Biomedical subjects

J Renner

Publications and source records attributed to J Renner.

7 recordsLinked to original sources

PubMed1992

Cigarette smoking and cognitive performance.

While some investigations into the relationship between smoking and cognitive performance have reported that smoking facilitates performance, other research has come to the opposite conclusion. A review of the literature suggests that this variance in results may be due to differences among studies in design (comparing smokers only with deprived smokers rather than with non-smokers) and also to differences in task demands. Therefore, performance of smokers having just smoked, matched smokers deprived for a brief period, and also non-smokers was contrasted on a series of tasks which ranged from repetitive and perceptually-bound tasks to complex, dynamic tasks dependent upon long-term memory. It was found that while cigarette smoking had no negative effect upon performance for simple perceptual tasks, smoking was found to exert measurable negative effects upon performance for more complex information processing tasks.

Adult↗

PubMed1992

[Quantitative analysis of lamina III pyramidal neurons in the parietal cortex of newborns].

The stage of neuronal development in the parietal (postcentral) cortex of human newborns was studied quantitatively in postmortem cases of different gestational (37th or 40th week) and postnatal age (2 hours or 3 weeks). In GOLGI-impregnated tissue obtained by autopsy, layer III pyramidal neurons were investigated. Comparatively, data were collected about dendrite parameters such as dendritic branching, length and spine density. The spine distribution (number and density) at the apical main dendrite, the apical tuft dendrites and in single basal dendritic fields as well, typically for the human layer III pyramidal neuron at the end of the gestational period, is described. Dendritic parameters from basal dendritic fields were compared in the three cases investigated (37th week with 2 hours or with 19 days of survival; 40th week of gestation with 2 days of survival). The large increase in spine number and density, especially in the second and higher orders of dendritic branching was obvious in the 19 days old infant brain. Special pathological aspects of the cases influencing the neuronal development are discussed. By means of a computerized method, quantitative data characterizing the human lamina III pyramidal neuron at the end of gestation are provided.

Cerebral Cortex↗

PubMed1991

Validity of digital subtraction of transcranial plain films in quantification of positional changes of the mandibular condyle.

Condylar positioning problems have been associated with temporomandibular joint signs and symptoms. The position of the mandibular condyle is difficult to predict and quantify with existing routinely used radiographic techniques. An investigation was implemented to test the validity and reliability of digital subtraction to enhance transcranial plain films and to quantify positional changes of the condyle in a laboratory model. The model consisted of a mounted dried human skull and a mandibular condyle attached to a micromanipulator. Controlled changes in condylar position were made, and the condyle and fossa were imaged. The data were analyzed with descriptive statistics, analyses of variance to evaluate the sources of variability, and linear contrasts to evaluate the differences between observed and expected values. The results indicated that digital subtraction detected posterior positional change within 10% of the expected value. However, inferior positional changes were poorly detected and lateral positional changes could not be evaluated by this technique. We conclude that digitally subtracted transcranial radiographs may be useful for detection of posterior condylar movements, assuming that appropriate head-holding devices are used to fix x-ray source and head geometry.

Analysis of Variance↗

PubMed1991

Modification of high-heeled shoes to decrease pronation during gait.

One of the reasons that high heels may contribute to the formation of halux valgus is that the wearers pronate during propulsion. This pilot study was performed to determine whether relocation of the heel under the counter of a fashion high-heeled pump could change the degree of pronation of the foot during the gait cycle. The authors report that more foot stability was experienced by the subjects when the center of the heel was offset between 2 and 4 mm medial to the center of the heel counter. This study is designed to promote further research into whether the shoe industry should change the design parameters of high-heeled fashion shoes in order to improve foot function.

Adult↗

PubMed1989

Total-body protein turnover in parenterally fed neonates: effects of energy source studied by using [15N]glycine and [1-13C]leucine.

The effects of nonprotein energy source (ie, glucose only vs glucose and lipid) on nitrogen retention and total-body protein turnover were studied in 20 parenterally fed newborn infants. All infants received approximately 3 g amino acids and 80-90 kcal.kg body wt.d. Total-body protein synthesis was estimated by using three constant-infusion, end-product methods: enrichment of urinary urea and ammonia in response to a [15N]glycine label and exhaled carbon dioxide enrichment in response to a [1-13C]leucine label. No differences were seen in nitrogen retention between the two energy sources. The estimate of total-body protein turnover obtained from the 13C label was similar to that obtained with the [15N]urea label. No differences in turnover rates were observed between the two diet groups. Use of the glucose-plus-lipid fuel system enhanced energy storage and the reutilization of amino acid for protein synthesis.

Ammonia↗

PubMed1989

A comparison of the estimates of whole-body protein turnover in parenterally fed neonates obtained using three different end products.

Protein turnover rates in neonates have been calculated largely by measuring urinary [15N]urea enrichment following administration of [15N]glycine. Although ammonia has been increasingly recognized as an end product of nitrogen metabolism, in neonates it yields a different estimate of protein turnover than does urea. Comparisons of ammonia and urea end products in parenterally fed neonates have not previously been reported. A third and independent way of estimating protein turnover, developed for adults, is to use breath 13CO2 as an end product following administration of [1-13C]leucine. We therefore carried out simultaneous measurements of protein turnover in 10 parenterally fed neonates, using the three end products. The infants were clinically stable, weighed 2.6 +/- 0.2 kg, and received 3.1 +/- 0.2 g.kg-1.d-1 of amino acid, 2.2 +/- 0.1 g.kg-1.d-1 of lipids, and an energy intake of 90 +/- 4 kcal.kg-1.d-1 (1 kcal = 4.186 kJ). The turnover estimates derived from the 13CO2 and [15N]urea end products were very similar. The [15N]ammonia end product produced values approximately 66% (p less than 0.01) of the other two. We conclude that the ammonia and urea end products probably originate in different precursor pools. The similarity of the urea and breath carbon dioxide results helps validate the use of the urea end product in studying the nitrogen metabolism of parenterally fed neonates. Ideally in future studies two or more end products should be used, since they provide information about different aspects of the neonates' protein metabolism.

Amino Acids↗

PubMedDate not supplied

Functional abnormalities of monocytes/macrophages in HIV1-infected patients as demonstrated by the skin window procedure.

Skin window (SW) tests were performed in ten HIV1-infected patients and in ten healthy volunteers. The chemotaxis of monocytes/macrophages is weakened in AIDS patients, since the number of monocytes/macrophages attracted by the SW stimulus decreases in HIV1-infected subjects during the observation time, whereas the number increases in control individuals. HLA-DR expression decreases faster in AIDS patients than in healthy volunteers. Giant cell formation occurs and disappears earlier in HIV1-infected patients than in healthy control individuals. The results suggest that, at least in part, the impairment of chemotaxis and other functional abnormalities of mononuclear phagocytes are caused by their accelerated aging in HIV1-infected patients.

Acquired Immunodeficiency Syndrome↗