Showing papers by "University of Birmingham published in 1991"
TL;DR: The authors considered the nature of styles and strategies and then surveyed work on cognitive styles, and suggested that the labels may be grouped into two principal cognitive styles: the Wholist-Analytic and Verbialiser-Imager dimensions.
Abstract: This review article considered the nature of styles and strategies and then surveyed work on cognitive styles. Different researchers have used a variety of labels for the styles they have investigated. Analysis of the way in which they assessed style, its effect on behaviour and performance, and studies of the relationship to other labels, suggested that the labels may be grouped into two principal cognitive styles. These were labelled the Wholist‐Analytic and Verbialiser‐Imager dimensions. A computer presented method of assessing the position of an individual on these dimensions was described.
1,188 citations
TL;DR: By DNA transfection into human B cells, it is shown that protection from apoptosis is conferred through expression of a single EBV latent protein, the latent membrane protein LMP 1, and it is demonstrated that L MP 1 mediates this effect by up-regulating expression of the cellular oncogene bcl-2.
1,186 citations
TL;DR: There is now compelling evidence that the other side of equation, the rate of cell death, must be considered, and the growing appreciation of the importance of apoptosis and its regulation should lead to fundamental advances in the understanding and potentially also the treatment of cancer.
859 citations
TL;DR: The authors showed that the eonvective term in the correlation should have a Prandtl number dependence and constructed an accurate predictive method with an explicit nucleate boiling term and without boiling number dependence.
803 citations
TL;DR: Blast cells in S phase were identified in tissue sections by staining cells which had been pulse labeled in vivo with 5‐bromo‐2′‐deoxyuridine and B blasts was distinguished from the strong cytoplasmic hapten binding by specific plasma cells and plasmablasts.
Abstract: Techniques which identify hapten-specific B cells in tissues have been used to determine the sites of B cell activation in rat spleens in response to T cell-dependent (TD) antigens and T cell-independent type-1 (TI-1) antigens. Surface-associated hapten binding by specific memory B cells and. B blasts was distinguished from the strong cytoplasmic hapten binding by specific plasma cells and plasmablasts. Blast cells in S phase were identified in tissue sections by staining cells which had been pulse labeled in vivo with 5-bromo-2′-deoxyuridine.
Hapten-specific B blast cells are found in three sites: (a) around interdigitating cells in the T cell-rich zones; (b) in the follicular dendritic cell network and (c) in association with macrophages in the red pulp. Hapten-binding memory B cells, which are not in cell cycle, accumulate in the marginal zones and to a lesser extent the follicular mantles in response to TD and TI-1 antigens. The hapten-specific blast response in T zones is confined to the first few days after antigen is given and is low for primary responses to TD antigens, but massive on secondary challenge, when marginal zone memory B cells migrate to the T zones. Both the primary and secondary T zone responses to TI-1 antigens are impressive and in these responses hapten-specific B blasts are also found in the splenic red pulp.
The follicular response to TD antigens starts with a small number of B blasts (fewer than five) entering each follicle. These increase in number exponentially so that by the 4th day after immunization they fill the follicle. The oligoclonality of the response is shown in simultaneous responses to two haptens where 6%–31% of the follicles on day 3 after immunization contain blasts specific for only one of the two haptens. During the 4th day classical zonal pattern of germinal centers develops. The surface immunoglobulin-positive B blasts are lost from the follicle center, while one pole of the follicular dendritic cell network fills with surface immunoglobulin-negative centroblasts. Centroblasts do not increase in numbers but divide to give rise to centrocytes, which re-express slg and migrate into the follicular dendritic cell network. Cell kinetic studies indicate that the centrocyte population is renewed from centroblasts every 7 h. Centrocytes either leave the germinal center within this time or die in situ. It is probable that the centroblasts and centrocytes are derived from the small number of B blasts which initiate the follicular reaction, for the centrocytes show the same oligoclonality observed at the B blast stage. The germinal center reaction declines gradually and 3 weeks after immunization centroblasts and centrocytes are no longer seen. At this time small clusters of B blasts can be found proliferating in the follicular dendritic cell network. These secondary B blasts characterize the third phase of the follicular reaction, which continues throughout the established phase of TD responses. Some follicular response is seen to TI-1 antigens but this is much less dramatic than that seen during TD responses.
754 citations
TL;DR: The findings suggest that EBV is associated with more cases of HD than was previously recognised, that in positive cases RS cells express a latent infection protein phenotype which differs from that of other EBV-associated lymphomas, and that LMP expression is related to histologically aggressive subtypes of HD.
701 citations
TL;DR: In this paper, the lateral distributions of depth-mean velocity and boundary shear stress for straight open channels with prismatic complex cross-sections are derived theoretically for channels of any shape, provided that the boundary geometry can be discretized into linear elements.
Abstract: The flow of water in straight open channels with prismatic complex cross-sections is considered. Lateral distributions of depth-mean velocity and boundary shear stress are derived theoretically for channels of any shape, provided that the boundary geometry can be discretized into linear elements. The analytical model includes the effects of bed-generated turbulence, lateral shear turbulence and secondary flows. Experimental data from the Science and Engineering Research Council (SERC) Flood Channel Facility are used to illustrate the relative importance of these three effects on internal shear stresses. New experimental evidence concerning the spatial distribution of Reynolds stresses τyx and τzx is presented for the particular case of compound or two-stage channels. In such channels the vertical distributions of τzx are shown to be highly nonlinear in the regions of strongest lateral shear and the depth-averaged values of τyx are shown to be significantly different from the depth mean apparent shear stresses. The importance of secondary flows in the lateral shear layer region is therefore established. The influence of both Reynolds stresses and secondary flows on eddy viscosity values is quantified. A numerical study is undertaken of the lateral distributions of local friction factor and dimensionless eddy viscosity. The results of this study are then used in the analytical model to reproduce lateral distributions of depth-mean velocity and boundary shear stress in a two stage channel. The work will be of interest to engineers engaged in flood channel hydraulics and overbank flow in particular.
591 citations
TL;DR: It is reported that during high-frequency transmission GABA depresses its own release by an action on GABAB autoreceptors, which permits sufficient NMDA receptor activation for the induction of LTP, and demonstrates a role for GABAB receptors in synaptic plasticity.
Abstract: UNDERSTANDING the mechanisms involved in long-term potenti-ation (LTP) should provide insights into the cellular and molecular basis of learning and memory in vertebrates1. It has been established that in the CA1 region of the hippocampus the induction of LTP requires the transient activation of the N-methyl-D-aspartate (NMDA) receptor system2. During low-frequency transmission, significant activation of this system is prevented by γ-aminobutyric acid (GABA) mediated synaptic inhibition3,4 which hyperpolarizes neurons into a region where NMDA receptor-operated channels are substantially blocked by Mg2+ (refs. 5, 6). But during high-frequency transmission, mechanisms are evoked that provide sufficient depolarization of the postsynaptic membrane to reduce this block7 and thereby permit the induction of LTP. We now report that this critical depolarization is enabled because during high-frequency transmission GABA depresses its own release by an action on GABAB autoreceptors, which permits sufficient NMDA receptor activation for the induction of LTP. These findings demonstrate a role for GABAB receptors in synaptic plasticity.
588 citations
TL;DR: Assessment of the thyroid status of 1210 patients aged over 60 registered with a single general practice by measurement of serum TSH using a sensitive assay finds the risk of thyrotoxicosis in those with TSH values below normal appears small.
Abstract: Increasing use of assays for TSH with improved sensitivity as a first-line test of thyroid function has raised questions regarding prevalence and clinical significance of abnormal results, especially values below normal. We have assessed the thyroid status of 1210 patients aged over 60 registered with a single general practice by measurement of serum TSH using a sensitive assay. High TSH values were more common in females (11.6%) than males (2.9%). TSH values below normal were present in 6.3% of females and 5.5% of males, with values below the limit of detection of the assay present in 1.5% of females and 1.4% of males. Anti-thyroid antibodies were found in 60% of those with high TSH but only 5.6% of those with subnormal TSH. Eighteen patients were hypothyroid (high TSH, low free thyroxine) and one thyrotoxic (low TSH, raised free thyroxine) at initial testing. Seventy-three patients with elevated TSH but normal free T4 were followed for 12 months; 13 (17.8%) developed low free T4 levels and commenced thyroxine, TSH returned to normal in four (5.5%) and 56 (76.7%) continued to have high TSH values. Sixty-six patients with TSH results below normal were followed. Of the 50 subjects with low but detectable TSH at initial testing, 38 (76%) returned to normal at 12 months; of those 16 with undetectable TSH followed, 14 (87.5%) remained low at 12 months. Only one subject (who had an undetectable TSH) developed thyrotoxicosis. In view of the marked prevalence of thyroid dysfunction in the elderly, we suggest that screening of all patients over 60 should be considered.(ABSTRACT TRUNCATED AT 250 WORDS)
559 citations
TL;DR: It is shown in an in vitro system that EBV, through expression of the full set of eight virus-coded 'latent' proteins, can protect human B cells from programmed cell death (apoptosis), the deletion mechanism which normally restricts entry into memory.
Abstract: Epstein-Barr virus (EBV), a human herpesvirus, establishes a persistent asymptomatic infection of the circulating B-lymphocyte pool. The mechanism of virus persistence is not understood but, given the limited lifespan of most B cells in vivo, it seems most likely that EBV-infected cells must gain access to the long-lived memory B-cell pool. Here we show in an in vitro system that EBV, through expression of the full set of eight virus-coded 'latent' proteins, can protect human B cells from programmed cell death (apoptosis), the deletion mechanism which normally restricts entry into memory. We have found that EBV-positive Burkitt's lymphoma (BL) cell clones retaining the original tumour cell phenotype and expressing only one of the virus latent proteins, the nuclear antigen EBNA 1, are extremely sensitive to apoptosis; in this respect they resemble the tumour's normal cell of origin found in the germinal centres of lymphoid tissue. By contrast, isogenic BL cell clones which have activated expression of all eight EBV latent proteins are resistant to the induction of apoptosis. The EBV latent proteins should therefore be seen not just as activators of B-cell proliferation but, perhaps more importantly, as mediators of enhanced B-cell survival.
527 citations
TL;DR: Dual‐fluorescence studies on small lymphocytes confirm the presence of bcl‐2 protein in mitochondria but show that this is also present in other extra‐nuclear areas.
Abstract: B cells undergo selection within germinal centers on the basis of their capacity to be activated by antigen held on follicular dendritic cells. Isolated germinal center B cells in culture kill themselves by apoptosis but this is prevented if their receptors for antigen are cross-linked. In this study it is confirmed that almost all germinal center B cells, unlike other B cells, do not express the 25-kDa protein encoded by the bcl-2 oncogene. Cross-linking the surface Ig of isolated germinal center cells causes them to express bcl-2 protein. Two other stimuli which inhibit the entry of germinal center cells to apoptosis result in the expression of bcl-2 protein. These stimuli are: (a) CD40 antibody and (b) recombinant 25-kDa fragment of the CD23 protein plus recombinant interleukin 1 alpha. Respectively, these induce germinal center cells to differentiate to resting B cells or plasmablasts. Dual-fluorescence studies on small lymphocytes confirm the presence of bcl-2 protein in mitochondria but show that this is also present in other extra-nuclear areas. Burkitt lymphoma cells have a phenotype which indicates that they are neoplastic cells of germinal center origin. The expression of bcl-2 protein by Burkitt lymphoma lines was also studied. Burkitt lines which retain the phenotype of fresh Burkitt lymphoma cells can be induced to enter apoptosis on culture with the Ca2+ ionophore ionomycin. These cells were found not to express bcl-2 protein. By contrast, Burkitt lines which have drifted towards a lymphoblastoid cell line phenotype and are resistant to the induction of apoptosis express high levels of the bcl-2 protein. The findings support the concept that the susceptibility of germinal center cells to entering apoptosis is associated with their lack of expression of bcl-2 protein. Aberrant expression of bcl-2 protein by some neoplastic germinal center cells may allow survival in situations where their normal counterparts die.
TL;DR: The accommodation of variations in antigenic structure by modest combining site flexibility could make an important contribution to immune defence by allowing antibody binding to distinct but closely related pathogens.
TL;DR: A number of priorities for future research into the effects of climatic changes on agricultural insect pests can be identified, including examination of the influence of Climatic variables on insect pests, long-term monitoring of pest population levels and insect behaviour, and consideration of possible climatic change in research into pest management systems and identification of potential migrants.
TL;DR: It is reported that a pharmacologically isolated NMDA receptor-mediated synaptic response can undergo robust, synapse-specific LTP, adding fundamentally to theories of synaptic plasticity because NMDA receptors activation may, in addition to causing increased synaptic efficiency, directly alter the plasticity of synapses.
Abstract: Neurotransmission at most excitatory synapses in the brain operates through two types of glutamate receptor termed alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors; these mediate the fast and slow components of excitatory postsynaptic potentials respectively. Activation of NMDA receptors can also lead to a long-lasting modification in synaptic efficiency at glutamatergic synapses; this is exemplified in the CA1 region of the hippocampus, where NMDA receptors mediate the induction of long-term potentiation (LTP). It is believed that in this region LTP is maintained by a specific increase in the AMPA receptor-mediated component of synaptic transmission. We now report, however, that a pharmacologically isolated NMDA receptor-mediated synaptic response can undergo robust, synapse-specific LTP. This finding has implications for neuropathologies such as epilepsy and neurodegeneration, in which excessive NMDA receptor activation has been implicated. It adds fundamentally to theories of synaptic plasticity because NMDA receptor activation may, in addition to causing increased synaptic efficiency, directly alter the plasticity of synapses.
TL;DR: A questionnaire survey of 710 Maltese primary schoolteachers revealed that the level of teacher stress, job satisfaction and career commitment was constituted differently in some of the teacher demographic subgroups as discussed by the authors.
Abstract: A questionnaire survey of 710 Maltese primary schoolteachers revealed that the level of teacher stress, job satisfaction and career commitment was constituted differently in some of the teacher demographic subgroups. A principal components analysis of the stress ratings of 20 items covering various aspects of the teacher's work environment yielded four factors described in terms of ‘pupil misbehaviour’, ‘time/ resource difficulties’, ‘professional recognition needs’ and ‘poor relationships’. Teacher sex and ability‐group taught interacted significantly with the stress factors. Results also showed that teachers who reported greater stress were less satisfied with their job and less committed to choose a teaching career were they to start life over again. Moreover, the association between the general measure of job stress and the stress due to each of the four stress factors was strongest for ‘pupil misbehaviour’ and ‘time/resource difficulties’. Of the four factors, ‘professional recognition needs...
TL;DR: English for specific purposes has established itself as a viable and vigorous movement within the field of TEFL/TEFL/TESL over the past 30 years and its distinguishing features have been examined in this paper.
Abstract: Over the past 30 years, English for specific purposes has established itself as a viable and vigorous movement within the field of TEFL/TESL. In this paper, English for specific purposes is defined and its distinguishing features examined. The international nature and scope of the movement are particularly emphasized. Finally, questions and controversies surrounding the movement are discussed.
TL;DR: Methodological issues in trial design, collection of resource use data,Collection of outcome data, and interpretation and extrapolation of results are discussed.
Abstract: Controlled clinical trials are recognized as the best source of data on the efficacy of health care interventions and technologies. Because economic evaluation is dependent on the quality of the underlying medical evidence, clinical trials have increasingly been viewed as a natural vehicle for economic analysis. However, the closer integration of economic and clinical research raises many methodological issues. This paper discusses these issues in trial design, collection of resource use data, collection of outcome data, and interpretation and extrapolation of results. Some guidelines are suggested for economic analysts wishing to undertake evaluations alongside clinical trials.
TL;DR: The present work shows that generally the human (hu) PBL-SCID tumors are distinct from Burkitt's lymphoma and instead resemble lymphoblastoid cell lines (LCLs) generated by EBV-infection of normal B cells in vitro in terms of their cell surface phenotype.
Abstract: When human peripheral blood lymphocytes (PBLs) from Epstein-Barr virus (EBV)-seropositive donors are injected intraperitoneally into SCID mice, EBV+ B cell tumors develop within weeks. A preliminary report (Mosier, D. E., R. J. Gulizia, S. M. Baird, D. D. Richman, D. B. Wilson, R. I. Fox, and T. J. Kipps, 1989. Blood. 74(Suppl. 1):52a) has suggested that such tumors resemble the EBV-positive malignancy, Burkitt's lymphoma. The present work shows that generally the human (hu) PBL-SCID tumors are distinct from Burkitt's lymphoma and instead resemble lymphoblastoid cell lines (LCLs) generated by EBV-infection of normal B cells in vitro in terms of: (a) their cell surface phenotype, with expression of B cell activation antigens and adhesion molecules, (b) normal karyotype, and (c) viral phenotype, with expression of all the transformation-associated EBV latent proteins and, in a minority of cells, productive cycle antigens. Indeed, in vitro-transformed LCLs also grow when inoculated into SCID mice, the frequency of tumor outgrowth correlating with the in vitro growth phenotype of the LCL which is itself determined by the identity of the transforming virus (i.e., type 1 or type 2 EBV). Histologically the PBL-derived hu-SCID tumors resemble the EBV+ large cell lymphomas that develop in immuno-suppressed patients and, like the human tumors, often present at multiple sites as individual monoclonal or oligoclonal foci. The remarkable efficiency of tumor development in the hu-SCID model suggests that lymphomagenesis involves direct outgrowth of EBV-transformed B cells without requirement for secondary genetic changes, and that selection on the basis of cell growth rate alone is sufficient to explain the monoclonal/oligoclonal nature of tumor foci. EBV+ large cell lymphoma of the immunosuppressed may arise in a similar way.
TL;DR: The post-translational acetylation of the core histories was first recognised more than a quarter of a century ago (Allfrey et al. 1964) and since then, considerable research effort has been expended in attempting to reveal the mechanisms by which acetylations is controlled and, most importantly, its functional significance as discussed by the authors.
Abstract: The post-translational acetylation of the core histories was first recognised more than a quarter of a century ago (Allfrey et al. 1964). Since then, considerable research effort has been expended in attempting to reveal the mechanisms by which acetylation is controlled and, most importantly, its functional significance. The reasons for the interest in this phenomenon are not hard to find. The intimate association of histones with cellular DNA and their extreme conservation through evolution both make it likely that any change in their structure, particularly one that involves a change in net charge, will have an effect on chromatin function. Thus, as frequently stated in introductory paragraphs, histone acetylation is potentially a major influence on events such as transcription, replication, DNA packaging through the cell cycle and DNA repair. However, despite the conceptual appeal of such a central role, definitive evidence is lacking and we have intriguing correlations rather than experimental data on which detailed molecular mechanisms can be based. Indeed, belief in the functional importance of histone acetylation has tended to rely on evolutionary arguments of the sort used to explain the popularity of sexual reproduction in the animal kingdom, namely: In evolutionary terms sexual reproduction must be important since so many species devote so much energy to it' (Leakey, 1976).
23 Mar 1991
TL;DR: In 2 patients with Angelman's syndrome the authors found evidence of uniparental paternal disomy, strong evidence in man for genomic imprinting, in which the same gene has different effects dependent upon its parental origin.
Abstract: Angelman's syndrome and Prader-Willi syndrome are both causes of mental retardation with recognisable, but quite different, clinical phenotypes. Both are associated with deletions of chromosome 15q11-13, of maternal origin in Angelman's and paternal in Prader-Willi. Prader-Willi can arise by inheritance of two chromosomes 15 from the mother and none from the father (uniparental maternal disomy). In 2 patients with Angelman's syndrome we found evidence of uniparental paternal disomy. The phenotypic effects of maternal and paternal disomy of chromosome 15 are very different and inheritance of two normal 15s from one parent does not lead to normal development—strong evidence in man for genomic imprinting, in which the same gene has different effects dependent upon its parental origin.
TL;DR: 3-year-olds' understanding of the representational capability of the mind is investigated by examining whether they would acknowledge that they had entertained a wrong belief, and the posting task made it possible for children simultaneously to focus on physical reality and acknowledge false belief.
07 Jul 1991-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a duplex plasma surface-engineering technique has been developed to improve the tribological properties and load-bearing capacity of low alloy steel, which is achieved by plasma nitriding the steel first so as to produce a thick, strong subsurface and then depositing a thin, hard and wear-resistant TiN coating on the nitrided substrate by ion plating.
Abstract: The surface of low alloy steel (En40B) has been engineered in the plasma of a glow discharge via plasma nitriding and ion plating of titanium nitride (TiN) coatings on the nitrided substrates with the purpose of enhancing the surface properties and fatigue strength. The nitriding response of the steel has been accessed by the evaluation of phase composition, layer thickness, hardness profile, residual stresses and nitrogen and carbon distributions. The wear and fatigue characteristics of the plasma-nitrided steel have been investigated and simple models have been developed to describe the influence of such properties as depth and strength of the nitrided case on the fatigue limit and load-bearing capacity of the nitrided steel. In order to further improve the tribological properties and load-bearing capacity of the low alloy steel, a duplex plasma surface-engineering technique has been developed. This is achieved by plasma nitriding the steel first so as to produce a thick, strong subsurface and then depositing a thin, hard and wear-resistant TiN coating on the nitrided substrate by ion plating. Dry-sliding wear tests demonstrated that the duplex-treated steel, i.e. the TiN coating-nitrided steel composite, not only exhibited enhanced wear resistance over the as-nitrided steel (by a factor of 2–8) but also had much higher load-bearing capacity than the TiN coating on unnitrided steel. Optimization of the coating-substrate combination can be achieved by correct control of the plasma-nitriding, surface preparation and ion-plating processes.
Journal Article•
TL;DR: It is demonstrated that human Fc Gamma RI interacts with a site in the lower hinge of human IgG and that this interaction dictates Fc gamma RI-mediated superoxide generation.
Abstract: Cellular receptors for IgG (Fc gamma R) mediate important protective functions. By using site-specific mutants of a chimeric antibody (mouse V H domain and L chain; human IgG3 C H domains), we have demonstrated that human Fc gamma RI interacts with a site in the lower hinge of human IgG (residues 234 to 237) and that this interaction dictates Fc gamma RI-mediated superoxide generation. Mutations at position 235 resulted in the most profound reductions in Fc gamma RI recognition. We have also mapped an interaction site for Fc gamma RII to the same region; however, mutations at position 234 and 237 resulted in the greatest reductions in Fc gamma RII recognition. The two receptors appear to recognize overlapping but nonidentical sites on the lower hinge of IgG. Deviations from the optimal motif 234-Leu-Leu-Gly-Gly-237 may then explain the human IgG subclass specificity profile for human Fc gamma RI and Fc gamma RII.
TL;DR: In this article, the authors reviewed the factors controlling denitrification and described the evidence for denitification in the groundwater environment and concluded that artificial denitization as an above-ground process affords the best nitrate removal rates and process control.
TL;DR: It is pointed out that both Naive and memory T-cell subsets are activated to the same extent by alloantigen and suggested that synergy may be an important event in initiating potent responses against transplanted allografts.
TL;DR: A monoclonal antibody to BZLF1 is generated which reacts in immunohistology, immunoblotting, and immunoprecipitation and which recognizes both the active, dimeric form and the inactive, monomeric form of the protein.
Abstract: The BZLF1 protein of Epstein-Barr virus (EBV) is a key immediate-early protein which has been shown to disrupt virus latency in EBV-infected B cells. We have generated a monoclonal antibody, BZ1, to BZLF1 which reacts in immunohistology, immunoblotting, and immunoprecipitation and which recognizes both the active, dimeric form and the inactive, monomeric form of the protein. Biopsies of oral hairy leukoplakia, an AIDS-associated lesion characterized by high-level EBV replication, were examined by immunohistochemistry using the BZ1 monoclonal antibody. A differentiation-associated pattern of BZLF1 expression was observed, BZ1 reacting with nuclei of the upper spinous layer of the lesion. This finding suggests that the BZLF1 promoter may be regulated by the degree of squamous differentiation. A comparison of in situ hybridization to EBV DNA and viral capsid antigen staining with BZ1 reactivity suggested that BZLF1 expression precedes rampant virus replication. The inability to detect EBV in the lower epithelial layers of oral hairy leukoplakia raises questions concerning the nature of EBV latency and persistence in stratified squamous epithelium.
TL;DR: It is hypothesized that the backache-producing mechanism is postural, occurring generally during labour, but exacerbated by epidural anaesthcsia, through loss of muscle tone, inability to move, and inhibition of discomfort-feedback in women giving birth to their most recent child.
TL;DR: Because the air is an important route of spread in joint prosthesis operations, the routine use of an ultraclean air system and exhaust-ventilated clothing is frequently recommended.
Abstract: Most surgical wound infections are acquired in the operating room from the patient's own microbial flora. The remainder are acquired mainly from the staff in the operating room during surgery. The inanimate environment (e.g., walls, floors, and surgical instruments) has little relevance to the spread of infection. Because the air is an important route of spread in joint prosthesis operations, the routine use of an ultraclean air system and exhaust-ventilated clothing is frequently recommended. The value of such a system in other types of clean surgery is doubtful, but other measures, such as the following, may provide similar results at less cost: reduction of the number of persons in the operating room; a policy of not opening doors during operations; the use of comfortable, washable, bacteria-impermeable clothing by the operating-room staff; and concentration of the airflow over the operation site rather than over the whole operating room.
TL;DR: The gene encoding a 23 kilodalton protein antigen has been cloned from Mycobacterium tuberculosis by screening of a recombinant DNA library with monoclonal antibodies and revealed a close similarity to manganese‐containing SODs from other organisms.
Abstract: Summary
The gene encoding a 23 kilodalton protein antigen has been cloned from Mycobacterium tuberculosis by screening of a recombinant DNA library with monoclonal antibodies. The product of the gene has been identified as the superoxide dismutase (SOD) of M. tuberculosis on the basis of sequence comparison and by expression of the recombinant protein in a functionally active form. The derived amino acid sequence of M. tuberculosis SOD reveals a close similarity to manganese-containing SODs from other organisms, in spite of the fact that previous studies using the purified enzyme have identified iron as the preferred metal ion ligand. SOD is present in the extracellular fluid of logarithmic-phase cultures of M. tuberculosis, but the structural gene is not preceded by a signal peptide sequence. Insertion of the M. tuberculosis SOD gene into a novel shuttle vector demonstrated the presence of a promoter which functions efficiently in mycobacteria but is ineffective in Escherichia coli
TL;DR: In this article, the early Triassic was a time when anoxic conditions spread widely over epicontinental seas, associated with marine transgression following the latest Permian regression, are likely to be a prime cause of the mass extinction of Palaeozoic marine faunas.
Abstract: Data from widespread dysaerobic facies, carbon/sulphur ratios and cerium anomalies suggest that the early Triassic was a time when anoxic conditions spread widely over epicontinental seas. These conditions, associated with marine transgression following the latest Permian regression, are likely to be a prime cause of the mass extinction of Palaeozoic marine faunas. The occurrence of many Lazarus taxa in the Middle and Upper Triassic indicates, however, that the extinctions at the end of the Permian were less severe than has been widely assumed, and that the turnover from Palaeozoic to Mesozoic faunas was considerably extended in time, being finally accomplished only after the end‐Triassic mass extinction event.