Jean-Pierre Tissier

Fouling of Heat Transfer Surfaces Related to β-Lactoglobulin Denaturation During Heat Processing of Milk

Denaturation of β‐lactoglobulin during heating of milk in a plate heat exchanger has been investigated as an important factor in fouling the heat transfer surface. Using, on one hand, data on chemical composition of deposits obtained from biochemical analysis technics and, on the other hand, kinetic data of β‐Iactoglobulin denaturation, the distribution profile of deposits along the surface and the experimental fouling curves can be adequately predicted.

A cytometric study of the red blood cells in Gaucher disease reveals their abnormal shape that may be involved in increased erythrophagocytosis

Background: Gaucher disease is a sphingolipidosis caused by a deficiency of the enzyme glucocerebrosidase. Macrophages transform into pathogenic Gaucher cells following the phagocytosis of red blood cells (RBCs) and subsequent accumulation of glucosylceramide. Enhanced erythrophagocytosis is one feature of the disease indicating abnormal macrophage‐RBC interactions. We hypothesized that the erythrophagocytosis observed in Gaucher disease may be at least partly due to abnormalities in the RBCs themselves.

Interaction of human Tamm-Horsfall glycoprotein with Bordetella pertussis toxin

Tamm-Horsfall glycoprotein (THP), which is synthesized by renal tubular cells, is the most abundant protein in normal human urine. Although its physiological function remains unclear, it has been proposed that THP may act as a defence factor against urinary tract infections by inhibiting the binding of S- and P-fimbriated Escherichia coli to renal epithelial cells. Because THP-related proteins are also found in the superficial layers of the oral mucosa, the authors investigated the ability of THP to interfere with the cytoadherence of pathogenic bacteria that colonize mucosal surfaces other than those of the urogenital tract. In this report, it is shown that THP binds to virulent Bordetella pertussis and reduces its adherence to both renal and pulmonary epithelial cells. This cytoadherence inhibitory effect was not observed with a B. pertussis mutant lacking the pertussis toxin (PTX) operon, and was dependent on the direct interaction of THP with the S2 subunit within the PTX B oligomer. The authors also show that the glycosylation moiety of THP is crucial for its binding to PTX. The THP-PTX interaction was exploited to develop an affinity chromatography method that allows a one-step purification of active PTX. These observations suggest that besides its anti-adherence activity, THP may also trap toxins produced by pathogenic bacteria that colonize mucosal surfaces.

Cloning and characterization of WMSU1, a Williopsis saturnus var. mrakii gene encoding a new yeast SUN protein involved in the cell wall structure

SUN proteins of Saccharomyces cerevisiae have been defined on the basis of high homologies in their C‐terminal domain. Recently, two of these four proteins were shown to be involved in cell wall morphogenesis (Mouassite et al., 2000a ). In the present study, we have isolated WMSU1 (Accession No. AF418983), a new SUN‐related gene, from W. saturnus var. mrakii MUCL 41968. Sequencing of the gene revealed an open reading frame coding for 402 amino acids. The predicted amino acid sequence of WMSU1 is closely related to the S. cerevisiae SUN proteins and to other yeast proteins involved in cell wall metabolism. WMSU1 is proposed to encode a cell wall protein since its predicted product contains a signal sequence, a Kex2p cleavage site and a serine/threonine‐rich N‐terminal domain. Southern blot analysis of the W. saturnus var. mrakii MUCL 41968 genome using the highly conserved domain of WMSU1 as a probe suggested that the isolated gene belongs to a multigenic family. Expression of WMSU1 in E. coli led to a 45 kDa protein, which appeared to be toxic to this host. Scanning electron microscopy analysis of a recombinant S. cerevisiae producing Wmsu1p showed that this strain exhibited an altered cell wall, thus pointing to a probable role of this protein in the cell wall structure. Copyright