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At least 199 records · Page 11Linked to original sources
PubMed1999

EAF1 regulates vegetative-phase change and flowering time in Arabidopsis.

We have identified a new locus that regulates vegetative phase change and flowering time in Arabidopsis. An early-flowering mutant, eaf1 (early flowering 1) was isolated and characterized. eaf1 plants flowered earlier than the wild type under either short-day or long-day conditions, and showed a reduction in the juvenile and adult vegetative phases. When grown under short-day conditions, eaf1 plants were slightly pale green and had elongated petioles, phenotypes that are observed in mutants altered in either phytochrome or the gibberellin (GA) response. eaf1 seed showed increased resistance to the GA biosynthesis inhibitor paclobutrazol, suggesting that GA metabolism and/or response had been altered. Comparison of eaf1 to other early-flowering mutants revealed that eaf1 shifts to the adult phase early and flowers early, similarly to the phyB (phytochrome B) and spy (spindly) mutants. eaf1 maps to chromosome 2, but defines a locus distinct from phyB, clf (curly leaf), and elf3 (early-flowering 3). These results demonstrate that eaf1 defines a new locus involved in an autonomous pathway and may affect GA regulation of flowering.

Alleles↗
PubMed2005

Establishment of the vernalization-responsive, winter-annual habit in Arabidopsis requires a putative histone H3 methyl transferase.

Winter-annual accessions of Arabidopsis thaliana are often characterized by a requirement for exposure to the cold of winter to initiate flowering in the spring. The block to flowering prior to cold exposure is due to high levels of the flowering repressor FLOWERING LOCUS C (FLC). Exposure to cold promotes flowering through a process known as vernalization that epigenetically represses FLC expression. Rapid-cycling accessions typically have low levels of FLC expression and therefore do not require vernalization. A screen for mutants in which a winter-annual Arabidopsis is converted to a rapid-cycling type has identified a putative histone H3 methyl transferase that is required for FLC expression. Lesions in this methyl transferase, EARLY FLOWERING IN SHORT DAYS (EFS), result in reduced levels of histone H3 Lys 4 trimethylation in FLC chromatin. EFS is also required for expression of other genes in the FLC clade, such as MADS AFFECTING FLOWERING2 and FLOWERING LOCUS M. The requirement for EFS to permit expression of several FLC clade genes accounts for the ability of efs lesions to suppress delayed flowering due to the presence of FRIGIDA, autonomous pathway mutations, or growth in noninductive photoperiods. efs mutants exhibit pleiotropic phenotypes, indicating that the role of EFS is not limited to the regulation of flowering time.

Alleles↗
PubMed2004

EARLY FLOWERING 5 acts as a floral repressor in Arabidopsis.

EARLY FLOWERING 5 (ELF5) is a single-copy gene involved in flowering time regulation in Arabidopsis. ELF5 encodes a nuclear-targeted protein that is related to the human nuclear protein containing a WW domain (Npw)38-binding protein (NpwBP). Lesions in ELF5 cause early flowering in both long days and short days. elf5 mutations partially suppress the late flowering of both autonomous-pathway mutants and FRIGIDA (FRI)-containing lines by reducing the expression of FLOWERING LOCUS C (FLC), a floral repressor upon which many of the flowering pathways converge. elf5 mutations also partially suppress photoperiod-pathway mutants, and this, along with the ability of elf5 mutations to cause early flowering in short days, indicates that ELF5 also affects flowering independently of FLC.

5' Untranslated Regions↗
PubMed2005

HUA2 is required for the expression of floral repressors in Arabidopsis thaliana.

The HUA2 gene acts as a repressor of floral transition. Lesions in hua2 were identified through a study of natural variation and through two mutant screens. An allele of HUA2 from Landsberg erecta (Ler) contains a premature stop codon and acts as an enhancer of early flowering 4 (elf4) mutants. hua2 single mutants, in the absence of the elf4 lesion, flower earlier than wild type under short days. hua2 mutations partially suppress late flowering in FRIGIDA (FRI )-containing lines, autonomous pathway mutants, and a photoperiod pathway mutant. hua2 mutations suppress late flowering by reducing the expression of several MADS genes that act as floral repressors including FLOWERING LOCUS C (FLC ) and FLOWERING LOCUS M (FLM ).

Arabidopsis↗
PubMed2006

The maize transfer cell-specific type-A response regulator ZmTCRR-1 appears to be involved in intercellular signalling.

Response regulators are signal-transduction molecules present in bacteria, yeast and plants, acting as relays for environmental challenges. This paper reports the characterization of a Zea mays gene, ZmTCRR-1, that codes for a member of the type-A response regulator class of proteins. The gene was found to be expressed exclusively in the endosperm transfer-cell layer 8-14 days after pollination, when transfer-cell differentiation is most active. The promoter of ZmTCRR-1 was strongly transactivated in heterologous systems by the transfer cell-specific transcription factor ZmMRP-1. The ZmTCRR-1 protein was detected not only in the transfer-cell layer, but also in the conductive tissue deep inside the endosperm, where there is no transcription of the gene. This suggests that two-component systems might be involved in intercellular signal transmission, in contrast to the generally held belief that these systems are involved only in cell-autonomous pathways.

Amino Acid Sequence↗
PubMed2000

A subthreshold persistent sodium current mediates bursting in rat subfornical organ neurones.

It is widely accepted that while release of amino acid neurotransmitters occurs with relatively high fidelity, peptidergic synapses require clustered bursts of action potentials for optimal transmitter release. Here we describe for the first time the occurrence and mechanisms of bursting by neurones in the subfornical organ (SFO), cells that utilize the peptide angiotensin II (ANG) in neurotransmission in autonomic pathways. In current clamp recording of isolated SFO neurones in vitro, 53 % (n = 74) showed either spontaneous or evoked burst-like discharge patterns. Bursts typically appeared as shifts in bistable membrane potential, with action potentials superimposed on a depolarizing afterpotential (DAP). Similarly, in vivo single unit recordings of identified SFO neurones showed that 9 of 15 neurones fired in bursts. The pattern of bursting, as well as duration of evoked DAPs was strongly dependent upon membrane potential, suggesting that the DAP contributes to burst generation. Based on our previous observation of calcium-sensing receptor (CaR)-activated bursts, we investigated the effects of NPS R-467, an allosteric agonist of the CaR, on evoked DAPs. NPS R-467 (1 microM) potentiated DAP duration throughout the voltage range tested. We observed a dependence of evoked DAPs upon Na+ channels, as shown by sensitivity to tetrodotoxin (0.5 microM) or reduction of external [Na+] from 140 to 40 mM. The duration of DAPs suggested that a persistent Na+ current mediates these events. Voltage-clamp analysis revealed the presence of a subthreshold sodium current, INaP. Pharmacological blockade of INaP with 100 microM lidocaine reduced the duration of evoked DAPs, and inhibited bursting in SFO neurones. Facilitation of INaP with 10 nM anemone toxin (ATX) increased DAP duration and led to marked excitation of bursting cells. These data indicate that INaP is the main current underlying bursting in SFO neurones. Our observations of receptor-mediated facilitation of bursting by SFO neurones represents an intriguing mechanism through which the release of the peptide neurotransmitter ANG may be regulated.

Action Potentials↗
PubMed2004

The therapeutic potential of botulinum toxin.

BACKGROUND: Botulinum toxin type A (BTX-A; commercial preparation BOTOX) is most well known for its effect on muscle contraction because of the BTX binding to the presynaptic nerve terminal, inhibiting the release of acetylcholine (ACH). The therapeutic benefit of BTX-A, however, can also be isolated to pain relief alone, suggesting that BTX-A also works through additional modes of action. OBJECTIVE: This article provides insight by an experienced physician into four different case reports. Each case demonstrates the therapeutic potential of BTX-A and the possibility of a different mechanism of action for BTX other than the inhibition of ACH release. RESULTS: Four patients, each with different symptoms such as relapsing-remitting multiple sclerosis, postherpetic neuralgia, peripheral neuropathy, and severe tingling caused by herniation of cervical vertebrae at the level of C8, were treated with BOTOX, and their symptoms were alleviated. CONCLUSIONS: The BTX-A mechanism providing pain relief is hypothesized to be something other than muscle relaxation by inhibiting the release of ACH at the neuromuscular juncture, such as inhibition of the release of substance P or the blocking of autonomic pathways, etc. This article is intended to continue to keep physicians using this substance for dermatologic indications aware of the potential unsuspected effects.

Adult↗
PubMedDate not supplied

Extratrigeminal cluster headache.

Three cases with periodicity and pain profile characteristic of episodic cluster headache, whose headaches were solely confined to the regions of the head and neck outside the trigeminal territory, are reported. Two were females, who had associated nausea and vomiting with severe attacks. The male patient exhibited autonomic symptoms in the eye during the attacks. Alcohol induced headache in one. All three patients responded to anticluster headache therapy. These cases are illustrative of a wider spectrum of clinical manifestations of cluster headache than was originally recognized. They question the theory that cluster headache may be due to a lesion involving the cavernous sinus. One the other hand, it points to involvement of a more complex pain circuit consisting of upper cervical nerves, posterior fossa innervation, trigeminal system and the autonomic pathways.

Adult↗
PubMed1993

Role of CRF in stress-related alterations of gastric and colonic motor function.

Major advances have been made in the understanding of the pathophysiology of stress-related alteration of gut function. A wealth of information indicates that CRF is involved in the central mechanisms by which stress inhibits gastric emptying while stimulating colonic motor function. CRF acts in the PVN to trigger both the inhibition of gastric emptying and the stimulation of colonic motor function in response to stress, in addition to previously established endocrine and behavioral responses. Preliminary evidence exists that CRF acts in the locus coeruleus to induce a selective stimulation of colonic transit without influencing gastric emptying. The central actions of CRF to alter gastric and colonic motor function are conveyed by autonomic pathways and are unrelated to the associated stimulation of pituitary hormone secretion. The demonstration that central CRF plays a role in mediating gastric stasis resulting from surgery, peritonitis or high levels of central interleukin-1 provides new insight into the mechanisms involved in gastric ileus induced postoperatively or by infectious disease. Likewise, the demonstration that CRF in the PVN and locus coeruleus induce the anxiogenic and colonic motor responses to stress and that colonic distention activates neurons in the locus coeruleus opens new avenues for the understanding of the pathogenesis of a subset of IBS patients with colonic hypersensitivity associated with psychopathological disturbance and diarrhea-predominant symptoms.

Animals↗
PubMed1982

Inhibitory interactions between colonic and vesical afferents in the micturition reflex of the cat.

1. In anaesthetized cats in which the only intact autonomic pathways innervating the colon and bladder were in the pelvis nerves, distension of the colon resulted in a graded inhibition of spontaneous bladder motility, and a decrease in the reflexly evoked waves of activity in the vesical branches of the pelvic nerves. 2. Electrical stimulation with voltages sufficient to excite only the myelinated fibres in the colonic branches of the pelvic nerve caused inhibition of spontaneous bladder motility, an increase in micturition threshold, and a reduction in the reflexly evoked waves of activity in the vesical efferents of the pelvic nerve. 3. The results demonstrate that the pelvic nerve afferent inflow from the colon produces a marked central inhibitory influence on the micturition reflex.

Animals↗
PubMed2006

Neurotransmitter mechanisms mediating low-glucose signalling in cocultures and fresh tissue slices of rat carotid body.

The mammalian carotid body (CB) is a polymodal chemosensor which can detect low blood glucose (hypoglycaemia), leading to increased afferent discharge and activation of counter-regulatory autonomic pathways. The underlying neurotransmitter mechanisms are unknown and controversy surrounds whether the action of low glucose is direct or indirect. To address this, we used a coculture model containing functional chemosensory units of rat CB receptor (type I) cell clusters and afferent petrosal neurones (PN). During perforated-patch, whole-cell recordings, low glucose (0-2 mM) stimulated sensory discharge in cocultured PN. When the background P(O2) was lowered to levels typical of arterial blood (approximately 90 mmHg), robust PN chemoexcitation could be induced by physiological hypoglycaemia (3.3-4 mM glucose). These sensory responses were reversibly inhibited by a combination of purinergic (suramin, 50 microM) and nicotinic (mecamylamine, 1 microM) receptor blockers, suggesting that transmission depended on corelease of ATP and ACh. Hypoglycaemic responses were additive with those evoked by hypoxia or hypercapnia; further, they could be potentiated by the GABAB receptor blocker (CGP 55845) and inhibited by 5-HT2A receptor blockers (ketanserin or ritanserin). During paired simultaneous recordings from a PN and a type I cell in an adjacent cluster, the afferent PN response coincided with type I cell depolarization, which was associated with a decrease in input resistance. In fresh tissue slices of rat CB, low glucose stimulated ATP secretion as determined by the luciferin-luciferase assay; this secretion was cadmium sensitive, potentiated by CGP 55845, and inhibited by ketanserin. Taken together these data indicate that CB receptors act as direct glucosensors, and that processing of hypoglycaemia utilizes similar neurotransmitter and neuromodulatory mechanisms as hypoxia.

Acetylcholine↗
PubMed2004

Nitric oxide represses the Arabidopsis floral transition.

The correct timing of flowering is essential for plants to maximize reproductive success and is controlled by environmental and endogenous signals. We report that nitric oxide (NO) repressed the floral transition in Arabidopsis thaliana. Plants treated with NO, as well as a mutant overproducing NO (nox1), flowered late, whereas a mutant producing less NO (nos1) flowered early. NO suppressed CONSTANS and GIGANTEA gene expression and enhanced FLOWERING LOCUS C expression, which indicated that NO regulates the photoperiod and autonomous pathways. Because NO is induced by environmental stimuli and constitutively produced, it may integrate both external and internal cues into the floral decision.

Arabidopsis↗
PubMed2000

Functional role of caspase-1 and caspase-3 in an ALS transgenic mouse model.

Mutations in the copper/zinc superoxide dismutase (SOD1) gene produce an animal model of familial amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disorder. To test a new therapeutic strategy for ALS, we examined the effect of caspase inhibition in transgenic mice expressing mutant human SOD1 with a substitution of glycine to alanine in position 93 (mSOD1(G93A)). Intracerebroventricular administration of zVAD-fmk, a broad caspase inhibitor, delays disease onset and mortality. Moreover, zVAD-fmk inhibits caspase-1 activity as well as caspase-1 and caspase-3 mRNA up-regulation, providing evidence for a non-cell-autonomous pathway regulating caspase expression. Caspases play an instrumental role in neurodegeneration in transgenic mSOD1(G93A) mice, which suggests that caspase inhibition may have a protective role in ALS.

Amino Acid Chloromethyl Ketones↗
PubMed1979

Finger clubbing in inflammatory bowel disease: its prevalence and pathogenesis.

Finger clubbing, measured objectively by using the hyponychial angle, was present in 75 out of 200 (38%) patients with Crohn's disease, 15 out of 103 (15%) with ulcerative colitis, and two out of 24 (8%) with proctitis. In Crohn's disease and ulcerative colitis the hyponychial angle was significantly correlated with both disease activity and the extent of fibrosis in the resected specimens from 47 surgically treated patients. The prevalence of finger clubbing in patients with macroscopic disease within the area of the gut innervated by the vagus nerve was significantly higher than that in patients in whom the disease was confined to the distal colon and rectum. Finger clubbing in patients with Crohn's disease tended to regress after resection of macroscopic disease. It is concluded that finger clubbing is significantly commoner in Crohn's disease than ulcerative colitis. The focal stimuli for finger clubbing include mucosal inflammatory change and fibrosis mediated by the vagus and possibly other autonomic pathways acting as the afferent arc of a finger-clubbing reflex.

Adolescent↗
PubMed1996

Differences in cardiovascular responses to supine exercise and to standing after exercise in two clinical subgroups of Shy-Drager syndrome (multiple system atrophy).

BACKGROUND: In chronic autonomic failure of varying aetiologies, there are differences in the cardiovascular responses to supine leg exercise and to standing after exercise. Whether this occurs between the different subgroups with Shy-Drager syndrome (SDS) is unknown. METHODS: Fourteen patients with the cerebellar form (SDS-C) and 11 patients with parkinsonian features (SDS-P) were studied. RESULTS: Both groups had a similar degree of autonomic failure and postural hypotension. Their responses were compared with nine patients with idiopathic Parkinson's disease (IPD) and 15 normal subjects (controls), all with normal autonomic function. With supine exercise, blood pressure and heart rate rose similarly in controls and patients with IPD and there was no fall in blood pressure on standing after exercise. In both SDS groups there were abnormal responses to exercise: blood pressure fell in SDS-C, but did not fall or rise in SDS-P. Heart rate increased similarly in both SDS groups, calculated systemic vascular resistance fell similarly, but cardiac index rose more in SDS-P than SDS-C. Resting plasma noradrenaline concentrations were subnormal in both forms of SDS, and did not increase with exercise. Postural hypotension was enhanced after exercise to the same extent in SDS-C and SDS-P. CONCLUSIONS: The greater cardiovascular abnormalities in response to exercise in SDS-C suggests that cerebellar or brain stem autonomic pathways are impaired to a greater extent in SDS-C than in SDS-P. Pooling SDS subgroups, therefore, may obscure pathophysiological differences to certain stimuli. Clinically when postural hypotension is being assessed, separation of the subgroups may not be essential, as they responded similarly.

Adult↗
PubMed1975

Factors influencing neurohumoral control of the heart in the newborn dog.

Several investigators have documented immaturity of cardiac autonomic innervation in neonates. To evaluate the integrity of afferent and efferent responses and to determine the role of circulating catecholamines in newborns, 50 puppies and 24 adult dogswere studied with the use of chloralose anesthesia. Interventions were: bilateralvagotomy, bilateral carotid occlusion, central vagus stimulation, stellate stimulation, bilateral adrenalectomy, infusion of norepinephrine or isoproterenol, and intravenoustyramine. Newborns exhibited supersensitivity to exogenous norepinephrine, isoproterenol, and stellate stimulation; responses to carotid occlusion and central vagal stimulation were comparable in both groups. Newborns had less resting vagal tone. After adrenalectomy, newborns exhibited a more marked decline in systemic pressureand heart compared to adults. Myocardial catecholamine content in newborns was 1/10 that in adults, whereas plasma catecholamine concentration in newborns was 30-fold greater than in adults. These data demonstrate functional integrity of afferent and efferent cardiac autonomic pathways in the newborn, define in vivo supersensitivity to the sympathetic neurotransmitter, and suggest a dominant role of circulating catecholamines in modulation of cardiovascular events in neonates.

Adrenal Glands↗
PubMed2005

Gastrointestinal tract innervation of the mouse: afferent regeneration and meal patterning after vagotomy.

Mice, with the variety of genotypes they provide, should be particularly useful for studies of growth factors and gene products in regeneration of autonomic pathways such as the vagus nerve. To provide a foundation for examinations of mouse vagal reorganization, two experiments assessed the rate, extent, and accuracy of afferent reinnervation of the stomach after vagotomy and related these patterns to feeding behavior. In experiment 1, the pattern of afferent regrowth into the gut after unilateral truncal vagotomy was characterized by labeling of these afferents with wheat germ agglutinin-horseradish peroxidase and Micro-Ruby. Regenerating neurites had reached and, in some cases, already reinnervated the stomach by 4 wk after axotomy. By 8 wk, regrowth was more extensive, and many fibers had redifferentiated terminals in the smooth muscle. By 16 wk, vagal projections had reached or exceeded normal density in the corpus, density in the forestomach was still reduced, and regrowth in the antrum was minimal. At all time points, not only appropriate terminals, but also growth cones and aberrant endings, were observed. In experiment 2, meal patterns of vagotomized mice were evaluated using a solid diet over the period of regeneration; cholecystokinin suppression of a liquid meal after unilateral and bilateral truncal vagotomies was also evaluated. Unilaterally, as well as bilaterally, vagotomized animals ate smaller and more frequent meals. These disturbed patterns became more pronounced in the first 8 wk after vagotomy, during regeneration. Cholecystokinin inhibition of intake was attenuated by bilateral, but not unilateral, vagotomy. Overall, the spatial and temporal patterns of structural and functional changes observed during regeneration verify that the mouse provides a useful preparation for examining the control of vagal plasticity.

Afferent Pathways↗
PubMed1998

Effect of antenatal glucocorticoids on sympathetic nerve activity at birth in preterm sheep.

Renal sympathetic nerve activity (RSNA) increases rapidly after delivery of term fetal sheep and parallels the rise in heart rate (HR) and arterial pressure. To examine the RSNA response at birth in immature lambs, experiments were performed in chronically instrumented preterm fetal sheep (118- to 125-day gestation, term 145 days) before and after delivery by cesarean section. HR remained unchanged from fetal values at 1 and 4 h after birth, whereas mean arterial blood pressure (MABP) decreased significantly (P < 0.05) by 4 h after delivery. RSNA significantly decreased after premature birth in all animals studied (n = 6), achieving only 39 +/- 17% of fetal RSNA (P < 0.05; all results are mean +/- SE). Because cardiovascular function after premature birth is improved by the use of antenatal corticosteroids, we also tested the hypothesis that corticosteroid administration would evoke a more pronounced sympathetic response in prematurely delivered lambs (n = 7, 118- to 125-day gestation). After maternal administration of dexamethasone (5 mg i.m., 48 and 24 h before delivery), RSNA increased after birth in six of seven fetuses to 166 +/- 32% of the fetal RSNA value. Dexamethasone treatment also decreased the sensitivity of baroreflex-mediated changes in HR in response to increases in MABP. Because the sympathetic response at birth is depressed in preterm compared with term lambs, we performed an additional study (n = 8) to determine if immature sheep are capable of mounting a sympathetic response to cold. In utero cooling produced rapid and sustained increases in MABP (20 +/- 4%), HR (26 +/- 6%), and RSNA (282 +/- 72%) (all P < 0.05), consistent with a generalized sympathoexcitation. These results suggest that sympathoexcitation is absent after premature delivery despite the presence of functional descending autonomic pathways. Furthermore, exogenous corticosteroids appear to have a maturational effect on the sympathetic response at birth, which may be one mechanism by which maternal steroid administration improves postnatal cardiovascular homeostasis.

Angiotensin II↗