Biomedical subjects

P Poindron

Publications and source records attributed to P Poindron.

At least 91 records · Page 5Linked to original sources

PubMed1991

Individual olfactory signatures as major determinants of early maternal discrimination in sheep.

Responses of recently parturient ewes to their familiar versus separated (i.e., unfamiliar) twin lambs were observed in an attempt to elucidate further the characteristics of the phenotypic traits (signatures) mediating maternal recognition and bonding. Ewes responded more positively to their familiar lamb than to its twin that had been isolated at birth. Nonetheless, those same mothers also discriminated between their separated twin and unfamiliar alien lambs. Alien lambs elicited similar rejection behavior regardless of whether they had been housed with their own mother or in isolation prior to testing. Lambs appear to have individually distinct (olfactory) signatures; however, the signatures of twin siblings may be sufficiently similar to enable the mother to detect a resemblance. No evidence suggests that acquired maternal labels play a role in either the acceptance of the ewe's own lamb(s) or rejection of aliens.

Animals↗

PubMed1991

Phase I trial of intravenous infusion of ex-vivo-activated autologous blood-derived macrophages in patients with non-small-cell lung cancer: toxicity and immunomodulatory effects.

The purpose of this phase I study was to evaluate the toxicity and biological activity of autologous blood-derived macrophages activated ex-vivo with recombinant human interferon gamma (rhuIFN gamma) [monokine-activated killer (MAK) cells] and administered intravenously to 11 lung cancer patients once a week for 6 consecutive weeks. Peripheral blood monocytes were collected by leukapheresis and then purified by counterflow elutriation. The MAK cells were generated by culturing the purified monocytes in Teflon bags for 7 days and adding rhuIFN gamma to the cultured cells for the last 18 h. These MAK cells expressed differentiation-associated surface antigen MAX1, and were cytotoxic in vitro against tumour cell line U937. The MAK cells were infused at dose levels from 1 x 10(7) to 5 x 10(8) on an intrapatient dose-escalating schedule. No severe adverse side-effects occurred. Toxicity was mild to moderate [primarly fever (75%) and chills (32%)], non-dose-dependent, and non-cumulative. No consistent change in haemostatic function, or liver or renal function was observed. Dose-limiting toxicity was not reached at 5 x 10(8) cells (optimal dose reproduced for each patient). The maximum tolerated dose was not determined. The immunomodulatory activity of i.v. infused MAK cells was demonstrated both in vivo by significant increases in granulocyte count and neopterin level in the patients' peripheral blood post-infusion and in vitro by secretory products (IL-1. TNF alpha, neopterin, and thromboplastin-like substance) in the culture supernatants. The in vivo traffic patterns of autologous MAK cells labelled ex-vivo with 111In oxine were studied in 7 patients. Gamma imaging showed an immediate but transient lung uptake (less than 24 h), and a progressive uptake of radioactivity in the liver and spleen was seen from 6 h to 72 h post-infusion. Our results indicate that the preparation of high numbers of autologous, blood-derived MAK cells is a feasible procedure, and their transfusion is safe for patients. This immunotherapeutic approach seems to be encouraging from the point of view of establishing an adjuvant therapeutic modality in cancer patients with minimal residual disease.

Aged↗

PubMed1991

Fluid phase endocytosis investigated by fluorescence with trimethylamino-diphenylhexatriene in L929 cells; the influence of temperature and of cytoskeleton depolymerizing drugs.

The temperature-dependence of fluid phase endocytosis was investigated in L929 cells, using a recently described fluorescence approach with trimethylamino-diphenylhexatriene (TMA-DPH). In interaction with cells, this probe is rapidly incorporated into the plasma membrane and follows its intracellular traffic of internalization-recycling, thus behaving as a suitable marker for fluid phase endocytosis. The kinetics of the process may be followed accurately by simple fluorescence intensity measurements, while complementary fluorescence anisotropy and micrographic data may be obtained in parallel with the same probe. It was shown that the formation of endocytic vesicles was not inhibited by cooling the cells, even down to 4 degrees C, but only reduced in a quasi-linear way with temperature. Conversely the further fusion events between the vesicles and large vacuolar bodies (endosomes, lysosomes) were strongly and discontinuously influenced: they were almost totally suppressed below 15 degrees C. The evolution of the membrane fluidity during endocytosis, which was monitored by fluorescence anisotropy measurements, indicated that the fusion inhibition was probably correlated with the inability of the endocytic vesicles to shed their initial clathrin coat at low temperature. Moreover, microscopic observations showed that at low temperature the endocytic vesicles hardly moved from the place of their formation. Pretreatment of the cells with microtubule and microfilament depolymerizing drugs (cytochalasin B, vinblastine) led to the conclusion that the cytoskeleton played little role in the vesicle movements. Altogether, the results suggested that the progression of the vesicles towards the cell core resulted from successive fusion events, which explained why they were considerably slowed down by cooling.

Animals↗

PubMed1991

Membrane fluidity aspects in endocytosis; a study with the fluorescent probe trimethylamino-diphenylhexatriene in L929 cells.

The fluorescent hydrophobic plasma membrane probe, trimethylamino-diphenylhexatriene (TMA-DPH) was previously shown to follow the plasma membrane throughout its internalization and recycling process and thus to behave as a marker for endo- and exocytosis in living cell systems. In this paper, we made use of these properties to investigate membrane fluidity effects associated with endocytosis in L929 cells. For that purpose we performed TMA-DPH fluorescence anisotrophy measurements which showed that endocytosis starts from particularly rigid regions of the plasma membrane (probably coated pits). The fluorescence anisotropy then continuously decreases to a lower limit corresponding to the membrane fluidity of the probe in the lysosomial membrane. Strikingly, the value of this limit is identical to the average anisotropy value in the peripheral membrane, which suggests that lysosomes and plasma membrane may have a similar phospholipidic composition and a possible common origin.

Animals↗

PubMed1991

Female effect in sheep. I. The effects of sexual receptivity of females and the sexual experience of rams.

When in contact with receptive or non-receptive ewes, the presence of females increased LH peak frequency both in experienced and inexperienced rams (P less than 0.05). The highest response was found in experienced rams stimulated by sexually receptive ewes. In this group only, the mean testosterone levels increased during stimulation (P less than 0.05). Sexual behavior did not differ between experienced and inexperienced males. The sexual receptivity of the females and the sexual experience of rams appear to interact and thus facilitate the rams' LH and testosterone responses to the presence of ewes.

Animals↗

PubMed1991

Female effect in sheep. II. Role of volatile substances from the sexually receptive female; implication of the sense of smell.

The importance of olfactory cues in inducing luteinizing hormone and testosterone secretion as a response to stimulation by sexually receptive ewes has been tested. In sexually experienced rams, olfactory stimulation with urine, wool and vaginal secretions from sexually receptive females placed in a mask did not induce an endocrine response. The female-induced secretion of LH and testosterone was similar in anosmic, sham-operated and in control rams. These results show that olfactory cues are not necessary in the mediation of interindividual stimulation of endocrine response in the sexually experienced ram.

Animals↗

PubMed1991

Activation of human monocytes by Streptococcus mutans serotype f polysaccharide: immunoglobulin G Fc receptor expression and tumor necrosis factor and interleukin-1 production.

Streptococcus mutans serotype f polysaccharide (poly f) was prepared from S. mutans whole cells by autoclaving. The poly f was purified by chromatography on DEAE Trisacryl M and Bio-Gel P100, treated with insoluble pronase, and resubjected to chromatography on DEAE Trisacryl M. Normal human blood monocytes, stimulated in vitro with purified poly f, produced extracellular tumor necrosis factor alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) in a dose-dependent fashion as determined by a heterologous two-site sandwich enzyme-linked immunosorbent assay. Poly f also increased the expression of monocyte cell surface receptors for the Fc part of human immunoglobulin G, activity which is correlated with an increase of the phagocytic activity of the stimulated monocytes. Polymyxin B had no effect on TNF-alpha and IL-1 beta release. Neutralization assays with anti-recombinant human TNF-alpha and anti-recombinant human IL-1 beta immunoglobulin G confirmed the fact that the cytotoxic and mitogenic mediators released by the poly f-stimulated monocytes were mainly TNF-alpha and IL-1 beta.

Antigens, Differentiation↗

PubMed1991

[Nasal chemoreception in utero: preliminary experiences in fetal sheep].

Intranasal injections of a fragrant solution of 2-methyl-2-thiazoline elicited significant heart rate decelerations in late pregnancy fetal sheep, while the injection of a control fluid (isotonic saline) had no effect. This result indicates that the ovine fetuses are able to detect nasally administered odorants, as previously demonstrated in the fetuses of murine rodents.

Administration, Intranasal↗

PubMed1990

Internalization of the lipophilic fluorescent probe trimethylamino-diphenylhexatriene follows the endocytosis and recycling of the plasma membrane in cells.

The lipophilic fluorescent probe trimethylamino-diphenylhexatriene (TMA-DPH) has been shown previously to behave as a marker of plasma membrane in living cell systems, and it has therefore been widely used in membrane fluidity studies via fluorescence anisotropy measurements. However, progressive internalization of this probe in cells could lead to unsuitable interferences, when long incubations times were required. The mechanism of this internalization had not yet been elucidated. We present here fluorescence-intensity kinetic results and fluorescence micrographic data on L929 cells and on mouse bone-marrow macrophages, which allow us to identify the mechanism as fluid-phase pinocytosis: the probe remains associated with the plasma membrane throughout its internalization-recycling flow and it is finally concentrated in lysosomes. The study was facilitated by the partition equilibrium property of TMA-DPH between plasma membranes and the external aqueous medium, which allowed to immediately distinguish the internalized fraction of the probe from the peripheral labelling, by simply washing cells. This conclusion is confirmed by the features of the influence of temperature on TMA-DPH internalization.

Animals↗

PubMed1990

The plasma-membrane internalization and recycling is enhanced in macrophages upon activation with gamma-interferon and lipopolysaccharide; a study using the fluorescent probe trimethylaminodiphenylhexatriene.

The lipophilic fluorescent probe trimethylaminodiphenylhexatriene (TMA-DPH), previously used as a plasma membrane marker in membrane fluidity and exocytosis studies, was shown, to monitor the plasma-membrane internalization-recycling shuttle movement in cells. Using this approach we present here kinetic and dose-response data, which give evidence that the plasma membrane flow is enhanced in bone marrow macrophages from various mouse strains, upon in vitro activation with gamma interferon (IFN-gamma) or bacterial lipopolysaccharide (LPS), within physiological dose ranges. The effect studied evolved in line with the usual development kinetics of macrophage activation. Complementary assays on membrane fluidity, surface charge density and membrane surface indicated no related changes. From these experiments it is concluded that the observed enhancement of the plasma membrane traffic does not originate from specific limited membrane modifications, but is merely a particular feature of the overall macrophage activation.

Animals↗

PubMed1990

Purification and partial characterization of rat macrophage Fc receptor and binding factor for IgA.

By using a biotinylated ligand and Western blotting techniques, a receptor (RFc alpha) and a binding factor (BF) for IgA were detected, respectively, on membrane and in the cell-free culture supernatant of rat peritoneal macrophages. Extraction of the RFc alpha was obtained by solubilization of macrophages with Nonidet P-40, and purification was performed by HPLC affinity chromatography on a column derivatized with IgA. RFc alpha is formed of two subunits, with molecular masses of 56 and 70 kDa, which are both involved in the IgA binding ability of rat peritoneal macrophages. IgABF was recovered from the cell-free supernatant of a short-term culture of rat macrophages and was affinity-purified in the same manner as RFc alpha. Like RFc alpha, IgABF retained its IgA binding activity in its native, as well as denatured form. Since the molecular masses of RFc alpha and IgABF are similar, and IgABF competes with RFc alpha for IgA binding, one can assume that IgABF probably represents a shed RFc alpha.

Animals↗

PubMed1990

Establishment and characterization of somatic hybrids between human differentiated macrophages and mouse myeloma NS1 cells.

Human macrophages obtained from circulating monocytes matured in vitro by culture for seven days in hydrophobic flexible teflon bags were successfully fused with murine myeloma NS1 cells. Six of 20 clones, selected for their adherence properties, were further studied. All possessed human chromosomes (mean number ranging from 4 to 14 depending on the clones studied), exhibited non-specific esterases (but no peroxidase activity) and expressed CD14 antigen and C3 receptors (but no MAX-1 antigen). Moreover, the hybridomas retained phagocytic activity and high interferon plus lipopolysaccharide-activable cytolytic activity against tumor cells.

Animals↗

PubMed1989

Development of mother discrimination by single and multiple newborn lambs.

Most research on recognition of the ewe by her lamb has focused on lambs several days or even several weeks old, whereas newly born lambs have received little attention. The aim of this work was therefore to study the attraction of Merino lambs to postparturient ewes and their ability to discriminate between their own and alien mothers in a two-choice situation 12, 18, 24, 48, and 72 hr after birth. A comparison between singles and multiples was also made in 18 and 24-hr-old lambs. When released in the testing pen, approximately 90% of the lambs in each group (older than 12 hr) spent more than 3 min with the two ewes during the 5-min test. It was only from 24 hr old, however, that a high proportion of lambs spent at least two-thirds of this time close to their own mothers (correct choice). The proportion of singles spending more than 3 min with the ewes or making a correct choice was higher than that of multiples. This effect was related to litter size but not to birth weight. It is concluded that a majority of Merino lambs are clearly attracted to ewes by the time they are 18 hr old and can discriminate their own dams from alien mothers at about 24 hr of age. At this stage singles perform better than multiples.

Animals↗

PubMed1989

Interferon inhibits the accumulation of glycerol phosphate dehydrogenase mRNA in oligodendrocytes and C6 cells.

We investigated the effect of rat interferon-alpha/beta (IFN) on the expression of glycerol phosphate dehydrogenase (E.C.1.1.1.8; GPDH), in both C6 cells and pure cultures of oligodendrocytes. IFNs are naturally produced inhibitors of cell growth that can also affect differentiated cell functions. GPDH is a biochemical marker for oligodendrocytes and is known to be developmentally regulated and steroid inducible. GPDH activity is induced by hydrocortisone (HC) 3.5 fold in C6 cells and 5 fold in oligodendrocytes compared to untreated cultures. A pretreatment of these cells with 75 U/ml of rat IFN-alpha/beta resulted in an inhibition of the HC induction of GPDH enzymatic activity by 50% and 40% in C6 cells and oligodendrocytes respectively. We also found that IFN impaired the accumulation of GPDH mRNA in both cell types. These results demonstrate that IFNs are capable of modifying the cellular response to hormones in cells of neuroepithelial origin, and suggest the possibility that IFNs may be able to influence the development and function of the brain.

Animals↗

PubMed1989

TMA-DPH a fluorescent probe of membrane dynamics in living cells. How to use it in phagocytosis.

Trimethylammonium-diphenylhexatriene (TMA-DPH), a hydrophobic fluorescent probe, has been shown in earlier studies to possess a variety of particular properties in interaction with intact living cells--specific and rapid incorporation into the plasma membrane and partition equilibrium between the membranes and the buffer. These properties offer promising applications in membrane fluidity studies and in monitoring exocytosis kinetics. Furthermore, these properties offer a method described here for quantitative monitoring of phagocytosis kinetics, by means of simple fluorescence intensity measurements. This method is original in that it evaluates only the particles which have actually been internalized by phagocytosis, and not those adsorbed on the cell surface, and that it gives quantitative information on the amount of plasma membrane involved in the process. It has been tested on mouse bone marrow macrophages.

Animals↗

PubMed1989

Genital stimulation facilitates maternal behavior in estrous ewes.

Only a small proportion of ewes at estrus have been found to respond maternally to newborn lambs, and this low maternal responsiveness may be partially attributable to the absence of the genital stimulation which occurs at parturition. Therefore, the effect of artificial genital stimulation on maternal behavior of estrous ewes was investigated. Estrus was synchronized in 33 ewes by placement and withdrawal of progestin-saturated vaginal sponges. Estrous ewes were divided into two groups, a control group and a group receiving 5 min of artificial genital stimulation, and observed following presentation of newborn lambs. Significantly more stimulated ewes licked the lamb and emitted low-pitched bleats in a 30-min test. When genital stimulation was subsequently administered to control ewes, more of them also became maternal so that the two groups were no longer significantly different. These results indicate that absence of genital stimulation is one of the factors contributing to the low maternal responsiveness of estrous ewes. They also demonstrate for the first time that artificial genital stimulation is effective in eliciting maternal behavior in nonpregnant ewes even at physiological concentrations of estradiol.

Animals↗

PubMed1989

Stimulating effects of prednisolone on acetylcholine receptor expression and myogenesis in primary culture of newborn rat muscle cells.

Prednisolone at concentrations of 10(-5) to 10(-8) mol/l, added to 3-day (day D + 2) tissue cultures of newborn rat myogenic cells at the time myoblasts are beginning to fuse, increases the level of myotube acetylcholine receptor expression at the 8th day (day D + 7) of culture. This effect is associated with increases in the number and size of the formed myotubes, not with a changed affinity of the receptor for its ligand, and is very probably mediated by one or more extracellular proteins the synthesis of which is induced early by the presence of prednisolone.

Animals↗

PubMed1988

Characterization of surface markers of continuously growing murine resident macrophages.

Conditions have been described which allow an in vitro indefinite multiplication of differentiated murine macrophages (Lombard et al: Biol Cell 53, 219, 1985). R. and MAY-1 cell lines, which were obtained, respectively, from mouse (Balb/c) spleen and resident peritoneal macrophages, have been further characterized. They present at their surface, besides the Mac-1 antigen and Fc-receptor, a mannose receptor which was characterized for its binding properties. This receptor is responsive for a specific phagocytosis of mannosylated particles, i.e., mannosylated latex beads or oil droplets containing mannosylated bovine serum albumin. Moreover, R and MAY-1 cells present an ectoenzyme profile (NAD+ glycohydrolase and nucleotide pyrophosphatase) similar to those of the corresponding resident macrophages.

Animals↗