Effects of beta-adrenergic stimulation with dobutamine on isovolumic relaxation in the normal and failing human left ventricle.

BACKGROUND. We tested the hypothesis that beta-adrenergic receptor-stimulated acceleration of left ventricular (LV) isovolumic relaxation (i.e., positive lusitropic response) is attenuated in patients with severe congestive heart failure (CHF) compared with patients without LV dysfunction or CHF. METHODS AND RESULTS. The beta-adrenergic agonist dobutamine was infused by the intracoronary route in 14 subjects (normal group, six; CHF patients, eight) and by the intravenous route in a second group of 14 subjects (normal group, four; CHF patients, 10). The positive inotropic response to intracoronary or intravenous dobutamine was substantially and significantly reduced in the patients with CHF. LV isovolumic relaxation rate was determined by the methods of Weiss (TL), Mirsky (T1/2), and by a nonlinear regression technique (TNL). LV isovolumic relaxation assessed by all three methods was significantly prolonged in CHF patients compared with normal subjects. Intracoronary and intravenous infusions of dobutamine caused significant acceleration of LV isovolumic relaxation in both normal subjects and patients with CHF. The magnitude of the dobutamine-stimulated acceleration of isovolumic relaxation in patients with CHF was comparable with that in normal subjects. CONCLUSIONS. These data demonstrate that beta-adrenergic receptor stimulation causes significant acceleration of LV isovolumic relaxation in both normal subjects and patients with severe CHF. Coronary to our hypothesis, the lusitropic response to beta-adrenergic stimulation is well preserved in patients with severe CHF despite substantial attenuation of the beta-adrenergic positive inotropic response. These findings have potentially important implications regarding the physiology and pharmacology of adrenergically mediated LV relaxation in humans.     

Characterization of cerebral infarction by multicomponent analysis of transverse magnetization decay curves.

RATIONALE AND OBJECTIVES. Individual components of the transverse magnetization decay curve (TDC) were assessed for their ability to characterize ischemia in photochemically induced cerebral infarcts. METHODS. Fifty rats were randomly divided into equal-sized experimental and control groups, which were subdivided into groups studied at five different time points, ranging from 6 hours to 22 days. All the rats received transcalvarial irradiation with 560-nm light. Five rats in each time group also received a sensitizing dye before irradiation. In these latter animals, lesions of uniform size and location developed. Lesions were compared with tissue of similar volume and location from the contralateral cortex of the experimental animals and with tissue from both hemispheres of the control animals. TDCs of all the samples were measured and fit with mono- and bi-exponential functions. RESULTS. Unlike the control tissue, infarcted tissue displayed definitive two-component TDC behavior. The time course of the bi-exponential parameters yielded information unavailable from mono-exponential analyses. CONCLUSIONS. Bi-exponential analysis of TDCs may have diagnostic use as a more sensitive indicator of cerebral infarction than mono-exponential analyses.     

Variations of lymphocyte sub-populations in vulvar condylomata during therapy with beta-interferon.

Several experiences induced us to consider genital HPV infection as an expression of a local immunodeficiency. The aim of our study was to research the effect of immunotherapy on the lymphocyte subpopulations and Langerhans cells in vulvar condyloma. Twenty women with persistent vulvar condylomata, treated with 2,000,000 IU/die of beta-interferon for 15 days, were submitted to vulvar biopsy before and 2-5 months after medical treatment. The frozen sections obtained were assayed with the following monoclonal antibodies: OKT 4 (T helper lymphocytes), OKT 8 (T suppressor lymphocytes), OKB 7 (B lymphocytes) and S-100 protein (Langerhans cells). Using a morphometric evaluation, the average number of both intraepithelial and stromal lymphocyte subsets and of the intraepithelial Langerhans cells was assessed. In all the biopsies preceeding the medical treatment we found a low number of T helper lymphocytes both in the epithelium and stroma, with inversion of T4/T8 lymphocyte ratio and rare presence of Langerhans cells. In patients with a good therapeutic response (50-100% of condyloma reduction) we observed an increase in intraepithelial T4 lymphocytes and a decrease in both intraepithelial and stromal T8 lymphocytes. In cases with persistent disease after therapy, the histological pattern was similar to that observed in the first biopsy, with the exception of a significant increase in the average number of Langerhans cells. Our data correlate the clinical response to the immunotherapy with the histology of lymphocyte subsets in the vulvar condylomata. The increase in Langerhans cells observed in patients with negative response may be interpreted with a probable inability of these cells to promote the immune reaction.     

Invited. Brain edema development after MRI-guided focused ultrasound treatment

The aim of this study was to investigate a potential technique for image-guided minimally invasive neurosurgical interventions. Focused ultrasound (FUS) delivers thermal energy without an invasive probe, penetrating the dura mater, entering through the cerebrospinal fluid (CSF) space, or harming intervening brain tissue. We applied continuous on-line monitoring by MRI to demonstrate the effect of the thermal intervention on the brain tissue. For this, seven rabbits had a part of their skull removed to create access for the FUS beam into the brain through an acoustic window of 11 mm in diameter. Dura was left intact and skin was sutured. One week later, the rabbits were sonicated for 3 seconds with 21 W acoustic power, and the FUS focus was visualized with a temperature-sensitive T1-weighted MRI pulse sequence. The tissue reaction was documented over 7 days with T2-weighted images of the brain. The initial area of the central low signal intensity in the axial plane was .4 ± .3 mm², and for the bright hyperintensity surrounding the lesion, it was 2.3 ± .6 mm² (n = 7). In the coronal plane, the corresponding values were .4 ± .1 mm² and 3.4 ± .9 mm² (n = 5). The developing brain edema culminated 48 hours later and thereafter diminished during the next 5 days. Histology revealed a central necrosis in the white matter surrounded by edematous tissue with inflammatory cells. In summary, the image-guided thermal ablation technique described here produced a relatively small lesion in the white matter at the targeted location. This was accomplished without opening the dura or the need for a stereotactical device. MRI allowed on-line monitoring of the lesion setting and the deposition of thermal energy and demonstrated the tissue damage after the thermal injury.     

The human desmin gene: A specific regulatory programme in skeletal muscle both in vitro and in transgenic mice

Desmin synthesis is restricted to cardiac, skeletal and smooth muscles. In several familial myopathies involving fibre disorganization, filamentous aggregation of desmin has been characterized. During the development of the mouse embryo, desmin is one of the first muscle proteins detected in both the heart and the somites. To identify the DNA sequences involved in the regulation of desmin gene expression a 4.5 kb 5′-flanking region of the human desmin gene has been isolated. Different mutants were used to characterize specific enhancers in vitro and in vivo. The results obtained with transgenic mice provide evidence that the 1 kb cis-regulatory sequences, functional in skeletal muscle cells in vitro, confer specific developmental control for skeletal muscles. Furthermore, distinct programmes for cardiac and skeletal muscle-specific expression of the desmin gene are revealed.     

Role of Qa-1(b)-binding receptors in the specificity of developing NK cells

NK cells acquire the ability to recognize MHC class I molecules during development. Studies with Qa-1(b) tetramers (Qa-1 tetramers) showed that nearly all NK1.1(+) cells from newborn C57BL/6 mice express Qa-1-binding receptors. Cytotoxic activity of these cells is fully inhibited by Qa-1 ligands on target cells. In contrast, neither receptors for H-2K(b) nor H-2D(b) were observed on NK1.1(+) cells from newborn mice. After birth, frequencies of Qa-1 tetramer(+)/ NK1.1(+) cells gradually decrease as the number of Ly49(+) /NK1.1(+) cells increases. Cell transfer studies showed that Qa-1 tetramer(+) cells from newborn mice do not lose expression of Qa-1 receptors, but that they further acquire expression of Ly49 molecules. Acquisition of Qa-1-binding receptors appears largely independent of host MHC class I molecules, as observed in studies using beta2-microglobulin-deficient (beta2m(-/-)) mice as well as K(b)/ D(b-/-) and K(b)/D(b)/beta2m(-/-) mice. The present results suggest that Qa-1-binding receptors play an important role in the specificity of developing NK cells, and suggest that these cells rely mainly on inhibitory receptors specific for non-classical MHC class I molecules to maintain self tolerance during the first weeks of life.     

Retinoids inhibit the respiratory burst and degranulation of stimulated human polymorphonuclear leukocytes

Retinoids exhibit a wide spectrum of activities, including antiinflammatory properties. We have investigated the effect of retinoic acid (RA) and retinyl acetate (RAc) on the production of reactive oxygen metabolites and the release of lysosomal enzymes by human polymorphonuclear leukocytes (PMN). Incubation of PMN with RAc or RA (1–100 μM) caused a dose-dependent inhibition (upto 90%) in O ₂ ^? production and chemiluminescence induced by phorbol myristate acetate (PMA), N-formyl-methionylleucyl-phenylanaline (fMLP), opsonized zymosan or ionophore A23187. Both retinoids (1–100 μM) also inhibited, in a dose-dependent way, degranulation induced by fMLP (upto 85% at the highest concentration of RA). These inhibitory effects appear irreversible, since they persist after the drugs are removed and the cells washed before stimulation. Inhibitors of cyclo-oxygenase activity such as acetylsalicylic acid and indomethacin did not influence the effects of RAc. In contrast, BW755, an inhibitor of both cyclooxygenase and lipoxygenase, reversed the inhibitory action of RAc, suggesting that the effect of retinoids occurs possibly through the mediation of lipoxygenase products. The modulation of PMN oxidative metabolism and degranulation might help explain the antiinflammatory properties of retinoids.