A reexamination of the role of the RAD52 gene in spontaneous mitotic recombination

Summary The RAD52 gene is required for much of the recombination that occurs in Saccharomyces cerevisiae. One of the two commonly utilized mutant alleles, rad52-2, increases rather than reduces mitotic recombination, yet in other respects appears to be a typical rad52 mutant allele. This raises the question as to whether RAD52 is really necessary for mitotic recombination. Analysis of a deletion/insertion allele created in vitro indicates that the null mutant phenotype is indeed a deficiency in mitotic recombination, especially in gene conversion. The data also indicate that RAD52 is required for crossing-over between at least some chromosomes. Finally, examination of the behavior of a replicating plasmid in rad52-1 strains indicates that the frequency of plasmid integration is substantially reduced from that in wild type, a conclusion consistent with a role for RAD52 in reciprocal crossing-over. Analysis of recombinants arising in rad52-2 strains suggests that this allele may result in the increased activity of a RAD52-independent recombinational pathway.     

Management of foreign tourists' diseases at the American Hospital in Neuilly

More and more foreign tourists are being treated at the American Hospital of Paris. The main reasons for this are the presence of a 24 hour medical and dental emergency service, in addition to the availability of MRI, CT scan and comprehensive laboratory facilities. The hospital is multidisciplinary, where short stay hospitalizations are the rule. English is the second most commonly used language. There is a permanent Japanese language service for Japanese patients. Qualitative data is presented concerning the management of patients according to specialty and nationality. American and Japanese patients admitted to the hospital in 1997 are surveyed according to their mean age, reasons for admission and appropriate specialty as well as mean length of stay noted. The greatest number of hospitalizations in decreasing order and according to nationality are as follows: American, Japanese, Moroccan Egyptian and Saudi Arabian. The consultations and hospitalizations of Japanese patients between 1990 and 1997 are compared.     

Interstrain variability of larval photokinesis inDrosophila melanogaster

Larvae from seven laboratory strains and eight isofemale lines ofDrosophila melanogaster differ significantly with regard to their responses to light in a photokinesis assay in which the larvae are tested en masse. Larvae from the CA-2 laboratorystock fail to disperse on assay plates, although observations of individual CA-2 larvae suggest that the larvae are repelled by light. Larvae from all of the other laboratory stocks and all of the isofemale lines (except LI2 and NC5) avoid light in the photokinesis assay. Larvae from some stocks are much more strongly repelled by light than larvae from other stocks. LI2 larvae are unresponsive to light in most replicates of the photokinesis assay, while NC5 larvae are consistently unresponsive to light. Observations of F₁ heterozygotes suggest that the allele(s) that affects the vision of LI2 and NC5 larvae has net effects on the animals' behavior that are partially dominant and recessive, respectively.     

Differences in host susceptibility to disease progression in the human challenge model of Haemophilus ducreyi infection

With human volunteers inoculated at two sites with Haemophilus ducreyi, outcomes for a subject were not independent. In a reinfection trial, 2 of 11 previous pustule formers and 6 of 10 previous resolvers resolved all sites of infection. There was no correlation between serum bactericidal or phagocytic activity and outcome in the trial. These data indicate that different hosts are differentially susceptible to disease progression versus resolution in the model.     

Transcallosally evoked responses in the visual cortex of normal and monocularly enucleated rabbits

Summary In visual cortex of normal adult rabbits, callosal projections are restricted to a 2 mm wide band at the area 17/18 border. In adult rabbits which are monocularly enucleated (ME) on the day of birth, the callosal zone extends 4 mm into the medial region of area 17 in the cortex ipsilateral to the remaining eye. In this study, the function of these anomalous callosal projections in ME rabbits was investigated using electrophysiological techniques. A microelectrode was placed in the visual cortex ipsilateral to the enucleated eye at the 17/18 border, bipolar stimulating electrodes were placed in a homotopic location in the contralateral cortex, and averaged evoked responses (AERs) to stimulation were recorded. The stimulating electrodes were then moved mediolaterally in 1 mm steps, and the AERs were recorded for each location of the stimulating electrodes. In the normal rabbit, a maximal short latency evoked response was recorded when the stimulating electrodes were at a location homotopic to the recording electrode. When the stimulating electrodes were moved a distance of 1 mm or more from this optimal position, this short latency response was either absent or dramatically decreased in amplitude, reflecting the precise topographic pattern of the normal callosal projection. In contrast, in ME rabbits, a consistent response was evoked at the 17/18 border when the stimulating electrodes were moved as much as 3 mm medial to the homotopic position. Since antidromically activated responses and both pre- and post-synaptic orthodromically activated responses contribute to the AER, recordings were also made from single cells in some animals. Orthodromically activated single cell responses were evoked by electrical stimulation in the abnormal medial callosal zone of ME rabbits. The data indicate that abnormal callosal projections in ME rabbits can mediate functional interactions between nonhomotopic areas of the primary visual cortices.     

HLA Antigens in 16 Families with Xeroderma Pigmentosum

Xeroderma pigmentosum is an autosomal recessive disease. HLA-A and -B typing was performed on peripheral blood lymphocytes and platelets. Sixteen Tunisian families were typed with 37 patients and 108 relatives. Genetic transmission of the disease and of the HLA system seemed to be independent in this study. Comparison of HLA gene frequencies between (unrelated) parents of patients and a control population showed no difference, proving that there is no clear association in populations between deleterious XP genes and a particular HLA gene. However, an excess of identical HLA among pairs of diseased siblings would suggest that the disease is polymorphic and a form of the XP could be linked to HLA.     

Anti-HIV effects of chloroquine: inhibition of viral particle glycosylation and synergism with protease inhibitors

OBJECTIVE: We tested the effects of chloroquine (CQ) on glycosylation of HIV particles and in combination with protease inhibitors (PIs) on HIV replication and on P-glycoprotein (P-gp)/multidrug resistance protein-1 (MRP1). DESIGN: CD4 cell lines were infected with laboratory strains and peripheral blood mononuclear cells were infected with primary isolates for evaluation of the anti-HIV effects. Peripheral blood lymphocytes were evaluated for of P-gp and MRP1 functions. METHODS: HIV replication was assessed by enzyme-linked immunosorbent assay. HIV glycosylation was measured by metabolic labeling of viral particles with [H] glucosamine. Synergism was tested using isobolograms. P-gp and MRP1 functions were assayed using rhodamine 123 (Rh123) and carboxyfluorescein (CF) efflux assays, respectively. RESULTS: CQ alone inhibited HIV replication and glycosylation in a dose-dependent manner. In combination with indinavir (IDV), ritonavir, or saquinavir (SQV), CQ had a synergistic effect at concentrations found in plasma of subjects receiving malaria prophylaxis. CQ decreased the 50% effective concentration of IDV in primary isolates from Africa and restored the response to IDV or SQV in 3 PI-resistant isolates. CQ increased the block of Rh123 and CF efflux activity exerted by PIs. CONCLUSION: The inhibitory effects of CQ on HIV glycosylation are associated with synergistic effects in combination with PIs. The CQ/PI combination exerts combined inhibitory effects on P-gp and MRP1 function.     

Analytical technique for quantification of selected resorbable calcium phosphate bone void fillers with the use of polarized-light microscopy

Synthetic calcium phosphate bone void fillers promote varying rates of bone formation and material resorption depending on chemistry, porosity, pore structure, and implant site. The objective of this study was to quantify the resorption of a novel ultraporous beta-tricalcium phosphate cancellous bone void filler with simultaneous quantification of bone formation in a canine humerus model. Potential measurement error involved in conventional histomorphometry using Von Kossa stains inspired the development of a new technique. This technique utilizes bright-field and polarized-light microscopy in conjunction with image analysis software, allowing more accurate histomorphometry. This technique was validated with two separate controlled experiments. Scanning electron microscopy further supported the results. The findings suggest that the use of polarized-light microscopy combined with image analysis software can be an effective tool in simultaneously quantifying calcium phosphate resorption and bone formation.     

Screening for Depression in the Medically Ill: a comparison of self-report measures, clinician judgment, and DSM-IV diagnoses

The performance of the self-report 10-item Depression in the Medically Ill scale was observed in 210 patients as part of clinical assessment by consultation-liaison psychiatry clinicians. Both the Depression in the Medically Ill scale and the Beck Depression Inventory for Primary Care were completed by the patient, and the clinicians made their judgment of the presence and severity of "clinical depression" and DSM-IV affective disorder diagnoses. Both the Depression in the Medically Ill scale and the Beck Depression Inventory for Primary Care detected 85% of patients with DSM-IV major depressive episode. The Depression in the Medically Ill scale was slightly superior to the Beck Depression Inventory for Primary Care in its relationship to clinicians' judgments of clinical depression caseness.     

Application of inter-simple sequence repeat PCR to mouse models: assessment of genetic alterations in carcinogenesis

Genomic instability is believed to play a significant role in cancer development by facilitating tumor progression and tumor heterogeneity. Inter-simple sequence repeat (inter-SSR) PCR has been proved to be a fast and reproducible technique for quantitation of genomic instability (amplifications, deletions, translocations, and insertions) in human sporadic tumors. However, the use of inter-SSR PCR in animal models of cancer has never been described. This new technique has been adapted in our laboratory for the analysis of spontaneous and induced mouse tumors. We established the best PCR conditions for each microsatellite-anchored primer and critically evaluated the reproducibility of the band patterns. We also studied the variation of the fingerprints between and within various inbred mouse strains, including wild-derived lines. Tumor-specific alterations were detected as gains, losses, or intensity changes in bands when compared with matched normal DNA. We quantitated the extent of alterations by dividing the number of altered bands in the tumor by the total number of bands in normal DNA (instability index). By means of inter-SSR PCR, we successfully analyzed genomic alterations in various mouse tumors, including spontaneous thymic lymphomas developed in Msh2 knockout mice as well as chemically induced squamous cell carcinomas and thymic lymphomas. Instability index values ranged between 0 and 9%, the highest levels observed in N-methyl-N-nitrosourea-induced thymic lymphomas generated in Trp53 (p53) nullizygote (-/-) mice. We report here, for the first time, the use of inter-SSR PCR to detect somatic mutations in mouse tumoral DNA, including laser-capture microdissected, methanol-fixed tissues. These PCR-based fingerprints provide a novel approach to assessing the number and onset of mutational events in mouse tumors and will help to understand better the mechanisms of carcinogenesis in mouse models.