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Biomedical subjects

D Porter

Publications and source records attributed to D Porter.

At least 91 records · Page 5Linked to original sources
PubMed1990

Stereological study of gonadotropes in the frog, Rana pipiens, after GnRH stimulation in vitro.

Previous physiological results have indicated the existence of two releasable pools of gonadotropins in amphibian pituitaries: an acute releasable pool that appears independent of protein synthesis, and a storage pool involved in chronic release that depends on protein synthesis. To elucidate the ultrastructural localization of these pools and the morphological changes induced in gonadotrope cells after treatment with gonadotropin-releasing hormone, we carried out a morphometric study of immuno-identified gonadotrope cells using an in vitro superfusion system. Treatment with gonadotropin-releasing hormone induced a degranulation of small (110-255 nm) and medium (236-360 nm) secretory granules as well as hypertrophy of the endoplasmic reticulum and Golgi complex. Simultaneous incubation with gonadotropin-releasing hormone and cycloheximide inhibited the release of secretory granules although the endoplasmic reticulum and Golgi complex were hypertrophied. These morphological results strongly suggest: (1) that gonadotropin-releasing hormone induces degranulation and hypertrophy of the biosynthetic machinery in gonadotrope cells; and (2) that the activation of the endoplasmic reticulum and Golgi complex by stimulation with gonadotropin-releasing hormone is independent of protein synthesis, while the release of secretory granules is protein synthesis-dependent. In addition, the second or "storage" pool of gonadotropin is associated mainly with the small and medium secretory granules.

Animals↗
PubMed1990

CT detection of cortical fracture of the femoral head associated with posterior hip dislocation.

Posterior dislocation of the femoral head is a common injury in automobile accidents and is frequently associated with fractures of the posterior acetabular rim. Fractures of the anterior cortex of the femoral head have not been described. One hundred sixty-four cases of posterior hip dislocation presenting consecutively to our shock trauma unit and emergency department during a 3-year period were evaluated with plain film radiology and CT. In 21 cases (13%), CT showed an anterior cortical fracture of the femoral head that could not be seen on plain radiographs. This injury is similar to the Hill-Sachs lesion of the humerus that results from anterior dislocation. The anterior cortical fracture was associated with fractures of the posterior acetabulum in 18 cases (86%). The anterior fracture is caused by impaction of the anterior femoral head against the posterior acetabular rim at the time of dislocation. We conclude that anterior cortical fracture of the femoral head is a common accompaniment to posterior acetabular dislocation.

Femoral Fractures↗
PubMed1989

ClinQuery: a system for online searching of data in a teaching hospital.

We designed a user-friendly computer program that permits physicians to search the clinical database of Boston's Beth Israel Hospital by clinical and demographic descriptors. For example, the user can identify all admissions in which diabetic ketoacidosis was diagnosed, the serum bicarbonate level was under 12 mmol/L, and the length of stay exceeded 7 days. Once particular admissions are identified, all data stored in the computerized record can be displayed. Authorized persons can also request the patient's complete medical record for further study. Over a 30-month period, 530 doctors, nurses, medical students, and administrators used the program to search the hospital's clinical database 1786 times. They displayed detailed information on 30,851 patients and requested the complete medical record 5319 times. In 1389 of the 1786 searches completed, the searcher responded to a computer-based questionnaire about motivation for the search. Responses indicated that 32% of the searches were for clinical research, 17% for patient care, 17% for teaching and education, 11% for hospital administration, and 12% for general exploration. In 58% of the searches, respondents indicated definite or probable success in finding the desired information. We conclude that physicians and allied personnel will repeatedly obtain, view, and analyze aggregate clinical information if they are provided with appropriate tools. We believe that such access to clinical information is an important resource for patient care, teaching, and clinical research.

Boston↗
PubMed1989

Immunocytochemical and ultrastructural study of the frog (Rana pipiens) pars distalis with special reference to folliculo-stellate cell function during in vitro superfusion.

The colloidal gold immunocytochemical technique was used to determine the ultrastructural features of the glandular cells in the pituitaries of male frogs, Rana pipiens, both in vivo and after superfusion in vitro. Specific reactions to antisera against bullfrog gonadotropins, human prolactin, and synthetic 1-39 corticotropin allowed identification of the 3 corresponding types of glandular cells. No immunoreaction was obtained with antisera against human or ovine-growth hormone, human beta-thyrotropin hormone, and bovine S-100 protein. General morphological features of these immunocytochemically identified glandular cells were similar to those of equivalent cells previously described in other amphibian species. Non-glandular folliculo-stellate cells were distinctive. In freshly removed pituitaries, these folliculo-stellate cells contained lysosome-like structures, but did not show phagocytic vacuoles in the cytoplasm; they contained many mitochondria, and the Golgi complex and endoplasmic reticulum were relatively undeveloped. After 4 or 18 h of superfusion, some immunoreactive gonadotropic, prolactin, and corticotropic cells showed degeneration and destruction. In the same gland, folliculo-stellate cells retained a viable appearance, but showed phagocytic vacuoles containing secretory granule-like structures which were immunoreactive to gonadotropic, prolactin, and corticotropic antibodies. Some folliculo-stellate cells showed phagocytic vacuoles containing complete glandular cells. These results suggest that superfusion causes a destruction of some of the glandular cells, and that folliculo-stellate cells act as phagocytes when cellular debris or moribund cells are present in the intercellular space in the pituitary parenchyma.

Adrenocorticotropic Hormone↗
PubMed1989

Evaluation of reproductive function of female rats exposed to radiofrequency fields (27.12 MHz) near a shortwave diathermy device.

In recent years, there has been increased concern regarding effects of operator exposure to the electromagnetic (EM) field associated with shortwave diathermy devices. The present study was designed to investigate the effects, on rats, of repeated exposure to such an EM field. Following repeated exposure for 5 wk, a reduction in fertility occurred as indicated by a reduced number of matings in exposed rats compared to sham-irradiated rats and a reduction in the number of rats that conceived after mating. The data suggest that female operators could experience reduced fertility, if they remained close to the console for prolonged periods. This has particular significant for the physiotherapy profession.

Animals↗
PubMed1989

The effect of footwear mass on the gait patterns of unilateral below-knee amputees.

This study reports an investigation into the effect of shoe mass on the gait patterns of below-knee (BK) amputees. Ten established unilateral BK, patellar-tendon-bearing prosthesis wearers were assessed using a VICON system of gait analysis. Incremental masses of 50g (up to 200g) were added to the subjects' shoes and data captured as they walked along a 15m measurement field. Coefficients of symmetry of various parameters of the swing phase (knee frequency symmetry, swing time symmetry) were measured and their correlation was tested with the patient's preferred shoe mass and also their own shoe mass, all expressed as a proportion of body mass. The subjects' 'preferred' shoe mass (139-318g) showed the greatest symmetry in all the parameters examined (correlations 0.78-0.81 p less than 0.01 and less than 0.005), whereas there was no correlation between the subjects' own shoe mass (121-325g) and the symmetry coefficients measured.

Amputation, Surgical↗
PubMed1989

Progressive systemic sclerosis: Part 2--Nursing management.

Multiple body systems can be affected by scleroderma. Satisfactory coping and life-style alterations will depend on numerous factors, including the nature and extent of organ involvement, individual coping style, and health professional services provided. Because of the low incidence of this disease, nurses may have little knowledge about the nursing management. Because of the nature of the disease's complications, the nephrology or dialysis nurse may care for more scleroderma patients than other hospital nurses.

Adaptation, Psychological↗
PubMed1989

Federal nutrition policies: impact on dietetic practice.

Current federal nutrition policies are likely to have a major impact on dietetic practice. Several examples have been selected to explain why and how members of the American Dietetic Association and other nutrition professionals should become involved in policy development and implementation.

Cholesterol↗
PubMed1988

Self-service computerized bibliographic retrieval: a comparison of Colleague and PaperChase, programs that search the MEDLINE data base.

Colleague and PaperChase are the two most widely used computer systems designed specifically for clinicians and scientists who wish to search the National Library of Medicine's MEDLINE data base of references to the biomedical literature. The present study compares the performance of these two systems. Two matched groups of second-year medical students each received 3 hr of instruction, one group in Colleague, the other in PaperChase. Each student then attempted 10 test searches. The next day the groups were reversed, and each student attempted 5 additional searches. During 3 1/2 hr allocated for searching, users of Colleague attempted 64 test searches and retrieved 326 target references; users of PaperChase attempted 78 searches and retrieved 496. Users of Colleague took a mean of 2.2 min and spent a mean of $1.20 to find each target reference; users of PaperChase took 1.6 min and spent $0.92. We conclude that after limited training, medical students find more references faster and at lower cost with PaperChase than with Colleague.

Computer User Training↗
PubMed1987

Specificity of amphibian and reptilian pituitaries for various forms of gonadotropin-releasing hormones in vitro.

In vitro perifusion was employed to compare the potencies of mammalian, avian, salmon, and lamprey gonadotropin-releasing hormones (GnRHs) on the release of luteinizing hormone (LH) from the pituitaries of an amphibian (Rana pipiens) and a reptile (Chrysemys picta). The chicken-I and salmon GnRH variants were equipotent with mammalian GnRH in both the frog and the turtle glands. By contrast, the lamprey GnRH was inactive (less than 1% as potent as the others). Lamprey GnRH also failed to stimulate LH release or to induce GnRH priming when administered chronically to the frog gland. These results support the hypothesis that the GnRH receptors on nonmammalian pituitary cells are much less specific than those of the mammal with regard to the amino acid at position 8 of the GnRH molecule. These data suggest that the native GnRH variant or the one most like that found in the brain of a species is not necessarily the most potent biologically in that species. However, the nonmammalian pituitary does show some specificity with regard to the structure of natural GnRHs in that none of the tetrapod species studied is responsive to lamprey GnRH.

Animals↗
PubMed1987

Growth of bacteria with dimorphic vegetative cell cycles.

A mathematical model of the growth of bacteria with dimorphic cell cycles is described. In these bacteria motile swarmer cells differentiate to stalked reproductive cells and the proportions of these cell types change in a characteristic fashion during growth. The selection of parameters to fit the model to experimental data can result in the elucidation of the factors controlling the differentiation of swarmer cells.

Bacteria↗