Thoracic duct variations may complicate the anterior spine procedures

The aim of this study is to localize and document the anatomic features of the thoracic duct and its tributaries with special emphasis on the spinal surgery point of view. The thoracic ducts were dissected from nine formaldehyde-preserved male cadavers. The drainage patterns, diameter of the thoracic duct in upper, middle and lower thoracic segments, localization of main tributaries and morphologic features of cisterna chyli were determined. The thoracic duct was detected in all cadavers. The main tributaries were concentrated at upper thoracic (between third and fifth thoracic vertebrae) and lower thoracic segments (below the level of ninth thoracic vertebra) at the right side. However, the main lymphatic tributaries were drained into the thoracic duct only in the lower thoracic area (below the level of the tenth thoracic vertebra) at the left side. Two major anatomic variations were detected in the thoracic duct. In the first case, there were two different lymphatic drainage systems. In the second case, the thoracic duct was found as bifid at two different levels. In formaldehyde preservation, the dimensions of the soft tissues may change. For that reason, the dimensions were not discussed and they may not be a guide in surgery. Additionally, our study group is quite small. Larger series may be needed to define the anatomic variations. As a conclusion, anatomic variations of the thoracic duct are numerous and must be considered to avoid complications when doing surgery.

Variation in hospital length of stay: do physicians adapt their length of stay decisions to what is usual in the hospital where they work?

OBJECTIVE

To test the hypothesis that physicians who work in different hospitals adapt their length of stay decisions to what is usual in the hospital under consideration.

DATA SOURCES

Secondary data were used, originating from the Statewide Planning and Research Cooperative System (SPARCS). SPARCS is a major management tool for assisting hospitals, agencies, and health care organizations with decision making in relation to financial planning and monitoring of inpatient and ambulatory surgery services and costs in New York state.

STUDY DESIGN

Data on length of stay for surgical interventions and medical conditions (a total of seven diagnosis-related groups [DRGs]) were studied, to find out whether there is more variation between than within hospitals. Data (1999, 2000, and 2001) from all hospitals in New York state were used. The study examined physicians practicing in one hospital and physicians practicing in more than one hospital, to determine whether average length of stay differs according to the hospital of practice. Multilevel models were used to determine variation between and within hospitals. A t-test was used to test whether length of stay for patients of each multihospital physician differed from the average length of stay in each of the two hospitals.

PRINCIPAL FINDINGS

There is significantly (p<.05) more variation between than within hospitals in most of the study populations. Physicians working in two hospitals had patient lengths of stay comparable with the usual practice in the hospital where the procedure was performed. The proportion of physicians working in one hospital did not have a consistent effect for all DRGs on the variation within hospitals.

CONCLUSION

Physicians adapt to their colleagues or to the managerial demands of the particular hospital in which they work. The hospital and broader work environment should be taken into account when developing effective interventions to reduce variation in medical practice.

The spectrum of NF1 mutations in Korean patients with neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders in humans. NF1 is caused by mutations in the NF1 gene which consists of 57 exons and encodes a GTPase activating protein (GAP), neurofibromin. To date, more than 640 different NF1 mutations have been identified and registered in the Human Gene Mutation Database (HGMD). In order to assess the NF1 mutational spectrum in Korean NF1 patients, we screened 23 unrelated Korean NF1 patients for mutations in the coding region and splice sites of the NF1 gene. We have identified 21 distinct NF1 mutations in 22 patients. The mutations included 10 single base substitutions (3 missense and 7 nonsense), 10 splice site mutations, and 1 single base deletion. Eight mutations have been previously identified and thirteen mutations were novel. The mutations are evenly distributed across exon 3 through intron 47 of the NF1 gene and no mutational hot spots were found. This analysis revealed a wide spectrum of NF1 mutations in Korean patients. A genotype- phenotype correlation analysis suggests that there is no clear relationship between specific NF1 mutations and clinical features of the disease.

Epigenetics and its implications for plant biology 2. The 'epigenetic epiphany': epigenetics, evolution and beyond

SCOPE

In the second part of a two-part review, the ubiquity and universality of epigenetic systems is emphasized, and attention is drawn to the key roles they play, ranging from transducing environmental signals to altering gene expression, genomic architecture and defence.

KEY ISSUES

The importance of transience versus heritability in epigenetic marks is examined, as are the potential for stable epigenetic marks to contribute to plant evolution, and the mechanisms generating novel epigenetic variation, such as stress and interspecific hybridization.

FUTURE PROSPECTS

It is suggested that the ramifications of epigenetics in plant biology are immense, yet unappreciated. In contrast to the ease with which the DNA sequence can be studied, studying the complex patterns inherent in epigenetics poses many problems. Greater knowledge of patterns of epigenetic variation may be informative in taxonomy and systematics, as well as population biology and conservation.

Variation, repetition, and choice

Experiment 1 investigated the controlling properties of variability contingencies on choice between repeated and variable responding. Pigeons were exposed to concurrent-chains schedules with two alternatives. In the REPEAT alternative, reinforcers in the terminal link depended on a single sequence of four responses. In the VARY alternative, a response sequence in the terminal link was reinforced only if it differed from the n previous sequences (lag criterion). The REPEAT contingency generated low, constant levels of sequence variation whereas the VARY contingency produced levels of sequence variation that increased with the lag criterion. Preference for the REPEAT alternative tended to increase directly with the degree of variation required for reinforcement. Experiment 2 examined the potential confounding effects in Experiment 1 of immediacy of reinforcement by yoking the interreinforcer intervals in the REPEAT alternative to those in the VARY alternative. Again, preference for REPEAT was a function of the lag criterion. Choice between varying and repeating behavior is discussed with respect to obtained behavioral variability, probability of reinforcement, delay of reinforcement, and switching within a sequence.

Severe sepsis: variation in resource and therapeutic modality use among academic centers

BACKGROUND

Treatment of severe sepsis is expensive, often encompassing a number of discretionary modalities. The objective of the present study was to assess intercenter variation in resource and therapeutic modality use in patients with severe sepsis.

METHODS

We conducted a prospective cohort study of 1028 adult admissions with severe sepsis from a stratified random sample of patients admitted to eight academic tertiary care centers. The main outcome measures were length of stay (LOS; total LOS and LOS after onset of severe sepsis) and total hospital charges.

RESULTS

The adjusted mean total hospital charges varied from 69 429 dollars to US237 898 dollars across centers, whereas the adjusted LOS after onset varied from 15.9 days to 24.2 days per admission. Treatments used frequently after the first onset of sepsis among patients with severe sepsis were pulmonary artery catheters (19.4%), ventilator support (21.8%), pressor support (45.8%) and albumin infusion (14.4%). Pulmonary artery catheter use, ventilator support and albumin infusion had moderate variation profiles, varying 3.2-fold to 4.9-fold, whereas the rate of pressor support varied only 1.92-fold across centers. Even after adjusting for age, sex, Charlson comorbidity score, discharge diagnosis-relative group weight, organ dysfunction and service at onset, the odds for using these therapeutic modalities still varied significantly across centers. Failure to start antibiotics within 24 hours was strongly correlated with a higher probability of 28-day mortality (r2 = 0.72).

CONCLUSION

These data demonstrate moderate but significant variation in resource use and use of technologies in treatment of severe sepsis among academic centers. Delay in antibiotic therapy was associated with worse outcome at the center level.

Variation in sepsis care: a wake-up call

There is important variation in the care of critically ill patients. While some of this variability is appropriate, and represents individually titrated care, residual variation indicates over- and under-use of precious resources and is clearly concerning. Recent advances in critical care medicine provide "road maps" to standardize care and use evidence-based medicine to improve patient outcomes. Knowledge about which therapies to use, and under what circumstances to use them, could form a basis for measuring the consistency and quality of our care processes. These simple process measures can be easily incorporated into daily rounds and serve to inform on the quality of our care.

Variation in the E2-binding domain of HPV 16 is associated with high-grade squamous intraepithelial lesions of the cervix

Human papillomaviruses (HPV) are strongly associated with cervical intraepithelial neoplasia (CIN) and invasive cancer mainly through the action of the E6 and E7 viral proteins, transcription of which is down-regulated by the E2 protein. To test the hypothesis that HPV 16 E2 variation is important in the development of high-grade squamous neoplasia of the cervix, we carried out a cross-sectional analysis of low-grade and high-grade squamous intraepithelial lesions (SILs) for specific mutations in the HPV 16 E2 gene and for E2 gene disruption in these regions. Isolates were also analysed for the HPV 16 350T-G variant. 22 of 178 low-grade SILs and 43 of 61 high-grade SILs examined, contained HPV 16. No relationship was found between the E6 350T-G variant, or the E2 hinge region 3410C-T variant, and lesion grade. However, disruption of the regions of E2 analysed was significantly more frequent in high-grade lesions, and there was a significant association between the 3684C-A variant in the E2 DNA binding domain and high-grade histology suggesting that this variant may be important in progression to high-grade intraepithelial disease.

Candidate genes and single nucleotide polymorphisms (SNPs) in the study of human disease

The genomic revolution has generated an extraordinary resource, the catalog of variation within the human genome, for investigating biological, evolutionary and medical questions. Together with new, more efficient platforms for high-throughput genotyping, it is possible to begin to dissect genetic contributions to complex trait diseases, specifically examining common variants, such as the single nucleotide polymorphism (SNP). At the same time, these tools will make it possible to identify determinants of disease with the expectation of eventually, tailoring therapies based upon specific profiles. However, a number of methodological, practical and ethical issues must be addressed before the analysis of genetic variation becomes a standard of clinical medicine. The currents of variation in human biology are reviewed here, with a specific emphasis on future challenges and directions.

Effect of elevated CO2 on the stomatal distribution and leaf physiology of Alnus glutinosa

Variation in stomatal development and physiology of mature leaves from Alnus glutinosa plants grown under reference (current ambient, 360 μmol mol^-1 CO₂ ) and double ambient (720 μmol mol^-1 CO₂ ) carbon dioxide (CO₂ ) mole fractions is assessed in terms of relative plant growth, stomatal characters (i.e. stomatal index and density) and leaf photosynthetic characters. This is the first study to consider the effects of elevated CO₂ concentration on the distribution of stomata and epidermal cells across the whole leaf and to try to ascertain the cause of intraleaf variation. In general, a doubling of the atmospheric CO₂ concentration enhanced plant growth and significantly increased stomatal index. However, there was no significant change in relative stomatal density. Under elevated CO₂ concentration there was a significant decrease in stomatal conductance and an increase in assimilation rate. However, no significant differences were found for the maximum rate of carboxylation (V_cmax ) and the light saturated rate of electron transport (J_max ) between the control and elevated CO₂ treatment.

Escape of HIV-1 is associated with lack of V3 domain-specific antibodies in vivo

This study was performed to analyse correlates of viral escape in AIDS patients. Peripheral blood mononuclear cells (PBMC) from HIV- donors were inoculated with AIDS patients' serum to detect neutralization-resistant cell-free virus. Infectious virus was detected by polymerase chain reaction (PCR) and analysed by sequencing the V3 region. The escaped virus species was compared with all V3 virus variants found in the patients' PBMC and plasma. In one patient escaped virus was also compared with variants found in CD4+ T cells isolated by FACS from blood, spleen and lymph node. The frequency of the virus variants was determined by cloning and sequence analysis of 20 V3 clones for each PCR amplification. To monitor anti-V3 antibodies by ELISA, each V3 sequence was expressed as fusion with glutathione S-transferase (GST-V3). In our AIDS patients, a V3-directed antibody response against the infectious virus V3 loop was not detectable. In contrast, virus variants unable to infect the donor PBMC in vitro were well recognized by homologous V3-directed antibody. After an interval of 1 year the frequency of these variants clearly decreased, while at the same time the escaped variants grew out and finally represented the predominant viral species both in plasma and PBMC. The infectious variants lacking V3 antibody response were also predominant in CD4+ T cells in spleen and lymph node. Our data indicate that the escape of virus variants is closely related to the lack of V3-directed antibody.

Further studies on the lobar heterogeneity in response to coumarin-mediated hepatotoxicity

A randomized sampling protocol coupled with quantitative morphometry has been used to evaluate the inter-lobe variation in centrilobular hepatic necrosis in the mouse, and periportal hepatic necrosis in the beta-naphthoflavone-induced rat, both in response to treatment with coumarin. The results of these studies indicate a random inter-lobe variation in xenobiotic-mediated hepatotoxicity.

Growth Variation Among Species and Strains of Listeria in Culture Broth

Culture suspensions of 45 species and strains of Listeria were prepared in tryptic soy broth with 0.6% yeast extract (TSBYE) for 24 h at 37°C, and were then diluted with phosphate buffer solution and standardized to 0.10 ± 0.01 absorbance at 600 nm. Spectrophotometer tubes containing 5 ml of TSBYE (pH 7.2) were inoculated with 0.1 ml of the standardized cultures and incubated at 4, 10 or 37°C. Absorbance readings were taken during storage. Growth curves were fitted using the Gompertz function, and growth parameters were calculated. There were major differences in lag phase duration (LPD), generation time (GT) and exponential growth rate (EGR) among species and strains of Listeria tested. Values for LPD and GT decreased (P <0.05) with increasing temperature of incubation, while EGR and maximum population density (MPD) values increased. Lag phase duration and GT values at a given temperature were lower for Listeria monocytogenes compared to other Listeria spp. At 4°C, LPDs for L. monocytogenes strains ranged from 69.8 to 270.8 h. Of the L. monocytogenes cultures tested, strain Scott A had the longest average (209.8 ± 0.1) h LPD at 4°C. At l0°C, LPDs ranged from 36.5 to 68.9 h, with Scott A being again one of the strains with the longest average LPD (62.8 ± 0.7 h). At 37°C, LPDs ranged from 4.4 to 11.1 h. Variation was also observed in GT and EGR, especially at 4°C. Although there were major variations in growth parameters due to strain and temperature, no significant (P >0.05) trends were observed in average values among different serotypes of L. monocytogenes tested.

Inter- and Intraspecific Variation in Wild-type and Single Female-derived Populations of Xiphinema americanum-group Nematodes

Ten populations of Xiphinema americanum-group nematodes were reared from individual females to evaluate inter- and intraspecific variation under identical host and environmental conditions. Data indicated that morphometric variability of X. americanum was the result of genetic variation rather than phenotypic plasticity and that genetic heterogeneity was greater than previously thought. Morphometrics of single female derived (SFD) populations identified different genotypes present in the field populations. Stylet length was the least variable morphometric character of SFD populations, but collectively stylet measurements of all individuals formed an uninterrupted continuum ranging from 107-148 mum. Range and frequency of stylet measurements of field populations could be accounted for by the relative proportion of different genotypes in the population. Nine SFD populations were identified as X. americanum sensu stricto, and one SFD population was similar to X. californicum.

Morphometric Evaluation of Hypotriploid and Triploid Populations of Meloidogyne arenaria

A morphometric comparison of seven hypotriploid populations with five pooled triploid populations of Meloidogyne arenaria was made using standard descriptive statistics, stepwise discriminant analysis (SDA), and cluster analysis. Six morphometric characters of females, 14 of second-stage juveniles (J2), and 18 of males were measured for each population. Useful differentiating characters included: body length in J2; stylet length in females and J2; stylet-knob dimensions in females and males; dorsal esophageal gland orifice distance in all three life stages; esophagus-length ratio in males and J2; excretory pore position in J2; and spicule length in males. SDA and cluster analysis showed that in each life stage, the hypotriploid populations were set off to varying degrees from the triploid populations. In addition, the relationships among populations differed when different life stages were compared. No consistent relationships could be detected among the populations, when morphometric data of the present study and morphological findings of the same populations in a parallel study were considered. Morphometric differences were not sufficient to propose any of the hypotriploid populations as new species.

Morphological Comparison of Seven Hypotriploid Populations of Meloidogyne arenaria with the Typical Triploid Populations

A morphological comparison of seven hypotriploid populations of Meloidogyne arenaria was made to clarify their taxonomic status, using light and scanning electron microscopy. All populations differed from each other and from the typical triploid M. arenaria by certain features. Differences were not regarded as sufficient to justify recognition of the variants as distinct species. Morphological divergence of populations from the typical M. arenaria was gradual. The most useful characters were stylet and head morphology of males and stylet morphology of females. Perineal patterns and cephalic, stylet, and tail morphologies of second-stage juveniles were of little taxonomic value. Host races 1 and 2 could not be distinguished morphologically. Populations E445 and E551 with the atypical esterase phenotypes M3-F1 and S1-M1, respectively, were morphologically more similar to the typical M. arenaria than populations E255 and E467, which have the most common A2 esterase phenotype of M. arenaria.

Measuring investment in carnivory: seasonal and individual variation in trap number and biomass in Utricularia vulgaris L

The partitioning of biomass between traps and leaves is a measure of the investment in carnivory of Utricularia vulgaris and is dependent on the relative values of three attributes: trap size, trap number and leaf size. Marked seasonal and individual variations in trap size, trap number and leaf size occur within a small population of U. vulgaris at Wicken Fen, Cambridgeshire, UK, with some plants consistently having fewer traps per leaf than others, and some smaller leaves than others, throughout the growing season. However, the three attributes vary independently, so that all combinations over the observed ranges of trap size, trap number and leaf size occur simultaneously in the population. In spite of the variation in the three constituent factors, the proportion of biomass invested in traps is close to 50% in the majority of plants and throughout most of the growing season. The contribution of traps to total biomass cannot be predicted from the number of traps per leaf. Although the proportion of biomass represented by traps is the most useful measure of a plant's investment in carnivory, the precise way in which the biomass is partitioned between a variable number of traps of different sizes may also be an important consideration in cost-benefit analyses.

Critical difference of some bovine haematological parameters

The purpose of the present study was to calculate the critical difference between 2 analytical results for the red blood cell count (RBC), the white blood cell count (WBC), the haemoglobin concentration (Hb), and the haematocrit (PCV) in blood from Red Danish Dairy cows. The critical difference can help to judge whether the difference between 2 consecutive analytical results from the same animal may be safely ascribed to natural variation or not. To calculate the critical differences, blood samples from 20 clinically healthy lactating cows were collected once daily for 5 consecutive days. The total variance of the analytical results was divided into the component of variance between cows (S2Inter), the component of variance for days within cows (S2Intra), and the component of variance for measurements (S2Anal) using nested analysis of variance. The critical difference was then calculated from S2Intra and S2Anal as 0.61 x 10(12)/l for RBC, 2.2 x 10(9)/l for WBC, 0.79 mmol/l for Hb, and 0.07 for PCV. The critical differences may be used as guidelines to indicate potentially important changes in the parameters. However, the analytical results should not be assessed by the critical differences alone, but should also be compared to the corresponding reference intervals.

Variation in salinity tolerance and ion uptake in accessions of brown beetle grass [Diplachne fusca (L.) Beauv.]

Significant variation in tolerance was found in natural populations of Diplachne fusca (L.) Beauv, grown under a range of NaCl concentrations, with greatest variation in accessions from different sites and a narrower range of tolerance from those within sites. Significant differences were found between accessions for Na, Cl and K uptake. Ma and Cl concentrations were found to be higher in sheaths than in leaf blades, indicating that D. fusca has the capacity to sequester high levels of Na and Cl in the sheath away from the leaf blade as well as maintaining a high selectivity for K. over Na. The salinity level of the site from which an accession was collected did not show any correlation with the salt-tolerance of that accession. While D. fusca was found generally to be highly tolerant of NaCl (with plants surviving at 400 mol m^-3 NaCl) there was variation in tolerance in its natural populations, indicating the potential for selecting to increase tolerance further.

Genetics of the Nematode Heterorhabditis bacteriophora Strain HP88: The Diversity of Beneficial Traits

Genotypic variation among infective juveniles of Heterorhabditis bacteriophora (strain HP88) in heat, desiccation, ultraviolet tolerance, and host-finding ability was assessed by comparing the performance of inbred lines of this entomopathogenic nematode in laboratory assays. Each line consisted of highly homozygous offspring originating from one individual obtained from a natural population. Considerable variation in all four traits was detected among the different inbred lines. The heritability values for heat or ultraviolet tolerance and for host-finding ability were high, indicating that selection should be an efficient way for improving these traits in the population. The results for desiccation tolerance varied considerably within each line. Heritability value was low, indicating that the results were influenced mainly by environmental variation and suggesting that selective breeding for higher desiccation tolerance would be inefficient. Improvement through induction of mutations may be a better alternative in this population.

Amino acids within hypervariable region 1 of avian coronavirus IBV (Massachusetts serotype) spike glycoprotein are associated with neutralization epitopes

The spike glycoprotein (S) gene of IBV codes for a precursor protein which is cleaved into the N-terminal S1 and C-terminal S2 glycopolypeptides. The S1 glycopolypeptide, which induces neutralizing antibody, comprises approximately 520 amino acid residues. We have determined the nucleotide sequence of S1 of seven strains of the Massachusetts (Mass) serotype and the first 337 bases of two additional Mass strains. Despite the fact that the strains had been isolated over three decades in Europe and the U.S.A. there was only 4% base and 6% amino acid variation within the group. Nearly one third of the 32 amino acid differences in S1 were in two hypervariable regions (HVRs 1 and 2) comprising residues 38-51 and 99-115, identified by Niesters et al. (1986), showing that HVRs 1 and 2 are a feature of the Mass serotype. Amino acid variation within HVRs 1 and 2 was 29% and 40% respectively. Five vaccine strains could be distinguished from each other by sequencing of the first 337 nucleotides. Variants of M41 which resisted neutralization by two monoclonal antibodies (A13 and A38) had the same, single base change at position 134, resulting in substitution of proline residue 45 by histidine. This indicates that residues within HVR 1 are associated with epitopes which induce neutralizing antibody.

coffeae

Three populations of Pratylenchus coffeae and two of P. brachyurus, each originating from a single female, were maintained on Citrus spp. or Solanum nigrum L. for several years under greenhouse conditions. Nematodes were extracted from roots, and adult female specimens were killed, fixed, and mounted in glycerine for microscopic study. Variables measured were distance between vulva and anus and lengths of the stylet, posterior uterine sac, and tail. The mean data and coefficients of variability suggest that styler length had the least variability, and length of posterior uterine sac the most. When males and distinct spermathecae are not evident in P. coffeae populations, the species can he distinguished from P. brachyurus by a shorter mean stylet length, longer mean posterior uterine sac length, and much longer distance between the vulva and anus.