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Biomedical subjects

R G Cooper

Publications and source records attributed to R G Cooper.

At least 37 records · Page 2Linked to original sources
PubMed1999

Recent developments in gene-directed enzyme prodrug therapy (GDEPT) for cancer.

Gene-directed enzyme prodrug therapy (GDEPT) is a promising two-step treatment for solid malignant tumors. In the first step, the gene for a foreign enzyme is administered and directed to the tumor, where it may be expressed using specific transcriptional elements. In the second step, prodrugs are administered and activated by the foreign enzyme expressed at the tumor. This review focuses on the progress from the end of 1997 to date. Important issues, such as viral and non-viral vectors, new enzyme/prodrug systems, new strategies, advances in the understanding of the bystander effects, the comparison of different systems used in GDEPT and clinical trials are outlined.

Adenoviridae↗
PubMed1998

An RGD-oligolysine peptide: a prototype construct for integrin-mediated gene delivery.

We have synthesized a linear, bifunctional peptide that comprises an integrin-targeting domain containing an arginine-glycine-aspartic acid tripeptide motif and a DNA-binding moiety consisting of a short stretch of 16 lysine residues. This peptide can form distinctive, condensed complexes with DNA and is capable of mediating its delivery and expression in a variety of mammalian cells in culture. Internalization is mediated by cell surface integrin receptors via a mechanism that is known to be phagocytic. We have analyzed the relationship between DNA and peptide and have investigated the conditions suitable for optimal gene delivery. The formation of condensed peptide DNA complexes leads to resistance to nuclease degradation. The level of reporter gene expression obtained is dependent on the peptide-to-DNA ratio and is enhanced in the presence of the endosomal buffer chloroquine, polyethyleneimine, and deactivated adenovirus during gene delivery. Under optimal conditions the levels of reporter gene expression obtained approach or even exceed those obtained with DNA delivered with the commercial liposome Lipofectamine. The ability to produce an efficient gene delivery system using small, easily modified, and well-defined constructs that have no constraint of particle size demonstrates the advantages of integrin-targeting peptides for gene transfer.

3T3 Cells↗
PubMed1998

The influence of muscle fiber size and type distribution on electromyographic measures of back muscle fatigability.

STUDY DESIGN: This was a cross-sectional study carried out on a group of 31 healthy, consenting volunteers with no history of low back pain (17 men, 14 women). OBJECTIVES: To evaluate the relationship between electromyographic measures of erector spinae fatigability and the muscle's fiber type characteristics. SUMMARY OF BACKGROUND DATA: Using electromyographic techniques, a pronounced fatigability of the muscles of patients with low back pain has been identified. It has been postulated that this is the result of an unfavorable back muscle fiber type distribution, although an association between electromyographic measures of fatigue and the muscle's fiber type characteristics has never been established. METHODS: Two tests of back extensor fatigability were performed (on separate days), each to the limit of endurance: 1) maintenance of 60% total maximum voluntary contraction of the back extensors, and 2) performance of the Biering-Sørensen test. Pairs of surface electrodes were attached to the skin overlying the belly of the erector spinae, bilaterally, at T10 and L3. The median frequency was computed from the electromyographic power spectrum, and fatigability was given by the slope of the linear regression of median frequency on time (MFgrad; %.s-1). One week later, two percutaneous erector spinae muscle biopsy samples were obtained from the same sites described for electromyography (left side only). Samples were prepared for histochemistry for the identification of muscle fiber types. Fiber sizes (cross-sectional areas) were quantified using computerized image analysis. RESULTS: The mean fiber size at each erector spinae region showed a significant correlation with maximum back extensor strength. In the thoracic region, the relative area of the muscle occupied by Type I fibers (which accounts for the relative size and distribution of the fiber types) showed a significant relationship with MFgrad recorded during each fatigue test. A similar relationship was observed for the lumbar region, but for the Biering-Sørensen test only. CONCLUSIONS: The electromyographic changes recorded in back muscles during fatigue appear to be related to the underlying muscle fiber type area distribution. This confirms the usefulness of electromyography in reflecting such muscle characteristics in a noninvasive manner, when monitoring changes in function consequent to the development of, or rehabilitation from, low back pain.

Adult↗
PubMed1998

Endothelial cell transfection with cationic liposomes and herpes simplex-thymidine kinase mediated killing.

Endothelial cells are a promising target for cancer gene therapy because neoangiogenesis is vital for the supply of oxygen and nutrients to solid tumours. However, endothelial cells have been reported to be difficult to transfect. We demonstrate high rates of transfection with the reporter gene pSV40 beta gal using DC-Chol/DOPE cationic liposomes and lower rates with the novel polyamine cationic liposomes ACHx/DC-Chol/DOPE and ACO/DC-Chol/DOPE. Endothelial cells transfected with HSV-thymidine kinase using DC-Chol/DOPE demonstrated 3 log10 increased cytotoxicity compared with controls when exposed to the prodrug ganciclovir, thereby demonstrating significant biological effect.

Cations↗
PubMed1998

Enhanced in vitro and in vivo gene delivery using cationic agent complexed retrovirus vectors.

Retroviruses are, at present, the most efficient integrative vectors available for gene delivery. However, these viruses are still limited by relatively low titres. Although several protocols exist to improve virus titre most of them are time-consuming and unable to provide sufficient virus for in vivo applications. Virus titre can be enhanced by polybrene and other cationic agents. By investigating a broad range of cationic agents for their ability to enhance virus infectivity we found that both ecotropic and amphotropic retrovirus infection could be increased. In particular, the lipopolyamine dioctadecylamidoglycylspermine (DOGS) gave up to one order of magnitude enhancement above polybrene-mediated infection without cytotoxicity. To increase virus infectivity further we combined the enhancing effect of DOGS on virus infectivity with concentration of virus particles by ultrafiltration to reach titres of 1 x 10(9) IU/ml. The in vivo transduction of regenerating rat liver, by an amphotropic retrovirus was increased approximately five-fold by the addition of DOGS compared with virus alone. There was no animal toxicity observed following the administration of DOGS. The improved transduction efficiency seen both in vitro and in vivo following the co-administration of DOGS/virus complexes may be useful for future gene therapy applications.

3T3 Cells↗
PubMed1998

Liposomes enhance delivery and expression of an RGD-oligolysine gene transfer vector in human tracheal cells.

Nonviral gene delivery systems consist predominantly of lipoplexes or receptor-targeting and nontargeting polyplexes. We examined integrin-mediated gene delivery using an Arg-Gly-Asp/oligo-L-lysine ([K]16RGD) cyclic peptide and investigated its gene transfer efficiency when associated with a cationic liposome. We demonstrated that human cystic fibrosis and noncystic fibrosis tracheal epithelial cells in culture express integrins that recognise the RGD integrin-binding motif. We found a 10-fold (P < 0.01) increased expression of a luciferase encoding plasmid in these cells when complexing the plasmid to the [K]16RGD peptide as compared with plasmid alone. This increase was specific to the [K]16RGD peptide since neither a [K]16RGE nor a [K]16 peptide gave a comparable increase. Expression was further enhanced 30-fold (P < 0.01) with lipofectamine and the ratio of DNA/peptide/lipofectamine was critical for specificity and expression. Fluorescence and radioactive labelling of the complex showed that the [K]16RGD peptide increased the endocytic uptake of DNA into cells. The cell association of both DNA and peptide increased even further with lipofectamine. Confocal microscopy showed that the [K]16RGD peptide and the DNA internalised together within 30 min and localised to vesicles in the perinuclear region. These results show that an integrin-binding ligand can deliver genetic material to airway cells and that a cationic liposome can enhance the efficacy of this nonviral vector system.

Cation Exchange Resins↗
PubMed1998

Electrical stimulation of human tibialis anterior: (A) contractile properties are stable over a range of submaximal voltages; (B) high- and low-frequency fatigue are inducible and reliably assessable at submaximal voltages.

OBJECTIVES: To investigate the validity and reliability of submaximal voltage stimulation for assessing the 'fresh' contractile properties of human tibialis anterior muscle (TA) and the efficacy of such stimulation in inducing and assessing high- and low-frequency fatigue. INTERVENTIONS: (A) Contractile properties of fresh TA were assessed in six normal volunteers using multifrequency stimulation trains (comprising 2 seconds at each of 10, 20 and 50 Hz, arranged contiguously) over a range of submaximal voltages. (B) On three separate occasions, fatigue was induced in the TA of 10 normal volunteers by means of a 3-minute unbroken sequence of the described multifrequency stimulation trains, delivered at a 'standardized' submaximal voltage. This fatiguing protocol was preceded by discrete multifrequency stimulation trains, at the same standardized voltage, but followed by discrete multifrequency trains delivered over a range of submaximal voltages (which included the standardized voltage). OUTCOME MEASURES: In experiment A the 10:50 Hz and 20:50 Hz force ratios were analysed for between-voltages variability using coefficients of variation (CVs), and for trends using Friedman tests and post-hoc Wilcoxon tests. In experiment B low-frequency fatigue was detected using 10:50 Hz and 20:50 Hz force ratios derived from the discrete multifrequency trains. High-frequency fatigue was calculated from the decline in high-frequency force which occurred during the fatiguing protocol itself. Each parameter was assessed for between-days repeatability using CVs. RESULTS: In experiment A the 'fresh' 10:50 Hz force ratio was clearly unreliable at voltages which generated <10% of maximal voluntary contractile force (MVC) (CV< or =29.7%), but was reasonably reliable at voltages which generated 20-30% of MVC (CV < or = 11.5%; p = 0.847). The 'fresh' 20:50 Hz force ratio was,in contrast, extremely reliable throughout the tested voltage range (CV< or =5.8%; p = 0.636) in fresh muscle. In experiment B paired t-tests indicated that the fatiguing protocol induced significant high-frequency fatigue (p <0.0037) and low-frequency fatigue (p <0.0008 for 'fresh' versus 'fatigued' 10:50 Hz force ratio; p <0.0001 for 'fresh' versus 'fatigued' 20:50 Hz force ratio). In muscle thus fatigued, the 20:50 Hz force ratio was extremely reliable in the 20-33% of MVC range (CV < or =7.3%; p = 0.847). Between-days repeatability was poor for the 10:50 Hz force ratio in both fresh and fatigued muscle (CV < or =23.8 and 44.4% respectively), but was highly acceptable for both voluntary and stimulated fatigue indices and for the 20:50 Hz force ratio, the latter in both fresh and fatigued muscle. CONCLUSIONS: These results confirm the validity and reliability of submaximal voltages in assessing contractile properties (including low-frequency fatiguability) and inducing fatigue of human TA.

Adult↗
PubMed1997

Optimization of liposome mediated transfection of a neuronal cell line.

A cell line derived from sensory neurons was transfected with high efficiency using cationic liposomes, formulated from 3 beta [N-(N',N'-dimethylaminoethane)carbamoyl]-cholesterol (DC-Chol) and dioleoyl L-alpha-phosphatidylethanolamine (DOPE). This is the first time that cationic liposomes of this type have been reported to transfect a neuronal cell line. We used a reporter gene construct expressing beta-galactosidase under the control of the cytomegalovirus immediate early promoter and routinely observed transfection efficiencies > 40%. Parameters affecting transfection efficiency were examined and the ratio of DNA to liposome proved to be crucial. Liposome formulation procedures and cell transfection protocols devised here will be used as a basis for further in vivo and in vitro work.

Animals↗
PubMed1997

Muscle fibre size and type distribution in thoracic and lumbar regions of erector spinae in healthy subjects without low back pain: normal values and sex differences.

This study sought to investigate the normal muscle fibre size and type distribution of the human erector spinae, both in thoracic and lumbar regions, in a group of 31 young healthy male (n = 17) and female (n = 14) volunteers. Two percutaneous muscle biopsy samples were obtained under local anaesthesia, from the belly of the left erector spinae, at the levels of the 10th thoracic and 3rd lumbar vertebrae. Samples were prepared for routine histochemistry for the identification of fibre types. Fibre size (cross-sectional area (CSA) and narrow diameter (ND)) was quantified using computerised image analysis. The mean CSA/ND for each fibre type was greater in the thoracic than the lumbar region, but there was no difference between the 2 regions either for percentage type I (i.e. percentage distribution by number), percentage type I area (i.e. relative area of the muscle occupied by type I fibres) or the ratio describing the size of the type I fibre relative to that of the type II. Men had larger fibres than women, for each fibre type and at both sampling sites. In the men, each fibre type was of a similar mean size, whereas in the women the type I fibres were considerably larger than both the type IIA and type IIB fibres, with no difference between the latter two. In both regions of the erector spinae there was no difference between men and women for the proportion (%) of a given fibre type, but the percentage type I fibre area was significantly higher in the women. The erector spinae display muscle fibre characteristics which are clearly very different from those of other skeletal muscles, and which, with their predominance of relatively large type I (slow twitch) fibres, befit their function as postural muscles. Differences between thoracic and lumbar fascicles of the muscle, and between the muscles of men and women, may reflect adaptive responses to differences in function. In assessing the degree of any pathological change in the muscle of patients with low back pain, it seems clear that (1) sex cannot be disregarded and (2) 'atrophied' (using the criteria from other muscles) type II fibres are not necessarily abnormal for the erector spinae, particularly in women.

Adult↗
PubMed1997

Urinary excretion of albumin and retinol binding protein in systemic lupus erythematosus.

We have measured the urinary excretion of total protein, albumin and retinol binding protein (RBP) in random urine specimens obtained from 40 female patients with systemic lupus erythematosus (SLE). Thirty-three of these patients had no clinical evidence of any renal impairment (non-renal SLE); seven had overt renal disease (renal SLE). RBP:creatinine ratios were significantly higher in non-renal SLE patients compared with female controls (P = 0.002). There was no significant difference between urine total protein concentrations, albumin:creatinine or total protein:creatinine ratios in non-renal SLE patients when compared with controls, despite approximately 20% of these patients having elevated excretion of total protein or albumin. All seven renal SLE patients had elevated albumin:creatinine ratios but only four of them had an increased RBP:creatinine ratio. Of 29 non-renal SLE patients who had urinary total protein concentrations below 0.2 g/L, (i.e. approximating to a negative protein dipstick), 14 had increases in either albumin or RBP:creatinine ratios. Only two patients had increases in both. In the absence of clinical evidence of renal disease, increases in urinary albumin or RBP excretion could indicate subclinical nephropathy and measurements may have a role in the early diagnosis and subsequent monitoring of renal disease in SLE.

Adult↗
PubMed1997

New products: benchmarking the critical success factors.

New-product development is emerging as the key strategic endeavour of companies in fields such as medical devices. Drawing on the findings of a recent study, the author suggests that the critical factors that influence the success of new products are process, strategy and resources. Process was found to have the strongest impact on the performance of a new product. This article describes a stage-gate process that provides companies with a template for driving new-product projects from idea through to launch.

Commerce↗
PubMed1995

Herniated intervertebral disc-associated periradicular fibrosis and vascular abnormalities occur without inflammatory cell infiltration.

STUDY DESIGN: Prospective histologic comparison of perineural tissues from patients requiring decompression surgery for herniated intervertebral disc with those from cadaveric controls. OBJECTIVES: To examine the significance of herniated intervertebral-disc-associated perineural vascular and fibrotic abnormalities with respect to back pain symptom generation. SUMMARY OF BACKGROUND DATA: Previous cadaveric studies have demonstrated perineural vascular congestion, dilatation, and thrombosis and perineural and intraneural fibrosis occurring in association with herniated intervertebral disc. It was suggested that these neural abnormalities were the result of ischemia, due to venous outflow obstruction, and also represented a possible cause of ongoing back pain symptoms. Criticisms of such a conclusion arose, however, because the possibility could not be excluded that these abnormalities were the result of postmortem artifact. METHODS: Histologic and immunohistochemical comparison of discal and peridiscal tissues removed from 11 patients with radiographically proven herniated intervertebral disc requiring decompressive surgery and from 6 fresh cadavers without history of back pain in life. RESULTS: Histology and immunohistochemistry of perineural and extraneural tissues from patients revealed vascular congestion, neovascularization, and endothelial abnormalities including luminal platelet adhesion, in association with reductions in von Willebrand factor levels, together with perivascular and perineural fibrosis. Elevated fibrogenic cytokine concentrations were also detected in patients' tissues. These changes occurred without evidence of inflammation and were absent in cadaveric control tissues. CONCLUSIONS: The vascular abnormalities detected in patients may represent an important etiopathologic factor predisposing to intraneural and perineural fibrosis, and hence to chronic pain symptoms, after disc herniation. It seems important to preserve the perineural microcirculation following disc herniation.

Adult↗
PubMed1995

Relative contributions of HLA-DQA and complement C4A loci in determining susceptibility to systemic lupus erythematosus.

The objective of this study was to reassess the role of C4A null alleles in systemic lupus erythematosus (SLE) susceptibility after taking into account the association of DQA*0501 with this disease. The frequency of C4A null alleles in 82 SLE patients and 59 controls was determined using both immunofixation and a TaqI RFLP method. HLA-DQA and DQB alleles were identified by sequence-specific oligonucleotide typing. Empirical logistic analysis was used to assess the interactive effects of C4 and DQA alleles. It was found that the strongest association with SLE was for the combination of DQA*0501 and C4A*Q0 [odds ratio (OR) = 5.4, 95% confidence interval (CI) 2.5-11.7]. Both DQA*0501 (P = 0.02) and C4A*Q0 (P = 0.03) appeared to have significant individual effects on SLE susceptibility, with a significant statistical interaction between the two loci (P = 0.01). However, when anti-La antibody negative patients were examined only C4A*Q0 had a significant individual effect (P = 0.04). A significant statistical interaction between DQA*0501 and C4A*Q0 was again detected (P = 0.02). These results support the hypothesis that susceptibility to SLE is influenced by several genes with differing functions: HLA-DQA*0501 may predispose to autoantibody formation while C4A*Q0 impairs immune complex clearance.

Adolescent↗
PubMed1994

HLA-DP does not contribute towards susceptibility to systemic lupus erythematosus.

OBJECTIVES: To determine whether HLA-DP genes are involved in determining susceptibility to systemic lupus erythematosus (SLE). METHODS: HLA-DPA1 and DPB1 genes were amplified by PCR of DNA samples from a panel of patients with SLE and normal controls. Amplified DNA was blotted on to nylon filters and probed with sequence-specific oligonucleotide (SSO) probes. RESULTS: No DPA1 or DPB1 allele was significantly associated with SLE, or with any immunological or clinical subset of SLE. Evidence was found for only limited linkage disequilibrium between HLA-DP and HLA-DQ/DR variants, and none between HLA-DP and the TAP2 gene. CONCLUSIONS: These data indicate that HLA-DP genes do not contribute towards determining susceptibility to SLE.

Adolescent↗
PubMed1993

HLA-DQ, DR and complement C4 variants in systemic lupus erythematosus.

We have defined HLA-DQA, DQB, DR and complement C4 variants in 92 subjects with SLE and 73 controls. Subjects with SLE showed an increased frequency of HLA-DQA*0501 (P < 0.01 corrected, odds ratio (OR) = 4.97; 95% C.I. = 2.52-9.81), DR3 (P < 0.001, OR = 3.18; 95% C.I. = 1.67-6.04) and C4A*Q0 (P < 0.05, OR = 1.91; 95% C.I. = 0.999-3.65) vs controls. These increases were particularly marked in those subjects positive for antibodies to both Ro and La. HLA-DQB*0501 (P < 0.01 corrected, OR = 0.03), DQA*0101 (P = 0.0012 uncorrected, OR = 0.23) and DR7 (P = 0.0018 uncorrected, OR = 0.28) were decreased in frequency in SLE. SLE patients with disease onset prior to age 30 yr were more likely to possess a DR3-bearing haplotype (P < 0.05 corrected) than those with onset after age 30 yr. No significant associations were found in patients with circulating antibodies to double-stranded DNA, Ro alone, U1 RNP, Sm or in those SLE patients with renal disease or vasculitis. The different associations found in different clinical and immunological subsets of SLE support the concept that SLE contains a variety of immunogenetic subgroups. Analysis of the associations between SLE and DR3, DQA*0501 and C4A*Q0 using the empirical logistic test suggests that the association of SLE with HLA-DQA*0501 is likely to be primary to the associations with both DR3 and C4A*Q0 (P < 0.001). Our results therefore raise the possibility that genes within the HLA-DQ region may have a direct effect upon susceptibility to SLE.

Adolescent↗
PubMed1993

Normal paraspinal muscle electromyographic fatigue characteristics in patients with primary fibromyalgia.

Paraspinal muscle fatigue mechanisms were compared in 14 primary fibromyalgia patients and 14 age and sex matched normal subjects using a standardized 60-s isometric endurance test of the paraspinal muscles, during which surface integrated electromyographic (IEMG) activity was recorded. Fatigue-induced IEMG increases were similar for both groups during the initial 40 s (up to 112 +/- 20% and 111 +/- 6% of initial values in patients and normal subjects respectively). Thereafter, IEMG fell significantly in patients (P < 0.05) but only slightly in controls, so that at 58 s IEMG was 102 +/- 13% in patients and 109 +/- 12% in controls. If patients were divided according to body mass index (BMI, range 19-25 in controls) those with a BMI < 26 (n = 5) showed IEMG changes similar to those of control subjects throughout the test, while obese patients with BMI > 26 (n = 9) showed greater IEMG declines after 40 s than either normal subjects or in the fibromyalgia group as a whole. Paraspinal muscle fatigue mechanisms appear normal in primary fibromyalgia patients. Isometric force maintenance in overweight patients, despite IEMG declines, illustrates the action of intrinsic fatigue resistance mechanisms which were presumably utilized to a greater extent in these patients to cope with the extra load.

Adult↗
PubMed1993

HLA associations in subjects with rheumatoid arthritis and bronchiectasis but not with other pulmonary complications of rheumatoid disease.

We have examined HLA-DR, DQA and DQB variants in 72 controls, 153 subjects with RA without extra-articular features and in subjects with the rheumatoid pulmonary complications of interstitial fibrosis (23) peripheral airways disease (13) and in 41 subjects with RA and bronchiectasis. Subjects with RA alone showed the expected association with HLA-DR4 (79%) but those with RA and co-existent pulmonary fibrosis were less likely to be DR4 positive (61%). No other HLA-DR variants were significantly increased in the different disease groups. HLA-DQB1*0501 which types serologically as DQw1 was increased in subjects with RA and peripheral airways disease as compared to rheumatoid subjects with normal lung function, but these differences were not statistically significant. DQB1*0601 was increased in subjects with bronchiectasis with or without RA (but only significantly so in RA-BR subjects) DQB1*0301, DQB1*0201 and DQA1*0501 frequencies were also increased in subjects with RA and bronchiectasis as compared to those with RA alone.

Aged↗