Quasi-thresholdless Photon Upconversion in Metal-Organic Framework Nanocrystals.

Photon upconversion based on sensitized triplet-triplet annihilation ( sTTA) is considered as a promising strategy for the development of light-managing materials aimed to enhance the performance of solar devices by recovering unused low-energy photons. Here, we demonstrate that, thanks to the fast diffusion of excitons, the creation of triplet pairs in metal-organic framework nanocrystals ( nMOFs) with size smaller than the exciton diffusion length implies a 100% TTA yield regardless of the illumination condition. This makes each nMOF a thresholdless, single-unit annihilator. We develop a kinetic model for describing the upconversion dynamics in a nanocrystals ensemble, which allows us to define the threshold excitation intensity  Ithbox required to reach the maximum conversion yield. For materials based on thresholdless annihilators, Ithbox is determined by the statistical distribution of the excitation energy among nanocrystals. The model is validated by fabricating a nanocomposite material based on nMOFs, which shows efficient upconversion under a few percent of solar irradiance, matching the requirements of real life solar technologies. The statistical analysis reproduces the experimental findings, and represents a general tool for predicting the optimal compromise between dimensions and concentration of nMOFs with a given crystalline structure that minimizes the irradiance at which the system starts to fully operate.

Highly Fluorescent Metal-Organic-Framework Nanocomposites for Photonic Applications.

Metal-organic frameworks (MOFs) are porous hybrid materials built up from organic ligands coordinated to metal ions or clusters by means of self-assembly strategies. The peculiarity of these materials is the possibility, according to specific synthetic routes, to manipulate both the composition and ligands arrangement in order to control their optical and energy-transport properties. Therefore, optimized MOFs nanocrystals (nano-MOFs) can potentially represent the next generation of luminescent materials with features similar to those of their inorganic predecessors, that is, the colloidal semiconductor quantum dots. The luminescence of fluorescent nano-MOFs is generated through the radiative recombination of ligand molecular excitons. The uniqueness of these nanocrystals is the possibility to pack the ligand chromophores close enough to allow a fast exciton diffusion but sufficiently far from each other preventing the aggregation-induced effects of the organic crystals. In particular, the formation of strongly coupled dimers or excimers is avoided, thus preserving the optical features of the isolated molecule. However, nano-MOFs have a very small fluorescence quantum yield (QY). In order to overcome this limitation and achieve highly emitting systems, we analyzed the fluorescence process in blue emitting nano-MOFs and modeled the diffusion and quenching mechanism of photogenerated singlet excitons. Our results demonstrate that the excitons quenching in nano-MOFs is mainly due to the presence of surface-located, nonradiative recombination centers. In analogy with their inorganic counterparts, we found that the passivation of the nano-MOF surfaces is a straightforward method to enhance the emission efficiency. By embedding the nanocrystals in an inert polymeric host, we observed a +200% increment of the fluorescence QY, thus recovering the emission properties of the isolated ligand in solution.

Neuroactive steroids influence peripheral myelination: a promising opportunity for preventing or treating age-dependent dysfunctions of peripheral nerves.

The process of aging deeply influences morphological and functional parameters of peripheral nerves. The observations summarized here indicate that the deterioration of myelin occurring in the peripheral nerves during aging may be explained by the fall of the levels of the major peripheral myelin proteins [e.g., glycoprotein Po (Po) and peripheral myelin protein 22 (PMP22)]. Neuroactive steroids, such as progesterone (PROG), dihydroprogesterone (5alpha-DH PROG), and tetrahydroprogesterone (3alpha,5alpha-TH PROG), are able to stimulate the low expression of these two myelin proteins present in the sciatic nerve of aged male rats. Since Po and PMP22 play an important physiological role in the maintenance of the multilamellar structure of PNS myelin, we have evaluated the effect of PROG and its neuroactive derivatives, 5alpha-DH PROG and 3alpha,5alpha-TH PROG, on the morphological alterations of myelinated fibers in the sciatic nerve of 22-24-month-old male rats. Data obtained clearly indicate that neuroactive steroids are able to reduce aging-associated morphological abnormalities of myelin and aging-associated myelin fiber loss in the sciatic nerve.

Tumor suppressor Nf2/merlin drives Schwann cell changes following electromagnetic field exposure through Hippo-dependent mechanisms.

Previous evidence showed mutations of the neurofibromin type 2 gene (Nf2), encoding the tumor suppressor protein merlin, in sporadic and vestibular schwannomas affecting Schwann cells (SCs). Accordingly, efforts have been addressed to identify possible factors, even environmental, that may regulate neurofibromas growth. In this context, we investigated the exposure of SC to an electromagnetic field (EMF), which is an environmental issue modulating biological processes. Here, we show that SC exposed to 50 Hz EMFs changes their morphology, proliferation, migration and myelinating capability. In these cells, merlin is downregulated, leading to activation of two intracellular signaling pathways, ERK/AKT and Hippo. Interestingly, SC changes their phenotype toward a proliferative/migrating state, which in principle may be pathologically relevant for schwannoma development.

Pregnancy-induced changes in thyroid function: role of human chorionic gonadotropin as putative regulator of maternal thyroid.

Marked changes in maternal thyroid activity occur in pregnancy. It has been suggested that hCG may stimulate maternal T4 secretion, given its in vitro thyrotropic activity ascribed to a significant degree of structural homology with TSH. In a longitudinal study of 32 normal pregnant women, we attempted to clarify the functional activity of the thyroid in early and late pregnancy and the possibility of a nonpituitary control on the thyroid. Total T4 and T4-binding globulin levels were increased from the first trimester onward. Free T4 levels did not differ in the first trimester from postpartum values, but were significantly decreased in second and third trimesters (P less than 0.001). A decrease in TSH levels was observed in the first trimester (0.72 +/- 0.09 vs. 1.23 +/- 0.12 mU/L; P less than 0.001), while second and third trimester values did not differ from those postpartum. A significant negative correlation (P less than 0.05) was observed between hCG and TSH levels in the earliest weeks (8-10) of the first trimester. No correlation was found between hCG and total T4 or free T4 levels. A stimulation of I- uptake in FRTL-5 cells was induced by first trimester serum, which also showed a different behavior at chromatofocusing, with a higher proportion of hCG eluting at acidic pIs compared to second trimester samples. However, neither hCG levels nor the amount of acidic hCG correlated with the thyroid-stimulating activity measured in vitro. Some correlation was found with the percentage of basic hCG (eluting at pI greater than 4.6), although these isoforms were equally present in first and second trimesters. The differing patterns of circulating hCG at various stages of gestation suggest that distinct hCG isoforms may regulate maternal thyroid activity.

Excess of beta-subunit of thyrotropin (TSH) in patients with idiopathic central hypothyroidism due to the secretion of TSH with reduced biological activity.

alpha-Subunit and beta-subunit of TSH were measured in the sera of five patients with idiopathic central hypothyroidism due to the secretion of biologically inactive TSH, in seven normal controls matched for bone age and sex, and in five subjects with mild primary thyroid failure before and after TRH (200 micrograms, iv) stimulation. Basal serum alpha-subunit concentration in patients did not differ from that in normal controls (mean +/- SD, 0.40 +/- 0.20 vs. 0.38 +/- 0.28 ng/ml; P, NS), whereas TSH and TSH-beta were significantly higher in patients (TSH, 1.51 +/- 0.74 vs. 0.59 +/- 0.53 ng/ml, P less than 0.025; TSH-beta, 0.56 +/- 0.18 vs. 0.10 +/- 0.02 ng/ml, P less than 0.001). The concentration of TSH-beta was also significantly higher in patients with central hypothyroidism than in subjects with mild primary thyroid failure (0.56 +/- 0.18 vs. 0.24 +/- 0.08 ng/ml; P less than 0.01), although serum TSH levels did not differ in the two groups (1.51 +/- 0.74 vs. 2.16 +/- 0.52 ng/ml; P, NS). alpha-Subunit was significantly higher in primary hypothyroid subjects (1.50 +/- 0.87, P less than 0.05 compared with patients with central hypothyroidism). After TRH, alpha-subunit, TSH, and TSH-beta net increases (peak) were significantly higher in patients with central hypothyroidism than in normal controls (alpha-subunit: 0.95 +/- 0.5 vs. 0.47 +/- 0.19 ng/ml, P less than 0.05; TSH: 7.1 +/- 3.1 vs. 2.9 +/- 1.8 ng/ml, P less than 0.005; TSH-beta: 0.89 +/- 0.35 vs. 0.22 +/- 0.18 ng/ml, P less than 0.005), whereas they did not significantly differ from those recorded in hypothyroid controls. The beta/alpha ratio, which was 1.67 +/- 0.86 in patients and 0.35 +/- 0.18 in normal controls (P less than 0.005), slightly decreased after TRH to 1.24 +/- 0.78 in patients, but remained unchanged in normal controls (0.39 +/- 0.1). After TRH the alpha-subunit peak occurred at 20 min both in patients and in controls, whereas TSH and TSH-beta peaked at 60 min in patients and at 20 min in controls. One patient was given oral TRH (40 mg/day for 4 weeks). The beta/alpha ratio fell from 1.85 to 0.13. Interestingly, serum thyroid hormones, which did not increase after iv TRH and after the first doses of oral TRH, showed a definite increase. Sera from two patients were filtered on Sephadex G-100: in one of them TSH-beta eluted in the same position as labeled reference standard, whereas in the other one radioimmunoassayable TSH-beta eluted near the void volume. The above data indicate that in patients with idiopathic central hypothyroidism due to biologically inactive TSH there is an excess of circulating TSH-beta and suggest that TRH is implicated in the secretion of TSH of full biological potency.

Endocrine, biochemical, and morphological studies of a pituitary adenoma secreting growth hormone, thyrotropin (TSH), and alpha-subunit: evidence for secretion of TSH with increased bioactivity.

A 40-yr-old man who had acromegaly and hyperthyroidism due to a GH/TSH-secreting pituitary adenoma is described. Serum free T4 was 2.8 ng/dl, free T3 was 1.1 ng/dl, and TSH was 1.2-1.5 microU/ml; the latter was measured in an immunoradiometric assay with a sensitivity of 0.07 microU/ml. Serum TSH was immunologically identical to standard TSH and did not decrease during a T3 suppression test. Serum free alpha-subunit and the molar alpha-subunit to TSH ratio were high (6.1 ng/ml and 31.2, respectively). TRH administration induced significant increases in both GH (+129%) and alpha-subunit (+156%) levels. Conversely, dopamine infusion resulted in a decrease in serum GH (-66%) and alpha-subunit (-43%) levels, and subsequent administration of the dopamine antagonist sulpiride induced significant increases in both GH and alpha-subunit (+393% and +106%, respectively). Similarly, somatostatin infusion inhibited GH (-43%) and alpha-subunit (-61%) secretion. Serum TSH levels were not affected by TRH, dopamine, or somatostatin. The biological to immunological activity ratio of serum TSH purified by immunoaffinity chromatography and measured in an adenylate cyclase assay was significantly increased compared to that in serum from hypothyroid or euthyroid subjects [biological to immunological activity ratio, 6.9 +/- 0.2 (+/- SD) vs. 4.4 +/- 1.1; P less than 0.001]. In gel chromatography, the apparent mol wt of the patient's TSH was smaller than that of the controls. After adenomectomy, all of the altered parameters of pituitary function became normal. Double gold particle immunostaining of the adenomatous tissue showed that all of the cells contained secretory granules positive for GH and alpha-subunit, while very few cells were positive for TSH beta as well as GH and alpha-subunit. These data indicate that in this patient serum TSH had an apparent mol wt smaller than that of normal TSH and an increased biological activity which, along with the autonomous TSH secretion, account for hyperthyroidism in the presence of low normal TSH levels; alpha-subunit originated from the same adenomatous cells that secreted GH but not TSH, thus explaining the in vivo observation that alpha-subunit responses to several agents were dissociated from TSH responses and parallel to GH responses; and TSH and GH were colocalized in a minority of the neoplastic cells.

Effect of maternal hypothyroxinaemia during fetal life on the calmodulin-regulated phosphatase activity in the brain of the adult progeny in the rat.

Calmodulin-regulated phosphatase activity was measured in the brain of 2-month-old rats born from hypothyroid and normal dams, using a fluorometric enzyme assay developed for this purpose. Calmodulin content was measured in the same brain regions by radioimmunoassay. Significant differences between groups in weight and protein content, basal phosphatase and calmodulin-regulated phosphatase activity were found. The brain region most affected was the cerebellum, where basal and calmodulin-regulated phosphatase activities, and protein content were increased. The data point towards a lasting effect of maternal hypothyroxinaemia on the brain function of the progeny.

Metabolism of steroids in pure cultures of neurons and glial cells: role of intracellular signalling.

In the brain, the 5 alpha-reductase converting testosterone (T) is present both in neurons and in glial cells, even if it prevails in neurons; the 3 alpha-hydroxysteroid-dehydrogenase (3 alpha-HSD), the enzyme converting dihydrotestosterone (DHT) into 3 alpha-diol, is particularly concentrated in type 1 astrocytes. In glial cells, since the 5 alpha-reductase is activated by a cAMP analogue, PKA seems to be involved in the control of this enzyme, postulating that nervous inputs utilizing cAMP as the second messenger might modify the activity of this enzyme in glial cells. Moreover, the results indicate that, in type 1 astrocytes, both the 5 alpha-reductase and the 3 alpha-HSD are stimulated by the co-culture with neurons and by the addition of neuron-conditioned medium, suggesting that secretory products released by neurons might intervene in the control of glial cell function.

Effects of neuroactive steroids on myelin of peripheral nervous system.

Peripheral nervous system (PNS) possess both classical (e.g. progesterone receptor, PR, androgen receptor, AR) and non-classical (e.g. GABA(A) receptor) steroid receptors and consequently may represent a target for the action of neuroactive steroids. Our data have indicated that neuroactive steroids, like for instance, progesterone, dihydroprogesterone, tetrahydroprogesterone, dihydrotestosterone and 3alpha-diol, stimulate both in vivo and in vitro (Schwann cell cultures), the expression of two important proteins of the myelin of peripheral nerves, the glycoprotein Po (Po) and the peripheral myelin protein 22 (PMP22). It is important to highlight that the mechanisms by which neuroactive steroids exert their effects on the expression of Po and PMP22 involve different kind of receptors depending on the steroid and on the myelin protein considered. In particular, at least in culture of Schwann cells, the expression of Po seems to be under the control of PR, while that of PMP22 needs the GABA(A) receptor. Because Po and PMP22 play an important physiological role for the maintenance of the multilamellar structure of the myelin of the PNS, the present observations might suggest the utilization of neuroactive steroids as new therapeutically approaches for the rebuilding of the peripheral myelin.

5 alpha-reductase activity in isolated and cultured neuronal and glial cells of the rat.

The distribution of the 5 alpha-reductase, the enzyme which converts testosterone into its 'active' metabolite dihydrotestosterone (DHT), has been studied in neurons, astrocytes and oligodendrocytes isolated from the brain of male rats by density gradient ultracentrifugation and in neurons and glial cells grown in cultures. Purity of cellular preparations was examined by electron and light microscopy. Purified neurons, astrocytes and oligodendrocytes, obtained from the brain of adult male rats, are all able to form DHT from testosterone and consequently possess a 5 alpha-reductase activity. Among the 3 cell types studied, neurons appear to be more active than oligodendrocytes and astrocytes. Moreover, between the two population of glial cells, the oligodendrocytes seem to possess a slightly higher enzymatic activity than that present in the astrocytes. Neurons appeared more active in metabolizing testosterone than glial cells also in cell culture experiments. It is presently believed that the 5 alpha-reduction of testosterone to DHT provides one of the mechanisms through which the hormone becomes effective in the CNS. This is supported by the present findings, which indicate that neurons are the cell population in which the 5 alpha-reductase is more concentrated. However, the presence of a considerable 5 alpha-reductase activity in glial cells indicates that also non-neuronal cells might participate in androgen-mediated events occurring in the brain.

Ontogenetic development of the 5 alpha-reductase in the rat brain: cerebral cortex, hypothalamus, purified myelin and isolated oligodendrocytes.

In the central nervous system of the rat, the 5 alpha-reductase, the enzyme which converts testosterone into dihydrotestosterone, appears to be concentrated in the white matter and in particular to be associated with myelin. In order to verify whether a temporal correlation might exist between the formation of myelin membranes and the variations of the 5 alpha-reductase activity observed in the brain, the enzymatic activity was studied in the cerebral cortex and in the hypothalamus of male rat in the age range of 3-60 days, in myelin purified from animals of 15-60 days of life and in oligodendrocytes (i.e. in the cells responsible for the formation of the myelin) isolated from the brain of adult and very young rats (7th day of life, when the myelination process is not yet initiated). The results show that the formation of 5 alpha-androstane-17 beta-ol-3-one (DHT) in the cerebral cortex and in the hypothalamus has a peak activity in the first two weeks of life, before the beginning of the myelination process; purified myelin has an enzymatic activity always much higher than that present in the cerebral cortex and in the hypothalamus and shows a peak in the formation of DHT in the first period of myelinogenesis, on the third week of life. Finally the oligodendrocytes of young rats possess a much higher ability to convert testosterone into the 5 alpha-reduced metabolites than the oligodendrocytes of adult animals. A possible involvement of this enzyme in the myelin function may be hypothesized.

Evaluation of lanreotide effects on human exocrine pancreatic secretion after a single dose: preliminary study.

BACKGROUND: Total parenteral nutrition and somatostatin or analogues represent a consolidated therapeutic approach for external fistulas, a frequent complication of major pancreatic surgery. AIMS: To establish the effects of the somatostatin analogue lanreotide on exocrine pancreatic secretion. METHODS: Eight patients, undergoing pancreaticoduodenectomy for malignancy, were enrolled in the trial. The volume and composition of pancreatic secretion were evaluated after one single subcutaneous injection of lanreotide 0.5 mg or placebo in a randomised, double-blind cross-over trial. RESULTS: In the seven patients completing the study, the 24-h output volume was 208.6+/-41.3 and 253.9+/-72.4 ml after lanreotide and placebo, respectively. During the first 6 hours values were 48.1+/-14.7 and 77.6+/-21.4 ml (p=0. 02). No significant difference between treatments was detected in the qualitative composition of 24-h pancreatic secretion, although bicarbonate secretion remained lower after the active drug at all the observation intervals. Peak lanreotide levels were detected 15-30 min after drug injection. Clinical and laboratory tolerability was good. CONCLUSIONS: Lanreotide induced a statistically significant reduction in the output volume with respect to placebo in the first 6 hours after administration, but not thereafter. The present results encourage a new study to be undertaken in a larger sample and with a multiple dosing scheme of treatment.

New anthracycline glycosides obtained by the nitrous acid deamination of daunorubicin, doxorubicin and their configurational analogues.

The new anthracyclines 7-O-(2,3,5-trideoxy-3-C-formyl-alpha-L-threo-pentofuranosyl)daunomyci none (8) and -adriamycinone (10) have been obtained upon nitrous acid deamination of daunorubicin and doxorubicin respectively. Deamination of the L-ribo analogue of daunorubicin (6) gave a mixture of 2,3,6-trideoxy-L-glycero-hexopyranosid-4-ulose (alpha-L-cinerulosyl) (11) and 2,6-dideoxy-alpha-L-arabino-hexopyranosyl (12) glycosides. The corresponding adriamycinone glycosides 13 and 14, obtained by deamination of the doxorubicin L-ribo analogue 7, were found to display an outstanding antileukemic activity in mice.

New biosynthetic anthracyclines related to barminomycins incorporating barbiturates in their moiety.

Three new anthracyclines, FCE 21424 (2), FCE 24366 (3) and FCE 24367 (4), were isolated from culture broths of Streptomyces peucetius and its mutant strains after addition of sodium barbiturates during the fermentation. Structural assignment, achieved through spectroscopic and degradative studies, that the new anthracyclines had a common barminomycin-like structure incorporating different barbiturate moieties. The new anthracyclines were found to display outstanding cytotoxicity and remarkable potency "in vivo" against P388 ascitic leukemia.

Novel rifamycins. III. Synthesis and antibacterial activity of 3-amidino- and of 4-aminoimidazolo[4,5-c]rifamycin derivatives.

A number of semisynthetic rifamycin derivatives modified at position 3 and/or 4, belonging to general structures 2 and 4 (see Scheme 1), have been obtained. The synthesis and the biological activities of the new compounds are described. Compounds 4p and 4q display very good antimycobacterial activity in mice.

Pharmacokinetics of fenfluramine enantiomers in man.

The pharmacokinetics of fenfluramine enantiomers were studied in normal volunteers following the administration of single of multiple doses of racemic fenfluramine hydrochloride. Plasma concentrations and half-lives were similar for both enantiomers after single 40 mg of 60 mg doses. However following chronic administration (2 x 40 mg for 10 days), significant differences were observed between the kinetic parameters of the two enantiomers, the l-form of fenfluramine and norfenfluramine accumulating in plasms more than the d-forms.

Antileptazol activity and kinetic of CP 1414 S (7-nitro-2-amino-5-phenyl-3-H-,1,5-benzodiazepine-4-one) in the rat and mouse.

The antileptazol effect of CP 1414 S (7-nitro-2-amino-3-phenyl-3H-1,5-benzodiazepine-4-one) a newly developed 1,5 benzodiazepine, lasts longer in mice than in rats. After intraperitoneal injection (10 mg/kg) brain levels of the drug were higher and persisted for longer in the mouse than in the rat. Although it cannot be excluded tht possible metabolites of CP 1414 S may contribute to the anticonvulsant effect of CP 1414 S, in both species the protective effect correlates well with the brain concentrations of the drug.