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PubMed2006

Molecular characterization of Listeria monocytogenes from natural and urban environments.

Characterization of 80 Listeria monocytogenes isolates from urban and natural environments differentiated 7 and 26 EcoRI ribotypes, respectively. Whereas the majority of isolates from the natural environment represented L. monocytogenes lineage II (12 of 13 isolates), urban isolates grouped evenly into lineages I and II (32 and 33 isolates, respectively) and included two lineage III isolates. Multilocus sequence typing of all natural isolates and a randomly selected subset of 30 urban isolates showed a higher overall diversity (Simpson index of discrimination [D] of 0.987 and 0.920, respectively) than did EcoRI ribotyping (D = 0.872 and 0.911, respectively). Combined analysis with ribotype and lineage data for 414 isolates from farm sources, 165 isolates from foods and food-processing environments, and 342 human clinical isolates revealed that lineage I was significantly more common among human (P < 0.0001) isolates, whereas lineage II was more common among isolates from the natural environment, farms, and foods (P < or = 0.05). Among a total of 92 ribotypes, 31 showed significant associations with specific isolate sources. One ribotype (DUP-1039C) was significantly associated with both natural environments and farms. A spatial analysis showed a marginal association between locations in the natural environment positive for L. monocytogenes and a proximity to farms. Our data indicate that (i) L. monocytogenes strains from different sources show a high level of diversity; (ii) L. monocytogenes subtypes differ significantly in their associations with different environments, even though populations overlap; and (iii) a higher proportion of isolates from environmental sources than from human clinical cases can be classified into L. monocytogenes lineage II, which supports the classification of this lineage as an environmentally adapted subgroup.

Colony Count, Microbial↗
PubMed2004

Reduced genetic structure of the Iberian peninsula revealed by Y-chromosome analysis: implications for population demography.

Europe has been influenced by both intra- and intercontinental migrations. Since the Iberian peninsula was a refuge during the Last Glacial Maximum, demographic factors associated with contraction, isolation, subsequent expansion and gene flow episodes have contributed complexity to its population history. In this work, we analysed 26 Y-chromosome biallelic markers in 568 chromosomes from 11 different Iberian population groups and compared them to published data on the Basques and Catalans to gain insight into the paternal gene pool of these populations and find out to what extent major demographic processes account for their genetic structure. Our results reveal a reduced, although geographically correlated, Y-chromosomal interpopulation variance (1.2%), which points to a limited heterogeneity in the region. Coincidentally, spatial analysis of genetic distances points to a focal distribution of Y-chromosome haplogroups in this area. These results indicate that neither old or recent Levantine expansions nor North African contacts have influenced the current Iberian Y-chromosome diversity so that geographical patterns can be identified.

Chromosomes, Human, Y↗
PubMed2002

Two-dimensional analysis of the spacing of ocular dominance columns in normally raised and strabismic kittens.

In the primary visual cortex of cats, ferrets and macaque monkeys, the thalamocortical afferents conveying signals from the two eyes terminate in alternating regions of layer IV known as ocular dominance columns. Previous experiments have indicated that the periodicity of these columns can be influenced by visual experience: compared to normally raised animals both strabismic cats and cats raised with alternating monocular exposure displayed an increased spacing of adjacent ocular dominance columns in the primary visual cortex (area 17). However, recently it was shown that the formation of ocular dominance columns begins much earlier than previously supposed, indicating that early visual experience might only have a limited influence on the development of the spatial pattern of ocular dominance columns. We therefore visualized the complete pattern of ocular dominance columns in area 17 of normally raised and strabismic kittens during early postnatal development (age 3-6 weeks), particularly focussing on littermates. In addition, we used a previously developed spatial analysis (period statistics) to quantify columnar spacing two-dimensionally. We observed a pronounced interindividual variability in both normally raised and strabismic animals, with column spacings ranging from 783 to 1362 microm. In contrast to previous reports, there were no significant differences in columnar periodicity between normally raised and strabismic cats. These data indicate that rearing has less influence on column spacing while the interindividual variability is much greater than previously supposed, suggesting that genetic differences have an influence on column spacing.

Animals↗
PubMed2007

Pulsed-field gel electrophoresis (PFGE) analysis of temporally matched Listeria monocytogenes isolates from human clinical cases, foods, ruminant farms, and urban and natural environments reveals source-associated as well as widely distributed PFGE types.

A total of 495 temporally and geographically matched Listeria monocytogenes isolates from human clinical cases, foods, ruminant farms, and urban and natural environments were used to investigate L. monocytogenes pulsed-field gel electrophoresis (PFGE) type diversity. Two-enzyme (AscI and ApaI) PFGE discriminated 310 PFGE types and exhibited higher overall discriminatory power (Simpson's index of discrimination [D] = 0.995) than either EcoRI ribotyping (D = 0.950) or AscI or ApaI single-enzyme PFGE (D = 0.992 for both). Seven PFGE types showed significant associations with specific sources, including one and four PFGE types, respectively, associated with human clinical cases and foods. Spatial analysis of 13 PFGE types occurring >5 times showed that two PFGE types were specific to a single processing facility each, where they appear to have persisted over time. Nine PFGE types were geographically widespread and occurred among isolates from multiple sources. For example, a PFGE type that matched isolates from listeriosis outbreaks in Los Angeles and Switzerland occurred among isolates from farms (n = 7), human clinical cases (n = 4), environmental sources (n = 3), and foods (n = 1). Our data indicate that (i) PFGE is highly discriminatory for the subtyping of L. monocytogenes, (ii) some L. monocytogenes PFGE types are associated with specific sources, and (iii) some L. monocytogenes PFGE types are widely distributed and appear to be stable and pandemic. Large PFGE type databases representing isolates from different sources are thus needed to appropriately interpret subtype data in epidemiological investigations and to identify common as well as source-specific PFGE types.

Animal Husbandry↗
PubMed1999

Co-infection with malaria and HIV in injecting drug users in Brazil: a new challenge to public health?

AIMS: To describe AIDS and malaria geography in Brazil, highlighting the role of injecting drug users (IDUs) in malaria outbreaks occurring in malaria-free regions, and the potential clinical and public health implications of malaria/HIV co-infection. DESIGN: Review of the available literature and original analyses using geoprocessing and spatial analysis techniques. FINDINGS: Both HIV/AIDS and malaria distribution are currently undergoing profound changes in Brazil, with mutual expansion to intersecting geographical regions and social networks. Very recent reports describe the first clinical case of AIDS in a remote Amazonian ethnic group, as well as malaria cases in Rio de Janeiro state (hitherto a malaria-free area for 20 years); in addition, two outbreaks of both infections occurred at the beginning of the 1990s in the most industrialized Brazilian state (São Paulo), due to the sharing of needles and syringes by drug users. Spatial data point to: (a) the expansion of HIV/AIDS towards malarigenic areas located in the centre-west and north of Brazil, along the main cocaine trafficking routes, with IDU networks apparently playing a core role; and (b) the possibility of new outbreaks of secondary malaria in urban settings where HIV/AIDS is still expanding, through the sharing of needles and syringes. CONCLUSIONS: New outbreaks of cases of HIV and malaria are likely to occur among Brazilian IDUs, and might conceivably contribute to the development of treatment-resistant strains of malaria in this population. Health professionals should be alert to this possibility, which could also eventually occur in IDU networks in developed countries.

AIDS-Related Opportunistic Infections↗
PubMed2002

Positron emission tomography imaging analysis of G2A as a negative modifier of lymphoid leukemogenesis initiated by the BCR-ABL oncogene.

G2A is a lymphocyte-expressed G protein-coupled receptor whose genetic ablation results in the development of autoimmunity. Using HSV-TK reporter gene directed positron emission tomography (PET), we demonstrate that prior to any indication of the onset of illness, mice transplanted with BCR-ABL transduced G2A-deficient bone marrow harbor expanded populations of leukemic cells compared to recipients of wild-type bone marrow. The target cell type and anatomical locations of leukemia development are indistinguishable in animals transplanted with G2A+/+ or G2A-/- cells. Shorter disease latency in the G2A-deficient background is associated with an increased rate of cellular expansion. PET can be successfully applied to the temporal and spatial analysis of Bcr-Abl driven leukemic progression and should have utility for the study of other leukemias and lymphomas.

Animals↗
PubMed1999

Leukocyte spreading behavior on vascular biomaterial surfaces: consequences of chemoattractant stimulation.

Chemoattractant-induced phenomena of polarity and migration of polymorphonuclear leukocytes (PMN) are believed to play a key physiological role in controlling bacterial infections on implantable vascular biomaterials. Our study targeted the spreading behavior of human PMN adherent to expanded polytetrafluoroethylene (ePTFE), pretreated with various plasma proteins, in response to the chemoattractant, N-formyl-methionyl-leucyl-phenylalanine (fMLP). To this end, a novel imaging configuration was developed to allow in situ reconstructive analysis of PMN 3-D morphology on opaque ePTFE surfaces, using optical sectioning confocal microscopy. Following fMLP stimulation, PMN morphological polarity was enhanced on all substrates studied except fibrinogen treated ePTFE. 3-D PMN morphometry revealed that in the absence of fMLP, overall cell spreading was minimized on albumin-treated ePTFE and maximized on fibrinogen and immunoglobulin-G-treated ePTFE. Following fMLP stimulation, overall PMN spreading increased markedly on untreated and albumin-coated ePTFE, while it stayed invariant on IgG and plasma treated ePTFE, and decreased on fibrinogen-treated ePTFE. Spatial analysis of PMN spreading following fMLP stimulation revealed enhanced PMN attachment on untreated and albumin treated ePTFE and diminished attachment on fibrinogen and plasma treated ePTFE. Thus, chemoattractant stimulation altered a wide range of PMN spreading attributes on ePTFE, including morphological polarity, substrate attachment, and 3-D membrane spreading, in a substrate dependent manner. These chemoattractant-induced spreading responses may also have important consequences for PMN phagocytosis. We report that fMLP stimulation led to enhanced unopsonized particulate phagocytosis on untreated and albumin treated ePTFE, but caused no discernible change in phagocytosis on other protein substrates. Thus, chemoattractant modulation of PMN spreading on ePTFE is highly substrate-regulated, and manifests in concerted effects on PMN phagocytosis.

Blood Vessel Prosthesis↗
PubMedDate not supplied

A descriptive analysis of giardiasis cases reported in Ontario, 1990-1998.

Cases of giardiasis in Ontario were described using notifiable disease data from the Ontario Ministry of Health for the years 1990-1998 inclusive. The mean annual age- and sex-adjusted incidence rate was 25.77 cases per 100,000 population for the 25,289 cases reported. Children under five years of age had the highest incidence of disease. Males had a higher mean annual incidence in all age groups. Four deaths occurred among cases. The most frequently reported symptoms were loose stools or watery diarrhea (50.1%). A seasonal pattern was noted, peaking in late summer and early autumn. The most frequently reported probable risk settings were the home (40.1%) and travel (39.1%). The study findings suggest that a high proportion of cases occur in urban areas and spatial analysis showed the highest incidence around Lake Huron and Georgian Bay. Unfiltered water and person-to-person contact are believed to be important sources of infection.

Adult↗
PubMed1991

Dynamic brain mapping methodology and application.

Brain mapping has opened important perspectives for the neurophysiological evaluation of patients, for the discrimination of drug effects on the brain and for the study of the relationship between the brain and behavior. Our Dynamic Brain Mapping System is the result of many years of EEG quantification. It was designed as a software-oriented system to favor the largest clinical application and simultaneously stimulate new research objectives. Data collection and analysis procedures are critically important in brain mapping for a good understanding of the results. For clinical use, the maps should answer relevant EEG questions and be interpretable with the consolidated knowledge. Therefore, we have developed a new type of brain mapping technology which is called "Field blending interpolation" mapping offered together with the conventional technology with user-selectable interpolation algorithms. In addition to diagnosis, the use of computer-analyzed EEG and brain mapping can be instrumental in drug monitoring, drug selection and drug discriminations. Prospective studies are, however, required to validate the use of brain mapping in each of these new areas. Spatial analysis is the original goal of brain mapping. The development of a new data collection procedure and analysis will be instrumental in the determination of an adequate time and space resolution.

Brain↗
PubMed2003

Spatial distribution of repolarization times in patients with coronary artery disease.

The potential clinical value of QT dispersion (QTd), a measure of the interlead range of QT interval duration in the surface 12-lead ECG, remains ambiguous. The aim of the study was the temporal and spatial analysis of the QT interval in healthy subjects and in patients with coronary artery disease (CAD) using magnetocardiography (MCG) and surface ECG. Standard 12-lead ECG and 37-channel MCG were performed in 20 healthy subjects, 23 patients with CAD without prior myocardial infarction (MI), 31 MI patients and 11 MI patients with ventricular tachycardia (VT). QTd was increased in CAD without MI compared to normals (ECG 46.1 +/- 6.0 vs 42.8 +/- 5.0, P < 0.05; MCG 66.8 +/- 20.3 vs 49.7 +/- 10.8, P < 0.01) and in VT compared to MI (ECG 66.8 +/- 16.5 vs 51.9 +/- 16.6, P < 0.05; MCG 93.6 +/- 29.6 vs 66.8 +/- 20.8, P < 0.005). In MCG, spatial distribution of QT intervals in patient groups differed from those in healthy subjects in three ways: (1) greater dispersion, (2) greater local variability, and (3) a change in overall pattern. This was quantified on the basis of smoothness indexes (SI). Normalized SI was higher in CAD without MI compared to normals (3.8 +/- 1.1 vs 2.7 +/- 0.6, P < 0.001) and in VT compared to MI (6.4 +/- 1.6 vs 4.2 +/- 1.4, P < 0.0005). For the normal-CAD comparison a sensitivity of 74% and a specificity of 80% was obtained, for MI-VT, 100% and 77%, respectively. The results suggest that examining the spatial interlead variability in multichannel MCG may aid in the initial identification of CAD patients with unimpaired left ventricular function and the identification of post-MI patients with augmented risk for VT.

Coronary Disease↗
PubMed1998

[Asynchrony of ventricular contraction and relaxation--pathophysiologically recognized phenomenon, now can be clinically assessed].

When regional myocardial dysfunction is present, the physiological pattern of ventricular filling and contraction is impaired. During acute coronary occlusion, characteristic changes are observed in the ischemic myocardial segment: the amplitude of the systolic wall thickening is reduced (hypokinesia), then virtually absent (akinesia) and finally replaced by a paradoxical outward motion (dyskinesia). The maximum amplitude is reached in early diastole ("post-ejection thickening"). Since hyperkinesis develops in the normal region, the ischemic and the normal region contract asynchronously. Experimentally left ventricular asynchrony can be detected by means of subendo- and subepicardially implanted ultrasonic crystals ("sonomicrometry") or by the analysis of the phase difference of the first Fourier harmonic of dysfunctional versus control myocardial wall motion. In the clinical setting, digitized cineventriculography, radionuclide angiography and digitized M-mode echocardiography were used to assess left ventricular asynchrony in patients with coronary artery disease and hypertrophic cardiomyopathy. However, these imaging modalities are time-consuming and require complicated off-line analysis. Tissue Doppler echocardiography (TDE) is a new ultrasound modality that is based on color Doppler principles and allows for quantification of myocardial wall motion velocity by detection of consecutive phase shifts of the ultrasound signal reflected from the myocardium. The Doppler signals are displayed as a color or pulsed Doppler image by rejecting low-amplitude echoes from the blood pool due to changes in thresholding and filtering algorithms. In addition, the ability to measure low velocity is improved in the TDE system so that the lowest measurable velocity is 0.2 cm/s, a velocity level associated with cardiac tissue motion (Table 1). Due to its high temporal and spatial resolution, TDE provides valuable information on regional myocardial wall motion during different intervals of the cardiac cycle. In healthy subjects, patients with coronary artery disease and patients with hypertrophic cardiomyopathy, tissue Doppler echocardiography was used to assess myocardial synchrony/asynchrony on a 2-fold temporal and spatial analysis. Peak myocardial velocities in different myocardial regions were detected during rapid ejection, isovolumic relaxation, rapid filling and atrial contraction (Figure 1). In the apical view, during the isovolumic relaxation time (IVRT) healthy subjects showed slow, synchronous outward motion of the septum and the lateral wall with homogeneous color-encoding (blue/green, Figure 2). Analysis of peak velocities revealed low, negative velocities in both the septum and the lateral wall (Figure 3). In patients with a significant luminal narrowing of the LAD myocardial asynchrony was detected during the isovolumic relaxation period: while the septum was moving inwards (red color-encoding with low, positive velocities), the lateral wall was moving outwards (blue/green encoding, low, negative velocities). A representative example of a patient with CAD is given in Figure 4. The M-mode analysis of the abnormally contracting interventricular septum reveals positive peak tissue velocities during the isovolumic relaxation period (Figure 5). In hypertrophic cardiomyopathy, TDE was able to detect an abnormal inward motion of the interventricular septum during IVRT and a delay in the onset of rapid filling (Figure 6). Thus, tissue Doppler echocardiography is a feasible method for the on-line detection of myocardial asynchrony. Sensitivity and specificity of the findings have to be explored in further, prospectively randomized trials.

Cardiomyopathy, Hypertrophic↗
PubMed2004

Geographic methods for understanding and responding to disparities in mammography use in Toronto, Canada.

OBJECTIVE: To use spatial and epidemiologic analyses to understand disparities in mammography use and to formulate interventions to increase its uptake in low-income, high-recent immigration areas in Toronto, Canada. DESIGN: We compared mammography rates in four income-immigration census tract groups. Data were obtained from the 1996 Canadian census and 2000 physician billing claims. Risk ratios, linear regression, multilayer maps, and spatial analysis were used to examine utilization by area for women age 45 to 64 years. SETTING: Residential population of inner city Toronto, Canada, with a 1996 population of 780,000. PARTICIPANTS: Women age 45 to 64 residing in Toronto's inner city in the year 2000. MEASUREMENTS AND MAIN RESULTS: Among 113,762 women age 45 to 64, 27,435 (24%) had received a mammogram during 2000 and 91,542 (80%) had seen a physician. Only 21% of women had a mammogram in the least advantaged group (low income--high immigration), compared with 27% in the most advantaged group (high income--low immigration) (risk ratio, 0.79; 95% confidence interval, 0.75 to 0.84). Multilayer maps demonstrated a low income-high immigration band running through Toronto's inner city and low mammography rates within that band. There was substantial geographic clustering of study variables. CONCLUSIONS: We found marked variation in mammography rates by area, with the lowest rates associated with low income and high immigration. Spatial patterns identified areas with low mammography and low physician visit rates appropriate for outreach and public education interventions. We also identified areas with low mammography and high physician visit rates appropriate for interventions targeted at physicians.

Cluster Analysis↗
PubMed2004

Heat capacity effects associated with the hydrophobic hydration and interaction of simple solutes: a detailed structural and energetical analysis based on molecular dynamics simulations.

We examine the SPCE [H. J. C. Berendsen et al., J. Chem. Phys. 91, 6269 (1987)] and TIP5P [M. W. Mahoney and W. L. Jorgensen, J. Chem. Phys 112, 8910 (2000)] water models using a temperature series of molecular-dynamics simulations in order to study heat-capacity effects associated with the hydrophobic hydration and interaction of xenon particles. The temperature interval between 275 and 375 K along the 0.1-MPa isobar is studied. For all investigated models and state points we calculate the excess chemical potential for xenon employing the Widom particle insertion technique. The solvation enthalpy and excess heat capacity is obtained from the temperature dependence of the chemical potentials and, alternatively, directly by Ewald summation, as well as a reaction field based method. All three methods provide consistent results. In addition, the reaction field technique allows a separation of the solvation enthalpy into solute/solvent and solvent/solvent parts. We find that the solvent/solvent contribution to the excess heat capacity is dominating, being about one order of magnitude larger than the solute/solvent part. This observation is attributed to the enlarged heat capacity of the water molecules in the hydration shell. A detailed spatial analysis of the heat capacity of the water molecules around a pair of xenon particles at different separations reveals that even more enhanced heat capacity of the water located in the bisector plane between two adjacent xenon atoms is responsible for the maximum of the heat capacity found for the desolvation barrier distance, recently reported by Shimizu and Chan [J. Am. Chem. Soc. 123, 2083 (2001)]. The about 60% enlarged heat capacity of water in the concave part of the joint xenon-xenon hydration shell is the result of a counterplay of strengthened hydrogen bonds and an enhanced breaking of hydrogen bonds with increasing temperature. Differences between the two models with respect to the heat capacity in the xenon-xenon contact state are attributed to the different water model bulk heat capacities, and to the different spatial extension of the structure effect introduced by the hydrophobic particles. Similarities between the different states of water in the joint xenon-xenon hydration shell and the properties of stretched water are discussed.

Journal Article↗
PubMed2005

Assessing spatio-temporal variability of risk surfaces using residential history data in a case control study of breast cancer.

BACKGROUND: Most analyses of spatial clustering of disease have been based on either residence at the time of diagnosis or current residence. An underlying assumption in these analyses is that residence can be used as a proxy for environmental exposure. However, exposures earlier in life and not just those in the most recent period may be of significance. In breast cancer, there is accumulating evidence that early life exposures may contribute to risk. We explored spatio-temporal patterns of risk surfaces using data on lifetime residential history in a case control study of breast cancer, and identified elevated areas of risk and areas potentially having more exposure opportunities, defined as risk surfaces in this study. This approach may be more relevant in understanding the environmental etiology of breast cancer, since lifetime cumulative exposures or exposures at critical times may be more strongly associated with risk for breast cancer than exposures from the recent period. RESULTS: A GIS-based exploratory spatial analysis was applied, and spatio-temporal variability of those risk surfaces was evaluated using the standardized difference in density surfaces between cases and controls. The significance of the resulting risk surfaces was tested and reported as p-values. These surfaces were compared for premenopausal and postmenopausal women, and were obtained for each decade, from the 1940s to 1990s. We found strong evidence of clustering of lifetime residence for premenopausal women (for cases relative to controls), and a less strong suggestion of such clustering for postmenopausal women, and identified a substantial degree of temporal variability of the risk surfaces. CONCLUSION: We were able to pinpoint geographic areas with higher risk through exploratory spatial analyses, and to assess temporal variability of the risk surfaces, thus providing a working hypothesis on breast cancer and environmental exposures. Geographic areas with higher case densities need further epidemiologic investigation for potential relationships between lifetime environmental exposures and breast cancer risk. Examination of lifetime residential history provided additional information on geographic areas associated with higher risk; limiting exploration of chronic disease clustering to current residence may neglect important relationships between location and disease.

Journal Article↗
PubMed1994

Spatial and temporal variations in local spike propagation in the myometrium of the 17-day pregnant rat.

Detailed spatial analysis of propagation of individual action potential was performed during spontaneous bursts of activity in the isolated 17-day pregnant rat myometrium. Use was made of high-resolution mapping with simultaneous recordings from 240 extracellular electrodes. Positioning of the electrode assembly by itself did not have any adverse effects, and no differences were found in the period or duration of spontaneous bursts recorded with and without the electrode assembly touching the tissue. The spread of propagation of individual action potentials was reconstructed at several moments during myometrial spike bursts. Both the direction and the sequence of activation of the myometrium were found to be highly variable and depended on 1) the level and spatial dispersion of excitability and 2) whether conduction occurred predominantly in the longitudinal or the circumferential direction. Furthermore, conduction was frequently complicated by the spontaneous occurrence of 1) lines of conduction block, 2) focal sites of pacemaking, or 3) merging of two or more wavelets into a single wave. In contrast, when the myometrium was divided into small segments, activity became much more regular, and both the location of the pacemaker and the direction of propagation were much more stable than in the whole myometrium. In conclusion, spontaneous spatial variations in local spike propagation at the preterm stage could provide for the necessary asynchrony in activation and play a role in the prevention of forceful contractions and premature labor.

Action Potentials↗
PubMed2000

A spatial statistical approach to malaria mapping.

BACKGROUND: Good maps of malaria risk have long been recognized as an important tool for malaria control. The production of such maps relies on modelling to predict the risk for most of the map, with actual observations of malaria prevalence usually only known at a limited number of specific locations. Estimation is complicated by the fact that there is often local variation of risk that cannot be accounted for by the known covariates and because data points of measured malaria prevalence are not evenly or randomly spread across the area to be mapped. METHOD: We describe, by way of an example, a simple two-stage procedure for producing maps of predicted risk: we use logistic regression modelling to determine approximate risk on a larger scale and we employ geo-statistical ('kriging') approaches to improve prediction at a local level. Malaria prevalence in children under 10 was modelled using climatic, population and topographic variables as potential predictors. After the regression analysis, spatial dependence of the model residuals was investigated. Kriging on the residuals was used to model local variation in malaria risk over and above that which is predicted by the regression model. RESULTS: The method is illustrated by a map showing the improvement of risk prediction brought about by the second stage. The advantages and shortcomings of this approach are discussed in the context of the need for further development of methodology and software.

Child↗
PubMed2002

[Towards < >: idea, principle and methodology of design and research results].

< >is the first atlas with spatial analysis methods to study on plague distributions, epidemics, controls, foci characters and their relationships with environment in China. This paper briefly introduces the idea, principle and methodology of its design and the main research results from it. The atlas include ten map groups as general maps, environmental background maps, plague epidemic and foci background maps in the world, maps of plague foci and their environments, epidemic maps, distribution maps of reservoirs, distribution maps of vectors, biotype distribution maps of yersinia pestis, maps of control institutions and control result maps. All map groups are composed together to focus the research on the relationship between plague and its environment for control. The atlas not only expatriates the temporal and spatial distribution of plague in last 200 years in China, but also reveals spatial distribution of plague foci and regional difference of the plasmid combination and biochemical types of yersnia pestis. The close relationship between plague and its geochemical environment (enriched in Fe or Ca) is one of the most important discovers which provide further study and control directions of plague.

Animals↗
PubMed1995

A rapid method for mRNA detection in single-cell biopsies from preimplantation-stage bovine embryos.

Major questions concerning the control of development and gene expression at the cellular level are still unanswered. Nowhere is this more evident than during the earliest stages of development and embryogenesis. This study describes the detection of specific gene transcripts in single cells derived from bovine embryos. Following in vitro fertilization (IVF) and in vitro culture (IVC) of bovine embryos, small groups of cells and even single blastomeres from 32 to 64-cell embryos were micromanipulated into individual tubes for analysis of cytoplasmic RNAs. Reverse transcriptase-PCR was applied to cell lysates for the amplification of beta-actin mRNA transcripts. Primers were designed to flank an intron expected to be present within genomic DNA sequences, thus allowing for simple differentiation between DNA- and RNA-derived amplification products. Using a 50-cycle amplification profile, a 260 bp band could be seen as a PCR product derived from a single blastomere following electrophoresis in an ethidium bromide-stained agarose gel. The identity of the band was verified by DNA sequence determination and diagnostic restriction digestion. Lysates derived from single blastomeres in this way have been used for simultaneously phenotyping multiple RNA products. This capability allows the spatial analysis of gene expression and development within embryos from the earliest stages of cellular differentiation.

Journal Article↗