Effect of atropine on escape mechanism of the subsidiary pacemakers in patients with dysfunction of the sinus node

Effects of intravenous atropine on postpacing impulse recovery time of the subsidiary pacemakers were studied by incremental atrial pacing in 9 patients with sinus nodal (SN) dysfunction. Patients having either or both of the following anomalies are used: 1) persistent sinus bradycardia (sinus cycle length greater than 1000 msec), or documented episodes of sinoatrial block or arrest and/or 2) maximum corrected SN recovery time of longer than 525 msec before and after atropine. Seven patients had a history of cerebral ischemic symptoms. The mean +/- SEM of the maximum A-V junctional recovery times (MJRTs) before and after atropine, measured in 5 patients, were 2,485 +/- 825 msec and 1,164 +/- 281 msec, respectively (p less than 0.01). The average percent reduction of the junctional escape times in these 5 patients was 53.2%. In all 9 patients MJRT shortened to less than 1,610 msec after atropine. Moreover, a low atrial pacemaker also was the escape mechanism following pacing in 2 patients after atropine; the maximum atrial recovery times were 2,500 msec and 1,220 msec, respectively. We conclude that atropine can markedly enhance escape mechanism of the subsidiary pacemakers in patients with SN dysfunction.

Hemin enhances the differentiation of mouse 3T3 cells to adipocytes

Hemin enhances the adipose differentiation of mouse 3T3-F442A cells in a medium containing high levels of adipogenic factor that is present in fetal calf serum or calf serum. This enhancement is more prominent in the presence of insulin. Hemin also promotes adipose differentiation in a medium containing 10% cat serum, which has very little adipogenic factor; this effect is in contrast to that of insulin, which is relatively ineffective in promoting adipose differentiation in this medium. Adipose differentiation of 3T3-F442A cells is inhibited by the addition of aminotriazole, an inhibitor of heme biosynthesis. The inhibition of adipose differentiation by aminotriazole is prevented by the simultaneous addition of hemin and aminotriazole. These results indicate that treatment with hemin can promote the differentiation of fibroblasts to adipocytes in vitro, and they raise the possibility that endogenous heme may have a physiological role in the differentiation of fibroblasts to adipocytes in vivo.

An improved method for concurrent isolation of human granulocytes and lymphocytes. Its application in isoelectric focusing electrophoresis

A modified method of Boyum's technique to isolate granulocytes and lymphocytes from human blood is described. The granulocytes and the lymphocytes separated by this isolation procedure are highly pure, viable, and in sufficient number for subsequent isoelectric focusing studies. Different proteins have been separated by isoelectric focusing. This technique can be useful in the investigation of granulocytic and lymphocytic disorders.

Automaticity of subsidiary pacemakers of patients with dysfunction of the sinus node

Automaticity (postpacing impulse recovery time) of the sinus node or subsidiary pacemakers (or both) was determined by intracardiac recordings and atrial overdrive pacing in three patients with disease of the sinus node. Their electrocardiographic manifestations included sinus bradycardia, sinoatrial block, sinus arrest, atrioventricular junctional rhythm, and atrioventricular dissociation. One patient, who initially had syncope, demonstrated prolonged time for recovery of the sinus node (maximum corrected value, 3,485 msec) and impaired atrioventricular junctional automaticity (maximum corrected junctional recovery time, 1,460 msec). Of the remaining two patients without syncopal attacks, one had an adequate low atrial or junctional escape mechanism following cessation of pacing. The maximum low atrial escape interval was 1,660 msec, and the maximum junctional recovery time was 1,770 msec (corrected value, 140 msec). The third patient disclosed a prolonged maximum corrected recovery time for the sinus node (870 msec), while the maximum junctional recovery time was only 1,810 msec (corrected value, 160 msec). We conclude that automaticity of the subsidiary pacemakers in disease of the sinus node can be determined in the presence of atrioventricular dissociation or total sinus arrest, and that determination of the recovery time of the subsidiary pacemakers may be useful in identifying symptomatic patients with sinus nodal dysfunction.

Electrophysiologic diagnosis of patients with sinus node dysfunction: with special reference to a modified method for calculating sinoatrial conduction time

The diagnostic value of maximum corrected sinus node recovery time (CSNRT) and sinoatrial conduction time (SACT) was assessed in 15 patients with clinical evidence of sinus node (SN) dysfunction and 16 control subjects. The SACT was calculated by a modified method using only those sinus cycles with A1-A1 intervals falling within one standard deviation of the mean. We also obtained a maximum SACT and a ratio of maximum/mean SACT. We found that the maximum/mean SACT ratio being useful for identifying patients with sinus arrest or sinoatrial block. Abnormal value of the ratio (greater than or equal to 1.85) was also more frequently observed in patients with syncope or dizzy spells than those without (55.6% vs. 33.3%). By applying mean SACT and maximum/mean SACT ratio, calculated by the modified method, together with maximum CSNRT, all patients with SN dysfunction could be completely isolated from the normal subjects.

RNA and protein synthesis in cultured human fibroblasts derived from donors of various ages

RNA synthesis in human fibroblasts from donors of various ages was studied in fibroblasts made permeable to nucleoside triphosphates with the nonionic detergent Nonidet P40. Cells from donors of 11 years and older showed a 30-40% decline in total RNA synthesis. The decrease in RNA synthesis was primarily due to a lowering of RNA polymerase II activity (alpha-amanitin sensitive). Studies on the incorporation of leucine into protein also showed a 30-40% decrease in cells from older donors.

Ruptured congenital aneurysm of the right sinus of Valsalva into the right ventricle: with special reference to pathoanatomic and hemodynamic characteristics in symptomless cases

Clinical features of 19 cases with congenital aneurysm of the right sinus of Valsalva rupturing into the right ventricular outflow region (Type 1) were analysed in relation to their pathoanatomic lesions and hemodynamic alterations. Sixteen cases were operated with one surgical death. All were catheterized together with ascending aortographic study. Rupture of the aneurysm in many cases was silent or symptomless and progressive heart failure was not quite common. Symptomatology of the patients did not seem to be related entirely to status of the pathoanatomical lesions or hemodynamic alterations. Time of the rupture, and inherent right ventricular characteristics, tolerating volume overload rather well, might be, in part, responsible for its better prognosis in some cases. However, all patients with ruptured aneurysm of the sinus of Valsalva should be treated surgically. Bacterial endocarditis is a serious complication leading to death.

Effect of 6-azauridine on de novo pyrimidine biosynthesis in cultured Ehrlich ascites cells. Orotate inhibition of dihydroorotase and dihydroorotate dehydrogenase

The inhibition of dihydro-orotase (E 3.5.2.3) and dihydroorotate (DHO) dehydrogenase (dihydro-orotate oxidase, EC 1.3.3.1) by cellular orotate (OA) in Ehrlich ascites cells was studied by measuring the accumulation of the intermediates of de novo pyrimidine biosynthesis at various times after the addition of 6-azauridine to the culture medium. The addition of 6-azauridine resulted in the accumulation of orotidine, OA, DHO, and carbamyl aspartate (CAA). The use of the observed ratios of [CCA]/[OA] and [DHO]/[OA] and other known constants allowed us to calculate that the increased cellular OA concentration caused primarily an inhibition of DHO dehydrogenase rather than an inhibition of dihydroorotase. A constant ratio of [CAA]/[DHO] was observed which probably indicates that the interconversion of these two intermediates catalyzed by dihydroorotase is near equilibrium in these cells as has been observed in vitro (Christopherson, R.I., Matsuura, T., and Jones, M.E. (1978) Anal. Biochem. 89, 225-234). It is suggested that the probable intracellular accumulation of CAA in patients with oroticaciduria may have significant secondary effects.

Electrophysiologic manifestations in so-called "sick sinus syndrome"

Electrophysiologic disorders in 17 patients with sick sinus syndrome (SSS) were assessed by recording of intracardiac electrograms, atrial overdrive pacing and extrastimulus technique. Significant suppression of the sinoatrial node (SAN) by overdrive pacing (maximum corrected SAN recovery time of longer than 560 msec) was noted in 14 or 16 patients studied. In nine patients, scanning with atrial extrastimuli, sinus rest was defined in all. In one patient there was a longer interpolation zone. Calculated sinoatrial conduction time (SACT) in individual patients varied considerably. The mean SACT was over 110 msec in 5 of 9 patients (56%). Sinus echo was demonstrated in 3; one manifested SAN- re-entrant tachycardia with rates of 72 to 77 beats/min. AV nodal echo was demonstrated in 3, two of them manifested AV nodal re-entrant tachycardia. Intracardiac electrograms revealed prolonged AV conduction time in 2 of 15 patients and prolonged His-Purkinje system conduction time in 2 of 17 patients studied. Two patients disclosed what we thought to be manifestation of intraatrial conduction disturbance. Both had considerable time interval between pacing impulse and atrial response. In one of them Mobitz type 1 and 2:1 intraatrial blocks were observed on atrial pacing and a possible internodal tract depolarization was also recorded. It is concluded that the electrophysiologic manifestations of patients with SSS cover a wide spectrum. The machanism of tachycardia can be due to either SAN or AV nodal re-entry.

Left ventricular performance in various heart diseases with or without heart failure:--an appraisal by quantitative one-plane cineangiocardiography

Quantitative one-plane cineangiocardiography in right anterior oblique position for evaluation of LV performance was carried out in 62 patients with various heart diseases and in 13 subjects with normal LV. Parameters for evaluating both pump and muscle performances were derived from volume and pressure measurements. Of 31 patients with either systolic hypertension or LV myocardial diseases (coronary artery disease or idiopathic cardiomyopathy), 14 had clinical evidence of LV failure before the study. It was found that mean VCF and EF were most sensitive indicators of impaired LV performance among the various parameters. There was a close correlation between mean VCF and EF, yet discordant changes of both parameters were noted in some patients. Furthermore, wall motion abnormalities were not infrequently observed in patients with coronary artery disease or primary cardiomyopathy. Therefore, assessment of at least three ejection properties (EF, mean VCF and wall motion abnormalities) are considered to be essential for full understanding of derangement of LV function in heart disease. This is especially true of patients with coronary artery disease. LV behavior in relation to different pathological stresses or lesions, such as chronic pressure or volume load, myocardial disease and mitral stenosis, was also studied and possible cause of impaired LV myocardial function in mitral stenosis was discussed.