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Biomedical subjects

F Ramirez

Publications and source records attributed to F Ramirez.

At least 235 records · Page 13Linked to original sources
PubMed1975

Relative numbers of human globin genes assayed with purified alpha and beta complementary human DNA.

Purified alpha and beta globin complementary DNAs (cDNAs) have been separated from total radioactively labeled human globin cDNA using mRNA purified from liver of a hydrops fetalis (alpha thalassemia). The beta cDNA hybridizes to the hydrops fetalis mRNA while the alpha cDNA remains single-stranded. the purified alpha and beta cDNAs were assayed for their purity by their hybridization to mRNA prepared from reticulocytes of nonthalassemia, alpha thalassemia, and beta thalassemia subjects. The results indicate that the separated cDNAs are selective in hybridization to alpha or beta globin mRNAs, respectively. The previously reported deficiency of globin mRNA in thalassemia cells has been confirmed with these purified cDNAs. The purified alpha and beta cDNAs were hybridized to cellular DNA to non-thalassemia, beta+ thalassemia, and hydrops fetalis (alpha thalassemia) DNA. The alpha cDNA hybridized to hydrops fetalis liver DNA to a much lower extent that beta cDNA, confirming the previously reported deletion of alpha globin genes in hydrops fetalis. By contrast, both the alpha and beta DNA probes hybridized to the same extent to spleen DNA from non-thalassemia and from beta+ thalassemia patients. Between two and five globin genes in non-thalassemia and beta+ thalassemia DNA hybridize to beta cDNA and one to five to alpha cDNA. These studies indicate that in beta+ thalassemia, there is no detectable deletion in beta globin genes. The genetic defect in beta+ thalassemia appears to be due to either repression of transcription of beta globin genes or abnormal processing of beta globin mRNA.

Bone Marrow↗
PubMed1975

Heart rate in fetuses and neonates in normal conditions and with mild depression.

The continuous recording of fetal and neonatal heart rate gives reliable information on the condition of the fetus and neonate. In the present study the results obtained in vigorous and mildly depressed newborns, by the continuous recording of fetal heart rate during labor and of neonatal heart rate during 90 minutes after birth, are presented. Twenty three pregnant women were studied during labor, as well as their newborns. They fulfilled the following conditions: --Mothers without known complications and good prenatal care. --Term pregnancies with single fetuses in vertex presentation with birthweight normal for age. --All labors started, progressed and delivered spontanously withoug signs of fetal distress. No drugs were given to the mother during labor or to the neonate. The umbilical cord was clamped immediately after birth. Seventeen neonates were vigorous at 1 and 5 minutes (Apgar score 7 or higher). Six neonates were slightly depressed at the first minute but all of them recovered at 5 minutes. Both groups are studied separately. Figure 1 shows the average values of BFHR and NHR corresponding to 17 vigorous newborns (Apgar scores 7-10 at the first and fifth minutes of life). No major variations were found in the average values of BFHR in the time period studied. No statistically significant differences were found in the BFHR of the same fetus at 60, 30 and 8 minutes before delivery (Fig. 2). A decrease in BFHR occurred during the 6 minutes preceding birth (fig. 1). After birth the average values of NHR were higher than the fetal ones (Fig. 1). This post-natal increase in heart rate (32 beats/min) is statistically significant when BFHR values 30 minutes before delivery are compared with NHR values recorded 10 minutes after birth (Fig. 3). After this initial increase, NHR starts a gradual fall, lasting about 50 minutes and then becomes stable at a level similar to that of fetal heart rate (Fig. 1). Figure 1 shows that puncture of the heel causes an increase in NHR. The difference between NHR before and after the puncture is significant (Fig. 6). The heart rate of 6 newborns which were slightly depressed at the first minute of life (Apgar score 4-6) but vigorous at the fifth minute, are not significantly different from those of the vigorous group of 17 neonates (Fig.7). The cases chosen for this study have been carefully selected with the aim of establishing the "normal" pattern of fetal and neonatal heart rate. We concluded that in normal term labors BFHR remains stable from 90 until 10 minutes before delivery; there is a tendency to fall during the last 6 minutes preceeding birth. Immediately after birth, neonatal heart rate rises significantly, then falls gradually and becomes stabilized 50 minutes after delivery, at levels similar to those of BFHR.

Adolescent↗
PubMed1974

A limited number of globin genes in human DNA.

The number of globin genes in human cells was determined by hybridizing DNA from human spleens to (3)H-labeled DNA complementary to human globin mRNA. Assuming the rates of reannealing of complementary DNA and cellular DNA are similar, the extent of hybridization of complementary DNA at various ratios of cellular DNA to complementary DNA indicate that there are fewer than 10 globin gene copies per haploid human genome. An alternative analysis of the data, which introduces no assumptions concerning the relative rates of reaction of complementary DNA and cellular DNA, indicates fewer than 20 globin gene copies are present. DNA isolated from the spleen of a patient with beta(+) thalassemia contained a number of globin gene copies similar to that of normal DNA.

Base Sequence↗
PubMed1974

Nucleotide sequence analysis of RNA synthesized from rabbit globin complementary DNA.

Rabbit globin complementary DNA made with RNA-dependent DNA polymerase (reverse transcriptase) was used as template for in vitro synthesis of (32)P-labeled RNA. The sequences of the nucleotides in most of the fragments resulting from combined ribonuclease T(1) and alkaline phosphatase digestion have been determined. Several fragments were long enough to fit uniquely with the alpha or beta globin amino-acid sequences. These data demonstrate that the cDNA was copied from globin mRNA and contained no detectable contaminants.

Alkaline Phosphatase↗
PubMed1973

Decreased globin messenger RNA in thalassemia detected by molecular hybridization.

In previous studies of patients with beta thalassemia, mRNA extracted from reticulocytes in peripheral blood when added to cell-free systems reproduces the deficient beta-chain synthesis characteristic of intact cells. The present studies with specific probes for alpha and beta mRNA were designed to decide whether the decreased beta mRNA activity is due to the presence of abnormal or reduced beta globin mRNA in these cells. Purified alpha and beta complementary DNAs (cDNAs) have been synthesized with RNA-instructed DNA polymerase; alpha and beta mRNAs isolated from heavy (beta-producing) and light (alpha-producing) polyribosomes of rabbit reticulocytes were used as templates. Each of the cDNAs is more than 80% pure by the criterion of biological activity. The alpha cDNA labeled with [(32)P]dCTP and the beta cDNA labeled with [(3)H]dCTP have been added simultaneously to reaction mixtures containing various concentrations of mRNA from thalassemic and nonthalassemic subjects. The extent and rate of hybridization were determined, permitting a comparison of relative alpha and beta mRNA content in the same annealing mixture. In six nonthalassemic patients, relatively equal amounts of hybridizable alpha and beta mRNA appear to be present. In five of seven patients with beta-thalassemia, significantly decreased amounts of beta mRNA compared to alpha mRNA can be demonstrated. In two patients with Hemoglobin H disease, there is a decreased amount of alpha mRNA compared to beta mRNA.

Animals↗
PubMed1969

Venography.

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Adult↗
PubMedDate not supplied

Internal deletion in a collagen gene in a perinatal lethal form of osteogenesis imperfecta.

Cloned probes specific for unique genes have proven to be powerful tools in defining the nature of genetic diseases such as the thalassaemias and growth hormone deficiencies. A similar approach should be useful in defining heritable diseases of type I collagen, the heterotrimer of two alpha 1(I) chains and one alpha 2(I) chain, which is the most abundant member of the collagen family of proteins. Recently, cloned cDNAs and genomic DNAs for the two polypeptide chains of the type I collagen have become available and have been used to elucidate the chromosomal location of the corresponding genes. Here, we have used several of these cloned DNAs to demonstrate the presence of an internal deletion of about 0.5 kilobases (kb) in one allele for the pro alpha 1(I) chain in a patient with osteogenesis imperfecta (OI), a group of heritable disorders which are characterized by brittle bones but which are highly heterogeneous both phenotypically and biochemically.

Animals↗
PubMedDate not supplied

Human pro alpha 1(I) collagen gene structure reveals evolutionary conservation of a pattern of introns and exons.

The collagens represent an interesting example of a structurally related but genetically distinct family of proteins. Type I, the most abundant of the vertebrate collagens, comprises two pro alpha 1(I) chains and one pro alpha 2(I) chain, each containing terminal propeptides and a central domain of 338 (Gly, X, Y) repeats. The structure of the chicken pro alpha 2(I) gene shows an intriguing relationship between exon organization and the arrangement of (Gly, X, Y) repeats (see ref. 2 for review). This has led to the suggestion that the collagens evolved from a common ancestral unit of 54 base pairs (bp). Here we present the structure of the entire human pro alpha 1(I) gene and compare this with the chicken pro alpha 2(I). The exon arrangement of the two genes is remarkably similar, although the human pro alpha 1(I) is more compact because of the shorter length of its introns. The data strongly support the notion that the type I genes have evolved from an ancestral multi-exon unit, and that once the gene was translated, a strong evolutionary pressure caused it to maintain this elaborate structure.

Amino Acid Sequence↗