Effects of Epixylic Vegetation Removal on the Dynamics of the Microbial Community Composition in Decaying Logs in an Alpine Forest

Ecosystems - Epixylic vegetation may be important in dead wood decay by altering the microenvironment and, thereby, microbial communities in logs. However, the interaction between epixylic...     

Detection of human papillomavirus types by the polymerase chain reaction and the differentiation between high-risk and low-risk cervical lesions.

By means of a consensus polymerase chain reaction (PCR) method, the prevalence of HPV types was determined in cervical biopsies from 137 women referred to the gynecological outpatient clinic for colposcopy because of an abnormal cervical smear. The prevalence of HPV was 80.3%. There was a statistically highly significant rise in the prevalence of the oncogenic HPV types (16, 18, 31, 33) with increasing severity of cervical intraepithelial neoplasia (CIN I to III), indicating a role for these HPV types in the pathogenesis of cervical cancer. The prevalence of other HPV types decreased significantly with the severity of the lesion, suggesting that these HPV types play a less significant role in this process. These data indicate that HPV typing with PCR may be a valuable tool for distinguishing between high-risk and low-risk cervical lesions. Furthermore, our results suggest that the detection of HPV types by consensus PCR in the cervix of patients with an abnormal smear but without histologically detectable CIN is a useful tool for predicting which of these patients will eventually develop CIN. Finally, a relatively low percentage (3%) of HPV double infections is reported in this study.     

A triangular relationship between leaf size and seed size among woody species: allometry, ontogeny, ecology and taxonomy

 A hypothesized relationship between seed weight and leaf size was investigated for 58 diverse British (semi-)woody species. Interspecific variation in leaf size of adult plants corresponded allometrically with interspecific variation in the weight of an infructescence (seed-bearing inflorescence). The relationship between seed size and leaf size of adult plants was triangular. The corners of the triangle were interpreted in terms of ecological strategy. Medium-sized infructescences, small seeds and large leaves were seen among medium-sized, fast-growing, earlier-successional, mostly deciduous shrubs and trees; small infructescences, small seeds and small leaves mostly among low, slow-growing evergreens from stress-prone, proclimax habitats; and large infructescences, large seeds and large leaves among slow-growing, later-successional trees of potential competitive vigour. The hypothesis that the combination of large seeds and small leaves is allometrically unlikely was supported by the data. The roles of ontogeny and taxonomic relatedness in the seed size-leaf size relationship were examined by correlative and taxonomic analyses of seed, plant and leaf size during the unfolding of the life history from seed through two seedling phases to adulthood. Deciduous versus evergreen leaf habit was a source of deviation from the otherwise linear allometric relationships during ontogenetic development, none of which were, individually, confounded significantly with taxonomy. Received: 2 March 1998 / Accepted: 15 October 1998     

Isospora (Toxoplasma) gondii: induction of sexuality

The role of the stomach and small intestine of cats and of the parasite's rate of multiplication on induction of sexuality in Isospora (Toxoplasma) gondii was studied by injecting cats either with free cystozoites or proliferative parasites directly into the intestinal lumen, after laparotomy. Oocyst production was similar in cats infected orally with cysts or cystozoites and in cats infected by inoculation into the duodenal lumen with free cystozoites, obtained by either mechanical rupture of by in vitro pepsin/HCl digestion of the cyst wall. When free cystozoites were injected into the lumen of the posterior part of the ileum, cats became seropositive but oocyst excretion during the first 4 weeks after infection was very low or absent; nevertheless a solid immunity to oral challenge was acquired in the former case. If no oocysts at all were produced after primary infection, the intestine remained susceptible to challenge, in spite of previous seroconversion. This lack of protective immunity in the presence of serum antibodies was observed in all cats primarily infected by direct injection of proliferative parasites into the duodenal lumen. It is concluded that previous gametogony rather than previous infection and seroconversion provokes local intestinal immunity against the development of sexual stages after oral challenge; the switch to gametogony of cystozoites is not triggered off by the low pH of the stomach but is probably related to their reduced rate of multiplication.