Biomedical subjects

Alexander Miller

Publications and source records attributed to Alexander Miller.

5 recordsLinked to original sources

PubMed2005

Brief psychiatric rating scale expanded version: How do new items affect factor structure?

Our goal was to suggest a factor structure for the Brief Psychiatric Rating Scale Expanded Version (BPRS-E) based upon a large and diverse sample and to determine which of the new items improved the factors derived from the 18-item version of the scale that have been used in clinical research for decades. We investigated the consistency of our proposed model over time and across demographic groups. As part of the Texas Medication Algorithm Project, the BPRS-E was administered to a total of 1440 psychiatric outpatients in three different diagnostic groups on multiple occasions. The sample was randomly split so that exploratory factor analysis could be done with the first half, and the model could be confirmed on the second half. A four-factor structure including factors assessing depression/anxiety, psychosis, negative symptoms, and activation was found. For each factor, we specify items in the expanded version that added to the breadth of the commonly used clinical factors while improving or maintaining goodness of fit and reliability. The final model proposed was consistent over time and across diagnosis, phase of illness, age, gender, ethnicity, and level of education. The BPRS-E has a stable four-factor structure, making it useful as a clinical outcome measure.

Adult↗

PubMed2005

Tattoo pigment in sentinel lymph nodes: a mimicker of metastatic malignant melanoma.

Tattoo pigment in the sentinel lymph nodes of melanoma patients represents a clinical challenge. If a tattoo is present in the area of the primary melanoma, the draining lymph nodes are likely to contain tattoo pigment, as well as being the site for metastatic deposits of melanoma. We describe a case report involving an elderly Caucasian male diagnosed with a Clark level-4 nodular malignant melanoma, wherein intraoperatively we encounter a darkly pigmented lymph node highly suspicious for metastatic disease. The patient had a tattoo in the vicinity of the malignant melanoma The specimen is sent for histological examination and is found to contain pigmented macrophages, but metastatic malignant melanoma is not identified. Histological confirmation of an enlarged pigmented node is essential before radical surgery is performed.

Aged↗

PubMed2004

Demonstration of a specific Escherichia coli SecY-signal peptide interaction.

Protein translocation in Escherichia coli is initiated by the interaction of a preprotein with the membrane translocase composed of a motor protein, SecA ATPase, and a membrane-embedded channel, the SecYEG complex. The extent to which the signal peptide region of the preprotein plays a role in SecYEG interactions is unclear, in part because studies in this area typically employ the entire preprotein. Using a synthetic signal peptide harboring a photoaffinity label in its hydrophobic core, we examined this interaction with SecYEG in a detergent micellar environment. The signal peptide was found to specifically bind SecY in a saturable manner and at levels comparable to those that stimulate SecA ATPase activity. Chemical and proteolytic cleavage of cross-linked SecY and analysis of the signal peptide adducts indicate that the binding was primarily to regions of the protein containing transmembrane domains seven and two. The signal peptide-SecY interaction was affected by the presence of SecA and nucleotides in a manner consistent with the transfer of signal peptide to SecY upon nucleotide hydrolysis at SecA.

Adenosine Triphosphatases↗

PubMed2002

SecB modulates the nucleotide-bound state of SecA and stimulates ATPase activity.

In Escherichia coli, the formation of SecA-SecB complexes has a direct effect on SecA ATPase activity. The mechanism of this interaction was evaluated and defined using controlled trypsinolysis, equilibrium dialysis at low temperature, and kinetic analyses of the SecA ATPase reaction. The proteolysis data indicate that SecB and the nonhydrolyzable ATP analogue AMP-P-C-P induce similar conformational changes in SecA which result in a more open or extended structure that is suggestive of the ATP-bound form. The effect is synergistic and concentration-dependent, and requires the occupation of both the high- and low-affinity nucleotide binding sites for maximum effect. The equilibrium dialysis experiments and kinetic data support the observation that the SecB-enhanced SecA ATPase activity is the result of an increased rate of ATP hydrolysis rather than an increase in the affinity of ATP for SecA and that the high-affinity nucleotide binding site is conformationally regulated by SecB. It appears that SecB may function as an intermolecular regulator of ATP hydrolysis by promoting the ATP-bound state of SecA. The inhibition of SecA ATPase activity by sodium azide in the presence of IMVs and a functional signal peptide further indicates that SecB promotes the ATP-bound form of SecA.

Adenosine Triphosphatases↗

PubMed2002

Cannabinoid receptor-G protein interactions: G(alphai1)-bound structures of IC3 and a mutant with altered G protein specificity.

The structure of the C-terminal region of the third cytoplasmic loop (IC3) of the cannabinoid receptor one (CB1) bound to G(alphai1) has been determined using transferred nuclear Overhauser effects (NOEs). The wild-type IC3 sequence is helical when associated with G(alphai1). In contrast, a peptide containing the amino-acid inversion, Ala(341)-Leu(342) adopts a single turn. These findings correlate with the attenuated G(i) association of CB1 with the Ala(341)-Leu(342) mutation previously observed in vivo and the diminished stimulation of G(alphai1) GTPase activity by the corresponding peptide demonstrated in vitro here. These results, the first to report the structure of a GPCR domain while associated with G protein, imply the C-terminus of CB1 IC3, a region with high-sequence conservation among G-protein coupled receptors, must be helical for efficient coupling and activation of the G(i) protein.

GTP-Binding Proteins↗