Outcomes of first emergency admissions for alcohol-related liver disease in England over a 10-year period: retrospective observational cohort study using linked electronic databases

OBJECTIVES

To examine time trends in patient characteristics, care processes and case fatality of first emergency admission for alcohol-related liver disease (ARLD) in England.

DESIGN

National population-based, retrospective observational cohort study.

SETTING

Clinical Practice Research Datalink population of England, 2008/2009 to 2017/2018. First emergency admissions were identified using the Liverpool ARLD algorithm. We applied survival analyses and binary logistic regression to study prognostic trends.

OUTCOME MEASURES

Patient characteristics; 'recent' General Practitioner (GP) consultations and hospital admissions (preceding year); higher level care; deaths in-hospital (including certified cause) and within 365 days. Covariates were age, sex, deprivation status, coding pattern, ARLD stage, non-liver comorbidity, coding for ascites and varices.

RESULTS

17 575 first admissions (mean age: 53 years; 33% women; 32% from most deprived quintile). Almost half had codes suggesting advanced liver disease. In year before admission, only 47% of GP consulters had alcohol-related problems recorded; alcohol-specific diagnostic codes were absent in 24% of recent admission records. Overall, case fatality rate was 15% in-hospital and 34% at 1 year. Case-mix-adjusted odds of in-hospital death reduced by 6% per year (adjusted OR (aOR): 0.94; 95% CI: 0.93 to 0.96) and 4% per year at 365 days (aOR: 0.96; 95% CI: 0.95 to 0.97). Exploratory analyses suggested the possibility of regional inequalities in outcome.

CONCLUSIONS

Despite improving prognosis of first admissions, we found missed opportunities for earlier recognition and intervention in primary and secondary care. In 2017/2018, one in seven were still dying during index admission, rising to one-third within a year. Nationwide efforts are needed to promote earlier detection and intervention, and to minimise avoidable mortality after first emergency presentation. Regional variation requires further investigation.

Rhizochalinin Exhibits Anticancer Activity and Synergizes with EGFR Inhibitors in Glioblastoma In Vitro Models

Rhizochalinin (Rhiz) is a recently discovered cytotoxic sphingolipid synthesized from the marine natural compound rhizochalin. Previously, Rhiz demonstrated high in vitro and in vivo efficacy in various cancer models. Here, we report Rhiz to be highly active in human glioblastoma cell lines as well as in patient-derived glioma-stem like neurosphere models. Rhiz counteracted glioblastoma cell proliferation by inducing apoptosis, G2/M-phase cell cycle arrest, and inhibition of autophagy. Proteomic profiling followed by bioinformatic analysis suggested suppression of the Akt pathway as one of the major biological effects of Rhiz. Suppression of Akt as well as IGF-1R and MEK1/2 kinase was confirmed in Rhiz-treated GBM cells. In addition, Rhiz pretreatment resulted in a more pronounced inhibitory effect of γ-irradiation on the growth of patient-derived glioma-spheres, an effect to which the Akt inhibition may also contribute decisively. In contrast, EGFR upregulation, observed in all GBM neurospheres under Rhiz treatment, was postulated to be a possible sign of incipient resistance. In line with this, combinational therapy with EGFR-targeted tyrosine kinase inhibitors synergistically increased the efficacy of Rhiz resulting in dramatic inhibition of GBM cell viability as well as a significant reduction of neurosphere size in the case of combination with lapatinib. Preliminary in vitro data generated using a parallel artificial membrane permeability (PAMPA) assay suggested that Rhiz cannot cross the blood brain barrier and therefore alternative drug delivery methods should be used in the further in vivo studies. In conclusion, Rhiz is a promising new candidate for the treatment of human glioblastoma, which should be further developed in combination with EGFR inhibitors.

The effect of the enhanced recovery programme on long-term survival following liver resection for colorectal liver metastases

BACKGROUND

Enhanced recovery programmes are associated with improved short-term outcomes following liver surgery. The impact of enhanced recovery programmes on medium- and long-term outcomes is incompletely understood. This study aimed to assess the impact of an enhanced recovery programme on long-term survival in patients undergoing surgery for colorectal liver metastases.

METHODS

At a tertiary hepatobiliary centre, we analysed short-, medium- and long-term outcomes in consecutive patients undergoing liver resection for colorectal liver metastases. A five-year retrospective review was carried out comparing the enhanced recovery programme to standard care.

RESULTS

A total of 172 patients were included in the analysis: 87 on standard care and 85 on an enhanced recovery programme. Open surgery was performed in 122 patients: 74 (85.1%) and 48 (56.5%) patients in the standard care and enhanced recovery programme, respectively (p < 0.001). There was a significant reduction in the median (IQR) length of hospital stay in the enhanced recovery programme compared with standard care (7 (5) days vs. 8 (3) days, p = 0.0009). There was no significant difference in survival between standard care and the Enhanced Recovery Programme at one (p = 0.818), three (p = 0.203), and five years (p = 0.247).

CONCLUSION

An enhanced recovery programme was associated with a reduced length of hospital stay. There was no effect on the one-, three- and five-year survival.

Protein kinase A mediates modality-specific modulation of the mechanically-gated ion channel PIEZO2

Protein kinase A is a downstream effector of many inflammatory mediators that induce pain hypersensitivity by increasing the mechanosensitivity of nociceptive sensory afferent. Here we examine the molecular mechanism underlying protein kinase-A-dependent modulation of the mechanically-activated ion channel PIEZO2, which confers mechanosensitivity to many nociceptors. Using phosphorylation site prediction algorithms, we identified multiple putative and highly conserved PKA phosphorylation sites located on intracellular intrinsically disordered regions of PIEZO2. Site-directed mutagenesis and patch-clamp recordings showed that substitution of one or multiple putative PKA sites within a single intracellular domain does not alter PKA-induced PIEZO2 sensitization, whereas mutation of a combination of nine putative sites located on four different intracellular regions completely abolishes PKA-dependent PIEZO2 modulation, though it remains unclear whether all or just some of these nine sites are required. By demonstrating that PIEZO1 is not modulated by PKA, our data also reveals a previously unrecognized functional difference between PIEZO1 and PIEZO2. Moreover, by demonstrating that PKA only modulates PIEZO2 currents evoked by focal mechanical indentation of the cell, but not currents evoked by pressure-induced membrane stretch, we provide evidence suggesting that PIEZO2 is a polymodal mechanosensor that engages different protein domains for detecting different types of mechanical stimuli.

Antimicrobial prescribing and antimicrobial resistance surveillance in equine practice

BACKGROUND

Antimicrobial resistance (AMR) is an increasingly serious threat to human and animal health, therefore responsible use of antimicrobials in equine practice is vital. There is a need to have accurate, up to date data on antimicrobial prescribing in equine practice in the UK.

OBJECTIVES

To characterise current antimicrobial prescribing practices by equine veterinarians and to describe surveillance, audit processes and identification of AMR.

STUDY DESIGN

Online cross-sectional, questionnaire-based survey.

METHODS

An online questionnaire targeting veterinarians who treat horses in the UK and Europe was distributed. The questionnaire collected data on participants' country of origin, practice policies, prescribing practices including use of high priority critical antimicrobials. Four common clinical case-based scenarios were included to further explore prescribing practice. Responses were compared using both descriptive statistics and multivariable logistic regression models.

RESULTS

Questionnaires were completed by 264 veterinarians from Europe (n=33/264) and the UK (n=231/264); 87% respondents worked only with horses and 67% worked at premises with hospitalisation facilities. Approximately half of respondents (54.4%) had a written antimicrobial use or stewardship policy within their practice. Over half of respondents did not perform any environmental surveillance (54.2%), audit of clinical infections (53.1%) or audit of infection control (57.1%). Potentiated sulphonamides were cited as the most used antimicrobial, although 44% reported using enrofloxacin in the last year and 66% used 3^rd or 4^th generation cephalosporins. Prophylactic antimicrobials before clean surgery were frequently/always prescribed by 48% respondents and 24% respondents frequently/always prescribed antimicrobials post-operatively in clean surgery.

MAIN LIMITATIONS

Potential selection bias of respondents, given individuals volunteered to take part in the survey.

CONCLUSIONS

Compared to a previous similar study conducted in 2009, overall antimicrobial usage appeared to be declining in clinical scenarios and a greater proportion of practices now have stewardship policies. However, the use of high priority critical antimicrobials is still relatively common in equine practice in the UK and Europe.

Effects of Human RelA Transgene on Murine Macrophage Inflammatory Responses

The NFκB transcription factors are major regulators of innate immune responses, and NFκB signal pathway dysregulation is linked to inflammatory disease. Here, we utilised bone marrow-derived macrophages from the p65-DsRedxp/IκBα-eGFP transgenic strain to study the functional implication of xenogeneic (human) RelA(p65) protein introduced into the mouse genome. Confocal imaging showed that human RelA is expressed in the cells and can translocate to the nucleus following activation of Toll-like receptor 4. RNA sequencing of lipid A-stimulated macrophages, revealed that human RelA impacts on murine gene transcription, affecting both non-NFκB and NFκB target genes, including immediate-early and late response genes, e.g., Fos and Cxcl10. Validation experiments on NFκB targets revealed markedly reduced mRNA levels, but similar kinetic profiles in transgenic cells compared to wild-type. Enrichment pathway analysis of differentially expressed genes revealed interferon and cytokine signaling were affected. These immune response pathways were also affected in macrophages treated with tumor necrosis factor. Data suggests that the presence of xenogeneic RelA protein likely has inhibitory activity, altering specific transcriptional profiles of key molecules involved in immune responses. It is therefore essential that this information be taken into consideration when designing and interpreting future experiments using this transgenic strain.

Serum amyloid A and plasma fibrinogen concentrations in horses following emergency exploratory celiotomy

BACKGROUND

Acute-phase proteins may help assess the nature and severity of lesions and outcome in horses undergoing colic surgery.

OBJECTIVES

To compare serum amyloid A and plasma fibrinogen concentrations ([SAA] and [fibrinogen]) in the immediate post-operative period after exploratory celiotomy and determine their value in assessment of post-operative complications and survival to discharge.

STUDY DESIGN

Observational study.

METHODS

This study included horses over 1 year of age undergoing exploratory celiotomy. Surgical procedures, lesions, post-operative care, complications and survival to discharge were recorded. [SAA] and [fibrinogen] were measured prior to surgery and 5 days post-operatively. Statistical analyses included Yate's Chi-square test, linear mixed effects model, Mann-Whitney U test and logistic regression.

RESULTS

Of 300 horses, 52.0% developed post-operative complications and 83.7% survived to discharge, with significantly reduced chance of survival in horses that developed post-operative complications (P<0.01). Median [SAA] at days 1, 2, 3, 4 and 5 and median [fibrinogen] at days 3, 4 and 5 were significantly different between horses that did and did not develop post-operative complications (P<0.05). Median [SAA] at days 1, 4 and 5 were significantly different between horses that did and did not survive to discharge (P<0.05). Logistic regression revealed post-operative complications to be associated with strangulating lesions (OR 2.35, 95% confidence interval [CI] 1.41-3.91, P≤0.001) and higher [fibrinogen] at admission (OR 1.21, 95% CI 1.00-1.45, P<0.05), and survival to discharge to be associated with lower [SAA] at 5 days post-operatively (OR 0.965, 95% CI 0.94-0.99, P = 0.002).

MAIN LIMITATIONS

A large variety of lesions and complications prevented detailed analysis of associations between inflammatory markers, lesions and complications.

CONCLUSIONS

Horses that develop post-operative complications have acute-phase responses of greater magnitudes and durations compared with those that do not develop complications. This is also seen in horses that do not survive to discharge. Measuring [SAA] daily and [fibrinogen] at admission, may help predict the development of post-operative complications.

Clinical Research Abstracts of the British Equine Veterinary Association Congress 2015

REASONS FOR PERFORMING STUDY

Pleural effusion (PE) is reported to occur most commonly secondary to bacterial pneumonia or lung abscesses, with neoplastic effusions contributing the minority of cases. The majority of these reports originate from America and Australia, where long distance transport of horses, a recognised risk factor, appears to occur more frequently. Anecdotally, neoplastic PE is more commonly diagnosed in the UK.

OBJECTIVES

To describe the causes of PE in horses resident in the UK, and to identify potential markers that can help differentiate between infectious and neoplastic causes of PE.

STUDY DESIGN

Retrospective clinical study.

METHODS

Medical records from 4 referral hospitals in southern England were searched for horses diagnosed with PE. Information gathered from medical records included signalment, diagnosis (infectious vs. neoplastic), admission physical examination and biochemical findings, and characteristics of the effusion (volume, cell count, total protein [TP] concentration). Statistical comparisons were made between the neoplastic and infectious group using appropriate testing.

RESULTS

Seventy horses were identified, of which 28 (40%) were neoplastic and 42 were infectious. Horses with infectious effusions were significantly younger (median 7 vs. 13 years; P = 0.002) and had significantly smaller volumes of pleural fluid drained at admission (9.8 vs. 32.3 l; P<0.001). Horses with infectious PE had a significantly higher rectal temperature (38.6 vs. 38.2°C; P = 0.03), fibrinogen concentration (7.8 vs. 5.7 g/l; P = 0.02) and serum amyloid A concentration (223 vs. 104 mg/l; P = 0.02). Pleural fluid characteristics identified a significantly greater cell count and TP concentration in horses with infectious PE (47 x 10(9)/l vs. 3.4 x 10(9)/l; P<0.001; 54 vs. 31 g/l; P = 0.001).

CONCLUSIONS

These results suggest that in the UK neoplastic effusions account for a greater proportion of PE than previously reported. A large volume of PE in an older horse with a low cell count and TP concentration should increase the index of suspicion of neoplasia. Ethical animal research: This was a retrospective study of clinical cases. Explicit owner informed consent for inclusion of animals in this study was not stated.

SOURCE OF FUNDING

None. Competing interests: None declared.

Spatiotemporal dynamics of glycolytic waves provides new insights into the interactions between immobilized yeast cells and gels

The immobilization of cells or enzymes is a promising tool for the development of biosensors, yet the interactions between the fixative materials and the cells are not fully understood, especially with respect to their impact on both cell metabolism and cell-to-cell signaling. We show that the spatiotemporal dynamics of waves of metabolic synchronization of yeast cells provides a new criterion to distinguish the effect of different gels on the cellular metabolism, which otherwise could not be detected. Cells from the yeast Saccharomyces carlsbergensis were immobilized into agarose gel, silica gel (TMOS), or a mixture of TMOS and alginate. We compared these immobilized cells with respect to their ability to generate temporal, intracellular oscillations in glycolysis as well as propagating, extracellular synchronization waves. While the temporal dynamics, as measured by the period and the number of oscillatory cycles, was similar for all three immobilized cell populations, significant differences have been observed with respect to the shape of the waves, wave propagation direction and velocity in the three gel matrices used.

Spatial control of the energy metabolism of yeast cells through electrolytic generation of oxygen

The metabolic dynamics of yeast cells is controlled by electric pulses delivered through a spatially extended yeast cell/Au electrode interface. Concomitant with voltage pulses, oxygen is generated electrolytically at the electrode surface and delivered to the cells. The generation of oxygen was investigated in dependence of the applied voltage, width of the voltage pulses and temperature of the electrolytic solution. The local oxygen pulses at the electrodes lead to a transient activation of the aerobic energy metabolism of the yeast cells causing a perturbation in their energy balance. The effect of these local perturbations on the temporal dynamics of glycolysis in yeast cells is quantified in dependence of the energy state of cells.

Deep erosions of the palmar aspect of the navicular bone diagnosed by standing magnetic resonance imaging

REASONS FOR PERFORMING STUDY

Erosion of the palmar (flexor) aspect of the navicular bone is difficult to diagnose with conventional imaging techniques.

OBJECTIVES

To review the clinical, magnetic resonance (MR) and pathological features of deep erosions of the palmar aspect of the navicular bone.

METHODS

Cases of deep erosions of the palmar aspect of the navicular bone, diagnosed by standing low field MR imaging, were selected. Clinical details, results of diagnostic procedures, MR features and pathological findings were reviewed.

RESULTS

Deep erosions of the palmar aspect of the navicular bone were diagnosed in 16 mature horses, 6 of which were bilaterally lame. Sudden onset of lameness was recorded in 63%. Radiography prior to MR imaging showed equivocal changes in 7 horses. The MR features consisted of focal areas of intermediate or high signal intensity on T1-, T2*- and T2-weighted images and STIR images affecting the dorsal aspect of the deep digital flexor tendon, the fibrocartilage of the palmar aspect, subchondral compact bone and medulla of the navicular bone. On follow-up, 7/16 horses (44%) had been subjected to euthanasia and only one was being worked at its previous level. Erosions of the palmar aspect of the navicular bone were confirmed post mortem in 2 horses. Histologically, the lesions were characterised by localised degeneration of fibrocartilage with underlying focal osteonecrosis and fibroplasia. The adjacent deep digital flexor tendon showed fibril formation and fibrocartilaginous metaplasia.

CONCLUSIONS

Deep erosions of the palmar aspect of the navicular bone are more easily diagnosed by standing low field MR imaging than by conventional radiography. The lesions involve degeneration of the palmar fibrocartilage with underlying osteonecrosis and fibroplasia affecting the subchondral compact bone and medulla, and carry a poor prognosis for return to performance.

POTENTIAL RELEVANCE

Diagnosis of shallow erosive lesions of the palmar fibrocartilage may allow therapeutic intervention earlier in the disease process, thereby preventing progression to deep erosive lesions.

Spatial desynchronization of glycolytic waves as revealed by Karhunen-Loeve analysis

The dynamics of glycolytic waves in a yeast extract have been investigated in an open spatial reactor. At low protein contents in the extract, we find a transition from inwardly moving target patterns at the beginning of the experiment to outwardly moving spiral- or circular-shaped waves at later stages. These two phases are separated by a transition phase of more complex spatiotemporal dynamics. We have analyzed the pattern dynamics in these three intervals at different spatial scales by means of a Karhunen-Loeve (KL) decomposition. During the initial phase of the experiment, the observed patterns are sufficiently described by the two dominant KL modes independently of the spatial scale. However, during the last stage of the experiment, at least 6 KL modes are needed to account for the observed patterns at spatial scales larger than 3 mm, while for smaller scales, 2 KL modes are still sufficient. This indicates that in the course of the experiment, the local glycolytic oscillators become desynchronized at spatial scales larger than 3 mm. Possible reasons for the desynchronization of the glycolytic waves are discussed.

Excitation-induced dynamics of external pH pattern in Chara corallina cells and its dependence on external calcium concentration

The influence of cell excitation and external calcium level on the dynamics of light-induced pH bands along the length of Chara corallina cells is studied in the present paper. Generation of an action potential (AP) transiently quenched these pH patterns, which was more pronounced at 0.05-0.1 mM Ca2+ than at higher concentrations of Ca2+ (0.6-2 mM) in the medium. After transient smoothing of the pH bands, some alkaline peaks reemerged at slightly shifted positions in media with low Ca2+ concentrations, while at high Ca2+ concentrations, the alkaline spots reappeared exactly at their initial positions. This Ca2+ dependency has been revealed by both digital imaging and pH microelectrodes. The stabilizing effect of external Ca2+ on the locations of recovering alkaline peaks is supposedly due to formation of a physically heterogeneous environment around the cell owing to precipitation of CaCO3 in the alkaline zones at high Ca2+ during illumination. The elevation of local pH by dissolving CaCO3 facilitates the reappearance of alkaline spots at their initial locations after temporal suppression caused by cell excitation. At low Ca2+ concentrations, when the solubility product of CaCO3 is not attained, the alkaline peaks are not stabilized by CaCO3 dissolution and may appear at random locations.

Transition from an excitable to an oscillatory state in dictyostelium discoideum

Under conditions of starvation, populations of the amoebae Dictyostelium discoideum aggregate are mediated by chemical excitation waves of cAMP. Two types of waves can be observed, either spiral or circular-shaped ones. We investigate transitions from rotating spirals to circular shaped waves (target patterns). Two different experiments demonstrating this phenomenon are presented. In the first case a continuous transition from the spiral type pattern to target waves was observed at the later stages of aggregation. In the second case the transition was induced by annihilation of waves by a spatially homogeneous cAMP pulse. Instead of the originally present spiral waves, oscillating spots bearing target patterns emerged. On the basis of a model for Dictyostelium aggregation, we provide a theoretical explanation for such transitions. It is shown that cell density can be an effective bifurcation parameter. Under certain conditions, the system is shifted from the excitable to the oscillatory state while the frequency of oscillations is proportional to the square root of the cell density. Thus, the regions with the highest cell density during the early stages of the spatial rearrangement of the cells become pacemakers and produce target patterns. The analytic results were confirmed in numerical simulations of the model.

Electrical stimulation of the energy metabolism in yeast cells using a planar Ti-Au-electrode interface

We report on the influence of dielectric pulse injection on the energy metabolism of yeast cells with a planar interdigitated electrode interface. The energy metabolism was measured via NADH fluorescence. The application of dielectric pulses results in a distinct decrease of the fluorescence, indicating a response of the energy metabolism of the yeast cells. The reduction of the NADH signal significantly depends on the pulse parameters, i.e., amplitude and width. Furthermore, the interface is used to detect electrical changes in the cell-electrolyte system, arising from glucose-induced oscillations in yeast cells and yeast extract, by dielectric spectroscopy at 10 kHz. These dielectric investigations revealed a beta(1)-dispersion for the system electrolyte/yeast cells as well as for the system electrolyte/yeast extract. In agreement with control measurements we obtained a glycolytic period of 45 s for yeast cells and of 11 min for yeast extract.

Comparison of glycolytic NADH oscillations in yeasts Saccharomyces cerevisiae and Saccharomyces carlsbergensis

The possible mechanism of synchronization of NADH oscillations in yeasts were studied. It was shown that the synchronization time depends on cell concentration in suspension. Synchronization of oscillations after acetaldehyde addition was found in Saccharomyces carlsbergensis whereas in S. cerevisiae oscillations were synchronized after adding potassium cyanide. It is possible, that synchronization of oscillations in S. cerevisiae requires low concentration of acetaldehyde and the high acetaldehyde concentration synchronizes oscillations in S. carlsbergensis. In addition, a possible mechanism of synchronization by acetaldehyde in proposed.

Analysis of the oscillatory kinetics of glycolytic intermediates in a yeast extract by FT-IR spectroscopy

In the present work we demonstrate that FT-IR spectroscopy is a powerful tool for the time resolved and noninvasive measurement of multi-substrate/product interactions in complex metabolic networks as exemplified by the oscillating glycolysis in yeast extract. We found that many of the glycolytic intermediates can be identified with FT-IR spectroscopy. For this, we have constructed a spectral library of most of the glycolytic intermediates and obtained the kinetics of single components in spectra from glycolysing yeast extract by the use of mathematical fitting procedures. The results are in good agreement with the known phase relationships of oscillatory glycolysis. They provide the basis for future application of this method to investigate the energy metabolism of living cells.

Glycolytic oscillations and waves in an open spatial reactor: Impact of feedback regulation of phosphofructokinase

An open spatial reactor has been designed for the investigation of spatio-temporal dynamics of glycolysis. The reactor consists of a diffusive layer made of gel-fixed yeast extract which is in contact with a continuously stirred reservoir to supply this layer with substrates. The coupling between reaction and diffusion in the gel layer enables the formation of spatio-temporal patterns. Temporal oscillations of glycolysis are simply induced by feeding the yeast extract with sugar. Under properly chosen conditions, these oscillations sustain for more than 12 h. A necessary prerequisite for the generation of oscillations is that the ATP concentration in the feeding solution must be high enough to allow for negative feedback of phosphofructokinase. Otherwise, the interplay between ATP-consuming and ATP-producing reactions leads to an unfavorable low ATP/AMP ratio. The generation of travelling NADH-waves is observed in the diffusive layer, when feeding the yeast extract with substrates. Break-up of circular-shaped waves is repeatedly observed, resulting in the formation of rotating NADH-spirals.

Control of glycolytic oscillations by temperature

External control of oscillatory glycolysis in yeast extract has been performed by application of either homogeneous temperature oscillations or stationary, spatial temperature gradients. Entrainment of the glycolytic oscillations by the 1/2- and 1/3-harmonic, as well as the fundamental input frequency, could be observed. From the phase response curve to a single temperature pulse, a distinct sensitivity of NADH-oxidizing processes, compared with NAD-reducing processes, is visible. Determination of glycolytic intermediates shows that the feedback-regulated phosphofructokinase as well as the glyceraldehyde-3-phosphate dehydrogenase are the most temperature-sensitive steps of glycolysis. We also find strong concentration changes in ATP and AMP at varying temperatures and, accordingly, in the energy charge. Construction of a feedback loop for spatial control of temperature by means of a Peltier element allowed us to apply a temperature gradient to the yeast extract. With this setup it is possible to initiate traveling waves and to control the wave velocity.

Extracellular potassium alters frequency and profile of retinal spreading depression waves

The phenomenon of spreading depression (SD) was observed in chicken retina by means of optical registration via a microscope and a CCD camera applying modern methods of image processing for optimized evaluation of the wave profiles. The propagation dynamics of SD waves was investigated as a function of extracellular potassium. Two main findings were obtained. Firstly, the frequency of spontaneous wave generation increased with the increase of K+ concentration. Secondly, there was an effect of potassium on the wave profile. In particular, the recovery zone of SD waves was shortened at increased K+. This effect was not only due to the dispersion relation of waves in excitable media as shown by the result of the mechanically induced wave trains. Applying the basic principles of chemical excitability for the interpretation of the data led us to the conclusion that these potassium effects are due to perturbations of an autocatalytic reaction to be further explored.

Antigen-specific IgG(T) responses in natural and experimental cyathostominae infection in horses

Equine clinical larval cyathostominosis is caused by simultaneous mass emergence of previously inhibited larvae from the mucosa of the colon. Clinical signs include diarrhoea, colic, weight loss and malaise, and in up to 50% of cases, the disease results in death. Cyathostominae spend a large part of their life cycle as larval stages in the intestinal mucosa. Definitive diagnosis is difficult due to the lack of diagnostic methods for pre-patent infection. In the present study, the enzyme-linked immunosorbent assay (ELISA) was used to investigate isotype responses to larval cyathostominae somatic antigen. Measurement of anti-larval IgG(T) responses appeared to have the most immunodiagnostic potential. An increase in IgG(T) response was detected to crude larval antigen by 5 weeks post-infection (PI) in individual infected ponies. Subsequently, IgG(T) responses to larval and adult somatic extracts were examined by Western blotting using sera from experimentally-infected horses and helminth-naive animals (n=6). Two antigen complexes, designated A and B, in larval somatic antigen were recognised specifically by the infected animals by 7 weeks PI. Sera taken from 23 endemically-infected animals, whose cyathostominae burdens had been enumerated, were also used to identify putative diagnostic antigens. Eighteen horses had positive mucosal worm burdens (range 723-3,595,725) and all but two of these animals had serum IgG(T) antibody specific to either complex. Moreover, IgG(T) responses specific to antigen complexes A and B were absent in all five parasite negative horses that were tested. Serum IgG(T) responses to either of the two complexes were identified in five clinical cases tested. IgG(T) responses to adult antigen somatic extracts were more heterogeneous, with no clear pattern between experimentally-infected ponies and helminth-free controls. The results indicate that increases in serum IgG(T) to mucosal larvae occur in the pre-patent period and that two antigenic complexes within somatic preparations of these stages have immunodiagnostic potential.

Spatio-temporal dynamics in glycolysis

During the glycolytic degradation of sugar in a thin layer of yeast extract, travelling waves of NADH and protons can be generated that carry a state of high enzymatic activity through the system. The controlled initiation of such waves with an activator of the enzyme phosphofructokinase (PFK) and the influence of various salts and co-factors on the propagation dynamics are investigated. Furthermore a first study of the dispersion of waves is presented. The experimental characterisation of this in vitro system contributes to unravelling the possible role of glycolysis for biological information processing. In this context, the provision of chemically available energy in the absence of compartmentation by glycolysis is of primary importance.

Traveling waves in yeast extract and in cultures of Dictyostelium discoideum

Biological self-organization was investigated in a biochemical and a cellular system: yeast extract and cultures of the slime mold Dictyostelium discoideum. In both systems traveling reaction-diffusion waves occur in response to oscillatory reactions. Glycolytic degradation of sugar in a yeast extract leads to the spontaneous formation of NADH and proton waves. Manipulation of the adenine nucleotide pool by addition of purified plasma membrane ATPase favors the formation of both reaction-diffusion waves and phase waves. The results indicate that the energy charge has an important impact for the dynamics of glycolytic patterns. When affecting the lower part of glycolysis by pyruvate addition the frequency of wave generation was increased with concomitant formation of rotating NADH and proton spirals. During morphogenesis of the cellular system Dictyostelium discoideum, circular and spiral shaped aggregation patterns of motile amoeboid cells form in response to traveling cAMP waves. Velocity analysis of the cell movements reveals that the cAMP waves guide the cells towards the site of wave initiation along optimized trajectories. The minimization of aggregation paths is based on a mechanism exploiting general properties of excitation waves. The resulting aggregation territories are reminiscent of Voronoi diagrams.

In vitro model for the evaluation of inferior vena cava filters: effect of experimental parameters on thrombus-capturing efficacy of the Vena Tech-LGM filter

PURPOSE

To determine the experimental parameters in an in vitro model that influence the thrombus-capturing efficacy of the Vena Tech-LGM filter.

MATERIALS AND METHODS

The Vena Tech-LGM filter was evaluated in an in vitro model of the vena cava with a computer-controlled flow system with a total of 5,200 thrombi. The influences of the following experimental parameters on the capture rate were analyzed with a multiple logistic regression model: type of testing (single, double, and multiple shot testing), thrombus diameter and length, IVC diameter and orientation, flow quality and quantity, flow velocity, and the length of the prepositioned thrombus.

RESULTS

A significant influence on the capture rate could be demonstrated for the type of testing, the thrombus diameter and length, the IVC diameter, and with double shot testing for the length of the prepositioned thrombus and the IVC orientation. The flow quality and the peak velocity were not significant. Based on these results, a protocol for in vitro testing of IVC filters was designed.

CONCLUSIONS

Experimental parameters influence the thrombus-capturing efficacy of the Vena Tech-LGM filter and should be taken into account when in vitro testing is performed.

A physiologic in vitro model of the inferior vena cava with a computer-controlled flow system for testing of inferior vena cava filters

RATIONALE AND OBJECTIVES

The authors develop a physiologic in vitro model of the inferior vena cava (IVC) for testing of filters.

METHODS

The model is driven by a centrifugal pump. A computer-controlled electromagnetic valve is used for generation of different flow patterns. Limitation of the pressure increase in case of IVC occlusion is achieved by a bypass circuit. A glycerin solution is used for perfusion. Artificial clots are made from polyacrylamide gel. Data acquisition includes continuous monitoring of flow and difference pressure over the filter and video recording of the testing events.

RESULTS

The model can generate constant and pulsatile flows. The pressure increase can be limited to 70 mm Hg in case of occlusion. Calculation of the flow velocities in the IVC is possible. A classification of thrombus capturing is presented. The testing of most of the results are reproducible.

CONCLUSIONS

The in vitro model simulates the physiologic conditions in the IVC. It can be used for comparative testing of different filters and the evaluation of new filter designs.

Traveling NADH and proton waves during oscillatory glycolysis in vitro

Propagation and mutual annihilation of circular and spiral NADH and proton waves were detected by spatially resolved spectrophotometry and fluorescent proton indicators in a biological in vitro system: an organelle-free yeast extract. Spontaneous wave generation during glycolytic sugar degradation is established after an induction period of about 1 h. Controlled wave initiation could be performed by local injection of the strong activator of phosphofructokinase, fructose 2,6-bisphosphate. A crucial role for wave initiation and control of pattern dynamics is attributed to the key enzyme of glycolysis, the allosterically regulated phosphofructokinase. An overall increase in the concentration of its positive effector AMP leads to the formation of rotating spirals. The dynamics of the observed wave patterns resemble that of self-organized calcium waves as recently found in frog eggs and heart cells.