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C Sepulveda

Publications and source records attributed to C Sepulveda.

14 recordsLinked to original sources
PubMed2003

Comparative studies of high performance swimming in sharks I. Red muscle morphometrics, vascularization and ultrastructure.

Tunas (family Scombridae) and sharks in the family Lamnidae are highly convergent for features commonly related to efficient and high-performance (i.e. sustained, aerobic) swimming. High-performance swimming by fishes requires adaptations augmenting the delivery, transfer and utilization of O(2) by the red myotomal muscle (RM), which powers continuous swimming. Tuna swimming performance is enhanced by a unique anterior and centrally positioned RM (i.e. closer to the vertebral column) and by structural features (relatively small fiber diameter, high capillary density and greater myoglobin concentration) increasing O(2) flux from RM capillaries to the mitochondria. A study of the structural and biochemical features of the mako shark (Isurus oxyrinchus) RM was undertaken to enable performance-capacity comparisons of tuna and lamnid RM. Similar to tunas, mako RM is positioned centrally and more anterior in the body. Another lamnid, the salmon shark (Lamna ditropis), also has this RM distribution, as does the closely related common thresher shark (Alopias vulpinus; family Alopiidae). However, in both the leopard shark (Triakis semifasciata) and the blue shark (Prionace glauca), RM occupies the position where it is typically found in most fishes; more posterior and along the lateral edge of the body. Comparisons among sharks in this study revealed no differences in the total RM quantity (approximately 2-3% of body mass) and, irrespective of position within the body, RM scaling is isometric in all species. Sharks thus have less RM than do tunas (4-13% of body mass). Relative to published data on other shark species, mako RM appears to have a higher capillary density, a greater capillary-to-fiber ratio and a higher myoglobin concentration. However, mako RM fiber size does not differ from that reported for other shark species and the total volume of mitochondria in mako RM is similar to that reported for other sharks and for tunas. Lamnid RM properties thus suggest a higher O(2) flux capacity than in other sharks; however, lamnid RM aerobic capacity appears to be less than that of tuna RM.

Adaptation, Biological↗
PubMed2001

Frequency of CCR5 gene 32-basepair deletion in Chilean HIV-1 infected and non-infected individuals.

A 32-basepair deletion polymorphism in the CCR5 chemokine receptor gene (CCR5Delta32) has been identified and shown to have functional significance in determining susceptibility to infection by human immunodeficiency virus type 1 (HIV-1) and possibly in influencing disease progression in HIV-1 positive individuals. These findings led to an interest in studies of DeltaCCR5 allele geographical distribution in human population, for complete understanding of the role of CCR5 in HIV-1 epidemiology. Inter-population variation in CCR5Delta32 frequency may be a significant factor in the prediction of AIDS endemicity. In this report we assessed the frequency of DeltaCCR5 in a Chilean population (63 HIV-1 infected and 62 non-infected individuals). No homozygous CCR5Delta32 individual was identified, and no significant difference was observed between HIV-1 infected (3/63) and non-infected (3/62) individuals for the heterozygote CCR5Delta32 state. This is the first evidence of the contribution of DeltaCCR5 allele to the genetic background of the Chilean population, which is characterized by intense ethnic admixture and by gene flow from the European Spanish gene pool.

Chile↗
PubMed2001

Water-tunnel studies of heat balance in swimming mako sharks.

The mako shark (Isurus oxyrinchus) has specialized vascular networks (retia mirabilia) forming counter-current heat exchangers that allow metabolic heat retention in certain regions of the body, including the aerobic, locomotor red muscle and the viscera. Red muscle, white muscle and stomach temperatures were measured in juvenile (5-13.6 kg) makos swimming steadily in a water tunnel and exposed to stepwise square-wave changes in ambient temperature (T(a)) to estimate the rates of heat transfer and to determine their capacity for the activity-independent control of heat balance. The rates of heat gain of red muscle during warming were significantly higher than the rates of heat loss during cooling, and neither the magnitude of the change in T(a) nor the direction of change in T(a) had a significant effect on red muscle latency time. Our findings for mako red muscle are similar to those recorded for tunas and suggest modulation of retial heat-exchange efficiency as the underlying mechanism controlling heat balance. However, the red muscle temperatures measured in swimming makos (0.3-3 degrees C above T(a)) are cooler than those measured previously in larger decked makos. Also, the finding of non-stable stomach temperatures contrasts with the predicted independence from T(a) recorded in telemetry studies of mako and white sharks. Our studies on live makos provide new evidence that, in addition to the unique convergent morphological properties between makos and tunas, there is a strong functional similarity in the mechanisms used to regulate heat transfer.

Animals↗
PubMed2000

Maximum sustainable speeds and cost of swimming in juvenile kawakawa tuna (Euthynnus affinis) and chub mackerel (Scomber japonicus).

Tunas (Scombridae) have been assumed to be among the fastest and most efficient swimmers because they elevate the temperature of the slow-twitch, aerobic locomotor muscle above the ambient water temperature (endothermy) and because of their streamlined body shape and use of the thunniform locomotor mode. The purpose of this study was to test the hypothesis that juvenile tunas swim both faster and more efficiently than their ectothermic relatives. The maximum sustainable swimming speed (U(max), the maximum speed attained while using a steady, continuous gait powered by the aerobic myotomal muscle) and the net cost of transport (COT(net)) were compared at 24 degrees C in similar-sized (116-255 mm fork length) juvenile scombrids, an endothermic tuna, the kawakawa (Euthynnus affinis) and the ectothermic chub mackerel (Scomber japonicus). U(max) and COT(net) were measured by forcing individual fish to swim in a temperature-controlled, variable-speed swimming tunnel respirometer. There were no significant interspecific differences in the relationship between U(max) and body mass or fork length or in the relationship between COT(net) and body mass or fork length. Muscle temperatures were elevated by 1.0-2.3 degrees C and 0.1-0.6 degrees C above water temperature in the kawakawa and chub mackerel, respectively. The juvenile kawakawa had significantly higher standard metabolic rates than the chub mackerel, because the total rate of oxygen consumption at a given swimming speed was higher in the kawakawa when the effects of fish size were accounted for. Thus, juvenile kawakawa are not capable of higher sustainable swimming speeds and are not more efficient swimmers than juvenile chub mackerel.

Animals↗
PubMed1998

Blue filter amblyopia treatment protocol for strabismic amblyopia: a prospective comparative study of 50 cases.

PURPOSE: Previous studies of monochromatic visual evoked potentials confirm the strong suppression of (the cortical representation of) paracentral retinal areas of functionally amblyopic eyes, by a flat response to a blue stimulus. A clinical trial stimulating these areas with blue light was encouraging, and justified a prospective comparison of this treatment with conventional classic treatment. SUBJECTS AND METHODS: In 50 strabismic children with amblyopia, the blue filter treatment protocol (flash stimulation with, and the wearing of, a blue filter during occlusion of the better eye for one hour daily) was compared with the classical treatment (full time total occlusion by patch) in a prospective matched and randomized study. Patients 3 to 7 years old without previous treatment and a visual acuity up to 0.3 were admitted to the study. Visual acuity and fixation behavior were used as the parameters of comparison. Visual Evoked Potentials by monochromatic flashes were also studied. Results of treatment were compared after 6 months. RESULTS: The visual acuity outcome for the blue filter treatment was "statistically significantly" better (p=0.005). The greatest improvement was seen in the subgroup of children with eccentric fixation (p=0.01). Fixation behavior also showed a better outcome from the blue filter treatment (p=0.05) favoring especially children between 3 and 5 years. In children of this age with a visual acuity better than 0.1 we found a very "statistically significant" difference between the two treatments (p=0.004). In children 3 to 5 years old with poorer visual acuity we also found a "statistically significant" difference in the two treatments (p=0.04). The interocular difference of amplitude on the Visual Evoked Potentials also demonstrated more improvement in children treated with the blue filter. This treatment improved especially the cortical response to blue flash stimulation, correlating to paracentral retinal areas. CONCLUSIONS: The blue filter treatment protocol provided better results for treating amblyopia than the conventional classic occlusion treatment method. We propose that stimulation of these paracentral retinal areas triggers a better disinhibition of a functionally amblyopic eye.

Amblyopia↗
PubMed1994

Enhancement of natural killer cell activity in septic shock patients by a mixture of the calcium ionophore A23187 and the phorbol ester TPA: in vitro studies.

Preincubation of peripheral blood lymphocytes from drug-free, healthy volunteers with a mixture of the calcium ionophore A23187 (Io) and the phorbol ester TPA (12-O-tetradecanoylphorbol-13-acetate) consistently resulted in a significant enhancement (dose-dependent; maximum immunostimulation obtained with the Io + TPA final mixture concentration of 10 uM + 250 ng/ml, respectively) of natural killer cell activity (NKCA) (n = 8; mean +/- SD of 16.8 +/- 8.9 and 52.0 +/- 18.0, paired Student's t-test p < 0.005; effector-to-target cell ratio of 30:1). Results from the same protocol, but using samples from septic shock patients followed a similar trend; however, and perhaps reflecting the significantly lower baseline NKCA in this group of individuals (n = 7), the mean value reached for this cellular immune function after incubation with Io + TPA was significantly lower than that of the treated controls' group (mean +/- SD of 19.8 +/- 11.6 and 52.0 +/- 18.0, respectively, Student's t-test p < 0.005). As expected from the role of calcium in the activation of NKCA, incubation with the Io significantly increased baseline NKCA, which was largely unchanged by TPA. Expression of the CD56+ and CD16+ phenotypes in septic shock patients did not correlate directly with NKCA, suggesting that this condition may be associated with changes in the function rather than the quantity of these cellular markers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

In vitro studies of natural killer cell activity in septic shock patients. Response to a challenge with alpha-interferon and interleukin-2.

Natural killer cell activity (NKCA) in patients with septic shock was statistically significantly lower than the value recorded for a group of drug-free, healthy volunteers [9.1 +/- 7.8 (n = 20) and 20.6 +/- 16.6 (n = 15), respectively; Student's test, p < 0.05]. As expected, preincubation of peripheral blood lymphocytes from samples taken from a group of controls with either alpha-interferon or interleukin -2 resulted in an enhancement of NKCA for each and everyone of the subjects studied; however, results from a similar protocol using patient samples showed a lack of consistency, both in the direction and magnitude, in the elicited changes in NK lytic function. Whereas samples from same patient responded with either an increase or a decrease in NKCA to preincubation with both immunostimulators, others responded with NKCA upmodulation to one and downmodulation to other of these test substances. A better knowledge of the mechanism(s) responsible for the depressed expression of NKCA in septic shock patients, and its altered response to alpha-interferon and interleukin-2, could generate new modalities in the diagnosis and therapy of this condition.

Adult↗
PubMed1992

Quantitation of pneumococcal C polysaccharide in sputum samples from patients with presumptive pneumococcal pneumonia by enzyme immunoassay.

Although the Gram stain and culture of expectorated sputum are considered standard methods for the diagnosis of presumptive pneumococcal pneumonia, these methods remain relatively insensitive and nonspecific. We developed an enzyme immunoassay (EIA) for the quantitation of pneumococcal C polysaccharide (PnC) in the sputum of patients with presumptive pneumococcal pneumonia. Of 34 patient sputum samples collected within 24 h of the first radiographic report of pneumonia, 12 grew Streptococcus pneumoniae on culture. By using a cutoff point of 0.5 micrograms of PnC per ml of sputum, all 12 specimens were positive (sensitivity, 100%) by EIA. PnC levels ranged from 1.43 to 57.53 micrograms/ml. Blood samples from 18 of the 34 patients were cultured. S. pneumoniae grew in the culture of a blood sample from one patient, whose sputum also had the highest PnC level. Of 22 sputum samples from patients with pneumonia that did not grow S. pneumonia, two were positive by EIA (specificity, 90.1%). Sputa from both patients had low levels of PnC (2.7 and 4.5 micrograms/ml), and both patients had received antibiotics before sputum collection. The positive predictive value of the quantitative EIA was 85.7%. Quantitation of PnC has the potential for improving the accuracy of sputum examination for S. pneumoniae, monitoring disease severity and the effectiveness of antibiotic therapy, and differentiating between those patients with invasive pneumococcal disease and those who are carriers of S. pneumoniae.

Bacteriological Techniques↗
PubMed1991

[Immunological defects in septic shock. Deficiency of natural Killer cells and T-lymphocytes].

It is well known that an immunosuppressive response occurs after acute trauma. Some cellular mediators participate in the pathogenesis of septic shock. However, the exact role of the lymphocyte subsets and natural killer (NK) activity in this condition is not clear. We studied NK cytolytic activity through a 51Cr liberation assay using K-562 target cells in 20 patients with initial septic shock (10 men and 10 females, mean age 41 years old). Lymphocyte subsets CD3 (T3), CD4 (T4), CD8 (T8), CD16 (Leu-11) and CD56 (Leu-19) were also studied by indirect immunofluorescence. Compared to results obtained in 20 healthy volunteers, patient's NK activity was decreased (4.6 +/- 3.9 vs 26.1 +/- 10, p less than 0.025), CD16 was lower (10%/187 vs 15%/280 per ul) and CD56 was also lower (6%/120 vs 12%/224 per ul), p less than 0.05. T lymphocyte subsets were also decreased: CD3 cells (1100 vs 1352 per ul) and CD4 cells (634 vs 873 per ul), p less than 0.05. Thus, a severe decrease in NK cells and NK cell function as well as decreases in CD3 and CD4 lymphocyte subsets are present in the initial stages of septic shock. The predictive value of these findings is currently under study.

Adolescent↗
PubMed1991

[A patient with AIDS: infection associated with pneumocystis carinii and cryptococcus neoformans].

A patient with AIDS developed pulmonary infiltrates typical of infection by P. carinii. However, therapy for this agent was unsuccessful. Further studies including blood cultures revealed the presence of C neoformans. Specific therapy for this agent led to recovery. Concomitant opportunistic infections may cause diagnostic and therapeutic problems in patients with AIDS.

AIDS-Related Opportunistic Infections↗