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Biomedical subjects

A C Perkins

Publications and source records attributed to A C Perkins.

At least 37 records · Page 2Linked to original sources
PubMed2000

Fetal expression of a human Agamma globin transgene rescues globin chain imbalance but not hemolysis in EKLF null mouse embryos.

Mice lacking the erythroid Kruppel-like factor (EKLF) die in utero at embryonic day 15 (E15) from severe anemia. EKLF(-/-) embryos display a marked deficit in beta-globin gene expression. To test whether beta-globin deficiency was solely responsible for the anemia and intrauterine death, we corrected the globin chain imbalance in EKLF(-/-) embryos by breeding with a strain of mice that express high levels of human gamma-globin. Despite efficient production of hybrid malpha(2)-hgamma(2) hemoglobin in the fetal livers of EKLF(-/-) animals, hemolysis was not corrected and survival was not prolonged. We concluded that deficiency of nonglobin EKLF target genes is a major contributor to the definitive red blood cell abnormalities and prenatal death in EKLF(-/-) embryos. These results suggest that strategies designed to antagonize EKLF function in adults with hemoglobinopathy, in an attempt to reactivate gamma-globin gene expression, may adversely affect other essential aspects of red blood cell physiology. (Blood. 2000;95:1827-1833)

Anemia↗
PubMed2000

Ermap, a gene coding for a novel erythroid specific adhesion/receptor membrane protein.

Ermap (erythroid membrane-associated protein), a gene coding for a novel transmembrane protein produced exclusively in erythroid cells, is described. It is mapped to murine Chromosome 4, 57 cM distal to the centromere. The initial cDNA clone was isolated from a day 9 murine embryonic erythroid cell cDNA library. The predicted peptide sequence suggests that ERMAP is a transmembrane protein with two extracellular immunoglobulin folds, as well as a highly conserved B30.2 domain and several phosphorylation consensus sequences in the cytoplasmic region. ERMAP shares a high homology throughout the entire peptide with butyrophilin, a glycoprotein essential for milk lipid droplet formation and release. A GFP-ERMAP fusion protein was localized to the plasma membrane and cytoplasmic vesicles in transiently transfected 293T cells. Northern blot analysis and in-situ hybridization demonstrated that Ermap expression was restricted to fetal and adult erythroid tissues. ERMAP is likely a novel adhesion/receptor molecule specific for erythroid cells.

Amino Acid Sequence↗
PubMed2000

Limited exposure of the healthy distal colon to orally-dosed formulation is further exaggerated in active left-sided ulcerative colitis.

BACKGROUND: Active distal ulcerative colitis is often resistant to topically acting oral formulations. We speculated that the left side of the colon is underexposed to orally-dosed topical agents in patients with active distal colitis. METHODS: Twenty-two healthy volunteers (12 males, aged 22-47 years), and 10 patients (6 males, aged 33-73 years) with active left-sided ulcerative colitis ingested a Eudragit-coated gelatine capsule containing 111In-labelled amberlite resin on four successive days. Regional colonic distribution, transit times and percentage of daily dose resident were calculated from the average of four serial gamma camera images on the 4th day. RESULTS: (mean [95% CI]). When compared to controls, patients with colitis had significantly faster total colon transit (24.3 h [9.5-39.1] vs. 51.7 h [41.1-62.3]) as well as faster proximal colon transit (18.7 h [9.1-28.3] vs. 36.7 [28.5-44.9]), and distal colon transit (3.1 h [-0.5 to 6.8] vs. 15.0 h [10.5-19.5]), respectively (all P < 0.01). Material was asymmetrically distributed in health (proximal colon 69% [63-76] vs. distal colon 31% [24-37]). This asymmetry was more extreme in colitis, with corresponding values of 91% [85-96] vs. 9% [4-15]. As a result colitics had less material in the left-sided colon (9% [4-15] vs. 31% [24-37]), P < 0. 001. Colitics had a significantly lower percentage of the daily dose resident within the left side of the colon compared to controls (13% [-2 to 28] vs. 63% [44-81]), P < 0.01. CONCLUSIONS: Delayed release oral formulation is asymmetrically distributed within the colon in health. This asymmetry is exaggerated in active left-sided ulcerative colitis and, together with faster colonic transit, results in reduced exposure of the distal colon to orally-dosed topical agents.

Administration, Oral↗
PubMed2000

Targeting superficial bladder cancer by the intravesical administration of copper-67-labeled anti-MUC1 mucin monoclonal antibody C595.

PURPOSE: More effective intravesical agents are required to limit the recurrence and progression of superficial bladder cancer. This study assessed the ability of copper-67 ((67)Cu)-C595 murine antimucin monoclonal antibody to bind selectively to superficial bladder tumors when administered intravesically, with a view to its development for therapy. PATIENTS AND METHODS: Approximately 20 MBq of (67)Cu-C595 monoclonal antibody was administered intravesically to 16 patients with a clinical indication of superficial bladder cancer. After 1 hour, the bladder was drained and irrigated. Tissue uptake was assessed by imaging and by the assay of tumor and normal tissues obtained by endoscopic resection. RESULTS: Tumor was correctly identified in the images of 12 of 15 patients who were subsequently found to have tumors. Assay of biopsy samples at 2 hours showed a mean tumor uptake of 59.4% of the injected dose per kilogram (SD = 48.0), with a tumor-to-normal tissue ratio of 14.6:1 (SD = 20). After 24 hours (n = 5), this decreased to 4.3% of the injected dose per kilogram (SD = 2.9), with a tumor-to-normal tissue ratio of 1.8:1 (SD = 0.8). CONCLUSION: This study indicates a promising method for the treatment of superficial bladder cancer. Although the mean initial tumor uptake was high, effective therapy of bladder tumors will require an increased retention of the cytotoxic radionuclide in tumor tissue.

Administration, Intravesical↗
PubMed1999

Esophageal transit of risedronate cellulose-coated tablet and gelatin capsule formulations.

Risedronate sodium is an orally active antiresorptive agent and a member of the pyridinyl class of bisphosphonates. It has been approved for the treatment of Paget's disease of the bone and is under development as a chronic therapy for the treatment and prevention of osteoporosis. A novel cellulose film-coated tablet formulation was developed to optimize esophageal transit of this bisphosphonate. The aim of the present study was to compare the esophageal transit of the film-coated tablet formulation of risedronate with its original gelatin capsule dose form. A total of 25 elderly, healthy volunteers (mean 66 years), who were dysphagia-free, participated in this randomized cross-over study. On separate occasions, volunteers swallowed radiolabeled placebo formulations with 50 ml water. Dynamic images with participants in a sitting position were recorded for 10 min using a gamma camera. Scintigraphic imaging showed a delay in esophageal transit (greater than 15 s) in 28% of patients in the capsule group but in none of the tablet group (P<0.05). The mean transit times of the capsules and tablets were 23.8 and 3.3 s, respectively. Esophageal transit of film-coated tablets was faster than gelatin capsules, suggesting that film-coated tablets would be the appropriate formulation for all pivotal trials with risedronate and for subsequent commercialization.

Aged↗
PubMed1999

Evaluation of the clearance characteristics of bioadhesive systems in humans.

This paper describes the characterisation, radiolabelling and clearance characteristics of three bioadhesive nasal delivery systems; starch microspheres, chitosan microspheres and chitosan solution. The time taken for 50% of these bioadhesive materials and a control to be cleared from the nasal cavity, after nasal administration to human volunteers, was evaluated using gamma scintigraphy. The data show that the control was cleared rapidly, with a half life of 21 min, whereas the bioadhesive delivery systems had much longer half lives. The clearance of the chitosan solution almost doubled to 41 min, whilst the half life of clearance for the starch microspheres more than tripled to 68 min and for the chitosan microspheres the half life of clearance quadrupled to 84 min. From the results reported in this study it is possible to determine that both chitosan systems and the starch microspheres have good bioadhesive characteristics. The results have supported the hypothesis that chitosan delivery systems can reduce the rate of clearance from the nasal cavity, thereby increasing the contact time of the delivery system with the nasal mucosa, providing the potential for increasing the bioavailability of drugs incorporated into these systems.

Adhesiveness↗
PubMed1999

Euglycaemic hyperinsulinaemia does not affect gastric emptying in type I and type II diabetes mellitus.

Hyperglycaemia slows gastric emptying in both normal subjects and patients with diabetes mellitus. The mechanisms mediating this effect, particularly the potential role of insulin, are uncertain. Hyperinsulinaemia has been reported to slow gastric emptying in normal subjects during euglycaemia. The purpose of this study was to evaluate the effect of euglycaemic hyperinsulinaemia on gastric emptying in Type I (insulin-dependent) and Type II (noninsulin-dependent) diabetes mellitus. In six patients with uncomplicated Type I and eight patients with uncomplicated Type II diabetes mellitus, measurements of gastric emptying were done on 2 separate days. No patients had gastrointestinal symptoms or cardiovascular autonomic neuropathy. The insulin infusion rate was 40 mU x m(-2) x min(-1) on one day and 80 mU x m(-2) x min(-1) on the other. Gastric emptying and intragastric meal distribution were measured using a scintigraphic technique for 3 h after ingestion of a mixed solid/liquid meal and results compared with a range established in normal volunteers. In both Type I and Type II patients the serum insulin concentration had no effect on gastric emptying or intragastric meal distribution of solids or liquids. When gastric emptying during insulin infusion rates of 40 mU x m(-2) x min(-1) and 80 mU x m(-2) x min(-1) were compared the solid T50 was 137.8+/-24.6 min vs. 128.7+/-24.3 min and liquid T50 was 36.7+/-19.4 min vs. 40.4+/-15.7 min in the Type I patients; the solid T50 was 94.9+/-19.1 vs. 86.1+/-10.7 min and liquid T50 was 21.8+/-6.9 min vs. 21.8+/-5.9 min in the Type II patients. We conclude that hyperinsulinaemia during euglycaemia has no notable effect on gastric emptying in patients with uncomplicated Type I and Type II diabetes; any effect of insulin on gastric emptying in patients with diabetes is likely to be minimal.

Adult↗
PubMed1999

Stool water content and colonic drug absorption: contrasting effects of lactulose and codeine.

PURPOSE: By varying stool water content using lactulose and codeine, we investigated the influence of luminal water content on the absorption of quinine, a transcellular probe, and 51Cr-EDTA, a paracellular probe, from the distal gut. METHODS: Sixteen volunteers entered a three-way cross-over trial in which absorption of probe markers from a timed-release delivery system was determined following treatment with lactulose 20 mls tds (increasing water content), or codeine 30 gms qds (decreasing water content), and compared with control untreated values. Stool water content was assessed by freeze drying stool samples. Site of release was determined by gamma scintigraphy, and absorption was measured by plasma levels and urinary recovery of the marker probes. RESULTS: Lactulose accelerated ascending colon transit (3.7 +/- 0.8 vs 4.5 +/- 1.4 hrs, p < 0.05), increased stool water content (75 +/- 2 vs 71 +/- 2%, p < 0.01), caused greater dispersion of released material (dispersion score 3.4 +/- 0.3 vs 1.8 +/- 0.2, p < 0.01), and enhanced absorption of the transcellular probe quinine (4.66 +/- 0.78 vs 3.02 +/- 0.63%, p < 0.05) compared to control. Conversely codeine slowed ascending colon transit (8.9 +/- 1.8 hrs), reduced stool water content (61 +/- 2 vs 71.2%, p < 0.05), and tended to diminish absorption (2.60 +/- 0.77 vs 3.02 +/- 0.63%, p = 0.20). Within the ascending colon specifically, there was a significant trend for treatments increasing luminal water content to enhance quinine absorption (medians: codeine = 1.2%, [n = 81 < control = 2.3%, [n = 5] < lactulose = 3.2%, [n = 71, p < 0.01). Delivery site also had an important influence on absorption, with more distal release resulting in less absorption in the control arm (medians: small intestine = 4.4% [n = 5] > ascending colon = 2.3% [n = 5] > transverse colon = 1.5% [n = 6], p < 0.005). CONCLUSIONS: Lactulose accelerates transit, increases stool water content, and enhances drug absorption from the distal gut whilst codeine slows transit, decreases stool water content, and tends to diminish absorption, compared to controls. We conclude that water content may be an important determinant in colonic drug absorption.

Adult↗
PubMed1999

Regional differences in quinine absorption from the undisturbed human colon assessed using a timed release delivery system.

PURPOSE: To investigate the regional absorption characteristics of the distal gut using two markers of permeability, quinine (a transcellular probe) and 51CrEDTA (a paracellular probe). METHODS: The permeability markers were delivered to the undisturbed gastrointestinal tract in 39 healthy volunteers using an oral timed-release delivery vehicle which allowed pulsed release within a particular site of the gut. Site of release was identified using gamma scintigraphy. Absorption of quinine and 51CrEDTA was assessed by measuring the percent excretion in the urine using HPLC and gamma counting respectively. Serial plasma samples allowed time-concentration curves for quinine to be plotted. RESULTS: There was a significant trend for diminished absorption with more distal delivery of the transcellular probe, quinine, which was: 6.26 +/- 0.87% (small intestine, n = 10); 4.65 +/- 0.93% (ascending colon, n = 16); and 2.59 +/- 0.52% (transverse colon, n = 10) of the ingested dose excreted respectively (p < 0.001). No such gradient was seen with the paracellular marker, 51CrEDTA. CONCLUSIONS: These results suggest that delayed release formulations should aim for release in the distal small bowel and proximal colon if absorption is to be maximised. Absorption by the transcellular route diminishes in the more distal colon, a fact which has implications for delayed or sustained release formulations.

Adult↗
PubMed1999

Night-time quiescence and morning activation in the human colon: effect on transit of dispersed and large single unit formulations.

OBJECTIVES: Controlling the delivery of drugs to different regions of the colon remains an elusive goal. The aim of this study was to define the diurnal variation in colonic transit and show how this influences the colonic distribution and residence time of different formulations given either in the morning or evening. METHODS: Colonic transit of small particulates and a large capsule was measured during nocturnal sleep and daytime wakefulness. Eighteen healthy volunteers participated in a randomised crossover study. 111In-labelled resin (150-300 microm) and a large 99mTc-labelled non-disintegrating capsule (22 x 8 mm) were swallowed at either 0800h or 1700h. MAIN OUTCOME MEASURES: The geometric centre of isotope (range 1-9) was calculated from serial scintiscans allowing comparison of overnight and daytime transit. RESULTS: Transit of resin was delayed in the overnight compared to daytime 8 h periods (change in geometric centres (GCs), mean +/- SEM, 0.59 +/- 0.14 vs 1.46 +/- 0.39 respectively, P < 0.02). Maximal resin movement occurred immediately after awakening, prior to breakfast, in 9/18 studies (P < 0.05). The capsule was more distal than the resin at the end of the study 15 h after dosing (P < 0.001). There was marked inter-individual variability in distribution of both resin and capsule at 15 h, the range of GCs being 2.8-9 and 2.2-9, respectively. CONCLUSION: Sleep delays colonic transit and large capsules travel faster than dispersed small particles. However, substantial inter-individual variability in transit makes targeting specific regions of the human colon unreliable with either dispersed or single unit formulations.

Administration, Rectal↗
PubMed1999

An immunoscintigraphic evaluation of the engineered human monoclonal antibody (hCTMO1) for use in the treatment of ovarian carcinoma.

OBJECTIVE: To assess the safety and targeting ability of the engineered human antibody (hCTMO1) in women with ovarian carcinoma. DESIGN: The monoclonal antibody labelled with Indium-111 was administered to women with suspected primary or recurrent ovarian carcinoma six days pre-operatively. The first group of women was given a dose of 0.1 mg per kg body weight of radiolabelled antibody. A second group of women received 1 mg per kg body weight and finally a third group was given 1 mg per kg body weight of unlabelled antibody followed one hour later by 0.1 mg per kg body weight of radiolabelled antibody. All the women were then imaged using a gamma camera one hour and up to 96 hours after injection. PARTICIPANTS: Fourty-four women in whom there was a high suspicion of primary ovarian carcinoma on the basis of ultrasound or CT imaging and serum CA125 and those in whom there was a suspicion of recurrent ovarian carcinoma after being treated for histologically confirmed carcinoma. SETTING: The Queen's Medical Centre, Nottingham and University Hospital Vrije Universiteit, Amsterdam, The Netherlands. RESULTS: At the low dose of antibody the sensitivity for detection of ovarian carcinoma was 70%. After increasing the dose of antibody and also after pre-dosing with unlabelled antibody the sensitivity increased to 100%, but there was a large number of false positive results at the higher dose, and therefore the specificity was low. The liver and bone marrow were the organs with the highest activities. CONCLUSION: The genetically engineered antibody hCTMO1 is safe for use in women. This antibody effectively targets ovarian carcinoma and has greater potential as a vector for therapeutic use than as a diagnostic agent.

Adult↗
PubMed1998

Erythroid Krüppel-like factor is essential for beta-globin gene expression even in absence of gene competition, but is not sufficient to induce the switch from gamma-globin to beta-globin gene expression.

Different genes in the beta-like globin locus are expressed at specific times during development. This is controlled, in part, by competition between the genes for activation by the locus control region. In mice, gene inactivation of the erythroid Krüppel-like factor (EKLF) transcription factor results in a lethal anemia due to a specific and substantial decrease in expression of the fetal/adult-stage-specific beta-globin gene. In transgenic mice carrying the complete human beta-globin locus, EKLF ablation not only impairs human beta-globin-gene expression but also results in increased expression of the human gamma-globin genes during the fetal/adult stages. Hence, it may appear that EKLF is a determining factor for the developmental switch from gamma-globin to beta-globin transcription. However, we show here that the function of EKLF for beta-globin-gene expression is necessary even in absence of gene competition. Moreover, EKLF is not developmental specific and is present and functional before the switch from gamma-globin to beta-globin-gene expression occurs. Thus, EKLF is not the primary factor that controls the switch. We suggest that autonomous repression of gamma-globin transcription that occurs during late fetal development is likely to be the initiating event that induces the switch.

Animals↗
PubMed1998

Effect of euglycaemic hyperinsulinaemia on gastric emptying and gastrointestinal hormone responses in normal subjects.

Several studies have shown that hyperglycaemia slows gastric emptying in normal subjects and patients with diabetes mellitus but whether hyperinsulinaemia per se has an effect remains debatable. In the present study we have assessed the effect of hyperinsulinaemia on gastric emptying of a solid and liquid meal in normal subjects. Ten men were studied three times in random order. After an overnight fast, subjects were infused with 0.9% NaCl on two occasions and on the third with insulin, at 40 mU x m(-2) x min(-1) with 20% glucose simultaneously to maintain euglycaemia. Steady-state glucose infusion rate was ensured before the subjects ate a standard meal of a pancake labelled with 99mTc and milkshake labelled with (111)In-DTPA. Gamma-scintigraphic images were then obtained every 20 min for the next 3 h. There were no significant differences between the mean half-emptying times (T50) of the solid and liquid during the two saline infusions (129.6 +/- 28.5 vs 128.4 +/- 23.8 min for the solid and 25.4 +/- 7.0 vs 34.7 +/- 18.0 min for the liquid, mean +/- SD). Hyperinsulinaemia delayed both solid (mean T50 149.6 +/- 30.7, p = 0.031) and liquid emptying (mean T50 39.8 +/- 13.9, p = 0.042). There were no significant differences in the cholecystokinin and glucagon-like peptide 1 responses to the meal during either saline or insulin infusions. There was a tendency towards a greater insulin response to the meal during the hyperinsulinaemic study. Thus, hyperinsulinaemia delayed emptying of both the solid and liquid components of the meal.

Adult↗
PubMed1998

The effect of single doses of pramlintide on gastric emptying of two meals in men with IDDM.

In a previous study we have shown that an intravenous infusion of pramlintide (an analogue of human amylin) delayed gastric emptying, but the dose of pramlintide was supraphysiological in relation to the amylin response to food in non-diabetic subjects. The purpose of this study was to examine the dose response relationship of subcutaneous injections of pramlintide on gastric emptying and to determine whether administration of the drug before one meal has an impact on the subsequent meal. Eleven men with insulin-dependent diabetes mellitus were studied in a double-blind, randomised, four-way crossover design. None had autonomic neuropathy. Euglycaemia was maintained overnight before the study day. At -30 min the patients self-injected their usual morning insulin and at -15 min they injected the study drug (either placebo or 30, 60 or 90 microg pramlintide) subcutaneously. At 0 min they ate a standard meal consisting of a pancake, labelled with 99mTc, and a milkshake containing 3-ortho-methylglucose (3-OMG). Gastric emptying images were obtained for the next 8 h. At 240 min the subjects ate a similar meal, but on this occasion the pancake was labelled with (111)In. All three doses of pramlintide delayed emptying of the solid component of the first meal (p < 0.004) with no significant difference between the drug doses. There were no differences between placebo and pramlintide after the second meal. All three doses of pramlintide resulted in a prolongation in the time to peak plasma 3-OMG level (p < 0.0001) after the first meal but there was no difference after the second meal.

3-O-Methylglucose↗
PubMed1998

Biodistribution of 111In-labelled engineered human antibody CTM01 (hCTM01) in ovarian cancer patients: influence of prior administration of unlabelled hCTM01.

mAb hCTM01 binds a carcinoma-associated antigen, the MUC1 gene product. The antigen is also present in the circulation, and administration of 111In-labelled hCTM01 results in the formation of immune complexes with enhanced accumulation in the liver. To avoid the unwanted effect of circulating radioactive immune complexes, a strategy to remove the circulating antigen was investigated using a split-dosage schedule. Eleven patients suspected of having ovarian carcinoma were injected with 1 mg/kg unlabelled hCTM01, 1 h before receiving 0.1 mg/kg 111In-labelled hCTM01 (100 M Bq). The amount of radioactivity was determined in resected tumour tissue, various normal tissues and blood samples obtained at laparotomy 6 days postinjection (p.i.). In all patients, the circulating antigen decreased to its nadir after the unlabelled antibody infusion and immune complex formation was demonstrated. Uptake in tumour deposits 6 days p.i. was 11.1 times higher than in normal tissues (P < 0.0001) and 5.9 times higher than in blood (P < 0.0001). 111In activity in liver tissue was comparable to 111In uptake in tumour tissue, and considerably lower than previously reported in patients not pretreated with unlabelled antibody. The split-dosing strategy would appear to be advantageous for use of hCTM01 as a specific carrier for the delivery of cytotoxic agents to patients with ovarian cancer.

Adult↗
PubMed1998

Enrichment of blood from embryonic stem cells in vitro.

Murine embryonic stem (ES) cells are pluripotent. When injected into blastocysts they can give rise to every cell type of a derived chimeric mouse including germ cells. Embryonic stem cells also possess remarkable in vitro differentiation potential. When removed from stromal support and leukaemia inhibitory factor (LIF), ES cells differentiate into structures known as embryoid bodies (EBs), in which all three germ layers develop and interact. As ES cells from humans become available there is increasing interest in the potential for EBs to provide an unlimited supply of stem cells for somatic transplantation therapies. Realisation of this potential will require greater understanding of the molecular determinants of cell fate within EBs. Also, culture techniques for selective expansion of cell lineages of interest will reduce the risks associated with transplantation of EB-derived cells. In this paper the kinetics of expression of mRNA and protein for early mesoderm markers within EBs is reported. In addition, a three-step culture system incorporating co-cultivation on the bone marrow derived stromal cell line, MC3T3-G2/PA6 (PA6), is explored as a way to select for haematopoietic progenitor cells (HPCs) and against undifferentiated ES cells. A system like this could enhance purification of haematopoietic stem cells (HSCs) from ES cells for bone marrow transplantation.

Animals↗