Red cell enzyme polymorphisms in the Yoruba.

In this study are presented the results of an investigation of variation in 17 red cell enzyme systems in the Yoruba, a Negro population of western Nigeria. Nine of the systems were found not to be polymorphic. The other eight systems revealed a close resemblance to the Negroes of Southern Africa, and a marked contrast with the San ('Bushmen'). The Yoruba have a history of many centuries of urbanization, while the Southern African Negroes have only recently begun to inhabit large towns. It would appear not only that the polymorphisms investigated are irrelevant to adaptation to urban conditions, but also that no selective forces, and very little drift, has operated on them since the remote ancestral separation of the populations. These results also suggest that the Khoisan contribution to the Southern African Negro gene pool might not be as uniform or as considerable as might be supposed.     

Adenosine as a natural prostaglandin antagonist in vascular smooth muscle

Adenosine has actions on smooth muscle similar to those of prostaglandin (PG) antagonists. Like some PG antagonists it is a phosphodiesterase inhibitor and seems to interfere with calcium effects. It has agonist/antagonist interactions with theophylline, a PG antagonist. In rat mesenteric vascular smooth muscle adenosine blocked responses to noradrenaline which depend on release of intracellular calcium but not those to potassium ions which depend on calcium entry from extracellular fluid. Partial inhibition of endogenous PG synthesis by indomethacin enhanced the adenosine effect. In preparations in which vascular reactivity had been abolished by indomethacin and then partly restored by 1 or 5 ng/ml PGE2, adenosine also inhibited responses to noradrenaline: the curve for the 5 ng/ml PGE2 concentration was to the right of and parallel to the 1 ng/ml curve consistent with a competitive interaction between adenosine and PGE2. Similar interactions between adenosine and PGE2 were shown in human lymphocytes in which activation also depends on calcium release. These findings suggest how calcium-dependent metabolic responses may be controlled and indicate further reasons for caution in the interpretation of cyclic AMP experiments.     

Endotoxins in Animal Feedstuffs

Microbial heat stable endotoxins comprise part of most animal feedstuffs. These components have become the subject of considerable interest in later years because of the demonstration of acute toxicity, intravascular coagulation and generalized Shwartzman’s reaction in connection with intravenous injections of endotoxins (Nordstoga 1976). Endotoxins are normally present in the intestine of man and animals, but seem only to be absorbed under special conditions. Of particular interest is the “sudden infant death syndrome” which has been described for infants receiving cow milk (Di Luzio & Friedmann 1973). Absorption of endotoxins may also occur in adults e.g. in connection with γ-irradiation, immunosuppression, transplantations, severe traumatic lesions and burns (Nordstoga). It is supposed that endotoxins play an important role in the development of shock under these conditions (Nordstoga). Fine (1972) reported that exogenously administered endotoxins may break down the defence mechanisms and lead to continuous absorption of endotoxins from the intestine.     

Comparative Studies on Enrichment And Selective Media for Isolation of Salmonellae from Faecal Specimens

Enrichment media (tetrathionate, selenite and Rapp ap ort broths) and selective media (desoxycholate citrate agar and brilliant green agar) were tested in different combinations to ascertain their capacity for isolation of salmonella bacteria. The material consisted of 299 samples of cattle faeces from two herds infected with salmonella (Table 1), and of 111 artificially contaminated samples of pig faeces (Table 3). The tetrathionate and selenite broths were equally useful for the material as a whole, whereas the results varied between different species of salmonella which is of great practical interest. The number of salmonella isolations was much lower when enrichment with Rappaport broth was used. The rate of salmonella isolations can often be increased by parallel enrichments with two different media. Of the selective agar media tested, brilliant green agar was superior to desoxycholate citrate agar.     

Induction of structural chromosome aberrations and sister chromatid exchanges in human lymphocytes in vitro by aristolochic acid

The medicinal use of Aristolochia clematitis has been known for some time. The main active agent of this medicinal plant is aristolochic acid, a nitrophenanthrenecarbonic acid. Very recently, however, the Federal Health Office withdrew the licence for all drugs containing aristolochic acid, because of the well-founded suspicion that aristolochic acid may be a very potent carcinogen. We investigated the induction of structural chromosome aberrations and sister chromatid exchanges (SCEs) by aristolochic acid in human lymphocytes in vitro. Cells were treated with the agent tested throughout culture time and during the G0 phase of the cell cycle. We tested concentrations over a range of 1 to 20 micrograms/ml. Both treatment conditions resulted in an increased aberration frequency. The induction of gaps and breaks as well as the induction of SCEs showed a dose-dependent increase. The number of SCEs per metaphase was enhanced by a factor of 2 to 3. If conventional cytogenetic methods had been applied in time, one would have recognized the mutagenic risk of aristolochic acid earlier.     

Cell culture studies on neurofibromatosis (von Recklinghausen). II. Occurrence of glial cells in primary cultures of peripheral neurofibromas

The occurrence of glial cells in primary cultures established from peripheral neurofibromas of 18 patients with neurofibromatosis (von Recklinghausen) is described. The spindle-shaped cells can be distinguished from fibroblasts on the basis of morphological and ultrastructural criteria. As demonstrated by immunocytochemical analysis, the spindle cells express S-100 protein. Neither glial fibrillar acidic protein nor myelin basic protein can be detected in these cells. In many respects the spindle cells resemble immature Schwann cells in culture.