Ecological conditions that favor the evolution of intermediate-virulence in an environmentally transmitted parasite

In this paper we develop and analyze several populaion-dynamic models of an environmentally transmitted symbiotic parasite infecting an isolated population of susceptible hosts. In our most basic model infection acts only to decrease the average lifetime of the infected host, parasites are only transmitted to uninfected hosts, there is no recovery from infection, and the rate of parasite transmission is an increasing function of the level of parasite virulence. It is shown that invasion of the parasite-free equilibrium cannot occur for virulence levels that are either too high or too low. We then incorporate a number of modifications to the model, among them the possibility that host fertility is reduced by infection, and that transmission rate depends additionally on susceptible host density. It is shown that the essential nature of the conditions for invasion are preserved. Thus, natural selection for intermediate virulence is a generic property of a broad class of population models.     

Stimulation and inhibition of the growth of mice carrying the human growth hormone gene

The human growth hormone gene, containing mouse metallothionein gene promotor, was injected into the male pronuclei of fertilized mouse ova. The progeny of transgenic mice included animals with both accelerated and inhibited growth. Radioimmunochemical analysis has revealed human growth hormone synthesis in both groups of transgenic mice. The molecular weight of the hormone synthesized in liver cells was 25,000 daltons. A possible mechanisms of foreign hormone effect on the growth of transgenic mice is discussed.     

Effect of aminopterin on pre-implantation rat embryos cultivated outside the body

The rat embryos at the stage of 8 blastomeres were explanted in the Biggers' medium with 20% of blood serum from the rats obtained different doses of aminopterin. The marked delay of cleavage rate, morphological anomalies of blastocysts, selective damaging effect of aminopterin upon the inner cells mass (embryoblast) and high resistance of trophectoderm cells against this drug were observed. The role of dihydrololate reductase at the preimplantation developmental stages, the resistance against aminopterin of the early rat embryos within the maternal organism and high sensitivity to this drug of the embryos in vitro are discussed. A conclusion is drawn on the presence of the barrier function of oviducts with respect to aminopterin.     

Formation of fusarenone X, nivalenol, zearalenone, alpha-trans-zearalenol, beta-trans-zearalenol, and fusarin C by Fusarium crookwellense

Fusarium crookwellense KF748 (NRRL A-28100) (isolated from dry rotted potato tubers in Central Poland) produced six mycotoxins on both rice and corn substrates at 25 degrees C. The metabolites detected were zearalenone, alpha-trans-zearalenol, beta-trans-zearalenol, fusarin C, and the trichothecenes fusarenone X and nivalenol. This is the first report of formation of alpha-trans-zearalenol, beta-trans-zearalenol, fusarenone X, and nivalenol by F. crookwellense.     

Fusarium Species Colonizing Spears and Forming Mycotoxins in Field Samples of Asparagus from Germany and Poland

The occurrence of Fusarium spp. and associated mycotoxins in asparagus spears was evaluated in Poland in 2002 and 2003 and in Germany in 2002. Spears of two cultivars, Eposs and Gijnlim, were collected from two locations in Poland, Swidwowiec and Poznan, on sandy and sandy loam soil, respectively. Fusarium oxysporum and F. proliferatum were detected at an average incidence of 38.3% and 15.8% in the spear sections sampled, respectively. In stands of 11 (tested) cultivars of asparagus sampled in Germany on sandy soil, the same species dominated, however, they were less frequent than in Poland (26.6% and 5.6% of the spears infected with F. oxysporum and F. proliferatum, respectively). Chemical analyses revealed that fumonisin B₁ (FB₁) and moniliformin (MON) were present in some of the spears sampled in Poland. FB₁ was not found and MON was not assessed in spears sampled in Germany in 2002, but F. proliferatum was able to form the toxin in vitro in the range from 101.4 up to 205.8 μg/kg maize kernel substrate. Asparagus samples in Poland contained FB₁ at up to 5.6 μg/kg spear fresh weight. The highest MON concentration (1350 μg/kg) was detected in cultivar Eposs in Marcelin, Poland, in 2002. MON and FB₁ were found in spears infected by both F. oxysporum and F. proliferatum, however, only the latter fungus was able to synthesize both toxins.     

Prophylactic Injection of Recombinant Alpha-Enolase Reduces Arthritis Severity in the Collagen-Induced Arthritis Mice Model

Objective

To evaluate the ability of the glycolytic enzyme alpha-enolase (ENO1) or its immunodominant peptide (pEP1) to reduce the severity of CIA in DBA/1 mice when injected in a prophylactic way.

Methods

Mice were treated with mouse ENO1 or pEP1 one day prior to collagen II immunization. Clinical assessment was evaluated using 4 parameters (global and articular scores, ankle thickness and weight). Titers of serum anti-ENO1, anti-cyclic citrullinated peptides (anti-CCP) and anti-CII (total IgG and IgG1/IgG2a isotypes) antibodies were measured by ELISA at different time-points. Disease activity was assessed by histological analysis of both anterior and hind paws at the end of experimentation.

Results

Prophylactic injection of 100 μg of ENO1 reduced severity of CIA. Serum levels of anti-CII antibodies were reduced in ENO1-treated mice. Concordantly, ENO1-treated mice joints presented less severe histological signs of arthritis. ENO1 did not induce a shift toward a Th2 response since IgG1/IgG2a ratio of anti-CII antibodies remained unchanged and IL-4 serum levels were similar to those measured in the control group.

Conclusions

Pre-immunization with ENO1 or its immunodominant peptide pEP1 reduces CIA severity at the clinical, immunological and histological levels. Effects of pEP1 were less pronounced. This immunomodulatory effect is associated with a reduction in anti-CII antibodies production but is not due to a Th1/Th2 shift.     

Formation of Avenacein Y by Fusarium avenaceum Fries Sacc. isolates from Germany and pathogenicity of the isolates to cereal seedlings

Twelve isolates ofFusarium avenaceum Fries Sacc. originating from diseased corn plants from Germany produced Avenacein Y in amounts ranging from 0.001 to 1.6 g/kg of wheat grain. The isolates proved most pathogenic to triticale seedlings, less pathogenic to rye seedlings and least to wheat. Pathogenicity of the isolates was not correlated with their ability to produce Avenacein Y.     

Sensitivity of the early mouse embryos to antifolic preparation chloridine]

A study was made of antifolic preparation chloridine (2,4-diamino-5-p-chlorphenyl-6-ethylpyrimidine) on the cleavage of CBA mouse embryos. Chloridine failed to influence the development of early mouse embryos in the maternal organism and considerably inhibited the cleavage of embryos explanted into the chloridine-containing medium. Chloridine sensitivity in the mouse and rat embryos was compared and a conclusion was drawn on the absence of interspecies differences in their reaction to teratogen at the level of the embryonic cells.