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Biomedical subjects

S Porter

Publications and source records attributed to S Porter.

At least 145 records · Page 8Linked to original sources
PubMed1992

Development of monoclonal antibodies for an assay of cardiac troponin-I and preliminary results in suspected cases of myocardial infarction.

To improve the specificity of biochemical markers of myocardial infarction (MI), we have developed a double monoclonal "sandwich" enzyme immunoassay to measure cardiac troponin-I (cTnI) in serum. We produced eight IgG monoclonal antibodies against human cardiac troponin-I (cTnI) and tested them against human and animal (canine, bovine, and rabbit) troponins. Five antibodies were cardiac-specific; none of the antibodies were species-specific. Two of the five cTnI-specific monoclonal antibodies were utilized in an immunoassay. Standards were made by adding purified human cTnI to affinity-stripped cTnI-free human sera to cover the range 0-100 micrograms/L for cTnI. The dose-response curve was nonlinear but reproducible. Total assay imprecision (CV) varied between 11% and 21%. The upper limit of the reference range (nonparametric 95% interval) was established as 3.1 micrograms/L by measuring cTnI concentration in sera of 159 hospitalized patients without evidence of cardiac disease. Purified human skeletal TnI up to 10,000 micrograms/L did not affect the assay (calculated cross-reactivity < 0.1%). Diagnostic sensitivities of creatine kinase MB isoenzyme (CK-MB) and cTnI were evaluated retrospectively in 49 consecutive patients with proven MI. In the 30 patients for whom sufficient information was available to establish an accurate time course, CK-MB was more sensitive during the first 4 h after the onset of chest pain, but thereafter the sensitivities were similar up to 48 h. However, cTnI is more cardiac-specific than is CK-MB and remains increased longer than does CK-MB.

Amino Acid Sequence↗
PubMed1992

Recurrent aphthous stomatitis: the efficacy of replacement therapy in patients with underlying hematinic deficiencies.

A group of thirty-four patients with recurrent aphthous stomatitis (RAS) and single hematinic deficiencies were given replacement therapy after any reason for the deficiency had been sought and excluded. The response of the RAS was assessed in an open trial. The aphthae in 70% of patients subjectively improved with hematinic replacement therapy, a benefit exceeding the defined placebo response in recurrent aphthous stomatitis.

Adolescent↗
PubMed1991

The level of risk of transmission of human immunodeficiency virus between patients and dental staff.

Almost a decade into the epidemic of acquired immunodeficiency syndrome (AIDS) there is adequate evidence to address the concerns of dental staff about possible transmission of human immunodeficiency virus (HIV) between patient and staff. This paper reviews that evidence and demonstrates that the risk of HIV transmission to health care workers is extremely low. Worldwide there are no reported proven cases of occupational transmission of HIV to dental staff.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Multiple alternatively spliced transcripts of the mouse tyrosinase-encoding gene.

We have isolated and characterized tyrosinase-specific cDNAs from wild-type mouse skin, to provide a basis for the structural and functional analysis of mutations at the mouse tyrosinase-encoding (Tyr) locus. The cDNAs were synthesized by the polymerase chain reaction. At least twelve alternatively spliced transcripts of the Tyr gene were found, including nine not previously described. Of 51 clones obtained, most (59%) correspond to the full-length cDNA encoding active tyrosinase. The others are shorter and apparently arose by alternative splicing. They are attributable to exon skipping, usage of alternative 5' and/or 3' splice sites, and (in one case) retention of an intronic sequence. Patterns of alternative splicing also occur in other pigmented tissues.

Animals↗
PubMed1991

Malignant melanoma in transgenic mice.

Ocular and cutaneous melanomas arose in new inbred lines of transgenic mice having an integrated recombinant gene comprised of the tyrosinase promoter, expressed in pigment cells, and the simian virus 40 early-region transforming sequences. The tumors were hypomelanotic and were histopathologically similar to corresponding human melanomas. Eye melanomas often originated at a young age, chiefly from the retinal pigment epithelium, also from the choroid, and rarely from the ciliary body. The eye tumors grew aggressively, were highly invasive, and metastasized to local and distant sites. The earliest formation of these tumors was associated with higher copy numbers of the transgene; mice of different single-copy lines varied greatly in age of onset and frequency of eye tumors. Coat pigmentation was reduced in almost all lines, to various extents. Primary skin melanomas arose later and less frequently than eye melanomas. Hence they were at early stages and of unknown long-range incidence in this investigation, in which autopsies covered the first half-year of life. For both ocular and cutaneous melanomas, the transgenic mice offer numerous possibilities for experimental study of mechanisms underlying formation and spread of melanomas.

Animals↗
PubMed1991

Melanosis and associated tumors in transgenic mice.

Melanosis was found to various extents in a wide array of tissues of all 23 autopsied mice whose transgene consisted of the tyrosinase promoter fused to the simian virus 40 early-region oncogenic sequences. Pigmentation in a given animal was attributable to any or all of the following; an increase in numbers of some normally pigmented cells of neural crest origin (a result compatible with early stages of transformation); elicitation of melanin synthesis in some cells that normally have little melanin, or none at all (the latter possibly signaling metaplasia); unusual intercellular transfer of pigment granules from melanocytes into certain normally unpigmented epithelia and endothelia; and profusion of melanin-phagocytizing cells. Neoplasms, occasionally also containing melanin, arose in association with some of these melanotic tissues and included three choroid plexus tumors, three endocardial tumors, two peripheral nerve sheath tumors (schwannomas), two cochlear tumors, two pineal gland tumors, one salivary gland tumor, and one nasal mucosa tumor. These apparently originated independently of the ocular and cutaneous melanomas found in the same animals. The events involved in melanosis may thus contribute to neoplastic conversion.

Animals↗
PubMed1991

Mosaicism of tyrosinase-locus transcription and chromatin structure in dark vs. light melanocyte clones of homozygous chinchilla-mottled mice.

The chinchilla-mottled (cm) mutation at the mouse tyrosinase-encoding locus leads to a transversely striped pattern of dark- and light-grey coat colors in homozygotes. The same basic pattern occurs in various other genotypes and has previously been found to represent the clonal developmental history of melanocytes. In a homozygote such as cm/cm, cis-acting mechanisms would be expected to account for the color differences. To search for these mechanisms, the genomic structure of the mutation was examined and compared with the wild-type, and its function was compared in cultured melanocyte clones of the respective colors. Evidence from restriction mapping indicated that the coding region of the mutant gene resembles that of the fully and uniformly pigmented wild-type. However, the upstream sequences are rearranged in the mutation. The rearrangement begins 5 kb 5' of the transcription initiation site and is estimated to encompass at least 30 kb of distal upstream sequence. At least two stable functional states of the cm gene were detectable: Light-cell clones have low levels of tyrosinase-specific transcription, reduced DNAase I sensitivity of tyrosinase chromatin, and no detectable hypersensitive sites near the gene; dark-cell clones have higher (but subnormal) levels of transcription, greater sensitivity of chromatin to DNAase I, and a hypersensitive site in the promoter region. The changed relation between the structural gene and its upstream region may separate it from cis-acting control elements, resulting in reduced and variable ability to achieve the appropriate chromatin configuration near the time of melanocyte determination; differences in expression among clonal initiator cells are then mitotically perpetuated.

Alleles↗
PubMed1991

Viruses and chronic disorders involving the human oral mucosa.

Viruses have been implicated in the etiology of several chronic disorders of the oral mucosa. Most of these associations have been with DNA viruses, particularly certain herpesviruses, which are associated, for example, with some cases of erythema multiforme and with hairy leukoplakia. Papillomaviruses are associated with various papillomatous lesions, focal epithelial hyperplasia, and possibly with some carcinomas. Viruses may possibly be associated with recurrent aphthae, Behçet's syndrome, and some dermatoses. The literature concerning these possible associations is reviewed. However, much more research needs to be done before the full story of viral associations with oral mucosal disorders can be written.

Burkitt Lymphoma↗
PubMed1991

Injuries to dental patients and visitors.

Reports were studied of all incidents of injury and accidents involving outpatients or visitors to Bristol Dental Hospital between 1980 and 1988 inclusive. Seventy-two incidents were reported, two-thirds of which occurred during or just after dental treatment, and usually involved oral soft tissues or teeth. Few accidents that occurred at this time could be attributed to faulty equipment. One-third of accidents occurred outside the treatment area, the resultant injuries were usually minor, although one injury was considered serious enough to warrant legal action to be taken against the Health Authority. Hence, it is important that the provisions of the Health and Safety at Work etc. Act (1974) are implemented in all parts of a dental practice to avoid injury to patients.

Accidents↗
PubMed1991

A cell culture model of the blood-brain barrier.

Endothelial cells that make up brain capillaries and constitute the blood-brain barrier become different from peripheral endothelial cells in response to inductive factors found in the nervous system. We have established a cell culture model of the blood-brain barrier by treating brain endothelial cells with a combination of astrocyte-conditioned medium and agents that elevate intracellular cAMP. These cells form high resistance tight junctions and exhibit low rates of paracellular leakage and fluid-phase endocytosis. They also undergo a dramatic structural reorganization as they form tight junctions. Results from these studies suggest modes of manipulating the permeability of the blood-brain barrier, potentially providing the basis for increasing the penetration of drugs into the central nervous system.

Animals↗
PubMed1991

A participant observation study of power relations between nurses and doctors in a general hospital.

The problem addressed in this paper is how nurse-doctor power relations are manifested in a hospital setting. A review of the literature identified four major ideal types of interaction between nurses and doctors in decision-making processes. These were unproblematic subordination, informal covert decision making, informal overt decision making and formal overt decision making on the part of nurses. Each of these types was tested against empirical data gained from participant observation of interactions between the nurses and doctors working in an intensive care unit and a general medical ward. It was concluded that while both the unproblematic subordination and the informal covert decision-making types of interaction appeared superficially to be used frequently, closer examination revealed that, with the exception of nurse-consultant interactions, nurses were less dependent on these subordinate modes of interaction than much of the literature suggested. Formal overt decision making, despite official encouragement, was also infrequently utilized. However, it was noticed that senior nurses especially used informal overt strategies to involve themselves in decision-making sequences. Use of such strategies had the effect of reducing though not eliminating the power differential between doctors and nurses.

Decision Making↗
PubMed1991

The physician as organizational leader.

The physician manager is becoming more common. Given the need to bridge the gap between the business and the practice of medicine and given the transformations taking place in health care, physicians will likely play an increasingly important role as leaders in clinics, hospitals, HMOs, and other health care organizations. As yet, a job description for a "leader" remains elusive. However, understanding the framework described here may help build the proper foundation for successful physician leaders.

Delivery of Health Care↗
PubMed1991

Technology's children: report of a statewide census of children dependent on medical supports.

In April 1987, a census of children dependent on medical technology was carried out in Massachusetts to determine the one-month point prevalence. All medical and educational providers in the state who were likely to interact with such children were contacted and asked to complete a two-sided data form on youngsters (aged 3 months to 18 years) with tracheostomies, supplementary oxygen, respirators, suctioning, gastric feeding, central venous lines, ostomies, ureteral diversion, urethral catheterization and dialysis. Nearly 1250 children were found meeting these criteria. Capture-recapture analysis set the lower bound for technology dependence at 0.08% of the state's children. An analysis of the organ systems involved showed that 57% of the children had neurologic involvement--13% multisystem, 7% gastrointestinal-metabolic, 4% renal-genitourinary, and 3% musculoskeletal. Less than 1% of the children were reported as having immunologic or "other" disorders. Review of putative etiologies indicated that 45% of the children had congenital anomalies, 33% chronic medical diseases, 9% perinatal conditions, 7% hereditary-genetic disorders, 5% injuries, 2% infections, and 3% "other." The substantial prevalence of technology dependency among children creates challenges at the social, economic, and policy-making levels. It will be important to carry out systematic reporting and monitoring activities throughout time and across sites. This census is an example of one such statewide effort.

Adolescent↗
PubMed1990

Recognition of oral lesions of HIV infection. 1. Candidosis.

Oral problems are often the first significant clinical manifestations of infection with human immunodeficiency virus (HIV). Their early recognition affords the best opportunity for effective therapeutic intervention of HIV infection and opportunistic infections, as well as for oral health education in order to avoid future problems. This also provides optimal time for behaviour modification and coming to terms with the psychosocial consequences of HIV disease. This series of three articles presents a pictorial review and update on the oral manifestations of HIV infection.

Candidiasis, Oral↗