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Biomedical subjects

M G Jones

Publications and source records attributed to M G Jones.

At least 73 records · Page 4Linked to original sources
PubMed1989

Transient gene expression in electroporated Solanum protoplasts.

Electroporation was used to evaluate parameters important in transient gene expression in potato protoplasts. The protoplasts were from leaves of wild potato Solanum brevidens, and from leaves, tubers and suspension cells of cultivated Solanum tuberosum cv. Désirée. Reporter enzyme activity, chloramphenicol acetyl transferase (CAT) under the control of the cauliflower mosaic virus (CaMV) 35S promoter, depended on the field strength and the pulse duration used for electroporation. Using field pulses of 85 ms duration, the optimum field strengths for maximum CAT activity were: S. brevidens mesophyll protoplasts--250 V/cm; Désirée mesophyll protoplasts--225 V/cm; Désirée suspension culture protoplasts--225 V/cm; and Désirée tuber protoplasts--150 V/cm. The optimum field strengths correlated inversely with the size of the protoplasts electroporated; this is consistent with biophysical theory. In time courses, maximum CAT activity (in Désirée mesophyll protoplasts) occurred 36-48 h after electroporation. Examination at optimised conditions of a chimaeric gene consisting of a class II patatin promoter linked to the beta-glucuronidase (gus) gene, showed expression (at DNA concentrations between 0-10 pmol/ml) comparable to the CaMV 35S promoter in both tuber and mesophyll protoplasts. At higher DNA concentrations (20-30 pmol/ml) the patatin promoter directed 4-5 times higher levels of gus expression. Implications and potential contributions towards studying gene expression, in particular of homologous genes in potato, are discussed.

Chloramphenicol O-Acetyltransferase↗
PubMed1989

Transient gene expression in aleurone protoplasts isolated from developing caryopses of barley and wheat.

Methods have been developed for the isolation of aleurone protoplasts from developing caryopses of Hordeum vulgare and Triticum aestivum in order to study transient expression of introduced genes. Chimaeric gene constructs were introduced into aleurone protoplasts by polyethylene glycol (PEG). Transient expression directed by the 35S promoter from cauliflower mosaic virus (CaMV) of the reporter gene encoding chloramphenicol acetyl transferase (CAT) was detected in aleurone protoplasts from developing barley and wheat grains. Using a similar construct, CAT activity increased when the alcohol dehydrogenase intron 1 fragment from maize was ligated between the 35S promoter and the CAT coding region. The demonstration of transient expression in protoplasts from developing aleurone layers indicates that they may be useful for investigating tissue and developmental control of genes coding for cereal seed proteins.

Brassica↗
PubMed1989

A system for accelerated provision of hearing aids to residents of homes for the elderly.

A study was undertaken to detect undiagnosed deafness in elderly people, living in Part III Residential Homes in North Tees, South Tees and Hartlepool Health Districts, to provide hearing aids and to estimate the subsequent success in rehabilitation. The residents were referred by the senior staff in the homes and assessed by a doctor and audiology technician in a domiciliary setting. Those found to have a significant hearing impairment were prescribed hearing aids without formal pure tone audiometry. A pilot study compared the method of hearing evaluation employed with such conventional testing. Six months after fitting, the degree of compliance with aiding was assessed. The results show a significant level of undiagnosed deafness in the community and, with this method of provision, an acceptance rate of 41.2 per cent of those recommended for aiding at six months which is higher than suggested by previous similar studies of this population.

Aged↗
PubMed1989

The evolution of a simplified method for interpretation of EEG in the preterm neonate.

We describe the evolution of a simplified method for the interpretation of serial EEG in preterm neonates which was tested in a first sample and revised and improved in a second sample of preterm neonates. There were 185 EEGs in the first sample and 206 EEGs in the second sample. The interpretation of the EEGs was related to mental, motor and neurological outcome in late infancy. Serial EEG is an excellent indicator of brain function in the preterm neonate.

Brain↗
PubMed1989

Antitussive agents as N-methylaspartate antagonists: further studies.

The relative potencies of ketamine and the morphinan derivatives dextrorphan, dextromethorphan, and levorphanol as antagonists of the excitatory actions of N-methylaspartate on rat spinal neurones in vivo were examined, both following their microelectrophoretic administration and, with the exception of levorphanol, after intravenous injection. Applied microelectrophoretically, dextrorphan was a more potent N-methylaspartate antagonist than ketamine, levorphanol, or dextromethorphan. After systemic administration, however, dextrorphan was rather less potent than ketamine in this respect, whereas dextromethorphan remained less potent than either ketamine or dextrorphan. Noscapine, an antitussive that lacks anticonvulsant activity, failed to reduce selectively responses to N-methylaspartate as did papaverine, an isoquinoline structurally related to noscapine, and triprolidine, an antihistamine commonly found in proprietary cough medicines. The results are discussed with particular reference to the potential of the compounds tested as anticonvulsant and neuroprotective agents in vivo.

Animals↗
PubMed1989

Fasting urinary hydroxyproline: creatinine ratios in silicosis.

Fasting urinary hydroxyproline: creatinine (HOP:C) ratios were measured in 74 patients with suspected (borderline) silicosis (10), simple silicosis (46) and complicated silicosis (9 silicotuberculosis, 4 massive fibrosis, and 5 combined silicotuberculosis and massive fibrosis) and in 18 healthy subjects (controls). There was no statistically significant difference in urinary HOP:C ratios between control subjects (mean 13.8, SD 3.6) and suspected silicotics (mean 18.0, SD 7.6); however, urinary HOP:C ratios were significantly higher in both simple silicosis (mean 25.0, SD 9.9, p less than 0.001) and complicated silicosis (silicotuberculosis and progressive massive fibrosis) (mean 28.6, SD 11.3; p less than 0.001). Urinary HOP:C ratios appeared to show a graduated increase to their highest levels in category 2 silicosis and thereafter remained constant or declined slightly in category 3 silicosis and massive fibrosis. The results support the suggestion that urinary hydroxyproline might be useful as an indicator of disease progression in established silicosis. However, further longitudinal studies are needed to confirm its predictive value.

Adult↗
PubMed1988

Use of initial ST-segment deviation for prediction of final electrocardiographic size of acute myocardial infarcts.

The decision to administer thrombolytic therapy for limitation of acute myocardial infarction (AMI) size must occur when only the history, physical examination and 12-lead electrocardiogram of a patient are available. A method that could quickly assess the amount of jeopardized myocardium would greatly aid the physician. This study developed formulas from 68 anterior and 80 inferior AMI patients using the extent of initial ST-segment deviation (ST delta) to predict the final AMI size estimated by the Selvester QRS score in a population not receiving reperfusion therapy. Inclusion required: initial anterior or inferior AMI; admission electrocardiogram less than or equal to 8 hours after the onset of symptoms with evidence of epicardial injury; elevated creatine kinase-MB; a predischarge electrocardiogram taken greater than or equal to 72 hours after admission; and no AMI extension before the predischarge electrocardiogram. The extent of epicardial injury was quantified by counting the number of leads with greater than or equal to 0.1 mm ST delta, by the sum (sigma) of ST delta in all leads and by the sigma ST delta in the lead groups associated with each AMI location. These results were compared to the AMI size estimated from the predischarge electrocardiogram. Univariable and multivariable analyses generated these formulas for AMI size: anterior = 3[1.5 (number leads ST increases) - 0.4]; inferior = 3[0.6 (sigma ST increases II, III, aVF) + 2.0]. Thus, formulas based on quantitative measurements of ST delta on the admission electrocardiogram are predictive of final QRS-estimated AMI size, and may be useful in determining the efficacy of acute reperfusion therapy.

Electrocardiography↗
PubMed1988

A comparison between the in vivo and in vitro activity of five potent and competitive NMDA antagonists.

1. Phosphonate analogues of glutamate have been tested and compared as N-methyl-D-aspartate (NMDA) antagonists in electrophysiological and binding experiments. The compounds tested were three established NMDA antagonists: D-2-amino-5-phosphonopentanoate (D-AP5), DL-2-amino-7-phosphonoheptanoate (DL-AP7), 3-(2-carboxypiperazin-4-yl)propyl-1-phosphonate (CPP), and two novel putative NMDA antagonists: 3-(2-carboxypiperidin-4-yl)propyl-1-phosphonate (CPPP) and 3-(2-carboxy-piperidin-4-yl)methyl-1-phosphonate (CPMP). 2. When administered electrophoretically to rat spinal neurones in vivo, these compounds were found to be selective NMDA antagonists with little effect on excitations evoked by quisqualate and kainate. CPMP and CPPP were approximately equipotent with CPP and about 5 times more potent than D-AP5. 3. Following systemic administration, 2-5 mg kg-1 i.v. of CPP, CPMP and CPPP reduced NMDA-evoked excitations by 70-100% whereas 50-100 mg kg-1 of D-AP5 and DL-AP7 produced a similar effect. The onset of the effects required 20-30 min and lasted more than six hours. 4. On bath application to cortical wedges, the IC50 values (microM) for antagonism of 40 microM NMDA were: CPP, 0.64 +/- 0.06 (mean +/- s.e.mean; n greater than 4); CPMP, 1.65 +/- 0.13; CPPP 0.89 +/- 0.09; D-AP5, 3.7 +/- 0.32; DL-AP7, 11.1 +/- 2.1; and DL-AP4 and DL-AP6 were inactive at 100 microM. 5. In binding studies with [3H]-CPP, the Ki values (nM) were: CPP, 446 + 150 (mean + s.e.mean; n > 3); CPMP, 183 + 74 and CPPP, 179 +/- 13 whereas against NMDA (lO microM)-stimulated [3H]- TCP (thienylcyclohexylpiperidine) binding the ICjo values (microM) for CPMP and CPPP respectively were 5.6 + 2.7 and 4.5 + 2.2. 6. Systemic administration of CPPP and CPMP, at doses sufficient to antagonize NMDA, also reduced cardiovascular responses to 5-hydroxytryptamine (Bezold-Jarisch reflex). This illustrates a role for NMDA receptors in central cardiovascular control. 7. The results indicate the systemic doses of piperidine and piperazine analogues of D-AP5 which may be used for assessing the role ofNMDA receptors in central synaptic function.

2-Amino-5-phosphonovalerate↗
PubMed1987

Identification of the optimal electrocardiographic leads for detecting acute epicardial injury in acute myocardial infarction.

Current coronary care electrocardiographic (ECG) monitoring techniques are aimed at detection of cardiac arrhythmias rather than myocardial ischemia. However, in patients with acute myocardial infarction (AMI) who undergo reperfusion therapy, monitoring ST-segment deviation could provide an early noninvasive indicator of coronary artery reocclusion. In this study, the admission 12-lead ECGs of patients with initial AMI were used to propose optimal lead locations for ST-segment monitoring. The study population was selected from consecutive Duke University Medical Center admissions during 1965 to 1981 who met the following inclusion criteria: chest pain for no more than 8 hours, initial AMI documented by ECG and 3 of 4 enzyme criteria, greater than or equal to 0.1 mV (1 mV = 10 mm) of ST elevation in at least 1 of the standard 12 leads (not aVR) on admission ECG, and no ECG evidence of conduction disturbances, ventricular hypertrophy or tachycardia. ST-segment deviation was quantified; AMI location was assigned based on the lead with maximal deviation. Of the 80 patients who had an inferior AMI, lead III was both the most frequent location for ST elevation (94%) and the most common site with maximal ST deviation. Lead V2 had the highest incidence of ST-segment depression (60%). In the 68 patients who had an anterior AMI, lead V2 had the highest frequency of ST elevation (99%). Leads V2 and V3 were the most common sites of maximal elevation. Thus, for monitoring ST deviation, leads III and V2 may be superior to leads II and V1, which are commonly used in arrhythmia monitoring.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1987

The effect of dietary protein on glomerular filtration rate in normal subjects.

The acute effect of the ingestion of 90 g of protein as meat and as milk protein (Casilan) on glomerular filtration rate (assessed by creatinine clearance) was examined in healthy subjects. The creatinine clearance increased 1.5 hours after the ingestion of meat and remained elevated for a further 2.5 hours. The mean maximal increase in creatinine clearance was 18 ml/min. Casilan on the other hand did not produce a significant increase in the creatinine clearance. When 6 subjects ingested 90 g of protein as Casilan daily for 5 days, the creatinine clearance increased after a delay of 3 to 4 days. When the same subjects increased their meat protein intake by 90 g as meat daily for 5 days, the creatinine clearance increased from the first day (by 23 ml/min) and remained elevated throughout the 5 days of study. We conclude that the effect of protein on glomerular filtration rate depends on the type of protein.

Adult↗
PubMed1986

The results of checking a scoring system for neonatal seizures.

We report the result of checking a scoring system for neonatal seizures in which information from the EEG, etiology, neurological examination, seizure type and birth weight are combined to predict neurological sequelae and to make decisions about treatment. The results for two samples are presented and compared. The first sample included 96 neonates; 103 neonates were evaluated in the second sample, yielding data from 199 neonates in the combined samples. The scoring system served to separate neonates who had neurological sequelae at age 10 months or more from those who did not. In addition, the scoring system provided an excellent guide for treatment of neonatal seizures. Neonates with scores less than or equal to 4 can be safely discharged from the hospital without anticonvulsant therapy. At age three months a score of less than or equal to 5 can be used as a guideline for discontinuing anticonvulsant therapy.

Developmental Disabilities↗
PubMed1986

Nutrition support service: role of the clinical dietitian.

A study was undertaken to determine: the qualifications necessary to function on a nutrition support team as perceived by clinical dietitians working in this capacity, the actual role of the clinical dietitian on a nutrition support team, the ideal role of the clinical dietitian on a nutrition support team, and the extent to which clinical dietitians perceive differences between the ideal role expectation and actual performance. A questionnaire was developed and sent to a random sample of 300 clinical dietitians listed as members of a nutrition support service. The respondents indicated that the clinical dietitian should have at least a B.S., R.D., and 2 years' prior work experience before assuming responsibility on a nutrition support team. The dietitians indicated that they consistently take and evaluate diet histories and assess energy and protein needs. Moreover, they viewed these tasks as appropriate. They rarely administer or interpret antigen skin tests and do not perceive this as a function of the dietitian. For all other tasks, dietitians indicated that they should perform the duty or responsibility more often. Over half reported that they did not have adequate educational preparation to assume all of the responsibilities of the clinical dietitian on a nutrition support team.

Adult↗
PubMed1985

Evaluation of methods of measurement and estimation of left ventricular function after acute myocardial infarction.

Using multiple gated cardiac blood pool imaging and single-plane ventriculography from cardiac catheterization, 2 independent measures of left ventricular (LV) ejection fraction (EF) were determined in each of 21 patients. Patients were seen 2 to 6 weeks after their first acute myocardial infarction and were free of electrocardiographic evidence of conduction abnormalities and left or right ventricular hypertrophy. Differences between the 2 measures of LVEF were examined and then compared with the extent of myocardial necrosis estimated from the standard 12-lead electrocardiogram using the complete 54-criteria/32-point Selvester QRS scoring system. Regression analysis yielded an r value of 0.81 (SEE = 8.05) for the overall relation between the 2 measures of LVEF. Correlation coefficients of -0.70, -0.66 and -0.72 were obtained for the relations of radionuclide LVEF, catheterization LVEF and the mean of these 2 determinations, respectively, compared with QRS score. A QRS score 4 or less achieved 100% specificity and that of 8 or less 100% sensitivity for predicting an LVEF greater than 40%. Thus, the Selvester QRS scoring system may be of value in identifying patients with or without markedly impaired LVEF. This risk stratification may be important in reaching optimal postinfarction therapeutic decisions.

Adult↗
PubMed1985

Mechanism of control of cytochrome oxidase activity by the electrochemical-potential gradient.

Cytochrome c oxidation by bovine cytochrome oxidase embedded into liposomal vesicles with high respiratory control ratio (RCR = 6-10) has been studied by rapid-mixing experiments in the presence and absence of different ionophores. Kinetic analysis of the reaction indicates a linkage between the intrinsic activity of the enzyme, the efficiency of coupling and the electrochemical potential across the membrane. A simple model, based on two allosteric states with different catalytic properties in rapid equilibrium, is presented and successfully applied in the simulation of the observed time-course.

Animals↗
PubMed1985

Kinetics of redox-linked proton pumping activity of native and subunit III-depleted cytochrome c oxidase: a stopped-flow investigation.

The kinetics of oxidation of reduced cytochrome c by cytochrome c oxidase reconstituted into unilamellar vesicles (COV) has been followed by stopped-flow method in the time range 3 msec-1 sec. In the presence of valinomycin, the oxidation of cytochrome c is linked to proton ejection in the external medium, with an apparent stoichiometry (H+/e-) of 0.93 +/- 0.22, under conditions in which the enzyme is in the more active "pulsed" state (i.e., having undergone oxidation-reduction cycles). The time course of reaction indicates that the conformational change(s) involved in coupling the redox reaction to proton translocation is fast. Similar experiments carried out with cytochrome c oxidase depleted of subunit III show that proton-pumping is maintained, although with a lower efficiency (H+/e- = 0.5). The number of protons ejected per electron appears to be correlated to the value of the respiratory control ratio; although this result is partly due to an increase in the rate of diffusion back into the vesicles, a relationship between the respiratory control ratio and the efficiency of the proton pump may be inferred, suggesting a control of the H+/e-ratio.

Animals↗