic abortion to pathological investigation of the products of conception, various parameters of growth were measured systematically. These included crown-rump and foot lengths and body weight. The analysis of the data indicated that in the embryosic stages of development the rate of growth is substantially slower than it had been assumed previously. In the more advanced fetal stages of development the findings supported the validity of the long-established standard of Streeter. Since the current study has been based on apparently normal gestations of healthy women, whereas earlier data had rested, to a great extent, on spontaneously aborted and extopic embryon and fetuses, it seems evident that pathological specimens are not suitable for the purpose of establishing reliable standards of normal intrauterine growth rate. The present data support the suggestion, based on various experimental and clinical observations, that pathological gestations often result from abnormal ovulations that occur at times other than the mid-cycle and that such conceptions are frequently followed by a bleeding episode that simulates menstruation. It is likely that the inclusion of a high number of such cases biased the results of earlier investigations concerning embryonic growth rate on account of the frequent incidence of erroneous menstrual histories. The material available did not permit the extension of the investigation beyond the 20th week of gestation. It appears, however, that the average growth rate in the mid-trimester may be slower than the data adopted by the American Academy of Pediatrics would indicate. The possible causes of some phenomena observed in the course of the investigation, such as unexplained scatter of growth-rate patterns at all developmental stages and discrepancies among various literary data, have been discussed in some detail. While a tentative attempt has been made to correlate the investigated parameters of fetal growth with biparietal diameters of the head, a measurement accessible to direct assessment by sonography during pregnancy, the necessity of improving these standards through a prospective study has been emphasized.

Factors affecting outcome of sarcoidosis. Influence of race, extrathoracic involvement, and initial radiologic lung lesions.

Chest roentgenograms of 152 patients with type 2/3 disease observed 3 or more years were reviewed using modified ILO/UC nomenclature. After a mean length of observation of 9.3 years, clinical recovery was observed in 71.7% and radiologic recovery in 48.0% of the patients. Age; duration of observation; mediastinal adenopathy; and character (xyz, pgr, stu), size, extent, and profusion of pulmonary densities were similar in the 53 white and 99 black patients, who differed significantly only in sex distribution. White patients achieved clinical recovery (84.9%) more often than black patients (64.7%) (p = .05). Factors influencing clinical recovery were analyzed by means of stepwise logistic linear regression. The initial roentgenographic features were unrelated to outcome; only race and extrathoracic disease proved to have significant predictive value. The probability of clinical recovery is estimated to be .894 in white patients with disease limited to the chest, .697 in white patients with extrathoracic disease, and .760 in black patients without and .454 in black patients with extrathoracic sarcoidosis. Recovery appears to be related not to the severity of the initial pulmonary reaction but to racially associated factors that influence extrathoracic dissemination as well as lung damage.

Acute electrical stimulation increases extramyocardial collateral blood flow after a cardiomyoplasty.

We hypothesized that acute electrical stimulation of a latissimus dorsi cardiomyoplasty would augment the collateral blood flow delivered by the skeletal muscle to the heart. This hypothesis was tested in an animal model (13 goats) of coronary artery disease. Six weeks after a cardiomyoplasty was performed, myocardial collateral blood flow derived from the latissimus dorsi muscle was measured with colored microspheres when the muscle was at rest and during electrical stimulation of the thoracodorsal nerve at 1.25 Hz. The area at risk for ischemia averaged 13.37 +/- 2.08 g (mean +/- standard error), or 18.4% of left ventricular mass (n = 13). At rest, significant skeletal muscle-derived collaterals developed in 9 animals, and formed predominantly to chronic ischemic myocardium (mean +/- standard error, 0.07 +/- 0.02 mL.g-1 x min-1; n = 9), rather than infarct (0.03 +/- 0.02 mL.g-1 x min-1; n = 5), or normal myocardium (0.0005 +/- 0.0001 mL.g-1 x min-1; n = 9). Stimulation increased skeletal muscle-derived collateral blood flow to chronic ischemic areas to 0.38 +/- 0.09 mL.g-1 x min-1 (n = 9) (p < 0.05). During stimulation, the collateral flow was greater in the epicardium (0.46 +/- 0.11 mL.g-1 x min-1) than in endocardium (0.14 +/- 0.09 mL.g-1.min-1) (p < 0.05). This study demonstrates that electrical stimulation of a latissimus dorsi cardiomyoplasty increases extramyocardial collateral blood flow to chronic ischemic myocardium.

Clinical predictive factors for development of recurrence and metastasis in conjunctival melanoma: a review of 68 cases.

Sixty eight cases of histologically proved conjunctival melanoma were reviewed in order to determine the clinical factors that were predictive of local recurrence and distant metastasis. All patients were treated with surgical excision and most had supplemental cryotherapy. The mean follow up was 7.5 years. Histopathologically, the conjunctival melanoma arose from primary acquired melanosis in 56%, from naevus in 26%, and de novo in 18%. Of the 68 patients, 38 (56%) developed at least one local tumour recurrence and 22 (32%) developed more than one recurrence. The method of initial treatment and the eventual development of metastasis were the two parameters statistically associated with tumour recurrence. Those patients treated initially with tumour excision alone had a statistically significant higher recurrence rate than those treated initially with excision and supplemental cryotherapy (p = 0.001). Fourteen patients (21%) developed metastasis and the mean period between treatment and metastasis was 3.6 years. Twelve (18%) died from metastatic melanoma with a mean interval of 4.4 years from the time of initial surgery until death. The only clinical parameter that was statistically associated with distant metastasis was local tumour recurrence (p = 0.015). Based on these observations, the authors make recommendations regarding the treatment of conjunctival malignant melanoma. It appears that initial complete excision of the tumour with supplemental cryotherapy offers the patient the best chance of remaining free of recurrence and metastasis.

Intermittent exposure to noise: effects on hearing.

Most studies of the effects of noise upon hearing have dealt with continuous noise exposure. Previous reports on intermittent exposure to noise concluded that it causes less damage to hearing than does continuous exposure to noise of the same intensity. In this investigation, 12,000 workers were screened to find 295 subjects who met the strict criteria of the study. Most of the subjects were exposed to jackhammer noise at peak levels of 118 dBA. Intermittent exposure to intense noise results in very severe loss in high frequencies but relatively little or no hearing loss in the lower frequencies even after many years of exposure. This differs substantially from the effects of continuous exposure to noise of the same intensity. It remains to be determined whether this pattern of hearing results from intermittent exposure to all sorts of noise or only from the kinds of sources investigated in this study.

The effect of a no-smoking policy on recruitment and retention in outpatient cocaine treatment.

Historically, directors of substance abuse treatment programs have been reluctant to adopt a smoke-free policy because of the fear of patient attrition. According to a recent survey, however, a number of program directors now believe that such fears may be unwarranted. The purpose of the present study was to examine the impact on admissions and attendance of adopting a smoke-free policy at a cocaine treatment program offering outpatient group therapy sessions 3 half days a week. Results indicated that implementation of this policy had no impact on the number of patients who sought treatment at the facility or the number of group sessions patients attended. It was also noteworthy that for a sample of cases active in the month prior to and the month following the ban there were no changes in attendance patterns or in the proportion of patients failing to return from a 10-15 minute therapy break despite the fact that 89% of these patients were cigarette smokers.

Analysis by gender and Visual Imagery Reactivity of conventional and imagery Rorschach.

Examined here are the effects of gender and Visual Imagery Reactivity in 80 consecutively selected psychiatric outpatients. The participants were grouped by gender and by the amounts of responsiveness to preceding therapy work using imagery (Imagery Nonreactors and Reactors). In the group of Imagery Nonreactors were 13 men and 22 women, and in the Reactor group were 17 men and 28 women. Compared were the responses to standard Rorschach (Conventional condition) with visual associations to memory images of Rorschach inkblots (Imagery condition). Responses were scored using the Visual Imagery Reactivity (VIR) scoring system, a general, test-nonspecific scoring method. Nonparametric statistical analysis showed that critical indicators of Imagery Reactivity encoded as High Affect/Conflict score and its derivatives associated with sexual or bizarre content were not significantly associated with gender; neither was Neutral Content score which categorizes "non-Reactivity." These results support the notion that system's criteria of Visual Imagery Reactivity can be applied equally to both men and women for the classification of Imagery Reactors and Nonreactors. Discussed are also the speculative consequences of extending the tolerance range of significance levels for the interaction between Reactivity and sex above the customary limit of p < .05 in borderline cases. The results of such an analysis may imply a trend towards more rigid defensiveness under Imagery and toward lesser verbal productivity in response to either the Conventional or the Imagery task among women who are Nonreactors. In Reactors, men produced significantly more Sexual Reference scores (in the subcategory not associated with High Affect/Conflict) than women, but this could be attributed to the effect of tester's and subjects' gender combined.

Long-term treatment of hypertension with methyldopa. I. Study objectives and design.

In this retrospective study, a group of 435 patients provided meaningful analyses of blood pressure and dosage data for treatment periods of up to 4.5 years. The protocol, study objectives, and pretreatment demographic characteristics of the group are summarized in this report, which is the first in a series in this issue describing the results of this survey.

Adenosine mediates the negative chronotropic action of adenosine 5'-triphosphate in the canine sinus node.

ATP exerts pronounced electrophysiologic effects in the mammalian heart. The present study tested the hypothesis that the negative chronotropic action of ATP in the canine sinus node is dependent on its degradation to adenosine. Increasing doses of the following compounds were administered in the sinus nodal artery of 12 open chest dogs (either sex, 30-35 kg) anesthetized with pentobarbital (30 mg/kg i.v.): adenosine, ATP, alpha,beta methylene-ATP (AMPCPP) and beta,gamma methylene-ATP (AMPPCP). Right atrial, His bundle and right ventricular electrograms as well as Lead II ECG and systemic arterial blood pressure were monitored continuously and recorded. The depressant effects of test compounds on the sinus node were assessed from the prolongation of sinus cycle length and the duration of junctional escape rhythm which they induced. Data were used to plot dose-response curves for the four test compounds. The order of potency was adenosine greater than or equal to ATP greater than or equal to AMPPCP much greater than AMPCPP = 0. In 3 of 12 dogs the emergence of junctional escape rhythm was observed after the highest dose of either adenosine, ATP or AMPPCP. In addition, aminophylline, a selective competitive inhibitor of adenosine at P1-purinoceptor site, reduced the effects of maximal doses of adenosine, ATP and AMPPCP by 52 +/- 7, 67 +/- 8 and 72 +/- 6%, respectively (each, P less than .05; AMPPCP vs. adenosine, P less than .05). The present data indicate that the negative chronotropic action of ATP is due to its rapid catabolism to adenosine and the action of adenosine at P1-purinoceptor sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Factors affecting descending binaural loudness balances as a manifestation of adaptation.

Three trained adults with normal hearing were exposed to a continuous 1-kc/s pure tone in both ears simultaneously at 100 db SPL. In the R ear the tone was attenuated at 1 db/sec until it was inaudible. In the L ear the tone was attenuated at 5 db/sec, and S was asked to adjust the loudness in the L ear by pushing and releasing a hand-switch as in Bekesy audiometry in order to maintain so far as possible a binaural loudness match. At every reduction of 10 db in the R ear (i.e., every 10 sec) the SPL to the L ear was measured from the Bekesy-type tracing which yielded binaural loudness match. While there were inter-subject variations, for all Ss the level of the tone in the L ear (5 db/sec) had to be increased above physical equality for equal loudness, indicating the presence of more rapid adaptation in that ear. The disparity in 2 Ss progressed regularly from near zero after 10 sec to 16-17 db after 1 min. For 1 S, a constant disparity of about 6 db existed throughout the session. Binaural loudness balances by this descending method may be considered a manifestation of normal adaptation, confirming a previous report (Harbert and Young, J. Acoust. Soc. Am., 1968, 43, 752-756) for threshold differences produced by various attenuation rates at various suprathreshold starting levels. An analogous ascending procedure with 1 S yielded results susceptible to the same interpretation.