Reproduction of lyssaviruses: ultrastructural composition of lyssavirus and functional aspects of pathogenesis.

Lyssaviruses are considerably adapted to neural tissue, although they can also be replicated in muscle and glandular cells. In neural tissue their reproduction takes place almost exclusively in neurons, and in the course of their dissemination they make use of the structural peculiarities of this highly differentiated cell type. The replication takes place completely in the cytoplasm, although rhabdovirus leader RNA enters the nucleus and by blocking host DNA and RNA synthesis promotes viral synthetic processes. In the cytoplasm the two phases of viral reproduction, the synthesis of nucleocapsids and the formation of the envelope together with the assembly of the virion, are separate in time and space. By this separation the transmission of infection by the incomplete form of the virus, i.e., by the synaptic transfer of ribonucleoprotein-transcriptase complexes is also possible. The formation of viral envelope and assembly of full viruses on the cisternal system of the host neurons is a highly complex process, as presented here in a three-dimensional analysis. Due to the high complexity of virus assembly, defects in construction are frequent, accounting for the high yield of defective interfering particles in the course of the reproduction of lyssaviruses.

Borna disease--neuropathology and pathogenesis.

Natural BD is a nonpurulent acute/subacute encephalitis of horses and sheep with a propensity to involve the olfactory and limbic systems, and the brain stem. The inflammation is concentrated primarily in the gray matter, but subcortical white matter may also be affected. Experimental BD can be produced in a series of animals from birds to primates. The neuropathology after experimental infection is similar to that in natural disease but the inflammatory changes are more diffuse. In the rat and mouse, a persistent/tolerant infection can also be induced, in which inflammatory changes are conspicuously absent. In the course of persistent infection of the rat, an elective, focal degeneration ensues that involves the dentate gyrus, retina, and, less frequently, the magnocellular part of the hippocampus. The cytopathic destruction of the dentate gyrus is the likely anatomical substrate of learning deficiencies and behavioral changes, prominent features of chronic infection. Later in infection, more diffuse and random degeneration of neurons can be found. In all species infected, viral antigens are produced in excess and fill all neuronal processes. Beside neurons, glial cells are infected as well. The agent spreads in the nervous system axonally and transsynaptically (transneuronally). The type of neurotransmitter receptors in the synapse and their interaction with viral proteins may modulate the spread of infection (Gosztonyi et al. 1994). Virus particles have not been visualized in the brain in any phase of the disease. During persistent infection of the rat, production of viral proteins has a phasic character. Some rats survive acute infection and develop an obesity syndrome. The anatomical basis of this syndrome is not fully clarified; inflammatory destruction of the infundibular region, vacuolar degeneration of the paraventricular nucleus of the hypothalamus and severe, progressive involution of the hippocampal formation most probably play an important role in the production of this neuroendocrine syndrome. In the acute disease, inflammatory reaction can severely aggravate virus-induced cytopathology, but cannot be the sole cause of the neurological disease, since infection with high passage virus can lead to a similarly severe disease in the absence of inflammatory changes.

Human immunodeficiency virus (HIV) distribution in HIV encephalitis: study of 19 cases with combined use of in situ hybridization and immunocytochemistry.

Brains of 19 AIDS patients with HIV encephalitis were examined by immunohistochemistry and in situ hybridization using antisense HIV DNA and RNA probes. Double immunohistochemical labeling, using antibodies against viral and cell-type specific antigens, was utilized to study lesions in some brains. Other combined studies included use of in situ hybridization and immunohistochemical labeling of the same section, using antibodies against either viral or cell-type specific antigens. Hybridization signals were abundant and were concentrated mainly in the white matter. Heavy labeling was found in the subcortical white matter, the corpus callosum, the internal capsule, and white matter regions of the brainstem and cerebellum. Deeper cortical layers often contained cells with hybridized probe when the subcortical white matter was intensely labeled. HIV nucleic acid sequences were found almost exclusively in macrophages. Counts showed that 16-25% of macrophages contained viral antigens and exhibited hybridized HIV probe. Almost all of these macrophages contained proviral DNA, viral RNA and viral proteins; i.e. they were actively replicating HIV. We also examined brains from three AIDS cases without clinical or pathological evidence of HIV encephalitis; no HIV sequences or immunoreactive proteins were detected.

Spongiform encephalopathy in AIDS dementia complex: report of five cases.

We describe the morphological findings in the brain of five AIDS patients who died with a clinical diagnosis of dementia. We have found a spongiform change (small rounded vacuoles) in different parts of the brain and a similar but morphologically different sponginess, the status spongiosus, characterized by looser and coarser microcystic cavitations of the grey matter in which the tiny cysts and vacuoles are enmeshed by glial fibrils. At the ultrastructural level, round and oval clear spaces, divided by septae into several smaller ones, appeared in the neuropil. The pathogenesis of the majority of the vacuoles and cavitations is not clear yet but a focal loss of cortical neurons was evident and furthermore some of the vacuoles were identified as remnants of dendrites. The light and electron microscopic findings can not be interpreted as artefacts or as a simple edema of the brain and also can not be explained by the different infective complications. We have found spongiform alterations in all cases of clinically diagnosed dementia and therefore it seems obvious that these findings are quite frequent in AIDS dementia.

Muscular involvement in Behçet's disease: case report and review of the literature.

Acute necrotizing myositis is described in a 22-yr-old man with clinically diagnosed Behçet's disease. Light microscopic examination revealed a prominently granulocytic-monocytic infiltration of the muscle with severe necrosis. An infectious (bacterial, fungal or parasitic) etiology could be excluded by specific staining techniques and by immunohistochemistry. Vascular deposition of immune complexes was detected by direct immunofluorescence. Electron microscopy revealed severe structural damage and phagocytosis of muscle fibers. In the endomysium, leukocytes and occasional erythrocytes were found. Virus-like particles were not seen. The relevant literature on muscular involvement in Behçet's disease is reviewed. It is suggested that two different stages of inflammation occur in Behçet's disease. In the acute stage it presents as a granulocytic-monocytic necrotizing reaction developing from a neutrophil-mediated vasculitis. In the later phase lymphocytic infiltrations predominate. Despite the rare involvement of muscles the diagnosis of Behçet's disease should be considered particularly in younger patients presenting with muscular symptoms like pain and swelling pre-dominantly of the lower extremities.

Purpura cerebri in gram-negative septicaemia. A histological and immunohistochemical study.

Two cases with brain purpura following Gram-negative septicaemia were examined morphologically and immunohistochemically. The brain lesions, including ball and ring haemorrhages, a few days old, with some microglial cells accumulated around the older foci, were restricted to the white matter. Immunohistochemically, scanty deposits of IgG, IgA and IgM mainly in the macrophages in brain, kidneys and lungs were found, whereas staining with antibodies directed against IgE and complement (C3, C4) remained negative. In the brain, immunoglobulin deposits were located mainly in the macrophages, furthermore, in and around the walls of a few intact (non-haemorrhagic) vessels; within the perivascular haemorrhagic foci no deposits could be demonstrated. The relevance of these observations to the pathogenesis of brain purpura is discussed.

Axonal and transsynaptic (transneuronal) spread of Herpesvirus simiae (B virus) in experimentally infected mice.

In order to study the pathogenesis of B virus infection of the nervous system, newborn and young mice were inoculated by four different routes: 1. Intramuscular (i.m.) in the forelimb; 2. I.m. in the hindlimb; 3. Subcutaneous (s.c.) in the abdominal wall; 4. Intraperitoneal (i.p.). Spread of virus was followed by immunohistochemical demonstration of viral antigen in tissue sections of the peripheral and central nervous system. Three distinct patterns emerged: 1. After i.m. limb inoculations, virus progressed along the ipsilateral dorsal column, the bilateral spinothalamic and bilateral spinoreticular systems and along central autonomic pathways. 2. After s.c. inoculation, the dorsal column was spared, otherwise the spread was similar to that following i.m. inoculations. 3. After i.p. inoculation, virus spread in the spinal cord bilaterally, mainly along spinothalamic and central autonomic pathways. The peripheral motoneurons were conspicuously spared, even in the i.m. inoculation mode. In the brain stem, B virus antigen appeared bilaterally, at multiple sites. In the cerebrum, virus infected cells appeared first in the thalamus, hypothalamus and the motor cortex. The mode of spread from spinal levels was mainly orthograde along the ascending systems (dorsal columns, spinothalamic, spinoreticular tracts), but also retrograde along descending systems (pyramidal tract, central autonomic pathways). Oligosynaptic systems transmitted virus more quickly than the polysynaptic ones. In the involvement of various neuronal systems in virus spread, a certain selectivity, sparing the peripheral motoneuron and the cerebellar systems, could be assessed.

Expression of Leu-19 (CD56, N-CAM) and nitric oxide synthase (NOS) I in denervated and reinnervated human skeletal muscle.

Neural cell adhesion molecule (N-CAM, Leu-19, CD 56) expression appears during muscle fiber regeneration and after denervation. Sarcolemma-associated nitric oxide synthase (NOS) I, however, disappears from denervated myofibers. The dynamics of expression of both proteins were studied in 5 cases of acute/subacute denervation, 28 cases of chronic denervation with and without collateral reinnervation, 5 cases of the intermediate type spinal muscular atrophy (SMA 2), and in 2 normal biopsies. NOS I and its NADPH diaphorase (NADPHd) activity disappeared from the sarcolemma region shortly after denervation, and before the appearance of denervation atrophy. N-CAM was found diffusely distributed in the sarcoplasm at the most severe phase of denervation atrophy in the majority of highly atrophic fibers. During reinnervation, NOS I expression remained absent and in part of the cases the target/targetoid phenomenon appeared. In parallel with the increase in volume of the reinnervated muscle fibers, the intensity of N-CAM immunoreactivity decreased progressively. After full restitution of muscle fiber caliber, the target/targetoid phenomenon and N-CAM immunostaining disappeared completely, and, finally, NOS I reappeared in the sarcolemma region. The sarcolemmal expression of dystrophin and dystrophin-associated proteins was unchanged during denervation. NOS I was completely absent in children with SMA 2, since the protein does not appear before 5 years of age in skeletal muscle, while N-CAM was very intensely expressed in the sarcoplasm of highly atrophic denervated muscle fibers. In conclusion, this study suggests that innervation is an important factor for selective gene expression and positioning of NOS I and N-CAM in skeletal muscle and gives practical information for the assessment of the phase and developmental stage of the denervation and reinnervation process.

Calcineurin A and calbindin immunoreactivity in the spinal cord of G93A superoxide dismutase transgenic mice.

A qualitative immunohistochemical study was performed on calcineurin A- and calbindin-positive neurons in the spinal cord of transgenic mice, an animal model of amyotrophic lateral sclerosis, carrying the G93A mutation of the Cu/Zn-superoxide dismutase gene. The results show that calcineurin A-immunoreactive motoneurons are affected by the neurodegenerative process; in contrast, calbindin-positive cells are selectively spared. The findings suggest that calcineurin plays a role as an accessory factor responsible for selective vulnerability in the neurodegenerative process of amyotrophic lateral sclerosis.

Wernicke's encephalopathy in two patients with acquired immunodeficiency syndrome.

Two non-alcoholic homosexual patients with acquired immunodeficiency syndrome (AIDS) are reported who developed acute Wernicke's encephalopathy in the terminal stage of their illness. The first patient presented with vascular congestion, minute haemorrhages, proliferation of microglia and of the vessel walls at the predilection sites of the Wernicke-Korsakoff process. In the second patient only the mamillary bodies were involved. Besides Wernicke's encephalopathy, a primary cerebral immunoblastoma and cerebral toxoplasmosis were found in the first patient, whereas the second showed severe encephalitis with numerous microglial and multinucleated giant cells reacting positively with anti-HIV antibody. Just as in the development of Wernicke's encephalopathy in malignant diseases, the catabolic trend of the metabolism of the immunodeficient patients with consecutive thiamine deficiency must be considered the principal pathogenetic mechanism.

Type 2a fibre rhabdomyolysis in myoadenylate deaminase deficiency.

A 31-year-old woman developed an acute, potentially fatal rhabdomyolysis of undetermined origin. Muscle biopsy revealed selective lysis involving exclusively type 2a fibers. Myoadenylate-deaminase (MAD) deficiency was proven by a negative histochemical reaction as well as by an enzymatic biochemical determination. The significantly greater energetic dependence of type 2a fibres on MAD explains their selective damage. The patient's mother also suffers from a similar muscle disease of still unclarified origin.

Stereotactic brain biopsy in AIDS.

In the hope of finding a treatable condition, the need for rapid diagnosis in HIV-seropositive patients with brain lesions is apparent. In order to evaluate the efficacy of stereotactic brain biopsy in AIDS patients, we retrospectively studied 25 HIV-infected patients undergoing stereotactic biopsy. Brain lesions were identified with gadolinium-enhanced MRI and/or contrast CT. Brain biopsy was performed using the system of Riechert. From 8 up to 15 small tissue samples from one or two targets were obtained in every patient. The biopsy material was examined cytologically, histologically (including electron microscopy), immunohistochemically and, in part, by animal test and polymerase chain reaction (PCR). A definite diagnosis was achieved in 92%. Diagnosis included primary central nervous system lymphoma (PCNSL) (10), toxoplasmosis (10), progressive multifocal leukoencephalopathy (2) and one case of co-existing toxoplasmosis and cytomegalovirus infection. Two biopsies were non-diagnostic. All PCNSLs showed polymorphic B-cell populations of high malignancy; accurate classification according to the Kiel classification was not possible. In 3 lymphomas Epstein-Barr nuclear antigen (EBNA) 2-mRNA could be detected by PCR and confirmed immunohistochemically by EBNA 2 expression. In 6 cases autopsy confirmed the biopsy diagnosis. Conventional histology was not sufficiently decisive for toxoplasmosis and progressive multifocal leukoencephalopathy, so that immunohistochemistry and animal tests became very important for a final diagnosis. With the help of different morphological and molecular biological techniques stereotactic brain biopsy appears to be an effective method in the diagnosis of HIV-associated brain lesions. In view of the marked radio- and chemosensitivity of PCNSLs it is mandatory to establish an early and accurate histological diagnosis for adequate treatment.

Herpes simplex virus encephalitis: cranial magnetic resonance imaging and neuropathology in a mouse model.

We performed a long-term magnetic resonance imaging (MRI) study in a mouse model of herpes simplex virus encephalitis. Mice were infected with herpes simplex virus type 1 (HSV-1) strain F. A 1.5-T cranial MRI scanner with standard spin-echo sequences was used. Neuropathological studies included immunohistochemistry. The presence of HSV DNA in brain tissue was determined with a polymerase chain reaction assay. Clinical assessment was performed daily: within the first 2 weeks the animals were severely affected and recovered thereafter. MRI and histopathological abnormalities corresponded well. HSV DNA was detectable initially and at 6 months. Extent and severity of structural abnormalities increased at 6 months. MRI offers a new in vivo approach for the detection of structural changes in the disease course of experimental herpes simplex virus encephalitis.

Focal-unilateral accentuation of changes observed in the early stage of Creutzfeldt-Jakob disease.

We report on a 67-year-old male patient with progressive right-sided hemiparesis predominating in the arm and right-sided myoclonias. The EEG showed periodic delta activity in the left hemisphere. The patient died of pulmonary embolism 10 weeks after the onset of the symptoms. The neuropathological examination was indicative of Creutzfeldt-Jakob disease: distinct spongiform changes, nerve cell loss and proliferation of astroglia in the left hemisphere were found; in the right hemisphere, however, only a few circumscribed spongiform foci were seen. There was a clear correlation between the unilateral predominance of the EEG abnormality and neuropathological changes. The hypothesized spread of infection along commissural projection pathways is supported by this pattern of lesions.

Maximal regeneration distance. How far can a peripheral axon regenerate?

Peripheral nerves of the fore- and hindlimbs of 20 rats were induced to regenerate over double and triple of their original lengths through consecutive orthograde and retrograde (zigzag) anastomoses along parallel nerves of the same limb. Morphological changes were followed on longitudinal sections of the whole-mount composite nerves by several histological techniques. Regeneration regularly took place along this pathway. The regenerated axonal segments were intensively remyelinated, demonstrating the capacity of the spinal neurons to produce and maintain disproportionately long axonal processes. These observations may be relevant for reconstructive neurosurgery when very long peripheral nerve gaps have to be bridged.

The geomagnetic field: a factor in cellular interactions? I. Magnetism and Schwann cell-axon interaction in the peripheral nerves of the newborn rat.

Axonal ensheathment and myelination, one form of axon-sheath cell interaction, was studied under normal earth magnetism, in the absence of terrestrial magnetic field, and under a 5 G (0.0005 T) magnetic field. Results indicate that the geomagnetic field is necessary for the fundamental biological activity of axonal ensheathment and myelination. The exact mechanism of action remains obscure.

Immunohistochemical and electron microscopic techniques in the diagnosis of viral encephalitides.

Electron microscopy and in particular, immunohistochemical examination techniques have substantially improved the chances to attain an etiologic diagnosis in viral encephalitis. The application of these techniques is needed first of all in the examination of cerebral biopsy specimens, but they can contribute to the clearing of the etiology at post mortem study of the brain, too. This review outlines the basic techniques and their application fields. In immunohistochemistry beside the demonstration of specific viral antigens the analysis of the humoral and cellular immune reactions and the identification of the cell types involved by cell specific markers is also important. The second part of the review gives a synopsis of the results of electron microscopic and immunohistochemical studies in the most important acute, subacute and chronic encephalitides occurring in Europe.

Morphometric study of muscle in congenital idiopathic club foot.

In congenital idiopathic club foot gross morphological changes cannot be assessed in muscle tissue by conventional histopathological techniques. Since, however, recent studies have indicated the presence of neuromuscular anomalies with preponderance of Type 1 fibres in this condition, we have performed histochemical, morphometric and electron microscopic examinations in muscle biopsies of 23 patients with congenital idiopathic club foot deformity. The age of the patients varied between 6 weeks and 12 years, respectively. Muscle biopsy was taken mainly from the flexor group of the affected leg(s) during the surgical correction of the anomaly. No gross pathological changes could be found by histochemical analysis. Morphometric study, however, disclosed abnormalities in the composition of the fibre types. The most prominent change was the percentual increase in Type 1 and decrease in Type 2 fibres in almost all the cases. Electron microscopically, only minor fine structural changes could be found. Since these changes could be assessed soon after birth just as in the later course, they cannot be regarded as the consequence of the abnormal position of the leg. More probably, Type 1 fibre predominance is related etiologically to the congenital club foot deformity.

The neuropathology and epidemiology of AIDS. A Berlin experience. A review of 200 cases.

The brains of 200 patients who died with Acquired Immunodeficiency Syndrome (AIDS) from Berlin were examined retrospectively. This study was specifically intended to evaluate and document the prevalence of neuropathologic abnormalities, establishing the frequency of the various types of structural lesions, their combinations, their relative incidence, and the risk factors involved in different age groups. The data were compared and contrasted with the findings reported from other parts of the world and other German cities. It was found that the mean age of this group of patients was 41.4 years old, 75% were homosexual/bisexuals (H/B) and 18.5% were drug abusers (DA). Only 5.5% were women. Brain parenchymal changes, called in this report, HIV-related encephalopathy (HIVRE), characterized by vacuolization or spongy changes and astrocytosis in the subcortical white matter, and occasionally in gray matter, were found in 67 patients (33.5%). Drug abusers had a higher incidence of HIVRE (59.5%) compared with homosexual/bisexuals (28%). This is statistically significant (p < 0.0005). CMV encephalitis was found in 26 patients (13%) (8% of the drug abusers in contrast to 13% in the homosexual/bisexuals group). Primary central nervous system lymphoma (PCNSL) was seen in 28 patients (14%) regardless of the risk factor involved. 20 (13%) of the 150 H/B and 3 (8%) of the 37 DA had CMV encephalitis. Of the 150 H/B, 24 (16%) had PCNSL compared with only 4 of 37 (11%) of the DA. A significant incidence of opportunistic infections, both protozoal and viral was found in all groups. Cerebral toxoplasmosis occurred in 68 patients (34%). Microglial (phagocytic) nodules, probably related to CMV or cerebral Toxoplasmosis, were observed in 40 cases (20%). Diffuse microglial proliferation was noted in 104 patients (52%). Cerebral cryptococcosis was found in three patients. Progressive multifocal leukoencephalopathy was seen in 16 patients (8%). Various combinations of CNS pathological processes were found in 44 of the patients (22%). These include concomitant infections with Toxoplasma gondii and HIVRE in 13 patients; Toxoplasmosis and PCNSL in 8 patients; Toxoplasmosis with CMV and HIVRE in 4 patients; Toxoplasmosis with CMV in 2 patients; Toxoplasmosis with PCNSL and CMV in 2 patients; Toxoplasmosis with PCNSL and HIVRE in 2 patients and Toxoplasmosis with PML and HIVRE in 2 patients; Cerebral CMV with PCNSL and HIVRE in 4 patients; Cerebral CMV with HIVRE in 2 patients; PML with PCNSL in one patient; PML with HIVRE in 2 patients; and PML with PCNSL and HIVRE in one patient. Cerebrovascular lesions were found in 34 patients (17%).(ABSTRACT TRUNCATED AT 400 WORDS)

Vasculitic, hypoxic-ischemic leukoencephalopathy.

The case of a 67-year-old woman with terminal renal insufficiency, who developed extensive encephalopathy with predominant involvement of the white matter is reported. The encephalopathy was the consequence of preexisting hypertensive alterations, acidosis, hypoxia, ischemia, bacteremia and varicella-zoster meningoencephalitis. The vasculitic alterations associated with meningoencephalitis had a major influence on the development and the extent of the leukoencephalopathy.