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Notes: Summary. When sequential single-node shoot segments (third to fifteenth node, counting from the apex) of the perennial grass weed Paspalum distichum L. were buried in soil, new shoot growth was significantly correlated with initial segment length. Growth from the youngest segment (third), which was about 2 cm long, was only half as great as that from segments 8 to 15, which were initially 2–3·5 times longer. When 14-node shoot segments were buried in soil, the apical bud exerted a dominating influence on shoot emergence and new shoot growth of axillary buds. The degree of suppression increased gradually up to node 8 and then decreased as the distance from the apex increased. A similar result was obtained in these shoot segments following decapitation. However, the degrees and patterns of apical and bud dominance varied in shoots collected during different seasons and also in shoots with different node numbers, node position, cutting and chilling treatments. A possible role of apical and bud dominance in P. distichum in keeping aerial shocks in reserve under adverse conditions, thus providing a survival mechanism for this weed, is discussed.

Notes: Germination of skotodormant (imbibed or redried dormant in the dark) seeds of Johnson grass [Sorghum halepense (L.) Pers.] is temperature dependent. There was better germination at 40°C than at lower temperatures. Alternating temperatures of 40/28 and 35/22°C were best, overall, for imbibed and re-dried dormant seeds, respectively. For the imbibed, dormant seeds, there was apparent stimulation of germination by light, gibberelent A3 (GA3) and immersion in 700 mm sodium hypochlorite (NaOC1). However, the combinations of GA3+light, NaOC1+light, and NaOC1+GA3+light all had synergistic effects on the stimulation of germination of imbibed, dormant seeds. Germination of dry seeds treated with 900 min H2O2 was not affected, whereas the same treatment given to imbibed, dormant seeds resulted in about 40–60% germination. Stimulation of germination by H2O2 depends not only upon seed moisture content, but also upon concentration of H2O2 and previous NaOC1 immersion. Dry seeds immersed for 15 min in concentrated H2SO4 and incubated on water gave almost complete germination while no imbibed, dormant seeds germinated following this treatment. However, as little as 4 h of re-drying of these imbibed, dormant seeds, prior to the same H2SO4 treatment, stimulated about 40% germination. It is suggested that the induction and breakage of skotodormancy in imbibed or re-dried seeds in response to seasonal fluctuations in temperature and moisture may provide a survival mechanism for S. halepense. Induction de la germination des graines dormantes de Sorgho D'Alep, Sorghum halepense (L.) Pers.La germination de graines dormantes (imbibées ou ressechées à l'obscurité) de Sorgho d'Alep dépend de la température. La germination est meilleure à 40°C qu'à des températures plus basses. Des alternances de 40/28 et 35/22C étaient optimales respectivement pour les graines imbibées ou ressechées. Pour les imbibées, il y a une stimulation par la lumière, la gibberelline A3 (GA3) et l'immersion dans une solution 700 mm d'hypochlorite de sodium (NaOC1). Cependant, les combinaisons GA3+lumière; NaOC1+lumière, et NaOC1+GA3+lumière ont toutes des effets de synergisme de la stimulation de la germination des graines dormantes imbibées. La germination des graines sèches traitées avec une solution 900 mm de H2O2 n'est pas affectée tandis que le même traitement appliqué aux imbibées résulte dans 40 à 60%de germination des semences dormantes. La stimulation de la germination pour H2O2 ne dépend pas uniquement de la teneur en humidité de la graine, mais également de la concentration en H2O2 et de la préimmersion dans NaOC1. Des graines sèches immergées pendant 15 min dans H2SO4 concentré et incubées à l'eau, donnent une germination presque complète tandis que des graines imbibées ne germent pas après ce traitement. Cependant, après un reséchage aussi petit que 4 h, les graines imbibées après un même traitement à H2SO4 germent à environ 40%. On peut conclure que l'induction et la levée de dormance des graines en relation avec les fluctuations saisonnières de température et d'humidité, fournissent un moyen de survie au Sorgho d'Alep. Keimungsinduktion bei skotodormanten Samen der Aleppo-Hirse (Sorghum halepense (L.) Pers.Die Keimung skotodormanter, d.h. im Dunkeln dormanter Samen (gequollen oder wiedergetrocknet) der Aleppo-Hirse (Sorghum halepense (L.) Pers.) ist temperaturabhängig: Die Keimung war bei 40°C besser als bei niedrigen Temperaturen, und Wechseltemperaturen von 40/28 und 35/22°C waren allgemein am wirkungsvollsten für vorgequollene bzw. wiedergetrocknete dormante Samen. Für gequollene donnante Samen waren offensichtlich Licht, Gibberellin A3 (GA3) und Tauchen in 700 mm Natriumhypochlorit (NaOC1) keimungswirksam, und die Kombinationen GA3+Licht, NaOC1+Licht und NaOC1+GA3+Licht hatten alle eine synergistische Wirkung auf die Stimulation der Keimung vorgequollener dormanter Samen. Die Keimung trokener Samen blieb von einer Behandlung mit 900 mm H2O2 unbeeinflusst, während sie bei vorge-quollenen dormanten Samen zu etwa 40 bis 60% Keimung führte. Diëse Art Keimungsstimulation hängt nicht nur vom Feuchtigkeitsgehalt der Samen ab, sondern auch von der H2O2-Konzentration und einer vorausgehenden Behandlung mit NaOC1. Wurden trockene Samen 15 Minuten in konzentrierte H2SO4 getaucht und danach über Wasser inkubiert, keimten sie fast vollzählig, während vorgequollene dormante Samen nach dieser Behandlung nicht keimten, doch keimten sie zu etwa 40%, wenn sie vor derselben H2O2-Behandlung nur 4 h getrocknet wurden. Es wird angenommen, dass die Induktion und Brechung der Skotodormanz der je nach jahreszeitlichem Wechsel der Temperatur und Feuchtigkeit gequollenen oder wiedergetrockneten Samen einen Überlebensmechanismus für Sorghum halepense bilden.

Notes: Seeds of Johnsongrass [Sorghum halepense (L.) Pers.] germinated to higher percentages (20–30% higher) when incubated at 28 and 35° C than at 10 or 22° C. After-ripening was accelerated by dry storage of these seeds at 50°C. Seeds pre-chilled at 6°C for 2–4 weeks followed by incubation at 28°C germinated 40–60%. Light effects on germination were related to incubation temperatures; inhibitory at 22°C; no response at 28°C; and stimulatory at 35°C. Effects of gibberellin A3 (GA3) also varied depending on incubation temperature, sodium hypochlorite (NaOCl) immersion and light conditions. Immersion of dry seeds in either 700 mM NaOCl, 900 mM H2O2 or concentrated H2SO4 before incubation in water was effective in breaking dormancy. This result suggests the modes of action of H2SO4 in the termination of dormancy may be similar to those of NaOCl and H2SO4 as previously suggested by Hsiao & Quick (1984), that is by modification or scarification of the hull or seed coat membranes, and also by the supply of additional oxygen to the seed.

Notes: The rate of sprouting, rooting and early growth of both single-node stem and rhizome segments of Paspalum distichum L. increased as incubation temperatures increase to about 30°C and then declined at 40°C. There was little growth at 10°C. Single-node shoots remained viable at cooler temperatures after 1 days’incubation at 45°C, and 35% remained viable after 2 days’incubation at 45°C. Both shoot and rhizome segments sprouted and rooted at alternating temperatures of 45°C/28°C and 45°C/22°C. Generally sprouting and rooting of shoot segments were faster than in rhizome segments, but the response to temperature was similar for both sprouting and rooting of single-node shoot and rhizome segments. Single-node shoot segments sprouted faster in 16-h day lengths than in the dark. Rooting was better in the dark at 10°C, unaffected by light at 22 and 28°C, and faster in the light at 35 and 40°C. Sprouting, rooting and early growth were enhanced by gibberellin A3, kinetin and indole-3-acetic acid. Shoots collected at different seasons differed in their sprouting and rooting responses at various incubation temperatures. These patterns varying in response to seasonal temperature fluctuations may provide a survival mechanism for P. distichum.

Notes: Summary. Bud sprouting, shoot height, and fresh and dry weights of plants arising from single-node stem segments of Paspalum distichum L. decreased as the depth of burial in the soil increased. Sprouting, rooting and shoot growth of single-node segments submerged in 5–15 cm of water were reduced significantly in the dark. Light alleviated this water-induced reduction in 1-, 3- and 7-node segments. Submergence actually promoted sprouting of the proximal bud and shoot growth from the distal bud in 3-node segments, and shoot growth of the first two buds from the distal end in 7-node segments, Flooding the roots of 3-week -old plants for one month had no effect, but markedly reduced tiller production and dry weights after 2 and 3 months. Treatment at 100% relative humidity promoted new shoot production in 4-month old plants only if all shoots were decapitated (clipped) but not in plants with 6 shoots left intact. Submergence of the whole plant in water drastically reduced new shoot production regardless of clipping treatment. Effects of flooding varied with its duration. It is concluded that though P. distichum, a wetland perennial weed, survives root flooding and submergence conditions, these conditions do not support maximum growth of the plants.

Notes: California-grown seeds of Paspalum distichum L., incubated at the optimum temperatures between 28°C and 35°C, gave 14% germination in darkness and 40% germination at 16-h day length. The maximum and minimum limits for germination with light were 〉45°C and 10–22°C, respectively. The process of after-ripening was accelerated by dry storage of the seeds at 50°C. Pre-chilling at 6°C and a 2-h heat treatment at 40°C had no effect on germination. Gibberellin A3 increased germination only up to 10%. The treatments that caused greater than 40% germination of seeds in the dark were immersion of the dry seeds in concentrated sulphuric acid (H2SO4) for 30–60 min, giving 60–95% germination; or in 700 mM sodium hypochlorite (NaOCl) for 1–8 h. giving 53–80% germination. The clearest results were obtained by treating the dry seeds with oxidants. H2SO4 being the most effective, followed by NaOCl and hydrogen peroxide (H2O2); the latter being effective only in the presence of light. The light-induced stimulatory effect was decreased with increasing exposure of dry seeds to both H2SO4 and NaOCl. However, the light effect was still apparent in imbibed dormant seeds with 2-h NaOCl immersion but not in dry seeds with the same treatment. The results of this study suggested that the seed dormancy in P. distichum was mainly imposed by seed coverings, including hull and seed coat membranes. Facteurs influençant la dormance et la germination des graines de Paspalum distichum L.Les semences d'origine californienne de Paspalum distichum L. incubées à des températures optimales entre 28 et 35°C, ont donné 14% de germination dans l'obscurité et 40% avec une longueur de jour de 16 heures. Les limites maximales et minimales pour la germination avec lumière étaient respectivement 〉45°C et entre 10 et 22°C. Le processus de maturation a été accéléré par un stockage des graines à 50°C. Un passage au froid à 6°C puis un traitement à chaud de 2 heures n'ont pas eu d'effet sur la germination. La gibberelline A3 a augmenté la germination de seulement 10%. Les traitements qui ont entraîné plus de 40% de germination dans l'obscurité sont l'immersion des graines sèches dans l'acide sulfurique concentre (H2SO4) pendant 30 à 60 minutes avec 60 à 95% de germination ou l'immersion dans l'hypochlorite de sodium 700 mM (NaOCl) pendant 1 à 8 heures avec 53 à 80% de germination. Les résultats les plus clairs ont été obtenus en traitant les grains secs avec des oxydants. H2SO4étant le plus efficace, suivi par NaOCl et le peroxyde d'hydrogène (H2O2); ce dernier étant efficace seulement en présence de lumière. L'effet inducteur de la lumière a moins d'importance avec une exposition accrue des graines sèches à H2SO4 et NaOCl. Cependant, l'effet lumière était encore apparent pour des graines en dormance immergées pendant 2 heures dans NaOCl mais pas pour des graines sèches ayant subi le même traitement. Les résultats de cette étude donnent à penser que la dormanee des graines chez P. distichum est due principalement à la couverture des graines téguments et gousses incluses. Faktoren. welche bei Paspalmn distichum Samenruhe und Keimung beeinflussenSamen von Paspalum distichum L. kalifornischer Herkunft, optimalen Temperaturen zwisehen 28 und 35°C ausgesetzt, keimten in der Dunkelheit zu 14% und zu 40% bei einer Tageslänge von 16 h. Die Maximal- und Minimalgrenzen für die Keimung in Gegenwart von Licht lagen 〉45°C and zwischen 10 und 22°C, Der Nachreifeprozess wurde durch eine trockene Lagerung der Samen bei 50°C beschleunigt. Eine, einer 2-stündigen Wärmebehandlung bei 40°C, vorausgegangene Kühlung bei 6°C hatte keine Veränderung der Keimungsrate zur Folge. Gibberellin A3 bewirkte nur eine Steigerung der Keimung von bis zu 10%. Behandlungen, welche höhere Keimungsraten als 40% in Dunkelheit verursachten, waren: (a) Eintauchen der trockenen Samen in konzen-trierte Schwefelsäure (H2SO4) während 30–60 min., was zur Keimung von 60 bis 95% der behandelten Samen führte, oder (b) Eintauchen in 700 mM Natriumhypochlorit (NaOCl) während 1–8 h; diese Behandlung erhöhte die Keimung auf 53–80%. Die eindeuligsten Resultate ergaben die Behandlungen der trockenen Samen mit Oxydationsmitteln, wobei H2SO4 am wirksamsten war, gefolgt von NaOCl und Wasserstoffperoxyd (H2O2); letzteres zeigte nur in Gegenwart von Licht eine Wirkung. Die durch Licht induzierte Keimungsstimulation wurde durch eine zunehmende Einwirkungsdauer von H2SO4 Oder NaOCl verringert. Allerdings war der ‘Lichteffekt’ bei dormanten, während 2 h in NaOCl eingetauchten Samen noch feststellbar, nicht aber bei trockenen Samen, welche derselben Behandlung unterworfen worden waren. Die Ergebnisse dieser Untersuehung lassen vermuten, dass die Samcnruhe bei P. distichum hauptsächlich durch die Umhüllungen des Samens, einschliesslich der Membranen der Samenschale, beeinflusst wird.

Notes: Summary The metastatic behaviour of renal cell carcinoma has been studied in a series of 687 necropsies. The observations were consistent with the concept of “metastatic inefficiency”, in that in 295 cases, including 25 with renal vein invasion, there were no detectable metastases. In the present series, renal vein involvement was not an important prognostic factor in stage 1 or 2 disease. In 73% of cases without lung metastases there were none in other sites, and in 84% of those with lung metastases there were others elsewhere, consistent with a metastatic “cascade” in which metastases first developed in the lungs and were later detected in other organs. However, the observations did not permit discrimination between anatomic cascades, in which other organs were seeded from metastasizing pulmonary metastases, and temporal cascades, in which the other were seeded at the same time as the lungs, but with fewer cancer cells. The patterns of arterial metastasis were consistent with the “seed-and-soil” hypothesis, and a novel index was developed to quantify differential organ “soils”. The contralateral kidney was not the best soil for metastases from renal carcinoma. Given the presence of lymph node metastasis, the probability of heamatogenous metastasis is 90%. However, in the absence of nodal metastasis, approximately half the cases had haematogenous metastasis.

Notes: Abstract In this study, we investigate systematically the role played by the reproductive number (the number of secondary infections generated by an infectious individual in a population of susceptibles) on single group populations models of the spread of HIV/AIDS. Our results for a single group model show that if R ⩽ 1, the disease will die out, and strongly suggest that if R 〉 1 the disease will persist regardless of initial conditions. Our extensive (but incomplete) mathematical analysis and the numerical simulations of various research groups support the conclusion that the reproductive number R is a global bifurcation parameter. The bifurcation that takes place as R is varied is a transcritical bifurcation; in other words, when R crosses 1 there is a global transfer of stability from the infection-free state to the endemic equilibrium, and vice versa. These results do not depend on the distribution of times spent in the infectious categories (the survivorship functions). Furthermore, by keeping all the key statistics fixed, we can compare two extremes: exponential survivorship versus piecewise constant survivorship (individuals remain infectious for a fixed length of time). By choosing some realistic parameters we can see (at least in these cases) that the reproductive numbers corresponding to these two extreme cases do not differ significantly whenever the two distributions have the same mean. At any rate a formula is provided that allows us to estimate the role played by the survivorship function (and hence the incubation period) in the global dynamics of HIV. These results support the conclusion that single population models of this type are robust and hence are good building blocks for the construction of multiple group models. Our understanding of the dynamics of HIV in the context of mathematical models for multiple groups is critical to our understanding of the dynamics of HIV in a highly heterogeneous population.

Notes: Forced Rayleigh scattering, a relatively recently developed optical technique, is used to measure tracer diffusion coefficients in polymer-solvent mixtures near the system glass transition temperature, Tg. The technique has a wider range of potential application than has yet been realized, and so is presented in some detail. The objectives were to obtain data necessary to scrutinize free volume theory, and to understand so-called anomalous, non-Fickian diffusion effects observed by others in polymer-solvent mixtures near Tg. Data on dye tracer diffusion coefficients in the systems polyvinyl acetate-toluene, polystyrene-toluene, and polystyrene-tri-m-tolyl phosphate were obtained over a polymer concentration range from infinite dilution to 96 wt. %. Small molecule diffusion coefficients are seen to vary by as much as nine orders of magnitude (10-14 to 10-5 cm2/s) over this concentration range. The data are in reasonable accord with expectations based on the Duda-Vrentas version of free-volume theory.