Inter-site and inter-scanner diffusion MRI data harmonization.

We propose a novel method to harmonize diffusion MRI data acquired from multiple sites and scanners, which is imperative for joint analysis of the data to significantly increase sample size and statistical power of neuroimaging studies. Our method incorporates the following main novelties: i) we take into account the scanner-dependent spatial variability of the diffusion signal in different parts of the brain; ii) our method is independent of compartmental modeling of diffusion (e.g., tensor, and intra/extra cellular compartments) and the acquired signal itself is corrected for scanner related differences; and iii) inter-subject variability as measured by the coefficient of variation is maintained at each site. We represent the signal in a basis of spherical harmonics and compute several rotation invariant spherical harmonic features to estimate a region and tissue specific linear mapping between the signal from different sites (and scanners). We validate our method on diffusion data acquired from seven different sites (including two GE, three Philips, and two Siemens scanners) on a group of age-matched healthy subjects. Since the extracted rotation invariant spherical harmonic features depend on the accuracy of the brain parcellation provided by Freesurfer, we propose a feature based refinement of the original parcellation such that it better characterizes the anatomy and provides robust linear mappings to harmonize the dMRI data. We demonstrate the efficacy of our method by statistically comparing diffusion measures such as fractional anisotropy, mean diffusivity and generalized fractional anisotropy across multiple sites before and after data harmonization. We also show results using tract-based spatial statistics before and after harmonization for independent validation of the proposed methodology. Our experimental results demonstrate that, for nearly identical acquisition protocol across sites, scanner-specific differences can be accurately removed using the proposed method.

Pregnenolone as a novel therapeutic candidate in schizophrenia: emerging preclinical and clinical evidence.

Emerging preclinical and clinical evidence suggests that pregnenolone may be a promising novel therapeutic candidate in schizophrenia. Pregnenolone is a neurosteroid with pleiotropic actions in rodents that include the enhancement of learning and memory, neuritic outgrowth, and myelination. Further, pregnenolone administration results in elevations in downstream neurosteroids such as allopregnanolone, a molecule with neuroprotective effects that also increases neurogenesis, decreases apoptosis and inflammation, modulates the hypothalamic-pituitary-adrenal axis, and markedly increases GABA(A) receptor responses. In addition, pregnenolone administration elevates pregnenolone sulfate, a neurosteroid that positively modulates NMDA receptors. There are thus multiple mechanistic possibilities for pregnenolone as a potential therapeutic agent in schizophrenia, including the amelioration of NMDA receptor hypofunction (via metabolism to pregnenolone sulfate) and the mitigation of GABA dysregulation (via metabolism to allopregnanolone). Additional evidence consistent with a therapeutic role for pregnenolone in schizophrenia includes neurosteroid changes following administration of certain antipsychotics in rodent models. For example, clozapine elevates pregnenolone levels in rat hippocampus, and these increases may potentially contribute to its superior antipsychotic efficacy [Marx et al. (2006a) Pharmacol Biochem Behav 84:598-608]. Further, pregnenolone levels appear to be altered in postmortem brain tissue from patients with schizophrenia compared to control subjects [Marx et al. (2006c) Neuropsychopharmacology 31:1249-1263], suggesting that neurosteroid changes may play a role in the neurobiology of this disorder and/or its treatment. Although clinical trial data utilizing pregnenolone as a therapeutic agent in schizophrenia are currently limited, initial findings are encouraging. Treatment with adjunctive pregnenolone significantly decreased negative symptoms in patients with schizophrenia or schizoaffective disorder in a pilot proof-of-concept randomized controlled trial, and elevations in pregnenolone and allopregnanolone post-treatment with this intervention were correlated with cognitive improvements [Marx et al. (2009) Neuropsychopharmacology 34:1885-1903]. Another pilot randomized controlled trial recently presented at a scientific meeting demonstrated significant improvements in negative symptoms, verbal memory, and attention following treatment with adjunctive pregnenolone, in addition to enduring effects in a small subset of patients receiving pregnenolone longer-term [Savitz (2010) Society of Biological Psychiatry Annual Meeting New Orleans, LA]. A third pilot clinical trial reported significantly decreased positive symptoms and extrapyramidal side effects following adjunctive pregnenolone, in addition to increased attention and working memory performance [Ritsner et al. (2010) J Clin Psychiatry 71:1351-1362]. Future efforts in larger cohorts will be required to investigate pregnenolone as a possible therapeutic candidate in schizophrenia, but early efforts are promising and merit further investigation. This article is part of a Special Issue entitled: Neuroactive Steroids: Focus on Human Brain.

Comorbid posttraumatic stress disorder is associated with suicidality in male veterans with schizophrenia or schizoaffective disorder.

The purpose of this study was to determine if patients with schizophrenia or schizoaffective disorders and comorbid posttraumatic stress disorder (PTSD) are at higher risk for suicidality than patients without comorbid PTSD. Participants were 165 male veterans with primary diagnoses of schizophrenia or schizoaffective disorder. Those with comorbid PTSD reported higher rates of suicidal ideation and suicidal behaviors compared to those without comorbid PTSD. These findings suggest that patients with comorbid PTSD are at higher risk for suicidality. Enhanced screening and targeted interventions may be warranted to address comorbid PTSD and increased suicide risk in this population.

Treatments for schizophrenia: a critical review of pharmacology and mechanisms of action of antipsychotic drugs.

The treatment of schizophrenia has evolved over the past half century primarily in the context of antipsychotic drug development. Although there has been significant progress resulting in the availability and use of numerous medications, these reflect three basic classes of medications (conventional (typical), atypical and dopamine partial agonist antipsychotics) all of which, despite working by varying mechanisms of actions, act principally on dopamine systems. Many of the second-generation (atypical and dopamine partial agonist) antipsychotics are believed to offer advantages over first-generation agents in the treatment for schizophrenia. However, the pharmacological properties that confer the different therapeutic effects of the new generation of antipsychotic drugs have remained elusive, and certain side effects can still impact patient health and quality of life. Moreover, the efficacy of antipsychotic drugs is limited prompting the clinical use of adjunctive pharmacy to augment the effects of treatment. In addition, the search for novel and nondopaminergic antipsychotic drugs has not been successful to date, though numerous development strategies continue to be pursued, guided by various pathophysiologic hypotheses. This article provides a brief review and critique of the current therapeutic armamentarium for treating schizophrenia and drug development strategies and theories of mechanisms of action of antipsychotics, and focuses on novel targets for therapeutic agents for future drug development.

Cytokine effects on cortical neuron MAP-2 immunoreactivity: implications for schizophrenia.

BACKGROUND: Cytokines demonstrate diverse actions in the brain and modulate systemic and central nervous system (CNS) responses to injury, infection, and inflammation. Cytokines in the CNS are elevated during infection and ischemia, two neurodevelopmental insults associated with increased schizophrenia risk. We hypothesize that cytokine-mediated neuronal injury during development may contribute to schizophrenia pathophysiology, causing subtle alterations in neuronal number and density. METHODS: We examined cytokine regulation of neuronal number in embryonic day 18 rat cortical cultures using MAP-2 immunohistochemistry. Mixed cultures derived from frontal cortex were fixed and stained after 48-hour exposure to the proinflammatory interleukin-1beta (IL-1beta), interleukin-6 (IL-6), or tumor necrosis factor-alpha (TNF-alpha; 0, 10, 100, or 1000 units/mL). RESULTS: IL-1beta (maximum effect 35%) and IL-6 (maximum effect 29%) produced dose-dependent decreases in the number of cells (neurons) immunoreactive for MAP-2 antibody, suggesting decreased neuronal survival. TNF-alpha also tended to decrease MAP-2 immunostaining at the highest dose tested. CONCLUSIONS: Our data suggest a role for cytokines in the modulation of neuronal survival during neurodevelopment, a finding potentially relevant to schizophrenia pathophysiology. If cytokine-mediated neuronal injury proves to be a common response to gestational insults associated with increased schizophrenia risk, the pharmacologic modulation of these molecules may have clinical utility.

Neurosteroid modulation of embryonic neuronal survival in vitro following anoxia.

Neurosteroids are synthesized de novo in the brain from cholesterol or peripheral steroid precursors and modulate inhibitory gamma-aminobutyric acid (GABA(A)) and excitatory N-methyl-D-aspartate (NMDA) receptors. Evidence indicates that neurosteroids are neuroprotective and important during neurodevelopment. We tested the hypothesis that neurosteroids increase embryonic neuronal survival following anoxia in rat embryonic day 18 cerebral cortical cultures to examine potential neurosteroid modulation of this insult during early development. Twenty-four hours after plating in serum-free medium, cultures were exposed to DHEA, DHEAS, or allopregnanolone (10(-10), 10(-8), or 10(-6) M), or vehicle, for 24 h (n=9 per treatment condition). Cultures were then subjected to anoxia for 2 h and subsequently reincubated for 24 h prior to neuron immunostaining with microtubule-associated protein 2 (MAP-2) antibody. Supernatant from DHEA and DHEAS-exposed cultures was tested for 17beta-estradiol metabolite formation by radioimmunoassay. DHEA 10(-6) and 10(-8) M significantly increased neuron survival by 85-87% following anoxia. DHEAS 10(-6) M significantly increased neuron survival by 74% following anoxia, but DHEAS 10(-10) M decreased neuron survival after this insult. Allopregnanolone had modest effects on neuron survival that did not attain statistical significance. 17beta-Estradiol concentrations were below the limit of detection in all specimens tested (sensitivity 4.7 nM). Our data indicate that pretreatment with DHEA and DHEAS at physiologically relevant concentrations promotes neuronal survival following anoxia in embryonic rat cerebral cortical cultures, and that these effects are not secondary to 17beta-estradiol metabolite formation. DHEA and DHEAS modulation of anoxia in embryonic neurons may be relevant to disorders of neurodevelopment involving this insult.

Olanzapine increases allopregnanolone in the rat cerebral cortex.

BACKGROUND: The neurosteroid allopregnanolone (3alpha-hydroxy-5alpha-pregnan-20-one) has anxiolytic and anticonvulsant properties, potentiating GABA(A) receptor chloride channel function with 20-fold higher potency than benzodiazepines. Behavioral studies demonstrate that olanzapine has anxiolyticlike properties in animals, but the mechanism responsible for these effects is not clear. We examined the effect of acute olanzapine administration on cerebral cortical allopregnanolone and its relationship to serum progesterone and corticosterone levels in rats. METHODS: Male Sprague-Dawley rats were habituated to intraperitoneal (IP) saline injection for 5 days. On the day of the experiment, rats were injected with olanzapine (0, 2.5, 5.0, or 10.0 mg/kg IP, 10-11 rats per condition). Rats were sacrificed 1 hour later, and cerebral cortical allopregnanolone levels and serum progesterone and corticosterone levels were measured by radioimmunoassay. RESULTS: Olanzapine increases cerebral cortical allopregnanolone up to fourfold, depending on dose. Positive correlations were observed between cerebral cortical allopregnanolone and serum progesterone levels and between cerebral cortical allopregnanolone and serum corticosterone levels. CONCLUSIONS: Olanzapine-induced increases in the potent GABA(A) receptor modulator allopregnanolone may alter GABAergic neurotransmission, possibly contributing to antipsychotic efficacy. If allopregnanolone alterations are linked to psychotic symptom relief, neurosteroids may represent molecules for pharmacologic intervention.

Nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 levels in human amniotic fluid.

OBJECTIVE: Neurotrophins are proteins that promote neuronal growth and differentiation. In this pilot study we determined whether the neurotrophins nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3 were present in amniotic fluid specimens to begin to elucidate their developmental regulation. We also explored associations between neurotrophin levels and central nervous system abnormalities and exposure to infection. STUDY DESIGN: One hundred thirty-four amniotic fluid specimens were obtained from women undergoing amniocentesis at University of North Carolina Hospitals. Each specimen was assayed by enzyme-linked immunosorbent assay for nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3. Associations of maternal age, gestational age, and maternal ethnicity with neurotrophin levels were explored. Neurotrophin levels in pregnancies in which there was enlargement of the fetal cerebral lateral ventricles or exposure to infection were compared with those in control pregnancies. Spearman correlational analyses and analyses of covariance were performed, with adjustment for gestational age. RESULTS: Nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3 were detected in all amniotic fluid specimens. Nerve growth factor increased with gestational age (P =.045). Brain-derived neurotrophic factor decreased with gestational age (P =.035). Patients with ventriculomegaly (with or without other central nervous system abnormalities) on ultrasonographic examination (n = 6) had significantly lower nerve growth factor levels than control subjects (P =.0046); patients with evidence of infection (n = 5) during pregnancy had significantly lower nerve growth factor (P =.0037) and brain-derived neurotrophic factor (P =.0362) levels. CONCLUSIONS: Nerve growth factor, brain-derived neurotrophic factor, and neurotrophin 3 are detectable in amniotic fluid and vary with gestational age. Decreased nerve growth factor and brain-derived neurotrophic factor levels in amniotic fluid may be a marker for the presence of central nervous system abnormalities, infectious insults in utero, or both.

Psychoneuroendocrinology of schizophrenia.

The study of psychoneuroendocrinology of schizophrenia has yielded an extensive but inconclusive body of data. Investigations to date have been limited by several factors, including the confounding effects of neuroleptic drugs, methodological limitations, and lack of appreciation for the heterogeneity of the illness. Previously, the focus of research has been on the measurement of anterior pituitary hormones, guided by the assumptions that these hormones are regulated by the central nervous system (CNS) to a significant degree and that the unique anatomic relationship of the pituitary gland to the hypothalamus and the CNS is potentially relevant. Patients with schizophrenia do appear to have distinct endocrinologic profiles. However, although the hormonal differences between patients with schizophrenia and the general population appear to be subtle in magnitude. Nonetheless, investigation, and the exploration of the possible effect of gonadal and posterior pituitary hormones merits particular attention.

Laboratory and clinical evaluation of Mycobacterium xenopi isolates.

Mycobacterium xenopi and Mycobacterium avium complex (MAC) are biochemically similar. To define the laboratory characteristics of M. xenopi that distinguish it from MAC, 53 M. xenopi isolates from different areas in the United States and 47 isolates recovered at one hospital were evaluated by 13 biochemical tests, AccuProbe MAC (Gen-Probe, Inc., San Diego, CA, USA), colony morphology, formation of X-colonies, pigmentation in response to light, growth on MacConkey agar without crystal violet, and relative growth rates at 25 degrees C, 36 degrees C, and 45 degrees C on solid media. Relative growth rates of 10 M. xenopi and 11 MAC isolates were measured at 25 degrees C, 36 degrees C, and 42 degrees C in Middlebrook broth processed using the BACTEC TB System. Ten M. xenopi were tested for p-nitro-alpha-acetylamino-beta-hydroxypropiophenone inhibition at 36 degrees C and 42 degrees C. Reevaluation of 81 isolates previously identified as MAC by biochemical tests alone revealed that two were M. xenopi. The most reliable characteristics distinguishing M. xenopi from MAC were the presence of X-colonies (M. xenopi 97% vs MAC 1%), positive 3-day arylsulfatase (M. xenopi 88% vs MAC 1%), growth at 25 degrees C (M. xenopi 0% vs MAC 100%), and AccuProbe MAC test results (M. xenopi 0% hybridized). Retrospective chart review of 37 patients using American Thoracic Society criteria revealed that six (16%) patients had clinically important isolates. At one of our hospitals M. xenopi was the second most common mycobacterial species isolated for 1990-1992, accounting for 27% of all isolates, whereas at our other hospital it accounted for 1% of isolates.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical impact of bacteria and fungi recovered only from broth cultures.

We prospectively evaluated 356 bacteria and fungi recovered from broth enrichment tubes from cultures with sterile direct plates to determine the clinical impact of isolates recovered only from broth cultures. These "broth only" isolates (BOI) were classified as contaminants or true on the basis of review of patient charts. True isolates were considered clinically relevant only if they altered or should have altered patient management. Of 356 BOI, 259 (73%) were considered contaminants (mostly coagulase-negative staphylococci and Propionibacterium spp.) and 97 (27%) were considered true. For individual microorganisms, 9 of 9 (100%) Staphylococcus aureus isolates, 13 of 13 (100%) members of the family Enterobacteriaceae, 10 of 12 (83%) fungi, 7 of 10 (70%) enterococci, 7 of 11 (64%) other gram-negative bacilli, 13 of 31 (45%) anaerobic bacteria, 10 of 24 (42%) streptococci, 22 of 140 (16%) coagulase-negative staphylococci, 6 of 92 (7%) Propionibacterium spp., and 0 of 14 (0%) diphtheroids and Bacillus spp. were classified as true. Eleven of 97 (11%) patients with true BOI had clinically relevant isolates. Fifty-nine of the 97 (61%) patients with true isolates already were on therapy, and no change was made because of the BOI. Six (6%) patients with contaminants received therapy for their BOI. We conclude that broth inoculated as an adjunct to direct plating seldom yields results that favorably alter patient management and could be omitted for most specimens without compromising patient care.

Fecal leukocytes in stool specimens submitted for Clostridium difficile toxin assay.

To determine their diagnostic utility, fecal leukocytes were sought by methylene blue stain in 502 consecutive stool specimens submitted for Clostridium difficile toxin assay. In addition, the stability of fecal leukocytes was assessed by daily examination of 23 stool specimens stored at 4 degrees C and room temperature. The sensitivity, specificity, and positive and negative predictive values of fecal leukocytes in predicting C. difficile toxin assay results were 28%, 92%, 27%, and 93%, respectively. At 4 degrees C, fecal leukocytes retained morphology for a minimum of 3 days. Leukocytes survived as long in stool specimens containing either C. difficile toxin or an enteric pathogen as they did in stool specimens with neither finding. We conclude that testing stool specimens for fecal leukocytes is not useful for predicting the presence of C. difficile toxin, because 72% of stool specimens positive for C. difficile toxin are negative for fecal leukocytes despite their stability.