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M Gallagher

Publications and source records attributed to M Gallagher.

At least 55 records · Page 3Linked to original sources
PubMed1997

The role of an amygdalo-nigrostriatal pathway in associative learning.

The present study examined the role of an amygdalo-nigrostriatal pathway in associative learning. An asymmetrical lesion model was used to test whether a circuit from the amygdala central nucleus to the dorsolateral striatum, via the substantia nigra, is critical for mediating conditioned orienting responses. Rats with an asymmetrical lesion, consisting of neurotoxic removal of central nucleus neurons in one hemisphere and depletion of the dopamine innervation of the dorsolateral striatum in the contralateral hemisphere, failed to acquire conditioned orienting responses. In contrast, the asymmetrical lesion had no effect on spontaneous orienting or learning another response directed to the source of the food unconditioned stimulus in the same task. A second experiment tested the effect of reversible inactivation of the dorsolateral striatum contralateral to a neurotoxic central nucleus lesion on acquisition of the conditioned orienting response. Although inactivation did not affect spontaneous orienting, rats failed to acquire the conditioned orienting response during sessions in which inactivation occurred. Immediately after the inactivation procedure was terminated, however, a significant increase in orienting to the conditioned stimulus was evident. These data support the interpretation that the dorsolateral striatum provides a route for the expression of the conditioned orienting response but is not essential for acquisition of this learned behavior.

Amygdala↗
PubMed1997

Acute non-A-E hepatitis in the United States and the role of hepatitis G virus infection. Sentinel Counties Viral Hepatitis Study Team.

BACKGROUND: Little is known about the relation of the newly discovered hepatitis G virus (HGV) to the cause and clinical course of acute and chronic viral hepatitis. METHODS: We selected patients from a surveillance study of acute viral hepatitis in four U.S. counties who had acute disease during 1985 to 1986 or 1991 to 1995. Serum samples were tested for HGV RNA by the polymerase chain reaction. RESULTS: HGV RNA was detected in 4 of 45 patients with a diagnosis of non-A-E hepatitis (9 percent), 23 of 116 patients with hepatitis C (20 percent), 25 of 100 patients with hepatitis A (25 percent), and 32 of 100 patients with hepatitis B (32 percent) (P<0.05 for the comparison of hepatitis B with hepatitis non-A-E or C). The clinical characteristics of the acute illness were similar for patients with HGV alone and those with hepatitis A, B, or C with or without HGV infection. During a follow-up period of one to nine years, chronic hepatitis did not develop in any of the patients with HGV alone, but 75 percent were persistently positive for HGV RNA, as were 87 percent of those with both hepatitis C and HGV infection. The rates of chronic hepatitis were similar in patients with hepatitis C alone (60 percent) and those with both hepatitis C and HGV infection (61 percent). CONCLUSIONS: The evidence from this surveillance study does not implicate HGV as an etiologic agent of non-A-E hepatitis. Persistent infection with HGV was common, but it did not lead to chronic disease and did not affect the clinical course in patients with hepatitis A, B, or C.

Acute Disease↗
PubMed1997

Hippocampal N-methyl-D-aspartate and kainate binding in response to entorhinal cortex aspiration or 192 IgG-saporin lesions of the basal forebrain.

Lesion models in the rat were used to examine the effects of removing innervation of the hippocampal formation on glutamate receptor binding in that system. Bilateral aspiration of the entorhinal cortex was used to remove the cortical innervation of the hippocampal formation and the dentate gyrus. The subcortical input to the hippocampus from cholinergic neurons of the basal forebrain was lesioned by microinjection of the immunotoxin 192 IgG-saporin into the medial septum and vertical limb of diagonal band. After a 30-day postlesion survival, the effects of these lesions on N-methyl-D-aspartate-displaceable [3H]glutamate and [3H]kainate binding in the hippocampus were quantified using in vitro autoradiography. The bilateral entorhinal lesion induced a sprouting response in the dentate gyrus, measured by an increase in the width of [3H]kainate binding. It also induced an increase in the density of [3H]kainate binding in CA3 stratum lucidum and an increase in N-methyl-D-aspartate binding throughout the hippocampus proper and the dentate gyrus. The selective lesion of cholinergic septal input did not have any effect on hippocampal [3H]kainate binding and induced only a moderate decrease in N-methyl-D-aspartate binding that was not statistically reliable. The entorhinal and cholinergic lesions were used as in vivo models of the degeneration of hippocampal input that occurs in normal aging and Alzheimer's disease. The results from the present lesion study suggest that some, but not all, of the effects on hippocampal [3H]kainate and N-methyl-D-aspartate binding induced by the lesions are consistent with the status of binding to these receptors in aging and Alzheimer's disease. Consistent with the effects of aging and Alzheimer's disease is an altered topography of [3H]kainate binding after entorhinal cortex lesion and a modest decline in N-methyl-D-aspartate binding after lesions of the cholinergic septal input to the hippocampus.

Acetylcholinesterase↗
PubMed1997

Spatial learning and memory at defined points of the estrous cycle: effects on performance of a hippocampal-dependent task.

Learning based on hippocampal-dependent spatial navigation in female rats was assessed at identified points in the estrous cycle corresponding to low (estrus) and high (proestrus) circulating estrogen. With background training in water-maze procedures, rats learned the location of an escape platform in the maze in a single session of 8 training trials. A strong spatial bias for the escape platform was also evident in a probe trial used to assess retention of learning 30 min after the training session. This entire protocol was completed in less than an hour. The performance of the estrus and proestrus rats was indistinguishable on all behavioral measures, irrespective of the stage of estrous cycle during the task. These results indicate that rapid learning and retention for spatial information over a relatively short interval may be preserved despite morphological alterations in hippocampal dendritic spine density in the normally cycling female rat.

Animals↗
PubMed1997

CBFA2, frequently rearranged in leukemia, is not responsible for a familial leukemia syndrome.

We have identified a family with an autosomal dominant platelet disorder with a predisposition for developing myeloid malignancies and have previously demonstrated linkage of this trait to chromosome 21q22.1-22.2. The nearest flanking markers, D21S1265 and D21S167, define the familial platelet disorder (FPD) critical region at a genetic distance of approximately 15.2 centimorgans and physical distance of approximately 6 megabases. This locus is of particular interest as it has previously been implicated in the pathogenesis of acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) through the (8;21), (3;21) and (12;21) chromosomal translocations. In each of these cases, the CBFA2 gene is rearranged. As well, there is a potential association of this locus with the hematologic abnormalities seen in Down syndrome (trisomy 21). To identify the mutant gene in this pedigree, a positional cloning strategy has been undertaken. Several candidate genes map to this locus including: CBFA2, IFNAR1, IFNAR2, CRFB4, GART, SON, KCNE1, SCL5A3 and ATP50. CBFA2, as well as IFNAR1 and CRFB4, were the focus of initial mutational analysis efforts. In this report, we exclude CBFA2 as a candidate by Northern and Southern blotting, RNase protection, single-strand conformational polymorphism (SSCP), direct sequencing and gel-shift analysis. Exons of the IFNAR1 and CRFB4 genes were also analyzed by SSCP and demonstrated no evidence of mutation. SSCP analysis identified a new polymorphism in the second exon of the CRFB4 gene and confirmed a previously described polymorphism in the fourth exon of IFNAR1. Efforts are currently underway to delimit further the FPD critical region and to analyze the other known candidate genes, as well as novel candidate genes, which map to this locus.

Core Binding Factor Alpha 2 Subunit↗
PubMed1997

Predictors of becoming redomiciled among older homeless women.

The authors test a model to predict residential outcome among 201 homeless women aged 50 and over. On two-year follow-up, 47% were successfully domiciled. Of 12 variables examined using logistic regression analysis, only 2 variables, perceived support and number of community facilities attended were significant predictors of being domiciled on follow-up. Three additional variables-absence of psychosis, a lifetime history of less than one year of homelessness, and number of entitlements-attained near-significance. Although residential outcome is predicted by a few individual characteristics, what is most striking is the lack of suitable housing options.

Female↗
PubMed1997

Open reduction and internal fixation of the distal humerus: functional outcome in the elderly.

OBJECTIVE: To examine the functional outcome of a cohort of elderly patients after open reduction and internal plate and screw fixation of distal humerus fractures. DESIGN: Retrospective review of a consecutive series of patients older than 60 years of age who underwent plate and screw fixation of a distal humerus fracture. MATERIALS AND METHODS: Eighteen patients, aged 63 to 85 years (average, 71 years), underwent open reduction and internal fixation of a displaced distal humerus fracture using plates and screws. Three were Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF) type A, 2 were type B, and 13 were type C fractures. The patients were reviewed at a minimum follow-up of 1 year after surgery. MEASUREMENTS AND MAIN RESULTS: All patients had a good or excellent clinical result using a standardized method of evaluation. General health status, as measured by the SF-36 Health Survey, was comparable to the published norms for U.S. male and female populations of similar age. CONCLUSION: Open reduction and internal fixation of the distal humerus in the elderly can provide good clinical results. Good clinical results, however, do not imply good general health status.

Aged↗
PubMed1997

The use of animal models to study the effects of aging on cognition.

This review addresses the importance of animal models for understanding the effects of normal aging on the brain and cognitive functions. First, studies of laboratory animals can help to distinguish between healthy aging and pathological conditions that may contribute to cognitive decline late in life. Second, research on individual differences in aging, a theme of interest in studies of elderly human beings, can be advanced by the experimental control afforded in the use of animal models. The review offers a neuropsychological framework to compare the effects of aging in human beings, monkeys, and rodents. We consider aging in relation to the role of the medial temporal lobe in memory, the information processing functions of the prefrontal cortex in the strategic use of memory, and the regulation of attention by distributed neural circuitry. We also provide an overview of the neurobiological effects of aging that may account for alterations in psychological functions.

Aged↗
PubMed1997

A residential summer camp for children with vertically transmitted HIV/AIDS: a six-year experience at the Hole in the Wall Gang Camp.

Residential camping sessions for children with vertically transmitted human immunodeficiency virus/acquired immunodeficiency syndrome have been offered at The Hole In The Wall Gang Camp for the past six summers. More than 600 children 6 to 12 years of age have attended. Such sessions are expensive and require extensive planning. Medical and nursing needs have increased greatly over the 6-year period, reflecting advances in treatment and especially an escalation of prescribed medications. We have found it possible for these children to have a fun-filled camping experience and participate in a wide variety of activities.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Treatment of grade III acromioclavicular separations. Operative versus nonoperative management.

Twenty-six patients with Grade III acromioclavicular joint separations were evaluated to determine the outcomes of nonoperative and operative management. Evaluation consisted of a detailed functional questionnaire, physical examination, and comprehensive isokinetic strength assessment. The patients were divided into two groups: operative (n = 16) and nonoperative (n = 10). Operative management consisted of coracoclavicular stabilization with heavy suture material and with nine of the sixteen patients treatment also consisted of coracoacromial ligament transfer and lateral clavicle resection. Nonoperative management consisted of short-term immobilization with early range of motion and rehabilitation. The two groups were similar in all characteristics except mean age: 30.7 years for the operative group and 49.6 years for the nonoperative group. Follow-up evaluation was performed an average of 32.9 months after either injury (nonoperative group) or surgery. Our results indicated that nonoperative management was superior to operative management with respect to time to return to work (0.8 months vs. 2.6 months), time to return to athletics (3.5 months vs. 6.4 months) and time of immobilization (2.7 weeks vs. 6.2 weeks). However, operative management was superior to nonoperative management in the following parameters: time to attain completely pain-free status, the patient's subjective impression of pain, range of motion, functional limitations, cosmesis, and long-term satisfaction. There were no significant differences between the two groups with respect to shoulder range of motion, manual muscle testing, or neurovascular findings. Isokinetic strength testing of the involved shoulder, expressed as a percentage of the uninvolved shoulder, showed no significant differences in peak torque, total work, or total power between the operative and nonoperative groups. However, comparison of the involved to the uninvolved extremity within each group did reveal a trend toward decreased peak torque, work, and power for abduction in the involved extremity regardless of the treatment used. These findings reached statistical significance only for power at the slower testing speed (60 degrees/sec). There was also a significant decrease in power in the involved extremity for external rotation at the faster speed (120 degrees/sec) in the nonoperative group. Finally, the absolute values for peak torque, work, and power were significantly greater for all motions tested in the operative group as compared to the nonoperative group. This may reflect the difference in age between the two groups. Based upon the patients studied, there are benefits to both nonoperative and operative methods of treatment of Grade III acromioclavicular separations. Recovery of strength did not differ between the two groups and therefore should be viewed as a less important factor in patient selection for operative versus nonoperative management. Careful patient selection should remain an important aspect of treatment for this controversial injury.

Acromioclavicular Joint↗
PubMed1996

Preserved neuron number in the hippocampus of aged rats with spatial learning deficits.

Hippocampal neuron loss is widely viewed as a hallmark of normal aging. Moreover, neuronal degeneration is thought to contribute directly to age-related deficits in learning and memory supported by the hippocampus. By taking advantage of improved methods for quantifying neuron number, the present study reports evidence challenging these long-standing concepts. The status of hippocampal-dependent spatial learning was evaluated in young and aged Long-Evans rats using the Morris water maze, and the total number of neurons in the principal cell layers of the dentate gyrus and hippocampus was quantified according to the optical fractionator technique. For each of the hippocampal fields, neuron number was preserved in the aged subjects as a group and in aged individuals with documented learning and memory deficits indicative of hippocampal dysfunction. The findings demonstrate that hippocampal neuronal degeneration is not an inevitable consequence of normal aging and that a loss of principal neurons in the hippocampus fails to account for age-related learning and memory impairment. The observed preservation of neuron number represents an essential foundation for identifying the neurobiological effects of hippocampal aging that account for cognitive decline.

Aging↗
PubMed1996

Neurotoxic lesions of basolateral, but not central, amygdala interfere with Pavlovian second-order conditioning and reinforcer devaluation effects.

Considerable evidence suggests that various discrete nuclei within the amygdala complex are critically involved in the assignment of emotional significance or value to events through associative learning. Much of this evidence comes from aversive conditioning procedures. For example, lesions of either basolateral amygdala (ABL) or the central nucleus (CN) interfere with the acquisition or expression of conditioned fear. The present study examined the effects of selective neurotoxic lesions of either ABL or CN on the acquisition of positive incentive value by a conditioned stimulus (CS) with two appetitive Pavlovian conditioning procedures. In second-order conditioning experiments, rats first received light-food pairings intended to endow the light with reinforcing power. The acquired reinforcing power of the light was then measured by examining its ability to serve as a reinforcer for second-order conditioning of a tone when tone-light pairings were given in the absence of food. Acquisition of second-order conditioning was impaired in rats with ABL lesions but not in rats with CN lesions. In reinforcer devaluation procedures, conditioned responding of rats with ABL lesions was insensitive to postconditioning changes in the value of the reinforcer, whereas rats with CN lesions, like normal rats, were able to spontaneously adjust their CRs to the current value of the reinforcer. The results of both test procedures indicate that ABL, but not CN, is part of a system involved in CSs' acquisition of positive incentive value. Together with evidence that identifies a role for CN in certain changes in attentional processing of CSs in conditioning, these results suggest that separate amygdala subsystems contribute to a variety of processes inherent in associative learning.

Acoustic Stimulation↗
PubMed1996

Intact spatial learning following lesions of basal forebrain cholinergic neurons.

The role of the basal forebrain cholinergic system in learning and memory has held considerable interest since the discovery of cholinergic neurodegeneration in the basal forebrain in Alzheimer's disease. Contrary to expectation, selective removal of basal forebrain cholinergic neurons projecting to either hippocampus or neocortex fails to impair learning in a spatial task widely used to study hippocampal/cortical function. If cholinergic neurons contribute to learning and memory by integrated regulation of hippocampal and cortical processing, combined removal of hippocampal and cortical cholinergic projections might be necessary to produce impairment. However, this combined lesion failed to impair spatial learning. These data argue against the view that basal forebrain cholinergic deficiency plays a prominent role in disorders of learning and memory.

Acetylcholine↗
PubMed1996

Molecular indices of neuronal and glial plasticity in the hippocampal formation in a rodent model of age-induced spatial learning impairment.

Spatial learning ability was quantitated in young and aged Long-Evans rats, and molecular markers were assessed in the striatum and hippocampal formation using immunocytochemical, immunoblotting, and in situ hybridization histochemical procedures. The mRNA for beta-amyloid precursor protein (beta APP), most likely the transcript encoding the 695-amino acid form of this protein, was elevated in pyramidal and granule cells in the hippocampus of aged rats exhibiting poorer spatial learning. In immunoblots of hippocampal protein extracts, however, the level of beta APP-like immunoreactivity was depressed in the more impaired subjects. Similarly, the level in hippocampus of the mRNA for manganese-dependent superoxide dismutase (Mn-SOD), a marker of oxidative stress, was positively correlated with the degree of behavioral impairment, but immunoblotting revealed that Mn-SOD protein was depressed in the aged hippocampus compared with young. The mRNAs for the neuronal form of nitric oxide synthase and for the astrocyte marker glial fibrillary acidic protein (GFAP) were elevated in the hippocampus in correlation with the extent of learning impairment. In the striatum, the levels of mRNA and protein for several candidate genes, including GFAP, were elevated in parallel with the learning index, but these were age effects. Several hippocampal proteins were unchanged (GFAP) or depressed (beta APP and Mn-SOD) in level, despite elevations in corresponding mRNAs. In the aged cohort, hippocampal GFAP mRNA, Mn-SOD mRNA, and beta APP emerged as predictors of behavioral impairment, suggesting the involvement of these hippocampal systems in age-related cognitive impairment.

Aging↗
PubMed1996

Molecular cloning and disease association of hepatitis G virus: a transfusion-transmissible agent.

An RNA virus, designated hepatitis G virus (HGV), was identified from the plasma of a patient with chronic hepatitis. Extension from an immunoreactive complementary DNA clone yielded the entire genome (9392 nucleotides) encoding a polyprotein of 2873 amino acids. The virus is closely related to GB virus C (GBV-C) and distantly related to hepatitis C virus, GBV-A, and GBV-B. HGV was associated with acute and chronic hepatitis. Persistent viremia was detected for up to 9 years in patients with hepatitis. The virus is transfusion-transmissible. It has a global distribution and is present within the volunteer blood donor population in the United States.

Acute Disease↗