Showing papers by "University of Würzburg published in 1987"

Improved silver staining of plant proteins, RNA and DNA in polyacrylamide gels

Abstract: A new modification of silver staining is presented which utilizes two chemical properties of thiosulfate: image enhancement by pretreatment of fixed gels, and formation of soluble silver complexes which prevents unspecific background staining during image development. This procedure provides high sensitivity for proteins, RNA and DNA in the nanogram range on a colorless, transparent background. The performance of this method is documented by staining one-and two-dimensional patterns of plant leaf proteins. Moreover, we achieved, for the first time, the detection of the non-structural, tobacco mosaic virus-specific 126 kDa protein directly in the one-dimensional protein pattern of infected protoplasts by a staining procedure.

Photoinhibition and zeaxanthin formation in intact leaves : a possible role of the xanthophyll cycle in the dissipation of excess light energy.

Abstract: Comparative studies of chlorophyll a fluorescence, measured with a pulse amplitude modulated fluorometer, and of the pigment composition of leaves, suggest a specific role of zeaxanthin, a carotenoid formed in the xanthophyll cycle, in protecting the photosynthetic apparatus against the adverse effects of excessive light. This conclusion is based on the following findings: (a) exposure of leaves of Populus balsamifera, Hedera helix, and Monstera deliciosa to excess excitation energy (high light, air; weak light, 2% O2, 0% CO2) led to massive formation of zeaxanthin and a decrease in violaxanthin. Over a wide range of conditions, there was a linear relationship between either variable, Fv, or maximum fluorescence, Fm, and the zeaxanthin content of leaves. (b) When exposed to photoinhibitory light levels in air, shade leaves of H. helix had a higher capacity for zeaxanthin formation, at the expense of β-carotene, than shade leaves of M. deliciosa. Changes in fluorescence characteristics suggested that, in H. helix, the predominant response to high light was an increase in the rate of nonradiative energy dissipation, whereas, in M. deliciosa, photoinhibitory damage to photosystem II reaction centers was the prevailing effect. (c) Exposure of a sun leaf of P. balsamifera to increasing photon flux densities in 2% O2 and 0% CO2 resulted initially in increasing levels of zeaxanthin (matched by decreases in violaxanthin) and was accompanied by fluorescence changes indicative of increased nonradiative energy dissipation. Above the light level at which no further increase in zeaxanthin content was observed, fluorescence characteristics indicated photoinhibitory damage. (d) A linear relationship was obtained between the ratio of variable to maximum fluorescence, Fv/Fm, determined with the modulated fluorescence technique at room temperature, and the photon yield of O2 evolution, similar to previous findings (O Bjorkman, B Demmig 1987 Planta 170: 489-504) on chlorophyll fluorescence characteristics at 77 K and the photon yield of photosynthesis.

Complementary observables and uncertainty relations.

Abstract: Two observables A and B of an n-level system (ie, a quantum system with n-dimensional state space) are called complementary, if knowledge of the measured value of A implies maximal uncertainty of the measured value of B, and vice versa Such observables exist for all n, but no classification (up to equivalence) of all possible pairs of complementary observables is known except for n\ensuremath{\le}4 Complementary observables are conjectured to satisfy an ``entropic'' uncertainty relation of the strongest possible form This relation has been verified for n\ensuremath{\le}4 by explicit calculations A recent attempt of substantiating the widespread interpretation of uncertainty relations in terms of mutual disturbances between measurements is criticized

Rapid assessment of stress effects on plant leaves by chlorophyll fluorescence measurements

Abstract: Chlorophyll fluorescence serves as an intrinsic indicator of the photosynthetic reactions in the chloroplasts of green plants. The relationship between chlorophyll fluorescence and the mechanisms of photosynthesis have been the subject of a great number of investigations, since Kautsky discovered (Kautsky and Hirsch 1931) that fluorescence intensity in green leaves displays characteristic changes upon illumination (Kautsky effect - for reviews, see Papageorgiou 1975; Lavorel and Etienne 1977; Krause and Weis 1984). For almost half a century fluorescence has been mainly a tool for biophysically oriented researchers in studies of the primary processes of photosynthesis. Practical applications of the Kautsky effect in ecophysiological work had been limited by the availability of suitable instrumentation and by the complexity of the fluorescence information obtained in vivo. In recent years considerable efforts have been put into the development of field oriented fluorescence equipment and into the development of the methodology for analysing fluorescence data from intact leaves.

Nerve fibres and their terminals of the dura mater encephali of the rat.

Abstract: The dura mater encephali of the rat is richly supplied by myelinated (A-axons) and unmyelinated (C-axons) nerve fibres. For the supratentorial part the main nerve supply stems from all three branches of the trigeminal nerve. Finally, 250 myelinated and 800 unmyelinated nerve fibres innervate one side of the supratentorial part. The vascular bed of the dura mater exhibits long postcapillary venules up to 200 μm in length with segments of endothelial fenestration. Lymphatic vessels occur within the dura mater. They leave the cranial cavity through the openings of the cribriform plate, rostral to the bulla tympani together with the transverse sinus, and the middle meningeal artery. The perineural sheath builds up a tube-like net containing the A- and C-axons. It is spacious in the parietal dura mater and dense at the sagittal sinus along its extension from rostral to caudal and at the confluence of sinuses. Terminals of both the A- and C-axons are of the unencapsulated type. Unencapsulated Ruffini-like receptors stemming from A-axons are found in the dural connective tissue at sites where superficial cerebral veins enter the sagittal sinus and at the confluence of sinuses. The terminations of single A-axons together with C-fibre bundles mix up in their final course in one Schwann cell to build up multiaxonal units or terminations (up to 15 axonal profiles). A morphological differentiation is made due to the topography of these terminations; firstly, in different segments of the vascular bed: postcapillary venule, venule, the sinus wall, lymphatic vessel wall, and secondly, within the dura mater: inner periosteal layer, collagenous fibre bundles of the meningeal layer and at the mesothelial cell layer of the subdural space.

The Polyphasic Rise of Chlorophyll Fluorescence upon Onset of Strong Continuous Illumination: II. Partial Control by the Photosystem II Donor Side and Possible Ways of Interpretation

Abstract: The fluorescence rise kinetics in saturating light display two well separated components with largely different properties. The rapid rise from F₀ to a first intermediate level, I₁ is photochemically controlled, while the following phases leading to a secondary intermediate level, I₂ and to a peak level, P, are limited by thermal reactions. Treatments which primarily affect components at the photosystem II donor side are shown to increase quenching at I₁ and/or to suppress the secondary fluorescence rise to I₂. Preillumination by single turnover saturating flashes causes I₁- quenching oscillating with period-4 in dependence of flash number. It is suggested that this quenching correlates with (S₂ + S₃) states of the watersplitting enzyme system. Suppression of the secondary, I₁ - I₂ rise component is invariably found with treatments which lower electron donation rate by the watersplitting system and are known to favor the low potential form of cyt b 559.Three different mechanisms are discussed on the basis of which donor-side dependent quench­ing could be interpreted: 1) Non-photochemical quenching by accumulation of the P 680⁺ radical cation. 2) Dissipative photochemical quenching at a special population of PS II centers (β- or non- B centers) displaying low donor capacity and high rates of charge recombination. 3) Dissipative photochemical quenching via cyclic electron flow around PS II, involving alternate donors to P 680⁺ (like cyt b 559 or carotenoid in their low potential forms), which can compete when donation rate from the water splitting system is slowed down. The possibility of donor-side limitation also being involved in “energy dependent” quenching is discussed.

Class E Power Amplifiers and Frequency Multipliers with finite DC-Feed Inductance

Abstract: Previous descriptions of class E amplifiers and frequency multipliers have required a radio frequency choke between the dc power supply and the active device "switch." In this paper, it is shown that class E operation may be maintained with the RF choke replaced by a smaller reactance. The analysis technique used is similar to that used by Raab in his description of class E amplifiers in that the equations describing circuit operation are obtained from Fourier series methods and the assumption of an infinite output network Q . The equations so obtained are used to determine (1) optimum operation (maximum power output capability at 100-percent efficiency) at any harmonic and (2) design equations that yield the requisite component values for optimum operation. The equations show that class E circuits may be configured to accommodate devices with arbitrary output capacitance and that class E amplifiers may be configured to provide greater power output capability than can be obtained using an RF choke design. Class E circuits with moderate values of output network Q were constructed and tested. The measured performance of these experimental circuits shows excellent agreement with the theoretical performance predicted by the equations.

The Polyphasic Rise of Chlorophyll Fluorescence upon Onset of Strong Continuous Illumination: I. Saturation Characteristics and Partial Control by the Photosystem II Acceptor Side

Abstract: Applying a rapid modulation system for measurement of chlorophyll fluorescence yield (U. Schreiber. Photosynth. Res. 9. 261-272 (1986)) the induction kinetics upon onset of strong actinic illumination previously studied by Delosme (Biochim, Biophys, Acta 143, 108-128 (1967)) are reinvestigated. With increasing actinic intensity the fluorescence rise is changed from the typical O-I-P characteristic to a more complex rise curve with two intermediary levels I₁ and I₂ both of which show saturation at high intensity. The typical kinetics at saturating light intensity (O-I₁-D-I₂-P) are observed in a variety of plant species. The properties of the kinetics with respect to light intensity, temperature, electron acceptors and PS II inhibitors suggest that the O-I₁ phase is controlled by photochemical charge separation (photochemical phase), while the I₁-D-I₂-P transients are limited by dark reactions (thermal phases). Dichlorophenyl-dimethylurea (DCMU) eliminates the thermal phases by raising I, to the original I level. While in principal the previous findings by Delosme are confirmed, there, is the new aspect of two distinct components in the thermal part of the rise curve, which display different properties. Electron acceptors suppress only the I₂-P phase, which appears to parallel the reduction of the plastoquinonc pool, which is a fluorescence quencher when oxidized. While the DCMU effect suggests quenching control during I₁-I₂ by reoxidation of PS II acceptors, this suggestion is contradicted by the observed saturation of I₁ with light intensity and at low temperatures. The relevance of these results with respect to quenching analysis of chlorophyll fluorescence by the saturation pulse method is discussed.

Mechanism of sugar transport through the sugar-specific LamB channel of Escherichia coli outer membrane.

Abstract: Lipid bilayer experiments were performed with the sugar-specific LamB (maltoporin) channel ofEscherichia coli outer membrane. Single-channel analysis of the conductance steps caused by LamB showed that there was a linear relationship between the salt concentration in the aqueous phase and the channel conductance, indicating only small or no binding between the ions and the channel interior. The total or the partial blockage of the ion movement through the LamB channel was not dependent on the ion concentration in the aqueous phase. Both results allowed the investigation of the sugar binding in more detail, and the stability constants of the binding of a large variety of sugars to the binding site inside the channel were calculated from titration experiments of the membrane conductance with the sugars. The channel was highly cation selective, both in the presence and absence of sugars, which may be explained by the existence of carbonyl groups inside the channel. These carbonyl groups may also be involved in the sugar binding via hydrogen bonds. The kinetics of the sugar transport through the LamB channel were estimated relative to maltose by assuming a simple one-site, two-barrier model from the relative rates of permeation taken from M. Luckey and H. Nikaido (Proc. Natl. Acad. Sci. USA 77:165–171 (1980a)) and the stability constants for the sugar binding given in this study.

Enhancement of the responses of ascending tract cells in the cat spinal cord by acute inflammation of the knee joint.

Abstract: 1. Recordings were made from 16 ascending tract cells in the spinal cords of anaesthetized, spinalized cats before and after an acute arthritis was produced by injection of kaolin and carrageenan into the knee joint. 2. The responses tested routinely were to passive flexion of the knee, an innocuous movement. In some cases, responses to other movements were also tested, and changes in background discharge rates were monitored. 3. Control recordings for a period of 1 h or in 3 cases of 3 h indicated that the responses to flexion were reasonably stationary. 4. Four tract cells that initially showed little or no response to flexion of the knee joint developed large responses within 1 to 2 h after inflammation of the joint. 5. Another 9 cells were tested that had responses to flexion of the knee joint prior to inflammation. In 6 cases, inflammation produced enhanced static or transient responses. In 2 cases, the effect of flexion was initially inhibitory or variable, but after inflammation these cells showed large excitatory responses. In the other case, inflammation had no effect. Background discharges were increased by inflammation in 6 of these 9 cells. 6. The effect of inflammation of the knee joint was tested on 3 tract cells that had no clearly defined receptive field in the knee. In 1 case, a response developed to knee flexion after acute inflammation was produced. In the other 2 cases, there were initially responses to knee flexion, but these were unchanged by inflammation. 7. Two of the cells tested had bilateral receptive fields in or around the knee joints. Inflammation of one knee joint enhanced the responses to flexion of the same but not of the contralateral knee in one case but greatly increased the responses to flexion of both knees in the other case. 8. Injections of prostaglandin (PGE2) caused an enhancement of the responses to knee flexion beyond that caused by inflammation in 5 of 7 cases. One cell whose responses to flexion of the knee were unaffected by inflammation showed inhibitory responses to prostaglandin injections into the inflamed knee joint. 9. The effects of inflammation on the responses of ascending tract cells of the spinal cord appear to serve as a useful neural model of the events responsible for the development of arthritic pain.

Voltage-dependent depolarization of bacterial membranes and artificial lipid bilayers by the peptide antibiotic nisin.

Abstract: The peptide antibiotic nisin is shown to disrupt valinomycin-induced potassium diffusion potentials imposed on intact cells of Staphylococcus cohnii 22. Membrane depolarization occurred rapidly at high diffusion potentials while at low potentials nisin-induced depolarization was slower suggesting that nisin requires a membrane potential for activity. This assumption was proven in experiments with planar lipid bilayers (black lipid membranes). Macroscopic conductivity measurements indicated a voltage-dependent action of nisin. The potential must have a trans-negative orientation with respect to the addition of nisin (added to the cis-side) and a sufficient magnitude (ca. -100 mV). With intact cells the threshold potential was lower (-50 to -80 mV at pH 7.5 and below -50 mV at pH 5.5). Single channel recordings resolved transient multistate pores, strongly resembling those introduced by melittin into artificial bilayers. The pores had diameters in the range of 0.2–1 nm, and lifetimes of few to several hundred milliseconds. The results indicate that nisin has to be regarded as a membrane-depolarizing agent which acts in a voltage-dependent fashion.

Vasodilator-stimulated protein phosphorylation in platelets is mediated by cAMP- and cGMP-dependent protein kinases

Abstract: Vasodilators such as sodium nitroprusside, nitroglycerin and various prostaglandins are capable of inhibiting platelet aggregation associated with an increase of either cGMP or cAMP. In our studies with intact platelets, prostaglandin E1 and sodium nitroprusside stimulated the phosphorylation of several proteins which could be distinguished from proteins known to be phosphorylated by a calmodulin-regulated protein kinase or by protein kinase C. Prostaglandin E1 (10 μM) or dibutyryl cAMP (2 mM) stimulated the phosphorylation of proteins with apparent relative molecular masscs, Mr, of 240000, 68 000, 50 000, and 22 000 in intact platelets. These proteins were also phosphorylated in response to low concentrations (1–2 μM) of cAMP in a particulate fraction of platelets. In intact platelets, sodium nitroprusside (100 μM) and the 8-bromo derivative of cGMP (2 mM) increased the phosphorylation of one protein of Mr 50000 which was also phosphorylated in response to low concentrations (1–2 μM) of cGMP in platelet membranes. An additional protein (Mr 24000) appeared to be phosphorylated to a lesser degree in intact platelets by prostaglandin E1 and sodium nitroprusside. Since the phosphorylation of the protein of Mr 50000 was stimulated both in intact platelets by cyclic-nucleotide-elevating agents and cyclic nucleotide analogs, as well as in platelet membranes by cyclic nucleotides, this phosphoprotein was analyzed by limited proteolysis, tryptic fingerprinting and phosphoamino acid analysis. These experiments indicated that the 50-kDa proteins phosphorylated by sodium nitroprusside and prostaglandin E1 were identical, and that the peptide of the 50-kDa protein phosphorylated by both agents was also the same as the peptide derived from the 50-kDa protein phosphorylated in platelet membranes by cGMP- and cAMP-dependent protein kinases, respectively. Regulation of protein phosphorylation mediated by cAMP- and cGMP-dependent protein kinases may be the molecular mechanism by which those vasodilators, capable of increasing either cAMP or cGMP, inhibit platelet aggregation.

Sulfur Oxides as Ligands in Coordination Compounds

Abstract: Donor molecules undergo dramatic changes in their chemical properties on coordination to a transition-metal atom. Highly reactive species can be trapped and studied as ligands. Conversely, stable compounds can be activated to undergo novel reactions. Sulfur dioxide complexes have generally been studied from a structural viewpoint, their reactivity having been somewhat neglected. The unstable sulfur oxides SO, S2O, and S2O2 are still often regarded as laboratory curiosities. Their successful stabilization in transition-metal complexes has now made them accessible to detailed study, in the course of which many relationships to the chemistry of SO2 complexes have become apparent.

Human autoantibodies: probes for nucleolus structure and function.

Abstract: Four distinct nucleolar proteins or RNA-protein complexes have recently been identified as targets of human autoimmune antibodies. These autoantigens areRNA polymer-ase I, PM-Scl (a particle possibly related to preribosomes), 7-2 RNP andfibrillarin (a U3-RNP associated protein). The four different nucleolar autoantigens could be assigned to distinct nucleolar subcompartments by light and electron microscopic immunocytochemistry. RNA polymerase I was located in the fibrillar centers, PM-Scl antigen and 7-2 RNP in the granular component and fibrillarin in the dense fibrillar component. Experimental evidence suggests that these naturally occurring antibodies could be helpful tools in further studying nucleolus structure and functions as well as molecular mechanisms involved in ribosome biogenesis. From a clinical viewpoint, we believe that it is important to identify the nature of reactive autoantigens in systemic autoimmune diseases in order to answer questions concerning the mechanisms which render conserved ubiquitous cellular proteins immunogenic. Revealing such mechanisms in return could give clues with regard to the etiology of certain systemic rheumatic diseases. Ribosome biogenesis, a highly dynamic process with its many well-defined intermediate biological steps related to specific nuclear structures could be amenable for such studies.

Are the structural changes in adult Drosophila mushroom bodies memory traces? Studies on biochemical learning mutants

Abstract: The pre-imaginal development of Drosophila mushroom bodies is under the influence of an unknown variable which causes populations of wild-type flies at eclosion to differ in the average number of Kenyon cell fibers. During the first week of adult life the number adjusts to an intermediate level which depends upon the experience of the flies. Under olfactory deprivation or social isolation it reaches a lower level than under favorable rearing conditions (/. Neurogenet., 1 (1984) 113–126). The biochemical learning mutants dunce and rutabaga show no experience-dependent modulation of fiber number (Fig. 2). In both strains the mushroom bodies of young adults seem to develop abnormally: in dunce a loss of about 600 fibers is observed, in rutabaga fiber number is low at eclosion and does not increase (Fig. la). The following model for long-term memory is proposed: in mushroom bodies outgrowth and decay of Kenyon cell fibers occur simultaneously. The fibers randomly form transient synapses onto extrinsic output ...

Convergent inputs from articular, cutaneous and muscle receptors onto ascending tract cells in the cat spinal cord

Abstract: 1.Responses were recorded from 160 ascending tract cells in segments L4 to L6 of the spinal cord in chloralose anaesthetized, spinalized cats. The tract cells were identified by antidromic activation following stimulation of pathways in the lateral and ventral funiculi at the level of the spinal cord transection at the thoracolumbar junction. Axonal conduction velocities ranged from 9 to 114 m/s. 2. A sample of 152 of the neurones examined could be subdivided according to the distribution of their receptive fields into 49 cells activated just from receptors located in skin (“s” cells), 17 neurones excited by receptors in deep tissues (“d” cells), 15 units with a convergent input from receptors in skin and deep tissues (“sd” cells), and 25 neurones with a convergent input from the knee joint and either skin (“sj” cells), deep tissues (“dj” cells) or both (“sdj” cells). No receptive fields could be demonstrated for the remaining 46 neurones. 3. “S” and “sj” cells were found almost exclusively in the dorsal horn, whereas many “d”, “sd”, “sdj” and “dj” units were in the ventral horn. Almost all of the cells that lacked receptive fields were in the ventral horn or intermediate grey. 4. Ninety-one of 158 cells (56%) demonstrated no background activity. Of these, 43 cells (27%) lacked receptive fields. Many of the silent neurones were in the ventral horn, but some were in the dorsal horn. Of 25 cells having knee joint input, 18 (72%) had background activity. 5. All of the neurones that had a receptive field in the knee joint also had a convergent input from receptors in other tissues. In 3 cases, there was a receptive field in the skin over the foot (“sj” cells). For 16 cells, receptive fields included not only the knee joint but also skin and deep tissue (“sdj” cells). Usually, the cutaneous receptive field was near the knee joint, but sometimes it was remote, such as on the foot. The deep receptive fields were chiefly in the muscles of the thigh and/or leg. For 6 “dj” cells, the receptive fields included not only the knee joint but also deep fields like those of “sdj” cells. 6. Cutaneous receptive fields were classified as “low threshold” (cells excited best by innocuous intensities of mechanical stimulation), “wide dynamic range” (cells activated by weak mechanical stimuli, but the best responses were to noxious stimuli) or high threshold (innocuous stimuli had little effect, but noxious mechanical stimuli produced a vigorous discharge). Similarly, stimulation of the knee joint with weak mechanical stimuli could excite some neurones, while others could be activated by weak or strong articular stimuli but were excited best by noxious stimuli, and still other neurones were activated by knee joint stimuli only if the intensity was noxious. 7. In several instances, contralateral receptive fields were noted. These were generally in deep tissue or in the knee joint. 8. It was concluded that many of the responses to articular stimulation of the spinal cord ascending tract cells examined in this study could have been mediated by the fine afferent fibres that supply the knee joint. Although further work will be required to determine which particular ascending tracts transmit nociceptive information concerning the knee joint, it can be proposed that many of the responses demonstrated here were likely to play a role in either joint pain of in triggering responses associated with joint pain.

Mutations affecting activity and transport of haemolysin in Escherichia coli.

Abstract: Temperature-sensitive mutants that exhibit an altered haemolytic phenotype were isolated from Escherichia coli harbouring the plasmid pHly152. Complementation with recombinant plasmids carrying one of the four hly genes (C, A, B or D) allowed localization of the hly ts mutations. A ts mutation in hlyC leads to a pro→leu exchange in amino acid position 53 of HlyC. Two ts mutations in HlyA were found in positions 312 (ser→pro) and 315 (thr→ile). Both amino acid exchanges are located in the same hydrophobic domain of HlyA which extends from amino acids 299 to 327. Two different mutations were introduced by site-specific mutagenesis in this hlyA domain: one by an exchange of ala, val to asp, glu (positions 313, 314) altering the hydrophobicity of this region and another which removes most of this hydrophobic portion. Both mutants have entirely lost the haemolytic activity but the mutant haemolysins are still efficiently transported across both membranes when hlyB and hlyD are provided. Functional HlyC is not required for the transport of the mutant haemolysins. Two site-specific mutations at the N-terminal end of hlyA (one at amino acid position 2 leading to a thr→pro exchange and another deleting ile and thr at positions 4 and 5) also do not affect the transport of the altered haemolysins. The thr→pro exchange enhances the haemolytic activity of the corresponding mutant, whereas the ile, thr deletion exhibits little or no effect on the haemolytic activity. Removal of the last 37 amino acids from the C-terminal end of HlyA leads to a truncated haemolysin which retains its haemolytic activity but is not secreted by the HlyB and HlyD transport system.

Evidence for a vasoconstriction-mediating receptor for UTP, distinct from the P2 purinoceptor, in rabbit ear artery.

Abstract: 1. The mechanism of uridine 5'-triphosphate-(UTP-)induced vasoconstriction was studied in the rabbit ear artery. The arteries were incubated and perfused at a constant rate of flow. Vasoconstriction was measured as an increase in perfusion pressure. 2. Noradrenaline, adenosine 5'-triphosphate (ATP) and UTP caused concentration-dependent vasoconstriction. ATP and UTP were approximately equipotent. 3. The vasoconstrictor effect of UTP 300 mumol/l was enhanced by a mixture of atropine, diphenhydramine and methysergide (1 mumol/l each) and not affected by indomethacin 10 mumol/l. 4. Prazosin (0.01-1 mumol/l) and phentolamine (1-10 mumol/l) reduced the vasoconstrictor effect of UTP 300 mumol/l by up to 34%. Prazosin 1 mumol/l failed to diminish the vasoconstrictor effect of UTP 300 mumol/l after the sympathetic nerves had been destroyed with 6-hydroxydopamine. 5. alpha, beta-Methylene-ATP (10-50 mumol/l) elicited transient vasoconstriction. Subsequently, vasoconstrictor responses to ATP 100 or 300 mumol/l were reduced by 88%, whereas responses to UTP 100 mumol/l were enhanced, responses to UTP 300 mumol/l decreased by only 32% and responses to UTP 1000 mumol/l reduced by 74%. After in vitro-denervation with 6-hydroxydopamine or in the presence of phentolamine 1 mumol/l throughout, alpha, beta-methylene-ATP (10-50 mumol/l) reduced the vasoconstrictor effect of UTP 300 mumol/l by 44% and 43%, respectively. 6. We suggest that, in the rabbit ear artery, the non-adrenergic and alpha, beta-methylene-ATP-resistant vasoconstrictor response to UTP is mediated by a separate receptor mechanism, distinct from the P2 purinoceptor.

Estimation of exposure of man to substances reacting covalently with macromolecules.

Abstract: Cancer continues to be one of the major human diseases. In highly industrialized countries 20-25% of the population dies from cancer. Effective treatment leading to cure is not available for most types of cancer. There is evidence, from epidemiology as well as from experimental research, that much if not the majority of human cancer is caused by tobacco smoke, by synthetic and natural chemicals of occupational, environmental, medicinal and very important at least on the quantitative level of dietary origin (Doll and Peto 1981). This suggests that most of these chemically-induced cancers could be prevented or drastically reduced in number by eliminating the causative chemicals (Higginson and Muir 1979). Unfortunately, however, the greater number of these chemicals, particularly in diet or of dietary origin, has not yet been identified. Also, the development of an effective strategy for prevention requires a knowledge of exposure to and carcino-

Tumor necrosis factor amplifies measles virus-mediated Ia induction on astrocytes.

Abstract: We describe the induction of Ia on cultured astrocytes by measles virus and the amplification of this induction by tumor necrosis factor (TNF). Measles virus induces Ia on rat astrocytes by direct interaction with these cells. TNF does not induce significant levels of Ia at any dose from 1 to 10,000 units/ml. As little as 10 units of TNF per ml, however, amplifies Ia-inducing signals generated by measles virus in astrocytes. In contrast, TNF and measles virus induce class I major histocompatibility complex (MHC) antigens, when applied individually, and TNF amplification of measles virus class I MHC induction is not apparent. The induction of either Ia or class I MHC antigens on rat astrocytes by measles virus does not depend on glial-derived soluble factors generated during infection. Since brain cells are normally lacking MHC antigens upon which T cells depend for interaction with antigen presenting cells, these data indicate that the ability of measles virus to directly stimulate MHC antigen expression and the ability of TNF to amplify Ia expression locally in the brain may be important in initiating cell-mediated immune response to viral infection.

Clinical anatomy of cardiac veins, Vv. cardiacae.

Abstract: New methods of cardiological examination and treatment, such as catheterization and arterialization of the coronary sinus, venous reperfusion and cardioplegia have made necessary an exact account of the distribution pattern and the mode of opening of the cardiac veins 350 hearts were prepared for examination with macroscopical techniques There are three systems of the major cardiac veins: tributaries of the coronary sinus, anterior cardiac veins, atrial cardiac veins Their openings lie in a circle-like arrangement between the ostia of both caval veins and just above the tricuspid valve In most cases there are variably sized intramural collecting chambers or sinuses just before the opening of all the cardiac veins These sinuses are interpreted to favour the return of cardiac venous bloodstream from the myocardium to the right atrial cavity The tributaries of the coronary sinus and of the anterior cardiac veins are very variable There is for instance only in 36% of cases a small cardiac vein, which belongs to the coronary sinus system In 64% a small cardiac vein does not exist, but its origin, the right marginal vein, joins the system of anterior cardiac veins This behaviour diminishes the function of the coronary sinus and increases the importance of the system of anterior cardiac veins Intramural courses of the great cardiac vein, crossing coronary arteries, ostial valves of cardiac veins, ostial valve of coronary sinus and of inferior vena cava, ostial occlusion of coronary sinus, and aneurysm like excavation of the posterodorsal wall of the right atrium have been described also These facts and structures may cause morphological hindrances fo catheterization of the right atrium and coronary sinus and for reperfusion of cardiac venous drainage pathways This report about a large conus vein, which is a great cardiac vein joining anterior cardiac veins and about intramural courses of great cardiac vein as well as semicircular venous sinuses in the wall of the right atrium is the first in the literature

Chlorophyll fluorescence as an indicator of heat induced limitation of photosynthesis in Arbutus unedo L.

Abstract: Chlorophyll fluorescence analysis may provide us with a sensitive indicator of stress induced limitations of photosynthesis (for recent reviews see Smillie and Hetherington (1983) and Schreiber and Bilger, this volume). High temperature treatment causes a variety of fluorescence changes: (1) At elevated temperatures the dark fluorescence level, Fo, is increased several-fold (Schreiber and Berry 1977), the critical temperature for the Fo-increase being closely correlated with the critical temperature for irreversible damage to the leaf tissue as determined from leaf necrosis (Bilger, Schreiber and Lange 1984). (2) Following heat treatment, there is a decrease in variable fluorescence, Fvar, as measured upon illumination at room temperature (Krause and Santarius 1975; Santarius and Muller 1979). In isolated chloroplasts this decrease in variable fluorescence has been correlated with damage to the watersplitting system (Yamashita and Butler 1968). (3) Mild heat treatment, which does not cause irreversible tissue damage, induces changes in the low temperature fluorescence emission spectra indicative of a heat induced state I – state II shift, i.e. of a change in energy distribution in favor of photosystem I (Weis 1984,1985).

The modulation of visceral functions by somatic afferent activity.

Abstract: We began by briefly reviewing the historical background of neurophysiological studies of the somato-autonomic reflexes and then discussed recent studies on somatic-visceral reflexes in combination with autonomic efferent nerve activity and effector organ responses. Most of the studies that have advanced our knowledge in this area have been carried out on anesthetized animals, thus eliminating emotional factors. We would like to emphasize again that the functions of many, or perhaps all visceral organs can be modulated by somato-sympathetic or somato-parasympathetic reflex activity induced by a appropriate somatic afferent stimulation in anesthetized animals. As mentioned previously, some autonomic nervous outflow, e.g. the adrenal sympathetic nerve activity, is involved in the control of hormonal secretion. John F. Fulton wrote in his famous textbook "Physiology of the Nervous System" (1949) that the posterior pituitary neurosecretion system (i.e. for oxytocin and vasopressin) could be considered a part of the parasympathetic nervous system. In the study of body homeostasis and environmental adaptation it would seem very important to further analyze the contribution of somatic afferent input to the autonomic nervous and hormonal regulation of visceral organ activity. Also, some immunological functions have been found to be influenced by autonomic nerves or hormones (e.g. adrenal cortical hormone and catecholamines). Finally, we must take into account, as we have briefly discussed, that visceral functions can be modulated by somatic afferent input via various degrees of integration of autonomic nerves, hormones, and immunological processes. We trust that such research will be expanded to higher species of mammals, and that ultimately this knowledge of somato-visceral reflexes obtained in the physiological laboratory will become clinically useful in influencing visceral functions.

Changes during summer drought in leaf CO2 uptake rates of macchia shrubs growing in Portugal: Limitations due to photosynthetic capacity, carboxylation efficiency, and stomatal conductance

Abstract: The classically described stresses to which plants are subjected in mediterranean type climates are water stress and heat stress during the summer and cold stress during the winter. The general behavioral tendencies in gas exchange of leaves of shrubs subjected to these climate conditions were summarized nicely by Larcher (1961).

Bioactivation of tetrachloroethylene. Role of glutathione S-transferase-catalyzed conjugation versus cytochrome P-450-dependent phospholipid alkylation.

Abstract: The metabolism of [14C]tetrachloroethylene (Tetra) and its metabolite S-(1,2,2-trichlorovinyl)-L-cysteine (TCVC) was investigated with in vitro systems to substantiate metabolic pathways of Tetra deduced from in vivo experiments. In the presence of NADPH, rat hepatic microsomal fractions metabolized Tetra to soluble metabolites, which were identified as trichloroacetic acid and oxalic acid by gas chromatography/mass spectroscopy and a metabolite largely bound to microsomal macromolecules. The majority of the alkylated macromolecules were identified as N-trichloroacetylated phospholipids by high performance liquid chromatography and GC/MS. When Tetra was incubated with hepatic microsomes and cytosol in the presence of 10 mM glutathione, but in the absence of NADPH, the formation of a polar metabolite other than trichloroacetic acid and oxalic acid was observed. This metabolite was identified, after hydrolysis to the corresponding cysteine conjugate, as S-(1,2,2-trichlorovinyl)-glutathione (TCVG). Microsomal GSH S-transferases catalyzed TCVG formation more efficiently than cytosolic GSH S-transferases; the competitive substrate 1-chloro-2,4-dinitrobenzene inhibited TCVG formation. In the presence of both NADPH and GSH, TCVG formation in microsomes was decreased, indicating that oxidative metabolism and GSH conjugation of Tetra are competitive reactions. The Tetra metabolite TCVC was cleaved by bacterial cysteine conjugate b-lyase to dichloroacetic acid and pyruvate. The obtained results substantiate the postulated pathways of Tetra biotransformation and demonstrate that both oxidative and conjugative reactions occur in hepatic Tetra metabolism. Phospholipid alkylation, which occurs during oxidative metabolism, may be a deactivation reaction, whereas TCVG formation, renal metabolism to TCVC, and cleavage of TCVC by b-lyase under formation of mutagenic intermediates may contribute to the nephrocarcinogenic effect of Tetra.