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Biomedical subjects

R Rössler

Publications and source records attributed to R Rössler.

At least 19 recordsLinked to original sources
PubMed1990

A predictive model for life expectancy curves.

Life expectancy curves have a characteristic ominous shape that has fascinated scientists for centuries. Medawar was the first to explain this shape, specifically the steeply rising proneness of an average individual to die as a function of age, in evolutionary terms. The idea was that the "selective value" of the individual decreases as it has triggered other individuals taking its place (and carrying its genes) into existence. We demonstrate that this idea can be turned into a quantitative model. The resulting 4-parameter function reproduces well two well-known life expectancy curves from the first half of this century. Moreover, the easily interpretable parameters (3 of the 4) seem intuitively reasonable.

Female↗
PubMed1990

Does a centralized clock for ageing exist?

It is proposed that a centralized clock controlling ageing is located in the pineal gland with the calcification process occurring there providing a highly accurate bio-inorganic timing mechanism and the secreted melatonin carrying a signal to all cells in the organism. An explicit programme of data gathering and experiments suitable for the falsification of the proposal, which is consistent with presently known anatomical and physiological facts, is presented. The underlying motivation comes from evolutionary biology and the invariance, that is the allometry, of life expectancy curves.

Aging↗
PubMed1989

Tono-Pen, a new tonometer.

UNLABELLED: The Tono-Pen is a miniaturized Mackay-Marg tonometer with electronic signal analysis and digital pressure display. In study 1, we compared the Tono-Pen with Goldmann tonometry in 108 healthy human subjects (216 eyes). In 33 of these subjects, the IOP was changed in a range between 0 and 50 mmHg by a scleral suction-cup system. In study 2, the Tono-Pen was compared with a Statham membrane manometer in 6 humans (12 eyes), 3-6h after death. The IOP was changed in a range between 0 and 60 mmHg by an infusion system. - RESULTS: Related to the Goldmann tonometer, the Tono-Pen gave a small overestimation of IOP below 16 mmHg (maximum deviation 1.5 mmHg at 0 mmHg Goldmann reading). Above 16 mmHg, however, the Tono-Pen increasingly underestimated the IOP determined by Goldmann tonometry (maximum deviation 8 mmHg at 50 mmHg Goldmann reading). Related to the manometer, the Tono-Pen gave a small overestimation of IOP below 17 mmHg and small underestimation above 17 mmHg (maximum deviation 2.5 mmHg at manometer readings of 0 and 60 mmHg, respectively). - CONCLUSIONS: Throughout the entire clinically relevant IOP range, an acceptable relationship between Tono-Pen and manometer readings was found in human cadaver eyes, whereas the relationship between Tono-Pen and Goldmann tonometric readings in the clinical study was found to be acceptable only in the low and physiological IOP range. The considerable deviation from the Goldmann readings in the high IOP range requires further modifications of the Tono-Pen.

Adolescent↗
PubMed1989

[Tono-pen versus manometer. Comparative measurements of intraocular pressure in human cadaver eyes].

A new hand-held tonometer, the Tono-Pen (TP), was compared with a Statham membrane manometer (MAN). The TP is a pen-sized Mackay-Marg tonometer with electronic signal analysis and digital pressure display. Comparative measurements of intra-ocular pressure (IOP) were performed on six cadavers (12 eyes in situ), 3-6 hours after death. The IOP was changed in 5 to 10 mm Hg steps in a range between 0 and 60 mm Hg by an infusion system. As compared to the manometrically determined IOP, the TP gave small overestimation of IOP below 17 mm Hg and a small underestimation above 17 mm Hg (maximum deviation 2.5 mm Hg). The mean values of 29.9 (TP) and 30.4 mm Hg (MAN) were not significantly different (p greater than 0.05, analysis of variance). The correlation coefficient was 0.99. The relationship between TP (y axis) and MAN (x axis) pressure readings is characterized exactly by a slightly curvilinear graph (y = 0.82x + 0.0002x2 + 2.52; mm Hg). This may be approximated by a regression line with a slope of 0.94, a y intercept of 1.46 mm Hg and a standard deviation of the TP readings in relation to the regression line of 2.36 mm Hg. In conclusion, the good agreement between TP and MAN pressure readings is superior to the recently described agreement between TP and Goldmann tonometer readings.

Electronics↗
PubMed1988

Comparison of intraocular pressure measurements with the Oculab Tono-Pen vs manometry in humans shortly after death.

We compared the Oculab Tono-Pen, a miniaturized Mackay-Marg tonometer, with a Statham membrane manometer in six humans (12 eyes), three to six hours after death. The intraocular pressure was changed in 5- to 10-mm Hg steps in a range between 0 and 60 mm Hg by an infusion system. The correlation coefficient of the relation of Tono-Pen readings vs manometrically determined intraocular pressures was .99. Compared to the manometer, the Tono-Pen gave a small underestimation of intraocular pressure above 17 mm Hg or overestimation below 17 mm Hg. The maximal deviation of the Tono-Pen readings from the manometer readings was 2.5 mm Hg. In our experience the correspondence between Tono-Pen and manometer readings was superior to the correspondence between the readings obtained with the original Mackay-Marg tonometer and manometry.

Aged↗
PubMed1988

[Tono-pen, a new position-independent tonometer. Comparison with the Goldmann tonometer by applanation measurement].

A new hand-held tonometer, Tono-Pen (TP), was compared with the Goldmann tonometer (GM). The TP utilizes the operating principle of the Mackay-Marg tonometer. However, the TP is battery-operated, only 18 cm long, weighs only 60 g, and features electronic signal analysis (single-chip microprocessor) and a digital pressure display (mm Hg). In 108 subjects (216 eyes) presenting no ocular abnormalities, comparative tonometric measurements were performed in randomized order by two investigators (A: TP; B: GM). In 33 of these subjects (66 eyes), the intraocular pressure (IOP) was changed by means of a scleral suction-cup system. A total of 457 pairs of values was obtained in an IOP range extending continuously from 0 to 50 mm Hg. The relationship between TP (y axis) and GM (x axis) pressure readings is described exactly by a slightly curvilinear graph (y = 0.96x - 0.003x2 + 1.48; mm Hg). This may be approximated by a regression line with a slope of 0.8, a y intercept of 2.76 mm Hg and a standard deviation of 2.5 mm Hg (y values) in relation to the regression line. The mean values were 17.6 (TP) and 18.6 mm Hg (GM), which were not significantly different (P less than 0.05). The correlation coefficient amounted to 0.97. Below an IOP (GM) of 16 mm Hg, the TP slightly overestimated the IOP by a maximum of 1.48 mm Hg at GM = 0). Above 16 mm Hg, the TP increasingly underestimated, the IOP by a maximum of 8 mm Hg at GM = 50). Summing up, the TP is unique among hand-held tonometers in its miniaturization. In the low and physiological pressure range, there is an acceptable relationship between TP and GM readings. In the high pressure range, however, its readings deviate considerably from those of the tonometer.

Adult↗
PubMed1977

Other mammalian histocompatibility systems. Skin graft rejection and graft-versus-host reaction across I-subregion differences: are there many more than three H loci within the H-2 complex?

The data confirm an earlier finding by Klein et al. that the I region harbors a strong histocompatibility locus, which by exclusion might be assigned to the IA subregion. In addition, it appears that intercalated between the IA subregion and S region there is a minor H locus since (DBA/2 X 4R)F1 rejects skin of 2R in a chronic fashion. In another combination, HTT versus 7R, which differs for the IC, S, and G regions but may also differ for genes between the D and TL locus, a similar chronic rejection pattern was observed indicating minor H gene(s) within or closely linked to the H-2 complex. The data reported here are in concordance with very recently published results by Klein et al..

Animals↗
PubMed1975

[Plasma-aldosterone and renin activity in Bartter's syndrome (author's transl)].

The temporal changes of aldosterone concentration and renin activity in plasma under the influence of stimulating and inhibiting factors were tested in two patients with Bartter's syndrome. There was a normal response to potassium and sodium administration, spironolactone, angiotensin II, ACTH and dexamethasone. Changes in plasma-aldosterone concentration, as measured at frequent intervals during angiotensin II infusion, suggest differential regulation of aldosterone synthesis by angiotensin II. In one patient the symptoms improved with administration of glucocorticoid derivatives.

Adrenocorticotropic Hormone↗