HIV therapeutics: past, present, and future.
Explore the source record for details and available documents.
Anti-HIV Agents↗
Biomedical subjects
S M Smith
Publications and source records attributed to S M Smith.
Ablation of P/Q-type Ca(2+) channel currents, altered synaptic transmission, and progressive ataxia in mice lacking the alpha(1A)-subunit.
The Ca(2+) channel alpha(1A)-subunit is a voltage-gated, pore-forming membrane protein positioned at the intersection of two important lines of research: one exploring the diversity of Ca(2+) channels and their physiological roles, and the other pursuing mechanisms of ataxia, dystonia, epilepsy, and migraine. alpha(1A)-Subunits are thought to support both P- and Q-type Ca(2+) channel currents, but the most direct test, a null mutant, has not been described, nor is it known which changes in neurotransmission might arise from elimination of the predominant Ca(2+) delivery system at excitatory nerve terminals. We generated alpha(1A)-deficient mice (alpha(1A)(-/-)) and found that they developed a rapidly progressive neurological deficit with specific characteristics of ataxia and dystonia before dying approximately 3-4 weeks after birth. P-type currents in Purkinje neurons and P- and Q-type currents in cerebellar granule cells were eliminated completely whereas other Ca(2+) channel types, including those involved in triggering transmitter release, also underwent concomitant changes in density. Synaptic transmission in alpha(1A)(-/-) hippocampal slices persisted despite the lack of P/Q-type channels but showed enhanced reliance on N-type and R-type Ca(2+) entry. The alpha(1A)(-/-) mice provide a starting point for unraveling neuropathological mechanisms of human diseases generated by mutations in alpha(1A).
Animals↗
Overview: surveillance for selected public health indicators affecting older adults--United States.
The United Nations has proclaimed October 1, 1998, through December 31, 1999, as the International Year of Older Persons (IYOP). Federal agencies are working together to sponsor IYOP activities in the United States. To commemorate the goals of IYOP, CDC has published these surveillance summaries to describe important health issues and to highlight the role of public health surveillance for older adults aged > or =65 years in the United States. Although older adults are the focus of these surveillance summaries, persons aged 55-64 years have also been included, when data were available, as a comparison group.
Aged↗
The expression and activity of D-type cyclins in F9 embryonal carcinoma cells: modulation of growth by RXR-selective retinoids.
The growth rate of malignant F9 embryonal carcinoma cells slows considerably following all-trans-retinoic acid-induced differentiation into benign parietal endoderm. To determine the mechanism of this process, we examined the expression of cyclins D1, D2, and D3 and the activity of their associated kinases. Cyclin D1 and D3 mRNA levels decreased during complete differentiation induced by all-trans-retinoic acid and dibutyryl cAMP, while the levels of cyclin D2 and the cyclin-dependent kinase (Cdk) inhibitor p27 mRNAs increased. Ultimately, terminally differentiated cells possessed 50% of the Cdk4-associated kinase activity observed in undifferentiated cells. Since numerous genes are differentially regulated during parietal endoderm differentiation, it is difficult to determine whether retinoic acid affects cell cycle gene expression directly or if these changes are caused by differentiation. We found that the retinoid X receptor (RXR)-selective agonists LG100153 and LG100268 significantly inhibited F9 cell growth without causing overt terminal differentiation as assessed by anchorage-independent growth and differentiation-associated gene expression. As seen in cells induced to differentiate by the RAR agonist all-trans-retinoic acid, RXR activation led to an increase in the number of cells in G1 phase. RXR agonists also sharply induced the levels of the Cdk regulatory subunits, cyclin D2 and D3. However, Cdk4-dependent kinase activity was reduced by RXR-selective retinoid treatment. These observations suggest that some retinoids can directly inhibit proliferation and regulate Cdk4-dependent kinase activity without inducing terminal differentiation.
Alitretinoin↗
Retrospective analysis of viral load and SIV antibody responses in rhesus macaques infected with pathogenic SIV: predictive value for disease progression.
The prognostic significance of SIV plasma viral load in macaques has not been well established, primarily owing to the small numbers of animals in experimental groups. In addition, many investigators have noted that animals that fail to develop an anti-SIV humoral response develop disease rapidly. To establish the prognostic significance of viral load and seroconversion, we retrospectively analyzed the plasma viral load and serology data from 74 rhesus macaques infected with SIVmac. Viral load was analyzed at three time points: in the peak (days 7-21), acute (days 30-55), and chronic (days 80-100) periods postinfection. High viral load in the peak and acute phases was associated with more rapid development of disease (p = 0.0086, p = 0.0004, respectively). We defined clinical outcome as rapid ( <1 year) or slow (> or =1 year) progression. When peak and acute viral loads were analyzed together, acute viral load was more strongly associated with rapid progression (p = 0.03). Slow progression was strongly associated with chronic viral loads below the median of 3.47 x 10(5) RNA copies/ml. Despite having preexisting anti-SIV antibodies, 7 of 23 vaccinated animals were rapid progressors. All unvaccinated animals that mounted a humoral response to SIV were slow progressors. Animals that received a formalin-fixed, microencapsulated SIV vaccine prior to infection had lower peak viral loads than unvaccinated animals (p = 0.0005), but developed disease at the same rate. Overall, in naive animals, viral load is an important prognostic indicator of the disease progression rate. We found that viral load measured during the chronic phase (days 80-100) of infection was most closely associated with disease progression. We also found that a formalin-fixed, microencapuslated SIV vaccine reduced viral load without affecting clinical outcome. This latter finding may have implications for the evaluation of HIV-1 human vaccine trials.
Animals↗
Clinicopathologic study of 85 similarly treated patients with anaplastic astrocytic tumors. An analysis of DNA content (ploidy), cellular proliferation, and p53 expression.
BACKGROUND: The biologic behavior of anaplastic (World Health Organization Grade III) astrocytomas and oligoastrocytomas is highly variable, ranging from rapid progression to prolonged survival. It is difficult to predict the outcome of an individual patient based on morphology alone. METHODS: To determine the prognostic value of commonly used clinicopathologic markers, we reviewed our experience with 85 similarly treated patients enrolled in 3 North Central Cancer Treatment Group high grade glioma protocols. The pathology was comprised exclusively of primary anaplastic astrocytic tumors (66 astrocytomas and 19 oligoastrocytomas). Variables examined included patient age, morphologic type, preoperative performance score, extent of surgery, solitary versus multiple mitoses, DNA flow cytometric and image morphometric parameters, and expression of proliferating cell nuclear antigen, MIB-1, and p53 expression. RESULTS: The study was comprised of 48 men and 37 women ranging in age from 14-79 years (median age, 47 years). Overall survival ranged from <1 month to >12 years (median, 21.6 months). Statistical analyses revealed that age accounted for the majority of this extensive variability in survival. The median survival times were 65. 5 months, 22.1 months, and 4.4 months, respectively, for the groups <40 years, 40-59 years, and >/=60 years, respectively (P < 0.0001). On univariate analyses, aneuploidy by flow cytometry and a low performance score also predicted a better survival (P values of 0.04 and 0.009, respectively). Statistical trends predicting a better survival were observed for patients with a solitary mitosis and p53 immunopositivity. However, only patient age remained significant in multivariate models. CONCLUSIONS: In a small but relatively uniformly treated cohort of patients with anaplastic astrocytomas and oligoastrocytomas, patient age was associated strongly and inversely with overall survival. Once patient age was taken into account, the clinical and pathologic markers tested appeared to be of limited prognostic value.
Adolescent↗
Neuronal voltage-activated calcium channels: on the roles of the alpha 1E and beta 3 subunits.
Many neurons of the central and peripheral nervous systems display multiple high voltage-activated (HVA) Ca2+ currents, often classified as L-, N-, P-, Q, and R-type. The heterogeneous properties of these channels have been attributed to diversity in their pore-forming alpha 1, subunits, in association with various beta subunits. However, there are large gaps in understanding how individual subunits contribute to Ca2+ channel diversity. Here we describe experiments to investigate the roles of alpha 1E and beta 3 subunits in mammalian neurons. The alpha 1E subunit is the leading candidate to account for the R-type channel, the least understood of the various types of high voltage-activated Ca2+ channels. Incubation with alpha 1E antisense oligonucleotide caused a 53% decrease in the peak R-type current density, while no significant changes in the current expression were seen in sense oligonucleotide-treated cells. The specificity of the alpha 1E antisense oligonucleotides was supported by the lack of change in the amplitude of P/Q current. These results upheld the hypothesis that members of the E class of alpha 1 subunits support the high voltage-activated R-type current in cerebellar granule cells. We studied the role of the Ca2+ channel beta 3 subunit using a gene targeting strategy. In sympathetic beta 3-/- neurons, the L-type current was significantly reduced relative to wild type (wt). In addition, N-type Ca2+ channels made up a smaller proportion of the total Ca2+ current than in wt due to a lower N-type current density in a group of neurons with small total currents. Voltage-dependent activation of P/Q-type Ca2+ channels was described by two Boltzmann components with different voltage dependence. The absence of the beta 3 subunit was associated with a shift in the more depolarized component of the activation along the voltage axis toward more negative potentials. The overall conclusion is that deletion of the beta 3 subunit affects at least three distinct types of HVA Ca2+ channel, but no single type of channel is solely dependent on beta 3.
Animals↗
V-Amylose at atomic resolution: X-ray structure of a cycloamylose with 26 glucose residues (cyclomaltohexaicosaose).
The amylose fraction of starch occurs in double-helical A- and B-amyloses and the single-helical V-amylose. The latter contains a channel-like central cavity that is able to include molecules, "iodine's blue" being the best-known representative. Molecular models of these amylose forms have been deduced by solid state 13C cross-polarization/magic angle spinning NMR and by x-ray fiber and electron diffraction combined with computer-aided modeling. They remain uncertain, however, as no structure at atomic resolution is available. We report here the crystal structure of a hydrated cycloamylose containing 26 glucose residues (cyclomaltohexaicosaose, CA26), which has been determined by real/reciprocal space recycling starting from randomly positioned atoms or from an oriented diglucose fragment. This structure provides conclusive evidence for the structure of V-amylose, as the macrocycle of CA26 is folded into two short left-handed V-amylose helices in antiparallel arrangement and related by twofold rotational pseudosymmetry. In the V-helices, all glucose residues are in syn orientation, forming systematic interglucose O(3)n...O(2)(n+l) and O(6)n...O(2)(n+6)/O(3)(n+6) hydrogen bonds; the central cavities of the V-helices are filled by disordered water molecules. The folding of the CA26 macrocycle is characterized by typical "band-flips" in which diametrically opposed glucose residues are in anti rather than in the common syn orientation, this conformation being stabilized by interglucose three-center hydrogen bonds with O(3)n as donor and O(5)(n+l), O(6)(n+l) as acceptors. The structure of CA26 permitted construction of an idealized V-amylose helix, and the band-flip motif explains why V-amylose crystallizes readily and may be packed tightly in seeds.
Carbohydrate Conformation↗
Retinoic acid is essential for Shh/Hoxd signaling during rat limb outgrowth but not for limb initiation.
Retinoids long have been implicated in limb development and their endogenous contributions to this process are finally being elucidated. Here we use an established model of retinoid depletion during specific gestational windows to investigate the role of endogenous retinoic acid (RA) in supporting limb outgrowth. Rat embryos were deprived of RA starting at days-postcoitum (dpc) 3.0, 5.5, or 7.0 and harvested at the 35-somite stage (dpc 12-12.5). Although embryos from all these windows possessed many characteristics of gestational retinoid deficiency (frontonasal hypoplasia, straight tail, reduced CRBPI and RAR beta), their limb buds emerged with only modest size reductions. Molecular analysis of RA-deficient limb buds revealed enhanced gli-3 and reduced hoxd-12, hoxd-13, shh, and fgf-4, while fgf-8, en-1, and wnt-7a expression remained unaltered. Occasional posterior truncations were observed at low incidence in the longest deficiency window; otherwise, the deficiency window length had no discernable impact on the severity of these changes. At the 45-somite stage, RA-deficient limbs had additional losses of hoxd-13 and fgf-8, accompanied by a flattened AER, suggestive of an ultimate failure in limb bud outgrowth. Results could not confirm a function for endogenous retinoids in limb initiation, but show they are required to maintain the signaling loops between the developing mesenchyme and AER that govern limb outgrowth after the initial emergence of limb bud.
Abnormalities, Multiple↗
The functions of 4-alpha-glucanotransferases and their use for the production of cyclic glucans.
Explore the source record for details and available documents.
Amino Acid Sequence↗
Gravity and space flight: effects on nutritional status.
The final decade of the millennium has seen an enormous amount of on-orbit life sciences research, including both short- and long-duration flight research. Life sciences dedicated Space Shuttle flights have made intensive research opportunities available to study on the acute adaptation to weightlessness. The NASA/Mir Science Program combined resources of the USA and Russia to provide the first long-duration flight opportunities for the United States since the Skylab program of the early 1970s. Many of the results of these studies are still being evaluated, and in some cases data are still being collected to assess long-term readaptation to gravity after several months in weightlessness. The surge in life sciences research during this decade serves as a preamble to the opportunities to be provided by the latest addition to the Earth-orbiting structures--the International Space Station.
Bone Density↗
Characterization of human Mycobacterium bovis bacille Calmette-Guérin-reactive CD8+ T cells.
Gamma interferon (IFN-gamma)-secreting CD4+ T cells have long been established as an essential component of the protective immune response against Mycobacterium tuberculosis. It is now becoming evident from studies with the murine model of tuberculosis that an important role also exists for major histocompatibility complex (MHC) class I-restricted CD8+ T cells. These cells are capable of acting as both IFN-gamma secretors and cytotoxic T lymphocyte (CTL) effectors; however, their exact role in immunity against tuberculosis remains unclear. This study demonstrates the presence of Mycobacterium bovis BCG-reactive CD8+ T cells in healthy BCG-vaccinated donors and that these CD8+ T cells are potent cytokine producers as well as cytotoxic effector cells. Using FACScan analysis, we have shown that restimulation with live M. bovis BCG induced more CD8+-T-cell activation than the soluble antigen purified protein derivative and that these cells are actively producing the type 1 cytokines IFN-gamma and tumor necrosis factor alpha (TNF-alpha). These CD8+ T cells also contain the cytolytic granule perforin and are capable of acting as potent CTLs against M. bovis BCG-infected macrophages. The mycobacterial antigens 85A and B (Ag85A and Ag85B, respectively), and to a lesser extent the 19- and 38-kDa proteins, are major antigenic targets for these mycobacterium-specific CD8+ T cells, while whole-M. bovis BCG activated effector cells from these BCG-vaccinated donors, as expected, failed to recognize the 6-kDa ESAT-6 protein. The use of metabolic inhibitors and blocking antibodies revealed that the CD8+ T cells recognize antigen processed and presented via the classical MHC class I pathway. These data suggest that CD8+ T cells may play a critical role in the human immune response to tuberculosis infection.
Antigen Presentation↗
Calcium metabolism before, during, and after a 3-mo spaceflight: kinetic and biochemical changes.
The loss of bone during spaceflight is considered a physiological obstacle for the exploration of other planets. This report of calcium metabolism before, during, and after long-duration spaceflight extends results from Skylab missions in the 1970s. Biochemical and endocrine indexes of calcium and bone metabolism were measured together with calcium absorption, excretion, and bone turnover using stable isotopes. Studies were conducted before, during, and after flight in three male subjects. Subjects varied in physical activity, yet all lost weight during flight. During flight, calcium intake and absorption decreased up to 50%, urinary calcium excretion increased up to 50%, and bone resorption (determined by kinetics or bone markers) increased by over 50%. Osteocalcin and bone-specific alkaline phosphatase, markers of bone formation, increased after flight. Subjects lost approximately 250 mg bone calcium per day during flight and regained bone calcium at a slower rate of approximately 100 mg/day for up to 3 mo after landing. Further studies are required to determine the time course of changes in calcium homeostasis during flight to develop and assess countermeasures against flight-induced bone loss.
Calcium↗
National probability samples in studies of low-prevalence diseases. Part II: Designing and implementing the HIV cost and services utilization study sample.
OBJECTIVE: The design and implementation of a nationally representative probability sample of persons with a low-prevalence disease, HIV/AIDS. DATA SOURCES/STUDY SETTING: One of the most significant roadblocks to the generalizability of primary data collected about persons with a low-prevalence disease is the lack of a complete methodology for efficiently generating and enrolling probability samples. The methodology developed by the HCSUS consortium uses a flexible, provider-based approach to multistage sampling that minimizes the quantity of data necessary for implementation. STUDY DESIGN: To produce a valid national probability sample, we combined a provider-based multistage design with the M.D.-colleague recruitment model often used in non-probability site-specific studies. DATA COLLECTION: Across the contiguous United States, reported AIDS cases for metropolitan areas and rural counties. In selected areas, caseloads for known providers for HIV patients and a random sample of other providers. For selected providers, anonymous patient visit records. PRINCIPAL FINDINGS: It was possible to obtain all data necessary to implement a multistage design for sampling individual HIV-infected persons under medical care with known probabilities. Taking account of both patient and provider nonresponse, we succeeded in obtaining in-person or proxy interviews from subjects representing over 70 percent of the eligible target population. CONCLUSIONS: It is possible to design and implement a national probability sample of persons with a low-prevalence disease, even if it is stigmatized.
Data Collection↗
Physiological adaptations to space flight.
Over the last 30 years, humans have extended their stays in space from a brief suborbial flight of 15 minutes to an orbital residence of 440+ days. Complex spacecraft now routinely transport humans into an environment more forbidding than any previously encountered. Nutrition can play an important role in counteracting some of the physiological effects of microgravity, and have a profound effect on the quality of life in space. As we embark on extended-duration flights, nutrition becomes a critical issue. This article reviews the physiological adaptations to space flight that affect nutritional requirements.
Adaptation, Physiological↗
Nutritional biochemistry of space flight.
Humans have flown in space for more than 35 years. Since that time, Americans have walked on the moon, launched two space stations (Skylab and the International Space Station), docked during orbit with a Soviet Soyuz space capsule and the Russian Mir space station, flown the only reusable space vehicle, and visited a Russian space station for more then 6 months at a time. Nutritional intake has not been considered a high priority during relatively brief flights of the Space Shuttle and other programs (i.e., less than 21 days). However, as we embark on extended-duration (i.e., > 30 days up to several years) missions, nutrition becomes a critical issue. The impact of weightlessness on human physiology is profound. We are in the very early stages of understanding how space flight affects nutrient requirements and related issues such as absorption, metabolism, and excretion. Apart from the obvious role of providing energy and required nutrients, nutrition is also important in terms of enhancing psychosocial interactions among crews, and ameliorating some of the effects of microgravity on the body (i.e., acting as a "countermeasure"). The interrelationships among space flight, nutrition, and physiology suggest that a program of specified nutritional intake may be required to enhance mission safety and crew productivity. Defining which nutrients are essential for the space flight environment depends on a more complete understanding of how weightlessness affects physiology. Providing the required nutrients is also limited by the types of foods that can be provided by the food system on board the space craft, and the dietary habits of space crews.
Adaptation, Physiological↗
Critical path plan for food and nutrition research required for planetary exploration missions.
In preparation for future planetary exploration, NASA-Johnson Space Center has developed a critical path plan for food and nutrition research needs. The plan highlights the risk factors pertaining to food and nutrition associated with exposure to the space flight environment as well as the possible consequences if no corrective measures are implemented. Included in the plan are the initiating events such as microgravity, remote environment and mission duration, which obviously impact the risk factors. The plan includes points of intervention where mitigating factors can be implemented to avoid outcomes such as malnutrition and unsafe foods. Physiological changes induced by lack of gravity, as well as increased exposure to radiation, may alter nutrient bio-availability, and/or nutrient requirements. An inadequate food system, whether due to technical limitations or nutritional shortcomings, can result in serious consequences. Additionally, microbial and chemical food contamination or psychological factors such as depression may lead to insufficient food intake. Critical questions define areas where further research is required to eliminate or ameliorate the risk from each of those factors. These questions delineate priorities for NASA food and nutrition research for planetary exploration missions.
Aerospace Medicine↗
Membrane capacitance changes induced by thrombin and calcium in single endothelial cells cultured from human umbilical vein.
1. Vesicular secretion from single human umbilical vein endothelial cells (HUVECs) was monitored by changes in membrane capacitance (Cm). Secretion was evoked by dialysis with strongly buffered intracellular free Ca2+ concentrations ([Ca2+]i), flash photolysis of Ca2+-loaded DM-nitrophen or caged InsP3, or by thrombin. [Ca2+]i was monitored spectrofluorimetrically with furaptra. The results show that a large, slowly rising component of vesicular secretion requires prolonged exposure to high [Ca2+]i. 2. Cm increased during intracellular perfusion with [Ca2+] buffered in the range 1.0-20 microM. Changes in Cm comprised an initial slowly rising small component of 0.1-0.5 pF followed by a faster rising larger component of up to approximately 7 pF, seen when [Ca2+]i > 2 microM and which was maximal at 10-20 microM Ca2+. 3. Thrombin evoked rapid initial elevations of [Ca2+]i to a peak of 7.1 +/- 1.5 microM (mean +/- s.e. m., n = 5) that declined within approximately 20-30 s with thrombin present either to resting levels or to a maintained elevated level of 2.0 +/- 0.7 microM (mean +/- s.e.m., range 1.0-3.6 microM, n = 3). Transient [Ca2+]i rises were associated with small, slowly rising increases in Cm of 0.1-0.2 pF, that recovered to pre-application levels over 2-3 min. Maintained elevations of [Ca2+]i caused larger, faster-rising sustained increases in Cm to 1.14 +/- 0.12 pF (mean +/- s.e.m., n = 3). Separate specific enzyme-linked immunosorbent assay (ELISA) showed that 1.0 U ml-1 thrombin produced secretion of von Willebrand factor in HUVEC cultures. 4. Short-lived [Ca2+]i elevations with a peak of 3-25 microM and a duration of approximately 20 s generated by flash photolysis of caged InsP3 or DM-nitrophen produced either no net change in Cm, or small slow increases of approximately 0.1-0.6 pF at up to 5 fF s-1 that recovered to pre-flash levels over 2-3 min. 5. Maintained elevations of [Ca2+]i in the range 1-28 microM produced by flash photolysis of DM-nitrophen caused large increases in Cm, up to approximately 4 pF, corresponding to approximately 25-30 % of the initial cell Cm. The maximum rate of change of Cm was up to 50 fF s-1 at steady [Ca2+] up to 20 microM; Cm recovered towards pre-flash levels only when [Ca2+] had declined.
Acetates↗