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F Yoder

Publications and source records attributed to F Yoder.

7 recordsLinked to original sources
PubMed1996

Entomopathogenic nematode (Heterorhabditidae and Steinernematidae) spatial distribution in turfgrass.

Understanding the temporal and spatial distribution of entomopathogenic nematodes is essential for determining the role of these insect parasites in soil communities and ultimately for their use in suppression of pest insect populations. We measured the vertical and horizontal distribution of endemic populations of entomopathogenic nematodes (Steinernema carpocapsae and Heterorhabditis bacteriophora) in turfgrass. Vertical distribution was determined by taking soil cores every 3 h from 05.00 to 23.00 h, over 4 days, and dividing the cores into 8, 1 cm deep sections. Steinernema carpocapsae was recovered primarily near the soil surface: 50% of positive sections were recovered in the thatch or first 1 cm of soil. S. carpocapsae recovery was lower during the middle of the day and none were recovered in the upper section. H. bacteriophora was recovered uniformly throughout the top 8 cm of soil and its vertical distribution did not change over the course of the day. Horizontal distribution was measured as the number of nematodes recovered from cores taken from 12 randomly selected 0.3 x 0.8 m sections from within four 15.3 x 15.3 m plots. Samples were collected biweekly over a 9-month period. H. bacteriophora had a patchier distribution than S. carpocapsae and both nematode species had more patchy distributions then their potential hosts. Our results support the hypothesis that these two species of nematode utilize different foraging strategies; S. carpocapsae primarily a surface adapted ambusher and H. bacteriophora as a cruise forager.

Animals↗
PubMed1991

Assessment of chronic gamma radiosensitivity as an in vitro assay for heterozygote identification of ataxia-telangiectasia.

Ataxia-telangiectasia (A-T) is a rare human autosomal recessive disorder characterized by, among other symptoms, catastrophic reaction to conventional radiotherapy. A-T heterozygotes are clinically asymptomatic and their fibroblasts are intermediate in radiosensitivity between homozygotes and normals. We have attempted to identify heterozygotes by assaying for cellular hypersensitivity to chronic gamma irradiation. Cultured dermal fibroblast strains from 13 control subjects and 55 members from a large Amish pedigree segregating for A-T were assayed for loss of colony-forming ability (CFA) in response to 137Cs gamma radiation delivered at a dose rate of 0.8 cGy/min. For each strain, multiple dose-response curves were summarized in a composite D10 value (dose, in cGy, reducing colony survival to 10%). The D10's of the clinically normal controls and of those pedigree members with known A-T genotype formed a trimodal distribution, with the seven obligate heterozygotes displaying an average value (516 cGy) intermediate between that of the 10 healthy controls (797 cGy) and that of the two affected patients (154 cGy). The D10's were modeled statistically using Gaussian penetrance functions. The most parsimonious model yielded a significant difference in D10 means for heterozygotes and normal homozygotes, a significant donor age effect, but no sex effect. We compared probabilistic identification of heterozygotes based on D10 values with identification based on linkage data for two markers, THY1 and D11S144, closely linked to the A-T gene. This comparison revealed that the D10 data were appreciably less informative than the linked markers. Indeed, the extensive overlap between D10 values for heterozygotes and normal homozygotes precludes the use of postirradiation CFA for either accurate identification of heterozygotes or chromosomal mapping of the A-T gene.

Ataxia Telangiectasia↗
PubMed1978

The Rieger syndrome.

Fourteen patients with hypodontia and the ocular features of the Rieger syndrome were examined for the presence of systemic anomalies. A periumbilical defect that consisted of failure of the periumbilical skin to involute was seen in ten of the thirteen evaluated for the defect. Three others had scars over the umbilical area and had a history of surgery for herniation. In addition, four males in one family and one male from another family had hypospadias. None of several other anomalies reported to be components of the Rieger syndrome by other authors was detected in the fourteen patients. The mode of inheritance in the familial cases studied was compatible with autosomal dominance. The results of this study indicate that the Rieger syndrome is an autosomal dominant syndrome whose cardinal features are hypodontia, goniodysgenesis, and failure of the periumbilical skin to involute properly.

Abnormalities, Multiple↗
PubMed1977

Flicker fusion thresholds in Best macular dystrophy.

Flicker fusion threshold intensities were measured as a function of flicker frequency for patients with Best macular dystrophy having normal or near-normal Snellen visual acuity. These data were found to differ from normal in ways that may be interpreted to be an abnormal elevation of the foveal cone threshold, a loss of cone temporal resolution, or both. The results led to the conclusion that Best macular dystrophy affects the neurosensory retina even when Snellen visual acuity is normal.

Flicker Fusion↗
PubMed1977

Familial aniridia with preserved ocular function.

Of 76 members of a large pedigree with familial aniridia, 61% of the 38 affected patients had visual acuity of 6/9 (20/30) or better and only 5% had acuity of 6/60 (20/200) or worse. Cataracts were present in 18% of affected patients; glaucoma in 13%; and strabismus in 34%. Sixteen percent of affected patients had strabismic amblyopia. No patient had nystagmus or corneal pannus. The good visual acuity in this family, as compared to that in others, indicates that the absence of iris tissue alone cannot account for the severe visual problems usually associated with aniridia.

Adolescent↗
PubMed1976

Familial nanophthalmos.

Four members of one sibship had microphthalmos with fundi having an irregular "rippled* appearance with alternating light and dark red coloration. Fluorescein angiography revealed patchy choriocapillaris perfusion with unusually rapid diffusion into the retina. Genealogic and geographic data strongly suggest autosomal-recessive inheritance. Only one patient developed glaucoma. The unique combination of abnormalities in this family suggests that a new recessive mutation may be responsible.

Aged↗