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Biomedical subjects

P Wiggins

Publications and source records attributed to P Wiggins.

18 recordsLinked to original sources
PubMed1998

Measuring the elastic modulus of small tissue samples.

Independent measurements of the elastic modulus (Young's modulus) of tissue are necessary step in turning elasticity imaging into a clinical tool. A system capable of measuring the elastic modulus of small tissue samples was developed. The system tolerates the constraints of biological tissue, such as limited sample size (< or = 1.5 cm3) and imperfections in sample geometry. A known deformation is applied to the tissue sample while simultaneously measuring the resulting force. These measurements are then converted to an elastic modulus, where the conversion uses prior calibration of the system with plastisol samples of known Young's modulus. Accurate measurements have been obtained from 10 to 80 kPa, covering a wide range of tissue modulus values. In addition, the performance of the system was further investigated using finite element analysis. Finally, preliminary elasticity measurements on canine kidney samples are presented and discussed.

Animals↗
PubMed1992

An antipodean perception of the mode of action of glycoprotein hormones.

Continuance of vertebrate species and maintenance of metabolism have an absolute requirement for the glycoprotein hormones of the anterior pituitary gland. It is now firmly accepted that the N-glycans of these and the related placental hormone, chorionic gonadotropin, have essential if undefined roles in their mechanism of action. However, recent investigations by Weisshaar and his colleagues on the oligosaccharides of human luteinizing hormone and chorionic gonadotropin, do not support the generally accepted view of carbohydrates in hormone-receptor interactions and a further concept is proposed that invokes negative charges and changes in structured water.

Animals↗
PubMed1992

Epidemiology of dermatitis among California farm workers.

To estimate the prevalence of dermatitis and risk factors for skin disease in California farm workers, a cross-sectional survey was conducted among grape, citrus, and tomato workers. The prevalence of contact dermatitis was 2% and lichenified hand dermatitis was 13%. Grape workers were more likely to report rashes in the last 12 months than were tomato workers or citrus workers. Grape workers were more likely to have contact dermatitis and lichenified hand dermatitis than were citrus or tomato workers. Increasing hours per week in agriculture, male sex, and not wearing gloves were associated with more lichenified hand dermatitis. We conclude that skin disease in agricultural workers may be causally associated with crop-specific exposures and lack of protective equipment.

Adult↗
PubMed1990

Adverse reproductive outcomes among female veterinarians.

Because female veterinarians are exposed to several known reproductive hazards, the authors conducted a reproductive survey of all female graduates of a US veterinary school (n = 537) and law school (comparison group, n = 794). Analysis was confined to pregnancies completed after the second year of professional school and from 1966 to 1986. Based on one randomly chosen eligible pregnancy per woman (veterinarians, n = 176; lawyers, n = 229), spontaneous abortion rates, adjusted for elective abortions, were 13.3% for the veterinarians and 15.1% for the lawyers; these did not differ significantly. A Cox life table regression model controlling for age, smoking, alcohol use, and prior spontaneous abortion also showed no significant difference in spontaneous abortion rates between the two populations. Using all pregnancies, veterinarians who reported performing five or more radiographic examinations per week had a marginally elevated risk of spontaneous abortion, but the statistical significance disappeared when analysis was limited to one random pregnancy per woman. For one random eligible birth per woman, the mean birth weight did not differ significantly between the veterinarians and lawyers, even after controlling for possible confounders in regression analyses. A higher rate of reportable birth defects was observed among the veterinarians than among the lawyers (relative risk = 4.2, 95% confidence interval 1.2-15.1), but this unexpected result must be considered hypothesis-generating. The authors did not find an overall increased risk for spontaneous abortion or low birth weight infants among veterinarians compared with lawyers, but veterinarians who reported performing five or more radiographic examinations per week may have been at increased risk for spontaneous abortion.

Abortion, Incomplete↗
PubMed1989

Prevalence of hazardous exposures in veterinary practice.

All female graduates of a major U.S. veterinary school were surveyed by mailed questionnaire to obtain details of work practice and hazard exposure during the most recent year worked and during all pregnancies. Exposure questions were based on previously implicated occupational hazards which included anesthetic gases, radiation, zoonoses, prostaglandins, vaccines, physical trauma, and pesticides. The response rate was 86% (462/537). We found that practice type and pregnancy status were major determinants of hazard exposure within the veterinary profession. Small-animal practitioners reported the highest rates of exposure to anesthetic gas (94%), X-ray (90%), and pesticides (57%). Large-animal practitioners reported greater rates of trauma (64%) and potential exposure to prostaglandins (92%), Brucella abortus vaccine (23%), and carbon monoxide (18%). Potentially hazardous workplace practices or equipment were common. Forty-one percent of respondents who reported taking X-rays did not wear film badges, and 76% reported physically restraining animals for X-ray procedures. Twenty-seven percent of the respondents exposed to anesthetic gases worked at facilities which did not have waste anesthetic gas scavenging systems. Women who worked as veterinarians during a pregnancy attempted to reduce exposures to X-rays, insecticides, and other potentially hazardous exposures. Some potentially hazardous workplace exposures are common in veterinary practice, and measures to educate workers and to reduce these exposures should not await demonstration of adverse health effects.

Anesthetics↗
PubMed1989

Assessing dermatitis in epidemiologic studies: occupational skin disease among California grape and tomato harvesters.

We conducted a cross-sectional investigation to determine whether table grape harvesters, who have significant cutaneous contact with crop-associated materials that may cause skin disease, are more likely to develop dermatitis than are a control group of tomato workers performing mechanical harvesting with minimal cutaneous contact with crop-associated substances. A secondary aim was to develop methods for studying skin disease in farm workers, including a standard questionnaire and physical examination. California table grape workers (n = 183) and tomato workers (n = 43) completed an interviewer-administered questionnaire and waist-up physical examination at their work site during harvest operations. On physical examination, pustular eruptions such as acne and folliculitis were present in 30% of subjects, and eczematous rashes were noted in 10% of subjects. Irritant or allergic contact dermatitis was diagnosed in 2% of subjects. No significant differences in prevalence for these skin conditions were observed between the two groups of workers. In contrast to the physical examination results, grape workers were more likely than tomato workers to report a rash occurring in the previous 3 months (52% vs. 19%, p less than 0.001). Explanations for this discrepancy are discussed. The sensitivity of the questionnaire for current skin conditions was 31%, and the specificity was 94%. Improved sensitivity was seen for eczematous skin conditions (55%). We conclude that questionnaires provide an efficient means of assessing subject characteristics, but may have limited sensitivity for some dermatologic outcomes.

Agricultural Workers' Diseases↗
PubMed1989

Epistaxis due to glutaraldehyde exposure.

Glutaraldehyde is commonly used as a cold disinfecting agent in the hospital setting and may cause irritation of skin, mucous membranes, and the upper respiratory tract in exposed workers. We report an unusual case of recurrent epistaxis associated with other symptoms of upper respiratory tract irritation and skin rash in a hospital employee using glutaraldehyde for sterilization of endoscopy equipment. A visit to the workplace revealed inadequate personal protective measures and inadequate local ventilation. High-risk work practices contributing to the hazard included soaking of endoscopy equipment in uncovered basins, manual pouring of concentrated glutaraldehyde solutions without the use of proper protective measures, and the use of paper masks, which provide inadequate protection from solvent vapors. The patient's symptoms resolved with the implementation of personal protective measures and engineering controls.

Adult↗
PubMed1989

Ammonia produced by Campylobacter pylori neutralizes H+ moving through gastric mucus.

We aimed to show that Campylobacter pylori infection increases the concentration of ammonia in the gastric mucus and alters the movement of H+ through the mucus. Mucus from uninfected and C. pylori-infected stomachs was collected at postmortem. Ammonia was measured enzymatically. The ammonia concentration in C. pylori-infected mucus was fourfold greater than in uninfected mucus. H+ movement experiments were carried out using an in vitro chamber, in which a layer of mucus separated a 0.1 M HCl solution from distilled H2O. The change in pH of the distilled H2O was measured over 30 min. A drop in pH was measured for uninfected mucus. A slight rise in pH was measured for C. pylori-infected mucus. We conclude that C. pylori infection is associated with reduced H+ movement through mucus and that this may be due to increased ammonia concentration within mucus.

Ammonia↗
PubMed1988

Na+/H+ ion-exchange property of postmortem human gastric mucus.

The Na+/H+ ion-exchange property of human gastric mucus and its relationship to age has been studied. Mucus was collected from 40 postmortem human stomachs (age range, 21-83 years) within 24 h of traumatic death. Twenty-one stomachs (age range, 21-76 years) were free of Campylobacter pylori infection and histologic gastritis. Mucus from these stomachs was consistently a cation exchanger at pH 6 in an in vitro system. The cation-exchange capacity of mucus from seven stomachs within the age range 55-70 years was 50% less than the cation-exchange capacity of mucus from eight stomachs within the age range 20-35 years. This study shows that human gastric mucus at pH 6 is a cation exchanger and that the ion-exchange capacity decreases with age.

Adult↗
PubMed1987

Hepatic perfusion index and the evolution of liver metastases.

A total of 150 patients with primary carcinoma of the gastrointestinal tract had first-pass technetium colloid scintigraphy to estimate the hepatic perfusion index (HPI). Postoperative follow-up over 2-4 years shows that the HPI remains a sensitive method of detecting hepatic metastases, even in patients whose liver appeared normal at laparotomy. HPI was elevated in 94% of patients with liver metastases found at laparotomy; 87% of patients with occult metastases which became overt within 3 years of surgery had elevated HPI; and 91% of all patients who have to date developed hepatic metastases had elevated HPI at presentation. Of all patients with elevated HPI, 82% had metastases which were either apparent at surgery or became detectable by other means within 3 years.

Gastrointestinal Neoplasms↗
PubMed1979

A randomized double-blind trial of two low dose combined oral contraceptives.

Fifty-five women using Loestrin-20 (20 microgram ethinyl oestradiol and 1 mg norethisterone acetate) as an oral contraceptive have been compared with a like number using Microgynon-30 (30 microgram ethinyl oestradiol and 150 microgram levonorgestrel) in a randomized, double-blind trial. Despite the small sample size, the main finding in the trial is clear-cut; Loestrin-20 provides poor cycle control and is thus less acceptable as an oral contraceptive than Microgynon-30. Although there is also a suggestion that Loestrin-20 may be less effective than Microgynon-30, the difference in the accidental pregnancy rates is not statistically significant.

Adolescent↗
PubMed1978

Fertility after stopping different methods of contraception.

Data on the return of fertility after discontinuing various methods of contraception were collected from among the women taking part in the Oxford-Family Planning Association contraceptive study. Return of fertility was measured as the time taken to give birth to a child. The fertility of both nulligravid and parous women who stopped taking oral contraceptives was initially impaired in comparison with that of women who stopped using other methods of contraception. But the effect of oral contraceptives on fertility had become negligible by 42 months after cessation of contraception in nulligravidae and by 30 months in multiparae. Impairment seemed to be independent of the length of use of oral contraceptives. Data relating to IUD users were sparse, but the figures that were available were reassuring. These results suggest that, although women may have temporary impairment of fertility after discontinuing oral contraception, they are unlikely to become permanently sterile through taking the pill.

Adult↗
PubMedDate not supplied

Hypothesis: hyperstructures regulate bacterial structure and the cell cycle.

A myriad different constituents or elements (genes, proteins, lipids, ions, small molecules etc.) participate in numerous physico-chemical processes to create bacteria that can adapt to their environments to survive, grow and, via the cell cycle, reproduce. We explore the possibility that it is too difficult to explain cell cycle progression in terms of these elements and that an intermediate level of explanation is needed. This level is that of hyperstructures. A hyperstructure is large, has usually one particular function, and contains many elements. Non-equilibrium, or even dissipative, hyperstructures that, for example, assemble to transport and metabolize nutrients may comprise membrane domains of transporters plus cytoplasmic metabolons plus the genes that encode the hyperstructure's enzymes. The processes involved in the putative formation of hyperstructures include: metabolite-induced changes to protein affinities that result in metabolon formation, lipid-organizing forces that result in lateral and transverse asymmetries, post-translational modifications, equilibration of water structures that may alter distributions of other molecules, transertion, ion currents, emission of electromagnetic radiation and long range mechanical vibrations. Equilibrium hyperstructures may also exist such as topological arrays of DNA in the form of cholesteric liquid crystals. We present here the beginning of a picture of the bacterial cell in which hyperstructures form to maximize efficiency and in which the properties of hyperstructures drive the cell cycle.

Bacteria↗