Endothelin ETA-receptors couple to inositol phosphate formation and inhibition of adenylate cyclase in human right atrium

To study signal transduction pathways of endothelin (ET) in human heart, we assessed, in isolated human right atria, the effects of ET-1 and ET-3 on inositol phosphate (IP) formation and on the adenylate cyclase/cyclic AMP system. In right atrial slices, ET-1 (10(-10)-10(-6)M) concentration-dependently increased [3H]IP accumulation and decreased 10-microM isoprenaline-induced or 1-microM forskolin-induced increases in cyclic AMP content. ET-3 was approximately 100 times less potent. The cyclic AMP-decreasing effect of ET-1 (10(-11)-10(-6)M) could also be demonstrated directly in adenylate cyclase assays in right atrial membranes; again, ET-3 was approximately 100 times less potent. We conclude that in human right atrium, ETA receptors couple to two different signal-transduction pathways: IP formation and inhibition of adenylate cyclase.

Analysis of the parsley chalcone-synthase promoter in response to different light qualities

We examined the chalcone synthase (chs) promoter from parsley [Petroselinum crispum Miller (A.W. Hill)] for the existence of separate promoter elements responsible for transcriptional activation of the chs gene by UV-B and by blue light. A combination of in-vivo foot-printing in parsley cells and light-induced transient expression assays with different chs promoter constructs in parsley protoplasts was used. Dark controls and blue-light-irradiated cells gave identical in-vivo footprints on the chs promoter. Pre-irradiation with blue light prior to a UV-B-light pulse is known to cause a shift in the timing of UV-B-light-induced increase in chs transcription rates. This shift was also manifested on the DNA template, since UV-B-light-induced in-vivo footprints in cells pretreated with blue light were detected earlier than in cells which had been irradiated with a UV-B-light pulse only. Although there was a clear shift in the timing of footprint appearance, the patterns of footprinting did not change. Light-induced transient-expression assays revealed that the shortest tested chs promoter which retained any light responsiveness, was sufficient for mediating both induction by UV light and the blue-light-mediated kinetic shift. These findings argue against a spatial separation of UV-B- and blue-light-responsive elements on the chs promoter. We interpret these data by postulating that the signal transduction pathways originating from the excitation of UV-B- and blue-light receptors merge at the chs promoter, or somewhere between light perception and protein-DNA interaction.

Two Tcp-1-related but highly divergent gene families exist in oat encoding proteins of assumed chaperone function

Tcp-1-related sequences have been isolated from a cDNA library of etiolated 6-day-old oat (Avena sativa) seedlings. This attempt was made to obtain cDNAs of a recently published 60 kDa plant chaperone that re-folds denatured phytochrome and which was biochemically characterised as a Tcp-1-related protein [(1993) Nature 363, 644-647]. The translation of the putative coding sequence from one full-length cDNA clone displays no specific homologies to amino acid sequences known from peptide sequencing of the oat 60 kDa chaperone. Antibodies raised against the 60 kDa chaperone and over-expressed protein from one full-length coding sequence for Tcp-1 from oat show no cross-reactivity, whereas a monoclonal antibody raised against mouse Tcp-1 protein recognizes both the 60 kDa protein purified from plant extracts and over-expressed protein from Tcp-1-related cDNA sequences.

In vitro formation of a photoreversible adduct of phycocyanobilin and tobacco apophytochrome B

The light-stable tobacco phytochrome apoprotein (PHYB) expressed in yeast can be assembled with phycocyanobilin to give a photoreversible adduct. The spectral properties of the reconstituted PHYB-phycocyanobilin species were determined by absorbacen and difference absorbance spectroscopies. The holoprotein exhibits absorbance maxima at 408 nm and 712 nm for the far-red-light-absorbing (Pfr) form and 356 nm and 658 nm for the red-light-absorbing (Pr) form. The ligation of the chromophores to the dimeric PHYB apoprotein resulted in a PHYB-phycocyanobilin adduct with the spectral properties of the Pr form. Kinetic analyses of the in vitro reconstitution for PHYB apoprotein under saturating concentrations of phycocyanobilin revealed a pseudo first-order rate constant of 2.8 x 10(-2)s.-1. The similarity with the reported rate constant for the reconstitution of light-labile phytochrome (PHYA) from oat [Li, L. & Lagarias, J.C. (1992) Phytochrome assembly, J. Biol. Chem. 267, 19,204-19,210] suggests that the mechanisms of chromophore attachment are probably very similar for PHYA and PHYB.

A TCP1-related molecular chaperone from plants refolds phytochrome to its photoreversible form

Folding of the major cytoskeletal components in the cytosol of mammalian cells is mediated by interactions with t-complex polypeptide-1 (TCP1) molecular chaperones, a situation analogous to the chaperonin 60-aided folding of polypeptides in bacteria, chloroplasts and mitochondria. We have purified a TCP1-related molecular chaperone from etiolated oat seedlings that has a unique structure. Although immunologically related to TCP1, and having amino-acid sequence similarity, its quaternary structure is different from animal TCP1 proteins. Electron microscopy and image analysis reveals that the chaperone has two stacked rings of six subunits each, and is distinct in size and configuration. The chaperone copurifies with the soluble cytosolic photoreceptor phytochrome, and can stimulate refolding of denatured phytochrome to a photoactive form in the presence of Mg-ATP. We propose that this protein is the cytosolic chaperone involved in phytochrome biogenesis in plant cells.

T cells migrate to tumour sites after extracorporeal interleukin 2 stimulation and reinfusion in a patient with metastatic melanoma

Peripheral blood mononuclear cells (PBMC) were taken by leukapheresis from a patient with melanoma skin metastases and stimulated in vitro using 1000 IU recombinant interleukin 2 (IL-2)/ml to generate lymphokine-activated killer cells (LAK cells). Two-colour immunofluorescence analysis demonstrated an IL-2-induced up-regulation of CD25 on natural killer cells (CD56+) as well as on T lymphocytes (CD3+). After radiolabelling with indium-111, the cells were reinfused. Gamma-camera imaging revealed an enrichment at the tumour sites. Immunostaining of tumour tissue taken before and after scintigraphy demonstrated CD25+ T lymphocytes (CD2+, CD3+), but no natural killer cells (CD16+, CD56+) infiltrating the metastases. LAK cell enrichment at melanoma metastases in vivo did not involve natural killer cells, but was characterized by increased numbers of activated T lymphocytes in this patient.

Comparison of the positive inotropic effects of serotonin, histamine, angiotensin II, endothelin and isoprenaline in the isolated human right atrium

The receptor systems through which serotonin (5-HT), histamine, angiotensin II and endothelin increase the force of contraction were studied in isolated right atria from patients without apparent heart failure. All agonists increased the atrial force of contraction in a concentration-dependent manner; maximal effects, however, were significantly less than those evoked by isoprenaline or Ca2+. 5-HT and histamine, but not angiotensin II and endothelin, activated adenylate cyclase, whereas endothelin and angiotensin II stimulated inositol phosphate generation. Experiments with subtype-selective antagonists revealed that histamine effects were mediated by H2-receptors (sensitive to ranitidine), 5-HT-effects by 5-HT4-receptors (sensitive to SDZ 205-557) and angiotensin II effects by AT1-receptors (sensitive to losartan). We conclude that in human right atria the force of contraction can be increased by cyclic AMP-dependent (histamine, 5-HT) and -independent (angiotensin II, endothelin) pathways. Compared to beta-adrenoceptors, however, all other receptor systems increase the force of contraction only submaximally indicating that the beta-adrenoceptor pathway is the most important physiological mechanism to regulate force of contraction and/or heart rate in the human heart.

Chaperonin-mediated reconstitution of the phytochrome photoreceptor

The native phytochrome photoreceptor was purified to homogeneity from etiolated seedlings of oat (Avena sativa L.) and used for renaturation experiments. Light scattering measurements showed that the GroEL molecular chaperone interacts with non-native phytochrome to suppress aggregation of the refolding polypeptide, following its dilution from a chaotrope. The binary complex formed between non-native phytochrome and GroEL was stable and could be isolated by size exclusion chromatography. Discharge of the photoreceptor from GroEL was obtained with 2 mM MgATP, although 6 mM adenosine 5'-O-(3-thiotriphosphate) was also effective. Phytochrome released from GroEL with MgATP was found primarily in the form of 124-kDa monomers, as judged by size exclusion chromatography and nondenaturing gel electrophoresis, although dimers and other oligomeric forms were also observed. The reconstituted dimers, and other oligomeric forms, preferentially cross-reacted with a monoclonal antibody that recognizes native-like epitopes. In vitro folding reactions, using chemically denatured phytochrome, revealed that successful reconstitution of the photoreceptor required the presence of the GroEL chaperonin and MgATP under the conditions tested. Reconstitution in the presence of GroEL yielded phytochrome that could exhibit photoreversibility between the red-light absorbing and far-red absorbing forms.

Uncoupling of human cardiac beta-adrenoceptors during cardiopulmonary bypass with cardioplegic cardiac arrest

BACKGROUND

It is well known that during cardiopulmonary bypass (CPB) with cardioplegic cardiac arrest, catecholamines are vigorously increased. We therefore investigated whether this might cause desensitization of human cardiac beta-adrenoceptors.

METHODS AND RESULTS

We assessed in 12 children with acyanotic congenital heart disease who underwent open-heart surgery right atrial beta-adrenoceptor number and subtype distribution [by (-)-[125I]iodocyanopindolol binding] and adenylate cyclase activation [by the beta-adrenoceptor agonist isoprenaline (100 microM) and by the non-receptor-mediated activators 10 microM GTP, 10 mM NaF, 100 microM forskolin, and 10 mM Mn2+] before and after CPB with cardiac arrest by means of St. Thomas' cardioplegic solution. CPB affected neither beta-adrenoceptor number of subtype distribution nor GTP-, NaF-, forskolin-, or Mn(2+)-induced activation of adenylate cyclase. In contrast, activation of adenylate cyclase by 100 microM isoprenaline was significantly (p = 0.0249) lower after CPB than before CPB.

CONCLUSIONS

CPB with cardioplegic cardiac arrest decreases beta-adrenoceptor-mediated adenylate cyclase activation in a manner compatible with an uncoupling of beta-adrenoceptors from the Gs-protein-adenylate cyclase complex. Such a beta-adrenoceptor desensitization may be the reason why after CPB many patients need inotropic support but do not respond sufficiently to catecholamines.

Auxin Redistribution during First Positive Phototropism in Corn Coleoptiles : Microtubule Reorientation and the Cholodny-Went Theory

In red-light grown corn (Zea mays L. cv Brio42.HT) coleoptiles, cortical microtubules adjacent to the outer cell wall of the outer epidermis reorient from transverse to longitudinal in response to auxin depletion and after phototropic stimulation in the lighted side of the coleoptile. This was used as an in situ assay of cellular auxin concentration. The fluence-response relation for the blue light-induced reorientation is compared with that for first positive phototropism and the dose-response relationship for the auxin-dependent reorientation. The result supports the theory by Cholodny and Went, claiming that phototropic stimulation results in auxin displacement across the coleoptile. In terms of microtubule orientation, this displacement becomes even more pronounced after preirradiation with a weak blue light pulse from above.

Soluble interleukin-2 receptors inhibit interleukin 2-dependent proliferation and cytotoxicity: explanation for diminished natural killer cell activity in cutaneous T-cell lymphomas in vivo?

In patients with cutaneous T-cell lymphomas (CTCL), soluble interleukin-2 receptor serum levels (sIL-2R) were determined by ELISA technique, and natural killer cell (NK) activity, by a 4-h chromium-51 release assay. Decrease of NK activity correlated with the augmentation of serum sIL-2R. After a 4-d stimulation with interleukin 2 CTCL patients' peripheral mononuclear cells (PMC) showed an increase of cytotoxic activity similar to that in healthy donors' PMC. Normal donors' PMC demonstrated a diminished IL-2-induced cytotoxic activity in 25% CTCL serum (sIL-2R of 3000, 7330, and 10700 U/ml, respectively) compared to control serum (sIL-2R of 400, 340, and 420 U/ml, respectively). IL-2-dependent proliferation of 2-d phytohemagglutinin (PHA) blasts was lower in CTCL serum than in control serum. sIL-2R was enriched from one CTCL patient's serum by IL-2 affinity chromatography. Transfection of the Tac gene into NIH/3T3 fibroblasts resulted in the production of a recombinant sIL-2R. The presence of enriched native or recombinant sIL-2R inhibited interleukin-2-dependent generation of cytotoxic activity and PHA blast proliferation. We suggest that elevated sIL-2R levels account for diminished NK activity by neutralizing interleukin 2 in CTCL patients.

[Microendoscopy of the Eustachian tube and the middle ear. Indications and clinical application]

Progressive miniaturization of flexible fibreoptic systems has made it possible for the first time to perform atraumatic endoscopy of the Eustachian tube and tympanic cavity with the ear drum intact. With the aid of special actively steerable microcatheters, flexible fibrescopes having outer diameters of 350 to 650 microns are inserted into the opening of the naso-pharyngeal tube and advanced into the tympanic cavity under direct visual control. This new technique is indicated for any disturbance of sound conduction and in those sensorineural hearing disorders in which direct inspection of the middle ear cavity can provide information on the pathogenesis of the disturbance. In the future it may thus replace purely diagnostic tympanoscopy. In combination with fibre-delivery laser systems, this new method forms the basis of "microendoscopically controlled laser surgery" of pathological changes within this anatomical region.

GroEL-related molecular chaperones are present in the cytosol of oat cells

In eukaryotic cells GroEL-related molecular chaperones (cpn 60) are considered to be restricted to plastids and mitochondria. Re-evaluation of the intracellular localization of chaperonins by electron microscopy, using two different anti-chaperonin antisera, revealed additionally their presence in the cytosol of oat primary leaf and coleoptile cells. The distribution of cpn 60 is not influenced by heat or light treatments.

[Pharmacokinetics of clonidine following intravenous administration of high doses for the treatment of delirium tremens]

Concentrations of clonidine (CAS 4205-09-7. Catapresan) were measured in the plasma and the urine of 6 patients with delirium tremens who received 1.8-13.8 mg clonidine on the third treatment day. There was a linear correlation between the daily dose of clonidine and the steady state concentration of clonidine in the plasma, even with the high doses of clonidine used in this study. The total clonidine clearance was 29-62% lower than in normal volunteers. The renal clearance were 49-75% lower than normal. The renal excretion of the non-metabolized clonidine was significantly lower than the normal range. The creatinine clearance on the other hand was only slightly reduced. The present study gives first hints that the metabolic clearance of clonidine in patients with delirium tremens is not decreased remarkably.

Development- and light-dependent regulation of the expression of two different chalcone synthase transcripts in mustard cotyledons

Two different chalcone synthase (CHS) transcripts show similar expression characteristics under different light regimes in cotyledons of mustard (Sinapis alba L.). Etiolated seedlings show an increase in dark-expression 36-42 h after sowing. Under continuous red or far-red irradiation both CHS transcripts start to accumulate to levels above those of the dark control at 24-27 h after sowing. This time point can therefore be considered as the starting (or competence) point for phytochrome control of CHS. Continuous far-red irradiation stimulates transcript accumulation more than red light, indicating the involvement of a high-irradiance response (HIR). Irradiation of etiolated seedlings with 5 min long-wavelength far-red light (RG9) at 6-21 h after sowing decreases CHS-mRNA levels below those of the dark control. It is concluded that CHS dark-expression in etiolated seedlings is controlled by a pool of stabletype phytochrome which is derived from seed tissue. By contrast, an RG9-light pulse given to etiolated seedlings 30 h after sowing causes accumulation of CHS-mRNA above the dark-control level. This response and the HIR are attributed to the action of labile phytochrome for which the seedling becomes competent at the starting point 24-27 h after sowing. The different starting points for CHS-mRNA expression in darkness and in light (36 h and 24 h, respectively, after sowing) also indicate that the tested CHS genes in mustard are under the photocontrol of two distinct phytochrome pools. Northern analysis shows that both CHS-mRNAs are expressed in primary leaves, epicotyls and young flower buds. In-situ hybridization with gene-specific CHS probes reveals similar expression patterns for both transcripts in cotyledons of seedlings grown under 42 h continuous far-red light.

A stable phytochrome pool regulates the expression of the phytochrome I gene in pea seedlings

Two different molecular species of phytochrome apoprotein in terms of amino-acid sequences, phytochrome I (PI) and phytochrome II (PII), are found in pea tissues (H. Abe et al., 1989, Plant Cell Physiol. 30, 1089-1097). The single-copy pea PI gene produces at least three distinct transcripts (mRNAs 1, 2 and 3), differing in the length of the 5' non-coding sequence. The abundance of PI mRNA1 and mRNA2 in pea (Pisum sativum L. cv. Alaska) seedlings was determined using a primer extension assay. When dark-grown seedlings pretreated with a red light pulse or white-light-grown seedlings were briefly irradiated with far-red light (FR) 4h after transfer to darkness, the abundance of PI mRNA1 and mRNA2 significantly increased within a few hours. This effect was also observed when the FR was given after a 16-h dark incubation period. This FR effect was reversed by a subsequent irradiation with red light. Therefore, this photoreversible effect, observed during the prolonged dark period, can be ascribed to a phytochrome pool that is stable in its FR-absorbing form (Pfr).

Partial purification of sequestered particles of phytochrome from oat (Avenu sativa L.) seedlings

Sequestered particles of phytochrome (SAPs) were partially purified from red-light-irradiated oat coleoptiles. Phytochrome pelletability was enhanced by using buffers containing 10 mM Mg(2+) or high concentrations (0.6-0.8 M) of orthophosphate (Pi). Combining the pelletability of phytochrome in the presence of Mg(2+) with that in the presence of 0.6 Pi resulted in a strong enrichment (about 100-fold) of pelletable phytochrome. Antisera were raised against Mg(2+)-Pi-pellets from darkgrown seedlings. Using these antisera, no evidence was found by Western blotting and immunocytochemistry that SAPs contain major proteins other than phytochrome. The major contamination of these enriched SAP preparations consisted of protein crystals which are probably catalase. The preparations contained methyltransferase and protein-kinase activities which were not associated with SAPs. Phytochrome purified from SAPs served as a substrate for protein-kinase activity but not for the methyltransferase activity. Phytochrome itself did not show any kinase activity.

Imaging pattern of radiolabelled lymphokine-activated killer cells in patients with metastatic malignant melanoma

In patients with metastatic malignant melanoma the distribution patterns of radiolabelled lymphokine-activated killer (LAK) cells were investigated. Peripheral mononuclear cells (PMC) were isolated from six patients. LAK cells were generated by culturing PMC in complete medium containing 1000 U interleukin (IL)-2/ml and labelled with indium 111 before retransfer. We obtained scans at 2.5, 24, 48 or 96 h after injection with a high resolution gamma-camera. Intravenously injected LAK cells distributed to the lungs, liver, spleen and bone marrow. External tumour detection of known lymph node and bone metastases was successful in four. It failed in one patient with a solitary lung metastasis and in another patient with subcutaneous metastases. Our results suggest that LAK cells show tumour homing, providing a direct interaction between tumour and cytotoxic cells. We conclude that PMC seem to retain their ability to migrate after IL-2 stimulation and 111In-labeling. This technique may be helpful for kinetics studies or external detection of metastases in patients with malignant melanoma.

Photocontrol of the Expression of Genes Encoding Chlorophyll a/b Binding Proteins and Small Subunit of Ribulose-1,5-Bisphosphate Carboxylase in Etiolated Seedlings of Lycopersicon esculentum (L.) and Nicotiana tabacum (L.)

Phytochrome and the blue ultraviolet-A photoreceptor control light-induced expression of genes encoding the chlorophyll a/b binding protein of photosystem II and photosystem I and the genes for the small subunit of the ribulose-1,5-bisphosphate carboxylase in etiolated seedlings of Lycopersicon esculentum (tomato) and Nicotiana tabacum (tobacco). A ;high irradiance response' also controls the induction of these genes. Genes encoding photosystem II- and I-associated chlorophyll a/b binding proteins both exhibit a transient rapid increase in expression in response to light pulse or to continuous irradiation. In contrast, genes encoding the small subunit exhibit a continuous increase in expression in response to light. These distinct expression characteristics are shown to reflect differences at the level of transcription.

Action dichroism in perception of vectorial photo-excitation in the solar-tracking leaf ofLavatera cretica L

The leaf lamina ofLavatera cretica L. exhibits a diaphototropic response that discriminates between two opposite, constant vectorial excitations by white light beams whose fluence rates differ by as little as 10% (50 versus 45 μmol·m(-2)·S(-1)). The relationship between the response (angular velocity of laminar reorientation) and the fluence-rate ratio is linear. The lamina similarly discriminates between two such excitations by polarized light, one with the electrical vector transverse to the plane of the two beams (θ) and the opposite one with the vector parallel to that plane ([Symbol: see text]). When two such beams were of equal fluence rate, the lamina reoriented towards the [Symbol: see text] beam. When the fluence rate of the θ beam was maintained at 50 μmol·m(-2)·s(-1) and that of the [Symbol: see text] beam was reduced, the response to the latter (angular velocity of laminar reorientation) was reduced progressively. Further reduction in the fluence rate of the [Symbol: see text] polarized beam eventually resulted in reorientation in the opposite direction (towards the θ beam) and the response to the latter increased progressively with the reduction in fluence rate. The equilibrium was at a [Symbol: see text]/θ ratio of 0.62. Measurements of reflectance of oblique beams of [Symbol: see text] and θ polarized light from the upper laminar surface, and of transmittance of such light ghrough the lamina, eliminated the possibility that optical dichroism of the lamina contributed significantly to these results. The implications of this action dichroism to the postulated mechanism of perception of vectorial excitation by these leaves is discussed.

[Systemic lysotherapy using recombinant tissue plasminogen activator for fulminant pulmonary embolism]

A 44-year-old woman sustained massive pulmonary embolization from a deep leg-vein thrombosis. She was given 70 mg recombinant tissue plasminogen activator (rt-PA) by continuous intravenous drip over two hours. Before this treatment perfusion scintigraphy had demonstrated complete absence of flow in the right lung due to embolic occlusion of the central hilar vessels. In addition there were several segmental filling defects in the left lung. Even during the two-hour infusion the circulatory state began to improve, as did echo- and electrocardiographic signs of acute right heart strain. Correspondingly there was a rapid raise in arterial pO2. Another scintigraphy after 48 hours revealed almost complete reperfusion of the right lung and the left lung segments. This case demonstrates that infusion of rt-PA can be an effective and relatively risk-free method of treating haemodynamically significant massive lung embolism, even in comparison with selective or systemic thrombolysis with urokinase or streptase or with surgical embolectomy.