Is the Nef protein of HIV-1 required for pathogenesis?
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AIDS Vaccines↗
Biomedical subjects
M D Miller
Publications and source records attributed to M D Miller.
The "N + 7 rule" for tibial tunnel placement in endoscopic anterior cruciate ligament reconstruction.
Tibial tunnel placement during endoscopic anterior cruciate ligament (ACL) reconstruction has received increased emphasis in the recent literature. Appropriate tunnel length is a critical technical consideration. A tunnel that is too short results in graft extrusion, necessitating supplemental fixation techniques. A tunnel that is too long may make distal fixation and femoral tunnel placement difficult. A simple rule is proposed that allows for correct tunnel length and allows placement of the bone plug consistently within the tibial tunnel, allowing interference screw fixation.
Anterior Cruciate Ligament↗
Differential effects of GTP gamma S on acid and pepsinogen secretion by permeable gastric glands.
Gastric glands isolated from rabbit stomach were permeabilized with Staphylococcus aureus alpha-toxin. Acid secretion by parietal cells, as measured by the accumulation of weak base, was inhibited by incubation with alpha-toxin but could be restored by addition of exogenous ATP (1 mM). The permeable glands were found to retain acid secretory responses to receptor-linked secretagogues, histamine and carbachol, as well as to intracellular mediators, forskolin and 8-bromoadenosine 3',5'-cyclic monophosphate, indicating the presence of intact, functional intracellular coupling mechanisms. Both basal and stimulated acid secretion by the permeable glands were blocked by the Mg2+ chelator, trans-1,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid (CDTA; 5 mM), whereas CDTA had no effect on nonpermeabilized glands. These results are interpreted to show that alpha-toxin permeabilizes parietal cells to moderate sized molecules without causing a loss of critical intracellular components. The acid secretory responses to histamine and carbachol persisted in media containing low ( < 50 nM) levels of free Ca2+ buffered by 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (0.5 mM), indicating that changes in bulk Ca2+ are not required for these responses. Inclusion of the nonhydrolyzable analogue of GTP, guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S; 100 microM), resulted in inhibition of spontaneous acid secretion, blocked responses to all agents tested, and inhibited stimulated acid secretion. GTP gamma S had no effect on nonpermeabilized glands. No effects on acid secretion by either permeable or nonpermeable glands were observed with GTP, guanosine diphosphate, or guanosine 5'-O-(2-thiodiphosphate). GTP gamma S had no effect on H+ gradient formation by gastric membrane vesicles, showing that it does not inhibit the gastric H(+)-K(+)-adenosinetriphosphatase directly. These results are interpreted to show that GTP gamma S interacts at a postreceptor site to inhibit or reverse a critical step in stimulus-secretion coupling in parietal cells. In contrast to the effect on parietal cells, GTP gamma S was found to stimulate pepsinogen secretion by alpha-toxin-permeabilized chief cells. The differential effects of GTP gamma S on acid and pepsinogen secretions suggest unique roles for GTP binding proteins in these two secretory processes. The use of alpha-toxin-permeabilized gastric glands should prove useful in defining the stimulus-secretion coupling mechanisms involved in both acid and pepsinogen secretions.
Animals↗
Changes in perceived health status of depressed elderly patients treated until remission.
OBJECTIVE: The authors predicted that depressed elderly patients who responded to treatment would rate their baseline health more positively than nonresponders, that responders would again rate their health more positively once they were in remission, and that lower baseline self-ratings of health would predict lack of response to protocol treatment. METHOD: The Perception of Illness Scale was administered to 61 depressed elderly patients at baseline and again upon completion of the acute phase of a depression treatment protocol. A logistic regression was performed to ascertain whether Perception of Illness Scale scores predicted response to protocol treatment. RESULTS: Baseline Perception of Illness Scale scores were poorer among the nonresponders, accurately predicted response or lack of response in 75% of the subjects, and showed before-to after-treatment improvement among the responders. CONCLUSIONS: Patients who initially rated their health as fair to poor were less likely to recover from depression in a standardized treatment protocol. Self-ratings of health improved with resolution of depression.
Age Factors↗
High relapse rate after discontinuation of adjunctive medication for elderly patients with recurrent major depression.
OBJECTIVE: The authors documented outcomes of elderly depressed patients requiring adjunctive medication during acute-phase pharmacotherapy because of slow or partial response to nortriptyline. Twenty-eight patients (17.7%) received inpatient care at some point during acute-phase treatment. METHOD: Rates of response, relapse, and sustained remission were examined in 158 elderly patients with recurrent major depression, grouped by whether they received brief treatment with adjunctive medication (lithium, perphenazine, or paroxetine) (N = 39) or did not (N = 119). RESULTS: The group receiving adjunctive medication had a lower rate of response to acute therapy (64.1% versus 83.2%), a higher relapse rate during continuation therapy (52.0% versus 6.1%), and a lower rate of sustained remission (recovery) (48.7% versus 76.5%) than did the group without augmentation. CONCLUSIONS: Elderly depressed patients requiring augmented pharmacotherapy to achieve remission may need continuation of adjunctive medication to remain well and to avoid early relapse. Alternatively, factors that lead to augmentation in the first place (e.g., heightened anxiety) may also increase the risk of relapse.
Age Factors↗
Bereavement-related depression in the elderly. Is drug treatment justified?
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Aged↗
Cross-language facilitation, semantic blindness, and the relation between language and memory: a reply to Altarriba and Soltano.
This comment corrects some inaccuracies, points to some methodological problems, and makes three substantive observations regarding the Altarriba and Soltano (1996) article. First, token individuation theory does not explain what is new and interesting in the Altarriba and Soltano data, namely cross-language semantic facilitation in lists and a list-sentence effect, that is, a large difference in the effect of semantic repetition when identical translation equivalents occurred in sentences versus lists. Second, Altarriba and Soltano's small and nonsignificant semantic blindness effect for translation equivalents in split-language sentences is attributable to the peculiar nature of their materials, procedures, analyses, and experimental design. These problems nullify their conclusion that semantic blindness does not occur, and we discuss several clear cases where semantic blindness has been demonstrated. Finally, we suggest an explanation for Altarriba and Soltano's unexplained effects (cross-language facilitation and the list-sentence effect) and show why these effects are important for the general issue of relations between language and memory.
Humans↗
Thawing the frozen shoulder: the "patient" patient.
Many different modalities have been advocated for the treatment of frozen shoulder (adhesive capsulitis), some of which can be associated with complications and morbidity. We retrospectively reviewed 50 patients with adhesive capsulitis treated by the senior author over a 10-year period. Treatment consisted of closely monitored home therapy using moist heat and antiinflammatory medication, and a physician-directed rehabilitation program. Without exception, every patient regained a significant amount of motion and returned to activities of daily living without pain.
Activities of Daily Living↗
Target DNA capture by HIV-1 integration complexes.
BACKGROUND: The early steps of human immunodeficiency virus 1 (HIV-1) replication involve reverse transcription of the viral RNA and integration of the resulting cDNA into a host chromosome. The DNA integration step requires the integration machinery ('preintegration complex') to bind to the host DNA before connecting the viral and host DNAs. Here, we present experiments that distinguish among three possible pathways of target-DNA capture: repeated binding and release of target DNA prior to the chemical strand-transfer step; binding followed by facilitated diffusion along target DNA (sliding); and integration at the initial target-capture site. The mechanism of target-DNA capture has implications for the design of gene therapy methods, and influences the interpretation of results on the selection of integration target sites in vivo. RESULTS: We present new in vitro conditions that allow us to assemble HIV-1 integrase--the virus-encoded recombination enzyme--with a viral DNA and then to trap assembled complexes bound to target DNA. We find that complexes of integrase and viral DNA do not slide along target DNA substantially after binding. We confirm and extend these results by analyzing target capture by a hybrid protein composed of HIV-1 integrase linked to a sequence-specific DNA-binding domain. We find that the integrase domain binds quickly and tightly under the above conditions, thereby obstructing function of the fused sequence-specific DNA-binding domain. We also monitor target-DNA capture by HIV-1 preintegration complexes purified from freshly infected cells. Partially purified complexes commit quickly and stably to the first target DNA added, whereas preintegration complexes in crude cytoplasmic extracts do not. The addition of extracts from uninfected cells to partially purified complexes blocks quick commitment. CONCLUSIONS: Under new conditions favorable for the analysis of target-DNA capture in vitro, HIV-1 integrase complexes bind quickly and stably to target DNA without subsequent sliding. Parallel studies of preintegration complexes support a model in which target-site capture in vivo is reversible as a result of the action of cellular factors.
Binding Sites↗
HIV integration. Ini1 for integration?
The newly discovered Ini1 cellular protein binds HIV-1 integrase and is part of a protein complex thought to alter nucleosomal structure; such alterations may influence the selection of sites for HIV-1 DNA integration.
Chromosomal Proteins, Non-Histone↗
Does recruitment method make a difference? Effects on protocol retention and treatment outcome in elderly depressed patients.
The specific aim of this study was to contrast effects of recruitment method (solicited, referred) on demographic, psychosocial, medical, and treatment outcome measures in an ongoing clinical trial of maintenance therapies in late-life depression. Data from 125 elderly patients (56 solicited via media campaign, 69 clinically referred) with recurrent, unipolar major depression were available for analysis. Several statistical contrast procedures, including group t tests, chi 2 tests, survival analysis, and logistic regression, were used to assess differences in patient profiles related to method of recruitment. Referred patients included a higher proportion of African Americans and had a lower level of education, fewer economic resources, and higher chronic medical burden. Solicited patients had been in the index episode longer than the referred patients at the time of protocol entry and were 3.4 times more likely to have experienced a "provoking agent" (severe life event or chronic difficulty) during the 6 months that preceded the onset of depressive symptoms. In contrast to these demographic and illness history differences, there were no differences in treatment response rates or time to response related to recruitment method. Solicited patients had an overall treatment response rate of 71% versus 62% in the referred group. Median time to response was 14.3 weeks in the solicited group and 13.6 weeks in the referred group. These results suggest that the inclusion of solicited patients in geriatric depression clinical trials does not bias short-term treatment outcome.
Adjustment Disorders↗
Arthroscopic Bankart repair with the Suretac device. Part I: Clinical observations.
Although arthroscopic Bankart repair has become an accepted surgical stabilization technique for anterior shoulder instability, the failure rate remains unacceptably high. Little information is available concerning healing of the Bankart repair. The purpose of this article is to clarify this issue by analyzing a cohort of 15 patients who underwent a "second-look" arthroscopy to evaluate and treat pain or recurrent instability following arthroscopic Bankart repair with the Suretac device (Acufex Microsurgical, Mansfield, MA). "Second-look" arthroscopy was performed at an average of 9 months following the index surgical procedure. The reasons for this second surgery were recurrent instability in 7, pain in 6, and pain and stiffness in 2. In the 7 patients with recurrent instability, the Bankart repair was found to be completely healed in 3 (43%), partially healed in 1 (14%), and had recurred in 3 (43%); however, 6 of 7 were observed to have lax capsular tissue. In 4 of these cases, retrospective review of the index surgical procedure showed that a technical error had been made during the repair. Two cases had biopsy of the repair site on "second-look" at 6 to 8 months, and this showed residual polyglyconate polymer debris surrounded by a histiocytic infiltrate. In the remaining 8 cases with stable shoulders, the Bankart repair had completely healed in 5 cases (62.5%) and partially healed in 3 cases (37.5%). The higher failure rate with this approach compared with open approaches appears to result from improper patient selection and errors in surgical technique. There is some question concerning healing strength of the Bankart repair, although complete healing of the Bankart does not seem to be a prerequesite for shoulder stability. Success of the procedure might be expected to improve by selecting only patients with unidirectional, posttraumatic, anterior instability who are found to have a discrete Bankart lesion and well-developed ligamentous tissue.
Adult↗
Arthroscopic Bankart repair with the Suretac device. Part II: Experimental observations.
Arthroscopic Bankart repair using the Suretac device (Acufex Microsurgical, Mansfield, MA) was developed as an alternative to both the staple and suture repair techniques. While offering some technical advantages compared with these other approaches, it's technical limitations and pitfalls have only been described anecdotally based on the clinical experience of several surgeons. The purpose of this study was to define these limitations and pitfalls. Eight cadaver shoulders underwent arthroscopic Bankart repair using the Suretac device after first arthroscopically creating a Bankart lesion. These shoulders were then dissected to reveal the placement of the Suretacs and the adequacy of the Bankart lesion repair. Glenoids were transected in the transverse plane and embedded in clear methylmethacrylate to show placement of the Suretac device relative to the articular surface. There were several technical errors that occurred: (1) Inadequate abrasion of the anterior and inferior juxta-articular scapular neck; (2) inadequate superior and medial shift of the inferior glenohumeral ligament before placement of the lowest Suretac, (3) medial placement of the Suretac relative to the articular margin; and (4) insufficient capture and compression of capsular tissue by the Suretac device. This procedure is technically difficult and careful attention must be paid to each step of preparation and repair. Recognition of the common errors may help the surgeon to avoid these pitfalls in the clinical situation.
Arthroscopy↗
Reducing nursing home use through community long-term care: an optimization analysis.
Can community services be made more effective in reducing nursing home use through better management of their mix and allocation? To test this idea, we used data from the National Long-Term Care Channeling Demonstration to estimate logistic regression models relating the use of various types of community services to nursing home use. We then used these estimates to form an objective function for a mathematical optimization procedure which minimizes total expected population nursing home use as a function of community service use, subject to a total expenditure constraint. We find through this simulated reallocation that, in theory, significant reductions in nursing home use can be produced without increasing total community expenditures.
Aged↗
Using telemedicine for continuing education for rural physicians.
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Education, Medical, Continuing↗
Expression of the human immunodeficiency virus type 1 (HIV-1) nef gene during HIV-1 production increases progeny particle infectivity independently of gp160 or viral entry.
The nef gene product of human immunodeficiency virus type 1 (HIV-1) promotes more-rapid kinetics of viral replication in primary peripheral blood mononuclear cells. We have previously shown that these enhancing effects of Nef on HIV-1 replication reflect an increase in viral infectivity detectable both in limiting dilution assays and through a single-cycle infection of the HeLa-CD4-long terminal repeat-beta-galactosidase indicator cell line. We now demonstrate that nef-defective HIV-1 can be rescued to near wild-type levels of infectivity by coexpressing Nef in trans in the cell line producing the virus. This observation indicates that HIV-1 virions produced in the presence of Nef are intrinsically different. However, we show that the major viral structural proteins are quantitatively similar in purified viral preparations. We also demonstrate the functional equivalence of the gp120-gp41 envelope glycoprotein complexes of Nef+ and Nef- HIV-1 through an assay for viral entry. Finally, we show that env-defective Nef+ HIV-1 pseudotyped with an amphotropic envelope is also more infectious than similarly pseudotyped Nef- HIV-1. Thus, the production of HIV-1 in the presence of Nef results in viral particles that are more infectious, and this increased infectivity is manifested at a stage after viral entry but prior to or coincident with HIV-1 gene expression.
Cells, Cultured↗
Human immunodeficiency virus type 1 preintegration complexes containing discontinuous plus strands are competent to integrate in vitro.
Despite intensive study, the mechanism by which many retroviruses complete reverse transcription has remained unclear. Most retroviruses and all lentiviruses fail to synthesize a full-length second strand of the viral cDNA (plus strand) efficiently in infected cells. For human immunodeficiency virus type 1, we find in synchronous infection experiments that full-length plus strands are rare (< 1% of products) at times when integration is likely taking place. Subviral nucleoprotein complexes containing such discontinuous cDNA can be extracted from infected cells and used to generate integration products in vitro. Analysis of such integration products using two-dimensional gel electrophoresis revealed that the discontinuous viral DNA was efficiently integrated into an added target DNA. These data support a model in which the discontinuities in the plus strand need not be sealed until after integration, potentially by the enzymes that are already thought to repair DNA gaps at the junctions between host and viral DNA.
Cell Line↗
Dissociation of the CD4 downregulation and viral infectivity enhancement functions of human immunodeficiency virus type 1 Nef.
Recent evidence indicates that the nef gene of human immunodeficiency virus type 1 augments rather than inhibits viral replication in both cell culture and in vivo models. In addition, nef alters various normal cellular processes, including the display of CD4 on the cell surface. However, it remains unknown whether the enhancement of infectivity and the downregulation of CD4 represent linked or independent biologic properties of this single protein. In the present studies, mutational analyses were performed to define structure-function relationships within the Nef protein that mediate these effects. To assess the functional consequences of these mutations, sensitive and reliable assays were developed to quantitate the viral infectivity enhancement and CD4 downregulation functions of Nef. The results indicate that membrane-targeting sequences at the N terminus of Nef are important for both functions of Nef, while certain other conserved regions are dispensable for both functions. A conserved proline-X-X repeat segment in the central core of the protein, which is reminiscent of an SH3-binding domain, is critical for the enhancement of infectivity function but is dispensable for CD4 downregulation. However, the downregulation of CD4 by Nef appears to involve a two-step process requiring the initial dissociation of p56lck from CD4 to permit engagement of the endocytic apparatus by CD4. Together, these findings demonstrate that the infectivity enhancement and CD4 downregulation activities of human immunodeficiency virus type 1 Nef can be dissociated. Thus, these processes may be independent of one another in the viral replication cycle.
Base Sequence↗