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C Ryan

Publications and source records attributed to C Ryan.

At least 73 records · Page 4Linked to original sources
PubMed1994

Cue conflict and stereoscopic surface slant about horizontal and vertical axes.

The way in which a planar surface is defined or configured may affect its apparent slant about a given axis, and the magnitude of slant-axis anisotropies. The authors have previously suggested that (i) these within-axis and between-axis configuration effects may be attributable, in part at least, to the perspective-disparity conflict generated when geometrically frontoparallel configured surfaces are slanted stereoscopically; and (ii) that implicit contours, defined by line endings or conjunctions, may have effects analogous to those seen with explicit contours. These possibilities were directly examined in two experiments. In experiment 1, slant-axis anisotropy was progressively induced by adding horizontal lines to a vertical-line (zero anisotropy) grid under conditions of cue conflict; slants about the vertical (but not the horizontal) were attenuated-demonstrating a clear and systematic nexus between surface configuration and slant-axis anisotropy. The presence of regular implicit horizontals similarly and selectively attenuated the slant perceived about the vertical. In experiment 2, cue conflict was seen to exacerbate slant-axis anisotropy, but clearly could not fully account for it. There was an axis asymmetry in the effect of degrading implicit contours: degradation had a marked impact on perceived slant about the horizontal but not the vertical axis.

Adult↗
PubMed1994

Verbal intellectual and verbal memory performance of youths with childhood-onset insulin-dependent diabetes mellitus.

Tested the hypothesis that memory dysfunction mediated the decline in verbal intellectual performance (as measured by the WISC-R Vocabulary test) that we detected previously in a prospective study of children who developed IDDM between the ages of 8 to 13 years. Three tests of verbal learning and memory were administered to 57 diabetic youths at end-of-study who had been followed for 8 years, on average. Memory performance at end-of-study was predicted only by Vocabulary test score at study entry. IDDM duration, long-term metabolic control, depression/anxiety, demographic variables, or blood glucose level at the time of assessment were not associated with memory test scores. Stepwise multiple regression revealed that level of performance on a test of short-term or working memory was associated with magnitude of decline in verbal intellectual performance over time, providing partial support for our hypothesis.

Age of Onset↗
PubMed1994

Preclinical findings with new antipsychotic agents: what makes them atypical?

Many early antipsychotics such as haloperidol, while effective in treating the symptoms of schizophrenia, cause detrimental side effects and moreover induce nonspecific sedation in many patients. Newer drugs such as remoxipride are as effective as the classical antipsychotics but induce fewer debilitating side effects. These clinical properties are reflected to some extent in their preclinical pharmacology, with drugs such as remoxipride having effects on various preclinical behavioural and biochemical models that are quite different to those exerted by drugs such as haloperidol. This article reports some new behavioural data and discusses the various mechanisms that can underlie the effect of new atypical antipsychotics.

Animals↗
PubMed1994

Muscle glyconeogenesis during recovery from a prolonged swim in rats.

Glyconeogenesis in muscle was assessed during a 3-h recovery period after prolonged submaximal exercise represented by a 4-h swim. Rats fasted for 12 h and previously catheterized underwent this protocol with the concomitant infusion of [6-3H]glucose and one of the following: 1) [14C]bicarbonate, 2) [U-14C]lactate, and 3) [1-14C]glucose. Rested rats served as controls. The incorporation of 14C label ([14C]bicarbonate and [U-14C]lactate) or its transfer to the sixth position of glucosyl units of glycogen, over and above that taken up from circulating glucose (and determined from [6-3H]glucose uptake), was used as an index of muscle glyconeogenesis. 14C from 14CO2 is not expected to be incorporated into glycogen in muscle, and any incorporation that is not from circulating glucose is used to define experimental error. [14C]lactate incorporation measures equilibration with circulating lactate, and label randomization in glucosyl units beyond that seen in plasma glucose is taken as evidence of glyconeogenesis from locally accumulated glycolytic products. The results of these studies demonstrate 1) no glyconeogenesis in the soleus; 2) in the red and white gastrocnemii, glyconeogenesis takes place only from glycolytic products within the muscle. Approximately 35-40% of the [6-14C]glucose in glycogen can only be accounted for by muscle glyconeogenesis. The substrate does not equilibrate with circulating lactate to a detectable extent. 3) Glyconeogenesis appears to persist throughout the recovery period and uses substrate at the level of pyruvate. This is consistent with a continuing elevation of glycolysis during this period.

Animals↗
PubMed1994

A pilot syringe exchange program in Washington, DC.

The Washington, DC City Council authorized a pilot syringe exchange program to operate for only 60 days at a single drug abuse treatment facility in the District. Only adults on the waiting list for treatment were eligible (n = 467). Of the 33 who enrolled, median duration of drug injection was 18 years. Twenty-seven participants denied needle sharing. Of 209 needles distributed, 69% were returned. Low enrollment might have been due to restrictive entry criteria, inconvenient location, incorrect syringe size, and attitudes of treatment staff. For future efforts to have a public health impact, wider accessibility will be needed.

Adult↗
PubMed1994

Hypoglycemia unawareness in IDDM.

OBJECTIVE: To assess the characteristics of patients with hypoglycemia unawareness (development of neuroglycopenia without appropriate prior autonomic warning symptoms) and its predisposing factors. RESEARCH DESIGN AND METHODS: We studied 43 insulin-dependent diabetes mellitus patients who were objectively categorized as having or not having hypoglycemia using the stepped hypoglycemic clamp technique in which plasma glucose was clamped at plateaus of 4.3, 3.6, 3.0, and 2.3 mmol/l and a statistical criterion (onset of autonomic warning symptoms at a plasma glucose concentration 2 SD below normal) and examined their clinical characteristics and hormonal, symptomatic, and cognitive responses. RESULTS: Eleven (26%) of the patients were classified as having hypoglycemia unawareness. Compared with the other patients, unaware patients had a lower HbA1c level (P < 0.01), a longer duration of diabetes (P < 0.01), and a history of more severe hypoglycemia (P < 0.003). During experimental hypoglycemia, counterregulatory hormone responses, neuroglycopenic symptoms, and cognitive dysfunction all began at lower plasma glucose concentrations in unaware patients (P < 0.01, 0.03, and 0.01, respectively). Moreover, although the magnitudes of their plasma catecholamine responses and autonomic symptoms were reduced (both, P < 0.01), the plasma catecholamine levels at which autonomic symptoms began was not altered. Finally, as seen from glucose infusion rates necessary to maintain identical plasma glucose levels, patients with hypoglycemia unawareness had increased sensitivity to insulin (P < 0.001). CONCLUSIONS: Our results confirm an association between hypoglycemia unawareness and duration of diabetes, glycemic control, and occurrence of severe hypoglycemia, and in addition provide evidence that both autonomic and neuroglycopenic symptoms are affected and that insulin sensitivity is increased, but beta-adrenergic sensitivity is not diminished.

Adult↗
PubMed1994

Parasuicide.

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Attitude of Health Personnel↗
PubMed1993

Digital supine bicycle stress echocardiography: a new technique for evaluating coronary artery disease.

OBJECTIVES: The objective of this study was to determine the accuracy of digital supine bicycle stress echocardiography, a new technique for evaluating coronary artery disease during peak exercise. BACKGROUND: Prior stress echocardiographic techniques have not utilized peak exercise imaging to determine the extent and location of coronary artery disease. METHODS: Two-hundred twenty-two patients were studied: 180 underwent both supine bicycle stress echocardiography and coronary arteriography; 42 had a < 5% likelihood of disease. Forty-three patients had normal coronary arteries, 55 had single-vessel, 42 had double-vessel and 40 had triple-vessel coronary artery disease. RESULTS: Supine bicycle stress echocardiography was 93% sensitive, 86% specific and 92% accurate for identifying patients with coronary artery disease irrespective of prior myocardial infarction or achievement of > or = 85% maximal predicted heart rate. The "normalcy" rate in the low probability group was 100%. Supine bicycle stress echocardiography was 87% sensitive, 89% specific and 88% accurate for specific vessel identification. The sensitivity was greatest for the left anterior descending compared with the right coronary artery and the left circumflex coronary artery (95% vs. 81% vs. 78%, p < 0.01) and for vessels in patients with double- and triple-vessel compared with single-vessel disease (90% vs. 89% vs. 78%, p < 0.05). The procedure was significantly more sensitive for detection of vessels with 90% to 100% compared with 50% to 70% diameter stenosis (91% vs. 81%, p < 0.05) and was 88% correct in the prediction of multivessel disease. CONCLUSIONS: Supine bicycle stress echocardiography is a highly accurate tool for evaluating coronary artery disease, identifying both the patient with coronary artery disease and the location and extent of disease.

Adult↗
PubMed1993

Usefulness of supine bicycle stress echocardiography for detection of restenosis after percutaneous transluminal coronary angioplasty.

The role of supine bicycle stress echocardiography (SBSE) for detecting restenosis after percutaneous transluminal coronary angioplasty (PTCA) was evaluated in 80 patients: 41 (51%) with single and 39 (49%) with multivessel PTCA (total 129 dilated vessels). Total revascularization was performed in 54 (68%) and partial revascularization in 26 (32%) patients. Restenosis was angiographically demonstrated in 60 patients (75%) and in 72 vessels (56%) 6.1 +/- 2.9 months after PTCA. The results for detecting restenosis were: (1) SBSE versus exercise electrocardiographic sensitivity, 87 versus 55% (p < 0.001); (2) specificity, 95 versus 79%; and (3) accuracy, 89 versus 61% (p < 0.001). SBSE was 83% sensitive, 95% specific and 88% accurate for restenosis detection in specific vessels with comparable results for single versus multivessel PTCA and total versus partial revascularization. Sensitivity, specificity and accuracy were: 91, 93 and 91% for the left anterior descending coronary artery; 77, 94 and 85% for the right coronary artery; and 76, 96 and 88% for the left circumflex coronary artery. Ninety-four percent of the nondilated diseased vessels were correctly identified. It is concluded that SBSE is an excellent tool for identifying restenosis after PTCA.

Aged↗
PubMed1993

Memory performance during the Amytal test in patients with non-temporal lobe epilepsy.

PROBLEM: The amobarbital (Amytal) sodium test has been considered an indispensable tool in the presurgical examination of patients for epilepsy surgery. However, the accuracy of the Amytal test for predicting memory deficits, especially the amnestic syndrome, has been questioned. METHOD: The Amytal test was administered bilaterally to three groups of patients with epilepsy: temporal lobe (n = 76), frontal lobe (n = 25), and primary generalized (n = 8). Each injected hemisphere for each patient was graded pass or fail for its ability to support memory. RESULTS: The percentages of hemispheres that failed the Amytal test were 31% for the temporal lobe group, 32% for the frontal lobe group, and 56% for the primary generalized group. CONCLUSIONS: The Amytal test may be a sensitive measure of memory dysfunction. However, the high percentage of failures remains at variance with the rare incidence of the amnestic syndrome, suggesting a low specificity for this test.

Adolescent↗
PubMed1993

Heat shock protein is a unique marker of growth arrest during macrophage differentiation of HL-60 cells.

Prior to morphologic and functional maturation, terminally differentiating hematopoietic cells first exit the cell cycle and undergo growth arrest. Relatively little is known about which molecules regulate differentiation-induced growth arrest. In the present report, we sought to determine whether the mammalian low molecular weight heat shock protein (hsp28) was a candidate growth-regulatory molecule during human hematopoiesis. To this end, hsp28 protein expression was examined during phorbol ester (PMA)-induced macrophage differentiation of the human HL-60 promyelocytic leukemic cell line. Whereas hsp28 was constitutively expressed at relatively low levels in an unphosphorylated state, hsp28 was rapidly phosphorylated within 4 hr following PMA-induced differentiation, preceding increased hsp28 protein levels at 24-48 h. In contrast to other differentiative agents, hsp28 steady state mRNA and protein were regulated concordantly in response to macrophage differentiation. More importantly, these changes were transient, and occurred concomitant with the down-regulation of cellular proliferation and the onset of G1 phase cell cycle arrest. In total, these observations implicate hsp28 as an intermediary in the myelomonocytic differentiative pathway of promyelocytic leukemic cells, and will shed light on the events regulating this process.

Biomarkers↗
PubMed1993

An in-frame insertion into the Sindbis virus 6K gene leads to defective proteolytic processing of the virus glycoproteins, a trans-dominant negative inhibition of normal virus formation, and interference in virus shut off of host-cell protein synthesis.

Encoded in the genomes of all alphaviruses is a hydrophobic polypeptide of 55 amino acids, which is post-translationally modified with 4 covalently bound palmitic acids. This protein, noted as 6K, associates with membranes and is transported along with the two virus transmembranal glycoproteins to the site of virus assembly at the infected cell's plasma membrane. Previous studies showed that mutations in the 6K protein led to the slow release of aberrant, multi-cored infectious virions. In this paper, we report that an in-frame insertion of 45 nucleotides into an internal site of the 6K gene of Sindbis virus produced single-cored infectious particles at about 5% the yield of wild-type virus when the mutant was grown on avian, mammalian, and insect cells. Although the 15 amino acids were inserted at position 29 of the 55-amino-acid 6K protein, the mutation interfered with the cotranslational proteolytic processing that cleaves the 6K at its amino terminus from the Sindbis virus p62 glycoprotein and at its carboxyl terminus from the E1 glycoprotein. As a result, the amounts of normal p62 and E1 proteins were only half that made in cells infected with wild-type virus. In addition, the post-translational proteolytic conversion of p62 to E2 occurred at 10% the rate of wild-type proteins and the extensive fatty acylation normally detected on wild-type 6K protein was not found on the altered 6K protein. None of the mutated 6K protein was detected in virions, which were morphologically indistinguishable from wild-type virus. The mutant 6K virions also were similar to wild type in their rate of attachment, uncoating, and formation of an early nonstructural virus protein in avian cells. When compared with the wild-type virus, 6K29-infected cells exhibited a decreased rate of host-cell protein synthesis shut off. However, the rates of virus capsid synthesis were the same, indicating that capsid protein, per se, is not involved in shut off of host-cell protein synthesis. In complementation studies, this mutant exhibited a trans-dominant phenotype. These data provide clues about the topology of 6K protein in the membrane and its function in virus maturation.

Amino Acid Sequence↗
PubMed1993

Coronary rotational ablation: initial experience in 302 procedures.

OBJECTIVES: The aim of this study was to assess the utility of percutaneous transluminal coronary rotational ablation in the treatment of coronary artery disease. BACKGROUND: Although numerous advances have been made in the treatment of coronary artery disease, there are lesions with complex morphology that are not amenable to current intravascular therapy. METHODS: A consecutive series of 242 patients having 302 coronary rotational ablation procedures was analyzed. One hundred nineteen (49%) of the patients had previously undergone attempted coronary angioplasty, which was unsuccessful in 31 patients (13%). The left ventricular ejection fraction was normal in 196 patients (81%). The ablation procedure was attempted in 308 vessels and 346 lesions. Of the 346 lesions treated, 26 (7.5%) were classified as American College of Cardiology/American Heart Association type A, and 320 (92.5%) as either type B or type C. RESULTS: Procedural success was achieved in 284 (94%) of the 302 procedures and 330 (95.4%) of the 346 lesions in which ablation was attempted. Five procedures (1.7%) were unsuccessful, but no cardiac event occurred during the hospital stay. A major cardiac event occurred in 13 cases (4.3%); 9 (3%) of these complications were due to the ablation procedure. Six patients sustained a Q wave myocardial infarction alone, two had a Q wave infarction and required emergency surgery and one needed emergency surgery but did not have a Q wave infarction. No procedural deaths were attributed to the ablation procedure. Follow-up has been obtained in 182 of the 242 patients at a mean interval of 9 +/- 5 months. Of the 182 patients, 174 (95.6%) were alive and free of myocardial infarction. Angiographic follow-up is available thus far in 87 patients. By combining angiographic and clinical outcome, an overall estimated restenosis rate of 37.4% (68 of 182) was calculated. CONCLUSIONS: These data suggest that coronary rotational ablation can be performed on lesions with a variety of morphologic features with high initial success rates. The overall rate of restenosis is similar to that of balloon angioplasty.

Angioplasty, Balloon, Coronary↗
PubMed1993

A proximity-contingent stereoscopic depth aftereffect: evidence for adaptation to disparity gradients.

Prolonged inspection of a surface slanted in the third dimension of visual space typically results in a negative aftereffect such that, after adaptation, a surface in the fronto-parallel plane will appear slanted in the opposite direction. Binocular disparity is not necessary to generate such effects, since they can be obtained monocularly, presumably via adaptation to texture gradient. Six experiments demonstrated durable stereoscopic depth aftereffects in the absence of a texture gradient--by using discrete disparate objects rather than slanted surfaces--and demonstrated that adaptation was to the interobject disparity gradient rather than to the relative disparity of the objects per se. The disparity required to null the obtained aftereffects was inversely proportional to the horizontal separation of elements, for a constant disparity, and directly proportional to the separation of subsequently presented probes. When elements differed in depth (disparity), but were not laterally separated, nulling disparity was significant but invariant with changes in the horizontal separation of probe elements. In that case, adaptation was (i) either to the disparity gradient generated by the vertical separation of probe elements (of which the relative disparity component was tapped); or (ii) to relative disparity per se.

Adult↗
PubMed1993

Glucose dynamics and gluconeogenesis during and after prolonged swimming in rats.

Glucose fluxes and, in particular, gluconeogenic rate were examined during and after prolonged submaximal exercise represented by a 4-h swim and 3-h recovery in 12-h-fasted previously catheterized rats. The metabolic clearance rate and production rate of glucose were measured using an infusion of [6-3H]glucose, and gluconeogenesis was assessed from the incorporation of 14C from [14C]bicarbonate into glucose. Immediately after exercise and after the 3-h recovery, liver glycogen was also determined. During exercise, euglycemia was maintained while glucose production and utilization doubled from 1.58 +/- 0.17 to 3.58 +/- 0.21 mg/min. During recovery, glucose concentrations increased to 131.0 +/- 5.8 vs. 110.8 +/- 5.1 mg/dl for controls (P < 0.05), because the decline in glucose production rate lagged behind the decline in metabolic clearance rate. The index of gluconeogenesis coupled with a metabolic correction factor indicates that gluconeogenesis was the primary source of glucose during swimming and recovery and that the principal substrates were at the level of pyruvate. CO2 production rates calculated using plasma CO2 and label concentrations doubled during exercise. Little repletion of liver glycogen was seen after exercise, indicating that the increased production of glucose after exercise is directed primarily toward the repletion of muscle glycogen. Swimming is therefore a useful model of low-intensity exercise easily implemented in untrained animals. [14C]bicarbonate can be used in the estimation of gluconeogenic rates during exercise.

Animals↗
PubMed1993

Influence of plasma glucose rate of decrease on hierarchy of responses to hypoglycemia.

To test the hypothesis that the rate of decrease in plasma glucose concentration may affect the hierarchy of responses to hypoglycemia, we compared plasma couterregulatory hormone concentrations, autonomic and neuroglycopenic symptom scores, and cognitive function test performance in 10 normal volunteers whose plasma glucose concentration was either rapidly (over 30 min) decreased to 3.7 mmol (66 mg/dL) or was slowly decreased in a stepwise manner to plateaus of 4.3 mmol (78 mg/dL), 3.7 mmol (66 mg/dL), 3.0 mmol (54 mg/dL), and 2.3 mmol (42 mg/dL). Comparable plasma counterregulatory hormone concentrations and autonomic symptom scores were observed in both sets of experiments during the 3.7 mmol (66 mg/dL) plateaus. In the stepwise decrement experiments, significant increases in neuroglycopenic symptom scores and deterioration in cognitive performance occurred only during the last glycemic plateau (2.3 mmol, 42 mg/dL). In the rapid decrement experiments, no increase in neuroglycopenic symptom score or deterioration in cognitive performance was observed during the 3.7 mmol (66 mg/dL) plateau. We, therefore, conclude that in normal volunteers the rate of decrease in plasma glucose concentration does not affect the hierarchy of responses to hypoglycemia.

Adult↗