RESUMEN
Insect herbivores must contend with constitutive and induced plant defenses. The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae, Scolytinae) has expanded its range east of the Rocky Mountains into the western boreal forest and is encountering evolutionarily naïve lodgepole pines (Pinus contorta) and jack pines (Pinus banksiana). Pinus contorta and P. banksiana in the expanded range have different constitutive and induced defenses in response to wounding and inoculation with fungal associates of D. ponderosae. In the historic range, previous studies have examined phloem terpene content prior to and just after D. ponderosae mass attack, but the terpene profile of attacked trees post-overwintering is unknown. We examined the response of mature P. contorta and P. banksiana trees to experimentally-applied mass attack by D. ponderosae and quantified phloem terpenes at three time points, pre-attack, post-attack (same season), and the following spring, post-overwintering. Phloem content of total terpenes as well as many individual terpenes increased after D. ponderosae attack but were only significantly higher than pre-attack levels at the post-overwintering time point in both P. contorta and P. banksiana. The absence of a significant increase in phloem terpenes in the month following attack in naïve pines is a potential cause for increased D. ponderosae offspring production reported in naïve P. contorta. Beetle attack density did not influence the phloem terpene profiles of either species and there was no significant interaction between attack density and sampling time on terpene content. High phloem terpenes in trees that are attacked at low densities could prime these trees for defense against attacks in the following season but it could also make these trees more apparent to early-foraging beetles and facilitate efficient mass attack at low D. ponderosae population densities in the expanded range.
Asunto(s)
Escarabajos , Pinus , Gorgojos , Animales , Escarabajos/fisiología , Terpenos , Estaciones del Año , Pinus/fisiología , Gorgojos/fisiologíaRESUMEN
Within the framework of the EURADOS Working Group 11, a comparison of passive neutron dosemeters in high-energy neutron fields was organised in 2011. The aim of the exercise was to evaluate the response of poly-allyl-glycol-carbonate neutron dosemeters from various European dosimetry laboratories to high-energy neutron fields. Irradiations were performed at the iThemba LABS facility in South Africa with neutrons having energies up to 66 and 100 MeV.
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Neutrones , Polímeros/química , Monitoreo de Radiación/instrumentación , Protección Radiológica/instrumentación , Aire , Aeronaves , Calibración , Carbonatos/química , Radiación Cósmica , Ciclotrones , Europa (Continente) , Humanos , Fantasmas de Imagen , Dosis de Radiación , Monitoreo de Radiación/métodos , Protección Radiológica/métodos , Conteo por Cintilación , Sudáfrica , Nave EspacialRESUMEN
Symptomatic treatment of stiff-person syndrome (SPS) might be challenging and a significant improvement of stiffness and rigidity is generally reached with high doses of benzodiazepines or baclofen causing side effects. A 71-year old woman diagnosed with SPS complained of marked stiffness of trunk and lower limb muscles with sudden painful spasms. She was unable to walk and she could not lean on her right leg. Cortical silent period (CSP) duration evaluated from right abductor pollicis brevis (APB) with transcranial magnetic stimulation was shortened. Polygraphic electromyographic (EMG) evaluation from paraspinal and leg muscles disclosed continuous motor unit activity at rest with interference muscular pattern. Symptomatic treatment with diazepam was withdrawn because of excessive sedation. In order to relieve the intense lumbar pain, she was prescribed pregabalin; since the day after, rigidity and painful spasms dramatically improved and she could walk without assistance. The clinical benefit persisted at 3 months follow-up and was paralleled by almost complete disappearance of EMG activity at rest and prolongation of CSP. The clinical and electrophysiological data in this SPS patient suggest the possible efficacy of pregabalin as symptomatic treatment without any significant side effects, which needs to be replicated in larger case series.
Asunto(s)
Analgésicos/uso terapéutico , Síndrome de la Persona Rígida/tratamiento farmacológico , Ácido gamma-Aminobutírico/análogos & derivados , Anciano , Dolor de Espalda/tratamiento farmacológico , Dolor de Espalda/etiología , Electroencefalografía , Electromiografía , Femenino , Glutamato Descarboxilasa/inmunología , Humanos , Músculo Esquelético/fisiopatología , Examen Neurológico , Pregabalina , Síndrome de la Persona Rígida/complicaciones , Síndrome de la Persona Rígida/fisiopatología , Estimulación Magnética Transcraneal , Ácido gamma-Aminobutírico/uso terapéuticoRESUMEN
AIM: Endoscopic variceal ligation (EVL) is recommended for the treatment of esophageal variceal bleeding. The aim of this study was to assess the most cost-effective timing of endoscopic follow-up after variceal eradication. METHODS: Cirrhotics with esophageal varices treated between January 2008 and January 2009 until reached variceal obliteration were retrospectively analyzed for technical aspects and for outcomes. RESULTS: Out of 127 patients treated with EVL, 103 were included. Number of sessions to achieve variceal obliteration and number of bands for each session were 2.8±1.3 (range 1-7) and 4.6±1 (range 2-7), respectively. The placement of >5 bands per session was not associated with higher incidence of complications (19.6% vs. 17.8%, P=ns). Esophageal ulcers were observed in 42% of patients when the interbanding interval was <20 days (versus 15% for interval >20 days, P<0.05). Once obliteration was achieved, varices reappeared in 28% of patients; the early appearance of small varices was not associated with bleeding. CONCLUSION: A longer interbanding interval reduces the incidence of procedural-related complications. After variceal obliteration an early endoscopic control is not useful because it does not influence the approach and does not change the patient outcome.
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Várices Esofágicas y Gástricas/cirugía , Esofagoscopía , Hemorragia Gastrointestinal/cirugía , Cirrosis Hepática/complicaciones , Várices Esofágicas y Gástricas/complicaciones , Várices Esofágicas y Gástricas/etiología , Esofagoscopía/métodos , Hemorragia Gastrointestinal/etiología , Humanos , Ligadura/métodos , Recurrencia , Estudios Retrospectivos , Resultado del TratamientoRESUMEN
BACKGROUND AND STUDY AIMS: The determinants of the observed variability of adenoma detection rate (ADR) in endoscopy screening have not yet been fully explained. PATIENTS AND METHODS: Between November 1999 and November 2006 13 764 people (7094 men, 6670 women; age range 55-64) underwent screening flexible sigmoidoscopy at five hospital endoscopy units in Turin. To study the determinants of the ADR for distal adenomas, accounting for patient, examiner, and hospital characteristics, we applied a multivariate multilevel regression model. RESULTS: Average ADRs for all adenomas and for advanced adenomas (size > or = 10 mm, villous component > 20 %, high grade dysplasia) were 13.5 % (range 5.2 %-25.0 %) and 6.4 % (3.1 %-10.7 %) for men, and 8.0 % (2.5 %-14.0 %) and 3.7 % (0.2 % - 7.4 %) for women. In multivariate analysis, increased ADR of advanced adenomas was associated with male gender (odds ratio [OR] 1.78, 95 %CI 1.49 - 2.11), self-report of one first-degree relative with colorectal cancer (CRC) (1.44, 1.11-1.86), or of recent-onset rectal bleeding (1.73, 1.24-2.40). Adjusting for these variables, a significantly lower ADR was found for endoscopists with either a lower rate of incomplete sigmoidoscopy (< 9 %; OR 0.59, 95 %CI 0.41-0.87) or a higher rate (> 12 %; 0.64, 0.45-0.91), or with low activity volume (< 85 sigmoidoscopies/year; 0.66, 0.50-0.86). Residual variability explained by the endoscopy center effect was about 1 % and statistically significant. CONCLUSIONS: Endoscopist performance in flexible sigmoidoscopy CRC screening is highly variable. Low volume of screening activity independently predicts lower ADR, suggesting that operators devoting more time to screening sigmoidoscopy may perform better. Variability among pathologists in adenoma classification might explain part of the residual variability across endoscopy units.
Asunto(s)
Adenoma/diagnóstico , Sigmoidoscopía , Adenoma/patología , Femenino , Humanos , Masculino , Tamizaje Masivo/estadística & datos numéricos , Persona de Mediana Edad , Variaciones Dependientes del Observador , Sigmoidoscopía/estadística & datos numéricosRESUMEN
T lymphocytes bearing the gammadelta T cell receptor are known to play an important role in the first-line defense against viral, bacterial and fungal pathogens. Two main subsets of gammadelta T cells are known, showing distinct functional behaviour: Vdelta2 T lymphocytes, circulating in the peripheral blood, are involved in the response to mycobacterial infections and certain viruses, including coxsakie virus B3 and herpes simplex virus type 2. Vdelta1 T cells are resident in the mucosal-associated lymphoid tissue and are reported to participate in the immunity against Listeria monocytogenes and cytomegalovirus. Vdelta2 T lymphocytes recognize non-peptidic phosphorylated metabolites of isoprenoid biosynthesis, expressed by mycobacteria, while Vdelta1 T cells mainly interact with MHC-related antigens (MIC-A and MIC-B) and with receptors, called UL-16 binding proteins, for the UL-16 protein produced by cytomegalovirus-infected cells. Both Vdelta1 and Vdelta2 T cells can produce interferon-gamma in response to MIC-A(+) cells or non-peptide antigens, respectively. Moreover, production of TNF-alpha by human Vgamma9/Vdelta2 T cells has been demonstrated in response to bacterial products and non-peptidic molecules. Recently, it has been reported that gammadelta T lymphocytes can produce IL-17 during Escherichia coli or Mycobacterium tuberculosis infections in mice. This is of interest as IL-17 is emerging as a cytokine crucial in the control of intracellular pathogens and fungi. In this review, we will discuss the possible role of IL-17 producing gammadelta T cells in the regulation of acute and chronic inflammation, focusing on the different response of the two subsets to mycobacterial, viral or fungal antigens.
Asunto(s)
Antígenos Bacterianos/inmunología , Candida albicans/inmunología , Inflamación/inmunología , Interferón gamma/metabolismo , Interleucina-17/metabolismo , Mycobacterium tuberculosis/inmunología , Receptores de Antígenos de Linfocitos T gamma-delta/análisis , Linfocitos T/inmunología , Enfermedad Aguda , Animales , Diferenciación Celular , Enfermedad Crónica , Humanos , RatonesRESUMEN
Appendiceal mucocele is an uncommon disorder caused by accumulation of mucus within the appendiceal lumen. Mucoceles represent a heterogeneous group comprising various histopathologic lesions including mucosal hyperplasia, cystoadenomas, and cystoadenocarcinomas and prognosis is related to these subtypes. The most common symptom is pain or a palpable mass in the right lower quadrant on physical examination. The preoperative diagnosis is performed with abdominal U.S. and confirmed with CT scan; typical CT scan image is a capsulated cystic mass with calcification of the wall while U.S. pattern shows cystic lesion with the onion skin sign considered a specific sonographic marker for appendiceal mucocele. In conclusion a cystic mass sonographically detected with onion skin sign, in the presence of normal female reproductive organs, suggest the diagnosis of appendiceal mucocele.
Asunto(s)
Apéndice , Mucocele , Adulto , Enfermedades del Ciego/diagnóstico , Enfermedades del Ciego/cirugía , Humanos , Masculino , Mucocele/diagnóstico , Mucocele/cirugíaAsunto(s)
Ligamento Cruzado Anterior/cirugía , Antibacterianos/uso terapéutico , Artritis Infecciosa/etiología , Artroscopía , Infecciones Estafilocócicas/tratamiento farmacológico , Staphylococcus/aislamiento & purificación , Infección de la Herida Quirúrgica/microbiología , Adulto , Algoritmos , Ligamento Cruzado Anterior/microbiología , Artritis Infecciosa/microbiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Procedimientos de Cirugía Plástica , Infecciones Estafilocócicas/etiología , Infecciones Estafilocócicas/microbiología , Infección de la Herida Quirúrgica/tratamiento farmacológico , Infección de la Herida Quirúrgica/etiologíaAsunto(s)
Complejo SIDA Demencia/complicaciones , Atetosis/virología , Ganglios Basales/patología , Corea/virología , VIH-1/aislamiento & purificación , Complejo SIDA Demencia/diagnóstico por imagen , Complejo SIDA Demencia/patología , Edad de Inicio , Antivirales/uso terapéutico , Atetosis/diagnóstico por imagen , Atetosis/patología , Atrofia/diagnóstico por imagen , Atrofia/patología , Atrofia/virología , Ganglios Basales/diagnóstico por imagen , Ganglios Basales/fisiopatología , Corea/diagnóstico por imagen , Corea/patología , Electroencefalografía , Trastornos Neurológicos de la Marcha/diagnóstico por imagen , Trastornos Neurológicos de la Marcha/patología , Trastornos Neurológicos de la Marcha/virología , VIH-1/genética , Humanos , Imagen por Resonancia Magnética , Masculino , Trastornos de la Memoria/diagnóstico por imagen , Trastornos de la Memoria/patología , Trastornos de la Memoria/virología , Persona de Mediana Edad , Trastornos del Humor/diagnóstico por imagen , Trastornos del Humor/patología , Trastornos del Humor/virología , Fibras Nerviosas Mielínicas/patología , Fibras Nerviosas Mielínicas/virología , Tomografía de Emisión de Positrones , Corteza Prefrontal/diagnóstico por imagen , Corteza Prefrontal/patología , Corteza Prefrontal/fisiopatología , Inhibidores de Proteasas/uso terapéutico , ARN Viral/sangre , ARN Viral/líquido cefalorraquídeo , Resultado del Tratamiento , Carga ViralRESUMEN
The accurate diagnosis of deep infection in total joint arthroplasty is difficult. No single test on its own is entirely reliable. Frozen section histology has been used for the last two decades as an adjunct to diagnose infection with variable results. In this retrospective analysis, experience of the use of frozen section histology as a diagnostic tool in 45 cases of suspected infected total joint arthroplasty is reported. Taking intraoperative cultures as the "gold standard", the results showed 50% sensitivity, 95% specificity, positive predictive value of 60%, negative predictive value of 92%, and an accuracy of 89%, which is similar to other existing reports in the literature. Based on these findings, the use of frozen section histology in diagnostic work-up of all suspected cases of total joint infection is recommended.
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Artroplastia de Reemplazo de Cadera , Artroplastia de Reemplazo de Rodilla , Infecciones Bacterianas/diagnóstico , Secciones por Congelación/normas , Infecciones Relacionadas con Prótesis/diagnóstico , Anciano , Anciano de 80 o más Años , Reacciones Falso Positivas , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Sensibilidad y EspecificidadAsunto(s)
Enfermedad de Alzheimer/diagnóstico , Quistes Óseos/diagnóstico , Demencia Vascular/diagnóstico , Linaje , Adulto , Anciano , Enfermedad de Alzheimer/genética , Quistes Óseos/genética , Preescolar , Demencia Vascular/genética , Femenino , Humanos , Italia , Imagen por Resonancia Magnética/métodos , Masculino , Persona de Mediana Edad , Mutación/genéticaRESUMEN
BACKGROUND: Endoscopic therapy is a safe and effective method for treating non-variceal upper gastrointestinal bleeding. However failure of therapy, in terms of continuing bleeding or rebleeding, is seen in up to 20%. Cyanoacrylate is a tissue glue used for variceal bleeding that has occasionally been reported as an alternative haemostatic technique in non-variceal haemorrhage. AIM: To retrospectively describe personal experience using cyanoacrylate injection in the management of bleeding ulcers after failure of first-line endoscopic modalities. PATIENTS AND METHODS: Between January 1995 and March 1998, 18 [12 M/6 F, mean age 68.1 years) out of 176 patients, referred to our Unit for non-variceal upper gastrointestinal bleeding, were treated with intralesional injection of adrenaline plus undiluted cyanoacrylate. Persistent bleeding after endoscopic haemostasis or early rebleeding were the indications for cyanoacrylate treatment. RESULTS: Definitive haemostasis was achieved in 17 out of 18 patients treated with cyanoacrylate. One patient needed surgery. No early or late rebleeding occurred during the follow-up. No complications or instrument lesions related to cyanoacrylate were recorded. CONCLUSIONS: In our retrospective series, cyanoacrylate plus adrenaline injection was found to be a potentially safe and effective alternative to endoscopic haemostasis when conventional treatment modalities fail in controlling bleeding from gastroduodenal ulcers.
Asunto(s)
Cianoacrilatos/administración & dosificación , Epinefrina/administración & dosificación , Hemostasis Endoscópica , Úlcera Péptica Hemorrágica/terapia , Anciano , Cianoacrilatos/uso terapéutico , Epinefrina/uso terapéutico , Femenino , Técnicas Hemostáticas , Humanos , MasculinoRESUMEN
Proteasomes, the proteolytic machinery of the ubiquitin/ATP-dependent pathway, have a relevant role in many processes crucial for cell physiology and cell cycle progression. Proteasome inhibitors are used to block cell cycle progression and to induce apoptosis in certain cell lines. Here we examine whether proteasomal function is affected by the anti-tumour drug vinblastine, whose cytostatic action relies mainly on the disruption of mitotic spindle dynamics. The effects of vinblastine on the peptidase activities of human 20 S and 26 S proteasomes and on the proteolytic activity of 26 S proteasome were assessed in the presence of specific fluorogenic peptides and (125)I-lysozyme-ubiquitin conjugates respectively. The assays of ubiquitin-protein conjugates and of inhibitory kappa B alpha (I kappa B alpha), which are characteristic intracellular proteasome substrates, by Western blotting on lysates from HL60 cells incubated with or without vinblastine, illustrated the effects of vinblastine on proteasomes in vivo. We also evaluated the effects of vinblastine on the signal-induced degradation of I kappa B alpha. Vinblastine at 3--110 microM reversibly inhibited the chymotrypsin-like activity of the 20 S proteasome and the trypsin-like and peptidyl-glutamyl-peptide hydrolysing activities of both proteasomes, but only at 110 microM vinblastine was the chymotrypsin-like activity of the 26 S proteasome inhibited; furthermore, at 25--200 microM the drug inhibited the degradation of ubiquitinated lysozyme. In HL60 cells exposed for 6 h to 0.5--10 microM vinblastine, the drug-dose-related accumulation of polyubiquitinated proteins, as well as that of a high-molecular-mass form of I kappa B alpha, occurred. Moreover, vinblastine impaired the signal-induced degradation of I kappa B alpha. Cell viability throughout the test was approx. 95%. Proteasomes can be considered to be a new and additional vinblastine target.
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Antineoplásicos Fitogénicos/metabolismo , Cisteína Endopeptidasas/metabolismo , Complejos Multienzimáticos/metabolismo , Vinblastina/metabolismo , Catálisis , Inhibidores de Cisteína Proteinasa/metabolismo , Electroforesis en Gel de Poliacrilamida , Células HL-60 , Humanos , Complejo de la Endopetidasa ProteasomalRESUMEN
BACKGROUND: Metal stents have been reported as an effective alternative to surgery for the palliation of patients with colorectal neoplastic obstruction. Because most of the published series describe the use of uncovered stents, the purpose of our study was to prospectively evaluate the effectiveness, feasibility, safety, and outcome of covered stents for the palliative treatment of malignant colorectal strictures. METHODS: Sixteen patients with advanced distal colorectal cancer underwent placement of 10 and 12 cm long, 23 mm diameter covered stents under fluoroscopic and endoscopic control. Clinical and endoscopic follow-up was scheduled at 3- to 6-week intervals. RESULTS: Stent insertion was successful in 15 of 16 patients (93%). Perforation occurred in one patient during stent placement requiring colostomy. Relief of bowel obstruction was documented in all successfully treated patients. The median follow-up was 21 weeks (range 1 to 46). No recurrence of obstruction was observed during the follow-up period. Stent migration occurred in 2 patients, 7 and 21 days after stent placement. CONCLUSIONS: Covered stents may provide safe and effective palliation of patients with malignant rectosigmoid strictures. Prolonged luminal patency and sealing of fistulous tracts are potential advantages of covered versus uncovered stents in the palliative treatment of colorectal malignancies. ¿
Asunto(s)
Neoplasias Colorrectales/terapia , Obstrucción Intestinal/terapia , Cuidados Paliativos/métodos , Stents , Anciano , Anciano de 80 o más Años , Materiales Biocompatibles Revestidos , Colonoscopía , Neoplasias Colorrectales/complicaciones , Neoplasias Colorrectales/mortalidad , Seguridad de Equipos , Femenino , Estudios de Seguimiento , Humanos , Obstrucción Intestinal/etiología , Obstrucción Intestinal/mortalidad , Masculino , Metales , Persona de Mediana Edad , Probabilidad , Estudios Prospectivos , Índice de Severidad de la Enfermedad , Tasa de SupervivenciaRESUMEN
Lymphocytic gastritis is a histopathological entity of unknown aetiology which is characterized by dense surface and foveolar epithelial T-cell infiltration. We report here an uncommon clinical presentation in a young female presenting with unexplained recurrent weight loss and peripheral oedema. Endoscopic and histological features before and after successful therapy with omeprazole are described.
Asunto(s)
Gastritis/patología , Linfocitos/patología , Enteropatías Perdedoras de Proteínas/etiología , Adulto , Femenino , Gastritis/tratamiento farmacológico , Humanos , Omeprazol/uso terapéuticoRESUMEN
BACKGROUND: Circulating lymphocytes of obese individuals with and without type 2 diabetes have derangements of pyruvate dehydrogenase (PDH) that are described as reflecting a disorder underlying systemic insulin resistance, namely basal activity below normal and, in vitro, unresponsiveness to insulin at 33 pmol/l and activation at 330 pmol/l instead of activation and inhibition as in controls. OBJECTIVE: To explore whether the above enzyme derangements are overcome in obese individuals on dexfenfluramine treatment, known to improve poor peripheral insulin sensitivity. METHODS: Fifteen obese diabetic patients and 15 age-matched euglycaemic obese subjects with normal glucose tolerance were enrolled for a trial composed of two 21-day periods; in the first (D-21-D0), participants received a placebo, and in the second (D0-D21), dexfenfluramine (30 mg/day). At D-21, D0 and D21 participants were evaluated for weight, BMI, fasting glycaemia (FG), fasting insulinaemia (FI), fasting insulin resistance index (FIRI), area under the glycaemic (G-AUC) and insulinaemic (I-AUC) curves from an OGT test, and for PDH activity assayed in their circulating lymphocytes before (basal activity) and after incubation with 33 or 330 pmol/l insulin. At D2, basal PDH activity and clinical parameters were assayed. RESULTS: In both groups of participants at D0 all parameters tested were constant with respect to D-21; at D2, only basal PDH activity rose significantly; at D21, basal and insulin stimulated PDH activities were normalized and weight decreased significantly, as did FG, FI, FIRI and G-AUC in the diabetic, and FI, FIRI, G-AUC and I-AUC in the non-diabetic participants. CONCLUSION: In obese, non-diabetic and diabetic individuals on dexfenfluramine treatment, amelioration of clinical parameters and indexes of poor insulin sensitivity of blood glucose homeostasis are preceded by correction, in their circulating lymphocytes, of PDH derangements described as reflecting a disorder underlying insulin resistance.
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Dexfenfluramina/uso terapéutico , Resistencia a la Insulina , Obesidad/tratamiento farmacológico , Complejo Piruvato Deshidrogenasa/sangre , Adulto , Glucemia/metabolismo , Índice de Masa Corporal , Diabetes Mellitus/sangre , Diabetes Mellitus/tratamiento farmacológico , Activación Enzimática/efectos de los fármacos , Femenino , Humanos , Insulina/sangre , Insulina/farmacología , Linfocitos/enzimología , Masculino , Persona de Mediana Edad , Obesidad/sangre , Placebos , Pérdida de PesoAsunto(s)
Enfermedades del Colon/terapia , Fístula Intestinal/terapia , Cuidados Paliativos/métodos , Fístula Rectal/terapia , Stents , Adenocarcinoma/complicaciones , Anciano , Femenino , Humanos , Obstrucción Intestinal/terapia , Neoplasias del Colon Sigmoide/complicaciones , Fístula de la Vejiga Urinaria/terapia , Fístula Vaginal/terapiaRESUMEN
Two proteins were isolated, in a stable form, from bovine brain by ion exchange chromatography, gel filtration and ultracentrifugation on glycerol gradient. They were identified as 20S and 26S proteasomes on the basis of molecular mass, migration velocity on non-denaturing gels, immunoreactivity, multipeptidase activity and the 26S proteasome also for dependence on ATP for the degradation of short peptides and ubiquitinylated proteins. However, the 26S proteasome has some properties not yet described for its counterpart of other tissues and from brain of this and other species. In particular, the ATP concentration required by the 26S proteasome to reach maximal peptidase activity was approximately 40-fold lower than the one required for maximal proteolytic activity on polyubiquitinylated substrates. Moreover, plots of substrate concentration vs. velocity gave a saturation curve for the 26S proteasome only, which, for the trypsin-like and post-glutamyl peptide hydrolase activities fitted the Michaelis-Menten equation, whereas for the chymotrypsin-like activity indicated multibinding site kinetics with positive cooperativity (n = 2.32+/-0.38). As concerns the 20S proteasome, its electrophoretic pattern on native gel revealed a single protein band, a feature, to our knowledge, not yet described for the brain particle of any species.