Simulated nitrogen deposition influences soil greenhouse gas fluxes in a Mediterranean dryland

Soil nitrogen (N) availability is a key driver of soil-atmosphere greenhouse gas (GHG) exchange, yet we are far from understanding how increases in N deposition due to human activities will influence the net soil-atmosphere fluxes of the three most important GHGs: nitrous oxide (N₂O), methane (CH₄) and carbon dioxide (CO₂). We simulated four levels of N deposition (10, 20 and 50 kg N ha^-1 yr^-1, plus unfertilised control) to evaluate their effects on N₂O, CH₄ and CO₂ soil fluxes in a semiarid shrubland in central Spain. After 8 years of experimental fertilisation, increasing N availability led to a consistent increase in N₂O emissions, likely due to simultaneous increases in soil microbial nitrification and/or denitrification processes. However, only intermediate levels of N fertilisation reduced CH₄ uptake, while increasing N fertilisation had no effects on CO₂ fluxes, suggesting complex interactions between N deposition loads and GHG fluxes. Our study provides novel insight into the responses of GHGs to N deposition in drylands, forecasting increases in N₂O emissions, and decreases in CH₄ uptake rates, with likely consequences to the on-going climate change.

Consensus for managing patients with chronic obstructive pulmonary disease according to the CODEX index

The comorbidity, obstruction, dyspnoea, exacerbations (CODEX) index is the first multicomponent scale designed to predict the risk of readmissions and mortality at 1 year for patients hospitalised for chronic obstructive pulmonary disease (COPD). The index includes the comorbidities (C) (measured by the Charlson index), the degree of obstruction (O) (assessed by the forced expiratory volume in 1 second percentage), dyspnoea (D) (stratified according to the modified Medical Research Council scale) and exacerbations (EX) in the previous year. Our objective was to prepare recommendations based on the index's various components for personalised therapeutic management. To this end, we performed a literature search based on guidelines, consensuses and systematic reviews, as a basis for preparing recommendations on basic concepts, comorbidities, dyspnoea, pulmonary obstruction, exacerbations and follow-up. The recommendations were then subjected to an external assessment process by a multidisciplinary group of 62 experts. In total, 108 recommendations were created, 96 of which achieved consensus, including the recommendation that COPD be considered a high-risk cardiovascular disease, as well as several specific recommendations on managing the various comorbidities. A consensus was reached on the recommended treatments in the guidelines for the various levels of obstruction, dyspnoea and exacerbations, adapted to the CODEX scores. Advice is also offered for patient follow-up after hospital discharge, which includes aspects on assessment, treatment and care coordination.

Nitrification inhibitor DMPSA mitigated N2O emission and promoted NO sink in rainfed wheat

Fertilized cropping systems are important sources of nitrous oxide (N₂O) and nitric oxide (NO) to the atmosphere, and biotic and abiotic processes control the production and consumption of these gases in the soil. In fact, the inhibition of nitrification after application of urea or an ammonium-based fertilizer to agricultural soils has resulted in an efficient strategy to mitigate both N₂O and NO in aerated agricultural soils. Therefore, the NO and N₂O mitigation capacity of a novel nitrification inhibitor (NI), 2-(3,4-dimethyl-1H-pyrazol-1-yl) succinic acid isomeric mixture (DMPSA), has been studied in a winter wheat crop. A high temporal resolution of fluxes of NO and NO₂, obtained by using automatic chambers for urea (U) and urea with DMPSA, allowed a better understanding of the temporal net emissions of these gases under field conditions. Seventy-five days after fertilization, the effective reduction of nitrification by DMPSA significantly decreased the production of NO with respect to the treatment without it, giving net consumption of NO in the soil (-61.72 g-N ha^-1) for U + DMPSA in comparison to net production (227.44 g-N ha^-1) for U. The explanation of NO deposition after NI application, due to biotic and abiotic processes in the soil-plant system, supposes a challenge that needs to be studied in the future. In the case of N₂O, the addition of DMPSA significantly mitigated the emissions of this gas by 71%, though the total N₂O emissions in both fertilized treatments were significantly greater than those of the control (43.69 g-N ha^-1). Regarding the fertilized treatments, no significant effect of DMPSA in comparison to urea alone was observed on grain yield nor bread-making wheat quality. To sum up, we got a significant reduction of N₂O and NO with the addition of DMPSA, without a loss in yield and quality parameters in wheat.

The effect of nitrification inhibitors on NH3 and N2O emissions in highly N fertilized irrigated Mediterranean cropping systems

There is an increasing concern about the negative impacts associated to the release of reactive nitrogen (N) from highly fertilized agro-ecosystems. Ammonia (NH₃) and nitrous oxide (N₂O) are harmful N pollutants that may contribute both directly and indirectly to global warming. Surface applied manure, urea and ammonium (NH₄⁺) based fertilizers are important anthropogenic sources of these emissions. Nitrification inhibitors (NIs) have been proposed as a useful technological approach to reduce N₂O emission although they can lead to large NH₃ losses due to increasing NH₄⁺ pool in soils. In this context, a field experiment was carried out in a maize field with aiming to simultaneously quantify NH₃ volatilization and N₂O emission, assessing the effect of two NIs 3,4‑dimethilpyrazol phosphate (DMPP) and 3,4‑dimethylpyrazole succinic acid (DMPSA). The first treatment was pig slurry (PS) before seeding (50 kg N ha^-1) and calcium ammonium nitrate (CAN) at top-dressing (150 kg N ha^-1), and the second was DMPP diluted in PS (PS + DMPP) (50 kg N ha^-1) and CAN + DMPSA (150 kg N ha^-1) also before seeding and at top-dressing, respectively. Ammonia emissions were quantified by a micrometeorological method during 20 days after fertilization and N₂O emissions were assessed using manual static chambers during all crop period. The treatment with NIs was effective in reducing c. 30% cumulative N₂O losses. However, considering only direct N₂O emissions after second fertilization event, a significant reduction was not observed using CAN+DMPSA, probably because high WFPS of soil, driven by irrigation, favored denitrification. Cumulative NH₃ losses were not significantly affected by NIs. Indeed, NH₃ volatilization accounted 14% and 10% of N applied in PS + DMPP and PS plots, respectively and c. 2% of total N applied in CAN+DMPSA and CAN plots. Since important NH₃ losses still exist even although abating strategies are implemented, structural and political initiatives are needed to face this issue.

[Study of the comorbidities in hospitalized patients due to decompensated chronic obstructive pulmonary disease attended in the Internal Medicine Services. ECCO Study]

OBJECTIVE

Evaluate comorbidity in patients hospitalized due to COPD in the Internal Medicine services.

METHODS

An observational, prospective and multicenter study. The Charlson index and a specific questionnaire were used.

RESULTS

A total of 398 patients, 353 men (89%), with mean age of 73.7 years (8.9) and mean FEV(1) of 43.2% (12.5), were included. The most frequent comorbidities were: arterial hypertension (55%), arrhythmias (27%) and diabetes mellitus (26%). A total of 27% suffered heart failure, 17% coronary disease and 9% previous myocardial infarction. The number of associated chronic diseases was 3.6 (1,8). Score on Charlson index was 2.72 (2).

CONCLUSIONS

The patients hospitalized due to decompensated COPD had an elevated comorbidity.

[Repercussion of age on management of neoplastic patients in an Internal Medicine Service]

AIM

To determine whether age is a factor affecting the management of patients diagnosed with neoplastic disease in an internal medicine service.

PATIENTS AND METHODS

Prospective study of 388 patients diagnosed with cancer in the internal medicine service of a large public health teaching hospital. We evaluated clinical characteristics, diagnostic procedures, types and stage of neoplasm, referral after hospital discharge and treatment. A comparative study based on age was performed between patients 65 years older and patients under this age.

RESULTS

The 388 cancer patients accounted for 12% of hospital admissions in our service. Among the total, 62% were > or = 65 years old. Constitutional syndrome, the most frequently associated symptom and the main reason for the consultation, was more common in the > or = 65-year-old group. Lung cancer was predominant in men and hematologic neoplasms in women. Patients > or = 65 were referred more frequently to internal medicine physicians, general practitioners and home palliative assistance services (p < 0.05) and they received only palliative treatment in a greater percentage of cases (50% vs. 37%, p = 0.001).

CONCLUSIONS

The incidence of neoplasms in our service was high (12%), with a considerable percentage of patients in advanced phases of the disease (83%). Age was not related to diagnostic methods nor was it determinant in the staging, but it did have repercussions on treatment; patients > or = 65 received palliative treatment alone more often than younger patients.

[Bronchiolitis obliterans organizing pneumonia associated with Legionella pneumophila]

Bronchitis obliterans organizing pneumonia (BOOP) is an unusual pulmonary condition. The clinical features and the radiologic findings are useful for the diagnosis of BOOP. However it is necessary to confirm its presence by an open or transbronchial pulmonary biopsy specimen. BOOP is usually idiopathic, although it may also occur in association with connective tissue disease, some haematologic disorders and in response to viral infections. The association of Legionella pneumophila infection with BOOP is very rare.

The circadian clock, light/dark cycle and melatonin are differentially involved in the expression of daily and photoperiodic variations in mt(1) melatonin receptors in the Siberian and Syrian hamsters

Mechanisms underlying the daily and photoperiodic variations in mt(1) melatonin receptors were investigated in the pars tuberalis (PT) and suprachiasmatic nuclei (SCN) of Siberian and Syrian hamsters. Whatever its daily profile, melatonin receptor density was strongly increased in both structures and species after constant light exposure or pinealectomy, and decreased after a single melatonin injection, indicating melatonin involvement in the daily regulation of the receptor protein. This was confirmed by a strong inverse correlation between melatonin binding capacity and plasma melatonin concentration. In contrast, regulation of mt(1) mRNA appeared more complex. The circadian clock, the light/dark cycle and melatonin are all implicated in mt(1) gene daily fluctuations, but the extent of their involvement depends upon the structure and the species studied. The photoperiodic decrease in melatonin receptor density observed in short photoperiod (PT of the two hamster species and Syrian hamster SCN) seems to be the consequence of a long-term mt(1) gene repression induced by the lengthening of the melatonin peak. Altogether, these results show that during daily variations, mt(1) melatonin receptor mRNA and protein are differentially regulated, while at the photoperiodic level, the mt(1) protein status depends on mRNA transcription.

Decreased sleep quality in patients suffering from retinitis pigmentosa

The purpose of this study was to assess the prevalence of sleep disturbance in subjects diagnosed with retinitis pigmentosa (RP), as well as the influence of age and gender. Sleep quality was assessed, by means of the Pittsburgh Sleep Quality Index (PSQI), in people with RP (n=177) and gender-and age-matched normally sighted individuals (n=491). The population was divided, according to their age, in eight decade groups. People on shift-work, with affective disorders or with visual impairment other than RP, were excluded. The influence of cataracts in sleep quality was also studied in non-RP people (n=57), with cataracts significantly impairing visual acuity. Another group of healthy controls (n=190) was studied in different seasons of the year for a possible seasonality in sleep disturbance. Global sleep quality decreased in an age-dependent manner in RP-patients, especially from the second decade of life. Retinitis pigmentosa-patients showed, in relation to age-matched controls: lower subjective sleep quality and efficiency, longer sleep latency, shorter sleep duration, higher daytime dysfunction and a higher use of sleeping medication. No significant differences in sleep quality were found among RP-patients or controls depending either on their gender or on the presence of cataracts. Normal sighted individuals did not show seasonality in their sleep quality. We conclude that the sleep quality of RP-patients decreases in an age-dependent manner and points to the probably degeneration of photoreceptors mediating the photic input to the suprachiasmatic nuclei of the hypothalamus in this disease.

Selective changes in the contents of noradrenaline, dopamine and serotonin in rat brain areas during aging

This study examines the age-associated changes in noradrenaline (NA), dopamine (DA), 3,4-dihydroxyphenyl-acetic acid (DOPAC), serotonin (5-HT) and 5-hydroxy-3-indoleacetic acid (5-HIAA) in different brain areas of rats. DA and DOPAC concentrations in striatum increased at third month of age, remaining without significant variations until 12th month of age, and decreasing in 24-month-old rats. DA concentration dropped in hippocampus, amygdala and brainstem of 24-month-old-rats, whereas DOPAC levels decreased only in hippocampus. These changes suggest an age-dependent deficit of the dopaminergic system, presumably related to a reduced number/activity of DA nigrostriatal and mesolimbic neurons. An age-induced decline in NA content was found in the pons-medulla, the area containing NA neuronal bodies. Concentrations of 5-HT were reduced with aging in frontal cortex, showing a tendency to decrease in all brain areas examined. The increased 5-HIAA/5-HT ratio found in frontal cortex, amygdala and striatum suggests an age-related decreased synthesis and an accelerated 5-HT metabolism. The 5-HIAA content decreased in brainstem of the oldest rats. These findings point to a selective impairment of nigrostriatal and mesolimbic DA in aging rats, whereas reductions in NA were restricted to cell bodies region and 5-HT showed changes of different extent in areas of terminals and neuronal cell bodies.

The value of chest roentgenography in the diagnosis of pneumothorax after thoracentesis

PURPOSE

We sought to assess the yield of chest roentgenography for the detection of pneumothorax among hospitalized patients with pleural effusion who have undergone diagnostic or therapeutic thoracentesis.

SUBJECTS AND METHODS

We performed a prospective study of 506 thoracentesis procedures in 370 patients. After the procedure, each operator filled out a note recording patient data and the characteristics of the thoracentesis. A chest radiograph was performed within 12 hours after the procedure in all patients.

RESULTS

Eighteen (4%) pneumothoraces occurred in 17 patients, 9 (2%) of which required chest tube drainage. Of the 488 patients without symptoms, only 5 (1%) developed a pneumothorax, only 1 of which required chest tube drainage. By contrast, of the 18 patients with symptoms, 13 developed a pneumothorax, 8 of which required chest tubes. There were two independent predictors of pneumothorax: presence of symptoms (odds ratio [OR] = 250; 95% confidence interval [CI]: 65 to 980) and male gender (OR = 5.4; 95% CI: 1.9 to 69).

CONCLUSIONS

Among the symptom-free patients in our sample, the risk of developing pneumothorax with clinical consequences was so low that the practice of routine chest roentgenography may not be justified.

Effects of two melatonin analogues, S-20098 and S-20928, on melatonin receptors in the pars tuberalis of the rat

By using quantitative autoradiography, we studied the effects of two drugs related to melatonin on the 2-(125)I-melatonin binding in the pars tuberalis (PT) of rats. The drugs tested were two naphthalenic analogues of melatonin, S-20098 (N-[2-(7-methoxy-1-naphthyl) ethyl] acetamide), an agonist, and S-20928 (N-[2-(1-naphthyl) ethyl] cyclobutyl carboxamide), a putative antagonist. Melatonin (s.c. and i.p.), S-20098 (s.c.), and S-20928 (i.p.) were injected 4 hr before sacrifice. Acute administration of both melatonin and S-20098 decreased melatonin receptor density. In contrast, the putative antagonist S-20928, at a low dose (1 mg/kg), was ineffective on melatonin receptors. It neither affected the 2-(125)I-melatonin specific binding observed in the control group nor did it prevent the decrease in binding induced by melatonin when injected 5 min before the hormone. At a high dose (10 mg/kg), S-20928 totally blocked the effect of melatonin on melatonin receptor density and induced a decrease in binding capacity as melatonin did when injected alone. These results indicate that in the rat pars tuberalis, the melatonin agonist, S-20098, is able to down-regulate melatonin receptors, whereas S-20928 seems to behave as a partial agonist.

Changes with age in daytime and nighttime contents of melatonin, indoleamines, and catecholamines in the pineal gland: a comparative study in rat and Syrian hamster

Previous studies in rodents showed a severe deterioration of pineal physiology with aging. The present study investigated the age-related changes in the content of monoamines and metabolites in rat and Syrian hamster pineal gland. In addition to melatonin, the levels of 5-hydroxytryptophan (5HTP), serotonin (5HT), 5-hydroxyindoleacetic acid (5HIAA), N-acetylserotonin (N-Ac-SHT), dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and noradrenaline (NA) were measured by HPLC. Pronounced reductions were found in 5HT and 5HIAA contents during daytime in rats of 24 months, which had not been observed in animals of 12 months. In addition, nighttime pineal 5HIAA, N-Ac-5HT, and melatonin contents were decreased in the old rats, although a significant day:night variation persisted. Also a diurnal fluctuation in NA, DA, and DOPAC contents was present in young and middle-aged rats but not for NA and DOPAC in the oldest rats due to a decrease in the nighttime levels. Pineal DA levels were also reduced in 24-month-old rats during the night, although a marked day:night change was still found. In the Syrian hamster pineal, significant reductions in daytime 5HT and 5HIAA were found respectively at 12 and 18 months, while nighttime levels of these compounds were decreased from 18 months. The nocturnal content of N-Ac-5HT dropped gradually from 12 months, and melatonin was reduced by 74% and 86% in hamsters of 18 and 24 months, respectively. In all these compounds, a significant day:night variation was observed irrespective of age. However, neither a day:night variation nor an effect of aging was found in terms of pineal NA content. In contrast, pineal DA and DOPAC levels displayed a diurnal variation in hamsters of 1.5 and 6 months, but not in animals of 12 and 18 months due a reduced nighttime content. These data suggest that the decline of pineal melatonin with age is a consequence of a deficit in the pathway of serotonin utilization. This probably is explained by a reduced N-acetyltransferase activity, which may be linked to impaired pineal catecholaminergic neurotransmission.

Regulation of melatonin receptors in the pars tuberalis of Syrian hamsters transferred from long to short photoperiod: implication of melatonin and testosterone

The exposure of long day seasonal breeders to a short photoperiod (SP) induces both sexual quiescence and a decrease in pars tuberalis (PT) melatonin receptor density. Therefore, we studied the respective roles of melatonin and testosterone on the regulation of PT melatonin receptors in Syrian hamsters transferred from long photoperiod (LP) to SP. Compared with intact sexually active animals in LP, the density of melatonin receptors was not affected by the absence of melatonin after removal of the pineal gland from animals kept in either SP or LP. In contrast, the presence of a long melatonin peak in the blood which induces gonadal atrophy induced a significant decrease in binding capacity. The SP-induced decrease in PT melatonin receptor density was also observed in castrated animals showing that it was directly regulated by melatonin, independently of circulating testosterone concentrations. However, the absence of testosterone induced an increased binding in LP, while increasing blood testosterone concentration after implantation of one testosterone-filled silastic tube resulted in a decrease in binding both in LP-and in SP-animals. These results indicate that testosterone induces a photoperiod-independent decrease in PT melatonin receptor density. In summary, these results show that both melatonin and testosterone have negative regulatory effects on the density of PT melatonin receptors.

Daily and photoperiodic 2-125I-melatonin binding changes in the pars tuberalis of the Syrian hamster (Mesocricetus auratus): effect of constant light exposure and pinealectomy

Using quantitative autoradiography, 2-125I-melatonin binding was investigated throughout the light/dark cycle in the pars tuberalis (PT) of the pituitary of adult Syrian hamsters kept for 8 weeks either in long or short photoperiod (LP or SP, respectively). Melatonin receptor density in the PT displayed photoperiod dependent daily variations (maximal values in LP). Indeed, in LP, melatonin receptor density underwent strong daily variations with maximal values during the first half of the light period and minimal values at the end of the night. These variations depended on changes in the maximal binding (Bmax) without differences in the dissociation constant (Kd). In contrast, PT melatonin receptor density was constant and at a very low level throughout the light:dark cycle in SP exposed animals. Daily PT melatonin receptor density variations of LP exposed animals were abolished by pinealectomy or continuous light exposure. These results show clearly that both at the daily and at the seasonal level the regulation of PT melatonin receptors is strongly dependent on circulating melatonin concentrations in the Syrian hamster, but that other regulatory factors, yet unclarified, might also play a role.

Synchronizing circadian rhythms in early infancy

Entrainment to the 24-hour light-dark cycle is of adaptive significance to mammals. Human infants are no exception, but some postnatal care habits prevalent in developed countries can interfere with the physiological mechanisms underlying circadian synchronization. We describe the physiological mechanisms of entrainment to the light-dark cycle in fetuses and newborns, and some common parental care behaviors which subject the developing circadian system of the newborn to conflicting temporal cues. Improvements in parental care are proposed which may improve the circadian synchronization of newborns, and their parents or caregivers.

[Study of 86 cases of Mediterranean boutonneuse fever hospitalized at a university hospital]

OBJECTIVES

To study the clinical manifestations of 86 patients with Mediterranean Boutonneuse Fever who were admitted in a University General Hospital.

PATIENTS AND METHODS

Between 1986 and 1994 we studied retrospectively the clinical manifestations, evolution and complications of 86 patients with Mediterranean Boutonneuse Fever. Diagnosis was based on clinical and serological findings.

RESULTS

We studied a total of 86 patients (64 males; 22 females) with a mean age of 55 years. 88% of cases were diagnosed between June and September, and 89% of them had contact with dogs. 53% of patients had an underlying disease. All patients presented with fever and a generalized erythematous rash. 60% of patients had a initial lesion (tache noire) especially in legs. All patients were treated with doxicycline during one week. 22% of patients had complications such as renal failure, respiratory failure, gastrointestinal bleeding and stroke. Old patients and those with underlying disease had severe complications with a higher significant frequency. No patients died.

CONCLUSIONS

22% of patients with Mediterranean Boutonneuse Fever, especially those with advanced age or underlying disease, who were admitted in the Hospital had severe complications.

Daily and photoperiodic melatonin binding changes in the suprachiasmatic nuclei, paraventricular thalamic nuclei, and pars tuberalis of the female Siberian hamster (Phodopus sungorus)

Using quantitative autoradiography, 2-(125)I-melatonin binding was investigated throughout the light:dark cycle in the suprachiasmatic nuclei (SCN), paraventricular nuclei (PVT), and pars tuberalis (PT) of adult female Siberian hamsters kept for 10 weeks in either long or short photoperiods (LP or SP, respectively). Plasma melatonin concentrations were measured by radioimmunoassay, and the sexual status of the animals was established by visual inspection of vaginal smears and by weighing uteri after sacrifice. The SCN displayed neither daily nor photoperiod-dependent variations in specific binding. Melatonin receptors in these nuclei would be regulated neither by plasma melatonin nor by the light:dark cycle or sexual steroids. By contrast, melatonin receptor density in the PT displayed both strong daily (maximal values during the first half of the light period and minimal values during the night) and photoperiod-dependent (maximal values in LP) variations. These variations dependent on changes in the maximal binding (Bmax) without differences in the dissociation constant (Kd). Daily melatonin receptor densities in the PT of LP- and SP-exposed animals might be regulated by the dark:light transition but not by melatonin. Daily profiles of 2-(125)I-melatonin-specific binding in the PT were independent of photoperiod. Factors underlying the photoperiod-related variations presently are unknown. Concerning the PVT, weak variations in specific binding were detected in SP only when time points were grouped according to the light or dark periods. It is not yet possible to conclude whether they have any physiological relevance. These results show clearly that the regulation of melatonin receptors varies among structures (SCN, PVT, and PT) in the Siberian hamster and is also totally different from that found in the rat.

Serotonergic modulation of photically induced increase in melatonin receptor density and Fos immunoreactivity in the suprachiasmatic nuclei of the rat

The mammalian suprachiasmatic nuclei (SCN) contain a circadian clock which is regulated by neuronal photic and non-photic afferences. Among these, the serotonergic input originating from the dorsal raphe nucleus (DRN) is extremely important. In rats, a light pulse administered during the dark period is known to induce the expression of the immediate early gene c-fos and to increase melatonin receptor density in the SCN. The aim of this study was to assess whether, in rats, these two phenomena were regulated by serotonin, acting via 5-HT1A receptors. Three days after pinealectomy, 4 groups of rats were injected i.p. 90 min before sacrifice with respectively: (1) vehicle, (2) the 5-HT1A-agonist 8-OH-DPAT (5 mg/kg), (3) the 5-HT1A-antagonist NAN-190 (10 mg/kg) or (4) NAN-190 and the 8-OH-DPAT. Half of the animals from each group were exposed to light for 60 min before sacrifice and the other half remained in darkness. Sacrifice took place 5 to 6 h after lights off. Our results show that the antagonist NAN-190: (1) completely blocked the photically-induced increase of melatonin receptor density in the SCN, with an IC50 = 0.352 +/- 0.103 mg/kg, and (2) partially blocked (30%) the photic induction of Fos (the protein product of c-fos) in the ventrolateral subdivision of the SCN. The agonist 8-OH-DPAT enhanced the photically-induced increase of melatonin receptors by 10% and decreased the photically-induced increase in Fos by 18%. Both drugs were devoid of any effect in non-light exposed animals. From these results we may suggest that, in rats, there is a serotonergic control of the neuronal path driving photic information to the SCN. This regulation seems to occur through 5-HT1A or 5-HT1a-like receptors.

Melatonin receptors in the suprachiasmatic nuclei and pars tuberalis of testosterone induced photoresponsive rats

The sexual axis of rats can be rendered photoresponsive by testosterone implants. We have studied in these conditions whether rat pars tuberalis (PT) melatonin receptor density would be decreased after exposure to short photoperiod (SP) like as observed in long day seasonal breeders. The answer is no, but we observed that testosterone induced a photoperiod independent decrease in PT melatonin receptor density. These results show that testosterone-induced photosensitivity in rat is not linked to an SP-induced decrease in PT melatonin receptor density. However, testosterone regulates PT melatonin receptors independently of the photoperiod.

Diurnal changes in the content of indoleamines, catecholamines, and methoxyindoles in the pineal gland of the Djungarian hamster (Phodopus sungorus): effect of photoperiod

Previous studies in Syrian hamster have shown that the correlations between the daily fluctuations in the contents of pineal indoleamines and methoxyindoles are influenced by the photoperiod, and that dopamine may play a role in the regulation of pineal function. The present study investigated the 24 hour changes in the content of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), N-acetylserotonin (NAS), melatonin, 5-methoxytryptophol (5-MT), noradrenaline (NA), dopamine (DA), and 3,4-dihydroxyphenylacetic acid (DOPAC) in the pineal gland of female Djungarian hamsters exposed to long (LP; LD 16:8) or short (SP; LD 10:14) photoperiods for 10 weeks. Pronounced nocturnal increases of N-acetylserotonin and melatonin content were observed irrespective of the photoperiod regime. The content of 5-HT was markedly decreased during the first hour of the night in LP, which contrasted with the lack of changes in NAS and melatonin content at this time. In SP, an increased 5-HTP content and a less obvious decrease in 5-HT content was observed during the night, although melatonin and NAS content were even higher than in LP. Similar daily patterns as for 5-HT were observed in the 5-HT oxidative metabolites (5-HIAA and 5-MT). When considering values throughout the day, a poor correlation for 5-HT vs.. NAS and melatonin content was observed, which was particularly evident during the nighttime. These data indicate that the daily variation of pineal indoles may not only be dependent on changes in the N-acetyltransferase activity but also in other mechanisms regulating pinealocyte 5-HT availability. As previously reported in other species of hamster, pineal NA content did not show daily variations in LP conditions, although a nocturnal increase was detected in SP. In contrast, pronounced nocturnal increases were observed in the content of DA and its acid metabolite, DOPAC, irrespective of the photoperiod. These data indicate the existence of an increased dopaminergic turnover during the night and further support a role for DA in the regulation of melatonin synthesis and in the synchronization of the pineal functions.

Modulation of the length of the cell cycle time of MCF-7 human breast cancer cells by melatonin

It has been shown that melatonin has a direct inhibitory effect on the proliferation of MCF-7 human breast cancer cells in culture. In the present work, we studied whether the length of the cell cycle of MCF-7 cells in increased by melatonin. In MCF-7 cells partially synchronized and labelled with [3H]thymidine, melatonin (10(-9)M), added to the culture medium, shifted the period of the labeling index rhythm from 20.36 hours to 23.48 hours. The fact that melatonin significantly increased (p<0.005) the duration of the cell cycle of human breast cancer cells, support the notion that this hormone exerts part of its antitumor effect through a cell-cycle-specific mechanism by delaying the entry of MCF-7 cells into mitosis.

Daily variation in the content of indoleamines, catecholamines and related compounds in the pineal gland of Syrian hamsters kept under long and short photoperiods

This study examined the diurnal changes in the content of 5-hydroxytryptophan (5-HTP), serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), N-acetylserotonin (NAS), melatonin, 5-methoxytryptophol (5-ML), noradrenaline (NA), dopamine (DA), and 3, 4-dihydroxyphenylacetic acid (DOPAC) in the pineal gland of Syrian hamsters kept under long (14L:10D) and short (10L:14D) photoperiods. The nocturnal increase in NAS and melatonin levels was dependent upon the prevailing photoperiod, with a prolonged duration when the night lengthened. In both photoperiods, NAS and melatonin contents increased several hours after the onset of darkness, and, in animals kept in short photoperiod, the levels of both compounds began to decrease before light onset. On the contrary, decreases were noted in 5-HT, 5-HIAA, and 5-ML contents during the night, which was directly proportional to the dark phase. 5-HTP levels did not show a rhythmic variation. Correlations between the mean values of 5-HT-related compounds showing daily rhythms were very high when group means were compared, but they decreased when values from individual animals were considered. In addition, when correlations were calculated on per-animal basis during the night phase, a weak negative correlation was found for 5-HT vs NAS and 5-HT vs melatonin, although the correlation of 5-HT with positively 5-HT-correlated compounds (5-HIAA and 5-ML) continued to be high. These results indicate that the nocturnal increase in the N-acetyl transferase activity is the major factor generating the rhythm of pineal 5-HT content, but that other photoperiod-dependent mechanisms (i.e., 5-HT synthesis or release) seem to be also implicated. On the other hand, this study shows that NA content in the Syrian hamster pineal gland does not exhibit daily variations, although marked nocturnal increases in the levels of DA and DOPAC were evident. These results suggest the existence of parallel daily alterations in pineal catecholamine synthesis and release, and suggest a role for DA in the pineal activation at night.

2-[125I]iodomelatonin binding sites in murine mammary tissue

2-[125I]iodomelatonin binds in vitro to murine mammary gland membranes, in a specific, saturable, reversible and temperature-dependent and pH-dependent way, displaying an affinity within the low nM range. The order of affinity to displace the radioligand from mammary membranes was: 6-hydroxy-melatonin > 5-hydroxyindoleamines > noradrenaline > 6-chloromelatonin > 5-methoxyindoles (melatonin included). There was a diurnal rhythm in Kd and Bmax of 2-[125I]iodomelatonin binding, displaying the highest affinity and the lowest binding site concentration during the scotophase. The functional significance of melatonin binding sites was indicated by changes in binding parameters related to different rates of mammary growth during puberty, estrous cycle, pregnancy, lactation and the postlactation period.

Pharmacological profile and diurnal rhythmicity of 2-[125I]-iodomelatonin binding sites in murine mammary tissue

Recent studies demonstrated that melatonin treatment decreased the growth of mammary glands in pubertal and pregnant mice. In vitro, melatonin inhibited murine mammary gland growth at microM concentrations and increased it at pM concentrations. Melatonin-induced changes of cyclic nucleotide synthesis was also demonstrated in mammary gland slices in vitro. The objective of the present study was to assess the possible existence of specific binding sites for melatonin in murine mammary gland by using 2-[125I]-iodomelatonin as a probe. The specific binding of 2-[125I]-iodomelatonin to murine mammary gland membranes was rapid, saturable, and reversible, showed an affinity in the low nM range, and displayed time, temperature, and pH dependence. Scatchard analysis indicated the existence of a single class of binding sites that exhibited a diurnal rhythmicity in affinity (Kd) and receptor density (Bmax). A maximum in Bmax (267 +/- 42 fmol/mg protein) was found at the light period, while affinity was maximal during darkness (Kd = 1.33 +/- 0.22 nM). In competition studies dopamine and dopamine-related agents, as well as 6-hydroxymelatonin and serotonin, but not melatonin, effectively displaced 2-[125I]-iodomelatonin from mammary binding sites. The results demonstrated a specific binding of 2-[125I]-iodomelatonin to murine mammary glands, with affinity in the low nM range, and a pharmacological profile that differed from that reported for 2-[125I]-iodomelatonin acceptor sites in other tissues.

[Severe heart arrhythmia secondary to magnesium depletion. Torsade de pointes]

We report a case of torsade de pointe ventricular tachycardia in a patient with chronic magnesium depletion. The etiological aspects implicated this unusual cardiac arrhythmia are: the congenital long QT syndrome; bradycardia, either sinusal or due to atrioventricular block; ionic depletions: hypokalemia, hypocalcemia and hypomagnesemia; treatment with antiarrhythmic class AI drugs (quinidine-like agents), tricyclic antidepressants, phenothiazines and erythromycin; organophosphate poisoning. After ruling out other factors, we concluded that it was caused by hypomagnesemia on the basis of laboratory findings and the good response to replacement therapy. We then discuss the several types of therapy proposed for this arrhythmia; finally, we emphasize the major role of magnesium in myocardial repolarization.

A two-year experience with cromolyn sodium in children with asthma

A two-year experience with cromolyn sodium in children with asthma drawn from inner city population, is presented. Though the initial response to the drug at six weeks was excellent, the response over a two-year period was only very moderate. The possible reasons for this are discussed.