The role of microtubules in vessel member differentiation inColeus

Summary The role of microtubules in tracheary element formation in cultured stem segments ofColeus has been investigated through the use of the antimicrotubule drug, colchicine. Colchicine treatment of the cultured stem segments produced a dual effect on xylem differentiation. If applied at the time of stem segment isolation or shortly thereafter, wound vessel member formation is almost completely blocked. However, if colchicine is applied after the third day of culture, it does not inhibit differentiation, but instead large numbers of xylem elements are formed which have highly deformed secondary walls. Both effects are related to colchicine's specific affinity for microtubules. In the first case it is shown that colchicine blocks mitosis, presumably by destroying the spindle apparatus, and thus inhibits divisions which are prerequisite for the initiation of xylem differentiation. While, if colchicine is applied after the necessary preparative divisions have taken place, it destroys specifically the cortical microtubules associated with the developing bands of secondary wall, thus causing aberrant wall deposition.Light and electron microscopic analysis of drug-treated cells reveals that the secondary wall becomes smeared over the surface of the primary wall and does not retain the discrete banded pattern characteristic of secondary thickenings in untreated cells. Examination of colchicine-treated secondary walls in KMnO₄ fixed material shows that in the absence of microtubules the cellulose microfibrils lose their normal parallel orientation and are deposited in swirls and curved configurations, and often lie at sharp angles to the axis of the secondary wall band. Microtubules, thus, appear to play a major role in defining the pattern of secondary wall deposition and in directing the orientation of the cellulose microfibrils of the wall. Factors in addition to microtubules also act in controlling the secondary wall pattern, since we observe that even in the absence of microtubules secondary thickenings of two adjacent xylem elements are deposited directly opposite one another across the common primary wall.     

New observations on the bioluminescence of echinoderms

Bioluminescence has been observed in two species of Ophiuroidea, six species of Asteroidea, nine species of Holothuroidea and two species of Crinoidea. The luminescent responses are described and the intensities and time courses of the responses of some species are given.
Histological investigations have indicated possible luminous cells in the Holothuroidea, but the results in other classes remain equivocal. Preliminary analyses of the chemistry of bioluminescence indicate that a similar system may be responsible for bioluminescence in all four classes, although the visible manifestations of the system vary considerably.     

Inhibition of transport systems in cultured rat hepatoma cells by colcemid and ethanol

The transport of uridine, hypoxanthine, and choline in cultures of Novikoff rat hepatoma cells is competitively inhibited by colcemid with apparent K_i values of 135, 60, and 250 μM respectively, whereas the transport of 2-deoxy-D-glucose is not affected. Ethanol at high concentrations inhibits the transport of all four substrates in an apparent competitive manner.     

Intermittent Chemotherapy for Tuberculosis in an Urban Community

A regimen designed for effective foolproof antituberculosis treatment, acceptable on a routine basis, was applied to all patients newly diagnosed at the Chest Clinic, Hammersmith Hospital, in 1963, 1964, and 1965. During the first three months of treatment patients received daily (six days a week) streptomycin 0.75 g. plus isoniazid 300 mg. plus sodium para-aminosalicylate (P.A.S.) 12 g. The P.A.S. was usually stopped when bacterial sensitivity reports made this possible. For a further 15 months streptomycin 1 g. plus isoniazid 600 mg. was given on three alternate days each week to complete a total of 18 months'' treatment.Of the total of 140 patients (66% sputum-positive) 112 (80%) completed the planned 18 months with intermittent streptomycin plus isoniazid and a further eight completed treatment on alternative regimens (a total of 85%). The equivalent figures for one year are 88% and 94%. Excellent clinical and radiological results, together with sputum conversion, were achieved in 138 of the 140 patients (99%). Only two patients were lost from surveillance, because of failure to co-operate, before quiescence was obtained.It is concluded that the total efficiency of supervised intermittent treatment is greater than that of unsupervised daily regimens. Since 100% arrest of tuberculosis is possible with co-operative patients, less should not be accepted in developed countries.     

Acute Abdominal Pain in Childhood,with Special Reference to Cases not due to Acute Appendicitis

Appendicitis is not the only common cause of acute abdominal pain in childhood. Almost equally common is an acute episode which in its early stages resembles acute appendicitis but which subsides without treatment in 24 to 48 hours. The clinical features of this syndrome are contrasted with those of appendicitis. The two conditions cannot always be distinguished on clinical grounds, leading to admission to hospital for observation and the finding of a normal appendix in 14% of operations for suspected appendicitis. Reasons are given for abandoning attempts to diagnose acute mesenteric adenitis at the bedside.     

Cell differentiation and pigment composition in Anabaena cylindrica

Summary Cell differentiation in Anabaena cylindrica is accompanied with characteristic changes in the pigment composition of heterocysts and spores. In both the absence of phycocyanin is consistent with the lack of CO₂-fixing ability previously reported. The presence of chlorophyll and -carotene suggests a functional photosystem I in heterocysts. In the spores chlorophyll is largely replaced by pheophytin. The quantitative distribution of carotenoids is also affected. An increase in the proportion of -carotene is characteristic of heterocysts while spores show a larger proportion of xanthophylls compared with the intact filament.     

Beobachtungen zur fortpflanzungsbiologie und zum verhalten der geißelspinne tarantula marginemaculata C. L. Koch (Chelicerata,Amblypygi)

The social behaviour of T. m. includes ritualized fights. Sperm transfer is achieved by means of a spermatophore deposited on the ground and by the male pulling the female over it. The behaviour and the spermatophore are described and compared to those of other arachnids and the phylogenetical implications are discussed.     

Die Feinstruktur der peribronchialen Mikroparaganglien beim Meerschweinchen

Zusammenfassung Das Parenchym der peribronchialen Mikroparaganglien wird von zwei Zellarten aufgebaut: Chromaffine Zellen (Typ I-Zellen) und Hüllzellen (Typ II-Zellen).Die chromaffinen Zellen sind durch ihren reichen Gehalt an Vesikeln mit elektronendichtem Inhalt gekennzeichnet, deren Durchmesser 700–1300 Å beträgt. Markfreie Nerven ziehen an die Typ I-Zellen heran und bilden synaptische Kontakte aus. Die chromaffinen Zellen sind dabei der postsynaptische Teil der Verbindung. Die Hüllzellen entsprechen strukturell und funktionell den Schwannschen Zellen.Ein Mikroparaganglion wird von 10 bis 15 chromaffinen Zellen und deren Hüllzellen aufgebaut. Sie liegen dicht um fenestrierte Kapillaren, die von den Aa. bronchiales aus versorgt werden. Die Paraganglien sind von den Nervenzellen des peribronchialen Plexus durch dessen Perineurium getrennt. Selten findet man solitäre chromaffine Zellen innerhalb der Nervengeflechte. Es wird angenommen, daß die Paraganglien endokrine Funktionen erfüllen.

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The fine structure of the guinea pig peribronchial micro-paraganglia

Summary The parenchyma of peribronchial microparaganglia consists of two different cell types: chromaffin cells (type I-cells) and surrounding cells (type II-cells).The chromaffin cells contain numerous vesicles with electron dense content, their diameter ranging from 700 to 1,300 Å. Unmyelinated nerves form synapses with type I-cells. The surrounding cells structurally and functionally correspond to Schwann cells.A micro-paraganglion consists of ten to fifteen chromaffin cells and their satellite cells. They are situated close to fenestrated capillaries, which are supplied from the Aa. bronchiales. A perineurial sheath separates the paraganglia from the nerve cells of the peribronchial plexus. Single chromaffin cells are found seldom within the nervous plexus.The paraganglia are thought to have an endocrine function.