bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of elevated atmospheric CO2on root decomposition in a scrub oak ecosystem
Authors: Dilustro John J. , Day Frank P. , Drake Bert G. 
Published: March 2003

AbstractThe effects of elevated atmospheric CO2on fine root decomposition over a 828‐day period were investigated using open top chambers with both ambient and elevated (700 ppm) CO2treatments in an oak–palmetto scrub ecosystem at Kennedy Space Center, Florida. Carbon dioxide enrichment of the chambers began 15 May 1996. The experiment included roots grown in ambient and elevated carbon dioxide. Vertical litterbags installed in September 1996 in each elevated and ambient chamber incubated from December 1996 to December 1998 showed no significant treatment effect on fine root or rhizome mass loss. Initial fine root percentage mass loss varied from 10.3% to 13.5% after three months; 55.5% to 38.3% of original mass had been lost after 828 days. A period of nitrogen immobilization occurred in both fine roots and rhizomes in the elevated CO2incubation, which is a potential mechanism for nitrogen conservation for this system in an elevated CO2world.
Elevated atmospheric CO2 stimulates aboveground biomass in a fire‐regenerated scrub‐oak ecosystem
Authors: Dijkstra Paul , Hymus Graham , Colavito Debra , Vieglais David A. , Cundari Christina M. , Johnson David P. , Hungate Bruce A. , Hinkle C. ROSS , Drake Bert G. 
Published: March 2003

AbstractThe effect of elevated atmospheric CO2 concentration (Ca) on the aboveground biomass of three oak species, Quercus myrtifolia, Q. geminata, and Q. chapmanii, was estimated nondestructively using allometric relationships between stem diameter and aboveground biomass after four years of experimental treatment in a naturally fire‐regenerated scrub‐oak ecosystem. After burning a stand of scrub‐oak vegetation, re‐growing plants were exposed to either current ambient (379 µL L−1 CO2) or elevated (704 µL L−1 CO2) Ca in 16 open‐top chambers over a four‐year period, and measurements of stem diameter were carried out annually on all oak shoots within each chamber. Elevated Ca significantly increased aboveground biomass, expressed either per unit ground area or per shoot; elevated Ca had no effect on shoot density. The relative effect of elevated Ca on aboveground biomass increased each year of the study from 44% (May 96–Jan 97), to 55% (Jan 97–Jan 98), 66% (Jan 98–Jan 99), and 75% (Jan 99–Jan 00). The effect of elevated Ca was species specific: elevated Ca significantly increased aboveground biomass of the dominant species, Q. myrtifolia, and tended to increase aboveground biomass of Q. chapmanii, but had no effect on aboveground biomass of the subdominant, Q. geminata. These results show that rising atmospheric CO2 has the potential to stimulate aboveground biomass production in ecosystems dominated by woody species, and that species‐specific growth responses could, in the long term, alter the composition of the scrub‐oak community.
Nitrogen‐15 budget in model ecosystems of white clover and perennial ryegrass exposed for four years at elevated atmospheric pCO2
Authors: Hartwig Ueli A. , Lüscher Andreas , Nösberger Josef , Van Kessel Chris 
Published: March 2003

AbstractAlthough there are many indications that N cycling in grassland ecosystems changes under elevated atmospheric CO2 partial pressure (pCO2), most information has been obtained in short‐term studies. Thus, N budgets were established for four years under ambient and 60 Pa pCO2 at two levels of N fertilization in two contrasting model ecosystems: Trifolium repens L. (white clover) and Lolium perenne L. (perennial ryegrass) were planted in soil in boxes in the Swiss FACE experiment. While T. repens showed an 80% increase in harvested biomass with no change in biomass allocation under elevated atmospheric pCO2 compared to ambient conditions, L. perenne showed an increase only in the biomass of the roots. During the four years of the experiment, the systems gained N both from N retained in the soil and from stubble/stolon and roots left after the final harvest; in total between 11 and 86 gN m−2. Nitrogen retention in the soil was between 4 and 64 g m2. The L. perenne system gained the most N and retained the most N in the soil at high N fertilization and elevated atmospheric pCO2. The input of new C and N into the soil correlated well in the L. perenne systems but not in the T. repens systems. Elevated atmospheric pCO2 led neither to an increase in N retention in the soil nor did it reduce the loss of N from the soil. In the L. perenne systems, N fertilization played the main role in both the retention of N and the sequestration of C, while in the T. repens systems symbiotic N2 fixation may have controlled N retention in the soil.
Stemwood volume increment changes in European forests due to climate change—a simulation study with the EFISCEN model
Authors: Nabuurs Gert‐Jan , Pussinen Ari , Karjalainen Timo , Erhard Markus , Kramer Koen 
Published: March 2003

AbstractThis paper presents the results of a modelling study of future net annual increment changes in stemwood of European forests owing to climate change. Seven process‐based growth models were applied to 14 representative forest sites across Europe under one climate change scenario. The chosen scenario was the HadCM2 run, based on emission scenario IS92a, and resulted in an increase in mean temperature of 2.5 °C between 1990 and 2050, and an increase in annual precipitation of 5–15%. The information from those runs was incorporated in a transient way in a large‐scale forest resource scenario model, EFISCEN (European forest information scenario). European scale forest resource projections were made for 28 countries covering 131.7 million ha of forest under two management scenarios for the period until 2050.The results showed that net annual increments in stemwood of European forests under climate change will further increase with an additional 0.9 m3 ha−1 y−1in 2030 compared to the ongoing increase under a current climate scenario, i.e. an extra 18% increase. After 2030 the extra increment increase is reduced to 0.79 m3 ha−1 y−1in 2050. Under climate change, absolute net annual increments will increase from the present 4.95, on average for Europe, to 5.93 m3 ha−1 y−1in 2025. After 2025, increments in all scenarios start to decline owing to ageing of the forest and the high growing stocks being reached.The results of the present study are surrounded by large uncertainties. These uncertainties are caused by unknown emissions in the future, unknown extent of climate change, uncertainty in process‐based models, uncertainty in inventory data, and uncertainty in inventory projection. Although the results are thus not conclusive, climate change may lead to extra felling opportunities in European forests of 87 million m3y−1. Because Europe's forests are intensively managed already, management may adapt to climate change relatively easily. However, this study also indicates that climate change may lead to a faster build‐up of growing stocks. That may create a less stable forest resource in terms of risks to storm damage.
Identification of activity‐regulated proteins in the postsynaptic density fraction
Authors: Satoh Keiko , Takeuchi Masakazu , Oda Yoshiya , Deguchi‐Tawarada Maki , Sakamoto Yoshimasa , Matsubara Kaho , Nagasu Takeshi , Takai Yoshimi 
Published: March 2003

AbstractBackground: The postsynaptic density (PSD) at synapses is a specialized submembranous structure where neurotransmitter receptors are linked to cytoskeleton and signalling molecules. Activity‐dependent dynamic change in the components of the PSD is a mechanism of synaptic plasticity. Identification of the PSD proteins and examination of their modulations dependent on synaptic activity will be valuable for an understanding of the molecular basis of learning and memory.Result: We attempted here to identify proteins in the PSD fraction by two‐dimensional (2D) gel electrophoresis and mass spectrometry. About 1.7 × 103 protein spots were detected on 2D gels. A total of 90 spots were identified, containing 47 different protein species. In addition to previously identified PSD proteins such as PSD‐95/SAP90, several new proteins were identified in the PSD fraction. They included stomatin‐like protein 2 and NIPSNAP1. We also examined activity‐dependent modulations of PSD proteins by 2D gel electrophoresis. The spot concentration of G protein β subunit 5 and NIPSNAP1 increased 2 h after kainate treatment that caused generalized seizures.Conclusion: These results indicate that the combination of 2D gel electrophoresis and mass spectrometry is an excellent tool for the identification of activity‐regulated PSD proteins.
Heroin use in New South Wales, Australia, 1996–2000: 5 year monitoring of trends in price, purity, availability and use from the Illicit Drug Reporting System (IDRS)
Authors: Darke Shane , Topp Ibby , Kaye Harlene , Hall Wayne 
Published: March 2003

ABSTRACTAimsTo document trends in the price, purity, availability and use of heroin in New South Wales detected by the Illicit Drug Reporting System (IDRS) between 1996 and 2000, and to demonstrate the utility of the IDRS in identifying such trends.DesignThe IDRS compares information derived from interviews with injecting drug users, key informants who work in the illicit drugs field, and key indicator data on illicit drug trends.SettingNew South Wales, Australia.FindingsThe price of heroin approximately halved over this period, from a median of A$400 per gram in 1996 to A$220 per gram in 2000. While the price of heroin fell dramatically over the study period, the purity of police seizures of the drug was high across all years, ranging between 62% and 71%. In all years heroin was considered easy to obtain by both heroin users who purchased the drug, and by key informants from the law enforcement and health fields. Concurrent with the large fall in heroin prices, there appeared to have been an increase in the number of heroin users. Between 1997 and 1998 there was a sharp increase in the injecting use of cocaine by heroin users in NSW, a pattern that has persisted.ConclusionsRegular and formal monitoring of illicit drug trends provides timely data in a systematic way to inform health and law enforcement policies towards current and emerging illicit drug problems.
Increased phasic activity of dopaminergic neurones in the rat ventral tegmental area following pharmacologically elevated levels of endogenous kynurenic acid
Authors: ERHARDT S. , ENGBERG G. 
Published: March 2003

ABSTRACTKynurenic acid (KYNA) is an antagonist of ionotropic glutamate receptors, preferentially blocking the glycine‐site of the N‐methyl‐D‐aspartate (NMDA) receptor. In the present electrophysiological study, the firing pattern of dopamine (DA) neurones of rat ventral tegmental area (VTA) was investigated following pharmacologically elevated endogenous levels of KYNA by means of an inhibitor of kynurenine 3‐hydroxylase (PNU 156561A). Pre‐treatment with PNU 156561A (40 mg kg–1, i.v., 5–9 h) caused a threefold increase in endogenous KYNA in whole brain levels and also evoked a significant increase in firing rate and bursting activity of VTA DA neurones. Administration of D‐cycloserine (2–128 mg kg–1, i.v.), a partial agonist at the glycine‐site of the NMDA‐receptor, was found to reverse the increase in firing rate and bursting activity as induced by elevated concentrations of KYNA. The electrophysiological effects of elevated KYNA levels were in all essential mimicked by administration of the NMDA‐receptor antagonist MK 801 (0.05–1.6 mg kg–1, i.v.). Thus, the effects of elevated endogenous brain KYNA observed in the present study are likely to be carried out by NMDA receptor antagonism. In conclusion, this study shows that an increase in endogenous KYNA levels produces significant actions on the tonic afferent control of the firing pattern of VTA DA neurones. Given the psychotomimetic effects of NMDA‐receptor antagonists, e.g. phencyclidine and ketamine, the state of hyperactivity of mesocorticolimbic DA system induced by elevated levels of KYNA may represent a pathophysiological condition analogous to that seen in schizophrenic patients.
Analysis of myogenic mechanisms in renal autoregulation
Authors: KIIL F. 
Published: March 2003

ABSTRACTTo examine whether local myogenic mechanisms account for autoregulation of renal blood flow, a theoretical analysis was undertaken on a model of the pre‐glomerular vascular tree consisting of a main and a short, narrow juxtaglomerular segment. At atmospheric extravascular pressure in vitro data are consistent with a relationship r=r0(1 + k – pk) between radius (r) and transmural pressure (p) at p > 60 mmHg, where k can be estimated from in vitro data and r=r0 at complete autoregulatory vasodilation. After introducing r=r0(1 + k – pk), Poiseuille's formula was integrated along the main segment, Δx long, between arterial pressure P1 and P2 at the end of the main segment. At the lowest autoregulatory pressure P1=65 mmHg pre‐glomerular blood flow is F=5Kr04/Δx. At P1=140 mmHg a pressure drop of only 17 mmHg to P2=123 mmHg is sufficient to fulfil the criterion for complete autoregulation: F=5Kr04/Δx. Thus, 80% of the total pre‐glomerular vascular resistance is localized to the juxtaglomerular segment. Loop diuretics may abolish juxtaglomerular contractility. Calculated flow/pressure relationships after eliminating juxtaglomerular contractility are similar to those obtained after administering ethacrynic acid. If a constant tension hypothesis (r=60r0/p) rather than the transmural pressure hypothesis [r=r0(1 + k – pk)] applies, complete autoregulation is maintained to P2=89 mmHg, but the effect of loop diuretics is not mimicked. In conclusion, high juxtaglomerular contractility may be attributed to a myogenic mechanism only if extravascular pressure in the juxtaglomerular segment is subatmospheric.
Comparison of viscoelastic characteristics in triceps surae between Black and White athletes
Authors: FUKASHIRO S. , ABE T. , SHIBAYAMA A. , BRECHUE W. F. 
Published: March 2003

ABSTRACTThe purpose of the present study was to investigate race differences in viscoelastic characteristics of triceps surae muscle group. Black and white college sprint type athletes (n=44) participated in this study. Viscoelastic properties were assessed using the free vibration technique: subjects sat with their forefeet on the edge of a force‐plate (Kistler, Switzerland) and support a frame loaded with weights (0–40 kg) on the knees. Oscillations of the triceps surae and Achilles tendon system were initiated with a hand‐held hammer by tapping the weight load. Oscillations occur at frequencies of 3–6 Hz and were slightly damped. The damped oscillations in conjunction with the equation of motion of a damped mass‐spring model were used to calculate the viscosity of muscle (b), and the elasticity of muscle fibres (kd) and tendon (kt) in each subject. There were little significant differences in most of physical characteristic variables between black and white athletes. Black athletes have significantly greater muscle viscosity and elasticity than white athletes while tendon elasticity is equivalent. Thus, muscle stiffness is greater among black athletes. Greater muscle stiffness could contribute to greater sprint/jump performance among black athletes, compared with white athletes, through alteration of foot/ground contact and take‐off phases during sprinting/jumping.
Cardiomyocyte contractility and calcium handling partially recover after early deterioration during post‐infarction failure in rat
Authors: Loennechen J. P. , Wisløff U. , Falck G. , Ellingsen Ø. 
Published: March 2003

ABSTRACTThe aim of the study was to determine whether progression of heart failure is associated with deterioration of cardiomyocyte function. Cell dimensions, contractility and calcium transients were measured in cardiomyocytes isolated from the left ventricle of female Wistar rats 1, 4, and 13 weeks after coronary artery ligation or sham‐operation. Relative cardiomyocyte shortening decreased from 26% in controls to 11% 1 week after myocardial infarction and recovered to 18 and 20% after 4 and 13 weeks, respectively. Diastolic and systolic calcium concentrations increased markedly 1 week after myocardial infarction with subsequent reduction after 4 and 13 weeks. Time to 50% relaxation was prolonged by 31% after 1 week and 20% after 4 and 13 weeks with corresponding changes in diastolic calcium clearance. Cardiomyocyte length increased by 6, 24, and 26% after 1, 4 and 13 weeks, respectively, whereas myocyte width increased by 4, 11 and 27%. Cardiomyocytes adjacent to the infarct hypertrophied more and initially had more markedly impaired function than in the remote area. Left ventricular diastolic diameter assessed by echocardiography increased by 47, 66 and 84% after 1, 4 and 13 weeks, respectively, and systolic diameter increased by 120, 162 and 194%. Left ventricular end‐diastolic pressure increased from 6 mmHg to 24, 25 and 36 mmHg. Whereas initial deterioration of cardiac function is associated with reduced cardiomyocyte contractile function, chronic heart failure progression is not accompanied by further impairment of intrinsic cardiomyocyte contractility in this model. Cardiomyocyte hypertrophy and dysfunction are more marked adjacent to the infarction.
Reduced rat renal vascular response to angiotensin II after chronic inhibition of nNOS
Authors: Ollerstam A. , Salomonsson M. , Persson A. E. G. 
Published: March 2003

ABSTRACTThe neuronal isoform of nitric oxide synthase (nNOS) in the kidney is predominantly located in the macula densa (MD) cells. These cells are known to be the sensor in the tubuloglomerular feedback, which influences the tonus of the afferent arteriole. This study investigated the effect of angiotensin II (Ang II) after chronic inhibition of nNOS on renal blood flow (RBF) and cytosolic calcium concentration [Ca2+]i in smooth muscle cells from afferent arterioles. Measurements of RBF were made in two control groups and two groups treated with a nNOS inhibitor, 7‐nitro indazole (7‐NI), for 1 and 4 weeks. At the time of the experiment Ang II bolus was given in the renal artery before and during i.v. l‐NNA. [Ca2+]i was measured in arterioles from control rats and from rats treated for 1 week with 7‐NI. RBF decreased after bolus Ang II by 60 ± 11% in the control vs. 23 ± 8% in the 1 week 7‐NI treated group. The decreased sensitivity to Ang II after 1 week of 7‐NI treatment compared with control rats persisted after l‐NNA infusion. There were no differences from control in the group treated for 4 weeks. Ang II gave a transient [Ca2+]i increase in vessels from control rats whereas this response was absent in 1 week 7‐NI‐treated rats. A possible explanation for these findings could be a down regulation of Ang II receptors. The renal vasculature of rats exhibits a diminished RBF and [Ca2+]i response to Ang II after 1 week blockade of nNOS.
Differential strain patterns of the human gastrocnemius aponeurosis and free tendon, in vivo
Authors: Magnusson S. P. , Hansen P. , Aagaard P. , Brønd J. , Dyhre‐Poulsen P. , Bojsen‐Moller J. , Kjaer M. 
Published: March 2003

AbstractAim:  The mechanical characteristics of the human free tendon and aponeurosis, in vivo, remains largely unknown. The present study evaluated the longitudinal displacement of the separate free Achilles tendon and distal (deep) aponeurosis of the medial gastrocnemius muscle during voluntary isometric contraction.Methods:  Ultrasonography‐obtained displacement of the free tendon and tendon–aponeurosis complex, electromyography of the gastrocnemius, soleus, and dorsiflexor muscles, and joint angular rotation were recorded during isometric plantarflexion (n = 5). Tendon cross‐sectional area, moment arm and segment lengths (Lo) were measured using magnetic resonance imaging. Tendon force was calculated from joint moments and tendon moment arm, and stress was obtained by dividing force by cross‐sectional area. The difference between the free tendon and tendon–aponeurosis complex deformation yielded separate distal aponeurosis deformation. Longitudinal aponeurosis and tendon strain were obtained from the deformations normalized to segment lengths.Results:  At a common tendon force of 2641 ± 306 N, the respective deformation and Lo were 5.85 ± 0.85 and 74 ± 0.8 mm for the free tendon and 2.12 ± 0.64 and 145 ± 1.3 mm for the distal aponeurosis, P < 0.05. Longitudinal strain was 8.0 ± 1.2% for the tendon and 1.4 ± 0.4% for the aponeurosis, P < 0.01. Stiffness and stored energy was 759 ± 132 N mm−1 and 6.14 ± 1.89 J, respectively, for the free tendon. Cross‐sectional area of the Achilles tendon was 73 ± 4 mm2, yielding a stress of 36.5 ± 4.6 MPa and Young's modulus of 788 ± 181 MPa.Conclusion:  The free Achilles tendon demonstrates greater strain compared with that of the distal (deep) aponeurosis during voluntary isometric contraction, which suggests that separate functional roles may exist during in vivo force transmission.
Sympathetic vasodilation in human muscle
Authors: Joyner M. J. , Dietz N. M. 
Published: March 2003

AbstractThe idea that there might be sympathetic vasodilator nerves to skeletal muscle is an old concept that fits with the archaic ‘fight or flight’ model of the sympathetic nervous system. Clear evidence for vasodilator nerves to skeletal muscle began to emerge in animals during the 1930s, when stimulation of selected brainstem areas was shown to evoke hypertension, tachycardia and skeletal muscle vasodilation (i.e. the ‘defense reaction’). By the 1940s and 1950s this idea was well established and it was shown in animals that the sympathetic dilator nerves to muscles were cholinergic. During this time, circumstantial evidence began to suggest the existence of sympathetic cholinergic vasodilator fibres in human skeletal muscle. In this context, the well‐ known forearm vasodilator response to mental stress was shown to be atropine‐sensitive, and absent after surgical sympathectomy. However, while there was clear histological evidence for sympathetic cholinergic dilator fibres in animal muscle, such evidence was not seen in humans. Additionally, attempts to record from sympathetic dilator fibres human muscle have never demonstrated clear evidence for dilator nerve traffic, and many ‘sympathetic dilator’ responses are still present after local anaesthetic nerve block. More recently, the skeletal muscle dilator response to sympathoexcitatory manoeuvres in both humans and animals appears to be nitric oxide (NO)‐dependent. While there are clearly atropine‐sensitive and NO‐dependent dilator nerves to skeletal muscles in animals, our current thinking is that most ‘sympathetic dilator’ responses in human muscle are due to adrenaline or local cholinergic mechanisms acting to stimulate NO release from the vascular endothelium.