Land-use type temporarily affects active pond community structure but not gene expression patterns

Changes in land use and agricultural intensification threaten biodiversity and ecosystem functioning of small water bodies. We studied 67 kettle holes (KH) in an agricultural landscape in northeastern Germany using landscape-scale metatranscriptomics, to understand the responses of active bacterial, archaeal, and eukaryotic communities, to land-use type. These KH are proxies of the millions of small standing water bodies of glacial origin spread across the northern hemisphere. Like other landscapes in Europe, the study area has been used for intensive agriculture since the 1950s. In contrast to a parallel eDNA study which revealed the homogenization of biodiversity across KH conceivably resulting from long-lasting intensive agriculture, land-use type affected the structure of the active KH communities during spring crop fertilization, but not a month later. This effect was more pronounced in eukaryotes than in bacteria. In contrast, gene expression patterns did not differ between months or across land-use type, suggesting a high degree of functional redundancy across the KH communities. Variability in gene expression was best explained by active bacterial and eukaryotic community structures, suggesting that these changes in functioning are primarily driven by interactions between organisms. Our results show that influences of the surrounding landscape result in temporary changes in the activity of different community members. Thus, even in KH where biodiversity has been homogenized, communities continue to respond to land management. This needs to be considered when developing sustainable management options for restoration purposes and for successful mitigation of further biodiversity loss in agricultural landscapes.

Registered Replication Report

Language can be viewed as a complex set of cues that shape people’s mental representations of situations. For example, people think of behavior described using imperfective aspect (i.e., what a person was doing) as a dynamic, unfolding sequence of actions, whereas the same behavior described using perfective aspect (i.e., what a person did) is perceived as a completed whole. A recent study found that aspect can also influence how we think about a person’s intentions (Hart & Albarracín, 2011). Participants judged actions described in imperfective as being more intentional ( d between 0.67 and 0.77) and they imagined these actions in more detail ( d = 0.73). The fact that this finding has implications for legal decision making, coupled with the absence of other direct replication attempts, motivated this registered replication report (RRR). Multiple laboratories carried out 12 direct replication studies, including one MTurk study. A meta-analysis of these studies provides a precise estimate of the size of this effect free from publication bias. This RRR did not find that grammatical aspect affects intentionality ( d between 0 and −0.24) or imagery ( d = −0.08). We discuss possible explanations for the discrepancy between these results and those of the original study.

RAxML-Light: a tool for computing terabyte phylogenies

MOTIVATION

Due to advances in molecular sequencing and the increasingly rapid collection of molecular data, the field of phyloinformatics is transforming into a computational science. Therefore, new tools are required that can be deployed in supercomputing environments and that scale to hundreds or thousands of cores.

RESULTS

We describe RAxML-Light, a tool for large-scale phylogenetic inference on supercomputers under maximum likelihood. It implements a light-weight checkpointing mechanism, deploys 128-bit (SSE3) and 256-bit (AVX) vector intrinsics, offers two orthogonal memory saving techniques and provides a fine-grain production-level message passing interface parallelization of the likelihood function. To demonstrate scalability and robustness of the code, we inferred a phylogeny on a simulated DNA alignment (1481 taxa, 20 000 000 bp) using 672 cores. This dataset requires one terabyte of RAM to compute the likelihood score on a single tree. CODE AVAILABILITY: https://github.com/stamatak/RAxML-Light-1.0.5 DATA AVAILABILITY: http://www.exelixis-lab.org/onLineMaterial.tar.bz2

CONTACT

alexandros.stamatakis@h-its.org

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Sickle cell blood flow in the microcirculation

The clinical symptomology, as well as the subclinical sequela, of sickle-cell (S-C) disease, or anemia, is thought to be largely the consequence of abnormal events in the capillaries, resulting primarily from theological changes SC erythrocytes undergo when deoxygenated. A model of the flow of such RBCs in a single capillary was formulated taking into account the principal characteristics of the disease. This has been extended to a microcirculatory bed, generated in a pseudo-random manner. S-C disease is characterized by episodic painful and debilitating clinical events, called S-C "crisis". These studies, undertaken to evaluate possible causative mechanisms, suggest that the pressure available to drive the S-C RBCs through the microcirculation might be the control parameter.

A turbulence model for pulsatile arterial flows

Difficulties in predicting the behavior of some high Reynolds number flows in the circulatory system stem in part from the severe requirements placed on the turbulence model chosen to close the time-averaged equations of fluid motion. In particular, the successful turbulence model is required to (a) correctly capture the "nonequilibrium" effects wrought by the interactions of the organized mean-flow unsteadiness with the random turbulence, (b) correctly reproduce the effects of the laminar-turbulent transitional behavior that occurs at various phases of the cardiac cycle, and (c) yield good predictions of the near-wall flow behavior in conditions where the universal logarithmic law of the wall is known to be not valid. These requirements are not immediately met by standard models of turbulence that have been developed largely with reference to data from steady, fully turbulent flows in approximate local equilibrium. The purpose of this paper is to report on the development of a turbulence model suited for use in arterial flows. The model is of the two-equation eddy-viscosity variety with dependent variables that are zero-valued at a solid wall and vary linearly with distance from it. The effects of transition are introduced by coupling this model to the local value of the intermittency and obtaining the latter from the solution of a modeled transport equation. Comparisons with measurements obtained in oscillatory transitional flows in circular tubes show that the model produces substantial improvements over existing closures. Further pulsatile-flow predictions, driven by a mean-flow wave form obtained in a diseased human carotid artery, indicate that the intermittency-modified model yields much reduced levels of wall shear stress compared to the original, unmodified model. This result, which is attributed to the rapid growth in the thickness of the viscous sublayer arising from the severe acceleration of systole, argues in favor of the use of the model for the prediction of arterial flows.

A phenomenological model for atherosclerotic plaque growth and rupture

The objective of this communication is to develop a computer-based framework for the overall coupled phenomena leading to growth and rupture of atherosclerotic plaques. The modeling is purposely simplified to expose the dominant phenomenological controlling mechanisms, and their coupled interaction. The main ingredients of the present simplified modeling approach, describing the events that occur due to the presence and oxidation of excess low-density lipoprotein (LDL) in the intima, are: (i) adhesion of monocytes to the endothelial surface, which is controlled by the intensity of the blood flow and the adhesion molecules stimulated by the excess LDL, (ii) penetration of the monocytes into the intima and subsequent inflammation of the tissue, and (iii) rupture of the plaque accompanied with some degree of thrombus formation or even subsequent occlusive thrombosis. The set of resulting coupled equations, each modeling entirely different physical events, is solved using an iterative staggering scheme, which allows the equations to be solved in a computationally convenient decoupled fashion. Theoretical convergence properties of the scheme are given as a function of physical parameters involved. A numerical example is given to illustrate the modeling approach and an a priori prediction for time to rupture as a function of arterial geometry, diameter of the monocyte, adhesion stress, bulk modulus of the ruptured wall material, blood viscosity, flow rate and mass density of the monocytes.

Mast cells stimulated by membrane-bound, but not soluble, steel factor are dependent on phospholipase C activation

The steel factor (SLF) and c-Kit growth factor/receptor pair are key molecules governing mast cell development and survival. SLF is expressed on stromal cells as a membrane-bound molecule (mSLF) which can be cleaved by proteases to release a soluble form (sSLF). We investigated the importance of phospholipase C (PLC) activation in mast cells stimulated by sSLF and mSLF. PLC antagonists U73122, neomycin sulfate and oleic acid inhibited mast cell thymidine incorporation stimulated by mSLF, but not by sSLF. These antagonists suppressed sSLF-induced Ca2+ transients but did not significantly interfere with c-Kit phosphorylation or PLC-gamma2 recruitment. p85, the regulatory subunit of phosphatidylinositol 3-kinase (PI3-kinase), was found to be efficiently recruited to c-Kit following stimulation by sSLF or mSLF. However PKB/Akt, a kinase activated by PI3-kinase products, was phosphorylated following sSLF stimulation, but not with mSLF. Taken together, these studies demonstrate the importance of PLC activation by mSLF in supporting mast cells.

Numerical analysis of flow through a severely stenotic carotid artery bifurcation

The results of computational simulations may supplement MR and other in vivo diagnostic techniques to provide an accurate picture of the hemodynamics in particular vessels, which may help demonstrate the risks of embolism or plaque rupture posed by particular plaque deposits. In this study, a model based on an endarterectomy specimen of the plaque in a carotid bifurcation was examined. The flow conditions include steady flow at Reynolds numbers of 300, 600, and 900 as well as unsteady pulsatile flow. Both dynamic pressure and wall shear stress are very high, with shear values up to 70 N/m2, proximal to the stenosis throat in the internal carotid artery, and both vary significantly through the flow cycle. The wall shear stress gradient is also strong along the throat. Vortex shedding is observed downstream of the most severe occlusion. Two turbulence models, the Chien and Goldberg varieties of k-epsilon, are tested and evaluated for their relevance in this geometry. The Chien model better captures phenomena such as vortex shedding. The flow distal to stenosis is likely transitional, so a model that captures both laminar and turbulent behavior is needed.

West Nile encephalitis in Israel, 1999: the New York connection

We describe two cases of West Nile (WN) encephalitis in a married couple in Tel Aviv, Israel, in 1999. Reverse transcription-polymerase chain reaction performed on a brain specimen from the husband detected a WN viral strain nearly identical to avian strains recovered in Israel in 1998 (99.9% genomic sequence homology) and in New York in 1999 (99.8%). This result supports the hypothesis that the 1999 WN virus epidemic in the United States originated from the introduction of a strain that had been circulating in Israel.

Differential stimulation of c-Kit mutants by membrane-bound and soluble Steel Factor correlates with leukemic potential

The authors investigated the roles of PI3-kinase and PLC-gamma in stimulation by Steel Factor (SLF) through c-Kit. c-Kit mutants YF719, YF728, and a YF719/YF728 double mutant were expressed in 32D myelomonocytic cells. KitYF719 fails to recruit PI3-kinase after stimulation with SLF, whereas KitYF728 fails to stimulate PLC-gamma phosphorylation or mobilize Ca(++). Both single mutants responded mitogenically to soluble SLF (sSLF) in a manner indistinguishable from wild type (WT), although sSLF failed to stimulate or promote the survival of cells expressing the double mutant. In contrast, although cells expressing WT or YF719 were mitogenically stimulated by membrane-bound SLF (mSLF), stimulation of cells expressing KitYF728 was impaired. Similarly, cells expressing WT or YF719 receptors were stimulated by plate-bound anti-Kit antibodies, whereas cells expressing the YF728 receptor were not stimulated. Neomycin sulfate, a PLC antagonist, inhibited cells expressing YF719 receptors stimulated by sSLF. Neomycin also inhibited cells expressing the WT receptor that were stimulated by mSLF or immobilized anti-Kit antibodies but did not inhibit stimulation of cells expressing WT or YF719 receptors by sSLF. 32D cells expressing KitWT, KitYF719, or KitYF728 were injected into mice and the presence of cells was evaluated by colony assays 6 to 7 weeks later. Although both KitWT and KitYF719 expressing cells could be recovered from the spleen and bone marrow, recovery of KitYF728 cells from these organs was severely reduced. These results indicate that Kit tyrosine 728 is of particular importance for mitogenic stimulation by mSLF or immobilized ligand and is required for full maintenance of cells in vivo, likely through activation of PLC-gamma. (Blood. 2000;96:3734-3742)

Clinical significance and antibiotic resistance patterns of Leminorella spp., an emerging nosocomial pathogen

Although Leminorella spp., members of the family Enterobacteriaceae, were previously isolated from feces and urine specimens, clinical correlates have not been studied. We conducted a retrospective study to investigate the clinical significance and disease spectrum of these organisms, as well as their antibiotic susceptibility patterns. Identification and susceptibility testing were performed by an automated system. Eighteen cases were identified retrospectively during a 28-month period (1/97 to 4/99), representing an incidence of 11 cases per 100,000 patient admissions. The medical records of 14 patients were reviewed. The average patient age was 67 years, and 78% were males. Patients had multiple and diverse underlying conditions which might have predisposed them to infection. Leminorella spp. were classified as definite pathogens in 43% of the cases, probable pathogens in 29%, and possible pathogens in 21%. In one case of asymptomatic bacteriuria, the isolate had no clinical significance. All infections but one were nosocomial. Clinical syndromes included urinary tract infection in six patients, surgical site infection in three patients, and primary bacteremia, peritonitis, respiratory tract infection, and soft tissue infection in one patient each. Isolates were uniformly susceptible to imipenem. Other beta-lactam agents had poor activity against the isolates. We conclude that Leminorella spp. are significant nosocomial pathogens that are capable of causing a variety of clinical syndromes and are resistant to multiple antibiotic agents.

Epo regulates erythroid proliferation and differentiation through distinct signaling pathways: implication for erythropoiesis and Friend virus-induced erythroleukemia

We have recently isolated the erythroleukemic cell line, HB60-5, that proliferates in the presence of erythropoietin (Epo) and stem cell factor (SCF), but undergoes terminal differentiation in the presence of Epo alone. Ectopic expression of the ets related transcription factor Fli-1 in these cells resulted in the establishment of the Epo-dependent cell line HB60-ED that proliferates in the presence of Epo. In this study, we utilized these two cell lines to examine the signal transduction pathways that are activated in response to Epo and SCF stimulation. We demonstrate that Epo, but not SCF, phosphorylates STAT-5 in both HB60-5 and HB60-ED cells. Interestingly, SCF activates the Shc/ras pathway in HB60-5 cells while Epo does not. However, both Epo and SCF are capable of activating the Shc/ras pathway in HB60ED cells. Furthermore, enforced expression of gp55 in HB60-5 cells by means of infection with the Spleen Focus Forming virus-P (SFFV-P), confers Epo independent growth, which is associated with the up-regulation of Fli-1. Activation of the Shc/ras pathway is readily detected in gp55 expressing cells in response to both Epo and SCF, and is associated with a block in STAT-5B tyrosine phosphorylation. These results suggest that STAT-5 activation, in the absence of Shc/ras activation, plays a role in erythroid differentiation. Moreover, Fli-1 is capable of switching Epo-induced differentiation to Epo-induced proliferation, suggesting that this ets factor regulated genes whose products modulate the Epo-Epo-R signal transduction pathway.

Influence of stenosis morphology on flow through severely stenotic vessels: implications for plaque rupture

Flow patterns and flow-related stresses contribute to the characterization of health risks, particularly the risk of plaque rupture, posed by a particular atherosclerotic stenosis. Blood flow in the presence of significant plaque deposits is investigated, and the influence of factors such as stenosis morphology and surface irregularity is evaluated. Solutions for three-dimensional, unsteady flow in these stenotic vessels are obtained for an incompressible, Newtonian fluid. The equations of motion are solved numerically using a finite volume formulation. The resulting flow patterns and shear and normal stresses are interpreted with respect to diagnostic implications, including the possibility of plaque rupture. The inadequacy of "percent stenosis" to characterize the risks posed by a particular plaque is demonstrated. Surface irregularity, stenosis aspect ratio, and the shape of the pulsatile waveform all have considerable influence on the flow field and on the stresses on the plaque. A measure of surface irregularity or plaque symmetry, in particular, may complement percent stenosis in diagnosing the risk of plaque rupture.

A transforming mutation enhances the activity of the c-Kit soluble tyrosine kinase domain

An activating mutation (DY814) located in the catalytic domain of the c-Kit receptor has been found in mastocytomas from human, mouse and rat. We evaluated the enzymic properties of purified wild-type (WT) and DY814 tyrosine kinase domains expressed in Pichia pastoris. A linker encoding the Flag epitope was fused to c-Kit cDNA species, enabling affinity purification of the proteins with anti-Flag antibodies. Yeast lysates expressing DY814 contained multiple tyrosine-phosphorylated proteins, whereas WT lysates had no detectable tyrosine phosphorylation. Purification of the WT and mutant kinases in the presence of vanadate demonstrated that both enzymes undergo autophosphorylation. Kinetic analyses of WT and DY814 kinases indicated that at 20 nM enzyme concentration the mutation increases the specific activity 10-fold and decreases the apparent Km for ATP 9-fold. WT activity displayed a hyperbolic dependence on enzyme concentration, consistent with a requirement for dimerization or aggregation for activity. This activity was also enhanced by anti-Flag antibodies. In contrast, the dependence of DY814 activity on enzyme concentration was primarily linear and only marginally enhanced by anti-Flag antibodies. Gel-filtration analysis showed that the WT kinase migrated as a monomer, whereas the DY814 mutant migrated as a dimer. These results indicate that this point mutation promotes dimerization of the c-Kit kinase, potentially contributing to its transforming potential in mast cells.

Protection from apoptosis by steel factor but not interleukin-3 is reversed through blockade of calcium influx

Steel factor (SLF), the ligand for the c-Kit receptor, protects hemopoietic progenitors and mast cells from apoptosis. We show here that protection of 32D-Kit cells or mast cells from apoptosis by SLF is abrogated through concurrent inhibition of Ca2+ influx. In contrast, cell survival promoted by interleukin-3 is not affected by Ca2+ influx blockers. In the presence of blockers, increasing stimulation by SLF leads to greater levels of cell death in the population, indicating that it is the combination of activation by SLF with concurrent blockade of Ca2+ influx that results in apoptosis. The p815 mastocytoma, which expresses a mutated, constitutively active c-kit receptor, dies apoptotically in the presence of Ca2+ influx blockers alone. Ionomycin protects cells from SLF plus blocker-induced apoptosis, confirming specificity for Ca2+ ion blockade in cell death induction. Overexpression of bcl-2, which protects 32D-Kit cells from factor withdrawal, does not protect cells from apoptosis by SLF plus blocker. In contrast, caspase inhibitors YVAD-CHO, DEVD-FMK, and Boc-Asp-FMK protect cells from SLF plus blocker-induced death. These observations highlight the importance of SLF-stimulated Ca2+ influx in the protection of cells from apoptosis and demonstrate a new mechanism for inducing bcl-2 insensitive, caspase-dependent apoptosis through the combination of SLF stimulation with Ca2+ influx blockade.

Phosphatidylinositol 3-kinase and Ca2+ influx dependence for ligand-stimulated internalization of the c-Kit receptor

We have evaluated the role of phosphatidylinositol 3-kinase (PI3-kinase) and Ca2+ influx in ligand-stimulated internalization of the c-Kit receptor. The wild type (wt) c-Kit receptor and YF719, a mutant receptor in which the SH2-mediated binding site for the p85 subunit of PI3-kinase is disrupted, were expressed in DA-1 cells. YF719 internalized with similar kinetics as wt c-Kit although the receptor remained localized close to the plasma membrane. However, in the absence of extracellular Ca2+, or in the presence of the competitive Ca2+ influx blocker Ni2+, the YF719 mutant failed to internalize. Failure to internalize in the absence of Ca2+ was also observed for the wt c-Kit receptor in cells that were pretreated with the PI3-kinase inhibitor, wortmannin. Following stimulation with ligand, clathrin heavy chains were found to co-immunoprecipitate with c-Kit. However, under conditions in which PI3-kinase activity is inhibited and Ca2+ influx is blocked, clathrin failed to co-immunoprecipitate with c-Kit. Our results demonstrate that both Ca2+ influx and PI3-kinase activity influence c-Kit endocytosis, and inhibition of these two signals disrupts the earliest stages of ligand-mediated internalization.

Re-emergence of Cholera Vaccine

Although epidemic cholera was first described in 1817, the disease probably has been common in the Indian subcontinent since ancient times.1 Until recently, a single bacterial type (Vibrio cholerae 01) has been responsible for each of the seven recorded cholera pandemics. The current epidemic began in Celebes (Sulawesi), Indonesia, in 1961, and is currently raging through all continents.2 During the 1990s, over 1 million cholera cases have been reported from Latin America, 2000 from Ukraine and the Russian Republic during 1994 alone (GIDEON computer software, C.Y. Informatics, Ramat Hasharon, Israel). Of the 208,755 cases of cholera (5034 fatal) officially reported to the World Health Organization in 1995,3 41.1% were from Latin America, 34.0% from Africa, 24.4% from Asia, and 0.5% from Europe and Oceania. Interest in our own country of Israel stems from the popularity of tourism (over 1 million travelers exit Israel yearly) and the presence of disease in neighboring areas. Following an epidemic of 397 cases in Jerusalem during 1970, periodic outbreaks have occurred in Gaza, Judea and Samaria.4 Three tourists returned with the infection to Israel during the 1980s, all from Egypt (which officially claims to have no cholera).5 Despite universal interest in this ancient disease, medical science has long been frustrated in its search for an effective vaccine. The most important 'vaccine' against cholera is common sense, and consists of intelligent eating and drinking while in endemic areas. For example, local raw fish (ceviche) is a common source of the disease in Latin America, while shellfish (particularly oysters) are often implicated along the American Gulf Coast. Virtually all forms of water purification are effective against Vibrio cholerae. Although antibiotic prophylaxis might be considered in some circumstances (doxycycline; or a quinolone in areas of tetracycline resistance), it is not routinely advocated.

Identification of a bacterial inhibitor of protein kinases. Mechanism and role in host cell invasion

We show that Escherichia coli produce a factor that inhibits the activity of tyrosine and serine/threonine protein kinases. The factor is a protein found in the periplasmic compartment and is also secreted into the culture medium. Using a particle concentration fluorescence immunoassay specific for tyrosine kinase activity and inhibition of the tyrosine kinase p56(lck), we purified this factor to apparent homogeneity. Analysis of trypsin-digested fragments by mass spectrometry identified the inhibitor as the bacterial periplasmic protein UDP-sugar hydrolase, an enzyme with potent and nonspecific 5'-nucleotidase activity. Overexpression of the enzyme in bacteria leads to coordinate increases in both 5'-nucleotidase and p56(lck) inhibitory activity, confirming the identity of the inhibitor. The kinase inhibitory activity appears to be due to the formation of adenosine, which we show is inhibitory for p56(lck), cAMP-dependent protein kinase, and casein kinase. Overexpression of UDP-sugar hydrolase leads to an increase in the recovery of enteropathogenic E. coli following infection of HeLa cell monolayers and corresponding alterations in tyrosine-phosphorylated host proteins. These results suggest that UDP-sugar hydrolase may be an important factor affecting host cell function following intracellular bacterial infection.

Penetration of clindamycin and metronidazole into inflamed appendiceal tissue

OBJECTIVE

To calculate the penetration of clindamycin and metronidazole into inflamed appendiceal tissue.

DESIGN

Prospective study.

SETTING

Teaching hospital, Israel.

SUBJECTS

20 Consecutive men and women operated on for acute appendicitis.

INTERVENTIONS

Appendicectomy. Each patient was given three intravenous injections of gentamicin 80 mg combined with either clindamycin 600 mg or metronidazole 500 mg immediately before operation over a period of 15 minutes.

MAIN OUTCOME MEASURES

Serum and tissue concentrations of the antibiotics.

RESULTS

There was no significant difference between the mean serum concentrations of the drugs (clindamycin 17.86 micrograms/ml and metronidazole 9.75 micrograms/ml) but the mean tissue concentrations of clindamycin (10.41 micrograms/g in the base and 9.86 micrograms/g in the tip of the appendix) were significantly higher than those of metronidazole (5.65 micrograms/g in the base and 5.89 micrograms/g in the tip; p = 0.02 and p = 0.05, respectively). Tissue concentrations of clindamycin and serum concentration of both drugs were more than twice their MIC90. The tissue concentrations of metronidazole were close to its MIC90.

CONCLUSIONS

Clinical trials are necessary before any conclusion about therapeutic superiority of one or other agent can be drawn.

Calculation of the magnetization distribution for fluid flow in curved vessels

The signal intensity in magnetic resonance angiography (MRA) images reflects both morphological and flow-related features of vascular anatomy. A thorough understanding of MRA, therefore, demands a careful analysis of flow-related effects. Computational fluid dynamics (CFD) methods are very powerful in determining flow patterns in 3D tortuous vessels for both steady and unsteady flow. Previous simulations of MRA images calculated the magnetization of flowing blood by tracking particles as they moved along flow streamlines that had been determined by a CFD calculation. This manuscript describes MRA simulations that use CFD calculations to determine magnetization variation at a fixed point and, therefore, do not require streamline tracking to calculate the distribution of magnetization in flowing fluids. This method inherently accounts for uniform particle density, avoids problems associated with tracking particles close to the wall, and is well-suited to modeling pulsatile flow.

Molecular genetic analysis of glucocorticoid and mineralocorticoid signaling in development and physiological processes

To understand the role of glucocorticoid and mineralocorticoid signalling during development and in whole animal physiology, we have disrupted the mouse glucocorticoid and mineralocorticoid receptor gene by gene targeting. Most of the mice with a disrupted glucocorticoid receptor gene die within the first hours after birth due to severe lung atelectasis. Perinatal induction of gluconeogenic enzymes in the liver is impaired. Regulation of the glucocorticoid synthesis via the hypothalamic-pituitary-adrenal axis is perturbed, leading to increased plasma levels of corticosterone and adrenocorticotrophic hormone. Activation of the hypothalamic-pituitary-adrenal axis results in extensive hypertrophy and hyperplasia of the cortical zones of the adrenal and induction of genes involved in steroid biosynthesis. The adrenal medulla is disorganized and severely reduced in size; no cells capable of adrenaline synthesis can be detected. Mineralocorticoid receptor deficient mice die mainly at day 9/10 after birth. Weightloss precedes death of homozygous mutant mice and is correlated with an increase in the haematocrit. As a consequence of this mutation, plasma levels of renin and aldosterone are high elevated.

Central intraluminal saturation stripe on MR angiograms of curved vessels: simulation, phantom, and clinical analysis

PURPOSE

To investigate the appearance of reduced signal intensity in the center of blood vessels on magnetic resonance (MR) angiograms that can mimic intraluminal thrombus.

MATERIALS AND METHODS

Simulations and phantom studies were performed to analyze MR angiogram appearance distal to a pronounced curve.

RESULTS

Saturation effects substantially lower the signal strength in the center of the vessel relative to that at the vessel periphery. These effects appeared even though the flow was well ordered and laminar. In curved geometries, secondary flow patterns produced counter-rotating vortices, which moved the fastest-moving particles to the outside of the curve and folded the slow-moving particles to the center of the vessel.

CONCLUSION

Imaging parameter choices that reduce saturation, such as acquisition of a two-dimensional section transverse to the vessel and through the questionable region, effectively eliminate the central hypointensity effect in vivo.

Computer Program for Diagnosing and Teaching Geographic Medicine

One of the unique aspects of infectious disease is its wide variety, both in time and place. The specialist practicing in India may have little or no expertise in Peruvian disease. A colleague in New York may be called upon to diagnose and treat conditions originating in Africa, Asia, South America, Fiji and Papua, New Guinea. At the same time, this colleague must be familiar with the pathogens that originate in Texas, Hawaii, and Canada. Indeed, even the full-time infectious diseases specialist may not be conversant in diseases such as lagochilascariasis, louping ill, and lobomycosis. War, famine, education, immigration, and business travel have contributed to the advent of specialists in Geographic Medicine and Emporiatrics, otherwise known as Travel medicine. The "art" of diagnosis is largely an ability (albeit subconscious) to rank probabilities based on the incidences of likely diseases and the chance of encountering given clinical features within each disease. In theory, Bayesian analysis could be employed to diagnose disease accurately when given proper input. A multicenter study was undertaken to test a comprehensive computer driven-software program that incorporates worldwide epidemiologic and clinical parameters.

c-KIT expression enhances the leukemogenic potential of 32D cells

The growth of human leukemic cells in culture and in vivo is dependent upon the presence of hematopoietic growth factors. Most populations of human leukemic acute myeloblastic leukemia (AML) cells express c-Kit on their surface and respond to Kit ligand (KL) in culture. To determine if this interaction was of potential significance in vivo we used a mouse model system. 32D cells, a murine IL-3-dependent myeloid cell line, were rendered KL responsive by transfection of the murine c-Kit. After injection of 32D or 32D-Kit cells into syngeneic hosts, animals bearing 32D-Kit cells, but not 32D cells, became moribund and were killed. These animals had circulating leukemic blast cells, infiltration of bone marrow, spleen, brain, liver, lung, and kidney. Cells recovered from some of the animals continued to be dependent upon IL-3 or KL for growth while in other cases the cells were factor independent. This model illustrates that the constitutive expression of c-Kit enhances the leukemic potential of 32D cells. The model will be useful for studying the progression of leukemia in vivo and testing whether interruption of the interaction of Kit and KL can affect the growth of leukemic cells.

Fifty years of language maintenance and language dominance in bilingual Hispanic immigrants

Spanish language tests of 801 Cuban and Mexican immigrants showed no evidence of language loss during 50 years of U.S. residence; a few years after immigration, their English vocabulary approximated that of English monolinguals. The critical-age hypothesis was not supported for the acquisition of English vocabulary when English schooling and language usage were controlled by multiple regression. Most Ss continued to speak about as much Spanish as English; but read, wrote, and heard (on television and radio) far more English than Spanish. Under these conditions, Ss maintained Spanish dominance on tests of vocabulary recognition, lexical decision, and oral comprehension. Dominance was task specific and shifted to English on a category generation task about 12 years after immigration. No evidence of bilingual language interference was found; this is attributed to the strong Spanish foundation of the participants.

Fifty years of language maintenance and language dominance in bilingual Hispanic immigrants

Spanish language tests of 801 Cuban and Mexican immigrants showed no evidence of language loss during 50 years of U.S. residence; a few years after immigration, their English vocabulary approximated that of English monolinguals. The critical-age hypothesis was not supported for the acquisition of English vocabulary when English schooling and language usage were controlled by multiple regression. Most Ss continued to speak about as much Spanish as English; but read, wrote, and heard (on television and radio) far more English than Spanish. Under these conditions, Ss maintained Spanish dominance on tests of vocabulary recognition, lexical decision, and oral comprehension. Dominance was task specific and shifted to English on a category generation task about 12 years after immigration. No evidence of bilingual language interference was found; this is attributed to the strong Spanish foundation of the participants.

Leukocyte common antigen (CD45) is required for immunoglobulin E-mediated degranulation of mast cells

We demonstrate using primary mast cell cultures derived from wild-type and CD45-deficient mice that mast cell triggering through the high-affinity immunoglobulin E (IgE) receptor requires the cell surface tyrosine phosphatase CD45. Unlike wild-type cells, cross-linking of surface-bound IgE in mast cells deficient in CD45 does not induce degranulation. Degranulation in these mutant cells does occur after treatment with the calcium ionophore A23187 indicating that the degranulation machinery is intact in these cells. We also demonstrate that the tyrosine phosphatase inhibitors orthoVanadate and perVanadate inhibit degranulation in wild-type mast cells, as does cross-linking of CD45 by anti-CD45 antibodies. Finally, we show that CD45-deficient mice are resistant to IgE-dependent systemic anaphylaxis. These results show that, like the T cell receptor and the antigen receptor on B cells, there is an absolute requirement for CD45 in signaling via the high affinity IgE receptor, expanding the number of receptors for which CD45 is an essential component.

[Health concerns of Israelis traveling to Third World countries--experience of a travel advisory clinic]

Following army service young Israelis often travel to remote third world regions for prolonged periods. During such tours, they are exposed to a variety of medical problems, including infections, environmental diseases, political violence and inability to obtain proper medical care. From May 1991 to Nov. 1992, 1,969 travelers aged 20-25 years old, and 926 older than 25, were given medical advice, vaccines and medications prior to travel. A clinic specializing in "emporiatrics" has been established to deal with pre- and post-travel medical problems associated with tourism.

[Serological screening for Lyme disease in Israel]

During 1989-1992, 123 serum samples from patients with dermatological or neurological disorders were tested for Lyme disease antibody. In only 1 case was a diagnosis of autochthonous Lyme disease confirmed. 8.9% of the samples were positive for antibody to the 41kD flagellar antigen of Borrelia burgdorferi (ELISA test) and 7.3% for the 39kD protein (immunodot test). The diagnosis of Lyme disease should be confirmed by carefully timed tests to detect antibody against multiple species-specific bacterial antigens.

Effect of inoculum size on antimicrobial susceptibility of Helicobacter pylori

An agar dilution assay was used to assess the effect of inoculum size and culture period on the susceptibility of 15 clinical isolates of Helicobacter pylori to ampicillin, erythromycin, tetracycline, chloramphenicol, metronidazole and tinidazole. The mean MIC of the isolates increased 2.2- to 21.2-fold as the inoculum size progressed from 10(3) to 10(7) cfu/spot. Identical results were noted when isolates were maintained for two or four days prior to testing. Inoculum size should be carefully controlled when assessing the in vitro susceptibility of Helicobacter pylori.

Health profile of Ethiopian immigrants in Israel: an overview

The health profile of two groups of Ethiopian immigrants in Israel was evaluated. Trichophytosis and active trachoma were observed in 5%-8.7% of prepubertal children. Among adults 13% had corneal opacities and 10.4% had cataracts. Goiter, spastic bronchitis, valvular heart disease, leprosy and onchocerciasis were prevalent. Malnutrition was common, with average body weights ranging from 72.4% to 85.2% of normal. Anemia was observed in 6.3% of young children and 70% of all immigrants. Fifty percent of children over 12 years and 98% of adults over 40 years of age had been exposed to hepatitis B virus; 9.8%-11.8% were HBsAg carriers. Tuberculin tests were positive in 9.8%-13%; and intestinal parasites were identified in 86%-98%. Hospitalization was required for 15.7% of immigrants arriving during the period 1978-90, and for 3.7% of those arriving in mid-1991 (Operation Solomon).

Transfer of bacteria associated with cryotherapy

The aim of this study was to determine whether living bacteria can be transmitted by cryosurgery with carbon dioxide. Cultures were taken from the outer layer of the ice before starting treatment, and again at the end of the working day during ten consecutive working days. Each of ten dry ice blocks was sterile prior to use. Staphylococcus epidermidis was isolated from six of the latter following use. This finding indicates that the dry ice was contaminated during the procedure and that bacteria were transmitted from the patient's skin to the dry ice and to culture media. The medical implications of this finding require serious consideration regarding the risk of infection to both patient and clinical personnel from this procedure.

Effect of surgical mask position on bacterial contamination of the operative field

The influence of surgical mask usage on bacterial contamination of the operative field was studied during 30 cardiac catheterization procedures. Mask position was varied during each procedure according to a predesigned random table. The number of bacterial colonies recoverable when no mask was worn was significantly higher than that detected when a full mask was worn (P < 0.002). Shedding of Staphylococcus epidermidis was greater when no mask was worn (mean 5.2 colonies 10 min-1) than shedding with full mask (mean 2.7 colonies 10 min-1; P < 0.004). Although mask placement below the nose was associated with higher mean colony counts than that above the nose, these differences were not statistically significant.

Fatal necrotizing esophagitis due to Penicillium chrysogenum in a patient with acquired immunodeficiency syndrome

Although blue-green molds of the genus Penicillium are ubiquitous in the human environment, invasive penicilliosis is uncommon and primarily encountered among immunosuppressed patients. A patient with HIV infection who died of severe necrotizing esophagitis caused by Penicillium chrysogenum is reported and the relevant English language literature on human penicilliosis is reviewed. Although infectious esophagitis is commonly associated with AIDS, Penicillium esophagitis has not been described in such patients.

Penetration of ceftriaxone and cefoperazone into bile and gallbladder tissue in patients with acute cholecystitis

The penetration of ceftriaxone and cefoperazone into bile and gallbladder tissue was prospectively studied in 21 adult patients undergoing early surgery for acute cholecystitis. Comparable tissue, bile, and serum concentrations of the drugs were demonstrable; however, significantly fewer preoperative doses of ceftriaxone were required for adequate perioperative treatment. In view of its higher serum half-life and superior antibacterial activity toward common biliary pathogens, ceftriaxone appears to be a useful drug for the perioperative management of acute cholecystitis.