The Dementias Platform UK (DPUK) Data Portal

The Dementias Platform UK Data Portal is a data repository facilitating access to data for 3 370 929 individuals in 42 cohorts. The Data Portal is an end-to-end data management solution providing a secure, fully auditable, remote access environment for the analysis of cohort data. All projects utilising the data are by default collaborations with the cohort research teams generating the data. The Data Portal uses UK Secure eResearch Platform infrastructure to provide three core utilities: data discovery, access, and analysis. These are delivered using a 7 layered architecture comprising: data ingestion, data curation, platform interoperability, data discovery, access brokerage, data analysis and knowledge preservation. Automated, streamlined, and standardised procedures reduce the administrative burden for all stakeholders, particularly for requests involving multiple independent datasets, where a single request may be forwarded to multiple data controllers. Researchers are provided with their own secure 'lab' using VMware which is accessed using two factor authentication. Over the last 2 years, 160 project proposals involving 579 individual cohort data access requests were received. These were received from 268 applicants spanning 72 institutions (56 academic, 13 commercial, 3 government) in 16 countries with 84 requests involving multiple cohorts. Projects are varied including multi-modal, machine learning, and Mendelian randomisation analyses. Data access is usually free at point of use although a small number of cohorts require a data access fee.

Tackling gaps in developing life-changing treatments for dementia

Since the G8 dementia summit in 2013, a number of initiatives have been established with the aim of facilitating the discovery of a disease-modifying treatment for dementia by 2025. This report is a summary of the findings and recommendations of a meeting titled "Tackling gaps in developing life-changing treatments for dementia", hosted by Alzheimer's Research UK in May 2018. The aim of the meeting was to identify, review, and highlight the areas in dementia research that are not currently being addressed by existing initiatives. It reflects the views of leading experts in the field of neurodegeneration research challenged with developing a strategic action plan to address these gaps and make recommendations on how to achieve the G8 dementia summit goals. The plan calls for significant advances in (1) translating newly identified genetic risk factors into a better understanding of the impacted biological processes; (2) enhanced understanding of selective neuronal resilience to inform novel drug targets; (3) facilitating robust and reproducible drug-target validation; (4) appropriate and evidence-based selection of appropriate subjects for proof-of-concept clinical trials; (5) improving approaches to assess drug-target engagement in humans; and (6) innovative approaches in conducting clinical trials if we are able to detect disease 10-15 years earlier than we currently do today.

Harnessing the power of cohort studies for dementia research

Purpose

– The purpose of this paper is to scope potential and gaps in European cohort studies with focus on brain ageing and neurodegeneration.

Design/methodology/approach

– Combined and augmented two scoping exercises conducted for European Union Joint Programme on Neurodegenerative Diseases (JPND) and the Alzheimer Society UK.

Findings

– In total, 106 cohorts initially identified with a further 52 found on second sweep. Strengths include gender balance, diversity of measures and much detail on health and health behaviours, and lifecourse representation. Major gaps identified were the oldest old, non-Caucasians, people in Eastern Europe, migrant populations, rural residents and people in long-term care. Quality of life, psychosocial and environmental factors were limited. Relatively few cohorts are population representative. Analytical methods for combining studies and longitudinal analysis require careful consideration.

Research limitations/implications

– European studies and published information only.

Practical implications

– Collaboration across disciplines and studies, greater dissemination of methods and findings will improve knowledge about cognitive and functional decline in current and future older populations.

Social implications

– Better understanding of brain ageing and the dementia syndrome will improve investment decisions for primary, secondary and tertiary prevention.

Originality/value

– Building on the work of JPND and the Alzheimer Society is the first study of the scope and limitations of current cohorts in Europe. It is designed to help researchers and policy makers in their planning.

Patent ductus arteriosus evaluation by serial echocardiography in preterm infants

BACKGROUND

Patent ductus arteriosus (PDA) is associated with morbidity and mortality in premature neonates.

METHODS

The effect of serial echocardiography performed by a neonatologist and early targeted medical PDA treatment was evaluated and compared to historical controls. One hundred ninety-two infants <1,500 g were included and 45 infants had a PDA.

RESULTS

Serial echocardiography allowed significantly earlier identification and treatment of PDA versus awaiting the evolution of clinical signs. Severe intraventricular haemorrhage and ventilator days were significantly decreased in the studied cohort following the introduction of echocardiography. In addition, hospital stay was also reduced in the non-PDA group and other outcomes were unchanged.

CONCLUSION

Serial echocardiography for PDA evaluation, performed by a neonatologist trained in echo, may reduce morbidity in preterm infant.

Natural Killer (NK) cell deficiency associated with an epitope-deficient Fc receptor type IIIA (CD16-II)

Susceptibility to herpes virus infections has been described in experimental animals depleted of NK cells and in patients with defective NK cell function. We have identified a child with recurrent infections, especially with herpes simplex virus, who had a decreased number of CD56(+)CD3(-) NK cells in circulation. Her NK cells expressed an altered form of the Fc receptor for IgG type IIIA (Fc gamma RIIIA or CD16-II) which was not reactive with the anti-CD16-II MoAb B73.1. Sequence analysis revealed the patient to be homozygous for a T to A substitution at position 230 of CD16-II cDNA, predicting a Leu(66) to His(66) change in the first immunoglobulin domain of CD16-II at the B73.1 recognition site. Spontaneous NK cell activity of the patient's peripheral blood mononuclear cells (PBMC) was markedly decreased, while antibody-dependent cellular cytotoxicity (ADCC) was unaffected. These results suggest that this child suffers from a defect affecting the development and function of NK cells, resulting in NK cytopenia and clinically significant immunodeficiency. The role of the CD16-II mutant in the pathogenesis of the patient's NK cell deficiency is discussed.

Intraoperative hemodynamic, renin, and catecholamine responses after prophylactic and intraoperative administration of intravenous enalaprilat

This study was designed to evaluate effects of enalaprilat, an angiotensin-converting enzyme inhibitor, on hemodynamic and hormonal responses during surgery at endotracheal intubation, incision, and limb-tourniquet inflation. Thirty patients undergoing limb procedures with general anesthesia (N2O/narcotic technique) and a pneumatic tourniquet were randomized to receive either preoperative enalaprilat (1.25 mg intravenously [i.v.] 20 min prior to induction) or intraoperative enalaprilat (0.625 mg i.v. at the onset of tourniquet-associated hypertension), with appropriate placebo controls. Arterial blood pressure and heart rate increased significantly in response to intubation in the placebo group. Although there were no significant differences in catecholamine levels, plasma renin activity was significantly increased at postincision in the preoperative-enalaprilat group versus the placebo group. This suggests that activation of the renin-angiotensin system may play a key role in mediation of intraoperative hemodynamic responses to endotracheal intubation. With respect to tourniquet hypertension, preoperative or intraoperative treatment with enalaprilat reduced neither the pressor response to tourniquet inflation nor the amount of enflurane subsequently required to control arterial blood pressure. These findings suggest that this response is mediated by pain pathways, and may be treated more effectively with anesthesia/analgesia.

The Impact of the First 3 Years of Breast Cancer Screening on the Overall Presentation of Breast Cancer

We have assessed the effect of the first round of the Breast Cancer Screening Programme on the presentation of breast cancer in the Southampton Health District with respect to number of cases and pathological characteristics. A retrospective comparative survey of the presentation of breast cancer in the 3 years prior to breast cancer screening (1985–1988) with the presentation of breast cancer during the prevalent round of breast cancer screening (1988–1991) was performed.

During the period of study 1536 cases of breast cancer presented. Six hundred and sixty presented in the years prior to screening and 864 during the first round of screening. All patients lived within the Southampton Health District.

The study was designed to assess the changes in breast cancer presentation with regard to age, pathological characteristics, and treatment.

Even allowing for the increases in the local population there was a significant increase in the number of cases of breast cancer diagnosed (χ2=23.7, df=1, P< 0.001). The majority of this increase was in the 50–64 age group. There was also a significant shift towards an earlier stage at diagnosis and a significant reduction in tumour size when all cases were included (mean 26 mm versus 34 mm P< 0.001). Screening also created the opportunity for less invasive treatment. Consequently there was a rise in the number of excisions by localization biopsy from 1% to 13% during the screening period.

In conclusion, the National Breast Cancer Screening Programme (NBCSP) has had a significant impact on the presentation of breast cancer. This has resulted in a greater awareness of the disease with earlier presentation, smaller tumours, and a higher local excision rate in the study group.

Identification of the proteoglycan versican in aorta and smooth muscle cells by DNA sequence analysis, in situ hybridization and immunohistochemistry

Versican is a large chondroitin sulfate proteoglycan (CSPG) initially identified in cultured human fibroblasts. Previous studies have shown that there is a versican-like molecule in cultured monkey smooth muscle cells. In this study, we have cloned and sequenced the large CSPG from cultured monkey smooth muscle cells, fetal and juvenile monkey aorta, and human fetal aorta. The cDNA sequence from human fetal aorta is completely homologous to the human fibroblast versican. We obtained 2.5 kb of cDNA sequence from monkey aortic RNA and cultured monkey smooth muscle cell RNA. This sequence covers three distinct domains of versican (hyaluronic acid binding domain, glycosaminoglycan attachment domain and protein binding domain) and demonstrates over 90% homology to the human versican sequence. In situ hybridization histochemistry indicates that the versican RNA transcript is located in the epithelium throughout the tunica media of the aorta. Western blot analysis and immunohistochemistry also confirm the presence of versican in human and monkey aorta.

The initiation of normal walking

Lower extremity electromyograms (EMGs), ground reaction forces, and body motion were measured during the brisk initiation of forward walking performed by 12 healthy adults, aged 20 to 82 years. Gait was initiated 20 times in response to a visual cue. During gait initiation, the body rotated about the ankles like a flexible inverted pendulum. The muscles of the lower extremities were activated stereotypically so as to create moments of force about the ankles that propelled the body toward the stance foot and into forward motion. All volunteers exhibited similar patterns of gait initiation, which were so reproducible that computer averaging of multiple steps by each person was possible. Gait initiation is a stereotyped sequence of postural shifts that culminates in a forward step. Disturbances of gait initiation could result from abnormalities in postural control, movement, or their integration.

Per-rectal pulsed irrigation versus per-oral colonic lavage for colonoscopy preparation: a randomized, controlled trial

The aim of this study was to compare the efficacy and patient tolerance of a new pulsed irrigation system to colonic lavage for colonoscopic preparation. Thirty-four prospective patients scheduled for routine colonoscopy were randomized to one of two preparations: a per-rectal pulsed irrigation device (18 patients) versus per-oral colonic lavage (15 patients). Colonoscopic preparation was assessed on a 0 to 4 plus scale by region and overall. This was done live and by video tape by two independent endoscopists who were blinded to the patient's preparation. There was no significant difference with respect to cleanliness of the colon with pulsed irrigation patients having an average overall preparation score of 3.00 +/- 0.19 (SEM) versus colonic lavage patients with a score of 3.14 +/- 0.19. There was also no statistically significant difference between the two groups with respect to demographics, time to reach the cecum, time for entire procedure, volume of aspiration or wash, or sedation given. We conclude that the new pulsed irrigation device provides an alternative to the standard per-oral lavage solution for colonoscopic preparation.

Induction of human T cell proliferation by a monoclonal antibody to CD5

A mouse mAb, TS 43, which recognized the human CD5 molecule, was found to induce the proliferation of human peripheral blood T cells. TS 43 mAb precipitated from 125I-radiolabeled T cells a 67-kDa band, which comigrated with the 67-kDa band precipitated by the anti-CD5 mAb OKT1. Preclearing of cell lysates with OKT1 mAb abolished the capacity of TS 43 mAb to precipitate radiolabeled material from T cell lysates. Furthermore, a mouse T cell hybridoma transfected with human CD5 was stained by TS 43 mAb. T cell proliferation mediated by TS 43 mAb was monocyte dependent, and was accompanied by IL-2R expression and by IL-2 synthesis. T cell activation by TS 43 mAb involved a rise in intracellular calcium level (CA2+)i and was dependent on the expression of the TCR/CD3 complex because no rise in (Ca2+)i was observed in a TCR-beta-deficient Jurkat T cell mutant. This study indicates that CD5 should be added to the list of surface molecules that can signal T cells to proliferate.

Induction of human T cell proliferation by a monoclonal antibody to CD5

A mouse mAb, TS 43, which recognized the human CD5 molecule, was found to induce the proliferation of human peripheral blood T cells. TS 43 mAb precipitated from 125I-radiolabeled T cells a 67-kDa band, which comigrated with the 67-kDa band precipitated by the anti-CD5 mAb OKT1. Preclearing of cell lysates with OKT1 mAb abolished the capacity of TS 43 mAb to precipitate radiolabeled material from T cell lysates. Furthermore, a mouse T cell hybridoma transfected with human CD5 was stained by TS 43 mAb. T cell proliferation mediated by TS 43 mAb was monocyte dependent, and was accompanied by IL-2R expression and by IL-2 synthesis. T cell activation by TS 43 mAb involved a rise in intracellular calcium level (CA2+)i and was dependent on the expression of the TCR/CD3 complex because no rise in (Ca2+)i was observed in a TCR-beta-deficient Jurkat T cell mutant. This study indicates that CD5 should be added to the list of surface molecules that can signal T cells to proliferate.

Thymopentin therapy reduces the clinical severity of atopic dermatitis

One hundred patients with moderate to severe atopic dermatitis were entered into a two-center, double-blind trial. Patients were randomized to receive either thymopentin (Timunox, n = 48) or placebo (n = 52), administered as daily subcutaneous injections for 6 weeks. Clinical extent of disease and severity parameters were measured at baseline and at regular time intervals during the study. Both the placebo- and thymopentin-treated groups demonstrated a progressive and statistically significant (p less than 0.001) decline in the overall severity of their disease, but reduction in the clinical severity score was higher in the thymopentin-treated group and statistically significant (p = 0.04) in comparison with the placebo-treated group after 6 weeks of treatment. Of the individual symptoms comprising the total severity score, pruritus (p = 0.02) and erythema (p = 0.04) were reduced significantly when thymopentin therapy was compared to placebo therapy. In addition, both the extent of body involvement and severity index (a combined severity/extent index) were significantly reduced after 6 weeks in the thymopentin-treated group in comparison to the placebo-treated group (p = 0.04). There were no serious adverse experiences in either treatment group. We conclude that treatment with thymopentin is safe and offers significant therapeutic promise for atopic dermatitis.

Caldesmon and the structure of smooth muscle thin filaments: electron microscopy of isolated thin filaments

Native and synthetic vertebrate smooth muscle thin filaments have been examined by electron microscopy in order to determine the arrangement of the regulatory protein caldesmon. In synthetic filaments of actin-caldesmon, long slender molecules were sometimes seen running along the thin filament, suggesting that caldesmon can associate with actin along its length, while at other times lateral projections were observed. In native filaments, containing actin, caldesmon and tropomyosin, we found no evidence for lateral projections extending from the filaments, suggesting that caldesmon does not act as a crosslinking protein in vivo. In contrast, elongated molecules were clearly seen following the long pitch actin helices. We suggest that these may represent an association of caldesmon and tropomyosin. Antibodies developed against an N-terminal fragment of caldesmon caused thin filaments to aggregate laterally into arrays displaying approximately 35-38 nm repeats; thin filament aggregates with this periodicity were obtained previously (Lehman et al., 1989) using antibodies to the C-terminal segment of caldesmon. These results suggest that both ends of caldesmon are closely associated with the shaft of the thin filament, supporting a model in which the elongated caldesmon molecule runs along the filament, possibly interacting with tropomyosin, following the long pitch actin helices.

Primary writing tremor. A form of focal dystonia?

Five patients exhibited severe tremor in the upper extremity, primarily when attempting to write or draw. Electromyography was performed to determine the patterns of muscle activity that were responsible for this tremor. Tremor was measured with an accelerometer and with a digitizing tablet. Two patients had postural tremor that was indistinguishable from mild, high-frequency essential tremor. All patients exhibited a severe 5-7-Hz tremor during the acts of writing and drawing. Muscles throughout the affected extremity exhibited rhythmic 5-7-Hz bursts of motor unit discharge, and the average level of motor unit activity was tonically increased in antagonistic muscles. This abnormal coactivation of antagonistic muscles produced subtle dystonic posturing of the affected limb that was overshadowed by severe tremor. Electromyography was useful in confirming the coexistence of tremor and dystonia in our patients. The nonspecificity of dystonia and postural tremor must be considered when discussing the nosology and pathophysiology of primary writing tremor.

An electron spin resonance study of oxyradical generation in superoxide dismutase- and catalase-deficient mutants of Escherichia coli K-12

The response of superoxide dismutase- and catalase-deficient strains of Escherichia coli to redox active compounds was examined by electron spin resonance. Levels of radicals formed in response to pyocyanine in situ were extremely low and were found to be predominantly extracellular, even in a strain completely deficient in both superoxide dismutase and catalase. In cell-free extracts of superoxide dismutase-minus strains incubated with NADPH and pyocyanine, the primary accumulating radical was the superoxide anion (O2-), although low levels of the hydroxyl radical (.OH) were also detected. In contrast, extracts from strains lacking catalase were found to accumulate higher levels of hydroxyl radicals.

Caldesmon and the structure of smooth muscle thin filaments: immunolocalization of caldesmon on thin filaments

Antibodies reacting with chicken gizzard caldesmon were used to determine the distribution of caldesmon on smooth muscle thin filaments. Antibodies developed against both the intact caldesmon molecule and a 40 kilodalton proteolytic fragment cause thin filaments to aggregate laterally. Aggregates produced with the latter antibody display regular periodic labelling with a repeat of approximately 38 nm, a distribution characteristic of proteins associated with tropomyosin on thin filaments. The stoichiometry of caldesmon on thin filaments has been critically reevaluated and alternative models of caldesmon distribution on thin filaments are proposed.

Tetrodotoxin-resistant release of ATP from guinea-pig taenia coli and vas deferens during electrical field stimulation in the presence of luciferin-luciferase

Guinea-pig taenia coli was superfused with medium containing luciferin-luciferase at 25 °C in order to directly detect the release of ATP. The resting lone of the tissue increased during the first 2–10 min of superfusion and then fell to a low level where spontaneous activity ceased. Under high tone conditions during the first 2–10 min of exposure to luciferin-luciferase, in the presence of atropine and guanethidine, ATP was released and the taenia coli relaxed when stimulated at 2–4 Hz, 70 V, 0.3-ms pulses for 15 s. Variable and continuous changes of tone made it difficult to test whether relaxation and release of ATP were tetrodotoxin sensitive. Field stimulation of preparations showing low tone after the initial exposure to luciferin-luciferase also resulted in ATP release. The muscle usually contracted during stimulation, even in the presence of atropine. Release was not due to movement of the muscle, since the release preceded the movement of the tissue and contraction with acetylcholine failed to release ATP. Neither release nor the contractile response of the tissue were blocked by tetrodotoxin (3 × 10−6 M), suggesting that under these conditions the release of ATP originated from the muscle or possibly directly from nerve terminals. A qualitatively similar release of ATP was also observed when desheathed guinea-pig vas deferens was field-stimulated electrically in the presence of luciferin-luciferase. Tetrodotoxin did not block ATP from this tissue either, but unlike the taenia coli, it did abolish the contractile response, which was not affected by luciferin-luciferase during the 1st h of exposure. It is concluded that in the presence of luciferin-luciferase the field-stimulation induced release of ATP observed in guinea pig taenia coli or vas deferens was not mediated by propagation of action potentials in nerve.

Regulation of immune response in allogeneic mixed spleen cell cultures. I. Influence of I-region on the generation of suppressor cells

The immune responses of allogeneic mixed spleen cell cultures (MLC) to the T-dependent antigen, SRBC, and to the T-independent antigen, DNP-PAA, were investigated. The immune response to DNP-PAA in MLC with certain strain combinations was always suppressed as compared with the expected PFC response calculated from the PFC responses of the individual strains. This suppression was eliminated by treating the spleen cells with RAMB antiserum plus complement before the incubation of the MLC with DNP-PAA. It can be concluded that the suppression in the PFC response to the T-independent antigen DNP-PAA in MLC is due to the generation of suppressor T-cells. The PFC response to the T-dependent antigen, SRBC, in MLC showed either suppression, no change, or rarely augmenation, suggesting that the allogeneic mixed spleen cell cultures can generate both suppressor and helper T cells and that the balance between helper and suppressor activity regulates the PFC response to a T-dependent antigen. Suppressor activity was also generated in a one-way MLC, but the degree of suppression depended upon which of the two strains was responding. Similar amounts of thymidine were incorporated in the one-way MLR irrespective of which strains was responding. Thus, the extent of proliferation in one-way MLR is not related to the degree of suppressor activity generated. The results further indicate that a difference between two strains in the I-C, S, and G regions of the major histocompatibility complex is required to generate suppressor activitiy that can depress the response to a T-independent antigen, MLC between strains differing in K, I-A, I-B, I-J, I-E, and D regions generate little or no suppressor activity in this system.

Regulation of immune response in allogeneic mixed spleen cell cultures. I. Influence of I-region on the generation of suppressor cells

The immune responses of allogeneic mixed spleen cell cultures (MLC) to the T-dependent antigen, SRBC, and to the T-independent antigen, DNP-PAA, were investigated. The immune response to DNP-PAA in MLC with certain strain combinations was always suppressed as compared with the expected PFC response calculated from the PFC responses of the individual strains. This suppression was eliminated by treating the spleen cells with RAMB antiserum plus complement before the incubation of the MLC with DNP-PAA. It can be concluded that the suppression in the PFC response to the T-independent antigen DNP-PAA in MLC is due to the generation of suppressor T-cells. The PFC response to the T-dependent antigen, SRBC, in MLC showed either suppression, no change, or rarely augmenation, suggesting that the allogeneic mixed spleen cell cultures can generate both suppressor and helper T cells and that the balance between helper and suppressor activity regulates the PFC response to a T-dependent antigen. Suppressor activity was also generated in a one-way MLC, but the degree of suppression depended upon which of the two strains was responding. Similar amounts of thymidine were incorporated in the one-way MLR irrespective of which strains was responding. Thus, the extent of proliferation in one-way MLR is not related to the degree of suppressor activity generated. The results further indicate that a difference between two strains in the I-C, S, and G regions of the major histocompatibility complex is required to generate suppressor activitiy that can depress the response to a T-independent antigen, MLC between strains differing in K, I-A, I-B, I-J, I-E, and D regions generate little or no suppressor activity in this system.

The pathophysiology of idiopathic mitral valve prolapse

Left ventricular structure, function, and the coronary circulation were studied in a subset of patients with mitral valve leaflet prolapse. This group of 26 patients (21 females, five males, with mean age of 46 years), had the syndrome identified as idiopathic mitral valve prolapse (IMVP), which was characterized by a systolic click-murmur, clinical symptoms that were highly variable in duration and intensity, angiographically-documented mitral prolapse, and no obvious associated systemic or cardiovascular disease. Mitral regurgitation was of moderate degree in four, mild in 14, and absent in eight. The left ventricular (LV) end-diastolic volume index was elevated in ten of 25 (40%), the LV mass index was elevated in six of 17 (35%), but the LV anterior wall thickness was increase in only one of 17. Three major patterns of ventricular contraction were identified: 1) normal in seven; 2) abnormal, usually an inferior deformity and/or anterior asynergy, in eight; and 3) hyperkinetic in 11. Normal resting left ventricular function, assessed as an ejection fraction greater than 55%, was present in 17 of 25 (68%). Selective coronary arteriography was essentially normal in all 25 patients studied. An ischemic ECG response was detected during only one of 12 maximal treadmill exercise tests and in none of ten atrial pacing stress tests (AP). Myocardial lactate extraction did not change significantly during AP in six patients. We conclude that cardiomyopathy does not appear to be a primary cause or an important associated component of the IMVP syndrome. Abnormalities of the coronary circulation or of myocardial metabolism were not demonstrated by available methods. A proposed pathophysiological mechanism to explain the clinical and angiographic findings in IMVP is discussed.

In vivo analysis of adrenergic receptor activity of dobutamine

Studies were performed in anesthetized dogs to evaluate the cardiac and systemic effects of intravenously administered dobutamine and to determine its direct effects on the renal and femoral vascular beds. The results demonstrated that dobutamine possessed an inotropic efficacy similar to that of isoproterenol and norepinephrine; its chronotropic effect was similar to or greater than that of norepinephrine. In contrast to norepinephrine, dobutamine increased cardiac output and reduced total peripheral resistance with minimal effects on mean aortic pressure. Studies on the denervated hind limb demonstrated that dobutamine stimulated both alpha and beta receptors. The dose of dobutamine which produced a 50% increase in femoral blood flow was 180 times the required dose of isoproterenol and the dose which produced a 50% increase in contractile force was 43 times the required dose of isoproterenol. Studies on the renal vasculature demonstrated that dobutamine caused no dopamine-like renal vasodilator activity and only minor vasodilation mediated by beta receptors. We concluded that dobutamine is more cardioselective than is isoproterenol. The dobutamine-induced decrease in peripheral resistance observed in the whole dog was presumably due to increased myocardial contractility coupled with a greater net effect of beta-adrenergic vasodilation than alpha-adrenergic vasoconstriction. Studies with reserpine-treated dogs showed that all dobutamine-induced effects were due to a direct action on receptors.