Demonstration of two anomalous bypasses in concealed Wolff-Parkinson-White syndrome

Two patients with a history of paroxysmal supraventricular tachycardia but no evidence of the Wolff-Parkinson-White syndrome in the conventional electrocardiograms were studied utilizing atrial and ventricular extrastimuli. The evidence obtained in these patients was consistent with a concealed Wolff-Parkinson-White syndrome. In one patient, ventricular extrastimuli revealed three different responses in the curve of ventriculoatrial conduction, depending upon the interval of stimulus. In the other patient, intracardiac recordings, including the left atrial potential, showed that paroxysmal supraventricular tachycardia was induced by an impulse via an anomalous bypass which diverged from the main bypass or stemmed independently from the left ventricle and was maintained by impulses via the main bypass which lay between the left ventricle and the left atrium. The mechanisms for initiation of the paroxysmal supraventricular tachycardia were discussed.     

Cognitive test performance among nondemented elderly African Americans and whites

We examined the neuropsychological test performance of a randomly selected community sample of English-speaking non-Hispanic African American and white elders in northern Manhattan. All participants were diagnosed as nondemented by a neurologist, whose assessment was made independent of neuropsychological test scores. African American elders obtained significantly lower scores on measures of verbal and nonverbal learning and memory, abstract reasoning, language, and visuospatial skill than whites. After using a stratified random sampling technique to match groups on years of education, many of the discrepancies became nonsignificant; however, significant ethnic group differences on measures of figure memory, verbal abstraction, category fluency, and visuospatial skill remained. Discrepancies in test performance of education-matched African Americans and whites could not be accounted for by occupational attainment or history of medical conditions such as hypertension and diabetes. These findings emphasize the importance of using culturally appropriate norms when evaluating ethnically diverse elderly for dementia.     

A streptavidin mutant with altered ligand-binding specificity

The biotin-binding site of streptavidin was modified to alter its ligand-binding specificity. In natural streptavidin, the side chains of N23 and S27 make two of the three hydrogen bonds with the ureido oxygen of biotin. These two residues were mutated to severely weaken biotin binding while attempting to maintain the affinity for two biotin analogs, 2-iminobiotin and diaminobiotin. Redesigning of the biotin-binding site used the difference in local electrostatic charge distribution between biotin and these biotin analogs. Free energy calculations predicted that the introduction of a negative charge at the position of S27 plus the mutation N23A should disrupt two of the three hydrogen bonds between natural streptavidin and the ureido oxygen of biotin. In contrast, the imino hydrogen of 2-iminobiotin should form a hydrogen bond with the side chain of an acidic amino acid at position 27. This should reduce the biotin-binding affinity by approximately eight orders of magnitude, while leaving the affinities for these biotin analogs virtually unaffected. In good agreement with these predictions, a streptavidin mutant with the N23A and S27D substitutions binds 2-iminobiotin with an affinity (Ka) of 1 x 10(6) M-1, two orders of magnitude higher than that for biotin (1 x 10(4) M-1). In contrast, the binding affinity of this streptavidin mutant for diaminobiotin (2.7 x 10(4) M-1) was lower than predicted (2.9 x 10(5) M-1), suggesting the position of the diaminobiotin in the biotin-binding site was not accurately determined by modeling.     

Transient Characteristics of Thermal Conduction in Dispersed Composites

The effective thermal conductivity of dispersed composites with a hot-melt-adhesive matrix, measured using the steady-state method, is compared with the apparent thermal conductivity calculated from the average heat capacity and from the thermal diffusivity measured by the laser-flash method. The transient effect has been observed obviously at higher volume percentages for various dispersed particle sizes and ratios of the thermal conductivity values of dispersed and continuous phases. All of the experimental results are compared with those calculated by existing models and by the finite element method (FEM). An attempt has been made to show how the criterion for the homogeneity of dispersed composites under transient conditions is affected by the percentages of dispersed phase, dispersed particle size, and ratio of the thermal conductivity values of dispersed and continuous phases.     

Solubility of BaS in BaO-BaF2 slag and the Influence of FeOx,SiO2, Cr2O3, BaCI2, CaO,and MgO on the sulfide capacity of this system

The influence of SiO₂, FeO_x, Cr₂O₃, BaCl₂, CaO, and MgO on the sulfide capacity of the BaO-BaF₂ system was measured at 1473 K, using a gas-slag-metal equilibration technique. It was found that the substitution of BaF₂ by SiO₂, FeO_x, Cr₂O₃, and BaCl₂ decreases the sulfide capacity of the BaO-BaF₂ system. Similar results were obtained for the carbonate capacity. The CaO-saturated BaO-BaF₂ flux, however, was found to have slightly higher sulfide and carbonate capacities than the pure BaO-BaF₂ flux. The solubility of CaO increased with increasing BaF₂ content and was 18 mol pet in BaF₂ at 1473 K. The solubility of MgO in the BaO-BaF₂ system at the same temperature is very low, and it has no effect on the sulfide and carbonate capacities. The solubility of BaS in the BaO-BaF₂ system was also measured at 1473 K and had its maximum for the slag containing 40 mass pet BaO. The activity of BaO in the system was calculated from those data. IVAN P. RACHEV, formerly Graduate Student, Department of Metallurgy, The University of Tokyo.     

Solubility of platinum in molten fluxes as a measure of basicity

The solubility of platinum in the molten BaO-Al₂O₃, BaO-SiO₂, CaO-Al₂O₃, CaO-SiO₂, Na₂O-SiO₂, and CaO-Al₂O₃-SiO₂ systems has been measured in order to seek a new measure of basicity. The solubility of platinum increases with increasing content of basic oxide. The correlations among the solubility of platinum, carbonate, sulfide, and phosphate capacities, basic oxide activities, and theoretical optical basicity are discussed.     

Diagnosis and treatment of tumours in the pineal region

In a series of 3.072 cases of intracranial neoplasms up to the end of 1973 there were 82 tumours in the pineal region (2.7%), excluding meningiomas of the falx and tentorium. More than half (forty seven) were pinealomas (two cell pattern type tumours, and pineoblastomas), twelve were teratomas, eight were ependymomas, three were epidermoids, and the remainder were gliomas. In addition to ventriculography, millipore filter-cell culture of cerebrospinal fluid, and fibre ventriculoscopy were found useful for diagnosis. Most of the patients were treated by surgery followed by radiotherapy. Results with the pinealomas were fairly good, the one year, five year, and ten year survival rates being 87.5%, 71.4%, and 33.3% in those below the age of 15 years, and 80.0%, 46.2%, and 12.5% in those above that age. The radiosensitivity of pinealomas and the beneficial effect of reduction of tumour bulk by direct surgery may both be important factors in the achievement of good results.