Prevalence of common bile duct stones according to the increasing number of risk factors present. A prospective study employing routinely intraoperative cholangiography in 477 cases

BACKGROUND/AIMS: To determine if the use of Intraoperative choliangiography (IOC) should be routinely performed and, if not, which criteria should be used to select patients requiring IOC during open or laparoscopic cholecystectomy. METHODOLOGY: 495 Patients with 1 or more gallstones were included in a two-year study. Twelve clinical, laboratory, ultrasonographic and intraoperative factors were chosen and evaluated in all cases. Prior to cholecystectomy, IOC was performed after having identified the common bile duct (CBD) and cystic duct. The majority of the patients were operated on by the same surgeon to avoid differences in criteria and techniques. Statistical evaluation made use of the exact Fisher test and chi square test and, a p-value less than 0.05 was considered as significant. RESULTS: IOC could be performed in 479 out of the 495 cases. IOC resulted in a normal CBD in 76.0%, had a false positive in 2.7%, a false negative in 0.48%, and a presence of 1 or more stones in the CBD in 20.9%. The study revealed that when none of the 12 risk factors were present, there were no cases with CBD stones. As the number of risk factors increased, so did the number of cases presenting with CBD stones. CONCLUSION: Not all 12 risk factors show the same index of predictability; only 5 in particular (jaundice, ultrasound diameter CBD 7 mm, bilirubin over 26 umol/it, cystic duct > 4 mm and CBI, diameter over 9 mm) showed a high rate of predictability. However, when careful measurement and evaluation of risk factors for CBD stones are undertaken, it is possible to avoid the routine use of IOC.     

Modulation of C-type inactivation by K+ at the potassium channel selectivity filter

With prolonged or repetitive activation, voltage-gated K+ channels undergo a slow (C-type) inactivation mechanism, which decreases current flow through the channel. Previous observations suggest that C-type inactivation results from a localized constriction in the outer mouth of the channel pore and that the rate of inactivation is controlled by the-rate at which K+ leaves an unidentified binding site in the pore. We have functionally identified two K+ binding sites in the conduction pathway of a chimeric K+ channel that conducts Na+ in the absence of K+. One site has a high affinity for K+ and contributes to the selectivity filter mechanism for K+ over Na+. Another site, external to the high-affinity site, has a lower affinity for K+ and is not involved in channel selectivity. Binding of K+ to the high-affinity binding site slowed inactivation. Binding of cations to the external low-affinity site did not slow inactivation directly but could slow it indirectly, apparently by trapping K+ at the high-affinity site. These data support a model whereby C-type inactivation involves a constriction at the selectivity filter, and the constriction cannot proceed when the selectivity filter is occupied by K+.     

The effects of geometrical parameters on synaptic transmission: a Monte Carlo simulation study

Monte Carlo simulations of transmitter diffusion and its interactions with postsynaptic receptors have been used to study properties of quantal responses at central synapses. Fast synaptic responses characteristic of those recorded at glycinergic junctions on the teleost Mauthner cell (time to peak approximately 0.3-0.4 ms and decay time constant approximately 3-6 ms) served as the initial reference, and smaller contacts with fewer postsynaptic receptors were also modeled. Consistent with experimental findings, diffusion, simulated using a random walk algorithm and assuming a diffusion coefficient of 0.5-1.0 x 10(-5) cm2 s(-1), was sufficiently fast to account for transmitter removal from the synaptic cleft. Transmitter-receptor interactions were modeled as a two-step binding process, with the double-bound state having opened and closed conformations. Addition of a third binding step only slightly decreased response amplitude but significantly slowed both its rising and decay phases. The model allowed us to assess the sources of response variability and the likelihood of postsynaptic saturation as functions of multiple kinetic and spatial parameters. The method of nonstationary fluctuation analysis, typically used to estimate the number of functional channels at a synapse and single channel current, proved unreliable, presumably because the receptors in the postsynaptic matrix are not uniformly exposed to the same profile of transmitter concentration. Thus, the time course of the probability of channel opening most likely varies among receptors. Finally, possible substrates for phenomena of synaptic plasticity, such as long-term potentiation, were explored, including the diameter of the contact zone, defined by the region of pre- and postsynaptic apposition, the number and distribution of the receptors, and the degree of vesicle filling. Surprisingly, response amplitude is quite sensitive to the size of the receptor-free annulus surrounding the receptor cluster, such that expansion of the contact zone could produce an appreciable increase in quantal size, normally attributed to either the presence of more receptors or the release of more transmitter molecules.     

Lower genital tract neoplasia in women with HIV infection

Women who are infected with human immunodeficiency virus (HIV) are at greater risk for the development of lower genital tract neoplasia than are HIV-negative women. Among HIV-positive women, those who are more severely immunosuppressed appear to be at higher risk for cervical intraepithelial neoplasia (CIN), also known as squamous intraepithelial lesions (SILs). Women who are HIV-positive also are more likely than HIV-negative women to have multifocal lower genital tract neoplasia. Cervical cancer is one of the most important acquired immune deficiency syndrome (AIDS)--related malignancies in women. Cancer and intraepithelial neoplasia of the lower genital tract can be persistent, progressive, recurrent, and difficult to treat in HIV-positive women. The most effective method for treating SILs has not been determined. Regular performance of Pap smears in HIV-positive women is of critical importance, as is careful examination of the entire lower genital tract. Also, women with high-grade intraepithelial or cervical cancer should be tested for HIV.     

Differential phase shift keying in two-path Rayleigh channel withadjacent channel interference

A formula is derived for the error probability of M-ary differential phase-shift keying with differential phase detection in a two-path Rayleigh fading channel taking into account adjacent channel interference (ACI), cochannel interference (CCI), intersymbol interference (ISI), and Doppler frequency shift. Square-root Nyquist filters are used with roll-off, β, the transmitter and receiver as in the proposed US digital mobile radio system. The presence of the second path has a profound effect on increasing the bit error probability (BEP) because it causes ISI. In the absence of ISI, ACI has a smaller effect on BEP than CCI. In the presence of ISI their effect is essentially the same. For a given bit energy-to-noise ratio, the binary system has the lowest BEP; however, the bit rate is also the lowest for a given bandwidth. When the main interference is ACI or CCI, a quaternary system has a lower BEP than the octal system. When the main interference is ISI, this is reversed     

Relation between bit and symbol error probabilities for DPSK andFSK with differential phase detection

In M-ary, Gray coded DPSK, and FSK with differential phase detection the bit error probability is usually approximated by the symbol error probability divided by the number of bits in a symbol. This approximation is known to be excellent for PSK with large signal-to-noise ratios in a Gaussian channel. In other cases this approximation may be questionable. Here we compute the exact values of bit error probability for DPSK and FSK in Gaussian, Rayleigh, and Rician channels. We also compute the relative error involved in this approximation. The conclusion is that except for very low values of signal-to-noise ratio the approximation is good for all channels     

Cross-linking of IgG receptors inhibits membrane immunoglobulin-stimulated calcium influx in B lymphocytes

By cross-linking membrane immunoglobulins (mIg), the antigenic stimulation of B lymphocytes induces an increase in intracellular free calcium levels ([Ca2+]i) because of a combination of release from intracellular stores and transmembrane influx. It has been suggested that both events are linked, as in a number of other cases of receptor-induced increase in [Ca2+]i. Conversely, in B lymphocytes, type II receptors for the Fc fragment of IgG (Fc gamma RII) inhibit mIg-mediated signaling. Thus, we have investigated at the level of single cells if these receptors could act on specific phases of mIg Ca2+ signaling. Lipopolysaccharide-activated murine B splenocytes and B lymphoma cells transfected with intact or truncated Fc gamma RII-cDNA were used to determine the domains of Fc gamma RII implicated in the inhibition of the Ca2+ signal. [Ca2+]i was measured in single fura-2-loaded cells by microfluorometry. The phases of release from intracellular stores and of transmembrane influx were discriminated by using manganese, which quenches fura-2, in the external medium as a tracer for bivalent cation entry. The role of membrane potential was studied by recording [Ca2+]i in cells voltage-clamped using the perforated patch-clamp method. Cross-linking of mIgM or mIgG with F(ab')2 fragments of anti-Ig antibodies induced a sustained rise in [Ca2+]i due to an extremely fast and transitory release of Ca2+ from intracellular stores and a long lasting transmembrane Ca2+ influx. The phase of influx, but not that of release, was inhibited by membrane depolarization. The increase in [Ca2+]i occurred after a delay inversely related to the dose of ligand. Co-cross-linking mIgs and Fc gamma RII with intact anti-Ig antibodies only triggered transitory release of Ca2+ from intracellular stores but no Ca2+ influx, even when the cell was voltage-clamped at negative membrane potentials. These transitory Ca2+ rises had similar amplitudes and delays to those induced by cross-linking mIgs alone. Thus, our data show that Fc gamma RII does not mediate an overall inhibition of mIg signaling but specifically affects transmembrane Ca2+ influx without affecting the release of Ca2+ from intracellular stores. Furthermore, this inhibition is not mediated by cell depolarization. Thus, Fc gamma RII represents a tool to dissociate physiologically the phases of release and transmembrane influx of Ca2+ triggered through antigen receptors.     

Heterogeneous distribution of glycinergic and GABAergic afferents on an identified central neuron

Age-related increases and decreases have been described in cortical dendritic neuropil. Here, we examine age-related changes in the basilar dendrites of supragranular pyramidal cells in human superior temporal gyrus (i.e., Wernicke's area) of left and right hemispheres. Tissue was obtained from 20 neurologically normal right-handers from 18-79 years: 10 males (Mage = 52.2 years; SDage = 17.4) and 10 females (Mage = 47.8; SDage = 20.5). In tissue prepared by a modified rapid Golgi technique, ten pyramidal cells were sampled from each hemisphere and evaluated according to the following parameters: total dendritic length, mean dendritic length, and dendritic segment count. Despite considerable interindividual variation, the data exhibited significant dendritic degeneration with aging. There was an age-related decrease in total dendritic length (r[20] = -0.44; P < 0.05) and especially in mean dendritic length (r[20] = -0.69; P < 0.001) with increasing age. Age-mean dendritic length correlations were negative for all segment orders and revealed a progressive decrease in segment length in more distal branches. The number of dendritic segments remained relatively stable across the age span sampled. The data also indicated that interhemispheric dendritic asymmetries decreased with age. Individuals under 50 years of age had significantly greater total dendritic length values in the left hemisphere. Interhemispheric dendritic differences were not significant in individuals over 50.     

Probability of Error in Binary Communication Systems with Causal Band-Limiting Filters--Part II: Split-Phase Signal

The probability of error is computed in four binary communication systems withNth order (N = 1, 2,...,10) Butterworth filters and split-phase signals. The systems have either a sampling detector or an integrating-and-dumping detector; the filter is either in the receiver only or both in the receiver and transmitter. A lower bound to the probability of error is also computed for modified binary communication systems in which prior to the decision the contribution of the past transmitted symbols is eliminated. In all systems the sampling time is optimized and the effect of nonoptimal sampling time on probability of error is demonstrated.     

Detection of 8-hydroxydeoxyguanosine, a marker of oxidative DNA damage, in white blood cells of workers occupationally exposed to styrene

Styrene-7,8-oxide (SO), the major in vivo metabolite of styrene, is a genotoxic compound and a potential carcinogenic hazard to occupationally exposed workers. The aim of the present work was to investigate the ability of styrene exposure to induce formation of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in white blood cells (WBC) of boatbuilders occupationally exposed to styrene. The study of these adducts was conducted to see if styrene exposure can cause oxidative damage of DNA. The 8-OHdG/10(5) dG ratio from 17 styrene-exposed workers showed significant increases (mean +/- SD, 2.23 +/- 0.54, median 2.35, P < 0.001) in comparison to the controls (1.52 +/- 0.45, median 1.50). However, 11 out of 17 workers who were between the ages of 32 and 60 years and had been occupationally exposed to styrene for > 10 years showed higher 8-OHdG/10(5) dG ratios (2.31 +/- 0.62, median 2.37) in comparison to 6 workers with < 6 years of occupational styrene-exposure (2.11 +/- 0.36, median 2.05; P > 0.05, no significant difference between the two groups of workers). The studies presented here provide an indication that styrene exposure can result in oxidative DNA damage.