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Biomedical subjects

M A Pastor

Publications and source records attributed to M A Pastor.

At least 19 recordsLinked to original sources
PubMed2006

Topography of cortical activation differs for fundamental and harmonic frequencies of the steady-state visual-evoked responses. An EEG and PET H215O study.

In humans, visual flicker stimuli of graded frequency (2-90 Hz) elicit an electroencephalographic (EEG) steady-state visual-evoked response (SSVER) with the same fundamental frequency as the stimulus and, in addition, a series of harmonic responses. The fundamental component of the SSVER is generated by increased synaptic activity in primary visual cortex (V1). We set out to determine the cortical origin of the harmonic responses in humans. For this purpose, we recorded the SSVERs at 5 different frequencies (5, 10, 15, 25, and 40 Hz) and measured regional cerebral blood flow (rCBF) with positron emission tomography-H(2)(15)O at rest and during visual stimulation at the same frequencies. The rCBF contrast weighted by the amplitude of the SSVERs first harmonics showed activation of a swath of cortex perpendicular to V1, including mostly the inferior half of the parieto-occipital sulcus. This area overlapped minimally with the primary visual cortex activated by the fundamental frequency. A different method, estimating EEG cortical source current density with low-resolution brain electromagnetic tomography, gave the same results. Our finding suggests that the inferior portion of the banks of the parieto-occipital sulci contains association visual cortex involved in the processing of stimuli that can be as simple as a flickering light source.

Adult↗
PubMed2005

The neural basis of temporal auditory discrimination.

When two identical stimuli, such as a pair of clicks, are presented with a sufficiently long time-interval between them they are readily perceived as two separate events. However, as they are presented progressively closer together, there comes a point when the two separate stimuli are perceived as one. This phenomenon applies not only to hearing but also to other sensory modalities. Damage to the basal ganglia disturbs this type of temporal discrimination irrespective of sensory modality, suggesting a multimodal process is involved. Our aim was to study the neural substrate of auditory temporal discrimination in healthy subjects and to compare it with structures previously associated with analogous tactile temporal discrimination. During fMRI scanning, paired-clicks separated by variable inter-stimulus intervals (1-50 ms) were delivered binaurally, with different intensities delivered to each ear, yielding a lateralised auditory percept. Subjects were required (a) to report whether they heard one or two stimuli (TD: temporal discrimination); or (b) to report whether the stimuli were located on the right or left side of the head mid-line (SD: spatial discrimination); or (c) simply to detect the presence of an auditory stimulus (control task). Our results showed that both types of auditory discrimination (TD and SD) compared to simple detection activated a network of brain areas including regions of prefrontal cortex and basal ganglia. Critically, two clusters in pre-SMA and the anterior cingulate cortex were specifically activated by TD. Furthermore, these clusters overlap with regions activated for similar judgments in the tactile modality suggesting that they fulfill a multimodal function in the temporal processing of sensory events.

Acoustic Stimulation↗
PubMed2002

Cutaneous metastases from Ewing's sarcoma: report of two cases.

Ewing's sarcoma is a malignant osseous neoplasm that affects mostly children and young adult males. Clinically, the neoplasm presents with oedema, swelling, and pain of the involved area. Histopathologically, Ewing's sarcoma consists of solid sheets of small round cells, with vesicular nuclei and scant cytoplasm, arranged in irregular masses separated by strands of fibrous tissue, with areas of necrosis en masse intermingled with intratumoural haemorrhage. Ewing's sarcoma is an extremely aggressive neoplasm and metastases to sites such as lung, pleura, other bones, central nervous system, liver, and regional lymph nodes frequently develop in early stages of the disease. Surprisingly, despite the highly aggressive biological behaviour of this neoplasm, cutaneous metastases from Ewing's sarcoma are very uncommon. We report two patients with Ewing's sarcoma of the bone who developed cutaneous metastases. As in other internal malignancies, the onset of cutaneous metastases in patients with Ewing's sarcoma indicates a poor prognosis.

Adult↗
PubMed2002

Drug eruption secondary to aciclovir with recall phenomenon in a dermatome previously affected by herpes zoster.

Classically, recall dermatitis refers to chemotherapy-induced reactivation of skin damage caused by radiotherapy months, or even years, earlier. The concept of recall dermatitis has now been extended to include radiation recall dermatitis induced by other drugs, ultraviolet radiation, extravasation of drugs, and allergic contact dermatitis. We now describe recall dermatitis along the residual cutaneous lesions of a previous thoracic herpes zoster in a patient who developed a drug eruption after oral administration of aciclovir. The most striking feature consisted of confluent linear erythema along the dermatomes previously involved by the herpes zoster episode. Histopathologic study demonstrated small foci of spongiosis, vacuolar changes involving the basal layer of the epidermis and single necrotic keratinocytes scattered within the epidermis. The papillary dermis appeared oedematous and with dilated blood capillaries surrounded by a sparse inflammatory infiltrate composed mainly of lymphocytes. Serial sections failed to demonstrate cytologic changes of herpes varicella zoster infection. We interpreted this case as an example of recall dermatitis because the widespread cutaneous eruption secondary to aciclovir was more intense in skin previously compromised by herpes varicella zoster infection. To the best of our knowledge, recall dermatitis has not been described before at the site of previous involvement by herpes zoster.

Acyclovir↗
PubMed2001

Epithelioid blue naevus of the genital mucosa: report of four cases.

Epithelioid blue naevi are an unusual cytological variant of blue naevus that have been recently described mostly in patients with the Carney complex, although they may also occur in isolation. This variant of blue naevus is composed of melanin-laden polygonal epithelioid melanocytes situated within the dermis. The neoplastic cells show no maturation with progressive depth of dermal infiltration and, in contrast with the usual stromal changes in blue naevi, epithelioid blue naevi exhibit no dermal fibrosis. We describe four cases of epithelioid blue naevus located on the genital mucosa in four patients with no evidence of the Carney complex. Three male patients showed an epithelioid blue naevus on the mucosa of the glans penis and a female patient had a lesion of the right labium minoris. Histopathologically, the lesions consisted of entirely intradermal melanocytic naevi composed mostly of heavily pigmented epithelioid melanocytes involving the dermis of the genital mucosa. Immunohistochemically, in all cases, epithelioid melanocytes expressed immunoreactivity for S-100 protein, HMB-45, Melan-A and MiTF antibodies.

Adult↗
PubMed2001

Postirradiation pseudosclerodermatous panniculitis.

Pseudosclerodermatous panniculitis is an unusual variant of panniculitis that results as a complication of megavoltage radiotherapy. Four women developed this unusual entity on the anterior chest and abdominal skin after receiving megavoltage therapy for either breast carcinoma or painful bone metastases from breast carcinoma. Histopathologically, the epidermis and dermis of the involved area showed little or no evidence of radiodermatitis. The main findings were confined to the subcutaneous tissue and consisted of thickened, sclerotic septa composed of both thick and thin collagen bundles, and a lobular panniculitis characterized by lipophagic granulomas and scattered lymphocytes and plasma cells. Additionally, one of the cases showed markedly dilated vascular spaces with the appearance of lymphatics in the upper part of the dermis. Pseudosclerodermatous panniculitis after irradiation is an unusual cutaneous complication of megavoltage radiotherapy that should be distinguished from subcutaneous metastatic disease, cellulitis, or connective tissue diseases involving the subcutaneous fat. The differential diagnosis can be established on the basis of the characteristic histopathologic features of postirradiation pseudosclerodermatous panniculitis.

Adult↗
PubMed2001

Olmsted syndrome: report of a case with study of the cellular proliferation in keratoderma.

Olmsted syndrome is a rare disorder that consists of sharply marginated keratoderma of the palms and soles, constriction of digits and toes that may result in spontaneous amputation of the distal phalanges, hyperkeratotic plaques around the body orifices, onychodystrophy, and other less common cutaneous and extracutaneous anomalies. Although some patients had other affected family members, most cases of Olmsted syndrome seem to be of sporadic occurrence. We describe a patient with the characteristic features of Olmsted syndrome. The symptoms consisted of diffuse transgrediens palmoplantar keratoderma and keratotic plaques around the mouth and nose. Our patient also had the associated anomalies of hyperhidrosis of the palms and soles and congenital deaf-mutism. Histopathologic study of the keratoderma demonstrated epidermal hyperplasia with acanthosis, papillomatosis, and orthokeratotic hyperkeratosis. Immunohistochemical study showed more basal and suprabasal keratinocytes of the epidermis with immunoreactivity for Ki-67 marker when compared with the keratinocytes of the epidermis of the adjacent non-involved skin. These results support the notion that Olmsted syndrome is a hyperproliferative disorder of the epidermis.

Adult↗
PubMed2001

Famciclovir treatment in transplant recipients with HBV-related liver disease: disappointing results.

OBJECTIVE: Long-term administration of hepatitis B immune globulin is effective as prophylaxis for hepatitis B virus (HBV) reinfection but is limited by cost, side effects, availability and a failure rate of 20%. Famciclovir has been shown to be effective in the treatment of hepatitis B in the immunocompetent patient. Fewer data exist in the liver transplant setting, particularly regarding its efficacy in de novo HBV infection. The aims of this pilot study were to determine the effectiveness and safety of long-term administration of famciclovir in recurrent (n = 3) and de novo (n = 3) HBV infection after liver transplantation. METHODS: Six patients with postransplant HBV infection (positivity of serum HBsAg and HBV DNA), four of whom were HBeAg positive, were treated with famciclovir (500 mg, 3 times a day) with a minimum follow-up period of 12 months. Biochemical, serological, virological (HBV DNA by hybridization assays and polymerase chain reaction), and histological (including HBV immunostaining) endpoints were evaluated. RESULTS: None of the patients had a complete biochemical response, with a near complete normalization of ALT levels being observed in 3/6 patients. There was a lack of correlation between virological and biochemical responses. None of the patients seroconverted to anti-HBs or anti-HBe. A virological clearance was observed in only two patients, whereas a moderate reduction in HBV DNA levels was present in one. HBV DNA levels were higher than levels during pretreatment in the three remaining patients. Histological improvement was only observed in one patient. CONCLUSION: Famciclovir alone appears of limited efficacy in the treatment of HBV infection after liver transplantation.

2-Aminopurine↗
PubMed1999

[Carcinoid syndrome: advances in diagnosis and treatment].

Carcinoid is the most common endocrine digestive tumor. The carcinoid syndrome resulting from the variety of amines and peptides produced by this tumor is usually apparent once there are metastases to the liver. Tumors with direct systemic venous drainage seldom produce a carcinoid syndrome without the presence of liver metastasis. This may occur because the hormone escapes the normal metabolic pathway (monoamine oxidase) in the liver. The most significant and important advance in diagnosis for tumor localization has been the introduction of scintigraphy using 111In-labeled octreotide. Current management of carcinoid syndrome should consider the spontaneous course of the disease and the severity of clinical symptoms, and includes different therapeutic options as hepatic resection, chemoembolization, medical treatment with the long-acting analogues of somatostatin and liver transplantation.

Digestive System Neoplasms↗
PubMed1999

[Acute hepatitis due to heatstroke].

The hepatic injury is a nearly constant event in the course of a heatstroke, which rarely evolves to a severe liver failure. In these cases, the patient's survival is conditioned to an early treatment and, sometimes, an orthotopic liver transplantation is needed. We report a case of severe acute hepatitis in a 17-year-old man, due to a heatstroke during a vigorous exercise in a training program. High ambient temperature and a long time without training predisposed to the development of heatstroke in this patient. Outcome was favourably, with a total recovery in a few weeks.

Acute Disease↗
PubMed1997

Human body-segment tilts induced by galvanic stimulation: a vestibularly driven balance protection mechanism.

1. We have studied the effects of changes in posture on the motor response to galvanic vestibular stimulation (GVS). The purpose of the experiments was to investigate whether the function of the GVS-evoked response is to stabilize the body or the head in space. Subjects faced forwards with eyes closed standing with various stance widths and sitting. In all cases the GVS-evoked response consisted of a sway of the body towards the anodal ear. 2. In the first set of experiments the response was measured from changes in (i) electromyographic activity of hip and ankle muscles, (ii) the lateral ground reaction force, and (iii) lateral motion of the body at the level of the neck (C7). For all measurements the response became smaller as the feet were placed further apart. 3. In the second set of experiments we measured the GVS-evoked tilts of the head, torso and pelvis. The basic response consisted of a tilt in space (anodal ear down) of all three segments. The head tilted more than the trunk and the trunk tilted more than the pelvis producing a leaning and bending of the body towards the anodal ear. This change in posture was sustained for the duration of the stimulus. 4. The tilt of all three segments was reduced by increasing the stance width. This was due to a reduction in evoked tilt of the pelvis, the bending of the upper body remaining relatively unchanged. Changing from a standing to a sitting posture produced additional reductions in tilt by reducing the degree of upper body bending. 5. The results indicate that the response is organized to stabilize the body rather than the head in space. We suggest that GVS produces a vestibular input akin to that experienced on an inclined support surface and that the function of the response is to counter any threat to balance by keeping the centre of mass of the body within safe limits.

Electric Stimulation↗
PubMed1996

Intracellular Localization and intercellular heterogeneity of the human DNA repair protein O(6)-methylguanine-DNA methyltransferase.

O(6)-Methylguanine-DNA methyltransferase (MGMT) is a DNA repair protein that removes alkyl adducts from DNA and may be important in tumor resistance to alkylation chemotherapy. MGMT was visualized in human cells and tumor tissues with monoclonal antibodies against MGMT and immunofluorescence microscopy, and fluorescent signals were quantified by digital image analysis. MGMT was found both in the cytoplasm and the nucleus, and in either locale the protein reacts with alkylated DNA bases and becomes inactivated and lost from the cell. Cell lines in culture and xenografts showed a broad normal distribution of nuclear MGMT levels, but human brain tumors often showed a skewed distribution, with a significant fraction of cells with high levels of MGMT. O(6)-Benzylguanine, a suicide substrate inactivator for MGMT activity, reduced MGMT in human cells and in a mouse xenograft to levels undetectable by antibody assay 1 h post-treatment. In melanoma specimens taken from a patient 3 h post-treatment with temozolomide, MGMT levels were reduced by 70%. This quantitative immunofluorescence assay can be used to monitor MGMT and it depletion in human tumors to improve the use of alkylating agents in cancer chemotherapy.

Animals↗
PubMed1996

Doctors' decision-making on giving information to cancer patients.

A major focus in the literature about doctor-patient communication is information-giving. In the case of cancer patients, one significant issue is which factors determine whether and how, general practitioners and oncologists give information to their patients. Whatever may be the content of information, the most important choice for the doctor is to give information or not. Our research group at the Department of Health Psychology has conducted investigations in order to identify the significant determinants of decisions concerning giving information to cancer patients. A sample of 60 doctors from Alicante province in Spain were asked their criteria for giving information about a cancer diagnosis. Results showed that perceived intelligence and emotional control in the patients were the best predictors of the decision by doctors to give information. Age and socio-economic status were also significantly associated with the doctors' information-giving practices. These data suggest that the criteria for giving information to cancer patients are subjective and show a strong cultural influence.

Health Knowledge, Attitudes, Practice↗
PubMed1993

Vestibular induced postural responses in Parkinson's disease.

We have tested the hypothesis that dysfunction of the vestibular control of posture is a principal cause of parkinsonian instability by measuring the body sway response induced by galvanic vestibular stimulation (0.5 mA for 2 s) in a group of patients with Parkinson's disease (n = 15). Responses were compared with those obtained from a group of age-matched control subjects (n = 10). Subjects were stimulated (randomized polarity) whilst standing with feet together, eyes closed and maintaining one of five head yaw angles. The motion of the body and the ground reaction forces were measured in three dimensions. There was no significant difference between patients and controls in the speed or direction of the induced body sway response. When the patients were subdivided into two groups according to a clinical assessment of postural deficit, the more disabled group was found to respond with significantly greater body speed than either the control group or the mildly affected patient group. However, the baseline speed of spontaneous body sway was also greater in these patients and it was found that response speed was linearly related to baseline body sway even for the control group. There were no significant differences between any of these groups in the latency to onset, latency to peak or peak amplitude of the initial horizontal ground reaction force response to the stimulus. We conclude that vestibular dysfunction does not explain the postural deficits of patients who are mildly or moderately affected by Parkinson's disease.

Biomechanical Phenomena↗
PubMed1993

Patients' beliefs about their lack of pain control in primary fibromyalgia syndrome.

This study had two aims, first, to determine the expectancies of control over pain experience ('pain locus of control') of patients with primary fibromyalgia syndrome (PFS) and to compare them with other chronic rheumatic diseases. Second, to analyse the relationships between health status and locus of control. We applied the Multidimensional Health Locus of Control-Pain and the Arthritis Impact Measurement Scales (AIMS), by interviewing 137 out patients (32 PFS, 32 RA, 20 SLE, 22 AS and 31 OA). Data were analysed by ANOVA and partial correlation tests. PFS patients believed that their symptoms depended on uncontrollable events and that they could not influence their disease by themselves. PFS patients were the most disabled on the 'Affect' (P < or = 0.001) and 'Symptom' factors (P < or = 0.01). In the PFS group, patients who showed a 'Fate' locus of control orientation reported more disability on 'Affect' and 'Social Interaction' AIMS factors.

Adult↗