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At least 109 records · Page 6Linked to original sources

PubMed2002

Optimizing fluid therapy in mechanically ventilated patients after cardiac surgery by on-line monitoring of left ventricular stroke volume variations. Comparison with aortic systolic pressure variations.

BACKGROUND: Mechanical ventilation causes changes in left ventricular preload leading to distinct variations in left ventricular stroke volume and systolic arterial pressure. Retrospective off-line quantification of systolic arterial pressure variations (SPV) has been validated as a sensitive method of predicting left ventricular response to volume administration. We report the real-time measurement of left ventricular stroke volume variations (SVV) by continuous arterial pulse contour analysis and compare it with off-line measurements of SPV in patients after cardiac surgery. METHODS: SVV and SPV were determined before and after volume loading with colloids in 20 mechanically ventilated patients. RESULTS: SVV and SPV decreased significantly after volume loading and were correlated (r=0.89; P<0.001). Changes in SVV and changes in SPV as a result of volume loading were also significantly correlated (r=0.85; P<0.005). Changes in SVV correlated significantly with changes in stroke volume index (SVI) (r=0.67; P<0.005) as did changes in SPV (r=0.56; P<0.05). SVV determined before volume loading correlated significantly with changes in SVI (R=0.67; P <0.005). Using receiver operating characteristics curves, the area under the curve was statistically greater for SVV (0.824; 95% confidence interval: [CI] 0.64-1.0) and SPV (0.81; CI: 0.62-1.0) than for central venous pressure (0.451; CI: 0.17-0.74). CONCLUSIONS: Monitoring of SVV enables real-time prediction and monitoring of the left ventricular response to preload enhancement in patients after cardiac surgery and is helpful for guiding volume therapy.

Aorta, Abdominal↗

PubMed1991

A comprehensive study of genic variation in natural populations of Drosophila melanogaster. IV. Mitochondrial DNA variation and the role of history vs. selection in the genetic structure of geographic populations.

Preliminary studies with restriction fragment length polymorphisms of mitochondrial DNA (mtDNA) in natural populations of Drosophila melanogaster revealed considerable variation in terms of nucleotide sequence and overall size. In this report we present data from more isofemale lines and more restriction enzymes, and explore the utility of the data in inferring a colonization history of this species. Size variation in the noncoding A + T-rich region is particularly plentiful, with size variants occurring in all restriction site haplotypes in all populations. We report here classes of small-scale mobility polymorphisms (apparent range of 20 bp) in specific restriction fragments in the coding region. The variation in one such fragment appears to be generated even more rapidly than in the noncoding region. On the basis of the distribution of restriction site haplotypes, the species range can be divided into three major regions along longitudinal lines: Euro-African populations are the most diverse and are taken to be oldest; Far East populations have a complex distribution of haplotypes; Western Hemisphere populations are the least diverse and are interpreted to be the youngest. The history inferred from mtDNA alone is remarkably similar to one based on several nuclear markers. The mtDNA haplotype distribution is also very different from that of allozymes in these same populations. We interpret this as further evidence that natural selection is still the most parsimonious explanation for the parallel latitudinal allozyme clines in this species.

Animals↗

PubMed1998

Explaining variation in birth outcomes of Medicaid-eligible women with variation in the adequacy of prenatal support services.

OBJECTIVES: This study examines the contribution of the adequacy of nutrition, psychosocial, and health education support service delivery in explaining variation in birth outcomes among Medicaid-eligible women, their provider sites, and practice settings. METHODS: Logistic regression models for low birthweight and preterm birth outcomes are first fitted with medical record data on maternal risks and use of prenatal visits for more than 3,485 women receiving care at 27 ambulatory sites, correcting for clustering of women within sites. RESULTS: The change in variation explained by these models with the addition of the adequacy of support services indicates that providing at least one nutrition, psychosocial, and health education service session each trimester of care contributes significantly to explaining better birth outcomes when compared with providing fewer sessions. When the expected outcome rates calculated with the estimated effects in the models are compared with their observed rates across provider sites and setting types, however, adequacy of service delivery does not help to explain differences in outcomes at individual sites or types of settings. CONCLUSIONS: Although repeated support service sessions during prenatal care improve the chances of avoiding poor birth outcomes in low income women, further adjustments for other differences between women or service delivery are needed to explain variation in outcomes at different sites and practice settings.

Adult↗

PubMed1997

Effect of sampling procedure and strain variation in Listeria monocytogenes on the discrimination of species in the genus Listeria by Fourier transform infrared spectroscopy and canonical variates analysis.

The ability to discriminate successfully among cultures of all species of the Listeria genus by infrared spectroscopy in combination with canonical variate analysis was confirmed. The robustness of the method was demonstrated by showing that the separation of L. monocytogenes and L. grayi was hardly affected by variations in broth medium, incubation temperature, incubation time and cell washing procedure. Discrimination among 24 strains of L. monocytogenes according to serotype allowed two groups to be recognised, one comprising serotypes 4 and 4b and the other containing serotypes 1, 1/2b and 1/2c. When strain variation was included in the species discrimination model, the classification of all the L. monocytogenes strains was virtually 100% correct.

Culture Media↗

PubMed1996

Relationship between phase variation in colony morphology, intrastrain variation in cell wall physiology, and nasopharyngeal colonization by Streptococcus pneumoniae.

Streptococcus pneumoniae undergoes phase variation in colony morphology, which has been implicated as a factor in the pathogenesis of pneumococcal disease. Phenotypic differences between opaque and transparent colony forms correlate with differences in rates of autolysis. This study examined whether differences in autolysis are caused by differences in expression of the major amidase, LytA, or the structure of its peptidoglycan substrate. No significant difference was detected by high-pressure liquid chromatography analysis of stem peptides released after treatment of purified peptidoglycan with amidase. Differences in the rate of digestion of purified cell walls, furthermore, did not correlate with susceptibility to autolysis. Lower levels of autolysis in opaque variants, however, was associated with decreased levels of immunodetectable LytA on colony immunoblots and Western blots (immunoblots). Diminished cell-surface-associated LytA in opaque variants was also demonstrated by whole-cell inhibition enzyme-linked immunosorbent assay. Since transparent variants have been shown both to colonize the nasopharynx more efficiently in an animal model and to express more surface-exposed LytA, it was determined whether LytA contributes to colonization in a neonatal rat model of pneumococcal carriage. Defined mutants in the lytA gene were used to show that there was no significant contribution by LytA to nasopharyngeal colonization in this model. Although the expression of LytA was shown to undergo phase variation in association with colony morphology, lytA mutants are still capable of phenotypic variation in colony morphology, which suggests that other factors are responsible for intrastrain differences which affect colonization.

Animals↗

PubMed1997

Angiotensinogen gene variation associated with variation in blood pressure in aboriginal Canadians.

We measured blood pressure and related clinical phenotypes in 497 adult native Canadians from an isolated community in Northern Ontario. We analyzed their DNA for genotypes of angiotensinogen. We found that the frequency of the T235 variant of the angiotensinogen gene was 0.89 in this sample. This variant was associated with a significantly increased systolic pressure but not diastolic pressure. We also found that sex and body mass were each highly significantly associated with variation in both systolic and diastolic pressures. We found a significant association between age and variation in systolic pressure but not diastolic pressure. We also found a highly significant association between plasma apolipoprotein B concentration and variation in diastolic pressure but not systolic pressure. The high frequency of the angiotensinogen T235 variant suggests that subjects in this young, essentially normotensive population might be predisposed to hypertension, which may become more apparent in the presence of secondary factors.

Adult↗

PubMed2006

Variation in prescribing for anxiety and depression: a reflection of health inequalities, cultural differences or variations in access to care?

BACKGROUND: There are large variations in mental health prescribing in UK populations. However the underlying reasons for these differences, which may be related to differences in prevalence, cultural expectations or practical difficulties in access to treatment, remain uncertain. METHODS: Linear modelling was used to investigate whether population characteristics or access to primary care account for variations in mental health prescribing across 39 deprived neighbourhoods. RESULTS: The proportion of sampled respondents whose first language was not English and the ratio of general practitioners to population explained 61% of variation. Deprivation and mental health status were not significant predictors of prescribing in these relatively deprived communities. CONCLUSION: These findings suggest that mental health prescribing, within deprived areas, as well as reflecting cultural and social differences in prescribing, may also be a proxy measure of access to care.

Journal Article↗

PubMed1989

[Baseline study of sleep electroencephalography--daily variation and individual variation].

The aims of the present study were to observe the daily habituation to night sleep in a laboratory environment and to make clear the daily and individual sleep variations by using polygraph parameters, including electroencephalography (EEG). Sleep EEG records were obtained from a subject who slept ten successive nights, and from six subjects who each slept one night in the laboratory. The parameters used were as follows: sleep stage %, sleep latency (SL), REM latency (RL), number of stage shifts, subjective sleep, integral EMG, and slope (a) and intersect (b) of a regression equation used to estimate the sleep depth against sleep time. Stage WAKE and SL, slope (a), intersect (b) and the mean depth of sleep were found to become stable from the fifth night. Stage MT, the number of stage shifts, and integral EMG increased significantly from the fifth night and later, showing p less than 0.01, p less than 0.01, and p less than 0.05, respectively. Judging from these findings, the sleep habituation of the subject in the laboratory was completed within the first four nights. Coefficients of variation of sleep stage 2 and stage REM of the ten-nights' EEG were the lowest among all the sleep parameters examined. Almost all the parameters of day-to-day sleep of the subject who slept for ten successive nights in the laboratory showed smaller variations than those of the other six subjects. It may be concluded that the mist effect on sleep could be assessed more precisely by using an individual repeatedly than by using a group of subjects.

Adult↗

PubMed1996

Variation in risk indicators of cardiovascular disease during the menstrual cycle: an investigation of within-subject variations in glutathione peroxidase, haemostatic variables, lipids and lipoproteins in healthy young women.

Variations in erythrocyte glutathione peroxidase activity, serum concentrations of lipids and lipoproteins and in blood coagulation and fibrinolysis during the menstrual cycle were studied in healthy young women. Blood samples were drawn twice a week for 9 weeks. A group of males was used for estimation of the influence on the results of factors which were not related to the menstrual cycle. Variations during the menstrual cycle were demonstrated in several of the factors analysed. The activity of glutathione peroxidase was lowest at ovulation. The clotting activity of factor II+ VII+X and the concentration of fibrinogen were lowest during mid-cycle, and the number of platelets increased in the follicular phase (days 5-9). Statistically significant variations in the fibrinolytic factors analysed (tissue plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) were not observed during the menstrual cycle. The serum concentrations of cholesterol and LDL cholesterol were significantly higher at the start of the menstrual cycle (days 3-8) than later in the cycle (days 19-24). The concentration of HDL cholesterol was lowest in the late luteal phase (days 23-28).

Adult↗

PubMed2006

Numerical variation of the celiac trunk and anatomical variation in origin and course of the dorsal pancreatic artery.

A numerical anomaly of the celiac trunk and anatomical variation in origin, and course of the dorsal pancreatic artery were encountered during a routine upper abdomen dissection of a 62-year-old male cadaver. The aim of this study was to describe a rare celiac trunk and dorsal pancreatic artery variation in detail, which can be a guide and precaution during operative procedures in this region. The abdominal aorta, its branches and the pancreas were cut and removed just above the celiac trunk and below the superior mesenteric artery to investigate the vascular distribution of the pancreas in detail. The celiac trunk divided into the left gastric, hepatic, splenic, and dorsal pancreatic arteries. The anatomical variation of the celiac trunk and splenic artery makes it vulnerable to iatrogenic surgery. Knowledge of the existing aberrations is important in planning and conducting surgical procedures.

Cadaver↗

PubMed1982

[Weight variations of adipose tissue and ovaries and variations in the length of ovocytes in Ips sexdentatus Boern (Coleoptera: Scolytidae); relation to parasitism by nematodes].

The variations of the weight of the fat body and the ovaries, as well as the length of the maturest oocyte, have been studied in Ips sexdentatus, from the end of the maturation of pre-swarming to the 24th hour after the copulation. In the healthy Insects, the weight of the ovaries and the size of the terminal oocyte grow till the swarming, but decline slightly at the 3rd hour after the copulation; the growth recovers afterwards, at first slow, then very steep after the 12th hour. The fat body declines at the swarming, but grows distinctly at the 6th hour; its weight decreases strongly at the 12th and 18th hour, then grows again considerably at the 24th hour. The variations of the weight of the ovaries (and of the size of the terminal oocyte) may be compared with that of the fat body, if we take into consideration the being of a delay in the "response" of the ovaries. This combined variations might be agreed with important periods of the biology of the bark-beetle: swarming, slow then steep maturation of the ovaries, oviposition. In the Insects parasitized by the Nematodes Parasitaphelenchus sp., P. sexdentati (Fuchs 1937) Rühm 1956, Contortylenchus diplogaster (V. Lins 1890) Rühm 1956, the fat body and the ovaries are always slighter, and the terminal oocyte less developed than in the healthy Insects. Moreover, the fat body of the infected Insects cannot accumulate the indispensable stocks for the maturation of the oocytes, just as these one seem to want that. Therefore the maturation of the oocytes of this Insects is delayed. This delay, by accumulating itself for the successive oocytes, might explain the important reduction of the oviposition in the parasitized Insects. The effect of the Nematodes on the ovaries of Ips sexdentatus might be indirect, the direct effect being related to the fat body or to the blood. On the otherside, the abdominal fat body seems to be more affected by the parasitism than the prothoracic one.

Adipose Tissue↗

PubMed1995

[The variation of the vestibular response vs. the variations of the auditory threshold after administration of glycerol in patients with Meniere's disease].

Vestibular and auditory functions after glycerol intake were assessed correlated in twenty-eight patients diagnosed as menieric according to AAOO criteria. All patients had unilateral Ménière's disease confirmed by monolateral hypoacusia and labyrinthine hypofunction. Hearing thresholds were tested by tone-audiometry, according to the standard glycerol test. Variation in vestibular response were assessed comparing the VOR during the rotatory sinusoidal test as well as the caloric test, before glycerol intake and 2 hours after drug administration. Slow phase angolar velocity, directional preponderance percentile and percentile variation between basic and control observation were calculated. The audiometric glycerol test was positive in 58% of the cases. The vestibular glycerol test was positive in 30% of the cases and no correlation between and individual results hearing threshold result was found. The findings reported by other Authors regarding auditory and vestibular responses to glycerol intake were verified. Possible reasons which may account for variation with regard to reaction patterns in the acoustic and non acoustic labyrinth after glycerin administration are discussed. In the Authors' view, incoherence between vestibular and cochlear response might be linked to differences in the physiology of the fluid in the two labyrinths. In the vestibular district, glycerol might induce an early depletive effect and a later paradoxal effects due to mechanical modification of the ampulla function.

Audiometry, Pure-Tone↗

PubMed2000

The streptococcal superantigen SMEZ exhibits wide allelic variation, mosaic structure, and significant antigenic variation.

The frequencies of the newly identified streptococcal superantigen genes smez, spe-g, and spe-h were determined in a panel of 103 clinical isolates collected between 1976 and 1998 at various locations throughout New Zealand. smez and spe-g were found in every group A Streptococcus (GAS) isolate, suggesting a chromosomal location. The spe-h gene was found in only 24% of the GAS isolates and is probably located on a mobile DNA element. The smez gene displays extensive allelic variation and appears to be in linkage equilibrium with the M/emm type. 22 novel smez alleles were identified from 21 different M/emm types in addition to the already reported alleles smez and smez-2 with sequence identities between 94. 5 and 99.9%. Three alleles are nonfunctional due to a single base pair deletion. The remaining 21 alleles encode distinct SMEZ variants. The mosaic structure of the smez gene suggests that this polymorphism has arisen from homologous recombination events rather than random point mutation. The recently resolved SMEZ-2 crystal structure shows that the polymorphic residues are mainly surface exposed and scattered over the entire protein. The allelic variation did not affect either Vbeta specificity or potency, but did result in significant antigenic differences. Neutralizing antibody responses of individual human sera against different SMEZ variants varied significantly. 98% of sera completely neutralized SMEZ-1, but only 85% neutralized SMEZ-2, a very potent variant that has not yet been found in any New Zealand isolate. SMEZ-specific Vbeta8 activity was found in culture supernatants of 66% of the GAS isolates, indicating a potential base for the development of a SMEZ targeting vaccine.

Alleles↗

PubMed1993

Genetic variation among the Mapuche Indians from the Patagonian region of Argentina: mitochondrial DNA sequence variation and allele frequencies of several nuclear genes.

DNA samples from 60 Mapuche Indians, representing 39 maternal lineages, were genetically characterized for (1) nucleotide sequences of the mtDNA control region; (2) presence or absence of a nine base duplication in mtDNA region V; (3) HLA loci DRB1 and DQA1; (4) variation at three nuclear genes with short tandem repeats; and (5) variation at the polymorphic marker D2S44. The genetic profile of the Mapuche population was compared to other Amerinds and to worldwide populations. Two highly polymorphic portions of the mtDNA control region, comprising 650 nucleotides, were amplified by the polymerase chain reaction (PCR) and directly sequenced. The 39 maternal lineages were defined by two or three generation families identified by the Mapuches. These 39 lineages included 19 different mtDNA sequences that could be grouped into four classes. The same classes of sequences appear in other Amerinds from North, Central, and South American populations separated by thousands of miles, suggesting that the origin of the mtDNA patterns predates the migration to the Americas. The mtDNA sequence similarity between Amerind populations suggests that the migration throughout the Americas occurred rapidly relative to the mtDNA mutation rate. HLA DRB1 alleles 1602 and 1402 were frequent among the Mapuches. These alleles also occur at high frequency among other Amerinds in North and South America, but not among Spanish, Chinese or African-American populations. The high frequency of these alleles throughout the Americas, and their specificity to the Americas, supports the hypothesis that Mapuches and other Amerind groups are closely related.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗

PubMed1978

Interindividual variation in the responses of cultured human lymphocytes to exposure from DNA damaging chemical agents: interindividual variation to carcinogen exposure.

Human population variability to standardized doses of N-acetoxy-2-acetylaminofluorene (NA-AAF) and 7, 12-dimethylbenz(a) anthracene (DMBA) was determined in cultured lymphocytes by measuring (a) differential stimulation of unscheduled DNA synthesis after 1 h induction of DNA damage by 10 micrometer NA-AAF, (b) the level of NA-AAF induced chromosome aberrations remaining after 8 h of DNA-repair synthesis, and (c) the level of [3H]DMBA bound to DNA after 18 h incubation of resting lymphocytes in 5 micrometer DMBA. All 3 parameters indicated individual variation to carcinogen exposure and were correlated to the population differences in age, sex, blood pressure and mortality rates. Males always had a greater potential to accumulate DNA-damage than did females regardless of the sampled population. DNA-damage potentials increased with increasing age, blood pressure or mortality rates. There was always proportionally greater DNA-damage potentials in the males than in females. The in vitro response of mature granulocytes to a 10 micrometer NA-AAF dose, as estimated by [3H] thymidine incorporation from unscheduled DNA synthesis, was much lower than lymphocyte response. Nevertheless, individual variations in granulocyte NA-AAF induced unscheduled DNA synthesis paralleled the inter-individual fluctuations observed in the lymphocyte responses to NA-AAF.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1985

Variation among hepatitis A virus strains. I. Genomic variation detected by T1 oligonucleotide mapping.

The genomes of eight hepatitis A virus (HAV) strains originating from far distant geographic regions such as Europe, North Africa, Middle and North America, Australia and The People's Republic of China were compared by RNase T1 oligonucleotide mapping. For this purpose, the viruses were propagated in cell cultures and viral RNA was isolated from highly purified mature virions. It could be shown that variation in nucleotide sequence is common among HAV isolates, but is in the order of magnitude reported for other picornaviruses. For viruses isolated in cell culture directly from stool samples of diseased individuals, changes usually amounted to 1-4% of RNA genome sites. Genomic differences between two virus strains derived from one fecal sample but replicating at either 32 or 37 degrees C were in the same order of magnitude. Thereby, the number of consecutive in vitro passages proved to have only limited influence on the development of genetic variation. For two HAV strains, however, adaptation to and passage in marmosets evidently had imposed highly selective conditions which had favored the appearance of viral genomes differing in up to 75% of their large oligonucleotides (about 10% in sequence) from the oligonucleotide map of a reference HAV strain.

Animals↗

PubMed1999

Slow EEG potentials (contingent negative variation and post-imperative negative variation) in schizophrenia: their association to the present state and to Parkinsonian medication effects.

Between warning signal (S1) and imperative signal (S2), the EEG shifts negatively (contingent negative variation, CNV) reflecting preparation and expectancy. Reduced CNV and continued negativity after S2 (post-imperative negative variation, PINV) have been repeatedly found in schizophrenic patients and have been interpreted as a deficit in attentional processes (CNV) and as uncertainty about the correctness of one's own response to the S2 (PINV). Recent studies obtained a CNV reduction specifically at central sites but not at frontal ones. The present study investigated whether these alterations of slow negative potentials depend on present state of symptoms, on the particular task used, and on neuroleptic medication. Therefore, out-patients and in-patients were studied, two different S1-S2 tasks were used, and the control groups were healthy subjects and patients with Parkinson's disease. The central CNV reduction was stable across tasks and across in-patients and outpatients. Frontal CNV was reduced in in-patients but in only one of the two tasks in outpatients. The schizophrenic patients' enhanced PINV was larger contralaterally than ipsilaterally to the responding hand, correlated with medication, and occurred in similar way in patients with Parkinson's disease. Thus, the PINV increase might reflect the Parkinsonian side effects of the anti-psychotic medication. In contrast, the central CNV reduction appears as a stable marker of schizophrenia, the frontal CNV reduction as a state-dependent effect. The central CNV reduction might reflect impairment in forming stable stimulus-response associations, the relative frontal enhancement might reflect the out-patients' attempt at compensating that impairment.

Adult↗

PubMed1981

Genetical variation for enzyme activity in a population of Drosophila melanogaster. VI. Molecular variation in the control of alcohol dehydrogenase (ADH) activity.

Four characters, ADH activity at 25 degrees, immunologically determined ADH protein level, total protein and body weight were measured upon 72 hour old adult female and male Drosophila melanogaster from 16 highly inbred lines, derived from the laboratory population, "Texas" (established 1966). The highest levels of ADH activity and ADH protein level were observed in the 2 lined homozygous for the AdhF allele. Amongst the 14 AdhS/S lines variation for ADH protein level was associated with genetical variation for ADH activity (r = 0.6). The genetical association between ADH activity or ADH protein level and either body weight or total protein in the 16 inbred lines was not statistically significant. A study of ADH activity, ADH protein and total protein in 8 lines representing all homozygous combinations of chromosomes I, II and III and derived from two inbred AdhS/S lines, chosen for their respective high and low ADH activities, showed that ADH activity was considerably modified by a post-translational event controlled from chromosome III. Total protein was controlled by different chromosomal effects from those controlling ADH activity. Michaelis constants for crude fly extracts of the two AdhF/F and the above two AdhS/S lines showed clear differences in affinity for isopropanol.

Alcohol Oxidoreductases↗