Functional association of essential splicing factor(s) with PRP19 in a protein complex

We have previously shown that the yeast PRP19 protein is a spliceosomal component, but is not tightly associated with small nuclear RNAs. It appears to associate with the spliceosome concomitant with or just after dissociation of the U4 small nuclear RNA during spliceosome assembly. We have found that PRP19 is associated with a protein complex in the splicing extract and that at least one of the associated components is essential for splicing. Taking advantage of the epitope tagging technique, we have isolated the PRP19-associated complex by affinity chromatography. The isolated complex is functional for complementation for the heat-inactivated prp19 mutant extract, and consists of at least seven polypeptides in addition to PRP19. At least three of these can interact directly with the PRP19 protein. We also show that the PRP19 protein itself is in an oligomeric form, which might be a prerequisite for its interaction with these proteins.

Regulation of calcitriol receptor and its mRNA in normal and renal failure rats

Homologous up-regulation of calcitriol receptor (VDR) by calcitriol is believed to be a transcriptional event. In this experiment, we studied the effect of calcitriol on VDR in normal and renal failure rats. The time course of the effect of calcitriol on VDR mRNA showed a biphasic change in VDR mRNA in response to calcitriol. The concentration of intestinal VDR mRNA increased at six hours and reached peak levels approximately 15 hours after calcitriol injection. Thereafter, the mRNA began to decrease and by 48 hours the level had declined to below the control values. The VDR levels also increased, though they lagged behind the VDR mRNA, and nearly plateaued at 24 hours after calcitriol treatment. In renal failure, the concentrations of VDR were lower and the levels of VDR mRNA were higher than the respective values of normal rats, suggesting that VDR synthesis was inhibited at post-transcriptional sites. Chronic administration of calcitriol increased the VDR but lowered the VDR mRNA levels in both normal and renal failure rats. Infusion of uremic ultrafiltrate to normal rats resulted in lower VDR and higher VDR mRNA levels similar to those found in rats with renal failure. The results indicate that uremic toxins are responsible for the low VDR and high VDR mRNA in renal failure.

Hormonal change in an adult with Prader-Willi syndrome: report of a case

We report a classical case of Prader-Willi syndrome (PWS) in an adult with typical interstitial deletion of chromosome 15, and emphasize the study of hormonal change. This 21-year-old female had PWS face characteristics, small hands and feet, marked obesity, mental retardation, growth retardation, absence of puberty and amenorrhea. She also had the characteristic history of infantile hypotonia, poor feeding, failure to thrive and then improved appetite, followed by obesity from the age of four years. She had compulsive hyperphagia, to the extent of stealing and lying to take food. Chromosome study with high resolution banding technique revealed a small interstitial deletion at band q12 of chromosome 15, which is characteristically found in a majority of patients with PWS. Hormonal study revealed hypogonadism and growth hormone deficiency of supposed hypothalamic origin. She also had non-insulin-dependent diabetes mellitus with decreased pancreatic insulin reserve.

The cardiovascular effects of ricin in rabbits

Ricin is a toxic lectin from the castor bean. The time course of its toxic effects on the cardiovascular system of rabbits was investigated after determining its LD50 and minimum lethal dose in rabbits by the Up and Down method, as a basis for dosing. Systolic and diastolic arterial pressures, electrocardiogram and heart rate were recorded for 48 hr following administration of either a toxic sublethal (0.22 microgram/kg) or minimum lethal dose (0.44 microgram/kg) of ricin. After a delayed onset of about 20 hr, the minimum lethal dose (0.44 microgram/kg) of ricin caused a significant decrease in both systolic and diastolic pressures (P < 0.05). The systolic and diastolic pressures decreased 0.47 and 0.39 mmHg/hr more so than control groups, respectively. A toxic sublethal dose (0.22 microgram/kg) of ricin did not significantly alter either systolic or diastolic pressure. Neither dose of ricin caused cardiac arrhythmias or significantly increased heart rate. We conclude that the lethal hypotensive sequelae of ricin toxicity in the rabbit were peripheral in origin and not cardiogenic at these two doses.

Prospective evaluation of insulin resistance and lipid metabolism in women receiving oral contraceptives

OBJECTIVES

It has been suggested that normal women receiving oral contraceptives (OC) may develop a series of metabolic side-effects which relate to the risk of cardiovascular disease. These metabolic disturbances include changes in glucose and insulin metabolism, raised serum lipid and lipoprotein concentrations and elevated blood pressure. All these changes indicate that OC might cause insulin resistance. We have prospectively examined the effect of OC on insulin resistance and lipid metabolism including Lp(a) values.

PATIENTS

The study group comprised 13 normally menstruating Chinese women.

DESIGN

The study subjects were given a combined triphasic oral contraceptive which was administered on a 21-day on, 7-day off medication cyclic regimen, the first pill being administered on day 5 from the beginning of menses. The metabolic investigations were carried out during luteal phase before OC and again the third week of the third month of OC administration.

MEASUREMENTS

Metabolic evaluation including insulin secretion and insulin-mediated glucose uptake were evaluated by oral glucose tolerance test and the modification of insulin suppression test. Fasting triglyceride, cholesterol, HDL-cholesterol and Lp(a) concentrations were also measured.

RESULTS

The plasma glucose and insulin responses during a 75-g oral glucose challenge increased significantly (P < 0.05 and P < 0.03, respectively). The steady-state plasma glucose (SSPG) concentrations achieved during constant infusion of glucose, insulin and somatostatin increased significantly after 3 cycles of OC administration (glucose 7.5 +/- 0.8 vs 12.4 +/- 0.7 mmol/l, P < 0.001) while the steady-state plasma insulin (SSPI) concentrations were relatively similar (410 +/- 14 vs 391 +/- 7 pmol/l, NS). Plasma triglyceride levels increased significantly (0.81 +/- 0.12 vs 1.09 +/- 0.19 mmol/l, P < 0.03) following OC administration. Fasting plasma cholesterol, HDL cholesterol and calculated LDL cholesterol concentrations did not change as compared with baseline values, nor did the ratio of total cholesterol to HDL cholesterol. The Lp(a) concentrations did not change during the administration of OC (81 +/- 25 vs 71 +/- 21 mg/l, NS).

CONCLUSIONS

These data indicated that intake of OC for 3 cycles induced glucose intolerance, hyperinsulinaemia and insulin resistance in normal menstruating Chinese women. These changes occurred in association with elevated plasma triglyceride concentrations and no alteration in Lp(a) or other lipid values.

Effect of vitamin D metabolites on calcitriol degradative enzymes in renal failure

We have demonstrated that in renal failure calcitriol degradation is decreased and that administration of vitamin D metabolites increases the degradation. In this study, we measured intestinal 24- and 26-hydroxylase activities and the effects of chronic infusion (7 days) of vitamin D metabolites on these enzymes' activities in rats with experimental renal failure. The enzymatic activity of intestinal 24-hydroxylase, but not 26-hydroxylase, was significantly lower in renal failure rats compared to control sham operated rats. Replacement of calcitriol (3 ng/day) significantly increased 24-hydroxylase activity by 17% in rats with renal failure (P < 0.01), although the activity remained 15% lower than the controls (P < 0.01). Intestinal 26-hydroxylase activity was not lower in renal failure; however, calcitriol treatment increased the activity beyond that of normal controls. In contrast, administration of 25(OH)D3 (600 ng/day) and 24,25(OH)2D3 (1 microgram/day) reduced the conversion of calcitriol to 1,24,25(OH)3D3 by more than 50% and to 1,25,26(OH)3D3 by more than 38%, respectively. We conclude that calcitriol increased its own degradation in renal failure by increasing the enzymatic activities of both 24- and 26-hydroxylase. However, the mechanisms of increased calcitriol degradation by 25(OH)D3 and 24,25(OH)2D3 in renal failure remain unknown.

Effects of terbutaline on alpha-adrenergic responses and Ca2+ influx in isolated rabbit aorta

Effects of terbutaline applied in vivo or in vitro on alpha-adrenergic receptors in the rabbit aorta in normal and Ca(2+)-free solution, and on basal, high potassium-, and phenylephrine-stimulated Ca2+ uptake into aorta were investigated. Three day terbutaline administration (25 mg/kg, subcutaneously three times daily) to rabbits increased the pKB for phentolamine in aorta rings (control 7.3 +/- 0.2, n = 9; terbutaline 7.8 +/- 0.2, n = 15). It also depressed phenylephrine-stimulated contractions of aorta rings in Ca(2+)-free but not those in normal Krebs solution. It did not significantly depress the basal, or phenylephrine-evoked Ca2+ influx into aorta rings, but decreased high potassium-induced Ca(2+)-influx (control 0.58 +/- 0.05 mumoles/g aorta; n = 3, terbutaline 0.41 +/- 0.06 mumoles/g aorta, n = 3). In vitro application of 50 microM terbutaline did not significantly alter phenylephrine-stimulated contractions of aorta rings in Ca(2+)-free Krebs solution or significantly depress basal or phenylephrine-induced Ca2+ influx into aortas, but did decrease high potassium-stimulated Ca(2+)-influx. Thus, 3-day terbutaline administration increased the affinity of alpha-adrenergic receptors for phentolamine and had a tendency to increase contractions of aorta rings to phenylephrine. It also decreased high potassium-stimulated Ca2+ influx, and depressed phenylephrine-induced contractions in Ca(2+)-free Krebs solution, while in vitro terbutaline application also decreased potassium-induced Ca2+ influx.

Tissue distribution of 3H-terbutaline in rabbits

Terbutaline is a widely used, selective beta 2-adrenergic agonist whose penetration into brain has not been demonstrated in laboratory animals. Although its tissue uptake has been reported in some animals, no uptake into brain has been demonstrated. A single dose of 20 microCi of 3H-terbutaline along with 10 mg/kg of unlabeled terbutaline was injected into a rabbit marginal ear vein. The distribution of 3H-terbutaline in several tissues was determined 0.5, 1, 3, or 6 hr later. Radioactivity in the brain was well-maintained over the 6 hr observation period. In most tissues, radioactivity peaked in less than 1 hr, then declined. Radioactivity in the urine was high at all time periods and was highest at 3 hr. Thus, terbutaline or a metabolite(s) does cross the blood-brain barrier in rabbits, and the radioactivity in the rabbit brain does not decrease during the 6 hours following terbutaline injection.

Acute segmental obstructing enteritis in children

We studied a group of 15 children with acute segmental enteritis associated with intestinal obstruction. The disease is characterized by fever, leukocytosis, copious bilious vomiting, and severe abdominal pain with signs of intestinal obstruction. Exploration revealed varying degrees of segmental ischemic change in the small bowel, but surgery seemed to be unnecessary in most cases. Antibiotics were effective in nonoperative cases. The clinical illness lasted 10-14 days. The disease was self-limited, and no mortality was found in our series. To our knowledge, this is the first report of this disease entity in Chinese children.

Duplex ultrasonographic assessment of gut blood flow velocity: effect of meal composition in normal full-term newborns after first feed

We used transcutaneous duplex Doppler ultrasound to measure superior mesenteric artery and celiac artery blood flow velocity in 45 normal healthy newborn infants. Doppler indices of PSV, TAMV, EDV, and PI were measured immediately before and after feeding at 15 minute intervals up to 75 minutes. Maximal changes were compared with preprandial baseline values. There were no significant differences between the preprandial and postprandial blood pressures and heart rates. In the superior mesenteric artery the PSV, TAMV, and EDV rose progressively and peaked 30 minutes after feeding in both the milk-fed group and the 5% glucose, water-fed group over baseline (73 versus 41% and 110 versus 63%, 130 versus 100%) (P < 0.05). The PI decreased significantly in the milk-fed group only. There were no significant changes in any blood flow velocity parameters derived from the celiac artery. We conclude that duplex ultrasonography provides a noninvasive means of studying the reactivity of the splanchnic arterial circulation to different stimuli. The chemical composition of the meal is a significant factor determining postprandial mesenteric hyperemia.

Computerized Dysmorphology Database Mackay (CDDM): preliminary report

A computerized dysmorphology database is useful for the pediatrician and geneticist in the task of diagnosing multiple malformation syndromes in children. We set up a new dysmorphology database "Computerized Dysmorphology Database Mackay (CDDM)" managed by the Clipper program. At present 278 disease entities with their clinical features and references are stored in the database. In this article, we report a practice analysis of ten dysmorphic patients by CDDM. A specific syndrome was accurately and rapidly diagnosed with the aid of CDDM in all ten cases. They serve as examples on how CDDM can be efficiently applied to obtain a short list of syndromes for differential diagnosis.

Obturator hernia: a report of eight cases

Obturator hernia is a rare problem that occurs predominantly in elderly, emaciated women. The diagnosis of obturator hernia is difficult to establish in most patients before an operation is performed. Both delayed diagnosis and delayed surgical intervention contribute to high mortality. From 1978 to 1992, eight cases of obturator hernia involved elderly females who had received operations at this hospital. Resection of the incarcerated bowel was required. The often debilitated condition of these patients and the frequent delay of diagnosis combined to produce significant operative mortality.

Pulmonary artery sling with tracheo-bronchial stenosis: report of one case

This patient is a 6-month-old female baby with intermittent symptoms of air-way obstruction for two months. The diagnostic examinations performed included: esophagogram, two-dimensional echocardiography, cardiac catheterization with selective right pulmonary arteriography, magnetic resonance imaging (MRI) and tracheo-bronchogram. The esophagogram revealed anterior indentation of the esophagus. The echocardiogram, cardiac catheterization and MRI all demonstrated anomalous origin of the left pulmonary artery from the right pulmonary artery instead of the main pulmonary artery. The tracheo-bronchogram showed long-segment stenosis of the lower portion of the trachea. A final diagnosis of pulmonary artery sling with tracheo-bronchial stenosis was made. Since the parents refused surgery, the baby expired after several episodes of cyanosis & cardiac arrest.

Effect of uric acid on plasma levels of 1,25(OH)2D in renal failure

Previous studies from these laboratories have demonstrated that uremic biologic fluids contain substances that suppress 1,25(OH)2D metabolism. Among these substances, it was found that uric acid suppresses 1 alpha-hydroxylase activity and synthesis of 1,25(OH)2D in rats. In this study, the effect of uric acid on plasma concentrations of 1,25(OH)2D in patients with renal failure was examined. Nine patients with stable chronic renal failure (serum creatinine, 1.9 to 6.4 mg/dL) were studied. None of the patients received vitamin D supplementation. Plasma concentrations of Ca, P, parathyroid hormone, creatinine, uric acid, 1,25(OH)2D, and 25(OH)D were measured before and 1 wk after the patients received allopurinol, 300 mg daily. Plasma creatinine, Ca, P, parathyroid hormone, and 25(OH)D did not change before or after allopurinol treatment. However, plasma uric acid decreased significantly from 7.3 +/- 0.4 to 4.0 +/- 0.4 mg/dL (P < 0.01) and plasma concentration of 1,25(OH)2D rose from 30.8 +/- 2.7 to 38.2 +/- 4.8 pg/mL (P < 0.01) after the ingestion of allopurinol. Allopurinol itself did not appear to directly enhance 1 alpha-hydroxylase activity in rats. It was concluded that a short-term administration of allopurinol suppresses plasmic uric acid and increases plasma 1,25(OH)2D in patients with chronic mild to moderate renal failure.

[Clinical study of infants with birth weight less than 1500 grams]

One hundred and seventy-seven infants of birth weight less than 1500 grams admitted to the neonatal intensive care unit of Mackay Memorial Hospital in 1987 were studied. The sex distribution, male to female ratio was 100:77, inborn 78 cases, outborn 99 cases. At one year follow-up, the mortality rate of these weighed between 500 gm and 799 gm was 100%, between 800 gm and 999 gm 54%, between 1000 gm and 1249 gm 17%, between 1250 gm and 1499 gm 19% respectively. The mortality rate of outborns was higher than that of inborns (X2 = 6.03, P < .05). The most common cause of mortality of these infants was intracranial hemorrhage, it accounts for 55% of the mortality. Seventy-three percent of the deceased cases expired during the first three hospitalization days. Of these 177 cases, 94 were put on respirator with IPPB initially, another 47 cases were on nasal CPAP. Only 36 cases didn't require respiratory therapy. Complications of the extreme prematurity and management including intraventricular hemorrhage, pulmonary hemorrhage, sepsis, pneumothorax, persistent pulmonary hypertension, disseminated intravascular coagulopathy, electrolyte imbalance, bronchopulmonary dysplasia and retinopathy of prematurity were discussed. In order to improve survival and reduce complications of these extreme prematurity, advanced monitoring system, early detection and prevention of intracranial hemorrhage, establishment of the transport system are essential.

Duplex Doppler assessment of visceral and cerebral blood flow velocity in full-term newborns

To assess postnatal visceral and cerebral blood flow velocity changes, transcutaneous duplex Doppler ultrasound was used to measure the superior mesenteric artery (SMA), celiac artery (CA) and anterior cerebral artery (ACA) blood flow velocity in 20 normal healthy newborns. Doppler indices of peak systolic velocity (PSV), time-averaged mean velocity, end-diastolic velocity and Pourcelot resistance index (PI) were measured immediately after delivery and consecutively for three days at 24-hour intervals. At 24 hours after delivery, PSV had risen significantly in the CA, SMA and ACA (p < 0.01). The PI had decreased significantly in all three vessels. We conclude that the most prominent hemodynamic changes in the splanchnic and cerebral artery circulation occur within 24 hours after delivery in normal healthy newborns. Possible mechanisms are discussed.

Monocyte 1 alpha-hydroxylase regulation: induction by inflammatory cytokines and suppression by dexamethasone and uremia toxin

Alveolar macrophages acquire 1 alpha-hydroxylase activity in inflammation, and thereby metabolize 25 hydroxyvitamin D3 (25 D3) to the active metabolite, 1 alpha,25-dihydroxyvitamin D3 (1,25 D3, calcitriol). Calcitriol is a potent differentiation agent that modulates mononuclear phagocyte activation and effector functions. The mediators that induce macrophage 1 alpha-hydroxylase activity are not well delineated. Furthermore, it is unclear whether calcitriol is a product only of terminally differentiated macrophages or whether less mature mononuclear phagocytes can produce it as well. The ability of newly recruited monocytes to produce calcitriol as an autocrine differentiation agent is particularly important in inflammation, as it may substantially expand the functional repertoire of these cells. To assess the effects of cytokines on 1 alpha-hydroxylase activity, blood monocytes were cultured in the presence and absence of human recombinant tumor necrosis factor alpha (TNF-alpha), interferon-gamma (IFN-gamma), and interleukins 1 and 2 and then incubated with 25 D3 substrate. The conditioned media were assayed for calcitriol by high-performance liquid chromatography and competitive receptor binding assay. No detectable calcitriol was produced by unstimulated monocytes. However, all the cytokines markedly increased monocyte calcitriol production (range 133-151 pg/mg protein; in all cases P < .001). We then determined whether calcitriol production was suppressed by preincubation with either dexamethasone or the putative uremia toxin guanidinosuccinic acid (GSA). Dexamethasone pretreatment significantly inhibited subsequent cytokine-induced calcitriol production by monocytes, as did GSA (average 69 and 63% of control, respectively).

Efficacy of plasmin-treated intravenous gamma-globulin for therapy of Kawasaki syndrome

In order to delineate the efficacy of plasmin-treated intravenous gamma-globulin (IVGG) in the treatment of Kawasaki syndrome, we compared the frequency of coronary artery abnormalities in children treated or not with IVGG for Kawasaki syndrome. Among 291 cases of Kawasaki syndrome diagnosed during the period of 1987 to 1991 without coronary abnormalities within 10 days of the onset of illness, 128 were treated with IVGG and aspirin and were compared with 163 treated with aspirin alone. IVGG was given in a dosage of 400 mg/kg/day for 4 consecutive days. The detection of coronary abnormalities was monitored by two dimensional echocardiography. Two weeks after enrollment coronary artery abnormalities were present in 37 (22.7%) of 163 children in the aspirin group and in 9 (9%) of 128 in the gamma-globulin group (P < 0.05). Seven weeks after enrollment, abnormalities were present in 20 (12.3%) of 163 children in the aspirin group and in 6 (4.6%) of 128 in the IVGG group (P < 0.05). We conclude that plasmin-treated IVGG is effective in reducing the prevalence of coronary artery abnormalities in Kawasaki syndrome and suggest a predominant role of the Fc gamma fragment of IgG in the therapeutic effect.

Mechanism of decreased intestinal calcitriol receptor concentration in renal failure

The biological actions of calcitriol and its receptor synthesis are believed to be mediated through the calcitriol-receptor complex interacting with nuclear chromatin of target cells. Thus inhibition of the receptor interaction with DNA could diminish the biological actions of calcitriol and upregulation of its receptor. We found that uremic ultrafiltrate reduced the receptor interaction with DNA in vitro. DNA-cellulose chromatography showed that the receptor from normal rats and rats infused with normal ultrafiltrate eluted as a single peak at 0.22 M KCl, whereas chronic renal failure rats and rats infused with uremic ultrafiltrate had two receptor peaks, i.e., one of normal activity at 0.22 M KCl and the other of weak activity at 0.12 M KCl. Furthermore, infusion of uremic ultrafiltrate to normal rats reduced the intestinal calcitriol receptor concentration (397 +/- 15.8 vs. 307 +/- 15.4 fmol/mg protein, both n = 4, P < 0.005). Uremic ultrafiltrate also suppressed the calcitriol-induced upregulation of the receptor (816 +/- 34.6 vs. 606 +/- 35.3 fmol/mg protein, P < 0.005). It appears that uremic toxins may reduce the biological action of calcitriol in renal failure by inhibiting receptor synthesis and the interaction of the hormone-receptor complex with nuclear chromatin.

Liver transplantation for a hepatitis B-related cirrhotic patient

A patient with chronic end-stage liver cirrhosis resulting from a hepatitis B viral infection had a successful liver transplantation performed on 1 July 1991. Preoperative serology revealed that both HBsAg and HBeAg were positive, and the anti-HBs antibody was negative. Immunoprophylaxis included active immunization, as well as injections of large doses of hepatitis B immunoglobulin (HBIG) given perioperatively to reverse the antigen status. The patient has been anti-HBs antibody positive for more than 10 months since the transplantation. The immunoprophylaxis protocol used has been effective in the prevention of hepatitis B viral reinfection.

Uremic plasma contains factors inhibiting 1 alpha-hydroxylase activity

The effect of uremic plasma ultrafiltrate on calcitriol synthesis was investigated. Renal 1 alpha-hydroxylase activity was measured in normal rats infused for 20 h with 20 mL of normal or uremic plasma ultrafiltrate. Renal 1 alpha-hydroxylase activity was determined by the generation of calcitriol measured 5, 10, 20, and 30 min after the reaction was initiated by the addition of cold 25(OH)D3. The activity was significantly lower in rats infused with uremic plasma ultrafiltrate. Kidney homogenates preincubated for 3 h with uremic plasma ultrafiltrate also had significantly lower renal 1 alpha-hydroxylase activity than did those preincubated with normal plasma ultrafiltrate. In addition, the effect of the putative uremic toxin, guanidinosuccinic acid (GSA), on renal 1 alpha-hydroxylase activity was studied. Normal rats infused for 20 h with 20 mL of saline solution containing 1.5 mg/dL of GSA had significantly lower renal 1 alpha-hydroxylase activity than did rats infused with normal saline. The enzyme activity was also lower in kidney homogenates preincubated for 3 h with 4 mg/dL of GSA. Enzyme kinetic analysis revealed that the inhibition of renal 1 alpha-hydroxylase by GSA was noncompetitive. It was concluded that uremic plasma contains substances that directly inhibit renal 1 alpha-hydroxylase activity.

Mechanism of decreased calcitriol degradation in renal failure

Metabolic clearance rate (MCR) of calcitriol is decreased in renal failure, and uremic toxins play a major role in the suppression of calcitriol degradation. In this experiment, we studied the effect of uremic toxins on renal 24- and 26-hydroxylase (HX) activities. Normal rats were infused for 20 h with 30 ml of normal or uremic plasma ultrafiltrates. At the end of infusion, renal enzymes activities were measured by the generations of 1,24,25- and 1,25,26-trihydroxyvitamin D3 10 min after the addition of 25 nM or 1 microM calcitriol. Renal 24-HX activity decreased approximately 50%, whereas 26-HX activity did not decrease in rats infused with uremic plasma ultrafiltrate. The induction of 24-HX activity by 100 ng calcitriol also decreased in rats infused with uremic ultrafiltrate. To examine whether uremic ultrafiltrate could directly inhibit the degradation enzymes, 24- and 26-HX activities were measured in kidney homogenates preincubated for 3 h with either normal or uremic ultrafiltrate. Uremic ultrafiltrate did not directly suppress 24- and 26-HX activities. Furthermore, the disappearance rate of calcitriol was similar for 90 min in kidney homogenates after they were preincubated for 3 h with uremic and normal ultrafiltrates. Because 24-HX synthesis is induced by the calcitriol-receptor complex binding to nuclear chromatin and activating genes coding for the enzyme, we studied the effect of uremic toxins on the binding affinity of calcitriol-receptor complex for DNA-cellulose. Uremic ultrafiltrate significantly reduced the binding affinity of the hormone receptor complex for DNA when the receptor was preincubated with the ultrafiltrate for 3 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Purification of radioiodinated human insulin by high performance liquid chromatography for a sensitive radioimmunoassay

The optimal sensitivity of a radioimmunoassay depends on the purity of the radiolabeled antigen. The conventional purification methods are not complete and are time consuming. The combination of a Sep-pak C18 cartridge and high performance liquid chromatography (HPLC) for the purification of 125I-labeled insulin in our study revealed that the Sep-pak cartridge can serve as the preliminary step to remove unreacted radioactive iodide, the reactants, and labeled but presumably damaged materials unadsorbed to the cartridge. The fractions eluted from the Sep-pak containing high radioactivity and high immunoreactivity to the antibody were chosen for further purification by HPLC to eliminate undesirable radiolabeled substances with a lesser immunoreactivity. The purified radiolabeled insulin was used to develop a sensitive radioimmunoassay with detecting limits of 0.03 microU/mL per tube.