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Biomedical subjects

M L Cruz

Publications and source records attributed to M L Cruz.

At least 19 recordsLinked to original sources
PubMed2006

Cardiovascular fitness and physical activity in children with and without impaired glucose tolerance.

OBJECTIVE: To examine differences in cardiovascular fitness (VO(2max)) and physical activity levels in overweight Hispanic children with normal glucose tolerance (NGT) vs impaired glucose tolerance (IGT). PARTICIPANTS: A total of 173 overweight (BMI percentile 97.0 +/- 3.1) Hispanic children ages 8-13 years with a family history of type 2 diabetes. METHODS: VO(2max) was measured via a maximal effort treadmill test and open circuit spirometry. Physical activity was determined by questionnaire. Glucose tolerance was established by a 2-h oral glucose challenge (1.75 g of glucose/kg body weight). IGT was defined from an oral glucose tolerance test as a 2-h plasma glucose level > or =140 and <200 mg/dl. RESULTS: IGT was detected in 46 of the 173 participants (approximately 27%); no cases of type 2 diabetes were identified. No significant differences were found between youth with NGT and those with IGT in absolute VO(2max) (2.2 +/- 0.6 vs 2.1 +/- 0.5 l/min), VO(2max) adjusted for gender, age, and body composition (2.2 +/- 0.2 vs 2.1 +/- 0.2 l/min), or recreational physical activity levels (8.7 +/- 8.2 vs 6.9 +/- 6.2 h/week). CONCLUSION: Overweight Hispanic youth with IGT exhibit similar levels of VO(2max) and physical activity compared to their NGT counterparts. Longitudinal analyses are necessary to determine whether fitness/activity measures contribute significantly to diabetes risk over time in this group.

Adolescent↗
PubMed2006

Birth weight, puberty, and systolic blood pressure in children and adolescents: a longitudinal analysis.

We examined the association between birth weight and systolic blood pressure (SBP) from pre-puberty to late puberty in a cohort of American children. Ninety-eight children aged 4-12 years at baseline were followed annually for 2-6 years with at least two Tanner stages. Annual measures included SBP, age, gender, race, birth weight, Tanner stage, and body composition using dual-energy X-ray absorptiometry and computed tomography. Birth weight was inversely correlated with SBP in pre-pubertal children (r=-0.23, P<0.05), especially in white children. SBP persisted at a higher level from pre-puberty through late puberty among children with low birth weight (<2500 g). However, SBP significantly increased from pre-puberty to early or late puberty among children with high birth weight (>or=4000 g). After adjusting for visceral fat, one unit change of birth weight category was associated with a 2.6 mm Hg reduction in SBP (P<0.05), but this association was attenuated as puberty progressed. The changes in SBP across puberty followed different trajectories in children with low vs high birth weight. Attenuation in the association between birth weight and SBP from pre-puberty to late puberty may be influenced by sexual maturation.

Adolescent↗
PubMed2005

Insulin sensitivity, insulin secretion and beta-cell function during puberty in overweight Hispanic children with a family history of type 2 diabetes.

OBJECTIVE: To examine cross-sectional differences in insulin sensitivity, insulin secretion and beta-cell function during puberty in overweight Hispanic boys and girls with a family history of type 2 diabetes. STUDY DESIGN AND PARTICIPANTS: This cross-sectional, observational study included 214 8-13-y-old Hispanic children with a BMI percentile > or = 85th percentile and family history of type 2 diabetes. METHODS AND ANALYSES: Participants underwent a physical examination, body composition measures, oral glucose tolerance test (OGTT), and frequently-sampled intravenous glucose tolerance test. Unadjusted and adjusted general linear models (GLM) tested whether insulin/glucose dynamics differed by Tanner stage and gender. RESULTS: Unadjusted group comparisons showed that fasting insulin increased whereas insulin sensitivity (SI) and the disposition index (DI) (a measure of pancreatic beta-cell function) decreased across Tanner stage groups (all P < 0.05). No differences in the acute insulin response to glucose (AIRg), fasting glucose or 2-h glucose were found. After adjusting for covariates, there was no independent effect of Tanner stage on SI (P = 0.9) or AIRg (P = 0.2), but DI was slightly lower in later Tanner stages suggesting decreased beta-cell function in the more mature groups (P = 0.10). CONCLUSIONS: Overweight Hispanic children with a family history of type 2 diabetes may represent a unique population given that pubertal insulin resistance was not evident once analyses controlled for body composition. Longitudinal analyses are required to determine whether the slightly diminished beta-cell function in later Tanner stages plays a role in the development of type 2 diabetes.

Adolescent↗
PubMed2005

Pediatric obesity and insulin resistance: chronic disease risk and implications for treatment and prevention beyond body weight modification.

The study of childhood obesity has continued to grow exponentially in the past decade. This has been driven in part by the increasing prevalence of this problem and the widespread potential effects of increased obesity in childhood on lifelong chronic disease risk. The focus of this review is on recent findings regarding the link between obesity and disease risk during childhood and adolescence. We describe recent reports relating to type 2 diabetes in youth (2), prediabetes (69, 166), metabolic syndrome (33, 35), polycystic ovarian syndrome (77), and nonalcoholic fatty liver disease (58, 146), and the mediating role of insulin resistance in these conditions. In addition, we review the implications of this research for the design of more effective treatment and prevention strategies that focus more on the improvement of obesity-related metabolic abnormalities and chronic disease risk reduction than on the conventional energy balance approach that focuses on weight management.

Adolescent↗
PubMed2001

Postprandial lipid metabolism and insulin sensitivity in young Northern Europeans, South Asians and Latin Americans in the UK.

The aim of this study was to determine whether the higher susceptibility to coronary heart disease and diabetes in South Asian immigrants to the United Kingdom compared with the Caucasian population may reflect insulin resistance and altered postprandial lipid metabolism. We also wished to study Latin Americans, an ethnic group that has not been previously studied in the United Kingdom. The intention was to carry out a detailed study in a relatively small number of subjects to provide essential baseline information for larger epidemiological studies. Postprandial lipaemia was measured in 25 subjects (eight South Asians, eight Latin Americans and nine Northern Europeans) who resided in the United Kingdom. Results from the postprandial studies were correlated to insulin sensitivity measured by the insulin tolerance test, food intake, anthropometry and adipose tissue fatty acid composition. In South Asians, postprandial glucose and insulin concentrations were greater than in the other groups (P<0.01 and <0.05, respectively), although there were no differences in postprandial triacylglycerol concentrations or in insulin sensitivity assessed with the insulin tolerance test. The decreased glucose tolerance in this group could not be explained by differences in percentage body fat, body mass index, or by dietary intake measured by food records or adipose tissue fatty acid composition. We conclude that postprandial lipaemia is not affected in young South Asians compared to Northern Europeans although glucose intolerance is detectable. The results from the present study should help in the design of further postprandial lipid studies in different ethnic groups.

Adipose Tissue↗
PubMed2001

Spatial distribution of EEG theta activity as a function of lifetime lead exposure in 9-year-old children.

The relationship between low-level childhood lead exposure and developmental retardation has been proposed but the existing evidence is weak. We examined the EEG of 42 children participating in the Mexico City Prospective Lead Study to determine if relative theta power and distribution across the scalp was related to history of lifetime lead exposure as measured by sequential blood lead concentration of the mother during pregnancy and the child after delivery. EEG was recorded from scalp electrodes placed according to the 10-20 system during eyes-closed. Theta activity (4-7 Hz) was filtered with a fast Fourier transform (FFT) and relative power calculated. The expected distribution of theta was found, with the greatest relative power centrally located and lesser amounts at frontal, occipital, and lateral derivations. Multiple regression models of theta at each electrode showed that increasing postnatal blood lead from 6 to 96 months was related to increasing relative theta power adjusted for age, sex and fetal suffering at delivery, in occipital derivations. The most significant increases in theta power were associated with blood lead levels (geometric mean = 10.3 microg/dl) measured between 54 and 72 months. Spatially weighted regression demonstrated that there was a significant antero-posterior gradient in lead-induced increase in relative theta power associated with postnatal blood lead levels at 54-72 months and 78-96 months. The greatest lead effect on both occipital relative theta power and the antero-posterior gradient of theta power was found with lead at an age during which relative theta power reaches its developmental maximum and starts to decrease. Results suggest that 54-72 months represent a critical period during which lead can exert lasting effects on the developmental pattern of theta activity. Occipital derivation of the largest effects of lead on theta activity may also be related to other lead-related developmental deficits.

Adult↗
PubMed2001

Dissociation and electrooxidation of primaquine diphosphate as an approach to the study of anti-chagas prodrugs mechanism of action.

This paper describes the voltammetric behavior of primaquine as a previous support to the further understanding of the delivery and action mechanisms of its respective synthesized prodrugs. There are few papers describing the drug behavior and most of the time no correlation between oxidation process and pH is done. Our results showed that primaquine oxidation is a one-step reaction involving two electrons with the charge transfer process being strongly pH-dependent in acid medium and pH-independent in a weak basic medium, with the neutral form being easily oxidized. This leads to the conclusion that quinoline nitrogen ring neutralization is a determinant step to the formation of the oxidized primaquine form. The existence of a relationship between the primaquine dissociation equilibrium and its electrooxidation process is shown. This work points the importance of voltammetric methodology as a tool for further studies on quantitative relationship studies between chemical structure and biological activity (QSAR) for electroactive drugs.

Antiprotozoal Agents↗
PubMed2000

A preliminary trial comparison of several anesthetic techniques in cats.

The aim of this study was to investigate the effect of several drug combinations (atropine, xylazine, romifidine, methotrimeprazine, midazolam, or fentanyl) with ketamine for short term anesthesia in cats. Twelve cats were anesthetized 6 times by using a cross-over Latin square protocol: methotrimeprazine was combined with midazolam, ketamine, and fentanyl; midazolam and ketamine; romifidine and ketamine; and xylazine and ketamine. Atropine was combined with romifidine and ketamine, and xylazine and ketamine. Temperature, heart rate, and respiratory rate decreased in all groups. Apnea occurred in 1 cat treated with methotrimeprazine, romifidine, and ketamine, suggesting that ventilatory support may be necessary when this protocol is used. Emesis occurred in some cats treated with alpha 2-adrenoceptor agonists, and this side effect should be considered when these drugs are used.

Anesthesia, General↗
PubMed1999

Assessing the feasibility of linkage disequilibrium methods for mapping complex traits: an initial screen for bipolar disorder loci on chromosome 18.

Linkage disequilibrium (LD) analysis has been promoted as a method of mapping disease genes, particularly in isolated populations, but has not yet been used for genome-screening studies of complex disorders. We present results of a study to investigate the feasibility of LD methods for genome screening using a sample of individuals affected with severe bipolar mood disorder (BP-I), from an isolated population of the Costa Rican central valley. Forty-eight patients with BP-I were genotyped for markers spaced at approximately 6-cM intervals across chromosome 18. Chromosome 18 was chosen because a previous genome-screening linkage study of two Costa Rican families had suggested a BP-I locus on this chromosome. Results of the current study suggest that LD methods will be useful for mapping BP-I in a larger sample. The results also support previously reported possible localizations (obtained from a separate collection of patients) of BP-I-susceptibility genes at two distinct sites on this chromosome. Current limitations of LD screening for identifying loci for complex traits are discussed, and recommendations are made for future research with these methods.

Bipolar Disorder↗
PubMed1998

Rapid chylomicron appearance following sequential meals: effects of second meal composition.

Previous studies have noted the presence of an early postprandial peak in plasma triacylglycerol concentrations following successive fat-rich meals. An earlier study has shown that the triacylglycerol in this early peak originates from a previous meal. The present study was performed to investigate the effects of different second meals on the plasma triacylglycerol response. Six healthy subjects were studied on four occasions each. At 5 h following a fat-rich breakfast they ingested one of the following in a balanced design: a fat-rich meal, a low-fat meal, water or nothing by mouth. Blood samples were taken for 2.5 h following the second meal. An early peak in chylomicron and plasma triacylglycerol concentrations was seen following both low-fat and fat-rich second meals but not following water. During studies investigating postprandial lipaemia, further meals must be avoided, even if they contain no fat, although water may be allowed.

Adult↗
PubMed1997

Reversal of progesterone-induced sequential inhibition by progesterone metabolites.

Previous reports have shown that intrabrain administration of progesterone (P) ring A-reduced metabolites into the medial preoptic area (MPOA) and ventromedial hypothalamus (VMH) induces facilitation of female sexual behavior in ovariectomized (ovx) rats pretreated with estrogen. Present studies were designed to explore the possibility that ring-A reduced progesterone metabolites might play a role in controlling the duration of estrous behavior. To this aim ovariectomized (ovx) Sprague Dawley rats implanted with guide cannulae directed towards the VMH or the MPOA were submitted to a systemic hormonal treatment to provoke P-induced sequential inhibition (estradiol benzoate (EB) at time O + P at 44 h + P at 68 h). The second dose of P was administered simultaneously with the i.c. implantation of one of the following P metabolites: 3 beta-hydroxy-5 beta-pregnan-20-one (5 beta,3 alpha P), 3 alpha-hydroxy-5 beta-pregnan-20-one (5 beta,3 alpha P) or 3 beta-hydroxy-5 beta- pregnan-20-one (5 alpha,3 beta P) into the MPOA or VMH. Lordosis behavior was evaluated by the lordosis quotient (LQ = number of lordosis/10 male mount x 100) and by the percentage of responding subjects. Results show that 5 beta,3 beta P implanted into the VMH or MPOA counteracted the sequential inhibitory effect induced by systemic administration of P.5 alpha,3 beta P was also able to counteract sequential inhibition, but with less potency and only in the VMFI. Results showed that P-induced sequential inhibition can be counteracted by intrabrain administration of ring-A reduced progestins in both the VMH and MPOA. Data are discussed in terms of a putative physiological role of naturally occurring P metabolites in P-mediated female sexual behavior expression.

Animals↗
PubMed1994

Effects of infant nutrition on cholesterol synthesis rates.

Nutrient effects on cholesterol fractional synthesis rates (FSR) in infancy by stable isotope determination have not been studied. We hypothesized that FSR is significantly reduced with high dietary cholesterol and phytoestrogen intake and increased with low dietary cholesterol and phytoestrogen intake. We prospectively studied 33 term male infants exclusively fed human milk (high cholesterol, low phytoestrogen, n = 12), cow milk-based formula (low cholesterol, low phytoestrogen, n = 8), soy milk-based formula (zero cholesterol, high phytoestrogen, n = 7), or soy milk-based formula modified to contain cholesterol (low cholesterol, high phytoestrogen, n = 6) during the first 4 mo of life. Cholesterol FSR was determined from rate of incorporation of deuterium into erythrocyte membrane cholesterol, and urinary isoflavone excretion (an index of dietary phytoestrogen exposure) was measured by gas chromatography-mass spectrometry. Significant differences in cholesterol FSR were found. FSR (%/d) was lowest in human milk (2.62 +/- 0.38), highest in soy milk-based formula (9.40 +/- 0.51), and intermediate in cow milk-based and modified soy milk-based formula (6.90 +/- 0.48 and 8.03 +/- 0.28, respectively), p < 0.0001. Cholesterol FSR was significantly lower in modified soy milk-based compared with soy milk-based formula, p < 0.05. We also show for the first time that dietary phytoestrogens are absorbed and excreted by the infant fed soy protein-based formula. Urinary isoflavone excretion was inversely related to cholesterol FSR, but it was not significantly related to serum cholesterol concentration. We conclude that the type of infant nutrition and dietary cholesterol are major factors influencing cholesterol fractional synthesis rates in infancy.

Adaptation, Physiological↗
PubMed1993

Effects of triiodothyronine administration on dietary [14C]triolein partitioning between deposition in adipose tissue and oxidation to [14C]CO2 in ad libitum-fed or food-restricted rats.

Refeeding a chow meal containing [1-14C]triolein to food-restricted rats results in increased accumulation of [14C]lipid in carcass and epididymal adipose tissue and lower oxidation to [14C]CO2 compared to ad libitum-fed rats (Biochem. J. 285, 773-778, 1992). In the present experiments the effects of treatment with triiodothyronine (T3) for three days on lipid accumulation in refed food-restricted rats has been examined. T3 decreased accumulation of [14C]lipid in carcass and epididymal adipose tissue (32 and 77%, respectively) of food-restricted rats on refeeding the chow-[1-14C]triolein meal. This decreased accumulation of [14C]lipid was accompanied by increased [14C]CO2 production (77%) and decreased heparin-elutable lipoprotein lipase activity in the epididymal fat pad (90%) and subcutaneous adipose tissue (80%). Accumulation of [14C]lipid in the latter did not decrease significantly. In contrast, T3 treatment of ad libitum-fed rats increased [14C]lipid deposition in carcass (44%) and in subcutaneous adipose tissue (240%) on refeeding, when compared to untreated ad libitum rats. Lipoprotein lipase activity in the two adipose tissue depots of the refed ad libitum+T3 rats, however, decreased. Thus, the effects of T3 on [14C]lipid deposition are adipose-tissue-depot-specific and depend on the previous dietary intake (over 14 days) of the rat. T3-treatment increased the lipoprotein lipase activity released from perfused hearts to a similar extent in both food-restricted and ad libitum-fed rats compared to the corresponding untreated groups. The rates of lipogenesis in-vivo in liver, epididymal and subcutaneous adipose tissue of food-restricted rats refed chow were not altered by T3. It is concluded that the increased deposition of dietary lipid in the food-restricted rat can be partially reversed by treatment with T3, suggesting that the low-T3 state associated with this condition may be in part responsible.

Adipose Tissue↗
PubMed1992

Refeeding meal-fed rats increases lipoprotein lipase activity and deposition of dietary [14C]lipid in white adipose tissue and decreases oxidation to 14CO2. The role of undernutrition.

Meal-fed (3 h) rats had a decreased food intake, body weight and carcass fat compared with rats fed ad libitum. On refeeding a chow meal containing [1-14C]triolein, the production of 14CO2 was lower (45%) and the accumulation of carcass [14C]lipid higher (37%) in the meal-fed rats. There was higher lipoprotein lipase activity and greater accumulation of [14C]lipid in the epididymal and subcutaneous adipose-tissue depots of the meal-fed rats. In contrast, heparin-releasable lipoprotein lipase was not increased in perfused hearts of meal-fed rats on refeeding. Return of meal-fed rats to feeding ad libitum reversed these changes before the restoration of body weight or carcass fat. Evidence is presented that decreased dietary intake rather than meal pattern is an important determinant of the alterations in adipose lipid metabolism in the meal-fed rat in response to a meal.

Adipose Tissue↗
PubMed1992

Effect of chronic maternal dietary magnesium deficiency on placental calcium transport.

Metabolisms of calcium (Ca) and magnesium (Mg) are closely interrelated in the intestine, bone, and kidney. Interaction of Ca and Mg at the placental level, however, is not well defined. The occurrence of decreased bone mineral content and hypocalcemia in infants of hypomagnesemic mothers led us to test the hypothesis that chronic dietary maternal Mg deficiency decreases placental Ca transport. On day 10 of gestation, 20 Sprague-Dawley rats were randomized to a Mg-deficient diet (3.3 mg/day, n = 10) or to a control diet (70 mg/day, n = 10). On day 20 of gestation (term = 22 days), intact placentas were perfused in situ through the umbilical artery and perfusate was collected through the umbilical vein. Calcium 45 (45Ca) and chromium 51-EDTA (51Cr-EDTA) (a diffusional marker for placental membrane integrity) were injected to the dam and steady state maternofetal clearance (Kmf45Ca, microliter/min/g placenta) of both isotopes were calculated. There was no difference in the clearance of 45Ca and 51Cr in both groups (55 +/- 10 vs 57 +/- 16 and 3.2 +/- 0.4 vs 3.6 +/- 0.4, respectively, mean +/- SEM). We conclude that, in the rat, placental Ca transfer is unaffected by chronic maternal dietary Mg deficiency. We speculate that Ca and Mg cross the placenta by independent mechanisms.

Animals↗