Development and management of a radon assessment strategy suitable for underground railway tunnelling projects.

The construction of underground tunnels through radon-bearing rock poses a radiation health risk to tunnelling workers from exposure to radon gas and its radioactive decay products. This paper presents the development and practical application of a radon assessment strategy suitable for the measurement of radon in tunnelling work environments in Hong Kong. The assessment strategy was successfully evaluated on a number of underground railway tunnelling projects over a 3 y period. Radon measurements were undertaken using a combination of portable radon measurement equipment and track etch detectors (TEDs) deployed throughout the tunnels. The radon gas monitoring results were used to confirm that ventilation rates were adequate or identified, at an early stage, when further action to reduce radon levels was required. Exposure dose estimates based on the TED results showed that the exposure of tunnel workers to radon did not exceed 3 mSv per annum for the duration of each project.

Tissue-specific expression of the Ets gene Xsap-1 during Xenopus laevis development.

We report the cloning of Xenopus laevis Xsap-1 cDNA, encoding a member of the ternary complex factor subfamily of ETS transcription factors. The expression pattern of Xsap-1 was examined during Xenopus embryogenesis using whole-mount in situ hybridization. Spatial expression of Xsap-1 mRNA is first detected at the animal pole at the mid-blastula stage. During neurulation Xsap-1 is expressed in cells participating in neural tube formation, in the sensorial layer of the epidermal ectoderm, and in an anterior region of the ventral mesoderm. Later, Xsap-1 expression is observed in the eye, ear vesicle, branchial arches, heart, pronephros, in the somites, and the developing nervous system, such as fore-, mid-, and hindbrain as well as in the cranial ganglion X.

Transcriptional regulation of Xvent homeobox genes.

The Xvent homeobox multigene family is essential for the patterning of the ventral mesoderm in Xenopus embryos. We have identified two novel members of this family, Xvent-1B and Xvent-2B, and have characterized their genomic structures. These two genes show a clustered organization and have probably arisen by gene duplication with subsequent inversion. Cis-regulatory elements within the promoters of both genes have been identified which contribute to their spatial activation. Xvent-2B is activated by BMP-2/4 in the absence of de novo protein synthesis, suggesting that this gene is a direct target of BMP-signalling. In contrast, Xvent-1B does not directly respond to BMP-2/4, but is activated by Xvent-2B. This activation is documented by Xvent-1B promoter/reporter studies, Xvent-2B overexpression and loss-of-function analysis using a dominant-negative Xvent-2 mutant. However, cycloheximide experiments reveal that Xvent-2B by itself is not sufficient to activate transcription of the Xvent-1B gene, but that there is a requirement for additional factor(s) being synthesized after midblastula transition.

buttonhead and D-Sp1: a novel Drosophila gene pair.

The Drosophila gene buttonhead (btd) is a gap-like head segmentation gene which encodes a triple zinc finger protein structurally and functionally related to the human transcription factor Spl. Here we report the pattern of btd expression during embryogenesis. btd is not only expressed and required in the blastoderm anlagen of the antennal, intercalary and mandibular segments as reported previously, but both expression and requirement extend into the anlage of the maxillary segment. From gastrulation onwards, btd is expressed in distinct spatial and temporal patterns, suggesting that btd might be required for a number of developmental processes beyond head segmentation. In fact, analysis of btd mutant embryos revealed that btd participates in the formation of the peripheral nervous system. However, no other morphologically apparent phenotype was observed. We identified a btd-related gene, termed D-Sp1, which is expressed in temporal and spatial patterns similar to btd during postblastodermal development. No localized expression domains of D-Sp1, which is located in the same X-chromosomal band as btd, were seen during the blastoderm stage. The results suggest that D-Sp1 and btd represent a novel gene pair with partially redundant functions after the blastoderm stage.

Epidermal egr-like zinc finger protein of Drosophila participates in myotube guidance.

We have cloned and molecularly characterized the Drosophila gene stripe (sr) required for muscle-pattern formation in the embryo. Through differential splicing, sr encodes two nuclear protein variants which contain a zinc finger DNA-binding domain in common with the early growth response (egr) family of vertebrate transcription factors. The sr transcripts and their protein products are exclusively expressed in the epidermal muscle attachment cells and their ectodermal precursors, but not in muscles or muscle precursors. The results suggest that sr activity induces a subset of ectodermal cells to develop into muscle attachment sites and to provide spatial cues necessary to orient myotubes along the basal surface of the epidermis to their targeted attachment cells.

Regulation, function and potential origin of the Drosophila gene spalt adjacent, which encodes a secreted protein expressed in the early embryo.

During early embryogenesis of Drosophila the spatial and temporal expression patterns of the region-specific homeotic gene spalt (sal) and the neighbouring gene spalt adjacent (sala) extensively overlap. We show that the initial expression patterns of the two genes in the blastoderm also have identical genetic controls. However, while sal encodes a transcription factor, sala encodes a precursor protein from which a functional signal peptide is cleaved off to generate the secreted sala protein. Ectopic expression or absence of sala protein does not affect embryonic development, adult viability or fertility. In addition to sal and sala, we identified a third gene nearby, termed spalt related (salr), which shares coding sequence similarity and a late embryonic expression pattern with sal, but lacks the early expression domains that are shared by sal and sala. These results suggest that the three genes and their present cis-regulatory regions arose through a chromosomal rearrangement involving local duplication and transposition events in the 32F/33A region on the left arm of the second chromosome.

The spalt-related gene of Drosophila melanogaster is a member of an ancient gene family, defined by the adjacent, region-specific homeotic gene spalt.

We report the full coding sequence of a new Drosophila gene, spalt-related, which is homologous and adjacent to the region-specific homeotic gene, spalt. Both genes have three widely spaced sets of C2H2 zinc finger motifs, but spalt-related encodes a fourth pair of C-terminal fingers resembling the Xenopus homologue, Xsal-1. The degrees of sequence divergence among all three members of this family are comparable, suggesting that the Drosophila genes originated from an ancient gene duplication. The spalt-related gene is expressed with quantitative variations from mid-embryogenesis (8-12 h) to the adult stage, but not in ovaries or early embryos. Expression is localized to limited parts of the body, including specific cell populations in the nervous system. In the wing disc, spalt and spalt-related are expressed in indistinguishable domains; in the nervous system and some other organs the expression patterns extensively overlap but are not identical, indicating that the genes have partially diverged in terms of developmental regulation. A characteristic central set of zinc fingers specifically binds to an A/T-rich consensus sequence, defining some DNA binding properties of this ancient family of nuclear factors.

Localized expression of a novel micropia-like element in the blastoderm of Drosophila melanogaster is dependent on the anterior morphogen bicoid.

We have identified a novel transposon-like element of Drosophila melanogaster that is present in approximately 20 copies in the genome. It codes for a polyprotein containing the diagnostic sequence motifs for a nucleic acid binding CCHC protein, a proteinase, a reverse transcriptase and an integrase as typically found in retroviruses. Owing to its early expression in the blastoderm embryo, and its close relationship to micropia, a previously identified Drosophila retrotransposon, we termed the novel element "blastopia". The spatially restricted expression of blastopia transcripts in head anlagen of the blastoderm embryo is under the direct or indirect control of the Drosophila morphogen bicoid, which is normally required to establish the anterior pattern elements in the embryo. Our results suggest that a blastopia element acts as an "enhancer trap", and thereby participates in the control of an as yet unidentified gene normally expressed in the head anlagen of the embryo.

spalt encodes an evolutionarily conserved zinc finger protein of novel structure which provides homeotic gene function in the head and tail region of the Drosophila embryo.

The region specific homeotic gene spalt (sal) of Drosophila melanogaster promotes the specification of terminal pattern elements as opposed to segments in the trunk. Our results show that the previously reported sal transcription unit was misidentified. Based on P-element mediated germ line transformation and DNA sequence analysis of sal mutant alleles, we identified the transcription unit that carries sal function. sal is located close to the misidentified transcription unit, and it is expressed in similar temporal and spatial patterns during embryogenesis. The sal gene encodes a zinc finger protein of novel structure composed of three widely spaced 'double zinc finger' motifs of internally conserved sequences and a single zinc finger motif of different sequence. Antibodies produced against the sal protein show that sal is first expressed at the blastoderm stage and later in restricted areas of the embryonic nervous system as well as in the developing trachea. The antibodies detect sal homologous proteins in corresponding spatial and temporal patterns in the embryos of related insect species. Sequence analysis of the sal gene of Drosophila virilis, a species which is phylogenetically separated by approximately 60 million years, suggests that the sal function is conserved during evolution, consistent with its proposed role in head formation during arthropod evolution.

Mood change preceding epileptic seizures.

Mood ratings were obtained for at least 56 days from 27 patients with diverse forms of epilepsy, 13 of whom suffered at least one seizure over the course of the study. For these 13 patients, mean ratings of mood on eight of the 10 scales showed a decline on the day(s) preceding the seizure and an increase after the seizure. Data from six patients accounted for most of the decline. Decline was most prominent on the Depression, Anxiety, Freedom, and Anger Scales. One patient's mood ratings rose significantly before seizures. Comments recorded before the seizures confirmed the decline in mood preceding seizures and showed an increase in negative life events for the patients whose mood declined before seizures. The relations of life events and mood to seizures apparently did not depend on each other.

Disruption of tactile discrimination in rats by bilateral stimulation of midbrain lemniscal pathways.

Bilateral stimulation in the midbrain medial lemniscus disrupted tactile discrimination in four of nine rats. Single conditioning shocks in the midbrain of these animals attenuated by more than 80% the somatosensory cortical evoked responses elicited by test shocks to the contralateral forepaw. Midbrain stimulation did not selectively disrupt discrimination in the remaining five rats, and midbrain conditioning shocks attenuated the cortical test response by less than 80% on at least one side. The four rats that showed disrupted discrimination and bilaterally strong attenuation of cortical responses also had both midbrain electrodes in or next to the medial lemniscus. The five rats that did not show these effects had at least one midbrain electrode away from that structure.

Deficits in visual discrimination performance following neglect-producing unilateral lateral hypothalamic lesions in the albino rat.

Adult male albino rats were trained with water reinforcement on a lateralized visual discrimination task. For six rats the correct head turn--nose poke response was to the same side as the discriminative stimulus (Turn Towards group). For six others the correct response was to the side opposite from the discriminative stimulus (Turn Away group). Immediately after a rat had mastered its task, a unilateral electrolytic lesion was made under ether anesthesia through a stainless steel electrode previously implanted in the lateral hypothalamus (LH). Discrimination training continued until the rat's performance returned to criterion. The lesions produced contralateral neglect as demonstrated by deficits in turning and orientation contralateral to the lesion. The lesions also disrupted all measures of discrimination performance (% correct, latency, and duration of observing response) for trials on which responses contralateral to the lesion were correct, regardless of whether the discriminative stimulus was also contralateral (Turn Towards group) or was ipsilateral (Turn Away group). These data are interpreted as showing that contralateral neglect following LH lesions is associated with a deficit in initiating instrumental responses contralateral to the lesion. They also confirm previous results from a similar task using tactile discriminative stimuli.

Observations of the organ of Corti under in vivo-like conditions.

The organ of Corti of the rat has been investigated within minutes after death in different fluids bathing the organ of Corti. Static compliance of the tectorial membrane across the membrane was measured by microsprings, and the response of the membrane to a vibrating micro-electrode was studied. In addition, fluid motion about the organ caused by the placement of a vibrating micro-electrode on the tectorial membrane was observed. The static compliance of the tectorial membrane was unaffected by the bathing solutions. Dynamic characteristics of the membrane could be completed altered by the addition of aldehyde solutions. As the cochleas used by von Békésy (1960) were preserved in formaldehyde solutions, it is concluded that his observations regarding the dynamic characteristics of the tectorial membrane were in part artifact. It is suggested that a proper description of the mechanisms of the organ of Corti must include a tectorial membrane whose limbal attachment allows for both rotation and displacement. Such a description is presented. A streaming of fluid was observed directed from Hensen's cells toward the cochlea wall. Possible mechanisms for the generation of this streaming are discussed.

Fluid motion in the mammalian organ of Corti. A possible source of the second filter.

A mechanical analysis of the functioning of the mammalian organ of Corti as deduced from experimental observations and electronmicroscopic studies of the organ has been conducted. It was found that the arch of Corti is responsible for initiating a fluid motion in the spiral sulcus and reticular lamina which could stimulate the inner hair cells. A three-dimensional linear mathematical model with no arbitrary parameters is proposed to describe the force acting on the inner hair cell cilia as a function of arch displacement. Analysis of the model results show that the model (a) correctly predicts the form of the neural response for a low frequency square wave of arch motion, (b) demonstrates a physiologically reasonable time constant of 245 musec, (c) shows a sharpening of neural stimulation of physiological importance, (d) can explain the qualitative difference of neural responses to arch motions of opposite polarity, (e) demonstrates a phase difference between outer and inner hair cell stimulation, and (f) appears to be chemically and metabolically vulnerable.

Somatosensory function and cortical unit activity in cats with only dorsal column fibers.

Cats received lesions that transected the entire thoracic cord except for partial sparing of the dorsal columns. The cats were required to discriminate the side on which they were touched, the size of simultaneously presented discs, or the direction their fur was stroked to obtain food reward. All cats found by anatomical and/or electrophysiological criteria to have any functional continuity in the dorsal columns were able to master the first of these tasks; some responded above chance on the second. Performance was at chance on blank trials, and cats with complete cord transection failed to discriminate. Lesioned cats did not orient or otherwise react to any nonrewarded stimulus below the level of the lesion. A total of 532 units were recorded under light barbiturate anesthesia from the hind paw projection near the tip of the ansate sulcus in these and other similarly prepared cats. Three-fourths of the units found before and acutely after the cord lesions were made were driven by hind limb stimulation. Only 27% of the units recorded 10 or more days afterwards could be driven. Of these driven units, 15 (38%) responded to foreleg stimulation, 13 exclusively so. No such units were found in intact or acutely lesioned cats.

Hypothalamic influences on sensory reinforcement.

Rats were tested in a darkened chamber containing two levers, one of which turned on a dim light when depressed. Rats receiving non-contingent electrical stimulation of the lateral hypothalamus made many more lever presses than did unstimulated controls and made more presses on the light producing lever than on the inactive one. Pretests had shown that the electrical stimulation elicited consummatory behavior in the presence of appropriate goal objects. Dynamic hyperphagic rats maintained on a restricted diet made more total responses early in testing than did their controls which also received the same restricted diet. They also preferred the light producing lever, but not reliably more than did their controls. Static hyperphagic rats made fewer total responses than did their controls, both groups receiving food ad lib. Neither group showed any preference between the two levers.