乳糖吸收不良、乳糖不耐受与人体健康关系探讨

由于乳糖在人体生长发育和新陈代谢中发挥着重要作用,LM或LI不仅可诱发小儿佝偻病、成人骨质疏松,而且还可造成人体腹泻、影响婴幼儿脑组织和神经系统的构建,对婴幼儿的体格发育和智力发育造成损害。本研究对乳糖不耐受的病因及发病因素、分型、流行病学、临床及实验室诊断方法等做一概述,为临床实践和科学研究提供参考。     

Evolution of milk oligosaccharides and lactose: a hypothesis

Mammalian milk or colostrum contains up to 10% of carbohydrate, of which free lactose usually constitutes more than 80%. Lactose is synthesized within lactating mammary glands from uridine diphosphate galactose (UDP-Gal) and glucose by a transgalactosylation catalysed by a complex of β4-galactosyltransferase and α-lactalbumin (α-LA). α-LA is believed to have evolved from C-type lysozyme. Mammalian milk or colostrum usually contains a variety of oligosaccharides in addition to free lactose. Each oligosaccharide has a lactose unit at its reducing end; this unit acts as a precursor that is essential for its biosynthesis. It is generally believed that milk oligosaccharides act as prebiotics and also as receptor analogues that act as anti-infection factors. We propose the following hypothesis. The proto-lacteal secretions of the primitive mammary glands of the common ancestor of mammals contained fat and protein including lysozyme, but no lactose or oligosaccharides because of the absence of α-LA. When α-LA first appeared as a result of its evolution from lysozyme, its content within the lactating mammary glands was low and lactose was therefore synthesized at a slow rate. Because of the presence of glycosyltransferases, almost all of the nascent lactose was utilized for the biosynthesis of oligosaccharides. The predominant saccharides in the proto-lacteal secretions or primitive milk produced by this common ancestor were therefore oligosaccharides rather than free lactose. Subsequent to this initial period, the oligosaccharides began to serve as anti-infection factors. They were then recruited as a significant energy source for the neonate, which was achieved by an increase in the synthesis of α-LA. This produced a concomitant increase in the concentration of lactose in the milk, and lactose therefore became an important energy source for most eutherians, whereas oligosaccharides continued to serve mainly as anti-microbial agents. Lactose, in addition, began to act as an osmoregulatory molecule, controlling the milk volume. Studies on the chemical structures of the milk oligosaccharides of a variety of mammalian species suggest that human milk or colostrum is unique in that oligosaccharides containing lacto-N-biose I (LNB) (Gal(β1 → 3)GlcNAc, type I) predominate over those containing N-acetyllactosamine (Gal(β1 → 4)GlcNAc, type II), whereas in other species only type II oligosaccharides are found or else they predominate over type I oligosaccharides. It can be hypothesized that this feature may have a selective advantage in that it may promote the growth of beneficial colonic bacteria, Bifidobacteria, in the human infant colon.     

Lymphadenopathy and selective IgA deficiency.

Four men presented with unexplained lymphadenopathy. Three had a history of recurrent respiratory infections for several years, and two had lymph node or hepatic granulomas. None was noted to have symptoms of immunodeficiency at the time of presentation. In one patient routine direct immunofluorescence study failed to detect IgA, and immunological investigations were therefore conducted in the rest. In all patients the findings were similar and characterised by a severe deficiency of IgA. In the absence of a more serious cause selective IgA deficiency may be enough to explain "idiopathic" lymphadenopathy.     

A novel mutation for TAP deficiency and its possible association with Toxoplasmosis

We describe two siblings (a male patient and his older sister) with a novel mutation in the peptide transporter associated to antigen processing (TAP). The index case presented with not only granulomatous skin lesions and recurrent sino-pulmonary infections, often associated with this deficiency, but also a severe pulmonary toxoplasmosis. His toxoplasmosis and skin lesions were successfully treated.     

Correlative secretion of protein, lactose and K + in milk of the goat

Rates of secretion of milk constituents (fat, protein, lactose, Na⁺ and K⁺) in the lactating goat were measured under normal circumstances and after injections of ouabain. In all experiments a close association was noted in the secretion rates for protein, lactose and K⁺. Under the influence of ouabain, the concentration of Na⁺ in the milk tended to rise and that of K⁺ to fall. The rate of milk fat secretion varied independently from the rates for the other constituents. It is reasonably assumed that the principal mechanism of milk protein secretion is by emptying of Golgi vesicles through the plasma membrane. The close correlation in rates for protein, lactose and K⁺ supports the contention that all three are assembled in Golgi vesicles and secreted by the same mechanism.     

Clinical aspects of cow milk protein and gluten intolerance in children

In two comparative groups of 50 children with cow milk proteins and 45 children with gluten intolerance retrospective analysis of initial symptoms was carried out. The initial symptoms of intolerance included: vomiting, loss of appetite, recurrent diarrhoea, and weight gain disorders. These symptoms closely correlated with the type of nutrition (mixed, artificial) and the duration of exposition to harmful component of the food. The symptoms appeared within first days after birth with peak intensity in 6-8 weeks of life in the group with cow milk proteins intolerance. The symptoms of intolerance were most frequent in children of group II in 7-12 months of life. To prevent food intolerance in Polish children, it is recommended to feed them naturally as long as possible and to introduce flour and 4 basic grains late (after the 6th months of life).     

Monoclonal antibodies to soluble, human milk galactosyltransferase (lactose synthase A protein)

Monoclonal antibodies have been produced against soluble human milk galactosyltransferase of a blood group O donor. After initial screening by radioimmunoassay, fourteen hybridomas were further characterized by enzyme-linked immunosorbent assay, immunoblotting of purified enzyme following sodium dodecyl sulfate-polyacrylamide gel electrophoresis, enzyme activity modification, and enzyme localization in HeLa cells by immunofluorescence. Of these fourteen clones, seven had titers between 1500 and 7800 as estimated by ELISA. In general, the titer correlated with staining intensity on immunoblots and in immunofluorescence. In the presence of monoclonal antibody, enzyme activity was usually slightly enhanced or stabilized. Subcloning yielded four monoclonal antibody preparations designated as GT2/24/108, GT2/36/118, GT2/61/14, and GT2/77/22, which belong to Ig class G2b, G3, M, and G1, respectively. They all recognized the enzyme in purified form or in defatted milk as a single, broad band on electrophoresis-immunoblotting and produced a concise juxtanuclear fluorescence typical for the Golgi apparatus in HeLa cells.     

Case report. Cervical carcinoma with selective IgA deficiency

A patient with cervical carcinoma was found to have selective IgA deficiency. The intact cell-mediated immunity, normal levels of IgG and IgM, and the absence of serum and salivary IgA established the diagnosis. Contrary to those of normal persons, salivary IgM was elevated and salivary IgA was not detectable in this patient. The patient had no signs attributable to IgA deficiency, but she always had dryness of the mouth. The association between cervical carcinoma and selective IgA deficiency was discussed.     

Placental steroid deficiency: association with arylsulfatase A deficiency

A family with an obstetric history consistent with placental sulfatase deficiency has X-linked ichthyosis. Steroid sulfatase deficiency was confirmed in placenta, leukocytes, and cultured skin fibroblasts of affected males; arylsulfatase A diminution was also observed in these tissues of both affected males and 2 generations of related females. No symptoms of metachromatic leukodystrophy are present in any family members. In this family, placental sulfatase deficiency, and arylsulfatase A pseudodeficiency are nonallelic.