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H Tönhardt

Publications and source records attributed to H Tönhardt.

12 recordsLinked to original sources
PubMed2002

Influence of long-term changes in incubation temperature on catecholamine levels in plasma of chicken embryos (Gallus gallus f. domestica).

Catecholamine concentrations were determined from day 18 to 21 of incubation (D18, D21) in developing chicken embryos. The control group was continuously incubated at 37.5 degrees C. The eggs of the two other groups were incubated at 37.5 degrees C until day 14. In the cold group, temperature was decreased to 35.0 degrees C and in the warm group, incubation temperature was increased to 38.5 degrees C for the remainder of incubation. Plasma catecholamine concentrations were measured in eggs exposed to a change in incubation temperature for 4, 5, 6 and 7 days. Embryos in the warm group had dopamine (DA) and noradrenaline (NA) concentrations that were significantly higher than in the control group. On the contrary, eggs incubated at the cooler temperature had hormone levels that were significantly lower than in the control group. Adrenaline (A) levels in the two experimental treatments were significantly lower compared to control eggs. Temperature modulated the time needed for development. Chicken embryos are supposed to hatch on day 21. However, on day 20, NA concentration in the cold-incubated group was too low to fulfill its essential physiological function, whereas in the warm group, the NA concentration seems to be sufficient. Long-term exposure to altered incubation temperature affects the quantitative catecholamine concentration during development, but the relative proportion of each catecholamine remained constant.

Animals↗
PubMed1997

Pulse oximetry: a new way of determining the heart rate in chicken embryos.

With pulse oximetry it is possible to record the pulse-synchronic variation of the oxygen saturation due to variable blood flow during systole and diastole. In the present study on chicken embryos, the pulse rate based on oximetry was compared with the heart rate recorded by means of ECG. We conclude that the pulse curve detected by means of pulse oximetry can be used to determine the heart rate in chicken embryos between day 12 and day 20 of incubation.

Animals↗
PubMed1976

[Endocrine and spermatogenic testicular function. 2. Correlations between food protein quality, testosterone level in testes, spermatogenesis and nuclear volume of interstitial cells of Leydig in the adult rat].

Male adult Wistar rats were given different food proteins through 21 days, including casein and four-per-cent methionine (K diet), maize gluten with amino acid added (M + As diet), maize gluten alone (M diet), and casein with four-per-cent methionine mixed one to three with gelatin (K/G diet). Testicular testosterone levels per 100 g live weight were about 411 ng (in animals aged 130 days) or 326 ng in animals aged 160 days) following 21 days of K or M + As feeding (rRP = ten per cent). Roughly 70 per cent of those values were obtained by M or K/G feeding. The use of 20 per cent rRP gave 342 ng in connection with M + As feeding or 289 ng when it accompanied M feeding (the latter figures being recorded from animals aged 160 days). The eight cyclic phases of the germinal epithelium were completely development, independent of RP quality, in all test animals. The nuclear volume of the interstitial cells of Leydig responded with highly significant variation (p less than 0.01) to diets with ten per cent rRP of different qualities, but no significant morphokinetic effect was recorded by karyometric from diets with 20 per cent rRP.

Animals↗
PubMed1976

[Endocrine and sperminogenic testicular function. 7. Relationship between testicular and plasma androgen concentrations in boars of different ages].

Testicular tissue and blood samples (V. spermatica interna) were taken from 32 boars during castration. The animals were of different age groups. Against this background, comparative studies were conducted into the relationships between testicular and plasma testosterone. A very close correlation was found to exist between the androgen values in testicular tissue and those in the blood plasma of V. spermatica interna (r = 0.9795), wich appeared to support the conclusion that by determination of blood plasma the androgen content in the testes can be established with high probability.

Age Factors↗
PubMed1976

[Endocrine and sperminogenic testicular function. 8. Relationships between testicular and plasma testosterone concentrations as well as between the number of Leydig cells in testicular tissue and their cell nucleus volume in boars of different ages].

Testicular tissue and blood samples (V. spermatica interna) were taken from 32 boars during castration. The animals were different age groups. Against this background, studies were conducted into the correlations between testicular and plasma testosterone, on the one hand, and the amount of interstitial cells of Leydig in testicular tissue as well as the latters' cell nuclei volumes, on the other. The results seemed to support the conclusion that any age-dependent increase of testicular and plasma testosterone concentrations was caused unambigously by an absolute increase in volume of androgenic testicular tissue, in concomitance with testicular growth, in other words, by rise in the total number of interstitial cells of Leydig.

Age Factors↗
PubMed1976

[Endocrine and spermatogenic testicular function. 9. Correlations between plasma testosterone and morphometric parameters of the testis in boars of different ages].

Close, statistically fully secured correlations were found to exist in boars, aged between four and four-a-half as well as seven and nine months, between the testosterone content in the blood of the V. spermatica interna, on the one hand, and morphometric parameters essential to quantitative sperm production, on the other (testicular volume, volume of germinativum, overall length of tubules, diameter of tubules, and cell density of the germinal epithelium).

Age Factors↗
PubMed1976

[Studies on endocrine and spermiogenic testis function. IV. Relations between the testosterone content of the testes cell nucleus volume of the Leydig cells and rat spermatogenesis (deduced from studies on the effect of the dietary protein quality on the function of the testes)].

The following relations were derived from large-scale testing of feed protein quality and its bearings on testicular function in growing Wistar rats: testicle weights and live weights r = 0.77 for juvenile animals and r = 0.36 for adult animals; nuclear volumes of Leydig's cells to testicle weights r = 0.84 for juvenile animals and r = 0.43 for adult animals; testosterone in testicular tissue, ng/g, to testicle weights r = 0.55 for juvenile animals and r = 0.80 for adult animals; testosterone per live weight, ng/100 g, to nuclear volumes of Leydig's cells r = 0.76 for juvenile animals and r = 0.46 for adult animals. Critical thresholds above which complete spermatogenesis is always ensured may be established for testosterone (50+/-5 ng/100 g live weight) and for the nuclear volume of Leydig's cells (30 mum3). Another conclusions drawn from the above results is that high testosterone levels in the testes of adult animals were not attributable to high testosterone biogenesis of Leydig's cells, as might have been assumed from high activities of that kind recordable from some nuclear volumes.

Animals↗
PubMed1976

[Studies on endocrine and spermatogenic testicular function. 5. Relationship between dietary protein quality and blood plasma levels of free and bound testosterone in adult rats].

The blood plasma content of testosterone-linking globulins, free testosterone, and total testosterone in 80 adult Wistar rats which received different qualities of feed proteins was determined by means of balancing dialysis and ultracentrifugation, using 3H-testosterone. The first group received casein with four per cent methionine added, the second maize gluten complement with amino acid, and the third casein with methionine and gelatin in a 2:3 ratio, while the fourth group was fed pure maize gluten diet. (Biological valence declined in the given order.) Assays of 100 ml blood plasma of each animal in the first and second groups gave 0.9 mug of testosterone-linking globulins (0.18 mug in third and fourth groups), about 9.0 mug total testosterone (2.5 mug in third and fourth groups), and some 1.4 mug free testosterone (0.55 mug in third and fourth groups). Discussed in this paper is the possible mechanism of regulation by which feed protein quality leads to variation of free testosterone levels in the blood plasma.

Animals↗
PubMed1976

[Studies on the endocrine and spermatogenetic testicular function 6. In-vitro biosynthesis of testosterone in fractions of the smooth endoplasmic reticulum from the rat's testis in relationship to age and quality of dietary proteins].

The metabolic activity of testosterone biosynthesis in fractions of the unstriated endoplasmatic reticulum of testicular tissue in animals in puberty living on corn gluten was about 20 per cent below that in animals that were fed corn gluten plus supplemented amino acids. Such lowered metabolic activity was recordable even from adult animals for another 30 days despite change of feed to high-quality proteins. The conversion rate of progesterone in testostrone still was lowered by some ten per cent. If change of enzyme activity in testosterone biosynthesis was caused by feeding different protein qualities, such variation could not be normalised within short time. Testosterone biosynthesis during postnatal development of rat was of two-phase nature even in the presence of temporary deficit due to low-quality feed protein. A regulation mechanism is assumed to exist and to enable completion of sexual maturity even on the basis of low-quality feed proteins. The metabolic activity at the time of qualitative transformation of the A/T ratio was significantly reduced, and this resulted in delayed occurrence of spermatogenesis as well as in retardation of body and testicular weight development.

Animal Feed↗
PubMed1975

[Studies on the endocrine and spermiogenic functions of testes. I. Relationship between the quality of dietary protein and testosterone content in testicular tissue of pubertal rats].

Growing, male Wistar rats were fed for 21 days one of four qualitatively different proteins, as follows: 1. casein and 4% methionine (group K) 2. maize meal and amino acid supplement (group M + As) 3. maize meal alone (group M) 4. casein plus 4% of a 1:3 mixture of methionine and gelatin (group K/G) (These rations constitute a decreasing range of biological activity of the diet.) After 21 days of feeding these rations, the testosterone content per 100 g body weight averaged 80 ng in groups K and M + As, compared with 8 ng in groups M and K/G. Body weight increment averaged 48 g in group K, 40 g in group M + As, 19 g in group M and -9g in group K/G. Total testicular mass averaged 1658, 1730, 1485 and 641 mg in the four groups, respectively.

Age Factors↗