Detection of HIV-1 gene sequences in hippocampal neurons isolated from postmortem AIDS brains by laser capture microdissection

We employed laser capture microdissection to remove individual pyramidal neurons from the CA1, CA3, and CA4 regions of formalin-fixed, paraffin-embedded hippocampus from 8 AIDS brains and 2 HIV-1-seronegative normal brains. We amplified HIV-1 gag and nef gene sequences using separate, double round PCR reactions for each of the primer sets. In all 3 hippocampal regions, amplification efficiency was best with sequence length between 284 and 324 bp; HIV-1 nef gene sequences were more common than HIV-1 gag sequences; and rank order for percent positive amplification was CA3 > CA4 > CA1 samples. These results are the first to detect HIV-1 gene sequences in microdissected human tissue. They indicate that brain neurons in vivo contain HIV-1 DNA sequences consistent with latent infection by this virus, and suggest that neurons display a selective vulnerability for HIV infection. Neuronal HIV infection could contribute to neuronal injury and death or act as a potential viral reservoir if reactivated.

Liquid chromatography-tandem mass spectrometric quantitation of cyclophosphamide and its hydroxy metabolite in plasma and tissue for determination of tissue distribution

Cyclophosphamide (CP) and its metabolite, hydroxycyclophosphamide (OH-CP) have been quantitated in mouse plasma and tissue by derivatization combined with liquid chromatography-tandem mass spectrometry (LC-MS-MS). The derivatization was conducted immediately upon sample collection, to trap the OH-CP metabolite intermediate prior to further conversion to phosphoramide mustard or other reaction products. This simple and straightforward derivatization procedure, combined with sample extraction via protein precipitation, allowed quantitation of CP and the oxime derivative of OH-CP in plasma for concentrations ranging from approximately 12.5-3333 ng/ml, and in spleen tissue for concentrations of 1,250-50,000 ng/g. The short cycle time (2.5 min) of the LC-MS-MS method allowed high throughput analysis with minimal matrix interference. Mouse plasma levels were quantitated for doses of 40, 65 and 120 mg/kg; spleen concentrations were determined for mice dosed at 120 mg/kg. The CP and oxime plasma levels correlated well with dose amounts. The CP levels in the spleen and plasma were similar while the oxime levels in the spleen were significantly lower than the plasma.

Uncertainty and opposition of medical students toward assisted death practices

To explore medical students' views of assisted death practices in patient cases that describe different degrees and types of physical and mental suffering, an anonymous survey was administered to all students at one medical school. Respondents were asked about the acceptability of assisted death activities in five patient vignettes and withdrawal of life support in a sixth vignette. In the vignettes, actions were performed by four possible agents: the medical student personally; a referral physician; physicians in general; or non-physicians. Of 306 medical students, 166 (54%) participated. Respondents expressed opposition or uncertainty about assisted death practices in the five patient cases that illustrated severe forms of suffering which were secondary to amyotrophic lateral sclerosis, treatment-resistant depressive and somatoform disorders, antisocial and sexually violent behavior, or AIDS. Students supported the withdrawal of life support in the sixth vignette depicting exceptional futility secondary to AIDS. Students were especially opposed to their own involvement and to the participation of non-physicians in assisted death activities. Differences in views related to sex, religious beliefs, and personal philosophy were found. Medical students do not embrace assisted death practices, although they exhibit tolerance regarding the choices of medical colleagues. How these attributes of medical students will translate into future behaviors toward patients and peers remains uncertain. Medical educators must strive to understand the perspectives of physicians-in-training. Expanded, empirically informed education that is attuned to the attitudes of medical students may be helpful in fulfilling the responsibility of imparting optimal clinical care skills.

Effects of asynchrony and ear of presentation on the pitch of mistuned partials in harmonic and frequency-shifted complex tones

When a partial of a periodic complex is mistuned, its change in pitch is greater than expected. Two experiments examined whether these partial-pitch shifts are related to the computation of global pitch. In experiment 1, stimuli were either harmonic or frequency-shifted (25% of F0) complexes. One partial was mistuned by +/- 4% and played with leading and lagging portions of 500 ms each, relative to the other components (1 s), in both monaural and dichotic contexts. Subjects indicated whether the mistuned partial was higher or lower in pitch when concurrent with the other components. Responses were positively correlated with the direction of mistuning in all conditions. In experiment 2, stimuli from each condition were compared with synchronous equivalents. Subjects matched a pure tone to the pitch of the mistuned partial (component 4). The results showed that partial-pitch shifts are not reduced in size by asynchrony. Similar asynchronies are known to produce a near-exclusion of a mistuned partial from the global-pitch computation. This mismatch indicates that global and partial pitch are derived from different processes. The similarity of the partial-pitch shifts observed for harmonic and frequency-shifted stimuli suggests that they arise from a grouping mechanism that is sensitive to spectral regularity.

Ultrastructure of the periductal area of comedo carcinoma in situ of the breast

We have previously shown that the different biological natures of comedo ductal carcinoma in situ (DCIS) and non-comedo DCIS may, in part, be explained by the different expression patterns of tenascin, a large extracellular matrix protein, as observed by immunohistochemical studies. In the present study, we compared 8 cases of comedo DCIS with 5 cases of non-comedo DCIS by ultrastructural analysis, focusing on the myoepithelium, basal lamina, and tenascin-positive extracellular periductal stromal matrix. Our observations show that the comedo type DCIS frequently has an altered basal lamina, a looser and more disorganized collagenous matrix, and a general increase in stromal cellularity, including fibroblasts, lymphocytes, histiocytes and small blood vessels. In addition, in comedo DCIS, the lateral intercellular spaces between large myoepithelial cells that border the basal lamina are often expanded, compared to those of non-comedo DCIS. These results identify structural characteristics of comedo DCIS that may play a role in its greater preinvasive potential. They may also provide a structural basis for the different strategies that are needed for for clinical management of comedo DCIS, compared to non-comedo DCIS.

Detection of widespread fluids in the Tibetan crust by magnetotelluric studies

Magnetotelluric exploration has shown that the middle and lower crust is anomalously conductive across most of the north-to-south width of the Tibetan plateau. The integrated conductivity (conductance) of the Tibetan crust ranges from 3000 to greater than 20,000 siemens. In contrast, stable continental regions typically exhibit conductances from 20 to 1000 siemens, averaging 100 siemens. Such pervasively high conductance suggests that partial melt and/or aqueous fluids are widespread within the Tibetan crust. In southern Tibet, the high-conductivity layer is at a depth of 15 to 20 kilometers and is probably due to partial melt and aqueous fluids in the crust. In northern Tibet, the conductive layer is at 30 to 40 kilometers and is due to partial melting. Zones of fluid may represent weaker areas that could accommodate deformation and lower crustal flow.

Improved orthopaedic bone cement formulations based on rubber toughening

Poly(methylmethacrylate) (PMMA) bone cements have been used for the fixation of hip and knee implants since the early 1960s. Aseptic loosening, related to fracture of the PMMA, continues to be the primary mode of failure for these prostheses. Failed prostheses must be replaced causing additional expense and patient trauma. Furthermore, the average lifetime of the revised prosthesis is significantly lower than that of a primary prosthesis. Recent work by Moseley and co-workers led to the development of a promising new rubber toughened cement. It is comprised of a matrix of the traditional PMMA with dispersed rubber particles to modify mechanical properties and, in particular, improve fracture toughness. The fracture toughness of the experimental material was 167% greater than the toughness of a nontoughened control; however, the elastic modulus and compressive strength were reduced. The reductions in properties should not pose a clinical problem based on results of the implant model reported by Moseley. More serious concerns were mixing and delivery problems and high residual monomer concentrations. The formulation and chemical/mechanical characterization of new toughened acrylic formulations that have residual monomer levels equivalent to Simplex and better mixing properties are reported.

Hippocampal injury and alterations in neuronal chemokine co-receptor expression in patients with AIDS

Hippocampal neurons express high levels of HIV chemokine co-receptors, activation of which causes injury or death in vitro. To determine if their in vivo expression correlates with injury, we evaluated neuronal CXCR4 and CCR5 immunoreactivity and reactive gliosis in autopsy hippocampus of 10 control cases, 11 AIDS cases without HIV encephalitis (HIVnE) or opportunistic infections/lymphomas (OI/L), and 11 AIDS cases with HIV encephalitis (HIVE). All groups had higher CXCR4 and CCR5 expression in CA3 and CA4 neurons than CA1 neurons (p < 0.05). HIVE cases had increased neuronal CXCR4 and decreased neuronal CCR5 expression as well as increased numbers of hippocampal GFAP-positive astrocytes and LN3-positive microglia. Changes were most severe in CA3 and CA4 and lowest in CA1 regions. These findings also were noted in the 4 HIVE cases with neither hippocampal HIVE nor brain OI/L and in the HIVnE groups. This study quantitates the regional distribution of hippocampal neuronal CXCR4 and CCR5 and shows their respective increase and decrease in AIDS. It suggests a relationship between neuronal loss and gliosis with intensity of neuronal chemokine expression and raises the possibility of a selective vulnerability of hippocampal neurons to AIDS-related injury.

Exposure of transformed and non-transformed phagocytic cells to novel glass ionomers in culture

The use of glass ionomers as a novel bone cement is currently being investigated. Although acceptable for use as a dental restorative material, there is little information regarding how ionomers interact with inflammatory macrophage cell types. The specific objective of this experiment was to investigate the possible interrelationship between RAW and human monocyte/macrophage cells at the biochemical and morphological level after being in contact with three different dental cement ionomers (Fuji Duet, Fuji IX, and GC-Fuji-Ortho, GC America Inc., Chicago IL) for 72 hours. Transformed RAW macrophages were obtained from the American Type Culture collection (ATCC), and the non-transformed human macrophages were obtained from the peripheral blood of 25 male and female volunteers. The cells were plated at a density of 4 x 10(6) cells/ml in twenty-four well plates. Each plate was divided into four groups of six cells/group. Twenty-four hours after plating, the cells in groups I-III were incubated with Fuji Duet, Fuji IX, GC Fuji Ortho, respectively, and cells in Group IV were incubated with media alone to serve as controls. Immediately after addition of the ionomers, the cellular morphology was monitored for both transformed and non-transformed cells. Cell number data revealed that normal non-transformed cells were similar in number to control cells in media alone. This result suggests that the polymer treatment did significantly alter cellular viability. On the other hand, RAW cell number was markedly reduced in cells treated with ionomers in comparison to cell growing in media alone. The data suggests that the prescence of the ionomer may reduce the proliferation rate of RAW cells. Biochemical analysis of cellular supernatants to determine cellular alterations at 72 hours revealed increased levels of lactate dehydrogenase activity and levels of malionaldehyde bis diethyl acetal in all ionomer-treated groups of RAW cells compared with media alone. Non-transformed macrophages treated with the same ionomers did not differ significantly from the control cells in media alone. However, when comparing the levels of lactate dehydrogenase activity between the transformed and non-transformed cells it was apparent that the normal cells exhibited statistically higher activity than the RAW transformed cells. The results of this study suggest that although the three ionomers tested were found to be highly biocompatible with fully differentiated non-transformed macrophages, the behavior of transformed and non-transformed phagocytic cells towards these ionomers may not be similar under similar conditions.

Bioceramics surface modification by means of osteoclasts in culture

The specific objectives of this study was: (I) to investigate the effect of various biomedical ceramics such as tricalcium phosphate (TCP), hydroxyapatite (HA), and aluminum-calcium-phosphorous oxide (ALCAP) on the adherence and viability of mice osteoclasts (OT) in vitro, and (II) to evaluate the role of OT that might have on the surfaces of such bioceramics. The OT cells were isolated from adult male mice and seeded at a density of 5 x 10(5) cells/well according to standard laboratory procedures. Cells were plated in each micrometer-well pretreated with ceramic capsules (HA, TCP and ALCAP) and buffered control. At the end of 1, 2, 3 and 5 days, the viability and cell number of OT were determined using an established assay. Cell number was determined in control wells with known number of cells, and a standard curve was generated by plotting absorbency units versus cell number. Biochemical analysis was performed on the aliquots obtained from the experimental and control wells at the end of each phase of the investigation. The data from this experiment suggest that: (I) OT are capable of adhering to the surface of HA, TCP and ALCAP in an in vitro environment for over a 5-day period. (II) Long-term incubation of ceramic capsules with OT revealed that the cells experienced gradual disassociation phenomenon with a greater numbers of cell detachments seen in the ALCAP contained wells. (III) SEM analysis of representative capsules demonstrated that there was an increase in the number of micro/macropores on the surface of the materials after contacting a cellular environment. This observation suggest that the material surface has been modified (TCP > HA = ALCAP). Information obtained from this study provided new insights on the interrelationship between bioceramics and the possible OT response during chronic inflammation at the site of implantation.

Upregulation of glial clusterin in brains of patients with AIDs

Since clusterin (CLU) production in reactive astrocytes may be neuroprotective, we examined its distribution in AIDS brains where brain injury and reactive astrocytosis are common. The relative area and number of CLU-positive astrocytes, as well as their percent total of all white matter glia, significantly increased in AIDS brains with and without HIV encephalitis (P<0.05). Proliferation markers were absent. In contrast, the relative area and number of GFAP-positive astrocytes and their percent of all white matter glia, increased in some cases but the mean increases were not significant. Clusterin is sensitive marker of glial reactivity in AIDS brains and its enhanced expression was not dependent on increases in GFAP.

Improving child welfare performance through supervisory use of client outcome data

Despite their benefits, there is little evidence that outcome data are being widely used by program managers or field level supervisors. Three interdependent factors that facilitate the use of outcome data are well-constructed reports, and organizational culture that supports learning and outcome achievement, and managerial skills in interpreting data and taking relevant action. This article describes an outcome reporting package and training oriented toward frontline supervisors to help them use outcome data, shape a learning culture, interpret data, and take focused action toward improving outcomes for children and families.

Comparison of neuregulin-1 expression in olfactory ensheathing cells, Schwann cells and astrocytes

Recently we demonstrated that a member of the neuregulin-1 (NRG-1) family of growth factors is a mitogen and survival factor for olfactory ensheathing cells (OECs). OECs are specialized glial cells within the olfactory system that are believed to play a role in the continual nerve re-growth of this tissue. OECs share properties with both astrocytes and Schwann cells but are likely to be a distinct glial cell type. NRG-1s have been found to be important regulators of Schwann cells in vivo, but the role of NRG-1 for OECs is less clear. The nrg-1 gene produces at least 12 different isoforms, that are likely to have different functions, due to alternative splicing of its mRNA. In this study, the expression of NRG-1 mRNAs in OECs was compared with other glial cells and their corresponding tissue sources. Cultured glial cells, unlike their tissue sources, expressed NRG-1 mRNAs containing the alpha EGF-like domain and expressed only the type 1beta isoform that lacks the glycosylated spacer domain. This correlated with expression of these isoforms during olfactory nerve degeneration in vivo. Although OECs expressed mRNA for all NRG-1 isoforms, the protein could not be detected in concentrated supernatant, or on the cell surface by immunofluorescence, but was detected in the nucleus or cytoplasm (depending on the isoform). These data support the hypothesis that NRG-1s play a functional role in OEC biology.

Effects of differences in timbre on sequential grouping

Differences in the timbre of sounds in a sequence can affect their perceptual organization. Using a performance measure, Hartmann and Johnson (1991) concluded that streaming could be predicted primarily by the extent to which sounds were passed by different peripheral channels. However, results from a rating task by Dannenbring and Bregman (1976) suggested that sounds in the same spectral region (passed by the same peripheral channels) can be allocated to different streams. In Experiment 1, it was found, using an interleaved melody task, that target sounds could be selected from distractors in the same spectral region more easily when they differed in timbre. This finding might result from primitive stream segregation or schema-driven selection, but not from peripheral channeling. In Experiment 2, a rhythm discrimination task was used, requiring the sounds to be integrated for good performance. Differences in timbre impaired performance, indicating the occurrence of primitive stream segregation.

Effects of similarity in bandwidth on the auditory sequential streaming of two-tone complexes

We investigated the perceptual grouping of sequentially presented sounds--auditory stream segregation. It is well established that sounds heard as more similar in quality, or timbre, are more likely to be grouped into the same auditory stream. However, it is often unclear exactly what acoustic factors determine timbre. In this study, we presented various sequences of simple sounds, each comprising two frequency components (two-tone complexes), and measured their perceptual grouping. We varied only one parameter between trials, the intercomponent separation for some of the complexes, and examined the effects on stream segregation. Four hypotheses are presented that might predict the extent of streaming. Specifically, least streaming might be expected when the sounds were most similar in either (1) the frequency regions in which they have energy (maximum spectral overlap), (2) their auditory bandwidths, (3) their relative bandwidths, or (4) the rate at which the two components beat together (intermodulation rate). It was found that least streaming occurred when sounds were most similar in either their auditory or their relative bandwidths. Although these two hypotheses could not be distinguished, the results were clearly different from those predicted by hypotheses (1) and (4). The implications for models of stream segregation are discussed.

Separate mechanisms govern the selection of spectral components for perceptual fusion and for the computation of global pitch

The perceptual fusion of harmonics is often assumed to result from the operation of a template mechanism that is also responsible for computing global pitch. This dual-role hypothesis was tested using frequency-shifted complexes. These sounds are inharmonic, but preserve a regular pattern of equal component spacing. The stimuli had a nominal fundamental (F0) frequency of 200 Hz (+/- 20%), and were frequency shifted either by 25.0% or 37.5% of F0. Three consecutive components (6-8) were removed and replaced with a sinusoidal probe, located at one of a set of positions spanning the gap. On any trial, subjects heard a complex tone followed by an adjustable pure tone in a continuous loop. Subjects were well able to match the pitch of the probe unless it corresponded with a position predicted by the spectral pattern of the complex. Peripheral factors could not account for this finding. In contrast, hit rates were not depressed for probes positioned at integer multiples of the F0(s) corresponding to the global pitch(es) of the complex, predicted from previous data [Patterson, J. Acoust. Soc. Am. 53, 1565-1572 (1973)]. These findings suggest that separate central mechanisms are responsible for computing global pitch and for the perceptual grouping of partials.

Gene therapy of hepatocellular carcinoma in vitro and in vivo in nude mice by adenoviral transfer of the Escherichia coli purine nucleoside phosphorylase gene

Expression of viral or bacterial enzymes in tumor cells to convert nontoxic prodrugs into highly toxic metabolites is an attractive gene-therapeutic approach for the treatment of hepatocellular carcinoma (HCC). The Escherichia coli purine nucleoside phosphorylase (PNP) converts purine analogs into freely diffusible metabolites, which are highly toxic to dividing and nondividing cells. We investigated the antitumor effects of PNP in the human HCC cell lines, HepG2, Hep3B, and HuH-7, and performed a comparison with herpes simplex thymidine kinase (TK). The genes for PNP, TK, and enhanced green fluorescent protein (EGFP) were delivered to HCC cells by identical adenoviral vectors. Fludarabine and ganciclovir (GCV) served as prodrugs for PNP and TK, respectively. Expression of PNP highly sensitized HCC cells to fludarabine treatment. Fludarabine concentrations between 0.5 and 1 microg/mL killed 100% of the cells expressing PNP with no detectable toxicity in control cells expressing EGFP. Expression of PNP in as few as 10% of HCC cells induced efficient killing of most bystander cells. Expression of TK followed by GCV treatment produced a potent growth inhibition but failed to kill all TK-expressing HCC cells. More importantly, the TK system exhibited a lower degree of bystander effect. Adenoviral delivery of PNP followed by fludarabine administration prevented subcutaneous and intrahepatic tumor formation in nude mice and was also effective for the treatment of established tumors. These results demonstrate the potential of the PNP/fludarabine system for the treatment of HCC.

Detection of viral ribonucleic acid and histologic analysis of inflamed synovium in Ross River virus infection

OBJECTIVE

To document the histology of Ross River virus (RRV) arthritis and to examine inflamed synovium for viral RNA.

METHODS

Biopsy tissue from the inflamed knees of 12 patients with RRV infection was studied using conventional and immunostaining techniques. Reverse transcriptase-polymerase chain reaction technology was used to probe for the presence of viral RNA in the synovial biopsy samples and in serum.

RESULTS

Hyperplasia of the synovial lining layer, vascular proliferation, and mononuclear cell infiltration were the main histologic changes. RRV RNA was found in knee biopsy tissue that was obtained from 2 patients at 5 weeks after the onset of symptoms.

CONCLUSION

RRV RNA was identified in inflamed synovium more than a month after symptoms began. Inflammation was apparent in the absence of detectable virus in the majority of patients.

Enhanced immune response to the melanoma antigen gp100 using recombinant adenovirus-transduced dendritic cells

Glycoprotein 100 (gp100) is one of a series of well-characterized human melanoma-associated antigens expressed by most melanoma cells. Immunization of C57BL/6 mice with an adenovirus (Ad) vector encoding human gp100 (Adhgp100) has been shown to induce limited protective immunity against challenge with murine melanoma B16 cells. In the current study we determined whether gp100-specific immunity can be enhanced using bone-marrow-derived dendritic cells (DCs) transduced with Adhgp100 ex vivo. Subcutaneous injection of Adhgp100-infected DCs resulted in potent T-cell-mediated protective immunity and a greater than 80% reduction of established tumors when administered to B16 tumor-bearing hosts. Compared to direct injection of Adhgp100 vector alone, immunization with Adhgp100-infected DCs induced markedly greater antitumor activity. In vitro CTL analysis demonstrated that DC-Adhgp100 immunization activated both CD4(+) and CD8(+) CTLs, while no lytic activity was generated by vaccination with Adhgp100 alone. In vivo depletion of CD4(+) T cells, but not CD8(+) T cells, completely abrogated CTL activity, suggesting that Adhgp100-transduced DCs result in activation of both CD4(+) and CD8(+) CTLs via a CD4(+)-dependent mechanism. We speculate that this improved efficacy of Adhgp100-transduced DCs compared to direct immunization with Adhgp100 may be the result of direct DC-mediated CD4(+) T cell activation. These results emphasize the importance of CD4(+) T cells in the development of therapeutic antigen-specific cancer vaccines.

HIV infection of choroid plexus in AIDS and asymptomatic HIV-infected patients suggests that the choroid plexus may be a reservoir of productive infection

The choroid plexus (CPx) may be an important site of viral dissemination since monocytes and dendritic cells in its stroma are infected with HIV in AIDS patients and since the ratio of CPx to brain infection is more than 2 : 1. In order to see if CPx infection also develops in asymptomatic (ASY) HIV-infected patients, we examined archival formalin-fixed brain and CPx from 14 AIDS and seven ASY cases, using routine histology, immunohistochemistry for HIV gp41, and DNA extraction and gene amplification for HIV DNA. Eight of 14 AIDS (57%) had HIV-positive cells in the CPx and four (29%) had HIV encephalitis. Two of seven ASY cases (29%) had HIV-positive cells in the CPx but none had HIV encephalitis. Extracted DNA from brain, CPx and systemic organs of five ASY cases was amplified by nested PCR with or without Southern blotting for HIV env gene. It was positive in systemic organs in five cases; in CPx in four cases; and in brain in one case. This study shows that the CPx is a site of HIV infection in ASY patients and that the frequency of CPx infection is higher than seen in brain in both AIDS and ASY cases. The results are consistent with the hypothesis that the CPx may be a site for hematogeneous spread and a reservoir for HIV infection during the period of clinical latency.

Observations on centrifugation: application to centrifuge development

This report outlines the background to the development of an automated, serial, discrete centrifuge, reporting on the criteria considered essential in such an instrument. We established the criteria by examining the detailed logistics of centrifuge operation in a hospital laboratory. The mean sample load per run, using six centrifuges, was 13.6 samples, and the user-selectable cycle time ranged from 00:01:10 to 00:12:33 (hours:minutes:seconds) with a fixed g value of 1050. During the laboratory working window, (0900-1700), only 50% of the centrifuge capacity was utilized and more than one-third of the sample workload was delayed for >5 min because the centrifuges were not emptied promptly. In addition, 35% of the sample workload was centrifuged for less than the time prescribed in the operational specifications. Based on these findings, we designed a new continuous, serial centrifuge to overcome some of the deficiencies noted in the logistics study. The centrifuge operates continuously, nominally treating 150 samples/h, with a cycle time of 5 min at 1,000 g. The cycle time and g value are variable between limits, and their selection governs the throughput rate. Each sample is centrifuged separately in individual rotors mounted in a sturdy carousel with a periphery that traverses a load/unload station. There is no sample delay because of operator absence, and the capacity is fully utilized. The centrifuge can operate in a stand-alone capacity or has the capability of being integrated into a sample preparation system or as a direct front end for high-throughput analyzers.

Psychiatric research ethics: an overview of evolving guidelines and current ethical dilemmas in the study of mental illness

The field of psychiatry has an opportunity to construct a more refined, perhaps more enduring understanding of the ethical basis of mental illness research. The aim of this paper is to help advance this understanding by 1) tracing the evolution of the emerging ethic for biomedical experimentation, including recent recommendations of the President's National Bioethics Advisory Commission, and 2) reviewing data and concepts related to compelling ethical questions now faced in the study of mental disorders. Empirical findings on informed consent, the ethical safeguards of institutional review and surrogate decision making, and the relationship between scientific and ethical imperatives are outlined. Psychiatric researchers will increasingly be called upon to justify their scientific approaches and to seek ways of safeguarding the well-being of people with mental illness who participate in experiments. Most importantly, psychiatric investigators will need to demonstrate their appreciation and respect for ethical dimensions of investigation with special populations. Further empirical study and greater sophistication with respect to the distinct ethical issues in psychiatric research are needed. Although such measures present many challenges, they should not interfere with progress in neuropsychiatric science so long as researchers in our field seek to guide the process of reflection and implementation.