Prostate-specific antigen: An unfamiliar protein in the human salivary glands

OBJECTIVES

The presence of prostate-specific antigen (PSA) in saliva and salivary glands has been reported. Nevertheless, its release pathway in these glands remains to be elucidated. Here, we showed PSA subcellular distribution focusing on its plausible route in human salivary parenchyma.

MATERIALS AND METHODS

Sections of parotid and submandibular glands were subjected to the immunohistochemical demonstration of PSA by the streptavidin-biotin method revealed by alkaline phosphatase. Moreover, ultrathin sections were collected on nickel grids and processed for immunocytochemical analysis, to visualize the intracellular distribution pattern of PSA through the observation by transmission electron microscopy.

RESULTS

By immunohistochemistry, in both parotid and submandibular glands PSA expression was detected in serous secretory acini and striated ducts. By immunocytochemistry, immunoreactivity was retrieved in the cytoplasmic compartment of acinar and ductal cells, often associated with small cytoplasmic vesicles. PSA labeling appeared also on rough endoplasmic reticulum and in the acini's lumen. A negligible PSA labeling appeared in most of the secretory granules of both glands.

CONCLUSIONS

Our findings clearly support that human parotid and submandibular glands are involved in PSA secretion. Moreover, based on the immunoreactivity pattern, its release in oral cavity would probably occur by minor regulated secretory or constitutive-like secretory pathways.

Male and Female Mitochondria Respond Differently after Exercising in Acute Hypoxia

The use of hypoxic devices among athletes who train in normobaric hypoxia has become increasingly popular; however, the acute effects on heart and brain metabolism are not yet fully understood. This study aimed to investigate the mitochondrial bioenergetics in trained male and female Wistar rats after acute hypoxia training. The experimental plan included exercising for 30 min on a treadmill in a Plexiglas cage connected to a hypoxic generator set at 12.5% O2 or in normoxia. After the exercise, the rats were sacrificed, and their mitochondria were isolated from their brains and hearts. The bioenergetics for each complex of the electron transport chain was tested using a Clark-type electrode. The results showed that following hypoxia training, females experienced impaired oxidative phosphorylation through complex II in heart subsarcolemmal mitochondria, while males had an altered ADP/O in heart interfibrillar mitochondria, without any change in oxidative capacity. No differences from controls were evident in the brain, but an increased electron transport system efficiency was observed with complex I and IV substrates in males. Therefore, the study's findings suggest that hypoxia training affects the heart mitochondria of females more than males. This raises a cautionary flag for female athletes who use hypoxic devices.

Melatonin ultrastructural localization in mitochondria of human salivary glands

The hormone melatonin was initially believed to be synthesized exclusively by the pineal gland and the enterochromaffin cells, but nowadays its production and distribution were observed in several other tissues and organs. Among others, the ultrastructural localization of melatonin and its receptors has been reported in human salivary glands. In these glands, the fine localization of melatonin in intracellular organelles, above all in mitochondria, remains to be explored comprehensively. Bioptic samples of parotid and submandibular glands were treated to search for melatonin using the immunogold staining method by transmission electron microscopy. Morphometric analysis was applied to micrographs. The results indicated that, both in parotid and submandibular glands mitochondria, a certain melatonin positivity was present. Within glandular cells, melatonin was less retrieved in mitochondria than in secretory granules; however, its presence in this organelle was clearly evident. Inside striated duct cells, melatonin staining in mitochondria was more prominent than in glandular cells. Our data provide an ultrastructural report on the presence of melatonin in mitochondria of human major salivary glands and represent a fundamental prerequisite for a better understanding of the melatonin role in this organelle.

Effect of the natural polymethoxylated flavone artemetin on lipid oxidation and its impact on cancer cell viability and lipids

The biochemical class of the polymethoxylated flavonoids represents uncommon phenolic compounds in plants presenting a more marked lipophilic behavior due to the alkylation of its hydroxylic groups. As a polymethoxylated flavone, which concerns a different bioavailability, artemetin (ART) has been examined in vitro against lipid oxidation and its impact on cancer cells has been explored. Despite this flavone only exerted a slight protection against in vitro fatty acid and cholesterol oxidative degradation, ART significantly reduced viability and modulated lipid profile in cancer Hela cells at the dose range 10-50 μM after 72 h of incubation. It induced marked changes in the monounsaturated/saturated phospholipid class, significant decreased the levels of palmitic, oleic and palmitoleic acids, maybe involving an inhibitory effect on de novo lipogenesis and desaturation in cancer cells. Moreover, ART compromised normal mitochondrial function, inducing a noteworthy mitochondrial membrane polarization in cancer cells. A dose-dependent absorption of ART was evidenced in HeLa cell pellets (15.2% of the applied amount at 50 μM), coupled to a marked increase in membrane fluidity, as indicate by the dose-dependent fluorescent Nile Red staining (red emissions). Our results validate the ART role as modulatory agent on cancer cell physiology, especially impacting viability, lipid metabolism, cell fluidity, and mitochondrial potential.

Role of Cardiac AMP-Activated Protein Kinase in a Non-pathological Setting: Evidence From Cardiomyocyte-Specific, Inducible AMP-Activated Protein Kinase α1α2-Knockout Mice

AMP-activated protein kinase (AMPK) is a key regulator of energy homeostasis under conditions of energy stress. Though heart is one of the most energy requiring organs and depends on a perfect match of energy supply with high and fluctuating energy demand to maintain its contractile performance, the role of AMPK in this organ is still not entirely clear, in particular in a non-pathological setting. In this work, we characterized cardiomyocyte-specific, inducible AMPKα1 and α2 knockout mice (KO), where KO was induced at the age of 8 weeks, and assessed their phenotype under physiological conditions. In the heart of KO mice, both AMPKα isoforms were strongly reduced and thus deleted in a large part of cardiomyocytes already 2 weeks after tamoxifen administration, persisting during the entire study period. AMPK KO had no effect on heart function at baseline, but alterations were observed under increased workload induced by dobutamine stress, consistent with lower endurance exercise capacity observed in AMPK KO mice. AMPKα deletion also induced a decrease in basal metabolic rate (oxygen uptake, energy expenditure) together with a trend to lower locomotor activity of AMPK KO mice 12 months after tamoxifen administration. Loss of AMPK resulted in multiple alterations of cardiac mitochondria: reduced respiration with complex I substrates as measured in isolated mitochondria, reduced activity of complexes I and IV, and a shift in mitochondrial cristae morphology from lamellar to mixed lamellar-tubular. A strong tendency to diminished ATP and glycogen level was observed in older animals, 1 year after tamoxifen administration. Our study suggests important roles of cardiac AMPK at increased cardiac workload, potentially limiting exercise performance. This is at least partially due to impaired mitochondrial function and bioenergetics which degrades with age.

The dietary flavonoid eupatilin attenuates in vitro lipid peroxidation and targets lipid profile in cancer HeLa cells

Eupatilin is a dietary flavonoid isolated from the alpine wormwoods, used for the genepy liqueur production. This flavone protects cells and tissues against oxidative stress and targets cancer cells, inducing cytotoxicity, cell circle arrest, apoptosis and mitochondrial dysfunction. This study examines the EUP in vitro antioxidant effects on cholesterol and phospholipid membrane oxidation and explores its ability to modulate the cancer cell lipid profile. This flavone remarkably protected fatty acids and cholesterol against oxidative degradation by scavenging lipoperoxyl radicals. EUP (24 h of incubation) significantly reduced viability and modulated the total lipid and fatty acid profiles in cancer HeLa cells. It induced marked changes in the phospholipid/cholesterol ratio, significant decreases in the levels of oleic and palmitic acids and a marked increase of stearic acid, involving an inhibitory effect on de novo lipogenesis and desaturation in cancer cells. Moreover, a noteworthy mitochondrial membrane depolarization, signs of apoptosis, abnormal mitosis with multi-nucleation (mitotic catastrophe) and morphological alterations were observed in cancer EUP-treated cells. Our results validate the EUP role as antioxidant agent for the treatment/prevention of disorders implicating a membrane lipid oxidative damage and substantiate cell lipid metabolism as another possible target of this dietary natural flavonoid in cancer HeLa cells.

STZ-diabetic rat heart maintains developed tension amplitude by increasing sarcomere length and crossbridge density

New Findings

What is the central question of this study?

In the papillary muscle from type I diabetic rats, does diabetes‐associated altered ventricular function result from changes of acto‐myosin interactions and are these modifications attributable to a possible sarcomere rearrangement?

What is the main finding and its importance?

For the first time, we showed that type‐I diabetes altered sarcomeric ultrastructure, as seen by transmission electron microscopy, consistent with physiological parameters. The diabetic condition induced slower timing parameters, which is compatible with a diastolic dysfunction. At the sarcomeric level, augmented β‐myosin heavy chain content and increased sarcomere length and crossbridges' number preserve myocardial stroke and could concur to maintain the ejection fraction.

Abstract

We investigated whether diabetes‐associated altered ventricular function, in a type I diabetes animal model, results from a modification of acto‐myosin interactions, through the in vitro recording of left papillary muscle mechanical parameters and examination of sarcomere morphology by transmission electron microscopy (TEM). Experiments were performed on streptozotocin‐induced diabetic and age‐matched control female Wistar rats. Mechanical isometric and isotonic indexes and timing parameters were determined. Using Huxley's equations, we calculated mechanics, kinetics and energetics of myosin crossbridges. Sarcomere length and A‐band length were measured on TEM images. Type I and III collagen and β‐myosin heavy chain (MHC) expression were determined by immunoblotting. No variation in resting and developed tension or maximum extent of shortening was evident between groups, but diabetic rats showed lower maximum shortening velocity and prolonged timing parameters. Compared to controls, diabetics also displayed a higher number of crossbridges with lower unitary force. Moreover, no change in type I and III collagen was associated to diabetes, but pathological rats showed a two‐fold enhancement of β‐MHC content and longer sarcomeres and A‐band, detected by ultrastructural morphometry. Overall, these data address whether a preserved systolic function accompanied by an altered diastolic phase results from a recruitment of super‐relaxed myosin heads or the phosphorylation of the regulatory light chain site in myosin. Although the early signs of diabetic cardiomyopathy were well expressed, the striking finding of our study was that, in diabetics, sarcomere modification may be a possible compensatory mechanism that preserves systolic function.

Reactivity of human labial glands in response to cevimeline treatment

Among the pathologies affecting the salivary glands, the Sjögren's syndrome (SS), an autoimmune disease, causes progressive destruction of the glandular tissue. The effect of SS is particularly evident on the labial glands and the morphological analysis of these minor glands is considered useful for diagnosis. Cevimeline hydrochloride (SNI), a selective muscarinic agonist drug, is one of the elective treatments for the hyposalivation due to SS, acting not only on major salivary glands, but also on labial glands since their secretion is primarily under parasympathetic control. Aim of this study is to describe the morphology of human labial glands treated with SNI by light, transmission, and high-resolution scanning electron microscopy. Moreover, a morphometric analysis was applied to the light and transmission electron microscopy micrographs to obtain data that were then compared with analogous data collected on control and carbachol-treated labial glands. Following SNI administration, the mucous tubules exhibited enlarged lumina, which were filled with a dense mucous secretion. Occasionally, small broken debris of the cells were retrieved into the lumen. In the mucous secretory cells, some mucous droplets fused to form a large vacuole-like structure. Similarly, the seromucous acini showed both dilated lumina and canaliculi. These above reported signs of secretion were confirmed through morphometric analysis and a milder action of SNI than carbachol on labial parenchyma was observed. This study confirmed that SNI also evoked secretion on labial glands and that its effect is more physiologic than that of the pan-muscarinic agonists.

The Role of Lipid Composition in the Sensory Attributes and Acceptability of the Salted and Dried Mullet Roes (Bottarga): A Study in Human and Animal Models

A taste component is implicated in the oro-sensory detection of dietary lipids and free fatty acids seem to be involved in fatty food recognition. Bottarga, the salted and semi-dried ovary product of mullet (Mugil spp.), is a rich-fat food. A comparative sensory assessment of different commercial bottarga samples was performed in insect and human models in relation to their lipid composition. The bottarga attractant effect to Ceratitis capitata was assessed by behavioral tests. The subjective odor and taste perception of bottarga samples was investigated in human determining the rate of pleasantness, familiarity, and intensity dimensions using the 7-points Likert-type scale. Bottarga samples showed similar lipid profiles, but differences emerged in total and free fatty acid levels. Significant differences were observed in the attractant effect/acceptability of samples to medflies, negatively correlated to their total and free fatty acids. Insect female exhibited the ability to select among bottarga samples based on their visual and olfactory properties. In the human model, a potential contribution of free fatty acid amount in the pleasantness and familiarity dimensions of taste of bottarga samples was evidenced. Women exhibited a greater ability than men to select bottarga samples based on their better olfactory perception. Our results increase the knowledge about this outstanding product with nutritional and nutraceutical properties.

Suitability of the thawed algae for transmission electron microscopy study: Ultrastructural investigation on Coccomyxa melkonianii SCCA 048

Morphological and ultrastructural investigations are crucial for the identification and characterization of species such as microalgae, microorganisms that greatly change their morphology and physiology during their life cycle. Transmission electron microscopy (TEM) is an excellent tool for the ultrastructural observation of cells and their components. To date, limited ultrastructural studies have been carried out on microalgae, due to the difficulties in sample preparation. The aim of this work is to establish an appropriate fixation method that allows to better preserve the algal ultrastructure and test the suitability of the thawed algae for TEM observation. Fresh and thawed algae (Coccomyxa melkonianii SCCA 048) were fixed with different TEM fixation methods (a mix of glutaraldehyde and paraformaldehyde for several incubation times, sometimes preceded by a prefixation in cold methanol). The ultrastructural images obtained from fresh algae were compared to those obtained from frozen biomass. The best morphological results were achieved by fixing fresh algae in 1% paraformaldehyde and 1.25% glutaraldehyde for 5 hr. Pretreating with frozen methyl alcohol reduced fixation time to 2 hr. Both fresh and frozen algae ultrastructure were rather well preserved also with 1% paraformaldehyde and 1.25% glutaraldehyde for 2 hr. Ultrastuctural morphological images of the thawed algae demonstrated that also frozen samples can be used in TEM research, widening specimen suitability by means of this technique.

Bioenergetic functions in subpopulations of heart mitochondria are preserved in a non-obese type 2 diabetes rat model (Goto-Kakizaki)

A distinct bioenergetic impairment of heart mitochondrial subpopulations in diabetic cardiomyopathy is associated with obesity; however, many type 2 diabetic (T2DM) patients with high-risk for cardiovascular disease are not obese. In the absence of obesity, it is unclear whether bioenergetic function in the subpopulations of mitochondria is affected in heart with T2DM. To address this issue, a rat model of non-obese T2DM was used to study heart mitochondrial energy metabolism, measuring bioenergetics and enzyme activities of the electron transport chain (ETC). Oxidative phosphorylation in the presence of substrates for ETC and ETC activities in both populations of heart mitochondria in T2DM rats were unchanged. Despite the preservation of mitochondrial function, aconitase activity in T2DM heart was reduced, suggesting oxidative stress in mitochondria. Our study indicate that metabolic function of heart mitochondria is unchanged in the face of oxidative stress and point to a critical role of obesity in T2DM cardiomyopathy.

Neuroprotection by the Immunomodulatory Drug Pomalidomide in the Drosophila LRRK2WD40 Genetic Model of Parkinson's Disease

The search for new disease-modifying drugs for Parkinson's disease (PD) is a slow and highly expensive process, and the repurposing of drugs already approved for different medical indications is becoming a compelling alternative option for researchers. Genetic variables represent a predisposing factor to the disease and mutations in leucine-rich repeat kinase 2 (LRRK2) locus have been correlated to late-onset autosomal-dominant PD. The common fruit fly Drosophila melanogaster carrying the mutation LRRK2 loss-of-function in the WD40 domain (LRRK2^WD40), is a simple in vivo model of PD and is a valid tool to first evaluate novel therapeutic approaches to the disease. Recent studies have suggested a neuroprotective activity of immunomodulatory agents in PD models. Here the immunomodulatory drug Pomalidomide (POM), a Thalidomide derivative, was examined in the Drosophila LRRK2^WD40 genetic model of PD. Mutant and wild type flies received increasing POM doses (1, 0.5, 0.25 mM) through their diet from day 1 post eclosion, until postnatal day (PN) 7 or 14, when POM's actions were evaluated by quantifying changes in climbing behavior as a measure of motor performance, the number of brain dopaminergic neurons and T-bars, mitochondria integrity. LRRK2^WD40 flies displayed a spontaneous age-related impairment of climbing activity, and POM significantly and dose-dependently improved climbing performance both at PN 7 and PN 14. LRRK2^WD40 fly motor disability was underpinned by a progressive loss of dopaminergic neurons in posterior clusters of the protocerebrum, which are involved in the control of locomotion, by a low number of T-bars density in the presynaptic bouton active zones. POM treatment fully rescued the cell loss in all posterior clusters at PN 7 and PN 14 and significantly increased the T-bars density. Moreover, several damaged mitochondria with dilated cristae were observed in LRRK2^WD40 flies treated with vehicle but not following POM. This study demonstrates the neuroprotective activity of the immunomodulatory agent POM in a genetic model of PD. POM is an FDA-approved clinically available and well-tolerated drug used for the treatment of multiple myeloma. If further validated in mammalian models of PD, POM could rapidly be clinically tested in humans.

Tyrosine-hydroxylase, dopamine β-hydroxylase and choline acetyltransferase-like immunoreactive fibres in the human major sublingual gland

OBJECTIVE

To study the innervation of the major sublingual gland by means of immunohistochemistry.

DESIGN

Bioptic and autoptic specimens of the major sublingual gland of humans were examined for the presence of immunoreactivity to tyrosine hydroxylase and dopamine-β-hydroxylase, on one hand, and choline acetyltransferase, on the other, to indicate adrenergic and cholinergic nerves, respectively.

RESULTS

Acini and ducts were supplied by both divisions of the autonomic nervous system.

CONCLUSIONS

Mucous and seromucous cells of the human major sublingual glands may respond with secretion not only to parasympathetic activity but also to sympathetic activity. The major sublingual gland is therefore a potential contributor to the mucin secretion recently reported in the literature in response to high sympathetic activity during physical exercise.

Dietary zerumbone from shampoo ginger: new insights into its antioxidant and anticancer activity

The dietary sesquiterpene dienone zerumbone (ZER) selectively targets cancer cells, inducing mitochondrial dysfunction and apoptosis, and protects non-cancerous cells towards oxidative stress and insult. This study examines the in vitro effects of ZER on lipid peroxidation in biological systems (cholesterol and phospholipid membrane oxidation) and explores its antitumor action in terms of its ability to modulate cancer cell lipid profile. Evaluation of the antioxidant activity of ZER showed that this compound is unable to trap lipoperoxyl radicals per se. ZER significantly modulated the total lipid and fatty acid profiles in cancer cells, inducing marked changes in the phospholipid/cholesterol ratio, with significant decreases in the levels of oleic and palmitic acids and a marked increase of stearic acid. Cell-based fluorescent measurements of intracellular membranes and lipid droplets using the Nile Red staining technique showed that in cancer cells, ZER induced significant accumulation of cytosolic lipid droplets and altered cell membrane organization/protein dynamics, depolarizing the mitochondrial membranes and inducing apoptosis and alteration of nuclear morphology. The modulatory activity of ZER on the total lipid and fatty acid profiles and lipid droplets may therefore represent another possible mechanism of its anticancer properties.

Melatonin release by exocytosis in the rat parotid gland

Several beneficial effects on oral health are ascribed to melatonin. Due to its lipophilic nature, non-protein-bound circulating melatonin is usually thought to enter the saliva by passive diffusion through salivary acinar gland cells. Recently, however, using transmission electron microscopy (TEM), melatonin was found in acinar secretory granules of human salivary glands. To test the hypothesis that granular located melatonin is actively discharged into the saliva by exocytosis, i.e. contrary to the general belief, the β-adrenergic receptor agonist isoprenaline, which causes the degranulation of acinar parotid serous cells, was administered to anaesthetised rats. Sixty minutes after an intravenous bolus injection of isoprenaline (5 mg kg^-1 ), the right parotid gland was removed; pre-administration, the left control gland had been removed. Samples were processed to demonstrate melatonin reactivity using the immunogold staining method. Morphometric assessment was made using TEM. Gold particles labelling melatonin appeared to be preferentially associated with secretory granules, occurring in their matrix and at membrane level but, notably, it was also associated with vesicles, mitochondria and nuclei. Twenty-six per cent of the total granular population (per 100 μm² per cell area) displayed melatonin labelling in the matrix; three-quarters of this fraction disappeared (P < 0.01) in response to isoprenaline, and melatonin reactivity appeared in dilated lumina. Thus, evidence is provided of an alternative route for melatonin to reach the gland lumen and the oral cavity by active release through exocytosis, a process which is under the influence of parasympathetic and sympathetic nervous activity and is the final event along the so-called regulated secretory pathway. During its stay in granules, anti-oxidant melatonin may protect their protein/peptide constituents from damage.

Marked Differences in the Submandibular Salivary Proteome between Sardinian Alcohol-Preferring and Sardinian Alcohol-Non Preferring Rats Revealed by an Integrated Top-Down-Bottom-Up Proteomic Platform

Sardinian alcohol-preferring (sP) and Sardinian alcohol-non preferring (sNP) rats have been selectively bred for opposite alcohol preference and consumption. Aiming to verify possible differences at the proteomics level between sP and sNP rats, we investigated the salivary proteome by a a liquid chromatography-mass spectrometry top-down-bottom-up integrated approach. For this purpose, submandibular saliva was collected from alcohol-naive sP and sNP rats under isoprenaline stimulation. A total of 200 peptides and proteins were detected and quantified in the two rat lines, 149 of which were characterized in their naturally occurring structure. The data are available via ProteomeXchange with identifier PXD006997. Surprisingly, sP rats exhibited marked quantitative and qualitative differences with respect to sNP rats, namely higher levels of proteoforms originating from submandibular gland protein C, and from submandibular rat protein 2, as well as those of several unidentified peptides and proteins. sP rats expressed some proteins not detectable in sNP rats such as the glutamine and glutamic acid-rich protein (GRP)-CB. The isoform GRP-B, detectable in both rat lines, was more abundant in sNP rats. The submandibular saliva of sNP rats was also characterized by very high levels of GRP-B proteolytic peptides and rat salivary protein 1. Whether these differences could contribute to the opposite alcohol preference and consumption of sP and sNP rats is currently unknown and requires further investigation.

Diabetic Status Influences the Storage of Melatonin in Human Salivary Glands

Recently we reported on the detailed localization of melatonin (and its receptors) in human salivary glands, revealing that serous cells are able to store and secrete melatonin into saliva. Since we found that type 2 diabetic patients display reduced melatonin content in saliva, our next step was to examine the presence of melatonin in salivary glands removed from type 2 diabetic subjects. The resulting data were compared with those previously obtained by identical procedures in non-diabetics, to establish if the diabetic status may affect melatonin distribution. Bioptic samples of diabetic parotid and submandibular glands were fixed, dehydrated, embedded in Epon Resin and processed to demonstrate melatonin reactivity by the immunogold staining method. The labeling density (expressed as the number of gold particles per μm² /granule) and the percentage of melatonin-positive granules were assessed in diabetic samples. These values were compared with those in non-diabetic samples and differences were evaluated. In parotid and submandibular diabetic glands the reactivity for melatonin was specifically associated with secretory granules and small vesicles in serous cells. Melatonin reactivity was higher in parotid than in submandibular glands. Our data were in line with those obtained in our previous study on non-diabetic glands. Diabetic salivary glands showed a higher labeling density and a lower number of melatonin-positive granules compared to non-diabetic glands. Taken together, these data might explain the decreased salivary melatonin content and the associated oral problems observed in diabetics. Anat Rec, 301:711-716, 2018. © 2017 Wiley Periodicals, Inc.

Dynamics of the melatonin MT1 receptor in the rat parotid gland upon melatonin administration

Our recent ultrastructural study of human parotid glands revealed that the melatonin receptors, MT1 and MT2, are localised in the plasma cell membranes of acinar and ductal cells but also, and intriguingly, predominantly in acinar secretory granules, giving rise to the working hypothesis that secretory granules are a part of a transcytotic transport system for melatonin. To put this hypothesis to the test in rat parotid glands, anaesthetised animals were exposed to a high melatonin dose (3 mg/kg per hour), infused intravenously over two hours and aiming to stimulate a glandular melatonin-receptor-dependent intracellular transport system, if any. Thirty minutes later, the right parotids were removed. Pre-stimulation, left parotid gland tissue was removed to serve as (untreated) controls. Gland tissues were processed for the gold post-embedding technique and for western blot analysis. In untreated glands, on transmission electron microscope images, melatonin receptors displayed a distribution pattern similar to that in human parotids, i.e. here, too, the receptors were principally associated with the acinar secretory granules. In melatonin- treated glands, the number of granules associated with the MT1 receptor was twice that in untreated glands, despite the same total granule number in the two glands. Moreover, the density of gold particles showing MT1-receptor immunoreactivity associated with granules in melatonin-treated glands was 2.5 times that in untreated glands. The number of MT1 receptors associated with the granule membrane was about three times higher in melatonin-treated glands than in untreated glands, while the number of MT1 receptors inside the granules was about twice that in untreated glands. The immunoblotting of membrane-enriched samples showed that the MT1-receptor expression was about three times that of untreated glands. When it came to the MT2 receptor, no changes were observed. Melatonin itself thus exerts dynamic effects on its MT1 receptor, which may reflect an adaptive receptor-linked carrier system for melatonin, delivering - upon gland stimulation - melatonin to the saliva by exocytosis.

Ultrastructural evidence of a secretory role for melatonin in the human parotid gland

In vivo animal studies show that pentagastrin, cholecystokinin and melatonin cause the secretion and synthesis of salivary proteins. Melatonin occurs in large amounts in the gut and is released into the blood on food intake. In vitro experiments suggest that pentagastrin exerts secretory activity in human salivary glands, as judged by ultrastructural changes, reflecting secretion, and an actual protein output. Currently, it is hypothesised that melatonin induces secretory exocytotic events in the human parotid gland. Human parotid tissues were exposed to a high single concentration of melatonin in vitro, processed for high resolution scanning electron microscopy and then assessed morphometrically with the emphasis on the membrane of the intercellular canaliculi, a site of protein secretion. Compared with controls and in terms of density, the melatonin-exposed parotid tissues displayed increases in protrusions (signalling anchored granules) and microbuds (signalling membrane recycling and/or vesicle secretion) and decreases in microvilli (signalling cytoskeletal re-arrangement related to exocytosis), phenomena abolished or very largely reduced by the melatonin receptor blocker, luzindole. In conclusion, acinar serous cells of parotid tissue displayed in vitro exocytotic activity to melatonin, signalling protein secretion. Whether, under physiological conditions, melatonin influences the secretion of human parotid glands remains to be explored, however.

VGF Peptide Profiles in Type 2 Diabetic Patients' Plasma and in Obese Mice

To address the possible involvement of VGF peptides in obesity and diabetes, we studied type 2 diabetes (T2D) and obese patients, and high-fat diet induced obese mice. Two VGF peptides (NAPP-19 and QQET-30) were identified in human plasma by HPLC-ESI-MS. The VGF C-terminus, the above two cleaved peptides, and the TLQP-21 related peptide/s were studied using ELISA and immunohistochemistry. In euglycemic patients, plasma NAPPE and TLQP like peptides were significantly reduced with obesity (74±10 vs. 167±28, and 92±10 vs. 191±19 pmol/ml, mean+SEM, n = 10 and 6, obese vs. normal BMI, respectively, p<0.03). Upon a standard glucose load, a distinct response was shown for VGF C-terminus, TLQP and QQET-like (ERVW immunoreactive) peptides in euglycemic normal BMI patients, but was virtually abolished in euglycemic obese, and in T2D patients independently of BMI. High-fat diet induced obese mice showed reduced plasma VGF C-terminus, NAPPE and QQET-like (ERVW) peptide/s (3±0.2 vs. 4.6±0.3, 22±3.5 vs. 34±1.3, and 48±7 vs. 100±7 pmol/ml, mean+SEM, n = 8/group, obese vs. slim, respectively, p<0.03), with a loss of the response to glucose for all VGF peptides studied. In immunohistochemistry, TLQP and/or VGF C-terminus antibodies labelled VGF containing perikarya in mouse celiac ganglia, pancreatic islet cells and thin beaded nerve fibres in brown adipose tissues, with fewer in white adipose tissue. Upon the glucose load, tyrosine hydroxylase and VGF C-terminus immunoreactive axons became apparent in pancreatic islets of slim animals, but not in obese animals. Alltogether, a significant loss of VGF peptide immunoreactivity and/or their response to glucose was demonstrated in obese patients, with or without T2D, in parallel with a similar loss in high-fat diet induced obese mice. An involvement of VGF in metabolic regulations, including those of brown and/or white adipose tissues is underlined, and may point out specific VGF peptides as potential targets for diagnosis and/or treatment.

A reliable model for gamma oscillations in hippocampal tissue

Gamma oscillations (30-100 Hz) reflect a fast brain rhythm that provides a fundamental mechanism of complex neuronal information processing in the hippocampus and in the neocortex in vivo. Gamma oscillations have been implicated in higher brain functions, such as sensory perception, motor activity, and memory formation. Experimental studies on synaptic transmission and bioenergetics underlying gamma oscillations have primarily used acute slices of the hippocampus. This study tests whether organotypic hippocampal slice cultures of the rat provide an alternative model for cortical gamma oscillations in vitro. Our findings are that 1) slice cultures feature well-preserved laminated architecture and neuronal morphology; 2) slice cultures of different maturation stages (7-28 days in vitro) reliably express gamma oscillations at about 40 Hz as induced by cholinergic (acetylcholine) or glutamatergic (kainate) receptor agonists; 3) the peak frequency of gamma oscillations depends on the temperature, with an increase of ∼ 3.5 Hz per degree Celsius for the range of 28-36 °C; 4) most slice cultures show persistent gamma oscillations for ∼ 1 hr during electrophysiological local field potential recordings, and later alterations may occur; and 5) in slice cultures, glucose at a concentration of 5 mM in the recording solution is sufficient to power gamma oscillations, and additional energy substrate supply with monocarboxylate metabolite lactate (2 mM) exclusively increases the peak frequency by ∼ 4 Hz. This study shows that organotypic hippocampal slice cultures provide a reliable model to study agonist-induced gamma oscillations at glucose levels near the physiological range.

Diabetes causes morphological changes in human submandibular gland: a morphometric study

BACKGROUND

Dataon structural alterations in human diabetic salivary glands are scanty and conflicting. The goal of this study is based on the evaluation of the morphological changes in submandibular glands of subjects with well-controlled diabetes and without evident salivary malfunctions.

METHODS

Submandibular gland pieces from diabetic and non-diabetic patients were fixed, dehydrated, and processed to obtain sections for light and electron microscopy. Randomly selected micrographs were statistically analyzed to reveal variations in serous acini.

RESULTS

Morphometrical evaluation allowed us to reveal significant changes such as enlargement of acinar and granule size, reduction of mitochondrial size, increased density of microbuds and protrusions along luminal membranes.

CONCLUSIONS

The results indicate that diabetes affects submandibular gland structure even when glandular function appears unaltered and suggest that morphological changes reflect functional changes chiefly regarding the secretory activity.

Animal models are reliably mimicking human diseases? A morphological study that compares animal with human NAFLD

Non-alcoholic fatty liver disease (NAFLD) is a clinical-pathological syndrome that includes a wide spectrum of morphological alterations. In research, animal models are crucial in evaluating not only the pathogenesis of NAFLD and its progression, but also the therapeutic effects of various agents. Investigations on the ultrastructural features of NAFLD in humans are not copious, due to the difficulty to obtain human samples and to the long time of NAFLD to evolve. Translational comparative studies on the reliability of animal models in representing the histopathologic picture as seen in humans are missing. To overcome this lack of investigations, we compared the ultrastructural NAFLD features of an animal model versus human. Sprague-Dawley rats were fed with a high fat diet (HFD) for 1-4 weeks, while control rats were fed with a standard diet. Human specimens were collected from patients with diagnosed fatty liver disease, undergoing liver biopsies or surgery. Rat and human samples were examined by light microscopy and by transmission and high resolution scanning electron microscopy. The present work demonstrated that NAFLD in animal model and in human, share overlapping ultrastructural features. In conclusion, animal HFD represent an appropriate tool in studying the pathogenesis of NAFLD.

The antipsychotic amisulpride: ultrastructural evidence of its secretory activity in salivary glands

OBJECTIVE

Amisulpride is reported to inhibit clozapine-induced sialorrhea. Preclinically, clozapine evokes muscarinic-M1-type-mediated secretion that, however, amisulpride does not reduce. Instead, amisulpride, without causing any overt secretion per se, enhances both nerve- and autonomimetic-evoked salivation by unknown mechanism(s). Hypothesizing that amisulpride prepares the gland for secretion, we looked for ultrastructural events indicating secretory activity in intercellular canaliculi of serous/seromucous cells, that is, density increase in protrusions (reflecting anchored granules) and in microbuds (reflecting recycling membranes and/or vesicle secretion) and decrease in microvilli (reflecting the cytoskeletal re-arrangement related to exocytosis).

MATERIAL AND METHODS

Rat parotid and submandibular glands were exposed to amisulpride in vivo or in vitro. Glands were processed for transmission electron and scanning electron microscopy and then morphometrically assessed.

RESULTS

Cells were packed with secretory granules. The density of protrusions increased in both glands, whereas significant and parallel changes in microvilli and microbuds occurred only in parotid glands, and in vitro.

CONCLUSIONS

Amisulpride induced ultrastructural signs of secretory activity but to varying extent; in submandibular glands, in contrast to parotid glands, changes were not brought beyond the granular anchoring stage. Amisulpride may provide an overall readiness for secretion that will result in augmented responses to agonists, a phenomenon of potential interest in dry-mouth treatment.

Subcellular distribution of melatonin receptors in human parotid glands

The hormone melatonin influences oral health through a variety of actions, such as anti-inflammatory, anti-oxidant, immunomodulatory and antitumour. Many of these melatonin functions are mediated by a family of membrane receptors expressed in the oral epithelium and salivary glands. Using immunoblotting and immunohistochemistry, recent studies have shown that the melatonin membrane receptors, MT1 and MT2, are present in rat and human salivary glands. To date, no investigation has dealt with the ultrastructural distribution of the melatonin receptors. This was the aim of the present study, using the immunogold method applied to the human parotid gland. Reactivity to MT1 and, with less intensity, to MT2 appeared in the secretory granules of acinar cells and in the cytoplasmic vesicles of both acinar and ductal cells. Plasma membranes were also stained, albeit slightly. The peculiar intracytoplasmic distribution of these receptors may indicate that there is an uptake/transport system for melatonin from the circulation into the saliva.

Cortical adrenal mitochondrial morphology changes in functional state: new insights

We compared changes in the morphology of mitochondrial cristae with those in the blood and adrenal content of steroid hormones after the stimulation or inhibition of steroidogenesis. Rats were treated with adrenocorticotrophic hormone or angiotensin II to elicit steroidogenesis and with dexamethasone to inhibit it. Blood and adrenal glands were collected after several time intervals for measurements of steroids and their main intermediates. In the zona fasciculata, mitochondrial ultrastructure was investigated by high resolution scanning electron microscopy. We found that the morphometric data correlated well with the measurements of hyper- or hypo-activity of steroidogenesis over short periods of time (4 h) but not over longer observation times. A peculiar finding was that, contrary to previous reports, 11-deoxycortisol was present in adult rat adrenal tissue.

Morphological evidence that pentagastrin regulates secretion in the human parotid gland

Salivary secretion is principally regulated by autonomic nerves. However, recent evidence from in vivo animal experiments suggests that gastrointestinal peptide hormones can also influence saliva production. The aim of the present study was to define the secretagogue activity of the gastrin-analogue pentagastrin in human salivary glands. For this purpose, parotid tissues were exposed to pentagastrin in vitro. Morphological techniques were used to evaluate modifications to serous acinar cells associated with secretion. Using a variant of the osmium maceration method, high resolution scanning electron microscopy allowed assessment of the morphology of the cytoplasmic aspect of the plasmalemma to demonstrate secretory activity. To quantify responses to pentagastrin, we recorded morphometric data on microvilli, microbuds, and protrusions. Dose-dependent morphological changes were observed, whereas protein concentration increased in the incubate. The use of selective receptor antagonists showed pentagastrin to act principally via cholecystokinin-A receptors. The morphological responses observed following exposure to pentagastrin differed from those elicited following exposure to the pan-muscarinic agonist carbachol. This study provides the first demonstration of a direct secretory action of gastrointestinal peptides on salivary glands in humans.

Suggestive evidence of a vesicle-mediated mode of cell degranulation in chromaffin cells. A high-resolution scanning electron microscopy investigation

In this study we used a modified osmium maceration method for high-resolution scanning electron microscopy to study some ultrastructural details fitting the schema of piecemeal degranulation in chromaffin cells. Piecemeal degranulation refers to a particulate pattern of cell secretion that is accomplished by vesicle-mediated extracellular transport of granule-stored material. We investigated adrenal samples from control and angiotensin II-treated rats, and identified a variable proportion of smooth, 30-60-nm-diameter vesicles in the cytoplasm of chromaffin cells. A percentage of these vesicles were interspersed in the cytosol among chromaffin granules but the majority appeared to be attached to granules. Remarkably, the number of unattached cytoplasmic vesicles was greatly increased in chromaffin cells from angiotensin II-treated animals. Vesicles of the same structure and dimension were detected close to or attached to the cytoplasmic face of the plasma membrane; these, too, were increased in number in chromaffin cells from rats stimulated with angiotensin II. In specimens shaken with a rotating agitator during maceration, the cytoplasmic organelles could be partially removed and the fine structure of the vesicular interaction with the inner side of the plasma membrane emerged most clearly. A proportion of chromaffin granules showed protrusions that we interpreted as vesicular structures budding from the granular envelope. In some instances, the transection plane intersected granules with putative vesicles emerging from the surfaces. In these cases, the protrusions of budding vesicles could be observed from the internal side. This study provides high-resolution scanning electron microscopy images compatible with a vesicle-mediated degranulation mode of cell secretion in adrenal chromaffin cells. The data indicating an increase in the number of vesicles observed in chromaffin cells after stimulation with the chromaffin cell secretagogue angiotensin II suggests that this secretory process may be susceptible to fine regulation.

Mitochondria of human Leydig cells as seen by high resolution scanning electron microscopy

The three-dimensional ultrastructure of over 1000 mitochondria in human Leydig cells (from twelve sexually mature patients) was examined by high resolution scanning electron microscopy (HRSEM) of osmium-macerated specimens, as well as by transmission electron microscopy of conventional ultrathin sections. The stereo-pair imaging of the osmium-macerated specimens by HRSEM is also very useful for investigating the three-dimensional structure of cytoplasmic membranous organelles with great clarity. The mitochondria, which mainly are elongated (although some are ovate), possess cristae that are almost exclusively tubular and that occasionally display constrictions and terminal bulbules. Lamelliform cristae are quite rare. Occasionally, the tubular cristae are joined together to form a simple network. Classic crista junctions could not be identified with certainty, although the base of the tubular cristae might correspond functionally to such junctions. As a whole, in line with the identical and common embryological origin of adrenal cortex and gonads, mitochondria of human Leydig cell closely resemble those of steroidogenic cells of human suprarenal cortex treated by the same maceration method.

Oxytocin immunoreactivity in the human urethral (Littrè's) glands

Oxytocin is a cyclic nonapeptide whose best known effects are stimulation of uterine smooth muscle cells during labor and of milk ejection during lactation. Circulating oxytocin originates from the hypothalamus, but its production has also been documented in peripheral tissues. Furthermore, seminal plasma also contains oxytocin, but its functional role is still unknown, although its secretion is generally ascribed to the prostate. In this study, we investigated the possibility that seminal oxytocin is also secreted by other exocrine glands of the human male genital tract. Intramural (Littrè's) glands isolated from bioptic specimens of normal urethrae were processed for immunogold localization of oxytocin. Immunostaining was detected in principal cells, with gold particles specifically found on secretory granules. Basal and endocrine cells were unstained. The present findings suggest that urethral glands not only produce the mucinous layer that protects and lubricates the urethral wall, but also are potential sources of other seminal components, such as oxytocin, which probably play still unclear roles in reproductive physiology.

The three-dimensional morphology of Candida albicans as seen by high-resolution scanning electron microscopy

The fine structure of Candida albicans has been repeatedly described by transmission electron microscopy, whereas studies by high-resolution scanning electron microscopy (HRSEM) are rare and devoted solely to the study of its external morphology. This report describes the results of an HRSEM study on C. albicans carried out by an osmium maceration protocol modified to better retain the structural characteristics of this yeast. Thus, we visualized various intracellular structures including invaginations of cell membrane (plasmalemmasomes), nuclear envelope, mitochondria, the vacuolar system, and two additional structures that might represent a form of endoplasmic reticulum and the Golgi apparatus. The present investigation, which for the first time shows the organelles of C. albicans at the 3D level, may lead to a better understanding of its cell physiology.

Acute nicotine changes dynorphin and prodynorphin mRNA in the striatum

RATIONALE

Nicotine displays rewarding and aversive effects, and while dopamine has been linked with nicotine's reward, the neurotransmitter(s) involved with aversion remains speculative. The kappa-dynorphinergic system has been associated with negative motivational and affective states, and whether dynorphin (Dyn) contributes to the behavioral pharmacology of nicotine is a pertinent question.

OBJECTIVE

We determined whether administration of a single dose of nicotine alters the biosynthesis of Dyn in the striatum of mice.

RESULTS

Nicotine free base, 1 mg/kg, sc, induced a biphasic, protracted increase of striatal Dyn, an initial rise by 1 h, which declined to control levels by 2 h, and a subsequent increase, between 6 and 12 h, lasting over 24 h. At 1 h, the nicotine effect was dose dependent, with doses>or=0.5 mg/kg inducing a response. Prodynorphin mRNA increased by 30 min for over 24 h, and in situ hybridization demonstrated elevated signal in caudate/putamen and nucleus accumbens. The nicotinic antagonist mecamylamine prevented the Dyn response, and a similar effect was observed with D1- and D2-like dopamine receptor antagonists, SCH 23390, sulpiride, and haloperidol. The glutamate NMDA receptor antagonist MK-801 reversed the nicotine-induced increase of Dyn, while the AMPA antagonist NBQX had a marginal effect.

CONCLUSIONS

We interpret our findings to indicate that acute nicotine enhances the synthesis and release of striatal Dyn. We propose that nicotine influences Dyn primarily through dopamine release and that glutamate plays a modulatory role. A heightened dynorphinergic tone may contribute to the aversive effects of nicotine in naive animals and first-time tobacco smokers.

Dynorphin and prodynorphin mRNA changes in the striatum during nicotine withdrawal

Nicotine withdrawal causes somatic and negative affective symptoms that contribute to relapse and continued tobacco smoking. So far, the neuronal substrates involved are not fully understood, and an opioid role has been suggested. In this regard, the opioid dynorphin (Dyn) is of interest as it produces aversive states and has been speculated to play a role in the nicotine behavioral syndrome. These studies explore whether Dyn metabolism is altered during withdrawal following chronic administration of nicotine. Mice were administered nicotine, 2 mg/kg, s.c., four times daily for 14 days, and Dyn and prodynorphin (PD) mRNA estimated in selective brain regions at various times (30 min to 96 h) following drug discontinuation. The content of Dyn, estimated by RIA, was decreased in the striatum for a protracted time, from 30 min to over 72 h. In contrast, the mRNA for PD, evaluated by Northern blot, was elevated, appearing by 8 h and lasting over 96 h. Dyn was decreased in both ventral and dorsal striatum, and PD mRNA was differentially increased in the two striatal compartments as demonstrated by in situ hybridization. PD message was predominantly augmented in the nucleus accumbens, rostral pole, core, and shell, and the medial aspects of caudate/putamen. We interpret these data to indicate increased activity of striatal, particularly accumbal, dynorphinergic neurons during nicotine withdrawal resulting in enhanced peptide release and compensatory synthesis. Heightened dynorphinergic tone might be responsible, in part, for the emergence of the negative affective states observed during nicotine withdrawal.

Histatin-induced alterations in Candida albicans: a microscopic and submicroscopic comparison

Despite the numerous studies performed in an attempt to clarify the issue, the mechanism of action of salivary histatins remains unclear. The aim of the present study was to correlate histatin-induced morphological changes in Candida albicans by fluorescence microscopy (FM), transmission electron microscopy (TEM), and high resolution scanning electron microscopy (HRSEM). Each of the fluorescent dyes used by FM (i.e., tetramethylrhodamine methyl ester perchlorate for mitochondrial potential, Lysotracker for lysosome acidic compartment, and 4',6-diamino-2-phenylindole dihydrochloride for DNA) exhibited a specific staining in control cells. Following histatin treatment, we observed a recurring staining pattern, corresponding to fluorescence concentration along the cell periphery, suggesting a loss of dye specificity. To assess histatin-induced cytoplasmic modifications, ultrastructural analysis was then carried out. After treatments with histatins, TEM revealed characteristic intracellular modifications including: vacuole overgrowth, nuclear disappearance, loss of organelle identity, as well as the appearance of electron-dense membranes, likely of mitochondrial origin. Additionally, structures resembling autophagosomes were occasionally observed. By HRSEM, mitochondrial swelling was invariably the first sign of a histatin-induced effect. Other modifications included intracellular membrane disarrangement, organelles in disarray, and a large central cavity with deformed bodies displaced to the cell periphery, similar to what was detected by TEM. In summary, our study illustrates the occurrence of ultrastructural modifications following administration of histatins. Observations made with FM, TEM, and HRSEM provided different views of the same signs, demonstrating a definite action of histatins on C. albicans morphology. The possible functional meanings of these morphological results is discussed in light of the most recent biochemical data on histatin fungicidal activity.

Intracellular distribution of fluorescent probes delivered by vesicles of different lipidic composition

In order to study mechanisms involved in liposome-cell interaction, this work attempted to assess the influence of vesicle composition on the delivery of liposomal content to Hela cells. In particular, to evaluate pH-sensitive properties and cell interaction of the prepared liposomes, the lipid formulations contained cholesterol (Chol) and they were varied by using phosphatidylcholines with different purity degree: soy lecithin (SL; 80% phosphatidylcholine), a commercial mixture of soy phosphatidylcholine (P90; 90% phosphatidylcholine) or dipalmitoylphosphatidylcholine (DPPC; 99% of purity). A second series of liposomes also contained stearylamine (SA). Dehydration-rehydration vesicles (DRV) were prepared and then sonicated to decrease vesicle size. Vesicle-cell interactions and liposomal uptake were examined by fluorescence microscopy using carboxyfluorescein (CF) and phosphatidylethanolamine-dioleoyl-sulforhodamine B (Rho-PE) as fluorescent markers. Fluorescence dequenching assay was used to study the influence of pH on CF release from the liposomal formulations. Liposome adhesion on the cell surface and internalization were strongly dependent on vesicle bilayer composition. SA vesicles were not endocytosed. DPPC/Chol liposomes were endocytosed but did not release their fluorescent content into the cytosol. SL/Chol and P90/Chol formulations displayed a diffuse cytoplasmic fluorescence of liposomal marker.

New findings on 3-D microanatomy of cellular structures in human tissues and organs. An HRSEM study

We present here findings obtained on a large number of human tissues over a period of more than ten years, by our modification of the Osmium maceration method for high resolution scanning electron microscopy (HRSEM). Data are documented by original pictures which illustrate both some 3-D intracellular features not previously shown in human tissues, and results obtained in our current studies on mitochondrial morphology and on the secretory process of salivary glands. We have demonstrated that mitochondria of cells of practically all human tissues and organs have usually tubular cristae, and that even the cristae that look lamellar are joined to the inner mitochondrial membrane by tubular connexions similar to the crista junctions later seen by electron tomography. Concerning salivary glands an important result is the development of a morphometric method that allows the quantitative evaluation of the secretory events.

High resolution scanning electron microscopy of the intracellular surface of intercalated disks in human heart

The three-dimensional architecture of human cardiac intercalated disks was examined by high resolution scanning electron microscopy of osmium-macerated specimens. This methodology permits viewing of in situ intercalated disks from a vantage point inside individual cardiomyocytes. The erose nature of these structures was rendered in stark relief. Areas covered with clusters of particles were present on some membranous projections--these may represent a combination of desmosomes and fasciae adherentes. On the other hand, areas devoid of particles may correspond to gap junctions.

Characterization of depolarization and repolarization phases of mitochondrial membrane potential fluctuations induced by tetramethylrhodamine methyl ester photoactivation

Depolarization and repolarization phases (D and R phases, respectively) of mitochondrial potential fluctuations induced by photoactivation of the fluorescent probe tetramethylrhodamine methyl ester (TMRM) were analyzed separately and investigated using specific inhibitors and substrates. The frequency of R phases was significantly inhibited by oligomycin and aurovertin (mitochondrial ATP synthase inhibitors), rotenone (mitochondrial complex I inhibitor) and iodoacetic acid (inhibitor of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase). Succinic acid (mitochondrial complex II substrate, given in the permeable form of dimethyl ester) abolished the rotenone-induced inhibition of R phases. Taken together, these findings indicate that the activity of both respiratory chain and ATP synthase were required for the recovery of the mitochondrial potential. The frequency of D phases prevailed over that of R phases in all experimental conditions, resulting in a progressive depolarization of mitochondria accompanied by NAD(P)H oxidation and Ca2+ influx. D phases were not blocked by cyclosporin A (inhibitor of the permeability transition pore) or o-phenyl-EGTA (a Ca2+ chelator), suggesting that the permeability transition pore was not involved in mitochondrial potential fluctuations.

Mitochondrial alterations and autofluorescent conversion ofCandida albicans induced by histatins

The mechanism of the candidacidal activity of histatins 3 and 5 (Hst) is still a matter of debate. Previous studies have indicated that Hst induce cell permeabilization, generation of reactive oxygen species (ROS) by mitochondria, inhibition of the respiratory chain, and energy-dependent cytotoxic release of ATP. On the other hand, the multiplicity of effects and the apparent contrast between experimental data continue to render the mechanism of Hst-induced killing of C. albicans unclear. In this investigation, using fluorescent probes (the potential-sensitive mitochondrial probe tetramethylrhodamine methyl ester perchlorate, TMRM; the ROS-sensitive probe dihydrofluorescein diacetate, DHF; the membrane-impermeant probe, calcein) and autofluorescence data we observed that Hst induce ROS generation by mitochondria undergoing a high energy swelling condition, accompanied by oxidation of cytosolic NAD(P)H and mitochondrial flavoproteins. ROS generation and swelling, attributable to an inhibition of the respiratory chain and to impairment of the K/H-exchanger, were followed by mitochondrial depolarization. Mitochondrial changes were accompanied by massive calcein influx, indicative of cell permeabilization, and prominent alterations of the cell size, shape, and optical density. The loss of proliferative activity was correlated, on a single cell basis, to the acquisition of a lipofuscin-like autofluorescence.

Mitochondrial localization of reactive oxygen species by dihydrofluorescein probes

Mitochondria are the main source of reactive oxygen species (ROS). The aim of this work was to verify the ROS generation in situ in HeLa cells exposed to prooxidants and antioxidants (menadione, tert-butyl hydroperoxide, antimycin A, vitamin E, N-acetyl-L-cysteine, and butylated hydroxytoluene) using the ROS-sensitive probes 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate di-acetomethyl ester (DCDHF) and dihydrofluorescein diacetate (DHF). Mitochondria were counterstained with the potential-sensitive probe tetramethylrhodamine methyl ester perchlorate (TMRM). Both DCDHF and DHF were able to detect the presence of ROS in mitochondria, though with distinct morphological features. DCDHF fluorescence was invariably blurred, smudged, and spread over the cytoplasm surrounding the major mitochondrial clusters. On the contrary, DHF fluorescence was sharp and delineated thin filaments which corresponded in all details to TMRM-stained mitochondria. These data suggest that DCDHF does not reach the mitochondrial matrix but is oxidized by ROS released by mitochondria in the cytosol. On the other hand, DHF enters mitochondria and reacts with ROS released in the matrix. Cytosolic (DCDHF+) ROS but not matrix (DHF+) ROS, were significantly decreased by vitamin E. N-acetyl-L-cysteine was effective in reducing DCDHF and DHF photooxidation in the medium, but was unable to reduce intracellular ROS. ROS generation was accompanied by partial mitochondrial depolarization.

Met-enkephalin and preproenkephalin mRNA changes in the striatum of the nicotine abstinence mouse

We studied the changes of met-enkephalin (Met-Enk) content and preproenkephalin (PPE) mRNA in the striatum in a mouse model of nicotine abstinence. Nicotine, 2 mg/kg, s.c., was administered four times daily for 14 days and Met-Enk and PPE mRNA evaluated at various times (4-96 h) following drug discontinuation. Met-Enk, assayed by radioimmunoassay, was increased in the ventral (nucleus accumbens) but not dorsal (putamen/caudate) striatum, while PPE mRNA, assayed in whole striatum by Northern blotting was elevated. Both changes were seen early during withdrawal and lasted over 72 h. In situ hybridization revealed enhanced signal in the dorsal striatum, mostly laterally, and smaller increases in the rostral pole, core and shell of the nucleus accumbens. These observations indicate that during nicotine withdrawal, striatal enkephalinergic neurons undergo adaptative responses, which might contribute to the abstinence behavioral syndrome.

Intra- and intercellular distribution of mitochondrial probes and changes after treatment with MDR modulators

Fluorescent probes are currently used to evaluate the mitochondrial transmembrane potential in situ. However, in parallel experiments using the probes JC-1 and TMRM in different cell types (human astrocytes, HEp-2, Vero, KB, and HeLa cells), we found that the distribution of JC-1 and TMRM is highly variable not only in different cell types but also in different cells of the same cell type, a condition that has never been documented until our work. This phenomenon depends on a hidden, widespread multidrug resistance (MDR) phenotype that can be recognized only by comparative assays with MDR inhibitors (progesterone, verapamil, and cyclosporin A) and represents a serious risk of error in the evaluation of the mitochondrial potential.

Glutamate receptors participate in the nicotine-induced changes of met-enkephalin in striatum

A single dose of nicotine given to mice induces first a rapid decrease (presumed release/enhanced degradation) and then a rise (presumed synthesis/enhanced accumulation) of met-enkephalin (Met-Enk) in dorsal and ventral striatum observed at 30 and 60 min post-treatment, respectively. These studies investigated whether the nicotine effect on Met-Enk was mediated indirectly, in part, via other neurotransmitters known to be released by nicotine. Based on the ability of selective antagonists of dopamine (Sch 23390, D1; Sulpiride, D2), glutamate (CPP, competitive NMDA; dizocilpine, non-competitive NMDA; NBQX, AMPA) and GABA (bicuculline, GABA(A); Sch 50911, GABA(B)) receptors, to inhibit or enhance the response to nicotine, we conclude that nicotine alters striatal Met-Enk, in part, via glutamate NMDA and AMPA receptors. These findings further support the notion that glutamate might play a role in the pharmacology of nicotine.

Homogeneous longitudinal profiles and synchronous fluctuations of mitochondrial transmembrane potential

This study reports for the first time (a) the longitudinal profile of the transmembrane potential (mDeltapsi) of single mitochondria using a Nernstian fluorescent probe and (b) the distribution of mDeltapsi fluctuations of mitochondria undergoing permanent depolarization. Our findings show that (1) mitochondria in different energetic conditions coexist in the same cell, (2) mDeltapsi is rather homogeneous along the entire length of single mitochondria, (3) mDeltapsi is not influenced by the surrounding cytoplasmic environment and (4) mDeltapsi fluctuations occur simultaneously in groups of mitochondria connected in a network. Taken together, these findings provide further evidence for a functional relationship between mitochondrial arrangement and energetic condition.