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Biomedical subjects

C Allan

Publications and source records attributed to C Allan.

At least 19 recordsLinked to original sources
PubMed2007

Highly concentrated monoclonal antibody solutions: direct analysis of physical structure and thermal stability.

Virtually all current analytical methods employed in the development of highly concentrated monoclonal antibody (MAb) formulations require dilution of the sample before acquiring data. Thus, there is an unmet need for methods to study proteins directly at high concentration, since extrapolation of stability indicating parameters obtained from dilute studies may not be representative of the high concentration solution. Only slight or no modifications of biophysical methods including fluorescence, UV absorbance, circular dichroism, and FTIR (ATR and transmittance) spectroscopies as well as differential scanning calorimetry (DSC) are described here that permit the direct study of immunoglobulins (and other proteins) at high concentrations. Although FTIR spectra show differences that are dependent upon sampling geometry, other spectroscopic data from two different recombinant MAbs suggests that structure of each antibody exists in a physically similar state in the concentration range of 0.1-190 mg/mL in 40 mM pH 6 citrate-phosphate buffer. Upon thermally stressing these proteins, spectroscopic techniques that probe tertiary structure demonstrate a decrease in the apparent thermal melting temperature of approximately 5-20 degrees C of both proteins with increasing concentration. In contrast, DSC thermograms and CD thermal experiments suggest a minor degree of stabilization (approximately 2 degrees C) for both antibodies although protein association could be responsible for these observations. Empirical phase diagrams produced from spectroscopic data also suggest (1) the existence of similar structural states at low temperatures independent of concentration and (2) a decrease in the temperature at which phase changes are observed with increasing concentration. The decrease in structural stability observed in these studies is probably the result of aggregation or self-association of the recombinant MAbs upon heating in crowded solutions and not due to a decrease in the intrinsic structural stability of the MAbs.

Antibodies, Monoclonal↗
PubMed2001

Von Willebrand factor-cleaving protease activity and proteolysis of von Willebrand factor in bone marrow transplant-associated thrombotic microangiopathy.

INTRODUCTION: Thrombotic microangiopathy (TM) of the fulminant type occurring in patients following bone marrow transplant (BMT) has clinical manifestations that are similar to thrombotic thrombocytopenic purpura (TTP) and hemolytic uremic syndrome, but the outcome is generally fatal despite conventional therapy. Idiopathic acquired TTP has been associated with IgG inhibitors to the cleaving protease of von Willebrand factor (vWF) in plasma. In this study, we investigated the role of the vWF protease and vWF proteolysis in the pathogenesis of BMT-associated TM of the fulminant type. METHODS: vWF antigen level, vWF multimeric pattern, and vWF metalloprotease activity were investigated in the plasma samples of six consecutive patients with acute BMT-associated TM. Histologic and immunohistochemical studies were also performed on autopsy kidney specimens from four of the patients. All six patients had the fulminant type of the disorder with a fatal outcome and none of the patients responded to plasma infusion. RESULTS: The vWF-cleaving protease activity in plasma was normal in all patients. However, analysis of the vWF multimeric pattern showed a decrease of high molecular weight multimers. The decrease of large multimers may be caused by vWF-platelet binding as well as shear enhanced proteolysis of vWF. In the four patients who had an autopsy, a pattern of arteriolar thrombosis, distinct from that of TTP, was detected in the kidneys. CONCLUSION: These findings suggest that BMT-associated TM of the fulminant type is a heterogeneous process and distinct from TTP in pathogenesis. Analysis of vWF protease and vWF multimeric distribution are valuable tools in making the distinction between BMT-associated TM and TTP.

ADAM Proteins↗
PubMed2001

Expression of the apolipoprotein E gene in the skin is controlled by a unique downstream enhancer.

A distal enhancer that specifies apolipoprotein E gene expression in the skin was identified and characterized by in situ hybridization in transgenic mice generated with constructs of the human apolipoprotein E/C-I/C-IV/C-II gene cluster. Transgene constructs containing the enhancer expressed high levels of apolipoprotein E mRNA in the germinative cell layer of the sebaceous gland and in epithelial cells of the hair follicle root sheath. Apolipoprotein E mRNA was also detected in basal epithelial cells of the epidermis. Expression of the human apolipoprotein E transgene at these sites was specified by a unique 1.0 kb enhancer domain located 1.7 kb downstream of the apolipoprotein E gene. No transgene expression was detected in skin epithelial cells in transgenic mice when this enhancer was deleted from the apolipoprotein E gene cluster. The enhancer was used to construct a transgene expression vector that faithfully directed a heterologous cDNA to the normal sites of apolipoprotein E gene expression in epithelial cells of the skin.

Animals↗
PubMed2001

Surgical anatomy of the nail unit.

Surgical procedures in the nail unit require intimate knowledge of the gross and microscopic anatomy of the distal digit in order to obtain accurate diagnostic information and achieve the desired results with minimal impact on appearance and function. This review of the surgical anatomy of the nail unit discusses normal anatomy with an emphasis on those aspects necessary to perform surgery with minimal residual impact.

Humans↗
PubMed2000

Duplicated downstream enhancers control expression of the human apolipoprotein E gene in macrophages and adipose tissue.

Two distal enhancers that specify apolipoprotein (apo) E gene expression in isolated macrophages and adipose tissue were identified in transgenic mice that were generated with constructs of the human apoE/C-I/C-I'/C-IV/C-II gene cluster. One of these enhancers, multienhancer 1, consists of a 620-nucleotide sequence located 3.3 kilobases (kb) downstream of the apoE gene. The second enhancer, multienhancer 2, is a 619-nucleotide sequence located 15.9 kb downstream of the apoE gene and 5.9 kb downstream of the apoC-I gene. The two enhancers are 95% identical in sequence, and they are likely to have arisen as a consequence of the gene duplication event that yielded the apoC-I gene and the apoC-I' pseudogene. Both enhancer sequences appear to have equivalent activity in directing apoE gene expression in peritoneal macrophages and in adipocytes, suggesting that their activity in specific cell types may be determined by common regulatory elements.

Adipose Tissue↗
PubMed2000

Detoxification from alcohol: a comparison of home detoxification and hospital-based day patient care.

An uncontrolled study was carried out to examine two types of ambulatory care for patients undergoing detoxification from alcohol. The safety, efficacy, and acceptability of home detoxification was compared to detoxification within a day hospital setting. Seventy-nine per cent of home detoxification patients, many of whom had major alcohol-related problems and were severely dependent on alcohol, were successfully detoxified at 10 days. The day hospital group overlapped in severity with the home group and 78% completed detoxification. At 60 days, 45% of home detoxification patients and 31% of the day hospital group showed significant improvements in a range of alcohol-related difficulties. Improved outcome was associated with attendance for further treatment for both groups. Both home and day hospital detoxifications were viable alternatives to in-patient detoxification for selected groups of patients.

Adult↗
PubMed2000

Primary hyperaldosteronism (Conn syndrome): MR imaging findings.

PURPOSE: To describe the magnetic resonance (MR) imaging features of the adrenal glands in primary hyperaldosteronism and assess MR imaging in the detection and characterization of aldosterone-producing adenoma (APA). MATERIALS AND METHODS: The authors retrospectively reviewed the cases of 20 patients (13 female and seven male patients; age range, 14-67 years; median age, 46 years) with primary hyperaldosteronism who underwent 1.5-T MR imaging between 1995 and 1998. All patients underwent transverse T1- and T2-weighted imaging, and chemical shift imaging was performed in 17 patients. Imaging results were correlated with findings at biochemical testing, venous sampling, or surgery. RESULTS: Among the 20 patients, 10 (50%) had APA and 10 (50%) bilateral adrenal hyperplasia (BAH). In the detection of APA, MR imaging had a sensitivity of 70%, specificity of 100%, and accuracy of 85%. APAs (mean size, 20 x 16 mm) were iso- or hypointense relative to the liver on T1-weighted images and slightly hyperintense on T2-weighted images. With chemical shift imaging, the signal intensity decreased on the out-of-phase images in six of seven (86%) patients with APA and in eight of nine (89%) patients with BAH. CONCLUSION: MR imaging has a high specificity in the detection of APA. As with nonhyperfunctioning adenoma, APA and BAH show evidence of intracellular lipid at chemical shift imaging.

Adenoma↗
PubMed1999

Variation of pesticide concentration in sheep dips operated according to traditional and revised methods.

OBJECTIVE: To quantify stripping in traditional dipping operations and to revise dipping methods, based on prediction of stripping so that a more stable concentration of pesticide in the dipwash is achieved. DESIGN AND METHODS: Plunge and shower dips were operated sequentially according to traditional and revised dipping instructions. Dips were operated by continuous and intermittent replenishment. Samples of mixed dipwash were collected periodically and assayed for pesticide (diazinon) concentration. RESULTS: Diagrammatic representations of pesticide concentration versus number of sheep dipped indicated traditional dipping leads to wide variations in the concentration of pesticide in dipwash during dipping. Intermittent replenishment led to a 'saw-tooth' pattern in the pesticide concentration. Traditional continuous replenishment (using the starting concentration of pesticide) indicated both the rate and extent of stripping was higher in shower dipping. If sufficient sheep were dipped, equilibrium was reached between the rate of pesticide replenishment and removal. An alternative method of dip operation by continuous replenishment, using a low starting concentration of pesticide and a replenishment concentration high enough to offset the pesticide loss through stripping resulted in a more stable concentration of pesticide in the dip. CONCLUSION: Revision of dipping instructions can lead to exposure of sheep to stable concentrations of stripping pesticide during dipping.

Administration, Topical↗
PubMed1997

Inflammatory markers in chronic hepatitis C.

To test the hypothesis that inflammation in hepatitis C follows mechanisms common to immune-activated pathways, the distributions of T and B cells, adhesion molecules and transforming growth factor-beta (TGF-beta) were assessed in liver biopsies with chronic inflammation due to hepatitis C (HCV, n = 8) and other causes (non-HCV, n = 10). Frozen sections were immunostained using primary antibodies to CD2, CD20, CD4, CD8, intercellular adhesion molecule (ICAM-1), vascular cell adhesion molecule (VCAM)-1, HLA-DR, lymphocyte function-associated antigen (LFA)-1, and TGF-beta. Inflammatory cells positive for each immunophenotypic marker were counted, and positive staining for adhesion molecules, HLA-DR and TGF beta was graded in triads and lobules and compared in HCV and non-HCV biopsies. In all biopsies, T cells were more frequent than B cells, both in triads and lobules. CD20+, CD4+, CD8+ and LFA-1+ cells were increased in HCV compared to non-HCV biopsies. Portal lymphoid aggregates were present in 6 of 8 HCV biopsies and 3 of 10 non-HCV biopsies. Aggregates consisted of CD20+, CD4+, CD8+ and LFA-1+ cells, and ICAM-1 and VCAM-1 were increased. Sinusoidal lining cells in HCV biopsies and non-HCV biopsies with inflammation expressed HLA-DR, ICAM-1, and CD4. TGF-beta was increased in foci of necrosis. Inflammation in chronic HCV involves common immune-mediated cellular effector pathways and the inflammation in the portal triads represents aggregation of both T and B cells, mediated in part by upregulation of adhesion molecules on portal stromal cells; this is possibly in response to antigens draining from necroinflammatory foci in the lobules. TGF-beta is increased in active necroinflammatory foci, but not in portal lymphoid aggregates.

Adult↗
PubMed1997

Correlates and perceived outcomes of four types of employee development activity.

Participation in 4 different types of development activity was studied in a sample of manufacturing employees (N = 1,798). It was found that similar sets of variables were linked to greater participation in 3 activities: required training courses in work time, work-based development activity in work time, and career planning activity in work time or an individual's own time. Three kinds of reported benefits were studied, and the occurrence of these benefits was found to vary between different types of development activity. Overall job satisfaction and organizational commitment were significantly associated with prior participation in required training courses and work-based development activity. However, voluntary learning in one's own time was completely unrelated to these work attitudes.

Adult↗
PubMed1996

Effect of interferon therapy on bile duct inflammation in hepatitis C.

Inflammation of the bile ducts was studied in liver biopsies from patients with chronic hepatitis C to determine whether the frequency of inflamed bile ducts changes with therapy and correlates with other histological variables and expression of class I and II MHC antigens on ductal epithelium. Twenty patients treated at UMMC between 1991 and 1994 underwent needle biopsies of the liver before and after therapy with interferon alpha 2B (IFN). A complete response to therapy was defined as a return to normal serum alanine aminotransferase levels occurring and persisting during therapy. The number of inflamed bile ducts/total ducts (%IBDs), presence of piecemeal necrosis and lymphoid aggregates, and grade of inflammation were assessed in each high-power field in all areas with bile ducts. The frequencies of these variables were compared in cirrhotics and non-cirrhotics and in patients with complete or incomplete responses to IFN. Frozen sections of biopsies from 5 patients were immunostained using antibodies to HLA-DR and B-2 microglobulin, and positive staining was noted on bile ducts. Before therapy, the %IBD was slightly greater in patients with cirrhosis. After IFN, both %IBD and serum alkaline phosphatase levels decreased in non-cirrhotics who responded to IFN. The change in frequency of IBD with IFN paralleled the changes in the other histological features. No correlation was noted between bile duct inflammation and expression of class I and II antigens. The conclusion is that inflammation of the bile ducts occurs frequently in chronic hepatitis C, correlates with other features of inflammation in the triads, and decreases in response to IFN therapy.

Adult↗
PubMed1996

High-dose interferon-alpha 2b for re-treatment of nonresponders or relapsing patients with chronic hepatitis C. A controlled randomized trial.

Relatively few patients with chronic hepatitis C treated with standard doses of interferon-alpha 2b (3 million units per week for 24 weeks) have a sustained response. Our aim was to evaluate whether higher doses of interferon would improve this rate of response. Twenty-four patients with chronic hepatitis C who had failed to respond to (N = 21) or had relapsed after (N = 3) an initial course of standard interferon therapy were randomized to 15 million units (N = 13) or 22.5-30 million units per week (N = 11) for 24 weeks. Five of 13 subjects given 15 million units per week and 3/11 of subjects given 22.5-30 million units per week had complete normalization of serum alanine aminotransferase levels during therapy. Five patients (24% who had not responded to standard interferon had a complete response to high-dose interferon during therapy. Only one patient had a sustained response, with normal serum alanine aminotransferase 24 weeks after stopping interferon. Six patients were withdrawn before completing treatment, five in the 22.5-30 million unit per week group. We conclude that higher doses of interferon ameliorate the severity of hepatitis in patients who failed to respond to or relapsed after standard interferon therapy, but are unlikely to produce a sustained response. High-dose therapy is associated with an increase in side effects.

Alanine Transaminase↗
PubMed1996

Efficiency of the flexor tendon pulley system in human cadaver hands.

The efficiency of the flexor tendon system was examined in a human cadaver model. Pulleys were randomly sectioned, and the results were evaluated on the basis of the tendon excursion, force generated at the fingertip, and the work (force multiplied by distance) involved, as compared to the intact pulley system. When a single minor pulley (A1 or A5) was cut, there was no statistical difference in work efficiency or excursion efficiency from controls. Cutting all minor pulleys (A1, A3, A5) lead to a significant loss in excursion efficiency. The intact three pulley systems of A2, A3, and A4 were near normal and statistically better than A2 and A4 together for work efficiency. Cutting one of the major pulleys (A2, A4) resulted in significant changes in efficiency, but what was unexpected was to find an 85% loss of both work and excursion efficiency for the loss of A4 but only an excursion difference of 94% for the loss of A2. Our findings demonstrated that in this model, with the influence of the skin removed, A4 absence produced the largest biomechanically measured efficiency changes and that a combination of A2, A3, and A4 was necessary to preserve both work and excursion efficiency.

Biomechanical Phenomena↗
PubMed1995

Structure of the hepatic control region of the human apolipoprotein E/C-I gene locus.

The specificity of expression in the liver of the human apolipoprotein (apo) E/C-I gene locus is determined by a hepatic control region (HCR) that is located 15 kilobases downstream of the apoE gene. DNase I footprint studies of this sequence using nuclear extracts identified a region of the HCR that is enriched in nuclear protein-binding sites. Nuclease analysis of chromatin revealed liver-specific DNase I-hypersensitive sites that were associated with this region, and additional liver-specific nuclease-sensitive sites associated with the apoE gene were identified. The HCR domain has a limited binding affinity for the nuclear scaffold. The specific domain required for liver expression was tested by ligating subfragments of the HCR to the apoE gene and examining their activity in transgenic mice. A segment of 319 nucleotides that contained several potential regulatory sequences was required for full activity of liver-specific transcription with shorter segments yielding much lower levels of expression in the liver. All constructs that contained a fully active HCR were expressed in approximately a copy-dependent manner, suggesting that transgene expression was independent of integration position. Taken together, the properties of the HCR are consistent with its function as a locus control region for the liver-specific expression of the apoE gene.

Animals↗
PubMed1994

The effect of bile acids and piroxicam on MHC antigen expression in rat colonocytes during colon cancer development.

The effect of bile acids and piroxicam on the expression of major histocompatibility complex (MHC) antigens in colonocytes was evaluated in rats treated with the colonic carcinogen azoxymethane (AOM). Male Fischer-344 rats were fed a basal diet (AIN-76) supplemented with 0.4% cholic acid, 0.4% ursodeoxycholic acid, 0.2% ursodeoxycholic acid plus 0.2% cholic acid, or 75 p.p.m. piroxicam. Rats were injected subcutaneously once a week for 2 weeks with AOM (15 mg/kg body weight/week) or vehicle, after being fed their respective diets for two weeks. The rats were killed at 16 weeks, while parallel identical groups of rats were killed at 28 weeks, and colon tumours were counted. None of the rats treated with AOM-vehicle developed tumours at 28 weeks, while in the AOM-treated rats the frequency of colonic tumours was as follows: AOM alone 50%, cholic acid 74%, ursodeoxycholic acid 17%, piroxicam 28%, ursodeoxycholic plus cholic acid 46%. The expression of RT1A, RT1B and RT1D was determined in isolated colonocytes by immune fluocytometry. Normal rat colonocytes express all three MHC antigens strongly. Neither the bile acids nor piroxicam affected MHC antigen expression in AOM-vehicle-treated rats. AOM did not effect MHC antigen expression compared to normal controls. Cholic acid had no significant effect on the expression of MHC antigens in AOM-treated rats. Ursodeoxycholic acid alone or in combination with cholic acid increased the expression of RT1A compared to normal controls, of RT1B compared to AOM-treated rats, and of RT1D compared to controls or AOM-treated rats. Piroxicam increased the expression of all three antigens compared to either control or AOM-treated rats. These findings indicate that (1) ursodeoxycholic acid and piroxicam up-regulate colonic MHC antigen expression in the AOM model of colonic carcinogenesis; (2) the colon of rats exposed to AOM responds differently than the normal colon with respect to MHC regulation; and (3) the protective effect of ursodeoxycholic acid and piroxicam on colon tumour formation seems to be paralleled by an increase in MHC antigen expression.

Animals↗
PubMed1989

Ventilatory responses to hypoxia and hypercapnia in asthmatics with previous respiratory failure.

The ventilatory response to hypoxia and the ventilatory and mouth occlusion pressure response to hypercapnia was measured in 13 subjects who had previously developed respiratory failure or respiratory arrest during an acute asthma attack. In 11 of 12 subjects tested there was a normal response to hypercapnia. Six of the 13 subjects had an impaired response to hypoxia. Impaired hypoxic responsiveness may contribute to the early onset of hypercapnic respiratory failure during acute severe asthma.

Acute Disease↗
PubMed1989

Quantitation of apolipoprotein A-IV in human plasma using a competitive enzyme-linked immunosorbent assay.

A method for measuring human apolipoprotein A-IV has been developed using the competitive enzyme-linked immunosorbent assay (ELISA) system. The assay described is relatively easy, rapid, and inexpensive to perform, uses convenient dilutions of plasma (1/8-1/32) but is sensitive enough to quantitate the apoA-IV content of lipoproteins following gel filtration of small (0.3-0.5 ml) volumes of plasma. The working range is 100-600 ng of apoA-IV per 50-microliters sample and the intra- and interassay coefficients of variations are 7.5 and 10.2% (means), respectively. The mean apoA-IV concentration of 100 subjects was found to be 16.4 +/- 5.4 mg/dl. The assay can be performed on untreated plasma samples which may be stored frozen (-20 degrees C) for up to 2 months.

Apolipoprotein A-I↗