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Biomedical subjects

M Walter

Publications and source records attributed to M Walter.

At least 253 records · Page 14Linked to original sources
PubMed1981

Psychophysical tuning functions for brief stimuli: preliminary report.

Observations from clinical and research applications of brain stem evoked response audiometry and electrocochleography have suggested that tone bursts of only a few milliseconds' duration can elicit frequency specific responses. Because such brief stimuli are not perceived as being total, the extent to which the auditory system can "tune" to such stimuli was questioned. In order to investigate this question, psychophysical tuning functions were determined for brief tone bursts (i.e., 1. to 2 msec. duration). The results suggest that in working near normal thresholds (and therefore at relatively low sound pressure levels), brief tone bursts do yield rather frequency specific information. However, the range of sound pressure levels of the stimulus for which the tuning is resonably sharp is limited. the tuning functions show signs of deterioration, particularly in the "tip region," with only modest increases in the sound pressure level above threshold (i.e., typically with 20 dB.). Differences also may be seen between tuning functions for these very brief tone bursts, which in turn are characterized by a so-called click pitch, and those of stimuli long enough to have tonal pitch (i.e., 20 msec.). Finally, tuning functions also were examined for click stimulation, which also revealed some degree of tuning at relatively low levels of stimulation.

Acoustic Stimulation↗
PubMed1981

Vitamin A effects on hepatic Golgi apparatus architecture.

Effects of dietary vitamin A deficiency and excess on Golgi apparatus architecture were determined for livers of male CDF rats. In deficient animals, Golgi apparatus stacks were reduced in diameter and characterized by small, often highly fenestrated, saccules. Total membrane surface occupied by Golgi apparatus membranes also was less. Golgi apparatus of livers of animals receiving vitamin A in excess were more variable ranging from nearly normal appearance to much larger than normal. Saccules were larger and lacked the numerous fenestrations shown by Gol;gi apparatus of vitamin A deficient animals. Numbers and appearance of secretory vesicles and total number of small vesicular profiles were unaffected by vitamin A status of the animal. Unusual cisternal configurations were encountered much more frequent at the mature face of Golgi apparatus of animals fed vitamin A excess than in animals receiving adequate vitamin A and were absent from Golgi apparatus of animals receiving no vitamin A. Except for slightly swollen mitochondria and a loss of the "zone of exclusion" surrounding the nucleus, both observed in vitamin A excess, the Golgi apparatus response was the only ultrastructural alteration in liver that responded consistently to changes in vitamin A status.

Acid Phosphatase↗
PubMed1981

Evaluation of ectodermal lesions in intravenous vaccinia infected mice as a method to investigate the antiviral activity of isatin beta-thiosemicarbazone derivative (TSK VI compound).

In this paper ectodermal lesions on the tails of mice inoculated intravenously with vaccinia virus were used to study the influence of N,N'-bis[methylisatin-beta-thiosemicarbazone]-2-methylpiperazine (TSKI VI) on the number and dynamics of lesion formations. The activity of this compound was compared to that of the antiviral drug, methisazone. The reduction in lesions after treatment with TSKI VI was similar to the reduction induced by methisazone, which, on the basis of earlier theroretical and experimental data as well as on the lower toxicity of TSKI VI for the tissues and a more favorable therapeutic index, makes this compound worth considering in the treatment of postvaccinal complications. This method proved very useful in examination of the substances having potential prophylactic properties in preventing generalized infections.

Animals↗
PubMed1979

Lymphomatoid granulomatosis in a renal transplant recipient.

Lymphomatoid granulomatosis is a multi-system disorder of high mortality and characterised by angiocentric and angiodestructive lymphoreticular proliferative and granulomatous change. A case is described of this disease occurring in a renal transplant patient. The patient underwent a rapid remission of the disease after a course of combined cytotoxic therapy and remains free of disease three years after treatment. This case is the second described renal transplant patient to develop the disease and the first to be successfully treated. It is likely that the disease originated as a consequence of immunosuppression similar to the development of lymphomas in allograft recipients.

Adult↗
PubMed1979

A data processing system for a group of three clinical chemistry laboratories. 1. Hardware and organisation.

A real time data processing system for a group of three clinical chemistry laboratories (one base and two satellite) has been developed as a successor to one used previously. This paper describes both the inadequacies of the previous worksheet-based system and the advantages of the new system, including flexibility, fast response and comprehensiveness, incorporating urgent routine and long delay (that is, endocrine) requests, and the use of a parallel flow work scheme.

Chemistry, Clinical↗
PubMed1979

[The mixing index in the argon breath holding test for the demonstration of pharmacologically induced airways reactions. A comparison with other methods (author's transl)].

In 42 patients with obstructive airways diseases the behavior of the mixing index (delta argon %/1 during phase III of the argon-volume diagram) was studied after beta2 stimulation or after provocation by acetylcholine. Changes in airways resistance resp. conductance (GAW), FEV1.0 and residual volume (RV) were also determined for comparison. In an inhomogeneous subgroup with obstructive airways disease of various aetiology the mixing index (MI) and FEV1.0 indicated changes in the airways system with about equal frequency. Distinct discrepancies between the two tests, observed in a few cases, suggest that the two methods register different pathophysiological reactions. These differences could be confirmed statistically in a more homogeneous subgroup with extrinsic bronchial asthma. A correlation could be established between MI and RV on the one hand and between FEV1.0 or GAW and RV on the other hand. The results indicate that the mixing index as a test of distribution of ventilation reflects mainly the reactions of the small airways. Its use offers the possibility of a more differentiated pharmacodynamic evaluation.

Acetylcholine↗
PubMed1978

The determination of antithrombin III. Comparison of six methods. Effect of oral contraceptive therapy.

At III levels measured with six methods in 36 people: 10 healthy controls, 10 women taking a progestagen Lynestrenol and 16 women taking a combined oestrogen-progestagen contraceptive pill. The reproducibility and the sensitivity of these methods as well as the correlation between methods were studied. The Hensen and Loeliger technique had a poor reproducibility and the results obtained with the Howie technique were not in good correlation with those obtained with other methods, especially in the group taking oral contraceptives. The two amidolytic methods using chromogenic substrates were found to be very accurate for antithrombin III activity determination. The rocket immunoelectrophoresis was more accurate and more practical than the radial immunodiffusion. With all methods--except the one of Howie--the 10 women taking progestagen Lynestrenol and the 16 taking combined oestrogen-progestagen had a low AT III and differed significantly from the 10 normals tested. No difference was observed between women taking progestagen only or an oestrogen-progestagen combination.

Antithrombin III↗
PubMed1977

The activation of plasma factor XIII with the snake venom enzymes ancrod and batroxobin marajoensis.

The snake venom enzymes Ancrod and Batroxobin marajoensis are able to activate human plasma factor XIII as shown by the formation of the gamma-dimers. The concentration of gamma-dimers increases with the concentration of the activating enzymes. Factor XIII activated by Ancrod or Batroxobin marajoensis is, however, unable to catalyse the incorporation of the amine dansyl-cadaverine into casein. The partially activated factor XIII is therefore not demonstrable by means of the artificial test system. This factor XIII loses little activity and remains activable by thrombin.

Ancrod↗
PubMed1977

Interaction study between phenprocoumon and flurbiprofen.

The effects of flurbiprofen on various coagulation and haemostasis parameters were studied in 19 patients adequately anticoagulated on a fixed dose of phenprocoumon. Laboratory controls were performed 5 times at weekly intervals. Flurbiprofen 50 mg 3-times daily was given for 2 weeks after an initial control period of 2 weeks. The last control followed 1 week after cessation of flurbiprofen. All changes observed during the administration of flurbiprofen were quantitatively moderate; some reached statistical significance. The prothrombin time (%) Factor II and Factor X values fell; Factor II values remained unchanged. Factor IX values fell only in the first week on flurbiprofen and reached control values thereafter. Phenprocoumon concentration remained constant throughout. There was no change in spontaneous platelet aggregation. Although there was a slight, statistically significant increase in the Ivy bleeding time, it remained within the normal range. These findings suggest that the interference of flurbiprofen with oral anticoagulation is minimal and probably of no clinical relevance.

4-Hydroxycoumarins↗
PubMed1974

Implementation of a British computer system for laboratory data handling.

This paper describes the development and implementation of a small real-time British computer system for the handling of patient and test result data in the chemical pathology laboratories of the King's Health District (Teaching). Work destined for subsequent reporting by the computer system is entered by continuous on-line teletype. Test result data from multichannel analyzers are input using an on-line trace reader. Cumulative reports are printed both by line printer at the central laboratory and by on-line teletypes at two peripheral hospital laboratories. In a working day over 4000 new items of data are generated and 300-500 reports printed. The use of a trace reader as an inputing device and the method of employing a high capacity disk to give both speed of operation and limited archive facility are discussed.

Computers↗