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Biomedical subjects

P Porter

Publications and source records attributed to P Porter.

At least 19 recordsLinked to original sources
PubMed2006

Frequency of resistance to Bacillus thuringiensis toxin Cry1Ab in southern United States Corn Belt population of European corn borer (Lepidoptera: Crambidae).

The high-dose refuge resistance management strategy is the main approach used to delay resistance in targeted pests to Bacillus thuringiensis (Bt) toxins in transgenic crops. We used an F2 screen to test a critical assumption of the high-dose refuge strategy, which is that resistance allele (R) frequencies are initially rare (<10(-3)) in Ostrinia nubilalis (Hübner) (Lepidoptera: Crambidae) from the southern Corn Belt. We expanded the methodological scope of the F2 screen so that both males and females may be used to initiate a screen and determined how the results from both sexes may be combined. In total, 62 female and 131 male O. nubilalis lines from Kansas and 39 female and four male lines from Texas were screened. No major resistance alleles were found and estimated R frequency for the southern Corn Belt was updated to between 0 and 0.0044 with 95% credibility. The experiment-wise detection probability was 98.7%. These results suggest the frequency of resistance alleles is low enough that the high-dose refuge resistance management strategy may be effective for delaying resistance evolution in O. nubilalis to Bt corn in the southern Corn Belt.

Animals↗
PubMed2005

Cyclin E expression in breast cancer: predicting germline BRCA1 mutations, prognosis and response to treatment.

BACKGROUND: Elevated levels of the cell cycle protein cyclin E, and low levels of its inhibitor, p27(Kip1), have been associated with a poor prognosis following breast cancer. Some studies have found that germline mutations in the breast cancer susceptibility gene, BRCA1, are also associated with an inferior survival rate. The relationship between cyclin E/p27(Kip1) levels, BRCA1 status and outcome has not been studied in detail. PATIENTS AND METHODS: We analyzed a historical cohort of 288 Ashkenazi Jewish women who were diagnosed with breast cancer between 1980 and 1995 and were previously tested for BRCA1/2 mutations. Protein levels of cyclin E and p27(Kip1) were assessed by immunohistochemistry. Breast cancer-specific survival (BCSS) was the main outcome measured. RESULTS: The median follow-up was 8 years. Thirty tumors carried germline BRCA1 mutations. These tumors were more likely to have high cyclin E protein levels [odds ratio (OR) 9.5; P <0.001] and low p27(Kip1) protein levels (OR 2.8; P=0.03) than tumors from patients without BRCA1/2 mutations. High cyclin E expression level was the strongest predictor of BRCA1 germline mutations (multivariate OR 4.7; P=0.004). On univariate analysis, high cyclin E protein levels [relative risk (RR) 2.6; P <0.001] and low p27(Kip1) protein levels (RR 2.3; P=0.006) were significant prognostic factors for a poorer BCSS. In Cox multivariate models, high cyclin E levels remained an independent indicator of poor outcome only in the subgroup of patients who did not receive chemotherapy (P=0.002). CONCLUSIONS: In this ethnically restricted cohort, a high level of cyclin E is a characteristic of BRCA1-related breast cancer, and is a marker of poor prognosis following breast cancer, particularly in the absence of adjuvant chemotherapy.

Adult↗
PubMed2004

Field trial of diatomaceous earth in cotton gin trash against the larger black flour beetle, Cynaeus angustus (Coleoptera: Tenebrionidae).

The larger black flour beetle, Cynaeus angustus (LeConte) (Coleoptera: Tenebrionidae), is an agricultural and home nuisance pest in North America. In the Southern High Plains of Texas, the larger black flour beetle is associated with cotton gin trash, by-products of cotton ginning that are field stored in large piles for economic reasons. Larger black flour beetle overwinter in gin trash piles but may disperse by the millions in summer and autumn, entering houses as far as 2 km away where they cause distress to homeowners. Because > 1.2 billion kg of gin trash is produced annually in Texas alone, the potential consequences of the larger black flour beetle are enormous. We conducted a field experiment that evaluated the efficacy of diatomaceous earth (DE) on the abundance of the larger black flour beetle in gin trash. There were no significant differences in numbers of larger black flour beetle among treatments and controls (mean number of adults summed over time: controls = 115.41, layered treatment = 87.60, top and bottom treatment = 96.50, bottom treatment = 115.16). There were sufficient numbers of beetles in treated piles to still pose a potential home nuisance problem, likely because the moisture content of field-stored gin trash is too high for DE to work effectively. Therefore, treating cotton gin trash with diatomaceous earth will probably be unable to prevent home infestations of larger black flour beetle. Location within a gin trash pile and season influenced pest numbers, which has implications for long-term field storage of cotton gin trash.

Animals↗
PubMed2004

Total hip arthroplasty using the Wroblewski golf ball cup inserted through the posterior approach. A high rate of dislocation.

The Wroblewski golf ball acetabular cup was introduced by surgeons using the trochanteric osteotomy approach for revision total hip replacement (THR) in order to reduce the rate of dislocation. We have routinely used the Ogee long posterior wall (Ogee LPW) and the Wroblewski angle bore cups in THR. Although the new Wroblewski golf ball cup performed well there was a significant early rate of dislocation of 20%. Our rate of dislocation over a period of ten years using the Ogee LPW and Wroblewski angle bore cups had been 0.52%. We present our findings and an investigation as to why the new cup has such a high rate of dislocation when used with the posterior approach. We show that a relatively small change in the design of the acetabular component resulted in significant adverse clinical results.

Adolescent↗
PubMed2002

Frequency of alleles conferring resistance to Bt maize in French and US corn belt populations of the European corn borer, Ostrinia nubilalis.

Farmers, industry, governments and environmental groups agree that it would be useful to manage transgenic crops producing insecticidal proteins to delay the evolution of resistance in target pests. The main strategy proposed for delaying resistance to Bacillus thuringiensis ( Bt) toxins in transgenic crops is the high-dose/refuge strategy. This strategy is based on the unverified assumption that resistance alleles are initially rare (<10(-3)). We used an F(2) screen on >1,200 isofemale lines of Ostrinia nubilalis Hübner (Lepidoptera: Crambidae) collected in France and the US corn belt during 1999-2001. In none of the isofemale lines did we detect alleles conferring resistance to Bt maize producing the Cry1Ab toxin. A Bayesian analysis of the data indicates that the frequency of resistance alleles in France was <9.20 x 10(-4) with 95% probability, and a detection probability of >80%. In the northern US corn belt, the frequency of resistance to Bt maize was <4.23 x 10(-4) with 95% probability, and a detection probability of >90%. Only 95 lines have been screened from the southern US corn belt, so these data are still inconclusive. These results suggest that resistance is probably rare enough in France and the northern US corn belt for the high-dose plus refuge strategy to delay resistance to Bt maize.

Alleles↗
PubMed2002

Modeling the development of resistance by stalk-boring lepidopteran insects (Crambidae) in areas with transgenic corn and frequent insecticide use.

We simulated the population dynamics and population genetics of two bivoltine species of corn borers, the European corn borer, Ostrinia nubilalis (Hübner), and the southwestern corn borer, Diatraea grandiosella Dyar, in a hypothetical region of irrigated transgenic and nontransgenic corn where insecticide was applied only to the nontransgenic refuge crop. Over the 100-yr time horizon, resistance developed quickly in both species and to both transgenic corn and the insecticide when the allele for resistance to the respective toxin was dominant. When the allele for transgenic resistance was not dominant and the refuge location was constant over the time horizon, spraying the refuge to control southwestern corn borer had no effect on how quickly resistance to the transgenic corn developed. In contrast, the European corn borer developed resistance to transgenic corn much sooner when the refuge was sprayed once per year, and the time to 3% resistance allele frequency decreased as efficacy of the insecticide increased. Only when the refuge was treated less than once every 5 yr (10 generations) did the frequency of application decline enough to permit resistance management for the European corn borer to approximate the effectiveness of an unsprayed refuge. A consistently sprayed refuge <40% of the corn acreage was an inadequate resistance management strategy for the European corn borer even when a low efficacy insecticide (70% mortality) was used. When assumptions about European corn borer adult behavior were changed and the adults behaved similarly to adult southwestern corn borer, the development of resistance to the transgenic crop was slowed significantly.

Animals↗
PubMed2002

The influence of age on outcome after operation for the carpal tunnel syndrome. A prospective study.

Decompression of the carpal tunnel is a common surgical procedure. Although the incidence of the carpal tunnel syndrome increases with age, there is no clear information available on the outcome of surgery in relation to age. We studied prospectively 87 consecutive patients who underwent decompression, using a validated self-administered questionnaire, and found that improvement in symptoms and function decreased with increasing age. This was most marked in patients over the age of sixty years.

Adult↗
PubMed2002

High-quality RNA and DNA from flow cytometrically sorted human epithelial cells and tissues.

Microarray technologies have made possible comprehensive analyses of nucleic acid sequence and expression. However, the technology to obtain efficiently high-quality RNA and DNA suitable for array analysis from purified populations of neoplastic cells from human tissues has not been well addressed. Microdissection can enrich for populations of cells present in various tumor tissues, but it is not easily automated or performed rapidly, and there are tissues in which cells of interest cannot be readily isolated based on morphologic criteria alone. Here we describe a protocol for efficient RNA and DNA isolation from flow cytometrically purified whole epithelial cells from primary tissue. The aqueous reagent, RNAlater, which preserves RNA, allows immunolabeling and purification of whole epithelial cells by flow sorting without special instrument preparation to reduce RNase activity. We used real-time PCR to determine RNA quality afterflow sorting. High-quality RNA and DNA suitable for expression and genotype analysis can be readily obtained from flow cytometrically purified populations of neoplastic cells from human tissues.

Base Sequence↗
PubMed2001

Human papillomavirus 16 and 18 L1 serology compared across anogenital cancer sites.

Human papillomavirus (HPV) DNA has been detected in the great majority of cancers of the uterine cervix and anus, whereas the association of HPV DNA with cancer at other anogenital sites has produced less consistent results. This study was designed to compare HPV exposure among anogenital cancer cases and matched controls. Cases (1782) of anogenital cancer diagnosed in the Seattle area from 1978 to 1998 were identified and interviewed. Their responses were compared with those of 2383 age- and sex-matched controls. Blood was drawn at interview from both cases and controls and tested for antibodies to HPV-16 and HPV-18. Tissue blocks were tested for HPV DNA for 649 cases. Serum antibodies to HPV-16 were associated with in situ and invasive cancer at all sites among men and women with the exception of in situ penile cancer. Anti-HPV-18 antibodies were associated with cancers at all sites among women. The increased risk of cancer associated with HPV-16 seropositivity ranged from odds ratio = 1.8 (95% confidence interval, 1.4-2.5) for adenocarcinoma of the cervix to odds ratio = 5.9 (95% confidence interval, 3.4-10.3) for anal cancer in men. Associations between seroprevalence and cancers were stronger when analyses were restricted to HPV-16- or HPV-18 DNA-positive cases. HPV DNA was detected in >80% of cancers from all sites tested. HPV-16 DNA was the type most frequently detected at all sites (range, 40.9-82.2%). HPV-18 DNA was detected in 44.7% of adenocarcinomas of the cervix but detected much less often (2.6-18.1%) at other sites. These findings support an important role for HPV infection in anogenital cancer at all sites. Differences in the proportion of seropositives among HPV-16 DNA-positive cases by site suggest either that the immune response varies by site or that cancer development may lead to changes in antibody responses in a site-specific fashion.

Adenocarcinoma↗
PubMed2001

Concepts and data model for a co-operative neurovascular database.

BACKGROUND: Problems of clinical management of neurovascular diseases are very complex. This is caused by the chronic character of the diseases, a long history of symptoms and diverse treatments. If patients are to benefit from treatment, then treatment decisions have to rely on reliable and accurate knowledge of the natural history of the disease and the various treatments. METHODS: Recent developments in statistical methodology and experience from electronic patient records are used to establish an information infrastructure based on a centralized register. RESULTS: A protocol to collect data on neurovascular diseases with technical as well as logistical aspects of implementing a database for neurovascular diseases are described. The database is designed as a co-operative tool of audit and research available to co-operating centres. CONCLUSION: When a database is linked to a systematic patient follow-up, it can be used to study prognosis. Careful analysis of patient outcome is valuable for decision-making.

Adult↗
PubMed2001

Human papillomavirus and long-term oral contraceptive use increase the risk of adenocarcinoma in situ of the cervix.

We examined United States Surveillance, Epidemiology, and End Results incidence data and conducted a population-based case-control study to examine the role of human papillomavirus (HPV) and oral contraceptive (OC) use in the etiology of adenocarcinoma in situ of the cervix (ACIS). One hundred and fifty women diagnosed with ACIS and 651 randomly selected control women completed in-person interviews. The presence of HPV DNA in archival ACIS specimens was determined by E6 and L1 consensus PCR. Serum samples from case and control subjects were collected at interview, and antibodies to HPV-16 L1 and HPV-18 L1 were detected by virus-like particle capture assays. The overall prevalence of HPV DNA was 86.6%, with 39.0% positive for HPV-16 DNA, 52.4% positive for HPV-18 DNA, and 13.4% positive for more than one HPV type. The age-adjusted relative risk of ACIS associated with HPV-18 seropositivity was 3.3 (95% confidence interval 2.2-4.9). No increased risk was associated with antibodies to HPV-16 L1. Among women born after 1945, the relative risk increased with duration of OC use, with the highest risk for 12 or more years of use (odds ratio, 5.5; 95% confidence interval, 2.1-14.6) relative to nonusers. The detection of HPV DNA in 86.6% of ACIS and the strong association of ACIS with HPV-18 L1 seropositivity underscore the importance of HPV, particularly HPV-18, in the etiology of ACIS. In addition, long-term OC use may contribute to the pathogenesis of these tumors in some women.

Adenocarcinoma↗
PubMed2000

Changing incidence rate of invasive lobular breast carcinoma among older women.

BACKGROUND: In 1998, an unusually large number of invasive lobular breast carcinoma cases were seen at the University of Washington. The purpose of this study was to assess whether the incidence rate of invasive lobular carcinoma has been increasing disproportionately compared with the incidence rate of invasive ductal carcinoma. METHODS: Age specific and age-adjusted breast carcinoma incidence rates from 1977-1995 were obtained from the nine population-based cancer registries that participate in the Surveillance, Epidemiology, and End Results (SEER) program. Three histologic groupings were used: lobular, ductal, and all invasive breast carcinomas. Overall incidence rates for each grouping, as well as for each stage (local, regional, and distant), were obtained. RESULTS: The rate of incidence of lobular carcinoma increased steadily from 1977-1995 in women age >/= 50 years whereas it remained stable in women age < 50 years. Alternatively, the rate of incidence of ductal carcinoma increased steadily from 1977-1987, but from 1987-1995 it remained relatively constant across all age groups. CONCLUSIONS: The incidence rates of invasive lobular breast carcinomas increased steadily since 1977 whereas the incidence rates of invasive ductal carcinoma have plateaued since 1987. This rise occurred specifically among women age >/= 50 years and may be related to postmenopausal status. Further epidemiologic, clinical, and laboratory research is required to assess what factors are contributing to this trend.

Adult↗
PubMed2000

Enterobacter agglomerans spondylodiscitis: a possible, unrecognized complication of tetracycline therapy.

STUDY DESIGN: This case report describes infection in a lumbar disc in a healthy young man with an organism of low pathogenicity. The patient was taking a prolonged course of antibiotics at the time the infection occurred. OBJECTIVE: To describe this unique case of infective spondylodiscitis. SUMMARY OF BACKGROUND DATA: To the authors' knowledge, spinal infection with Enterobacter agglomeranshas never been reported. This organism is a transient gut colonizer, and may have established itself secondary to the patient's prolonged ingestion of tetracycline for acne. METHODS: This 22-year-old farmer had spontaneous lumbar back pain. Radiologic investigations showed an abnormality in the L4-L5 disc region, and together with other investigations, were suggestive of infection. The diagnosis was confirmed by surgical aspiration. RESULTS: Antibiotic therapy was administered, and the patient made a complete recovery. Follow-up radiographs showed a complete loss of the L4-L5 disc space with only minimal bone destruction. CONCLUSION: A unique cause of infective lumbar discitis is presented. Several features of this case are unusual. The magnetic resonance findings were not readily diagnostic. The cultured organism is usually nonpathogenic. The infection may have been secondary to prolonged tetracycline therapy.

Acne Vulgaris↗
PubMed1999

Primary lymphoma of the bladder treated successfully with mitozantrone gel.

We describe a young man who presented with a short history of painless haematuria. Subsequent investigations and biopsy of lesions found in his bladder at cystoscopy confirmed the diagnosis of primary lymphoma of the bladder. Computed tomography studies confirmed the disease was localised to his bladder. Unfortunately, the tumour was not eradicated by radiotherapy. However, it was successfully treated with intravesical mitozantrone given in a novel gel formation. Three years after diagnosis the patient remains well with no evidence of recurrence.

Administration, Intravesical↗
PubMed1998

Variation in mammographic breast density by time in menstrual cycle among women aged 40-49 years.

BACKGROUND: Mammography is less effective for women aged 40-49 years than for older women, which has led to a call for research to improve the performance of screening mammography for younger women. One factor that may influence the performance of mammography is breast density. Younger women have greater mammographic breast density on average, and increased breast density increases the likelihood of false-negative and false-positive mammograms. We investigated whether breast density varies according to time in a woman's menstrual cycle. METHODS: Premenopausal women aged 40-49 years who were not on exogenous hormones and who had a screening mammogram at a large health maintenance organization during 1996 were studied (n = 2591). Time in the menstrual cycle was based on the woman's self-reported last menstrual bleeding and usual cycle length. RESULTS: A smaller proportion of women had "extremely dense" breasts during the follicular phase of their menstrual cycle (24% for week 1 and 23% for week 2) than during the luteal phase (28% for both weeks 3 and 4) (two-sided P = .04 for the difference in breast density between the phases, adjusted for body mass index). The relationship was stronger for women whose body mass index was less than or equal to the median (two-sided P<.01), the group who have the greatest breast density. CONCLUSIONS/IMPLICATIONS: These findings are consistent with previous evidence suggesting that scheduling a woman's mammogram during the follicular phase (first and second week) of her menstrual cycle instead of during the luteal phase (third and fourth week) may improve the accuracy of mammography for premenopausal women in their forties. Breast tissue is less radiographically dense in the follicular phase than in the luteal phase.

Adult↗
PubMed1998

Decreased epinephrine responses to hypoglycemia during sleep.

BACKGROUND: In patients with type I diabetes mellitus, hypoglycemia occurs commonly during sleep and is frequently asymptomatic. This raises the question of whether sleep is associated with reduced counterregulatory-hormone responses to hypoglycemia. METHODS: We studied the counterregulatory-hormone responses to insulin-induced hypoglycemia in eight adolescent patients with type I diabetes and six age-matched normal subjects when they were awake during the day, asleep at night, and awake at night. In each study, the plasma glucose concentration was stabilized for 60 minutes at approximately 100 mg per deciliter (5.6 mmol per liter) and then reduced to 50 mg per deciliter (2.8 mmol per liter) and maintained at that concentration for 40 minutes. Plasma free insulin, epinephrine, norepinephrine, cortisol, and growth hormone were measured frequently during each study. Sleep was monitored by polysomnography. RESULTS: The plasma glucose and free insulin concentrations were similar in both groups during all studies. During the studies when the subjects were asleep, no one was awakened during the hypoglycemic phase, but during the final 30 minutes of the studies when the subjects were awake both the patients with diabetes and the normal subjects had symptoms of hypoglycemia. In the patients with diabetes, plasma epinephrine responses to hypoglycemia were blunted when they were asleep (mean [+/-SE] peak plasma epinephrine concentration, 70+/-14 pg per milliliter [382+/-76 pmol per liter]; P=0.3 for the comparison with base line), as compared with when they were awake during the day or night (238+/-39 pg per milliliter [1299+/-213 pmol per liter] P=0.004 for the comparison with base line, and 296+/-60 pg per milliliter [1616+/-327 pmol per liter], P=0.004, respectively). The patients' plasma norepinephrine responses were also reduced during sleep, whereas their plasma cortisol concentrations did not increase and their plasma growth hormone concentrations increased slightly. The patterns of counterregulatory-hormone responses in the normal subjects were similar. CONCLUSIONS: Sleep impairs counterregulatory-hormone responses to hypoglycemia in patients with diabetes and normal subjects.

Adolescent↗