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At least 919 records · Page 51Linked to original sources
PubMed1990

Identification of germination gene of Bacillus megaterium.

Glucose, KNO3, proline and leucine initiate the spore germination of B. megaterium ATCC 12872, but not of B. megaterium ATCC 19213. In order to isolate the gene concerning germination of B. megaterium ATCC 12872, we constructed its gene library in plasmid vector, and introduced into B. megaterium ATCC 19213. We obtained a transformant whose spores differed from those of the wild type strain with respect to germinability. Spores of this transformant could be germinated by glucose, proline or leucine. The recombinant plasmid prepared from this transformant was found to carry 2 kilobase pairs fragment of B. megaterium ATCC 12872 DNA. This fragment may contain the gene encoding the protein which plays an important role in germination.

Amino Acids↗
PubMed1990

Effect of optic nerve lesions and intraocular colchicine on cell proliferation in the germinal zone of the optic tectum and in the torus longitudinalis in the goldfish.

Postembryonic development of the optic tectum occurs in part through proliferation of cells in the germinal zone located at the caudal edges of each lobe. Autoradiography experiments by others have shown that [3H]thymidine labeling in the germinal zone is decreased following optic nerve crush or enucleation and restored above normal levels during optic nerve regeneration. The present autoradiography experiments examined the relationship between retinal innervation and the rate of mitotic activity in the tectum germinal zone and in the torus longitudinalis. The fish received optic nerve crush to temporarily deafferent the tectum, enucleation for permanent deafferentation, or an intraocular injection of 0.01-1.0 microgram of colchicine to reversibly inhibit axonal transport in the optic nerve. Thymidine labeling in the tectum germinal zone showed that nerve crush resulted in decreased mitotic activity in most fish within 6 days followed by recovery by 21 days; enucleation decreased mitotic activity more uniformly and for more than 42 days with recovery by 84 days postaxotomy; colchicine produced a dose-dependent inhibition of mitotic activity which was reversed by 42 days postinjection. Axonal transport was restored by 42 days postinjection. In the torus longitudinalis, nerve crush produced a brief increase in mitotic activity followed by a return to normal; enucleation and colchicine resulted in a lasting decrease in mitotic activity and atrophy indicating a loss of cells or neuropil. The data are consistent with the proposal that cell proliferation in the tectum germinal zone is stimulated by the accretion of fibers from developing retinal ganglion cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

A neuroectoderm-associated ganglioside participates in fibronectin receptor-mediated adhesion of germinal cells to fibronectin.

Previous studies with a rat neural cell line have shown that the D1.1 ganglioside, an O-acetylated derivative of GD3, is involved in cellular adhesion to fibronectin. In vivo, D1.1 is present on germinal cells of the developing rat central nervous system, but not on postmitotic cells that migrate away from the germinal zones. These observations suggest that D1.1 could participate in adhesive interactions with germinal zones and that the loss of D1.1 could be involved in the decision to being migration. In support of this hypothesis, immunofluorescence histochemistry shows that both fibronectin and fibronectin receptor are colocalized with D1.1 in the ventricular zones of the embryonic rat brain and in the external granule cell layer of the postnatal cerebellum. Dishes coated with monoclonal antibody against D1.1 were used to isolate D1.1-positive germinal cells from Embryonic Day 14 cerebrum and from Postnatal Day 6 cerebellum. These cells are able to adhere to fibronectin-coated dishes by a mechanism that is inhibitable by a synthetic hexapeptide containing the arg-gly-asp cell recognition sequence of fibronectin. Adhesion is also partially inhibited by antibody against fibronectin receptor and is slowed by anti-D1.1 antibody, implicating both the receptor and the ganglioside in the adhesion process. During 3 days in culture these D1.1-positive, fibronectin receptor-positive cells exhibit a neuronal phenotype, as judged by morphology and staining with tetanus toxin. This further confirms the neuroepithelial origin of the cells. The cells do not synthesize detectable amounts of fibronectin, thus leaving unidentified the source of the fibronectin seen in the germinal zones in tissue sections. Immunoprecipitation experiments show that the fibronectin receptors present on these cells are heterodimers. Under nonreducing conditions, the immunoprecipitates contain an alpha-subunit of 150-160 kDa and a beta-subunit of 115-125 kDa.

Age Factors↗
PubMed1985

ESS germination strategies in randomly varying environments. II. Reciprocal Yield-Law models.

The study of ESS germination fractions in S. Ellner (1985, Theor. Pop. Biol. 27, 000-000) is applied and extended in the case of annuals obeying the Reciprocal Yield Law. The effects of parameter changes on the value of the ESS germination fraction are determined in some limiting cases by analyses of approximations. Numerical solutions of the ESS criterion are used to check the robustness of the conclusions and the accuracy of the approximations. In general, the ESS germination fraction decreases with an increased survivorship of buried seeds and with increased "variability" of seed yields. However, different measures of "variability" are appropriate in different circumstances. To avoid the possibility of conflicting predictions depending on the measure of variability, it is suggested that tests of the theory be limited to co-occurring species, and to variability due to climatic fluctuations. The ESS theory based on the Reciprocal Yield Law is compared with D. Cohen's (1966, J. Theor. Biol. 12, 119-129; 1968, J. Ecol. 56, 219-228) density-independent theory of "optimal" germination. The theories differ qualitatively and quantitatively regarding the influence of mean yield, seed survivorship, and the frequency of favorable years on the predicted germination fraction.

Biological Evolution↗
PubMed1991

Maturation of the immune response in germinal centers.

Germinal centers develop in peripheral lymphatic tissue during the primary immune response and may play a crucial role in affinity maturation. We have compared the diversification of the antigen-specific repertoire of B cells, both from within and from outside the germinal centers, during the murine response to 2-phenyloxazolone (phOx). By sequencing V kappa Ox1 L-chains characteristic of phOx-specific antibodies, we show that somatic mutations accumulate in germinal center B cells and that a mutation conferring high affinity binding is found with increasing frequency. An analysis of V/D/J rearrangements suggests that this mutation occurred independently in many B cells, which were then preferentially expanded. We conclude that, although the hypermutation mechanism may be activated before germinal centers develop, affinity maturation by hypermutation and selection takes place in the germinal centers.

Amino Acid Sequence↗
PubMed1989

Comparison of the structural organization and expression of germinal and somatic rat histone H4 genes.

A rat somatic histone H4 gene was isolated by screening a rat genomic library using a cloned cell-cycle-regulated human histone H4 gene as a probe. The somatic histone H4 gene was subcloned and the nucleotide sequence was determined. The structural organization and expression of the somatic histone H4 gene and the rat germinal histone H4t gene were compared. Although the predicted amino-acid sequences of the two histones were identical, 49 out of 102 codons differed. The leader sequence of the germinal histone H4t mRNA was 17 bases compared to 40 bases for the somatic histone H4 mRNA, and the 3' terminal sequence of the germinal histone H4t mRNA was 52 bases compared to 75 bases for the somatic histone H4 mRNA. The germinal histone H4 gene also lacked a consensus purine-rich motif which was present in the 5' noncoding region of the somatic histone H4 gene. Northern blot analyses and S1-nuclease protection analyses revealed that the germinal histone H4t and H1t genes were expressed during spermatogenesis in rat pachytene spermatocytes, and the somatic histone H4 gene was expressed only in nongerminal rat cells and tissues. The histone H4t gene was also expressed in some other rat cell types. The differences in expression of the histone H4t and H1t genes may reflect differences in transcription, differences in turnover rates of the mRNAs, or a combination of these factors.

Amino Acid Sequence↗
PubMed1981

In vitro screening of potential anti-cancer chemicals: effect of purine pyrimidine analogues on seed germination.

Germinating Cicer arietinum seeds were used to simulate embryonic tissue for evaluating toxicity of purine and pyrimidine analogues. 6-Mercaptopurine stimulated germination, whereas 8-azaadenine, 8-azaguanine, 2,6-diaminopurine, 6-amino, 2-hydroxypurine and 5-fluorouracil inhibited germination. 6-Methyluracil, 5-aminouracil and methylxanthines, viz. caffeine, theophylline, theobromine and uric acid exhibited little inhibitory effects. RNA synthesis ensued immediately after water imbibition and reached maximum at 12 h of germination. 2,6-Diaminopurine, 8-azaadenine, 8-azaguanine and 5-fluorouracil inhibited RNA synthesis. Cyclic-AMP, adenosine, indole-3-acetic acid (IAA) and folic acid partially reversed the inhibitory effects produced by purine pyrimidine analogues. Several hitherto untested pyrimidine analogues inhibited germination as well as RNA synthesis. Inhibition of Escherichia coli dihydrofolate reductase was used for purposes of comparison.

Antineoplastic Agents↗
PubMed1983

Massive increase in splenic germinal centres of chickens experimentally-infected with Trypanosoma brucei brucei.

Domestic chickens infected with Trypanosoma brucei brucei developed a latent parasitaemia which lasted for one year. Six distinct variable antigen types were isolated. Spleens from infected birds were studied histologically at different stages of the infection. Trypanosome infection produced a progressive increase in the number of germinal centres during the early stages of the infection. Peak numbers of germinal centres were reached in the spleen at Day 84 after which the numbers were maintained during an active infection. A tenfold increase in the number of germinal centres was found in trypanosome-infected birds compared to controls. No splenomegaly was observed. Lymphoid cells of the caecal tonsil and the thymus remained apparently normal during the course of infection. Chemotherapeutic termination of infection with berenil resulted in an initial increase in the number of germinal centres. A gradual return to normal level was observed on Day 100 post cure. It is suggested that the development of such a large number of germinal centres reflects the bird's response to the elaboration of a succession of trypanosome variable antigens.

Animals↗
PubMed1994

Calmodulin function and calmodulin-binding proteins during autoactivation and spore germination in Dictyostelium discoideum.

Dictyostelium discoideum spores can be activated to initiate germination either endogenously via a diffusible autoactivator, or exogenously via heat. Following activation, three successive stages of germination occur, the lag stage, spore swelling and amoebal emergence. A previous study [Lydan M. A. and Cotter D. A. (1994) FEBS Lett. 115, 137-142] has shown that spore swelling is dependent on the activity of calmodulin. In this study, the calmodulin antagonists trifluoperazine and calmidazolium inhibited autoactivation, but had no effect upon heat activation. These agents also inhibited amoebal emergence following either form of activation. The effects caused by the anti-calmodulin agents were specific to an inhibition of calmodulin function since agents which modulate the activity of protein kinase C had no effect upon spore germination. A calcium-dependent calmodulin-binding protein of about 64,000 M(r) may be associated with the process of autoactivation since it was only seen in those spores which respond to the autoactivator. Overall, this study provides evidence to show that calmodulin plays a regulatory role during autoactivation and amoebal emergence during spore germination in D. discoideum and provides evidence for the calmodulin-dependent mechanisms which mediate each of these phases of germination.

Animals↗
PubMed2004

Recovery of natural fertility after grafting of cryopreserved germinative tissue in ewes subjected to radiotherapy.

OBJECTIVE: To recover natural fertility of ewes that were subjected to ovarian failure induced by radiotherapy with an autologous orthotopic graft of cryopreserved germinative tissue. DESIGN: Experimental surgery study. SETTING: University hospital unit. ANIMAL(S): Adult ewes. INTERVENTION(S): Four ewes were submitted to right oophorectomy and posterior dissecting and freezing of the germinative tissue. Afterward, they were administered radiotherapy to induce infertility on the remaining left ovary. Later, two of the ewes had the thawed fragments of the right ovary injected inside the cortex of the irradiated left ovary in a "sowing" procedure that eliminated the need for sutures. MAIN OUTCOME MEASURE(S): Recovery of fertility in ewes after transplantation of germinative tissue into the ovary destroyed by radiotherapy. RESULT(S): The ewes were housed with fertile rams. Six months following the grafting, the rams impregnated the transplanted ewes. More than 2 years after radiotherapy, the nongrafted (control) ewes have not become pregnant. CONCLUSION(S): Intracortical grafting of the germinative tissue circumvents the obstacle of vascular anastomosis with autologous ovarian implants. Patients could benefit from the subcortical grafting of germinative tissue in one of the ovaries, recovering fertility after radiotherapy treatment for malignancy.

Animals↗
PubMed2005

Modelling of effects of water activity and temperature on germination and growth of ochratoxigenic isolates of Aspergillus ochraceus on a green coffee-based medium.

Influence of water activity (0.75-0.99 a(w)) and temperature (10, 20 and 30 degrees C) on germination and mycelial growth on green coffee extract agar medium of three ochratoxigenic isolates of Aspergillus ochraceus was studied. Optimal conditions for germination and growth were observed at 0.95-0.99 a(w) and 20-30 degrees C for the three isolates. Minimum a(w) level for germination was 0.80, and 0.85 for mycelial growth. At marginal a(w) and temperature levels assayed, the lag phases prior to germination increased and the growth rates showed a significant decrease in comparison with the optimal conditions. Data were modelled by a multiple linear regression (MLR) and response surface models were obtained. Germination and growth of A. ochraceus in green coffee beans could be prevented or at least inhibited to some extent by minimising the time that coffee beans are exposed to temperature and humidity conditions near to the optimum during processing and storage. This could be an empirical approach to predict the effects of water activity and temperature conditions on the development of ochratoxigenic isolates of A. ochraceus during handling and storage of green coffee.

Aspergillus ochraceus↗
PubMedDate not supplied

Variations in UV-B tolerance and germination speed of Metarhizium anisopliae conidia produced on insects and artificial substrates.

Solar ultraviolet radiation (UV-A and UV-B) is a major factor in failure of programs using the insect pathogenic fungus Metarhizium anisopliae as a biological control agent. Studies were conducted to determine if growth conditions, viz. artificial (agar media or rice grain) or natural (infected insects) substrates for conidial production affect two traits that directly influence performance of conidia after field application: tolerance to UV-B radiation and conidial germination speed. Conidia of two isolates (ARSEF 23 and ARSEF 2575) of M. anisopliae var. anisopliae produced on potato dextrose agar plus yeast extract (PDAY) or on fungus-killed larvae of two insect species, Galleria mellonella and Zophobas morio, were inactivated by exposure to UV-B radiation. Conidia of both isolates when produced on insect cadavers were significantly more sensitive to UV-B radiation than conidia produced on PDAY. Also, conidia from insect cadavers germinated slower than those from PDAY cultures. A comparison of conidia from artificial substrates showed that conidia produced on Czapek's and Emerson's YpSs agar media or rice grains had higher tolerance to UV-B radiation and germinated faster than conidia raised on PDA and PDAY. Accordingly, the growth substrate and nutritional environment in which conidia are produced influences M. anisopliae conidial UV-B tolerance and speed of germination; and manipulation of these variables could be used to obtain conidia with increased tolerance to UV-B radiation and shorter germination times.

Animals↗
PubMed1999

Oncogenic Ras-induced germinal vesicle breakdown is independent of phosphatidylinositol 3-kinase in Xenopus oocytes.

A number of reports have identified phosphatidylinositol 3-kinase as a downstream effector of Ras in various cellular settings, in contrast to others supporting the notion that phosphatidylinositol 3-kinase acts upstream of Ras. Here, we used Xenopus oocytes, a model of Ras-mediated cell cycle progression (G2/M transition) to analyze the contribution of phosphatidylinositol 3-kinase to insulin/Ras-dependent signaling pathways leading to germinal vesicle breakdown and to ascertain whether phosphatidylinositol 3-kinase acts upstream or downstream of Ras in those signaling pathways. We analyzed the process of meiotic maturation induced by progesterone, insulin or micro-injected oncogenic Ras (Lys12) proteins in the presence and absence of specific inhibitors of phosphatidylinositol 3-kinase activity. As expected, the progesterone-induced maturation was independent of phosphatidylinositol 3-kinase since similar rates of germinal vesicle breakdown were produced by the hormone in the presence and absence of wortmannin and LY294002. In contrast, insulin-induced germinal vesicle breakdown was completely blocked by pre-incubation with the inhibitors prior to insulin treatment. Interestingly, similar rates of germinal vesicle breakdown were obtained in Ras (Lys12)-injected oocytes, independently of whether or not they had been pre-treated with phosphatidylinositol 3-kinase inhibitors. The effect of wortmannin or LY294002 on MAPK and Akt activation by progesterone, insulin or Ras was also analyzed. Whereas insulin activated those kinases in a phosphatidylinositol 3-kinase-dependent manner, progesterone and Ras were able to activate those kinases in the absence of phosphatidylinositol 3-kinase activity. Since Ras is a necessary and sufficient downstream component of insulin signaling pathways leading to germinal vesicle breakdown, these observations demonstrate that phosphatidylinositol 3-kinase is not a downstream effector of Ras in insulin/Ras-dependent signaling pathways leading to entry into the M phase in Xenopus oocytes.

Androstadienes↗
PubMed2002

Deposition and germination of conidia of the entomopathogen Entomophaga maimaiga infecting larvae of gypsy moth, Lymantria dispar.

Germination of conidia of Entomophaga maimaiga, an important fungal pathogen of gypsy moth, Lymantria dispar, was investigated on water agar and larval cuticle at varying densities. Percent germination was positively associated with conidial density on water agar but not on larval cuticle. When conidia were showered onto water agar, the rate of germination was much slower than on the cuticle of L. dispar larvae. From the same conidial showers, the resulting conidial densities on water agar were much higher than those on larval cuticle in part because many conidia adhered to setae and did not reach the cuticle. A second factor influencing conidial densities on larval cuticle was the location conidia occurred on larvae. Few conidia were found on the flexible intersegmental membranes in comparison with the areas of more rigid cuticle, presumably because conidia were physically dislodged from intersegmental membranes when larvae moved. Conidia were also exposed to heightened CO(2) to evaluate whether this might influence germination. When conidia on water agar were exposed to heightened CO(2) levels, germinating conidia primarily formed germ tubes while most conidia exposed to ambient CO(2) rapidly formed secondary conidia.

Animals↗
PubMed2000

Changes in wheat germination following gamma-ray irradiation: an in vivo electronic paramagnetic resonance spin-probe study.

Embryos excised from wheat (Triticum aestivum) grains following gamma-ray irradiation at different doses were analyzed on membrane permeability by electron paramagnetic resonance (EPR) technique with 4-oxo-2, 2, 6, 6-tetramethyl-1-piperidinyloxy (TEMPONE) as spin probe to acquire an EPR spectrum. The broadening agent ferricyanide added leads to changes in the high-field region of the EPR spectrum, which reflects differences in membrane permeability. R-value, defined as the ratio of water (W) to lipid (L) component in height in the high-field region of the EPR spectrum, symbolizes membrane permeability for a given sample. The R-values corresponding to a certain dose treatment of grains displayed a definitive distribution pattern. A unit row vector with 20 components was used to describe the R-value distribution pattern for a given treatment. The transaction angle between vectors corresponding to grains irradiated and unirradiated, &theta;, was used as quantitative index for membrane permeability changes following gamma-ray irradiation. gamma-Ray irradiated grains germinated at low rates, and the regression equation of germination rate as a function of the irradiation dose is: Germination Rate (%)=94.8 exp[-0.264xIrradiation Dose (kGy)] (r(2)=0.991, P<0.001). Embryos excised from grains following gamma-ray irradiation show increases in &theta; values with irradiation dose. The &theta; value is negatively linearly correlated with the germination rate. It suggests that gamma-ray irradiation leading to increases in membrane permeability is consistent with that leading to low germination rate of grains. The introduction to vector analysis method on membrane permeability changes in this study is very practical.

Journal Article↗
PubMed1978

Early ontogeny of germinal center formation in the chicken.

Germinal center formation was studied in the spleen of young chickens immunized in ovo and at the time of hatching. When immunization was performed on day 18 in ovo and on the day of hatching, the first germinal centers were observed at 4 days. This is markedly earlier than in unimmunized chickens, where the first germinal centers appear at the age of 10 days or later. Germinal center formation preceded significant antibody production. The possible role of germinal centers in the generation of immunological memory is discussed in the light of these and earlier observations.

Aging↗
PubMed2002

Antitumor activity of the sporoderm-broken germinating spores of Ganoderma lucidum.

The inhibitory effects of the dormant spores, the germinating spores, the sporoderm-broken germinating spores (SBGS), and the lipids extracted from the germinating spores of Ganoderma lucidum on the growth of mouse hepatoma, sarcoma S-180, and reticulocyte sarcoma L-II cells were investigated, respectively. The dormant spores could be activated by germination, and thus the bioactivities of the spores might be enhanced. The sporoderm-broken spores could show much higher bioactivities than the whole spores. Both the lipids extracted from the germinating spores and the SBGS of G. lucidum had remarkable antitumor effects in a dose-dependent manner, and could significantly inhibit three tumors with an inhibition of 80-90%.

Administration, Oral↗
PubMed1997

Endogenous autoinhibitors regulate changes in actin tyrosine phosphorylation during Dictyostelium spore germination.

Phosphorylation of proteins on tyrosine residues has been shown to govern many cellular processes, but little work has focused on the role of tyrosine phosphorylation during germination. Under optimal conditions, D. discoideum spores synchronously germinate each liberating a single amoeba. The total amount of phosphotyrosine containing proteins observed in spores was greatest during quiescence with a gradual decline during spore activation and emergence of nascent amoeba. During dormancy, tyrosine residues of actin were heavily phosphorylated, but they gradually underwent dephosphorylation upon spore activation and this process continued through emergence. Interestingly, an endogenous autoinhibitor(s), which blocks germination, induces tyrosine phosphorylation of actin. Conversely, the removal of the autoinhibitor(s) was followed by a decrease in phosphorylation. Thus, during germination of Dictyostelium spores, actin is dephosphorylated, with the level of phosphorylation regulated by the autoinhibitor(s) and/or the autoactivator. This change in actin phosphorylation appears to play a direct role since actin dephosphorylation and reorganization is a necessary prelude to germination.

Actins↗