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Biomedical subjects

C Gibson

Publications and source records attributed to C Gibson.

At least 37 records · Page 2Linked to original sources
PubMed1995

Regulation of host cell recognition in Streptococcus pyogenes.

Protein F, a fibronectin-binding protein, and the M protein of Streptococcus pyogenes both play important roles in directing adherence to different populations of host cells in the skin. Expression of both proteins is regulated in response to alterations in atmosphere. Transcriptional control of mry, a positive-acting regulator of expression of the gene which encodes the M protein (emm) in response, to elevated levels of CO2, is a mechanism for control of emm expression in response to atmosphere. Expression of protein F is controlled at the level of transcription in response to the concentration of O2, and its expression is stimulated in the presence of superoxide. Further support for a role of superoxide in regulation of prtF expression comes from the observation that an S. pyogenes mutant which contains an insertionally inactivated gene for superoxide dismutase (sod) becomes hypersensitive to superoxide and will express prtF constitutively. A second strain also demonstrates constitutive expression of prtF but contains a functional sod. Complementation analyses in this strain using a prtF allele cloned from a regulating host and a novel method for shuttle mutagenesis which utilized the transposon mini-gamma delta have been used to identify rofA, a positive-acting regulator of prtF expression. A model for the role of the surface proteins, F and M and their regulatory genes mry and rofA in streptococcal infections of the skin will be discussed.

Antigens, Bacterial↗
PubMed1994

Sterilisation of implantable devices.

The pathogenesis and rates of infection associated with the use of a wide variety of implantable devices are described. The multi-factorial nature of post-operative periprosthetic infection is outlined and the role of sterilisation of devices is explained. The resistance of bacterial spores is highlighted as a problem and a full description is given of the processes of sterilisation by heat, steam, ethylene oxide, low temperature steam and formaldehyde, ionising radiation and liquid glutaraldehyde. Sterility assurance and validation are discussed in the context of biological indicators and physical/chemical indicators. Adverse effects upon the material composition of devices and problems of process control are listed. Finally, possible optimisations of the ethylene oxide process and their potential significance to the field of sterilisation of implants is explored.

Biocompatible Materials↗
PubMed1992

A survey of nuclear cardiological practice in Great Britain. The British Nuclear Cardiology Group.

There is little information on the practice of nuclear cardiology in Great Britain. On behalf of the British Nuclear Cardiology Group in October 1988 we sent a postal questionnaire to 143 hospitals with nuclear medicine facilities (at least 70% of such hospitals). Sixty nine replies were received (48%), of which 23 (33%) were from teaching hospitals and 46 (39%) non-teaching. In these hospitals 147,904 isotope investigations were performed annually (mean 2311 per centre) of which 17,298 (12%) (mean 254 per centre) were cardiac studies. Of these, 59% were equilibrium radionuclide ventriculograms, 14% first pass ventriculograms, and 27% thallium-201 scans. Rest studies were performed more commonly by radiographers or technicians (63%) than by doctors (20%), but doctors were more commonly involved in stress studies (48%). Radiologists reported the studies more often (28%) than they performed them (6%). Methods of acquisition and analysis were varied and, for instance, the lower limit of normal left ventricular ejection fraction ranged from 35% to 75% (mean 49%). For thallium imaging 42% of centres used dipyridamole in some patients and 24% used tomography. These data show that nuclear cardiology techniques are used much less frequently in Great Britain than in countries such as the United States and Germany, that the ratio of blood pool to myocardial perfusion imaging is much higher than elsewhere, and that methods are poorly standardised. They may provide the impetus to improve the service and serve as a baseline for future surveys.

Cardiology↗
PubMed1991

Structure and expression of the bovine amelogenin gene.

In order to define further the mechanisms responsible for tooth amelogenin heterogeneity, seven bovine amelogenin cDNAs were sequenced. On the basis of these sequences, five of the cDNAs could be grouped into one class which differed appreciably in sequence from the second group of two cDNAs. Two overlapping bovine genomic clones were then isolated and shown by sequencing to contain six exons encoding the entire consensus sequence of the class I cDNA. Southern blot analysis of DNA from male and female animals using class I or class II specific oligonucleotide probes suggested that the class I gene sequence was located on the X chromosome while the class II sequence was located on the Y chromosome. Therefore, these results also suggest that the genes on the X and Y chromosomes are both transcribed. Furthermore, the results are consistent with alternative splicing of the class I primary transcript as a potential mechanism for generating amelogenin heterogeneity.

Amelogenin↗
PubMed1990

Psychosocial rehabilitation: the role of the psychiatric nurse.

The roles and functions of Nurses working in Rehabilitation Psychiatry are varied and complex, new challenges are arising out of historical and emerging contexts. This paper explores problems faced by the Psychiatric Nurse and explains some of the functions and roles that contribute to the rehabilitation process.

Humans↗
PubMed1989

Easily assembled digital data acquisition system for the analytical ultracentrifuge.

A system for the acquisition of digital data from the analytical ultracentrifuge which uses a commercially available data acquisition board, a standard IBM compatible personal computer (PC), and an interface circuit has been developed. The system uses the signal from the standard Beckman scanner. Preliminary analysis and data reduction are performed at the PC within minutes of data acquisition using simple commercially available software, and final data fitting is performed with a mainframe computer. Procedures are described which allow approach to equilibrium to be followed and attainment of equilibrium to be demonstrated. Data density of approximately 200 points per millimeter column height (approximately 500 points per 100 microliters of sample) allows the use of short columns and hence short run times. Only 2 min are required to collect a complete scan, which is recorded in a format suitable for direct analysis by standard spreadsheet software. This allows multiple sequential scans to be quickly recorded at equilibrium and averaged to reduce noise prior to analysis. The combination of characteristics allows molecular weight determinations to be performed relatively quickly with only a few micrograms of protein. The system is inexpensive and easy to assemble given the centrifuge and a PC.

Computer Systems↗
PubMed1989

Enhancement of the kinetics of the aeration of ethylene oxide sterilized polymers using microwave radiation.

Ethylene oxide (EO) is used extensively to sterilize medical supplies that are heat sensitive. EO residues in materials post sterilization can present a hazard to patients at the point of use. Protracted aeration (i.e. degassing) times are necessary post sterilization to reduce EO residues to an accepted level. The sorption of EO into polyvinylchloride was found to be an active process given that at sorption equilibrium (i.e. when the net flow of diffusant into the host material has reduced to zero) the number of molecules of EO per unit volume was greater in PVC than in its external environment. The diffusion coefficient (D) was concentration (c) dependent and the relationship which best describes this dependence was D(c) alpha ln c. The diffusion of EO was dramatically accelerated (as evidenced by a time saving in degassing of up to 400%) if microwave heating (2.45 GHz) was used instead of conventional heating for the same macroscopic temperature. The values of activation energy for diffusion were obtained from the respective Arrhenius plots of diffusion coefficient versus inverse temperature for each process. In general, even small reductions in activation energy can greatly increase the specific rate of reaction. The relative efficacy of microwaves in eliminating EO residues as evidenced by this data occurs as a result of microwaves reducing the activation energy for diffusion by almost a factor of two. The relative efficiency of microwave desorption compared to conventional aeration offers considerable gains in the cost-effectiveness of gas sterilization since it will permit a much greater throughput of material, thereby obviating the need for excessively large inventories of equipment.

Air↗
PubMed1989

Computerized model for accurate determination of ethylene oxide diffusion in sterilized medical supplies.

A computerized numerical model is described which is shown to be more generally applicable than analytical methods in the determination of ethylene oxide diffusion in polymeric material. Diffusion coefficients of ethylene oxide in poly(vinyl chloride) were determined from the rates of desorption both for conventional aeration with warm air and for microwave-assisted desorption and found to be concentration dependent. The model takes account of device geometry and concentration dependence of diffusion coefficient and its predictions are in agreement with experimental results for desorption. The model is also used to simulate the whole sterilization process with a view to a planned diminution of EO residuals after sterilization.

Biocompatible Materials↗
PubMed1989

A study of headaches and migraine in Sjögren's syndrome and other rheumatic disorders.

Migraine occurs with increased frequency in patients with systemic lupus erythematosus and in subjects suffering from Raynaud's phenomenon without any underlying connective tissue disorders. A possible link between migraine and Raynaud's phenomenon has been suggested. Two rheumatic conditions where Raynaud's phenomenon occurs very commonly are scleroderma and primary Sjögren's syndrome. It is possible that migraine is also common in these disorders but has been unrecognised. Therefore, the prevalence of migraine was assessed by a questionnaire in 191 subjects suffering from various connective tissue disorders and control subjects. Migraine was diagnosed in 16/35 (46%) patients with primary Sjögren's syndrome, 31/97 (32%) patients with scleroderma, 4/33 (12%) patients with rheumatoid arthritis/Sjögren's syndrome compared with 3/26 (11%) control subjects. A family history of headaches was more common in the patient groups than controls. There was a significant association between occurrence of Raynaud's phenomenon and migraine. Small vessel pathology may underlie both migraine and Raynaud's phenomenon in these connective tissue disorders--as has been suggested in systemic lupus erythematosus. The findings stress the need to ask specifically about complaints of headaches/migraines in patients with scleroderma and primary Sjögren's syndrome for the appropriate total management of these patients.

Female↗
PubMed1989

Optimization of the ethylene oxide sterilization process.

Hospitals and manufacturers of medical supplies use ethylene oxide (EO) gas almost exclusively to sterilize devices that are heat sensitive. However, the evidence relating the mutagenicity and cytogeneticity shows the desirability of reducing personal exposure to a practical minimum.

Central Supply, Hospital↗
PubMed1988

A comparison of laparoscopy and laparotomy for the treatment of ectopic pregnancy.

A case-control method was used to examine differences in outcome between laparoscopy and laparotomy for the treatment of ectopic pregnancy. Cases and controls, 25 each, were matched by criteria selected to minimize differences in preoperative morbidity and technical difficulty. Patients treated laparoscopically had significantly shorter hospital stays (1.34 +/- 0.8 versus 3.92 +/- 1.1 days; mean +/- SD; P less than .01) and less operating time (77.5 +/- 26.1 versus 103.6 +/- 26.7 minutes; P less than .05). In addition, a laparoscopic approach resulted in a shorter convalescence (8.7 +/- 7.8 versus 25.7 +/- 16.2 days; P less than .01) and reduced postoperative analgesia requirements (0.84 +/- 2.3 versus 4.64 +/- 2.9 doses; P less than .01). We conclude that laparoscopic treatment of ectopic pregnancy is well tolerated by patients and, in comparison with laparotomy, requires fewer medical resources, thereby significantly reducing cost.

Convalescence↗
PubMed1988

Microwave desorption: a combined sterilizer/aerator for the accelerated elimination of ethylene oxide residues from sterilized supplies.

Ethylene oxide gas is widely used in medical and related facilities for low-temperature sterilization of surgical devices. Evidence of its toxicity and, in particular, its mutagenicity and carcinogenicity provide sufficient reasons for caution in its use and for minimizing exposure. Little advancement has been made in the removal of ethylene oxide residuals from plastics into which the gas is heavily absorbed during sterilization, despite the fact that the gas has been used for 20 years or more. This article describes a novel process (PCT Application/GB85/00509) in which microwave irradiation of ethylene oxide-sterilized materials is utilized to enhance the rate at which the gas is desorbed. The experimental apparatus is described, and an explanation of the effect of microwaves on the energy of activation for diffusion is given. Data are presented in support of the authors' claim of a 400% improvement in the efficiency of the new process over conventional aeration procedures. The advantages and economy of an integrated sterilizer/microwave-enhanced desorber are discussed in the context of the implications that arise from the current regulatory debate.

Air↗