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Biomedical subjects

H Lam

Publications and source records attributed to H Lam.

At least 109 records · Page 6Linked to original sources
PubMed1982

Hb F-Columbus-Ga or alpha 2 G gamma 2 94(FGl) Asp replaced by Asn.

A new gamma chain variant with an electrophoretic mobility at pH 8.1 between those of Hb S and Hb C was isolated and quantitated by DEAE-cellulose chromatography. It was readily identified with the use of various micro-chromatographic and sequencing procedures as alpha 2 G gamma 2 94(FGl)Asp replaced by Asn. The hemoglobin was named Hb F-Columbus-Ga. The quantity of this G gamma chain variant (as % total gamma chain) was about 39% and the percentages of the normal G gamma and A gamma I chains were 37% and 24%, respectively.

Amino Acid Sequence↗
PubMed1982

Hb F-Bonaire-Ga or alpha 2 A gamma 2 39(C5) Gln replaced by Arg, characterized by high pressure liquid chromatographic and microsequencing procedures.

A slowly moving gamma chain variant was discovered in the cord blood of a baby of English-Vietnamese descent. The abnormality concerned the substitution of Gln residue in position 39(C5) of the A gamma chain by an Arg residue resulting in an -Arg-Arg- sequence at positions 39 and 40. The quantity of the A gamma chain variant was nearly 10% of the total Hb F with 15% of the Hb F having normal A gamma chains and 75% of Hb F having G gamma chains. High pressure liquid chromatographic and microsequencing methods greatly facilitated the structural analyses.

Amino Acid Sequence↗
PubMed1982

Abnormal hemoglobins in Northwestern Mexico.

Blood samples from 9,929 individuals in Northwestern Mexico were assayed for abnormal hemoglobins (Hbs). alpha-thal, beta-thal, beta s and beta c traits, as well as rare abnormal Hbs were observed with variable low frequencies (0 to 0.45%). Eight out of eleven rare abnormal Hbs detected so far have been characterized: Three Hb Riyadh, one Hb J Georgia, one Hb Fannin-Lubbock, one Hb Chiapas and two Hb Tarrant. These results suggest that abnormal Hbs do not constitute a regional public health problem and reflect a wide ethnologic heterogeneity.

Female↗
PubMed1981

Local regulation of blood flow in subcutaneous tissue in patients with acute myocardial infarction.

1. Local regulation of subcutaneous blood flow in the forearm was studied in the acute phase of myocardial infarction. Blood flow was measured by the local 133Xe-washout technique. 2. Plasma concentrations of noradrenaline and adrenaline were increased on day 1, suggesting an increase in sympathetic neuronal activity, but gradually returned to normal thereafter. 3. Subcutaneous blood flow on day 1 was far below normal (38%) and steadily increased to reach normal at day 7 after coronary occlusion. The sympathetic vasoconstrictor activity that caused the initial reduction in flow could be blocked by proximal nervous blockade, increasing the subcutaneous blood flow by 130, 63 and 14% on days 1, 3 and 7 respectively after coronary occlusion. A normal response to decrease in arterial perfusion pressure was observed, suggesting that intrinsic vascular reactions responsible for autoregulation of blood flow were not affected by the increase in sympathetic vasoconstrictor activity. The vasoconstrictor response to increase in venous transmural pressure could not be demonstrated on day 1 after coronary occlusion but gradually reappeared during the following days. 4. Abolition of the vasoconstrictor response is most likely to be due to a centrally elicited increase in sympathetic activity, as a normal vasoconstrictor response was obtained after proximal nervous blockade. Thus the local sympathetic reflex mechanism underlying the vasoconstrictor response appears to be suppressed by a centrally elicited increase in sympathetic discharge rate.

Adult↗
PubMed1981

Hb F-Meinohama or alpha 2 gamma 2 (5 Glu replaced by Gly; 75 Ile; 136 Gly).

During a survey of blood samples from newborn babies, a new fetal hemoglobin variant was observed which had a substitution of the normally occurring glutaminyl residue at position gamma 5 (A2) for a glycyl residue. The abnormal gamma chain had an isoleucyl residue at position 75 and a glycyl residue at position 136.

Amino Acids↗
PubMed1981

Heterozygosity and homozygosity for the high oxygen affinity hemoglobin Tarrant or alpha 126 (H9) Asp replaced by Asn in two Mexican families.

Two Mexican families from the State of Jalisco have been studied in which 11 members were carriers of Hb Tarrant. Ten subjects were Hb Tarrant heterozygotes producing about 25% of the abnormal hemoglobin. One 9-year-old boy was homozygous for Hb Tarrant. About 50% of his hemoglobin was of the variant type. The heterozygotes had mild erythrocytosis which was considerably more severe in the homozygote. The average P50 value for blood of the heterozygote was 15.1 mm Hg (controls: 22.5 mm Hg) while this value was decreased to 9 mm Hg in the homozygote. The clinical condition of the homozygote is compatible with a mild chronic tissue hypoxia.

Aspartic Acid↗
PubMed1981

Hb Wuming or alpha 2 11(A9)Lys substituting for Gln beta 2.

A fast-moving hemoglobin variant was found in five members of a Chinese family of the Wuming district. The relative amount of this alpha chain variant in the heterozygote was about 20%. The abnormality caused no ill effects in its carriers. Sequence analysis identified a Lys substituting for Gln substitution at position alpha-11 (A9).

Adult↗
PubMed1979

Separation of tryptic peptides of normal and abnormal alpha, beta, gamma, and delta hemoglobin chains by high-performance liquid chromatography.

High-performance liquid chromatography (HPLC) was used to separate tryptic peptides of the normal alpha, beta, gamma, and delta chains of human hemoglobins A, F, and A2 and of the abnormal chains of 25 hemoglobin variants. In addition, the separation of chymotryptic peptides of the oxidized core of the normal alpha chain by HPLC was evaluated. HPLC has several advantages over conventional methods used for the separation of proteolytic fragments of hemoglobin chains. The method is fast, and reproducible, and requires only small quantities of material. Several peptides are eluted as single zones, thus eliminating the need of rechromatography for further purification. Characteristic changes in the elution pattern of the peptides often indicate specific modifications.

Chromatography, High Pressure Liquid↗
PubMed1979

Further studies of the frequency and significance of the Tgamma-chain of human fetal hemoglobin.

A further study of the Tgamma-chain in a variety of conditions has revealed its presence in the cord bloods of ethnic groups previously unstudied. Heterozygous newborn average 17-19% Tgamma-chain while the mean value in four presumed homozygotes was 31%. The Tgamma-chain is readily detectable in beta-thalassemia of various ethnic groups (although infrequent in Blacks) as well as in deltabeta-thalassemia. Studies of a few families have provided an opportunity to determine whether or not certain individuals are heterozygous or homozygous for the Tgamma-gene. The Tgamma-chain has not been detected in the human fetal hemoglobin that is synthesized in increased amounts in persons with the hereditary persistence of fetal hemoglobin. Although the Tgamma-chain is detectable in sickle cell anemia, its frequency appears to be lower than in normal individuals. By focusing upon the relationship of the percentage of Tgamma-chain to the sources of human fetal globulin from determinants in cis and in trans, the conclusion has been reached that the Tgamma-chain is the product of a mutant Agamma-locus which should be named the TAgamma-chain.

Adult↗
PubMed1979

Hemoglobin Riyadh-beta 0-thalassemia in an Indian family.

An Indian (Asian) patient with compound heterozygosity for Hb Riyadh and beta 0-thalassemia is described. Hb Riyadh forms about 95% of the hemoglobin present. The clinico-pathological picture is identical to that of simple beta-thalassemia trait confirming the harmless nature of the substitution beta 120(GH3) Lys leads to Asn.

Adult↗
PubMed1979

The structure of goat hemoglobins. V. A fourth beta chain variant (beta-D-Malta; 69 Asp is replaced by Gly) with decreased oxygen affinity and occurring at a high frequency in Malta.

During a survey of hemoglobin types in goats in the Republic of Malta a variant (Goat Hb D-Malta) was discovered which differs from normal goat Hb A by the substitution of an aspartyl residue in position beta 69 (E13) by a glycyl residue. The gene frequency of the beta D allele was 0.255; 29 homozygous Hb D goats were present among 327 animals sampled. Homozygous Hb D goats also produce Hb C, whose beta chains are the product of a non-allelic beta C structural gene. Goat Hb D-Malta has a distinctly decreased affinity for molecular oxygen.

Amino Acid Sequence↗