Motor neuronal loss and neurofilament-ubiquitin alteration in MoMuLV-ts1 encephalopathy

A temperature-sensitive mutant of Moloney murine leukemia virus (MoMuLV-ts1) induces immunosuppression and spongiform encephalopathy in susceptible newborn mice. The associated neuronal degeneration primarily involves the motor neurons in specific target areas of the central nervous system (CNS). Neuronal loss occurs in the absence of direct viral infection of neurons and is the most dramatic pathological change in the CNS of infected mice. To quantitatively demonstrate neuronal loss, an unbiased morphometric stereological study was undertaken using the optical disector method. Using highly susceptible FVB/N mice, neuronal loss was quantitated in the tissue sections of brain stem from infected and noninfected mice at 20 and 35 days post inoculation (dpi). Results indicated that there was no significant neuronal loss at 20 dpi, but significant (P < 0.05) at 35 dpi. In addition, histology, transmission electron microscopy and immunohistochemistry revealed Lewy body-like inclusions consisting of aggregates of neurofilaments and cellular organelles. Degenerated neurons and glial cells were heavily ubiquitinated. Together, these results suggest that significant neuronal loss occurs at the end of the disease process and that Lewy body-like formation and protein ubiquitination are part of the pathogenic process in ts1-induced encephalopathy.

Retinopathy of prematurity in very low birth weight infants

This study aims to determine the prevalence of and risk factors associated with retinopathy of prematurity (ROP) in very low birth weight (VLBW) infants. All premature VLBW infants, admitted into the neonatal intensive care unit of the University Hospital Kuala Lumpur, were screened from 4 weeks of life. Perinatal and neonatal data were retrieved from the infants' medical notes. Between August 1994 and July 1996, 100 infants had their eyes examined serially. Of the 15 (15%) infants with ROP, all were less than 31 weeks gestation, and only 1 infant had birth weight above 1250 g. Five (5%) infants had severe ROP; 4 infants underwent cryotherapy for stage 3 threshold disease. Infants with ROP, as compared to infants without ROP, had lower birth weight [mean (SEM) 993 (50) g versus 1205 (22) g, P < 0.001], lower gestational age [mean (SEM) 28.0 (0.4) weeks versus 30.1 (0.2) weeks, P < 0.001], higher rates of patent ductus arteriosus and chronic lung disease, greater number of radiographic examinations and episodes of late-onset suspected/confirmed sepsis, and required longer duration of supplemental oxygen, ventilation, xanthine, antibiotics and intralipid use, but were slower to establish full enteral feeds. On multivariate logistic regression analysis, birth weight < or = 1000 g [OR 2.38, 95% CI 1.25, 4.55, P = 0.009] and gestational age < or = 28 weeks [OR 2.86, 95% CI 1.47, 5.56, P = 0.002] were significant predictors of increased risk of this disease. In conclusion, ROP is strongly associated with smaller, more immature and sicker neonates. Prevention of prematurity would help reduce the incidence of this disease.

Neuroimmunopathogenesis of ts1 MoMuLV viral infection

Newborn mice infected with ts1, a mutant of the Moloney murine leukemia virus, develop neuroimmunodegeneration with death and damage of thymocytes, astrocytes, and motor neurons by 24-38 days. T cells, B cells, and astrocytes, but not neurons, are infected by the virus. Primary splenocytes and thymocytes isolated from age-matched infected or control mice, when incubated in serum-deficient media containing phytohemagglutinin-L, either homotypically aggregate and survive or swell, expose their inner membrane phospholipids, and then shrink as they fragment their nuclei and excrete DNA-containing hypoploid minicells. In our present studies, the rates of these apoptotic changes were greatly increased in the infected cells. This thymocyte death was ameliorated in vitro by addition of Th2 cytokines, but not by Th1 cytokines, or by redox agents. In contrast, death of splenocytes, which were already mitogenically activated in vivo by the virus, was prevented by Th1 and Th2 cytokines plus redox support. In vivo, this ts1-induced neuroimmunodegenerative syndrome could be completely prevented by the immunomodulator polyinosine-cytosine and partially prevented by cytokines or redox modifiers. Viral titer primarily in the brain was also diminished by polyinosine-cytosine therapy. These observations indicate that the cell death in T cells and neurons in these ts1-infected neonatal mice can be prevented in vitro and in vivo by appropriate upregulation of the immune system.

Quantitative variation of free amino acids in the central nervous system of MoMuLV-ts1-infected mice

A temperature-sensitive mutant of Moloney murine leukemia virus (MoMuLV-ts1) induces polioencephalomyelopathy and hind limb paralysis in highly susceptible FVB/N strains of neonatal mice. This disease is characterized by progressive motor neurons loss and severe gliosis within specific target areas of the central nervous system (CNS). The mechanism(s) of this neurodegeneration is unknown. In the neonatal infection of the CNS, the MoMuLV-ts1 virus was reported to replicate within the endothelial, ependymal, astrocytes and microglial cells. Since no virus or viral products were recognized in the degenerating neurons, it is postulated that an indirect mechanism(s) caused the loss of neurons in the neonatally infected mice. This study was undertaken to investigate the possible pathogenic role of excitatory amino acids (EAAs) such as glutamate and other nonneurotransmitters amino acids (NAAs) in this animal model. The free amino acids concentration was analysed by a fluorometric HPLC method. The temporal measurements of the free amino acids concentration, glutamate, glutamine and arginine from the brain stem and spinal cord of MoMuLV-ts1-infected mice was significantly decreased when compared with the control non-infected mice. The concentration of EAAs during the course of this infection indicated a sharp decline in glutamate and its precursor, glutamine with early infection (10 days post infection-dpi). This deficiency persisted (20 and 30 dpi) in the spinal cord, where the neuronal loss was most severe, but not in the brain stem. A similar pattern occurs with the amino acid arginine. These observations suggest that an astrocyte-induced metabolic disturbance of glutamate and arginine in the CNS of developing mice, could be, in part responsible for the loss of motor neurons observed in this model.

Decolourization and biodegradation of N,N'-dimethyl-p-phenylenediamine by Klebsiella pneumoniae RS-13 and Acetobacter liquefaciens S-1

Klebsiella pneumoniae RS-13 and Acetobacter liquefaciens S-1, both methyl red (MR)-degrading bacterial strains, degraded N,N'-dimethyl-p-phenylenediamine (DMPD) under aerobic conditions. DMPD, a toxic and mutagenic aromatic amine, is formed during the reductive cleavage of azo dyes such as MR. The effects of physical parameters, such as temperature and aeration, and chemical parameters, such as pH and concentrations of glucose, ethanol and ammonium sulphate in the culture medium, on the degradation of DMPD by these bacteria were determined. Klebsiella pneumoniae RS-13 degraded DMPD more efficiently than A. liquefaciens S-1 under all physicochemical conditions, except in the presence of ethanol as carbon and energy sources. In addition, Kl. pneumoniae RS-13 degraded DMPD at low levels of carbon and nitrogen at pH 6-8. These results indicate that it is feasible to use Kl. pneumoniae RS-13 to completely degrade the detoxify MR under aerobic conditions.

The effect of mivacurium pretreatment on intra-ocular pressure changes induced by suxamethonium

Forty patients without eye disease, undergoing elective nonophthalmic surgery, were studied in a double-blind, randomised, placebo-controlled study evaluating the efficacy of mivacurium pretreatment in attenuating the rise in intra-ocular pressure in response to suxamethonium administration, laryngoscopy and intubation. The patients were randomly allocated to receive either mivacurium 0.02 mg.kg-1 or normal saline as pretreatment 3 min before a rapid sequence induction technique using alfentanil, propofol and suxamethonium. Suxamethonium induced a significant increase in intra-ocular pressure in the control group but not in the mivacurium pretreatment group (mean (SEM) increase = 3.5 (1.2) mmHg vs. 0.4 (0.8) mmHg, p < 0.05). There was a decrease in intra-ocular pressure in both groups after laryngoscopy and intubation with no significant difference between the two groups. These results show that mivacurium pretreatment is effective in preventing the increase in intra-ocular pressure after suxamethonium administration.

Unilateral alpha reactivity: an electroencephalographic finding in albinism

Persons with various forms of albinism frequently have misrouting of their optic nerve fibers. Visual evoked potential (VEP) studies can confirm this because monocular stimulation tends to result in asymmetrical rather than symmetrical occipital response. This type of decussation abnormality is associated only with albinism. In the electroencephalogram (EEG) of normal subjects, unilateral eye opening or closing does not affect the frequency, reactivity, regulation, and symmetry of alpha rhythm. In contrast, in our study, 6 of 19 persons with oculocutaneous and ocular albinism responded to unilateral eye opening with contralateral disappearance or significant attenuation of their alpha rhythm. The most likely explanation of this phenomenon is that the visual pathway misrouting is complete or nearly complete in some children with albinism so that one rather than both occipital lobes receive visual information from each eye. This type of alpha behavior, like VEP studies, supports the diagnosis of albinism, and such testing can be easily performed during a routine EEG recording.

Potential fields, EEG maps, and cortical spike generators

From analysis of the interictal discharge, one can deduce the location of the underlying generator or source. Despite the geometric complications of cortical convolutions and major fissures, clinical neurophysiologists fearlessly make statements about localization of the source. In fact, this is usually nothing more than a qualitative dipole localization, which is seldom discussed with the concern of non-unique mathematical solutions. However, further information can be gleaned from the spike topography if one applies some simple constraints or assumptions (discrete point source, columnar organization). An explanation of the tangential and radial fields of centrotemporal spikes is offered, together with an attempt to rationalize why the tangential topography is associated with a more benign clinical picture than the radial topography. It is suggested that there is differential epileptogenicity between gyral and fissural cortex. Extension of this is made to multiple subpial transection.

Neurodegeneration induced by MoMuLV-ts1 and increased expression of Fas and TNF-alpha in the central nervous system

Infection of neonatal mice with ts1, the neuropathogenic mutant of the Moloney murine leukemia virus, results in motor neuronal death in the brainstem and the spinal cord, with gliosis and demyelination, but no inflammatory cell infiltration into the CNS. To evaluate the possible mechanism(s) of ts1-induced neuropathogenesis, we measured CNS expression of cytokines and cell death-related genes in ts1-infected mice with neurological signs and compared with control uninfected mice. In the brainstem, the expression of Fas and tumor necrosis factor alpha (TNF-alpha) was increased in the ts1-infected mice. Both TNF-alpha and Fas were detected in astrocytes, and Fas was also detected in neurons in the brainstem. Some TNF-alpha-immunolabeled cells also appeared to be microglial cells. Most Fas-positive cells, including astrocytes and neurons, showed cytoplasmic vacuolization and other degenerative changes. In addition, Fas ligand-immunolabeled cells were also detected in sites where spongiform degeneration occurred. This study suggests that neural cell death in ts1-induced neurodegeneration is likely due to Fas- and TNF-alpha-mediated cell death mechanisms.

Possible control of cell death pathways in ataxia telangiectasia. A case report

Peripheral blood monocytes (PBMCs) obtained from a boy with the neuroimmunodegenerative syndrome of ataxia telangiectasia (AT) failed to aggregate or replicate efficiently when mitogenically activated under serum-depleted conditions. These cells rapidly swelled, then slowly shrank, and flattened as they excreted vesicles containing chromatin. This accelerated cell death with loss of homoadhesiveness could be prevented in vitro in most of the homozygous PBMCs by adding large amounts of autologous serum or by adding mixtures of Th1 cytokines, serum factors, and redox agents. However, even in high-serum media containing added cytokines, 20-30% of the homozygous PBMCs quickly flattened, produced minicells, and died. Since the defective functions of the human ataxia-telangiectasia nuclear kinase gene (ATM) could be bypassed in vitro in these defective AT PMBCs by addition of appropriate cytokines and redox survival factors, it may be possible to slow the progressive losses of ATM-deficient lymphoid cells seen in vivo. Since the neuronal degeneration in AT, as seen in the retrovirus-induced neuroimmunodegenerative syndromes, may also be a consequence of impairment of the central and peripheral immune system, it may become possible to prevent the neurodegeneration in AT by using signaling therapies that upregulate the ATM-induced signal deficiencies in the developing immune system.

Development of pathological lesions in the central nervous system of transgenic mice expressing the env gene of ts1 Moloney murine leukemia virus in the absence of the viral gag and pol genes and viral replication

The ts1 Moloney murine leukemia virus causes a degenerative neurologic disease in mice characterized by the development of noninflammatory spongiform encephalomyelopathy. To determine whether gag and pol gene products and viral replication are necessary for the ts1-env gene product to cause neurodegeneration, we generated transgenic mice harboring only ts1-env. Neuropathological lesions were observed in mice expressing the transgene in the central nervous system. This implies that gag and pol gene products and viral replication are not necessary for ts1-env to cause a mild form of neurodegeneration in mice.

Molecular studies of loss of heterozygosity in retinoblastoma

Retinoblastoma (Rb) is a paediatric intraocular tumour in which predisposition can be inherited. Cases of Rb tumours can be divided into three types: familial cases, sporadic bilateral cases and sporadic unilateral cases. Familial and sporadic bilateral cases are usually categorised as hereditary while sporadic unilateral cases as non-hereditary. In both familial and non-familial forms of Rb, loss of heterozygosity of the Rb locus has been reported although its frequency in tumours has not so far been accurately determined. The cloning of the gene responsible for retinoblastoma (Rb1) has facilitated DNA studies and genetic counselling of patients. We have examined forty-five cases of retinoblastoma at five intragenic sites of the Rb1 locus, namely intron 1/BamH1, intron 17/Xba1, intron 24/TthIII1, intron 25/Dra1 and Rb1.20 VNTR. Thirty-six out of the forty-five cases (80%) were informative for these markers. Comparison of results between genomic DNA from peripheral blood and from tumours revealed that loss of heterozygosity of alleles could be detected in 50% of cases studied in which tumour samples were available. Investigation of parental origin of retained alleles showed that in all these cases, the paternal alleles were preferentially retained. The analysis of the genetic origin of mutations predisposing to retinoblastoma can facilitate new approaches for identifying recessive mutant genes that lead to cancer as well as to provide a conceptual basis for accurate prenatal predictions of cancer predisposition.

Establishment and characterization of conditionally immortalized astrocytes to study their interaction with ts1, a neuropathogenic mutant of Moloney murine leukemia virus

The cytopathic infection of primary astrocytes with ts1, a neuroimmunopathogenic mutant of Moloney murine leukemia virus (MuLV), has been correlated to intracellular accumulation of viral precursor envelope protein gPr80env. To further study this specific virus-astrocyte interaction in a homogenous population, several immortal astrocyte lines were established from neonatal FVB/N mice using the temperature-sensitive SV40 tsA58 T antigen. These cells expressed glial fibrillary acidic protein, vimentin and T antigen; appeared nontransformed; were star-shape with long processes. They were susceptible to ts1 infection and suffered a cytopathic effect similar to that caused by ts1 infection of primary astrocytes. This cytopathic effect was characterized by growth inhibition, loss of cell processes and syncytium formation. Some cells also rounded up, formed mini cells and became detached from the culture dish. As in primary astrocytes, the processing of gPr80env in the immortalized astrocytes was inefficient. Since the envelope proteins interact with the ecotropic MuLV receptor both intracellularly and on the cell surface and since the receptor has been shown to be an arginine transporter, we attempted to determine the effect of ts1 on arginine uptake by these cells. Our results showed that in both immortalized and primary astrocytes, ts1 infection reduced the uptake of arginine more than did wild-type virus infection. Since arginine localizes predominantly in astrocytes in the CNS and has diverse functions, the decrease of arginine uptake in ts1-infected astrocytes may alter the metabolism of these cells, leading to impairment of their functions.

Luxation of the globe and Crouzon's disease--the first reported case in Singapore

A case of spontaneous luxation of the globe and Crouzon's disease is described. The luxation was reduced under general anaesthesia. Bilateral permanent tarsorrhaphies were performed to prevent further luxations and to decrease the lagophthalmos and corneal exposure. There was also mild bilateral optic atrophy and a left superior oblique palsy. The patient exhibited turricephaly, maxillary hypoplasia and shallow orbits with proptosis. Major reconstructive surgery is not indicated as the patient is already 9 years old and has no mental impairment.

Rhesus thymic/liver xenografts in severe combined immunodeficient mice: immunologic reconstitution and intrathymic infection with simian immunodeficiency virus

By serving as host recipients of xenografts from both humans and animals, severe combined immunodeficient (SCID) mice have become valuable to many laboratories interested in examining the pathophysiology of different diseases. To gain insight into the usefulness of the SCID mutation in retrovirus research, rhesus monkey fetal hematolymphoid tissues (liver and thymus) were used to construct a SCID-rhesus chimeric mouse (SCID-rh) and were engrafted in the renal capsule. The size and maturation of the thymic engrafts were monitored grossly, histologically, and immunologically. SCID mice were tolerant to rhesus tissues, and thymic engrafts contained thymocytes at different stages of maturation and differentiation that had morphologic features similar to age-matched rhesus thymus. Mature single positive CD2+, CD4+, and CD8+ T lymphocytes that were phenotypically similar to rhesus T lymphocytes were present at low levels (2% to 5%) in the peripheral blood and at moderately higher levels (7% to 15%) in the spleens of SCID-rh mice obtained between 12 and 15 weeks after thymus/liver engraftment. Within 3 weeks after engraftment, > 85% of the thymocytes in the thymic engrafts were immature double positive CD4+CD8+ T cells. The highest number of positive cells were seen in thymic engrafts obtained at 12 to 18 weeks. During these weeks, > 90% of the cells were double positive (CD2+CD4+, CD2+CD8+, and CD4+CD8+). After infection of the engrafted thymus tissue with simian immonodeficiency virus (SIVmac239), PCR analysis revealed successful viral infection of engrafts at 2 and 4 weeks after infection. No significant histopathologic and flow cytometric changes were observed in the thymic engrafts at 2 and 4 weeks after infection. An unrelated lesion of thymic lymphomas involving the SCID host thymus was seen in 12% of the mice. The data presented herein suggest that the SCID-rh is a valuable model for specific studies related to thymus-retrovirus interaction and that it could be used for further studies. The results are discussed in relation to current knowledge of thymus involvement during simian and human immunodeficiency virus infection.

Melioidosis presenting with orbital cellulitis

Melioidosis is known to present with many diverse manifestations but orbital cellulitis from melioidosis has never been described. We report a case of melioidosis in a 42-year-old diabetic male who presented with orbital cellulitis. He succumbed to recurrent empyema of the paranasal sinuses, rupture of an intracranial mycotic aneurysm and pulmonary empyema despite early antibiotic treatment.

Quantitative analysis of epileptic discharges

The methods for analysing the EEG epileptiform activity are discussed and compared. Particular emphasis is placed on studying interictal spike activity recorded from scalp. The results of these analyses should be interpreted in terms of underlying physiological events. An example is the hypothetical model of benign rolandic epilepsy of childhood.

A novel device for patient-controlled sedation: laboratory and clinical evaluation of the Baxter Intermate LV250 infusor and patient-control module

The Baxter Intermate LV250 infusor is a large capacity, high flow mechanical infusor, designed to deliver viscous solutions and suspensions. The objective of the laboratory study was to evaluate the LV250 infusor when used with either 0.9% sodium chloride solution or an emulsion, propofol 1%. Following this, the LV250 infusor with the patient-control module was assessed in the clinical setting as to its suitability for use in patient-controlled sedation with a propofol and lignocaine mixture. Between reservoir volumes of 250 and 55 ml, the LV250 infusor was found to infuse a propofol 1% and lignocaine mixture at a lower flow compared with the sodium chloride solution, 170 ml.h-1 and 260 ml.h-1 respectively. The lower flow with the propofol mixture may be a result of its higher viscosity. All patients using the LV250 infusor for patient-controlled sedation found it easy to use and stated that they were able to achieve their desired level of sedation. All patients maintained arterial oxygen saturations above 95%. The LV250 infusor performed reliably and with little inter-device variation, and with the patient-control module could be used as an alternative to electronic devices for providing patient-controlled sedation. Compared with electronic infusors, its advantages include compactness and simplicity of design.

Long-term cultivation and productive infection of primary thymocyte cultures by a thymocytopathic murine retrovirus

ts1, a mutant of MoMuLV, selectively kills T cells and neurons in the infected host resulting in neuroimmunodegeneration. In the infected thymus there is an early increase in mitosis of thymocytes followed by rapid death, suggesting that thymocyte death may be induced by viral mitogenic activation. Studies on thymocytes obtained from ts1-infected mice indicated that the ts1-induced depletion of thymocytes is mediated through activation-induced death by apoptosis. To further investigate the interaction between ts1 and thymocytes, we have established long-term primary murine thymocyte cultures by placing the thymocytes together with thymic remnants in culture medium containing IL-2 and IL-7. These thymocytes retained their immature phenotype and we susceptible to infection by ts1 and its parental wild-type MoMuLV. ts1-infected thymocytes proliferated initially at accelerated rate but subsequently produced more infectious virus and died much faster than control or MoMuLV-infected thymocytes. These in vitro studies to some extent reflect our in vivo studies reported previously.

Seizures involving the supplementary sensorimotor area in children: a video-EEG analysis

Most reports of supplementary sensorimotor seizures have been of adults with medically refractory epilepsy. Typically, supplementary sensorimotor seizures have onset in childhood. We describe the electroclinical features in 12 children. Cases were selected from an EEG laboratory population in whom video-EEG was performed routinely on all children. Supplementary sensorimotor seizures were diagnosed when there was bilateral tonic posturing of the upper or lower extremities, preserved consciousness, and lack of postictal confusion. Sensory auras were reported by 8 of 9 children aged > 3 years who had daytime seizures. Speech arrest occurred in all patients in whom it could be assessed, and abnormal vocalization was observed in 7 children. Interictal EEGs were often normal (49% of recordings), and ictal EEG changes could be subtle. An etiology was demonstrated in only 2 children, and brain imaging studies were normal in the other 10 patients. Seizures were controlled with antiepileptic drugs (AEDs) in 6 of the 12 children. The clinical manifestations of supplementary sensorimotor seizures in children are similar to those reported in adults; misdiagnosis is common at all ages.

Neuroimmunodegeneration: do neurons and T cells use common pathways for cell death?

In syndromes of pediatric neuroimmunodegeneration (NID), certain neurons and T cells degenerate and disappear during early development at an accelerated rate without alerting the peripheral immune cells. Current studies of some of these NID syndromes suggest that the primary cause of neuronal and T cell death is an imbalanced cytokine signaling system with a dysfunctional redox status, and that the loss of T cells and neurons may be secondary to impaired functions of their accessory supportive cells. These dysfunctions include inappropriate production of developmental cytokines, inadequate secretion of reductants, and disregulation of excitotoxic amino acid metabolism. Two examples of pediatric NID in humans are ataxia telangiectasia and pediatric human immunodeficiency virus infection. An animal model is retrovirus-induced T and neuronal cell loss in neonatal mice infected with a neuroimmunopathogenic mutant, ts1, of the Moloney murine leukemia virus. Because both thymic and neuronal components share many growth factors and developmental signals, it is likely that disregulation of these signals would lead to concomitant dysfunction of neuronal and thymic cells. In this review, we focus on the pathogenic mechanisms involved in these developmental NID syndromes with the objective of identifying common pathogenic factors and pathways responsible for the concurrent losses of both neurons and T cells.

Ocular manifestations in shaken baby syndrome

In the absence of external physical signs, child abuse is not easy to diagnose. Shaken baby syndrome is a unique form of child abuse where the only consistent external physical signs are its ocular manifestations. We report two cases which illustrate the typical presentation, with hallmarks of this syndrome, namely intraocular and intracranial haemorrhages. The visual prognosis of these infants are usually poor.