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A Diez

Publications and source records attributed to A Diez.

At least 37 records · Page 2Linked to original sources
PubMed1993

Correlation between densitometric and hystomorphometric values in isolated vertebrae of Sprague-Dawley rats.

The study of bone mass in experimental animals usually requires invasive techniques. Dual energy X-ray absorptiometry (DEXA) may be an alternative as a non-invasive method (1). Bone mineral density (BMD) and bone mineral content (BMC) of 62 vertebrae of Sprague Dawley rats (SDr) measured by DEXA densitometry were compared with histomorphometric bone volume measurements, and a statistically significant correlation was found (r = 0.79 and 0.75, respectively, p < 0.001). In conclusion, DEXA is an accurate and feasible technique for the study of trabecular bone mass in SDr.

Absorptiometry, Photon↗
PubMed1992

Unfolding and trypsin inactivation studies reveal a conformation drift of glucose-6-phosphate dehydrogenase upon binding of NADP.

Binding of NADP to glucose-6-phosphate dehydrogenase (G6PD) from Dicentrarchus labrax liver has stabilized its native structure against thermal inactivation, guanidine hydrochloride unfolding and inactivation by tryptic digestion. The time-course of G6PD inactivation by guanidine hydrochloride in the presence of NADP has provided experimental evidence in favor of a conformational drift upon NADP binding to the bass enzyme. Based on the inactivation patterns obtained when the enzyme was treated with guanidine hydrochloride and trypsin, it is proposed that the enzyme conformation induced upon NADP binding is in slow equilibrium with the conformation stabilized in the absence of NADP. FPLC studies have shown that micromolar concentrations of NADP induced oligomerization of G6PD. In addition, the different K0.5 values of NADP binding to the enzyme, ranging from 1-2 microM (from trypsin inactivation) to 90 microM (from titration of the intrinsic fluorescence), suggest a step-wise binding of NADP to the oligomer, with negative cooperativity in the saturation process.

Animals↗
PubMed1990

Effect of isotypes and allelic polymorphism on the binding of staphylococcal exotoxins to MHC class II molecules.

Interaction of staphylococcal exotoxins (SE) with MHC class II molecules plays a central role in the activation of immune cells by SE. We have recently demonstrated directly that toxic shock syndrome toxin-1 (TSST-1) binds to MHC class II molecules with high affinity, and similar results have been reported for SEA and SEB. The ability of T cells to respond to individual SE is associated with the expression of particular TCR-V beta gene elements. In the present study we have examined the effect of polymorphism on the ability of MHC class II molecules to bind SEB and TSST-1. We have used a panel of L cell transfectants that express different allelic forms of each of the three human class II isotypes. Radioligand binding assays detected binding of SEB and TSST-1 to most, but not all of the MHC class II molecules examined. Toxin-driven MHC class II-dependent T cell proliferation occurred with all transfectants examined even in the absence of detectable toxin binding. These results indicate that SE can bind to human MHC class II molecules of diverse phenotypes.

Antibodies, Monoclonal↗
PubMed1990

Binding of toxic shock syndrome toxin-1 to murine major histocompatibility complex class II molecules.

The staphylococcal exotoxin toxic shock syndrome toxin-1 (TSST-1) has potent stimulatory effects on murine and human lymphocytes. This is the consequence of TSST-1 binding to major histocompatibility complex (MHC) class II molecules and the engagement in a V beta-restricted fashion of the T cell receptor by the TSST-1-MHC class II complex. Using radioligand and functional assays we have recently shown that TSST-1 binds to all HLA-DR (n = 14), HLA-DQ (n = 2) and HLA-DP (n = 2) phenotypes tested. In this study, we have examined the ability of murine MHC class II molecules to bind TSST-1. Specific high-affinity binding of TSST-1 was detectable to unfractionated BALB-c (H-2d) and C57BL/6 (H-2b), but not to C3H (H-2k) spleen cells. The Kd of this binding estimated from Scatchard analysis was in the same nanomolar range as the Kd of binding of TSST-1 to HLA-DR. Binding of 125I-labeled TSST-1 to BALB/c-derived B cell lymphoma lines and to L cell transfectants correlated with the expression of I-A molecules, but not with the expression of I-E molecules. Furthermore, I-A+, I-E- cells but not I-A-, I-E+ cells were able to support TSST-1-induced T cell proliferation. The binding affinity of TSST-1 for I-Ak appears to be much lower than for I-Ad. L cell transfectants expressing hybrid DR alpha: I-E beta k molecules, but not those expressing I-E alpha k: DR1 beta molecules, could bind TSST-1 and efficiently support TSST-1-induced T cell proliferation. This suggests that minor differences in the highly homologous I-E alpha and DR alpha chains are critical in determining the affinity of the MHC class II molecule for TSST-1. These results demonstrate that the binding of TSST-1 to MHC class II molecules in the mouse, in contrast to humans, is strongly influenced by phenotype. Analysis of the molecular basis of these differences may help to localize staphylococcal exotoxin binding sites on MHC class II molecules.

Animals↗
PubMed1990

Properties of arginase immobilized in a fibrin clot.

Rat liver arginase was covalently trapped in a fibrin clot. Among the physicochemical properties of the enzyme studied were Mn2+ requirement, pH behavior, temperature and time stability, effect of denaturing agents, and kinetic properties. The immobilized arginase showed the same substrate affinity as soluble arginase, but had higher stability at room temperature, was more resistant to denaturation, and had a higher catalytic activity at physiological pH. The properties so far examined may enhance the use of immobilized arginase in cancer therapy.

Animals↗
PubMed1989

Staphylococcal enterotoxin B and toxic shock syndrome toxin-1 bind to distinct sites on HLA-DR and HLA-DQ molecules.

Staphylococcal enterotoxins (SE) activate human T cells in vitro. This requires the presence of Ia+ accessory cells but does not require processing of the toxin by the accessory cell. We and others have recently demonstrated direct binding of SE to human MHC class II molecules. In this study, we have compared in detail the ability of class II molecules to bind two SE, toxic shock syndrome toxin-1 (TSST-1) and SEB. Scatchard analysis of equilibrium binding data indicate that SEB binds to Ia+ human cell lines with a 10-fold lower affinity than TSST-1. Likewise, SEB precipitates HLA-DR alpha- and beta-chains from detergent lysates of Ia+ cells less efficiently than TSST-1. The binding of TSST-1 and SEB to transfected L cells expressing HLA-DR and HLA-DQ gene products was differentially inhibited by anti-HLA-DR mAb. There was virtually no cross-inhibition of TSST-1 and SEB in competitive binding assays. We conclude that TSST-1 and SEB bind to two MHC class II sites which can be distinguished by their relative accessibility to blocking by anti-class II mAb and heterologous toxin.

Antibodies, Monoclonal↗
PubMed1989

Interaction of the local anesthetics dibucaine and tetracaine with sarcoplasmic reticulum membranes. Differential scanning calorimetry and fluorescence studies.

The local anesthetics dibucaine and tetracaine inhibit the (Ca2+ + Mg2+)-ATPase from skeletal muscle sarcoplasmic reticulum [DeBoland, A. R., Jilka, R. L., & Martonosi, A. N. (1975) J. Biol. Chem. 250, 7501-7510; Suko, J., Winkler, F., Scharinger, B., & Hellmann, G. (1976) Biochim. Biophys. Acta 443, 571-586]. We have carried out differential scanning calorimetry and fluorescence measurements to study the interaction of these drugs with sarcoplasmic reticulum membranes and with purified (Ca2+ + Mg2+)-ATPase. The temperature range of denaturation of the (Ca2+ + Mg2+)-ATPase in the sarcoplasmic reticulum membrane, determined from our scanning calorimetry experiments, is ca. 45-55 degrees C and for the purified enzyme ca. 40-50 degrees C. Millimolar concentrations of dibucaine and tetracaine, and ethanol at concentrations higher than 1% v/v, lower a few degrees (degrees C) the denaturation temperature of the (Ca2+ + Mg2+)-ATPase. Other local anesthetics reported to have no effect on the ATPase activity, such as lidocaine and procaine, did not significantly alter the differential scanning calorimetry pattern of these membranes up to a concentration of 10 mM. The order parameter of the sarcoplasmic reticulum membranes, calculated from measurements of the polarization of the fluorescence of diphenylhexatriene, is not significantly altered at the local anesthetic concentrations that shift the denaturation temperature of the (Ca2+ + Mg2+)-ATPase.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Epidemiology of fractures of the proximal femur associated with osteoporosis in Barcelona, Spain.

We studied the epidemiology of osteoporotic fractures of the proximal femur (cervical and trochanteric fractures) in residents of Barcelona, aged 45 years or over, for a 1-year period. Fractures resulting from metastases were not included. During the period of observation, a total of 1,358 patients with hip fractures were treated at acute-care hospitals in Barcelona. Of those, 1,163 were researched. For each case, age, sex, and home address were registered. The incidence of hip fractures per 100,000 inhabitants aged 45 years or over was 115.6 in men and 252.2 in women. Age was the most influencing factor in the occurrence of hip fractures. Women presented fractures of the proximal femur more frequently than men. The epidemiological curve was similar to that reported in other western countries, although the crude rate was lower than that found in northern countries. We conclude that osteoporotic fractures of the proximal femur are common processes in the Mediterranean area, and reflect the impact of osteoporosis in our environment; however, the lower incidence compared with northern geographical areas may probably reflect the influence of climatic, ethnic, or other factors.

Aged↗
PubMed1989

Toxic shock syndrome toxin 1 binds to major histocompatibility complex class II molecules.

Toxic shock syndrome toxin 1 (TSST-1) is a 22-kDa exotoxin produced by strains of Staphylococcus aureus and implicated in the pathogenesis of toxic shock syndrome. In common with other staphylococcal exotoxins, TSST-1 has diverse immunological effects. These include the induction of interleukin 2 receptor expression, interleukin 2 synthesis, proliferation of human T lymphocytes, and stimulation of interleukin 1 synthesis by human monocytes. In the present study, we demonstrate that TSST-1 binds with saturation kinetics and with a dissociation constant of 17-43 nM to a single class of binding sites on human mononuclear cells. There was a strong correlation between the number of TSST-1 binding sites and the expression of major histocompatibility complex class II molecules, and interferon-gamma induced the expression of class II molecules as well as TSST-1 binding sites on human skin-derived fibroblasts. Monoclonal antibodies to HLA-DR, but not to HLA-DP or HLA-DQ, strongly inhibited TSST-1 binding. Affinity chromatography of 125I-labeled cell membranes over TSST-1-agarose resulted in the recovery of two bands of 35 kDa and 31 kDa that comigrated, respectively, with the alpha and beta chains of HLA-DR and that could be immunoprecipitated with anti-HLA-DR monoclonal antibodies. Binding of TSST-1 was demonstrated to HLA-DR and HLA-DQ L-cell transfectants. These results indicate that major histocompatibility complex class II molecules represent the major binding site for TSST-1 on human cells.

Animals↗
PubMed1988

Osteodystrophy of diabetics in chronic dialysis: a histomorphometric study.

A decreased incidence of hyperparathyroidism in diabetic uremic patients has been reported, but comprehensive bone histomorphometric studies on uremic diabetic osteodistrophy are scarce. We present here the results of static and dynamic bone morphometry in 13 diabetic patients on dialysis (DCD) and their comparison with a pair-matched group of nondiabetic uremics with similar age, sex, and time on dialysis (NCDC), and with a group of 17 normals (N). Diabetic bone showed: (1) Low trabecular volume (Vt 9.9% in DCD and 22.8% in N), (2) Moderately increased remodeling values of intermediate intensity between N and NDCD values (Sf = 19.3% in DCD, 37.4% in NDCD, and 8.8 +/- 6% in N, Sr = 4.3% in DCD, 7.3% in NDCD and 2.04 +/- 0.9% in N), and (3) Moderate fibrosis (Sfib 1.2% in DCD, 12.9% in NDCD). Besides these confirmatory results, two suggestions emerged from the study: (1) The relative number of cells: osteoclast density (OI) and osteoblasts (Ob/OID) appears to be lower, not only than NDCD values but also lower than N values (OI = 0.04 c/mm. in DCD, 0.31 in NDCD, and 0.14 in N; Ob/OID = 5.58% in DCD, 14.6 in NDCD and 22.12 +/- 9% m N). (2) Dynamic behavior in tetracycline based studies disclosed the appearance of two populations of DCD: a subgroup of preserved calcification dynamics with values not quite different than the NDCD group and a subgroup with a significant derangement of mineralization with no measurable bone trabecular dynamics. This late subgroup also showed significantly lower number of Ob/OID values compared with the former with preserved calcification.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1985

Antitumor activity of phenyl substituted dihalogenobis (1-phenyl-1,3-butanedionato)titanium (IV) compounds.

14 phenyl substituated dihalogenobis(1-phenyl-1.3-butanedionato)titanium(IV) compounds were synthesized and characterized by their elemental analyses, IR and/or H-NMR spectra. Their antitumor activity was tested using the intraperitoneally transplanted sarkoma 180 tumor system in mice. Cisplatin was used in several doses as positive control compound. Compared to the recently discovered activity of dihalogenobis(1-phenyl-1.3-butanedionato)titanium (IV) agents, most of the new materials have similar antineoplastic effects. The ratio of median survival time of treated to untreated control animals ranged up to 300% for these compounds. Significance according to Kruskal-Wallis-Test and long-time survivors are given. The possible mechanism of action compared to cisplatin is discussed.

Animals↗
PubMed1984

An interaction of testosterone with cell membranes.

The existence of an early effect of testosterone, prior to the effects dependent upon interaction between the hormone-citosolic receptor complex and the cellular nucleus, has been explored in the present paper, in 3-day old chickens. Liver glycogen phosphorylase activity is increased before protein synthesis activation, and furthermore this effect is not blocked by antibiotics (actinomicin D and cycloheximide) inhibitor of protein synthesis. When liver phosphorylase is activated, cAMP levels are not enhanced, as would be expected, but deeply depleted. The hypothesis of a phosphorylase-kinase activation due to an increase in the intracellular Ca++ concentration is considered.

Animals↗
PubMedDate not supplied

Mitochondrial DNA haplotyping of Testudo graeca on both continental sides of the Straits of Gibraltar.

Testudo graeca is an endangered species of tortoise that inhabits Mediterranean areas of Africa, Asia, and Europe. Western populations are found on both sides of the Straits of Gibraltar. The effects of geographical isolation on genetic divergence were assessed by the sequence analysis of two mitochondrial DNA regions of the 12S rRNA and cytochrome b genes. Four different haplotypes were identified. A single haplotype was shared by all Spanish and some east Moroccan specimens. Two haplotypes were unique to the west Moroccan T. graeca populations and allowed the clear discrimination between individual specimens found west of the Moulouya River. Phylogenetic analysis based on the estimation of nucleotide sequence distances of the haplotypes suggests an African origin for the Spanish populations and a subspecies status for the west Moroccan pool.

Animals↗