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Fischer A, Muller M. [Perceptions of nursing service managers in the South African Military Health Service on their level of motivation]. Curationis 2000; 23:63-71. [PMID: 11949294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023] Open
Abstract
The process of transformation in the South African Military Health Services, has influenced the nursing service managers' level of motivation and the following research question is applicable: what are the perceptions of the nursing service managers within the South African Military Health Services on their level of motivation? The purpose with this study was to explore and describe the perceptions of nursing service managers on their level of motivation within these health services. A qualitative research design was utilized and four focus group interviews were conducted with 33 nursing service managers country wide. The transcribed interviews were exposed to a content analysis. The results confirm that the level of motivation amongst these nursing service managers is low. The demotivators relate mainly to the following: inadequate acknowledgement, job insecurity in relation to the future, problems with the process of integration, transformation and rationalization, problems with management, many labour related issues, poor/inadequate communication, inadequate support, increased work load, poor physical environment, negative publicity and poor self motivation. Although there were a few motivators identified, they were of less importance. These results were interpreted within Herzberg's motivation theory to identify the hygiene/maintenance factors and to assess whether the important motivators were in place. During any process of change, and/or when the level of motivation amongst employees is low, it is important to adequately manage the environment (hygiene/maintenance factors within the Herzberg theory). But it is even more important to ensure that the motivators are in place or to intensify them. It is therefore recommended that a motivation strategy, based on the Herzberg theory as well as the Hackman-Oldham job enrichment model, be developed, implemented and evaluated.
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Laurincik J, Zakhartchenko V, Avery B, Stojkovic M, Brem G, Wolf E, Muller M, Hyttel P. Activation of ribosomal RNA genes in pre-implantation In Vitro-produced and nuclear transfer bovine embryos. Reprod Domest Anim 2000. [DOI: 10.1046/j.1439-0531.2000.00275.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Baier G, Perales H, Rivera M, Muller M, Leder R, Parmananda P. Self-exciting chaos as a dynamic model for irregular neural spiking. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 62:R7579-R7582. [PMID: 11138105 DOI: 10.1103/physreve.62.r7579] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2000] [Indexed: 05/23/2023]
Abstract
We introduce a nonlinear dynamical system with self-exciting chaotic dynamics. Its interspike interval return map shows a noisy Poisson-like distribution. Spike sequences from different initial conditions are unrelated but possess the same mean frequency. In the presence of noisy perturbations, sequences started from different initial conditions synchronize. The features of the model are compared with experimental results for irregular spike sequences in neurons. Self-exciting chaos offers a mechanism for temporal coding of complex input signals.
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Hilscher G, Haferl R, Kirchmayr H, Muller M, Guntherodt HJ. Breakdown of magnetism in the amorphous alloy system (Fe1-xNix)77Si10B13. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0305-4608/11/11/024] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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255
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Foulon M, Amoureux JP, Sauvajol JL, Cavrot JP, Muller M. Different aspects of an interesting glassy crystal: 1-cyanoadamantane. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3719/17/24/005] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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256
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Andrès E, Pflumio F, Knab MC, Muller M, Ott C, Ubrich M, Baumann R, Geisler F. [Splenic thrombosis and celiac disease: a fortuitous association?]. Presse Med 2000; 29:1933-4. [PMID: 11244621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/19/2023] Open
Abstract
BACKGROUND Rare cases of venous thrombosis associated with celiac disease have been reported. CASE REPORT We report a case of 40-year-old woman with splenic infarction and splenic venous thrombosis associated with celiac disease. This patient was homozygous for the C677T mutation of the methyltetrahydrofolate reductase (MTHFR) gene and had moderately elevated homocysteinemia. DISCUSSION We discuss the link between celiac disease and thrombosis as well as the interest and appropriate duration of anticoagulation and hypothesize a mechanism of thrombotic disease in this setting with hyperhomocyseinemia.
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Polak M, Mierzwiński J, Lasek W, Piziewicz A, Muller M. [Isolated sphenoiditis treated with endoscopic surgery in a child]. OTOLARYNGOLOGIA POLSKA 2000; 54:181-4. [PMID: 10961079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
Isolated sphenoiditis in childhood is a rare entity which is often very difficult to diagnose with conventional techniques. The authors present a case of sphenoiditis in nine years old boy, where chronic rhinitis and persistent cephalqia where the main symptoms. The diagnosis was made on the base of computed tomography and nasal endoscopy. Because of lack of effect after pharmacological treatment the child was submitted to endoscopic surgery--sphenoethmoidectomy, which resulted it total recovery. The diagnosis, indications to computed tomography of paranasal sinuses in children, options of both conservative and surgical treatment and possible complications of the diseases are discussed.
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Muller M, Albano EV, Binder K. Symmetric polymer blend confined into a film with antisymmetric surfaces: interplay between wetting behavior and the phase diagram. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 62:5281-5295. [PMID: 11089090 DOI: 10.1103/physreve.62.5281] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2000] [Indexed: 05/23/2023]
Abstract
We study the phase behavior of a symmetric binary polymer blend that is confined in a thin film. The film surfaces interact with the monomers via short-range potentials. We calculate the phase behavior within the self-consistent field theory of Gaussian chains. Over a wide range of parameters we find strong first-order wetting transitions for the semi-infinite system, and the interplay between the wetting/prewetting behavior and the phase diagram in confined geometry is investigated. Antisymmetric boundaries, where one surface attracts the A component with the same strength as the opposite surface attracts the B component, are applied. The phase transition does not occur close to the bulk critical temperature but in the vicinity of the wetting transition. For very thin films or weak surface fields one finds a single critical point at straight phi(c)=1 / 2. For thicker films or stronger surface fields the phase diagram exhibits two critical points and two concomitant coexistence regions. Only below a triple point there is a single two-phase coexistence region. When we increase the film thickness the two coexistence regions become the prewetting lines of the semi-infinite system, while the triple temperature converges toward the wetting transition temperature from above. The behavior close to the tricritical point, which separates phase diagrams with one and two critical points, is studied in the framework of a Ginzburg-Landau ansatz. Two-dimensional profiles of the interface between the laterally coexisting phases are calculated, and the interfacial and line tensions analyzed. The effect of fluctuations and corrections to the self-consistent field theory are discussed.
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Detmar SB, Aaronson NK, Wever LD, Muller M, Schornagel JH. How are you feeling? Who wants to know? Patients' and oncologists' preferences for discussing health-related quality-of-life issues. J Clin Oncol 2000; 18:3295-301. [PMID: 10986063 DOI: 10.1200/jco.2000.18.18.3295] [Citation(s) in RCA: 258] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE This study investigated (1) the attitudes of cancer patients toward discussing health-related quality-of-life (HRQL) issues; (2) the association between such attitudes and patients' characteristics; and (3) oncologists' attitudes and self-reported behavior regarding these same issues. PATIENTS AND METHODS Two hundred seventy-three patients receiving palliative chemotherapy and ten physicians were asked to complete a series of questionnaires. RESULTS Almost all patients wanted to discuss their physical symptoms and physical functioning and were also willing to address their emotional functioning and daily activities. However, 25% of the patients were only willing to discuss these latter two issues at the initiative of their physician. Patients varied most in their willingness to discuss their family and social life, with 20% reporting no interest in discussing these issues at all. Female patients were more reluctant to discuss various HRQL issues than male patients. Older and less well-educated patients were more likely to prefer that their physician initiate discussion of HRQL issues. All physicians considered it to be primarily their task to discuss the physical aspects of their patients' health, whereas four physicians indicated that discussion of psychosocial issues was a task to be shared with other health care providers. All physicians indicated that they generally defer to their patients in initiating discussion of psychosocial issues. CONCLUSION Although both patients and oncologists seem willing to discuss a wide range of HRQL issues, communication regarding psychosocial issues may be hampered by competing expectations as to who should take the lead in initiating such discussions.
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Jarski RW, Loniewski EG, Williams J, Bahu A, Shafinia S, Gibbs K, Muller M. The effectiveness of osteopathic manipulative treatment as complementary therapy following surgery: a prospective, match-controlled outcome study. Altern Ther Health Med 2000; 6:77-81. [PMID: 10979164] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
Abstract
CONTEXT Osteopathic manipulative treatment has been reported to relieve a variety of conditions, but no studies have examined the outcome effects of osteopathic manipulative treatment as a complementary modality for treating musculoskeletal problems during postoperative recovery. OBJECTIVE To assess osteopathic manipulative treatment as a complementary therapy for patients undergoing elective knee or hip arthroplasty. DESIGN Prospective, single-blinded, 2-group, match-controlled outcome study. SETTING Osteopathic teaching hospital. PATIENTS Of 166 eligible patients, 38 were assigned to a treatment group and matched with 38 control subjects. INTERVENTION The treatment group received osteopathic manipulative treatment on postoperative days 2 through 5. MAIN OUTCOME MEASURES Days to independent negotiation of stairs, distance ambulated, supplemental intramuscular analgesic use, length of hospital stay, and patients' perceptions of treatment. RESULTS Compared to control subjects, the intervention group negotiated stairs 20% earlier (mean = 4.3 postoperative days, SD = 1.2; control subjects 5.4, SD = 1.6, P = .006) and ambulated 43% farther on the third postoperative day (mean = 24.3 m, SD = 18.3; controls = 13.9, SD = 14.4, P = .008). The intervention group also required less analgesia, had shorter hospital stays, and ambulated farther on postoperative days 1, 2, and 4. CONCLUSIONS Patients receiving osteopathic manipulative treatment in the early postoperative period negotiated stairs earlier and ambulated greater distances than did control group patients.
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Pedarzani P, Kulik A, Muller M, Ballanyi K, Stocker M. Molecular determinants of Ca2+-dependent K+ channel function in rat dorsal vagal neurones. J Physiol 2000; 527 Pt 2:283-90. [PMID: 10970429 PMCID: PMC2270078 DOI: 10.1111/j.1469-7793.2000.t01-1-00283.x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Using in situ hybridisation histochemistry in combination with patch-clamp recordings and specific pharmacological tools, the molecular nature of the channels underlying Ca2+-dependent K+ currents was determined in dorsal vagal neurones (DVNs) of rat brainstem slices. In situ hybridisation analysis at cellular resolution revealed the presence of 'big'-conductance Ca2+- and voltage-activated K+ (BK) channel alpha-subunit mRNA, and of only one 'small'-conductance Ca2+-activated K+ (SK) channel subunit transcript, SK3, at very high levels in DVNs. By contrast, SK1 and SK2 mRNAs were below the threshold limit of detection. The SK channel-mediated after-hyperpolarising current (IAHP) was blocked by apamin with a half-maximal inhibitory concentration of approximately 2.2 nM. This is consistent with homomultimeric SK3 channels mediating IAHP in DVNs. IAHP was also blocked by scyllatoxin (20-30 nM) and curare (100-200 microM). Application of apamin (100 nM) or scyllatoxin (20 nM) invariably caused a substantial increase to 146.1 +/- 10.4 and 181.8 +/- 12.9 % of control, respectively, in the spontaneous firing rate of DVNs. Action potential duration was not affected by these SK channel blockers. The selective BK channel blocker iberiotoxin (50 nM) increased action potential duration by 22.5 +/- 7.3 %, as did low concentrations of tetraethylammonium (0.5 mM; 99.3 +/- 16.4 %) and the Ca2+ channel blocker Cd2+ (100 microM; 49.5 +/- 20.9 %). BK channel blockade did not significantly affect the firing rate of DVNs. These results allow us to establish a tight correlation between the properties of cloned and native BK and SK channels, and to achieve an understanding, at the molecular level, of their role in regulating the spontaneous firing frequency and in shaping single action potentials of central neurones.
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Abstract
Infection of burn patients with the Aeromonas organism is an uncommon event. This paper documents four cases of Aeromonas hydrophila and one case involving both A. hydrophila and A. caviae occurring in burn patients between 1990 and 1998 at the Royal Brisbane Hospital burns unit. The organism was isolated from either skin swabs, tissue samples, blood cultures or cultured lines. In all patients there was a history of immersion in water immediately post burn. There is one case of invasion and destruction of deeper tissues and one fatality. Appropriate management requires a high index of suspicion if a history of immersion in untreated water post burn is given and the treatment involves aggressive excision and antibiotic therapy.
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Eitinger T, Degen O, Bohnke U, Muller M. Nic1p, a relative of bacterial transition metal permeases in Schizosaccharomyces pombe, provides nickel ion for urease biosynthesis. J Biol Chem 2000; 275:18029-33. [PMID: 10748059 DOI: 10.1074/jbc.m001978200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Schizosaccharomyces pombe genome sequencing project identified an open reading frame (O74869 and O74912, named Nic1p in the present study) with significant similarity to members of a family of bacterial transition metal permeases. These uptake systems transport Ni(2+) ion with extremely high affinity across the bacterial cytoplasmic membrane, but they differ in selectivity toward divalent transition metal cations. An S. pombe mutant harboring an interrupted nic1 allele (nic1-1) was strongly impaired in (63)Ni(2+) uptake in the presence of a high molar ratio of Mg(2+) relative to Ni(2+), conditions that reflect the natural situation. Under these conditions, the nic1-1 mutant contained only background activities of the nickel-dependent cytoplasmic enzyme urease and could not catabolize urea. Among a series of divalent transition metal cations tested (Cd(2+), Co(2+), Cu(2+), Mn(2+), and Zn(2+)), only Co(2+) caused considerable inhibition of Nic1p-mediated Ni(2+) uptake. On the other hand, experiments with (57)Co(2+) (at nm concentrations) did not show significant differences in Co(2+) uptake between the nic1-1 mutant and the parental strain. Our data suggest that Nic1p acts as a plasma-membrane nickel transporter in fission yeast, a finding that invites searches for isologous counterparts in higher eukaryotes.
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Stahl B, Kankeleit E, Gellert R, Muller M, Kamzin A. Magnetic phase in the near-surface region of an FeBO3 single crystal. PHYSICAL REVIEW LETTERS 2000; 84:5632-5635. [PMID: 10991012 DOI: 10.1103/physrevlett.84.5632] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/1999] [Indexed: 05/23/2023]
Abstract
An FeBO3 single crystal was studied from 291 K up to the Neel temperature T(N) = 348.35 K by depth selective conversion electron Mossbauer spectroscopy in ultrahigh vacuum (10(-9) mbar). A new magnetic near-surface phase was found. Its thickness D diverges on approaching T(N) and gives a critical exponent for the correlation length of nu = 0.59(4). The phase boundary between the bulk and near-surface phase could be identified.
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Tsele N, Muller M. Clinical accompaniment: the critical care nursing students' experiences in a private hospital. Curationis 2000; 23:32-6. [PMID: 11949141 DOI: 10.4102/curationis.v23i2.638] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The quality of clinical accompaniment of the student enrolled for the post-basic diploma in Medical and Surgical Nursing Science: Critical Care Nursing (General) is an important dimension of the educational/learning programme. The clinical accompanist/mentor is responsible for ensuring the student's compliance with the clinical outcomes of the programme in accordance with the requirements laid down by the Nursing Education Institution and the South African Nursing Council. The purpose of this study was to explore and describe the experiences of the students enrolled for a post-basic diploma in Medical and Surgical Nursing Science: Critical Care Nursing (General), in relation to the clinical accompaniment in a private hospital in Gauteng. An exploratory, descriptive and phenomenological research design was utilised and individual interviews were conducted with the ten students in the research hospital. A content analysis was conducted and the results revealed both positive and negative experiences by the students in the internal and external worlds. The recommendations include the formulation of standards for clinical accompaniment of students, the evaluation of the quality of clinical accompaniment of students and empowerment of the organisation, clinical accompanists/mentors and clinicians.
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266
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Mahlo S, Muller M. Problems experienced by role players within the managed healthcare context in Gauteng. Curationis 2000; 23:37-41. [PMID: 11949142 DOI: 10.4102/curationis.v23i2.641] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Role players within the context of managed healthcare in Gauteng experience problems in the delivery of healthcare, which negatively affect their working relationships. This is turn, affects the quality of care provided to patients. The purpose of this study is to explore and describe the problem experienced by different role players within the context of managed healthcare in Gauteng, as well as the suggested solutions to counteract these problems. These results will be utilised as the basis of a conceptual framework to formulate a strategy to enhance the working relationships amongst these role players. The strategy will not be discussed in this article as the focus is on the problems experienced by the role players in the delivery of healthcare, as well as suggested solutions in the counteraction thereof. A qualitative, exploratory, descriptive and contextual study was followed to explore and describe the problems, as well as the suggested solutions to counteract these problems. Focus group interviews were conducted to collect data from three private hospitals, three managed care organisations and four general medical practitioners in Gauteng. The participants were purposively and conveniently selected. Content analysis as described by Tesch (1990) was followed to analyse the data. The main problems experienced were related to inadequate communication, inadequate staff competence, cost saving versus quality care, procedural complexity, perceived loss of power by doctors and patients and the system of accounts payment. The suggested solutions focused mainly on empowerment and standardisation of procedures. It is recommended that replication studies of this nature be conducted in other provinces and that ethical standards are formulated within the managed healthcare context.
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Buys R, Muller M. The experiences and perceptions of nursing service managers regarding transformation of health services in selected provincial academic health complexes. Curationis 2000; 23:50-6. [PMID: 11949145 DOI: 10.4102/curationis.v23i2.652] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Nursing service managers are challenged with enormous transformations within the new political dispensation in South Africa. The objective of the study was to explore and describe the experiences and perceptions of the nursing service managers regarding transformation of health services in selected Provincial Academic Health Complexes. A qualitative, exploratory, descriptive and phenomenological design was employed utilising focus group interviews and narratives as methods of data collection. After content analysis was performed, results were grouped into management of health service transformation and quality of patient care in relation to the levels of the organisation. The levels in the organisation are individual level, group level, departmental level and organisational level. Positive and negative experiences and perceptions were identified.
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Pflumio F, Andres E, Dervaux T, Muller M, Ubrich M, Geisler F. [Ehlers-Danlos syndrome disclosed by an intramural hematoma of the duodenum]. ANNALES DE MEDECINE INTERNE 2000; 151:320-1. [PMID: 10922965] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/17/2023]
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269
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Abstract
The purpose of this study is to determine--explore and describe--the quality of nursing service management in South African hospitals. A combined qualitative and quantitative pre- and post-test research strategy, in accordance with the COHSASA programme, was utilised. The hospitals implement the national standards during the preparatory phase, after having entered into an agreement with COHSASA. They determine their baseline status by means of an assisted self-evaluation. This is followed by an external survey phase where the hospital's compliance with the standards is evaluated. The nursing service is one of the professional services included in the accreditation programme. Their performance is compared with selected other professional services and their compliance with the core elements is also evaluated. The nursing services in South Africa are compliant with the national standards. The deficiencies are mainly within the quality improvement programmes that require further development and refinement.
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Molina A, Biemar F, Müller F, Iyengar A, Prunet P, Maclean N, Martial JA, Muller M. Cloning and expression analysis of an inducible HSP70 gene from tilapia fish. FEBS Lett 2000; 474:5-10. [PMID: 10828441 DOI: 10.1016/s0014-5793(00)01538-6] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
We isolated and characterized the tilapia (Oreochromis mossambicus) HSP70 gene, highly homologous to other HSP70 genes. A dramatic increase of tilapia HSP70 mRNA levels was observed after heat shock of whole animals in all organs tested. Reporter constructs were tested for transient expression in carp cells and in microinjected zebrafish embryos. The entire isolated regulatory region (-851/+157) was able to mediate heat shock inducible expression of the reporter gene, with no preference for a particular tissue. Our studies represent the first transcriptional analysis of a HSP70 promoter from fish, revealing a powerful tool to direct controlled, tissue-independent gene expression in fish.
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271
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Kranenbarg S, Muller M, Gielen JL, Verhagen JH. Physical constraints on body size in teleost embryos. J Theor Biol 2000; 204:113-33. [PMID: 10772852 DOI: 10.1006/jtbi.2000.1093] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
All members of the subphylum "Vertebrata" display the characteristics of the vertebrate body plan. These characteristics become apparent during the phylotypic period, in which all vertebrate embryos have a similar body shape and internal organization. Phylogenetic constraints probably limit the morphological variation during the phylotypic period. Physical laws, however, also limit growth and morphogenesis in embryos. We investigated to what extent oxygen availability-as a physical constraint-might limit morphological variation during embryonic development. This paper gives an analysis of time-dependent diffusion into spherical embryos without a circulatory system. Equilibrium appeared to settle in about 1.5 min in running water and in about 10min in stagnant water. Hence, steady-state conditions were assumed and expressions for maximum body size were obtained for spherical, cylindrical and sheet-like embryos in running water and spherical embyros in stagnant water. Predictions of the model based on literature data suggest that in running water-both for spherical, cylindrical and sheet-like embryos-diffusion alone suffices to cover the oxygen needs of a teleost embryo in its phylotypic period. The size of carp (Cyprinus carpio) and African catfish (Clarias gariepinus) embryos is very close to the predicted maximum. This suggests that in these species the development of a functional circulatory system is correlated with the onset of oxygen shortage. Oxygen availability is therefore a potentially important physical constraint on embryonic morphology, though in most species the circulatory system becomes functional well in advance of the onset of oxygen shortage and other demands than oxygen delivery (e.g. nutrient distribution, waste disposal, osmoregulation) might require the development of a circulatory system.
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Muller M, Lucchini R, Sogo JM. Replication of yeast rDNA initiates downstream of transcriptionally active genes. Mol Cell 2000; 5:767-77. [PMID: 10882113 DOI: 10.1016/s1097-2765(00)80317-2] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the yeast S. cerevisiae, ARS (autonomously replicating sequence) elements located in the intergenic spacers of the rRNA gene locus are infrequently activated as origins of replication. We analyzed the rARS activation with a combination of neutral/neutral (N/N) two-dimensional (2D) gel electrophoresis and either the intercalating drug psoralen, which in vivo specifically marks the transcribing gene copies, or the selective accessibility of restriction sites in transcriptionally active genes. We found that initiation of replication starts at those rARSs placed immediately downstream of transcribing rRNA genes. This correlation between transcription and replication is consistent with the presence of nucleosome-free enhancers at each transcriptionally active gene copy and suggests that the transcription factor Abf1p is involved in replication initiation at the ARS in the rDNA gene locus.
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Abstract
BACKGROUND The management of splenic injury resulting from blunt trauma in adults is controversial, with an increasing trend towards non-operative management and conservation of the spleen. A retrospective review was performed on adult patients treated in a single institution for splenic injury resulting from blunt trauma in an attempt to identify factors important in selecting an appropriate management option and predicting the success of that option. METHODS Associated injuries (standardized using Injury Severity Scores), clinical signs at presentation, computed tomographic grading of splenic injury, and transfusion requirements were documented. Statistical analysis was performed using non-parametric Mann-Whitney, Chi-squared, Kolmogorov-Smirnov and multivariate logistic regression tests. RESULTS Eighty-five patients were identified. Non-operative management was used on 39 patients, splenic conservation on 14 patients, and splenectomy on 32 patients. The mean Injury Severity Score was significantly lower in the non-operative group. Computed tomographic grading of the splenic injury was not found to correlate well with intraoperative findings. Transfusion requirements were lower in the non-operative group. Non-operative management failed in four patients; two had continued splenic bleeding, and two required surgery for other intra-abdominal injuries. Overall mortality was 7%. There was one death in the splenic conservation group, unrelated to the splenic injury, and two patients required a second laparotomy and splenectomy for persistent splenic bleeding. There were five deaths in the splenectomy group, only one of which was related to the splenic surgery. CONCLUSION Management of blunt splenic injury remains controversial. The decision to pursue non-operative management rather than splenic conservation or splenectomy depends on the individual merits of each case. There is an increasing trend towards splenic conservation, particularly in younger, stable patients with single organ injury.
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Muller M, Wittmer JP, Cates ME. Topological effects in ring polymers. II. Influence Of persistence length. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 2000; 61:4078-89. [PMID: 11088200 DOI: 10.1103/physreve.61.4078] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/1999] [Indexed: 11/07/2022]
Abstract
The interplay of topological constraints and the persistence length of ring polymers in their own melt is investigated by means of dynamical Monte Carlo simulations of a three-dimensional lattice model. We ask if the results are consistent with an asymptotically regime where the rings behave like (compact) lattice animals in a self-consistent network of topological constraints imposed by neighboring rings. Tuning the persistence length provides an efficient route to increase the ring overlap required for this mean-field picture to hold: The effective Flory exponent for the ring size decreases down to nu less, similar1/3 with increasing persistence length. Evidence is provided for the emergence of one additional characteristic length scale d(t) approximately N0, only weakly dependent on the persistence length and much larger than the excluded volume screening length xi. At distances larger than d(t) the conformational properties of the rings are governed by the topological interactions; at smaller distances rings and their linear chain counterparts become similar. (At distances smaller than xi both architectures are identical.) However, the crossover between both limits is intricate and broad, as a detailed discussion of the local fractal dimension (e.g., obtained from the static structure factor) reveals. This is due to various crossover effects which we are unable to separate even for the largest ring size (N=1024) presented here. The increased topological interactions also influence the dynamical properties. Mean-square displacements and their distributions depend crucially on the ring overlap, and show evidence of the existence of additional size and time scales. The diffusion constant of the rings goes down from effectively D(N) approximately N-1.22 for flexible rings with low overlap to D(N) approximately N-1.68 for strongly overlapping semiflexible rings.
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