Different Growth Responses of Hamster Dermal Fibroblasts and Chondrocytes to Platelet–derived Growth Facter in Cell Culture

The growth responses of dermal fibroblasts and chondrocytes obtained from 1-week-old hamsters to a growth factor from platelets [platelet-derived growth factor (PDGF)] were compared. Autoradiography showed that most of the whole nuclei of dermal fibroblasts were labeled with ³H-thymidine in 5% whole blood serum (WBS), which contains platelet releasate, but only a few percent were labeled in 5% plasma-derived serum (PDS), which is free of platelet releasate. Addition of platelet releasate to PDS restored the growth stimulatory activity of the serum for dermal fibroblasts. In contrast, most of the nuclei of chondrocytes were labeled with ³H-thymidine both in 5% WBS and 5% PDS. Dermal fibroblasts grew in 5% WBS, but not in 5% PDS, whereas chondrocytes grew in both 5% WBS and 5% PDS. Partially purified PDGF added to the medium with 0.5% fetal calf serum stimulated DNA synthesis in dermal fibroblasts, but not in chondrocytes.     

Changes in Endogenous Growth Regulators in the Gladiolus Corm during Dormancy

Changes in endogenous growth regulators in gladiolus corms during dormancy were studied using paper and column chromatography followed by a bioassay with the test for straight growth of Avena coleoptile. Corms were grown in the field or in a glass room of a phytotron at 20°C in the light. Another lot was grown in a dark room at 20°C in the dark. Half of the daughter corms in each lot were cold-treated for about one month and the other half were stored at room temperature after harvest. The earliest sprouting was seen in dark grown corms with cold treatment, and the latest sprouting in light grown corms without cold. This pattern was similar in each cultivar over a period of three years. Corms from both lots contained considerable amounts of inhibiting substance just after harvest. However, dark grown corms treated with cold showed a rapid decrease in inhibitor activity and an increase in promoter activity. On the other hand, in light grown corms without cold treatment there was inhibitor activity found consistently even after two months. —There appear to be two inhibiting zones in the chromato-grams. One of these contains two inhibitory substances, one of which was assumed to be abscisic acid.     

Selective light transmittance of translucent bracts in the Himalayan giant glasshouse plant Rheum nobile Hook. f. & Thomson (Polygonaceae)

Translucent bract transmittance of ultraviolet (UV) to infrared (IR) radiation (between 320 and 800 nm) and leaf anatomy were examined in a glasshouse plant, Rheum nobile Hook. f. & Thomson (Polygonaceae) to assess the function of avoiding injury by UV radiation while keeping the inflorescence warm by photosynthetically active (PA) and IR radiation. Although the translucent bracts and rosulate leaves transmitted little UV radiation, the former always transmit more PA and IR radiation. Additionally, the bracts transmit much more scattered solar radiation than direct radiation. The bracts are also anatomically different from the rosulate leaves. They have two or three layers of mesophyll cells with neither palisade nor spongy parenchymatous cells; in addition, the uppermost layer of mesophyll and the epidermis stain easily, and both are thought to play a role in attenuating UV radiation. The leaf epidermis of many land plants has UV absorbing pigments such as flavonoids, which absorb almost all UV radiation. Thus the role of the bracts of R. nobile is to protect the reproductive organs by absorbing UV radiation and to keep them warm by transmitting PA and IR radiation. The bracts are believed to have adapted function and form to the environment, in particular, to the weather conditions of the eastern Himalaya.     

Maturation-Inducing Substances in Asteroid and Echinoid Oocytes

In starfish a hormonal peptide, gonad-stimulating substance(GSS), which is released from nervous tissue, acts on the gonadto produce a maturation-inducing substance (MIS), an inducerof oocyte maturation and spawning. MIS is 1-methyladenine (1-MA).This substance acts on the surface of the oocyte. Cytoplasmicmaturation as revealed by fertilizability is also induced by1-MA. The amount of 1-MA can be determined very accurately witha bioassay method using isolated oocytes. In 1-MA formation,GSS seems to enhance the methylation of some compound whichcontains a purine nucleus at its N1 site. The methyl donor isprobably S-adenosylmethionine. 1-Methylated precursor seemsto be transformed to 1-methyl AMP and then hydrolyzed into 1-methyladenosineand phosphate by phosphomonoesterase. 1-Methyladenosine is finallysplit into 1-MA and ribose by 1-methyladenosine ribohydrolase.So-called spontaneous maturation of oocytes isolated in seawater is due to the action of 1-MA produced in follicle cellseven in the absence of GSS. 1-MA is present in echinoid gonadsand seems to act as MIS also in these animals. Disulfidereducingagents such as dithiothreitol and 2,3-dimercapto-1-propanolinduce starfish oocyte maturation. On the other hand, sulfhydrylreagents such as p-chloromercuribenzoate, iodoacetamide, andN-ethylmaleimide suppressed 1-MA-induced oocyte maturation.Since Concanavalin A acts on the follicle cells to produce 1-MA,the action of this substance seems to be quite similar to thatof GSS.     

Differentiation in Lilium bulbscales grown in vitro. Effects of activated charcoal, physiological age of bulbs and sucrose concentration on differentiation and scale leaf formation in vitro

Organ differentiation and growth of tissue cultured bulbscales of Lilium auratum Lindl. was investigated. Benzyladenine stimulated bulb and bulbscale differentiation but inhibited root formation. Addition of activated charcoal to the medium negated the effect of BA on differentiation, while the growth of bulbs was markedly stimulated. Organ formation was also influenced by the physiological age of bulbs. From bulbscales of a 3-week-old bulb, a large number of bulbs and roots was formed but callus was not produced. A high sucrose concentration (90 g/1) reduced the subsequent sprouting after planting in soil. Scale leaf formation was also regulated. Sucrose (30 g/1) stimulated scale leaf formation but 90 g/1 were inhibitory.     

INDUCTION OF SPAWNING AND OOCYTE MATURATION IN STARFISH BY 1-METHYL-ADENOSINE MONOPHOSPHATE

l-Methyladenosine monophosphate (l-McAMP) induces ovulation and oocyte maturation when applied to isolated ovarian fragments of Asterina pectinifera . However, isolated oocytes fail to mature even in the presence of this substance. When ovarian or testis fragments are incubated with l-McAMP, the supernatant of the incubation mixture acquires the maturation-inducing activity. Also, superantants of gonadal homogenates incubated with l-McAMP have the capacity to convert it to a maturation-inducing substance, suggesting that l-McAMP is decomposed to l-methyladenine, which is believed to be a general inducer of oocyte maturation and ovulation in starfishes. Thus l-MeAMP seems to be an intermediate in l-methyladenine formation when the latter is produced under the influence of the gonad-stimulating hormonal peptide.     

Morphological difference and reproductive isolation: morphometries in the millipede Parafontaria tonominea and its allied forms

Thin-plate spline and other multivariate statistical methods were used to examine the variation in genital morphology and body size in 74 populations of the millipede Parafontaria tonominea and its allied forms in central Japan. Although the study populations included nine sympatric pairs of two reproductively isolated forms, the variations in genital morphology and body size observed were continuous across the study group. Analyses of the sympatric pairs using bootstrapping revealed that the degree of morphological difference between sympatric populations varied considerably from pair to pair. These results demonstrate that the degree of difference in genital morphology and body size may not correspond with the establishment of reproductive isolation. Significant correlation in the pattern of geographic variation was observed for many combinations of morphological components. However, it was not possible to detect a significant correlation between morphology and geographic distance in many of the morphological components studied. This study suggests that the incorporation of genital characters in classification should be done carefully, particularly for animal groups with low vagility, such as millipedes.