Persistence of infection in mice inoculated intranasally with Cryptococcus neoformans

Cryptococcus neoformans was instilled intranasally into mice which were periodically sacrificed to determine the course of infection. Cryptococci persisted within the nasal passages throughout the 90 day study. Extranasal dissemination began 14–28 days after instillation and was still demonstrable 90 days post-exposure. Ten percent mortality was observed in mice receiving 10⁶ cryptococci, while no mortality was observed in mice exposed to 10³ or 10⁴ cryptococci. Our research suggests that nasal colonization with C. neoformans can precede pulmonary and systemic cryptococcosis by weeks or months.     

Immunocytochemical investigations on the presence of neuron-specific antibodies in the CSF of Parkinson's disease cases

The CSF and sera of 7 patients with Parkinson's disease were investigated immunocytochemically, in order to see if antibodies were present which recognized DA-ergic cell bodies in glutaraldehyde fixed rat brain. In 2 patients a marked labeling of DA-ergic neurons in the substantia nigra was observed, identified by anti-DA antiserum and by 6-OHDA induced degeneration, but also other neurons in the ventral mesencephalon were recognized. The other patients were weakly positive or negative. Sera gave unspecific labelling of all neurons. In one patient the sub-classes of IgG were investigated and found to be of IgG₃ (labeling nerve terminals) and of IgG_1–2, low affinity type (recognizing perikarya). The epitopes recognized have not been identified, but are unlikely to be DA-like, since blocking experiments and ELISA-tests gave negative results. The possible clinical importance of the results are discussed.Special Issue dedicated to Prof. Holger Hydén.     

The relationship between auto-agglutination, cell surface hydrophobicity and virulence of the fish pathogen Renibacterium salmoninarum

Abstract The cell surface hydrophobicity of Renibacterium salmoninarum strains was examined using a salt aggregation method. Those strains which were virulent in the test animal were sticky, auto-agglutinating and possessed a hydrophobic cell surface. Those strains with a low virulence were non-sticky, non-agglutinating and failed to aggregate in a high molar salt. Strains could not be distinguished using biochemical tests. There was no change in hydrophobicity following re-isolation of the bacteria from experimentally infected rainbow trout, Salmo gairdneri .     

In vitro expression of partial resistance toPhytophthora palmivora by shoot cultures of papaya

Shoot apices ofCarica papaya were multiplied in vitro on solidified nutrient media supplemented with -naphthyl-acetic acid and 6-benzylaminopurine. The micropropagated shoots were inoculated in vitro, through a stem wound, with a sporangial suspension (1.2×10⁴ sporangia ml^-1) ofPhytophthora palmivora. The symptoms exhibited by the shoots in vitro were similar to those described previously for infection of the whole plant in the field. The time taken for the host tissue to become brown and to wilt and the time to sporulation of the pathogen were all recorded for each shoot of four varieties of papaya challenged with each of ten isolates ofP. palmivora. Significant differences were observed between host-pathogen combinations for these variables and host-specificity was detected amongst the isolates ofP. palmivora. The time taken for the shoot to wilt was positively correlated with the time to sporulation of the isolated but both these variables were negatively correlated with the time to browning of the shoot. In vitro selection for disease resistance will be useful during breeding programmes involving papaya genotypes which are maintained through clonal propagation.     

Antibodies to Cholinergic Neurons in Alzheimer''s Disease

Alzheimer's disease (AD) is associated with degenerative changes in nuclei of the basal forebrain which provide most of the cholinergic input to the cortex and hippocampus and with a reduction in presynaptic cholinergic parameters in these areas. Although the etiology and pathogenesis of AD are not known, several reports indicate the involvement of immunological mechanisms. In the present work we examined the existence of antibodies in sera of AD patients that bind specifically to cholinergic neurons. As antigens we employed the purely cholinergic electromotor neurons of the electric fish Torpedo which are chemically homogeneous and cross-react antigenically with human and other mammalian cholinergic neurons. Our findings show that immunoglobulins from sera of AD patients bind to a specific antigen (molecular mass 200 kilodaltons) in the cell bodies and axons of Torpedo electromotor neurons and that the levels of such antibodies are significantly higher in AD patients than in controls. The possible role of these antibodies in the cholinergic dysfunction in AD and their diagnostic potential are discussed.     

Galanin-Like Immunoreactivity Is Unchanged in Alzheimer''s Disease and Parkinson''s Disease Dementia Cerebral Cortex

Galanin is a recently isolated neuropeptide that is of particular interest in dementing disorders because of its known colocalization with choline acetyltransferase in magnocellular neurons of the basal nucleus of Meynert. These neurons degenerate in Alzheimer's disease, and there is a corresponding deficiency of cortical choline acetyltransferase activity. In the present study, galanin-like immunoreactivity was measured in the postmortem cerebral cortex and hippocampus of 10 controls and 14 patients who had had Alzheimer's disease. Significant reductions of choline acetyltransferase activity (50-60%) were found in all regions examined; however, there was no significant effect on concentrations of galanin-like immunoreactivity. Similar measurements were made in postmortem tissues of 12 control and 13 demented Parkinsonian patients who had had Alzheimer-type cortical pathology. Choline acetyltransferase activity was again significantly decreased in all regions examined but there were no significant reductions in galanin-like immunoreactivity. Experimental lesions of the fornix in rats produced parallel significantly correlated reductions of both choline acetyltransferase activity and galanin-like immunoreactivity in the hippocampus. Galanin-like immunoreactivity in the human hypothalamus consisted of two molecular-weight species on gel-permeation chromatography, and two forms were resolved by reverse-phase HPLC. The paradoxical preservation of galanin-like immunoreactivity, despite depletion of the activity of choline acetyltransferase, with which it is colocalized, is as yet unexplained. Recent studies have shown that galanin inhibits both acetylcholine release in the hippocampus and memory acquisition; therefore, preserved galanin may exacerbate the cholinergic and cognitive deficits that accompany dementia.     

Glycosaminoglycans in Cortical Autopsy Samples from Alzheimer Brain

Each of the known classes of mammalian glycosaminoglycans, with the exception of keratan sulphate, was found in cerebral cortex samples from patients with Alzheimer-type dementia and age-matched controls. These molecules were quantitated, after electrophoresis and staining with Alcian Blue dye, by scanning densitometry. No significant differences were found between the mean levels of each of the above glycosaminoglycans in frontal cortex from patients with dementia compared with controls. An increase (26%; p less than 0.05) in the mean level of hyaluronate, but not of other glycosaminoglycans, was found in temporal cortex samples. On the other hand, the uronic acid content of hyaluronate degradation products following Streptomyces hyaluronidase treatment of brain glycosaminoglycans did not reveal any statistically significant changes in Alzheimer's disease. HPLC of disaccharide products from Arthrobacter chondroitinase AC digests did not reveal any significant changes in sulphate substitution of chondroitin sulphate in Alzheimer brain.     

Effects of fire season on flowering of forbs and shrubs in longleaf pine forests

Summary Effects of variation in fire season on flowering of forbs and shrubs were studied experimentally in two longleaf pine forest habitats in northern Florida, USA. Large, replicated plots were burned at different times of the year, and flowering on each plot was measured over the twelve months following fire. While fire season had little effect on the number of species flowering during the year following fire, fires during the growing season decreased average flowering duration per species and increased synchronization of peak flowering times within species relative to fires between growing seasons. Fires during the growing season also increased the dominance of fall flowering forbs and delayed peak fall flowering. Differences in flowering resulting from variation in fire season were related to seasonal changes in the morphology of clonal forbs, especially fall-flowering composites. Community level differences in flowering phenologies indicated that timing of fire relative to environmental cues that induced flowering was important in determining flowering synchrony among species within the ground cover of longleaf pine forests. Differences in fire season produced qualitatively similar effects on flowering phenologies in both habitats, indicating plant responses to variation in the timing of fires were not habitat specific.     

Relation of light and nitrogen source to growth, nitrate reductase and glutamine synthetase activity of jack pine seedlings

Two-month-old jack pine ( Pinus banksiana Lamb.) seedlings were placed in a greenhouse where both nitrogen source and light level were varied. After 4 months, whole seedling biomass, leaf biomass and relative growth rate were greatest in seedlings grown with NH⁺₄/NO/NO⁻₃-N and full light (FL) and least in seedlings grown with NO ⁻₃-N and low light (LL). NO ⁻₃-seedlings grown under full light and NH⁺₄/NO⁻₃-seedlings grown under low light were approximately equal. This indicates that the extra carbon costs of assimilating only NO⁻₃-N were similar to the reduction of carbon fixation resulting from a 50% decrease in photon flux density. Percentage and total nitrogen content of needles were greater in seedlings grown under low light independent of nitrogen fertilization. Percentage and total nitrogen content of roots were higher under low light and lower when fertilized with NO⁻₃.
Nitrate reductase (NR) activity was higher in roots than in needles, while glutamine synthetase (GS) activity was higher in needles than in roots. Low light resulted in decreased NR activity (mg N)⁻¹ in needles, but not in roots. However, no nitrate was detected in the needles in any treatment. GS activity, on the other hand, was greater under low light in both needles and roots. GS activity in needles is most likely involved with the reassimilation rather than the initial assimilation of ammonium. Some implications of these shifts in enzymatic activity for ecological phenomena in forests are discussed.     

Variation in host susceptibility among and within populations ofPlantago lanceolata L. infected by the fungusPhomopsis subordinaria (Desm.) Trav.

Summary Susceptibility toPhomopsis stalk disease ofPlantago lanceolata genotypes, sampled in three different populations with a variable degree of infection by the fungusPhomopsis subordinaria, was determined under greenhouse conditions. Susceptibility of the host varied within, but not among populations. No relationship between the intensity of the disease in the field and the mean susceptibility of the host genotypes sampled at those locations could be established. Host susceptibility appeared to be composed of the host genotypes sampled at those locations could be established. Host susceptibility appeared to be composed of different (uncorrelated) plant characteristics. Determining whether host genotypes are highly or slightly susceptible can only be achieved by field trials, where the plants are exposed to the whole set of disease inducing factors. The relevance of host susceptibility to the intensity of disease in the field is discussed in relation to the variation in pathogenicity of the fungus and the variation in environmental factors prevailing inP. lanceolata populations underP. subordinaria pathogen pressure. Grassland Species Research Group Number 123