Search PubMed⌕ Search

Biomedical subjects

C W Fox

Publications and source records attributed to C W Fox.

At least 19 recordsLinked to original sources
PubMed2006

Selection on body size and sexual size dimorphism differs between host species in a seed-feeding beetle.

Sexual size dimorphism varies substantially among populations and species but we have little understanding of the sources of selection generating this variation. We used path analysis to study how oviposition host affects selection on body size in a seed-feeding beetle (Stator limbatus) in which males contribute large ejaculates (nuptial gifts) to females. Females use nutrients in these ejaculates for egg production. Male body size, which affects ejaculate size, affects female fecundity and is thus under fecundity selection similar in magnitude to the fecundity selection on female body size. We show that when eggs are laid on a host on which larval mortality is low (seeds of Acacia greggii) fecundity predicts fitness very well and fecundity selection is the major source of selection on both male and female adult size. In contrast, when eggs are laid on a host on which larval mortality is high (seeds of Parkinsonia florida) fecundity poorly predicts fitness such that fecundity selection is relaxed on both male and female size. However, because egg size affects larval mortality on this poor host (P. florida) there is selection on female size via the female size --> egg size --> fitness path; this selection via egg size offsets the reduction in fecundity selection on female, but not male, body size. Thus, differences in host suitability (due to differences in larval mortality) affect the relative importance of two sources of selection on adult body size; fecundity selection on both male and female body size is lower on the poor quality host (P. florida) relative to the high quality host (A. greggii) whereas selection on female body size via effects of egg size on offspring survival (body size --> egg size --> fitness) is greater on the poor quality host relative to the high quality host. Because selection via the egg size path affects only females the difference in larval survival between hosts shifts the relative magnitude of selection on female vs. male size. Researchers working on other study systems should be alerted to the possible importance of subtle, but consequential, indirect selection on their study organisms.

Animals↗
PubMed2004

Evolutionary genetics of lifespan and mortality rates in two populations of the seed beetle, Callosobruchus maculatus.

The age at which individuals die varies substantially within and between species, but we still have little understanding of why there is such variation in life expectancy. We examined sex-specific and genetic variation in adult lifespan and the shape of mortality curves both within and between two populations of the seed beetle, Callosobruchus maculatus, that differ in a suite of life history characters associated with adaptation to different host species. Mean adult lifespan and the shape of the logistic mortality curves differed substantially between males and females (males had lower initial mortality rates, but a faster increase in the rate of mortality with increasing age) and between populations (they differed in the rate of increase in mortality with age). Larger individuals lived longer than smaller individuals, both because they had lower initial mortality rates and a slower increase in the rate of mortality with increasing age. However, differences in body size were not adequate to explain the differences in mortality between the sexes or populations. Both lifespan and mortality rates were genetically variable within populations and genetic variance/covariance matrices for lifespan differed between the populations and sexes. This study thus demonstrated substantial genetic variation in lifespan and mortality rates within and between populations of C. maculatus.

Animals↗
PubMed2004

Genetic architecture of population differences in oviposition behaviour of the seed beetle Callosobruchus maculatus.

Few studies have examined the genetic architecture of population differences in behaviour and its implications for population differentiation and adaptation. Even fewer have examined whether differences in genetic architecture depend on the environment in which organisms are reared or tested. We examined the genetic basis of differences in oviposition preference and egg dispersion between Asian (SI) and African (BF) populations of the seed beetle, Callosobruchus maculatus. We reared and tested females on each of two host legumes (cowpea and mung bean). The two populations differed in mean oviposition preference (BF females preferred cowpea seeds more strongly than did SI females) and egg dispersion (SI females distributed eggs more uniformly among seeds than did BF females). Observations of hybrid and backcross individuals indicated that only the population difference in oviposition preference could be explained by complete additivity, whereas substantial dominance and epistasis contributed to the differences in egg dispersion. Both rearing host and test host affected the relative magnitude of population differences in egg dispersion and the composite genetic effects. Our results thus demonstrate that the relative influence of epistasis and dominance on the behaviour of hybrids depends on the behaviour measured and that different aspects of insect oviposition are under different genetic control. In addition, the observed effect of rearing host and oviposition host on the relative importance of dominance and epistasis indicates that the genetic basis of population differences depends on the environment in which genes are expressed.

Adaptation, Physiological↗
PubMed2004

Complex genetic architecture of population differences in adult lifespan of a beetle: nonadditive inheritance, gender differences, body size and a large maternal effect.

Evolutionary responses to selection can be complicated when there is substantial nonadditivity, which limits our ability to extrapolate from simple models of selection to population differentiation and speciation. Studies of Drosophila melanogaster indicate that lifespan and the rate of senescence are influenced by many genes that have environment- and sex-specific effects. These studies also demonstrate that interactions among alleles (dominance) and loci (epistasis) are common, with the degree of interaction differing between the sexes and among environments. However, little is known about the genetic architecture of lifespan or mortality rates for organisms other than D. melanogaster. We studied genetic architecture of differences in lifespan and shapes of mortality curves between two populations of the seed beetle, Callosobruchus maculatus (South India and Burkina Faso populations). These two populations differ in various traits (such as body size and adult lifespan) that have likely evolved via host-specific selection. We found that the genetic architecture of lifespan differences between populations differs substantially between males and females; there was a large maternal effect on male lifespan (but not on female lifespan), and substantial dominance of long-life alleles in females (but not males). The large maternal effect in males was genetically based (there was no significant cytoplasmic effect) likely due to population differences in maternal effects genes that influence lifespan of progeny. Rearing host did not affect the genetic architecture of lifespan, and there was no evidence that genes on the Y-chromosome influence the population differences in lifespan. Epistatic interactions among loci were detectable for the mortality rate of both males and females, but were detectable for lifespan only after controlling for body size variation among lines. The detection of epistasis, dominance, and sex-specific genetic effects on C. maculatus lifespan is consistent with results from line cross and quantitative trait locus studies of D. melanogaster.

Animals↗
PubMed2001

Genetic architecture of adaptive differentiation in evolving host races of the soapberry bug, Jadera haematoloma.

To explore genetic architecture and adaptive evolution, we conducted environmental and genetic experiments with two recently (ca. 100 generations) diverged, geographically adjacent races of the soapberry bug. One race occurs on a native host plant species, the other on an introduced host. We focused on three traits: length of the mouthparts, body size and development time. The first experiment was an environmental manipulation, comparing individuals of each population reared on one or the other host species ('cross-rearing') and estimating three evolutionary rates for each trait. The first rate, 'evolutionary path' compares ancestral-derived populations when both were reared on the introduced host. The second, 'current ecological contrast' compares populations with each reared on its natal host. The third, 'evolved tradeoff' compares the two races when reared on the native host. Differences among these rates are striking and informative. For example, development time, which appears to be relatively undifferentiated phenotypically, has actually evolved very rapidly via countergradient selection. The pattern differs for each trait, and clear developmental tradeoffs have evolved as quickly as adaptation to the new host in each. The second experiment was a two-generation 'line cross' study. With joint-scaling analyses, we compared purebred, hybrid and backcrossed individuals to describe genetic architecture. Additive genetic variance for mouthpart length was consistently large (ca. 60%), but the interaction of dominance, maternal effects and epistasis was important in the other traits. Rearing host strongly affected genetic architecture. There was no clear relationship between genetic architecture and rate of evolution. Selection has produced both additive and nonadditive differentiation between the host races with surprising speed, consistent with theoretical predictions about evolution in fitness-associated traits.

Adaptation, Biological↗
PubMed2000

Evolutionary ecology of progeny size in arthropods.

Most models of optimal progeny size assume that there is a trade-off between progeny size and number, and that progeny fitness increases with increasing investment per young. We find that both assumptions are supported by empirical studies but that the trade-off is less apparent when organisms are iteroparous, use adult-acquired resources for reproduction, or provide parental care. We then review patterns of variation in progeny size among species, among populations within species, among individuals within populations, and among progeny produced by a single female. We argue that much of the variation in progeny size among species, and among populations within species, is likely due to variation in natural selection. However, few studies have manipulated progeny environments and demonstrated that the relationship between progeny size and fitness actually differs among environments, and fewer still have demonstrated why selection favors different sized progeny in different environments. We argue that much of the variation in progeny size among females within populations, and among progeny produced by a single female, is probably nonadaptive. However, some species of arthropods exhibit plasticity in progeny size in response to several environmental factors, and much of this plasticity is likely adaptive. We conclude that advances in theory have substantially outpaced empirical data. We hope that this review will stimulate researchers to examine the specific factors that result in variation in selection on progeny size within and among populations, and how this variation in selection influences the evolution of the patterns we observe.

Animals↗
PubMed1994

Determination of indwelling ureteral stent patency: comparison of standard contrast and nuclear cystography, and lasix renography.

OBJECTIVE: Because of the difficulty in determining patency of Double-J ureteral catheters, a study was devised at Madigan Army Medical Center to determine the best method to demonstrate stented ureteral patency. METHODS: Forty-two patients requiring Double-J ureteral stenting for various clinical reasons were the study group. Outpatients underwent contrast retrograde cystography, nuclear cystography, and diuretic renography every four to six weeks during the stent duration or just prior to stent removal if the stents were indwelling for less than four weeks. In addition, four weeks after stent removal diuretic renography alone was done to evaluate for possible delayed obstructive effect of the ureteral stenting. RESULTS: A total of 53 stents and 42 patients were evaluated. Seventy-seven sets of studies were obtained. In only four instances did all three imaging methods agree on the obstruction. In the remaining 73 sets of data, at least one imaging technique indicated stented ureteral patency. The contrast retrograde cystogram was positive for reflux 52 times (71%). Nuclear cystography showed patency 54 times (74%) and an unobstructed diuretic renogram was obtained 59 times (81%). In addition, five of the six diuretic renograms accomplished with patients in the supine position only and which showed obstruction were repeated with patients in the upright position, and they showed unobstructed function. The overall sensitivity for diuretic renography was 89 percent when the diuretic renogram was done with patients in the supine and upright positions. CONCLUSIONS: Diuretic renography is the most sensitive test for detecting stented ureteral patency. This test needs to be performed with patients in both the supine and upright positions.

Adult↗
PubMed1994

Preservation of pulmonary function by an outer membrane protein F vaccine. A study in rats with chronic pulmonary infection caused by Pseudomonas aeruginosa.

This study investigated the ability of a protein F vaccine to reduce macroscopic evidence of lung damage and preserve pulmonary function in immunized animals in a rat model of chronic pulmonary infection caused by Pseudomonas aeruginosa. Other membrane protein F of P aeruginosa was purified by extraction from polyacrylamide gels of cell envelope proteins of the PAO1 immunotype 7 strain. Rats were immunized intramuscularly with either 25 micrograms of the purified protein F or bovine serum albumin on days 0 and 14 and then challenged on day 28 via intratracheal inoculation of agar beads containing cells of an immunotype 3 clinical isolate of P aeruginosa. Also, included was a noninfected control group which received only sterile agar beads. On day 35, the lungs were excised, pulmonary compliance measured, and the lungs examined macroscopically for the presence and severity of lesions. The protein F-immunized rats had a significant (p < 0.01) reduction in the number of severe pulmonary lesions as compared with bovine serum albumin-immunized rats. Lung compliance (CL) was significantly (p < 0.001) reduced in rats which were immunized with bovine serum albumin (n = 17, CL = 0.12 +/- 0.008), whereas CL of protein F-immunized rats (n = 12, CL = 0.17 +/- 0.006) was similar to that of noninfected control rats (n = 5, CL = 0.15 +/- 0.008). This study demonstrated that a protein F vaccine has the ability to decrease macroscopic lung lesions from infection and preserve pulmonary function in actively immunized rats upon subsequent challenge with P aeruginosa in this model of chronic lung infection.

Animals↗
PubMed1992

Cavitary lung disease. How to read the radiographic patterns.

Many disorders and abnormalities are accompanied by cavitary lesions of the lung, including various diseases that may destroy or replace lung tissue. The most common causes of cavitary lung disease are primary and metastatic neoplasms, granulomas, and necrotizing pulmonary infections. These diseases often have radiographic patterns, clinical signs, and symptoms that are characteristic and may suggest a diagnosis.

Adult↗
PubMed1992

Current concepts in the management and prevention of tuberculosis in adults.

After a steady decline in incidence during most of this century, tuberculosis case rates stabilized in the mid-1980s, and since then have steadily increased. Several factors may have been responsible for the increase, including the influx of immigrants from endemic areas and the appearance of AIDS. This review outlines the current recommendations for treatment of tuberculosis in the otherwise normal patient, then discusses special problems which may affect treatment, including primary drug failure and relapse, pregnancy and lactation, extrapulmonary disease, AIDS, renal failure, and liver disease. The appearance and significance of multiple-drug-resistant tuberculosis (MDRT) in AIDS victims is discussed, and current recommendations for screening patients for the presence of tuberculosis are reviewed.

Acquired Immunodeficiency Syndrome↗
PubMed1990

A solitary testicular relapse of a rhabdomyosarcoma in an adult.

A case of recurrent rhabdomyosarcoma in an adult is reported. The primary disease at presentation was in the maxillary sinus with metastatic spread to regional lymph nodes. A complete response (CR) and a 14-month disease-free interval (DFI) were obtained with combination therapy. The sole site of relapse was an intratesticular mass. Management implications are discussed.

Adult↗
PubMed1985

Protrusive positioners.

Techniques were described for fabricating maxillary and mandibular protrusive positioners for treatment of disk-condyle derangements. Treatment time with the splints varies from 4 to 12 months depending on the age of the patient, the degree of existing symptoms, and patient motivation. At the end of the treatment period and after removal of the splints, the patient may have (1) no pain or internal derangement, (2) no pain but internal derangement with or without reduction, or (3) pain and internal derangement with or without reduction. If dental treatment is required, patients in the first two categories can be treated at a physiologically acceptable treatment position with existing treatment modalities. For patients in the third category, definitive, irreversible stabilization should be reevaluated. For these patients a mandibular cast splint can be changed to an interim splint by replacing the self-polymerizing resin with Isosit (Ivoclar-Vivadent, Schaan, Liechtenstein) or heat-processed acrylic resin.

Age Factors↗
PubMed1984

Provisional restorations for altered occlusions.

A method for fabricating provisional restorations with specific criteria has been outlined and offers the following advantages: Altered occlusion can be restored. Select steps can be delegated to auxiliary personnel. Commercial laboratory fees are eliminated. It is inexpensive. The restorations are durable and esthetic. Restorations are readily modified intraorally. This flexible procedure is used for short or long spans, and/or for segmented treatment. Casts of acceptable anterior provisional restorations can provide a template for developing anterior guidance in the final restorations.

Denture Design↗
PubMed1976

Lecithin agar for detection of microbial phospholipases.

Lecithin agar was developed on which phospholipase C produced turbid zones and phospholipase A produced clear zones. Reactions on lecithin agar agreed 74% of the time with reactions in egg yolk broth. On lecithin agar, interpretation was easier, phospholipase A was detectable, and opaque zones were visible 1 or 2 days earlier than on egg yolk agar. All constituents of the medium can be autoclaved.

Agar↗
PubMed1976

Incidence and identification of phospholipase C-producing bacteria in fresh and spoiled homogenized milk.

Bacteria which produced phospholipase C were isolated from 13 of 34 fresh and 15 of 35 spoiled samples of homogenized milk. No single off flavor was assigned consistently to samples with phospholipase producers, but 75% of them were bitter. Pseudomonads constituted 62% of the isolates. Other phospholipase C-producing genera and their numbers were Acinetobacter, two; Alcaligenes, three; Bacillus, two; Citrobacter, one; Enterobacter, three; and Flavobacterium, two. Two unidentified yeasts also were isolated.

Acinetobacter↗