The effect of HFE genotypes on measurements of iron overload in patients attending a health appraisal clinic.

BACKGROUND: The gene that causes most cases of hereditary hemochromatosis is designated HFE. Three mutations exist at this locus at a relatively high gene frequency. OBJECTIVE: To determine the gene frequency of the three HFE mutations and to relate genotypes to various clinical and laboratory variables. DESIGN: Observational study. SETTING: Health appraisal clinic. PATIENTS: 10,198 adults who registered for health appraisal and consented to DNA examination for hemochromatosis. Consenting patients were slightly older and had attained a slightly higher educational level than nonconsenting patients. MEASUREMENTS: Extensive medical history and laboratory tests, including complete blood count, transferrin saturation, and other chemistries; serum ferritin levels; and HFE genotype. RESULTS: In white participants, the gene frequencies were 0.063 for the C282Y mutation, 0.152 for the H63D mutation, and 0.016 for the S65C mutation. Gene frequencies were lower in other ethnic groups. In participants with HFE mutations, the average serum transferrin saturation and ferritin levels were slightly increased, as were mean hemoglobin levels and mean corpuscular volume. A transferrin saturation of 50% had a sensitivity of only 0.52 (95% CI, 0.345 to 0.686) and a specificity of 0.908 (CI, 0.902 to 0.914) for detection of homozygosity. A ferritin level of 200 microg/L in women and 250 microg/L in men had a sensitivity of 0.70 (CI, 0.540 to 0.854) and a specificity of 0.803 (CI, 0.796 to 0.811). The prevalence of iron deficiency anemia was lower in women who carried HFE mutations. CONCLUSIONS: Screening for transferrin saturation and ferritin levels does not detect all homozygotes for the major hemochromatosis mutation. Heterozygotes for HFE mutations had a lower prevalence of iron deficiency anemia.

Assessment of roles of surface histidyl residues in the molecular basis of the Bohr effect and of beta 143 histidine in the binding of 2,3-bisphosphoglycerate in human normal adult hemoglobin.

Site-directed mutagenesis has been used to construct two mutant recombinant hemoglobins (rHbs), rHb(betaH116Q) and rHb(betaH143S). Purified rHbs were used to assign the C2 proton resonances of beta116His and beta143His and to resolve the ambiguous assignments made over the past years. In the present work, we have identified the C2 proton resonances of two surface histidyl residues of the beta chain, beta116His and beta143His, in both the carbonmonoxy and deoxy forms, by comparing the proton nuclear magnetic resonance (NMR) spectra of human normal adult hemoglobin (Hb A) with those of rHbs. Current assignments plus other previous assignments complete the assignments for all 24 surface histidyl residues of human normal adult hemoglobin. The individual pK values of 24 histidyl residues of Hb A were also measured in deuterium oxide (D(2)O) in 0.1 M N-(2-hydroxyethyl)piperazine-N'-2-ethanesulfonic acid (HEPES) buffer in the presence of 0.1 M chloride at 29 degrees C by monitoring the shifts of the C2 proton resonances of the histidyl residues as a function of pH. Among those surface histidyl residues, beta146His has the biggest contribution to the alkaline Bohr effect (63% at pH 7.4), and beta143His has the biggest contribution to the acid Bohr effect (71% at pH 5.1). alpha20His, alpha112His, and beta117His have essentially no contribution; alpha50His, alpha72His, alpha89His, beta97His, and beta116His have moderate positive contributions; and beta2His and beta77His have a moderate negative contribution to the Bohr effect. The sum of the contributions from 24 surface histidyl residues accounted for 86% of the alkaline Bohr effect at pH 7.4 and about 55% of the acid Bohr effect at pH 5.1. Although beta143His is located in the binding site for 2,3-bisphosphoglycerate (2,3-BPG) according to the crystal structure of deoxy-Hb A complexed with 2, 3-BPG, beta143His is not essential for the binding of 2,3-BPG in the neutral pH range according to the proton NMR and oxygen affinity studies presented here. With the accurately measured and assigned individual pK values for all surface histidyl residues, it is now possible to evaluate the Bohr effect microscopically for novel recombinant Hbs with important functional properties, such as low oxygen affinity and high cooperativity. The present study further confirms the importance of a global electrostatic network in regulating the Bohr effect of the hemoglobin molecule.

The effect of transferrin polymorphisms on iron metabolism.

The effect of five different transferrin variants (TFv1, TFv2, TFv3, TFv4, and TFv5) on the hemoglobin level, mean corpuscular volume (MCV), ferritin level, percent transferrin saturation (%TS), and the unsaturated iron binding capacity (UIBC) was investigated in subjects with defined HFE haplotypes, 919 persons undergoing health screening and 113 patients with clinical hemochromatosis. The most common variant is TFv4; the population distribution of this variant was also studied. None of the variants were found to have an effect on any of the parameters of iron metabolism that were investigated. Moreover, the frequency of these variants in patients with clinically significant hemochromatosis was no different from that in the general population. We conclude that these polymorphisms in transferrin do not play a role in the expression of hemochromatosis, nor do they produce any other significant changes in iron metabolism.

Perinatal infections--problems in developing countries.

The transmission of infections from the biologic mother to her offspring is popularly known as perinatal infection (PI). It is not synonymous to infections during the perinatal or neonatal period. Physicians should avoid focusing attention only on the TORCH agents in the evaluation of suspected PI. Perinatal period begins from 28 weeks of gestation. Would one consider in utero infections in the first or second trimester of pregnancy as PIs? Developing countries have difficulty in collecting reliable and accurate data of PIs. These data are useful to define the magnitude of the problems, to monitor the trends, to recognise the mode of spread, and to find a solution of PIs. Most PIs are asymptomatic and diagnosis is extremely difficult. Developing countries need rapid, easy-to-operate, simple, and cheap diagnostic tools urgently. Access to health care in the remote city is limited. Newer drugs are too expensive and very few patients can benefit from these. Each developing country should prioritize its PI problems and tackle those that have serious public health problems and socio-economic impact. Most developing countries should focus on HIV (human immunodeficiency virus) and HBV (hepatitis B virus) infections. Other countries where ophthalmia, malaria or tuberculosis are prevalent or endemic, should focus on these. Developing countries are more willing to allocate the budget for prevention of diseases than for treatment. There may be problem of promulgating the information on prevention of diseases because of illiteracy, multi-lingual community. Vaccines where available, should be affordable. Other effective prevention guidelines should be workable in poorer nations. The government should play an important role in enforcing immunisation program by intensive promotion program or by legislation.

A starch-hemoglobin resuscitative compound.

A resuscitative compound in freeze-dried form has been synthesized between a modified starch and a tetremerically stabilized hemoglobin. In order to complex the hemoglobin, the starch has been prepared in mono-, di-, tri-, and tetra-aldehyde moieties. The hemoglobin was stabilized with low molecular weight diacids. Electrophoretic densitometric patterns indicate compound formation. The resulting polymers were characterized with respect to oxygen transport (biotonometry), Hill constant and P50. The in vivo evaluation indicates that these compounds are effective in exchange-transfusion experiments with rats to a level of about 85% replacement of whole blood. The final product is a cost-effective acellular resuscitative compound which can be stored in freeze-dried form at room temperature for extended periods of time. This artificial blood substitute can be reconstituted upon the addition of water.

Outcome of the extremely low birth weight infants (less than 999 grams): what messages are we getting?

The outcome of the extremely low birth weight (less than 1,000g or ELBW) babies continues to improve. More ELBW babies are surviving, though some of them may have various degrees of impairment or disability. The chance of dying or surviving with a major disability or cerebral palsy declines significantly in recent years in the developed countries. The implication of these findings is that application of neonatal care does not increase the risk of disabled survival as has been often feared but promoted normal survival. Great effort has been put in to achieve good results and better outcome. Developing countries however, will face a problem of achieving similar results because of limited resources or priority of allocation of limited resources, inadequate facilities, lower socio-economic status, poor home environment and lack of follow-up services, training and rehabilitation set-ups or intervention programme. What is the relevance of these good results in relation to the developing or third world countries? The limit of viability may have to be redefined. Nevertheless, it should be the aim to lower the mortality of these high risk babies and to reduce complications and morbidity of the survivors. Maintenance and control of body temperature, control of infections, blood sugar monitoring, antenatal steroids for the mother in premature labour, resuscitation at birth or even simple nasal continuous positive airway pressure (CPAP) should come a long way in fulfilling these goals. Those ELBW children who survive without neurological damage may have learning difficulties. It is necessary to find out the reasons for that such as the impact of the home environment on mental development. Do the children have a good background conducive for learning? Are there establishments for intervention programme in the community for these high risk children? The ratio of neonatal beds per 1,000 deliveries may have to be reviewed now that more ELBW infants are staying in the hospital for a longer period, and surviving.

Resuscitation of the small baby--is there a limit?

Innovations in perinatal care in the last decade, in particular delivery room resuscitations and advanced technologies have probably contributed greatly to improved survival of the small newborns. As a result, progressively smaller and less mature infants are being resuscitated; but some survive with severe neurodevelopmental handicap. There should be guidelines about the lower limits of viability below which no resuscitation should be done. It is the view of many that resuscitation of critically ill small babies should be initiated at birth. Further management will be decided depending on the baby's progress and response. Clinicians have to look into the question of withdrawal of life support in small babies who survive with impairment and chronic illnesses.

Economical modification of a radioimmunoassay of digoxin with negligible interference from cord and neonatal sera.

The Amerlex digoxin radioimmunoassay was modified to reduce the running cost by five times. The modified method compared well with the original method (y = 1.0138x + 0.00916, r = 0.9936). Using the modified method, the performance with the American Association for Clinical Chemistry quality control program was consistently satisfactory for 1 year. When normal cord and neonatal sera were tested with the modified method, 41% of the 22 samples of cord serum and 68% of the 19 samples of neonatal serum produced digoxin levels less than or equal to 0.05 ng/ml. The highest digoxin level produced by cord and neonatal sera was 0.3 ng/ml.