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Biomedical subjects

M A Johnson

Publications and source records attributed to M A Johnson.

At least 325 records · Page 18Linked to original sources
PubMed1990

Heterogeneity of dystrophin expression in patients with Duchenne and Becker muscular dystrophy.

This report documents the results of an integrated biochemical and immunocytochemical investigation into the expression of dystrophin (the protein product of the Duchenne muscular dystrophy gene) in muscle biopsies from 226 patients. It is the first study in which dystrophin has been analysed on blots and on tissue sections in such a large number of patients using the same (monoclonal) antibody. The 140 patients with Xp21 muscular dystrophy who were included in this study represent a continuous spectrum of disease severity and this range was reflected in the heterogeneity of dystrophin expression which was observed with respect to abundance, size and the pattern of tissue localisation. Approximately 40% of biopsies obtained from patients diagnosed as having Duchenne muscular dystrophy (DMD) contained isolated clearly positive fibres and a further 20% had very weak labelling on a large number of fibres. Biopsies from patients with Becker muscular dystrophy (BMD) showed labelling patterns which varied from weak labelling on the majority of fibres to clear labelling on all fibres. Typically, however, there was inter- and intra-fibre variation in labelling intensity. Approximately 85% of the 52 BMD and 54 DMD patients who had unequivocal labelling on blots demonstrated a protein of abnormal size. The remaining 15% had a protein of normal size but reduced abundance. Overall, the estimated abundance of dystrophin correlated well with clinical assessments of the disease severity expressed in patients. We conclude that dystrophin analysis is an essential and dependable technique for the differential diagnosis of patients with Xp21 muscular dystrophy.

Adolescent↗
PubMed1990

Neonatal sacrococcygeal teratoma: multiimaging modality assessment.

Neonatal sacrococcygeal teratoma (SCT) is a rare and potentially malignant tumor. We report on four cases of neonatal SCT, in which ultrasound (US), computed tomography (CT), and magnetic resonance imaging (MRI) were used preoperatively to accurately establish the extent of the tumor and its relationship to the surrounding anatomic structures. This approach facilitates complete surgical resection and optimal outcome.

Female↗
PubMed1990

Structure and physical map of the genome of parma wallaby herpesvirus.

The DNA of parma wallaby herpesvirus (macropodid herpesvirus 1; MHV-1) was analysed by restriction mapping and Southern hybridizations, and clones of EcoRI and SalI fragments were prepared which represented approximately 85% of the genome. It has a length of about 135 kbp consisting of a long unique sequence joined to a short unique sequence bounded by inverted repeat sequences, and occurs as 2 isomers. These findings place MHV-1 in the herpesvirus structural classification Group D, along with equine herpesvirus 1 and pseudorabies virus, and differentiates it from the other known herpesvirus of Australian marsupials.

Animals↗
PubMed1990

Is skin necessary for intraoral reconstruction with myocutaneous flaps?

Intraoral defects may be reconstructed in many ways following cancer resection. Following the advent of the myocutaneous flap, this has been very much the mainstay in intraoral reconstructive surgery. Although it has proved to be a reliable flap it has certain innate disadvantages which can often be attributed to the skin component of the flap. This paper attempts to make a case for using muscle-only pedicle flaps such as pectoralis major, masseter transfer and latissmus dorsi flaps.

Aged↗
PubMed1990

Serial magnetic resonance imaging in neonatal hypoxic-ischemic encephalopathy.

We prospectively performed magnetic resonance imaging (MRI) studies during the neonatal period, and at 4 and 8 months of age, on 15 term infants with hypoxic-ischemic encephalopathy, and compared the results with their neurodevelopmental outcome at 18 months of age. Cerebral palsy developed in nine infants, two infants were classified as having abnormalities of tone and delayed motor milestones that were suggestive of cerebral palsy, and four infants were normal. Structural abnormalities, delayed myelination, or a combination of the two were detected with MRI at 8 months of age in all nine infants with later development of cerebral palsy. Three of the four normal infants and one infant with suggestive abnormalities had normal serial MRI findings. Each of the remaining two infants (one normal, one with suggestive abnormalities) had isolated persistent ventricular dilation on all three MRI studies. Our results suggest that 8 months appears to be the earliest time at which MRI findings correlate well with later adverse neurodevelopmental outcome in this population.

Age Factors↗
PubMed1990

High K diets markedly reduce atherosclerotic cholesterol ester deposition in aortas of rats with hypercholesterolemia and hypertension.

High K diets prevent hypertensive endothelial injury and intimal thickening. Cholesterol esters often deposit during hypercholesterolemia. Would a high K diet influence cholesterol ester deposits? In a normal rat on a normal diet, no cholesterol esters are detected in the aorta. Stroke prone SHR rats were fed for 3 months a basic diet containing 4% cholesterol, 14% coconut oil and 7% NaCl. One group of 13 rats had normal (.5%) K in the diet. Another group of 10 rats ate high (2.1%) K. Mean intraarterial blood pressures averaged 165 mm Hg in the normal K group and 161 mm Hg in the high K group (P = NS). The serum cholesterol averaged 229 mg/dL in the normal K group and 214 in the high K group (P = NS). Total aortic cholesterol esters per rat involving 16 and 18 carbon chain fatty acids averaged 187 micrograms in normal K v 68 micrograms in high K, measured by gas chromatography. These were the main esters; other esters were negligible. Thus high K reduced cholesterol ester deposits by 64% (P less than .0003), even though blood pressure and cholesterol levels were quite similar in the two groups. Both high cholesterol and high BP injure endothelial cells and increase invasion of macrophages and vascular smooth muscle cells into the intima and increase endothelial permeability to proteins. With high plasma cholesterol, these processes lead to atherosclerosis with cholesterol ester deposition. The high K diet, by protecting endothelial cells, can greatly decrease this cholesterol ester deposition. This effect could possible be useful for preventing atherosclerotic complications such as heart attacks in human hypertension.

Animals↗
PubMed1990

Iron: nutrition monitoring and nutrition status assessment.

The majority of anemias in the United States are characterized by low mean corpuscular volume and thus are classified as microcytic. Iron deficiency, chronic disease and thalassemia traits are the three leading causes of microcytic anemia. The true cause of anemia must always be sought so that the prevalence estimates of iron deficiency are accurate and so that appropriate treatment can be initiated for the anemic individual. In both the clinical setting and in surveys, the most frequent differential diagnosis of microcytic anemia will involve distinguishing between iron deficiency and chronic disease. Erythrocyte sedimentation rate (ESR), zeta-sedimentation rate (ZSR), and C-reactive protein (CRP) are elevated in a variety of diseases. These indicators may help differentiate the anemia of chronic disease from iron deficiency, so that iron deficiency is not overestimated in hospitalized and aged populations. The red cell distribution width (RDW) appears to be elevated to a greater extent in iron deficiency than in chronic disease or thalassemia traits. RDW and CRP are two of several indicators of iron status in the third National Health and Examination Survey (NHANES III).

Anemia, Hypochromic↗
PubMed1990

Analysis of human papillomavirus type 16 E6-E7 transcription in cervical carcinomas and normal cervical epithelium using the polymerase chain reaction.

Cervical biopsies were collected from Birmingham women having cervical intraepithelial neoplasia or invasive cervical carcinoma and normal controls, and examined for the presence of human papillomavirus type 16 (HPV-16) E6-E7 DNA and mRNA using an adaptation of the polymerase chain reaction. HPV-16 E6-E7 sequences were detected in all abnormal biopsies and in 90% of the normal biopsies examined, confirming previous studies describing the high prevalence of cervical HPV-16 infection. While we were unable to identify any qualitative differences in RNA transcripts from the p97 promoter, substantial quantitative differences in HPV-16-specific early region transcripts between normal and cytologically abnormal cervices were observed. These results suggest that although the level of E6-E7 transcription may contribute to the malignant phenotype, additional factors are likely to be important in the development of cervical neoplasia.

Cervix Uteri↗
PubMed1990

Metabolism in human leukocytes of anti-HIV dideoxypurine nucleosides.

Of the dideoxynucleosides described to date, the purine analogues ddA and ddI have exhibited very favorable therapeutic ratios in vitro. ddI is presently undergoing extensive phase I-II clinical trials. Whereas the action of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) is usually to convert a given analogue of Ado to an inactive or less active form, ddI appears to retain the same biological activity as that of the parent ddA. An explanation for these observations was possible when we found that ddI (1) underwent only a slow cleavage to hypoxanthine through the action of PNP and (2) accumulated the same active antiviral metabolite (i.e., ddATP) as ddA in human lymphoid cells. The use of human lymphoid cells with deficiencies in cellular nucleoside kinases and of inhibitors of pathways of nucleotide metabolism have also revealed new aspects of dideoxypurine metabolism in human lymphoid cells, including the identification of a salvage pathway (phosphotransferase/5'-nucleotide pathway) by which ddA/ddI may be metabolized preferentially to the active nucleotide. The effectiveness of ddA and ddI as orally administered antiviral agents may be limited by their susceptibility to acid hydrolysis and the low efficiency for nucleotide conversion in human lymphoid cells. The presence of a fluorine atom in the arabinose configuration on C-2 confers resistance to solvolysis and renders the analogue less susceptible to enzymatic deamination and resistant to phosphorylytic cleavage by PNP. In addition, human lymphoid cells accumulated several fold higher levels of the putative active triphosphate, 2'-F-dd-ara-ATP, than those of ddA or ddI. This increased accumulation of the analogue triphosphate could be accounted for by a more direct conversion of 2'-F-dd-ara-A by a direct phosphorylation through dCyd kinase than ddA. Thus, a single substitution with fluorine at the 2' "up" position of the sugar moiety of ddA markedly improves several biochemical properties relating to dideoxynucleotide accumulation in human lymphoid cells. Whether there are significant alterations of other biochemical properties, such as the ability of the analogue triphosphate to interact with the target enzyme reverse transcriptase, has not yet been determined. Thus, a definitive resolution of the relative merit of ddA/ddI and its 2'-fluoro-arabinosyl analogue is not yet possible on the basis of the studies described here.

5'-Nucleotidase↗
PubMed1990

Alveolar targeting of aerosol pentamidine. Toward a rational delivery system.

Nebulizer systems that deposit a high proportion of aerosolized pentamidine on large airways are likely to be associated with marked adverse side effects, which may lead to premature cessation of treatment. We have measured alveolar deposition and large airway-related side effects (e.g., cough, breathlessness, and effect on pulmonary function) after aerosolization of 150 mg pentamidine isethionate labeled with 99mTc-Sn-colloid. Nine patients with AIDS were studied using three nebulizer systems producing different droplet size profiles: the Acorn System 22, Respirgard II, and Respirgard II with the inspiratory baffle removed. Alveolar deposition was greatest and side effects least with the nebulizer producing the smallest droplet size profile (Respirgard II), whereas large airway-related side effects were prominent and alveolar deposition lowest with the nebulizer producing the largest droplet size (Acorn System 22). Values for alveolar deposition and adverse airway effects were intermediate using the Respirgard with inspiratory baffle removed, thus indicating the importance of the baffle valve in determining droplet size. Addition of a similar baffle valve to the Acorn System 22 produced a marked improvement in droplet size profile. Selection of a nebulizer that produces an optimal droplet size range offers the advantage of enhancing alveolar targeting of aerosolized pentamidine while reducing large airway-related side effects.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Nursing home placement: the daughter's perspective.

The decision for nursing home placement of a parent has been identified as one of the most difficult decisions for adult children to make. These decisions are made in a family context and are characterized by moral dilemmas. Expressions of loss of attachment or bonding, desires to maintain affective roles with parents following admission, and hurt avoidance for parents, family, and self appear in the decision for nursing home placement and are carried through into the actual admission. Knowledge about adult daughter's perceptions surrounding the decision for nursing home placement can aid nursing staff in anticipatory socialization for daughter and parent. Involvement of daughters in the decision for placement and the period immediately after admission could promote family interactions, foster trust in building relationships with the staff, and possibly decrease the incidence of relocation to other nursing homes.

Adult↗
PubMed1990

Integrated dystrophin analysis using immunocytochemical, biochemical and genetic techniques.

Immunocytochemistry is a powerful tool for the elucidation of clinical problems, particularly when used in conjunction with complementary techniques such as immunoblotting and DNA analysis. We would like to present an experimental example which illustrates the way these three different disciplines were brought together to investigate the defective gene product in X-linked muscular dystrophy.

Chromosome Deletion↗
PubMed1990

Low body weight and weight loss in the aged.

Low body weight and rapid unintentional weight loss are highly predictive of mortality and morbidity in the elderly population. Weight loss is frequently reported in elderly patients. Acute and chronic diseases are leading causes of involuntary weight loss. Whereas physical disease probably accounts for a majority of cases of involuntary weight loss, psychiatric disorders such as dementia and depression also may result in severe nutritional deficiencies. Additional physiological, psychological, and social factors may affect food intake and body weight. Changes in body composition include loss of height and lean body mass and lower basal metabolic rate. Energy requirements decrease because of the lower basal metabolic rate and reduced physical activity. These low energy requirements make it more difficult for the elderly to obtain adequate amounts of required nutrients. Food intake regulation, taste, and olfactory sensitivity may be altered. As 50% of Americans have lost all of their teeth by age 65, chewing problems are often present. Other factors that contribute to poor nutritional status include alterations in the gastrointestinal tract, functional disabilities, lowered socioeconomic status, and social isolation. Finally, because of the increase in both physical and psychiatric disease, the elderly are major users of prescription drugs. Drug/nutrient interactions can result in anorexia and weight loss. The findings indicate that factors causing unintentional weight loss are highly interrelated and difficult to separate. Health care professionals must monitor body weight in elderly persons and carefully evaluate any cases of rapid, unintentional weight loss to prevent further deterioration of health status.

Aged↗
PubMed1990

Influence of copper nutrition on gentamicin nephrotoxicity in rats.

Lipid peroxidation may play a role in the acute nephrotoxicity of gentamicin (GM). Copper (Cu) depletion is associated with reduced activity of certain antioxidant enzymes in tissues, and with kidney lesions and impaired renal function. This study, therefore, investigated the effect of Cu nutrition on GM nephrotoxicity. Weanling male Sprague-Dawley rats were fed Cu adequate or Cu depleted diets for 16 days, then injected intraperitoneally with GM (0-100 mg.kg body weight-1.day-1) for 8 days. GM, but not mild Cu depletion, induced lesions in the kidney and increased plasma urea and urinary excretion of n-acetyl-beta-glucosaminidase. Lower iron in Cu-depleted kidneys and normal Cu, Zn-superoxide dismutase may have prevented additional GM damage during mild Cu depletion.

Animals↗