Pseudomonas marianensis sp. nov., a marine bacterium isolated from deep-sea sediments of the Mariana Trench.

A novel marine Gram-stain-negative, aerobic, rod-shaped bacterium, designated as strain PS1T, was isolated from the deep-sea sediments of the Mariana Trench and characterized phylogenetically and phenotypically. Bacterial optimal growth occurred at 35 °C (ranging 10-45 °C), pH 6 (ranging pH 5-10) and with 11% (w/v) NaCl (ranging 0-17%). The 16S rRNA gene sequence similarity results revealed that strain PS1T was most closely related to Pseudomonas stutzeri ATCC 17588T, Pseudomonas nitrititolerans GL14T, Pseudomonas zhaodongensis NEAU-ST5-21T, Pseudomonas xanthomarina DSM 18231T and Pseudomonas kunmingensis HL22-2T with 98.3-98.7%. The digital DNA-DNA hybridization values and the average nucleotide identity between strain PS1T and the reference strains were 20.4-40.1% and 78.7-79.4%, respectively. The major respiratory quinone is ubiquinone Q-9. The major polar lipids were phosphatidylethanolamine, diphosphatidyglycerol, phosphatidylglycerol, phosphatidylcholine, aminoglycolipid, two unidentified glycolipids and one unidentified lipid. The predominant cellular fatty acids of strain PS1T were summed feature 8 (C18:1ω7c and/or C18:1ω6c), summed feature 3 (C16:1ω7c and/or C16:1ω6c), C16:0 and cyclo-C19:0 ω8c. The G + C content of the genomic DNA was 63.0%. The combined genotypic and phenotypic data indicated that strain PS1T represents a novel species of the genus Pseudomonas, for which the name Pseudomonas marianensis sp. nov. is proposed, with the type strain PS1T (= DSM 112238T = MCCC 1K05112T).

Cyclocytidine hydrochloride inhibits the synthesis of relaxed circular DNA of hepatitis B virus.

Background: Cyclocytidine hydrochloride (HCl) has been reported to inhibit DNA synthesis by affecting DNA polymerase. Here, we tested the antiviral effect of cyclocytidine on hepatitis B virus (HBV) DNA synthesis, which is reliant on DNA polymerase activity. Materials and Methods: Cyclocytidine HCl was treated to HBV-producing HepAD38 cells or added to an endogenous polymerase reaction, and HBV DNA was detected by Southern blot. Results: Treatment of 20 µM cyclocytidine HCl significantly decreased the production of relaxed circular (rc) DNA in HepAD38 cells and block rcDNA synthesis in endogenous polymerase reaction (EPR), a cell free assay, possibly by inhibiting the HBV DNA polymerase activity. Conclusion: Cyclocytidine HCl could inhibit the synthesis of HBV rcDNA, the precursor of covalently closed circular DNA, and this result provides a case for the usage of "old" drugs for "new" applications.

Virtual screening, ADME/T, and binding free energy analysis of anti-viral, anti-protease, and anti-infectious compounds against NSP10/NSP16 methyltransferase and main protease of SARS CoV-2.

Recently, a pathogen has been identified as a novel coronavirus (SARS-CoV-2) and found to trigger novel pneumonia (COVID-19) in human beings and some other mammals. The uncontrolled release of cytokines is seen from the primary stages of symptoms to last acute respiratory distress syndrome (ARDS). Thus, it is necessary to find out safe and effective drugs against this deadly coronavirus as soon as possible. Here, we downloaded the three-dimensional model of NSP10/NSP16 methyltransferase (PDB-ID: 6w6l) and main protease (PDB-ID: 6lu7) of COVID-19. Using these molecular models, we performed virtual screening with our anti-viral, inti-infectious, and anti-protease compounds, which are attractive therapeutics to prevent infection of the COVID-19. We found that top screened compound binds with protein molecules with good dock score with the help of hydrophobic interactions and hydrogen bonding. We observed that protease complexed with Cyclocytidine hydrochloride (anti-viral and anti-cancer), Trifluridine (anti-viral), Adonitol, and Meropenem (anti-bacterial), and Penciclovir (anti-viral) bound with a good docking score ranging from -6.8 to -5.1 (Kcal/mol). Further, NSP10/NSP16 methyltransferase complexed with Telbivudine, Oxytetracycline dihydrate (anti-viral), Methylgallate (anti-malarial), 2-deoxyglucose and Daphnetin (anti-cancer) from the docking score of -7.0 to -5.7 (Kcal/mol). In conclusion, the selected compounds may be used as a novel therapeutic agent to combat this deadly pandemic disease, SARS-CoV-2 infection, but needs further experimental research.HighlightsNSP10/NSP16 methyltransferase and main protease complex of SARS CoV-2 bind with selected drugs.NSP10/NSP16 methyltransferase and protease interacted with drugs by hydrophobic interactions.Compounds show good DG binging free energy with protein complexes.Ligands were found to follow the Lipinski rule of five.

Ultrastructural histochemical studies of secretory granule replenishment in rat submandibular granular tubules after cyclocytidine-induced secretion.

Rat submandibular glands have been examined electron microscopically at various times after degranulating the granular tubules by injecting cyclocytidine (75 mg/kg i.p.), to study events in the reformation of secretory granules in these cells. The changes were progressive but not synchronous in the cells. The first evidence of recovery was the re-appearance of glycogen particles 6 h after injection. Residual secretory granules were small and located periluminally at that time. More granules were present at 15 h after injection but they were still small and placed periluminally. There was more glycogen in the cells and some was present in aggregates. At 1 day after injection there were more secretory granules and they tended to be larger than previously. The secretory granules increased in size and number progressively thereafter and the cells appeared like normal controls by day 7. During the recovery, fusion profiles were seen between granules from 2 days onwards. Throughout, few Golgi complexes were detected and this may be related with the low glycosylation of the secretory proteins in these cells. The results confirm that the reformation of the secretory granules in granular tubule cells is a slow process that involves fusions of smaller granules.

Ultrastructural histochemical studies of secretory processes in rat submandibular granular tubules during intermittent sympathetic nerve stimulation.

Secretory changes in the cells of granular tubules in rat submandibular glands have been studied sequentially during electrical stimulation of their sympathetic nerves. Results were assessed in a series of biopsied lobes from the same gland, taken at different times during the sympathetic stimulation. Changes were not synchronous between adjacent cells and it appeared that the time for the onset of secretory events differed between cells but, once set in action, a chain of similar events occurred. Nevertheless, some cells appeared to remain refractory throughout. Initially, some alignment of granules to the adjacent plasma membrane occurred and occasional evidence for classical exocytosis was seen. However, from early on microvesicles appeared in more luminally located granule membranes and were associated with granule fusions, that became common and led to the formation of large irregular aggregates. Most of the secretion of granule contents appeared to be through openings of aggregates into lumina. With granule fusions the intra-membrane microvesicles became internalised and tended to increase in size with time; they were commonly expelled with the contents of the aggregates. Fragments of cytoplasm also became incorporated in aggregate formation. Cytoplasm, often containing glycogen, also formed luminal blebs over some granular tubule cells and appeared to pass into the secretion by an apocrine process. At the end of stimulation multivesicular bodies were seen in association with redundant aggregates.

Protection against irradiation-induced damage to salivary glands by adrenergic agonist administration.

PURPOSE: Irradiation [IR]-induced damage to major salivary glands is an entity first described at the beginning of our century, yet its underlying mechanism is still enigmatic. Exposure of the salivary glands to IR is often inevitable when delivering radiotherapy for malignancies of the head and neck region. Frequently, this results in rapidly developing, life-long severe xerostomia for which no adequate prevention or treatment is available. The purpose of this study was to examine the role of secretion granules in serous cells of the parotid (P) and submandibular (SM) glands as mediators in the IR-induced salivary damage. Functional parameters (flow rate and gland weight), and total body weight were examined at both early term (4 days) and extended term (2 months) post-IR in male Wistar rats exposed to 15 Gy of head and neck irradiation following stimulation for granule secretion (degranulation). METHODS AND MATERIALS: At 4 days, it was demonstrated that IR reduced P flow rate, P gland weight, total body weight, and submandibular/sublingual gland weight by 89, 33, 30, and 32% (p < 0.01), respectively, while SM flow rate was not altered significantly. At 2 months, these parameters were reduced by 59, 37, 31, and 37%, respectively, and the SM flow rate was reduced by 39% (p < 0.01). RESULTS: Pilocarpine, a muscarinsic agonist which, albeit its efficacy as a salivary watery secretion stimulator, causes only limited degranulation, did not protect significantly any of the reduced parameters at either term. In contrast, cyclocytidine, an adrenergic agonist that is a very potent salivary degranulating agent, protected the P against the weight loss at 4 days and 2 months, and against the flow rate reduction at 2 months. The P weight and flow rate were protected to the extent that their values were not significantly different than those of the nonirradiated controls. Cyclocytidine also partially protected against the body weight reduction at 2 months. Our results emphasize the importance of secretion granules as mediatory agents in IR-induced P damage, and more so at the extended term. The demonstrated protective role of adrenergic agonists against IR damage to the P may be of importance in the clinical setting.

Antioxidant activity of rat parotid saliva.

BACKGROUND: The healing-promotion property of saliva has been observed in the past, but its underlying mechanism has never been elucidated. We hypothesized a mechanism based on salivary proteins binding to redox active metal ions, rendering them nonactive in their capacity for free radical production. METHODS: Examination of this mechanism was conducted by comparing the redox activity of protein-rich saliva with protein-poor saliva. We also examined the redox activity mediated by these 2 kinds of saliva following the in vitro addition of iron, copper, and manganese. Saliva samples were analyzed for their redox activity by measuring the ascorbate-driven and saliva (diluted 1:2)-mediated conversion of salicylate to its 2,3- and 2.5-dihydroxybenzoates and catechol metabolites. RESULTS: The concentrations of salicylate metabolites formed by protein-rich saliva were significantly lower by 45% (P < .05), 66% (P < .01), and 54% (P < .05), respectively, when compared with those formed by protein-poor saliva. The capacity of saliva in suppressing redox activity was found to be inversely related to the concentrations of iron and copper added (but not manganese), but correlated well with the protein content. When the highest concentrations of iron (15 mumol/L) and copper (10 mumol/L) were added to protein-rich saliva, the concentrations of salicylate metabolites produced were only 0.3% to 1% of those of non-saliva-containing controls (P < .01). However, when these concentrations of iron and copper were added to protein-poor saliva, significantly higher values of redox activity were detected, and the concentrations of the salicylate derivatives produced were 2.1% to 8.1% of those of non-saliva-containing controls (P < .01). In contrast, when the lowest concentrations of iron (2 mumol/L) and copper (0.1 mumol/L) were added, 2.8 to 4 times lower concentrations of salicylate derivatives were produced (P < .01). CONCLUSION: These results substantiate our hypothesis that saliva has a profound capacity for reducing redox activity rendered by transition metal ions, correlating well with its protein content.

Irradiation-induced damage to the salivary glands: the role of redox-active iron and copper.

The mechanism of irradiation-induced hypofunction of the salivary glands is a process that is not fully understood. Here we examine the hypothesis that intracellular and redox-active ions of iron and copper, which are associated with the secretion granules, play a catalytic role in the irradiation-induced damage. Rats were subjected to head and neck irradiation (15 Gy X rays) and allowed to recover for 2 months. The function of the parotid and submandibular glands was then determined by pilocarpine-stimulated salivary secretion. A 45% decrease in the function of both glands was obtained when compared to nonirradiated controls. Treatment prior to irradiation (90 min) with cyclocytidine (200 mg/kg) led to a massive degranulation of the parotid gland and yielded nearly complete protection from radiation-induced damage. In contrast, pilocarpine stimulation prior to irradiation led to a marginal degranulation of the parotid gland and yielded only 13% protection. Neither agent caused degranulation of the submandibular gland mucous cells or yielded functional protection of this gland. Treatment with both agents yielded a marked increase in iron, copper and manganese levels in the parotid gland saliva. An analogous marked increase in the redox activity of iron and copper ions was recorded for the parotid saliva stimulated by pilocarpine and cyclocytidine. Pilocarpine-stimulated submandibular gland saliva contained metal levels similar to those of the parotid gland saliva. However, no redox activity and no increase in metal mobilization could be demonstrated in the submandibular gland saliva stimulated by both agents. The correlation between the patterns of gland degranulation, mobilization of redoxactive metals and the protection of gland function, for both parotid and submandibular glands, focuses attention on the catalytic roles played by transition metal ions in promoting free radical reactions, which likely participate in the process of injury to the tissue.

Exocytosis from rat submandibular granular tubules during cyclocytidine stimulation shows unusual features, including changes in the granule membrane.

Sequential secretory changes in granular tubule cells caused by the secretagogue cyclocytidine (75 mg/kg i.p.) were studied at the ultrastructural level, in perfusion (n = 5 animals) and immersion (n = 8 animals) fixed rat submandibular glands, using the periodic acid-thiocarbohydrazide-silver proteinate technique (PA-TCH-SP). The onset of secretion varied from 45 to 75 minutes after administering the cyclocytidine. During the initial stages of overt secretion, structural changes occurred irregularly in a progressive fashion with: (1) an increase in granule membrane staining with PA-TCH-SP and a parallel alignment of the secretory granules with the adjacent apical plasma membrane, which developed a honeycomb-like appearance; (2) docking of these secretory granules to the apical plasma membrane; (3) early secretion of some secretory granules in a semiclassical exocytotic fashion (but this was rarely witnessed). During stages (1) and (2), the cytochemical characteristics of the membrane of the secretory granules, as well as of the plasma membrane, suggest a priming process is occurring. After these initial preparatory phases, further structural changes occurred in the granule membranes with a gradually progressive formation of microvesicles and granule fusions; secretion continued in an explosive manner with proteinaceous material being transferred to lumina in at least three different ways: (1) by typical exocytosis (but it was infrequent); (2) from granules fused intracellularly into aggregates (compound exocytosis); and (3) some apocrine-type of secretion through bleb formation. The formation of these intracellular aggregations was associated with the microvesicles in the granule membranes and some aggregates became very large. Secretion of their contents into lumina occurred through elongated membrane channels. The material secreted included microvesicular forms that had become interiorised in the granular aggregates, and any cytoplasm that may also have been entrapped.

[Anti-herpes simplex virus action of combined therapy with cyclocytidine and ganciclovir].

OBJECTIVE: The study was designed to investigate the combined effect of cyclocytidine (CC) and ganciclovir (GCV) on herpes simplex virus-1 (HSV-1) in cell culture. METHODS: The 50% inhibition concentrations of HSV-1 plaque formation (IC50) of CC, GCV alone and in combination were determined by the inhibitory test of plaque formation. The combined anti-HSV-1 effect of CC and GCV was evaluated by a graphic method and fractional inhibitory concentration (FIC) indexes. RESULTS: IC50 of CC and GCV was 0.19 and 0.1 micrograms/ml, respectively. The combination of CC with GCV produced significantly synergistic activity against HSV-1 in cell culture. FIC indexes were all below 0.75. The combined therapy of CC and GCV can also decrease and delay the emergence of drug-resistant variants. CONCLUSION: These results suggest that this combined therapy of CC and GCV may be a potentially effective means in the management of patients with HSV-1 ocular infection.

In vitro antileukemic activity and chemical transformation of the 5'-chloro-5'-deoxy derivative of cyclocytidine.

Hydrochloride of 5'-chloro-5'-deoxy-cyclocytidine (Cl-cC) is an analogue of cyclocytine hydrochloride (cC), a prodrug of the compound with the strong antileukemic activity arabinosylcytosine (araC). This paper is devoted to the study of its cytotoxic activity in vitro and to the effect of acid and alkaline conditions and temperature on its stability. Cl-cC inhibits not only the growth of L1210 leukemia cells in vitro and the DNA synthesis (IC50 = 0.09 mumol/l) but, at the same time, it has a weak effect on RNA synthesis (IC50 > 250 mumol/l) and no effect on proteosynthesis. In alkaline conditions Cl-cC is transformed to 5'-chloro-araC and 2',5'-anhydro-araC but is more stable in acid solutions.

Comparative genotoxicity of 2,3'-O-cyclocytidine, beta-xylocytidine and 1-beta-D-arabinofuranosylcytosine in human tumor cell lines.

We have investigated the genotoxicity of two 3'-derivatives of cytidine, 2,3'-O-cyclocytidine (3'-cycloC) and beta-xylocytidine (xyloC), in human leukemia and solid tumor cell lines. Both derivatives were found to be cytotoxic at micromolar concentrations. For example, in the alveolar tumor cell line A549 which was included in all experiments as a reference, drug concentrations required to induce 50% inhibition of cell growth (D50 values) equalled 55 microM for 3'-cycloC and 80 microM for xyloC. Compared with the response of this reference cell line, none of the solid tumor cell lines tested--representing five different malignancies--displayed significant hypersensitivity to these drugs, while the acute lymphoblastic leukemia cell lines proved to be hypersensitive (range of D50 values, 5-13 microM). To gain insight into the modes of cytotoxic action of xyloC and 3'-cycloC, we compared the effect on DNA metabolism of these compounds with that of 1-beta-D-arabinofuranosylcytosine (araC), a potent inhibitor of semi-conservative DNA replication and long-patch excision repair. As seen with araC, the xylo compound strongly inhibited both DNA replicative synthesis and the repair of DNA damage induced by UV light and 60Co gamma-radiation. In gamma-irradiated A549 cells, the extent of repair inhibition by 1 mM xyloC was approximately 40% of that inhibited by araC, and concomitant exposure of the irradiated cultures to xyloC plus araC gave rise to a synergistic response. Since araC was employed at a concentration (0.1 mM) which produced a maximal effect on DNA repair when applied alone, the observed synergistic response implies that the mode of action of xyloC on DNA repair is different from that of araC. In contrast to that observed with xyloC, 3'-cycloC proved to be a very weak inhibitor of DNA replication and repair, strongly suggesting that the genotoxic action of the latter analog may be through a mechanism other than inhibition of DNA synthesis.

The fate of glycogen in granular tubule cells of rat submandibular glands during secretory events.

Glycogen, studied electron microscopically in granular tubule cells by means of the periodic acid-thiocarbohydrazide-silver proteinase technique, was found to be scattered abundantly throughout the cytoplasm. Parasympathetic nerve stimulation caused no detectable change in the glycogen. Degranulation of the granular tubule cells after either sympathetic nerve stimulation or cyclocytidine injection caused loss of the glycogen from the cells. Study of tubule cells undergoing secretion in the early stages after cyclocytidine injection indicated that glycogenolysis was occurring. Glycogen had reaccumulated in the cells within 24 h, before extensive reformation of the secretory granules had occurred, and remained abundant throughout the subsequent granule formation. It is concluded that glycogen provides an important source of energy during secretory degranulation of the granular tubule cells.

Effect of arabinosylcytosine derivative cyclocytidine on hepatal functions in rats and on Zajdela hepatoma.

1. The effectivity of the arabinosylcytosine (araC) derivative, cyclocytidine (cC), against Zajdela hepatoma was evaluated. It was established that the cC effect was dose-dependent. 2. Zajdela hepatoma-bearing rats, given a single dose of 500 mg of cC per kg of body weight, showed an increased life span of 48 and 39%. 3. cC significantly decreased the number of Zajdela hepatoma cells in ascitic fluid and affected the cytochrome content in hepatal mitochondria. 4. The overall cC effect on the hepatal function of normal and hepatectomized liver was marginal, thus making this araC derivative an interesting candidate for further evaluation of its effectivity against non-hematological tumors.

Asynchronous reformation of individual kallikrein-related secretory proteinases in rat submandibular glands following degranulation by cyclocytidine.

Time scales for the reformation of the secretory granules in granular tubules and their constituent proteinases were assessed after inducing a massive degranulation by intraperitoneal injection of cyclocytidine in conscious animals. The minimum working dose of cyclocytidine to produce the maximum degranulation and depletion of proteinase activity, at 3 h after injection, was 75 mg/kg. Histologically, although most granular tubule cells then appeared to be extensively degranulated, isolated individual cells showing little or no degranulation always persisted. Acinar cells also showed some depletion of secretory material. At 15 h after injecting cyclocytidine the formation of new granules had begun in the granular tubule cells, but it was not extensive or uniform in adjacent cells; however, the acinar cells already appeared to be regranulated. The pattern of granule reformation in granular tubule cells progressed gradually, so that 7-10 days after cyclocytidine-induced degranulation the cells were mostly packed with granules and showed similar appearances to those of normal resting control glands. Individual proteinases in extracts of the glands were assayed specifically using fluorogenic oligopeptide amidase substrates, with and without appropriate inhibitors. This revealed a 95% reduction in total proteinase activity 3 h after cyclocytidine (75 mg/kg). In the same extracts, acinar peroxidase was reduced by 28%. Peroxidase levels recovered to control values within 15 h after cyclocytidine but recovery of proteinases progressed more gradually and did not occur uniformly for the different constituent proteinases. Tissue kallikrein (rK1) showed the most rapid recovery and had reached levels approaching normal within 3 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of type 2 cystatin in rat submandibular glands by systemically administered agents.

An inducible type 2 cystatin has earlier been characterized in submandibular glands and kidneys of rats treated with isoproterenol, as well as in kidneys of rats with experimental renal disease. The purpose now was to determine whether giving agents that have systemic toxicity could also be associated with induction of cystatin in rat salivary glands. Female Wistar rats (200-250 g) were given isoproterenol, cyclocytidine, potassium dichromate or turpentine oil. After autopsy, the organs were sectioned, fixed in 10% formalin, and processed routinely. Paraffin sections were processed for both the peroxidase-antiperoxidase and the avidin-biotin-alkaline phosphatase immunocytochemical methods. The submandibular glands of rats given cyclocytidine had generalized, strong staining of acinar cells, as well as occasional weak staining within granular convoluted tubules. Animals given either potassium dichromate or turpentine oil exhibited moderate staining for cystatin in submandibular acini. Rats given isoproterenol as a positive control exhibited strong acinar staining throughout the submandibular gland, while the glands of untreated rats were unreactive. Inducible type 2 cystatin could not be detected in the parotid or sublingual glands, or in trachea, lung, stomach, small intestine, large intestine, spleen, liver and pancreas, after treatment with any of the systemic agents evaluated. The results indicate that elaboration of type 2 cystatin can be induced by a variety of systemically administered agents other than isoproterenol, and suggest that elaboration of type 2 cystatin may represent a more generalized response to tissue injury.

Ultrastructural changes in salivary glands after different adrenergic and cholinergic stimulations. A long-term morphological study in the rat.

We have compared four different sialogogues and their degranulating effect on serous and mucous cells, and their long-term effects. From this and earlier experiments, even within the groups of alpha- and beta-adrenergic agents used, the effects varied on the serous and mucous cells. Previous studies have shown that cyclocytidine effectively degranulates serous cells without signs of cellular damage, while carbachol predominantly affects mucous acinar cells but gives early rise to permanent gland damage. Noradrenaline affects both serous and mucous cells, predominantly affecting serous cells with initial mitochondrial damage. Clonidine partially depletes both serous and mucous cells of their granules, producing permanent cellular damage. One month after a single injection of cyclocytidine the early findings described had disappeared. Carbachol showed permanent damage to salivary gland parenchyma, and both noradrenaline and clonidine demonstrated a long-term effect on acinar mucinous cells.

Effects of nerve growth factor on cyclocytidine-induced growth responses of sympathectomized parotid or parotid of partially desalivated rat.

Cyclocytidine (CC), a potent antitumor agent, caused a 2.4- to 3.9-fold increase in [3H]thymidine uptake of rat parotid gland after 3 days of daily administration of the CC in a dose of 500 mg/kg body weight. Gland weight also was increased. Ablation of the submandibular-sublingual glands prior to initiation of the CC regimen prevented the usual CC-induced increase in [3H]thymidine uptake but this inhibition was partially reversed when nerve growth factor (NGF) was administered with the CC; values for [3H]thymidine uptake into parotid DNA were 81, 54, and 73% of those of glands of intact CC-treated rats. Submandibular gland ablation did not prevent the usual CC-induced increase in parotid size, and administration of NGF had no effect. Sympathectomy of the salivary glands also inhibited the thymidine increase in parotid gland usually induced by CC but in addition it also inhibited the usual CC-induced increase in gland weight. NGF, however, failed to reverse the effects of sympathectomy on [3H]thymidine uptake or gland size: both remained at the same level observed in sympathectomized parotid not given NGF.

Studies on the regranulation of salivary gland serous cells. An electron microscopical study in the rat.

The degranulation and regranulation process was investigated after alpha-adrenergic stimulation on the rat submandibular gland. The submandibular gland in rat contains both serous and mucous cells. It has earlier been shown that serous cells filled with heavy-metal granules, are markedly more radiosensitive than cells without granules. In experiments with emptying the serous cell of their content of granules by administering an alpha-adrenergic stimulant, cyclocytidine, there has been found a decrease in irradiation damage in salivary gland tissue after irradiation. Injection of cyclocytidine, 150 mg/kg, was given i.p. to the rat. After 1 h there was almost complete depletion of granules in the serous cells, no morphological aberration was seen in the mucous cells. This effect still remained after 6 h. A beginning of regranulation with apical granules was seen 12 h after injection. After 24 h an almost complete regranulation had occurred in the salivary gland serous cells. The mucous cells did not show any morphological aberration. Our intent is to reduce unwanted salivary gland damage in patients with head and neck cancer when treated with radiotherapy. Depletion of heavy-metal granules in serous cells, before irradiation may diminish morphological destruction in the salivary glands. As a nearly total degranulation is present between 1-6 h after stimulation, this should be the optimal time for radiotherapy.