Tailoring the refractive index of impedance-matched ferrite composites.

Independent control of the magnetic and electric properties of two-part and three-part ferrite composites is demonstrated through variation of particle size and volume fraction of ferrite inclusions. This provides a route to creating broadband impedance-matched composites with tailored high refractive-index values. A two-part composite comprising NiZn ferrite in a PTFE dielectric host with approximately equal values of relative real permittivity and permeability up to 100 MHz is manufactured. The refractive index for NiZn-PTFE composites, measured at 20 MHz, is 6.1 for NiZn volume fraction of 50%vol. and 6.9 for NiZn volume fraction of 70%vol. Similarly, we have characterised a three-part composite with a refractive index of approximately 16 up to 60 MHz. The three-part composite comprises NiZn and MnZn ferrites in a PTFE dielectric host matrix with a percentage volume ratio of 65%: 15%: 20%, respectively.

Cost-effective methods for isolation of Salmonella enterica in the clinical laboratory.

Data from 8,717 fecal specimens indicate that primary inoculation of xylose lysine deoxycholate (XLD) agar may enhance the speed, but not the sensitivity, of isolation of Salmonella enterica over that achieved with Selenite enrichment only. Plating of Selenite broth onto both brilliant green and XLD agar offers no advantage over plating onto XLD alone.

The possible relationship between visual deficits and dyslexia: examination of a critical assumption.

Numerous studies have found that visual deficits are associated with dyslexia. The prevailing theory regarding this association is that dyslexia is the result of a deficit in the magnocellular system (earlier called the transient system) in the visual pathway. An essential assumption of this theory is that the parvocellular system (formerly called the sustained system) is suppressed by the magnocellular system at the time of saccadic eye movements. This assumption is examined on the basis of published studies of saccadic suppression. The evidence from six studies indicates quite unequivocally that the magnocellular system, not the parvocellular system, is suppressed during saccadic eye movements. It seems, therefore, that an essential premise of the magnocellular deficit theory of dyslexia is incorrect.

Simultaneous determination of sulfasalazine and its metabolites sulfapyridine and N-acetylsulfapyridine in human serum by ion-pair high-performance liquid chromatography using a polymer-based column.

An HPLC method is described for the simultaneous and rapid determination of sulfasalazine (salicylazosulfapyridine) and two of its metabolites, sulfapyridine and N-acetylsulfapyridine, in human serum. The range of quantitation is 0.1 to 12 micrograms/mL for sulfasalazine and sulfapyridine and 0.25 to 12 micrograms/mL for N-acetylsulfapyridine. Serum is mixed with acetonitrile containing the internal standard sulfamethazine and the ion-pairing agent tetraethylammonium chloride. The acetonitrile extract is concentrated and analyzed by HPLC, using a new polymer-based column, and detected by UV spectroscopy at 270 nm. This paper is the first both to describe the simultaneous analysis of all three of the compounds from serum and to present sulfasalazine concentration-time data following oral administration to humans.

Resolution of acute malarial infections by T cell-dependent non-antibody-mediated mechanisms of immunity.

While it is generally accepted that acute blood stage malarial infections are resolved through the actions of protective antibodies, we observed that resistance to acute infection with Plasmodium chabaudi adami was mediated by T cell-dependent cellular immune mechanisms independent of antibody. We now report that acute blood stage infections caused by three additional murine hemoprotozoan parasites, Plasmodium vinckei petteri, Plasmodium chabaudi chabaudi, and Babesia microti, appear to be controlled by similar T cell-dependent mechanisms of immunity. Mice rendered B cell deficient by lifelong treatment with goat anti-mouse immunoglobulin M (IgM) had IgM levels in serum of less than 0.6 micrograms/ml and contained precipitating amounts of goat anti-mouse IgM. When these B cell-deficient mice were infected with blood stage P. vinckei petteri, P. chabaudi chabaudi, or B. microti, they resolved their infections with kinetics similar to those seen in immunologically intact mice. Infected B cell-deficient mice did not produce antiparasite antibodies. As assayed by immunofluorescence, significant titers of parasite-specific antibody were present only in the sera of infected immunocompetent mice. In addition, only sera from infected immunocompetent mice immunoprecipitated metabolically labeled parasite antigens. In contrast to B cell-deficient mice, athymic nude mice failed to resolve acute P. vinckei petteri or B. microti infections. These data suggest that antibody-independent, T cell-mediated immune mechanisms play a more significant role in resisting acute blood stage infections caused by hemoprotozoa than was recognized previously.

Reassessment of the role of splenic leukocyte oxidative activity and macrophage activation in expression of immunity to malaria.

The role of splenic leukocyte oxidative activity and macrophage activation in the development of protective immunity was examined during acute Plasmodium chabaudi adami malaria. Splenic leukocyte oxidative activity was compared in infected BALB/c and P/J mice; the latter are known to suffer from defects in macrophage function. Phorbol myristate acetate-stimulated chemiluminescence and superoxide anion production by splenic leukocytes from infected BALB/c mice were found to be increased dramatically, while the response of splenic leukocytes from infected P/J mice was elevated only minimally. Hydrogen peroxide release was slightly increased in splenic leukocytes from infected BALB/c mice but remained essentially unchanged in those from infected P/J mice. Macrophage function was assessed on the basis of measurements of tumoricidal activity. Splenic macrophages from uninfected BALB/c mice displayed significant tumoricidal activity against L929 target cells. As a result of splenomegaly during infection, tumoricidal activity, when calculated on a per-spleen basis, was increased further in infected BALB/c mice. In contrast, the tumoricidal activity of splenic macrophages from P/J mice was minimal, regardless of infection. Despite these differences, both strains of mice developed malarial infections that resolved within 16 days. Thus, while the production of reactive oxygen radicals by splenic leukocytes and the phenomenon of macrophage activation have traditionally been associated with the resolution of malarial infection, this study failed to establish a correlation between these parameters and the development of protective immunity to blood-stage infection with P. chabaudi adami.

A protective monoclonal antibody recognizes a variant-specific epitope in the precursor of the major merozoite surface antigen of the rodent malarial parasite Plasmodium yoelii.

The precursor of the major merozoite surface Ag (PMMSA) represents one of the principal molecules of the erythrocytic stages of malarial parasites. Previously we reported that mAb 302 recognizing the 230-kDa PMMSA of Plasmodium yoelii provided passive protection to mice challenged with this parasite. We now report that the protective capacity of mAb 302 is variant specific, affording protection against infection with only three of five P. yoelii lines. Immunoprecipitation analyses of their PMMSA revealed that the expression of the epitope recognized by mAb 302 also varied and correlated completely with the results of the passive protection studies. Although this specific determinant was not present on the merozoite Ag of all P. yoelii lines, the common expression of other B cell epitopes was noted by the demonstration of serologic cross-reactivity between these molecules. Furthermore, the relatedness of the genes encoding the PMMSA of several murine plasmodial strains and species was clearly shown in nucleic acid hybridization studies. Although strain-common and strain-variable epitopes have been observed in the PMMSA of the human parasite, Plasmodium falciparum, little is known concerning the variability of its biologically relevant epitopes. The current studies using the P. yoelii model system demonstrate that the epitope recognized by a protective mAb is strain variable. Because of the similarities between these antigens of P. falciparum and P. yoelii, this information may impact on the construction of an effective blood-stage malarial vaccine.

Assay of lactogenic hormones using receptors isolated from rabbit liver.

Using 125-I-labelled ovine prolactin and receptors isolated from the livers of rabbits, a sensitive method has been developed suitable for the assay of ovine, bovine, porcine, human and rat prolactins. These hormones showed competitive displacement of 125-I-ovine prolactin which was in general agreement with their respective activities in the pigeon crop sac bioassay. Human and monkey growth hormones and human placental lactogen, which have marked prolactin-like actions on mammary tissue were also effective competitors. Non-primate growth hormones (ovine, bovine, equine and canine) which do not have prolactin-like activity gave little if any displacement as did human FSH, LH, TSH, ACTH and bovine insulin. Preparations of equine and canine prolactin of varying purity gave dose-response curves although their activity as competitors relative to ovine prolactin was poor and not related to their pigeon crop stimulating activity. This indicates species differences between prolactins in hormone-receptor interaction. Experiments with antiserum to human growth hormone have suggested an effective method of making the assay specific in species such as man in which prolactin is not the sole hormone with lactogenic activity.

Galactorrhoea: successful treatment with reduction of plasma prolactin levels by brom-ergocryptine.

In five patients with inappropriate lactation and amenorrhoea or impotence brom-ergocryptine was found to suppress the lactation and to diminish the raised plasma prolactin levels. The responses to treatment suggest that there may be an inverse relationship between prolactin secretion and gonadotrophin secretion in man.