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Biomedical subjects

D W Johnson

Publications and source records attributed to D W Johnson.

At least 181 records · Page 10Linked to original sources
PubMed1988

Accumulation of pristanic acid (2, 6, 10, 14 tetramethylpentadecanoic acid) in the plasma of patients with generalised peroxisomal dysfunction.

The plasma of some patients with biochemical evidence of a generalised peroxisomal dysfunction (GPD) show greatly increased levels of phytanic acid as well as its alpha-oxidation product, pristanic acid (2, 6, 10, 14-tetramethylpentadecanoic acid). Increased amounts of 14- and 16- carbon branched chain fatty acids are also found in some of these patients. As pristanic acid is present in normal or near-normal amounts in classical Refsum disease and rhizomelic chondrodysplasia, two disorders characterised by deficiencies in phytanic acid oxidation, we speculate that its accumulation is not secondary to a defect in the alpha-oxidation of phytanic acid, but is indicative of a block in the peroxisomal beta-oxidation of pristanic acid. The finding of phytanic acid, as well as a number of its metabolites in patients with inherited defects in peroxisomal biogenesis indicates that a number of the steps in phytanic acid degradation may be confined to peroxisomes.

Adrenoleukodystrophy↗
PubMed1988

Early and long-term effects of acute caloric deprivation in obese diabetic patients.

PURPOSE: It is generally assumed that diet therapy can ameliorate the metabolic derangements experienced by obese type 2 diabetic patients, thereby leading to discontinuation of insulin or oral sulfonylurea drug therapy. We decided to retrospectively investigate which clinical and biochemical parameters affect therapeutic responses. PATIENTS AND METHODS: Sixty-four poorly controlled obese diabetic patients were hospitalized and placed on a precisely defined, hypocaloric diet. Known duration of diabetes, type of pharmacologic therapy, body weight, weight loss, fasting plasma glucose concentrations, C-peptide levels, hemoglobin A1C, and plasma lipid levels were assessed, as were nitrogen and electrolyte balances. RESULTS: Average weight loss was 13 pounds in a mean of 23 days. During hospitalization, the mean fasting plasma glucose value for the group fell from 221 +/- 10 to 122 +/- 5 mg/dl. In 45 patients (73 percent), the final fasting plasma glucose level was less than 125 mg/dl (mean: 102 +/- 2 mg/dl). Oral glucose tolerance even in those patients in whom fasting plasma glucose levels normalized was still grossly diabetic at the end of the hospital stay, deteriorating further after three days of liberalized caloric intake. In part this may have been due to decreased insulin secretory reserve as reflected by blunted plasma C-peptide response. Forty of 42 patients who entered the study taking insulin were able to discontinue the drug within one to seven days of hospitalization. After a mean follow-up period of 19 months, only 10 of 50 patients continued to maintain fasting euglycemia; five were on diet alone, and five were receiving oral hypoglycemic agents. Thirteen patients were receiving insulin therapy. CONCLUSION: Diet therapy in these patients resulted in short-term improvement of glycemic control and, in the majority, normalization of fasting plasma glucose levels. However, long-term outpatient follow-up revealed that relapse occurred in most patients.

Blood Glucose↗
PubMed1988

Structure-activity studies of melatonin analogues in prepubertal male rats.

Comparison has been made between the activity of the pineal hormone melatonin, and several analogues and metabolites in inhibiting sexual development in a protein-restricted prepubertal rat model. Eleven melatonin analogues or metabolites were tested with the aim of evaluating the model as a test of the hypothesis that melatonin acts as a prohormone and that the ring schism metabolites (kynurenamines) mediate many of the effects attributable to melatonin. Although the hypothesis could not be confirmed, modification of the melatonin structure by lengthening the acrylamide side chain or by replacing the 5 methoxy function with fluorine resulted in loss of biological potency. Modification of the melatonin structure to block the two known points of metabolism resulted in no significant alteration in biological activity. Thus 6-chloromelatonin (blocking 6-hydroxylation) and 2,3-dihydromelatonin (blocking oxidative cleavage of the C2-C3 bond) and 6-chloro-2,3-dihydromelatonin remained biologically active. The metabolic products of brain indoleamine-2,3-dioxygenase, N-acetyl-N2-formyl-5-methoxy kynurenamine (aFoMK) and N-acetyl-5-methoxy kynurenamine (aMK), paradoxically were also biologically active.

Animals↗
PubMed1988

Cost justification for materials management.

Recently, a study was conducted to determine the potential cost savings resulting from the implementation of an on-line, real-time materials management system for the surgical department of a 900-bed, multi-hospital facility in Little Rock, Ark. As a result of this study, anticipated savings of more than $600,000 annually have been identified. The following text highlights cost savings and features recommendations for those healthcare organizations interested in conducting a similar review.

Arkansas↗
PubMed1988

[Epidemiology of diarrhea caused by Escherichia coli and rotavirus in calves and lambs in Morocco].

An epidemiological survey on E coli and rotavirus associated diarrheas in one to twenty five days old calves and lambs was made in three regions: Rabat-Kenitra, Marrakech and Agadir. Isolated E coli K99 stains have been studied of a biochemical, serotypical (O antigen) and antibiotypical point of view. The identification of rotavirus was made by ELISA test. Persistence of K99 antigen and heat stable toxin A was examined after a conservation of 5 weeks at - 18 degrees C. The frequency of E coli K99 or rotavirus associated diarrheas is respectively 26.9% and 29.7% in calf, 10% and 30% in lamb. This incidence considerably decreases from the 20th day in calf and from the 11th day in lamb. It must be observed that 34.8% of cases of diarrheas in calf and 55% in lamb cannot be ascribed to investigated agents. Only 12 out of 42 E coli K99 strains belong to serogroups O101, O8 and O9. Preservation of strains to - 18 degrees C comes with the loss of K99 antigen. These strains are not toxinogens. Among the strains having kept this antigen, 29% are toxinogens. Surveyings of antibiotics resistance was discussed.

Animals↗
PubMed1988

Determination of phospholipid base structure by CA MIKES mass spectrometry.

The fast atom bombardment spectra of three phospholipids containing a secondary, tertiary, and quaternary nitrogenous base attached to a 1,2-dipalmitoyl-sn-glycero-3-phosphate skeleton were shown to each contain an ion derived from the intact nitrogenous base. The collisional activation mass analyzed ion kinetic energy spectroscopy (CA MIKES) spectrum produced from each of these ions was shown to be unique for the particular base. The technique thus provides a non-destructive rapid identification of the phosphorylated base of phospholipids.

Humans↗
PubMed1987

Occurrence of unusual molecular species of sphingomyelin containing 28-34-carbon polyenoic fatty acids in ram spermatozoa.

The high levels of very long chain fatty acids found in ram spermatozoa are located almost exclusively in one of two separable species of sphingomyelin. Mass spectral analysis, including fast atom bombardment of the purified sphingomyelin, has shown the fatty acids to have a carbon chain length of between 28 and 34, with between four and six double bonds, and to belong predominantly to the n-3 series.

Animals↗
PubMed1987

Discovery of multiple organofluorophosphate hydrolyzing activities in the protozoan Tetrahymena thermophila.

Recently it has been found that homogenates of Tetrahymena thermophila can hydrolyze the potent acetylcholinesterase inhibitors O,O-diisopropylphosphofluoridate (DFP) and O-1,2,2-trimethylpropylmethylphosphonofluoridate (soman). Upon purification of the DFP hydrolyzing activity 10-fold it had been noted that the soman hydrolyzing activity increased only 2-3 fold. Treatment with manganous ion and comparison of the soman and DFP hydrolysis rates of the homogenate indicated that a mixture of the squid-type and Mazur-type DFPases may be present. Subsequent purification of the enzymatic activities within the Tetrahymena-homogenate demonstrated that there are at least five functioning proteins of molecular weights 67,000 to 96,000. None are directly homologous to the DFPases found in hog kidney or squid. The enzymatic activities are designated DFPase-1 through DFPase-5. A hypothesis is presented that the functions of DFPases are in the normal metabolism of organophosphates naturally synthesized by T. thermophila.

Animals↗
PubMed1987

Pathogenicity of Mycoplasma capricolum in sheep after experimental infection.

Mycoplasma (M.) capricolum has been frequently isolated from diseased as well as from healthy sheep in Morocco. In order to determine its pathogenicity for sheep, experiments were performed in three trials with the Moroccan isolate 012. The following results were obtained: Ewes inoculated intramammarily developed acute mastitis; the organism was transmitted to lambs suckling these ewes. Only a mild mastitis appeared after a second inoculum, performed 5 weeks after the first. Young lambs, 1 month of age, fed four times with M. capricolum broth culture, died during the septicemic phase, showing a generalized septicemia, polyarthritis and a diffuse interstitial pneumonia. Lambs, 2 and 3 months of age inoculated intrabronchially developed a disease, which appeared to be age and weight dependent. The more susceptible animals died within 1-2 weeks after infection. The older lambs recovered gradually from the disease, which was characterized by pneumonia, conjunctivitis and arthritis. A significant increase of antibodies against M. capricolum developed in the older animals in the complement fixation test.

Animals↗
PubMed1987

Intracarotid chemotherapy with 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) in 5% dextrose in water in the treatment of malignant glioma.

After radiotherapy, 20 patients, 18 with documented progression of malignant glioma and 2 with Grade II astrocytoma, received a total of 52 courses of intracarotid 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) at a dose of 150 mg/m2 dissolved in 5% dextrose in water. The patients were treated at 6-week intervals for a maximum of five courses of chemotherapy per patient. Response to treatment was analyzed on computed tomographic scans by measuring the volume of the enhancing tumor and any central low density. From these data, tumor doubling times ranging from 110 to 968 days were obtained. An 11 to 60% reduction in enhancing tumor volume was noted in 8 patients, 2 of whom had a greater than 50% decrease in tumor volume. One patient had no change in tumor volume 110 weeks after the initiation of BCNU chemotherapy. Four patients had tumor in more than one vascular territory; tumor growth was arrested in the perfused territory, but continued in the nonperfused area. In 1 of the 4 patients, tumor also grew along a shunt catheter tract and spread over the surface of the ipsilateral hemisphere. One patient developed clinically asymptomatic leukoencephalopathy after five courses of BCNU. Two patients had postradiation leukoencephalopathy before BCNU treatment. Seventeen patients had peritumoral low density with mass effect after BCNU; thus, the true incidence of BCNU-related leukoencephalopathy could not be determined. All patients experienced transient unilateral orbital pain during the infusion and scleral erythema that lasted for several hours afterward. Loss of vision was noted in 2 patients, although it seemed to be related to the therapy in only 1 patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Using cooperative learning strategies to teach nutrition.

There are three ways in which student-student interaction may be organized for nutrition education. Of the three, cooperation is the only instructional strategy congruent with the goals of nutrition education. The essential elements of cooperative learning and the specific actions teachers need to take to implement it are presented. When cooperative learning is implemented effectively, long-term modifications of nutrition knowledge, attitudes and behavior result. Nutrition education classes will more successfully fulfill their purposes when cooperative learning is primarily used.

Adolescent↗
PubMed1986

Acute toxicity of brass particles to Daphnia magna.

The aquatic toxicity of brass particles was examined. Acute, 48 hour bioassays were performed using the water flea, Daphnia magna. Tests were conducted with uniform suspensions of uncoated brass particles, brass particles coated with a Teflon solution, silica particles, and titanium dioxide particles. The Teflon coating solution and the supernatant of the brass suspension (after settling of the brass) also were tested. All tests were conducted according to guidelines set forth by the US Environmental Protection Agency and the Organization for Economic Cooperation and Development. Mean EC50 determinations of 20.0 micrograms l-1 and 23.6 micrograms l-1 were calculated for uncoated brass particles and coated brass particles, respectively. The silica, titanium dioxide, and Teflon each had an EC50 greater than 1 g l-1. Chemical fate studies demonstrated that the brass dissociated to its ionic components of copper and zinc quickly at pH 2.0. At pH 5.0 and 6.5, the dissociation occurred too slowly to account for the observed toxicity. The data suggested that the toxicity is due to filtration by the daphnids and subsequent ingestion. EC50 determinations for the brass particles are nearly identical with published EC50 values for copper salts.

Alloys↗
PubMed1986

The toxicity of brass dust to the microalgae Ankistrodesmus falcatus and Selenastrum capricornutum.

The toxicity of brass dust was examined by conducting 96 h growth inhibition tests. Two species of algae were used, Ankistrodesmus falcatus (EC50 = 0.316 mg brass/l) and Selenastrum capricornutum (EC50 = 0.056 mg brass/l). Brass dissociates into two components, Cu (68.5%) and Zn (27.5%). Enhanced algal growth was exhibited at concentrations of 0.01 and 0.001 mg brass/l. Available literature on the toxicity of copper to S. capricornutum (EC50 = 0.047 mg Cu/l), indicate that the toxicity of brass dust is due to the ionized copper. Reported toxicities of zinc are orders of magnitude lower than copper. The ionization of the brass is dependent on pH and hardness. The literature cites cases in which copper toxicity varies with pH, clay content and dissolved organics. At present little is known of the fate and distribution of brass dust upon the release into the environment. However, the presence of heavy metals has consistently been shown to impact aquatic systems.

Chemical Phenomena↗
PubMed1986

Neutralization kinetics of bovine viral diarrhea virus by hyperimmune serum: one or multi-hit mechanism.

The kinetics of bovine viral diarrhea (BVD) virus neutralization (VN) by hyperimmune serum followed first order kinetics at low dilutions (1:8 and 1:16) of hyperimmune bovine serum. A lag phase in the VN curve occurred when the serum was further diluted. Addition of rabbit anti-bovine IgG, but not anti-IgM, significantly increased the degree of VN after BVD virus was reacted with further diluted (1:256 dilution) anti-BVD bovine hyperimmune serum. Incubation of virus-hyperimmune serum (1:64 dilution) at 4 degrees C for 0 to 60 min, followed by incubation at 37 degrees C indicated VN occurred as a two-stage process: a binding (temperature-independent) phase that was followed by a triggering (temperature-dependent) phase. The data favor the thesis that neutralization of BVD virus occurs by a multi-hit mechanism and requires combination of at least two molecules of antibody with each virus.

Animals↗
PubMed1986

Mediastinal lymphangioma and chylothorax: the role of radiotherapy.

An 11-year-old boy with a capillary/cystic lymphangioma of the posterior mediastinum is described, in whom a symptomatic chylothorax proved to be refractory to surgical management. The addition of low dose mediastinal radiotherapy (2,000 cGy/10 fractions) resulted in prompt and permanent resolution of the chylothorax. Although operation is the primary modality of treatment for these lesions, the addition of radiotherapy in such refractory patients appears to be well tolerated and efficacious and should result in few long-term complications.

Child↗
PubMed1986

Isolated teenagers, cooperative learning, and the training of social skills.

The effects of individual and group contingencies on the achievement and social integration of isolated, learning-disabled students were studied. Five socially isolated and withdrawn eighth-grade students in foreign-language and math classes were subjects. The choice of working alone or in a group with no academic contingency (i.e., bonus points) was compared with working in cooperative learning groups with a group-academic contingency (i.e., bonus points), a group-academic contingency with social-skills training, and a group-academic contingency in combination with a social-skills contingency (i.e., bonus points). The results indicated that the combination of group-academic and social-skills contingencies produced in the socially isolated and withdrawn students the highest rates of appropriate social interaction with peers, acceptance and liking by peers, positive attitudes toward the subject area, and achievement.

Achievement↗