Search Results - (Author, Cooperation:D. A. Carter)

2014-08-15

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Embryo, Mammalian/blood supply/metabolism ; Endothelial Cells/*cytology/*physiology ; Female ; *Friction ; Hemorheology ; Ion Channels/*metabolism ; Male ; Mice ; *Stress, Mechanical

1539-6924

Blackwell Publishing Journal Backfiles 1879-2005

Energy, Environment Protection, Nuclear Power Engineering

Electronic Resource

1539-6924

Blackwell Publishing Journal Backfiles 1879-2005

Energy, Environment Protection, Nuclear Power Engineering

Electronic Resource

1365-2826

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The pineal gland is a major output of the endogenous vertebrate circadian clock, with melatonin serving as the output signal. In many species, elevated nocturnal melatonin production is associated with changes in pineal gene expression. In the current study, cDNA array analysis was used in an attempt to identify additional genes that exhibit day/night differential expression in the rat pineal gland. This revealed 38 candidate genes, including Id-1 (inhibitor of DNA binding and differentiation). Id-1 encodes a helix-loop-helix (HLH) protein that lacks a basic DNA binding domain and could affect pineal physiology via a dominant negative trans-acting regulatory activity. For this reason Id-1 was selected for further analysis. Id-1 was expressed in a major population of pineal cells and the Id-1 protein was associated with a nuclear complex. The levels of Id-1 mRNA and protein exhibit approximately six-fold day/night rhythms. In contrast, the related genes Id-2 and Id-3 do not exhibit marked day/night differences in pineal expression. Rhythmic Id-1 expression is primarily limited to a C-terminally extended splice variant of Id-1, which would restrict the functional output of the rhythm to protein binding partners of this isoform of Id-1. Our findings add to the body of evidence indicating that transcriptional regulators play a role in neuroendocrine rhythms, and extend this by introducing the concept of a dominant negative HLH involvement. The rhythm in Id-1 in the pineal gland provides an experimental opportunity to identify Id-1-binding partners which may also be involved in Id-1 activity in other functional contexts.

Electronic Resource

1572-8099

Fires ; combustion products ; dispersion

Springer Online Journal Archives 1860-2000

Architecture, Civil Engineering, Surveying

Conclusions The computer models discussed here are used by MHAU to give an initial indication of the possible hazards to the local population from the dispersion of combustion products from large fires. Agreement between the computer model and the wind tunnel data is encouraging, particularly at relatively low values of the buoyancy flux parameterF U −3 L −1. HSE is proposing to commence large-scale dispersion trials in the open air in the near future. It is hoped that this will enable greater confidence to be had in the predictions of the computer models.

Electronic Resource

0992-7689

Springer Online Journal Archives 1860-2000

Geosciences

Physics

Abstract Since May 1992 a small, 915-MHz profiler has been operated continuously in downtown Montreal. It is a five-beam system employing a microstrip array antenna, located atop a 14-story office building that houses several academic departments of McGill University. The data are used for research on precipitation physics and the clear-air reflectivity in addition to wind profiling. We are especially interested in situations in which the reflectivities of the clear air and the precipitation are comparable. This permits the study of interactions between the precipitation and the clear air, a new area of research made possible by wind profilers. On clear days in the summer, 30-min consensus winds can often be measured to an altitude of 3 km, but ground clutter in the antenna sidelobes interferes with measurements below 600 m. Rain when present often permits wind profiling down to 100 m and up to 6 km or higher. On cold winter days there are some periods when the reflectivity is too weak at all levels to permit wind estimation. Falling snow, however, provides readily detectable echoes and serves as a good tracer of the wind and so allows profiling over its full altitude extent. The best conditions for observing interactions between precipitation and the clear air are when light rain falls through a reflective layer associated with a frontal surface or inversion. Unexpectedly, flocks of migrating birds sometimes completely dominate the signal at night in the spring and fall seasons.

Electronic Resource

1432-1106

Noradrenergic pathways ; Nucleus tractus solitarius ; Opiates ; Blood pressure ; Vasopressin

Springer Online Journal Archives 1860-2000

Medicine

Summary The role of ascending noradrenergic pathways in the mediation of central opiate-induced cardiovascular effects has been investigated. The effects of selective χ- and δ-opiate agonists microinjected into the nucleus tractus solitarius (NTS) of urethane anaesthetized rats were compared following 6-hydroxydopamine lesions of either the dorsal (DNAB) or ventral (VNAB) noradrenergic bundles. In sham lesioned animals both opiates elicited a significant pressor effect and a variable but consistent bradycardia. The δ-agonist responses were not modified in lesioned rats. In marked contrast the pressor effect of the χ-agonist was abolished in both DNAB and VNAB lesioned rats. The bradycardic response was not significantly modified. These findings are consistent with previous observations that the cardiovascular effects of χ- and δ-opiates in the NTS are mediated via different mechanisms, and provide evidence for selective functional actions of endogenous opioids within brain nuclei.

Electronic Resource

1433-0350

Hydrocephalus ; Leukemia ; Leukoencephalopathy ; Magnetic resonance imaging ; Shunt surgery

Springer Online Journal Archives 1860-2000

Medicine

Abstract We report the case histories of identical twin brothers who developed concordant acute lymphoblastic leukemia at the age of 4 years and who later developed leukoencephalopathy and hydrocephalus related to central nervous system prophylaxis by, in the first case intrathecally administered methotrexate and, in the second by intrathecally administered methotrexate and cranial irradiation. The delayed encephalopathy developed 9 and 22 months respectively after the first dose of intrathecal methotrexate. Both patients underwent cerebrospinal fluid shunting mainly for their hydrocephalus. The imaging studies have shown that both hydrocephalus and leukoencephalopathy have improved significantly after ventriculoperitoneal shunt insertion. We review the pathophysiology of prophylaxis-related encephalopathy in leukemia patients and summarize its clinical, histological, and radiological characteristics. We also discuss the possible contribution of altered cerebrospinal fluid dynamics in the development of leukoencephalopathy.

Electronic Resource

1432-2072

Haloperidol ; Pimozide ; 6-hydroxydopamine ; Self-stimulation ; Dopamine ; Operant behaviour

Springer Online Journal Archives 1860-2000

Medicine

Abstract Rats were implanted with electrodes in the lateral hypothalamus, put on a 22-h food deprivation schedule and trained to bar-press for ICS and for food on a CRF schedule. Haloperidol (0.08 mg/kg) and pimozide (0.22 mg/kg) significantly decreased responding for both reinforcers, although responding for ICS was decreased more than it was for food. The same doses of these drugs did not decrease food consumption on a 15-min ad libitum test after 22-h of food deprivation, suggesting that the decreased bar-pressing for food was not the result of anorexia or reduced motivation for food. When similar rates of responding for ICS and for food were obtained on a V1 60 schedule, haloperidol (0.1 mg/kg) reduced responding for food and ICS to a similar extent. Thus, when baseline rate is controlled for, neuroleptics do not selectively reduce responding for ICS. In addition, examination of cumulative response records revealed that rather than producing an extinction curve, as would be predicted if neuroleptics reduced the rewarding properties of ICS, haloperidol produced a uniform decrease in the rate of responding throughout the experimental session. Similar results were obtained with intraventricular 6-hydroxydopamine (6-OHDA) injections. While these experiments do not exclude the possibility that dopaminergic (DA) systems participate in some central reinforcement mechanisms, they suggest that neuroleptics and 6-OHDA decrease responding for food or ICS primarily by impairing the function of DA systems critically involved in the initiation or maintenance of operant behaviour rather than by interfering with reward.

Electronic Resource

1573-7381

Springer Online Journal Archives 1860-2000

Medicine

Abstract Regenerated retinal ganglion cell (RGC) axons can re-form functional synapses with target neurons in the superior colliculus (SC). Because preterminal axon branching determines the size, shape and density of innervation fields, we investigated the branching patterns and bouton formation of individual RGC axons that had regrown along peripheral nerve (PN) grafts to the SC. Within the superficial layers of the SC, the regenerated axons formed terminal arbors with average numbers of terminal boutons that were similar to the controls. However, axonal branches were shorter than normal so that the mean area of the regenerated arbors was nearly one-tenth that of control arbors and the resulting fields of innervation contained greater than normal numbers of synapses concentrated in small areas of the target. Our results have delineated a critical defect in the reconstitution of retino-collicular circuitry in adult mammals: the failure of terminal RGC branches to expand appropriately. Because recent studies have documented that brain-derived neurotrophic factor (BDNF) can specifically lengthen RGC axonal branches not only during development in the SC but also within the adult retina after axotomy, the present quantitative studies should facilitate experimental attempts to correct this deficit of the regenerative response. © 1998 Chapman and Hall

Electronic Resource

1573-6830

milk deprivation ; starvation ; vasopressin mRNA poly(A) tail length

Springer Online Journal Archives 1860-2000

Biology

Summary 1. The vasopressin mRNA in the adult male rat hypothalamus is modulated in two distinct ways by a dehydration stimulus. In addition to the well-established increase in transcript abundance, it has recently been demonstrated that the vasopressin mRNA poly(A) tail increases in length. 2. We have studied the ontogeny of poly(A) tail length modulation in neonates in response to milk deprivation and found that poly(A) tail length changes are age dependent. In neonates older than 12 days of age, the vasopressin mRNA poly(A) tail length increased with milk deprivation and this effect became more marked in older animals. However, in rats 5 to 9 days old, milk deprivation resulted in a detectable though not significant decrease in vasopressin mRNA poly(A) tail length. 3. As milk deprivation is a combination of dehydration and starvation, we investigated the effect of the latter stimulus in more mature animals. We found that starvation modifies the length of the vasopressin mRNA poly(A) tail in a manner opposite that due to dehydration. 4. Our data indicate a novel mode of regulation of the vasopressin mRNA, namely, poly(A) tail shortening. This system provides a model for future studies concerning the adaptive role of poly(A) tail length modulation in response to physiological stimuli.

Electronic Resource

1573-6830

c-fos ; c-jun ; supraoptic nucleus ; osmolality ; transcription ; mRNA

Springer Online Journal Archives 1860-2000

Biology

Summary 1. We have investigated induction of the nuclear proto-oncogenes c-fos and c-jun in the rat supraoptic nucleus (SON) during physiological stimulation. 2. Dehydration (0-24 hr) was asssociated with modest, but significant increases in both c-fos and c-jun mRNA at 8 hr and 16 hr as determined by Northern analysis of total RNA extracted from microdissected SON. Prior to 8 hr, and beyond 24 hr, no consistent changes in c-fos and c-jun mRNA were found. Levels of c-fos and c-jun mRNA in the hippocampus were not altered over 24 hr of dehydration. 3. Acute stimulation with hypertonic saline (1.5M, i.p.) resulted in a marked increase in SON c-fos mRNA at 1 hr (6-fold) and 2 hr (3.5-fold). Small increases in SON c-jun mRNA were observed at these time points. Treatment with a similar volume of 0.9% saline did not elevate SON c-fos and c-jun mRNA levels. 4. Analysis of transcriptional activity with a nuclear run-on assay showed that activation of transcription appears to mediate the induction of c-fos and c-jun mRNA following acute hypertonic saline treatment. During dehydration transcriptional activation is apparent for c-jun but is not well defined for c-fos. 5. The results are discussed with reference to the hypothesis that products of c-fos and c-jun may mediate adaptive changes in hypothalamic gene expression.

Electronic Resource