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Biomedical subjects

A Wennberg

Publications and source records attributed to A Wennberg.

At least 91 records · Page 5Linked to original sources
PubMed1977

In vitro study of cellular influence on 45Ca uptake in developing rat enamel.

The in vitro method for culture of molar teeth from eight-day-old rats, as reported in this study, appeared to sustain reasonably normal activity in the cells of the enamel organ and pulp through culture periods of four to eight hours. Inhibition of metabolic activity in the explants by addition of 5 mM iodoacetate or 2,4-dinitrophenol to the culture medium, or by heating at 70 C for 10 minutes, did not appear to affect the intensity or pattern of 45Ca uptake in the more advanced, rapidly mineralizing areas of the enamel. Neither did stripping of the enamel organ from the surface of the enamel have a demonstrable effect in those areas. However, metabolic inhibition with 2,4-dinitrophenol, heat killing or stripping of the enamel organ resulted in increased 45Ca uptake in newly formed enamel adjacent to the secreting ameloblasts. It is hypothesized that calcium flux into newly formed enamel matrix is controlled, in part, by movement of the calcium, which diffuses between the ameloblasts toward the enamel surface, away from the enamel through the ameloblasts.

Ameloblasts↗
PubMed1977

Operative treatment of ulnar nerve neuropathy in the elbow region. A clinical and electrophysiological study.

Thirty-three patients with ulnar nerve neuropathy due to a lesion in the ulnar groove were operated upon during a 5-year period. All the patients were analyzed preoperatively. One-third of the patients had a history of alcohol abuse. Twenty-five of the patients were subjected to anterior transposition of the ulnar nerve. The results after transposition have been compiled according to etiology, duration, age and alcohol abuse. All seven patients with only subjective symptoms improved; 11 out of 18 (61 per cent) with motor and/or sensory loss also improved but only six (33 per cent) recovered completely. Overall, 21 patients (84 per cent) were improved by the operation. In 11 of the transposition cases the ulnar nerve was examined electrophysiologically before and after operation and an improvement of the motor conduction velocity within the elbow segment of the nerve was found in 10 cases.

Adolescent↗
PubMed1976

Visible and non-visible EEG changes demonstrated by spectral parameter analysis.

A change of the heart rate in patients with complete AV-block and externally controllable cardiac pace-makers was earlier shown to influence cerebral function, as measured by psychological tests. To determine whether this influence manifests itself in the EEG, 9 patients aged 43-83 years were examined, all having complete AV-block and externally controllable pace-makers. Their EEGs were recorded at different heart rates between 40 and 100/min at rest and during a mental arithmatic test. The EEG record was evaluated visually and analysed by means of Spectral Parameter Analysis (SPA), introduced by Zetterberg (1969). The changes in the spectral parameters in relation to the heart rates were analysed statistically, In several cases significant changes appeared but the interindividual variations were large. Certain typical patterns could, however, be observed and their importance as a measure of cerebral function due to changes in the cerebral blood flow are discussed. These EEG changes revealed through SPA did not correspond to any visually observable changes in the EEG records. Differences in the spectral parameters between rest and test situations were analysed. Some of the differences found could easily be observed by visual inspection of the EEG. The advantage with SPA was that the changes could be described both qualitatively and quantitavely because SPA separates the spectral properties of the signals into components corresponding to well-known components of the EEG signal.

Adult↗
PubMed1976

An in vitro method for toxicity evaluation of water-soluble substances.

The purpose of the present investigation was to develop a simple method for the evaluation of reversible and irreversible toxic influences in a cell culture system. A cell monolayer established on the bottom of glass scintillation vials was exposed to a toxic substance (phenol). Changes in the DNA synthesis of the cells were utilized as a criterion of toxic influence, and were measured by recording the incorporation of tritium labelled thymidine using a liquid scintillation technique. The exposure of the cells to phenol caused a marked decrease in the rate of DNA synthesis when the phenol concentration was increased from 0.01 to 0.1%. The decrease in the DNA synthesis could be reversed by maintaining the cells in growth medium for 4 hours after the cell-phenol contact. The degree of reversibility was dependent on the cell-phenol contact time, the phenol concentration, and the cell line used. The simple test procedures and the quick and convenient obtainment of results simplify the assay of large test series and make the method particularly useful for screening tests.

Cell Count↗
PubMed1976

Biologic tests of a proposed pulp capping agent (Reocap).

A calcium hydroxide-containing cement (Reocap) was tested with regard to its suitability as a pulp capping agent. The pulp of 34 monkey teeth was exposed and Reocap was applied to the pulp wound and the cavity floor, after which the cavities were filled with amalgam. The observation periods were 8 days (10 teeth) and 80 days (24 teeth). After 8 days a necrotic area was seen in the pulp subjacent to the pulp capping agent and the surrounding tissue was inflamed to varying degree. After 80 days hard tissue formation was observed at the exposure site in 21 teeth. The hard tissue enclosed areas of necrotic and/or vital tissue and a complete bridge had not formed. In 7 teeth the pulp was necrotic whereas 3 teeth presented a pulp free of inflammation. In the remaining teeth the pulp showed a chronic inflammatory reaction. As judged by these results, Reocap does not appear to be as well suited as a pulp capping agent as pure calcium hydroxide.

Animals↗
PubMed1975

An EEG simulator-a means of objective clinical interpretation of EEG.

In 1969 Zetterberg presented a method for describing the spectral properties of an EEG signal, starting from the assumption that the signal is essentially stationary during the analysis epoch. The method involves determination of the parameters for a model consisting of a lenear filter with the ability to produce a signal with the same spectral properties as the EEG signal. Zetterberg and Ahlin described in 1975 an analogue simulator based on this model theory. With this simulator it is possible to reproduce practically all types of stationary, as well as a number of non-stationary, EEG signals. We have used this simulator to demonstrate in an illustrative manner the relation between the properties of a signal in the spectral domain and in the time domain. We have also endeavoured to anser the question: if one starts from the frequency spectrum, what does the EEG signal corresponding to this spectrum look like? We also draw attention to the usefulness of the simulator in connection with training and as an instrument for testing computer and other systems of EEG analysis.

Computers↗
PubMed1975

Visual evaluation and computer analysis of the EEG--a comparison.

Spectral parameter analysis (SPA) of the EEG provides a description of the distribution of spectral power in the EEG signal in the form of a rational spectrum with not more than 8 parameters. The spectrum is divided into 1-3 components described by frequency and power parameters: bandwidth (delta), peak frequency (f) and power (G). These spectral parameters are determined with the aid of a computer. The character of the EEG signal decides whether 1, 2 or 3 components (delta, alpha, beta) are needed to describe the spectrum. To test its practical value, the result of SPA was compared with that of ordinary visual evaluation of the EEG of 65 healthy men between the ages of 18 and 22 years. 20 sec sections from different leads were analysed and evaluated visually. Each EEG section was graded according to the amount of visually evaluated slow activity (VESA). To investigate the relation between the degree of VESA and the SPA result, statistical calculations (variance and regression analyses) were carried out, both for single SPA parameters and for the general type of spectrum, i.e., the number of components composing the spectrum. The SPA results from sections with artefacts were treated separately and compared statistically with results from artefact-free sections. In records with a high degree of VESA, all the leads analysed showed a tendency to have a power spectrum of low order, i.e., with few components. In most leads there was a linear regression between the degree of VESA and the bandwidth and power of the delta and alpha components. In several cases this relation was an expression of a significant linear change of the SPA parameter as a function of the degree of VESA. On the other hand the parameters of the beta component showed no relation to the degree of VESA. It was found that muscle activity could influence any spectral component thereby providing it with a strongly increased bandwidth. This is probably due to the fact that muscle activity resembles white noise in this particular frequency range. Low frequency artefacts affected only the delta component the bandwidth of which was significantly smaller than in the artefact-free sections.

Adolescent↗