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W C Black

Publications and source records attributed to W C Black.

At least 19 recordsLinked to original sources
PubMed1992

Genetic diversity at electrophoretic loci in the house fly, Musca domestica L.

Vertical polyacrylamide gel electrophoresis was used to separate enzyme proteins at 73 putative loci in natural house fly populations sampled in central Iowa. Thirty-nine of the loci were polymorphic (53%). The mean effective number of alleles per polymorphic locus was 1.93 and 1.47 alleles among 68 scored loci. Observed and expected heterozygosities at 34 house fly loci were 0.1628 and 0.1834, respectively. No statistically significant differentiation was detected among nine central Iowa fly populations in 1989 or among nine Iowa and three Minnesota populations in 1990.

Animals↗
PubMed1992

Analysis of isozyme loci in the face fly, Musca autumnalis DeGeer.

Vertical polyacrylamide gel electrophoresis was used to resolve enzymes at 50 putative loci in Iowa face flies, a recently arrived, colonizing, Palearctic species. Sixty-two percent of the 50 loci were polymorphic. The mean number of alleles per polymorphic locus was 3.2 +/- 1.38; the mean among all loci was 2.38 +/- 1.62 alleles. The effective number of alleles among 50 loci was 1.4 +/- 0.62. Mean observed and expected heterozygosities for the 50 face fly loci were 0.167 +/- 0.037 and 0.186 +/- 0.031, respectively. Comparison of the electrophoretic data for Musca autumnalis and for M. domestica L. showed similar high levels of gene diversity. A survey of gene diversity at 12 loci among six geographically independent laboratory colonies demonstrated statistically significant genetic differentiation that was probably due to drift after colonization.

Animals↗
PubMed1992

Random amplified polymorphic DNA of mosquito species and populations (Diptera: Culicidae): techniques, statistical analysis, and applications.

A polymerase chain reaction (PCR)-based method is described for the identification and differentiation of mosquito species and populations. The method, described first by Williams et al. (1990), employs single 10 base-long primers of arbitrary DNA sequence and results in the amplification of random segments of DNA known as random amplified polymorphic DNA (RAPD). We wished to determine if RAPD of mosquito DNA could be used for the differentiation of species and populations, identification of unknown specimens, and the reconstruction of phylogeny. RAPD of mosquito DNA results in the amplification of a series of DNA fragments of varying length. Most amplified fragments are unique to an individual; however, our data indicated that in each of the five species of Aedes examined, some fragments are species-specific and are present in all individuals of that species. This enabled us to derive a diagnostic profile for each of the five species. A nearest-neighbor analysis of all the amplified DNA fragments discriminated among species on a multivariate basis. Several individuals of Aedes albopictus (Skuse), included in the analysis as "unknowns," were correctly identified as belonging to Ae. albopictus. UPGMA clustering of presence-absence data enabled the separation of different Aedes species as well as different populations of Ae. albopictus. The entomological applications of RAPD include the construction of diagnostic profiles for species identification and differentiation among conspecific populations.

Aedes↗
PubMed1992

Use of genetic polymorphisms detected by the random-amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) for differentiation and identification of Aedes aegypti subspecies and populations.

Amplification of random regions of genomic DNA using 10-base primers in the random-amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) was used to differentiate and identify mosquito populations based on genetic variation. Genomic DNA was extracted from individual mosquitoes from 11 geographic populations of Aedes aegypti and amplified in PCR reactions using single primers of arbitrary nucleotide sequence. Discriminant analysis of the population frequencies of RAPD fragments produced using three different primers allowed accurate discrimination between the geographic populations in 89% of individuals and between subspecies (Ae. aegypti aegypti versus Ae. aegypti formosus) in 100% of mosquitoes tested. The genetic relatedness of the populations was estimated using three different statistical methods, and unknown populations were correctly classified in a blind test. These results indicate that the RAPD-PCR technique will be useful in studies of arthropod molecular taxonomy and in epidemiologic studies of the relatedness of geographic populations and vector movement.

Aedes↗
PubMed1991

Geographic origin of the US and Brazilian Aedes albopictus inferred from allozyme analysis.

A survey of genetic variation using allozymes was conducted on 57 populations of Aedes albopictus, an Asian mosquito that was introduced into the US and Brazil in the mid-1980s. Our objective was to quantify the patterns of genetic variation among its populations and to use that information to trace genetically the geographic origin of the US and Brazilian populations. Populations from the various regions were genetically distinct from one another. Populations from within a region were genetically similar to one another, which resulted in a significant positive correlation between geographic and genetic distances. A discriminant analysis of allele frequencies separated populations from the various countries into nine non-overlapping clusters; the US, Japanese, Chinese and Brazilian populations formed closely placed, but distinct, clusters. The probability of assigning a population to the correct country was 98 per cent. The US and the Brazilian populations were closest in terms of genetic distance from the Japanese populations. Based on discriminant and genetic distance analyses, we conclude that the US and the Brazilian Aedes albopictus originated in Japan.

Aedes↗
PubMed1990

Temporal variation in genetic structure of a colonising species: Aedes albopictus in the United States.

The medically important mosquito, Aedes albopictus, has recently become established in several locations within the United States. A three-year survey of temporal variation in allele frequencies at ten enzymatic loci in 17 populations was undertaken to determine the extent and direction of change since the colonization event. Significant, but non-directional, changes were detected in allele frequencies at most of the loci in all populations. Some alleles detected at low frequencies in earlier samples were not found in subsequent samples. Variance of allele frequencies remained unchanged. In at least two locations, there was an increase in mean heterozygosity, perhaps because of gene flow. There was no significant change in the levels of genetic variation within and among populations. The results from this study indicate that the breeding structure of Ae. albopictus in the U.S. did not differ substantially from that in a native habitat, either soon after colonisation or after several generations in the new habitat. We suggest that a large founder population, gene flow and a rapid population expansion could explain the present breeding structure of Ae. albopictus.

Aedes↗
PubMed1990

Histologic correlations with the clinical diagnosis of dysplastic nevus.

In melanoma kindreds the presence of dysplastic nevi correlates with greatly increased melanoma risk. The relative importance of sporadic, nonfamilial dysplastic nevi as a risk factor for melanoma is less certain. Although the clinical features of dysplastic nevi have been well described, the histologic basis for the diagnosis is not as firmly established. This study examines the degree of correspondence between the clinical and histopathologic diagnosis of dysplastic nevus. Histologic review of nevi with clinical features of dysplasia from 1,000 individuals demonstrated classic histologic features of dysplasia (as previously demonstrated in melanoma kindreds) in 54.7%. In 20.4% of patients, nevi displayed less convincing or only partially developed features of dysplasia. The remaining patients (24.9%) had nevi of other types. Correspondence between the clinical and histologic diagnosis of dysplasia was best for lesions from the trunk and in individuals beyond the age of 20 years. This study supports the validity of the dysplastic nevus as a clinical and pathologic entity.

Adolescent↗
PubMed1989

Patterns of variation in the rDNA cistron within and among world populations of a mosquito, Aedes albopictus (Skuse).

A restriction map was constructed of the ribosomal cistron in a mosquito, Aedes albopictus (Skuse). The 18s, 28s and nontranscribed spacer (NTS) regions were subcloned and used to probe for intraspecific variation. Seventeen populations were examined throughout the world range of the species. No variation was detected in the coding regions but extensive and continuous variation existed in the NTS. The NTS consisted of two nonhomologous regions. The first region contained multiple 190-bp AluI repeats nested within larger XhoI repeats of various sizes. There was a large number of length variants in the AluI repeat region of the NTS. No repeats were found in the second region and it gave rise to relatively fewer variants. An analysis of NTS diversity in individual mosquitoes indicated that most of the diversity arose at the population level. Discriminant analysis was performed on spacer types in individual mosquitoes and demonstrated that individuals within a population carried a unique set of spacers. In contrast with studies of the NTS in Drosophila populations, there seems to be little conservation of spacers in a population. The importance of molecular drive relative to drift and selection in the generation of local population differentiation is discussed.

Aedes↗
PubMed1989

Laboratory study of competition between United States strains of Aedes albopictus and Aedes aegypti (Diptera: Culicidae).

Mosquito abatement workers in Houston, Tex., and New Orleans, La., have observed that the recent introduction of Aedes albopictus (Skuse) has been accompanied by a decline and virtual disappearance of Ae. aegypti (L.). This suggests competitive displacement but contradicts the direction of displacement observed in native habitats of Ae. albopictus. The paper reports a series of laboratory studies on competition between U.S. strains of the two species. Larval survivorship, size, and development time were monitored in increasing densities of pure and mixed cultures of the two species under limited and optimal diets. Oviposition preferences were examined by offering gravid females cups containing first or fourth instars of either species. Ethological isolation was studied by simultaneously offering virgin females of one species to males of both species and monitoring courtship behavior as well as rates of oviposition, percentage of hatch, and embryonation. The results of the larval competition studies suggest that interspecific competition increased development time only slightly and had no effect on survival of Ae. albopictus. Competition increased survival in Ae. aegypti. Size of both species was influenced by interspecific competition, but the magnitude and direction of the effect was inconsistent between strains and diets such that neither species emerged consistently larger. The results of the oviposition study indicated a higher fecundity in Ae. aegypti but otherwise demonstrated that both species oviposit without regard to the presence, age, or species of larvae in the oviposition container. The ethological isolation tests demonstrated that Ae. aegypti males were more sexually aggressive than males or Ae. albopictus. However, Ae. albopitus females placed with increasing densities of Ae. aegypti males demonstrated no decrease in rates of oviposition, and eggs laid showed equal rates of hatch and embryonation. In general, the results do not suggest that the U.S Ae. albopictus population is inherently more competitive in the laboratory than Ae. aegypti. Other reasons for the observed decline in Ae. aegypti in the United States are discussed.

Aedes↗
PubMed1988

Residual dysplastic and other nevi in superficial spreading melanoma. Clinical correlations and association with sun damage.

Excision biopsies of 500 invasive superficial spreading melanomas were examined for evidence of residual melanocytic dysplasia (remnants of dysplastic nevi). Melanocytic dysplasia was identified in 32.4% of tumors. Remnants of nevi without melanocytic dysplasia were found in 9.8%. Sun damage as evidenced by solar elastosis was histologically estimated in contiguous skin. Patients' age at diagnosis, tumor site, pathologic stage, evidence of tumor regression, and coexisting sun damage were correlated with the presence or absence of melanocytic dysplasia. Patients whose tumors displayed residual dysplasia were younger and demonstrated a more favorable tumor stage and less evidence of sun damage. Melanomas on the trunk were more likely to be associated with melanocytic dysplasia than those from other areas. The findings support the belief that dysplastic nevi have an important role in the genesis of superficial spreading melanoma. The influence of ultraviolet radiation in the development of dysplastic nevi and in their potential malignant progression is discussed.

Adult↗
PubMed1988

Radiologic features of retroperitoneal cystic hamartoma.

Retroperitoneal cystic harmartoma is a rare tumor believed to originate from small portions of the embryonic tailgut that normally disappear in early fetal development. Depending on the location and size of the mass, a wide range of clinical presentations is associated with the lesion. Most lesions are found in the presacrococcygealretrorectal space, but they may also occur in other retroperitoneal locations. Computed tomography (CT) is the most sensitive radiologic study for detecting these tumors, which usually are small, round, sharply marginated, and of homogeneous soft tissue density. We describe the clinical, radiographic, and pathologic features in four patients. In three cases, the lesions occurred in the perirectal space, and in one it was found in the iliac fossa. In this last case, there was an additional lesion in the perinephric region.

Adolescent↗