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PubMed1986

Observer variation in interactive computerized morphometry.

The validity of a test system in morphometric histopathology depends on the variation sources involved. Biological variation is one of the variation sources, but is also the object to be studied with morphometry. We studied the variation sources in interactive computerized morphometry in two test systems involving two different commercially available image analyzers. The measurements were made on nuclei in a microscopic field of 5 transitional cell tumors (papilloma and WHO grade I-III carcinomas) of the urinary bladder. It turned out that different observers selected a variable number of nuclei for measurements, the coefficient of variation (CV) in the number of nuclei being 11-11.5%. Mean CV in nuclear perimeter measurements was 4.4-4.8%, and in nuclear area measurements 8.2-8.6%. The variation in measurements by 1 observer was smaller, the CV values being 2.8% for the number of nuclei, 1.2% for nuclear perimeter, and 2.4% for nuclear area. The results showed that interobserver variation can be considerable in these systems. It is suggested that special sampling rules should be tested with the idea of finding the relevant approach with the smallest interobserver variation.

Carcinoma, Transitional Cell↗

PubMed1987

Intra-individual variation of some analytes in serum of patients with insulin-dependent diabetes mellitus.

Biological intra-individual variation in concentrations of 16 clinical biochemical analytes in serum was estimated for 27 patients with insulin-dependent diabetes mellitus (IDDM), and results were compared with those for apparently healthy individuals. In general, the variation was significantly higher in the patients. The ratio of the average intra-individual variation in IDDM patients to that in normal subjects exceeded 2.0 for Na+, K+, creatinine, and alpha-amylase; 1.50 to 2.0 for Cl-, total protein, albumin, cholesterol, and hemoglobin; and 1.2 to 1.5 for urea, uric acid, high-density-lipoprotein cholesterol, and aspartate aminotransferase. This increased variability in IDDM patients may be caused by variations in osmotic diuresis. Average intra-individual variations were greater for women than for men for Na+, total protein, albumin, and hemoglobin. Individual values showed a gaussian distribution for all analytes, including enzymes and triglycerides. No intra-individual variation was time dependent. For practical purposes, decision-making criteria in monitoring IDDM can be derived from the estimated biological component of intra-individual variation and the analytical variation established for each laboratory.

Adult↗

PubMed1982

[Clinico-experimental study of daily variations in depressed patients].

Forty hospitalized depressive patients of both sexes with primary depressive syndrome and concomitant diurnal variations were investigated at defined times with the following method: special questionnaire on subjective evaluation of depressive diurnal variation (TSF), mood scale (Bf-S of v. Zerssen), Necker cube, tests of autonomic function (amount of saliva and circulatory variables), global assessment of the depth of depression.--The quantitative differentiation into diurnal variations of different extents undertaken by means of the TSF were validated by the daily difference of the Bf-S. Between the extent of the depressive diurnal variation and the nosological group as well as the depth of depression no relationship could be found. Also the rate of turning over the Necker cube did not show any alteration in the diurnal rhythmicity. On the other hand, the inverse diurnal rhythmicity of the amount of saliva, also according to the corresponding results in the literature, can be interpreted as influence of the depressive diurnal variation. The resting values of pulse rate and blood pressure followed the diurnal physiological rhythm, but in addition they revealed a quantitative influence of the depressive diurnal variation (amplification). No systematic influences could be demonstrated for the orthostatic values.--The results show that in this methodological procedure only a few variables could be demonstrated to be associated with the depressive diurnal variation. On the other hand, it could be proved that not only mental but also certain autonomic components of the depressive syndrome undergo an alteration with the depressive diurnal variation.

Adult↗

PubMed1995

Small area variation analysis: a tool for primary care research.

Small area variation analysis is a research tool used by health services researchers to describe how rates of health care use and events vary over well-defined geographic areas. Significant variation has been shown to exist in the rates of hospitalization for chronic obstructive lung disease, pneumonia, hypertension, and in surgical procedures, such as hysterectomy, cholecystectomy, and tonsillectomy. Potential sources of variation include differences in underlying morbidity, access to care, physician judgment, quality of care delivered, patient demand for services, and random variation. Small area variation studies have been used to determine if significant variation exists across geographic areas and to describe relationships between the observed variation and potential causal factors. Methodologic concerns include the definition of small areas, defining the at-risk population within each small area, sample size, case mix adjustments, and stability of rates over time. The use of small area analysis in primary care will require definition of appropriate small areas for ambulatory care, description of the variation in ambulatory events across small areas, development of appropriate measures for ambulatory case mix, and development of appropriate tools to measure the outcomes of ambulatory care.

Episode of Care↗

PubMed1994

Variations in hysterectomy rates in Ontario: does the indication matter?

OBJECTIVES: To examine variations in rates of hysterectomy for the five main indications for the procedure in regions of Ontario. DESIGN: Cross-sectional population-based analysis of hospital discharge abstracts. SETTING: All acute care facilities in Ontario. PARTICIPANTS: All 65,599 women whose hospital record contained a procedure code indicating that a hysterectomy was performed between Apr. 1, 1988, and Mar. 31, 1991. Duplicate cases, records of cancelled procedures and nonresidents were excluded. MAIN OUTCOME MEASURES: Crude and age-adjusted rates of hysterectomy, by indication, for each region of Ontario. RESULTS: Five indications accounted for more than 80% of hysterectomies performed. The median age-adjusted rate of hysterectomy for Ontario regions during the study period was 6.25 per 1000 women, with a 2.7-fold variation among regions. The regions with rates of hysterectomy in the highest quartile tended to be rural, and those with rates in the lowest quartile tended to be urban areas with teaching hospitals. When rates of hysterectomy for specific indications were examined, they showed substantial variations among regions in the rate of the procedure for menstrual hemorrhage (18-fold variation), uterine prolapse (9.3-fold) and endometriosis (6.3-fold). A smaller but still significant variation was shown in the rate of hysterectomy for leiomyoma (2.3-fold). Regional variation in the rate of hysterectomy for cancer (2.5-fold) was not statistically significant. CONCLUSIONS: There are large interregional variations in rates of hysterectomy, especially for indications that are more discretionary than others (i.e., menstrual hemorrhage, uterine prolapse and endometriosis) and less variation in rates when treatment options and diagnosis are clear-cut. This result suggests the need for more definitive practice guidelines on treatment of the indications for which the rate is more variable.

Adult↗

PubMed1993

[Endoscopic paranasal sinus surgery. The most important anatomic variations of the main paranasal sinus and accessory paranasal sinus].

Anatomic variations of the nasal cavity and paranasal sinuses are described in order of their appearance in endoscopy. Variations of the pyriform aperture are followed by variations of the agger nasi, inferior and middle conchas, inferior and middle nasal meati, and variations of the bulla ethmoidea, uncinate process and fontanelles. Variations of the maxillary sinus are described from their anterior and lateral views. Partial and total septation of the maxillary sinus, variations of its dimensions and its relation to dental roots are stressed. The dimensions of the frontal sinus, frontal bulla or bullae are noted. The variation of the sphenoid sinus and its dimensions and relationships to the structures of the cavernous sinus and the endocranium are described. Pneumatization of the anterior clinoid process and the region around the optic canal by the frontal sinus, ethmoid labyrinth or sphenoid sinus is discussed. Knowledge of these different variations will help the rhinologic surgeon in his orientation during endoscopic surgical interventions.

Adolescent↗

PubMed1993

Variations in surgical rates in Quebec: does access to teaching hospitals make a difference?

OBJECTIVE: To document the geographic variations in the rates of 10 common surgical procedures in Quebec and to examine the relation between surgical rates and level of access to teaching hospitals. DESIGN: Population-based rates standardized for age and sex were calculated from 1985-88 data from MED-ECHO (the provincial hospital discharge database) for each of the 32 community health districts (départements de santé communautaire [DSCs]) in Quebec. Variation across DSCs was analysed with the use of the ratio of the highest to the lowest rate, the coefficient of variation and the systematic component of variation. On the basis of an urbanization index designed by Statistics Canada, DSCs were classified as having a low, medium, high or very high level of access to teaching hospitals. PATIENTS: All Quebec residents except those whose DSC of residence could not be traced (accounting for no more than 1.7% of patients for any study procedure) and aboriginal people from northern Quebec. SURGICAL PROCEDURES STUDIED: Appendectomy, cesarean section, cholecystectomy, coronary artery bypass grafting (CABG), hysterectomy, inguinal hernia repair, prostatectomy, tonsillectomy with or without adenoidectomy, total hip replacement and varicose vein stripping. RESULTS: There was considerable systematic variation in the surgical rates for all 10 procedures. Cesarean section, the rates of which varied the least, still exhibited almost a twofold variation between the highest and lowest rates. The rates of tonsillectomy varied the most, by a factor of more than five. With a few exceptions there was relatively little relation between the rates of the procedures within the DSCs. The rates of appendectomy, cholecystectomy, hysterectomy and tonsillectomy tended to be lower in the DSCs containing teaching hospitals, whereas the reverse was true for CABG. For the other procedures the relation between the rates and the level of access to teaching hospitals was nonsignificant. CONCLUSIONS: The overall consistency of the observed variations with those of previous studies invites a closer look at the practice patterns and the scientific basis of the clinical decisions associated with procedures showing high variations in rates. The lack of a systematic relation between the surgical rates and the level of access to teaching hospitals challenges the belief that remote regions are underserved with respect to the procedures studied.

Female↗

PubMed1996

Ambulatory care practice variation within a Medicaid program.

STUDY QUESTIONS: What is the extent of variation in patterns of ambulatory care practice across one state's Medicaid program once case mix is controlled for? How much of this variation in resource consumption is explained by factors linked to the provider, patient, and geographic subarea? DATA SOURCES/STUDY SETTING: Practices of all providers delivering care to persons who were continuously enrolled in the Maryland Medicaid program during FY 1988 were studied. A computerized summary of all services received during this year for 134,725 persons was developed using claims data. We also obtained data from the state's beneficiary and provider files and the American Medical Association's masterfile. Each patient was assigned a "usual source of care" (primary provider) based on the actual patterns of service. The Ambulatory Care Group (ACG) measure was used to help control for case mix. STUDY DESIGN: This was a cross-sectional study based on the universe of continuously enrolled Medicaid enrollees in one state. PRINCIPAL FINDINGS: After controlling for case mix, the variation in patient resource use by type of primary provider was 19 percent for ambulatory visits, 46 percent for ancillary testing, 61 percent for prescriptions, and 81 percent for hospitalizations. Across Maryland counties, comparing the low- to high-use jurisdiction, there was 41 percent variation in case mix-adjusted visit rates, 72 percent variation in pharmacy use, and 325 percent variation in hospital days. At the individual practice level, physician characteristics explain up to 17 percent of ambulatory resource use and geographic area explains only a few percent, while patient characteristics explain up to 60 percent of variation. CONCLUSIONS: Since a large proportion of variation was explained by patient case mix, it is evident that risk adjustment is essential for these types of analyses. However, even after adjustment, resource use varies considerably across types of ambulatory care provider and region, with consequent implications for efficiency of health services delivery.

Ambulatory Care↗

PubMed1996

Trends and variations in the use of vascular surgery in Ontario.

OBJECTIVE: To measure changes over time in overall surgical rates and geographic rate variations for three major vascular procedures (abdominal aortic aneurysm repairs, peripheral vascular disease procedures and carotid endarterectomies). BACKGROUND: There is little research literature on population-based usage profiles of vascular procedures. The three procedures profiled were all subject to marked shifts in evidence or surgical opinions, raising the issue of the interplay between temporal trends and geographic variations in their use. METHODS: Based on Ontario's hospital discharge abstracts and census data, population-based usage rates were calculated by site of patient residence from 1981 to 1991. Extent of rate variation was summarized with the coefficient of variation, systematic component of variation and the adjusted-likelihood ratio chi2. Spearman rank correlations were also calculated to assess stability of county rankings for each procedure. RESULTS: The overall rates of peripheral vascular procedures and repair for abdominal aortic aneurysms fell 24% and increased 42% respectively. The overall rate of carotid endarterectomies dropped from 46/100,000 in 1981 to 20/100,000 in 1989, but by 1991 had increased to 37/100,000. Through the decade measures of variation fell minimally for all three procedures. CONCLUSION: Overall use of vascular procedures shifted in apparent response to new research evidence and technologies. Despite marked changes in surgical rates, the extent of geographic variation was stable, suggesting that differing factors influence overall surgical rates and geographic rate variations. Audit at the local level using primary clinical data is needed to understand why disparities in use persist.

Aortic Aneurysm, Abdominal↗

PubMed1997

Variation in prostate cancer survival explained by significant prognostic factors.

PURPOSE: Traditional survival analytical tools do not reveal the ability of significant prognostic factors to predict (that is, explain variation in) survival. We used survival data in patients with prostate cancer to illustrate how the association of factors with survival diverges from their ability to explain variation in survival; bladder cancer was included as a point of general comparison. MATERIALS AND METHODS: We used the 1973 to 1990 records of the Surveillance Epidemiology and End Results program. Multivariate proportional hazards models were used to identify factors that significantly associated with survival. The proportion of variation explained by these factors was estimated with the Schemper method. RESULTS: The dataset included 10,636 patients with prostate cancer and 1,070 with bladder cancer. Median survival was significantly longer in prostate than bladder cancer; other characteristics were similarly distributed. Age, stage and marital status were associated with survival in both cancers (p value range 0.0001 to 0.0009). The total proportion of variation explained was 7.1% and 32.1% for prostate and bladder cancer, respectively. In prostate cancer, age, stage and marital status explained 0.6, 5.5 and 0.4%, of the adjusted proportion of variation explained, respectively, and in bladder cancer, they explained 14.7, 8.9 and 0.6%, respectively. CONCLUSIONS: Proportional hazards models identified but did not reveal the ability of significant prognostic factors to explain variations in survival. The proportion of variation explained analyses illustrate why predicting survival is so difficult, especially in prostate cancer. The prognostic factors used do not possess the ability to explain variation in survival; new prognostic factors must be identified.

Aged↗

PubMed2000

A novel mechanism for control of antigenic variation in the haemagglutinin gene family of mycoplasma synoviae.

High-frequency phase and antigenic variation of homologous lipoprotein haemagglutinins has been seen in both the major avian mycoplasma pathogens, Mycoplasma synoviae and Mycoplasma gallisepticum. The expression and, hence, antigenic variation of the pMGA gene family (encoding these lipoproteins in M. gallisepticum) is controlled by variation in the length of a trinucleotide repeat motif 5' to the promoter of each gene. However, such a mechanism was not detected in preliminary observations on M. synoviae. Thus, the basis for control of variation in the vlhA gene family (which encodes the homologous haemagglutinin in M. synoviae) was investigated to enable comparison with its homologue in M. gallisepticum and with other lipoprotein gene families in mycoplasmas. The start point of transcription was identified 119 bp upstream of the initiation codon, but features associated with control of transcription in other mycoplasma lipoprotein genes were not seen. Comparison of three copies of vlhA revealed considerable sequence divergence at the 3' end of the gene, but conservation of the 5' end. Southern blot analysis of M. synoviae genomic DNA revealed that the promoter region and part of the conserved 5' coding sequence occurred as a single copy, whereas the remainder of the coding sequence occurred as multiple copies. A 9.7 kb fragment of the genome was found to contain eight tandemly repeated regions partially homologous to vlhA, all lacking the putative promoter region and the single-copy 5' end of vlhA, but extending over one of four distinct overlapping regions of the 3' coding sequence. Examination of sequential clones of M. synoviae established that unidirectional recombination occurs between the pseudogenes and the expressed vlhA, with duplication of pseudogene sequence and loss of the corresponding region previously seen in the expressed gene. Expression of the 5' end of two variants of the vlhA gene showed that they differed in their reaction with monoclonal antibodies specific for this region. These data suggest that the control of vlhA antigenic variation in M. synoviae is achieved by multiple gene conversion events using a repertoire of coding sequences to generate a chimeric expressed gene, with the greatest potential for variation generated in the region encoding the haemagglutinin. Thus, completely distinct mechanisms have been adopted to control antigenic variation in homologous gene families.

Amino Acid Sequence↗

PubMed1994

Craniometric variation among modern human populations.

Previous studies of genetic markers and mitochondrial DNA have found that the amount of variation among major geographic groupings of Homo sapiens is relatively low, accounting for roughly 10% of total variation. This conclusion has had implications for the study of human variation and consideration of alternative models for the origin of modern humans. By contrast, it has often been assumed that the level of among-group variation for morphological traits is much higher. This study examines the level of among-group variation based on craniometric data from a large sample of modern humans originally collected by W. W. Howells. A multivariate method based on quantitative genetics theory was used to provide an estimate of FST--a measure of among-group variation that can be compared with results from studies of genetic markers. Data for 57 craniometric variables on 1,734 crania were analyzed. These data represent six core areas: Europe, Sub-Saharan Africa, Australasia, Polynesia, the Americas, and the Far East. An additional set of analyses was performed using a three-region subset (Europe, Sub-Saharan Africa, and the Far East) to provide comparability with several genetic studies. The minimum FST (assuming complete heritability) for the three-region analysis is 0.065, and the minimum FST for the six-region analysis is 0.085. Both of these are less than the average FST from genetic studies (average estimates of 0.10-0.11). The smaller value of the minimum FST estimates is expected since it provides an estimate of FST expected under complete heritability. Using an estimate of average craniometric heritability from the literature provides an estimate of FST of 0.112 for the three-region analysis and 0.144 for the six-region analysis. These results show that genetic and craniometric data are in agreement, qualitatively and quantitatively, and that there is limited variation in modern humans among major geographic regions.

Africa↗

PubMed2005

Studying the biological and technical sources of variation in telomere length of individual chromosomes.

BACKGROUND: Consistent average length differences between species and chromosome arm differences within species indicate that telomere length is genetically determined. This seems to contradict an observed large variation in lengths of the same human telomere between metaphases of the same individual. We examined the extent to which the variation in the telomeres of the human X and Y chromosomes is heritable, induced, or technical in origin. METHODS: Metaphase chromosomes were stained by fluorescence in situ hybridization with a telomere repeat-specific probe, and fluorescence intensities of the X and Y chromosomes were measured. If telomere length variation is predominantly genetically determined and a 50% probability of meiotic recombination between the pseudo-autosomal regions of Yp and Xp in the father is taken into account, one expects an equal chance that the Yp telomere of a son is derived from his father's Xp or Yp telomere. This implies that the Yp/Yq telomere ratios in fathers and sons will be identical in the absence of paternal meiotic recombination and different when recombination occurs. RESULTS: Among five father-son pairs, four showed similar Yp/Yq ratios (P > 0.05), whereas one pair exhibited a large difference in the Yp/Yq ratio that was attributable to a significantly longer Xp than Yp telomere in the father and a presumptive meiotic exchange between X and Y during paternal meiosis. Further, the Xq telomere exhibited a generally shorter telomere length than the others. CONCLUSIONS: The high variation in telomere length appeared to be intracellular (between sister chromatids) and, hence, technical in nature. We found no measurable induced variation in the cells studied, implying that, if induced variation exists, it is small compared with the technical variation.

Adult↗

PubMed1990

Genetic variation at the apolipoprotein gene loci contribute to response of plasma lipids to dietary change.

Dietary intervention studies (from a low polyunsaturated/saturated fatty acid ratio P/S diet to a high P/S diet), carried out on a group of healthy individuals from North Karelia, Eastern Finland between 1981-1984, provided evidence that there may be a genetic component contributing to variation in response to dietary change. We have resampled blood from 107 individuals involved in the original studies and used Restriction Fragment Length Polymorphisms (RFLPs) to study the genetic contribution of variation at a number of candidate gene loci to the response to dietary change. The genes investigated in this study were the apolipoprotein (apo) genes: apo B, apo AII, apo E (protein polymorphism), apo AI-CIII-AIV gene cluster, and the LDL-receptor gene. On the basal diet the major effect of genotype on lipid traits was due to variation at the apo E gene locus; this protein polymorphism explained 14.6% of the phenotypic variance in LDL cholesterol levels and 12.7% of the phenotypic variance in total cholesterol levels. When switched to low fat high P/S diet, these effects of variation at the apo E gene locus on the phenotypic variation of LDL and total cholesterol levels disappeared. The major effect on the response to dietary change, delta, was seen on the difference in apo AI levels mediated by variation at the apo B gene locus (MspI RFLP) explaining 6.3% of the phenotypic variance in apo AI change. For the RFLPs of the apo AI-CII-AIV gene cluster, small but not significant differences on delta were found. Our results indicate that within the limits of the candidate genes studied, the major effects in response to dietary change was on apo AI levels mediated through variation at the apo B gene locus.

Adult↗

PubMed2003

Use of a curved-array transducer to reduce interobserver variation in sonographic measurement of thyroid volume in healthy adults.

PURPOSE: Sonographic calculation of thyroid volume is used in the diagnosis and follow-up of thyroid diseases. Since the calculated volume of thyroid lobes is highly influenced by the longest (ie, craniocaudal) diameter, we examined whether using a curved-array transducer as opposed to a linear-array transducer to measure the craniocaudal diameter would reduce interobserver variation. METHODS: Three sonographers with different levels of expertise each used a 5-12-MHz linear-array transducer and a 2-5-MHz curved-array transducer to measure the craniocaudal diameter of both thyroid lobes of 25 healthy volunteers. On the basis of these measurements, thyroid lobe volumes were calculated. Single-factor analysis of variance was used to evaluate the interobserver variations between the measurements made by all 3 observers as well as between measurements taken by pairs of observers. A p value of less than 0.05 was considered significant. RESULTS: Using the linear-array transducer to measure the craniocaudal diameter resulted in significant interobserver variation in thyroid volume calculation (p = 0.02), whereas using the convex-array transducer did not. Using either transducer resulted in a highly significant interobserver variation in measurements of the craniocaudal diameter, although the variation was far more pronounced for measurements made with the linear-array transducer (p = 0.0005) than for those made with the curved-array transducer (p = 0.04). For both transducers, the interobserver variations were most pronounced between the most and the least experienced sonographers. CONCLUSIONS: To avoid significant interobserver variation in calculating thyroid lobe volume, we recommend using a curved-array transducer to measure the craniocaudal diameter of the thyroid lobes.

Adult↗

PubMed1998

Molar morphology and variation in two malagasy lemur families (Lemuridae and Indriidae).

The lemurs of Madagascar represent a radiation of primates exhibiting considerable ecological and morphological diversity. Dentally, all lemurs possess the characteristic strepsirhine anterior tooth comb, but exhibit variation in their postcanine teeth that may be related to dietary differences. In this study, I examine two factors that could complicate a strictly functional interpretation of tooth form variation in two families of Malagasy primates, the Lemuridae and Indriidae. (1) Allometry may be responsible for observed variation. Body size, not specific tooth features, may be the object of selection; tooth features may vary among taxa as a consequence of differences in body size. (2) Taxonomic affiliation may "explain" variation without recourse to functional explanations. Tooth morphology among closely-related taxa may be constrained developmentally or as a result of stabilizing selection. Morphological variation between families, therefore, may not be the result of current functional differences related to physical dietary properties, but may result from past events that are lineage-specific. Morphological features from the upper and lower second molars of seven lemurid and four indriid taxa are compared. The results of this study indicate that the majority of second molar features scale isometrically. Initial separation by families is warranted by the homogeneous slopes but different elevations in analyses of covariance between families. Intrafamilial variation is considerable for lemurids, but more discrete among indriids. Functional explanations for tooth form variability should take into consideration the degree of variation within taxa. For this particular dataset, the two families should be analyzed separately, and, because of the considerable overlap of subspecies with full species among lemurids, the lowest taxonomic unit recognized should be used.

Analysis of Variance↗

PubMed2000

Subtyping for TNFa microsatellite sequence variation.

The microsatellite locus TNFa is frequently used as an additional genetic marker in studies of the major histocompatibility complex (MHC). Novel sequence variations at the TNFa locus have been described, and which may have implications for genetic analyses. In this study, we set up a nested polymerase chain reaction-sequence-specific primer (PCR-SSP) approach to type for these TNFa sequence variations. First, sequencing analysis of workshop B lymphoblastoid cell lines (n=13) showed the presence of three sequence variations upstream of the dinucleotide repeat at TNFa. Using nested PCR-SSP, we were able to detect these variations in a larger B lymphoblastoid cell line panel (n=34). Furthermore, we were able to show that TNFa alleles a7 and a10 are present in two distinct conformations leading to "splitting" of TNFa alleles exhibiting identical fragment lengths. To establish the frequency of the TNFa alleles and their variants, we performed microsatellite typing of a large panel of random individuals from the Dutch population (n=272). Subsequent nested PCR-SSP typing showed the presence of three previously described sequence variations in the Dutch population. Furthermore, the presence of a fourth subtype was established. The described variations of allele TNFa7 and TNFa10 are present in the random population with significant frequencies. Haplotyping analysis between HLA-DR, TNFa, and HLA-B showed that allele TNFa7.2 is present in an extended DR7-TNFa7.2-B13 haplotype. In this way, we were able to show that the additional sequence variations behave like distinct TNFa alleles.

Cell Line↗

PubMed2003

Intraspecific sequence variation of chloroplast DNA among the component species of evergreen broad-leaved forests in Japan.

For the purpose of phylogeographic study of lucidophyllous (evergreen broad-leaved) forests in Japan, we surveyed intraspecific chloroplast DNA (cpDNA) variation in 41 component species of such forests. Intraspecific cpDNA variations were detected in 14 species. In 15 species and one species group, 16 non-coding cpDNA regions were examined to find intraspecific sequence variation. The extent of variation in these regions was compared. The largest amount of intraspecific variation was detected in the rps16 region. A relatively large amount of intraspecific variation was detected in the petD-rpoA, rpl16, and trnL-F regions. It is suggested that these regions of cpDNA would be useful for detecting intraspecific variation in plant species, and could provide valuable information for various research purposes.

DNA, Chloroplast↗