Dissipation of spin angular momentum in magnetic switching.

Applying one ultrashort magnetic field pulse, we observe up to 10 precessional switches of the magnetization direction in single crystalline Fe films of 10 and 15 atomic layers. We find that the rate at which angular momentum is dissipated in uniform large angle spin precession increases with time and film thickness, surpassing the intrinsic ferromagnetic resonance spin lattice relaxation of Fe by nearly an order of magnitude.

Surface roughness induced extrinsic damping in thin magnetic films.

The ferromagnetic relaxation caused by the surface roughness induced 2-magnon scattering is investigated. Approximate analytical solution predicts nonexponential decay of the uniform precession excitations of the form exp[-|t/tau3/2|3/2]. This behavior as well as the dependence of the decay time tau(3/2) on roughness parameters are confirmed by micromagnetic simulations.

Intrinsic nonlinear ferromagnetic relaxation in thin metallic films.

We propose an intrinsic mechanism for ferromagnetic relaxation in thin films that can dominate competing linear mechanisms even for rapidly relaxing metals. In particular, we use an analytic theory of four-magnon scattering to demonstrate rapid decay for technologically important systems involving high moment materials subject to large rotations. A micromagnetic simulation is used to verify the results.

Exchange field induced magnetoresistance in colossal magnetoresistance manganites.

The effect of an exchange field on the electrical transport in thin films of metallic ferromagnetic manganites has been investigated. The exchange field was induced both by direct exchange coupling in a ferromagnet/antiferromagnet multilayer and by indirect exchange interaction in a ferromagnet/paramagnet metallic superlattice. The electrical resistance of the metallic manganite layers was found to be determined by the magnitude of the vector sum of the effective exchange field and the external magnetic field.

Genetic heterogeneity of Usher syndrome type II in a Dutch population.

The Usher syndromes are a group of autosomal recessive disorders characterised by retinitis pigmentosa (RP) with congenital, stable (non-progressive) sensorineural hearing loss. Profound deafness, RP, and no vestibular responses are features of Usher type I, whereas moderate to severe hearing loss and RP with normal vestibular function describe Usher type II. The gene responsible for most cases of Usher II, USH2a, is on chromosome 1q41; at least one other Usher II gene (as yet unlinked) is known to exist. Usher III presents with a progressive hearing loss that can mimic the audiometric profile seen in Usher II. A gene causing Usher III in a group of Finnish families, USH3, resides on chromosome 3q. Since the phenotypes for Usher II and III overlap, it is important to determine how frequently Usher IIa, Usher IIb, and Usher III occur in a clinical population of non-Usher I patients. DNA was collected from 29 Dutch families and genotyped with six DNA markers known to flank the USH2a gene closely, and with five markers that flank USH3. Results of haplotype and linkage analysis were consistent with linkage to the USH2a locus in 26 of these 29 Dutch families. Three families displayed no linkage to 1q41 markers, and one of these three families appeared unlinked to 3q markers as well; current haplotypes of the other two families are inconclusive for linkage with the USH3 locus without further genotyping. While an A test for heterogeneity of USH2a was statistically significant, no convincing evidence of linkage to USH3 was found in this Dutch sample. Consequently, the frequency of the unlinked variety of Usher IIa (Usher IIb) in The Netherlands was estimated as 0.104. To determine if marker alleles could be used to differentiate Usher type IIa from Usher IIb, parental chromosomes of the 26 Usher IIa families were analysed for significant non-random association of specific alleles from flanking loci with USH2a, but no linkage disequilibrium was observed in this Dutch population.

Sexual dimorphism of renal alpha2-adrenergic receptor regulation in Dahl rats.

Male Dahl salt-sensitive hypertensive (S) rats develop hypertension faster than females. We measured renal alpha2-adrenergic receptor density of inbred Dahl salt-sensitive (SS/JR) and salt-resistant (SR/JR) rats, using [3H]-rauwolscine saturation binding studies. Male and female SS/JR rats were gonadectomized or sham-operated at 6 weeks of age and fed a high salt diet for 4 weeks. Additional intact SS/JR and SR/JR rats of both sexes were fed the high salt diet for a longer period of time (7 weeks instead of 4 weeks). Both blood pressure and renal alpha2-adrenergic receptor density were significantly higher in male than female SS/JR rats on high salt diet for 4 weeks. Gonadectomy did not change blood pressure nor did it change renal alpha2-adrenergic receptor density measured at the 4th week of high salt feeding in either male or female SS/JR rats. When the SS/JR rats were fed high salt diet for a longer period (for 7 weeks), blood pressure of female SS/JR reached the level of males, but the density of renal alpha2-adrenergic receptors was still significantly lower than that of males. Both renal alpha2-adrenergic receptor density and blood pressure were higher in male than female SR/JR. We conclude that higher blood pressure in male Dahl SS/JR and SR/JR rats is associated with higher renal alpha2-adrenergic receptor density compared with their female counterparts.

Cardiovascular abnormalities in children with autosomal dominant polycystic kidney disease.

It is known that adults with autosomal dominant polycystic kidney disease (ADPKD) have an increased incidence of cardiovascular abnormalities, including mitral valve prolapse. The cardiac manifestations of ADPKD in the pediatric population have not been well established. To determine the cardiac manifestations of children with ADPKD, echocardiography was performed in 154 children of 66 families in which one parent has ADPKD. Eighty-six affected children and 68 unaffected children were evaluated in a prospective, single-blinded manner by echocardiography. Affected children were defined as those with any cysts on a concurrent renal ultrasound or those predicted to be gene carriers by gene linkage analysis. A 12% incidence of mitral valve prolapse was found in the affected children compared with only 3% of the unaffected children (P < 0.05). ADPKD children, but not their unaffected siblings, demonstrate a significant correlation between left ventricular mass index and systolic blood pressure. Moreover, hypertensive ADPKD children have significantly larger left ventricular mass index than do normotensive ADPKD children. A 3.5% incidence of congenital heart disease was found in the affected group, whereas 2.9% of the unaffected children had congenital heart disease. It was concluded that systemic manifestations of ADPKD, particularly cardiovascular abnormalities, are present even in childhood and these warrant the clinician's attention.

Sex influence on renal alpha 2-adrenergic receptor density in the spontaneously hypertensive rat.

Male spontaneously hypertensive rats (SHR) have higher blood pressure than females. We compared renal alpha 2-adrenergic receptor density among intact SHR and Wistar-Kyoto (WKY) rats of both sexes, male and female SHR gonadectomized at 4 weeks of age, and gonadectomized SHR supplemented with testosterone. Additional groups of SHR were treated with enalapril (30 mg/kg per day), an angiotensin-converting enzyme inhibitor, from 5 to 14 weeks of age. Renal alpha 2-adrenergic receptor density was higher in males than females in both SHR and WKY rats. Female SHR and WKY rats had identical low renal alpha 2-adrenergic receptor density. Castration of male SHR reduced the male-female differences in blood pressure and renal alpha 2-adrenergic receptor density by 60%. Treatment with testosterone raised blood pressure and renal alpha 2-adrenergic receptor density to the intact male levels in both gonadectomized males and females. Treatment with enalapril decreased blood pressure but not renal alpha 2-adrenergic receptor density in both male and female SHR. We conclude that (1) both renal alpha 2-adrenergic receptor density and blood pressure are influenced by sex in SHR and WKY, (2) renal alpha 2-adrenergic receptor density like blood pressure is regulated by androgens, and (3) increased renal alpha 2-adrenergic receptor density is not a consequence of high blood pressure in male SHR.

Segregation analysis of autosomal dominant polycystic kidney disease.

The results of classical segregation analysis on 159 families with polycystic kidney disease (PKD) are presented. It had been previously estimated that about 95% of autosomal dominant PKD (ADPKD) families have PKD1, the gene localized to chromosome 16p. The main purpose of the study was to determine if PKD shows any segregation distortion and to obtain new estimates of the age-dependent penetrance. Penetrance at the early ages of onset has increased during the last decade, presumably because of improvements in renal imaging and consequent earlier age of diagnosis. In the current study, the mean age of diagnosis was estimated to be 20 years, with a standard deviation (SD) of 15.94. Under the best fitting model (autosomal dominant), over 70% penetrance was estimated by age 30 years, over 95% by 50 years, and 99% by 55 years. Thus, diagnosis of this disease at an early age is possible without total reliance on DNA typing. The segregation ratio defined through the transmission probability in our model was not significantly different from 0.50, but its confidence limits were broad: 0.36 to 0.64. Neither transmission probability nor penetrance was significantly influenced by gender. The mutation rate was estimated to be 6.9 x 10(-5), in accordance with the previously observed high mutation rate for PKD. However, the mutation rate in our study may be overestimated because it neglects low penetrance alleles and phenocopies.

AIDS in pregnancy.

A brief description of AIDS and suggested guidelines for providing nursing care to the parturient AIDS victim are provided. The current literature in defining the syndrome, its course, and its statistics is surveyed. Infection control precautions that need to be adapted when caring for the mother and infant who are affected by AIDS during the perinatal period are described. The possible emotional consequences that AIDS may inflict on its victims are also described. Finally, methods are suggested for setting up a communications system for sharing necessary information about these patients and their care.

Prevention of endomyometritis by local application of antibiotic solution during cesarean section.

Previous studies have demonstrated a reduction in the incidence of endomyometritis by using irrigation with 1000 ml of saline as a diluent at cesarean section. In this study 2 gm of cefoxitin sodium in 20 ml of saline solution was used for local application to the uterus and abdominal wound in 100 patients undergoing emergency cesarean section; results were compared to those in 100 patients who received no antibiotic at operation. Six patients in the treatment group developed endomyometritis as opposed to 33 in the untreated group (p less than 0.001) and hospital stay was reduced by almost 2 days (p less than 0.001). Local use of cefoxitin sodium appears effective in reducing the incidence of endomyometritis. A prospective double-blind study, however, is imperative before definite conclusions can be made.

Left ventricular ejection times during exercise testing with scintigraphy. Their use in the detection of ischemic heart disease.

Left ventricular ejection times ( LVETs ) were obtained in a group of 20 control subjects (group 1) during maximal treadmill exercise testing, using a Bruce protocol, and in conjunction with myocardial scintigraphy. Heart rates (HRs) and LVETs were recorded during standing rest, each minute of exercise, and for eight minutes in the postexercise period. A linear regression equation was constructed and separate correction factors of 1.04 X HR + observed LVET (correlation coefficient, -.86) for the exercise period and 0.73 X HR + LVET (correlation coefficient, -.71) for the postexercise period were derived. The LVETs were also recorded in 31 subjects with positive ECGs and defects on myocardial scanning with thallous chloride TL201 (group 2) during a similar exercise protocol. Comparison of groups 1 and 2 disclosed that the former had a higher HR and shorter LVET than the latter at peak effort (consonant with the significantly longer duration of exercise achieved by the control subjects). The LVETs in group 1 remained significantly shorter than that of group 2 through the fifth minute postexercise. In the postexercise period, the LVET indexes were significantly shorter in group 1 than group 2 at 1, 3, and 5 minutes. Subjects with presumptive coronary disease (positive ECG and defects on thallium 201 scanning) not only have a decreased exercise tolerance and HR, but after exercise, their ejection times are substantially longer than in normal subjects. This may be attributed to a slower rate of ejection in patients with coronary disease when venous pooling on quiet standing after exercise delivers a smaller volume to the heart. In normal subjects, the lesser volume may be ejected more rapidly.

[A new vaccinating antigenic fraction obtained from "Vibrio cholerae" II. Biological properties of the Ch1+2 fraction compared with the bacterial vaccine (author's transl)]. / Mise en évidence d'une fraction antigénique vaccinante de Vibrio cholerae. II. - Propriétés biologiques de la fraction Ch1+2 comparées a celles du vaccin bactérien classique

This fraction inoculated into mice protects against experimental infection. This fraction induces in various experimental animals serological modifications which are characterized by a rise in the vibriocidal effect of the serum. Controlled experiments in animals and humans showed that the vibriocidal effect is greater than the one obtained by the bacterial vaccine and persist far more longer. The vibriocidal power of the serum can also be obtained at titers relatively high when the fraction is given by the oral route. The in situ vaccination reduces the duration and the numbers of the excreted bacteries in germ free and pathogen free mice.