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D L Edwards

Publications and source records attributed to D L Edwards.

51 records · Page 3Linked to original sources
PubMed1976

Selection of extranuclear mutants of Neurospora crassa.

A procedure is described that produce primarily extranuclear mutants, of Neurospora carassa. An analysis of five mutants. [cni-3], [rsp-2], [rsp-3], E1RSP-4], IS PRESENTED. All five mutants segregate in an extranuclear manner. They can be assorted into two classes based on their respiratory properties: (1) those with cyanide-insensitive respiration (cni); (2) those with slow respiration (rsp). All of the mutants are female sterile. The respiratory trait can be placed in different nuclear backgrounds by heterokarytoic transfer. The abnormal respiratory traits are observed in mitochondria isloated from the mutants and it is likely that the mutations are in mitochondrial DNA.

Cell Nucleus↗
PubMed1975

Regulation of mitochondrial membrane assembly in Neurospora crassa. Transient expression of a respiratory mutant phenotype.

Cultures of mutant cni-1, a chromosomal mutant of Neurospora crassa, undergo a marked change in respiratory properties as the age of the culture increases. Early log phase cultures have a high level of respiration that is insensitive to inhibition by cyanide or antimycin A. Late log and stationary phase cultures have reduced rates of respiration. A high percentage of this respiration is inhibited by cyanide. Mitochondria from early log phase cni-1 have an excess of cytochrome c and little or no detectable cytochrome aa3. Mitochondria from late log and stationary phase cultures have levels of c-, b-, and a-type cytochromes that are not significantly different in concentration from those found in wild type cells. The cytochrome aa3 content and the cytochrome oxidase activity of cni-1 mitochondria increase 5- to 10-fold as the age of the culture increases. Mitochondria from early log phase cells of cni-1 synthesize only polypeptides of apparent molecular weights 7,000 to 10,000 and donot synthesize any of the mitochondrial components of cytochrome oxidase. Mitochondria from late log and stationary phase cells synthesize the normal complement of mitochondrial translation products including the mitochondrial components of cytochrome oxidase. The assembly of cytochrome oxidase is likely due to the availability of the mitochondrially synthesized components of the enzyme. The regulation of mitochondrial translation in the cni-1 mutant is independent of the nutrient content of the growth medium and is due to the accumulation or depletion of some component within the cell.

Cell Division↗
PubMed1973

Selection of respiratory mutants of Neurospora crassa.

A method is described that permits the isolation of mutants that are defective in mitochondrial respiration. The techniques of inositol-less death and overlay with 2,3,5-triphenyl-2H-tetrazolium chloride are utilized to select for mutant colonies. Colonies that survive inositol-less death and fail to reduce the tetrazolium dye are then tested polarographically for cyanide-sensitive respiration. A preliminary characterization of three mutants obtained by this method is presented. The mutants have been characterized by their cyanide-sensitive respiration rate, growth rate, the state III respiration rate of isolated mitochondria, inhibition of the respiration of isolated mitochondria by cyanide and antimycin A, and cytochrome spectra. All of the mutants described differ from the parent strain in some of these aspects.

Antimycin A↗
PubMed1973

Altered mitochondrial respiration in a chromosomal mutant of Neurospora crassa.

A mutant of Neurospora crassa (cni-1) has been isolated that has two pathways of mitochondrial respiration. One pathway is sensitive to cyanide and antimycin A, the other is sensitive only to salicyl hydroxamic acid. Respiration can proceed through either pathway and both pathways together in this mutant account for greater than 90% of all mitochondrial respiration. The cni-1 mutation segregates as a nuclear gene in crosses to other strains of Neurospora. Absorption spectra of isolated mitochondria from cni-1 show typical b- and c-type cytochromes but the absorption peaks corresponding to cytochrome aa(3) are not detectable. Extraction of soluble cytochrome c-546 from these mitochondria followed by reduction with ascorbate reveals a new absorption peak at 426 nm that is not present in wild-type mitochondria. This peak may be due to an altered cytochrome oxidase with abnormal spectral properties. Mitochondria from cni-1 have elevated levels of succinate-cytochrome c reductase but reduced levels of nicotinamide adenine dinucleotide reduced form cytochrome c reductase and of cyanide- and azide-sensitive cytochrome c oxidase. These studies suggest that the cni-1 mutation results in the abnormal assembly of cytochrome c oxidase so that the typical cytochrome aa(3) spectrum is lost and the enzyme activity is reduced. As a consequence of this alteration, a cyanide-insensitive respiratory pathway is elaborated by these mitochondria which may serve to stimulate adenosine 5'-triphosphate production via substrate level phosphorylation by glycolysis and the Krebs cycle.

Antimycin A↗
PubMedDate not supplied

Effect of verbal self-disclosure on natural killer cell activity: moderating influence of cynical hostility.

One objective of the present research was to examine the immunological effects of self-disclosing personal information regarding a traumatic or stressful experience. A second objective was to examine the hypothesis that the effect of self-disclosure on immune function is moderated by individual differences in cynical hostility. Forty-three male college undergraduates, classified as high or low on the Cook-Medley Hostility scale were randomly assigned to either a verbal self-disclosure or a nondisclosure discussion condition. Task-induced change in natural killer (NK) cell activity (i.e., cytotoxicity) served as the dependent variable. As predicted, a significant interaction between discussion condition and hostility was obtained. Among subjects in the self-disclosure condition, high hostility subjects exhibited a significantly greater increase in NK cell cytotoxicity than low hostility subjects. The effect of self-disclosure on NK cell activity is moderated by an individual's level of cynical hostility. The greater short term enhancement in NK cell activity observed for hostile persons is a likely correlate of a more pronounced acute arousal response elicited by the self-disclosure task.

Anxiety Disorders↗
PubMedDate not supplied

Orthodontic treatment for an adolescent with a history of acute lymphoblastic leukemia.

This case report describes the treatment of a Class I malocclusion that involved ectopic position of the maxillary permanent left canine and the mandibular permanent right second molar. The patient was an adolescent who presented with a medical history that was remarkable for diagnosis and treatment of acute lymphoblastic leukemia (ALL). Dental history was remarkable for significant, generalized shortened roots that were more severe in the mandibular arch. The treatment included fixed appliance therapy in the maxillary arch only and surgical luxation of the mandibular second molar. Successful integration of the maxillary permanent left canine was accomplished without excessive flaring of the maxillary permanent incisors or disruption of the buccal segment occlusion. The risk of external root resorption on teeth with abnormal root morphology, as a result of fixed appliance therapy, should be weighed against the relative benefits that are expected from treatment.

Adolescent↗
PubMedDate not supplied

Preventing Haemophilus influenzae type b disease.

The pathogenesis of Haemophilus influenzae type b (Hib) disease and methods for limiting spread of outbreaks of Hib disease are reviewed. Many strains of H. influenzae are surrounded by an outer polysaccharide capsule; of the six antigenically distinct capsular types, Hib is the predominant cause of such serious infections as meningitis, especially among children younger than five years of age. The age-specific incidence of Hib disease appears to be related to the relatively small concentrations of anti-Hib antibody present in young children. Children younger than 48 months of age who reside in the same house or attend the same day-care center as a child who develops Hib disease appear to be at increased risk for contracting systemic Hib infections. Prophylactic administration of rifampin 20 mg/kg once daily for four days can substantially decrease asymptomatic carriage of Hib in household contacts of the index patient and reduce the incidence of secondary Hib disease. The index patient should also receive prophylactic rifampin therapy before discharge from the hospital; i.v. antibiotics may cure the systemic infection but allow nasopharyngeal colonization to persist. A vaccine formulated from purified Hib capsular polysaccharide confers protection to more than 90% of children vaccinated at a minimum age of 24 months. Other candidates for vaccination include children between the ages of two and five years who attend day-care centers and children with anatomic or functional asplenia or malignancies. The vaccine is not effective in children younger than 18 months of age (who account for 60% of Hib disease in the U.S.); methods to increase vaccine immunogenicity in young infants are being evaluated. Reduction of Hib disease in the U.S. may be possible through widespread use of the new vaccine.

Adolescent↗