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Biomedical subjects

C Castro

Publications and source records attributed to C Castro.

At least 55 records · Page 3Linked to original sources
PubMed2000

Determinants of leisure time physical activity in rural compared with urban older and ethnically diverse women in the United States.

STUDY OBJECTIVE: Determinants of leisure time physical activity (LTPA) in rural middle aged and older women of diverse racial and ethnic groups are not well understood. This study examined: (1) urban-rural differences in LTPA by sociodemographic factors, (2) urban-rural differences in LTPA determinants, and (3) the pattern of relations between LTPA determinants and LTPA. DESIGN: A modified version of the sampling plan of the Behavioral Risk Factor Surveillance Survey (BRFSS) was used. Zip codes were selected with 20% or more of each of the following race/ethnic groups: African American, American Indian/Alaskan Native (AI/AN), and Hispanic. A comparison group of white women were also surveyed using standard BRFSS techniques. PARTICIPANTS: Rural (n=1242) and urban (n=1096) women aged 40 years and older from the US Women's Determinants Study. MAIN RESULTS: Rural women, especially Southern and less educated women, were more sedentary than urban women. Rural women reported more personal barriers to LTPA, cited caregiving duties as their top barrier (compared with lack of time for urban women), and had greater body mass indices. Rural women were less likely to report sidewalks, streetlights, high crime, access to facilities, and frequently seeing others exercise in their neighbourhood. Multivariate correlates of sedentary behaviour in rural women were AI/AN and African American race, older age, less education, lack of enjoyable scenery, not frequently seeing others exercise, greater barriers, and less social support (p<0.05); and in urban women, older age, greater barriers, less social support (p<0.05), and less education (p<0.09). CONCLUSIONS: Rural and urban women seem to face different barriers and enablers to LTPA, and have a different pattern of determinants, thus providing useful information for designing more targeted interventions.

Adult↗
PubMed2000

[Analysis of the resonant frequency of the middle ear in otosclerosis].

Multifrequency tympanometry scans pressures and frequencies from 226 to 2000 Hz to analyze the resonant frequency of the middle ear, which determines the balance between stiffness and mass. We studied 143 patients (a total of 200 ears) diagnosed as otosclerosis at the E.N.T. Service of Santiago de Compostela University Hospital Complex, and 136 control subjects. The mean age of patients was 47.7 years; women were predominant (female/male ratio 2.25:1). The mean duration of the disease was 10.4 years. Using the Virtual model 310 tympanometer, we calculated the resonant frequency through the susceptance tympanogram, corresponding to the minimal frequency at which the central notch of the tympanograrn was equal to or less than the negative tail. The mean resonant frequency was 1230 Hz, the tympanometric amplitude was 88.32 daPa, and the admittance of the middle ear was 0.63 cc. We confirmed an increase in the resonant frequency in patients with otosclerosis compared with normal subjects (1132.33 Hz), and a decrease in the admittance of the middle ear. The relation between the two values was significant.

Acoustic Impedance Tests↗
PubMed1999

Creation of a functional S-nitrosylation site in vitro by single point mutation.

Here we show that in extrahepatic methionine adenosyltransferase replacement of a single amino acid (glycine 120) by cysteine is sufficient to create a functional nitric oxide binding site without affecting the kinetic properties of the enzyme. When wild-type and mutant methionine adenosyltransferase were incubated with S-nitrosoglutathione the activity of the wild-type remained unchanged whereas the activity of the mutant enzyme decreased markedly. The mutant enzyme was found to be S-nitrosylated upon incubation with the nitric oxide donor. Treatment of the S-nitrosylated mutant enzyme with glutathione removed most of the S-nitrosothiol groups and restored the activity to control values. In conclusion, our results suggest that functional S-nitrosylation sites can develop from existing structures without drastic or large-scale amino acid replacements.

Cysteine↗
PubMed1999

Methionine adenosyltransferase S-nitrosylation is regulated by the basic and acidic amino acids surrounding the target thiol.

S-Adenosylmethionine serves as the methyl donor for many biological methylation reactions and provides the propylamine group for the synthesis of polyamines. S-Adenosylmethionine is synthesized from methionine and ATP by the enzyme methionine adenosyltransferase. The cellular factors regulating S-adenosylmethionine synthesis have not been well defined. Here we show that in rat hepatocytes S-nitrosoglutathione monoethyl ester, a cell-permeable nitric oxide donor, markedly reduces cellular S-adenosylmethionine content via inactivation of methionine adenosyltransferase by S-nitrosylation. Removal of the nitric oxide donor from the incubation medium leads to the denitrosylation and reactivation of methionine adenosyltransferase and to the rapid recovery of cellular S-adenosylmethionine levels. Nitric oxide inactivates methionine adenosyltransferase via S-nitrosylation of cysteine 121. Replacement of the acidic (aspartate 355) or basic (arginine 357 and arginine 363) amino acids located in the vicinity of cysteine 121 by serine leads to a marked reduction in the ability of nitric oxide to S-nitrosylate and inactivate hepatic methionine adenosyltransferase. These results indicate that protein S-nitrosylation is regulated by the basic and acidic amino acids surrounding the target cysteine.

Amino Acids↗
PubMed1999

Altered formation of hemichannels and gap junction channels caused by C-terminal connexin-32 mutations.

Hexamers of connexins (Cxs) form hemichannels that dock tightly in series via their extracellular domains to give rise to gap junction channels. Here we examined the ability of a variety of C-terminal Cx32 mutations, most of which have been identified in X-linked Charcot-Marie-Tooth disease, to form hemichannels and to complete gap junction channels using the Xenopus oocyte system. First, we show that undocked wild-type Cx32 hemichannels at the plasma membrane can be detected as opening channels activated by depolarization. We have been able to estimate the efficiency of assembly of complete channels by measuring the time-dependent incorporation of preformed hemichannels into gap junction channels after cell-to-cell contact. These data offer strong evidence that hemichannels are the direct precursors of gap junction channels. Of 11 Cx32 mutants tested, a group of 5 mutations prevented the formation of functional hemichannels at the cell surface, whereas 4 mutations were fully able to form precursors but reduced the ability of hemichannels to assemble into complete channels, and 2 mutants formed channels normally. The data revealed that a minimum length of human Cx32 including the residue Arg-215 is required for the expression of hemichannels at the cell surface and that the efficiency of hemichannel incorporation into complete channels decreased gradually with the progressive shortening of the cytoplasmic C-terminal domain.

Animals↗
PubMed1999

Treponema pallidum major sheath protein homologue Tpr K is a target of opsonic antibody and the protective immune response.

We have identified a family of genes that code for targets for opsonic antibody and protective immunity in T. pallidum subspecies pallidum using two different approaches, subtraction hybridization and differential immunologic screening of a T. pallidum genomic library. Both approaches led to the identification of a polymorphic multicopy gene family with predicted amino acid homology to the major sheath protein of Treponema denticola. One of the members of this gene family, tpr K, codes for a protein that is predicted to have a cleavable signal peptide and be located in the outer membrane of the bacterium. Reverse transcription polymerase chain reaction analysis of T. pallidum reveals that Tpr K is preferentially transcribed in the Nichols strain of T. pallidum. Antibodies directed to purified recombinant variable domain of Tpr K can opsonize T. pallidum, Nichols strain, for phagocytosis, supporting the hypothesis that this portion of the protein is exposed at the surface of the treponeme. Immunization of rabbits with the purified recombinant variable domain of Tpr K provides significant protection against infection with the Nichols strain of T. pallidum. This gene family is hypothesized to be central to pathogenesis and immunity during syphilis infection.

Amino Acid Sequence↗
PubMed1999

Generation of null alleles for the functional analysis of six genes from the right arm of Saccharomyces cerevisiae chromosome II.

Using PCR-ligated long flanking homology cassettes, null alleles of six open reading frames (ORFs) from chromosome II have been created in Saccharomyces cerevisiae. Deletants were constructed in three genetic backgrounds: FY1679, W303 and CEN.PK2. Tetrad analysis of heterozygous deletants revealed that none of the ORFs is essential for vegetative growth. Basic phenotypic analysis of haploid deletants showed that deletion of the YBR283c ORF causes a slight growth defect at 30 degrees C and 37 degrees C on glycerol-complete, glucose-complete, and glucose-minimal media only in the FY1679 and W303 backgrounds. Transformation of these deletants with the corresponding cognate gene in a centromeric plasmid complements the defects. Deletion of the YBR287w ORF leads to poor growth on glucose-minimal medium at 15 degrees C in the FY 1679 background. None of the six ORFs seems to be involved in mating or sporulation.

Alleles↗
PubMed1999

Molecular dissection of transjunctional voltage dependence in the connexin-32 and connexin-43 junctions.

Most gap junction channels are sensitive to the voltage difference between the two cellular interiors, termed the transjunctional voltage (V(j)). In several junctions, the conductance transitions induced by V(j) show more than one kinetic component. To elucidate the structural basis of the fast and slow components that characterize the V(j )dependence of connexin-32 (Cx32) and connexin-43 (Cx43) junctions, we created deletions of both connexins, where most of the carboxy-terminal (CT) domain was removed. The wild-type and "tailless" mutants were expressed in paired Xenopus oocytes, and the macroscopic gating properties were analyzed using the dual voltage clamp technique. Truncation of the CT domain of Cx32 and Cx43 abolished the fast mechanism of conductance transitions and induced novel gating properties largely attributable to the slow mechanism of gating. The formation of hybrid junctions comprising wild-type and truncated hemichannels allowed us to infer that the fast and slow components of gating reside in each hemichannel and that both gates close at a negative V(j) on the cytoplasmic side. Thus we conclude that the two kinetic components of V(j)-sensitive conductance are a result of the action of two different gating mechanisms. They constitute separate structures in the Cx32 and Cx43 molecules, the CT domain being an integral part of fast V(j) gating.

Animals↗
PubMed1999

Noninvasive evaluation of cardiac dysfunction by echocardiography in streptozotocin-induced diabetic rats.

BACKGROUND: There has not been a noninvasive in vivo longitudinal evaluation of cardiac function in diabetic rats. The objective of this study is to examine the time course of development of cardiac dysfunction in streptozotocin (STZ)-induced diabetic rats. METHODS AND RESULTS: Cardiac function was evaluated by M-mode and Doppler echocardiography in anesthetized Wistar rats at 2, 4, 5, 6, and 8 weeks after injection with 65 mg of STZ/kg and in age-matched control rats before and after the administration of isoproterenol. Body weight (BW) was significantly less and blood glucose level significantly greater in diabetic rats compared with controls at 2 weeks and remained at these levels at all time points. The calculated left ventricular (LV) mass appeared slightly decreased in diabetic rats. However, LV mass-BW ratios were similar in controls and diabetic rats at 2, 4, and 5 weeks, but were significantly greater in diabetic rats at 6 and 8 weeks. Basal heart rate (HR) was significantly lower in diabetic rats at all time points studied. Basal LV systolic and diastolic dimensions, fractional shortening (FS), velocity of circumferential shortening (Vcf), peak emptying rate (PER), peak filling rate (PFR), and aortic peak velocity (APV) were not significantly different between controls and diabetic rats at 2 and 4 weeks. PER and PFR were significantly less in 5-week diabetic rats. However, Vcf, PER, and PFR were significantly less and FS and APV were similar at 6 and 8 weeks. Administration of isoproterenol increased HR, Vcf, FS, PFR, and PER in controls at all time points, but the increases in diabetic rats at 5, 6, and 8 weeks were less compared with those in controls. The increase in APV was significantly less in diabetic rats at all time points studied. CONCLUSION: STZ-induced diabetic rats showed bradycardia before contractile dysfunction. Overt and covert contractile dysfunction unmasked by isoproterenol begins at 5 weeks of diabetes. The overt LV systolic and diastolic dysfunction are fully manifested after 6 weeks of diabetes.

Animals↗
PubMed1999

Isokinetic assessment of spasticity in subjects with traumatic spinal cord injury (ASIA A).

OBJECTIVE: To assess resistance to passive isokinetic movements at specified speeds and range of motion, as a measure of muscular tonus. METHODS: A group of 12 subjects with complete traumatic spinal cord injury and a group of 12 able-bodied subjects were analysed, distinguishing the level of spasticity in the SCI group. Maximum eccentric peak torque was observed in passive isokinetic flexion (F) and extension (E) knee movement in displacements of 30, 60 and 120 per second. RESULTS: The Student t-test showed that the average torque in the injured group was significantly higher than in the control group (F= 120 degrees per second, P<0.001). Variance analysis showed that the lower level presented lower torque levels (E=60 and 120 degrees per second, P<0.032), while those in the higher level presented higher torque levels (F and E=60 and 120 per second, P<0.032) when compared to the control group. In the control group the Student t-test (P<0.0006) showed a significantly different muscle behavior (Flexion>Extension Torque). CONCLUSION: By using isokinetic assessment it was possible to quantify hypertonic spasticity in a group of subjects with spinal cord injury, distinguishing groups with higher and lower levels of spasticity as compared to a control group.

Adolescent↗
PubMed1999

Sequence conservation of glycerophosphodiester phosphodiesterase among Treponema pallidum strains.

Previous investigations have demonstrated that immunization with Treponema pallidum subsp. pallidum glycerophosphodiester phosphodiesterase significantly protects rabbits from subsequent treponeme challenge. In this report, we show that the glycerophosphodiester phosphodiesterase amino acid sequence is conserved among 12 strains from a total of five pathogenic treponemes. The invariant nature of this immunoprotective antigen makes it an attractive candidate for inclusion in a universal subunit vaccine against T. pallidum infection. In addition, these studies show a silent nucleotide substitution at position 579 of the gpd open reading frame which is consistently observed in the non-T. pallidum subsp. pallidum strains. This sequence alteration introduces a PleI restriction site in the nonsyphilis strains and thus allows genetic differentiation from T. pallidum subsp. pallidum strains.

Animals↗
PubMed1999

Calcification of presumed ovarian carcinoma brain metastases following radiotherapy.

Multiple brain metastases from ovarian carcinoma are rare. CT findings are reported in a case treated with whole brain radiation therapy and chemotherapy. Radiological complete-calcified brain metastases following treatment and long morphological changes occurred. Delayed neurological findings in relation to treatment are considered. Long survival with unmodified calcified lesions may suggest a stabilization of CNS disease.

Adenocarcinoma, Papillary↗
PubMed1998

Structure of a microbial homologue of mammalian platelet-activating factor acetylhydrolases: Streptomyces exfoliatus lipase at 1.9 A resolution.

BACKGROUND: Neutral lipases are ubiquitous and diverse enzymes. The molecular architecture of the structurally characterized lipases is similar, often despite a lack of detectable homology at the sequence level. Some of the microbial lipases are evolutionarily related to physiologically important mammalian enzymes. For example, limited sequence similarities were recently noted for the Streptomyces exfoliatus lipase (SeL) and two mammalian platelet-activating factor acetylhydrolases (PAF-AHs). The determination of the crystal structure of SeL allowed us to explore the structure-function relationships in this novel family of homologous hydrolases. RESULTS: The crystal structure of SeL was determined by multiple isomorphous replacement and refined using data to 1.9 A resolution. The molecule exhibits the canonical tertiary fold of an alpha/beta hydrolase. The putative nucleophilic residue, Ser131, is located within a nucleophilic elbow and is hydrogen bonded to His209, which in turn interacts with Asp177. These three residues create a triad that closely resembles the catalytic triads found in the active sites of other neutral lipases. The mainchain amides of Met132 and Phe63 are perfectly positioned to create an oxyanion hole. Unexpectedly, there are no secondary structure elements that could render the active site inaccessible to solvent, like the lids that are commonly found in neutral lipases. CONCLUSIONS: The crystal structure of SeL reinforces the notion that it is a homologue of the mammalian PAF-AHs. We have used the catalytic triad in SeL to model the active site of the PAF-AHs. Our model is consistent with the site-directed mutagenesis studies of plasma PAF-AH, which implicate Ser273, His351 and Asp296 in the active site. Our study therefore provides direct support for the hypothesis that the plasma and isoform II PAF-AHs are triad-containing alpha/beta hydrolases.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed1998

Assembly of chimeric connexin-aequorin proteins into functional gap junction channels. Reporting intracellular and plasma membrane calcium environments.

Chimeric proteins comprising connexins 26, 32, and 43 and aequorin, a chemiluminescent calcium indicator, were made by fusing the amino terminus of aequorin to the carboxyl terminus of connexins. The retention of function by the chimeric partners was investigated. Connexin 32-aequorin and connexin 43-aequorin retained chemiluminescent activity whereas that of connexin 26-aequorin was negligible. Immunofluorescent staining of COS-7 cells expressing the chimerae showed they were targeted to the plasma membrane. Gap junction intercellular channel formation by the chimerae alone and in combination with wild-type connexins was investigated. Stable HeLa cells expressing connexin 43-aequorin were functional, as demonstrated by Lucifer yellow transfer. Paris of Xenopus oocytes expressing connexin 43-aequorin were electrophysiologically coupled, but those expressing chimeric connexin 26 or 32 showed no detectable levels of coupling. The formation of heteromeric channels constructed of chimeric connexin 32 or connexin 43 and the respective wild-type connexins was inferred from the novel voltage gating properties of the junctional conductance. The results show that the preservation of function by each partner of the chimeric protein is dictated mainly by the nature of the connexin, especially the length of the cytoplasmic carboxyl-terminal domain. The aequorin partner of the connexin 43 chimera reported calcium levels in COS-7 cells in at least two different calcium environments.

Aequorin↗
PubMed1998

Evidence for a low temperature transition state binding preference in bovine adenosine deaminase.

Arrhenius plots of the interactions of bovine adenosine deaminase (ADA) and of coformycin-inhibited ADA with adenosine are non-linear and reveal that coformycin significantly increases the activation energy for reaction only at temperatures well below the normal operating temperature of the enzyme (38.3 degrees C). This apparent enhanced affinity of the enzyme for the transition state analog at low temperature is confirmed from determinations of coformycin binding at 38.3 degrees C (KI = 5.3 x 10(-11) M) and at 21 degrees C (KI = 1.1 x 10(-11) M). It is suggested that these data are inconsistent with a model for general enzyme catalysis that requires an initial transition state complementary active site. Instead, it is suggested that an initial active site transition state complementarity is undesirable and the tendency of the enzyme to exist in this conformer at low temperatures is responsible for its inefficient interaction with adenosine substrate.

Adenosine↗