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PubMed1987

Different virus-precipitating activities of neutralizing monoclonal antibodies that recognize distinct sites of poliovirus particles.

Two neutralizing monoclonal antibodies (4 C 4 and 4 F 2) against type 1 poliovirus, Mahoney strain, recognized distinct antigenic sites of the virus particles; 4 C 4 antibody bound to vertices of native and heated (56 degrees C, 30 minutes) virus of Mahoney strain, while 4 F 2 antibody reacted with specific surface protrusions of native virus of Mahoney and Sabin strains. The difference in the location of neutralization epitopes with which the two antibodies react was confirmed in the neutralization reaction by the use of mutants resistant to 4 C 4 and 4 F 2 antibody. In immune electron microscopy, double immunodiffusion and sucrose density gradient analysis of virus-antibody complexes, the two antibodies showed a marked difference in their virus-precipitating activities. The 4 C 4 antibody recognizing vertices of the virus particle had little virus-precipitating activity. In contrast, the 4 F 2 antibody that bound to specific surface protrusions of native virus aggregated virus particle efficiently. In neutralization assays, however, the 4 C 4 antibody exhibited a slightly stronger neutralizing activity than the 4 F 2 antibody. Thus, it was suggested that the strength in precipitating activities of the two antibodies did not correlate with that in their neutralizing activities.

Antibodies, Monoclonal↗
PubMed1995

Increased locus coeruleus glutamate levels are associated with naloxone-precipitated withdrawal from butorphanol in the rat.

Extracellular fluid levels of glutamate were measured in the locus coeruleus during butorphanol (a mixed agonist at mu-, delta-, and kappa-opioid receptors) withdrawal by using microdialysis in conscious butorphanol-dependent Sprague-Dawley rats. Guide cannulae were implanted chronically and rats were given intracerebroventricular (i.c.v.) infusions of butorphanol (26 nmol/1 microliter/hr) or saline (1 microliter/hr) for 3 days. Microdialysis probes (2 mm tip) were inserted into the locus coeruleus 24 hr before precipitation of withdrawal by i.c.v. injection of naloxone (48 nmol/5 microliters). A separate series of rats was rendered dependent by peripheral injection of butorphanol (20 mg/kg, s.c., b.i.d.) for 5 days and naloxone (5 mg/kg, i.p.) was given to precipitate withdrawal. Single injections of butorphanol (26 nmol/5 microliters, i.c.v.) had no effect on the extracellular fluid levels of glutamate, compared to rats injected with vehicle. Behavioral evidence of withdrawal was detected following naloxone challenge in butorphanol-dependent rats (both i.c.v. and s.c. models), but not in non-dependent, vehicle-treated rats. Significant increases (P < 0.05) in levels of glutamate were noted after naloxone-precipitated withdrawal only in the butorphanol group. The glutamate levels in the locus coeruleus increased from 8.37 +/- 2.01 before, to 21.93 +/- 4.58 microM in the first 15 min sample following i.c.v. injections of 48 nmol/5 microliters naloxone and from 10.84 +/- 1.74 before, to 26.01 +/- 6.19 microM in the 15-30 min sample following i.p. injections of 5 mg/kg naloxone in the butorphanol-dependent rats, respectively. These results provide direct evidence to support the role of excitatory amino acids within the locus coeruleus in butorphanol withdrawal.

Animals↗
PubMed1984

The effect of compound 48/80 on the precipitated withdrawal syndrome of dogs.

The aim of this study was to eliminate endogenous stores of histamine before inducing the precipitated withdrawal syndrome. Results demonstrate that histamine plays a role in the emergence of some of the symptoms which characterize the precipitated abstinence syndrome in morphine-dependent dogs. Morphine-dependent dogs receiving 0.5 mg/kg n-allyl-normorphine exhibit the precipitated abstinence syndrome. Injection of compound 48/80, 0.5 mg/kg, a potent histamine liberator, produced, on the other hand, typical signs of the abstinence syndrome. A second injection of this compound 24 hours later, however, failed to induce these signs. An injection of n-allyl-normorphine also failed to induce these signs in dogs pretreated with compound 48/80 despite the fact that the dogs were still on their morphine regime. Control experiments on naive animals showed that injection of 0.5 mg/kg n-allyl-normorphine failed to produce signs of the abstinence syndrome. Injection of compound 48/80, a potent histamine liberator, on the other hand, did produce the typical signs of the abstinence syndrome. Animals pretreated with n-allyl-normorphine followed by compound 48/80 responded similarly to animals treated with compound 48/80 alone.

Animals↗
PubMed1986

Induced precipitation of calcium-oxalate crystals and its prevention in laboratory animals.

Induced precipitation of Ca-oxalate crystals and the possibility of its prevention were studied in dogs. In the first phase of the experiments precipitation of Ca-oxalate crystals in canine renal tubules was induced by intraperitoneal administration of Na-glyoxylate. Preventive medication (lipoic acid, vitamin B1, Milurit), applied in the second phase, resulted in a significant depression of induced precipitation. The successful experiments serve as a basis for clinical research aimed at a preventive medication of recurrent Ca-oxalate stone formation.

Animals↗
PubMed1996

Effects of diltiazem, a Ca2+ channel blocker, on naloxone-precipitated changes in dopamine and its metabolites in the brains of opioid-dependent rats.

The effects of diltiazem, an L-type Ca2+ channel blocker, on naloxone (an opioid receptor antagonist)-precipitated withdrawal signs and changes in extracellular levels of dopamine (DA) and its metabolites in various brain regions of morphine (a mu-opioid receptor agonist) or butorphanol (a mu/delta/kappa mixed opioid receptor agonist) dependent rats were investigated using high performance liquid chromatography fitted with an electrochemical detector (HPLC-ED). Rats were rendered opioid-dependent by continuous intracerebroventricular (i.c.v.) infusion with morphine (26 nmol/microliters per h) or butorphanol (26 nmol/microliters per h) for 3 days. The expression of physical dependence produced by these opioids, as evaluated by naloxone (5 mg/kg. i.p.)-precipitated withdrawal signs, was reduced by concomitant infusion of diltiazem (10 and 100 nmol/microliters per h). Under the same condition, naloxone decreased the levels of: DA in the cortex, striatum, and midbrain; 3,4-dihydroxyphenylacetic acid (DOPAC) in the cortex, striatum, limbic areas, and midbrain: and homovanilic acid (HVA) in the striatum, limbic areas, and midbrain regions. In animals rendered dependent on butorphanol, the results obtained were similar to those of morphine-dependent rats except for the changes in DOPAC levels. Furthermore, concomitant infusion of diltiazem and opioids blocked the decreases in levels of DA, DOPAC, and HVA in a dose-dependent manner. These results suggest that the augmentation of intracellular Ca2+ mediated through L-type Ca2+ channels during continuous opioid infusion results in a decrease in extracellular levels of DA and its metabolites in some specific regions, which are intimately involved in the expression of withdrawal syndrome precipitated by naloxone.

Animals↗
PubMed1998

Chronic recurrent stress due to panic disorder does not precipitate Graves' disease.

A role of psychic stress in precipitating hyperthyroid Graves' disease has been suggested, but the evidence in support of this pathogenetic mechanism is conflicting. In this study we investigated the possible occurrence of Graves' disease in patients with panic disorder, a psychiatric condition characterized by recurrent endogenous stress. The study group included 87 consecutive patients suffering from panic disorder since 1 to 30 years: 17 males (mean age 31.3, range 26-43 years) and 70 females (mean age 37.6, range 15-73 years). Two hundred and sixty-two normal subjects with no present or past history of psychiatric disorder served as controls. Patients were submitted to a full evaluation of the thyroid that included physical examination, assays for free thyroid hormones, TSH, thyroglobulin (TgAb), thyroperoxidase (TPOAb) and TSH receptor (TRAb) antibodies, and thyroid echography. The prevalence of circulating TgAb and/or TPOAb in patients with panic disorder did not differ from that in the control group. Twelve patients with panic disorder (13.7%) had circulating TgAb and/or TPOAb, but none had TRAb. Three out of 12 patients with thyroid antibodies, indicating a genetic susceptibility to autoimmune thyroid disease, had a family history of clinical thyroid autoimmunity, and 4 of them had a hypoechogenic pattern of the thyroid at ultrasound suggesting autoimmune thyroiditis. None of the patients with panic disorder had a previous history of hyperthyroidism. On examination, clinical hyperthyroidism or endocrine ophthalmopathy were not found in any of them. A small goiter was appreciated by palpation in 16 patients (18.3%). Free thyroid hormones and TSH were within the normal range in all patients but one: a 55-year old lady with normal serum free thyroid hormones and undetectable TSH. During an 18-month follow-up she did not develop hyperthyroidism and her TSH spontaneously returned in the normal range. Considering the individual duration of panic disorder, evidence for previous or present Graves' hyperthyroidism was not found for a total of 478 patient-years of exposure to recurrent endogenous stress in the whole study group, and for a total of 39 patient-years in patients with a genetic susceptibility to autoimmune thyroid disease. In conclusion, we found that recurrent endogenous stress did not precipitate Graves' hyperthyroidism in a series of 87 patients with panic disorder, encompassing a total of 478 patient-years of exposure to stress. Failure to activate the hypothalamic-pituitary-adrenal axis by endogenous stress due to panic disorder as opposed to exogenous stress due to life-events might explain why panic disorder does not precipitate Graves' hyperthyroidism.

Adolescent↗
PubMed2004

Analysis of the Henze precipitate from the blood cells of the ascidian Phallusia mammillata.

The Henze precipitate, a peculiar blue-green microparticulate obtained by lysis of the blood cells of the ascidian Phallusia mammillata (Protochordata), was investigated with atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray microanalysis. The precipitate was collected from the Henze solution, an unstable red-brown product obtained by treating blood with distilled water, whose degradation yields a characteristic blue-green product. The microparticulates measured 50-100 micro m in diameter and appeared irregular in shape. SEM examination showed smooth, roughly round boundaries. The microparticulate surface examined with AFM appeared as an irregular matrix formed by 70-320-nm-wide mammillate composites, including and embedding small (500-800 nm wide) crystal-like multilayered formations. X- ray analysis showed that the elements present in these same precipitates were mainly C, Si, Al and O. The microparticulate composition appeared close to those of natural waxes or lacquers, embedding amorphous silicates and/or other Si-Al components. The unusual occurrence of Si in ascidian blood and its role are discussed.

Animals↗
PubMed2003

Involvement of noradrenergic system within the central nucleus of the amygdala in naloxone-precipitated morphine withdrawal-induced conditioned place aversion in rats.

RATIONALE: We previously reported that the central nucleus of the amygdala (CeA) plays a crucial role in the negative affective, rather than somatic, component of morphine withdrawal. However, numerous studies have reported that the central ascending noradrenergic system is implicated in morphine withdrawal syndrome, although the roles of the noradrenergic system within the CeA in the negative affective component remains less clear. OBJECTIVES: The possible role of the noradrenergic system within the CeA in the negative affective component of morphine withdrawal was investigated. METHODS: The extracellular noradrenaline level within the CeA during naloxone-precipitated morphine withdrawal was measured using an in vivo microdialysis experiment on unanesthetized and freely moving rats. The effects of microinjection of beta-adrenoceptor antagonists into the bilateral CeA on the naloxone-precipitated morphine withdrawal-induced conditioned place aversion (CPA) and somatic signs were examined. RESULTS: The extracellular noradrenaline level within the CeA was transiently elevated during morphine withdrawal. Intra-CeA injections of beta-adrenoceptor antagonists propranolol (30 nmol per side) and timolol (10 nmol per side) significantly attenuated the morphine withdrawal-induced CPA. Similarly, beta(1)-antagonist atenolol (30 nmol per side) or beta(2)-antagonist butoxamine (30 nmol per side) significantly attenuated the CPA. In contrast, they did not affect morphine withdrawal-induced somatic signs, except for propranolol. CONCLUSION: These results suggest that the activation of the noradrenergic system within the CeA contributes to naloxone-precipitated morphine withdrawal-induced CPA, rather than somatic signs, through beta(1)- and beta(2)-adrenoceptors.

Adrenergic beta-Antagonists↗
PubMed2000

Modulation of opioidergic system on mecamylamine-precipitated nicotine-withdrawal aversion in rats.

RATIONALE: Several lines of evidence indicate that central opioid systems may be involved in the behavioral effects of nicotine. We previously reported that mecamylamine-precipitated nicotine-withdrawal aversion can be evaluated using the conditioned place preference paradigm. OBJECTIVES: In the present study, modulation of opioidergic systems in mecamylamine-precipitated nicotine-withdrawal aversion was investigated. METHODS: Male Sprague-Dawley rats were chronically treated s.c. with 10 mg/kg/day (-)-nicotine tartrate using an osmotic minipump. After nicotine treatment for 7 days, conditioning sessions were performed. In the morning, the rats were treated with mecamylamine (0.3-3.0 mg/kg, s.c.), hexamethonium (1.0-3.0 mg/kg, s.c.), naloxone (0.1-1.7 mg/kg), or saline (1.0 ml/kg, s.c.) in one compartment for 60 min. In the evening of the same day, rats were treated with the other treatments and confined to the other compartment for 60 min. Rats were treated with morphine (3.0 mg/kg, s.c.) or TAN-67 (56.0 mg/kg, s.c.) 30 min prior to mecamylamine injection in the conditioning session. On the next day of conditioning, tests were performed. RESULTS: Mecamylamine, which is known to pass the blood-brain barrier, produced a dose-dependent place aversion. However, hexamethonium, which fails to penetrate the blood-brain barrier, failed to produce a place aversion. Mecamylamine-precipitated nicotine-withdrawal aversion was significantly attenuated by pretreatment with the mu-opioid receptor agonist morphine and the highly selective delta-opioid receptor agonist TAN-67, which was administered 30 min before mecamylamine injection in the conditioning session. Moreover, naloxone at doses (0.1-1.7 mg/kg) that alone failed to show a place aversion in non-treated rats, produced a dose-dependent place aversion in rats that had been chronically treated with nicotine. CONCLUSIONS: These results suggest that central opioid systems may be involved in nicotine-withdrawal aversion.

Analgesics↗
PubMed1996

Mecamylamine does not precipitate withdrawal in cigarette smokers.

Mecamylamine is an antihypertensive that acts via nicotinic antagonism and has been suggested as an aid in smoking cessation. Nicotine dependent patients may not accept mecamylamine if it precipitates withdrawal, as it does in nicotine dependent rats. This study examined mecamylamine's effects using procedures designed to measure precipitated withdrawal symptoms in humans. Ten cigarette smokers (mean of 37.5 cigarettes/day) and ten non tobacco-using subjects participated in three 6-h sessions. After a 2-h baseline period in which smokers smoked one cigarette every 30 min, oral mecamylamine (0, 10, or 20 mg randomly ordered across sessions) was administered (double-blind). No smoking was allowed for the remainder of the session. Mecamylamine reduced blood pressure and increased heart rate relative to placebo in both the smokers and the non-tobacco users. No reliable direct subjective effects of mecamylamine were observed. Smokers' subjective reports of cigarette craving and tobacco withdrawal increased, and DSST performance was disrupted over the last 4 h of each session. Effects were independent of dose (placebo versus active). These results suggest that up to 20 mg mecamylamine will not precipitate nicotine withdrawal and that this medication would be acceptable for use in smoking cessation.

Adult↗
PubMed1997

Opiate withdrawal signs precipitated by naloxone following a single exposure to morphine: potentiation with a second morphine exposure.

Recent studies in humans with no prior history of opiate abuse indicated that naloxone-precipitated signs of opiate withdrawal could be observed after a single exposure to morphine, and that the severity of withdrawal was enhanced following a second morphine exposure 24 h later. The current study was conducted to establish a paradigm in rodents that resembled these conditions described in humans. To that end, naloxone-precipitated (0.03-3.0 mg/kg) suppression of operant response rates and somatic signs of withdrawal following single or repeated treatments with morphine (5.0 mg/kg) were assessed in previously opiate-naive rats. In one group of rats, naloxone was administered 4 h after both the first and second morphine pretreatment, while in a separate group of rats naloxone was administered 4 h after the second morphine pretreatment only. A single morphine pretreatment significantly increased naloxone's potency to suppress operant response rates, and resulted in the precipitation by naloxone of certain somatic signs of withdrawal. The effects of naloxone on both dependent measures (operant response rates and somatic signs) were potentiated following a second morphine pretreatment, regardless of whether naloxone was administered following both morphine exposures or only following the second morphine exposure. Thus, repeated morphine administration appears to be the critical factor underlying the progressive increase in antagonist potency, whereas prior experience with naloxone is not a necessary factor. The results provide additional support for the hypothesis that the development of dependence on opiates is a progressive phenomenon that may begin with a single dosing.

Animals↗
PubMed1997

Comparison of abstinence syndromes precipitated by flumazenil and PK 11195 in female diazepam-dependent rats.

The abilities of the central (CBR) and the peripheral (PBR) benzodiazepine receptor antagonists, flumazenil (FLU) and PK 11195 (PK), to precipitate an abstinence syndrome in diazepam (DZ)-dependent rats have been evaluated. Female rats were exposed for 5 weeks to DZ slowly released from SC implanted silastic capsules (90 mg/capsule per week) and thereafter they were challenged in weekly intervals with IV injections of FLU (10, 20, 40 mg/kg) or PK (5, 10, 20 mg/kg), respectively. The maximum abstinence scores tended to increase with the dose of FLU but not with the dose of PK. Although FLU and PK precipitated some common abstinence signs, there were marked differences between these antagonists. FLU evoked dose-related tonic-clonic and clonic convulsions (five out of six rats), whereas PK (10 mg/kg) induced convulsions in only one rat (out of five); tachypnea tended to increase with the dose of both FLU and PK; twitches and jerks, backing and writhing had a significant regression on the dose of FLU; rearing tended to decrease with the dose of PK whereas FLU-evoked head bobbing and PK-evoked twitches and jerks had inverse U-shaped dose-response curves. In comparison to FLU, similar doses of PK (10 and 20 mg/kg) induced a lower precipitated abstinence score (P < 0.05) and a less intense tachypnea (P < 0.05). The data indicate that the chronic continuous exposure to DZ (and/or its active metabolites) affects both CBR and PBR in the rat; however, the abstinence syndromes produced by the CBR and PBR antagonists, FLU and PK, differ in overall intensities and in the diversity of evoked abstinence signs.

Animals↗
PubMed2005

Direct and rapid analysis of ambient air and exhaled air via electrostatic precipitation of aerosols in an atomizer furnace and Zeeman spectrometry.

Techniques that allow the elements present in the air to be determined in a simple and rapid manner are very attractive. Direct aerosol sampling techniques avoid the need to pretreat the filter via wet digestion in order to remove any sources of contamination, and they decrease the precipitation time significantly. Analyzers based on this technique can also determine the concentrations of elements in the air automatically in situ. This paper is concerned with the development of a novel analytical system that is based on electrostatically precipitating aerosols from the air into a graphite furnace. The equipment includes a Zeeman spectrometer with high frequency modulation polarization (MGA-915), and an electrostatic precipitation system incorporated into the analyzer. The high sensitivity of the system developed here means that it can be used to determine element concentrations in the air exhaled by humans, as well as those in ambient air.

Aerosols↗
PubMed2000

A simple co-precipitation inductively coupled plasma mass spectrometric method for the determination of uranium in seawater.

Inductively coupled plasma mass spectrometry (ICP-MS) was used in the determination of 238uranium in seawater after concentration by a simplified co-precipitation with iron hydroxide. Ocean water and reference seawater were used in the study. The co-precipitation method required a smaller sample volume (10 fold less), and less column separation to recover the uranium from the seawater matrix, compared to the original iron hydroxide method. The direct seawater dilution technique requires only a small seawater volume (0.5 mL) and offers a rapid, reliable method for uranium analysis in seawater compared to traditional methods. Comparison of the results for simple co-precipitation, direct dilution of seawater, and theoretical uranium values based on salinity concentrations, yielded negligible differences. Data from this work show that the certified value for NASS-4 is low.

Journal Article↗
PubMed2002

Comparison of inhibitory activity on calcium phosphate precipitation by acidic proline-rich proteins, statherin, and histatin-1.

This study quantitatively compares the inhibition of calcium phosphate (CaP) precipitation by the salivary acidic proline-rich proteins (PRPs) statherin and histatin-1. Saliva and CaCl2 in 125 mM imidazole buffer (pH 7.0) were incubated with potassium phosphate and a hydroxyapatite (HAP) suspension, for 30 min at 25 degrees C, then filtered through nitrocellulose. The calcium (Ca) concentration in the filtrate was measured by atomic absorption spectrophotometry, then deducted from that in the initial solution to determine the amount of CaP precipitation after 30 min. The values of the inhibitory activities on CaP precipitation relative to crude parotid saliva were 4.7, 4.9, 6.9, and 65.8 for histatin-1, large PRPs, small PRPs, and statherin, respectively.

Adult↗
PubMed1998

Purification, amino acid sequence, and cDNA sequence of a novel calcium-precipitating proteolipid involved in calcification of corynebacterium matruchotii.

Corynebacterium matruchotii is a microbial inhabitant of the oral cavity associated with dental calculus formation. It produces membrane-associated proteolipid capable of inducing hydroxyapatite formation in vitro. This proteolipid was purified from chloroform:methanol extracts by chromatography on Sephadex LH-20 and migrated on SDS-polyacrylamide gel electrophoresis at 6-9 kDa. Removal of covalently attached acyl moieties by methanolic KOH decreased its molecular mass to approximately 5.5 kDa. The amino acid sequence of the apoproteolipid indicated a peptide of 50 amino acids, a calculated molecular weight of 5354 Da, and an isoelectric point of 4.28. Sequence analysis revealed an 8 amino acid sequence with homology to human phosphoprotein phosphatase 2A as well as several potential acylation sites and one phosphorylation site. The purified proteolipid induced calcium precipitation in vitro. Deacylation of the proteolipid by hydroxylamine treatment resulted in >50% loss of calcium-precipitating activity, suggesting that covalently attached lipids are required. Degenerate oligonucleotide primers, based on the amino acid sequence, were used to amplify the gene for the 5.5 kDa proteolipid from total chromosomal DNA of C. matruchotii by PCR. A 166 bp cDNA was isolated and sequenced, confirming the amino acid sequence of the proteolipid. Thus, we have sequenced a unique bacterial proteolipid that is involved in the formation of dental calculus by precipitating Ca2+ and possibly in transport of inorganic phosphate, necessary for hydroxyapatite formation.

Amino Acid Sequence↗
PubMed2002

Specific visualization of precipitated cerium by energy-filtered transmission electron microscopy for detection of alkaline phosphatase in immunoenzymatic double labeling of tyrosine hydroxylase and serotonin in the rat olfactory bulb.

To understand in detail the functional morphology of neuronal circuits it is important to identify at the ultrastructural level the incoming axon, its target neuron, and members of the signaling cascades involved. This, however, represents a formidable task, requiring highly sophisticated electron microscopic multiple-labeling techniques. To extend available double-labeling procedures such as combinations of immunogold and peroxidase methods, an additional, gold- and peroxidase-independent procedure would represent a considerable advantage. The present investigation therefore aimed to use alkaline phosphatase as the immunoenzymatic label at the electron microscopic level via cerium phosphate precipitates. To our surprise we found that available techniques, which are well established for the visualization of endogenous enzymes in sections from various tissues, are not suitable for application to immunocytochemistry. Careful characterization of the individual reaction conditions, however, resulted in an optimized procedure with largely increased sensitivity. The novel technique yields cerium-containing precipitates which are massive enough to allow the detection of the immunoenzymatic reaction product in the electron microscope. Using the rat olfactory bulb as the model system we showed further that our technique allows the combination with the peroxidase/diaminobenzidine system for ultrastructural double labeling. For this purpose, the alkaline phosphatase product is identified by its cerium content via energy-filtered transmission electron microscopy and thereby differentiated from cerium-free peroxidase-derived precipitates. Doing so, we found that ascending serotoninergic fibers do not establish synapses with dopaminergic periglomerular cells in the rat olfactory bulb.

Alkaline Phosphatase↗
PubMed2004

Coordinated changes in photosynthesis, water relations and leaf nutritional traits of canopy trees along a precipitation gradient in lowland tropical forest.

We investigated leaf physiological traits of dominant canopy trees in four lowland Panamanian forests with contrasting mean annual precipitation (1,800, 2,300, 3,100 and 3,500 mm). There was near complete turn-over of dominant canopy tree species among sites, resulting in greater dominance of evergreen species with long-lived leaves as precipitation increased. Mean structural and physiological traits changed along this gradient as predicted by cost-benefit theories of leaf life span. Nitrogen content per unit mass (Nmass) and light- and CO2-saturated photosynthetic rates per unit mass (Pmass) of upper canopy leaves decreased with annual precipitation, and these changes were partially explained by increasing leaf thickness and decreasing specific leaf area (SLA). Comparison of 1,800 mm and 3,100 mm sites, where canopy access was available through the use of construction cranes, revealed an association among extended leaf longevity, greater structural defense, higher midday leaf water potential, and lower Pmass, Nmass, and SLA at wetter sites. Shorter leaf life spans and more enriched foliar delta15N values in drier sites suggest greater resorption and re-metabolism of leaf N in drier forest. Greater dominance of short-lived leaves with relatively high Pmass in drier sites reflects a strategy to maximize photosynthesis when water is available and to minimize water loss and respiration costs during rainless periods. Overall, our study links coordinated change in leaf functional traits that affect productivity and nutrient cycling to seasonality in lowland tropical forests.

Analysis of Variance↗