High seroprevalence of toxoplasma gondii and HIV-1 co-infection among drug users in Yunnan province,southwest China

正Dear Editor,Toxoplasma gondii was discovered more than 100 years ago and has a broad-spectrum of intermediate hosts in addition to its definitive host,felids.Although it does not cause symptomatic illness in most adults,it can lead to mental retardation in congenitally infected children and serious     

Development of HIV infection epidemic among intravenous drug users in the Sverdlovsky region

The Sverdlovsky region takes the fourth place among the 89 subjects of the Russian Federation by the number of registered cases of HIV infection. Drug addiction has reached an excessive scale in this region: according to the data of express evaluation carried out by the Regional Narcological Hospital and the Regional AIDS Center, not less than 7-8% of persons aged 15-30 years constantly use injection drugs. The large-scale epidemic of injection drug addiction has led to the rapid spread of HIV among addicts. The first penetration of HIV into this population took place in 1996 and, starting from the year 2000, rapid, development of the epidemic began, taking the character of an avalanche. The peak of new cases of HIV infection fell on 2001 (9,230 cases were registered). The concentrated stage of the epidemic development is observed in the region at present, the prevalence of HIV infection among drug addicts being 13.8%. Children born from HIV-infected drug addicted mothers now represent a new risk group due to great difficulties in the prophylaxis of the vertical virus transmission.     

Mutational analysis of the CCR5 and CXCR4 genes (HIV-1 co-receptors) in resistance to HIV-1 infection and AIDS development among intravenous drug users

We analysed a group of Spanish intravenous drug users and controls to determine the role of mutations at the chemokine receptor-5/HIV-1 cofactor (CCR5), previously implicated in resistance to HIV-1 infection, and CXCR4 genes in susceptibility to HIV-1 infection. The complete coding sequence of both genes was amplified by the polymerase chain reaction from genomic DNA of 50 seropositive slow progressors and 10 long-term non-progressors, and analysed by the single-strand conformation polymorphism technique in a search for mutations. No mutation in CXCR4 was found, and Δccr5 was the only mutation identified at the CCR5 gene. We genotyped (Δccr5 allele) 150 HIV-1+ intravenous drug users and 250 healthy controls from the same population (Asturias, Northern Spain). Patients were divided into rapid progressors, presenting an event indicating progression to the acquired immunodeficiency syndrome (AIDS) in the 2 years after infection (100 patients), and slow progressors, remaining asymptomatic for 2–10 years (50 patients). The frequencies of the Δccr5 allele were 0.105 and 0.040 in controls and HIV-1+ patients, respectively. Eighteen per cent of the controls (45/250) and 8% (12/150) of the patients carried the Δccr-5 allele (P=0.013). The frequency of Δccr5 carriers among rapid and slow disease progressors was 3 and 15%, respectively. A highly significant difference was found between rapid progressors and controls (P=0.0014). No patient (0/150) was Δccr5 homozygous compared with 1% among controls. Thus, the Δccr5 allele (the only CCR5 mutation found in our HIV-1 patients) was rare among seropositive intravenous drug users, suggesting that the absence of this mutation confers an advantage to the virus when infecting cells in vivo. In addition, patients carrying the Δccr5 allele tend to show a slow progression towards HIV-1-related disease, remaining asymptomatic for longer periods of time. Received: 15 October 1997 / Accepted: 12 January 1998     

Distribution and status of lynx in the border region between Czech Republic, Germany and Austria

This paper summarizes available information concerning the presence of the Eurasian lynxLynx lynx Linneaus, 1758 in the Šumava Mountains and adjacent areas along the common border of Czech Republic, Germany and Austria. Our data give an overview of the lynx population occupying the border region between the three countries from 1990 to 1999. We estimated population size using radiotracking data. From 1990 to 1998, population increased from under 20 to nearly 70 resident animals. During this time, reproduction increased as well, with a maximum of 55 kittens observed in the rearing period of 1998 to 1999. Mortality data indicated that illegal hunting was widespread. Our paper discusses possible links with other lynx populations and describes the legal status of lynx in the three different countries. Current management approaches are outlined and steps toward a long-term conservation plan for the population are proposed.     

HIV-1/parasite co-infection and the emergence of new parasite strains

HIV-1 and parasitic infections co-circulate in many populations, and in a few well-studied examples HIV-1 co-infection is known to amplify parasite transmission. There are indications that HIV-1 interacts significantly with many other parasitic infections within individual hosts, but the population-level impacts of co-infection are not well-characterized. Here we consider how alteration of host immune status due to HIV-1 infection may influence the emergence of novel parasite strains. We review clinical and epidemiological evidence from five parasitic diseases (malaria, leishmaniasis, schistosomiasis, trypanosomiasis and strongyloidiasis) with emphasis on how HIV-1 co-infection alters individual susceptibility and infectiousness for the parasites. We then introduce a simple modelling framework that allows us to project how these individual-level properties might influence population-level dynamics. We find that HIV-1 can facilitate invasion by parasite strains in many circumstances and we identify threshold values of HIV-1 prevalence that allow otherwise unsustainable parasite strains to invade successfully. Definitive evidence to test these predicted effects is largely lacking, and we conclude by discussing challenges in interpreting available data and priorities for future studies.     

No evidence of association between HIV-1 and malaria in populations with low HIV-1 prevalence

Background

The geographic overlap between HIV-1 and malaria has generated much interest in their potential interactions. A variety of studies have evidenced a complex HIV-malaria interaction within individuals and populations that may have dramatic effects, but the causes and implications of this co-infection at the population level are still unclear. In a previous publication, we showed that the prevalence of malaria caused by the parasite Plasmodium falciparum is associated with HIV infection in eastern sub-Saharan Africa. To complement our knowledge of the HIV-malaria co-infection, the objective of this work was to assess the relationship between malaria and HIV prevalence in the western region of sub-Saharan Africa.

Methodology/Principal Findings

Population-based cross-sectional data were obtained from the HIV/AIDS Demographic and Health Surveys conducted in Burkina Faso, Ghana, Guinea, Mali, Liberia and Cameroon, and the malaria atlas project. Using generalized linear mixed models, we assessed the relationship between HIV-1 and Plasmodium falciparum parasite rate (PfPR) adjusting for important socio-economic and biological cofactors. We found no evidence that individuals living in areas with stable malaria transmission (PfPR>0.46) have higher odds of being HIV-positive than individuals who live in areas with PfPR≤0.46 in western sub-Saharan Africa (estimated odds ratio 1.14, 95% confidence interval 0.86–1.50). In contrast, the results suggested that PfPR was associated with being infected with HIV in Cameroon (estimated odds ratio 1.56, 95% confidence interval 1.23–2.00).

Conclusion/Significance

Contrary to our previous research on eastern sub-Saharan Africa, this study did not identify an association between PfPR and infection with HIV in western sub-Saharan Africa, which suggests that malaria might not play an important role in the spread of HIV in populations where the HIV prevalence is low. Our work highlights the importance of understanding the epidemiologic effect of co-infection and the relevant factors involved in this relationship for the implementation of effective control strategies.     

Anti-nef antibodies and other predictors of disease progression in HIV-1 seropositive injecting drug users.

A cross-sectional and retrospective longitudinal study has been conducted in three Italian infectious disease centres to evaluate the role of anti-nef antibodies and other markers (HIV-1 p24 antigen, p24 Ag; Beta 2-microglobulin, B2-M; and number of CD4+ lymphocytes) as predictors of disease progression in HIV seropositive injecting drug users (IDUs). The selected patients were: 1) HIV-seropositive IDUs in different stages of HIV infection; 2) HIV-seropositive IDUs who had developed AIDS, from whom serial serum samples were available during the asymptomatic stage, and 3) HIV seropositive IDUs who remained asymptomatic through a follow-up period of the same duration as the patients who developed AIDS. Absence of anti-nef antibodies was associated with symptomatic HIV infection. A significant association between the absence of anti-nef antibodies, the presence of p24 Ag, high levels of B2-M, a number of CD4+ lymphocytes less than 500/ml at first visit and disease progression was found. Subjects who were persistently positive for antibody to nef were less likely to develop AIDS than those who were transiently or persistently negative. This difference was statistically significant (p = 0.03). The results of this study show that absence or disappearance of anti-nef antibodies may be used as predictor of disease evolution in HIV seropositive IDUs. This study also confirms the usefulness of other markers, such as p24 Ag, B2-M and number of CD4+ lymphocytes previously shown to be predictive of rapid disease progression for predicting the course of HIV seropositive IDUs.     

Influence of land use and host species on parasite richness,prevalence and co-infection patterns

Tropical forests are experiencing increasing impacts from a multitude of anthropogenic activities such as logging and conversion to agricultural use. These perturbations are expected to have strong impacts on ecological interactions and on the transmission dynamics of infectious diseases. To date, no clear picture of the effects of deforestation on vector-borne disease transmission has emerged. This is associated with the challenge of studying complex systems where many vertebrate hosts and vectors co-exist. To overcome this problem, we focused on an innately simplified system – a small oceanic island (São Tomé, Gulf of Guinea). We analyzed the impacts of human land-use on host-parasite interactions by sampling the bird community (1735 samples from 30 species) in natural and anthropogenic land use at different elevations, and screened individuals for haemosporidian parasites from three genera (Plasmodium, Haemoproteus, Leucocytozoon). Overall, Plasmodium had the highest richness but the lowest prevalence, while Leucocytozoon diversity was the lowest despite having the highest prevalence. Interestingly, co-infections (i.e. intra-host diversity) involved primarily Leucocytozoon lineages (95%). We also found marked differences between bird species and habitats. Some bird species showed low prevalence but harbored high diversity of parasites, while others showed high prevalence but were infected with fewer lineages. These infection dynamics are most likely driven by host specificity of parasites and intrinsic characteristics of hosts. In addition, Plasmodium was more abundant in disturbed habitats and at lower elevations, while Leucocytozoon was more prevalent in forest areas and at higher elevations. These results likely reflect the ecological requirements of their vectors: mosquitoes and black flies, respectively.     

Functional association between the nef gene product and gag-pol region of HIV-1

Nef gene function is diverse among virus isolates of primate immunodeficiency viruses. We found differential effects of nef mutation on the virus replication between two HIV-1 clones, NL432 and LAI. The nef mutation in NL432 affected the infectivity more severely compared with that in LAI, although the Nef functions of both clones were comparable. Analysis with a series of chimeric viruses between NL432 and LAI revealed that the gag-pol region was responsible for the differential effect of nef mutation. The functional association between Nef and gag-pol suggested that one of the potential targets of Nef was located within the gag-pol region.     

The prevalence of the intravenous use of psychoactive preparations in Nizhegorod Province and the possible ways to prevent HIV infection among the users

The number of users of intravenous drugs (UID), altogether from 35,000 to 25,000 persons, was determined by the method of coefficients. The analysis of 130 anonymous questionnaires, including 75 street questionnaires (61%) and 51 questionnaires (39%) distributed among UID in narcological and infectious hospitals showed that out of 130 respondents 60% underwent hospital treatment. The study revealed that most of the questioned users used crudely made opiates, 48 (37%) out of 130 persons made injections with used syringes and needles (in younger age groups the proportion of such UID amounted to 63%). 70% of the respondents used individual injection instruments (in a group of persons older than 25 years they amounted to 90%). The conclusion was made on the necessity of introducing a school program on the healthy mode of life and information programs on the prevention of the spread of infection among UID with due regard to different age groups, as well as training outreach workers for disseminating information on the prophylaxis of HIV infection among UID.     

Dynamics of two separate but linked HIV-1 CRF01_AE outbreaks among injection drug users in Stockholm, Sweden, and Helsinki, Finland

Detailed phylogenetic analyses were performed to characterize an HIV-1 outbreak among injection drug users (IDUs) in Stockholm, Sweden, in 2006. This study investigated the source and dynamics of HIV-1 spread during the outbreak as well as associated demographic and clinical factors. Seventy Swedish IDUs diagnosed during 2004 to 2007 were studied. Demographic, clinical, and laboratory data were collected, and the V3 region of the HIV-1 envelope gene was sequenced to allow detailed phylogenetic analyses. The results showed that the Stockholm outbreak was caused by a CRF01_AE variant imported from Helsinki, Finland, around 2003, which was quiescent until the outbreak started in 2006. Local Swedish subtype B variants continued to spread at a lower rate. The number of new CRF01_AE cases over a rooted phylogenetic tree accurately reflected the transmission dynamics and showed a temporary increase, by a factor of 12, in HIV incidence during the outbreak. Virus levels were similar in CRF01_AE and subtype B infections, arguing against differences in contagiousness. Similarly, there were no major differences in other baseline characteristics. Instead, the outbreak in Stockholm (and Helsinki) was best explained by an introduction of HIV into a standing network of previously uninfected IDUs. The combination of phylogenetics and epidemiological data creates a powerful tool for investigating outbreaks of HIV and other infectious diseases that could improve surveillance and prevention.     

大弹涂鱼和中华乌塘鳢肠刷状缘膜消化酶活性的比较

采用酶学分析的方法,研究了大弹涂鱼和中华乌塘鳢肠刷状缘膜的麦芽糖酶、蔗糖酶、乳糖酶、海藻糖酶、纤维二糖酶、碱性磷酸酶、氨基肽酶和γ-谷氨酰转肽酶等8种消化酶的活性。结果表明:1)大弹涂鱼肠Ⅱ刷状缘膜的麦芽糖酶、蔗糖酶、乳糖酶、海藻糖酶和纤维二糖酶等5种二糖酶的比活力均显著高于肠Ⅰ和肠Ⅲ(P<0·05);中华乌塘鳢肠Ⅰ刷状缘膜除乳糖酶外,其余4种二糖酶的比活力均显著高于肠Ⅱ和肠Ⅲ(P<0·05);大弹涂鱼肠Ⅲ碱性磷酸酶、氨基肽酶和γ-谷氨酰转肽酶等3种消化酶的比活力均显著高于肠Ⅰ和肠Ⅱ(P<0·05);中华乌塘鳢肠Ⅱ的这3种消化酶的比活力均显著高于肠Ⅰ和肠Ⅲ(P<0·05);2)大弹涂鱼各段肠刷状缘膜的5种二糖酶的比活力均显著高于中华乌塘鳢(P<0·05),前者肠刷状缘膜碱性磷酸酶、氨基肽酶和γ-谷氨酰转肽酶等3种消化酶的比活力整体上也稍微高于后者。由此说明:8种消化酶的活性在大弹涂鱼和中华乌塘鳢肠刷状缘膜中的分布模式明显不同,大弹涂鱼和中华乌塘鳢对二糖的消化和吸收的主要部位分别是在肠Ⅱ和肠Ⅰ,而二者对蛋白质、脂类和无机盐等营养吸收的主要部位分别是在肠Ⅲ和肠Ⅱ;大弹涂鱼和中华乌塘鳢肠刷状缘膜的5种二糖酶的活性与两者的食性关系密切,而碱性磷酸酶、氨基肽酶和γ-谷氨酰转肽酶等3种消化酶的活性与两者的食性并无密切的相关性。     

Refugee and migrant women's views of antenatal ultrasound on the Thai Burmese border: a mixed methods study

Background

Antenatal ultrasound suits developing countries by virtue of its versatility, relatively low cost and safety, but little is known about women’s or local provider’s perspectives of this upcoming technology in such settings. This study was undertaken to better understand how routine obstetric ultrasound is experienced in a displaced Burmese population and identify barriers to its acceptance by local patients and providers.

Methodology/Principal Findings

Qualitative (30 observations, 19 interviews, seven focus group discussions) and quantitative methods (questionnaire survey with 644 pregnant women) were used to provide a comprehensive understanding along four major themes: safety, emotions, information and communication, and unintended consequences of antenatal ultrasound in refugee and migrant clinics on the Thai Burmese border. One of the main concerns expressed by women was the danger of childbirth which they mainly attributed to fetal malposition. Both providers and patients recognized ultrasound as a technology improving the safety of pregnancy and delivery. A minority of patients experienced transitory shyness or anxiety before the ultrasound, but reported that these feelings could be ameliorated with improved patient information and staff communication. Unintended consequences of overuse and gender selective abortions in this population were not common.

Conclusions/Significance

The results of this study are being used to improve local practice and allow development of explanatory materials for this population with low literacy. We strongly encourage facilities introducing new technology in resource poor settings to assess acceptability through similar inquiry.     

Comparison of the prevalence and distribution of human papillomavirus infection and cervical lesions between urban and native habitants of an Amazonian region of Peru

We made a study of the prevalence of human papillomavirus (HPV) and cervix lesions in an Amazonian Bora native population (Bn) and compared it with the prevalence in an urban population in Iquitos (Iq). We also examined the distribution of HPV types among abnormal cervical smears in the Iq population. Swabs and cytologies were collected from 472 females. DNA consensus PCR, followed by direct sequencing, were used to determinate the HPV types in the swabs. Cytologies were classified based on the lesion grade. HPV prevalence was 43.9% in Iq and 35.4% in Bn. Cervix lesion prevalence was 20.0% in Iq and 0.3% in Bn. The frequency of high-risk HPV types among HPV+ females was 71.9% in Iq and 56.3% in Bn. The frequencies of low-risk and undetermined risk HPV types were 19.3/6.3% (Iq/ Bn) and 12.3/37.5% (Iq/Bn), respectively. In lesIq (women seeking cytological services with a previous cervix lesion diagnosis) the prevalence of HPV, was 72.9%. The incidence of carcinoma and high-grade squamous intraepithelial cervix lesions in lesIq were 31.2 and 18.8%, respectively. The Bn population had a lower incidence of high-risk HPV and cervix lesions. The high-risk strain HPV16 was significantly more frequent in Iq compared with Bn. lesIq high-risk HPVs were more frequent in high-grade squamous intraepithelial lesions and carcinoma. High-risk HPV16 prevalence was significantly higher than the prevalence of the other high-risk HPVs, especially in the high-grade squamous intraepithelial lesions and carcinoma.     

Modeling within-host HIV-1 dynamics and the evolution of drug resistance: trade-offs between viral enzyme function and drug susceptibility

There are many biological steps between viral infection of CD4(+) T cells and the production of HIV-1 virions. Here we incorporate an eclipse phase, representing the stage in which infected T cells have not started to produce new virus, into a simple HIV-1 model. Model calculations suggest that the quicker infected T cells progress from the eclipse stage to the productively infected stage, the more likely that a viral strain will persist. Long-term treatment effectiveness of antiretroviral drugs is often hindered by the frequent emergence of drug resistant virus during therapy. We link drug resistance to both the rate of progression of the eclipse phase and the rate of viral production of the resistant strain, and explore how the resistant strain could evolve to maximize its within-host viral fitness. We obtained the optimal progression rate and the optimal viral production rate, which maximize the fitness of a drug resistant strain in the presence of drugs. We show that the window of opportunity for invasion of drug resistant strains is widened for a higher level of drug efficacy provided that the treatment is not potent enough to eradicate both the sensitive and resistant virus.     

Clinical symptoms associated with seroconversion for HIV-1 among misusers of intravenous drugs: comparison with homosexual seroconverters and infected and non-infected intravenous drug misusers.

OBJECTIVE--To study the clinical symptoms associated with seroconversion for HIV-1 among misusers of intravenous drugs. DESIGN--Case-control study in cohorts of drug misusers and homosexual men. SETTING--Outpatient clinic, Municipal Health Service, Amsterdam. SUBJECTS--Misusers of intravenous drugs from our prospective cohort who seroconverted for HIV. Controls were drug users positive for HIV, drug users negative for HIV, and homosexual men who had seroconverted. RESULTS--Five out of 18 (28%) drug users were admitted to hospital with bacterial pneumonia in the four to six months between their last visit at which they were HIV negative and their first visit when they were HIV positive. For comparison none of the 27 homosexual men who seroconverted for HIV, three out of 177 (2%) drug users negative for HIV, and 10 out of 112 (9%) drug users positive for HIV reported bacterial pneumonia. One out of the 18 drug users who seroconverted suffered from oesophageal candidiasis at the time of seroconversion. Other clinical symptoms did not differ between drug users who seroconverted and those who remained negative for HIV, probably due to the high background morbidity among the drug users. CONCLUSIONS--Seroconversion to HIV-1 among intravenous drug misusers is associated with bacterial pneumonia. Those drug users with previously negative test results for HIV who are admitted to hospital for bacterial pneumonia should be tested to detect primary infection with HIV-1.     

The functional and structural border of the neurohemal region of the median eminence

Summary In stressed rats the tanycytes of the ventrolateral wall of the third ventricle exhibit by light microscopic immunohistochemistry a positive staining for neurohormones which is distinctly limited to the distal perivascular end of the tanycyte process. Since by electron microscopic immuncytochemistry the tanycyte cytoplasm does not show any reaction product, the light microscopic reaction most likely results from a labeling of the intercellular space in the direct vicinity of the subendothelial cleft. Whether this subendothelial space is permeable to neurohormones was tested by injection of HRP¹. In the region of the arcuate nucleus 30 min after intravenous application, the marker is affixed to the membranes of the perivascular tanycyte processes in the subendothelial cleft of capillaries possessing non-fenestrated endothelia. Occasionally, HRP penetrates for a short distance between the tanycytes. Then the labeling of the intercellular cleft ends abruptly. Here, several parallel ridges of tight junctions between the perivascular distal tanycyte processes are found by the freezeetching technique. Since HRP cannot reach the subendothelial clefts of this region by passing through capillary walls due to the presence of a blood-brain barrier, it is suggested that the marker penetrates from the median eminence this far via the subendothelial extracellular space. It is prevented from spreading further by the tight junctions of the perivascular tanycyte endings. The same way may be taken by the neurohormones. Hence, a border area exists adjacent to the dorsolateral aspect of the neurohemal region of the median eminence where the tanycytes isolate the neuropil from the cerebrospinal fluid not only by their apical tight junctions, but also by basal tight junctions from the subendothelial cleft. This communicates with the perivascular space of the portal vessels.Supported by the Deutsche Forschungsgemeinschaft (Grant Nr. Kr. 569/2) and Stiftung VolkswagenwerkDedicated to Professor Dr. R. Ortmann on the occasion of his 65th birthday.The skilful technical assistance of Miss K. Bielenberg, Mrs. A. Hinz and Mrs. H. Prien is thankfully acknowledged     

Seroprevalence of and risk factors for HIV-1 infection in injection drug users in Montreal and Toronto: a collaborative study.

OBJECTIVE: To determine the prevalence of antibodies to HIV-1 and risk factors for HIV-1 infection among injection drug users. DESIGN: Questionnaire survey. A venous blood sample was taken for HIV-1 antibody testing. SETTING: Montreal and Toronto. PARTICIPANTS: A total of 810 subjects who had used injection drugs in the previous 6 months recruited mainly from treatment centres and from the street in Montreal (425 subjects) and from treatment centres in Toronto (385 subjects) between September 1988 and September 1990. The overall participation rate was 82%. OUTCOME MEASURES: HIV-1 seropositivity, sociodemographic and behavioural risk factors for HIV-1 infection. RESULTS: The overall seroprevalence rate of HIV-1 infection was 4.8% (95% confidence limits [CL] 3.5 and 6.5). In Montreal the rate was 8.2% (95% CL 6.0 and 11.2), and in Toronto 1.0% (95% CL 0.4 and 2.6) (p < 0.001). Seropositive subjects were significantly older (p = 0.041) and were more likely to have a history of imprisonment (p = 0.006) than seronegative subjects. In univariate analysis seropositivity was associated with the following behaviours: more frequent cocaine use (p < 0.001), injecting drugs in "shooting galleries" (p = 0.002), sharing equipment with a person known to be HIV-1 seropositive (p = 0.006), "booting" fresh blood (p = 0.004), homosexual or bisexual orientation (p = 0.006), engaging in prostitution (p < 0.001) and, for men, number of male sexual partners in the previous 6 months (p = 0.007). In multivariate analysis the determinants of HIV-1 seropositivity were Montreal as the city of recruitment (odds ratio [OR] 6.7, 95% CL 2.32 and 19.42), engaging in prostitution (OR 2.13, 95% CL 1.01 and 4.75), a history of imprisonment (OR 3.51, 95% CL 1.33 and 9.29) and sharing equipment with a person known to be HIV-1 seropositive (OR 4.43, 95% CL 1.43 and 13.74). CONCLUSIONS: Our findings show that HIV-1 is circulating among injection drug users in Montreal and Toronto and that both drug use and sexual behaviours are implicated in the transmission of infection in the populations studied. Adapted preventive programs should be developed to prevent further spread of HIV-1 infection in this population.     

HIV-1 and the brain: connections between HIV-1-associated dementia, neuropathology and neuroimmunology

AIDS patients frequently exhibit neurological disorders due to the neurotoxic events that result from HIV-1 and/or opportunistic infections in the brain. This review examines recent clinical findings related to HIV-1-associated dementia, and outlines current areas of basic research that may clarify how HIV-1-associated encephalopathy produces clinical symptoms of brain dysfunction.