Biomedical subjects

D Santos

Publications and source records attributed to D Santos.

At least 19 recordsLinked to original sources

PubMed2006

Immunogold localization of trehalose-6-phosphate synthase in leaf segments of wild-type and transgenic tobacco plants expressing the AtTPS1 gene from Arabidopsis thaliana.

Following the establishment of a transgenic line of tobacco (B5H) expressing the trehalose-6-phosphate synthase (TPS) gene from Arabidopsis thaliana, a preliminary immunolocalization study was conducted using leaves of adequately watered B5H and wild-type plants. Immunocytochemical staining, followed by electron microscopy showed that the enzyme could be detected in both B5H and wild-type plants at two different levels. Quantification showed the signal to be two to three times higher in transgenic plants than in the wild type. This enzyme was markedly present in the vacuoles and the cell wall, and to a lesser extent in the cytosol. Moreover, a high profusion of gold particles was detected in adjacent cells and in the sieve elements. Occasional spots were also detected in chloroplasts and the nucleus, especially in the transgenic B5H line. No labeling signal was detected in mitochondria. Protein localization seems to confirm the important role of TPS in sugar metabolism and transport through the plant, which could explain its role in plant stress tolerance. Finally, it can be expected that TPS from tobacco has a relatively high similarity to the TPS of Arabidopsis thaliana.

Arabidopsis↗

PubMed2006

Frictional adhesion: A new angle on gecko attachment.

Directional arrays of branched microscopic setae constitute a dry adhesive on the toes of pad-bearing geckos, nature's supreme climbers. Geckos are easily and rapidly able to detach their toes as they climb. There are two known mechanisms of detachment: (1) on the microscale, the seta detaches when the shaft reaches a critical angle with the substrate, and (2) on the macroscale, geckos hyperextend their toes, apparently peeling like tape. This raises the question of how geckos prevent detachment while inverted on the ceiling, where body weight should cause toes to peel and setal angles to increase. Geckos use opposing feet and toes while inverted, possibly to maintain shear forces that prevent detachment of setae or peeling of toes. If detachment occurs by macroscale peeling of toes, the peel angle should monotonically decrease with applied force. In contrast, if adhesive force is limited by microscale detachment of setae at a critical angle, the toe detachment angle should be independent of applied force. We tested the hypothesis that adhesion is increased by shear force in isolated setal arrays and live gecko toes. We also tested the corollary hypotheses that (1) adhesion in toes and arrays is limited as on the microscale by a critical angle, or (2) on the macroscale by adhesive strength as predicted for adhesive tapes. We found that adhesion depended directly on shear force, and was independent of detachment angle. Therefore we reject the hypothesis that gecko toes peel like tape. The linear relation between adhesion and shear force is consistent with a critical angle of release in live gecko toes and isolated setal arrays, and also with our prior observations of single setae. We introduced a new model, frictional adhesion, for gecko pad attachment and compared it to existing models of adhesive contacts. In an analysis of clinging stability of a gecko on an inclined plane each adhesive model predicted a different force control strategy. The frictional adhesion model provides an explanation for the very low detachment forces observed in climbing geckos that does not depend on toe peeling.

Adhesiveness↗

PubMed2004

Paradoxical increases in serum IgM and viscosity levels following rituximab in Waldenstrom's macroglobulinemia.

BACKGROUND: The anti-CD20 monoclonal antibody rituximab is an important therapeutic in Waldenstrom's macroglobulinemia (WM), producing response rates of 50-70%. Responses, which are based on serum IgM levels, have typically been evaluated at 12 weeks. Paradoxically, we have observed that serum IgM levels can abruptly rise following rituximab therapy in patients with WM, and can often lead to morbidity on the basis of hyperviscosity. PATIENTS AND METHODS: Eleven WM patients with CD20+ tumor cells who received rituximab at our Institution and had serum IgM levels measured within a 12-week period following start of therapy were evaluated. Therapy consisted of four weekly infusions of rituximab at 375 mg/m(2). Pre- and post-therapy serum IgM levels were determined by nephelometry and corresponding serum viscosity levels were determined by viscometry. RESULTS: Ten of the 11 patients demonstrated an abrupt rise in serum IgM levels, with a >25% increase occurring in eight (73%) patients. Mean serum IgM levels for all 10 spiking patients rose from 4370 (range, 655-7940) to a peak of 5865 (range, 872-11 800) mg/dl (P=0.004), which occurred at a mean of 4 (range, 1-8) weeks following initiation of therapy. Mean serum viscosity levels also increased from 3.5 to 5.6 centipoise (CP) (P=0.09) in eight patients for whom pre- and post-therapy studies were obtained. A subdural hemorrhage occurred in one patient when serum IgM levels rose from 7530 to 11 800 mg/dl, and serum viscosity increased from 3.9 to 10.1 CP. Two other spiking patients with pre-therapy IgM levels of >5000 mg/dl experienced worsening headaches and/or epistaxis attributed to increasing serum viscosity. CONCLUSIONS: Abrupt increases in serum IgM levels commonly occur following rituximab therapy in WM. Careful clinical and laboratory monitoring is warranted, particularly if patients have pre-therapy serum IgM levels of >5000 mg/dl. The mechanism of this effect is under active investigation, and may be related to CD20 signaling triggered by rituximab.

Antibodies, Monoclonal↗

PubMed2003

Predictive factors for motile sperm recovery using testicular biopsy in nonobstructive azoospermic patients.

OBJECTIVE: The objective of the present study was to assess the predictive value of hormone values, histological analysis for the finding of motile spermatozoa on testicular biopsy in nonobstructive azoospermia. METHODS: This cross-sectional study assessed serum follicle-stimulating hormone (FSH), luteinizing hormone, prolactin and total testosterone values in 50 patients undergoing testicular biopsy prior to ICSI. P < 0.05 was considered significant. RESULTS: Recovery was successful in 28 cases, and motile spermatozoa were retrieved in 7. Significant differences were detected between presence of motile spermatozoa and absence of spermatozoa in terms of FSH values (P = 0.003, one-way ANOVA). The other variables did not present statistical differences. A receiver operating characteristic curve showed that FSH levels below 17.00 IU/L were predictive of motile spermatozoa recovery. CONCLUSIONS: FSH values can serve as a predictive factor for the recovery of motile spermatozoa using biopsy in azoospermic patients. On the other hand, histological analysis and other hormone values were not helpful in the prediction of motile sperm.

Biopsy↗

PubMed2002

Determination of Cd and Pb in food slurries by GFAAS using cryogenic grinding for sample preparation.

A simple method combining slurry sampling after cryogenic grinding and the use of a permanent modification of the integrated platform inside the transversely heated graphite atomizer (THGA) was proposed for the determination of Cd and Pb in foods. Potentialities of the cryogenic grinding were evaluated for grinding different materials of difficult homogenization such as high fat and high fiber tissues. Animal and vegetal samples were cut into small pieces and ground in liquid nitrogen for 2 min. Slurries were prepared directly in the autosampler cup after cryogenic grinding by transferring an exact amount of homogeneous powdered material (5-20 mg) to the cup, followed by 1.00 mL of 0.2% (v/v) HNO3 containing 0.04% (v/v) Triton X-100 and sonication for 30 s, before transferring into the platform previously coated with 250 microg W and 200 microg Rh. Use of a tungsten carbide-rhodium permanent modifier combined with NH4H2PO4 conventional modifier improves tube lifetime and increases the pyrolysis temperature for Cd. Homogeneity tests, carried out by comparing the between- and within-batch precision for each kind of sample, showed no significant differences at the 95% confidence level, indicating good homogeneity for 5-20 mg masses. Detection limits were 3.3 ng g(-1) Cd and 75 ng g(-1) Pb for 1% m/v slurries. Results for determination of Cd and Pb in foods slurries were in agreement with those obtained with digested samples, since no statistical differences were found by the paired t-test at the 95% level.

Cadmium↗

PubMed2001

Evaluation of carboxymethylcellulose, hydroxypropylmethylcellulose, and aluminum hydroxide as potential carriers for rhBMP-2.

Conventional iliac crest nonvascularized corticocancelous bone grafts and bone flaps have been used to treat bony defects. However, these treatments have some limitations, namely, the availability of donor tissue, donor site morbidity, difficulty to shape the bone flap to the defect, and complexity of the surgery. The bone morphogenetic protein (rhBMP-2) is osteoinductive. However, its implantation requires a matrix (carrier) in order to define the shape of the resulting bone and to retain the protein at the site for the time required for induction to occur. When the ideal carrier is found, an unlimited supply of material would be available for all applications where bone is needed. In this in vitro study, we evaluated the suitability of some potential carriers for rhBMP-2 by measuring the alkaline phosphatase (ALP) activity of fibroblast cultures. Either rhBMP-2 or sodium carboxymethylcellulose significantly increased the ALP activity, when used alone. When sodium carboxymethylcellulose was combined with rhBMP-2, there was an increase in the ALP activity, but lower than those obtained when the products were used alone. Hydroxypropylmethylcellulose alone did not affect ALP activity. However, the combination of rhBMP-2 with hydroxypropylmethylcellulose did not increase the ALP activity, despite the presence of rhBMP-2. Aluminium hydroxide proved to be an unsuitable rhBMP-2 adsorbent.

Alkaline Phosphatase↗

PubMed2001

Cervical cancer screening in Porto Alegre, Brazil: alternative methods for detecting cancer precursors in a developing country.

OBJECTIVE: This study was conducted to test the performance characteristics of cervical cancer screening by visual inspection of the cervix with acetic acid and iodine solution. METHODS: A total of 100 women were screened for cervical cancer by Pap smear and naked eye inspection of the cervix after application of acetic acid and iodine solution. RESULTS: Comparing visual inspection to the Pap test, a sensitivity of 85.7%, specificity of 78.5%, and concordance of 79% (p < .0011) was established. Comparing the Pap test with colposcopy, the corresponding figures were 42.9%, 92.3%, and 66.6% (p < .077), respectively. Visual inspection compared to colposcopy showed corresponding figures of 100%, 7.7%, and 55.5% (p = .48), respectively. Colposcopy and biopsy had an agreement of 100%. CONCLUSIONS: Visual inspection with acetic acid and iodine solution proved to be a reasonable method of screening for cervical cancer precursors.

Journal Article↗

PubMed2000

Examination of the lower limb in high risk patients.

When 'at risk' patients say that their feet are killing them, they may be right. Diabetes mellitus accounts for 50 to 70% of all nontraumatic amputations with a three year survival rate of those who undergo a lower limb amputation of 50%. Furthermore, when compared to the 'normal' foot, the 'at risk' foot is more likely to develop complications, thus it is vital to identify such 'at risk' individuals in an attempt to prevent the risk of deformity, ulceration, infection and/or necrosis/gangrene. The assessment involves history taking, the examination and further investigations, providing the necessary information to make a clinical diagnosis and identify 'at risk' groups. During the examination the foot-wear should be checked, nails and skin condition should be closely inspected and tests should be carried out for signs of peripheral neuropathy, ischaemia and venous/lymphatic deficiency. Other complications like deformity and increases in foot pressure may cause ulceration. Where ulcers are present, an in-depth systematic inspection is necessary. A thorough lower limb examination of high risk patients provides the necessary information to make a clinical diagnosis and plan preventative measures to avoid future complications.

Diabetic Foot↗

PubMed2000

Expression of antisense hsp70 is a major determining factor in heat-induced cell death of P-19 carcinoma cells.

Overexpressed heat shock protein 70 (Hsp70) is known to be associated with thermoprotection in a number of cell lines and transgenic animals. We hypothesized that because overexpression of Hsp70 protects cells from lethal heat stress, inhibition of expression should make cells susceptible to heat stress. The model used for this study was a stably transfected P-19 carcinoma cell line expressing antisense hsp70 under the control of the hsp70b promoter. The results showed marked inhibition of Hsp70 expression after heat shock correlated with heat-induced cell death. Hsp90 and Hsc70 protein expression were not affected by the antisense construct. Unexpectedly, heme oxygenase (HO-1), another highly inducible heat shock protein, was not induced after heat shock in the antisense hsp70 cell line. Heat shock transcription factor-1 (HSF-1) was in a highly phosphorylated state in the antisense cell line before and after heat shock. This was in contrast to the untransfected control P-19 cells where HSF-1 was primarily highly phosphorylated after heat shock. A control cell line expressing only the vector, pMAMneo, without the antisense construct also showed partial loss of Hsp70 induction but not increased cell death after heat shock. The findings support the role of Hsp70 in thermoresistance.

Animals↗

PubMed2000

Induction of cell death by L-alpha-aminoadipic acid exposure in cultured rat astrocytes: relationship to protein synthesis.

The excitotoxin, L-alpha-aminoadipic acid (L-AAA), kills primary astrocytes in the brain. The mechanism underlying the induction of cell death is not well understood although many possible mechanisms are theorized. Previous studies have reported that astrocytes die after prolonged exposure to L-AAA suggesting a delayed programmed cell death and apoptosis. In this study rat cortical astrocytes exposed to continuous 1 mM L-AAA exposure for 24-, 48-, or 72 hours demonstrated increased DNA laddering, a characteristic of apoptosis. Unexpectedly, this was not ameliorated by the presence of cycloheximide at 0.1 microg/ml medium. Because of our interest in cytoprotective heat shock proteins induced by excitoxic stress, we studied the effect of prolonged exposure of L-AAA on the synthesis of stress proteins and protein synthesis in rat cortical astrocytes. Protein synthesis as measured by [35S]-methionine labeling showed a marked and significant decrease in incorporation of radiolabel after 24 hours of exposure to L-AAA and prior to induction of significant cell death noted at 48- and 72 hours of L-AAA exposure. The inhibition of protein synthesis was partially reversible at 24 hours if cells were labeled in medium without L-AAA during the radiolabeling period. Heat shock or stress proteins, HSP70 and heme oxygenase-1 (HO-1), were analyzed after a 24 hour exposure to L-AAA and showed no significant induction of HSP70 or HO-1. The findings suggest that the prolonged inhibition of protein synthesis and associated lack of induction of HSP70 and HO-1 synthesis contributed to apoptotic cell death induced by the excitoxin L-AAA.

2-Aminoadipic Acid↗

PubMed1998

[Radiotherapy-induced pemphigus].

The authors report the clinical case of a woman exposed to ionizing radiotherapy, for the treatment of breast carcinoma, in whom a pemphigus lesion developed within the area of irradiation. This is, to the authors' knowledge, the 14th case of ionizing radiation-induced pemphigus.

Aged↗

PubMed1997