[Women physicians are performing research--but few will become professors].
Explore the source record for details and available documents.
Career Mobility↗
Biomedical subjects
E Nexø
Publications and source records attributed to E Nexø.
Conformational changes of transcobalamin induced by aquocobalamin binding. Mechanism of substitution of the cobalt-coordinated group in the bound ligand.
Binding of aquo-, cyano-, or azidocobalamin (Cbl.OH(2), Cbl.CN, and Cbl.N(3), respectively) to the recombinant human transcobalamin (TC) and haptocorrin from human plasma was investigated via stopped-flow spectroscopy. Association of cobalamins with haptocorrin always proceeded in one step. TC, however, displayed a certain selectivity for the ligands: Cbl.CN or Cbl.N(3) bound in one step with k(+1) = 1 x 10(8) M(-1) s(-1) (20 degrees C), whereas binding of Cbl.OH(2) under the same conditions occurred in two steps with k(+1) = 3 x 10( 7) M(-1) s(-1) (E(a) = 30 kJ/mol) and k(+2) = 0.02 s(-1) (E(a) = 120 kJ/mol). The second step of Cbl.OH(2) binding was interpreted as a transformation of the initial "open" intermediate TC.Cbl.OH(2) to the "closed" conformation TC(Cbl) with displaced water. The backward transition from the closed to the open conformation was the reason for the identical rate-limiting steps during substitution of H(2)O in TC.Cbl.OH(2) for cyanide or azide according to the reaction TC(Cbl) --> TC.Cbl.OH(2) + CN(-)/N(3)(-). The cyano and azido forms of holo-TC which were produced behaved as the open proteins. Different conformations of holo-TC, determined by the nature of the active group in the bound Cbl, may direct transportation of cobalamins in the organism.
Humans↗
Epidermal growth factor and lung development in the offspring of the diabetic rat.
Fetuses of diabetic mothers who were exposed to excessive glucose show delayed maturation. Under these conditions, altered growth factor expression or signaling may have important regulatory influences. We examined the role of epidermal growth factor (EGF) in lung development and maternal diabetes in the rat. In order to evaluate the possible role of glucose for the expression of EGF and the growth of lung tissue, we performed in vitro studies with organotypic cultures of fetal alveolar cells obtained from control rats. Compared to pups of normal rats, the newborn rats of untreated diabetic rats had reduced body weight, but normal lung weight relative to body weight. The air:mesenchyme ratio and the average size of alveoli per mm(2) lung tissue were reduced. The immunoreactivity (IR) of EGF, which was quantified using a computerized image analysis system, appeared with increased intensity and was associated with a reduced intensity of surfactant protein A-IR. The only difference observed between pups of treated diabetic rats and controls was a decrease in the lung weight:body weight ratio. In organotypic cultures, the presence of 13 mmol/L glucose in the cell media increased immunoreactive staining against EGF, but decreased the incorporation of thymidine as compared to the results obtained with alveolar cells grown in a normophysiological concentration of glucose (3 mmol/L). Addition of EGF increased the thymidine incorporation only in cells grown in 3 mM glucose. These findings may indicate immaturity of the lungs of pups of untreated diabetic rats, and subtle alterations in the lungs of pups from treated diabetic rats. The results also suggest that glucose plays a role in the expression of EGF, and that cells exposed to high concentrations of glucose are less responsive to EGF.
Animals↗
Systemic treatment with epidermal growth factor but not insulin-like growth factor I decreases the involution of the prostate in castrated rats.
Epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I) are strong inducers of proliferation to prostate cells cultured in serum-free medium. Accordingly we wanted to study the growth of the prostate gland in castrated rats after treatment with EGF, IGF-I and testosterone. Castrated Wistar rats were treated with growth factors (EGF 35 microg/rat per day; IGF-I 350 microg/rat per day) or testosterone (2 mg/rat per day) for 3 days either immediately after or 10 days after castration. Prostate tissue was examined by stereological and immunohistochemical techniques and by enzyme-linked immunosorbent assay (ELISA). Treatment with EGF inhibited the involution of the prostate (P < 0.05), whereas treatment with IGF-I did not affect the prostate involution as compared to castrated controls. EGF treatment significantly increased the endogenous rat EGF in the ventral prostate, but cellular proliferation was not affected. Testosterone treatment increased the weight of the prostate, by increase of all tissue components of the prostate, and significantly increased cellular proliferation. Systemic administration of EGF but not IGF-I decreased the involution of the rat prostate induced by castration. Compared with testosterone, the effects of EGF treatment on the prostate involution were moderate, and the effects of EGF were not related to cellular proliferation.
Animals↗
Epidermal growth factor and insulin-like growth factor I upregulate the expression of the epidermal growth factor system in rat liver.
BACKGROUND/AIM: Both epidermal growth factor and insulin-like growth factor I play a role in connection with the liver. In the present study, the possible interaction of these two growth factor systems was studied by investigating the effect of epidermal growth factor or insulin-like growth factor I treatment on the expression of the epidermal growth factor receptor, and its activating ligands, transforming growth factor-alpha and epidermal growth factor. METHODS: Fifty-five male rats received no treatment, human recombinant epidermal growth factor or human recombinant insulin-like growth factor I for either 3 or 7 days. The amount of epidermal growth factor receptor, transforming growth factor-alpha, and epidermal growth factor mRNA was quantitated by a calibrated user-friendly RT-PCR assay (CURT-PCR), and the expression of transforming growth factor-alpha and epidermal growth factor peptides was quantitated by ELISA. RESULTS: Control liver (n=16) contained a mean (+/-SD) value of 12.7+/-7.4x10(-18) mol epidermal growth factor receptor mRNA, 3.8+/-2.0x10(-18) mol transforming growth factor-alpha mRNA and 0.8+/-0.4x10(-18) mol epidermal growth factor mRNA per microg total RNA and 9.8+/-1.6 fmol/mg protein epidermal growth factor and 144+/-22 fmol/mg protein transforming growth factor-alpha. Both epidermal growth factor and insulin-like growth factor I treatment increased the expression of mRNA for transforming growth factor-alpha and epidermal growth factor receptor, as well as the expression of transforming growth factor-alpha peptide. The level of epidermal growth factor receptor and transforming growth factor-alpha mRNA expression was found to correlate both in control and growth factor-treated animals, whereas the expression of epidermal growth factor receptor and epidermal growth factor showed no correlation. Marked differences were seen upon activation of the two growth factor systems, as epidermal growth factor, but not insulin-like growth factor I treatment, increased the plasma concentration of urea and decreased the concentration of insulin-like growth factor I and the liver enzymes, alanine aminotransferase and alkaline phosphatase. CONCLUSION: Our results show that epidermal growth factor and insulin-like growth factor I, which belong to two different growth factor systems, both induce a correlated upregulation of transforming growth factor-alpha and epidermal growth factor receptor mRNA in rat liver. Although marked differences were observed after treatment with either epidermal growth factor or insulin-like growth factor I on the liver as reflected in the plasma concentrations of e.g. liver enzymes, a common motif in their action involves an upregulation of the expression of the epidermal growth factor system.
Animals↗
Simultaneous quantitation of several mRNA species by calibrated reverse transcription polymerase chain reaction and capillary electrophoresis: analysis of the epidermal growth factor receptor and its activating ligands EGF, TGF-alpha, and HB-EGF in rat liver.
Explore the source record for details and available documents.
Animals↗
The marker of cobalamin deficiency, plasma methylmalonic acid, correlates to plasma creatinine.
OBJECTIVE: To examine the relationship between the two diagnostic tests, plasma methylmalonic acid and plasma cobalamins, and their association with plasma creatinine, age and sex. DESIGN: Cross-sectional study of simultaneous laboratory measurements. SETTING: County of Aarhus, Denmark. SUBJECTS: Records on 1689 patients who had their first plasma methylmalonic acid measurement during 1995 and 1996, and who had a simultaneous measurement of plasma cobalamins. Plasma creatinine values measured within a week of measurements of plasma methylmalonic acid and plasma cobalamins were available for 1255 of the patients. MAIN OUTCOME MEASURES: Predictors of variation in plasma methylmalonic acid; plasma cobalamins, plasma creatinine, age and sex. RESULTS: Plasma methylmalonic acid was positively correlated with plasma creatinine, even for plasma creatinine within the normal range. These associations remained in a multiple regression analysis. For plasma cobalamins below 200 pmol L-1, there was a strong negative correlation between plasma methylmalonic acid and plasma cobalamins, whilst the association was weak for higher plasma cobalamin levels. Plasma methylmalonic acid increased and plasma cobalamins decreased with age. CONCLUSIONS: The strong correlation between plasma methylmalonic acid and plasma creatinine suggests that plasma creatinine - also within the normal range - must be taken into consideration when interpreting plasma methylmalonic acid.
Adolescent↗
Physicians' use of plasma methylmalonic acid as a diagnostic tool.
OBJECTIVES: To investigate physicians' reasons for requesting plasma methylmalonic acid and their reactions to an increased concentration of plasma methylmalonic acid. DESIGN: Study of medical records. SETTING: Three somatic district hospitals in Denmark. SUBJECTS: Medical records of 198 patients with a plasma methylmalonic acid measurement above the reference interval. Information on diagnostic decisions was available for 177 patients. MAIN OUTCOME MEASURES: Reasons for requesting plasma methylmalonic acid and the reactions to the finding of elevated plasma methylmalonic acid. RESULTS: An explicit reason for requesting plasma methylmalonic acid was stated in 57% of 198 examined medical records, known or suspected anaemia being the most frequent reason. No further action was taken in 109 (62%) of the 177 cases available for follow-up. Amongst the remaining 68 patients, the finding of an increased plasma methylmalonic acid led to diagnosis of cobalamin deficiency in 46 patients. Six patients with a markedly increased plasma methylmalonic acid (above 0.99 micromol L-1) and clearly decreased plasma cobalamins (below 200 pmol L-1) were not recognized as having cobalamin deficiency. CONCLUSIONS: This lack of response to an increased plasma methylmalonic acid raises an important question. Is the clinical response inadequate, or is the connection between an increased level of plasma methylmalonic acid and signs of clinical significant cobalamin deficiency less clear?
Adult↗
Quantification of melanoma cell-specific MART-1 mRNA in peripheral blood by a calibrated competitive reverse transcription-PCR.
BACKGROUND: Reverse transcription-PCR (RT-PCR) amplification of melanoma cell-specific mRNA can detect melanoma cells in the peripheral blood of patients with malignant melanoma. We present a method to quantify mRNA coding for the melanoma-specific melanoma antigen recognized by T cells #1 (MART-1) in RNA isolated from peripheral blood. METHODS: To establish a calibration curve, we measured the concentration of MART-1 mRNA in SK-MEL-28 melanoma cells grown in vitro by competitive RT-PCR. Serial dilutions of these cells were used as calibrators in the assay. The assay was conducted by adding a fixed amount of a RNA internal standard to RNA isolated from either peripheral blood or the calibrators before RT-PCR amplification with MART-1 primers in a nested PCR design. The amount of MART-1 mRNA in blood samples was calculated from the calibration curve. RESULTS: Addition of melanoma cells grown in vitro to blood from healthy donors demonstrated that the method can detect a single SK-MEL-28 melanoma cell in 1 mL of blood (1.5 x 10(-21) mol MART-1 mRNA/mL). MART-1 mRNA was observed in 4 of 12 blood samples from patients with malignant melanoma, at concentrations of 3-18 x 10(-21) mol MART-1 mRNA/mL of blood. No MART-1 mRNA was detected in blood samples from 25 controls without malignant melanoma. Intra- and interassay CVs were 15% (n = 12; mean = 44 x 10(-21) mol MART-1 mRNA/mL) and 33% (15 samples analyzed in two different analytical runs; mean = 30 x 10(-21) mol MART-1 mRNA/mL), respectively. CONCLUSIONS: Our method is the first competitive RT-PCR assay for quantification of melanoma cells in blood samples that compensates for the variation of both the reverse transcription and PCR reactions. The method allows the inclusion of control samples for continuous quality assessment.
Adult↗
[Human EGF receptor 2 and treatment of breast cancer].
Explore the source record for details and available documents.
Biomarkers, Tumor↗
Molecular dissection of the intrinsic factor-vitamin B12 receptor, cubilin, discloses regions important for membrane association and ligand binding.
Cubilin, the receptor for intrinsic factor-vitamin B12, is a novel type of high molecular weight receptor consisting of a 27 CUB (complement components C1r/C1s, Uegf, and bone morphogenic protein-1) domain cluster preceded by 8 epidermal growth factor repeats and a short N-terminal sequence. In addition to binding the vitamin B12-carrier complex, cubilin also binds receptor-associated protein. To delineate the structures for membrane association and ligand binding we established a panel of stable transfected Chinese hamster ovary cells expressing overlapping segments of rat cubilin. Analysis of conditioned media and cell extracts of transfected cells revealed that the N-terminal cubilin region conveys membrane association. Helical plotting of this region demonstrated a conserved amphipathic helix pattern (Lys74-Glu109) as a candidate site for hydrophobic interactions. Ligand affinity chromatography and surface plasmon resonance analysis of the secreted cubilin fragments showed ligand binding in the CUB domain region. Further dissection of binding-active fragments localized the binding site for intrinsic factor-vitamin B12 to CUB domains 5-8 and a receptor-associated protein-binding site to CUB domains 13-14. In conclusion, the N-terminal cubilin region seems crucial for membrane association, whereas the CUB domain cluster harbors distinct sites for ligand binding.
Amino Acid Sequence↗
Ureteral growth in animal models with increased renal excretion of urine.
The influence of increased functional load on the macroscopical and histological appearance of the ureter was investigated. Sixty rats were divided into five groups: (1) sucrose-fed rats with non-osmotic polyuria; (2) diabetic rats with osmotic polyuria; (3) uninephrectomized rats; (4) sham-operated control rats; and (5) control rats. The 24-hour urinary volume was measured on days 7, 14 and 21. Growth of the kidney, ureter and bladder was investigated and the histological appearance of the ureter was further evaluated. Diabetic and sucrose-fed rats had comparable polyuria with a seven-fold increase in urinary output. The urinary volume for the remaining kidney was doubled in uninephrectomized rats. After 3 weeks, diabetic rats had increased weight of the kidney, ureter and bladder, sucrose-fed rats had increased weight of the bladder, whereas uninephrectomized rats had increased weight of the kidney and ureter. The cross-sectional area (CSA) of the ureter wall from control rats increased from the proximal to the distal portion. The size of the whole ureter from diabetic rats was dramatically increased, the CSA of the wall of the distal ureter portion being four times that of the controls. The CSA of the ureter wall from sucrose-fed rats was increased only in the distal portion, whereas the ureter from uninephrectomized rats was increased only in the proximal portion. The results demonstrate the importance of differentiating between different portions of the rat ureter when examining histological sections of this organ. Moreover, polyuria per se is shown to induce growth of the bladder and of the adjacent distal part of the ureter, whereas uninephrectomy and diabetes caused growth of the kidney and the upper parts of the ureter, in addition to the growth induced by polyuria.
Administration, Oral↗
Holotranscobalamin - a sensitive marker of cobalamin malabsorption.
BACKGROUND: No simple and reliable method of identifying patients with cobalamin malabsorption is available at present. The measurement of plasma holotranscobalamin, i.e. the metabolically active cobalamins bound to the transport protein transcobalamin, has been suggested as a means of fulfilling such criteria. DESIGN: We describe a method that directly quantifies cobalamins attached to transcobalamin. The method is evaluated in patients referred for gastrointestinal examination because of suspected cobalamin malabsorption. RESULTS: Of the 101 patients referred, all 48 with gastrointestinal conditions compatible with cobalamin malabsorption had plasma holotranscobalamin below 35 pmol L-1 (interval of 35-160pmol L-1). None of the patients with plasma holotranscobalamin above the lower reference limit had conditions compatible with cobalamin malabsorption. CONCLUSION: The values obtained for plasma holotranscobalamin showed a better correlation with possible malabsorption than the values obtained for plasma cobalamins. The specificity of the test, however, needs to be elucidated further.
Adolescent↗
Expression of transforming growth factor alpha and epidermal growth factor receptor in human bladder cancer.
We analysed the expression of epidermal growth factor receptor (EGFr) and transforming growth factor alpha (TGF-alpha) in human bladder tumours. Tumour biopsies were obtained from 54 patients with primary bladder cancer (18 stage T1 and 36 stage T2-4). The protein and mRNA expression of EGFr and TGF-alpha were quantified by ELISA and competitive RT-PCR, respectively. The EGFr protein level was significantly increased in T2-4 tumours (0.44 x 10(-11); 0.0-27.5 x 10(-11) mol/g) compared with T1 tumours (0.0; 0.0-2.0 x 10(-11) mol/g) (median; range; 2p<0.01). The EGFr protein and mRNA level correlated (Spearman r=0.45, 2p<0.005, n=40). Co-expression of TGF-alpha protein and EGFr protein was significantly associated with muscle invasive tumours (T2-4) (chi-squared=7.9, df=3, p<0.05) and the TGF-alpha protein level correlated significantly with EGFr protein expression (Spearman r=0.56, 2p<0.0001, n=54). While tumour stage correlated with survival, no correlation was observed between survival and the expression of EGFr and/or TGF-alpha. In conclusion, human bladder tumours express both EGFr and TGF-alpha. The expression of EGFr and TGF-alpha are closely correlated, and the expression of EGFr and co-expression of EGFr and TGF-alpha correlate with tumour stage.
Enzyme-Linked Immunosorbent Assay↗
Adsorption of EGF receptor ligands to test tubes--a factor with implications for studies on the potency of these peptides.
Studies on the relative potency of ligands for the epidermal growth factor receptor are usually performed with highly purified ligand specimens. However, adsorption of ligands to glass and plastic surfaces may affect the results by reducing the ligand concentration in an unpredictable way. The aim of this study was to examine the adsorption of four epidermal growth factor (EGF) receptor ligands, EGF, transforming growth factor alpha (TGF-alpha), heparin binding-EGF (HB-EGF) and betacellulin, to commonly used test tubes of polyethylene, polystyrene and glass, respectively. The ligands were kept in a sodium phosphate buffer, both with and without 0.1% human albumin as carrier protein. Adsorption was examined after 20 minutes at room temperature as well as after overnight storage at 4 degrees C. The ligands were quantitated by ELISAs. In the buffer not containing 0.1% human albumin there was a marked adsorption, which differed both among the ligands and among the test tubes. After 20 minutes the ligand concentrations were reduced to 33-73% in polyethylene tubes, to 15-46% in polystyrene tubes and to 12-29% in glass tubes. The adsorption was even more pronounced after storage overnight. The use of 0.1% human albumin in the buffer solved the problem in polyethylene and polystyrene tubes, but not in glass tubes. The results demonstrate that adsorption to surfaces can be a significant problem for EGF receptor ligands and emphasize the need for controlling the growth factor concentration in the final experimental setting.
Adsorption↗
Adrenergic blockade in diabetic and uninephrectomized rats: effects on renal size and on renal and urinary contents of epidermal growth factor.
The present study reports on the effects of adrenergic blocking agents on the renal growth and on the renal content and urinary excretion of epidermal growth factor (EGF) in streptozotocin-induced diabetic or uninephrectomized rats. Diabetic and uninephrectomized rats were allocated to groups treated with either saline or adrenergic antagonists and compared to controls and sham-operated controls, respectively. 24-hour urine samples were obtained on days 7, 14, and 21 and renal tissue samples on day 21. The 24-hour urinary excretion of EGF from controls and saline-treated diabetic rats was comparable. In adrenergic antagonist treated diabetic rats, it was reduced by at least 40% throughout the study period. Uninephrectomy caused a 50% reduction in the urinary excretion of EGF. This was not influenced by treatment with an adrenergic antagonist. After 3 weeks, saline-treated diabetic rats had an increase of 33% in kidney weight when compared to controls. The adrenergic antagonist treated diabetic groups had a significantly lower increase of 15%. Postnephrectomized renal growth was not affected by adrenergic antagonists. The total renal content of EGF was comparable in the saline-treated diabetic group and the control group, but was reduced by approximately 50% in the kidneys from the adrenergic antagonist treated diabetic groups. Renal EGF mRNA levels were also reduced in adrenergic antagonist treated diabetic rats. In contrast to diabetes, the renal growth following nephrectomy was not affected by adrenergic blocking agents. These results provide evidence for fundamental differences between diabetes-related renal growth and that observed in compensation to nephrectomy and suggest a connection between adrenergic activity, renal growth, and EGF in diabetes.
Adrenergic alpha-Antagonists↗
Time-dependent changes of levels of endogenous epidermal growth factor in submandibular glands, in kidneys, and in urine in rats during systemic treatment with EGF.
BACKGROUND: Exogenous EGF influences the levels of endogenous EGF differently in the submandibular glands (SMG) and the kidneys. The aim of the present study was to examine the time-dependent changes in levels of endogenous EGF during 1-4 weeks of EGF treatment. METHODS: Female rats were allocated into five groups receiving EGF subcutaneously (150 microg/kg/day) for 0 (controls), 1, 2, 3 and 4 weeks prior to sacrifice at an age of 12 weeks. At the end of the study period, 24-h urine samples were collected. RESULTS: The weight of the SMG increased during EGF treatment (303+/-33 (controls), 359+/-37 (1 week EGF, P < 0.01), 390+/-30 (4 weeks EGF, P < 0.001) (mg mean+/-S.D.)). The EGF content of the SMG was unchanged after 1 week but threefold decreased after 4 weeks of treatment, respectively. The expression of EGF mRNA was decreased after 1 and 4 weeks as assessed with in situ hybridization. The weight of the kidneys was unchanged after 1 week and increased after 4 weeks of treatment (828+/-105 mg (controls) vs. 935+/-44 mg (4 weeks EGF, P < 0.005)). The renal content and the urinary excretion of EGF were significantly increased by 20-30% only in the group treated for 4 weeks. CONCLUSION: EGF treatment induces a time-dependent decrease in the EGF content in the SMG most likely by reducing the biosynthesis of endogenous EGF. In contrast, the EGF content in kidneys and in urine was unchanged after 1 week and increased after prolonged treatment.
Animals↗
[Vitamin B12 uptake: a new insight into molecular mechanisms].
Explore the source record for details and available documents.
Humans↗