Low-power laser irradiation promotes the proliferation and osteogenic differentiation of human periodontal ligament cells via cyclic adenosine monophosphate.

Retaining or improving periodontal ligament (PDL) function is crucial for restoring periodontal defects. The aim of this study was to evaluate the physiological effects of low-power laser irradiation (LPLI) on the proliferation and osteogenic differentiation of human PDL (hPDL) cells. Cultured hPDL cells were irradiated (660 nm) daily with doses of 0, 1, 2 or 4 J⋅cm(-2). Cell proliferation was evaluated by the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay, and the effect of LPLI on osteogenic differentiation was assessed by Alizarin Red S staining and alkaline phosphatase (ALP) activity. Additionally, osteogenic marker gene expression was confirmed by real-time reverse transcription-polymerase chain reaction (RT-PCR). Our data showed that LPLI at a dose of 2 J⋅cm(-2) significantly promoted hPDL cell proliferation at days 3 and 5. In addition, LPLI at energy doses of 2 and 4 J⋅cm(-2) showed potential osteogenic capacity, as it stimulated ALP activity, calcium deposition, and osteogenic gene expression. We also showed that cyclic adenosine monophosphate (cAMP) is a critical regulator of the LPLI-mediated effects on hPDL cells. This study shows that LPLI can promote the proliferation and osteogenic differentiation of hPDL cells. These results suggest the potential use of LPLI in clinical applications for periodontal tissue regeneration.

Neuronal regulation of photo-induced pineal photoreceptor proteins in carp Catla catla.

In the present in vitro study on the pineal in carp Catla catla, specific agonist and antagonists of receptors for different neuronal signals and regulators of intra-cellular Ca(++) and cAMP were used to gather basic information on the neuronal signal transduction cascade mechanisms in the photo-induced expression of rod-like opsin and alpha-transducin-like proteins in any fish pineal. Western-blot analysis followed by quantitative analysis of respective immunoblot data for both the proteins revealed that photo-induced expression of each protein was stimulated by cholinergic (both nicotinic and muscarinic) agonists and a dopaminergic antagonist, inhibited by both cholinergic antagonists and a dopaminergic agonist, but not affected by any agonists or antagonists of adrenergic (alpha(1), alpha(2) and beta(1)) receptors. Moreover, expression of each protein was stimulated by voltage gated L type calcium channel blocker, adenylate cyclase inhibitor and phosphodiesterase activator; but suppressed by the activators of both calcium channel and adenylate cyclase, and by phosphodiesterase inhibitor. Collectively, we report for the first time that both cholinergic and dopaminergic signals play an important, though antagonistic, role in the photo-induced expression of photoreceptor proteins in the fish pineal through activation of a signal transduction pathway in which both calcium and cAMP may act as the intracellular messengers.

Cyclic AMP levels in several macroalgae and their relation to light quantity and quality.

Total cAMP levels were measured in the macroalgae Dictyota dichotoma, Gelidium sesquipedale and Ulva rigida under different light conditions in order to study its regulation either by phytochrome or photosynthesis. Incubation in red or far-red light did not promote a phytochrome-like response; instead, it showed a synergistic effect upon cAMP accumulation. cAMP levels seemed to depend on the amount of energy applied. The correlation between photosynthetic oxygen evolution and cAMP variations at sub-saturating white light irradiance pointed to photosynthetic electron transport as involved in the regulation of cAMP accumulation at least in G. sesquipedale and U. rigida. Inhibitors of thylakoidal and mitochondrial electron transport chains reduced cAMP levels in 70 to 99%. We conclude that cAMP accumulation could be regulated by photosynthetic activity rather than phytochrome in the macroalgae studied.

Regulation of cAMP-mediated photosignaling by a phytochrome in the cyanobacterium Anabaena cylindrica.

Changes in cellular adenosine 3',5'-cyclic monophosphate (cAMP) content induced by monochromatic light of various wavelengths were determined in the cyanobacterium Anabaena cylindrica. Irradiation with monochromatic red light caused a rapid decrease in cAMP content. In contrast, far-red light caused a rapid increase in its content. The effects of red and far-red light were reversible, suggesting the involvement of a prototype phytochrome as the photoreceptor for cAMP-mediated light-responsive signal transduction.

Magnetic field desensitizes 5-HT(1B) receptor in brain: pharmacological and functional studies.

It was previously suggested that exposure to magnetic fields (MFs) could generate dysfunction of the CNS. The physiological manifestations described lead us to postulate that these symptoms might be related to a dysfunction of the serotonergic system and particularly of the 5-HT(1B) receptors. Accordingly, MFs could modify the conformation of these receptors altering their functional activities. In rat brain membrane preparations, we showed that the affinity constant of 5-HT for 5-HT(1B) receptors was modified under exposure to MFs since K(d) varied from 4.7+/-0.5 to 12+/-3 nM in control and exposed (2.5 mT) membranes, respectively. This effect was intensity-dependent (the sigmoidal dose-response curve was characterized by an EI(50) of 662+/-69 microT and a maximal increase of 321+/-13% of the control K(d)), reversible, temperature-dependent and specific to the 5-HT(1B) receptors. Similar results have also been obtained with the human 5-HT(1B) receptors. In parallel assays, the functional activity of 5-HT(1B) receptors was investigated. The capacity of a 5-HT(1B) agonist to inhibit the cAMP production was reduced by 37% (53.7+/-3.5% to 33.7+/-4.1%) following exposure to MFs and the cellular activity of the receptors (inhibition of the synaptosomal release of 5-HT) also was markedly reduced (66.5+/-3.2% to 28.5+/-4.2%). These results clearly show that in in vitro assays, MF specifically interacts with 5-HT(1B) receptors, inducing structural changes of the protein that result in a functional desensitization of the receptors. Thus, in vivo, exposure to MFs may lead to physiological changes, particularly in the field of mood disorders where the 5-HT system is strongly involved.

Light affects cAMP signaling and cell movement activity in Dictyostelium discoideum.

The multicellular, slug stage of the slime mould Dictyostelium discoideum lacks specific sensory cells and organs but can nevertheless respond in a very sensitive manner to external stimuli such as temperature and light. Within the migrating slug, the behavior of up to 100,000 individual amoebae is coordinated by cAMP mediated cell-cell signaling and chemotaxis. We report here the striking result that light directly modulates the cAMP cell-cell signaling system. Light-induced secretion of cAMP from the slug tips decreased the period length of optical density waves and speeded up cell movement. A local effect of light on cAMP release within the slug tip could modulate cell movement within the slug and thus control its phototactic turning and orientation toward a light source.

Dose-related effect of irradiation on circadian rhythm of cellular messengers in neural and immune system of mouse.

OBJECTIVE: To explore toxic effect of gamma-irradiation on circadian rhythms of cAMP and cGMP in signal pathway between the central nuclei and peripheral lymphocyte. METHODS: 60Co gamma-ray of 0.5 Gy and 5.0 Gy was applied to groups of mice at each circadian timepoint of a day. 24 hours after the irradiation, the pineal and suprachiasmatic nuclei (SCN) were removed, and the T lymphocytes in blood were separated by a step-centrifugal and nylon-filter treatment, for measurements of cAMP and cGMP by using the RIA procedure. The results were expressed as circadian rhythms of the cAMP/cGMP ratio derived from the Cosinor analysis. RESULTS: The daily average cAMP/cGMP ratio in cells of SCN, pineal, serum and lymphocyte changed according to the dose of irradiation at which the mice were exposed. The high dose of 5 Gy increased the ratio, and the low dose of 0.5 Gy decreased the ratio. There was a significant difference of cAMP/cGMP levels between the irradiated and the control groups, as well as between CT00:00 and CT12:00 of a day. In addition, the peak phases of the cAMP/cGMP ratio at the low-dose groups appeared in advance from about 2 to 8 hours, whereas those at the high-dose groups were delayed from about 3 to 6 hours in comparison to that of the normal mice. CONCLUSION: Toxic effect of gamma-irradiation on the cAMP/cGMP circadian rhythm in the central nuclei and peripheral lymphocyte could be characterized by a low-dose hormesis.

A spontaneous change in the intracellular cyclic AMP level in Aspergillus niger is influenced by the sucrose concentration in the medium and by light.

A spontaneous rise in intracellular cyclic AMP (cAMP) levels was observed in the early stages of Aspergillus niger growth under conditions yielding large amounts of citric acid. The amount of cAMP formed was found to depend on the initial concentration of sucrose in the medium. Under higher-sucrose conditions, the cAMP peak appeared earlier and was higher, while in lower-sucrose media a flattened peak was observed later in fermentation. Since in media with higher concentrations of sucrose intracellular citric acid starts to accumulate earlier and more rapidly, cAMP synthesis may be triggered by intracellular acidification, which is caused by the dissociation of citric acid. No spontaneous increase in cAMP concentrations could be detected when the cells were grown in continuously illuminated cultures, suggesting that A. niger phosphodiesterase (PDE) is photoregulated. More evidence for the activation of PDE by light was obtained from morphological studies under light and dark conditions in the presence of cAMP or N6,O2'-dibutyryl cAMP, and this idea was additionally supported by experiments in which PDE inhibitors were tested.

Photoreactive (caged) cyclic AMP analogs induce DNA synthesis in mammary epithelial cells.

Dimethoxy-2-nitrobenzyl adenosine-3',5' cyclic monophosphate (DMNB) is a metabolically active, photolabile cyclic AMP analog that yields free cyclic AMP upon UV hydrolysis. The analog is useful in that it permits short term, transient elevations of intracellular cyclic AMP. Addition of DMNB (1-10 microM) to mouse mammary epithelial cells, followed by UV irradiation of cells, caused a significant increase in DNA synthesis over that observed with controls, UV irradiation alone or DMNB alone. In subsequent studies, DMNB exhibited a modest, but statistically significant, interaction with epidermal growth factor in promoting DNA synthesis. Effects of DMNB were observed if DNA synthesis was measured as either 3H-thymidine incorporation into DNA or as percent S-phase cells. These results indicate that previously observed effects of agents such as cholera toxin and phosphodiesterase resistant cyclic AMP analogs on mammary epithelial proliferation can be mimicked, at least in part, by a short term pulse of cyclic AMP.

[Post-radiation disturbances in the cyclic nucleotide system in rat spleen and thymus lymphocytes]. / Postradiatsionnye narusheniia v sisteme tsiklicheskikh nukeltidov limfotsitov selezenki i timusa krys.

The changes in cAMP and cGMP content in rat spleen and thymus lymphocytes after irradiation in doses of 0.5 and 1 Gy, are determined, indicating to significant disturbances in the system of cyclic nucleotides. Radiation affected the functioning of enzymes both of synthesis and hydrolysis of cAMP and cGMP in spleen lymphocytes. The activity of adenylate cyclase and guanylate cyclase did not change in thymocytes after the exposure, while the activity of phosphodiesterase of cyclic nucleotides slightly increased.

[The role of the sex hormones in regulating the spermatogenesis process in different strains of mice irradiated at low doses of gamma quanta]. / Rol' polovykh gormonov v reguliatsii protsessa spermatogeneza u myshei raznykh linii, obluchennykh v malykh dozakh gamma-kvantami.

Intact BALB/c and CBA mice distinct in the total number of germ cells and testosterone level in blood plasma were exposed to doses of 0.1 and 0.25 Gy. Being tested 4-8 days after irradiation the BALB/c mice display compensatory-protective reaction which promote the maintenance of the germ cell number by active division of all spermatogonia types including the reserve ones. The CBA mice use the reserve later and only when the cells have reduced their proliferation activity or died. Testosterone plays a significant role in the process as the increase in its concentration stimulates proliferation activity and promotes mitosis block.

Cyclic AMP response in cells exposed to electric fields of different frequencies and intensities.

The action on intracellular cyclic AMP (cAMP) of therapeutically used 4000-Hz electric fields was investigated and compared with 50-Hz data. Cultured mouse fibroblasts were exposed for 5 minutes to 4000-Hz sine wave internal electric fields between 3 mV/m and 30 V/m applied within culture medium. A statistically significant decrease in cellular cAMP concentration relative to unexposed cells was observed for fields higher than 10 mV/m. The drop in cAMP was most pronounced at lower field strengths (71% of controls at 30 mV/m) and tended to disappear at higher field strengths. An increase of cAMP content was observed with 50-Hz electric fields, as was also the case when 4000-Hz fields were modulated with certain low frequencies.

[The molecular mechanisms of exposure to ionizing radiation]. / Molekuliarnye mekhanizmy vozdeistviia ioniziruiushchikh izluchenii.

The article studies biochemical processes which occur in man's organism after the influence of ionizing radiation. The authors thoroughly describe the mechanisms of radioactively induced free radical reactions, radiation injuries of membranes, post-radiation disorders in cellular energy supply and cellular cyclatic system.

[Cyclic nucleotides in rat tissues under long-term irradiation]. / Tsiklicheskie nukleotidy v tkaniakh krys pri dlitel'nom radiatsionnom vozdeistvii.

Considerable changes in concentrations of cAMP and cGMP and in the CAMPOcGMP ratio were found in the thymus and blood plasma of rats subjected to long-term irradiation at cumulative doses of 10 to 20 Gy. This might be a manifestation of adaptation reactions that develop in response to the effect of ionizing radiation.

[The effect of the dose rate on the development of rat pups under chronic gamma irradiation]. / Vliianie moshchnosti dozy na razvitie krysiat pri khronicheskom gamma-obluchenii.

Chronic exposure of rat pups to gamma radiation, during their intensive growth, at a dose rate of 0.01, 0.11 and 0.5 cGy/day did not affect their development throughout a two-month period of observation. At a dose rate of 12.9 cGy/day rat growth was inhibited during the first 15 days. With further exposure at the same dose rate (over a period of up to five months) the rate of rat pup growth was restored, which indicated the presence of adaptation processes.

[The individual characteristics of the postradiation reaction of the cyclic nucleotides in rat thymocytes]. / Individual'nye osobennosti postradiatsionnoi reaktsii tsiklicheskikh nukleotidov timotsitov krys.

It was shown that X-irradiation of rats (4.3 Gy), which were preliminarily divided into two groups by the neutrophilic reaction in the peripheral blood to the effect of a three-hour immobilization, induced different reactions of the cyclic nucleotide system. Thus, in animals hyper-reactive to stress radiation injury to the above system was severe: relative reactivity made 22.8% of the initial value, and adenylate cyclase ability to respond to a hormonal stimulus was drastically inhibited. In hyporeactive animals, relative reactivity of adenylate cyclase system after irradiation made 47% throughout the same period of observation; inhibition of adenylate cyclase activity was also less pronounced.

[The cyclic nucleotide content of the blood plasma in mice irradiated at different doses]. / Soderzhanie tsiklicheskikh nukleotidov v plazme krovi myshei, obluchennnykh v raznykh dozakh.

Cyclic nucleotide content of plasma was shown to increase after irradiation of mice within a wide range of doses. Compared was the dynamics of changes in the cyclic nucleotide content 24 hr following irradiation with supralethal doses.