Immunohistolocalization and Gene Expression of the Secretory Carbonic Anhydrase Isozymes (CA-VI) in Canine Oral Mucosa, Salivary Glands and Oesophagus

The immunohistolocalization of secretory carbonic anhydrase isoenzymes (CA-VI) in canine salivary glands, parotid, submandibular, sublingual and zygomatic glands, oral and oesophageal mucosa was studied using a specific antiserum against a canine CA-VI. In addition, the gene expression of CA-VI from the same tissue was studied using a real-time reverse-transcriptase polymerase chain reaction. In all salivary glands and oesophageal gland, immunostaining intensely localized CA-VI antiserum throughout the cytoplasm of serous acinar cells, including serous demilune and ductal epithelial cells. In contrast, no immunoreaction localized CA-VI in the mucous acinar cells of the gland. CA-VI gene transcripts were also detected in the same areas. The physiological significance of secretory CA-VI in the oral and oesophageal cavity is thought to play a highly specialized role in the maintenance of bicarbonate level in saliva and to protect mucosa from acid injury. It is shown that the major sites of the CA-VI secretion in dogs were in serous (demilune) secretory cells in all four major salivary glands and oesophageal glands in particular.

cAMP phosphodiesterase activity evaluation in human carcinoma of salivary glands

The aim of this study was to evaluate differences of cAMP-PDE activity in human salivary glands, between a control group and some different benign tumours groups and, where present, with 2 malignant tumors groups. The value of the enzymatic activity in the groups analysed was 50% lower than control samples. The differences between the control group (82 +/- 7.9 nmols/mg of protein) and the 3 pathologic groups (Benign A: 44 +/- 6.2; Malignant A: 40 +/- 16; Benign B: 40 +/- 14.2; Malign A: 9.1; Benign C: 22 nmols/mg of protein) are statistically significant.

Molecular characterization and comparative study of 6 salivary gland metalloproteases from the hard tick, Haemaphysalis longicornis

Six genes encoding metalloproteases were identified from the salivary gland of the hard tick, Haemaphysalis longicornis. Comparative analyses have shown the evolutionary distinct and different mRNA expression patterns of each gene during blood feeding. The proteins are synthesized as proenzymes with a prodomain and a metalloprotease/cysteine-rich domain of the reprolysin family. Within the active site, amino acid substitutions were observed. The recombinant Escherichia coli expression of one gene, hlESTMP1, was performed. The immunoblot analysis and indirect fluorescent assay using anti-hlESTMP1 suggested that this protein is mainly expressed in the cytoplasm of the salivary glands and only the mature form of 34 kDa was detectable. The proenzyme expressed by baculovirus was processed into a mature domain, suggesting that proenzyme activation possibly occurs through a pro-protein convertase dependent pathway. The presence of these diverse enzymes might contribute to the greater functional complexity of bioactive molecules in tick saliva to facilitate blood feeding.

Rhipicephalus (Boophilus) microplus (Canestrini, 1887) (Acari: Ixodidae): Acid phosphatase and ATPase activities localization in salivary glands of females during the feeding period

This study investigates the presence and the localization of acid phosphatase and ATPase in the salivary glands of Rhipicephalus (Boophilus) microplus female ticks during feeding. Semi-engorged females showed a larger amount of acid phosphatase compared to those at beginning of feeding, localized mainly in the apical portion of the secretory cells, and in the basal labyrinth of the interstitial cells. Ultrastructural observations also demonstrated its presence in secretion granules and inside some nuclei of secretory cells at beginning of feeding. Acid phosphatase in a free form probably has a hemolymph and/or ribosomal origin and participates in salivary gland secretion control. ATPase was detected in basal membrane of all types of acini and/or in the cytoplasm of the secretory cells at both feeding stages. The enzyme activities found strongly suggests that cell death by apoptosis occurs during the degenerative process.

A novel secreted endonuclease from Culex quinquefasciatus salivary glands

Previous analysis of the salivary gland transcriptome of Culex quinquefasciatus showed the potential presence of an endonuclease with sequence similarities to shrimp, crab and two tsetse salivary proteins. Indeed, not only was the cloned cDNA shown to encode an active double-stranded endonuclease, but also the same activity was demonstrated to be secreted by salivary glands of Cx. quinquefasciatus. Preliminary studies with salivary gland extracts confirmed the presence of a highly active nuclease. This enzyme was shown to be present in the saliva of female mosquitoes by allowing starved mosquitoes to probe DNA-containing agarose gel. The recombinant Cx. quinquefasciatus endonuclease (CuquEndo) produced in mammalian cells showed no sequence specificity for DNA substrate except that it only cleaves double-stranded DNA. Recombinant Cx. quinquefasciatus endonuclease was active in the presence of Mg(2+) ions at pH 7.0-8.0, but no endonuclease activity was detected in the presence of calcium ions. The final hydrolysis products of this enzyme, detected by ion exchange chromatography, yielded DNA fragments ranging form 8-12 base pairs. Although endonucleases have been associated with a variety of cellular functions, their role in mosquito saliva is not clear. This female-specific secreted endonuclease may assist blood meal intake by lowering the local viscosity created by the release of host DNA in the bite site and/or acting as an indirect anticoagulant factor by producing a defibrotide-like mixture of DNA haptamers.

The salivary gland and salivary enzymes of the giant waterbugs (Heteroptera; Belostomatidae)

The giant waterbugs are predators that utilize extra-oral digestion and are known to capture a wide variety of prey. Herein we describe the differences in salivary enzyme composition between large and small species of giant waterbug (Lethocerus uhleri, Lethocerinae and Belostoma lutarium, Belostomatinae, respectively). The saliva of L. uhleri contains 3 proteolytic enzymes and no amylase, while the salivary gland of B. lutarium produces 2 proteolytic enzymes and amylase. This fundamental difference in salivary enzyme composition correlates with the difference in diet preference between the Lethocerinae and Belostomatinae. Furthermore, we describe the ultrastructure of the salivary gland complex of B. lutarium and present data on the division of labor with respect to compartmentalization of enzyme production. Proteolytic enzymes are produced in the accessory salivary gland and amylase is produced in the main salivary gland lobe. This is the first reported evidence of protease production in the accessory salivary gland in the Heteroptera.

Evidence by signal peptide trap technology for the expression of carbonic anhydrase 6 in rat incisor enamel organs

During screening of a rat incisor enamel organ cDNA library by signal peptide trap technology, we identified a DNA fragment matching a predicted translation sequence for rat carbonic anhydrase 6 (CA6). This result was unexpected because CA6, to date, has been associated primarily with secretions from glandular tissues. To further characterize this observation, reverse transcription-polymerase chain reaction (RT-PCR) amplifications were carried out on total RNA extracted from freeze-dried secretory and maturation-stage rat incisor enamel organs. A cDNA fragment of the expected size was detected in control samples from rat salivary glands as well as within maturation-stage enamel organ samples. This CA6 RT-PCR fragment was further cloned and sequenced and found to match the nucleotide sequence 770-1079 from clone XM_216584 of GenBank. Northern blot analyses with the rat CA6 cDNA fragment confirmed its expression relative to maturation-stage enamel organ samples. It is at present unclear whether the CA6 expressed by enamel organ cells is secreted into the enamel layer or into the intercellular spaces of the enamel organ itself to assist in neutralizing excess protons arising from the growth of apatite crystals during the maturation stage of amelogenesis.

Establishment and characterization of amylase-producing lung adenocarcinoma cell line, IMEC-2

BACKGROUND

Few studies have successfully established an amylase-producing lung cancer cell line or have examined its cytological, biochemical and biological features.

PATIENTS AND METHODS

Cancer cells, isolated from pleural effusion using a gradient method, were cultivated.

RESULTS

Amylase production from the newly established cell line was confirmed by positive staining for alpha-amylase and increased amylase levels in the culture supernatant. Electron microscopy revealed zymogen granule-like structures. Sialylation of salivary-type amylase was confirmed directly from the cell line by examining the neuraminidase sensitivity and amylase elution profile under high-performance liquid chromatography. Neither EGFR or KRAS mutation were found.

CONCLUSION

This cell line offers a useful tool for analyzing the pathogenesis and pathophysiology of amylase-producing lung cancers. Moreover, it might be useful for probing the metastasis and invasiveness of lung cancer cells and for developing an early diagnostic method based on sialylated salivary-amylase production.

Characterization of digestive proteolytic activity in Lygus hesperus Knight (Hemiptera: Miridae)

The tarnished plant bug, Lygus hesperus Knight, is a pest that causes considerable economic losses to vegetables, cotton, canola, and alfalfa. Detailed knowledge of its digestive physiology will provide new opportunities for a sustainable pest management approach to control this insect. Little is known about the different protease class contributions to the overall digestion of a specific protein. To this end, the proteolytic activities in female adult L. hesperus salivary gland and midgut homogenates were quantified over a range of pH's and time points, and the contribution of different classes of proteases to the degradation of FITC-casein was determined. In the salivary gland, serine proteases were the predominant class responsible for caseinolytic activity, with the rate of activity increasing with increasing pH. In contrast, both aspartic and serine proteases contributed to caseinolytic activity in the midgut. Aspartic protease activity predominated at pH 5.0 and occurred immediately after incubation, whereas serine protease activity predominated at pH 7.5 after a 9h delay and was resistant to aprotinin. The salivary serine proteases were distinctly different from midgut serine proteases, based on the tissue-specific differential susceptibility to aprotinin and differing pH optima. Collectively, the caseinolytic activities complement one another, expanding the location and pH range over which digestion can occur.

Dual oxidases

Reactive oxygen species (ROS) have an important role in various physiological processes including host defence, mitogenesis, hormone biosynthesis, apoptosis and fertilization. Currently, the most characterized ROS-producing system operates in phagocytic cells, where ROS generated during phagocytosis act in host defence. Recently, several novel homologues of the phagocytic oxidase have been discovered and this protein family is now designated as the NOX/DUOX family of NADPH oxidases. NOX/DUOX enzymes function in a variety of tissues, including colon, kidney, thyroid gland, testis, salivary glands, airways and lymphoid organs. Importantly, members of the enzyme family are also found in non-mammalian species, including Caenorhabditis elegans and sea urchin. The physiological functions of novel NADPH oxidase enzymes are currently largely unknown. This review focuses on our current knowledge about dual oxidases.

Morphology and preliminary enzyme characterization of the salivary glands from the predatory bug Podisus nigrispinus (Heteroptera: Pentatomidae)

Podisus nigrispinus (Dallas) is a common predator in agricultural and natural systems in Neotropical America. Its feeding strategy involves extra-oral digestion and to better understand this process its salivary glands were extracted and subjected to morphological and preliminary enzyme characterization. The salivary glands of P. nigrispinus are formed by a pair of main and accessory gland complexes. The main salivary glands are further divided into an anterior and a posterior lobe. The compartmentalization of the salivary gland complex is likely to be important for the production, activation and release of the digestive enzymes used in the extra-oral digestion of prey items. Proteases and lipase, important digestive enzymes involved in zoophagy, were detected in the salivary glands of P. nigrispinus. The prevailing trypsin-like protease activity was characterized by using the serine-protease substrate N-alpha-benzoyl-L-Arg-p-nitroanilidine (L-BApNA) and the trypsin inhibitors tosyl-L-lysine chloromethyl ketone (TLCK) and benzamidine. The KM value obtained for trypsin-like activity was 1.57 mm and the different peaks of optimum pH and temperature activity suggest the presence of multiple forms of this enzyme in P. nigrispinus. Detection of amylase activity in the salivary glands of this predator suggests its ability to digest starch and obtain nutrients from plants, which may have adaptative value under prey scarcity.

Influence of different restorative materials on lysozyme and amylase activity of the salivary pellicle in situ

Lysozyme and amylase are the most abundant enzymatic components in the salivary pellicle. The purpose of the present study was to determine the influence of different substrata on amylase and lysozyme activity in salivary pellicles formed in situ. Slabs (5 mm diameter) of bovine dentine and enamel, of titanium, gold alloy, resin composite, PMMA, amalgam, and feldspar ceramic were fixed on the buccal sites of individual splints worn by six subjects for 30 min to allow pellicle formation. Thereafter, slabs were removed from the trays and rinsed with running water. Lysozyme activity was determined via lysis of Micrococcus lysodeicticus. Amylase activity was measured with a photometric method using 2-chloro-4-nitrophenyl-4-O-beta-D-galactopyranosylmaltotriosid (GalG2CNP) as substrate. Both pellicle enzymes were evaluated in the immobilized as well as in the desorbed state. Salivary enzyme activities were also measured. All investigated pellicles exhibited lysozyme and amylase activity. Great intraindividual and interindividual differences were observed. Over all samples, immobilized amylase activity amounted to 0.65 +/- 0.64 mU/cm2. Immobilized lysozyme activity was 5.04 +/- 1.55 U/cm2. There were no major effects of the substratum on pellicle-bound amylase and lysozyme activity. Immobilized and desorbed enzyme activities revealed a strong correlation (lysozyme: r = 0.700; amylase: r = 0.990). Salivary enzyme activities had only little impact on pellicle-bound enzyme activities. Amylase and lysozyme are incorporated in the acquired in situ pellicle on different solid surfaces in an active conformation. Dental material and enzyme activity in the saliva have only little impact on enzymatic activity in the pellicle in situ.

Ablation of caterpillar labial salivary glands: technique for determining the role of saliva in insect-plant interactions

There has been an ardent interest in herbivore saliva due to its roles in inducing plant defenses and its impact on herbivore fitness. Two techniques are described that inhibit the secretion of labial saliva from the caterpillar, Helicoverpa zea, during feeding. The methods rely on cauterizing the caterpillar's spinneret, the principal secretory structure of the labial glands, or surgically removing the labial salivary gland. Both methods successfully inhibit secretion of saliva and the principal salivary enzyme glucose oxidase. Caterpillars with inhibited saliva production feed at similar rates as the untreated caterpillars, pupate, and emerge as adults. Glucose oxidase has been suggested to increase the caterpillar's survival through the suppression of inducible anti-herbivore defenses in plants. Tobacco (Nicotiana tabacum) leaves fed on by caterpillars with ablated salivary glands had significantly higher levels of nicotine, an inducible anti-herbivore defense compound of tobacco, than leaves fed upon by caterpillars with intact labial salivary glands. Tomato (Lycopersicon esculentum) leaves fed upon by caterpillars with suppressed salivary secretions showed greatly reduced evidence of hydrogen peroxide formation compared to leaves fed upon by intact caterpillars. These two methods are useful techniques for determining the role that saliva plays in manipulating plant anti-herbivore defenses.

Activity, distribution and regulation of phosphofructokinase in salivary gland of rats with streptozotocin-induced diabetes

Although the influence of diabetes on salivary glands is well studied, it still presents conflicting results. In this work, the regulation of the phosphofructokinase-1 enzyme (PFK-1) was studied utilizing the salivary glands of rats. Diabetes was induced by a single intraperitoneal injection of streptozotocin (60 mg/Kg of body weight) in rats (180-200 g). The animals were killed 30 days after the induction of diabetes and the submandibular and parotid salivary glands were used. Hyperglycemia was evaluated by blood sugar determination. The distribution of PFK-1 between the soluble and cytoskeleton fractions, the phosphate content of PFK-1, the content of fructose-2,6-bisphosphate and the activity of the PFK-2 enzyme were determined. The calculated relative glandular weight showed a higher value for the parotid gland in comparison with the control, but not for the submandibular gland. The activity of PFK-1 expressed per gland showed no variation between diabetic and control animals. However, considering the specific activity, the soluble enzyme presented a value 50% higher than that of the control and the cytoskeleton bound form increased by 84% compared to the control. For the parotid gland, no difference in the specific activity between diabetic and control animals was observed. On the other hand, the activity per gland of the soluble enzyme increased in the diabetic animals. The phosphate content of PFK-1 increased in the submandibular and parotid glands of diabetic rats. Both the content of fructose-2,6-bisphosphate and the active form of PFK-2 were reduced in the diabetic glands. In conclusion, the increase in the activity of PFK-1 observed in the salivary glands of rats with streptozotocin-induced diabetes does not seem to be due to its modulator fructose-2,6-bisphosphate.

Flat-chip microanalytical enzyme sensor for salivary amylase activity

It is considered that measurement of salivary alpha-amylase activity is a useful tool for evaluating the sympathetic nervous system. The purpose of this research is to demonstrate a new design of a flat-chip microanalytical enzyme sensor (flat-chip sensor) for salivary amylase activity as a Micro-Electro-Mechanical Systems (MEMS), which may be used for wearable analytical systems. To meet this purpose, the biosensor needs to be miniaturized and to possess high-sensitivity. A pre-column and a flat-enzyme electrode were incorporated in a flow cell of volume 25.7 ml. In order to miniaturize the flow cell, two enzymatic membranes containing maltose phosphorylase obtained from Enterococcus hirae (MP membrane) and glucose oxidase and peroxidase (GOD-POD membrane) were immobilised on the same planar surface. As a result, a flat-chip sensor incorporating a flow cell as small as a C battery was produced. The optimum conditions of three parameters of the fabricated flat-chip sensor, the immobilising method of the enzymatic membrane, dropping volume of the mixed enzymatic solution and flow rate of the sample solution, were examined. An analytical system for 0-190 kU/l amylase activity with R(2) of 0.97 was fabricated with a sample volume of 50 microl. This research indicates the possibility of a wearable biosensor for continuous monitoring of salivary amylase activity.

FOXO-independent suppression of programmed cell death by the PI3K/Akt signaling pathway in Drosophila

Signaling through the PI3K/Akt/FOXO pathway plays an important role in vertebrates in protecting cells from programmed cell death. PI3K and Akt have been similarly shown to be involved in survival signaling in the invertebrate model organism Drosophila. However, it is not known whether PI3K and Akt execute this function by controlling a pro-apoptotic activity of Drosophila FOXO. In this study, we show that elevated signaling through PI3K and Akt can prevent developmentally controlled death in the salivary glands of the fruit fly. We further show that Drosophila FOXO is not required for normal salivary gland death and that the rescue of salivary gland death by PI3K occurs independent of FOXO. These results give support to the notion that FOXOs have acquired pro-apoptotic functions after separation of the vertebrate and invertebrate lineages.

Effect of gamma-secretase inhibitors on muscarinic receptor-mediated calcium signaling in human salivary epithelial cells

Altered intracellular Ca(2+) signaling has been observed in cells derived from Alzheimer's disease patients, and a possible link between gamma-secretase activity and the content of intracellular Ca(2+) stores has been suggested. To test this hypothesis we studied the effects of several gamma-secretase inhibitors on muscarinic receptor-mediated intracellular calcium release in the human salivary gland cell line HSG. Although several inhibitors in the peptide aldehyde class partially blocked carbachol-induced Ca(2+) transients, these effects did not appear to be due to gamma-secretase inhibition, and overall we found no evidence that inhibition of gamma-secretase activity had any significant effect on agonist-induced intracellular calcium release in HSG cells. In complementary experiments with presenilin-null cells we found that the reconstitution of gamma-secretase activity by transfection with wild-type presenilin 1 likewise had no significant effect on thapsigargin-induced Ca(2+) release. In a test of the specific hypothesis that the level of APP intracellular domain (AICD), the intracellular fragment of the beta-amyloid precursor protein (APP) resulting from gamma-secretase cleavage, can modulate the Ca(2+) content of the endoplasmic reticulum, we were unable to demonstrate any effect of APP small interfering RNA on the magnitude of carbachol-induced intracellular calcium release in HSG cells. Together our data cast considerable doubt on the hypothesis that there is a direct link between gamma-secretase activity and the content of intracellular Ca(2+) stores.

Characterization of a serine carboxypeptidase in the salivary glands and fat body of the orange wheat blossom midge, Sitodiplosis mosellana (Diptera: Cecidomyiidae)

A full-length cDNA encoding a serine carboxypeptidase (designated SmSCP-1) was recovered from an ongoing salivary gland EST project of the wheat midge. The deduced 461-amino acid sequence had a putative signal sequence at the amino terminus, indicating it was a secreted protein. The protein shared homology with serine carboxypeptidases from other insects, mammals, plants, and yeasts. SmSCP-1 mRNA was expressed in all stages of development and detected in salivary gland and fat body tissues but not in midgut tissue. Expression analysis and quantitative real-time PCR assays in male and female wheat midges and the fat body tissue of adult midges revealed that SmSCP-1 was up-regulated nearly four-fold in the female midges compared to males and nearly two-fold in female fat body compared to male fat body. The wheat midge serine carboxypeptidase (SmSCP-1) most likely has a dual function. As a secreted digestive enzyme, it could play a role in mobilizing host-plant seed reserves for feeding larvae and as expressed in fat body could function as an exopeptidase in degradation of vitellogenin and/or in post-translational processing of other enzymes.

Immunohistochemistry of the Bovine Secretory Carbonic Anhydrase Isozyme (CA-VI) in Bovine Alimentary Canal and Major Salivary Glands

In the present study, we firstly demonstrated immunohistochemical expressions of secretory carbonic anhydrase (CA-VI) isozyme in bovine forestomach, large intestine and major salivary glands. CA-VI was detected in basal layer epithelial cells of esophageal and forestomach stratified epithelium, in mucous cells of upper glandular region of large intestine, in serous acinar cells of the parotid gland, in serous demilune cells and some ductal liner cells of mandibular, monostomatic sublingual and esophageal glands. These immunohistolocalizations suggested that bovine CA-VI plays various roles in pH regulation, maintenance of ion and fluid balance, and cell proliferation.

Origin, structure, and biological activities of peroxidases in human saliva

Human whole saliva contains two peroxidases, salivary peroxidase (hSPO) and myeloperoxidase (hMPO), which are part of the innate host defence in oral cavity. Both hSPO as well as human milk lactoperoxidase (hLPO) are coded by the same gene, but to what extent the different producing glands, salivary and mammary glands, affect the final conformation of the enzymes is not known. In human saliva the major function of hSPO and hMPO is to catalyze the oxidation of thiocyanate (SCN(-)) in the presence of hydrogen peroxide (H(2)O(2)) resulting in end products of wide antimicrobial potential. In addition cytotoxic H(2)O(2) is degraded. Similar peroxidation reactions inactivate some mutagenic and carcinogenic compounds, which suggests another protective mechanism of peroxidases in human saliva. Although being target of an active antimicrobial research, the structure-function relationships of hSPO are poorly known. However, recently published method for recombinant hSPO production offers new tools for those investigations.

Nitric oxide synthase in human salivary glands

The distribution of the three nitric oxide synthase (NOS) isoforms was determined immunohistochemically in the human minor and major salivary glands with comparison to that of rat salivary glands. In contrast to rat glands, which contained a dense plexus of neuronal NOS-immunoreactive nerve fibers, only a minority of the nerve fibers in human glands showed neuronal NOS immunoreactivity. Human labial and submandibular glands contained sparse NOS-immunoreactive fibers, while only occasional nerve fibers in the parotid or sublingual glands were stained. Furthermore, in contrast to the animal glands, most duct epithelial cells in all human salivary glands were immunoreactive for neuronal NOS. No specific immunoreactivity for inducible or endothelial NOS were observed in the nerve fibers or duct epithelium. We provide evidence to suggest that the role of nitric oxide in the regulation of salivary gland function is different in human as compared to experimental animals. Nitricergic innervation in human tissue is very sparse and thus nitric oxide is probably of minor importance as a neural regulator of salivary glands. Instead, NOS localized in duct epithelial cells suggests that nitric oxide might directly regulate saliva secretion and it is a putative source of nitrates previously reportedly secreted into the saliva.

Laccase-type phenoloxidase in salivary glands and watery saliva of the green rice leafhopper, Nephotettix cincticeps

The activity and composition of leafhopper saliva are important in interactions with the host rice plant, and it may play a physiological role in detoxifying toxic plant substances or ingesting sap. We have characterized diphenoloxidase in the salivary glands of Nephotettix cincticeps, its activity as a laccase, and its presence in the watery saliva with the objective of understanding its function in feeding on rice plants. Nonreducing SDS-PAGE of salivary gland homogenates with staining by the typical laccase substrate 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), hydroquinone or syringaldazine revealed a band at a molecular mass of approximately 85 kDa at pH 5. A band also appeared at a molecular mass of approximately 200 kDa when the gels were treated with dopamine, L-3,4-dihydroxyphenylalanine (DOPA) or catechol at pH 7. The ABTS-oxidizing activity of the homogenates was drastically inhibited by N-hydroxyglycine, a specific inhibitor of laccase. However, the dopamine-oxidizing activity was not inhibited by N-hydroxyglycine, while it was inhibited by phenylthiourea (PTU). Thus, the salivary glands of N. cincticeps contain two types of phenoloxidases: a laccase (85 kDa) and a phenoloxidase (200 kDa). Laccase activity was detected in a holidic sucrose diet that was fed on for 16 h by two females, but only a trace of catechol oxidase activity was observed, suggesting that the laccase-type phenoloxidase was the predominant phenoloxidase secreted in watery saliva. The laccase exhibited an optimum pH of 4.75-5 in McIlvaine buffer and had a PI of 4.8. Enzyme activity was histochemically localized in V cells of the posterior lobe of the salivary glands. It remained at the same level throughout the adult stage from 2 days after eclosion. A possible function of N. cincticeps salivary laccase may be rapid oxidization of potentially toxic monolignols to nontoxic polymers during feeding on the rice plant. This is the first report proving that laccase occurs in the salivary glands of Hemiptera species and is secreted in the watery saliva.

Influence of streptozotocin-induced diabetes on hexokinase activity of rat salivary glands

The influence of diabetes on the enzyme hexokinase (HK) was examined in the salivary glands of rats. Diabetes was induced by an intraperitoneal injection of streptozotocin (60 mg/Kg body weight) in overnight fasted rats (180-200 g). The animals were killed 48 hours and 30 days after the induction of diabetes and the submandibular and parotid salivary glands extracted for use. Hyperglycemia was evaluated by determining the blood sugar. The area occupied by each intralobular component, acini, ducts, total parenchyma and stroma was measured, and no differences were observed compared with control. In the soluble fraction of the submandibular gland, no difference in the specific activity of HK was observed, between the diabetic and control animals, however, the activity per gland and per g of tissue showed lower values than control. The specific activity of the bound form was reduced in the diabetic gland. The results obtained for the parotid gland were different from the submandibular. The specific activity of both the soluble and bound forms were increased in the diabetic animals. The DEAE-cellulose column chromatography of the soluble and bound forms of the enzyme from both glands showed a first peak appearing during the washing of the column and two other peaks were eluted by the gradient. Thus, three isoenzymes in the submandibular and parotid salivary glands for the control and diabetic rats have been found.

Tec29 controls actin remodeling and endoreplication during invagination of the Drosophila embryonic salivary glands

Epithelial invagination is necessary for formation of many tubular organs, one of which is the Drosophila embryonic salivary gland. We show that actin reorganization and control of endocycle entry are crucial for normal invagination of the salivary placodes. Embryos mutant for Tec29, the Drosophila Tec family tyrosine kinase, showed delayed invagination of the salivary placodes. This invagination delay was partly the result of an accumulation of G-actin in the salivary placodes, indicating that Tec29 is necessary for maintaining the equilibrium between G- and F-actin during invagination of the salivary placodes. Furthermore, normal invagination of the salivary placodes appears to require the proper timing of the endocycle in these cells; Tec29 must delay DNA endoreplication in the salivary placode cells until they have invaginated into the embryo. Taken together, these results show that Tec29 regulates both the actin cytoskeleton and the cell cycle to facilitate the morphogenesis of the embryonic salivary glands. We suggest that apical constriction of the actin cytoskeleton may provide a temporal cue ensuring that endoreplication does not begin until the cells have finished invagination.