THE PRESENT STATUS OF THE GERM-CELL PROBLEM IN VERTEBRATES

(i) Morphological studies relating to the origin and differentiation of the definitive germ cells in vertebrates have, as indicated, resulted in conflicting views. In many instances two or more competent investigators who have studied the same form have reached different conclusions. (2) Some contend that the germ cells are set aside from the soma during the early stages of embryonic development, and that these alone serve as the progenitors of the functional sex cells. (3) Others recognize an early differentiation of sex cells but hold that these are supplemented by others produced from the somatic epithelium of the gonad in late embryonic or post-embryonic stages. (4) Another group recognizes the early differentiated cells as germ cells but contend that these all degenerate and that the definitive ones are formed from the germinal epithelium. These degenerating germ cells are believed by certain authors to be a phylogenetic recapitulation of the condition in lower forms. (5) Finally, yet another group contends that the so-called primordial germ cells are not germ cells at all but are enlarged cells in some stage of mitosis or in some specific metabolic phase. This group believes that all germ cells are derived from the somatic cells of the germinal epithelium. (6) Experimental work supports the view that the primordial germ cells, which are recognized early, are the progenitors of the definitive sex cells. When these primordial germ cells are prevented from reaching the site of the developing gonad the individual fails to develop sex cells, although a sterile gonad and its associated structures may develop. (7) I suggest that the observed proliferation of germ cells from the germinal epithelium, reported by numerous investigators, can be interpreted in another way by a thorough study of the enlarged germ cells in relation to the epithelium. It seems probable that the cells of the epithelium, which form functional sex elements, are not and never were a part of the mesothelial covering, but are cells which were segregated early, and are merely stored in the epithelium.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74677/1/j.1469-185X.1945.tb00313.x.pd

Wie lässt sich die Eliminierung von Hepatitis B, C und D in Deutschland messen? Ergebnisse eines interdisziplinären Arbeitstreffens

Background!#!In 2016, the World Health Organization (WHO) released a strategy to eliminate hepatitis B, C, and D and defined indicators to monitor the progress. The Robert Koch Institute organized an interdisciplinary working meeting in 2019 to identify data sources and gaps.!##!Objectives!#!The objectives were to network, to create an overview of the data sources available in Germany on hepatitis B and C, and to discuss how to construct indicators.!##!Materials and methods!#!We extracted the WHO indicators relevant for Germany and determined how they can be constructed on the basis of available data. Stakeholders from public health services, clinics, laboratories, health insurance companies, research institutes, data holders, and registries attended a workshop and discussed methods of constructing the indicators for which data are lacking. Data sources and data were evaluated and prioritized with regard to their quality and completeness.!##!Results!#!Indicators on prevalence, incidence, prevention, testing and diagnosis, treatment, cure, burden of sequelae, and mortality for the general population can be constructed using secondary data such as diagnosis, health service, and registry data, data from laboratories and hospitals as well as population-based studies. Data sources for vulnerable groups are limited to studies among drug users, men who have sex with men, and about HIV coinfected patients. Data for migrants, prisoners, and sex workers are largely lacking as well as data on burden of disease from chronic viral hepatitis in the general population.!##!Conclusions!#!We identified data sources, their limitations, and methods for construction for all selected indicators. The next step is to convert the ideas developed into concrete projects with individual stakeholders