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Biomedical subjects

M Castro

Publications and source records attributed to M Castro.

At least 217 records · Page 12Linked to original sources
PubMed1992

Alterations in oxytocin prohormone processing during early development in the fetal sheep.

Oxytocin (OT) prohormone processing was studied in fetal sheep. Using specific antisera that recognize the amidated and the COOH-terminal extended forms of OT, we measured arterial and venous levels of the OT peptides in fetal sheep plasma at 94 and 138 days of gestation. Plasma levels of the COOH-terminal extended forms, OT-X, were highest early in development, 35.7 +/- 9.8 vs. 14.3 +/- 5.7 pg/ml (94 vs. 138 days). The ratio of the plasma peptides, OT-X to OT, was higher in the young fetus (35 +/- 11.6 vs. 3.1 +/- 1.3, 94 vs. 138 days). There were also developmental changes in the umbilical artery-umbilical vein differences, with positive values noted in late gestation. These results demonstrate that the changes in the processing of the OT precursor that occur during fetal development are reflected by alterations in the relative amounts of prohormone and amidated hormone found in fetal plasma.

Animals↗
PubMed1992

A rapid and sensitive method for HPLC cholesterol determination in bile.

A relatively little time consuming simple method based on the treatment of bile with cholesterol oxidase and subsequent high performance liquid chromatography measurement of the 3-ketocholesterol produced in order to determine the level of the cholesterol concentration is described. The method avoids bilirubin interferences, has high reproducibility and recovery assays give 100% values. It is highly sensitive and suitable for use in the determination of cholesterol concentrations in bile and other bilirubin containing biological fluids.

Animals↗
PubMed1992

Community health centers: a resource for service and training.

The American Medical Student Association (AMSA) Foundation is assisting the U.S. Public Health Service in increasing the number of primary care physicians trained and committed to practice in medically underserved areas. In collaboration with the American Academy of Family Physicians, the Ambulatory Pediatrics Association, and the Society of General Internal Medicine, AMSA conducted an assessment of federally-funded residency programs to identify and describe their affiliations with federally-funded community and migrant health centers (C/MHCs). Of the 260 programs assessed and the 147 responses, 125 offer community-based training. Of these, 73 offer training in primary care centers and 39 offer training in federally-funded C/MHCs. Residents training in the C/MHCs have positive experiences in both personal and professional development and are frequently hired by the health centers upon graduation. Benefits realized by the affiliations include a community orientation for the residents and enhancement of service and education missions for the collaborating institutions.

Community Health Centers↗
PubMed1992

Combination of an enzymatic method and HPLC for the quantitation of cholesterol in cultured cells.

The study of the cellular events that lead to the foam cell formation requires the development of fast, accurate, and sensitive methods to quantify cholesterol in cultured cells. Here we describe a procedure that allows the rapid determination of free and total cholesterol in a reduced number of cells, which makes it very suitable for cholesterol determination in cell cultures. The method consists of the enzymatic conversion of cholesterol to cholest-4-ene-3-one by cholesterol oxidase followed by the analysis of the sample by high performance liquid chromatography (HPLC) to detect this oxidized product. Due to the relatively high wavelength at which cholest-4-ene-3-one has its maximum absorption (240 nm), other cellular components do not interfere with the chromatographic procedure and prior lipid extraction is not required. Moreover, the duration of each chromatogram is about 3 min, contributing to the celerity of the method. All the cholesteryl esters used (oleate, palmitate, stearate and linoleate) were quantitatively hydrolyzed by incubation with cholesterol esterase; this was observed to occur with both pure standards and in cell homogenates. Sensitivity is enough to allow the determination of free and total cholesterol in less than 5 x 10(3) cells. We have applied this method to human monocyte-derived macrophages and the values obtained for free and total cholesterol are in close agreement with published data.

Cells, Cultured↗
PubMed1991

Rheumatic manifestations in myelodysplastic syndromes.

The myelodysplastic syndromes are characterized by ineffective hematopoiesis with possible transformation to acute nonlymphocytic leukemia. We describe a patient with refractory anemia with excess blasts with unusual rheumatic manifestations of vasculitis, migratory synovitis, arthralgias, and myalgias. A retrospective review over a 6-month period of 162 patients with myelodysplastic syndromes found 16 patients (10%) with several rheumatic manifestations. We divided these manifestations into 4 different categories: cutaneous vasculitis, "lupus-like syndrome," neuropathy, and patients with both a rheumatic disease and a myelodysplastic syndrome. There were 7 with cutaneous vasculitis including leukocytoclastic vasculitis and other individual cases of urticarial vasculitis and panniculitis; 3 with lupus-like manifestations with histological evidence of an inflammatory process; 3 with neuropathic manifestations including peripheral neuropathy, mononeuritis with foot drop, and chronic inflammatory demyelinating polyneuropathy; and 3 patients in which their myelodysplastic syndrome was diagnosed after their rheumatic disease was known, including rheumatoid arthritis. Sjögren's syndrome and mixed connective tissue disease. The class with refractory anemia with excess blasts had 9 patients with rheumatic manifestations but also had the largest number of patients in the study (46/162 or 29%). Three of the 16 patients died, all from the refractory anemia with excess blasts class, reflecting the known mortality in this group of patients. We believe there is a significant association between myelodysplastic syndromes and rheumatic manifestations.

Adult↗
PubMed1991

Biocompatibility of dialysis membranes: a comparative study.

White blood cell counts and plasma C5a anaphylatoxin values were studied during haemodialysis with cuprophane, ethylenevinylalcohol, polycarbonate, polymethylmethacrylate, acrylonitrile, polysulphone and polyacrylonitrile membrane dialysers. Cuprophane induced marked leukopenia with striking plasma generation of C5a. Ethylenevinylalcohol, polycarbonate, polymethylmethacrylate and acrylonitrile promoted an intermediate degree of leukopenia with mild but significant complement activation; however, leukopenia and C5a generation were not time-related with some of these membranes. In contrast, polysulphone and polyacrylonitrile showed neither leukopenia nor C5a increase. These data suggest that although there must be further factors involved, complement-derived anaphylatoxin C5a generation may have a relevant role in the mechanism of haemodialysis-induced leukopenia. At the present time evaluation of the leukopenic effect and the C5a generation capability of a membrane seem worthwhile for estimating its degree of biocompatibility.

Anaphylatoxins↗
PubMed1991

[Primary segmental sclerosing cholangitis associated with Sjögren's syndrome].

We report the case of a patient with primary sclerosing cholangitis associated with Sjögren's syndrome and Raynaud's phenomenon, an uncommon association. The presence of periportal lymph nodes with features similar to those described in autoimmune diseases suggests an immune pathogenesis of the disease. The localized and segmentary involvement of the common duct is also an uncommon finding. The pathogenetic and therapeutic aspects are discussed.

Aged↗
PubMed1991

Whipple procedure for trauma: is duct ligation a safe alternative to pancreaticojejunostomy?

The use of pancreatic duct ligation (DL) during a Whipple procedure for trauma has been reported but not analyzed. We reviewed 13 cases of DL and compared the results with that reported for the Whipple procedure for trauma with pancreaticojejunostomy (PJ). The mortality rate of DL was 53.8%. Pancreatitis occurred in three cases (23.1%) and caused one death. Pancreatic fistulae occurred in 50% of patients surviving two or more days after DL. No long-term survivor developed overt diabetes mellitus. Malabsorption occurred in 50% of the long-term survivors of DL. When the DL and PJ groups were compared no statistically significant difference could be found in either mortality or pancreatic morbidity. The 46.2% survival rate for DL warrants its consideration as a technique available to trauma surgeons when faced with an unstable patient unable to tolerate further operative therapy.

Abdominal Injuries↗
PubMed1990

[Wine as a source of lead contamination: study in the southern region of Sevilla].

To assess whether the wines from the south of Sevilla constitute a source of lead intoxication we have prospectively studied the blood levels of lead in 100 healthy controls, 100 patients with alcoholic and nonalcoholic hepatopathy and at the same time the lead content in 135 samples of water and in 176 samples of alcoholic drinks consumed by the above patients. The results demonstrate: 1) presence of normal amounts of lead (mean +/- SD = 62 +/- 5 micrograms/l) in 97 of wines analyzed; 2) a higher content of lead in wines from areas close to the highway A-4 (100 +/- 10 micrograms/l) than in those from more remote zones (42 +/- 3 micrograms/l, p less than 0.005); and 3) although the blood levels of lead in alcohol consumers are not at the toxic range (22.9 +/- 8.9 micrograms/l) are, however, significantly higher (p less than 0.0007) than in patients with no alcohol intake (16.8 +/- 9.9 micrograms/l) or in healthy persons (17.1 +/- 7.4 micrograms/l, p less than 0.0008). Blood levels of lead correlate with the condition of "usual drinker" but not with the amount of alcohol consumed, number of cigarettes, lead content of water and wine, nor with the existence of severe hepatopathy among the studied factors. Our results suggest that alcohol influences the lead metabolism and that the usual drinkers constitute a risk population for saturnism.

Alcoholism↗
PubMed1990

Does the Kunitz domain from the Alzheimer's amyloid beta protein precursor inhibit a kallikrein responsible for post-translational processing of nerve growth factor precursor?

Alternative splicing of the Alzheimer's amyloid beta protein precursor (ABPP) message leads to the production of several variants of this precursor polypeptide. Two of these variants contain a domain that is highly homologous to members of the Kunitz class of protease inhibitors. In order to initiate a study of the physiological role of this domain, we have produced active ABPP Kunitz inhibitor by constructing and expressing a synthetic gene in E. coli. Nerve growth factor (NGF) deficiency has been suggested as a possible cause of the neural degeneration characteristic of Alzheimer's disease, and trypsin and gamma-NGF are the two enzymes that have been shown to be capable of processing beta-NGF precursor to active, mature beta-NGF in vitro, therefore, the specificity of purified recombinant ABPP Kunitz inhibitor was analyzed with respect to these two proteases. Binding of isolated ABPP Kunitz domain both to trypsin (Ki,app less than 10 nM and to gamma-NGF (Ki,app = 300 nM) was observed. This difference in binding to the two proteases correlates with the approximately 20-fold higher rate observed for in vitro processing of the beta-NGF precursor by trypsin compared to processing by gamma-NGF, indicating that perhaps the inhibitor mimics the interaction of the beta-NGF precursor with proteases. The kallikrein actually responsible for beta-NGF precursor processing in vivo is unknown, but these results suggest that it is capable of being significantly inhibited by exposure to the ABPP Kunitz domain.

Alzheimer Disease↗
PubMed1990

Variation in glycogen and mucins in the equine uterus related to physiologic and pathologic conditions.

Histochemical stains were applied to six equine uterine biopsies representative of the physiologic breeding season, Spring and Fall transition, and Winter anestrus periods. These were compared with uterine biopsies from six mares with intrauterine urine pooling, eight mares used to study the uterine response to indwelling catheterization, and necropsy specimens from four pregnant mares at approximately 60 or 100 d of gestation. Alcian blue staining at pH 2.5 or 1.0 was used to identify the presence of carboxylated and sulfated acid mucins or only suflated acid mucins, respectively. Periodic acid-Schiff staining was used to identify neutral mucosubstances or glycogen, with or without prior diastase digestion. The uterine glands contained glycogen, which was most abundant during the physiologic breeding season. The luminal epithelial cells during the physiologic breeding season and Spring and Fall transition contained predominately carboxylated acid mucins. Carboxylated acid mucin secretion also was stimulated by indwelling catheterization and intrauterine urine pooling. It is hypothesized that secretion of carboxylated acid mucins by the endometrial epithelium may be elicited by hormonal or irritative/inflammatory stimuli, and it may be a protective response.

Journal Article↗
PubMed1990

Characterization of adrenocorticotropin secretion in a patient with 17 alpha-hydroxylase deficiency.

17 alpha-Hydroxylase deficiency (17-OHDS) is a peculiar type of adrenal insufficiency because of elevated corticosterone (B) production. Episodic and circadian ACTH secretion and the responses to ovine CRH and metyrapone were examined in a female with 17-OHDS under conditions of normal sodium (NSI) and low sodium (LSI) intake. Plasma ACTH and B were higher on LSI than on NSI (mean +/- SD: ACTH, 58 +/- 20 vs. 33 +/- 14 pmol/L; B, 508 +/- 107 vs. 381 +/- 69 nmol/L). ACTH pulses were concomitant with or followed by B pulses. An increase in the amplitude, but not the number, of ACTH and B pulses was found on LSI. Circadian ACTH and B rhythms persisted on LSI. Aldosterone levels were higher on LSI than on NSI. After metyrapone, plasma B decreased in the afternoon (NSI, 220 +/- 10; LSI, 275 +/- 35 nmol/L) and rose on the following morning. Plasma ACTH increased substantially on the following morning (NSI, 135 +/- 47; LSI, 307 +/- 77 pmol/L). The ACTH peak levels after ovine CRH increased after metyrapone administration. These data indicate that B may also have a negative feedback effect at the pituitary level. In all maneuvers, there were no changes in PRA, plasma sodium and potassium, or cortisol. We conclude that in 17-OHDS, in the absence of cortisol production, ACTH and B may interact to modulate the brain-pituitary-adrenocortical system.

Adolescent↗
PubMed1990

Blood platelet formation in vitro. The role of the cytoskeleton in megakaryocyte fragmentation.

We have developed a unique in vitro model that promotes differentiation of megakaryocytes into platelets. When megakaryocytes isolated from guinea pig bone marrow were cultured on hydrated rat tail collagen gels, cells spontaneously formed elongated, beaded processes that fragmented to yield cytoplasmic pieces with the same size and internal composition as individual platelets. Addition of nocodazole at the initiation of cultures blocked process formation, while addition of nocodazole to cells with previously established processes resulted in their retraction. The addition of taxol to cultures resulted in abnormally thick processes that were tightly adherent to the underlying substratum, and did not bead or fragment. Cytochalasin D accelerated process formation and fragmentation of megakaryocytes cultured on collagen gels by twofold. On the basis of these results, we propose a model for platelet formation in culture that involves the following steps: adherence of megakaryocytes to the underlying extracellular matrix; dilation of the demarcation membrane system and breakdown of the actin-rich peripheral zone; microtubule-based extension of pseudopodia, which are no longer adherent to the substratum; and fragmentation into platelets by the coalescence and fusion of demarcation membrane vesicles with the plasma membrane. We feel that this distinctive culture system closely approximates thrombocytopoiesis in vivo, thus allowing detailed elucidation of this important process.

Actins↗
PubMed1990

Prevalence and comparison of serologic assays, necropsy, and tongue examination for the diagnosis of porcine cysticercosis in Peru.

Swine cysticercosis, a severe zoonotic disease which is part of the Taenia solium life cycle, causes major economic losses in pig husbandry. Throughout South America, farmers diagnose cysticercosis by examining the tongues of their pigs for cysticercus nodules. Farmers do not bring pigs believed to be infected to the slaughterhouse for fear of confiscation. Therefore, reliable statistics on porcine cysticercosis can only be acquired at the household level. We examined the utility of the tongue test as a diagnostic tool for porcine cysticercosis. The results of the tongue test was compared with 2 serologic methods for the detection of cysticercosis, the enzyme-linked immunosorbent assay (ELISA) and the enzyme-linked immunoelectrotransfer blot assay (EITB), and with necropsy results. We examined 11 animals from an endemic area (Huancayo) and 42 animals from an area free of cysticercosis (Lima). The tongue test has a sensitivity of 70% and a specificity of 100%, the EITB a sensitivity and specificity of 100%, and the ELISA a sensitivity of 79% and a specificity of 75%. Thus, the tongue examination, being a test essentially without cost and having fair sensitivity and high specificity, can be useful in epidemiological surveys. Prevalence for porcine cysticercosis in Huancayo is 23.4% by tongue examination, 31.2% by necropsy, 37.7% by ELISA, and 51.9% by EITB.

Animals↗