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Biomedical subjects

J T Daniels

Publications and source records attributed to J T Daniels.

At least 19 recordsLinked to original sources
PubMed2006

Current prospects for adult stem cell-based therapies in ocular repair and regeneration.

Recent advances in stem cell biology have led to the exploration of stem cell-based therapies to treat a wide range of human diseases. In the ophthalmic field, much hope has been placed on the potential use of these cells to restore sight, particularly in those conditions in which other established treatments have failed and in which visual function has been irreversibly damaged by disease or injury. At present, there are many limitations for the immediate use of embryonic stem cells to treat ocular disease, and as more evidence emerges that adult stem cells are present in the adult human eye, it is clear that these cells may have advantages to develop into feasible therapeutic treatments without the problems associated with embryonic research and immune rejection. Here we discuss the current prospects for the application of various adult ocular stem cells to human therapies for restoration of vision.

Adult↗
PubMed2004

T lymphocyte mediated lysis of mitomycin C treated Tenon's capsule fibroblasts.

AIMS: To evaluate the effect of T cell co-culture on mitomycin C treated and untreated Tenon's capsule fibroblasts. METHODS: IL-2 dependent allogeneic T cells were incubated over a monolayer of mitomycin C treated or control fibroblasts. Fibroblast numbers were evaluated by direct counts using phase contrast microscopy. To determine whether T cell mediated lysis was a consequence of MHC mismatch, co-culture experiments were repeated with autologous T cells. The effect of Fas receptor blockade was established by co-incubation with a Fas blocking (M3) antibody. RESULTS: T cell co-culture resulted in a dramatic reduction in fibroblast survival compared to mitomycin C treatment alone (p = 0.032). T cell killing required fibroblast/lymphocyte cell to cell contact and was observed in both allogeneic and autologous co-culture experiments. Fas blocking antibodies did not significantly inhibit T cell killing (p = 0.39). CONCLUSION: T cells augment mitomycin C treated fibroblast death in vitro. Similar mechanisms may contribute to the cytotoxic effect of mitomycin C in vivo and account for the largely hypocellular drainage blebs that are observed clinically.

Antibiotics, Antineoplastic↗
PubMed2004

MMP inhibition prevents human lens epithelial cell migration and contraction of the lens capsule.

PURPOSE: The development of posterior capsule contraction following cataract surgery is caused by the activity of residual lens epithelial cells. Matrix metalloproteinases (MMPs) are a group of proteolytic enzymes, which are essential for cell migration and cell mediated contraction following wound healing. The authors investigated whether inhibiting MMP activity can reduce lens epithelial cell migration and as a result, lead to a reduction in cell mediated capsule contraction. METHODS: Human donor lens capsules were cultured and treated with a broad spectrum MMP inhibitor, Ilomastat (GM6001). MMP-2 and MMP-9 production were determined by ELISA. Cell migration onto the posterior capsule and capsule contraction were digitally measured. RESULTS: MMP inhibition significantly reduced lens epithelial cell migration onto the posterior capsule (p<0.05), and a reduction in capsule contraction was observed (p<0.05). CONCLUSIONS: Ilomastat significantly reduced lens epithelial cell migration onto the posterior capsule surface and inhibited capsule contraction. MMP inhibition may have a role in the therapeutic treatment of posterior capsule opacification.

Cataract Extraction↗
PubMed2002

Serum alpha-tocopherol and immune function in yearling ewes supplemented with zinc and vitamin E.

Yearling Targhee ewes (n = 24; not pregnant or lactating) were used in a 2 x 2 factorial arrangement of treatments to determine the effects of supplemental vitamin E (0 IU [0vitE] vs 330 IU vitamin E x ewe(-1) x d(-1) [+vitE]) and Zn (0 mg [0Zn] vs 140 mg Zn x ewe(-1) x d(-1) [+Zn]) on serum alpha-tocopherol concentrations, antibodies to parainfluenza type 3 (PI3), ewe BW, Zn liver concentrations, and serum alkaline phosphatase activity. Ewes were managed as one group, grazed native pasture, and had ad libitum access to white salt and water. Ewes that received supplemental vitamin E were orally dosed every other day with 660 IU of DL-alpha-tocopherol acetate in a gelatin capsule beginning on d 1 and continuing to d 63 of the study. Ewes that received Zn supplement were orally dosed every other day with 280 mg of Availa-Zn 100 (Zinpro Corp., Eden Prairie, MN, IFN 6-32-054) in gelatin capsules for 63 d. All ewes were vaccinated with killed PI3 on d 22 and 42. No interactions were detected (P > 0.35); however, serum alpha-tocopherol concentrations and PI3 antibody titer dilutions changed (P = 0.001) over the length of the study. Ewe BW change, serum alkaline phosphatase activity, and liver Zn concentrations did not differ (P > 0.22) between 0Zn and +Zn or 0vitE and +vitE ewes. Serum a-tocopherol tended to be higher (P = 0.08) in +vitE than 0vitE ewes and was numerically higher (P = 0.16) in +Zn than 0Zn ewes. Antibody titer dilutions were higher (P = 0.06) in 0Zn than +Zn ewes and did not differ (P = 0.83) between 0vitE and +vitE ewes. These results indicate that high levels of supplemental Zn may have a tendency to improve serum alpha-tocopherol concentrations but may have negative impacts on humoral immune function.

Administration, Oral↗
PubMed2001

Modulation of wound healing after glaucoma surgery.

The healing process after glaucoma filtration is the main determinant of surgical failure and, even more important, the final intraocular pressure. The ability to fully control wound healing may ultimately give us the ability to set the intraocular pressure in the low teens for all patients undergoing glaucoma filtration surgery. The authors review the changes in how to use antimetabolites to improve safety, and many of the exciting new areas of progress, including growth factor neutralization and future molecular therapies to control wound healing.

Antimetabolites↗
PubMed2001

Autologous serum eyedrops for dry eyes and epithelial defects: clinical and in vitro toxicity studies.

BACKGROUND/AIMS: Autologous serum drops have been reported to be beneficial in keratoconjunctivitis sicca (KCS) and persistent epithelial defects (PED). A clinical pilot study was carried out to examine these potential uses and in vitro toxicity testing on corneal epithelial cell cultures was performed to compare the effect of serum drops with unpreserved hypromellose (hydroxypropylmethylcellulose 0.3%). METHODS: Patients with KCS and PED, unresponsive to conventional treatment were recruited. Patients were examined before treatment, at 1 and 2 weeks after initiation, and then 2 weekly until treatment ceased. Symptoms were assessed at each visit. Clinical examination included Schirmer's test without anaesthesia, rose bengal staining, and fluorescein staining. Epithelial defects were measured with the slit beam. In the laboratory, cultured human corneal epithelial cells were exposed to serum drops and hypromellose, and their viability evaluated with fluorescent viability staining (Calcein AM ethidium homodimer) and an ATP assay. RESULTS: Autologous serum was used in 15 eyes of 13 patients with PED and 11 eyes of nine patients with KCS. In two patients serum drops were started after penetrating keratoplasty (PK). The PKs were performed for perforations secondary to PEDs. Of the 15 eyes with PED, nine healed at a mean of 29 days and six failed. The mean duration of PED before the use of serum drops was 48.2 days. Of the 11 eyes with KCS, six had improved subjective scores and fluorescein scores, and five had improved rose bengal scores after the use of serum drops. For the two patients who used serum eyedrops post-PK, there was a stable and intact epithelium at 1 week. Cessation of serum drops during the postoperative period led to deterioration in the subjective and objective scores in both patients. One developed a PED that responded to reinstitution of serum drops. The morphology and ATP levels of cultured epithelial cells exposed to serum were better maintained than those exposed to hypromellose. CONCLUSION: Autologous serum drops are useful for PED and KCS. This effect may be related to a number of active factors in serum including growth factors, fibronectin, vitamin A, and anti-proteases. In vitro toxicity testing demonstrated that serum drops have reduced toxicity compared with unpreserved hypromellose. Currently regulatory restrictions in the UK have prevented the establishment of a prospective randomised controlled trial examining the efficacy of autologous serum drops for the management of this group of ocular surface disorders.

Administration, Topical↗
PubMed2001

Toxicity of natural tear substitutes in a fully defined culture model of human corneal epithelial cells.

PURPOSE: Serum and saliva have recently been advocated as natural tear substitutes for intractable aqueous-deficient dry eyes, but the effects of these fluids on corneal epithelium have not been well characterized. A laboratory study was performed in a defined test model to compare the toxicity of natural and pharmaceutical tear substitutes and to identify potentially toxic factors in natural tear substitutes, such as amylase, hypotonicity, and variations in preparation. METHODS: Primary human corneal epithelial cells were cultured with defined keratinocyte serum-free medium. The cells were incubated with hypromellose (hydroxypropylmethylcellulose 0.3%) with and without benzalkonium chloride 0.01%, saliva with differing osmolalities, 100% serum, and 50% serum (1:1 vol/vol with chloramphenicol 0.5%) for varying times and concentrations. Toxicity was examined in four ways. Microvillous density was assessed with scanning electron microscopy. Cell membrane permeability and intracellular esterase activity were analyzed after staining with fluorescent calcein-AM/ethidium homodimer and cellular adenosine triphosphate (ATP) was quantified using a luciferin-luciferase-based assay. RESULTS: The toxicity ranking of the tear substitutes correlated in all assays. The ATP assay was the most sensitive, followed by ethidium cell permeability, and finally the esterase activity. Preserved hypromellose was more toxic than the unpreserved preparation. Among natural tear substitutes, natural saliva was most toxic. Isotonic saliva and 50% serum were of similar toxicity, and 100% serum was least toxic. Natural tear substitutes were-except for natural saliva-less toxic than unpreserved hypromellose. Hypotonicity, but not amylase, was the major toxic effect associated with saliva. The dilution of serum with chloramphenicol induced toxicity. CONCLUSIONS: This is the first toxicity study using human primary corneal epithelial cells cultured under fully defined conditions as an in vitro model. Cellular ATP is a sensitive parameter for quantifying toxicity. Isotonic saliva and serum offer greater therapeutic potential for severely aqueous-deficient dry eyes than do pharmaceutical tear substitutes.

Adenosine Triphosphate↗
PubMed2001

Multiple myeloma-associated amyloidosis manifesting as fulminant hepatic failure.

We report a case of amyloidosis associated with K light chain multiple myeloma in a 42-year-old African American man. The patient initially had mild dyspepsia, which rapidly progressed to include anorexia, fulminant hepatic failure, and death within 9 weeks. This is only the fourth reported case of hepatic failure from myeloma-associated amyloidosis and the second reported case of light chain myeloma with amyloidosis resulting in a progressive clinical course of hepatic failure. Our patient was unique in that, despite severe disease, he had mild symptoms without laboratory abnormalities until 2 weeks prior to death.

Adult↗
PubMed2000

Infected endovascular stents managed with medical therapy alone.

More than 400,000 endovascular stents are put in place in the United States annually. Infectious complications have been reported in fewer than one in 10,000 cases. It remains unclear whether the optimal management strategy for these patients is with medicine alone or surgery. We report two cases of endovascular stent infections that were treated successfully with antibiotics alone.

Aged↗
PubMed2000

Modulating conjunctival wound healing.

Advances in molecular and cell biology have led to an expansion in our knowledge and understanding of the processes involved in wound healing. We review existing and potential therapies modulating the conjunctival scarring response, with particular reference to glaucoma filtration surgery. We discuss how the refinement of present antimetabolite regimens can minimise complications and improve surgical results, and advocate their use in carefully selected patient groups. Perhaps the most promising approach is targeting biological molecules. Hence, use of fully human neutralising monoclonal antibodies to the growth factor TGF beta has potential as a useful strategy for modifying conjunctival scarring. Combination therapies may also afford an improved therapeutic index. It is hoped that future therapies can offer safer, more specific, focal and titratable treatment, with far-reaching clinical applications.

Antimetabolites↗
PubMed2000

Evaluation of ewe and lamb immune response when ewes were supplemented with vitamin E.

Fifty-two Targhee twin-bearing ewes were used in a factorial arrangement of treatments to investigate the role of supplemental vitamin E (vit E); 0 (NE) vs 400 IU of vit E x ewe x (-1)d(-1) (E) and parainfluenza type 3 (PI3) vaccination; none (NP) vs PI3 vaccination (P) in immune function. Parainfluenza type 3 vaccination was used to evoke an immune response. Ewes receiving PI3 were vaccinated at 49 and 21 d before the expected lambing date. Ewes receiving vit E were orally dosed daily, 32 to 0 d before lambing. Blood was collected from ewes at the time of the initial PI3 vaccination and 4 h postpartum. Blood was collected from lambs (n = 104) at 3 d postpartum. Ewe and lamb sera were analyzed for anti-PI3 antibody titers, immunoglobulin G (IgG) titers, and vit E concentrations. Colostrum was collected 4 h postpartum and analyzed for IgG. The model for ewe and lamb analysis included the main effects of vit E and PI3, sex (lambs model only), and their interactions. No interactions were detected (P > 0.20) for any ewe or lamb variables. Serum anti-PI3 titers were greater (P < 0.01) in P ewes and their lambs than NP ewes and their lambs. Serum vit E concentrations were greater (P < 0.01) in E ewes and their lambs than NE ewes and their lambs. Colostral IgG titers and serum anti-PI3 titers did not differ (P > 0.20) between E and NE ewes. Serum IgG titers in E ewes and their lambs did not differ (P > 0.15) from IgG titers in NE ewes and their lambs. Lamb anti-PI3 titers did not differ (P = 0.76) between lambs reared by E and NE ewes. These results indicate that, although supplemental vit E to the ewe increased lamb serum vit E concentration, it had no effect on measures used in this study to assess humoral immunity in the ewe or passive immunity to the lamb.

Animals↗
PubMed2000

Temporal stimulation of corneal fibroblast wound healing activity by differentiating epithelium in vitro.

PURPOSE: To determine whether differentiating corneal epithelium can temporally stimulate fibroblast activity. METHODS: Corneal epithelial cells were cultured to confluence and then stimulated to mature into multilayered epithelia with addition of serum-containing medium. Differentiation was assessed morphologically and immunocytochemically using a monoclonal antibody to cytokeratin 3. At intervals after onset of differentiation serum-free conditioned medium was collected up to 28 days. Preliminary experiments deduced the optimum concentration of conditioned medium to be used for assessing fibroblast activity. Conditioned medium (25% vol/vol) was added to donor-matched corneal fibroblasts in migration chambers, WST-1 reagent proliferation assays, and fibroblast-populated collagen gel contraction assays. Platelet-derived growth factor (PGDF)-AB and interleukin (IL)-1beta in conditioned media were quantified by enzyme-linked immunosorbent assay (ELISA). Fibroblast migration and collagen contraction assays were performed with concentrations of PDGF-AB. RESULTS: Conditioned medium collected from differentiating epithelium stimulated fibroblast migration and collagen gel contraction, with activity peaks occurring with medium collected on day 14 (P < 0.05). No significant difference was detected between fibroblast growth rates in each of the conditioned media. Levels of PDGF-AB increased during epithelial culture up to 22 days (up to approximately 360 pg/ml) with a subsequent decrease by 28 days. IL-1beta inversely correlated with fibroblast activity induced by conditioned medium, with a trough in concentration (2 pg/ml) occurring at 14 days. Both fibroblast migration and collagen contraction were stimulated in a dose-dependent manner by PDGF-AB. CONCLUSIONS: Corneal epithelium is capable of temporally stimulating fibroblast wound-healing characteristics during its differentiation. One of the growth factors potentially involved in this epithelial-stromal interaction is PDGF. This work demonstrated that developing epithelium (possibly similar to repairing epithelium in vivo) regulated fibroblast behavior and may indicate a mechanism of fibroblast recruitment to a wound after epithelial closure.

Animals↗
PubMed1999

Effects of antimetabolite induced cellular growth arrest on fibroblast-fibroblast interactions.

The use of single five-minute applications of antimetabolites during glaucoma filtration surgery has significantly reduced the occurrence of post-operative scarring and bleb failure. However, surgery for some patients is still unsuccessful, despite the use of antiproliferative agents, due to formation of scar tissue at the drainage site. It is not known if cells growth arrested in the treated area with a single application of antimetabolites influence the activity of adjacent non-treated cells. We hypothesise that the activity of non-treated cells recruited to the wound site may be involved in post-operative scarring. The aim of this study was to investigate the effects of antimetabolite induced cellular growth arrest on cell-cell interactions using in vitro techniques.Tenon's capsule fibroblast cultures were growth arrested by exposure for 5 minutes to mitomycin-C (0.001, 0.01 and 0.1 mg ml-1), 5-fluorouracil (0.25, 2.5 and 25 mg ml-1) or phosphate buffered saline (PBS). Following a period of serum-starvation, conditioned media (CM) were subsequently collected from the cells at intervals up to 29 days post-treatment. Correction for cell number was made prior to supplementation of serum-free medium with CM. CM were assessed for ability to support or inhibit normal non-treated fibroblast proliferation, migration and collagen contraction. Conditioned media collected from cells growth arrested with MMC or 5FU stimulated normal fibroblast proliferation, migration and collagen contraction in excess of non-conditioned serum-free medium. Peaks of fibroblast activity in CM differed according to which drug and concentration had originally been given to the treated cells. This study has demonstrated that CM collected from fibroblasts treated for 5 minutes with a range of concentrations of antimetabolites can differentially influence normal non-treated fibroblast activity. This in vitro data suggests that despite entering growth arrest, fibroblasts may still influence the behaviour of other cells via soluble mediators. They may have implications in the clinical setting, in that it may not be sufficient to suppress proliferation alone to prevent fibroblast behaviour associated with scarring after glaucoma filtration surgery.

Antimetabolites↗
PubMed1999

Clonal selection of CD56+ t(8;21) AML blasts: further suggestion of the adverse clinical significance of this biological marker?

Although patients with acute myelogenous leukaemia (AML) and t(8;21)(q22;q22) have a favourable prognosis, a subset die despite receiving appropriate treatment. Recent reports suggest that expression of the CD56 antigen might predict for both extramedullary disease and poor outcome in these patients. We describe a patient who presented with CD56-negative t(8;21) AML who achieved a complete remission and was subsequently treated with three consolidative courses of high-dose cytarabine therapy. She relapsed 9 months later with extramedullary and bone marrow involvement of CD56-positive t(8;21) AML. This case demonstrates clonal evolution and provides further support that blast expression of CD56 might be an unfavourable prognostic factor in t(8;21) AML.

Adult↗
PubMed1998

Understanding and controlling the scarring response: the contribution of histology and microscopy.

In response to injury, the body usually initiates a full and swift wound healing response resulting in reconstructed, repaired tissue. In certain instances, due to a variety of factors, this may not happen, an example being chronic granulating venous leg ulcers. At the other extreme, the wound may heal excessively, producing disabling hypertrophic scarring such as can occur following large, deep burn injuries. Our group is interested in the surgical treatment of the eye disease glaucoma. As will be explained, the successful surgical treatment of this disease depends on a reduced scarring response at the end of wound healing. The purpose of this article is to give an overview of our microscopic and histological experimental work which has furthered our understanding of tissue repair, particularly the scarring response and its potential modification for successful glaucoma surgery.

Antimetabolites↗
PubMed1998

Antimetabolite-induced apoptosis in Tenon's capsule fibroblasts.

PURPOSE: To determine whether treatment with mitomycin-c and 5-fluorouracil induces apoptotic death in cultured subconjunctival fibroblasts. METHODS: Cultured human subconjunctival Tenon's capsule fibroblasts were exposed to 5-minute applications of mitomycin-C (up to 1 mg/ml) or 5-fluorouracil (up to 50 mg/ml) or phosphate-buffered saline solution (PBS). Fibroblast apoptosis was determined by cell morphology, apoptosis-specific protein expression, and DNA fragmentation by TdT-mediated dUTP nick-end labeling (TUNEL). In addition, apoptosis was quantified by direct cell counts based on morphology or lactate dehydrogenase release. RESULTS: Morphologic changes characteristic of apoptosis included nuclear and cytoplasmic condensation and occasional nuclear fragmentation while the plasma membrane remained intact. Apoptosis-specific protein expression and DNA fragmentation was observed in fibroblasts 48 hours after mitomycin-C treatment but not in control PBS-treated fibroblasts. The amount of apoptosis induced was dose dependent and partially inhibited by the addition of fetal calf serum to growth medium immediately after treatment. CONCLUSIONS: Mitomycin-C and high-dose 5-fluorouracil induce apoptosis in cultured Tenon's fibroblasts. Mitomycin-C-induced apoptosis is inhibited by fetal calf serum, indicating that exogenous factors influence the susceptibility of a fibroblast population to apoptosis. The induction and regulation of fibroblast apoptosis provides a novel target for the potential regulation of scarring.

Antimetabolites↗