Adsorption of bacteria to roots as related to host specificity in the Rhizobium-clover symbiosis

Quantitative microscope techniques were utilized to examine the adsorption of rhizobial cells to clover root hairs. Adsorption of cells of noninfective strains of Rhizobium trifolii or infective R. meliloti strains to clover root hairs was four to five times less than that of the infective R. trifolii strains. Attachment of the rod-shaped bacteria to clover root cells occurred in a polar, end-on fashion. Viable or heat-killed R. trifolii cells precoated with a clover lectin having 2-deoxyglucose specificity had increased adsorption to clover roots. Adsorption of bacteria to roots was not increased if the clover lectin was inactivated by heat or 2-deoxyglucose treatment prior to incubation with R. trifolii. Adsorption of R. trifolii to clover root hairs was inhibited by 2-deoxyglucose (30 mM) but not by 2-deoxygalactose or alpha-D-glucose. Adsorption of R. meliloti cells to alfalfa root hairs was not affected by 2-deoxyglucose at that concentration. These results suggest that expression of host specificity in the Rhizobium-clover symbiosis involves a preferential adsorption of infective cells to clover root hairs through a 2-deoxyglucose-sensitive receptor site.     

The COW1 locus of arabidopsis acts after RHD2, and in parallel with RHD3 and TIP1, to determine the shape, rate of elongation, and number of root hairs produced from each site of hair formation

Two recessive mutant alleles at CAN OF WORMS1 (COW1), a new locus involved in root hair morphogenesis, have been identified in Arabidopsis thaliana L. Heynh. Root hairs on Cow1- mutants are short and wide and occasionally formed as pairs at a single site of hair formation. The COW1 locus maps to chromosome 4. Root hairs on Cow1- plants form in the usual positions, suggesting that the phenotype is not the result of abnormal positional signals. Root hairs on Cow1- roots begin hair formation normally, forming a small bulge, or root hair initiation site, of normal size and shape and in the usual position on the hair-forming cell. However, when Cow1- root hairs start to elongate by tip growth, abnormalities in the shape and elongation rate of the hairs become apparent. Genetic evidence from double-mutant analysis of cow1-1 and other loci involved in root hair development supports our conclusion that COW1 is required during root hair elongation.     

Functional characterization of caudal hypoglossal neurons by spectral patterns of neuronal discharges in the rat

This study evaluated the spectral characteristics of neuronal discharges in the caudal hypoglossal nucleus and their physiological relevance in adult, male Sprague Dawley rats which were anaesthetized and maintained with pentobarbital sodium. Based on auto-spectral analysis of extracellular single-neuron activity, three spectral patterns were identified in the spontaneous discharges of hypoglossal neurons. Neurons that exhibited a rhythmic pattern manifested a concentrated peak in the auto-spectrogram that corresponded to the mean discharge rate. A majority of hypoglossal neurons displayed the modulated pattern, which was manifested either as scattered power densities (wide-band modulated pattern) or with a peak frequency component that was different from the mean discharge rate (narrow-band modulated pattern). Neurons that exhibited a mixed pattern displayed both rhythmic and modulated spectral patterns. Cross-spectral analysis further revealed that respiratory modulation constituted a major physiological influence on caudal hypoglossal neurons. The respiratory modulated pattern, however, could be converted to a mixed pattern in the presence of a central dipsogen, angiotensin III. The results suggest that the spectral patterns of neuronal discharges in caudal hypoglossal neurons represent manifestations of multiple physiological information, including that regarding respiration and dipsogenesis, which is encoded in these neurons. It was also shown that this information may only be revealed by auto-spectral and cross-spectral analysis of neuronal discharge signals.     

Preservation of pudendal afferents in sacral rhizotomies

OBJECTIVE: To assess the effectiveness of pudendal afferent mapping as a tool to minimize the risk of postoperative bowel, bladder, and sexual dysfunction in patients undergoing selective posterior rhizotomies in whom the S2 roots are candidates for rhizotomy. METHODS: One-hundred fourteen children with the diagnosis of cerebral palsy and debilitating spasticity were selected to undergo selective posterior rhizotomies at New York University Medical Center during 1991 through 1995. There were 72 male and 42 female patients with a mean age of 3.8 years. At the time of surgery, none of the patients had clinically relevant bladder dysfunction. Dorsal root action potentials were recorded intraoperatively to map the distribution of pudendal afferent fibers in S1-S3 roots bilaterally before performing the rhizotomies. RESULTS: Pudendal afferent mapping was successful in 105 of 114 patients. In the majority of these patients (56%), the distribution was asymmetrical. S1 roots contributed 4%, S2 roots 60.5%, and S3 roots 35.5% of the overall pudendal afferent activity. The pudendal afferent distribution was often confined to a single level in 18% of the patients or even to a single root in 7.6%. Fifty-six percent of the pathologically responding S2 roots during rhizotomy testing were preserved because of the significant afferent activity, as demonstrated during pudendal mapping. None of the 105 patients so mapped developed long-term bowel or bladder complications. CONCLUSIONS: Pudendal afferent mapping identifies S2 roots that carry a significant number of fibers involved with genital sensation. The preservation of such roots during surgical procedures may be important for sexual function and may also contribute to decreasing postoperative bladder and bowel disturbances.     

Sleep and breathing disorders in patients with brain stem lesions

Most information about the structures within the brain stem that modulate respiration and sleep are gathered from animal experiments. Therefore we examined 10 patients several weeks after an infarction of the brain stem by means of polysomnography and tested the chemosensitive drives of respiration. None of these patients complained about symptoms of sleep disordered breathing. In each case polysomnographic measurements and ventilatory response curves revealed pathologic findings. The respiratory response to CO2 was diminished or completely abolished in each patient. In some cases hypoventilation or disturbances of the respiratory rhythmicity could be seen. In several cases missing REM sleep, sleep fragmentation or the reduction of slow wave sleep were observed. The study indicates that on the base of results from animal research the comparison of morphological and pathophysiological data is helpful to gain a better understanding on the coupling of the respiratory system with sleep at the brain stem level as well as on the pathomechanism of sleep related breathing disorder.     

Effect of 5-hydroxytryptamine on the peripheral chemoreceptors in the rat

5-Hydroxytryptamine (5-HT), in the doses of 2-5 mug/kg injected into the carotid body area, produced a significant increase in the respiratory rate and carotid sinus nerve activity. Selective ablation of the ipsilateral carotid sinus nerve abolished the respiratory stimulation produced by the drug. On the other hand, the same doses of 5-HT injected into the ascending aorta did not produce stimulation of respiration when the carotid sinus nerves were sectioned. The activity of the aortic nerves did not increase after injecting the drug into the ascending aorta or at the root of the right subclavian artery. These results indicate that 5-HT stimulates the chemoreceptors in the carotid body of the rat. The lack of responses to the injections of the drug in the aortic or subclavian region was due to the absence of chemoreceptors in these regions of the rat.     

Expression of the smooth-muscle proteins alpha-smooth-muscle actin and calponin, and of the intermediate filament protein desmin are parameters of cardiomyocyte maturation in the prenatal rat heart

Tip growth of plant cells has been suggested to be regulated by a tip-focused gradient in cytosolic calcium concentration ([Ca2+]c). However, whether this gradient orients apical growth or follows the driving force for this process remains unknown. Using localized photoactivation of the caged calcium ionophore Br-A23187 we have been able to artificially generate an asymmetrical calcium influx across the root hair tip. This led to a change in the direction of tip growth towards the high point of the new [Ca2+]c gradient. Such reorientation of growth was transient and there was a return to the original direction within 15 min. Root hairs forced to change the direction of their growth by placing a mechanical obstacle in their path stopped, reoriented growth to the side, and grew past the mechanical blockage. However, as soon as the growing tip had cleared the obstacle, growth returned to the original direction. Confocal ratio imaging revealed that a tip-focused [Ca2+]c gradient was always centered at the site of active growth. When the root hair changed direction the gradient also reoriented, and when growth returned to the original direction, so did the [Ca2+]c gradient. This normal direction of apical growth of Arabidopsis thaliana (L.) Heynh, root hairs was found to be at a fixed angle from the root of 85 +/- 6.7 degrees. In contrast, Tradescantia virginiana (L.) pollen tubes that were induced to reorient by touch or localized activation of the caged ionophore, did not return to the original growth direction, but continued to elongate in their new orientation. These results suggest that the tip-focused [Ca2+]c gradient is an important factor in localizing growth of the elongating root hair and pollen tube to the apex. However, it is not the primary determinant of the direction of elongation in root hairs, suggesting that other information from the root is acting to continuously reset the growth direction away from the root surface.     

Meningioma associated with acute subdural hematoma--case report

1. The aim of the present study was to determine the brain sites mediating aspects of respiratory and cardiovascular control in adult humans using non-invasive functional magnetic resonance (fMRI) procedures, thereby avoiding the spatial and temporal sampling limitations associated with classic neural assessment techniques. 2. We examined activity changes across the entire brain following application of respiratory loads and upon induction of blood pressure and heart rate alterations. Magnetic resonance signals were visualized with a 1.5 Tesla scanner in healthy volunteers (22-52 years of age) using procedures that optimally assess changes in brain tissue microcirculation. Images were collected during a Valsalva manoeuvre, inspiratory loading, hypercapnia, cold pressor challenges to the hand and forehead and during intervening baseline states. 3. Image values from experimental conditions were compared with corresponding baseline values on a pixel-by-pixel basis to identify brain regions in which the experimental conditions produced physiological activation. 4. Ventilatory and pressor challenges elicited significant changes in regional image signal intensity in areas within the orbital cortex, amygdala, hypothalamus and hippocampus. Cerebellar, medullary and pontine areas were also recruited. However, while particular brain regions were only activated during specific stimuli, other regional signal changes occurred with multiple experimental manipulations. 5. The findings indicate that respiratory and cardiac challenges elicit discrete activity changes over multiple brain sites. Activated regions include structures not often related to respiratory or cardiovascular regulation, such as the cerebellum; a prominent role for limbic forebrain structures in mediating the response is also suggested. The fMRI visualization procedures may greatly assist in the determination of neural structures that mediate respiratory and cardiovascular control in humans.     

Linoleic acid-induced activity of plant uncoupling mitochondrial protein in purified tomato fruit mitochondria during resting, phosphorylating, and progressively uncoupled respiration

An uncoupling protein was recently discovered in plant mitochondria and demonstrated to function similarly to the uncoupling protein of brown adipose tissue. In this work, green tomato fruit mitochondria were purified on a self-generating Percoll gradient in the presence of 0.5% bovine serum albumin to deplete mitochondria of endogenous free fatty acids. The uncoupling protein activity was induced by the addition of linoleic acid during the resting state, and in the progressively uncoupled state, as well as during phosphorylating respiration in the presence of benzohydroxamic acid, an inhibitor of the alternative oxidase and with succinate (+ rotenone) as oxidizable substrate. Linoleic acid strongly stimulated the resting respiration in fatty acid-depleted mitochondria but had no effect on phosphorylating respiration, suggesting no activity of the uncoupling protein in this respiratory state. Progressive uncoupling of state 4 respiration decreased the stimulation by linoleic acid. The similar respiratory rates in phosphorylating and fully uncoupled respiration in the presence and absence of linoleic acid suggested that a rate-limiting step on the dehydrogenase side of the respiratory chain was responsible for the insensitivity of phosphorylating respiration to linoleic acid. Indeed, the ADP/O ratio determined by ADP/O pulse method was decreased by linoleic acid, indicating that uncoupling protein was active during phosphorylating respiration and was able to divert energy from oxidative phosphorylation. Moreover, the respiration rates appeared to be determined by membrane potential independently of the presence of linoleic acid, indicating that linoleic acid-induced stimulation of respiration is due to a pure protonophoric activity without any direct effect on the electron transport chain.     

Hairy root nodulation of Casuarina glauca: a system for the study of symbiotic gene expression in an actinorhizal tree

The purpose of this study was to establish a fast system for producing transgenic actinorhizal root nodules of Casuarina glauca. Agrobacterium rhizogenes strain A4RS carrying the p35S-gusA-int gene construct was used to induce hairy roots on hypocotyls of 3-week-old C. glauca seedlings. Three weeks after wounding, the original root system was excised, and composite plants consisting of transgenic roots on untransformed shoots were transferred to test tubes to be inoculated with Frankia. The actinorhizal nodules formed on transformed roots had the nitrogenase activity and morphology of untransformed nodules. beta-Glucuronidase (GUS) activity was examined in transgenic roots and nodules by fluorometric and histochemical assays. The results indicate that transgenic nodules generated with this root transformation system could facilitate the molecular study of symbiotic nitrogen fixation in actinorhizal trees.     

Hemodynamics, cerebral circulation, and oxygen saturation in Cheyne-Stokes respiration

Because cardiovascular disorders and stroke may induce Cheyne-Stokes respiration, our purpose was to study the interaction among cerebral activity, cerebral circulation, blood pressure, and blood gases during Cheyne-Stokes respiration. Ten patients with heart failure or a previous stroke were investigated during Cheyne-Stokes respiration with recordings of daytime polysomnography, cerebral blood flow velocity, intra-arterial blood pressure, and intra-arterial oxygen saturation with and without oxygen administration. There were simultaneous changes in wakefulness, cerebral blood flow velocity, and respiration with accompanying changes in blood pressure and heart rate approximately 10 s later. Cerebral blood flow velocity, blood pressure, and heart rate had a minimum occurrence in apnea and a maximum occurrence during hyperpnea. The apnea-induced oxygen desaturations were diminished during oxygen administration, but the hemodynamic alterations persisted. Oxygen desaturations were more severe and occurred earlier according to intra-arterial measurements than with finger oximetry. It is not possible to explain Cheyne-Stokes respiration by alterations in blood gases and circulatory time alone. Cheyne-Stokes respiration may be characterized as a state of phase-linked cyclic changes in cerebral, respiratory, and cardiovascular functions probably generated by variations in central nervous activity.     

Hair analysis for drugs of abuse. XVIII. 3,4-Methylenedioxymethamphetamine (MDMA) disposition in hair roots and use in identification of acute MDMA poisoning

Disposition of 3,4-methylenedioxymethamphetamine (MDMA) in hair roots was studied using rats and the hair root samples were evaluated to prove acute MDMA poisoning. The back hair of male pigmented hairy rats (n = 6) was shaved and 5 d later the animals were intraperitoneally administered with acute poisonous doses (20, 40, 60, 80 and 100 mg/kg) of MDMA. Roots of the hairs were then plucked out with a hair nipper 5 min and, 0.5, 1, 2, 6 and 24 h after injection. The hair root samples were, directly or after being washed with detergent, extracted with methanol-5 N HCl (20:1) under ultrasonication in ice-cold water for 4 h. After filtration and evaporation, the residue was derivatized with pentafluoropropionic anhydride and analyzed by GC/MS. From all samples including the 5 min sample, MDMA was detected at high concentrations (up to 156 ng/mg) accompanied by 3,4-methylenedioxyamphetamine (MDA). Some of the animals died within 2 h after administration, but in the surviving rats the MDMA concentrations in the hair roots increased up to 6 h and then slowly decreased until 24 h. The remaining MDMA after washing apparently increased from 13-31% at 0.5 h to 51-83% at 24 h in the surviving rats. These facts show that most of drugs in the hair roots are not yet immobilized in the early stage and are thereafter gradually incorporated into the hair shaft. Increase of the MDMA concentration stopped soon after death of the animal, probably due to the cessation of hair growth. Although the ratios of MDA/MDMA steadily increased over time, those after death plateaued, probably due to the cessation of metabolism after death. It was clearly shown that MDMA is more quickly incorporated into and more firmly retained in hair than methamphetamine (MA) by comparing their disposition in hair roots.     

Effect of Lanthanum on Rice Growth and Physiological Parameters with Split-Root Nutrient Solution Culture

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Bcl-2 potentiates the maximal calcium uptake capacity of neural cell mitochondria

Expression of the human protooncogene bcl-2 protects neural cells from death induced by many forms of stress, including conditions that greatly elevate intracellular Ca2+. Considering that Bcl-2 is partially localized to mitochondrial membranes and that excessive mitochondrial Ca2+ uptake can impair electron transport and oxidative phosphorylation, the present study tested the hypothesis that mitochondria from Bcl-2-expressing cells have a higher capacity for energy-dependent Ca2+ uptake and a greater resistance to Ca(2+)-induced respiratory injury than mitochondria from cells that do not express this protein. The overexpression of bcl-2 enhanced the mitochondrial Ca2+ uptake capacity using either digitonin-permeabilized GT1-7 neural cells or isolated GT1-7 mitochondria by 1.7 and 3.9 fold, respectively, when glutamate and malate were used as respiratory substrates. This difference was less apparent when respiration was driven by the oxidation of succinate in the presence of the respiratory complex I inhibitor rotenone. Mitochondria from Bcl-2 expressors were also much more resistant to inhibition of NADH-dependent respiration caused by sequestration of large Ca2+ loads. The enhanced ability of mitochondria within Bcl-2-expressing cells to sequester large quantities of Ca2+ without undergoing profound respiratory impairment provides a plausible mechanism by which Bcl-2 inhibits certain forms of delayed cell death, including neuronal death associated with ischemia and excitotoxicity.     

Hair

The psychologic importance of hair to man is in inverse ratio to its physical function. Except for scalp hair and desultory areas of sexual hair, most of man's hair follicles are vestigial. Three problems of hair growth remain to be solved: (1) how the intermittent activity of hair follicles in both animals and man is controlled; (2) how the male hormone alters the hair cycle in human skin; and (3) why larger hairs are produced by testosterone in some areas of the body when in some individuals the hair follicles in the scalp regress. Studies in which skin grafts from rats of different ages were exchanged showed that hair follicles are innately programmed but can be slowly influenced by systemic factors. Steroid hormones, especially estrogens, slow down the moult cycle whereas thyroid hormones accelerate it. What establishes the innate rhythm remains problematical. The fact that plucking out the club hair initiates activity in resting follicles has been explained by the hypothesis that the mitotic inhibitor which accumulates during anagen is normally used up or dispersed during telogen or by wounding. However, contrary to this theory, follicular activity is not prolonged by epilation during anagen. Moreover, if rats are epilated within one or two days of eruption, only club hairs are removed since forceps cannot grasp the tips of the new hairs. Such epilation does not affect the anagen in progress, but remarkedly enough the subsequent resting phase is shortened. Both sexual hair and male-pattern baldness depend on androgenic hormones. Target organs of testosterone convert the hormone to active metabolites, chiefly 5alpha-dihydrotestosterone. In skin, however, 5alpha-dihydrotestosterone may not be the only active tissue androgen. The major metabolite of testosterone incubated with hair roots in androstenedione, and hirsute women without other obvious endocrine abnormality sometimes excrete high levels of androstanediol. Both steroids stimulated the sebaceous glands of hypophysectomized-castrated rats, which, however, showed only a limited response to testosterone. The androgenic steroids, the enzymes that convert them to their active metabolites, and the proteins that bind them are undoubtedly very important to the problems of the growth of sexual hair and male-pattern baldness.     

Structural requirements of synthetic and natural product lipo-chitin oligosaccharides for induction of nodule primordia on Glycine soja

Rhizobia synthesize a class of lipo-chitin oligosaccharides that induce root hair deformation and induce the initiation of nodule structures on legume roots. These lipo-chitin oligosaccharides are tetra- and penta-lipo-oligosaccharides of N-acetylglucosamine with an acyl substitution on the nonreducing end and are commonly known as Nod factors. In this study, we demonstrate that synthetic analogs of natural product Nod factors have the same biological activities. To determine structure-activity relationships, a collection of synthetic and natural product lipo-chitin oligosaccharides was assayed on Glycine soja. All biologically active lipo-chitin oligosaccharides induced both root hair deformation and nodule initiations on G. soja. The most active lipo-chitin oligosaccharides deformed root hairs at 10(-15) M and induced nodules at 1 ng of lipo-chitin oligosaccharide per spot inoculation. Plant responses demonstrate an interdependence of backbone length and the presence of substitutions on the reducing end. Lipo-chitin oligosaccharides containing four N-acetylglucosamine residues were active only without a reducing end modification, whereas lipo-chitin oligosaccharides containing five N-acetylglucosamine residues were active only with reducing end modification. The plant thus recognizes lipo-chitin oligosaccharides without reducing end substitutions despite the importance of these modifications for host range.     

Electrophysiology of respiration

Neurological respiratory insufficiency may be the primary cause of admission to an intensive care unit or may develop during care in an intensive care ward. Severe respiratory insufficiency due to nervous system causes either involves a lack of central drive or weakness of the respiration muscles. The former are induced by a wide variety of encephalopathies and the latter by diseases of anterior horn cells, peripheral nerve, the neuromuscular junction, or muscles of the chest wall or diaphragm. In an intensive care unit, it is often not possible clinically to determine whether there is a lack of central drive or a neuromuscular problem. It is now possible by electrophysiological methods to pinpoint the site of nervous system cause of respiratory insufficiency. This review will describe the various electrophysiological techniques currently available and describe how they have been successfully applied in investigating some conditions that cause severe respiratory failure.     

Correction method for end-tidal xenon concentration in CBF measurements with xenon-enhanced CT

PURPOSE: The goal of this work is to show how variations in respiratory rate and tidal volume affect calculated cerebral blood flow (CBF) values on xenon-enhanced CT. In xenon-enhanced CT examination, the patient often takes shallow and rapid breaths. Thus, it is less likely that end-tidal xenon concentration reflects arterial xenon concentration, and appropriate correction measures should be taken for the end-distal respiratory data to obtain reliable CBF values. METHOD: Preliminary breathing tests were performed using a lung phantom to determine the influence of respiratory volume and rate on end-tidal xenon concentration. Two xenon-enhanced CT studies were conducted of a healthy person with completely different respiratory manners between two studies. One was deep and slow respiration. The other was shallow and rapid respiration. RESULTS: The lung phantom results prove that deep and slow respiration is essential for the end-tidal method. The results of xenon-enhanced CT studies of the same person show that the direct use of end-tidal data for shallow and rapid respiration leads to CBF values much lower than the actual values. CONCLUSION: Differences in respiratory rate and tidal volume during xenon inhalation can significantly affect calculated CBF values on xenon-enhanced CT. With use of the correction methods described herein, these effects can be minimized. We have derived the end-tidal correction method on the assumption that a person's CBF values should be kept unchanged regardless of different respiratory manners.     

Respiration and oxidative phosphorylation in the apicomplexan parasite Toxoplasma gondii

Respiration, oxidative phosphorylation, and the mitochondrial membrane potential (DeltaPsi) of tachyzoites of the apicomplexan parasite Toxoplasma gondii were assayed in situ using very low concentrations of digitonin to render their plasma membrane permeable to succinate, ADP, safranin O, and other small molecules. The rate of basal respiration was slightly increased by digitonin when the cells were incubated in medium containing succinate. ADP promoted an oligomycin-sensitive transition from resting to phosphorylating respiration. Respiration was sensitive to antimycin A and cyanide, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) was oxidized by antimycin A-poisoned mitochondria. The addition of ADP after TMPD/ascorbate also resulted in phosphorylating respiration. The antitoxoplasmosis drug atovaquone, at a very low concentration (0.03 microM), totally inhibited respiration and disrupted the mitochondrial membrane potential. Atovaquone was shown to inhibit the respiratory chain of T. gondii and mammalian mitochondria between cytochrome b and c1 as occurs with antimycin A1. Phosphorylation of ADP could not be obtained in permeabilized tachyzoites in the presence of either pyruvate, 3-oxo-glutarate, glutamate, isocitrate, dihydroorotate, alpha-glycerophosphate, or endogenous substrates. Although ADP phosphorylation was detected in the presence of malate, this activity was rotenone-insensitive and was probably due to the conversion of malate into succinate through a fumarate reductase activity that was detected in mitochondrial extracts. Together these results provide the first direct biochemical evidence that the respiratory chain and oxidative phosphorylation are functional in apicomplexan parasites, although the terminal respiratory pathway is different from that in the mammalian host.