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Biomedical subjects

C Saavedra

Publications and source records attributed to C Saavedra.

At least 37 records · Page 2Linked to original sources
PubMed1994

An unusual type of mitochondrial DNA inheritance in the blue mussel Mytilus.

In animals, mitochondrial DNA (mtDNA) inheritance is predominantly maternal. In a few cases incidental transmission of paternal mtDNA was observed and estimated to account for only 10(-4)-10(-3) of an individual's mtDNA content. In contrast, biparental inheritance is common in mussels of the genus Mytilus. Here we present direct evidence that sex and mtDNA inheritance are coupled in Mytilus. Females inherit mtDNA only from their mother, but they transmit it to both daughters and sons. Males inherit mtDNA from both parents, but they transmit to sons only the mtDNA they inherited from their father. In pair matings, this mtDNA inheritance pattern is associated with a strong sex-ratio bias. These findings establish a newly discovered type of cytoplasmic DNA transmission. We also present evidence that the phenomenon breaks down in interspecific hybrids.

Aging↗
PubMed1994

The expression of the bstVIM gene from Bacillus stearothermophilus V is restricted to vegetative cell growth.

The activity of BstVI DNA methyltransferase was monitored during the sporulative cycle of Bacillus stearothermophilus V. Significant methylase activity was found only in bacteria growing vegetatively. This was confirmed by Northern hybridization, which indicated that the bstVIM gene was not transcribed in cells undergoing sporulation. Supporting evidence came from experiments which demonstrated that the RNA polymerase holoenzyme from these cells did not recognize the promoter elements upstream of the bstVIM gene.

Bacterial Proteins↗
PubMed1994

Anti-EBNA-1 (carboxy-half) IgG antibodies as a seroepidemiological marker for Epstein-Barr virus infection.

A population of 2,024 voluntary blood donors was tested for anti-EBNA-1 IgG and anti-VCA IgG serum antibodies to define the EBV infection rate and to compare two different epidemiological markers. Initial screening was performed with a sensitive EBNA-1-IgG ELISA based on recombinant antigen (Biotest) and a VCA-IgG ELISA based on conventional antigen. Both ELISAs had concordant results in 90.4% of the sera. The infection rate was found to be 96.8%. The expected immune status VCA+/EBNA+ was observed in 98.1% of the seropositives. The comparison of sensitivity, specificity, and predictive values between the two screening assays underlines the superiority of the EBNA-1 ELISA. The marker anti-EBNA-1 IgG as detected by a sensitive ELISA (Biotest anti-EBV recombinant) is suitable for defining previous EBV infection (positive predictive value 99.8%). The high infection rate in the adult population, however, renders the supply with EBV-negative blood rather difficult.

Adult↗
PubMed1992

[Development of HLA antibodies in thrombocyte substitution with cell separator products].

In a retrospective study we investigated the development of HLA antibodies in patients who received platelet concentrates from cell separators. 118 hematological/oncological patients from the Frankfurt University Clinics were investigated. They received between 4 and 66 platelet concentrates for the duration of 30 months. All patients had a negative antibody screening on admission. 31% developed either transient (15%) or permanent (16%) lymphocytotoxic antibodies. The increasing number of platelet transfusions did not correlate with the development of HLA antibodies, but the appearance of these antibodies seemed to be dependent on the disease. Permanent antibodies appeared in 8% of patients with acute leukemia, whereas 38% of patients suffering from CL, lymphoma, MDS and myeloma produced antibodies. Some patients (18) received granulocyte transfusions as well. It is striking that 11% of these patients developed permanent and 28% transient HLA antibodies. There exist no data about recent transfusions or previous pregnancies. To lower the rate of sensitization in patients with diseases such as CL, lymphoma, MDS and myeloma, it should be discussed whether leukocyte-depleted platelet concentrates should be given to these patients.

Blood Component Transfusion↗
PubMed1991

Cloning the BstVI restriction-modification system in Escherichia coli.

A standard DNA modification methyltransferase (MTase) selection protocol was followed to clone the BstVI restriction and modification system from Bacillus stearothermophilus in Escherichia coli. Both genes were contained in a 4.4-kb EcoRI fragment from B. stearothermophilus V chromosomal DNA. The heterologous expression of these genes did not depend on their orientation in the vector, suggesting that the genes are expressed in E. coli under the control of promoters located on the cloned fragment. Subcloning experiments demonstrated that the bstVIR gene was expressed in the absence of its cognate MTase.

Cloning, Molecular↗
PubMed1991

Maximal anaerobic performance of the knee extensor muscles during growth.

The extent of the growth changes in maximal work output during 10 s (MWO10), 30 s (MWO30), and 90 s (MWO90) of maximal repetitive knee flexions and extensions assessed on a modified Hydra-Gym machine was investigated in 84 boys and 83 girls, 9-19 yr of age. Body weight, fat mass and fat free mass by underwater weighing, and thigh volume and cross-sectional area were also determined. No difference was observed in the absolute MWO10, MWO30, and MWO90 between girls and boys at 9 and 11 yr of age. However, significant differences appeared between genders from 13 yr of age onward, anaerobic performances of the knee extensor muscles of girls representing about 75% or even less of those of boys. The analysis of variance revealed that maximal work ouput during the three knee extension tests was significantly greater in males as well as in females from 9 to 18 yr, regardless how performance was related to morphological characteristics. Performance in absolute values or expressed per unit of body weight, fat free mass, and thigh cross-sectional area for the MWO10, MWO30, and MWO90 tests were almost always significantly lower in both genders when performances of the 9-yr-old group were compared with those of the 13-yr-old group or older groups. Improvement in maximal work output during the 10-s, 30-s, or 90-s knee extension tests with age occurred mainly between 9 and 15 yr in both genders. The results of the present study show that there are gender differences in predominantly anaerobic performances during growth and reveal that increase in muscle mass does not appear to be the only factor responsible for the age-related increment in the anaerobic working capacity of the knee extensor muscles.

Adolescent↗