Cell types in the central nervous system infected by murine retroviruses: implications for the mechanisms of neurodegeneration

Retroviruses are an important cause of neurologic disease in humans but the pathogenic mechanisms are poorly understood. To delineate pathogenic mechanisms in any neurologic disease in humans is extremely difficult and will continue to rely on the use of animal models. This review presents several murine models to study the pathogenic mechanisms of neurodegenerative disease which manifest noninflammatory spongiform lesions in the CNS. The cell types in the CNS infected by these murine retroviruses and their role in disease induction are discussed.

Outpatient video-EEG monitoring in children

Video-EEG monitoring enables correlation of behavioral activity with EEG activity, which is useful in recognition of pseudoepileptic seizures and in investigation of patients for epilepsy surgery. Because most patients are monitored for a prolonged time as in-patients, the cost of the procedure is high. We investigated the value of brief (2-3 h) outpatient video-EEG monitoring in 43 children with frequent seizures, most of whom had symptomatic generalized epilepsy. Indications for monitoring included differentiation of epileptic from nonepileptic behavior, seizure classification, and determination of seizure frequency. Clinical episodes were recorded in 36 of 43 children (83%). A definite diagnosis was established in 9 of the 17 patients investigated to determine the nature of the clinical behavior. Seizures were classified in 15 of the 25 patients investigated to determine seizure type, and classification was different from the original in 9 of the 15 children. A change in epilepsy syndrome classification was made in 9 children. The video-EEG allowed diagnosis in 25 of the 43 children (59.5%). Video-EEG appears to be an effective method for outpatient investigation of children with frequent seizures, particularly those with symptomatic generalized epilepsy.

Murine retrovirus-induced depletion of T cells is mediated through activation-induced death by apoptosis

ts1, a mutant of Moloney murine leukemia virus, causes neurologic disorders and acute immunodeficiency associated with the destruction of thymocytes and helper T cells. In this study, we examined whether apoptosis was involved in ts1-induced killings of T cells. Neonatal mice were inoculated with ts1, and 20 to 23 days postinoculation, when cytopathic effects on T cells normally appear, thymocytes and splenic lymphocytes were isolated and examined. Our results showed that several features of apoptosis were present in ts1-infected thymocytes and splenic lymphocytes. Apoptotic fragmented DNA, condensation of the chromatin, and enhanced cell death after stimulation with mitogens which was preventable with protein synthesis inhibitors, all of which are common features of apoptotic cell death, were observed in ts1-infected cells. Several other viruses, including human immunodeficiency virus, have been shown to cause apoptotic death of T cells. Here we show for the first time that a murine retrovirus which also induces immunodeficiency can cause apoptotic T-cell death. Future studies with this murine retrovirus may provide important results to help us better understand the mechanisms of retrovirus-induced apoptosis of T cells.

A simple method for obtaining highly viable virus from culture supernatant

Traditionally density-gradient methods are used to purify viruses. However, these procedures are not only time consuming and cumbersome, recovery of viable viruses are often quite low. In this report, a single-step concentration technique was used to concentrate a mutant of Moloney murine leukemia virus (ts1) virus from culture supernatants by ultrafiltration. A special ultrafiltration unit with a 100,000 mol wt cut-off was able to concentrate viruses about 30-fold without losing any infectivity. In comparison, traditional sucrose density gradient purified viruses lost a significant portion of their infectivity. This technique could be used for concentrating other viruses for many useful purposes where more viable viruses are needed, e.g., study of virus-cell binding.

Mother-to-baby transfer of humoral immunity against retrovirus-induced neurologic disorders and immunodeficiency

Neonatal FVB/N mice inoculated with ts1, a temperature-sensitive mutant of Moloney murine leukemia virus TB, developed fatal immunodeficiencies and neurologic disorders. In this study, we tested the role of transfer of maternal humoral immunity in preventing ts1-induced disease syndrome in the neonatal mice. We compared the levels of protection provided through maternal antibodies both pre- and postnatally by separating infected neonatal mice into four different groups. The first group was born of and nursed by nonimmune mothers, the second was born of immune mothers but nursed by nonimmune mothers, the third was born of nonimmune mothers but nursed by immune mothers, and the fourth was born of and nursed by immune mothers. Our major findings are: (1) adult mice generate a strong antiviral antibody response; (2) maternal antibody is protective for the newborns and primarily transferred by breast milk; (3) virus titers were cleared in the periphery and the CNS of neonates nursing on immune mothers; and (4) the majority of antiviral antibody generated was specific for the gp70. These results indicate that humoral immunity can be passed efficiently from mother to baby through breast milk and can provide strong protection against neurotropic retrovirus.

Temporal central and peripheral nervous system changes induced by a paralytogenic mutant of Moloney murine leukemia virus TB

BACKGROUND

The temporal localization of cellular targets for viral replication and the morphopathogenesis of neurodegeneration in the central nervous system (CNS) and peripheral nervous system induced by ts1, a neuropathogenic and lymphocytopathic mutant of Moloney murine leukemia virus-TB, were studied in the highly susceptible FVB/N mouse strain in order to better understand the mechanisms of this neurodegenerative disease.

EXPERIMENTAL DESIGN

Newborn FVB/N mice were inoculated intraperitoneally with 0.1 ml of viral suspension containing 10(6) to 10(7) infectious units/ml. The mice were observed daily for clinical signs of disease and killed at specific time points. Their nervous system tissues were collected and processed for light and electron microscopy and for immunohistochemical viral-antigen detection.

RESULTS

ts1-Infected FVB/N mice developed a rapidly progressive wasting disease that culminated in hindleg paralysis or paraplegia 30 to 35 days postinoculation (pi).

CONCLUSIONS

Clear evidence of CNS lesions involving the cerebellar ventricular system, the grey and white matter of the brain stem and the spinal cord were seen as early as 5 to 10 days pi. These lesions, which began as mild perivascular and paraventricular neuropil spongiform changes and cytoplasmic vacuolation of neuronal and glial cell processes, progressed in severity with time and culminated in almost complete destruction of the white and gray matter in the brain stem and the cervical and lumbar spinal cord. Viruses were detected as early as 5 to 10 days pi in the fourth ventricle choroid plexus and ventricular lumen and budding from endothelial cells within the brain stem and cerebellum. Endothelial, ependymal, microglial, astroglial, and oligodendroglial cells were positive for gp70env. Astroglial and microglial cell proliferation with microglial syncytia formation was detected only within the areas showing spongiform degeneration. Viral replication was consistently high in the capillary endothelial cells of those areas showing spongiform degeneration, whereas in the glial cells, relatively few budding viruses were present. Neurodegeneration was accompanied by demyelinization within the CNS and peripheral nervous system and by hindleg muscle degeneration and necrosis. Multiple cellular targets for ts1 viral infection and replication were detected within the nervous system. The presence of budding virus and the immunodetection of viral antigen in the choroid plexus and ependymal cells of the fourth ventricle and the central canal of the spinal cord demonstrated that cerebrospinal fluid as well as blood can disseminate virus within the CNS. Pathologic and functional changes within the blood-brain barrier and glial system probably account for the neuronal necrosis and spongiform changes that result in paralysis induced by ts1 infection.

The importance of source behavior in distinguishing populations of epileptic foci

The interictal spike discharge is usually analyzed in terms of amplitude, morphology, location of spike negativity, frequency or pattern of occurrence, and the effect of sleep/wake cycle. Such information derived from the routine EEG supports the clinician in the diagnosis, treatment, and management of the epileptic patient. Detailed analytical or computerized studies of spike characteristics have not had a great deal of clinical impact to date. This communication presents an argument for characterizing the epileptic focus based on interictal spikes. Some findings from quantitative analysis of spike properties are reviewed. By facilitating the creation and refinement of hypotheses relating to the underlying neuronal mechanisms, mathematical source modeling (or dipole modeling) may enhance our understanding of the epileptic process. Such an approach is applied to rolandic epilepsy as an example, and a model is proposed that is parsimonious with experimental data and clinical observations.

Rudimentary thymus of SCID mouse plays an important role in the development of retrovirus-induced neurologic disorders

The role of the thymus in neurologic disorders induced by the murine retrovirus, ts1, a neuropathogenic and lymphocytopathic mutant of the Moloney murine leukemia virus-TB, was examined using severe combined immune deficiency (SCID) mice. Athymic nude mice are resistant to ts1-induced neurologic disease. All SCID mice inoculated neonatally with ts1 developed neurologic disorders similar to those of inoculated BALB/c mice, albeit after a longer latency period. In some experiments, instead of inoculating ts1 directly, purified thymocytes, CD4+, or CD8+ T cells from ts1-infected BALB/c mice were transferred to neonatal H-2 compatible SCID mice. We found that SCID mice that received infected thymocytes developed the disease faster than those that received infected CD4+ T cells. SCID mice that received infected CD8+ T cells did not develop any disease. Thus, the (rudimentary) thymus of SCID mouse plays a key role in ts1-induced neurologic disease. In addition, flow cytometric analysis of the reconstituted SCID mice showed that CD8+ T cells migrate and preferentially colonize the thymus while CD4+ T cells were found in the spleen and to a lesser extent in the thymus. However, the significance of this organ specific movements of transferred cells in relation to the virus infection remains unclear. In view of the involvement of the thymus and the CD4+ T cells in human immunodeficiency virus infection, which also infects the central nervous system (CNS) in most cases, our findings in this murine model may help us better understand how the thymus may contribute to the damage of the CNS in retrovirus infections.

Correlation of specific virus-astrocyte interactions and cytopathic effects induced by ts1, a neurovirulent mutant of Moloney murine leukemia virus

ts1 is a highly neuropathogenic and lymphocytopathic mutant of Moloney murine leukemia virus TB (MoMuLV-TB). We previously reported that the primary neuropathogenic determinant of ts1 maps to a single amino acid substitution, Val-25-->Ile, in precursor envelope protein gPr80env. This Val-25-->Ile substitution apparently renders gPr80env inefficient for transport from the endoplasmic reticulum to the Golgi apparatus. These findings suggest that the cytopathic effect of ts1 in neural cells might be due to the accumulation of gPr80env in the endoplasmic reticulum. Since endothelial and glial cells are targets of ts1 infection in the central nervous system, we established primary endothelial and astrocyte cultures to investigate the mechanism of cell killing caused by ts1. A continuous cell line, TB, was used as a control. Our results showed that both ts1 and MoMuLV-TB replicated and induced a cytopathic effect in astrocyte cultures, albeit to different degrees; ts1 appeared to be more lethal than MoMuLV-TB. On the other hand, ts1 and MoMuLV-TB infections of endothelial or TB cells were not cytopathic. The cytopathic effect in infected astrocytes correlated with the inefficiency of gPr80env transport and the intracellular accumulation of gPr80env as well as aberrant virus particles.

Expression of major histocompatibility complex antigens and serum neutralizing antibody in murine retroviral encephalitis

Murine leukemia virus infection serves as a model for noninflammatory degeneration of the central nervous system (CNS). During the course of infection with either of the molecularly cloned viruses pNE-8 or ts-1, we observed that ts-1 spread twice as rapidly as pNE-8, and ascended higher in the neuraxis. Endothelial cells were infected first, followed by oligodendrocytes and neurons, while astrocytes containing glial fibrillary acidic protein were not infected. Additionally, ts-1 also infected macrophages/microglia. Major histocompatibility complex (MHC) class I beta 2-microglobulin expression was minimal in pNE-8 infected mice, while it was elevated in endothelial cells of early ts-1 lesions, and in macrophages/microglia during later stages. Occasional infected cells expressed beta 2-microglobulin while rare endothelial and parenchymal cells expressed MHC class II in both viral infections. Limited intra-CNS MHC expression may be one of the mechanisms of viral persistence and will present a barrier to developing immunotherapy for CNS retroviral infections. The few mice that escaped lethal infection had higher serum titers of neutralizing antibodies and showed no neuropathologic changes or detectable virus in the CNS. Higher titers of neutralizing antibodies may protect the CNS from infection.

Copper accumulation by a strain of Pseudomonas putida

A study on the copper accumulation by resting cells of copper-resistant bacteria, isolated from activated sludge and electroplating effluent, was conducted. The best selected strain, identified as Pseudomonas putida II-11, retained copper ions, Cu(II), as high as 6.5% of its dry weight. Bacterial cells grown in the sulphate-limiting medium had the highest copper removal capacity [RC, mg of Cu(II)/g of dry cells], while the presence of glucose or sodium azide did not affect Cu(II) RC of the bacterial cells. A possible mechanism of Cu(II) accumulation by this bacterium is suggested.

A computerised out-patient medical records programme based on the Summary Time-Oriented Record (STOR) System

Advances in microcomputer hardware and software technology have made computerised outpatient medical records practical. We have developed a programme based on the Summary Time-Oriented Record (STOR) system which complements existing paper-based record keeping. The elements of the Problem Oriented Medical Record (POMR) System are displayed in two windows within one screen, namely, the SOAP (Subjective information, Objective information, Assessments and Plans) elements in the Reason For Encounter (RFE) window and the problem list with outcomes in the Problem List (PL) window. Context sensitive child windows display details of plans of management in the RFE window and clinical notes in the PL window. The benefits of such innovations to clinical decision making and practice based research and its medico-legal implications are discussed.

Retrovirus-induced immunodeficiency in mice exacerbates gastrointestinal candidiasis

Dysfunction of neutrophils in patients infected with human immunodeficiency virus is at least partly responsible for secondary microbial diseases in these individuals, including invasive gastrointestinal (GI) candidiasis. Immunoregulatory disturbances associated with the development of AIDS in human immunodeficiency virus-infected patients exacerbates Candida albicans infection of the upper GI tract and frequently leads to oropharyngeal and esophageal candidiasis. In this article, we present the first report of a murine model of invasive GI candidiasis associated with an AIDS-related murine immunodeficiency syndrome that results from infection of C57BL/6 mice with a previously described retrovirus complex (LP-BM5). Mice of the inbred strain were infected with C. albicans by oral-intragastric inoculation as infants and with the retrovirus by the intraperitoneal route 30 days later. Control mice of the same strain were infected with C. albicans as above and subsequently infected with the avirulent, ecotropic helper virus (MBI-5). Animals were killed 90 days after retroviral challenge. Total and differential blood cell counts, CD4+ T-cell counts in the spleen, and the histopathology of the gastric mucosa of experimental and control animals were determined. The virulent LP-BM5-infected animals developed murine AIDS and showed eruptive and suppurative lesions, with associated C. albicans mainly in regions of the cardial-atrium fold of the stomach. Well-defined abscesses with entrapped C. albicans hyphae were observed in the region of the cardial-atrium fold of control mice. A significant increase in the number of C. albicans CFU in homogenized and plated segments of the GI tract was recognized in mice with murine AIDS versus the control animals. The murine model of GI candidiasis reported here permits examination of the nature of C. albicans interaction with the gastric mucosa both in the immunocompetent host under conditions in which the yeast exists predominantly as a commensal organism and in the immunosuppressed host during progressive stages of AIDS induced by a retroviral infection.

Pathogenesis of age dependent paralysis by a temperature sensitive mutant (tsl) of Moloney murine leukemia virus-TB

The tsl mutant of Moloney murine leukemia virus-TB produces neurological disease leading to fatal hind limb paralysis when inoculated in newborn BALB/c mice. The present study was under taken to assess the role of T and B lymphocytes in age dependent resistance to tsl induced paralysis in BALB/c mice. The adoptive transfer of non-immune splenic unseparated lymphoid cells, T cells and B cells and tsl immune B cells and T cells to newborn BALB/c mice infected with tsl did not prevent the development of paralysis. However, adoptive transfer of immune splenic unseparated lymphoid cells and immune T cells delayed the onset of paralysis by 5 to 10 days as compared to the mice which did not receive the immune lymphocytes. Athymic BALB/c nude mice inoculated with tsl at days 1 and 10 after birth failed to develop the paralytic disease. Transfer of tsl neutralising antibody also delayed the onset of paralysis. Mice (10 days old) treated with cyclophosphamide, cyclosporine A, cortisone acetate and anti-T cell serum when inoculated with tsl also did not develop neurological disease. The results suggest that age related resistance to neurological disease may not be associated with B cell mediated immunity.

A simple method of concentrating monoclonal antibodies from culture supernatant by ultrafiltration

How to obtain concentrated monoclonal antibodies from culture supernatant is of great importance to many scientists today. In this report, a simple, single-step technique is described to concentrate monoclonal antibodies directly from hybridoma-culture supernatant. The contaminants can be removed from the supernatant by using an ultrafiltration unit which allows macromolecules of less than 100,000 MW to pass through leaving behind monoclonal antibodies which is purified and concentrated more than 25-fold.

Protective role of cytotoxic lymphocytes against murine leukemia virus-induced neurologic disease and immunodeficiency is enhanced by the presence of helper T cells

We examined the role of T cells and their separated subsets in providing immunity against ts1 (a mutant of the Moloney murine leukemia virus) induced paralysis and immunodeficiency. Adoptive transfer of syngeneic total T cells from immunized mice protected newborn mice, at least partially, from ts1-induced disease syndrome. In infected mice who received total immune T cells, virus replication was reduced and the mice survived longer. When only separated immune CD8+ T cells were transferred to infected mice, similar protection, albeit to a lesser extent, was observed. Transfer of separated immune CD4+ T cells alone gave no protection. However, when recombined CD4+ and CD8+ cells were transferred together, an immune response similar to that when total T cells were transferred was observed. Cytotoxic assays from ts1-immunized mice revealed the presence of virus-specific CD8+ cytotoxic T lymphocytes that could lyse virus-expressing cells at a high effector/target ratio. We conclude that CD8+ T cells alone can provide immunity against ts1-induced paralysis and immunodeficiency and that the simultaneous presence of CD4+ T cells can also significantly enhance the immune response.

Studies on compartmentation and turnover of murine retrovirus envelope proteins

Several aspects of turnover and degradation of cell membrane proteins were studied in an NIH 3T3 cell clone expressing the env gene of Moloney murine leukemia virus ts1. Both internalization and shedding of the extracellular domain of the envelope protein gp70 occurred at the cell surface, albeit, in the case of shedding, only a very small fraction of gp70 was shed. The turnover rate of gp70 at the cell surface was similar to that of the same protein in the postendoplasmic reticulum intracellular compartment. In the presence of L-methionine methyl ester, the transmembrane domain of the envelope protein Prp15E was degraded faster than gp70.

Characterization of a continuous lymphocyte cell line derived from BALB/c mice inoculated with a recombinant Moloney murine leukemia virus-TB

Neonatal BALB/c mice were inoculated (ip) with a recombinant Moloney murine leukemia virus-TB. Majority of the inoculated mice developed lymphoma within 5-7 months post infection. The cells from splenic lymphomas were cultured and 3 continuous cell lines (GP1, GP2 and GP3) developed. GP1 was single cell cloned and characterized. Based on Thy 1.2 (98.4%) phenotypic marker, the cell line was categorized as T cell line. The percent positivity for different cell surface markers on analysis with FACS was 98.4, 4.8, 5.5, 2.2, 1.8, 1.2 and 9.5 for Thy 1.2, mu, L3T4, Lyt2, Ia, IL2R and PNA receptor, respectively. A total of 16.5% GP1 cells was also positive for Moloney murine leukemia virus envelope protein (gp 70). Incomplete retrovirus like particles were demonstrated in the cytoplasm of GP1 cells by electron microscopy. The cell line on inoculation(ip) in neonatal BALB/c mice produced lymphomic lesions in almost all the vital organs of the mice.

ts1, a temperature-sensitive mutant of Moloney murine leukemia virus TB, can infect both CD4+ and CD8+ T cells but requires CD4+ T cells in order to cause paralysis and immunodeficiency

When neonatal FVB/N mice were inoculated with ts1, a temperature-sensitive mutant of Moloney murine leukemia virus TB, they developed a progressive bilateral hindlimb paralysis and immunodeficiency leading to death 4 to 6 weeks after inoculation. T lymphocytes have been shown to be primarily responsible for this ts1-induced syndrome. Here we compare the role played by each subset of T lymphocytes, i.e., CD4+ and CD8+ T cells, in disease development. Mice were depleted of a specific subset for the first 10 days of their lives by using either anti-CD4 or anti-CD8 monoclonal antibodies in vivo. Disease development in these mice was then monitored. Depletion of CD4+ T cells significantly attenuated the ts1-induced syndrome: virus replication was decreased, disease latency was extended, and death was prevented in 60% of the mice. Similar treatment with anti-CD8 antibody had almost no effect on disease progression. However, when depletion was begun 2 weeks after neonatal ts1 inoculation, CD4+ T cell depletion did not affect disease development. ts1 infected CD4+ and CD8+ T lymphocytes equally well in vivo, as shown by flow cytometric analysis, but virus replication was restricted primarily to the CD4+ subset of T cells, as found by in vitro assay. Hence, CD4+ T lymphocytes play an important role in the development of ts1-induced paralysis and immunodeficiency. The mechanism of this CD4+ T-cell-mediated disease production by ts1 is not clear; however, increased replication of ts1 in the CD4+ T cells, especially in the early stages of the disease, seems to play a crucial role.

Temporal lymphoreticular changes caused by ts1, a paralytogenic mutant of Moloney murine leukemia virus TB

Inoculation of newborn FVB/N mice with ts1, a mutant of Moloney murine leukemia virus TB, induced severe thymic atrophy, spongiform polioencephalomyelopathy, and fatal posterior paralysis of the affected mice 35-40 days after inoculation. During the early course of infection viral replication was found in the spleen and, more importantly, within the thymus. Of these organs, the thymus was affected most severely by ts1-infection. Thymic weights of infected mice decreased markedly during disease progression, culminating in severe atrophy at the time of paralysis. During the first 10 days after inoculation, the virus replicated within the endothelial lining of splenic and thymic capillaries and was released albuminally into the basement membrane before spreading outwardly into perithelial, epithelial, and reticuloendothelial cells. Within these cells there was productive viral replication and subsequent dissemination of the virus to the thymic T cell population. Early infection (up to 10 days after inoculation) of the thymus induced an increase in thymocytic mitosis, followed by a progressive increase in thymocytic death between 15 and 35 days after inoculation. Thymuses from paralyzed mice killed 30-39 days after inoculation, demonstrated pronounced involution, characterized by loss of lobular architecture, effacement of the cortex and medulla, severe depletion of thymocytes, and partial or complete loss of Hassall's corpuscles. Immunohistochemistry for viral antigens showed positive labeling of splenic megakaryocytes, reticuloendothelial cells, and thymocytes in mitosis, and reticulo-epithelial-endothelial cells of the thymus. The thymic phase of viral replication appeared to be crucial for development of neurological lesions and posterior paralysis.

Comparative studies of water quality in two brackish ponds for shrimp cultivation in a salt marsh

Physical, chemical and microbiological characteristics of two 'keiwais' (brackish ponds built along the coastal area for shrimp cultivation) in the Mai Po Marshes, Hong Kong, were measured and compared. One keiwai, located closer to the domestic and agricultural areas, had lower shrimp production than the other. Physical, microbiological and most of the chemical parameters of two keiwais showed no significant difference, while the keiwai closer to the domestic and agricultural areas had higher biochemical oxygen demand (BOD5), and higher levels of phosphate (PO4(3-)-P) and cadmium (Cd2+). Results of the present study indicate that these keiwais were polluted by sewage discharged from nearby domestic, agricultural and industrial areas. The possibility that water received by the less polluted keiwai was purified by surrounding mangroves and sediments in the Mai Po Marshes is discussed.

Clinical Relevance of a Dipole Field in Rolandic Spikes

The clinical presentation of 366 children with rolandic spikes was examined to determine whether the presence of a temporal-frontal dipole field is associated with a lower incidence of clinical abnormality. Comparisons were made between the clinical presentation of 99 children with temporal-frontal dipole discharges versus 267 children with nondipole rolandic discharges. Criteria examined were birth history, developmental milestones, school history, total number of seizures, neurological examination, and computed tomography (CT) findings. For all clinical parameters, except birth history and CT finding, there was a lower incidence of clinical abnormality in the group with dipole discharges (p less than 0.001). The clinical profile seen with temporal-frontal dipole discharges was very different than with nondipole rolandic spikes. Children with dipole discharges less often presented with frequent seizures (10%), developmental delay (18%), school difficulties (34%), or abnormal neurological exam (22%). In contrast, children with nondipole rolandic discharges often presented with a history of frequent seizures (55%), developmental delay (55%), school difficulties (60%), and an abnormal neurological exam (63%). The incidence of clinical abnormalities in the nondipole group exceeded that found in our control population in all areas. Temporal-frontal dipole discharges are associated with a lower incidence of clinical abnormality than are nondipole rolandic spikes. These discharges may represent a benign functional focus.

Computer simulation of blood flow patterns in arteries of various geometries

The purpose of this study is to illustrate the application of computer simulation to the study of blood flow through arteries and to demonstrate the relationship between geometry of the vessels and local flow patterns. A finite element computer program was developed to simulate steady and pulsatile blood flow by solving the continuity and Navier-Stokes equations. The accuracy of the computational method has been confirmed by comparing the numeric results to analytic solutions and to published experimental data from physical models. The results are presented as plots of the velocity vectors, streamlines, and pressure contours. The computational model has been applied to illustrate flow patterns in the following situations: pulsatile flow in a cylindric artery and an artery with an axisymmetric stenosis, steady flow in cylindric arteries with stenoses of varying severity and with different flow rates, steady flow in an artery containing a fusiform aneurysm, steady flow in a two-dimensional model of a symmetric Y-shaped bifurcation, and steady flow in a two-dimensional model of the carotid bifurcation. Regions that are commonly associated with arterial disease often coincide with zones of reversed or stagnant flow. In conclusion, the versatility and feasibility of computational simulation of blood flow is illustrated by this study. Although this mathematic model is a simplification of the real flow phenomena, it yields results that provide useful insights into the understanding of local blood flow patterns for a variety of complex geometries.