Energy-dispersive X-ray microanalysis of membrane-associated inclusions in hydrogenosomes isolated from Trichomonas vaginalis

Energy-dispersive X-ray microprobe analysis of electron-dense inclusions in hydrogenosomes isolated from the aerotolerant anaerobic protozoal human parasite Trichomonas vaginalis, Bushby strain, indicated the presence of high levels of Mg, P and Ca. This suggested that divalent cation (e.g. Ca2+ or Mg2+) accumulation by hydrogenosomes may be important in the regulation of intracellular ion concentrations.     

Chondroitin sulphate at the endothelial lumen of pig aorta: Assay by radiolabelling and by X-ray microanalysis

Trypsin-releasable glycosaminoglycans from the luminal surface of intact pig aorta were measured following metabolic labelling with³⁵S]sulphate. Chondroitin sulphate was found to be present at a surface density equal to that already established for heparan sulphate (5×10¹¹ chains per cm²). This result was confirmed by X-ray microanalysis of the luminal sulphur content before and after treatment with specific glycosaminoglycan-degrading enzymes. This result implies that approximately half of the luminal surface is occupied by sulphated glycosaminoglycans.     

Electric organ polyamines and their effects on the acetylcholine receptor

1. The electric organ of Torpedo nobiliana contained putrescine (PUT), spermidine (SPD), spermine (SPM), and cadaverine (CAD). Traces of acetylated SPD and SPM were occasionaly seen. 2. Upon fractionation of the tissue by differential centrifugation, the polyamines (PA) were found predominantly in the soluble fraction. The postsynaptic membrane fraction, containing a high concentration of acetylcholine receptor (AChR), was proportionally enriched in SPM. The molar ratio of SPM to AChR was approximately two in these membranes. 3. The effect of exogeneous PA on AChR function was studied by two methods: carbamoylcholine (CCh)-dependent 86Rb+ influx into receptor-rich membrane vesicles and [alpha-125I]bungarotoxin (Bgt) binding to the AChR. 4. SPM inhibited both ion influx and the rate of Bgt binding at concentrations above 1 mM, and therefore it appears to act as a competitive antagonist of the AChR. 5. At submicromolar concentrations, and only after preincubation with the receptor-rich membrane, SPM and PUT increased the ion influx by about 20% over control values. 6. Preincubation with 100 nM SPM did not affect the equilibrium binding of iodinated toxin or the rate of toxin binding, and therefore SPM was not uncovering new receptors. 7. By measuring the initial rate of toxin binding after different periods of preincubation with 1 microM CCh, the rate of the slow phase of receptor desensitization was determined. This rate was not changed by 100 nM SPM. 8. Although these results suggest that at low concentrations SPM is a positive modulator of the AChR, the precise mechanism of action is not determined yet.     

Radical functionalism: The life and work of Karl Polanyi

Conclusion In concluding, let us restate the main theoretical arguments concerning Austria-Hungary and Malinowski-Polanyi. There are many more aspects of this latter contrast which I have not dwelt on, including those of temper and personality. My concern was to show that it is not enough to trace ideas back to their origin in an undifferentiated Central Europe, for we need to be quite clear about the context in which those ideas were initially taken on board. Mach was an appropriate philosopher for the ordered bureaucracy of Austria, and he embodies the individual-centered and fundamentally conservative message, which I see articulated later in very different (and non-positivist) styles by Popper, Hayek, Schumpeter, etc. This was the message accepted in its fundamentals by Malinowski in Cracow. The Hungarian half of the Empire had quite different traditions, and one might even say that political dilemmas in this half of the Empire were so pressing that they had no time for philosophy. By the time Polanyi was growing up in Budapest, nationalist fervor was at its height, and a nineteenth century heritage of liberal, even radical thought, was under pressure from the extreme right. Polanyi's Jewish family background probably pushed him towards the Left in his early years, though it in no way interfered with this Hungarian patriotism. When he read Mach, he accepted the individualist and positivist aspects of the message, but he could never endorse the conservative respect for tradition that underpinned Malinowski's functionalism. This is what makes his position so interesting, and he maintained it throughout his career.In this light, Polanyi's economic anthropology is an authentic cultural product of Central Europe. Malinowski, to the extent that he took on board the basic social theory of Austrian liberal conservatism, sold out to the West, and to an ideological tradition which has an alternative home in another country on the periphery of industrial capitalism: Enlightenment Scotland. Austria-Hungary also produced intellectuals who sold out in the other direction, and abandoned all notion of intellectual autonomy for the individual by capitulating to the total discipline of the revolutionary Party. This tradition is that of Russia and Lenin, and the best known Central European intellectual recruit was Lukács, perhaps because he studied idealists in Germany rather than the positivists in Vienna. Karl Polanyi was unable to give unswerving loyalty either to the capitalist ideology of the West, or to the ideology of the new tributary mode of production in the East. The middle position, which I believe he occupied throughout his life, is one that will never satisfy ideologues, and it is hard to infuse it with the same intellectual elegance. Still, just as his historical researches showed the real possibilities for combining modes of economic integration, and his life experiences showed the folly of concentration on only one, so Hungarians have learned from history that they are best off with the sort of mixed economy they have today. His popularity in Hungary is therefore unsurprising, and one may hope that the practical message of his anthropology will not be permanently forgotten in the West.Christopher H. Hann is a Professor of Social Anthropology, University of Kent, Canterbury.     

Spreading of wheat germ agglutinin-induced erythrocyte contact by formation of spatially discrete contacts.

The time dependence of agglutination and cell-cell contact spreading in human erythrocytes exposed to wheat germ agglutinin (WGA) was characterized by light and electron microscopy. Cells (3 x 10(7)/mL) had a threshold lectin concentration in the range of 0.6-2.0 micrograms/mL for initial cell contact. Spreading was essentially completed within 60 and 2 min in undisturbed and gently agitated suspensions, respectively. The cells in large WGA agglutinates retained features of their initial disk form in contrast to the convex outlines of polycation or polyethylene glycol-induced agglutinates. Spreading of contact area was accompanied by development of a pattern of discrete contact regions separated by a distance of the order of 1 micron. Freeze fracture electron microscopy and studies with ferritin-labeled WGA showed no significant aggregation of intramembrane particles or specific lectin receptors under conditions when contact spreading occurred. It is argued that flow stress effects on cells in suspended agglutinates give rise to a situation where opposite membranes, at the leading edge of cell contact, are separated by a thin aqueous layer. When this intercellular water layer exceeds a critical length, it becomes unstable. The layer breaks up by surface wave development to form an array of intracellular water spaces. Formation of the aqueous spaces causes opposite membrane regions to move synchronously toward each other. Lectin molecules crosslink the wave crests to give spatially periodic contact points.     

Telomeric repeat [TTAGGG]n sequences of human chromosomes are conserved in chimpanzee (Pan troglodytes)

Summary Using a series of genetic parameters, attempts have been made for more than two decades to establish the close kinship of human (Homo sapiens) with chimpanzee (Pan troglodytes). Molecular and cytogenetic data presently suggest that the two species are closely related. The recent isolation of a human telomeric probe (P5097-B.5) has prompted us to cross hybridize it to chimpanzee chromosomes in order to explore convergence and/or divergence of the telomeric repeat sequences (TTAGGG)_n. On hybridization, the human probe bound to both ends (telomeres) of chimpanzee chromosomes, suggesting a concerted evolution of tandemly repeated short simple sequences (TTAGGG)_n. Even the terminal heterochromatin of chimpanzee chromosomes was found to be endowed with telomeric repeats, suggesting that evolution of heterochromatin and capping with tandemly repeated short sequences are highly complex phenomena.     

Endocytotic uptake of fluorescent dextrans by pollen tubes grown in vitro

Summary Pollen tubes grow by tip growth, with high levels of exocytosis at the apex. The commercial availability of FITC labelled -linked dextrans provides a source of biologically inert tracers for endocytotic activity in pollen tubes. Growing tubes ofNicotiana andTradescantia were transferred to media containing 1% FD-4 for varying period of time before washing in control media and observation in a fluorescence microscope. Fluorescent material appeared to enter the pollen tubes only at the tip region, and to accumulate in vacuoles, starting with smaller vacuoles near the tip and spreading to the main vacuolated part of the tube. Mature tubes, with callose plugs, were only labelled up to the first complete plug from the tip, younger tubes without plugs were labelled into the pollen grain vacuole. The fluorescent material within the pollen tubes was shown to represent uptake of intact high molecular weight dextran by the following criteria: (i) free FITC and low molecular weight dextrans could not be detected in any of the media or pollen tubes using thin layer chromatography and (ii) pollen tube growth rates were unaffected by the fluorescent dextran, but were severely inhibited by low levels of free FITC. It was concluded that the dextrans entered the tubes by endocytosis, possibly in the tip region, and were then transferred to the vacuole system of the pollen tube.Abbreviations FITC fluorescein isothiocyanate - FD fluorescent dextran     

Oxytetracycline production by Streptomyces rimosus in solid-state fermentation of corncob

Corn-cob was used as a substrate in the production of oxytetracycline by Streptomyces rimosus TM-55 in a solidstate fermentation. Oxytetracycline was detected on day 4, and reached its maximum on day 8. Optimal conditions for oxytetracycline production were an initial pH of 5.2 to 6.3, an initial moisture content of 64% to 67%, supplementation with 20% (w/w) rice bran or 1.5% to 2.5% (w/w) (NH₄)₂SO₄ as sole N source, 1.0% (w/w) CaCO₃, 2% (w/w) MgSO₄.7H₂O, and 0.5% (w/w) KH₂PO₄, with incubation for 8 days at 25 to 30°C. Each g substrate produced 7 to 8 mg oxytetracycline.