Notes on some African hepatic genera 1–5

The present study deals with five genera of hepatics in Africa, Isotachis Mitt., Anastrophyllum (Spruce) Steph., Tritomaria Schiffn. ex Loeske, Gymnocoleopsis (Schust.) Schust. and Lophozia (Dum.) Dum. All African populations of the genus Isotachis Mitt. are considered to be one species, I. aubertii (Schwaegr.) Mitt. Four species of Anastrophyllum (Spruce) Steph. (s.l.), A. auritum (Lehm.) Steph., A. piligerum (Nees) Spruce, A. subcomplicatum (Lehm. et Lindenb.) Steph. and A. minutum (Schreb.) Schust., and two species of Tritomaria Schiffn. et Loeske, T. camerunensis S. Arnell and T. exsecta (Schrad.) Schiffn. ex Loeske occur in Africa. Gymmocoleopsis multiflora (Steph.) Schust. represents a genus and species hitherto unreported for the African flora. Finally, five Lophozia (Dum.) Dum. species, L. argentina (Steph.) Schust., L. capensis S. Arnell, L. decolorans (Limpr.) Steph., L. hedbergii S. Arnell and L. tristaniana (S. Arnell) Váňa, are reported from central and southern Africa; two of these (L. argentina (Steph.) Schust. and L. decolorans (Limpr.) Steph.) represent the first reports from Africa.     

Direct infection of hepatocytes by sporozoites of Plasmodium berghei

To identify the unknown liver cell type initially invaded by sporozoites of mammalian malaria, young rats were inoculated intravenously with large numbers of Plasmodium berghei sporozoites obtained from infected Anopheles stephensi mosquitoes. Fine structural studies of liver specimens obtained from the rats within 2 min after inoculation demonstrated the presence of morphologically unaltered sporozoites in the cytoplasm of hepatocytes. Many sporozoites were also observed undergoing cytolysis within the lysophagosomes of Kupffer cells, as well as other phagocytic cells. These observations strongly suggest direct infection of the hepatocyte by the sporozoite.     

The capability of the algaeChlorella vulgaris andScenedesmus obliquus of utilizing amino acids as the sole nitrogen source

The capability of utilizing 20 amino acids and 2 amides as the sole nitrogen source for growth was studied in two green algae (Chlorophyceae). A comparison was made of the growth rate of algae in a mineral nutrient solution containing nitrate as the nitrogen source, with that in the same solution in which nitrogen in the form of nitrate was substituted by an equivalent nitrogen amount in the form of various amino acids. In addition to this, another series of experiments was carried out in whioh both culture media were supplied with glucose. The results show that both algae utilize a series of amino acids in dependence of their structure (mostly 3-carbon amino acids). The growth rate ofChlorella in the presence of these sources is the same as in nitrate, that ofScenedesmus even much higher. In the cultures containing glucose both algal species exhibit a higher growth rate in the media with the nitrate nitrogen source than in those with amino acids (with the exception of glycine inScenedesmus).     

Some observations on the morphological evidence for mechanism of the bile secretion

The morphological evidence of the intracellular route of bile secretion was investigated in the liver of goldfish (Carassius auratus) as revealed by electron microscopy. Smooth surfaced tubules or cisterns within or adjacent to the Golgi apparatus showed linear saccular forms and contained sparse particulate or cloudy materials of low electron density. The isolated vacuoles were restrictedly found between the Golgi apparatus and the intracellular bile canaliculus or hepatocytic side at the zone of transition. These vacuoles showed no reaction for acid phosphatase activity, and contained only a few cloudy materials similar to those found in the saccular tubules and within the bile canaliculus. Some of these vacuoles fused with the luminal cytolemmas of the bile canaliculus. Bases on these findings, it was assumed that these vacuoles are structures participating in transport and secretion of bile constituents and derive from the linearly sacculated tubules or cisterns in the Golgi zone. Duct cells showed no morphological evidence to suggest bile secretion.     

Cellular tumorigenicity in nude mice. Role of susceptibility to natural killer cells

The athymic nude mouse is a useful animal model for assaying the neoplastic growth potential in vivo of animal cells transformed in vitro. Despite the demonstrated absence of thymus-dependent immunological functions, however, the nude mouse has now been shown to reject transplants of certain highly malignant heterologous tumors. In addition, a few transformed mammalian cell lines that exhibit all or most of the cellular phenotypes usually associated with malignancy fail to grow as tumors when injected into nude mice. In a continuing study to identify the in vitro phenotypes associated with tumor-forming ability in vivo, we investigated the role of cellular susceptibility to the naturally occurring, thymus-independent lymphocytes (natural killer or NK cells) in determining tumor induction by animal cells in nude mice. A representative collection of animal cells (ranging from normal human diploid cell strains to highly tumorigenic clonal cell lines, either transformed in vitro or derived from experimental tumors) was tested to see if the ability of cells to form tumors is consistently correlated with their susceptibility to NK cell-mediated lysis measured in vitro with splenic leukocytes from nude mice. If the physiological role of the NK cells in vivo were to recognize, and possibly to destroy, incipient tumor cells in situ, a direct association between cellular tumorigenicity and susceptibility to NK activity, might be expected. If, on the other hand, the formation of growing tumors by animal cells in nude mice depended on their ability to escape the cytolytic activity of NK cells, cellular tumorigenicity would be associated with cellular resistance to NK cells. Results obtained in this study failed to confirm either of these associations. Thus, cellular suscepbibility to NK cells, at least as determined by direct cytotoxicity assay in vitro, is not a useful predictive indicator of cellular tumorigenicity in nude mice.     

Recovery from ethyl methanesulphonate-induced genetical damage in barley. Independence of sodium azide treatment

Barley seeds were treated for 3 h at 25°C with 240 mM ethyl methanesulphonate (EMS), washed for 18 h, treated with various concentrations of unbuffered sodium azide (pH 6.7–7.3) for 3 h at 25°C, re-dried to 30% water content and either sown immediately or stored at 25°C for 12 days and then sown. The synergistic action of sodium azide post-treatment has been demonstrated only for the EMS-induced M₁ germination reduction, while the EMS-induced M₁ sterility and the yield of M₂ chlorophyll mutants were unaffected. The ?storage” recovery from EMS-induced mutagenic effects was insensitive to sodium azide post-treatment. The 12 day-seed storage at 25°C brought about an improvement of M₁ germination, M₁ survival, M₁ fertility and a decrease in the amount of M₂ mutants, regardless of whether sodium azide post-treatment was applied or not.     

Retention of endocrine function by an insulin-secreting pancreatic islet cell tumour from Syrain hamster through serial transplantation in nude mice.

An insulin-secreting islet cell tumour of the Syrian hamster has been transplanted serially in the congenitally immune-deficient nude mouse, in order to test the potential usefulness of this mouse mutant as a graft carrier of heterologous tumours with stable differentiated phenotypes. The incidence of tumour growth was very high, and the hamster tumour retained its functional and histologic characteristics during consecutive passages in nude mice. These results show that nude mice may be useful carriers of differentiated tumours from non-inbred species including man, and for the isolation of cell lines from such tumours.