Electron microscopy of monkey kidney cell cultures infected with rubella virus

RANBP2 evolution and human disease

Ran-binding protein 2 (RANBP2)/Nup358 is a nucleoporin and a key component of the nuclear pore complex. Through its multiple functions (e.g., SUMOylation, regulation of nucleocytoplasmic transport) and subcellular localizations (e.g., at the nuclear envelope, kinetochores, annulate lamellae), it is involved in many cellular processes. RANBP2 dysregulation or mutation leads to the development of human pathologies, such as acute necrotizing encephalopathy 1, cancer, neurodegenerative diseases, and it is also involved in viral infections. The chromosomal region containing the RANBP2 gene is highly dynamic, with high structural variation and recombination events that led to the appearance of a gene family called RANBP2 and GCC2 Protein Domains (RGPD), with multiple gene loss/duplication events during ape evolution. Although RGPD homoplasy and maintenance during evolution suggest they might confer an advantage to their hosts, their functions are still unknown and understudied. In this review, we discuss the appearance and importance of RANBP2 in metazoans and its function-related pathologies, caused by an alteration of its expression levels (through promotor activity, post-transcriptional, or post-translational modifications), its localization, or genetic mutations.

Annulate lamellae and intracellular pathogens

Annulate lamellae (AL) have been observed many times over the years on electron micrographs of rapidly dividing cells, but little is known about these unusual organelles consisting of stacked sheets of endoplasmic reticulum-derived membranes with nuclear pore complexes (NPCs). Evidence is growing for a role of AL in viral infection. AL have been observed early in the life cycles of the hepatitis C virus (HCV) and, more recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), suggesting a specific induction of mechanisms potentially useful to these pathogens. Like other positive-strand RNA viruses, these viruses induce host cells membranes rearrangements. The NPCs of AL could potentially mediate exchanges between these partially sealed compartments and the cytoplasm. AL may also be involved in regulating Ca²⁺ homeostasis or cell cycle control. They were recently observed in cells infected with Theileria annulata, an intracellular protozoan parasite inducing cell proliferation. Further studies are required to clarify their role in intracellular pathogen/host-cell interactions.

Viral Appropriation: Laying Claim to Host Nuclear Transport Machinery

Protein nuclear transport is an integral process to many cellular pathways and often plays a critical role during viral infection. To overcome the barrier presented by the nuclear membrane and gain access to the nucleus, virally encoded proteins have evolved ways to appropriate components of the nuclear transport machinery. By binding karyopherins, or the nuclear pore complex, viral proteins influence their own transport as well as the transport of key cellular regulatory proteins. This review covers how viral proteins can interact with different components of the nuclear import machinery and how this influences viral replicative cycles. We also highlight the effects that viral perturbation of nuclear transport has on the infected host and how we can exploit viruses as tools to study novel mechanisms of protein nuclear import. Finally, we discuss the possibility that drugs targeting these transport pathways could be repurposed for treating viral infections.

Hepatitis C virus-induced cytoplasmic organelles use the nuclear transport machinery to establish an environment conducive to virus replication

Hepatitis C virus (HCV) infection induces formation of a membranous web structure in the host cell cytoplasm where the viral genome replicates and virions assemble. The membranous web is thought to concentrate viral components and hide viral RNA from pattern recognition receptors. We have uncovered a role for nuclear pore complex proteins (Nups) and nuclear transport factors (NTFs) in the membranous web. We show that HCV infection leads to increased levels of cytoplasmic Nups that accumulate at sites enriched for HCV proteins. Moreover, we detected interactions between specific HCV proteins and both Nups and NTFs. We hypothesize that cytoplasmically positioned Nups facilitate formation of the membranous web and contribute to the compartmentalization of viral replication. Accordingly, we show that transport cargo proteins normally targeted to the nucleus are capable of entering regions of the membranous web, and that depletion of specific Nups or Kaps inhibits HCV replication and assembly.

Do viruses subvert cholesterol homeostasis to induce host cubic membranes?

Biological membranes with cubic morphology are a hallmark of stressed or diseased cellular conditions; both protein–protein interactions and lipid alterations appear to contribute to their biogenesis, yet their specific cellular functions are unknown. The occurrence of cubic membranes strikingly correlates with viral infections; notably, virus entry, proliferation, and release are processes closely linked to cellular cholesterol metabolism, and dys-regulation of cholesterol synthesis at the level of HMG-CoA reductase also induces cubic membrane formation, in the absence of viral infection. We propose that virus-induced cubic membranes could result from viral interference of cellular cholesterol homeostasis, generating a protective membrane environment to facilitate virus assembly and proliferation. Preventing cubic membrane formation might thus disrupt the ‘virus factory’ and offer new avenues to combat viral infections.

Chapter 6: cubic membranes the missing dimension of cell membrane organization

Biological membranes are among the most fascinating assemblies of biomolecules: a bilayer less than 10 nm thick, composed of rather small lipid molecules that are held together simply by noncovalent forces, defines the cell and discriminates between “inside” and “outside”, survival, and death. Intracellular compartmentalization—governed by biomembranes as well—is a characteristic feature of eukaryotic cells, which allows them to fulfill multiple and highly specialized anabolic and catabolic functions in strictly controlled environments. Although cellular membranes are generally visualized as flat sheets or closely folded isolated objects, multiple observations also demonstrate that membranes may fold into “unusual”, highly organized structures with 2D or 3D periodicity. The obvious correlation of highly convoluted membrane organizations with pathological cellular states, for example, as a consequence of viral infection, deserves close consideration. However, knowledge about formation and function of these highly organized 3D periodic membrane structures is scarce, primarily due to the lack of appropriate techniques for their analysis in vivo. Currently, the only direct way to characterize cellular membrane architecture is by transmission electron microscopy (TEM). However, deciphering the spatial architecture solely based on two-dimensionally projected TEM images is a challenging task and prone to artifacts. In this review, we will provide an update on the current progress in identifying and analyzing 3D membrane architectures in biological systems, with a special focus on membranes with cubic symmetry, and their potential role in physiological and pathophysiological conditions. Proteomics and lipidomics approaches in defined experimental cell systems may prove instrumental to understand formation and function of 3D membrane morphologies.

Rubella virus replication and links to teratogenicity

Rubella virus (RV) is the causative agent of the disease known more popularly as German measles. Rubella is predominantly a childhood disease and is endemic throughout the world. Natural infections of rubella occur only in humans and are generally mild. Complications of rubella infection, most commonly polyarthralgia in adult women, do exist; occasionally more serious sequelae occur. However, the primary public health concern of RV infection is its teratogenicity. RV infection of women during the first trimester of pregnancy can induce a spectrum of congenital defects in the newborn, known as congenital rubella syndrome (CRS). The development of vaccines and implementation of vaccination strategies have substantially reduced the incidence of disease and in turn of CRS in developed countries. The pathway whereby RV infection leads to teratogenesis has not been elucidated, but the cytopathology in infected fetal tissues suggests necrosis and/or apoptosis as well as inhibition of cell division of critical precursor cells involved in organogenesis. In cell culture, a number of unusual features of RV replication have been observed, including mitochondrial abnormalities, and disruption of the cytoskeleton; these manifestations are most probably linked and play some role in RV teratogenesis. Further understanding of the mechanism of RV teratogenesis will be brought about by the investigation of RV replication and virus-host interactions.

Rubella virus replication and links to teratogenicity

Rubella virus (RV) is the causative agent of the disease known more popularly as German measles. Rubella is predominantly a childhood disease and is endemic throughout the world. Natural infections of rubella occur only in humans and are generally mild. Complications of rubella infection, most commonly polyarthralgia in adult women, do exist; occasionally more serious sequelae occur. However, the primary public health concern of RV infection is its teratogenicity. RV infection of women during the first trimester of pregnancy can induce a spectrum of congenital defects in the newborn, known as congenital rubella syndrome (CRS). The development of vaccines and implementation of vaccination strategies have substantially reduced the incidence of disease and in turn of CRS in developed countries. The pathway whereby RV infection leads to teratogenesis has not been elucidated, but the cytopathology in infected fetal tissues suggests necrosis and/or apoptosis as well as inhibition of cell division of critical precursor cells involved in organogenesis. In cell culture, a number of unusual features of RV replication have been observed, including mitochondrial abnormalities, and disruption of the cytoskeleton; these manifestations are most probably linked and play some role in RV teratogenesis. Further understanding of the mechanism of RV teratogenesis will be brought about by the investigation of RV replication and virus-host interactions.

Annulate lamellae and lytic HAV infection in vitro

The aim of this study was to examine the relationship between viral infection and annulate lamellae (AL) production by using quantitative and qualitative electron microscopy to document the size and numbers of AL in BS-C-1 cells infected with a lytic strain of hepatitis A virus (HAV). The progress of the HAV infection was found to occur in two phases. In phase 1, cell proliferation and cell death were roughly the same as that of the mock infected control, but there was an increase with time in the amount of hepatitis A antigen in the infected cells. In phase 2 cell division was minimal and cell death became manifest. AL were detected in both infected and control cells. Quantitative analysis indicated that the average number of AL was greater in infected cells compared to that in control cells in phase 1; in infected cells there were greater numbers of AL in phase 1 than in phase 2; the average number of membraneous leaves/AL was greater in infected cells than in control cells. Quantitative analysis also indicated that AL were very rare, with only about three AL per entire control cell and eight AL per entire infected cell. The study clearly establishes that viral infection can stimulate AL production. The data suggest stimulation of AL production in the virus infected cells was linked to the synthesis of viral antigen. Ultrastructural observations indicated that AL could be derived from either the rough endoplasmic reticulum or the nuclear membrane.

Molecular biology of rubella virus

This chapter summarizes the present medical significance of rubella virus. Rubella virus infection is systemic in nature and the accompanying symptoms are generally benign, the most pronounced being a mild rash of short duration. The most common complication of rubella virus infection is transient joint involvement such as polyarthralgia and arthritis. The primary health impact of rubella virus is that it is a teratogenic agent. The vaccination strategy is aimed at elimination of rubella and includes both universal vaccination of infants at 15 months of age with the trivalent measles, mumps, rubella (MMR) vaccine and specific targeting with the rubella vaccine of seronegative women planning pregnancy and seronegative adults who could come in contact with women of childbearing age, although it is recommended that any individual over the age of 12 months without evidence of natural infection or vaccination be vaccinated. Medically, the current challenge posed by rubella virus is to achieve complete vaccination coverage to prevent resurgences.

Tubuloreticular structures in pyridoxine deficiency

Electron microscopic studies on renal tissue obtained from animals subjected to pyridoxine deficiency have revealed the presence of round and/or tubular bodies in the cytoplasm of endothelial cells of the glomeruli. The bodies generally occur as aggregates in association with the endoplasmic reticulum. Along with the round forms other profiles are also observed. It is believed that they represent one of the many images of a system of undulating tubules. Since these bodies occur irrespective of the presence of virus particles in the tissue under study it is concluded that they are not viral in nature.

Morphological changes in HAV-infected Frp/3 cells and immunolocalization of HAAg

Electron and immunoelectron microscopic studies were carried out on HAV-infected Frp/3 cells. The infection led to a distinctive cytopathic effect (CPE) arising on day 3 up to the complete detachment of monolayers on day 7. Infected cells exhibited progressive modifications, beginning from the formation of long helical polyribosomes. Subsequently, hypertrophy, cisternal dilatation and degranulation of the RER could be observed. Furthermore, the formation of concentric membranous bodies (CMB), large myelin-like structures and annulate lamellae could be revealed at later times of infection. 24-27 nm virus-like particles were observed within cytoplasmic vesicles or outside extensively degenerated cells. Indirect immunoperoxidase staining were used to localize HAV antigen (HAAg) in thin sectioned infected Frp/3 cells. Vesicular inclusion bodies, often seen to contain electron-lucent particles, resulted darkly stained as well as tracts of the RER and myelin-like structures. Negatively stained preparations from cell lysates revealed small clusters of HAV particles which sometimes appeared to be still associated with residual membrane fragments. Our findings seem to suggest that HAV replication occurs in close association with cytoplasmic membranes and a direct involvement of the RER seems to be demonstrated.

The annulate lamellae--from obscurity to spotlight

This review aims to provide a comprehensive and in-depth survey of a cell organelle, the annulate lamellae, that is widely distributed and especially prevalent in both female and male sex cells as well as tumor and cancer cells. The organelle is also present in many somatic cells and plant cells. Emphasis is placed on the contributions that electron microscopy and associated experimental approaches have made in providing information about the distribution, ultrastructure, morphogenesis and relationships of annulate lamellae to other cellular organelles, especially the nuclear envelope and endoplasmic reticulum, as well as cell product. An increasing number of experimental manipulations have recently been shown to alter, either increase or decrease, the amount of annulate lamellae and these studies are explored in depth. Information about the origin and morphogenesis of annulate lamellae in different cells is summarized and extensive coverage is given to several hypotheses about possible annulate lamellae function. A detailed bibliography provides a thorough compilation of research dealing with annulate lamellae. A major goal of this extensive review is to generate increased awareness of, and interest in, this cell organelle for students and investigators of the cell who, by bringing current techniques in cell and molecular biology to bear, might focus and intensify studies on the function of an organelle whose precise role in the cell is presently enigmatic.

Cellular changes associated with persistent hepatitis A infection in vitro

The rate of division, morphology and ultrastructure of BSC-1 cells, persistently infected with hepatitis A virus (HAV), were compared with uninfected cells for 60 days after splitting of the cells. Both control and infected cells showed a biphasic growth pattern marked firstly by increasing cell density and high mitotic rate (exponential phase) and then high constant cell density and little mitosis (stationary phase). Immunoperoxidase studies showed that hepatitis A antigen (HAAg) appeared as cytoplasmic granules approximately one third of the way through the exponential phase in infected cells. The percentage of cells with HAAg rose until the early stationary phase when virtually all cells contained antigen. Radioimmunoassay demonstrated an increase in HAAg per cell in the stationary phase. Radioimmunofocus assay and immune electron microscopy confirmed the presence of HAV in infected cells in the stationary phase. Thin sectioning electron microscopy showed cytoplasmic annulate lamellae in infected cells of both phases but not in control cells.

Cytoplasmic tubular structures in liver of HBsAg carrier chimpanzees infected with delta agent and comparison with cytoplasmic structures in non-A, non-B hepatitis

Electron microscopic observations were carried out on five HBsAg carrier chimpanzees infected with delta (delta) agent and two chimpanzees infected with human non-A, non-B hepatitis. The cytoplasmic tubular structures, which have been recognized in the liver of chimpanzees infected with human non-A, non-B hepatitis, were found also in the liver of HBsAg carrier chimpanzees infected with delta agent. The quantity of the cytoplasmic structures in serial studies was associated with SGPT elevation rather than with expression of delta antigen in sera and liver tissues. This indicates that the cytoplasmic structures reflect a pathologic change of the hepatocytes in chimpanzees infected with delta agent or human non-A, non-B hepatitis. These and other similarities between the two agents suggest a similar nature.

The coexistence of ribosome-lamella complex and annulate lamellae in chronic lymphocytic leukemia

An electron microscopic study of peripheral blood and lymph node from a patient with chronic lymphocytic leukemia revealed ribosome-lamella complexes in 11-16% of the peripheral lymphocytes and in 14% of the nodal lymphocytes. Annulate lamellae were seen in 2-8% of the peripheral lymphocytes and in 8% of the nodal lymphocytes. One peripheral blood specimen revealed coexistence annulate lamellae and ribosome-lamella complexes within the same cells in an additional 4% of the lymphocytes. The two structures were connected by continuous strands of apparent endoplasmic reticulum. Although annulate lamellae and ribosome-lamella complex have each been described in chronic lymphocytic leukemia, albeit uncommonly, their unusual association with one another has not previously been documented and might offer a clue as to the origin and role of these interesting structure. The possible ramifications of these observations include relationship of the structures to endoplasmic reticulum and protein synthesis, to in vitro and possible clinical induction by drugs including "antitubulins," and to induction in vitro by viral infection.

Tubular arrays in cerebrospinal fluid cells: their location within smooth endoplasmic reticulum cisternae

Unique ultrastructural formations termed tubular arrays have been reported in a variety of renal diseases, viral infections, malignant tumors, and other circumstances. This report describes identical structures in monocytes in the cerebrospinal fluid in a case of pneumococcal meningitis. The occurrence, previously unreported, of tubular arrays in this infection and this kind of cell supports the growing view that tubular arrays probably do not represent viral components, but rather a general reactive phenomenon of the cell. In addition, ultrastructural findings are presented suggesting that tubular arrays appear to be located in the cisternae of the endoplasmic reticulum with major involvement of its smooth compartment.

Synovial pathologic changes in spontaneous canine rheumatoid-like arthritis

The synovial fluid and membrane were studied in 10 dogs meeting the American Rheumatism Association criteria for classic human rheumatoid arthritis (RA). Light microscopic pathologic features were consistent with those found in the human disease. Neutrophilic infiltration of synovium was somewhat more prominent than in chronic human RA, and activated lymphocytes in fluid or membrane were less frequent. The proliferative and plasma cell reaction seemed identical. Electron microscopy (EM) suggested microvascular injury with findings which included electron dense deposits in the vessel walls of 2 dogs. Seven dogs had meshworks of 20--25 nm tubules in tubuloreticular structures (TRS) similar to those seen in human systemic lupus erythematosus and only occasionally in human RA. There were also crystalline arrays of tubules, a configuration previously reported in tumors and virus infections and possibly suggestive of a cellular reaction to virus infection. To date no initiating agent has been identified, but this spontaneous canine disease which is very similar to human RA can provide a valuable model in which to examine pathogenesis of chronic arthritis.

Morphological observations of the replication of herpesvirus tamarinus in RL-33 cells

The replication in RL-33 cells (rabbit lung cell line) of herpesvirus tamarinus isolated from cotton-topped marmosets (Saguinus oedipus) was investigated by electron microscopy. In the early stages of infection, ring-shaped and granular structures, and fibrillar materials were recognized in the nucleus. Immature particles were often found in such nuclei. The envelope of the virus was formed by budding through intracytoplasmic membranes, the inner nuclear membrane or the membrane of intracytoplasmic vacuoles. Virus particles which appeared to be budding through the plasma membrane were also observed. Aberrant viral forms were produced by independent budding of both the inner and outer nuclear membranes. The mature particles once enveloped acquired a second envelope by budding through intracytoplasmic double membranes or the outer nuclear membrane. Unusual virus-associated structures were observed in the cytoplasm and nucleus. Virus particles appeared to be released by the process of reverse phagocytosis.

Rod-shaped bodies and crystalloid inclusions in ocular vascular endothelia of adult and developing Macaca mulatta

In addition to the usual organelles, endothelial cells of ocular blood vessels and Schlemm's canal in adult and fetal Macaca mulatta, contain two types of inclusions: rod-shaped bodies and crystalloids. The rod-shaped bodies are similar to those first described in arterial endothelia of the rat. They are between 0.2 to 0.35 micrometer in diameter, up to 2.5 micrometers in length, and are membrane bounded. The crystalloid inclusions are up to 1.2 micrometers in diameter and are associated with the granular endoplasmic reticulum. Their crystalline lattice consists of subunits, 28 nm in diameter, which are either arranged in rows separated by amorphous matrix or tightly packed in a honeycomb-like lattice. The rod-shaped bodies are much more numerous than the crystalloids; however, both kinds of inclusions are consistently found in both adult and fetal vessels. The represent normal components of ocular vascular endothelia which appear very early in the development of the eye.

Intracisternal tubular inclusions in nasopharyngeal carcinoma

Biopsy specimens obtained from 20 cases of nasopharyngeal carcinoma were examined under electronmicroscope for the presence of Intracisternal Tubular Inclusions (ITI). In eight (40 per cent) of them these inclusions could be identified. Although the morphogenesis and significance of these ITI are not clearly understood, they have been found in several autoimmune and viral diseases, including infectious mononucleosis, a disease caused by EBV, and Burkitt's lymphoma, which is closely associated with EBV. Hence, the presence of ITI in NPC, another disease associated with EBV, seems to be of some significance. It is proposed that these inclusions could be the result of an immunological reaction initiated by injured cells infected with EBV, which acted as an antigen. The presence of another type of cytoplasmic inclusion, hitherto unknown, has also been reported.

Annulate lamellae in phloem cells of virus-infected Sonchus plants

The occurrence of annulate lamellae (AL) in differentiating phloem of Sonchus oleraceus (Compositae) singly infected with sowthistle yellow vein virus (SYVV) and doubly infected with a combination of SYVV and beet yellow stunt virus is documented by electron microscopy. Cell types in which AL were found were immature sieve elements and phloem parenchyma cells. AL were found only in cells that also contained SYVV particles although a direct association between the virus and AL was not apparent. The substructure of the AL and the relationships between the AL and the nuclear envelope and endoplasmic reticulum are similar to those reported in other descriptions of this organelle in the literature. This report appears to be the first one concerning the association of AL with a plant virus disease.

Fine structural study of annulate lamellae complexes in human tumors

Specific intracytoplasmic organelles, annulate lamellae and radial cisternae, have been studied in several human tumours. Annulate lamellae are observed in all cases of leiomyoma, leiomyosarcoma, rhabdomyosarcoma and malignant melanoma, whereas radial cisternae are only found in a case of leiomyosarcoma. Annulate lamellae are characterized by stacks of parallel arrayed long cisternae showing alternative arrangement of annuli and sacs. Some of these cisternae are connected directly with rough-surfaced endoplasmic reticulum and there is continuity with the lumen and membrane. Radial cisternae are mainly composed of two structures: numerous short cisternae, which are a variant of annulate lamellae, and numerous spherical particles derived from the cisternae. The cisternae are arranged parallel or radially around particles measuring up to 1100 A in diameter. These particles consisting of an amorphous high electron dense material without distinct limiting membrane are organized in groups and vary in number. There is no evidence of a direct relationship between these structures and viral infection.

Cytoplasmic tubular arrays in cells of American Burkitt's type lymphoma

Aggregates of tubular arrays associated with cysternae of endoplasmic reticulum were observed in untreated primary American form Burkitt's lymphoma. The tumor occurred in a white female child who died with severe central nervous system (CNS) involvement. Although the significance of the tubular structures and the mechanism by which they are formed remains unknown, the predilection of these structures for lymphoid and reticuloendothelial cells and their frequent association with either viral or suspected viral conditions cannot be overlooked. However, it is possible that the tubular structures may reflect an increased production of antibody protein in response to a viral antigen.

Annulate lamellae and crystalline inclusions in granular endoplasmic reticulum of the islet organ and associated tissues of a cyclostome, Myxine glutinosa

Cytoplasmic annylate lamellae were found in the islet organ of a cyclostome, the hagfish (Myxine glutinosa), predominantly in cells interpreted as young proliferating beta-cells, and also in endocrine cells and enterocytes of the bile duct and gut and in the endothelial cells of small blood vessels. A close association was observed annulate lamellae and granular endoplasmic reticulum. Both in cells with and in those without annulate lamellae, crystalline inclusions of proteinaceous nature were seen in granular endoplasmic reticulum. These inclusions were occasionally closely associated to annulate lamellae, and a direct continuity could be seen between granular endoplasmic reticulum and the outer nuclear membrane surrounding an inclusion partially situated in the perinuclear cisterna. Rod-shaped structures and rounded electron dense bodies were seen in the nuclei of some islet parenchymal cells. The presence of annulate lamellae in the islet organ and associated tissues of Myxine glutinosa is believed to be related to the very high phylogenetic age of this species. The close association observed between annulate lamellae, granular endoplasmic reticulum, crystalline inclusions, and sometimes also nuclear membranes, may be of functional significance.

Clinical observations and neuropathology of rabbits in the acute stages of type 2 herpes simplex infections

Herpes simplex virus, MS (type 2) was inoculated intramuscularly into the medial gastrocnemius muscle of both hind legs of 6-8 week New Zealand white rabbits. The animals were observed for clinical evidence of infection for 17 days. Abnormal signs were first noticed on the sixth and seventh days after inoculation. These increased in severity until the twelfth and thirteenth days. None of the animals ever became paralyzed.

Gross haemorrhagic lesions were first seen in the spinal cord at 9 days. Light microscopic sections of the S2 through L7 spinal cord segments at 9 days showed meningitis, perivascular cuffing with hypertrophy and multiplication of the lining epithelium, and adherence of white blood cells to the lumen of the vessels. A large damaged area was noted in the dorsal horn of the S2 spinal cord segment, which contained cells having intranuclear inclusion bodies characteristic of HSV-infected cells. By electron microscopy, the infected cells in this area were shown to contain intranuclear immature HSV particles. Mature virus particles in the cytoplasm were rarely seen. The ultrastructural aspects of the infection at 9 days were studied in detail.

Direct immunofluorescent microscopy of the rabbits from 4 to 16 days after injection of MS showed no significant fluorescence over controls in any of the nervous tissue examined on Days 4-6. On the seventh day, however, significant fluorescence was observed in the S1 spinal cord segment and the right S1 ganglion. This specific fluorescence in the S1 and L7 spinal cord segments and spinal ganglia was seen in the remaining rabbits which had been inoculated 8-16 days previously.

The findings in this study were correlated with those of other workers in the field, special emphasis being placed on the significance of the various HSV strains used and the differences in dosage levels, points of inoculation and species of experimental animals.

Significance of cytoplasmic microtubules in lupus nephritis

Twenty-five renal and three skin biopsies from 14 cases of systemic lupus erythematosus with lupus nephritis were examined by electron microscope. Seventy-five renal biopsies from nonlupus cases consisting of 35 adults and 40 children were used for comparative study. Clusters of cytoplasmic microtubules, which have been referred to as virus-like particles, were observed in the endothelial cells of glomerular and peritubular capillaries in renal biopsies of all lupus cases. The clusters of microtubules were larger and more numerous in the initial biopsies with mild glomerular changes and in the second biopsies from two cases during a period of more severe relapse. Clusters of microtubules were fewer and smaller in renal biopsies with more advanced glomerular changes. Skin biopsies showed similar cytoplasmic inclusions in arterioles and capillaries. Cytoplasmic microtubules were also observed in 3 adults and 13 children of 75 patients who had no systemic lupus erythematosus. Although the formation of the cytoplasmic microtubules may be related to a virus infection, this suggestion cannot be confirmed from the morphologic findings of this study. Of additional interest is the evidence that these microtubules are not cytoplasmic changes secondary to corticosteroid therapy. It is concluded that the presence of many large clusters of cytoplasmic microtubules is specific for lupus nephritis, and it may be substantiated by similar findings in the skin.