Aberrant Morphogenesis Research Articles

Mutations at the ASP locus of Drosophila lead to multiple free centrosomes in syncytial embryos, but restrict centrosome duplication in larval neuroblasts

Mutations at abnormal spindle result in abnormally long and wavy microtubules in the meiotic spindles of males. Some of these spindles have a single pole and take the form of unopposed hemi-spindles. Unfertilised eggs produced by homozygous asp females may have either no nuclei, or a small number of large nuclei, consistent with there also being an effect upon female meiosis. Such eggs also display free centrosomes and independent arrays of microtubules. Embryos that have this phenotype are also present among the progeny of fertilised homozygous asp females, together with embryos that undergo varying degrees of aberrant morphogenesis, developing a variety of abnormal cuticle patterns. This latter category shows asynchronous mitoses prior to cellularisation, and has abnormal arrays of spindle microtubules. Such embryos can develop large areas that are either devoid of or have a reduced number of nuclei, in which there are centrosomes that have dissociated from the mitotic spindles. Neuroblasts in the brains of homozygous asp larvae display a high mitotic index, and have condensed chromosomes aligned as if blocked at metaphase. Immunostaining reveals that many cells contain a single centrosome connected to the metaphase chromosomes by microtubules in a hemi-spindle-like structure.

Morphological Alterations of the Fission Yeast Schizosaccharomyces pombe in the Presence of Aculeacin A: Spherical Wall Formation

The fission yeast Schizosaccharomyces pombe, grown in the presence of aculeacin A (Acu), an antifungal antibiotic, forms spherical rather than cylindrical walls. This aberrant morphogenesis was studied in the presence of Acu at 1 μg ml–1 under conditions in which over 90% of the cells continued to grow but with altered morphology. Microscopic observations and chemical analyses revealed that the spherical walls had a looser structure than the cylindrical wall and that their syntheses of alkali-insoluble glucan and mannan were reduced whereas the synthesis of alkali-soluble glucan was enhanced. Spherical walls of glutaraldehyde-fixed cells were hardly digested by Zymolyase 60000 [a (1→3)-β-glucanase] but were digested by Novozym 234 [a (1→3)-α-glucanase]. From these results the components and morphology of the spherical walls are discussed in comparison with the cylindrical walls.

Stage-dependent effects of retinoic acid on regenerating urodele limbs

Following amputation through the distal zeugopodium, regenerating limbs of larvalAmbystoma mexicanum and pre and post-metamorphicPleurodeles waltlii were treated with 150 μg of retinoic acid (RA) per gram of body weight, at the dedifferentiation, early bud, medium bud, late bud or early redifferentiation stages of regeneration. The effect of RA on regenerate morphogenesis differed as a function of the stage at which it was administered. When given during dedifferentiation or at early bud stages, RA evoked proximodistal duplications of stump segments in the regenerates. The maximum duplication index (DI) inAbystoma was achieved when RA was injected at 4 days post-amputation, which corresponds to the stage of dedifferentiation; and inPleurodeles at 10 days post-amputation, which corresponds to a stage midway between early bud and medium bud. When RA was administered at later stages, the DI declined progressively to zero or nearly zero by the stage of early redifferentiation in both species. The decline in DI was due to a decreased frequency of duplication, not to a decrease in the magnitude of duplication in individual regenerates. At the same time, there was an increase in hypomorphism and aberrant morphogenesis of both duplicating and non-duplicating regenerates. These results indicate that regenerative cells are differentially sensitive to RA in a stage-dependent way.

Laser microbeam induction of incomplete doublets of Oxytricha fallax.

SUMMARYDestruction by laser microbeam of oral and ventral cirral primordia for the future opisthe of 1/2 of a pre-fission doublet results in the permanent loss of ability to form oral and ventral cirral primordia on the irradiated half. This observation provides further evidence for the postulated ‘determinative region’ present on each ventral surface of these organisms. The opisthe of the irradiated doublet retains both original rows of marginal cirri, which are located mid-dorsally with respect to the remaining ventral surface. These two rows of marginal cirri are reproduced faithfully in all future opisthes, but are lost in most proter lines. The pattern of loss in proters involves migration of the extra rows of marginal cirri to the cell's right margin followed by aberrant morphogenesis and subsequent resorption. These results show that the reproduction of marginal cirri is at least partially dependent upon the presence of marginal cirri and their inherent structural characteristics as well as upon their position on the cell surface.

PATTERN OF MALFORMATION IN OFFSPRING OF CHRONIC ALCOHOLIC MOTHERS

Abstract Eight unrelated children of three different ethnic groups, all born to mothers who were chronic alcoholics, have a similar pattern of craniofacial, limb, and cardiovascular defects associated with prenatal-onset growth deficiency and developmental delay. This seems to be the first reported association between maternal alcoholism and aberrant morphogenesis in the offspring.

PATTERN OF MALFORMATION IN OFFSPRING OF CHRONIC ALCOHOLIC MOTHERS

Eight unrelated children of three different ethnic groups, all born to mothers who were chronic alcoholics, have a similar pattern of craniofacial, limb, and cardiovascular defects associated with prenatal-onset growth deficiency and developmental delay. This seems to be the first reported association between maternal alcoholism and aberrant morphogenesis in the offspring.

Epitheliomesenchymal interaction in pancreatic morphogenesis

The intact 11-day dorsal pancreatic rudiment, cultured in vitro, develops to a stage of differentiation roughly corresponding to the pancreas of an embryo of 15 days. Epithelium cultured alone does not develop. Epithelium recombined with pancreatic mesenchyme, or with a number of heterogenous mesenchymes, undergoes morphogenesis resembling that of the intact rudiment. Though the detailed pattern of lobulation varies for each mesenchyme used, differentiation at cell and tissue levels was never anything other than pancreatic in type. In transfilter experiments epithelial growth and aberrant morphogenesis were promoted strongly by salivary mesenchyme, to somewhat lesser degree by pancreatic mesenchyme, and little or not at all by metanephrogenic mesenchyme.

Dilated composite odontome: Reports of two cases, one bilateral and one radicular

A plea has been entered to discontinue the name dens in dente and to substitute for it the term dilated composite odontome which conforms more to the present-day theory of aberrant morphogenesis. A search of the dental literature has brought to light an earlier report and description of this condition, thus giving the primary authorship to Salter. Two additional cases have been presented for the record, one being bilateral, the other an example of the radicular type.