Biomedical subjects

W Irwin

Publications and source records attributed to W Irwin.

11 recordsLinked to original sources

PubMed2006

High concordance of drug-induced human hepatotoxicity with in vitro cytotoxicity measured in a novel cell-based model using high content screening.

To develop and validate a practical, in vitro, cell-based model to assess human hepatotoxicity potential of drugs, we used the new technology of high content screening (HCS) and a novel combination of critical model features, including (1) use of live, human hepatocytes with drug metabolism capability, (2) preincubation of cells for 3 days with drugs at a range of concentrations up to at least 30 times the efficacious concentration or 100 microM, (3) measurement of multiple parameters that were (4) morphological and biochemical, (5) indicative of prelethal cytotoxic effects, (6) representative of different mechanisms of toxicity, (7) at the single cell level and (8) amenable to rapid throughput. HCS is based on automated epifluorescence microscopy and image analysis of cells in a microtiter plate format. The assay was applied to HepG2 human hepatocytes cultured in 96-well plates and loaded with four fluorescent dyes for: calcium (Fluo-4 AM), mitochondrial membrane potential (TMRM), DNA content (Hoechst 33,342) to determine nuclear area and cell number and plasma membrane permeability (TOTO-3). Assay results were compared with those from 7 conventional, in vitro cytotoxicity assays that were applied to 611 compounds and shown to have low sensitivity (<25%), although high specificity ( approximately 90%) for detection of toxic drugs. For 243 drugs with varying degrees of toxicity, the HCS, sublethal, cytotoxicity assay had a sensitivity of 93% and specificity of 98%. Drugs testing positive that did not cause hepatotoxicity produced other serious, human organ toxicities. For 201 positive assay results, 86% drugs affected cell number, 70% affected nuclear area and mitochondrial membrane potential and 45% affected membrane permeability and 41% intracellular calcium concentration. Cell number was the first parameter affected for 56% of these drugs, nuclear area for 34% and mitochondrial membrane potential for 29% and membrane permeability for 7% and intracellular calcium for 10%. Hormesis occurred for 48% of all drugs with positive response, for 26% of mitochondrial and 34% nuclear area changes and 12% of cell number changes. Pattern of change was dependent on the class of drug and mechanism of toxicity. The ratio of concentrations for in vitro cytotoxicity to maximal efficaciousness in humans was not different across groups (12+/-22). Human toxicity potential was detected with 80% sensitivity and 90% specificity at a concentration of 30x the maximal efficacious concentration or 100 microM when efficaciousness was not considered. We conclude that human hepatotoxicity is highly concordant with in vitro cytotoxicity in this novel model and as detected by HCS.

Animal Testing Alternatives↗

PubMed2001

In vivo analysis of intramuscular gene transfer in human subjects studied by on-line ultrasound imaging.

The current study was designed to test the hypothesis that intramuscular (i.m.) injection of naked DNA leads to distribution of the injectate remote from the site of needle placement, a finding that might be expected to facilitate i.m. gene transfer. Transcutaneous ultrasound imaging was employed to monitor online the extent to which a solution of phVEGF165 was distributed among the skeletal musculature during 288 i.m. injections in 18 consecutive patients. In 237 (82.3%) of 288 muscle sites, the injection was performed into the distal calf muscle. In 51 (17.7%) of 288 muscle sites, injection was performed into the first and/or second interosseous muscles of the dorsal foot. Unperturbed muscle was recognized by a characteristic echogenic, stippled texture that was bounded by more intensely echogenic fascia. When i.m. gene transfer was performed into the calf muscles, the injectate was distributed along a longitudinal dimension of 3.59 +/- 0.79 cm (1.39-5.87 cm); the corresponding area of injectate measured by on-line planimetry was 1.83 +/- 0.51 cm2 (0.62-3.41 cm2). When i.m. gene transfer was performed into the interosseous muscles of the foot, the longitudinal extent of injectate distribution was 2.49 +/- 0.66 cm (1.61-3.91 cm), with a corresponding injectate area of 1.71 +/- 0.54 cm2 (0.51-2.86 cm2). These findings establish that a solution of plasmid DNA administered by direct i.m. injection into the skeletal muscles of the limb is distributed well beyond the site of needle entry. Thus, the use of multiple injections performed at different sites is likely to result in broad distribution of DNA injectate, a physical factor that may act to facilitate naked DNA and/or other gene transfer strategies.

DNA↗

PubMed2001

The effect of isolated soy protein on plasma biomarkers in elderly men with elevated serum prostate specific antigen.

PURPOSE: We performed a randomized double-blind crossover pilot study in elderly men with elevated prostate specific antigen (PSA) on the effects of the daily consumption of 2 soy beverages, each containing 20 gm. of isolated soy protein, on the isoflavone concentration in blood and urine, and on the 3 serum biomarkers cholesterol, PSA and the soluble p105 component of the p185erbB-2 proto-oncogene. MATERIALS AND METHODS: A total of 34 men supplemented their diet by consuming 1 of 2 soy protein beverages assigned randomly twice daily for a 6-week period. In a second 6-week period they consumed the other soy protein beverage. The beverage ISP+ provided 42 mg. of genistein and 27 mg. of daidzein daily, whereas the other beverage, ISP-, provided only 2.1 and 1.3 mg. of these isoflavones daily, respectively. Blood and 24-hour urine samples were obtained before the study, at 2-week intervals during the study and 2 weeks after study completion. RESULTS: ISP+ and to a lesser extent ISP- substantially increased the serum concentration and urinary output of the isoflavones and their metabolites. Serum cholesterol was significantly decreased by ISP+ irrespective of the order in which the 2 soy beverages were administered and in apparent correlation with the total isoflavone concentration. There was no significant effect of the soy beverages on serum PSA and p105erbB-2 values. CONCLUSIONS: This study reveals that short-term exposure of elderly men with elevated serum PSA values to soy protein containing isoflavones decreases serum cholesterol but not the serum biomarkers PSA and p105erbB-2.

Aged↗

PubMed2001

The brain decade in debate: III. Neurobiology of emotion.

This article is a transcription of an electronic symposium in which active researchers were invited by the Brazilian Society of Neuroscience and Behavior (SBNeC) to discuss the advances of the last decade in the neurobiology of emotion. Four basic questions were debated: 1) What are the most critical issues/questions in the neurobiology of emotion? 2) What do we know for certain about brain processes involved in emotion and what is controversial? 3) What kinds of research are needed to resolve these controversial issues? 4) What is the relationship between learning, memory and emotion? The focus was on the existence of different neural systems for different emotions and the nature of the neural coding for the emotional states. Is emotion the result of the interaction of different brain regions such as the amygdala, the nucleus accumbens, or the periaqueductal gray matter or is it an emergent property of the whole brain neural network? The relationship between unlearned and learned emotions was also discussed. Are the circuits of the former the underpinnings of the latter? It was pointed out that much of what we know about emotions refers to aversively motivated behaviors, like fear and anxiety. Appetitive emotions should attract much interest in the future. The learning and memory relationship with emotions was also discussed in terms of conditioned and unconditioned stimuli, innate and learned fear, contextual cues inducing emotional states, implicit memory and the property of using this term for animal memories. In a general way it could be said that learning modifies the neural circuits through which emotional responses are expressed.

Amygdala↗

PubMed2000

Functional neuroanatomy of the cognitive process of mapping during discourse comprehension.

We used functional magnetic resonance imaging (fMRI) to identify brain regions involved in the process of mapping coherent discourse onto a developing mental representation. We manipulated discourse coherence by presenting sentences with definite articles (which lead to more coherent discourse) or indefinite articles (which lead to less coherent discourse). Comprehending connected discourse, compared with reading unrelated sentences, produced more neural activity in the right than left hemisphere of the frontal lobe. Thus, the right hemisphere of the frontal lobe is involved in some of the processes underlying mapping. In contrast, left-hemisphere structures were associated with lower-level processes in reading (such as word recognition and syntactic processing). Our results demonstrate the utility of using fMRI to investigate the neural substrates of higher-level cognitive processes such as discourse comprehension.

Adult↗

PubMed1999

The functional neuroanatomy of emotion and affective style.

Recently, there has been a convergence in lesion and neuroimaging data in the identification of circuits underlying positive and negative emotion in the human brain. Emphasis is placed on the prefrontal cortex (PFC) and the amygdala as two key components of this circuitry. Emotion guides action and organizes behavior towards salient goals. To accomplish this, it is essential that the organism have a means of representing affect in the absence of immediate elicitors. It is proposed that the PFC plays a crucial role in affective working memory. The ventromedial sector of the PFC is most directly involved in the representation of elementary positive and negative emotional states while the dorsolateral PFC may be involved in the representation of the goal states towards which these elementary positive and negative states are directed. The amygdala has been consistently identified as playing a crucial role in both the perception of emotional cues and the production of emotional responses, with some evidence suggesting that it is particularly involved with fear-related negative affect. Individual differences in amygdala activation are implicated in dispositional affective styles and increased reactivity to negative incentives. The ventral striatum, anterior cingulate and insular cortex also provide unique contributions to emotional processing.

Journal Article↗

PubMed1998

Reproducibility of fMRI results across four institutions using a spatial working memory task.

Four U.S. sites formed a consortium to conduct a multisite study of fMRI methods. The primary purpose of this consortium was to examine the reliability and reproducibility of fMRI results. FMRI data were collected on healthy adults during performance of a spatial working memory task at four different institutions. Two sets of data from each institution were made available. First, data from two subjects were made available from each site and were processed and analyzed as a pooled data set. Second, statistical maps from five to eight subjects per site were made available. These images were aligned in stereotactic space and common regions of activation were examined to address the reproducibility of fMRI results when both image acquisition and analysis vary as a function of site. Our grouped and individual data analyses showed reliable patterns of activation in dorsolateral prefrontal cortex and posterior parietal cortex during performance of the working memory task across all four sites. This multisite study, the first of its kind using fMRI data, demonstrates highly consistent findings across sites.

Adult↗

PubMed1997

Manipulating affective state using extended picture presentations.

Separate, extended series of positive, negative, and neutral pictures were presented to 24 (12 men, 12 women) undergraduates. Each series was presented on a different day, with full counterbalancing of presentation orders. Affective state was measured using (a) orbicularis oculi activity in response to acoustic startle probes during picture presentation, (b) corrugator supercilii activity between and during picture presentation, and (c) changes in self-reports of positive and negative affect. Participants exhibited larger eyeblink reflex magnitudes when viewing negative than when viewing positive pictures. Corrugator activity was also greater during the negative than during the positive picture set, during both picture presentation and the period between pictures. Self-reports of negative affect increased in response to the negative picture set, and self-reports of positive affect were greatest following the positive picture set. These findings suggest that extended picture presentation is an effective method of manipulating affective state and further highlight the utility of startle probe and facial electromyographic measures in providing on-line readouts of affective state.

Adult↗

PubMed1997

Functional magnetic resonance imaging studies of emotional processing in normal and depressed patients: effects of venlafaxine.

BACKGROUND: Functional magnetic resonance imaging (fMRI) techniques were used to identify the neural circuitry underlying emotional processing in control and depressed subjects. Depressed subjects were studied before and after treatment with venlafaxine. This new technique provides a method to noninvasively image regional brain function with unprecedented spatial and temporal resolution. METHOD: Echo-planar imaging was used to acquire whole brain images while subjects viewed positively and negatively valenced visual stimuli. Two control subjects and two depressed subjects who met DSM-IV criteria for major depression were scanned at baseline and 2 weeks later. Depressed subjects were treated with venlafaxine after the baseline scan. RESULTS: Preliminary results from this ongoing study revealed three interesting trends in the data. Both depressed patients demonstrated considerable symptomatic improvement at the time of the second scan. Across control and depressed subjects, the negative compared with the positive pictures elicited greater global activation. In both groups, activation induced by the negative pictures decreased from the baseline scan to the 2-week scan. This decrease in activation was also present in the control subjects when they were exposed to the positive pictures. In contrast, when the depressed subjects were presented with the positive pictures they showed no activation at baseline, whereas after 2 weeks of treatment an area of activation emerged in right secondary visual cortex. CONCLUSION: While preliminary, these results demonstrate the power of using fMRI to study emotional processes in normal and depressed subjects and to examine mechanisms of action of antidepressant drugs.

Adolescent↗

PubMed1996

Human amygdala activation detected with echo-planar functional magnetic resonance imaging.

Echo-Planar functional magnetic resonance imaging (EP-fMRI) was used to study the activity of the amygdala while three normal female subjects viewed alternating blocks of affectively neutral and affectively negative still pictures. Bilateral activation in the amygdala that was significantly correlated with the changing valence of the visual stimuli was found in all three subjects. These findings are consistent with the large corpus of data from non-human studies suggesting that the amygdala is a key structure for extracting the affective significance from external stimuli. This is the first known report of phasic amygdala activation detected with EP-fMRI in normal human subjects responding to affective stimuli.

Adult↗

PubMed1995

Isla Vista virus: a genetically novel hantavirus of the California vole Microtus californicus.

Prospect Hill virus (PH) was isolated from a meadow vole (Microtus pennsylvanicus) in 1982, and much of its genome has been sequenced. Hantaviruses of other New World microtine rodents have not been genetically characterized. We show that another Microtus species (the California vole M. californicus) from the United States is host to a genetically distinct PH-like hantavirus, Isla Vista virus (ILV). The nucleocapsid protein of ILV differs from that of PH by 11.1% and a portion of the G2 glycoprotein differs from that of PH by 19.6%. ILV antibodies were identified in five of 33 specimens of M. californicus collected in 1975 and 1994-1995. Enzymatic amplification studies showed that 1975 and 1994-1995 ILV genomes were highly similar. Secondary infection of Peromyscus californicus was identified in Santa Barbara County, California. A long-standing enzootic of a genetically distinct hantavirus lineage is present in California voles.

Animals↗