The host range and selectivity of a parasitic plant: Rhinanthus minor L.

Summary Rhinanthus minor (Yellow-rattle) is a widespread hemiparasitic plant of grassland habitats throughout Britain. Association analysis of the dune vegetation at Holme-next-the-Sea in eastern England revealed only two potential host plants through positive association. In contrast direct examination of the root systems revealed haustorial connections with 20 host species. The number of species parasitized by one plant ranged from one to seven. Data from another four sites in Britain and one in central Europe indicate that the natural host range of R. minor encompasses at least 50 species from 18 families with 22% in the Leguminosae and 30% in the Gramineae. Comparison of the number of haustorial connections made to each species with the abundance of roots in the soil shows that R. minor is a highly selective parasite, but that the selectivity is not consistent between populations or between plants from different parts of the same population. The reasons for host selectivity are discussed.     

Differential accumulation of catecholamines, proenkephalin- and chromogranin A-derived peptides in the medium after chronic nicotine stimulation of cultured bovine adrenal chromaffin cells

We have used an antiserum to a synthetic peptide fragment of bovine chromogranin A (ChrgA)[Tyr0] bovine ChrgA (306-313): YLSKEWEDA, together with antibodies to proenkephalin-derived peptides, to measure the release of immunoreactive peptides from nicotine-stimulated cultured bovine adrenal chromaffin cells. Over a period of 6 hr the accumulation of YLSKEWEDA immunoreactivity and Met-enkephalin Arg6Gly7Leu8 (MERGL) immunoreactivity in the medium of 10 microM nicotine-stimulated cells was shown to be biphasic; the initial phase occurred in the first 15-30 min and the second phase reached a peak after 4 hr. In contrast, catecholamine release occurred monophasically over the initial 15-30 min. Investigation of the second phase of peptide accumulation revealed that it was due in part to nicotine-evoked exocytosis and in part to extracellular processing of high molecular weight precursor proteins.     

Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat

Asp, Sven, Allan Watkinson, Nicholas D. Oakes, and Edward W. Kraegen. Prior eccentric contractions impair maximal insulin action on muscle glucose uptake in the conscious rat.J. Appl. Physiol. 82(4):1327-1332, 1997.Our aim was to examine the effect of prioreccentric contractions on insulin action locally in muscle in theintact conscious rat. Anesthetized rats performed one-leg eccentriccontractions through the use of calf muscle electrical stimulationfollowed by stretch of the active muscles. Two days later, basal andeuglycemic clamp studies were conducted with the rats in the awakefasted state. Muscle glucose metabolism was estimated from2-[¹⁴C(U)]deoxy-D-glucoseandD-[3-³H]glucose administration, and comparisons were made between the eccentrically stimulated and nonstimulated (control) calfmuscles. At midphysiological insulin levels, effects ofprior eccentric exercise on muscle glucose uptake were notstatistically significant. Maximal insulin stimulation revealed reducedincremental glucose uptake above basal(P < 0.05 in the red gastrocnemius;P < 0.1 in the white gastrocnemiusand soleus) and impaired net glycogen synthesis in all eccentricallystimulated muscles (P < 0.05). Weconclude that prior eccentric contractions impair maximal insulin action (responsiveness) on local muscle glucose uptake and glycogen synthesis in the conscious rat.

     

The role of the hemiparasitic annual Rhinanthus minor in determining grassland community structure

Summary Rhinanthus minor (yellow-rattle) is a widespread hemiparasitic plant of grassland habitats throughout Great Britain. It is usually considered to be indicative of species-rich grassland, but in a survey of 14 habitats throughout Britain it was found that R. minor at the time of flowering normally occupied relatively low-diversity patches within areas of high diversity as determined by the number of species, Simpson's Index and the Shannon-Wiener Index. Following the death of adult plants of R. minor in the summer it was shown that the pattern of species diversity changed such that by the time R. minor germinated in the following spring the differences between the areas containing and not containing R. minor were much less distinct. A perturbation experiment in which R. minor was removed from four sites indicated that the effect of the removal of R. minor on the development of community structure over the next year was to increase species diversity on three of the sites and decrease it on the fourth. Those species which responded to the removal of R. minor by an increase in abundance were shown to be preferred hosts. All three lines of evidence point to the fact R. minor has a significant effect on the species diversity of the communities in which it grows by selectively parasitizing components of the flora and modifying the competitive relationships between plants. However, as the communities generally responded to the removal of R. minor by an increase in diversity and as the general survey indicated that R. minor is generally associated with areas of low diversity it would appear that the plants which are selectively parasitized are generally not the competitive dominants in the community.     

Diagnosis of inflammatory bowel disease: an international multicentre scoring system.

Inflammatory bowel disease is being studied by the World Organisation of Gastroenterology (OMGE) Research Committee in a survey (currently) affecting 1696 patients presenting to 30 hospitals in 16 countries. A computer-aided diagnostic prediction system (when tested in 1056 patients) showed an accuracy of match between computer prediction and clinical diagnosis in 94% of these patients. Most centres, however, do not possess appropriate computing facilities. A simple diagnostic "scoring system", based on likelihood ratios, has therefore been developed, using a series of numbers set out on a single sheet of paper. The overall accuracy of the simple scoring system in the same 1056 patients was equivalent (93%) to the computer-aided system. In a further series of 510 "new" patients from eight fresh centres the diagnostic scoring system made a firm prediction in 490 cases (96%). Where made, the accuracy of match between the scoring system prediction and clinical diagnosis was 96%. It is suggested that this simple system, which requires no analytical resource and could be used by any gastroenterologist, might be of some value in clinical research and clinical practice.     

Habitat use and hybridisation between the Rocky Mountain sculpin (Cottus sp.) and slimy sculpin (Cottus cognatus)

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