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Biomedical subjects

R Dunn

Publications and source records attributed to R Dunn.

At least 109 records · Page 6Linked to original sources
PubMed1990

Suboptimal choice in a percentage-reinforcement procedure: effects of signal condition and terminal-link length.

Pigeons' choice between reliable (100%) and unreliable (50%) reinforcement was studied using a concurrent-chains procedure. Initial links were fixed-ratio 1 schedules, and terminal links were equal fixed-time schedules. The duration of the terminal links was varied across conditions. The terminal link on the reliable side always ended in food; the terminal link on the unreliable side ended with food 50% of the time and otherwise with blackout. Different stimuli present during the 50% terminal links signaled food or blackout outcomes under signaled conditions but were uncorrelated with outcomes under unsignaled conditions. In signaled conditions, most pigeons displayed a nearly exclusive preference for the 100% alternative when terminal links were short (5 or 10 s), but with terminal links of 30 s or longer, preference for the 100% alternative was sharply reduced (often to below .5). In unsignaled conditions, most pigeons showed extreme preference for the 100% alternative with either short (5 s) or longer (30 s) terminal links. Thus, pigeons' choice between reliable and unreliable reinforcement is influenced by both the signal conditions on the unreliable alternative and the duration of the terminal-link delay. With a long delay and signaled outcomes, many pigeons display a suboptimal tendency to choose the unreliable side.

Animals↗
PubMed1990

Managed care: quality management differentiates the product.

Comprehensive quality management is a goal that requires major corporate commitment to implement and maintain. The best results in a quality management program will be achieved when all components are tied together in a comprehensive program. To do that, a significant investment in personnel and equipment is required. As the benefits of having a program such as the one as described above become more widely known and accepted, more and more managed care insurers and providers will adopt these or similar standards. The question, "How do you know that patients are getting high-quality and sufficient care?" cannot be answered today by insurers who do not have such a program.

Consumer Behavior↗
PubMed1990

125I-insulin binding to circulating erythrocytes, monocytes and cultured fibroblasts in non-obese patients with polycystic ovarian disease.

The insulin receptor status of circulating erythrocytes, monocytes and cultured fibroblasts were studied in non-obese Indian women with polycystic ovarian disease (PCOD) with no clinical evidence of acanthosis nigricans and age, height and weight matched reference subjects. The women with polycystic ovaries had decreased mean maximum specific binding to erythrocytes (PCOD 7.4 +/- 0.6%, normal women 11.5 +/- 0.3%; p less than 0.0001) and monocytes (PCOD 2.4 +/- 0.3%, normal women 4.1 +/- 0.4%; p less than 0.003) when compared to the normal women. This decreased binding was attributed to a change in both receptor number and affinity. 125I-insulin binding to cultured fibroblasts revealed similar mean maximum specific binding and affinity values in both groups studied. Although further work is necessary to exclude genetic or post-receptor defects, it is likely that an environmental factor is implicated in the decreased 125I-insulin binding to erythrocytes and monocytes.

Adult↗
PubMed1989

Pedigree analysis of aryl hydrocarbon hydroxylase inducibility in acute leukemia of childhood.

We determined lymphocyte aryl hydrocarbon hydroxylase (AHH) inducibility for members of 13 families with one or more children with acute lymphoblastic leukemia (ALL) and 12 control families. Pedigree analysis suggested that aromatic hydrocarbon responsiveness (i.e. inducibility) is a codominant trait. Heterozygotes were found to be moderately responsive with IR values intermediate between homozygous minimally responsive and homozygous highly responsive individuals. Homozygous recessive and heterozygous genotypes accounted for 54% and 36% of ALL children respectively. The risk of ALL among minimally aromatic hydrocarbon responsive children was twice that of highly responsive children.

Aryl Hydrocarbon Hydroxylases↗
PubMed1987

[Differential diagnosis of a hemorrhagic-necrotizing epiploic appendix].

In a 52 year old pyknic patient in whom very violent pain had suddenly occurred in the left lower abdomen, an acute hemorrhagic infarction of an epiploic appendix of the sigmoid colon with adhesion to the anterior abdominal wall was found to be the cause of the symptoms. A hernia, above all a hernia of the semilunar line of Spigelius, an inflammatory process and a granuloma had to be considered in the differential diagnosis.

Abdomen, Acute↗
PubMed1987

Reduction in S100 protein beta subunit mRNA in C6 rat glioma cells following treatment with anti-microtubular drugs.

S100 protein is a calcium-binding protein found in vertebrate nervous tissue. Synthesis of S100 protein in the rat glioma cell line, C6, is inhibited by the addition of anti-microtubular drugs. We have cloned a cDNA for the beta subunit of S100 protein from rat brain in a lambda gt 11 expression vector and used this cDNA to measure the amounts of S100 beta subunit mRNA in C6 cells after treatment with anti-microtubular drugs. Levels of alpha-tubulin and beta-actin mRNAs were also measured. All measurements were performed using RNA-RNA hybridization techniques at high stringency with rat mRNA-specific probes. After 24 h of treatment, the S100 beta subunit mRNA was reduced to levels of 25% by colchicine and 32% by vinblastine when compared to untreated controls. In contrast, the levels of tubulin and actin mRNAs were only slightly changed by these treatments. These studies demonstrate that disruption of the microtubular cytoskeleton causes a specific reduction in the level of S100 protein mRNA in C6 cells.

Amino Acid Sequence↗
PubMed1987

The myelin-associated glycoprotein gene: mapping to human chromosome 19 and mouse chromosome 7 and expression in quivering mice.

Myelin-associated glycoprotein (MAG), a membrane glycoprotein of 100 kDa, is thought to be involved in the process of myelination. A cDNA encoding the amino-terminal half of rat MAG has recently been isolated and sequenced. We have used this cDNA in Southern blot analysis of DNA from 32 somatic cell hybrids to assign the human locus for MAG to chromosome 19 and the mouse locus to chromosome 7. Since the region of mouse chromosome 7-known to contain several other genes that are homologous to genes on human chromosome 19-also carries the quivering (qv) locus, we considered the possibility that a mutation in the MAG gene could be responsible for this neurological disorder. While MAG-specific DNA restriction fragments, mRNA, and protein from qv/qv mice were apparently normal in size and abundance, we have not ruled out the possibility that qv could be caused by a point mutation in the MAG gene.

Animals↗
PubMed1987

Molecular cloning and primary structure of myelin-associated glycoprotein.

Myelin-associated glycoprotein (MAG) may play a role in the cellular interactions leading to myelination. Using monoclonal antibodies and conventional antisera against MAG, we have isolated a cDNA clone from an expression library prepared from rat brain mRNA. The identity of the clone was confirmed by the exact match between its nucleotide sequence and two peptide sequences of 13 and 9 amino acids that we obtained by Edman degradation of two CNBr fragments of MAG. The cDNA clone hybridized to two size species of mRNA in rat approximately 3.5 kilobases in length. These mRNAs were present in brain but not liver and were expressed most abundantly at the time of active myelination (day 14). The mRNA for MAG was present at barely detectable levels in hypomyelinating jimpy mice compared to normal littermate controls. Therefore the MAG cDNA clone is both brain and myelin specific. DNA sequence analysis revealed that our MAG cDNA was derived from the same mRNA as clone p1B236, a randomly selected, brain-specific, partial cDNA isolated by Sutcliffe et al. [Sutcliffe, J. G., Milner, R. J., Shinnick, T. M. & Bloom, F. E. (1983) Cell 33, 671-682]. Analysis of the predicted protein sequence suggests that MAG has a long extracellular domain (499 amino acids), followed by a short transmembrane segment (20 amino acids) and an intracellular carboxyl-terminal domain (90 amino acids). The molecule has several glycosylation sites, three internal repeats homologous to a repeat in the neural cell adhesion molecule (N-CAM), and sites for phosphorylation near the carboxyl terminus. The primary structure reported here provides a molecular framework for further investigations into the function of the MAG molecule.

Amino Acid Sequence↗
PubMed1987

Tissue-specific expression of the RI and RII sodium channel subtypes.

Anti-peptide antibodies that distinguish between the rat brain sodium channel subtypes referred to as RI and RII were prepared and used to determine their relative expression in nerve and muscle tissues. Sodium channels purified from rat brain are approximately 18% RI and 80% RII. In brain, the RII subtype is preferentially expressed with RI/RII ratios ranging from 0.07 in the hippocampus to 0.17 in the cerebral cortex. The RI subtype is preferentially expressed in more caudal areas of the central nervous system with values of RI/RII of 0.98 for medulla oblongata and 2.2 for spinal cord. Expression of additional unidentified sodium channel subtype(s) is detected in midbrain, medulla, and spinal cord, and expression of unidentified sodium channel subtypes predominates over expression of RI and RII in retina and optic nerve. The RI and RII subtypes are primarily expressed in the central nervous system and are not detected in significant numbers in skeletal or cardiac muscle, sympathetic ganglia, adrenal medulla, sciatic nerve, or cauda equina. The RII subtype appears first in development of both brain and spinal cord but declines in adult spinal cord as the RI subtype increases. The strict regional expression of these two sodium channel subtypes suggests that they may have distinct functional properties or physiological roles.

Animals↗
PubMed1987

Comparison of the MCMI and MMPI-168 as psychiatric inpatient screening inventories.

The Millon Clinical Multiaxial Inventory (MCMI) has been recently developed as an alternative to the Minnesota Multiphasic Personality Inventory (MMPI) and shares some of its psychometric advantages and disadvantages with the MMPI-168, a short form of the MMPI. The current study compared the structure and utility of the MCMI and MMPI-168 for a general hospital inpatient psychiatric population. Overall, the two instruments were highly correlated and found to have conceptually similar factor structures. Empirical comparison of the factor structures indicated that construct validity is greatest for neurotic traits. Both instruments demonstrated a similar utility in predicting discharge diagnosis.

Adolescent↗
PubMed1987

Choice between reliable and unreliable outcomes: mixed percentage-reinforcement in concurrent chains.

Pigeons' choices between alternatives that provided different percentages of reinforcement in mixed schedules were studied using the concurrent-chains procedure. In Experiment 1, the alternatives were terminal-link schedules that were equal in delay and magnitude of reinforcement, but that provided different percentages of reinforcement, with one schedule providing, reinforcement twice as reliably as the other. All pigeons preferred the more reliable schedule, and their level of preference was not systematically affected by variation in the absolute percentage values, or in the magnitude of reinforcement. In Experiment 2, preference for a schedule providing 100% reinforcement over one providing 33% reinforcement increased systematically with increases in the duration of the terminal links. In contrast, preference decreased systematically with increases in the duration of the initial links. Experiment 3 examined choice with equal percentages of reinforcement but unequal delays to reinforcement. Preference for the shorter delay to reinforcement was not systematically affected by variation in the absolute percentage of reinforcement. The overall pattern of results supported predictions based on an extension of the delay-reduction hypothesis to choice procedures involving mixed schedules of percentage reinforcement.

Animals↗
PubMed1987

Devaluation of stimuli contingent on choice: evidence for conditioned reinforcement.

Pigeons were presented a concurrent-chains schedule of reinforcement that had terminal links of equal duration. The initial links of the schedule were periodically interrupted by 15-s periods during which an extinction schedule was in effect. The extinction periods were presented on either a response-contingent or a noncontingent basis. Relative response rate for the left alternative decreased when the extinction periods were accompanied by the left terminal-link stimulus. Relative response rate for the right alternative decreased when the extinction periods were accompanied by the right terminal-link stimulus. Relative response rate varied inversely with the frequency of presentation of the extinction periods but was unaffected by presence versus absence of the response contingency in the schedule of extinction-period presentation. Furthermore, relative response rate was unaffected by presentation of extinction periods accompanied by a novel stimulus. When the extinction periods were presented after reinforcement in the left terminal link instead of as interruptions of the initial links, relative response rate for the left alternative was reduced if the postreinforcement extinction period was accompanied by the terminal-link stimulus for the left chain and reduced less if the extinction period was accompanied by the terminal-link stimulus for the right chain. The results demonstrate that the correlation between the terminal-link stimulus and extinction influenced the relative response rate in the initial link.

Animals↗
PubMed1986

Evaluation by computerized axial tomography of eclamptic women with seizures refractory to magnesium sulfate therapy.

Over a 1-year period, seven eclamptic patients with repetitive seizures while receiving therapeutic levels of intravenous magnesium sulfate were evaluated by computerized axial tomography. In five patients brain abnormalities were identified, which included diffuse cerebral edema (one), cerebral venous thrombosis (two), and low density white matter (two). Clinical management of eclamptic women on the basis of structural central nervous system abnormalities documented by computerized tomography appears to warrant further investigation.

Adolescent↗
PubMed1986

Messenger RNA coding for only the alpha subunit of the rat brain Na channel is sufficient for expression of functional channels in Xenopus oocytes.

Several cDNA clones coding for the high molecular weight (alpha) subunit of the voltage-sensitive Na channel have been selected by immunoscreening a rat brain cDNA library constructed in the expression vector lambda gt11. As will be reported elsewhere, the amino acid sequence translated from the DNA sequence shows considerable homology to that reported for the Electrophorus electricus electroplax Na channel. Several of the cDNA inserts hybridized with a low-abundance 9-kilobase RNA species from rat brain, muscle, and heart. Sucrose-gradient fractionation of rat brain poly(A) RNA yielded a high molecular weight fraction containing this mRNA, which resulted in functional Na channels when injected into oocytes. This fraction contained undetectable amounts of low molecular weight RNA. The high molecular weight Na channel RNA was selected from rat brain poly(A) RNA by hybridization to a single-strand antisense cDNA clone. Translation of this RNA in Xenopus oocytes resulted in the appearance of tetrodotoxin-sensitive voltage-sensitive Na channels in the oocyte membrane. These results demonstrate that mRNA encoding the alpha subunit of the rat brain Na channel, in the absence of any beta-subunit mRNA, is sufficient for translation to give functional channels in oocytes.

Animals↗
PubMed1985

Use of peritoneal lavage to evaluate abdominal penetration.

A retrospective study was undertaken to evaluate peritoneal lavage in detecting abdominal penetration. Two hundred thirty-five patients with thoracoabdominal, flank, or tangential abdominal gunshot wounds were lavaged. Of these patients, 44 (18.7%) had positive lavages, defined as red blood cell counts greater than 10,000 cells/mm3, white blood cell counts greater than 500 cells/mm3, or the presence of bile, feces, or vegetable matter. There were 13.6% false positives and 1.0% false negatives, with an overall accuracy of 96.6%. The results were unaffected by mechanism or site of injury. If the criteria were changed to include red blood cell counts greater than 100,000 cells/mm3, there would have been no false positives, but an unacceptably high 11.1% false negative rate. Therefore we conclude that peritoneal lavage can be a reliable indicator of abdominal penetration provided sufficiently sensitive criteria are used. These criteria should include red blood cell counts greater than 10,000 cells/mm3 instead of 100,000 cells/mm3.

Abdominal Injuries↗