Biomedical subjects

J Hooyberghs

Publications and source records attributed to J Hooyberghs.

5 recordsLinked to original sources

PubMed2001

Generalized contact process with n absorbing states.

We investigate the critical properties of a one-dimensional stochastic lattice model with n (permutation symmetric) absorbing states. We analyze the cases with n</=4 by means of the nonhermitian density-matrix renormalization group. For n=1 and n=2 we find that the model is, respectively, in the directed percolation and parity conserving universality class, consistent with previous studies. For n=3 and n=4, the model is in the active phase in the whole parameter space and the critical point is shifted to the limit of one infinite reaction rate. We show that in this limit, the dynamics of the model can be mapped onto that of a zero temperature n-state Potts model. On the basis of our numerical and analytical results, we conjecture that the model is in the same universality class for all n>/=3 with exponents z=nu( ||)/nu( perpendicular)=2, nu( perpendicular)=1, and beta=1. These exponents coincide with those of the multispecies (bosonic) branching annihilating random walks. For n=3 we also show that, upon breaking the symmetry to a lower one (Z2), one gets a transition either in the directed percolation, or in the parity conserving class, depending on the choice of parameters.

Journal Article↗

PubMed2001

One-dimensional contact process: duality and renormalization.

We study the one-dimensional contact process in its quantum version using a recently proposed real-space renormalization technique for stochastic many-particle systems. Exploiting the duality and other properties of the model, we can apply the method for cells with up to 37 sites. After suitable extrapolation, we obtain exponent estimates that are comparable in accuracy with the best known in the literature.

Journal Article↗

PubMed1990

Sites of replication of a porcine respiratory coronavirus in 5-week-old pigs with or without maternal antibodies.

On farms, where the porcine respiratory coronavirus (PRCV) is enzootic, pigs usually become infected between 5 and 10 weeks of age while losing their maternal antibodies. It was examined whether PRCV replicates in the small intestine in such pigs. This point is important since intestinal replication with PRCV might induce immunity against TGEV not only by stimulating mucosal intestinal immunity, but also by the induction of a lactogenic IgA response at later age via the gut-mammary link. Five week old pigs with and without maternal antibodies were inoculated by aerosol or directly into the intestinal lumen. In aerosol inoculated pigs, virus replication was observed to high titres in the respiratory tract. Replication occurred in epithelial cells of nasal mucosa, trachea, bronchi bronchioli and alveoli and in alveolar macrophages. Small amounts of virus produced in the respiratory tract were ingested, but no intestinal replication of PRCV was demonstrated. Differences were not observed in virus titre and sites of replication in seronegative pigs compared to those in pigs with maternal antibodies. Upon inoculation of 10(5) or 10(7) TCID50 directly into the lumen of the cranial jejunum, no intestinal replication could be demonstrated.

Animals↗

PubMed1990

Sites of replication of a porcine respiratory coronavirus related to transmissible gastroenteritis virus.

A porcine respiratory coronavirus (PRCV) was inoculated by aerosol into nine hysterectomy-derived and colostrum-deprived pigs at the age of one week. They were killed at different times after inoculation and tissues were sampled for virus isolation and immunofluorescence. Results indicate that virus replicated to high titres in the respiratory tract. Replication mainly occurred in alveolar cells but also in epithelial cells of nasal mucosa, trachea, bronchi, bronchioli, in alveolar macrophages and in tonsils. After primary replication in the respiratory tract, viraemia occurred. Virus also reached the gastrointestinal tract after swallowing. Subsequently, PRCV was observed to replicate in the ileum. The infection spread within a few days from the ileum to the duodenum. Replication in the small intestine remained limited to a few cells located in or underneath the epithelial layer of villi and, or, crypts. The cell type could not be identified. Virus was isolated from mesenteric lymph nodes in all pigs, but immunofluorescence was not observed. Results show that small changes in molecular structure between transmissible gastroenteritis virus and PRCV resulted in important changes in host cell tropism.

Animals↗

PubMed1989

A competitive inhibition ELISA for the differentiation of serum antibodies from pigs infected with transmissible gastroenteritis virus (TGEV) or with the TGEV-related porcine respiratory coronavirus.

A competitive inhibition ELISA was developed to detect non-neutralizing antibodies to the peplomer protein of transmissible gastroenteritis virus (TGEV) in porcine sera using a monoclonal antibody as an indicator. It was demonstrated that field strains of the TGEV-related porcine respiratory coronavirus (PRCV) did not induce this antibody, whereas the Miller strain and field strains of TGEV did. The sensitivity of the competitive inhibition ELISA appeared to be similar to that of the virus neutralization (VN) test. The test enables differentiation of pigs which were previously infected with TGEV or PRCV and which cannot be distinguished by the classical anti-TGEV neutralization test. The present test is useful for selective serodiagnosis.

Animals↗