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Biomedical subjects

A Cao

Publications and source records attributed to A Cao.

At least 271 records · Page 15Linked to original sources
PubMed1983

Effect of subcutaneous desferrioxamine on iron balance in young thalassemia major patients.

In this study we evaluated the effect of 1-year, subcutaneous desferrioxamine daily infusion on iron balance in 23 thalassemia major children, aged 8-74 months, with transfusional iron accumulation less than 3.8 g at the outset of the trial. Statistical analysis showed a significant correlation between transfusional iron accumulation and percentage of transfusional iron eliminated. Confidence limits analysis of these data indicated that over 3.5 g of transfusional iron load, 95% of the patients may achieve balance. The appropriate time to begin desferrioxamine infusion, therefore, seems to be after about 30 transfusions of packed red blood cells when iron accumulation of approximately 3 g is reached. As we found a statistically significant correlation between transfusional iron eliminated and serum ferritin levels, the evaluation of serum ferritin alone can also predict when balance can be obtained.

Age Factors↗
PubMed1982

An analytical approach to single photon emission computed tomography with the attenuation effect.

The problem of transverse plane reconstruction from an ensemble of projections is considered in its general formulation and an analytically exact solution to the attenuated tomographic operator is proposed. Such a technique, called the regularizing iterative method (RIM), allows the introduction of a priori knowledge on the size and shape of the activity distribution and in principle on the exact attenuation distribution. The relaxation factor used is so named because it provides noise filtering for a small number of iterations. The effectiveness of RIM was studied in the single photon emission computed tomography (SPECT) problem with the aim of correcting for attenuation before quantitative study. Its application involves the use of a rotating scintillation camera connected to a mini-computer system. Various mathematical and physical phantoms were studied, and a satisfactory attenuation correction was always obtained in the final image with an improvement in the contrast and signal-to-noise ratio. Preliminary clinical studies on liver transverse sections seems to indicate an improvement in deep lesion detectability, compared with images obtained by the filtered (Ramp) back projection technique.

Models, Structural↗
PubMed1982

Molecular comparison of delta beta-thalassemia and hereditary persistence of fetal hemoglobin DNAs: evidence of a regulatory area?

The hematological phenotypes of several Mediterranean patients with delta beta-thalassemia and hereditary persistence of fetal hemoglobin have been characterized. Although clinical and hematological characteristics are essentially superimposable in all heterozygous delta beta-thalassemics, these patients show typical G gamma/A gamma ratios in their Hb F, ranging from approximately 0.07 in Sardinian to approximately 0.15 in Sicilian and approximately 0.35 in Spanish patients. A gamma Sardinian-(isoleucine-75 leads to threonine) is found in Spanish patients and accounts for all of the A gamma production in heterozygotes, indicating that persistent production of gamma chains occurs cis to the delta beta-thalassemia gene. The molecular heterogeneity of these conditions is demonstrated by restriction enzyme mapping of DNA; Sicilian and Calabrian patients show a deletion starting from the delta-globin intron and extending several kilobases 3' to the beta-globin gene; in Spanish patients the deletion starts approximately 2-3 kilobases 5' to the delta-globin gene and extends well beyond the beta-globin gene. Comparison of these deletions with previously described ones in Negro and in a new Southern Italian case of hereditary persistence of fetal hemoglobin suggests that the deletion of a region centered at a cluster of repetitive sequences approximately 3.5 kilobases 5' to the delta-globin gene may be critical for the persistent expression of high levels of gamma-globin in hereditary persistence of fetal hemoglobin compared to delta beta-thalassemia. The concept that the deletion or mutation of specific areas (rather than nonspecific changes brought about by large deletions in the globin cluster) is important in determining the persistent expression of gamma-globin genes is supported by the finding of a nondeletion type of delta beta-thalassemia in Sardinians.

Chromosome Deletion↗
PubMed1982

The interaction of alpha thalassaemia with heterozygous beta thalassaemia.

The alpha globin genotypes of 55 beta thalassaemia heterozygotes have been determined by restriction endonuclease analysis to identify those with interacting alpha thalassaemia genes. A comparison of the haematological and haemoglobin synthesis findings of individuals with normal alpha genotypes (alpha alpha/alpha alpha) with those with one (-alpha/alpha alpha) or two (-alpha/-alpha) alpha genes deleted shows that the latter two groups have more balanced globin chain synthesis ratios, higher haemoglobin levels, and larger, better haemoglobinized red cells. This suggests that the degree of globin chain imbalance is a significant factor in determining the red cell characteristics in heterozygous beta thalassaemia. Screening programmes for thalassaemia, based on the detection of low MCVs, could miss cases of the interaction of alpha and beta thalassaemia.

Chromosome Mapping↗
PubMed1982

Haematological and obstetric aspects of antenatal diagnosis of beta-thalassaemia: experience with 200 cases.

The results of 200 antenatal diagnoses in pregnancies at risk for homozygous beta-thalassaemia, carried out on fetal blood samples obtained by placental aspiration in the second trimester, are described. Globin chain synthesis in the fetuses was measured by means of 3H-leucine incorporation and separation of the chains on carboxy-methyl-cellulose columns. Fetal red cell enrichment was performed by NH4Cl-NH4HCO3 differential lysis of maternal cells or anti-i differential agglutination. Sufficient fetal blood for analysis was obtained in 97.5% of the cases. The overall fetal loss rate was 6.5%, but it declined from 10% in the first consecutive 100 cases to 3% in the last 100 cases. Fetal loss was the result of early or late intrauterine death or spontaneous abortion. Forty-two homozygous fetuses had no beta-chain synthesis and one had a very low beta/gamma ratio (0.005). Of the pregnancies, 37 were terminated at parental request and four aborted spontaneously. Absence of beta-chain radioactivity was confirmed in 12 abortuses with suitable cord blood samples for analysis. Two pregnancies with homozygous fetuses were not terminated, as one member of each couple was a devout Catholic. As expected, both infants developed Cooley's anaemia. Follow-up of the 146 infants, diagnosed in utero as non-homozygotes, showed cerebral palsy in one and a small cutaneous needle injury in three. None of these developed homozygous beta-thalassaemia. Even beta-thalassaemia trait with a beta/gamma ratio of 0.046 +/- 0.012 can be distinguished from normal, showing a beta/gamma ratio of 0.086 +/- 0.019 with a high degree of certainty.

Abortion, Induced↗
PubMed1982

Delta beta (F)-thalassaemia in Sardinia.

A population survey carried out in southern sardinia on more than 5000 people has shown that delta beta (F)-thalassaemia, with a gene frequency of 0-00088, is a rare trait in this population. We examined the members of three families segregating for both delta beta- and beta(0)-thalassemia and a number of delta beta carriers identified during the screening. The doubly heterozygous children suffer from a mild form of Cooley's disease with non-alpha/alpha biosynthetic ratios within the range of values observed in beta (0)-thalassaemia homozygotes. Three of them have been transfusion dependent for some time. The delta beta carriers, although in many respects showing the usual picture of delta beta-thalassaemia, such as abnormal red cell indices, normal Hb A2, Hb F heterogeneously distributed in the erythrocytes, and low beta/alpha synthetic ratios, have unusually high levels of Hb F (range 10 to 20%) and particularly low glycine content (range 0.02 to 0.14 residues) in the isolated gamma CB3 peptide. These results have led us to the conclusion that the delta beta-thalassaemia found in Sardinia is different from the similar kind of delta beta defect found in Negroes and in other Mediterranean populations, including continental Italians.

Adolescent↗
PubMed1982

Iron chelation in transfusion-dependent thalassemia with chronic hepatitis.

In this study maximum urinary iron elimination with continuous desferrioxamine subcutaneous infusion was obtained in thalassemia major patients with chronic persistent or active hepatitis with lower doses (60 mg/kg) than those necessary in patients without hepatitis (80 mg/kg). Since dose-response curves were highly variable the treatment schedule should be tailored to the individual needs of each patient. Both groups may achieve iron balance but chronic hepatitis patients have more frequently a net urinary iron excretion. In patients with chronic hepatitis no correlation was found between serum ferritin levels or serum ferritin/aspartate aminotransferase ratios and transfusional iron overload while serum ferritin/aspartate aminotransferase ratios were seen to be correlated with liver iron stores.

Adolescent↗
PubMed1982

Determination of organ volume by single-photon emission tomography.

A method for estimation of organ volume is proposed, based on analysis of individual slices obtained from SPET images. In a phantom simulating clinical circumstances, the data show that the level a threshold at 46% of the maximum activity predicts most closely the true volume over a wide range above one liter. The level at 45% predicted better volumes of less than one liter. For phantoms of 839 ml or less, the error was 6.3 ml (one standard error of estimation). This level seems to be independent of the plane or position of the phantom and also independent of the amount of scattering material around it. Nonradioactive voids ("holes") within a phantom may be included or excluded at will when their edges are not tangent to the edge of the phantom. In such cases, their edges are not distinguishable from the edge of the phantom and their volumes are excluded. Knowledge of organ volumes has both diagnostic and therapeutic importance and could lead to a more precisely quantitated total of the radioactivity contained in an organ or space.

Models, Structural↗
PubMed1982

Alpha-thalassemia in two Mediterranean populations.

We used restriction endonuclease analysis to determine the incidence of alpha-thalassemia in two Mediterranean islands. In a random population sample, the gene frequency of deletion-type alpha-thalassemia-2 (-alpha) was 0.18 in Sardinians and 0.07 in Greek Cypriots. All cases were the rightward crossover type. From these frequencies and the known incidence of hemoglobin-H disease in these populations, we calculated the frequency of the alpha-thalassemia-1 genotype (--) and determined that it was low. We also found that beta-thalassemia homozygotes in sardinia have a higher incidence of alpha-thalassemia than normals and beta thalassemia heterozygotes because a significantly greater number of these homozygotes are also homozygous for the alpha-thalassemia-2 lesion. These findings support the theory that coinheritance of alpha-thalassemia mitigates the severity of beta-thalassemia and suggest that the protection is most pronounced when two alpha-globin genes are deleted.

Cyprus↗
PubMed1981

Iron overload and desferrioxamine chelation therapy in beta-thalassemia intermedia.

This study on serum ferritin levels in urinary iron excretion after 12h subcutaneous infusion of desferrioxamine in 10 thalassemia intermedia patients shows that even nontransfusion-dependent patients may have positive iron balance resulting in iron overload from 5 years of age. However, the iron overload found in these patients appears to be much lower than in age matched patients with transfusion-dependent thalassemia major. Iron overload increases with advancing age, as shown by increasing serum ferritin levels and desferrioxamine-induced urinary iron elimination. After a six month trial of 12h continuous subcutaneous desferrioxamine administration there was a significant decline in serum ferritin levels. From this study it seems that iron chelation is indicated in thalassemia intermedia patients over 5 years of age in order to prevent iron accumulation. However, the appropriate treatment schedule should be tailored to the individual needs of each patients, established by close monitoring of serum ferritin levels and desferrioxamine-induced urinary iron elimination.

Adolescent↗