Apical Plasmalemma Research Articles

Mammary lipid secretion: a reassessment.

Mammary lipid secretion is generally held to be unique and remarkably uniform between the many different orders of mammals. It produces a unit membrane-bounded milk fat globule (MFG). The unit membrane is separated from the lipoprotein boundary of what was the cytoplasmic lipid droplet (CLD) boundary by a uniform layer of cytoplasmic proteins. In 3-8% of the MFG in all species examined this cytoplasmic layer widens to include cytoplasmic organelles which are referred to as 'crescents'. This defines the MFG secretion as apocrine indicating a closely regulated process which minimises the loss of mammary epithelial cell (MEC) cytoplasm. The apocrine nature of the secretion might be expected since the evolution of the mammary gland is considered to be from an apocrine secreting skin gland. This short Research Reflection review is designed to investigate the exact cytoplasmic interactions which allow such efficient lipid secretion. There are two main scenarios: one which assumes that the observed close association between CLD and GV results in the CLD being released as a consequence of sequential exocytosis of the content of the associated GV. The second assumes that the CLD and the MEC apical plasmalemma interact in some way which causes the CLD to rise out of the cytoplasm enveloped in the plasmalemma. Here I present the evidence for the two possibilities. The first scenario is favoured, but the second cannot be ruled out.

The Autophagy Marker LC3 Is Processed during the Sperm Capacitation and the Acrosome Reaction and Translocates to the Acrosome Where It Colocalizes with the Acrosomal Membranes in Horse Spermatozoa

Despite its importance in somatic cells and during spermatogenesis, little is known about the role that autophagy may play in ejaculated spermatozoa. Our aim was to investigate whether the molecular components of autophagy, such as microtubule-associated protein 1 light chain 3 (LC3), are activated in stallion spermatozoa during the capacitation and acrosome reaction and if this activation could modulate these biological processes. To analyze the autophagy turnover, LC3I and LC3II proteins were assessed by western blotting, and the ratio between both proteins (LC3II/LC3I) was calculated. In somatic cells, this ratio indicates that autophagy has been activated and similar LC3 processing has been described in mammalian spermatozoa. The subcellular localization of autophagy-related proteins was assessed by immunofluorescence with specific antibodies that recognized Atg16, Beclin-1, and LC3. The colocalization of acrosomal membranes (PNA) and LC3 was studied by confocal microcopy, and the acrosome reacted cells were quantified by flow cytometry. The incubation of stallion sperm in capacitating conditions (BWW; 3 h) significantly increased LC3 processing. This increment was three to four times higher after the induction of the acrosome reaction in these cells. LC3 was mainly expressed in the head in mature ejaculated sperm showing a clear redistribution from the post-acrosomal region to the acrosome upon the incubation of sperm in capacitating conditions (BWW, 3 h). After the induction of the acrosome reaction, LC3 colocalized with the acrosome or the apical plasmalemma membranes in the head of the stallion spermatozoa. The inhibition or activation of autophagy-related pathways in the presence of autophagy activators (STF-62247) or inhibitors (E-64d, chloroquine) significantly increased LC3 processing and increased the percent of acrosome reacted cells, whereas 3-methyladenine almost completely inhibited LC3 processing and the acrosome reaction. In conclusion, we found that sperm capacitation and acrosome reaction could be regulated by autophagy components in sperm cells ex vivo by processes that might be independent of the intraluminal pH of the acrosome and dependent of LC3 lipidation. It can be speculated that, in stallion sperm, a form of noncanonical autophagy utilizes some components of autophagy machinery to facilitate the acrosome reaction.

Detection and characterization of rice orange leaf phytoplasma infection in rice and Recilia dorsalis

Phytoplasmas are small bacterial parasites that lack cell walls and are transmitted in a persistent-propagative manner by insect vectors. However, detailed multiplication patterns and movements of phytoplasmas within host plant and insect vector remain elusive. In this study, a specific antibody against the immunodominant membrane protein (Imp) of rice orange leaf phytoplasma (ROLP) was generated and subjected to the frozen section immune gold labeling assay, immune gold labeling microscopy, and immune fluorescence labeling assay to investigate how ROLP enters, propagates, and spreads in rice and its leafhopper vector Recilia dorsalis at the ultrastructural level. During acquisition and transmission by insect vectors, ROLPs could squeeze and penetrate the multiple membrane/tissue barriers such as microvilli, apical plasmalemma, and basal lamina in the intestines or salivary glands by endocytosis- and exocytosis-like mechanism. Furthermore, ROLP infection is restricted to the type IV and V cells of salivary glands. In contrast to the classical binary fission used by most bacteria, electron microscopy reveals that ROLP exploits an asymmetrical budding strategy to replicate in plant hosts and insect vectors. In this process, a cellular protrusion of ROLP forms a bud to reproduce the offspring by fission at the junction between the bud and the ROLP main body. These results clarify the infection characteristics of ROLP in rice and R. dorsalis, which will help guide the formulation of ROLP prevention and control strategies.

A leafhopper saliva protein mediates horizontal transmission of viral pathogens from insect vectors into rice phloem

Numerous insects transmit viruses together with saliva to plant phloem, but the roles of saliva components remain elusive. Here, we report that calcium-binding protein (CBP), a universal insect saliva protein, is modified to benefit horizontal transmission of a devastating rice reovirus into plant phloem. CBP effectively competes with virus-induced filaments to target and traverse actin-based apical plasmalemma into saliva-stored cavities in salivary glands of leafhopper vector. Thus, the inhibition of CBP expression by viral infection facilitates filament-mediated viral secretion into salivary cavities and then into plant phloem. Furthermore, virus-mediated reduction of CBP secretion causes an increase of cytosolic Ca2+ levels in rice, triggering substantial callose deposition and H2O2 production. Thus, viruliferous vectors encounter stronger feeding barriers, probe more frequently, and secrete more saliva into plants, ultimately enhancing viral transmission. We thus conclude that the inhibition of CBP secretion facilitates viral secretion and increases host defense response to benefit viral transmission.

Exosomes mediate horizontal transmission of viral pathogens from insect vectors to plant phloem.

Numerous piercing-sucking insects can horizontally transmit viral pathogens together with saliva to plant phloem, but the mechanism remains elusive. Here, we report that an important rice reovirus has hijacked small vesicles, referred to as exosomes, to traverse the apical plasmalemma into saliva-stored cavities in the salivary glands of leafhopper vectors. Thus, virions were horizontally transmitted with exosomes into rice phloem to establish the initial plant infection during vector feeding. The purified exosomes secreted from cultured leafhopper cells were enriched with virions. Silencing the exosomal secretion-related small GTPase Rab27a or treatment with the exosomal biogenesis inhibitor GW4869 strongly prevented viral exosomal release in vivo and in vitro. Furthermore, the specific interaction of the 15-nm-long domain of the viral outer capsid protein with Rab5 induced the packaging of virions in exosomes, ultimately activating the Rab27a-dependent exosomal release pathway. We thus anticipate that exosome-mediated viral horizontal transmission is the conserved strategy hijacked by vector-borne viruses.

Aminoglycerophospholipid flipping and P4-ATPases in Toxoplasma gondii

Lipid flipping in the membrane bilayers is a widespread eukaryotic phenomenon that is catalyzed by assorted P4-ATPases. Its occurrence, mechanism, and importance in apicomplexan parasites have remained elusive, however. Here we show that Toxoplasma gondii, an obligate intracellular parasite with high clinical relevance, can salvage phosphatidylserine (PtdSer) and phosphatidylethanolamine (PtdEtn) but not phosphatidylcholine (PtdCho) probes from its milieu. Consistently, the drug analogs of PtdCho are broadly ineffective in the parasite culture. NBD-PtdSer imported to the parasite interior is decarboxylated to NBD-PtdEtn, while the latter is not methylated to yield PtdCho, which confirms the expression of PtdSer decarboxylase but a lack of PtdEtn methyltransferase activity and suggests a role of exogenous lipids in membrane biogenesis of T. gondii. Flow cytometric quantitation of NBD-probes endorsed the selectivity of phospholipid transport and revealed a dependence of the process on energy and protein. Accordingly, our further work identified five P4-ATPases (TgP4-ATPase1-5), all of which harbor the signature residues and motifs required for phospholipid flipping. Of the four proteins expressed during the lytic cycle, TgP4-ATPase1 is present in the apical plasmalemma; TgP4-ATPase3 resides in the Golgi network along with its noncatalytic partner Ligand Effector Module 3 (TgLem3), whereas TgP4-ATPase2 and TgP4-ATPase5 localize in the plasmalemma as well as endo/cytomembranes. Last but not least, auxin-induced degradation of TgP4-ATPase1-3 impaired the parasite growth in human host cells, disclosing their crucial roles during acute infection. In conclusion, we show selective translocation of PtdEtn and PtdSer at the parasite surface and provide the underlying mechanistic and physiological insights in a model eukaryotic pathogen.

Expression of endogenous phospholipase D1, localized in mouse submandibular gland, is greater in females and is suppressed by testosterone.

To clarify the signal transduction mechanism in the differentiation and secretion of salivary glandular cells, the present study was attempted to examine in the submandibular gland (SMG) of mice, the expression and localization of phospholipase D1 (PLD1), one of the important effector molecules working in response to the activation of intramembranous receptors by first messengers. In immunoblotting analysis, the expression of PLD1 was high at postnatal 4weeks (P4W) and decreased at P8W, and it was at negligible levels at newborn stage (P0W) and postnatal 2weeks (P2W). The expression of PLD1 was greater in females, and it was suppressed by administration of testosterone to female mice. In immuno-light microscopy, immunoreactivity for PLD1 at P4W was moderate to intense, in the forms of dots and globules mainly in the apical domains of immature granular convoluted tubule (GCT)-cells localized largely in the proximal portion of the female GCT. By P8W, it decreased in intensity and remained weak to moderate along the apical plasmalemma of cells throughout the course of the female GCT, whereas it was faint throughout the GCT of the male SMG at P4W and negligible at P8W. In immuno-electron microscopy, immature GCT-cells characterized by electron-lucent granules were immunoreactive and the immunoreactive materials were deposited close to, but not within, those granules. Typical GCT cells, characterized by electron-dense granules, were immunonegative. No significant immunoreaction for PLD1 was seen in acini of SMGs of either sex at any time point examined. It is suggested that PLD1 is involved in the signaling for secretion of immature GCT cells and influences differentiation of these cells, probably through their own secretory substances.

Localization of phosphatidylinositol 4-phosphate 5-kinase (PIP5K) α, β, γ in the three major salivary glands insitu of mice and their response to β-adrenoceptor stimulation.

Phosphatidylinositol 4-phosphate 5-kinase (PIP5K), which is composed of three isozymes (α, β and γ), catalyzes the production of phosphatidylinositol bisphosphate (PIP2). This phospholipid functions in membrane trafficking, as an anchor for actin cytoskeletons and as a regulator of intramembranous channels/transporters. It is also a precursor of such second messengers as diacylglycerol, inositol triphosphate and phosphatidylinositol (3,4,5)-triphosphate. In the present study, the expression and localization of endogenous PIP5Ks were examined in the three major salivary glands of young adult mice insitu. In western blotting of normal control glands, immunoreactive bands for individual PIP5Ks were detectable, with the highest density in the parotid gland and the weakest density in the submandibular gland. In immuno-light microscopy under non-stimulated condition, weak immunoreactivity for PIP5Kα was confined to the apical plasmalemma in parotid, but not sublingual or submandibular, acinar cells. Immunoreactivity for PIP5Kβ was weak to moderate and confined to ductal cells but not acinar cells, whereas that for PIP5Kγ was selectively and intensely detected in myoepithelial cells but not acinar cells, and it was weak in ductal cells in the three glands. In western blot of the parotid gland stimulated by isoproterenol, a β-adrenoceptor agonist, no changes were seen in the intensity of immunoreactive bands for any of the PIP5Ks. In contrast, in immuno-light microscopy, the apical immunoreactivity for PIP5Kα in parotid acinar cells was transiently and distinctly increased after the stimulation. The increased immunoreactivity was ultrastructurally localized on most apical microvilli and along contiguous plasma membrane, where membranous invaginations of various shapes and small vesicles were frequently found. It was thus suggested that PIP5Kα is involved in post-exocytotic membrane dynamics via microvillous membranes. The present finding further suggests that each of the three isoforms of PIP5K functions through its product PIP2 discretely in different cells of the glands to regulate saliva secretion.

Co-localization of endogenous Arf6 and its activator EFA6D in the granular convoluted tubule cells of mouse submandibular glands under normal conditions and when stimulated by isoproterenol, noradrenaline and carbachol

ObjectiveThis study proposed to investigate the localization at light and electron microscopic levels of Arf6 and its activator EFA6D in the mouse submandibular gland (SMG) under normal conditions and when stimulated by adrenergic or cholinergic agonists. Materials and methodsSMGs of male adult mice were utilized for immunoblotting and immuno-light and -electron microscopic analyses. Isoproterenol and noradrenalin were used as adrenergics, while carbachol was used for the cholinergic stimulant. SMGs were examined at 15, 30, 60 and 120min after intraperitoneal injection of these agents. ResultsImmunoreactivities for both Arf6 and its activator EFA6D were similarly intense in the basolateral domain of GCTs, but no significant immunoreactivities were seen in the apical domain of GCT cells or any domain of acinar cells under normal conditions. In immuno-electron microscopy, the immunoreactive materials were mainly deposited on the basolateral plasma membranes and subjacent cytoplasm. Shortly after injection of isoproterenol and noradrenaline, but not carbachol, the immunoreactivities for both molecules were additionally seen on the apical plasmalemma of most, if not all, GCT cells, but not acinar cells. ConclusionThe present findings suggest that the direct involvement of Arf6/EFA6D in regulatory exocytosis at the apical plasma membrane of acinar and GCT cells is apparently to be smaller, if present, than that of endocytosis at the basolateral membranes of GCT cells under normal conditions. This also suggests that the two molecules function additionally at the apical membrane of GCT cells for modulation of saliva secretion under β-adrenoceptor stimulation.

Filamentous Structures Induced by a Phytoreovirus Mediate Viral Release from Salivary Glands in Its Insect Vector.

Numerous viral pathogens are persistently transmitted by insect vectors and cause agricultural or health problems. These viruses circulate in the vector body, enter the salivary gland, and then are released into the apical plasmalemma-lined cavities, where saliva is stored. The cavity plasmalemma of vector salivary glands thus represents the last membrane barrier for viral transmission. Here, we report a novel mechanism used by a persistent virus to overcome this essential barrier. We observed that the infection by rice gall dwarf virus (RGDV), a species of the genus Phytoreovirus in the family Reoviridae, induced the formation of virus-associated filaments constructed by viral nonstructural protein Pns11 within the salivary glands of its leafhopper vector, Recilia dorsalis Such filaments attached to actin-based apical plasmalemma and induced an exocytosis-like process for viral release into vector salivary gland cavities, through a direct interaction of Pns11 of RGDV and actin of R. dorsalis Failure of virus-induced filaments assembly by RNA interference with synthesized double-stranded RNA targeting the Pns11 gene inhibited the dissemination of RGDV into salivary cavities, preventing viral transmission by R. dorsalis For the first time, we show that a virus can exploit virus-induced inclusion as a vehicle to pass through the apical plasmalemma into vector salivary gland cavities, thus overcoming the last membrane barrier for viral transmission by insect vectors.IMPORTANCE Understanding how persistent viruses overcome multiple tissue and membrane barriers within the insect vectors until final transmission is the key for viral disease control. The apical plasmalemma of the cavities where saliva is stored in the salivary glands is the last barrier for viral transmission by insect vectors; however, the mechanism is still poorly understood. Here we show that a virus has evolved to exploit virus-induced filaments to perform an exocytosis-like process that enables viral passage through the apical plasmalemma into salivary cavities. This mechanism could be extensively exploited by other persistent viruses to overcome salivary gland release barriers in insect vectors, opening new perspectives for viral control.

Immunohistochemical localization of cannabinoid receptor 1 (CB1) in the submandibular gland of mice under normal conditions and when stimulated by isoproterenol or carbachol

ObjectiveWe wished to investigate the subcellular localization of CB1, a receptor for the endocannabinoids in mouse submandibular glands (SMGs) under normal conditions and when stimulated by adrenergic or cholinergic agonists. Materials and methodsSMGs of both male and female adult mice were utilized for immunoblotting and immuno-light and –electron microscopic analyses. Isoproterenol and carbachol were used as adrenergic and cholinergic stimulants, respectively. SMGs were examined at 15, 30, 60 and 120min after intraperitoneal injection of these agents. ResultsSelective localization of intense immunoreactivity for CB1 in the granular convoluted ductal cells was confirmed by immunoblotting and the antigen absorption test. In SMGs of control male mice, CB1-immunoreactivity was evident on the basolateral plasma membranes, including the basal infoldings, but was absent on the apical membranes in the ductal cells. Localization and intensity of CB1-immunoreactivity were essentially the same in SMGs of female mice. The immunoreactivity was transiently localized in the apical plasmalemma of some acinar and granular ductal cells of male SMGs shortly after stimulation by isoproterenol, but not by carbachol. ConclusionThe present finding suggests that CB1 functions primarily in the basolateral membranes of the granular convoluted ductal cells of SMGs under normal conditions, and that the CB1 can function additionally in the apical membrane of acinar and granular ductal cells for modulation of the saliva secretory condition via adrenoceptors.

The ultrastructure of the integument and proventriculus in the raptorial rotifer Cupelopagis vorax (Monogononta: Collothecaceae: Atrochidae)

AbstractMembers of the sessile rotifer species Cupelopagis vorax are unusual ambush predators that live permanently attached to submerged freshwater plants. Previous light microscopical research has revealed several uncommon features in this species including a stellate‐patterned integument and an expansive foregut region called the proventriculus. In this study, we apply transmission electron microscopy to explore the ultrastructure of both the integument and foregut to determine how they differ from other rotifers. Our results reveal that the integument is covered by a thick glycocalyx and is patterned with tubercles that originate from the intracytoplasmic lamina (ICL) within the syncytial epidermis. The ICL forms an apical layer within the syncytium, is electron dense and mostly amorphous, and forms tubercles up to 2.3 μm; these tubercles probably account for the patterned appearance of the integument and are similar to what has been found in other gnesiotrochan rotifers. The basal cytoplasm is highly granular and contains two types of membrane‐bound vesicles: large ovoid vesicles (320–411 nm) with amorphous, opaque contents, and secretory bulbs (110–264 nm) with electron‐lucent cores and occasionally electron‐dense contents. Only the secretory bulbs were observed to form connections to the apical plasmalemma, and so are probably exocytotic. Internally, the proventriculus is a large distensible sack that connects the anterior pharyngeal tube to the posterior mastax. The proventricular epithelium is a thin syncytium mostly covered with a dense glycocalyx and a strong brush border of microvilli underlain by a thin terminal web. The cytoplasm contains few organelles and there is no evidence that it is either secretory or has features (e.g., ICL) that might aid in maceration. We hypothesize that the thick glycocalyx might serve a protective function against the movements of live prey and/or against enzymes released from the rotifer's gastric glands that become regurgitated during feeding.

Ultrastructure, development and histochemistry of the polysaccharide‐containing subcuticular compartments in Origanum dictamnus L. peltate glandular hairs

AbstractPeltate glandular hairs of Origanum dictamnus at the stage of secretion create two subcuticular chambers; one large and bladder‐like, at the apex of the head (containing essential oil), and one small and ring‐like, at the bottom of the head (containing polysaccharides). In the apical chamber, along with the essential oil, a small lateral compartment containing polysaccharides, also exists. This compartment surrounds peripherally the apical chamber creating a second ring‐like structure. The apical plasmalemma of the head cells exhibits a high electron density and presumably has a specific substructure to facilitate passing to the subcuticular chamber of the secretory product. The latter probably exists in the form of glucosides, which, after passing across the plasmalemma and entering the apical chamber, become hydrolysed into the aglycone fraction (essential oil) and the sugar fraction (polysaccharides). Copyright © 2010 John Wiley & Sons, Ltd.

The fine structure of the midgut in the mite Anystis baccarum (L.) (Acari, Actinedida: Anystidae)

The ventriculus and the midgut caeca of the fed females of Anystis baccarum (L.) were investigated by using light and electron microscopy. In addition to the main type of polyfunctional digestive cells, special secretory cells were detected in the anterior region of the ventriculus. The shape and the ultrastructure of the digestive cells vary depending on their physiological state. Intracellular digestion, absorption or excretion processes prevail at different stages of the cell cycle. The secretory cells are characterized by the presence of extensive rough endoplasmic reticulum, filling whole space of the cell. These cells do not contain the apical network of pinocytotic canals, which are typical for the digestive cells. Three types of secretory granules were found in the cytoplasm of the secretory cells that probably correspond to three sequential stages of granulogenesis. The primary secretory granules are formed by the fusion of Golgi vesicles. The primary granules fuse to form complex vesicles with heterogeneous contents. These secondary granules aggregate to form very large inclusions of high electron density (tertiary secretory granules), which probably represent the storage of the secretory product. All types of secretory granules were observed close to the apical plasmalemma.

Collectrin, a homologue of ACE2, its transcriptional control and functional perspectives

Collectrin is a type I membrane protein and shares significant homology with C-terminal domain of angiotensin-converting enzyme-2 (ACE2). However, collectrin lacks catalytic domain and it suggests the presence of uncharacterized physiological functions of collectrin. Collectrin is transcriptionally regulated by hepatocyte nuclear factor-α and -β and is highly expressed on renal proximal tubules and collecting ducts as well as pancreatic β-cells. Recent in vitro and in vivo studies demonstrated interesting physiological roles of collectrin related to insulin secretion, formation of primary cilia, renal cyst formation and amino acid transport. The common underlying molecular mechanism may be suggested by the evidence that collectrin binds to SNARE complex by interacting with snapin. Collectrin is involved in the process of vesicle transport and membrane fusion and thus it delivers insulin for exocytosis or various membrane proteins to apical plasmalemma and primary cilia. Collectrin may be the new therapeutic target for various pathological processes such as diabetes, polycystic kidney disease, hypertension and aminoaciduria.

Features of the peritoneal covering of the lesser pelvis with special reference to stomata regions

Occasional reports describe various aspects of the fine morphology of the pelvic peritoneum, but its complete organ characteristics remain undefined. The peritoneal covering of the urinary bladder, rectum, uterus, uterine tube, ovary, broad ligament (BL) and testis in Wistar rats was examined by means of transmission and scanning electron microscopy (TEM, SEM). Unusually complicated relief and stomata between the cubic mesothelial cells characterized the surface of the BL. Deep, parallel furrows separated the wide longitudinal folds over the entire length of the uterine tube. The uterus and the ovary formed less numerous, shallow or extremely deep crypt-like invaginations, as well as serous villus-like or papilla-like evaginations. The flat cells were the predominant cell type over the BL, while the cubic mesothelium was the basic covering of the organs. Most of the cubic cells were located in the invagination of the submesothelial layer (SML). Such cells formed an almost smooth surface over the urinary bladder or formed larger areas of the rectum and the testis surfaces. Numerous microvilli, ciliae, round evaginations and complex lamellar bodies characterized their apical plasmalemma. In conclusion, the mesothelial heterogeneity is a stable feature of the lesser pelvis peritoneum, confirmed by TEM and SEM. The cubic mesothelium characterizes the organ peritoneum, while the BL plays the role of the parietal sheet, involving lymphatic units in the SML. The different types of contacts between the mesothelio-endothelial cells, large lymphatic vessels and occasional stomata are the usual components of the lymphatic units in norm, visible by TEM. Images of stomata, seen by SEM, demonstrate oval-shaped deep channel-like gaps surrounded by cubic mesothelium. The last data extend the evidence on stomata regions, which resemble the diaphragmatic ones. Clusters of cells (macrophages, mastocytes and Lymphocytes), small vessels (blood or lymphatic) and nerve fibers (unmyelinated and rare myelinated) form highly specialized complexes in the SML of the ovary, the uterus and the testis.

Placentation in the African Elephant, Loxodonta africanus: III. Ultrastructural and Functional Features of the Placenta

Successful transfer of nutrients to the elephant fetus during pregnancy relies on a variety of placental modifications. Our light and electron microscopical investigations show that the structure is endotheliochorial from implantation to term, with unicellular, never syncytial trophoblast. Light and electron microscope immunocytochemistry shows the restriction of the glucose transporter 1 isoform to the basolateral surfaces of the trophoblast, with the glucose transporter 3 restricted to the apical plasmalemma of the trophoblast. Glucose transport to the fetus therefore requires a sequential use of both isoforms. Light and electron microscope cytochemistry indicate the presence of iron deposits only in the haemophagous zones confirming their iron transport function. No trophoblast areas with high concentrations of Calcium binding protein, specialised for Calcium transport were found. In situ hybridisation demonstrated the presence of IGF-II mRNA in the trophoblast from the earliest stage, with TGFbeta1 and HGF-SF mRNA expressed subsequently but only IGF-II and HGF mRNA present in the second half of pregnancy. The results are briefly discussed in terms of placental growth and function and indicate that the elephant placenta is another example of a unique solution to the variety of problems posed by a resident fetus.

Structural and functional changes in gastric epithelium in Helicobacter pylori-associated chronic gastroduodenal pathologies

Complex structural analysis of the gastric mucosa was carried out in patients with Helicobacter pylori-associated chronic gastroduodenal ulcers, chronic gastritis, and vibration gastropathy. Microscopic examination showed stereotypical changes in the epithelium in all diseases: degeneration, focal intestinal metaplasia, dysplasia, and glandular atrophy. The severity of these changes depended on the disease entity. The most typical ultrastructural modifications of epitheliocytes were damage to the apical plasmalemma, heterogeneity of the secretory compartment of the cytoplasm, dilatation of the cytoplasmic reticulum, vacuolation, and signs of cytolysis. Plastic reactions of the gastric epithelium reflected disproportional changes in all cell metabolites caused by increased proliferative activity of the epithelium under conditions of uneven inhibition of intracellular protein synthesis.

Structural and functional characteristics of lung macro- and microvascular endothelial cell phenotypes

Lung macro- and microvascular endothelial cells exhibit unique functional attributes, including signal transduction and barrier properties. We therefore sought to identify structural and functional features of endothelial cells that discriminate their phenotypes in the fully differentiated lung. Rat lung macro- (PAEC) and microvascular (PMVEC) endothelial cells each exhibited expression of typical markers. Screening for reactivity with nine different lectins revealed that Glycine max and Griffonia ( Bandeiraea) simplicifolia preferentially bound microvascular endothelia whereas Helix pomatia preferentially bound macrovascular endothelia. Apposition between the apical plasmalemma and endoplasmic reticulum was closer in PAECs (8 nm) than in PMVECs (87 nm), implicating this coupling distance in the larger store operated calcium entry responses observed in macrovascular cells. PMVECs exhibited a faster growth rate than did PAECs and, once a growth program was initiated by serum, PMVECs sustained growth in the absence of serum. Thus, PAECs and PMVECs differ in their structure and function, even under similar environmental conditions.

The gastric shield and the underlying epithelium ofChlamys farreri: Morphological, histological and histochemical characterizations

The gastric shield and underlying stomach epithelium ofChlymas farreri were examined at the light and ultrastructural levels. The results showed that the gastric shield consisted of two different size lobes joined together by a narrow middle piece, the thicker lobe was shaped like a funnel, but unclosed at the lateral side; the other lobe was irregularly triangular-shaped. The transverse section of the thicker lobe was obviously laminated and gradually decreased in thickness from the peak to the margins of the shield. The underlying epithelium bore numerous about 3μm diameter spherical processes formed by the apical plasmalemma of the epithelial cells becoming blunt pseudopodia. Microvilli and some interspersed cilia were present in the areas among the spherical processes regions where only microvilli existed. Rough endoplasmic reticulum, Golgi apparatus, different-sized electron-dense secretory granules and electron-lucent vacuoles as well as abundant mitochondria were present in the underlying epithelial cells. Fused droplets of the secretion from the underlying epithelial cells formed the gastric shield.