Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Cornus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8Linked to original sources
PubMed2006

p53 potentiates hippocampal neuronal death caused by global ischemia.

Although p53 controls cell death after various stresses, its role in neuronal death after brain ischemia is poorly understood. To address this issue, we subjected p53-deficient (p53-/- and p53+/-) mice (backcrossed for 12 generations with C57BL/6 mice) and wild-type mice (p53+/+) to transient global ischemia by the three-vessel occlusion method. Despite similar severity of ischemia, as shown by anoxic depolarization and cortical blood flow, neuronal death in the hippocampal cornus ammonis (CA)1 region was much more extensive in p53+/+ than in p53-/- mice (surviving neuronal count, 9.3%+/-3.0% versus 61.3%+/-34.0% of nonischemic p53+/+ controls, respectively, P<0.0037). In p53+/- mice, a similar trend was also observed, though not statistically significant (43.5% of nonischemic p53+/+ controls). In p53+/+ mice, p53-like immunoreactivity in hippocampal CA1 neurons was enhanced at 12 h after ischemia, and messenger ribonucleic acid for Bax, a direct downstream target of p53, was also increased. These results indicate that p53 potentiates ischemic neuronal death in vivo and suggest that this molecule could be a therapeutic target in neuronal death after cerebral ischemia.

Animals↗
PubMed2006

EAAC1 glutamate transporter expression in the rat lithium-pilocarpine model of temporal lobe epilepsy.

Glutamate excitotoxicity has been involved in the pathophysiology of epilepsy. Normal functioning of glutamate transporters clears the synaptically released glutamate to prevent excitotoxic neuronal death. Using densitometric immunohistochemical analysis, we examined the temporal expression of the neuronal glutamate transporter (EAAC1) in the lithium-pilocarpine rat model of temporal lobe epilepsy. During the acute period of lithium-pilocarpine-induced status epilepticus, EAAC1 transporter expression increased in the pyramidal neurons of cornus ammonis (CA)1, CA2 and CA3 (fields of the hippocampus), in dentate gyrus (DG) granule cells and in olfactory tubercle (Tu). During the latent period, EAAC1 expression was strongly expressed in the DG granular and molecular layers, Tu, cerebral cortex and septum, and went back to control levels in CA1, CA2 and CA3 layers. The overexpression of EAAC1 occurred mainly in structures prone to develop Fluoro-Jade-B-positive degenerating neurons. It is, however, not clear to what extent the overexpression of EAAC1 contributes to epileptogenesis and in which area it may represent a preventive or compensatory or response to injury.

Animals↗
PubMed1999

Host race or species? Allozyme characterization of the 'flowering dogwood fly', a member of the Rhagoletis pomonella complex.

The term 'flowering dogwood fly' has been used in the literature for a poorly understood member of the Rhagoletis pomonella sibling species complex infesting the fruits of flowering dogwood (Cornus florida). Electrophoretic analysis of 17 allozyme loci in 21 populations reveals significant frequency differences between the flowering dogwood fly and its closest relative the apple maggot fly, R. pomonella, and between it and the somewhat more distant 'sparkleberry fly'. Frequency differences between the flowering dogwood fly and R. pomonella are as great as 0.817 in the north, but are less in the south, with a maximum difference at one site of only 0.328. No fixed allozyme differences distinguish the flowering dogwood fly anywhere; its only consistent, unique feature is the highest frequency of Aat-259 in the pomonella species group. Population structure of the flowering dogwood fly is moderate with FST=0.084 and fewer latitudinal clines than R. pomonella. The conclusion from the allozyme and life history data is that the flowering dogwood fly is a species, although some interspecific gene flow may be occurring. Additional issues discussed include how to estimate interspecific gene flow when genetic markers are under divergent selection, the appropriate species concept when there is gene flow, and the future of the flowering dogwood fly in the face of the dogwood anthracnose epidemic. The possible utility of a new species concept for phytophagous insects, using as a criterion the capacity of a host race to regenerate the ancestral population, is also discussed.

Animals↗
PubMed2000

Gluco- and mineralocorticoid receptor-mediated regulation of neurotrophic factor gene expression in the dorsal hippocampus and the neocortex of the rat.

Gluco- and mineralocorticoid receptors (GR and MR) act via common promoter elements but may exert different effects on gene regulation in various regions of the forebrain. In order to separately analyse the role of GR and MR in the regulation of neurotrophic factor genes and their receptors, we used adrenalectomy and subsequent hormone injections in the rat as a model system. Twenty-four hours after adrenalectomy rats were injected with a single dose of corticosterone (2 and 10 mg/kg), aldosterone (0.5 mg/kg) or the synthetic glucocorticoid agonist RU 28362 (4 mg/kg). Gene expression of basic fibroblast growth factor (bFGF) and its high-affinity receptors [fibroblast growth factor receptor subtypes 1-3 (FGF-R1, FGF-R2, FGF-R3)], as well as brain-derived growth factor (BDNF) and neurotrophin-3 (NT-3) was analysed at 4 h after the hormone injection in CA1-CA4 (cornus of Ammon areas of the hippocampus) and dentate gyrus of the dorsal hippocampus and in neocortex by means of in situ hybridization. We found that bFGF is regulated in CA2, CA3 and dentate gyrus by GR and MR together, and in CA1, CA4 and neocortex by GR alone. FGF-R2 expression in the hippocampus seems to be regulated only by MR, while BDNF expression appears to depend on both receptors. FGF-R1, FGF-R3 and NT-3 were only moderately affected by the hormone activation of GR and MR acting in concert or alone in the various regions. Thus, the present findings suggest that the adrenal cortical system through GR and MR participate in the control of neurotrophic factor signalling in a highly subregion- and cellular-dependent manner.

Adrenalectomy↗
PubMed2006

Quantitative analysis and subcellular distribution of mRNA and protein expression of the hyperpolarization-activated cyclic nucleotide-gated channels throughout development in rat hippocampus.

The properties of the hyperpolarization-activated current (I(h)) and its roles in hippocampal network function evolve radically during development. Because I(h) is conducted by the hyperpolarization-activated cyclic nucleotide-gated (HCN) cation channels, we tested the hypothesis that understanding the quantitative developmental profiles of HCN1, HCN2, and HCN4 expression, and the isoform- and age-specific progression of their subcellular distribution, should shed light on the established modifications of the properties of I(h) throughout development. Combined quantitative in situ hybridization, regional western blots, and high-resolution, dual-label immunocytochemistry revealed striking and novel information about the expression and distribution of the HCN channel isoforms in the developing hippocampal formation. In cornus ammon 1 (CA) pyramidal cell layer, a robust increase of HCN1 mRNA and protein expression occurred with age, with reciprocal reduction of HCN4 and relatively stable HCN2 levels. These distinct expression patterns raised the contribution of HCN1 to the total HCN channel pool from 33% to 65% consonant with acceleration and reduced cyclic adenosine mono phosphate (cAMP) sensitivity of I(h) in this region with age. In CA3, strong expression of HCN1 already neonatally supports the recently established role of this conductance in neonatal, age-specific, hippocampal oscillations (giant depolarizing potentials). Notably, HCN1 channels were present and probably transported to dendritic compartments already on postnatal day (P) 2, whereas HCN2 channel protein was not evident in dendrites for the first 2 weeks of life. HCN2 mRNA and protein expression remained fairly constant subsequent to the first week of life in all hippocampal subfields examined, whereas HCN4 mRNA and protein expression declined after maximal neonatal expression, so that the contribution of this isoform to the total HCN channel pool dropped from 43% (CA1) and 34% (CA3) on P11 to 8% (CA1) and 19% (CA3) on P90. Interneuronal expression of all HCN channel isoforms in stratum pyramidale was robust in parvalbumin-but not in cholecystokinin-expressing populations and with a subunit-specific subcellular distribution. Taken together, these data suggest that early in life, HCN4 may contribute significantly to the functions of I(h) in specific hippocampal regions. In addition, these evolving, differential quantitative, and subcellular expression patterns of the HCN channel isoforms support age-specific properties and functions of I(h) within the developing hippocampal formation.

Animals↗
PubMed1995

Effects of "near-lethal" stress on bud dormancy and stem cold hardiness in red-osier dogwood.

We studied the effects of "near-lethal" (NL, 47 degrees C for 1 h) heat stress, applied to intact shoots of red-osier dogwood (Cornus sericea L.) during early (October), deep (November) or late (December) dormancy, on bud dormancy release and development of stem tissue cold hardiness under natural conditions and at a constant temperature of 0 or 23 degrees C in the dark. The NL heat-stress treatment overcame bud dormancy when applied during the early and late stages of dormancy. During October and December, all plants in the 23 degrees C + dark post-stress environment broke bud within 35 and 12 days, respectively, whereas the corresponding values for days to bud break in the control plants were more than 150 and 110 days, respectively. Application of NL heat stress during deep dormancy caused only slightly earlier bud break compared to the control plants. In the 0 degrees C + dark post-stress environment, all NL heat-treated plants died within 9 weeks. Under natural post-stress conditions, bud break in plants receiving NL heat stress during early and deep dormancy occurred at the same time as in control plants, whereas bud break of plants receiving NL heat stress during late dormancy occurred 55 days earlier than in control plants. Under both natural and 23 degrees C + dark post-stress conditions, cold hardiness of plants receiving NL heat stress during early dormancy was similar to that of controls. Application of NL heat stress during deep dormancy hastened the rate of deacclimation under the 23 degrees C + dark post-stress conditions but had no effect on deacclimation under natural post-stress conditions. Application of NL heat stress during late dormancy enhanced deacclimation of plants in both the 23 degrees C + dark and natural post-stress environments.

Journal Article↗
PubMed1995

Gas exchange, leaf structure and nitrogen in contrasting successional tree species growing in open and understory sites during a drought.

Seasonal ecophysiology, leaf structure and nitrogen were measured in saplings of early (Populus grandidentata Michx. and Prunus serotina J.F. Ehrh.), middle (Fraxinus americana L. and Carya tomentosa Nutt.) and late (Acer rubrum L. and Cornus florida L.) successional tree species during severe drought on adjacent open and understory sites in central Pennsylvania, USA. Area-based net photosynthesis (A) and leaf conductance to water vapor diffusion (g(wv)) varied by site and species and were highest in open growing plants and early successional species at both the open and understory sites. In response to the period of maximum drought, both sunfleck and sun leaves of the early successional species exhibited smaller decreases in A than leaves of the other species. Shaded understory leaves of all species were more susceptible to drought than sun leaves and had negative midday A values during the middle and later growing season. Shaded understory leaves also displayed a reduced photosynthetic light response during the peak drought period. Sun leaves were thicker and had a greater mass per area (LMA) and nitrogen (N) content than shaded leaves, and early and middle successional species had higher N contents and concentrations than late successional species. In both sunfleck and sun leaves, seasonal A was positively related to predawn leaf Psi, g(wv), LMA and N, and was negatively related to vapor pressure deficit, midday leaf Psi and internal CO(2). Although a significant amount of plasticity occurred in all species for most gas exchange and leaf structural parameters, middle successional species exhibited the largest degree of phenotypic plasticity between open and understory plants.

Journal Article↗
PubMed1996

Estimates of net photosynthetic parameters for twelve tree species in mature forests of the southern Appalachians.

Leaf gas exchange, temperature, and incident radiation were measured in situ for 20 mature trees of 12 deciduous species spanning a range of heights from 7.9 to 30.1 m and growing in the southern Appalachian Mountains. Air temperature, water vapor pressure, total radiation, photosynthetically active radiation, and carbon dioxide concentration were also measured. Estimated mean, light-saturated net assimilation rates ( micro mol m(-2) s(-1)) were: Quercus coccinea Muenchh. (10.3), Q. prinus L. (9.9), Q. rubra L. (8.9), Betula lenta L. (8.1), Liriodendron tulipifera L. (7.9), Q. alba L. (7.6), Carya glabra Mill. (7.2), Acer rubrum L. (5.6), Nyssa sylvatica Marsh. (3.9), Cornus florida L. (3.5), and Acer pensylvanicum L. (1.7). There were significant differences in both net assimilation rates and quantum yield efficiencies between species, with the understory species C. florida and A. pensylvanicum exhibiting lower net assimilation rates at saturation and higher estimated quantum yield efficiencies than the other species. Average temperature and light decreased from the canopy top to bottom, whereas ambient CO(2) concentration increased, and vapor pressure and vapor pressure deficits were inconsistent. We observed curvilinear effects of temperature and vapor pressure deficit on net assimilation response to light, and these effects varied by species. Errors in predicted net assimilation ranged from 1 to 3 micro mol m(-2) s(-1) under the environmental conditions prevailing during the study.

Journal Article↗
PubMed1998

Osmotic potential of several hardwood species as affected by manipulation of throughfall precipitation in an upland oak forest during a dry year.

Components of dehydration tolerance, including osmotic potential at full turgor (Psi(pio)) and osmotic adjustment (lowering of Psi(pio)), of several deciduous species were investigated in a mature, upland oak forest in eastern Tennessee. Beginning July 1993, the trees were subjected to one of three throughfall precipitation treatments: ambient, ambient minus 33% (dry treatment), and ambient plus 33% (wet treatment). During the dry 1995 growing season, leaf water potentials of all species declined to between -2.5 and -3.1 MPa in the dry treatment. There was considerable variation in Psi(pio) among species (-1.0 to -2.0 MPa). Based on Psi(pio) values, American beech (Fagus grandifolia Ehrh.), dogwood (Cornus florida L.), and sugar maple (Acer saccharum Marsh.) were least dehydration tolerant, red maple (A. rubrum L.) was intermediate in tolerance, and white oak (Quercus alba L.) and chestnut oak (Quercus prinus L.) were most tolerant. During severe drought, overstory chestnut oak and understory dogwood, red maple and chestnut oak displayed osmotic adjustment (-0.12 to -0.20 MPa) in the dry treatment relative to the wet treatment. (No osmotic adjustment was evident in understory red maple and chestnut oak during the previous wet year.) Osmotic potential at full turgor was generally correlated with leaf water potential, with both declining over the growing season, especially in species that displayed osmotic adjustment. However, osmotic adjustment was not restricted to species considered dehydration tolerant; for example, dogwood typically maintained high Psi(pio) and displayed osmotic adjustment to drought, but had the highest mortality rates of the species studied. Understory saplings tended to have higher Psi(pio) than overstory trees when water availability was high, but Psi(pio) of understory trees declined to values observed for overstory trees during severe drought. We conclude that Psi(pio) varies among deciduous hardwood species and is dependent on canopy position and soil water potential in the rooting zone.

Journal Article↗
PubMed1999

Foliar temperature-respiration response functions for broad-leaved tree species in the southern Appalachians.

We measured leaf respiration in 18 eastern deciduous forest tree species to determine if there were differences in temperature-respiration response functions among species or among canopy positions. Leaf respiration rates were measured in situ and on detached branches for Acer pensylvanicum L., A. rubrum L., Betula spp. (B. alleghaniensis Britt. and B. lenta L.), Carya glabra (Mill.) Sweet, Cornus florida L., Fraxinus spp. (primarily F. americana L.), Liriodendron tulipifera L., Magnolia fraseri Walt., Nyssa sylvatica Marsh., Oxydendrum arboreum L., Platanus occidentalis L., Quercus alba L., Q. coccinea Muenchh., Q. prinus L., Q. rubra L., Rhododendron maximum L., Robinia psuedoacacia L., and Tilia americana L. in the southern Appalachian Mountains, USA. Dark respiration was measured on fully expanded leaves at 10, 15, 20, 25, and 30 degrees C with an infrared gas analyzer equipped with a temperature-controlled cuvette. Temperature-respiration response functions were fit for each leaf. There were significant differences in response functions among species and by canopy position within species. These differences were observed when respiration was expressed on a mass, nitrogen, or area basis. Cumulative nighttime leaf respiration was calculated and averaged over ten randomly selected nights for each leaf. Differences in mean cumulative nighttime respiration were statistically significant among canopy positions and species. We conclude that effects of canopy position and species on temperature-respiration response functions may need to be considered when making estimates of whole-tree or canopy respiration.

Journal Article↗
PubMed2000

A comparison of root growth dynamics of silver maple and flowering dogwood in compacted soil at differing soil water contents.

Many bottomland tree species are tolerant of compacted soil and perform well in urban environments; however, the mechanism underlying this tolerance is unknown. Increased soil water content has been shown to alleviate some of the effects of soil compaction on plant growth, presumably because increasing soil water reduces soil strength. We hypothesized that tree species tolerant of very wet soils would have opportunities for root growth in compacted soil when high soil water contents reduced soil strength, whereas species intolerant of bottomland conditions would not. We tested this hypothesis on flowering dogwood (Cornus florida L.), a mesic species intolerant of inundation, and silver maple (Acer saccharinum L.), a bottomland species. Seedlings of both species were grown in pots for 21 and 30 days, respectively, in a growth chamber in native loam soil maintained at various combinations of soil strength and soil water tension. Downward root growth rate decreased in response to increasing soil strength in both species. At low soil strength (0.6 MPa), downward root growth rate of dogwood seedlings slowed when soil was either excessively wet or dry, whereas root growth rate of silver maple seedlings increased linearly with soil water content. In moderately compacted soil (1.5 g cm(-3) bulk density), silver maple seedlings had greater root growth rate, root length per plant, and ratio of root length to root dry weight in wet soil (0.006 MPa soil water tension) than in moist and dry soils (0.026 and 0.06 MPa, respectively), even though mean oxygen diffusion rate (ODR) was only 0.28 &mgr;g cm(-2) (SE = 0.05). No such effect was detected in highly compacted soil (1.7 g cm(-3) bulk density) in either species. Mean ODR showed a weak positive correlation with soil water tension (r = 0.40, P = 0.07), but was unrelated to soil strength. We conclude that silver maple roots can grow in moderately compacted soil when high soil water content decreases soil strength, whereas dogwood is unable to take advantage of this opportunity.

Journal Article↗
PubMed1969

Multiple freezing points as a test for viability of plant stems in the determination of frost hardiness.

A technique is presented for a simple, rapid, and reliable means of determining the viability of plant tissue subjected to freezing temperatures. Freezing curves of excised stems of Cornus stolonifera Michx., and several other genera were studied. Tissue temperature was recorded during freezing of plant stem sections. The heat of crystallization deflected the resultant freezing curves at points where tissue froze. Living stem sections of all genera studied revealed 2 freezing points, while dead tissue exhibited only 1. The influence of variables such as moisture content, sample size, thermocouple placement, and cooling rate on freezing curves was analyzed. Stem samples wrapped in moisture-proof film with a thermocouple inserted into the pith were frozen to a predetermined test temperature, thawed, and subjected to a second freezing cycle. The presence or absence of 2 freezing points in the second freezing cycle was used as a criterion for establishing viability. The results were immediately available and identical to results from regrowth tests which took about 20 days.

Journal Article↗
PubMed1973

Factors affecting electrical impedance of internodal stem sections.

A sample holder was designed and built to facilitate measuring the magnitude and phase angle of the electrical impedance of internodal stem sections from Cornus stolonifera Michx. A nonpolarizing, electrically conducting manganese dioxidecarbon paste used between the stem sample and the electrodes of the sample holder allowed measurement of impedance at frequencies from 50 hertz to 500 kilohertz without electrode polarization or electrical interference. The impedance magnitude was linearly dependent on the sample length, but this dependence was minimized by computing a normalized impedance magnitude. The normalized impedance magnitude (Z(nf)) was calculated using the impedance magnitude (Z) at any specified frequency (f) and the impedance magnitude at 500 kilohertz (Z(500 khz)) in the following formula: Z(nf) = (Z - Z(500 khz))/Z(500 khz). The normalized impedance magnitude was sensitive to injury produced by boiling and peeling the sample. Electrical impedance measurements on the bark and wood separately demonstrated that they have different electrical properties.

Journal Article↗
PubMed1973

Short term increases in the cold tolerance of red osier dogwood stems induced by application of cysteine.

Bark tissues of Cornus stolonifera stems, treated with cysteine at 24 hours after treatment, survived exposure to -11 C (the tissue temperature) with little or no injury. An initiation of increase in the cold tolerance was usually observed when plants were treated with cysteine at 12 hours after treatment. Neither plants at 36 or 48 hours after treatment nor plants 12 hours before treatment had shown increases in the cold tolerance. They were killed below -5 C, which was the survival temperature of untreated control plants. Two weeks or more of short day induction before cysteine application were required for a significant effect of short term 5 C increase in the cold tolerance.

Journal Article↗
PubMed1974

Nuclear magnetic resonance of water in cold acclimating red osier dogwood stem.

The pulsed and continuous-wave nuclear magnetic resonance of water in cold-acclimating red osier dogwood (Cornus stolonifera Michx) stem showed reduced relaxation times and increased line width. The reduction of relaxation times suggests an over-all restriction in the motional characteristics of the water. The increased line width is not related to a molecular property of the water, but is useful in estimating the initiation of cold acclimation. Biphasic relaxation characteristics may be related to partitioning of the water at the cellular level. The liquid water content of the stem was a weak function of temperature between -25 and -55 C, corresponding to approximately 0.15 gram of water per gram of dry stem. The quantity of unfrozen water at subfreezing temperatures was not strongly dependent on the degree of cold acclimation. It is concluded that the ability of dogwood to survive low temperatures depends on its ability to tolerate diminished quantities of liquid water.

Journal Article↗
PubMed1978

Water Relations, Stomatal Behavior, and Root Conductivity of Red Osier Dogwood during Acclimation to Freezing Temperatures.

Red osier dogwood (Cornus stolonifera Michx.) was artificially acclimated by exposing plants to 8-hour short days (SD) and low (15/5 C) temperatures for 54 to 63 days. Several factors including transpiration rate, stomatal resistance, and root conductivity were correlated so that the rate of water loss in acclimating plants was higher during the first 30 to 40 days of the acclimation sequence. Six days after transferring plants to SD conditions, the stomatal resistance (r(8)) decreased significantly below the r(8) of the 16-hour long day (LD) control plants at the same temperature. Transpiration rate increased by approximately 20 to 30% in the plants transferred to SD. After the initially higher transpiration rate and greater stomatal opening, the stomates closed tightly during the last 2 weeks of acclimation and the transpiration rate of the SD plants dropped to well below the LD control plants. By the end of the acclimation sequence, root conductivity to water uptake was two to three times lower in the SD plants. Leaf xylem water potentials were similar or slightly lower in the plants kept under SD conditions during the first 5 to 7 weeks of the acclimation sequence. During the last 10 to 15 days of acclimation when the stomates closed, SD leaf water potential rose significantly above the plants in the LD conditions. During acclimation, stem water content decreased by 40 to 50%. Changes in tissue hydration can be indirectly related to plant hardiness and may be affected by alteration of stomatal resistance, transpiration rate, and root conductivity during acclimation.

Journal Article↗
PubMed1978

Interactions of low temperature, water stress, and short days in the induction of stem frost hardiness in red osier dogwood.

The induction of stem frost hardiness by low temperature, water stress, short days, and their combinations in 2- and 4-month-old growing dogwoods (Cornus stolonifera) were investigated. When plants were subjected to more than one factor, the increased hardiness was the sum of the effects of the individual factors involved. No interactions among these factors on hardiness were observed during a 3-week treatment. Results indicate that low temperature, water stress, and short days initially trigger independent frost-hardening mechanisms. Plant ages significantly influenced the change in low temperature-induced frost hardiness, but not the water stress or short day-induced frost hardiness.

Journal Article↗
PubMed1978

Freezing of water in red-osier dogwood stems in relation to cold hardiness.

Studies of stem water in red-osier dogwood (Cornus stolonifera Michx.) using nuclear magnetic resonance spectroscopy indicated that most freezing occurs at temperatures above -30 C in cold-hardy and tender stems. Hardy and tender stems had about the same amount of unfrozen water at -40 C (0.28 gram of water per gram dry weight). When hardy stems were slowly cooled below -20 C, the temperature below which little additional freezing occurs, they survived direct immersion in liquid N(2) (-196 C). Fully hardy samples not slowly precooled to at least -15 C did not survive direct immersion in liquid N(2). The results support the hypothesis that cooling rate is an unimportant factor in tissue survival at and below temperatures where there is little freezable water.

Journal Article↗