RESUMEN
Over the past three decades, insights into the role of the cerebellum in emotional processing have substantially increased. Indeed, methodological refinements in cerebellar lesion studies and major technological advancements in the field of neuroscience are in particular responsible to an exponential growth of knowledge on the topic. It is timely to review the available data and to critically evaluate the current status of the role of the cerebellum in emotion and related domains. The main aim of this article is to present an overview of current facts and ongoing debates relating to clinical, neuroimaging, and neurophysiological findings on the role of the cerebellum in key aspects of emotion. Experts in the field of cerebellar research discuss the range of cerebellar contributions to emotion in nine topics. Topics include the role of the cerebellum in perception and recognition, forwarding and encoding of emotional information, and the experience and regulation of emotional states in relation to motor, cognitive, and social behaviors. In addition, perspectives including cerebellar involvement in emotional learning, pain, emotional aspects of speech, and neuropsychiatric aspects of the cerebellum in mood disorders are briefly discussed. Results of this consensus paper illustrate how theory and empirical research have converged to produce a composite picture of brain topography, physiology, and function that establishes the role of the cerebellum in many aspects of emotional processing.
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Cerebelo/fisiología , Emociones/fisiología , Animales , HumanosRESUMEN
BACKGROUND: Previous reports have indicated that ketamine anesthesia may produce significant improvement if not complete recovery of patients with complex regional pain syndrome (CRPS). AIMS: Here we report on a patient who had CRPS affecting mainly the right side of her body who underwent functional magnetic resonance imaging (fMRI) scans prior to and in the months following apparent successful treatment with anesthetic doses of ketamine. MATERIALS AND METHODS: The patient underwent two imaging sessions: one during her pain state (CRPS+) and 1 month after her ketamine treatment in her pain-free state (CRPS-). Both spontaneous and evoked (brush, cold, and heat) pain scores decreased from 79/10 on a visual analog scale prior to the treatment to 01 immediately following and for months after the treatment. For each imaging session, the identical mechanical (brush) and thermal (cold and heat) stimuli were applied to the same location (the skin of the dorsum of the right hand). RESULTS: Comparison of CRPS+ vs CRPS- for the three stimuli showed significant changes throughout the cerebral cortex (frontal, parietal, temporal, cingulate, and hippocampus), in subcortical regions such as caudate nucleus, and in the cerebellum. In addition, resting state network analysis showed a reversal of brain network state, and the recovered state paralleled specific default networks in healthy volunteers. DISCUSSION: The observed changes in brain response to evoked stimuli provide a readout for the subjective response. CONCLUSION: Future studies of brain function in these patients may provide novel insight into brain plasticity in response to this treatment for chronic pain.
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Mapeo Encefálico/métodos , Encéfalo/fisiopatología , Síndromes de Dolor Regional Complejo/tratamiento farmacológico , Síndromes de Dolor Regional Complejo/fisiopatología , Ketamina/administración & dosificación , Adulto , Encéfalo/efectos de los fármacos , Síndromes de Dolor Regional Complejo/diagnóstico , Potenciales Evocados Somatosensoriales/efectos de los fármacos , Femenino , Humanos , Imagen por Resonancia Magnética/métodos , Resultado del TratamientoRESUMEN
AIMS: The purpose of this study was to determine the effect of insulin on ceramide metabolism in skeletal muscle. METHODS: Skeletal muscle cells were treated with insulin with or without palmitate for various time periods. Lipids (ceramides and TAG) were isolated and gene expression of multiple biosynthetic enzymes were quantified. Additionally, adult male mice received daily insulin injections for 14 days, followed by muscle ceramide analysis. RESULTS: In muscle cells, insulin elicited an increase in ceramides comparable to palmitate alone. This is likely partly due to an insulin-induced increase in expression of multiple enzymes, particularly SPT2, which, when knocked down, prevented the increase in ceramides. In mice, 14 days of insulin injection resulted in increased soleus ceramides, but not TAG. However, insulin injections did significantly increase hepatic TAG compared with vehicle-injected animals. CONCLUSIONS: This study suggests that insulin elicits an anabolic effect on sphingolipid metabolism in skeletal muscle, resulting in increased ceramide accumulation. These findings reveal a potential mechanism of the deleterious consequences of the hyperinsulinemia that accompanies insulin resistance and suggest a possible novel therapeutic target to mitigate its effects.
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Ceramidas/biosíntesis , Insulina/farmacología , Músculo Esquelético/metabolismo , Animales , Línea Celular , Chaperonas de Histonas/metabolismo , Insulina/administración & dosificación , Resistencia a la Insulina , Lípidos/sangre , Lípidos/química , Masculino , Ratones , Ratones Endogámicos C57BL , Mioblastos/citología , Palmitatos/química , Reacción en Cadena de la Polimerasa , Esfingolípidos/químicaRESUMEN
The amygdala is a key brain region with efferent and afferent neural connections that involve complex behaviors such as pain, reward, fear, and anxiety. This study evaluated resting state functional connectivity of the amygdala with cortical and subcortical regions in a group of chronic pain patients (pediatric complex regional pain syndrome) with age-sex matched control subjects before and after intensive physical-biobehavioral pain treatment. Our main findings include (1) enhanced functional connectivity from the amygdala to multiple cortical, subcortical, and cerebellar regions in patients compared with control subjects, with differences predominantly in the left amygdala in the pretreated condition (disease state); (2) dampened hyperconnectivity from the left amygdala to the motor cortex, parietal lobe, and cingulate cortex after intensive pain rehabilitation treatment within patients with nominal differences observed among healthy control subjects from time 1 to time 2 (treatment effects); (3) functional connectivity to several regions key to fear circuitry (prefrontal cortex, bilateral middle temporal lobe, bilateral cingulate, hippocampus) correlated with higher pain-related fear scores; and (4) decreases in pain-related fear associated with decreased connectivity between the amygdala and the motor and somatosensory cortex, cingulate, and frontal areas. Our data suggest that there are rapid changes in amygdala connectivity after an aggressive treatment program in children with chronic pain and intrinsic amygdala functional connectivity activity serving as a potential indicator of treatment response.
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Adaptación Psicológica/fisiología , Amígdala del Cerebelo/fisiopatología , Síndromes de Dolor Regional Complejo/fisiopatología , Síndromes de Dolor Regional Complejo/rehabilitación , Red Nerviosa/fisiopatología , Adolescente , Encéfalo/fisiopatología , Mapeo Encefálico , Niño , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética , Masculino , Vías Nerviosas/fisiopatología , PsicoterapiaRESUMEN
The habenula, located in the posterior thalamus, is implicated in a wide array of functions. Animal anatomical studies have indicated that the structure receives inputs from a number of brain regions (e.g., frontal areas, hypothalamic, basal ganglia) and sends efferent connections predominantly to the brain stem (e.g., periaqueductal gray, raphe, interpeduncular nucleus). The role of the habenula in pain and its anatomical connectivity are well-documented in animals but not in humans. In this study, for the first time, we show how high-field magnetic resonance imaging can be used to detect habenula activation to noxious heat. Functional maps revealed significant, localized, and bilateral habenula responses. During pain processing, functional connectivity analysis demonstrated significant functional correlations between the habenula and the periaqueductal gray and putamen. Probabilistic tractography was used to assess connectivity of afferent (e.g., putamen) and efferent (e.g., periaqueductal gray) pathways previously reported in animals. We believe that this study is the first report of habenula activation by experimental pain in humans. Since the habenula connects forebrain structures with brain stem structures, we suggest that the findings have important implications for understanding sensory and emotional processing in the brain during both acute and chronic pain.
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Habénula/fisiopatología , Red Nerviosa/fisiopatología , Dolor/fisiopatología , Adulto , Vías Aferentes/fisiología , Mapeo Encefálico , Imagen de Difusión Tensora , Calor , Humanos , Procesamiento de Imagen Asistido por Computador , Imagen por Resonancia Magnética , Masculino , Dimensión del DolorRESUMEN
During migraine attacks, alterations in sensation accompanying headache may manifest as allodynia and enhanced sensitivity to light, sound, and odors. Our objective was to identify physiological changes in cortical regions in migraine patients using painful heat and functional magnetic resonance imaging (fMRI) and the structural basis for such changes using diffusion tensor imaging (DTI). In 11 interictal patients, painful heat threshold + 1°C was applied unilaterally to the forehead during fMRI scanning. Significantly greater activation was identified in the medial temporal lobe in patients relative to healthy subjects, specifically in the anterior temporal pole (TP). In patients, TP showed significantly increased functional connectivity in several brain regions relative to controls, suggesting that TP hyperexcitability may contribute to functional abnormalities in migraine. In 9 healthy subjects, DTI identified white matter connectivity between TP and pulvinar nucleus, which has been related to migraine. In 8 patients, fMRI activation in TP with painful heat was exacerbated during migraine, suggesting that repeated migraines may sensitize TP. This article investigates a nonclassical role of TP in migraineurs. Observed temporal lobe abnormalities may provide a basis for many of the perceptual changes in migraineurs and may serve as a potential interictal biomarker for drug efficacy.
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Calor/efectos adversos , Hiperalgesia/fisiopatología , Trastornos Migrañosos/patología , Umbral del Dolor/fisiología , Lóbulo Temporal/fisiopatología , Adulto , Mapeo Encefálico , Imagen de Difusión por Resonancia Magnética , Femenino , Humanos , Hiperalgesia/patología , Procesamiento de Imagen Asistido por Computador/métodos , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Oxígeno/sangre , Lóbulo Temporal/irrigación sanguíneaRESUMEN
Photophobia, or painful oversensitivity to light, occurs in a number of clinical conditions, which range from superficial eye irritation to meningitis. In this case study, a healthy subject with transient photophobia (induced by the overuse of contact lenses) was examined using functional magnetic resonance imaging (fMRI). While being scanned in a darkened environment, the subject was presented with intermittent 6-s blocks of bright light. The subject was scanned twice, once during his photophobic state and once after recovery. The subject reported that the visual stimuli produced pain (pain intensity=3/10 and unpleasantness=7/10) only during the photophobic state. During photophobia, specific activation patterns in the trigeminal system were seen at the level of the trigeminal ganglion, trigeminal nucleus caudalis, and ventroposteromedial thalamus. The anterior cingulate cortex, a brain structure associated with unpleasantness, was also active during photophobia. After recovery from photophobia, no significant activations were detected in these areas. This study may contribute to a better understanding of the pathways involved in photophobia in the human condition.
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Imagen por Resonancia Magnética/métodos , Fotofobia/patología , Núcleo Caudal del Trigémino/irrigación sanguínea , Ganglio del Trigémino/irrigación sanguínea , Encéfalo/irrigación sanguínea , Encéfalo/patología , Mapeo Encefálico , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Luz/efectos adversos , Masculino , Persona de Mediana Edad , Vías Nerviosas/irrigación sanguínea , Vías Nerviosas/fisiopatología , Oxígeno/sangre , Dimensión del Dolor/métodos , Fotofobia/etiología , Núcleo Caudal del Trigémino/fisiopatología , Ganglio del Trigémino/fisiopatologíaRESUMEN
Complex regional pain syndrome (CRPS) in paediatric patients is clinically distinct from the adult condition in which there is often complete resolution of its signs and symptoms within several months to a few years. The ability to compare the symptomatic and asymptomatic condition in the same individuals makes this population interesting for the investigation of mechanisms underlying pain and other symptoms of CRPS. We used fMRI to evaluate CNS activation in paediatric patients (9-18 years) with CRPS affecting the lower extremity. Each patient underwent two scanning sessions: once during an active period of pain (CRPS(+)), and once after symptomatic recovery (CRPS(-)). In each session, mechanical (brush) and thermal (cold) stimuli were applied to the affected region of the involved limb and the corresponding mirror region of the unaffected limb. Two fundamental fMRI analyses were performed: (i) within-group analysis for CRPS(+) state and CRPS(-) state for brush and cold for the affected and unaffected limbs in each case; (ii) between-group (contrast) analysis for activations in affected and unaffected limbs in CRPS or post-CRPS states. We found: (i) in the CRPS(+) state, stimuli that evoked mechanical or cold allodynia produced patterns of CNS activation similar to those reported in adult CRPS; (ii) in the CRPS(+) state, stimuli that evoked mechanical or cold allodynia produced significant decreases in BOLD signal, suggesting pain-induced activation of endogenous pain modulatory systems; (iii) cold- or brush-induced activations in regions such as the basal ganglia and parietal lobe may explain some CNS-related symptoms in CRPS, including movement disorders and hemineglect/inattention; (iv) in the CRPS(-) state, significant activation differences persisted despite nearly complete elimination of evoked pain; (v) although non-noxious stimuli to the unaffected limb were perceived as equivalent in CRPS(+) and CRPS(-) states, the same stimulus produced different patterns of activation in the two states, suggesting that the 'CRPS brain' responds differently to normal stimuli applied to unaffected regions. Our results suggest significant changes in CNS circuitry in patients with CRPS.
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Encéfalo/fisiopatología , Síndromes de Dolor Regional Complejo/fisiopatología , Adolescente , Mapeo Encefálico/métodos , Niño , Frío , Síndromes de Dolor Regional Complejo/psicología , Femenino , Humanos , Hiperalgesia/etiología , Hiperalgesia/fisiopatología , Imagen por Resonancia Magnética/métodos , Plasticidad Neuronal , Dimensión del Dolor/métodos , Estimulación Física/métodos , PsicofísicaRESUMEN
Though human pain imaging studies almost always demonstrate activation in the cerebellum, the role of the cerebellum in pain function is not well understood. Here we present results from two studies on the effects of noxious thermal heat and brush applied to the right side of the face in a group of healthy subjects (Group I) and a group of patients with neuropathic pain (Group II) who are more sensitive to both thermal and mechanical stimuli. Statistically significant activations and volumes of activations were defined in the cerebellum. Activated cerebellar structures were identified by colocalization of fMRI activation with the 'MRI Atlas of the Human Cerebellum'. Functional data (obtained using a 3T magnet) were defined in terms of maximum voxels and volume of activation in the cerebellum. Volume maps were then mapped onto two millimeter serial slices taken through the cerebellum in order to identify activation within regions defined by the activation volume. The data indicate that different regions of the cerebellum are involved in acute and chronic pain processing. Heat produces greater contralateral activation compared with brush, while brush resulted in more ipsilateral/bilateral cerebellar activation. Further, innocuous brush stimuli in healthy subjects produced decreased cerebellar activation in lobules concerned with somatosensory processing. The data also suggest a dichotomy of innocuous stimuli/sensorimotor cerebellum activation versus noxious experience/cognitive/limbic cerebellum activation. These results lead us to propose that the cerebellum may modulate the emotional and cognitive experience that distinguishes the perception of pain from the appreciation of innocuous sensory stimulation.
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Cerebelo/fisiología , Cerebelo/fisiopatología , Mononeuropatías/fisiopatología , Enfermedades del Sistema Nervioso/fisiopatología , Núcleos Cerebelosos/patología , Núcleos Cerebelosos/fisiología , Núcleos Cerebelosos/fisiopatología , Cerebelo/patología , Emociones , Femenino , Calor , Humanos , Imagen por Resonancia Magnética , Masculino , Mononeuropatías/diagnóstico por imagen , Mononeuropatías/patología , Mononeuropatías/psicología , Enfermedades del Sistema Nervioso/diagnóstico por imagen , Enfermedades del Sistema Nervioso/patología , Enfermedades del Sistema Nervioso/psicología , Estimulación Física , Tomografía de Emisión de Positrones , Radiografía , Valores de ReferenciaRESUMEN
Cortical responses to painful and nonpainful heat were measured using functional magnetic resonance imaging (fMRI) region of interest analysis (ROI) of primary somatosensory cortex (S1), secondary somatosensory cortex (S2), anterior cingulate (ACC), supplementary motor area (SMA), insula, and inferior frontal gyrus (IFG). Previous studies indicated that innocuous and noxious stimuli of different modalities produce responses with different time courses in S1 and S2. The aim of this study was to 1) determine whether temporally distinct nociceptive blood oxygen level-dependent (BOLD) responses are evoked in multiple somatosensory processing cortical areas and 2) whether these responses discriminate small noxious stimulus intensity differences. Thirty-three subjects underwent fMRI scanning while receiving three intensities of thermal stimuli, ranging from innocuous warm (41 degrees C) to 1 degrees C below tolerance, applied to the dorsum of the left foot. Innocuous and noxious responses were distinguishable in contralateral S1, the mid-ACC, and SMA. The peak of the nociceptive response was temporally delayed from the innocuous response peak by 6-8 s. Responses to noxious but not to innocuous stimuli were observed in contralateral posterior insula. Responses to innocuous and noxious stimuli were not statistically different in contralateral S2. In contralateral S1 only, the nociceptive response could differentiate heat stimuli separated by 1 degrees C. These results show that 1) multiple cortical areas have temporally distinguishable innocuous and noxious responses evoked by a painfully hot thermode, 2) the nociceptive processing properties vary across cortical regions, and 3) nociceptive responses in S1 discriminate between painful temperatures at a level unmatched in other cortical areas.
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Mapeo Encefálico/métodos , Encéfalo/fisiología , Calor/efectos adversos , Imagen por Resonancia Magnética/métodos , Dimensión del Dolor/métodos , Adulto , Análisis de Varianza , Femenino , Humanos , Masculino , Factores de TiempoRESUMEN
INTRODUCTION: Some general practice registrars (GPRs) have substance abuse problems, and course organisers and trainers need to be vigilant to this possibility. We describe a critical incident involving this type of problem, and how the learning was shared with other GP educators. By using the humanities, we attempted to generate an emotional as well as an intellectual response, with the aim of achieving deeper learning. METHODS: We gave a presentation to a group of GP educators, using a variety of material from the creative arts (visual, auditory and creative writing) to raise awareness of the issues. The presentation was designed to enable participants to experience some of the feelings of surprise and lack of preparedness that we had experienced ourselves. RESULTS: The presentation stimulated an in-depth discussion about the challenges faced by educators when they discover that their learners may have substance abuse problems. Early and late evaluation indicated that awareness of the problem had been raised and attitudes challenged and changed. Participation in the presentation had stimulated educators to consider including this area within their teaching, to be more vigilant to the possibility of registrars with substance abuse problems and to think about developing systems to manage such registrars. CONCLUSION: Diverse educational methods can be effective when teaching within difficult and complex areas that challenge attitudes.
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Cuerpo Médico de Hospitales/psicología , Estudiantes de Medicina/psicología , Trastornos Relacionados con Sustancias/diagnóstico , Actitud del Personal de Salud , Educación Médica/métodos , Docentes , Humanidades/educación , HumanosRESUMEN
To understand the regulation of CC chemokine receptor 3 (CCR3) expression, its gene structure and promoter have been characterized. The CCR3 gene contains 4 exons that give rise to multiple messenger RNA (mRNA) species by alternative splicing. Exon 1 is present in all transcripts, whereas exon 2 or 3 is present at low frequency (< 10%). Exon 4 contains the open reading frame and 11 bp of the 5' untranslated region. Northern analysis revealed 4 species of CCR3 mRNA. Direct sequencing revealed that the first 1 kb of the promoter and exon 1 contained only one mutation in 19 individuals, indicating that the CCR3 promoter and exon 1 are conserved between individuals. The first 1.6 kb of the 5' flanking region of exon 1 contained promoter elements including a TATA box and motifs for myeloid transcription factors and had strong promoter activity in eosinophilic, lymphoid, myeloid, and respiratory epithelial cell lines. Deletion analysis revealed differential regulation of the CCR3 promoter in eosinophilic and epithelial cells suggesting the presence of lineage-specific elements. Interestingly, exon 1 enhanced the activity of the promoter and this effect was especially prominent in eosinophilic cells. Thus, the human CCR3 gene has a complex 5' exon structure, a conserved promoter with strong activity in multiple cell types, and a functional 5' untranslated exon.
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Eosinófilos/metabolismo , Exones , Regiones Promotoras Genéticas , Receptores de Quimiocina/genética , Regiones no Traducidas , Empalme Alternativo , Secuencia de Bases , Northern Blotting , Línea Celular , ADN/química , Eliminación de Gen , Regulación de la Expresión Génica , Células Madre Hematopoyéticas , Humanos , Datos de Secuencia Molecular , Mutagénesis , Sistemas de Lectura Abierta , Reacción en Cadena de la Polimerasa , Polimorfismo Genético , ARN Mensajero/genética , Receptores CCR3 , Análisis de Secuencia de ADN , TransfecciónRESUMEN
To identify patterns of failure following curative resection of gastric carcinoma, the records of 130 patients undergoing resection with curative intent at the Massachusetts General Hospital were reviewed. The total local-regional failure rate was 38% (49/130 patients), with 21 patients having local-regional failure alone and 28 patients having local-regional failure and distant metastases. The incidence of local failure rose with the more advanced stages of disease. Tumors staged B2, B3, C2, and C3 had local-regional failure rates in excess of 35%. This group of patients might benefit from adjuvant radiation therapy to the tumor bed and regional lymphatics. Local-regional failure rate was highest in the anastomosis or stump 33/130 (25%), followed by the stomach bed 27/130 (21%). The overall incidence of distant metastases was 52% (67/130 patients) and rose in the more advanced disease stages. Tumors staged B2, B3, C2, and C3 had rates of distant metastases greater than 50%. Sixty-one patients (77%) had failure in the abdomen (liver, peritoneal surface, adrenal, kidney, and spleen, but excluding tumor bed, anastomosis, or regional nodes). Patients with Stage B2, B3, C2, and C3 tumors had total abdominal failure rates greater than 40%. The highest failure rates in the liver were in Stages B3 and C3, in which the subsequent development of liver metastasis was 40% and 47%, respectively. Peritoneal seeding occurred in 30/130 (23%) of patients and was highest in Stages C2 and C3, with rates of 27% and 41%, respectively.
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Metástasis de la Neoplasia , Recurrencia Local de Neoplasia , Neoplasias Gástricas/cirugía , Abdomen/efectos de la radiación , Adulto , Anciano , Anciano de 80 o más Años , Terapia Combinada , Femenino , Gastrectomía , Humanos , Masculino , Persona de Mediana Edad , Estadificación de Neoplasias , Neoplasias Gástricas/mortalidad , Tasa de SupervivenciaRESUMEN
In 1988, a combination of efforts by the press, the Maryland General Assembly, the Department of Health and Mental Hygiene (DHMH), and an advisory panel of pathologists and cytotechnologists led to broader and stricter regulation of cytopathology laboratories in Maryland. A new law called for standards covering the maximum number of slides a cytotechnologist may examine, unsatisfactory specimens, slide and records retention, a limitation on the use of out-of-state laboratories by Maryland physicians, and a mandatory, state-run proficiency testing program. Maryland's proficiency testing program is modeled on that of New York State but incorporates improvements in diagnostic definitions, testing mechanisms, and retraining requirements.
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Laboratorios/normas , Patología Clínica/normas , Laboratorios/legislación & jurisprudencia , Maryland , Patología Clínica/legislación & jurisprudencia , Escuelas para Profesionales de Salud/normasAsunto(s)
Cuerpo Vítreo/cirugía , Adolescente , Adulto , Anciano , Niño , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Complicaciones Posoperatorias , Agudeza VisualRESUMEN
An improved recovery method and testing strategy were devised for recovery of low numbers of enteric viruses from each of three commercially important shellfish species. Effective recovery of virus depended as much upon details of the test strategy adopted for use of the improved method with each species as on the method itself. The most important test details involved sample composition, pool size, and method of use of cell cultures. Recovery sensitivity measured permitted detection of 25 to 3 plaque-forming units of enteroviruses and 100 to 27 plaque-forming units of reovirus through their recovery in cell culture, with effectivenesses averaging 64 and 46%, respectively. Test samples prepared by the improved recovery method were virtually cytotoxicity free. Optimal recovery of virus on 45-cm2 cell culture monolayers was obtained with 1-ml inocula adsorbed for 2 h. The most effective recovery of virus from shellfish samples was made by a sequential adsorption procedure which allowed equal exposure of an entire sample to each of two or more cell cultures. Removal of nonviral contaminants from test samples by antibiotic treatment was preferable to the use of ether or membrane filtration procedures.
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Bivalvos/microbiología , Enterovirus/aislamiento & purificación , Microbiología de Alimentos , Ostreidae/microbiología , Mariscos , Animales , Línea Celular , Enterovirus/crecimiento & desarrollo , Filtración , Floculación , Humanos , MétodosRESUMEN
A method for recovery of small numbers of enteric viruses from oysters and hard and soft shell clams was developed. As few as 3 plaque forming units (PFU) of virus per 100 g of shellfish homogenate could be detected with an overall accuracy of ca. 60 percent in each of the three species tested.
RESUMEN
Low levels of feces-associated natural virus, simulating virus numbers estimated to exist in moderately polluted shellfish-growing waters, were used to evaluate the effectiveness of depuration as a virus depletion procedure in soft-shell clams. Depuration effectiveness depended upon the numbers of virus bioaccumulated and whether virus was solids associated. Virus uptake was greatest when viruses were solids associated and pollution levels were equivalent or greater than those likely to be found in grossly polluted growing waters. Virtually all bioaccumulated feces-associated natural virus was deposited within either the hepatopancreas or siphon tissues. Viruses usually were eliminated within a 24- to 48-h depuration period. Dependence upon depuration of clams to elimate health hazards of virus etiology involved a risk factor not measureable in the study. The greatest reduction of health risks would come from the routine depuration of clams harvested from growing waters of good sanitary quality.