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.

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.

Effect of the neuropeptides vasoactive intestinal peptide, peptide histidine methionine and substance P on human major salivary gland secretion.

OBJECTIVE: The parasympathetic transmitters vasoactive intestinal peptide (VIP) and substance P (SP) are secretagogues in salivary glands of animals. Currently, we hypothesise that in human salivary glands, these neuropeptides and the VIP-related peptide histidine methionine (PHM) also exert secretory actions, reflected morphologically by exocytosis of acinar protein/glycoprotein-storing granules. MATERIALS AND METHODS: Submandibular and parotid gland tissues, exposed in vitro to VIP and PHM, and SP, respectively, were examined by light and transmission electron microscopy. For comparison, the response to in vitro stimulation of isoproterenol, phenylephrine and carbachol was examined. Moreover, the peptidergic innervation of the glands was examined by immunohistochemistry. RESULTS: Vasoactive intestinal peptide- and PHM-immunoreactive nerves were in close proximity to acini and ducts in the two glands, while these elements lacked a SP-positive innervation. While no morphological changes occurred in response to SP (parotid glands), VIP and PHM administration (submandibular glands) caused conspicuous acinar degranulation accompanied by luminal space broadening. In the two glands, both α1 - and ß-adrenergic receptor stimulation and muscarinic receptor stimulation caused similar changes as to VIP/PHM, although to varying extent. CONCLUSIONS: Vasoactive intestinal peptide and PHM, but not SP, are likely transmitters in the parasympathetic control of salivary (protein) secretion in humans.

Decellularized ovine arteries as small-diameter vascular grafts.

Atherosclerosis and its complications still represent the leading cause of death in the developed countries. While autologous blood vessels may be regarded as the best solution for peripheral and coronary bypass, they are unavailable in most patients. Even though tissue engineering techniques are often applied to the development of small-diameter vascular grafts, limiting factors of this approach are represented by the lack of essential extracellular matrix proteins and/or poor biomechanical properties of the scaffolds used. Along these lines, the aim of this study was to develop a decellularization protocol for ovine carotids to be used as suitable small-diameter vascular grafts. Samples were treated either with sodium dodecyl sulphate (SDS) or with Trypsin and Triton X-100; a final nuclease digestion was performed for both protocols. Morphological analyses demonstrate complete removal of nuclei and cellular components in treated vessels, also confirmed by significant reduction in wall thickness and DNA content. Essential extracellular matrix proteins such as collagen, elastin, and fibronectin are well preserved after decellularization. From a mechanical point of view, Trypsin and Triton X-100 treated arteries show elastic modules and compliance comparable to native carotids, whereas the use of SDS makes samples stiffer, with a significant decrease in the compliance mean value and an increase in longitudinal and circumferential Young's modules. It is demonstrated that the treatment where Trypsin and Triton X-100 are combined guarantees complete decellularization of carotids, with no significant alteration of biomechanical and structural properties, thus preserving a suitable environment for adhesion, proliferation, and migration of cells.

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.

Parasympathetic vasoactive intestinal peptide (VIP): a likely contributor to clozapine-induced sialorrhoea.

OBJECTIVE: The parasympathetic transmitter vasoactive intestinal peptide (VIP) increases salivary gland blood flow and evokes protein secretion and, in some species, such as rats, a small fluid secretion. It interacts synergistically with muscarinics for protein and fluid output. Human salivary acini are supplied with VIP-containing nerves. We hypothesise that VIP and clozapine, acting together, evoke a volume of saliva greater than the sum of those induced by each drug given separately. It was further considered whether, in the current test situation, circulatory events influenced the magnitude of the secretory response. MATERIAL AND METHODS: Saliva from parotid glands deprived of their autonomic innervation, and saliva and blood from innervated submandibular glands were collected in adrenoceptor antagonist-pretreated pentobarbitone-anaesthetised rats. Initially, the individual and then the combined effects of intravenous doses of VIP and clozapine were established. RESULTS: The submandibular volume response to the combination was 2-3 times higher, while blood pressure and glandular blood flow did not differ from those to VIP alone. The synergism occurred independent of nerves as shown in denervated parotid glands. CONCLUSIONS: From the current preclinical data, we speculate that VIP of parasympathetic origin, by its synergistic interaction with clozapine, may contribute to the clozapine (muscarinic M1-receptor)-induced sialorrhoea in schizophrenics.

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.

Diabetes reduces statherin in human parotid: immunogold study and comparison with submandibular gland.

BACKGROUND AND OBJECTIVE: Alteration of salivary gland secretion is one of the consequences of diabetes. In a recent study on the submandibular gland of diabetic subjects, we found changed expression of statherin, a salivary protein of fundamental importance in preserving tooth integrity, whose reduction was related with the high incidence of oral diseases in patients with diabetes. The goal of this report is to extend the study to human parotid gland and to compare the effects of diabetes on statherin expression with those previously described in submandibular gland. MATERIALS AND METHODS: Fragments of parotid glands obtained from diabetic and non-diabetic patients were fixed, dehydrated, embedded in Epon Resin and processed for the immunogold histochemistry. The staining density was expressed as number of gold particles per µm(2) and statistically evaluated. RESULTS AND CONCLUSIONS: In all samples, statherin reactivity was specifically localized in secretory granules of acinar cells. The statistical analysis showed that labelling density was significantly lower in diabetic than in non-diabetic parotid glands and that diabetes affects protein expression at identical extent in parotid and submandibular glands. The results strengthen the hypothesis that a reduced statherin secretion may be responsible for the higher incidence of oral disorders in diabetic subjects.

Diabetes affects statherin expression in human labial glands.

BACKGROUND AND OBJECTIVE: Salivary statherin, which plays a special role in the defense of tooth integrity, is secreted by both major and minor salivary glands. A significantly reduced expression of this was recently found in human major salivary glands removed from diabetic subjects and was correlated with the high incidence of dental diseases occurring in patients with diabetes. In this study, we measured the density of gold particles indicating statherin immunoreactivity in labial glands to reveal a significant difference between diabetic and non-diabetic patients. MATERIALS AND METHODS: Surgical samples of labial glands obtained from both diabetic and non-diabetic patients were fixed with a glutaraldehyde and paraformaldehyde mixture, embedded in Epon, and treated for immunogold histochemistry using a polyclonal antibody specific for statherin. RESULTS: Statherin immunoreactivity was detected onto small vesicles diffused throughout the cytoplasm of serous cells. Statistical analysis revealed that the number of stained particles was significantly lower in the samples from diabetic subjects than from non-diabetic subjects. CONCLUSIONS: The results indicate that diabetes affects statherin secretion in labial glands and support the hypothesis that the increased susceptibility to oral diseases associated with diabetes could be related with a reduced statherin secretion.

[Genetic aspects of growth hormone deficiency]. / Quelles causes génétiques rechercher en présence d'un déficit en hormone de croissance ?

Congenital growth hormone deficiency (GHD) is a rare cause of growth delay. It should be suspected when other causes of hypopituitarism (sellar tumor, postsurgical or radioinduced hypopituitarism, etc.) have been ruled out. GHD can be isolated (IGHD) or associated with at least one other pituitary hormone deficiency (CPHD) including thyrotroph, lactotroph, corticotroph, or gonadotroph deficiencies. CPHD is caused by mutations of genes coding for pituitary transcription factors involved in pituitary ontogenesis or in the hypothalamic-pituitary axis. Clinical presentation varies, depending on the type and severity of GHD, the age at diagnosis, the association with other pituitary hormone deficiencies, or extrapituitary malformations. Clinical, biological, and radiological work-up is very important to determine for which transcription factor the patient should be screened. There is a wide variety of phenotypes depending on the transcription factor involved: PROP1 (somatolactotroph, thyrotroph, gonadotroph, and sometimes corticotroph deficiencies ; pituitary hyper- or hypoplasia), POU1F1 (somatolactotroph and thyrotroph deficiencies, pituitary hypoplasia), HESX1 (variable pituitary deficiencies, septo-optic dysplasia), and less frequently LHX3 (somatolactotroph, thyrotroph, and gonadotroph deficiencies, deafness, and limited head and neck rotation), LHX4 (variable pituitary deficiencies, ectopic neurohypophysis, cerebral abnormalities), and OTX2 (variable pituitary deficiencies, ectopic neurohypophysis, ocular abnormalities). Mutations of PROP1 remain the first identified cause of CPHD, and as a consequence the first to be sought. POU1F1 mutations should be looked for in the postpubertal population presenting with GH/TSH deficiencies and no extrapituitary malformations. Once genetic diagnosis has been concluded, a strict follow-up is necessary because patients can develop new deficiencies (for example, late-onset corticotroph deficiency in patients with PROP1 mutations). Identification of gene defects allows early treatment of pituitary deficiency and prevention of their potentially lethal consequences. If untreated, the main symptoms include short stature, cognitive alterations, or delayed puberty. An appropriate replacement of hormone deficiencies is therefore required. Depending on the type of transmission (recessive transmission for PROP1 and LHX3, dominant for LHX4, autosomal dominant or recessive for POU1F1 and HESX1), genetic counseling might be proposed. Genotyping appears highly beneficial at an individual and familial level.

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.

Morphological alterations induced by cytochalasin D on serous cells of human submandibular gland in basal and stimulated conditions.

Cytochalasin D (CD) is a fungal toxin which binds to the faster growing end of actin microfilament and inhibits actin polymerization. By an in vitro incubation system of slices of human submandibular glands obtained at surgery, we investigated by light microscope (LM), transmission electron microscope (TEM), and high resolution scanning electron microscope (HRSEM) the morphological changes caused by CD on serous cells. We studied the effects of the drug on secretory events induced by isoproterenol (I) and carbachol (C). With LM, following CD incubation, canaliculi were enlarged and prominent vacuoles were seen throughout the cytoplasm. By TEM, the vacuoles, which in many cases were in continuity with the lumen, represented the distinctive feature of secretory cells. With HRSEM, intercellular canaliculi, seen from their cytoplasmic side, exhibited many small spherical bulges, corresponding to the coated pits seen with TEM and indicating that the retrieval of plasma membrane was arrested at an early phase by the disruption of the actin cytoskeleton. In specimens treated with secretagogues and CD, a consequence reported here for the first time was the presence of dense granules within the vacuoles. The protrusions seen by HRSEM on the cytoplasmic side of intercellular canaliculi, following secretagogues stimulations, appeared peculiar to each stimulants, even if combined with CD, suggesting that besides actin filaments, other components, unaffected by CD, also are involved in the process of exocytosis and related phenomena.

Serous and mucous cells of human submandibular salivary gland stimulated in vitro by isoproterenol, carbachol and clozapine: an LM, TEM, and HRSEM Study.

We have investigated by LM, TEM, and HRSEM the effects of D,L-isoproterenol (beta-adrenergic agent), carbachol (muscarinic agent) and clozapine on biopsy specimens of human submandibular gland stimulated in vitro in an inorganic oxygenated medium. Clozapine is a dibenzodiazepine derivative used in psychotic patients that provokes hypersalivation, a displeasing side effect that often causes discontinuance of therapy. Our findings demonstrate that clozapine acts on salivary mucous and seromucous (serous) cells of the gland as a muscarinic agonist. However, the induced secretory response seems to differ qualitatively and quantitatively from that resulting from carbachol. Thus, in agreement with published data resulting from therapeutic treatments and from experimental studies on rats, the mechanism of clozapine induced hypersialorrhea remains open to further investigation.

Determination of the post-translational modifications of salivary acidic proline-rich proteins.

Human salivary acidic proline-rich proteins were analyzed by electrospray-ion trap mass spectrometry and by matrix-assisted laser desorption/ionization-time of flight mass spectrometry. All acidic-PRP isoforms share a common N-terminal region, which contains a pyroglutamic acid residue at the N-terminus, and two phosphorylation sites on Ser 8 and 22. At the same time, HPLC-MS spectra revealed isoforms of PRP-1 and PRP-3 having a different number of phosphoserine residues, namely, a mono-phosphorylated form of PRP-1 and PRP-3 and a tri-phosphorylated form of PRP-1. The analysis of the masses of tryptic digests suggested that the third phosphate residue should be located on Ser 17. Another protein with a mass of 30,923 amu was detected along the HPLC pattern and MS data of its tryptic digest suggested that it corresponds to the dimer of Pa, the isoform of PRP-1 with a substitution Arg-Cys at 103 position. Finally, structural identification is pending for another post-translational modification of acidic-PRP that provides an increase of 111-114 amu.

Morphofunctional studies on human labial salivary glands.

In this study, the first experimental investigation carried out at the ultrastructural level on mucous cells of human salivary glands, we have examined by light microscopy (LM), transmission electron microscopy (TEM), high resolution scanning electron microscopy (HRSEM), the secretory response of labial glands stimulated in vitro by the beta-adrenergic agent, D,L isoproterenol, and by the muscarinic agent carbachol. For comparison we have used identical methods to study samples of mixed portions of human submandibular glands. Morphological findings obtained here on both submandibular and labial glands mucous cells demonstrate that mucous droplets are released solely by muscarinic stimulation, and that cytological events occurring during secretory discharge are similar to those described by others, using TEM, on stimulated mucous cells of rat sublingual glands. Despite the fact that human labial glands are said to have a prominent cholinergic innervation with scanty adrenergic nerves, the response of seromucous cells in these organs to stimulation with carbachol and with isoproterenol was similar to that observed by us, (using LM, TEM and HRSEM), in serous cells of human major salivary glands.

A high resolution sem study of human minor salivary glands.

By SEM we have investigated the human minor salivary glands using the NaOH method for the visualization of endpieces and myoepithelial cells, and the osmium maceration technique that reveals membranous intracellular structures. With the former method all minor glands, including the posterior deep (Ebner's) lingual glands, consist of tubules sometimes dilated into alveoli, while true acini of the kind observed in human major salivary glands, are absent. Tubules of the posterior deep lingual gland exhibit stellate myoepitelial cells that leave a substantial part of the secretory cells uncovered. The latter cells, at variance with serous cells of major glands, do not show basal folds. In contrast, tubules of the other minor glands, like the mucous ones of major glands, are covered almost completely by band-like myoepithelial cells. The osmium maceration method clearly demonstrates that posterior deep lingual glands are serous in character and that all the other minor glands, together with the predominant mucous cells, possess a variable number of seromucous cells that, despite variations among individuals, increase in order from palatine and posterior superficial lingual (Weber's), to minor sublingual, labial, anterior lingual (Blandin and Nuhn's), and buccal glands.

Application of the Cajal-De Castro method to the laser scanning confocal microscope in studying the peripheral nervous system.

We tested the Cajal-De Castro method with the Laser Scanning Confocal Microscope (LSCM). This method is a valid investigatory tool for anatomical-morphological study and for the tridimensional reconstruction of the structures of the peripheral nervous system. The combination technique makes it possible to exploit the properties of reflection and fluorescence of the deposited reduced silver. The quantity of which is dependent on the different tissue affinity. On the other hand, since scanning in fluorescence is not selective, both the nerve structures and the surrounding tissue are evidenced and the structures that demonstrate more specific affinity for silver salt are more prominent. Being able to study the preparations using both methods contemporaneously makes it possible to obtain very significant tridimensional images that abound in detail. The Cajal-De Castro method also offers interesting possibilities in the morphometric field and in image analysis.