Biomedical subjects

G M Walker

Publications and source records attributed to G M Walker.

At least 19 recordsLinked to original sources

PubMed2005

Treatment of hazardous shipyard wastewater using dolomitic sorbents.

Hazardous shipyard wastewater is a worldwide problem, arising from ship repair. In this study an experimental programme was undertaken to establish the suitability of dolomite and dolomitic sorbent materials to remove contaminants from wastewater arising from a commercial shipyard. Experimental data indicate that dolomite and dolomitic sorbents have the ability to significantly reduce the COD concentration of the shipyard effluent (98% reduction). The data gained from trials at a shipyard indicated that the dolomite treatment process could be undertaken in a 8000 L pilot scale reaction vessel. Analysis of the wastewater using ICP-MS during the pilot trial indicated that the dolomite significantly reduced the concentrations of metallic impurities. The concentration of Sn ions, which is indicative of organo-tin complexes commonly found in shipyard wastewater, was reduced by 80% from its initial concentration in the pilot trial. The mechanism for the removal process using dolomite has been ascribed to a metal complexation/sorption process.

Adsorption↗

PubMed2003

Case report: the transvesical approach to a traumatic rectovesical fistula.

A case of traumatic rectovesical fistula in a 14-year-old boy is presented. A transvesical approach was employed to access the defect. This approach provided excellent exposure, ease of surgery, and an uncomplicated post-operative course. The operative procedure is described, and aspects of the case are discussed.

Accidental Falls↗

PubMed2003

Kinetics of a reactive dye adsorption onto dolomitic sorbents.

A novel wastewater treatment technique has been investigated, for reactive dye removal, in batch kinetic systems. These experimental studies have indicated that charred dolomite has the potential to act as an adsorbent for the removal of Brilliant Red reactive dye from aqueous solution. The effect of initial dye concentration, adsorbent mass:liquid volume ratio, and agitation speed on dye removal have been determined with the experimental data mathematically described using empirical external mass transfer and intra-particle diffusion models. The experimental data show conformity with an adsorption process, with the removal rate heavily dependent on both external mass transfer and intra-particle diffusion.

Adsorption↗

PubMed2003

Early perfluorodecalin lung distension in infants with congenital diaphragmatic hernia.

BACKGROUND/PURPOSE: Pulmonary hypoplasia contributes to mortality in infants with severe congenital diaphragmatic hernia (CDH). Accelerated postnatal lung growth with perfluorocarbon lung distension has been demonstrated in animals. The authors present a study measuring perfluorodecalin distension in neonates with severe CDH on extracorporeal membrane oxygenation (ECMO) support. METHODS: Six consecutive neonates with CDH requiring ECMO support were recruited. The lungs were filled with perfluorodecalin, and continuous positive airway pressure was applied for 6 to 10 days (mean, 7.7 days +/- 0.7). The perfluorodecalin was exchanged 4 times a day. Radiographic lung projections were measured, and from 2-dimensional measurements an estimated lung volume was calculated using the ECMO cannula as reference. RESULTS: Perfluorodecalin instillation started soon after starting ECMO support (mean, 13.5 +/- 5.3 hours). The volume required to fill the lungs increased significantly (P <.02). The radiographic dimension of the affected lung increased significantly (mean percentage increase, 272%; P <.02). The contralateral lung dimension also increased (mean percentage increase 51%; P <.02). CDH repair was undertaken on ECMO in all cases. All patients survived (follow-up, 3 to 42 months). CONCLUSIONS: This protocol of early perfluorodecalin lung distension in infants with severe CDH on ECMO support resulted in significant radiographic lung enlargement. Clinical outcomes are encouraging. Possible mechanisms include alveolar recruitment, alveolar dilatation, and accelerated postnatal lung growth.

Extracorporeal Membrane Oxygenation↗

PubMed2003

Paediatricians' perception of the use of extracorporeal membrane oxygenation to treat meconium aspiration syndrome.

This questionnaire study was designed to determine how consultant paediatricians perceived the value of extracorporeal membrane oxygenation (ECMO) in the treatment of meconium aspiration syndrome (MAS). A significant number believed that the survival of infants with MAS who received ECMO was lower than reported. Early discussion with an ECMO centre will ensure appropriate timing of referral.

Attitude of Health Personnel↗

PubMed2002

Continuous ethanol production in a nonconventional five-stage system operating with yeast cell recycling at elevated temperatures.

Three ranges of increasing temperatures (35-43, 37-45, 39-47 degrees C) were sequentially applied to a five-stage system continuously operated with cell recycling so that differences of 2 degrees C (between one reactor to the next) and 8 degrees C (between the first reactor at the highest temperature and the fifth at the lowest temperature) were kept among the reactors for each temperature range. The entire system was fed through the first reactor. The lowest values of biomass and viability were obtained for reactor R(3) located in the middle of the system. The highest yield of biomass was obtained in the effluent when the system was operated at 35-43 degrees C. This nonconventional system was set up to simulate the local fluctuations in temperature and nutrient concentrations that occur in different regions of the medium in an industrial bioreactor for fuel ethanol production mainly in tropical climates. Minimized cell death and continuous sugar utilization were observed at temperatures normally considered too high for Saccharomyces cerevisiae fermentations.

Biomass↗

PubMed2001

Prolonged two-man basic life support may result in hypocarbia in the ventilating rescuer.

OBJECTIVES: To determine whether the quality of expired air given during mouth-to-mouth ventilation differs between one- and two-person basic life support. METHODS: 15 young fit volunteers performed 15-min simulated resuscitation on a manikin. The oxygen and carbon dioxide concentration of their expired breath and the total ventilation was continuously monitored. Compression:ventilation ratios of 15:2 for one-person and 5:1 for two-person resuscitation were used. RESULTS: In two-man resuscitation, where the rescuer who is ventilating the patient is not performing chest compressions, the oxygen content of the expired breath rises (P<0.01), and the carbon dioxide content falls (P<0.01). The carbon dioxide concentration declined gradually throughout the 15-min session. Most participants complained of light-headedness on completion of the two-man session. Total ventilation did not differ between the two methods (P=0.757, 95% CI=-0.329, 0.242). CONCLUSION: Trainees in basic life support should be informed that symptoms of hypocarbia may occur in prolonged mouth-to-mouth ventilation, when acting in a two-man team. We would advise rescuers using these protocols to change places every 5 min to avoid these symptoms. These findings add further weight to the recommendations that all resuscitation should be carried out using 15:2 compression:ventilation ratio.

Adult↗

PubMed2001

The effect of introducing a dedicated emergency theatre and altering consultant on-call commitments in a large children's hospital.

BACKGROUND: Two recommendations of NCEPOD were the introduction of dedicated emergency theatres and a higher level of consultant involvement in emergency cases. In May 1998 a dedicated emergency theatre was introduced in the Royal Hospital for Sick Children, Glasgow. At the same time the on-call rota of the Consultant Paediatric Surgeons was changed from days on-call to a period of one week, during which elective commitments were cancelled. METHOD: A retrospective audit was conducted for the 12-month periods before and after these changes. Start times of emergency cases and grades of surgeons were obtained from the theatre database. RESULTS: The proportion of emergency operations carried out during on call periods (weekends and weekdays after 5 pm) decreased for general paediatric and neonatal surgery (OR = 0.7, p < 0.01). There was an increase in the proportion of daytime emergency cases performed before 1 pm (OR = 0.28, p < 0.01). The Consultant Paediatric Surgeons were involved in more emergency cases (OR = 0.60, p < 0.01). CONCLUSIONS: The provision of a dedicated emergency theatre increased the proportion of emergency cases performed during normal working hours, particularly before 1 pm. Cancelling elective commitments for Consultant Paediatric Surgeons ensured higher levels of consultant input into daytime emergency cases.

Consultants↗

PubMed2000

Biodegradation and biosorption of acid anthraquinone dye.

The acid anthraquinone dye Tectilon Blue (TB4R) is a major coloured component from the aqueous effluent of a carpet printing plant in Northern Ireland. The aerobic biodegradation of TB4R has been investigated experimentally in batch systems, using three strains of bacteria, namely, Bacillus gordonae (NCIMB 12553), Bacillus benzeovorans (NCIMB 12555) and Pseudomonas putida (NCIMB 9776). All three strains successfully decolourised the dye, and results were correlated using Michaelis-Menten kinetic theory. A recalculation of the reaction rate constants, to account for biosorption, gave an accurate simulation of the colour removal over a 24-h period. Up to 19% of the decolorisation was found to be caused by biosorption of the dye onto the biomass, with the majority of the decolorisation caused by utilisation of the dye by the bacteria. The reaction rate was found to be intermediate between zero and first order at dye concentrations of 200-1000 mg/l.

Journal Article↗

PubMed1999

Synchronization of yeast cell populations.

The study of synchronous populations of yeast cells has provided a wealth of information into regulatory aspects of the eukaryotic cell division cycle. Synchronized yeast cultures may also have potential benefit when exploiting yeasts in biotechnology. This paper provides an overview of the methods which have been used in the synchronization of cell division in budding and fission yeasts. The relative merits of these methods are outlined and protocols for preferred synchronization methods, based on size selection techniques, are described. In particular, centrifugal elutriation protocols for Saccharomyces cerevisiae (budding yeast) and Schizosaccharomyces pombe (fission yeast) are detailed as this method is regarded as one of the best ways of preparing 'unperturbed' synchronous yeast cultures for cell cycle studies.

Cell Cycle↗

PubMed1999

Biotechnological implications of the interactions between magnesium and calcium.

At the biochemical level, magnesium and calcium are known to act antagonistically towards each other. For example, many enzymes whose activities critically depend on sufficiency of intracellular magnesium, especially transphosphorylases, will be detrimentally affected by small increments in levels of cellular calcium ions. Growth of cells, cell division cycle progress and intermediary metabolism are also absolutely dependent on the bioavailability of magnesium, which can be compromised if excess calcium is present. Many biotechnological processes, therefore, which fundamentally exploit cellular growth and metabolism, will be influenced strongly by relative concentrations of the two cations and the ratio of bioavailable magnesium to calcium in external growth media. This paper surveys the interactive effects of magnesium and calcium at the bioinorganic level and discusses some examples of how these interactions may play important roles in governing the physiology of cells which are widely exploited in modern industrial bioprocesses.

Biological Transport↗

PubMed1998

Fixed bed adsorption of acid dyes onto activated carbon.

The context of the study here is the adsorption of acid dyes from wastewater arising from a nylon carpet printing plant which currently receives no treatment. Since nylon is a particularly difficult fibre to dye, acid dyes are required for successful coloration. However, their presence, in high concentrations, in aqueous effluent arising from the plant can create major problems with respect to disposal. A treatment method based on adsorption onto granular activated carbon (GAC F400) in a fixed column configuration is described and breakthrough data of the dyes determined. The breakthrough data were correlated using a model based on liquid and pore diffusion with a good fit of experimental results obtained. Trends in the effective diffusivity used in the model correlated with other authors. A slight decrease in effective diffusivity was found with decrease in particle size and was attributed to interactions between the relatively large molecular sized dye and the microspore structure found in granular activated carbon.

Journal Article↗

PubMed1997

Accumulation of magnesium ions during fermentative metabolism in Saccharomyces cerevisiae.

When cells of Saccharomyces cerevisiae were grown aerobically under glucose-repressed conditions, ethanol production displayed a hyperbolic relationship over a limited range of magnesium concentrations up to around 0.5 mM. A similar relationship existed between available Mg2+ and ethanol yield, but over a narrower range of Mg2+ concentrations. Cellular demand for Mg2+ during fermentation was reflected in the accumulation patterns of Mg2+ by yeast cells from the growth medium. Entry of cells into the stationary growth phase and the time of maximum ethanol and minimum sugar concentration correlated with a period of maximum Mg2+ transport by yeast cells. The timing of Mg2+ transport fluxes by S. cerevisiae is potentially useful when conditioning yeast seed inocula prior to alcohol fermentations.

Biological Transport↗

PubMed1996

Patient satisfaction in government health facilities in the state of Qatar.

There is an increasing interest in assessing patients' satisfaction with medical care in the United States and other countries. Patient satisfaction studies have, however, received comparatively little attention in public or government-sponsored settings, and in developing countries in particular. The research reported upon here is based on a mail, self-administered survey of patients receiving care in two major government outpatient health care facilities-Hamad General Hospital and the Khalifa Town Health Center-in the State of Qatar, for the purpose of providing data to improve service delivery and the quality of primary care provided in that country. Analysis was performed on data from 444 patients on seven dimensions of patient satisfaction with medical care: general satisfaction, availability of services, convenience of services, facilities (physical environment), humaneness of doctors, quality of care, and continuity of care. The study pointed to a number of deficiencies in the availability and delivery of services in government health facilities in the State of Qatar. It also surfaced methodological issues that should be addressed in comparable studies of culturally diverse populations.

Adolescent↗

PubMed1995

Interactions between killer yeasts and pathogenic fungi.

A total of 17 presumptive killer yeast strains were tested in vitro for growth inhibitory and killing activity against a range of fungal pathogens of agronomic, environmental and clinical significance. Several yeasts were identified which displayed significant activity against important pathogenic fungi. For example, isolates of the opportunistic human pathogen, Candida albicans, were generally very sensitive to Williopsis mrakii killer yeast activity, whilst killer strains of Saccharomyces cerevisiae and Pichia anomala markedly inhibited the growth of certain wood decay basidiomycetes and plant pathogenic fungi. Results indicate that such yeasts, together with their killer toxins, may have potential as novel antimycotic biocontrol agents.

Antifungal Agents↗

PubMed1995

Reconstructive surgery during Operations Just Cause and Desert Storm.

Operations Just Cause and Desert Storm were of relatively brief duration; however, severe wounds were produced that required complex reconstructive procedures. This paper describes the type of wounds managed in theater and subsequently at three U.S. military medical centers. Specific reconstructive techniques included local and free muscle, fasciocutaneous, and composite flaps. Emphasis is placed on the application of microsurgical techniques to battle-related injuries.

Adult↗

PubMed1994

A rapid colorimetric assay of killer toxin activity in yeast.

The pale yellow redox indicator 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) is reduced to a dark blue end-product, MTT-Formazan, by the mitochondrial dehydrogenases of living cells. MTT reduction can be measured spectrophotometrically at a wavelength of 570 nm and a method is described to assay the cidal activity of Williopsis mrakii killer toxin against sensitive cells of Candida glabrata. The MTT assay is rapid, quantitative and compares favourably with traditional plating techniques for the assessment of sensitive viability.

Candida↗

PubMed1994

The roles of magnesium in biotechnology.

This review highlights the important roles played by magnesium in the growth and metabolic functions of microbial and animal cells, and therefore assigns a key role for magnesium ions in biotechnology. The fundamental biochemical and physiological actions of magnesium as a regulatory cation are outlined. Such actions are deemed to be relevant in an applied sense, because Mg2+ availability in cell culture and fermentation media can dramatically influence growth and metabolism of cells. Manipulation of extracellular and intracellular magnesium ions can thus be envisaged as a relatively simplistic, but nevertheless versatile, means of physiological cell engineering. In addition, biological antagonism between calcium and magnesium at the molecular level may have profound consequences for the optimization of biotechnological processes that exploit cells. In fermentation, for example, it is argued that the efficiency of microbial conversion of substrate to product may be improved by altering Mg:Ca concentration ratios in industrial feedstocks in a way that makes more magnesium available to the cells. With particular respect to yeast-based biotechnologies, magnesium availability is seen as being crucially important in governing central pathways of carbohydrate catabolism, especially ethanolic fermentation. It is proposed that such influences of magnesium ions are expressed at the combined levels of key enzyme activation and cell membrane stabilization. The former ensures optimum flow of substrate to ethanol and the latter acts to protect yeasts from physical and chemical stress.

Animals↗