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Biomedical subjects

J Paquet

Publications and source records attributed to J Paquet.

16 recordsLinked to original sources
PubMed1998

Seasonal and diurnal patterns of human illumination under natural conditions.

Little is known about the natural pattern of seasonal and diurnal illumination to which normal people are exposed, especially in northern latitudes. In this study, ambient illumination of normal volunteers living at a latitude of 45 degrees 31' N was recorded with ambulatory photosensors worn for 5 to 6 days in winter and summer. Results from 12 normal subjects (6 men, 6 women) aged 18 to 35 years were included in the analyses. The mean daily duration of time awake was similar in both seasons: 14.6h in the summer and 14.9h in the winter. However, the phase of the sleep-wake cycle was advanced in the summer compared to the winter, as shown by an earlier average waketime and bedtime in the summer. Illumination recorded by the ambulatory monitor between waketime and bedtime was categorized according to four ranges of light intensities: very dim (< 1 lux), dim (1-100 lux), moderate (100-1000 lux), and bright (> 1000 lux) illumination. There was no seasonal difference for the time spent in illumination lower than 1000 lux, but the duration of daily exposure to bright light averaged 2.6h in the summer compared to only 0.4h in the winter (p = 0.0004). To evaluate the diurnal distribution of ambient illumination, time spent awake was divided into four time intervals: morning (waketime to 12:00), afternoon (12:00 to 16:00), early evening (16:00 to 20:00), and late evening (20:00 to bedtime). Except for late evening, the time spent in bright illumination was significantly longer during the summer for all time intervals, but the relative distribution of bright light exposure throughout the day was the same in both seasons. The subjects spent more than 50% of their time awake in illumination dimmer than 100 lux, even in the summer. More naturalistic studies are needed to determine whether very short exposure to bright light or longer exposure to light of moderate intensity (100-1000 lux) are sufficient to maintain circadian entrainment and euthymia in normal young subjects.

Adult↗
PubMed1995

Chloroquine treatment affects T-cell priming to minor histocompatibility antigens and graft-versus-host disease.

Graft-versus-host disease (GVHD) caused by T-cell recognition of minor histocompatibility (MiHC) antigens is a major complication of bone marrow transplantation. GVHD therapy has focused on removal or suppression of donor T cells, but modulation of MiHC antigen presentation to CD4+ T cells may represent an alternative approach. Chloroquine is known to inhibit major histocompatibility complex (MHC) class II presentation of antigen in vitro by affecting invariant chain dissociation from MHC class II. The goal of this study was to evaluate the role of chloroquine in abrogating T-cell priming to MiHC and GVHD in mice after transplantation of an MiHC incompatible donor. C57BL/6 mice were treated with phosphate-buffered saline or chloroquine at 400 micrograms intraperitoneally every day for 5 days before priming with BALB.B cells (MiHC-incompatible) followed by weekly injections of chloroquine at 400 micrograms for 4 to 8 weeks. Chloroquine treatment decreased the proliferative T-cell response to MiHC by 67% and the cytolytic T-cell activation by greater than 50%. After bone marrow transplantation (LP/J into C57BL/6; MiHC-incompatible), GVHD was significantly decreased in chloroquine-treated mice (17% with GVHD) as compared with that in controls (92% with GVHD). Chloroquine treatment did not have other effects in vivo on the normal T- and B-cell mitogenic responses, T-cell allogeneic responses, and MHC class II and I surface expression. Chloroquine treatment does decrease the ability of C57BL/6 antigen-presenting cells to stimulate C3H.SW T cells reactive with MiHC expressed on C57BL/6 cells, suggesting an effect on MHC class II presentation of MiHC in vivo. Treatment with chloroquine in vivo appears to result in decreased CD4+ T-cell priming to MiHC and GVHD by decreased class II MHC antigen presentation. Thus, chloroquine treatment may represent an alternative approach to control GVHD.

Animals↗
PubMed1995

Requirement for B cells in T cell priming to minor histocompatibility antigens and development of graft-versus-host disease.

Increased understanding of minor histocompatibility complex (MiHC) antigen presentation to donor T cells may permit methods to modulate graft-versus-host disease (GVHD), a major complication of allogeneic bone marrow transplantation (BMT). Previously, we described the importance of B cells as antigen presenting cells in T cell responses to a virally induced murine leukemia. Using a B cell deficient mouse model in which mice receive either control rabbit immunoglobulin (RIgG) or rabbit anti-IgM mu chain from birth (B cell deficient), we evaluated whether B cells were necessary for T cell responses to MiHC and the induction of GHVD. Normal and B cell deficient C57BL/6 (H-2b) mice were primed with BALB.B (H-2b; MiHC incompatible) spleen cells and evaluated > 4 weeks later in vitro. While splenic or lymph node T cells obtained from BALB.B primed control C57BL/6 mice demonstrated strong in vitro proliferative responses to MiHC mismatched targets, B cell deficient hosts were markedly reduced to 14-42% of controls. Similarly, a strong MiHC specific cytolytic T cell response was observed in control C57BL/6 mice (53-100% specific cytotoxicity) whereas B cell depleted recipients had no activity (< or = 5% specific lysis). The role of B cells in GVHD was evaluated using a MiHC disparate mouse model (LP/J donor into C57BL/6 recipient). We found that 12% of B cell depleted recipient mice receiving B cell depleted donor cells developed GVHD compared to 50% of RIgG control mice. B cell depletion of donor cells only, resulted in a similar result with 0% of mice receiving B cell depleted donor cells developing GVHD compared to 38% of controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Lifeline.

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Emergencies↗
PubMed1976

[Osteoid osteoma. 5 cases].

With reference to five cases of osteoid osteoma, including two para-articular cases with articular reaction, two cases with neurological manifestations, and one case with a rare costal lesion, the authors demonstrate the difficulty of diagnosis in this disease, which is, in principle, well known. In some cases the observations extended over seven years. The authors also review the literature on this subject.

Adolescent↗
PubMed1975

[Neurosensory complications of Paget's disease].

The authors made a bibliographic study and report their conclusions with reference to problems concerning a personal series of 17 patients who had undergone an ocular examination, a cranial radiography studying the joint, a bilateral radiotomographic study of the ossicles and of the petrosal bone, an audiogram, and a bilateral electronystagmogram: 1. the rarity of angioid striae, the existence of which, in the view of the authors, does not allow Paget's disease to be included within the framework of the systemized elastorrhexis, 2. the frequency of ocular vascular lesions, 3. deafness is a constant phenomenon, when the cranial arch is affected usually in combination with other lesions ; the deafness is sometimes of transmission or sometimes of perception, but it can precede the cranial lesions. The signs of these can be found radiologically in the chain of ossicles and in the cochlea by means of special projections. The part played by basilar pressure in this deafness is negligible. Labyrinth disorders are rarely met.

Angioid Streaks↗
PubMed1974

[Rheumatic manifestations of primary hypogammaglobulinemia in the adult].

With reference to 27 cases reported in the literature (of which 1 was personal) of primary hypogammaglobulinaemia in adults (PHGGA) with rheumatic manifestations, and following a statistical study, the authors think that the rheumatic manifestations that precede, accompany, or follow primary hypogammaglobulinaemia in adults are not coincidental. These manifestations occur in 10 percent of patients. The clinical and radiological pictures, and the associated infections and immunological disorders form a particular clinical entity and lead to therapeutic difficultires. In this connexion, the authors mention in particular pathogenic problems related to hypogammaglobulinaemia in adults and the rheumatic manifestations.

Adolescent↗