Biomedical subjects

M D Perez

Publications and source records attributed to M D Perez.

At least 37 records · Page 2Linked to original sources

PubMed1995

Calcium tracer kinetics show decreased irreversible flow to bone in glucocorticoid treated patients.

Osteopenia resulting from pharmacologic doses of glucocorticoids is well known. Previously, there has been no satisfactory quantitative model describing the kinetics of calcium flow in subjects on chronic steroid use. A mathematical model of calcium isotope interaction with bone is described and applied to determine an estimate of kinetic parameters characterizing these changes. Calcium tracer dilution kinetics after a bolus injection of 42Ca were measured in 14 subjects with juvenile dermatomyositis, 6 on prednisone regimens and 8 on treatment regimens without prednisone. Irreversible tracer loss from plasma bone is found to be significantly reduced (P = 0.043) in the glucocorticoid-treated patients compared with patients on nonsteroid regimens. Reversible flow to bone is noted to be similar in the two groups. These results suggest a direct effect of glucocorticoids on osteoblast function.

Adolescent↗

PubMed1995

A three-hour measurement to evaluate bone calcium turnover.

It is well established that short-term clearance of an intravenous calcium load in vivo reflects bone uptake. Using results from isotope-dilution experiments with 42Ca, a 3-h test has been developed to measure a quantity, gamma, related to bone accretion. This test is proposed as a useful, clinically applicable measure of bone status. For early times, t, after a bolus of 42Ca, plasma tracer dilution was well approximated by t-gamma, where gamma is related to the fractional rate of loss of tracer, q, from blood into bone (1/q)(dq/dt) = -gamma/t). Gamma was evaluated from kinetic measurements on 91 normal female children, adolescents, and adult women in the age range 4-50 years. For t < or = 3 h, all clearance curves were well fit by a power function. Gamma was found to vary from 0.244 +/- 0.031 for adult premenopausal women (N = 22) to 0.392 +/- 0.056 for prepubertal children (N = 29). Using the Spearman rank-order correlation test, gamma was correlated with bone accretion measured from classic calcium kinetic studies with a correlation coefficient of 0.721, significant at p < 0.005. In those cases in which accretion and resorption remain tightly linked, gamma also provides information on the state of calcium loss from bone. Gamma was evaluated in 14 subjects with bone disease characterised by increased resorption (osteoporosis, Paget's disease) and in 27 subjects with decreased accretion (osteogenesis imperfecta, types I, III, IV; steroid-treated juvenile dermatomyositis). All subjects with Paget's disease and with osteoporosis showed increased gamma, consistent with high bone turnover. The osteoporotic patients furthermore exhibited gamma increasing monotonically by approximately 1% per year after age 55.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Fatal myocardial infarction in an 8-year-old girl with systemic lupus erythematosus, Raynaud's phenomenon, and secondary antiphospholipid antibody syndrome.

An 8-year-old black girl with a 5 month history of systemic lupus erythematosus (SLE) and secondary antiphospholipid syndrome (APS) developed Raynaud's phenomenon, marked hemolytic anemia, and a fatal myocardial infarction (MI). Pathologic evaluation of the heart demonstrated a transmural acute MI associated with a recent thrombus of the circumflex coronary artery, thrombosis of small intramural arteries, and a coronary arteriopathy resembling fibromuscular dysplasia. Inflammatory or atherosclerotic changes of the coronary arteries were distinctly absent. This case represents the youngest reported patient with SLE, MI, and pathologic confirmation of nonatheromatous coronary artery disease. The observed coronary pathological findings may have accentuated the thrombogenic potential of the APS, resulting in coronary thrombosis. Cardiac lesions in SLE and APS are reviewed, and pathogenetic considerations for the coronary vasculopathy are discussed.

Anemia, Hemolytic↗

PubMed1994

Pediatric rheumatic diseases.

The rheumatic diseases of childhood are a relatively common and extraordinarily diverse group of illnesses; nevertheless, they are at least distantly related by similarities of immunodysregulation. These pathophysiologic relationships are reflected in affected children in similarities of historical, physical, and laboratory data as well as therapeutic intervention.

Adrenal Cortex Hormones↗

PubMed1994

Mineral metabolism in children with dermatomyositis.

OBJECTIVE: To measure calcium metabolism in 12 children with juvenile dermatomyositis (JDM). METHODS: We used dual-tracer stable isotope studies to measure calcium metabolism in 12 children with JDM and a group of 43 healthy children (Group HC) of similar ages. Five of the JDM subjects were receiving steroids (Group JDM-ST) and 7 were not (Group JDM-NS). RESULTS: The rate of calcium absorption in Group JDM-ST was lower than that in Group HC (19 +/- 10% vs 30 +/- 11%, p < 0.05). The lower rate of absorption was associated with a net loss of calcium each day (calculated calcium retention, Vbal, of -35 +/- 14 mg/day compared to +140 +/- 97 mg/day in Group HC, p < 0.01). Group JDM-NS showed slightly lower calcium absorption than Group HC and significantly lower Vbal (+33 +/- 70 mg/day, p < 0.01 vs Group HC) than Group HC. Group JDM-ST subjects also had decreased bone calcium deposition rates. CONCLUSION: Patients with JDM may be at risk for significant loss of bone mineral associated with decreased calcium absorption, especially in the acute phase of their disease when they are receiving steroid therapy.

Absorption↗

PubMed1992

Effect of beta-lactoglobulin on the activity of pregastric lipase. A possible role for this protein in ruminant milk.

The interaction of bovine beta-lactoglobulin with palmitic and oleic acids has been studied by a partition equilibrium method. Bovine beta-lactoglobulin displays only one high affinity binding site for fatty acids whose association constants for palmitic and oleic acids are 4.2 x 10(6) and 2.3 x 10(6) M-1, respectively. However, other binding sites with low affinity are also present. The existence of one high affinity binding site is in accordance with the amount of fatty acids naturally bound to beta-lactoglobulin isolated from milk. The effect of beta-lactoglobulin on ruminant pregastric lipases from a pharyngeal extract has been assayed. The activity of pharyngeal lipase on a triglyceride emulsion is increased about 200%, 250% and 190% in the presence of 10 mg/ml, 20 mg/ml and 40 mg/ml of beta-lactoglobulin, respectively, the last concentration representing that found physiologically in colostrum. Albumin, another ligand-binding protein, increases the activity of this enzyme to a lesser extent and high levels tend to inhibit enzyme action. These results indicate that beta-lactoglobulin could participate in the digestion of milk lipids during the neonatal period by enhancing the activity of pregastric lipase through removal of the fatty acids that inhibit this enzyme.

Animals↗

PubMed1991

Insulin in bovine colostrum and milk: evolution throughout lactation and binding to caseins.

The changes in insulin concentration in bovine milk in the first period of lactation and its association with other milk proteins were studied. Highest concentration was found in the first milking (327 ng/ml). This concentration fell within the first 24 h postpartum to about 50% of its initial value. By d 3, the level was about 25%, and, on d 7, a stable concentration was reached at approximately 46 ng/ml (about 14% of its initial value). This concentration is about 100 times higher than that in serum, which suggests a specific mechanism of transfer from blood to milk. Colostral whey obtained by ultrafiltration or ultracentrifugation contains much less insulin than colostrum. When colostrum or milk was incubated with [125I]insulin and whey and casein fractions were separated by precipitation, it was observed that most insulin remained with the casein. However, when colostrum was incubated with [125I]insulin and subjected to gel filtration, most of the radioactivity corresponded to free insulin, indicating that insulin is associated with the precipitated casein but not with the casein micelles in solution.

Animals↗

PubMed1990

Negative inotropic effect induced by diethylamiloride (DEA) in rabbit myocardium.

The effects of the Na+/H+ exchange blocking drug diethylamiloride (DEA) on mechanical function have been studied in the rabbit isolated, arterially perfused interventricular septum. At concentrations of 10(-6)-10(-5) M, DEA induced a significant, dose-dependent, negative inotropic effect (a 54% decrease from control values at the highest concentration), which was slow to develop. After a 45 min washout, recovery was almost complete (95 +/- 3.4%). At concentrations greater than 5 x 10(-5) M, DEA induced a rapid and marked decrease in developed tension, associated with a progressive decrease in excitability and incomplete recovery. Resting tension was not significantly modified at any of the concentrations tested. At greater than 10(-6) M DEA enhanced significantly the transient negative inotropic effect of the brief intracellular acidosis induced by removal of NH4Cl perfusion, both by decreasing the minimal value of developed tension and by increasing the time required to produce this effect. These effects suggest that the dose-dependent DEA negative inotropic effect could be mediated by a progressive intracellular acidosis produced by inhibition of the Na+/H+ exchange system.

Amiloride↗

PubMed1990

Synthesis and evolution of concentration of beta-lactoglobulin and alpha-lactalbumin from cow and sheep colostrum and milk throughout early lactation.

Synthesis of beta-lactoglobulin and alpha-lactalbumin by explants of ovine mammary gland and evolution of concentration of these proteins in cow and sheep colostrum and milk throughout early lactation have been studied. The evolution of both proteins was similar in cow and sheep species. The highest concentration was found in the first milking (19 and 2 mg/ml for beta-lactoglobulin and alpha-lactalbumin, respectively). Then, levels of beta-lactoglobulin decreased sharply and those of alpha-lactalbumin slowly during the first days of lactation, reaching stable values during the second week postpartum (4 and 1.5 mg/ml). The concentration ratio beta-lactoglobulin/alpha-lactalbumin was four times greater in colostrum than in mature milk. On the other hand, synthesis of these proteins represented about 25-30% of the synthesized total soluble proteins. The synthesis ratio beta-lactoglobulin/alpha-lactalbumin in explants obtained at 12 and 30 hours postpartum was found to be 3.5 and 1.7. These results indicate that the synthesis and secretion of beta-lactoglobulin are comparatively greater than those of alpha-lactalbumin during colostral period, suggesting that beta-lactoglobulin could have some specific function during this period.

Animals↗

PubMed1989

Time-course levels of alpha 2-macroglobulin and albumin in cow colostrum and milk and alpha 2-macroglobulin levels in mastitic cow milk.

Time-course levels of alpha 2-macroglobulin and albumin in cow's colostrum and milk during lactation were investigated in order to obtain data that could help to elucidate the biological role of alpha 2-macroglobulin in mammary secretions. Levels of these proteins were also studied in mastitic cow milk and were related to the degree of mastitis, which could allow its use as a mastitis marker. The highest concentration of alpha 2-macroglobulin was found in the first milking (386.7 micrograms/ml). This value decreased very rapidly during the colostral period, attaining its definitive value during the 2nd wk postpartum (4.5 micrograms/ml). The albumin/alpha 2-macroglobulin ratio increased by 6.8 in the first milking to 44.4 at 2 wk postpartum, indicating that the increase of alpha 2-macroglobulin was greater than that of albumin. In mastitic cow's milk, the concentration of alpha 2-macroglobulin (48.1, 71.4, and 89.0 microgram/ml) was also higher than that in normal milk. This increase was found to be related to the degree of mastitis as determined by the California Test.

Animals↗

PubMed1986

Large-surface hemodialysis.

A hemodialysis device with a surface of 5 m2, a blood flow (QB) of 500 ml/min, and a dialysate flow (QD) of 1,000 ml/min has enabled the authors to obtain in 6 h/week the same clearances for urea, creatinine, uric acid, phosphates, and vitamin B12 as has conventional hemodialysis (CH), which takes from 12 to 15 h/week. Twenty-five patients were hemodialyzed throughout 1 year with CH and another year with large-surface hemodialysis, 20 with a creatinine clearance (CCr) of 0.5 ml/min and 5 with a CCr between 0.5 and 4.5 ml/min. All followed a free diet and led a normal life. Hemodialysis time was 6 h/week, and the results obtained were equal to those of the previous year with a CH of 12 h/week. The use of a bicarbonate dialysate rich in glucose, with a relatively high level of potassium and sodium, can avoid the disequilibrium syndrome caused by quick hemodialysis and makes possible the removal of excess liquid in only 6 h/week, without disturbances for the patient.

Adult↗

PubMed1974