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Biomedical subjects

G D Green

Publications and source records attributed to G D Green.

At least 37 records · Page 2Linked to original sources
PubMed1979

Failure of pacemaker electrode leads.

With the application of new power sources to pacemakers, considerable improvement has been achieved in the theoretical implant lifetime of current pulse generators, and equally reliable electrode leads will be necessary to ensure long-term pacing. The durability of the electrodes implanted in the past ten years in this centre has been carefully studied. The findings suggest that the use of a more durable conductor material and development of the concept of a 'fail safe' lead (using multi-filament conductors or a secondary conductive pathway along the electrode) will be necessary to match with the implant lifetime of the newer pulse generators. The diagnosis and management of broken conductors is discussed.

Electrodes, Implanted↗
PubMed1978

Inactivation of trypsin-like proteases by sulfonylation. Variation of positively charged group and inhibitor length.

Attempts to achieve selective inactivation of serine proteases of closely related specificity (trypsin-like) by aryl sulfonylation have been extended. Nitrophenyl esters of benzenesulfonic acid and phenylmethanesulfonic acid containing various positively charged groups have been synthesized and examined as inactivators of trypsin, thrombin, plasmin, plasma kallikrein, and urokinase. Examples of selective inactivation by isothiouronium derivatives were found and attributed to differences among these enzymes in geometry and flexibility of the primary specificity sites.

Chemical Phenomena↗
PubMed1977

Long-term epicardial ventricular pacing from endocardial bipolar pacemaker lead: perforation of right atrial wall.

One of the hazards of endocardial cardiac pacing is that the pacemaker lead may perforate the myocardial wall or interventricular septum although the incidence of such perforations is believed to be small. This paper describes what is believed to be a unique case in which a pacemaker lead perforated the atrial wall at implantation (or possibly shortly afterwards) and yet gave satisfactory right ventricular epicardial pacing for more than five years. The perforation was discovered during a routine postmortem examination but earlier lateral x-ray examinations would probably have identified the abnormal position of the electrodes. Moreover, the present implantation technique would not have allowed perforation of the atrial wall at implantation to go undetected.

Aged↗
PubMed1976

The kinetics of hydrolysis of some extended N-aminoacyl-l-lysine methyl esters.

1. The action of two active forms of bovine trypsin (alpha and beta-trypsin) on a series of specific methyl ester substrates of general formula: N-acetyl-(glycyl)n-L-lysine methyl ester (n = 0, 1, 2) and N2-benzoyl-L-arginine ethyl ester have been investigated. With the L-lysine methyl esters the catalytic rate constant for hydrolysis (kcat) was found to be significantly lower for alpha-trypsin than for beta-trypsin, whereas with N2-benzoyl-L-arginine ethyl ester there was no significant difference for the two enzymes. 2. By measurement of the kinetic constants (kcat and Km) in the presence of a nucleophile, which competes with water in the deacylation process, it has been shown that, in common with the specific ester substrates of trypsin, the rate-determining step for the extended L-lysine methyl esters is decaylation of the enzyme. 3. It has been found that by extending the aminoacyl group of N-acetyl-L-lysine methyl ester by one glycine residue (n = 1), a greatly enhanced deacylation rate constant is observed for both alpha and beta-trypsin. The higher rate constants were maintained at the higher levels by the addition of a further glycine residue (n = 2). These results have been interpreted in terms of the 'induced fit' hypothesis the substrates binding to an enzyme subsite adjacent to the active site. 4. The beta-trypsin-catalysed hydrolysis of the L-lysine substrates was investigated over a range of temperature (15--35 degrees C). The Arrhenius law was obeyed, within experimental error, by all three substrates allowing the estimation of the thermodynamic function of activation (delta S not equal to and deltaH note equal to) for the deacylation reactions. The significantly higher values of deltaS not equal to and deltaH not equal to obtained for the two extended substrates are interpreted in terms of additional hydrogen bonding between the longer aminoacyl chains and the enzyme molecule. The results are compared with those for non-extended specific substrates, which have a possible hydrophobic interaction with the enzyme surface.

Animals↗
PubMed1976

Cardiac pacing.

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Congresses as Topic↗
PubMed1975

The reliability of pacemaker electrode-leads.

Extensive experience has been obtained with Medtronic pacemakers, in Glasgow where over 400 patients have received their primary implant. In this review, which covers a period of seven and a half years ending December 31, 1973, the technical reliability of electrode-leads is considered in terms of failed implant lifetimes and incomplete implant lifetimes. Too few myocardial electrode-leads have been used to reach firm conclusions about its reliability, but the incidence of failures with the endocardial bipolar electrode-lead (Type 5818) has so far been small and it is evidently more reliable than its predecessor (Type 5816). More time must elapse, however, before it can be claimed with confidence that the present design of bipolar catheter will match the theoretical implant lifetimes of generators with the long-life power sources. Insulation failures are usually of no immediate clinical significance whereas any broken conductor is hazardous. The use of multistranded conductors is therefore advocated. All pacemakers should be retrieved after the deaths of patients.

Electrodes, Implanted↗
PubMed1975

Computer storage of pacemaker data.

An important factor in the choice of a pacemaker ought to be its reliability following implantation. Unfortunately, as the total number of patients increases, handling of basic data becomes a tedious and time consuming task. Analysis of data becomes an even more arduous task. Proposals are made for somputer storage of pacemaker data so that regulare up-dated "print-outs" can be made available. Analysis by computer then becomes a trivial task. The advantage of a single data handling centre for the whole of the United Kingdom is particularly attractive.

Computers↗
PubMed1975

Hazards of cardiac pacing.

The implantation of a cardiac pacemaker is now widely accepted as the preferred method of therapy for heartblock, and is increasingly used for treatment of other cardiac abnormalities. Many thousands of pacemakers have been implanted since 1960. Some of the problems which arise from such implants are not urgent and are in the "low risk" category, whilst others require immediate remedial action. The hazards which are discussed are based on experience in Glasgow with over 500 pacemaker patients, over two thirds of whom are currently attending pacemaker clinics. If all pacemaker patients are to derive maximum benefit from their implants with minimum inconvenience and risk, there is a need for continued vigilance and better technology. There is also a need for retrieval of all pacemakers after death to confirm that death has not arisen from any of the technical faults which can place the lives of certain patients at great risk.

Electricity↗