RESUMO
Substitution of cadmium into bulk hydroxyapatite Ca((10-x))Cd(x)(PO(4))(6)(OH)(2) (CdHA: x = 0.12, 1.3, 2.5) is studied by combining X-ray diffraction data from synchrotron radiation, Fourier transform infra-red spectroscopy (FTIR) and density functional theory (DFT) calculations. Energetic and electronic analyses are carried out for several configurations of Cd substitution for Ca at both cationic sites. Rietveld analysis shows preferential occupation of the Ca2 site by cadmium. FTIR data suggest a non-negligible covalent character of Cd-OH. The much-discussed cation site preference for substitution is determined on the basis of relaxed-lattice energetics, and interpreted in terms of chemical concepts; theory indicates that the Ca2 site is clearly favored and this preference is related to the more covalent character of this site compared to that of site 1.
Assuntos
Cádmio/química , Durapatita/química , Modelos Químicos , Cálcio/química , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios XRESUMO
Bone density and turnover was assessed in a longitudinal study of healthy lactating women who initiated use of Norplant((R)) implants (NOR, n = 29), progesterone vaginal rings (PVR, n = 28) or Copper T 380A intrauterine devices (T-Cu, n = 51, control group) around day 60 postpartum. Bone density, serum calcium, phosphorus, alkaline phosphatases, parathyroid hormone (PTH), follicle stimulating hormone (FSH), oestradiol and prolactin, and urinary hydroxyproline and creatinine were measured at postpartum months 1 (PM1), and 12 (PM12) and 6 or 12 months after weaning; at month 6 postpartum (PM6) serum and urine tests alone were performed. Baseline characteristics and lactation performance were similar between groups. Biochemical markers of bone turnover were higher at PM1, PM6 and PM12 than after weaning, with no differences between groups. Bone density in the lumbar spine (L2-L4) and femoral neck at PM1 and PM12 ( approximately 1.11 g/cm(2)) was similar in three groups. Lumbar spine values were found to be lower in lactating women than those present in non-lactating women, but increased after weaning to similar values. The two progestin-only contraceptives studied appear to have no deleterious effect upon bone density and metabolism in healthy lactating women.
Assuntos
Densidade Óssea/efeitos dos fármacos , Remodelação Óssea/efeitos dos fármacos , Anticoncepção/métodos , Anticoncepcionais Femininos/uso terapêutico , Lactação/efeitos dos fármacos , Levanogestrel/uso terapêutico , Progesterona/uso terapêutico , Administração Intravaginal , Adolescente , Adulto , Implantes de Medicamento , Feminino , Humanos , Dispositivos Intrauterinos de Cobre , DesmameRESUMO
In recent evidence from the United States, there generally are no male-female differences in the probability of drug use among persons who report an opportunity to try the drugs. This is an important observation that might help us understand male-female differences in later drug use and dependence, but the observation needs to be replicated elsewhere. We begin this replication process using data from a 1996 national school survey of drug involvement among 6,477 students age 12-18 in Panama. We first examine the occurrence of an opportunity to use drugs by grade. We then follow these analyses with an examination of male-female differences in drug opportunity patterns. We found opportunities to use drugs and actual drug use to be greater at higher grade levels. Also, we found the probability of making a transition to use, given an opportunity, to be more likely among upper-grade students. Consistent with results observed in the United States, we found males in Panama to be more likely to have an opportunity to use marijuana, crack-cocaine, and other forms of cocaine, but not more likely than females to make a transition into drug use once an opportunity had occurred to try each drug. These findings are discussed in relation to the epidemiology and prevention of drug use in Panama and elsewhere, and future research on male-female differences in drug involvement.
Assuntos
Transtornos Relacionados ao Uso de Substâncias/epidemiologia , Transtornos Relacionados ao Uso de Substâncias/psicologia , Adolescente , Idade de Início , Criança , Feminino , Humanos , Masculino , Panamá/epidemiologia , Probabilidade , Instituições Acadêmicas , Distribuição por Sexo , Estudantes/psicologia , Inquéritos e QuestionáriosRESUMO
To assess whether plasma prolactin (PRL) characteristics relate to lactogenesis and absence or presence of menstrual cycles, we measured bioactive PRL (BIO-PRL) using the Nb2 assay, immunoreactive PRL (IR-PRL) by radio-immunoassay, calculated equations describing the BIO-PRL-IR-PRL relationship and separated charged PRL isoforms (by chromatofocusing) in five amenorrhoeic and five cycling nursing women at 6 months postpartum and in 10 cycling non-nursing women. Plasma samples were drawn before and 30 min after a suckling episode at 0800, 1600 and 2400 h in nursing women and at the same hours in non-nursing women. BIO-PRL and IR-PRL concentrations were highest in amenorrhoeic nursing women, intermediate in cycling nursing women and lowest in cycling non-nursing women. The BIO-PRL-IR-PRL relationship shows that a given amount of IR-PRL corresponds to equivalent amounts of BIO-PRL in cycling nursing and cycling non-nursing women, and to a larger extent in amenorrhoeic nursing women. IR-PRL was present in plasma as several charge isoforms. Bioactive isoforms eluting at pH 6.0-5.1 were found in amenorrhoeic and cycling nursing women, reaching similar concentrations after suckling. Bioactive isoforms eluting at pH 7.0-6.1 were found only in amenorrhoeic nursing women. We speculate that isoforms eluting at pH 6.0-5.1 may play a role in lactation and isoforms eluting at pH 7.0-6.1, in lactational amenorrhoea.
Assuntos
Lactação/fisiologia , Prolactina/fisiologia , Adulto , Aleitamento Materno , Feminino , Humanos , Ciclo Menstrual/fisiologia , Isoformas de Proteínas/fisiologiaRESUMO
This report provides the first epidemiological evidence on tobacco, alcohol, and other drug use among school students in Panama, using data from a student survey completed in 1996. Specifically, we examine sex, age, grade level, type of school, and urban-rural variations in the occurrence of tobacco, alcohol, and other drug use. Estimates of lifetime prevalence and past-year use of these products were obtained using data from Panama's 1996 National Youth Survey on Alcohol and Drug Use (n = 6,477). To account for the multistage sampling design of the survey, all estimates and respective standard errors are derived by the Taylor series approximation method using Epi Info 6.0 CSAMPLE software. In general, more males, more older students, and more students in higher grades have used licit and illicit drugs, even though male-female differences tend to be small. Public-private school differences and urban-rural trends vary depending on the drug. The findings of this study are discussed in relation to the epidemiology and prevention of drug use in Panama. Based on these data, we seek to provide information to be used by the Government of Panama in its planning for prevention programs directed toward students in Panamanian schools.