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Biomedical subjects

D W Johnson

Publications and source records attributed to D W Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1994

Plasma cis-dec-4-enoic acid measured by isotope dilution mass spectrometry; an improved assay to diagnose medium-chain acyl-CoA dehydrogenase deficiency.

An isotope dilution mass spectrometric assay for plasma cis-dec-4-enoic acid is described. It is quicker, more reliable and more accurate than previous methods. It confirmed previous findings that cis-dec-4-enoic acid is a reliable indicator for medium-chain acyl-CoA dehydrogenase deficiency (MCAD). The plasma cis-dec-4-enoic acid levels of both asymptomatic and symptomatic MCAD patients (3.5-71 mumol/L) are demonstrably higher than those of normal children (0.2-1.7 mumol/L), MCAD heterozygotes (0.1-1.5 mumol/L), those with other fatty acid oxidation defects (0.2-2.2 mumol/L) or those receiving high doses of valproic acid (0.2-0.4 mumol/L).

Acyl-CoA Dehydrogenase↗
PubMed1994

Handling and/or saline injections alter basal and morphine-evoked changes in dopamine metabolites in the striatum and nucleus accumbens of rats.

The effect of IP saline injections on basal dopamine (DA), homovanillic acid (HVA), and dihydroxyphenylacetic acid (DOPAC), and morphine-evoked levels of DA, DOPAC, and HVA in the striatum (STR) and nucleus accumbens (NAC) of female Sprague-Dawley rats was quantified, using in vivo microdialysis. In the STR, saline injections twice daily over 3 days, then once on day 4 (2x /day group), resulted in higher basal DOPAC and HVA levels compared to unhandled rats (naive group), or rats injected with saline once daily for 4 days (1x /day group). DOPAC and HVA were greater after IP injection of 30 mg/kg morphine in the saline 2x /day group compared to the saline 1x /day and naive groups. In the NAC, DOPAC was higher after injection of morphine in saline-pretreated rats, compared to naive rats. These results suggest that handling and/or IP saline injections affect basal and morphine-evoked changes in DA metabolites in the STR, and morphine-evoked DOPAC in the NAC.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1994

Endoglin, a TGF-beta binding protein of endothelial cells, is the gene for hereditary haemorrhagic telangiectasia type 1.

Hereditary haemorrhagic telangiectasia (HHT) is an autosomal dominant disorder characterized by multisystemic vascular dysplasia and recurrent haemorrhage. Linkage for some families has been established to chromosome 9q33-q34. In the present study, endoglin, a transforming growth factor beta (TGF-beta) binding protein, was analysed as a candidate gene for the disorder based on chromosomal location, expression pattern and function. We have identified mutations in three affected individuals: a C to G substitution converting a tyrosine to a termination codon, a 39 base pair deletion and a 2 basepair deletion which creates a premature termination codon. We have identified endoglin as the HHT gene mapping to 9q3 and have established HHT as the first human disease defined by a mutation in a member of the TGF-beta receptor complex.

Amino Acid Sequence↗
PubMed1994

In vitro activation of rat brain protein kinase C by polyenoic very-long-chain fatty acids.

A variety of fatty acids including the cis-polyunsaturated very-long-chain fatty acids (VLCFA) (> 22 carbon atoms) common in retina, spermatozoa, and brain were examined for their ability to activate protein kinase C (PKC) purified from rat brain. Arachidonic [20:4(n-6)], eicosapentaenoic [20:5(n-3)], and docosahexaenoic [22:6(n-3)] acids as well as the VLCFA dotriacontatetraenoic [32:4(n-6)] and tetratriacontahexaenoic [34:6(n-3)] were equally capable of activating PKC in vitro with maximal activity being between 25 and 50 microM. The phorbol ester 12-O-tetradecanoylphorbol 13-acetate further enhanced the in vitro activation of PKC when added to the protein kinase assay system with the fatty acids. The fully saturated arachidic acid (20:0) was inactive in both assay systems. The potential significance of the in vitro activation of PKC by the VLCFA is discussed.

Animals↗
PubMed1994

Neutrophil migration inhibitory properties of polyunsaturated fatty acids. The role of fatty acid structure, metabolism, and possible second messenger systems.

The n-3 polyunsaturated fatty acids (PUFA) appear to have antiinflammatory properties that can be partly explained by their biological activity on leukocytes. Since leukocyte emigration is an essential component of the inflammatory response, we have examined the effects of the n-3 PUFA (eicosapentaenoic and docosahexaenoic acids) on neutrophil random and chemotactic movement. Preexposure of neutrophils for 15-30 min to 1-10 micrograms/ml PUFA reduced the random and chemotactic migration to both FMLP- and fungi-activated complement. The inhibitory effect diminished with increasing saturation and carbon chain length, and methylation abolished this activity. Arachidonic and docosahexaenoic acids were the most active fatty acids. The PUFA concentration required to inhibit migration was dependent on cell number, suggesting that the fatty acid effects on leukocyte migration in vivo may be governed by the stage of the inflammatory response. It was concluded that the PUFA rather than their metabolites were responsible for the inhibition since: (a) antioxidants did not prevent the PUFA-induced migration inhibition and the hydroxylated intermediates were less active, and (b) inhibitors of the cyclooxygenase and lipoxygenase pathways were without effect. Inhibitors of protein kinases and calmodulin-dependent enzyme system did not prevent the PUFA-induced migration inhibition, which was also independent of phospholipase D-catalyzed hydrolysis of phospholipids. It is also shown that PUFA decrease the FMLP-induced Ca2+ mobilization.

Calcium↗
PubMed1993

Recruitment of primary care physicians to care for patients with human immunodeficiency virus infection in a large northwestern county.

BACKGROUND: We evaluated an initiative to recruit and to educate physicians to care for persons with human immunodeficiency virus (HIV) infection in King County, Washington, and to refer patients to them through a centralized telephone referral service (the acquired immunodeficiency syndrome [AIDS]/HIV Care Access Project). METHODS: Six physicians trained in AIDS care recruited primary care physicians in clinics throughout King County; the physician cohort was monitored for behavior in accepting referrals during the ensuing year. RESULTS: Of 250 primary care physicians contacted initially, 79 of 120 who met with AIDS-trained physicians were willing to accept patient referrals. Willingness was not related significantly to age, sex, years in practice, or specialty, but was related to level of experience with HIV/AIDS care and current practice. The recruitment initiative increased the physicians available to the telephone referral service by 93% (from 85 to 164). More physicians (41) joined the referral service in the ensuing year, during which 647 patient referrals were made to these 205 physicians (median referral rate of one patient per quarter). Four physicians requested cessation of referrals, however, two later asked for referrals to continue. CONCLUSION: The recruitment initiative was successful in increasing the number of primary care physicians available to accept patients with HIV infection into their practices (thereby reducing the burden of HIV referrals on a small pool of providers), and in establishing a county-wide telephone service to coordinate these referrals. The initiative was self-sustaining, with an ongoing influx of new providers willing to take referrals.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Germline manipulation of glucose homeostasis via alteration of glucose transporter levels in skeletal muscle.

Transgenic mice were constructed that overexpress the human Glut1 glucose transporter in skeletal muscle. Transcription of the human Glut1 cDNA was driven by the rat myosin light chain 2 promoter. Soleus and quadriceps muscles from transgenic mice expressed increased levels of Glut1 protein relative to muscles obtained from nontransgenic littermates, but there was no difference in the level of Glut4 protein between the two groups. Skeletal muscles isolated from the transgenic animals exhibited 3-4-fold increases in basal glucose uptake relative to muscles obtained from nontransgenic littermates. Muscles isolated from nontransgenic littermates exhibited 2-3-fold increases in glucose transport after incubation in the presence of insulin, but no insulin-stimulated increase in transport was observed in the muscles of transgenic mice. Plasma glucose levels were reduced by 18 and 30%, respectively, in fed and fasted transgenic mice relative to their nontransgenic siblings, but insulin and glucagon levels were not significantly different between the two groups. Glucose disposal following an oral glucose load was markedly enhanced in the transgenic animals, and plasma lactate and beta-OH-butyrate levels were elevated in both fed and fasted transgenic mice. These data strongly support the hypothesis that glucose transport plays a key role in whole body glucose homeostasis. They also demonstrate that the level of a glucose transporter in skeletal muscle can significantly influence the blood glucose set point and alter the levels of other fuel metabolites in the blood.

3-Hydroxybutyric Acid↗
PubMed1993

Evidence from transgenic mice that glucose transport is rate-limiting for glycogen deposition and glycolysis in skeletal muscle.

A line of transgenic mice was constructed in which the human Glut1 glucose transporter is overexpressed in skeletal muscle. Overexpression of Glut1 protein was evident in epitrochlearis, extensor digitorum longus (EDL), and quadriceps muscles, and resulted in 6.6-7.4-fold elevations in basal glucose transport activity as measured in isolated muscles in vitro. The elevated glucose transporter activity in the skeletal muscles of transgenic mice was associated with a 10-fold increase in glycogen concentration in EDL and quadriceps muscles that was not due to an increase in muscle glycogen synthase activity or a decrease in glycogen phosphorylase activity. The increased glucose transport activity also resulted in a 2-fold increase in muscle lactate concentration, with no increase in muscle glucose 6-phosphate. Despite a slight (10%) increase in muscle hexokinase activity, there was a 4-fold increase in total muscle free glucose in transgenic mice, indicating that hexokinase becomes rate-limiting for glucose uptake when the rate of glucose transport is very high. These results demonstrate that the muscle glycogen content can be dramatically elevated by increasing the muscle Glut1 protein level and that glucose transport is a rate-limiting step for muscle glucose disposal in normal, resting mice.

Animals↗
PubMed1993

Long and very long chain polyunsaturated fatty acids of the n-6 series in rat seminiferous tubules. Active desaturation of 24:4n-6 to 24:5n-6 and concomitant formation of odd and even chain tetraenoic and pentaenoic fatty acids up to C32.

The formation of long and very long chain (VLC) n-6 polyunsaturated fatty acids (PUFA) in isolated rat seminiferous tubules was investigated by following the metabolism of three 1-14C-labeled n-6 tetraenoic fatty acids (20:4, 24:4, and 32:4) and [U-14C]acetate. In contrast to [14C]32:4, which was poorly incorporated and altered, [14C]20:4 and [14C]24:4 were efficiently taken up by the tubules, esterified into lipids, elongated to VLCPUFA, and desaturated to pentaenoic fatty acids; the rate of [14C]24:4 desaturation to [14C]24:5 was notably high. The main products with [14C]acetate as precursor were labeled saturates and VLCPUFA, most of the label in tetraenoic and pentaenoic acids appearing in 24:4 and 24:5, respectively. These two C24 polyenes, connected by a delta 6 desaturation, may play a central role in n-6 PUFA metabolism, in their capacity as potential precursors of longer polyenes via elongation and of shorter ones, such as 22:5n-6, via retroconversion. Triacylglycerols, rich in C22 and C24 polyenes, incorporated the greatest amounts of both [14C] acetate-derived and exogenous 14C-PUFA, suggesting that this lipid class is involved in the traffic and metabolism of testicular PUFA. The detection of a series of unusual odd-chain tetraenoic and pentaenoic acids, also labeled with [U-14C]acetate, suggests that a PUFA chain shortening mechanism occurs in testis involving alpha- in addition to beta-oxidation. We speculate that alpha-oxidation plays a role in the retroconversion of PUFA.

Acetates↗
PubMed1993

Formic acid is a product of the alpha-oxidation of fatty acids by human skin fibroblasts: deficiency of formic acid production in peroxisome-deficient fibroblasts.

Human skin fibroblasts in culture can oxidize beta-methyl fatty acids, such as phytanic acid and 3-methylhexadecanoic acid, to CO2 and water-soluble products. The latter are released largely into the culture medium. The major water-soluble product formed from [1-14C]phytanic and [1-14C]3-methylhexadecanoic acids is [14C]formic acid. As phytanic acid and 3-methylhexadecanoic acids contain beta-methyl groups and theoretically cannot be degraded by beta-oxidation, we postulate that formic acid is formed from fatty acids by alpha-oxidation. The marked reduction in formic acid production from beta-methyl fatty acids in peroxisome-deficient skin fibroblasts suggests that peroxisomes are involved in the generation of C1 units.

Cells, Cultured↗
PubMed1993

Percutaneous biopsy in the anterior thoracic spine.

Over a 24-month period, seven patients have undergone nine diagnostic closed percutaneous biopsies of thoracic vertebral body lesions. Seven of the nine biopsies were performed using the Craig trephine biopsy set. All seven biopsies provided diagnostic material. Two biopsies were performed with 22-gauge needles and aspiration technique. One provided diagnostic material. The only complication was a small pneumothorax that spontaneously resolved. Current editions of orthopedic texts give mixed recommendations as to the route of vertebral body biopsy in the thoracic spine. Most recommend open rather than percutaneous biopsy, particularly above T10. Review of current orthopedic literature, however, reveals overwhelming support for the use of closed biopsy techniques as the procedure of choice for tissue diagnosis of thoracic vertebral body lesions. As in this limited series, the reported positive biopsy ratio is high and the complication rate acceptably low.

Adolescent↗
PubMed1993

Dopamine release and metabolism in nucleus accumbens and striatum of morphine-tolerant and nontolerant rats.

Morphine administered at high doses produces a biphasic locomotor effect, characterized by an initial locomotor depression, followed a short time later by hyperlocomotion. Prior exposure to morphine produces tolerance to the motor-depressive effects and sensitization to the motor-activating effects of morphine. Little is known of the neurochemical changes that occur to produce tolerance and sensitization to morphine. In the present study, we developed a morphine pretreatment regimen in rats that produced both tolerance and sensitization to a high (30 mg/kg) dose of morphine. Using in vivo microdialysis, we then measured dopamine (DA), dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA) release in the nucleus accumbens (NAC) and striatum (STR) in morphine- and saline-pretreated rats after acute morphine administration. In morphine-tolerant/sensitized rats, basal DA concentrations in the NAC were higher and levels of DOPAC and HVA in the NAC after acute morphine injection were greater compared to controls. These results suggest that the NAC, but not the STR, may be important in mediating tolerance and sensitization to opiates.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Effects of cooperative and individualistic learning on prospective elementary teachers' music achievement and attitudes.

The effects of cooperative and individualistic learning on the achievement and attitudes of prospective elementary school teachers (non-music majors) in a course in music teaching methods were examined. Forty-three American college students were randomly assigned to conditions stratified on the basis of previous musical experience. Cooperation promoted higher achievement than did individualistic efforts on assignments for which each student's grade was affected by the quality of groupmates' work. In addition, students in the cooperative condition were off-task academically (such as walking around the room) less frequently, initiated fewer interactions with the instructor, perceived the instructor to be more supportive, perceived the grading system to be fairer, and perceived the feedback received as being more helpful.

Adult↗
PubMed1993

Sequence of a DNA probe specific for Anopheles quadrimaculatus species A (Diptera: Culicidae).

The nucleotide sequence was determined for a portion of a 12-kb genomic DNA clone specific for Anopheles quadrimaculatus species A. Four short, internally repeated sequences were identified. Synthetic oligonucleotide probes were prepared based on these four repeats. The oligonucleotides are highly specific and can be reliably used to separate individuals of An. quadrimaculatus species A from members of other species of the complex.

Animals↗
PubMed1993

Endobronchial nocardial infection.

The rare presentation of nocardial infection as an endobronchial "tumour" is reported. Haematogenous dissemination occurred after fibreoptic bronchoscopy and biopsy, a phenomenon not previously described in nocardial infections. This case highlights the difficulties in diagnosing pulmonary nocardial infection and the potential for invasive procedures to disseminate the disease.

Aged↗
PubMed1993

Hydrocortisone and tumor necrosis factor in severe community-acquired pneumonia. A randomized controlled study.

BACKGROUND: Community-acquired pneumonia is a major cause of death in third world countries. Antimicrobial therapy may have little impact on the natural history of patients with severe pneumonia. We hypothesized that the intrapulmonary production of tumor necrosis factor-alpha (TNF-alpha) may be responsible for the progressive lung injury and shock commonly seen in patients with severe pneumonia after commencing antibiotic therapy. AIM: To investigate the effects of a single bolus of hydrocortisone on the clinical course and serum TNF-alpha levels of patients with severe community-acquired pneumonia. DESIGN: Randomized placebo-controlled study. SETTING: Multidisciplinary ICU of a tertiary care teaching hospital. PATIENTS AND METHODS: Patients with three or more British Thoracic Society criteria of severe pneumonia were studied. Patients were randomized to receive either a single dose of hydrocortisone (10 mg/kg) or placebo 30 min prior to commencing antibiotic therapy. Patients were treated with cefotaxime and other antibiotics as clinically indicated. Blood for TNF-alpha was taken at the time of hospital admission and repeated 2, 6, and 12 h after starting antibiotic therapy. RESULTS: Thirty patients were studied: 16 received placebo and 14 received hydrocortisone. The patients who received placebo tended to be sicker than the patients who received hydrocortisone. The baseline TNF-alpha value was 989 +/- 374 pg/ml in the placebo group and 827 +/- 394 pg/ml in the hydrocortisone group. In both groups of patients, the TNF-alpha levels did not change significantly with time. There was no correlation between the TNF-alpha levels and the APACHE II score, lung injury score, or outcome. The only variable that predicted outcome was the APACHE II score. CONCLUSION: Bactericidal antibiotics do not increase serum TNF-alpha levels in patients with severe pneumonia. Hydrocortisone given prior to antibiotic treatment had no effect on the serum TNF-alpha levels or the clinical course of patients with severe community-acquired pneumonia.

Adult↗