Carlos Suarez

Usefulness of the myocardial performance index for early detection of Anthracycline-induced cardiotoxicity in children

Serial surveillance for cardiotoxicity in patients receiving anthracyclines has most commonly centered on the assessment of left ventricular (LV) systolic function by either shortening fraction or ejection fraction. A myocardial performance index (MPI) has been described as a noninvasive Doppler measurement of global (systolic and diastolic) ventricular function.1,2 The MPI has been shown to correlate well with other invasive and noninvasive measures of LV function in adults.3 Recent studies in pediatric and adult patients have demonstrated that this index can quantitatively assess right ventricular dysfunction as well. 4‐6 The MPI has also been shown to have significant clinical utility. Studies have demonstrated the MPI to be a powerful predictor of outcome in adult patients with dilated cardiomyopathy and primary pulmonary hypertension.7,8 This study evaluates the clinical utility of the MPI in the serial measurement of global left and right ventricular function in pediatric cancer patients who received anthracycline antibiotics. ••• The study population consisted of 26 pediatric patients who were treated with anthracycline antibiotics as part of their chemotherapeutic regimen for childhood malignancy (age range 0.5 to 18 years, mean 9.3 6 5.4). A group of normal children served as the control population; their characteristics have

CD81 Regulates Neuron-Induced Astrocyte Cell-Cycle Exit

Astrocytes respond to contact with neurons by cell-cycle arrest and complex process formation. In our effort to discover the molecular mechanisms that underlie this phenomenon we have identified a known tetraspanin, CD81, as a critical component of astrocyte responses to neuronal differentiation signals. Here we show that CD81 is expressed on the surface of the astrocyte and that its expression level can be modulated by contact with neurons. Further, using three separate antibodies, 2F7, Eat1, and Eat2, which recognize unique epitopes in the extracellular domains of the CD81 protein, we show that there is a unique domain, recognized by Eat1, that is required for astrocyte cell-cycle withdrawal in response to neurons. This is likely due to conformational changes in the CD81 molecule, as inclusion of 2F7 actually augments neuron-induced astrocyte growth arrest. The critical nature of CD81 in normal astrocyte-neuron biology was confirmed by using mice in which CD81 had been deleted by homologous recombination. Astrocytes null at the CD81 locus were blind to the proliferative arrest encoded on the neuronal cell surface. Taken together, these data strongly suggest that CD81 is a critical regulator of neuron-induced astrocytic differentiation.

Up-Regulation of Carbonic Anhydrase Isozyme IV in CNS Myelin of Mice Genetically Deficient in Carbonic Anhydrase II

Abstract: Carbonic anhydrase (CA) II is the major CA isozyme in the brain, where it participates in acid‐base homeostasis, fluid transport, and myelin synthesis. The CA II deficiency [CA(II)D] mutation in the mouse results in structural changes in the glial cells in the CNS and in decreased susceptibility to seizures, but no detectable changes in myelin yield and ultrastructure. We compared the CA isozymes in brain and spinal cord fractions, as well as in purified myelin, between CA(II)D and control mice. CA(II)D resulted in a much lower total CA specific activity in all tissues examined but in higher CA IV specific activities in soluble and membrane‐associated fractions and pure myelin. Western blots of purified myelin showed a band corresponding to CA IV in CA(II)D mice. This band was weak or undetectable in myelin samples from normal mice. Immunocytochemical staining demonstrated CA IV in oligodendrocytes and myelinated tracts in normal mouse brains and stronger staining of the same structures in brains of CA(II)D mutants. We conclude that CA(II)D mutation in the mouse up‐regulates CNS CA IV. We speculate that this up‐regulation could mitigate the effect of CA(II)D on myelin formation and maintenance.

Disturbances of growth hormone-insulin-like growth factor axis and response to growth hormone in acidosis

Severe chronic metabolic acidosis (CMA) in rats is associated with poor food intake and downregulation of growth hormone (GH), insulin-like growth factors (IGFs), and liver receptors; the administration of recombinant GH (rGH) fails to improve the growth failure. In mice with carbonic anhydrase II deficiency (CAD), a model of moderate CMA with food intake close to normal, we studied serum levels of GH, IGFs, and IGF-binding proteins, and the growth response to rGH. CAD was associated with low serum levels of GH in males. Randomized administration of rGH from ∼5 to ∼12 wk to CAD mice improved food efficiency and increased serum IGF-I levels, final length, and weight compared with placebo without affecting blood pH. Although administration of rGH also increased linear growth in healthy animals, the effect was less than that in CAD mice and was only observed when started before 6 wk of life. Thus growth failure in CAD mice is associated with a decrease in GH secretion in males but not in females. Long-term administration of rGH increases linear growth in CAD mice despite persistent CMA.

Time course of the response to recombinant growth hormone in acidotic mice

Abstract Long-term administration of recombinant growth hormone (GH) increases growth, despite persistent acidosis, in mice with carbonic anhydrase II deficiency (CAD). In contrast, short-term administration of GH to acidotic rats fails to improve growth. To determine the factors affecting the rate of growth response to GH in acidosis, we analyzed serial measurements obtained during a randomized trial of GH in CAD mice and healthy controls. Administration of GH increased standardized growth progressively up to 5–9 weeks. These data suggest that assessment of the response to GH in rodents requires prolonged administration.

Postnatal disappearance of type A intercalated cells in carbonic anhydrase II-deficient mice.

Abstract Despite chronic acidosis, collecting ducts in adult carbonic anhydrase II-deficient (CAD mice) are depleted of intercalated cells, including those of type A, which are acid-secreting cells. We hypothesized that this depletion could occur during postnatal development. Principal cells were identified by immunofluorescence using an antibody to rat aquaporin-2 (AQP-2), and type A intercalated cells using an antibody specific for anion exchanger (AE1). In CAD mice the proportion of AQP2-positive cells, normal at 11 days, increased progressively in the cortical (CCD) and outer medullary collecting duct (OMCD), to reach almost 100% in the OMCD in adults. The percentage of AE1-positive cells in the OMCD of CAD mice decreased by half by 6 weeks of age and further by adulthood. In controls, however, the proportion of AQP2-positive cells and that of AE1-positive cells in the OMCD remained stable after 10 days of age. AE1-positive cells accounted for the majority of intercalated cells in the OMCD. The mechanisms leading to selective postnatal cell depletion in the collecting duct in CAD mice remain to be determined.

Expression of Carbonic Anhydrase IV in Mouse Placenta

Carbonic anhydrase (CA) facilitates acid-base transport in several tissues. Acidosis upregulates membrane-bound SDS-resistant hydratase activity in various tissues and CA IV mRNA in rabbit kidney. This study was designed to assess whether the expression of membrane-bound CA IV isozyme in mouse placenta is regulated developmentally and by maternal ammonium chloride loading at the end of pregnancy. For this purpose we used Northern blot analysis, Western blots of microsomal membranes, and immunocytochemistry. The expression of CA IV mRNA on Northern blots tripled from day 11 to day 15 and then remained stable until the end of pregnancy. Expression of CA IV immunoreactive protein on Western blot tripled from day 11 to day 15 and decreased almost to baseline by day 19. Strong staining for CA IV was detected by immunocytochemistry in labyrinthine trophoblast, in the endodermal layer of the yolk sac (both intra- and extraplacental) and in the uterine epithelium. Weak staining was observed in most fetal endothelial cells at 11 days but not later in gestation. Maternal acidosis did not upregulate the expression of CA IV mRNA or CA IV immunoreactive protein. Thus CA IV expression in mouse placenta is developmentally regulated. Maternal acidosis during the last quarter of pregnancy does not upregulate CA IV mRNA or CA IV immunoreactive protein.

LONG-TERM ADMINISTRATION OF RECOMBINANT GROWTH HORMONE (rGH) IMPROVES GROWTH IN CARBONIC ANHYDRASE II-DEFICIENT (CAD) MICE DESPITE CHRONIC METABOLIC ACIDOSIS (CMA). • 391

LONG-TERM ADMINISTRATION OF RECOMBINANT GROWTH HORMONE (rGH) IMPROVES GROWTH IN CARBONIC ANHYDRASE II-DEFICIENT (CAD) MICE DESPITE CHRONIC METABOLIC ACIDOSIS (CMA). • 391

HORMONAL MECHANISMS OF GROWTH FAILURE IN MODERATE CHRONIC METABOLIC ACIDOSIS(CMA) WITH NORMAL FOOD INTAKE. 392

Hormonal changes in rats subjected to high doses of NH4Cl are similar to those observed in non acidotic rats with similar degree of food deprivation. To assess the effect of CMA with normal food intake on the growth hormone (GH)-insulin-like growth factor (IGF) axis, we compared 3-6 month-old mice with congenital deficiency in carbonic anhydrase II (CAD) to B6AF1 controls (Con). Because of the differences in secretory pattern of GH in rats, genders were analyzed separately. We measured hourly serum GH concentrations(avg±sem) by ELISA using a species-specific antiserum (provided by Genentech), and assessed free serum levels of IGF-1 and IGF-2 by the ratio of the concentration of total IGF-1 or IGF-2 (measured by RIA) to that of high molecular weight IGF-binding protein (IGF-BP3, measured by densitometric analysis of western ligand blots). In male Con (n=6) the number of peak GH levels (defined as > 5 ng/ml) and the average daytime GH concentration were similar to nocturnal values. The average daytime GH concentration and the incidence of GH peaks (8%) in Con males were approximately twice as high as in the other groups. Table

MILD TO MODERATE CHRONIC METABOLIC ACIDOSIS (CMA) IN THE MOUSE IS ASSOCIATED WITH LOW SERUM LEVELS OF GROWTH HORMONE (GH). ▴ 493

MILD TO MODERATE CHRONIC METABOLIC ACIDOSIS (CMA) IN THE MOUSE IS ASSOCIATED WITH LOW SERUM LEVELS OF GROWTH HORMONE (GH). ▴ 493