Apolipoprotein E promotes the binding and uptake of β-amyloid into Chinese hamster ovary cells in an isoform-specific manner

The 4 allele of apolipoprotein E gene is a major risk factor for Alzheimer's disease. However, the mechanism by which the E4 isoform of apolipoprotein E increases the risk of Alzheimer's disease is poorly understood. To determine whether the isoform-specific effects of apolipoprotein E may be mediated via clearance of bound β-amyloid, we examined the uptake of β-amyloid 1–40 into Chinese hamster ovary cells in the presence or absence of the apolipoprotein E isoforms E2, E3 and E4. Apolipoprotein E2 and E3 treatments were associated with higher association of β-amyloid with cells as compared to treatment with E4. Heparin blocked the association of β-amyloid with cells, as did an antibody to one of the apolipoprotein E receptors (the low-density lipoprotein receptor-related protein).

Thus, the apolipoproteins E2 and E3, but not E4, may play important roles in the clearance of β-amyloid from the extracellular space via the low-density lipoprotein receptor-related protein.     

Intercomparison of calibration procedures for 192Ir HDR sources in Brazil

The lack of well established dosimetry protocols for HDR sources is a point of great concern regarding the uniformity of procedures within a particular country and worldwide. The main objective of this paper is to report the results from ten institutions of an intercomparison of calibration procedures for 192Ir HDR sources currently in use in Brazil. The treatment irradiator of one institution was calibrated by a reference system and used by all participants with their own measuring electrometers and ionization chambers under the same experimental conditions. Two methods were used: the calibration jig and the well-type ionization chamber. Each participant was allowed to use their own method and formalism. The results of this exercise were very positive since this was the first time in Brazil that a group of users gathered to share their experience and openly discuss the physical concepts behind the calibration procedures. The results were all within +/-3.0%, except one case where -4.6% was observed and later identified as a problem with the Nk value for x-rays. Though the magnitude of the deviations found was generally acceptable considering the diversity of formalisms currently in use, a proposal is now being prepared to be adopted as a national protocol. The identification of the institutions was left out for the sake of confidentiality.     

Alzheimer disease: curly fibers and tangles in organs other than brain.

The filamentous brain lesions that define Alzheimer disease (AD) consist of senile plaques and neurofibrillary tangles. Undulated pathological filaments--curly fibers or neuropil threads--also occur in the neuropil. Beta-amyloid precursor proteins are synthesized by many cells outside the central nervous system and recently, deposition of beta-amyloid-protein was reported to occur in non-neuronal tissues. In addition, increasing data claim the importance of chronic inflammation in the pathogenesis of AD. These observations suggest that AD may be a widespread systemic disorder. Here we report that pathological argyrophilic filaments with histochemical properties of amyloid showing striking morphological similarity to curly fibers and/or tangles accumulate not only in ependymal layer and in epithelial cells of choroid plexus, but also in several other organs (e.g. liver, pancreas, ovary, testis, thyroid) in AD. The ependyma, choroid plexus, and various organs of 39 autopsy cases were analyzed. In search of curly fiber and tangle-like changes in organs other than brain, 395 blocks from 21 different tissues of 24 AD cases, 5 cases with discrete or moderate AD-type changes, and 10 control cases were investigated. We found in non-neuronal cells "curly fibers" or "tangles" immunoreactive with antibodies to P component, Tau-protein, ubiquitin, fibronectin, and Apolipoprotein-E, but lacking immunoreactivity with antibodies to neurofilament proteins. Ultrastructurally they consist of densely packed straight and paired helical filaments and closely resemble neurofibrillary tangles and neuropil threads. These observations indicate that the formation of "curly fibers" and "tangles" is not unique to the central nervous system. The results suggest that AD might be a systemic disorder or that similar fibrillary changes to tangles and curly fibers may also be associated with other amyloidosis than beta-amyloidosis. Further investigations are necessary to understand the pathogenetic interest of these fibrillary changes outside the CNS.     

Diagnostic accuracy of physician review, expert algorithms and data-derived algorithms in adult verbal autopsies

BACKGROUND: The verbal autopsy (VA) is used to collect information on cause-specific mortality from bereaved relatives. A cause of death may be assigned by physician review of the questionnaires, or by an algorithm. We compared the diagnostic accuracy of physician review, an expert algorithm, and data-derived algorithms. METHODS: Data were drawn from a multicentre validation study of 796 adult deaths that occurred in hospitals in Tanzania, Ethiopia, and Ghana. A 'gold standard' cause of death was assigned using hospital records and death certificates. The VA interviews were carried out by trained fieldworkers 1-21 months after the subject's death. A cause of death was assigned by physician review and an expert algorithm. Data-derived algorithms that most accurately estimated the cause-specific mortality fraction (CSMF) for each cause of death were identified using logistic regression. RESULTS: The most common causes of death were tuberculosis/AIDS (CSMF = 18.6%), malaria (CSMF = 10.7%), meningitis (CSMF = 8.3%), and cardiovascular disorders (CSMF = 8.2%). The CSMF obtained using physician review was within +/-20% of the gold standard value for 12 causes of death including the four common causes. The CSMF obtained using the expert algorithm was within +/-20% of the gold standard for eight causes of death, including tuberculosis/AIDS, malaria, and meningitis. The CSMF obtained using the data-derived algorithms was within +/-20% of the gold standard for seven causes of death, including tuberculosis/ AIDS, meningitis, and cardiovascular disorders. All three methods yielded a specificity of at least 80% for all causes of death, and a sensitivity of at least 80% for deaths due to injuries and rabies. CONCLUSIONS: For those settings where physician review is not feasible, expert and data-derived algorithms provide an alternative approach for assigning many causes of death. We recommend that the algorithms proposed herein are validated further.     

Investigation of under-ascertainment in epidemiological studies based in general practice

BACKGROUND: One of the aims of the Study of Infectious Intestinal Disease (IID) in England is to estimate the incidence of IID presenting to general practice. This sub-study aims to estimate and correct the degree of under-ascertainment in the national study. METHODS: Cases of presumed IID which presented to general practice in the national study had been ascertained by their GP. In 26 general practices, cases with computerized diagnoses suggestive of IID were identified retrospectively. Cases which fulfilled the case definition of IID and should have been ascertained to the coordinating centre but were not, represented the under-ascertainment. Logistic regression modelling was used to identify independent factors which influenced under-ascertainment. RESULTS: The records of 2021 patients were examined, 1514 were eligible and should have been ascertained but only 974 (64%) were. There was variation in ascertainment between the practices (30% to 93%). Patient-related factors independently associated with ascertainment were: i) vomiting only as opposed to diarrhoea with and without vomiting (OR 0.37) and ii) consultation in the surgery as opposed to at home (OR 2.18). Practice-related factors independently associated with ascertainment were: i) participation in the enumeration study component (OR 1.78), ii) a larger number of partners (OR 0.3 for 7-8 partners); iii) rural location (OR 2.27) and iv) previous research experience (OR 1.92). Predicted ascertainment percentages were calculated according to practice characteristics. CONCLUSION: Under-ascertainment of IID was substantial (36%) and non-random and had to be corrected. Practice characteristics influencing variation in ascertainment were identified and a multivariate model developed to identify adjustment factors which could be applied to individual practices. Researchers need to be aware of factors which influence ascertainment in acute epidemiological studies based in general practice.     

Inward transport of 3H-MPP+ in freshly isolated rat hepatocytes: evidence for interaction with catecholamines

1-Methyl-4-phenylpyridinium (MPP⁺), the neurotoxic metabolite of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), is efficiently taken up and accumulated by rat hepatocytes. However, the nature of the mechanism(s) involved in the hepatic uptake of MPP⁺ remains partially unknown. The aim of the present study was to further characterize the hepatic uptake of ³H-MPP⁺, namely by investigating the interactions of catecholamines (which are also efficiently taken up by rat hepatocytes) with MPP¹ transport.The accumulation of ³H-MPP⁺ in isolated rat hepatocytes occurred through saturable and non-saturable mechanisms. The kinetics of the saturable component of ³H-MPP⁺ uptake was as follows: V_max = 181.3 ± 11.1 pmol mg protein^–1 min^–1 and K_m = 47.1 M (27.9, 66.3) (n = 5). The diffusion constant (in ml mg protein^–1 min^–1) for the non-saturable uptake of ³H-MPP⁺ was 0.00068 (0.00052, 0.00083) (n = 5). From the analysis of the time course of ³H-MPP⁺ accumulation at a substrate concentration of 100 nM ³H-MPP⁺, it was found that the rate constant of inward transport of ³H-MPP⁺ into hepatocytes (k_in) was 15.7 ± 3.8 l mg protein^–1 min^–1, the rate constant of outward transport of ³H-MPP⁺ from hepatocytes (k_out) was 0.077 ± 0.023 min^–1 and the equilibrium accumulation (A_max) of ³H-MPP⁺ was 20.2 ± 2.0 pmol mg protein^–1 (n = 36). Decynium22 (1,1-diethyl-2,2-cyanide; 1 M) significantly reduced k_in to 6.1 ± 1.8 l mg protein^–1 min^–1 (P < 0.05) and the equilibrium accumulation (A_max) of ³H-MPP⁺ to 9.6 ± 1.3 pmol mg protein^–1 (P < 0.005) (n = 36). ³H-MPP⁺ accumulation (in cells incubated with 200 nM ³H-MPP⁺) was sensitive to (–)-adrenaline, (–)-isoprenaline, (–)-dopamine, (±)-adrenaline and (–)-noradrenaline. The most potent catecholamine in inhibiting ³H-MPP⁺ uptake was (–)-adrenaline, with an IC₅₀ of 99 (22, 449) M (n = 6). (–)-Adrenaline competitively inhibited ³H-MPP⁺ uptake, as it significantly increased the K_m value of ³H-MPP⁺ uptake (to 125.4 M (63.6; 187.1); P < 0.02; n = 3) but did not change the V_max value. The cyanide-derivatives decynium22 and cyanine863 (1-ethyl-2-([1,4-dimethyl-2-phenyl-6-pyrimidinylidene]methyl)quinolinium), which inhibit uptake₂ as well as the apical type of the renal transporter for organic cations, potently inhibited ³H-MPP⁺ uptake with IC₅₀'s of 1.4 (0.4–5.3) (n = 6) and 6.5 (2.6–16) (n = 4) M, respectively. Under conditions of monoamine oxidase (MAO) and catechol-O-methyl transferase (COMT) inhibition with either pargyline (500 M + Ro01-2812) (3,5-dinitropyrocatechol; 2 M) or pargyline (500 M) + U-0521(3,4-dihidroxy-2-methyl-propiophenone; l2 M)), (–)-adrenaline (up to 1 mM) had no inhibitory effect on the uptake of ³H-MPP⁺. Moreover, the uptake of ³H-MPP⁺ in the presence of pargyline + Ro 01-2812 was significantly lower (66.9 ± 30.4%; P < 0.05; n = 4) than in the absence of these compounds. Therefore, the effect of these MAO and COMT inhibitors on ³H-MPP⁺ uptake was examined. Interestingly enough, pargyline, Ro 01-2812 and U-0521 were found to inhibit the uptake of ³H-MPP⁺ (in cells incubated with 200 nM ³H-MPP⁺): 500 M pargyline, 2 M Ro 012812 and 100 M U-0521 decreased the accumulation of ³H-MPP⁺ to 38.1 ± 6.8 (n = 5), 60.5 ± 10.1(n = 7) and 71.3 ± 14.5 (n = 7) % of control, respectively.It is concluded that ³H-MPP⁺ is efficiently taken up by rat hepatocytes by a carrier-mediated mechanism sensitive to catecholamines, decynium22 and cy anine863, and to the enzyme inhibitors pargyline, Ro 01-2812 and U-0521.     

Methodology to prevent mercury exposure among adolescents from goldmine areas in Mariana, state of Minas Gerais, Brazil

The main objective of this study was to promote the evaluation of an educational method to identify health risks among adolescents exposed to mercury by their work in gold mining production.The project was carried out with adolescents from a public school from the District of Monsenhor Horta, Municipality of Mariana, state of Minas Gerais. Statistical evaluation of the results revealed a significant increase in the amount of correct answers between the first and fifth stage concerning the definition of work accidents and its importance in relation to work-related diseases, accidents on route to and from the work place and violence at work site itself.     

Postnatal depression and infant growth and development in low income countries: a cohort study from Goa, India.

BACKGROUND: Postnatal depression is a recognised cause of delayed cognitive development in infants in developed countries. Being underweight is common in South Asia. AIMS: To determine whether postnatal depression contributes to poor growth and development outcomes in Goa, India. METHODS: Cohort study for growth outcomes with nested case-control study for developmental outcomes. A total of 171 babies were weighed and measured at 6-8 weeks following birth. The following measures were used: Edinburgh Postnatal Depression Scale for maternal mood, and sociodemographic and infant health variables. Outcome measures were: weight (<5th centile), length (<5th centile), and Developmental Assessment Scale for Indian Infants scores at six months. RESULTS: Postnatal depression was a strong, and independent, predictor of low weight and length and was significantly associated with adverse mental development quotient scores. CONCLUSIONS: This study provides evidence for the first time that postnatal depression, a potentially treatable disorder, is a cause of poor growth and development in South Asia.     

Use of the microorganism Bacillus stearothermophilus as a model to evaluate toxicity of the lipophilic environmental pollutant endosulfan.

Microorganisms are very powerful tools for the supply of information about the toxic effects of lipophilic compounds, since an impairment of cell growth usually occurs as a result of perturbations related, in most cases, with the partition of toxicants in membranes. The thermophilic eubacterium Bacillus stearothermophilus has been used as a model system to identify - and β-endosulfan interactions with the membrane possibly related with the insecticide toxicity. Two approaches have been pursued: (a) bacterial growth is followed and the effects of endosulfan isomers determined; (b) biophysical studies with the fluorescent fluidity probe 1,6-diphenyl-1,3,5-hexatriene (DPH) were performed to assess the effects of - and β-endosulfan on the organization of the membrane lipid bilayer. The effects on growth were quantitatively evaluated by determination of growth parameters, namely the lag phase, the specific growth rate and the cell density reached by cultures in the stationary phase. Growth inhibition by and β-endosulfan dependent on the concentration is diminished or removed by the addition of 2.5 m Ca²⁺ to bacterial cultures. Fluorescence DPH polarization consistently showed opposite effects of Ca²⁺ and - and β-endosulfan on the physical state of bacterial polar lipid dispersions.