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Biomedical subjects

G D Jones

Publications and source records attributed to G D Jones.

68 records · Page 4Linked to original sources

Bilateral below-knee amputations: experience with 80 patients.

This review expands information concerning the bilateral below-knee (BK) amputee, describing the findings of a retrospective assessment of 80 such patients. Factors evaluated included etiology, associated conditions, time between amputations, late revisions, use of prostheses, and survival. In 63 patients both amputations were because of atherosclerosis. Of these patients, 86% were diabetic and 84% hypertensive. Peak incidence of the second amputation was during the 7th decade. Average time between amputations was 23 months. Forty-five (71%) of the atherosclerotic patients achieved some functional use of bilateral prostheses. The five patients employed at the time of the second amputation returned to work using prostheses. Average survival after the second amputation was 44 months for those deceased, and 64 months for those alive at the end of the study period. Nine patients had amputations because of various forms of injury, including one for sequential developments due to alcohol-related sensory loss. Eight of this group had a diagnosis of alcohol abuse of psychosis. Reasons for amputations included frostbite, burns, suicide attempt and sensory loss. Five achieved long-term but generally suboptimal prostheses use. The findings support the impression that most atherosclerotic bilateral BK amputees can use prostheses and that their survival and low rate of late stump revisions justify restorative efforts. Mental status was the major determinant of amputation and prostheses use among the non-atherosclerotic patients; discharge from psychiatric hospitals without adequate community support systems was probably contributory. Management and prevention require close collaboration between the rehabilitation, surgical, psychosocial, and public health disciplines.

Age Factors↗

Differentiation of asymptomatic patients from symptomatic patients by the slope of the forced vergence fixation disparity curve.

Eighty-nine optometry students were divided into an asymptomatic group and a symptomatic group on the basis of a case history. A forced vergence fixation disparity (FD) curve was generated for each subject using a Disparometer (Vision Analysis, Columbus, Ohio). Slopes were calculated for each curve. In addition, each curve was labeled steep or flat based on a previously determined cutoff point of -0.96 min/delta (Sheedy, 1980). Steep curves did not correlate well with symptomatic patients, whereas flat curves did not correlate well with asymptomatic patients. An independent t-test found no significant difference between the two groups.

Fixation, Ocular↗

A comparison of the reactions of cytochrome c oxidase, cytochrome c and azurin with Cr2+ ions.

The reduction of cytochrome c oxidase (EC 1.9.3.1) by Cr2+ ions has been studied by stopped-flow spectrophotometry and is compared with the Cr2+ reduction of cytochrome c and azurin. The effects of temperature, pH, and added anions (e.g., SCN-) have been investigated. The behavior of the electron acceptor site of cytochrome c oxidase stands in contrast to that of the other redox proteins with regard to the effects of added anions and we suggest that this reflects the more buried nature of this site in the complex enzyme.

Animals↗

Labeling of the electron entry site of cytochrome c oxidase using 51Cr2+.

51Cr2+ has been used as a probe to locate the electron entry site of bovine cytochrome c oxidase. The results of static titrations, column chromatography, and low pH LDS polyacrylamide gradient gel electrophoresis are reported. Of the protein subunits of cytochrome c oxidase, only subunit II is specifically labeled during electron transfer from Cr2+ to the electron accepting site. We therefore conclude that this site is located in subunit II. Our results provide experimental evidence to corroborate the view that this subunit is associated with redox centers of the enzyme, an hypothesis based on indirect evidence provided by the amino acid sequences and analogy with the bacterial enzyme.

Animals↗

Reactions of cytochrome c oxidase with sodium dithionite.

The reduction of cytochrome c oxidase (EC 1.9.3.1) by dithionite was investigated by stopped-flow spectrophotometry and flow-flash techniques in the presence of CO. Of the two haem groups present in the enzyme, that associated with cytochrome alpha is the first reduced. The second-order rate constants for reduction of a number of redox proteins (cytochrome c, stellacyanin and azurin) by the S2O4(2-) and SO2.- anions are reported, and the values are compared with those determined for cytochrome c oxidase. These results are discussed in terms of the accessibility and charge distribution of the electron-entry site of cytochrome c oxidase.

Dithionite↗

A method for the preparation of low-pH dodecyl sulphate/polyacrylamide-gradient gels.

1. A low-pH lithium dodecyl sulphate/polyacrylamide-gradient slab-gel system, suitable for electrophoresis, is described, and the migration properties of standard proteins are compared on this and conventional high-pH gels. 2. Cytochrome oxidase may be partially resolved into its component polypeptides. The order of migration of these is, however, dependent on the pH of the gel system.

Electron Transport Complex IV↗

Structure and mobility of electron gain and loss centres in proteins.

Radiation damage to proteins is a topic of intense interest to those involved in radiation effects in biology, and also to those involved in radiotherapy. Although it has been widely studied, fundamental processes in protein damage are very hard to specify because of the complexity of the final damage products. But the non-invasive technique of electron-spin resonance is ideally suited to the task of detecting and identifying the primary and secondary products as these are expected to contains unpaired electrons (that is, free-radicals) and such species are uniquely detected by this sensitive form of spectroscopy. Our present study shows that a major radical species formed by electron loss in a range of proteins is the backbone amido radical, -N.(CO)-, characterized by hyperfine coupling to one 14N nucleus. These centres are efficiently trapped in proteins at low temperatures. In contrast, the expected backbone electron-capture centres, -NH(CO.-)-, are not readily trapped and electron transfer occurs until the ejected electron is trapped by some electrophilic centre. Such electron mobility was in fact established in our previous work on oxyhaemoglobin (FeO2----FeO2-), superoxide dismutase (Cu(II)----Cu(I] haemocyanin (Cu(II)O2Cu(I)----Cu(I)O2Cu(II] and various proteins containing S-S bonds (-S-S-)----(-S.-S-) (refs 1-4 respectively). This is strongly supported by our observation that such electrons are captured by DNA molecules, giving T.- centres, when nucleohistones are irradiated, and that Fe(CN)3-(6) ions readily scavenge such electrons from proteins which are devoid of highly electrophilic centres.

Electron Spin Resonance Spectroscopy↗

Electron transfer from protein to DNA in irradiated chromatin.

Irradiation of dry or fully hydrated frozen DNA systems (conditions of direct damage) has been shown by electron-spin resonance spectroscopy to give rise to electron-gain centres localized on thymine (T.-) and electron loss centres ('holes') localized on guanine (G.+) with approximately equal yields. Our parallel studies on the development of both single- and double-strand breaks under comparable conditions provide good evidence that these radical centres are the precursors to such damage, and we and others have argued that this may be of relevance to the damage pathways in vivo. We now report evidence that when DNA is complexed to proteins as it is in the nuclei of eukaryotes, electron transfer from the histone to DNA is facile, leading to a significant increase in the yield of electron-gain centres in DNA as judged from their electron-spin resonance spectra. In contrast 'holes' generated in the protein are trapped and do not lead to any detectable increase in the yields of G.+.

Animals↗

The role of drugs and alcohol in urban minority adolescent suicide attempts.

This study examined psychopathology and substance use in 15 African American adolescents who attempted suicide and 15 African American adolescents who did not attempt suicide (control group). Both groups of adolescents and their parents completed questionnaires that addressed depression, behavior problems, family functioning, and drug and alcohol use. On the basis of group means of the Children's Depression Inventory (Kovacs & Beck, 1977), the Youth Self-Report (Achenbach & Edelbrock, 1987), and the Child Behavior Checklist (Achenbach & Edelbrock, 1983), the suicidal youth were found to have a significant level of depression in addition to a variety of internalizing and externalizing behavior disorders. Similarly, on the Multigating Substance Use Evaluation System (Jurkovic & Bruce, 1991), the suicidal youth were at a high risk for alcohol and drug abuse. The suicidal group reported more alcohol and drug abuse than the control group. The results indicated that suicidal African American adolescents used significant amounts of drugs and alcohol, which may be associated with suicide attempts.

Adolescent↗