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).

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.

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.

Synergistic effects of the combination of cis-platinum diamminodichloride and 2,2'-anhydro-1-beta-D-arabinofuranosyl-5-fluorocytosine in transplanted mouse leukemias.

cis-Platinum diamminodichloride has been studied in combination with 2,2'-anhydro-1-beta-D-arabinofuranosyl-5-fluorocytosine on an every-4-day schedule in various lines of mouse leukemia. This combination is synergistic in leukemias L1210 and P388 and sublines made resistant to 5-fluorouracil or methotrexate. There is no cross-resistance between cis-platinum diamminodichloride and 2,2'-anhydro-1-beta-D-arabinofuranosyl-5-fluorocytosine, but the combination is no more effective against lines of leukemia made resistant to cis-platinum diamminodichloride or to 2,2'-anhydro-1-beta-D-arabinofuranosyl-5-fluorocytosine than either single active compound alone. Since these compounds have no cross-resistance, act by quite different mechanisms of action, and have different limiting toxicity, the combination is now being evaluated clinically.

The enzymatic hydrolysis of the phosphate ester bond in some thionucleotides.

We prepared the 5'- and 3'-O-phosphorothioate esters of the antitumor agent O2 : 2'-anhydro-1-beta-D-arabinosylcytosine. We also included in this study esters of 2'-thio-2'-deoxycytidine, namely, 2'-S-dCyd-2' : 3'-P, 2'-S-dCyd-2'-P, and 2'-S-dCyd-3'-P, along with natural nucleotides. These compounds were subjected to the action of Escherichia coli alkaline phosphatase, potato acid phosphatase, and bovine pancreatic ribonuclease A. The data were analyzed by Lineweaver-Burk plots to obtain Km and KI values. Only 2'-S-dCyd-2'-P was a substrate for alkaline phosphatase; the anhydro-araCyt phosphorothioates were good competitive inhibitors, while 2'-S-dCyd-3'-P did not associate with the enzyme. Acid phosphatase hydrolyzed all four monoesters investigated, including the S-phosphorothioate. The cyclic phosphorothioate, 2'-S-dCyd-2' : 3'-P was neither hydrolyzed by, nor associated with, ribonuclease A. ORD spectroscopy was also used in an attempt to relate the structural features of analogs to the peculiarity of their hydrolysis.

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.

1-(2,3-Anhydro-beta-D-lyxofuranosyl)cytosine derivatives as potential inhibitors of the human immunodeficiency virus.

We report here that 1-(2,3-anhydro-beta-D-lyxofuranosyl)cytosine has activity against the human immunodeficiency virus in vitro. A number of 2',3'-anhydro-beta-D-lyxofuranosyl nucleoside derivatives were prepared, but none had the activity of the title compound. New efficient procedures were developed for the synthesis of 3'-deoxy-3'-alkyl- and 3'-deoxy-beta-D-arabinosylpyrimidine derivatives.

Fluorinated Pyrimidine nucleosides. 1. Synthesis of a nitrogen analogue of the antitumor agent 2,2'-anhydro-1-beta-D-arabinofuranosyl-5-fluorocytosine hydrochloride.

The nitrogen-bridged compound 2,2'-anhydro-1-beta-D-arabinofuranosyl-2,4-diamino-5-fluoropyrimidinium chloride (2), an analogue of the antitumor agent anhydro-ara-FC (1), has been synthesized. 5-Fluorocytidine was converted into 1-beta-D-ribofuranosyl-2,4-diamino-5-fluoropyrimidinium chloride (4), but cyclization of 4 was not achieved due to a competing side reaction. The nitrogen bridge was therefore introduced by cyclization of 5-fluoroisocytidine (10) to give the 2,2'-imino-bridged compound 16. The latter was converted into 2 by the standard procedure of thiation, S-methylation, and treatment with ammonia. Compound 2, as well as a number of the synthetic intermediates, was tested for activity against S180 sarcoma in mice. None of the new compounds exhibited any antitumor activity.

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.

Physiologically based pharmacokinetic models for anticancer drugs.

The rationale and history of the development of physiologically based pharmacokinetic models are briefly reviewed in this paper. The methods of model construction and the previous application of this type of model to anticancer drugs are discussed. Future research should be focused on the following areas: (1) interspecies scaling, (2) the effects of disease states on the pharmacokinetics of anticancer drugs, and (3) the applications of pharmocokinetics to the studies of growth behavior of cancer cells. The ultimate goal will be to utilize this basic information to design an optimal dosage regimen and treatment schedule for the safe and effective cancer chemotherapy of each individual patient.

Cyclocytidine-induced release of nerve growth factor from mouse submandibular glands enhances regeneration of sympathetic fibers in adult mice.

The injection of a drug endowed with the property of stimulating alpha-adrenergic receptors, cyclocytidine (Cyclo-C), produces drastic depletion of NGF from the granular convoluted tubules (GCT) of the mouse submaxillary salivary gland and a marked NGF level increase in the bloodstream. The NGF discharged from the gland gains access to the blood. Histological studies, immunohistochemistry, in vitro biological assays and radioimmunoassays gave evidence for the growth response elicited by the endogenously released salivary NGF in intact and surgically axotomized sympathetic ganglia. These results suggest that the mouse salivary NGF displays a biological activity on its target sympathetic nerve cells.

Mathematical model for cyclocytidine pharmacokinetics.

The pharmacokinetics of the drug cyclocytidine in humans were modeled by using a physiological and anatomical approach. Each pertinent tissue is represented by a single compartment, and these compartments are linked together by the circulatory system. Each compartment is then represented by an ordinary differential equation that represents the rate of change in drug concentration as function of convecting transport, metabolism, and urinary clearance. The models for cyclocytidine and cytarabine are linked together by a hydrolysis term in each equation set. The resulting equation sets are then solved numerically to predict the concentration of both drug species in situ. The models use physiological blood flows, tissue volumes, and clearance parameters. The results of the model show that cyclocytidine can act as a reservoir for cytarabine in vivo over the time studied. This effect is confined to relatively long times and relatively low plasma concentrations.

Pharmacokinetic prodrug modeling: in vitro and in vivo kinetics and mechanisms of ancitabine bioconversion to cytarabine.

Conversion rates of the prodrug ancitabine to the antileukemic cytarabine have been measured in vivo (rabbits) and in vitro (in the presence of rabbit blood and human red blood cells, blood, and plasma) using HPLC analyses for the prodrug, drug, and its inactive metabolite, 1-beta-D-arabinosyluracil. These observed pH-dependent in vitro rate constants were consistent with those for chemical hydrolysis determined from controls using Tris buffers. Hydrolysis of ancitabine to cytarabine is chemically, not enzymatically, mediated. The blood concentration-time course for administered compound was described by a two-compartment open model following a rapid intravenous injection of prodrug, drug, or metabolite in each of three rabbits. The in vivo conversion rate constant (kc) following a rapid intravenous prodrug injection was estimated by simultaneous nonlinear regression of ancitabine and cytarabine blood concentration-time courses using equations for two-compartment prodrug and drug with all possible models describing potential conversion sites. The best fit was obtained for the case allowing simultaneous conversion of the prodrug in both central and peripheral compartments to the drug in the central compartment with a common value for kc. The resulting kc value (0.09 h-1, three rabbits) is similar to that for chemical hydrolysis (0.07 h-1) at 38.8 degrees C. Reasons why this agreement is regarded as fortuitous are discussed.

Drug stability in liposomal suspensions: hydrolysis of indomethacin, cyclocytidine, and p-nitrophenyl acetate.

First-order rate constants (kL) for hydrolysis of p-nitrophenyl acetate, cationic cyclocytidine, and anionic indomethacin in the presence of buffered liposomal suspensions of positive, negative, and neutral charge were compared to those determined in the corresponding buffers (kB) using the ratio, Rk = kL/kB. Association between the reactants and the liposomes was evaluated by comparing assays for concentration in the filtrates (CF) with the total concentration in the liposomal suspension (CT) using RC = CF/CT. Liposomes did not influence cyclocytidine hydrolysis rates and no association was observed (Rk congruent to RC congruent to 1). In contrast, indomethacin showed approximately 80% reduction in hydrolysis rate and approximately 80% liposome association value (Rk congruent to 0.2 congruent to RC). In neutral and negatively charged liposomal suspensions, p-nitrophenyl acetate displayed approximately 30% decrease in kB (Rk congruent to 0.7) together with approximately 90% liposomal association (RC congruent to 0.1). However, hydrolysis was greatly accelerated in positively charged liposomal suspensions. Loss was described by a biexponential equation where alpha is the fast and beta is the slow pre-exponential coefficient and alpha/beta/kB = 39:6:1. The observed relationships between hydrolysis rates and reactant-liposome associations are reconciled in terms of the hydrophilicity of the reactants and the potential influence of the liposomes on the expected transition states for the hydrolysis reactions.

Aqueous conversion kinetics and mechanisms of ancitabine, a prodrug of the antileukemic agent cytarabine.

The kinetics of conversion of the prodrug ancitabine to the anticancer drug cytarabine have been studied in aqueous solutions in the pH range of 1.5-10.7, temperature range of 19.5-80.0 degrees C, ionic strength range of 10(-4) to 1.5, and in the presence of several general-base catalysts. Under all conditions ancitabine was quantitatively converted to cytarabine. The pH-rate profiles were linear with slope = 1 in alkaline pH, becoming pH independent in the region of maximum stability at pH less than or equal to 4, where buffer catalysis was found to be insignificant and kobs approximately equal to (1.12 X 10(11) h-1)-exp [-10121 deg/T]. At 30 degrees C, pH less than or equal to 4, it is calculated that an aqueous ancitabine solution will maintain 90% of its initial concentration for 12 d. A novel method for measuring general-base catalysis in competition with predominating specific-base catalysis and in the presence of secondary salt effects at constant ionic strength was developed. Three mechanisms of hydrolytic prodrug conversion are proposed: nucleophilic hydroxide addition, general base-assisted nucleophilic water attack, and spontaneous water attack.

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.

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.

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.

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)