PubMed Health⌕ Search

Biomedical subjects

P Laporte

Publications and source records attributed to P Laporte.

At least 19 recordsLinked to original sources
PubMed2001

p62dok negatively regulates CD2 signaling in Jurkat cells.

p62(dok) belongs to a newly identified family of adaptor proteins. In T cells, the two members that are predominantly expressed, p56(dok) and p62(dok), are tyrosine phosphorylated upon CD2 or CD28 stimulation, but not upon CD3 ligation. Little is known about the biological role of Dok proteins in T cells. In this study, to evaluate the importance of p62(dok) in T cell function, we generated Jurkat clones overexpressing p62(dok). Our results demonstrate that overexpression of p62(dok) in Jurkat cells has a dramatic negative effect on CD2-mediated signaling. The p62(dok)-mediated inhibition affects several biochemical events initiated by CD2 ligation, such as the increase of intracellular Ca(2+), phospholipase C gamma 1 activation, and extracellular signal-regulated kinase 1/2 activation. Importantly, these cellular events are not affected in the signaling cascade induced by engagement of the CD3/TCR complex. However, both CD3- and CD2-induced NF-AT activation and IL-2 secretion are impaired in p62(dok)-overexpressing cells. In addition, we show that CD2 but not CD3 stimulation induces p62(dok) and Ras GTPase-activating protein recruitment to the plasma membrane. These results suggest that p62(dok) plays a negative role at multiple steps in the CD2 signaling pathway. We propose that p62(dok) may represent an important negative regulator in the modulation of the response mediated by the TCR.

CD2 Antigens↗
PubMed2001

Pectin secretion and distribution in the anther during pollen development in Lilium.

Using the monoclonal antibodies JIM 5 and 7, pectin was immunolocalized and quantitatively assayed in three anther compartments of Lilium hybrida during pollen development. Pectin levels in both the anther wall and the loculus increased following meiosis, were maximal during the early microspore stages and declined during the remainder of pollen ontogenesis. In the microspores/pollen grains, pectin was detectable at low levels during the microspore stages but accumulated significantly during pollen maturation. During early microspore vacuolation, esterified pectin epitopes were detected both in the tapetum cytoplasm and vacuoles. In the anther loculus, the same epitopes were located simultaneously in undulations of the plasma membrane and in the locular fluid. At the end of microspore vacuolation, esterified pectin epitopes were present within the lipids of the pollenkitt, and released in the loculus at pollen mitosis. Unesterified pectin epitopes were hardly detectable in the cytoplasm of the young microspore but were as abundant in the primexine matrix as in the loculus. During pollen maturation, both unesterified and esterified pectin labelling accumulated in the cytoplasm of the vegetative cell, concurrently with starch degradation. In the mature pollen grain, unesterified pectin epitopes were located in the proximal intine whereas esterified pectin epitopes were deposited in the distal intine. These data suggest that during early microspore development, the tapetum secretes pectin, which is transferred to the primexine matrix via the locular fluid. Further, pectin is demonstrated to constitute a significant component of the pollen carbohydrate reserves in the mature grain of Lilium.

Antibodies, Monoclonal↗
PubMed1997

Determination of NADH in the rat brain during sleep-wake states with an optic fibre sensor and time-resolved fluorescence procedures.

The present paper reports a nanosecond time-resolved fluorescence derived from the cortex and the area of the periaqueductal gray including the nucleus raphe dorsalis (PAG-nRD) in unanaesthetized freely moving rats. The measurements were acquired through a single optic fibre transmitting a subnanosecond nitrogen laser pulse (337 nm, 15 Hz) and collecting the brain fluorescence occurring at 460 nm which might depend on mitochondrial NADH (reduced form of nicotinamide adenine dinucleotide). The fluorometric method was combined with polygraphic recordings, and this procedure allowed us to define, for the first time, variations of the 460 nm signal occurring throughout the sleep-wake cycle. In the PAG-nRD, the signal exhibited moderate heterogeneous variation in amplitude during slow-wave as compared to the waking state. Constant increases were observed during paradoxical sleep as compared to the waking state. For this state of sleep the magnitude of the variations depended on the optic fibre location. In the cortex and during either slow-wave sleep or paradoxical sleep, the signal presented moderate increases which were significant during paradoxical sleep. The magnitude of the redox variations observed either in the PAG-nRD or in the cortex might be ascribed to the oxidative energy balance which is related to sleep states.

Animals↗
PubMed1991

Monocytic origin of fibroblasts: spontaneous transformation of blood monocytes into neo-fibroblastic structures in osteomyelosclerosis and Engelmann's disease.

We describe here two pathological situations, osteomyelosclerosis and Engelmann's disease, in which HLA-DR blood monocytes modulate to the fibroblastic class, in long-term culture. Monocytes/macrophages were identified by immunofluorescence, using monoclonal antibodies against surface markers (Leu M3, CD 68, and HLA-DR) and the neo-fibroblasts by electron microscopy and immunofluorescence using monoclonal antibodies against a cytoplasmic enzyme specifically involved in the synthesis of collagen (5B5). Macrophages makers were found on the neo-fibroblasts, whereas HLA-DR macrophages expressed the cytoplasmic marker 5B5. Since osteoblasts are classically derived from fibroblasts, the significance of the in vitro differentiation of monocytes/macrophages into fibroblasts to the in vivo mechanism leading to excessive osteoblastic proliferation in both osteomyelosclerosis and Engelmann's disease, is discussed. The possible involvement of this pathway leading from monocytes to fibroblasts and osteoblasts in the normal process of bone modeling and remodeling in questioned.

Camurati-Engelmann Syndrome↗
PubMed1990

[Leptospirosis in Mayotte].

We have got 42 leptospirosis cases from 1984 to 1989, in a retrospective study. The annual incidence is now, in a very high level (3.8/10,000 pers.). This rapid increasing is function of new diagnostics facilities. The leptospirosis epidemiology is not different from anywhere else in tropical countries, but the complicated cases are an important problem in public health in the island. The actual development of collective hygienic equipment is indispensable for any progress.

Adult↗
PubMed1985

Changes in testicular fluid production and plasma hormones in the adult rat after testicular 60Co irradiation.

Adult Wistar rats exposed to testicular radiocobalt irradiation (0.8 Gy) were alloted to four groups: sham control, protected control, unilaterally irradiated and bilaterally irradiated. The rats of each group were killed 30, 45, 60, 75 and 105 days after gamma-ray exposure and/or general anaesthesia. Tubular fluid (TF) production, estimated by ligature of the efferent ducts of both unilaterally and bilaterally irradiated testes, 24h prior to sacrifice, was transiently increased 30 and 45 days after irradiation (P less than 0.001); there was no increment in the interstitial fluid (or lymph) collected compared to sham and protected control testes. At 30 and 45 days, irradiated testis weight decreased significantly. From 60 to 105 days after gamma-ray exposure, TF gradually returned to control levels, while the testicular weight increased. The plasma FSH, LH, PRL and testosterone of the irradiated rats did not change significantly compared to the controls. Consequently, it is presumed that TF secretion was regulated locally by a germ cell-Sertoli cell interrelationship.

Animals↗
PubMed1985

Production of seminiferous and interstitial fluid in the growing rat after unilateral testicular irradiation.

The production of tubular fluid (TF) and interstitial fluid (IF) in normal and irradiated testes was compared in the same growing rats submitted at 25 days of age to unilateral, scrotal X-ray, exposure. Twelve rats were sacrificed each week from 32 to 81 days of age. In both normal and irradiated testes, IF increased in parallel with the testicular weight until 67 days of age and declined slightly thereafter. TF secretion of normal testes increased significantly until 53 days of age, declined significantly until 67 days, and stabilized thereafter. A similar pattern of TF secretion was observed for irradiated testes but with a greater production between days 32 and 46, a lower maximal level at day 53 and a lower but non-significant level from day 67 onwards. All these observations combined with previous results led us to suggest the quantitative influence of germ cells on both TF and IF secretion, the stimulatory effect of diploid germ cells (spermatogonia) and the inhibitory effect of haploid germ cells (probably spermatids) on Sertoli cell secretion. The latter qualitative influence seemed preponderant in adulthood.

Animals↗