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Biomedical subjects

D L Hwang

Publications and source records attributed to D L Hwang.

At least 19 recordsLinked to original sources
PubMed1992

Release of different fractions of epidermal growth factor from human platelets in vitro: preferential release of 140 kDa fraction.

Platelet-rich plasma in acidic-citrate-dextrose anticoagulant was kept for 5 days in an oxygen-permeable bag at 22 degrees C in an incubator/rotator. Platelet count remained stable throughout the experiment. On days 0, 3 and 5, aliquots were removed; platelets were isolated by centrifugation at 22 degrees C, 1500 g for 20 min, reconstituted to the original volume with PBS buffer, and the contents of alpha-granules were released by repeated freezing and thawing. Epidermal growth factor (EGF) and beta-thromboglobulin (beta-TG) in the platelet-poor plasma and platelet lysates were determined by radioimmunoassays. Results indicated that in platelet-free plasma, both total EGF and beta-TG increased 3-5-fold after 5 days; this amount represented 10-20% of the factors stored in the platelets. Correspondingly, the EGF and beta-TG contents of the platelet lysates exhibited accompanying decreases. HPLC fractionation showed that the main EGF fraction which progressively decreased in the lysates and increased in plasma had a molecular mass of 140 kDa. The contents of the 67 kDa and 6 kDa fractions did not change substantially. We conclude that under these conditions, the 140 kDa fraction was released preferentially. In view of these and previous experiments, it seems likely that different organs contribute to plasma EGF fractions.

Adolescent↗
PubMed1992

Effects of platelet-contained growth factors (PDGF, EGF, IGF-I, and TGF-beta) on DNA synthesis in porcine aortic smooth muscle cells in culture.

Platelet-derived growth factor (PDGF), epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), and transforming growth factor-beta (TGF-beta) are potent mitogens present in human platelets. Since they are likely to be released simultaneously at the site of vessel injury, their combined effects on vascular smooth muscle cells are more relevant physiologically than their individual actions. Therefore, we added various concentrations of growth factors to quiescent porcine aortic smooth muscle cells cultured in low-serum (0.5%) medium and measured the amount of [3H]thymidine incorporated into DNA. Effect of TGF-beta alone was concentration-dependent: stimulatory (1.5-fold increase over the basal) at 0.025 ng/ml and inhibitory at greater than or equal to 0.1 ng/ml. Effects of the other three growth factors on DNA synthesis were only stimulatory; their maximally effective concentrations were 20 ng/ml for PDGF (eightfold over the basal), 40 ng/ml for EGF (six-fold increase), and 20 ng/ml for IGF-I (fourfold increase). When PDGF, EGF, and IGF-I were added at submaximally effective concentrations, their effects were additive. TGF-beta at 1 ng/ml inhibited at least 50% of the effects of 20 ng/ml EGF and of 10 ng/ml IGF-I, whereas inhibition of the effect of 10 ng/ml PDGF required 10 ng/ml of TGF-beta. The concentration of TGF-beta needed to inhibit 50% of the combined effect of EGF, IGF-1, and PDGF was 5 ng/ml. These results show complex interrelationships between the growth factors contained in the alpha-granules of human platelets in their effects on porcine aortic smooth muscle cells.

Animals↗
PubMed1992

Effect of extracellular magnesium on platelet activation and intracellular calcium mobilization.

A dose-dependent effect of magnesium on the inhibition of platelet aggregation and release of ATP from dense granules was observed in human platelets (in whole blood, platelet-rich plasma, or washed platelets) against various aggregation agents (ADP, U46619, collagen, or thrombin). The synthesis and release of the proaggregatory cyclooxygenase (CO) and lipoxygenase (LO) products, thromboxane A2 (TXA2) and 12-hydroxyeicosatetraenoic acid (12-HETE), respectively, in platelets were also inhibited by Mg in a dose-dependent manner (IC50 4 to 6 mmol/L). These Mg-mediated activities were further enhanced when platelets were preincubated with insulin (100 microU/mL). The effect of extracellular Mg on the change of intracellular calcium concentration ([Ca2+]i) was assessed using Fura-2/AM loaded cells in the presence or absence of extracellular Ca. Thrombin-stimulated influx of Ca ions decreased from 194 +/- 30 nmol/L to 156 +/- 21 nmol/L in the presence of 5 mmol/L Mg and to 111 +/- 16 nmol/L in 10 mmol/L Mg. However, the intracellular Ca release (as determined in the presence of 5 mmol/L EGTA) was not affected by Mg. The intracellular Ca-dependent protein kinase C and myosin light chain kinase activities on the phosphorylation of endogenous p47 and p20 proteins studied after 2 min of thrombin addition decreased only 10 to 25% in the presence of 5 to 10 mmol/L Mg. Similar results were obtained when EGTA was added prior to the initiation of protein phosphorylation. We conclude that Mg can dose dependently inhibit a wide variety of agonists on platelet aggregation. Furthermore, insulin can potentiate the inhibitory effects of Mg on platelet activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Proteins↗
PubMed1992

Origin of urinary epidermal growth factor in humans: excretion of endogenous EGF and infused [131I]-human EGF and kidney histochemistry.

1. This study examined (i) whether blood-infused epidermal growth factor (EGF) can pass into urine; (ii) whether infused labelled EGF behaves like endogenous plasma immunoreactive EGF; and (iii) which parts of the human nephron show morphological evidence of EGF synthesis? 2. We infused human [131I]-EGF into a volunteer. After 6 min, only 66% of the plasma counts represented intact EGF. At the end of infusion, the T1/2 of EGF was calculated to be 1.6 min. The tail of the curve lasted for at least another 2 h. The total excretion of the labelled EGF was 2.45% of the infused dose and was proportional to the urine volume. 3. After a water load, the excretion of endogenous EGF was, on the contrary, inversely related to urine volume. 4. Immunohistochemically, human kidneys were not stained by monoclonal anti-EGF antibodies but showed positive in situ hybridization for EGF mRNA in the nuclei of glomerular mesangial cells, distal convoluted tubules and collecting tubules. 5. We conclude that human kidneys synthesize EGF and release it into urine. Plasma-derived EGF constitutes under normal conditions only a small part of the urinary EGF. Contrasting volume-dependency of the excretion of endogenous and [131I]-EGF requires further study and cautions against extrapolating results obtained with labelled EGF to physiological conditions.

Epidermal Growth Factor↗
PubMed1991

Trauma, especially of the submandibular glands, causes release of epidermal growth factor into bloodstream in mice.

Submandibular glands in mice were traumatized by handling and then removed. Immunoreactive epidermal growth factor (EGF) in serum increased after 5 min and continued to increase, reaching at 1 h a peak of 50-fold normal in males and twice normal in females. If after traumatization the glands were repositioned with their blood supply intact, maximal increase of serum EGF at 1 h was 190-fold control values in males and 2-fold in females. In male mice, incision of abdominal wall skin led to a 15-fold increase of EGF in the serum; this rise was absent 3 days after sialoadenoectomy. After traumatization, repositioned submandibular glands lost 80% of their EGF; after the abdominal wall incision, only 30%. Following removal of submandibular glands, decrease of EGF level in serum was very slow: to 60% of the initial value after 3 days and to 40% after 10 days. By the HPLC characteristics, immunoreactive EGF in control serum and at its peak were indistinguishable. Urinary excretion of EGF was significantly elevated only when its serum level was 190-fold normal. We conclude that traumatized submandibular glands discharge into circulation a large part of their stored EGF. A similar but much less pronounced process takes place after abdominal skin incision. The presence of EGF in serum after its slow decline in sialoadenoectomized mice shows that a fraction of circulating EGF may recirculate prolonging its apparent half-life.

Animals↗
PubMed1991

Immunoreactive epidermal growth factor in serum, plasma, platelets, and urine in patients on chronic dialysis.

In 25 patients with chronic renal failure undergoing hemodialysis the level of epidermal growth factor (EGF) was significantly increased in plasma (61 +/- 10 vs. 36 +/- 12 pM in 23 aged-matched controls; p less than 0.0001) and serum (189 +/- 51 vs. 138 +/- 69 pM, p less than 0.006) and slightly increased in platelets (391 +/- 134 vs. 308 +/- 87 aM/10(6) platelets in controls; p less than 0.0582). In those 15 patients who produced urine, EGF was absent or close to the low limit of the sensitivity of the method (17 pM). Thus, kidneys are not delivering EGF to blood but their role in EGF removal is possible. Urinary EGF virtually disappears in severe chronic renal failure.

Aged↗
PubMed1990

Excretion of epidermal growth factor (EGF) in diabetes.

Excretion of epidermal growth factor (EGF) is decreased in renal failure. We assayed it in diabetes mellitus in an attempt to relate it to clinical parameters, esp. those of diabetic nephropathy. EGF excretion declined with age but in all age groups of diabetic patients was below the first percentile for controls. In 26 control and 34 prepubertal diabetic children excretion was correspondingly 1126 +/- 442 and 932 +/- 489 pmol/mmol creatinine (P = 0.087); in 26 control and 42 diabetic adolescents below age 18, 778 +/- 222 and 676 +/- 335 (P = 0.023) and in 81 control and 83 diabetic adults, 371 +/- 153 and 235 +/- 140 (P less than 0.0001). Decreased excretion of EGF was seen in some patients without any diabetic complications. Excretion of EGF was independently and inversely correlated with age and duration of diabetes but not with type of diabetes, treatment, body built, C-peptide, plasma glucose, glycohemoglobin or retinopathy. A positive correlation was seen with creatinine clearance and a negative correlation, with albuminuria, but the strongest and the only independent correlation found by stepwise multiple variable selection was with serum creatinine (r -0.711, P less than 0.0001). EGF excretion was not elevated in patients with hyperfiltration. We conclude that EGF excretion is abnormal in many patients with diabetes and that this abnormality reflects a kidney function different from glomerular filtration or glomerular permeability.

Adolescent↗
PubMed1990

Infusion of epidermal growth factor in mice: organ distribution and urinary excretion.

Anesthetized mice were infused into the tail vein with 7.5% mannitol in saline (0.1 ml/min for 60 min) alone or with EGF at 0.5 microgram/min. Urine was collected every 10 min starting 20 min after the beginning of the infusion and ending 20 min after its termination. EGF concentration in the serum of mice infused with EGF increased from the baseline level of 0.6 +/- 0.4 to 70.7 +/- 16.0 ng/ml at 80 min. Total excretion of EGF for 80 min was 117 +/- 49 ng with mannitol alone and 1916 +/- 420 ng (6.4% of the EGF infused) after mannitol with EGF. Serum and urine EGF was indistinguishable from the native mouse EGF by its radioimmunoassay and HPLC characteristics. Intact labeled EGF was also found in urine when mice were infused with 125I-EGF (1 x 10(6) cpm/ml) in mannitol. After 5 min infusion with 125I-EGF (6 x 10(6) cpm/ml in saline), more than 80% of the label was found in the liver and kidneys and more than 90% of it was intact EGF. However, 30 min after infusion more than 95% of the labeled EGF was degraded. We conclude that at least part of the urinary EGF in mice originates in blood and that liver and kidneys are the main organs of EGF degradation.

Animals↗
PubMed1990

Epidermal growth factor in serum, urine, submandibular glands and kidneys of diabetic mice.

Levels of epidermal growth factor (EGF) in serum were significantly decreased in streptozotocin (STZ)-diabetic mice (446 +/- 168 pg/ml after 1 week and 423 +/- 52 after 4 weeks vs 766 +/- 162 pg/ml in controls, P.002 and less than .001. respectively) and in genetically diabetic ob/ob mice (455 +/- 285 vs 962 +/- 453 pg/ml in nondiabetic ob/+ controls, P.043). The urinary excretion of EGF was significantly increased in STZ mice (104 +/- 53 vs 51 +/- 23 ng/h, P.013) but unchanged in ob/ob mice (33 +/- 9 vs 45 +/- 16 ng/h, P.134). However, when expressed per mg creatinine it was decreased in both cases: in STZ mice to 680 +/- 250 ng/mg at 1 week and 684 +/- 211 at 4 weeks vs 1250 +/- 303 ng/mg in controls (P less than .01); and in the ob/ob mice to 552 +/- 117 vs 1237 +/- 300 ng/mg in ob/+ controls (P less than .01). EGF content of the submandibular glands of STZ mice remained unchanged at 1 week (13.1 +/- 2.9 vs 11.0 +/- 1.8 micrograms/mg protein, P.170) but dropped by 4 weeks (4.7 +/- 1.2 micrograms/mg, P less than .001); in the ob/ob mice it was less than 20% that of controls (2.1 +/- 0.8 vs 12.2 +/- 3.6 micrograms/mg protein). In kidneys, the EGF content was not altered in either ob/ob (524 +/- 50 vs 571 +/- 33 pg/mg protein) or STZ mice (652 +/- 183 vs 665 +/- 80 pg/mg). The preproEGF mRNA level in STZ-treated mice was reduced after 4 weeks in submandibular glands but not in kidneys. The results show that diabetes affects EGF production, utilization and/or excretion in mice and that kidneys are spared from suppression of EGF synthesis that is pronounced in the submandibular glands.

Animals↗
PubMed1990

Hepatotoxicity induced by diethylnitrosamine causes no significant disturbances of systemic glucose homeostasis in rats.

In rats, a moderately hepatotoxic single dose of diethylnitrosamine (DEN) 100 mg/kg causing depletion of liver glycogen, elevation of aspartate aminotransferase and decreased liver uptake of 3-O-methylglucose, resulted in substantial changes in insulin and glucagon balance. Two days after DEN, insulin binding to liver membranes and insulin removal by the liver were sharply reduced whereas its binding to muscle and adipocyte membranes remained unaltered. Serum insulin (random and after an overnight fast) remained normal. Intravenous (I.V.) insulin (10 U/kg) caused the usual degree of hypoglycemia that, however, lasted longer than in the control animals. Removal of glucagon by liver was also depressed in spite of its normal binding to hepatocytes, and peripheral serum glucagon was increased three-fold. I.V. glucagon (40 micrograms/kg) resulted in a blunted response of plasma glucose. I.V. glucose tolerance test (1 g/kg) remained normal in spite of the insulin increase to a level twice as high as in the controls, and in spite of nonsuppressed glucagon. These changes were still present after 1-3 months, but disappeared by 6 months. The results demonstrate remarkable ability of homeostatic mechanisms to preserve normal plasma glucose and glucose tolerance in spite of dramatic changes in insulin and glucagon.

Animals↗
PubMed1990

Human serum and plasma have different sources of epidermal growth factor.

Epidermal growth factor (EGF) was determined by radioimmunoassay in serum, plasma, and urine of 23 patients undergoing ablative therapy followed by bone marrow transplantation. The difference between the serum and plasma values reflected the amount of EGF released from the platelets at the time of blood coagulation. Platelet-derived EGF strongly correlated with platelet count (r + 0.850, P less than 0.0001), and the intercept of the regression line was very close to zero; one platelet contained approximately 2.5 x 10(-18) g EGF. Correspondingly, when the platelet count dropped after bone marrow ablation from 222 +/- 97 to 33 +/- 13 x 10(9)/l, the serum EGF decreased from 603 +/- 222 to 65 +/- 41 pg/ml (P less than 0.0001). Plasma EGF content did not correlate with the platelet count and did not change significantly after bone marrow ablation (before and after the ablation, correspondingly, 290 +/- 80 and 332 +/- 99 pg/ml, P = 0.194). High-performance liquid chromatographic fractionation of serum and plasma showed different molecular mass distribution of EGF-immunoreactive fractions. The main molecular mass components of the plasma EGF did not change after bone marrow ablation. Urine excretion remained unchanged (320 +/- 133 and 314 +/- 173 pmol EGF/mmol creatinine). We conclude that whereas platelets are the source of serum EGF, the origin of plasma EGF is different and the search of its origin is warranted.

Adult↗
PubMed1990

Epidermal growth factor and platelet-derived growth factor in blood in diabetes mellitus.

Epidermal and platelet-derived growth factors are potent mitogens for many types of cells, including smooth muscle cells. Epidermal growth factor in blood of humans is present both in platelets (as reflected in its serum level) and in plasma, the source(s) of which remains unknown. We assayed its level in 82 diabetic patients and 53 age-matched controls. In diabetes, epidermal growth factor level was increased in serum (191 +/- 43 vs 155 +/- 64 pmol/l, p = 0.0002) and plasma (53 +/- 9 vs 38 +/- 14 pmol/l, p less than 0.0001), without any difference between the patients with and without complications. Platelet-derived growth factor level was assayed only in serum of 19 patients with uncomplicated diabetes and found elevated (222 +/- 47) as compared with 13 controls (160 +/- 26 pmol/l), (p = 0.0002). Type of diabetes, its duration, mode of therapy, control, presence of retinopathy or albuminuria (in case of epidermal growth factor), as well as C-peptide age and sex did not correlate with epidermal or platelet-derived growth factor levels. Serum but not plasma epidermal and platelet-derived growth factor were negatively correlated with serum creatinine (correspondingly, r = -0.373, p = 0.0008 and r = -0.564, p = 0.0285). It is concluded that diabetes itself and not its complications cause increased levels of epidermal growth factor in plasma and serum and of platelet-derived growth factor in serum.

Adult↗
PubMed1990

Epidermal growth factor in blood and urine of athyreotic adults.

The total contribution of the thyroid to epidermal growth factor (EGF) levels in blood and urine was determined in 18 patients cured from thyroid cancer at the time of thyroxine treatment and 6 weeks off it in the state of athyroidism. As compared to the euthyroid state, the athyrodism was associated with a drop in the urinary EGF excretion from 24.8 +/- 8.4 to 11.8 +/- 4.6 ng/mg creatinine (p less than 0.0001) and some increase in the EGF level in blood serum from 159.5 +/- 55.0 to 191.2 +/- 41.0 pM (p = 0.023). We conclude that the thyroid affects the synthesis and/or blood delivery of EGF and is responsible for approximately one half of its urinary excretion.

Adult↗
PubMed1990

Megakaryocyte synthesis is the source of epidermal growth factor in human platelets.

Epidermal growth factor (EGF) is known to be present in the alpha granules of human platelets; however the source of this EGF, ie, whether it is taken up by the platelets from the circulation, or whether it is packaged into the platelets from the megakaryocyte during thrombopoiesis, is unknown. To determine whether EGF is taken up by platelets, platelets for EGF receptors were assayed and it was attempted to detect uptake of EGF by the platelets from culture medium. Platelets were found to lack EGF receptors, and no uptake of EGF from the culture medium was detected. To assess whether EGF is packaged into platelets from the megakaryocyte, megakaryocytes in frozen section bone marrow cores were stained for EGF protein by immunohistochemistry, and it was demonstrated that EGF is present in megakaryocytes. In addition, staining of megakaryocytes by in situ hybridization for EGF mRNA demonstrated its presence in these cells. Therefore it is concluded that the source of EGF in human platelets is the megakaryocyte and that this EGF is synthesized in the megakaryocyte rather than being taken up from its environment.

Base Sequence↗
PubMed1989

Epidermal growth factor excretion and receptor binding in diabetic rats.

Urinary epidermal growth factor (EGF) excretion was calculated as ng EGF per mg creatinine and ng EGF per 24 hr. It was increased 4-9 fold in rats with genetic (BB) or streptozotocin-induced diabetes. It decreased to 2-3 fold control values in insulin-treated animals. In contrast, EGF concentration in serum was lower in diabetic than in control rats (360 +/- 72 vs 524 +/- 150 pg/ml, P .086); EGF level in plasma was unchanged (319 +/- 67 vs 313 +/- 96 pg/ml). In diabetic rats EGF content was increased in submaxillary glands (1018 +/- 259 vs 738 +/- 122 pg/mg protein, P .060) but unchanged in the kidneys (70 +/- 18 vs 65 +/- 6 pg/mg protein in controls). EGF binding to the liver microsomes in diabetic rats was decreased by 30-40% and was not restored by insulin therapy. Binding to the kidneys also showed a tendency to decrease in diabetic animals. The EGF excretion and receptor binding were normal in obese normoglycemic Zucker fa/fa rats. We suggest that hyperglycemia and/or glucosuria may affect EGF synthesis and/or excretion in the kidneys and EGF synthesis or accumulation in the megakaryocytes. The mechanism of decreased EGF receptor binding remains to be clarified.

Animals↗
PubMed1987

Hepatocarcinogens induce decrease in mRNA transcripts of receptors for insulin and epidermal growth factor in the rat liver.

Gene expression of the receptors for insulin and epidermal growth factor (EGF) was studied in the livers of rats after a single injection of a hepatocarcinogen diethylnitrosamine (DEN) 100 mg/kg or after feeding the animals N-acetylaminofluorene (AAF) 0.02% w/w. DEN induced a time-dependent decrease in mRNA transcription of the receptors for insulin (10.3 and 8.5 Kb) and EGF (10.0, 5.8 and 2.8 Kb), evident already after 4 hours, reaching a nadir of 10-20% of the initial level between 16 and 24 hours and returning to normal by 10 days. In rats fed AAF, transcription of both receptor genes decreased to less than 20% of the control values after 2 days. In the livers of rats treated with DEN, that developed hepatocellular carcinomas one year later, expression of both receptors was also very low. DNA showed no changes. The results suggest that the hepatocarcinogens or their metabolites decrease RNA transcription or destabilize the steady state RNA level of both receptors in the early phase of toxic effect and that some tumor-derived products may be involved in the same phenomenon in the later stage of tumor development.

Animals↗
PubMed1987

Insulin-like activity of chromium-binding fractions from brewer's yeast.

51CrCl3 was added to the incubation medium of Saccharomyces cerevisiae for up to 48 hr. After repeated freezing and thawing, lysing in 9 M urea with 1% NP-40 detergent, and dialysis against water, the lower molecular weight (Mr less than 3500) dialysate was retained on a SE53 cationic exchange column, eluted with 0.25 M NH4OH and fractionated on a Bio-gel P-2 column. The insulin-like biological activity of the fractions was measured by the 14C-glucose oxidation in isolated rat adipocytes. The biological activity that was found in two of nine fractions did not correspond to their chromium content. Moreover, identical findings were obtained when chromium was added not to the live yeast but to the yeast extract, which showed that its binding was a chemical process not requiring cellular activity. No fraction demonstrated insulin-potentiating activity on rat adipocytes.

Adipose Tissue↗