Structure-activity relationships of actively FhuE transported rifabutin derivatives with potent activity against Acinetobacter baumannii.

Hospital-acquired infections are on the rise and represent both, a clinical and financial burden. With resistance emerging and an ever-dwindling armamentarium at hand, infections caused by Acinetobacter baumannii are particularly problematic, since these bacteria have a high level of resistance and resilience to traditional and even last-resort antibiotics. The antibiotic rifabutin was recently found to show potent in vitro and in vivo activity against extensively drug resistant A. baumannii. Building on this discovery, we report on the synthesis and activity of rifabutin analogs, with a focus on N-functionalization of the piperidine ring. The antimicrobial testing uncovered structure activity relationships (SAR) for A. baumannii that were not reflected in Staphylococcus aureus. The cellular activity did not correlate with cell-free transcription inhibition, but with bacterial intracellular compound accumulation. Mass spectrometry-based accumulation studies confirmed the involvement of the siderophore receptor FhuE in active compound translocation at low concentrations, and they showed a strong impact of the culture medium on the accumulation of rifabutin. Overall, the study underlines the structural feature required for strong accumulation of rifabutin in A. baumannii and identifies analogs as or more potent than rifabutin against A. baumannii.

The target cell of transformation is distinct from the leukemia stem cell in murine CALM/AF10 leukemia models.

The CALM/AF10 fusion gene is found in various hematological malignancies including acute myeloid leukemia (AML), T-cell acute lymphoblastic leukemia and malignant lymphoma. We have previously identified the leukemia stem cell (LSC) in a CALM/AF10-driven murine bone marrow transplant AML model as B220+ lymphoid cells with B-cell characteristics. To identify the target cell for leukemic transformation or 'cell of origin of leukemia' (COL) in non-disturbed steady-state hematopoiesis, we inserted the CALM/AF10 fusion gene preceded by a loxP-flanked transcriptional stop cassette into the Rosa26 locus. Vav-Cre-induced panhematopoietic expression of the CALM/AF10 fusion gene led to acute leukemia with a median latency of 12 months. Mice expressing CALM/AF10 in the B-lymphoid compartment using Mb1-Cre or CD19-Cre inducer lines did not develop leukemia. Leukemias had a predominantly myeloid phenotype but showed coexpression of the B-cell marker B220, and had clonal B-cell receptor rearrangements. Using whole-exome sequencing, we identified an average of two to three additional mutations per leukemia, including activating mutations in known oncogenes such as FLT3 and PTPN11. Our results show that the COL for CALM/AF10 leukemia is a stem or early progenitor cell and not a cell of B-cell lineage with a phenotype similar to that of the LSC in CALM/AF10+ leukemia.

Short communication: Fractional milking distribution of immunoglobulin G and other constituents in colostrum.

The provision of quality colostrum with a high concentration of immunoglobulins is critical for newborn calf health. Because first colostrum may be low in overall concentration to effectively reduce the risk of newborn infections, we tested equivalent milking fractions of colostrum for possible IgG differences. The objective of this study was to determine if the fractional composition of colostrum changes during the course of milking with a focus on immunoglobulins. Twenty-four Holstein and Simmental cows were milked (first colostrum) within 4h after calving. The colostrum of 1 gland per animal was assembled into 4 percentage fractions over the course of milking: 0 to 25%, 25 to 50%, 50 to 75%, and 75 to 100%. The IgG concentration among the various fractions did not change in any significant pattern. Concentration of protein, casein, lactose and somatic cell count remained the same or exhibited only minor changes during the course of fractional milking colostrum. We determined that no benefit exists in feeding any particular fraction of colostrum to the newborn.

The spatio-temporal arrangement of different tissues during bone healing as a result of simple mechanobiological rules.

During secondary bone healing, different tissue types are formed within the fracture callus depending on the local mechanical and biological environment. Our aim was to understand the temporal succession of these tissue patterns for a normal bone healing progression by means of a basic mechanobiological model. The experimental data stemmed from an extensive, previously published animal experiment on sheep with a 3 mm tibial osteotomy. Using recent experimental data, the development of the hard callus was modelled as a porous material with increasing stiffness and decreasing porosity. A basic phenomenological model was employed with a small number of simulation parameters, which allowed comprehensive parameter studies. The model distinguished between the formation of new bone via endochondral and intramembranous ossification. To evaluate the outcome of the computer simulations, the tissue images of the simulations were compared with experimentally derived tissue images for a normal healing progression in sheep. Parameter studies of the threshold values for the regulation of tissue formation were performed, and the source of the biological stimulation (comprising e.g. stem cells) was varied. It was found that the formation of the hard callus could be reproduced in silico for a wide range of threshold values. However, the bridging of the fracture gap by cartilage on the periosteal side was observed only (i) for a rather specific choice of the threshold values for tissue differentiation and (ii) when assuming a strong source of biological stimulation at the periosteum.

Solubilizing agents in nasal formulations and their effect on ciliary beat frequency.

The purpose of this study was to determine the concentration-dependent effect of selected solubilizers, used in common nasal drug formulations, on ciliary beat frequency (CBF) in human nasal epithelial cell cultures. CBF was measured by a high-speed digital imaging method. Excised ciliated human nasal epithelial cells were incubated for 60min with the solubilizers and determination of the half maximal inhibitory concentration (IC(50)), followed by a reversibility test. LDH test was performed on human nasal epithelial cells with the solubilizing agents. These were applied to nasal epithelial cells in IC(50) values. The following rank order in IC(50) values was obtained for the solubilizers: glycerol>propylene glycol>polyethylene glycol 300>N,N-dimethylacetamide>polyethylene glycol 400>ethanol>ethylendiamindihydrochloride>polyvinylpyrrolidon 25>polyvinylpyrrolidon 90. The highest reversibility of approximately 75% was shown by propylene glycol and polyethylene glycol 300 at a concentration of 30% (v/v). Results from the LDH test showed that N,N-dimethylacetamide displayed the highest cytotoxicity with 5.2% at a concentration of 14.5% (v/v). According to these results, several solubilizers can alter the CBF frequency and thus, have an impact on the nasal mucosa. Therefore, CBF studies with solubilizers used at a concentration relevant for nasal formulations are essential in the design of efficient and most notably safe nasal medicinal products.

[Quality of life, stress management and health promotion in medical and dental students. A comparative study]. / Lebensqualität, Stressbewältigung und Gesundheitsförderung bei Studierenden der Human- und Zahnmedizin. Eine Vergleichsuntersuchung.

OBJECTIVE: Which are the differences in health-related quality of life and stress management in medical and dental students? METHODS: 101 dental and 237 medical students from different years of Justus-Liebig University Giessen were examined during winter term 2008/09 and summer term 2009 using the specific Questionnaire on Health Promotion, Life Satisfaction, and Stress Management in Dental or Medical Students (addressing work satisfaction and choice of subject, private life, relaxation behavior and stress management, and health behavior), Beck Depression Inventory (BDI) and SF-36 Health Survey. For statistical analysis, Mann-Whitney-U-Test, analysis of variance (ANOVA), Pearson correlation and Chi2-Tests were primarily used. RESULTS: Dental and medical students showed considerable mental impairment in SF-36. Every fifth dental student suffered from slight to moderate depression. Though averaging more hours per week, medical students were more satisfied with their studies. More than half of the dental and medical students did not have appropriate strategies of coping with stress. CONCLUSIONS: Concerning the mental impairment in both groups and regarding a higher health-related quality of life, specific prevention courses or mentoring programs should already be offered at the beginning of medical training in order to cope with strains of medical school and future job strains in the medical or dental profession.

Disconnecting the yin and yang relation of epidermal growth factor receptor (EGFR)-mediated delivery: a fully synthetic, EGFR-targeted gene transfer system avoiding receptor activation.

The epidermal growth factor receptor (EGFR) is upregulated within a high percentage of solid tumors and hence is an attractive target for tumor-targeted therapies including gene therapy. The natural EGFR ligand epidermal growth factor (EGF) has been used for this purpose, despite the risk of mitogenic effects due to EGFR activation. We have developed a fully synthetic, EGFR-targeted gene delivery system based on PEGylated linear polyethylenimine (LPEI), allowing evaluation of different EGFR-binding peptides in terms of transfection efficiency and EGFR activation. Peptide sequences directly derived from the human EGF molecule enhanced transfection efficiency with concomitant EGFR activation. Only the EGFR-binding peptide GE11, which has been identified by phage display technique, showed specific enhancement of transfection on EGFR-overexpressing tumor cells including glioblastoma and hepatoma, but without EGFR activation. EGFR targeting led to high levels of cell association of fluorescently labeled polyplexes after only 30 min of incubation. EGF pretreatment of cells induced enhanced cellular internalization of all polyplex types tested, pointing at generally enhanced macropinocytosis. EGF polyplexes diminished cell surface expression of EGFR for up to 4 hr, whereas GE11 polyplexes did not. In a clinically relevant orthotopic prostate cancer model, intratumorally injected GE11 polyplexes were superior in inducing transgene expression when compared with untargeted polyplexes.

Identification of recurring tumor-specific somatic mutations in acute myeloid leukemia by transcriptome sequencing.

Genetic lesions are crucial for cancer initiation. Recently, whole genome sequencing, using next generation technology, was used as a systematic approach to identify mutations in genomes of various types of tumors including melanoma, lung and breast cancer, as well as acute myeloid leukemia (AML). Here, we identify tumor-specific somatic mutations by sequencing transcriptionally active genes. Mutations were detected by comparing the transcriptome sequence of an AML sample with the corresponding remission sample. Using this approach, we found five non-synonymous mutations specific to the tumor sample. They include a nonsense mutation affecting the RUNX1 gene, which is a known mutational target in AML, and a missense mutation in the putative tumor suppressor gene TLE4, which encodes a RUNX1 interacting protein. Another missense mutation was identified in SHKBP1, which acts downstream of FLT3, a receptor tyrosine kinase mutated in about 30% of AML cases. The frequency of mutations in TLE4 and SHKBP1 in 95 cytogenetically normal AML patients was 2%. Our study demonstrates that whole transcriptome sequencing leads to the rapid detection of recurring point mutations in the coding regions of genes relevant to malignant transformation.

The mechanical heterogeneity of the hard callus influences local tissue strains during bone healing: a finite element study based on sheep experiments.

During secondary fracture healing, various tissue types including new bone are formed. The local mechanical strains play an important role in tissue proliferation and differentiation. To further our mechanobiological understanding of fracture healing, a precise assessment of local strains is mandatory. Until now, static analyses using Finite Elements (FE) have assumed homogenous material properties. With the recent quantification of both the spatial tissue patterns (Vetter et al., 2010) and the development of elastic modulus of newly formed bone during healing (Manjubala et al., 2009), it is now possible to incorporate this heterogeneity. Therefore, the aim of this study is to investigate the effect of this heterogeneity on the strain patterns at six successive healing stages. The input data of the present work stemmed from a comprehensive cross-sectional study of sheep with a tibial osteotomy (Epari et al., 2006). In our FE model, each element containing bone was described by a bulk elastic modulus, which depended on both the local area fraction and the local elastic modulus of the bone material. The obtained strains were compared with the results of hypothetical FE models assuming homogeneous material properties. The differences in the spatial distributions of the strains between the heterogeneous and homogeneous FE models were interpreted using a current mechanobiological theory (Isakson et al., 2006). This interpretation showed that considering the heterogeneity of the hard callus is most important at the intermediate stages of healing, when cartilage transforms to bone via endochondral ossification.

Thiolated polyacrylic acid-modified iron oxide nanoparticles for in vitro labeling and MRI of stem cells.

PURPOSE: The purpose of this study was to develop and characterize new surface-modified iron oxide nanoparticles demonstrating the efficiency to be internalized by human endothelial progenitor cells (EPCs) from umbilical cord blood. METHODS: Iron oxide nanoparticles were coated with polyacrylic acid-cysteine (PAA-Cys) by either in situ precipitation or postsynthesis. The nanoparticles were characterized by X-ray powder diffraction. EPCs were labeled with PAA-Cys-modified iron oxide nanoparticles or with uncoated nanoparticles. The relaxivity of uncoated and coated iron oxide nanoparticles as well as EPCs labeled with PAA-Cys-modified iron oxide were determined. RESULTS: Addition of PAA-Cys increased the particle size from 10.4 to 144 and 197 nm, respectively. The X-ray powder diffraction pattern revealed that the particles consist of Fe(3)O(4) with a spinal structure. Postsynthesis coated particles showed a cellular uptake of 85% and 15.26 pg iron/cell. For both types of particles the relaxivity ratio was at least 2-fold higher than that of the gold standard Resovist(®). CONCLUSION: The PAA-Cys coated iron oxide nanoparticles are a promising tool for labeling living cells such as stem cells for diagnostic and therapeutic application in cell-based therapies due to their high relaxivities and their easy uptake by cells.

[Depression and stress management in medical students. A comparative study between freshman and advanced medical students]. / Depressivität und Stressbewältigung bei Medizinstudierenden. Eine Vergleichsuntersuchung des 1. und 7. Fachsemesters Humanmedizin.

International studies have indicated a high prevalence of depression and a lack of coping with stress in medical students. Freshman and advanced medical students were investigated using a specific questionnaire and the Beck Depression Inventory (BDI) with a response rate of 100%. Of the subjects studied 81.1% did not have any depression, 13.1% slight and 5.8% clinically relevant symptoms of depression. The severity of symptoms was highly associated with subjective appraisal of stressors. Coping skills of first year students significantly influenced the depression symptoms calling for preventative measures even in freshman medical students.

Development and in vivo bioavailability study of an oral fondaparinux delivery system.

Fondaparinux is an agent of choice for the prevention and initial treatment of venous thromboembolism (VTE) as well as myocardial infarction. Nevertheless, as a negatively charged molecule fondaparinux can pass the intestinal epithelial barrier after oral administration only partially. It was therefore the aim of this study to design a highly efficient small-intestinal-targeted oral delivery system for fondaparinux based on thiolated polycarbophil (PCP-Cys) and glutathione (GSH) combined with sodium decanoate. The formulations were tested in vitro with regard to their release, cytotoxicity profiles and their permeation-enhancing properties across small-intestinal mucosa. For the in vivo study, rats were treated with a single oral dose of fondaparinux gels or mini-tablets (5mg/kg) and the subcutaneous and intravenous groups with a dose of 200µg/kg fondaparinux. The anti-factor Xa activity in the plasma was measured. In the presence of PCP-Cys/GSH/sodium decanoate the uptake of fondaparinux from the intestinal mucosa was 4.1-fold improved. The area under concentration-time curve in rat plasma from 0 to 24h with PCP-Cys/GSH/sodium decanoate gel was 135.3µgmin/ml and 1.3-fold improved with the tablets. C(max) value of mini-tablets was 0.23µg/ml and the absolute bioavailability of 4.4% was 6.2-fold improved, while the control solution was not absorbed orally. PCP-Cys/GSH/sodium decanoate demonstrated potential for increasing the oral bioavailability of the indirect factor Xa inhibitor as an alternative to currently used subcutaneous delivery.

Nasal delivery of antisense oligonucleotides: in vitro evaluation of a thiomer/glutathione microparticulate delivery system.

PURPOSE: The aim of this study was to develop a nasal mucoadhesive microparticulate delivery system for phosphorothioate antisense oligonucleotides (PTO-ODNs) utilizing the thiomer technology. METHODS: PTO-ODN microparticles, coated with either the mucoadhesive polymer polycarbophil-cysteine (PCP-Cys) or unmodified PCP and reduced glutathione (GSH) were prepared by the emulsification solvent evaporation technique. Particle size, drug load, decrease in thiol groups on microparticles, swelling properties, release of incorporated PTO-ODN, and mucoadhesive properties were examined. Permeation enhancing effect of the deployed thiomer conjugate was investigated on excised porcine respiratory mucosa of the nasal cavity. RESULTS: Results demonstrated that microparticles were almost of spherical structure displaying particle diameter up to 30 microm. In addition, a controlled drug release of the incorporated PTO-ODN was achieved from these particles. Mucoadhesion studies revealed that thiolated PCP-Cys microparticles display 3-fold higher mucoadhesive properties than the corresponding unthiolated polycarbophil microparticles. The uptake of PTO-ODN, incubated in thiolated polycarbophil and glutathione microparticles, from the nasal mucosa was 2.2-fold improved. CONCLUSIONS: According to these results, the thiolated polycarbophil/reduced GSH microparticles might be a promising formulation for systemic delivery of PTO-ODNs via the nasal route.

Thiolated polycarbophil as an adjuvant for permeation enhancement in nasal delivery of antisense oligonucleotides.

The purpose of this study was to investigate the effect of thiolated polycarbophil as an adjuvant to enhance the permeation and improve the stability of a phosphorothioate antisense oligonucleotide (PTO-ODN) on the nasal mucosa. Polycarbophil-cysteine (PCP-Cys) was synthesized by the covalent attachment of L-cysteine to the polymeric backbone. Cytotoxicity tests were examined on human nasal epithelial cells from surgery of nasal polyps confirmed by histological studies. Deoxyribonuclease I activity in respiratory region of the porcine nasal cavity was analyzed by an enzymatic assay. The enzymatic degradation of PTO-ODNs on freshly excised porcine nasal mucosa was analyzed and protection of PCP-cysteine toward DNase I degradation was evaluated. Permeation studies were performed in Ussing-type diffusion chambers. PCP-Cys/GSH did not arise a remarkable mortal effect. Porcine respiratory mucosa was shown to possess nuclease activity corresponding to 0.69 Kunitz units/mL. PTO-ODNs were degraded by incubation with nasal mucosa. In the presence of 0.45% thiolated polycarbophil and 0.5% glutathione (GSH), this degradation process could be lowered. In the presence of thiolated polycarbophil and GSH the uptake of PTO-ODNs from the nasal mucosa was 1.7-fold improved. According to these results thiolated polycarbophil/GSH might be a promising excipient for nasal administration of PTO-ODNs.

Therapeutic equivalence, long-term efficacy and safety of HX575 in the treatment of anemia in chronic renal failure patients receiving hemodialysis.

BACKGROUND: The recombinant human epoetin-a HX575 (Sandoz Pharmaceuticals GmbH/Hexal AG, Holzkirchen, Germany) is the first biosimilar erythropoiesis-stimulating agent (ESA) with marketing authorization in Europe. The primary objective of the study was the evaluation of therapeutic equivalence in terms of hemoglobin (Hb) response of HX575 compared with the comparator product (EPREX/ ERYPO, Janssen-Cilag/Ortho Biotech, Neuss, Germany) in the long-term intravenous (i.v.) treatment of anemia in chronic renal failure patients on hemodialysis following a 1 : 1 dose conversion from the comparator product to HX575. METHODS: Hemodialysis patients with Hb levels of 10.0 - 13.0 g/dl were randomized to either continue their current i.v. epoetin-a treatment or switch to HX575. During treatment, epoetin dosages were titrated to maintain Hb values. The primary endpoint was the difference between treatment groups in the mean absolute change of Hb levels between baseline and evaluation period (Weeks 25 - 28). RESULTS: Therapeutic equivalence of HX575 and the comparator epoetin-alpha, assessed during the evaluation period, was statistically confirmed: mean changes in Hb levels were 0.15 +/- 0.09 g/dl in the HX575 and 0.06 +/- 0.12 g/dl in the comparator epoetin-a group, with a difference between groups of 0.08 g/dl (95% confidence interval: -0.17; 0.34). Hb levels and epoetin dosages remained stable throughout the entire study period of 56 weeks. The long-term safety profile of HX575 was similar to that of the comparator epoetin-alpha. No antibody formation was detected. CONCLUSIONS: The study demonstrated therapeutic equivalence of biosimilar HX575 to the comparator epoetin-a, together with a comparable safety profile.

Biosimilarity of HX575 (human recombinant epoetin alfa) and epoetin beta after multiple subcutaneous administration.

OBJECTIVE: To compare the steady-state pharmacokinetics and pharmacodynamics following multiple subcutaneous administration of a new erythropoiesis stimulating agent (HX575, Binocrit, Sandoz GmbH, Holzkirchen, Germany) with that of epoetin beta (NeoRecormon, Roche Ltd., Welwyn Garden City, UK). METHODS: An open, randomized, parallel group study was conducted in 80 healthy adult males. Subjects were randomized to multiple subcutaneous doses of 100 IU/kg body weight of HX575 or epoetin beta three-times-weekly for 4 weeks. Serum epoetin concentrations were measured using an enzyme-linked immunosorbent assay (ELISA) and pharmacokinetic parameters for the two treatments were compared. The time course and area under the effect curve ratios of hematological characteristics were used as surrogate parameters for efficacy evaluation. RESULTS: The pharmacokinetic profiles after multiple doses were similar for both treatments. HX575 was bioequivalent to epoetin beta with respect to the rate and extent of exposure of exogenous epoetin, as indicated by the ratios (90% confidence intervals) of AUC(tau) (96.1 (86.4 - 106.9)) and C(max,ss) (98.5 (85.2 - 113.9)). The hematological profiles of both treatments were similar as determined from the population mean curves and the AUEC(Hb) ratio (90% confidence interval] (99.2 (97.7 - 100.7)), the primary endpoint of this study. Study medication was well tolerated with no clinically relevant differences between safety profiles of the treatments. Anti-epoetin antibodies were not detected at any time. CONCLUSIONS: HX575 and epoetin beta were bioequivalent with respect to their steady-state pharmacokinetic profile and pharmacodynamic action. These results support the conclusion that HX575 and epoetin beta will be equally efficacious and may be interchangeable as therapy.

Effects of essential oils from fennel (Foeniculi aetheroleum) and caraway (Carvi aetheroleum) in pigs.

The ban of antibiotics as a feed additive requires alternatives to stabilize the health and performance particularly of the young animals. Essential oils obtained from fennel seed (Foeniculi aetheroleum) and caraway seed (Carvi aetheroleum) were tested in diets for weaned piglets in comparison with either a diet without feed additive or with a combination of formic acid and copper (positive control). Four groups of sixteen piglets (live weight 7 kg, age 26 days) received diets without (1) or with supplements of 7.5 g formic acid + 160 mg Cu/kg (2), 100 mg fennel oil/kg (3) or 100 mg caraway oil/kg (4) during 3 weeks after weaning. In the subsequent 4 weeks, all piglets were fed a diet without these additions. Fennel oil contained almost 2/3 anethol, approximately 1/5 fenchon and the remaining part consisting of alpha + beta-pinen, limonen (p-mentha-1,8-dien) and estragol. In the caraway oil, half of the contents was represented by limonen and the other half by carvon. There were no piglet losses and only few cases of diarrhoea. The combination of formic acid and copper increased feed consumption by 27% and daily weight gain by 25%. There were no differences in the performance between the group fed fennel oil and the control without additives. Piglets fed caraway oil tended to consume less feed and to gain approximately 10% less. In feed choice experiments, pigs consumed the same two diets from two troughs with 50% of total feed amount, as expected. The diets containing fennel or caraway oils were consumed at less than 50%. If the diet contained 100 mg fennel oil/kg, the decrease of percentual feed intake was significant. The results of the feeding experiment and of the feed choice experiment question the classification of fennel and caraway oils as flavour additives or as 'appetite promoters' in diets for weaned piglets.

Investigation of the mechanism of alkane reductive elimination and skeletal isomerization in Tp'Rh(CNneopentyl)(R)H complexes: the role of alkane complexes.

Experiments are described that provide indirect evidence for the involvement of alkane sigma-complexes in oxidative addition/reductive elimination reactions of Tp'Rh(L)(R)H complexes (Tp' = tris-3,5-dimethylpyrazolylborate, L = CNCH(2)CMe(3)). Reductive elimination rates in benzene-d(6) were determined for loss of alkane from Tp'Rh(L)(R)H, where R = methyl, ethyl, propyl, butyl, pentyl, and hexyl, to generate RH and Tp'Rh(L)(C(6)D(5))D. The isopropyl hydride complex Tp'Rh(L)(CHMe(2))H was found to rearrange to the n-propyl hydride complex Tp'Rh(L)(CH(2)CH(2)CH(3))H in an intramolecular reaction. The sec-butyl complex behaves similarly. These same reactions were studied by preparing the corresponding metal deuteride complexes, Tp'Rh(L)(R)D, and the scrambling of the deuterium label into the alpha- and omega-positions of the alkyl group monitored by (2)H NMR spectroscopy. Inverse isotope effects observed in reductive elimination are shown to be the result of an inverse equilibrium isotope effect between the alkyl hydride(deuteride) complex and the sigma-alkane complex. A kinetic model has been proposed using alkane complexes as intermediates and the selectivities available to these alkane complexes have been determined by kinetic modeling of the deuterium scrambling reactions.

Effects of multisite ventricular pacing on cardiac function in normal dogs and dogs with heart failure.

INTRODUCTION: We studied the effects on cardiac function of pacing two right and two left ventricular sites in normal and failing hearts with a normal QRS duration. METHODS AND RESULTS: Hemodynamic parameters were studied in isoflurane-anesthetized dogs with normal hearts and dogs with heart failure induced by rapid ventricular pacing. Unipolar intramyocardial electrodes were placed at the high right atrium and the apex (A) and base (B) of the left (L) and right (R) ventricles (V). Data were collected after pacing for 5 to 20 minutes. In normal dogs, without bundle branch block (BBB), pacing at either the apex or the base of the left ventricle increased cardiac output by approximately 10% compared with right ventricular apex (RVA) pacing with an AV delay of 0 msec. Positive dP/dt increased approximately 10% during four-site left and right ventricular apex and base (LRVAB) pacing compared with RVA pacing. In dogs with heart failure but without BBB, cardiac output increased by 8.5% (P < 0.01) during four-site ventricular pacing with AV delays of 0 and 60 msec compared with RVA pacing. Positive dp/dt increased by 23.5% (P < 0.001) with an AV delay of 0 msec and 9.6% (P < 0.001) with an AV delay of 60 msec during LRVAB pacing compared with RVA pacing. His-bundle pacing was associated with increased cardiac output compared with RVA pacing. CONCLUSIONS: We conclude that pacing simultaneously at two right and two left ventricular sites significantly improves cardiac function compared with single RVA pacing, with or without sequential AV synchrony, in dogs with rapid ventricular pacing-induced heart failure and no BBB.