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Biomedical subjects

M J Castro

Publications and source records attributed to M J Castro.

At least 55 records · Page 3Linked to original sources
PubMed1997

Mechanisms of and facility types involved in hazardous materials incidents.

The purpose of this study was to systematically investigate hazardous materials (hazmat) releases and determine the mechanisms of these accidents, and the industries/activities and chemicals involved. We analyzed responses by Massachusetts' six district hazmat teams from their inception through May 1996. Information from incident reports was extracted onto standard coding sheets. The majority of hazardous materials incidents were caused by spills, leaks, or escapes of hazardous materials (76%) and occurred at fixed facilities (80%). Transportation-related accidents accounted for 20% of incidents. Eleven percent of hazardous materials incidents were at schools or health care facilities. Petroleum-derived fuels were involved in over half of transportation-related accidents, and these accounted for the majority of petroleum fuel releases. Chlorine derivatives were involved in 18% of all accidents and were associated with a wide variety of facility types and activities. In conclusion, systematic study of hazardous materials incidents allows the identification of preventable causes of these incidents.

Data Collection↗
PubMed1996

Alanine point-mutations in the reactive region of bovine pancreatic trypsin inhibitor: effects on the kinetics and thermodynamics of binding to beta-trypsin and alpha-chymotrypsin.

In an effort to relate structural, kinetic, and thermodynamic features in a model macromolecular recognition process, the amino acid residues in the reactive surface of bovine pancreatic trypsin inhibitor (BPTI) and surrounding residues were substituted individually by alanine, and the effects of the point-mutations on the kinetics and thermodynamics of inhibition by BPTI toward trypsin and chymotrypsin were investigated. Fifteen alanine mutants were produced. The majority of the BPTI mutants exhibited a binding affinity similar to that of the wild-type protein. The exceptions were the primary specificity site (PI) mutant and those mutants that seem to have nonlocal perturbations of structure, as revealed by circular dichroism and thermostability measurements. The mutation at the P1 site caused a reduction in the binding free energy of 10 and 1.8 kcal mol-1 for trypsin and chymotrypsin, respectively. The losses in binding affinity were determined almost exclusively by an increase in the dissociation rate constant. However, the rate of association of the P1 mutant, Lys-15-Ala, with trypsin was also drastically reduced (> 200-fold). Calorimetric measurements of the heats of binding for the association of chymotrypsin with the wild-type inhibitor and its alanine mutants allowed determination of the relative contributions of the changes in enthalpy and entropy to the free energy of binding. Compensatory changes in the two parameters were observed in several cases, which were attributed to desolvation effects at the binding interface.

Alanine↗
PubMed1996

Allelic diversity at the primate Mhc-G locus: exon 3 bears stop codons in all Cercopithecinae sequences.

Twenty-seven major histocompatibility complex (Mhc)-G exon 2, exon 3, and exon 2 and 3 allelic sequences were obtained together with 12 different intron 2 sequences. Homo sapiens, Pan troglodytes, Pan paniscus, Gorilla gorilla, Pongo pygmaeus, Macaca fascicularis, Macaca mulatta, and Cercopithecus aethiops individuals were studied. Polymorphism does not follow the classical pattern of three hypervariable regions per domain and is found in all species studied; exon 3 (equivalent to the alpha 2 protein domain) shows stop codons in the Cercopithecinae group but not in the Pongidae and human groups. Dendrograms show that cotton top tamarin (Saguinus oedipus) Mhc-G sequences are closer to Homo sapiens and Pongidae than to Cercopithecinae, probably due to the stop codons existing at exon 3 of the latter. There is a clear trans-species evolution of allelism in Cercopithecinae and also in exon 2 of all the other apes studied, but a generation of allelism within each species may be present on exon 3 sequences. This discrepancy may be due to the preferential use of exon 2 over exon 3 at the mRNA splicing level within each species in order to obtain the appropriate functional G product. Mhc-G intron 2 shows conserved motifs in all species studied, particularly a 23 base pair deletion between positions 161 and 183 which is locus specific, and some of the invariant residues, important for peptide presentation, conserved in classical class I molecules from fish and reptiles to humans were not found in Mhc-G alleles; the intron 2 dendrogram also shows a particular pattern of allelism within each species. In summary, Mhc-G has substantial differences from other classical class I genes: polymorphism patterns, tissue distribution, gene structure, splicing variability, and probably an allelism variability within each species at exon 3. The G proteins may also be different. This indicates that the Mhc-G function may not be peptide presentation to the clonotypic T-cell receptor.

Alleles↗
PubMed1996

Adaptive metabolic responses in females of the fighting breed submitted to different sequences of stress stimuli.

The objectives of this study were to evaluate the stress reaction and the metabolic adaptive effort in females of the fighting breed when submitted to different manipulation sequences. Nine 4- to 8-year-old bovine fighting breed females slaughtered to establish the basal levels of different blood parameters. A study was, then, conducted to examine the metabolic response in 30 2-year-old females, divided into 3 groups of 10 animals and submitted to different manipulations in each group: restraint- "open-field" -restraint, "open-field" -restraint, and transportation-restraint- "open-field" -restraint. The basal levels of the different blood parameters found were, in general, similar to the levels for cattle given in the literature. All the manipulations resulted in increases that were statistically different (p < 0.001) from basal levels, in terms of both cortisol plasma levels and the Specie Specific Experimental Response to Stress index (SSERTS). The stress of restraint (and the prior manipulations) seemed to mask the stress associated with the open-field and transport situations. In general, animals responded to 13 of the 15 parameters examined in the various experimental manipulations.

Adaptation, Physiological↗
PubMed1996

Epidemiology of hazardous materials responses by Massachusetts district HAZMAT teams.

Hazardous materials releases can cause substantial morbidity and mortality, but very few studies have systemically investigated them. We analyzed responses by Massachusetts' six district hazardous materials (HAZMAT) teams from the time of their inception through February 1994. Spills, leaks, and other escapes of materials caused or contributed to 67 of 85 (79%) incidents. Transportation-related accidents accounted for 13 of 83 (16%), whereas the remainder of the releases occurred at fixed facilities. The chemicals most frequently involved were various hydrocarbons and corrosive materials. Most incidents (60 of 85 [70%]) had no reported injuries. Civilians were injured in 18 of 85 (21%) incidents; regular fire fighter and/or police were injured in eight of 85 (9%) incidents; and HAZMAT team members in one of 85 incidents (1%). Systematic study is needed to identify preventable causes of HAZMAT responses as well as ideas for better control of secondary health effects.

Accidents, Occupational↗
PubMed1996

Silicone stents in the management of benign tracheobronchial stenoses. Tolerance and early results in 63 patients.

STUDY OBJECTIVE: To assess tolerance and early results of Dumon silicone stents inserted in patients with nonneoplastic airway obstruction. DESIGN: Tracheobronchial stenting for palliative or curative restoration of airway narrowing has been evaluated in a retrospective study. SETTING: Tertiary-referral teaching hospital. PATIENTS: Between May 1991 and September 1994, 64 patients with a mean age of 52 years had endobronchial silicone stent insertion for benign tracheal stenosis (82% secondary to intubation or tracheostomy injury). Lesions were pure fibrous stenosis in 25 patients and fibroinflammatory stenosis in 38. Prostheses were used for temporary stenting of the airway during 18 months in 48 patients in whom cure was expected and as a procedure for palliation in the remaining 15 patients. INTERVENTIONS: In all cases, the Dumon tracheobronchial stent was implanted with the rigid bronchoscope under general anesthesia. RESULTS: Five patients died (four from unrelated causes); one was due to hypersecretion and airway obstruction at the time of an emergency tracheostomy 20 days after stent insertion. Complications included migration of prostheses in 11 (17.5%) patients, granuloma formation in 4 (6.3%) patients, and airway obstruction due to heavy secretion in 4 (6.3%). In 48 patients who received silicone stents with curative expectations, removal of the device was accomplished in 21 patients. Therapy proved successful in 17 patients with a mean follow-up of 259+/- 173 days and stenosis recurred in 4. In 16 patients, stents still remain for a mean period of 364+/-119 days. In the series of 15 patients in whom silicon stents were implanted for palliation, prostheses were placed permanently in 11 with a mean follow-up of 486+/-260 days. In the remaining four patients with tracheostomy, silicone stents were used after inability to expand the upper limb of the T-tube (two patients) or placed above the tracheostomy stoma to maintain laryngotracheal patency and preserve phonation when a T-tube was poorly tolerated (two patients). CONCLUSIONS: Silicone tracheobronchial stents are effective in the maintenance of airway patency and are associated with good tolerance and infrequent complications that are rarely life-threatening.

Adolescent↗
PubMed1995

A spectrophotometric assay for the determination of the catalytic efficiency of plasminogen activators using a slowly hydrolyzed plasmin substrate.

A simple spectrophotometric assay for the determination of the catalytic efficiency and activity of plasminogen activators is presented. The assay system contains activator, plasminogen, and the chromogenic substrate N-benzoyl-L-arginine-p-nitroanilide (BAPA). Plasmin production is monitored continuously by the hydrolysis of BAPA under non-steady-state, first-order conditions with respect to plasminogen. Apparent catalytic efficiency constants are calculated from the values obtained for the apparent first-order rate constant of activation. The results obtained with the present method were compared with the catalytic efficiency determined through the measurement of kcat and Km, using a different system, under steady-state conditions. Tissue plasminogen activator in the absence and presence of fibrinogen and high-molecular-weight urokinase were used as model activators. Potential applications are discussed.

Benzoylarginine Nitroanilide↗
PubMed1995

In vitro stimulation of tissue-type plasminogen activator by Alzheimer amyloid beta-peptide analogues.

We have studied the effects of amyloid beta-peptide analogues on the activity of tissue-type plasminogen activator (t-PA) in vitro. We have found that these peptides have a marked stimulatory effect upon plasminogen activation by t-PA, comparable to that of known stimulators of t-PA. This stimulatory activity appears to increase when beta-peptides form aggregated fibrillar structures similar to those found in amyloid deposits. This finding is significant in that it may provide insights into the pathogenesis of hereditary cerebral haemorrhage with amyloidosis-Dutch type (HCHWA-D) and cerebral amyloid angiopathy-related cerebral haemorrhage. It may also provide an explanation for the deaths resulting from intracerebral haemorrhage that have occurred in patients undergoing t-PA treatment for acute myocardial infarction.

Amino Acid Sequence↗
PubMed1995

Peak torque per unit cross-sectional area differs between strength-trained and untrained young adults.

It is unclear whether gender differences in the relative strength of the upper and lower body are due to differences in muscle mass distribution or dissimilarity of use. There is also controversy as to whether prolonged resistance training increases strength per unit cross-sectional area (CSA). To help resolve these questions, maximum isometric torque per unit muscle and bone (M+B) CSA was measured in the upper arm and thigh of 26 trained (13 males; 13 females) and 26 untrained (13 males; 13 females) young adults. Muscle and bone CSA values were calculated from limb circumferences and skinfolds. Maximal isometric torque values were recorded by a LIDO isokinetic dynamometer. There was no significant difference (P > 0.05) in mean upper arm or thigh torque per unit M+B CSA between the trained males and trained females, or between the untrained males and untrained females. However, mean torque per unit M+B CSA was significantly higher for the trained subjects of both genders compared with the untrained subjects of both genders for the upper arm (28.9%; P < 0.0001) and thigh (18.8%; P < 0.0001). These results suggest that muscle quality (peak torque/CSA) is equal between genders, and that the increase in muscle strength per unit area that occurs with resistance training is not gender-dependent.

Adolescent↗
PubMed1993

Peritoneal resting is beneficial in peritoneal hyperpermeability and ultrafiltration failure.

Ultrafiltration failure (UFF) is one of the most frequent causes of continuous ambulatory peritoneal dialysis (CAPD) dropout and is a common consequence of peritoneal hyperpermeability secondary to inappropriate regeneration of mesothelial cells. In this paper we present the results of 25 peritoneal resting periods of 4 weeks in 16 patients who showed UFF. The mean duration of CAPD was 44 +/- 22 months. All patients had been free of peritonitis for at least 3 months when included in the peritoneal resting trial. UFF was always defined as a long-lasting decrease of UF capacity such that dry weight could no longer be achieved by CAPD. The former incidence of peritonitis was 3.9 +/- 2.3 episodes. Results compared to the preresting data: urea MTC (mass transfer coefficient) decreased from 24.9 +/- 6.8 to 21.0 +/- 6.1 (p < 0.05), creatinine MTC from 16.5 +/- 6.0 to 13.8 +/- 4.0 (p < 0.05), and UF increased from 493.8 +/- 278.0 to 881.3 +/- 388.1 (p < 0.001). The response in terms of UF in patients with low permeability ultrafiltration (creat MTC less than 13) was heterogeneous and lower than in patients with criteria of hyperpermeability (greater than 13): 720 +/- 396 to 1150 +/- 533 (NS) versus 491 +/- 310 to 808 +/- 205, respectively. Simultaneously, creatinine MTC did not change in the former group (10.2), while hyperpermeability patients showed a remarkable decrease (19 +/- 5 to 15 +/- 2, p < 0.05). In conclusion, peritoneal resting is a useful tool in the management of ultrafiltration failure in CAPD patients, primarily in those with peritoneal hyperpermeability.

Adult↗
PubMed1992

Staphylococcus aureus nasal carrier status (SANCS) in CAPD patients; is it induced or favored by subcutaneous rHu-erythropoietin?

Staphylococcus aureus nasal carriage status (SANCS) has been recognized as a risk factor for patients on CAPD, due to a higher probability of suffering peritoneal catheter infections. The use of subcutaneous drugs (insulin dependent diabetics, drug addicts, HD patients and antiallergic vaccines), has been associated with increased risk of SANCS. On CAPD, erythropoietin (EPO) is almost universally used by the subcutaneous route. The objective of this paper was to evaluate the incidence and prevalence of SANCS in 85 CAPD patients by means of nasal smear and the influence of SANCS on peritoneal and catheter infection rate. Patients were divided in four groups according to diabetic status and EPO treatment (mean dose 2000 u. twice a week). The prevalence of SANCS in control groups was 30% in non-diabetics and 23% in diabetics. EPO treated patients showed a prevalence of SANCS of 39% in non-diabetics and 45% in diabetics due to the presence of 7 and 5 carrier patients respectively. SANCS patients (29% of the population), suffered 45% of peritonitis and 42% of exit-site infections caused by S. aureus. In a prospective part of the study, there was no difference in the frequency of developing positive cultures among EPO and control (30% of patients). No male EPO treated patients developed SANCS. We conclude that it is necessary to monitor S. aureus nasal carrier status periodically in CAPD patients especially in women. Whether or not subcutaneous erythropoietin treatment is implicated pathogenetically with SANCS, is not clarified by our data because of the frequent spontaneous appearance of SANCS among CAPD patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Cross-Sectional Studies↗
PubMed1989

Slowly progressive aphasia followed by Alzheimer's dementia: a case report.

Slowly progressive aphasia has been found in 8 published cases, 2 of whom progressed over a period of years to generalized dementia. Positron emission tomography demonstrated decreased glucose metabolism in the left perisylvian region in 2 cases. We describe a patient who had slowly progressive aphasia and developed generalized Alzheimer's dementia 7 years after presentation. There was no clinical or laboratory evidence of concomitant disease. Computerized tomography showed generalized atrophy more marked on the left perisylvian region late in the disease, when EEG showed generalized slowing more marked on the same area. Slowly progressive aphasia of old age should be considered a separate entity until further studies elucidate its relation to Alzheimer's dementia.

Aged↗
PubMed1988

Illiteracy and brain damage. 3: A contribution to the study of speech and language disorders in illiterates with unilateral brain damage (initial testing).

This report bears on the behavior of 188 unilateral stroke subjects when administered an aphasia screening test comprising a short interview as well as naming, repetition, word-picture matching and sentence-picture matching tasks. All subjects were unilingual lusophone adult (40 yr of age or older) right-handers. Furthermore, they were either totally unschooled illiterates or they had received school education and thereafter retained writing skills and reading habits. Subjects were tested less than 2 months after a first unilateral stroke. In all tasks, global error scores were greater among left and right brain-damaged illiterate and literate subjects than among their controls. In repetition and matching, these differences were statistically significant for the left but not for the right-stroke groups, irrespective of the literacy factor. In naming, on the other hand, significant differences were found not only for the two left-stroke groups but also for the right-stroke illiterate group although not for the right-stroke literate one. Likewise, some degree of word-finding difficulty and of reduction in speech output as well as sizeable production of phonemic paraphasias were observed in the interviews of several right-stroke illiterates, clearly less in those of right-stroke literates. These findings lead us to suggest that cerebral representation of language is more ambilateral in illiterates than it is in school educated subjects although left cerebral "dominance" remains the rule in both.

Aphasia↗
PubMed1987

Illiteracy and brain damage--1. Aphasia testing in culturally contrasted populations (control subjects).

One hundred neurologically healthy adults were tested for their pointing (choosing one of four or six line drawings as the match to an auditorily presented linguistic stimulus), naming (from line drawings), and repetition abilities. All subjects were unilingual adult right-handers. Fifty-seven subjects were totally unschooled illiterates and 43 were fluent readers. Statistically significant differences were found to exist between the scores of the illiterate and literate subpopulations across all tasks. With the focus being placed on these cultural differences, the discussion bears on: (a) the interaction between linguistic and iconographic factors in certain types of naming and pointing tasks currently used in clinical and research aphasiology, (b) some of the linguistic parameters which are apparently at stake in repetition behavior, and (c) the circumstances in which aphasiological research dealing with groups of patients cannot yield reliable data without reference to neurologically healthy controls. It is argued that, when testing brain-damaged patients of different cultural backgrounds, one runs the risk of over- or underestimating the frequency of aphasia if one does not refer to norms which explicitly take educational level into account.

Adult↗
PubMed1987

Illiteracy and brain damage. 2. Manifestations of unilateral neglect in testing "auditory comprehension" with iconographic materials.

This report concerns the sentence-picture matching behavior of 100 neurologically healthy and 169 brain-damaged subjects, all of whom were unilingual adult right-handers. Within this population, 144 subjects were totally unschooled illiterates and the remaining 125 had received school education and thereafter had retained writing skills and reading habits. Brain-damaged subjects were tested less than 2 months after a first left- or right-hemisphere stroke. All subjects were administered an aphasia screening battery including, among other subtests, a set of six sentence-picture matching stimuli. For each of these six stimuli, subjects heard a sentence uttered by the examiner and were then requested to match this sentence with one of four drawings presented within a single display divided into four quadrants of equal surface. Three sentences were syntactically "simple" (noun subject + verb) and three were relatively more "complex" (noun subject + verb + one or two noun complements). Evidence of unilateral neglect was found in both left- and right-brain-damaged illiterates and literates. Moreover, the right neglect of left-brain-damaged subjects was manifest mostly when target sentences were relatively "complex" whereas the left neglect of right-brain-damaged subjects was manifest irrespective of the syntactic complexity of target sentences. Our data are interpreted as indicative of an interaction between two cognitive disorders resulting from dysfunctions of asymmetrically represented cognitive mechanisms. The implications of these findings with respect to clinical and research aphasia testing are discussed.

Attention↗
PubMedDate not supplied

Post insertion catheter care in peritoneal dialysis centers across Europe: results of the Post Insertion Project of the Research Board.

The EDTNA/ERCA survey of Post Insertion Catheter Care in Peritoneal Dialysis (PICC) was a project organised through the Collaborative Research Programme (CRP) of the EDTNA/ERCA. In this survey, data were collected from 54 participating centres in 20 countries. From this survey it became clear that there is no standardised approach to immediate post-catheter insertion treatment protocols. If we want to reduce technique failure of PD related to catheter failure, a first step will be to investigate the different policies used in Europe in order to evaluate the outcome results derived from different policies in post insertion catheter care.

Bandages↗
PubMedDate not supplied

Articulatory representation and speech technology.

In this paper we demonstrate the feasibility and usefulness of articulation-based approaches in two major areas of speech technology: speech recognition and speech synthesis. Our articulatory recognition model estimates probabilities of categories of manner and place of articulation, which establish the articulatory feature vector. The transformation from the articulatory level to the symbolic level is performed by hidden Markov models or multi-layer perceptions. Evaluations show that the articulatory approach is a good basis for speaker-independent and speaker-adaptive speech recognition. We are now working on a more realistic articulatory model for speech recognition. An algorithm based on an analysis by synthesis model maps the acoustic signal to 10 articulatory parameters which describe the position of the articulators. EMA (electro-magnetic articulograph) measurements recorded at the University of Munich provide good initial estimates of tongue coordinates. In order to improve articulatory speech synthesis we investigated an accurate physical model for the generation of the glottal source with the aid of a numerical simulation. This model takes into account nonlinear vortical flow and its interaction with sound-waves. The simulation results can be used to improve the articulatory synthesis model developed by Ishizaka and Flanagan (1972).

Equipment Design↗