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Biomedical subjects

M Allen

Publications and source records attributed to M Allen.

At least 163 records · Page 9Linked to original sources
PubMed1993

Four-state MVR-PCR: increased discrimination of digital DNA typing by simultaneous analysis of two polymorphic sites within minisatellite variant repeats at D1S8.

Minisatellite variant repeat mapping by PCR (MVR-PCR) provides a digital approach to DNA typing that can reveal huge levels of variation at minisatellite loci. MVR-PCR has so far been applied to three human minisatellites, including the hypervariable locus D1S8. Previous analysis at D1S8 was based on the discrimination of repeat unit types that differ by a single base substitution. We now show that a second polymorphic site within D1S8 repeats may be assayed simultaneously with the first to define four classes of repeat units ('four-state MVR-PCR'). This approach can also be applied to the other end of D1S8 alleles in 'reverse four-state MVR-PCR'. Both of these procedures substantially increase the informativeness of MVR analysis at D1S8 and should prove useful in studies of minisatellite biology and potentially in forensic DNA typing.

Alleles↗
PubMed1993

Multicentre survey of the comparative in-vitro activity of piperacillin/tazobactam against bacteria from hospitalized patients in the British Isles.

Twenty-nine British and Irish hospitals each collected up to 300 bacterial isolates from in-patients. The organisms were identified by an appropriate API system or, for staphylococci, by their Gram and coagulase reactions. Disc susceptibility tests were performed. Isolates that gave zones < or = 25 mm to piperacillin/tazobactam (75 micrograms + 10 micrograms) discs were sent to a central laboratory for re-examination and determination of MIC, together with a sample of the more susceptible organisms. Results were evaluated for 6724 isolates. Over 95% of the isolates of Escherichia coli, klebsiellae, Proteus mirabilis, Pseudomonas aeruginosa, Haemophilus, Moraxella and Bacteriodes, spp. streptococci, pneumococci and Enterococcus faecalis were susceptible to piperacillin/tazobactam (defined as giving a zone > or = 22 mm to a 75 micrograms + 10 micrograms disc), as were 86% of Acinetobacter spp. and 82% of the Citrobacter, Enterobacter, Morganella and Serratia group. Tazobactam particularly extended the activity of piperacillin against E. coli isolates (96% susceptible cf. 61% to piperacillin alone) klebsiellae (95% cf. 70%), P. mirabilis (99% cf. 86%), and Acinetobacter spp. (86% cf. 53%). Occasional (18%) resistance in Enterobacter, Serratia and Citrobacger spp. was probably caused by stable depression of Class I beta-lactamases, which are inhibited poorly by tazobactam. High resistance frequencies (> 25%) were found for Enterococcus faecium and Xanthomonas maltophilia. Tazobactam potentiated piperacillin against beta-lactamase-producing methicillin-susceptible Staphylococcus aureus, but the mode inhibition zone of piperacillin/tazobactam discs was only 26 mm, compared to 38 mm for beta-lactamase-negative isolates. Nevertheless, fewer than 5% of the enzyme producers appeared resistant to 8 + 4 mg/L piperacillin/tazobactam in MIC tests. Similar behaviour was noted for coagulase-negative staphylococci. Amongst the eleven comparator drugs, ceftazidime, gentamicin and ciprofloxacin were as active as piperacillin/tazobactam against most enterobacteria. However, Acinetobacter and Bacteroides spp. and enterococci were resistant to ceftazidime, and Bacteroides spp., enterococci, pneumococci and other streptococci were inherently resistant to ciprofloxacin and gentamicin. Cefuroxime, ampicillin and co-amoxiclav had narrower spectra. Only imipenem showed a consistently wider spectrum and lower frequency of resistance than piperacillin/tazobactam.

Bacteria, Anaerobic↗
PubMed1993

Wellness: the dialectic of illness.

From a review of empirical and theoretical work, a model of wellness-illness evolved. The unfolding of events associated with wellness-illness is depicted as a generic paradigm with health, disease, wellness and illness existing in a dialectical relationship. Although distinct, health-disease and wellness-illness are neither mutually exclusive nor polar opposites. Rather, they are one in the same process, acknowledging the changing person in the changing world. Wellness-illness is the human experience of actual or perceived function-dysfunction through the interaction of cognitive-affective dimensions. This experience arises out of intrapersonal, interpersonal, health-disease-related and extra-personal factors.

Disease↗
PubMed1993

Evaluation of whiplash injuries by technetium 99m isotope scanning.

Despite the frequency with which whiplash injuries present to accident and emergency (A&E) departments, there lacks an objective investigation to define the severity of the initial injury or the morbidity that may ensue. Following reports on the effectiveness of isotope bone scanning for soft tissue and ligament injuries a study was undertaken of isotope scanning of whiplash injuries. The objectives of the study were to isolate the anatomic site of the injury and to quantify the severity of the injury with relation to the concentration of isotope uptake and subsequent morbidity.

Adolescent↗
PubMed1993

Use of psychopathology vignettes by patients with schizophrenia or schizoaffective disorder and by mental health professionals to judge patients' insight.

OBJECTIVE: The goal of this study was to clarify more precisely where patients with psychotic disorders and the mental health professionals who care for them disagree regarding whether the patient is ill or needs treatment. METHOD: The authors prepared brief vignettes in everyday descriptive language that provided examples of the classical positive and negative psychopathological features of schizophrenia. Fifteen men and 11 women diagnosed as having schizophrenia or schizoaffective disorder and one physician used these vignettes as a common frame of reference to rate 1) the degree to which the patients demonstrated the features described in each vignette and 2) the degree to which the features signified the presence of mental illness. RESULTS: Disagreements between the physician's and patients' ratings, indicating deficits in insight, were associated with the recognition of the presence of conceptual disorganization, avolition-apathy, and affective blunting in the patients by the physician but not the patients and with the conceptualization of hallucinatory behavior and suspiciousness as signs of mental illness by the physician but not the patients. CONCLUSIONS: The authors conclude that the failure to acknowledge conceptual disorganization, avolition-apathy, and affective blunting and the failure to view hallucinatory behavior and suspiciousness as signs of mental illness, which proved to be additive in this study, contribute to deficits in insight.

Adult↗
PubMed1993

Submucous resection: is it a simple procedure?

With the need to cut costs in the health care system, there has been a rapid increase in the number of surgical procedures performed on an outpatient basis. It is therefore important that patients have enough information to enable them to cope at home. To determine the informational needs of patients undergoing several surgical procedures and examine their postoperative course, a telephone survey was conducted. The results from one group, those undergoing a submucous resection (SMR), stood out. When compared with the 292 patients in the overall study, the 33 SMR patients complained of considerably more discomfort, tiredness, and nausea. Sixty percent of these patients were not satisfied with the information they received. Most would have liked more information about how they would feel postoperatively and how they could cope with their various concerns and problems. The teaching materials and approach to postoperative care for these patients may need to be altered.

Adult↗
PubMed1993

AccuMeter noninstrumented quantitative assay of high-density lipoprotein in whole blood.

A novel noninstrumented technology (ChemTrak AccuMeter) for the quantitative measurement of analytes in biological fluids was reported at the 1990 Oak Ridge Conference (Clin Chem 1990;36:1591-7). This instrument-free technology has been adapted for the quantitative measurement of high-density lipoprotein (HDL). An in situ lipoprotein separation method has been developed and incorporated into the test for HDL determination. The sensitivity of the assay system has been adjusted so that HDL is measured over a clinically significant range of 250 to 1000 mg/L. This compares to a range of 1000 to 4000 mg/L for the total cholesterol in the earlier reported assay. Like the AccuMeter total cholesterol test, the Accumeter HDL test system is self-contained and consolidates blood separation, lipoprotein separation, and specimen measurement into a single step. The test procedure is simple, and the results are accurate.

Blood Chemical Analysis↗
PubMed1993

A clinical study monitoring low-intensity anticoagulant therapy with a standard-sensitivity thromboplastin.

The ability of the prothrombin time to measure the anticoagulant effect of warfarin sodium varies depending on the particular tissue thromboplastin used in performing the test. Based on studies using sensitive thromboplastins, lower therapeutic ranges of anticoagulation are recommended. The adequacy of monitoring therapy in this lower range with the relatively insensitive thromboplastins commonly used in North America is unestablished. This 16-month prospective study used a standard North American thromboplastin to monitor 157 anticoagulated patients treated in a low therapeutic range. Of the 1734 prothrombin times generated, 876 (56%) were therapeutic, with 400 (23%) below and 458 (26%) above the therapeutic range. These results are comparable with those published in trials in which more sensitive thromboplastins were used in a similar therapeutic range. We conclude that standard North American thromboplastins are adequately suited to monitor therapy in this lower range.

Aged↗
PubMed1993

Genetic typing of HLA class II genes in Swedish populations: application to forensic analysis.

In an attempt to determine the value of DNA based typing of HLA class II loci to forensic analysis, allele and genotype frequencies at DQA1, DQB1, DPB1, and DRB1 were determined in samples from two Swedish populations using hybridization with sequence specific oligonucleotides to PCR amplified DNA. Significant allele frequency differences were observed at the DQB1 and DRB1 loci between the two populations, as well as between one of the Swedish and a Norwegian population. The average heterozygosity varies between 0.74 to 0.91 and the power of discrimination between 0.90 to 0.98, with the highest values obtained for the DRB1 locus. The probability of genotype identity by chance differs on average 2% between the populations. When applied to a paternity case with one parent deceased and a criminal case, typing of class II loci proved in both cases informative. Analyses of DR and DQ genes does not increase the power of discrimination, due to strong linkage, but offers through the reconstruction of putative haplotypes an internal control for the consistency of the typing results at several loci. Typing of the DRB1 and DPB1 loci was found to result in an approximate combined average probability of genotype identity by chance of one in a thousand.

Alleles↗
PubMed1992

Solar control of the upper atmosphere of Triton.

If the upper atmosphere and ionosphere of Triton are controlled by precipitation of electrons from Neptune's magnetosphere as previously proposed, Triton could have the only ionosphere in the solar system not controlled by solar radiation. However, a new model of Triton's atmosphere, in which only solar radiation is present, predicts a large column of carbon atoms. With an assumed, but reasonable, rate of charge transfer between N2(+) and C, a peak C+ abundance results that is close to the peak electron densities measured by Voyager in Triton's ionosphere. These results suggest that Triton's upper atmospheric chemistry may thus be solar-controlled. Measurement of key reaction rate constants, currently unknown or highly uncertain at Triton's low temperatures, would help to clarify the chemical and physical processes occurring in Triton's atmosphere.

Atmosphere↗
PubMed1992

Enhancement of atmospheric radiation by an aerosol layer.

The presence of a stratospheric haze layer may produce increases in both the actinic flux and the irradiance below this layer. Such haze layers result from the injection of aerosol-forming material into the stratosphere by volcanic eruptions. Simple heuristic arguments show that the increase in flux below the haze layer, relative to a clear sky case, is a consequence of "photon trapping." We explore the magnitude of these flux perturbations, as a function of aerosol properties and illumination conditions, with a new radiative transfer model that can accurately compute fluxes in an inhomogenous atmosphere with nonconservative scatterers having arbitrary phase function. One calculated consequence of the El Chichon volcanic eruption is an increase in the midday surface actinic flux at 20 degrees N latitude, summer, by as much as 45% at 2900 angstroms. This increase in flux in the UV-B wavelength range was caused entirely by aerosol scattering, without any reduction in the overhead ozone column.

Atmosphere↗
PubMed1992

Validity of postnatal assessments of gestational age: a comparison of the method of Ballard et al. and early ultrasonography.

This study investigates the accuracy of the postnatal gestational age assessment method of Ballard et al. to predict very preterm, preterm, term, postterm, and small-for-gestational-age infants, with gestational age by early ultrasonography used as the gold standard. Sensitivity, specificity, and predictive value were examined for each gestational age category, with 4193 single live births occurring during the period from 1982 through 1989 with an ultrasonographic examination done by 20 weeks' gestation and a postnatal assessment at 28 to 44 weeks. These data indicate that the postnatal assessment overestimated the gestational age of preterm births, resulting in an underestimation of very preterm and preterm percentages. Nearly three fourths of the postterm births by ultrasonography were misclassified by the method of Ballard et al. because of underestimation of postterm gestational ages. These data indicate that, for research purposes, appreciable misclassification of preterm, postterm, and small-for-gestational-age infants will occur if gestational age is determined by the technique of Ballard et al.

Evaluation Studies as Topic↗
PubMed1992

The relative abundance of ethane to acetylene in the Jovian stratosphere.

The observed ratio of C2H6 to C2H2 in the Jovian stratosphere increases from approximately 55 at 2 mbar to approximately 277 at 12 mbar. In current photochemical models this ratio typically increases between 2 and 12 mbar by a factor of < or = 3. Recent laboratory kinetics studies on the reaction between C2H3 and H2 to form C2H4 suggest an efficient chemical mechanism for hydrogenation of C2H2 to C2H6. Inclusion of this scheme as part of a comprehensive updated model for hydrocarbon photochemistry in the atmosphere of Jupiter provides an explanation of the altitude variation of the C2H6/C2H2 ratio. The sensitivity of these results to uncertainties in the key rate constants at low temperatures is illustrated, identifying needs for additional laboratory measurements. Since the key reaction rate constants decrease with decreasing temperature, the hydrogenation of C2H2 as proposed predicts a qualitatively decreasing trend in the C2H6/C2H2 value with decreasing distance from the Sun. The observed variation between Jupiter and Saturn is consistent with this prediction.

Acetylene↗
PubMed1992

Hydrocarbon nucleation and aerosol formation in Neptune's atmosphere.

Photodissociation of methane at high altitude levels in Neptune's atmosphere leads to the production of complex hydrocarbon species such as acetylene (C2H2), ethane (C2H6), methylacetylene (CH3C2H), propane (C3H8), diacetylene (C4H2), and butane (C4H8). These gases diffuse to the lower stratosphere where temperatures are low enough to initiate condensation. Particle formation may not occur readily, however, as the vapor species become supersaturated. We present a theoretical analysis of particle formation mechanisms at conditions relevant to Neptune's troposphere and stratosphere and show that hydrocarbon nucleation is very inefficient under Neptunian conditions: saturation ratios much greater than unity are required for aerosol formation by either homogeneous, heterogeneous, or ion-induced nucleation. Homogeneous nucleation will not be important for any of the hydrocarbon species considered; however, both heterogeneous and ion-induced nucleation should be possible on Neptune for most of the above species. The relative effectiveness of heterogeneous and ion-induced nucleation depends on the physical and thermodynamic properties of the particular species, the abundance of the condensable species, the temperature at which the vapor becomes supersaturated, and the number and type of condensation nuclei or ions available. Typical saturation ratios required for observable particle formation rates on Neptune range from approximately 3 for heterogeneous nucleation of methane in the upper troposphere to greater than 1000 for heterogeneous nucleation of methylacetylene, diacetylene, and butane in the lower stratosphere. Thus, methane clouds may form slightly above, and stratospheric hazes far below, their saturation levels. When used in conjunction with the results of detailed models of atmospheric photochemistry, our nucleation models place realistic constraints on the altitude levels at which we expect hydrocarbon hazes or clouds to form on Neptune.

Atmosphere↗