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1.
Dispersed ovine luteal cells collected on day 7 or 16 postestrus were incubated in vitro with hCG, PGE1 or PGE2 in the presence or absence of adenosine, dipyridamole (inhibitor of adenosine uptake) or PGF2 alpha in two separate experiments. Secretion of progesterone was increased by hCG, PGE1 or PGE2 when incubated with day 7 luteal cells (P less than or equal to 0.05) which was increased further when co-incubated with adenosine (P less than or equal to 0.05). PGF2 alpha alone or in the presence of hCG decreased (P less than or equal to 0.05) the secretion of progesterone by day 7 luteal cells, PGF2 alpha decreased post treatment cell viability with or without hCG (P less than or equal to 0.05) and adenosine reduced (P less than or equal to 0.05) the inhibitory effect of PGF2 alpha on hCG actions and luteal cell viability. Day 16 luteal cells were not functional based on jugular progesterone (P less than or equal to 0.05) and did not respond to hCG, PGE1, or PGE2 in the presence of adenosine or PGF2 alpha (P greater than or equal to 0.05). It is concluded that adenosine enhances the response of functional luteal cells to the luteotropins hCG, PGE1 or PGE2 and adenosine reduces the luteolytic response to PGF2 alpha by hCG-stimulated ovine luteal cells in vitro.  相似文献   

2.
Experimental intrauterine growth retardation was studied in sheep. Endometrial caruncles (anlagen of maternal cotyledon) were removed before pregnancy and at a second operation, catheters were implanted into the ewe and fetus at 105-135 days of pregnancy. Three groups of fetuses were defined: low birthweight-for-dates (small-caruncle), normal birthweight-for-dates (normal-sized-caruncle) from ewes which had endometrial caruncles removed and the controls. The mean placental weights in these groups were 139 plus or minus 5 g, 283 plus or minus 46 g, 334 plus or minus 22 g respectively. The brains, kidneys and adrenals of the small-caruncle-fetuses were significantly greater in proportion to body weight than in the controls and the appearance of ossification centres was delayed. Arterial oxygen tension was lower and packed cell volume higher in the small-caruncle-fetuses (PaO2 15 plus or minus 0.6 mmHg; packed cell volume 37.3 plus or minus 1.6%) and normal sized caruncles (PaO2 20.7 plus or minus 1.2 mmHg; packed cell volume 35.2 plus or minus 0.7%) than in the controls (PaO2 23.2 plus or minus 0.7 mmHg; packed cell volume 29.8 plus or minus 0.7%). Plasma concentrations of glucose (0.65 plus or minus 0.12 micromol/ml), lactate (0.9 plus or minus 0.1 micromol/ml) and pyruvate (0.08 plus or minus 0.025 micromol/ml) were lower in small-caruncle fetuses than in the control fetuses (glucose 1.05 plus or minus 0.06 micromol/ml, lactate 1.83 plus or minus 0.7 micromol/ml, pyruvate 0.21 plus or minus 0.06 micromol/ml). The corresponding values for the normal-sized-caruncle fetuses were glucose 0.71 plus or minus 0.12, lactate 1.18 plus or minus 0.7 and pyruvate 0.12 plus or minus 0.03 micromol/ml. The plasma concentration of alanine in the small-caruncle-fetuses (0.25 plus or minus 0.09 micromol/ml) was higher than in the normal-sized-caruncle (0.073 plus or minus 0.009 micromol/ml) or control fetuses (0.12 plus or minus 0.013 micromol/ml). The results indicate that fetal growth retardation due to restriction of placental growth after removal of endometrial caruncles is associated with chronic hypoxaemia, polycythaemia and hypoglycaemia. The restriction of nutrient supply probably accounts for the altered pattern of fetal growth but the relative importance of the changes observed remains uncertain.  相似文献   

3.
中国红豆属植物的叶表皮形态学   总被引:3,自引:0,他引:3  
用光学显微镜和扫描电子显微镜观察了红豆属(Ormosia)35种的叶表皮形态,这些植物的叶上下表皮细胞为不规则形或多边形,垂周壁有平直、弓形、浅波状或深波状,表皮细胞形状和垂周壁在种间有一些差异。气孔仅存在于下表皮,形状为椭圆形或卵形,以平列型为主;此外还有其他类型的气孔,如长脐红豆、海南红豆等的气孔为不规则形、不等型;少数种类如亮毛红豆、茸荚红豆等的气孔不明显。气孔外拱盖光滑,呈浅波状、波状或不明显,气孔内拱盖光滑、近光滑、浅波状或不明显;蜡被近光滑、颗粒状、鳞片状、条纹状或结网状;多数种具毛被。叶表皮与气孔器特征可作为区分种、变种或亚种的依据。叶表皮微观形态特征支持红豆属成为一个自然类群。  相似文献   

4.
Summary Neonate rat endocranial osteoblasts were cultured on their bone surfaces in control medium (CC) or medium to which either parathyroid extract (PTE) or calcitonin (CT) had been added for 2, 4, 8 or 24 h. Some were cultured for 24 h in CC, then for 2, 4, 8 or 24 h in either CT or PTE medium; or for 24 h in PTE, then for 2, 4, 8 or 24 h in either CC or CT; or 24 h in CT and 2, 4, 8 or 24 h in CC. The dorsal ruffling of the cells in CC was found to be suppressed by later culturing with PTE and the disoriented cells reorganized to form arrays of parallel cells. The effects of PTE were also reversed by CC or CT: the osteoblasts in the second culture (CC) lost elongation and order, and proceeded through a proliferative phase before exhibiting the ruffling form similar to a single CC 24 h culture. PTE-cultured osteoblasts showed an increase in cell overlap and contact so that a more competent barrier was formed separating the bone from the medium. In control or CT medium, however, intercellular gaps were greater than in vivo.We are grateful for the expert technical assistance of Elaine Bailey, for laboratory facilities kindly provided by Dr. Martin Evans, and for financial support from the Medical Research Council  相似文献   

5.
Induction and persistence of adaptive response by aluminium (Al), 1 or 10 microM, and paraquat (PQ), 5 or 10 microM, against genotoxicity of methyl mercuric chloride (MMCl), 1.26 microM, a standard environmental genotoxin, was investigated in root meristem cells of Allium cepa. Subsequently, three metabolic inhibitors, namely, 3-aminobezamide (3-AB, 10 or 100 microM), an inhibitor of poly(ADP-ribose) polymerase (PARP) implicated in DNA repair and/or apoptosis, cycloheximide (CH, 0.1 or 1 microM), an inhibitor of protein synthesis, and buthionine sulfoximine (BSO, 100 microM or 1mM), an inhibitor of glutathione synthesis were tested for their ability to prevent the adaptive response induced by conditioning doses of Al, 10 or 100 microM; and PQ, 5 or 100 microM, against MMCl-challenge, 1.26 or 100 microM, in root meristems of A. cepa or embryonic shoots of Hordeum vulgare, respectively. The findings demonstrated that once triggered, the Al- or PQ-adaptive response to MMCl could persist for at least 48h in root meristems of A. cepa. Furthermore, the adaptive response could effectively be prevented by 3-AB, to a lesser degree by CH, and the least by BSO, suggesting primarily the involvement of PARP and implicating DNA repair in the underlying mechanisms of adaptive response in plant cells in vivo.  相似文献   

6.
Mechanically-induced stress (MIS) occurs naturally in plants as the aerial parts are moved, usually by wind, but also by such agents as rain and animals. It can be induced indoors by various actions such as rubbing or bending the stem or shaking or brushing the entire shoot. The most noticeable effect of MIS is a reduction in stem, leaf or petiole length invariably resulting in plants which are smaller and more compact than unstressed controls. However, the response of other variables can often differ between species and there may be either increases or decreases in stem or petiole diameter, root: shoot weight ratio, chlorophyll content or drought resistance. Why species should differ in this way, and what is the endogenous control mechanism for MIS responses, are inanswered questions. Ethylene, which increases as a result of MIS in several species may cause some MIS responses such as increased stem diameter, epinasty or a change in sex expression. However, evidence suggests that MIS retardation of extension growth may equally be due to lower or supraoptimal auxin levels or lower gibberellin levels.The uses in the field of the growth promoter gibberellin or the growth retardant chlormequat chloride (CCC) appear to be examples of respectively reversing or stimulating MIS growth response. MIS may be applied indoors if short compact plants are needed, either for aesthetic purposes as with floral crops, or if hardier and more manageable plants are needed, such as seedlings for transplanting in the field. Much more research is needed to estimate the importance of MIS in the field and to assess how such knowledge may be used to improve crop yield.  相似文献   

7.
Central nervous system dopaminergic mechanisms have been implicated in the cytokine response to stress and sepsis. We here describe the effects of haloperidol or clozapine in the treatment of sepsis induced by cecal ligation and puncture. Male Wistar rats were subjected to the CLP procedure were treated with haloperidol or clozapine and plasma cytokines, myeloperoxidase activity, markers of organ injury and survival was analyzed. The addition of haloperidol or clozapine to basic support did not diminished hepatic, renal, pancreatic or muscular damage observed after sepsis. Neither haloperidol, nor clozapine, modulates pro and antiinflammatory cytokines after sepsis induction. In addition, haloperidol treatment did not diminished myeloperoxidase activity in the kidney, lung or liver, or altered BALF markers of lung damage or inflammatory infiltration. Our data did not support a role of haloperidol or clozapine as an immunomodulator agent in the treatment of sepsis in an animal model of peritonitis.  相似文献   

8.
Preface     
The legal process is often invoked to resolve scientific or economic problems such as may arise when a bridge collapses, or an aeroplane crashes, or a ship sinks; or when a mishap occurs on the operating table; or when patent protection is sought for an invention claimed to be novel; or when it is necessary to assess the effect of a commercial practice on competition in a market; or when a baby dies, for no apparent reason, in its cot; or when it is sought to identify a fingerprint on a murder weapon.  相似文献   

9.
The approach that most animal cells employ to regulate intracellular pH (pH(i)) is not too different conceptually from the way a sophisticated system might regulate the temperature of a house. Just as the heat capacity (C) of a house minimizes sudden temperature (T) shifts caused by acute cold and heat loads, the buffering power (beta) of a cell minimizes sudden pH(i) shifts caused by acute acid and alkali loads. However, increasing C (or beta) only minimizes T (or pH(i)) changes; it does not eliminate the changes, return T (or pH(i)) to normal, or shift steady-state T (or pH(i)). Whereas a house may have a furnace to raise T, a cell generally has more than one acid-extruding transporter (which exports acid and/or imports alkali) to raise pH(i). Whereas an air conditioner lowers T, a cell generally has more than one acid-loading transporter to lower pH(i). Just as a house might respond to graded decreases (or increases) in T by producing graded increases in heat (or cold) output, cells respond to graded decreases (or increases) in pH(i) with graded increases (or decreases) in acid-extrusion (or acid-loading) rate. Steady-state T (or pH(i)) can change only in response to a change in chronic cold (or acid) loading or chronic heat (or alkali) loading as produced, for example, by a change in environmental T (or pH) or a change in the kinetics of the furnace (or acid extrudes) or air conditioner (or acid loaders). Finally, just as a temperature-control system might benefit from environmental sensors that provide clues about cold and heat loading, at least some cells seem to have extracellular CO(2) or extracellular HCO(3)(-) sensors that modulate acid-base transport.  相似文献   

10.
The primary radiologic evidence of intra-abdominal hernia is disturbance of normal small intestine arrangement. Loops of intestine are crowded together as if in a bag, giving the appearance of clumping or sacculation. Dilatation and loss of mobility may occur with varying degrees of stasis. Displacement of viscera or pressure deformity may be observed.Studies of the small bowel are necessary to demonstrate these conditions and must be made with the patient in the erect as well as the horizontal position. Repeated studies may be required, and the best time to make them is during an acute attack, as the hernia may be temporarily reduced during a remission.The clinical symptoms are sufficiently characteristic to suggest the diagnosis in most cases. The usual history is of repeated attacks of abdominal pain or discomfort, usually accompanied by distention, varying in periodicity and intensity, with or without nausea or vomiting, and not accompanied by laboratory data or clinical signs indicative of inflammatory disease.Similar or identical clinical and roentgenologic evidence may be produced by torsion of the small bowel or by peritoneal adhesions.The hernia or torsion may reduce spontaneously before or at the time of operation. Therefore, a careful search for abnormal fossae, mesenteric defects or adhesive bands is necessary if herniation or torsion is not found.  相似文献   

11.
Two experiments were conducted to determine the luteotropin of pregnancy in sheep and to examine autocrine and paracrine roles of progesterone and estradiol-17 beta on progesterone secretion by the ovine corpus luteum (CL). Secretion of progesterone per unit mass by day-8 or day-11 CL of the estrous cycle was similar to day-90 CL of pregnancy (P > or = 0.05). In experiment 1, secretion of progesterone in vitro by slices of CL from ewes on day-8 of the estrous cycle was increased (P < or = 0.05) by LH or PGE2. Secretion of progesterone in vitro by CL slices from day-90 pregnant ewes was not affected by LH (P > or = 0.05) while PGE2 increased (P < or = 0.05) secretion of progesterone. Day 8 ovine CL of the estrous cycle did not secrete (P > or = 0.05) detectable quantities of PGF2alpha or PGE while day-90 ovine CL of pregnancy secreted PGE (P < or = 0.05) but not PGF2alpha. Secretion of progesterone and PGE in vitro by day-90 CL of pregnancy was decreased (P < or = 0.05) by indomethacin. The addition of PGE2, but not LH, in combination with indomethacin overcame the decreases in progesterone by indomethacin (P < or = 0.05). In experiment 2, secretion of progesterone in vitro by day-11 CL of the estrous cycle was increased at 4-h (P < or = 0.05) in the absence of treatments. Both day-11 CL of the estrous cycle and day-90 CL of pregnancy secreted detectable quantities of PGE and PGF2alpha (P < or = 0.05). In experiment 1, PGF2alpha secretion by day-8 CL of the estrous cycle and day-90 ovine CL of pregnancy was undetectable, but was detectable in experiment 2 by day-90 CL. Day 90 ovine CL of pregnancy also secreted more PGE than day-11 CL of the estrous cycle (P < or = 0.05), whereas day-8 CL of the estrous cycle did not secrete detectable quantities of PGE (P > or = 0.05). Trilostane, mifepristone, or MER-25 did not affect secretion of progesterone, PGE, or PGF2alpha by day- 11 CL of the estrous cycle or day-90 CL of pregnancy (P > or = 0.05). It is concluded that PGE2, not LH, is the luteotropin at day-90 of pregnancy in sheep and that progesterone does not modify the response to luteotropins. Thus, we found no evidence for an autocrine or paracrine role for progesterone or estradiol-17 36 on luteal secretion of progesterone, PGE or PGF2alpha.  相似文献   

12.
W. C. Watson 《CMAJ》1977,116(7):739-741
Elucidation of the cause of diarrhea is facilitated by considering which of three principal determinants are of relevance in a particular case. These determinants relate to the onset (whether diarrhea is acute or chronic), to infection or an absence ofinfection and to the presence in the stool of blood or mucus, or both. Diagnosis is also facilitated by taking an accurate and full history, conducting a physical examination, performing sigmoidoscopy and, with proper care, attempting a therapeutic diagnosis. Findings from investigations should then enable one to arrive at a diagnosis. The diagnosis can be reached in an orderly fashion by classifying the types of diarrhea into eight categories: with respect to the acute or chronic onset a case of diarrhea may be noninfectious, without blood or mucus in the stool; noninfectious, with blood or mucus, or both; infectious, without blood or mucus; and infectious, with blood or mucus in the stool.  相似文献   

13.
Batch cultures of Chlorella vulgaris and C. variegata reproducing about twice every 5 d within 0-15 d had vegetative cells and autospore mother cells in the ratio of about 19 : 1. Continuous slow or negligible and/or no growth in > 15-d-old control cultures or in young cultures supplied with the antibiotics streptomycin, penicillin, amoxycillin (10-1000 ppm) or tetracycline (10, 100 ppm), and pesticides carbofuran, gammaxine, moticop or iralon (1-100 ppm) was due to slow autospore mother cells dehiscence (leading to an increase in their percentage); while negligible and/or no growth of both algal species in sewage water (100, 25%), detergent (0.1-1%), petrol or kerosene (5-20 %), benzene, toluene or phenol (5, 10%) and pesticides rogor or endosulfan (1, 10 ppm) was due to vegetative cells failure to differentiate into auto-spore mother cells (leading to decreased/zero autospore mother cells percentage) and/or rapid death of all cells. C. variegata was equally or slightly more sensitive to different chemical stress than C. vulgaris.  相似文献   

14.
We have previously reported that mycolyl glycolipids from Nocardia rubra such as glucose or trehalose mycolates induced granuloma formation in mice. The structure of the carbohydrate moiety of the mycolyl glycolipids influenced the granuloma forming activity profoundly. Here, we have examined the macrophage-chemotactic activity in the culture supernatants stimulated with various glycolipids differing in carbohydrate moiety (trehalose 6,6'-dimycolate, or TDM; glucose monomycolate, or GM; mannose monomycolate, or MM; and fructose monomycolate, or FM). A distinctive chemotactic activity was detected with TDM or GM, but, little or none with MM or FM.  相似文献   

15.
对武夷山天然槠栲林光照、温度和湿度与林隙结构和年龄的关系进行了回归分析。结果表明:光照、温度及湿度指数均与林隙面积关系不密切;光照指数、温度指数均与1.5m以上植物种密度、平均高和优势度,均与每个林隙的边界木优势度和平均高、单位边界木优势度及林隙年龄都存在显著或极显著负相关关系;湿度指数与1.5m以上植物种密度、平均高和优势度,与每个林隙的边界木优势度和平均高、单位边界木优势度和林隙年龄都存在显著或极显著正相关关系。随着林隙年龄的增大和结构特征的改变,光照指数和温度指数下降,而湿度指数却上升。应根据不同年龄林隙的环境特征进行森林经营。  相似文献   

16.
Existing protein tagging and detection methods are powerful but have drawbacks. Split protein tags can perturb protein solubility or may not work in living cells. Green fluorescent protein (GFP) fusions can misfold or exhibit altered processing. Fluorogenic biarsenical FLaSH or ReASH substrates overcome many of these limitations but require a polycysteine tag motif, a reducing environment and cell transfection or permeabilization. An ideal protein tag would be genetically encoded, would work both in vivo and in vitro, would provide a sensitive analytical signal and would not require external chemical reagents or substrates. One way to accomplish this might be with a split GFP, but the GFP fragments reported thus far are large and fold poorly, require chemical ligation or fused interacting partners to force their association, or require coexpression or co-refolding to produce detectable folded and fluorescent GFP. We have engineered soluble, self-associating fragments of GFP that can be used to tag and detect either soluble or insoluble proteins in living cells or cell lysates. The split GFP system is simple and does not change fusion protein solubility.  相似文献   

17.
The eye rudiments of 10 and 11 days old mouse embryos of the genotypes +/+ +/+, fi/fi +/+, +/+ or/or, fi/fi or/or and 11 days old embryos of the genotype fi/+ or/+ were cultivated in vitro during 24, 48 and 72 hrs. The expression of the fi gene was shown in the cells of the cultivated fi/fi +/+ retina: its proliferative activity was inhibited. The fi gene was not active in the cells of the developing lens and the anomalies of the latter in homozygotes arose secondarily, due to the inhibition of growth of the retinal rudiment. The fi and or genes interacted synergically in the cultivated fi/fi or/or retina, thus resulting in the marked inhibition of its mitotic activity. This suggests that both the genes act in the retinal cells and, apparently, affect different links of the biochemical chain of events in the preparation of DNA replication.  相似文献   

18.
The instability of cell cultures containing plasmid vectors is a major problem in the commercial exploitation of molecular cloning techniques. Plasmid stability is influenced by the nature of the host cell, the type of plasmid and/or environmental conditions. Plasmid encoded properties may confer a selective advantage on the host cell but can be an energy drain due to replication and expression. Stability of recombinant cultures ultimately may be determined by the cost to benefit ratio of plasmid carriage.The relative competition between plasmid containing and plasmid-free or indigenous populations can determine the degree of dominance of recombinant cultures. The use of inocula in biotechnological processes in which dynamic environmental conditions dominate may also result in instabilities resulting from the characteristics of the ecosystem. In such dynamic conditions plasmid stability is just one contribution to culture stability.Strategies to enhance plasmid stability, within such environments, based on manipulation of physiological state of host cells, must consider the responsiveness or plasticity of both cells and populations. The robustness of cells or the responses to stresses or transient environmental conditions can influence the levels of instability detected; for example, instability or mutation in the host genome may lead to enhanced plasmid stability. Competition among subpopulations arising from unstable copy number control may determine the levels of recombinant cells in open versus closed fermenter systems.Thus the ecological competence (ability to survive and compete) of recombinant cells in dynamic or transient environments is fundamental to the understanding of the ultimate dominance or survival of such recombinant cultures and may form the basis of a strategy to enhance or control stability either in fermenter systems or dynamic process environments. The creation of microniches in time and/or space can enhance plasmid stability. Transient operation based on defined environmental stresses or perturbations in fermenter systems or in heterogeneous or dynamic environments found in gel immobilized cultures have resulted in enhanced stability. Spatial organization resulting from immobilization has the additional advantage of regulated cell protection within defined microenvironments and controlled release, depending on the nature of the gel, from these microenvironments or microcosms. This regulation of ecological competence allied to the advantages of microbial cell growth in gel microenvironments combined with the spatial organization (or juxtapositioning of cells, selective agents, nutrients, protectants, etc.) possible through immobilization technology offers new strategies to enhance plasmid and culture stability.  相似文献   

19.
The objectives of the experiment were to evaluate the efficacy of using progesterone concentrations in milk and palpation per rectum on days 21 or 22 postbreeding to estimate pregnancy and evaluate management practices; and to investigate physiological occurrences leading to incorrect diagnosis of pregnancy when serial samples of milk were collected. Of particular interest were indications of early embyronic death and insemination of cows not in estrus. Milk samples were collected at the afternoon milking of days 0 or 1 (day 0 = day of estrus), 9 or 10, 21 or 22 and 27 or 28 following breeding in 200 lactating dairy cows. Tentative diagnosis of pregnancy was made based on concentrations of progesterone in milk on days 21 and 22 alone and on days 21 or 22 and 27 or 28. In addition all cows were palpated per rectum on days 21 or 22 postbreeding and a tentative pregnancy diagnosis was made. Pregnancy was confirmed by examination of the genital tract per rectum between 35 and 50 days after breeding. Values of 4 ng/ml or greater and/or the presence of a mature corpus luteum were considered positive signs of pregnancy. Progesterone in milk ranged from 0.1 to 18 ng/ml. On days 0 or 1, 9 or 10, 21 or 22 and 27 or 28 concentrations of progesterone in milk averaged 1.5 +/- 0.3, 11.1 +/- 0.5, 12.0 +/- 0.4 12.5 +/- 0.5 ng/ml for pregnant cows. Corresponding samples from nonpregnant cows averaged 1.2 +/- 0.2, 10.3 +/- 0.4, 3.0 +/- 0.4, 6.8 +/- 0.6 ng/ml, respectively. Ninety-six and 104 cows were classified as pregnant and nonpregnant on days 21 or 22 as compared to 78 and 118 cows diagnosed as pregnant and nonpregnant on days 21 or 22 and 27 or 28 combined. Pregnancy detection by progesterone in milk on days 21 or 22 with pregnancy determined via rectal palpation 35 to 50 days postbreeding was 77 and 100% accurate for positive and negative diagnosis, respectively. The percent agreement using progesterone in milk on days 21 or 22 and 27 or 28 combined was 95 and 100%, respectively, for positive and negative diagnosis. Diagnosis based on rectal palpation 21 or 22 days postbreeding was 63 92 (69%) and 76 88 (87%) for pregnant and nonpregnant cows, respectively. Ten of the 200 cows had progesterone concentratins in milk of > 4 ng/ml at the time of breeding. Six of these cows were pregnant from a previous insemination. The other four cows were nonpregnant and were inseminated during the luteal phase of the cycle. In conclusion, measurement of progesterone in milk is a useful tool in early detection of pregnant and nonpregnant cows and may be useful in detecting reproductive problems in a dairy herd. It will probably be most useful when used in combination with later pregnancy diagnosis per rectum .  相似文献   

20.
Eight patients (4 suffering from acute myeloid leukemia) exhibiting a loss of ABO red cell antigens, as seen by a mixed-field reaction pattern in agglutination tests, were selected and examined for the level of the A, -B, -H blood group glycosyltransferases within membranes prepared from erythrocyte subpopulations (A or B positive and A or B negative red cells). A or B enzyme activities were largely decreased in membranes which had lost A or B antigens (A or B negative subpopulations) but were within normal level in membrane from cells which had not lost A or B antigens (A or B positive subpopulations). The H enzyme level which was frequently low in the serum was within normal limits in the membrane preparations examined. Since A or B negative subpopulations were normally glycosylated in vitro into A or B reactive structures, the results demonstrate that loss of A or B antigens is related to some alteration of the blood group gene products rather than to significant abnormalities of the membrane precursors.  相似文献   

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