Effect of plant density and seed position on mother plant on physiological characteristic of cocklebur (Xanthium strumarium) seeds

Experiments were conducted in 2010 to determine the influence of plant density and seed position on the mother plant on seed physiological characteristics of cocklebur (Xanthium strumarium). Cocklebur burs were collected in fall of 2010 from Research Farm of University of Agricultural Sciences and Natural Resources of Gorgan, Iran. The experiment was established as factorial arrangement using a completely randomized design with three replications. The factors included different densities of cocklebur (0, 2, 4, 6 and 8 plant m-2) and the top and bottom parts of the canopy. Non dormant seeds were used for determining cardinal temperatures and tolerance to salinity and drought stresses. Base, optimum and ceiling germination temperatures were estimated between 7.09 to 12.33, 32 to 35 and 44 to 45 respectively in different treatments. Salinity stress up to 300 Mm and osmotic potential 8 bar inhibited the germination completely. Comparison of base temperatures and sigmoid equation coefficients showed that seeds produced in the top had higher germination than those that produced at the bottom of the mother plant. It seems plant densities through seed position on the mother plant affect seed quality. Likewise changes of light quality and quantity in shade environment increased seed dormancy in matured seeds. Shade environment affect seed germination on mother plant that increased dormancy of seeds maturing under shade be an adaptive response that reduces the probability of germination of offspring under unfavorable (shade, competitive) conditions.

Population density and weed infestation in organic no-tillage corn cropping system under different soil covers

Currently, one of the biggest challenges faced by organic no-tillage farming is weed control. Thus, the use of cropping practices that help in the control of weeds is extremely important. The objective of this study was to evaluate population density and level of weed infestation in an organic no-tillage corn cropping system under different soil covers. The experiment was conducted in a randomized block design with six repetitions and five treatments, consisting of three soil covers in an organic no-tillage system, and an organic and a conventional system, both without soil cover. The treatments with soil cover used a grass species represented by the black oat, a leguminous species represented by the white lupine, and intercropping between both species. Corn was sown with spacing of 1.0 m between rows and 0.20 m between plants, using the commercial hybrid AG 1051. Infestation in corn was evaluated at stages V5 and V10, and weed density was evaluated at stage V5. The use of black oat straw alone or intercropped with white lupine, in the organic no-tillage corn cropping system, reduced the percentage of weed infestation and absolute weed density. Management-intensive systems and systems without soil cover showed higher relative densities for species Oxalis spp., Galinsoga quadriradiata and Stachys arvensis. The species Cyperus rotundus showed the highest relative density on organic no-tillage corn cropping systems. Black oat straw in the organic no-tillage cropping system limited the productive potential of corn.

Estimated frequency of B-chromosomes and population density of Astyanax scabripinnis paranae in a small stream

A study was made of the frequency of B-chromosomes and the population density of Astyanax scabripinnis paranae (Pisces, Characidae, Tetragonopterinae) from three stretches of the Cascatinha stream (Botucatu, SP). In the first stretch the population was estimated to be about 212 individuals and among 35 karyotyped specimens, 23 carried one macro B-chromosome; in the second stretch the population was estimated to be about 650 individuals and among 20 specimens karyotyped, two possessed one macro B-chromosome; in the third stretch the population was estimated to be about 107 individuals and among 10 specimens karyotyped, one carried one macro B-chromosome. A significant difference was observed in the frequency of macro B-chromosomes in females (57%) and males (8.7%) (P = 0.0001). These data suggest that the B-chromosome frequency and the populational density are not directly related. The hypothesis of the existence of some adaptive effect conferred by the B-chromosomes to the specimens from the first stretch of the Cascatinha stream is presented and discussed

Vitamin D receptor alleles and bone mineral density in a normal premenopausal Brazilian female population

Studies on the association between vitamin D receptor (VDR) polymorphism and bone mineral density (BMD) in different populations have produced conflicting results probably due to ethnic differences in the populations studied. The Brazilian population is characterized by a very broad genetic background and a high degree of miscegenation. Of an initial group of 164, we studied 127 women from the city of São Paulo, aged 20 to 47 years (median, 31 years), with normal menses, a normal diet and no history of diseases or use of any medication that could alter BMD. VDR genotype was assessed by PCR amplification followed by BsmI digestion of DNA isolated from peripheral leukocytes. BMD was measured using dual energy X-ray absorptiometry (Lunar DPX) at the lumbar site (L2-L4) and femoral neck. Most of the women (77.6%) were considered to be of predominantly European ancestry (20.6% of them reported also native American ancestry), 12.8% were of African-Brazilian ancestry and 9.6% of Asian ancestry, 41.0% (52) were classified as bb, 48.8% (62) as Bb and 10.2% (13) as BB. The BB, Bb and bb groups did not differ in age, height, weight, body mass index or age at menarche. Lumbar spine BMD was significantly higher in the bb group (1.22 ± 0.16 g/cm²) than in the BB group (1.08 ± 0.14; P<0.05), and the Bb group presented an intermediate value (1.17 ± 0.15). Femoral neck BMD was higher in the bb group (0.99 ± 0.11 g/cm²) compared to Bb (0.93 ± 0.12) and BB (0.90 ± 0.09) (P<0.05). These data indicate that there is a significant correlation between the VDR BsmI genotype and BMD in healthy Brazilian premenopausal females.

Risk factors for decreased bone density in premenopausal women

Osteoporosis is a major health problem. Little is known about the risk factors in premenopause. Sixty 40-50-year old patients with regular menses were studied cross-sectionally. None of the patients were on drugs known to interfere with bone mass. Patients answered a dietary inquiry and had their bone mineral density (BMD) measured. The Z scores were used for the comparisons. A blood sample was taken for the determination of FSH, SHBG, estradiol, testosterone, calcium and alkaline phosphatase. Calcium and creatinine were measured in 24-h urine. A Z score less than -1 was observed for the lumbar spine of 14 patients (23.3%), and for the femur of 24 patients (40%). Patients with a Z score less than -1 for the lumbar spine were older than patients with a Z score ³-1 (45.7 vs 43.8 years) and presented higher values of alkaline phosphatase (71.1 ± 18.2 vs 57.1 ± 14.3 IU/l). Multiple regression analysis showed that a lower lumbar spine BMD was associated with higher values of alkaline phosphatase, lower calcium ingestion, a smaller body mass index (BMI), less frequent exercising, and older age. The patients with a Z score less than -1 for the femur were shorter than patients with a Z score ³-1 (158.2 vs 161.3 cm). Multiple regression analysis showed that a lower femoral BMD was associated with lower BMI, higher alkaline phosphatase and caffeine intake, and less frequent exercising. A lower than expected BMD was observed in a significant proportion of premenopausal women and was associated with lower calcium intake, relatively lower physical activity and lower BMI. We conclude that the classical risk factors for osteoporosis may be present before ovarian failure, and their effect may be partly independent of estrogen levels.

Structural basis for the pathophysiology of lipoprotein(a) in the athero-thrombotic process

Lipoprotein Lp(a) is a major and independent genetic risk factor for atherosclerosis and cardiovascular disease. The essential difference between Lp(a) and low density lipoproteins (LDL) is apolipoprotein apo(a), a glycoprotein structurally similar to plasminogen, the precursor of plasmin, the fibrinolytic enzyme. This structural homology endows Lp(a) with the capacity to bind to fibrin and to membrane proteins of endothelial cells and monocytes, and thereby to inhibit plasminogen binding and plasmin generation. The inhibition of plasmin generation and the accumulation of Lp(a) on the surface of fibrin and cell membranes favor fibrin and cholesterol deposition at sites of vascular injury. Moreover, insufficient activation of TGF-ß due to low plasmin activity may result in migration and proliferation of smooth muscle cells into the vascular intima. These mechanisms may constitute the basis of the athero-thrombogenic mode of action of Lp(a). It is currently accepted that this effect of Lp(a) is linked to its concentration in plasma. An inverse relationship between Lp(a) concentration and apo(a) isoform size, which is under genetic control, has been documented. Recently, it has been shown that inhibition of plasminogen binding to fibrin by apo(a) is also inversely associated with isoform size. Specific point mutations may also affect the lysine-binding function of apo(a). These results support the existence of functional heterogeneity in apolipoprotein(a) isoforms and suggest that the predictive value of Lp(a) as a risk factor for vascular occlusive disease would depend on the relative concentration of the isoform with the highest affinity for fibrin

Reduced bone mineral density in men after heart transplantation

Heart transplantation is associated with rapid bone loss and an increased prevalence and incidence of fractures. The aim of the present study was to compare the bone mineral density (BMD) of 30 heart transplant (HT) recipients to that of 31 chronic heart failure (CHF) patients waiting for transplantation and to determine their biochemical markers of bone resorption and hormone levels. The BMD of lumbar spine and proximal femur was determined by dual-energy X-ray absorptiometry. Anteroposterior and lateral radiographs of the thoracic and lumbar spine were also obtained. The mean age of the two groups did not differ significantly. Mean time of transplantation was 25.4 ± 21.1 months (6 to 88 months). Except for the albumin levels, which were significantly higher, and magnesium levels, which were significantly lower in HT patients when compared to CHF patients, all other biochemical parameters and hormone levels were within the normal range and similar in the two groups. Both groups had lower BMD of the spine and proximal femur compared to young healthy adults. However, the mean BMD of HT patients was significantly lower than in CHF patients at all sites studied. Bone mass did not correlate with time after transplantation or cumulative dose of cyclosporine A. There was a negative correlation between BMD and the cumulative dose of prednisone. These data suggest that bone loss occurs in HT patients mainly due to the use of corticosteroids and that in 30% of the patients it can be present before transplantation. It seems that cyclosporine A may also play a role in this loss.

Polymorphisms of the low-density lipoprotein receptor gene in Brazilian individuals with heterozygous familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a metabolic disorder inherited as an autosomal dominant trait characterized by an increased plasma low-density lipoprotein (LDL) level. The disease is caused by several different mutations in the LDL receptor gene. Although early identification of individuals carrying the defective gene could be useful in reducing the risk of atherosclerosis and myocardial infarction, the techniques available for determining the number of the functional LDL receptor molecules are difficult to carry out and expensive. Polymorphisms associated with this gene may be used for unequivocal diagnosis of FH in several populations. The aim of our study was to evaluate the genotype distribution and relative allele frequencies of three polymorphisms of the LDL receptor gene, HincII1773 (exon 12), AvaII (exon 13) and PvuII (intron 15), in 50 unrelated Brazilian individuals with a diagnosis of heterozygous FH and in 130 normolipidemic controls. Genomic DNA was extracted from blood leukocytes by a modified salting-out method. The polymorphisms were detected by PCR-RFLP. The FH subjects showed a higher frequency of A+A+ (AvaII), H+H+ (HincII1773) and P1P1 (PvuII) homozygous genotypes when compared to the control group (P<0.05). In addition, FH probands presented a high frequency of A+ (0.58), H+ (0.61) and P1 (0.78) alleles when compared to normolipidemic individuals (0.45, 0.45 and 0.64, respectively). The strong association observed between these alleles and FH suggests that AvaII, HincII1773 and PvuII polymorphisms could be useful to monitor the inheritance of FH in Brazilian families.

Bone mineral density in Brazilian men 50 years and older

Bone mineral density (BMD) in the lumbar spine (LSBMD), femoral neck (FNBMD) and whole body (WBBMD) and whole body tissue composition were evaluated in 288 Brazilian men 50 years and older, 80% white and 20% Mulattoes. Age was inversely correlated with WBBMD (r = -0.20) and FNBMD (r = -0.21) but not with LSBMD (r = 0.03). Body mass index and weight showed a strong positive correlation with WBBMD (r = 0.48 and 0.54), LSBMD (r = 0.37 and 0.45) and FNBMD (r = 0.42 and 0.48). Correlation with height was positive but weaker. No significant bone loss at the lumbar spine level was observed as the population aged. FNBMD and WBBMD decreased significantly only in the last decade (age 70-79) studied. BMD was higher for Brazilian men as compared to Brazilian women at all sites. No significant differences were observed between Brazilian and the US/European male population for BMD in the femoral neck. BMD measured by dual-energy X-ray absorptiometry in South American men is reported here for the first time. A decrease in FNBMD was detected only later in life, with a pattern similar to that described for the US/European male population.

Hypomagnesemia in critically ill cancer patients: a prospective study of predictive factors

Hypomagnesemia is the most common electrolyte disturbance seen upon admission to the intensive care unit (ICU). Reliable predictors of its occurrence are not described. The objective of this prospective study was to determine factors predictive of hypomagnesemia upon admission to the ICU. In a single tertiary cancer center, 226 patients with different diagnoses upon entering were studied. Hypomagnesemia was defined by serum levels <1.5 mg/dl. Demographic data, type of cancer, cause of admission, previous history of arrhythmia, cardiovascular disease, renal failure, drug administration (particularly diuretics, antiarrhythmics, chemotherapy and platinum compounds), previous nutrition intake and presence of hypovolemia were recorded for each patient. Blood was collected for determination of serum magnesium, potassium, sodium, calcium, phosphorus, blood urea nitrogen and creatinine levels. Upon admission, 103 (45.6%) patients had hypomagnesemia and 123 (54.4%) had normomagnesemia. A normal dietary habit prior to ICU admission was associated with normal Mg levels (P = 0.007) and higher average levels of serum Mg (P = 0.002). Postoperative patients (N = 182) had lower levels of serum Mg (0.60 ± 0.14 mmol/l compared with 0.66 ± 0.17 mmol/l, P = 0.006). A stepwise multiple linear regression disclosed that only normal dietary habits (OR = 0.45; CI = 0.26-0.79) and the fact of being a postoperative patient (OR = 2.42; CI = 1.17-4.98) were significantly correlated with serum Mg levels (overall model probability = 0.001). These findings should be used to identify patients at risk for such disturbance, even in other critically ill populations.

Bone mineral density of the lumbar spine of Brazilian children and adolescents aged 6 to 14 years

The authors performed a study of bone mass in eutrophic Brazilian children and adolescents using dual-energy X-ray absorptiometry (DXA) in order to obtain curves for bone mineral content (BMC) and bone mineral density (BMD) by chronological age and correlate these values with weight and height. Healthy Caucasian children and adolescents, 120 boys and 135 girls, 6 to 14 years of age, residents of São Paulo, Brazil, were selected from the Pediatric Department outpatient clinic of Hospital São Paulo (Universidade Federal de São Paulo). BMC, BMD and the area of the vertebral body of the L2-L4 segment were obtained by DXA. BMC and BMD for the lumbar spine (L2-L4) presented a progressive increase between 6 and 14 years of age in both sexes, with a distribution that fitted an exponential curve. We identified an increase of mineral content in female patients older than 11 years which was maintained until 13 years of age, when a new decrease in the velocity of bone mineralization occurred. Male patients presented a period of accelerated bone mass gain after 11 years of age that was maintained until 14 years of age. At 14 years of age the mean BMD values for boys and girls were 0.984 and 1.017 g/cm², respectively. A stepwise multiple regression analysis of paired variables showed that the "vertebral area-age" pair was the most significant in the determination of BMD values and the introduction of a third variable (weight or height) did not significantly increase the correlation coefficient.

Effects of lipopolysaccharide on low- and high-density cultured rabbit vascular smooth muscle cells: differential modulation of nitric oxide release, ERK1/ERK2 MAP kinase activity, protein tyrosine phosphatase activity, and DNA synthesis

Previous studies have shown that exogenously generated nitric oxide (NO) inhibits smooth muscle cell proliferation. In the present study, we stimulated rabbit vascular smooth muscle cells (RVSMC) with E. coli lipopolysaccharide (LPS), a known inducer of NO synthase transcription, and established a connection between endogenous NO, phosphorylation/dephosphorylation-mediated signaling pathways, and DNA synthesis. Non-confluent RVSMC were cultured with 0, 5, 10, or 100 ng/ml of the endotoxin. NO release was increased by 86.6% (maximum effect) in low-density cell cultures stimulated with 10 ng/ml LPS as compared to non-stimulated controls. Conversely, LPS (5 to 100 ng/ml) did not lead to enhanced NO production in multilayered (high density) RVSMC. DNA synthesis measured by thymidine incorporation showed that LPS was mitogenic only to non-confluent RVSMC; furthermore, the effect was prevented statistically by aminoguanidine (AG), a potent inhibitor of the inducible NO synthase, and oxyhemoglobin, an NO scavenger. Finally, there was a cell density-dependent LPS effect on protein tyrosine phosphatase (PTP) and ERK1/ERK2 mitogen-activated protein (MAP) kinase activities. Short-term transient stimulation of ERK1/ERK2 MAP kinases was maximal at 12 min in non-confluent RVSMC and was prevented by preincubation with AG, whereas PTP activities were inhibited in these cells after 24-h LPS stimulation. Conversely, no significant LPS-mediated changes in kinase or phosphatase activities were observed in high-density cells. LPS-induced NO generation by RVSMC may switch on a cell density-dependent proliferative signaling cascade, which involves the participation of PTP and the ERK1/ERK2 MAP kinases.

Plasma and testicular testosterone levels, volume density and number of Leydig cells and spermatogenic efficiency of rabbits

Plasma and tissue testosterone concentrations were determined by radioimmunoassay in 12 eight-month-old sexually mature New Zealand White rabbits and evaluated for possible associations with spermatogenic efficiency as well as with volume density and number of Leydig cells. Testicular tissue was processed histologically and histometry was performed in order to quantify germ cells, Sertoli cells and Leydig cells. Spermatogenic efficiency, reported as the ratios among germ cells (spermatogonia, primary spermatocytes and round spermatids) and by the ratio of germ cells to Sertoli cells, was not associated with testosterone levels. However, Leydig cell parameters such as number of Leydig cells per gram of testis, total number of Leydig cells per testis and percent cell volume of Leydig cell nuclei were correlated significantly with testosterone levels. The statistically significant correlation (r = 0.82, P<0.05) observed between testosterone levels and the number of Leydig cells per gram of testis suggests that, in the rabbit, the latter parameter can serve as a criterion for monitoring testosterone levels in this species under normal conditions.

Bone mineral density in young women of the city of São Paulo, Brazil: correlation with both collagen type I alpha 1 gene polymorphism and clinical aspects

Osteoporosis is a multifactorial disease with great impact on morbidity and mortality mainly in postmenopausal women. Although it is recognized that factors related to life-style and habits may influence bone mass formation leading to greater or lower bone mass, more than 85% of the variation in bone mineral density (BMD) is genetically determined. The collagen type I alpha 1 (COLIA1) gene is a possible risk factor for osteoporosis. We studied a population of 220 young women from the city of São Paulo, Brazil, with respect to BMD and its correlation with both COLIA1 genotype and clinical aspects. The distribution of COLIA1 genotype SS, Ss and ss in the population studied was 73.6, 24.1 and 2.3%, respectively. No association between these genotypes and femoral or lumbar spine BMD was detected. There was a positive association between lumbar spine BMD and weight (P<0.0001), height (P<0.0156), and body mass index (BMI) (P<0.0156), and a negative association with age at menarche (P<0.0026). There was also a positive association between femoral BMD and weight (P<0.0001), height (P<0.0001), and BMI (P<0.0001), and a negative correlation with family history for osteoporosis (P<0.041). There was no association between the presence of allele s and reduced BMD. We conclude that a family history of osteoporosis and age at menarche are factors that may influence bone mass in our population.

Bone mineral density in juvenile systemic lupus erythematosus

We evaluated spine bone mineral density (BMD) in Brazilian children with juvenile systemic lupus erythematosus (JSLE) in order to detect potential predictors of reduction in bone mass. A cross-sectional study of BMD at the lumbar spine level (L2-L4) was conducted on 16 female JSLE patients aged 6-17 years. Thirty-two age-matched healthy girls were used as control. BMD at the lumbar spine was measured by dual-energy X-ray absorptiometry. Weight, height and pubertal Tanner stage were determined in patients and controls. Disease duration, mean daily steroid doses, mean cumulative steroid doses and JSLE activity measured by the systemic lupus erythematosus disease activity index (SLEDAI) were determined for all JSLE patients based on their medical charts. All parameters were used as potential determinant factors for bone loss. Lumbar BMD tended to be lower in the JSLE patients, however, this difference was not statistically significant (P = 0.10). No significant correlation was observed in JSLE girls between BMD and age, height, Tanner stage, disease duration, corticosteroid use or disease activity. We found a weak correlation between BMD and weight (r = 0.672). In the JSLE group we found no significant parameters to correlate with reduced bone mass. Disease activity and mean cumulative steroid doses were not related to BMD values. We did not observe reduced bone mass in female JSLE.