Continuous quantum measurement and the emergence of classical chaos

We formulate the conditions under which the dynamics of a continuously measured quantum system becomes indistinguishable from that of the corresponding classical system. In particular, we demonstrate that even in a classically chaotic system the quantum state vector conditioned by the measurement remains localized and, under these conditions, follows a trajectory characterized by the classical Lyapunov exponent.

Synaptogenesis in the giant-fibre system of Drosophila: interaction of the giant fibre and its major motorneuronal target

The tergotrochanteral (jump) motorneuron is a major synaptic target of the Giant Fibre in Drosophila. These two neurons are major components of the fly's Giant-Fibre escape system. Our previous work has described the development of the Giant Fibre in early metamorphosis and the involvement of the shaking-B locus in the formation of its electrical synapses. In the present study, we have investigated the development of the tergotrochanteral motorneuron and its electrical synapses by transforming Drosophila with a Gal4 fusion construct containing sequences largely upstream of, but including, the shaking-B(lethal) promoter. This construct drives reporter gene expression in the tergotrochanteral motorneuron and some other neurons. Expression of green fluorescent protein in the motorneuron allows visualization of its cell body and its subsequent intracellular staining with Lucifer Yellow. These preparations provide high-resolution data on motorneuron morphogenesis during the first half of pupal development. Dye-coupling reveals onset of gap-junction formation between the tergotrochanteral motorneuron and other neurons of the Giant-Fibre System. The medial dendrite of the tergotrochanteral motorneuron becomes dye-coupled to the peripheral synapsing interneurons between 28 and 32 hours after puparium formation. Dye-coupling between tergotrochanteral motorneuron and Giant Fibre is first seen at 42 hours after puparium formation. All dye coupling is abolished in a shaking-B(neural) mutant. To investigate any interactions between the Giant Fibre and the tergotroachanteral motorneuron, we arrested the growth of the motorneuron's medial neurite by targeted expression of a constitutively active form of Dcdc42. This results in the Giant Fibre remaining stranded at the midline, unable to make its characteristic bend. We conclude that Giant Fibre morphogenesis normally relies on fasciculation with its major motorneuronal target.

Ascertainment adjustment: where does it take us?

It is commonly assumed that the parameter estimates of a statistical genetics model that has been adjusted for ascertainment will estimate parameters in the general population from which the ascertained subpopulation was originally drawn. We show that this is true only in certain restricted circumstances. More generally, ascertainment-adjusted parameter estimates reflect parameters in the ascertained subpopulation. In many situations, this shift in perspective is immaterial: the parameters of interest are the same in the ascertained sample and in the population from which it was drawn, and it is therefore irrelevant to which population inferences are presumed to apply. In other circumstances, however, this is not so. This has important implications, particularly for studies investigating the etiology of complex diseases.

Retrospective radon assessment by means of 210Po activity measurements

A method for retrospectively assessing the average radon concentration in a dwelling, for a period as long as 40 years or more, is described. It is based on the free penetration of radon gas into bulky spongy materials called volume traps, and subsequent trapping of radon decay products inside them. This leads to a build-up of 210Pb, a radon decay product with a half life of 22.3 years, which reaches an equilibrium with the alpha emitter 210Po, indicative of the average radon concentration over the exposure period. The stuffing of mattresses, chairs, cushions, etc. can be considered a good volume trap. A chemical separation procedure is described, transforming the volume trap into a 210Po alpha source, whose activity is determined through alpha spectroscopy. The technique has been applied in over 300 samples, retrieved from dwellings in Serbia, Germany, Norway and Sweden. The technique has proven to be very robust and reproducible. In cases where radon data were available during the exposure period of the volume trap, a remarkable agreement was found. The best volume traps appeared to be polyester sponges found in many stuffings. The major drawback is the destructive nature of the method, its major advantage is the direct relationship between the radon gas and the 210Po signal. The technique can be useful in epidemiological studies of the lung cancer risk from indoor radon, for assessing the long term radon exposure.

Pathfinding, target recognition, and synapse formation of single regenerating fibers in the adult grasshopper Schistocerca gregaria

After lesion of the peripheral tympanal nerve of the adult locust (Schistocerca gregaria), sensory axons regenerate into their original target areas. We examined the individual behavior of single regenerating auditory afferents during pathway and target selection by intracellularly recording and labeling them at different times postlesion. During axotomy, spontaneous activity is not increased in either the distal or proximal part of the cells. Stimulus response properties of lesioned cells with or without regenerating axons are not influenced. Surprisingly, only 55% of sensory neurons regenerate through the lesion site and often give rise to more than one axonal fiber. Within the central nervous system, 70% of regenerated axons consistently follow an incorrect pathway to reach the correct target region. Often, one of two processes formed by a cell chooses the correct pathway, and the other the incorrect one. In the target region, regenerated axons reconstitute somatotopically ordered projections and form synapses that resemble those of intact fibers in number and structure. The regeneration process does not induce a detectable expression of antigens that are known to be expressed during neural development in these neurons. Our study clearly demonstrates that precise synaptic regeneration is possible in adult animals within a completely differentiated central nervous system, although pathfinding and formation of arborizations are disturbed in a particular and probably system-related manner. The results strongly suggest that accurate pathfinding is unlikely to be a decisive factor in target area recognition and synaptogenesis.

Lenticonus

Lenticonus is a bulging of the lens capsule and the underlying cortex. The diagnosis of lenticonus is essentially a clinical diagnosis which is made by biomicroscopic examination. According to the localization of the conus a distinction is made between lenticonus anterior and lenticonus posterior. Whereas lenticonus anterior is part of the Alport syndrome, lenticonus posterior is not associated with systemic disease. A case report of each of both types is presented and the clinical presentation, the aetiology, the pathogenesis and the treatment are discussed.

Linkage of chromosome 1 markers to alcoholism-related phenotypes by sib pair linkage analysis of principal components

Using the Collaborative Study on the Genetics of Alcoholism data and affected-sib-pair linkage methods, Reich et al. [1998] reported linkage of alcohol dependence to a region near D1S1588 on chromosome 1. In this paper, we assessed the ability of multivariate sib-pair linkage analysis of the neurophysiologic measurements (including age and sex) to evaluate evidence for linkage to chromosome 1. Principal components of 16 neurophysiologic measurements, plus age and sex, were analyzed separately using sib-pair linkage analysis, and a cumulative sum of the resulting t2-statistics computed at each point on the chromosome. The first four principal components, which accounted for 74% of the total variation, showed little or no evidence for linkage in the D1S1588 region, while the remaining components showed substantial evidence for linkage. We conclude that potentially important linkage results can be missed if investigators limit attention only to major sources of variability.

Axonal degeneration with tympanal nerve of Schistocerca gregaria

This study describes time course and ultrastructural changes during axonal degeneration of different neurones within the tympanal nerve of the locust Schistocerca gregaria. The tympanal nerve innervates the tergit and pleurit of the first abdominal segment and contains the axons of both sensory and motor neurones. The majority of axons (approx. 97%) belong to several types of sensory neurones: mechano- and chemosensitive hair sensilla, multipolar neurones, campaniform sensilla and sensory cells of a scolopidial organ, the auditory organ. Axons of campaniform sensilla, of auditory sensory cells and of motor neurones are wrapped by glial cell processes. In contrast, the very small and numerous axons (diameter <1 microm) of multipolar neurones and hair sensilla are not separated individually by glia sheets. Distal parts of sensory and motor axons show different reactions to axotomy: 1 week after separation from their somata, distal parts of motor axons are invaded by glial cell processes. This results in fascicles of small axon bundles. In contrast, distal parts of most sensory axons degenerate rapidly after being lesioned. The time to onset of degeneration depends on distance from the lesion site and on the type of sensory neurone. In axons of auditory sensory neurones, ultrastructural signs of degeneration can be found as soon as 2 days after lesion. After complete lysis of distal parts of axons, glial cell processes invade the space formerly occupied by sensory axons. The rapid degeneration of distal auditory axon parts allows it to be excluded that they provide a structure that leads regenerating axons to their targets. Proximal parts of severed axons do not degenerate.

gamma-Aminobutyrate-A receptor modulation by 3-aryl-1-(arylsulfonyl)- 1,4,5,6-tetrahydropyridazines

A series of 3-aryl-1-(arylsulfonyl)-1,4,5,6-tetrahydropyridazine allosteric modulators of the GABAA receptor was synthesized, and biological activity was examined in vitro and in vivo. Beginning with 1a, stepwise modification of the substituents and conservation of the scaffold yielded a chemical series in which the modulatory activity was enhanced by the presence of GABA. The SAR suggests, but does not establish, that the compounds bind to the steroid binding site on the GABAA receptor. The GABA shift for each compound indicates that all compounds in this series are either agonists or partial agonists.

The effect of keeping an end-product on intrinsic motivation

OBJECTIVE

According to literature in occupational therapy and psychology, intrinsic motivation is thought to be enhanced if people can keep the end-product of an activity. The purpose of this study was to examine the effect of keeping an end-product on intrinsic motivation.

METHOD

Fifty participants chose one of four activities (painting a ceramic vase, decorating cookies, stringing beads for a necklace, creating stationery) and performed two conditions (keep, no-keep) in counterbalanced order. Participants were timed in each condition and, after each condition, ranked their self-determination and competence, which are psychological needs underlying intrinsic motivation. Participants were interviewed at the end of the study to examine their experiences.

RESULTS

Participants worked significantly longer on a chosen activity when the end-product could be kept and rated themselves significantly more self-determined and competent after performing the keep condition. However, further analysis revealed that these results depended on the activity chosen.

CONCLUSION

The findings support that keeping an end-product can enhance performance of an activity. However, because results were not consistent across all activity choices, further research is needed to characterize the meaningfulness of particular activities.

Spinodal dewetting in liquid crystal and liquid metal films

Theory predicts that dewetting of a homogeneous liquid film from a solid surface may proceed via unstable surface waves on the liquid. This phenomenon, usually termed spinodal dewetting, has been sought after in many systems. Observations in liquid crystal and liquid metal films showed that, as expected, the emerging structures were similar to those found for spinodal decomposition in mixtures. Certain differences, however, could be attributed to peculiarities of the wetting forces in these two dissimilar systems, thereby demonstrating the role of nonlinearities inherent in the wetting forces.

Inhibitory function in two models of chronic epileptogenesis

Although drug-induced disinhibition is a potent method for producing acute epileptogenesis, data with respect to possible disorders of GABAergic inhibitory function in models of chronic epilepsy are incomplete and inconsistent. We examined rat models of cortical post-traumatic epilepsy, and epileptogenic cortical microgyri. Results suggest enhanced rather than decreased inhibitory function in cortical networks in these preparations. In brain slices from epileptogenic chronically isolated cortex, the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs) and miniature (m)IPSCs in layer V pyramidal neurons is increased compared to control. In the epileptogenic zone adjacent to the microgyrus, both spontaneous and stimulus-induced IPSCs are larger in amplitude than control, and the frequency of sIPSCs is more dependent upon glutamatergic excitation of interneurons than in control layer V neurons of homotopic cortex. Immunocytochemical studies show that there is enhanced immunoreactivity for several proteins in GABAergic interneurons of chronic cortical isolations, and suggest that there may be sprouting of GABAergic axons in the area of injury. This conclusion is supported by anatomic data showing an approximate doubling of the number of presumed inhibitory synapses on somata of layer V pyramidal neurons. These anatomic findings are consistent with the increased frequency of mIPSCs on these neurons. Inhibition is robust in both of these chronic models of epileptogenesis. Increased inhibitory electrogenesis might be pictured as part of the epileptogenic process, e.g. a mechanism for synchronizing the discharge of pyramidal neurons, or as a compensatory mechanism that might prevent the development of abnormal activities in some cases, or limit the intensity of epileptogenesis in others.

The insulin gene region and susceptibility to insulin-dependent diabetes mellitus in four races; new insights from Afro-Caribbean race-specific haplotypes

The IDDM2 component of the genetic susceptibility to insulin-dependent diabetes mellitus (IDDM) has been mapped to chromosome 11p15.5. The exact identity of IDDM2 remains uncertain. It has been suggested that IDDM2 maps within the 5' VNTR (variable number tandem repeat) polymorphism upstream of the insulin gene (INS). This has not been confirmed and a contribution from other INS gene region polymorphisms cannot be excluded. We present INS region genotype data from four racial groups: the Japanese, Hong Kong Chinese, North Indian Asians and Afro-Caribbeans (two groups; one born and resident in the UK, one in Jamaica). These races have not been previously studied with the range of INS region polymorphisms included here. No INS polymorphism was associated with IDDM across all races. These data from this study thus do not identify any INS polymorphism as IDDM2. The Afro-Caribbean race showed a very different distribution of INS genotypes from the other races and novel race-specific INS haplotypes were identified. Analysis of these excluded a contribution to susceptibility to IDDM from the- 23HphI INS polymorphism. An Afro-Caribbean INS haplotype which differed only at the VNTR from the very protective INS haplotype (VPH) identified in white Caucasians was detected. Population analysis of this haplotype will allow direct assessment of the role of the VNTR in susceptibility to IDDM. In conclusion, the diverse Afro-Caribbean TH/INS/IGF2 haplotypes identified in this study will be valuable in mapping IDDM2 more precisely.

Tracing of a neuronal network in the locust by pressure injection of markers into a synaptic neuropil

Central neuronal circuits of vertebrates have often been investigated using injection of markers into synaptic neuropils, whereas similar techniques have rarely been applied in invertebrates. In this study we tested several neuroanatomical tracers for their ability to mark central neuronal circuits in insects, using the well described auditory network of the locust, Locusta migratoria. After physiological localization of an auditory neuropil various tracers were pressure injected. Horseradish peroxidase, dextrans (3 and 10 kDa) and especially biocytin and neurobiotin were effectively incorporated by auditory interneurons, which resulted in their extensive labeling. Postsynaptic regions turned out to be the major, if not exclusive sites of uptake of injected markers, which is deduced from two lines of evidence: (i) for labeling of identified auditory neurons it was necessary to apply the tracer to postsynaptic sites of the neuron; (ii) only a few non-auditory neurons were labeled (probably by lesioning axons during electrode impalement). No evidence could be found for an activity dependent uptake. We conclude that pressure injection of certain tracers into synaptic areas can be used to identify central nervous circuits in insects.

Glutathione conjugation of trichloroethylene in rats and mice: sex-, species-, and tissue-dependent differences

Glutathione (GSH) conjugation of trichloroethylene (Tri) to form S-(1,2-dichlorovinyl)glutathione (DCVG) has been implicated in the nephrotoxicity and nephrocarcinogenicity of Tri. Marked sex- and species-dependent differences exist, however, in the susceptibility to Tri-induced renal toxicity, with the male rat being the most susceptible. The present study, therefore, focuses on potential differences in the initial step of the GSH pathway. Rates of DCVG formation were measured in suspensions of isolated renal cortical cells and isolated hepatocytes from male and female Fischer 344 rats and in kidney and liver microsomes and cytosol from male and female Fischer 344 rats and B6C3F1 mice to determine if sex- and species-dependent differences in GSH conjugation correlate with susceptibility to renal toxicity from Tri. Rates of gamma-glutamyltransferase (GGT) with gamma-glutamyl-p-nitroanilide and glycylglycine as substrates and GSH S-transferase (GST) with 1-chloro-2,4-dinitrobenzene as substrate were also measured in liver and kidney subcellular fractions to provide further information on the biochemical basis of susceptibility to Tri. Rates of DCVG formation in rat kidney cells and kidney subcellular fractions were 5- to 20-fold lower than those in rat hepatocytes and liver subcellular fractions. Rates of DCVG formation in kidney cells and subcellular fractions were comparable in male and female rats with the exception of male rat kidney microsomes, where DCVG formation was below the limit of detection, and those in liver cells and subcellular fractions were >3-fold higher in male rats than in female rats. Rates of DCVG formation in mouse kidney subcellular fractions were approximately 10-fold higher than in corresponding fractions from the rat, whereas those in mouse liver subcellular fractions were 4- to 8-fold higher than in corresponding rat tissues, with rates in male mouse liver cytosol and microsomes being modestly higher than in corresponding fractions from female mice. GGT activity was barely detectable in livers, was about 20-fold higher in rat kidneys than in mouse kidneys, and was slightly higher in female rat kidneys than in male rat kidneys. GST activity with 1-chloro-2,4-dinitrobenzene as substrate exhibited tissue-, sex-, and species-dependent patterns that were generally similar to those with Tri as the substrate. These results suggest that the higher susceptibility to Tri-induced renal toxicity of male rats as compared with female rats correlates with rates of DCVG formation. The high rates of DCVG formation in mice, however, indicate that other factors, possibly including differences in activities of cysteine conjugate beta-lyase or N-acetyltransferase, may also be important determinants of the susceptibility to Tri.

Lectin histochemistry of the metathoracic ganglion of the locust Schistocerca gregaria before and after axotomy of the tympanal nerve

The thoracic ganglia of insects exhibit a highly ordered organization. It seems possible that the information underlying the emergence of this order during development and its maintenance throughout insect life is given via a distinct pattern of molecules distributed within the ganglion. The question we asked was whether the adult insect ganglion is subdivided by the distribution of specific carbohydrates and furthermore whether or not this distribution changes during degeneration and regeneration of neurons. In order to determine the normal carbohydrate distribution, we stained sections of the intact metathoracic ganglion of the locust Schistocerca gregaria with fluorescence-coupled lectins. We succeeded in labeling three sensory neuropil areas with either peanut agglutinin (PNA): Phaseolus vulgaris erythrolectin (PVE), soybean agglutinin, wheat germ agglutinin (WGA), or Vicia villosa agglutinin. Apart from this, PNA, WGA, and succinylated WGA also selectively labeled some neuronal cell bodies, including dorsal unpaired median neurons. Datura stramonium lectin (DSL), Griffonia simplicifolia lectin II, and Solanum tuberosum lectin (STL) bound to glial cells or glia surrounding extracellular matrix. A few lectins stained all structures within the ganglion; some showed no binding at all. In the second part of our study, we tested whether carbohydrates were differentially regulated during transient deafferentation after the axotomy of the tympanal nerve. Binding of PNA and PVE within the auditory neuropil did not change. However, binding of the two glia-associated markers, DSL and STL, clearly differed from that found in intact animals; they bound transiently (day 3-4 until day 10-20 post-surgery) to axonal tracts and neuropils of the axotomized sensory afferents.

A new species of Ophiostoma from North America, similar to Ophiostoma penicillatum

Ophiostomatoid fungi that resemble Ophiostoma penicillatum were isolated from insect-infested spruce (Picea sp.) in Japan as well as Larix decidua Mill. (European larch) in North America. Isolates were characterized based on morphology and could be separated into two distinct groups. Those from spruce in Japan represent O. penicillatum, and are characterized by allantoid, slightly curved conidia. The North American isolates from Larix decidua are of a previously undescribed species, characterized by long, narrow conidia. The latter fungus is described as Ophiostoma americanum with an anamorph, Leptographium americanum. Key words: Ophiostoma penicillatum, Ips typographus, Ophiostoma americanum, Dendroctonus simplex, Larix decidua.

A reforming accountability: GPs and health reform in New Zealand

Over the last ten years or so, many countries have undertaken public sector reforms. As a result of these changes, accounting has come to play a more important role. However, many of the studies have only discussed the reforms at a conceptual level and have failed to study how the reforms have been implemented and operated in practice. Based on the work of Lipsky (1980) and Gorz (1989), it can be argued that those affected by the reforms have a strong incentive to subvert the reforms. This prediction is explored via a case study of general practitioner (GP) response to the New Zealand health reforms. The creation of Independent Practice Associations (IPAs) allowed the State to impose contractual-accountability and to cap their budget exposure for subsidies. From the GP's perspective, the IPAs absorbed the changes initiated by the State, and managed the contracting, accounting and budgetary administration responsibilities that were created. This allowed individual GPs to continue practising as before and provided some collective protection against the threat of state intrusion into GP autonomy. The creation of IPAs also provided a new way to manage the professional/financial tension, the contradiction between the professional motivation noted by Gorz (1989) and the need to earn a living.

Improved P1/P1' substituents for cyclic urea based HIV-1 protease inhibitors: synthesis, structure-activity relationship, and X-ray crystal structure analysis

We present several novel P1/P1' substituents that can replace the characteristic benzyl P1/P1' moiety of the cyclic urea based HIV protease inhibitor series. These substituents typically provide 5-10-fold improvements in binding affinity compared to the unsubstituted benzyl analogs. The best substituent was the 3,4-(ethylenedioxy)benzyl group. Proper balancing of the molecule's lipophilicity facilitated the transfer of this improved binding affinity into a superior cellular antiviral activity profile. Several analogs were evaluated further for protein binding and resistance liabilities. Compound 18 (IC90 = 8.7 nM) was chosen for oral bioavailability studies based on its log P and solubility profile. A 10 mg/kg dose in dogs provided modest bioavailability with Cmax = 0.22 microg/mL. X-ray crystallographic analysis of two analogs revealed several interesting features responsible for the 3,4-(ethylenedioxy)benzyl-substituted analog's potency: (1) Comparing the two complexes revealed two distinct binding modes for each P1/P1' substituent; (2) The ethylenedioxy moieties are within 3.6 A of Pro 81 providing additional van der Waals contacts missing from the parent structure; (3) The enzyme's Arg 8 side chain moves away from the P1 substituent to accommodate the increased steric volume while maintaining a favorable hydrogen bond distance between the para oxygen substituent and the guanidine NH.