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Biomedical subjects

J Durand

Publications and source records attributed to J Durand.

At least 73 records · Page 4Linked to original sources
PubMed1993

Residual cornea and the degenerate eye of the cryptophthalmic Typhlotriton spelaeus.

The cave-dwelling Typhlotriton spelaeus larvas live in daylight. The larvas undergo a metamorphosis when the thyroxin level (T3 and T4) increases. They leave aquatic life for terrestrial and subterranean aphotic life. The larval eyes are normal and show good vision response to tests. On the contrary, in the oldest larva and the adult, the eyes are small with poor vision or no vision at all. The lens can disappear but in any case the eyelids grow over the eye. The retinal degeneration takes place during and after metamorphosis. The admitted statement that "after metamorphosis . . . the developing lids close over the eye and invade the cornea" is not confirmed concerning the invasion, because it is now evident that the eyelids separate spatially from the residual cornea. Consequently, the fibroblasts of the eyelids are not able to invade the corneal stroma. In fact, the periocular tissues do not invade the cornea but invade the eyelids' tissues. We are able to confirm that the development of the larval eyes is complete and apparently normal. After metamorphosis, the eyes decrease in size. The cornea "sinks" with the eye into orbit tissues. The eyelids cover the eye and are themselves replaced by a supraocular skin. This fits the description of the human cryptophthalmia. We also demonstrate that even in the degenerate eye the residual cornea retains the main structure of a normal salamander cornea. The preservation of the endothelium and of the Descemet membrane is exceptional in blind cave-dwelling vertebrates because in the other degenerate corneas the edema of the stroma depends on the spatial disjunction of the underepithelial stroma and the supraendothelial stroma. Perhaps, the very advanced development of the eye and the late start of the degenerative processes could explain the relative preservation of the cornea. Thus, the arguments put forward tend to prove that the thyroxinic metamorphosis sets off the growth and fusion of the eyelids but that the eye degeneration is related to hereditary processes.

Animals↗
PubMed1993

An analysis of synaptic transmission to motoneurones in the cat spinal cord using a new selective receptor blocker.

We have investigated the role of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors on synaptic transmission in vivo between Ia primary afferents and cat spinal motoneurones using a selective non-N-methyl-D-aspartate (non-NMDA) receptor antagonist, GYKI 52466. Both microionophoretic and intravenous application of GYKI 52466 depressed the excitatory post-synaptic potential (Ia EPSP) in a dose-dependent manner, without any apparent effect on membrane conductance or resting potential of the motoneurone. GYKI 52466 reduced selectively alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)- but not N-methyl-D-aspartate (NMDA)-induced depolarizations. Our results suggest that a large part of the Ia EPSP is mediated by AMPA receptors. The participation of other excitatory amino-acid receptors in the Ia EPSP is also discussed.

Animals↗
PubMed1992

Enzymatic synthesis of structural analogs of PAF-acether by phospholipase D-catalysed transphosphatidylation.

PAF-acether can be transformed into analogs by the phospholipase D enzyme activity of Streptomyces sp. In this reaction choline is replaced by primary cyclic alcohols (acceptors). The reaction products, cyclic phospholipid and phosphatidic acid, were separated by silicic acid chromatography. This procedure enabled us to synthetize five analogs of PAF-acether, with a cyclic ring structure. The primary cyclic alcohols used in this work were: 3-(2-hydroxyethyl)-indol, OH-Et-I; 2-(hydroxymethyl)-1,4-benzodioxan, OH-Met-BZD; N-(2-hydroxyethyl)-phthalimide, OH-Et-PHT; 2-(2-thienyl)-ethanol, Th-EtOH; (1-R)-(-)-Nopol, R-NOP.

Mass Spectrometry↗
PubMed1992

New chamber for flow cytometric analysis over an extended range of stream velocity and application to cell adhesion measurements.

When analyzed in a flow cytometer, particles are suddenly accelerated to high velocities (1-10 m.s-1) over very short distances. This feature is essential to obtain high analysis rates and low coincidence levels, but translates into very strong velocity gradients (greater than 10(5) s-1): particles experience strong hydrodynamic stresses that elongate them and tend to dissociate weakly associated complexes. In order to analyze fragile conjugates formed by heterotypic adhesion between two cell types, a flow cytometer was modified to make hydrodynamic stress not only much weaker but also adjustable. A new and easily adaptable flow cell was designed for the instruments of the FACS series; it provided satisfactory hydrodynamic conditions on a wide continuous range of flow rates. Accompanying electronic adaptations permitted standard analysis between 0.01 and 10 m.s-1. At 0.01 m.s-1, the velocity gradient roughly amounts to 50 s-1. Conjugates formed by the adhesion between human B and resting T lymphocytes, disrupted in conventional flow cytometers, could be detected and precisely quantified provided analysis velocity was kept below 0.1 m.s-1. We conclude that low velocity flow cytometry makes possible the quantification of weak intercellular adhesion phenomena, and is potentially useful for the future development of new biomechanical techniques and other applications.

B-Lymphocytes↗
PubMed1992

Coupling between the intracellular pH and the active transport of sodium in an epithelial cell line from Xenopus laevis.

1. The relationship between the rate of active Na+ transport and intracellular pH (pHi, measured as the BCECF fluorescence) was studied in A6 monolayers in the presence of CO2. The total buffering power (beta total) and its components (beta i and beta CO2) were assessed at various pHi. 2. The activity of Na+/H+ and Cl-/HCO3- exchangers were expressed in A6 cells; both antiports were found to participate in pHi homeostasis under standard conditions. 3. Alterations in the rate of Na+ transport induced variations in pHi. 4. Na+ transport rate was a hyperbolic function of external Na+ concentration. The curve was shifted by changing pHi: a mixed inhibition of Na+ transport by pHi was found. 5. The pHi appears as a possible mediator coupling the rate of Na+ transport across the apical and the basolateral membrane in tight epithelia.

Amiloride↗
PubMed1992

Agonist-induced production of inositol phosphates in human airway smooth muscle cells in culture.

Smooth muscle cells (SMC) from human bronchi were isolated by elastase treatment, subcultured, and characterized by their positive reaction with a monoclonal antibody against alpha-smooth muscle actin (alpha SMA). In each cell line tested, at least 95% of the cells were positively stained. The functional properties of these cells were examined by measuring the metabolism of inositol phosphates (IPs). For that purpose, cells were incubated for 3 days before reaching confluency in the presence of myo-[3H]inositol in order to label the phosphoinositide pool, and the various [3H]IPs were separated by HPLC on a SAX column with a phosphate gradient. IP1 isomers were separated in three peaks; IP2, IP3, IP4, IP5 and IP6 (phytic acid) were each eluted as single peaks. The identity of the [3H]peaks was verified with corresponding [3H]IP standards. The accumulation of [3H]IPs was measured by incubating cells up to 30 min in the presence of 10 mM LiCl, with or without a bronchoconstrictor agent (carbachol, histamine, PGF2 alpha). Histamine, 10(-4) M, elicited a four times larger IP accumulation than carbachol, 10(-4) M, and than PGF2 alpha, 5 10(-5) M. Dose-response curves were established for histamine and carbachol in the range 10(-7)-10(-4) M. At 10(-7) M, carbachol was more effective than histamine in stimulating the IP metabolism. Atropine blocked the response to carbachol, and diphenhydramine inhibited the effect of histamine, indicating the specificity of the response to the agonists. These results indicate that cultured human bronchial SMC are a suitable preparation for studying physiological aspects of membrane transduction in the airways.

Bronchi↗
PubMed1992

Stemming the tide? Assessing the deterrent effects of the Immigration Reform and Control Act.

This study uses a new source of data to assess the degree to which the Immigration Reform and Control Act (IRCA) deterred undocumented migration from Mexico to the United States. Data were collected from migrants interviewed in seven Mexican communities during the winters of 1987 through 1989, as well as from out-migrants from those communities who subsequently located in the United States. We conduct time-series experiments that examine changes in migrants' behavior before and after passage of the IRCA in 1986. We estimate trends in the probability of taking a first illegal trip, the probability of repeat migration, the probability of apprehension by the Border Patrol, the probability of using a border smuggler, and the costs of illegal border crossing. In none of these analyses could we detect any evidence that IRCA has significantly deterred undocumented migration from Mexico.

Age Factors↗
PubMed1991

[Femoral osteosarcoma revealing onset of unifocal Paget's disease. Favourable course with 7-year follow-up].

Sarcomatous degeneration is the most serious complication of Paget's disease, and few cases survive beyond 5 years. The authors report a new case, which occurred in a 62-year-old woman, in which calcifying periarthritis of the hip revealed the presence of a sarcoma developed in a context of a single bone case of Paget's disease affecting the upper extremity of the femur. Diagnosis was histological. The prognostic factors of Paget-related sarcomas are reviewed. The most important are the early timing of diagnosis and a site permitting radical surgical exeresis.

Female↗
PubMed1991

GYKI 52466 antagonizes glutamate responses but not NMDA and kainate responses in rat abducens motoneurones.

A new non-N-methyl-D-aspartate (non-NMDA) glutamate receptor antagonist, GYKI 52466, was tested on L-glutamate (Glu)-, kainate (KAI)- and NMDA-induced responses in vivo, using both extracellular recording of antidromic field potentials and intracellular recording from rat abducens motoneurones. Intravenous (5-10 mg/kg) or iontophoretic applications of GYKI 52466 blocked the Glu-induced depression of antidromic field potentials only. Furthermore, intravenous application of ketamine blocked the NMDA-induced depression only. Iontophoretic application of GYKI 52466 reduced the Glu-induced neuronal depolarization but not those induced by NMDA and KAI. Our results show a selective blockade of Glu responses by GYKI 52466, probably by acting at the AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptor subtype in rat abducens motoneurones.

Abducens Nerve↗
PubMed1991

Antihypertensive effect of cicletanine is exaggerated in NaCl-sensitive hypertension.

Cicletanine (CIC), a furopyridine derivative, lowers blood pressure in hypertensive animals and humans. We have previously identified an NaCl-sensitive substrain of spontaneously hypertensive rat (SHR-S) that displays enhanced sensitivity to the depressor effects of exogenous atrial natriuretic peptide (ANP) when fed a high NaCl diet. The current study tested the hypotheses that CIC has an exaggerated antihypertensive effect in NaCl-supplemented SHR-S and that this effect might be ANP dependent. CIC (40 mg/kg/day) or vehicle was administered by gavage in a single daily dose for three weeks beginning immediately prior to initiation of 1% or 8% NaCl diets in seven-week-old male SHR-S. CIC significantly decreased mean arterial pressure (MAP) and the ratio of left ventricular and septum weight to body weight (LV + S/BW) in both 8% NaCl- and 1% NaCl-fed SHR-S. The depressor effect of CIC was greater in the 8% NaCl group (-26 mmHg) than in the 1% NaCl group (-13 mmHg). CIC was associated with significant reduction in RAP in the 8% NaCl group but not in the 1% NaCl group. Neither CIC treatment nor 8% NaCl significantly altered plasma ANP or cyclic guanosine monophosphate (GMP) levels in plasma, aorta, or kidney. CIC was associated with significant decreases in plasma norepinephrine (NE) levels in the 1% NaCl group but not in the 8% NaCl group. The data demonstrate that the antihypertensive effect of CIC is exaggerated in NaCl-sensitive hypertension. The antihypertensive effect of CIC appears not to be related to ANP or cyclic GMP but may be related to a combination of a sympatholytic and natriuretic/diuretic effects in SHR-S.

Animals↗
PubMed1991

Ion transport in epithelial cells from the bovine trachea in culture: effects of dexamethasone and aldosterone.

The ion transport properties of epithelial cells from the bovine trachea grown in culture were investigated. The cellular uptake of 22Na+, 36Cl- and 86Rb+ was measured and the sensitivity of ion uptake to amiloride and bumetanide revealed the presence of the transport pathways that exist in the native tissue. The action of corticosteroids, dexamethasone and aldosterone (0.1 or 1.0 microM), was studied by measuring the short-circuit current and the uptake of Na+ and Cl- following a treatment of 18 h, 2 or 8 days. The results showed that, in each situation, dexamethasone enhanced markedly the amiloride-sensitive current and Na+ uptake. In contrast, aldosterone exerted no detectable effect on the ion transport and electrical properties.

Absorption↗
PubMed1991

[Preoperative cephalometric simulation in orthodontic surgery].

The authors expand their method of cephalometric simulation, which was designed for maxillofacial surgeons performing orthognathic surgery. This method has been developed to make up for the insufficiencies of the usually available cephalometric simulations, ie. poor legibility and the lack of data that may be necessary for surgery. The authors only deal with CS on profile teleradiographs at the end of the orthodontic preparation. This method utilizes models cut out of colored polyester and representing the profile of the maxillary and mandible. All the possible movements of the skeletal parts can also be simulated and the analysis of their direction and amplitude is possible, as is, more importantly, the influence of vertical movements of the maxillary on the mandible due to the mandibular autorotation phenomenon. This method is essential to accurately assess the degree of differential impaction or egress of the mandible in the region of the incisors and of the molars, according to the accompanying movements of the mandible moving around the condyle. Examples illustrate the use of this simulation method in the various types of orthognathic surgery. Finally, the authors point out the limitations of the method and the complementary usefulness of anteroposterior cephalometric simulation and of gnathologic simulation on casts, in particular for osteotomies for the transverse direction and for asymmetria.

Bone Transplantation↗
PubMed1990

Does arterial PCO2 interfere with hypoxia in muscular metabolism in man?

To answer the question whether PCO2 affects the muscular metabolism, PO2, PCO2, pH, lactic acid concentration and hemoglobin were measured in the efferent muscular venous blood from common flexor digitorum, during forearm rhythmic exercise corresponding to VO2max. Exercise was carried out either in hypocapnic hypoxia i.e. in permanent high altitude residents and translocated lowlanders, or in hypercapnic hypoxia i.e. in chronic obstructive lung disease (COLD) patients. The results show that, during exercise: i) PO2 in muscular venous blood remains around 20 Torr in normoxia and hypocapnic hypoxia and even higher (25 torr) in COLD patients, despite low arterial PaO2, and ii) arterial and/or local PCO2 play a role in the control of the muscular blood flow. But we cannot conclude that a change in PaCO2 affects muscular metabolism itself, because lactic acid in the muscular venous blood, that we used to check this effect, is likely dependent on mechanisms other than anaerobic glycolysis, such as a change in lactic acid efflux from the myocytes. The increase in muscular venous PCO2 may enhance the myocyte permeability to lactic acid during exercise.

Acclimatization↗
PubMed1990

[Changes in the blood flow of the primary carotid and its branches during modifications of the O2 and CO2 composition of alveolar gas].

We measured common carotid blood flow using a range gated Doppler velocimeter, and internal and external blood velocities using a continuous Doppler in 20 lowlanders at sea level, under normal barometric pressure, in 10 subjects in an altitude chamber under a barometric pressure of 462 Torr (61.6 KPa) and then in 5 of them over a 3-weeks period at 3850 m of elevation (475 Torr = 63.3 KPa). The same measurements were also performed in 20 permanent residents at 3850 m. Common carotid blood flow was 15% higher in all subjects exposed to high altitude, due to a lowering in downstream resistances since systemic blood pressure did not change at high altitude. The increase in common carotid blood flow was the result of an immediate increase in internal carotid blood velocities observed in the altitude chamber as well as after the arrival at high altitude, but a few days later those velocities in the internal carotid artery declined to values similar to those observed at sea level. In the same time velocities in external carotid artery rose at high altitude, remained steadily elevated and the result is a permanent increase in common carotid blood flow at altitude. In all subjects we performed the same measurements, during an acute inhalation of gas mixtures to try to quantify the mechanisms controlling the changes in common carotid blood flow while changing gas inhalation. In the limits of the variations in PO2 (60 to 400 Torr) and in PCO2 (30 to 50 Torr) the stimulation by CO2 is twice more efficient than the O2 stimulation on vasomotion.

Adult↗
PubMed1989

Electrophysiological and morphological properties of rat abducens motoneurones.

The electrical and morphological properties of abducens motoneurones were investigated in the rat with intracellular recordings and intracellular HRP-staining. Motoneurones were identified by their antidromic response to electrical stimulation of the lateral rectus muscle. The antidromic action potential was followed by a delayed depolarization and an after hyperpolarization lasting 20 ms to 45 ms. The whole neurone input resistance (RN) calculated from I/V curves, was found to lie between 2 M omega and 15 M omega with a bimodal distribution (mean values 4.9 M omega and 12 M omega). In some cases, anomalous rectification was observed with low current intensities. Prolonged hyperpolarizing current pulses revealed the presence of a time dependent inward rectification and slow rebound depolarization. The intensity/frequency curves suggest the existence of three ranges of discharge. The average intensity frequency slope during the steady state was 43 imp/s/nA. Eight abducens motoneurones were intracellularly labelled with HRP and full reconstructed. The soma (23 microns to 40 microns in diameter) gave off 5 to 7 primary dendrites. The general organization and extension of the dendritic trees depended on the location of the soma within the abducens nucleus. The mean diameter of primary dendrites was 4.17 microns with similar average values in all motoneurones. The soma size of abducens motoneurones was not correlated with either the size of the proximal tree or the whole neurone input resistance.

Abducens Nerve↗