Effects of oral disopyramide phosphate on induction and sustenance of atrioventricular reentrant tachycardia incorporating retrograde accessory pathway conduction

We performed electrophysiologic studies before and after oral administration of disopyramide phosphate, 200 mg every 6 hours, in 20 patients with atrioventricular (AV) reentrant tachycardia using a retrogradely conducting accessory pathway. Disopyramide markedly depressed retrograde accessory pathway conduction by increasing the mean ventricular paced cycle length that produced ventriculoatrial block (less than or equal to 287 +/- 4 to greater than or equal to 392 +/- 22 msec, p less than 0.01); it also depressed antegrade normal pathway AV conduction by increasing the atrial paced cycle length that produced AV block (287 +/- 9 to 328 +/- 7 msec, p less than 0.01). In 14 patients, tachycardia could not be induced or sustained after disopyramide phosphate. In 13 patients, this reflected depression of the retrograde limb with either absence of atrial echoes (nine patients) or induction of nonsustained tachycardia that terminated after the QRS complex (four patients), and in one, it reflected depression of the antegrade limb with induction of a single atrial echo not followed by a QRS response. In six patients, sustained tachycardia could still be induced after disopyramide. Oral disopyramide phosphate is effective in preventing induction of sustained AV reentrant tachycardia in most patients. This effect is achieved by depression of the retrograde limb of the reentrant circuit.

The surface morphology and ultrastructure of renal arterial smooth muscle cells in patients with renovascular hypertension

The surface and internal ultrastructure of renal arterial smooth muscle cells were investigated in 3 patients with renovascular hypertension. The most characteristic features of the surface pathology in hypertrophied smooth muscle cells consisted of various degrees of surface defects, including both extensive loss of surface details and an irregular thickening and disruption of the basement membrane, which was widely separated from the plasma membrane by a clear space. Ultrastructural changes include the appearance of highly lobulated nuclei, multinucleation, disorganization of myofilaments and increased numbers of rough-surfaced sarcoplasmic reticulum and mitochondria, which are usual manifestations of cellular hypertrophy. These results suggest that ionic movement across the cell membranes, particularly of Ca2+, is probably abnormal in hypertrophied smooth muscle cells. This may result in functional disorders of hypertensive arteries.

The pattern of hydatidiform moles in Singapore

Hydatidiform mole is common in Singapore, and the the incidence of malignant trophoblastic neoplastic neoplasia is significantly higher than in Western countries. Within a 10-year period (1968-1977), 538 cases of hydatidiform mole were diagnosed. On retrospective study, 498 (92.6%) were considered to be complete and 40 (7.4%) partial. The ratios of complete to partial moles were similar for the major population groups. In the present study, only complete moles were found to give rise to persistent trophoblastic disease. The lack of such association in partial hydatidiform moles is in keeping with their known low malignant potential. Occasional abnormal post-evacuation hCG curves, however, are being described from other centres, and while the underlying pathology remains largely undocumented, partial moles have to be dealt with on an empirical basis in the light of the hCG follow-up levels.

The surface morphology of the infundibular muscle in patients with tetralogy of fallot

The surface morphology of the infundibular muscles obtained from open heart surgery was investigated in 10 patients with tetralogy of Fallot. Various degrees of abnormal surface morphological changes were observed from the endocardium to the myocardium. In the endocardium striking proliferation of the endothelial cells was usually accompanied by focal loss of the endothelium with fibrotic change. Based on the characteristic alterations of the surface morphology 4 different groups of myocardial cells could be identified: normal myocytes, defective myocytes, sclerotic myocytes, and necrotic myocytes. Because intact surface morphology is responsible for integrated cellular function these pathological findings observed on the surface morphology of the endocardium and myocardium can provide a valuable reference to further understanding of functional disorders of the infundibular muscle in patients with tetralogy of Fallot.

Preoperative and postoperative echocardiographic studies of pulmonic valvular endocarditis

The echocardiographic manifestations of pulmonic valvular endocarditis in a patient with underlying heart disease consisting of a ventricular septal defect and infundibular stenosis are reported. The abnormal shaggy echoes observed on the pulmonic valve were confirmed to be vegetations based on surgical and pathologic findings. This was further proven by the disappearance of the shaggy echoes after surgical excision of the vegetations. We conclude that echocardiograms can detect the presence and disappearance of pulmonic valvular vegetations, which may be of aid in the diagnosis of pulmonic valvular endocarditis.

A fatal congenital myopathy with severe type I fibre atrophy, central nuclei and multicores

An unusual fatal congenital myopathy in a Chinese female infant is described. Muscle biopsy showed type I fibre smallness with central nuclei and focal decrease in oxidative enzyme activities affecting mainly larger type II fibres. Longitudinal sections from glutaldehyde-fixed araldite-embedded material stained with toluidine blue revealed multiple small foci of myofibrillar degeneration (multicores) along the muscle fibres. Electron-microscopic examination confirmed the presence of multicore lesions affecting mainly the larger fibres. In addition, there were definite degenerative changes involving the smaller fibres with central nuclei. The degenerative process started around the pericentronuclear zones with diffuse extension along the whole length of the muscle fibres resulting in severe atrophy. These degenerative changes were similar to those described in pericentronuclear myopathy. It is therefore suggested that the patient might have either had 2 co-existing myopathies viz. multicore disease and pericentronuclear myopathy or a single entity with combinations of features which had not hitherto been described.

Cloning of Epstein-Barr virus (EBV) DNA fragments in pBR32 and Charon3A

Restriction fragments of Epstein-Barr virus (EBV; B95-8) DNA were cloned in the Tc gene of pBR322 (HindIII-F, -G, -I, -J, -K, -L, and -M) and in Charon3A (EcoRI-GI and -G2). Altogether these cloned fragments covered 39% of the entire viral genome. The cloned EcoRI-G2 fragment of EBV (B95-8) DNA was shown to contain, in addition to HindIII-J, two more HindIII-fragments : HindIII-M, which had not been located on the linkage map of the viral genome (Given and Kieff, 1978) and HindIII-N, which had been unrecognized up to now. The utility of this cloning method is discussed in regard to the detailed mapping of a viral genome and large-scale production of the viral DNA.

Linkage map of the fragments of herpesvirus papio DNA

Herpesvirus papio (HVP), an Epstein-Barr-like virus, causes lymphoblastoid disease in baboons. The physical map of HVP DNA was constructed for the fragments produced by cleavage of HVP DNA with restriction endonucleases EcoRI, HindIII, SalI, and PvuI, which produced 12, 12, 10, and 4 fragments, respectively. The total molecular size of HVP DNA was calculated as close to 110 megadaltons. The following methods were used for construction of the map; (i) fragments near the ends of HVP DNA were identified by treating viral DNA with lambda exonuclease before restriction enzyme digestion; (ii) fragments containing nucleotide sequences in common with fragments from the second enzyme digest of HVP DNA were examined by Southern blot hybridization; and (iii) the location of some fragments was determined by isolating individual fragments from agarose gels and redigesting the isolated fragments with a second restriction enzyme. Terminal heterogeneity and internal repeats were found to be unique features of HVP DNA molecule. One to five repeats of 0.8 megadaltons were found at both terminal ends. Although the repeats of both ends shared a certain degree of homology, it was not determined whether they were identical repeats. The internal repeat sequence of HVP DNA was found in the EcoRI-C region, which extended from 8.4 to 23 megadaltons from the left end of the molecule. The average number of the repeats was calculated to be seven, and the molecular size was determined to be 1.8 megadaltons. Similar unique features have been reported in EBV DNA (D. Given and E. Kieff, J. Virol. 28:524-542, 1978).

Comparative studies of herpesvirus papio (baboon herpesvirus) DNA and Epstein-Barr virus DNA

An Epstein-Barr virus (EBV)-like herpesvirus has been isolated from a baboon cell line (594S/F9) by induction with the tumour promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). The herpesvirus papio (HVP) DNA was mixed with B95 EBV DNA and was characterized by sedimentation in neutral glycerol gradient as 55S DNA, with a buoyant density of approx. 1.718 g/ml after equilibrium centrifugation in caesium chloride. DNA-DNA reassociation kinetics between B95 EBV and HVP DNA showed that HVP DNA shares about 40% homology with B95 EBV DNA. Blot hybridization of EcoRI fragments of HVP DNA with a 32P-B95 EBV DNA probe showed that most of the EcoRI fragments of HVP DNA were hybridized to B95 EBV DNA, suggesting that the homologous sequences were dispersed throughout the virus DNA.

Isoproterenol-stimulated C-peptide and insulin secretion in diabetic and nonobese normal subjects: decreased hepatic extraction of endogenous insulin in diabetes

After the iv injection of 2 micrograms isoproterenol, peripheral plasma insulin and C-peptide concentrations were measured in 16 nonobese normal subjects and 53 maturity-onset diabetic subjects. Basal insulin (P < 0.01) and C-peptide (P < 0.05) levels were increased in obese diabetic subjects compared to nonobese normal subjects. Isoproterenol-stimulated insulin (P < 0.01) and C-peptide (P < 0.05) increments were increased in obese diabetic subjects compared to nonobese diabetic subjects. Hepatic insulin extraction, measured by comparing the ratios of insulin increment to C-peptide increment after isoproterenol injection, was decreased in both nonobese and obese diabetics compared to normals (P < 0.05). No significant differences in the ratios were found between nonobese and obese diabetics or between patients on diet or sulfonylurea therapy. Age, sex, duration of disease, familial predisposition to diabetes, and diabetic retinopathy did not influence the ratios. Isoproterenol-stimulated C-peptide increments (P < 0.05) and fasting blood glucose levels (P < 0.05) were decreased in diabetics showing decreased hepatic insulin extraction compared to diabetics with normal hepatic insulin extraction. Isoproterenol-stimulated insulin increments in diabetics showing decreased hepatic insulin extraction were higher than in normals (P < 0.05). These studies indicate that hepatic insulin extraction decreases in nonobese and obese diabetic subjects. It might be postulated that the lesser amount of secreted insulin is able to show biological activities more efficiently in diabetics with decreased hepatic insulin extraction.

Physical mapping of adeno-associated virus serotype 4 DNA

The organization of adeno-associated virus serotype 4 (AAV 4) DNA was probed by using restriction enzymes. The cleavage sites of the following enzymes were mapped: BglII, BamI, HincII, KpnI, PstI, SalI, SstI, and XhoI. The orientation of transcription on the physical cleavage map was determined by locating the fragments which contain the 3' end of the mRNA. Strand separation gels were run for HinII fragments of AAV 4 DNA. By hybridizing AAV 4 mRNA to the resolved strands, the polarity of the DNA strands was identified. Restriction digestion of AAV 4 DNA sometimes produced terminal fragments which migrated in agarose gels as doublets. However, when AAV 4 DNA was prepared devoid of any single-stranded nicks, these terminal doublet bands were not observed upon subsequent restriction analysis. During these studies, the molecular weights of both AAV 4 and AAV 2 duplex DNA were measured and were found to be somewhat larger than previously reported (3.18 x 10(6) and 3.10 x 10(6), respectively).

Studies of plasma beta-N-acetylglucosaminidase activity in experimental and clinical diabetes mellitus

Plasma beta-N-acetylglucosaminidase (NAG) activity was measured in streptozotocin diabetic rats, in non-diabetic rats during starvation and refeeding, and in diabetic patients and normal subjects. The enzyme activity increased significantly in the diabetic rats and in the starved non-diabetic rats. The activity decreased markedly after insulin injection in diabetic rats and after refeeding in non-diabetic rats. The plasma NAG activity (532 +/- 24 nmole/hr/ml, M +/- SE) in 21 diabetics with FBS value less than 100 mg/dl was higher than the enzyme activity (455 +/- 15) in 42 normal subjects (p < 0.01), supporting the idea that a more intensive treatment is necessary to normalize the metabolic derangement of diabetes. There was no significant difference between diabetics with and without microangiopathy. While the influence of age and abnormal liver function was noted, there was no correlation between the NAG activity and the platelet adhesiveness or between the NAG activity and the plasma triglyceride. The results suggest that the plasma NAG activity increases in diabetes mellitus, either with microangiopathy or not. The reason for the failure to demonstrate a significant correlation between the total plasma NAG activity and microangiopathy is discussed. The analysis of the subfractionation of the plasma NAG may be necessary to disclose a significant correlation with microangiopathy.