Summary. Insulin secretion by pancreatic tissue in vitro in response to glucose was related to plasma glucose and plasma insulin levels during life, and to the degree of granulation of the islets of Langerhans in 22 normal, 6 diabetic and 8 intermittently glycosurie Chinese Hamsters. Secretion was directly related to the insulin content of the pancreas and to the ratio of insulin to glucose in plasma, irrespective of the metabolic state of the animal, but was lowest in diabetic animals and highest in those with intermittent glyeosuria. The relevance of these findings to current theories concerning "prediabetes" is discussed. Sdergtion d'insuline in vitro par le pancrgas du hamster chinois.Rdsumd. Nous avons mesurd la sderdtion d'insuline du tissu pancrdatique in vitro en prdsence de glucose chez 22 hamsters chinois normaux, 6 diab6tiques et 8 ayant montrd une glueosurie intermittente. Les valeurs obtenues ont 6t6 compardes avee l'hyperglycdmie et l'insulindmie de ees m6mes animaux avant leur mort. Nous avons observd que la sderdtion insulinique in vitro dtait proportionnelle au contenu en insu]ine du pancrdas et au quotient de l'insulindmie divisde par lc glucose plasmatique inddpendammcnt de l'6tat mdtabolique de l'animal. Pourrant, la sderdtion insulinique in vitro la plus basse a dtd observde chez les animaux diabdtiques, et la plus 61evde ehez eeux qui avaient prdsentd une glucosurie intermittente. La relation possible de ees observations avee les thdories actuelles du ,)prd-diabgte(~ est diseutde. Insulinsekretion des Pankreas chinesischer Hamster in vitro.Zusammenfassung.

Various clinical and histologic approaches to the study of the retinal vasculature of the chinese hamster are described. The techniques include hindus photography, fluorescein angiogTaphy and the labeling of possibly damaged capillaries with carbon particles. A small group of untreated juvenile diabetic and control chinese hamsters were investigated. I-Iistologie study showed evidence suggestive of pathology at the capillary level in the diabetics. The endothelial cell (E) to intramural pericyte (IMP) ratio was significantly elevated in the diabetic animals. Etudes prdliminaires des vaisseaux rdtiniens du hamster chinois Rgsumd. Diff6rentes approehes cliniques et histologiques sent d6crites pour l'dtude du syst6me vaseulaire r6tinien des hamsters chinois. Ces m6thodes comportent l'examen photographique du fond de l'oeil, l'angiographie la fluoresc6ine et le marquage des eapillaires susceptibles d'Stre endommagds par des particules de carbone. Un petit groupe de hamsters chinois normaux ou avec un diab6te juv6nile non-trait6 a 6t6 6tudi6. L'examen histologique suggbre clairement la prdsence d'une pathologic capillaire ehez les animaux diab6tiques. Chez ces derniers, le rapport entre eellule endoth61iale (E) et p6rizyte intramural (IMP) est significativement 61evd. Erste Beobaehtungen i~ber alas retinale Gef(~fisystem des chinesisehen Hamsters Zusammenfassung. Versehiedene)/Iethoden zur Untersuchung des Netzhautgef~systems chinesischer Hamster in vivo oder post mortem werden beschrieben. Es handelt sich um die Fundusphotographie, die Fluorescein-Angiographic und die Markierung besch~digter Capillaren mit Kohlepartikeln. Eine kleine Gruppe unbehandelter diabetiseher nnd normaler chinesischer Hamster wurde untersucht. Histologisch waren die Netzhauteapillaren diabetischer Tiere ver~ndert. Im Verh/iltnis zur Zahl tier Endothelzellen waren die intramuralen Pericyten bei diabetischen Tieren deutlich vermindert.

Summary. The nuclear and plasma membranes of islet cells from non-glyeosurie and diabetic Chinese hamsters were examined by freeze-etching. The B-cells of diabetic animals presented a slight increase in the number of nuclear pores and marked alterations in the number, size and distribution of membrane-associated particles in the plasma membrane. In A-cells, identified by the presence of characteristic bundles of coarse filaments in the perinuclear region, a definite increase in the number of nuclear pores was found in the most severely diabetic animals.These preliminary findings point to alterations in the membrane systems as possible determinants for the abnormalities of islet function in diabetes mellitus.