Abnormal Polarity Research Articles

Directional non-cell autonomy and the transmission of polarity information by the frizzled gene of Drosophila.

The function of the frizzled (fz) locus is required for the development of a parallel array of bristles and hairs on the adult cuticle of Drosophila melanogaster. Marked fz mitotic clones from five alleles were generated and examined in the wing. Three alleles have a non-cell-autonomous hair polarity phenotype; wild-type cells distal to fz clones produce hairs that have an abnormal polarity. In contrast, fz clones of the other two fz alleles examined do not disrupt the polarity of neighbouring cells. These data suggest that fz has two mutably separate functions in establishing hair polarity on the wing. One function involves the transmittance and/or generation of a polarity signal along the proximal-distal axis of the wing. The second function involves the cellular interpretation of a polarity signal.

The segment polarity gene costal-2 in Drosophila: II. The origin of imaginal pattern duplications

Imaginal pattern duplications caused by hypomorphic expression of the segment polarity gene costal-2 are described. These affect the anteroposterior coordinate of the imaginal disc. A very small part of the pattern is deleted and a large number of additional pattern elements arise in a progressive order, anterior-most first followed by more and more posterior structures. Mosaic analyses show that the duplications arise nonautonomously in the larval stages but that the costal-2 gene is not required after early embryogenesis. Arguments that the duplications are the result of cell interactions and intercalary growth that themselves arise from an abnormal polarity of the embryonic segment are presented.

Abnormal Polarity of Thunderclouds Grown from Negatively Charged Air

Experiments were carried out in New Mexico to determine whether the electrification processes that lead to the formation of lightning in clouds are influenced by the polarity of the charges in the air from which the clouds grow. The normal, positive space charge in the sub-cloud air was reversed by negative charge released from an electrified wire, suspended across a 2-kilometer-wide canyon. On more than four occasions when the clouds over the wire grew and became electrified, they were of abnormal polarity with dominant positive charges instead of the usual negative charges in the lower part of the cloud. The formation of these abnormally electrified clouds suggests both that the electrification process in thunderclouds can be initiated and that its polarity may be determined by the small charges that are present in the atmosphere.

Abnormal polarity of bristles and joints on [formula omitted] legs : [formula omitted]. [formula omitted]. [formula omitted], [formula omitted]. Developmental Biology Center, University of California, Irvine, California 92717, USA

Abnormal polarity of bristles and joints on [formula omitted] legs : [formula omitted]. [formula omitted]. [formula omitted], [formula omitted]. Developmental Biology Center, University of California, Irvine, California 92717, USA

Illustration of the emergent magnetic flux model: Observations of the large flare of 1981 May 16

Using the high-resolution data in white light and in Hα of the large, double-ribbon flare of 1981 May 16 obtained at Purple Mountain Observatory, we discussed the changes in the photosphere and chromosphere 8 hours before, and during the initial phase of the flare and analysed the relationship between the emergent magnetic flux, surges, dark filaments and the onset of the flare. We found that an increase in the magnetic flux with the abnormal polarity beside the neutral line produced surges, which in turn gave rise to disturbances and eruptions in the dark filament at the neutral line and led to the large flare. The emergent magnetic flux model of flares is thus verified and extended.

Neuroanatomical study of somatomotor cortex in microcephalic mice induced by cytosine arabinoside

Somatomotor cortex of mice with microcephaly induced by DNA polymerase inhibitor cytosine arabinoside (Ara-C), has been studied with a modified Golgi-Cox staining and a HRP retrograde tracing method. Microcephalic mice were prepared by prenatal injections of cytosine arabinoside on days 13.5 and 14.5 of pregnancy. Cytoarchitectonically, the cerebral cortices of adult microcephalic mice are characterized by atypical pyramidal cells with abnormal dendrites and irregular patterns of cellular lamination. Semiquantitative analyses of the abnormality of dendrites in Golgi-Cox preparation indicate that both the degree and direction of ramification are severely affected in Ara-C treated mice. In adult control cerebrum, original neurons of corticospinal tract labeled after HRP injection into the lumbar cord were situated in layer V. In the microcephalic brains, however, HRP labeled neurons, some of which had abnormal polarity, were scattered throughout all layers. This HRP study for corticospinal tract neurons also confirms the irregular pattern of the cortex in which only three layers are recognized.

Abnormal Limb Regeneration without Tumor Production in Adult Newts Directed by Carcinogens, 20-Methylcholanthrene and Benzo (α) pyrene: (amphibia/limb regeneration/carcinogen/teratogenesis).

The effects of potent carcinogens, 20-methylcholanthrene (MC) and benzo(α)pyrene (BP), on limb regeneration were studied in adult newts. A microcrystal of these carcinogens was administered directly to the blastema of forelmibs on day 7 after amputation. The formation of the regeneration cone was delayed and the cone was shifted in abnormal polarity depending upon the site of micro-crystal administration. These carcinogens affected morphogenesis of skeletal structures of regenerating limbs. Subregeneration and superregeneration of either or both carpals and digits, absence of either or both ulna and radius, and accessory limb formation have been recorded as abnormalities caused by these carcinogens. Non-carcinogenic benzocompounds did not show such effects as those of MC and BP. The regeneration blastema of the limb appears to be resistant to carcinogenic effects of the carcinogens used since tumor formation has never been observed in our study so far.

Modification of regeneration in Dugesia tigrina by actinomycin D.

AbstractDifferences in regeneration of isolated postpharyngeal body sections were observed in two laboratory groups of Dugesia tigrina. One group regenerated 14.8% of bipharyngeal specimens, which in some cases, also showed abnormal polarity. The other group regenerated only 1.19% of bipharyngeal forms under similar conditions, with no indications of seriously deviant polarity.In the first strain, the application of actinomycin D at early stages of regeneration of the body sections increased greatly the incidence of multipharyngeal regenerates (with 2–5 pharynges); it also slightly enhanced the occurrence of abnormal polarity in the reconstituted worms. In the second strain, the increase in percentage of bipharyngeal forms regenerated from similar body fragments was insignificant (up to 5%). It was without effect on either strain if introduced to the regenerating sections at later stages of regeneraton. A test for incorporation of 32P into RNA showed that actinomycin, as used in the present study, suppressed over 90% of synthesis of total RNA in the regenerating body fragments.From these findings a hypothetical model is developed to explain reorganization in the isolated postpharyngeal section as a sequence of certain local inductions and inhibitions of differentiation. The significance of synthesis of RNA in relation to these developmental events is discussed.