Analysis of the effects of oxygen supply and demand on hypoxic fraction in tumors

The extent of hypoxic regions in a tumor tissue depends on the arrangement, blood flow rate and blood oxygen content of microvessels, and on the tissue's oxygen consumption rate. Here, the effects of blood flow rate, blood oxygen content and oxygen consumption on hypoxic fraction are simulated theoretically, for a region whose microvascular geometry was derived from observations of a transplanted mammary andenocarcinoma (R3230AC) in a rat dorsal skin flap preparation. In the control state, arterial PO2 is 100 mmHg, consumption rate is 2.4 cm3 O2/100 g/min, and hypoxic fraction (tissue with PO2 < 3 mmHg) is 30%. Hypoxia is abolished by a reduction in consumption rate of at least 30%, relative to control, or an increase in flow rate by a factor of 4 or more, or an increase in arterial PO2 by a factor of 11 or more. These results suggest that reducing oxygen consumption rate may be more effective than elevating blood flow or oxygen content as a method to reduce tumor hypoxia.

Endoscopy-based triage significantly reduces hospitalization rates and costs of treating upper GI bleeding: a randomized controlled trial

BACKGROUND

Many patients with upper gastrointestinal (GI) bleeding have a benign outcome and could receive less intensive and costly care if accurately identified. We sought to determine whether early endoscopy performed shortly after admission in the emergency department could significantly reduce the health care use and costs of caring for patients with nonvariceal upper GI bleeding without adversely affecting the clinical outcome.

METHODS

All eligible patients with upper GI bleeding and stable vital signs were randomized after admission to undergo endoscopy in 1 to 2 days (control) or early endoscopy in the emergency department. Patients with low-risk findings on early endoscopy were discharged directly from the emergency department. Clinical outcomes and costs were prospectively assessed for 30 days.

RESULTS

We randomized 110 consecutive stable patients with nonvariceal upper GI bleeding during the 12-month study period. The baseline demographic features, endoscopic findings, and the clinical outcomes were no different between the two groups. However the findings of the early endoscopy allowed us to immediately discharge 26 of 56 (46%) patients randomized to that group. No patient discharged from the emergency department suffered an adverse outcome. The hospital stay (median of 1 day [interquartile range of 0 to 3 days] vs. 2 days [interquartile range of 2 to 3 days], p = 0.0001) and the cost of care ($2068 [interquartile range of $928 to $3960] versus $3662 [interquartile range of $2473 to $7280], p = 0.00006) were significantly less for the early endoscopy group.

CONCLUSIONS

Early endoscopy performed shortly after admission in the emergency department safely triaged 46% of patients with nonvariceal upper GI bleeding to outpatient care, which significantly reduced hospital stay and costs.

Mutations in FAM20C are associated with lethal osteosclerotic bone dysplasia (Raine syndrome), highlighting a crucial molecule in bone development

The generation and homeostasis of bone tissue throughout development and maturity is controlled by the carefully balanced processes of bone formation and resorption. Disruption of this balance can give rise to a broad range of skeletal pathologies. Lethal osteosclerotic bone dysplasia (or, Raine syndrome) is an autosomal recessive disorder characterized by generalized osteosclerosis with periosteal bone formation and a distinctive facial phenotype. Affected individuals survive only days or weeks. We have identified and defined a chromosome 7 uniparental isodisomy and a 7p telomeric microdeletion in an affected subject. The extent of the deleted region at the 7p telomere was established by genotyping microsatellite markers across the telomeric region. The region is delimited by marker D7S2563 and contains five transcriptional units. Sequence analysis of FAM20C, located within the deleted region, in six additional affected subjects revealed four homozygous mutations and two compound heterozygotes. The identified mutations include four nonsynonymous base changes, all affecting evolutionarily conserved residues, and four splice-site changes that are predicted to have a detrimental effect on splicing. FAM20C is a member of the FAM20 family of secreted proteins, and its mouse orthologue (DMP4) has demonstrated calcium-binding properties; we also show by in situ hybridization its expression profile in mineralizing tissues during development. This study defines the causative role of FAM20C in this lethal osteosclerotic disorder and its crucial role in normal bone development.

Analysis of oxygen transport to tumor tissue by microvascular networks

We present theoretical simulations of oxygen delivery to tumor tissues by networks of microvessels, based on in vivo observations of vascular geometry and blood flow in the tumor microcirculation. The aim of these studies is to investigate the impact of vascular geometry on the occurrence of tissue hypoxia. The observations were made in the tissue (thickness 200 microns) contained between two glass plates in a dorsal skin flap preparation in the rat. Mammary adenocarcinomas (R3230 AC) were introduced and allowed to grow, and networks of microvessels in the tumors were mapped, providing data on length, geometric orientation, diameter and blood velocity in each segment. Based on these data, simulations were made of a 1 mm x 1 mm region containing five unbranched vascular segments and a 0.25 mm x 0.35 mm region containing 22 segments. Generally, vessels were assumed to lie in the plane midway between the glass plates, at 100 microns depth. Flow rates in the vessels were based on measured velocities and diameters. The assumed rate of oxygen consumption in the tissue was varied over a range of values. Using a Green's function method, partial pressure of oxygen (PO2) was computed at each point in the tissue region. As oxygen consumption is increased, tissue PO2 falls, with hypoxia first appearing at points relatively distant from the nearest blood vessel. The width of the well-oxygenated region is comparable to that predicted by simpler analyses. Cumulative frequency distributions of tissue PO2 were compared with predictions of a Krogh-type model with the same vascular densities, and it was found that the latter approach, which assumes a uniform spacing of vessels, may underestimate the extent of the hypoxic tissue. Our estimates of the maximum consumption rate that can be sustained without tissue hypoxia were substantially lower than those obtained from the Krogh-type model. We conclude that the heterogeneous structure of tumor microcirculation can have a substantial effect on the occurrence of hypoxic micro-regions.

Motion of red blood cells in a capillary with an endothelial surface layer: effect of flow velocity

Interior surfaces of capillaries are lined with macromolecules forming an endothelial surface layer (ESL). A theoretical model is used to investigate effects of flow velocity on motion and axisymmetric deformation of red blood cells in a capillary with an ESL. Cell deformation is analyzed, including effects of membrane shear and bending elasticity. Plasma flow around the cell and through the ESL is computed using lubrication theory. The ESL is represented as a porous layer that exerts compressive forces on red blood cells that penetrate it. According to the model, hydrodynamic pressures generated by plasma flow around the cell squeeze moving red blood cells into narrow elongated shapes. If the ESL is 0.7 microm wide, with hydraulic resistivity of 2 x 10(8) dyn x s x cm(-4), and exerts a force of 20 dyn/cm2, predicted variation with flow velocity of the gap width between red blood cell and capillary wall agrees well with observations. Predicted gap at a velocity of 0.1 mm/s is approximately 0.6 microm vs. approximately 0.2 microm with no ESL. Predicted flow resistance increases markedly at low velocities. The model shows that exclusion of red blood cells from the ESL in flowing capillaries can result from hydrodynamic forces generated by plasma flow through the ESL.

Fecal Microbiota Transplantation Is Highly Effective in Real-World Practice: Initial Results From the FMT National Registry

BACKGROUND & AIMS

Fecal microbiota transplantation (FMT) is used commonly for treatment of Clostridioides difficile infections (CDIs), although prospective safety data are limited and real-world FMT practice and outcomes are not well described. The FMT National Registry was designed to assess FMT methods and both safety and effectiveness outcomes from North American FMT providers.

METHODS

Patients undergoing FMT in clinical practices across North America were eligible. Participating investigators enter de-identified data into an online platform, including FMT protocol, baseline patient characteristics, CDI cure and recurrence, and short and long-term safety outcomes.

RESULTS

Of the first 259 participants enrolled at 20 sites, 222 had completed short-term follow-up at 1 month and 123 had follow-up to 6 months; 171 (66%) were female. All FMTs were done for CDI and 249 (96%) used an unknown donor (eg, stool bank). One-month cure occurred in 200 patients (90%); of these, 197 (98%) received only 1 FMT. Among 112 patients with initial cure who were followed to 6 months, 4 (4%) had CDI recurrence. Severe symptoms reported within 1-month of FMT included diarrhea (n = 5 [2%]) and abdominal pain (n = 4 [2%]); 3 patients (1%) had hospitalizations possibly related to FMT. At 6 months, new diagnoses of irritable bowel syndrome were made in 2 patients (1%) and inflammatory bowel disease in 2 patients (1%).

CONCLUSIONS

This prospective real-world study demonstrated high effectiveness of FMT for CDI with a good safety profile. Assessment of new conditions at long-term follow-up is planned as this registry grows and will be important for determining the full safety profile of FMT.

Synchrotron X-ray Studies of LiNbO3 and LiTaO3

The structural geometry, vibrations and deformation density Δρ for lithium niobate, LiNbO3, and lithium tantalate, LiTaO3, are derived from synchrotron radiation diffraction measurements. Electron density is transferred from the Nb (Ta) atom towards the large O3 triangle near the Li atom. Spontaneous polarizations of 0.43 (LiNbO3) and 0.33 cm−2 (LiTaO3), calculated with Hirshfeld charges, agree qualitatively with experimental values of 0.71 and 0.50 −2, respectively. Both strong Li...Nb (Ta) interactions in the structure are markedly shorter than all Li...Li, Nb...Nb or Ta...Ta vectors, as expected if the Li and Nb (Ta) cations carry charges of opposite sign. The Li atom's negative charge plays a pivotal role in the polarization responsible for ferroelectricity. LiNbO3, space group R3c, rhombohedral, M r = 147.8, a = 5.493 (2) Å, α = 55.89 (3)°, V = 106.02 (4) Å3, Z = 2, D x = 4.629 Mg m−3, F(000) = 136, μ(0.7 Å) = 5.01 mm−l, y min = 0.27, T = 293 K, R = 0.015, wR = 0.015, S = 3.276 (84) for 773 unique reflections. LiTaO3, R3c, rhombohedral, M r = 235.9, a = 5.471 (2) Å, α = 56.16 (3)°, V = 105.51 (4) Å3, Z = 2, D x = 7.412 Mg m−3, F(000) = 200, μ(0.7 Å) = 50.03 mm−1, y min = 0.32, T = 293 K, R = 0.016, wR = 0.022, S = 1.372(35) for 773 unique reflections.

A model for red blood cell motion in glycocalyx-lined capillaries

The interior surfaces of capillaries are lined with a layer (glycocalyx) of macromolecules bound or absorbed to the endothelium. Here, a theoretical model is used to analyze the effects of the glycocalyx on hematocrit and resistance to blood flow in capillaries. The glycocalyx is represented as a porous layer that resists penetration by red blood cells. Axisymmetric red blood cell shapes are assumed, and effects of cell membrane shear elasticity are included. Lubrication theory is used to compute the flow of plasma around the cell and within the glycocalyx. The effects of the glycocalyx on tube hematocrit (Fahraeus effect) and on flow resistance are predicted as functions of the width and hydraulic resistivity of the layer. A layer of width 1 micron and resistivity 10(8) dyn.s/cm4 leads to a relative apparent viscosity of approximately 10 in a 6-micron capillary at discharge hematocrit 45% and flow velocity of approximately 1 mm/s. This is consistent with experimental observations of increased flow resistance in microvessels in vivo, relative to glass tubes with the same diameters.

Extensive homology between the subunits of the phytohemagglutinin mitogenic proteins derived from Phaseolus vulgaris

The phytohemagglutinin mitogenic proteins derived from Phaseolus vulgaris comprise a class of five glycoproteins that are isomeric tetramers composed of varying proportions of two different subunits (L and R). Within the native tetramer, the L subunit is a potent leukoagglutinin and mitogen that lacks hemagglutinating properties, whereas the R subunit is a potent hemagglutinin with little or no mitogenic activity. The subunits have been isolated in homogeneous form by isoelectric focusing in 8 M urea. Previous work has shown that they have equal molecular weights and differ in amino-acid sequence from residues 1-7, but are identical in positions 8-24 [(1973) J. Exp. Med. 138, 939-951]. We now report amino-acid composition studies which reveal striking similarities between the subunits. Both lack methionine and cysteine. The twelfth residue in each subunit is a glycosylated asparagine, with the identical carbohydrate composition in each. The last three residues of the subunits, as determined by carboxypeptidase A digestion, are identical. Tryptic peptide mapping of the succinylated phytohemagglutinin subunits reveals a high degree of similarity. We conclude that the substantial difference in biological properties among the tetrameric phytohemagglutinin mitogens is a result of relatively restricted differences in the primary structure of their constituent subunits.

Vastus medialis obliquus and vastus lateralis activity in open and closed kinetic chain exercises in patients with patellofemoral pain syndrome: an electromyographic study

OBJECTIVES

To evaluate the electromyographic activities of vastus medialis obliquus (VMO) and vastus lateralis (VL) muscles in open and closed kinetic chain exercises in subjects with patellofemoral pain syndrome (PFPS).

DESIGN

Case-controlled study.

SETTING

Rehabilitation science center in a tertiary medical center.

PARTICIPANTS

Ten patients with bilateral knee pain diagnosed with PFPS and 10 healthy volunteers.

INTERVENTIONS

Subjects performed open kinetic chain exercise on an isokinetic dynamometer and closed kinetic chain exercise by squat-to-stand and stand-to-squat tasks. Surface electromyography was done for the VMO and VL muscles.

MAIN OUTCOME MEASURES

VMO/VL ratios were calculated after normalization of muscle activities.

RESULTS

The VMO/VL ratios of PFPS subjects were significantly lower than were those of unimpaired subjects during knee isokinetic closed kinetic chain exercises (p = .047). However, there was no statistical difference in VMO/VL ratio between subjects with and without PFPS during closed kinetic chain exercises (p = .623). Maximum VMO/VL ratio was obtained at 60 degrees knee flexion in closed kinetic chain exercise.

CONCLUSION

In closed kinetic chain exercises, more selective VMO activation can be obtained at 60 degrees knee flexion. Maximal VMO/VL ratio was observed at this knee flexion angle, and muscle contraction intensity was also greatest.

A Green's function method for analysis of oxygen delivery to tissue by microvascular networks

A theoretical model is formulated for analyzing oxygen delivery from an arbitrary network configuration of cylindrical microvessels to a finite region of tissue. In contrast to models based on the classical Krogh cylinder approach, this model requires no a priori assumptions concerning the extent of the tissue region supplied with oxygen by each vessel segment. Steady-state conditions are assumed, and oxygen consumption in the tissue is assumed to be uniform. The nonlinear dissociation characteristics of oxyhemoglobin are taken into account. A computationally efficient Green's function approach is used, in which the tissue oxygen field is expressed in terms of the distribution of source strengths along each segment. The utility of the model is illustrated by analyses of oxygen delivery to a cuboidal tissue region by a single segment and by a six-segment network. It is found that the fractional contribution of the proximal segments to total oxygen delivery increases with decreasing flow rate and metabolic rate.

Mucosal morbidity in patients with epidermolysis bullosa acquisita

BACKGROUND

Epidermolysis bullosa acquisita is an acquired inflammatory and/or dermolytic subepidermal blistering disease characterized by IgG autoantibodies to type VII collagen. Four patients with documented epidermolysis bullosa acquisita were evaluated by a multidisciplinary team of care providers (4 dermatologists, an ophthalmologist, a radiologist, a voice and speech specialist, and an otolaryngologist) for 1 to 5 years to characterize mucosal involvement and its complications and response to treatment. Patients were evaluated clinically and by slitlamp examinations, endoscopies, computed tomographic scans, and videofluorographic swallowing studies. Spiral computed tomographic scans for virtual endoscopy were used for the nontraumatic evaluation of airways in 2 patients with respiratory tract compromise.

OBSERVATIONS

Involvement of 5 or more mucosal sites--mouth, nose, conjunctiva, pharynx, and larynx--was documented in all patients. Complications included ankyloglossia, periodontal disease, scarring and crusting of nasal mucosa, symblepharon formation, obstruction of nasolacrimal ducts, deformation of the epiglottis, impaired phonation, dysphagia, esophageal strictures, and supraglottic stenosis requiring emergency tracheostomy.

CONCLUSIONS

Epidermolysis bullosa acquisita may extensively (or predominantly) affect mucosal epithelia in a manner resembling cicatricial pemphigoid. Mucosal disease in these patients is often subclinical, can lead to serious complications, and is best managed using a multidisciplinary approach.

Blood flow and red blood cell deformation in nonuniform capillaries: effects of the endothelial surface layer

OBJECTIVE

A theoretical model is used to examine the mechanics of red blood cell (RBC) motion in nonuniform capillaries. The model includes effects of the endothelial surface layer (ESL), which is a layer of macromolecules adjacent to the endothelium and which impedes plasma flow.

METHODS

The motion of an RBC traversing a capillary with diameter varying sinusoidally between 5.4 microm and 7.4 microm is simulated numerically. The ESL is assumed to be 0.7-microm wide and deformable. Axisymmetric RBC shapes are assumed. Lubrication theory is used to analyze the motion of plasma around the RBC and through the ESL.

RESULTS

In a nonuniform capillary with no ESL, moving RBCs undergo large transient deformations and predicted flow resistance is substantially higher than in a uniform capillary with the same mean diameter. The presence of a deformable ESL reduces the transient fluid shear stresses and deformations experienced by RBCs traversing a nonuniform capillary. With an ESL, the increase in flow resistance resulting from nonuniformity is less than twofold versus three- to fourfold with no ESL in vessel geometries with the same ESL-free luminal region.

CONCLUSIONS

The presence of the ESL reduces the impact of capillary irregularity on flow resistance and may protect RBCs traversing irregular capillaries from damage due to large, rapidly fluctuating external stresses.

Characteristics of general practices associated with emergency admission rates to hospital: a cross-sectional study

OBJECTIVES

To identify characteristics of general practices associated with emergency hospital admission rates, and determine whether levels of performance and patient reports of access are associated with admission rates.

DESIGN

A cross-sectional study.

SETTING

Two primary care trusts (Leicester City and Leicestershire County and Rutland) in the East Midlands of England.

PARTICIPANTS

145 general practices.

METHODS

Hospital admission data were used to calculate the rate of emergency admissions from 145 practices, for two consecutive years (2006/7 and 2007/8). Practice characteristics (size, distance from principal hospital, quality and outcomes framework performance data, patient reports of access to their practices) and patient characteristics (deprivation, ethnicity, gender and age), were used as predictors in a two-level hierarchical model, developed with data for 2007/8, and evaluated against data for 2006/7.

RESULTS

Practice characteristics (shorter distance from hospital, smaller list size) and patient characteristics (higher proportion of older people, white ethnicity, increasing deprivation, female gender) were associated with higher admission rates. There was no association with quality and outcomes framework domains (clinical or organisation), but there was an association between patients reporting being able to see a particular general practitioner (GP) and admission rates. As the proportion of patients able to consult a particular GP increased, emergency admission rates declined.

CONCLUSIONS

The patient characteristics of deprivation, age, ethnicity and gender are important predictors of admission rates. Larger practices and greater distance from a hospital have lower admission rates. Being able to consult a particular GP, an aspect of continuity, is associated with lower emergency admission rates.

Human anti-laminin 5 autoantibodies induce subepidermal blisters in an experimental human skin graft model

Patients with one form of cicatricial pemphigoid have IgG antibasement membrane autoantibodies against laminin 5 (alpha3beta3gamma2). Although passive transfer of rabbit anti-laminin 5 IgG to neonatal mice has been shown to induce subepidermal blisters that mimic those in patients, it has not been possible to directly assess the pathogenic activity of human autoantibodies in this animal model because the latter do not bind murine skin. To address this question, a disease model in adult mice as well as SCID mice bearing human skin grafts was developed. Adult BALB/C mice challenged with rabbit anti-laminin 5 IgG developed, in a concentration-related fashion, erythema, erosions, and crusts surrounding injection sites, histologic evidence of noninflammatory, subepidermal blisters, and deposits of rabbit IgG and murine C3 in epidermal basement membranes. Anti-laminin 5 IgG also induced subepidermal blisters in: adult complement-, mast cell-, and immuno-deficient mice; adult BALB/C mice pretreated with dexamethasone; and human skin grafts on SCID mice. Alterations did not develop in matching controls challenged with identical amounts of purified normal rabbit IgG or bovine serum albumin. Using this adult mouse model, human skin grafts on SCID mice were challenged with purified IgG from patients with alpha subunit-specific, anti-laminin 5 autoantibodies, or normal controls. Patient (but not control) IgG induced epidermal fragility as well as noninflammatory, subepidermal blisters in grafted human (but not adjacent murine) skin. Moreover, whereas all mice that received patient autoantibodies had anti-laminin 5 IgG in their circulation, deposits of human IgG were present only in the epidermal basement membranes of grafts. Interestingly, these in situ and circulating autoantibodies were predominately of the IgG4 subclass. These studies demonstrate that human anti-laminin 5 autoantibodies are pathogenic in vivo and describe an animal model that can be used to define disease pathomechanisms and biologically important domains within this autoantigen.

Antiepiligrin cicatricial pemphigoid represents an autoimmune response to subunits present in laminin 5 (alpha3beta3gamma2)

Sera from 20 patients with antiepiligrin cicatricial pemphigoid were studied to define the specific reactivity of their IgG autoantibodies. IgG from all patients bound exclusively to the dermal side of 1 mol/L NaCl split skin and immunoprecipitated laminin 5 (alpha3beta3gamma2) from extracts of human keratinocytes (HKs). Immunoblot studies on purified laminin 5 subunits demonstrated that patient IgG bound alpha3 alone in 16 patients. In two patients, IgG autoantibodies were directed predominantly to the gamma2 subunit, yet showed trace reactivity to alpha3 as well. Sera from two patients did not immunoblot any laminin 5 subunits, their IgG presumably immunoprecipitating laminin 5 via a conformational epitope. Sera from patients with alpha3 subunit-specific IgG immunoprecipitated all subunits of laminin 5 as well as polypeptides of 190 and 200 kDa from the conditioned media of HKs. Preclearance studies and experiments utilizing affinity-purified patient IgG demonstrated that the latter signified laminin 6 (alpha3beta1gamma1) that was bound by cross-reactive alpha3 subunit-specific patient IgG. Sera from patients with gamma2 subunit-specific IgG showed no reactivity to laminin 6, except for faint reactivity provided by low levels of their alpha3 subunit-specific IgG. Taken together, these findings indicate that antiepiligrin cicatricial pemphigoid signifies an autoimmune response to subunits present in laminin 5.

Simulation of O2 transport in skeletal muscle: diffusive exchange between arterioles and capillaries

Theoretical simulations of oxygen transport in skeletal muscle are used to study the role of arterioles in oxygen delivery. A three-dimensional configuration of capillaries and arterioles in a cuboidal tissue region is simulated, based on observations of hamster cheek pouch retractor muscle. Equations describing convective and diffusive oxygen transport are solved using a Green's function method. In resting muscle, predicted oxygen saturation of capillary blood increases as it flows toward arterioles, and adjacent capillaries flowing in opposite directions show very similar variations in saturation. Diffusive oxygen loss from arterioles equals about 85% of consumption. Capillaries absorb much of this oxygen (equal to approximately 45% of consumption) and deliver it at downstream locations. Thus diffusive exchange between arterioles and capillaries plays an important part in distributing oxygen throughout the tissue. At higher flow and consumption rates, the relative amounts of oxygen diffusing out of arterioles and into capillaries decrease. The results are consistent with the hypothesis that oxygen content of arteriolar blood participates in metabolic regulation of blood flow.

Potentially avoidable emergency department attendance: interview study of patients' reasons for attendance

OBJECTIVES

To explore the reasons for attendance at the emergency department (ED) by patients who could have been managed in an alternative service and the rate of acute admissions to one acute hospital.

DESIGN

Interview study.

SETTING

One acute hospital (University Hospitals of Leicester) in the East Midlands.

PARTICIPANTS

23 patients and/or their carers.

METHODS

A purposive sample of patients attending the ED and the linked urgent care centre was identified and recruited. Patients in the sample were approached by a clinician and a researcher and invited to take part in an interview. Patients of different ethnicities and from different age groups, arriving at the ED via different referral routes (self-referral, emergency ambulance, GP referral, out-of-hours services) and attending at different times of the day and night were included. The interviews were recorded and transcribed with the individuals' permission and analysed using the framework analysis approach.

RESULTS

Patients' anxiety or concern about the presenting problem, the range of services available to the ED and the perceived efficacy of these services, patients' perceptions of access to alternative services including general practice and lack of alternative pathways were factors that influenced the decision to use the ED.

CONCLUSIONS

Access to general practice, anxiety about the presenting problem, awareness and perceptions of the efficacy of the services available in the ED and lack of alternative pathways are important predictors of attendance rates.

Are self-expanding metal mesh stents useful in the treatment of benign esophageal stenoses and fistulas? An experience of four cases

OBJECTIVE

The aim of this study was to review the long-term results of treating benign esophageal fistula and stenosis using self-expanding metal stents.

METHODS

We treated four patients using covered mesh or coiled stents. We removed the stents electively in two patients (one endoscopically and one during planned partial esophagectomy) and unexpectedly in one patient who developed bleeding. One stent migrated and required laparotomy for removal.

RESULTS

Placement of self-expanding metal stents successfully sealed the benign fistula in two patients and reestablished swallowing in two other patients with complicated achalasia. Two patients were swallowing normally on long-term follow-up, one died of the underlying disease, and one required gastrostomy.

CONCLUSION

Temporary use of self-expanding metal stents as a feasible option for treating benign esophageal stenosis and fistula in patients who have failed other conventional treatments.

Analysis of red blood cell motion through cylindrical micropores: effects of cell properties

Filtration through micropores is frequently used to assess red blood cell deformability, but the dependence of pore transit time on cell properties is not well understood. A theoretical model is used to simulate red cell motion through cylindrical micropores with diameters of 3.6, 5, and 6.3 microns, and 11-microns length, at driving pressures of 100-1000 dyn/cm2. Cells are assumed to have axial symmetry and to conserve surface area during deformation. Effects of membrane shear viscosity and elasticity are included, but bending resistance is neglected. A time-dependent lubrication equation describing the motion of the suspending fluid is solved, together with the equations for membrane equilibrium, using a finite difference method. Predicted transit times are consistent with previous experimental observations. Time taken for cells to enter pores represents more than one-half of the transit time. Predicted transit time increases with increasing membrane viscosity and with increasing cell volume. It is relatively insensitive to changes in internal viscosity and to changes in membrane elasticity except in the narrowest pores at low driving pressures. Elevating suspending medium viscosity does not increase sensitivity of transit time to membrane properties. Thus filterability of red cells is sensitively dependent on their resistance to transient deformations, which may be a key determinant of resistance to blood flow in the microcirculation.

Fab fragments directed against laminin 5 induce subepidermal blisters in neonatal mice

Patients with one form of cicatricial pemphigoid have IgG autoantibodies directed against laminin 5 (alpha3beta3gamma2), an adhesion protein in epidermal basement membrane. Anti-laminin 5 autoantibodies are not found in patients with other skin or mucosal diseases and hence serve as a specific marker for this autoimmune blistering disorder. The demonstration that experimental and patient anti-laminin 5 IgG are pathogenic in animal models indicated that such autoantibodies are central to disease pathophysiology. To investigate further the role of antibody valence and complement in triggering lesion formation in vivo, rabbit anti-laminin 5 (or normal, control) Fab fragments were passively transferred to neonatal BALB/c mice. Mice receiving anti-laminin 5 Fab fragments developed, in a dose-related fashion, circulating anti-basement membrane antibodies, deposits of immunoreactive rabbit IgG (but not murine C3) in epidermal basement membranes, and subepithelial blisters of skin and mucous membranes. Such alterations were not observed in mice treated with equivalent concentrations of normal rabbit Fab fragments. These studies demonstrated that neither complement activation nor cross-linking of laminin 5 in epidermal basement membranes was required for induction of subepidermal blister formation in this animal model of a human autoimmune bullous disease.

Characteristics of general practices associated with emergency-department attendance rates: a cross-sectional study

BACKGROUND

Strategies are needed to contain emergency-department attendance. Quality of care in general practice might influence the use of emergency departments, including management of patients with chronic conditions and access to consultations.

AIM

The aim was to determine whether emergency-department attendance rates are lower for practices with higher quality and outcomes framework performance and lower for practices with better patient reported access.

DESIGN

A cross-sectional study.

SETTING

Two English primary-care trusts, Leicester City and Leicestershire County and Rutland, with 145 general practices.

METHOD

Using data on attendances at emergency departments in 2006/2007 and 2007/2008, a practice attendance rate was calculated for each practice. In a hierarchical negative binomial regression model, practice population characteristics (deprivation, proportion of patients aged 65 or over, ethnicity, gender) and practice characteristics (total list size, distance from the emergency department, quality and outcomes framework points, and variables measuring satisfaction with access) were included as potential explanatory variables.

RESULTS

In both years, greater deprivation, shorter distance from the central emergency department, lower practice list size, white ethnicity and lower satisfaction with practice telephone access were associated with higher emergency-department attendance rates.

CONCLUSIONS

Performance as indicated by the quality and outcomes framework did not predict rates of attendance at emergency departments, but satisfaction with telephone access did. Consideration should be given to improving access to some general practices to contain the use of emergency departments.

Motion of nonaxisymmetric red blood cells in cylindrical capillaries

We analyze theoretically the single-file flow of asymmetric red blood cells along cylindrical capillaries. Red cells in narrow capillaries are typically nonaxisymmetric, with the cell membrane moving continuously around the cell. In our analysis, cell shape and streamlines of membrane motion are prescribed. Lubrication theory is used to compute velocities and pressures in the fluid surrounding the cell. Conditions of zero lift, zero torque, zero drag, and energy conservation in the cell are imposed. Predicted tank-treading frequency, cell inclination and transverse displacement are small. Cell asymmetry and tank-treading are found to have little effect on the apparent viscosity of blood in capillaries with diameters up to 7 microns.