Biomedical subjects
Publications and source records attributed to K Jessen.
Details are given of the standardization of ophthalmodynamometers after H.-K. Müller and its consequences for the practical application of these instruments. Conversion tables for the relationship between divisions and pressure, including special correction values of Bedavanija (7) are provided.
To assess human thermoregulation independent of muscular activity, a method was developed exposing adult man not previously acclimatized to cold under simultaneous vasodilatation, resulting in a heat debt from the body. During exposure, a significant increase in oxygen consumption was found in two groups, the increases were 0.06 mmol . kg-1, . min-1 (41%) (range: 0.023--0.113) and 0.046 mmol . kg-1 . min-1 (30%) (range: --0.013--0.078), respectively. The change in plasma concentration of catecholamines showed a significant increase in noradrenaline of 4.58 nmol/l (300%) (range: 1.86--9.56), whereas adrenaline did not change measureably. The plasma concentration of non-esterified fatty acids (NEFA) showed a significant increase of 0.47 l mmol/l (96%) (range: 0.033 to 0.687), whereas the plasma concentration of glucose fell by only 0.3 mmol/l (6%) (range: 0.1--0.9). The results obtained by this method mirror findings from studies on small mammals acclimatized to cold, indicating that man without visible shivering and discomfort can increase heat production by an increased secretion of noradrenaline and by utilizing the fat stores in adipose tissue as the major substrate for this increased energy demand.
By a standardized exposure to cold air under simultaneous vasodilation, it was possible to elucidate the chemical factors responsible for heat production independent of muscular activity in seven patients with thyrotoxicosis and in nine patients with hypothyroidism. The results showed that hyperthryroid patients have a thermoregulatory reserve equal to normal persons, as they were able to increase their oxygen consumption significantly by an average of 0.035 mmol . kg-1 . min-1 (16%) (range: 0.014--0.064). The plasma concentration of non-esterified fatty acids (NEFA) increased significantly by an average of 0.675 mmol/l (64%) (range: 0.015--2.220). The hypothyroid patients also increased their oxygen consumption significantly by an average of 0.032 mmol . kg-1 . min-1 (30) (range: -0.016--0.066), but in this group the normal fat mobilization was inhibited as no rise in plasma NEFA was seen. Administration of exogenous thyroxine restored thermoregulation to the level and pattern seen in normothyroid persons, as the increase in plasma NEFA after treatment was on average 0.483 nnol/l (192%) (range: 0.342--0.733).
It is known that many stressful situations are accompanied by an increase in plasma cortisol concentration. This study was undertaken to see if a standardized and moderate exposure to cold under simultaneous peripheral vasodilation, which is known to result in increased oxygen consumption and plasma concentration of noradrenaline, can be considered a stress, based on changes in plasma cortisol concentration. Since the nonshivering thermogenesis induced is dependent on normal thyroid function, nine of the 19 adult humans exposed to cold were normo-, four hyper-, and six hypothyroid. The cold exposure was carried out in every case between 9 a.m. and 11 a.m. Since the cortisol secretion reflects the circadian cycle, a further six normothyroid persons were exposure to cold between 5 a.m. and 7 a.m. The exposure in this study does not reflect any stress condition, as the plasma cortisol concentration during the investigations between 9 a.m. and 11 a.m. decreased significantly by mean values of 0.1 mmol/l (29%) (range: -0.07--0.2 mmol/l) in the normothyroid group, by 0.23 mmol/l (68%) (range: 0.09--0.44 mmol/l) in the hyperthyroid group, and by 0.16 mmol/l (29%) (range: 0.03--0.38 mmol/l) in the hypothyroid group. The normothyroid persons investigated between 5 a.m. and 7 a.m. showed a significant fall similar to that mentioned above. The differences in the results obtained between the normo- and dysthyroid groups, before and during the exposure, merely reflected variations known from non-stressful conditions.
To investigate thermoregulation independent of muscular contractions in adult man during a short period of exposure to cold, five examinations were carried out on four individuals who were unconscious due to persistent brain damage and who were totally curarized during the exposure. An increase was found in total body oxygen consumption of 0.043 mmol . kg-1 (range 0.038-0.049) or 25%, in plasma noradrenaline of 5.05 nmol . 1-1 (range: 2.48-6.73) or 132%, and in plasma non-esterified fatty acids of 0.6 mmol . -1 (range: 0.049-0.095) or 44%. No changes occurred in plasma adrenaline or plasma glucose. Splanchnic oxygen consumption increased and contributed significantly to that of the total body in only one of the four cases. These results indicate that regulatory nonshivering thermogenesis exits in adult man not acclimatized to cold, that it is mediated by noradrenaline, that the major fuel substrate for the increased energy demand is the triglycerides from the fat stores, and that the splanchnic area contributes only irregularly and to a small degree to this part of thermogenesis.
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Using the applanation tonometry of Goldmann (mechanical-optical applanation principle with constant diameter of the applanation circle) as a reference system, a test plan inclusive of the necessary conditions for the clinical control measurements of new tonometer types and guiding values for judging the usefulness of these new developments are described. For calculation of the statistical values a computer program in BASIC system is specified.
The intraocular pressure, the ophthalmic artery pressure, and the episcleral venous pressure increased after changes from sitting to recumbent body position, whereas the subclavian artery pressure remained unchanged or decreased slightly. Changing from recumbent to sitting position was followed by a decrease in IOP, ophthalmic pressure, and subclavian artery pressure. Comparing the last measurement in the first position to the first value after change, it was found that the IOP alters by about 20%, the ophthalmic artery pressure by 15%, and the episcleral venous pressure by 50%. In all series a decrease in subclavian artery pressure was observed during the first 15 min. The mean pressure in the ophthalmic artery diminished in the series that changed from sitting to recumbent position, whereas it increased in the other series during the first 15 min. The episcleral venous pressure increased more than the corresponding IOP after changing to the recumbent position.
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Comparing measurements with Non-Contact-Tonometer and handapplanation tonometer on 462 eyes with normal and elevated intraocular tension are statistically evaluated. The 2-s-limits for normal i.o. pressure at +/- 6.52 mm Hg (+/- 8.6 mbar), for elevated intraocular pressure +/- 13.2 mm Hg (+/- 17.6 mbar). This means less reliability than conventional applanation tonometers or even Schiötz-tonometers. The unability to read the tension when the corneal surface is rough means remarkable disadvantages to clinical use.
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