Resprouting as a key functional trait: how buds, protection and resources drive persistence after fire.

Resprouting as a response to disturbance is now widely recognized as a key functional trait among woody plants and as the basis for the persistence niche. However, the underlying mechanisms that define resprouting responses to disturbance are poorly conceptualized. Resprouting ability is constrained by the interaction of the disturbance regime that depletes the buds and resources needed to fund resprouting, and the environment that drives growth and resource allocation. We develop a buds-protection-resources (BPR) framework for understanding resprouting in fire-prone ecosystems, based on bud bank location, bud protection, and how buds are resourced. Using this framework we go beyond earlier emphases on basal resprouting and highlight the importance of apical, epicormic and below-ground resprouting to the persistence niche. The BPR framework provides insights into: resprouting typologies that include both fire resisters (i.e. survive fire but do not resprout) and fire resprouters; the methods by which buds escape fire effects, such as thick bark; and the predictability of community assembly of resprouting types in relation to site productivity, disturbance regime and competition. Furthermore, predicting the consequences of global change is enhanced by the BPR framework because it potentially forecasts the retention or loss of above-ground biomass.

Survival among hospital in-patients with troponin T elevation below levels defining myocardial infarction.

BACKGROUND: Cardiac troponin T (cTnT) has an accepted place in the management of patients presenting with suspected acute coronary syndrome (ACS). Uncertainty remains about the significance and interpretation of elevated cTnT below the cut-off levels defining myocardial infarction (0.1 microg/l). AIM: To compare the mortality risks for elevation of cTnT in the ranges 0.01-0.029 microg/l, 0.03-0.099 microg/l and <0.01 microg/l. DESIGN: Retrospective record study in three hospitals. METHODS: All cTnT measurements with values in the range >0.01-0.099 microg/l analysed during January 2002 were extracted from clinical biochemistry laboratory databases. Following agreed exclusion criteria, 179 patients with cTnT in the range 0.01-0.099 microg/l and 60 patients <0.01 microg/l were selected at random from across the three sites. Six-month follow-up was completed by review of case notes and contact with the patients' GP. RESULTS: There was a graded increase in mortality with increasing cTnT, although only achieving statistical significance for patients in the 0.03-0.099 microg/l range. The graded increase in relative risk with cTnT was weaker after adjustment for potential confounding factors DISCUSSION: We found a trend for worse survival with increasing cTnT within the range 0.01-0.099 microg/l in unselected patient populations presenting with possible acute coronary syndrome. This suggests that the combined effects of assay imprecision and co-morbidity should be taken into account when interpreting borderline elevation of cTnT. The use of a cut-off based on current standards of assay precision should be used to define the sensitivity of cTnT as biochemical evidence of ischaemic cardiac damage and as an indicator of mortality risk. This level is likely to be between 0.03 and 0.1 microg/l.

Alprazolam in panic disorder and agoraphobia: results from a multicenter trial. I. Efficacy in short-term treatment.

Following promising preliminary evidence, the benzodiazepine-derivative alprazolam was studied in a large, placebo-controlled, eight-week, flexible-dose trial in patients with agoraphobia with panic attacks and panic disorder. Of 526 patients, 481 completed three weeks of treatment; however, significantly more placebo (102/234) than alprazolam (21/247) recipients subsequently dropped out of the trial, primarily citing ineffectiveness (of placebo) as the reason. Alprazolam was found to be effective and well tolerated. There were significant alprazolam-placebo differences in improvement for (1) spontaneous and situational panic attacks, (2) phobic fears, (3) avoidance behavior, (4) anxiety, and (5) secondary disability, all significant by the end of week 1. At the primary comparison point (week 4), 82% of the patients receiving alprazolam were rated moderately improved or better vs 43% of the placebo group. At that point, 50% of the alprazolam recipients vs 28% of placebo recipients were free of panic attacks.

Secondary depression in panic disorder and agoraphobia. I. Frequency, severity, and response to treatment.

Depressive symptomatology in 481 subjects with panic disorder and phobic avoidance was studied as part of an investigation of the efficacy of alprazolam in panic disorder. Subjects who had a major depressive episode (MDE) before the onset of their panic disorder were not included in the trial. With this exclusion criterion, 31% of subjects had a secondary MDE occurring after the onset of the panic disorder. The occurrence of secondary MDE was related to the length of time subjects were ill with panic disorder. Compared with the subjects without depression, those subjects with current MDE had higher scores on measures of anxiety and depression but not on the number of panic attacks per week. The presence of depression and the degree of phobic avoidance contributed independently to measures of the severity of the panic illness. Alprazolam was effective in reducing panic and depressive symptomatology in both depressed and nondepressed subjects with panic disorder. The presence of an MDE was not predictive of the outcome of treatment for the panic and phobic symptoms. Subjects with or without depression responded similarly to alprazolam.

Alprazolam in panic disorder and agoraphobia: results from a multicenter trial. II. Patient acceptance, side effects, and safety.

In a multicenter placebo-controlled study, the safety, side effects, and patient acceptance of alprazolam for the treatment of panic disorder and agoraphobia were examined. A total of 525 patients meeting DSM-III criteria for agoraphobia with panic attacks or panic disorder were randomly assigned to receive alprazolam or placebo, which they took for eight weeks. The mean daily dose at the end of the study was 5.7 mg of alprazolam or 7.5 capsules of placebo daily. Potentially serious reactions to alprazolam occurred in ten of 263 subjects who received the drug. These included acute intoxication (three), hepatitis (two), mania (two), amnesia (one), aggressive behavior (one), and depression (one). Treatment-related side effects that were worse in patients taking alprazolam than in those taking placebo included sedation, fatigue, ataxia, slurred speech, and amnesia. Sedation was the most frequent but tended to subside with dose reduction or continued administration of the drug. Patient acceptance of alprazolam, as measured by the rate of completion for study participants, was high. Eighty-four percent of patients receiving active drug completed the study compared with 50% receiving placebo.

Human TCR as antigen: homologies and potentially cross-reactive HLA-DR2-restricted epitopes within the AV and BV CDR2 loops.

The major function of the T-cell receptor is to confer antigen specificity to T cells. However, nascent TCR proteins that are not assembled into functional heterodimers may be processed and displayed with self MHC molecules on the T-cell surface, and are thought to be the genesis of autoregulatory T cells that can limit inflammatory responses through T-T network interactions. In previous work, we and others have exploited this natural regulatory system using TCR peptides to amplify regulatory T cells that potentially can treat human autoimmune diseases such as multiple sclerosis (MS) and arthritis. The development of this approach is limited by the diversity of human TCR V gene sequences, and by lack of knowledge of exactly which regions of the V gene proteins are immunogenic in association with various MHC alleles. To identify similar amino acid sequences within and among human V gene families that might have immunologic cross reactivity, we aligned 74 known AV and 109 known BV protein sequences into homologous groups using the ClustalX program. Moreover, with a focus on CDR2 peptides that have previously been used to induce regulatory T cells in clinical trials, we established homologous peptide groups, and then identified the optimal amino acid motifs for binding to two alleles, HLA-DRB1*1501 and DRB5*0101, that have been associated with susceptibility to MS. From this analysis, > 75% of AV and BV CDR2 sequences were predicted to bind with at least moderate avidity to each of the DR2 alleles, thus enhancing the likelihood that they could be antigenic. Further ordering of putative TCR contact residues revealed a different set of homology groupings, including many intrafamily sequence matches and some interfamily matches that might allow immunological cross reactivity. Particularly striking were DRB1*1501-restricted IH-S and IY-S motifs shared by BV11, BV12, and BV13 and BV3, BV12, BV13, and BV17 family members, respectively, and DRB5*0101-restricted RL-H and RL-Y motifs shared by BV11, BV12, and BV13 and BV13 and BV17 family members, respectively. This analysis may be useful in designing an array of clinically useful homologous peptides with optimal MHC binding properties and highly cross-reactive TCR binding motifs.

Copper stimulates the release of luteinizing hormone releasing hormone from isolated hypothalamic granules.

Copper, administered to female rabbits, stimulates LHRH release into the hypophyseal portal blood (5) and induces ovulation (1-3). To gain further understanding of the mechanism of action of copper, in this study we addressed the question: Does copper, in the form of CuATP, stimulate LHRH release from isolated hypothalamic granules? Isolated hypothalamic granules, obtained from adult male rats, were incubated under in vitro conditions in the absence (control) or presence of CuATP (0.1 - 2.5 mM). In the presence of CuATP, we noted that LHRH release was stimulated, and the magnitude of stimulation was a saturable function of the concentration of copper, being maximal at 2.5 mM. In addition, we compared the effects of a series of divalent cations (Cu, Zn, Mg, Ca, Fe, Ba, Sr, Mn; 2.5 mM each) on LHRH release and found that copper stimulated release seventeenfold, zinc--sixfold, and the other divalent cations--twofold or less. Thus, copper appears to be a unique releaser of LHRH, and it may act at the level of the LHRH granule.

Cigarette smoking and plasma nortriptyline levels.

Cigarette smoking was found to have no effect on the steady-state plasma levels of nortriptyline in a group of 22 smokers and 31 nonsmokers. Smokers achieved a mean steady-state nortriptyline concentration of 191.2 +/- 141.3 ng/ml; nonsmokers had a level of 169.3 +/- 92.4 ng/ml. Age, sex, and number of cigarettes smoked had no effect on the plasma concentrations achieved.

Plasma concentrations of melatonin in panic disorder.

Nocturnal plasma melatonin concentrations were measured in seven patients with panic disorder and eight healthy control subjects. The five patients who had never received psychotropic medication had significantly greater melatonin concentrations from 4:00 a.m. to 7:00 a.m. than the control subjects. In addition it is possible that a phase delay occurred in these unmedicated patients. The findings are discussed in terms of previous studies showing increased melatonin in manic patients and the effect of intense stress on melatonin synthesis. The two patients who had been medication free for only 1 week showed a decreased melatonin rhythm, which is consistent with previous findings in medicated patients.

Melatonin sensitivity to dim white light in affective disorders.

Both dim and bright light has been shown to suppress the nocturnal secretion of the pineal hormone melatonin. Early reports suggests that an abnormal response to light occurs in patients with bipolar affective disorder, where as patients with major depressive disorder respond similarly to controls. It has been suggested that this abnormal sensitivity of the melatonin response to light could be a trait marker of bipolar affective disorder. However reports lack consistency. Hence, we investigated the melatonin suppression by dim light (200 lux) in patients with bipolar affective disorder, seasonal affective disorder and major depressive disorder. Results suggest that a supersensitive melatonin suppression to light in bipolar affective disorder (p < .005), and seasonal affective disorder (p < .05), whereas patients with major depressive disorder display similar suppression to controls. The supersensitivity may be a mechanism where by phase-delayed rhythms, are resynchronised to a new circadian position. Conversely, an abnormality may exist in the pathway from the retina to the suprachiamatic nucleus.

Antioxidants, von Willebrand factor and endothelial cell injury in hypercholesterolaemia and vascular disease.

The relationship between antioxidants and endothelial cell injury was examined in 119 patients with (n = 48) or without (n = 71) vascular disease who were attending a hyperlipidaemia clinic. Serum levels of total antioxidant capacity, glutathione peroxidase (a protein antioxidant), von Willebrand factor (vWf, a specific endothelial cell product and marker of injury) and routine lipids were measured in the patients and from 58 healthy controls. Compared to controls, total antioxidant capacity (P < 0.01) and glutathione peroxidase (P < 0.0001) were lower whilst vWf was higher (P < 0.0001) amongst the patients. Comparing patients with and without vascular disease, glutathione peroxidase was lower (P < 0.03) and vWf was higher (P < 0.05) in the presence of vascular disease but there was no difference in levels of serum lipids or total antioxidant capacity. vWf and glutathione peroxidase were inversely correlated (r = -0.26, P < 0.005). We conclude that patients with hypercholesterolaemia have reduced antioxidant capacity and this is most severe in patients with clinically apparent vascular disease. This, linked to the finding of increased vWf in hypercholesterolaemia with highest levels in those patients with vascular disease, suggests that loss of antioxidant capacity may expose the vascular endothelium to excess oxidative damage. These results suggest a link between hypercholesterolaemia, impaired ability to resist free radical attack, and the development of atherosclerosis.

Renal function related changes in lithium kinetics.

The renal clearance of lithium will decrease, and hence the risk of acute lithium toxicity will increase, in any situation leading to dehydration and sodium depletion. Patients on long term lithium therapy with progressively declining urinary concentrating ability may be at special risk in this regard. Chronic histological changes in the kidney attributed to lithium therapy correlate with age rather than with the duration of lithium therapy. Age-related renal histological changes are associated with decreased glomerular filtration rate and therefore reduced renal lithium clearance. Thus, the dose of lithium should be reduced with advancing age.

Clinical pharmacokinetics of dothiepin. Single-dose kinetics in patients and prediction of steady-state concentrations.

The pharmacokinetics of dothiepin were evaluated in 9 depressed patients following a single oral dose of 75 mg. Blood and plasma concentrations of dothiepin and 2 major metabolites, northiaden and dothiepin S-oxide, were measured by gas chromatography/mass fragmentography. The mean (+/-SD) peak plasma concentrations of dothiepin were 49 +/- 27 micrograms/L at 3 +/- 1.2h. Mean (+/-SD) estimates of other parameters were as follows: absorption half-life 1.1 +/- 1.1h; distribution half-life 2.2 +/- 0.8 h; elimination half-life 25 +/- 7h; apparent volume of distribution 70 +/- 62 L/kg; and oral clearance 2.1 +/- 1.6 L/kg/h. The mean (+/-SD) peak plasma concentration of dothiepin S-oxide was 125 +/- 43 micrograms/L at 3.5 +/- 1.3h with an elimination half-life of 22 +/- 12 h. The mean peak plasma concentration of northiaden was 6 +/- 3 micrograms/L at 4.5 +/- 1.1h, with an elimination half-life of 31 +/- 12 h. No significant differences were found in pharmacokinetic parameters compared with a previous study in 7 healthy volunteers. When data for the patients and healthy volunteers were combined (n = 16), pharmacokinetic parameters were not found to be affected by age. However, a significant difference was found between males and females for the elimination half-lives of dothiepin and northiaden, and for the apparent volume of distribution of dothiepin. The 24-hour blood/plasma concentrations of dothiepin and dothiepin S-oxide accurately predicted the steady-state concentrations obtained following 4 weeks' treatment with dothiepin 150 mg nocte.

Prolactin response to dl-fenfluramine in panic disorder.

The objective of this study was to test the hypothesis that serotonin receptors are hypersensitive in patients with panic disorder. Eleven patients and 12 controls received a single PO dose of 60 mg of dl-fenfluramine at 0900h on a single occasion. Blood samples were collected with an indwelling intravenous catheter at 30-min intervals from 0930h to 1530h and prolactin determined by radioimmunoassay. In both groups, fenfluramine induced a rise in the plasma prolactin concentration from baseline. The patients showed a greater increase in prolactin response than the normal controls. This result is consistent with the hypothesis of increased serotonin receptor function in patients with panic disorder.

Effect of the menstrual cycle stage on the melatonin suppression by dim white light.

Patients with bipolar disorder have been shown to have a supersensitive melatonin suppression to dim white light (200 and 500 lux) compared to normal healthy subjects. Previous studies suggest menstrual cycle dependent changes in the melatonin rhythm, but it is not known if the melatonin sensitivity to light changes during the menstrual cycle. The present study investigated the melatonin suppression to dim white light (200 lux) in different stages of the menstrual cycle. No significant differences in the percent suppression of melatonin were found across the stages of the menstrual cycle (p = .97). Our findings suggest that the menstrual cycle hormonal changes do not affect the melatonin sensitivity to dim light in healthy controls.

Melatonin, cortisol and prolactin response to acute nocturnal light exposure in healthy volunteers.

An investigation of the cortisol and prolactin responses accompanying acute melatonin suppression by light (600 lux) in humans is described. Light given from midnight to 0300h suppressed nocturnal plasma melatonin concentrations by 65%. Despite this significant suppression of melatonin, no significant effect on plasma cortisol or prolactin concentrations was observed. These data support recent studies which argue that, if there is a relationship between melatonin, the hypothalamo-pituitary, and the hypothalamo-pituitary-adrenal axis in humans, it is neither direct nor simple.

Human melatonin response to light at different times of the night.

Normal control subjects were examined on three separate occasions with light of sufficient intensity to suppress nocturnal plasma melatonin concentrations. One hour of light was given at each of the following times: (a) 2100-2200h; (b) midnight to 0100h; (c) 0400-0500h. Melatonin synthesis was just becoming apparent at 2100h. There was significant suppression of melatonin by light when given at midnight-0100h and 0400-0500h, but not when light was given at 2100-2200h. In each case following light, melatonin synthesis was shown to resume, even after light applied in the second half of the dark period (0400-0500h). A second experiment was undertaken to examine a possible "rebound" in melatonin levels following light given at 2100-2200h. Six further control subjects were exposed to light at this time, and plasma melatonin levels were measured until 0400h. No rebound in melatonin concentrations was observed. These results are compared with other studies of melatonin response to evening light exposure.

Managing long-term therapy for panic disorder.

Diagnostic criteria for panic disorder have been well defined; but treatment modalities, less so. Combined psychotherapy and pharmacotherapy is the most effective treatment for these disorders. Benzodiazepines, tricyclic antidepressants, monoamine oxidase inhibitors, and other medications have been found effective in clinical studies. Alprazolam, a triazolo analog of the 1,4 benzodiazepine class, recently was proved effective in a cross-national study involving approximately 1700 patients, with minimal side effects. Therapy with the medication is advised for at least 6 months. Medications should be tapered over a prolonged period, at least 8 weeks, especially where high doses are employed.

Long-term clinical management of depressive disorders.

The author provides evidence that depression is an often chronic and recurrent illness. He then provides World Health Organization (WHO) and other well-established recommendations for acute treatment of depression and describes maintenance treatment, which usually lasts 3 to 6 months. He lists WHO recommendations for prophylaxis, which should probably be continued for 2 or more years in patients with chronic depression, and reviews the following problems commonly associated with continued antidepressant treatment: cardiac toxicity, drug overdose, suicide/parasuicide, drug toxicity, drug interactions, and noncompliance. Finally, the author discusses discontinuation, which should always be accomplished according to a tapered, individualized schedule with the patient as an active partner in the process. Despite this knowledge, researchers must look for additional therapies for the one third of depressed patients who are not helped by currently available measures.

Antidepressant efficacy and tolerability of the selective norepinephrine reuptake inhibitor reboxetine: a review.

Reboxetine is a unique selective norepinephrine reuptake inhibitor (NRI) with proven antidepressant efficacy in pharmacologic and biochemical tests predictive of antidepressant properties. Comprehensive clinical trials, including 8 placebo-controlled and/or active treatment-controlled studies, plus 4 open studies, have assessed the short-term and long-term efficacy and tolerability of reboxetine in patients with major depressive disorders and dysthymia. Results from a total of 690 patients who entered 5 open or placebo-controlled studies are summarized in this paper. Four hundred forty-nine patients with a diagnosis of either major depressive disorder or dysthymia were treated with reboxetine in these clinical studies of 4 weeks' to 12 months' duration. In a 6-week placebo-controlled study, clinically significant improvement (> or = 50% reduction in Hamilton Rating Scale for Depression total score) was observed at last assessment in 74% of reboxetine-treated patients compared with 20% of patients in the placebo group. Similar results were observed in the 6-week run-in phases of the 3 long-term studies, where the efficacy of reboxetine was maintained over the 12-month study period. Reboxetine was well tolerated; adverse events reported were mainly mild to moderate in severity, and there were no clinically significant changes in vital signs or laboratory parameters. The first in its class, reboxetine, a selective NRI, will provide a valuable addition to the existing armamentarium of agents used in the treatment of depression.