Types Of Acini Research Articles

Morphology and ultrastructure of salivary glands of male treehopper <i>Tricentrus brunneus</i> Funkhouser (Hemiptera: Membracoidea)

The salivary glands of male treehopper Tricentrus brunneus Funkhouser comprise a pair of acinous principal glands each with an anterior lobe and a posterior lobe; a pair of elbow-shaped accessory glands. Every accessory gland connects with the principal gland via a thin accessory salivary duct. The anterior lobe contains three types of acini (I, II and III), whereas the posterior lobe possesses only one type of acinus (IV). Two efferent salivary ducts fuse into a common salivary duct. Different acinis cells are filled with secretory granules that are distinct in size, number, shape and electron-density, indicating a maturation process before secreted. Infoldings in different acini suggest dilution of substances before being secreted. The presence of microvilli in acinus IV and the accessory gland duct possibly indicates the undergoing maturation of secretions. Electron-dense fine granules existed in the accessory gland cells, possibly related to virus transmission.

Ultrastructural mapping of salivary gland innervation in the tick Ixodes ricinus

The salivary gland of hard ticks is a highly innervated tissue where multiple intertwined axonal projections enter each individual acini. In the present study, we investigated the ultrastructural architecture of axonal projections within granular salivary gland type II and III acini of Ixodes ricinus female. Using immunogold labeling, we specifically examined the associations of SIFamide neuropeptide, SIFamide receptor (SIFa_R), neuropeptide pigment dispersing factor (PDF), and the invertebrate-specific D1-like dopamine receptor (InvD1L), with acinar cells. In both acini types, SIFamide-positive axons were found to be in direct contact with either basal epithelial cells or a single adlumenal myoepithelial cell in close proximity to the either the acinar duct or its valve, respectively. Accordingly, SIFa_R staining correlated with SIFamide-positive axons in both basal epithelial and myoepithelial cells. Immunoreactivity for both InvD1L and PDF (type II acini exclusively) revealed positive axons radiating along the acinar lumen. These axons were primarily enclosed by the adlumenal myoepithelial cell plasma membrane and interstitial projections of ablumenal epithelial cells. Our study has revealed the detailed ultrastructure of I. ricinus salivary glands, and provides a solid baseline for a comprehensive understanding of the cell-axon interactions and their functions in this essential tick organ.

Presence of Granular Ducts in Mandibular Gland in Rabbit

The present study focuses on the intralobular ducts present in rabbit mandibular gland, from a histological and histochemical point of view. We harvested mandibular gland samples from five rabbits (approximately six month old), which were paraffin embedded and subsequently stained for histological investigation with hematoxylin-eosin. PAS and Alcian blue reactions were used for histochemical assessment. Results show that mandibular gland in rabbit contains one type of acini, namely serous. Concerning the intralobular ducts, there were three types identified: intercalated, granular and striated. Granules present in the cytoplasm of the cells lining the granular ducts appear acidophilic on hematoxylin-eosin staining procedure. Histochemically, granular cells present a moderately PAS positive material (meaning they secrete neutral mucosubstances) and negative staining to Alcian blue reaction (no acid and sulfated mucosubstances were detected). We highlighted the presence of granular ducts in rabbit mandibular gland, which synthesize neutral mucosubstances according to the histochemical reactions applied.

Structure and Mucopolysaccaride Type of Major Salivary Glands of the Sunda Porcupines ( Hystrixjavanica )

Sunda porcupines are one of the rodent species endemic to Indonesia. There is lack information related to the anatomical structure of their major salivary glands. The study aims to identify the anatomical structures and types of mucopolysaccharides produce d by the major salivary glands of Sunda porcupine. Four tissue samplesof major salivary glands of Sunda porcupine were processed for paraffin method and analyzed by Hematoxylin - Eosin, Alcian Blue - Periodic Acid Schiff, and lectin histochemistry for saphora japonica agglutinin and wheat germ agglutinin . The parotid gland found in the preauricular region and along the posterior surface of the mandible, while the submandibular and sublingual glands were located on the floor of the mouth posterior to each mandib ular canine. The parotid gland was divided into two lobules, each composed by different types of acini in a separate lobulation. HE staining showed that parotid gland looks unique because in the anterior lobe, the acini are dominated by serous cell - type, w hile in posterior lobe are composed by mixed of serous and mucous cell - types. The acini of submandibular gland consist of serous cells - type, but sublingual gland acini covered by mucous cell - type. All of three major salivary glands have complete duct syste m comprising intercalated, striated and excretory ducts. The acini of parotid, submandibular, and sublingual glands contain acid and neutral, neutral, and acid mucopolysaccharides, respectively. Lectin staining using SJA and WGA indicates that acini in sal ivary glands of sunda porcupine contain sugar residue of N - acetylgalactosamine and N - acetylglucosamine which is a derivative of galactose and glucose by the order of intensity from weak to strong in the parotid, sublingual and submandibular glands.The pres ent results provide for the first time data on the anatomical structure and mucopolysaccharides type produced by major salivary glands of Sunda porcupines. Sunda porcupine, major salivary gland, anatomical structure, mucopolysaccharides.

Observations regarding the structure of the parotid and mandibular glands in rabbit

Our study aims to investigate the histological structure of two major salivary glands in adult rabbit. We used 5 adult rabbits, 3 males and 2 females, from a private breeder in Cluj. We harvested the salivary glands, fixed them in 10% buffered formalin, dehydrated in ethanol (increasing concentration), clarified in n-butanol and embedded in paraffin. The sections (5 µm thickness) were stained with Goldner’s trichrome method and examined with an Olympus BX41 light microscope. Histologically, parotid gland in rabbit contains only one type of acini, which presents morphological characteristics of serous acini. In mandibular gland, the acini are all the same, similar to the ones in parotid gland. Concerning the general aspect and dimension they are much larger and polymorphic.

Observations Concerning the Structure of the Major Salivary Glands in Chinchilla (Chinchilla lanigera)

The structure of the salivary glands is different depending on the species and diet. The glandular secretion can be serous, mucous or mixed. Within the same order, for instance in rodents, there are dissimilarities between the major salivary glands, even if the diet is similar. In this study, we used three chinchillas, slaughtered for their fur. We harvested the major salivary glands which were histologicaly processed. The parotid gland in chinchilla is highly similar to the one in other mammal species, regarding its general microscopic aspect. It contains only one type of acini (serous) and numerous secretory ducts. On the other hand, the submaxillary gland has a particular type of acini, with a narrow lumen and cells with a round nucleus. They resemble the serous ones, but the glanular aspect of the cytoplasm suggests that the secretion of this gland is different in comparison to the one in the parotid gland. The structure of the sublingual gland in chinchilla is similar to the one in most of the mammals, containing typical mucous acini, with a foamy cytoplasm. The major salivary glands in chinchilla, highly resemble those in most of the mammal species. The parotid gland presents serous acini and the sublingual one, typical mixed acini. Instead, the submaxillary gland has a particular aspect: its acini do not present the serous demilune, they resemble the typical serous acini (contain round nuclei), but they are larger.

Role of Connexins and Pannexins in the Pancreas.

The pancreas produces enzymes with a digestive function and hormones with a metabolic function, which are produced by distinct cell types of acini and islets, respectively. Within these units, secretory cells coordinate their functioning by exchanging information via signals that flow in the intercellular spaces and are generated either at distance (several neural and hormonal inputs) or nearby the pancreatic cells themselves (inputs mediated by membrane ionic-specific channels and by ionic- and metabolite-permeant pannexin channels and connexin "hemichannels"). Pancreatic secretory cells further interact via the extracellular matrix of the pancreas (inputs mediated by integrins) and directly with neighboring cells, by mechanisms that do not require extracellular mediators (inputs mediated by gap and tight junction channels). Here, we review the expression and function of the connexins and pannexins that are expressed by the main secretory cells of the exocrine and endocrine pancreatic cells. Available data show that the patterns of expression of these proteins differ in acini and islets, supporting distinct functions in the physiological secretion of pancreatic enzymes and hormones. Circumstantial evidence further suggests that alterations in the signaling provided by these proteins are involved in pancreatic diseases.

Morpho-histochemical characterization of the salivary glands of semi-engorged Amblyomma triste (Koch, 1844) (Acari: Ixodidae) female ticks

This study presents the morphological and physiological characterization of the salivary glands of semi-engorged Amblyomma triste females. Unfed individuals were placed on New Zealand White rabbits for feeding and the females, after 4 days, were collected, dissected and the salivary glands were submitted to the application of histological (hematoxylin–eosin technique) and histochemical tests for the detection of protein (bromophenol blue technique, polysaccharides (periodic acid–Schiff technique), lipid (Nile blue technique) and calcium (von Kossa technique). The histological results show that the glandular tissue is composed by a system of ducts and three types of acini (I, II and III). The acini I are formed by a large central cell surrounded by several smaller agranular peripheral cells. Acini II are formed by cells a, c1, c2, c3 and c5, which are full of secretion granules. Acini III are constituted by cells d, e and f; the former two contain secretion granules, the latter is agranular. The glandular histochemical composition was also verified. Data obtained here will certainly help in the understanding of the cellular morphology and of the general physiology of these organs in this specie, providing important information for the creation of scientific bases which will contribute for the development of more specific and efficient methods of control.

Morphology and Ultrastructure of the Salivary Glands of the SpittlebugLepyronia coleopterata(L.) (Hemiptera: Aphrophoridae)

We investigated the salivary glands in Lepyronia coleopterata (L.), and found that the salivary glands are paired structures and consist of principal and accessory glands. Each principal gland contains an anterior lobe and a posterior lobe. Three types of acini (I, II, III) are observed in the anterior lobe, whereas the posterior lobe contains only one type of acini (IV). Rhabdus emerges from the middle portion of the acini III and IV. The oval-shaped accessory gland connects with the principal gland via a long duct. The long duct consists of a slightly coiled basal segment and a highly convoluted distal segment, with the terminal end of the latter constricted and connected with the accessory gland. A slightly convoluted transparent tube connects with the accessory gland at the former's distal end. The accessory gland, accessory salivary duct and the accessory salivary tube are observed for the first time in spittlebugs. Ultrastructurally, each type of acinus is made up of one type of secretory cells, but the rhabdus comprises two types of cells. Secretory granules in different type of cells are different in size, shape and electron density, which indicate either different materials are synthesized or these materials undergo a process of maturation. The rhabdus is empty in structure and contains several channels, with the lumen filled with abundant fine granular materials. Fine dark granules existed in the periphery of some secretory granules are probably virus particles. Microorganisms are observed in the cells of the acini I, III and rhabdus.

Análise microscópica e ultraestrutural das glândulas salivares mandibulares de Procyon cancrivorus

Devido a importância ecológica dos Procyon cancrivorus, o objetivo deste trabalho foi caracterizar morfologicamente e ultra estruturalmente a glândula salivar mandibular desta espécie. Foram utilizadas 10 pares (direita e esquerda) de glândulas salivares mandibulares de cinco animais adultos. As glândulas salivares mandibulares foram dissecadas e mensuradas com paquímetro de precisão e posteriormente processadas por técnica rotineira de histologia e coradas por HE (hematoxilina e eosina) e Picrossírius. Fragmentos das glândulas foram processados para análise em microscopia eletrônica de varredura (MEV). As glândulas salivares mandibulares direitas e esquerdas de P. cancrivorus apresentaram-se lobuladas, formato ovalado, e posicionadas entre a fossa atlantis e o osso basihyoideum do crânio. Microscopicamente, estas glândulas estavam revestidas por uma cápsula de tecido conjuntivo denso não modelado, a qual adentra a glândula através de septos, dividindo-a em lóbulos. Nos septos de tecido conjuntivo estão presentes vasos sanguíneos e nervos, além de ductos interlobulares excretores. Dentro dos lóbulos das glândulas salivares mandibulares, são encontrados ductos do tipo estriado e intercalar, além de predomínio de ácinos do tipo mucoso. Os resultados permitem concluir que as glândulas salivares mandibulares dos Procyon cancrivorus, seguem o padrão estrutural descrito em outras espécies de mamíferos. No entanto os tipos de ácinos podem variar entre as espécies, sendo, portanto, necessários futuros estudos histoquímicos e de biologia celular para desvendar a importância dessa variação para a espécie aqui estudada, comparando com seu hábito alimentar.

Cytotoxic effects of permethrin in salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi-engorged females

Because of the medical and veterinary importance of ticks and the wide use of synthetic chemical substances such as permethrin (active ingredient of Advantage® Max3 – Bayer)for their control, this study evaluated the effects of different concentrations (206, 1031 and 2062ppm) of the acaricide on the salivary glands of Rhipicephalus sanguineus semi-engorged females. Results showed that permethrin is a potent substance that acts morpho-physiologically in the tick glandular tissue, causing changes in the acini shape intense vacuolation in acinar cells, and disruption of the tissue by cell death process, with subsequent formation of apoptotic bodies, especially at higher concentrations, thus precluding the accurate identification of different types of acini. Importantly, it is demonstrated that permethrin acts on salivary gland tissue, as well as affecting the nervous system, accelerating the process of glandular degeneration, and interfering with the engorgement process of female ticks, preventing them from completing the feeding process.

Salivary glands of Amblyomma cajennense (Acari: Ixodidae): a histological and an ultrastructural overview

The present study on the salivary glands of semi-engorged Amblyomma cajennense females has identified the various cell types present in this tissue and allowed its morphohistochemical characterization. Marking techniques were applied to detect polysaccharides (PAS), proteins (bromophenol blue), lipids (Nile blue) and calcium (von Kossa), as well as those of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results obtained by TEM showed and confirmed that these individuals' glands are also formed by round acini that are connected to the common excretory duct through acinar and intermediate ducts. Histological data as well as ultrastructural ones showed that the glands are formed by types I, II and III acini. In this study with salivary glands polysaccharides, proteins, lipids and calcium were observed in the cytoplasm and/or cell secretion granules-both free or forming complexes, as the intensity of the marking varied according to the cell as well as the type of acini analyzed, showing the structural and functional complexity of the tick salivary glands, characteristics that give the multifunctional character to this organ.

Role of an aquaporin in the sheep tick Ixodes ricinus: Assessment as a potential control target

Ticks undergo tremendous osmoregulatory stress as they take on up to 100 times their body weight in blood, returning about 75% of the ingested water and ions via their saliva into the host. We postulated that water channels, or aquaporins, involved in this mass water transport might be good targets for acaricide development. An aquaporin ( IrAQP1) identified in the sheep tick, Ixodes ricinus, was present only in tissues involved in mass water flux, namely the gut, rectal sac and especially abundant in the salivary glands. IrAQP1 was localised by in situ hybridisation in specific cell and acini types, possibly Type III acini, but absent from the type I acini that are responsible for rehydration of ticks in the non-feeding phase. Gene knockdown of IrAQP1 in isolated salivary glands completely inhibited dopamine-stimulated secretion. Further, IrAQP1 knockdown adult females had 50% reduced body weight gains over the first 5 days feeding on an artificial feeding apparatus and 21% at the point of engorgement on hosts. Haemolymph osmolarity was increased in the IrAQP1-knockdown ticks. Importantly, the blood volume ingested per body weight was reduced by 30%. Overall, it would appear that water passage from the gut to the saliva was disrupted and tick guts were simply too “full” to ingest more blood. However, double-stranded RNA interference of IrAQP1 did not affect mortality of the ticks which successfully fed to detachment at day 9. Overall, our data indicate that IrAQP1 plays a pivotal role in blood meal water handling through the gut and salivary gland, and although its disruption by double-stranded RNA interference dramatically affects feeding performance, ticks remained feeding on the host with subsequent potential pathogen transmission and, therefore, IrAQP1 is not a suitable candidate target for tick control.

Markers of cell death in salivary glands of males of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari, Ixodidae)

The salivary glands of Rhipicephalus sanguineus males at stages: unfed (control), at day seven post-attachment, and at days three and seven post-detachment from the host were examined using methods of enzymatic analysis and cell viability. At these stages of feeding, different staining patterns were observed in the cells of type IV, III, II and I acini, which were affected by degeneration in this sequence. Acid phosphatase reaction was inversely proportional to that of ATPase, while ATPase reaction was proportional to membrane integrity. Salivary gland cells of unfed males exhibited intact nucleus and plasma membrane, suggesting that the acid phosphatase detected may participate in the normal physiology of acini. In males at day seven post-attachment, intact membranes were observed in almost all types of acini, as well as stronger reaction for acid phosphatase, nuclear changes, and decrease in ATPase reaction, changes associated with the degenerative process. At days three and seven post-detachment degeneration progress, being observed loss of membrane integrity, nuclear changes, prominent decrease in ATPase reaction, and an increase in acid phosphatase reaction in the first case and a decreased of it at day seven post-detachment from the host. During cell death, alterations occurred in the following sequence: a) nuclear changes, b) loss of ATPase reaction, c) loss of integrity of the plasma membrane, and d) increase of acid phosphatase. The latter might be associated with the late degradation of cytoplasmic remnants, characterizing the process of cell death in glands of R. sanguineus males as atypical or non-classic apoptosis.

Death by apoptosis in salivary glands of females of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae)

The salivary glands of females of the tick Rhipicephalus sanguineus at three feeding stages: unfed, engorged, and at day three post-engorgement, were subjected to cytochemical methods of enzymatic analysis and cell viability. Comparing glands at these stages, was observed distinct staining patterns in cells of different types of acini, specially in degenerating types III, II, I, which were affected in this sequence by cell death. This study also revealed changes in: nuclei, staining intensity for acid phosphatase and ATPase activities, and permeability of the plasma membrane. Acid phosphatase activity was inversely proportional to that of ATPase, while ATPase activity was always proportional to membrane integrity. The glands of unfed females exhibited high metabolic activity and cells with intact nucleus and plasma membrane, suggesting that the presence of acid phosphatase detected in these individuals may participate in the normal physiology of some acini, as they were not undergoing degeneration. In acini I and II of engorged females, we observed cells with intact membranes, as well as changes characterized by nuclear changes, decrease in ATPase activity, and stronger acid phosphatase activity. At day three post-engorgement, degeneration progressed to more advanced stages, loss of membrane integrity was observed in most cells (of some type I acini, most type II acini, and all type III acini), as well as prominent nuclear changes, decrease in ATPase activity, and intense acid phosphatase activity, resulting in apoptotic bodies. During the death of cells nuclear changes preceded cytoplasmic ones in the following sequence: nuclear changes, loss of ATPase activity, loss of integrity of the plasma membrane, increase in acid phosphatase activity, and formation of apoptotic bodies. The presence of acid phosphatase with a secondary role (late) during cell death, degrading final cell remnants, characterized this process in the glands of R. sanguineus females as atypical or non-classic apoptosis.

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

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

Relevant role of the labrum associated with the mandibles in the Lophogaster typicus digestive function

This study was aimed at understanding the diet and the digestive function of the deep-living Lophogastrida species Lophogaster typicus (Mysidacea: Lophogastrida). Scanning electron microscopy (SEM) investigations have revealed that the mandibles exhibit typical features of a carnivorous diet, i.e. large and sharp incisor process and small molar one with only few scales. The analysis of gut contents confirms morphological data as crustacean remains have been recognized. However, the presence of a large quantity of unidentifiable soft particulate matter also indicates a saprophagous tendency. The external asymmetrical edge of the labrum consists of a small grinding area. The entire external face of the labrum exhibits numerous pores, which are related with glandular units. These units are organized into acini of two to four large cells. Two types of acini have been observed, i.e. with dark or clear cells. According to ultrastructural and cytochemical data, labral secretions are believed to be mucopolysaccharidic (for clear acini) and enzymatic components (for dark acini), and are therefore involved both in coating and in digesting the food. Moreover, presence of neuronal endings and endocrine cells, both associated with glandular units, and comparison between glandular units in starved and fed animals suggest a controlled release of the secretions. Therefore, the labrum plays a crucial role in the digestive function of the lophogastrid crustacean L. typicus, as it involves both mechanical and chemical breakdown of the food.

Evidence to Suggest Morphological and Physiological Alterations of Lacrimal Gland Acini with Ageing

This study investigates changes in the morphology and physiology of lacrimal gland acinar cells with age. Changes in microstructural appearance of the acinar cells, the type and distribution of the different acini in glands and the secretory granules within the acini were examined in glands from animals of 3–5, 9, 12, 20, 24 and 28 month old rats. Differences in the secretory capacity of the acinar cells were also examined in animals of each age-group, with the exception of 28 months.The typical acini of young glands (3–5 months) were of the serous type. This was also true of 9 month glands, although there was a significant reduction in their overall distribution compared to young glands. The acini in the 12 month glands were predominantly of the seromucous type and appeared to be at the expense of the serous acini which were further significantly reduced compared to 3–5 and 9 month glands. This remained the prevalent acini type in 20 month glands, however by 24 months there was a significant increase in the occurrence of mucous acini and this time appeared to be at the expense of the seromucous acini which were significantly reduced in glands of this age-group. The predominant acinar cell in 28 month glands, like 24 month glands, was of the mucous variety. Qualitative EM studies revealed a progressive change in the secretory products of the lacrimal gland acini, strongly correlating to changes in acinar cell type. Typical acini of both 3–5 and 9 month glands contained numerous protein secretory granules. The seromucous acini also of these age groups contained both protein and mucous secretory granules, with the protein secretory granules in higher abundance. By 12 months the typical seromucous acini was packed with both protein and mucous secretory granules of equal proportions. However, by 20 months the predominant seromucous acini contained fewer protein secretory granules and elevated occurrence of mucous secretory granules. By 24 and 28 months the acini contained even fewer protein secretory granules and the typical acinar cell was of the mucous type containing exclusively mucous secretory granules. The secretory capacity of the acini was also altered with age. Maximum protein output in response to cholinergic stimulation resulted in an initial significant increase with ageing from 3–5 months to 9 and 12 months followed by a later significant age-dependent reduction in output. However, maximal peroxidase release from acinar cells of 3–5 and 9 month glands was the same. This was followed by a significant age-dependent reduction in peroxidase release. Furthermore, the concentrations required to evoke these responses differed with age.These results present evidence to suggest that acinar cells of the lacrimal gland undergo progressive alterations with age. The type of acini changing initially from serous to seromucous acini (intermediate phase) followed by a gradual transformation of the seromucous acini to mucous acini. This in turn changes the properties of the acini from protein producing and secreting acini to mucous producing and secreting acini. The results also suggest a reduction in the ability of the acini to synthesise proteins with age and altered responsiveness to cholinergic stimulation to secrete proteins. These findings may help in explaining the occurrence of altered protein/tear secretion with ageing.

Age-related changes in morphology and secretory responses of male rat lacrimal gland

This study investigates the differences in the outward appearance and morphology of lacrimal glands, the morphology within the lacrimal acinar cells and the secretion of protein from acinar cells of young (3–5 months) and aged (20 and 24 months) male rats. The appearance of the glands, as seen by the naked eye, differed between the three age-groups. The lacrimal gland of young animals was a smooth pink tissue, while the tissue from aged animals appeared lobular and white in colour, thought to result from infiltration of fatty/connective tissue. Glands from 24 month old animals had a more pronounced lobular appearance than the glands from 20 month old animals. Light microscopy studies revealed that as the animals aged there was evidence of progressive morphological changes. These changes included thickening of the connective tissue sheath, chronic inflammation with increased infiltration by mast cells, patchy destruction of ductal and vascular tissues, enlargement of lacrimal ducts, luminal swelling of the acini, and changes in acinar type. Electron microscopy (EM) studies revealed the presence of 3 types of acini in the rat lacrimal gland: acini which contained only protein secretory granules (serous acini), acini which contained protein and mucous secretory granules (seromucous acini), and acini which contained only mucous secretory granules (mucous acini). In young glands the majority of acini were serous with a few seromucous acini and even fewer mucous acini. In aged glands there were significant reductions in serous acini (ANOVA; P<0.01) when compared to the young glands. In 20-month-old glands, there were marked increases in the percentage occurrence of seromucous acini, while in 24 month old glands, there were large increases in the relative number of mucous acini. Qualitative EM studies demonstrated that the typical acini from young glands contained numerous protein secretory granules. Ageing was associated with a progressive loss of protein (serous) secretory granules. Furthermore, marked changes and patchy destruction of the endoplasmic reticulum and Golgi apparatus were observed in acini of glands from aged rats when compared to acini of glands from young rats. Measurement of total protein output from acini revealed a significant (Student's t-test, P<0.05) decrease in protein secretion from aged glands compared to glands from young animals. These results suggest that not only is there considerable structural damage, chronic inflammation and mast cell infiltration to the lacrimal gland with ageing, but also possible redifferentiation of acini from serous to seromucous and then to mucous acini. Furthermore, the results also suggest a reduction or an inability of the acini to synthesise and to secrete protein from glands of aged animals compared to glands of young rats. All of these changes appear to occur more rapidly as the rats mature between 20 and 24 months. These findings provide a morphological basis to explain the phenomenon of reduced tear/protein secretion with ageing.

Morphology of the Digestive and Reproductive Systems of Dalbulus maidis and Graminella nigrifrons (Homoptera: Cicadellidae)

The corn leafhopper, Dalbulus maidis (DeLong and Wolcott) (Homoptera: Cicadellidae) is the principal vector of maize rayado fino marafivirus, corn stunt spiroplasma and maize bushy stunt phytoplasma in tropical and subtropical areas of the Western Hemisphere. The black-faced leafhopper, Graminella nigrifrons (Fobes) (Homoptera: Cicadellidae) is the principal vector of maize chlorotic dwarf waikavirus in North America. The morphology of their digestive and reproductive systems was studied by light microscopy, and illustrations were made to aid in dissection and injection of pathogenic inoculum for various vector-pathogen relation studies. In both species, two salivary glands, located one on each side of the head, extend into the mesothorax. Each gland consists of principal and accessory glands. The former contains an anterior lobe and posterior lobe. Two types of acini are present in the anterior lobe, whereas the posterior lobe has four acini. The accessory glands of D. maidis and G. nigrifrons are very similar rod to elbow-shaped structures. The esophagus of both species is a narrow tube originating from the pharynx and extending to the anterior midgut below the filter chamber. The anterior midgut is a large sac-like structure extending from the metathorax through the entire length of the abdomen, and then ascends backward to the anterior of the midgut to form the filter chamber. The filter chamber of D. maidis has a more complex structure than that of G. nigrifrons. There are two pairs of Malpighian tubules in both species. The central tubule is formed from a pair of fused tubules within the filter chamber; the other tubules extend along the front of the hindgut. In G. nigrifrons the three tubules run parallel to each other along the top of the posterior midgut. In D. maidis, the central tubule and one tubule from the other pair run along the interior of the deep loop of the posterior midgut; the other tubule runs along the exterior of the loop. The ovaries of both species contain six ovarioles. Each ovariole consists of a terminal filament, a germarium, developing oocytes and eggs within follicles and a pedicle. The ovarioles contain six follicles. In G. nigrifrons each ovariole usually contains only one egg within the last follicle whereas the ovarioles of D. maidis often contain two eggs. The ovarioles open into the lateral oviduct, common oviduct and the vagina. The spermathecae open into the common oviduct. A collaterial gland and accessory glands are present. The male of both species has two lateral testes each with six follicles. A pair of accessory glands arise at the posterior of each seminal vesicle and open into the lateral ejaculatory duct.