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An intricate link is becoming apparent between metabolism and cellular identities. Here, we explore the basis for such a link in an in vitro model for early mouse embryonic development: from naive pluripotency to the specification of primordial germ cells (PGCs). Using single-cell RNA-seq with statistical modelling and modulation of energy metabolism, we demonstrate a functional role for oxidative mitochondrial metabolism in naive pluripotency. We link mitochondrial tricarboxylic acid cycle activity to IDH2-mediated production of alpha-ketoglutarate and through it, the activity of key epigenetic regulators. Accordingly, this metabolite has a role in the maintenance of naive pluripotency as well as in PGC differentiation, likely through preserving a particular histone methylation status underlying the transient state of developmental competence for the PGC fate. We reveal a link between energy metabolism and epigenetic control of cell state transitions during a developmental trajectory towards germ cell specification, and establish a paradigm for stabilizing fleeting cellular states through metabolic modulation.

Testicular cancer is by far the most common neoplasm among young males between the ages of 20 and 40 years and with an increasing incidence rate worldwide. Congenital malformations of the male genitals, such as cryptorchidism or inguinal hernia are established risk factors. Men with a family history of testicular cancer are also associated with an increased risk of the disease. In the testes more than 90 % of tumors develop from germ cells (progenitor cells) and represent a histologically heterogeneous group. Germ cell tumors in extragonadal localizations are rare. Isochromosome i(12p), the typical marker chromosome in testicular germ cell tumors, occurs as an early event in tumorigenesis. Spermatocytic seminoma is a rare variant of germ cell tumors and according to the current classification is a distinct entity with different morphological, clinical and also cytogenetical features compared with other germ cell tumors.

We established a culture system for immature rat germ cells, which allows the analysis of differentiation and apoptosis of germ cells. For this purpose, we used testicular tissue from 20 day-old Wistar rats. By mechanical dissociation we obtained testicular cells and tissue fragments of well defined size. We examined the differentiation of germ cells in different culture systems: the culture of whole testes, fragments of tubuli seminiferi and of individual cells. In fragments of tubuli seminiferi pachytene spermatocytes differentiated into round spermatids. This development took place within a period of two weeks under the influence of testosterone and follicle stimulating hormone. The stage of differentiation was determined by the expression of stage specific markers, e.g. transition protein 1, transition protein 2 and protamine 1. We analysed the apoptosis of germ cells after stimulation with transforming growth factors-beta (beta-1 and beta-2) and used activation of caspase-3 as a measure of apoptosis. There were indications that TGF-betas induce germ cell apoptosis, but we could not definitely determine this., Diese Arbeit beschreibt die Etablierung eines in vitro-Systems für primäre männliche Keimzellen, das die Analyse von Differenzierung und Apoptose der Keimzellen ermöglicht. Es wurde Hodengewebe 20 Tage alter Wistar Ratten verwendet. Mittels mechanischer Dissoziation wurden daraus testikuläre Zellen und Gewebefragmente definierter Größe gewonnen. Die Differenzierung der Keimzellen wurde in verschiedenen Kultursystemen untersucht: der Organkultur, Kultur von Tubulusfragmenten und Kultur vereinzelter Zellen. Im System der Tubulusfragmente differenzierten sich pachytäne Spermatocyten zu runden Spermatiden. Dieser Entwicklungsschritt vollzog sich unter dem Einfluss von Testosteron und Follikel stimulierendem Hormon innerhalb von zwei Wochen. Der Differenzierungsgrad der Keimzellen wurde anhand der Expression stadienspezifischer Marker, wie Transition Protein 1, Transition Protein 2 und Protamin 1, bestimmt. Die Keimzellapoptose wurde nach Stimulation durch die Transforming Growth Factors-beta (beta-1 und beta-2) anhand der Aktivierung der Caspase-3 gemessen. Es gab Hinweise dafür, dass die TGF-betas die Keimzellapoptose induzieren, jedoch konnte dies nicht definitiv gezeigt werden.

Neuroendocrine tumors (NETs) are a heterogeneous group of benign and malignant neoplasias, detectable in the context of hereditary tumor syndromes in up to 30% of cases. The pathogenic understanding of NETs has increased considerably during the last decade, mainly due to the identification of underlying genetic defects and the availability of genetically modified animal models. These developments are reflected in a revised WHO classification of gastrointestinal NETs. In contrast to a variety of rare neuroendocrine tumor syndromes, multiple endocrine neoplasia syndrome type 1 (MEN1) and type 2 (MEN2) play clinically significant roles due to their common incidence. MEN1 and MEN2 are classic autosomal-dominant familial tumor diseases with a high penetrance and variable clinical expression, caused by germ line mutations of the MEN1 tumor suppressor gene and the RET protooncogene, respectively. The clinical management of patients with NETs has changed significantly after the introduction of clinical genetic screening. The detection of MEN1 mutations allows for risk-adapted treatment and follow-up. RET gene analysis can identify individuals with a very high risk to develop familial medullary cancer (MEN2), who may be successfully treated by prophylactic thyroidectomy. NETs thus represent a paradigmatic example of the successful link between basic genetic science and clinical care in molecular medicine.

Germ cell mutagenesis is required by the 7th amendment of the directive 67/548 EEC into the national regulations on existing chemicals. Officially accepted in vivo test systems for stage specific mutagenicity are the dominant lethal (DL) test and the specific locus test (SLT) in mice. An acceptable in vitro alternative designed to address germ cell mutagenesis and discriminate between male and female specific effects is not available at present. In order to offer a sensitive and predictive in vitro method to assess the genotoxic potential of chemical agents on male and female reproduction, we established primordial germ (PG) cell-derived permanent embryonic germ (EG) cell lines of the mouse (strain BALB/cJ). The differences in developmental sensitivity of the EG(3) cell line and differentiated fibroblast cells 3T3 were comparatively tested with cytotoxicity assay (MTT test ) and genotoxic studies (SCE-assay) under identical test conditions. The concentration-response curves reflected the female cell line EG(3) to be extremely sensitive concerning cytotoxic and genotoxic endpoints. Therefore this cell line was used to classify in vivo genotoxic and non-genotoxic test substances with different potential endpoints. Applying linear discriminant analysis three endpoints were identified for the correct classification (100%) of all test chemicals, namely the SCE(200) value (increase of 200% in the mean number of SCEs per metaphase spread) for EG(3) (3 hrs and 24 hrs assay) and the IC(5)0 value for EG(3) after 3 hrs of exposure to test chemicals.

Segmental neurofibromatosis, also designated "NF-V" according to Riccardi's classification, should be considered a mosaic manifestation of one of the other types of neurofibromatosis, mostly of NF-I. Irrespective of the site and size of the body area affected, the patients are always at risk of germ-line mosaicism and they may therefore transmit the phenotype, but not the mosaic, to the next generation. Hence it follows that segmental neurofibromatosis does not constitute a distinct entity, and it is not reasonable to discriminate unilateral from bilateral or "hereditary" from "nonhereditary" forms.

If "early cells of the germ line" or stem cells of a man or other male mammals are irreversibly damaged by noxious agents, such as ionizing rays, cytostatic drugs or others, you will find Sertoli-cells-only-syndrome. In contrast, the loss of differentiating spermatogonia, spermatocytes, or spermatids is a temporal phenomenon, as long as the systems of the somatic cells in the testis are intact. Irreversible damage of these cell systems, however - e.g. Leydig cell system and vascular system which are both situated in the extratubular compartment, the boundary tissue, or the Sertoli cells - results in permanent infertility just as in case of irreversible damage of cells of the "early germ line" or stem cells. On the other hand, a temporary damage of the somatic cell systems in the testis brought about by irritations of the extra- or intratesticular control systems may be neutralized by cure of the impairment. Mutations of the genetic matter caused by exogenous agents in the cells of the germ line are of limited importance to the fertility of the individual but have considerable significance for the genetic state of the population as a whole. Genetic damage of "early cells of the germ line" or stem cells is of higher consequence than negative alteration of the genome in cells belonging to the differentiating part of the germ line. On the other hand, the sensitivity of the genome is especially pronounced in spermatocytes and spermatids, the most advanced cells of the male germ line. The sensitivity of the cell (CS) and the sensitivity of the genome (GMS) frequently do not coincide.

The maximal tolerable risk for mankind due to radiation and chemically induced mutations has been accepted as an increased mutation rate of 25%. A linear dose-effect relationship has been assumed and from the experimentally obtained mutation rate due to irradiation of mouse spermatogonia, the following risk factors were obtained: 1. The doubling dose for specific locus in the mouse is representative of recessive conditions. 2. The mutation rate depends on dose rate and fractionation of the irradiation. 3. The extrapolation factor for using these mammalial results in man is about 1.2. 4. The results of specific locus investigations are representative of all the mutation-types in a mouse that have been investigated. 5. Both sexes are similarly affected. On the above premises, a radiation dose of approximately 75 mrem per annum would increase the spontaneous mutation rate in man by about 9% per generation. The risk due to chemical mutagens should not exceed that due to radiation. Methods similar to those used for radiation risks are able to estimate the chemical risk to the population. The tolerable risk to the population from chemical mutagens depends partly on the radiation burden, but the extent of the chemical burden is unknown. This can only be estimated if the law provides for measurements of mutagenicity for drugs, food additives, biocydal agents and industrial chemicals. A risk analysis should be carried out for those chemo-mutagens which are essential. The chemical burden of all permitted mutagens should not exceed the spontaneous mutation rate by 10% per generation at the most. The human hereditory stock can be protected from irreparable damage only if one succeeds in establishing norms for the controlled use of chemical mutagens similar to the regulations which already exist for radiation protection.

Drosophila, a higher organism with a short generation period, which can be reproduced quickly, cheaply, and in large numbers, offers, at the present time, the most rapid process for detecting point mutations and small deletions in animals. A technique perfected in the last decades provides subtle methods for detecting all mutation types relevant to humans. Of the different testing procedures, the extremely sensitive Basc-technique is most highly recommended for ascertaining X-chromosomal recessive lethal mutations; forward mutations and small deletions may be demonstrated in 115 of the total genomes. Enzyme systems in Drosophila are similar to liver microsomes in their metabolic capacity and indirect carcinogens can be detected as mutagens. Thus Drosophila procedures can be used to corroborate findings of preliminary tests with microorganisms. A further advantage of Drosophila is the practicable identification of substances with short-lived metabolites as end products of activation processes in the gonads.

The author persues earlier considerations regarding a quantitative evaluation of the usefulness against risks of radiological examinations, with a detailed discussion of the radiological and diagnostic problems. The possibilities of accurately quantifying degrees of urgency are discussed in practical terms, particularly for new forms of investigation in widespread use. In addition to a consideration of the usefulness and risks based on days gained or lost in the life of the patient, it is suggested that the cost of the examination should also be borne in mind. A model is illustrated by a number of examples. Finally, certain psychological problems are outlined which are concerned with the valuation and use of protective measures and with subjective estimates of risks involved.

Investigations were conducted on the composition of fatty acids in the fat of the embryo, the endosperm and several crush fractions of the maize kernel. The following results were obtained: 1. The embryo fat contained relatively lower contents of palmitin-, stearin- and linolenic acid, on the other hand higher contents of oleic- and linoleic acid in comparism to endosperm fat. 2. This result was identical to each one of the seven varieties examined. 3. The examined varieties presented clear differences both in the absolute contents of single fatty acids in the embryo and in the endosperm, as well as in the relationship between the components in the germ and in the endosperm. 4. The differences observed between the germ- and the endosperm fat in the crush fractions in some cases were clearly visible, while in other cases were not traceable.

Ionizing radiation during the whole developmental phase induces high radiation sensitivity in the human embryo and fetus. Particularly in the phase of organogenesis, increased malformations result in a lower quality of life for the fetus after birth. In a suspected or existing pregnancy, it is, therefore, necessary to limit the indication for examination or treatment of the mother with ionizing radiation or radioactive elements more than in other phases of life. The probability of unfavorably influencing development in the womb by ionizing radiation depends on the dose received by the fetus. For this reason, all measures should be taken to keep the radiation exposure to a minimum. Since up until now no uniform recommendations regarding indication for therapeutic abortion following irradiation have been drawn up in Western Germany, it is advisable to fall back on those recommendations drawn up by Scandinavian countries on the basis of thorough radiobiological knowledge and experience. In cases where the probability of unfavorable effects exceeds 10% and/or the natural malformation rate doubles, a therapeutic abortion should be considered. In a properly conducted examination, this level is generally not reached. A few tips are also presented in regard to the proper execution of the examination during pregnancy.

The so-called sex glands are not glands but germ hives. The germ cells are surrounded by nurse cells which alone build the tubulus or follicle epithelium (spermio- and oonutricytes). In the testis there is being differentiated between intra- and extratubular blood-germ cell barriers. The sperm cells should ultimately be called spermiocytes, the egg cells no longer be confused with the egg. The 4 germ cell generations and their 4 developmental phases in both organs are compared point by point. The interstitial cells are named andro- and gynocytes for considered reasons. The search for suitable names promotes knowledge and teaching.