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Biomedical subjects

G Leon

Publications and source records attributed to G Leon.

15 recordsLinked to original sources
PubMed2001

cis Recognition elements in plant mitochondrion RNA editing.

RNA editing in higher plant mitochondria modifies mRNA sequences by means of C-to-U conversions at highly specific sites. To determine the cis elements involved in recognition of an editing site in plant mitochondria, deletion and site-directed mutation constructs containing the cognate cox II mitochondrial gene were introduced into purified mitochondria by electroporation. The RNA editing status was analyzed for precursor and spliced transcripts from the test construct. We found that only a restricted number of nucleotides in the vicinity of the target C residue were necessary for recognition by the editing machinery and that the nearest neighbor 3' residues were crucial for the editing process. We provide evidence that two functionally distinguishable sequences can be defined: the 16-nucleotide 5' region, which can be replaced with the same region from another editing site, and a 6-nucleotide 3' region specific to the editing site. The latter region may play a role in positioning the actual editing residue.

Apoproteins↗
PubMed2000

Hemophilia treatment. Predicting the long-term risk of HIV exposure by cryoprecipitate.

Most of the world's haemophilia population lives in countries with few medical or financial resources. As such, they cannot easily obtain viral-inactivated clotting product. Many patients are treated with cryoprecipitate made from locally supplied blood. The reasoning for using cryoprecipitate, instead of viral-inactivated products, is based on an unspoken belief that because blood banks can provide reasonably safe products by using modern testing procedures, transmission of HIV and other blood-borne viruses is rare. However, the risk of acquiring a blood-borne infection increases with every exposure, and haemophilia patients treated with cryoprecipitate or fresh-frozen plasma are exposed to hundreds or thousands of donors during their lifetime. The risk that a person infected with HIV will donate blood during the 'window period' is directly related to the incidence of HIV in the country where the donation occurs. To demonstrate the extent of this problem, we devised a model for estimating the risk that a person with haemophilia will encounter HIV-contaminated cryoprecipitate based on the years of treatment and the underlying incidence rate of HIV among blood donors. We applied the model to two countries with different incidence rates of HIV: Venezuela and the United States. We found that a person with haemophilia who receives monthly infusions of cryoprecipitate prepared from plasma of 15 donors over a lifetime of treatment (60 years) is at significant risk of being exposed to HIV. In the United States there is a 2% risk of being exposed to HIV-contaminated blood product, and in Venezuela, the percentage of risk is 40%. Given this degree of risk, medical care providers should carefully evaluate the use of cryoprecipitate except in emergencies or when no viral-inactivated products are available.

Blood Donors↗
PubMed1999

Haemophilia therapy: assessing the cumulative risk of HIV exposure by cryoprecipitate.

Most of the world's haemophilia population live in countries with developing or emerging economies. As such, they do not have access to viral inactivated clotting product. Many are treated with cryoprecipitate made from locally supplied blood. The rationale for using cryoprecipitate instead of viral inactivated products is based on an implicit belief that because blood banks can provide reasonably safe products by using modern testing procedures, transmission of HIV and other blood-borne viruses is rare. However, the risk of acquiring a blood-borne infection is cumulative, and haemophilia patients treated with cryoprecipitate or fresh-frozen plasma are exposed to hundreds or thousands of donors during their lifetime. The risk that an HIV-infected person will be a donor during the 'window period' is directly related to the incidence of HIV in the country where the donation occurs. To illustrate the extent of this problem, we devise a model for estimating the risk that a person with haemophilia will encounter HIV-contaminated cryoprecipitate as a function of years of treatment and the underlying incidence rate of HIV among blood donors. We apply the model to two countries with different incidence rates of HIV, Venezuela and the USA. Over a lifetime of treatment (60 years), the cumulative risk of HIV exposure for a person with haemophilia receiving monthly infusion of cryoprecipitate prepared from plasma of 15 donors is significant, 2% in the USA and 40% in Venezuela. Considering the cumulative risk for transmitting HIV to patients with haemophilia through cryoprecipitate treatment, medical care providers should carefully evaluate the use of cryoprecipitate in any but emergency conditions or when no virally inactivated products are available.

Blood Preservation↗
PubMed1996

Plasma neurotransmitters, blood pressure and heart rate during supine resting, orthostasis and moderate exercise in severely ill patients: a model of failing to cope with stress.

BACKGROUND: Previous clinical research has shown that severely ill (somatic) as well as many psychosomatic patients show raised noradrenaline (NA), adrenaline (AD), cortisol, free serotonin (f5HT) and platelet aggregability. Conversely, they show reduced NA/AD plasma ratio and platelet serotonin (p5HT). They also show adrenal hyperresponsiveness to an oral glucose load. These findings are opposed to those observed in depressed patients who show adrenal gland sympathetic hyporesponsiveness and neural sympathetic hyperactivity. OBJECTIVE: To investigate adrenal gland and neural sympathetic systems as well as the other parameters in nondrepressed severely ill patients through the orthostasis exercise stress test which in normals triggers NA but no AD rise. METHODS: We investigated 35 severely ill patients and their age- and sex-paired controls. Systolic, diastolic pulse pressure (PP), heart rate and neuroendocrine parameters were measured supine (0 min), at orthostasis (1 min) and exercise (5 min). A second test was performed 2 weeks later, after atropine injection. Multivariate analysis of variance, paired t test and Pearson product-moment test were employed. RESULTS: The normal PP orthostasis fall was not observed in patients. At this period, an abnormal AD peak substituted the normal NA peak. The normal p5HT-f5HT orthostasis-exercise peaks were absent in patients. Cortisol and platelet aggregability were raised in patients. CONCLUSIONS: Severely ill (somatic) patients responded to the orthostasis-exercise stress test with adrenal and corticosuprarenal but not neural sympathetic activity. They did not show the normal parasympathetic activity at orthostasis. This adrenal gland sympathetic hyperactivity registered in somatic patients is similar to that observed in mammals which fail to cope with stress and contrary to the profile registered in depressed subjects who show NA but not AD rise.

Adolescent↗
PubMed1995

Ethanol intake, plasma catecholamine levels, and ST-segment changes without myocardial injury in rats with short-term ethanol consumption.

The authors studied the effect of short-term ethanol consumption on the ST-segment and the association between ST-segment changes and the amount of daily ethanol intake and levels of plasma catecholamines. The study used 63 rats (control group n = 20, study group n = 43). The rats in the study group were exposed for 6 days to progressively larger doses of ethanol followed by 15 days of continuous exposure to ethanol. At baseline an electrocardiogram (ECG) was recorded, and on day 25 the ECG was repeated and plasma catecholamine levels were measured. The animals' hearts were removed and processed for histologic study. Repolarization abnormalities were observed in 68% of the ethanol-consuming rats. Two factors differentiated the subgroup of ethanol-consuming rats with ST-segment changes from the subgroup without ST-segment changes: amount of daily ethanol intake (0.0077 +/- 0.02 mL/g/d vs 0.0058 +/- 0.019 mL/g/d) and plasma epinephrine levels (3,881 +/- 733 pg/mL vs 1,478 +/- 406 pg/mL). No myocardial damage was detected. Our results suggest that in ethanol-consuming rats, high-volume daily ethanol intake and increased plasma catecholamines may mediate changes in the ST-segment.

Animals↗
PubMed1993

Reprogramming of nucleolar gene expression during the acclimatization of the carp.

During seasonal acclimatization of eurythermal fish, the nucleolus of the hepatocyte undergoes ultrastructural reprogramming. In winter acclimatized carp, the nucleolar components are segregated, a condition that suggests a decreased transcription of rRNA. The same nucleolar reorganization was observed when pituitary cells from winter- and summer-acclimatized carp were examined. In situ analyses of nucleolar RNA revealed a marked lowering of RNA content in the segregated nucleoli. Accordingly, in vitro synthesis of RNA was shown to be significantly lower in pituitary tissue from cold-acclimatized fish where precursor accumulated. Conversely, in pituitary tissue from summer-adapted fish the rate and extent of synthesis and of rRNA processing was notably higher. The involvement of pre-rRNA processing events during seasonal acclimatization was corroborated by the strong differences of U3 RNA content detected by in situ hybridization in pituitary cells from summer- and winter-fish. When RNA polymerase I activity from both acclimatized states were assayed, no differences were detected. Thus, it appears that in fish RNA polymerase I itself does not play an important role in the control of nucleolar gene expression and the nucleolar gene expression reprogramming that the seasonal rearrangement represents might involve, among the many nucleolar-specific proteins, transcription factors.

Acclimatization↗
PubMed1992

An overview of interventions to improve compliance with appointment keeping for medical services.

OBJECTIVE: To determine, by a quantitative meta-analysis of randomized trials, the effectiveness of strategies to improve patient compliance with screening, referral, and clinic appointments for health services that are provided at the time of the visit. DATA SOURCES: Computerized searches of MEDLINE (1966 through 1990) were done using two search strategies: (1) (Patient Compliance OR Adhere* OR Dropout*) AND (Appointment*) AND (Screen* OR Follow* OR Refer*); and (2) (Patient Compliance OR Adhere* OR Dropout*) AND (Attend* OR Screen*) OR (Appointment*). A computerized search of PSYCHLIT was done with the terms Compliance AND Appointment*. In addition, the reference list of each retrieved article was reviewed and relevant citations retrieved. STUDY SELECTION: Only randomized trials with quantitative data concerning the effect of interventions to improve attendance at appointments for supervised administration of care were considered for detailed review. Studies of appointment keeping for self-administered treatments or tests were excluded. Two independent reviewers assessed each article for inclusion (kappa, for agreement, 0.66 for MEDLINE; 0.95 for PSYCHLIT) and validity (kappa, 0.62) using a priori criteria. Twenty-three (26%) of 88 relevant articles met all criteria. DATA EXTRACTION: Data on study populations, interventions, and outcomes were extracted and analyzed using pooled odds ratios (ORs). DATA SYNTHESIS: The average rate of compliance with appointments was 58%. Mailed reminders and telephone prompts were consistently useful in reducing broken appointments (OR, 2.2; 95% confidence interval [CI], 1.7 to 2.9; and OR, 2.9, CI, 1.9 to 4.3, respectively). An "orientation statement" (OR, 2.9; CI, 1.5 to 5.6), "contracting" with patients (OR, 1.9; CI, 1.04 to 3.5), and prompts from physicians (OR, 1.6; CI, 1.4 to 2.0) showed positive effects as well. CONCLUSIONS: In clinic settings where kept appointments can be an accurate measure of patient compliance with health care interventions, broken appointments can be reduced by mail, telephone, or physician reminders; orienting patients to the clinic; or contracting with patients.

Appointments and Schedules↗
PubMed1992

Mycetoma.

Explore the source record for details and available documents.

Humans↗
PubMed1984

Cloning, physical mapping and genome organization of mitochondrial DNA from Cyprinus carpio oocytes.

The mitochondrial genome from Cyprinus carpio oocytes is a 10.5 megadalton, circular DNA molecule. The carp mitochondrial DNA was cloned in pBR325. Three recombinant plasmids accounted for the entire genome. Mapping of this DNA using 11 different restriction endonucleases is reported here. Both the large and small rRNA genes were then localized using Southern blot analysis. The subunit I of the cytochrome oxidase, the cytochrome b, the tRNAGlu and the URF 4 genes were localized by nucleotide sequence analysis and homology studies with human mtDNA. Our results suggest that a similar gene order has been maintained in the mitochondrial genomes of Chordata and support the hypothesis of a common ancestor for all vertebrate organelle genomes. This study constitutes the first report on the genome organization of a fish mtDNA and provides information for further investigation in connection with sequence determination, replication, and gene expression in carp mitochondria.

Animals↗
PubMed1980

Detection of persistent ductus in hypoplastic left heart syndrome by contrast echocardiography.

A patient with hypoplastic left heart syndrome was studied using contrast echocardiography after peripheral venous injection of dextrose. The combination of the parasternal and suprasternal approach allowed for identification of the right ventricular cavity, excluded the presence of right-to-left intracardiac shunts, and established normal ventriculoarterial connections. From the abdominal approach, the abdominal aorta was identified as an echo-free space corresponding to this structure in position, which became opacified after peripheral injections of dextrose into the left-hand vein. In view of the suprasternal and parasternal findings opacification of the abdominal aorta could only have occurred in the presence of a pulmonary artery to descending aorta shunt through a persistent ductus arteriosus.

Ductus Arteriosus, Patent↗