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Biomedical subjects

P Leon

Publications and source records attributed to P Leon.

At least 37 records · Page 2Linked to original sources
PubMed1989

Study of C. burnetii human and animal seroprevalence in a rural population in Madrid community.

A pilot study on human seroprevalence of antibodies to C. burnetii in the Madrid region, initiated in a small rural population, shows a 15.4% positivity by the indirect immunofluorescence test. An urban sample shows an 8.8% positivity. Animal seroprevalence in livestock located in the village under study is 76.6% in caprine and 17.7% in bovine. A high risk epidemiological situation is detected.

Animals↗
PubMed1989

Diadenosine 5",5"'P1,P4-tetraphosphatase in Drosophila embryos: developmental regulation and characterization.

1. An enzyme has been isolated from Drosophila embryos which specifically hydrolyzes dinucleoside tetraphosphates to the corresponding nucleoside tri- and tetraphosphates, with Km values around 4 microM. 2. Nucleoside mono-, di- and triphosphates are competitive inhibitors with K1 values i the 0.01 mM range. 3. The inhibition is particularly strong by adenosine tetraphosphate (Ki = 10 nM). 4. The enzyme is maximally active at pH 7.5 and is quite stable at acid pH. 5. The enzyme requires divalent cations for activity: Co(2+) much greater than [corrected] Mn(2+) Mg(2+) x Co(2+) stimulated about 90-fold at 6 mM. 6. The specific stimulation by Co(2+) has been described before, but at lower concentrations, for the enzyme of procaryotes which splits diadenosine tetraphosphate symmetrically. Zn(2+) and Ca(2+) are inhibitors of the Drosophila enzyme. Co(2+) is also inhibitor in the presence of Mg(2+). 7. The Drosophila enzyme has essential sulphydryl group(s) and a molecular weight of 26,000. 8. Diadenosine tetraphosphatase is present in mature oocytes and increases after fertilization to reach a peak 1.5 hr later. 9. From this time to 3.5 hr the activity decreased to remain at a plateau until the end of embryogenesis. 10. The profile of activity is compatible with its involvement in the regulation of nuclear division.

Acid Anhydride Hydrolases↗
PubMed1989

Isoenzyme patterns of phosphatases and esterases in Fasciola hepatica and Dicrocoelium dendriticum.

A study was made of alkaline and acid phosphatase isoenzymes and non-specific esterases in homogenates of the trematodes Fasciola hepatica and Dicrocoelium dendriticum obtained from infected tissues of Capra hircus and Ovis aries using horizontal polyacrylamide gel electrophoresis. The esterase patterns in F. hepatica and D. dendriticum were different. Homogenate of F. hepatica from both hosts gave four enzyme bands. For D. dendriticum, however, while homogenates of parasites from C. hircus also gave four bands, those of O. aries gave only three bands. Acid and alkaline phosphatases in homogenates of both parasites showed three enzyme bands, but there was a host species difference between the enzyme patterns of specimens collected from C. hircus versus O. aries.

Acid Phosphatase↗
PubMed1989

Superoxide dismutase in cestodes. Isoenzymatic characterization and studies of inhibition by a series of benzimidazoles and by pyrimidine derivatives of recent synthesis.

The activities of superoxide dismutase (SOD) (E.C.1.15.1.1) in extracts of five cestode parasites (Moniezia expansa, M. benedeni, Avitellina centripunctata. Taenia hydatigena and Dipylidium caninum) were investigated. The polyacrylamide gel electrophoretic patterns revealed that each of the five species had four isoenzyme bands; they could be differentiated principally by their displacements and, less clearly, by their intensities. Determinations were made of the inhibitory activities of four benzimidazoles and six recently synthesised pyrimidine derivatives on the SOD enzymes from the cestodes. The results confirm that the percentage of inhibitions of SOD by the same pyrimidine derivatives are markedly superior to those of the benzimidazoles.

Animals↗
PubMed1988

Superoxide dismutase activity in extracts of specimens of Ascaris suum and several analogous tissues in both sexes.

1. The activities of the enzymes superoxide dismutase (EC.1.15.1.1), and catalase (EC.1.11.1.6) in purified extracts of whole Ascaris suum adult males and females, and also in several analogous tissues of each sex, were studied. 2. No catalase activity was found in any of the extracts. 3. Considerable superoxide dismutase activity was detected in both sexes and the levels of this activity showed sexual differences in the values found in different tissue locations. 4. The sexual organs of both males and females showed the highest SOD activity of all the tissues examined. 5. Polyacrylamide gel electrophoresis pattern analysis confirmed that the female tissues had more SOD enzyme components than the corresponding tissues in the male.

Animals↗
PubMed1987

Superoxide dismutase activity in nematodes.

The activities of the enzymes superoxide dismutase (E.C.:1.15.1.1) and catalase (E.C.:1.11.1.6) were studied in purified extracts of four nematodes: Ascaris suum, Toxascaris leonina, Toxocara canis and T. cati adult males and females. No catalase activity was found in any of the extracts. The results reveal that the SOD activities of the four parasites presented species differences and also sexual differences within each species. Polyacrylamide gel electrophoresis pattern analysis confirmed that the mobilities, widths and band intensities varied according to the species and sex of the parasite from which the enzyme was obtained.

Animals↗
PubMed1987

Malate dehydrogenase in helminth parasites. Inhibition by benzimidazoles and pyrimidine derivatives.

A study was performed of the activities of both cytoplasmic and mitochondrial, malate dehydrogenase (MDH) (E.C.1.1.1.37) in purified extracts of whole specimens of male and female nematodes of four species: T. canis, T. cati, T. leonina and A. suum (and tissues), two trematodes: F. hepatica and D. dendriticum, and four cestodes: M. expansa, M. benedeni, D. caninum and T. hydatigena. The results show that there exist species and sexual differences in the enzyme activities of both enzymes. The relative importance of this energy pathways of these helminth species is discussed. Determinations were made of the in vitro inhibitory activities of four benzimidazoles and six synthesised pyrimidine derivatives on MDH (soluble and mitochondrial) from helminth parasites. Several pyrimidine derivatives (6-amino-5-methyl-5-nitro-uracil, 4-amino-1-methyl-2-methylthio-5-nitro-6-oxo-1,2,3,4-tetrahydropyrimid ine and 4-amino-2-methylthio-5-nitro-6-oxo-1,2,3,4-tetrahidropyrimidine) produced double percent in vitro inhibitions of those shown by the benzimidazoles.

Animals↗
PubMed1987

Superoxide dismutase in trematodes. Isoenzymatic characterization and studies of inhibition by a series of benzimidazoles and by pyrimidines of recent syntheses.

A comparative study was carried out of superoxide dismutase (E.C.1.15.1.1) (SOD) and catalase activities in purified extracts of two trematodes: Fasciola hepatica and Dicrocoelium dendriticum. The superoxide dismutase activity was very similar to that measured in other eukaryotic cells. As no catalase activity was detected, the possibility that SOD in these trematodes might have the particular importance of removing superoxide radicals is discussed. The SOD isoenzymes of each species were analysed by polyacrylamide gel electrophoresis and the patterns revealed a quantitative difference in the number of isoenzyme bands: F. hepatica showed three, and D. dendriticum only two. Determinations were made of the in vitro inhibitory activities of four benzimidazoles and six synthesised pyrimidine derivatives on SOD from trematodes. The present results confirm that the percentage inhibitions of the pyrimidine derivatives are markedly superior to those produced by the benzimidazoles.

Animals↗
PubMed1986

Cloning and characterization of a linear 2.3 kb mitochondrial plasmid of maize.

A linear 2.3 kb DNA molecule found in maize mitochondria was cloned into pUC8. A natural deletion of this plasmid, found in cmsT and some N (fertile) types of maize plants, was mapped to one end of the plasmid. A minor sequence homology to S-2, another linear mitochondrial plasmid, was detected, as well as more significant sequence homology with chloroplast and maize nuclear DNA. Hybridization to teosinte mitochondrial DNA (mtDNA) revealed the presence of part of the maize plasmid in the high molecular weight mtDNA of the maize relatives. RNA dot hybridization indicates that the plasmid is transcribed in mitochondria. The termini of the 2.3 kb linear plasmid contain inverted repeated sequences; of the first 17 nucleotides of the termini, 16 are identical to the terminal inverted repeats of the linear S plasmids found in the mitochondria of cmsS maize plants.

Chromosome Deletion↗
PubMed1985

Absence of chorionic gonadotropin in sera of women who use intrauterine devices.

A controlled study was undertaken to determine whether unnoticed pregnancies routinely occur in users of the intrauterine contraceptive device (IUD). Starting on day 10 of the menstrual cycle and continuing through the onset of menstruation or until the diagnosis of pregnancy, we collected daily blood samples from three groups of normally menstruating young women. The study groups were (A) IUD users (n = 30), (B) women with tubal ligation (n = 30), and (C) women trying to become pregnant (n = 15). The sequential serum samples were analyzed by radioimmunoassay for progesterone (P), human luteinizing hormone (hLH), and human chorionic gonadotropin (hCG). No positive hCG assays in luteal phase blood sera of IUD users were observed. The only positive hCG determinations of IUD users coincided with the preovulatory surge of hLH. Two subjects who became pregnant, as judged by progressive increases in hCG and P levels in the luteal phase, belonged to the group planning pregnancy. The finding of two pregnancies in 15 months of exposure is consistent with the assumption of natural fertility. The probability of no pregnancies in 30 months at risk, as observed among the IUD users, is between 1 in 200 and 1 in 100,000, depending on the assumption made for natural fertility. The study demonstrates that IUD users do not retain their natural fertility, and that IUDs do not exert their antifertility effect as abortifacient agents. If a confirmed pregnancy is detected in an IUD user, it may be assumed to represent an isolated case of contraceptive failure.

Adult↗
PubMed1981

Lipoprotein patterns in women in Santo Domingo using a levonorgestrel/estradiol contraceptive ring.

Ten healthy, normally menstruating women attending a family planning clinic in Santo Domingo Participated in a study to determine the effects on plasma lipid levels of levonorgestrel and estradiol released from a contraceptive ring. A schedule of 21 days of use followed by 7 days of non-use was followed for 6 cycles. During the first two cycles of use, concentrations of cholesterol, HDL cholesterol, triglycerides and LDL cholesterol declined significantly from control levels, up to 25% for cholesterol, 28% for HDL cholesterol, 45% for friglycerides and 24% for LDL cholesterol. There were no subsequent changes with continued use. These declines are similar in direction but of lesser magnitude than those reported from clinics in other countries where pretreatment plasma levels of the same lipids are considerably higher. There was no significant change in the total cholesterol to HDL cholesterol ratio during treatment.

Adolescent↗
PubMed1981

Pituitary-ovarian function after tubal ligation.

Pituitary-ovarian function was evaluated by measurement of daily serum levels of luteinizing hormone (LH), 17 beta-estradiol, and progesterone in women with a previous history of tubal ligation. Normally menstruating women served as controls. The duration of the proliferative and luteal phase was similar for both groups. The midluteal progesterone level averages did not differ between the two groups. Preovulatory LH and 17 beta-estradiol peaks were significantly lower in the tubal ligation group; average midluteal LH and 17 beta-estradiol levels were also lower. These results reveal that pituitary-ovarian function can be altered following surgical sterilization.

Adult↗
PubMed1980

The menstrual cycle in women using an intrauterine device.

The duration and hormonal characteristics of the menstrual cycles of women using Copper T intrauterine devices (IUDs) were studied. Daily load samples were obtained during both the pre- and postovulatory phases of 30 IUD-associated cycles and the hormone values were compared with those of 15 normally menstruating women not using contraception. The ovulation rate and peak levels of 17 beta-estradiol and luteinizing hormone (LH) were not significantly different between the two groups. The average number of days from the 1st day of menstrual bleeding to the LH peak (the proliferative phase) was longer in the IUD users. The number of days from the LH peak to the onset of menstrual bleeding (the luteal phase) was shorter in the IUD users. Because of the compensating nature of these statistically significant differences, the total cycle length appeared to be unchanged. At the time of menstruation, the plasma levels of both progesterone and 17 beta-estradiol were significantly higher among IUD users. It is concluded that the presence of an IUD does not influence ovarian function, but that ovarian steroid production and endometrial events become asynchronous.

Adolescent↗
PubMed1979

Pregnancies associated with sperm concentrations below 10 million/ml in clinical studies of a potential male contraceptive method, monthly depot medroxyprogesterone acetate and testosterone esters.

A potential male contraceptive approach was evaluated in clinical trials involving monthly injections of depot medroxyprogesterone acetate and either subdermal implants of testosterone propionate or monthly injections of testosterone enanthate. Pregnancies occurred in partners of 9 men with recent sperm counts of 10 million/ml or below. In 5 of the 9 instances, the sperm counts were less than 1 million/ml. It appears that male contraceptive methods involving spermatogenic suppression may require attainment and maintenance of azoospermia. The pregnancy rate cannot be calculated, because the extent of other contraceptive use is uncertain. There were no spontaneous abortions. 6 pregnancies were carried to term, and all progeny were normal, based on physical examination at birth or 3 months after birth.

Contraceptive Agents, Male↗
PubMed1979

First year clinical experience with six levonorgestrel rods as subdermal contraception.

Previous clinical experience with six levonorgestrel subdermal capsules showed a very good contraceptive effectiveness and continuation rate, but with a high proportion of bleeding disturbances, particularly of increased bleeding. It was hypothesized that bleeding could be reduced by higher plasma levels of the steroid, using subdermal rods instead of capsules, as rods have been shown to have a release rate 3 or 4 times that of the capsules. Fifty volunteers were enrolled in a study of the clinical performance of 6 subdermal levonorgestrel rods. Results were compared with a previous experience with 100 volunteers who wore 6 levonorgestrel capsules for a year in the same clinic. Requirement for volunteers to enter the study were the same for capsules and rods. The proportion of women wearing 6 subdermal rods who had increased bleeding was about one half as for the women using 6 levonorgestrel capsules. On the other hand, women using rods had about twice the incidence of amenhorrea, and about four times more hypomenorrhea (4 days or less of bleeding in a 90-day period). There were no pregnancies among the rod users and the discontinuation rate for medical reasons was not higher than for capsule users in the same clinic.

Adolescent↗