Tubuloreticular structures within labial salivary glands in Sjögren's syndrome

The Role of Membranes and Lipid-Protein Interactions in the Mg-Branch of Tetrapyrrole Biosynthesis

Chlorophyll (Chl) is essential for photosynthesis and needs to be produced throughout the whole plant life, especially under changing light intensity and stress conditions which may result in the destruction and elimination of these pigments. All steps of the Mg-branch of tetrapyrrole biosynthesis leading to Chl formation are carried out by enzymes associated with plastid membranes. Still the significance of these protein-membrane and protein-lipid interactions in Chl synthesis and chloroplast differentiation are not very well-understood. In this review, we provide an overview on Chl biosynthesis in angiosperms with emphasis on its association with membranes and lipids. Moreover, the last steps of the pathway including the reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide), the biosynthesis of the isoprenoid phytyl moiety and the esterification of Chlide are also summarized. The unique biochemical and photophysical properties of the light-dependent NADPH:protochlorophyllide oxidoreductase (LPOR) enzyme catalyzing Pchlide photoreduction and located to peculiar tubuloreticular prolamellar body (PLB) membranes of light-deprived tissues of angiosperms and to envelope membranes, as well as to thylakoids (especially grana margins) are also reviewed. Data about the factors influencing tubuloreticular membrane formation within cells, the spectroscopic properties and the in vitro reconstitution of the native LPOR enzyme complexes are also critically discussed.

Cytomegalovirus: a virus of increasing relevance to oral medicine and pathology

Human cytomegalovirus (HCMV) is a ubiquitous herpesvirus, emerging as an opportunistic pathogen in immunocompromised persons, particularly those infected with human immunodeficiency viruses (HIV). Clinical syndromes caused by HCMV are usually not specifically identifiable without laboratory investigations. However, it is now apparent that HCMV may cause oral ulceration in immunocompromised persons and it may play a role in other diverse conditions in these and other patients.

Reactivation of Epstein-Barr virus in Sjögren's syndrome

Sjögren's syndrome (SS) is a chronic autoimmune disease characterized by severe dryness of the eyes and mouth, resulting from lymphocytic infiltration of the lacrimal and salivary glands. SS may exist as a primary condition (primary SS, 1.SS) or as a secondary condition (2.SS) in association with rheumatoid arthritis, systemic lupus erythematosus, or progressive systemic sclerosis. In some 1.SS patients, there may be involvement of the extraglandular organs, including skin, kidney, liver, lung and nervous system. Furthermore, these patients may develop a lymphoproliferative syndrome that includes lymphadenopathy and increased risk of lymphoma. In the pathogenesis of SS, a role for Epstein-Barr virus (EBV) has been suggested because: (a) EBV is present in salivary gland epithelial cells of normal individuals and exaggerated immune responses against EBV could play a role in the destruction of salivary glands in SS; (b) SS salivary gland biopsies contain increased levels of EBV DNA in comparison to normal salivary glands, indicating viral reactivation and inability of lymphoid infiltrates to control EBV replication in SS patients; and (c) salivary gland epithelial cells in SS patients express high levels of HLA-DR antigens and may present EBV-associated antigens to immune T cells in SS patients. Therefore, SS may represent a situation in which genetically predisposed individuals (i.e., HLA-DR3-DQA4-DQB2) have a persistent but ineffectual T cell immune response against EBV at its site of latency. Among 14 non-Hodgkin's lymphomas that developed in SS patients, EBV DNA was detected in increased amounts in the tumor tissue of one patient. Characterization of this tumor DNA revealed: (a) polyclonal immunoglobulin gene rearrangements; (b) EBV DNA with an unusual restriction fragment length polymorphism pattern involving the Bam M fragment; and (c) EBV terminal repeat sequences suggestive of viral replication, similar to those reported in EBV lymphomas occurring in other immunocompromised individuals. Early recognition of this clinical problem may allow beneficial use of antiviral agents.

Tubuloreticular structures and cylindrical confronting cisternae: a review

Tubuloreticular structures (TRS) and cylindrical confronting cisternae (CCC) are unique subcellular structures that arise from the membranes of the rough endoplasmic reticulum of a variety of cell types. In vivo, they occur most frequently in endothelial cells and lymphocytes from patients with autoimmune diseases and viral infections; they are seen in these cells in almost all acquired immunodeficiency syndrome (AIDS) patients. The inducer(s) of TRS and CCC in vivo is (are) not firmly established. However, clinical and experimental studies indicate that the occurrence of these structures in these diseases is directly related to the endogenous elevation of alpha- and beta-interferon but not to gamma-interferon. Although CCC have been seen and reported to occur in human and primate cells since the late 1970s, their presence did not arouse much clinical and scientific interest until 1983 when they were observed in lymph node tissues of AIDS patients. The nature and pathogenesis of TRS and CCC are obscure. Through the years, many hypotheses have been proposed. They range from suggestions of these structures being incomplete viral particles to being nothing more than accumulated proteins; and from reference to these structures as specific markers for diseases to a generalized cell reaction to certain biological stimuli. In vitro investigations with lymphoblastoid cell lines have contributed a great deal in illuminating the potential clinical significance and the in vivo inducer(s) of TRS and CCC. Both the TRS and CCC are now known to be induced in vitro by alpha- and beta-interferon in some lymphoblastoid cell lines. However, only TRS and not CCC are induced in healthy donor lymphocytes and endothelial cells. Isolation of TRS and CCC using the lymphoblastoid cell system will help clarify the nature, the pathogenesis, and the importance of TRS and CCC in human diseases.

Viruses and salivary gland disease: are there associations?

Viruses can cause sialadenitis and may be associated with other diseases of salivary glands, particularly immunologically mediated and neoplastic lesions. The evidence that such an association with Sjögren's syndrome is causal is reviewed here and shown to be fairly tenuous at present.

Ultrastructural and immunocytochemical aspects of lymphocytic submandibulitis in the non-obese diabetic (NOD) mouse

The submandibular glands of female non-obese diabetic (NOD) mice (22-26 weeks of age) were studied by light and electron microscopy. Mononuclear cells consisting mostly of lymphocytes were recognized in and among the acini and secretory ducts. Some parts of the secretory ducts and mucous acini surrounded by lymphocytes showed destructive changes. In the secretory ducts lymphocytes invaded the duct epithelial lining and the duct lumen was occluded by these cells. The duct epithelial cells in such lesions were extremely distorted and tonofilament bundles running in various directions were present in the cytoplasm. Lymphocytes were in close contact with the duct epithelial cells. In the mucous acini some acinar cells, which appeared to be compressed by the infiltrating lymphocytes, showed degenerative changes. Immunocytochemical study revealed that both T- and B-lymphocytes were involved, T-lymphocytes tending to occupy the center of the infiltrate, while B-lymphocytes occupied the periphery. Although autoantibody against duct epithelial cells was identified, damage to duct epithelial cells was not correlated with the presence of this antibody. The morphological changes in the submandibular gland of the NOD mouse are very similar to those reported in the salivary gland of patients with Sjögren's syndrome.

Sjögren's syndrome: clinical and laboratory features, immunopathogenesis, and management

Sjögren's syndrome may be accompanied by local oral problems such as dry mouth, rampant caries, candidosis, or sialadenitis, but it is a systemic autoimmune disorder with wide repercussions, including a small premalignant potential. This article reviews the clinical and immunopathogenic features, as well as the etiology, of Sjögren's syndrome and discusses the diagnosis and management of oral complications.

Primary Sjogren syndrome: clinical and immunopathologic features

Primary Sjogren syndrome is an autoimmune condition in which dry eyes (keratoconjunctivitis sicca) and dry mouth (xerostomia) result from lymphocytic infiltration of lacrimal and salivary glands. Clinical and laboratory features of 60 primary Sjogren syndrome patients seen at our clinic during the past three years are presented. These patients illustrate the wide spectrum of extraglandular features that may occur as a result of lymphoid infiltration of lung, kidney, skin, stomach, liver, and muscle. They further emphasize the difficulty in classifying a patient as primary or secondary Sjogren syndrome (ie, sicca symptoms associated with systemic lupus erythematosus, rheumatoid arthritis, or scleroderma), particularly early in the disease course. As an initial step in understanding the pathogenesis, the lymphocytes that infiltrate the salivary glands and lymph nodes were characterized by using monoclonal antibodies that recognize distinct lymphocyte subsets and by using in vitro functional assays. These studies have demonstrated that affected tissues have infiltrates of T cells with helper/inducer activity and with a high frequency of "activation antigens." The immunohistologic techniques are useful in differentiating "benign" and "pseudolymphoma" lesions (both due predominantly to T cells) from non-Hodgkin lymphoma (usually due to B-cell infiltrates). Although there is no "cure" for primary Sjogren syndrome patient's symptoms may be significantly improved by measures aimed at prevention of ocular and dental complications and by the recognition of extraglandular features that may be amenable to specific treatment.

Labial salivary gland biopsy in Sjögren's syndrome. Assessment as a diagnostic criterion in 362 suspected cases

Xerostomia is an unsatisfactory diagnostic criterion for the salivary component of Sjögren's syndrome (SS). To determine the diagnostic usefulness of the presence of focal sialadenitis in labial salivary gland (LSG) biopsy specimens, 362 patients suspected of having SS prospectively underwent a unique LSG biopsy procedure. The pattern and severity of LSG inflammation were compared with measurements of parotid flow rate, and the presence or absence of symptomatic xerostomia, major salivary gland enlargement, keratoconjunctivitis sicca (KCS), and other connective tissue diseases (CTD). LSG biopsy focus scores of greater than 1 correlated more closely with the diagnoses of KCS alone and with KCS plus a CTD than did either reduced parotid flow rate or symptoms of xerostomia (P less than 0.0005 and P less than 0.05, respectively). Focal sialadenitis in an adequate LSG specimen is an objective criterion and a more disease-specific feature of SS than xerostomia or any other feature of salivary disease. The salivary component of SS should be redefined as the presence of LSG focal sialadenitis.

Ultrastructural aspects of nailfold capillaries in a case of eosinophilic fasciitis

An ultrastructural study was made on the nailfold capillaries in an 18-year-old female with eosinophilic fasciitis. Scleroderma-like capillaroscopic lesions were visible at the sites where biopsy was performed. Light microscopy revealed ectasic capillaries at the apex of dermal papillae. Aspects of thickening and duplication of the epidermal basement membrane as well as an activation of endothelial cells were visualized at the ultrastructural level. These cells contained many virus-like tubulo-reticular inclusions, associated with cisternae of endoplasmic reticulum. Aspects of degeneration of nerve fibres and Schwann cells were also present. Large, homogeneously electron-dense deposits could be seen in the basement membrane at the dermo-epidermal junction. This study not only confirms previous observations on the microangiopathy in eosinophilic fasciitis, but also documents two new aspects: electron-dense deposits at the dermo-epidermal junction and tubulo-reticular inclusions within endothelial cells.

Fine structure of nuclei and cytoplasm of osteoclasts in Paget's disease of bone

To investigate the fine structural features of nuclei and cytoplasm in osteoclasts from patients with Paget's disease of bone, eight bone biopsies were examined. Unusual paracrystalline filamentous formations were found with the nuclei of both actively resorbing and degenerating osteoclasts. These formations were made up of parallel arranged filaments which, in most cases, clustered together regularly. The filaments were slightly argyrophilic and this helped to differentiate them from the surrounding nuclear matrix, even when they were not aggregated in clusters. Argyrophilic filaments were also found loosely aggregated inside the cytoplasm of osteoclasts. In three biopsies two additional and unusual cytoplasmic inclusions were found. The first consisted of irregularly branching, highly argyrophilic membranous strands which were located inside membrane-bound vacuoles. The second consisted of spindle-shaped structures enclosed by two membranes and containing three or more tubules. It is suggested that these results stand as further morphological evidence in favour of the view that a virus, possibly of the paramyxovirus class, has a pathogenetic role in Paget's disease of bone.

Lip biopsy in connective tissue diseases. A review and study of seventy cases

The labial salivary glands from seventy patients with systemic lupus erythematosus (twenty cases), systemic progressive sclerosis (twenty-two cases), rheumatoid arthritis (twenty-three cases), and Sjögren's syndrome (five cases) and from fifty subjects without connective tissue diseases were studied by means of light and fluorescence microscopy. The availability of the lip biopsy as a diagnostic tool is stressed, but a differential diagnosis between the different connective tissue diseases was not achieved. Yet some of the latter disclosed peculiar lesions. The role of the inflammatory and degenerative components, as well as the pathogenesis of the lesions, is discussed.

Acute optic neuritis: a virological study in relation to multiple sclerosis

Previous ultrastructural examination of peripheral blood lymphocytes revealed the presence of intranuclear filamentous structures in multiple sclerosis (MS) and in some optic neuritis (ON) patients. The present investigation was undertaken in the attempt to correlate the presence of such structures with the etiology of ON and MS and possibly to demonstrate the viral origin of the filaments. Suitable virological and serological techniques were used to detect and isolate infectious agents from peripheral blood samples and body excretions of 12 monosymptomatic ON patients at their first acute attack. Nevertheless, any efforts to demonstrate the presence of a virus in these patients have been unsuccessful: no evidence of active viral infection was obtained by serological studies of serum and cerebrospinal fluid samples, nor could viral antigens or inclusions be observed by immunofluorescence and cytochemical analysis. Negative results were also obtained from studies performed in parallel on MS patients and various controls. The significance of the failure to isolate infectious agents from either ON and MS patients is discussed.