Embryonic development and molting of the antennal coeloconic no pore- and double-walled wall pore sensilla in Locusta migratoria (Insecta,Orthopteroidea)

Summary The embryonic development of antennal coeloconic sensilla was studied at four stages between 132 and 252 h after oviposition in Locusta migratoria. Initially the anlagen of the sensilla consist of 2–4 sensory cells and 3 enveloping cells. Two additional cells contribute later to the formation of socket and pit. The dendritic outer segments of the sensory cells elongate before the trichogen process grows out (ecdysis type I) with exception of one sensory cell in anlagen of poreless (np) sensilla. Other differences between np and double-walled wall pore (dw wp) sensilla are not visible until at least about 220 h after oviposition. Molting, which was studied in four stages, follows ecdysis type I in both sensillum types. The fourth enveloping cell maintains its tight connection to the socket of the sensillum even after apolysis. Its apical portion is torn off and shed together with the old cuticle. The electron-dense material between the dendritic sheath and the cuticular wall of the peg in np sensilla, which is regarded important for stimulus transmission, is not deposited during retraction of the trichogen cell. The concentric walls and spoke channels characteristic of dw wp sensilla result from deposition of cuticular material around wedge-shaped projections of the trichogen cell. The typical trilaminar 15 nm cuticulin layer is produced only on the ridges of these sensilla. The first cuticular lining of the spoke channels is only 7 nm thick and of a different structure. A flocculent material surrounds the outgrowing trichogen process. It is continuous with the filling of the spoke channels and can thus be considered as component of the stimulus-transmitting material in the functioning intermolt dw wp sensilla.     

Identification of two types of keratin polypeptides within the acidic cytokeratin subfamily I

Cytoskeletal filaments of the α-keratin type (cytokeratins) are a characteristic of epithelial cells. In diverse mammals (man, cow and rodents) these cytokeratins consist of a family of approximately 20 polypeptides, which may be divided into the more acidic (I) and the more basic (II) subfamilies. These two subfamilies show only limited amino acid sequence homology. In contrast, nucleic acid hybridization experiments and peptide maps have been interpreted to show that polypeptides of the same subfamily share extended sequence homology.We compare two polypeptides of the acidic cytokeratin subfamily, VIb (M_r 54,000) and VII (M_r 50,000), which are co-expressed in large amounts in bovine epidermal keratinocytes. These two epidermal keratins can be distinguished by specific antibodies and show different patterns of expression among several bovine tissues and cultured cells. In addition, they differ in the stability of their complexes with basic keratin polypeptides and in their tryptic peptide maps. The amino acid sequences deduced from the nucleotide sequences of complementary DNA clones containing the 3′ ends of the messenger RNAs for these keratins are compared with each other and with available amino acid sequences of human, murine and amphibian epidermal keratins. Bovine keratins VIb and VII share considerable sequence homology in the α-helical portion (68% residues identical) but lack significant homology in the extrahelical portion. Bovine keratin VIb shows, in its α-helical region, a pronounced sequence homology (88% identity) to the murine epidermal keratin of M_r 59,000. In addition, the non-helical carboxy-terminal regions of both proteins are glycinerich and contain a canonic sequence GGG^S_GYGG, which may be repeated several times. Moreover, their mRNAs present a highly conserved stretch of 236 nucleotides containing, in the murine sequence, the end of the coding and all of the non-coding region (81% identical nucleotides). Bovine keratin VII is considerably different from the murine M_r 59,000 keratin but is almost identical to the human cytokeratin number 14 of M_r 50,000, both in the α-helical and in the non-α-helical regions of the proteins, and the mRNAs of the human and the bovine keratins also display a high homology in their 3′ non-coding ends.The results show that in the same species keratins of the same subfamily can differ considerably, whereas equivalent keratin polypeptides of different species are readily identified by characteristic sequence homologies in the α-helical and the non-helical regions as well as in the 3′ non-coding portions of their mRNAs. Among the members of the acidic subfamily I of cytokeratin polypeptides that are co-expressed in bovine epidermis, at least two types can be distinguished by their carboxy-terminal sequences. One type is characterized by its abundance of glycine residues, a consensus GGG^S_GYGG heptapeptide sequence, which may be repeated several times, and an extended stretch of high RNA sequence homology in the 3′ non-coding part. The other type shows a predominance of serine and valine residues, a subterminal GGG^S_GYGG sequence (which has been maintained in Xenopus, cow and man) and also a high level of homology in the 3′ non-coding part of the mRNA. The data indicate that individual keratin type specificity overrides species diversity, both at the protein and the mRNA level. We discuss the evolutionary conservation and the tissue distribution of these two types of acidic keratin polypeptides as well as their possible biological functions.     

CO2 sensitive receptors on labial palps ofRhodogastria moths (Lepidoptera: Arctiidae): physiology,fine structure and central projection

Summary The tips of the labial palps ofRhodogastria possess a pit housing uniform sensilla (Fig. 1), histologically characterized by wall-pores and receptor cells with lamellated outer dendrites (Fig. 2). The receptor cell axons project to glomeruli in the deutocerebrum (cf. Fig. 3) which are not innervated by antennal receptors. From their histology as well as from their central projection these sense organs are identical with palpal pit organs of other Lepidoptera (Lee et al. 1985; Kent et al. 1986; Lee and Altner 1986).Physiologically, the palp-pit receptors respond uniformly; they are most excitable by stimulation with carbon dioxide (Fig. 6) while they exhibit relatively moderate responses to various odorants (Fig. 4). The responses to CO₂ (Fig. 7) show a steep dose-response characteristic. In ambient atmosphere (i.e., ca. 0.03% CO₂) the cells are in an excited condition already; the seeming spontaneous activity exhibited in air is decreased if the preparation is kept under N₂ or O₂ or CO₂-free air (Figs. 7, 10). There is hardly any adaptation of the responses to continuous or repeated stimulation (Fig. 8). Perhaps CO₂ sensitivity is correlated with sensilla characterized by both wall-pores and lamellated dendrites. Pilot tests indicate that CO₂ perception might be widespread in the Lepidoptera (cf. Fig. 12), but the biological significance remains obscure.     

Determination of the region of rDNA involved in polytenization in salivary glands of Drosophila hydei

During the formation of polytene chromosomes in salivary glands of Drosophila hydei, the genes for ribosomal RNA (rDNA) are underreplicated relative to the rest of the genome. We have measured the number of rRNA genes with and without intervening sequences (ivs+ and ivs- genes) in polytene chromosomes of different genotypes. In the group of genotypes having a large number of ivs- rRNA genes polytenization only occurs within the cluster of ivs- genes. In each of these genotypes rDNA polytenization reaches a constant level of 150 ivs- genes per two chromatid sets (2C); X/X constitutions having two nucleolus organizers (NOs) in the diploid set polytenize the same amount of rDNA as X/O constitutions. In the group of genotypes with small ivs- gene numbers, the rDNA region involved in polytenization is longer and has an average length of 1,700 kb per NO, which is constant in these genotypes. Polytenization of rDNA is extended into the cluster of ivs+ genes, in spite of the fact that these genes appear to be nonfunctional. The smaller the number of ivs- genes, the greater the number of ivs+ genes that are polytenized in the NO. In these genotypes, X/X females replicate twice as much rDNA as X/O males, suggesting that both NOs of the diploid set are polytenized. A comparison of the pattern of spacer length heterogeneity in hybrids between different stocks also demonstrates that both NOs are replicated during polytenization.     

Über das gleichzeitige Vorkommen von zweierlei Eiweißkörpern in den Zellkernen vonPseudolysimachion spicatum und einigen anderen Scrophulariaceen

Zusammenfassung Die Zellkerne vonPseudolysimachion spicatum, Veronica cymbalaria undV. gentianoides enthalten zweierlei Eiweißkörper von je nach dem Entwicklungszustand unterschiedlicher Konsistenz. Bis zum Höhepunkt ihrer Entwicklung liegen sie als anscheinend amorphe flüssige oder gelartige Gebilde vor. Später tritt — mit gewebespezifischen Unterschieden — Verfestigung und Kristallisation ein, und zwar bei beiden nicht gleichzeitig und z. T. auch nur beim großen. Beiderlei Körper unterscheiden sich deutlich in physikalischer und chemischer Hinsicht, außerdem in ihrer Entwicklungsgeschichte und Strukturveränderung. Sie fehlen in den Schließzellen, im Antherentapetum, in den Pollenmutterzellen, Pollenkörnern, im Embryosack, im Endosperm und im Embryo.Die Zellkerne in der Blattepidermis vonPenstemon barbatus enthalten ebenfalls zweierlei Eiweißkörper. Davon liegt einer als kugeliges Gebilde, der andere als Kristallstapel vor.

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Summary In the nuclei ofPseudolysimachion spicatum, Veronica cymbalaria, V. gentianoides there occur two different kinds of protein bodies. They clearly differ from one another in physical and chemical regard as well as in their ontogeny. At first they are amorphous, liquid or geluous. As a rule a consolidation or crystallization with differences according to the tissue takes place after the climax of the development, and that not at the same time within both bodies. In the stomata cells, pollen mother cells, in the embryo sac, in the endosperm, in the endothelium and in the embryo both bodies do not occur.The nuclei in the epidermis of the leaves ofPenstemon barbatus also contain two different kinds of protein bodies, one of them appearing as a round body, and the other one as a pile of crystal plates.