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Biomedical subjects

R Gilmore

Publications and source records attributed to R Gilmore.

At least 109 records · Page 6Linked to original sources
PubMed1986

Quantum cusp.

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Journal Article↗
PubMed1986

Effect of sleep position on sleep apnea and parafunctional activity.

Parafunctional activity (toothgrinding, toothclenching and bruxism) is a common problem which may lead to masticatory muscle and temporomandibular joint pain, and may result from sleep arousal or disturbances. Sleep apnea is another common sleep disorder which results in disrupted sleep architecture and frequent arousals. Because sleep apnea leads to sleep arousals, and because sleep arousals are thought to result in increased parafunctional activity, we undertook the present study to determine the relationship between sleep apnea and parafunctional activity. We were also interested in assessing the effects of sleep posture on sleep disordered breathing and parafunctional activity. We prospectively studied 24 patients who were referred to the clinical sleep apnea laboratory for study. They underwent standard nocturnal polysomnographic examination; in addition, masticatory activity was measured with a masseter electromyogram. Patients slept in the supine and lateral decubitus positions. Nocturnal clenching was slightly higher in patients with sleep apnea than those without (12.2 vs 7.6 clenches/hr, p = 0.18), and there was a correlation between the clench index (CI) and apnea plus hypopnea index (A + HI) by linear regression (r = 0.49, p less than 0.05). There were significant falls in both the A + HI (64.4 +/- 28.8 vs 36.5 +/- 36.7, p = 0.02) and CI (12.5 +/- 12.1 vs 7.0 +/- 8.6, p = 0.04) in the lateral decubitus vs supine sleeping positions. We conclude that there is an association between obstructive sleep apnea and parafunctional activity, that sleep position affects the incidence of both sleep disordered breathing and parafunctional activity, and that analysis of apneas and hypopneas in both supine and lateral decubitus sleeping positions may be helpful.

Adolescent↗
PubMed1985

Translocation of secretory proteins across the microsomal membrane occurs through an environment accessible to aqueous perturbants.

We have characterized the association of a nascent secretory protein with the microsomal membrane at two distinct stages in cell-free synthesis and translocation. Stage one corresponded to a nascent chain of approximately 70 residues generated via elongation arrest by the signal recognition particle (SRP). Binding to microsomal membranes occurred independently of chain elongation and required SRP receptor. Following binding, the 70-mer remained attached to the membrane after extraction of the ribosome. However, protein denaturants (4 M urea or alkaline pH) extracted the 70-mer from the membrane. Stage two of synthesis corresponded to nascent chains of approximately 158 residues generated by oligonucleotide-mediated hybrid arrest of translation. Again, these partially translocated nascent chains were extracted by 4 M urea. Therefore, the initial interaction of the signal sequence with the membrane as well as subsequent chain conductance occur in a microenvironment that is accessible to aqueous reagents. Thus, both processes probably require integral membrane proteins.

Animals↗
PubMed1983

Transient involvement of signal recognition particle and its receptor in the microsomal membrane prior to protein translocation.

We have shown that neither the signal recognition particle (SRP) nor the SRP receptor is directly involved in the maintenance of a ribosome-membrane junction for the translocation of secretory proteins. We found that the purified SRP receptor releases the signal-sequence-induced and SRP-mediated elongation arrest of synthesis by displacing SRP from the ribosome. This SRP displacement was not accompanied by binding of the SRP receptor to the ribosome. Using intact microsomal membranes as a source of the SRP receptor, we found that both SRP displacement and binding of the elongation-arrested ribosome to the membrane can occur at 0 degrees C, by a mechanism that is independent of chain elongation.

Animals↗
PubMed1982

The protein translocation machinery of the endoplasmic reticulum.

The rough endoplasmic reticulum (r.e.r.) has been postulated to possess a single translation-coupled translocation system (in multiple copies) that effects signal sequence-mediated translocation of all secretory and lysosomal proteins and integration of all integral membrane proteins whose port of entry is the rough endoplasmic reticulum (G. Blobel 1980 Proc. natn. Acad. Sci. U.S.A. 77, 1496-1500). Two proteins have been isolated that are components of the r.e.r. translocation system. Their properties and function in protein translocation across and integration into membranes are discussed.

Animals↗
PubMed1982

Preparation of a fluorescent derivative of cytochrome b5 and its interaction with phospholipids.

A fluorescence derivative of bovine cytochrome b5 was prepared by using 5-(dimethylamino)naphthalene-1-sulfonyl chloride (dansyl chloride) in deoxycholate. Reaction conditions were established to specifically label the hydrophobic membrane-binding domain of the protein at a ratio of 0.9 +/- 0.1 dansyl group per cytochrome b5. Fluorescence measurements on the dansyl-labeled protein reflected the state of aggregation of the protein and its binding to lipids. The cytochrome b5 derivative was a sensitive probe for the detection of phospholipid phase transitions in reconstituted phospholipid vesicles. The rotational relaxation time of the labeled protein was strongly influenced by the phospholipid composition and the cholesterol content of the lipid bilayer, but it was largely insensitive to the integrity of the hydrophilic domain of the protein. When the membrane-binding domain of cytochrome b5 was bound to phospholipid vesicles, a preferential association with either the gel or the liquid-crystalline phase was not observed. The results suggest that the two domains of cytochrome b5 undergo predominantly independent motion and that the motion of the dansyl-labeled membrane-binding domain directly reflects the properties of the bulk lipids in the bilayer.

Animals↗
PubMed1982

Protein translocation across the endoplasmic reticulum. I. Detection in the microsomal membrane of a receptor for the signal recognition particle.

Salt-extracted microsomal membranes (K-RM) contain an activity that is capable of releasing the signal recognition particle (SRP)-mediated elongation arrest of the synthesis of secretory polypeptides (Walter, P., and G. Blobel, 1981, J. Cell Biol., 91:557-561). This arrest-releasing activity was shown to be a function of an integral microsomal membrane protein, termed the SRP receptor (Gilmore, R., P. Walter, and G. Blobel, 1982, J. Cell Biol., 95:470-477). We attempted to solubilize the arrest-releasing activity of the SRP receptor by mild protease digestion of K-RM using either trypsin or elastase. We found, however, that neither a trypsin, nor an elastase "solubilized" supernatant fraction exhibited the arrest-releasing activity. Only when either the trypsin- or elastase-derived supernatant fraction was combined with the trypsinized membrane fraction, which by itself was also inactive, was the arrest-releasing activity restored. Release of the elongation arrest was followed by the translocation of the secretory protein across the microsomal membrane and the removal of the signal peptide. Thus, although we have been unable to proteolytically sever the arrest-releasing activity from K-RM and thereby to uncouple the release of the elongation arrest from the process of chain translocation, we have been able to proteolytically dissect and reconstitute the arrest-releasing activity. Furthermore, we found that the arrest-releasing activity of the SRP receptor can be inactivated by alkylation of K-RM with N-ethylmaleimide.

Endoplasmic Reticulum↗
PubMed1982

Protein translocation across the endoplasmic reticulum. II. Isolation and characterization of the signal recognition particle receptor.

The signal recognition particle (SRP)-mediated elongation arrest of the synthesis of nascent secretory proteins can be released by salt-extracted rough microsomal membranes (Walter, P., and G. Blobel, 1981, J. Cell Biol, 91:557-561). Both the arrest-releasing activity and the signal peptidase activity were solubilized from rough microsomal membranes using the nonionic detergent Nikkol in conjunction with 250 mM KOAc. Chromatography of this extract on SRP-Sepharose separated the arrest-releasing activity from the signal peptidase activity. Further purification of the arrest-releasing activity using sucrose gradient centrifugation allowed the identification of a 72,000-dalton polypeptide as the protein responsible for the activity. Based upon its affinity for SRP, we refer to the 72,000-dalton protein as the SRP receptor. A 60,000-dalton protein fragment (Meyer, D. I., and B. Dobberstein, 1980, J. Cell Biol., 87:503-508) that had been shown previously to reconstitute the translocation activity of protease-digested membranes, was shown here by peptide mapping and immunological criteria to be derived from the SRP receptor. Findings that are in part similar, and in part different from these reported here and in our preceding paper were made independently (Meyer, D. I., E. Krause, and B. Dobberstein, 1982, Nature (Lond.). 297:647-650) and the term "docking protein" was proposed for the SRP receptor. A lower membrane content of both SRP and the SRP receptor than that of membrane bound ribosomes suggests that the SRP-SRP receptor interaction may exist transiently during the formation of a ribosome-membrane junction and during translocation.

Centrifugation, Density Gradient↗