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Biomedical subjects

A Stacey

Publications and source records attributed to A Stacey.

At least 19 recordsLinked to original sources
PubMed2002

A UK historical perspective on operating theatre ventilation.

As part of the preparation for the report of the Hospital Infection Society Working Party on Infection Control and Operating Theatres, studies published from the UK on the subject of operating theatre ventilation were reviewed. Few have convincingly demonstrated a direct relationship between the microbiological quality of operating theatre air and postoperative wound infection. Nevertheless, the findings from these studies have had a major influence on the development of official UK guidance on the design, performance and testing of ventilation in both conventional and ultraclean operating theatres.

Air Microbiology↗
PubMed2000

The effect of intraoperative autotransfusion on antibiotic pharmacokinetics during elective abdominal aortic aneurysm repair.

AIM: Blood loss during aortic surgery has been reduced by the use of cell-salvage techniques (CS). Antibiotics are used routinely to prevent prosthetic graft infection. The influence of CS on antibiotic levels is unknown. This study measured antibiotic levels in serum and cell-salvage fluid during aortic reconstruction. METHODS: Teicoplanin, a glycopeptide with activity against gram positive bacteria was the antibiotic studied. Serial blood levels were measured after a single intravenous dose (400 mg) in five patients undergoing elective aortic aneurysm repair. Patient ages ranged from 67 to 82 yr. Cell-salvage (Dideco compact A75171) fluid was also assayed. SETTING: District General Hospital RESULTS: Serum teicoplanin levels peaked at mean 67.8 mg/l (SD 8.9 mg/l) 5 min after administration, and fell to mean 2.88 mg/l (SD 0.4 mg/l) at 720 min. This is less than levels in healthy volunteers but above the MIC90 for most Gram positive bacterial pathogens encountered in aortic surgery. Teicoplanin levels in discarded CS fluid at the end of the procedure were 0.56 mg/l (SD 0.71 mg/l). CONCLUSIONS: Teicoplanin blood levels are reduced during aortic surgery. Levels remain adequate for antibacterial prophylaxis for 12 h postoperatively other than for methicillin-resistant staphylococcus epidermidis (MRSE). Compared with patients undergoing arterial reconstruction without the use of a cell-salvage device there is no significant loss due to CS use.

Aged↗
PubMed2000

Infectious diseases in rugby players: incidence, treatment and prevention.

Participation in rugby football can expose individuals to a variety of infectious diseases both on and off the field of play. The close physical contact and trauma inherent in playing rugby facilitates the transmission of viral, bacterial and fungal pathogens between players and may also lead to the acquisition of potentially lethal infections from the environment, such as tetanus. In the past few years there have been a number of reported outbreaks of infection amongst rugby players in the medical literature. The appearance of HIV infection has focused attention on the potential for transmission of this and other blood-borne viruses such as hepatitis B and C viruses from bleeding wounds sustained on the rugby field. As a result, various expert bodies have produced guidelines on the management of players with bleeding wounds. Opportunities are now available to rugby players to play outside their own countries, including the third world. This can bring them into contact with a wide range of travel-associated infections, some of which may be life threatening. In view of the above it is clear that rugby players and those who coach and manage rugby teams require information and education on the subject of infection and its prevention, as well as access to appropriate medical care and expertise. Many of the infections seen in rugby players are preventable, e.g. by promoting hygienic facilities and conduct in changing rooms and on the field of play, by exclusion of infected players from contact with others and, in some cases, by immunisation or chemoprophylaxis. Players who present with infections should be assessed, correctly diagnosed (using laboratory investigations where appropriate) and treated, and measures should be taken to prevent spread to team-mates and other contacts while respecting the confidentiality of the individual. Any outbreaks of infection should be reported to the appropriate authorities. There is evidence to suggest that strenuous physical exercise such as playing rugby can make individuals susceptible to certain types of infection and prolong time to recovery. More information is required on the true frequency and effects of infection in rugby players.

Anti-Infective Agents↗
PubMed1998

Optical properties of retinal photoreceptors and the Campbell effect.

In 1958, Campbell observed that certain artificial pupil displacements could considerably change acuity (measured by viewing gratings) while others had very little effect. He sought an explanation of the small retinal contribution to those effects that was consistent with the Stiles-Crawford effect. This paper suggests an explanation that satisfies that requirement using a waveguide model of the retinal cones. We show that the waveguiding properties of the receptors make them sensitive to obliquely incident exciting waves and this provides some support for the hypothesis that both the Stiles-Crawford and Campbell effects are manifestations of the same underlying waveguide nature of the receptors.

Fovea Centralis↗
PubMed1997

Use of the critical incident technique in primary care in the audit of deaths by suicide.

OBJECTIVE: To explore the usefulness of the critical incident technique in primary care to improve policy and practice to prevent cases of suicide. DESIGN: Inviting all primary care teams in County Durham with a patient who committed suicide between 1 June 1993 and 31 May 1994 to take part in a critical incident audit with an external facilitator. RESULTS: 49 cases of suicide were available for study, registered with 31 practices. 19 (61%) practices accounting for 27 (55%) cases agreed to take part. Case discussions showed areas where practice could be improved, but no substantive preventive measures were identified within primary care, which would reduce the number of people committing suicide. The wider social and economic context was thought to be more important. CONCLUSIONS: The use of the critical incident technique in primary care may have only a limited role in improving the management of people at risk from suicide. However, one of the potential strengths of this approach is to encourage reflection on practice in a difficult emotional area.

England↗
PubMed1995

Lactation is disrupted by alpha-lactalbumin deficiency and can be restored by human alpha-lactalbumin gene replacement in mice.

Mice carrying either a deletion of the murine alpha-lactalbumin (alpha-lac) gene (null allele) or its replacement by the human alpha-lac gene (humanized allele) have been generated by gene targeting. Homozygous null females are alpha-lac-deficient, produce reduced amounts of thickened milk containing little or no lactose, and cannot sustain their offspring. This provides definitive evidence that alpha-lac is required for lactose synthesis and that lactose is important for milk production. Females homozygous for the humanized allele lactate normally, indicating that human alpha-lac can replace murine alpha-lac. Mouse and human alpha-lac expression was compared in mice heterozygous for the humanized allele. The human gene expressed approximately 15-fold greater mRNA and approximately 14-fold greater protein than the mouse, indicating that the major determinants of human alpha-lac expression are close to, or within, the human gene and that the mouse locus does not exert a negative influence on alpha-lac expression. Variations in alpha-lac expression levels in nondeficient mice did not affect milk lactose concentration, but the volume of milk increased slightly in mice homozygous for the humanized allele. These variations demonstrated that alpha-lac expression in mice is gene dosage dependent.

Alleles↗
PubMed1995

Isolation of Arcobacter butzleri from a neonate with bacteraemia.

We describe the case of a neonate with bacteraemia from whom the recently described organism Arcobacter butzleri was isolated. This appears to be the first report of the organism causing neonatal infection. Clinical details suggest that the infection was contracted in utero, although the mother showed no evidence of disease before delivery. Treatment of the preterm infant was ultimately successful in resolving the infection but the organism proved resistant to a wide range of antibiotics. Similar patterns of antibiotic resistance were also observed in 39 reference and field strains of the genus Arcobacter. These findings, combined with available data on the distribution of Arcobacter species, suggest that these organisms may be important human pathogens. Optimized methods for their isolation and identification are therefore required so as to ascertain their role in human disease.

Bacteremia↗
PubMed1994

Transgenic cattle resulting from biopsied embryos: expression of c-ski in a transgenic calf.

Producing transgenic cattle by microinjection of DNA into pronuclei has been inefficient and costly, in large part because of the cost of maintaining numerous nontransgenic pregnancies to term. We designed a system for early identification of transgenic embryos in which biopsies of embryos were assayed by polymerase chain reaction for presence of the transgene before embryo transfer. A total of 2555 embryos were microinjected with one of two DNA constructs. Of the 533 embryos biopsied, 112 were judged to be potentially transgenic and were transferred nonsurgically to recipients, resulting in production of 29 putative transgenic fetuses. One fetus and one calf (7% of offspring) were subsequently shown to be definitively transgenic. The calf was transgenic for a chicken c-ski cDNA, and several months after birth developed dramatic muscular hypertrophy followed by muscle degeneration. This phenotype was associated with expression of high levels of mRNA from the transgene.

Animals↗
PubMed1994

Use of double-replacement gene targeting to replace the murine alpha-lactalbumin gene with its human counterpart in embryonic stem cells and mice.

The mouse alpha-lactalbumin gene has been replaced with the human gene by two consecutive rounds of gene targeting in hypoxanthine phosphoribosyltransferase (HPRT)-deficient feeder-independent murine embryonic stem (ES) cells. One mouse alpha-lactalbumin allele was first replaced by an HPRT minigene which was in turn replaced by human alpha-lactalbumin. The end result is a clean exchange of defined DNA fragments with no other DNA remaining at the target locus. Targeted ES cells at each stage remained capable of contributing efficiently to the germ line of chimeric animals. Double replacement using HPRT-deficient ES cells and the HPRT selection system is therefore a powerful and flexible method of targeting specific alterations to animal genes. A typical strategy for future use would be to generate a null mutation which could then be used to produce multiple second-step alterations at the same locus.

Animals↗
PubMed1994

Spatial-frequency response of a photoreceptor and its wavelength dependence. I. Coherent sources.

The response of an isolated model foveal cone to a coherent sinusoidal intensity source is explored with use of the methods of photoreceptor optics. The dielectric waveguide model of a foveal cone that was previously used to explain the Stiles-Crawford effect and its wavelength dependence [Vision Res. 13, 1115 (1973)] is applied to photoreceptor excitation by coherent gratings with variable spatial frequency and light wavelength. The results indicate that the photoreceptors themselves contribute to visual acuity through a wavelength-dependent response at each spatial frequency. In particular, the isolated photoreceptor has a characteristic low-pass spatial-frequency-filter effect for wavelengths between 410 and 654 nm (where two waveguide modes are carried) and a flat response for wavelengths greater than 654 nm (the single-mode region).

Fovea Centralis↗
PubMed1993

Genomic sequence of mouse COL1A1 encoding the collagen propeptides.

The nucleotide sequences of the mouse pro alpha 1(I) gene regions coding for the N- and C-propeptides is reported. The exon-intron structure was highly homologous to human COL1A1 and the deduced amino acid sequences of the N- and C-propeptides showed 67% and 91% identity with the human sequence. This gene sequence information will allow the production of specific gene mutations by site-directed mutagenesis to study the structure and function of these important propeptide domains.

Amino Acid Sequence↗
PubMed1992

Deletion of the pro-alpha 1(I) N-propeptide affects secretion of type I collagen in Chinese hamster lung cells but not in Mov-13 mouse cells.

We have introduced two mutations into a full-length human pro-alpha 1(I) cDNA that delete 114 amino acids or the entire 139 amino acids of the N-propeptide domain. Wild-type and mutated versions of the cDNA were introduced into cultured Chinese hamster lung (CHL) cells, which do not produce endogenous type I collagen, and into Mov-13 mouse cells, which produce endogenous pro-alpha 2(I) chains but not pro-alpha 1(I) chains. As judged by resistance to proteases, neither mutation impaired intracellular triple helical assembly of human alpha 1(I) homotrimers in CHL cells, or of chimeric type I collagen comprised of human alpha 1(I) and mouse alpha 2(I) chains in Mov-13 cells. Thus, the N-propeptide is not necessary for intracellular assembly of the main helical collagen domain of type I collagen. In CHL cells the rate of secretion of the mutant homotrimers was greatly reduced as compared to wild type homotrimers, and by immunofluorescence and immunoelectron microscopy, the mutant chains were shown to be accumulated in large vesicular expansions of the rough endoplasmic reticulum. When such cells were retransfected with cDNA encoding wild-type human alpha 2(I) chains, mutant alpha 1(I) chains were not rescued and heterotrimers containing the mutant chains were also retained in the intracellular vesicles. By contrast, deletion of the N-propeptide did not affect secretion of heterotrimers containing mutant chains from Mov-13 cells. Thus, an intact N-propeptide appears necessary for efficient secretion of type I collagen from some but not all cell types.

Amino Acid Sequence↗
PubMed1990

Generation of collagenase-resistant collagen by site-directed mutagenesis of murine pro alpha 1(I) collagen gene.

Collagenase (matrix metalloproteinase 1) cleaves type I, II, and III collagen helices at a specific site between Gly-Ile or Gly-Leu bonds (residues 775 and 776, P1-P1'). To understand the mechanism of collagen processing, mutations around the cleavage site have been introduced into the cloned murine pro alpha 1(I) collagen (Col1a1) gene. These mutant constructs have been transfected into homozygous Mov13 fibroblasts that do not express the endogenous Col1a1 gene due to a retroviral insertion. Secreted triple-helical type I collagens containing substitutions of Pro for Ile (position 776) (P1') were not cleaved by human rheumatoid synovial collagenase, whereas those containing substitutions of Met for Ile (position 776) were cleaved. Type I collagens containing double substitutions of Pro for Gln-774 (P2) and Ala-777 (P2') were not cleaved regardless of whether they contained the wild-type residue Ile at position 776 or the substitution of Met for Ile at position 776. The wild-type alpha 2(I) chains derived from the endogenous Col1a2 gene were also resistant to enzyme digestion when they were complexed with the mutant alpha 1(I) chains, indicating that the presence of normal alpha 1(I) sequences is critical for cleavage of the alpha 2(I) chains in the type I heterotrimer.

Amino Acid Sequence↗