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Biomedical subjects

L Green

Publications and source records attributed to L Green.

At least 199 records · Page 11Linked to original sources
PubMed1988

Information on response requirements compared with information on food density as a reinforcer of observing in pigeons.

On a variable-interval schedule, pecking the key to the pigeon's right (observing response) produced red or green displays relating to the delivery of grain and its dependence on pecking the key to the left (food key). During various blocks of sessions, mixed (no stimulus change) schedules including the following pairs of components were temporarily converted by the observing response to their corresponding multiple (correlated stimuli) schedules: variable-interval 60-s, extinction; variable-interval 60-s, variable-time (response-independent) 60-s; extinction, variable-time 60-s. Differences in food delivery maintained substantial rates of responding on the observing key, without regard to pecking requirements on the food key. Although stimuli correlated with differences in the response requirement on the food key maintained higher observing rates than those maintained by uncorrelated stimuli, they were much lower than those based on food. The value of predictive stimuli as reinforcers is determined by the value of the events predicted. In particular, the cost of pecking appears to be low, and this may place limitations on the applicability of energy-based and economic models of behavior.

Journal Article↗
PubMed1988

Is there a decisive test between matching and maximizing?

Reinforcers under typical concurrent variable-interval, variable-ratio schedules may be (a) earned and obtained during the variable-interval component, (b) earned and obtained during the variable-ratio component, or (c) earned during the variable-ratio component and obtained during the variable-interval component. Categories a and b, which have no bearing on matching versus maximizing accounts of choice, were set at zero. The rate of Category c reinforcers and the duration of a changeover delay were varied. Simple matching, which predicts exclusive choice of the variable-interval component, and strict maximizing of overall reinforcement rate, which predicts a bias towards the variable-ratio component, were both disconfirmed: Subjects spent approximately 25% of their time in the variable-ratio component, contrary to the matching prediction, but earned only about one third of the reinforcers predicted by strict maximizing. However, maximizing describes the findings functionally in terms of discounting of delayed reinforcers; matching may describe the data in terms of a restructuring of the alternatives. Matching and maximizing are not competing theories about the fundamental nature of choice, but compatible points of view that may reveal environmental function and behavioral structure.

Journal Article↗
PubMed1988

Maternal language environment of children with mental retardation.

Maternal language directed towards children with mental retardation and children matched either for language ability or chronological age was compared in free-play and instruction situations. Results were consistent with the hypothesis that mothers of children with retardation match their verbal behavior to their children's language ability while at the same time adopting a more pervasive teaching role. Specifically, they were more directive, but only in free-play. When explicitly asked to instruct their child, they changed very little in comparison with control mothers, whose directive behavior altered to levels previously adopted in free-play by mothers of children with mental retardation.

Child Language↗
PubMed1988

Severe reversible interstitial pneumonitis induced by low dose methotrexate: report of a case and review of the literature.

A patient treated with 7.5 mg methotrexate/week (MTX) for rheumatoid arthritis (total dose 300 mg) developed high fever, dry cough and progressive dyspnea and hypoxemia due to a severe interstitial pneumonitis. MTX was discontinued and an infectious etiology was ruled out by cultures, serology and lung biopsy. Corticosteroids administered intravenously in high dose led to a dramatic improvement and a complete amelioration of all symptoms and signs. Pulmonary toxicity is a rare adverse effect of low dose MTX therapy and a review of the literature reveals 6 additional cases. Since MTX induced pneumonitis is a potentially fatal, yet completely reversible, disease, attention should be paid to even mild early respiratory symptoms in patients treated with low dose MTX and patient monitoring should include pulmonary function tests.

Adrenal Cortex Hormones↗
PubMed1988

Evaluation of two acute cardiac ischemia decision-support tools in a rural family practice.

This study investigated the applicability in a primary care setting of two decision-support tools for evaluating the necessity of admitting patients with suspected acute cardiac ischemic disease to a cardiac intensive care unit. The heart disease predictive instrument (HDPI) of Pozen et al and the electrocardiogram scoring method of Brush et al were applied to records from all patients with cardiac-related diagnoses admitted to a family practice service. A retrospective review of medical records of all patients admitted with suspected acute ischemic heart disease to a rural community hospital family practice service was conducted. Of 147 patients identified, 108 were admitted primarily for suspected ischemia. Twenty-four myocardial infarctions occurred among these 108 patients (22.2 percent). Patients with HDPI probabilities of less than 50 percent were very unlikely to sustain infarction and in no case required intensive intervention for any problem not apparent at admission. Only 15 instances of the four types of complications that the instrument of Brush et al is designed to predict occurred; this incidence was too low to allow statistical testing. In summary, the heart disease predictive instrument reliably identified patients unlikely to require intensive care services in this population. Because of the low incidence of complications in this population, the instrument described by Brush et al was not found to be clinically useful.

Adult↗
PubMed1987

What happens to opiate addicts immediately after treatment: a prospective follow up study.

In the first British study to investigate systematically what happens to opiate addicts after treatment 50 opiate addicts admitted for inpatient treatment of their drug dependence were followed up for six months after discharge. All had been withdrawn from opiates before follow up. Six months later 26 were not using opiates: 12 had not used opiates at any time since discharge. When subjects in hospital or in prison were excluded from the analysis 21 (47%) of the subjects living in the community were not taking opiates. Many subjects used opiates within days of leaving the inpatient unit, but this first lapse did not necessarily lead to a full relapse into addictive use. During the six months after discharge several subjects used opiates on a less than daily basis. During each two month period throughout the six months of follow up the proportion of subjects who were occasional users fell, the proportion of abstinent subjects grew, and the proportion of daily users (assumed to be readdicted) remained constant. Although many of the addicts relapsed soon after treatment, it was encouraging that almost half were opiate free after six months. These results have important implications for the treatment of drug addicts.

Adolescent↗
PubMed1987

A rat histone H4 gene closely associated with the testis-specific H1t gene.

A rat histone H4 gene closely associated with the testis-specific H1t gene was isolated by screening the Sargent-Bonner rat genomic library using cloned human histone genes as probes. Both the H4 gene and the H1t gene are located on a 7-kb EcoRI genomic DNA fragment. Although the deduced amino acid sequence of the rat H4 histone is identical to that of the sequence of human histone H4, the nucleotide sequence of the coding region differs significantly from the coding region of the human H4 gene. Moreover, the relative spacing between the 5'-consensus sequence elements is unique for an H4 gene. S1-nuclease protection analyses reveal that both the H4 and H1t mRNA species are present in a fraction of rat testis cells highly enriched in pachytene spermatocytes, while only the H4 mRNA species is present in a rat myeloma cell line (Y3-Ag1.2.3). During a 1-h hydroxyurea treatment of the Y3 cells, which produces a 99% inhibition of DNA synthesis, the level of this H4 mRNA drops by only 50%, indicating that the stability of this mRNA is only partially coupled with DNA synthesis.

Amino Acid Sequence↗
PubMed1987

Effects of medial frontal cortex lesions on DRL performance in rats.

Rats with medial frontal cortical lesions (MFC) and control animals with sham operations were tested on an ascending series of 8 DRL schedules of reinforcement ranging from 5 to 70 seconds. Rats with MFC lesions did not differ from the control group in performance when response rate, responses per reinforcement and efficiency were analyzed. These results indicate that deficits in "response inhibition" often displayed by rats with MFC lesions may be task-specific.

Animals↗
PubMed1987

Distribution and abundance of insertion sequences among natural isolates of Escherichia coli.

A reference collection of 71 natural isolates of Escherichia coli (the ECOR collection) has been studied with respect to the distribution and abundance of transposable insertion sequences using DNA hybridization. The data include 1173 occurrences of six unrelated insertion sequences (IS1, IS2, IS3, IS4, IS5 and IS30). The number of insertion elements per strain, and the sizes of DNA restriction fragments containing them, is highly variable and can be used to discriminate even among closely related strains. The occurrence and abundance of pairs of unrelated insertion sequences are apparently statistically independent, but significant correlations result from stratifications in the reference collection. However, there is a highly significant positive association among the insertion sequences considered in the aggregate. Nine branching process models, which differ in assumptions regarding the regulation of transposition and the effect of copy number on fitness, have been evaluated with regard to their fit of the observed distributions. No single model fits all copy number distributions. The best models incorporate no regulation of transposition and a moderate to strong decrease in fitness with increasing copy number for IS1 and IS5, strong regulation of transposition and a negligible to weak decrease in fitness with increasing copy number for IS3, and less than strong regulation of transposition for IS2, IS4 and IS30.

Base Sequence↗
PubMed1987

Using the emergency department as a screening site for high blood pressure. A method for improving hypertension detection and appropriate referral.

This study describes the development and testing of a high blood pressure protocol for use in emergency departments (ED) to enhance detection of those patients appropriate for subsequent referral. The protocol involves two serial blood pressure measurements and a patient interview to determine: 1) previous history of high blood pressure (HBP), 2) treatment in past year for HBP, and 3) usual source of medical care. The accuracy of patient reporting was validated by comparison with the patients' hospital record (reflecting outpatient and inpatient visits). Results indicate that these self-reports have high levels of sensitivity (range 90-100%) and specificity (range 79-96%). Use of the additional patient information increased the sensitivity of the screening protocol in identifying when and where a patient should be referred. Use of this methodology indicates that the protocol is a simple and effective method for HBP screening. The findings also suggest that the ED is an ideal site for screening the "hard-to-reach" hypertensive population.

Adult↗