Biomedical subjects
A Franco
Publications and source records attributed to A Franco.
CAPD with three bag exchanges and one day rest. Results of a new protocol.
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[Gastroenteritis caused by adenovirus].
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[Superior vena cava syndrome: radiologic study].
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[A new method for the approach to the lateral cerebral ventricle of the ewe (Ovis aries)].
The proposed technique consists of placing a catheter in the olfactory recess of the lateral ventricle of the brain of a sheep. Twenty adult ewes were used in the study. The olfactory recess is in the frontal region 25 +/- 3 mm below the skin, just caudal to the line joining the supraorbital foramen and approximately 8-10 mm from the median plane. The approach is relatively easy under normal experimental conditions. The wall of the olfactory bulb, however, is fragile, and the animals must not have been injured by Oestrus ovis.
[Streptococcus pyogenes not producing beta hemolysis during aerobiosis].
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Structural study of spongiosa tissue in growing sheep.
A study was made of 160 long bones taken from 40 native Merino sheep of both sexes. These animals, which represented uniform growth (mean growth-curve values), were divided into four groups which were slaughtered consecutively at 0, 45, 105 and 270 days old (0, 6.4, 15 and 38.5 weeks, respectively). The following bones were studied; humerus, femur, tibia and os coxae. Thin lamellae taken from the metaphyses of the bones obtained were fixed, decalcified and stained with hematoxylin-eosin to assess the development of the various components of growing bony tissue. The bones studied followed the same maturation pattern; the os coxae proved to be the best histological indicator in differentiating the age of the animals studied.
Significance of anti-HBx antibodies in hepatitis B virus infection.
Serological responses to hepatitis B virus-X determinants have been noted in human sera, but conflicting findings concerning the correlation of anti-HBx antibodies with different stages of hepatitis B virus infection or pathological sequelae have been reported. Using an adenovirus-based eukaryotic vector, the 17 kD X protein was efficiently expressed in 293 cells. Cellular extracts containing the eukaryotic X protein have been used to screen for anti-HBx antibodies by immunoblot analysis in a large panel of sera from patients affected by hepatitis B virus chronic hepatitis, hepatocellular carcinoma and acute viral hepatitis. Sera from 32 of 171 (19%) chronic hepatitis B virus patients were positive for anti-HBx antibodies. Only one of thirty-two (3%) HBsAg-negative, anti-HBs/anti-HBc-positive chronic hepatitis serum was anti-HBx positive. Very few sera from primary hepatocellular carcinoma patients showed positivity for anti-HBx (8 of 149 or 5%). Anti-HBx were also detected in 8 of 48 (17%) acute viral hepatitis patients. In the four cases that were followed up weekly, anti-HBx antibodies appeared 3 to 4 wk after the onset of the clinical signs. To compare the X protein expressed in eukaryotic and prokaryotic cells as a substrate for anti-HBx antibody detection, 171 sera were screened with HBx fusion proteins expressed in Escherichia coli. The prokaryotic cell extract test seems to be more sensitive. During the chronic phase of hepatitis B virus infection, the presence of anti-HBx antibodies detected with the eukaryotic cell extract correlates with the presence of well-established markers of ongoing viral replication: serum hepatitis B virus-DNA (p less than 0.001) and intrahepatic HBcAg expression (p less than 0.001).
[Arterial aging and lower limb arteriopathy].
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[The pleural line sign].
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[Computerized tomographic and echographic findings in a peritoneal mass].
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Tumour necrosis factor-alpha synthesis by cerebrospinal-fluid-derived T cell clones from patients with multiple sclerosis.
T cell clones derived from cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS) were analysed for their ability to produce interferon-gamma (IFN-gamma), tumour necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2) and interleukin-4 (IL-4). The CSF-T clones were compared for their ability to produce cytokines with autologous peripheral T clones and with liver-infiltrating T cell clones from patients with chronic active hepatitis. IL-4 production was also compared with that by peripheral T clones derived from atopic patients. All the CSF-T clones (both CD4+ and CD8+) produced large amounts of IFN-gamma and particularly of TNF-alpha. These cytokines were synthesized in significantly larger amounts by CSF T clones than by reference clones. Moreover, they were capable of secreting IL-2, but not IL-4. We conclude that the CSF-CD4+ T clones could constitute a subset with functional properties similar to those of T helper 1 (Th1)inflammatory cells of the mouse; and that the large amounts of TNF produced by CSF T cell clones strongly suggest a significant role for this cytokine in MS immunopathogenesis.
Selective killing of hepatitis B envelope antigen-specific B cells by class I-restricted, exogenous antigen-specific T lymphocytes.
Specific B lymphocytes can act as very efficient antigen-presenting cells. They bind antigen with high affinity via their immunoglobulin receptors, process it through the class II major histocompatibility complex (MHC) pathway, and present its fragments to class II-restricted T lymphocytes. In general, exogenous antigens and noninfectious viral particles enter the class II pathway and are selectively associated with class II MHC molecules. The presentation of an exogenous antigen in association with class I molecules has been reported for only a few antigens, including the hepatitis B envelope antigen (HBenvAg). Here we demonstrate that antigen-specific B cells can efficiently deliver HBenvAg to the class I pathway, presenting its fragments to class I-restricted cytotoxic T lymphocytes (CTLs) which kill the specific B cells. This could represent a mechanism of suppression of neutralizing anti-hepatitis B virus (HBV) antibody response, a phenomenon that accompanies the development of the chronic HBV-carrier state.
Calcium entry through stretch-inactivated ion channels in mdx myotubes.
Recent advances in understanding the molecular basis of human X-linked muscular dystrophies have come from the identification of dystrophin, a cytoskeletal protein associated with the surface membrane. Although there is little or virtually no dystrophin in affected individuals, it is not known how this causes muscle degeneration. One possibility is that the membrane of dystrophic muscle is weakened and becomes leaky to Ca2+. In muscle from mdx mice, an animal model of the human disease, intracellular Ca2+ is elevated and associated with a high rate of protein degradation. The possibility that a lack of dystrophin alters the resting permeability of skeletal muscle to Ca2+ prompted us to compare Ca2(+)-permeable ionic channels in muscle cells from normal and mdx mice. We now show that recordings of single-channel activity from mdx myotubes are dominated by the presence of Ca2(+)-permeable mechano-transducing ion channels. Like similar channels in normal skeletal muscle, they are rarely open at rest, but open when the membrane is stretched by applying suction to the electrode. Other channels in mdx myotubes, however, are often open for extended periods of time at rest and close when suction is applied to the electrode. The results show a novel type of mechano-transducing ion channel in mdx myotubes that could provide a pathway for Ca2+ to leak into the cell.
"NEONATE"--an expert application for the "HELP" system: comparison of the computer's and the physician's problem list.
NEONATE is a prototype of an expert application for the HELP Hospital Information System. Its goal is to improve documentation in the Newborn Intensive Care Unit. The decision module of NEONATE is designed to produce an admission problem list. In this paper, the admission problem list that NEONATE generates was compared to the admission problem list of the current CETUS system for 30 patients. These were compared to a retrospectively constructed gold standard problem list. Of 101 problems in the gold standard list, 56 were on the current admission reports; 82 were found by NEONATE. NEONATE found 31 problems missed on the current admission reports; the current admission reports contained 5 problems missed by NEONATE. The current admission reports contained 9 false positives; whereas NEONATE's reports contained 27. Of the 27, 16 were caused by a single rule in NEONATE. We conclude that an expert system has great potential for improving the documentation of the patient problem list.
Liver-derived T cell clones in autoimmune chronic active hepatitis: accessory cell function of hepatocytes expressing class II major histocompatibility complex molecules.
Thirty T cell clones were generated from T cell blasts, infiltrating the liver of autoimmune chronic active hepatitis (CAH) patients, stimulated with autologous hepatocytes expressing class II major histocompatibility complex (MHC) molecules and interleukin 2 (IL2). Sixteen clones were CD4+ and 14 were CD8+; all were CD25+ and WT31+, revealing that all cell lines expressed the alpha/beta chains of T cell receptor. Five CD4+ and 4 CD8+ T clones proliferated in response to hepatocytes expressing both class I and class II antigens. The hepatocyte recognition was MHC restricted because only class II MHC-matched hepatocytes were able to stimulate the CD4+ T clones, while only class I-matched hepatocytes stimulated CD8+ T clones, and because MoAbs to monomorphic determinants of class II antigens or to class I antigens appeared to block the response of the CD4+ and CD8+ T clones, respectively. These findings, together with the observation that autologous irradiated peripheral blood mononuclear cells (iPBMC) were unable to stimulate the clones, indicate that the response of these clones was directed to a liver membrane antigen in association with class II or class I MHC molecules on the surface of the hepatocytes. All the CD8+ T clones and 5 CD4+ T clones expressed high cytotoxic activity in a lectin-dependent cell-mediated cytotoxicity assay; 10 CD8+ and 3 CD4+ T clones also showed natural killer (NK)-like function. The cytolytic machinery was also present in those clones (both CD8 and CD4) recognizing the HLA-matched hepatocytes. All liver-derived T clones were able to produce high amounts of interferon (IFN)-gamma, as well as being capable of secreting IL2, following PHA stimulation.
Properties of embryonic and adult muscle acetylcholine receptors transiently expressed in COS cells.
We used transient transfection in COS cells to compare the properties of mouse muscle acetylcholine receptors (AChRs) containing alpha, beta, delta, and either gamma or epsilon subunits. gamma- and epsilon-AChRs had identical association rates for binding 125I-alpha-bungarotoxin, and identical curves for inhibition of toxin binding by d-tubocurarine, but epsilon-AChRs had a significantly longer half-time of turnover in the membrane than gamma-AChRs. A myasthenic serum specific for the embryonic form of the AChR reduced toxin binding to gamma-, but not epsilon-AChRs. The gamma-AChRs had channel characteristics of embryonic AChRs, whereas the major class of epsilon-AChR channels had the characteristics of adult AChRs. Two minor channel classes with smaller conductances were also seen with epsilon-AChR. Thus, some, but not all, of the differences between AChRs at adult endplates and those in the extrasynaptic membrane can be explained by the difference in subunit composition of gamma- and epsilon-AChRs.
Stretch-sensitive channels in developing muscle cells from a mouse cell line.
1. Recordings of single-channel activity were made from cell-attached patches on mouse C2 muscle cells at morphologically identifiable stages of myogenesis in vitro. We have identified Ca2(+)-permeable, cation-selective channels that are gated by applying suction to the patch electrode and by changes in membrane potential and have analysed single-channel properties as well as channel expression during myogenesis. 2. Single-channel activity could be detected when the membrane was held at steady negative potentials. With monovalent cations in the electrode, the single-channel current-voltage (i-V) relations were linear. The channel is permeable to Li+, Na+, K+, Rb+ and Cs+, but is not strongly selective among the monovalent cations as judged by measurements of single-channel conductance and reversal potential. 3. With 110 mM of either CaCl2 or BaCl2 as the only inward change carrier, slope conductances were approximately 13 and 24 pS and currents reversed at approximately +22 and +17 mV, respectively. The relative permeability of Ca2+ to K+ calculated from the constant-field equation was PCa/PK = approximately 2. 4. Channel openings occurred as bursts of brief openings and closings separated by much longer closed periods. Closed-time histograms were best fitted with three exponential components, while histograms of burst duration were best fitted with two exponential components, reflecting the short and long bursts in the single-channel records. 5. Applying suction to the patch electrode while recording at steady negative membrane potentials produced channel openings to discrete current levels. Mean channel open probability depended linearly on the square of the applied pressure and was greater at positive membrane potentials. The permeability of the channel to monovalent and divalent cations was indistinguishable from the spontaneous activity recorded at steady negative potentials. 6. Channel activity recorded from cell-attached patches in the absence of applied pressure depended on membrane potential increasing approximately e-fold per 38 mV with depolarization. Analysis of the kinetics of the response to membrane potential showed that the depolarization reduced the duration of the slowest component of the closed-time distribution. 7. The lanthanide cation gadolinium (Gd) reduced the amplitude of the unitary currents in a concentration-dependent manner. The amplitudes of both inward and outward currents were reduced to the same extent suggesting block is voltage-independent. Gd produced half-maximal inhibition of the unitary current at approximately 6 microM.(ABSTRACT TRUNCATED AT 400 WORDS)