Biomedical subjects

C Vogl

Publications and source records attributed to C Vogl.

At least 19 recordsLinked to original sources

PubMed2006

Hybrid origin and differentiation of two tetraploid Achillea species in East Asia: molecular, morphological and ecogeographical evidence.

Achillea (Asteraceae-Anthemideae) offers classical models for speciation by hybridization and polyploidy. Here, we test the suspected allotetraploid origin of two species, Achillea alpina and Achillea wilsoniana between phylogenetically distinct lineages in East Asia. A total of 421 AFLP bands from 169 individuals and 19 populations of five 2x- and two 4x-species were obtained. The data set was analysed with a newly developed model that accounts for polyploidy and assumes lack of recombination between the parental chromosome sets (i.e. disomic inheritance). A. alpina and A. wilsoniana then appear to be allotetraploids between Achillea acuminata-2x (sect. Ptarmica) and Achillea asiatica-2x (sect. Achillea). The two 4x-species share 44% and 48% of their AFLP bands with A. acuminata-2x, and 39% and 38% with A. asiatica-2x, respectively. Eight plastid haplotypes (A-H) were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analyses. A. alpina-4x and A. wilsoniana-4x share haplotype F only with A. asiatica-2x. This is consistent with the hybrid origin(s) involving the latter as the maternal ancestor. This result corroborates our previous DNA sequence data, where A. alpina-4x and A. wilsoniana-4x are also placed close to A. asiatica-2x. Morphology, ecology, and amplified fragment length polymorphism (AFLP) profiles of the two 2x-species are distinct, whereas the two 4x-species, grouped as A. alpina aggregate, form a nearly continuous link between them. Considering all evidence, this 4x-aggregate is regarded as the product of a hybridization between genetically distant 2x-ancestors limited to China and adjacent areas: one A. acuminata-like, and the other A. asiatica-like. The allopolyploid A. alpina agg. exhibits considerable morphological variation and ecological flexibility, and has expanded throughout eastern Asia and to northern North America, far beyond the ranges of their presumed 2x-ancestors.

Achillea↗

PubMed2006

Analysis of microsatellite variation in Pinus radiata reveals effects of genetic drift but no recent bottlenecks.

Most conifer species occur in large continuous populations, but radiata pine, Pinus radiata, occurs only in five disjunctive natural populations in California and Mexico. The Mexican island populations were presumably colonized from the mainland millions of years ago. According to Axelrod (1981), the mainland populations are relicts of an earlier much wider distribution, reduced some 8,000 years ago, whereas according to Millar (1997, 2000), the patchy metapopulation-like structure is typical of the long-term population demography of the species. We used 19 highly polymorphic microsatellite loci to describe population structure and to search for signs of the dynamics of population demography over space and time. Frequencies of null alleles at microsatellite loci were estimated using an approach based on the probability of identity by descent. Microsatellite genetic diversities were high in all populations [expected heterozygosity (H(e)) = 0.68-0.77], but the island populations had significantly lower estimates. Variation between loci in genetic differentiation (F(ST)) was high, but no locus deviated statistically significantly from the rest at an experiment wide level of 0.05. Thus, all loci were included in subsequent analysis. The average differentiation was measured as F(ST) = 0.14 (SD 0.012), comparable with earlier allozyme results. The island populations were more diverged from the other populations and from an inferred common ancestral gene pool than the mainland ones. All populations showed a deficiency of expected heterozygosity given the number of alleles, the mainland populations more so than the island ones. The results thus do not support a recent important contraction in the mainland range of radiata pine.

California↗

PubMed2005

A fully Bayesian model to cluster gene-expression profiles.

MOTIVATION: With cDNA or oligonucleotide chips, gene-expression levels of essentially all genes in a genome can be simultaneously monitored over a time-course or under different experimental conditions. After proper normalization of the data, genes are often classified into co-expressed classes (clusters) to identify subgroups of genes that share common regulatory elements, a common function or a common cellular origin. With most methods, e.g. k-means, the number of clusters needs to be specified in advance; results depend strongly on this choice. Even with likelihood-based methods, estimation of this number is difficult. Furthermore, missing values often cause problems and lead to the loss of data. RESULTS: We propose a fully probabilistic Bayesian model to cluster gene-expression profiles. The number of classes does not need to be specified in advance; instead it is adjusted dynamically using a Reversible Jump Markov Chain Monte Carlo sampler. Imputation of missing values is integrated into the model. With simulations, we determined the speed of convergence of the sampler as well as the accuracy of the inferred variables. Results were compared with the widely used k-means algorithm. With our method, biologically related co-expressed genes could be identified in a yeast transcriptome dataset, even when some values were missing. AVAILABILITY: The code is available at http://genome.tugraz.at/BayesianClustering/

Algorithms↗

PubMed2002

QTL analysis in arbitrary pedigrees with incomplete marker information.

Mapping quantitative trait loci (QTL) in arbitrary outbred pedigrees is complicated by the combinatorial possibilities of allele flow relationships and of the founder allelic configurations. Exact methods are only available for rather short and simple pedigrees. Stochastic simulation using Markov chain Monte Carlo (MCMC) integration offers more flexibility. MCMC methods are less natural in a frequentist than in a Bayesian context, which we therefore adopt. Among the MCMC algorithms for updating marker locus genotypes, we implement the descent-graph algorithm. It can be used to update marker locus allele flow relationships and can handle arbitrarily complex pedigrees and missing marker information. Compared with updating marker genotypic information, updating QTL parameters, such as position, effects, and the allele flow relationships is relatively easy with MCMC. We treat the effect of each diploid combination of founder alleles as a random variable and only estimate the variance of these effects, ie, we model diploid genotypic effects instead of the usual partition in additive and dominance effects. This is a variant of the random model approach. The number of QTL alleles is generally unknown. In the Bayesian context, the number of QTL present on a linkage group can be treated as variable. Computer simulations suggest that the algorithm can indeed handle complex pedigrees and detect two QTL on a linkage group, but that the number of individuals in a single extended family is limited to about 50 to 100 individuals.

Chromosome Mapping↗

PubMed2000

Maximum likelihood analysis of quantitative trait loci under selective genotyping.

Selective genotyping is a cost-saving strategy in mapping quantitative trait loci (QTLs). When the proportion of individuals selected for genotyping is low, the majority of the individuals are not genotyped, but their phenotypic values, if available, are still included in the data analysis to correct the bias in parameter estimation. These ungenotyped individuals do not contribute much information about linkage analysis and their inclusion can substantially increase the computational burden. For multiple trait analysis, ungenotyped individuals may not have a full array of phenotypic measurements. In this case, unbiased estimation of QTL effects using current methods seems to be impossible. In this study, we develop a maximum likelihood method of QTL mapping under selective genotyping using only the phenotypic values of genotyped individuals. Compared with the full data analysis (using all phenotypic values), the proposed method performs well. We derive an expectation-maximization (EM) algorithm that appears to be a simple modification of the existing EM algorithm for standard interval mapping. The new method can be readily incorporated into a standard QTL mapping software, e.g. MAPMAKER. A general recommendation is that whenever full data analysis is possible, the full maximum likelihood analysis should be performed. If it is impossible to analyse the full data, e.g. sample sizes are too large, phenotypic values of ungenotyped individuals are missing or composite interval mapping is to be performed, the proposed method can be applied.

Algorithms↗

PubMed2000

Multipoint mapping of viability and segregation distorting loci using molecular markers.

In line-crossing experiments, deviations from Mendelian segregation ratios are usually observed for some markers. We hypothesize that these deviations are caused by one or more segregation-distorting loci (SDL) linked to the markers. We develop both a maximum-likelihood (ML) method and a Bayesian method to map SDL using molecular markers. The ML mapping is implemented via an EM algorithm and the Bayesian method is performed via the Markov chain Monte Carlo (MCMC). The Bayesian mapping is computationally more intensive than the ML mapping but can handle more complicated models such as multiple SDL and variable number of SDL. Both methods are applied to a set of simulated data and real data from a cross of two Scots pine trees.

Alleles↗

PubMed1998

Studies on canine bone marrow long-term culture: effect of stem cell factor.

Long-term culture of canine marrow cells allows in vitro studies of the hematopoietic system of the dog and characterization of early progenitor cells. Colonies of fresh marrow cells grew equally good in both agar or methylcellulose supplemented with fetal calf serum, while colonies of long-term cultures required agar-based medium containing human serum. Optimum colony growth was obtained when stem cell factor (SCF) and granulocyte-macrophage-colony-stimulating factor (GM-CSF) were used as growth stimuli of colony forming units (CFU). Similar results were achieved with several cell culture media. Addition of hydrocortisone to long-term cultures improved clonogenic growth of cultured cells. Addition of 2-mercaptoethanol had no effect. Strong differences were observed in long-term culture with different horse serum lots and the addition of fetal calf serum to long-term culture suppressed CFU growth of cultured cells. Recharging of cultures with fresh marrow cells on day 7 of culture improved CFU growth only in the following week but had little effect on the outcome. Adding SCF to long-term cultures led to differentiation of more primitive cells and destruction of the stromal layer. Investigation of purified and cultured cell populations was possible when preestablished long-term cultures as stromal layers were used. Loss of long-term culture-initiating ability could be demonstrated in this system with lineage negative marrow cells expanded ex vivo with SCF and GM-CSF.

Animals↗

PubMed1998

Immunohistochemical characterization of inflammatory cells in brains of dogs with granulomatous meningoencephalitis.

The inflammatory cells of eleven dogs with canine granulomatous meningoencephalitis were characterized immunohistochemically. Macrophages were identified by antibodies directed against lysozyme and the DH82 antigen (expressed by cells of a malignant histiocytosis). T cells were demonstrated by CD3, CD43, and CD45R antigen, and B cells by immunoglobulin G and immunoglobulin M expression. Furthermore, staining for the major histocompatibility complex (MHC) class II antigen was evaluated. Diseased animals ranged from 1 to 9 years of age. Small and medium-sized breeds were affected predominantly. Lesions were widespread and localized mainly in the brain stem, less frequently in the cerebrum or cerebellum. Alterations were represented by perivascular cuffs, parenchymal granulomas, and leptomeningeal infiltrates. Lymphocytes and macrophages comprised the dominant cell populations; their percentage varied substantially between different animals and between sections from the same individual. Immunohistochemically, the bulk of lymphocytes were CD3 antigen-positive T cells, while only a few cells were CD43 and CD45R antigen-positive or were classified as B cells. The majority of macrophages expressed both lysozyme and DH82 antigen; however, some were positive for only one antigen. MHC class II antigen-expression, observed only within and in close proximity to the lesions, was found on all inflammatory cells, pericytes/endothelial cells, and microglia. Results were negative for canine distemper virus antigen and nucleoprotein mRNA, rabies virus antigen, fungi, bacteria, and protozoal agents. This immunomorphologic study reveals that inflammatory lesions in canine granulomatous meningoencephalitis consist of a heterogeneous population of MHC class II antigen-positive macrophages and predominantly CD3 antigen-positive lymphocytes. The data suggest a T cell-mediated delayed-type hypersensitivity of an organ-specific autoimmune disease as a possible pathogenic mechanism for this unique canine brain lesion.

Animals↗

PubMed1997

Acute non-insulin-like stimulation of rat muscle glucose metabolism by troglitazone in vitro.

1. The direct short-term effects of troglitazone on parameters of glucose metabolism were investigated in rat soleus muscle strips. 2. In muscle strips from Sprague-Dawley rats, troglitazone (3.25 micromol l(-1)) increased basal and insulin-stimulated glucose transport by 24% and 41%, respectively (P<0.01 each). 3. In the presence of 5 nmol l(-1) insulin, stimulation of glucose transport by 3.25 micromol l(-1) troglitazone was accompanied by a 36% decrease in glycogen synthesis, while glycolysis was increased (112% increase in lactate production) suggesting a catabolic response of intracellular glucose handling. 4. Whereas insulin retained its stimulant effect on [3H]-2-deoxy-glucose transport in hypoxia-stimulated muscle (by 44%; c.p.m. mg(-1) h(-1): 852+/-77 vs 1229+/-75, P<0.01), 3.25 micromol l(-1) troglitazone failed to increase glucose transport under hypoxic conditions (789+/-40 vs 815+/-28, NS) suggesting that hypoxia and troglitazone address a similar, non-insulin-like mechanism. 5. No differences between troglitazone and hypoxia were identified in respective interactions with insulin. 6. Troglitazone acutely stimulated muscle glucose metabolism in a hypoxia/contraction-like manner, but it remains to be elucidated whether this contributes to the long-term antidiabetic and insulin enhancing potential in vivo or is to be regarded as an independent pharmacological effect.

Animals↗

PubMed1997

Polymorphism and locus-specific effects on polymorphism at microsatellite loci in natural Drosophila melanogaster populations.

We have studied the natural variation at microsatellite loci in two African and five non-African populations of Drosophila melanogaster. Ten dinucleotide simple sequence loci were cloned from chromosomally mapped P1 clones and typed for single individuals from isofemale lines of the respective populations. We find that the African populations harbor the largest degree of diversity, while the non-African populations show a lower diversity. This supports previous results that D. melanogaster originated in Africa and spread across the rest of the world in historic times. Using genetic distance measures, we find also a distinct population subdivision between the non-African populations. Most interestingly, we find for some loci in some populations a strongly reduced variability, which cannot be explained by bottleneck effects. Employing a conservative test based on the variance in repeat number, we find that at least one locus in one population deviates significantly from the expectations of mutation-drift equilibrium. We suggest that this may be due to a recent selective sweep in this chromosomal region that may have been caused by a linked locus that was involved in local adaptation of the population.

Adaptation, Physiological↗

PubMed1997

Immune phenotype of canine hematopoietic progenitor cells.

The immune phenotype of canine hematopoietic progenitor cells was studied by immunoseparation and culturing of separated cells. Two separation methods were used, the magnetic cell sorting system (MACS) and the fluorescence activated cell sorter (FACS). For separation rat anti dog antibodies Dog 13 and Dog 14 directed against Thy-1, and Dog 26 as well as cross-reactive mouse anti human antibodies IOT2a and 7.2 directed against MHC class II were used. Separated cell populations were cultured in semisolid agar before and after long-term culture on a pre-established irradiated stromal cell layer. After 28 days, adherent and nonadherent cells were harvested from long-term culture. The MACS system allowed separation of cells into positive and negative fractions. Long-term culture-initiating cells (LTC-IC) were found in both the Thy-1+ and the Thy-1- fraction, but the content of LTC-IC was higher in the Thy-1+ fraction. The MACS system did not allow separation of progenitor cells according to the expression of MHC class II antigen detected by Dog 26 and the cross-reactive antibodies IOT2a and 7.2. In contrast to the MACS system the FACS allowed separation of negative, low-positive and high-positive cell populations. Low-positive fractions were well defined for Thy-1 and less well defined for MHC class II. CFU before and after long-term culture were exclusively observed in the low positive fraction (Thy-1(lo+)). Using MHC class II antibody Dog 26 LTC-IC were found mainly in the negative and low positive fraction, and CFU were observed mainly in the low and high positive fraction. In conclusion pluripotent canine hematopoietic precursor cells are low positive for Thy-1 and for MHC class II. In this respect canine hematopoietic progenitor cells are comparable to those of mouse and man.

Animals↗

PubMed1996

Insulin-like vs. non-insulin-like stimulation of glucose metabolism by vanadium, tungsten, and selenium compounds in rat muscle.

The direct impact of vanadate, tungstate, selenate, and selenite on glucose metabolism of isolated rat soleus muscle was investigated. All compounds stimulated glucose transport, but only vanadate exerted an insulin-like effect on glycogen synthesis (mumol glucose into glycogen*g-1*h-1: control 1.43 +/- 0.11 vs. 1 mmol/l vanadate, 2.08 +/- 0.11, p < 0.0001), which was more distinct in the presence of 1 mmol/l H2O2 (control, 1.44 +/- 0.13 vs. 1 mmol/l vanadate, 3.49 +/- 0.12, p < 0.001). Glucose handling of muscles exposed to tungstate, selenate, or selenite resembled that of hypoxic muscle, i.e. the induced rise in glucose uptake was inhibited by dantrolene and associated with high rates of glycolysis and rapid glycogen depletion (glycogen content after incubation, mumol glucosyl units/g: control, 16.2 +/- 0.7 vs. hypoxia, 2.7 +/- 0.5, p < 0.0001; control, 17.0 +/- 0.5 vs. 100 mmol/l tungstate, 5.5 +/- 0.4, p < 0.001; control, 16.2 +/- 0.7 vs. 100 mmol/l selenate, 1.5 +/- 0.3, and vs. 300 mumol/l selenite, 1.7 +/- 0.3, p < 0.0001 each). The results suggest that vanadate (and more pronounced it's peroxides) exerts true insulin-like action on isolated muscle glucose metabolism, whereas tungsten and selenium salts trigger glucose transport in association with a catabolic response, which may represent an unspecific response to toxic/osmotic stress.

Androstadienes↗

PubMed1995

Hormone gradients and cartilage cell kinetics.

We present a model of growth control in mammalian cartilage growth plates by hormones. The model is based on the distribution of insulin-like growth factors I and II (IGF-I and IGF-II) and their receptors, and assumes that a hormone-receptor complex of IGF controls cells proliferation. A system of differential equations is derived and solved with simplifications in extreme cases, for the one-dimensional time independent case. Even if opposite extremes, such as proliferation control by factors extrinsic to the cell versus intrinsic to the cell, are assumed, similar distributions of hormones and proliferating cells are produced. Hence, choice between alternative models of growth control must be based on empirical observations. On the positive side, similarities between our model for cartilage growth and other models for differentiation and proliferation are evident and might be exploited for unifying these systems on an abstract level.

Animals↗

PubMed1994

Developmental quantitative genetic models of evolutionary change.

Discussions about evolutionary change in developmental processes or morphological structures are predicated on specific quantitative genetic models whose parameters predict whether evolutionary change can occur, its relative rate and direction, and if correlated change will occur in other related and unrelated structures. The appropriate genetic model should reflect the relevant genetical and developmental biology of the organisms, yet be simple enough in its parameters so that deductions can be made and hypotheses tested. As a consequence, the choice of the most appropriate genetic model for polygenically controlled traits is a complex tissue and the eventual choice of model is often a compromise between completeness of the model and computational expediency. Herein, we discuss several developmental quantitative genetic models for the evolution of development and morphology. The models range from the classical direct effects model to complex epigenetic models. Further, we demonstrate the algebraic equivalency of the Cowley and Atchley epigenetic model and Wagner's developmental mapping model. Finally, we propose a new multivariate model for continuous growth trajectories. The relative efficacy of these various models for understanding evolutionary change in developmental and morphological traits is discussed.

Animals↗

PubMed1993

The epigenetic influence of growth hormone on skeletal development.

We studied the epigenetic effect of growth hormone using mice that were transgenic for a sheep metallothionein 1a-sheep growth hormone, which was expressed beginning at 21 days postnatal age. The impact of exogenous growth hormone (GH) on various skeletal traits with special emphasis on the mandible was examined by conventional statistical analysis and finite element scaling analysis. In long bones, growth hormone enhances the proliferation rate of cartilage cells in the growth plate and should thus lead to increased lengths. Further, growth hormone is known to increase muscle mass. Our results are consistent with these developmental considerations. We found that the lengths of long bones increased in the transgenic mice compared to the control mice, while the differences in long bone width were less pronounced. In the mandible and skull, the impact of GH is most pronounced in areas of major muscle attachment, i.e., the proximal part of the mandible and the occipital and malar bones in the skull.

Animals↗

PubMed1991

[Proton spin tomography in HIV 1-induced diseases in head and neck region].

Most HIV-infected patients present with associated diseases (inflammations, hyperplastic disorders of the lymphatic tissue and malignancies) in the head and neck region. Speculum, endoscopy, ultrasound and computed tomography are important tools in the diagnostic management of HIV presentations. Moreover, MR is known to be an excellent technique especially in the evaluation of soft tissue disorders. -A prospective study of 23 out of 161 HIV-seropositive patients was performed to determine the efficiency of magnetic resonance imaging in HIV-related disorders. T1- and T2-sequences, as well as the contrast medium uptake (Gd-DTPA), presentation in three planes and the morphology of the tissue were useful parameters to distinguish the different HIV-related diseases (lymphatic hyperplasia, inflammation, Kaposi's sarcoma, Hodgkin's und Non-Hodgkin lymphoma, lymphoepithelial cysts and carcinoma) in most cases even prior to histological examination. -MR proved to be a significant non-invasive diagnostic tool especially in HIV-associated soft tissue disorders in the head and neck.

Adult↗

PubMed1990

Effect of the PAF antagonist BN 52021 in ovine endotoxin shock.

It has been reported that a platelet-activating factor (PAF) antagonist ONO-6240 had little effect on pulmonary hypertension and lung lymph in sheep injected with endotoxin lipopolysaccharide (LPS); consequently we evaluated a new PAF antagonist, BN 52021. Twelve adult sheep were surgically prepared for chronic study including lung lymph drainage. LPS (S. abortus equii, 36 ng/kg/h over 7 h) was then administered with (BN group) or without (control group) infusion (1 h before LPS) of the PAF antagonist BN 52021 (4 mg/kg/30 min). Comparison of the hemodynamic data between the control group and the BN group reveals an almost identical pattern. In contrast, we find differences in the pulmonary response of the two experimental groups. The early elevation of pulmonary artery pressure after LPS administration is less in the treatment group, as is the duration of pulmonary hypertension. Similarly, thromboxane levels are lower in the treated animals. The increases in lymph flow (LQ) and transvascular protein clearance (L/P X LQ) as well as the protein flux were less prominent in the treatment group. The mean lymph flow per hour was significantly higher in the control group. The mean lymph flow per hour was significantly higher in the control group, as were the corresponding parameters for clearance and protein flux. Thus the pulmonary vasculature and lung fluid balance disruption produced by LPS was markedly reduced by treatment with the PAF blocker.

Animals↗

PubMed1990

Net inotropic plasma activity in canine hypovolemic traumatic shock: low molecular weight plasma fraction after prolonged hypotension depresses cardiac muscle performance in vitro.

Numerous studies report controversial results about the occurrence and role of cardiodepressant substances in various forms of circulatory shock. We investigated the net inotropic effect of the low molecular weight fraction (mol wt less than or equal to 1,000) of plasma in prolonged canine hypovolemic traumatic shock using an in vitro guinea pig papillary muscle assay (isotonic mode). The shock plasma fractions (ultrafiltrates) after 4 hr of hypotension (mean arterial blood pressure 40-50 mm Hg) and immediately post-reinfusion significantly depressed papillary muscle function (P less than .02). The extent of papillary muscle shortening was decreased by 49.5 +/- 9.9% in pre- and 50.6 +/- 10.0% in post-reinfusion plasma ultrafiltrates (mean values +/- standard error of the mean; n = 6 shock experiments). In contrast, both the plasma ultrafiltrates from ten non-anesthetized healthy dogs and the control ultrafiltrates obtained prior to onset of shock in the experiments (-6.4 +/- 2.6; n = 6) induced no significant change of the in vitro performance of papillary muscle contraction. These results were achieved with plasma fractions in which ionized calcium and pH were adjusted to concentrations equivalent to the bioassay solution. Lactate acidosis and severe hypoglycemia (1.97 +/- 0.43 mM post-reinfusion) occurred in the shock experiments. Lack of energy substrate (glucose) was not responsible for the in vitro depression. Four depressive shock ultrafiltrates with glucose concentrations adjusted to control ultrafiltrate levels induced a 66.6 +/- 8.8% decrease in the extent of papillary muscle shortening. These results suggest that the possible occurrence of high net negative inotropic activity in plasma, especially just post-reinfusion, may play a role in the pathogenesis of irreversible circulatory shock.

Animals↗