Endoplasmic reticulum stress: A possible connection between intestinal inflammation and neurodegenerative disorders

BACKGROUND

Different studies have shown the key role of endoplasmic reticulum (ER) stress in autoimmune and chronic inflammatory disorders, as well as in neurodegenerative diseases. ER stress leads to the formation of misfolded proteins which affect the secretion of different cell types that are crucial for the intestinal homeostasis.

PURPOSE

In this review, we discuss the role of ER stress and its involvement in the development of inflammatory bowel diseases, chronic conditions that can cause severe damage of the gastrointestinal tract, focusing on the alteration of Paneth cells and goblet cells (the principal secretory phenotypes of the intestinal epithelial cells). ER stress is also discussed in the context of neurodegenerative diseases, in which protein misfolding represents the signature mechanism. ER stress in the bowel and consequent accumulation of misfolded proteins might represent a bridge between bowel inflammation and neurodegeneration along the gut-to-brain axis, affecting intestinal epithelial homeostasis and the equilibrium of the commensal microbiota. Targeting intestinal ER stress could foster future studies for designing new biomarkers and new therapeutic approaches for neurodegenerative disorders.

Expression and role of cocaine-amphetamine regulated transcript (CART) in the proliferation of biliary epithelium

Cholangiocytes, the epithelial cells that line the biliary tree, can proliferate under the stimulation of several factors through both autocrine and paracrine pathways. The cocaine-amphetamine-regulated-transcript (CART) peptide has several physiological functions, and it is widely expressed in several organs. CART increases the survival of hippocampal neurons by upregulating brain-derived neurotrophic factor (BDNF), whose expression has been correlated to the proliferation rate of cholangiocytes. In the present study, we aimed to evaluate the expression of CART and its role in modulating cholangiocyte proliferation in healthy and bile duct ligated (BDL) rats in vivo, as well as in cultured normal rat cholangiocytes (NRC) in vitro. Liver samples from both healthy and BDL (1 week) rats, were analyzed by immunohistochemistry and immunofluorescence for CART, CK19, TrkB and p75NTR BDNF receptors. PCNA staining was used to evaluate the proliferation of the cholangiocytes, whereas TUNEL assay was used to evaluate biliary apoptosis. NRC treated or not with CART were used to confirm the role of CART on cholangiocytes proliferation and the secretion of BDNF. Cholangiocytes proliferation, apoptosis, CART and TrkB expression were increased in BDL rats, compared to control rats. We found a higher expression of TrkB and p75NTR, which could be correlated with the proliferation rate of biliary tree during BDL. The in vitro study demonstrated increased BDNF secretion by NRC after treatment with CART compared with control cells. As previously reported, proliferating cholangiocytes acquire a neuroendocrine phenotype, modulated by several factors, including neurotrophins. Accordingly, CART may play a key role in the remodeling of biliary epithelium during cholestasis by modulating the secretion of BDNF.

The Effects of Taurocholic Acid on Biliary Damage and Liver Fibrosis Are Mediated by Calcitonin-Gene-Related Peptide Signaling

BACKGROUND & AIMS

Cholangiocytes are the target cells of liver diseases that are characterized by biliary senescence (evidenced by enhanced levels of senescence-associated secretory phenotype, SASP, e.g., TGF-β1), and liver inflammation and fibrosis accompanied by altered bile acid (BA) homeostasis. Taurocholic acid (TC) stimulates biliary hyperplasia by activation of 3',5'-cyclic cyclic adenosine monophosphate (cAMP) signaling, thereby preventing biliary damage (caused by cholinergic/adrenergic denervation) through enhanced liver angiogenesis. Also: (i) α-calcitonin gene-related peptide (α-CGRP, which activates the calcitonin receptor-like receptor, CRLR), stimulates biliary proliferation/senescence and liver fibrosis by enhanced biliary secretion of SASPs; and (ii) knock-out of α-CGRP reduces these phenotypes by decreased cAMP levels in cholestatic models. We aimed to demonstrate that TC effects on liver phenotypes are dependent on changes in the α-CGRP/CALCRL/cAMP/PKA/ERK1/2/TGF-β1/VEGF axis.

METHODS

Wild-type and α-CGRP-/- mice were fed with a control (BAC) or TC diet for 1 or 2 wk. We measured: (i) CGRP levels by both ELISA kits in serum and by qPCR in isolated cholangiocytes (CALCA gene for α-CGRP); (ii) CALCRL immunoreactivity by immunohistochemistry (IHC) in liver sections; (iii) liver histology, intrahepatic biliary mass, biliary senescence (by β-GAL staining and double immunofluorescence (IF) for p16/CK19), and liver fibrosis (by Red Sirius staining and double IF for collagen/CK19 in liver sections), as well as by qPCR for senescence markers in isolated cholangiocytes; and (iv) phosphorylation of PKA/ERK1/2, immunoreactivity of TGF-β1/TGF- βRI and angiogenic factors by IHC/immunofluorescence in liver sections and qPCR in isolated cholangiocytes. We measured changes in BA composition in total liver by liquid chromatography/mass spectrometry.

RESULTS

TC feeding increased CALCA expression, biliary damage, and liver inflammation and fibrosis, as well as phenotypes that were associated with enhanced immunoreactivity of the PKA/ERK1/2/TGF-β1/TGF-βRI/VEGF axis compared to BAC-fed mice and phenotypes that were reversed in α-CGRP-/- mice fed TC coupled with changes in hepatic BA composition.

CONCLUSION

Modulation of the TC/ α-CGRP/CALCRL/PKA/ERK1/2/TGF-β1/VEGF axis may be important in the management of cholangiopathies characterized by BA accumulation.

Distribution of α-synuclein in normal human jejunum and its relations with the chemosensory and neuroendocrine system

Alpha-synuclein (α-syn) is a presynaptic neuronal protein and its structural alterations play an important role in the pathogenesis of neurodegenerative diseases, such as Parkinson’s disease (PD). It has been originally described in the brain and aggregated α-syn has also been found in the peripheral nerves including the enteric nervous system (ENS) of PD patients. ENS is a network of neurons and glia found in the gut wall which controls gastrointestinal function independently from the central nervous system. Moreover, two types of epithelial cells are crucial in the creation of an interface between the lumen and the ENS: they are the tuft cells and the enteroendocrine cells (EECs). In addition, the abundant enteric glial cells (EGCs) in the intestinal mucosa play a key role in controlling the intestinal epithelial barrier. Our aim was to localize and characterize the presence of α-syn in the normal human jejunal wall. Surgical specimens of proximal jejunum were collected from patients submitted to pancreaticoduodenectomy and intestinal sections underwent immunohistochemical procedure. Alpha-syn has been found both at the level of the ENS and the epithelial cells. To characterize α-syn immunoreactive epithelial cells, we used markers such as choline acetyltransferase (ChAT), useful for the identification of tuft cells. Then we evaluated the co-presence of α-syn with serotonin (5-HT), expressed in EECs. Finally, we used the low-affinity nerve growth factor receptor (p75NTR), to detect peripheral EGCs. The presence of α-syn has been demonstrated in EECs, but not in the tuft cells. Additionally, p75NTR has been highlighted in EECs of the mucosal layer and co-localized with α-syn in EECs but not with ChAT-positive cells. These findings suggest that α-syn could play a possible role in synaptic transmission of the ENS and may contribute to maintain the integrity of the epithelial barrier of the small intestine through EECs.

Different iron-handling in inflamed small and large cholangiocytes and in small and large-duct type intrahepatic cholangiocarcinoma

Cholangiocarcinoma (CCA) represents the second most common primary hepatic malignancy and originates from the neoplastic transformation of the biliary cells. The intrahepatic subtype includes two morpho-molecular forms: large-duct type intrahepatic CCA (iCCA) and small-duct type iCCA. Iron is fundamental for the cellular processes, contributing in tumor development and progression. The aim of this study was to evaluate iron uptake, storage, and efflux proteins in both lipopolysaccharide-inflamed small and large cholangiocytes as well as in different iCCA subtypes. Our results show that, despite an increase in interleukin-6 production by both small and large cholangiocytes, ferroportin (Fpn) was decreased only in small cholangiocytes, whereas transferrin receptor-1 (TfR1) and ferritin (Ftn) did not show any change. Differently from in vitro models, Fpn expression was increased in malignant cholangiocytes of small-duct type iCCA in comparison to large-duct type iCCA and peritumoral tissues. TfR1, Ftn and hepcidin were enhanced, even if at different extent, in both malignant cholangiocytes in comparison to the surrounding samples. Lactoferrin was higher in large-duct type iCCA in respect to small-duct type iCCA and peritumoral tissues. These findings show a different iron handling by inflamed small and large cholangiocytes, and small and large-duct type iCCA. The difference in iron homeostasis by the iCCA subtypes may have implications for the tumor management.

Epidermal growth factor-like domain multiple 7 (EGFL7): Expression and possible effect on biliary epithelium growth in cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive biliary tract malignancy with limited treatment options and low survival rates. The intrahepatic subtype comprises two forms: mucin-iCCA and mixed-iCCA. Epidermal growth factor-like domain multiple (EGFL7) is overexpressed in less differentiated liver tumors. The aim of this study was to assess the presence of EGFL7 due to its possible role in the growth of CCA. Hematoxylin & Eosin and periodic acid- Schiff staining were used to evaluate the morphological aspects and glycogen deposition. Immunohistochemistry and immunofluorescence were performed to identify the presence of EGFL7 both in tumor sections ex vivo and in appropriate cell lines in culture. We found that EGFL7 is expressed in malignant cholangiocytes of mixed-iCCA and absent in mucin-iCCA. In conclusion the expression of EGFL7 might be useful in the classification of CCA subtypes.

Retinal Microcirculation as Revealed by SEM Corrosion Casts in the Rat

The morphology of the retinal microcirculation has been extensively studied by different techniques. Nevertheless, some problems concerning the capillary bed lamination and pre- and postcapillary patterns have not yet been clarified. In the present study the SEM corrosion cast technique was employed to study the three-dimensional relationships of rat retinal vessels and to follow the smallest vascular branches. Rat retina is considered a useful experimental model for a number of pathologies which affect the microvascular bed deeply. Two precapillary patterns have been observed. Precapillary arterioles gave rise to capillaries both as terminal branches or as collaterals. The former pattern of ramification allows only a regulation of flow in a whole group of capillaries downstream, the latter pattern could provide a finer regulation of blood flow. SEM corrosion casts have shown very well the lamination of the capillary bed: one can easily realize this by seeing the overlapped meshes of the two different planes, vessels in between the two capillary laminae can always be followed from one meshwork to the other. This three-dimensional organization is an interesting model for retinal circulation because it shows many features in common with the retina of humans and primates.

A Tridimensional Study of Microcirculation in Skeletal Muscle

The authors used a microcorrosion cast technique to study the microvascular bed of skeletal muscles in the rat.

They also tried to clarify the differences, in this respect, between fast twitch and slow twitch muscles. For this purpose they studied as fast twitch muscles, the tibialis anterior muscle and the pectineus muscle and, as a slow twitch mus cle, the soleus muscle.

Thanks to the peculiar technique used, they were able to distinguish differ ent sections of the microvascular bed.

They also found astonishing differences between the capillary networks in the soleus and tibialis anterior muscles, on the original bases of peculiar charac teristics of the capillary network in the soleus.

Ischemia reperfusion of the hepatic artery induces the functional damage of large bile ducts by changes in the expression of angiogenic factors

Liver transplantation and cholangiocarcinoma induce biliary dysfunction following ischemia reperfusion (IR). The function of the intrahepatic biliary tree is regulated by both autocrine and paracrine factors. The aim of the study was to demonstrate that IR-induced damage of cholangiocytes is associated with altered expression of biliary angiogenic factors. Normal and bile duct ligation rats underwent 24-h sham or hepatic reperfusion after 30 min of transient occlusion of the hepatic artery (HAIR) or portal vein (PVIR) before collecting liver blocks and cholangiocyte RNA or protein. We evaluated liver histology, biliary apoptosis, proliferation and expression of VEGF-A/C, VEGFR-2/3, Ang-1/2, and Tie-1/2 in liver sections and isolated small and large cholangiocytes. Normal rat intrahepatic cholangiocyte cultures (NRICC) were maintained under standard conditions in normoxic or under a hypoxic atmosphere for 4 h and then transferred to normal conditions for selected times. Subsequently, we measured changes in biliary proliferation and apoptosis and the expression of VEGF-A/C and VEGFR-2/3. In vivo, HAIR (but not PVIR) induced damage of large bile ducts and decreased proliferation and secretin-stimulated cAMP levels. HAIR-induced damage of large bile ducts was associated with increased expression of VEGF-A/C, VEGFR-2/3, Ang-1/2, and Tie-1/2. In vitro, under hypoxic conditions, there was increased apoptosis and reduced proliferation of NRICC concomitant with enhanced expression of VEGF-A/C and VEGFR-2/3. The functional damage of large bile ducts by HAIR and hypoxia is associated with increased expression of angiogenic factors in small cholangiocytes, presumably due to a compensatory mechanism in response to biliary damage.

Taurocholic acid prevents biliary damage induced by hepatic artery ligation in cholestatic rats

BACKGROUND

Ischemic injury by hepatic artery ligation (HAL) during obstructive cholestasis induced by bile duct ligation (BDL) results in bile duct damage, which can be prevented by administration of VEGF-A. The potential regulation of VEGF and VEGF receptor expression and secretion by bile acids in BDL with HAL is unknown.

AIMS

We evaluated whether taurocholic acid (TC) can prevent HAL-induced cholangiocyte damage via the alteration of VEGFR-2 and/or VEGF-A expression.

METHODS

Utilizing BDL, BDL+TC, BDL+HAL, BDL+HAL+TC, and BDL+HAL+wortmannin+TC treated rats, we evaluated cholangiocyte apoptosis, proliferation, and secretion as well VEGF-A and VEGFR-2 expression by immunohistochemistry. In vitro, we evaluated the effects of TC on cholangiocyte secretion of VEGF-A and the dependence of TC-induced proliferation on the activity of VEGFR-2.

RESULTS

In BDL rats with HAL, chronic feeding of TC prevented HAL-induced loss of bile ducts and HAL-induced decreased cholangiocyte secretion. TC also prevented HAL-inhibited VEGF-A and VEGFR-2 expression in liver sections and HAL-induced circulating VEGF-A levels, which were blocked by wortmannin administration. In vitro, TC stimulated increased VEGF-A secretion by cholangiocytes, which was blocked by wortmannin and stimulated cholangiocyte proliferation that was blocked by VEGFR-2 kinase inhibitor.

CONCLUSION

TC prevented HAL-induced biliary damage by upregulation of VEGF-A expression.

Three-dimensional organization of the hepatic artery terminal branches: a scanning electron microscopic study of vascular corrosion casts of rat liver

The hepatic artery plays an important role in the nourishment of liver parenchyma. The arterial distribution generates debate on where the artery terminates in the liver although is accepted that terminal branching of hepatic artery opened into sinusoids and form arterio-portal anastomosis. This implies that sinusoids are fed by both arterial and portal vessels characterized by different pressures. The presence of a double feeding to the sinusoids from the vena porta, at a pressure of 6-7 cm H2O, and from the hepatic artery, at a pressure of 12-25 cm H2O, has generated many studies for the need to explain the prevalence of flow from the vena porta. For this reason, we have studied the terminal hepatic artery branches in the rat by using special microvascular corrosion casting procedure which makes possible to better follow the hepatic artery terminal branches. Twelve young sexually mature male and female Wistar rats were used in this study. More than one hundred vascular corrosion casts of terminal hepatic arterioles were studied by Scanning Electron Microscopy. Histological samples were prepared using standard techniques for light microscopy. The experimental approach allow to easily follow the three-dimensional course of hepatic artery branches which is extremely difficult in standard injections. In all our observations of the rat liver vascular corrosion casts, terminal hepatic artery branches do not end directly in the sinusoidal beds. Terminal hepatic artery branches end into peribiliary plexus, periportal plexus and single capillaries of the portal space. We have not found any arterio-venous shunt nor any arterial vessel flowing into a venous vessel or a sinusoid. This means that only venous blood at a lowered pressure reaches the vena porta branches and the sinusoids.

Cholangiocytes and blood supply

The microvascular supply of the biliary tree, the peribiliary plexus (PBP), stems from the hepatic artery branches and flows into the hepatic sinusoids. A detailed three-dimensional study of the PBP has been performed by using the Scanning Electron Microscopy vascular corrosion casts (SEMvcc) technique. Considering that the PBP plays a fundamental role in supporting the secretory and absorptive functions of the biliary epithelium, their organization in either normalcy and pathology is explored. The normal liver shows the PBP arranged around extra- and intrahepatic biliary tree. In the small portal tract PBP was characterized by a single layer of capillaries which progressively continued with the extrahepatic PBP where it showed a more complex vascular network. After common duct ligation (BDL), progressive modifications of bile duct and PBP proliferation are observed. The PBP presents a three-dimensional network arranged around many bile ducts and appears as bundles of vessels, composed by capillaries of homogeneous diameter with a typical round mesh structure. The PBP network is easily distinguishable from the sinusoidal network which appears normal. Considering the enormous extension of the PBP during BDL, the possible role played by the Vascular Endothelial Growth Factor (VEGF) is evaluated. VEGF-A, VEGF-C and their related receptors appeared highly immunopositive in proliferating cholangiocytes of BDL rats. The administration of anti-VEGF-A or anti-VEGF-C antibodies to BDL rats as well as hepatic artery ligation induced a reduced bile duct mass. The administration of rVEGF-A to BDL hepatic artery ligated rats prevented the decrease of cholangiocyte proliferation and VEGF-A expression as compared to BDL control rats. These data suggest the role of arterial blood supply of the biliary tree in conditions of cholangiocyte proliferation, such as it occurs during chronic cholestasis. On the other hand, the role played by VEGF as a tool of cross-talk between cholangiocytes and PBP endothelial cells suggests that manipulation of VEGF release and function could represent a therapeutic strategy for human pathological conditions characterized by damage of hepatic artery or the biliary tree.

Microvascular adaptation to growth in rat humeral head

The aim of this work is to investigate the growth of the vasculature in the rat humeral head cartilage after the initial development of the secondary ossification centre until the adult organization. Rats aging from 5 weeks to 12 months were used. Histological observations on humeral heads were implemented with morphometrical analysis. Subsequently, vascular corrosion cast, that permits a three-dimensional observation of the vasculature, were prepared and observed by scanning electron microscopy. In young animals the epiphysis contains thin bone trabeculae and most of the epiphysis is occupied by bone marrow spaces. With age, the bone trabeculae progressively enlarge up to double their thickness. The percentage of bone tissue increases from 33.6 to 58.6% of the entire epiphysis, while the bone marrow spaces tend to increase very little in their mean dimension. Vascular corrosion casts show that the epiphyseal microcirculation is well distinguished from that of the diaphysis, and arises from the vessels present in the capsule and the periosteal networks. In young animals the only capillaries are bone marrow sinusoids and few subchondral capillaries. In adult animals small vessels run between the clusters of sinusoids forming the trabecular circulation. Capillary sprouts from sinusoids are always observed both in the young and adult animals. Thus, in adult rats different proper microcirculatory districts can be distinguished in the epiphysis: (a) the sinusoidal network, that supplies the hematopoiesis of the bone marrow and the adjacent osteogenic tissue; (b) the bone tissue microcirculation, limited to small vessels that supply the metabolism and the remodelling of the bone tissue. The reported microvascular organization and its adaptation to the epiphyseal growth represent the morphological basis for understanding the reciprocal interaction among the different tissues in developing and adult rat epiphysis.

Fractal and Fourier analysis of the hepatic sinusoidal network in normal and cirrhotic rat liver

The organization of the hepatic microvascular network has been widely studied in recent years, especially with regard to cirrhosis. This research has enabled us to recognize the distinctive vascular patterns in the cirrhotic liver, compared with the normal liver, which may explain the cause of liver dysfunction and failure. The aim of this study was to compare normal and cirrhotic rat livers by means of a quantitative mathematical approach based on fractal and Fourier analyses performed on photomicrographs and therefore on discriminant analysis. Vascular corrosion casts of livers belonging to the following three experimental groups were studied by scanning electron microscopy: normal rats, CCl(4)-induced cirrhotic rats and cirrhotic rats after ligation of the bile duct. Photomicrographs were taken at a standard magnification; these images were used for the mathematical analysis. Our experimental design found that use of these different analyses reaches an efficiency of over 94%. Our analyses demonstrated a higher complexity of the normal hepatic sinusoidal network in comparison with the cirrhotic network. In particular, the morphological changes were more marked in the animals with bile duct-ligation cirrhosis compared with animals with CCl(4)-induced cirrhosis. The present findings based on fractal and Fourier analysis could increase our understanding of the pathophysiological alterations of the liver, and may have a diagnostic value in future clinical research.

Hepatic microcirculation and cholangiocyte physiopathology

BACKGROUND

The peribiliary plexus (PBP) plays a fundamental role in supporting the functions of the biliary epithelium. After common bile duct ligation (BDL) progressive PBP proliferation is demonstrated. We have, recently, demonstrated that the biliary epithelium express Vascular Endothelial Growth Factor (VEGF), both subtype -A and -B and VEGF receptors. Taking in consideration the wide extension of PBP during BDL, aim of our study is to investigate the role of VEGF in stimulating angiogenesis and also in the modulation of epithelial cells proliferation.

MATERIAL AND METHODS

Experimental studies were performed by evaluating the effects of: a) endogenous VEGF neutralization by chronic administration of anti VEGF-C antibody on cholangiocyte proliferation in BDL rats and; b) the hepatic artery ligation (HAL) immediately after BDL followed by treatment (7 days) with a recombinant of VEGF-A (administered through IP implanted minipumps) on cholangiocyte proliferative activities.

RESULTS

Both administration of antiVEGF-C antibody and HAL decreases cholangiocyte proliferation. The decrease of cholangiocyte proliferation was associated with depressed VEGF-A protein expression. The administration of rVEGF-A to BDL, hepatic artery ligated rats prevented the decrease of cholangiocyte proliferation and VEGF-A expression as compared to BDL control rats.

CONCLUSION

These data suggest that VEGF-C modulates the proliferative activities of cholangiocytes in experimental cholestasis and that circulating factors (i.e., VEGF) in the blood supply of the intra-hepatic biliary epithelium, play an important role in the balance between cholangiocyte proliferation/loss.

Development of the microcirculation of the secondary ossification center in rat humeral head

This work investigated the origin and development of microcirculation in the rat humeral head and the expression of vascular endothelial growth factor (VEGF) as a factor supporting the vascular growth and the development of the secondary ossification centers. Sixty rats aging 1, 3-4, 6-8, 11, and 21 days, 5 weeks, and 4 and 8 months were used. Samples of humeral head were collected for histology and immunohistochemistry for VEGF. Some animals were perfused with Mercox resin in order to obtain vascular corrosion casts (vcc) observed by scanning electron microscopy (SEM). No cartilage canals were present at birth. At 6 days postnatal, blood vessels coming from the perichondrium and the region near the capsule attachment invaded the cartilage; at 11 days postnatal, signs of calcification were present and within the third week some bone trabeculae were formed. Just before the vascular invasion of the epiphysis, a positive reaction for VEGF was localized in chondrocytes of the epiphyseal cartilage close to the capsule insertion. During the development and expansion of the secondary ossification center, VEGF expression was higher in chondrocytes but decreased when epiphysis was diffusely ossified. VEGF was expressed also by mesenchymal cells present in and around the fibrous tissue where the secondary ossification center will develop. SEM vcc confirmed that vessels penetrating into the epiphysis arose merely from the periosteal and the capsular networks, and vascular connections with the diaphyseal circulation were not evident. These observations demonstrated that VEGF production by chondrocytes begun some days after birth, supported the rapid vascular growth from the surrounding soft tissues, and was chronologically related to the development of the secondary ossification center in rat proximal humerus. Finally, the possible role of VEGF as mediator of angiogenesis and, at least indirectly, as a trigger factor also in the ossification and the bone remodeling of the secondary ossification centers has been discussed.

Hepatic microcirculation as a morpho-functional basis for the metabolic zonation in normal and pathological rat liver

The hepatic microcirculation is well known as a fundamental component of the liver structure, deeply involved in the zonal organization of the acinar structure. In cirrhosis, the microvascular tree shows dramatic changes that would heavily influence the development of the disease. When the cirrhosis becomes evident the result is a progressive organ failure, also in presence of only moderately decreased hepatocyte volume. The aim of this research was to compare the role of microcirculation of the hepatic zonation in normal and cirrhotic livers. Cirrhosis was experimentally induced in 36 rats following a controlled intragastric CCl4 administration. Cirrhotic and control normal livers were processed for routine light microscopy, histoenzimology, and scanning electron microscopy vascular corrosion cast. Control livers showed normal hepatic structure and microvascularization; enzymatic activities were constantly and normally distributed. In CCl4-treated animals LM showed a characteristic micronodular cirrhosis in all livers. Vascular corrosion casts under the scanning electron microscope displayed a progressive reduction of the distance between pre- and post-sinusoidal vessels and the presence of newly formed perinodular plexus. The histoenzymatic analysis demonstrated the loss of zonation in the cirrhotic parenchyma. Moreover, the sinusoid/hepatocyte ratio was significantly reduced, because of the presence of two or more hepatocyte thick laminae during the scarring development. The altered microcirculation in cirrhosis also changed the normal acinous metabolic gradient. The histoenzymatic study revealed a zonal rearrangement of the cirrhotic liver metabolic activity, that leads to a progressive hepatic failure. These data confirm the fundamental importance of the normal relationship between the hepatocyte laminae and the sinusoids for the preservation of a normal zonation which represents the basis for a normal liver function.

Felodipine protects human atrial muscle from hypoxia-reoxygenation dysfunction: a force-frequency relationship study in an in vitro model of stunning

AIMS

We aimed at investigating contractile changes after hypoxia-reoxygenation and dobutamine challenge in superfused human atrial pectinate muscle to see whether high versus low stimulation rate during hypoxia might account for outcome differences compatible with the definition of an in vitro model of myocardial stunning and whether pretreatment with the dihydropyridine Ca2+ entry blocker felodipine might afford protection.

METHODS

Human right atrial trabeculae obtained from adult patients were superfused in an organ bath with oxygenated (O2 content 16 ml/l) and modified (NaHCO3 25.7 mmol/l) Tyrode's solution at 37 degrees C. Dobutamine (1 nmol/l to 10 micromol/l) was superfused in 10 oxygenated preparations to select the optimal drug concentration to be used in another 22 which were randomized. Group (A) consisted of time-related controls (Tyrodes's solution for 225 min at cycle length (CL) 1600 ms and no dobutamine). There were two test groups, respectively: (B) low (1600 ms CL) and (C) high (400 ms CL) stimulation rate. After 60 min of stabilization, in groups B and C, hypoxic superfusion (O2 content 5 ml/l) lasted 60 min, then reoxygenation (60 min) and dobutamine challenge (1 micromol/l, 15 min) were performed. Analysis of variance for repeated measures with the Greenhouse-Geisser correction, and a repeated measures model with structured covariance (preparation mass, length, width and time-varying time to peak tension) matrices were used whereby grouping (G), time (T) and G x T interaction were weighted. Force-frequency relationship and post-pausal potentiation were studied after each phase. Electrophysiology, histomorphometry and electron microscopy were carried out (n=6). Felodipine (0.1 micromol/l, n=5) pretreatment (15 min before hypoxia) was given in parallel experiments.

RESULTS

Time-related controls showed approximately 10% per hour decrease of developed tension and the Paradise test provided approximately 80% of control values. In test groups (as compared to baseline values) contractility was decreased approximately 65% after hypoxia-reoxygenation and it increased approximately 25% after dobutamine (G, 0.0065<P<0.0155; T, P=0.00005; G x T, P=0.00005). High stimulation rate during hypoxia worsened hypoxia-reoxygenation contractile changes, whereas reversibility after dobutamine was less. In both B and C groups during hypoxia, contractility decreased quite rapidly, although by 10 min or so a plateau (approximately 50%) was reached in group B, whereas in group C contractility decreased to <20%. None of the covariates contributed significantly to predict the dependent variables investigated. Force-frequency relationship and post-pausal potentiation were repeatable, paralleled overall changes due to hypoxia, reoxygenation and dobutamine challenge and were useful to discriminate Ca2+-related diastolic processes thus helping index myocardial contractile reserve. Force-frequency relationship was negative at high stimulation rates, concomitant to an abrupt change of shape and duration of action potential with little time for Ca2+-related Ca2+ release and ensuing systolic processes. Felodipine pretreatment enabled an unblunted response to dobutamine. Histomorphometry showed an unexpected 'fibrotic core'. At electron microscopy, subendocardial and deep part of the same pectinate muscles showed identical degrees of degenerative lesions. Superfused samples showed, unexpectedly, less anoxic lesions than preparations fixed within 15 min from surgical explant, although lesions were higher than in samples fixed immediately after explant.

CONCLUSIONS

This might be a relevant model, whereby pharmacological or physical interventions are tested. Native human atrial trabeculae might be used without dissection and/or preservatives. If high stimulation rate during hypoxia is used the power of hypothesis testing is maximized. Future studies with this material will be easier and comparatively smaller series might be investigated. Felo

SEM corrosion-casts study of the microcirculation of the flat bones in the rat

BACKGROUND

Little is known about the organization of microcirculation in flat bones in comparison with long bones. This study, therefore, helps us to determine the design of this vascular system in flat bones in relation to their structure and function.

METHODS

The organization of microvasculature in parietal, scapula, and ileum bones of 15 young sexually mature rats, aged 6-7 weeks, was studied by light and scanning electron microscopy (SEM) from vascular corrosion cast (vcc), a resin-cast obtained material.

RESULTS

Our observations show that the pattern of the microcirculation in flat bones is different in the thick and thin parts of such bones. Where the bone is thinner than 0.4 mm, only periosteal and dural network exist. Larger vessels which do not form a real network connect the two tables of the bones in these regions. In thicker areas, the organization of the microvasculature is similar to that in long bones, with distinct periosteal, cortical and bone marrow networks. Moreover, in different bones, outer networks show slightly different characteristics according to the different adjacent structures (dura mater, muscles etc.). Different types of vessels were recognized by comparing their different diameter, course and endothelial imprints.

CONCLUSIONS

The microvascular patterns of the flat bones are strongly influenced by the bone thickness. The different microvascular systems can interact both with the bone modelling and remodeling and with the variable metabolic needs, modifying the microvascular pattern and the blood flow. This is even more important in view of the reciprocal influence of the different networks within the same bone.

Hepatic microcirculation and peribiliary plexus in experimental biliary cirrhosis: a morphological study

BACKGROUND & AIMS

The peribiliary plexus plays a fundamental role in supporting the secretory and absorptive functions of biliary epithelium. Little information is available on the rearrangement of the peribiliary plexus during conditions associated with ductular proliferation. This study investigated the chronological modulation of bile duct and peribiliary plexus proliferation after common bile duct ligation in the rat.

METHODS

Light microscopy and scanning electron microscopy vascular corrosion cast technique was used to study the architecture of the peribiliary plexus in rats with 1, 2, and 4 weeks of common bile duct ligation or in sham-operated controls.

RESULTS

After 1 week of common bile duct ligation, no evident change of hepatic microvasculature was observed despite significant proliferation of bile ducts. After 2 and 4 weeks, significant microvasculature proliferation was observed extending from the peribiliary plexus of bile tracts. Vascular proliferation coincides with the extension of portal tract connective tissue. No evidence of vascular proliferation or other morphological modifications was present at the level of sinusoids around the portal tracts.

CONCLUSIONS

After common bile duct ligation, the peribillary plexus undergoes marked proliferation, thus supporting the increased nutritional and functional demands from the proliferated bile ductal system. However, the proliferation of the peribillary plexus only occurs after that of the bile ductal system.

Precapillary patterns and perivascular cells in the retinal microvasculature. A scanning electron microscope study

The microvasculature of the rat retina was studied in male Wistar rats in order to examine the features of the precapillary vascular pattern and structure that could affect blood flow regulation. Vascular corrosion casts and partially digested tissue specimens were observed by scanning electron microscopy. Side branching rather than bifurcation was the predominant microvascular pattern in the arterial tree. Two types of precapillary arteriole were present, one with the characteristic pattern of a preferential channel; the other gave off capillaries as terminal branches. At the origin of arteriolar side branches, smooth muscle cells appeared to buckle the endothelial nuclei into the vascular lumen. It is concluded that the rat retinal microvasculature appears to be characterised by 2 distinctive features: (1) side branching of arterioles which allows preferential flow in the most superficial layers of the retina; (2) peculiar luminal restrictions of arterioles and capillaries which permit fine regulation of blood flow.

Ibopamine in glaucoma diagnostics: a new pharmacological provocative test

PURPOSE

Ibopamine is used when performing provocative tests, thanks to its pharmacological property of increasing ocular pressure in eyes with outflow system impairment. This study summarizes the latest results that we have achieved with reference to its clinical-diagnostic use.

METHODS

175 (250 eyes) POAG patients, 101 (190 eyes) glaucoma suspects with mild ocular hypertension, 39 (64 eyes) NTG patients and 163 (326 eyes) healthy volunteers underwent an ibopamine provocative test. Among the POAG and the glaucoma suspects, 49 (92 eyes) and 20 (38 eyes) patients were selected who, starting from the performing of ibopamine test, had at least one year of perimetric follow-up. These patients have been assessed for the perimetric defect progression in relation to the (negative or positive) response to ibopamine.

RESULTS

the ibopamine test was positive for 92% of the glaucomatous patients, 61% of the glaucoma suspects, 52% of the NTG patients and 0% of the healthy volunteers. It was observed that 28% of the ibopamine-positive glaucoma suspects showed a perimetric deterioration during an average 2.5-year follow-up. No perimetric deterioration was found on ibopamine-negative glaucoma suspects (Fisher's exact test: p = 0.038). Among glaucomatous patients, 46% of the test-positive individuals showed a progressive trend of the perimetric defect, as against about 8% of glaucomatous test-negative patients (Fisher's exact test: p = 0.003).

CONCLUSIONS

We believe that the ibopamine provocative test can be usefully applied especially to epidemiological screening studies to identify patients who might develop ocular hypertension or glaucoma and in the follow-up of glaucoma suspects, to identify individuals who have a greater risk of developing perimetric defects.

A morphological study on femoral heads in human hip joint osteoarthrosis

Several pathogenetical and clinical interpretation of osteoarthritic modifications are given in the literature. In this work we tried to compare in humans macroscopic, structural and ultrastructural observations on eight osteoarthritic with four femural heads from control patients. The sample for Light Microscopy and Scanning Electron Microscopy observations came from selected regions of the femural head, which included both cartilage and bone tissue of loaded and unloaded regions. The cartilage showed superficial lesions, such as erosions and fissures, and deep lesions that included matrix alterations and chondrocyte proliferation. In relation to the thickening of the subchondral bone we noticed an irregular bone-cartilage surface with signs of bone tissue proliferation. The trabeculae appeared thickened in loaded zones and rarefied in unloaded ones. Cavities were sometimes present at different depths in cancellous bone. Our observations allow us to conclude that cartilage lesions are precocious, diffusely located and relatively independent of the considered zone of the femural head, while bone tissue alterations seem evenly sited and chronologically subsequent. The cavities in the cancellous bone could produce load modifications and consequent bone deformity.

Topical ibopamine and corticosteroids in the treatment of post-surgery ocular hypotony

PURPOSE

The aim of the present preliminary study, performed on post-surgical hypotony, was the evaluation of the effects on ocular hypotony of the concomitant administration of ibopamine and corticosteroids.

METHODS

14 patients (11 males-3 females; mean age 47 years) with ocular hypotony following several vitroretinal surgical intervention in different districts, were enrolled. The inclusion criteria were: mean IOP during tonometric curve equal or lower than 6 mmHg, stable IOP for at least 60 days, ongoing treatment with 0.1% dexamethasone (4 times/day), successful surgical intervention, 2% ibopamine (4 times/day) was added to the corticosteroid therapy for 30-60 days.

RESULTS

Before ibopamine administration, mean IOP was 4.07 mmHg SD 1.71. At the end of the treatment period, mean IOP increased by 89% in comparison to baseline values (+ 3.64 mmHg SD 5.57). This difference was statistically significant (paired t = 2.39; P = 0.03). One month after ibopamine-treatment discontinuation, mean IOP decreased to pre-treatment values (4.86 mmHg SD 3.50).

CONCLUSIONS

The results of the present study, although preliminary, suggest the possibility of a future pharmacological treatment of ocular hypotony with ibopamine, whose rationale is based on the increase of aqueous humor production by stimulating the D1 dopaminergic receptor.

Scanning electron microscopy of collagen fiber orientation in the bone lamellar system in non-decalcified human samples

Previous studies on collagen fiber orientation have led to different interpretations and theories about the fiber arrangement in the lamellar compact bone. The purpose of this investigation was to provide new and more in-depth data on fiber arrangement in the lamellar bone system in order to explain the orientation of the fiber bundles. This was carried out by applying a simple method of preparation which permitted observation of non-decalcified samples. A previously isolated Haversian system was subjected to slow bending up to reaching the fracture point. Hence, the fracture surface was observed by SEM. The same samples were also observed by polarized light microscopy. A significant alternation of fiber orientation in the adjacent lamellae was observed. Different domains of differently oriented fibers were present within the same lamella; conjugating fibers connecting adjacent lamellae were also shown. This method avoided most of the artifacts due to chemical treatment of bone samples. The results can be easily interpreted by means of the same criteria applied in mechanics for the studying of composite materials.

Zinc supplementation in experimental liver cirrhosis: a morphological, structural and ultrastructural study

Zinc treatment in liver cirrhosis is known to prevent a number of clinical symptoms. Previous studies have also indicated that Zn has a protective effect on the development of the clinical, biochemical and morphological manifestations of hepatic injury if administered simultaneously with the noxious agent. In this study, the protective effects of zinc treatment against the development of liver cirrhosis have been tested in cirrhotic rats treated by intragastric administration of CCl4. The development of morphological lesions has been investigated by means of standardized and comparable techniques, LM, TEM, SEM, microvascular casts and measurements of liver collagen content by colorimetric determination in paraffin embedded sections. LM and EM observations showed typical morphological features of cirrhosis in all CCl4 treated rats. In the same group of animals, the microvascular casts showed the development of the typical 'perinodular' branching and the various anastomoses of pre and post-sinusoidal vessels. Colorimetric evaluation has shown a significant increase in collagen content after CCl4 treatment. Qualitative and quantitative data of livers of CCl4 treated rats supplemented or not with zinc were significantly similar. In conclusion, zinc treatment influences biochemical parameters, but not the morphology of liver cirrhosis.

A scanning electron microscopic study of liver microcirculation disarrangement in experimental rat cirrhosis

Hepatic microcirculation has been related to liver function in several studies. The principle of this relationship lies in the sequential distribution of blood from the feeding vessels of the hepatic acinus to the central vein. This study was undertaken to investigate the progressive changes at different sites of the liver microvascular bed in the developing cirrhosis, both by light microscopy and scanning electron microscopy of corrosion casts. Experimental cirrhosis was induced with intragastric carbon tetrachloride. The most important vascular changes progressively observed are the reduction of the distance between the pre- and postsinusoidal vessels, the presence of newly formed shunting vessels bypassing the sinusoids and, finally, the development of a perinodular vascular plexus composed of pre- and postsinusoidal vessels. Newly formed vessels grow through preformed tissue septa. These vascular modifications make any zonal gradient hardly possible. The loss of the zonal gradient of perfusion could highly modify liver function, along with the structural changes of hepatic laminae. Hepatocyte regeneration cannot recover the original vascular relationships: this makes the morphological and functional destructuralization of cirrhotic liver irreversible.

Microcirculation of the extrahepatic biliary tree: a scanning electron microscopy study of corrosion casts

The microvascular arrangement of the extrahepatic biliary tree of the rat was studied by light microscopy (LM) and scanning electron microscopy (SEM) of vascular corrosion casts. The plexus that encircles the lumen of the common bile duct, observed by LM, showed a network of vessels of different diameter situated under the epithelium in the lamina propria. Parallel SEM observations of the same structure demonstrated the presence of 2 main vascular layers: an outer arterial and venous layer, corresponding to the larger vessels seen by LM, and a richer inner capillary layer just under the epithelium. On the luminal part of the corrosion casts, there were many round avascular empty pits that corresponded to the presence of small acinar glands distributed along the epithelium of the common bile duct. The rich subepithelial capillary network present in the rat, an animal without a gallbladder, may play an important role in the reabsorption of water and solutes from bile. Moreover, in pathological conditions (e.g. portal hypertension), liver blood flow may take a preferential collateral route through the intrahepatic peribiliary plexus into the relatively large diameter vessels of the extrahepatic peribiliary plexus because of the continuity of the 2 plexi.

Electrophysiologic monitoring of diabetic retinopathy in pregnancy

The authors studied the correlations between electroretinographic, ophthalmologic, and clinical parameters in 30 pregnant women (20 with diabetes and 10 control subjects). Diabetic patients were divided into two groups: group 1 included 11 cases of insulin-dependent diabetes (IDDM); and group 2 included 6 cases of noninsulin-dependent diabetes (NIDDM) and 3 cases of gestational diabetes (GDM). Adapto-electroretinography (AERG) was used as the main monitoring parameter, and in particular, the relationship between the cone-mediated (b1) and rod-mediated (b2) components of the b wave (b2/b1 ratio) 7 minutes after photobleaching was studied. The results indicate that the b2/b1 ratio can detect functional modifications before the onset of ophthalmoscopically detectable retinopathy. Significant statistical correlations were demonstrated both between the type of diabetes and AERG responses, and between metabolic control (HbA1c values) and AERG alterations. A higher maternofetal complication rate in those patients with severe and frequent AERG alterations during pregnancy also was found.

Microcirculation of the extra-ocular muscles of rats. A scanning electron-microscopic corrosion cast study

Specific researches, employing corrosion casts, were performed on different skeletal muscles, but not on extra-ocular muscles (EOMs). The microvascular bed of EOMs was studied by the corrosion cast technique in the rat. Two histologically and physiologically different layers were present in the EOMs. On the whole, the capillary pattern of EOMs was less dense than in the other skeletal muscles. The EOM orbital layer turned out to have a higher number of transverse anastomoses and tuning-fork divisions than the global layer had. These different microcirculatory patterns can be related with the physiological function and the anatomical situation of the EOMs.

A scanning electron microscopy morphometric study of the rabbit peritoneal surface

Rabbit peritoneum was studied by SEM to obtain information and statistically meaningful morphometric data of different sites of visceral and parietal peritoneum and to verify the existence of "stomata." Samples were fixed by intraperitoneal infusion of glutaraldehyde, and were photographed by SEM under standard conditions. Morphometric data were obtained by Kontron MOP Videoplan. Variable cell surface patterns were present even within limited areas; however, "stomata" were not observed. The heterogeneity of data obtained can be related to the dynamism of mesothelial cell activity and to the different motilities of the underlying organs.

A three-dimensional study of the morphology and topography of pericytes in the microvascular bed of skeletal muscle

Digested tissue specimens and corrosion casts of rat soleus and tibialis anterior muscles were employed for this Scanning Electron Microscopy (SEM) study. The shape, morphology, and position of pericytes were compared to corresponding imprints on the cast surfaces. Pericytes, observed in digested tissue specimens, showed a typical morphological pattern: a central body with two primary processes that run along the capillary in opposite directions. From these primary processes, secondary ones arise and often encircle the vessel almost completely. On the surface of corrosion casts, roundish imprints were found in the microvascular tree at the same level where digested tissue specimens showed the presence of pericyte bodies. Along and around the cast surface, shallow grooves reproduced the course of the primary and secondary processes. The peculiar tridimensional arrangement of pericytes at the level of capillary bifurcations underlines their role in red cell flow regulation. However, if the mechanical linkage of the pericytes to the endothelium and their contractability is taken into account, additional roles of these perivascular cells may be hypothesized.

Microcorrosion casting in normal and pathological biliary tree morphology

The organization of the intrahepatic biliary tree was studied in three dimensions by scanning electron microscopic (SEM) corrosion casts, in normal and cholestatic rat liver. In the normal liver the observation revealed the features of the biliary passages from the bile canaliculi to the canaliculo-ductular junction, to the ductules and the bile ducts, confirming previous SEM observations. In cholestatic liver, the modifications and the proliferation of bile ductules appear clearly. Resin flow from canalicular to sinusoidal network was never observed. The method was found to be very useful in the evaluation of the architecture of the intrahepatic biliary tree, under normal as well as under pathological conditions.

Surface morphology of the human pleura. A scanning electron microscopic study

The superficial morphology of the pleura has been observed in humans by scanning electron microscopy (SEM). Pleural samples from the visceral, mediastinal, diaphragmatic and costal normal human pleura were observed, and a thorough morphometric study was performed. The most evident feature was the ubiquitous presence of microvilli and micropores. The secretion and absorption activities therefore should not be regarded as accomplished by different topographic zones of the pleura. Discontinuities and clefts were observed at the level of cellular junctions; absorption of high weight molecules and cells from the pleural space may be facilitated at this level, but the structures which were observed in humans may not be considered "stomata," according to the definition of such morphologic units as we give in the present study. Cilia and blebs, described in the experimental animal or in other mesothelia, were not seen in the human pleura.

An S.E.M. corrosion cast study on pericyte localization and role in microcirculation of skeletal muscle

The authors used the microcorrosion cast technique to study the localization and the role of pericytes in the microcirculation of skeletal muscle. Both fast twitch muscles, the tibialis anterior and the pectineus muscles, and a slow twitch one, the soleus muscle, were studied, because of morphological differences of their capillary networks. The observation of peculiar imprints on the surface of vascular casts, strategically sited in the microvascular bed, were related to the presence of pericytes apposed to the endothelial lining. The role of pericytes in equalizing the local blood flow to metabolic needs and in maintaining capillary blood flow despite pinching of vessels is discussed.