Cerebral [15O]water clearance in humans determined by PET: I. Theory and normal values

When used to measure blood flow in the brain, water leaves a residue in the vascular bed that influences the estimation of blood flow by current methods. To assess the magnitude of this influence, we developed a two-compartment model of blood flow with separate parameters for transport and vascular distribution of brain water. Maps of the water clearance, K1 into brain tissue, separated from the circulation by a measurably resistant blood-brain barrier (BBB), were generated by time-weighted integration. Depending on the validity of the assumptions underlying the two-compartment model presented here, the maps revealed a significant overestimation of the clearance of water when the vascular residue was ignored. Maps of Vo, the estimate of the apparent vascular distribution volume of tracer H2(15)O, clearly revealed major cerebral arteries. Thus, we claim that the accumulation of radioactive water in brain tissue also reflects the volume of the arterial vascular bed of the brain.

Functional imaging of cerebral arteriovenous malformations with a comment on cortical reorganization

Functional brain imaging is poised to become a standard diagnostic tool. The authors review their experience using functional positron emission tomography (fPET) in patients with cerebral arteriovenous malformations (AVMs).

Twelve patients, three males and nine females aged 16 to 30 years, 11 with a cerebral AVM and one with a cavernous angioma, of which five were located in the central area and seven in a speech region, underwent fPET and three-dimensional magnetic resonance imaging. These studies were coregistered in stereotactic space and correlated to Brodmann's areas that were identified from the atlas of Talairach and Tournoux. Vibrotactile and/or motor stimulation of the contralateral hand were used to identify the central region in patients whose AVM resided within, or close to, the motor strip, and language tasks specifically designed to activate visual, auditory, expressive, or semantic language were used in patients whose AVM resided within, or close to, Broca's or Wernicke's areas.

Somatosensory and motor activation reliably identified the central region in all cases as validated by identification of Brodmann's areas and by intraoperative cortical mapping, which was performed with the patient under local anesthesia. Similarly, language tasks accurately lateralized major language function to one hemisphere concordantly with neuropsychological assessment, including dichotic listening and intracarotid Amytal tests, and localized language areas appropriately as verified by stereotactic coordinates.

Functional cerebral imaging is feasible in patients with structural brain lesions. It is a reliable method to identify the relationship of a cerebral AVM to the central region. The determination of a similar relationship to language areas is dependent on the development and further validation of language-based tasks designed to activate visual, auditory, expressive, and semantic aspects of language specific to particular sites within the anterior and posterior speech regions.

Abnormal postprandial apolipoprotein B-48 and triglyceride responses in normolipidemic women with greater than 70% stenotic coronary artery disease: a case-control study

Because remnants of triglyceride-rich lipoproteins (TRLP) are potentially atherogenic, the postprandial lipoprotein metabolism was studied in 12 normocholesterolemic, normotriglyceridemic women, aged 60 +/- 2 years, with angiographically proven coronary artery disease (CAD+; cholesterol 5.7 +/- 0.1 (S.E.) mmol/l, triglyceride 1.35 +/- 0.10 mmol/l) and in 12 individually matched controls, aged 59 +/- 2 years, without angiographical abnormalities (CAD-; cholesterol 5.1 +/- 0.2 mmol/l and triglyceride 1.16 +/- 0.13 mmol/l). Following an oral retinyl palmitate-fat load, the CAD+ women showed a significantly higher triglyceride response in the chylomicron, or Sf > 1000, fraction (P < 0.05 vs. controls). Total plasma apolipoprotein (apo) B and retinyl palmitate concentrations were similar in both groups. Fasting apo B-48 levels in the d < 1.006 g/ml fraction were significantly higher in CAD+ cases (0.25 +/- 0.03 integrated optical density (iod) units) than CAD- controls (0.15 +/- 0.03; P < 0.05). Furthermore, after the fat load, a greater absolute and incremental apo B-48 response in the intermediate density lipoprotein (IDL) fraction (d = 1.006-1.019 g/ml) was observed in CAD+ cases (incremental area under the curve (Delta-AUC)8: 0.40 +/- 0.12 h.iod) than CAD- controls (0.01 +/- 0.06 h.iod; P = 0.01). Post-heparin hepatic lipase (HL) activities were higher in the CAD+ group: 422 +/- 22 mU/l vs 288 +/- 20 mU/ml in the CAD- group (P < 0.001) while lipoprotein lipase (LPL) activities were identical. The results provide evidence that the metabolism of intestinal TRLP is significantly different in normolipidemic women with angiographically proven CAD compared with individually matched controls without coronary disease. Fasting apo B-48 levels in d< 1.006 g/ml fractions represent a potentially useful marker in women at risk for CAD.

Complex mutational events at the HumD21S11 locus

We have studied length and sequence variability at the HumD21S11 locus in five different populations to obtain more detailed information about the structure of this short tandem repeat system. In all populations studied so far two types of alleles have been described. The consensus alleles (type I) consist of three regions with variable numbers of TCTR units and one constant region comprising 43 bp. Alleles of type II (so-called interalleles) show the same basic sequence structure except for the occurrence of a TA insertion at a fixed position in variable region 3. Additional sequence variability exists in the Ovambo and Papuan populations with gross changes in two of the three variable regions and in the constant region. Due to these extreme variations the Ovambos and Papuans showed a better fit to the infinite allele model than to the stepwise mutation model. In the German, Japanese and Chinese populations no significant bias towards one of the two models could be observed. Population genetic studies showed no significant deviation from Hardy-Weinberg equilibrium.

A Mendelian mutation affecting mating-type determination also affects developmental genomic rearrangements in Paramecium tetraurelia

In Paramecium tetraurelia, mating type is determined during the differentiation of the somatic macronucleus from a zygotic nucleus genetically competent for both types, O and E. Determination of the developing macronucleus is controlled by the parental macronucleus through an unknown mechanism resulting in the maternal inheritance of mating types. The pleiotropic mutation mtFE affects macronuclear differentiation. Determination for E is constitutive in mutant homozygotes; a number of unrelated mutant characters are also acquired during development. We have examined the possibility that the mutation causes a defect in the developmental rearrangements of the germ-line genome. We show that the excision of an IES (internal eliminated sequence) interrupting the coding sequence of a surface antigen gene is impaired in the mutant, resulting in an alternative macronuclear version of the gene. Once established, the excision defect is indefinitely transmitted across sexual generations in the cytoplasmic lineage, even in a wild-type genetic context. Thus, the processes of mating-type determination and excision of this IES, in addition to their common sensitivity to the mtFE mutation, show a similar maternal inheritance of developmental alternatives in wild-type cells, suggesting a molecular model for mating-type determination.

Identification of alpha-phenylethylamine in judicial samples

alpha-Phenylethylamine was recently identified in samples from several judicial cases using chromatographic (high-performance liquid chromatography-diode-array detection, gas chromatography-mass spectrometry, and gas chromatography-Fourier transform infrared detection) and spectrometric (nuclear magnetic resonance) techniques. In the first case, 1 kg of a white powder was found in a basement laboratory. It contained caffeine and more than 15% alpha-phenylethylamine. In the second case, two white powders were seized from a female. One powder consisted of pure amphetamine, and the other was a mixture of caffeine, amphetamine, and alpha-phenylethylamine. Four months later, a couple, who were known drug users, were found dead in their apartment. Urine samples of both victims contained large amounts of amphetamine together with alpha-phenylethylamine. Recently, 0.13 kg of a white powder and 0.30 kg of an orange powder were seized during a law enforcement operation. Both powders were mixtures of caffeine, amphetamine, and alpha-phenylethylamine. The data presented demonstrate the recent and unrelated repetitive occurrence of alpha-phenylethylamine in the circuit of illicit drugs.

PET studies of phonetic processing of speech: review, replication, and reanalysis

Positron emission tomography was used to investigate cerebral blood flow (CBF) changes associated with the processing of speech. In a first experiment, normal right-handed volunteers were scanned under two conditions that required phonetic processing (discrimination of final consonants and phoneme monitoring), and one baseline condition of passive listening. Analysis was carried out by paired-image subtraction, with MRI overlay for anatomical localization. Comparison of each phonetic condition with the baseline condition revealed increased CBF in the left frontal lobe, close to the border between Broca's area and the motor cortex, and in a left parietal region. A second experiment showed that this area was not activated by a semantic judgement task. Reanalysis of data from an earlier study, in which various baseline conditions were used, confirmed that this region of left frontal cortex is consistently involved in phonetic tasks. The findings support a model whereby articulatory processes involving a portion of Broca's area are important when phonetic segments must be extracted and manipulated, whereas left posterior temporal cortex is involved in perceptual analysis of speech.

Hydroxyethyl cyclosporin A induces and decreases P4503A and P-glycoprotein levels in rat liver

1. A new immunosuppressant SDZ IMM 125 (IMM), the hydroxyethyl derivative of D-serine8-cyclosporin (cyclosporin A, CSA), induced or decreased the liver P450s of rat, in particular the 3A proteins, depending on the dose and duration of exposure. Doses of 20 mg/kg/day for 2 weeks and 10 mg/kg/day for 26 weeks induced the rat liver 3A levels 2- and 1.8-fold respectively, whereas 52 weeks of 24 mg/kg/day decreased the 3A levels by 22%. High doses of IMM, 100 mg/kg/day for 26 weeks, significantly decreased the 3A levels by 56%. 2. Changes in the rate of IMM biotransformation paralleled the changes in the levels of liver 3A indicating that liver 3A levels could influence the clearance of IMM. 3. Both IMM and CSA affected liver and kidney P-glycoprotein (Pgp) levels. The increases measured after short-term treatment (20 mg/kg/day for 2 weeks) in the liver (1.8-fold) and kidney (1.3-fold) were less pronounced in the long-term studies in which liver Pgp levels were increased 1.4-fold (48 mg/kg/day for 52 weeks). At higher doses (100 mg/kg/day for 26 weeks) Pgp levels were significantly decreased. The modulation of Pgp levels by IMM did not parallel the changes in 3A levels, indicating that Pgp regulation is most likely due to a direct effect of the cyclosporin rather than a co-regulation mechanism linked to 3A or P4501A modulation. 4. Increased arachidonic metabolism to the 19- and 20-HETE metabolites, a possible mechanism of the cyclosporin-induced renal hypertension, occurred in the liver microsomes and not the kidney S9 fraction of the 2-week study, and only at very high doses (100 mg/kg/day) in the longer studies (26 weeks).

Analysis of zopiclone (Imovane) in postmortem specimens by GC-MS and HPLC with diode-array detection

A 26-year-old black female was found dead at home. Her mouth was covered with a fluid containing chalky particles. Empty strips of Imovane (zopiclone) and an empty bottle of Fortal (pentazocine) were also found. No urine was available at autopsy. Screening of postmortem blood and stomach contents with enzyme-multiplied immunoassay technique (EMIT) detected only caffeine. Further screening using routine high-performance liquid chromatography (HPLC) with diode-array detection and gas chromatography (GC) with mass spectrometric detection revealed the presence of large amounts of pentazocine in the blood and stomach contents. In the HPLC chromatogram, a second peak that was only partially resolved from the solvent front was observed. Thin-layer chromatography demonstrated the presence of zopiclone, but optimized HPLC and GC conditions had to be used for proper identification and quantitation. This case illustrates the fact that zopiclone can be easily overlooked during routine forensic screening.

Erythropoietin-Induced Iritis-Like Reaction

The present report describes an iritis-like reaction found in 13 patients treated with recombinant human erythropoietin (Eprex), a drug given to hemodialysis patients for their chronic anemia. Among 120 patients being treated by hemodialysis in two centers affiliated with our medical center, ten out of 30 Eprex-treated patients but none of 90 not being treated with Eprex developed this reaction. The observations described support a causal relation between Eprex treatment and the iritis-like reaction. Further investigative effort is needed to establish the mechanism.

Population study of 3 STR loci in the Basque Country (northern Spain)

The tetrameric STRs, HUMTH01, HUMVWA31A and HUMFES/FPS, were studied in a population from the Basque Country (northern Spain) for their frequency distribution and applicability to identity and paternity testing. All systems conformed to Hardy-Weinberg equilibrium; pairwise comparisons demonstrated the allelic independence between loci, and furthermore, all systems seemed to be in agreement with expectations from the Stepwise Mutation Model (SMM) of the mutation-drift theory, which indicates the homogeneity of the population and suggests a replication slippage mechanism as a possible model for generating alleles. A comparison with other population groups appeared to indicate that frequencies are well conserved in Caucasians, but differ from other racial groups. The calculated parameters "a priori probability of exclusion" (PEX) and "index of discrimination" (ID), show the informativeness of these loci for the determination of identity and relatedness of individuals.

Epigenetic self-regulation of developmental excision of an internal eliminated sequence on Paramecium tetraurelia

Differentiation of the somatic macronucleus of ciliates after sexual events involves the programmed excision of thousands of single-copy internal eliminated sequences (IESs) from the germ-line genome. We have studied two cell lines of Paramecium tetraurelia that have identical germ-line genomes but differ in their macronuclear genomes. In the IES- cell line, a 222-bp IES interrupting a coding sequence is reproducibly excised during macronuclear differentiation, whereas it is not in the IES+ cell line. In a cross between the two lines, the developmental alternative in maternally inherited, suggesting that it is epigenetically controlled by the old (prezygotic) macronucleus in each cell. Transformation of the macronucleus of both lines with plasmids carrying fragments of either version of the gene shows that the presence of the IES sequence in the old macronucleus results in retention of the IES in the new macronuclear genome of sexual progeny. This could be attributable to (1) inhibition of excision, or (2) repair of a double-strand gap left in the genomic sequence after constitutive excision of the IES, by a polymerization mechanism using a homologous IES+ template from the old macronucleus. The latter possibility is ruled out by experiments showing that modified IESs can inhibit excision without being copied in the new macronuclear genome. Possible mechanisms are discussed in the light of a quantitative analysis of excision inhibition by the maternal IES sequence.

Functional neuroanatomy of CCK4-induced anxiety in normal healthy volunteers

OBJECTIVE

The authors tested the prediction of temporal cortex activation during experimentally induced anxiety by using positron emission tomography and the [15O]H2O bolus-subtraction method to determine regional cerebral blood flow (CBF) changes in normal volunteers challenged with a bolus injection of cholecystokinin tetrapeptide (CCK4).

METHOD

Eight right-handed healthy subjects (five male, three female; mean age, 26.4 years) underwent four 60-second [15O]H2O scans separated by 15-minute intervals; each scan followed an intravenous bolus injection of either saline (placebo) or CCK4 (50 micrograms). Each subject received CCK4 once, as the first or second bolus, in a random-order, placebo-controlled, double-blind fashion. Two of the three placebo conditions were nominally identical, and the remaining placebo was used to control for anticipatory anxiety. Magnetic resonance imaging scans were obtained for subsequent anatomical correlation of blood flow changes.

RESULTS

CCK4, but not placebo, elicited a marked anxiogenic response, reflected by robust increases in subjective anxiety ratings and heart rate. CCK4-induced anxiety was associated with 1) robust and bilateral increases in extracerebral blood flow in the vicinity of the superficial temporal artery territory and 2) CBF increases in the anterior cingulate gyrus, the claustrum-insular-amygdala region, and the cerebellar vermis.

CONCLUSIONS

Some of the temporopolar cortex CBF activation peaks previously reported in humans in association with drug- and non-drug-induced anxiety, as well as the increase in regional CBF in the claustrum-insular-amygdala region, may be of vascular and/or muscular origin.

[Purtscher's retinopathy]

A 20-year-old soldier trapped under a minibus for 90 minutes sustained a crush injury to his chest and a maxillofacial fracture. 2 days later he complained of decreased visual acuity in both eyes. Funduscopy revealed Purtscher's retinopathy. The traumatologist should be aware of this type of indirect eye injury, and should request ophthalmological assessment and follow-up in such patients.

Microsatellite polymorphisms reveal phylogenetic relationships in primates

We amplified, via PCR, DNA segments from intron 1 of the tyrosine hydroxylase gene (TH01) and intron 40 of the von Willebrand factor gene (VWA) in ten nonhuman primate genera. In humans both introns contain polymorphic microsatellites with tetrameric repeats. Compared to the allelic ranges in human populations relatively short repeat arrays could be detected for the nonhuman primates typed, presumably reflecting an ancient precursor state at both microsatellite loci. Furthermore, our results provide evidence for an association of the average number of repeats present in different primate genera and their divergence time from man. DNA sequencing of VWA orthologues revealed a relatively high variability in the arrangement of repeats in the 5'-repeat arrays, the generation of which could probably be explained by polar mutational events.

Phenotype differences of STRs in 7 human populations

A maximum of 6 STR systems (TH01, VWA, ACTBP2, FES, F13B, D21S11) was investigated in 7 human populations (Germans, Turks, Moroccans, Japanese, Chinese, Papuans, Ovambos). In each population no deviations from Hardy-Weinberg equilibrium were observed. Out of each population the phenotypes of 50 individuals (comprising 3 to 6 STRs) were randomly selected. Based on the phenotype frequencies interpopulation comparisons were carried out using the frequencies of each other population. Within major ethnic groups only minor differences in phenotype frequencies were found. Between major ethnic groups differences of up to several orders of magnitude could be observed. The most discriminative STRs for interpopulation comparisons were TH01, FES and F13B.