Small-scale vegetation pattern related to the growth of Lycopodium annotinum and variations in its micro-environment

Small-scale variations in topography, soil depth and species occurrence were studied in a sub-arctic/sub-alpine brich forest in Swedish Lapland in order to evaluate the effects of various micro-habitats on the growth and distribution of Lycopodium annotinum. Micro-topographical variation in the study plot (280 by 420 cm) reached 100 cm, while soil depth varied from 0 to more than 50 cm over small distances of 10's of centimetres. Nineteen species were recorded in the plot and dwarf shrubs and L. annotinum were the most frequent. A micro-scale vegetation pattern was detected by a polythetic agglomerative cluster analysis and also by the divisive TWINSPAN analysis. The distribution patterns of the species appeared to be associated with variation in moisture regimes, which in turn were associated with variations in micro-topography. Lycopodium annotinum performed best when growing on the sides of valleys with deciduous dwarf shrubs and Deschampsia flexuosa, and when evergreen dwarf shrubs were absent.     

In vitro tracheal mechanics by nuclear magnetic resonance imaging

Images of rabbit tracheal cross sections were obtained at a series of transmural pressures ranging from 22 to -95 cmH2O by use of a nuclear magnetic resonance imaging microscope. The excised, washed tracheas were immersed in a solution of phosphate-buffered saline made up in deuterium oxide (D2O, pH 7.3). The images are maps of proton density in the image slice (2.5 mm thick). All but one series of images showed a collapse process in which the trachealis muscle invaginated asymmetrically, i.e., the muscle appeared to favor one side of the cartilage ring system more than the other. The connecting tissue between the cartilage rings appeared to be more compliant than the rings themselves, thus suggesting that the tracheal lumen became corrugated at negative pressures. In the plane of a cartilage ring, the lumen appeared to remain patent at pressures as low as -95 cmH2O. However, between rings, where the tracheal wall was more compliant, the lumen appeared to be totally occluded at -53 cmH2O. Lumen areas in both the plane of the cartilage rings and in a plane between rings were measured from each series of printed images for six tracheas. These measurements, when normalized, averaged, and plotted against transmural pressure gave asymptotic logarithmic compliances (n1 in the model of Lambert et al., J. Appl. Physiol. 52: 44-56, 1982) of 1.2 +/- 0.4 and 20 +/- 7 for the interring and ring regions, respectively. These values are greater than the critical value of 0.5 (J. Appl. Physiol. 62: 2426-2435, 1987) and are thus consistent with wave speed flow limitation being possible anywhere in the trachea during forced expiration.     

Long-term survival after isolated replacement of mitral valve with ball-valve prosthesis.

In 111 patients whose diseases mitral valve was replaced with a ball-valve prosthesis the actuarial survival rate, including the hospital mortality of 10.8%, was 66% after 5 years and 59% after 8 years of follow-up. This suggests that in patients with moderate or severe symptoms due to mitral valve disease, replacing the valve can prolong life. However, in patients with no cardiac symptoms or with sinus rhythm and mild symptoms, it is doubtful that mitral valve replacement can prolong life, for the prognosis in these patients is favourable without operation.     

Asynchronous and density-dependent germination: the spreading of risk in Plumatella emarginata

I examined both temporal and spatial aspects of the germination of asexually produced sessoblasts of the phylactolaemate bryozoan Plumatella emarginata. The majority of sessoblasts germinated over a 5-week period from April to May; low frequencies of germination were observed from June to September. During May and June high sessoblast density further enhanced asynchrony. Risk spreading in response to both unpredictable disturbances and high sessoblast density may explain asynchronous germination in this system.     

Some biophysical applications of motional contrast in n.m.r. microscopy

The principal advantage of the n.m.r. imaging method lies in the specific contrasts which are available. In this work we describe the use of velocity and diffusion contrast methods in biophysical applications and at microscopic spatial resolution. In the first example, involving water-protein interactions, the relationship between water self-diffusion and water concentration, as measured using pulsed gradient spin echo n.m.r., is shown. It is demonstrated that this relationship can be used to provide a water concentration image. The result is compared with the conventional proton density and transverse relaxation maps. The next example concerns the use of dynamic n.m.r. microscopy to obtain water diffusion and velocity maps for wheat grain in vivo. Finally we suggest how the method may be used in the study of polymer-water interactions in an unusual adjunct to conventional polymer self-diffusion studies.     

Hearing disability in people aged 50-65: effectiveness and acceptability of rehabilitative intervention.

OBJECTIVE--To determine the best means of detecting hearing disability in subjects aged 50-65 and whether rehabilitative intervention is acceptable in this age group. DESIGN--Questionnaire survey of patients on general practice age-sex registers. Two types of questionnaire were used, one being based on the closed set approach of the Institute of Hearing Research questionnaire, which had been used in a pilot study, and the other being a simplified version of this questionnaire developed by the Welsh Hearing Institute and based on open set questions. Questionnaires were sent up to three times, and any patients who had not responded two months after the last posting were personally contacted. SETTING--Two general practices in Glyncorrwg and Blaengwynfi in the Afan valley, West Glamorgan. PATIENTS--271 Patients in Glyncorrwg (136 men, 135 women) and 333 patients in Blaengwynfi (173 men, 160 women) aged 50-65. INTERVENTIONS--All patients indicating hearing disability in answering the questionnaires were invited to attend for a evaluative session in their village. After audiometric testing advice and arrangements for fitting a hearing aid were offered as appropriate. MAIN OUTCOME MEASURES--Response rates and prevalence of hearing disability before intervention and of possession of hearing aids before and after intervention. RESULTS--After three postings and personal contact the response rate was 98% (266/271) in Glyncorrwg, where the complex questionnaire was used, and 97% (322/333) in Blaengwynfi. The prevalence of hearing disability was respectively 53% (141/266) and 46% (148/322) and the prevalence of owning a hearing aid 7% (19/266) and 8% (24/322). After intervention the possession of hearing aids rose to 24% (64/266) in Glyncorrwg and 22% (71/322) in Blaengwynfi; six months later the aids were being used regularly. A direct comparison of the two questionnaires in 69 subjects from Blaengwynfi showed no significant differences in the amount of disability detected by each one. The first posting of questionnaires detected 65% (189/289) of the hearing disability in the two villages or 78% (72/92) of those prepared to accept hearing aids for the first time; 96% (88/92) of those who accepted hearing aids were detected by two postings. CONCLUSIONS--Simple questionnaires are effective in detecting hearing disabilities in people aged 50-65, and intervention was acceptable in many of those who reported having difficulties in hearing. The response rates from successive postings suggest that two postings are sufficient in terms of the return in detecting those who will accept intervention.     

Phosphorylation and biosynthesis of high molecular weight proteins of tumor nuclear matrix

INTRODUCTIONAsearlyasin1948wehavefr8CtionatedisolatednucleifromnormalandtumorcellsbyextractionwithiMNaCIanddilutealkali[1].Thenuclearresiduewasthenstudiedmorethoroughly[2,3].Lateron,sillillarproteinousnuclearresidueswereisolatedbyotherworkers[46]andasstud…     

The use of variance in enzyme activity as an indicator of long-term exposure to toxicant-stressed environments in Culex pipiens mosquitoes

1. The identification of easy to use and cheap biomarkers is important as a means of determining whether animals are developing under stressful environmental conditions. Previous studies have indicated that the variance about the mean esterase activity in toxic environments increases in the absence of a significant shift in the mean value, suggesting that variance levels may have potential as a biomarker of toxicant-stressed or otherwise stressful environments.
2. Several field and laboratory populations of the mosquito, Culex pipiens , were examined for esterase activities using a colorimetric assay and levels of polymorphism using polyacrylamide gel electrophoresis. Some of these populations had been exposed to environmental toxicants (organophosphorus (OP) insecticides).
3. The OP-stressed field population had lower levels of polymorphism as indicated by fewer electromorphs than the populations that had not been exposed to OPs. However, the mean level of esterase activity was higher in the OP-stressed populations.
4. Despite having lower genetic variation, the OP-stressed populations showed much higher levels of variation about the mean enzyme activity, at least two orders of magnitude higher, than the unstressed populations. Knowledge of the genetics of OP resistance in these populations confirmed that the increase in variance was not due to the general switching on of genes in response to stress.
5. One field population that had been exposed to heavy metal pollution had similar levels of esterase activity and variation about the mean as the unstressed populations, suggesting that variation only increases in characters directly affected by the environmental pollutant.
6. The probable factors causing the increase in variance and the potential of this type of variation as a biomarker of stressful environments are discussed.     

Algorithms and software for support of gene identification experiments

MOTIVATION: Gene annotation is the final goal of gene prediction algorithms. However, these algorithms frequently make mistakes and therefore the use of gene predictions for sequence annotation is hardly possible. As a result, biologists are forced to conduct time-consuming gene identification experiments by designing appropriate PCR primers to test cDNA libraries or applying RT-PCR, exon trapping/amplification, or other techniques. This process frequently amounts to 'guessing' PCR primers on top of unreliable gene predictions and frequently leads to wasting of experimental efforts. RESULTS: The present paper proposes a simple and reliable algorithm for experimental gene identification which bypasses the unreliable gene prediction step. Studies of the performance of the algorithm on a sample of human genes indicate that an experimental protocol based on the algorithm's predictions achieves an accurate gene identification with relatively few PCR primers. Predictions of PCR primers may be used for exon amplification in preliminary mutation analysis during an attempt to identify a gene responsible for a disease. We propose a simple approach to find a short region from a genomic sequence that with high probability overlaps with some exon of the gene. The algorithm is enhanced to find one or more segments that are probably contained in the translated region of the gene and can be used as PCR primers to select appropriate clones in cDNA libraries by selective amplification. The algorithm is further extended to locate a set of PCR primers that uniformly cover all translated regions and can be used for RT-PCR and further sequencing of (unknown) mRNA.