In vitro three-dimensional modelling of human ovarian surface epithelial cells

OBJECTIVES

Ninety percent of malignant ovarian cancers are epithelial and thought to arise from the ovarian surface epithelium (OSE). We hypothesized that biological characteristics of primary OSE cells would more closely resemble OSE in vivo if established as three-dimensional (3D) cultures.

MATERIALS AND METHODS

OSE cells were cultured as multicellular spheroids (MCS) (i) in a rotary cell culture system (RCCS) and (ii) on polyHEMA-coated plastics. The MCSs were examined by electron microscopy and compared to OSE from primary tissues and cells grown in 2D. Annexin V FACS analysis was used to evaluate apoptosis and expression of extracellular matrix (ECM) proteins was analysed by immunohistochemical staining.

RESULTS

On polyHEMA-coated plates, OSE spheroids had defined internal architecture. RCCS MCSs had disorganized structure and higher proportion of apoptotic cells than polyHEMA MCSs and the same cells grown in 2D culture. In 2D, widespread expression of AE1/AE3, laminin and vimentin were undetectable by immunohistochemistry, whereas strong expression of these proteins was observed in the same cells grown in 3D culture and in OSE on primary tissues.

CONCLUSIONS

Physiological and biological features of OSE cells grown in 3D culture more closely resemble characteristics of OSE cells in vivo than when grown by classical 2D approaches. It is likely that establishing in vitro 3D OSE models will lead to greater understanding of the mechanisms of neoplastic transformation in epithelial ovarian cancers.

Abnormalities in neuromuscular junction structure and skeletal muscle function in mice lacking the P2X2 nucleotide receptor

ATP is co-released in significant quantities with acetylcholine from motor neurons at skeletal neuromuscular junctions (NMJ). However, the role of this neurotransmitter in muscle function remains unclear. The P2X2 ion channel receptor subunit is expressed during development of the skeletal NMJ, but not in adult muscle fibers, although it is re-expressed during muscle fiber regeneration. Using mice deficient for the P2X2 receptor subunit for ATP (P2X2(-/-)), we demonstrate a role for purinergic signaling in NMJ development. Whereas control NMJs were characterized by precise apposition of pre-synaptic motor nerve terminals and post-synaptic junctional folds rich in acetylcholine receptors (AChRs), NMJs in P2X2(-/-) mice were disorganized: misapposition of nerve terminals and post-synaptic AChR expression localization was common; the density of post-synaptic junctional folds was reduced; and there was increased end-plate fragmentation. These changes in NMJ structure were associated with muscle fiber atrophy. In addition there was an increase in the proportion of fast type muscle fibers. These findings demonstrate a role for P2X2 receptor-mediated signaling in NMJ formation and suggest that purinergic signaling may play an as yet largely unrecognized part in synapse formation.

Alterations in Purinoceptor Expression in Human Long Saphenous Vein during Varicose Disease

OBJECTIVES

Varicose veins are dilated tortuous veins of varying tone. Purinergic signalling is important in the control of tone and in mediating trophic changes in blood vessels. The expression of P2 receptors in control and varicose veins will be examined.

METHODS

Purinergic signalling in circular and longitudinal smooth muscle of the human long saphenous vein was studied in control and varicose tissues using immunohistochemistry, organ bath pharmacology and electron microscopy.

RESULTS

P2X1, P2Y1, P2Y2, P2Y4 and P2Y6 receptors were present on circular and longitudinal smooth muscle. Purine-mediated circular and longitudinal muscle contractions were weaker in varicose veins. Electron microscopy and immunohistochemistry findings support the view that smooth muscle cells change from the contractile to synthetic phenotype in varicose veins, associated with an upregulation of P2Y1 and P2Y2 receptors and a down regulation of P2X1 receptors.

CONCLUSIONS

Down regulation of P2X1 receptors on the smooth muscle of varicose veins is associated with loss of contractile activity. Upregulation of P2Y1 and P2Y2 receptors is associated with a shift from contractile to synthetic and/or proliferative roles. The phenotype change in smooth muscle is associated with weakening of vein walls and may be a causal factor in the development of varicose veins.

Increased expression of NOS and ET-1 immunoreactivity in human colorectal metastatic liver tumours is associated with selective depression of constitutive NOS immunoreactivity in vessel endothelium

The absence of perivascular nerves in tumour vessels suggests that endothelium derived vasoactive substances [nitric oxide (NO) and endothelin-1 (ET-1)] may be key factors in controlling tumour blood flow during tumour growth and metastasis. We have studied the ultrastructural distribution and immunoreactivity of different NO synthase (NOS) isoforms and ET-1 in human colorectal metastatic liver tumour tissues using pre-embedding peroxidase-anti-peroxidase and post-embedding immunoelectron microscopic triple gold labelling techniques. Dramatically lower NOS 1 immunoreactivity was observed in tumour vascular endothelium (1-3% and 15-20% in tumour and normal groups, respectively). As compared to control groups there were significantly less NOS3 immunopositive EC in metastatic tumour vessels (45-50% and 1-3% in normal and tumour groups, respectively). A striking rise in NOS2 was observed in tumour vessel endothelium (< 1% in normal and 65-70% in tumour vessel endothelium). ET-1 immunoreactivity levels were also significantly higher in tumour vessel endothelium (85-90% in tumour, 15-20% in normal group). This increased expression of NOS2 and ET-1 immunoreactivity was accompanied by the increased expression of three NOS isoforms and ET-1 immunoreactivity in liver parenchymal cells. These data suggest that metastatic tumour vessel endothelium is characterized by increased expression of NOS2 and ET-1 and by decreases in NOS1 and NOS3. These characteristics are associated with the overexpression of all three NOS isoforms and ET-1 immunoreactivity in non-vascular cells.

Atherosclerotic lesions are associated with increased immunoreactivity for inducible nitric oxide synthase and endothelin-1 in thoracic aortic intimal cells of hyperlipidemic Watanabe rabbits

The development and progression of atherosclerotic lesions in Watanabe heritable hyperlipidemic rabbits is associated with increases in inducible nitric oxide synthase (NOS2) and endothelin-1 (ET-1) immunoreactivity. In contrast, there is a reduction of immunoreactivity for neuronal NOS (NOS1) in aortic endothelial cells, but no change in endothelial NOS (NOS3) immunoreactivity. However, subendothelial macrophages and smooth muscle showed a different pattern of immunoreactivity of NADPH-diaphorase (NADPH-d), NOS2, ET-1, and NOS1. The lipid-rich macrophages in the intima were positively labeled for NADPH-d, NOS1, NOS2, NOS3, and ET-1. Smooth muscle cells in the subendothelium and the medial layers of the vascular wall were also positive for these markers. These results are consistent with the reduction of endothelium-dependent vasorelaxation that is known to occur during the development and progression of atherosclerosis in familial hypercholesterolemia. The data suggest a key role for vasoactive substances in the development of atherosclerosis.

Mesenchymal cells engulf and clear apoptotic footplate cells in macrophageless PU.1 null mouse embryos

Apoptosis is one of the key tools used by an embryo to regulate cell numbers and sculpt body shape. Although massive numbers of cells die during development, they are so rapidly phagocytosed that very few corpses are ever seen in most embryonic tissues. In this paper, we focus on the catastrophic cell death that occurs as the developing footplate is remodelled to transform webbed regions into free interdigital spaces. In the wild-type embryo, these dead cells are rapidly engulfed and cleared by macrophages. We show that in a macrophageless mouse embryo, null for the haemopoetic-lineage-specific transcription factor, PU.1, the task of phagocytosis is taken over by ‘stand-in’ mesenchymal neighbours in a clear example of cell redundancy. However, it takes three times as many of these mesenchymal phagocytes to complete the task and, at each stage of the clearance process - in the recognition of apoptotic debris, its engulfment and finally its digestion - they appear to be less efficient than macrophages. A molecular explanation for this may be that several of the engulfment genes expressed by macrophages, including the ABC1 transporter (believed to be part of the phagocytic machinery conserved from Caenorhabditis elegans to mouse), are not upregulated by these ‘stand-in’ phagocytes.

Dynamic actin-based epithelial adhesion and cell matching during Drosophila dorsal closure

BACKGROUND

The adhesion of two epithelial sheets is a fundamental process that occurs throughout embryogenesis and during wound repair. Sealing of the dorsal epidermis along the midline of the Drosophila embryo provides a genetically tractable model to analyse the closure of such holes. Several studies indicate that the actin cytoskeleton plays a critical role in dorsal closure. Although many components of the signalling cascade directing this process have been identified, the precise cell-biological events upon which these signals act remain poorly described.

RESULTS

By confocal imaging of living fly embryos expressing green fluorescent protein (GFP)-tagged actin, we found that dorsal closure relies on the activity of dynamic filopodia and lamellipodia that extend from front-row cells to actively zipper the epithelial sheets together. As these epithelial fronts approach one another, we observed long, thin filopodia, apparently 'sampling' cells on the opposing face. When the assembly of these actin-based protrusions was blocked (by interfering with the activities of Cdc42 and Jun N-terminal kinase signalling), the adhesion and fusion of opposing epithelial cells was prevented and their ability to 'sense' correct partners was also blocked, leading to segment misalignment along the midline seam.

CONCLUSIONS

Dynamic, actin-based protrusions (filopodia and lamellae) are critical, both in the mechanics of epithelial adhesion during dorsal closure and in the correct 'matching' of opposing cells along the fusion seam.

Nonapoptotic neurodegeneration in a transgenic mouse model of Huntington's disease

Huntington's disease (HD) is a fatal inherited neurodegenerative disorder characterized by personality changes, motor impairment, and subcortical dementia. HD is one of a number of diseases caused by expression of an expanded polyglutamine repeat. We have developed several lines of mice that are transgenic for exon 1 of the HD gene containing an expanded CAG sequence. These mice exhibit a defined neurological phenotype along with neuronal changes that are pathognomonic for the disease. We have previously observed the appearance of neuronal intranuclear inclusions, but did not find evidence for neurodegeneration. In this study, we report that all lines of these mice develop a late onset neurodegeneration within the anterior cingulate cortex, dorsal striatum, and of the Purkinje neurons of the cerebellum. Dying neurons characteristically exhibit neuronal intranuclear inclusions, condensation of both the cytoplasm and nucleus, and ruffling of the plasma membrane while maintaining ultrastructural preservation of cellular organelles. These cells do not develop blebbing of the nucleus or cytoplasm, apoptotic bodies, or fragmentation of DNA. Neuronal death occurs over a period of weeks not hours. We also find degenerating cells of similar appearance within these same regions in brains of patients who had died with HD. We therefore suggest that the mechanism of neuronal cell death in both HD and a transgenic mouse model of HD is neither by apoptosis nor by necrosis.

Schwann cell-derived Desert hedgehog controls the development of peripheral nerve sheaths

We show that Schwann cell-derived Desert hedgehog (Dhh) signals the formation of the connective tissue sheath around peripheral nerves. mRNAs for dhh and its receptor patched (ptc) are expressed in Schwann cells and perineural mesenchyme, respectively. In dhh-/- mice, epineurial collagen is reduced, while the perineurium is thin and disorganized, has patchy basal lamina, and fails to express connexin 43. Perineurial tight junctions are abnormal and allow the passage of proteins and neutrophils. In nerve fibroblasts, Dhh upregulates ptc and hedgehog-interacting protein (hip). These experiments reveal a novel developmental signaling pathway between glia and mesenchymal connective tissue and demonstrate its molecular identity in peripheral nerve. They also show that Schwann cell-derived signals can act as important regulators of nerve development.

Transgenic models of Huntington's disease

Huntington's disease (HD) is an inherited neurodegenerative disorder caused by a CAG-polyglutamine repeat expansion. A mouse model of this disease has been generated by the introduction of exon 1 of the human HD gene carrying highly expanded CAG repeats into the mouse germ line (R6 lines). Transgenic mice develop a progressive neurological phenotype with a movement disorder and weight loss similar to that in HD. We have previously identified neuronal inclusions in the brains of these mice that have subsequently been established as the pathological hallmark of polyglutamine disease. Inclusions are present before symptoms, which in turn occur long before any selective neuronal cell death can be identified. We have extended the search for inclusions to skeletal muscle, which, like brain, contains terminally differentiated cells. We have conducted an investigation into the skeletal muscle atrophy that occurs in the R6 lines, (i) to provide possible insights into the muscle bulk loss observed in HD patients, and (ii) to conduct a parallel analysis into the consequence of inclusion formation to that being performed in brain. The identification of inclusions in skeletal muscle might be additionally useful in monitoring the ability of drugs to prevent inclusion formation in vivo.

From neuronal inclusions to neurodegeneration: neuropathological investigation of a transgenic mouse model of Huntington's disease

Huntington's disease (HD) is an inherited progressive neurodegenerative disease caused by the expansion of a polyglutamine repeat sequence within a novel protein. Recent work has shown that abnormal intranuclear inclusions of aggregated mutant protein within neurons is a characteristic feature shared by HD and several other diseases involving glutamine repeat expansion. This suggests that in each of the these disorders the affected nerve cells degenerate as a result of these abnormal inclusions. A transgenic mouse model of HD has been generated by introducing exon 1 of the HD gene containing a highly expanded CAG sequence into the mouse germline. These mice develop widespread neuronal intranuclear inclusions and neurodegeneration specifically within those areas of the brain known to degenerate in HD. We have investigated the sequence of pathological changes that occur after the formation of nuclear inclusions and that precede neuronal cell death in these cells. Although the relation between inclusion formation and neurodegeneration has recently been questioned, a full characterization of the pathways linking protein aggregation and cell death will resolve some of these controversies and will additionally provide new targets for potential therapies.

Formation of polyglutamine inclusions in non-CNS tissue

Huntington's disease (HD) is one of a class of inherited progressive neurodegenerative disorders that are caused by a CAG/polyglutamine repeat expansion. We have previously generated mice that are transgenic for exon 1 of the HD gene carrying highly expanded CAG repeats which develop a progressive movement disorder and weight loss with similarities to HD. Neuronal inclusions composed of the exon 1 protein and ubiquitin are present in specific brain regions prior to onset of the phenotype, which in turn occurs long before specific neurodegeneration can be detected. In this report we have extended the search for polyglutamine inclusions to non-neuronal tissues. Outside the central nervous system (CNS), inclusions were identified in a variety of post-mitotic cells. This is consistent with a concentration-dependent nucleation and aggregation model of inclusion formation and indicates that brain-specific factors are not necessary for this process. To possibly gain insights into the wasting that is observed in the human disease, we have conducted a detailed analysis of the timing and progression of inclusion formation in skeletal muscle and an investigation into the cause of the severe muscle atrophy that occurs in the mouse model. The formation of inclusions in non-CNS tissues will be particularly useful with respect to in vivo monitoring of pharmaceutical agents selected for their ability to prevent polyglutamine aggregation in vitro, without the requirement that the agent can cross the blood-brain barrier in the first instance.

Are neuronal intranuclear inclusions the common neuropathology of triplet-repeat disorders with polyglutamine-repeat expansions?

Neuronal intranuclear inclusions have been found in the brain of a transgenic mouse model of Huntington's disease and in necropsy brain tissue of patients with Huntington's disease. We suggest that neuronal intranuclear inclusions are the common neuropathology for all inherited diseases caused by expansion of polyglutamine repeats. We also suggest that patients with a pathological diagnosis of neuronal intranuclear hyaline inclusion disease may also have polyglutamine repeat expansions.

Blood vessels in liver metastases from both sarcoma and carcinoma lack perivascular innervation and smooth muscle cells

Hepatic arterial infusion (HAI) chemotherapy as treatment for human colorectal liver metastases is promising, but not entirely satisfactory. Improved drug delivery during HAI may be achieved by manipulating the different control mechanisms of normal versus tumour blood vessels. The peptidergic/aminergic innervation of vessels in normal liver and in two animal models of liver metastasis (Lister Hooded rat with syngeneic MC28 sarcoma; athymic (nude) rat with human HT29 carcinoma) was investigated to assess the suitability of these models for future pharmacological studies. Normal liver and metastases were studied immunohistochemically for the presence of protein gene product 9.5 (PGP), neuropeptide Y (NPY), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and substance P (SP). Perivascular innervation was also examined by transmission electron microscopy. In Lister rat normal livers, perivascular immunoreactive nerve fibres containing PGP, NPY, TH, CGRP and SP were observed around the interlobular blood vessels near the hilum and in the portal tracts. The highest density was seen for PGP, followed in decreasing order, by NPY, TH, CGRP and SP. VIP-immunoreactive nerves were absent. No immunoreactive nerves were observed in the hepatic lobule. In athymic rat livers, the pattern of innervation was similar, except that SP immunoreactivity was more sparse. No perivascular immunoreactive nerves were observed in either MC28 or HT29 tumours. Electron microscopy confirmed the absence of perivascular nerves. Smooth muscle cells were not observed in tumour blood vessel walls. These results are comparable with previous observations on human liver metastases and suggest that the animal models may be suitable for pharmacological studies on vascular manipulation of HAI chemotherapy.

Neuropeptide Y-immunoreactive intracardiac neurones, granule-containing cells and nerves associated with ganglia and blood vessels in rat and guinea-pig heart

Intrinsic neuropeptide Y-containing neurones in rat and guinea-pig hearts were studied at the ultrastructural level by the pre-embedding peroxidase-antiperoxidase immunocytochemical technique. Intracardiac neuronal cell bodies were often weakly or moderately immunostained, and the labelling was usually pronounced in the Golgi complex, multivesicular bodies, some cisterns of granular endoplasmic reticulum and large granular vesicles. Neuropeptide Y-immunoreactive nerve fibres were also observed in association with intracardiac neurones. A subpopulation of neuropeptide Y-immunoreactive granule-containing cells in the rat heart are described for the first time and were very heavily labelled; other granule-containing cells were non-immunoreactive, but were contacted by neuropeptide Y-containing nerves. Preterminal regions of nerve fibres that were located in nerve bundles were only weakly neuropeptide Y-immunoreactive, in contrast to the heavy labelling observed in varicosities that contained many synaptic vesicles. Many neuropeptide Y-immunoreactive nerve fibres were associated with the coronary vasculature and were particularly prominent in the walls of small arteries and arterioles where labelled nerve varicosities were present close to the smooth muscle cells. Immunoreactive nerves were also seen in the myocardium, usually near to capillaries. In axonal varicosities, the central core of large granular vesicles was immunolabelled, and electron-dense immunoreactive material outlined the membranes of small and large clear vesicles. The significance of neuropeptide Y-immunoreactive intracardiac neurones and granule-containing cells and the origin of associated labelled nerve fibres in the heart are discussed.

Formation of neuronal intranuclear inclusions underlies the neurological dysfunction in mice transgenic for the HD mutation

Huntington's disease (HD) is one of an increasing number of human neurodegenerative disorders caused by a CAG/polyglutamine-repeat expansion. The mutation occurs in a gene of unknown function that is expressed in a wide range of tissues. The molecular mechanism responsible for the delayed onset, selective pattern of neuropathology, and cell death observed in HD has not been described. We have observed that mice transgenic for exon 1 of the human HD gene carrying (CAG)115 to (CAG)156 repeat expansions develop pronounced neuronal intranuclear inclusions, containing the proteins huntingtin and ubiquitin, prior to developing a neurological phenotype. The appearance in transgenic mice of these inclusions, followed by characteristic morphological change within neuronal nuclei, is strikingly similar to nuclear abnormalities observed in biopsy material from HD patients.

Huntingtin-encoded polyglutamine expansions form amyloid-like protein aggregates in vitro and in vivo

The mechanism by which an elongated polyglutamine sequence causes neurodegeneration in Huntington's disease (HD) is unknown. In this study, we show that the proteolytic cleavage of a GST-huntingtin fusion protein leads to the formation of insoluble high molecular weight protein aggregates only when the polyglutamine expansion is in the pathogenic range. Electron micrographs of these aggregates revealed a fibrillar or ribbon-like morphology, reminiscent of scrapie prions and beta-amyloid fibrils in Alzheimer's disease. Subcellular fractionation and ultrastructural techniques showed the in vivo presence of these structures in the brains of mice transgenic for the HD mutation. Our in vitro model will aid in an eventual understanding of the molecular pathology of HD and the development of preventative strategies.

Increase in immunoreactivity for endothelin-1 in blood vessels of rat liver metastases: experimental sarcoma and carcinoma

Using electron immunocytochemistry, blood vessels in the normal rat liver and in 2 different animal models of liver metastases: (1) Hooded Lister rat with MC28 tumour, a sarcoma, and (2) nude rat with HT29 tumour, a carcinoma, were investigated for the presence of endothelin-1. In the normal livers, small subpopulations of vascular endothelial cells displayed discrete immunoreactivity for endothelin-1. In the livers with malignant tumours, there was a substantial increase in endothelin-1-immunoreactive endothelial cells in vessels located at the tumour periphery. In the controls, antibody to endothelin-1 also labelled sporadically some fibroblast/fibroblast-like cells associated with the blood vessels. In contrast, intense immunoreactivity for endothelin-1 was frequently associated with the tumour cells and/or fibroblast cells in both types of tumour examined.

Intrinsic versus extrinsic factors in determining the regeneration of the central processes of rat dorsal root ganglion neurons: the influence of a peripheral nerve graft

The relative contribution of intrinsic growth capacity versus extrinsic growth-promoting factors in determining the capacity of transected dorsal root axons to regenerate long distances was studied. L4 dorsal root axons regenerating into 4-cm peripheral nerve grafts on transected dorsal roots were counted. Few dorsal root myelinated axons regenerated to the distal end of the grafts by 10 weeks unless the sciatic nerve was also crushed. Regeneration of unmyelinated axons was also increased by peripheral lesions. Crush or transection of the dorsal roots without grafting did not alter GAP-43 mRNA expression in L4 dorsal root ganglion (DRG) cells. Grafting a peripheral nerve onto the cut end of an L4 dorsal root doubled the number of DRG cells expressing high levels of GAP-43 mRNA after a delay of several weeks. Peripheral nerve crush at the time of nerve grafting resulted in a very rapid rise in GAP-43 mRNA expression, which then declined to a steady level, twice that of controls, by 7 weeks. Thus, the rapid increase in the number of DRG neurons expressing high levels of GAP-43 mRNA after peripheral but not central axotomy correlates with the regeneration of central axons through nerve grafts. Because GAP-43 mRNA is slowly upregulated in a subpopulation of sensory neurons in response to exposure of their central axons to a peripheral nerve environment, environments favourable for axonal growth may act by increasing the intrinsic growth response of neurons. Lack of intrinsic growth capacity may contribute to the failure of dorsal root axons to regenerate into the spinal cord.

Nitric oxide synthase-containing neurones and nerve fibres within cardiac ganglia of rat and guinea-pig: an electron-microscopic immunocytochemical study

The nitric oxide synthase-immunoreactivity and NADPH-diaphorase activity of intracardiac neurones in the rat and guinea-pig was studied at the ultrastructural level. While some nitric oxide synthase-containing intracardiac neurones were very heavily labelled, with electron-dense immunoprecipitate distributed throughout the neuronal cell bodies and their processes, most of the labelled neurones exhibited a lighter and more patchy distribution of nitric oxide synthase-immunoreactive material. Synapses made by nitric oxide synthase-negative nerve fibres with labelled intracardiac neurones were seen. Conversely, many nitric oxide synthase-containing nerve fibres that made synaptic contacts with unlabelled intracardiac neurones were also observed. Some small granule-containing cells were nitric oxide synthase-immunoreactive and were associated with unlabelled nerve terminals, while non-immunoreactive small granule-containing cells that were innervated by nitric oxide synthase-immunoreactive nerves were also seen. Small patches of osmiophilic electron-dense material were observed in the cytoplasm of NADPH-diaphorase-positive intracardiac neurones. This is the first description of the ultrastructural distribution of nitric oxide synthase-immunoreactivity and NADPH-diaphorase activity in a subpopulation of intracardiac neurones of rat and guinea-pig heart and provides further evidence in support of a role for nitric oxide in the local control of the heart by intrinsic neurones.

Electron-microscopic immunolabelling of vasoactive substances in human umbilical endothelial cells and their actions in early and late pregnancy

Human umbilical vessels are devoid of nerves and therefore endothelial cells may play an important role in the control of feto-placental blood flow. The pharmacological effects of 5-hydroxytryptamine, histamine and endothelin were examined in umbilical arteries and veins from legal terminations (gestational age 8-17 weeks, n=12) and normal term vaginal deliveries (gestational age 38-41, n=12). Immunocytochemistry of human unbilical vessels indicated that 5-hydroxytryptamine, histamine and endothelin were localised in subpopulations of endothelial cells of both artery and vein in late, but not early, pregnancy. 5-Hydroxytryptamine (10 nM-30 microM) caused sustained concentration-dependent contractions in all vessels from early and late pregnancy. Histamine (0.1 microM-30 mM) also caused sustained contractions in all vessels from late pregnancy but only 27% of arteries and 41% of veins from early pregnancy responded. Endothelin (10 pM-30 nM) caused slow long-lasting contractions in all vessels from early and late pregnancy. Atrial natriuretic peptide and neuropeptide Y did not alter vascular tone. The endothelium may thus play an autocrine/paracrine role, by synthesizing and releasing the above reactive substances in late pregnancy to influence feto-placental blood flow.

The absence of autonomic perivascular nerves in human colorectal liver metastases

The peptidergic/aminergic innervation of normal liver and tumour blood vessels was investigated in order to determine vascular control with a view to improving the efficacy of hepatic arterial cytotoxic infusion in the treatment of colorectal liver metastases. Selected areas of liver metastases and macroscopically normal liver from resection specimens (n = 13) were studied using light microscope immunohistochemistry for the presence of protein gene product 9.5 (PGP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), calcitonin gene-related peptide (CGRP), substance P (SP) and tyrosine hydroxylase (TH). The ultrastructure of blood vessels supplying liver metastases and their perivascular innervation were also examined by transmission electron microscopy. In the normal liver, perivascular immunoreactive nerve fibres containing PGP, NPY and TH were observed around the interlobular blood vessels and along the sinusoids and the central vein of the hepatic lobule. The greatest density of immunoreactive nerve fibres was seen for PGP, followed (in decreasing order) by NPY and TH. VIP, SP and CGRP immunoreactivity was observed only in nerve bundles associated with the large interlobular blood vessels. In contrast, no perivascular immunoreactive nerves were observed in colorectal liver metastases. Electron microscopy confirmed the absence of perivascular nerves in liver metastases. In addition, it showed that the walls of these blood vessels were composed of a layer of endothelial cells surrounded by an incomplete or, very rarely in the periphery of the tumour, a complete, layer of synthetic phenotype of smooth muscle-like cells. These results imply that the blood vessels supplying liver metastases are bereft of normal neuronal regulation; whether there is a role for endothelial cell control of blood flow in these vessels is not yet known.

A study of the ultrastructure of developing human umbilical vessels

Electron microscopic techniques were used to examine the ultrastructure of developing human umbilical arteries and vein (8-12, 13-17 and 37-40 wk gestational age). These showed that with increasing age there is (1) an increase in the size of the lumen and the thickness of the media; (2) an increase in the ratio of contractile smooth muscle phenotypic cells; (3) an increase in the myofilament content of the smooth muscle cells and the number of Weibel-Palade bodies; (4) a decrease in the glycogen content; (5) an appearance of microvilli on the luminal surface of the endothelium. Lipid vesicles, nerves and vasa vasorum were not observed in any region of the umbilical vein or arteries.

An ultrastructural and immunocytochemical study of thoracic aortic endothelium in aged Sprague-Dawley rats

The distribution of various vasoactive agents [nitric oxide synthase (NOS)- type I, endothelin-1 (ET-1), arginine-vasopressin (AVP), serotonin (5-HT), histamine and substance P (SP)] in the thoracic aortic endothelium of aged Sprague-Dawley rats was investigated using electron microscopic immunocytochemical methods. The aged thoracic aortic intima was characterized by a large number of leukocytes that adhered to the endothelium, an accumulation of a flake-like precipitate and clusters of leukocytes and smooth muscle cells (SMC) in the subendothelium. Age-associated alterations were also seen in the medial and adventitial layers of the vascular wall. An extensive vasa-vasorum was present in the adventitia from which leukocytes penetrated into perivascular tissue. Some vasa-vasorum showed mast cells adhered to perivascular pericytes. Immunocytochemistry showed about 70% endothelial cells (EC) with positive immunostaining for the brain isoform NOS-type I, compared to 10% in adult mature rats. About 10% of cells showed a positive immunoreaction for ET-1, which is about the same as for the mature adult thoracic aorta (8-9%). Subendothelial macrophages often showed positive immunostaining for antibodies against ET-1. The percentage of EC immunopositive to AVP, 5-HT, and histamine was 16-18, 15 and 12%, respectively compared to 5-8, 7-8 and 6% in mature adult rats. A few cells showed an immunopositive reaction for SP. In summary, the ageing vessel was characterized by a large number of leukocytes adhering to the endothelium and also by the presence of many macrophages and SMC in the subendothelial layer. The percentage of EC in rat thoracic aorta showing NOS immunostaining increased substantially from 10% in mature rats to 70% in aged rats. The percentage of EC immunopositive for AVP, 5-HT and histamine also increased about twofold compared to mature adult rats, while no changes were seen for ET-1.

Ultrastructural investigation of nitric oxide synthase-immunoreactive nerves associated with coronary blood vessels of rat and guinea-pig

Ultrastructural investigation of nitric oxide synthase-immunoreactive nerves closely associated with blood vessels in rat and guinea-pig hearts revealed many labelled nerve fibres in the walls of the main branches of the coronary arteries, and in arterioles, capillaries and post-capillary venules. The number of nitric oxide synthase-containing nerve fibres associated with different vessels, even those of the same calibre, varied. Terminal regions of nitric oxide synthase-immunoreactive fibres were observed in the endocardium and myocardium. Nitric oxide synthase-labelled fibres displayed electron-dense immunoproduct in both varicose and intervaricose regions. Immunoreactive axonal varicosities contained both small and large synaptic vesicles. The characteristics of the nitric oxide synthase-immunoreactive nerve fibres observed in the heart and the possibility that these fibres represent the processes of intracardiac neurones and/or sensory neurones of extrinsic origin are discussed.

Nitric oxide and human umbilical vessels: pharmacological and immunohistochemical studies

Human umbilical vessels are devoid of nerves and therefore endothelial cells may play an important role in the control of fetoplacental blood flow. In this study we examined the pharmacological effects of various substances, known to produce endothelial-mediated vasodilation in many blood vessels, on the human umbilical artery and vein from legal terminations [mean gestational age, 15 (8-17) weeks; n = 12] and normal term vaginal deliveries [mean gestational age, 39 (38-41) weeks; n = 12]. Acetylcholine, adenosine 5'-triphosphate, the calcium ionophore A23187 and substance P had no effect on raised vascular tone, whereas sodium nitroprusside relaxed 5-hydroxytryptamine (5-HT) preconstricted, umbilical artery and vein from both early and late pregnancy. L-NG-Nitroarginine methyl ester (L-NAME) had no effect on basal tone or on high tone, after it was raised by 5-HT. Localization of nitric oxide synthase [NOS, type I (neuronal)] was examined in the same umbilical vessels using electron immunocytochemistry. No NOS-immunoreactive endothelial cells were observed in the umbilical vessels taken during early pregnancy. However, the percentage of NOS-immunoreactive endothelial cells in umbilical artery and vein from late pregnancy was 3 and 10 per cent, respectively. These results suggest that nitric oxide contributes little, if any, to the local control of umbilical blood flow throughout pregnancy, despite the presence of NOS-immunoreactivity in a subpopulation of endothelial cells in late pregnancy.

The fine structure of the human ovarian vein

The human ovarian vein is of particular interest as an adult vessel which changes with the different phases of reproductive life. At the ultrastructural level we have characterised the endothelium, vascular smooth muscle and autonomic innervation of the human ovarian vein. Transmission electron micrographs were prepared from surgical specimens of the human ovarian vein (n = 11) to demonstrate the features of the vessel wall. The pattern of innervation was investigated using an image analysis system which was also used with high-magnification micrographs to count and measure axonal vesicle types. Possible relationships between ultrastructural features and age and reproductive history were investigated. Endothelial cells contained Weibel-Palade bodies and numerous microfilaments. There were 3 muscle coats: no elastic lamina separated the endothelium from an inner layer of smooth muscle; a middle smooth muscle layer consisted of cells orientated in a circular fashion; an outer smooth muscle layer was made up of longitudinally arranged smooth muscle bundles with collagen and nerves penetrating throughout. The percentage of the vessel thickness occupied by the middle circular smooth muscle layer ranged from 0 to 33% and fell with increasing age (r = -0.67, P < 0.05). Penetration of nerves into the circular layer was observed only in 2 of 9 specimens. The observed ultrastructural features are consistent with the ability of the ovarian vein to distend substantially in response to changing circulatory demands. The vascular endothelium may have a role in the local control of haemostasis via the synthesis and storage of von Willebrand factor.(ABSTRACT TRUNCATED AT 250 WORDS)

The downregulation of GAP-43 is not responsible for the failure of regeneration in freeze-killed nerve grafts in the rat

Freeze-killed nerve grafts in rats are able to support limited axonal regeneration from severed peripheral nerves, but by 6 weeks postoperation, axonal elongation through the grafts ceases. To find out whether this limited regeneration may be related to GAP-43 expression, 4-cm freeze-killed nerve grafts were attached to the proximal stumps of severed tibial nerves in adult inbred Fischer rats. For comparison, tibial nerve crush, to allow functional regeneration, or section and ligation, which allows only abortive axonal sprouting, were also performed. After survival for 3 or 6 weeks, the lumbar spinal cord and L4 dorsal root ganglia were stained for GAP-43 mRNA. Freeze-killed grafts of 3-8 weeks duration were processed for GAP-43 immunocytochemistry. Three weeks after all three operations, comparable numbers of axotomized spinal motorneurons and primary sensory DRG neurons reexpressed high levels of GAP-43 mRNA. Six weeks after tibial nerve crush, the number of tibial motorneurons and DRG cells expressing GAP-43 mRNA returned to control levels but after section and ligation or freeze-killed nerve grafting many positively stained cells were still visible. GAP-43 immunoreactivity was detectable using immunocytochemistry in many unmyelinated axons which had regenerated into the freeze-killed grafts at all times. Both axonal profiles in contact with Schwann cells and those which lacked such contact were GAP-43 positive. These results suggest that the cessation of axonal regeneration into freeze-killed tibial nerve grafts is not the result of a down-regulation of GAP-43. Furthermore, the presence of high levels of GAP-43 alone is not sufficient to ensure prolonged axonal regeneration.

Colocalization of vasoactive substances in the endothelial cells of human umbilical vessels

Human umbilical vessels are unique in lacking any innervation; thus endothelial cells may play the major role in local control and regulation of the blood flow. In the present study, we examined ultrathin sections of cultured human umbilical vein endothelial cells and tissue preparations of umbilical vein and artery, immunostained by the post-embedding colloidal gold double-labelling technique. We observed colocalization of atrial natriuretic peptide and neuropeptide Y, as well as colocalization of atrial natriuretic peptide and neuropeptide Y with other vasoactive substances, namely, vasoactive intestinal peptide, substance P, calcitonin gene-related peptide and arginine vasopressin. The functional significance of the colocalization of these vasoactive substances in the human umbilical vessel endothelial cells is discussed.

Regeneration of adult rat CNS axons into peripheral nerve autografts: ultrastructural studies of the early stages of axonal sprouting and regenerative axonal growth

If one end of a segment of peripheral nerve is inserted into the brain or spinal cord, neuronal perikarya in the vicinity of the graft tip can be labelled with retrogradely transported tracers applied to the distal end of the graft several weeks later, showing that CNS axons can regenerate into and along such grafts. We have used transmission EM to examine some of the cellular responses that underlie this regenerative phenomenon, particularly its early stages. Segments of autologous peroneal or tibial nerve were inserted vertically into the thalamus of anaesthetized adult albino rats. The distal end of the graft was left beneath the scalp. Between five days and two months later the animals were killed and the brains prepared for ultrastructural study. Semi-thin and thin sections through the graft and surrounding brain were examined at two levels 6-7 mm apart in all animals: close to the tip of the graft in the thalamus (proximal graft) and at the top of the cerebral cortex (distal graft). In another series of animals with similar grafts, horseradish peroxidase was applied to the distal end of the graft 24-48 h before death. Examination by LM of appropriately processed serial coronal sections of the brains from these animals confirmed that up to several hundred neurons were retrogradely labelled in the thalamus, particularly in the thalamic reticular nucleus. Between five and 14 days after grafting, large numbers of tiny (0.05-0.20 microns diameter) nonmyelinated axonal profiles, considered to be axonal sprouts, were observed by EM within the narrow zone of abnormal thalamic parenchyma bordering the graft. The sprouts were much more numerous (commonly in large fascicles), smoother surfaced, and more rounded than nonmyelinated axons further from the graft or in corresponding areas on the contralateral side of animals with implants or in normal animals. At longer post-graft survival times, the number of such axons in the parenchyma around the graft declined. At five days, some axonal sprouts had entered the junctional zone between the brain and the graft. By eight days there were many sprouts in the junctional zone and some had penetrated the proximal graft to lie between its basal lamina-enclosed columns of Schwann cells, macrophages and myelin debris. Within the brain, sprouts were in contact predominantly with other sprouts but also with all types of glial cell.(ABSTRACT TRUNCATED AT 400 WORDS)

GAP-43 in the axons of mammalian CNS neurons regenerating into peripheral nerve grafts

Although mature mammalian CNS neurons do not normally regenerate axons after injury, it is well established that they will regrow axons over long distances into peripheral nerve implants. We have autografted segments of sciatic nerve into the brains of adult albino rats and have used light and electron microscopic immunocytochemistry to examine the distribution of the growth associated protein GAP-43 in and around the graft in the first two weeks following implantation. GAP-43 was present, 3-14 days after grafting, in small non-myelinated axonal sprouts in the brain parenchyma around the proximal tip of the graft. At 11-14 days after implantation similar sprouts within the graft itself were GAP-43 immunoreactive. The sprouts were either naked or associated with other cell processes (chiefly of Schwann cells; to a lesser extent of astrocytes). We also show that small numbers of neuronal perikarya around the tip of the graft become GAP-43 immunoreactive 11-14 days after implantation. Thus mature mammalian CNS neurons regenerating axons into a PNS graft display a marked increase in their content of GAP-43. In addition, we report that small plaques of GAP-43 reaction product are sometimes present on the plasma membranes of Schwann cells or astrocytes adjacent to immunoreactive axons, and that narrow sheet-like or filopodial processes of astrocytes, Schwann cells and possibly other non-neuronal cell types, may contain small amounts of GAP-43.

Schwann cell migration through freeze-killed peripheral nerve grafts without accompanying axons

Freeze-dried tibial nerve grafts were anastomosed to either the proximal stump or the distal stump of severed tibial nerves in adult inbred Fischer rats. In the case of grafts attached to the proximal stump the tibial nerve was ligated three times, the most distal ligature from the spinal cord being 1 cm from the site of anastomosis. In both types of experiment Schwann cells were, therefore, free to enter the initially acellular grafts without accompanying axons. The grafts were examined 17 days to 12 weeks after operation. Immunofluorescence for S-100 protein was used to evaluate the distance migrated by the Schwann cells and electron microscopy was used to examine the morphology of the cells which invaded the grafts. Schwann cell migration was similar from the proximal and distal stumps. The migrating Schwann cells formed columns which resembled bands of Bungner. They were found mainly, but not exclusively, inside the pre-existing basal lamina tubes left behind by the killed nerve fibres. Some Schwann cells secreted a thin, patchy basal lamina even though they lacked axonal contact. Schwann cell columns became partially compartmentalized by fibroblast processes. Myelin and other debris were removed most rapidly in those parts of the grafts penetrated by large numbers of Schwann cells. The maximum distance the Schwann cells penetrated into the grafts was 8.5 mm and this was achieved by 6 to 8 weeks after operation. This is about half the maximum distance migrated by Schwann cells accompanying regenerating axons through similar grafts.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of Schwann cells and basal lamina tubes in the regeneration of axons through long lengths of freeze-killed nerve grafts

The ability of long acellular nerve grafts to support axonal regeneration was examined using inbred rats. Grafts (40 mm long) of tibial/plantar nerves were used either as live grafts or after freeze-drying to render the grafts acellular. The grafts were sutured to the proximal stump of severed tibial nerves in host animals which were then killed 1-12 weeks later. Axons rapidly regenerated through the living grafts but only extended 10-20 mm into the acellular grafts. This distance was achieved by 6 weeks and thereafter no significant further axonal extension occurred in the acellular grafts. A few naked axons lacking Schwann cell contact were identified in all acellular grafts, but became more numerous near the distal extent of axonal penetration into 6-12 week grafts. These axons contained large numbers of neurofilaments. When the distal 20 mm of 6 week acellular grafts (segments into which axons had not penetrated) were sutured to freshly severed tibial nerves, axons grew readily into the grafted tissue to a maximum distance of 9 mm. It is therefore likely that the limits to axonal regeneration through initially acellular grafts were set by factors intrinsic to the severed nerve. It is suggested that the limited migratory powers of Schwann cells may be one such factor. The concept that basal lamina tubes are not essential for axonal regeneration but may act as low resistance pathways for both axonal elongation and Schwann cell migration is discussed.

Satellite cells surrounding axotomised rat dorsal root ganglion cells increase expression of a GFAP-like protein

Segments of sciatic nerve, 8-10 mm long, were removed from the left thigh of adult Sprague-Dawley rats. One day to 6 weeks after operation the animals were killed and the 4th and 5th lumbar dorsal root ganglia dissected out on both the operated and the unoperated side. A monoclonal and two polyclonal antibodies to glial fibrillary acidic protein (GFAP) were used to localize GFAP-like molecules in cryostat sections of the ganglia by means of indirect immunofluorescence. Expression of GFAP in satellite cells, demonstrable by the binding of polyclonal antibodies, had increased noticeably by three days post operation and remained at a high level throughout the remaining period of the experiment. Whereas on the unoperated side only about 15% of the neurons in the ganglia were surrounded by GFAP-positive satellite cells, on the operated side about 88% of the neurons were surrounded by GFAP-positive cells. Satellite cells could not be labelled with the monoclonal antibodies to GFAP.

Peripheral nerve regeneration through optic nerve grafts

Grafts of optic nerve were placed end-to-end with the proximal stumps of severed common peroneal nerves in inbred mice. It was found that fraying the proximal end of adult optic nerve grafts to disrupt the glia limitans increased their chances of being penetrated by regenerating peripheral nerve fibres. Suturing grafts to the proximal stump also enhanced their penetration by axons. The maximum distance to which the axons grew through the CNS tissue remained about 1.5 mm from 2-12 weeks after grafting. Schwann cells were seldom identified in the grafts. Varicose and degenerating nerve fibres were often seen within the grafts. Some varicose profiles were shown to be the terminal parts of axons within the grafts. Axons containing clusters of organelles resembling synaptic vesicles became more abundant in the longer-term grafts. Immunohistochemical studies performed on sutured grafts using a polyclonal antiserum to neurofilaments confirmed the impressions given by the electron microscopical observations. Grafts of neonatal optic nerve lacked myelin debris but were not usually penetrated by regenerating peripheral axons within a 6-week period. Sixty minutes after the intravenous injection of horseradish peroxidase, reaction product could be detected in the extracellular spaces around blood vessels in all types of living optic nerve graft. This indicates that blood-borne macromolecules could penetrate the grafts. However, the profiles of axons which were found within living optic nerve grafts had no obvious relationship to blood vessels and were usually surrounded by astrocytic processes. These results suggest that living astrocytes, rather than the absence of serum-derived trophic factors or the presence of CNS myelin, constitute the major barrier to the extension of axons and the migration of Schwann cells into CNS tissue.

Schwann cells support extensive axonal growth into skeletal muscle implants in adult mouse brain

The ability of striated muscle to support CNS axonal regeneration was tested by grafting pieces of the lateral rectus muscle of the orbit into the hippocampus or neocortex of adult inbred CBA mice. The mice were perfused with fixative 4-5 weeks after operation and ultrathin sections of the grafts examined by electron microscopy. Many axons were present in the grafts and some were traced into the surrounding brain tissue. Most axons were in contact with Schwann cells, or their processes, and both were often associated with basal lamina material left behind by degenerating muscle cells. A few axons and their accompanying Schwann cells were found in contact with the plasma membrane of muscle cells. Fenestrated capillaries were present in the grafts. It is suggested that Schwann cells form the substratum for axonal extension into muscle implants in the CNS, although other factors may contribute to the extensive axonal invasion of the tissue.

Peripheral nerve fibres regenerate through myenteric plexus

The ability of myenteric glia and neurons to support peripheral nerve regeneration was tested by grafting pieces of muscularis externa 5 mm long from the distal colon of inbred CBA mice adjacent to the proximal stump of cut common peroneal nerves. By two weeks after operation many axons had invaded the plexus and after 3 weeks regeneration common peroneal nerve fibres could be identified in all parts of the plexus throughout the grafts. Some axonal profiles within the plexus appeared to be in the early stages of myelination by enteric glia. Axons surrounded by compact myelin were found at the periphery of ganglia, but the cells involved resembled Schwann cells and could not be positively identified as enteric glia. Profiles similar to those of regenerating axons were only very rarely seen in control experiments in which grafts were placed adjacent to intact common peroneal nerves. It is suggested that the cellular elements of the myenteric plexus can support peripheral nerve regeneration.

Axonal regeneration through arterial grafts

The left common peroneal nerves of adult inbred mice were severed and allowed to regenerate through the lumina of Y-shaped tubes comprising grafts of abdominal aorta and its bifurcation. Very little regeneration took place within the grafts unless the distal nerve stump was inserted into one limb of the Y-tube. Using syngeneic grafts virtually all the axons regenerating through the lumen grew down the limb of the Y-tube containing the distal nerve. Using non-syngeneic grafts, however, a substantial minority of the axons grew down the 'open' limb of the Y-tube. Axonal regeneration was more successful in non-syngeneic grafts.

Peripheral nerve regeneration through grafts of living and freeze-dried CNS tissue

The ability of peripheral nerve fibres to regenerate through the central nervous system (CNS) extracellular matrix in the presence of CNS myelin debris was examined using living and freeze-dried optic nerve grafts. The grafts were placed end-to-end with the proximal stumps of severed common peroneal nerves of inbred mice. Within a 4 week period, regenerating peripheral nervous system fibres were found in only two of 14 living grafts. However axons always grew into freeze-dried grafts within one week, despite the presence of CNS myelin debris. The regenerating axons in freeze-dried grafts were accompanied by Schwann cells and were initially found associated with the inner aspect of the glial basal lamina. Although the extracellular matrix of the freeze-dried CNS tissue was subsequently reorganized by invading cells, it seems likely that neither the nature of the CNS extracellular matrix nor the presence of CNS myelin debris had a major inhibitory influence on peripheral nerve regeneration. It is suggested that the presence of living astrocytes covered by a basal lamina at the proximal end of the living optic nerve grafts may inhibit their penetration by regenerating axons.

Evaluation of the rat thyroid cell strain FRTL-5 as an in-vitro bioassay system for thyrotrophin

The cyclic AMP response to bovine TSH was characterized in a strain of rat thyroid follicular cells ( FRTL -5) maintained in continuous culture. Significant stimulation of intracellular cyclic AMP was attained at a TSH dose of 5 muu./ml. Cyclic AMP accumulation continued to increase, at higher TSH doses, with no evidence for attainment of a maximum level at the highest dose tested (5 mu./ml). The precision of TSH measurement was better than 10% over the range 50-5000 muu./ml, comparing favourably with that observed with analogous assays based on human cells, tissue slices or membrane preparations. Using sequential subcultures of FRTL -5 cells, the between-assay variation in response to a single dose of a standard preparation of bovine TSH (53/11; 370 muu./ml) was of the order of 20% which compared favourably with the between-assay variation observed with different cultures of human thyroid cells. Prolongation of the incubation of FRTL -5 cells with TSH to 3 h revealed a progressive increase in the extracellular accumulation of cyclic AMP. Addition of TSH to resting FRTL -5 cells resulted in a stimulation of inorganic iodide uptake with pronounced bell-shaped dose-response characteristics. Thus a maximum uptake was observed at a TSH dose of 100 muu./ml with a significant reduction at higher doses. Acute stimulation of cells with TSH (100 muu./ml) resulted in a rapid and marked alteration in cell morphology, with evidence of cellular retraction and surface ruffling.