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At least 667 records · Page 37Linked to original sources
PubMed2005

Temporal control of conditioned responding in goldfish.

The peak procedure was used to characterize response timing during acquisition and maintenance of conditioned responding in goldfish. Subjects received light-shock pairings with a 5- or 15-s interstimulus interval. On interspersed peak trials, the conditioned stimulus light was presented for 45 s and no shock was delivered. Peaks in the conditioned response, general activity, occurred at about the time of the expected unconditioned stimulus, and variability in the activity distribution was scalar. Modeling of the changes in the activity distributions over sessions revealed that the temporal features of the conditioned response changed very little during acquisition. The data suggest that times are learned early in training, and, contrary to I. P. Pavlov's (1927/1960) concept of "inhibition of delay," that timing is learning when to respond rather than learning when not to respond.

Animals↗
PubMed2006

Pavlovian contingencies and temporal information.

The effects of altering the contingency between the conditioned stimulus (CS) and the unconditioned stimulus (US) on the acquisition of autoshaped responding was investigated by changing the frequency of unsignaled USs during the intertrial interval. The addition of the unsignaled USs had an effect on acquisition speed comparable with that of massing trials. The effects of these manipulations can be understood in terms of their effect on the amount of information (number of bits) that the average CS conveys to the subject about the timing of the next US. The number of reinforced CSs prior to acquisition is inversely related to the information content of the CS.

Animals↗
PubMed2006

Dopamine receptor blockade and extinction differentially affect behavioral variability.

Dopamine (DA) neurons respond to unexpected food delivery and are inhibited during the omission of expected reward. DA receptor blockade mimics some, but not all, aspects of non-reward (extinction) conditions. It was therefore of interest to ask whether DA receptor blockade produces extinction-like increases in behavioral variability in addition to its well-known operant response-suppressing effects. In the current experiment, rats were trained drug-free on an operant task in which they pressed on a keyboard. Two of the keys led to food on a continuous reinforcement schedule. Both response rates and behavioral variability were measured. Test day administration of D(1) and D(2) antagonists SCH23390 and raclopride, like extinction, suppressed responding but, unlike extinction, did not lead to an increase in variability.

Analysis of Variance↗
PubMed2004

Pioneers in partnership: lesbian and gay male couples in civil unions compared with those not in civil unions and married heterosexual siblings.

This study compared 212 lesbians and 123 gay men who had civil unions in Vermont (during the first year legislation made this available) with 166 lesbians and 72 gay men in their friendship network who had not had civil unions, and also with 219 heterosexual married women and 193 heterosexual married men consisting of civil union couples' siblings and their spouses. Married heterosexual couples had been together longer and had more traditional division of labor and child care than did lesbians and gay men in both types of couples. Lesbians in civil unions were more open about their sexual orientation than those not in civil unions, and gay men in civil unions were closer to their family of origin than gay men not in civil unions. This is the first study on same-sex couples with civil unions, and the first to compare lesbians and gay men with their married siblings. At a time of legal changes for same-sex couples, these results indicate that legalized same-sex relationships are related to visibility of same-sex couples to their family and the general public.

Adult↗
PubMed2004

Culture, trauma, and wellness: a comparison of heterosexual and lesbian, gay, bisexual, and two-spirit native americans.

In a community-based sample of urban American Indian and Alaska Native adults, 25 lesbian, gay, bisexual, and two-spirit participants were compared with 154 heterosexual participants with respect to sociodemographic characteristics, Native, cultural participation, trauma, physical and mental health, and substance use. Compared with their heterosexual counterparts, two-spirit participants reported higher rates of childhood physical abuse and more historical trauma in their families, higher levels of psychological symptoms, and more mental health service utilization. Two-spirit participants reported differences in patterns of alcohol use and were more likely to have used illicit drugs other than marijuana. Discussion and recommendations for health promotion interventions and future research are presented in consideration of an "indigenist" health model and the multiple minority status of two-spirit people.

Adolescent↗
PubMed2004

Haematopoietic stem cells adopt mature haematopoietic fates in ischaemic myocardium.

Under conditions of tissue injury, myocardial replication and regeneration have been reported. A growing number of investigators have implicated adult bone marrow (BM) in this process, suggesting that marrow serves as a reservoir for cardiac precursor cells. It remains unclear which BM cell(s) can contribute to myocardium, and whether they do so by transdifferentiation or cell fusion. Here, we studied the ability of c-kit-enriched BM cells, Lin- c-kit+ BM cells and c-kit+ Thy1.1(lo) Lin- Sca-1+ long-term reconstituting haematopoietic stem cells to regenerate myocardium in an infarct model. Cells were isolated from transgenic mice expressing green fluorescent protein (GFP) and injected directly into ischaemic myocardium of wild-type mice. Abundant GFP+ cells were detected in the myocardium after 10 days, but by 30 days, few cells were detectable. These GFP+ cells did not express cardiac tissue-specific markers, but rather, most of them expressed the haematopoietic marker CD45 and myeloid marker Gr-1. We also studied the role of circulating cells in the repair of ischaemic myocardium using GFP+-GFP- parabiotic mice. Again, we found no evidence of myocardial regeneration from blood-borne partner-derived cells. Our data suggest that even in the microenvironment of the injured heart, c-kit-enriched BM cells, Lin- c-kit+ BM cells and c-kit+ Thy1.1(lo) Lin- Sca-1+ long-term reconstituting haematopoietic stem cells adopt only traditional haematopoietic fates.

Animals↗
PubMed2005

Mice with chronically elevated dopamine exhibit enhanced motivation, but not learning, for a food reward.

Dopamine has been critically implicated in learning and motivation, although its precise role remains to be determined. In order to investigate the involvement of dopamine in learning and motivation for a food reward, we used dopamine transporter knockdown mice (DAT KD) that have chronically elevated levels of extracellular dopamine. The present study demonstrates that chronically elevated dopamine enhances tendency to work for a food reward without apparent effects on Pavlovian and operant learning for this reward. The increase in dopamine is associated with elevated levels of dynorphin and Fos B expression in the dorsal caudate-putamen and the core but not the shell subregion of the nucleus accumbens. These data suggest that motivation to work, but not learning, for a food reward appears to be under the critical influence of tonic dopaminergic activity in discrete brain areas relevant for a reward-directed behavior.

Animals↗
PubMed2005

Haematopoietic stem cells and repair of the ischaemic heart.

HSCs (haematopoietic stem cells) are multipotent stem cells that give rise to all cells of the blood cell lineage. In recent years, it has been proposed that bone marrow serves as a reservoir for cardiomyogenic precursors and that, following cardiac injury, these stem cells circulate to the site of injury where they contribute to myocardial repair and regeneration. This concept of stem cell plasticity has been controversial and, in fact, several key studies on the cardiomyogenic potential of HSCs have not been reproducible in the hands of independent investigators. Despite this controversy, the clinical community has pushed forward with clinical trials of bone marrow transplantation for the treatment of ischaemic heart disease. The following review summarizes the mechanistic underpinnings of bone marrow transplantation into ischaemic myocardium, focusing on the basic science that forms the foundation of this field, and highlights the controversies and new avenues for research that have emerged. It also describes the current state of the art in clinical trials of bone marrow transplantation for heart failure.

Animals↗
PubMed2000

Diminished leakage along root canals filled with gutta-percha without sealer over time: a laboratory study.

AIM: The aim of this study was to investigate the long-term seal of gutta-percha (GP) without sealer. METHODOLOGY: Extracted human maxillary central incisors were prepared and obturated using heat- or chloroform-softened GP only, or GP in combination with a root canal sealer. Leakage along root fillings was measured at 48 h and after a period of 6 months using a fluid transport model. RESULTS: At 48 h the GP-filled roots without sealer leaked more than the control roots filled with GP and sealer (P < 0.0001). At 6 months a significant reduction in leakage was found in the GP-only groups (P < 0.05 for both heat- and chloroform-softened GP). After 6 months, roots filled by vertical condensation of GP-only had similar leakage as vertically condensed GP with a sealer (P > 0.05). CONCLUSIONS: The long-term seal of root fillings is affected by the volume change of both GP and sealer. Leakage reduction due to expansion of GP may compensate to a certain extent for leakage that may occur from sealer dissolution.

Balsams↗
PubMed2003

Clinical and angiographic outcome after Guglielmi detachable coil embolization of intracranial aneurysms.

BACKGROUND: Between July 1997 and April 2001, forty patients underwent Guglielmi detachable coil (GDC) embolization of intracranial aneurysms at Wellington Hospital. METHODS: The clinical notes and imaging were reviewed retrospectively. RESULTS: Complete initial occlusion was achieved in 28 patients (70%). Eleven patients (27.5%) had small residual neck (>90% occlusion) and one patient (2.5%) had substantial filling of the aneurysm. Follow up angiographic assessment was obtained in 28 patients (70%) of whom 24 patients (85.7%) had no recurrence or stable residual neck and four patients (14.3%) had recurrence or enlargement of the residual neck. Stable occlusion was achieved in 100% of small and medium sized aneurysms and 50% of large and giant aneurysms. Technical complications occurred in 10% including aneurysms perforated in two patients (5%) and presumed parent artery occlusion in another two (5%). CONCLUSIONS: The findings of the present study demonstrate the safety of GDC embolization. The initial clinical grade at presentation strongly predicted the clinical outcome. Although the number of patients in this study is small, there is evidence that the angiographic outcome is better for small and medium sized aneurysms. Our results are comparable to other published series.

Adult↗
PubMed2001

Patch testing discordance alert: false-negative findings with rubber additives and fragrances.

From July 1996 through June 1998, the North American Contact Dermatitis Group evaluated 318 patients for suspected contact dermatitis by patch testing simultaneously with Finn Chambers and the T.R.U.E. Test allergen system. Discrepancies between the two systems were found in some of the results, particularly with fragrance and rubber allergens. These results suggest that positive reactions to fragrance, thiuram, and carba mix allergens may be missed if the T.R.U.E. Test is used alone.

Allergens↗
PubMed2004

The learning curve: implications of a quantitative analysis.

The negatively accelerated, gradually increasing learning curve is an artifact of group averaging in several commonly used basic learning paradigms (pigeon autoshaping, delay- and trace-eye-blink conditioning in the rabbit and rat, autoshaped hopper entry in the rat, plus maze performance in the rat, and water maze performance in the mouse). The learning curves for individual subjects show an abrupt, often step-like increase from the untrained level of responding to the level seen in the well trained subject. The rise is at least as abrupt as that commonly seen in psychometric functions in stimulus detection experiments. It may indicate that the appearance of conditioned behavior is mediated by an evidence-based decision process, as in stimulus detection experiments. If the appearance of conditioned behavior is taken instead to reflect the increase in an underlying associative strength, then a negligible portion of the function relating associative strength to amount of experience is behaviorally visible. Consequently, rate of learning cannot be estimated from the group-average curve; the best measure is latency to the onset of responding, determined for each subject individually.

Algorithms↗
PubMed1989

Styles of connection in analysis. Clinical instances.

This paper elaborates on the meaning of Loewald's metaphor of the analyst as sculptor as it relates to the transformation toward new object relatedness. The mutuality of the process is stressed and clinical vignettes are offered.

Adolescent↗
PubMed1997

Active neutrality and Loewald's metaphor of theater.

The value of neutrality as an integral aspect of a desirable analytic stance is viewed here through Hans Loewald's metaphor of theater, applied to the analytic situation. His emphases on both the analyst's subjectivity and objectivity and their influence on the "new object" are explored through clinical vignettes. James Strachey's 1934 views on similar concepts are used to highlight derived contemporary shifts influenced by Loewald's work.

Humans↗
PubMed2003

Clinically established hemostatic scaffold (tissue fleece) as biomatrix in tissue- and organ-engineering research.

Various types of three-dimensional matrices have been used as basic scaffolds in myocardial tissue engineering. Many of those are limited by insufficient mechanical function, availability, or biocompatibility. We present a clinically established collagen scaffold for the development of bioartificial myocardial tissue. Neonatal rat cardiomyocytes were seeded into Tissue Fleece (Baxter Deutschland, Heidelberg, Germany). Histological and ultrastructural examinations were performed by DAPI and DiOC(18) staining and electron microscopy, respectively. Force measurements from the spontaneously beating construct were obtained. The constructs were stimulated with agents such as adrenalin and calcium, and by stretching. Passive stretch curves were obtained. Spontaneous contractions of solid bioartificial myocardial tissue (BMT), 20 x 15 x 2 mm, resulted. Contractions continued to week 12 (40% of BMTs) in culture. Histology revealed intercellular and also cell-fibril junctions. Elasticity was similar to that of native rat myocardium. Contractile force increased after topical administration of Ca(2+) and adrenaline. Stretch led to the highest levels of contractile force. In summary, bioartificial myocardial tissue with significant in vitro longevity, spontaneous contractility, and homogeneous cell distribution was produced using Tissue Fleece. Tissue Fleece constitutes an effective scaffold to engineer solid organ structures, which could be used for repair of congenital defects or replacement of diseased tissue.

Animals↗