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Biomedical subjects

J R Morgan

Publications and source records attributed to J R Morgan.

At least 55 records · Page 3Linked to original sources
PubMed1995

Genetically modified human epidermis overexpressing PDGF-A directs the development of a cellular and vascular connective tissue stroma when transplanted to athymic mice--implications for the use of genetically modified keratinocytes to modulate dermal regeneration.

We investigated the hypothesis that keratinocyte-produced platelet-derived growth factor-AA (PDGF-AA) is involved in epidermal-dermal interactions and that PDGF-AA is an important mediator of the temporal and spatial events of tissue repair. Retroviral-mediated gene transfer was used to introduce the gene encoding human PDGF-A into cultures of human diploid keratinocytes. Genetic modification boosted the endogenous in vitro level of PDGF-AA secretion by over 300 fold. When PDGF-secreting cells were transplanted as epithelial sheets to athymic mice, modified keratinocytes underwent terminal differentiation and generated a stratified epithelium comparable to unmodified cells. Seven days after grafting the newly synthesized connective tissue layer subjacent to the PDGF-A-modified grafts was significantly thicker, was rich in mononuclear cells and fibroblasts, and had increased numbers of blood vessels when compared to control grafts of unmodified cells. These results suggest that PDGF-AA secreted by the epidermis is an important mediator of epithelial-mesenchymal interactions and helps to promote growth and vascularization of the underlying dermal tissue. Further, these data demonstrate the feasibility of using genetically modified cells to modulate tissue regeneration.

Animals↗
PubMed1995

Sustained production of human transferrin by transduced fibroblasts implanted into athymic mice: a model for somatic gene therapy.

Somatic gene therapy has been proposed as a means of treating inherited diseases involving defective or absent plasma proteins, viral diseases, and cancer. Introduction of the gene of interest into fibroblasts and implantation of these genetically modified fibroblasts using a skin equivalent system may be an attractive model for gene therapy because skin fibroblasts are easily obtained and propagated in culture. This study evaluated expression of the gene for human transferrin (hTf) by genetically modified fibroblasts in vitro and in vivo. NIH 3T3 fibroblasts, which form non-metastasizing tumors in athymic mice, were transduced with a retroviral vector encoding hTf. The transduced cells were cloned by limiting dilution and hTf production by the cloned cells measured. Two clones of cells producing high levels of hTf were used to seed collagen-coated nylon matrices, which were maintained in culture for up to 53 d. The rate of synthesis of hTf by the seeded matrices was constant after 22 d in vitro. Matrices seeded with cloned, transduced cells were implanted subcutaneously into seven athymic mice, and plasma levels of hTf were assessed biweekly. In all animals, the plasma level of hTf was detectable at week 6 after implantation. Levels of hTf remained elevated in the animals until the implants were removed at week 12. At week 10, the level of hTf in the plasma correlated with tumor volume in tumors less than 2000 mm3 in size. The half-life of hTf in the mice was 39.5 h. In this model, gene expression did not decline for the 12-week observation period.

3T3 Cells↗
PubMed1995

Retrovirus infection: effect of time and target cell number.

Using a model amphotropic recombinant retrovirus encoding the Escherichia coli lacZ gene and quantitative assays to measure virus infection, we have determined the effects of time and target cell number on infectivity. Infection of various numbers of NIH 3T3 fibroblasts showed that the extent of lacZ virus infection was dependent on virus concentration and independent of target cell number. These results demonstrate that multiplicity of infection is not an accurate predictor of the efficiency of retroviral infection. Varying the time of viral infection revealed that maximal infection occurred after greater than 24 h of exposure of the cells to the lacZ virus. Half-maximal infection occurred after 5 h of exposure. After 2 h of adsorption at 37 degrees C, the majority of infectious virus was not adsorbed to cells but was unbound and able to infect other cells. These results are discussed in terms of both their relevance to the fundamental biology of retrovirus infection and the use of recombinant retroviruses for retrovirus-mediated gene transfer with purposes of gene therapy.

3T3 Cells↗
PubMed1994

Genetically modified skin to treat disease: potential and limitations.

Molecular definition of disease at the level of the gene and advances in recombinant DNA technology suggest that many diseases are amenable to correction by genes not bearing the defective elements that result in disease. Many questions must be answered before this therapy can be used to correct chronic diseases. These questions fall into safety and efficacy categories. Experience with transplanting cellular elements of skin or skin substitutes (defined as skin that possess the cell types and a dermal structure to develop into a functioning skin) to athymic rodents is considerable and is seen as a system where these questions can be answered. This paper reviews these questions and presents our early analysis of genetically modified cells in skin substitutes in vivo and in vitro. Experimental data demonstrate that both a matrix of woven nylon, housing a fibroblast generated collage, and dead dermis can be utilized to shuttle genetically modified human fibroblasts from the laboratory to an in vivo setting. Genetically modified fibroblasts do not migrate from the shuttle to the surrounding tissue. The survival of significant numbers, approximately 70%, of genetically modified fibroblasts for at least 6 weeks in these shuttles, supports this general approach as having clinical utility. It is also concluded that skin substitute systems can be used to generate a genetically modified skin in vitro that has the capacity to develop into functional skin in vivo. Further, as genetically modified keratinocytes differentiate there is increased production by the transgene, supporting the concept that keratinocytes have true potential as shuttles for therapeutic genes. This work demonstrates that transplantation of systems containing genetically modified cells of the skin can be used to experimentally define many aspects of gene therapy using skin before this technology is taken to the clinic. Examples include determining the effect of gene transduction and expression on structure and function of the genetically modified skin as well as on distant skin and an assessment of the translational capacity of the transgene as function of time and cell number.

3T3 Cells↗
PubMed1993

Proline-mediated enhancement of hepatocyte function in a collagen gel sandwich culture configuration.

Isolated rat primary hepatocytes were cultured between two layers of gelled collagen in a sandwich configuration that reinstates the cellular polarity necessary for long-term function in vitro. Maintenance of hepatocyte function, as measured by the secretion of albumin, was shown to be dependent on both the sandwich gel configuration and the continued presence of L-proline in the culture media. Cis-hydroxyproline, an analog of proline known to prevent the proper folding of triple helical collagen molecules, inhibited the response of sandwiched hepatocytes to proline in a dose-dependent and reversible manner. The addition of cis-hydroxyproline to cultures established for 7 days also resulted in the inhibition of hepatocyte function. These data support the hypothesis that continued collagen synthesis by hepatocytes is critical for hepatocyte function in the sandwich gel configuration.

Animals↗
PubMed1992

The effects of antimicrobial acrylic strips on the subgingival microflora in chronic periodontitis.

This study investigated the effects of root planing and/or the placement of acrylic strips containing chlorhexidine, metronidazole or tetracycline on the composition and antimicrobial susceptibility of the subgingival flora in chronic periodontitis. 101 periodontal pockets from 73 patients were entered into 6 treatment groups which were, chlorhexidine, metronidazole or tetracycline strips, root planing, root planing followed by metronidazole strips and a control, no treatment group. Total anaerobic counts and anaerobe/aerobe ratios were estimated from samples taken before treatment and 1, 2, 4, 8 and 12 weeks after treatment. In addition, a more detailed analysis of the effects of the treatments on the subgingival flora was carried out on 12 pockets in 12 patients. Tetracycline strips, metronidazole strips and root planing and metronidazole strips were more effective than chlorhexidine strips in causing reductions in total anaerobic count and anaerobe/aerobe ratio. However, the changes in microbial parameters rebounded to approach baseline levels 4 weeks after treatment. Chlorhexidine caused no detectable changes in the composition of the subgingival microflora, while metronidazole had a variable effect. Tetracycline appeared to effect major shifts in the composition of the microflora of treated pockets but caused a marked selection of tetracycline-resistant organisms.

Acrylic Resins↗
PubMed1990

The "clam": indications and complications.

We have reviewed 78 patients who underwent "clam" enterocystoplasty as part or all of their lower urinary tract reconstruction. Nearly half (32) were non-neuropathic; the remainder were either overtly neuropathic (mainly spina bifida) or suspected neuropathic (mainly the older primary enuretics). Only 5 were non-walkers--all neuropathic. Most patients were operated on for incontinence but 12 had upper tract damage related either to urinary diversion or to poor bladder compliance in the early phase of filling; 69 patients became dry, voiding spontaneously (30), by activation of an artificial urinary sphincter (17) or by self intermittent catheterisation (22). Four patients still have nocturnal enuresis, 3 diurnal enuresis and 2 have stress incontinence. One patient has had a continent diversion. The "clam" procedure has revolutionised bladder reconstruction. Careful review has failed to predict the small number who do not achieve a perfect result.

Adolescent↗
PubMed1989

The effects of atrial peptide in humans with chronic renal failure.

The role of atrial peptide in humans with chronic renal insufficiency is uncertain. Therefore, the effects of synthetic atrial peptide (atriopeptin III, 24 amino acids) infusion on renal function and solute excretion were examined in 16 subjects with chronic renal insufficiency of diverse etiologies. After a two-hour baseline period, atrial peptide was infused for four hours in doses ranging from 0.005 to 0.1 micrograms/kg/min. When all doses were combined, absolute and fractional excretions of sodium increased significantly from baseline values (130 +/- 15 to 231 +/- 28 microEq/min and 3.57 +/- 0.57 to 6.03 +/- 1.26%, respectively, P less than 0.05). Significant increases in urinary excretion of chloride, calcium, and phosphorus were also seen during atrial peptide infusion. Increased absolute and fractional phosphorus excretion persisted during the two-hour postinfusion period, while excretion of other solutes returned to baseline. Glomerular filtration rate (GFR) increased by greater than 20% in five of 16 subjects. Two subjects with severe renal insufficiency (GFR = 9 and 12 mL/min) had no apparent response to atrial peptide infusion. Subjects receiving doses of 0.05 and 0.1 microgram/kg/min had significant falls of mean arterial pressure by the last hour of infusion. A dose-dependent effect of atrial peptide on sodium excretion was suggested, but not statistically significant. No apparent dose-dependent effect was seen on GFR or other solute excretions. Despite the presence of chronic renal insufficiency, atrial peptide increased renal solute excretion in most subjects. The demonstration that atrial peptide retains its diuretic and natriuretic effect in the presence of renal insufficiency supports the hypothesis that atrial peptide plays an important adaptive role in sodium homeostasis of the failing kidney.

Adult↗
PubMed1989

Restoration of growth potential in paraclones of human keratinocytes by a viral oncogene.

Human diploid keratinocytes may be divided into three clonal types with differing capacities for proliferation. The paraclone, which has the shortest life span, is limited to 15 divisions, after which all the cells undergo programmed terminal differentiation. By means of a retroviral vector, paraclones which have not completed their life span and which consist of not more than a few hundred cells can be transduced at a high frequency with DNA complementary to the 12S transcript of the adenovirus early region 1A gene. Transformation can be detected within a single cultivation by the formation of progressively growing colonies. The transformants appear to have an unlimited growth potential, and they form a disorganized epidermis when they are grafted as an epithelium onto athymic mice. These experiments clearly show that, in order to be transformed by a viral oncogene, the target cell need not be a stem cell.

Aged↗
PubMed1989

A case of Down's syndrome, insulinoma and anorexia.

The report describes a case of a 35-year-old female with Down's syndrome, insulinoma and anorexia. It is believed to be the first time such an association has been reported. Diagnostic and management problems are discussed with particular reference to people with a mental handicap.

Adenoma, Islet Cell↗
PubMed1988

Amoxycillin-clavulanic acid (Augmentin) versus metronidazole as prophylaxis in hysterectomy: a prospective, randomized clinical trial.

In order to determine the most effective regimen for the prevention of infection after elective hysterectomy, 300 patients were randomly assigned to receive three perioperative doses of either amoxycillin-clavulanic acid (1.2 g intravenous) or metronidazole (1 g suppository). Of the 280 patients who were assessable 138 were given amoxycillin-clavulanic acid and 142 received metronidazole; 268 underwent abdominal hysterectomy and 12 had vaginal hysterectomy. Patients in the amoxycillin-clavulanic acid group had significantly less infectious morbidity (13.8%) than those in the metronidazole group (33.1%). There were also statistically significant differences in favour of amoxycillin-clavulanic acid with respect to operative site infection, duration of hospital stay, need for postoperative antimicrobials, and surgery for operative site infection. But for one isolate of Bacteroides fragilis, all pathogens isolated from wound infections in the metronidazole group were aerobes. No anaerobes were isolated from patients in the amoxycillin-clavulanic acid group. The results suggest that prophylaxis for hysterectomy should consist of an agent, or combination of agents, with activity against both aerobic and anaerobic bacteria. Amoxycillin-clavulanic acid fulfils this criterion and appears to be effective and safe.

Adult↗
PubMed1988

Inflammatory joint disease: a comparison of liposome scanning, bone scanning, and radiography.

Patients with rheumatoid arthritis, psoriatic arthritis, and osteoarthritis were assessed by clinical evaluation, radiography, and joint scintigraphy using technetium labelled methylene diphosphonate (MDP) and technetium labelled liposomes. Although both scanning techniques were more sensitive than radiographs in detecting joint disease, the liposomes scans were positive only in clinically active inflammatory disease. In patients with rheumatoid arthritis liposome scintigraphy was also able to discriminate between different grades of joint tenderness. In inactive inflammatory polyarthropathies, although the MDP bone scans continued to show increased activity, the liposome scans did not and were therefore a more accurate reflection of the clinical state. The increased uptake in the liposome scans may be due to incorporation of the liposomes into the phagocytic cells of the synovium. This scan may, therefore, by reflecting the activity of cells involved in the disease process, provide a useful way of assessing disease activity and progression.

Arthritis↗
PubMed1987

Expression of an exogenous growth hormone gene by transplantable human epidermal cells.

Retrovirus-mediated gene transfer was used to introduce a recombinant human growth hormone gene into cultured human keratinocytes. The transduced keratinocytes secreted biologically active growth hormone into the culture medium. When grafted as an epithelial sheet onto athymic mice, these cultured keratinocytes reconstituted an epidermis that was similar in appearance to that resulting from normal cells, but from which human growth hormone could be extracted. Transduced epidermal cells may prove to be a general vehicle for the delivery of gene products by means of grafting.

DNA, Recombinant↗
PubMed1987

Comparative susceptibility of hospital isolates of gram-negative bacteria to antiseptics and disinfectants.

The sensitivity of hospital isolates of Gram-negative bacteria to cationic antiseptics, mercuric chloride and two organomercury compounds has been measured. A comparison was made with laboratory strains of known sensitivity which acted as standards. All strains of Escherichia coli showed a uniformly high sensitivity to chlorhexidine diacetate; other organisms tended to be less sensitive to the biguanide. Quaternary ammonium compounds were less effective than chlorhexidine. Resistance to mercuric chloride was observed frequently, but there was little evidence of organomercurial resistance except in Pseudomonas aeruginosa isolates.

Anti-Infective Agents, Local↗