Dictyostelium mucoroides cells exhibit cell cycle-dependent sorting behavior as observed in D. discoideum development

Evidence has been obtained indicating that the cell's position in the cell cycle at the onset of starvation is a naturally occurring variable closely involved in the subsequent sorting and pattern formation during the development of Dictyostelium discoideum Ax2. It is of interest to know whether a similar phenomenon is also noticed in species other than D. discoideum and also without any treatment of cells for cell synchronization. For this, the sorting behavior of D. mucoroides-7 ( Dm7 ) cells and its relation to the cell-cycle phase at the onset of starvation were analyzed, using non-synchronized Dm7 cells pulse-labeled with 5'-bromo-2-deoxyuridine (BrdU). The results demonstrate that Dm7 cells starved at the early G2 phase aggregate most rapidly, but are eventually sorted out to the posterior prespore zone of migrating slugs. In contrast, cells starved at the mid late G2 phase exhibited slower aggregation, but were sorted out to the anterior zone (tip), this being basically similar to the sorting behavior of D. discoideum cells. Measurements of cell numbers and nuclearity provided evidence that approximately 80% of cells progressed their cell-cycle after the formation of multicellular structures (mounds), probably coupling with prespore differentiation as in the case of D. discoideum . Thus, cell cycle-dependent sorting during Dictyostelium development is most likely to be a common phenomenon in different species.     

Self-incompatibility (S) alleles of the rosaceae encode members of a distinct class of the T2/S ribonuclease superfamily

Stylar riboncleases (RNases) are associated with gametophytic self-incompatibility in two plant families, the Solanaceae and the Rosaceae. The self-incompatibility-associated RNases (S-RNases) of both the Solanaceae and the Rosaceae were recently reported to belong to the T2 RNase gene family, based on the presence of two well-conserved sequence motifs. Here, the cloning and characterization of S-RNase genes from two species of Rosaceae, apple (Malus × domestica) and Japanese pear (Pyrus serotina) is described and these sequences are compared with those of other T2-type RNases. The S-RNases of apple specifically accumulated in styles following maturation of the flower bud. Two cDNA clones for S-RNases from apple, and PCR clones encoding a further two apple S-RNases as well as two Japanese pear S-RNases were isolated and sequenced. The deduced amino acid sequences of the rosaceous S-RNases contained two conserved regions characteristic of the T2/S-type RNases. The sequences showed a high degree of diversity, with similarities ranging from 60.4% to 69.2%. Interestingly, some interspecific sequence similarities were higher than those within a species, possibly indicating that diversification of S-RNase alleles predated speciation in the Rosaceae. A phylogenetic tree of members of the T2/S-RNase superfamily in plants was obtained. The rosaceous S-RNases formed a new lineage in the tree that was distinct from those of the solanaceous S-RNases and the S-like RNases. The findings suggested that self-incompatibility mechanisms in Rosaceae and Solanaceae are similar but arose independently in the course of evolution.     

Mutations associated with floral organ number in rice

How floral organ number is specified is an interesting subject and has been intensively studied in Arabidopsis thaliana. In rice (Oryza sativa L.), mutations associated with floral organ number have been identified. In three mutants of rice, floral organ number 1 (fon1) and the two alleles, floral organ number 2-1 (fon2-1) and floral organ number 2-2 (fon2-2), the floral organs were increased in number centripetally. Lodicules, homologous to petals, were rarely affected, and stamens were frequently increased from six to seven or eight. Of all the floral organs the number of pistils was the most frequently increased. Among the mutants, fon1 showed a different spectrum of organ number from fon2 -1 and fon2 -2. Lodicules were the most frequently affected in fon1, but pistils of more than half of fon1 flowers were unaffected; in contrast, the pistils of most flowers were increased in fon2 -1 and fon2-2. Homeotic conversion of organ identity was also detected at a low frequency in ectopically formed lodicules and stamens. Lodicules and stamens were partially converted into anthers and stigmas, respectively. Concomitant with the increased number of floral organs, each mutant had an enlarged apical meristem. Although meristem size was comparable among the three mutants and wild type in the early phase of flower development, a significant difference became apparent after the lemma primordium had differentiated. In these mutants, the size of the shoot apical meristem in the embryo and in the vegetative phase was not affected, and no phenotypic abnormalities were detected. These results do not coincide with those for Arabidopsis in which clavatal affects the sizes of both shoot and floral meristems, leading to abnormal phyllotaxis, inflorescence fasciation and increased floral organs. Accordingly, it is considered that FON1 and FON2 function exclusively in the regulation of the floral meristem, not of the vegetative meristem.Abbreviation DIC differential interference contrast This work was supported in part by Grant-in-Aid for Scientific Research on Priority Areas from the Ministry of Education, Science and Culture of Japan.     

Immunohistochemical distribution of basic fibroblast growth factor in experimental retinal ischaemia and reperfusion in the rat

Summary It has been proposed that basic fibroblast growth factor (basic FGF) mediates the neovascular response in a variety of conditions, including diabetic retinopathy and branch retinal vein occlusion. To test the hypothesis that basic FGF was released from retinal stores as a result of retinal ischaemia, transient retinal ischaemia was induced, followed by 48 h of reperfusion, in the rat by combined central retinal vasculature and optic nerve ligation. The immunolocalization of basic FGF was studied in the retina. We found that basic FGF in the normal retina is present around the deeper retinal vessels and in the neuronal tissue of the outer plexiform layer. In the eyes that had ischaemia followed by reperfusion, there was moderate cellular oedema with retinal swelling, and mitoses in the inner nuclear and plexiform layers. There were no changes evident at the immunohistochemical level either in the intensity or distribution of stores of basic FGF. We conclude from these data that stores of basic FGF are not altered dramatically under the conditions of transient experimental ischaemia and reperfusion in the rat, despite the presence of cellular proliferation.     

Seasonal changes in the spermatogenic epithelium of adult Japanese macaques (Macaca fuscata fuscata)

A histological study was undertaken to clarify seasonal changes in the spermatogenic epithelium of Japanese macaques. Testicular tissue samples were excised by biopsies from five adult laboratory-maintained males in mating and non-mating seasons. The samples were fixed with Bouin's solution, embedded in paraffin, and stained with PAS and hematoxylin. Microscopic observations on cross-sections of seminiferous tubules revealed that the seminiferous epithelium in the mating season was thicker than in the non-mating season. PAS-stained granules were found in some of the dark A-type spermatogonia, which significantly increased in the non-mating season. Spermatids of the steps preceding the appearance of the acrosomic cap in stages I to III were observed significantly more often than those in the step coinciding with the formation of the acrosomic cap in stage IV. In stage I, the ratio of mature spermatids or spermatozoa to immature spermatids in the mating season was higher than that in the non-mating season. These findings suggest that spermiogenesis, as well as spermatocytogenesis, is inhibited in the non-mating season.     

Interfacial and micellar behavior of glucose lipid

Summary Glucose lipid of notable surfactant properties was produced by using hydrocarbon assimilating bacterium of the bacterial strain MM1. Its surface active properties were notable in spite of ,-hydrophilic and bulky molecule. The critical micelle concentration (cmc) was small (0.165 M); surface and interfacial tension for hexadecane at 0.1 % (pH 7.35) solution, 24.6 and 13.3 mN/m, respectively. The emulsifying action was excellent and comparable to those of rhamnolipids. The micelle has the outer radius. 28.5 Å and inner core, 6.7 Å on the basis of the concentric spherical shell model by means of the small angle X-ray solution scattering measurement.Dedicated to Professor Fritz Wagner on the occasion of his 65th birthday.     

Selective changes of neurotransmitter receptors in middle-aged gerbil brain

Age-related alterations in major neurotransmitter receptors and voltage dependent calcium channels were analyzed by receptor autoradiography in the gerbil brain. [³H]Quinuclidinyl benzilate (QNB). [³H]cyclohexyladenosine (CHA), [³H]muscimol, [³H]MK-801, [³H]SCH 23390, [³H]naloxone, and [³H]PN200-110 were used to label muscarinic acetylcholine receptors, adenosine A₁ receptors, γ-aminobutyric acid_A (GABA_A) receptors, (NMDA) receptors, dopamine D₁ receptors, opioid receptors, and voltage dependent calcium channels, respectively. In middle-aged gerbils (16 months old), the hippocampus exhibited a significant elevation in [³H]QNB, [³H]MK-801, [³H]SCH 23390, [³H]naloxone, and [³H]PN200-110 binding, whereas [³H]CHA and [³H]muscimol binding showed a significant reduction in this area, compared with that of young animals (1 month). On the other hand, the cerebellum showed a significant alteration in [³H]QNB, [³H]CHA, and [³H]naloxone binding and the striatum also exhibited a significant alteration in [³H]SCH 23390 and [³H]CHA binding in middle-aged gerbils. The neocortex showed a significant elevation only in [³H]CHA binding in middle-aged animals. The nucleus accumbens and thalamus also showed a significant alteration only in [³H]muscimol binding. However, the hypothalamus and substantia nigra exhibited no significant alteration in these bindings in middle-aged gerbils. These results demonstrate the age-related alterations of various neurotransmitter receptors and voltage dependent calcium channels in most brain regions. Furthermore, they suggest that the hippocampus is most susceptible to aging processes and is altered at an early stage of senescence.     

Purification and Heterogeneous Localization of Sarcophaga Lectin Receptor on the Surface of Imaginal Discs of Sarcophaga peregrina (Flesh Fly)

Previously, we reported autocrine involvement of Sarcophaga lectin in the development of Sarcophaga imaginal discs (Kawaguchi et al. , Dev. Biol. 144 , 86–93 (1991)). In this study, we purified Sarcophaga lectin binding protein from the membrane fraction of cultured embryonic cells of Sarcophaga to near homogeneity and raised a monoclonal antibody against it. Histochemical analysis using the monoclonal antibody revealed that this binding protein is distributed heterogeneously on the surface of leg imaginal discs. This binding protein was especially clearly localized in the central region of the basal side of leg discs which forms the junction between the leg and body, suggesting the participation of Sarcophaga lectin in morphogenesis of the basal region of the developing leg.     

Promotion of Zygote Formation by Protein Kinase Inhibitors during the Sexual Development of Dictyostelium mucoroides

To analyze the possible involvement of protein kinases in the sexual development (macrocyst formation) of the cellular slime mold Dictyostelium mucoroides-7 (Dm7), the effects of several protein kinase inhibitors were examined. K252a, a potent inhibitor of protein kinase activities, promoted the sexual cell fusion, through enhancement of gamete formation. In contrast, staurosporine (structurally and functionally similar to K252a) inhibited markedly the progress of development including cell aggregation, thus resulting in the failure of cells to form mature macrocysts. The effective period of K252a was 5–7 hr after starvation, during which Dm7 cells could acquire fusion competence, and the inhibitory effect of cAMP on zygote formation was nullified by the co-application of K252a. Although KT5720 (a specific inhibitor of cAMP-dependent protein kinase) and W7 (a calmodulin inhibitor) had no effects on zygote formation when applied separately, their combined application enhanced zygote formation like K252a did. Neither calphostin C (a specific inhibitor of Ca²⁺-dependent protein kinase) nor herbimycin A (a specific inhibitor of tyrosine kinase) exerted a stimulative influence upon macrocyst formation. These results strongly suggest that the two signal transduction pathways mediated by cAMP-dependent protein kinase (PKA) and calmodulin are closely related to zygote formation, their blockage being favorable to zygote formation.