Summary From in vitro experiments it is concluded that there is no evidence for the existence of specific dopaminergic receptors in the ruminal smooth muscle. The responses produced by dopamine in isolated ruminal smooth muscle preparation of the goat appear to involve primarily a direct mechanism of action because inhibition of dopamine-β-hydroxylase failed to modify the action of this amine. Further, only large doses of cocaine caused reduction — a small one — in the response to dopamine. This mechanism of action is related to α-adrenergic receptors because dibenamine and phentolamine were very effective antagonists in contrast to propranolol. Dopamine was about 50 to 100 times less potent than adrenaline, while adrenaline appeared to be about 1.5 times as active as noradrenaline. It is concluded that the α-adrenergic receptors mediating the biphasic or motor responses to dopamine, noradrenaline and adrenaline are located on smooth muscle cells rather than on a nervous pathway. In the conscious goat dopamine, noradrenaline and adrenaline caused inhibition of the extrinsic reticulo-ruminal contractions. The mean doses of noradrenaline and dopamine which were equally active to 1 μg per kg. per min. of adrenaline were approximately 2 μg and 10 μg per kg. per min., respectively. The cardiovascular effects produced by dopamine were different from those produced by adrenaline or noradrenaline. Zusammenfassung Die Wirkung von Dopamin auf die adrenergischen Magenrezeptoren der Ziege In vitro-Versuche sprechen für das Fehlen von spezifischen dopaminergischen Rezeptoren in der glatten Pansenmuskulatur. Die Reaktionen von isolierten Präparaten von glatter Pansenmuskulatur der Ziege dürften auf einem direkten Wirkungsmechanismus beruhen, da eine Hemmung der Dopamin-β-Hydroxylase den Effekt dieses Amins nicht veränderte. Nur große Kokaindosen vermögen den Dopamineffekt ein wenig zu vermindern. Dieser Wirkungsmechanismus steht mit α-adrenergischen Rezeptoren in Beziehung, denn Dibenamin und Phentolamin waren im Gegensatz zu Propranolol sehr starke Antagonisten. Dopamin war etwa 50 bis 100 mal weniger wirksam als Adrenalin, während Adrenalin ungefähr 1,5 mal aktiver war als Noradrenalin. Die α-adrenergischen Rezeptoren, welche den biphasischen oder motorischen Effekt auf Dopamin, Noradrenalin und Adrenalin vermitteln, dürften sich eher an den glatten Muskelzellen denn an den Nerven befinden. An der wachen Ziege hemmten Dopamin, Noradrenalin und Adrenalin die Hauben-Pausenmotorik. Die mittleren Noradrenalin- und Dopamindosen, welche einen gleich starken Effekt wie 1 μg Adrenalin pro kg Körpergewicht und pro Minute auslösten, betrugen 2 μg bzw. 10μg pro kg und Minute. Die kardiovaskulären Effekte von Dopamin unterschieden sich von denjenigen des Adrenalins und Noradrenalins. Résumé Action de la dopamine sur les récepteurs adrénergiques stomacaux chez la chèvre Des recherches in vitro ont montré l'absence de récepteurs dopaminergiques spécifiques dans la musculature lisse de la panse. Les réactions de préparations isolées de musculature lisse de la panse chez la chèvre doivent reposer sur un mécanisme d'action direct, car une inhibition de la dopamine-β-hydrolase n'a pas changé l'effet de cette amine. Seules de grandes quantités de cocaïne ont un peu diminué l'effet de la dopamine. Ces mécanismes d'action doivent être en relation avec les récepteurs α-adrénergiques car la dibenamine et la phentolamine étaient fortement antagonistes contrairement au propanolol. La dopamine fut environ 50 à 100 fois moins active que l'adrénaline alors que cette dernière fut à peu prés 1,5 fois plus active que la noradrénaline. Les récepteurs α-adrénergiques qui manifestent l'effet biphasique et moteur par l'action de la dopamine, de la noradrénaline et de l'adrénaline, devraient plus se situer au niveau des cellules de la musculature lisse que des nerfs. La dopamine, la noradrénaline et l'adrénaline ont inhibé la motricité de la panse et du bonnet chez la chèvre éveillée. Pour produire un effet aussi fort que 1 μg d'adrénaline par kg de poids et par minute, la dose moyenne de noradrénaline et de dopamine a été de 2 μg, respectivement de 10 μg, par kg et par minute. Les effets cardiovasculaires de la dopamine étaient différents de ceux de l'adrénaline et de la noradrénaline. Resumen El efecto de la dopamina sobre los receptores gástrico-adrenérgicos en la cabra De los experimentos realizados in vitro, se infiere que no hay evidencia de la existencia de receptores dopaminérgicos específicos en el músculo liso de la panza. Las respuestas de preparaciones aisladas de músculo liso de la panza de cabra deberían basar en un mecanismo directo de acción, ya que la inhibición de la dopamina-β-hidroxilasa no alteraba la acción de esta amina. Dosis elevadas de cocaína nada más daban lugar a disminuir un poco el efecto dopamínico. Este mecanismo de acción está relacionado con los receptores α-adrenérgicos, ya que la dibenamina y la fentolamina eran unos antagonistas muy efectivos, en contraste con el propanolol. La dopamina era unas 50 a 100 veces menos potente que la adrenalina, mientras que ésta era 1,5 veces más activa que la noradrenalina. Los receptores α-adrenérgicos, que transmiten las respuestas bifásicas o motoras a la dopamina, noradrenalina y adrenalina, deberían estar localizados más bien en las células del músculo liso que en los nervios senderos. En la cabra consciente inhibían la dopamina, noradrenalina y adrenalina las contracciones extrínsecas retículo-ruminales. Las dosis medias de noradrenalina y dopamina, que desencadenaban el mismo efecto intenso que 1 μg de adrenalina por kg peso en pie y minuto, eran del orden de 2 μg resp. 10 μg por kg y minuto. Los efectos cardiovasculares producidos por la dopamina se diferenciaban de aquellos ocasionados por la adrenalina o noradrenalina.

In adultFasciola hepatica glucose is broken down to volatile fatty acids, carbon dioxide and lactate. In the cytosol glucose is converted into malate and lactate and malate is metabolized further in the mitochondrial compartment via a dismutation. The dismutation of malate can proceed under anaerobic conditions. To a limited extent oxygen can function as terminal electron acceptor.

The synthesis of ketone bodies by intact isolated rat-liver mitochondria has been studied at varying rates of acetyl-CoA production and of acetyl-CoA utilization in the Krebs cycle. Factors which enhanced the rate of acetyl-CoA production caused an increase in the fraction of acetyl-CoA which was incorporated into ketone bodies. On the other hand, it was found that factors which stimulated the formation of citrate lowered the relative rate of ketogenesis. It is concluded that acetyl-CoA is preferentially used for citrate synthesis, if the level of oxaloacetate in the mitochondrial matrix space is adequate. The intramitochondrial level of oxaloacetate, which is determined by the malate concentration and the ratio of NADH over NAD+, is the main factor controlling the rate of citrate synthesis. The ATP/ADP ratioper se does not affect the activity of citrate synthase in thisin vitro system. Ketogenesis can be described as an overflow of acetyl-groups: Ketone-body formation is stimulated only when the rate of acetyl-CoA production increases beyond the capacity for citrate synthesis.

1. The phospholipid composition of Fasciola hepatica, the common liver fluke, was compared to that of the liver of the host animals (rats and cattle). Considerable differences were found:monoacyl-sn-glycero-3-phosphorylcholine, hardly detectable in the liver, was found in significant amounts in the parasite. On the other hand, sphingomyelin, a normal constituent in the liver, appears to be absent in the liver fluke. Fasciola hepatica isolated from rat and cow liver had a strikingly similar phospholipid composition. 2. Qualitative and quantitative differences were also found between the fatty acyl constituents of the phospholipids of the parasite and the liver. The major difference was the presence of eicosaenoic and eicosadienoic acids in the parasite, whereas these acids were not detected in the liver. 3. In vitro incubations of Fasciola hepatica in the presence of (32P)phosphate and (2-3H)glycerol resulted in the labelling of all phospholipids of the parasite, except that the 3H label did not incorporate into ethanolamine plasmalogen. This is in agreement with the concept that in animals, glycerol is introduced into plasmalogens via dihydroxyacetonephosphate. 4. Homogenates of liver flukes were found to catalyze the synthesis of phosphatidylcholine from 1,2-diacyl-sn-glycerols and CDPcholine. 5. These results strongly suggest that Fasciola hepatica is capable of synthesizing at least part of its fatty acids and phospholipids.

Sheets of rumen epithelium from several ruminant species were incubated with L-lactate or D-lactate as the only added substrate offered over a wide concentration range. With increasing concentrations of L-lactate, increasing amounts of carbon dioxide were produced, usually more acetoacetate was synthesized, and more oxygen was taken up by the tissue.

Seven strains of isolated from the bovine rumen are described and their characteristics compared with those of strains described in the literature. On the basis of fermentation products two groups can be distinguished within this species. One group includes the type strain and is almost completely homofermentative. The other group includes strains that produce hydrogen, formate, butyrate and valerate in addition to lactate.

Seven strains ofEubacterium (Cillobacterium) cellulosolvens isolated from the bovine rumen are described and their characteristics compared with those of strains described in the literature. On the basis of fermentation products two groups can be distinguished within this species. One group includes the type strain and is almost completely homofermentative. The other group includes strains that produce hydrogen, formate, butyrate and valerate in addition to lactate.