ABSTRACT
The mammalian high mobility group proteins HMGI/Y and HMG1/2 are thought to play an architectural role in assembly of nucleoprotein structures. Counterparts to these proteins have recently been found in the cells of the Dipteran insect Chironomus. In this report we investigate the distribution of three abundant HMG proteins in interphase giant chromosomes of the midge, Chironomus. By means of the indirect immunofluorescence technique the cHMG1b and cHMGI proteins were localized in chromosomal puffs, suggesting their involvement in the organization of transcriptionally active chromatin. In contrast, the highly abundant protein cHMG1a was rather uniformly distributed in the chromosomes. The cHMGI protein, but not cHMG1a or cHMG1b, was detected in nucleoli, which may indicate a role in the transcription of ribosomal genes. The regions of the interphase chromosomes containing AT-rich DNA did not contain higher levels of the cHMGI and cHMG1b proteins. A correlation between the specific location of these proteins in chromatin and their synthesis and turnover rates was observed.
Subject(s)
Chironomidae/genetics , Chromosomes/chemistry , Ecdysone/pharmacology , High Mobility Group Proteins/metabolism , Hydroxymethylglutaryl CoA Reductases/metabolism , Amino Acid Sequence , Animals , Antibody Specificity , Cell Differentiation/drug effects , Cell Differentiation/genetics , Cell Nucleolus/genetics , Chromatin/chemistry , Chromatin/genetics , Chromatin/metabolism , Chromosomes/genetics , Female , Fluorescent Antibody Technique, Indirect , Gene Expression Regulation , HMGA1a Protein , Half-Life , High Mobility Group Proteins/genetics , High Mobility Group Proteins/immunology , Histones/drug effects , Histones/genetics , Histones/metabolism , Hydroxymethylglutaryl CoA Reductases/genetics , Hydroxymethylglutaryl CoA Reductases/immunology , Hydroxymethylglutaryl-CoA-Reductases, NADP-dependent , Interphase , Molecular Sequence Data , RNA, Messenger/biosynthesis , RNA, Ribosomal/genetics , Rabbits , Transcription, GeneticABSTRACT
The presence of secondary sensory cells in the Octopus gravity receptor system has been demonstrated. In serial thin sections of the receptor cells (hair cells) no axons were found leaving the cells. Instead, synapses were observed with synaptic vesicles lying inside the receptor cells. Both data clearly indicate that the receptor hair cells represent secondary sensory cells. In addition, efferent contacts to the receptor cells could be confirmed.
Subject(s)
Octopodiformes/anatomy & histology , Sense Organs/ultrastructure , Animals , Axons , Gravitation , Sensory Receptor Cells/ultrastructure , Synapses , Synaptic VesiclesABSTRACT
A postantennal organ occurs in three different families in Collembola. In spite of considerable diversity in their outer structures, the organs manifest many similarities in their internal structure (pore system with pores of about 50-100 A diameter, a single sensory cell with two branching ciliary outer segments, reduction of the outer receptor lymph cavity and occurrence of an electron dense secretion around the dendrites). A tendency towards an enlargement of the outer surface of the organ and towards an incorporation of the sensory cell into the protocerebrum appears to be correlated with adaptations to a strict euedaphic life. An appropriate stimulus for the organ cannot be derived from the structure unequivocally, however, it could be hygro-, chemo- or thermosensitive. Perforated surface and number of pores in the postantennal organ correspond to the values found in insect sensory hairs.
