Porphyromonas gingivalis Impairs Oral Epithelial Barrier through Targeting GRHL2

Oral mucosa provides the first line of defense against a diverse array of environmental and microbial irritants by forming the barrier of epithelial cells interconnected by multiprotein tight junctions (TJ), adherens junctions, desmosomes, and gap junction complexes. Grainyhead-like 2 (GRHL2), an epithelial-specific transcription factor, may play a role in the formation of the mucosal epithelial barrier, as it regulates the expression of the junction proteins. The current study investigated the role of GRHL2 in the Porphyromonas gingivalis (Pg)-induced impairment of epithelial barrier functions. Exposure of human oral keratinocytes (HOK-16B and OKF6 cells) to Pg or Pg-derived lipopolysaccharides (Pg LPSs) led to rapid loss of endogenous GRHL2 and the junction proteins (e.g., zonula occludens, E-cadherin, claudins, and occludin). GRHL2 directly regulated the expression levels of the junction proteins and the epithelial permeability for small molecules (e.g., dextrans and Pg bacteria). To explore the functional role of GRHL2 in oral mucosal barrier, we used a Grhl2 conditional knockout (KO) mouse model, which allows for epithelial tissue-specific Grhl2 KO in an inducible manner. Grhl2 KO impaired the expression of the junction proteins at the junctional epithelium and increased the alveolar bone loss in the ligature-induced periodontitis model. Fluorescence in situ hybridization revealed increased epithelial penetration of oral bacteria in Grhl2 KO mice compared with the wild-type mice. Also, blood loadings of oral bacteria (e.g., Bacteroides, Bacillus, Firmicutes, β-proteobacteria, and Spirochetes) were significantly elevated in Grhl2 KO mice compared to the wild-type littermates. These data indicate that Pg bacteria may enhance paracellular penetration through oral mucosa in part by targeting the expression of GRHL2 in the oral epithelial cells, which then impairs the epithelial barrier by inhibition of junction protein expression, resulting in increased alveolar tissue destruction and systemic bacteremia.

Cellular Components Mediating Coadherence of Candida albicans and Fusobacterium nucleatum

Candida albicans is an opportunistic fungal pathogen found as part of the normal oral flora. It can be coisolated with Fusobacterium nucleatum, an opportunistic bacterial pathogen, from oral disease sites, such as those involved in refractory periodontitis and pulp necrosis. The physical coadherence between these 2 clinically important microbes has been well documented and suggested to play a role in facilitating their oral colonization and colocalization and contributing to polymicrobial pathogenesis. Previous studies indicated that the physical interaction between C. albicans and F. nucleatum was mediated by the carbohydrate components on the surface of C. albicans and the protein components on the Fusobaterium cell surface. However, the identities of the components involved still remain elusive. This study was aimed at identifying the genetic determinants involved in coaggregation between the 2 species. By screening a C. albicans SN152 mutant library and a panel of F. nucleatum 23726 outer membrane protein mutants, we identified FLO9, which encodes a putative adhesin-like cell wall mannoprotein of C. albicans and radD, an arginine-inhibitable adhesin-encoding gene in F. nucleatum that is involved in interspecies coadherence. Consistent with these findings, we demonstrated that the strong coaggregation between wild-type F. nucleatum 23726 and C. albicans SN152 in an in vitro assay could be greatly inhibited by arginine and mannose. Our study also suggested a complex multifaceted mechanism underlying physical interaction between C. albicans and F. nucleatum and for the first time revealed the identity of major genetic components involved in mediating the coaggregation. These observations provide useful knowledge for developing new targeted treatments for disrupting interactions between these 2 clinically relevant pathogens.

[Development, Application and Evaluation of a Concept for Safe Patient Identification in Hospital - How can Knowledge Transfer Succeed?]

Aim of the Study: In order to minimise the risk of patient misidentification in clinical settings, the German Coalition for Patient Safety published recommendations for safety patient identification in 2008. The aim of this study was to develop, implement and evaluate a theoretical framework of knowledge transfer. The purpose of the framework was to enhance hospital staff's ability to apply the recommendations for safe patient identification in the daily routine of patient care. Method: A data bank-based research and literature review have been conducted. Research topics were: knowledge transfer, change management and implementation science. Within the application of the concept group interviews were held with hospital staff and the interview material was evaluated using content analysis. On this basis a tailored multifaceted implementation strategy has been developed and applied in 8 hospital wards of 4 hospitals belonging to a communal hospital concern. The evaluation of the developed knowledge transfer concept was conducted 4 weeks after the concept application with a written questionnaire. Results: The developed framework concept of knowledge translation consisted of 4 phases built on top of each other: initiation phase; analysis phase; implementation phase; evaluation phase. The multifaceted implementation strategy included 3 interventions: a poster, a computer-based training and a guideline for team meetings. The survey yielded responses from 56 individuals: 96% declared that they know about the existence of the recommendations for safe patient identification; 86% said that they know about the content of the recommendations; 91% have striven to apply the recommendations in the daily routine of patient care; 71% stated that the recommendations for safe patient identification have become integral part in the daily routine of patient care. To become aware of the recommendations and its content the respondents have used on average 2.3 interventions, however the effect of the CBS was relatively small. Conclusion: The developed theoretical framework concept for knowledge transfer provides a way to integrate the recommendations for safe patient identification in the daily routine of patient care and to counteract risk factors promoting misidentification. Therefore a multifaceted implementation strategy is promising.

[Can Quality of Patient Identification be Influenced by Training? - Results of a Randomised Multicentre Study with Multimodal Intervention]

Background: Attributing clinical care to patients unambiguously is a precondition for patient safety. The German Coalition for Patient Safety has published a recommendation on this topic. Issue: The here presented study examined whether and to what extent documentation quality as one determining factor of correct patient identification can be improved positively by inter-professional training. Method: In our randomised multi-centric study physicians and nurses from 8 units in 4 hospitals were trained. The control group consisted of untrained unit teams. Effects of the intervention were measured by investigating documentation errors in clinical records before and after the training. Results: As a result of our intervention the number of documents with documentation errors/patient charts could be reduced by 37.3% (p<0.001). Conclusion: The results of the study point to the training of recommendations on preventing errors as an effective instrument for the improvement of patient safety.

[Improvement of medication safety by identification of genetically predisposed subjects. Personalized clinical strategies and regulatory advices]

BACKGROUND

Because adverse drug events (ADEs) have a high socio-economic impact there is an urgent need for effective prevention. In addition to process-related avoidable errors personalised approaches for the prevention of ADEs should also focus on genetic polymorphisms as potential causative agents.

AIM

Using five case reports as examples therapeutic modalities are described to illustrate the clinical impact of prospective testing aimed at estimating the individual risk of susceptible subjects.

MATERIAL AND METHODS

The role of the HLA system, the cytochrome P450 family, other metabolic enzymes and transport proteins are described to illustrate the broad range of genetic susceptibility. It is shown, why, when and for whom pretherapeutic tests on genetic polymorphisms are recommended to reduce the risk of ADEs.

RESULTS

The determination of genetic susceptibility is already implemented in clinical practice prior to (1) carbamazepine therapy in south-east Asians and (2) treatment with abacavir independent of ethnicity. Before prescribing carbamazepine or abacavir, it is recommended that therapeutic decisions be based on these test results.

CONCLUSION

The broad application of personalised medicine used as an effective tool for minimizing ADE risks is limited by the evidence-based benefit for the patient on the one hand and the costs of the test on the other hand.

The effect of massage on heart rate variability in preterm infants

OBJECTIVE

To test the hypothesis that massage would improve autonomic nervous system (ANS) function as measured by heart rate variability (HRV) in preterm infants.

STUDY DESIGN

Medically stable, 29- to 32-week preterm infants (17 massage, 20 control) were enrolled in a masked, randomized longitudinal study. Licensed massage therapists provided the massage or control condition twice a day for 4 weeks. Weekly HRV, a measure of ANS development and function, was analyzed using SPSS generalized estimating equations.

RESULTS

Infant characteristics were similar between groups. HRV improved in massaged infants but not in the control infants (P<0.05). Massaged males had a greater improvement in HRV than females (P<0.05). HRV in massaged infants was on a trajectory comparable to term-born infants by study completion.

CONCLUSION

Massage-improved HRV in a homogeneous sample of hospitalized, medically stable, preterm male infants and may improve infant response to exogenous stressors. We speculate that massage improves ANS function in these infants.

In vitro study of biofilm formation and effectiveness of antimicrobial treatment on various dental material surfaces

Elevated proportions of Candida albicans in biofilms formed on dentures are associated with stomatitis whereas Streptococcus mutans accumulation on restorative materials can cause secondary caries. Candida albicans, S. mutans, saliva-derived and C. albicans/saliva-derived mixed biofilms were grown on different materials including acrylic denture, porcelain, hydroxyapatite (HA), and polystyrene. The resulting biomass was analysed by three-dimensional image quantification and assessment of colony-forming units. The efficacy of biofilm treatment with a dissolved denture cleansing tablet (Polident(®)) was also evaluated by colony counting. Biofilms formed on HA exhibited the most striking differences in biomass accumulation: biofilms comprising salivary bacteria accrued the highest total biomass whereas C. albicans biofilm formation was greatly reduced on the HA surface compared with other materials, including the acrylic denture surface. These results substantiate clinical findings that acrylic dentures can comprise a reservoir for C. albicans, which renders patients more susceptible to C. albicans infections and stomatitis. Additionally, treatment efficacy of the same type of biofilms varied significantly depending on the surface. Although single-species biofilms formed on polystyrene surfaces exhibited the highest susceptibility to the treatment, the most surviving cells were recovered from HA surfaces for all types of biofilms tested. This study demonstrates that the nature of a surface influences biofilm characteristics including biomass accumulation and susceptibility to antimicrobial treatments. Such treatments should therefore be evaluated on the surfaces colonized by the target pathogen(s).

Using DGGE profiling to develop a novel culture medium suitable for oral microbial communities

More than 700 bacterial species have been detected in the human oral cavity. They form highly organized microbial communities and are responsible for many oral infectious diseases, such as dental caries and periodontal disease. The prevention and treatment of these diseases require a comprehensive knowledge of oral microbial communities, which largely relies on culture-dependent methods to provide detailed phenotypic and physiological analysis of these communities. However, most of the currently available laboratory media can only selectively support the growth of a limited number of bacterial species within these communities, and fail to sustain the original oral microbial diversity. In this study, using denaturing gradient gel electrophoresis (DGGE) as an index to systematically survey and analyse the selectivity of commonly used laboratory media, we developed a new medium (SHI medium) by combining the ingredients of several selected media that can support different subpopulations within the original oral microbial community derived from pooled saliva. DGGE and 454 pyrosequencing analysis showed that SHI medium was capable of supporting a more diversified community with a microbial profile closer to that of the original oral microbiota. Furthermore, 454 pyrosequencing revealed that SHI medium supported the growth of many oral species that have not before been cultured. Crystal violet assay and the confocal laser scanning microscope analysis indicated that, compared with other media, SHI medium is able to support a more complex saliva-derived biofilm with higher biomass yield and more diverse species. This DGGE-guided method could also be used to develop novel media for other complex microbial communities.

Effect of glucose on Treponema denticola cell behavior

INTRODUCTION

Treponema denticola inhabits the oral subgingival environment and is part of a proteolytic benzoyl-dl-arginine-naphthylamide-positive 'red complex' associated with active periodontal disease. Spirochetes have a unique form of chemotactic motility that may contribute to their virulence. Chemotaxis is essential for efficient nutrient-directed translocation.

METHODS

We examined the effect of glucose on T. denticola cell velocity, expression of periplasmic flagella proteins, and chemotaxis, e.g. translocation into capillary tubes.

RESULTS

The presence of glucose did not significantly effect T. denticola cell velocity in high viscosity conditions nor did it alter periplasmic flagella protein expression. The addition of glucose to capillary tubes resulted in greater numbers of T. denticola cells in tubes containing glucose. A non-motile mutant did not migrate into capillary tubes containing glucose.

CONCLUSION

These results are consistent with a chemotactic response to glucose that is motility dependent.

Fusobacterium nucleatum apoptosis-inducing outer membrane protein

The periodontal pathogen Fusobacterium nucleatum induces apoptosis in lymphocytes. We previously identified the autotransporter protein Fap2 in F. nucleatum strain PK1594 that induced apoptosis in lymphocytes when expressed in Escherichia coli. In this study, we identified protein homologs of Fap2 in the transformable F. nucleatum strain ATCC 23726, to determine their role in the induction of apoptosis in lymphocytes. We used a new gene-inactivation vector conferring thiamphenicol resistance (pHS31) to construct a mutant deficient in one of the homologs, aim1. Transcriptional analyses demonstrated disruption of aim1 expression, and phenotypic analyses revealed a 41% decrease in the ability of the mutant to induce apoptosis in Jurkat cells, as compared with the parental strain. These studies demonstrate, in the native host cell background, the contribution of aim1 to F. nucleatum induction of apoptosis and, to the best of our knowledge, represent the first report of a genetically defined and phenotypically characterized mutation in F. nucleatum.

Bevölkerungsbezogene Etablierung präventiv wirksamer Nahrungs- und Lebensmittelzusätze: Barrieren und Widerstände

The population-wide and individual preventive potentials of nutritional and food additives such as vitamins and trace elements are generally accepted in the international literature. Iodisation and fluoridation were and are a main focus of activity. The enrichment of food with folic acid is also partly population-related. Until now, however, the theoretical possibilities of nutritional supplementations have not been fully exploited. Various barriers and resistances arise in programme development and implementation. Interviews with key stakeholders and community groups can clarify decade-long discussions in the literature and the media. The study on hand is based on a structural analysis. It shows the various arguments as well as beneficial and impeding factors for a population-wide prevention programme, for specific target groups and individuals. The findings of this research could also be applied to other Public Health challenges.

Motility and chemotaxis in tissue penetration of oral epithelial cell layers by Treponema denticola

The ability to penetrate tissue is an important virulence factor for pathogenic spirochetes. Previous studies have recognized the role of motility in allowing pathogenic spirochetes to invade tissues and migrate to sites favorable for bacterial proliferation. However, the nature of the movements, whether they are random or controlled by chemotaxis systems, has yet to be established. In this study, we addressed the role of motility and chemotaxis in tissue penetration by the periodontal disease-associated oral spirochete Treponema denticola using an oral epithelial cell line-based experimental approach. Wild-type T. denticola ATCC 35405 was found to penetrate the tissue layers effectively, whereas a nonmotile mutant was unable to overcome the tissue barrier. Interestingly, the chemotaxis mutants also showed impaired tissue penetration. A cheA mutant that is motile but lacks the central kinase of the chemotaxis pathway showed only about 2 to 3% of the wild-type penetration rate. The two known chemoreceptors of T. denticola, DmcA and DmcB, also appear to be involved in the invasion process. The dmc mutants were actively motile but exhibited reduced tissue penetration of about 30 and 10% of the wild-type behavior, respectively. These data suggest that not only motility but also chemotaxis is involved in the tissue penetration by T. denticola.

Determinants of chemotactic signal amplification in Escherichia coli

A well-characterized protein phosphorelay mediates Escherichia coli chemotaxis towards the amino acid attractant aspartate. The protein CheY shuttles between flagellar motors and methyl-accepting chemoreceptor (MCP) complexes containing the linker CheW and the kinase CheA. CheA-CheY phosphotransfer generates phospho-CheY, CheY-P. Aspartate triggers smooth swim responses by inactivation of the CheA bound to the target MCP, Tar; but this mechanism alone cannot explain the observed response sensitivity. Here, we used behavioral analysis of mutants deleted for CheZ, a catalyst of CheY-P dephosphorylation, or the methyltransferase CheR and/or the methylesterase CheB to examine the roles of accelerated CheY-P dephosphorylation and MCP methylation in enhancement of the chemotactic response. The extreme motile bias of the mutants was adjusted towards wild-type values, while preserving much of the aspartate response sensitivity by expressing fragments of the MCP, Tsr, that either activate or inhibit CheA. We then measured responses to small jumps of aspartate, generated by flash photolysis of photo-labile precursors. The stimulus-response relation for Delta cheZ mutants overlapped that for the host strains. Delta cheZ excitation response times increased with stimulus size consistent with formation of an occluded CheA state. Thus, neither CheZ-dependent or independent increases in CheY-P dephosphorylation contribute to the excitation response. In Delta cheB Delta cheR or Delta cheR mutants, the dose for a half-maximal response, [Asp](50), was ca 10 microM; but was elevated to 100 microM in Delta cheB mutants. In addition, the stimulus-response relation for these mutants was linear, consistent with stoichiometric inactivation, in contrast to the non-linear relation for wild-type E. coli. These data suggest that response sensitivity is controlled by differential binding of CheR and/or CheB to distinct MCP signaling conformations.

Chemotaxis in pathogenic spirochetes: directed movement toward targeting tissues?

Chemotaxis is an important feature of motile organisms that allows navigation through various environments. It enables them to detect nutrients and to avoid unfavorable or dangerous conditions. Motility and chemotaxis are widely acknowledged as important virulence factors for pathogenic bacteria. In this review, we try to explore the role of chemotaxis in the pathogenesis of spirochetes. Chemotaxis might be involved in tissue identification and penetration, and represents a possible mechanism for evasion of the host's immune defense. The recent development of genetic tools for pathogenic spirochetes and "tracking" techniques, employing fluorescent in situ hybridization (FISH), could revolutionize our understanding of the importance of chemotaxis for infection and persistence of these bacteria in their host.

Overproduced Salmonella typhimurium flagellar motor switch complexes

Three Salmonella typhimurium flagellar motor proteins, FliG, FliM and FliN, are required for the switching of rotation sense. The proteins have been localized to the cytoplasmic module of the flagellar base. Structures, which were morphologically indistinguishable from the native transmembrane MS-ring and cytoplasmic C-ring basal body modules, formed in Escherichia coli upon plasmid-encoded synthesis of these proteins together with FliF. The structures localized to the cell membrane and contained all three motor proteins, as determined by immuno-electron microscopy. This result supports the deduction, based on earlier biochemical analysis, that the C-ring is composed entirely of these proteins and, therefore, functions as a dedicated motor component. In addition, it demonstrates that the morphologically correct assembly of the C-ring onto the MS-ring proceeds independently of other structural components of these modules.

Elucidation of a PTS-carbohydrate chemotactic signal pathway in Escherichia coli using a time-resolved behavioral assay

Chemotaxis of Escherichia coli toward phosphotransferase systems (PTSs)-carbohydrates requires phosphoenolpyruvate-dependent PTSs as well as the chemotaxis response regulator CheY and its kinase, CheA. Responses initiated by flash photorelease of a PTS substrates D-glucose and its nonmetabolizable analog methyl alpha-D-glucopyranoside were measured with 33-ms time resolution using computer-assisted motion analysis. This, together with chemotactic mutants, has allowed us to map out and characterize the PTS chemotactic signal pathway. The responses were absent in mutants lacking the general PTS enzymes EI or HPr, elevated in PTS transport mutants, retarded in mutants lacking CheZ, a catalyst of CheY autodephosphorylation, and severely reduced in mutants with impaired methyl-accepting chemotaxis protein (MCP) signaling activity. Response kinetics were comparable to those triggered by MCP attractant ligands over most of the response range, the most rapid being 11.7 +/- 3.1 s-1. The response threshold was <10 nM for glucose. Responses to methyl alpha-D-glucopyranoside had a higher threshold, commensurate with a lower PTS affinity, but were otherwise kinetically indistinguishable. These facts provide evidence for a single pathway in which the PTS chemotactic signal is relayed rapidly to MCP-CheW-CheA signaling complexes that effect subsequent amplification and slower CheY dephosphorylation. The high sensitivity indicates that this signal is generated by transport-induced dephosphorylation of the PTS rather than phosphoenolpyruvate consumption.

Optimal lead selection for detection of ST segment shifts

A comparison was made to determine the ability of optimal sets of 2-6 unipolar leads and a normal Holter lead set to estimate ST potential distributions changes induced by balloon inflation during angioplasty. The performance of these lead sets was compared to measurements observed in recorded 32-lead body surface maps. Unipolar lead potentials were estimated using a linear, least mean squared error estimator of the total body surface map. The correlation between maximum ST potential change in the body surface map and that predicted by the unipolar lead sets ranged from 0.84-0.93. The correlation between maximum ST segment change measured from the body surface map and measured from the Holter leads was 0.29. Therefore, shifts in ST segment potentials can accurately be estimated from a small number of unipolar leads. In contrast, current bipolar ambulatory recording techniques may introduce significant bias to such estimates.

Coupling the phosphotransferase system and the methyl-accepting chemotaxis protein-dependent chemotaxis signaling pathways of Escherichia coli

Chemotactic responses in Escherichia coli are typically mediated by transmembrane receptors that monitor chemoeffector levels with periplasmic binding domains and communicate with the flagellar motors through two cytoplasmic proteins, CheA and CheY. CheA autophosphorylates and then donates its phosphate to CheY, which in turn controls flagellar rotation. E. coli also exhibits chemotactic responses to substrates that are transported by the phosphoenolpyruvate (PEP)-dependent carbohydrate phosphotransferase system (PTS). Unlike conventional chemoreception, PTS substrates are sensed during their uptake and concomitant phosphorylation by the cell. The phosphoryl groups are transferred from PEP to the carbohydrates through two common intermediates, enzyme I (EI) and phosphohistidine carrier protein (HPr), and then to sugar-specific enzymes II. We found that in mutant strains HPr-like proteins could substitute for HPr in transport but did not mediate chemotactic signaling. In in vitro assays, these proteins exhibited reduced phosphotransfer rates from EI, indicating that the phosphorylation state of EI might link the PTS phospho-relay to the flagellar signaling pathway. Tests with purified proteins revealed that unphosphorylated EI inhibited CheA autophosphorylation, whereas phosphorylated EI did not. These findings suggest the following model for signal transduction in PTS-dependent chemotaxis. During uptake of a PTS carbohydrate, EI is dephosphorylated more rapidly by HPr than it is phosphorylated at the expense of PEP. Consequently, unphosphorylated EI builds up and inhibits CheA autophosphorylation. This slows the flow of phosphates to CheY, eliciting an up-gradient swimming response by the cell.

Testing the porphyrinogenicity of propofol in a primed rat model

We evaluated the porphyrinogenicity of propofol in a rat model. After a pilot study had been conducted to determine an optimal dose, 48 fasting male Sprague-Dawley rats were allocated randomly to six groups. The animals in groups 1-3 received saline i.p. In groups 4-6, the animals were given allylisopropylacetamide (AIA). Twelve hours later, animals in groups 1 and 4 received saline, groups 2 and 5 were given propofol 150 mg kg-1 i.p., followed by 75 mg kg-1 3 h later, and groups 3 and 6 received phenobarbitone 50 mg kg-1 i.p. and 25 mg kg-1 i.p. The animals were anaesthetized and killed 3 h after the second drug bolus and we measured the concentration of cytochrome P450, total porphyrin content and the activity of delta-aminolaevulinic acid synthase (ALAS) in the liver. Urinary delta-aminolaevulinic acid (ALA) and porphobilinogen (PBG) concentrations were measured. Analysis of variance and the t test with Bonferroni's correction were used to compare data. The hepatic cytochrome P450 concentration in the non-primed groups varied from 28.1 to 31.1 nmol g-1; administration of AIA decreased this to 20.1-20.9 nmol g-1. Total hepatic porphyrins were between 0.78 and 1.22 nmol g-1 in the non-primed groups and between 2.71 and 3.54 nmol g-1 in the AIA-primed groups. Hepatic ALAS activity was 29.2 and 35.5 nmol h-1 g-1 in groups 1 and 2. In the primed saline group, ALAS activity was measured at 134.5 nmol h-1 g-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of activation and recovery sequences and local repolarization durations from distant electrocardiographic leads

Experiments using an isolated heart, perfused by a support dog were done to compare estimates of activation times, recovery times and activation recovery intervals from cardiac surface electrograms to estimates from distant electrocardiographic leads and to known features concerning normal activation and recovery sequences. The isolated heart was suspended in a tank with 600 electrodes located at sites 0.5 cm to 7.5 cm from the surface of the heart. In some experiments up to 330 electrodes, spaced 2.5 mm to 5 mm apart on a nylon matrix, were placed on the cardiac surface. Recordings were made during atrial and ventricular drives at cycle lengths of 400 msec to 700 msec. The minimum QRS and maximum T derivatives and the interval between them were taken as the estimates of activation times, recovery times and activation recovery intervals respectively. Maps of activation sequence, and the distribution of activation recovery intervals were constructed from cardiac surface data and from data recorded at various distances from the heart. Regions of earliest and latest activation and recovery times, range between the earliest and latest activation and recovery times and the average activation recovery interval could be determined from data recorded at distances from the heart comparable to the distance between the cardiac and thoracic surfaces. The results indicate that electrocardiographic signals, recorded with regionally sensitive distant leads, contain considerable detail concerning local activation and recovery sequences and the distribution of repolarization properties. This information should be useful in the evaluation of patients and in guiding drug therapy.

Quantitative comparison of pre-mortem ECG's with those reconstructed from activation data of a revived heart

The pioneering work of Durrer and associates has made available unique data showing activation isochrones in human hearts. To be certain that the complex experimental procedures do not seriously affect the activation sequence and also to validate accepted basic premises concerning the genesis of the electrocardiogram (ECG), it appears to be essential to show a reasonable correspondence between the subject's ECG before death and ECG's reconstructed from the activation data and heart-lead models. This paper reports the results of such a study. The comparison is evaluated in quantitative terms using several types of correlation coefficient. The significance of these is further evaluated through comparisons of similar coefficients from a random sample of normal records. The correlation coefficient considered to have the most general applicability gives a value of .80; only one subject from the random group showed a higher correspondence. A particular set of leads chosen to minimize the effects of inhomogeneities not accounted for in the modelling process, clearly selected the subject's records from all others with a correlation coefficient of .91 compared to .87, the highest from the random set. Considering the practical limitations on the accuracy of the models underlying these tests, the results are considered, with certain exceptions, to be supportive of the accuracy of the activation experiments and the assumption of a uniform double layer as the ECG source.

Hypotensive action of an intra-nasally applied angiotensin II-antagonist

Intranasal administration of the specific angiotensin II-antagonist (1-NSuc-5-Val-8-Phg) A II was investigated in anaesthetized rats with different forms of experimentally elevated blood pressure. Renin- or angiotensin II-induced blood pressure increases were markedly reversed by the angiotensin II-antagonist applied intra-nasally. In rats with acute accelerated elevation of blood pressure the analogue induced also a significant decrease. No change could be observed in rats with chronic renal hypertension.