Estimation of the forces generated by the thigh muscles for transtibial amputee gait.

The forces generated by the muscles with origin on the human femur play a major role in transtibial amputee gait, as they are the most effective of the means that the body can use for propulsion. By estimating the forces generated by the thigh muscles of transtibial amputees, and comparing them to the forces generated by the thigh muscles of normal subjects, it is possible to better estimate the energy output needed from prosthetic devices. The purpose of this paper is to obtain the forces generated by the thigh muscles of transtibial amputees and compare these with forces obtained from the same muscles in the case of normal subjects. Two transtibial amputees and four normal subjects similar in size to the amputees were investigated. Level ground walking was chosen as the movement to be studied, since it is a common activity that most amputees engage in. Inverse dynamics and a muscle recruitment algorithm (developed by AnyBody Technology(®)) were used for generating the muscle activation patterns and for computing the muscle forces. The muscle forces were estimated as two sums: one for all posterior muscles and one for the anterior muscles, based on the position of the muscles of the thigh relative to the frontal plane of the human body. The results showed that a significantly higher force is generated by the posterior muscles of the amputees during walking, leading to a general increase of the metabolic cost necessary for one step.

VO2 kinetics in 200-m race-pace front crawl swimming.

Studies that aim to characterize oxygen uptake kinetics in efforts above maximal oxygen consumption intensity are scarce. Our aim was to analyze the oxygen kinetics in a maximal 200-m front crawl, all measurements being conducted in swimming pool conditions. 10 high-level male swimmers performed a maximal 200-m bout and oxygen uptake was directly measured through breath-by-breath gas analysis. Mean (±SD) peak oxygen uptake was 68.58 (±5.79) ml.kg(-1).min(-1), evidencing a fast component phase. As expected, peak oxygen uptake presented a direct relationship with mean swimming speed of the first 50-m lap and with the 200-m effort, and was also correlated with the amplitude of the fast component (r=0.75, r=0.72, r=0.73, p<0.05, respectively). The observed mean amplitude value was higher than those observed in the literature for other exercise intensity domains. However, the time for its onset, as well as the duration for attaining the steady state, was shorter, as the peak oxygen uptake was not correlated with these 2 components. Moreover, as previously described for swimming at high intensities, the slow component phenomenon was not observed. Aerobic metabolic pathway accounted for 78.6%, confirming the high aerobic contribution in middle distance swimming events.

Coronary heart disease risk assessment in HIV-infected patients: a comparison of Framingham, PROCAM and SCORE risk assessment functions.

OBJECTIVES: The aim of this was to compare the performance of the Framingham, Systematic Coronary Risk Evaluation (SCORE) and Prospective Cardiovascular Munster (PROCAM) scoring systems in the risk assessment of HIV-infected patients with no overt vascular disease. METHODS: A cross-sectional study of 220 HIV-infected patients was conducted at the outpatient clinic of a referral and training centre in infectious and parasitic diseases in Belo Horizonte, Brazil. The Framingham, SCORE and PROCAM equations were calculated. Patients were classified as having low, moderate or high risk, which according to the Framingham and PROCAM equations corresponded to < 10%, 10-20% and > 20% respectively, and according to SCORE corresponded to < 3%, 3-4% and > or = 5% respectively. Cohen's kappa coefficient was used to assess agreement between the methods. RESULTS: Of a total of 220 HIV-infected patients, 56 were antiretroviral (ARV)-naïve while 164 had already been treated with ARV. The prevalence of patients with a high 10-year cardiovascular risk was 3.7%, 2.5% and 1.9% according to the Framingham, PROCAM and SCORE equations respectively. The degree of agreement was moderate between the Framingham and PROCAM risk estimates (kappa = 0.433; p < 0.001), poor-to-fair between the Framingham and SCORE estimates (kappa = 0.220; p < 0.001) and moderate between the PROCAM and SCORE systems (kappa = 0.478; p < 0.001). CONCLUSIONS: There are differences in risk assessment and in the identification of high risk individuals between the three risk functions under evaluation and only a prospective study will be capable of assessing which offers the best current sensitivity, specificity and predictive values for the population under investigation.

Time limit at VO2max velocity in elite crawl swimmers.

The purpose of this study is to assess, with elite crawl swimmers, the time limit at the minimum velocity corresponding to maximal oxygen consumption (TLim-vVO2max), and to characterize its main determinants. Eight subjects performed an incremental test for vVO2max assessment and, forty-eight hours later, an all-out swim at vVO2max until exhaustion. VO2 was directly measured using a telemetric portable gas analyzer and a visual pacer was used to help the swimmers keeping the predetermined velocities. Blood lactate concentrations, heart rate and stroke parameter values were also measured. TLim-vVO2max and vVO2max, averaged, respectively, 243.2 +/- 30.5 s and 1.45 +/- 0.08 m . s (-1). TLim-vVO2max correlated positively with VO2 slow component (r = 0.76, p < 0.05). Negative correlations were found between TLim-vVO2max and body surface area (r = - 0.80) and delta lactate (r = - 0.69) (p < 0.05), and with vVO2max (r = - 0.63), v corresponding to anaerobic threshold (r = - 0.78) and the energy cost corresponding to vVO2max (r = - 0.62) (p < 0.10). No correlations were observed between TLim-vVO2max and stroking parameters. This study confirmed the tendency to TLim-vVO2max be lower in the swimmers who presented higher vVO2max and vAnT, possibly explained by their higher surface area, energy cost and anaerobic rate. Additionally, O2SC seems to be a determinant of TLim-vVO2max.

Biomaterial with chemically engineered surface for protein immobilization.

The last 3 decades have been a revolution in the area of sol-gel-derived materials. They can be used to encapsulate biomolecules such as enzymes, antibodies, hormones, and proteins retaining their functional state. Proteins can be immobilized in many ways but it is crucial that they retain their native conformational structure and, therefore, bioactivity. Porous silica gel matrixes with modified surfaces offer unlimited possibilities to control the protein-solid interaction behavior. The bioimmobilization process on sol-gel biomaterials with chemically engineered surface has driven applications on solid-phase materials, affinity chromatography, biosensors and many others. In the present work, we have aimed to produce surface-modified silica glass materials obtained via sol-gel route to be used as solid support on drug delivery systems and as solid-phase in immunodiagnostic. The functionalization process was carried out by reacting alkoxysilanes with 5 different silane surface modifying chemical groups: tetraethoxysilane (TEOS), 3-mercaptopropyltrimethoxysilane (MPTMS) and 3-aminopropyltriethoxysilane (APTES), 3-glycidoxypropyltrimethoxysilane (GPTMS) and 3-isocyanatopropyltriethoxysilane (ICPES). The bioactivity assays were based on two main tests: (a) An in vivo bioresponse of rats with sol-gel disk implants with insulin protein incorporated. In vivo tests with adult male rats were used to verify the immobilized insulin bioactivity after implantation of different biomaterial with functionalized surfaces. All surface modified materials have presented hypoglycemic peak response associated with the insulin bioactivity. (b) The produced solid-phase sol-gel disks with protein substrates were tested through Enzyme Linked Immuno Sorbent Assay (ELISA). The immunoassay results have showed that glasses with chemically functionalized surfaces regulated the extent of bioimmobilization of protein. The amine, thiol and hydroxyl terminated porous gels have showed significant interaction with the antibody-antigen, during the coupling process. We believe that it is due to balance of forces associated with Van der Waals interaction, hydrophilic and hydrophobic forces and steric hindrance acting at the surface. Therefore, such novel biomaterial could be advantageously used in drug delivery systems and in immunoassays of diagnostic kits.

Evidence of angiotensin II involvement in prolactin secretion in response to hemorrhage in adrenodemedullated and guanethidine-treated rats.

OBJECTIVE: The present experiments were designed to investigate the influence of the renin--angiotensin system (RAS) on prolactin secretion in response to hemorrhage (1.2 ml/100 g body weight (bw)/2 min). METHODS AND RESULTS: Male Wistar rats (250-300 g) were divided into the following experimental groups. (i) Sham-operated animals submitted to intravenous administration of [Sar(1),Thr(8)]-angiotensin II (sarthran), an angiotensin II antagonist (750 ng/100 g bw as a bolus plus an infusion of 25 ng/100 g bw/min over 30 min), which did not alter the prolactin secretion in response to hemorrhage. (ii) Animals submitted to adrenodemedullation which by itself increased the prolactin secretion in response to hemorrhage by 274% (P<0.01). However, sarthran infusion into adrenodemedullated rats completely blocked this increased prolactin secretion in response to hemorrhage (P<0.01). (iii) Intact animals submitted to blockade of sympathetic noradrenergic pathways by pretreatment with guanethidine (10 mg/100 g bw), which also increased the prolactin secretion in response to hemorrhage by 55% (P<0.01). This increased prolactin secretion in response to hemorrhage observed in guanethidine-treated rats was completely blocked by sarthran preinfusion (P<0.01). (iv) Adrenodemedullated animals pretreated with guanethidine, which abolished the prolactin secretion induced by hemorrhage. CONCLUSIONS: Our data suggest a role for circulating catecholamines in the prolactin secretion response to stress. In addition, the experiments reported here demonstrate that RAS has a stimulatory effect on prolactin secretion in circumstances in which sympathetic activity or adrenomedullary secretion is suppressed. These are the first data demonstrating that a physiological prolactin secretion response to stress depends on the RAS.

Identification of a p28 gene in Ehrlichia ewingii: evaluation of gene for use as a target for a species-specific PCR diagnostic assay.

PCR was used to amplify a 537-bp region of an Ehrlichia ewingii gene encoding a homologue of the 28-kDa major antigenic protein (P28) of Ehrlichia chaffeensis. The E. ewingii p28 gene homologue was amplified from DNA extracted from whole blood obtained from four humans and one canine with confirmed cases of infection. Sequencing of the PCR products (505 bp) revealed a partial gene with homology to outer membrane protein genes from Ehrlichia and Cowdria spp.: p30 of Ehrlichia canis (< or =71.3%), p28 of E. chaffeensis (< or =68.3%), and map1 of Cowdria ruminantium (67.3%). The peptide sequence of the E. ewingii partial gene product was deduced (168 amino acids) and the antigenicity profile was analyzed, revealing a hydrophilic protein with < or =69.1% identity to P28 of E. chaffeensis, < or =67.3% identity to P30 of E. canis, and < or =63.1% identity to MAP1 of C. ruminantium. Primers were selected from the E. ewingii p28 sequence and used to develop a species-specific PCR diagnostic assay. The p28 PCR assay amplified the expected 215-bp product from DNA that was extracted from EDTA-treated blood from each of the confirmed E. ewingii infections that were available. The assay did not produce PCR products with DNA extracted from E. chaffeensis-, E. canis-, or E. phagocytophila-infected samples, confirming the specificity of the p28 assay for E. ewingii. The sensitivity of the E. ewingii-specific PCR assay was evaluated and determined to detect as few as 38 copies of the p28 gene.

Infections with Ehrlichia chaffeensis and Ehrlichia ewingii in persons coinfected with human immunodeficiency virus.

The clinical course and laboratory evaluation of 21 patients coinfected with human immunodeficiency virus (HIV) and Ehrlichia chaffeensis or Ehrlichia ewingii are reviewed and summarized, including 13 cases of ehrlichiosis caused by E. chaffeensis, 4 caused by E. ewingii, and 4 caused by either E. chaffeensis or E. ewingii. Twenty patients were male, and the median CD4(+) T lymphocyte count was 137 cells/microL. Exposures to infecting ticks were linked to recreational pursuits, occupations, and peridomestic activities. For 8 patients, a diagnosis of ehrlichiosis was not considered until > or =4 days after presentation. Severe manifestations occurred more frequently among patients infected with E. chaffeensis than they did among patients infected with E. ewingii, and all 6 deaths were caused by E. chaffeensis. Ehrlichiosis may be a life-threatening illness in HIV-infected persons, and the influence of multiple factors, including recent changes in the epidemiology and medical management of HIV infection, may increase the frequency with which ehrlichioses occur in this patient cohort.

Surface functionalization of porous glass networks: effects on bovine serum albumin and porcine insulin immobilization.

Biomolecules can be immobolized in many different ways. They can also be entrapped or tightly adsorbed within porous gels, clays, membranes, resins, and several other materials, but it is crucial that they retain their active conformation after the incorporation procedure. Porous gel matrixes with functionalized surfaces offer unlimited possibilities to control the protein-substrate interaction behavior. In the present work, we have studied the adsorption and the relative stability of bovine serum albumin (BSA) and porcine insulin(PI) incorporated in gels of SiO2 glass matrixes. The porous gel matrixes were obtained using tetramethoxysilane (TMOS)/metanol and functionalized with (3-mercaptopropyl) trimethoxysilane and (3-aminopropyl) triethoxysilane. The relative adsorption kinetics and stability of BSA and PI incorporated in glass networks were evaluated by immersion in phosphate buffer saline (PBS) and alkaline elution media for different periods of time. The kinetics of protein release from the gel matrix was monitored by UV-visible spectroscopy. A significantly larger PI release was observed compared to BSA in PBS solutions. We believe this is mainly associated with the difference on protein interactions with the modified surface, according to the characterization results of porosity, surface area, and contact angle of different functionalized gel matrixes. We could not observe any evidence of denaturation with either proteins after their desorption from gel matrixes using the ultraviolet spectroscopy technique. These results have also been confirmed with the strong bioactivity response from "in vivo" test conducted in rats, where porous gels with PI incorporated were implanted, showing that released proteins retained their native conformation.

The hyperglycemia induced by angiotensin II in rats is mediated by AT1 receptors

We have shown that the renin-angiotensin system (RAS) is involved in glucose homeostasis during acute hemorrhage. Since almost all of the physiological actions described for angiotensin II were mediated by AT1 receptors, the present experiments were designed to determine the participation of AT1 receptors in the hyperglycemic action of angiotensin II in freely moving rats. The animals were divided into two experimental groups: 1) animals submitted to intravenous administration of angiotensin II (0.96 nmol/100 g body weight) which caused a rapid increase in plasma glucose reaching the highest values at 5 min after the injection (33 per cent of the initial values, P<0.01), and 2) animals submitted to intravenous administration of DuP-753 (losartan), a non-peptide antagonist of angiotensin II with AT1-receptor type specificity (1.63 µmol/100 g body weight as a bolus, iv, plus a 30-min infusion of 0.018 µmol 100 g body weight-1 min-1 before the injection of angiotensin II), which completely blocked the hyperglycemic response to angiotensin II (P<0.01). This inhibitory effect on glycemia was already demonstrable 5 min (8.9 ñ 0.28 mM, angiotensin II, N = 9 vs 6.4 ñ 0.22 mM, losartan plus angiotensin II, N = 11) after angiotensin II injection and persisted throughout the 30-min experiment. Controls were treated with the same volume of saline solution (0.15 M NaCl). These data demonstrate that the angiotensin II receptors involved in the direct and indirect hyperglycemic actions of angiotensin II are mainly of the AT1-type.

The hyperglycemia induced by angiotensin II in rats is mediated by AT1 receptors.

We have shown that the renin-angiotensin system (RAS) is involved in glucose homeostasis during acute hemorrhage. Since almost all of the physiological actions described for angiotensin II were mediated by AT1 receptors, the present experiments were designed to determine the participation of AT1 receptors in the hyperglycemic action of angiotensin II in freely moving rats. The animals were divided into two experimental groups: 1) animals submitted to intravenous administration of angiotensin II (0.96 nmol/100 g body weight) which caused a rapid increase in plasma glucose reaching the highest values at 5 min after the injection (33% of the initial values, P < 0.01), and 2) animals submitted to intravenous administration of DuP-753 (losartan), a non-peptide antagonist of angiotensin II with AT1-receptor type specificity (1.63 mumol/100 g body weight as a bolus, i.v., plus a 30-min infusion of 0.018 mumol 100 g body weight-1 min-1 before the injection of angiotensin II), which completely blocked the hyperglycemic response to angiotensin II (P < 0.01). This inhibitory effect on glycemia was already demonstrable 5 min (8.9 +/- 0.28 mM, angiotensin II, N = 9 vs 6.4 +/- 0.22 mM, losartan plus angiotensin II, N = 11) after angiotensin II injection and persisted throughout the 30-min experiment. Controls were treated with the same volume of saline solution (0.15 M NaCl). These data demonstrate that the angiotensin II receptors involved in the direct and indirect hyperglycemic actions of angiotensin II are mainly of the AT1-type.

Effect of [1-Sar,8-Thr]-angiotensin II on the hyperglycemic response to hemorrhage in adrenodemedullated and guanethidine-treated rats.

The present experiments were designed to further investigate the action of an angiotensin II antagonist on the hyperglycemic response to hemorrhage (1.2 ml/100 g b.wt./2 min). The animals were divided into 3 experimental groups; (1) sham-operated animals submitted to intravenous administration of [1-Sar,8-Thr]-angiotensin II (sarthran), an antagonist of angiotensin II (750 ng/100 g b.wt. as a bolus plus an infusion of 25 ng/100 g b.wt./min over 30 min), which greatly attenuated (51.8% lower than controls; P < 0.01) the hyperglycemic response to hemorrhage; (2) animals submitted to adrenodemedullation which decreased the hyperglycemic response to hemorrhage by 64% (P < 0.01). However, sarthran infusion into adrenodemedullated rats caused a 38.5% further decrease in hyperglycemic response to hemorrhage (P < 0.01); and (3) intact animals submitted to blockade of sympathetic noradrenergic pathways by treatment with guanethidine (10 mg/100 g b.wt.), which greatly decreased the baseline value of plasma glucose (64.1 +/- 3.5 mg% vs. 125.3 +/- 4.5 mg%, P < 0.01), and reduced the hyperglycemic response to hemorrhage by 34% (P < 0.01). Sarthran infusion into guanethidine-treated rats caused a further 34% decrease in hyperglycemic response to hemorrhage (P < 0.01). These data indicate that angiotensin II has a direct hyperglycemic effect in addition to its action on sympathetic nervous system activation and adrenomedullary secretion.

Hyperglycemic action of angiotensin II in freely moving rats.

Angiotensin II has been implicated in the regulation of liver glycogen phosphorylase. Although it has been suggested that angiotensin II can raise blood glucose levels during hemorrhage, experimental data have not been presented. In the present study, the effect of angiotensin II on blood glucose levels was studied in freely moving rats, divided in three experimental groups: 1) intravenous administration of angiotensin II (0.48, 1.9, or 4.8 nmol) caused a dose-dependence response; 2) intracerebroventricular administration of angiotensin II (1.9 or 4.8 nmol) did not cause any significant change in glycemia compared with saline-treated controls; 3) intravenous administration of [Sar1,Thr8]angiotensin II, an antagonist of angiotensin II (750 ng/100 g b. wt. as a bolus plus a continuous injection of 25 ng/100 g b. wt./min over 30 min), greatly attenuated (39.2% lower than controls; p < 0.01) the hyperglycemic response to hemorrhage (1.2 ml/100 g b.wt.). These data indicate an in vivo involvement of angiotensin II in blood glucose regulation.