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Results for “Observer Variation”

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PubMed1991

Differential distribution of excitatory amino acid receptors on embryonic rat spinal cord neurons in culture.

1. Excitatory amino acid (EAA) receptors mediate synaptic transmission in many areas of the vertebrate CNS. To map the distribution of the EAA receptors, three agonists selective for EAA receptor subtypes [kainate, quisqualate, and N-methyl-D-aspartate (NMDA)] were applied by pressure to the cell bodies and neurites of voltage-clamped, embryonic rat spinal cord neurons in culture. 2. Current loss along the neurite between the site of activation and the recording electrode at the soma was estimated independently of variations in receptor density by focal application of high [K+] solution. This estimate was used to compensate agonist-evoked responses for current loss due to leak. K(+)-evoked current amplitudes progressively decreased as applications were made at more distal positions along the neurite. 3. Response amplitudes to EAAs showed a monotonic decay, similar to that with high [K+] solution, in only a few of the cells tested with each agonist. The majority of neurons had areas of high agonist sensitivity along the neurites, implying a nonuniform density of receptors. Such regions sometimes occurred at the most proximal segment of the neurite. Most neurites had distal regions of agonist sensitivity that ranged from 40 to 300% higher than at the soma. 4. The relative distributions of the three EAA receptors were compared by applying two agonists to the same sites along neurites and observing variations in normalized response amplitudes. When comparing NMDA versus non-NMDA receptor distributions on the same neurite, approximately 40% of the cells had similar patterns to two agonists, and the remaining 60% had different patterns. When sensitivity to the two non-NMDA agonists kainate and quisqualate were compared, about one-half of the cells tested had different patterns of agonist sensitivity. 5. Areas of high sensitivity persisted after block of calcium channels by addition of La3+ to the bath solution and after prevention of evoked transmitter release by a low [Ca2+]/high [Mg2+] solution. 6. These results show that spinal cord neurons can have regions of high agonist sensitivity to NMDA, kainate, and quisqualate along their neurites and that the sensitivity to any one of the EAA receptor subtypes can be elevated independently of the others.

Animals↗

PubMed2004

Continuous measurement of oxygen consumption during cardiopulmonary bypass: description of the method and in vivo observations.

BACKGROUND: Systemic oxygen consumption is not routinely measured during cardiopulmonary bypass, despite its potential benefits. We aimed to develop a noninvasive method to continuously measure oxygen consumption using respiratory mass spectrometry during hypothermic cardiopulmonary bypass in pigs. METHODS: Nine pigs weighing 18.5 (1.6) kg underwent hypothermic (32 degrees C) cardiopulmonary bypass for 180 minutes with 120 minutes of aortic cross clamping. An AMIS 2000 mass spectrometer (Innovision A/S, Odense, Denmark) was adapted for the on-line measurement of oxygen consumption by sampling the inlet and outlet gases of the membrane oxygenator together with measurement of the "expired" gas volume. RESULTS: Active cooling for 60 minutes reduced the venous blood temperature by 2.9 (0.8) degrees C and VO(2) by 0.70 (0.33) mL/kg/min. The 40-minute active rewarming restored the venous blood temperature by 4.4 (0.4) degrees C and oxygen consumption increased by 1.36 (0.33) mL/kg/min. There was wide interanimal variability, however, particularly at higher venous blood temperatures. Immediately after the release of aortic cross clamp, there was a noticeably acute increase in oxygen consumption in all the pigs (0.64 [0.21] mL/kg/min). CONCLUSIONS: A simple and safe adaptation of mass spectrometry allows continuous measurement of oxygen consumption during hypothermic cardiopulmonary bypass. The wide interindividual variations observed in this pilot study underscore the need to more accurately describe changes in oxygen consumption and how they are affected by temperature, oxygen delivery, and other interventions during cardiopulmonary bypass. As such, the technique may have an important role in clinical research and management of oxygen transport in patients undergoing cardiac surgery.

Animals↗

PubMed1993

Effects of power and electrical current density variations in an in vitro endometrial ablation model.

OBJECTIVE: To investigate the thermal effects of electrical power and waveform on uterine tissue in vitro, using the gynecologic resectoscope with a 2.5-mm roller-bar electrode. METHODS: The power setting was increased in a serial fashion using both the modulated or damped (coagulating) and unmodulated or undamped (cutting) current to ablate endometrial uterine tissue, using a technique similar to that employed in clinical situations. The power setting ranged from 20-75 W with the modulated waveform and 40-160 W with the unmodulated waveform. Measurements of tissue damage were made by staining for hematoxylin and eosin and the respiratory enzyme dehydronicotinamide adenine dinucleotide phosphate diaphorase. RESULTS: The amount of thermal injury present correlated linearly with the amount of wattage used for either current. Regardless of the power used, the maximum amount of injury into the myometrium was 4.2 mm, representing 19% of the uterine wall thickness, well within the limits of safety. Destruction to 3 mm of myometrium was achieved significantly more often using an unmodulated waveform at greater than 90 W (chi 2, P = .03). CONCLUSIONS: Although the correlation between power and tissue damage achieved statistical significance, the relationship was weak; less than 12% of the observed variation was attributable to increasing wattage. Power and waveform alone do not appear to be clinically significant determinants of the amount of thermal injury occurring during endometrial ablation.

Burns↗

PubMed1998

Why GHQ threshold varies from one place to another.

BACKGROUND: No convincing explanation has been forthcoming for the variation in best threshold to adopt for the GHQ in different settings. METHODS: Data dealing with the GHQ and the CIDI in 15 cities from a recent WHO study was subjected to further analysis. RESULTS: The mean number of CIDI symptoms for those with single diagnoses, or those with multiple diagnoses, does not vary between cities. However, the best threshold is found to be related to the prevalence both of single and of multiple diagnoses in a centre. Variations in the diagnoses to be included in the 'gold standard' did not account for the variation observed. There was a strong relationship between area under the ROC curve (as a measure of the discriminatory power of the GHQ) and the best threshold, with higher thresholds being associated with superior performance of the GHQ. The items on the GHQ-12 that provided most discrimination between cases and non-cases varied from one centre to another. CONCLUSIONS: The GHQ threshold is partly determined by the prevalence of multiple diagnoses, with higher thresholds being associated by higher rates of both single and multiple diagnosis. The mean GHQ score for the whole population of respondents provides a rough guide to the best threshold. In those centres where the discriminatory power of the GHQ is lowest, it is necessary to use a low threshold as a way of ensuring that sensitivity is protected, but the positive predictive value of the GHQ is then lower. Some of the variation between centres is due to variation in the discriminatory power of different items.

Global Health↗

PubMed2001

99Tcm-dimercaptosuccinic acid renal scintigraphy for detection of renal cortical defects in acute pyelonephritis: posterior 180 degrees SPECT versus planar image and 360 degrees SPECT.

To evaluate the usefulness of the posterior 180 degrees acquisition technique for renal defects in acute pyelonephritis (APN), a prospective study was conducted using planar imaging, 360 degrees and posterior 180 degrees renal single photon emission computed tomography (SPECT) with 99Tcm-dimercaptosuccinic acid. Sixty subjects with the suspicion of APN were included. The kidneys were divided into three zones: each was graded as positive, equivocal or negative for renal defects. To evaluate inter-observer variation, each study was read in a double-blind fashion by two nuclear physicians. Renal defects were found in 24 patients (31 kidneys and 47 zones) with posterior 180 degrees SPECT, 23 patients (29 kidneys and 44 zones) with 360 degrees SPECT (McNemar's test, P = 0.375 for zones) and 15 patients (16 kidneys and 24 zones) with planar image (P = 0.001 for zones, vs 180 degrees and 360 degrees SPECT). The proportion of positive agreement for posterior 180 degrees and 360 degrees SPECT between readers for the presence of renal defects was 0.81 and 0.62, respectively, whereas the proportion of negative agreement was 0.92 and 0.87, respectively. Both posterior 180 degrees and 360 degrees SPECTs significantly detected more renal defects than planar imaging. The detectability of renal defects in APN by posterior 180 degrees renal SPECT was equal to 360 degrees SPECT but inter-observer agreement was better.

Adolescent↗

PubMed1992

Distinct hemagglutinin and neuraminidase epitopes involved in antigenic variation of recent human parainfluenza virus type 2 isolates.

A panel of fourteen neutralizing anti-HN monoclonal antibodies (mAbs) to the prototype Greer strain of human parainfluenza virus type 2 (PI2) was used to determine the extent of antigenic variation in recent virus isolates. Competitive binding analysis with the mAbs indicated the presence of at least five distinct antigenic sites (I to V) on the HN glycoprotein molecule. MAbs recognizing different antigenic sites were found to be associated with the hemagglutinin (sites I, IV and V), hemagglutinin and neuraminidase (site II), or neuraminidase (site III) activities. The location of two distinct epitopes identifying the neuraminidase sites (II and III) was further verified from the generation of escape mutants. Antibodies directed to sites I and III failed to show any detectable binding or neutralizing activity against a number of natural PI2 virus isolates collected in Texas between 1986 and 1987. Interestingly, these natural variants, unlike the prototype virus, did not show any detectable neuraminidase activity with fetuin as a substrate and the enzyme activity was only detected with N-acetylneuramin-lactose as an alternative substrate. Despite the observed variation in the antigenic sites, primary infection with the prototype virus or the natural variants generated a protective immune response against challenge infection with the other virus strains.

Animals↗

PubMed1999

Genetic and morphological characterization of the Aedes (Ochlerotatus) dorsalis (Diptera: Culicidae) group in North America.

An examination of the electrophoretically detectable variation among the North American members of the Aedes (Ochlerotatus) dorsalis group revealed large genetic differences among all 4 species. At least 9 of 18 loci examined (50%) were diagnostic for each species pair. However, morphological variation observed among species was low. Only Aedes canadensis (Theobald) was separated readily from the other members of this group [Aedes dorsalis (Meigen), Aedes melanimon Dyar and Aedes campestris Dyar & Knab] in all life stages. Characters traditionally used to separate the remaining 3 species were less reliable. In the adult female, Ae. melanimon may be distinguished from Ae. campestris by the scaling patterns of the wings and abdomen, but Ae. dorsalis could not be distinguished reliably by these characters. Adults of Ae. dorsalis may be separated reliably from those of Ae. campestris and Ae. melanimon only by the length of the subapical tooth relative to the length of the tarsal claw. Ae. melanimon was identified in the larval stage by the short mesothoracic hair 1. Eight larval characters differed between Ae. dorsalis and Ae. campestris. However, the ranges of these characters overlapped and no character was truly diagnostic. Genetic variation within species was low as measured by average heterozygosity and Nei's genetic distance coefficients. No allozymes were diagnostic for coastal and inland populations of Ae. dorsalis, and the pattern of genetic differentiation within this species did not correspond to the geographic location of the populations examined. Therefore, the genetic data did not support the hypothesis that Ae. dorsalis represents a complex of 2 or more cryptic species.

Abdomen↗

PubMed1994

Variation in use of breast surgery and characteristics of hospitals' surgical staff.

OBJECTIVE: To assess whether and how the characteristics of hospitals' surgical staff can predict utilization of breast conserving surgery. We anticipated that the use of the procedure was more frequent in hospitals with a greater proportion of younger and female surgeons on their staff. SETTING: Sixty-two hospitals with different level of organization for the care of cancer patient from eight Italian regions were included. DESIGN: We collected information on the personal characteristics (age and sex) of all surgeons on the staff of the participating centers. A concurrent pattern of care study was undertaken, in order to assess the utilization of breast conserving procedures. RESULTS: The use of conservative surgery was 16%, 20%, 31%, in centers with 0%, < 20% and 20-50% female surgeons respectively (p = 0.003), while no associations emerged between the mean age of the surgical staff and the use of conservative surgery. This relationship also held true after adjusting for other patients' characteristics, such as stage of disease, age and presence of comorbidity. However, overall the use of patient-related and staff-related characteristics to predict the number of breast conserving surgeries performed in each area was able to explain only 16% of the observed variability in the use of breast conserving surgery. CONCLUSIONS: Even though in this study a large proportion of the observed variation in the use of breast conserving surgery was still left unexplained, this finding suggests that assessing the relationship between doctors' characteristics and the use of scientific evidence is an important topic for health service research and can be of some help in exploring variations in clinical practice styles.

Adult↗

PubMedDate not supplied

Quantitative complete tooth variation among east Asians and Native Americans: developmental biology as a tool for the assessment of human divergence.

The quantification of total tooth structure derived from X-rays of Vietnamese, Southern Chinese, Mongolians, Western Eskimos, and Peruvian pre-Inca (Huari Empire) populations was used to examine dental divergence and the morphogenetics of change. Multivariate derived distances between the samples helped identify a quasicontinuous web of ethnic groups with two binary clusters ensconced within the web. One cluster was composed of Mongolians, Western Eskimos, and pre-Inca, and the other group consisted of the Southern Chinese and Vietnamese. Mongolians entered the quasicontinuum from a divergent angle (externally influenced) from that of the Southeast Asians. The Chinese and pre-Inca formed the polar samples of the distance superstructure. The pre-Inca sample was the most isolated, its closest neighbor being the Western Eskimos. Univariate and multivariate analyses suggested that the pre-Inca, whose ancestors arrived in America perhaps approximately 30,000 years ago, was the least derived sample. Clearly, microevolutionary change occurred among the samples, but the dental phenotype was resistant to environmental developmental perturbations. An assessment of dental divergence and developmental biology suggested that the overall dental phenotype is a complex multigenic morphological character, and that the observed variation evolved through total genomic drift. The quantified dental phenotype is greater than its highly multigenic algorithm and its development homeostasis is tightly controlled, or canalized, by the deterministic organization of a complex nonlinear epigenetic milieu. The overall dental phenotype quantified here was selectively neutral and a good character to help reconstruct the sequence of human evolution, but if the outlying homeostatic threshold was or will be exceeded in antecedents and descendants, respectively, evolutionary saltation occurs.

Analysis of Variance↗

PubMed1994

Heterogeneity in the plasma levels of two acute-phase proteins in mice from inbred strains infected with Trypanosoma cruzi.

We analyzed the variations observed in the plasma levels of both alpha-macroglobulins (AM) and serum amyloid P (SAP) in mice from three different inbred strains (C3H, Balb/C and C57black/6) acutely infected with Trypanosoma cruzi. SAP levels increased in C57black/6 and Balb/C mice but not C3H mice. AM levels increased in all C3H mice but not in C57black/6 mice and rose slightly in only 43% of the Balb/C mice. AM and SAP levels are differently modulated in patterns that may be strain-determined.

Animals↗

PubMed1997

Red blood cell abnormalities in hereditary elliptocytosis and their relevance to variable clinical expression.

Marked variations are seen in the clinical manifestations of hereditary elliptocytosis (HE). To define the cellular alteration(s) that best reflect the variable expression of the disease, we evaluated the pathobiologic features of red blood cells in a series of 18 patients with HE, 15 persons from six families with HE as a result of defects in spectrin, and 3 persons from one family with HE caused by partial or total deficiency of protein 4.1. We found that decreased cellular deformability is a distinguishing feature of red blood cells in all patients studied. Comparison of volume and hemoglobin content histograms of red blood cells and reticulocytes revealed that cell fragmentation is a feature of mature red blood cells. The extent of red blood cell fragmentation as reflected by increased percentage of microcytic red blood cells was the best indicator of the severity of hemolytic anemia. Furthermore, we found that the observed variations in cellular properties of HE red blood cells in different persons is the consequence of varying amounts of mutant protein assembled into the membrane. These findings enabled us to define the mechanistic basis for cellular changes in this red blood cell membrane disorder better and also to obtain insight into the cellular basis for variable clinical expression.

Elliptocytosis, Hereditary↗

PubMed1994

Variation in foliar delta(13)C values within the crowns of Pinus radiata trees.

Although herbaceous species generally show little within plant variation in delta(13)C, trees show large spatial and temporal differences. We found that the aspect of exposure and branch length accounted for up to 6 per thousand delta(13)C difference within the foliage of individual trees of Pinus radiata D. Don. The foliage on branches 0.5 m in length was as much as 4 per thousand more depleted in (13)C than foliage on 10-m long branches, and an additional 2 per thousand more depleted on the shaded side than on the exposed side. We confirmed that on clear days, relative branch hydraulic conductivity, defined as the ratio of transpiration to the water potential gradient, was much higher in short branches than in long branches. Stomatal conductance remained high in foliage on short branches during the day, whereas it declined progressively in long-branch foliage under similar conditions. These differences were sufficient to explain the observed variation in delta(13)C in foliage on long and short branches.

Journal Article↗

PubMed1992

Modulation of transcription factor activity by a distant steroid modulatory element.

Variations in the biological activity of antisteroids, as determined by their percent agonist activity, is a well known but poorly understood phenomenon. For example, in tyrosine aminotransferase (TAT) induction by the antiglucocorticoid dexamethasone 21-mesylate in rat hepatoma tissue culture cells, the percent agonist activity varies with the density of cultured cells. A 21-basepair sequence of the rat TAT gene has now been isolated which confers all of the induction properties of the endogenous TAT gene to homologous and heterologous promoters and genes. We call this 21-basepair sequence, which acts in concert with a trans-acting factor identified by gel shift experiments, a glucocorticoid modulatory element. The changes in induction properties were found to be independent of the fold induction by dexamethasone, thus arguing that the GME does not synergize with the glucocorticoid response element. A model incorporating this new element is advanced which can explain the observed variations of TAT induction and may be generally applicable for the mechanism of action of other steroid hormones.

Base Sequence↗

PubMed1976

Early formation of synapses in the molecular layer of the fetal rat cerebellum.

The initial phase of synaptogenesis in the molecular layer of the albino rat cerebellum has been studied quantitatively and qualitatively with the electron microscope. Using both aldehyde-osmium (AL-OS) and ethanolic phosphotungstic acid (E-PTA) preparations, synapses were observed as early as embryonic day 19 throughout the entire rostro-caudal extent of the vermal molecular layer. The undeveloped nature of the elements participating in the formation of these synapses precluded their identification, for at this stage of cerebellar development, the Purkinje cells have not developed characteristic dendrites and both the massive production of cells within the external granule layer and the migration of neuroblasts through the molecular layer are in their initial phases. Evidence of synapse formation at this early stage of molecular layer development indicates that the rudiments of neuronal systems are present before the bulk of the molecular layer has come into existence and before most of the constituent elements of the cerebellum have differentiated. From embryonic day 19 to embryonic day 22, the number of E-PTA synaptic contacts was always less than the number of AL-OS synapses. This decrepancy and the variations observed in the morphology of the presynaptic components of E-PTA stained synaptic contacts, indicate that E-PTA morphology, and particularly the development of presynaptic dense projections, represents a late stage of synapse formation.

Animals↗

PubMedDate not supplied

Purification, biochemical characterisation and partial primary structure of a new alpha-amylase inhibitor from Secale cereale (rye).

Plant alpha-amylase inhibitors show great potential as tools to engineer resistance of crop plants against pests. Their possible use is, however, complicated by the observed variations in specificity of enzyme inhibition, even within closely related families of inhibitors. Better understanding of this specificity depends on modelling studies based on ample structural and biochemical information. A new member of the alpha-amylase inhibitor family of cereal endosperm has been purified from rye using two ionic exchange chromatography steps. It has been characterised by mass spectrometry, inhibition assays and N-terminal protein sequencing. The results show that the inhibitor has a monomer molecular mass of 13,756 Da, is capable of dimerisation and is probably glycosylated. The inhibitor has high homology with the bifunctional alpha-amylase/trypsin inhibitors from barley and wheat, but much poorer homology with other known inhibitors from rye. Despite the homology with bifunctional inhibitors, this inhibitor does not show activity against mammalian or insect trypsin, although activity against porcine pancreatic, human salivary, Acanthoscelides obtectus and Zabrotes subfasciatus alpha-amylases was observed. The inhibitor is more effective against insect alpha-amylases than against mammalian enzymes. It is concluded that rye contains a homologue of the bifunctional alpha-amylase/trypsin inhibitor family without activity against trypsins. The necessity of exercising caution in assigning function based on sequence comparison is emphasised.

Animals↗

PubMed1994

Mitochondrial DNA "clock" for the Amerinds and its implications for timing their entry into North America.

Students of the time of entry of the ancestors of the Amerinds into the New World are divided into two camps, one favoring an "early" entry [more than approximately 30,000 years before the present (YBP)], the other favoring a "late" entry (less than approximately 13,000 YBP). An "intermediate" date is unlikely for geological reasons. The correlation of the appropriate data on mtDNA variation in Amerinds with linguistic, archaeological, and genetic data offers the possibility of establishing a time frame for mtDNA evolution in Amerinds. In this paper, we estimate that the separation of the Chibcha-speaking tribes of Central America from other linguistic groups/nascent tribes began approximately 8000-10,000 YBP. Characterization of the mtDNA of 110 Chibcha speakers with 14 restriction enzymes leads on the basis of their time depth to an estimated mtDNA nucleotide substitution rate for Amerinds of 0.022-0.029% per 10,000 years. As a first application of this rate, we consider the mtDNA variation observed in 18 Amerind tribes widely dispersed throughout the Americas and studied by ourselves with the same techniques, and we estimate that if the Amerinds entered the New World as a single group, that entry occurred approximately 22,000-29,000 YBP. This estimate carries a large but indeterminate error. The mtDNA data are thus at present equivocal with respect to the most likely times of entry of the Amerind into the New World mentioned above but favor the "early" entry hypothesis.

Anthropology↗

PubMed1989

Primary structure of prion protein may modify scrapie isolate properties.

Scrapie is an infectious neurodegenerative disease caused by unusual pathogens called prions, in which no scrapie-specific nucleic acid has been detected to date. The only known component of the prion is the scrapie isoform of prion protein (PrPSc), which is encoded by a host gene (Prn-p). Isolates of scrapie agent were prepared by passage of infectivity through inbred strains of mice that differ in scrapie incubation time and produce PrPSc molecules differing by two amino acids. Both the length and variability of the incubation period were increased by inocula containing allogeneic PrPSc. For example, Prn-pb I/Ln mice inoculated with scrapie isolate passaged through Prn-pa NZW mice had incubation times of 283 +/- 21 days compared with a 193 +/- 6 day incubation time seen with isolate passaged once through isologous I/Ln mice. No further shortening of incubation time was observed following further isologous passage. NZW incubation times were prolonged by inoculation with prions from I/Ln mice. Results from (NZW x I/Ln)F2 mice and from using inocula from donors isologous for Prn-p but otherwise allogeneic with respect to the recipient suggest that the primary structure of PrPSc is responsible for these incubation time results. Incubation times in (NZW x I/Ln)F1 mice were constant regardless of the passage histories of the scrapie isolates and were equivalent to those of I/Ln mice inoculated with I/Ln prions, contending that prolongation of scrapie incubation time by the prion incubation time gene Prn-i is fully dominant. I/Ln incubation times longer than those in F1 hybrids may reflect a reduced efficiency of allogeneic PrPSc in initiating disease. Although some investigators propose that differences in behavior among scrapie isolates reflect host selection and argue for a nucleic acid genome, we suggest that the variation observed among our scrapie isolates is epigenetic, reflecting host-directed differences in the amino acid sequence of PrPSc.

Animals↗

PubMed1987

Distribution of type 1 and P pili on uropathogenic Escherichia coli O6.

The distribution of type 1 and P pili on individual cells of an O6 uropathogenic Escherichia coli strain, 6260, was determined immunologically with pilus-specific monoclonal antibodies by indirect immunofluorescence and immunogold electron microscopy. Variations in pilus expression under different culture conditions were monitored with an indirect immunofluorescence assay; 63% of piliated cells expressed type 1 pili when grown on agar at 37 degrees C versus 14 to 38% when grown in broth at 37 degrees C. In contrast, generally fewer cells with P pili (18 to 44%) were detected on agar than when grown in broth (up to 86%). Both type 1 and P pili were absent from cells cultured at 20 degrees C. Immunogold and immunofluorescence double labeling techniques with monoclonal antibodies 11-2 and 91-1 were used to study subpopulations of cells with type 1 and P pili; 39 to 41% of the piliated cells demonstrated only type 1 pili, and 12 to 16% of the cells showed only P pili. The immunogold method proved more sensitive than the immunofluorescence technique for detecting subpopulations expressing both pili types simultaneously, 19 versus 7%. We observed variations between type 1 and P pili, both in expression on individual cells and in the distribution of subpopulations of cells.

Adult↗