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Biomedical subjects

P Andre

Publications and source records attributed to P Andre.

At least 73 records · Page 4Linked to original sources
PubMed1991

Noradrenergic agents into the cerebellar anterior vermis modify the gain of vestibulospinal reflexes in the cat.

The noradrenergic (NA) afferent projection to the cerebellar cortex, which originates mainly from the locus coeruleus (LC), may act on the target neurons by utilizing both alpha- and beta-adrenoceptors. Experiments performed in decerebrate cats have shown that unilateral injection into the vermal cortex of the cerebellar anterior lobe of 0.25 microliter of the alpha 1-adrenergic agonist metoxamine or the alpha 2-agonist clonidine (at 2-8 micrograms/microliters of saline) as well as of the non-selective beta-agonist isoproterenol (at 8-16 micrograms/microliters) decreased the postural activity in the ipsilateral forelimb, while the extensor tonus either remained unmodified or slightly increased on the contralateral side. The same agents also increased the gain of the vestibulospinal (VS) reflexes elicited by recording the multiunit EMG responses of the ipsilateral and the contralateral triceps brachii to roll tilt of the animal (at 0.15 Hz, +/- 10 degrees), leading to sinusoidal stimulation of labyrinth receptors. The crossed effects were more prominent for the alpha 2- than for the alpha 1- and beta-agonists. Only slight changes in the phase angle of the responses were observed. The effects described above appeared 5-10 min after the injection, reached the peak values after 15-30 min and disappeared within 2 h. The effective area was located within the third and/or the fourth folium of the culmen rostral to the fissura prima, 1.4-1.8 mm lateral to the midline. This area corresponded to zone B of the cerebellar cortex, which projects to the ipsilateral lateral vestibular nucleus (LVN), on which it exerts a prominent inhibitory influence. In fact, monopolar stimulation of this area with three negative pulses (at 300/sec) performed prior to the local injection inhibited the spontaneous EMG activity of the ipsilateral triceps brachii. The effects described above were dose-dependent; injection of an equal volume of saline was ineffective. All changes in posture and reflexes elicited by metoxamine or clonidine were impaired by previous injection into the same corticocerebellar area of the corresponding alpha 1- or alpha 2-adrenergic antagonist prazosin or yohimbine, respectively (0.25 microliters at 8-16 micrograms/microliters). However, cross-interactions between alpha 1- and alpha 2-adrenergic agonists and antagonists were also observed. In fact, injection of the alpha 2-adrenergic antagonist yohimbine prevented the occurrence of all the metoxamine effects, while administration of the alpha 1-adrenergic antagonist prazosin prevented the occurrence of the ipsilateral, but not of the contralateral effects induced by clonidine injection.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1991

Comparison of three selective isolation media for the detection of L. monocytogenes in foods.

391 different foods were examined in order to compare three selective isolation media for Listeria: blood agar with nalidixic acid, Palcam agar, Listeria selective Oxford medium (Oxford agar). The percentage of positive samples (presence of Listeria in 25 g) obtained on the three media after an enrichment procedure is identical: 15.8%. The species L. monocytogenes is found in respectively 8.43%, 8.43% and 8.18% of the foods examined on Palcam agar, Oxford agar and nalidixic acid agar; this represents more than 50% of the isolates of the genus Listeria. However, Palcam agar and Oxford agar offer the advantages of a great reduction of the development of the contaminating microflora and a clearly less fastidious reading. The technique used for the direct counting of L. monocytogenes on these two selective media does not allow the detection of a low contamination of foods (theoretical positivity threshold = 100 Listeria/g): 65.2% of the positive samples would not have been detected without prior enrichment. 41.1% of the isolated L. monocytogenes belong to serovar 1/2a, 5.8% to serovar 1/2b, 20.58% to serovar 1/2c, 5.8% to serovar 3b and 24.47% to serovar 4b.

Animals↗
PubMed1991

Microinjections of alpha 1- and alpha 2-noradrenergic substances in the cerebellar vermis of decerebrate cats affect the gain of the vestibulospinal reflexes.

1. In addition to mossy and climbing fibers, the Purkinje (P)-cells of the cerebellar cortex receive noradrenergic (NA) afferents which originate mainly from the locus coeruleus. Since these fibers impinge also on the vermal cortex of the cerebellar anterior lobe, which receives a labyrinth input and projects to the lateral vestibular nucleus, experiments were performed in precollicular decerebrate cats to find out whether unilateral injection of alpha-adrenergic substances into the vermal cortex of the cerebellar anterior lobe exerted some influence on posture as well as on the dynamic characteristics of vestibulospinal (VS) reflexes evaluated by recording the multiunit EMG responses of the forelimb extensor triceps brachii of both sides to roll tilt of the animal at 0.15 Hz, +/- 10 degrees. 2. Unilateral injection into the vermal cortex of the culmen of the alpha 1-adrenergic agonist metoxamine or the alpha 2-adrenergic agonist clonidine (0.25 microliters at the concentration of 4 micrograms/microliters of saline) produced a postural asymmetry, characterized mainly by a slight decrease of the extensor tonus in the ipsilateral forelimb and an increased tonus in the contralateral forelimb. The same substances significantly increased the gain (imp./sec/deg) of the first harmonic component of the EMG responses of the ipsilateral and the contralateral triceps brachii to animal tilt. The crossed effects were more prominent for the alpha 2- than for the alpha 1-agonist. However, no significant changes in the phase angle of the responses were observed in both instances. The effects described above occurred within 5-10 min after the injection, reached the peak values after 15-20 min, and disappeared within 2 hours. 3. The postural and reflex changes described above were not due to irritative events following the injection, since they were not observed in control experiments after injection of 0.25 microliter of saline into the same corticocerebellar area prior to the administration of the alpha 1- or the alpha 2-adrenergic agonist. Moreover, the resulting effect were dose-dependent. 4. Both the ipsilateral as well as the contralateral effects induced by the alpha 1- or the alpha 2-adrenergic agonist metoxamine or clonidine were impaired by previous injection into the same corticocerebellar area of the corresponding alpha 1- or alpha 2-adrenergic antagonist prazosin or yohimbine, respectively (0.25 microliter at the concentration of 8-16 micrograms/microliters in both cases).(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic alpha-Agonists↗
PubMed1991

Microinjections of beta-noradrenergic substances in the cerebellar vermis of decerebrate cats modify the gain of the vestibulospinal reflexes.

1. The noradrenergic (NA) afferent system, which originates mainly from the locus coeruleus and projects to the cerebellar cortex, may act on the corresponding neurons by utilizing not only alpha- but also beta-adrenoceptors. Since the vermal cortex of the cerebellar anterior lobe receives a labyrinth input and projects to the lateral vestibular nucleus (LVN), experiments were performed in precollicular decerebrate cats to find out whether the noradrenergic system intervenes in the control of posture as well as of the dynamic characteristics of vestibulospinal (VS) reflexes elicited by recording the multiunit EMG responses of the forelimb extensor triceps brachii of both sides to roll tilt of the animal at 0.15 Hz, +/- 10 degrees. In particular, we used the method of local microinjection into the vermal cortex of the cerebellar anterior lobe of the non-selective beta-adrenergic agonist ((+/-) -isoproterenol hydrochloride) or antagonist (dl-propranolol hydrochloride) to act on both beta 1- and beta 2-adrenoceptors. 2. Unilateral injection into the vermal cortex of the culmen of isoproterenol (0.25-0.50 microliters at the concentration of 8-16 micrograms/microliter of saline stained with pontamine 5%) decreased the extensor tonus in the ipsilateral forelimb, while the postural activity either remained unmodified or slightly increased in the contralateral fore-limb. The same injection significantly increased the gain (imp./sec/deg) of the first harmonic component of the EMG responses of the ipsilateral and to a lesser extent also of the contralateral triceps brachii to animal tilt. This effect was also associated with slight changes in the phase angle of the responses, which remained positional throughout the experiments. The effects described above occurred within 5-10 min after the injection and reached the highest values after 20-30 min; they were then followed for about 2 hours after the injection, before disappearing. 3. In contrast to these findings, injection in other experiments of 0.25-0.50 microliter of a solution of propranolol at the concentration of 16 micrograms/microliter of saline increased the extensor tonus in the ipsilateral limbs, while the decerebrate rigidity either remained unmodified or slightly decreased in the contralateral limbs. In addition, the amplitude of modulation and thus the response gain of the ipsilateral triceps brachii to the same parameters of animal tilt decreased. This effect was associated with slight changes in the phase angle of the responses. There was also a slight but insignificant decrease in gain of the responses recorded contralaterally to the side of the propranolol injection.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenergic beta-Agonists↗
PubMed1990

Aortic smooth muscle cells are able to convert angiotensin I to angiotensin II.

The role of vascular smooth muscle cells (VSMC) in the intraparietal conversion of angiotensin I (AngI) to angiotensin II (AngII) was investigated in rat aortic tissue. The responses of rat aortic vascular smooth muscle cells to AngI and AngII were assessed by studying contraction of endothelium-denuded aortic rings and by measuring intracellular Ca++ ion concentration in primary cultures of VSMC free of endothelial cells. In both preparations, AngI and AngII induced identical responses which were inhibited by saralasin, a blocker of AngII receptors. In the presence of captopril, an inhibitor of the angiotensin converting enzyme, the increase in calcium caused by AngI was abolished in VSMC cultures and the contractile effect of this peptide in aortic rings was strongly decreased, whereas the responses to AngII remained unaffected. These results demonstrate that VSMC are able to convert AngI to AngII.

Angiotensin I↗
PubMed1990

Splitting cell adhesiveness into independent measurable parameters by comparing ten human melanoma cell lines.

The concept of cell adhesiveness was analyzed by looking for correlations between the adhesive behavior and measurable biological properties of different cell populations. Ten established lines of melanoma cells were assayed for passive deformability (by micropipet aspiration), active spreading (by measuring the height/diameter ratio after incubation on different surfaces), density and mobility of concanavalin A binding sites (by quantitative analysis of fluorescence microscopic images), spontaneous and concanavalin A-mediated agglutination (by measuring the number of cell conjugates resisting calibrated shearing forces), and binding to glass capillary tubes (with a quantitative assay of binding strength). Forty-four different parameters were thus measured, and each set of determinations was repeated 2 or 3 t at different days on each cell line. Analysis of variance was performed to assess the capacity of each parameter to discriminate between different lines. Correlations between different parameters were studied in order to understand a possible influence of cell intrinsic properties on the behavior of individual cells. The following conclusions were suggested by experimental data 1. Cell spreading ability, resistance to slow deformation within a micropipette and ability to form shear-resistant bonds, are independent properties. It is therefore suggested that different mechanisms rule the cell deformations on time scales of several minutes, tens of seconds, and fractions of a second. 2. Cell spreading ability may effectively influence binding strength only when adhesive stimuli are low, since in this case, cell stiffness is likely to impair the formation of extensive contact areas. 3. Individual cells may display marked heterogeneity within a given population, that emphasizes the danger of using averaged parameters to predict rare events (such as metastasis formation). 4. The most useful parameters to discriminate between different cell lines were, spreading ability and shear-resistant lectin agglutination, and substrate adhesion. It is concluded that cell adhesion is influenced by several measurable cellular properties that may display independent variations. The importance of a given parameter depends on the conditions of bond formation and rupture.

Cell Adhesion↗
PubMed1990

Pertussis toxin abolishes the effect of neuropeptide Y on rat resistance arteriole contraction.

Pertussis toxin (PTX) was used to investigate the possible involvement of a G protein in the mechanism of action of neuropeptide Y (NPY) on rat mesenteric arterioles. ADP ribosylation of membrane protein was assessed by gel electrophoresis followed by autoradiography. The effect of NPY was studied on contractions elicited either by addition of calcium to depolarized vessels or by the calcium agonist BAY K 8644. Under conditions in which PTX ADP-ribosylated a 40-41 kDa protein, the potentiation of contractions induced by NPY in both protocols was abolished. In contrast, the contraction induced by norepinephrine was unaffected by PTX. It is concluded that a G protein mediates the potentiating effect of NPY on external calcium-dependent contractions in rat mesenteric arterioles.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1990

A method for the assessment of the output of irregularly shaped electron fields.

A simple approach to the calculation of dose in cone-collimated electron fields is presented. The method accounts for variations in lateral scatter with field size using a Clarkson Integration. The reduction in output by an irregularly shaped aperture is evaluated based on measurements of the output at various distances from the aperture in a field 2.5 cm in diameter. The first 14 months of clinical use were analysed and it is shown that in 42 out of 600 calculations, the cutout factor was less than 0.95 and that in 77% of these, the calculation method was accurate to +/- 3%.

Electrons↗
PubMed1988

Zymosan but not phorbol myristate acetate induces an oxidative burst in rat bone marrow-derived macrophages.

We found that rat bone marrow-derived macrophages responded to opsonized zymosan by releasing superoxide anion. However, these cells were defective in the response to the potent oxidative burst activator phorbol myristate acetate (PMA). This result was observed whatever the concentration of agonist used and with different concentrations of cells. Since it is strongly suspected that protein kinase C (PKC) is involved in the transductional pathway induced by PMA in numerous cell types, and particularly in phagocytes, we studied PKC and we observed that it was functional in rat bone marrow-derived macrophages, but only present at a low level. Thus, we suggest that our results are consistent with the possibility that zymosan-induced respiratory burst may be independent of PKC and that these cells may not possess the minimal level of PKC required for responding to PMA.

Animals↗
PubMed1988

Myotonic dystrophy: defective oxidative burst of polymorphonuclear leukocytes.

Because myotonic dystrophy (MD) is an autosomal dominant multisystemic disorder affecting plasma membrane, we have studied the oxidative burst of PMNs. The PMA and fMet-Leu-Phe-stimulated superoxide generation is defective in the patient group as compared to controls: the response is both delayed and low. The kinetic parameters of the NADPH oxidase complex are not affected. We have not found any abnormalities in the membrane potential changes. In addition, the cytosolic protein kinase C (PKC) activity of resting PMNs is similar in MD patients and controls, and the translocation of protein kinase C in response to PMA is not impaired. The decrease of the oxidative response of PMNs from MD patients may be related to an abnormality of the environment of the NADPH oxidase.

Adult↗
PubMed1988

Interferon production in severe hemophiliacs with and without HIV antibodies.

The interferon (IFN) system, both serum IFN levels and the in vitro IFN production, was investigated in 38 clinically asymptomatic multitransfused hemophiliacs, half positive and half negative for HIV antibodies. In most patients, no circulating IFN was detected; similar levels of IFN-alpha were obtained after peripheral blood mononuclear cell (PBMC) stimulation with Sendai virus both in hemophiliacs and controls, while production of IFN-gamma following stimulation with phytohemagglutin (PHA) was diminished in a large number of patients irrespective of their HIV serology. These data indicate that the deficiency in IFN-gamma generation is not only related to HIV contamination but may be a direct consequence of the chronic antigenic stimulation through Factor VIII concentrates.

HIV Seropositivity↗
PubMed1986

Mechanical responses of rat vascular smooth muscle cells to rat interferon.

Mechanical responses elicited by rat interferon (IFN) were investigated in rat vascular smooth muscle cells (RVSMC) in primary culture. IFN induced a dose-dependent reduction in the apparent cell surface area, which was quantitatively comparable to, or even greater than, the response elicited by the alpha-adrenergic agent, phenylephrine. Neither mock-IFN nor rat IFN-neutralized with specific antibodies elicited such a response. The sensitivity of RVSMC to the mechanical effect of IFN was species specific. In addition, the effect of IFN was inhibited by the Ca2+ entry blocker, verapamil.

Animals↗