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Biomedical subjects

A Sanchez

Publications and source records attributed to A Sanchez.

At least 199 records · Page 11Linked to original sources
PubMed1991

Rotavirus infection alters Na+ and K+ homeostasis in MA-104 cells.

Infection of MA-104 cells with the OSU strain of rotavirus induced an increase in Na+ and a decrease in K+ intracellular concentrations, starting at 4 h post-infection. These changes were not related to an inhibition of the Na+/K+ pump since ouabain-sensitive 86Rb uptake was augmented in rotavirus-infected cells compared to control cells, whereas the [3H]ouabain binding and Na+/K+ ATPase activity in the cell homogenate were unaffected. Furosemide-sensitive 86Rb uptake (Na+/K+/2Cl- cotransport) was not modified by the infection. Passive 86Rb efflux and 22Na influx were augmented in infected cells suggesting an increase in the plasma membrane permeability. The increase in intracellular Na+ concentration might be responsible for the observed stimulation of the Na+/K+ pump. This effect was dependent upon the synthesis of viral proteins because it was abolished by addition of cycloheximide up to 4 h post-infection. Prevention of the increase in intracellular Na+ by the use of low Na(+)-containing media did not modify the pattern of protein synthesis. This suggests that changes in intracellular Na+ and K+ concentrations were not related to shutoff of cellular protein synthesis. Alterations of ion contents in the rotavirus-infected enterocytes might impair intestinal absorptive capacity before the appearance of histopathological lesions.

Animals↗
PubMed1991

Fructosamine levels in CAPD: its value as glycemic index.

We have studied fructosamine (measured by colorimetric methods) and glycosylated hemoglobin (HbA1c) using a high pressure liquid chromatography (HPLC) in 20 uremic patients managed conservatively (8 diabetics and 12 non-diabetics) and 20 patients treated with continuous ambulatory peritoneal dialysis (CAPD) including 12 diabetics and 8 non-diabetics. Twenty healthy subjects were used as control group. We have correlated the mean blood glucose (MBG) of the preceding days to fructosamine and HbA1c measurements. No differences were detected in mean fructosamine and HbA1c levels in non-diabetics patients in the CAPD or conservatively treated groups compared to controls. In diabetic patients undergoing conservative treatment or CAPD, mean fructosamine and HbA1c values were elevated when compared with control group. Both glycemic indicators were increased in most of the diabetic patients, was higher values in those patients with higher MBG. There was a good correlation in CAPD diabetic patients between fructosamine and HbA1c with MBG of the 21 previous days (r = 0.84, p less than 0.01 and r = 0.74, p less than 0.01 respectively). There was also correlation between fructosamine and HbA1c in CAPD diabetic patients (r = 0.78, p less than 0.01). We conclude that fructosamine does not seem to be influenced by uremia or by CAPD. Fructosamine and also glycosylated hemoglobin, when c-fraction is measured and HPLC method is used, can be utilized as glycemic indexes in CAPD diabetic patients.

Adult↗
PubMed1991

Virus zoonoses and their potential for contamination of cell cultures.

Silent virus infections of laboratory animals present a human health hazard, from direct exposure and from contamination of biological products for human use. Here we report two recent examples. In 1989, an outbreak of lymphocytic choriomeningitis virus (LCMV) infections was recognized among workers at a cancer research center after an animal caretaker developed viral meningitis. Investigation revealed that multiple tumor cell lines at the facility were infected with LCMV, as were research animals injected with these cell lines. Of 82 workers tested, eight (10%) were found to have been infected. The infected workers were more likely than other animal handlers to report handling athymic (nude) mice (p less than .0.007). The number of nude mice used in this facilty had increased five-fold in the previous year, possibly explaining the timing of the outbreak. This is the first reported LCMV outbreak since 1975, and the first to implicate nude mice as a source of human LCMV infections. In November 1989 and January 1990, infections caused by two distinct Ebola-like filoviruses were discovered in non-human primates at quarantine facilities in Virginia and Pennsylvania. Although 22 persons were considered to have high- or medium-risk exposures for Ebola infection, no Ebola-compatible illnesses occurred. One of the medium-risk persons had Ebola IgG antibodies confirmed by IFA and Western blot. Rigorous use of barrier precautions may have limited exposure and infection with these filoviruses. In February 1990, new groups of filovirus-infected monkeys were identified in Virginia and in Texas. Seroconversion occurred in four animal handlers, including one to very high titer, but again no illness was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Attained height of lacto-ovo vegetarian children and adolescents.

The relationship between diet and attained height was studied in children and adolescents in Southern California. Diet pattern was determined from an extensive food frequency questionnaire in 1765 Caucasian children of 7-18 years, attending state schools (452 m and 443 f) and Seventh-day Adventist schools (427 m and 443 f). The major difference in diet pattern between state and Adventist school children was in meat consumption. The Adventist children were split evenly between three categories of frequency in meat consumption (less than 1/week, 1/week-less than 1/d, and greater than or equal to 1/d), while 92 percent of state school children consumed meat daily. Vegetarians (those consuming meat less than 1/week) differed significantly in the consumption of other major food groups, such as fruit and vegetables. All school and diet subgroups were at or above the 50th percentile of the National Center for Health Statistics. Age-adjusted regression analysis showed that on average Adventist vegetarian children were taller than their meat-consuming classmates (2.5 and 2.0 cm for boys and girls, respectively). These results did not change materially when adjusting for other food groups. Nor did adjustment for parental height and socioeconomic factors in a sub-sample of 518 children. The results indicate that vegetarian children and adolescents on a balanced diet grow at least as tall as children who consume meat.

Adolescent↗
PubMed1990

Arachidonic acid-induced calcium influx in human platelets. Comparison with the effect of thrombin.

The effects of arachidonic acid and thrombin on calcium movements have been studied in fura-2-loaded platelets by a procedure which allows simultaneous monitoring of the uptake of manganese, a calcium surrogate for Ca2+ channels, and the release of Ca2+ from intracellular stores. Arachidonic acid induced both Ca2+ (Mn2+) entry through the plasma membrane and Ca2+ release from the intracellular stores. The release of Ca2+ was prevented by cyclo-oxygenase inhibitors and mimicked by the prostaglandin H2/thromboxane A2 receptor agonist U46619. Ca2+ (Mn2+) entry required higher concentrations of arachidonic acid and was not prevented by either cyclo-oxygenase or lipoxygenase inhibitors. Several polyunsaturated fatty acids reproduced the effect of arachidonic acid on Ca2+ (Mn2+) entry, but higher concentrations were required. The effects of maximal concentrations of arachidonic acid and thrombin on the uptake of Mn2+ were not additive. Both agonists induced the entry of Ca2+, Mn2+, Co2+ and Ba2+, but not Ni2+, which, in addition, blocked the entry of the other divalent cations. However, arachidonic acid, but not thrombin, increased a Ni2(+)-sensitive permeability to Mg2+. The effect of thrombin but not that of arachidonic acid was prevented either by pretreatment with phorbol ester or by an increase in cyclic-AMP levels. Arachidonic acid also accelerated the uptake of Mn2+ by human neutrophils, rat thymocytes and Ehrlich ascites-tumour cells.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1990

Mouse embryonic stem cells express the cardiac myosin heavy chain genes during development in vitro.

In the mouse embryo, early organogenesis is characterized by the formation of a functional cardiac muscle, such that 9-day embryos exhibit beating, although not fully developed hearts. In light of this observation, we found it intriguing that mouse embryoid bodies (EB), which can develop in vitro from totipotential embryonic stem cells, undergo spontaneous contractile activity. To determine if these cells are capable of recapitulating aspects of cardiogenesis, a cDNA library was prepared from beating EB and screened with a chicken skeletal myosin heavy chain cDNA. We found that the predominant myosin transcripts in the library encode the alpha- and beta-cardiac isoforms. In addition, an embryonic skeletal myosin cDNA was isolated. The myosin heavy chain transcripts in both EB and 9-day embryonic hearts were found to be the same. Transcript-specific primers were prepared, and polymerase chain reaction analyses on single EB were carried out. The data show that a single EB is capable of expressing both the alpha- and beta-isoforms as well as very low amounts of the embryonic skeletal transcript. These data indicate that EB transcribe the appropriate tissue- and developmental stage-specific myosin heavy chain genes and therefore serve as a model system for studying early cardiogenic processes at the molecular level.

Animals↗
PubMed1990

Hantavirus strains isolated from rodentia and insectivora in rural China differentiated by polymerase chain reaction assay.

Polymerase chain reaction (PCR) assay and other techniques were applied to differentiate Hantavirus strains isolated from different animal hosts and geographic regions in China. Two groups of related strains, Hantaan and Seoul, have been classified by cross-neutralization, radioimmunoprecipitation (RIP), and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) assays. The molecular weights of glycoprotein 1 (G1) of Hantaan and Seoul viruses were 72k and 80k, whereas those of the nucleocapsid (N) and glycoprotein 2 (G2) remained the same, respectively. The PCR assay was used to differentiate these isolates using synthetic oligonucleotide primers selected from various regions of the M genome of 76118 and R22 strains. 76118-specific primers amplified only the RNAs extracted from Hantaan strains while R22-specific primers, the RNAs from Seoul strains. The PCR results for classification are consistent with those obtained by cross-neutralization, RIP and SDS-PAGE assays.

Animals↗
PubMed1990

Retinoic acid modulation of the early development of the inner ear is associated with the control of c-fos expression.

The effects of retinoic acid (RA) on the early development of the inner ear were studied in vitro using isolated chick embryo vesicles. Low concentrations of RA (1-50 nM) inhibited vesicular growth in stage 18 otic vesicles that were made quiescent and then reactivated by either serum or bombesin. Growth inhibition was concentration-dependent and was paralleled by a reduction in the rate of DNA synthesis as measured by [3H]thymidine incorporation. Half-inhibition occurred between 1 and 10 nM RA, and the full effect at 20 nM. Retinoic acid, in the presence of serum, induced the precocious differentiation of (1) secretory epithelium, the tegmentum vasculosum and endolymphatic sac and (2) early sensory and supporting epithelia. These structures were positioned in their corresponding normal presumptive areas. The overall direction of growth was reversed by RA and the ratio of the internal to the external vesicular surface area increased with RA concentration. The expression of the nuclear proto-oncogene c-fos in the developing otic vesicle was transient and stage-dependent. High levels of c-fos mRNA were positively correlated with cell proliferation. Incubation of growth-arrested otic vesicles with bombesin plus insulin at concentrations that induced cell proliferation produced a strong induction of c-fos. This mitogen-induced expression was suppressed by 25 nM RA. The results suggest (1) a role for retinoic acid in controlling the early development of the inner ear and (2) that this control is effected through the regulation of the proto-oncogene c-fos.

Animals↗
PubMed1990

Diabetic patients on CAPD need less aluminum hydroxide as a phosphate binder than non-diabetics.

A retrospective study was done in 86 patients on dialysis in order to evaluate the doses of aluminum hydroxide (OH3 Al) received to achieve a better serum phosphate control. Thirty-seven patients were treated with continuous ambulatory peritoneal dialysis (CAPD) divided in 22 diabetics and 15 non-diabetics. Forty-nine patients were treated with hemodialysis (HD), 12 diabetics and 37 non-diabetics. The doses of 1-25 Dihidroxycholecalciferol (1-25 DOH-D3) were similar in all patients. The serum phosphate levels were similar in CAPD and HD patients with smaller doses of OH3 AL in CAPD patients (p less than 0.001). Diabetics on either technique need less OH3 AL in CAPD (CAPD p less than 0.01; HD p less than 0.05) to achieve the same or better control of serum phosphorus than non-diabetics. The overload of glucose on CAPD and the maintained hyperglycemia on diabetes mellitus would shift phosphorus into the cell and could explain these results. Finally, the less needs of aluminum hydroxide on diabetic patients could contribute to their protection against aluminum deposition and its effects.

Aluminum Hydroxide↗
PubMed1989

Intracellular Ca2+ potentiates Na+/H+ exchange and cell differentiation induced by phorbol ester in U937 cells.

The human cell line U937 differentiates to monocyte macrophage-like cells in response to tumour-promoting phorbol esters. This effect is attributed to activation of protein kinase C. We show here that U937 cell differentiation induced by 12-O-tetradecanoylphorbol 13-acetate (TPA) is associated with cytoplasmic alkalinization. Ethyl-isopropyl-amiloride (EIPA), a potent inhibitor of Na+/H+ exchange, blocked both cytoplasmic alkalinization and cell differentiation. Cell acidification by addition of 2-4 mM sodium propionate also blocked TPA-induced U937 cell differentiation. These results suggest that a sustained cell alkalinization mediated by activation of Na+/H+ exchange is essential for TPA-induced differentiation in U937 cells. The increase of cytoplasmic free calcium concentration ([Ca2+]i) by addition of the calcium ionophore ionomycin enhanced TPA-induced alkalinization by increasing the apparent affinity of the Na+/H+ antiporter for intracellular H+. Treatment with ionomycin also potentiated differentiation of U937 cells induced by TPA. This synergism suggests that [Ca2+]i either potentiates the activation of protein kinase C or triggers additional transducing mechanisms. The key events of this interaction occur during the first 30 min of treatment, even though cell differentiation manifests much later.

Amiloride↗
PubMed1989

Monitoring of the activation of receptor-operated calcium channels in human platelets.

Activation of receptor-operated calcium channels has been monitored by measurements of the quenching of the fluorescence of intracellularly trapped fura-2 by Mn entering from the extracellular medium. Release of calcium from intracellular stores was followed simultaneously by measurements of the ratio of the fluorescence excited at 340 and 380 nm. Thrombin, ADP, platelet-activating-factor (PAF) and collagen, all produced both release of calcium from the intracellular stores and uptake of Mn from the extracellular medium. The uptake of Mn, but not the increase of (Ca2+)i, was blocked by nickel. These results suggest the existence of plasma membrane calcium channels which can be activated by the different agonists tested here. The activation of calcium channels was very fast and transient with ADP and PAF, fast and maintained with thrombin, and delayed with collagen.

Adenosine Diphosphate↗
PubMed1989

Effects of sodium removal on calcium mobilization and dense granule secretion induced by thrombin in human platelets.

Removal of extracellular sodium decreased calcium mobilization from intracellular stores induced by thrombin in aspirin-treated human platelets. ATP and serotonin secretion were also significantly reduced. Secretion was positively correlated with calcium mobilization, but the presence or absence of sodium did not modify the slope of the regression line. Half-maximal secretion was reached when [Ca2+]i was increased by about 0.1 microM. Calcium mobilization induced by the divalent cation ionophore ionomycin was not modified by sodium removal. Secretion induced by ionomycin was much smaller than the thrombin-induced one for the same increases of [Ca2+]i. These results suggest that the presence of external sodium is required for normal thrombin-induced calcium release from the intracellular stores and hence for dense granule secretion. However, secretion cannot be only attributed to the increase of cell [Ca2+]i but also to other process(es) which are not affected by external sodium.

Adenosine Triphosphate↗
PubMed1989

Mutagenesis of bacterial elongation factor Tu at lysine 136. A conserved amino acid in GTP regulatory proteins.

We have studied the effects of specific amino acid replacements in EF-Tu upon the protein's interactions with guanine nucleotides and elongation factor Ts (EFTs). We found that alterations at the lysine residue of the Asn-Lys-Cys-Asp sequence, the guanine ring-binding sequence, differentially affect the protein's ability to bind guanine nucleotides. Wild type EF-Tu (Lys-136) binds GDP and GTP much more tightly than do many of the altered proteins. Replacing lysine by arginine lowers the protein's affinity for GDP by about 20-fold relative to the change in its affinity for EF-Ts. Substitutions at residue 136 by glutamine (K136Q) and glutamic acid (K136E) further lower the protein relative affinity for GDP by factors of about 4 and 10, respectively. In contrast, replacement of the residue by isoleucine (K136I) eliminates guanine nucleotide binding as well as EF-Ts binding. Apparently, the distortion of this loop by substitution at residue 136 of a bulky hydrophobic residue can hamper the binding for both substrates or disrupt the folding of the protein. All altered proteins except EF-Tu(K136I) are able to bind tRNA(Phe); however, they require much higher concentrations of GTP than wild type EF-Tu. In minimal media, Escherichia coli cells harboring plasmids encoding EF-Tu(K136E) or EF-Tu(K136Q) suffer growth retardation relative to cells bearing the same plasmid encoding wild type EF-Tu. Co-transformation of these cells with a compatible plasmid bearing the EF-Ts gene reverses this growth problem. The growth retardation effect of some of the altered proteins can be explained by their sequestering EF-Ts. These results indicate that EF-Ts is essential to the growth of E. coli and suggest a technique for studying EF-Ts mutants as well as for identifying other guanine nucleotide exchange enzymes.

Amino Acid Sequence↗