Emergency Resection in Treatment of Diverticular Disease of Colon Complicated by Peritonitis

Of a consecutive series of 25 patients with peritonitis secondary to colonic diverticular disease all, except one with faecal peritonitis, underwent some form of emergency resection.All the three patients with faecal peritonitis died, but the 22 with purulent peritonitis survived. The average duration of the emergency admission of the 22 survivors was 25.4 days, and in nine (41%) of them intestinal continuity had been restored by the end of that admission.Thus some form of emergency resection is the operation of choice in patients with spreading peritonitis due to diverticular disease of the sigmoid colon.     

Statistical inference from single channel records: two-state Markov model with limited time resolution

Though stochastic models are widely used to describe single ion channel behaviour, statistical inference based on them has received little consideration. This paper describes techniques of statistical inference, in particular likelihood methods, suitable for Markov models incorporating limited time resolution by means of a discrete detection limit. To simplify the analysis, attention is restricted to two-state models, although the methods have more general applicability. Non-uniqueness of the mean open-time and mean closed-time estimators obtained by moment methods based on single exponential approximations to the apparent open-time and apparent closed-time distributions has been reported. The present study clarifies and extends this previous work by proving that, for such approximations, the likelihood equations as well as the moment equations (usually) have multiple solutions. Such non-uniqueness corresponds to non-identifiability of the statistical model for the apparent quantities. By contrast, higher-order approximations yield theoretically identifiable models. Likelihood-based estimation procedures are developed for both single exponential and bi-exponential approximations. The methods and results are illustrated by numerical examples based on literature and simulated data, with consideration given to empirical distributions and model control, likelihood plots, and point estimation and confidence regions.     

Cell-free translation of mRNA encoding an arterial smooth muscle cell proteoglycan core protein

The size and immunological reactivity of the primary gene products of a small non-aggregating dermatan sulfate proteoglycan from bovine and monkey arterial smooth muscle cells were examined after cell-free translation of mRNA. Antisera against the dermatan sulfate proteoglycans from bovine articular cartilage, DSPG II [Rosenberg et al. J. Biol. Chem. 260, 6304 (1985)] and human skin fibroblasts [Glossl et al. J. Biol. Chem. 259, 14144 (1984)] were used to show that the unmodified smooth muscle precursor core protein was immunologically related to both the cartilage and fibroblast core proteins. The size of the precursor core proteins within each species was identical regardless of the tissue source. Comparison of the precursor core proteins synthesized by primate and bovine cells revealed that the bovine core proteins were approximately 1500 Da larger than the primate core proteins as determined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. A similar size difference was observed when the mature core proteins of monkey smooth muscle cells and bovine articular chondrocytes were compared after removal of the glycosaminoglycan chains. These results indicate that arterial smooth muscle cells synthesize a dermatan sulfate proteoglycan whose core protein is similar to, if not the same as, the cartilage and fibroblast dermatan sulfate proteoglycan core proteins. These core proteins may be encoded by the same gene that has diverged in size during speciation.     

Swainsonine treatment accelerates intracellular transport and secretion of glycoproteins in human hepatoma cells

We are interested in determining whether carbohydrates are important regulatory determinants in the intracellular transport and secretion of glycoproteins. In the present study, we have used swainsonine, an indolizidine alkaloid, to modify the structure of N-glycosidically linked complex oligosaccharides. By inhibiting Golgi mannosidase II, swainsonine prevents the trimming of GlcNAc(Man)5(GlcNAc)2 to GlcNAc-(Man)3(GlcNAc)2, resulting in the formation of hybrid-type oligosaccharides. We find, from pulse-chase experiments using [35S]methionine and immunoprecipitation of individual proteins from culture media, that swainsonine treatment (1 microgram/ml) accelerated the secretion of glycoproteins (transferrin, ceruloplasmin, alpha 2-macroglobulin, and alpha 1-antitrypsin) by decreasing the lag period by 10-15 min relative to untreated cultures. The enhanced secretion was specific for glycoproteins since the secretion of albumin, a nonglycoprotein, was unaffected. When alpha 1-antitrypsin was immunoprecipitated from the cell lysates, sodium dodecyl sulfate-polyacrylamide gel electrophoresis fluorographic analysis demonstrated that the conversion of the high-mannose precursor to the hybrid form in swainsonine-treated cells occurred more rapidly (by about 10 min) than the conversion to the complex form in control cells. Since both the hybrid and complex forms of alpha 1-antitrypsin are terminally sialylated by sialyltransferase in the trans-Golgi, these results suggest that swainsonine-modified glycoproteins traverse the Golgi more rapidly than their normal counterparts. Therefore, accelerated transport within this organelle may account for the decreased lag period of glycoprotein secretion in the swainsonine-treated cultures.     

The phylogeny of the hominoid primates: a statistical analysis of the DNA-DNA hybridization data

Sibley and Ahlquist compared the single-copy nuclear DNA sequences of the hominoid primates using DNA-DNA hybridization. From this data set they estimated a phylogeny that clusters man and chimpanzees using a distance Wagner procedure. However, no assessment of statistical confidence in this estimated phylogeny was made, despite the fact that their data set contains internal inconsistencies concerning the correct branching order. This paper presents a modification of Pielou's Q- statistic that allows one to make nonparametric tests of phylogenetic relationship from distance data. The results of this analysis indicate that the estimated phylogeny of Sibley and Ahlquist is without statistical significance owing to the internal inconsistencies of the data set. A survey and additional analyses of other types of molecular data indicate that the phylogeny that clusters chimpanzees and gorillas and has the human lineage splitting off earlier is statistically consistent with all the molecular data (including the DNA-DNA hybridization data), whereas the phylogeny estimated by Sibley and Ahlquist can be rejected at the 5% level using the data on restriction- endonuclease sites in the mitochondrial genome.      

Screening of rice (Oryza sativa L.) genotypes for physiological characters contributing to salinity resistance,and their relationship to overall performance

Summary Phenotypic resistance of salinity is expressed as the ability to survive and grow in a salinised medium. Some subjective measure of overall performance has normally been used in plant breeding programmes aimed at increasing salinity resistance, not only to evaluate progeny, but to select parents. Salinity resistance has, at least implicitly, been treated as a single trait. Physiological studies of rice suggest that a range of characteristics (such as low shoot sodium concentration, compartmentation of salt in older rather than younger leaves, tolerance to salt within leaves and plant vigour) would increase the ability of the plant to cope with salinity. We describe the screening of a large number of rice genotypes for overall performance (using an objective measure based on survival) and for the aforementioned physiological traits. There was wide variation in all the characters studied, but only vigour was strongly correlated with survival. Shoot sodium concentration, which a priori is expected to be important, accounted for only a small proportion of the variability in the survival of salinity. Tissue tolerance (the cellular component of resistance reflecting the ability to compartmentalise salt within leaves) revealed a fivefold range between genotypes in the tolerance of their leaves to salt, but this was not correlated positively with survival. On the basis of such (lack of) correlation, these traits would be rejected in normal plant breeding practice, but we discuss the fallacies involved in attempting correlation between individual traits and the overall performance of a salt-sensitive species in saline conditions. We conclude that whilst overall performance (survival) can be used to evaluate the salt resistance of a genotype, it is not the basis on which parents should be selected to construct a complex character through breeding. It was the norm for varieties which had one good characteristic affecting salt resistance to be unexceptional or poor in the others. This constitutes experimental evidence that the potential for salt resistance present in the rice genome has not been realised in genotypes currently extant. The results are discussed in relation to the use of physiological traits in plant breeding, with particular reference to environmental stresses that do not affect a significant part of a species' ecological range.     

Interactions ofCandida albicans with bacteria and salivary molecules in oral biofilms

The yeastCandida albicans coaggregates with a variety of streptococcal species, an interaction that may promote oral colonization by yeast cells.C. albicans andCandida tropicalis are the yeasts most frequently isolated from the human oral cavity and our data demonstrate that both these species bind toStreptococcus gordonii NCTC 7869 while two otherCandida species (Candida krusei andCandida kefyr) do not. Adherence ofC. albicans was greatest when the yeast had been grown at 30° C to mid-exponential growth phase. For 21 strains ofC. albicans there was a positive correlation between the ability to adhere toS. gordonii and adherence to experimental salivary pellicle. Whole saliva either stimulated or slightly inhibited adherence ofC. albicans toS. gordonii depending on the streptococcal growth conditions. The results suggest that the major salivary adhesins and coaggregation adhesins ofC. albicans are co-expressed.     

Superposition properties of interacting ion channels.

Quantitative analysis of patch clamp data is widely based on stochastic models of single-channel kinetics. Membrane patches often contain more than one active channel of a given type, and it is usually assumed that these behave independently in order to interpret the record and infer individual channel properties. However, recent studies suggest there are significant channel interactions in some systems. We examine a model of dependence in a system of two identical channels, each modeled by a continuous-time Markov chain in which specified transition rates are dependent on the conductance state of the other channel, changing instantaneously when the other channel opens or closes. Each channel then has, e.g., a closed time density that is conditional on the other channel being open or closed, these being identical under independence. We relate the two densities by a convolution function that embodies information about, and serves to quantify, dependence in the closed class. Distributions of observable (superposition) sojourn times are given in terms of these conditional densities. The behavior of two channel systems based on two- and three-state Markov models is examined by simulation. Optimized fitting of simulated data using reasonable parameters values and sample size indicates that both positive and negative cooperativity can be distinguished from independence.