Biomedical subjects

D J Tate

Publications and source records attributed to D J Tate.

At least 19 recordsLinked to original sources

PubMed2001

Association between cancer chemotherapy and canine distemper virus, canine parvovirus, and rabies virus antibody titers in tumor-bearing dogs.

OBJECTIVE: To determine the association between cancer chemotherapy and serum canine distemper virus (CDV), canine parvovirus (CPV), and rabies virus antibody titers in tumor-bearing dogs. DESIGN: Prospective study. ANIMALS: 21 client-owned dogs with various malignancies and 16 client-owned dogs with lymphoma. PROCEDURE: In study A, serum antibody titers were measured by use of hemagglutination inhibition (CPV titers) or serum neutralization (CDV titers) before and at least 1 month after initiation of chemotherapy. Baseline values were compared with values obtained from a control population of 122 healthy dogs seen for routine revaccination. Titers were considered protective at > or = 1:96 for CDV and > or = 1:80 for CPV. In study B, serum IgG titers were measured by use of immunofluorescent assay (CDV and CPV titers) and rapid fluorescent focus inhibition test (RFFIT, rabies titers) at baseline and again at weeks 5, 8, and 24 of a standard chemotherapy protocol for treatment of lymphoma. An IgG titer of > or = 1:50 was considered protective for CPV and CDV. An RFFIT titer of > or = 0.5 U/ml was considered protective for rabies virus. RESULTS: Significant changes were not detected in CDV, CPV, and rabies virus titers following chemotherapy in tumor-bearing dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that established immunity to CDV, CPV, and rabies virus from previous vaccination is not significantly compromised by standard chemotherapy used to treat tumor-bearing dogs.

Animals↗

PubMed2000

Assessment of five portable blood glucose meters, a point-of-care analyzer, and color test strips for measuring blood glucose concentration in dogs.

OBJECTIVE: To compare blood glucose concentrations obtained using a point-of-care (POC) analyzer, 5 portable blood glucose meters (PBGM), and a color reagent test strip with concentrations obtained using a reference method, and to compare glucose concentrations obtained using fresh blood samples in the PBGM with concentrations obtained using blood anticoagulated with lithium heparin. DESIGN: Case series. SAMPLE POPULATION: 110 blood samples from 34 dogs; glucose concentration of the samples ranged from 41 to 596 mg/dl. PROCEDURE: Logistic regression was used to compare blood glucose concentrations obtained with the various devices with reference method concentrations. Ease of use was evaluated subjectively. Percentage of times a clinical decision would have been altered if results of each of these methods had been used, rather than results of the reference method, was calculated. RESULTS: For 3 of the PBGM, blood glucose concentrations obtained with fresh blood were not significantly different from concentrations obtained with blood samples anticoagulated with lithium heparin. None of the devices provided results statistically equivalent to results of the reference method, but the POC analyzer was more accurate than the others. For some samples, reliance on results of the PBGM or the color test strip would have resulted in erroneous clinical decisions. CONCLUSIONS AND CLINICAL RELEVANCE: Although commercially available PBGM and color test strips provided blood glucose concentrations reasonably close to those obtained with reference methods, some devices were more accurate than others. Use of results from these devices could lead to erroneous clinical decisions in some cases.

Animals↗

PubMed2000

Pathologic changes in the retinal pigment epithelium and Bruch's membrane of fat-fed atherogenic mice.

PURPOSE: Due to a possible link in humans between atherosclerosis, a high-fat diet, and the development of age-related retinal degenerations, we investigated retinal changes with age and diet in high-fat-fed C57BL/6 mice, a mouse model of human atherosclerosis. METHODS: We fed C57BL/6J mice either a normal chow diet or an atherogenic diet containing 15% total fat for either 15, 30 or 45 weeks. We sacrificed the animals and examined the eyes using fluorescence microscopy, light microscopy and transmission electron microscopy. RESULTS: At 15 weeks, in high-fat-fed mice, there was an increase in the number of autofluorescent granules in the retinal pigment epithelium (RPE) compared to chow-fed mice. By light microscopy, we noted no remarkable differences in the inner retinal layers between mice fed either diet for 15 or 30 weeks. In contrast, we noted major changes in transmission electron micrographs from the 30 week high-fat group. In the RPE, these included: (1) an increase in the number and size of autophagocitic and empty cytoplasmic vacuoles; (2) accumulations of lipid-like droplets in the cytoplasm, and (3) RPE atrophy. Changes in Bruch's membrane included: (1) thickening; (2) fragmentation of the elastic lamina, and (3) the accumulation of electron dense particulate and vesicular structures within the inner and outer collagenous zones. These changes were not seen in mice fed normal diets even at 45 weeks. CONCLUSIONS: We suggest that this model may prove useful for investigations into mechanisms on the effects of diet on the RPE and Bruch's membrane.

Animals↗

PubMed1999

Stereotactic radiosurgical boost following radiotherapy in primary nasopharyngeal carcinoma: impact on local control.

PURPOSE: Treatment of patients with nasopharyngeal carcinoma using external beam radiation therapy (EBRT) alone results in significant local recurrence. Although intracavitary brachytherapy can be used as a component of management, it may be inadequate if there is extension of disease to the skull base. To improve local control, stereotactic radiosurgery was used to boost the primary tumor site following fractionated radiotherapy in patients with nasopharyngeal carcinoma. METHODS AND MATERIALS: Twenty-three consecutive patients were treated with radiosurgery following radiotherapy for nasopharyngeal carcinoma from 10/92 to 5/98. All patients had biopsy confirmation of disease prior to radiation therapy; Stage III disease (1 patient), Stage IV disease (22 patients). Fifteen patients received cisplatinum-based chemotherapy in addition to radiotherapy. Radiosurgery was delivered using a frame-based LINAC as a boost (range 7 to 15 Gy, median 12 Gy) following fractionated radiation therapy (range 64.8 to 70 Gy, median 66 Gy). RESULTS: All 23 patients (100%) receiving radiosurgery as a boost following fractionated radiation therapy are locally controlled at a mean follow-up of 21 months (range 2 to 64 months). There have been no complications of treatment caused by radiosurgery. However, eight patients (35%) have subsequently developed regional or distant metastases. CONCLUSIONS: Stereotactic radiosurgical boost following fractionated EBRT provides excellent local control in advanced stage nasopharynx cancer and should be considered for all patients with this disease. The treatment is safe and effective and may be combined with cisplatinum-based chemotherapy.

Adolescent↗

PubMed1999

Zinc protects against oxidative damage in cultured human retinal pigment epithelial cells.

This study was undertaken to determine whether bioavailable zinc can influence the effects of oxidative stress on cultured human retinal pigment epithelial (RPE) cells. RPE cells were maintained for 7 d in culture medium containing 14 microM total zinc, or in medium containing 0.55 microM total zinc. After 1 week, MTT assays were performed to determine the relative cytotoxicity of H2O2 or paraquat on RPE cells. Conjugated dienes and thiobarbituric acid reactive substances (TBARS) were measured in RPE cells treated with 0, 0.5 mM H2O2, 10 microM FeSO4 + 0.5 mM H2O2 or 10 microM FeSO4 + xanthine/xanthine oxidase for 24 h or paraquat for 7 d. Oxidized proteins were determined by the formation of carbonyl residues. The antioxidants metallothionein, catalase, superoxide dismutase, and glutathione peroxidase were also measured. The MTT assays showed that zinc protected cultured RPE from the toxicity of H2O2 and paraquat. RPE cells in 0.55 microM zinc medium contained higher levels of TBARS, conjugated dienes and protein carbonyls due to the oxidative stresses, compared to cells in 14 microM zinc. Catalase and MT content were reduced in cells cultured in 0.55 microM zinc medium and were reduced additionally when treated with above stresses. Superoxide dismutase activity increased in 0.55 microM zinc medium in response to these stresses. Our results show RPE cells cultured in zinc-reduced medium are more susceptible to oxidative insult.

Biological Availability↗

PubMed1999

Treatment of nasopharyngeal carcinoma: stereotactic radiosurgical boost following fractionated radiotherapy.

Treatment of patients with nasopharyngeal carcinoma (NPC) using external beam radiation therapy (XRT) alone results in significant local recurrence. To improve local control, stereotactic radiosurgery (SRS) was used to boost radiation to the primary tumor site following XRT in 23 patients with NPC. SRS was delivered utilizing a frame-based linear accelerator as a boost (range 7-15 Gy, median 12 Gy) following XRT (range 64.8- 70 Gy, median 66 Gy). In all 23 patients (100%) receiving SRS following XRT local control was achieved at a mean follow-up of 21 months (range 2-64 months). There have been no complications of treatment caused by SRS. However, 8 patients (35%) have subsequently developed regional or distant metastases. SRS boost following XRT provides excellent local control in NPC and should be considered for patients with skull base involvement.

Adolescent↗

PubMed1999

Zinc deficiency and oxidative stress in the retina of pigmented rats.

PURPOSE: To determine the effect of moderate zinc deficiency on antioxidant defenses and measures of oxidative stress in the retina and retinal pigment epithelium (RPE) of Brown Norway Rats. METHODS: Twenty-four rats were housed individually and divided into three groups of 8 rats each. Group 1 was fed ad libitum a semipurified control diet formulated to contain 50 parts per million [ppm] total zinc; group 2 was fed ad libitum an identical diet but containing 5 ppm total zinc; and group 3 was pair-fed the control diet but restricted in amount to that consumed by group 2. Food intake was measured daily and the rats weighed weekly. After 6 weeks, the rats were killed and the following measurements were made: serum zinc, serum alkaline phosphatase, retinal zinc, RPE-choroid zinc, RPE-choroid catalase, liver metallothionein (MT), retinal MT, RPE-choroid MT, retinal catalase, and retinal thiobarbituric reactive substances (TBARS). RESULTS: The following showed statistically significant differences between groups 2 and 3, respectively: serum Zn (1216 micro/l versus 1555 microg/l, P < or = 0.01), serum alkaline phosphatase (3.75 U/mg versus 5.10 U/mg, P < or = 0.05), liver MT (4.3 microg/mg protein versus 16.7 microg/mg, P < or = 0.0001), RPE-choroid MT (1.3 microg/mg protein versus 2.2 microg/mg, P < or = 0.02), retinal MT (0.85 microg/mg protein versus 2.8 microg/mg, P < or = 0.05), and retinal TBARS (6.2 nM/mg protein versus 2.2 nM/mg, P < or = 0.05). CONCLUSIONS: The results show that retinal MT and RPE MT concentrations are very sensitive to intake of dietary zinc. The increase in retinal TBARS in group 2 indicates that moderate zinc deficiency increases oxidative stress to the retina. The results also suggest that MT is protective against lipid peroxidation of retinal membranes.

Alkaline Phosphatase↗

PubMed1999

Effects of chromium supplementation on glucose tolerance in obese and nonobese cats.

OBJECTIVE: To determine effects of dietary supplementation with chromium (Cr) picolinate on health and response to i.v. glucose tolerance testing (IVGTT) in obese and nonobese cats. ANIMALS: 7 obese and 12 nonobese cats. PROCEDURE: 6 nonobese cats were untreated controls, whereas 6 different nonobese cats and 7 obese cats received oral administration of 100 microg Cr/d for 6 weeks. All cats were evaluated before and immediately after the treatment period by use of physical examination, CBC, serum biochemical analyses, and IVGTT. Calculated values included glucose half-life, coefficient of glucose disappearance, insulin peak response, insulinogenic index, and insulin secretion rate determined at various times after start of IVGTT. RESULTS: Adverse effects on cats' health were not observed during or after treatment, and significant changes in body weight, hematologic values, or most serum biochemical values were not detected. Serum potassium concentration decreased significantly after treatment in obese cats but was within reference range. Compared with nonobese cats, obese cats had significantly higher insulin peak response, insulinogenic index, and insulin secretion rate before and after treatment. Chromium supplementation did not alter responses to IVGTT in either treatment group. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary supplementation with 100 microg of Cr/d for 6 weeks is safe but does not affect glucose tolerance in obese or nonobese cats.

Animals↗

PubMed1998

Effect of combined transient androgen deprivation and irradiation following radical prostatectomy for prostatic cancer.

PURPOSE: To evaluate whether transient androgen deprivation improves outcome in patients irradiated after radical prostatectomy for locally advanced disease, persistent or rising postoperative prostate specific antigen (PSA), or local recurrence. METHODS AND MATERIALS: Records of 105 consecutive patients who were treated with pelvic irradiation after radical retropubic prostatectomy between August 1985 and December 1995 were reviewed. Seventy-four patients received radiation alone (mean follow up: 4.6 years), and 31 received transient androgen blockade with a gonadotropin-releasing hormone agonist (4) androgen receptor blocker (1) or both (24) beginning 2 months prior to irradiation (mean follow-up 3.0 years) for a mean duration of 6 months. Two of these patients were excluded from further analysis because they received hormonal therapy for more than 1 year. Patients received a prostatic fossa dose of 60-70 Gy at 2 Gy per fraction; 48 patients also received pelvic nodal irradiation to a median dose of 50 Gy. Survival, freedom from clinical relapse (FFCR), and freedom from biochemical relapse (FFBR) were evaluated by the Kaplan-Meier method. Biochemical relapse was defined as two consecutive PSA measurements exceeding 0.07 ng/ml. RESULTS: At 5 years after irradiation, actuarial survival for all patients was 92%, FFCR was 77%, and FFBR was 34%. FFBR was significantly better among patients who received transient androgen blockade before and during radiotherapy than among those treated with radiation alone (56 vs. 27% at 5 years, p = 0.004). FFCR was also superior for the combined treatment group (100 vs. 70% at 5 years, p = 0.014). Potential clinical prognostic factors before irradiation did not differ significantly between treatment groups, including tumor stage, summed Gleason histologic score, lymph node status, indication for treatment, and PSA levels before surgery or subsequent treatment. Multivariate analysis revealed that transient androgen deprivation was the only significant predictor for biochemical failure. CONCLUSION: This retrospective study of irradiation after radical prostatectomy suggests that transient androgen blockade and irradiation may improve freedom from early biochemical and clinically evident relapse compared to radiotherapy alone, although more prolonged follow-up will be needed to assess durability of impact upon clinical recurrence and survival rates.

Aged↗

PubMed1998

Intracoronary radiation with a 32P source wire.

The Proliferation REduction with Vascular ENergy Trial (PREVENT) is a prospective randomized study of the safety and efficacy of intracoronary brachytherapy to reduce restenosis. A beta-emitter, 32P, is embedded on a wire tip and delivered to the target site through a centering catheter immediately following a coronary intervention. The radiation doses are 16, 20, and 24 Gy measured at 1 mm within the vessel wall. Follow-up includes an angiogram and IVUS at 6 months. Phase I of this trial has been completed with results expected in early 1999.

Angioplasty, Balloon, Coronary↗

PubMed1998

Second cancers following pediatric Hodgkin's disease.

PURPOSE: To define the magnitude of second cancer risk among pediatric Hodgkin's disease survivors and to determine which factors influence this risk. PATIENTS AND METHODS: At Stanford,694 children and teenagers were monitored for 1 to 31.6 years (mean, 13.1) after treatment for Hodgkin's disease. Relative risks (RRs), actuarial risks, and absolute excess risks for second malignancies were calculated. The influences of sex, age, stage, splenectomy, treatment and relapse were assessed by multivariate analysis. RESULTS: Fifty-six patients developed 59 secondary malignancies: 48 solid tumors, eight leukemias, and three non-Hodgkin's lymphomas. The RR of developing a second cancer was 15.4 (95% confidence interval [CI], 10.6 to 21.5) for females and 10.6 (95% CI, 6.6 to 16.0) for males. Breast cancer (n = 16) and sarcoma (n = 13) were the most common solid tumors. The actuarial risk at 20 years follow-up evaluation was 9.7% for males, 16.8% for females, and 9.2% for breast cancer. The median interval to diagnosis of a second malignancy was shortest for leukemia, 4.3 years, and longest for lung cancer, 18.4 years. Relapse of Hodgkin's disease increased the risk of second malignancy (hazards ratio [HR] = 2.6, P < .001). Hodgkin's disease stage, patient age, splenectomy, and treatment modality did not appear to alter overall risk, although chemotherapy was associated with subsequent leukemia. CONCLUSION: Aggressive Hodgkin's disease therapy is successful, but patients have a significant risk of second malignancy. Newer treatment programs focus on obtaining a relapse-free cure of Hodgkin's disease with judicious use of radiation and alkylating agent chemotherapy. Survivors of pediatric Hodgkin's disease require lifelong evaluation and cancer screening.

Actuarial Analysis↗

PubMed1997

Long-term results of total lymphoid irradiation in the treatment of cardiac allograft rejection.

PURPOSE: To evaluate the short and long-term effects of total lymphoid irradiation (TLI) in the treatment of cardiac transplant rejection. METHODS AND MATERIALS: Between 1986 and 1995, 48 courses of TLI were delivered to 47 cardiac transplant patients. In 37 patients, TLI was administered for intractable allograft rejection despite conventional therapy while 10 patients received TLI prophylactically. The prescribed radiation dose was 8 Gy in 0.8 Gy fractions twice weekly to mantle and inverted-Y plus spleen fields. Postirradiation follow-up ranged from 6 months to 9.1 years, with a mean of 3.1 years. RESULTS: The actual mean dose was 7.3 Gy delivered over a mean of 39 days. Fifty-six percent of patients required treatment delay or abbreviation because of thrombocytopenia, leukopenia, infection, or unrelated problems. In patients treated for intractable rejection, rejection rates dropped from 0.46 to 0.14 and to 0.06 episodes/patient/month before, during, and after TLI (p < 0.0001). Rejection rates continued to drop throughout follow-up. Prednisone requirements decreased from 0.41 mg/kg before treatment to 0.21 mg/kg afterward (p < 0.0001). The ratio of helper to cytotoxic-suppressor T-cells decreased during TLI from 1.33 to 0.89, and remained low at 0.44, 2-4 months after treatment. Infection rates were not increased and two patients developed malignancy. Rejection rates were high during prophylactic treatment and this protocol was abandoned. Three-year actuarial survival after irradiation was 60% for patients with intractable rejection and 70% for the prophylactic cohort. CONCLUSION: TLI is an effective treatment for control of intractable cardiac rejection. Episodes of rejection and steroid dosage requirements are decreased for up to 9.1 years. A possible mechanism of action is long term alteration in T-lymphocyte subsets. Patients experience transient bone marrow suppression but no increase in infection or bleeding. Long-term complications of TLI are not appreciably different than conventional immunosuppression.

Adolescent↗

PubMed1997

Zinc induces catalase expression in cultured fetal human retinal pigment epithelial cells.

PURPOSE: We have previously shown that an experimental, low-zinc environment decreased catalase activity in cultured human fetal retinal pigment epithelial (RPE) cells. The purpose of this study was to investigate the effect of zinc supplementation on catalase expression in cultured human fetal RPE cells. METHODS: Confluent fetal RPE cells incubated in Coon's modified Ham's F12 (CMF-12) were treated (18 h) with zinc chloride (ZnCl2) (15, 30, or 100 microM) to assess changes in catalase enzyme activity or for 6 h to assess the induction of catalase mRNA by Northern analysis and in situ hybridization. RPE cells were also treated with 30 microM ZnCl2 for 2, 6, 24, 48 and 72 h to assess the time course of changes in catalase enzyme activity, changes in mRNA levels and status of the Sp1 transcription factor. RESULTS: Catalase activity was increased above control by the addition of 15, 30 and 100 microM ZnCl2. Catalase gene expression was induced by 30 microM zinc in 6 h, but decreased to non-treated control levels by 24 h. The transcription factor Sp1 was also activated by zinc treatment (30 microM) which peaked at 2 h and declined to non-treated control levels by 24 h. Catalase enzyme activity peaked at 24 h and decreased to control levels by 72 h. CONCLUSIONS: Our results demonstrate that zinc treatment of RPE cells increases catalase expression and activates the transcription factor Sp1. The results suggest zinc may play a role in the transcriptional regulation of catalase in RPE cells.

Blotting, Northern↗

PubMed1997

Vitronectin is responsible for serum-stimulated uptake of rod outer segments by cultured retinal pigment epithelial cells.

PURPOSE: To examine whether the vitronectin (VN) in serum is responsible for the serum stimulation of phagocytosis in the rod outer segment (ROS) by cultured retinal pigment epithelial (RPE) cells. METHODS: Vitronectin was removed from fetal bovine serum by heparin-agarose affinity chromatography. Concentrations in normal and depleted serum were determined by enzyme-linked immunosorbent assay, using a polyclonal antibody against bovine VN and commercially prepared human VN as a standard. A monoclonal antibody against human alpha v beta 5 was used in localization and in blocking experiments. Rod outer segment phagocytosis was measured using a flow cytometric assay. RESULTS: Affinity chromatography removed 95% of the VN from serum as determined by enzyme-linked immunosorbent assay. Vitronectin-depleted serum did not stimulate ROS phagocytosis by RPE cells. Commercially prepared VN added to serum-free medium stimulated ROS phagocytosis in a dose-dependent manner. Pretreatment of RPE cells with an antibody against alpha v beta 5, an integrin receptor for VN, had no effect on phagocytosis in the absence of serum but completely blocked the serum stimulation of ROS phagocytosis. Antibody against alpha v beta 5 demonstrated a variable labeling pattern on the cultured RPE cell surface with morphologically distinct cell clusters exhibiting less labeling. Those cell clusters exhibiting less receptor labeling also showed less uptake of fluorescent-labeled ROS. CONCLUSIONS: Vitronectin is the component responsible for serum stimulation of ROS uptake, and this uptake appears to be mediated by an alpha v beta 5 integrin. Although clearly important in vitro, a role for VN in ROS uptake by RPE cells in situ remains to be determined.

Animals↗

PubMed1995

Pelvic relapse following subtotal lymphoid irradiation in early stage Hodgkin's disease--an analysis of risk, management, and outcome.

PURPOSE: To evaluate the time of onset, method of identification, management, and outcome of pelvic relapse following subtotal lymphoid irradiation (STLI) alone (mantle and paraaortic/spleen or splenic pedicle fields, excluding the pelvis) in supradiaphragmatic Stage I-II Hodgkin's disease. METHODS AND MATERIALS: A retrospective analysis was performed of the initial, relapse, and regular follow-up evaluations of patients with pelvic relapse following STLI alone from 1968 to the present for supradiaphragmatic Stage I-II Hodgkin's disease after pathologic staging (PS-laparotomy staging) and clinical staging (CS-no laparotomy staging). RESULTS: Following staging, which included bipedal lymphangiography, 482 patients (408 PS and 74 CS), were treated with STLI alone for supradiaphragmatic Stage I-II Hodgkin's disease. The actuarial freedom from relapse at 20 years was 75% in PS patients and 81% in CS patients. The actuarial pelvic failure at 20 years was 7% for PS patients and 3% for CS patients. Of the 29 patients with pelvic relapse, 97% (28 of 29) occurred within 5 years of treatment, including 1 patient who progressed during initial treatment. Pelvic relapse was most commonly initially identified by abnormalities involving patient symptoms (62%), physical examination (55%), erythrocyte sedimentation rate (48%), and bipedal lymphangiogram and/or abdominal radiograph (38%). Relapse was limited to previously unirradiated sites in 17 patients (58%). In addition to pelvic lymph node disease, 3 patients (10%) had involvement of bone, and 4 patients (14%) had bone marrow involvement. Following relapse, all patients were treated with chemotherapy (MOP[P], MOP[P]/ABV[D], ABVD, or PAVe) and 19 of 29 patients received involved field consolidative irradiation. Twenty-one of 29 (72%) remained relapse free at the time of last follow-up evaluation, including 15 of 19 (79%) treated with combined therapy. Eight patients experienced a second relapse despite salvage therapy, and all eight expired with recurrent Hodgkin's disease. Two patients died of complications related to prior treatment. Therefore, the actuarial risk of death at 20 years associated with pelvic failure in the entire cohort of 482 patients was 2%. CONCLUSION: Pelvic relapse occurred in 7% of patients following STLI alone and was effectively diagnosed by regular follow-up, which included a combination of patient history, physical examination, and radiographic laboratory evaluation. Seventy-two percent of patients remained relapse free following salvage treatment, which included chemotherapy, resulting in an overall survival rate associated with pelvic control of 98%. This approach, therefore, spared the majority of patients the long-term risks associated with pelvic irradiation and/or chemotherapy, such as infertility, but maintained an excellent prognosis.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1995

Influence of zinc on selected cellular functions of cultured human retinal pigment epithelium.

Zinc is a necessary micronutrient, usually abundant in human RPE. Our study was undertaken to determine the effects of short-term, zinc deficiency on human retinal pigment epithelium (RPE) using a culture model of fetal human RPE cells. Human fetal RPE cells were isolated and cultured in Coon's modified Ham's F-12 medium. For zinc depletion studies, cells were cultured for 1 week in Chelex-treated Dulbecco's modified Eagle's medium containing low (0.25 microM) or physiologic (11 microM) total zinc concentrations as determined by flame atomic absorption spectroscopy. Protein synthesis was determined by incorporation of 35S-cysteine/methionine and labeled proteins analysed by polyacrylamide gel electrophoresis. Several cell parameters and enzymes were significantly reduced below control when cultured in low zinc: zinc content (40%), proliferation (63%), protein/well (50%), catalase activity (68%), alkaline phosphatase activity (61%), alpha-mannosidase activity (68%), and metallothionein (82%). No statistically significant decline was seen in acid phosphatase activity, superoxide dismutase activity, glutathione peroxidase activity and dexamethasone induction of metallothionein. Zinc repletion (100 microM, 1 h) increased catalase and alpha-mannosidase activities from 32% and 33% of control to 75% and 73%, respectively. Cycloheximide did not inhibit this short-term zinc-induced repletion of catalase or alpha-mannosidase. Protein synthesis in low zinc medium was depressed, but not significantly, as shown by incorporation of radiolabeled 35S-cysteine/methionine into newly synthesized proteins. The effects of zinc deficiency in cultured human RPE are selective. Adequate intracellular zinc was required for maximal activity of some enzymes. The dependence of catalase activity on zinc was not predicted and may help explain the observed decline in catalase activity seen with age in RPE. Our model of zinc deficiency should prove useful in elucidating the complex effects of zinc deficiency and repletion in human RPE.

Cell Division↗

PubMed1995

Phagocytosis and H2O2 induce catalase and metallothionein gene expression in human retinal pigment epithelial cells.

PURPOSE: Reactive oxygen intermediates have been implicated in the aging process and degenerative diseases of the eye, including retinopathy of prematurity, cataractogenesis, and macular degeneration. The purpose of this study was to investigate the effect of phagocytosis of photoreceptor outer segments and the addition of exogenous H2O2 on catalase and metallothionein expression in human retinal pigment epithelial cells. METHODS: Confluent RPE cells were treated with bovine photoreceptor outer segments or H2O2 for either 6 or 18 hours. Slot blot hybridization was used to assess catalase and metallothionein gene expression after 6 hours. Catalase enzyme activity and metallothionein content were measured after 18 hours. RESULTS: Phagocytosis or the addition of H2O2 increased catalase enzyme activity and metallothionein twofold above control levels. The addition of n-acetyl cysteine abrogated the inductive effect caused by either stress. Catalase and metallothionein gene expression, measured by slot blot hybridization, also were measurably induced by either stress. Phagocytosis of photoreceptor outer segments increased extracellular H2O2 concentration nine times above control. CONCLUSIONS: The response of the retinal pigment epithelial cells to phagocytosis was indistinguishable from the response observed after the addition of exogenous H2O2. The generation of H2O2 during phagocytosis may act as an intracellular signal in retinal pigment epithelial cells that leads to increased levels of key antioxidant enzymes and other proteins important for protecting the cells from oxidative damage.

Adolescent↗

PubMed1993

Age-dependent change in the hyaluronic acid content of the human chorioretinal complex.

OBJECTIVE: Hyaluronic acid (HA) has a key role in the structure and organization of the extracellular matrix. We sought to identify the distribution of HA in human eye tissue with regard to age using a biotinylated HA-binding protein. METHODS: Fetal and adult (from donors ranging from 28 to 94 years of age) eye tissues were fixed less than 24 hours post mortem and embedded in JB-4 medium (Polysciences, Warrington, Pa). Sections of 2-microns thickness were used. Control sections were pretreated either with Streptomyces hyaluronidase or HA-binding protein inactivated by HA. The binding of the protein to HA was detected with avidinbiotin alkaline phosphatase and developed by incubation with naphthol as-mx phosphate and Texas Red Salt (Pierce, Rockford, Ill). RESULTS: Specific staining for HA was observed in fetal eyes in the choroid, Bruch's membrane, sclera, retinal pigment epithelium, and developing retina from the vitreoretinal interface to the inner plexiform layer. Specific staining decreased with age in the choroid, retinal pigment epithelium, and Bruch's membrane. Hyaluronic acid-specific staining was undetectable in tissues from donors over 50 years of age. CONCLUSIONS: The localization of HA in the chorioretinal complex and its disappearance after the fifth decade of life may play a role in aging and age-related retinal disorders.

Adult↗