Cryptosporidium parvum infection requires host cell actin polymerization

The intracellular protozoan parasite Cryptosporidium parvum accumulates host cell actin at the interface between the parasite and the host cell cytoplasm. Here we show that the actin polymerizing proteins Arp2/3, vasodilator-stimulated phosphoprotein (VASP), and neural Wiskott Aldrich syndrome protein (N-WASP) are present at this interface and that host cell actin polymerization is necessary for parasite infection.     

Comparison of six Australian isolates of Bovine herpes virus 2 based on UL24 gene after a passage in MDBK cells

A region of the UL24 gene of six Australian field isolates of Bovine herpesvirus 2 (BHV-2) was sequenced after a passage in Madin-Darby bovine kidney (MDBK) cells by polymerase chain reaction (PCR). While the PCR product covered the first half of the UL24 gene, a particular interest was focused on the 274-297 nucleotide (nt) region in which a two nt deletion had previously been detected in the BHM-1 strain of BHV-2. Most isolates tested did not generate any defective UL24 genes during the passage. However, a third of the UL24 genes of BHM-1 strain contained the two nts deletion, but only when a high multiplicity of infection (MOI) was used. Also in the isolate 554 at least a half of the UL24 genes were found to be altered independently of the MOT used. These UL24 genes had an insertion of four nts within the 274-297 nt region. The predicted truncation of the UL24 protein of both viruses occurred at the same stop codon. The region of the gene in which these mutations of the UL24 gene occurred is common to all herpesviruses.     

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Coping with dental treatment: The potential impact of situational demands

Coping strategies and anxiety responding of dental patients were studied in order to test the generalizability of previous findings based on volunteer blood donors. State and trait coping measures were administered once, and a process coping scale was administered at three points throughout treatment. Self-report, behavioral observation, and psychophysiological measures of anxiety were sampled for the same periods as process coping. Findings included the replication of a negative relationship between avoidant coping and patient anxiety ratings. Fluctuations in coping were evident across periods, and impact of situational demands and constraints was introduced as an explanation for these variations. A method for direct assessment of coping consistency was introduced. On the basis of the replicable associations with anxiety measures, the ability to detect changes in coping within a situation, and the ability to provide direct evidence of coping consistency, the use of process methodology for coping assessment is encouraged.This research was conducted while the first author was supported by funding from the Medical Research Council of Canada.Portions of this research were presented at the annual convention of the Society of Behavioral Medicine, Philadelphia, 1984.     

SV40-related T-antigen expression in human meningiomas with normal and G-22-monosomic karyotype.

Six of 16 meningiomas tested in early subcultures by indirect immunofluorescence showed SV40 T-antigen. Two different antisera specific for T-antigen were used. One serum gave a positive reaction with six tumours and the other with only two. In one T-antigen positive meningioma, the typical nuclear fluorescence changed, beginning with the second subculture, into an unusual brilliant granular pattern irregularly distributed over the nuclei. In six meningiomas, a specific chromosome aberration (monosomy G 22) was established. However, up to now, no clear correlation between karyotype and T-antigen expression could be found: cells from three meningiomas with positive reactions had normal karyotypes, whereas those from three tumours with typical chromosome loss showed no T-antigen.     

Imbalance of matrix metalloproteinase-1 and tissue inhibitor of metalloproteinases: a novel approach for explaining the parenchymal liquefaction of the septic spleen?

OBJECTIVE: The causal pathophysiological mechanisms involved in the parenchymal liquefaction of the septic spleen are still far from clear. The balance between matrix metalloproteinases (MMPs) and their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs), is largely responsible for the remodelling of tissues. Deregulation of this balance is a characteristic of extensive tissue degradation in certain chronic inflammatory diseases. METHODS: This study focuses on a search for alterations in the balance between MMP-1 (interstitial collagenase) and TIMP-1 by means of immunostaining, by immunoblotting, and by gel zymography. RESULTS: We found a deregulation of the balance between MMP-1 and TIMP-1 in the septic spleen in favor of the active form of MMP-1. CONCLUSION: Our findings suggest that active MMP-1 is involved in collagenolytic extracellular matrix breakdown in the septic spleen.     

Selectivity of excitotoxic mechanisms in Alzheimer's disease

Dysfunction of glutamatergic neurons in Alzheimer's disease may actually participate in some of the neurodegenerative processes via potential excitotoxic mechanisms. Two hypotheses are advanced which describe how a generalized excitotoxic mechanism could interact with unique metabolic properties of specific cell types leading to their selective vulnerability in Alzheimer's disease.     

Characterization of SV40 enhancer motifs involved in positive and negative regulation of the constitutive late promoter activity; effect of T-antigen.

By analyzing the late promoter activity of a series of nonreplicative recombinants mutated within the different enhancer motifs of SV40 we identified both positive and negative regulatory elements. In the absence of T-antigen, the motifs Sph and/or octamer, and to a lesser extent the motifs GTI and P, account for the constitutive expression of the late promoter. The motif GTII overlaps elements that negatively regulate the expression of the late promoter. These results indicate that the late promoter is down-regulated not only at the level of the GC motifs but also at the enhancer level. Moreover, we showed that T-antigen interacts with both positive and negative regulatory elements.