Abnormal centrifugal axons in streptozotocin-diabetic rat retinas.

PURPOSE: To characterize the effects of diabetes on the expression of histidine decarboxylase mRNA and on the morphology of the histaminergic centrifugal axons in the rat retina. METHODS: Rats were made diabetic by streptozotocin. After 3 months, retinal histidine decarboxylase expression was analyzed by in situ hybridization in radial sections. Flatmount retinas from a second group of rats were labeled with an antiserum to histamine or an antibody to phosphorylated neurofilament protein. RESULTS: Histidine decarboxylase mRNA was expressed in cells in the inner and outer nuclear layers of diabetic retinas, but not in normal retinas. However, immunoreactive (IR) histamine was not localized to perikarya in either the normal or the diabetic retinas. Instead, a population of centrifugal axons was labeled. These axons emerged from the optic disc and had varicose terminal branches in the inner plexiform layer (IPL) of the peripheral retina. Some branches ended on large retinal blood vessels and others in dense clusters in the IPL. In rats with streptozotocin-induced diabetes, the centrifugal axon terminals developed many large swellings that contained neurofilament immunoreactivity; these swellings were rare in normal retinas. CONCLUSIONS: Diabetes perturbs the retinal histaminergic system, causing increases in histidine decarboxylase mRNA expression in neurons or glia and abnormal focal swellings on the centrifugal axons.

Coccidioidomycosis in human immunodeficiency virus-infected persons in Arizona, 1994-1997: incidence, risk factors, and prevention.

From 1 January 1995 through 31 June 1997, 153 cases of coccidioidomycosis in human immunodeficiency virus (HIV)-infected persons were identified in Arizona (incidence, 41/1000 persons living with AIDS). A case-control study was conducted to evaluate risk factors for coccidioidomycosis in HIV-infected persons. A case was defined as laboratory-confirmed, incident coccidioidomycosis in a person infected with HIV for > or =3 months, and each case patient had 3 control patients matched by county, age group, sex, HIV/AIDS status, and CD4 lymphocyte count. Multivariable analysis identified black race and a history of oropharyngeal or esophageal candidiasis to be associated with increased risk of coccidioidomycosis; protease inhibitor therapy was associated with a reduced risk. In persons with previous history of oropharyngeal or esophageal candidiasis, having received an azole drug was associated with a reduced risk (odds ratio, 0.4; 95% confidence interval, 0.2-0.9; P=.04). Physicians may need to consider azole chemoprophylaxis for HIV-infected persons who live in areas of endemicity, have CD4 cell counts <200/microL, are black, or have a history of thrush.

Mercury toxicity due to use of a cosmetic cream.

The Arizona Department of Health Services performed an investigation to determine the health effects associated with the use of a mercury-containing beauty cream. A urine test for mercury was offered to cream users who contacted the Arizona Department of Health Services. Those with urine mercury levels > 20 micrograms/L were offered clinical evaluation. Eighty-nine urine specimens were submitted for testing. Of these, 66 showed an elevated urine mercury level (> 20 micrograms/L), and 55 people were evaluated in clinic. There were no major abnormalities found through physical examination or laboratory testing. Urine mercury levels declined from an initial mean of 170 micrograms/L to 32 micrograms/L at the final test (mean, 139 days later). The high urine mercury levels indicate that the use of this cosmetic cream constitutes a significant exposure. Neuropsychiatric symptoms were frequently reported, but few objective signs were noted.

T1 and T2 of ferritin at different field strengths: effect on MRI.

Nuclear magnetic relaxation times T1 and T2 were measured in ferritin solutions at field strengths from 0.04 to 1.5 T. T1 was relatively constant, but 1/T2 increased linearly with field strength, in agreement with earlier MRI observations in the monkey brain. This finding supports the theory that ferritin is responsible for T2 shortening in brain nuclei containing iron. The linear dependence of 1/T2 on magnetic field is unique and not explained by present theories of the magnetic properties of ferritin.

Mutations in both the 2B and 2C genes of hepatitis A virus are involved in adaptation to growth in cell culture.

Oligonucleotide-directed mutagenesis of an infectious cDNA clone of wild-type hepatitis A virus was performed to determine which mutations acquired in the nonstructural 2B and 2C genes during adaptation to growth in cell culture were effective in enhancing virus growth in vitro. Results of transfection assays demonstrated that one mutation in the 2B gene and two mutations in the 2C gene were responsible for an increased efficiency in growth, but growth enhancement required the participation of at least two of the three mutations.

Molecular basis of virulence and growth of hepatitis A virus in cell culture.

The ability of engineering variants of hepatitis A virus (strain HM175) to replicate in cell culture or to cause disease in marmosets was evaluated. Virus variants were encoded by chimeric genomes constructed from infectious cDNA clones of two viruses (wild type and cell-culture-adapted) which differed in their ability to grow in vitro and to cause acute hepatitis in marmosets. Transfection and infectivity assays indicated that virus growth in vitro could be enhanced by subcloning the cell substrate prior to infection or by introducing multiple combinations of two or more mutations into the wild type genome. Various chimeric viruses induced liver enzyme elevations in marmosets, indicating that attenuation of virulence also required multiple mutations.

Mutations responsible for adaptation of hepatitis A virus to efficient growth in cell culture.

Chimeric genomes of hepatitis A virus strain HM-175 were constructed from cDNA clones of the wild-type virus and its cell culture-adapted variant. RNA transcribed in vitro from each construct was assayed for infectivity by transfection of cultured cells. RNA transcribed from the wild-type cDNA clone was minimally infectious and produced virus that grew inefficiently in vitro, whereas that transcribed from certain chimeric genomes consistently produced virus that grew efficiently in cultured cells. Mutations in the P2 region were found to be necessary for efficient virus growth in vitro, while mutations in the 5' noncoding region imparted a conditional enhancement of growth in vitro.

Assembly of the membrane attack complex promotes decay of the alternative pathway C3 convertase on Neisseria gonorrhoeae.

C3, C4, factor B, properdin, and C2 binding to serum-sensitive and serum-resistant gonococci was quantitated in C8-deficient and normal human serum by using fluorescein-conjugated antibodies and 3H-labeled components. Organism and serum-specific differences were noted, the most striking of which involved factor B and properdin binding to the serum-sensitive strains in the different sera. C3 binding to these organisms was quantitatively and kinetically equivalent in C8-deficient and normal human serum. In contrast, factor B and properdin binding reached a plateau after 5 min in C8-deficient serum but peaked and fell to control values in normal human serum. Identical results were obtained with normal human serum immunochemically depleted of C8. Between 7 and 15% of the bound C3 participated in formation of the alternative pathway convertase C3bBb/P. Reconstitution of the C cascade by adding purified C8 to C8-deficient serum led to the loss of factor B previously bound to the organisms. Factor B loss occurred coincident with bacterial killing and membrane disruption as observed by electron microscopy. Prevention of membrane disruption by depleting normal human serum of lysozyme had no effect on killing and failed to prevent factor B loss. Stabilization of the C3bBb complex with Ni2+ prevented factor B loss as well as gross membrane disruption but not bacterial killing. C2 (the classical pathway analog of factor B) binding to gonococci was equivalent in C8-deficient and normal human serum peaking within 2.5 min and falling to control values in both sera thereafter. We conclude that the assembly of the membrane attack complex promotes decay of C3bBb/P with release of factor B and properdin but not C3 from the organism surface. Membrane disruption does not appear to be required for this effect. This activity may represent a mechanism to limit continued C consumption.

Differential functional expression of the C8 subunits. Primary role of C8 beta in assembly of intact C8.

The eighth component of C (C8) is composed of two subunits C8 beta and C8 alpha-gamma, which are non-covalently bound in a 1/1 ratio in the intact molecule. The genes encoding the polypeptide chains composing the subunits demonstrate close genetic linkage. To assess the functional expression of these genes at the protein level, normal human serum and C8-deficient sera were electrophoresed in native polyacrylamide gels following which C8, C8 beta, and C8 alpha-gamma were detected using hemolytic overlays. These experiments demonstrated that normal sera contained free C8 alpha-gamma in addition to intact C8. Free C8 alpha-gamma was not observed when C8 was reconstituted by mixing C8 beta-deficient serum with C8 alpha-gamma-deficient serum in a ratio optimized for C8 activity, suggesting that the free C8 alpha-gamma observed in normal serum was not due to dissociation of intact C8. Inasmuch as this technique did not adequately separate C8 and C8 beta, sera were also examined by anion exchange chromatography. C8 alpha-gamma-deficient serum contained C8 beta in a single peak in the 1.4 ms/cm fall through. C8 beta-deficient serum contained a major peak of C8 alpha-gamma at 7.1 ms/cm and a lesser peak coeluting with C9 at 9.5 ms/cm. Normal serum contained both intact C8 eluting between 2.4 to 5.5 ms/cm and C8 alpha-gamma eluting at 7.1 ms/cm. Free C8 beta was not detectable in normal serum indicating that free C8 alpha-gamma was not due to C8 dissociation. Mixing aliquots from the chromatographic peak of C8 beta activity with the peaks of C8 alpha-gamma activity in C8 beta-deficient serum or in normal serum generated intact C8 hemolytic activity. Non-reducing SDS-PAGE and Western blotting with anti-C8 confirmed the presence of antigenic material of appropriate m.w. in each peak. These findings demonstrate that serum contains excess C8 alpha-gamma relative to C8 beta, despite the equimolar presence of the subunits in intact C8. Thus the availability of C8 beta determines the quantity of C8 produced. Further, these data suggest the possibility that the C8 structural genes may be differentially expressed despite their close genetic linkage.

Application of the peroxidase-antiperoxidase immunoassay to the identification of Salmonellae from pure culture and animal tissue.

The peroxidase-antiperoxidase immunoassay was developed by using selected Salmonella serotypes to evaluate its potential for use in diagnostic bacteriology. S. choleraesuis var, kunzendorf, S. dublin, and S. typhimurium were the test organisms. Strong specific staining with corresponding antiserum was achieved with smears of each Salmonella serotype on microscope slides from formalinized cell suspensions, live broth cultures of clinical isolates, and tissue suspensions from the livers and spleens of experimentally infected mice. In addition, S. choleraesuis var. kunzendorf was detected in Formalin-fixed and fresh frozen tissues from experimentally infected pigs. The results of this study indicate that the peroxidase-antiperoxidase assay is well-suited for the rapid identification of Salmonella from pure cultures and that the technique can be useful in research for the detection of this pathogen in histological sections.

Effects of cyclophosphamide on the immune response of pigs to Salmonella cholerae-suis var kunzendorf.

The effects of the immunosuppressive agent cyclophosphamide (CY) on the immune response of pigs given IM challenge inoculations of a moderately virulent strain of Salmonella cholerae-suis var kunzendorf were examined. Five groups of Yorkshire-cross pigs (approx 6 kg) were given Salmonella, CY, or both at various times after the 1st of a series of doses of CY was given. The drug was administered subcutaneously in 3 doses, 2 days between doses, at a rate of 20 mg/kg of body weight. Cyclophosphamide was observed to produce significant numerical decrease of circulating leukocytes, especially the polymorphonuclear neutrophils. Circulating lymphocyte numbers were reduced to 40% to 60% of base-line values. Pigs (group 4) given 3 x 10(6) S cholerae-suis IM at the time the initial CY dose was given were clinically ill during days 6 to 12; 2 of the 5 pigs died. In contrast, pigs (group 5) given 3 x 10(6) S cholerae-suis at the time of the 3rd dosing with CY did not become clinically ill until 10 days later. A significant increase in antibody titer to S cholerae-suis was delayed in this latter group beyond that of the groups of pigs (group 4) inoculated on the 1st dosing with CY and of pigs (group 6) not given CY. A significant and prolonged increase in mean rectal temperature was observed in those pigs challenge inoculated at the time of the initial CY dose. Pigs also were sensitized to Mycobacterium avium 2 weeks before CY administration. Delayed hypersensitivity reactions were depressed in pigs treated with CY at the time of testing.