Growth and Mating of <Emphasis Type="Italic">Cryptococcus neoformans</Emphasis> var. <Emphasis Type="Italic">grubii</Emphasis> on Woody Debris

A total of 36 Cryptococcus neoformans strains originating from South Africa were screened for wood degrading enzymes. All strains tested positive for cellulase activity while none where capable of xylan degradation. Three C. neoformans var. grubii strains, originating from clinical and environmental samples, representing the same genotype (VNI/AFLP1—C. neoformans var. grubii) and MATα, were evaluated for growth on debris of two common tree species in South Africa: Acacia mearnsii and Eucalyptus camaldulensis. The mating capability of all the C. neoformans strains was evaluated on similar debris. Strains grown on A. mearnsii yielded substantially greater yeast populations. A total of 26%, 6%, 46%, and 80% of the 36 C. neoformans strains tested were either able to mate or develop filaments when crossed on A. mearnsii and E. camaldulensis debris, V8 juice, and yeast carbon base (YCB) agar, respectively. Filamentation and monokaryotic fruiting was observed in 3% of strains when C. neoformans was cultured on either A. mearnsii, E. camaldulensis debris, or YCB. The results indicate that this fungus is capable of completing its life cycle and can produce basidiospores on woody debris. In the future, these findings should be considered when studying the epidemiology, microbial ecology, and proposed infection process of this global pathogen.     

The effects of palm oil breakdown products on lipid turnover and morphology of fungi

The oleaginous fungi Cryptococcus curvatus and Mucor circinelloides were used to determine the effect of palm oil breakdown products, measured as polymerized triglycerides (PTGs), on lipid turnover and on fungal growth and morphology. In M. circinelloides, we found after 7 days of growth, a decrease in biomass and in lipid utilization and accumulation at increased PTG levels, both at low and neutral pH. In C.?curvatus, there was also a decrease in lipid utilization and biomass production at increased PTG levels, at both low and neutral pH. However, an increase in oil accumulation was observed at low pH while it remained similar at neutral pH for all PTG levels tested. Hairy and warty protuberances on the cell surface were observed when C. curvatus was grown on oils with 15% and 45% PTGs, respectively. Using nano scanning Auger microscopy, we found no evidence to suggest a difference in elemental composition of the surfaces of the warty protuberances compared with the rest of the cell wall surface. We conclude that the warty protuberances are outgrowths of cell walls and that the changes observed in lipid turnover in both fungi are due to the presence of palm oil breakdown products.     

Malaria vectors and transmission dynamics in coastal south-western Cameroon

Background

Malaria is a major public health problem in Cameroon. Unlike in the southern forested areas where the epidemiology of malaria has been better studied prior to the implementation of control activities, little is known about the distribution and role of anophelines in malaria transmission in the coastal areas.

Methods

A 12-month longitudinal entomological survey was conducted in Tiko, Limbe and Idenau from August 2001 to July 2002. Mosquitoes captured indoors on human volunteers were identified morphologically. Species of the Anopheles gambiae complex were identified using the polymerase chain reaction (PCR). Mosquito infectivity was detected by the enzyme-linked immunosorbent assay and PCR. Malariometric indices (plasmodic index, gametocytic index, parasite species prevalence) were determined in three age groups (<5 yrs, 5–15 yrs, >15 yrs) and followed-up once every three months.

Results

In all, 2,773 malaria vectors comprising Anopheles gambiae (78.2%), Anopheles funestus (17.4%) and Anopheles nili (7.4%) were captured. Anopheles melas was not anthropophagic. Anopheles gambiae had the highest infection rates. There were 287, 160 and 149 infective bites/person/year in Tiko, Limbe and Idenau, respectively. Anopheles gambiae accounted for 72.7%, An. funestus for 23% and An. nili for 4.3% of the transmission. The prevalence of malaria parasitaemia was 41.5% in children <5 years of age, 31.5% in those 5–15 years and 10.5% in those >15 years, and Plasmodium falciparum was the predominant parasite species.

Conclusion

Malaria transmission is perennial, rainfall dependent and An. melas does not contribute to transmission. These findings are important in the planning and implementation of malaria control activities in coastal Cameroon and West Africa.

     

The complete karyotype of Aspergilius niger: the use of introduced electrophoretic mobility variation of chromosomes for gene assignment studies

A method is described for unambiguous assignment of cloned genes to Aspergillus niger chromosomes by CHEF gel electrophoresis and Southern analysis. All of the eight linkage groups (LGs), with the exception of LG VII, have previously been assigned to specific chromosomal bands in the electrophoretic karyotype of A. niger. Using a LG VII-specific probe (nicB gene of A. niger) we have shown that LG VII corresponds to a chromosome of about 4.1 Mb. Furthermore, genetic localization of three unassigned genes (glaA, agIA and pepA) in strains in which these genes had been replaced by a selectable marker gene led to a revised karyotype for the chromosomes corresponding to LGs VIII and VI. The revised electrophoretic karyotype reveals only 5 distinct bands. The presence of three pairs of equally sized chromosomes precluded assignment of genes to one specific chromosome in the wild-type strain. However, unambiguous chromosome assignment of cloned genes using CHEF-Southern analysis was demonstrated using a set of A. niger strains with introduced chromosomal size variation. The availability of these tester strains obviates the need to isolate or construct mutant. strains for the purpose of chromosome assignment.     

Preparation of agarose with low net negative charge density using an inexpensive anion exchanger

A method of preparing agarose of low net negative charge density by the use of Chromium tanned gelatin is described. Using commercial agarose (agarose c) as standard of comparison the product has a sulphate content approximately 0.1 that of agarose c and its pyruvate content was reduced to zero as shown by NMR in DMSO. The product was still able to adsorb and desorb serum glycoproteins similar to agarose c indicating that charge on the agarose c gel particles played a minor role if any on the binding of the serum glycoproteins.     

Induction of the catalytic protein of (Na+ plus K+)-ATPase in the salt gland of the duck.

The (Na+ plus K+)-ATPase activities in salt gland homogenates increased 3- to 4-fold after saline treatment of ducks for 3 weeks. The ATPase was purified to a specific activity of 460 and 1015 mumol Pi/mg protein per h, respectively, in control and saline-treated ducks. The catalytic protein was identified on polyacrylamide electrophoresis gels by phosphorylating the enzyme with (32P)ATP. The molecular weight of the protein was estimated to be 98 000. The amount of catalytic unit increased commensurately with the enzyme activity after saline treatment. It is therefore concluded that the increased enzyme activity is due to a de novo enzyme synthesis and is not an activation effect. Phospholipid concentration in the salt gland tissue increased 1.7-fold after the saline treatment. Significant increases occurred in the percentage of the total phospholipids as phosphatidylserine and sphingomyelin. In the partially purified (Na+ plus K+)-ATPase preparation, the percentage composition of phosphatidylserine and phosphatidylethanolamine increased after saline treatment.     

Note on the plasmodium ofLamproderma violaceum

Report on observations made on the growth and the appearance of a plasmodium which later could be identified asLamproderma violaceum.     

The Duffy system: a population genetics study in Portugal, Guinea-Bissau and Brazil

2225 blood samples from Portugal (classed according to historical provinces), 301 blood samples from Guinea-Bissau (classed in tribes) and 697 blood samples from Brazil (classed according to colour of skin) have been tested in the Duffy system. The Portuguese seem to be a sufficiently uniform and autonomous population. This is also true for the (non-rejected) blood-samples from Guinea-Bissau. The Brazilians differ in accordance with their colour of skin. The expected relations between Portugal and its former colonies can be proved. The Duffy system is suited for the distinction of black and non-black populations and enables to recognize extraneous admixtures.     

Measles Immune Suppression: Lessons from the Macaque Model

Measles remains a significant childhood disease, and is associated with a transient immune suppression. Paradoxically, measles virus (MV) infection also induces robust MV-specific immune responses. Current hypotheses for the mechanism underlying measles immune suppression focus on functional impairment of lymphocytes or antigen-presenting cells, caused by infection with or exposure to MV. We have generated stable recombinant MVs that express enhanced green fluorescent protein, and remain virulent in non-human primates. By performing a comprehensive study of virological, immunological, hematological and histopathological observations made in animals euthanized at different time points after MV infection, we developed a model explaining measles immune suppression which fits with the “measles paradox”. Here we show that MV preferentially infects CD45RA⁻ memory T-lymphocytes and follicular B-lymphocytes, resulting in high infection levels in these populations. After the peak of viremia MV-infected lymphocytes were cleared within days, followed by immune activation and lymph node enlargement. During this period tuberculin-specific T-lymphocyte responses disappeared, whilst strong MV-specific T-lymphocyte responses emerged. Histopathological analysis of lymphoid tissues showed lymphocyte depletion in the B- and T-cell areas in the absence of apoptotic cells, paralleled by infiltration of T-lymphocytes into B-cell follicles and reappearance of proliferating cells. Our findings indicate an immune-mediated clearance of MV-infected CD45RA⁻ memory T-lymphocytes and follicular B-lymphocytes, which causes temporary immunological amnesia. The rapid oligoclonal expansion of MV-specific lymphocytes and bystander cells masks this depletion, explaining the short duration of measles lymphopenia yet long duration of immune suppression.