Middle Cortex Research Articles

The southernmost myco-heterotrophic plant, Arachnitis uniflora: root morphology and anatomy

Root morphology and anatomy of the myco-heterotrophic Arachnitis uniflora (Corsiaceae) were studied in relation to their association with a Glomus species (Glomeromycota). The mycorrhizal features were studied in three distinctive stages of development: (i) shoot and flower restricted to a small, underground bud; (ii) shoot and flower bud up to 1.5 cm; and (iii) shoot and flower already withered. The hyphae penetrate through and between the epidermal and exodermal cells; the exodermis and outer cortical cells become colonized in an inter- and intracellular manner, with some coils being formed in these layers. The fungi colonize the middle cortex, where intracellular vesicles in bundles are abundant. Arbuscules are formed profusely at very early stages of development, while in older stages they almost disappear and abundant vesicles are formed. Except for some details, the pattern of root colonization corresponds to a Paris-type. Presence of storage substances (starch and oil) also was recorded. Starch is produced and stored within root cells, mainly in the outer and inner root cortex. In senescent stages, plant and fungal tissues collapse.

Comparison of pulsatile and non‐pulsatile cardiopulmonary bypass on regional renal blood flow in sheep

Objective—The purpose of the present study was to evaluate the effects of pulsatile cardiopulmonary bypass (CPB) on sheep regional renal blood flow by comparing pulsatile and non‐pulsatile perfusion at two different flow rates.Design—Seven female Suffolk sheep were used and the animals were perfused with pulsatile and non‐pulsatile CPB at flow rates of 60 and 100 ml/min/kg. Regional renal blood flow was measured by the colored microsphere method. General linear model ANOVA was performed to analyze the data.Results—Regional renal blood flow was significantly higher in both outer and middle cortices of pulsatile CPB compared with non‐pulsatile CPB (outer cortex: pulsatile CPB, 381 ± 192 ml/min/100 g, non‐pulsatile CPB, 255 ± 151 ml/min/100 g, p = 0.002; middle cortex: pulsatile CPB, 239 ± 114 ml/min/100 g, non‐pulsatile CPB, 176 ± 80 ml/min/100 g, p = 0.02). The increase of flow rate from 60 to 100 ml/min/kg improved renal cortical blood flow significantly.Conclusion—The regional renal blood flow was significantly higher in both outer and middle cortices of pulsatile CPB compared with the non‐pulsatile CPB.

Ameliorative effects of nucleosides on senescence acceleration and memory deterioration in senescence-accelerated mice

We investigated the effects of a mixture of dietary nucleosides and nucleotides (NS+NT) on memory in senescence-accelerated mice (SAM). Memory retention was studied with passive avoidance and active avoidance tests. In old mice, the time of passive avoidance was significantly higher in the NS+NT group than in the control group at days 1 and 7. However, such an effect of NS+NT was not observed in young mice. In the active avoidance test, the incidence of successful avoidance in old mice was significantly higher in the NS+NT group than in the control group at days 1 and 2. The percentages of specific brain cells containing lipofuscin were significantly lower in NS+NT groups than in the control groups in both young and old mice. The number of monovacuoles and multiple vacuoles in specific brain regions tended to be lower in NS+NT than in control groups, with significant differences in the microvacuoles of the middle cortex of young mice and in the multiple vacuoles in the hind cortex of old mice. These results suggest that increased dietary NS+NT may be associated with decreases in the age-induced deterioration of brain morphology and certain memory tasks.

Aprotinin uptake in the proximal tubules in the rat kidney I.: Length of proximal tubular uptake segment

Aprotinin (Ap), a basic polypeptide with a molecular weight of 6500, is filtered at the glomerular membrane without steric restriction and is completely absorbed by the proximal tubule cells. Here Ap is broken down to amino acids, but no breakdown products enter the peritubular circulation during the first 20 min following an intravenous injection. These properties have recently been exploited for measurement of local glomerular filtration rate, based on the assumption that the proximal tubular uptake site is located at the level of the filtering glomerulus. To evaluate that assumption we have now made serial autoradiographs of the rat kidney 20 min after intravenous injection of 2–750 μg of 125 I -Aprotinin. With all doses the percent 125 I -containing proximal tubular transections were about 50 in the outer and middle cortex and 35 in the inner third. We interpret these numbers to mean that all filtered Ap is taken up in the first two thirds of the proximal convoluted tubular length and does not reach the pars recta. Since the proximal tubule on average is located more superficial than its glomerulus, measurement of local Ap uptake will tend to overestimate glomerular filtration rate in outer layers of the cortex. Quantitative estimate of this “displacement” will be presented in a companion article.

Effect of α-ketoglutarate and oxaloacetate on brain mitochondrial DNA damage and seizures induced by kainic acid in mice

The effects of α-ketoglutarate and oxaloacetate on brain mitochondrial DNA (mtDNA) damage and seizures induced by kainic acid were examined both in vivo and in vitro. An intraperitoneal (ip) injection of kainic acid (45 mg/kg) produced broad-spectrum limbic and severe sustained seizures in all of the treated mice. The seizures were abolished when α-ketoglutarate (2 g/kg) or oxaloacetate (1 g/kg) was injected intraperitoneally in the animals 1 min before kainic acid administration. In addition, the administration of kainic acid caused damage to mtDNA in brain frontal and middle cortex of mice. These effects were completely abolished by the ip preinjection of α-ketoglutarate (2 g/kg) or oxaloacetate (1 g/kg). In vitro exposure of kainic acid (0.25, 0.5 or 1.0 mM) to brain homogenate inflicted damage to mtDNA in a concentration-dependent manner. The damage of mtDNA induced by 1.0 mM kainic acid was attenuated by the co-treatment with α-ketoglutarate (2.5 or 5.0 mM) or oxaloacetate (0.75 or 1.0 mM). Furthermore, in vivo and in vitro exposure of kainic acid elicited an increase in lipid peroxidation. However, the increased lipid peroxidation was completely inhibited by cotreatment of α-ketoglutarate or oxaloacetate. These results suggest that α-keto acids such as α-ketoglutarate and oxaloacetate play a role in the inhibition of seizures and subsequent mtDNA damage induced by the excitotoxic/neurotoxic agent, kainic acid.

Apical organization and maturation of the cortex and vascular cylinder inArabidopsis thaliana (Brassicaceae) roots

Developmental and physiological studies of roots are frequently limited to a post-germination stage. In Arabidopsis, a developmental change in the root meristem architecture during plant ontogenesis has not previously been studied and is addressed presently. Arabidopsis thaliana have closed root apical organization, in which all cell file lineages connect directly to one of three distinct initial tiers. The root meristem organization is dynamic and changes as the root ages from 1 to 4 wk post-germination. During the ontogeny of the root, the number of cells within the root apical meristem (RAM) increases and then decreases due to changes in the number of cortical layers and number of cell files within a central cylinder. The architecture of the initial tiers also changes as the root meristem ages. Included in the RAM's ontogeny is a pattern associated with the periclinal divisions that give rise to the middle cortex and endodermis; the three-dimensional arrangement of periclinally dividing derivative cells resembles one gyre of a helix. Four- or 5-wk-old roots exhibit a disorganized array of vacuolated initial cells that are a manifestation of the determinate nature of the meristem. Vascular cambium is formed via coordinated divisions of vascular parenchyma and pericycle cells. The phellogen is the last meristem to complete its development, and it is derived from pericycle cells that delineate the outer boundary of the root.

Preventive effect of melatonin against brain mitochondria DNA damage, lipid peroxidation and seizures induced by kainic acid

The effects of kainic acid on mitochondria DNA (mtDNA) or lipid peroxidation in mice brain and, preventive effects of melatonin against its effects were investigated in vivo. Broad-spectrum limbic and severe sustained seizures were observed in all mice when kainic acid (45 mg/kg) was injected intraperitoneally (ip) to eight mice. These seizures were completely abolished by the simultaneous administration of melatonin (20 mg/kg, ip), a potent scavenger of hydroxyl radical. However, slight limbic seizures or severe sustained seizures were observed when melatonin was injected in animals 30 min before or 15 min after the kainic acid administration. The administration of kainic acid caused damage to mtDNA in brain frontal and middle cortex. These effects were abolished when melatonin was injected in animals 0 or 30 min before, but not 15 min after the kainic acid administration. In vitro or in vivo exposure of kainic acid elicited an increase in lipid peroxidation in a concentration- or dose-dependent manner. The increased lipid peroxidation induced by kainic acid was attenuated by co-treatment with melatonin. These results indicate that there may be a positive relationship among seizures, brain mtDNA damages and increased lipid peroxidation. Hence, our present results suggest that the hydroxyl radicals produced by kainic acid cause damage on mtDNA and the increase of lipid peroxidation in brain, leading to severe seizures. These effects were completely prevented by co-treatment with melatonin, a potent scavenger of hydroxyl radicals.

A Nucleoside-Nucleotide Mixture May Reduce Memory Deterioration in Old Senescence-Accelerated Mice

We investigated the effects of a mixture of dietary nucleosides and nucleotides (NS + NT) on memory in 1- and 7-mo-old senescence-accelerated mice (SAM). Memory retention was studied with passive avoidance (step-through) and active avoidance (shuttle) tests. For 14 wk, mice in the control groups were fed a 20 g of casein/100 g diet, whereas the NS + NT groups were fed this diet supplemented with a 0.5 g of NS + NT mixture/100 g. All mice were killed at wk 14, and we studied the brain histopathology. Lipofuscin, monovacuoles and multiple vacuoles of various brain regions were measured. Body weight, food intake and ambulatory activity did not differ between the control and NS + NT groups. In old mice, the time of passive avoidance was significantly higher in the NS + NT group than in the control group at d 1 and 7 (P: < 0.05). However, such an effect of NS + NT was not observed in young mice. In the active avoidance test, the incidence of successful avoidance in old mice was higher in the NS + NT group than in the control group at d 1 and 2 (P: < 0.05). The percentages of specific brain cells containing lipofuscin were lower in NS + NT groups than in the control groups in both young and old mice (P: < 0.05). The number of monovacuoles and multiple vacuoles in specific brain regions tended to be lower (P: = 0.1-0.25) in NS + NT than in control groups, with significant differences in the microvacuoles of the middle cortex of young mice and in the multiple vacuoles in the hind cortex of old mice (P: < 0. 05). These results suggest that increased dietary NS + NT may be associated with decreases in the age-induced deterioration of brain morphology and certain memory tasks.

The effect of AVP-V2 receptor stimulation on local GFR in the rat kidney.

The effect of AVP-V2 receptor agonist desmopressin, dDAVP, its non-peptide antagonist OPC-31260 and vehicle infusion on glomerular filtration rate (GFR) in the outer, middle and inner cortex was studied in both hydropenic and water diuretic Inactin anaesthetized female Sprague-Dawley rats using the aprotinin method. Two subsequent GFR measurements were carried out in the same kidney by injection of 125I- and 131I-labelled aprotinin before and after i.v. infusion of dDAVP, OPC-31260 or the vehicle. Acute infusion of dDAVP in hydropenic rats increased total GFR by 14% relative to vehicle infusion, whereas in water diuretic rats it had no effect relative to vehicle. No significant changes in arterial pressure (Pa) or renal blood flow (RBF) were recorded. Infusion of OPC-31260 reduced total GFR by 11% compared with vehicle. These results are consistent with the findings that a presensitization of the vasculature by high plasma levels of AVP is necessary for the renal vascular effects mediated by the V2 or V2-like receptors to occur. The ratio between inner and outer cortex GFR remained unchanged from control to experimental condition as follows: dDAVP infusion in hydropenic rats, 0.504 vs. 0.494 in control; vehicle infusion in hydropenic rats, 0. 393 vs. 0.392; OPC-31260 infusion in hydropenic rats, 0.517 vs. 0. 523; dDAVP in water diuretic rats, 0.547 vs. 0.543; vehicle in water diuretic rats, 0.413 vs. 0.417. Thus no significant difference in the GFR response was observed between superficial and deep cortical layers of the rat kidney.

Two new species of Solenostelopteris from the Upper Jurassic Morrison Formation in Wyoming and Utah

Permineralized rhizomes of two new species of Solenostelopteris Kershaw, S. leithii, and S. medlynii, are described from the Upper Jurassic Morrison Formation from the Steiner and Scott's localities north of Greybull, Wyoming, and from Fremont Junction, east of Mt. Ellen, and Mussentuchit Wash sites in Utah. The species are characterized by having a heterogeneous ( S. leithii) to homogeneous ( S. medlynii) pith, rhizomes with branches ( S. leithii), a sclerenchymatous ( S. leithii) or parenchymatous ( S. medlynii) inner cortex, and both with a parenchymatous middle cortex. The outer cortex of S. leithii is parenchymatous, whereas in S. medlynii, it is composed of round to irregularly shaped, thick-walled cells. The C-shaped leaf traces in S. leithii usually arise single ranked, sometimes two ranked, with short leaf gaps and short internodes. Although the rhizomes of S. medlynii are incomplete and lack leaf traces, they still suggest very long internodes. Because fronds and epidermal trichomes are lacking in both, the affinity of these species to modern taxa, such as members of the Loxsomaceae, remains uncertain.

A new vascular plant from the Lower Devonian Windyfield chert, Rhynie, NE Scotland

AbstractTwo plants are described from fragmentary remains preserved in the Windyfield chert, situated c. 600 m from the classic Rhynie chert locality. Both are sometimes coated by a microbial film. The larger, fertile axes are placed in the new genus and species Ventarura lyonii. They possess a distinctive, sclerenchymatous middle cortex and terete xylem, and marginally dehiscent, lateral sporangia. The new taxon is similar to the Rhynie zosterophyll Trichopherophyton teuchansii, but is placed in a new genus on sporangial differences. Associated smaller axes with unicellular epidermal outgrowths lack the middle cortex of the larger axes and often have medullated protosteles. They are interpreted as subterranean rhizomes and probably belong to the new fertile taxon, but organic continuity between the two has not been demonstrated.

Subterranean structures and mycotrophy of the achlorophyllous Triuris hyalina (Triuridaceae)

Triuris hyalina Miers, an unusual achlorophyllous plant, was investigated for subterranean morphology, root anatomy, and mycotrophy. Stems with scale leaves extend subterraneously to a depth of 15 cm. Pairs of adventitious roots develop at the scale leaves and clumps of apparently radiating roots, formed by accumulations of side shoot and scale leaf developments, occur. Roots consist of epidermis, short cell exodermis, three distinct layers of cortex parenchyma, endodermis, and an extremely reduced central cylinder with one or two central tracheidal xylem elements. The fungus associated with T. hyalina roots exhibits thick-walled, 6-9 µm thick, aseptate external hyphae. It penetrates the epidermis by developing appressoria and enters the cortex solely through the short cells of the exodermis. In the cortex cells, the aseptate hyphae start to coil. In the outer cortex layer, hyphae are thin, frequently branched, and most densely coiled. In the middle cortex layer they are thicker and less densely coiled, and mostly appear degenerated to clumps of amorphous fungal material. The inner cortex layer rarely becomes colonized. Vesicles occur in the outer and the middle cortex layers. This mycorrhizal pattern is interpreted as an adaption to attain a sustainable use from the endophyte. It is suggested that the mycorrhiza in Triuris hyalina be interpreted as a type of arbuscular mycorrhiza (AM). Implications for systematics and ecology are discussed.Key words: Triuris, Triuridaceae, root structure, anatomy, arbuscular mycorrhiza, myco-heterotrophy.

Subcellular localization of glycoprotein epitopes during the development of lupin root nodules

The monoclonal antibodies MAC236 and MAC265, raised against a soluble component of pea nodules, were used to elucidate the presence and subcellular localization of glycoprotein epitopes during the development of lupin (Lupinus albus L. cv. Multolupa) nodules, by means of immunocytochemistry and Western blot analysis. These antibodies recognize a single band of 95 kDa in pea, soybean and bean nodules, whilst two different bands of 240 and 135 kDa cross-react with MAC236 and MAC265 respectively in lupin nodules. This fact may indicate that the recognized epitopes can be present in different subcellular compartments and/or play different roles through the development of functional nodules. The results show that MAC265 is mainly associated with Bradyrhizobium infection and with the development of nodule primordium, in the first stages of nodulation. MAC265 is also detected when glycoprotein transport takes place across the cytoplasm and the cell wall, and also in the intercellular spaces of the middle cortex, attached to cell walls. The amount of MAC265 remains constant through nodule development. In contrast the amount of MAC236 increases with nodule age, parallel to the establishment of nitrogenase activity. This antibody is localized in cytoplasmic globules attached to the inner side of cell walls in the middle cortex, and mainly in the matrix filling the intercellular spaces of the middle and inner cortex. This main site of localization of MAC236 may indicate a role in the functioning of the oxygen diffusion barrier.

Transgeniculate signal transmission to middle suprasylvian cortex in intact cats and following early removal of areas 17 and 18: a morphological study.

Removal of cat areas 17 and 18 early, but not late, in postnatal development results in the sparing of certain reflexive and nonreflexive visually guided behaviors. These spared behaviors are accompanied by an expansion of geniculocortical projections to middle suprasylvian (MS) cortex. However, little is known about the types of visual signals relayed along these pathways. The purpose of our study was to reveal the morphologies of the neurons participating in the rewired circuits and, by relating them to the morphologies of functionally characterized neurons described by others, infer the types of visual signals transmitted via the lateral geniculate nucleus (LGN) to MS cortex. To do this, we retrogradely labeled LGN neurons from MS cortex with fluorescent microspheres, and subsequently intracellularly filled them with Lucifer Yellow. We then classified well-filled neurons according to a battery of morphological parameters (such as soma size and shape, and dendritic field-form and specializations), and compared them with already defined structure/function relationships. By doing this, we found that the large majority of visual thalamic relay neurons to MS cortex of both normal cats and cats that incurred removal of areas 17 and 18 were types I and IV. These results indicate that visual Y and W signals, respectively, are relayed directly from LGN to MS cortex in both types of cats. Following the early lesions, some of the MS-projecting type I neurons were found in layers A and A1, where they are never found in intact cats. Thus, some layer A and A1 type I neurons redirect axons to MS cortex following early removal of areas 17 and 18. For the type IV MS-projecting neurons in early lesioned cats, the somas were hypertrophied and they had more profuse and broader dendritic arbors than equivalent neurons in intact cats. These results suggest that dynamic interactions take place between inputs and outputs of LGN neurons during development that influence final LGN neuron morphology. Moreover, they suggest that signals transferred to MS cortex by type IV neurons may be modified by early lesions of areas 17 and 18. Overall, these results contribute to our understanding of the types of behaviors that may be spared by early lesions of areas 17 and 18.

Ultrastructural and physiological changes in root cells of Sorghum plants (Sorghum bicolor x S. sudanensis cv. Sweet Sioux) induced by NaCl

The xerophytic, but salt-sensitive Sorghum cultivar ‘Sweet Sioux’ is known as an ion excluder with a high K/Na selectivity at the plasmalemma and tonoplast of epidermal root cells. The aim of this study is the correlation of salt-effected changes in physiological parameters with structural and ultrastructural changes in root cells. The investigation was carried out with root cells because these cells are most directly exposed to the growth medium. Sorghum bicolor × S. sudanensis cv. Sweet Sioux plants were grown under steady-state conditions on nutrient solutions with or without 40 mol m−3 NaCl. Sorghum sustained this treatment but showed several salt-induced structural and physiological changes which were studied in various cell types of the root tip. (1) NaCl salinity led to a shorter growth region and to salt-induced alterations in the chemical and physical properties of the cell walls in the root tips. (2) Salt treatment also increased the membrane surface in root cells: root cells showed an increase in the quantity of vesicles in the epidermis and in the middle cortex cells. Additionally, some of the epidermis cells of salt-treated plants revealed a characteristic build-up of transfer cells, suggesting an increase in membrane surfaces to increase the uptake and storage of substances. (3) The number of mitochondria increased in the epidermal and in the cortex cells after salt stress thus indicating an additional supply of energy for osmotic adaptation and for selective uptake and transport processes. (4) In the epidermal cytoplasm NaCl stress led to a significant decrease of the P, K, Ca, and S concentrations accompanied by an increase of Na concentration. Electron micrographs show an increase in electron optical contrast within the cytosol and in the matrix of the mitochondria. These results are discussed with regard to the possibility of influence on the part of metabolic functions. (5) The NaCl concentrations were seen to increase and the K concentrations to decrease during salt stress in the vacuoles of the epidermis and cortex cells. The salt-induced increase in vacuolar NaCl concentrations of epidermis and cortex cells are in the region 2 cm behind the root tip, which is sufficient for an osmotic balance towards the growth medium. Additional solutes are necessary 0.5 mm behind the root tip to facilitate osmotic adaptation. The results show ultrastructural changes caused by an Na-avoiding mechanism characterized by a high level of energy consumption. The exclusion of Na from the symplast seems to lead additionally to a decrease in cytoplasmic concentrations of such essential elements as Mg, P, S, and Ca and is thus responsible directly (via energy supply in mitochondria, homeostasis, selectivity of K over Na) or indirectly (via enzyme conformation, cytoplasmic hydration) for the ultra-structural degradation indicated. The salinity-induced multiplicity of structural and functional changes within cell compartments constitutes a group of indicators for the limited NaCl tolerance of Sorghum.

Acute Effects of Angiotensin II Receptor Antagonist on Autoregulation of Zonal Glomerular Filtration Rate in Renovascular Hypertensive Rats

This study was designed to assess the renal capability to autoregulate total blood flow, glomerular filtration rate (GFR) and local GFR in outer, middle and inner cortical layers (OC, MC, IC) in the two-kidney, one-clip (2K-1C) renovascular hypertensive rat, with or without acute infusion of the angiotensin II receptor antagonist losartan (5 mg/kg, i.v.). Age-matched, sham-operated Wistar rats were used as controls. The hemodynamic study in all animals was performed 4 weeks after clipping. The clipping increased blood pressure significantly, whereas losartan reduced the renal arterial pressure (RAP) from 165+/-8 to 125+/-6 mm Hg (p < 0.01) in 2K-1C hypertensive rats and reduced the RAP from 107+/-2 to 101+/-1 mm Hg (p < 0.05) in normotensive animals. Renal blood flow (RBF), total and local GFR were decreased in the nonclipped kidney of 2K-1C hypertensive rats compared with sham-operated rats, but losartan significantly increased the RBF and GFR. RBF was well maintained in response to reduction in RAP in the nonclipped kidneys with and without losartan treatment. The capability of total GFR autoregulation was impaired in untreated 2K-1C hypertensive rats and losartan-treated sham-operated rats, whereas losartan completely abolished GFR autoregulation in the nonclipped kidney of 2K-1C hypertensive rats. Losartan impaired autoregulation of zonal GFR to the same extent in all three cortical layers of sham-operated rats, whereas in the nonclipped kidney of 2K-1C hypertensive rats losartan had a more pronounced effect on the superficial GFR autoregulation than in middle and inner cortex, indicating that angiotensin II plays a major role in regulating the GFR response to the acute changes of renal arterial pressure.

Root apical organization inArabidopsis thaliana ecotype ?WS? and a comment on root cap structure

Arabidopsis thaliana roots have closed apical organization with three initial tiers. The dermatogen/calyptrogen tier consists of two parts - the central initials form the columella root cap, and the peripheral initial cells form the protoderm (epidermis) and the peripheral root cap. These peripheral initials divide in a sequence to form a root cap consisting of interconnected cones. The periblem initial tier forms the ground meristem (cortex). For the first week after germination the periblem consists of one layer of initial cells. The peripheral cells of the tier divide periclinally and then anticlinally (a T-division) to form the two-layered cortex (outer cortex and endodermis). After about one week, all the peripheral cells have divided periclinally forming two initials; the outermost produces the outer cortex while the inner initial produces the endodermis and middle cortex layer. The latter two cells arise via a periclinal division. During this time, other cells within the tier divide periclinally to form a two-layered tier. The plerome forms the cells of the procambium (vascular cylinder) by simple anticlinal divisions followed by longitudinal divisions to fill out the cell files of the vascular cylinder. A survey (27 dicot species in 17 families) of roots with closed apical organization revealed that there are three different types of root cap - concentric cylinders of cells (e.g. Linum), interconnecting cones (e.g. Arabidopsis) or overlapping arcs (e.g. Gossypium).

Increased oxidative metabolism in middle suprasylvian cortex following removal of areas 17 and 18 from newborn cats.

We measured changes in metabolic activity in middle suprasylvian (MS) cortex of cats subjected to early or late removal of areas 17 and 18 to localize shifts in activity possibly indicative of regions within MS cortex that may receive expanded inputs and be involved in the sparing of some visual behaviors following early primary visual cortex damage. Cytochrome oxidase (CO) activity was measured in MS cortex of mature, intact cats and of others with areas 17 and 18 removed in adulthood (P180), or on postnatal day 28 (P28) or postnatal day 1 (P1). Not less than 9 months after the ablation, brain sections were prepared and reacted for the presence of CO. The density of CO reactivity in each of the six cortical layers in MS cortex was measured and standardized against densities from ventral periaqueductal gray or hypothalamus on the same section. Following lesions on P1, significant increases in CO activity occurred in deep layer III and in layer IV of the medial bank of the MS sulcus, including all of area PMLS and the posterior portion of AMLS. In contrast, there were no significant differences in the level of CO activity among P28, P180, or intact cats for any of the cortical layers, and all had lower levels than the P1 cats. This metabolic change provides an anatomical marker for localizing adjustments in MS cortex and can be linked to amplified projections into MS cortex from the thalamus (LPm and A and C laminae of the dorsal lateral geniculate nucleus) and ventral posterior suprasylvian cortex following P1 ablations. Furthermore, this neurochemical analysis implicates a distinct region of MS cortex as the cortical locus of some spared visual functions following early primary visual cortex damage.

A re-evaluation of the mechanism of root contraction in Monocotyledons using the example of Arisarum vulgare Targ.-Tozz. (Araceae)

Summary Within the Monocotyledons the anatomical ring-collapsing type of root contraction is very common. However, up to the present there has been no overall view of the anatomical changes and how they relate to the pulling and moving function of the root. The careful maceration of contractile roots of Arisarum vulgare makes it possible to measure the dimension of the cells, particularly the dimensional change during root contraction. It can be shown that the outer and middle cortical cells expand radially (increase in volume, growth) with simultaneous longitudinal shortening, and finally collapse. The inner cortical cells of Arisarum show a longitudinal shortening which is synchronous to that of the outer and middle cortical cells. The inner cortical cells retain their original volume, which means that no cell growth occurs. Occasionally, expansion and shortening of the outer and middle cortical cells occur at different times. Then, first a radial expansion of the cells is seen, followed by their shortening. A consideration of the early results shown in Acidanthera seem to make it possible to suggest a unified anatomical model of root contraction. In this model, radial expansion and longitudinal shortening are two processes of activity of the cortical cells which, in principle, take place separately in time and space. Both activities are important for underground plant movement. Contrary to all earlier models it is assumed that the inner cortical cells shorten actively and thus produce a pulling force acting on the innovation system of the plant. This shortening activity can be limited to the inner cells (e. g. Acidanthera ), but it may be that it also takes place in the middle, and even in the outer cortex ( Arisarum ). However, the main activity of the middle and outer cortex is the radial expansion which has nothing immediately to do with root shortening! Radial expansion develops a force which results in a sideward pushing of the soil (pushing force, work of expansion) and therefore makes movement in the soil easier (channel effect). The collapse of these cells promotes shortening passively.

Evidence that short‐term regulation of nodule permeability does not occur in the inner cortex

Regulation of nodule permeability in response to short‐term changes in environmental and physiological conditions is thought to occur by occlusion of intercellular spaces in the nodule inner cortex. To test this hypothesis, the permeability of legume nodules was altered by adapting them to either 20 or 80% O2 over a 2.5‐h period. The nodules were then rapidly frozen, cryo‐planed and examined under cryo‐scanning electron microscopy for differences in the number, area or shape factor of intercellular spaces. Comparisons were made between whole nodules and specific nodule zones (outer cortex, middle cortex, inner cortex and central zone) in each treatment. Gas analysis measurements indicated that nodules equilibrated at 20% O2 had a 6.6‐fold higher permeability than those equilibrated at 80% O2 However, no significant differences were observed between pO2 treatments in the number of open intercellular spaces, the cross‐sectional area of those spaces, or the proportion of the tissue area present as open space in whole nodules or any nodule zone. Also, although nodules in both treatments possessed a boundary layer of tightly packed cells in the inner cortex, the total area of intercellular spaces between cells bordering this layer did not differ between treatments. Together these observations do not support the currently favored hypothesis that nodule permeability is regulated by opening or occlusion of intercellular spaces in the nodule inner cortex. Highly significant differences (P= 0.0006) were observed between O2 treatments in the shape factor of the open intercellular spaces in all nodule zones. Nodules equilibrated at 80% O2 had significantly more isodiametric spaces while those equilibrated at 20% O2 had more long, narrow spaces. This observation suggests that the critical step in the regulation of nodule permeability to O2 may be localized in the central, infected zone and involve changes in the ratio of the surface area of the intercellular space to the volume of the infected cell.