Beiträge zur Biosynthese von Nicotinsäure und Chinolinsäure bei Mycobacterium bovis Stamm BCG

Zusammenfassung Zur Untersuchung der Nicotinsäurebiosynthese werden an wachsenden Kulturen von Mycobacterium bovis Stamm BCG Einbauversuche mit ¹⁴C-markierten Precursoren durchgeführt und die spezifischen Inkorporationsraten sowie die ¹⁴C-Verteilung der isolierten Nicotinsäure bestimmt. Formiat-(¹⁴) und D-Ribose-(U-¹⁴C) werden nicht in Nicotinsäure eingebaut. Im Gegensatz zu Befunden anderer Autoren an Clostridium butylicum zeigen Formiat-(¹⁴C) und Acetat-(¹⁴C) im Rohhomogenat von BCG-Bakterien keinen Einbau in Nicotinsäure und sind als Nicotinsäurevorstufen auszuschließen.Glycerin-(1,3-¹⁴C) und Glycerinsäure-(3-¹⁴C) gehen bevorzugt in die C-Atome 4, 5 und 6. Das C-Atom 6 der Nicotinsäure entspricht dem C-3 der Glycerinsäure. Somit erfolgt der Einbau der Glycerinsäure nicht über ein symmetrisches Intermediärprodukt.Durch Isotopen verdünnungsanalyse wird Chinolinsäure als Ausscheidungsprodukt von M. bovis Stamm BCG nachgewiesen. Ihre Biosynthese erfolgt in Analogie zur Nicotinsäurebildung aus Aspartat und Glycerin.

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Biosynthesis of nicotinic acid and quinolinic acid by Mycobacterium bovis strain BCG

Summary Biogenesis of nicotinic acid was studied by feeding ¹⁴C-labelled precursors in growing cultures of Mycobacterium bovis strain BCG. The incorporation rate as well as the distribution of ¹⁴C in the isolated nicotinic acid were determined. Formate-(¹⁴C) and D-ribose-(U-¹⁴C) were not incorporated into nicotinic acid. In contrast to experiments performed with Clostridium butylicum, crude homogenates of M. bovis strain BCG showed no incorporation of formate-(¹⁴C) and acetate-(¹⁴C) under the experimental conditions applied and therefore, these compounds should be excluded as possible precursors. Glycerol-(1,3-¹⁴C) and glyceric acid-(3-¹⁴C) are incorporated into positions 4, 5 and 6, as expected. The carbon atom 6 of nicotinic acid was almost exclusively derived from C-3 of glyceric acid. Incorporation of glyceric acid therefore does not follow through a symmetrical intermediate.By isotope dilution technique quinolinic acid has been found in the culture medium indicating to be an excretary product of M. bovis strain BCG. Its biosynthesis occurs, in analogy to nicotinic acid formation, from aspartate and glycerol.

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Herrn Prof. Dr. Dr. h. c. mult. K. Mothes zum 70. Geburtstag in Dankbarkeit gewidmet.     

Thrombospondins and tumor angiogenesis

The thrombospondins (TSPs) are a family of five secreted proteins that are widely distributed in the extracellular matrix of numerous tissues. TSPs are multimodular and each domain specifies a distinct biological function through interaction with a specific receptor. TSP1 and TSP2 have anti-angiogenic activity, which, at least for TSP1, involves interaction with the microvascular endothelial cell receptor CD36. Expression of TSP1 and TSP2 is modulated by hypoxia and by oncogenes. In several tumors (thyroid, colon, bladder carcinomas), TSP1 expression is inversely correlated with tumor grade and survival rate, whereas in others (e.g. breast carcinomas), it is correlated with the stromal response and is of little prognostic value. Recent studies suggest that TSPs or TSP-derived peptides retaining biological activity could be developed into promising new therapeutic strategies for the anti-angiogenic treatment of solid tumors.     

Cultured endothelial cells produce heparinlike inhibitor of smooth muscle cell growth

Using cultured cells from bovine and rat aortas, we have examined the possibility that endothelial cells might regulate the growth of vascular smooth muscle cells. Conditioned medium from confluent bovine aortic endothelial cells inhibited the proliferation of growth-arrested smooth muscle cells. Conditioned medium from exponential endothelial cells, and from exponential or confluent smooth muscle cells and fibroblasts, did not inhibit smooth muscle cell growth. Conditioned medium from confluent endothelial cells did not inhibit the growth of endothelial cells or fibroblasts. In addition to the apparent specificity of both the producer and target cell, the inhibitory activity was heat stable and not affected by proteases. It was sensitive flavobacterium heparinase but not to hyaluronidase or chondroitin sulfate ABC lyase. It thus appears to be a heparinlike substance. Two other lines of evidence support this conclusion. First, a crude isolate of glycosaminoglycans (TCA-soluble, ethanol-precipitable material) from endothelial cell-conditioned medium reconstituted in 20 percent serum inhibited smooth muscle cell growth; glycosaminoglycans isolated from unconditioned medium (i.e., 0.4 percent serum) had no effect on smooth muscle cell growth. No inhibition was seen if the glycosaminoglycan preparation was treated with heparinase. Second, exogenous heparin, heparin sulfate, chondroitin sulfate B (dermatan sulfate), chondroitin sulfate ABC, and hyaluronic acid were added to 20 percent serum and tested for their ability to inhibit smooth muscle cell growth. Heparin inhibited growth at concentrations as low as 10 ng/ml. Other glycosaminoglycans had no effect at doses up to 10 μg/ml. Anticoagulant and non- anticoagulant heparin were equally effective at inhibiting smooth muscle cell growth, as they were in vivo following endothelial injury (Clowes and Karnovsk. Nature (Lond.). 265:625-626, 1977; Guyton et al. Circ. Res. 46:625-634, 1980), and in vitro following exposure of smooth muscle cells to platelet extract (Hoover et al. Circ. Res. 47:578-583, 1980). We suggest that vascular endothelial cells may secrete a heparinlike substance in vivo which may regulate the growth of underlying smooth muscle cells.     

Offshore refuges support higher densities and show slower population declines of wintering Ruddy Turnstones Arenaria interpres

ABSTRACT

Capsule: Wintering Ruddy Turnstones Arenaria interpres occur in higher densities and their populations decline less on, or close to, offshore refuges than on mainland sites subject to greater levels of human disturbance.

Aim: To compare wintering densities of Ruddy Turnstones and changes in counts across time from sites with differing levels of human disturbance.

Methods: Long-term counts of Ruddy Turnstones (1998/1999 to 2015/2016) were used from 19 sites (two offshore refuges and 17 mainland sites subject to higher levels of human disturbance) in northeast England. No direct measure of human disturbance was available for our mainland sites; instead we used questionnaires (n?=?690) to understand how far people travelled to visit the coast and then used this distance with human population densities in a buffer around each site as a proxy for human disturbance levels.

Results: After controlling for the extent of their preferred habitat at each site (rocky shore) we found: (i) the closer each of the 19 sites was to the nearest offshore refuge the higher the density of Ruddy Turnstones and (ii) bird counts were stable at the two refuge sites, whereas, on average, counts declined at the 17 mainland sites. However, no relationship was found between Ruddy Turnstone counts from 17 mainland sites and human population densities within differing distances from each site (up to 10?km).

Conclusions: Our work suggests that Ruddy Turnstones made greater use of relatively undisturbed areas (offshore refuges) than those subject to greater disturbance by humans (mainland sites). Although the use of refuges and mainland in our study area was not well known, observations from 11 radio-tagged Ruddy Turnstones suggest that individual birds did use both locations. In a broader context, our work concurs with other studies that highlight the need for refuges with limited or no human access.