Biomedical subjects
Publications and source records attributed to H Lam.
A second instance of the unstable mutant Hb Nottingham (alpha2beta2 (FG5) 98 Val leads to Gly) is reported in a 7-year-old boy. Because of splenomegaly, cholelithiasis, and frequent episodes of abdominal pain, he underwent a splenectomy and cholecystectomy at age 6. The surgery resulted in both an amelioration of his RBC destruction and an acceleration of his rate of growth.
Hb Hofu, alpha 2 beta 2 [126 (H4) Va1 leads to Glu], was found in 10 members of 2 apparently unrelated Valmiki families in central India. None showed evidence of hemolysis and hemoglobin levels were normal in most. In two individuals, Hb Hofu occurred in combination with Hg S, but neither had clinical manifestations of sickle cell disease. In samples containing Hb Hofu, the isopropanol precipitation test was positive. Quantitation of the hemoglobin fractions by DEAE-cellulose chromatography showed that Hb Hofu constituted a mean of 23--25% of the total whether in combination with Hb A or Hb S.
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The T gamma chain of human fetal hemoglobin has a threonyl in stead of an isoleucyl residue in position 75. When the cord bloods from infants from varied ethnic backgrouds and geographic areas were tested for the presence of the T gamma chain, it was present in 28 or 98 samples. In some groups as many as 40% had the T gamma chain whereas none was detected in other. When the T gamma chain was present, its quantity was about 20% of the total gamma chains, but one case had 35%. Among beta-thalassemia homozygotes of the Mediterranean region, 70% and the T gamma chain in the amount of 20-50% of the total gamma chains, but seven Black beta-thalassemia homozygotes were negative for the T gamma chain. The fetal hemoglobin of 16 adult patients with sickle cell anemia had no T gamma chains, but 2 of 9 newborn children with sickle cell anemia had the T gamma chain. The frequency of the T gamma gene (16), the relationship of the T gamma gene to the G gamma and A gamma genes, and the significance of the T gamma gene are discussed.
The improved microchromatographic procedure for the detection of Hb-S and/or Hb-C in cord blood at birth (Schroeder et al.: J. Lab Clin Med 86:528-532, 1975) as well as a modification thereof may also be used for the quantitative determination of Hb-F in the presence of Hb-S and/or Hb-C. However, Hb-A interferes and must be absent. The methods use 0.5 X 6 cm columns of CM-cellulose with Tirs or Bis-tris developers and require 2-4 hr to complete. At low percentages of Hb-F, the sharper zone of the Tris method is more easily visible than that of the Bis-tris method, but the latter is a somewhat more rapid procedure. About 300 cases with Hb-S and/or Hb-C have been examined by the microchromatographic procedure. Most of these results (Fmicro) have been compared with data from the determination of Hb-F by one or more of the following methods: alkali denaturation (FAD), conventional DEAE-Sephadex chromatography (FDES), or isoleucine analyses of zones from DEAE-Sephadex chromatography (FIle). The accuracy and precision of the microchromatographic method is estimated to be 5-10%. The microchromatographic methods require much less time than conventional chromatography but more time than alkali denaturation procedures. Compared to the latter, the new methods use whole blood and less blood and permit the physical separation of Hb-F.
Substitution of CM-cellulose for CM-Sephadex had yielded a superior microchromatographic method for distinguishing the AS, AC, SS, SC, and CC conditions at birth. On the translucent columns of CM-Sephadex, the hemoglobin zones are somewhat diffuse. However, the compact, well-defined zones on the CM-cellulose column facilitate the interpretation of the results even though the amount of sample is only 20 per cent as great. The CM-cellulose method is as simple and rapid as the original CM-Sephadex procedure.