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Biomedical subjects

D McCall

Publications and source records attributed to D McCall.

At least 19 recordsLinked to original sources
PubMed2001

Training agrammatic subjects on passive sentences: implications for syntactic deficit theories.

We trained two subjects with chronic agrammatic aphasia on production of passive sentences using a computerized, iconic-based communication system. After training, one of the subjects demonstrated significant improvements in his abilities to comprehend and verbally produce English passive voiced sentences, including sentences with conjoined subjects and objects. These results suggest that agrammatism does not represent a fixed syntactic deficit.

Aged↗
PubMed2001

Comparison of major and trace element concentrations in Danish greenhouse tomatoes (Lycopersicon esculentum Cv. Aromata F1) cultivated in different substrates.

The concentration of major and trace elements was determined for tomato (Lycopersicon esculentumcv. Aromata F1) fruits grown in three different substrate systems. The systems were soil and rockwool irrigated with a normal nutrient solution and rockwool irrigated with a nutrient solution with elevated electrical conductivity (EC). At three harvest times, tomato fruits were analyzed for Ca, Cu, Fe, K, Mg, Mn, Na, P, S, Sr, and Zn by ICP-AES and for Cd, Cr, Mo, Ni, Pb, Sn, and V by HR-ICPMS. The concentrations of Ca, Cd, Fe, Mn, Mo, Na, Ni, Sr, and Zn were significantly different (p < 0.05) for tomato fruits grown on the different substrates. Between the harvest times different levels (p < 0.05) were shown for Ca, Cd, Fe, Mn Na, Ni, Sr, Zn Cu, K, Mg, P, Sn, and V. The concentration of Cd was >15 times higher and the concentration of Ca was 50-115% higher in soil-grown fruits than in rockwool-grown fruits. Principal component analysis applied on each harvest split the data into two groups. One group includes soil-grown fruits, and the other group includes rockwool-grown fruits with the two different nutrient solutions.

Solanum lycopersicum↗
PubMed2001

Individuals with cystic fibrosis do not display impaired endothelial function or evidence of oxidative damage in endothelial cells exposed to serum.

Heightened systemic oxidative stress is increasingly recognized as a feature of cystic fibrosis (CF). The consequences of long-term exposure to free radical attack include a predisposition to diseases such as cancer and atherosclerosis. An increased incidence of malignancy among adult patients with CF has been reported, but the absence of atherosclerotic disease is well described. The aim of the present study was to assess endothelial function in vivo and relate this to the potential of serum from patients with CF to induce oxidative-mediated damage in cultured human endothelial cells. A group of 11 CF patients was matched with a group of healthy volunteers with regard to age and sex. Endothelial function was assessed as endothelium-dependent and -independent vasodilation by measuring forearm blood flow in response to infused acetylcholine and sodium nitroprusside respectively. Confluent monolayers of cultured human endothelial cells were exposed to serum from CF patients and control subjects. Following exposure, cell death was assessed by lactate dehydrogenase release, and the degree of lipid peroxidation in the membrane was assessed by measuring the content of lipid hydroperoxides, malondialdehyde and 4-hydroxynonenal. Endothelial monolayers exposed to serum from CF patients released significantly less lactate dehydrogenase following exposure than those exposed to serum from healthy controls (1.8% and 3.0% respectively; mean difference -1.2%; 95% confidence intervals -1.9% to -0.1%; P<0.05) and contained significantly less 4-hydroxynonenal (0.75 and 3.41 micromol/g of protein respectively; mean difference -2.66 micromol/g; 95% confidence intervals -5.10 to -0.22 micromol/g; P<0.05). There was no significant difference between patients and controls in the extent of serum-induced membrane peroxidation, as assessed by malondialdehyde or lipid hydroperoxides, or in endothelial function, as assessed by forearm blood flow. In conclusion, despite evidence for heightened systemic oxidative stress in CF, patients displayed no impairment of endothelial function, and their serum caused significantly less damage to human endothelial cells than that from matched controls.

Adolescent↗
PubMed1999

Representation of linguistic rules in the brain: evidence from training an aphasic patient to produce past tense verb morphology.

We trained a patient with expressive aphasia and a deficit in phoneme-to-grapheme conversion to produce spoken English verbs with correct tense morphology. After training, he showed evidence of generalization to production of written regular, but not irregular, verbs in a sentence completion task. These data support dual-route, rule-based models within the brain for morphosyntactic operations.

Aged↗
PubMed1998

A multistakeholder-driven model for developing an outcome management system.

Increasing demands for accountability in the delivery of public mental health services are engendering organized systems of treatment outcome monitoring. As such systems are designed and implemented, it is critical that key stakeholders be involved to the greatest extent possible in developing assessment instruments and methodologies so as to ensure relevance and acceptability of the outcome management system. A multistakeholder-based initiative for developing standardized outcome assessment for public mental health services in Virginia is described. Key components of the initiative include the process by which stakeholders were enlisted, the identification of recommended assessment instruments, and a pilot project that began the evaluation of the feasibility, utility, and cost-benefit of using the instruments. To illustrate features of this initiative, the child/adolescent mental health pilot project is described in detail. Implications for behavioral health administrators and next steps for Virginia's outcome management system are discussed, highlighting the role of key stakeholders.

Adolescent↗
PubMed1997

Generalization from single sentence to multisentence production in severely aphasic patients.

Multisentence production was examined in three nonfluent aphasic patients who had undergone a single sentence production training program using a computerized visual communication system (C-VIC). Patients were required to describe videotaped vignettes in English and using C-VIC. C-VIC allowed for an investigation of production abilities previously impossible to measure in severely aphasic patients, since C-VIC does not require internal generation of appropriate lexical items or phonological and articulatory realization. Results are discussed in the context of language production models in an attempt to determine the breakdown(s) in the production system that result in difficulty in trying to produce multiple sentences.

Adult↗
PubMed1997

Remediating production of tense morphology improves verb retrieval in chronic aphasia.

Production of tense markers in C-VIC, a computerized visual communication system, was utilized as a treatment for three patients with severe expressive aphasia. Patients practiced constructing C-VIC tense marked sentences and then producing English equivalents. After training, all patients demonstrated significant improvements in English verb retrieval and production of correct tense morphology. Generalization of morphological rules for past tense production was seen for regular, but not irregular verbs. These results support the LaPointe and Dell (1989) extension of the Garrett (1975, 1992) model specifying a search through so-called verb phrase notion stores as a process mediating transition from functional to positional levels, but also suggest an additional constraint on the output of the verb notion store search.

Adult↗
PubMed1995

Thematic role assignment in two severely aphasic patients: associations and dissociations.

Two severely aphasic patients were compared in their abilities to comprehend and produce locative prepositional phrases and reversible S-V-O sentences using English and C-VIC, a computer-based iconographic communication system. One patient demonstrated a significant dissociation between his performance in interpreting symbol order in C-VIC prepositional phrases vs. S-V-O sentences. Patients were able to comprehend order in C-VIC S-V-O sentences significantly better than they were able to assign symbol order when they produced these sentences. These data suggest that the procedures for assigning thematic roles to nouns in sentences are at least partially distinct for comprehension and production and that the ordering of nouns around prepositions involves conceptual processes distinct from those involved in ordering nouns around verbs.

Adult↗
PubMed1994

Listeners' expectations about echoes can raise or lower echo threshold.

Echo threshold increases with exposure to redundant trains of stimuli. Three experiments were conducted to test the hypothesis that a change in the ongoing train would affect listeners' perception of the echo, but only if it signified an unusual change in room acoustics. The stimulus train was composed of 4-ms narrow-band noise bursts, with the leading sound from a loudspeaker placed 45 degrees left of midline and the lagging sound or simulated echo from 45 degrees right, delivered in an anechoic chamber. The lagging sound in the test noise, which followed the train after a 750-ms pause, came randomly from loudspeakers at 35 degrees or 55 degrees right, and the listener's task was to choose which position the echo came from on each trial. In experiment 1 the delay between onsets of the leading and lagging bursts was varied between train and test bursts, which simulated a sudden movement of the reflecting surface either toward the listener (if the delay of the test burst was shorter than the train) or away (if the delay was longer). In both cases listeners detected the echo's direction more easily, compared to trials when there was no change between train and test burst delays. In order to check whether any change between train and test bursts would increase echo discriminability, experiment 2 varied frequency and experiment 3 varied intensity. These variations were not expected to affect the echo's detectability because such changes signify that the original sound changed in these characteristics and the echo reflected these changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1993

Locative prepositional phrases in severe aphasia.

Six severely aphasic patients were trained on C-VIC, a computerized alternative communication system. Patients with both global and Broca's aphasia were able to produce and comprehend locative prepositions using C-VIC. The Broca's aphasic patients were able to produce and interpret symbol order correctly in C-VIC locative prepositional phrases, despite their difficulties in performing the same tasks using English. One patient's verbal production of locative prepositional phrases improved markedly after C-VIC training. These results suggest that the "mapping" impairment suffered by some Broca's aphasics may be ameliorated by use of alternative communication system, such as C-VIC.

Aphasia↗
PubMed1992

Recognition and management of asymptomatic patients with left ventricular dysfunction.

In recent years there have been encouraging developments in the therapy for congestive heart failure. Vasodilator therapy, as an adjunct to digitalis and diuretics, has made a major impact. Vasodilator therapy results in improved left ventricular (LV) ejection fraction, improved functional capacity, and enhanced quality of life. When an angiotensin-converting enzyme (ACE) inhibitor is used, several studies published since 1988 show that these improvements are accompanied by improved survival. Yet many questions remain. Principal among these is how to approach the patient who has significantly depressed LV function, but is asymptomatic or has only minimal symptoms. In these patients the prognosis cannot be based on New York Heart Association (NYHA) functional class, but must reflect objective measurements of ventricular function. Any intervention should be specifically designed to improve survival, since functional capacity and quality of life are apparently unimpaired. On the other hand, there are no data at present to suggest that intervention in these patients will improve survival. This article considers the evaluation of such asymptomatic patients and potential therapeutic approaches. These are the use of cardiac glycosides, the use of ACE inhibitors, or their combination. Circumstantial evidence supporting their use in this select patient population is considered. It is stressed that any decision to intervene therapeutically in the asymptomatic patient must be made by the physician on an individual basis.

Digitalis Glycosides↗
PubMed1990

Effect of atriopeptin II on Ca influx, contractile behavior and cyclic nucleotide content of cultured neonatal rat myocardial cells.

The present study was carried out to evaluate the effects of biologically active atriopeptin II (APII) in synchronously contracting monolayer cultures of rat ventricular myocytes. The effects of 10 nM APII on Ca influx, contractile behavior and cyclic nucleotide content of the cells were measured. Applied acutely APII had no effect on Ca influx. There was however a time-dependent effect such that after 30 min Ca influx (pmol/cm2/s) had declined from a control (mean +/- S.E.M.) of 1.53 +/- 0.16 to 1.02 +/- 0.07 (P less than 0.001; n = 6). There was parallel decline in both the magnitude and velocity of cell edge motion which was maximal in 30 min at which time cell edge motion measured 65.3 +/- 4.4% of control. Treatment with APII for 30 min decreased cAMP (pmol/mg protein) from 5.35 +/- 0.17 to 2.86 +/- 0.24 (P less than 0.001; n = 5). At the same time cGMP (pmol/mg protein) increased from 0.86 +/- 0.21 to 2.14 +/- 0.33 (P less than 0.001; n = 5). Further studies elucidated the fact that the decline in Ca influx and contractile behavior was dependent on the decrease in cAMP rather than the increase in cGMP. Pre-treatment of the cells with 5 ng/ml of pertussis toxin to ADP-ribosylate the Gi protein abolished the effects of APII on cAMP, Ca influx and contractile behavior. The results indicate that in myocardial cells, as in other cells, APII stimulates guanylate cyclase and inhibits adenylate cyclase. The resultant fall in cAMP decreases Ca influx and negatively influences the contractile behavior of the cells.

Adenylyl Cyclase Inhibitors↗
PubMed1989

Ethanol effects on active Na+ and K+ transport in cultured fetal rat hepatocytes.

To define further the influence of ethanol on membranes, its effects on Na+ pump function were studied in monolayer cultures of fetal rat hepatocytes. The effects of ethanol (2 and 4 mg/ml) on total K+ influx, ouabain-sensitive K+ influx, Na+ pump density (from specific [3H]ouabain binding), pump turnover rates and intracellular Na+ were measured following exposure of the cells to ethanol for 1-24 hr. In parallel studies, the effects of ethanol (2 mg/ml) on cell water content and membrane fluidity were measured. Ethanol had no immediate effect on K+ influx, but after 1 hr ethanol in concentrations of 2 and 4 mg/ml decreased the total K+ influx (mumol/10(11) cells/sec) from a control of 8.5 +/- 0.64 to 4.46 +/- 0.50 and 4.09 +/- 0.26 respectively (N = 6 for each experiment; P less than 0.001). This represented the maximum effect of ethanol since after 6 and 24 hr of ethanol treatment the K+ influx had increased towards control levels but remained significantly (P less than 0.01 for 2 mg/ml and P less than 0.001 for 4 mg/ml) below that in control cells even at 24 hr. The decrease in K+ influx reflected a decrease in mean ouabain-sensitive K+ influx from a control of 5.87 to 3.24 and 2.70 (mumol/10(11) cells/sec) after a 1-hr treatment with 2 and 4 mg ethanol/ml medium respectively. Ethanol (2 mg/ml) treatment for 1-hr decreased Na+ pump density (x 10(5) molecules ouabain per cell) from a control of 2.80 +/- 0.30 to 1.70 +/- 0.11 (P less than 0.001). At 6 and 24 hr [3H]ouabain binding showed a pattern similar to that seen with the K+ influx, tending to return to pretreatment levels. There was no change in individual pump turnover rates in the presence of ethanol. Following exposure to ethanol, cellular Na+ content steadily increased over the first 6 hr and then returned to control levels. When corrected for parallel changes in cell volume, however, intracellular Na+ concentration increased by 17% (P less than 0.01) after 1 hr and thereafter remained at this higher level throughout the 24-hr period. Measurements of membrane fluidity showed that it was increased markedly by ethanol at a concentration of 2 mg/ml and that the effect bore a close temporal relationship to the changes in active K+ influx and Na+ pump density. We conclude that ethanol has a depressant effect on hepatic Na+ pump function, resulting in an increase in intracellular Na+ and an eventual gain in cell water.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

L-tryptophan.

Explore the source record for details and available documents.

Chronic Disease↗
PubMed1987

The effect of ethanol and acetaldehyde on Na pump function in cultured rat heart cells.

To further define the sarcolemmal effects of ethanol and acetaldehyde, their effects on Na pump function were studied in synchronously contracting monolayers of neonatal rat myocardial cells. The effects of ethanol (10 mg/dl to 1000 mg/dl: 2 X 10(-3) M-0.2 M) and acetaldehyde (10(-6) M to 10(-4) M) on total 42K influx, ouabain-sensitive 42K influx, Na pump density (from specific 3H-ouabain binding) and pump turnover rates were measured. Applied acutely ethanol had no effect on 42K influx but after 30 min of treatment 42K influx was decreased by 13%, 23% and 48% in 100 mg/dl, 300 mg/dl and 1000 mg/dl ethanol respectively. This primarily reflected a decrease in mean ouabain-sensitive K+ influx from a control of 12.54 to 9.90, 8.95 and 6.68 (p-mol/cm2/s) in 100, 300 and 1000 mg/dl (2 X 10(-2) M, 6 X 10(-2) M) ethanol. Acetaldehyde in the concentrations tested had no effect on K+ influx. Ethanol treatment produced a decrease in Na pump density, maximum within 30 min and dose-dependent, at concentrations of 100 mg/dl (22%), 300 mg/dl (37%) and 1000 mg/dl (55%). Acetaldehyde had no effect on Na pump density. In the presence of ethanol (300 mg/dl and 1000 mg/dl) intracellular Na+ increased significantly and the Na+ efflux declined in parallel with the K+ influx. From the ouabain-sensitive K+ and Na+ fluxes and the Na pump density individual pump turnover rates were calculated at 62.5/s in control cells and 66/s and 84/s in cells treated with 300 mg/dl (6 X 10(-2) M) and 1000 mg/dl (0.2 M) respectively. We conclude that ethanol, but not acetaldehyde has a depressant effect on sarcolemmal Na pump function. The results suggest this is due primarily to a decrease in the number of sarcolemmal Na pump sites.

Acetaldehyde↗
PubMed1987

Excitation-contraction coupling in cardiac and vascular smooth muscle: modification by calcium-entry blockade.

In recent years therapy with the calcium entry-blocking drugs nifedipine, verapamil, and diltiazem has made a major impact on the treatment of cardiovascular disease. Although all three of these drugs are approved for the treatment of angina pectoris, some are effective in treating supraventricular tachyarrhythmias and all appear to be effective in the treatment of mild-to-moderate hypertension. Reports of their therapeutic potential, however, are not confined to the cardiovascular system, which reflects the ubiquity of calcium ions as stimulus-effect couplers in a wide variety of organ systems. Although chemically heterogeneous, all three drugs produce similar negative inotropic effects in the myocardium and similar relaxant effects in vascular smooth muscle. From a review of the excitation-contraction coupling process in cardiac and smooth muscle it is apparent that "calcium blockade" could occur at any one of several loci. Our present understanding is that the effect of nifedipine, verapamil, and diltiazem is confined to an inhibitory one on channel-mediated membrane calcium influx. There is, in fact, a close parallel between their ability to decrease slow-channel calcium influx in the myocardium and the negative inotropic action of the drugs. Similarly, in vascular smooth muscle their ability to inhibit voltage- or receptor-mediated calcium influx parallels their vasorelaxant properties. With the use of radiolabeled ligands, particularly of the dihydropyridines (nifedipine, nitrendipine, nicardipine, nisoldipine) it has been shown that the drugs show high-affinity stereospecific binding to vascular smooth muscle channels in the same concentration range as their relaxant properties. In contrast, it was originally thought that myocardial binding was of a lower affinity and correlated poorly with the negative inotropic effect. More recent data, however, have cast some doubt on the validity of these observations. Attempts to define specific drug receptors are incomplete at this time. It appears that the dihydropyridine receptor is a 30-60 K D peptide subunit of the calcium channel. Distinct receptors for verapamil and diltiazem are poorly defined, but appear to be allosterically related to the dihydropyridine receptor. By their interactions with the calcium channel, the calcium entry-blocking drugs modulate excitation-contraction coupling, which produces their negative inotropic and vasorelaxant effects. They also interact with other slow channel-dependent functions in the specialized conducting tissues of the heart to slow the spontaneous sinus rate and decrease atrioventricular conduction.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗