Liver transplantation in HBsAg-positive HBV-DNA--negative cirrhotics: immunoprophylaxis and long-term outcome

The presence of a positive hepatitis B surface antigen (HBsAg) has been considered a highly questionable indication for orthotopic liver transplantation. We report our experience in the treatment of HBsAg-positive HBV-DNA-negative cirrhotics with liver transplantation, whether or not followed by passive prophylaxis with specific immunoglobulins. Of the 123 cirrhotics who received transplants at our institution since May 1986, 39 (31.7%) were HBsAg positive; of these, 1 was HBV-DNA positive, and 4 were hepatitis Be antigen (HBeAg) positive. Since April 1991, 25 HBsAg-positive HBV-DNA-negative cirrhotics have undergone an original protocol with the periodical intramuscular administration of 5,000 IU of specific immunoglobulins starting in the anhepatic phase and lasting for at least 1 year. There were no differences among cirrhotics in terms of operative mortality and long-term survival with respect to the presence of the HBsAg. Of the 35 HBsAg-positive HBV-DNA-negative patients having a follow-up of 1 month or longer, 12 (34.3%) developed HBsAg recurrence; of them, 4 (33.3%) had received a complete prophylaxis, whereas 8 (66.7%) had not. The recurrence rate was 80% (8 out of 10) in the group of patients who had not received the prophylaxis and 16% (4 out of 25) in the group who had received the prophylaxis (P = .0003). The actuarial recurrence rate in the treated patients was 20.2% and 20.2% after 1 and 3 years, respectively, whereas in the untreated group it was 60.0% and 70.0% (P < .01). The hazard of recurrence of treated patients was reduced to 24.9% compared with untreated patients. Liver transplantation can be performed in HBsAg-positive HBV DNA negative patients without an increase in the operative risk or a worsening of long-term results. Immunoglobulin prophylaxis seems to be effective in preventing hepatitis recurrence after transplantation.     

Blind Multiuser Detection in Multirate CDMA Based on Cyclic LMS Adaptation

The problem of blind adaptive multiuser detection in multirateCDMA systems is considered. Indeed, since symboldetection in multirate CDMA systems requires periodicallytime-varying processing of the observables, classical LMS and RLSadaptive algorithms, which assume that the solution to be trackedis time-invariant or slowly time-varying, are not suited for blindadaptive multiuser detection in a multirate system. While a cyclicRLS algorithm has recently appeared in the literature, thispaper focuses on the development of LMS-based cyclic filteringalgorithms. In particular, cyclic versions of the standard LMSalgorithm, of the LMS algorithm with iterate averaging and of theLMS algorithm with adaptive step-size are derived. Interestingly,the last two algorithms are shown to exhibit a convergence speed close to thatof the cyclicRLS procedure, but with an order of magnitude lower computationalcomplexity.An adaptive procedure for the automatic selection ofthe algorithm periodicity is also presented, which is based on aminimum mean-output-energy criterion, and that obviates theneed for knowledge of the transmitted data-rates from theinterfering signals.Moreover, the case of known multipathfading channels is also examined. In particular, it is shown that theproposed cyclic LMS algorithms can be used to achieve RLS-likeperformance also in the presence of multipath distortion.Extensive computer simulation results, along with some analyticalconvergence results, confirmthat the proposed algorithms are effective and achieve very satisfactoryperformance.     

Response of cat cortical neurons to position and movement of the femur

The contribution of joint afferents to the response of cortical neurons in area 3a to mechanical stimulation of the contralateral hindlimb was evaluated in cats anesthetized with sodium pentobarbital and paralyzed with pancuronium bromide. The hindlimb projection to the pericruciate cortex was established by recording the evoked potentials to electrical stimulation of the sciatic nerve and some of its branches, the bicepssemitendinosus and the quadratus femoris. Out of 169 neurons, 63 responded exclusively to cutaneous stimuli (superficial), whereas the others could be activated by local pressure of hindlimb muscles and/or by joint rotation (deep). Deep neurons were classified as slowly adapting (SA) or rapidly adapting (RA) units. In the neurons responding exclusively to joint rotation, the site of the receptive field could not be identified with certainty. In 13 deep neurons, their firing was affected by rotation of multiple joints of the contralateral hindlimb. In an attempt to identify the source of activation of cortical neurons, partial denervations and muscle disconnections were performed in five animals to isolate and stimulate the hip capsule. In these preparations, in 14 of 15 cortical neurons the source of activation was localized in the periarticular muscles, with no response to mechanical stimulation of the joint capsule. Only one neuron (SA) could be selectively excited by punctate pressure on the hip capsule. Our results suggest that in neurons of area 3a of the cat, the information about the position of the femur relies mainly on muscle afferents.     

Scale effect on concrete in tension

Scale effects in the mechanical behaviour of concrete are important phenomena and are the object of many studies internationally. The Laboratoire Central des Ponts et Chaussées has been working for several years on the scale effect on the distribution function of the tensile strength of concrete. Very many direct tensile tests have been performed on specimens of different volumes, made of concretes having different formulations. From these experimental investigations has been derived a general law that can be used to determine the distribution function (mean and standard deviation) of the tensile strength of the concrete versus the volume of the tensile specimen, for concretes having compressive strengths betwen 30 MPa and 130 MPa, from knowledge of just the compressive strength obtained on a standardized cylinder (in France) and the ratio of the volume of the tensile specimen to the volume of the coarsest aggregate in the concrete. It should be emphasized that this law is valid only if, on the one hand, the mode of preservation of the direct tensile specimens is identical to that of the compressive specimens and, on the other, the aggregates used in the concretes are common aggregates, which eliminates light aggregates and very hard aggregates with a high Young's modulus.

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Resume Les effets d'échelle dans le comportement mécanique du béton sont des phénomènes importants qui font l'object de nombreuses études au niveau international. Le Laboratoire Central des Ponts et Chaussées travaille depuis plusieurs années sur l'effet d'échelle existant sur la fonction de distribution de la résistance à la traction du béton. De très nombreux essais de traction directe ont ainsi été réalisés sur des éprouvettes de volume différent constituées de bétons de formulation également différente. De ces études expérimentales, il a été tiré une loi assez générale qui permet de déterminer, à partir de la seule connaissance de la résistance à la compression obtenue sur cylindre normalisé (en France), et du rapport du volume de l'éprouvette de traction au volume du plus gros grain de béton, la fonction de distribution (moyenne et écart-type) de la résistance à la traction du béton en fonction du volume de l'éprouvette de traction, cela pour des bétons dont la résistance à la compression est comprise entre 30 et 130 MPa. Il faut souligner que cette loi est valable uniquement si, d'une part le mode de conservation des éprouvettes de traction directe est identique à celui des éprouvettes de compression, et d'autre part les granulats utilisés dans les bétons sont des granulats courants, ce qui élimine les granulats légers et les granulats très durs et à fort module de Young.

     

Early ischemia-induced alterations of the outer mitochondrial membrane and the intermembrane space: a potential cause for altered energy transfer in cardiac muscle?

Our aim was to carefully analyse the time-dependent changes that affect the mitochondrial function of myocardial cells during and after an ischemic episode. To this end, variables characterizing mitochondrial function have been evaluated on myocardial samples from isolated rat hearts subjected to different conditions of ischemia. The technique of permeabilized fibers was used in order to evaluate the mitochondrial function whilst retaining intracellular structure. The earliest alteration that could be detected was a decrease in the stimulatory effect of creatine on mitochondrial respiration. This alteration became more pronounced as the severity (or duration) of the ischemia increased. Afterwards, a significant decrease in the apparent Km of mitochondrial respiration for ADP also appeared, followed by a diminution of the maximal respiration rate which was partly restored by adding cytochrome c. Finally, for the most severe conditions of ischemia, the basal respiratory rate also increased. These observations are indicative of a sequence of alterations affecting first the intermembrane space, then the outer mitochondrial membrane, and finally the inner membrane. The discussion is focused on the very early alterations, that could not be detected using the conventional techniques of isolated mitochondria. We postulate that these alterations to the intermembrane space and outer mitochondrial membrane can induce disturbances both in the channelling of energy from the mitochondria, and on the signalling towards the mitochondria. The potential consequences on the regulation of the production of energy (ATP, PC) by the mitochondria are evoked.     

Venezuelan equine encephalitis and Oropouche virus infections among Peruvian army troops in the Amazon region of Peru

An outbreak of a febrile illness characterized by headache, ocular pain, myalgia, and arthralgia occurred during June 1994 among Peruvian army troops in Northern Peru. On June 14-16, 1994, clinical data and blood samples were obtained from eight soldiers with a febrile illness, and from 26 others who had a history of febrile illness during the past three months. A follow-up blood sample was obtained 107 days later from four of the febrile and seven of the afebrile soldiers. Serum samples were tested for dengue (DEN), Oropouche (ORO), and Venezuelan equine encephalitis (VEE) IgM and IgG antibodies by an enzyme-linked immunosorbent assay (ELISA). Virus isolation was performed by inoculation of newborn mice and Vero cell cultures. Viral isolates were identified by immunofluorescence, ELISA, and nucleotide sequencing. A VEE virus infection was confirmed in three of the eight febrile soldiers, two by virus isolation, and one by serology. Antigenic analysis indicated that one of the virus isolates was similar to VEE subtype I, variety ID, viruses previously isolated in Colombia and Venezuela. Nucleotide sequence data showed that both viral isolates were identical to one another and closely related to VEE ID viruses previously isolated in Peru, Colombia, and Venezuela. Serologic results showed that two of 26 afebrile soldiers had IgM antibody to VEE and four had IgG antibody to VEE; two febrile soldiers had IgG antibody in their first serum samples. Oropouche-specific IgM antibody was detected in one of the eight febrile and five of the afebrile soldiers, and 18 of the 34 soldiers had low titers of ORO IgG antibody titers, which did not meet the diagnostic criteria for confirmed cases. All soldiers were negative for DEN IgM antibody, and 10 had flavivirus IgG antibody that reacted with DEN antigens. These data indicated that VEE ID virus was one of the causes of illness among Peruvians soldiers and that this was the first association of this VEE subtype with human disease in Peru.     

The membrane topology of the amino-terminal domain of the red cell calcium pump

A systematic study of the membrane-associated regions in the plasma membrane Ca2+ pump of erythrocytes has been performed by hydrophobic photolabeling. Purified Ca2+ pump was labeled with 3-(trifluoromethyl)-3-(m-[125I]iodophenyl)-diazirine ([125I]TID), a generic photoactivatable hydrophobic probe. These results were compared with the enzyme labeled with a strictly membrane-bound probe, [3H]bis-phosphatidylethanolamine (trifluoromethyl) phenyldiazirine. A significant light-dependent labeling of an M(r) 135,000-140,000 peptide, corresponding to the full Ca2+ pump, was observed with both probes. After proteolysis of the pump labeled with each probe and isolation of fragments by SDS-PAGE, a common pattern of labeled peptides was observed. Similarly, labeling of the Ca2+ pump with [125I]TID, either in isolated red blood cell membranes or after the enzyme was purified, yields a similar pattern of labeled peptides. Taken together, these results validate the use of either probe to study the lipid interface of the membrane-embedded region of this protein, and sustain the notion that the conformation of the pump is maintained throughout the procedures of solubilization, affinity purification, and reconstitution into proteoliposomes. In this work, we put special emphasis on a detailed analysis of the N-terminal domain of the Ca2+ pump. A labeled peptide of M(r) 40,000 belonging to this region was purified and further digested with V8 protease. The specific incorporation of [125I]TID to proteolytic fragments pertaining to the amino-terminal region indicates the existence of two transmembrane stretches in this domain. A theoretical analysis based on the amino acid sequence 1-322 predicts two segments with high probability of membrane insertion, in agreement with the experimental data. Each segment shows a periodicity pattern of hydrophobicity and variability compatible with alpha-helical structure. These results strongly suggest the existence of a transmembrane helical hairpin motif near the N-terminus of the Ca2+ pump.     

Another look at a Bayesian direct deconvolution method

The paper points out that a certain iterative method of direct deconvolution is a particular manifestation of the so-called Expectation-Maximisation (EM) algorithm. Recognition of this leads to the establishment of general convergence results by reference to existing work.