NPY-, galanin-, VIP/PHI-, CGRP- and substance P-immunoreactive neuronal subpopulations in cat autonomic and sensory ganglia and their projections

Summary The neuronal subpopulations in the cat stellate, lower lumbar and sacral sympathetic ganglia were studied with regard to the cellular distribution of immunoreactivity to tyrosine hydroxylase (TH), acetylcholinesterase (AChE) and various neuronal peptides. Coexistence of neuropeptide Y (NPY)- and galanin (GAL)-like immunoreactivity (LI) was found in a high proportion of the neuronal cell bodies; these cells also contained immunoreactivity to TH, confirming their presumably noradrenergic nature. Some TH- and GAL-immunoreactive principal ganglion cells lacked NPY-LI. Two populations (scattered and clustered) of vasoactive intestinal polypeptide (VIP)- and peptide histidine isoleucine (PHI)-positive cell bodies were found in the sympathetic ganglia studied. The scattered VIP/PHI neurons also contained AChE-LI, calcitonin gene-related peptide (CGRP)-and, following culture, substance P (SP)-LI. The clustered type only contained AChE-LI. In the submandibular and sphenopalatine ganglia, neurons were AChE- and VIP/ PHI-immunoreactive but lacked CGRP- and SP-LI. Many GAL- and occasional TH-positive neurons were found in these ganglia. In the spinal ganglia, single NPY-immunoreactive sensory neuronal cells were observed, in addition to CGRP- and SP-positive neurons. The present results show that there are at least two populations of sympathetic cholinergic neurons in the cat. Retrograde tracing experiments indicate that the scattered type of cholinergic neurons contains four vasodilator peptides (VIP, PHI, CGRP, SP) and provides an important input to sweat glands, whereas the clustered type (containing VIP and PHI) mainly innervates blood vessels in muscles.     

The effect of an intermittent water-table gradient on soil and xylem nitrate in cotton

Summary Cotton (Gossypium hirsutum cv Deltapine 61) was grown in a sloping plot of soil in the field to examine the effect of a gradient of water-table depth on soil nitrate availability and plant uptake during two periods of the growing season. Before the water-table was imposed NO₃ was less concentrated at the lower end of the sloping plot. This was attributed to slow denitrification at microsites within the soil at the lower end which was wetter than further up the plot. At flooding NO₃ disappeared only slowly due to a carbon substrate limitation to denitrification in the soil. This loss occurred primarily in areas where the water-table was high and oxygen concentration in the soil solution was low. Plant NO₃ uptake, assessed by measuring the concentration in the xylem, parallelled the distribution of NO₃ in the soil solution. Under high water-tables xylem NO₃ levels fell but it was not possible to say whether this was due to impaired root function or to the reduced concentration of NO₃ observed in the soil solution. At intermediate water-table depths where soil NO₃ availability remained high xylem NO₃ concentration fell relative to the well drained control plants, suggesting that flooding had damaged the root system.Manufactured by Merck. Mention of commerical names does not imply endorsement by either CSIRO or USDA.     

Peroxidase-mediated integration of tyramine into xylem cell walls of tobacco leaves

When [2-¹⁴C]tyramine was fed in vivo by petiolar uptake to Nicotiana tabacum Xanthi n.c. leaves partially inoculated with tobacco mosaic virus, radioactivity accumulated in inoculated areas bearing necrotic lesions, mainly in the veins and around the lesions. Light-microscopic autoradiography showed that integration of radioactivity was especially evident in xylem cell walls. This was confirmed in sections of petiole by electron-microscopic autoradiography. Study of the mechanism of insolubilisation of tyramine showed that the amine was integrated in regions in which peroxidase activity could be located cytochemically using 3,3-diaminobenzidine and H₂O₂ as substrates. When sections of petiole were incubated with labelled tyramine and H₂O₂ after fixation in glutaraldehyde, a distribution of radioactivity similar to that obtained after feeding tyramine by petiolar uptake was observed. It is concluded that simple phenols such as tyramine can be integrated in vivo into cell walls because they are oxidised by peroxidases. This result illustrates the difficulty of studying the metabolism of exogenous phenols in plants, especially in lignifying tissues which contain active wall-bound peroxidases.Abbreviations DAB 3,3-diamino-benzidine - TMV tobacco mosaic virus     

Soil and plant resistances to water uptake byVicia faba L.

Summary The hydraulic resistivity ofVicia faba L. roots grown in soil was estimated from steady state measurements of transpiration rate and leaf and soil water potentials. Root and stem axial resistivities, estimated from xylem vessel radii, were negligible. Root radial resistivity was estimated to be 1.3×10¹² sm⁻¹. This root radial resistivity value was used to estimate, root resistance to water uptake for a field crop ofVicia faba. Previously published results were used for root distribution and soil water contents at the drained upper limit (DUL) and the lower limit (LL) of extractable soil water. Soil resistance to water uptake was estimated from single root theory using the steady rate solution. At the DUL, root resistance was about 10⁵ times greater than soil resistance. At the LL, soil resistance exceeded root resistance for depths less than 0.3 m, but for depths greater than this soil resistance was smaller than root resistance. Estimates of possible uptake rates at given leaf water potentials indicated that overall soil resistance had a negligible influence upon uptake, even at the LL. The reliability of this result is examined in detail. It is concluded that over the complete range of extractable soil water contents soil resistanceper se would not have limited water use by this crop. This conclusion may also be valid for a wide range of soil and crop combinations.     

Nitrogen retranslocation in plants of maize,lupin and cocklebur

Summary In a split root experiment translocation of N from shoot to root was studied using¹⁵NO ₃ ^– . The three plant species selected for this experiment differed significantly with respect to root NRA. For lupin, maize and cocklebur about 80, 50 and 6% of all absorbed NO ₃ ^– was assmilated in the roots, respectively.Although NO ₃ ^– was reduced in the roots of lupin and maize plants to a greater extent than required for the roots' demand for organic N, a significant phloem flow of N from shoot to roots was found in these plants. Unexpectedly, for cocklebur, the plant with the very low root NRA, the fraction of total N present in the root that has been imported from the shoot was only half that as found for lupin and maize.     

Glucomannan-synthase activity in differentiating cells of Pinus sylvestris L.

Particulate membrane preparations have been isolated from cambial cells, and from differentiating and differentiated xylem cells of the main stem of pine trees. These preparations synthesise a 14 glucomannan from guanosine 5-diphosphate-mannose. The polysaccharide and the synthase have been characterized and the K_m and V_max for the synthase determined as 85 M and 52.9 M·min^-1, respectively. The enzymic activity was inhibited by the addition of guanosine 5-diphosphate-D-glucose so that the presence of an epimerase on the particulate fraction in conjunction with the synthase probably allowed the heteropolymer to be formed with the optimal ratio of the concentrations of the nucleoside-diphosphate sugar donors. No evidence for a polyprenyl-phosphate derivative as an intermediate during the polymer synthesis was obtained. Part of the control mechanism for the deposition of the large amounts of the glucomannan during the secondary thickening of the tracheids of the vascular system is by an increase in the amount of synthase activity at the endomembrane system of the cells. This probably occurs by an increase in the amount of enzyme which is modulated by gene regulation during differentiation.Abbreviations GDP guanosine 5-diphosphate - GLC gasliquid chromatography     

Microvasculature of the human testis and excurrent duct system

Summary The vascular microarchitecture of the human testis and excurrent duct system was examined by use of a casting method combined with scanning electron microscopy. In the testicular parenchyma, the capillaries form a fine plexus around the seminiferous tubules. The commonly described rope-ladder-like pattern of the peritubular capillaries is absent in the human testis. The microvasculature of the rete testis consists of a poorly organized plexus. Throughout the epididymis including the ductuli efferentes, the peritubular capillary network encircles each tubule cylindrically. In the cauda epididymidis, a coarse venous network surrounds the capillary network externally. Small arteries of the epididymis not only penetrate the connective tissue septa, but also run along the surface. In the ductus deferens, three distinct microvascular systems are distinguished: (1) a venous network located in the connective tissue surrounding the muscular coat, (2) a microvascular plexus within the muscular coat, and (3) a peritubular capillary network. The plexus within the muscular coat interconnects the venous and the peritubular capillary networks.     

The adrenergic innervation of the renal artery and vein of the rat

Summary The adrenergic innervation of the extrarenal blood vessels of the rat left kidney was investigated by fluorescence histochemistry and by electron microscopy. The trunk of the renal artery proximal to the aorta is elastic and appears to be very sparsely innervated. In contrast, near the kidney the renal artery—which divides into 3 to 4 large branches of the muscular type possesses a dense adrenergic innervation. The adrenergic terminal axons are situated in the adventitia close to the external elastic lamella, but only rarely in close contact with smooth muscle cells. In most instances several terminal axons are grouped and enclosed by a Schwann cell, single axons being rare. All terminal axons are able to take up and to store 5-hydroxydopamine which strongly suggests that they are adrenergic. The innervation of the renal vein is more sparse than that of the muscular arteries but somewhat denser than that of the elastic artery. In addition, close to the origin of the renal artery the presence of small intensively fluorescent (SIF) cells as well as of some adrenergic ganglion cells is noted. The latter are situated in the adrenergic nonterminal axon bundles, which run parallel to the blood vessels.It is concluded that the uneven adrenergic innervation along the artery as well as individual variations in the branching of the artery are the main causes of the unusually high individual variations of the NA content of this organ such as used in pharmacological experiments.     

Innervation of the umbilical vessels

Summary Umbilical vessels of guinea-pig fetuses were studied shortly before birth. In all umbilical cords investigated an innervation of the umbilical vessels is lacking. The intrafetal parts of the umbilical vessels on the other hand are richly innervated. A marked difference in the amount of nerve fibres and the pattern of innervation is found between artery and vein. The artery is supplied by a dense nerve plexus which spins around the media and which originates from nerve bundles within the outer adventitial layers. The comparatively scanty innervation of the vein exhibits a more coarsely meshed net pattern. The nerve bundles in the vein exhibit a close affinity to the vasa vasorum.Number and type of the close contacts between the muscle cells are different in the various sections of the umbilical vessels. Similar to the distribution of nerves they are almost absent in the vessels of the umbilical cord, numerously, however, in the intrafetal parts. Contrary to the innervation, the close contacts in the vein are developed more numerously and more broadly than in the corresponding artery.     

Sulphate deprivation depresses the transport of nitrogen to the xylem and the hydraulic conductivity of barley (Hordeum vulgare L.) roots

During the first 4 d after the removal of SO ₄ ^2- from cultures of young barley plants, the net uptake of ¹⁵N-nitrate and the transport of labelled N to the shoot both decline. This occurred during a period in which there was no measurable change in plant growth rate and where the incorporation of [³H]leucine into membrane and soluble proteins was unaffected. Reduced N translocation was associated with six- to eightfold increases in the level of asparagine and two- to fourfold increases in glutamine in root tissue; during the first 4 d of SO ₄ ^2- deprivation there were no corresponding increases in amides in leaf tissue. The provision of 1 mol · m^–3 methionine halted, and to some extent reversed the decline in NO ₃ ^- uptake and N translocation which occurred during continued SO ₄ ^2- deprivation. This treatment had relatively little effect in lowering amide levels in roots. Experiments with excised root systems indicated that SO ₄ ^2- deprivation progressively lowered the hydraulic conductivity, Lp, of roots; after 4 d the Lp of SO ₄ ^2- -deprived excised roots was only 20% of that of +S controls. In the expanding leaves of intact plants, SO ₄ ^2- deprivation for 5 d was found to lower stomatal conductance, transpiration and photosynthesis, in the order given, to 33%, 37% and 18% of control values. The accumulation of amides in roots is probably explained by a failure to export either the products of root nitrate assimilation or phloem-delivered amino-N. This may be correlated with the lowered hydraulic conductivity. Enhanced glutamine and-or asparagine levels probably repressed net uptake of NO ₃ ^- and ¹³NO ₃ ^- influx reported earlier (Clarkson et al. 1989, J. Exp. Bot. 40, 953–963). Attention is drawn to the similar hydraulic signals occurring in the early stages of several different types of mineral-nutrient stresses.Abbreviations Asn asparagine - Gln glutamine - Lp hydraulic conductivity J.L.K. is extremely grateful to the British Council for supporting his working visit to Long Ashton. We thank John Radin for helpful discussion and encouragement.