Hückel and Möbius annulenes: relationships between their Hückel-level orbitals and their Hückel-level energies

The problem of convenient access to quantitative Hückel-level descriptions of Möbius and Hückel annulenes for undergraduate lectures about aromaticity is discussed. Frost circle, Zimmerman circle, double circle and Langler semicircular mnemonics are described. The relationship between spectra (complete sets of secular equation roots) for an isoconjugate pair of Hückel and Möbius annulenes and the corresponding acyclic polyene with one less carbon is fully developed. In addition to providing an alternative path to exact spectrum roots, this relationship provides immediate access to almost half of the eigenfunctions for an isoconjugate annulene pair. The remaining eigenfunctions may be obtained very easily.

Quantitative structure-retention relationships analysis of retention index of essential oils

Genetic algorithm and multiple linear regression (GA-MLR), partial least square (GA-PLS), kernel PLS (GA-KPLS) and Levenberg-Marquardt artificial neural network (L-M ANN) techniques were used to investigate the correlation between retention index (RI) and descriptors for 116 diverse compounds in essential oils of six Stachys species. The correlation coefficient LGO-CV (Q²) between experimental and predicted RI for test set by GA-MLR, GA-PLS, GA-KPLS and L-M ANN was 0.886, 0.912, 0.937 and 0.964, respectively. This is the first research on the QSRR of the essential oil compounds against the RI using the GA-KPLS and L-M ANN.

Relationships and estimates of longitudinal growth stress in Eucalyptus dunnii at different ages

The objective of this study was to obtain estimates of longitudinal growth stresses in standing trees of the Eucalyptus dunnii Maiden at eight, thirteen, fifteen and nineteen years of age and to determine their relationships with wood characteristics. The longitudinal growth stresses were indirectly measured by the "CIRAD-Forêt" method and estimated from both the dynamic modulus of elasticity and the modulus of elasticity in tension parallel to the grain. The longitudinal residual strain (LRS) and the estimates of the longitudinal growth stresses tended to increase with the age of the material. The LRS correlated positively and significantly with all the growth stresses estimates. The largestes magnitudes were at 13, 15 and 19 years of age. The basic density presented high, positive and significant correlations with the dynamic modulus of elasticity, estimated in the longitudinal direction, for wood saturated and at 12% moisture content, for all the ages assessed. All the growth stresses estimates presented high, positive and significant correlations between themselves.

SOIL ORGANIC CARBON, CARBON STOCK AND THEIR RELATIONSHIPS TO PHYSICAL ATTRIBUTES UNDER FOREST SOILS IN CENTRAL AMAZONIA

ABSTRACT The soil carbon under Amazonian forests has an important roles in global changing, making information on the soil content and depths of these stocks are considerable interest in efforts to quantify soil carbon emissions to the atmosphere.This study quantified the content and soil organic carbon stock under primary forest up to 2 m depth, at different topographic positions, at Cuieiras Biological Reserve, Manaus/ ZF2, km 34, in the Central Amazon, evaluating the soil attributes that may influence the permanence of soil carbon. Soil samples were collected along a transect of 850 m on topographic gradient Oxisol (plateau), Ultisol (slope) and Spodosol (valley). The stocks of soil carbon were obtained by multiplying the carbon content, soil bulk density and trickiness of soil layers. The watershed was delimited by using STRM and IKONOS images and the carbon contend obtained in the transects was extrapolated as a way to evaluate the potential for carbon stocks in an area of 2678.68 ha. The total SOC was greater in Oxisol followed by Spodosol and Ultisol. It was found direct correlations between the SOC and soil physical attributes. Among the clay soils (Oxisol and Ultisol), the largest stocks of carbon were observed in Oxisol at both the transect (90 to 175.5 Mg C ha-1) as the level of watershed (100.2 to 195.2 Mg C ha-1). The carbon stocks under sandy soil (Spodosol) was greater to clay soils along the transect (160-241 Mg C ha-1) and near them in the Watershed (96.90 to 146.01 Mg C ha-1).

Long term dietary deficiency in steers: vital functions and T3 and IGF-1 relationships

To evaluate the influence of diets with different degrees of energy deficiency on the hormonal profile and vital functions, 12 steers were randomly distributed into 3 groups of 4 animals. For 140 days, each group received (G1) a diet to promote a weight gain of 900gr/day (17.7 Mcal/d DE and 13% CP), (G2) 80% of the maintenance requirements (5.8 Mcal/d DE and 7% CP), or (G3) 60% of the maintenance requirements (4.7 Mcal/d DE and 5% CP). In G2 and G3, the energy deficit caused a marked decrease in the heart rate and respiratory rate and a reduction in the blood levels of Insulin like growth factor-1 (IGF-1) and triiodothyronine (T3). The decrease in heart rate, respiratory movement and, to a lesser extent, reduction of the rectal temperature, reflected the low status of energy and was negatively impacted by the low levels of T3. There was a strong correlation between the hormones T3 and IGF-1 (r=0.833). There were also strong correlations between T3 and HR (r=0.701), T3 and RR (r=0.632), IGF-1 and HR (r=0.731), and IGF-1 and RR (r=0.679). There were intermediate correlations between T3 and TºC (r=0.484), T3 and insulin (r=0.506), IGF-1 and insulin (r=0.517), and IGF-1 and TºC (r=0.548). This study showed the influence of a long period of providing an energy-deficient diet on animal performance, correlating hormonal status and vital functions in growing cattle. The results indicated that the evaluated parameters represent an important tool for the early detection of dietary deficiency.

Climate, soil and tree flora relationships in forests in the state of São Paulo, southeastern Brasil

ABSTRACT - (Climate, soil and tree flora relationships in forests in the state of São Paulo, southteastern Brasil). With the aim of verifying possible influences of abiotic features on the spatial distribution of forest tree species and families, thirteen surveys in the state of São Paulo were selected, representing different conditions (localization at the extreme coordenates and altitudes, succesional stages, surveying methods). By applying Jaccard's Index to the binary matrices of 806 synonymized specific binomina and 79 families (Cronquist's system) phenograms were constructed using the method of the unweighted pair grouping by mathematical average (UPGMA). The species formed two floristic blocks: hygrophyllous (yearly rainfall greater than 2000 mm without dry season) and mesophyllous (yearly rainfall about 1400 mm with variable dry season). The latter was divided in two other groups: the high-altitudinal (median altitudes higher than 750 m, frost average frequency greater than 3 days/year) and low-altitudinal. Both mesophyllous floristic blocks were subdivided according to soil conditions (texture, eutrophism, acid or allic dystrophism, iron content). At the family level the relations were weak, but also showed the soil nutritional status as a possible constraint to the spatial partition of families.

The seed coat as a modulator of seed-environment relationships in Fabaceae

The seed coat is one of the main determinants of seed germination, vigor and longevity potentials. It is also intimately associated with temporal and spatial dispersion of seed germination in a large number of plant species. The understanding of its properties and characteristics may explain, anticipate or even allow the modification of seed performance under certain environmental conditions. There is a growing volume of evidence associating seed coat characteristics to specific seed problems. For example, susceptibility to mechanical damage is related to lignin content of the seed coat, while seed longevity and tolerance to field weathering depends on seed coat integrity. Seed performance in many legumes has been associated with certain seed coat structures, such as the hilum, strophiole and micropyle. In soybean, permeability is also related with porosity, color, and cerosity, that affect seed vigor, storage potential, resistance to shrinking and fungi infection, and to susceptibility to imbibition damage. The understanding of these associations is necessary before genetic alterations through breeding for desirable characteristics and is fundamental for the development and improvement of seed pre-sowing treatments, production, handling and quality evaluation procedures, which may ultimately result in reduction of seed quality losses and increase the efficiency of agricultural production systems.

Floristic relationships among inland swamp forests of Southeastern and Central-Western Brazil

We evaluated the floristic relationships among 20 swamp forests of Southeastern and Central-Western Brazil using multivariate analyses. Detrended correspondence analysis (DCA) and TWINSPAN (Two way indicator species analysis) indicated two distinct floristic groups among forests, according to the Phytogeographic Province (Paranaense or Cerrado) and their climate conditions, phytophysiognomies, and species composition. Within the same province, edaphic conditions and geographical distance, among other factors, may be responsible for similarities or dissimilarities among the forests floras. Our results indicated that, despite the low a diversity, γ diversity is high among the forests, as a result of the low floristic similarities among the remnants and the high number of unique species (55% of all species). Although floristically distinct, we concluded that the inland swamp forests of Southeastern Brazil and the gallery swamp forests of Central Brazil are part of the same forest formation. These forests have in common, in addition to the swampy environment, low plant species diversity and species that have high local densities, such as Calophyllum brasiliense Cambess., Cecropia pachystachya Trécul, Dendropanax cuneatus Decne. & Planch., Guarea macrophylla Vahl, Magnolia ovata (A. St.-Hil.) Spreng., Protium spruceanum (Benth.) Engl. and Tapirira guianensis Aubl.

Relationships between crown architecture and available irradiance in two cerrado species with different leaf phenologies

Structural differences between cerrado species with different leaf phenologies are linked to crown architecture, leaf production, and biomass allocation to shoots and leaves. The present study characterized crown structures and the patterns of biomass allocation to leaves and shoots in two woody cerrado species with contrasting leaf phenologies and quantified the irradiance reaching their leaves to determine the best period during the day for photosynthetic activity. The shoots and leaves of five individuals of both Annona coriacea (deciduous) and Hymenaea stigonocarpa (evergreen) were collected along a 50 m transect in a cerrado fragment within the urban perimeter of Catalão - GO, to determine their patterns of biomass allocation in their crowns. The evergreen H. stigonocarpa had significantly higher mean values of shoot inclination (SI), petiole length (PL), leaf area (LA), leaf display index (LDI), and individual leaf area per shoot (ILA), while the deciduous species A. coriacea had significantly higher leaf numbers (LN). The more complex crown of H. stigonocarpa had shoots in more erect positions (orthotropic), with intense self-shading within shoots; A. coriacea, on the other hand, had slanting (plagiotropic) shoots in the crown, allowing similar irradiance levels to all leaf surfaces. The production of plagiotropic shoots by the deciduous species (A. coriacea) is a strategy that enables its use of incident sunlight early in the morning and preventing excessive water loss or excessive irradiance. Hymenaea stigonocarpa (an evergreen), by contrast, had orthotropic shoots and uses intense self-shading as a strategy to avoid excessive irradiance, especially at midday. Differences in crown architectures between evergreen and deciduous species of cerrado sensu stricto can therefore be viewed as adaptations to the environmental light regime.

Atrial natriuretic peptide and feeding activity patterns in rats

This review presents historical data about atrial natriuretic peptide (ANP) from its discovery as an atrial natriuretic factor (ANF) to its role as an atrial natriuretic hormone (ANH). As a hormone, ANP can interact with the hypothalamic-pituitary-adrenal axis (HPA-A) and is related to feeding activity patterns in the rat. Food restriction proved to be an interesting model to investigate this relationship. The role of ANP must be understood within a context of peripheral and central interactions involving different peptides and pathways

Feeding manipulation elicits different proliferative responses in the gastrointestinal tract of suckling and weanling rats

Food deprivation has been found to stimulate cell proliferation in the gastric mucosa of suckling rats, whereas the weanling period has been reported to be unresponsive in terms of proliferative activity. In the present study we analyze regional differences in the effect of milk or food deprivation on cell proliferation of the epithelia of the esophagus and of five segments of small intestine in suckling, weanling and newly weaned Wistar rats of both sexes. DNA synthesis was determined using tritiated thymidine to obtain labeling indices (LI); crypt depth and villus height were also determined. Milk deprivation decreased LI by 50% in the esophagus (from 15 to 8.35%) and small intestine (from 40 to 20%) of 14-day-old rats. In 18-day-old rats, milk and food deprivation decreased LI in the esophagus (from 13 to 5%) and in the distal segments of the small intestine (from 36-40 to 24-32%). In contrast, the LI of the epithelia of the esophagus (5%) and of all small intestine segments (around 30%) of 22-day-old rats were not modified by food deprivation. Crypt depth did not change after treatment (80 to 120 µm in 14- and 22-day-old rats, respectively). Villus height decreased in some small intestine segments of unfed 14- (from 400 to 300 µm) and 18-day-old rats (from 480 to 360 µm). The results show that, contrary to the stomach response, milk deprivation inhibited cell proliferation in the esophagus and small intestine of suckling rats, demonstrating the regional variability of each segment of the gastrointestinal tract in suckling rats. In newly weaned rats, food deprivation did not alter the proliferation of these epithelia, similarly to the stomach, indicating that weanling is a period marked by the insensitivity of gastrointestinal epithelia to dietary alterations

P-glycoprotein-mediated resistance to chemotherapy in cancer cells: using recombinant cytosolic domains to establish structure-function relationships

Resistance to chemotherapy in cancer cells is mainly mediated by overexpression of P-glycoprotein (Pgp), a plasma membrane ATP-binding cassette (ABC) transporter which extrudes cytotoxic drugs at the expense of ATP hydrolysis. Pgp consists of two homologous halves each containing a transmembrane domain and a cytosolic nucleotide-binding domain (NBD) which contains two consensus Walker motifs, A and B, involved in ATP binding and hydrolysis. The protein also contains an S signature characteristic of ABC transporters. The molecular mechanism of Pgp-mediated drug transport is not known. Since the transporter has an extraordinarily broad substrate specificity, its cellular function has been described as a "hydrophobic vacuum cleaner". The limited knowledge about the mechanism of Pgp, partly due to the lack of a high-resolution structure, is well reflected in the failure to efficiently inhibit its activity in cancer cells and thus to reverse multidrug resistance (MDR). In contrast to the difficulties encountered when studying the full-length Pgp, the recombinant NBDs can be obtained in large amounts as soluble proteins. The biochemical and biophysical characterization of recombinant NBDs is shown here to provide a suitable alternative route to establish structure-function relationships. NBDs were shown to bind ATP and analogues as well as potent modulators of MDR, such as hydrophobic steroids, at a region close to the ATP site. Interestingly, flavonoids also bind to NBDs with high affinity. Their binding site partly overlaps both the ATP-binding site and the steroid-interacting region. Therefore flavonoids constitute a new promising class of bifunctional modulators of Pgp.

Involvement of the caudal raphe nuclei in the feeding behavior of rats

Involvement of the caudal raphe nuclei (raphe pallidus, RPa; raphe magnus, RMg, and raphe obscurus, ROb) in feeding behavior of adult rats was studied by measuring c-Fos protein expression, in animals submitted to the "meal-feeding" model of food restriction in which the rats were fed ad libitum only from 7:00 to 9:00 h, for 15 days. The experimental groups submitted to chronic fasting, named 'search for food' (SF), 'ingestion of food' (IF) and 'satiety of food' (SaF) were scheduled after a previous study in which the body weight and the general and feeding behaviors were evaluated by daily monitoring. Acute, 48-h fasting (AF) was used as control. In the chronic group, the animals presented a 16% reduction in body weight in the first week, followed by a continuous, slow rise in weight over the subsequent days. Entrainment of the sleep-wake cycle to the schedule of food presentation was also observed. The RPa was the most Fos immunopositive nucleus in the chronic fasting group, followed by the RMg. The ANOVA and Tukey test (P<0.05) confirmed these results. The IF group was significantly different from the other three groups, as also was the number of labeled cells in the RPa in SF and IF groups. Nevertheless, no significant difference was observed between RMg and RPa, or RMg and ROb in the SaF and AF. However, it is interesting to observe that the groups in which the animals were more active, searching for or ingesting food, presented a larger number of labeled cells. These results suggest a different involvement of the caudal raphe nuclei in the somatic and autonomic events of feeding behavior, corroborating the functions reported for them earlier.

Meal-feeding scheme: twenty years of research in Brazil

Naomi Shinomiya Hell was the first researcher to investigate the physiological adaptations to a meal-feeding scheme (MFS) in Brazil. Over a period of 20 years, from 1979 to 1999, Naomi's group determined the physiological and metabolic adaptations induced by this feeding scheme in rats. The group showed the persistence of such adaptations even when MFS is associated with moderate exercise training and the performance to a session of intense physical effort. The metabolic changes induced by the feeding training were discriminated from those caused by the effective fasting period. Naomi made an important contribution to the understanding of the MFS but a lot still has to be done. One crucial question still remains to be satisfactorily answered: what is the ideal control for the MFS?

Effect of dietary (n-3) highly unsaturated fatty acids on growth and survival of fat snook (Centropomus parallelus, Pisces: Centropomidae) larvae during first feeding

The effect of rotifers, Brachionus rotundiformis (S-type), fed three different diets: A (rotifer fed Nannochloropsis oculata), B (rotifer fed N. oculata and baker's yeast, 1:1), and C (rotifer fed N. oculata and baker's yeast, 1:1, and enriched with Selcoâ), was evaluated based on the survival, growth and swim bladder inflation rate of fat snook larvae. Rotifers of treatment A had higher levels (4.58 mg/g dry weight) of eicosapentaenoic acid (EPA) than B (1.81 mg/g dry weight), and similar levels (0.04 and 0.06 mg/g dry weight, respectively) of docosahexaenoic acid (DHA). Rotifers of treatment C had the highest levels of EPA (13.2 mg/g dry weight) and DHA (6.08 mg/g dry weight). Fat snook eggs were obtained by spawning induction with human chorionic gonadotropin. Thirty hours after hatching, 30 larvae/liter were stocked in black cylindric-conical tanks (36-liter capacity). After 14 days of culture, there were no significant differences among treatments. Mean standard length was 3.13 mm for treatment A, 3.17 mm for B, and 3.39 mm for C. Mean survival rates were very low (2.7% for treatment A, 2.3% for B, and 1.8% for C). Swim bladder inflation rates were 34.7% for treatment A, 27.1% for B, and 11.9% for C. The lack of differences in growth and survival among treatments showed that the improvement of the dietary value of rotifer may not have been sufficient to solve the problem of larval rearing. Some other factor, probably pertaining to the quality of the larvae, may have negatively influenced survival.