Cellular response to Schistosoma mansoni infection in Biomphalaria alexandrina strains selected for susceptibility and resistance.

Exposure of juvenile and adult Biomphalaria alexandrina to Schistosoma mansoni miracidia resulted, typically, in three susceptibility patterns: a) non-infected snails; b) normal infections, and c) retarded infections. Under laboratory conditions, a vigorous resistant-type cellular response to invading miracidia was seen in the histological sections of non-susceptible snails. Accordingly, they were classified as resistant snails. Data pertaining to the influence of host size on suceptibility to S. mansoni indicates that adult snails (i.e. 10-20 mm shell diameter) were significantly less likely to harbour sporocysts than juvenile ones (i.e. 5-10 mm shell diameter). Cellular reaction to the infection varied with sporocysts location and length of infection. At 2 days post-exposure (DPE), most sporocysts were viable. Approximately 8-12% of the sporocysts had elongated shaped transverse constriction and were categorized "normal", while those showing no elongation were categorized "retarded". All remaining sporocysts at 4 DPE were categorized "dead", while at 30 DPE, most sporocysts were "amorphous" with eosinophilic masses. Although encapsulation of sporocysts never occurred in susceptible snails, haemocyte aggregations could sometimes be observed in the proximity of well developed sporocysts. In resistant snails, this cellular response continued to increase and resulted in the encapsulation of the sporocysts. In susceptible snails, the nucleus of secretory cells of the albumen cytoplasm were different in susceptible and resistant snails.

Pathological changes in testes and liver of male albino rats after dermal exposure to DDVP insecticide.

Exposure of male albino rats to DDVP insecticide at sublethal dose of 30 mg/kg/day through dermal painting for a period of 90 days didn't show any intoxication symptoms or mortality. However, cytopathological changes in testicular and liver tissues were evident. There was a positive correlation between the degree of cellular damage and the period of insecticide administration. In general, damages were prominent in rats treated for 30 days or more. Histological examination of testes showed degenerative seminiferous tubules and fewer leydig cells. Hepatic cells were congested, atrophied and showed different stages of necrobiotic changes. This suggests a great care and caution for workers during different phases of DDVP insecticide handling.

Prevalence of airborne Aspergillus flavus in Khartoum (Sudan) airspora with reference to dusty weather and inoculum survival in simulated summer conditions.

Khartoum air was scanned for airborne Aspergillus flavus for 12 months using the horizontal gravitational settling method. Frequency of occurrence was related to total fungal catch and dusty weather. The Aspergilli were prevalent (68% of total isolated/plate/month) and A. flavus constituted 31% of the total Aspergilli. In June (hot, dry & dusty) Aspergilli constituted 79% of the total isolates, whilst A. flavus represented 30% from amongst the other Aspergilli. A. flavus, A. niger, A. nidulans (conidial & ascosporic states), A. terreus, Eurotium amstelodami and A. fumigatus, in descending order of prevalence were isolated in June. Other pathogenic or potentially pathogenic forms, isolated, were Cladosporium, Curvularia and Penicillium. Amongst winter isolations A. flavus was sporadic to absent in occurrence. A. flavus spore inocula that underwent hourly intermitted exposure to 45 degrees C, showed a decrease in spore germinability as well as reduced germ length.

Isolation of aflatoxin from Acacia and the incidence of Aspergillus flavus in the Sudan.

A total of 1300 seeds from 13 commodities were surveyed for Aspergillus flavus. An additional inoculum was obtained from 6 divergent sources. A. flavus isolants, randomly selected on the bases of visual cultural characteristics and inoculum source, were assayed for aflatoxin yielding capacity. Out of 97 analyzed isolates 76 (78.3%) were aflatoxin-elaborators of which 27 (27.8%) colonies were classified as very highly toxinogenic (greater than 1000 micrograms/kg). Acacia, described a new source of aflatoxin (81 to greater than 1000 micrograms/kg), is herein first described from Sudan as a substrate for A. flavus.

Studies on the interaction between Sclerotium bataticola and Aspergillus flavus.

Metabolic products of Aspergillus flavus Link had a toxigenic effect upon Sclerotium bataticola Maub., decreasing its radial expansion and dry weight and enhancing sclerotial production. Metabolites of S. bataticola significantly lowered conidial output, slightly decreased the mycelial harvest but did not influence the linear spread of A. flavus. A. flavus, elaborating aflatoxin B1 (Rf 0.56), showed fluorescent spots identical to the original but with lower Rf value of 0.25 upon treatment with metabolic products of S. bataticola which itself exhibited fluorescent spots.

Growth responses of two phytopathogenic fungi to fernasan in culture media.

The toxic effect of fernasan (containing 25% thiram) was tested on Rhizoctonia solani and Fusarium solani in liquid and agar media. The fungicide was more effective in liquid (at 100 p.p.m.) than in solid media, where 400 p.p.m. checked the growth of R. solani, but was ineffective against F. solani. Both fungi exhibited a zone of inversion growth in liquid culture whereby certain intermediate concentrations were less inhibitory than lower or subsequently higher doses. Similar reaction was recorded for F. solani alone in fungicide-containing agar media. Sclerotium formation by R. solani was highly significant, in relation to controls, at 40 p.p.m. The abundance of chlamydospores of F. solani was coupled with cessation of conidium formation increasing fernasan doses.