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Biomedical subjects

A White

Publications and source records attributed to A White.

At least 253 records · Page 14Linked to original sources
PubMed1993

Discrimination between beta-endorphin and beta-lipotrophin in human plasma using two-site immunoradiometric assays.

OBJECTIVE: We wished to discriminate between the opioid peptide beta-endorphin (beta-EP) and its non-opioid precursor beta-lipotrophin (beta-LPH) in normal subjects and patients with ACTH-related disorders. DESIGN: We produced monoclonal antibodies to beta-EP and beta-LPH for the development of two-site immunoradiometric assays (IRMAs) which specifically quantitate beta-EP and beta-LPH. PATIENTS: Samples were obtained from patients with a range of ACTH-related disorders and compared with 18 normal subjects. Peptide levels were also compared in six patients with Cushing's syndrome undergoing bilateral inferior petrosal sinus sampling with corticotrophin releasing hormone administration. MEASUREMENTS: In the beta-EP IRMA, antibody 6B2, specific for beta-EP 18-27, is radiolabelled and antibody 2E10, recognizing beta-EP 1-5, is coupled to Sephacryl S-300 as solid phase. The IRMA is specific for beta-EP (beta-LPH cross-reacts < 0.02%), has a detection limit of 1.4 +/- 0.7 pmol/l (n = 7) and has a within-assay coefficient of variation of < 10% between 4.9 and 1200 pmol/l. In the beta-LPH IRMA, antibody 6B2, which recognizes an epitope common to beta-LPH and beta-EP, is radiolabelled and paired with solid-phase antibody 5C11 which recognizes beta-LPH 39-56. The binding site of this antibody ensures that beta-EP cannot be measured in the beta-LPH assay. The detection limit is 0.8 +/- 0.1 pmol/l (n = 9) and the within-assay coefficient of variation is < 10% at concentrations 1.7-870 pmol/l. RESULTS: In normal subjects, beta-EP and beta-LPH levels were < 1.4-1.7 pmol/l (< 5-6 ng/l) and 2.5-6.7 pmol/l (29-77 ng/l) at 0930 h and < 1.4-1.7 pmol/l (< 5-6 ng/l) and 1.9-4.5 pmol/l (22-49 ng/l) at 1600 h, respectively. In patients with ACTH-related pathologies concentrations of beta-EP and beta-LPH paralleled those of ACTH. The ratio of beta-LPH:beta-EP in plasma varied between 3.2:1 and 38:1 in these patients demonstrating that beta-LPH is the major circulating peptide derived from the C-terminal of pro-opiomelanocortin in man. However, in two patients undergoing bilateral inferior petrosal sampling with corticotrophin releasing hormone for diagnosis of Cushing's disease beta-EP concentrations increased rapidly during the first 5 minutes of the test, resulting in a sharp decrease in the beta-LPH: beta-EP ratio. These results suggest that beta-EP is preferentially released in response to acute corticotrophin releasing hormone stimulation. CONCLUSIONS: It is concluded that two-site IRMAs for beta-EP and beta-LPH provide an easy approach to study the dynamic changes in processing of beta-LPH to beta-EP.

ACTH Syndrome, Ectopic↗
PubMed1993

The management of renal cell carcinoma with inferior vena-caval involvement.

Seven patients with renal cell carcinoma involving the inferior vena cava underwent surgical resection between 1975 and 1991. Pre-operative staging defined five patients with stage T3bNoMo disease, one patient with stage T3bN1Mo, and one patient with stage T3bNoM1 disease. At operation one patient had tumour thrombus filling the right atrium. Two patients had tumour thrombus within the intrahepatic vena cava and four infrahepatic tumour thrombus. The mean follow-up is 34.4 months (median 40 months). Four patients have been followed for over 4 years. Three of these patients are survivors, two have remained disease-free since their initial surgery. The other patient had a liver resection at 49 months for a solitary metastases; he is currently disease free. One patient died at 38 months from a gastrointestinal haemorrhage. Three patients are 12 months or less postoperation. Operative mortality was zero. The mean postoperative hospital stay was 14.7 days. Data suggests that 3-10% of renal cell carcinomas will involve the inferior vena cava. The small number of patients in this series suggests that many patients with renal cell carcinoma involving the inferior vena cava are not referred for surgical assessment. These patients are potential surgical candidates. Their survival after surgical resection, excluding the group with extension of tumour thrombus into the hepatic cava or above, is not reduced when compared with other patients with renal carcinoma.

Adult↗
PubMed1993

Diabetic neuropathy is associated with increased activity of the hypothalamic-pituitary-adrenal axis.

This study has sought to investigate whether diabetic neuropathy is a major determinant of the basal tone of the hypothalamic-pituitary-adrenal axis in diabetes mellitus. We have analyzed the changes in ACTH and cortisol by measuring hourly samples from 0800-1900 h in diabetic patients carefully characterized for the presence of neuropathy. The circadian variation for ACTH and cortisol was normal in these patients. However, integrated secretion (area under the curve) of both ACTH and cortisol was increased specifically in the 25 diabetic patients with symptomatic polyneuropathy (43 +/- 20 pmol/L and 3609 +/- 169 nmol/L, respectively) compared to 19 diabetic patients without neuropathy (30 +/- 10 pmol/L and 2800 +/- 690 nmol/L, respectively) (P < 0.02) and to 11 normal controls (26 +/- 10 pmol/L and 2694 +/- 476 nmol/L, respectively) (P < 0.007). These differences occurred independently of the type of diabetes and were significant for most individual time points. ACTH and cortisol concentrations correlated with most clinical and neurophysiological parameters of neuropathy (P < 0.05-0.001), but not with glycemic control, retinopathy, or proteinuria. Overall, these results suggest that diabetic neuropathy is associated with a specific and persistent increase in the activity of the hypothalamic-pituitary-adrenal axis.

Adrenocorticotropic Hormone↗
PubMed1993

Proopiomelanocortin is the predominant adrenocorticotropin-related peptide in human cerebrospinal fluid.

High mol wt forms of immunoreactive ACTH and beta-endorphin (beta EP) are present in cerebrospinal fluid (CSF). We have quantified these peptides directly in the CSF of 26 patients undergoing routine myelography, using a panel of monoclonal antibody-based two-site immunoradiometric assays, specific for ACTH precursors (both POMC and pro-ACTH cross-react 100%), POMC, ACTH, and beta EP. The mean +/- SD levels of POMC in CSF were 530 +/- 150 pmol/L similar to total ACTH precursor immunoreactivity (414 +/- 83 pmol/L). By comparison, the CSF levels of ACTH (3.2 +/- 0.6 pmol/L) and beta EP (6.7 +/- 2.9 pmol/L) were 100-fold lower. POMC, by virtue of its 1% cross-reactivity in the ACTH immunoradiometric assay, could have also accounted for the ACTH immunoreactivity in CSF. Sephadex G-75 chromatography of CSF confirmed the presence of a single major peak of ACTH precursors eluting at the position of POMC (31K), while ACTH immunoreactivity was not detected at the position of ACTH-(1-39) (4.5K). We also studied the effect of exogenous glucocorticoids on CSF POMC peptides by giving 2.5 mg dexamethasone (0.5 mg, orally, every 6 h for 24 h) to a similar group of age-matched patients before lumbar puncture. No significant differences in CSF peptide content were observed between the two groups. These data suggest that the unprocessed precursor molecule POMC is the predominant peptide of the POMC family in human CSF and should always be considered when interpreting data involving ACTH or other component peptide immunoreactivity in this biological fluid.

Administration, Oral↗
PubMed1993

Glucocorticoid inhibition of ACTH peptides: small cell lung cancer cell lines are more resistant than pituitary corticotroph adenoma cells.

In the normal pituitary, glucocorticoids are the principal negative regulatory of the pro-opiomelanocortin (POMC) gene which gives rise to the biologically active peptides ACTH and beta-endorphin. In Cushing's syndrome, ACTH-secreting pituitary tumours show a degree of glucocorticoid resistance, whilst ACTH-secreting extra-pituitary tumours have an even greater resistance to glucocorticoid excess. In an attempt to understand the mechanism of this phenomenon, we have compared the effects of glucocorticoids on POMC mRNA and peptide secretion in human and mouse corticotroph adenoma cells and in small cell lung carcinoma (SCLC) cells. ACTH precursor peptides were inhibited within 24 h by 25-50 nM hydrocortisone in primary cultures from a human corticotroph adenoma. In the mouse corticotroph adenoma cell line (AtT20), inhibition of both ACTH precursors and ACTH was not observed after 24 h but, by 10 days, glucocorticoids suppressed peptide levels with a concentration causing 50% inhibition of 50 nM hydrocortisone and maximal inhibition at 500 nM hydrocortisone. In marked contrast, there was no response to 500 nM hydrocortisone in the five SCLC cell lines (COR L103, COR L42, COR L24, COR L31, DMS 79) all of which secrete ACTH precursors. However, two of the five SCLC cell lines (COR L31 and DMS 79) were responsive to 1000 nM hydrocortisone. POMC mRNA, quantitated by slot-blot analysis, gave similar results for the five SCLC cell lines, implying that the abnormality may occur at the level of gene expression. When one of the three resistant cell lines (COR L103) was incubated with 2000 nM hydrocortisone or 2000 nM dexamethasone a clear suppression of precursor peptides and POMC mRNA was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1993

Measurement of insulin-like growth factor-II in human plasma using a specific monoclonal antibody-based two-site immunoradiometric assay.

An immunoradiometric assay (IRMA) for the measurement of insulin-like growth factor-II (IGF-II) in human plasma has been developed, optimized and evaluated clinically in normal subjects and patients with disorders of the GH/IGF-I axis. Six monoclonal antibodies (MAbs) to recombinant human IGF-II (rhIGF-II) were produced, all of which had low cross-reactivity with rhIGF-I (< 0.01%) and insulin (< 0.01%). Compatibility of pairs of MAbs was tested in two-site IRMAs using three radioiodinated MAbs and three MAbs linked to Sephacryl S-300 (with separation of bound and free radiolabelled MAb by sucrose layering). Seven pairs of MAbs bound rhIGF-II and the combination of 125I-labelled W3D9 and W2H1 linked to solid phase was selected. The optimized assay had a completion time of 4 h, a minimum detection limit of 30 ng/ml (2.5 standard deviations from the zero standard) and detected a single peak of endogenous IGF-II in normal plasma which co-eluted with rhIGF-II after acid gel chromatography. IGF-II was measured in formic acid/acetone extracts of plasma from 16 normal subjects (mean 685, range 516-1008 micrograms/l), four acromegalic patients (mean 637, range 553-700 micrograms/l), fourteen patients with type-1 diabetes (mean 635, range 247-753 micrograms/l), nine patients with uraemia (mean 423, range 78-850 micrograms/l), and three patients with Laron-type GH insensitivity (75, 35 and 36 micrograms/l). No significant fluctuations were detected between samples obtained hourly from 08.00 to 19.00 h in normal subjects. Low levels of IGF-binding proteins (IGFBPs) remaining in plasma extracts may interfere with the measurement of IGF-II and give rise to falsely elevated IGF-II levels in radioimmunoassays or falsely suppressed levels in IRMAs. Such interference did not occur with the IRMA when used to measure IGF-II in extracts from normal subjects, acromegalic patients and patients with type-1 diabetes, and the addition of excess rhIGF-I in order to displace IGF-II from residual IGFBPs had no effect on IGF-II measurements in these samples. However, levels of IGF-II measured in extracts from patients with Laron-type GH insensitivity and patients with uraemia increased markedly after preincubation with excess rhIGF-I. The accurate measurement of IGF-II by IRMA in extracts from these subjects therefore requires the displacement of IGF-II from IGFBPs prior to assay. We conclude that, in contrast to radioimmunoassays, the two-site IRMA developed here provides a practical, rapid and specific method for the measurement of IGF-II in human plasma.

Antibodies, Monoclonal↗
PubMed1993

Plasma norepinephrine in sensory diabetic polyneuropathy.

OBJECTIVE: To examine whether changes in circulating norepinephrine are associated with the sensory disturbances of diabetic polyneuropathy. Experimental studies have indicated that NE can excite sprouts from injured nerves, producing pain. RESEARCH DESIGN AND METHODS: We measured supine and erect plasma NE in 13 normal, nondiabetic control subjects and three groups of diabetic patients: 20 without clinical neuropathy, 20 with chronic painful neuropathy, and 15 with painless neuropathy and foot ulceration. Neuropathy was characterized by symptom and deficit scores, sensory thresholds, electrophysiology, and cardiovascular autonomic function tests. Neuropathic pain was scored by the patients on a linear analogue scale. RESULTS: In painless neuropathy, NE levels were greatly reduced (supine, 1.3 nM; erect, 2.2 nM) compared with control subjects (supine, 2.4 nM; erect, 4.0 nM; P < 0.001) and were combined with grossly abnormal autonomic reflexes. NE also was reduced in the diabetic group without neuropathy (supine, 1.7 nM; erect, 2.7 nM; P < 0.01 vs. control subjects). By contrast, in painful neuropathy NE levels (supine, 2.2 nM; erect, 3.6 nM) were similar to control subjects and significantly higher than in painless neuropathy (P < 0.01). Furthermore, NE correlated with the severity of neuropathic pain (r = 0.46, P = 0.02). To assess whether pain, acting as a stressor, could account for the observed differences in NE, we also measured the stress hormones epinephrine and cortisol. They did not differ among the diabetic groups. CONCLUSIONS: Circulating NE is higher in painful than painless diabetic neuropathy. We suggest that painful neuropathy is associated with a relatively higher number of functioning sympathetic fibers that may contribute to pain.

Adult↗
PubMed1993

Monoclonal antibodies recognising stage and region specific epitopes in embryonic mouse palatal epithelial cells.

Four monoclonal antibodies raised against murine embryonic palatal epithelium were used to stain frontal cryosections of embryonic mouse heads (d 11-15). One antibody (6A11) recognised the nasal epithelium at the angle of the palate prior to shelf elevation (embryonic d 11-d 13) and the epithelia at the tips of the approximated shelves (embryonic d 14.5). Two further antibodies (2H6 and 3H2) recognised epitopes on the entire palatal epithelium until shelf elevation (embryonic d 14.5) when their expression ceased. The epitope recognised by antibody 6D3 was absent from the palatal epithelium until embryonic d 13 when it displayed region specific expression, being present on the nasal aspect in the midpalate and the tip of the palate posteriorly. On embryonic d 14.5 staining of the medial edge epithelia was present in all regions. Whilst the nasal palatal epithelium stained in the anterior and mid regions, only patchy staining of the oral epithelium was detected. By embryonic d 15 staining was present throughout the palatal epithelia. These antibodies are directed against intracellular epitopes, possibly keratins. Indeed, immunoblotting assays revealed that antibody 2H6 recognised keratin 18. The developmental regulation of the epitopes recognised by the antibodies corresponds with differentiative events occurring during murine palatogenesis.

Animals↗
PubMed1993

Polymorphic microsatellites and Wilson disease (WD).

Wilson disease (WD), an autosomal recessive disorder of copper metabolism, has been previously mapped to chromosome 13q. Highly informative PCR-based polymorphic microsatellites closely linked to the WD locus (WND) at 13q14.3, as well as sequence-tagged sites for closely linked loci, are described. Two polymorphic microsatellite markers at D13S118 and D13S119 lie within 3 cM of WND. Two others (D13S227 and D13S228) were derived from a yeast artificial chromosome containing D13S31. These were placed on a genetic linkage map of chromosome 13 and were typed in 74 multiplex WD families from a variety of geographic origins (166 affected members). Multipoint analysis provides very high odds that the location of WND is between D13S31/D13S227/D13S228 and D13S59. Previous odds with RFLP-based markers were only 7:1 more likely than any other location. Current odds are 5,000:1. Preclinical testing of three cases of WD by using the highly informative polymorphic microsatellite markers is described. The markers described here ensure that 95% of predictive tests using DNA from both parents and from at least one affected sib will have an accuracy > 99%.

Adolescent↗
PubMed1993

Blood contamination of the feet during orthopaedic procedures.

Contamination of the feet with blood represents a potential hazard for the surgeon. The incidence of such contamination during major orthopaedic surgery has been shown in this study to be 54%. The use of protective leggings during surgery is recommended.

Blood↗
PubMed1993

Use of fluorescent cholesteryl ester microemulsions in cholesteryl ester transfer protein assays.

In the present report we describe a simple and practical method to assess CETP activity in a defined system by use of microemulsions containing a fluorescent cholesteryl ester analog. The microemulsions are stable, simple to prepare, and can be made to defined composition. Initial transfer rates are easily determined by monitoring changes in fluorescence. We have used the fluorescent cholesteryl ester analog, cholesteryl 4,4-difluoro-5,7-dimethyl-4-boro-3 alpha, 4 alpha-diaza-3-indacenedodecanoate (BODIPY-CE), to demonstrate the utility of this assay. The assay takes advantage of the concentration-dependent self-quenching of BODIPY-CE, when this analog is incorporated into microemulsions. We have used this new assay to demonstrate fluorescent lipid transfer facilitated by rabbit and human d > 1.21 g/ml plasma fraction and recombinant human CETP. A known inhibitory monoclonal antibody (Mab) to human CETP blocked BODIPY-CE transfer in a dose-dependent manner. We have also used BODIPY-CE microemulsions to measure CETP activity in whole plasma.

Animals↗
PubMed1993

Hypothalamo-pituitary-adrenal axis in uraemia: evidence for primary adrenal dysfunction?

To study hypothalamo-pituitary-adrenal axis disturbances in chronic renal failure, we administered corticotrophin-releasing hormone to patients undergoing haemodialysis and CAPD and to normal controls. Cortisol, ACTH, and ACTH precursors were measured before and after corticotrophin-releasing hormone using sensitive and specific two-site assays. Baseline ACTH and cortisol were similar in all groups. Peak values occurred at 30 min (ACTH) and between 30 and 60 min (cortisol). The cortisol (but not the ACTH) responses were significantly reduced in patients with renal failure (P < 0.05). ACTH precursors did not change from baseline following corticotrophin-releasing hormone but were significantly elevated in patients with renal failure compared to controls (P < 0.01). The reduced cortisol response to corticotrophin-releasing hormone may reflect a primary defect of adrenal function in renal failure.

Adolescent↗
PubMed1992

The injuries to JFK.

Explore the source record for details and available documents.

Craniocerebral Trauma↗
PubMed1992

Altered cell cycle arrest and gene amplification potential accompany loss of wild-type p53.

Gene amplification occurs at high frequency in transformed cells (10(-3)-10(-5)), but is undetectable in normal diploid fibroblasts (less than 10(-9)). This study examines whether alterations of one or both p53 alleles were sufficient to allow gene amplification to occur. Cells retaining one wild-type p53 allele mimicked the behavior of primary diploid cells: they arrested growth in the presence of drug and failed to demonstrate amplification. Cells losing the second p53 allele failed to arrest when placed in drug and displayed the ability to amplify at a high frequency. Thus, loss of wild-type p53 may lead to amplification, possibly caused by changes in cell cycle progression. Other determinants can by-pass this p53 function, however, since tumor cells with wild-type p53 have the ability to amplify genes.

Animals↗
PubMed1992

Length regulation in the Dictyostelium discoideum slug is a late event.

Time-lapse video light microscopy was used to study the emergence and maturation of the migratory slug from a D. discoideum aggregate. The anterior part, the tip of this simple multicellular organism, establishes migration prior to the definition of the rear, and hence the length of the slug. It was found that newly formed slugs of wild-type strain WS380B can reach lengths greater than 1 cm, yet mature slugs of this strain are rarely longer than 2-3 mumm. Often the tip extended out of the aggregation mound upon an arching pillar of cells. After the tip first touched the substratum, it commenced migration with a rapid succession of movement steps. Here we show that at the initiation of migration, a differential rate of cell movement along the developing slug axis results in a series of complicated changes, before the stable and mature shape of the slug is formed. Our results lead to new conclusions about D. discoideum slug formation and shape maintenance. Evidence is presented for regulation of slug length.

Animals↗
PubMed1992

The assembly and secretion of ApoB 100-containing lipoproteins in Hep G2 cells. ApoB 100 is cotranslationally integrated into lipoproteins.

The possibility that apoB 100 is cotranslationally translocated to the endoplasmic reticulum lumen and integrated into lipoproteins has been investigated. ApoB 100 nascent polypeptides were shown to be secreted from pulse-labeled Hep G2 cells after treatment with puromycin and chase for 1 or 2 h in the presence of puromycin and cycloheximide. These nascent polypeptides banded during sucrose gradient ultracentrifugation between the position of the high (HDL) and the low (LDL) density lipoproteins, revealing an inverse relationship between the length of the polypeptide and the density of the fraction. ApoB 100 occurred in the position of LDL and very low density lipoproteins (VLDL). Electronmicroscopy studies of the apoB-containing particles from the gradient indicated an increase in size with increasing length of the polypeptide. Furthermore, labeling studies indicated that the triglyceride load increased with the length of the polypeptide. An inverse relationship between the size of C-terminally truncated apoB polypeptides and the density of the assembled lipoproteins was also observed in experiments with transfected minigenes coding for apoB 41, apoB 29, and apoB 23. These proteins appeared on HDL particles. Pulse-chase experiments indicated that 80-200-kDa apoB nascent polypeptides on particles with HDL density, with time, were converted into larger polypeptides on lighter particles, to be fully replaced by apoB 100 on LDL-VLDL particles. The formation of these LDL-VLDL particles could be blocked by cycloheximide. Sixty-five percent of pulse-labeled apoB nascent polypeptides present in the microsomal fraction was released by sodium carbonate treatment, and 77% of these polypeptides could be recovered on the immature particles (banding between HDL and LDL) after sucrose gradient ultracentrifugation. Pulse-chase experiments indicated that these nascent polypeptides, on the immature lipoproteins, had the capacity to be precursors for all the apoB 100-containing LDL and VLDL particles formed in the cell. The obtained results indicate that a major portion of the apoB nascent polypeptides in the cell form lipoproteins cotranslationally during the translocation to the lumen of the endoplasmic reticulum.

Apolipoprotein B-100↗