Ultracytochemical identification of catecholamine-containing vesicles in the ligated sciatic nerve of the rat. Comparison with sympathetic nerve terminals

Summary Using the fixation procedure of Tranzer, three kinds of granular vesicles were identified in certain unmyelinated fibres of rat sciatic nerves proximal to a ligature: (1) small vesicles (SGV: 30–60 nm in diameter), (2) large vesicles (LGV: 60–100nm in diameter), and (3) large elongated vesicles (LEV: 60–100nm in diameter). A comparative study concerning the distribution of these granular vesicles was carried out using a cytopharmacological method (reserpine) and employing different fixatives (aldehydes + OsO₄, or OsO₄ alone) in periarterial nerve plexus of the femoral artery, vas deferens and the pineal organ.Use of Tranzer's method allows preservation in almost all granular vesicles of a strongly electron-dense core, while with the other fixatives mainly small, eccentric dense cores occur in the vesicles. Two main features were observed in ligated sciatic nerves: (i) a clear increase in the number of LGV, and (ii) the presence of LEV, considered as a variety of LGV rather than a new population of granular vesicles. Reserpine caused the cores of SGV to disappear almost completely, while LGV and LEV remained only partly depleted. The original method combining Tranzer's fixation procedure with radioautography revealed radioautographic labelling only in the unmyelinated fibres of ligated sciatic nerves and mainly superimposed over SGV, LGV and LEV. It is suggested that (i) SGV, LGV and also LEV represent possible storage sites of catecholamines, and (ii) a local morphogenesis of SGV from the large vesicles occurs in ligated sympathetic nerve fibres.     

Regulation of the efficacy of adrenergic synaptic transmission by adrenergic autoreceptors in rat brain slices

A mathematical model was developed based on the putative functional role of adrenergic autoreceptors for quantifying processes of synaptic depression, facilitation, stabilization of PSP amplitude, and rise in this amplitude produced by increased stimulation rate. Synaptic depression and facilitation are brought about by activation of - and -adrenergic autoreceptors respectively. A "steady release zone" is found between curves of adrenergic autoreceptor activity and this is responsible for stabilizing noradrenaline release during a series of presynaptic impulses. Experimental findings on labeled noradrenaline (³H-NA) release from rat brain slices showed that adrenergic autoreceptors do in fact form a stable release zone responsible for autofacilitation and stabilization of³H-NA release produced by 5-fold consecutive K⁺ depolarizations of slices spaced 30 min apart. Lack of a stable release zone in curves showing adrenergic autoreceptor activity produces destabilization of³H-NA release. These curves (together with the stable release zone) shift in the direction of high noradrenaline concentrations when stimulus intensity is increased.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 19, No. 3, pp. 390–399, May–June, 1987.     

Changes in the quantities of violaxanthin de-epoxidase,xanthophylls and ascorbate in spinach upon shift from low to high light

Zeaxanthin, a carotenoid in the xanthophyll cycle, has been suggested to play a role in the protection against photodestruction. We have studied the importance of the parameters involved in zeaxanthin formation by comparing spinach plants grown in low light (100 to 250 mol m^-2 s^-1) to plants transferred to high light (950 mol m^-2 s^-1). Different parameters were followed for a total of 11 days. Our experiments show that violaxanthin de-epoxidase decreased between 15 and 30%, the quantity of xanthophyll cycle pigments doubled to 100 mmol (mol Chl)^-1, corresponding to 27 mol m^-2, and the rate of violaxanthin to zeaxanthin conversion was doubled. Lutein and neoxanthin increased from 50 to 71 mol m^-2 and from 16 to 23 mol m^-2, respectively. On a leaf area basis, chlorophyll and -carotene levels first decreased and then after 4 days increased. The chlorophyll a/b ratio was unchanged. The quantity of ascorbate was doubled to 2 mmol m^-2, corresponding to an estimated increase in the chloroplasts from 25 to 50 mM. In view of our data, we propose that the increase in xanthophyll cycle pigments and ascorbate only partly explain the increased rate of conversion of violaxanthin to zeaxanthin, but the most probable explanation of the faster conversion is an increased accessibility of violaxanthin in the membrane.     

The hypothalamo-hypophysial system in acipenseridae

Summary The distribution of adrenergic and peptidergic (Gomori-positive) structures of the hypophysial neuro-intermediate complex in Acipenseridae has been studied by means of light, fluorescence, and electron microscopy. Adrenergic fibres (B-fibres) and their terminals have been detected in the neurohypophysis of these fishes. The terminal swellings of B-fibres as well as the terminals of the neurosecretory peptidergic fibres (A₁ and A₂) make contact with the basement membrane of the connective tissue layer separating the neurohypophysis from the intermediate lobe. Capillaries are situated within this layer and, therefore, the main part of the fibre terminals is in contact with the pericapillary space. The release of catecholamines from the adrenergic terminals into the capillaries connected with the general circulation is supposed. The diffusion of catecholamines through the connective tissue layer into the parenchyma of the intermediate lobe is also suggested. Hence, the glandular activity of the intermediate lobe seems to be under the dual control of adrenergic and peptidergic elements of the hypothalamus.The authors wish to express their deep appreciation to G. M. Persov, Dr. Sc. Biol., Head of the Laboratory of Experimental Ichthyology, Petershof Biological Institute of the University of Leningrad, for the material supplied for fluorescence microscopy, and to Mr. G. V. Sabinin for photographic services.     

L'innervation monoaminergique de l'Eminence Médiane — Etude radioautographique et pharmacologique chez le CanardAnas platyrhynchos

Résumé Dans l'Eminence Médiane du Canard, la Noradrénaline et la Dopamine tritiées sont captées et retenues auniveau de la zone interne et en périphérie des vaisseaux portes hypophysaires. Cette rétention, observée par radioautographie après incubation in-vitro ou injection intraventriculaire des médiateurs, est considérablement diminuée par la réserpine. Une ou deux injections intraventriculaires de 6-Hydroxy-Dopamine laissent subsister quelques fibres capables de capter la Noradrénaline-³H. Après trois injections de 6-Hydroxy-Dopamine, on n'observe plus aucune incorporation du médiateur.Ces données radioautographiques et pharmacologiques attestent que les fibres de la zone interne de l'Eminence Médiane, qui captent la Noradrénaline et ses précurseurs et qui sont détruites par la 6-Hydroxy-Dopamine, sont de nature catécholaminergique.En microscopie électronique, on constate que les fibres marquées contiennent des vésicules de types divers avec fréquemment un coeur dense excentré. Ces fibres présentent des contacts synaptiques avec des dendrites ou péricaryons neuronaux qui ne retiennent pas le traceur et qui reçoivent également d'autres afférences synaptiques non marquées. Ce fait permet d'établir que les neurones infundibulaires présents dans l'Eminence Médiane sont susceptibles d'une régulation mettant en jeu des catécholamines et d'autres types de neurotransmetteurs.

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Monoaminergic innervation of the median eminence—Radioautographic and pharmacological study in the duck,Anas platyrhynchos I. Catecholaminergic innervation

Summary When³H-norepinephrine or³H-dopamine are given to the median eminence of the Duck after an injection into the IIIrd ventricle or afterin vitro incubation, an intense and preferential accumulation of the tracer is observed in the internal zone and in the vicinity of the primary portal vessels.The amount of labeled catecholamines in the median eminence is greatly diminished by reserpine. After one or two injections of 6-hydroxy-dopamine into the third ventricle followed by application of³H-norepinephrine, only a few fibers are labeled; after three injections of this drug, nearly no uptake of³H-norepinephrine is seen.This radioautographic and pharmacological approach indicates that the axons of the internal zone of the median eminence, which are able to take up and store labeled norepinephrine and its precursors and which are destroyed by 6-hydroxy-dopamine, are catecholaminergic.The ultrastructural examination of the internal zone shows that the label is confined to axonal varicosities containing various types of vesicles possessing frequently an eccentric core. The labeled axonal varicosities were found in synaptic contact with unlabeled dendrites and also with unlabeled perikarya. The postsynaptic structures which receive labeled presynaptic axons display also synaptic contacts with other unlabeled axons. This fact suggests that neurons of the median eminence are probably modulated by catecholamines and other neurotransmitters either on their dendrites and even on their soma.

Avec la collaboration de Melle. S. Bosc.     

Cellular localization of monoamines in the median eminence and the infundibular stem of some mammals

Summary A histochemical analysis of the monoamines which are strongly accumulated in the median eminence and the proximal part of infundibular stem of all species examined (mouse, rat, guinea pig, hamster, rabbit, and cat) was performed with the help of a highly specific and sensitive fluorescence method. Strong evidence was obtained for the view that the monoamines are localized in very high concentrations to the terminal parts of non-sympathetic nerve fibres, which — mainly at least — converge to the primary plexus of the hypophyseal portal system. The capillaries are densely and closely surrounded by the nerve fibres.Pharmacological experiments, involving the administration of reserpine, nialamide, m-tyrosine and -methyl-m-tyrosine, furnished good evidence for the view that primary catecholamines, probably mainly DA but also NA, are the predominant monoamines present. The experiments also revealed the existence of catecholamine-containing nerve cells in the arcuate nuclei and the ventral portion of the anterior periventricular nuclei. These nerve cells, situated in the regions where the tubero-infundibular tract arises, may be the cell bodies of adrenergic neurons to which the amine-containing nerve fibres at least partly belong.The findings indicate that primary catecholamines are released to the primary plexus of the hypophyseal portal system and thus transported to the anterior lobe. These amines may consequently act as neuro-humoral transmittors for the regulation of the activity of the anterior pituitary. — No direct adrenergic innervation of the cells in the pars tuberalis and anterior lobe was found. The portal vesstes in the pars tuberalis receive a very sparse adrenergic innervation and the vessels in the anterior lobe receive no or very few adrenergic nerves. Pars intermedia, on the other hand, may have a non-sympathetic adrenergic innervation.The Following Abbreviations are Used DA Dopamine - NA Noradrenaline - A Adrenaline - 5-HT 5-hydroxytryptamine For generous supplies of drugs we are indepted to Swedish Ciba, Stockholm (reserpine), and Swedish Pfizer, Stockholm (nialamide). The investigation was supported by research grants from the United States Public Health Service (NB 02854-03), the Swedish Medical Research Council, and the Therese and Johan Andersson Memorial Foundation. The excellent technical assistance of Miss M. Gustafsson is gratefully acknowledged.     

Cytofluorometric quantitation of apoptosis-driven inner mitochondrial membrane permeabilization

The mitochondrial matrix can be specifically labeled by loading cells with calcein and simultaneous quenching of the non-mitochondrial calcein fluorescence with cobalt (Co²⁺). Positive staining of mitochondria thus requires that the inner mitochondrial membrane functions as a barrier separating calcein (within the matrix) from Co²⁺ (outside of the matrix). Upon induction of apoptosis, such calcein/Co²⁺-labeled cells, demonstrate a decrease in the overall calcein fluorescence resulting from inner mitochondrial membrane permeabilization. This decrease can be quantified by cytofluorometry and can be dissociated from other apoptosis-associated mitochondrial perturbations such as the loss of the mitochondrial transmembrane potential ( _m ), the local overproduction of reactive oxygen species, and the mitochondrial release of cytochrome c. In some paradigms of apoptosis the loss of calcein/Co²⁺ (CC) staining can be dissociated from the _m loss, both of which may occur in a caspase-dependent or caspase-independent fashion, depending on the apoptosis inducer. Importantly, inner membrane permeabilization to CC may occur without a permanent _m dissipation in apoptosis, suggesting that transient permeabilization events could participate at the apoptotic cascade. Altogether, our data demonstrate that inner mitochondrial membrane permeabilization constitutes an early event in the apoptotic cascade.     

Mitochondria in fine afferent nerve fibres of the knee joint in the cat: a quantitative electron-microscopical examination

The distribution of mitochondria, their content and concentration (expressed as the ratio of the mean volume of mitochondria and the surface of the sensory axon) were determined in group-III and-IV nerve fibres innervating the knee joint capsule in the cat. Mitochondria mainly accumulated in axonal swellings (beads) and end bulbs of the terminal branches. Between single nerve fibres, marked differences in the content and the concentration of mitochondria were obtained in proximal portions (inside of the perineurium) and in distal portions (unmyelinated sensory endings). In group-III nerve fibres, the mitochondrial concentration ranged from 0.005 to 0.030 m³/m² (proximal portion) and from 0.016 to 0.080 m³/m² (distal portion). In unmyelinated group-IV nerve fibres, the values also showed a broad variation ranging from 0.001 to 0.011 m³/m² (proximal portion) and from 0.003 to 0.019 m³/m² (distal portion). The wide range of mitochondrial concentrations may reflect different energy consumption during receptive processes: nerve fibres with a low mechanical threshold and a high probability of excitatory events may be rich in mitochondria, whereas fibres with a high mechanical threshold and a low probability of excitatory events may be poor in mitochondria.     

AT-1 Receptor and Phospholipase C Are Involved in Angiotensin III Modulation of Hypothalamic Noradrenergic Transmission

SUMMARY 1. We previously reported that angiotensin III modulates noradrenergic neurotransmission in the hypothalamus of the rat. In the present work we studied the effects of angiotensin III on norepinephrine release and tyrosine hydroxylase activity. We also investigated the receptors and intracellular pathways involved in angiotensin III modulation of noradrenergic transmission.2. In rat hypothalamic tissue labeled with [³H]norepinephrine 1, 10, and 100 nM and 1 M losartan (AT1 receptor antagonist) had no effect on basal neuronal norepinephrine release, whereas 10 and 100 nM and 1 M losartan partially diminished norepinephrine secretion evoked by 25 mM KCl. The AT2 receptor antagonist PD 123319 showed no effect either on basal or evoked norepinephrine release. The increase in both basal and evoked norepinephrine output induced by 1 M angiotensin III was blocked by 1 M losartan, but not by 1 M PD 123319.3. The phospholipase C inhibitor 5 M neomicin inhibited the increase in basal and evoked norepinephrine release produced by 1 M angiotensin III.4. Tyrosine hydroxylase activity was increased by 1 M angiotensin III and this effect was blocked by 1 M LST and 5 M neomicin, but not by PD 123319. On the other hand, 1 M angiotensin III enhanced phosphatidyl inositol hydrolysis that was blocked by 1 M losartan and 5 M neomicin. PD 123319 (1 M) did not affect ANG III-induced phosphatidyl inositol hydrolysis enhancement.5. Our results confirm that angiotensin III acts as a modulator of noradrenergic transmission at the hypothalamic level through the AT1-phospholipase C pathway. This enhancement of hypothalamic noradrenergic activity suggests that angiotensin III may act as a central modulator of several biological processes regulated at this level by catecholamines, such as cardiovascular, endocrine, and autonomic functions as well as water and saline homeostasis.     

On the ultrastructural localization of catecholamines in the beta lobes (corpora pedunculata) of Periplaneta americana

Summary In the brain of the cockroach Periplaneta americana, the beta lobes of the corpora pedunculata respond with an intense positive reaction to a specific fluorescence histochemical method for catecholamines. The fluorescence reaction disappears completely after prolonged treatment of the cockroaches with reserpine. An ultrastructural examination of the beta lobes in formaldehyde-glutaraldehyde-osmium fixed preparations reveals the presence of two types of fibres: 1) Fibres and nerve endings containing small clear vesicles and sligthly larger vesicles with a semi-dense content. The appearance and size distribution of these vesicles ist not affected by treatment with reserpine. 2) Fibres containing larger and denser vesicles, but practically no clear vesicles. The size distribution of these dense vesicles is only slightly affected by treatment of the cockroaches with reserpine.If brain slices are incubated in a medium containing noradrenaline or -methyl-noradrenaline and fixed in permanganate, small vesicles with electron-dense central cores show up, similar to those which have been described in vertebrate adrenergic nerve fibres (small granular vesicles). They are confined to one of the two types of fibres (a and b) visible in these preparations, namely to type b, whose correspondence with type 2 fibres of formaldehyde-glutaraldehyde-osmium fixed preparations is discussed.The authors wish to thank Mr. E. Chessa and Mr. F. Piccirilli for technical assistance in photography.     

Sympathetic nervous control of the vasculature in the tail of the Atlantic cod,Gadus morhua

Summary The effects of some drugs and electrical stimulation of the sympathetic chain on the vasculature of the isolated perfused tail of the cod has been studied. Adrenaline, phenylephrine and isoprenaline all constricted the tail vasculature, isoprenaline also producing dilation in some preparations at lower concentrations (10^–9–10^–6M). Electrical stimulation of the sympathetic chain produces vasoconstriction, which can be abolished by phentolamine in concentrations expected to be selective for -adrenoceptor blockade in the cod. A small dilatory response to nerve stimulation was seen in some preparations after phentolamine. Carbachol produced weak and irregular effects, and a contribution by cholinergic fibres therefore seems unlikely. It is concluded that the excitatory nervous control of the cod tail vasculature is solely by adrenergic sympathetic fibres, which act via an -adrenoceptor mechanism.     

External adrenergic innervation of the three neuron types of dogiel in the plexus myentericus and the plexus submucosus externus of the porcine small intestine

Summary For the simultaneous demonstration of intramural enteric ganglion cells and the adrenergic nerve fibres in the porcine small intestine a combined histochemical method was developed using a hypertonic solution, the main chemicals of which were glyoxylic acid, Nitro-BT^* and NADH. By means of the enzymatic histochemical method reaction for the NADH-dependent dehydrogenase activity with Nitro-BT as an electron acceptor, the identification of the three neuron types of Dogiel (i.e. type I, type II, type III) was for the first time realized in relation with the glyoxylic acid induced fluorescence (GIF) of the plexus myentericus (Auerbach) and the plexus submucosus externus (Schabadasch). Besides the close topographic relationship between the adrenergic varicose axons on the one hand and the perikarya and dendrites of the multidendritic uniaxonal type I cells characterized by radially oriented short and lamellar dendrites and the multidendritic uniaxonal type III cells, characterized by radially oriented long and tapering dendrites on the other hand, it is striking that for the adendritic multiaxonal type II cells the fluorescent varicose fibres adhere closer to the cell bodies and their processes. In principle, the relation between adrenergic varicose axons and neuron types is identical in plexus myentericus (Auerbach) and plexus submucosus externus (Schabadasch), yet with the exception that in the latter no type I neurons are observed.2,2-Di-p-nitrophenyl-5,5-diphenyl-3,3-(3,3-dimethoxy-4,4-diphenylene) ditetrazolium chloride     

Uptake and accumulation in vitro of 3H-noradrenaline in adrenergic nerves of human atrium

Summary The adrenergic innervation and the in vitro uptake of ³H-noradrenaline has been investigated in human atrial tissue slices from patients undergoing thoracic surgery. The atrial appendage was richly innervated, but the density of the adrenergic nerve plexus varied considerably between different tissues examined. The nerve terminals were of characteristic varicose appearance, running singly or in bundles along the long axis of the muscle fibers. The nerve fibers seemed to penetrate in between the muscle cells. The distribution and appearance of the adrenergic nerves were quite similar to those described in earlier investigations of heart tissue from other species. The uptake and accumulation of ³H-noradrenaline in vitro increased with increasing concentration in the medium and with time, and the uptake process could efficiently be blocked by desmethylimipramine (DMI), a potent inhibitor of the uptake mechanism located at the axonal membrane, the so called membrane pump. There was a true accumulation of ³H-noradrenaline in the atrial tissue during the incubation, compared to the medium. The metabolism of ³H-noradrenaline during the incubation has also been studied. The data presented speak in favour of the view that the adrenergic nerves of human atria possess an efficient uptake accumulation mechanism for noradrenaline.Abbreviations used DMI desmethylimipramine - NA noradrenaline - NM normetanephrine     

Histochemical characteristics of chemoreceptor organs (Glomera)

Summary Some important histochemical characteristics of the carotid, aortic and coronary glomera have been studied in man and the rabbit.All glomera present a similar histochemical pattern. Type I glomus cells contain acetylcholinesterase, monoamine oxidase and norepinephrine. Type II glomus cells are highly positive for cholinesterase, carbonic anhydrase and nucleoside phosphatases hut they do not contain acetylcholinesterase nor catecholamines. It is postulated that the type I glomus cell is the true chemoreceptor cell. Together with the type II glomus cell, which is considered to be a special type of glial cell, a functional metabolic unit is established. Efferent nerve fibres could be adrenergic; by way of cholinergic transmission action potentials could be initiated in the afferent nerve fibres.The following Abbreviations will be used AChE acetylcholinesterase - ChE cholinesterase - iso-OMPA tetraisopropylpyrophosphoramide - DFP di-isopropylfluorophosphate - 62C47 15-bis-(4-trimethylammonium-phenyl) pentan-3-one-diiodide - CAH carbonic anhydrase - ATP-ase adenosine triphosphatase - NP-ases nucleoside phosphatases - UDP uridine diphosphate - UTP uridine triphosphate - IDP inosine diphosphate - CTP cytidine triphosphate - CaFoMa calcium-formol-macrodex - Glut glutaraldehyde - TPP-ase thiamine pyrophosphatase - MAO monoamine oxidase - CA catecholamines - NE norepinephrine     

Remarkable adrenergic nerves in the exocrine pancreas

Summary The adrenergic nerves in the pancreas of mice, rats, guinea-pigs, rabbits, and cats were investigated with the fluorescence method of Falck and Hillarp. The relations between the adrenergic fibres and the vessels were studied by the injection of india ink into the vessels.Besides the normal manifestation of adrenergic fibres at the large vessels, some vessels of capillary size were also accompanied by adrenergic fibres. These fibres had a very weak fluorescence, and showed up regularly only when the animal had been treated with Nialamide and L-DOPA or dopamine to increase the catecholamine content of the adrenergic fibres. The weakness of the fluorescence is perhaps due to low transmitter concentration or to small size of the nerve fibres, or to both. A rough estimate indicated that either the transmitter concentration of the nerve fibre is at least approximately 100 times below that seen in adrenergic nerves in other tissues, or that the radius of the varicosities of the nerve fibres is less than 0.2 . Neither alternative has previously been recognized.The secretory acini of the pancreas seem to lack a direct adrenergic supply. In the intrapancreatic ganglia, non-fluorescent nerve cells were reached by adrenergic terminals. No adrenergic nerve cells were detected in the pancreas of rats and cats. Small intensely fluorescent catecholamine-containing cells were observed in connexion with the intrapancreatic ganglia of rats.The research reported in this document has been sponsored by the Air Force Office of Scientific Research under grant AF EOAR 67-15 through the European Office of Aerospace Research (OAR), United States Air Force, by the United States Public Health Service (grant NB 06701-01) by the Swedish Medical Research Council (project B 67-12X-712-02A), and by the Faculty of Medicine, University of Lund, Sweden.     

Elucidation of the origin of multiple conformations of the human α3-chain type VI collagen C-terminal Kunitz domain: The reorientation of the Trp21 ring

Summary The human 3-chain type VI collagen C-terminal Kunitz domain fragment (3(VI)) has been studied by two-dimensional ¹H–¹H and ¹H–¹³C NMR spectroscopy at 303 K. It is shown that the secondary structure of the protein is strikingly similar to that of BPTI, and that a number of unusual H chemical shifts, which are highly conserved in Kunitz-domain proteins, are also observed for 3(VI). Further-more a series of exchange cross peaks observed in ¹H–¹H spectra shows that a large number of protons in the central -sheet exist in two different chemical environments, corresponding to two unequally populated conformations that are slowly exchanging on the NMR time scale. Several protons, including Ser⁴⁷⁽⁵³⁾ H, Arg³²⁽³⁸⁾ H², and Gln⁴⁸⁽⁵⁴⁾ H², all located in the vicinity of the Trp²¹⁽²⁷⁾ ring in the crystal structure of 3(VI) [Arnoux, B. et al. (1995) J. Mol. Biol., 246, 609–617], have very different chemical shifts in the two conformations, the most affected being Gln⁴⁸⁽⁵⁴⁾ H² (=1.53 ppm), which is placed directly above the Trp²¹⁽²⁷⁾ ring in the crystal structure of 3(VI). It is concluded that the origin of the multiple conformations of the central -sheet is a reorientation of the Trp²¹⁽²⁷⁾ ring. From the intensities of corresponding signals in the two conformations, the population of the minor conformation was found to be 6.4±0.2% of that of the major conformation, while a rate constant k_M=1.01±0.05 s^-1 for the major to minor interconversion was obtained from a series of NOESY spectra with different mixing times. In addition, it is shown that Cys¹⁴⁽²⁰⁾-Cys³⁸⁽⁴⁴⁾ disulfide bond isomerization, previously observed in BPTI [Otting, G. et al. (1993) Biochemistry, 32, 3570–3582], is also likely to occur in 3(VI).     

Electrical properties of parenchymal cell membranes in the oat coleoptile

Summary Parenchymal cells of oat (Avena sativa) coleoptiles had an osmotic concentration of 410 mM (determined by plasmolysis); of this only 22 mM was K⁺ and 1 mM Na⁺ (flame photometry). Cells were impaled with micropipette electrodes. Iontophoretic injection of the dye Niagara sky-blue from the micropipette showed that the tip of the electrode penetrated the vacuole. When sections of tissue were immersed in a solution of 22 mM KCl, 1 mM CaCl₂, and 50 mM glucose, average membrane potential was found to be 38.5 mV inside negative specific membrane resistance was 510 cm², and specific membrane capacitance, 2 f cm^-2. The cell membranes showed <25% retification and no electrical excitability. Electrotonic coupling of adjacent cells could not be demonstrated.     

Autonomic nervous control of blood pressure and heart rate during hypoxia in the cod,Gadus morhua

Summary The autonomic nervous and possible adrenergic humoral control of blood pressure and heart rate during hypoxia was investigated in Atlantic cod. The oxygen tension in the water was reduced to 4.0–5.3 kPa (i.e.. P_wO₂=30–40 mmHg), and the fish responded with an immediate increase in ventral and dorsal aortic blood pressure (P _va P _da), as well as a slowly developing bradycardia. The plasma concentrations of circulating catecholamines increased during hypoxia with a peak in the plasma level of noradrenaline occurring before the peak for adrenaline. Bretylium was used as a chemical tool to differentiate between neuronal and humoral adrenergic control of blood pressure and heart rate (f _H) during hypoxia. The increase in P _va and P _da in response to hypoxia was strongly reduced in bretylium-treated cod, which suggests that adrenergic nerves are responsible for hypoxic hypertension. In addition, a small contribution by circulating catecholamines to the adrenergic tonus affecting P _va during hypoxia was suggested by the decrease in P _va induced by injection of the -adrenoceptor antagonist phentolamine. The cholinergic and the adrenergic tonus affecting heart rate were estimated by injections of atropine and the -adrenoceptor antagonist sotalol. The experiments demonstrate an increased cholicholinergic as well as adrenergic tonus on the heart during hypoxia.     

Ultrastructure and innervation of the swimbladder of Tetractenos glaber (Tetraodontidae)

Summary The general structure, ultrastructure and innervation of the swimbladder of the smooth toadfish, Tetractenos glaber, were examined with light-microscopic, fluorescence-histochemical, and transmission electron-microscopic techniques. The structure of the swimbladder is similar to that of other euphysoclists. Fluorescence histochemistry showed adrenergic fibres in both the secretory and resorptive areas of the swimbladder. Transmission electron microscopy revealed two morphologically distinct axon profiles type-I profiles containing many small, flattened vesicles; type-II profiles containing both large, granular vesicles and rounded, small clear vesicles in varying proportions.The gas-gland cells and surrounding muscularis mucosae are innervated by both type-I and type-II fibres. Type-I fibres also innervate pre-rete arteries. The rete- and gas-gland capillaries do not appear to be innervated. Arteries running to the resorptive area are innervated by type-I fibres. Both type-I and type-II profiles make contact with the muscularis mucosae in the resorptive area. Only type-I fibres innervate the radial dilator muscle in the oval sphincter region, whereas only type II fibres innervate the circular muscle of the oval sphincter.Type-I fibres took up -methyl-noradrenaline, and could not be found after pre-treatment with 6-hydroxydopamine. They are, therefore, assumed to be adrenergic. Type-II fibres were tentatively identified, by exclusion, as cholinergic.