Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “eggshell”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1986

Gene regulation and evolution in the chorion locus of Bombyx mori. Structural and developmental characterization of four eggshell genes and their flanking DNA regions.

We report on the detailed structural and developmental characterization of four chorion genes and a truncated pseudogene located within a 9.5 X 10(3) base chromosomal segment. These genes belong to the A and B multigene families and, like previously characterized moth chorion genes, are arranged in tightly linked pairs, which are divergently transcribed (A/B.L11 and A/B.L12). On the basis of their high degree of sequence divergence, the A genes define two distinct subfamilies, while the more homologous B genes represent different copies of the same gene type. The A.L11 and B.L11 introns are much longer, in each case because of a single inserted DNA segment that is missing from A.L12 or B.L12. The 2.1 X 10(3) base insertion in A.L11 is the first retrovirus-like transposable element characterized in Bombyx mori. The very short 5' flanking sequences of A/B.L11 and A/B.L12 (277 and 276 base-pairs) are distinct as shown by hybridization but both recur in additional chorion gene pairs, forming two respective classes that are expressed during distinctly different developmental periods. The divergently transcribed genes of each pair, which border the same 5' flanking sequence, are expressed co-ordinately, during the same developmental period. Detailed comparisons of the 5' flanking regions, and of the corresponding region of the Drosophila s15-1 chorion gene, revealed numerous, very short sequence elements that are shared. One such element, T-C-A-C-G-T, is also associated with all five sequenced Drosophila chorion genes. Some elements are repeated in a dyad symmetrical pattern, i.e. are associated with each of the two genes in a pair, while others, including T-C-A-C-G-T, occur only once per 5' flanking region, and, if functionally important, would presumably act bi-directionally on both genes of the pair.

Animals↗
PubMed1988

The effects of DDE, PCB and chlordane on the binding of progesterone to its cytoplasmic receptor in the eggshell gland mucosa of birds and the endometrium of mammalian uterus.

1. The specific binding of progesterone to its cytoplasmic receptor in the mucosa of the shell gland from egg-laying ducks, domestic fowls and from the endometrium of the rabbit uterus was compared. The effect of DDE, PCBs and chlordane added in vitro was also studied. 2. The KD value for progesterone with regard to its receptor was about four times lower in the domestic fowl and the rabbit than in the duck. 3. The chlorinated hydrocarbons decreased the binding of progesterone to its receptor. Their potency was higher in the duck than in the domestic fowl. In rabbit uterine mucosa their effects were similar to those observed in the duck. 4. DDE is an inhibitor of calmodulin: other calmodulin inhibitors as calmidazolium and trifluoperazin also reduced the binding of progesterone in similar concentrations. It is suggested that DDE reduced the progesterone binding by inhibiting calmodulin.

Animals↗
PubMedDate not supplied

Some ESR observations on bone, tooth enamel and eggshell.

ESR measurements have been made on bone and teeth samples excavated from historical sites on three New Zealand offshore islands and on Taumako, one of the Duff Islands (southeastern Solomons). All of the samples have ages ranging from A.D. 1350 to A.D. 1800. The New Zealand offshore island samples show a very weak natural dating signal, characteristic of recent specimens, virtually obscured by a signal from an organic carbon radical. A detailed analysis of results from these samples suggests that the supralinearity hypothesis (Hennig and Grün, 1983) previously proposed is, in fact, an artifact of the analysis. In addition, all the samples from Taumako show an intense dating signal and evidence of electron trap saturation. The implications of these results are discussed.

Animals↗
PubMed1984

Development of preferred orientation in the eggshell of the domestic fowl.

Preferred orientation in the shell of the domestic fowl is shown by x-ray diffractometry to develop gradually throughout the shell, beginning immediately after the start of shell deposition and reaching a maximum at the exterior surface. Only 2 out of 20 shells examined exhibited a single preferred orientation: This was one in which the pole of the (001) plane lies parallel to the shell surface normal. The remaining shells had two preferred orientations present simultaneously, one in which the (001) pole is parallel and the other in which the (104) pole is parallel to the surface normal. Previous work has resulted in conclusions that are in conflict with these; they are discussed in relation to the present work.

Animals↗
PubMed1996

The eggshell of Drosophila melanogaster: IX. Synthesis and morphogenesis of the innermost chorionic layer.

Synthesis and morphogenesis of the innermost chorionic layer (ICL) was investigated by conventional EM methods, freeze-fracturing, tissue culture in Robb's medium, and EM autoradiography. Both autoradiography and fine structure results have shown that ICL-components are secreted prior to other chorion proteins. Their secretion starts on stage 12a but the first layer of ICL molecules is visible at stage 12b. Its thickness is gradually increased during the next stages, taking first, a bilaminar form along with the inner endochorion. Later, at the end of choriogenesis, ICL is detached from the endochorion and takes its final thickness and configuration, consisting of a 3-dimensional crystal, about 40 nm thick. The isolated ICL in conditions of air water interface is a monolayer crystal 10 nm thick. Studies on chorion mutants showed that the amount of protein secreted by the follicle cells is independent to the process of crystallisation. These data show how a proteinaceous extracellular substance is gradually assembled to form a 3-D crystal and how it can be organised to perform functions such as the physiological resistance of the insect eggs against water loss or water uptake, whenever they are laid on substrates with extreme environmental conditions. These functions are performed by ICL in conjunction with the underlying wax layer.

Animals↗