Endoplasmic reticulum enzyme systems in developing human fetal trachea.
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Embryonic and Fetal Development↗
Biomedical subjects
R Hume
Publications and source records attributed to R Hume.
Glucose-6-phosphatase in developing human oesophagus.
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Adult↗
Human fetal testis endoplasmic reticulum glucose-6-phosphatase enzyme protein.
Microsomal glucose-6-phosphatase (EC 3.1.3.9) is an enzyme system traditionally thought to be present only in gluconeogenic tissues. We have used microassay techniques, immunohistochemistry using monospecific antibodies to the liver enzyme, and specific DNA probes and primers to examine whether glucose-6-phosphatase is present in human and rat testis. Microsomal glucose-6-phosphatase activities in human fetal testis (weeks 15-20 of gestation) are approximately 25% of corresponding liver values. Localization is predominantly in Leydig cells, with variable and weak immunoreactivity in developing seminiferous tubules. Kinetic analysis of glucose-6-phosphatase in intact and disrupted microsomes and Southern blot analysis of polymerase chain reaction products indicated that the specific glucose-6-phosphatase enzyme system was also present in rat testis. We have shown for the first time that specific microsomal glucose-6-phosphatase activity, protein, and mRNA are present in testis, and that the predominant site of expression is the Leydig cell in human fetal testis.
Animals↗
What is the future of amalgam?
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Composite Resins↗
The ontogeny of the glucose-6-phosphatase enzyme in human embryonic and fetal red blood cells.
We have shown for the first time that the microsomal glucose-6-phosphatase enzyme protein is present in human embryonic and fetal red blood cells and the ontogeny of its expression has been determined. In the earliest embryos, red cells are predominantly of the primitive megaloblastic type. Circulating red cells in the primitive megaloblastic series are predominantly nucleated and glucose-6-phosphatase immunopositive. Non-nucleated, immunoreactive megaloblastic cells are in a minority. In fetuses > 12 weeks gestation, the erythrocytes are of the definitive normoblastic series and in the transitional period of switch-over in late embryonic-early fetal life, up to 30% of glucose-6-phosphatase immunopositive cells are definitive normoblastic in type, with a variable contribution from nucleated and non-nucleated cells. Thereafter, the number of immunopositive cells in the definitive normoblastic series decreases such that after 12 weeks gestation it is less than 5%. The fact that a predominantly hepatic protein in adults (glucose-6-phosphatase) is present in embryonic and fetal red blood cells, particularly nucleated red cells, raises the possibility of diagnosis of disorders of liver protein expression in nucleated fetal red cells isolated from the first trimester maternal circulation.
Embryo, Mammalian↗
Differential localisation of UDP-glucuronosyltransferase in kidney during human embryonic and fetal development.
The aim of our study was to localise UDP-glucuronosyltransferase (UDPGT) in the developing mesonephric and metanephric kidneys of the human embryo and fetus, using immunohistochemical methods and an antibody preparation with broad specificity to the human isoforms. In embryonic and early fetal development of the metanephric kidney, UDPGT is located primarily in derivatives of the ureteric bud such as the ureter, pelvis, calyces and collecting ducts. This early predominance of UDPGT to ureteric bud derivatives declines by mid-fetal life: a) as nephrons evolve and develop they become increasingly UDPGT immunoreactive such that in mature metanephric kidney, the proximal tubules are highly UDPGT reactive, with other elements of the nephron also immunopositive (albeit at lower reactivities) and b) with the formation of an immunonegative transitional epithelium in ureter, pelvis and calyces, the reactivity retained in collecting ducts is only a small proportion of the total. The distribution of UDPGT immunoreactivity is relatively uniform in proximal tubular cells throughout development. This is in contrast to collecting ducts where, in fetal life, this reactivity is displaced to apices and bases by intracellular glycogen deposits. Parietal cells of Bowman's capsule are immunoreactive, but glomeruli are negative. In mesonephric kidney, as early as 32 days post-ovulation, tubules and the mesonephric duct are UDPGT immunoreactive and mesonephric immunopositivity overlaps with that in the developing metanephric kidney.
Embryonic and Fetal Development↗
Percutaneous fetal cystoscopy and endoscopic fulguration of posterior urethral valves.
Percutaneous fetal cystoscopy was performed in a male fetus with ultrasonographic evidence of lower urinary tract obstruction at 19 weeks of gestation. The diagnosis of posterior urethral valves was confirmed. Percutaneous endoscopic fulguration of the valves was successfully performed at 22 weeks of gestation, and urethral patency was established. This case illustrates the feasibility of performing diagnostic and therapeutic endoscopic procedures within the human fetus for the management of a congenital anomaly. While we believe that fetal cystoscopy may improve our diagnostic, prognostic, and therapeutic capabilities in the management of fetuses with lower obstructive uropathy, studies are needed to establish the actual value, risks, and limitations of this new approach in fetal medicine.
Adult↗
Human fetal adrenal hydroxysteroid sulphotransferase: cDNA cloning, stable expression in V79 cells and functional characterisation of the expressed enzyme.
Dehydroepiandrosterone sulphate (DHEAS) is a major adrenal secretory product, particularly in the fetus where it serves as a substrate for oestrogen biosynthesis by the placenta. The enzyme in the adrenal responsible for synthesising DHEAS, hydroxysteroid sulphotransferase (HST), is therefore essential for human development. We have isolated a full-length cDNA clone, encoding human fetal adrenal HST, and constructed a stable cell line expressing it by transfection into V79 Chinese hamster lung fibroblast cells. This cDNA was essentially identical to that isolated from adult human liver, where the role of HST is less well understood. This recombinant cell line allowed determination of the substrate specificity and kinetic properties of this enzyme towards various steroid hormones, and by comparison of these activities with human liver cytosol we have shown that HST is the major sulphotransferase responsible for the sulphation of DHEA, androsterone and pregnenolone in man and that, functionally, the hepatic and adrenal enzymes are very similar. The expressed HST was also active with testosterone, cortisol (although at low levels) and the xenobiotic 17 alpha-ethinyloestradiol, but not with oestrone or 1-naphthol. We have therefore created a valuable resource for the study of this important enzyme.
Adrenal Glands↗
Preparation and characterization of anti-peptide antibodies directed against human phenol and hydroxysteroid sulphotransferases.
Sulphotransferases (STs) catalyze the sulphation and, in general, detoxication of a large number of xenobiotics and endogenous compounds. A total of six synthetic peptides derived from the cDNA-derived amino acid sequences of the human phenol-sulphating form of phenosulphotransferase (P-PST) and human hydroxysteroid sulphotransferase (HST)--three from each sequence--were separately conjugated to the carrier protein keyhole limpet hemocyanin, and used to immunize rabbits. One successful antibody preparation was produced from among the P-PST peptides, and two from the HST peptides. On immunoblot analysis following SDS/PAGE, the anti-P-PST antibodies recognized two major forms of phenol ST in man, P-PST and the monoamine-sulphating form of PST, M-PST, and the two antibody preparations against HST recognized the human HST. These experiments demonstrate that it is possible to design specific antibodies against human sulphotransferases based on their amino acid sequences.
Adjuvants, Immunologic↗
The human adrenal microsomal glucose-6-phosphatase system.
Microsomal glucose-6-phosphatase (EC 3.1.3.9) is a multicomponent enzyme system traditionally thought only to be present in gluconeogenic tissues. The enzyme is associated with transport systems, for its substrate glucose-6-phosphate, and its products phosphate and glucose. It has been shown, using immunohistochemical methods and monospecific antibodies, that the component proteins of the enzyme system are present in human embryonic and fetal adrenal gland and are predominantly located in the fetal zone with lesser reactivities in the definitive zone. In addition, specific glucose-6-phosphatase activity was shown, and the rates of entry of glucose-6-phosphate, phosphate, and glucose into microsomes isolated from human fetal adrenals were measured. Although the complete enzyme system is present, the ratio of the component activities and comparison with human fetal and adult liver indicate that the regulation of the adrenal and liver glucose-6-phosphatase systems is different. In the human postnatal adrenal, immunoreactivies to the protein components decrease dramatically and are confined predominantly to the zona reticularis, suggesting a specialized role for adrenal glucose-6-phosphatase in fetal life.
Adrenal Glands↗
The glucose-6-phosphatase system in human development.
The classical role of glucose-6-phosphatase in liver and kidney is the production of glucose for release into blood. In liver, glucose-6-phosphatase catalyses the terminal step of glycogenolysis and gluconeogenesis. Abnormally low hepatic glucose-6-phosphatase activity is found in human genetic deficiencies i.e. glycogen storage disease type I and in cases of developmental delay, found predominantly in preterm infants. In contrast, abnormally high liver glucose-6-phosphatase occurs in poorly controlled or untreated diabetes mellitus. Hepatic glucose-6-phosphatase is an integral endoplasmic reticulum (and nuclear membrane) protein and it is part of a multicomponent system. Its active site is situated inside the lumen of the endoplasmic reticulum and transport proteins are needed to allow its substrates glucose-6-phosphate (and pyrophosphate) and its products phosphate and glucose to cross the endoplasmic reticulum membrane. In addition, a calcium binding protein is also associated with the glucose-6-phosphatase enzyme. Immunohistochemical studies, in combination with image analysis, have shown that glucose-6-phosphatase is present in liver and kidney and also in specific cell types in a variety of human tissues, for example Leydig cells in the testis and some astrocytes in the brain. Where practicable, enzymatic analysis, direct transport assays and/or immunological detection of the endoplasmic reticulum glucose and phosphate transport proteins have been used to demonstrate the presence and activity of the whole glucose-6-phosphatase system. The distribution of the human glucose-6-phosphatase system changes dramatically during development with a different spatial and temporal pattern in each tissue. The most unexpected localization was in circulating, predominantly nucleated, embryonic and early fetal red blood cells.
Glucose-6-Phosphatase↗
Sulphation of N-hydroxy-4-aminobiphenyl and N-hydroxy-4-acetylaminobiphenyl by human foetal and neonatal sulphotransferase.
Sulphation of the genotoxic compounds N-hydroxy-4-aminobiphenyl (N-OH-4ABP) and N-hydroxy-4-acetylaminobiphenyl (N-OH-4AABP) was determined in cytosolic preparations of human foetal, neonatal and adult liver and foetal and neonatal adrenal gland. Sulphotransferase (ST) activity capable of sulphating these compounds was present in foetal liver and adrenal gland by 14 weeks of gestation. Sulphation of N-OH-4ABP was higher in foetal and neonatal adrenal cytosol than was sulphation of N-OH-4AABP and in general, N-OH-4ABP ST activity was also greater than that towards 1-naphthol. In foetal and neonatal liver cytosol the sulphation of N-OH-4ABP was also higher than that of N-OH-4AABP (approximately 2-fold). In adult liver cytosols, however, N-OH-4AABP ST activity was higher than that for N-OH-4ABP and 1-naphthol sulphation. Aromatic hydroxylamines and hydroxamic acids are known to be converted by sulphotransferase into reactive, electrophilic compounds capable of reacting with DNA. Our data show that the human foetus and neonate have the capacity to sulphate these compounds and thus is able to produce the reactive mutagenic metabolites. Therefore, this class of genotoxic compounds may be bioactivated by humans during development--a time when they are most vulnerable to the effects of genotoxins.
Adrenal Glands↗
Phenolsulphotransferase: localization in kidney during human embryonic and fetal development.
The aim of our study was to localize phenolsulphotransferase (PST) in the developing mesonephric and metanephric kidneys of the human embryo and fetus using immunohistochemical methods with an antibody preparation recognizing members of the human phenolsulphotransferase enzyme family. In embryonic and early fetal development of the metanephric kidney, PST is located primarily in derivatives of the ureteric bud such as the ureter, pelvis, calyces and collecting ducts. This predominance declines by mid-fetal life: first, as nephrons evolve and develop they become increasingly PST-immunoreactive such that in mature metanephric kidney, the proximal tubules are highly PST-reactive, with other elements of the nephron also immunopositive (albeit at lower reactivities) and secondly, with the formation of an immunonegative transitional epithelium in ureter, pelvis and calyces, the reactivity retained in collecting ducts is only a small proportion of the total. The distribution of PST immunoreactivity is relatively uniform in proximal tubular cells throughout development, in contrast to collecting ducts, where, in fetal life, this reactivity is displaced to apices and bases by intracellular glycogen deposits. Mesonephric kidney tubules and the mesonephric duct are PST-immunoreactive and although mesonephric immunopositivity overlaps with that in the developing metanephric kidney the renal contribution to sulphation is absent or low at a time when the developing conceptus is most vulnerable to the potential toxic effects of teratogens.
Adult↗
Immunohistochemical localisation of glucose-6-phosphatase in developing human kidney.
The objective of our study was to determine the cellular localisation of glucose-6-phosphatase in developing human kidney using monospecific antiserum and a standard immunohistochemical method (peroxidase-antiperoxidase, PAP) on formalin fixed and paraffin embedded tissue. In embryonic and early fetal development of the metanephric kidney, glucose-6-phosphatase is located primarily in derivatives of the ureteric bud such as the pelvis, calyces and collecting ducts. In mid-fetal life as nephrons evolve and develop they become increasingly immunoreactive to glucose-6-phosphatase, such that in mature metanephric kidney the proximal tubules are highly reactive for glucose-6-phosphatase with other elements of the nephron also immunopositive albeit at lower reactivities. In addition the parietal layer of Bowman's capsule and some cells of the visceral layer are immunopositive. Only with the development of nephrons does the early predominance of glucose-6-phosphatase immunoreactivity to ureteric bud derivatives change: in mature kidney the reactivity in the collecting ducts is a small proportion of the total. In proximal tubular cells the distribution of glucose-6-phosphatase immunoreactivity is relatively uniform throughout development in contrast to collecting ducts where in fetal life this reactivity is displaced to the apices and basal areas by intracellular glycogen deposits. The mesonephric kidney has a similar pattern of glucose-6-phosphatase immunoreactivity to that of metanephric kidney. The availability of monospecific antiserum to glucose-6-phosphatase and immunohistochemical methods now allows an alternative approach to cellular localisation. Many of the difficulties in the fixation of tissue and assay of glucose-6-phosphatase activity inherent in conventional histochemical methods are avoided by such methods.
Female↗
Sulfation of endogenous compounds and xenobiotics--interactions and function in health and disease.
Sulfation is a major detoxication mechanism for endogenous compounds and xenobiotics performed by a family of sulfotransferase isoenzymes. Understanding the normal cellular functions of these different sulfotransferases and the way in which endogenous and exogenous factors are able to influence their activity and expression will provide us with the information necessary to develop novel therapeutic strategies for conditions where sulfation may be implicated. This concept is discussed and is illustrated by examples including adverse drug reactions, fetal development and cancer.
Amino Acid Sequence↗
Low birthweight: a 10-year outcome study of the continuum of reproductive casualty.
Disability rates among low-birthweight infants, particularly those related to congenital abnormality and cerebral palsy, are high. Both prenatal and perinatal factors are likely to be involved in the aetiology of most types of disability. IQ tends to be lower among low-birthweight infants, but does not appear to be closely related to birthweight alone. The confounding effect of social class should be considered when assessing aetiology and outcome. The long-term outcome for the increasing number of low-birthweight infants who survive and receive intensive neonatal care requires to be continually assessed; however, studies should not be confined to the very- and extremely-low-birthweight infant requiring prolonged intensive care, but should include abortions, stillbirths and neonatal deaths. As disability in survivors can relate to preterm birth but not perinatal complications, all low-birthweight infants require to be studied if selective bias is to be solved.
Case-Control Studies↗
Dehydroepiandrosterone sulfotransferase in the developing human fetus: quantitative biochemical and immunological characterization of the hepatic, renal, and adrenal enzymes.
The sulfation of the adrenal steroid dehydroepiandrosterone (DHEA) is a critical step in the provision of substrates for estrogen biosynthesis by the placenta during pregnancy. This enzyme reaction is catalyzed by a cytosolic sulfotransferase (ST) found in many key body tissues, and we have examined the ontogeny and localization of expression of this important enzyme in three tissues: the liver, adrenal, and kidney. Hepatic DHEA ST expression increased with advancing gestational age before reaching near-adult levels in the early postnatal period, suggesting an increased requirement for this enzyme in the liver as development progresses, whereas in the adrenal and kidney there was no obvious ontogenic pattern. The enzyme was expressed at a 5-fold higher level in the adrenal than in the liver and some 40-fold higher than in the kidney. Comparison of enzyme activity measurements and quantitation of the expression of DHEA ST by immunodot blot analysis with an anti-DHEA ST antibody preparation demonstrated the fragility of the enzyme activity and suggested that immunoquantitation was a superior method for assessment of levels of expression of this enzyme in widely different tissue sources. Examination of the localization of DHEA ST in these tissues by immunohistochemistry showed that in liver, DHEA ST was expressed in embryonic hepatocytes and continued to be expressed in these cells into adulthood, when there was some concentration of immunostaining around central veins. In the fetus, the adrenal enzyme was expressed in the fetal zone, whereas in adult tissue, staining was localized principally to the zona reticularis. Renal DHEA ST was present in the proximal and distal tubules, loops of Henle, collecting ducts, and their progenitors, but was at no time expressed in the vascular glomerulus. In light of the broad substrate specificity of this enzyme toward other steroids, in particular bile acids and cholesterol, the information presented forms a strong basis for further studies into the role of DHEA ST in modulating the activity of a number of biologically active and potentially toxic steroids in the developing human.
Adrenal Glands↗