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Biomedical subjects

G Roy

Publications and source records attributed to G Roy.

At least 127 records · Page 7Linked to original sources
PubMed1987

Phenotypic changes in monocytes and alveolar macrophages in patients with acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC).

The expression of Class II histocompatibility antigens (HLA-DR and HLA-DQ), leukocyte function associated antigen (LFA-1) and complement receptor type 3 (CR3) on peripheral blood monocytes and alveolar macrophages (M phi) from patients with acquired immune deficiency syndrome (AIDS) and AIDS-related complex (ARC) and age-matched controls was studied. The percentage of HLA-DR+ monocytes from 4 AIDS patients and 12 ARC patients was 52.4 +/- 16.4% (p less than 0.05) and 50.2+21.2% (p less than 0.01) respectively (Controls, 75.4 +/- 12.6%). HLA-DQ expression in monocytes from one AIDS and two ARC patients was 31%, 39% and 18% respectively (in normal individuals, DQ was expressed by approximately 40% monocytes). HLA-DR and HLA-DQ expression on alveolar M phi from one AIDS patient and 2 ARC patients were also depressed. CR3 was expressed by 65.9 +/- 11.1% monocytes from normal controls. Patients with AIDS had a slightly, but significantly lower, proportion of CR3+ monocytes (43.9 +/- 15.9%, p less than 0.05) (in normal controls, CR3 monocytes were 65.9 +/- 11.1%). However, monocytes from ARC patients and alveolar M phi from one AIDS and 2 ARC patients expressed CR3 in a normal range. LFA-1 was significantly depressed in monocytes from both AIDS (45.7 +/- 1%, p less than 0.005) and ARC (57.5 +/- 10.9%, p less than 0.005) patients in comparison with controls (87.4 +/- 8.7%). Only alveolar M phi from one AIDS patient could be studied for LFA-1 antigen and this was into the normal range.(ABSTRACT TRUNCATED AT 250 WORDS)

AIDS-Related Complex↗
PubMed1986

Single-channel analysis of the potassium permeability in HeLa cancer cells: evidence for a calcium-activated potassium channel of small unitary conductance.

Cell-attached and inside-out patch-clamp experiments (O.P. Hamill et al., Pfluegers Arch. 391:85-100, 1981) were undertaken in order to characterize the molecular mechanisms responsible for the calcium-dependent potassium permeability observed in HeLa cancer cells. Our result essentially indicate that the HeLa cell external membrane contains potassium channels whose activity can be triggered within an internal calcium concentration range of 0.1 to 1 microM. This particular channel was found to behave as an inward rectifier in symmetrical 200 mM KCl with a conductance of 50 and 10 pS at large negative and large positive membrane potentials, respectively. I/V curves were also measured in 10, 20, 75, 200 and 300 mM KCl and the data interpreted in terms of a one-site-two-barrier model. The channel activity appeared to be nearly voltage independent within the voltage range -100 to +100 mV, an increase of Po, the open channel probability, being observed at large negative potentials only. In addition, the results obtained from inside-out experiments on the relationship between Po and the cytoplasmic free-calcium concentration have led to conclude that four calcium ions are probably required in order to open the channel. In this regard it was found that an increase of the internal free-calcium level affects more the number of channel openings per second than the actual channel mean lifetime. Finally, it is concluded following a time interval distribution analysis, that this particular channel has at least three closed states and two open states.

Calcium↗
PubMed1985

[Infectious mononucleosis and splenic pseudocyst: presentation of a case].

The authors report the clinical case of an 18-year-old patient who presented with a symptomatic mass in the left upper quadrant 6 months after having infectious mononucleosis. The preoperative investigation consisted principally of echography and computerized axial tomography of the abdomen, which demonstrated a cystic mass of the lower pole of the spleen. Splenectomy was carried out. Histologic examination showed a pseudocyst of the spleen with a fibrous capsule without an epithelial lining. The treatment and pathogenesis of pseudocysts of the spleen secondary to infectious mononucleosis are discussed.

Adolescent↗
PubMed1985

[Splenectomy for idiopathic thrombopenic purpura. A retrospective study of 40 cases].

The authors analysed retrospectively the files of 40 patients who underwent splenectomy for idiopathic thrombocytopenic purpura and who were totally or partially (relapse) resistant to a therapeutic trial of corticosteroids. There was no operative mortality but morbidity, especially respiratory, was substantial, being 40%. Drainage of the splenic bed should be avoided because this is clearly associated with a greater frequency of pulmonary complications. In 37 patients with a mean follow-up of 30.3 months, there was complete remission in 89.2% after splenectomy. This confirms the therapeutic value of splenectomy in idiopathic thrombocytopenic purpura, especially in those who showed a partial (transitory) response to corticosteroids.

Adolescent↗
PubMed1984

A mouse DNA sequence that mediates integration and excision of polyoma virus DNA.

In mouse cells transformed by a temperature-sensitive polyoma virus (Py) genome, the integrated viral genome recombines with adjacent chromosomal DNA to yield a small cyclic molecule (RmI) with defined viral and cellular components. We have cloned the cellular component (Ins), determined its sequence, and examined its distribution in normal mouse DNA. The sequence of Ins displays several homologies with that surrounding the replication origin (ori) of Py or SV40 DNA.

Animals↗
PubMed1983

Single channel K+ currents from HeLa cells.

The extracellular patch-clamp technique was used in order to investigate the presence of ionic channels in HeLa cells, a well-known cultured cell type obtained from an epidermoid carcinoma of the cervix. Under Gigohm-seal conditions, discrete current jumps could be observed with patch electrodes containing KCl. These channels were found to be mainly permeable to K+ and showed multiple levels of conductance. From single-channel I-V curve measurements, a strong rectification effect, characterized by a large inward and no detectable outward current, was observed. For negative membrane potentials (0 to -90 mV), the measured current-voltage relationship was found to be mostly linear, corresponding to a single-channel conductance of 40 pS. An analysis of some selected time records has revealed in addition that the probability of the channel to be in the open state was a function of the KCl concentration in the patch pipette.

Electric Conductivity↗
PubMed1983

Stable membrane potentials and mechanical K+ responses activated by internal Ca2+ in HeLa cells.

Stable membrane potentials have been measured with microelectrodes in HeLa cells and their average value (-38 mV) compares well with the Cl- electrochemical potential (-34 mV). A hyperpolarizing response is observed upon microelectrode penetrations and following a mechanical or electrical shock; this response is due to a large increase in the K+ permeability, which can also be triggered by Ca2+ injection or blocked by EGTA injection through the microelectrode. Stable hyperpolarizations are obtained with the Ca2+ ionophore A 23187.

Calcium↗
PubMed1983

[Role of passerine birds in the ecology of influenza viruses].

A total of 267 passerine birds distributed among 37 species were netted during spring 1980 and summer 1981 in the Laurentian and Montreal areas. All the cloacal swabs collected at that time wer free of influenza viruses. Three and five days after oral administration of avian or human influenza A virus strains, 108 isolates were obtained from 42 of 134 passerine birds. Positive samples were recovered mainly from the respiratory and the digestive tract and also from liver. Spleen and kidneys. Viral replication is cells from trachea, lungs, gizzard and caecum was detected by indirect immunofluorescence using a monoclonal antibody to influenza A virus nucleoprotein. Viral transmission from inoculated to non inoculated birds placed in the same cages was not observed. On the other hand a similar experimental inoculation of young mallard ducks showed that extensive viral transmission occurred from inoculated to non inoculated ducklings and that infection was found exclusively in the digestive tract. Furthermore viruses were detected in samples of drinking water from all cages containing infected ducks. Passerine birds do not represent an important reservoir of influenza viruses but might contribute to the formation and spreading of recombinants potentially pathogenic for man and animals.

Animals↗
PubMed1982

Surface potential and conductance induced in lipid bilayers by the negatively charged ionophore Br-X537A.

The adsorption of Br-X537Z and its effect on the surface potential of monoolein lipid bilayers was measured using the nonactin conductances as a probe to determine the surface charge density. Because of the pH dependence of this adsorption, it was concluded that not only the negatively charged molecules X- could induce a surface charge but also a dimer HX2- made from X- and the neutral molecule HX. Also an important bilayer conductance was induced by Br-X537A. From the BrX537A concentration dependence of this conductance, the effect of pH, and the induced surface potential, it was found that two charged complexes are transported across the bilayer depending on pH. At pH greater than or equal to 7 the conducting molecule is X- and at pH less than or equal to 5 the complex is H2X3-. A quantitative model is obtained to calculate both the induced surface potential and the conductance.

Adsorption↗
PubMed1982

Cation and local anesthetic conductance induced by the negatively charged ionophore Br-X537A in lipid bilayers.

The cation conductance induced by Br-X537A was measured for K+ and Ca2+ at different pH and different Br-X537A concentrations. The K+-concentration dependence was different depending on the pH of the solution. At pH 4.3, the conductance depended linearly on [K+] while at pH 7 it depended on [K+]2. About the same dependence on [Br-X537A] was found at these pH values. From these results it was concluded that two complexes were transporting K+; at pH greater than or equal to 7 the complex is mostly K2X3- and at pH less than or equal to 5 the complex is mostly KHX3-. From the conductance dependence on [Ca2+], pH, and [Br-X537A] it was found that the only conducting complex is CaX3-. It was also observed that Br-X537A could transport tetracaine. Taking into account the surface charge induced by tetracaine, the conductance depended linearly on the tetracaine concentration. Correcting for the surface charged induced by Br-X537A, the tetracaine conductance was found to depend on [Br-X537A]2. Consequently, the conducting complex is TX2- at pH greater than or equal to 7. No other conducting complexes are formed at the pH is decreased and at pH 4 tetracaine is not conducted. It was found that procaine was not conducted between pH 8 and 4.

Anesthetics, Local↗
PubMed1978

Oscillation of membrane potential in L cells: III K + current-voltage curves.

Cultured L cells were found previously to have an oscillating membrane potential. Current-voltage (I--V) curves were measured during these oscillations. Two I--V curves were recorded, one at the maximum and one at the minimum of oscillations. Each curve is nonlinear, and when they are subtracted from one another, the result gives the I--V curve for the K+ current producing oscillations. This Ik--V curve is zero for -85 to -90 mV and saturates for positive and high negative membrane potentials. When the external K+ is increased the I--V curve is shifted and its zero current potential is reduced. The K+ zero current potential follows a Nernst relation when plotted against the external K+ concentration. The Ik--V curves all have a similar shape at different K+ concentrations, showing a saturation on each side of the zero current potential. The results can be explained satisfactorily in term of a carrier model for K+ ions.

L Cells↗
PubMed1977

Oscillations of membrane potential in L cells. I. Basic characteristics.

The membrane potentials and resistances of L cells were measured using a standard electrophysiological technique. The values obtained in physiological media were around--15 mV and 37Momega, respectively. Almost all the large nondividing L cells (giant L cells) showed spontaneous oscillations of the membrane potential between around -15 and -40 mV. Application of an appropriate electrical or mechanical stimulus was also capable of eliciting responses but such were usually induced only once. The total membrane conductance increased significantly and in parallel with such a hyperpolarizing response. Cooling of the cells and application of metabolic inhibitors to the cells completely blocked the spontaneous oscillation despite the fact that the electrically induced hyperpolarizing response remained. Intracellular K+, Na+ and Cl- concentrations were measured by means of a flame photometer and a chloridometer, and the equilibrium potential for each ion was estimated.

Acetylcholine↗