ACETALDEHYDE ADDUCTS WITH HAEMOGLOBIN: DETERMINATION OF ACETALDEHYDE RELEASED FROM HAEMOGLOBIN BY ACID HYDROLYSIS

Acetaldehyde, the first metabolite of ethanol, reacts with haemoglobinin vitro to produce acetaldehyde—haemoglobin adducts.Some clinical studies on the minor haemoglobins have suggestedthat these adducts may be formed in people abusing alcohol.Under hydrolysis of haemoglobin, with oxalic acid at 100°Cin sealed vials, some acetaldehyde was released and then specificallydetermined by HPLC. The kinetics of hydrolysis were studiedusing haemoglobin previously labelled with ¹⁴[C] acetaldehyde.The maximum liberation of ¹⁴[C] acetaldehyde was obtained after3 hr 30 min hydrolysis and this time factor was then utilizedin the analysis of alcoholic and control haemoglobin. Thus,we have confirmed the formation of acetaldehyde haemoglobinadducts in vivo. It must be noted that the released acetaldehydecorresponds only to an index of the stable adducts. The levelswere higher in alcoholics than in controls (1.417±0.171and 1.295±0.139 nmol/mg Hb, respectively, P<0.001).In conclusion, this marker is not a convenient tool for themonitoring of alcohol exposure levels because of the low differencesbetween alcoholic and control haemoglobins.     

Expression of Haemophilus influenzae type b idiotype 1 on naturally acquired antibodies

The Chinese population in Hong Kong has a low incidence of invasive Haemophilus influenzae type b (Hib) disease, as well as carriage of the microorganism. Likely stimuli for the natural antibodies to Hib, which might protect against Hib infection, are cross-reactive antigens of bacteria like Escherichia coli K100. Our aim was to determine the isotype and idiotype distribution and cross-reactivity of natural antibodies against Hib capsular polysaccharide (CP) in healthy Hong Kong Chinese. Titration of 20 sera by ELISA showed IgG antibodies reacting with Hib CP in all individuals. The antibodies were mainly IgG2, and their avidity index ranged widely. Isoelectric focusing (IEF) combined with immunoblotting showed patterns of IgG2 antibody clones against the CP of Hib and E. coli K100 which were similar in 10 cases. Absorption with Hib CP only eliminated some bands in two sera. Absorption with K100 CP did not remove any anti-Hib CP bands. In three sera additional clones of antibodies reacting to K100 CP only, disappeared after absorption with this CP. Spectrotypic analyses of IgG antibodies reacting with anti-Hib idiotype 1 (Id-1) revealed stronger IEF patterns with bands in differing locations compared with anti-Hib CP antibodies. The strong reactivity of serum IgG, IgA and IgM antibodies with monoclonal anti-Hib Id-1 was confirmed by ELISA. This reactivity was not abolished after absorption of the sera with either Hib CP, or K100 CP. The data indicate a high prevalence of Id-1 among Hong Kong Chinese. However, only one individual had Id-1 antibodies specific for Hib CP, judging from absorption experiments. Others had much lower activity of Id-1 anti-Hib CP antibodies compared with the total IgG Id-1, suggesting that Hong Kong subjects have Id-1-positive antibodies in their serum which are not specific for Hib CP. This is consistent with the nature of Id-1, which is a marker of A2V_L region usage rather than a marker of a Hib CP paratope. We suggest that natural antibodies reacting with Hib CP in healthy Hong Kong Chinese are the product of exposure to some cross-reactive antigen(s), different from both Hib and E. coli K100 CP.     

The use of interferon-γ-treated U937 cells in chemiluminescence assays to detect red cell,platelet and granulocyte antibodies of potential clinical significance

Summary The chemiluminescent (CL) response of interferon-γ-treated U937 (IFN-U937) cells to sensitized target cells has been used to detect red cell, platelet and granulocyte antibodies. A clone of U937 cells was selected which expressed Fc receptor I (FcγRI) and which, after incubation with IFN-γ for 72 h, was capable of generating high levels of lucigenin-enhanced CL. The CL responses of IFN-U937 cells and peripheral blood human monocytes to sensitized red cells, platelets or granulocytes were then compared. Assays using monocytes or IFN-U937 cells were of comparable sensitivity for detection of antibodies against all three types of target cell. In addition, the use of IFN-U937 cells reduced interassay variation and simplified assay performance. The potential clinical usefulness of these CL assays was suggested by the ability of both monocytes and IFN-U937 cells to respond to red cells, platelets or granulocytes sensitized with sera from pregnant women whose babies had either haemolytic disease of the newborn (HDN), alloimmune thrombocytopenia or alloimmune neutropenia respectively. In addition, monocytes and IFN-U937 cells both responded to red cells sensitized with antibodies against a variety of specificities of assumed (although not documented) clinical significance for blood transfusion recipicnts. In contrast, monocytes and IFN-U937 cells responded only weakly to red cells sensitized with either anti-D in sera from mothers of babies unaffected by HDN, or with antisera containing high titre antibodies with specificities not normally associated with significantly reduced red cell survival.     

Inflammation and protein metabolism studies of carbon-14-labeled proteins in dogs with sterile abscesses

Carbon-14-labeled plasma proteins given by mouth to dogs with sterile abscesses undergo decreased absorption, presumably owing to impaired digestion of protein. The turnover of plasma albumin is greatly accelerated but the globulins, excluding fibrinogen, show little change during the acute stage of the sterile inflammation. Fibrinogen shows very rapid production and utilization during acute inflammation. Large amounts of C¹⁴ are incorporated in fibrinogen within a few hours after ingestion of the labeled material. The labeled fibrinogen largely disappears within 2 to 4 days after its production. The appearance of C¹⁴ in new red cells from labeled protein or amino acid sources is reduced by inflammation—evidence of impaired synthesis. The pus of the sterile abscess contains a good deal of C¹⁴ activity which at times is as much as that found in the liver. Pus cell C¹⁴ activity per milliliter is similar after injection of labeled plasma and ingestion of labeled plasma or lysine. However, the pus cell fraction contains 3 to 4 times more C¹⁴ activity per milliliter than does the supernatant fluid when the isotope is fed. In the supernatant fluid the activity is all within precipitable protein, much of which is probably derived from the blood plasma. In spite of increased loss of C¹⁴ as CO₂ in the expired air and in the pus, there is evidence of conservation of protein-building materials for maintenance of new plasma proteins and tissue proteins in the more active organs (e.g. liver)—a shift of protein C¹⁴ from the less active tissues (muscle and skin).     

Susceptibility of Riboflavin and Vitamin A in Breast Milk to Photodegradation and Its Implications for the Use of Banked Breast Milk in Infant Feeding

ABSTRACT. Up to 50 % of the riboflavin and up to 70 % of the vitamin A in human drip breast milk samples were destroyed during controlled exposure to daylight, either in translucent polythene bottles, or where the milk was pumped through naso-gastric tubing from a syringe to mimic the conditions of enteral feeding. Losses were also observed in milk which was exposed to standard phototherapy illumination under conditions similar to those encountered in the ward, and in this case riboflavin was destroyed to a greater extent than vitamin A. Photodegradation of riboflavin may contribute to the high incidence of biochemical riboflavin deficiency reported in preterm infants receiving breast milk without vitamin supplements. The implications of these findings for feeding high risk term and preterm infants on donor milk are discussed, and the use of low actinic vessels and tubing to minimise photodegradation is recommended.     

GROWTH HORMONE RESPONSE TO FEEDING IN TERM AND PRETERM NEONATES

ABSTRACT. Plasma growth hormone concentrations were measured in 248 healthy term and preterm infants. At birth growth hormone concentrations in cord blood from both term and preterm babies were approximately 100-fold higher than those in blood drawn from healthy adults. By the sixth postnatal day basal pre-feed levels had fallen in term neonates by 65% and a marked postprandial rise was apparent; preterm infants did not show this initial fall in preprandial hormone levels nor was any response to feeding seen. However a fall in preprandial concentrations accompanied by the development of postprandial surges in growth hormone occurred during the next 2 weeks so that by 24 days the postprandial rise was similar to that of term neonates on the sixth day. We conclude that although the initial postnatal changes in plasma growth hormone concentrations are different in preterm and term infants, feeding is a major stimulus to growth hormone secretion in both groups of neonates. Further work is needed to define the precise role of this hormone in neonatal metabolic adaptation.