Comparative investigation of the cleavage step in the synthesis of model peptide resins: Implications for N-alpha-9-fluorenylmethyloxycarbonyl-solid phase peptide synthesis

Based on our studies of the stability of model peptide-resin linkage in acid media, we previously proposed a rule for resin selection and a final cleavage protocol applicable to the N-alpha-tert-butyloxycarbonyl (Boc)-peptide synthesis strategy. We found that incorrect choices resulted in decreases in the final synthesis yield, which is highly dependent on the peptide sequence, of as high as 30%. The present paper continues along this line of research but examines the N-alpha-9-fluorenylmethyloxycarbonyl (Fmoc)-synthesis strategy. The vasoactive peptide angiotensin II (All, DRVYIHPF) and its [Gly(8)]-All analogue were selected as model peptide resins. Variations in parameters such as the type of spacer group (linker) between the peptide backbone and the resin, as well as in the final acid cleavage protocol, were evaluated. The same methodology employed for the Boc strategy was used in order to establish rules for selection of the most appropriate linker-resin conjugate or of the peptide cleavage method, depending on the sequence to be assembled. The results obtained after treatment with four cleavage solutions and with four types of linker groups indicate that, irrespective of the circumstance, it is not possible to achieve complete removal of the peptide chains from the resin. Moreover, the Phe-attaching peptide at the C-terminal yielded far less cleavage (50-60%.) than that observed with the Gly-bearing sequences at the same position (70-90%). Lastly, the fastest cleavage occurred with reagent K acid treatment and when the peptide was attached to the Wang resin.

Physiology of temperature regulation: Comparative aspects

Few environmental factors have a larger influence on animal energetics than temperature, a fact that makes thermoregulation a very important process for survival. In general, endothermic species, i.e., mammals and birds, maintain a constant body temperature (Tb) in fluctuating environmental temperatures using autonomic and behavioural mechanisms. Most of the knowledge on thermoregulatory physiology has emerged from studies using mammalian species, particularly rats. However, studies with all vertebrate groups are essential for a more complete understanding of the mechanisms involved in the regulation of Tb. Ectothermic vertebrates-fish, amphibians and reptiles-thermoregulate essentially by behavioural mechanisms. With few exceptions, both endotherms and ectotherms develop fever (a regulated increase in Tb) in response to exogenous pyrogens, and regulated hypothermia (anapyrexia) in response to hypoxia. This review focuses on the mechanisms, particularly neuromediators and regions in the central nervous system, involved in thermoregulation in vertebrates, in conditions of euthermia, fever and anapyrexia. (c) 2006 Elsevier B.V. All rights reserved.

COMPARATIVE INVITRO ACTIVITY OF 3 CEPHALOSPORINS AGAINST STAPHYLOCOCCUS-AUREUS ISOLATED FROM BOVINE MASTITIS

This report compares the in vitro activity of three cephalosporins (cephalothin, cefoxitin and ceftriaxone) against 57 Staphylococcus aureus strains isolated from cows with clinical mastitis on the basis of the minimal inhibitory (MIC) and minimal bactericidal concentrations (MBC). The majority of the S aureus strains showed resistance to cefoxitin and ceftriaxone and sensitivity to cephalothin. The highest MICs and MBCs were found for cefoxitin and ceftriaxone. Antimicrobial tolerance (MBC/MIC greater-than-or-equal-to 32:1) was observed in relation to cephalothin and ceftriaxone. The data suggest that these cephalosporins may not be effective for the treatment of staphylococcal bovine mastitis. The precise definition of their antimicrobial efficacies requires more detailed in vitro and in vivo studies.

A comparative study of the corrosion of high copper dental amalgams

Metallographic studies carried out for Tytin-Plus and Dispersalloy amalgams show a porous multiphase material, whose surface phases are: gamma-(Ag3Sn), gamma(1)-(Ag2Hg3), eta'-(Cu6Sn5) and epsilon-(Cu3Sn). Additionally, Dispersalloy is present in the Ag-Cu eutectic. The application of surface analysis by SEM reveal a heterogeneous distribution of the above mentioned phases. Microstructures consisting of colonies or clusters were not observed. The corrosion testing of these materials was done in 0.9% NaCl aerated solution at 25 degrees C using potentiodynamic polarization curves and ac impedance measurements. The corrosion process in these multiphase systems can be interpreted as the sum of more than one electrodissolution process and the posterior formation of corrosion films. on each electrode, the corrosion film is formed by different mechanisms. (C) 1998 Elsevier B.V. B.V. All rights reserved.

Studies on the respiration rate of free and immobilized cells of Cephalosporium acremonium in cephalosporin C production

Bioprocesses using filamentous fungi immobilized in inert supports present many advantages when compared to conventional free cell processes. However, assessment of the real advantages of the unconventional process demands a rigorous study of the limitations to diffusional mass transfer of the reagents, especially concerning oxygen. In this work, a comparative study was carried out on the cephalosporin C production process in defined medium containing glucose and sucrose as main carbon and energy sources, by free and immobilized cells of Cephalosporium acremonium ATCC 48272 in calcium alginate gel beads containing alumina. The effective diffusivity of oxygen through the gel beads and the effectiveness factors related to the respiration rate of the microorganism were determined experimentally. By applying Monod kinetics, the respiration kinetics parameters were experimentally determined in independent experiments in a complete production medium. The effectiveness factor experimental values presented good agreement with the theoretical values of the approximated zero-order effectiveness factor, considering the dead core model. Furthermore, experimental results obtained with immobilized cells in a 1.7-L tower bioreactor were compared with those obtained in 5-L conventional fermenter with free cells. It could be concluded that it is possible to attain rather high production rates working with relatively large diameter gel beads (ca. 2.5 mm) and sucrose consumption-based productivity was remarkably higher with immobilized cells, i.e., 0.33 gCPC/kg sucrose/h against 0.24 gCPC/kg sucrose/h in the aerated stirred tank bioreactor process. (C) 1999 John Wiley & Sons, Inc.

Comparative mechanical study of isolated papillary muscle from Wistar-Kyoto and Wistar rats

Isolated papillary muscles have often been used in myocardial mechanical function studies. The objective of the present study was to compare the mechanical function of papillary muscle isolated from left ventricle between Wistar (W) and Wistar-Kyoto (WKY) rats of different ages (1, 3, 6 and 12 months), in order to examine whether there is a difference in intrinsic mechanical properties of muscle between the two rat strains. Muscles were perfused with Krebs-Henseleit solution at 28°C and studied isometrically and isotonically at a stimulation rate of 0.2 Hz. The W and WKY showed statistically significant differences during both isometric and isotonic contractions. During isometric contraction? (l) the peak developed tension (DT) and + dT/dt were lower in WKY rats in the 1 mo groups, (2) the resting tension (RT) was greater in WKY at 3, 6 and 12 mo. (3) time to peak tension (TPT) was greater in WKY at 3 and 12 mo, (4) time for tension to fall from peak to 50% of peak tension (RT 1/2) was greater in WKY at 3 mo and (5) - dT/dt was lower in WKY at 1 and 3 mo. During isotonic contraction, (1) the peak shortening (PS) and -dL/dt were lower in WKY at 12 mo, (2) the time to peak shortening (TPS) was greater in WKY at 3 and 12 mo; (3) + dL/dt was lower in WKY at 3, 6, and 12 mo and (4) the relative variation of length (Lmax-PS)/Lmax was greater in WKY at 6 and 12 mo. These data showed a difference in mechanical behaviour of the papillary muscle between Wistar and Wistar-Kyoto rats of different age.

Paracentric inversion involving a NOR-bearing chromosome of rainbow trout (Oncorhyncus mykiss): Electron microscopy studies of the synaptonemal complex

Cytogenetic studies conduced on a sample of 19 specimens of rainbow trout (Oncorhyncus mykiss) showed that 6 presented two chromosomes with a single subterminal AgNOR on the short arms and 13 presented one chromosome with a single subterminal Ag-NOR and a second chromosome with two small subterminal Ag-NORs. Synaptonemal complex studies showed the presence of a pairing failure involving the two lateral elements (LEs) of the NOR-bearing chromosomes only in those specimens with two different NOR-bearing chromosomes, suggesting that the chromosomes with two Ag-NORs originated from a paracentric inversion involving a terminal segment of the original NOR-bearing chromosome. A comparative analysis between three normal and three heterozygous fishes suggest that in the latter group the LEs of the NOR-bearing chromosomes initiate the synaptic process in a more delayed manner, the synapsis develops more quickly, and the nucleolus stays associated with chromosomes for a longer time.

Treatment of gingival recession: Comparative study between subepithelial connective tissue graft and guided tissue regeneration

Background: Various procedures have been proposed to treat gingival recession, but few studies compare these procedures to each other. The purpose of this study was to evaluate a clinical comparison of subepithelial connective tissue graft (SCTG) and guided tissue regeneration (GTR) with a collagen membrane in the treatment of gingival recessions in humans. Methods: Twenty-four defects were treated in 12 patients who presented canine or pre-molar Miller Class I and/or II bilateral gingival recessions. Both treatments were performed in all patients, and clinical measurements were obtained at baseline and 18 months after surgery. These clinical measurements included gingival recession height (GR), root coverage (RC), probing depth (PD), keratinized tissue width (KT), and final esthetic result. Results: Both SCTG and GTR with a bioabsorbable membrane and bone graft demonstrated significant clinical and esthetic improvement for gingival recession coverage. The SCTG group was statistically significantly better than GTR for height of GR (SCTG = 0.2 mm, GTR = 1.12 mm, P = 0.02) and KT (SCTG = 4.58 mm, GTR = 2.5 mm, P <0.0001). However, PD was statistically significantly better for GTR than SCTG treatment (GTR = 1.66 mm, SCTG = 1.00, P = 0.01). The 2 procedures were statistically similar in root coverage (SCTG = 95.6%, GTR = 84.2%, P = 0.073). The esthetic condition after both treatments was satisfactory (P = 0.024). Conclusions: It was concluded that the gingival recessions treated with the SCTG group were superior for GR, RC, and KT clinical parameters, while GTR demonstrated better PD reduction. The final esthetic results were similar using both techniques.

A comparative study of protein and enzymatic activity in venoms of some common wasps (Hymenoptera: Vespidae) from São Paulo State

The Hymenoptera Aculeata venoms, with few exceptions, have been poorly studied and characterized. Nevertheless, they have raised increasing interest due to their medical importance, since accidents with these insects are fairly frequent in Brazil and may cause severe allergic reactions. The objectives of the present work were the quantitative characterization of the main allergenic enzymes present in the venom of the species Polybia paulista, Polybia ignobilis, Polistes simillimus, and Agelaia pallipes pallipes through biochemical assays for the determination of total protein content, as well as the level of the enzymatic activity of phospholipase, hyaluronidase, acid phosphatase and esterase. These results, in addition to providing biochemical knowledge about the venom of the species in question, also supply studies that allow phylogenetic inferences among them.

Comparative therapeutic use of Risedronate and Calcarea phosphorica - Allopathy versus homeopathy - In bone repair in castrated rats

Osteoporosis, a disease characterized by progressive bone loss, has been the target of several studies in the past few years. It results in a much higher risk for fractures and might cause slower bone lesion healing. The aim of this work was to study the effects of Risedronate (allopathic medicine) and Calcarea phosphorica 6CH (homeopathic medicine) on the repair of bone lesions in male rats with osteoporosis induced by castration. Eighty-four three-month-old rats were used divided into four groups of twenty-one animals each. Three groups where castrated and one group was submitted to Sham surgery. One month later, cortical lesions were made in all animals' tibiae and, after one day, the different experimental treatments began according to the following groups: CR - castrated/Risedronate (1 mg/kg/day); CCp - castrated/ Calcarea phosphorica 6CH (3 drops/day); CP - castrated/placebo and SP - Sham/placebo. The animals were sacrificed at seven, fourteen and twenty-eight days after the beginning of the treatments and had their tibiae removed. Digital radiographs of the tibiae were taken and analyzed in order to evaluate the optical density of the defect area. Then, they were decalcified and processed for histological and histomorphometrical analysis. The data were submitted to ANOVA, and to the Tukey and Dunnett tests (5%). The allopathic and homeopathic treatments led to different bone formation as regards remodeling and maturation aspects. Further research is necessary to access the resistance and quality of the newly formed bone.

Comparative study of multiple dosage of quercetin against cisplatin-induced nephrotoxicity and oxidative stress in rat kidneys

Quercetin, a typical bioflavonoid ubiquitously present in fruits and vegetables, is considered to be helpful for human health. Cisplatin (cDDP) is one of the most active cytotoxic agents in the treatment of a wide range of solid tumors. The aim of this study was to investigate the possible effect of quercetin, a bioflavonoid with antioxidant potential, on cisplatin-induced nophrotoxicity and lipid peroxidation in rats. Gavage administrations of water, propylene glycol and quercetin (50 mg/kg) were made 24 and 1 h before saline or cDDP (5 mg/kg) ip injections and were repeated daily for 2, 5 or 20 subsequent days. Rats were killed 2, 5 and 20 days after ip injections, and blood and urine samples were collected to determine plasma creatinine, urine volume and osmolality. The kidneys were removed to determine the levels of thiobarbituric acid-reactive substances (TBARS) and for histological studies. Cisplatin increased lipid peroxidation, urine volume and plasma creatinine levels and decreased urine osmolality. Treatment with quercetin attenuated these alterations. These results demonstrate the role of oxidative stress and suggest a protective effect of quercetin on cisplatin-induced nephrotoxicity in adult Wistar rats. Copyright © 2006 by Institute of Pharmacology Polish Academy of Sciences.

A comparative study of cytoarchitecture and serotonergic afferents in the suprachiasmatic nucleus of primates (Cebus apella and Callithrix jacchus) and rats (Wistar and Long Evans strains)

The suprachiasmatic nucleus, an essential diencephalic component of the circadian timing system, plays a role in the generation and modulation of behavioral and neuroendocrine rhythms in mammals. Its cytoarchitecture, neurochemical and hodological characteristics have been investigated in various mammalian species, particularly in rodents. In most species, two subdivisions, based on these aspects and considered to reflect functional specialization within the nucleus, can be recognized. Many studies reveal a typical dense innervation by serotonergic fibers in this nucleus, mainly in the ventromedial area, overlapping the retinal afferents. However, a different pattern occurs in certain animals, which lead us to investigate the distribution of serotonergic afferents in the suprachiasmatic nucleus of the Capuchin monkey, Cebus apella, compared to the marmoset, Callithrix jacchus, and two Rattus norvegicus lines (Long Evans and Wistar), and to reported findings for other mammalian species. Our morphometric data show the volume and length of the suprachiasmatic nucleus along the rostrocaudal axis to be greatest in C. apella > C. jacchus > Long Evans ≥ Wistar rats, in agreement with their body sizes. In C. apella, however, the serotonergic terminals occupy only some 10% of the nucleus' area, less than the 25% seen in the marmoset and rats. The distribution of the serotonergic fibers in C. apella does not follow the characteristic ventral organization pattern seen in the rodents. These findings raise questions concerning the intrinsic organization of the nucleus, as well as regarding the functional relationship between serotonergic input and retinal afferents in this diurnal species. © 2007 Elsevier B.V. All rights reserved.

Comparative Analysis of 2 Techniques of Double-Gloving Protection During Arch Bar Placement for Intermaxillary Fixation

Purpose: This study was conducted to comparatively evaluate, in a prospective and randomized manner, 2 techniques for providing double-gloving protection during arch bar placement for intermaxillary fixation. Materials and Methods: A total of 42 consecutive patients in whom application of an Erich bar was indicated for intermaxillary fixation were equally divided into 2 groups. In group 1, 2 sterile surgical gloves were used; in group 2, a nonsterile disposable inner glove was used under a sterile surgical glove. Wilcoxon, Mann-Whitney, Kruskal-Wallis, and binomial statistical tests were used to analyze the findings. Results: A total of 103 perforations were found in the outer gloves (47 in group 1 and 56 in group 2), along with 5 perforations in inner gloves in both groups (α = .01). No significant statistical difference was found between groups in terms of inner glove perforations (α = .05). The nondominant hand presented with 70.9% of the perforations, statistically significant to 1%. Conclusions: Both double-gloving techniques were found to provide effective clinician protection. The use of a nonsterile disposable glove under the surgical glove is possible for less-invasive procedures, offering the same safety as using 2 sterile surgical gloves while decreasing operational costs. This method does not eliminate the need to change gloves when a perforation is suspected or noted during the surgery, however. © 2007 American Association of Oral and Maxillofacial Surgeons.

Respiratory chemoreceptor function in vertebrates - Comparative and evolutionary aspects

The sensing of blood gas tensions and/or pH is an evolutionarily conserved, homeostatic mechanism, observable in almost all species studied from invertebrates to man. In vertebrates, a shift from the peripheral O2-oriented sensing in fish, to the central CO2/pH sensing in most tetrapods reflects the specific behavioral requirements of these two groups whereby, in teleost fish, a highly O2-oriented control of breathing matches the ever-changing and low oxygen levels in water, whilst the transition to air-breathing increased the importance of acid-base regulation and O2-related drive, although retained, became relatively less important. The South American lungfish and tetrapods are probably sister groups, a conclusion backed up by many similar features of respiratory control. For example, the relative roles of peripheral and central chemoreceptors are present both in the lungfish and in land vertebrates. In both groups, the central CO2/pH receptors dominate the ventilatory response to hypercarbia (60-80), while the peripheral CO2/pH receptors account for 20-30. Some basic components of respiratory control have changed little during evolution. This review presents studies that reflect the current trends in the field of chemoreceptor function, and several laboratories are involved. An exhaustive review on the previous literature, however, is beyond the intended scope of the article. Rather, we present examples of current trends in respiratory function in vertebrates, ranging from fish to humans, and focus on both O2 sensing and CO2 sensing. As well, we consider the impact of chronic levels of hypoxia - a physiological condition in fish and in land vertebrates resident at high elevations or suffering from one of the many cardiorespiratory disease states that predispose an animal to impaired ventilation or cardiac output. This provides a basis for a comparative physiology that is informative about the evolution of respiratory functions in vertebrates and about human disease. Currently, most detail is known for mammals, for which molecular biology and respiratory physiology have combined in the discovery of the mechanisms underlying the responses of respiratory chemoreceptors. Our review includes new data on nonmammalian vertebrates, which stresses that some chemoreceptor sites are of ancient origin.