The extent and differences in mitotic activity of the root tip ofVicia faba L.

Mitotic activity does not stop for different meristematic cells of the root apex at the same distance from the initials. The differences are connected with the functional heterogeneity of the apical meristem of the root. The arrangement of vascular bundles,i.e. the alternation of independent xylem and phloem groups, is of major importance. In broad bean roots, the protophloem sieve elements stop dividing first. The centre of the stelei. e. late metaxylem elements stop dividing next. Division in the stele gradually ceases centrifugally, while it ceases centripetally in the peripheral part of the root. The cylindrical region with prolonged cell division includes internal layers of the cortex including endodermis, pericycle and adjoining cells of the stele. Proximally apical meristem is reduced to isolated strands of cells adjacent to the protoxylem poles. Pericycle cells stop dividing last at a distance of approx. 9–10 mm from the initials. The number of the division cycles is limited and is specific for individual cell types. Epidermal and cortical cells divide in broad bean roots transversely approximately seven times, cells of late metaxylem approximately five times. Root apical meristem is an asynchronous cell population with a different duration of the mitotic cycle. We determined local variations in the duration of the mitotic cycle in the apical meristem of broad bean root by means of colchicine-induced polyploidy. The cells of the quiescent centre had the longest mitotic cycle after colchicine treatment. The region of the proper root adjacent to the quiescent centre was mixoploid (2n and 4n). Isolated cells with a long cycle occurred also in the cortex and in the central cylinder. Cells with a division cycle of 18h were found in the root cap, in the epidermis, in the cortex and in the central cylinder. Relatively numerous cells with the shortest division cycle, approx. 12 h, occurred farther of the quiescent centre in the epidermis, in the cortex, in the pericycle, and in adjacent layers of the stele through-out the entire meristematic region. The results derived from the analysis of the apical meristem are discussed in connection with the ontogenesis of different types of cells taking part in the primary structure of the root.     

The Occurence of δ-Tocopherylquinone in Higher Plants and Its Relation to Senescence

δ-Tocopherylquinone (δTQ) content was determined in tobacco and yellow maple leaves, green ivy leaves and cactus tissues. It was found that the concentration of δ-TQ was highest in mature or senescent tissues, such as white tobacco leaves (0.02 μmole/g dry wt) while its detection was uncertain in young, green leaves from the apex of tobacco plants. Fractionation by centrifugation of senescent tobacco leaves showed that the osmiophilic globule fraction was enriched in δ-TQ. Electron microscope studies of young, mature and senescent tobacco tissues showed progressive changes in the size and number of osmiophilic globules. After chloroplast breakdown in senescent tobacco leaves, these globules became the predominant constituents of the organelle. δ-TQ which is associated with osmiophilic globules may play a role in the development of plants, particularly during senescence.     

Der Einfluß einiger Hormone auf die heteroplastische Knorpel- und Knochenbildung im Herzmuskel der Ratte

Zusammenfassung Es wird über histopathologische Untersuchungen des chronologischen Verlaufs an der durchSelyes Ventrikel-Ligatur hervorgerufenen Herzspitzennekrose bei Ratten berichtet. In dem der Nekrose verfallenen Myokard setzt alsbald Organisation ein; dann wandelt sich allmählich das Granulationsgewebe in eine zellarme und faserreiche Narbe um. In den subendokardialen Schichten des Narbengewebes entstehen erst Knorpel-, später Knochenherde. Der Prozeß der Knorpelbildung wird nicht von Verkalkung eingeleitet; vielmehr werden zuerst die Fibroblasten zu Knorpelzellen, um die sich dann sekundär Kalziumsalze ablagern; danach spielt sich eine typische endochondrale Ossifikation ab. Schließlich erscheint Knochenmarkgewebe zwischen den Knochenbalken.Triamcinolon hemmt geringgradig die Bindegewebsproliferation, Thyroxin steigert die Knorpel- und Knochenbildung, während Östradiol diese Vorgänge nicht beeinflußt.

---

The effect of hormones on the heteroplastic cartilage and bone formation in the cardiac muscle of the rat

Summary A chronologic study was made of the histopathologic changes which occur in the cardiac apex of the rat following the application of Selye's ventricular ligature. Organisation in the necrotic cardiac muscle begins soon after ligature. Later, the granulationtissue is gradually replaced by scar tissue which is poor in cells but rich in fibers. In the subendocardial fibrous tissue, cartilage and bone develop. It is emphasized that cartilage formation is not initiated by calcification. Instead, the fibroblasts are converted to cartilage cells and, later, calcium salts are deposited in the matrix. This is followed by endochondral bone formation. Finally, bone marrow appears in the intertrabecular spaces.Triamcinolone mildly hindered connective-tissue proliferation, thyroxine increased cartilage and bone formation, while estradiol did not influence these processes.

---

---

Die Versuche, die diesem Bericht zugrunde liegen, wurden durch das Ministère de la Santé, Québec, die Quebec Heart Foundation, Montreal, das Medical Research Couneil of Canada (Block Term Grant MT-1829) und das USPHS, Child Welfare (Grant HDO 2612-02) unterstützt. Die Autoren danken an dieser Stelle der Firma Lederle Laboratories Div., Pearl River, N.Y., USA für das bei diesen Versuchen verwendete Triamcinolon (Aristocort^®) und der Firma Schering Corporation Ltd., Pointe Ciaire, Quebec, für die Bereitstellung von Estradiol.     

Wirtskreis und Infektionscyclus eines neu isolierten Bdellovibrio bacteriovorus-Stammes

Zusammenfassung Der neu isolierte Stamm W von Bdellovibio bacteriovorus infiziert und lysiert Rhodospirillum rubrum F und alle anderen untersuchten Athiorhodaceae, nicht aber Pseudomonas aeruginosa und Spirillum serpens. Er befällt auch zahlreiche Enterobacteriaceae und von den grampositiven Bakterien Streptococcus faecalis und Lactobacillus plantarum.Nach dem Festheften an der Zellwand wird diese in 3–20 min durchdrungen. In 10–60 min ist Bdellovibrio vollständig in die Zelle eingedrungen und hat sich im Raum zwischen Zellwand und cytoplasmatischer Membran angesiedelt.In 3–5 Std wird der gesamte Zellinhalt bis auf die Membranen aufgelöst. In dieser Phase erfolgt die Vermehrung von Bdellovibrio. In den ghosts sind die Parasiten in lebhafter Bewegung. Die Geißel hat einen Gesamtdurchmesser von 29 m und eine Länge von etwa 3 . Sie ist von einer Geißelscheide umgeben, die in Verbindung zur Zellwand steht. Der Durchmesser der Geißel ohne Scheide beträgt etwa 18 m. Bdellovibrio kann oberhalb eines Sauerstoffpartialdruckes von 4–5 mm Hg infizieren und sich vermehren. Der Titer von Bdellovibrio nimmt bei Aufbewahrung in lysierten Kulturen in 36 Tagen von 10⁸ auf 10¹ pfu (plaque forming units) je ml ab. Bei Aufbewahrung in Nährkultur sinkt der Titer nur auf 10⁴ pfu/ml ab. Die Zahl der Plaques im Verhältnis zum Titer der Impfsuspension von Bdellovibrio schwankt in Abhängigkeit vom Wirtsstamm. Wenn man die Plaque-Bildungsrate bei R. rubrum gleich 1 setzt, beträgt sie bei Serratia marcescens 0,0001, bei Proteus vulgaris 10. Bd. bacteriovorus, Stamm W wächst nicht in synthetischer Nährlösung oder Lysaten. Ein geringes Wachstum ohne Zellteilung findet in Zellextrakten von R. rubrum statt. Der Stamm vermehrt sich jedoch in hitzeinaktiviertem R. rubrum. Die Plaque-Bildungsrate ist unter diesen Bedingungen aber sehr niedrig.In Lysaten treten encystierte Dauerformen von Bdellovibrio bacteriovorus auf.

---

The host range and the infectious cycle of a new isolated, on gram-positive and gram-negative bacteria parasiting Bdellovibrio bacteriovorus strain

Summary Rhodospirillum rubrum and all other investigated Athiorhodaceae are infected and lysed by the new isolated strain W of Bdellovibrio bacteriovorus. This strain W parasites on numerous Enterobacteriaceae and the gram-positive bacteria Streptococcus faecalis and Lactobacillus plantarum, but not on Pseudomonas aeruginosa and Spirillum serpens.After attachment of Bdellovibrio to the host, the cell wall is penetrated in 3 to 20 min. In 10 to 60 min Bdellovibrio has completely entered the host cell. He remains in the space between cell wall and cytoplasmic membrane of the host.The host cell is completely lysed within 3 to 5 hours. During this phase the size and cell number of Bdellovibrio are increased and a new flagellum is likely to be formed. In the ghosts of the host cell a strong movement is observed. The single polar flagellum of Bdellovibrio has a diameter of 29 m. The flagellum consists of an inner core ( 18 m) and an outer sheath which is continued into the cell wall. Bdellovibrio is able to grow and to infect only under aerobic or semiaerobic conditions (oxygen partial pressure 4 to 5 mm Hg and more). The titer of Bdellovibrio is gradually decreased from 10⁸ to 10¹ plaque forming units (pfu) per ml, when kept in the lysate for 36 days. In a synthetic medium there is a diminution of 10⁴ pfu/ml only. The plating efficiency is dependent of the host strain. If the plating efficiency of Bdellovibrio with Rhodospirillum rubrum is 1.0, the rate varies from 0.0001 with Serratia marcescens to 10 with Proteus vulgaris. Bdellovibrio bacteriovorus strain W does not grow in a synthetic medium. However, it grows but does not multiply in cell free extracts of Rhodospirillum rubrum. The parasite is also able to infect and lyse heat inactivated R. rubrum. But the plating efficiency in this case is very low.It has been observed that in lysed cells of R. rubrum certain amount of Bdellovibrio is encysted. The morphology and fine structure of these cells is quite different from the normal virulent type.

     

Alternation of respiratory pathways during the development of wheat leaf

P?i vývoji listu p?enice se zmen?uje stupeň inhibice dýchání fluoridem, monojodacetátem a malonátem a poměr mezi radioaktivitami¹⁴CO₂ uvolněného z glukosy-6-¹⁴C a glukosy-l-¹⁴C (C₆/C₁), co? svěd?í o zvět?ování podílu pentosovího cyklu v celkové respiraci. Tato změna v?ak neni zp?sobena absolutním zvět?ením aktivity pentosového eyklu u star?ích list?, nýbr? p?edev?ím poklesem aktivity glykolytického systému. Naproti tomu u list? oddělených od obilky se pri sní?ení vlhkosti atmosféry méní poměr mezi dýchacími cestami v d?sledku aktivace pentosového cyklu. Na základě disproporce mezi procentem glykolytického podílu respirace vypo?tenym ze sní?ení poměru C₆/C₁ p?i inhibici dýchání fluoridem a procentem inhibice dý chání fluoridem bylo diskutováno o mo?ných p?íoinách vysokých poměr? C₆/C₁ u mladých list?, u nich? byly v některých p?ípadech zji?těny hodnoty těchto poměr? dokonce vy??í ne? jedna.     

Intensity of photosynthesis and chlorophyll content as related to leaf age inNicotiana Sanderae hort

U r?zně starých list? v listové r??ici 90 a? 110 denních rostlin Nicotiana sanderae hort. byly sledovány rozdály v intensitě ?isté fotosynthesy a v obsahu chlorofylu (a + b). Ke stanovení intensity fotosynthesy bylo pou?ito dvou odli?ných metod, a to váhového stanovení p?ír?stku su?iny podle Barto?e, KubÍna a ?et-lÍka (1960) a gazometrického stanovení infra?erveným analyzátorem CO₂. Nejvy??í intensitu fotosynthesy i nejvy??í obsah chlorofylu (vzhledem k plo?e listové) mají mladé, ale ji? dob?e rozvinuté listy, tj. t?etí a? ?tvrté od vrcholu (prvním listem se rozumí list o plo?e asi 20 cm²). Tyto listy nazýváme ?fotosyntheticky dospělými“. Listy nejmlad?í a zejména pak listy star?í mají intensitu fotosynthesy i obsah chlorofylu ni??í; u nejstar?ích list? je intensita fotosynthesy prakticky nulová. Intensita fotosynthesy i obsah chlorofylu se během vývoje mění: jejich momentální rozdíly u list? v genetické spirále jsou z?ejmě shodné s jejich změnami v ontogenesi listu. Pokles intensity fotosynthesy p?i stárnutí list? je rychlej?í ne? pokles obsahu chlorofylu. P?i ur?itém obsahu chlorofylu (tj. asi 2,25 a? 2,45 mg/dm²) klesá intensita ?isté fotosynthesy k nule. Intensita fotosynthesy je v lineárním vztahu k mno?ství chlorofylu (p?i p?epo?tu na plo?nou jednotku), a to nezávisle na poloze listu v genetické spirále. Obě pou?ité metody ke stanovení intensity fotosynthesy poskytly obdobné výsledky.     

The effect of physical conditions of cultivation on the respiratory metabolism of algae

V práci jsem zji?tovala, zda podmínky kultívace ?as ovlivńují ?espira?ní metabolismus. Rasy Chlorella pyrenoidosa (82), Scenedesmus obliquus (125) a Euglena gracilis (259) byly pěstovány ve t?epané a stojaté kultu?e. T?epáním kultur je podstatně ovlivněn respira?ní metabolismus ?as. T?épané kultury mají na rozdíl od stojatých sní?enou spot?ebu O₂ a vět?inou odli?né RQ. Je mo?né, ?e zji?těné rozdíly jsou podmíněny zrychleným vývojem a stárnutím t?epaných kultur. Je tedy t?epání jako zp?sob kultivace významným faktorem, který je nutno respektovat p?i pěstování experimentálního materiálu. Namě?ené hodnoty respira?ního kvocientu okolo 1,3 svěd?í pro to, ?e anaerobní glykolytické pochody mohou probíhat i za dokonalého p?ístupu vzduchu do media. Kultura Scenedesmus obliquus (125) má pravděpodobně málo p?izp?sobivý metabolismus a na změny prost?edí nereaguje tak citlivě jako Euglena gracilis nebo Chlorella pyrenoidosa.     

Effect of Temperature on the Potential and Current Thresholds of Axon Membrane

The effect of temperature on the potential and current thresholds of the squid giant axon membrane was measured with gross external electrodes. A central segment of the axon, 0.8 mm long and in sea water, was isolated by flowing low conductance, isoosmotic sucrose solution on each side; both ends were depolarized in isoosmotic KCl. Measured biphasic square wave currents at five cycles per second were applied between one end of the nerve and the membrane of the central segment. The membrane potential was recorded between the central sea water and the other depolarized end. The recorded potentials are developed only across the membrane impedance. Threshold current values ranged from 3.2 µa at 267deg;C to 1 µa at 7.5°C. Threshold potential values ranged from 50 mv at 26°C to 6 mv at 7.5°C. The mean Q₁₀ of threshold current was 2.3 (SD = 0.2), while the Q₁₀ for threshold potentials was 2.0 (SD = 0.1).     

Pigment composition and plastid structure in leaves of carotenoid mutants of maize

Summary In monogenic, recessive chloroplast mutants of maize which contain chlorophylls, and lycopene or -carotene but no normal carotenoids, great variability in the size of plastids was associated with a number of ultrastructural abnormalities. In the mutant accumulating lycopene some plastids contain dense bundles of lamellae, whereas the chloroplasts of the -carotene mutant show poor thylakoid development. Neither of the mutants was able to form normal grana.A comparison of chlorophyll/carotenoid ratios in different chloroplast fractions of normal and mutant leaves showed that plastids of small size and delicate structure contain relatively less chlorophyll than fully differentiated chloroplasts.