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At least 379 records · Page 21Linked to original sources
PubMed2003

Defective proventriculus is required for pattern formation along the proximodistal axis, cell proliferation and formation of veins in the Drosophila wing.

Many genes have been identified that are required for the establishment of the dorsoventral (DV) and anteroposterior (AP) axes of the Drosophila wing. By contrast, little is known about the genes and mechanisms that pattern the proximodistal (PD) axis. Vestigial (Vg) is instrumental in patterning this axis, but the genes that mediate its effects and the mechanisms that operate during PD patterning are not known. We show that the gene defective proventriculus (dve) is required for a region of the PD axis encompassing the distal region of the proximal wing (PW) and a small part of the adjacent wing pouch. Loss-of-function of dve results in the deletion of this region and, consequently, shortening of the PD axis. dve expression is activated by Vg in a non-autonomous manner, and is repressed at the DV boundary through the combined activity of Nubbin and Wg. Besides its role in the establishment of the distal part of the PW, dve is also required for the formation of the wing veins 2 and 5, and the proliferation of wing pouch cells, especially in regions anterior to wing vein 3 and posterior to wing vein 4. The study of the regulation of dve expression provides information about the strategies employed to subdivide and pattern the PD axis, and reveals the importance of vg during this process.

Animals↗
PubMed1991

Mutations in a newly identified Drosophila melanogaster gene, mago nashi, disrupt germ cell formation and result in the formation of mirror-image symmetrical double abdomen embryos.

The mago nashi (mago) locus is a newly identified strict maternal effect, grandchildless-like, gene in Drosophila melanogaster. In homozygous mutant mago females reared at 17 degrees C, mago+ function is reduced, the inviable embryos lack abdominal segments and 84-98% of the embryos die. In contrast, at 25 degrees C, some mago alleles produce a novel gene product capable of inducing the formation of symmetrical double abdomen embryos. Reciprocal temperature-shift experiments indicate that the temperature-sensitive period is during oogenetic stages 7-14. Furthermore, embryos collected from mago1 homozygous females contain no apparent functional posterior determinants in the posterior pole. In viable F1 progeny from mago mutant females, regardless of genotype and temperature, polar granules are reduced or absent and germ cells fail to form (the grandchildless-like phenotype). Thus, we propose that the mago+ product is a component of the posterior determinative system, required during oogenesis, both for germ cell determination and delineation of the longitudinal axis of the embryo.

Abdomen↗
PubMed1999

The four populations of myoblasts involved in human limb muscle formation are present from the onset of primary myotube formation.

To understand how and when myogenic precursor cells become committed to their particular developmental programs, we have analysed the different populations of myoblasts which grow out from explants of muscle tissue isolated from human limb buds from the beginning of primary fibre formation throughout subsequent development and post-natal growth. Four phenotypically distinct types of myoblasts were identified on the basis of their expression of desmin, myogenin and myosin heavy chain isoforms (MyHC), and after 5 and 20 divisions, cells were cloned. All four types of myoblasts were present at the beginning of primary myogenesis. Each respective phenotype was stably heritable through cloning and subsequent proliferation. The type 1 clones correspond to a novel class of myoblasts never described during human development, that biochemically differentiates, but does not fuse. Type 2 clones are composed of small myotubes expressing only embryonic MyHC. Type 3 clones are composed of thin and long myotubes expressing both embryonic and fetal MyHCs. The type 4 clones are composed of myotubes that have a phenotype very similar to human satellite cells. Contrasting with others species, no other population of myoblasts appear during fetal development and only the relative number of these four types changes.

Cell Differentiation↗
PubMed1994

Gatekeeping through media format: strategies of voice for the HIV-positive via human interest news formats and organizations.

This research examines the extent to which HIV-positive voices are marginalized in the mainstream versus the "alternative" press. The central claim of this research is that news media format considerations, constructed around what has come to be called "media logic," leave persons who are HIV-positive with comparatively little voice in the mainstream press. By utilizing techniques of content analysis, the research examines 535 major HIV/AIDS-specific stories published in two oppositional papers toward an assessment of the level of HIV-positive voice in each outlet. While arguments of "homophobia" have been previously used to explain bias in mainstream HIV/AIDS-coverage, this article asserts that "hetero-centric" bias is, in fact, embedded in the routinized practices of mainstream "news production." The article concludes by suggesting that successful future HIV/AIDS activism demands a recognition of "media logic" and an adoption of its tactics.

HIV Seropositivity↗
PubMed1997

Gatekeeping through media format: strategies of voice for the HIV-positive via human interest news formats and organizations.

This research examines the extent to which HIV-positive voices are marginalized in the mainstream versus the "alternative" press. The central claim of this research is that news media format considerations, constructed around what has come to be called "media logic," leave persons who are HIV-positive with comparatively little voice in the mainstream press. By utilizing techniques of content analysis, the research examines 535 major HIV/AIDS-specific stories published in two oppositional papers toward an assessment of the level of HIV-positive voice in each outlet. While arguments of "homophobia" have been previously used to explain bias in mainstream HIV/AIDS-coverage, this article asserts that "heterocentric" bias is, in fact, embedded in the routinized practices of mainstream "news production." The article concludes by suggesting that successful future HIV/AIDS-activism demands a recognition of "media logic" and an adoption of its tactics.

HIV Seropositivity↗
PubMed2000

Evidence of the formation of different hydroperoxides in irradiated gamma-linolenate solutions: effect of micelle formation.

Peroxidation of unconjugated polyunsaturated fatty acids such as linolenic acid proceeds through a free radical chain mechanism and is accompanied by the formation of conjugated dienes such as hydroperoxides. In an investigation of radiation-induced oxidation of aqueous linolenate, we have measured two indexes of peroxidation: (1) conjugated dienes by means of absorption spectroscopy and (2) hydroperoxides by high-pressure liquid chromatography using detection of chemiluminescence. The experimental results indicate a strong effect of the concentration of linolenate on the yields of oxidized products. In addition, this work shows the quantitative production of two kinds of hydroperoxides. The ratio of these hydroperoxides is independent of the radiation dose but is dependent on the linolenate concentration. One hydroperoxide is formed predominantly below the critical micellar concentration (3 mM under our conditions), while the second is observed predominantly when micelles are formed in the aqueous medium. The influence of the composition of the medium on the nature of both hydroperoxides is discussed. [bj163]

Chromatography, High Pressure Liquid↗
PubMed1988

Formation of hydroxyl radicals in biological systems. Does myoglobin stimulate hydroxyl radical formation from hydrogen peroxide?

Incubation of horse-heart oxymyoglobin or metmyoglobin with excess H2O2 causes formation of myoglobin(IV), followed by haem degradation. At the time when haem degradation is observed, hydroxyl radicals (.OH) can be detected in the reaction mixture by their ability to degrade the sugar deoxyribose. Detection of hydroxyl radicals can be decreased by transferrin or by .OH scavengers (mannitol, arginine, phenylalanine) but not by urea. Neither transferrin nor any of these scavengers inhibit the haem degradation. It is concluded that intact oxymyoglobin or metmyoglobin molecules do not react with H2O2 to form .OH detectable by deoxyribose, but that H2O2 eventually leads to release of iron ions from the proteins. These released iron ions can react to form .OH outside the protein or close to its surface. Salicylate and the iron chelator desferrioxamine stabilize myoglobin and prevent haem degradation. The biological importance of .OH generated using iron ions released from myoglobin by H2O2 is discussed in relation to myocardial reoxygenation injury.

Animals↗
PubMed1984

Plasmids of Streptomyces kasugaensis MB273: their pock formation, their dispensable endonuclease cleavage sites for pock formation, and transformation of S. kasugaensis MB273 by them.

Plasmid-free strains of Streptomyces kasugaensis MB273 were isolated. In mating experiments S. kasugaensis MB273 was found to cause a lethal zygosis (pock) phenotype in a plasmid-free host. The pock-forming plasmids were identified as either pSK1* or pSK2* on the basis of their endonuclease cleavage-sites. The strain carrying pSK1* was found to induce pocks on the strain bearing pSK2*, and vice versa. The endonuclease cleavage-sites in pSK1* and pSK2* that were nonessential for pock formation were determined in deletion or insertion derivatives. The single sites for Bcl I and Sal I in pSK1* and for Bgl II in pSK2*, respectively, could be useful for DNA cloning without destroying pock-forming ability. Protoplasts of S. kasugaensis MB273-derivatives prepared in stationary phase of mycelial growth were competent for transformation, however, regeneration frequencies decreased during this phase.

Endonucleases↗
PubMed1999

In Hydra magnipapillata the activator of protein kinase C diC8 causes multiple head formation along the body axis only when accompanied by feeding, but heavy feeding alone is sufficient to cause multiple head formation.

In Hydra magnipapillata additional head structures can be induced to form by daily feeding accompanied by a daily treatment with diC8, an activator of protein kinase C. Based on these results, it was proposed that the PKC- pathway plays a central role in head formation in hydra. The results described here show that ectopic structures, as well as the ectopic localization of nerve cells, can be induced by heavy feeding alone. Furthermore, diC8 treatment does not induce ectopic head structures in starved animals. DiC8 reduces the rate of budding, leading to an unusual lengthening of the body column in reasonably fed animals.

Animals↗
PubMed2002

Signalling via type IA and type IB bone morphogenetic protein receptors (BMPR) regulates intramembranous bone formation, chondrogenesis and feather formation in the chicken embryo.

Bone morphogenetic proteins (BMPs) signal via complexes of type I and type II receptors. In this study, we mapped the expression of type IA, type IB and type II receptors during craniofacial chondrogenesis and then perturbed receptor function in vivo with retroviruses expressing dominant-negative or constitutively active type I receptors. BmprIB was the only receptor expressed within all cartilages. BmprIA was initially expressed in cartilage condensations, but later decreased within cartilage elements. BmprII was expressed at low levels in the nasal septum and prenasal cartilage and at higher levels in other craniofacial cartilages. The maxillary prominence, which gives rise to several intramembranous bones, expressed both type I receptors. Misexpression of dnBMPRIB decreased the size of cartilages and bones on the treated side. In contrast, dnBMPRIA had no effect on the skeletal phenotype. The phenotypes of caBMPRIA and caBMPRIB were similar; both led to overgrowth of cartilage elements, thinner bones with fewer trabeculae and inhibition of feather development. Infection with constitutively active viruses resulted in ectopic expression of Msx1, Msx2 and Fgfr2 throughout the maxillary mesenchyme. These data suggest that the pattern of trabeculation in membranous bones derived from the maxillary prominence was related to the change in expression pattern and that Msx and Fgfr2 genes were downstream of both type I BMP receptors. We conclude that the requirement for the type IB is greater than for the type IA receptor but, when active, both receptors play similar roles in regulating bone, cartilage and feather formation in the skull.

Animals↗
PubMedDate not supplied

[Formation by Actinomyces malachitospinus sp. nov. of a physiologically active substance that stimulates zygote formation in Mucorales].

A new species Actinomyces malachitospinus sp. nov. is described. It has spiral catenulate spores with spines, a gray aerial mycelium, and a green colonial mycelium, and contains no soluble pigments (including melanoid pigments). The strain of Act. malachitospinus INMI 217 produces a physiologically active substance that stimulates the formation of zygotes in Phycomyces blakesleeanus.

Culture Media↗
PubMedDate not supplied

Oxygen free radicals and pelvic adhesion formation: I. Blocking oxygen free radical toxicity to prevent adhesion formation in an endometriosis model.

Intraperitoneal superoxide dismutase (SOD) and catalase were used to block the toxic effects of superoxide anion (O2) and hydrogen peroxide (H2O2), associated with the production of endometriosis and inflammation in a rabbit model. In a two-part animal study, the combined instillation of SOD and catalase significantly reduced the formation of intraperitoneal adhesions at endometriosis sites.

Animals↗
PubMed1991

[Prevention of in vivo formation of NMBz A and the formation of oesophageal tumour by tea in rats].

Five groups of rats (22 per group) were intubated with precursors of N-Nitrosomethylbenzylamine (NMBzA), i.e. methylbenzylamine (1 mmol/kg) and sodium nitrite (0.5 mmol/kg), and five varieties of Chinese tea. One positive control group was intubated with precursors of NM2A without tea and one negative control group with tap water and sodium nitrite. After 12 week's treatment, significantly less lesions and papillomas in esophageal mucosa, examined by naked eye or by microscope, were found in the tea-treated groups than in the non-tea-treated positive control group. The results confirmed the anti-tumour ability of Chinese tea by blocking the in vivo formation of NMBzA in rats.

Animals↗
PubMed1991

The formation and application of an overseas mental health crisis intervention team, Part I: Formation.

The creation of an overseas mental health crisis intervention team is described. The authors discuss the unique aspects of an overseas low intensity conflict environment and the importance of immediate mental health responses to disaster situations in such theaters. Key elements in the formation of the team are the use of local resources, command endorsement, and an emphasis on education of commanders and team members. Examples are cited of other military response team deployments. The authors present their experience in Panama as a model for other providers in similar environments.

Crisis Intervention↗
PubMed1990

Kinetics of the formation and removal of cisplatin-DNA adducts in blood cells and tumor tissue of cancer patients receiving chemotherapy: comparison with in vitro adduct formation.

During chemotherapy with a cisplatin-containing combination of drugs, 217 blood samples from 30 cancer patients were analyzed for the presence of the main cisplatin-DNA adduct cis-Pt(NH3)2d(pGpG) (Pt-GG). Cisplatin was administered during 3-h infusions on each of 5 consecutive days, resulting in increasing adduct levels which, on the average, were about twice as high after the fifth as after the first infusion. Higher levels were found in blood samples of patients who received the same total amount of cisplatin in one single 3-h infusion. No significant differences in adduct levels were found during first and repeated courses. The nonlinear dependence of adduct levels on total dose can be attributed to removal of adducts. At 21 h after a very first cisplatin infusion 76% of the adducts were removed. Lower percentages of removal were observed over the 21-h periods following the fourth and fifth infusions of 5-day courses (49 and 53%, respectively). After the initial 21 h the removal of adducts continued, albeit at a slower rate. Substantial interindividual variation was found in the adduct levels, which did correlate with the levels obtained after in vitro cisplatin treatment of blood samples from the same patients but not with their age or gender. Testicular cancer patients with complete tumor response showed higher adduct levels in their blood than those with partial response or progressive disease. When blood samples from 8 healthy volunteers were treated with cisplatin in vitro, the person-to-person variation in adduct levels and the intraindividual variation observed over a 2-year period were found to be in the same range, which was narrower than that observed with samples from treated patients. In vitro studies with human blood showed that the formation of the Pt-GG adduct is proportional to cisplatin concentration and complete after about 1 hour. In some of the in vivo and in vitro cisplatin-treated blood samples, all 4 known platinum-DNA adducts were determined. In all cases Pt-GG was by far the major adduct, and no significant differences were observed with respect to the relative amounts of the 4 adducts. Similar adduct ratios were found in DNA from a testicular tumor obtained from a patient who underwent orchidectomy; the Pt-GG adduct level was about 10-fold higher than that in his blood cells.

Adult↗
PubMed1988

Formation of aggregates from a thermolabile in vivo folding intermediate in P22 tailspike maturation. A model for inclusion body formation.

The in vivo accumulation of polypeptide chains in the form of aggregated non-native states is a problem in many applications of biotechnology. In the maturation pathway of the thermostable P22 tailspike endorhamnosidase, the folding and chain association intermediates can be distinguished from the native tailspikes in crude extracts of phage-infected Salmonella cells. Temperature-sensitive folding mutations, at many sites in the chain, destabilize these conformational intermediates preventing the formation of native tailspikes at restrictive temperatures (Goldenberg, D. P., Smith, D. H., and King, J. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 7060-7064). We report here that both wild type and mutant tailspike polypeptide chains which fail to reach the native state accumulate in an aggregated state. These off-pathway aggregates form from a thermolabile intermediate in the productive folding pathway. These aggregation reactions are suppressed by lowering the temperature of maturation. Similar off-pathway steps from folding intermediates may account for the non-native aggregates often found in the expression of cloned genes in heterologous hosts.

Kinetics↗
PubMed1987

[Dynamics of endogenous bacterial nitrite formation in the stomach. 6. Redox potential and nitrite formation in stomach secretions].

The redox potential depending on the pH-value and the concentration of nitrite was examined in the fasting gastric juice samples of 132 anamnestically healthy, young, voluntary test-persons. It turned out that small pH-values (acid) are associated with high redox potentials and big pH-values (neutral) with smaller redox potentials. Therefore the hydrogen ion pressure (rH-value) resulting from these two quantities generally is situated in the indifferent range. Reducing properties of the whole juice can only occasionally be found, and apparently only then, if a neutral juice is acidified. Oxidizing properties have to be classified as exceptional cases. It cannot absolutely be traced on behalf of the findings, that can be raised with natural juices, if and when answered affirmatively, which effects the redox potential has on the formation of bacterial nitrite.

Bacteria↗
PubMed1988

Formation of tone-US associations does not interfere with the formation of context-US associations in pigeons.

In four experiments we investigated whether signaled and unsignaled US presentations resulted in differential context conditioning. Experiments 1 and 2 showed that the presence of a tone during grain presentation facilitated the formation of tone-food associations in pigeons. Experiment 2 also showed that the acquisition of associative value by the tone did not diminish associations between context and the unconditioned stimulus (US). Experiment 3 showed that signaled USs did not interfere with the acquisition of context-US associations, and Experiment 4 showed that even when the signal was extensively pretrained, context-US associations could not be blocked. The results of these experiments are inconsistent with conditioning models that require competition between cues and contexts for associative value.

Animals↗