Biomedical subjects

S Pelikan

Publications and source records attributed to S Pelikan.

5 recordsLinked to original sources

PubMed1999

Genetic diversity of Typha latifolia (Typhaceae) and the impact of pollutants examined with tandem-repetitive DNA probes.

Genetic diversity at variable-number-tandem-repeat (VNTR) loci was examined in the common cattail, Typha latifolia (Typhaceae), using three synthetic DNA probes composed of tandemly repeated "core" sequences (GACA, GATA, and GCAC). The principal objectives of this investigation were to determine whether: (1) the previously reported almost complete lack of polymorphism at allozyme loci in this species was indicative of a reduced amount of genetic diversity at VNTR loci as well; (2) VNTR markers were informative about possible clonal propagation; and (3) significant differences in genetic structure of sampling sites were associated with differences in environmental levels of pollutants at those sites. Previously, widespread sampling across the eastern United States, surveying across ten allozyme loci, has detected only two genotypes, involving a difference at a single locus, among 104 populations. In this study, the amount of genetic diversity detected at VNTR loci: (1) among ramets (N = 40; 40 genotypes detected) collected at ∼8-km intervals along a 320-km transect; (2) among ramets (N = 220; 117 genotypes detected) from five study sites separated by 50-3000 m; and (3) even among ramets within each study site [N = 44 per site; from 13 to 34 genotypes detected per site (270 m(2))] exceeds that previously found in those more geographically widespread allozyme surveys. Among the 260 ramets analyzed here, the mean number of bands scored per individual was 48.61 (SD = 2.80). Mean genetic similarity among ramets collected along the 320-km transect was 0.91, which was within the range of mean genetic similarity within the five study sites (range: 0.89-0.95). Among the five study sites, 61% of the samples analyzed appeared to be clonal ramets, with up to 12 clones detected for 44 ramets sampled within a site. Clones grew intermingled and ranged up to 39 m in extent. Permutation tests of genetic similarity revealed significant genetic differentiation between each of the five study sites. Consistent with the previous allozyme studies, T. latifolia was characterized by extremely low genetic variation relative to levels of polymorphism detected at VNTR loci in other plant species. Estimated heterozygosity among ramets along the 320-km transect ranged from 0.11 to 0.13, while that within the five study sites ranged from 0.05 to 0.12. Estimates of F(st) (0.32-0.41) also indicated considerable genetic subdivision among these stands. Significantly higher genetic diversity was detected at the two study sites that chemistry and toxicity data indicate to be the most severely impacted by pollutants. Although this correlation does not establish cause and effect, the results of this study indicate that the analysis of genetic diversity at VNTR loci may be a useful tool for monitoring anthropogenic-induced changes in the genetic structure of natural populations of plants.

Journal Article↗

PubMed1996

GELSTATS: a computer program for population genetics analyses using VNTR multilocus probe data.

GELSTATS, a computer program for population genetics analyses utilizing genetic markers revealed with variable number tandem repeat (VNTR) multilocus probes, is described and made available (both as C++ source code and as an executable DOS program). The program calculates several population genetics parameters, including: (i) individual and population band numbers; (ii) population bands exhibiting complete linkage (redundant examples of such bands can be removed in subsequent analyses); (iii) similarity (fraction of bands shared) between individuals and average similarity within and between designated groups; (iv) estimated probability that two individuals chosen at random will have identical band profiles; (v) heterozygosity estimates for designated groups; and (vi) Fst estimates. Nonparametric permutation methods are used to assess the significance of differences in both within- and between-group similarity. A jackknife test for heterozygosity differences between groups is also computed. Examples of GELSTATS analyses illustrate some features of the program.

Animals↗

PubMed1993

Effects of lead time, length bias, and false-negative assurance on screening for breast cancer.

This article presents a model of breast cancer screening programs. The model shows the effects of the screening threshold, screen sensitivity, and false-negative assurance on the cumulative mortality rate in the screened population. It shows that factors of screen design and a penalty associated with false-negative assurance can result in excess mortality rates in screened populations--especially in those age classes in which the incidence of rapidly growing tumors is high. Factors related to the magnitude of this effect are described.

Adult↗

PubMed1992

Microvascular ischemia-reperfusion injury in striated muscle: significance of "reflow paradox".

Ischemia-reperfusion (I/R)-induced microvascular injury is characterized by capillary "no-reflow" and reflow-associated events, termed "reflow paradox," including leukocyte-endothelium interaction and increase in microvascular permeability. The major objectives of this study were 1) to elucidate the significance of reflow paradox after 4 h of tourniquet-induced ischemia in striated muscle and 2) to determine the role of reactive oxygen metabolites in the pathogenesis of reflow paradox-dependent microcirculatory alterations. By use of in vivo fluorescence microscopy in a striated muscle preparation of hamsters, leukocyte-endothelium interaction in postcapillary venules and macromolecular extravasation from capillaries and venules were quantified before ischemia and after 30 min, 2 h, and 24 h of reperfusion. I/R elicited marked enhancement (P < 0.01) of leukocyte rolling during initial reperfusion and a 20-fold increase of leukocyte adherence (P < 0.01) lasting for the entire postischemic reperfusion period (n = 7). These phenomena were accompanied by significant leakage (P < 0.01) of macromolecules from capillaries and in particular from postcapillary venules (n = 9). Both superoxide dismutase (SOD, 20 mg/kg body wt, n = 7) and allopurinol (50 mg/kg body wt, n = 7) were effective in attenuating I/R-induced leukocyte rolling and adherence. In addition, microvascular leakage was significantly reduced by allopurinol (n = 9) and completely abolished by SOD (n = 9) (P < 0.01). These results support the concept that reactive oxygen metabolites contribute to I/R-induced reflow paradox, resulting in leukocyte accumulation, adherence, and increase in microvascular permeability.

Allopurinol↗

PubMedDate not supplied

Buflomedil hydrochloride attenuates tourniquet-induced microvascular reperfusion injury in striated muscle.

With the use of intravital fluorescence microscopy and the dorsal skinfold chamber model we studied the effect of buflomedil hydrochloride on microvascular reperfusion injury after 4 h of tourniquet-induced ischemia in hamster striated muscle. Animals (n = 15) received 3 mg/kg buflomedil (i.v. bolus) 5 min before onset of reperfusion, and 3 mg/kg buflomedil (continuous i.v. infusion) during the first 20 min of reperfusion. Animals (n = 13) receiving equivalent volumes of saline served as controls. Tourniquet-induced ischemia resulted in (a) a marked decrease of functional capillary density and (b) accumulation and adherence of leukocytes in postcapillary venules after 30 min and 2 h of reperfusion. This was associated with an increased microvascular permeability (leakage of macromolecules), reflecting the alteration of endothelial cell integrity. Treatment with buflomedil significantly reduced both post-ischemic capillary perfusion failure and leukocyte adherence in venules. Concomitantly, the increase of microvascular permeability in postcapillary venules was almost prevented, indicating the beneficial effect of buflomedil on the manifestation of microvascular reperfusion injury following tourniquet ischemia in striated muscle.

Animals↗