The essence of phase transitions in condensed matter by an information theoretic approach

Our information theoretic considerations suggest that the essence of phase transitions in condensed matter is the change in entropy as reflected in the change in the number of isomers between two phases. The explicit number of isomers as a function of size is computed using a graph theoretic approach that is compared to a direct count for smaller systems. This allows us to apply a common approach to both nanosystems and their macroscopic limit. The entropy increases very rapidly with size with the results that replacing the actual distribution over size by an average is not an accurate approximation. That the phase transition is a sharp function of the temperature is due to the high heat capacity of both the solid and liquid phases. The difference in entropy at the transition is related to the Trouton-Richards considerations. The finite width of the boundary between two phases of a finite system is related to the inherent uncertainty product that is derived from the maximum entropy formalism and that is a result of the fluctuations about equilibrium. As the system size increases, the boundary becomes sharper and one recovers the usual thermodynamic description.

Post-partum concentrations of serum progesterone, oestradiol and prolactin in Arabian mares demonstrating normal maternal behaviour and Arabian mares demonstrating foal rejection behaviour

The aim of this prospective study was to investigate possible endocrine components to foal rejection behaviour in post-partum Arabian mares. Arabian mares were divided into two groups based on their maternal behaviour: (1) mares with normal post-parturient behaviour (8 mares); and (2) mares that demonstrated foal-rejecting behaviour post-partum (15 mares). Most mares were visited and sampled twice, in the first and third days post-partum. Serum samples were used for measurement of progesterone, oestradiol and prolactin concentrations. There were no statistically significant differences in oestradiol, progesterone or prolactin concentrations between the groups. In the rejecting mares, there was a statistically significant decrease in the progesterone (mean±standard deviation, SD, 3.14±6.2ng/dL on day 1 and 0.49±0.18ng/dL on day 3) and prolactin (mean±SD 216.2±325.4ng/mL on day 1 and 145.2±311.4ng/mL on day 3) concentrations between days 1 and 3, while the oestradiol concentration did not change significantly. In the non-rejecting mares, progesterone concentrations decreased significantly (mean±SD 0.8±0.23ng/dL on day 1 and 0.43±0.22 on day 3) while the oestradiol and prolactin concentrations did not change significantly. The oestradiol to progesterone ratio was significantly higher in non-rejecting mares on day 1 (mean±SD 114.8±140.2 on day 1 and 143.4±72.6 on day 3) and this ratio increased significantly from days 1 to 3 in the rejecting mares (mean±SD 47.3±21.1 on day 1 and 122.1±123.7 on day 3).

Efficiency of superovulation and in vivo embryo production in eFSH-treated donor mares after estrus synchronization with progesterone and estradiol-17beta

Reliable methods of regulating estrus and stimulating superovulations in equine embryo transfer programs are desirable. Our objectives were to investigate the efficacy of a progesterone and estradiol-17beta (P&E) estrus synchronization regimen in mares with and without subsequent equine follicle-stimulating hormone (eFSH) treatment and to examine the effects of eFSH on folliculogenesis and embryo production. Cycling mares were treated with P&E daily for 10 d. On the final P&E treatment day, prostaglandin F(2alpha) was administered, and mares were randomly assigned to one of two treatment groups (n=20 mares/group). In both groups, mares were examined daily by transrectal ultrasonography. In the eFSH group, twice-daily eFSH treatments were initiated at follicle diameter 20 to 25 mm and ceased at follicle > or =35 mm; human chorionic gonadotrophin (hCG) was administered after 36 h. In the control group, eFSH treatments were not given, but hCG was administered at follicle > or =35 mm. Mares were inseminated with fresh semen, and embryo recovery attempts were performed 8 d postovulation. Synchrony of ovulations within each group appeared to be similar. Six mares in the eFSH group failed to ovulate. The eFSH treatment resulted in higher (P<0.05) numbers of preovulatory follicles and ovulations; however, embryo recovery rate did not increase (eFSH 1.0+/-0.4 vs. control 0.95+/-0.1 embryos/recovery attempt), and embryo per ovulation rate was significantly lower (36% vs. 73%). The eFSH-treated mares had significantly higher frequency of nonovulatory follicles (28% vs. 0) and higher periovulatory serum concentrations of estradiol-17beta. Based on our findings, combined P&E and eFSH regimens cannot be recommended for cycling donor mares.

Quantitative monitoring by polymerase colony assay of known mutations resistant to ABL kinase inhibitors

Resistance to molecularly targeted chemotherapy, and the development of novel agents that are active against resistant forms of target proteins create the need for a sensitive and quantitative assay to monitor drug-resistant mutations in patients to guide treatment and assess response. Here, we describe an application of the polymerase colony (polony) method to identify and quantify known point mutations in the BCR-ABL oncogene in patients with chronic myelogenous leukemia who evolve resistance to ABL kinase inhibitors. The assay can detect mutations with a sensitivity of 10(-4), quantify the burden of drug-resistant cells, and simultaneously monitor the dynamics of several coexisting mutations. As a proof of concept, we analysed blood samples from three patients undergoing therapy with ABL kinase inhibitors and found that the patients' response to therapy correlated with our molecular monitoring. We were also able to detect mutations emerging in patients long before clinical relapse. Therefore, the polony assay could be applied to a larger patient sample to assess the utility of early mutation detection in patient-specific treatment decisions. Finally, this methodology could be a valuable research tool to shed light on the natural behavior of mutations pre-existing kinase inhibitors therapy and either disappearing over time or slowly taking over.

Increased growth of young citrus trees under reduced radiation load in a semi-arid climate

This study investigated the effects of radiation heat-load reduction by shading on the growth and development of citrus trees in a warm subtropical region. The experiment was conducted from mid-June until late October when daily maximal air temperature averaged 29.3 degrees C. Two-year-old de-fruited Murcott tangor (Citrus reticulata BlancoxCitrus sinensis (L.) Osb.) trees were grown under 30% or 60% shade tunnels, or 60% flat shade (providing midday shade only), using highly reflective aluminized nets. Non-shaded trees were used as the control. Shading reduced direct more than diffuse radiation. Daily radiation was reduced by 35% for the 30% Tunnel and 60% Flat treatments, and by 55% for the 60% Tunnel. Two days of intensive measurement showed that shading increased average sunlit leaf conductance by 44% and photosynthesis by 29%. Shading did not significantly influence root and stem dry weight growth, but it increased the increment in leaf dry weight during the three month period by an average of 28% relative to the control, while final tree height in the 30% Tunnel treatment exceeded the control by 35%. Shoot to root and shoot mass ratios increased and root mass ratio decreased due to shading because of the increase in leaf dry weight. Shading increased starch concentration in leaves while the shadiest treatment, 60% Tunnel, decreased starch concentration in the roots. Carbon isotope ratio (delta(13)C) of exposed leaves that developed under shading was significantly reduced by 1.9 per thousand in the 60% Tunnel, indicating that shading increased CO(2) concentrations at the chloroplasts (C(c)), as would be expected from increased conductance. Substomatal CO(2) concentrations, C(i), computed from leaf net CO(2) assimilation rate and conductance values, also indicate that shading increases internal CO(2) concentrations. Based on tree dry mass, tree height, and total carbohydrates fractions, the 30% Tunnel and the 60% Flat were the optimal shade treatments.

The spectrum of mutations, including four novel ones, in the thiamine-responsive megaloblastic anemia gene SLC19A2 of eight families

Thiamine responsive megaloblastic anemia (TRMA) is an autosomal recessive disorder with a triad of symptoms: megaloblastic anemia, deafness, and non-type 1 diabetes mellitus. Occasionally, cardiac abnormalities and abnormalities of the optic nerve and retina occur as well. Patients with TRMA often respond to treatment with pharmacological doses of thiamine. Recently, mutations were found in patients with TRMA in a thiamine transporter gene (SLC19A2). We here describe the mutations found in eight additional families. We found four novel mutations and three that were previously described. Of the novel ones, one is a nonsense mutation in exon 1 (E65X), two are missense mutations in exon 2 (S142F, D93H), and another is a mutation in the splicing donor site at the 5' end of intron 4 (C1223+1G>A). We also summarize the state of knowledge on all mutations found to date in TRMA patients. SLC19A2 is the first thiamine transporter gene to be described in humans. Reviewing the location and effect of the disease causing mutations can shed light on the way the protein functions and suggest ways to continue its investigation.

Mutations in SLC19A2 cause thiamine-responsive megaloblastic anaemia associated with diabetes mellitus and deafness

Thiamine-responsive megaloblastic anaemia (TRMA), also known as Rogers syndrome, is an early onset, autosomal recessive disorder defined by the occurrence of megaloblastic anaemia, diabetes mellitus and sensorineural deafness, responding in varying degrees to thiamine treatment (MIM 249270). We have previously narrowed the TRMA locus from a 16-cM to a 4-cM interval on chromosomal region 1q23.3 (refs 3,4) and this region has been further refined to a 1.4-cM interval. Previous studies have suggested that deficiency in a high-affinity thiamine transporter may cause this disorder. Here we identify the TRMA gene by positional cloning. We assembled a P1-derived artificial chromosome (PAC) contig spanning the TRMA candidate region. This clarified the order of genetic markers across the TRMA locus, provided 9 new polymorphic markers and narrowed the locus to an approximately 400-kb region. Mutations in a new gene, SLC19A2, encoding a putative transmembrane protein homologous to the reduced folate carrier proteins, were found in all affected individuals in six TRMA families, suggesting that a defective thiamine transporter protein (THTR-1) may underlie the TRMA syndrome.

Atrichia with papular lesions maps to 8p in the region containing the human hairless gene

Atrichia with papular lesions (APL) (OMIM 209500) is a hereditary form of alopecia. Hair loss occurs soon after birth and is followed years later by the development of a diffuse papular eruption. Its mode of transmission is still uncertain. A related but clinically distinct form of alopecia, known as alopecia universalis (OMIM 203655), has recently been found to be associated with a mutation in the human hairless gene. The present report describes the largest consanguineous kindred of APL reported to date and provides strong evidence for autosomal recessive inheritance of this rare disorder. On the basis of a linkage analysis of this kindred using six microsatellite markers spanning the human hairless gene region, we found that the APL locus maps to chromosome region 8p12 in a 5 cM interval between marker D8S560 and marker D8S1739. A maximum lodscore of 3.7 was obtained with marker D8S1786, at a recombination fraction of 0. Our results suggest phenotypic variability at the hairless locus although they do not rule out the existence of a gene cluster associated with hair disorders in the same region.

Early events in mammalian egg activation

The fertilizing spermatozoon initiates a series of events in the mammalian egg, referred to as 'egg activation'. These biochemical and morphological events include a transient rise in intracellular Ca2+ concentration ([Ca2+]i) that leads to the cortical reaction (CR) and the establishment of the block to polyspermy on the one hand, and to the resumption of meiosis and later embryonic mitotic divisions on the other. The initial increase in [Ca2+]i appears to be critical for the initiation of egg activation. However, another second messenger, protein kinase C (PKC), was also suggested as a possible inducer of some aspects of egg activation. The review focuses on early events during mammalian sperm-egg interaction and discusses possible roles of Ca2+ and PKC in egg activation.

Mechanisms leading to cortical reaction in the mammalian egg

Activation of the mammalian egg results in cortical reaction (CR), which is correlated with an increase in intracellular Ca2+ concentration and PKC activation. The CR is a gradual rather then an "all or none" response, and can be regulated by different concentrations of parthenogenetic activators. To evaluate the biological significance of parthenogenetic induced CR, rat eggs were fertilized or activated by different concentrations of ionomycin and TPA. Cortical granules (CG) were monitored by electron microscopy, while the CG exudate was visualized by Lens culinaris lectin and Texas Red, using light and confocal microscopy. The ability of the CR to trigger a full block to polyspermy was examined in an IVF system. Our study demonstrates the existence of light and dark CG, which differ by number, distribution in the egg cortex, and sensitivity to parthenogenetic activators. Sperm penetration or high concentration of activators, trigger depletion of both light and dark CG, leading to a full CR. Low concentration of activators altered the CG density, the ratio of dark/light CG, and induced partial CR that was sufficient to cause a block to polyspermy. The results imply that Ca2+ rise or PKC activation have different effects on light and dark CG. In recently fertilized or parthenogenetically activated eggs, CG exudate appeared as evenly distributed spots, whereas in more advanced stages of fertilization the exudate was scattered as patchy aggregates. This observation suggests a difference in the dispersion of CG exudate after fertilization as compared to parthenogenetic activation.

Refined mapping of the gene for thiamine-responsive megaloblastic anemia syndrome and evidence for genetic homogeneity

Thiamine-responsive megaloblastic anemia (TRMA, also known as Rogers syndrome, OMIM 249270) is a rare autosomal recessive disorder characterized by a triad of megaloblastic anemia, diabetes mellitus, and sensorineural deafness. Patients respond, to varying degrees, to treatment with megadoses of thiamine. We have recently shown genetic linkage of the TRMA gene to a 16-centimorgan (cM) region on 1q23.2-1q23.3 based on the analysis of four large, inbred families of Alaskan, Italian, and Israeli-Arab origin. Here we narrow the TRMA interval down to 4 cM based on genetic recombination, homozygosity mapping, and linkage disequilibrium (highest LOD score of 12.5 at D1S2799, at a recombination fraction of 0). We provide further evidence that the TRMA gene is located in this region and confirm the homogeneity of the disease. In this analysis, we genotyped seven additional families of diverse ethnic origin (Pakistani, Indian, Italian, Brazilian, and Japanese), and analyzed additional markers in two previously reported families showing evidence of linkage disequilibrium in a large area of their haplotypes. The multi-system manifestations of TRMA suggest that thiamine has a pivotal role in a multiplicity of physiological processes. Mapping the TRMA gene and understanding the molecular basis of the disease might, thus, shed light on the role of thiamine in common disorders such as deafness, anemia, and diabetes.

Profile of protein kinase C isozymes and their possible role in mammalian egg activation

Western blot analysis was used to investigate protein kinase C (PKC) profile of rat eggs. The presence of eight PKC isozymes was demonstrated: conventional PKC alpha, beta and gamma; novel PKC delta, epsilon and mu; atypical PKC zeta and lambda. PKC alpha was detected by RT-PCR as well. PKC translocation from the cytosol to the plasma membrane served as a marker for enzyme activation. Immunofluorescence confocal microscopy demonstrated a relatively uniform distribution of PKC alpha, betaI, and betaII throughout the cytosol of metaphase II arrested eggs. PKC accumulation at the plasma membrane was detected 5 min after exposure to 12-O-tetradecanoyl phorbol-13-acetate and increased with time, thus demonstrating activation of these PKCs.

Cortical granules reaction after intracytoplasmic sperm injection

The cortical reaction (CR) in mammalian oocytes is induced following sperm-egg membrane fusion. During intracytoplasmic sperm injection (ICSI) the physiological cascade of gamete interaction events is bypassed. The aim of this study was to explore CR occurrence after the ICSI procedure and its correlation with the meiotic status of the oocytes. Unfertilized and abnormally fertilized (one- or three-pronucleate) human oocytes were investigated. The chromosomal status was analysed by Hoechst staining. The CR occurrence and its fluorescent pattern were assessed by confocal scanning laser microscope using the lectin lens culinaris and Texas Red staining. Our results reveal a positive correlation between the activation of oocytes and their CR. No CR was demonstrated in unfertilized-unactivated oocytes with or without sperm in their cytoplasm. In partially activated oocytes showing resumption of meiosis but no formation of pronuclei, a moderate CR was observed. In fully activated oocytes displaying one or three pronuclei, a strong CR was monitored. It was concluded that in ICSI, as in physiological fertilization, oocyte activation is a prerequisite for CR.

Segregation of the pathways leading to cortical reaction and cell cycle activation in the rat egg

At fertilization of the mammalian egg, resumption of the cell cycle and the cortical reaction are two events of egg activation, correlated with an increase in intracellular Ca2+ concentration and activation of protein kinase C. To evaluate the pathways leading to both events, rat eggs were parthenogenetically activated by the calcium ionophore ionomycin, or by the protein kinase C activators 12-O-tetradecanoyl phorbol-13-acetate (TPA) or 1-oleoyl-2-acetylglycerol (OAG). Cortical granule exudate was visualized by the lectin Lens culinaris and Texas Red streptavidin, using a confocal microscope. Resumption of meiosis was detected by Hoechst dye, and intracellular Ca2+ concentration by fura-2. Ionomycin triggered both a cortical reaction and resumption of meiosis, while chelation of intracellular Ca2+ rise by BAPTA-AM (1,2-bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid-acetoxymethyl ester) revealed a segregation between these two events. A low Ca2+ transient (approximately 150 nM) induced a partial cortical reaction in half of the eggs, but the meiotic status was not affected. TPA triggered a cortical reaction with neither resumption of meiosis nor intracellular Ca2+ rise, while OAG induced both aspects of activation, as well as a significant intracellular Ca2+ rise. We conclude that in the cascade of events leading to egg activation, the initial Ca2+ rise is followed by a segregation in the pathway. A relatively low Ca2+ rise is sufficient to induce a partial cortical reaction. However, a higher level of Ca2+ is required to complete the cortical reaction and resumption of meiosis. The activation of the cell cycle is Ca2+-dependent, but protein kinase C-independent.

Localization of the gene for thiamine-responsive megaloblastic anemia syndrome, on the long arm of chromosome 1, by homozygosity mapping

Thiamine-responsive megaloblastic anemia, also known as "TRMA" or "Rogers syndrome," is an early-onset autosomal recessive disorder defined by the occurrence of megaloblastic anemia, diabetes mellitus, and sensorineural deafness, responding in varying degrees to thiamine treatment. On the basis of a linkage analysis of affected families of Alaskan and of Italian origin, we found, using homozygosity mapping, that the TRMA-syndrome gene maps to a region on chromosome 1q23.2-23.3 (maximum LOD score of 3.7 for D1S1679). By use of additional consanguineous kindreds of Israeli-Arab origin, the putative disease-gene interval also has been confirmed and narrowed, suggesting genetic homogeneity. Linkage analysis generated the highest combined LOD-score value, 8.1 at a recombination fraction of 0, with marker D1S2799. Haplotype analysis and recombination events narrowed the TRMA locus to a 16-cM region between markers D1S194 and D1S2786. Several heterozygote parents had diabetes mellitus, deafness, or megaloblastic anemia, which raised the possibility that mutations at this locus predispose carriers in general to these manifestations. Characterization of the metabolic defect of TRMA may shed light on the role of thiamine deficiency in such common diseases.

The role of carbohydrate residues in mammalian fertilization

The fertilization process in mammals involves binding and fusion of free-swimming sperm and ovulated eggs. This review focuses on the role of carbohydrate residues in the process of sperm-egg interaction in mammals. The zona pellucida (ZP), the acellular glycoprotein coat surrounding the egg is highly glycosylated and possess both Asn- (N-) linked and Ser/Thr- (O-)linked oligosaccharides, with an extreme structural heterogeneity between the different species. Different carbohydrates on ZP3, such as Galactose in alpha-linkage, N-acetylglucosamine in beta-linkage, were suggested as the complementary sperm receptors, mediating the primary binding between the spermatozoon and the ZP. Several suggested complementary ZP3 binding proteins on the sperm are sp56, beta-1,4-galactosyltransferase and p95. Some carbohydrate residues of the ZP undergo post-fertilization modifications that might alter the sperm receptor, thus assisting in the establishment of the block to polyspermy. The studies summarized in this review imply a main role for the carbohydrate residues in the process of sperm egg interaction.

Post-fertilization changes in the zona pellucida glycoproteins of rat eggs

The zona pellucida (ZP) is the extracellular coat surrounding the mammalian egg. Numerous evidence supports the role of ZP carbohydrate residues as the specific sperm receptors. In this study we used lectins to study different distribution patterns of carbohydrate residues in the rat ZP, and to follow changes at fertilization. ZP were collected from follicular, ovulated, and fertilized eggs, incubated with one of 11 different biotin-labeled lectins, followed by avidin-fluorescein isothiocyanate (FITC) complex, and visualized by epifluorescent microscopy. For electron microscope (EM) histochemistry, eggs were embedded in LR white and ultrathin sections were stained with the complex Ricinus communis lectin (RCA-1)-colloidal gold. Some lectins (RCA-I, Glycine max) bound to the entire ZP while others were restricted to the inner or outer zones [Griffonia simplicifolia, Concanovalia ensiformis, Triticum vulgaris (WGA), succinyl-WGA]. Other lectins (Lens culinaris, Ulex europhaeus) were totally excluded. The RCA-1 binding pattern changed following sperm penetration, from homogeneous in ZP of ovulated eggs (57%) to uneven in ZP of fertilized (71%) or activated (68%) eggs. Our results demonstrate an uneven distribution of different sugar residues in the rat ZP, and a post-fertilization change in the distribution of beta-galactose, which is specifically recognized by RCA-I, presumably correlated with other changes in the ZP that lead to the block to polyspermy.

Structure-function relationship of a recombinant human galactoside-binding protein

A galactoside-binding lectin (hL-31) containing a collagen-like sequence was identified in human tumor cells. It was found to be the homologue of the IgE-binding protein, the macrophage cell-surface Mac-2 antigen, and the murine CBP35, RL-29, and mL-34 lectins. Here we report on the expression in Escherichia coli and functional analysis of recombinant hL-31 (rhL-31). The rhL-31 was purified in one step through an asialofetuin affinity column. The rhL-31 was reactive to anti-lectin antibodies and retained its lactose-dependent hemagglutination of trypsin-treated glutaraldehyde-fixed rabbit erythrocytes. The rhL-31 elutes from an affinity column as a 31-kDa monomer and undergoes homodimerization at relatively high protein concentrations, comparable to those used to mediate hemagglutination. Electron microscopy showed that the rhL-31 appears as a Y-shaped structure. Lactoperoxidase-catalyzed iodination of murine tumor cell-surface proteins followed by collagenase treatment revealed that the lectin is probably a peripheral membrane protein whereby both the amino and the carboxy termini are exposed on the outer cell membrane. These results point to the membrane disposition and orientation of the lectin and suggest a mechanism for a structure-function relationship of lectin activity.

Purification of human tumor cell autocrine motility factor and molecular cloning of its receptor

Tumor autocrine motility factor (AMF) has been detected in and purified from serum-free conditioned medium of human HT-1080 fibrosarcoma cells. Under nonreducing conditions, AMF migrates in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a single band of 55 kDa but under reducing conditions as a band of 64 kDa. Two-dimensional polyacrylamide gel electrophoresis of the purified AMF resolved two groups of polypeptides with isoelectric points of 6.1 and 6.2 (majors), 6.35 and 6.4 (minors). Purified AMF stimulated HT-1080 cell migration in a dose-dependent fashion. The motility stimulation of the fibrosarcoma cells with AMF is associated with the phosphorylation of the AMF receptor, a 78-kDa cell surface glycoprotein (gp78), suggesting protein kinase participation in migratory signal transduction. The gene encoding gp78 was cloned from an HT-1080 fibrosarcoma complementary DNA library. The deduced sequence encodes a polypeptide of 323 amino acids. The nucleotide and predicted amino acid sequence of the gp78 reveals significant homology with the human suppressor/oncogene p53 protein.

Molecular cloning and chromosomal mapping of a human galactoside-binding protein

A human galactoside-binding protein with an Mr of 31,000 was cloned from the human HT-1080 fibrosarcoma complementary DNA library. A partial complementary DNA clone containing the complete coding region was characterized and the deduced sequence encodes a polypeptide of 242 amino acids with the characteristics of a carbohydrate-binding protein. The gene coding for the human galactoside-binding protein was mapped to the chromosomal band 1p13. The deduced amino acid sequence of the human galactoside-binding protein revealed 95 residues at the amino terminus, homologous to the predicted amino acid sequence of the second exon of the human L-myc gene.

Evidence for the role of 34-kDa galactoside-binding lectin in transformation and metastasis

The endogenous Mr 34,000 galactoside-binding lectin (L-34) is found at elevated levels in a wide variety of neoplastic cells and correlative evidence suggests that it is involved in tumor metastasis in vivo and in transformation in vitro. We demonstrate here that introduction of recombinant L-34 into tumorigenic, weakly metastatic UV-2237-cl-15 fibrosarcoma cells results in an increased incidence of experimental lung metastases in syngeneic and nude mice. Transfection of normal BALB/c-A31 cloned fibroblasts with functional L-34 results in acquisition of anchorage-independent growth and in morphological transformation in vitro but not in tumorigenicity in vivo. These results provide direct evidence that the cellular expression of L-34 is associated with some aspects of transformation and with metastasis, but not with tumorigenicity per se.

Prediction of medication error probability based on patient characteristics

This paper describes the development of a model for classifying the patient population into risk groups according to their medication error probability. The methodology utilizes patient demographic and health care data combined with medication error reports. Variable selection is based on a measure of the amount of information that they provide. Using data from a 360-bed hospital, the model identified patient characteristics related to the health care services received as being the main variables related to medication error probability and divided the patient population into three risk groups defined in terms of these characteristics. The model provides information valuable to risk management and quality assurance efforts in the areas of detection of risk exposure, performance monitoring and resource allocation.

Factors affecting the incidence of patient falls in hospitals

Patient falls affect the cost and quality of patient care in hospitals. Published studies of risk factors for patient falls are inconsistent and often methodologically weak. Existing programs of patient risk assessment rely on large sets of patient characteristics, not all of which may be necessary. This article describes an information-theoretic technique that is able to identify a limited set of patient characteristics that provide most of the statistically significant information regarding risk of falls that is available in a hospital's adverse patient incident data set. Analysis of data from four hospitals with different institutional and data system characteristics revealed a consistent pattern of risk factors.

An information theoretic method for classifying patients according to the risk of adverse hospital incidents

The measure of Mutual Information is used to select, out of a large number of possibly interrelated qualitative patient variables, those that are most related to the probability of occurrence of adverse incidents. The subpopulations defined by the variables selected are grouped according to risk levels while minimizing the loss of information. Results of the application of the method to predict the occurrence of three types of incidents in four hospitals are reported.

ARMIS: a microcomputer-based hospital risk management information system

Information processing is a major element of hospital risk management programs. A microcomputer-based information system has been designed and implemented in a medium-size university hospital. The design principles and the functional capabilities of the system are described here, followed by an evaluation based on the first year of operation.

A process related to membrane potential involved in bacterial chemotaxis to galactose

Attractants, in the presence of respiration and ATPase inhibitors, stimulate a hyperpolarization in Escherichia coli [Eisenbach, M. (1982) Biochemistry 21, 6818-6825]. In order to examine whether this hyperpolarization is correlated with chemotaxis, the effect of the attractant D-galactose and its analogues on the membrane potential of wild-type E. coli strains and some of their mutants was studied. The main observations were the following: (i) Wild-type cells became hyperpolarized by either galactose or its nonmetabolizable analogues, D-fucose and L-sorbose. (ii) A mutant defective in galactose metabolism became hyperpolarized by galactose. (iii) Inhibiting the galactose permease system did not prevent the hyperpolarization, rather it facilitated the observation of the hyperpolarization. (iv) Mutants unable to transport galactose via the methyl beta-galactoside (Mgl) transport system but having normal chemotaxis to galactose became normally hyperpolarized by D-fucose. (v) Mutants which cannot bind galactose were not hyperpolarized by galactose. (vi) The hyperpolarization in flaI mutants, in which the whole chemotaxis machinery is repressed, was reduced to 12-15% of the hyperpolarization in the parent strains. (vii) Nonattractant sugars did not stimulate hyperpolarization. It is concluded that the hyperpolarization is the consequence of neither galactose metabolism nor transport but rather is correlated with galactose taxis.