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Biomedical subjects

B L Johnson

Publications and source records attributed to B L Johnson.

At least 55 records · Page 3Linked to original sources
PubMed1996

In situ repair of mycotic abdominal aortic aneurysms with rifampin-bonded gelatin-impregnated Dacron grafts: a preliminary case report.

Treatment of mycotic aortic aneurysm by excision and extraanatomic bypass is difficult to apply when the infectious process involves the visceral arteries. On the basis of experimental studies in our laboratory that demonstrated prolonged antistaphylococcal activity of rifampin-bonded, gelatin-impregnated Dacron grafts after implantation in the arterial circulation, this conduit was successfully used for in situ replacement of a native aortic infection in two patients. Both patients had fever, leukocytosis, abdominal or back pain, and a computed tomographic scan that demonstrated contained rupture of a mycotic aneurysm. Preoperative computed tomography-guided aspiration and culture of periaortic fluid from one patient grew Staphylococcus aureus. Treatment consisted of prolonged (6 weeks) culture-specific parenteral antibiotic therapy, excision of involved aorta, oxychlorosene irrigation of the aortic bed, and restoration of aortic continuity by in situ prosthetic replacement. A preliminary right axillobifemoral bypass was performed in the patient who had an infection involving the suprarenal and infrarenal aorta. In both patients intraoperative culture of aorta wall recovered S. aureus. Patients were discharged at 20 and 21 days. Clinical follow-up and computed tomographic imaging of the replacement graft beyond 10 months after surgery demonstrated no signs of residual aortic infection. In the absence of gross pus and frank sepsis, the use of an antibiotic-bonded prosthetic graft with antistaphylococcal activity should be considered in patients who have arterial infections caused by S. aureus when excision and ex situ bypass are not feasible.

Aged↗
PubMed1996

Brca1 deficiency results in early embryonic lethality characterized by neuroepithelial abnormalities.

The breast and ovarian cancer susceptibility gene, BRCA1, has been cloned and shown to encode a zinc-finger protein of unknown function. Mutations in BRCA1 account for at least 80% of families with both breast and ovarian cancer, as well as some non-familial sporadic ovarian cancers. The loss of wild-type BRCA1 in tumours of individuals carrying one nonfunctional BRCA1 allele suggests that BRCA1 encodes a tumour suppressor that may inhibit the proliferation of mammary epithelial cells. To examine the role of BRCA1 in normal tissue growth and differentiation, and to generate a potential model for the cancer susceptibility associated with loss of BRCA1 function, we have created a mouse line carrying a mutation in one Brca1 allele. Analysis of mice homozygous for the mutant allele indicate that Brca1 is critical for normal development, as these mice died in utero between 10 and 13 days of gestation (E10-E13). Abnormalities in Brca1-deficient embryos were most evident in the neural tube, with 40% of the embryos presenting with varying degrees of spina bifida and anencephaly. In addition, the neuroepithelium in Brca1-deficient embryos appeared disorganized, with signs of both rapid proliferation and excessive cell death.

Anencephaly↗
PubMed1996

Optic nerve elongation: does it exist?

The length of the optic nerves is a reflection of normal postnatal cranio-orbital development. Unilateral elongation of an optic nerve has been observed in two patients with orbital and skull base neoplasms. In the first case as compared to the patient's opposite, normal optic nerve, an elongated length of the involved optic nerve of 45 mm was present. The involved optic nerve in the second patient was 10 mm longer than the normal opposite optic nerve. The visual and extraocular function was preserved in the second patient. The first patient had only light perception in the affected eye. In this paper, the embryology, anatomy, and physiology of the optic nerve and its mechanisms of stretch and repair are discussed.

Journal Article↗
PubMed1996

Assessment of mercury neurotoxicity through psychometric and neurobehavioral testing: session summary.

Neurobehavioral disorders are well-recognized among the adverse health effects of exposure to mercury. The effort to characterize these effects in animals and humans has progressed steadily over several decades. This has included a variety of study designs, and employed a variety of measurement techniques to evaluate exposure of individuals and populations. The Twelfth International Neurotoxicology Conference, Neurotoxicity of Mercury: Indicators and Effects of Low-Level Exposure, included a plenary session on the predictive value of psychometric and neurobehavioral testing of animals and humans in assessing neurotoxic effects. This session provided a broad view of the methods currently in use to measure adverse effects on the nervous system, in particular those effects that might be attributed to mercury exposure.

Central Nervous System Diseases↗
PubMed1996

A comparison of three subjective tests for astigmatism and their interexaminer reliabilities.

BACKGROUND: Astigmatism is a common cause of blurred vision and asthenopia. Several different tests for the measurement of astigmatism have been described in the literature, but there are few studies that have compared the results of various tests. METHODS: The results of three astigmatism tests performed on 40 subjects by two examiners were compared. Two of the tests, the Jackson cross cylinder (JCC) and the Humphriss immediate contrast (HIC), utilized distance targets; one test, the Pratt test, involved a near target. RESULTS: The mean differences between all tests were less than 0.25D. There was a slight tendency for higher cylinder power to be found on the Pratt test. The three tests agreed within +/- 0.25D on cylinder power 80 to 98 percent of the time and within 10 degrees of cylinder axis 85 to 98 percent of the time. Interexaminer reliability showed mean differences less than 0.12D for each of the three tests, agreement within +/- 0.25D on cylinder power 88 to 90 percent of the time and within 10 degrees on cylinder axis 85 to 93 percent of the time. CONCLUSIONS: The results suggested that any of the three techniques could be substituted for another for astigmatism testing. On theoretical grounds, a binocular refraction method for cylinder axis determination, such as the HIC, is advisable for patients with cyclophorias and significant amounts of astigmatism. The results showed good reliability for each of the three methods.

Adolescent↗
PubMed1995

Chemical mixtures released from hazardous waste sites: implications for health risk assessment.

Uncontrolled hazardous waste sites (HWS) and exposure to hazardous substances continue to pose complex public health problems. This paper presents an overview of chemicals, including chemical mixtures, that have been released into environmental media in the vicinity of HWS. We describe how this type of information is being used to assess the public health implications of exposures to chemical mixtures and to develop an integrated program of applied research to more accurately characterize the potential health effects of chemical mixtures. A narrative, weight-of-evidence approach, incorporating mechanistic insights on chemical interactions is described. The utility of this information in the context of risk analysis and public health practice is discussed.

Animals↗
PubMed1995

The effect of target site transcription on gene targeting in human cells in vitro.

We evaluate the effect of target site transcription on gene targeting in cultured human fibrosarcoma cells. A number of cell lines that harbored a plasmid recombination substrate within their chromosomal DNA were created. Gene targeting frequency was then measured at these different loci in the presence and absence of an agent that stimulated target site transcription. We observed that gene targeting was significantly enhanced by RNA transcription. The magnitude of transcription-stimulated gene targeting varied from 3-fold to > 20-fold. No increase in gene targeting was observed, however, when transcription proceeded away from, rather than through, the recombination site. Transcription-stimulated gene targeting was also observed when single-stranded plasmid vectors complementary to either the coding or template strand were used as recombination substrates. Our results indicate that gene targeting, like other forms of DNA recombination, can be stimulated by target site transcription. The implications of our observations on current models of transcription-stimulated recombination are discussed.

Binding Sites↗
PubMed1995

Nature, extent, and impact of Superfund hazardous waste sites.

Uncontrolled hazardous waste sites are major environmental and public health concerns in the United States and elsewhere. The identification and remediation of and public health responses to these sites are mandated by the U.S. federal Superfund statute. Since its enactment into law in 1980, approximately 40,000 uncontrolled waste sites have been identified in the United States. Approximately 1,300 of these sites constitute the current national Superfund priority list of sites for remediation. Results from analyses are described that characterize the priority hazardous substances released from Superfund sites and the extent of hazard posed to residential communities. Findings from the United States' experience in responding to uncontrolled waste sites are relevant to other countries as they address similar environmental and public health concerns.

Conservation of Natural Resources↗
PubMed1995

ATSDR's information databases to support human health risk assessment of hazardous substances. Agency for Toxic Substances and Disease Registry.

The American public, like persons in many other nations, is concerned about the potential adverse impacts of uncontrolled hazardous wastes. The concerns are often predicated on the fear that adverse health effects will occur because of releases of hazardous substances into community environments. To respond to these concerns, government agencies and private sector organizations must rely on credible, accessible, up-to-date information databases. These databases should be relevant to the needs of the people who respond to uncontrolled releases of hazardous substances. Of particular importance are databases that profile the toxicity of hazardous substances and other information useful to physicians and other health care providers. This paper describes how the federal Agency for Toxic Substances and Diseases Registry (ATSDR) has developed several toxicologic and human health information databases under mandates in the Superfund statute for responding to the public's concerns about hazardous substances.

Databases, Factual↗
PubMed1995

Episcleral osteocartilaginous choristoma.

PURPOSE/METHOD: A 31-year-old woman had a hypertropia and an episcleral choristoma in the superotemporal quadrant of the globe. The choristoma was examined. RESULTS/CONCLUSIONS: Gross and histopathologic examination showed bone and cartilage components in the tumor, which refutes the previously accepted membranous growth pattern of episcleral osseous choristomas.

Adult↗
PubMed1995

Failure of foot salvage in patients with end-stage renal disease after surgical revascularization.

PURPOSE: This report ascertained factors responsible for for failure of foot salvage in patients with end-stage renal disease (ESRD) after undergoing infrainguinal bypass for critical ischemia. METHODS: A retrospective review of 69 distal arterial reconstructions performed in 53 patients with ESRD (hemodialysis [n = 37], kidney transplantation [n = 10], peritoneal dialysis [n = 6]) for foot gangrene (n = 28), nonhealing ulcer (n = 25), or ischemic rest pain (n = 16) was conducted. Endpoints of surgical morbidity, limb loss, and graft patency were correlated with extent of preoperative tissue loss and presence of diabetes mellitus. RESULTS: The 30-day operative mortality rate was 10%, and the patient survival rate at 2 years was 38%. The primary graft patency rate was 96% at 30 days, 72% at 1 year, and 68% at 2 years. Eleven of 22 foot amputations performed during the mean follow-up period of 14 months (range 3 to 96 months) occurred within 2 months of revascularization. Mechanisms responsible for limb loss included graft failure (n = 9), foot ischemia despite a patent bypass (n = 8), and uncontrolled infection (n = 5). Overall, 59% of amputations were performed in limbs with a patent bypass to popliteal or tibial arteries. Healing of forefoot amputations was prolonged, but all limb loss beyond 9 months of revascularization was due to graft failure. The limb salvage rate at 1 year decreased (p = 0.13) from 74% to 51% in patients admitted with gangrene. Only two of seven patients admitted with forefoot gangrene experienced foot salvage. CONCLUSION: Failure of foot salvage in patients with ESRD and critical ischemia was due to wound healing problems rather than graft thrombosis. Earlier referral for revascularization, before development of extensive tissue ischemia and infection, is recommended. Primary amputation should be considered in patients admitted with forefoot gangrene, particularly if it is complicated by infection.

Adult↗
PubMed1995

Uncomplicated cat-scratch disease: findings at CT, MR imaging, and radiography.

PURPOSE: To describe the epidemiologic, clinical, and imaging features of cat-scratch disease (CSD) to facilitate prompt recognition and noninvasive diagnosis of this condition. MATERIALS AND METHODS: Eight otherwise healthy patients with pet cats presented with the subacute onset of epitrochlear, axillary, or groin masses. All underwent cross-sectional imaging with computed tomography (CT) (n = 1) or magnetic resonance (MR) imaging (n = 7). Five patients underwent radiography of the elbow. RESULTS: In all patients, MR imaging and CT showed a poorly defined soft-tissue mass with extensive surrounding edema in an efferent lymphatic distribution. Radiography revealed only soft-tissue edema in two patients and an ill-defined soft-tissue mass with soft-tissue edema in three patients. Six patients underwent biopsy; the findings of all pathologic specimens supported the diagnosis of CSD. No patients underwent serologic evaluation. All patients were asymptomatic within 4 weeks of beginning antibiotic therapy. CONCLUSION: CSD should be considered in all patients with upper extremity or head and neck adenopathy and a history of cat exposure. Although generally not required for diagnosis, cross-sectional imaging will reveal a mass with surrounding edema in an area of lymphatic drainage.

Adolescent↗
PubMed1994

Familial occurrence of multiple cutaneous chondromas.

True cutaneous chondromas are rare lesions with an uncertain pathogenesis. We report an unusual case of a patient with multiple cutaneous chondromas of the face. One of the patient's siblings, a brother, and that brother's son had similar facial lesions. We conclude that this familial pattern suggests an autosomal dominant mode of transmission.

Adult↗
PubMed1993

Neurobehavioral toxicology in the 21st century: a future or a failure? The 1991 Hänninen Lecture.

Toxic substances in the workplace and general environment have been shown to cause adverse health effects in human populations. This has occurred as the result of such factors as industrialization, environmental pollution, and increased reliance on chemicals in agriculture. Effects of toxic substances on the human nervous system have been identified and characterized through use of neurobehavioral methods, essentially over the past 20 years. This paper examines 10 key publications in neurotoxicology and relates them to the future of neurobehavioral toxicology in the next century. The view is expressed that the future of neurobehavioral methods lies in more firmly rooting them in basic mechanisms of neurotoxicity.

Behavior↗
PubMed1993

Environmental epidemiologic issues and minority health.

There exist great differences in morbidity and mortality across racial, cultural, and socioeconomic groups. Certain factors, like limited access to health care, are known to contribute to these differences. The contribution of other factors, like disparities in exposure to environmental hazards, is largely unknown as to the effect on minority groups' morbidity and mortality. This article describes select environmental hazards faced by minorities, such as lead toxicity in children, proximity to hazardous waste sites, and consumption of food contaminated with toxic substances, as well as the role of epidemiologists in documenting adverse health effects and participation in interventions to prevent them.

Child, Preschool↗