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J Peil

Publications and source records attributed to J Peil.

At least 19 recordsLinked to original sources
PubMed1991

[Pharmacokinetic parameters as criteria for clinical use of hydroxyethyl starch preparations].

Pharmacokinetic Parameters as Criteria for Clinical Use of Hydroxyethyl Starch Preparations In a study with volunteers (n = 2 x 6) pharmacokinetic data of two only marginally differing starch preparations were investigated. We were able to demonstrate that there exist significant differences in raw materials used which determined the pharmacokinetic data in humans. Newly implemented analyzing methods (LALLS) were used. In addition to the degree of substitution, further differences concerning the position of hydroxyethylization at the anhydroglucose molecule could be documented. The C2/C6 positions of hydroxyethylization at the molecule seem to be most essential. To classify and to differentiate starch preparations we propose to include these data in general informations for clinicians because these differences might determine clinical usage and efficacy.

Chromatography, Gas↗
PubMed1990

Circannual oscillations of function compared with morphometric changes in the thyroid gland of the Wistar-rat.

To investigate biological rhythms of the thyroid gland circannual oscillations of thyroxine (T4), triiodothyronine (T3), and thyrotropin (TSH) were compared in serum samples of untreated young male Wistar-rats with the circannual changes of thyroid weights and with the relative proportion of colloid, epithelium, and interstitium of the thyroids. Animals were kept under standard environmental conditions, however, lighting conditions simulated the natural day-night changes. Thyroid weights, T4, T3, and TSH showed a statistically significant circannual rhythm with maxima in winter and spring and minima in summer and autumn. The same circannual patterns were observed in the proportion of epithelium and interstitium of the thyroids, while the colloid exhibited an inverse circannual pattern. These data were verified by biomathematical methods, like locally adjusted functional approximation, analysis of variance, and Spearman rank correlation. Our results represent an example for the concordance between functional and morphometrical changes in the course of circannual oscillations. Furthermore, these data confirm our earlier results describing higher T4-levels in the winter time (short-day) and lower serum titers in the summer time (long-day).

Animals↗
PubMed1990

[The effect of ganglionectomy and cold exposure on the ventromedial hypothalamic nucleus, blood glucose and liver glycogen in regard to circadian rhythms].

To analyse the importance of the ventromedial hypothalamic nucleus (VMH) for the circadian regulation of the carbohydrate metabolism rats were investigated after bilateral cervical sympathetic ganglionectomy (SCGx) 30 d earlier and exposure to cold (10 degrees C) 72 h earlier. In order to assess the circadian rhythms of nuclear volume oscillations of the VMH, blood glucose, and liver glycogen 4 times a day (light-dark cycle: 14L:10D, light on 05.00 h) rats were sacrificed at midlight and middark as well as 1 h after the onset of the light and dark periods. The circadian curves were calculated in a model-free way by the procedures of locally adjusted polynomial approximation. Ganglion removal and exposure to cold resulted in an increase of blood sugar and of nuclear volume of the VMH, but only of its lateral part. The liver glycogen decreased. Additionally, both the coordination between the circadian curves of the nuclear volume and of the blood glucose as well as of the inverse curves of the liver glycogen was destroyed after SCGx. These results are in agreement with the conviction that the enhanced blood glucose activates the VMH. The augmentation of blood glucose was discussed in connection with influences of the likewise increased thyrotropin-releasing hormone and thyrotropin on the increased plasma levels of catecholamines, with secondary increased plasma levels of glucagon as well as decreased insulin levels after SCGx and exposure to cold. The sympathetic denervation of the pineal gland (SCGx) produced the mentioned desynchronization of the curves. At the present we are not able to explain the approximate restitution of the circadian rhythms after additional exposure to cold.

Animals↗
PubMed1989

Circannual serum creatine kinase patterns after ganglionectomy and pinealectomy of the Wistar rat.

Previous investigations have shown that an inverse correlation exists between serum thyroxine levels (T4) and serum creatine kinase activity (CK) both in hypothyroid and hyperthyroid states. In the present study, serum T4 levels and total serum CK activity were analysed after thyroidectomy (TX), ganglionectomy (extirpation of the superior cervical sympathetic ganglion) (GX), or pinealectomy (PX) four times a year (March, June, September, and December). Blood samples were taken four times daily (at midlight, middark, and at 1 hour after the onset of the light and dark periods). Animals were kept under an artificial light schedule that simulated natural light-dark periods. The annual main values of serum T4 levels were significantly decreased after the operations, whereas serum CK activities were increased. Our circannual investigations demonstrated an inverse correlation between serum T4 levels and total serum CK activity (under hypothyroid circumstances). In addition, the circannual pattern of the serum CK activity demonstrated maxima under short-day (winter) conditions and minima under long-day (summer) conditions. GX and PX provoke an unimportant shift (a little longer than 2 months) in maxima and minima of the annual rhythm. Circannual curves exhibited differences in the degree of the increase of serum CK activity of GX and PX groups. These results indirectly confirm the assumption that experimental sympathetic denervation or removal of the pineal gland will induce a hypothyroid state over the long term.

Animals↗
PubMed1989

[Biomathematical aspects of numerical evaluation and mathematical modelling of non-monotonous exponential measuring processes].

Measurements of endocrinological and pharmacological processes often yield courses of time series with exponentially saturated increasing first part followed by an exponentially decreasing part. Such measured courses may be mathematically modelled by the so-called BATEMAN function type, an expression consisting of 2 e-function terms. In this paper, the method of locally adjusted functional approximation for model-free quantitative evaluation of measured time series is sketched. By means of 2 real examples of measured data, it will be demonstrated how the results of the model-free evaluation may serve for internal regression to estimate starting parameter values for an iterative fitting of a BATEMAN function to measured data courses. Furthermore, it is shown that the model-free approach of data evaluation may give substantial hints for the mathematical model building process and for model verification.

Animals↗
PubMed1989

Local approximation and its applications in statistics.

For the discrete and for the continuous case, the problem of evaluating the derivatives of a function f(x) in a given interval of x is solved by local approximation method. Examples of application of the resulting numerical procedures are quoted relating the estimation of smooth function and its derivative for measured values (of a growth process), internal regression, trend elimination of time series, Bernstein polynomial, and kernel estimation of a density function.

Mathematics↗
PubMed1989

[Periodic local approximation for the model free description of measurement courses of biorhythmic processes--demonstration example for the selection of smoothness parameters].

Measured time series with known basic periodicity may be modelfreely evaluated by procedures of local adjusted approximation. Examples of motility time series recorded in chronobiological experiments in the seasonal course of a year demonstrate aspects of choosing values of the smoothing parameter and the resulting effects for the quantitative description of the measured variations as well as for their interpretation.

Animals↗
PubMed1989

Morphometric investigations of the pineal gland after ganglionectomy and thyroidectomy under the aspect of circadian and seasonal variations.

It is well established that the pineal gland is involved in the regulation of thyrotropin (TSH) secretion. Previous investigations in our laboratory showed that under hypothyroid conditions the nuclear size of pinealocytes was diminished while an increase in the size of nuclei was seen under hyperthyroid conditions. In the present study we confirmed these results while considering circadian and circannual oscillations. After ganglionectomy (GX, removal of the sympathetic superior cervical ganglia) the mean annual values of the nuclear size of pinealocytes, pineal weights and thyroxine (T4) levels were diminished, whereas the pituitary weights increased. Comparable, but more drastical reactions were found after thyroidectomy (TX). The diminution of the nuclear size of pinealocytes was more pronounced in the wintertime (December, L: D = 8: 16), the finding for the summertime (June, L: D = 16: 8) being similar. Under short-day conditions the nuclear size was larger than under long-day regimes. In the winter the enhancement of the nuclear size was accompanied by decreased pituitary weights and increased T4 levels while under long-day conditions lower size of pinealocytes and T4 levels were associated with higher weights of pituitary glands. The statistically significant circadian patterns of the nuclear size of pinealocytes showed that the largest nuclei occurred at the end of the light phase or at the onset of the dark phase. In June, the largest nuclei were found in the middle of dark (control) or in the early light phase (ganglionectomy). Considering the circadian patterns of pineal weights and T4 levels, these results underline the existence of a functional connection between the pineal gland and the thyroid axis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

[Estimation of median regression from measured values].

The median regression function is defined and demonstrated by examples. A lemma with sufficient conditions for continuity and differentiation of the median regression function is proved. Its estimation from a random sample is deduced firstly based on the empirical distribution function and secondly based on a kernel estimation with Gaussian kernels. Both estimations are demonstrated by GALTONS historical example. A comparison between the empirical median regression function and the empirical regression of the first kind is made by an example. A hint for curve fitting with the median estimation equation is also given by an example.

Mathematics↗
PubMed1979

[Quantification of environmentally influenced differences in physical and mental development of infants by a phenomenologic-mathematical separation of the body length growth into growth spurts (author's transl)].

Retardation phenomena in the physical development--especially in the increase of body length--of infants taken care of in social institutions (day-nursery, week-nursery, residential nursery) in relation to those growing up in the family will be represented in a quantitative-analytical form on the basis of a phenomenologic-mathematical model. This kind of modelling consists in the separation into 7 successive growth periods (growth spurts) of the whole growth process during the time interval from conception until the age of 3 years. For the time interval from birth until the end of 3 years we have 4 such growth spurts. The second one (fifth in the former numbering) determines mainly the growth during the 2nd year of the individual's life and makes evident the delay in the mean increase of body length of infants taken care of in social institutions, which is most evident for children who grow up in a residential nursery. The quantitative statements derived from the mathematical model concerning the physical development will be confronted with the known facts concerning the retardation in the mental-psychial development--especially in the ontogenesis of speech--of the same groups of children. There is an astonishingly close accordance of the values of time delays in reaching the levels of the physical and of the psychical development. The model may help to perceive and to diagnose the complex of causes responsible for these retardation phenomena from a social-medical and biological point of view. On the other hand this may also give a critizism and assessment of the real relevance of the biomathematical separation of the growth process into single growth spurts practiced here.

Body Height↗
PubMed1979

[The determination of the parameter of Bertalanffy's growth differential equations by means of nonlinear internal regression].

A short survey is given on various parameterized versions of the logistic law of growth and of Bertalanffy's growth differential equations. To examine the validity of these various growth expressions internal nonlinear regressions were performed, and the results of the calculations are presented. The body length growth of man within the embryonic development serves as examples of a growth process. The parameters in the differential equations will be adjusted to the course of the divided central differences calculated from means of measured values of this growth process.

Body Height↗
PubMed1979

[The description of growth course using a generalized logistic growth function].

For a quantitative description of measured growth courses the generalized logistic function will be used which is derived on the basis of the well-known logistic function of VERHULST. Numerical properties of this expression and possibilities for its computerized adjustment to measured courses are discussed. Examples of growth processes and their mathematical description by adjusted generalized logistic functions demonstrate the effectiveness of an ALGOL-program system for nonlinear approximation which is specialized to this function type. Especially the numerical improvement of approximation quality is demonstrated for expressions containing an absolute term in form of an also adjustable parameter.

Body Height↗
PubMed1979

[Quantitative mathematical evaluation of growth studies from the viewpoint of exogenously or genetically influenced variability].

Firstly, the ideas are sketched which serve as the basis for the phenomenologic-mathematical kind of modeling of the body length growth process of man. For proving the biological relevance of the spurts analyzed by numerical procedures one has to consider the social and the biological circumstances in which the growth process takes place. An analysis of longitudinal data series of the body length of (monozygotic) twins will give further hints to the possible meaning of the growth spurts by way of separation of exogenous and of genetic determined endogenous agents on the growth process. The data available for our examinations cover the time interval of the praepubertal and the postpuberal development as well as the time interval in which the puberal growth spurt takes place. The way to proceed in evaluation these time series will be presented.

Adolescent↗
PubMed1978

[Report on the round-table discussion of the subject "idea and experience" in connection with the 1977 annual meeting "process kinetics" of the German Academy of Natural Scientists Leopoldina (Halle/S., October 16, 1977)].

A report is given about a round-table-discussion upon the role and meaning of "idea and experience" in the creative scientific process. Notable representatives of mathematics, theoretical physics and geophysics, chemistry, theoretical and general experimental biology, and of medicine contribute in the discussion guided by C. F. V. WEIZSACKER to this theme from point of view of their disciplines. The components of meaning of "idea and experience" in their connection one to another may be paraphrased by such pairs of terms as "theory and practice", "theoretical or empirical", "law and appearance of a single phenomenon", "unity and diversity", abstract and concrete". It was demonstrated that in each of the mentioned scientific disciplines there is a natural, and that, starting from mathematics and going to biology and medicine, the weight in that relation will shift more and more to "experience". Many of the known methodological problems and difficulties will arise in the mentioned scientific branches if one stresses immoderately only one component of "idea and experience" by leaving the natural, discipline-related range of variation of the relation "idea and experience".

Academies and Institutes↗
PubMed1978

[Logistic law of growth and its implications].

The "morphological" (i.e. structural and quantitative) properties of VERHULST's "Logistic Law of Growth" in its versions as differential equations and as analytical functions will be discussed. It follows the attempts of generalizations of the logistic law of growth by parameterization or by changing its structure due to adding parameters. Such an additional parameter is the constant term paying regard to the level (in y-direction) on which the (growth) process may start. The second manner of introducing additional parameters is the substitution of the independent variable in its linear form by a polynomial of degree k. These generalizations will be called "generalized logistic (growth-) function". Its "morphology" will be discussed. Special points there are the use of this function as empirical expression for smoothing and quantitative description of courses of measured values (of growth variables), and the genesis of the function type as solution of a first order differential equation. "Philosophy of the generalized law of growth" means a detailed discussion of properties which could be interpreted as "time structure", and of the modelling relevancy of the differential equations resp. of the analytical function expressions which represent the versions of the generalized logistic law.

Humans↗