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Biomedical subjects

R Roelofs

Publications and source records attributed to R Roelofs.

11 recordsLinked to original sources
PubMed2000

The alternative oxidase in roots of poa annua after transfer from high-light to low-light conditions.

The activity of the alternative pathway can be affected by a number of factors, including the amount and reduction state of the alternative oxidase protein, and the reduction state of the ubiquinone pool. To investigate the importance of these factors in vivo, we manipulated the rate of root respiration by transferring the annual grass Poa annua L. from high-light to low-light conditions, and at the same time from long-day to short-day conditions for four days. As a result of the low-light treatment, the total respiration rate of the roots decreased by 45%, in vitro cytochrome c oxidase capacity decreased by 49%, sugar concentration decreased by 90% and the ubiquinone concentration increased by 31%, relative to control values. The absolute rate of oxygen uptake via the alternative pathway, as determined using the 18O-isotope fractionation technique, did not change. Conversely, the cytochrome pathway activity decreased during the low-light treatment; its activity increased upon addition of exogenous sugars to the roots. Interestingly, no change was observed in the concentration of the alternative oxidase protein or in the reduction state of the protein. Also, there was no change in the reduction state of the ubiquinone pool. In conclusion, the concentration and activity of the alternative oxidase were not changed, even under severe light deprivation.

Carbohydrate Metabolism↗
PubMed1999

Clinical and genetic characteristics of a five-generation family with a novel form of myotonic dystrophy (DM2).

We report the clinical and genetic characteristics of a five-generation family (MN1) with an unusual form of myotonic dystrophy (DM). Affected individuals have clinical features that are similar to DM including myotonia, distal weakness, frontal balding, polychromatic cataracts, infertility and cardiac arrhythmias. Genetic analyses reveal that affected individuals do not have the CTG expansion associated with DM, nor is the disease locus linked to the DM region of chromosome 19. We have also excluded the MN1 disease locus from the chromosomal regions containing the genes for the muscle sodium (alpha- and beta-subunits) and chloride channels, both of which are involved in other myotonic disorders. We have recently mapped the disease locus (DM2) in this family to a 10 cM region of chromosome 3q [Ranum LPW, Rasmussen PF, Benzow KA, Koob MD, Day JW. Nat Genet 1998;19:196-198]. The genetically distinct form of myotonic dystrophy in the MN1 kindred shares some of the clinical features of previously reported families with proximal myotonic myopathy (PROMM). The size of the MN1 family (25 affected individuals) makes it a unique resource for both clinical and genetic studies. This second form of myotonic dystrophy may help resolve the confusion that remains about how the CTG repeat expansion in the 3' untranslated portion of the myotonin protein kinase gene causes the multisystem involvement of DM.

Adolescent↗
PubMed1993

Effects of argon laser light, alternate source light, and cyanoacrylate fuming on DNA typing of human bloodstains.

Restriction fragment length polymorphism (RFLP) profile results were obtained from deoxyribonucleic acid (DNA) isolated from human bloodstains that had been subjected to cyanoacrylate ester ("superglue") fuming, argon ion laser light and alternate light sources. All RFLP profile results obtained from treated samples were consistent with the DNA pattern from untreated bloodstains.

Argon↗
PubMed1985

Cisplatin neurotoxicity: failure to demonstrate vitamin B12 inactivation.

Cisplatin binds in vitro with vitamin B12 coenzymes at physiologic pH and temperature. We have hypothesized that cisplatin-induced neurotoxicity is due to an in vivo inactivation of the cobalamin coenzymes. Vitamin B12 metabolism was studied in patients treated with cisplatin for advanced cancer. Serum levels of B12 and B12-binding capacity remained normal during cisplatin therapy. Excessive urinary excretion of methylmalonic acid and homocystine, which are both metabolic correlates of cellular cobalamin deficiency, was not demonstrated after cisplatin administration. Thus, we find no evidence to implicate cellular B12 deficiency as a mechanism of cisplatin neurotoxicity.

Analysis of Variance↗
PubMed1979

Reactions of families to children with Duchenne muscular dystrophy.

Twenty-five families were interviewed to examine their adjustments to having a child with Duchenne muscular dystrophy (DMD). Chronic emotional stress experienced by families of DMD children was found to be a significant problem in the overall management of the illness. Based on information obtained from the assessment of families' adaptation to their child's illness, recommendations are made concerning parent education, school placement, facilitation of marital harmony, informing the child about his illness, and sensitivity to the responses of other family members.

Adaptation, Psychological↗
PubMed1979

Mechanism of action of penicillamine in the treatment of avian muscular dystrophy.

Penicillamine, a cysteine analog with a reduced sulfhydryl group, has been used in this laboratory for the treatment of hereditary avian dystrophy. The drug delays the onset of symptoms and alleviates the debilitating aspects of the disease. To study the mechanism of drug action, the effects of penicillamine on white and red muscles of dystrophic chickens were examined with regard to the specific activities of the soluble enzymes glyceraldehyde-3-phosphate dehydrogenase, acetylphosphatase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glutathione reductase, glutathione preoxidase, superoxide dismutase, and catalase. The sulfhydryl contents of the soluble proteins and the concentration of myoglobin were also determined. In white dystrophic muscle (pectoral), there were large alterations in the various enzymatic activities compared to normal levels. In the DISCUSSION, these changes are related to the pathogenesis of the disease and to the adaptive response for protection of the severely affected fast fibers. Red dystrophic muscles (thigh) were minimally involved, in accordance with the known sparing action of the slow fiber type. The results suggested that the disease process in dystrophic muscle may be due to oxidation of the essential sulfhydryl groups of proteins. Penicillamine may produce therapeutic effects by altering the intracellular redox status, thereby promoting better regulation of enzymatic activity, membrane stability, and improved muscle function.

Animals↗
PubMed1978

Erythrocyte membrane abnormalities in Duchenne muscular dystrophy monitored by saturation transfer electron paramagnetic resonance spectroscopy.

Saturation transfer electron paramagnetic resonance and the spin label 2-(3-carboxypropyl)-4,4-dimethyl-2-tridecyl-3-oxazolidinyloxyl were used to study erythrocytes from patients with Duchenne muscular dystrophy or Becker syndrome and from age-matched normal boys. There were significant differences in the spectral intensities of erythrocytes from Duchenne patients when compared to controls. Spectral intensities increased with time in the former; no such change was observed in the latter. Saturation transfer electron paramagnetic resonance spectra of erythrocytes from patients with Becker syndrome were significantly different from those from Duchenne patients but were not significantly different from normals. These observations suggest the possible usefulness of these techniques in the differential diagnosis of Duchenne muscular dystrophy. Spin label concentration spectral studies suggest that the observed spectral differences between Duchenne patients and controls were due to differential spin exchange phenomena.

Adolescent↗
PubMed1975

Beneficial effects of penicillamine treatment on hereditary avian muscular dystrophy.

Hereditary muscular dystrophy in chickens of the New Hampshire strain was treated with penicillamine from the 9th day after hatching to the 425th day. The adult maintenance dose for males was 50 mg/kg per day and for females, 13-65 mg/kg per day. In avian dystrophy, deterioration of the muscle fibers is evidenced in the 2nd mo by an inability of the birds to rise after falling on their backs and by a progressive rigidity of the wings. The drug delayed the onset of symptoms and partially alleviated the debilitating aspects of the disease. Penicillamine produced three major improvements: (a) better righting ability when birds were placed on their backs; (b) greater wing flexibility; (c) and suppression of plasma creatine phosphokinase activity. The results are statistically analyzed and discussed in relationship to Duchenne dystrophy. Normal birds were not affected by penicillamine as judged by these parameters. The rationale for using penicillamine, a sulfhydryl compound with reducing properties, was (a) to attempt to protect essential thiol enzymes in the anabolic and glycolytic pathways against inactivation and (b) to prevent collagen cross-linking and deposition in muscle. Although the precise mechanism of drug action has not been determined. the possible role of penicillamine in mitigating the symptoms of genetic dystrophy in man is under consideration. Further, penicillamine may have a more generalized application i the prevention of contractures in a variety of neuromuscular disorders.

Animals↗