Showing papers by "Dalhousie University published in 1992"

Content analysis: Method, applications, and issues

Abstract: Content analysis research methodology is detailed, its procedures are described, some examples of its application are provided, and the controversial issues surrounding its use are discussed. Unlike strictly qualitative designs, content analysis has external validity as a goal. Because of its focus on human communication, content analysis offers practical applicability, promise, and relevance for research involving the practice and education of nurses and other helping professionals.

Estuarine facies models; conceptual basis and stratigraphic implications

Abstract: The nature and organization of facies within incised-valley estuaries is controlled by the interplay between marine processes (waves and tides), which generally decrease in intensity up-estuary, and fluvial processes, which decrease in strength down-estuary. All estuaries ideally possess a three-fold (tripartite) structure: an outer, marine-dominated portion where the net bedload transport is headward; a relatively low-energy central zone where there is net bedload convergence; and an inner, river-dominated (but marine-influenced) part where the net transport is seaward. These three zones are not equally developed in all estuaries because of such factors as sediment availability, coastal zone gradient and the stage of estuary evolution. Two distinct but intergradational types of estuaries (wave- and tide-dominated) are recognized on the basis of the dominant marine process. Wave-dominated estuaries typically possess a well-defined tripartite zonation: a marine sand body comprised of barrier, washover, tidal inlet and tidal delta deposits; a fine-grained (generally muddy) central basin; and a bay-head delta that experiences tidal and/or salt-water influence. The marine sand body in tide-dominated estuaries consists of elongate sand bars and broad sand flats that pass headward into a low-sinuosity ("straight") single channel; net sand transport is headward in these areas. The equivalent of the central basin consists of a zone of tight meanders where bedload transport by flood-tidal and river currents is equal in the long term, while the inner, river-dominated zone has a single, low-sinuosity ("straight") channel. These facies models and their conceptual basis provide a practical means of highlighting the differences and similarities between estuaries. They also allow the predication of the stratigraphy of estuarine deposits within a sequence-stratigraphic context.

The endosymbiont hypothesis revisited.

Abstract: Publisher Summary This chapter highlights endosymbiont hypothesis. All contemporary genomes (including those of plastids and mitochondria) ultimately derive from a single genome—the genome of a single, presumably cellular, entity which was the ancestor of all surviving forms of live. The construction and interpretation of phylogenetic trees based on small subunit (SSU, or 16S-like) and large subunit (LSU, or 23S-like) rRNA sequences have proven especially informative in instances where morphological diversity tends to confound traditional methods of phylogenetic analysis. In addition to ribosomal RNA (rRNA) sequence, there are a number of traits that characterize the archaebacteria as a distinct group of organisms, separate from all other prokaryotes. These include (1) cell walls that, when present, lack peptidoglycan and muramic acid; (2) the presence of lipids containing phytanyl side groups in ether linkage; and (3) the presence of RNA polymerases that are distinct from those of eubacteria in subunit composition, response to RNA synthesis inhibitors or stimulators, immunological reactivity, and gene sequence. Two major divisions of archaebacteria include (1) sulfur-dependent, extreme thermophiles; and (2) methane-producers (methanogens) and their relatives, including the extreme halophiles.

Afferent connections of the laterodorsal and the pedunculopontine tegmental nuclei in the rat: A retro‐ and antero‐grade transport and immunohistochemical study

Abstract: Increasingly strong evidence suggests that cholinergic neurons in the mesopontine tegmentum play important roles in the control of wakefulness and sleep. To understand better how the activity of these neurons is regulated, the potential afferent connections of the laterodorsal (LDT) and pedunculopontine tegmental nuclei (PPT) were investigated in the rat. This was accomplished by using retrograde and anterograde axonal transport methods and NADPH-diaphorase histochemistry. Immunohistochemistry was also used to identify the transmitter content of some of the retrogradely identified afferents. Following injections of the retrograde tracer wheatgerm agglutinin-conjugated horseradish peroxidase (WGA-HRP) into either the LDT or the PPT, labelled neurons were seen in a number of limbic forebrain structures. The medial prefrontal cortex and lateral habenula contained more retrogradely labelled neurons from the LDT, whereas in the bed nucleus of the stria terminalis and central nucleus of the amygdala, more cells were labelled from the PPT. Moderate numbers of neurons were seen in the magnocellular regions of the basal forebrain, and many labelled neurons were observed in the lateral hypothalamus, the zona incerta, and the midbrain central gray from both the LDT and the PPT. Accessory oculomotor nuclei in the midbrain as well as eye movement-related structures in the lower brainstem contained some neurons labelled from the LDT, and fewer neurons from the PPT. A few labelled neurons were seen in somatosensory and other sensory relay nuclei in the brainstem and the spinal cord. Retrograde labelling was seen in a number of extrapyramidal structures, including the globus pallidus, entopenduncular and subthalamic nuclei, and substantia nigra following PPT injections; with LDT injections, labelling was similar in density in the substantia nigra but virtually absent in the entopeduncular and subthalamic nuclei. Data with the fluorescent retrograde tracer fluorogold combined with immunofluorescence indicated that many neurons in the zona incerta-lateral hypothalamic region that were retrogradely labelled from the LDT contained alpha-melanocyte-stimulating hormone. Numerous neurons were labelled throughout the reticular formation of the brainstem following either LDT or PPT injections. Many neurons retrogradely labelled in the LDT and PPT, the dorsal and median raphe nuclei, and the locus ceruleus contained choline acetyltransferase, serotonin, and tyrosine hydroxylase, respectively. The anterograde tracers WGA-HRP and phaseolus vulgaris leucoagglutinin were used to confirm some of the projections indicated by the retrograde labelling data; anterograde labelling was seen in the LDT and PPT following injections of one of these tracers into the medial prefrontal cortex, lateral hypothalamus, and the contralateral LDT.(ABSTRACT TRUNCATED AT 400 WORDS)

Erosional control of active compressional orogens

Abstract: Denudation has long been acknowledged as a process that contributes to the unroofing of compressional orogens. It has, however, mainly been considered as a passive process, not one that can dictate or control the tectonic evolution. This view prevails despite the knowledge that the style of deformation is controlled by the interplay of gravitational and tectonic stresses: an interplay that is sensitive to the mass removed by denudation.

The membranous skeleton: the role of cell condensations in vertebrate skeletogenesis.

Abstract: Elements of the vertebrate skeleton are initiated as cell condensations, collectively termed the 'membranous skeleton' whether cartilages or bones by Gruneberg (1963). Condensations, which were identified as the basic cellular units in a recent model of morphological change in development and evolution (Atchley and Hall 1991) are reviewed in this paper. Condensations are initiated either by increased mitotic activity or by aggregation of cells towards a centre. Prechondrogenic (limb bud) and preosteogenic (scleral ossicle) condensations are discussed and contrasted. Both types of skeletogenic condensations arise following epithelial-mesenchymal interactions; condensations are identified as the first cellular product of such tissue interactions. Molecular characteristics of condensations are discussed, including peanut agglutinin lectin, which is used to visualize prechondrogenic condensations, and hyaluronan, hyaladherins, heparan sulphate proteoglycan, chondroitin sulphate proteoglycan, versican, tenascin, syndecan, N-CAM, alkaline phosphatase, retinoic acid and homeo-box-containing genes. The importance for the initiation of chondrogenesis or osteogenesis of upper and lower limits to condensation size and the numbers of cells in a condensation are discussed, as illustrated by in vitro studies and by mutant embryos, including Talpid3 in the chick and Brachypod, Congenital hydrocephalus and Phocomelia in the mouse. Evidence that genes specific to the skeletal type are selectively activated at condensation is discussed, as is a recent model involving TGF-beta and fibronectin in condensation formation. Condensations emerge as a pivotal stage in initiation of the vertebrate skeleton in embryonic development and in the modification of skeletal morphology during evolution.

A Canadian population survey on the clinical, epidemiologic and societal impact of migraine and tension-type headache.

Abstract: Trained telephone interviewers contacted 1,573 adults across Canada about the nature and frequency of headaches suffered by them or by others in their households. Using a table of pain symptoms and other characteristics abstracted from the International Headache Society (IHS) classification, the headaches were assigned to migraine headache, tension-type headache or other diagnostic groups. Of the households sampled, 59% had at least one headache sufferer in residence. The proportion of headache sufferers with migraine was 14%; with tension-type, 36%; and with both, 14%. Migraine headache caused more disability than tension-type headache, with nearly 20% of migraine sufferers taking time off work and disability lasting for a mean of 1 day. It is concluded that the current prevalences of migraine and tension-type headache in Canada fall around the mean of previous studies, that the IHS criteria can form a basis for diagnostic classification and that the functional impact of migraine has been seriously underestimated in the past.

D1-like and D2-like dopamine receptors synergistically activate rotation and c-fos expression in the dopamine-depleted striatum in a rat model of Parkinson's disease.

Abstract: Selective agonists for D1-like and D2-like dopamine receptors can interact synergistically to enhance each other's actions on locomotion and behavior in experimental animals. Clinically, the combination of the D2 agonist bromocriptine with L-dopa (which has pronounced D1 effects) is a highly effective treatment for Parkinson's disease. The mechanisms underlying this important receptor interaction are poorly understood and are the subject of intense study in vitro. In rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the nigrostriatal pathway, D1-selective (but not D2-selective) dopamine agonists produce a marked increase in expression of the immediate-early gene c-fos in the striatum ipsilateral to the 6-OHDA lesion. In the experiments reported here, we have used this in vivo model to explore the possibility that combinations of D1-selective and D2-selective agonists might have effects on c-fos transcription that are different from those exhibited by D1 or D2 agonists administered alone. We examined the effects of the D1-selective agonist SKF-38393 and the D2-selective agonist quinpirole (LY 171555) on the expression of Fos-like protein and c-fos mRNA in the caudoputamen and made parallel behavioral observations in the same animals. A low dose of SKF-38393 produced little contraversive rotation and little induction of Fos-like immunoreactivity in the striatum. A low dose of quinpirole elicited contralateral rotation but little or no induction of Fos-like immunoreactivity in the caudoputamen; there was, however, induction of Fos in the globus pallidus ipsilateral to the 6-OHDA lesion. Combination of the low dose of SKF-38393 and quinpirole produced a synergistic effect on rotation and elicited, in the dopamine-depleted caudoputamen, a striking pattern of Fos-like protein expression in which Fos-positive neurons were concentrated in striosomes and in the dorsolateral caudoputamen. Northern blot analysis showed that c-fos mRNA was expressed following combined agonist treatment but was not detectable after the single-agonist treatments. Both the contraversive rotation and the induction of Fos-like immunoreactivity were blocked by the preadministration of the D1-preferring antagonist SCH-23390 and the D2-selective antagonist raclopride in combination. Pretreatment with the glutamate NMDA receptor antagonist MK-801 also blocked the induction of Fos-like immunoreactivity, and it reversed the rotation. These findings suggest a D1/D2 synergistic mechanism that involves the participation of D1-responsive striatonigral and D2-responsive striatopallidal output pathways, and that is sensitive to glutamatergic modulation.

Partially finite convex programming, Part I: Quasi relative interiors and duality theory

Abstract: We study convex programs that involve the minimization of a convex function over a convex subset of a topological vector space, subject to a finite number of linear inequalities. We develop the notion of the quasi relative interior of a convex set, an extension of the relative interior in finite dimensions. We use this idea in a constraint qualification for a fundamental Fenchel duality result, and then deduce duality results for these problems despite the almost invariable failure of the standard Slater condition. Part II of this work studies applications to more concrete models, whose dual problems are often finite-dimensional and computationally tractable.

The treatment of depression in chronic low back pain: review and recommendations

Abstract: The prevalence of major depression in patients with chronic low back pain (CLBP) is approximately three to four times greater than that reported in the general population. In spite of these high prevalence rates, there have been few systematic attempts to investigate the efficacy of treatment for major depression in patients with CLBP. While several studies have examined the efficacy of antidepressant medication and psychological treatment in patients with chronic pain, most of these studies have focused on treating chronic pain rather than depression. The few studies that have specifically addressed the treatment of depression in CLBP indicate that tricyclic antidepressants and cognitive-behavioral approaches may be effective means of treating depressed chronic pain patients. Clinical issues related to diagnostic confounds, rehabilitation outcome, and conceptualizations of the relation between pain and depression are discussed. It is argued that, in patients with clinical levels of depression, treatment modalities specifically targeting depressive symptomatology deserve serious consideration as an integral component of pain management programs.

Bannayan-Riley-Ruvalcaba syndrome.

Abstract: Here we report on 12 affected members of a family with Bannayan-Riley-Ruvalcaba syndrome. We present clinical evidence of overlap between Bannayan-Zonana syndrome. Riley-Smith syndrome, and Ruvalcaba-Myhre syndrome in this autosomal dominantly inherited condition. We expand the phenotypic spectrum to include Hashimoto thyroiditis, which occurred in 7 of our cases. Finally, we discuss the relationship between the syndrome and juvenile polyposis of infancy.

Photosynthetic characteristics and estimated growth rates indicate grazing is the proximate control of primary production in the equatorial Pacific

Abstract: Macronutrients persist in the surface layer of the equatorial Pacific because the production of phytoplankton is limited; the nature of this limitation has yet to be resolved. Measurements of photosynthesis as a function of irradiance (P-I) provide information on the control of primary productivity, a question of great biogeochemical importance. Accordingly, P-I was measured in the equatorial Pacific along 150 deg W, during February-March 1988. Diel variability of P-I showed a pattern consistent with nocturnal vertical mixing in the upper 20 m followed by diurnal stratification, causing photoinhibition near the surface at midday. Otherwise, the distribution of photosynthetic parameters with depth and the stability of P-I during simulated in situ incubations over 2 days demonstrated that photoadaptation was nearly complete at the time of sampling: photoadaptation had not been effectively countered by upwelling or vertical mixing. Measurements of P-I and chlorophyll during manipulations of trace elements showed that simple precautions to minimize contamination were sufficient to obtain valid rate measurements and that the specific growth rates of phytoplankton were fairly high in situ, a minimum of 0.6/d. Diel variability of beam attenuation also indicated high specific growth rates of phytoplankton and a strong coupling of production with grazing. It appears that grazing is the proximate control on the standing crop of phytoplankton. Nonetheless, the supply of a trace nutrient such as iron might ultimately regulate productivity by influencing species composition and food-web structure.

Serotonin hyperpolarizes cholinergic low-threshold burst neurons in the rat laterodorsal tegmental nucleus in vitro.

Abstract: Serotonergic suppression of cholinergic neuronal activity implicated in the regulation of rapid eye movement sleep and its associated phenomenon, pontogeniculooccipital waves, has long been postulated, but no direct proof has been available. In this study, intracellular and whole-cell patch-clamp recording techniques were combined with enzyme histochemistry to examine the intrinsic electrophysiological properties and response to serotonin (5-HT) of identified cholinergic rat laterodorsal tegmental nucleus neurons in vitro. Sixty-five percent of the recorded neurons demonstrated a prominent low-threshold burst, and of these, 83% were cholinergic. In current-clamp recordings 64% of the bursting cholinergic neurons tested responded to the application of 5-HT with a membrane hyperpolarization and decrease in input resistance. This effect was mimicked by application of the selective 5-HT type 1 receptor agonist carboxamidotryptamine maleate. Whole-cell patch-clamp recordings revealed that the hyperpolarizing response was mediated by an inwardly rectifying K+ current. Application of 5-HT decreased excitability and markedly modulated the discharge pattern of cholinergic bursting neurons: during a 5-HT-induced hyperpolarization these neurons exhibited no rebound burst after hyperpolarizing current input and a burst in response to depolarizing current input. In the absence of 5-HT, the relatively depolarized cholinergic bursting neurons responded to an identical hyperpolarizing current input with a burst and did not produce a burst after depolarizing current input. These data provide a cellular and molecular basis for the hypothesis that 5-HT modulates rapid eye movement sleep phenomenology by altering the firing pattern of bursting cholinergic neurons.

Direct evidence for extensive paternal mitochondrial DNA inheritance in the marine mussel Mytilus

Abstract: Inheritance of mitochondrial DNA in animals was thought to be strictly maternal. Recently, evidence for incidental paternal mtDNA leakage was obtained in hybrid crosses of Drosophila and mice. In mice, the frequency of paternal mtDNA contributions was estimated at 10(-4), compared with maternal contributions. The common occurrence in the marine mussel Mytilus of heteroplasmic individuals with two or more types of highly diverged mtDNA molecules was interpreted as strong evidence for biparental mtDNA inheritance by some, but not by others. We report here results from pair-matings involving two species of mussels, Mytilus edulis and Mytilus trossulus. Extensive contribution of paternal mtDNA, amounting to several orders of magnitude higher than that inferred for Drosophila or mice, was observed in both intra- and interspecific crosses.

Birth prevalence study of the apert syndrome

Abstract: Estimates of the Apert syndrome birth prevalence and the mutation rate are reported for Washington State, Nebraska, Denmark, Italy, Spain, Atlanta, and Northern California. Data were pooled to increase the number of Apert births (n = 57) and produce a more stable birth prevalence estimate. Birth prevalence of the Apert syndrome was calculated to be approximately 15.5/1,000,000 births, which is twice the rate determined in earlier studies. The major reason appears to be incomplete ascertainment in the earlier studies. The similarity of the point estimates and the narrow bounds of the confidence limits in the present study suggest that the birth prevalence of the Apert syndrome over different populations is fairly uniform. The mutation rate was calculated to be 7.8 x 10(-6) per gene per generation. Apert syndrome accounts for about 4.5% of all cases of craniosynostosis. The mortality rate appears to be increased compared to that experienced in the general population; however, further study of the problem is necessary.

Avian Movement Imitation and a New Form of Mimicry: Tracing the Evolution of a Complex Form of Learning

Abstract: [1. The spontaneous imitation of movements, previously known in two orders of mammals, is demonstrated in a psittacine bird. 2. The animal, a Grey parrot which has bonded to humans, utilizes its torso, legs, wings, head, beak, and tongue in the imitation of human movements. 3. A new form of imitation, ''non-vocal mimicry,'' is tentatively identified. It is defined by the use of skeletal movements to produce mimetic sounds. 4. Hierarchical relationships and phylogenetic patterns of occurrence suggest that imitative learning in birds may have evolved through the sequence: song/call learning → vocal mimicry → non-vocal mimicry→ movement imitation. 5. These relationships and patterns, and possible differences in function and incubation time, suggest that movement imitation in birds is not homologous to that in mammals., 1. The spontaneous imitation of movements, previously known in two orders of mammals, is demonstrated in a psittacine bird. 2. The animal, a Grey parrot which has bonded to humans, utilizes its torso, legs, wings, head, beak, and tongue in the imitation of human movements. 3. A new form of imitation, ''non-vocal mimicry,'' is tentatively identified. It is defined by the use of skeletal movements to produce mimetic sounds. 4. Hierarchical relationships and phylogenetic patterns of occurrence suggest that imitative learning in birds may have evolved through the sequence: song/call learning → vocal mimicry → non-vocal mimicry→ movement imitation. 5. These relationships and patterns, and possible differences in function and incubation time, suggest that movement imitation in birds is not homologous to that in mammals.]

The incidence and impact of early rejection episodes on graft outcome in recipients of first cadaver kidney transplants.

Abstract: The objective of this study was to define the incidence and significance of acute rejection occurring in the first year following transplantation. The influence of contemporary induction immunosuppression on rejection, as well as the effect of rejection on graft and patient loss, renal function, and maintenance immunosuppression during the first year in 110 recipients of first cadaver renal transplants were analyzed. All patients received CsA, Aza, and prednisone for 30 days with withdrawal of Aza at 30 days and then prednisone at 105 days; 57 patients were prospectively randomized to receive ALG (Merieux) until serum creatinine was less than 300 mumol/L. Short-term ALG administration did not influence the incidence, severity, nature, or outcome of rejection episodes. Fifty-five (50%) patients had at least 1 rejection in the first 90 days. All patients with delayed graft function and 7/8 (88%) sensitized patients (current PRA greater than 50%) had at least 1 rejection episode; 71% (n = 35) of all rejection episodes occurred in the first 30 days posttransplant. Patients rejection free at 90 days remained rejection free the entire first year. Graft loss was 18% for rejections in the first month, 13% for rejections occurring later (P = NS); 20% (n = 11) of patients had a second rejection and 1% (n = 2) had a third rejection. The risk of graft loss was 9% with a first rejection, 38% with a second rejection, and 50% with a third rejection. Of 12 (22%) rejections that were steroid resistant, 10 (83%) were reversed with OKT3. One-year graft survival for patients without rejection, with steroid-sensitive rejection, and with steroid-resistant rejection was 96%, 88% (P = ns), and 58% (P less than 0.001), respectively; 1 year SCr was 168 +/- 93, 196 +/- 77 (P = ns), and 268 +/- 96 microMol/L (P less than 0.05), respectively. Patients free of rejection and with stable renal function continued to do well on maintenance CsA monotherapy, and they were more likely to be on CsA monotherapy than those with rejection episodes (P less than 0.01).

Biochemical and chemical studies on strains designated Prevotella intermedia and proposal of a new pigmented species, Prevotella nigrescens sp. nov.

Abstract: A total of 31 strains of Prevotella intermedia were subjected to DNA-DNA hybridization and were characterized by performing physiological tests and by performing a multilocus enzyme analysis, using malate dehydrogenase and glutamate dehydrogenase. All of the strains assigned to P. intermedia fermented glucose and sucrose, hydrolyzed starch but not esculin, and produced indole, acetic, isobutyric, isovaleric, and succinic acids as metabolic end products. The results of DNA reassociation experiments performed with the reference probe permitted separation of the strains into two well-defined homology groups. In addition, strains with DNAs that hybridized with DNA from strain ATCC 25611T (T = type strain) had high levels of peptidase activity and cleaved lipid substrates (4-methylumbelliferyl laurate and 4-methylumbellifelyl elaidate). Multilocus enzyme electrophoresis revealed two electromorphic profiles, one characteristic of strain ATCC 25611T and the other characteristic of strain ATCC 33563T. We propose that a new species, Prevotella nigrescens, should be created for the genetically distinct group of strains that hybridized with strain ATCC 33563T. Strain ATCC 33563 is designated the type strain of P. nigrescens.

Sea Carousel--A Benthic, Annular Flume

Abstract: A benthic annular flume (Sea Carousel) has been developed and tested to measure in situ the erodibility of cohesive sediments. The flume is equipped with three optical backscatter sensors, a lid rotation switch, and an electromagnetic (EM) flow meter capable of detecting azimuthal and vertical components of flow. Data are logged at rates up to 10·66 Hz. Erodibility is inferred from the rate of change in suspended sediment concentration detected in the annulus. The energy-density/wave number spectrum of azimuthal flow showed peaks in the energy spectrum at paddle rotation wave numbers (k) of 14 and 7 m −1 (macroturbulent time scales) but were not significant. Friction velocity ( U *), measured (1) at 1 Hz using a flush-mounted hot-film sensor, and (2) derived from measured velocity profiles in the inner part of the logarithmic layer gave comparable results for Ū * −1 . At higher values of U*, method (2) underpredicted by up to 20%. Method (1) showed radial increases in Ū * in the annulus for Ū y > 0·32 m s −1 . Radial velocity gradients were proportional to ( Ū y − 0·32 m s −1 ). Maximum radial differences in U * were 10% for Ū y = 0·5 ms −1 . Suspended sediment mass concentration ( S ) in the annulus resulted in a significant decrease (10·5%) in Ū * derived by method (1) over the range 0 S −1 . These decreases were not evident in method (2). Method (1) may, therefore, be subject to changes in stress sensor calibration with changes in S . Subaerial deployments of Sea Carousel caused severe substrate disturbance, water losses, and aeration of the annulus. Submarine deployments produced stable results, though dispersion of turbid flume water took place. Results clearly demonstrated the existence of ‘Type I’ and ‘Type II’ erosion documented from laboratory studies.