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At least 595 records · Page 33Linked to original sources
PubMed2003

Ligand structure-activity requirements and phospholipid dependence for the binding of phorbol esters to protein kinase D.

Although protein kinase D (PKD), like protein kinase C (PKC), possesses a C1 domain that binds phorbol esters and diacylglycerol, the structural differences from PKC within this and other domains of PKD imply differential regulation by lipids and ligands. We characterized the phorbol ester and phospholipid binding properties of a glutathione S-transferase-tagged full-length PKD and compared them with those of PKC-alpha and -delta. We found that PKD is a high-affinity phorbol ester receptor for a range of structurally and functionally divergent phorbol esters and analogs and showed both similarities and differences in structure-activity relations compared with the PKCs examined. In particular, PKD had lower affinity than PKC for certain diacylglycerol analogs, which might be caused by a lysine residue at the 22 position of the PKD-C1b domain in place of the tryptophan residue at this position conserved in the PKCs. The membrane-targeting domains in PKD are largely different from those in PKC; among these differences, PKD contains a pleckstrin homology (PH) domain that is absent in PKC. However, phosphatidylinositol-4,5-bisphosphate PIP2, a lipid ligand for some PH domains, reconstitutes phorbol 12,13-dibutyrate (PDBu) binding to PKD similarly as it does to PKC-alpha and -delta, implying that the PH domain in PKD may not preferentially interact with PIP2. Overall, the requirement of anionic phospholipids for the reconstitution of [3H]PDBu binding to PKD was intermediate between those of PKC-alpha and -delta. We conclude that PKD is a high-affinity phorbol ester receptor; its lipid requirements for ligand binding are approximately comparable with those of PKC but may be differentially regulated in cells through the binding of diacylglycerol to the C1 domain.

Animals↗
PubMed1997

Identification and molecular genetic analysis of multiple loci contributing to high-level tellurite resistance in Rhodobacter sphaeroides 2.4.1.

The ability of the facultative photoheterotroph Rhodobacter sphaeroides to tolerate and reduce high levels of tellurite in addition to at least 10 other rare earth metal oxides and oxyanions has considerable potential for detoxification and bioremediation of contaminated environments. We report the identification and characterization of two loci involved in high-level tellurite resistance. The first locus contains four genes, two of which, trgAB, confer increased tellurite resistance when introduced into the related bacterium Paracoccus denitrificans. The trgAB-derived products display no significant homology to known proteins, but both are likely to be membrane-associated proteins. Immediately downstream of trgB, the cysK (cysteine synthase) and orf323 genes were identified. Disruption of the cysK gene resulted in decreased tellurite resistance in R. sphaeroides, confirming earlier observations on the importance of cysteine metabolism for high-level tellurite resistance. The second locus identified is represented by the telA gene, which is separated from trgAB by 115 kb. The telA gene product is 65% similar to the product of the klaB (telA) gene from the tellurite-resistance-encoding kilA operon from plasmid RK2. The genes immediately linked to the R. sphaeroides telA gene have no similarity to other components of the kilA operon. R. sphaeroides telA could not functionally substitute for the plasmid RK2 telA gene, indicating substantial functional divergence between the two gene products. However, inactivation of R. sphaeroides telA resulted in a significant decrease in tellurite resistance compared to the wild-type strain. Both cysK and telA null mutations readily gave rise to suppressors, suggesting that the phenomenon of high-level tellurite resistance in R. sphaeroides is complex and other, as yet uncharacterized, loci may be involved.

Amino Acid Sequence↗
PubMed2007

Yersiniabactin is a virulence factor for Klebsiella pneumoniae during pulmonary infection.

Iron acquisition systems are essential for the in vivo growth of bacterial pathogens. Despite the epidemiological importance of Klebsiella pneumoniae, few experiments have examined the importance of siderophores in the pathogenesis of this species. A previously reported signature-tagged mutagenesis screen identified an attenuated strain that featured an insertional disruption in ybtQ, which encodes a transporter for the siderophore yersiniabactin. We used this finding as a starting point to evaluate the importance of siderophores in the physiology and pathogenesis of K. pneumoniae. Isogenic strains carrying in-frame deletions in genes required for the synthesis of either enterobactin or yersiniabactin were constructed, and the growth of these mutants was examined both in vitro and in vivo using an intranasal infection model. The results suggest divergent functions for each siderophore in different environments, with enterobactin being more important for growth in vitro under iron limitation than in vivo and the reverse being true for the yersiniabactin locus. These observations represent the first examination of isogenic mutants in iron acquisition systems for K. pneumoniae and may indicate that the acquisition of nonenterobactin siderophores is an important step in the evolution of virulent enterobacterial strains.

Animals↗
PubMed1994

Competition between rBPI23, a recombinant fragment of bactericidal/permeability-increasing protein, and lipopolysaccharide (LPS)-binding protein for binding to LPS and gram-negative bacteria.

Lipopolysaccharide (LPS)-binding protein (LBP) and bactericidal/permeability-increasing protein (BPI) are two structurally related lipid A-binding proteins with divergent functional activities. LBP mediates activation of macrophage and other proinflammatory cells. In contrast, BPI has potent bactericidal and LPS-neutralizing activities. A recombinant fragment of BPI (rBPI23) retains the potent biological activities of the holo protein and may represent a novel therapeutic agent for the treatment of gram-negative infections, sepsis, and endotoxemia. For therapeutic effectiveness in many clinical situations, rBPI23 will have to successfully compete with high serum levels of LBP for binding to endotoxin and gram-negative bacteria. The relative binding affinities of rBPI23 and human recombinant LBP (rLBP) for lipid A and gram-negative bacteria were evaluated. The binding of both proteins to lipid A was specific and saturable with apparent Kds of 2.6 nM for rBPI23 and 58 nM for rLBP. rBPI23 was approximately 75-fold more potent than rLBP in inhibiting the binding of 125I-rLBP to lipid A. The binding affinity of rBPI23 (Kd = 70 nM) for Escherichia coli J5 bacteria was also significantly higher than that of rLBP (Kd = 1,050 nM). In addition, rBPI23 at 0.2 micrograms/ml was able to inhibit LPS-induced tumor necrosis factor release from monocytes in the presence of 20 micrograms of rLBP per ml. These results demonstrate that rBPI23 binds more avidly to endotoxin than does rLBP and that, even in the presence of a 100-fold weight excess of rLBP, rBPI23 effectively blocks the proinflammatory response of peripheral blood mononuclear cells to endotoxin.

Acute-Phase Proteins↗
PubMed1991

Sequence analysis of the clpG gene, which codes for surface antigen CS31A subunit: evidence of an evolutionary relationship between CS31A, K88, and F41 subunit genes.

The clpG gene coding for the CS31A subunit was localized on a 0.9-kb SphI fragment from the recombinant plasmid pAG315. This was established by testing the ability of subclones to hybridize with a 17-meric oligonucleotide probe obtained from N-terminal analysis of the CS31A subunit. The nucleotide sequence of the region coding for CS31A was determined. From primer extension analysis, two initiation translation start sites were detected. Two possible promoterlike sequences were identified; the ribosome binding site and the translation terminator are proposed. Inverted repeat sequences leading to the formation of possible hairpin structures of the transcripts were found on the 5' untranslated region of clpG. The deduced amino acid composition was in close agreement with the chemical amino acid composition and sequence match with the first 25 N-terminal amino acids from the published N-terminal sequence of the purified CS31A subunit. The clpG gene codes for a mature protein of 257 amino acids with a molecular size of 26,777 Da. An obvious homology was observed when the amino acid sequence of CS31A was compared with those of K88 and F41. This homology includes five different conserved sequences of up to 19 identical amino acids, which is associated with conserved proline. An extensive change in the CS31A region homologous to that identified to contain the K88 receptor binding site might be responsible for the functional divergence between CS31A and K88.

Amino Acid Sequence↗
PubMed2006

The streptococcal Blr and Slr proteins define a family of surface proteins with leucine-rich repeats: camouflaging by other surface structures.

Regions with tandemly arranged leucine-rich repeats (LRRs) have been found in many prokaryotic and eukaryotic proteins, in which they provide a remarkably versatile framework for the formation of ligand-binding sites. Bacterial LRR proteins include the recently described Slr protein of Streptococcus pyogenes, which is related to internalin A of Listeria monocytogenes. Here, we show that strains of the human pathogen Streptococcus agalactiae express a protein, designated Blr, which together with Slr defines a family of internalin A-related streptococcal LRR proteins. Analysis with specific antibodies demonstrated that Blr is largely inaccessible on S. agalactiae grown in vitro, but surface exposure was increased approximately 100-fold on mutants lacking polysaccharide capsule. In S. pyogenes, surface exposure of Slr was not affected in a mutant lacking hyaluronic acid capsule but was increased >20-fold in mutants lacking M protein or protein F. Thus, both Blr and Slr are efficiently camouflaged by other surface structures on bacteria grown in vitro. When Blr and Slr exposed on the bacterial surface were compared, they exhibited only little immunological cross-reactivity, in spite of extensive residue identity, suggesting that their surface-exposed parts have been under evolutionary pressure to diverge functionally and/or antigenically. These data identify a family of immunologically diverse streptococcal LRR proteins that show unexpected complexity in their interactions with other bacterial surface components.

Amino Acid Sequence↗
PubMed2000

Heterogeneous spectrum of coreceptor usage among variants within a dualtropic human immunodeficiency virus type 1 primary-isolate quasispecies.

Human immunodeficiency virus type 1 (HIV-1) variants that use the coreceptor CCR5 for entry (R5; macrophage tropic) predominate in early infection, while variants that use CXCR4 emerge during disease progression. Some late-stage variants use CXCR4 alone (X4; T-cell tropic), while others use both CXCR4 and CCR5 (R5X4; dualtropic). It has been proposed that dualtropic R5X4 strains are intermediates in the evolution from R5 to X4, and we hypothesized that a dualtropic primary-isolate quasispecies might contain variants that represent the spectrum of coreceptor use in vivo. We generated a panel of 35 functional full-length env clones from the primary-isolate quasispecies of a dualtropic prototype strain, HIV-1 89.6(PI). Thirty of the functional env clones (86%) were R5X4, four (11%) were R5, and one (3%) was predominantly X4. V3 to V5 sequences did not reveal clustering by coreceptor usage, and no specific sequence motif or V3 charge pattern corresponded to coreceptor utilization. Complete sequencing of seven functionally divergent Env proteins revealed > or =98.7% homology and conservation of structurally important domains. Chimeras between the R5X4 89.6 prototype and an R5 variant indicated that multiple regions contributed to the use of CXCR4, while chimeras with the X4 variant implicated a single residue in V4 in CCR5 use. These results confirm, at the molecular level, both that dualtropic variants are a predominant component of late-stage syncytium-inducing isolates and that variants restricted to each coreceptor coexist with dualtropic species in vivo. Coreceptor-restricted minority variants may reflect residual R5 species from earlier in disease as well as emerging X4 variants.

Amino Acid Sequence↗
PubMed1998

Functional replacement of the mouse E2A gene with a human HEB cDNA.

The mammalian E2A, HEB, and E2-2 genes encode a unique class of basic helix-loop-helix (bHLH) transcription factors that are evolutionarily conserved and essential for embryonic and postnatal development. While the structural and functional similarities among the gene products are well demonstrated, it is not clear why deletion of E2A, but not HEB or E2-2, leads to a complete arrest in B-lymphocyte development. To understand the molecular basis of the functional specificity between E2A and HEB/E2-2 in mammalian development, we generated and tested a panel of E2A knockin mutations including subtle mutations in the E12 and E47 exons and substitution of both E12 and E47 exons with a human HEB cDNA. We find that the alternatively spliced E12 and E47 bHLH proteins of the E2A gene play similar and additive roles in supporting B lymphopoiesis. Further, we find that HEB driven by the endogenous E2A promoter can functionally replace E2A in supporting B-cell commitment and differentiation toward completion. Finally, the postnatal lethality associated with E2A disruption is fully rescued by the addition of HEB. This study suggests that the functional divergence among E12, E47, and HEB in different cell types is partially defined by the context of gene expression.

Alleles↗
PubMed2004

Characterization of mouse Rsk4 as an inhibitor of fibroblast growth factor-RAS-extracellular signal-regulated kinase signaling.

Receptor tyrosine kinase (RTK) signals regulate the specification of a varied array of tissue types by utilizing distinct modules of proteins to elicit diverse effects. The RSK proteins are part of the RTK signal transduction pathway and are thought to relay these signals by acting downstream of extracellular signal-regulated kinase (ERK). In this study we report the identification of ribosomal S6 kinase 4 (Rsk4) as an inhibitor of RTK signals. Among the RSK proteins, RTK inhibition is specific to RSK4 and, in accordance, is dependent upon a region of the RSK4 protein that is divergent from other RSK family members. We demonstrate that Rsk4 inhibits the transcriptional activation of specific targets of RTK signaling as well as the activation of ERK. Developmentally, Rsk4 is expressed in extraembryonic tissue, where RTK signals are known to have critical roles. Further examination of Rsk4 expression in the extraembryonic tissues demonstrates that its expression is inversely correlated with the presence of activated ERK 1/2. These studies demonstrate a new and divergent function for RSK4 and support a role for RSK proteins in the specification of RTK signals during early mouse development.

Animals↗
PubMed2005

Functional comparison of the Tup11 and Tup12 transcriptional corepressors in fission yeast.

Gene duplication is considered an important evolutionary mechanism. Unlike many characterized species, the fission yeast Schizosaccharomyces pombe contains two paralogous genes, tup11+ and tup12+, that encode transcriptional corepressors similar to the well-characterized budding yeast Tup1 protein. Previous reports have suggested that Tup11 and Tup12 proteins play redundant roles. Consistently, we show that the two Tup proteins can interact together when expressed at normal levels and that each can independently interact with the Ssn6 protein, as seen for Tup1 in budding yeast. However, tup11- and tup12- mutants have different phenotypes on media containing KCl and CaCl2. Consistent with the functional difference between tup11- and tup12- mutants, we identified a number of genes in genome-wide gene expression experiments that are differentially affected by mutations in the tup11+ and tup12+ genes. Many of these genes are differentially derepressed in tup11- mutants and are over-represented in genes that have previously been shown to respond to a range of different stress conditions. Genes specifically derepressed in tup12- mutants require the Ssn6 protein for their repression. As for Tup12, Ssn6 is also required for efficient adaptation to KCl- and CaCl2-mediated stress. We conclude that Tup11 and Tup12 are at least partly functionally diverged and suggest that the Tup12 and Ssn6 proteins have adopted a specific role in regulation of the stress response.

Amino Acid Sequence↗
PubMed1988

Two different mRNAs are transcribed from a single genomic locus encoding the chicken erythrocyte anion transport proteins (band 3).

The chicken erythrocyte anion transport protein (band 3 of the erythrocyte cytoskeleton) is a central component taking part in two widely divergent functions of erythroid cells; it is a primary determinant of cytoskeletal architecture and responsible for electroneutral Cl-/HCO3- exchange across the plasma membrane. To analyze interesting aspects of the developmental regulation of this gene, we have cloned the cDNA and genomic counterparts of the erythroid-specific anion transport protein. We show that a single genetic locus for band 3 encodes two different erythroid cell-specific mRNAs, with different translational initiation sites, which predict polypeptides of sizes very close to those observed in vivo. In vitro translation and immune precipitation of synthetic mRNA derived from one putative fully encoding cDNA clone demonstrate that this clone gives rise to a protein which is identical in size and antigenicity to bona fide chicken erythroid band 3.

Amino Acid Sequence↗
PubMed1993

Transcription termination and polyadenylation in retroviruses.

The provirus structure of retroviruses is bracketed by long terminal repeats (LTRs). The two LTRs (5' and 3') are identical in nucleotide sequence and organization. They contain signals for transcription initiation as well as termination and cleavage polyadenylation. As in eukaryotic pre-mRNAs, the two common signals, the polyadenylation signal, AAUAAA, or a variant AGUAAA, and the G+U-rich sequence are present in all retroviruses. However, the AAUAAA sequence is present in the U3 region in some retroviruses and in the R region in other retroviruses. As in animal cell RNAs, both AAUAAA and G+U-rich sequences apparently contribute to the 3'-end processing of retroviral RNAs. In addition, at least in a few cases examined, the sequences in the U3 region determine the efficiency of 3'-end processing. In retroviruses in which the AAUAAA is localized in the R region, the poly(A) signal in the 3' LTR but not the 5' LTR must be selectively used for the production of genomic RNA. It appears that the short distance between the 5' cap site and polyadenylation signal in the 5' LTR precludes premature termination and polyadenylation. Since 5' and 3' LTRs are identical in sequence and structural organization yet function differently, it is speculated that flanking cellular DNA sequences, chromatin structure, and binding of transcription factors may be involved in the functional divergence of 5' and 3' LTRs of retroviruses.

Animals↗
PubMed2000

Repetitive speech phenomena in Parkinson's disease.

OBJECTIVES: Repetitive speech phenomena are morphologically heterogeneous iterations of speech which have been described in several neurological disorders such as vascular dementia, progressive supranuclear palsy, Wilson's disease, and Parkinson's disease, and which are presently only poorly understood. The present, prospective study investigated repetitive speech phenomena in Parkinson's disease to describe their morphology, assess their prevalence, and to establish their relation with neuropsychological and clinical background data. METHODS: Twenty four patients with advanced Parkinson's disease and 29 subjects with mid-stage, stable idiopathic disease were screened for appearance, forms, and frequency of repetitive speech phenomena, and underwent a neuropsychological screening procedure comprising tests of general mental functioning, divergent thinking and memory. Patients with advanced Parkinson's disease had a significantly higher disease impairment, longer disease duration, and an unstable motor response to levodopa with frequent on-off fluctuations. Both groups were well matched as to their demographical, clinical, and cognitive background. Perceptual speech evaluation was used to count and differentiate forms of repetitive speech phenomena in different speech tasks. To compare the effect of the motor state, the appearance of repetitive speech phenomena was also assessed in a subgroup of patients with advanced Parkinson's disease during the on versus the off state. RESULTS: Speech repetitions emerged mainly in two variants, one hyperfluent, formally resembling palilalia, and one dysfluent, stuttering-like. Both forms were present in each patient producing repetitive speech phenomena. The repetitive speech phenomena appeared in 15 patients (28.3 %), 13 of whom belonged to the advanced disease group, indicating a significant preponderance of repetitive speech phenomena in patients with a long term, fluctuating disease course. Repetitive speech phenomena appeared with almost equal frequency during the on and the off state of patients with advanced Parkinson's disease. Their distribution among different variants of speech was disproportional, with effort demanding speech tasks producing a significantly higher number of repetitive speech phenomena over semiautomatic forms of speech. CONCLUSIONS: In idiopathic Parkinson's disease repetitive speech phenomena seem to emerge predominantly in a subgroup of patients with advanced disease impairment; manifest dementia is not a necessary prerequisite. They seem to represent a deficit of motor speech control; however, linguistic factors may also contribute to their generation. It is suggested that repetitions of speech in Parkinson's disease represent a distinctive speech disorder, which is caused by changes related to the progression of Parkinson's disease.

Adult↗
PubMed2006

Varying signals of the effects of natural selection during teleost growth hormone gene evolution.

The growth hormone (GH) gene of teleost fish exhibits a higher degree of variability compared with other vertebrate groups. However, the different selective constraints at the sequence level are not well understood. In this study, maximum-likelihood (ML) models of codon substitutions were used to investigate Darwinian adaptive evolution of the GH gene in teleost fishes. Complete GH gene sequences of 54 fish species were classified into 4 orders, and the variable nature of GH was examined by determining the dN and dS rate variation and the rates of molecular evolution for each teleost order. The results indicate that although the overall evolution rate for teleost GH is high ((1.15 +/- 0.01) x 10(-9) substitutions/(aa site x y)) compared with the "slow phases" in mammals ((0.21 to 0.28 +/- 0.05) x 10(-9)), the vital structure of this gene has been retained. While the majority of the amino acid changes appear to be due to relaxation of purifying selection, some positively selected sites were detected in regions with no specifically identified role in protein function. The positively selected regions observed in salmoniformes lineage suggests a possible role for positive selection driving functional divergence in paralogous forms of the GH gene after whole-genome duplication in this lineage.

Amino Acid Sequence↗
PubMed2005

Eukaryotic translesion synthesis DNA polymerases: specificity of structure and function.

This review focuses on eukaryotic translesion synthesis (TLS) DNA polymerases, and the emphasis is on Saccharomyces cerevisiae and human Y-family polymerases (Pols) eta, iota, kappa, and Rev1, as well as on Polzeta, which is a member of the B-family polymerases. The fidelity, mismatch extension ability, and lesion bypass efficiencies of these different polymerases are examined and evaluated in the context of their structures. One major conclusion is that, despite the overall similarity of basic structural features among the Y-family polymerases, there is a high degree of specificity in their lesion bypass properties. Some are able to bypass a particular DNA lesion, whereas others are efficient at only the insertion step or the extension step of lesion bypass. This functional divergence is related to the differences in their structures. Polzeta is a highly specialized polymerase specifically adapted for extending primer termini opposite from a diverse array of DNA lesions, and depending upon the DNA lesion, it contributes to lesion bypass in a mutagenic or in an error-free manner. Proliferating cell nuclear antigen (PCNA) provides the central scaffold to which TLS polymerases bind for access to the replication ensemble stalled at a lesion site, and Rad6-Rad18-dependent protein ubiquitination is important for polymerase exchange.

Amino Acid Motifs↗
PubMed2005

Spatiotemporal analysis of exocytosis in mouse parotid acinar cells.

Exocrine cells of the digestive system are specialized to secrete protein and fluid in response to neuronal and/or hormonal input. Although morphologically similar, parotid and pancreatic acinar cells exhibit important functional divergence in Ca(2+) signaling properties. To address whether there are fundamental differences in exocytotic release of digestive enzyme from exocrine cells of salivary gland versus pancreas, we applied electrophysiological and optical methods to investigate spatial and temporal characteristics of zymogen-containing secretory granule fusion at the single-acinar cell level by direct or agonist-induced Ca(2+) and cAMP elevation. Temporally resolved membrane capacitance measurements revealed that two apparent phases of exocytosis were induced by Ca(2+) elevation: a rapidly activated initial phase that could not be resolved as individual fusion events and a second phase that was activated after a delay, increased in a staircaselike fashion, was augmented by cAMP elevation, and likely reflected both sequential compound and multivesicular fusion of zymogen-containing granules. Optical measurements of exocytosis with time-differential imaging analysis revealed that zymogen granule fusion was induced after a minimum delay of approximately 200 ms, occurred initially at apical and basolateral borders of acinar cells, and under strong stimulation proceeded from apical pole to deeper regions of the cell interior. Zymogen granule fusions appeared to coordinate subsequent fusions and produced persistent structures that generally lasted several minutes. In addition, parotid gland slices were used to assess secretory dynamics in a more physiological context. Parotid acinar cells were shown to exhibit both similar and divergent properties compared with the better-studied pancreatic acinar cell regarding spatial organization and kinetics of exocytotic fusion of zymogen granules.

Animals↗
PubMed1998

Airway smooth muscle cell proliferation: characterization of subpopulations by sensitivity to heparin inhibition.

Growth and maturation state of airway smooth muscle cells (SMCs) are determinants of asthma pathophysiology. Heparin reduces airway SMC proliferation and arterial SMC replication and phenotypic modulation. Distinct arterial SMC subtypes, differing in heparin sensitivity, have been characterized. We assessed the cellular mechanisms underlying the growth and phenotype of heparin-treated canine tracheal myocytes in primary culture. Heparin reduced replication by 40%. Immunoblot assay of myosin, actin, and myosin light chain kinase revealed heparin had no effect on rapid spontaneous phenotypic modulation after the cells were plated. Heparin increased cellular protein and vimentin contents in confluent cultures, suggesting that it may induce hypertrophic growth. Cell cycle analysis revealed that heparin decreased serum-stimulated replicating myocyte number by 40%. Also, G2-M transit was 20% slower for the set of SMCs that proceeded past G1 in the presence of heparin. These data indicate that heparin does not inhibit airway SMC replication by blocking modulation from the contractile state. Moreover, airway smooth muscle is composed of distinct SMC populations differing in mitogen and antiproliferative mediator responsiveness. Identification of functionally divergent subgroups suggests that distinct sets of SMCs may contribute differentially to airway physiology and pathophysiology.

Animals↗
PubMed1979

Interactions among an ensemble of chordotonal organ receptors and motor neurons of the crayfish claw.

1. Action potentials of crayfish propodite-dactyl (PD) chordotonal organ receptors and two claw motor neurons, the opener inhibitor (OI) and slow closer excitor CE) were simultaneously monitored during imposed step and ramp movements of the dactyl or while the dactyl was held at various positions. 2. The activities of the cells during imposed displacements were analyzed using peristimulus time histograms and response and contour planes. The proprioceptive fields (PFs) of individual receptors resemble components of the more complex motor neuron PFs. Some receptors are briefly active after each successive opening step, while others do not respond to steps near the closed position but respond as the joint angle increases, becoming active when the claw is held open. Another type of receptor responds to closing movements. 3. Interactions among the various types of receptors and the two motor neurons were detected and analyzed by various statistical methods and intracellular recording techniques. The results indicate that receptors activated during opening movements and when the dactyl is held at open positions excite OI and CE via divergent functional connections. The efficacies of the connections made by a receptor may differ. Receptors activated by closing movements produce hyperpolarizing synaptic potentials in both efferents, possible directly or via interneurons. 4. It is concluded that several types of chordotonal organ receptors form an ensemble of parallel input channels, which modulates the activities of OI and CE and contributes to the generation of the spatial-temporal nonuniformities of their proprioceptive reflex responses.

Animals↗