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

Meeting the International Health Regulations (2005) surveillance core capacity requirements at the subnational level in Europe: the added value of syndromic surveillance

BACKGROUND: The revised World Health Organization's International Health Regulations (2005) request a timely and all-hazard approach towards surveillance, especially at the subnational level. We discuss three questions of syndromic surveillance application in the European context for assessing public health emergencies of international concern: (i) can syndromic surveillance support countries, especially the subnational level, to meet the International Health Regulations (2005) core surveillance capacity requirements, (ii) are European syndromic surveillance systems comparable to enable cross-border surveillance, and (iii) at which administrative level should syndromic surveillance best be applied? DISCUSSION: Despite the ongoing criticism on the usefulness of syndromic surveillance which is related to its clinically nonspecific output, we demonstrate that it was a suitable supplement for timely assessment of the impact of three different public health emergencies affecting Europe. Subnational syndromic surveillance analysis in some cases proved to be of advantage for detecting an event earlier compared to national level analysis. However, in many cases, syndromic surveillance did not detect local events with only a small number of cases. The European Commission envisions comparability of surveillance output to enable cross-border surveillance. Evaluated against European infectious disease case definitions, syndromic surveillance can contribute to identify cases that might fulfil the clinical case definition but the approach is too unspecific to comply to complete clinical definitions. Syndromic surveillance results still seem feasible for comparable cross-border surveillance as similarly defined syndromes are analysed. We suggest a new model of implementing syndromic surveillance at the subnational level. In this model, syndromic surveillance systems are fine-tuned to their local context and integrated into the existing subnational surveillance and reporting structure. By enhancing population coverage, events covering several jurisdictions can be identified at higher levels. However, the setup of decentralised and locally adjusted syndromic surveillance systems is more complex compared to the setup of one national or local system. SUMMARY: We conclude that syndromic surveillance if implemented with large population coverage at the subnational level can help detect and assess the local and regional effect of different types of public health emergencies in a timely manner as required by the International Health Regulations (2005)

Évaluation des méthodes de contention par arcs linguaux inférieurs collés

Cinquante arcs linguaux de contention ont été collés en pont de canine à canine et de prémolaire à prémolaire. Pour les uns et les autres, le pourcentage d'échecs s'est élevé à 14 %, et reste surtout imputable à une technique de collage défectueuse, la majorité des arcs décollés ayant intéressé les premiers dispositifs placés en bouche. Après une étude du dessin possible de ces divers types de mainteneurs, de leur extension latérale et de leur mode de réalisation, une description de la technique utilisée a été étayée de recommandations d'ordre pratique. Les avantages propres aux arcs collés et scellés, en fonction de leur portée, ont ensuite fait l'objet d'une discussion. Il en ressort que les arcs collés de prémolaire à prémolaire constituent un moyen fiable de stabilisation de l'arcade antéro-inférieure au cours des phases de contention. Ils associent, en effet, les caractéristiques bénéfiques, propres aux arcs collés et aux stabilisateurs scellés. Leur réalisation, effectuée indirectement au laboratoire, ne soulève aucune difficulté particulière dès que la hauteur coronaire linguale est suffisante. Ils représentent la suite logique d'un traitement conduit à l'aide de boîtiers collés et demeurent invisibles vestibulairement. Ils permettent de contrôler l'axe de la canine après sa rétraction, d'empêcher une ouverture secondaire de l'espace d'extraction et de maintenir l'expansion transversale produite. Leur dernier intérêt, non moins essentiel, réside dans le fait que leur emplacement leur permet d'échapper aux forces occlusales, puisqu'ils se situent régulièrement dans une zone coronaire déflectrice

Évaluation de la thérapeutique fonctionnelle de H. P. Bimler : étude de 10 cas traités, par superpositions de Ricketts

Les changements, dus simultanément à la croissance et au traitement, ont été analysés sur dix cas présentant des dysmorphoses du type Classe II, division 1 et traités par appareillage standard de H. P. BIMLER. La méthode des superpositions de R. M. RICKETTS a, seule, été utilisée à cet effet, permettant d'enregistrer les modifications de l'étage dento-alvéolaire et du profil esthétique