Cable properties of dendrites in hippocampal neurons of the rat mapped by a voltage-sensitive dye

Dendrites of pyramidal neurons from embryonic rat hippocampus are investigated in culture using a voltage-sensitive fluorescent dye. The electrical response to somatic stimulation is observed as a time-resolved map with a resolution of 0.9 microm at a time constant of 0.4 ms without signal averaging. The data are interpreted in terms of a tapering cable with Hodgkin-Huxley parametrization. The spread of short hyperpolarizing transients is damped by capacitive shunting. The invasion of an action potential is boosted by voltage-gated conductances of a low density. No irregularity is observed at a bifurcation. The passive cable parameters of internal resistance and membrane resistance at resting voltage are Ri = 300 omega cm and Rm = 40 (k)omega cm2 respectively, at a maximum sodium conductance of approximately 4.4 mS/cm2. The electrotonic length constant and the dynamic length constant at 1 kHz are 580 and 90 microm respectively. These results are compatible with electrophysiological data of dendrites in slices of adult hippocampus and with optical data of narrow processes of leech neurons in culture. The functional implications of boosting an action potential by voltage-gated channels of low density are considered.

L-arginine infusion increases basal but not activated cerebral blood flow in humans

Nitric oxide is a potent vasodilator. Infusion of its precursor, L-arginine, results in increased cerebral blood flow (CBF) in experimental animals. We examined the effects of L-arginine infusion on CBF in humans using positron emission tomography and the quantitative H2(15)O method. Six subjects received 500 ml of 0.9% NaCl solution, and six subjects received an infusion of L-arginine (16.7 mg/kg/min; 500 mg/kg). Before and after the i.v. infusion, paired CBF measurements were performed at baseline and with vibrotactile stimulation of the right hand. In scans performed without vibrotactile stimulation, mean whole-brain CBF increased from 34.9 +/- 3.7 ml 100 g-1 min-1 to 38.2 +/- 4.4 ml 100 g-1 min-1. (9.5%; p < 0.005) after L-arginine infusion. The temporal pattern of CBF changes differed from that of plasma growth hormone and insulin levels and of arterial pH. In contrast, in the saline group, mean whole-brain CBF did not change significantly (35.8 +/- 5.9 ml 100 g-1 min-1 to 35.9 +/- 6.4 ml 100 g-1 min-1; 0.3%). Vibrotactile stimulation produced significant focal increases in CBF, which were unaffected by L-arginine infusion. L-arginine infusion was associated with an increase in plasma L-citrulline, a byproduct of nitric oxide synthesis.

The internal burden of lead among children in a smelter town--a small area analysis

Hettstedt, a city in former East Germany with a history of mining and smelting of nonferrous ores, has multiple lead waste deposits and the remains of a former lead and copper-silver smelter. A small-area analysis of lead concentrations in blood and in household dust was undertaken in a cross-sectional study to determine if children living near the sources had particularly high burdens of lead. The overall geometric mean of the region was 38.0 micrograms Pb/liter blood with a 95% confidence interval (CI) of 36.5-39.5. The burden of lead among children living in the region containing the lead tailings piles and adjacent smelters was almost twice as high (77.4 micrograms Pb/liter blood; 95% CI 65.0-92.0). It decreased in the areas farther northeast from the smelter. Lead levels in the children residing in areas southwest of the smelters were not appreciably elevated. The same pattern was found in house dust lead concentrations. This analysis helped target areas where follow-up is needed and found that not only distance from lead sources, but also meteorological factors played an important role in lead exposure.

Cerebral [15O] water clearance in humans determined by positron emission tomography: II. Vascular responses to vibrotactile stimulation

When used to measure blood flow, water leaves a residue in the vascular bed, which may contribute to the calculation of increased blood flow during functional activation of brain tissue. To assess the magnitude of this contribution with the two-compartment positron emission tomography (PET) method, we mapped the water clearance (K1) of the brain as an index of cerebral blood flow (CBF) and the apparent vascular distribution of nonextracted H2 15O (Vo). The latter map represented mainly the cerebral arterial and arteriolar volume. We also prepared subtraction maps (delta K1, delta Vo) of the response to vibrotactile stimulation of the fingertips of the right hand of six normal volunteers. Using magnetic resonance (MR) images of all subjects, the data were rendered into Talairach's stereotaxic coordinates and the averaged subtraction images (activation minus baseline) merged with the corresponding averaged MRI image. The delta K1 map revealed the expected response in the primary sensory hand area; the delta Vo response was located about 13 mm more anteriorly, close to the central fissure, most likely reflecting changes of the arteries feeding the primary sensory hand area. We conclude that cerebral perfusion and cerebrovascular responses to vibrotactile stimulation may occur in disparate locations that can be identified separately by using the two-compartment method.

STR analysis on perforating FMJ bullets and a new VWA variant allele

In three separate shooting incidents involving multiple gunshots, two FMJ bullets and one bullet fragment found at the scene (one from each case) were investigated for the presence of biological material from the victim after perforation. The surface of the missiles, which did not show obvious tissue traces when examined under a macroscope, was swabbed. PCR typing of up to five STR loci was performed on the small amounts of DNA extracted, which were seen below the detection limit of the slot blot quantification in one case. Nevertheless, individualisation of cellular material from the perforating projectiles was successful in each of the three cases presented. Consequently, identification of the victim wounded by a perforating bullet can reliably be achieved if contamination or removal of evidentiary material by improper handling is prevented. This technique is especially useful in cases where more than one person has fired a gun because the bullet carrying DNA can be linked to the firearm by investigation with a comparison microscope. As a by-product of this investigation, a variant allele 14 (14+4) at the VWA locus was detected.

Chromosome Y microsatellites: population genetic and evolutionary aspects

By means of a multicenter study, a large number of males have been characterized for Y-chromosome specific short tandem repeats (STRs) or microsatellites. A complete summary of the allele frequency distributions for these Y-STRs is presented in the Appendix. This manuscript describes in more detail some of the population genetic and evolutionary aspects for a restricted set of seven chromosome Y STRs in a selected number of population samples. For all the chromosome Y STRs markedly different region-specific allele frequency distributions were observed, also when closely related populations were compared. Haplotype analyses using AMOVA showed that when four different European male groups (Germans, Dutch, Swiss, Italians) were compared, less than 10% of the total genetic variability was due to differences between these populations. Nevertheless, these pairwise comparisons revealed significant differences between most population pairs. Assuming a step-wise mutation model and a mutation frequency of 0.21%, it was estimated that chromosome Y STR-based evolutionary lines of descent can be reliably inferred over a time-span of only 1950 generations (or about 49,000 years). This reduces the reliability of the inference of population affinities to a historical, rather than evolutionary time scale. This is best illustrated by the construction of a human evolutionary tree based on chromosome Y STRs in which most of the branches connect in a markedly different way compared with trees based on classical protein polymorphisms and/or mtDNA sequence variation. Thus, the chromosome Y STRs seem to be very useful in comparing closely related populations which cannot probably be separated by e.g. autosomal STRs. However, in order to be used in an evolutionary context they need to be combined with more stable Y-polymorphisms e.g. base-substitutions.

Evaluation of Y-chromosomal STRs: a multicenter study

A multicenter study has been carried out to characterize 13 polymorphic short tandem repeat (STR) systems located on the male specific part of the human Y chromosome (DYS19, DYS288, DYS385, DYS388, DYS389I/II, DYS390, DYS391, DYS392, DYS393, YCAI, YCAII, YCAIII, DXYS156Y). Amplification parameters and electrophoresis protocols including multiplex approaches were compiled. The typing of non-recombining Y loci with uniparental inheritance requires special attention to population substructuring due to prevalent male lineages. To assess the extent of these subheterogeneities up to 3825 unrelated males were typed in up to 48 population samples for the respective loci. A consistent repeat based nomenclature for most of the loci has been introduced. Moreover we have estimated the average mutation rate for DYS19 in 626 confirmed fatherson pairs as 3.2 x 10(-3) (95% confidence interval limits of 0.00041-0.00677), a value which can also be expected for other Y-STR loci with similar repeat structure. Recommendations are given for the forensic application of a basic set of 7 STRs (DYS19, DYS3891, DYS389II, DYS390, DYS391, DYS392, DYS393) for standard Y-haplotyping in forensic and paternity casework. We recommend further the inclusion of the highly polymorphic bilocal Y-STRs DYS385, YCAII, YCAIII for a nearly complete individualisation of almost any given unrelated male individual. Together, these results suggest that Y-STR loci are useful markers to identify males and male lineages in forensic practice.

DNA typing of cellular material on perforating bullets

DNA typing of cellular debris from perforating bullets was investigated following shooting experiments. A total of 14 perforating gunshots were fired into 9 calves. PCR typing of tissue fragments was done using bovine-specific primers flanking a 247 bp segment within the bovine lactoglobulin gene. Positive amplification results were obtained for all 9 hollow point (HP) and all 5 full metal jacket (FMJ) bullets. In contrast to HP bullets the smooth surfaces of the FMJ bullets did not have visible biological material, which resulted in weaker bands in the DNA analysis compared to HP bullets. Tissue seemed to accumulate at the base of the projectiles. Due to the lack of a suitable marker in bovines, only a species identification was carried out on the DNA from tissue on the bullets. The small amount of DNA extract (up to 5%) required for specification is promising for the successful application of a set of short tandem repeat (STR) systems for individualization in humans. By individualizing tissue on perforating bullets, the bullet and the victim it passed through can be linked. This can assist the investigation of gunshot deaths, especially when several persons are involved in a gun fight.

Epigenetic regulation of programmed genomic rearrangements in Paramecium aurelia

In ciliates, development of the polyploid somatic macronucleus after sexual events involves extensive and reproducible rearrangements of the germ-line genome, including chromosome fragmentation and precise excision of numerous internal sequence elements. In Paramecium aurelia, alternative macronuclear versions of the same germ-line genome can be maternally inherited across sexual generations, showing that rearrangement patterns are not strictly determined by the germ-line sequence. Homology-dependent maternal effects can be evidenced by transformation of the vegetative macronucleus with cloned macronuclear sequences: new fragmentation patterns or internal deletions are specifically induced during differentiation of a new macronucleus, in sexual progeny of transformed clones. Furthermore, transformation of the maternal macronucleus with germ-line sequences containing internal eliminated sequences (short single-copy elements) can result in a specific inhibition of the excision of the same elements in the zygotic macronucleus. These experiments show that the processing of many germ-line sequences in the developing macronucleus is sensitive to the structure and copy number of homologous sequences in the maternal macronucleus. The generality and sequence specificity of this trans-nuclear, epigenetic regulation of rearrangements suggest that it is mediated by pairing interactions between germ-line sequences and sequences imported from the maternal macronucleus.

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.