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Biomedical subjects

D Porter

Publications and source records attributed to D Porter.

At least 19 recordsLinked to original sources
PubMed1992

Triaxial force transducer for investigating stresses at the stump/socket interface.

Although normal pressures at the stump socket interface of the lower-limb amputee have been investigated, little is known about the shear stresses that also occur. Studies suggest that the combination of both shear and normal stresses significantly exacerbates discomfort and vascular and tissue damage. A means of simultaneously measuring normal and shear stresses will aid in the investigation and improvement of prosthetic fit. A miniature triaxial force transducer (4.9 x 16 mm diameter) has been developed which can be recessed into the socket wall. The principle of operation, construction, performance and limitations of the device are described. Preliminary measurements of the interface stress variations over the gait cycle in a supra-condylar PTB socket are presented. These show clear differences in the stress patterns present when two different prosthetic feet are used.

Amputation Stumps↗
PubMed1992

Prospective trial comparing the use of sulphasalazine and auranofin as second line drugs in patients with rheumatoid arthritis.

Two hundred patients with rheumatoid arthritis were studied in a prospective open trial comparing treatment with sulphasalazine and auranofin in patients with active disease over 12 months. The two drugs improved many parameters of disease activity at 12, 24, and 48 weeks. At 12 weeks, the group treated with sulphasalazine had a lower platelet count (Mann-Whitney U test), erythrocyte sedimentation rate, and articular index, with a greater decrease in erythrocyte sedimentation rate (Students t test) and C reactive protein between 0 and 12 weeks. There were no significant differences between sulphasalazine and auranofin treatment after 24 and 48 weeks. Life table analysis showed no significant differences in the rate of side effects which caused treatment to be stopped. Sulphasalazine works more rapidly, may be a more effective disease modifying antirheumatic drug, and is as well tolerated as auranofin.

Adult↗
PubMed1992

Action of sodium aurothiomalate on erythrocyte membrane.

The number of sulphydryl groups on the erythrocyte membrane has been assessed as a function of nutritional status for two groups of patients, one receiving non-steroidal anti-inflammatory drugs (NSAIDs) and the other receiving sodium aurothiomalate (Myocrisin). The patients receiving NSAIDs had a significantly higher number of sulphydryl groups in both the glucose depleted and glucose activated states than the patients receiving sodium aurothiomalate. The study focuses on the hexose transport protein where there is a specific binding site for gold using the two sulphydryl residues on helices 11 and 12 of the protein. The data suggest that the strong binding of gold to the erythrocyte membrane occurs via thiol pairs rather than by isolated sulphydryl groups and that there are possibly two further binding sites for gold on the membrane, the identities of which are still unclear.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1992

Analysis of heat-denatured DNA using native agarose gel electrophoresis.

The use of native or neutral gels to resolve denatured DNA affords a rapid and convenient analytical method for assessing the consequences of a number of procedures employed in molecular biology research. We demonstrate that this method can be used to analyze transition melting temperature (Tm) and strand breakage in heat-denatured duplex DNA. This shows that some commonly recommended denaturation procedures can result in significant degradation of DNA and that reannealing or aggregation can occur when samples are concentrated or ionic conditions altered.

DNA↗
PubMed1991

Fluorescence of tryptophan dipeptides: correlations with the rotamer model.

The multiexponential decay of tryptophan derivatives has previously been explained by the presence of rotamers having different fluorescence lifetimes, but it has been difficult to correlate rotamer structure and physical properties. New time-resolved and static data on dipeptides of the type Trp-X and X-Trp, where X is another aminoacyl residue, are consistent with the rotamer model and allow some correlations. That a dominant rotamer of Trp-X zwitterion has the -NH3+ group near the indole ring was inferred from absorption and fluorescence spectra, titrimetric determination of pKa values, photochemical hydrogen-deuterium-exchange experiments, decay-associated spectra, quantum yields, and decay kinetics. Analysis of the lifetime and quantum yield data for Trp dipeptides, especially X-Trp, suggests that static self-quenching is not uncommon. Highly quenched and weak components of the fluorescence do not contribute to the calculated mean lifetime, thus resulting in apparent static quenching. We propose the term quasi-static self-quenching (QSSQ) to distinguish this phenomenon from quenching due to ground-state formation of a dark complex. Mechanisms of quenching and the structure of statically quenched rotamers are discussed. The occurrence of QSSQ supports the idea that rotamers interconvert slowly. A major perceived deficiency of the rotamer model, namely, the apparent inability to predict reasonable rotamer populations from fluorescence decay data, may result from the presence of statically quenched species, which do not contribute to the fluorescence.

Dipeptides↗
PubMed1991

An H3-H4 histone gene pair in the marine copepod Tigriopus californicus, contains an intergenic dyad symmetry element.

Histone genes are one of the most widely studied multigene families in eucaryotes. Over 200 histone genes have been sequenced, primarily in vertebrates, echinoderms, fungi and plants. We present here the structure and genomic orientation of an H3-H4 histone gene pair from the marine copepod, Tigriopus californicus. These histone gene sequences are the first to be determined for the class Crustacea and among the first to be determined for protostomes. The H4 and H3 genes in Tigriopus are shown to be adjacent, to have opposite polarity, and to contain a 26 bp region of dyad symmetry centrally located within the spacer region between the two genes. A similarly located dyad element has been found in yeast which contributes to the coordinated cell cycle control of the adjacent histone genes. The Tigriopus H3-H4 histone gene pair is clustered with one H2A and two H2B histone genes on a 15 kb genomic Bam H1 fragment. The H4 gene sequence predicts an H4 protein with an unusual serine to threonine substitution at the amino terminal residue. The H3 gene sequence predicts an H3 protein which is identical to the vertebrate H3.2 histone.

Amino Acid Sequence↗
PubMed1991

Mycobacterial infections after renal transplantation.

Mycobacterial infections occurred in 11 of 633 (1.7 per cent) recipients of successful renal transplants. There were no cases of tuberculosis in patients receiving chemoprophylaxis, but amongst those who did not receive prophylaxis disease occurred in six of the 27 (22 per cent) high-risk patients. The major cause of morbidity during treatment was renal allograft rejection, largely due to reduction in immunosuppressive drug therapy.

Adult↗
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↗