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Biomedical subjects

C Castillo

Publications and source records attributed to C Castillo.

At least 19 recordsLinked to original sources
PubMed1992

Reconstitution of sodium channels in large liposomes formed by the addition of acidic phospholipids and freeze-thaw sonication.

Phosphatidylcholine (PC) alone or with phosphatidylethanolamine (PE) are sufficient for the reconstitution of Na+ channels in planar lipid bilayers. However, when Na+ channels were first reconstituted into liposomes using the freeze-thaw-sonication method, addition of acidic phospholipids, such as phosphatidylserine (PS), to the neutral phospholipids was necessary to obtain a significant toxin-modulated 22Na uptake. To further investigate the acidic phospholipid effect on reconstitution into liposomes, Na+ channels purified from Electrophorus electricus electrocytes were reconstituted into liposomes of different composition by freeze-thaw sonication and the effect of batrachotoxin and tetrodotoxin on the 22Na flux was measured. The results revealed that, under our experimental conditions, the presence of an acidic phospholipid was also necessary to obtain a significant neurotoxin-modulated 22Na influx. Though neurotoxin-modulated 22Na fluxes have been reported in proteoliposomes made with purified Na+ channels and PC alone, the 22Na fluxes were smaller than those found using lipid mixtures containing acidic phospholipids. Electron microscopy of negatively stained proteoliposomes prepared with PC, PC/PS (1:1 molar ratio), and PS revealed that the acidic phospholipid increases the size of the reconstituted proteoliposomes. The increment in size caused by the acidic phospholipid, due to the associated increase in internal volume for 22Na uptake and in area for Na+ channel incorporation, appears to be responsible for the large neurotoxin-modulated 22Na fluxes observed.

Animals↗
PubMed1992

Alkaloid-modified sodium channels from lobster walking leg nerves in planar lipid bilayers.

Alkaloid-modified, voltage-dependent sodium channels from lobster walking leg nerves were studied in planar neutral lipid bilayers. In symmetrical 0.5 M NaCl the single channel conductance of veratridine (VTD) (10 pS) was less than that of batrachotoxin (BTX) (16 pS) modified channels. At positive potentials, VTD- but not BTX-modified channels remained open at a flickery substate. VTD-modified channels underwent closures on the order of milliseconds (fast process), seconds (slow process), and minutes. The channel fractional open time (f(o)) due to the fast process, the slow process, and all channel closures (overall f(o)) increased with depolarization. The fast process had a midpoint potential (V(a)) of -122 mV and an apparent gating charge (z(a)) of 2.9, and the slow process had a V(a) of -95 mV and a z(a) of 1.6. The overall f(o) was predominantly determined by closures on the order of minutes, and had a V(a) of about -24 mV and a shallow voltage dependence (z(a) approximately 0.7). Augmenting the VTD concentration increased the overall f(o) without changing the number of detectable channels. However, the occurrence of closures on the order of minutes persisted even at super-saturating concentrations of VTD. The occurrence of these long closures was nonrandom and the level of nonrandomness was usually unaffected by the number of channels, suggesting that channel behavior was nonindependent. BTX-modified channels also underwent closures on the order of milliseconds, seconds, and minutes. Their characterization, however, was complicated by the apparent low BTX binding affinity and by an apparent high binding reversibility (channel disappearance) of BTX to these channels. VTD- but not BTX-modified channels inactivated slowly at high positive potentials (greater than +30 mV). Single channel conductance versus NaCl concentrations saturated at high NaCl concentrations and was non-Langmuirian at low NaCl concentrations. At all NaCl concentrations the conductance of VTD-modified channels was lower than that of BTX-modified channels. However, this difference in conductance decreased as NaCl concentrations neared zero, approaching the same limiting value. The permeability ratio of sodium over potassium obtained under mixed ionic conditions was similar for VTD (2.46)- and BTX (2.48)-modified channels, whereas that obtained under bi-ionic conditions was lower for VTD (1.83)- than for BTX (2.70)-modified channels. Tetrodotoxin blocked these alkaloid-modified channels with an apparent binding affinity in the nanomolar range.

Alkaloids↗
PubMed1992

[Colonic fermentation in humans: effect of the ingestion of meat associated to milk].

The amount of breath H2 produced for 6 h following the ingestion of 240 ml of milk was used as an index of the rate of colonic fermentation of undigested lactose in 8 lactase non-persistent Guatemalan adults. Treatments in separate days included milk alone, milk with 400 g cooked beef, lactose pre-hydrolyzed milk with the same amount of beef, beef alone and fasting for 6 h. Excess excretion of H2, calculated as the mean area under the curve were 178 +/- 31 ppm h with milk alone, 50 +/- 17 with milk plus beef, -1 +/- 26 with prehydrolyzed milk (p > 0.001). Peak increments of breath H2 followed the same trend: all 8 subjects over 20 ppm with milk alone, 2 with milk plus beef and none with hydrolyzed milk, beef alone or fasting. Thus, cooked beef significantly reduces the rate of appearance of intact lactose in the large bowel of lactase deficient adults.

Adult↗
PubMed1992

[Gonococcal urethritis in men: clinical experience in 1978-1988].

Nine hundred thirty four samples of urethral secretion proceeding from male subjects without previous treatment were analyzed with Gram stain. These subjects consulted in Santiago Western area, and belong to medium and low socioeconomical status. In 82.5% of samples, intracellular gram-negative diplococci were found, that made the presumptive diagnosis of gonococcal urethritis. The importance of direct examination of urethral secretion for the diagnosis and immediate treatment of gonococcal urethritis is emphasized.

Gonorrhea↗
PubMed1992

[Changes in the serum lipid fractions of malnourished children with and without clinical infection. Paradoxical hypertriglyceridemia in malnutrition].

We have studied the levels of total triglycerides, total cholesterol and high, low and very low density lipoproteins, in serum from undernourished children and from eutrophic controls matched by age, race and socioeconomical condition with the undernourished group. Malnourished children were classified according to the severity of the nutritional deficiency and according to the presence or absence of associated overt infections. Serum lipids fractions were evaluated by colorimetric procedures and by electrophoretic isolation and elution of the desired lipoprotein followed by colorimetric evaluation of the cholesterol content. Increased levels of total triglycerides and very low density lipoproteins were observed in the undernourished group. The rise in the levels of total triglycerides and very low density lipoproteins was more marked in children with moderate and severe undernutrition as well as in undernourished with associated overt infection. In contrast, as expected, serum levels of total cholesterol, high density and low density lipoproteins were significantly diminished in undernourished children. The depression in the amount of total cholesterol, high density and low density lipoproteins was more marked in the severe forms of undernutrition. Increased levels of total triglycerides and very low density lipoprotein could be determined by a defect in the clearance of these lipid fractions due to depressed activity of lipoprotein lipase.

Child↗
PubMed1991

Racial differences in the relation between blood pressure and insulin resistance.

BACKGROUND: Insulin resistance and the concomitant compensatory hyperinsulinemia have been implicated in the pathogenesis of hypertension. However, reports on the relation between insulin and blood pressure are inconsistent. This study was designed to investigate the possibility of racial differences in this relation. METHODS: We studied 116 Pima Indians, 53 whites, and 42 blacks who were normotensive and did not have diabetes; the groups were comparable with respect to mean age (29, 30, and 31 years, respectively) and blood pressure (113/70, 111/68, and 113/68 mm Hg, respectively). Insulin resistance was determined by the euglycemic-hyperinsulinemic clamp technique during low-dose (40 mU per square meter of body-surface area per minute) and high-dose (400 mU per square meter per minute) insulin infusions. RESULTS: The Pima Indians had higher fasting plasma insulin concentrations than the whites or blacks (176, 138, and 122 pmol per liter, respectively; P = 0.002) and lower rates of whole-body glucose disposal during both the low-dose (12.7, 17.1, and 19.5 mmol per minute; P less than 0.001) and the high-dose (38.0, 43.1, and 45.7 mmol per minute; P less than 0.001) insulin infusions. After adjustment for age, sex, body weight, and percentage of body fat, mean blood pressure (calculated as 1/3 systolic pressure + 2/3 diastolic pressure) was significantly correlated with the fasting plasma insulin concentration (r = 0.42) and the rate of glucose disposal during the low-dose (r = -0.41) and high-dose (r = -0.49) insulin infusions (P less than 0.01 for each) in whites, but not in Pima Indians (r = -0.06, -0.02, and -0.04, respectively) or blacks (r = -0.10, -0.04, and 0.02, respectively). CONCLUSIONS: The relations between insulinemia, insulin resistance, and blood pressure differ among racial groups and may be mediated by mechanisms active in whites, but not in Pima Indians or blacks.

Adult↗
PubMed1991

Exaggerated early insulin release and insulin resistance in a diabetes-prone population: a metabolic comparison of Pima Indians and Caucasians.

Pima Indians have the highest reported prevalence rate of noninsulin-dependent diabetes mellitus (NIDDM) in the world, so that metabolic comparisons with caucasians, who have a much lower rate, should provide insights into the pathogenesis of NIDDM. We have compared 81 caucasians with 211 Pima Indian nondiabetic subjects similar in age, sex, degree of obesity, and glucose tolerance. During a hyperinsulinemic euglycemic clamp at physiological insulin concentrations, Pima Indians were 17% more insulin resistant than caucasians after accounting for any differences in degree of obesity (P less than 0.0001). During oral glucose tolerance testing, mean plasma insulin concentrations were 33% higher in the Pimas (P less than 0.0001), but these differences were largely explained by the greater insulin resistance in the Pimas. Insulin clearance did not differ between the races. However, early insulin responses were exaggerated in the Indians and not explained by insulin resistance. After accounting for differences in insulin action, plasma insulin concentrations in Pima Indians were 50% higher than those in caucasians 3-5 min after iv glucose (P less than 0.0001), 38% higher 10 min after the end of a meal (P less than 0.0001), and 20% higher 30 min after an oral glucose load (P less than 0.006). These data suggest that in addition to insulin resistance, Pima Indians have exaggerated early insulin release and either increased beta-cell mass or enhanced beta-cell sensitivity to glucose. The data argue against low or delayed insulin secretion as primary factors leading to NIDDM in Pima Indians and favor insulin resistance as the underlying and initiating cause of the disease.

Administration, Oral↗
PubMed1989

Comparison of the isozyme phenotypes of the morphologically similar ticks Amblyomma cajennense and A. imitator (Acari: Ixodidae) from south Texas.

A survey of Amblyomma Koch tick populations in southern Texas revealed that A. imitator Kohls was restricted to the two most southern counties, but that A. cajennense (Fabricius) ranged at least as far north as Kingsville, Tex. Females of the two species could be distinguished by the presence of chitinous tubercles on the festoons of A. cajennense and the presence of projections over both sides of the apron of the genital aperture in A. imitator. Males were distinguished by size, ornamentation, and the elongate ventral scutes of A. imitator. In addition, six enzymes, AATA, ACONA, IDH2, LDH, MPI, and PEP, were diagnostic for the two species and two others, aGPD and ACONC, had high diagnostic values. Resulting interspecific divergence was significant, I = 0.582. Genetic variability was higher in A. imitator (h = 0.092) than in A. cajennense (h = 0.057), but neither species exhibited marked interpopulation divergence (I = 0.991 in A. imitator, I = 0.994 in A. cajennense).

Animals↗
PubMed1989

[Acute extradural hematoma in pediatrics].

The authors review the clinical reports of twelve children with craniocerebral trauma admitted to the Children's Hospital of Panama from January 1979 to March 1987 who underwent neurosurgery for supratentorial acute extradural hematoma. The age range was 7 months to 14 years. Findings in relation to age, cause of injury, location of the extradural hematoma, lucid interval period, mortality rate, prognosis, plain roentgenograms, cerebral angiograms, and computerized axial tomography are discussed.

Acute Disease↗
PubMed1987

Expression, inheritance, and linkage relationships among eight enzyme genes in Dermacentor albipictus (Packard) (Acarina: Ixodidae).

Starch gel electrophoresis was used to examine the inheritance, expression, and linkage relationships among eight enzyme genes in the winter tick, Dermacentor albipictus. A fructose-specific hexokinase (FHK), adenylate kinase (ADK), and two forms of aconitase (ACON-A, ACON-C) appeared to have monomeric quaternary structures. A glycylleucine peptidase (PEP), isocitrate dehydrogenase (IDH), and anodally migrating malate dehydrogenase (MDH-A) were apparently dimers. The quaternary structure of glucose phosphate isomerase (GPI) could not be determined because of the similarity in relative mobility of the two available electromorphs. The genes for GPI, FHK, and ADK are located on the X chromosome in the following order: Adk - 37.4 - Gpi - 24.6 - Fhk, with Adk - Fhk being 46.5 map units apart. The remaining five genes were autosomally inherited. Of the 10 possible paired combinations of these genes, only the data for two pairs, Idh-Mdh (44.5% recombinants) and Acon-A--Acon-C (46.4% recombinants), suggested statistically significant linkage.

Animals↗
PubMed1986

An auxiliary protein for DNA polymerase-delta from fetal calf thymus.

An auxiliary protein which affects the ability of calf thymus DNA polymerase-delta to utilize template/primers containing long stretches of single-stranded template has been purified to homogeneity from the same tissue. The auxiliary protein coelutes with DNA polymerase-delta on DEAE-cellulose and phenyl-agarose chromatography but is separated from the polymerase on phosphocellulose chromatography. The physical and functional properties of the auxiliary protein strongly resemble those of the beta subunit of Escherichia coli DNA polymerase III holoenzyme. A molecular weight of 75,000 has been calculated from a sedimentation coefficient of 5.0 s and a Stokes radius of 36.5 A. A single band of 37,000 daltons is seen on sodium dodecyl sulfate gel electrophoresis, suggesting that the protein exists as a dimer of identical subunits. The purified protein has no detectable DNA polymerase, primase, ATPase, or nuclease activity. The ability of DNA polymerase-delta to replicate gapped duplex DNA is relatively unaffected by the presence of the auxiliary protein, however, it is required to replicate templates with low primer/template ratios, e.g. poly(dA)/oligo(dT) (20:1), primed M13 DNA, and denatured calf thymus DNA. The auxiliary protein is specific for DNA polymerase-delta; it has no effect on the activity of calf thymus DNA polymerase-alpha or the Klenow fragment of E. coli DNA polymerase I with primed homopolymer templates. Although the auxiliary protein does not bind to either single-stranded or double-stranded DNA, it does increase the binding of DNA polymerase-delta to poly(dA)/oligo(dT), suggesting that the auxiliary protein interacts with the polymerase in the presence of template/primer, stabilizing the polymerase-template/primer complex.

Animals↗