Biomedical subjects

P Canu

Publications and source records attributed to P Canu.

At least 19 recordsLinked to original sources

PubMed2005

Cassini measurements of cold plasma in the ionosphere of Titan.

The Cassini Radio and Plasma Wave Science (RPWS) Langmuir probe (LP) sensor observed the cold plasma environment around Titan during the first two flybys. The data show that conditions in Saturn's magnetosphere affect the structure and dynamics deep in the ionosphere of Titan. The maximum measured ionospheric electron number density reached 3800 per cubic centimeter near closest approach, and a complex chemistry was indicated. The electron temperature profiles are consistent with electron heat conduction from the hotter Titan wake. The ionospheric escape flux was estimated to be 10(25) ions per second.

Atmosphere↗

PubMed2005

Characterization of platelet adhesion under flow using microscopic image sequence analysis.

A method for quantitative analysis of platelet deposition under flow is discussed here. The model system is based upon perfusion of blood platelets over an adhesive substrate immobilized on a glass coverslip acting as the lower surface of a rectangular flow chamber. The perfusion apparatus is mounted onto an inverted microscope equipped with epifluorescent illumination and intensified CCD video camera. Characterization is based on information obtained from a specific image analysis method applied to continuous sequences of microscopical images. Platelet recognition across the sequence of images is based on a time-dependent, bidimensional, gaussian-like pdf. Once a platelet is located,the variation of its position and shape as a function of time (i.e., the platelet history) can be determined. Analyzing the history we can establish if the platelet is moving on the surface, the frequency of this movement and the distance traveled before its resumes the velocity of a non-interacting cell. Therefore, we can determine how long the adhesion would last which is correlated to the resistance of the platelet-substrate bond. This algorithm enables the dynamic quantification of trajectories, as well as residence times, arrest and release frequencies for a high numbers of platelets at the same time. Statistically significant conclusions on platelet-surface interactions can then be obtained. An image analysis tool of this kind can dramatically help the investigation and characterization of the thrombogenic properties of artificial surfaces such as those used in artificial organs and biomedical devices.

Algorithms↗

PubMed2004

Radio and plasma wave observations at Saturn from Cassini's approach and first orbit.

We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 +/- 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings.

Journal Article↗

PubMed1994

Modifications in tissue histamine levels in mast cell-deficient mice (W/Wv) and in their littermates (Wv/+, W/+ and +/+) grafted with a methylcholanthrene-induced fibrosarcoma: correlation with tumour rejection.

There is evidence that mast cells and their degranulation products are involved in resistance against tumours. Previously, we have shown that tumour incidence and growth were inversely correlated with basal histamine levels, i.e. mast cell numbers, in tissues of W/Wv (mast cell-deficient), Wv/+ (partially mast cell-depleted), and +/+ (mast cell-sufficient) mice, and that histamine levels were increased in numerous tissues of tumour-bearing animals, including C57BL/6 and C3H mice, Sprague-Dawley and Commentry rats. The aim of this work was to analyse the incidence and growth of a grafted tumour (fibrosarcoma MC-B6-1) in W/+ mice, as compared with W/Wv, Wv/+ and +/+ mice, and to study the modifications in tissue histamine levels in W/+, W/Wv, Wv/+ and +/+ tumour-grafted mice, in order to determine whether or not these modifications were correlated with resistance to tumours. We report confirmation that tumour incidence and growth are inversely correlated with basal tissue histamine levels in W/Wv, Wv/+, and +/+ fibrosarcoma-bearing mice. However, in W/+ mice (normal tissue histamine levels), tumour incidence was the same as in Wv/+ mice. Histamine levels in tissues of W/Wv, Wv/+, W/+ and +/+ tumour bearing mice were not significantly different from those in controls. They were higher in some tissues of Wv/+ mice rejecting the tumour than in Wv/+ mice not rejecting the tumour. However, in W/+ and +/+ mice, histamine levels were not significantly different, and even tended to be lower in most tissues of mice rejecting the tumour than in mice accepting the tumour. Overall, these results suggest that resistance to tumours cannot be ascribed solely to mast cells, and that other mechanisms may also be involved. Thus, further experiments are needed to clarify the exact role of mast cells and mast cell-derived mediators and cytokines in the defence against tumours.

Animals↗

PubMed1992

Modifications in tissue histamine levels in mice treated with chronic epicutaneous application of phorbol-12-myristate-13-acetate.

Chronic epicutaneous application of phorbol-12-myristate-13-acetate (PMA) on the right flank of C 57 BL/6 mice induces an inflammatory reaction and a selective increase in skin histamine level at the site of treatment. Tissue histamine levels were not increased at other sites such as contralateral skin, stomach rumen and skeletal muscle, and were decreased in stomach fundus and dorsal skin. These results are in agreement with the hypothesis that mast cells play a significant role in cutaneous inflammation induced by PMA.

Administration, Cutaneous↗

PubMed1988

[Failure of chemotherapy and radiotherapy in pulmonary fibrosis caused by paraquat].

A case is reported of severe interstitial paraquat poisoning in a 23 year old man. Initial treatment consisted of gastric lavage, fuller's earth, haemoperfusion on activated charcoal and peritoneal dialysis. On the third day, appeared both renal and early respiratory failure, with hypocapnia and hypoxia. Peritoneal dialysis was kept up to the thirteenth day. Pulmonary function tests showed a restrictive syndrome. Chemotherapy with 1 mg.kg-1.24 h-1 prednisone and 3 mg.kg-1.24 h-1 cyclophosphamide was started on day 4. Radiotherapy (13 Gy) was also given to both lung fields between days 6 and 10. Despite this treatment, respiratory failure worsened, and the patient died at the 28th day, with resistant severe hypoxaemia and pneumothorax on fibrous lungs. Several reports have shown conflicting results with chemotherapy and radiotherapy in the treatment of pulmonary fibrosis due to paraquat poisoning. The failure of such treatment in the case reported showed the need for large prospective clinical trials of the treatment of paraquat poisoning, as well as for urgent preventive measures.

Adult↗

PubMed1985

Tissue histamine levels in male and female mast cell deficient mice (W/Wv) and in their littermates (Wv/+, W/+ and +/+).

Histamine levels have been determined in nine tissues of four kinds (W/Wv, Wv/+, W/+, +/+) of WBB6F1 male and female mice, and mast cells have been counted in the skin and the fundus of W/Wv and +/+ mice. By comparison with +/+ mice (1) the association of the two alleles Wv and W induced a drastic decrease in tissues histamine levels and in mast cell number. (2) The allele Wv alone induced a marked decrease in tissue histamine levels but less important than the two alleles W and Wv. (3) In contrast, the allele W alone induced at least in some tissues, an increase in tissue histamine levels. In W/+, Wv/+ and +/+ fertile mice, tissue histamine levels were higher in females than in males. In contrast, in W/Wv mice which are sterile, no difference between males and females was observed.

Alleles↗

PubMed1985

In vivo and in vitro anti-tumour activity of dimaprit.

Dimaprit, a histamine H2-receptor agonist, injected daily i.p. to fibrosarcoma-bearing mice, induced a decrease in tumour growth and an increase in survival. Dimaprit, added to tumour cell cultures (10(-4) M), inhibited the incorporation of 3H-thymidine while embryonic cell cultures were unaffected. This particular anti-tumour activity is probably H2-independent as histamine and impromidine have no effect on tumour cell cultures.

Animals↗

PubMed1985

Inverse correlation between tumor incidence and tissue histamine levels in W/WV, WV/+, and +/+ mice.

The influence of mast cells on tumor incidence and growth rate was studied in 2 grafted tumor models (fibrosarcoma MC-B6-1 and the Lewis lung carcinoma 3LL). Three kinds of WBB6F1 mice (a cross between WB/ReJ-W/+ and C57BL/6J-WV/+ mice) were used: W/WV (deeply mast cell depleted), WV/+ (partially mast cell depleted), and +/+ (normal mast cell number). The presumed resistance of F1 hybrids to tumor cells of parental origin was observed in 12 of 13 +/+ mice, but only in 11 of 22 WV/+ mice and in none of 39 W/WV mice. Tumor incidence and metastasis incidence were inversely correlated with tissue histamine levels and mast cell number. Growth rates of tumors were similar in W/WV and WV/+ mice, but the tumor growth rate was much slower in the only +/+ mouse in which the tumor grew. These results confirm the protective role of mast cells against tumors.

Animals↗

PubMed1984

Tissue histamine levels and mast cell numbers in tumour-bearing mice.

In C57BL/6 mice bearing the 3LL carcinoma and in C3H mice bearing the McC3 -1 fibrosarcoma (18th passage), the increase in skin histamine levels was correlated with the increase in mast cell number. The number of cells able to incorporate tritiated thymidine was proportional to the mast cell number. These results strengthen the notion that, in tumour-bearing rodents, the increase in tissue histamine is an active phenomenon.

Animals↗

PubMed1984

Noninvolvement of histamine and prostaglandins in the dermatosis of magnesium-deficient hairless rats.

Hairless rats receiving a deprived Mg2+ diet developed long-lasting inflammatory dermatosis which was not influenced by treatments with mepyramine, cimetidine, aspirin or indomethacin. Dermatosis did not appear in deprived rats treated with intraperitoneal injections of Mg2+, or with dexamethasone. Histamine and prostaglandins did not seem to be involved in this dermatosis. The possible role of leucotrienes is discussed.

Animals↗

PubMed1983

Selective increased tissue histamine levels in tumour-bearing rodents.

Histamine levels increased in the fundus of mice bearing a primary 3-methylcholanthrene-induced fibrosarcoma, and in the ventral skin, skeletal muscle and rumen of rats bearing a D.M.B.A. induced mammary adenocarcinoma; they did not increase in the tissues of mice bearing a McC3-1 fibrosarcoma (38th passage) or a Lewis lung carcinoma before the appearance of metastasis, but an increase in histamine levels was observed in dorsal skin, ventral skin and fundus, after the appearance of metastasis.

Animals↗

PubMed1982

Tissue histamine levels in male and female normal and nude mice.

In comparison with those in normal (+/+) mice, tissue histamine levels were lower in athymic (nu/nu) female mice and higher in athymic male mice. The sexual difference was less marked or absent in nu/nu mice. These results show (a) that endocrine factors are involved in the distribution of tissue histamine, and (b) that the thymus cannot be considered as the main source of tissue histamine in pathogen-free mice.

Animals↗

PubMed1982

Decrease in tumour growth by injections of histamine or serotonin in fibrosarcoma-bearing mice: influence of H1 and H2 histamine receptors.

C3H and C57 BL/6 mice carrying methylcholanthrene-induced fibrosarcomas were injected i.p. daily with histamine, metiamide (anti-histamine type-2 receptor), histamine + metiamide, mepyramine (anti-histamine type-1 receptor), serotonin and methysergide (anti-serotonin). Inhibition of tumour growth and lengthened survival were observed with histamine and histamine + metiamide. The best results (both on tumour growth and survival) were obtained with serotonin. Survival was increased by metiamide and decreased by mepyramine and methysergide. In histamine-treated and in serotonin-treated mice, histological studies of the tumours showed large and numerous foci of haemorrhagic necrosis. Stimulation of histamine type-1 or serotonin receptors and inhibition of histamine type-2 receptors play a beneficial role in the host's defence against tumours.

Animals↗

PubMed1981

The influence of intraperitoneal injections of histamine on tumour growth in fibrosarcoma-bearing mice.

Twenty C57BL/6 male and 20 C3H female mice carrying a methyl cholanthrene-induced fibrosarcoma received, daily, intraperitoneal injections of histamine dihydrochloride (1.8 mg or 6 mg histamine base/mouse). In all histamine-treated C57BL/6 mice, tumour growth was significantly slower than in control mice until day 18. Thereafter, the tumour growth rate of treated compared to control mice was accelerated. In 10 out of 20 C3H mice, tumour growth was significantly slower until day 25; in histamine responsive C3H mice, histological studies showed numerous and large loci of acute haemorrhagic necrosis in the tumours.

Animals↗

PubMed1981

Increased tissue histamine in tumour-bearing mice and rats.

Tissue histamine levels were studied in C3H and C57BL/6 mice bearing a methylcholanthrene-induced fibrosarcoma, in Wag rats bearing an aflatoxin B1-induced hepatoma, and in Commentry rats bearing a grafted hepatoma. Histamine levels were significantly higher (1.5 to 3 fold) in the tumour-bearing animals for ventral and dorsal skin, skeletal muscle and stomach fundus. Total histamine content was increased in the spleen. In C3H mice with McC3-1 fibrosarcoma, the excision of the tumour or its partial regression by intratumoral injections of corynebacterium parvum induced a reversion to normal values. The tumour thus appears responsible for the increased histamine levels in tissues distant from the tumour.

Animals↗

PubMed1980

Histamine levels in mouse tissues of different strains: influence of sex.

The sex related difference in histamine levels of various mouse tissues was investigated in several mouse strains. In all of them the histamine levels were higher in female animals than in males. Thus experiments on histamine in mice must be carried out in animals matched for sex and strain.

Animals↗

PubMed1980

Histamine levels in mouse tissues: influence of castration.

The influence of castration on histamine levels in mouse tissues was investigated in Swiss mice. Only in female mice castration led to a significant decrease in the histamine content of dorsal and ventral skin, skeletal muscle and kidney. This effect was found 2 weeks after castration. A long-term study is being presently undertaken.

Animals↗