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Biomedical subjects

S Kemper

Publications and source records attributed to S Kemper.

12 recordsLinked to original sources
PubMed1992

Adults' reading comprehension: effects of syntactic complexity and working memory.

Two experiments investigated the relationship between working memory and reading comprehension. In the first, college students, 18 to 26 years of age, and adults, 60 to 92 years of age, were given a battery of tests of working memory, a standard timed reading comprehension test, and a reading test designed to explore how syntactic complexity affects comprehension. In a follow-up study, the adults were retested on a modified version of the syntax comprehension text. Age group declines in working memory and reading comprehension were obtained in Experiment I; age group declines in reading rate but not comprehension were obtained in Experiment II. The results suggest that working memory limitations affect elderly adults' ability to process complex syntactic constructions, lowering comprehension in the timed test (Experiment I) and reducing reading rates in the untimed test (Experiment II).

Adolescent↗
PubMed1991

Syntactic complexity and adults' running memory span.

This study investigated age group differences in adults' running memory span for prose. College students and adults 60 to 94 years of age listened to a prose passage that was interrupted occasionally by pauses. At each pause, the adults attempted to recall the immediately preceding text. The pauses followed either two single-clause sentences, a two-clause right-branching sentence, or a two-clause left-branching sentence. There was a significant Age Group x Syntactic Form x Clause Order interaction such that the age group differences in verbatim recall were exacerbated by the effects of syntactic complexity. The elderly recalled 25% fewer words from the first embedded clause of the left-branching sentences than the college students, whereas they recalled only 4% fewer words from the first of two successive single-clause sentences. Performance on the running memory span task was also correlated with two measures of the adults' working memory: forward digit span and backward digit span. The pattern of correlations indicated that working memory limitations determine adults' running memory span for prose and contribute to age-group deficits in comprehension.

Adolescent↗
PubMed1990

Peroxidation-induced perturbations of erythrocyte lipid organization.

Peroxidation of erythrocyte membrane lipids by hydrogen peroxide perturbs the lipid bilayer and increases phagocytosis by macrophages. This study addresses the underlying mechanism of these processes, and in particular the role of malondialdehyde, a major byproduct of lipid peroxidation. When erythrocytes were treated with hydrogen peroxide or ascorbate/iron to generate malondialdehyde, or with malondialdehyde itself, only those cells treated with hydrogen peroxide showed increased phospholipid spacing and enhanced phagocytosis. This result indicates that the alterations observed are unique to hydrogen peroxide treatment, and that malondialdehyde does not play a role in inducing these changes in surface properties. Comparison of adherence to human umbilical vein endothelial cells and phagocytosis showed that increased phagocytosis was not mirrored by enhanced adherence. This result suggests that two different signals may mediate recognition of erythrocytes by macrophages and by endothelial cells.

Cell Adhesion↗
PubMed1990

Adults' word recall and word repetition.

This experiment investigated age group differences in working memory by examining the effects of word length on adults' recall span and repetition rate. College students and adults, 60 to 94 years of age, recalled lists of one-, two-, or three-syllable words and repeated aloud pairs of one-, two- or three-syllable words. Word recall spans and word repetition rates were computed. Main effects of age group and word length were obtained on both measures, although the interactions were not significant. A second analysis examined the relationship between individuals' recall span and their repetition rate. Across all age groups combined, recall span was a linear function of repetition rate and accounted for 25 percent of the variance on the recall task. A reanalysis of the word repetitions revealed that older adults' word durations and inter-word pauses are longer than young adults'.

Adult↗
PubMed1988

Organ blood flow haemodynamics and metabolism of the albacore tuna Thunnus alalunga (Bonnaterre).

Metabolic haemodynamic, and organ blood flow measurements were made in tabled, partially anaesthetized albacore Thunnus alalunga. Heart rates were 115 +/- 9 beats/min: blood pressure 98/75 mm Hg (systolic/diastolic): cardiac output 36.1 +/- 5 (ml/min/kg): oxygen consumption 3.4 +/- 0.7 (ml O2/min/kg) and cardiac contractility (dP/dt) 6342 +/- 822 mm Hg/s. Organ blood flows were measured with radiolabelled microspheres. The red muscle, kidney, and spleen received the highest flows and the white-muscle the least. There was a flow gradient in the white-muscle with the inner portion near the red-muscle receiving the highest flows. Arterial and venous blood gas measurements showed a reverse temperature effect on arterial PO2 and a P50 of 15.9 Torr corrected to 37 degrees C. Red-muscle temperature was 7 degrees C higher than ambient water temperature. These measurements record the albacore's markedly high cardiovascular capability.

Animals↗
PubMed1987

Life-span changes in syntactic complexity.

Adults' diaries were examined for age-related changes in syntactic complexity. The diaries in the longitudinal sample were kept by 8 adults, born between 1856 and 1876, for seven or more decades. The diaries in the cohort-sequential sample were kept by 10 adults born between 1820 and 1829 and recorded during 1860 to 1869 or during 1900 to 1909 and 10 adults born between 1860 and 1869 and recorded during 1900 to 1909 and again in 1940 to 1949. Sentences from the two longest, usable entries from each half-decade were analyzed. The analysis determined the incidence of left- and right-branching embeddings and of coordinate and subordinate phrases and sentence fragments as well as the mean length of sentences in words and in clauses. The analysis revealed an age-related decline in the syntactic complexity of adults' sentences.

Adult↗
PubMed1970

Endo-N-acetyl-glucosaminidase from Clostridium perfringens, lytic for cell wall murein of gram-negative bacteria.

An endo-N-acetyl-glucosaminidase which degrades the murein (peptidoglycan) sacculi of the cell walls of Escherichia coli and Spirillum serpens, but not those of Micrococcus lysodeikticus and Sarcina lutea, is present as a contaminant in a "phospholipase C" from Clostridium perfringens. The specificity of enzyme action was elucidated by reduction of liberated glycosidic groups with NaBH(4) and identification of glucosaminol as the reduction product. This finding contradicts previous reports associating cell wall breakdown with specific phospholipase action.

Acyltransferases↗
PubMedDate not supplied

Syntactic complexity and elderly adults' prose recall.

Elderly adults in their 70s and 80s and middle-aged adults in their 40s and 50s recalled a series of paragraphs made up of single-clause sentences and sentences with right-branching or left-branching embedded or subordinate clauses. Overall, the middle-aged adults recalled 65% of the propositions regardless of syntactic form. While the elderly adults recalled 43% of the propositions from the single-clause sentences, they recalled 60% of the propositions from the right-branching clauses but only 22% of the propositions from the left-branching clauses. These results, in conjunction with prior research on elderly adults' production and imitation of complex syntactic constructions, demonstrate age-related changes in syntactic processing.

Adult↗