Clustering autism: using neuroanatomical differences in 26 mouse models to gain insight into the heterogeneity.

Autism is a heritable disorder, with over 250 associated genes identified to date, yet no single gene accounts for >1-2% of cases. The clinical presentation, behavioural symptoms, imaging and histopathology findings are strikingly heterogeneous. A more complete understanding of autism can be obtained by examining multiple genetic or behavioural mouse models of autism using magnetic resonance imaging (MRI)-based neuroanatomical phenotyping. Twenty-six different mouse models were examined and the consistently found abnormal brain regions across models were parieto-temporal lobe, cerebellar cortex, frontal lobe, hypothalamus and striatum. These models separated into three distinct clusters, two of which can be linked to the under and over-connectivity found in autism. These clusters also identified previously unknown connections between Nrxn1α, En2 and Fmr1; Nlgn3, BTBR and Slc6A4; and also between X monosomy and Mecp2. With no single treatment for autism found, clustering autism using neuroanatomy and identifying these strong connections may prove to be a crucial step in predicting treatment response.

Altered brain development in an early-onset murine model of Alzheimer's disease.

Murine models of Alzheimer's disease (AD) have been used to draw associations between atrophy of neural tissue and underlying pathology. In this study, the early-onset TgCRND8 mouse model of AD and littermate controls were scanned longitudinally with in vivo manganese-enhanced MRI (MEMRI) before and after the onset of amyloid plaque deposition at 12 weeks of age. Separate cohorts of mice were scanned at 1 week (ex vivo imaging) and 4 weeks (MEMRI) of age to investigate early life alterations in the brain. Contrary to our expectations, differences in neuroanatomy were found in early post-natal life, preceding plaque deposition by as much as 11 weeks. Many of these differences remained at all imaging time points, suggesting that they were programmed early in life and were unaffected by the onset of pathology. Furthermore, rather than showing atrophy, many regions of the TgCRND8 brain grew at a faster rate compared to controls. These regions contained the greatest density of amyloid plaques and reactive astrocytes. Our findings suggest that pathological processes as well as an alteration in brain development influence the TgCRND8 neuroanatomy throughout the lifespan.

In vivo regulation of DOPA decarboxylase by dopamine receptors in rat brain.

To test the hypothesis that dopamine (DA) receptors influence cerebral DOPA-decarboxylase (DDC) activity in vivo, we used HPLC to measure the kinetics of the cerebral uptake and metabolism of [3H]DOPA in carbidopa-treated rats, and in rats also treated acutely with a DA receptor antagonist (flupenthixol, 2 mg/kg, intraperitoneally) or a DA receptor agonist (apomorphine, 200 microg/g, subcutaneously). The unidirectional blood-brain clearance of [3H]DOPA (K1DOPA, 0.030 mL g(-1) min(-1)) increased by 50% after flupenthixol. The magnitudes of the relative DDC activity (k3DOPA) in striatum (0.20 min(-1)), olfactory tubercle (0.11 min(-1)), and hypothalamus (0.15 min(-1)) of carbidopa-treated rats were doubled with flupenthixol, but cortical DDC activity was unaffected (0.02 min(-1)). Apomorphine reduced the magnitude of k3DOPA in striatum by 20%. The rate constant for catabolism of [3H]DA formed in brain (k7', monoamine oxidase [MAO] activity), which ranged from 0.025 min(-1) in striatum to 0.08 min(-1) in hypothalamus of carbidopa-treated rats, globally increased 2- to 4-fold after flupenthixol, and decreased to 0.003 min(-1) in striatum after apomorphine. These in vivo results confirm the claim that acute blockade of DA receptors with flupenthixol stimulates the synthesis of [3H]DA from [3H]DOPA, and that this [3H]DA is subject to accelerated catabolism. Conversely, activation of the DA receptors with apomorphine inhibits DDC activity and DA catabolism.

Dioxin-like compounds in fishing people from the Lower North Shore of the St. Lawrence River, Quebec, Canada.

In this study, investigators assessed exposure to dioxin-like compounds in a fishing population that inhabits small coastal communities along the Lower North Shore of the St. Lawrence River, Quebec. This population relies heavily on wildlife foods for sustenance. Investigators analyzed chemically the most popular marine foods (i.e., fish, crustaceans, sea mammals, and sea-bird eggs), and they also obtained 25 human plasma samples from individuals in two villages along the river. The mean level of total polychlorinated biphenyls in this population was approximately twice that found in the entire fishing cohort. Plasma levels of dioxin-like compounds, expressed as tetrachlorodibenzodioxin toxic equivalents, were approximately eight times higher than levels in urban residents. Most of the increase in tetrachlorodibenzodioxin toxic equivalents in the selected fish eaters resulted primarily from an elevation in polychlorinated biphenyls. Concentrations of dioxin-like compounds from the Lower North Shore were low in fish and seals, but concentrations were elevated in the eggs of sea birds. Given that there was also a significant statistical correlation in the entire population between human plasma levels and consumption of birds' eggs-and not other traditional foods-much of the increased human dose appeared to originate from this one food source. Because there appear to be increased, but uncertain, health risks from this elevated body burden, investigators advised the residents of the area to avoid consumption of wild birds' eggs (i.e., a food source of minor nutritional importance).

The effect of unilateral neurotoxic lesions to serotonin fibres in the medial forebrain bundle on the metabolism of [3H]DOPA in the telencephalon of the living rat.

We used quantitative autoradiography to measure the contribution of the 5-hydroxytryptamine (5-HT, serotonin) innervation of rat telencephalon to the synthesis of dopamine (DA) from exogenous L-DOPA. One week after stereotaxic infusions of 5,7-dihydroxy-tryptamine (5,7-DHT, 1.6 micrograms) into the right medial forebrain bundle (MFB), rats received [3H]DOPA (200 microCi,i.v.), which circulated for 90 min. The specific bindings in vitro of the 5-HT uptake site ligand [3H]citalopram and the DA uptake site ligand [125I]RTI-55 were measured in cryostat sections from the prosencephalon. In most structures ipsilateral to the lesion, [3H]citalopram specific binding was substantially reduced (50-90%). In the lateral habenula specific binding declined by only 30-40%, reflecting the presence of a 5-HT pathway deviating from the MFB at the mesencephalic flexure. [125I]RTI-55 binding in the basal ganglia was reduced by 50% on the side of the 5,7-DHT lesion, but was unperturbed in rats pretreated with desmethylimipramine (DMI). 5,7-DHT infusions decreased the synthesis of [3H]DA from [3H]DOPA in vivo in the basal ganglia by (40-90%). Pretreatment with DMI protected [3H]DA synthesis in the basal ganglia, but not in the olfactory tubercle and amygdala ipsilateral to the lesion. Whereas the 5-HT innervation does not contribute greatly to [3H]DA synthesis in the basal ganglia, a substantial proportion of [3H]DA synthesis in olfactory tubercle and amygdala requires an intact 5-HT innervation.

Polychlorinated biphenyl (PCB) and dichlorodiphenyl dichloroethylene (DDE) concentrations in the breast milk of women in Quebec.

OBJECTIVES: This study documented the concentration of polychlorinated biphenyls (PCBs) and dichlorodiphenyl dichloroethylene (DDE) in the breast milk of women from Quebec, Canada, and assessed the impact of various sociodemographic and lifestyle factors on these levels. METHODS: From 1988 to 1990, milk samples were obtained from 536 Quebec women and analyzed for seven PCB congeners and p,p'-DDE. Information was obtained on subjects' physical, sociodemographic, and lifestyle characteristics. RESULTS: Mean concentrations were 0.52 mg/kg lipids (95% confidence interval [CI] = 0.50, 0.54) and 0.34 mg/kg lipids (95% CI = 0.32, 0.35) for PCBs (Aroclor 1260) and DDE, respectively. Age and history of breast-feeding showed statistically significant correlations with PCB and DDE concentrations. CONCLUSIONS: Concentrations of PCBs and DDE measured in this study are at the lower end of the concentration range recently reported for women living in industrialized countries. The modulating factors identified here should be considered when conducting studies on organochlorine exposure and disease.

Metabolism and blood-brain clearance of L-3,4-dihydroxy-[3H]phenylalanine ([3H]DOPA) and 6-[18F]fluoro-L-DOPA in the rat.

6-[18F]fluoro-L-DOPA (FDOPA) has been used as a tracer for the cerebral activity of L-3,4-dihydroxyphenylalanine (DOPA)-decarboxylase in studies of positron emission tomography (PET). However, the substitution of fluorine on the aromatic ring may alter the disposition and metabolism of FDOPA from that of endogenous DOPA. In the present study, the kinetics of the peripheral metabolism and the facilitated unidirectional blood-brain clearance of [3H]DOPA and FDOPA were compared in Wistar rats pretreated with carbidopa. In arterial plasma, FDOPA was O-methylated with an apparent rate constant (0.031 min-1) 3-fold that of [3H]DOPA in the same rats. The O-methylated metabolite of FDOPA (OMe-FDOPA) was eliminated from plasma at a rate constant (0.018 min-1) 3-fold that of OMe-[3H]DOPA. The mean unidirectional blood-brain clearance of FDOPA (4.5 mL.hg-1.min-1) in six brain regions was 60% higher than that of [3H]DOPA.

Distribution of histamine H3 binding in forebrain of mouse and guinea pig.

To map the unknown distribution of histamine H3 binding sites, we compared autoradiographs of the binding of the H3 agonist N alpha-[3H]methylhistamine ([3H]NAMH) in the forebrain of mouse and guinea pig. Saturation binding revealed the presence of a single site with apparent affinity of 0.75 nM in the mouse and 1.2 nM in the guinea pig. Binding constants were nearly identical in male and female mice. The rank order of [3H]NAMH binding in mouse brain was striatum > insular cortex > neocortex, as previously observed in the rat. In the guinea pig, the rank order was insular cortex > striatum approximately neocortex. The Bmax of [3H]NAMH in insular cortex of both species was close to 60 fmol/mg. Thus, the guinea pig differs from the rodent in that the highest density of H3 binding was present in cortical rather than subcortical structures.

Exposure of remote maritime populations to coplanar PCBs.

Two remote maritime populations were evaluated for their biological exposure to organochlorines in 1989-1990. Because of their high intake of seafood, these two populations have high biological levels. One hundred nine breast milk samples from Inuit women from Arctic Québec were analyzed to determine levels of polychlorodibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) including non-ortho, mono-ortho, and di-ortho congeners. Total 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEqs) for PCBs were 3.5 times higher in Inuit milk samples than in 96 Caucasian milk samples. Among the 185 fishermen from the Lower North Shore of the Gulf of the St. Lawrence River, we evaluated 10 highly exposed fishermen for their coplanar PCB blood levels. Total TEqs were 900 ng/kg for highly exposed individuals with 36 ng/kg for controls. In these two nonoccupationally exposed populations, coplanar PCBs make a larger contribution to the TEq than PCDDs and PCDFs. However, the mono-ortho penta CB No. 118 is the major contributor for the total toxicity.

Inuit exposure to organochlorines through the aquatic food chain in arctic québec.

Inuit people (Eskimos) are likely exposed to persistent organochlorine compounds because their traditional diet includes fatty tissues of the arctic marine biota. Here we present the results of organochlorine compound analysis in milk fat samples from arctic Québec Inuit women and in fat tissues from various animal species inhabiting that region. The total concentration of polychlorinated biphenyl congeners in Inuit milk fat was similar to that of the beluga, while the profile of the 10 congeners resembled that of the polar bear. Mean concentrations of various organochlorines in milk-fat samples from Inuit women were between 2 and 10 times greater than those found in samples previously collected from southern Québec women. The Inuit mothers exhibit the greatest body burden known to occur from exposure to organochlorine residues present in the environment by virtue of their location at the highest trophic level of the arctic food web.

Gas chromatographic/mass spectrometric analysis of 19-nortestosterone urinary metabolites in man.

A sensitive and highly specific method based on capillary column gas chromatography/mass spectrometry has been developed for the detection of 19-nortestosterone (17 beta-hydroxy-4-estren-3-one) metabolites in urine. After intramuscular administration of 19-nortestosterone decanoate to man, urine samples were collected during several days and treated with Helix pomatia digestive juice. The free steroids were extracted and converted into O-methyl-oxime-trimethylsilyl or the trimethylsilyl ether derivatives and analysed by capillary column gas chromatography/mass spectrometry (GC/MS). Three isomeric metabolites were detected and identified as 3 alpha-hydroxy-5 alpha-extran-17-one (19-norandrosterone), 3 alpha-hydroxy-5 beta-estran-17-one (19-noretiocholanolone) and 3 beta-hydroxy-5 alpha-estran-17-one (19-norepiandrosterone). Packed column GC/MS was also employed in the selected ion monitoring mode for the specific detection of 19-norandrosterone, the most abundant urinary metabolite of 19-nortestosterone. These gas chromatographic/mass spectrometric methods are highly specific tests which can be used on a routine basis for the confirmation of 19-nortestosterone administration to athletes as well as for therapeutic monitoring following administration of the drug.

Plasma methyl sterol sulfates in familial hypercholesterolemia after partial ileal bypass.

We demonstrate, in this study, the presence of several unidentified components in the sterol sulfate fraction of familial hypercholesterolemia patients treated with partial ileal bypass surgery. The sterols obtained after solvolysis and derivatization of this fraction had a retention time, on gas-liquid chromatography, intermediate between cholesterol and beta-sitosterol. They were not present in the sterol sulfate fraction obtained from normal subjects, hypercholesterolemic patients, or ileal bypass subjects before surgery or after reanastomosis. The substances isolated from the sterol sulfate fraction were identified by combined gas-liquid chromatography and mass spectrometry to be 24,25-dihydrolanosterol, 4,4-dimethyl-5alpha-cholest-8-en-3beta-ol, 4,4-dimethyl-5alpha-cholest-9(11)-en-3beta-ol, 4alpha-methyl-5alpha-cholest-7-en-3beta-ol, and 4alpha-methyl-5alpha-cholest-8-en-3beta-ol. Their free forms are known to be biosynthetic intermediates in the transformation of lanosterol into cholesterol.