Increased drug susceptibility of HIV-1 reverse transcriptase mutants containing M184V and zidovudine-associated mutations: analysis of enzyme processivity, chain-terminator removal and viral replication

The presence of the HIV reverse transcriptase (RT) resistance mutation, M184V, induced by lamivudine and abacavir treatment results in increased tenofovir, adefovir and zidovudine susceptibility for HIV-1 with zidovudine-associated RT mutations in vitro. Treatment with oral prodrugs of tenofovir and adefovir has resulted in substantial HIV-1 RNA reductions in antiretroviral-experienced patient populations who have lamivudine- and zidovudine-resistant HIV-1. An enzymatic analysis was undertaken to elucidate the mechanisms of altered drug susceptibilities of HIV-1 containing zidovudine-associated mutations in the presence or absence of M184V. The inhibition constants (Ki) for the active metabolites of tenofovir, adefovir and zidovudine did not vary significantly between recombinant mutant and wild-type RT enzymes. Although increased removal of chain-terminating inhibitors by pyrophosphorolysis and ATP-dependent unblocking correlated with reduced susceptibility of viruses with zidovudine-associated mutations, a reduction in the removal of chain-terminators was not observed, which would explain the increased drug susceptibility of mutants containing M184V plus zidovudine-associated mutations. However, analyses of single-cycle processivity of the mutant RT enzymes on heteropolymeric RNA templates showed that all M184V-containing mutant RT enzymes were less processive than wild-type RT, most notably for mutants expressing both zidovudine-associated mutations and M184V. Similarly, the in vitro replication capacity of a mutant virus expressing a zidovudine-associated mutation and M184V was significantly reduced compared with wild-type virus. The observed decrease in enzymatic processivity of the M184V-expressing RT enzymes might result in decreased viral replication, which then might contribute to the increased drug susceptibility of HIV-1 expressing these RT mutations.

Comparison of knowledge-based and distance geometry approaches for generation of molecular conformations

A knowledge-based approach for generating conformations of molecules has been developed. The method described here provides a good sampling of the molecule's conformational space by restricting the generated conformations to those consistent with the reference database. The present approach, internally named et for enumerate torsions, differs from previous database-mining approaches by employing a library of much larger substructures while treating open chains, rings, and combinations of chains and rings in the same manner. In addition to knowledge in the form of observed torsion angles, some knowledge from the medicinal chemist is captured in the form of which substructures are identified. The knowledge-based approach is compared to Blaney et al.'s distance geometry (DG) algorithm for sampling the conformational space of molecules. The structures of 113 protein-bound molecules, determined by X-ray crystallography, were used to compare the methods. The present knowledge-based approach (i) generates conformations closer to the experimentally determined conformation, (ii) generates them sooner, and (iii) is significantly faster than the DG method.

CCR5, CXCR4, and CD4 are clustered and closely apposed on microvilli of human macrophages and T cells

The chemokine receptors CCR5 and CXCR4 act synergistically with CD4 in an ordered multistep mechanism to allow the binding and entry of human immunodeficiency virus type 1 (HIV-1). The efficiency of such a coordinated mechanism depends on the spatial distribution of the participating molecules on the cell surface. Immunoelectron microscopy was performed to address the subcellular localization of the chemokine receptors and CD4 at high resolution. Cells were fixed, cryoprocessed, and frozen; 80-nm cryosections were double labeled with combinations of CCR5, CXCR4, and CD4 antibodies and then stained with immunogold. Surprisingly, CCR5, CXCR4, and CD4 were found predominantly on microvilli and appeared to form homogeneous microclusters in all cell types examined, including macrophages and T cells. Further, while mixed microclusters were not observed, homogeneous microclusters of CD4 and the chemokine receptors were frequently separated by distances less than the diameter of an HIV-1 virion. Such distributions are likely to facilitate cooperative interactions with HIV-1 during virus adsorption to and penetration of human leukocytes and have significant implications for development of therapeutically useful inhibitors of the entry process. Although the mechanism underlying clustering is not understood, clusters were observed in small trans-Golgi vesicles, implying that they were organized shortly after synthesis and well before insertion into the cellular membrane. Chemokine receptors normally act as sensors, detecting concentration gradients of their ligands and thus providing directional information for cellular migration during both normal homeostasis and inflammatory responses. Localization of these sensors on the microvilli should enable more precise monitoring of their environment, improving efficiency of the chemotactic process. Moreover, since selectins, some integrins, and actin are also located on or in the microvillus, this organelle has many of the major elements required for chemotaxis.

Tenofovir (PMPA) is less susceptible to pyrophosphorolysis and nucleotide-dependent chain-terminator removal than zidovudine or stavudine

Pyrophosphorolysis, the removal of nucleoside chain-terminators by a pyrophosphate (PPi) acceptor molecule, and a similar mechanism (nucleotide-dependent chain-terminator removal) which uses ATP as an acceptor molecule have been proposed as mechanisms of zidovudine (AZT) resistance. Recombinant HIV-1 wild-type reverse transcriptase (RT) and a mutant RT enzyme containing the AZT/thymidine analog resistance mutations D67N/K70R/T215Y were analyzed for pyrophosphorolysis and nucleotide-dependent chain-terminator removal activities. Our results confirm that pyrophosphorolysis and nucleotide-dependent chain-terminator removal are potential mechanisms of AZT and d4T resistance. However, tenofovir is less efficiently removed by pyrophosphorolysis and by nucleotide-dependent mechanisms. These results are consistent with the minor changes in susceptibility to tenofovir of the AZT/thymidine analog-resistant HIV RT mutants and the corresponding resistance of these mutants to AZT. The inability to remove tenofovir efficiently by these mechanisms may contribute to the durability of the HIV RNA response observed in patients treated with the oral prodrug, tenofovir disoproxil fumarate.

Antiviral activity of tenofovir (PMPA) against nucleoside-resistant clinical HIV samples

The presence of the lamivudine-associated M184V RT mutation increases tenofovir susceptibility in multiple HIV genotypes. Tenofovir is uniquely active against multinucleoside-resistant HIV expressing the Q151M mutation, but shows reduced susceptibility to the T69S insertion mutations. HIV with common forms of zidovudine and lamivudine resistance are susceptible to tenofovir, corroborating phase II clinical results demonstrating the activity of tenofovir DF in treatment-experienced patients.

The posttreatment illness course of depression in bereaved elders. High relapse/recurrence rates

Losing close attachments through death in late life is common and can lead to depression. Previous work has shown the clinical benefits of treating these depressions. This article describes the 2-year course of 53 elderly subjects with bereavement-related depression after responding to various treatments. Forty-six patients experienced a full response to acute treatment, but 36% experienced relapse or recurrence. This finding suggests that the treatment response in depressed bereaved older patients is more brittle than expected.

A double-blind randomized comparison of nortriptyline and paroxetine in the treatment of late-life depression: 6-week outcome

BACKGROUND

Some studies have suggested that selective serotonin reuptake inhibitors may be less efficacious than tricyclic antidepressants in the treatment of severe depression in older patients. The objective of this study was to compare the 6-week outcome of treatment with nortriptyline and paroxetine in older patients with a major depressive episode.

METHOD

A double-blind randomized comparison of nortriptyline and paroxetine was conducted in 80 elderly (mean +/- SD age = 75.0 +/- 7.4 years) psychiatric inpatients and outpatients who presented with a major depressive episode. Dropout and response rates were compared in patients who began or completed treatment. Rates of response of inpatients and patients with melancholic depression were also compared.

RESULTS

Over 6 weeks, there were no significant differences in dropout rates due to side effects (nortriptyline, 14% vs. paroxetine, 19%) or for any reason (27% vs. 33%). Similarly, there were no significant differences between the rates of favorable response to nortriptyline or paroxetine (intent-to-treat analysis, 57% vs. 44%; completer analysis, 78% vs. 66%). Analyses restricted to inpatients or to patients with melancholic depression yielded similar results.

CONCLUSION

Nortriptyline and paroxetine appear to have similar efficacy and tolerability in the acute (6-week) treatment of older depressed patients, including hospitalized patients and those with melancholic features.

Bereavement and late-life depression: grief and its complications in the elderly

Spousal bereavement is a common event in later life and, not infrequently, an important cause of psychiatric and medical morbidity. Depression (along with suicide), anxiety, substance abuse, and symptoms of "complicated" grief are among the more important psychiatric sequelae of spousal bereavement. They may represent, in part, forms of abnormal reaction to the stress of loss and the challenges of adaption to becoming widowed. This paper summarizes current knowledge about the clinical phenomenology of the psychiatric sequelae to late-life attachment bereavement, some of the hypothesized antecedents of abnormal stress response to bereavement, psychobiologic correlates of bereavement-related depression, and the long-term course (including preliminary evidence on response to treatment with psychotherapy and antidepressant medication).

Recruitment methods for intervention research in bereavement-related depression. Five years' experience

The authors compared various strategies for recruiting elderly subjects with bereavement-related depression into a randomized clinical trial. Over 5 years, they empaneled 65 patients from a total of 441 subjects screened (14.7%). Response to media advertisements was the single most effective strategy (54% of subjects). Another effective, but labor-intensive, strategy was using letters to bereaved spouses found through newspaper obituaries (14%); another 14% were referred by friends who had seen study advertisements. Information letters to healthcare providers yielded no study participants. Pathways to study participation did not differ as a function of race or gender and did not influence study retention or remission rates. Our experience suggests that successful intake depends on a personal mode of recruitment.

The art of clinical management in pharmacologic trials with depressed elderly patients: lessons from the Pittsburgh Study of Maintenance Therapies in Late-Life Depression

The authors outline the clinical management methods used in a long-term study of depressed elderly patients and comment on the positive aspects of such interventions on the successful recruitment and retention of subjects. Psychosocial or clinical management (CM) is the "glue" that holds a successful drug trial together. CM is recognized to be an essential element for success in drug trials for geriatric depression. The authors also discuss potentially negative aspects of comprehensive CM, such as those obscuring a psychotherapeutic effect in comparative studies.

Long-term ECG changes in depressed elderly patients treated with nortriptyline. A double-blind, randomized, placebo-controlled evaluation

ECGs of 50 patients who completed a long-term nortriptyline (NT) study are presented at baseline, after 7 weeks on NT, and after 1 year. The ECGs of patients with preexisting cardiac disease were compared with non-cardiac patients. Significant ECG changes and increases in heart rate were observed by Week 7 and persisted at a mean of 55 weeks (range: 24-111) in patients who were continued on NT. No significant difference was found in long-term ECG effects in patients with preexisting cardiac disease; ECG changes reverted to baseline when placebo was substituted. Patients with known cardiac disease did not show significantly worse ECG changes on NT than non-cardiac patients.

Accelerating antidepressant response in geriatric depression: a post hoc comparison of combined sleep deprivation and paroxetine versus monotherapy with paroxetine, nortriptyline, or placebo

Speed of response is an important clinical issue in the treatment of depressed elderly patients. Our objective was to compare rapid response rates in a study combining therapeutic sleep deprivation (TSD) with paroxetine with two earlier randomized, double-blind studies in late-life depression, one of paroxetine versus nortriptyline and another of nortriptyline versus placebo. We measured depressive symptoms with the 17-item Hamilton Rating Scale of Depression (HRSD), defining rapid response as an HRSD < or = 10 by 2 weeks. With combination therapy (TSD + paroxetine), 9 of 13 patients (69%) experienced a rapid response. In the nortriptyline versus paroxetine study, nortriptyline brought about rapid response in 12 of 37 (32%) and paroxetine in 11 of 43 patients (26%). In the third study, rapid response to nortriptyline occurred in 10 of 41 patients (24%) and to placebo in 6 of 39 patients (15%). The overall chi square, including the rate of rapid response to placebo, was 14.87 (P = .005). The chi square on the four active treatment groups, excluding placebo, was 10.28 (P = .016). This preliminary observation suggests that combined therapy with TSD plus paroxetine may be twice as successful at achieving rapid response in elderly depressed patients than conventional monotherapy with medication or placebo. A prospective, placebo-controlled evaluation of this dual therapy is warranted.

Digital imaging considerations for gel electrophoresis analysis systems

Gel analysis system purchasers have a large variety of digital imaging products to choose from today. Understanding the specifications presented by the manufacturers is important to ensure that the system fits the needs ofthe researcher using the system. The background information contained in this paper explains the terminology and many of the specifications along with their significance.

Mechanisms of HIV-1 nucleoside reverse transcriptase inhibitor resistance: is it all figured out?

The mechanistic basis for some examples of HIV-1 NRTI-resistance can be examined using altered incorporation of nucleoside analogs and surveying what is known about the more recently described mechanisms of chain-terminator removal. The complexity of these resistance mechanisms and the interplay with other factors that contribute to NRT1 resistance are only just beginning to be appreciated.

Fluvoxamine pharmacotherapy of anxiety disorders in later life: preliminary open-trial data

The authors present data from an open trial of fluvoxamine (median daily dosage: 200 mg) in the treatment of generalized anxiety disorder, panic disorder, and obsessive-compulsive disorder in 19 older outpatients (mean age = 66.8). Of the 12 subjects completing the 21-week trial, 8 achieved a good response (50% reduction in symptom measures) and 7 were rated as much or very much improved. Fluvoxamine pharmacotherapy also had a significant effect in reducing comorbid depressive symptoms and in increasing levels of functioning. These data support the effectiveness of fluvoxamine in older subjects with anxiety disorders (particularly generalized anxiety disorder) and warrant further double-blind, placebo-controlled evaluation.

Magnetic resonance imaging at different time periods following hamstring harvest for anterior cruciate ligament reconstruction

PURPOSE

The purpose of this study was to evaluate the magnetic resonance imaging (MRI) appearance of the hamstring graft harvest site after harvesting the hamstring tendons to reconstruct a torn anterior cruciate ligament (ACL).

TYPE OF STUDY

Case series.

METHODS

We performed MRI on 21 patients who had previously undergone hamstring harvest and ACL reconstruction. Twenty of the patients (7 female and 13 male; mean age, 37 years; range, 16 to 84 years), all volunteers, were selected from a series of 45 ACL reconstructions performed by the senior author during a 20-month period. Another patient, a 32-year-old man, underwent ACL reconstruction elsewhere 32 months before. Both the semitendinosus and gracilis tendons were harvested in all cases. All MRIs were obtained on a 1.5-T magnet and were prospectively evaluated by 2 experienced musculoskeletal radiologists who were blinded to the time interval between graft harvest and MRI.

RESULTS

Two weeks after graft harvest, MRI showed ill-defined intermediate signal on T1-weighted images and increased signal on T2-weighted images, consistent with fluid in the harvest site, with no discernable tendon. At 6 weeks, structures were seen at the level of the superior pole of the patella that had morphology and signal characteristics similar to native tendon. By 3 months, structures with normal morphology and signal characteristics were seen to the level of the joint line, and by 12 months, to the level of 1 to 3 cm above that of the tibial attachment. At 32 months, the tendons appeared on MRI to normalize to a level of 1 to 2 cm above their tibial attachment.

CONCLUSION

Following hamstring tendon harvest, MRI demonstrates an apparent regeneration of tendons beginning proximally and extending distally over time.

Anterior cruciate ligament reconstruction in an 84-year-old man

Anterior cruciate ligament (ACL) reconstruction is typically reserved for younger patients. Several recent articles have reported expanding traditional age barriers for ACL reconstruction in patients up to 62 years old. We report a case of a successful ACL reconstruction in an active 84-year-old rancher. Physiologic age is more important than chronologic age when considering ACL reconstruction.

Interpersonal psychotherapy for late-life depression: past, present, and future

Interpersonal psychotherapy (IPT) has demonstrated efficacy in protecting against a recurrence of major depression in elderly subjects when used alone on a monthly basis and when combined with antidepressant medication. The authors summarize their experience using IPT over the past 10 years and discuss a variety of treatment correlates. In addition, preliminary results using IPT combined with paroxetine in depressed elders reveals no difference in remission rates between cognitively intact and cognitively impaired depressed elders.

Retroviral cDNA integration: stimulation by HMG I family proteins

To replicate, a retrovirus must synthesize a cDNA copy of the viral RNA genome and integrate that cDNA into a chromosome of the host. We have investigated the role of a host cell cofactor, HMG I(Y) protein, in integration of human immunodeficiency virus type 1 (HIV-1) and Moloney murine leukemia virus (MoMLV) cDNA. Previously we reported that HMG I(Y) cofractionates with HIV-1 preintegration complexes (PICs) isolated from freshly infected cells. PICs depleted of required components by treatment with high concentrations of salt could be reconstituted by addition of purified HMG I(Y) in vitro. Here we report studies using immunoprecipitation that indicate that HMG I(Y) is associated with MoMLV preintegration complexes. In mechanistic studies, we show for both HIV-1 and MoMLV that each HMG I(Y) monomer must contain multiple DNA binding domains to stimulate integration by HMG I(Y)-depleted PICs. We also find that HMG I(Y) can condense model HIV-1 or MoMLV cDNA in vitro as measured by stimulation of intermolecular ligation. This reaction, like reconstitution of integration, depends on the presence of multiple DNA binding domains in each HMG I(Y) monomer. These data suggest that binding of multivalent HMG I(Y) monomers to multiple cDNA sites compacts retroviral cDNA, thereby promoting formation of active integrase-cDNA complexes.

Local loss of proprioception results in disruption of interjoint coordination during locomotion in the cat

To investigate the role of localized, proprioceptive feedback in the regulation of interjoint coordination during locomotion, we substantially attenuated neural feedback from the triceps surae muscles in one hindlimb in each of four cats using the method of self-reinnervation. After allowing the recovery of motor innervation, the animals were filmed during level and ramp walking. Deficits were small or undetectable during walking on the level surface or up the ramp, behaviors that require a large range of forces in the triceps surae muscles. During walking down the ramp, when the triceps surae muscles normally undergo active lengthening, the ankle joint underwent a large yield and the coordination between ankle and knee was disrupted. The correlation of the deficit with the direction of length change and not muscle force suggested that a loss of feedback from muscle spindle receptors was primarily responsible for the deficit. These results indicate an important role for the stretch reflex and stiffness regulation during locomotion.

Effect of nortriptyline and paroxetine on extrapyramidal signs and symptoms: A prospective double-blind study in depressed elderly patients

Selective serotonin-reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs) have been reported to induce extrapyramidal signs and symptoms (EPS). The authors examined the change from baseline EPS, measured by an objective rating scale, in a group of elderly depressed patients participating in an ongoing randomized, double-blind comparison of nortriptyline and paroxetine. Mild baseline EPS were present in both groups. After 6 weeks of antidepressant treatment, patients in the nortriptyline group showed a significant decrease in total EPS scores. Patients in the paroxetine group showed a similar decrease in EPS from baseline, which did not reach statistical significance. There was no significant difference between nortriptyline and paroxetine in the change in EPS.

Which elderly depressed patients remain well on maintenance interpersonal psychotherapy alone?: report from the Pittsburgh study of maintenance therapies in late-life depression

The aim of this study was to identify elderly depressed patients who can remain well on maintenance Interpersonal Psychotherapy (IPT) alone, after discontinuation of antidepressant medication. Using Cox proportional hazards models, increased severity of depression at pretreatment was associated with increased recurrence rates, to an extent greater in patients maintained on monthly IPT than in those maintained on nortriptyline. The long-term response to maintenance IPT was correctly identified in 20/25 cases by a pretreatment Hamilton score of > or = 20. Fourteen of sixteen patients with pretreatment scores of > or = 20 experienced recurrence of major depression on maintenance IPT, while 6/9 patients with pretreatment scores of less than 20 did not. (Fisher exact P = .01). The same pattern of recurrence in relation to severity was not evident in maintenance placebo, nortriptyline, or combination treatment. In addition, Hamilton scores during continuation treatment were lower (< or = 7) among those who remained well on maintenance IPT than among those who had recurrences. Elderly patients whose depressions are milder at baseline and who show excellent symptomatic remission during acute and continuation therapy may be good candidates for monthly maintenance IPT after initial successful treatment with antidepressant medication and psychotherapy.

Knee dislocation. Complications of nonoperative and operative management

Because of the nature and extreme severity of the injury, complications will continue to be a common denominator in traumatic knee dislocations. The major complications that cause significant morbidity, including amputation and death, are now relatively infrequent. Prompt recognition and treatment of these complications are of utmost importance to assure functional viability of the extremity. These complications must continue to be addressed preoperatively and postoperatively. Minor complications will persist after significant knee surgery. New complications will evolve as newer techniques, instrumentation, and procedures are introduced. Ligament reconstructive surgery is relatively new and technically demanding. The surgeon must continue to use meticulous technique and attention to detail. Orthopedic surgeons must continue to closely evaluate the procedures they perform, making sure they are as technically correct as possible. Each surgeon must observe and determine what technique will be of true benefit to the patient. Most complications that do occur can be corrected or at least improved if they are handled early and with a true understanding of the problem.

Intracorporeal lithotripsy with the Alexandrite laser

BACKGROUND AND OBJECTIVE

The objective of this study was to evaluate clinical use of an Alexandrite laser lithotripter for intracorporeal lithotripsy of urinary calculi.

STUDY DESIGN/MATERIALS AND METHODS

We prospectively evaluated a flash lamp pumped, Q-switched Alexandrite solid-state laser for use in conjunction with ureteroscopy (30 cases) or percutaneous nephrolithotripsy (2 cases). The laser operates at a wavelength of 755 nm in a pulsed mode with pulses of 150-800 ns duration at energy settings of 30-80 mJ.

RESULTS

The fragmentation rate with the Alexandrite laser alone was 50% (16/32). Failure of the laser was due to equipment malfunction or technical problems in 11 cases and inability to fragment the stone in 5. All cases of failed Alexandrite laser lithotripsy were successfully salvaged with alternative modalities of endoscopic stone destruction and removal. One intraoperative complication, a ureteral perforation, occurred; however, no long-term sequelae related to laser use was documented.

CONCLUSION

Clinical results with the Alexandrite laser appear to be inferior to those reported with Alternative laser systems and other forms of intracorporeal lithotripsy. Whereas some of the inadequacies we have noted may be addressed in the future by modifications in the unit and delivery systems, we would not recommend this device for intracorporeal lithotripsy of urinary calculi in its current form.