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Biomedical subjects

J I Clark

Publications and source records attributed to J I Clark.

At least 55 records · Page 3Linked to original sources
PubMed1997

Loss of cytoskeletal proteins and lens cell opacification in the selenite cataract model.

This study of lens protein composition found that some cytoskeletal proteins were degraded during the earliest stages of cataract formation. Cataract was induced in 13-14 day old rats by a single subcutaneous injection of sodium selenite (19 mumol kg-1). By 24 hr after the injection of selenite, the ratio of insoluble to soluble protein increased as lens opacification began. The increase in insoluble protein aggregates was correlated with an accelerated loss of proteins having molecular weights of 42, 55/57 and 235 kDa which reacted with antibodies to the cytoskeletal proteins actin, tubulin/vimentin and spectrin, respectively. We observed the loss of 49, 60 and 90 kDa proteins which were not identified. In the lenses of animals protected from protein aggregation and opacification by administration of 1.5 mmol kg-1 pantethine, the pattern of proteins in SDS-PAGE gels resembled the pattern for proteins from transparent lenses of normal untreated animals and loss of cytoskeletal proteins was prevented.

Actins↗
PubMed1997

Induction of multiple anti-c-erbB-2 specificities accompanies a classical idiotypic cascade following 2B1 bispecific monoclonal antibody treatment.

The bispecific monoclonal antibody (bsmAb) 2B1, targeting the extracellular domain of c-erbB-2, the protein product of the HER-2/neu proto-ocogene, and Fc gamma RIII (CD16), expressed by human natural killer cells, neutrophils and differentiated monocytes, mediates the specific cytotoxic activity of these effector cells to tumor cells. A group of 24 patients with c-erbB-2-overexpressing tumors were treated with intravenously administered 2B1 in a phase I clinical trial and followed after treatment to evaluate the diversity and extent of the 2B1-induced humoral immune responses. As expected, 17 of 24 patients developed human anti-(murine Ig) antibodies (HAMA) to whole 2B1 IgG in a range from 100 ng/ml to more than 50000 ng/ml; 10 of these patients (42%) had strong (at least 1000 ng/ml) HAMA responses, some of which were still detectable at day 191. These responses were usually associated with similar reactivity to the F(ab')2 fragments of the parental antibodies 520C9 (anti-c-erbB-2) and 3G8 (anti-CD16). We sought evidence of an idiotypic cascade induction, indicating a prolonged specific treatment-induced effect on at least one selected target of 2B1. Using competition-based enzyme-linked immunosorbent assays, specific anti-idiotypic antibodies (Ab2) were detectable against 520C9 in 11 patients and against 3G8 in 13 patients. Peak anti-idiotypic antibodies generally occurred 3-5 weeks from treatment initiation, with a downward trend thereafter. There was a statistically significant correlation among the induction of significant HAMA responses, anti-idiotypic antibody production and the development of antibodies to c-erbB-2. The anti-c-erbB-2 responses, which were distinct from anti-anti-idiotypic (Ab3) antibodies, were detected in the post-treatment sera of 6/16 patients examined. No obvious correlation could be made between the development of humoral immune responses, the dose received, and the clinical response. Future investigation involving 2B1 therapy will concentrate on investigating an association of these humoral responses to any c-erbB-2-specific cellular responses. Manipulations of 2B1 therapy effects that augment immunity to c-erbB-2 could provide additional avenues for immunotherapy with this and other bispecific antibodies.

Adenocarcinoma↗
PubMed1997

Quasielastic light scattering study of the living human lens as a function of age.

PURPOSE: To determine contributions of molecular scattering elements to the increase with age in the light scattered from the human ocular lens in vivo. METHODS: We used quasielastic light scattering to measure autocorrelation functions of the intensity of light scattered in vivo from three locations (anterior, nuclear and posterior) along the optic axis in ocular lenses of 225 subjects, ranging from 17 to 63 years of age. We deduced probability distributions of key parameters (Is, If, Ii, IT), which describe contributions of slowly diffusing (Is), rapidly diffusing (If) and relatively immobile (Ii) scattering elements to the total light intensity (IT) scattered into the collection optics. We deduced characteristic time tau s and tau f that describe the Brownian motion of scattering elements. RESULTS: Probability distributions for each age decile show clearly defined shifts in key parameters with age. IT at the nucleus increases by a factor of three from age 20 to 60 years. This increase is produced principally by an approximate five-fold increase is Is. IT and Is and can be detected with an accuracy of approximately +/- 10%. We estimate threshold values for IT, which mark the boundary beyond which clinical cataract becomes manifest. This boundary represents 6 to 8 times the light scattering efficiency expected from the newborn lens. CONCLUSIONS: This methodology permits a sensitive, quantitative, clinically useful representation of the pre-cataractous molecular changes associated with aging in the living human lens.

Adolescent↗
PubMed1997

Protein changes during aging and the effects of long-term cortisol treatment in macaque monkey lens.

Macaca nemestrina pig-tail macaques were administered daily oral doses of 3.85 or 5.78 mg/kg of cortisol for 1 year. The ages of the macaques were from 19 to 29 years. After 1 year, lenses were observed using a slitlamp ophthalmoscope and the stage of cataract was classified in each eye. Enucleated lenses were analyzed for content of soluble and insoluble proteins. Lens proteins were analyzed using SDS polyacrylamide gel electrophoresis (SDS-PAGE) and the changes in lens proteins were quantified using densitometry of the individual gels. Untreated control lenses were obtained over the range of 4 to 29 years of age and the proteins were analyzed. A slow progressive increase in the cataract stage and in the proportion of insoluble protein aggregates corresponded with the animal age, not the cortisol treatment. The observed changes in the protein components may suggest an important role for cytoskeletal proteins in lens transparency during aging. Exposure to high doses of oral steroids over a period of 1 year did not result in detectable modification of crystallin or cytoskeletal proteins. Even at high doses, longer exposure may be necessary to produce the cataract associated with steroid administration.

Administration, Oral↗
PubMed1996

Modulation of the chaperone-like activity of bovine alpha-crystallin.

The effects of pantethine, glutathione, and selected chemical reagents on the anti-aggregation activity of alpha-crystallin was evaluated. Protein aggregation was monitored by light scattering of solutions of denatured beta L-crystallin or alcohol dehydrogenase (ADH). The ratios of beta L-crystallin/alpha-crystallin and ADH/alpha-crystallin were adjusted so that partial inhibition of protein aggregation at 60 degrees C or 37 degrees C, respectively, was observed and modulation of the chaperone action of alpha-crystallin could be evaluated easily with selected endogenous metabolites. Enhancement of the anti-aggregation activity in the beta L-crystallin assay was strongest with pantethine, which appeared to interact with alpha-crystallin. Enhancement of the anti-aggregation activity in the ADH assay was strongest with glutathione which appeared to interact with ADH. The results indicated that the products of common metabolic pathways can modulate the chaperone-like effects of alpha-crystallin on protein aggregation.

Alcohol Dehydrogenase↗
PubMed1996

Binding characteristics and antitumor properties of 1A10 bispecific antibody recognizing gp40 and human transferrin receptor.

The bispecific murine monoclonal antibody (MAb) 1A10 has specificity for the human transferrin receptor (TfR) and the human tumor-associated antigen gp40. This antibody, therefore, functions as an "antigen fork" by binding to two distinct antigens on the same malignant cell. Highly purified 1A10 inhibits the growth of cells coexpressing high levels of human TfR and the tumor-associated antigen gp40 by binding to both target antigens. In SW948 cells, the majority of 1A10 binding is via its gp40 specificity, and half-maximal inhibition of cell growth by 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay requires 20-30-micrograms/ml concentrations of 1A10. The binding of 1A10 correlates with growth inhibition in the cell lines HT-29, SK-OV-3, OVCAR-2, and OVCAR-3. The growth of OVCAR-10 cells, which express little gp40 and TfR, is not inhibited by 1A10. However, SK-BR-3 cells, which express abundant gp40 and extremely high levels of TfR, are insensitive to the effects of 1A10. In some cell lines, combined exposure to 1A10 and the iron chelator deferoxamine mesylate has synergistic antiproliferative effects. A single i.p. dose of 600 micrograms 1A10 is sufficient to achieve an estimated tumor concentration of at least 30 micrograms/ml for 7 days in C.B17/Icr-scid mice bearing SW948 human tumor xenografts. Treatment of scid mice bearing day 2 or day 4 SW948 xenografts with single or multiple 1A10 doses inhibits tumor growth in a dose-related fashion. Antitumor effects are not seen with therapy using either parental antibody of 1A10. The antiproliferative properties of 1A10 in tumor cells overexpressing gp40 and TfR suggest avenues for the development of new bispecific antibody-promoted treatment strategies.

Animals↗
PubMed1996

Effect of selected anti-cataract agents on opacification in the selenite cataract model.

A systematic study of the anti-cataract activity of 14 reagents was conducted using the selenite model. The reagents or their derivatives were identified from literature reports of their potential effectiveness against cataract formation. The effects of each reagent were measured on the phase separation temperature, Tc, of lens homogenate in vitro. Tc is a direct measure of molecular interactions leading to protein aggregation. The protective effect of a single subcutaneous injection of each reagent [at a dose of 1.5 mmol (kg body weight)-1] on lens opacification was evaluated in vivo using rats administered selenite [at a dose of 19 mumol (kg body weight)-1] to initiate cataract formation. The strongest effects on lens opacification in vivo were observed with reagents having the strongest effect on Tc, in vitro. The weakest effects in vivo were observed with the reagents having the weakest effect on Tc, in vitro. The results were suggestive of a relationship between the effect of a reagent on Tc and protection against cataract formation in vivo.

Animals↗
PubMed1996

Delay or inhibition of rat lens opacification using pantethine and WR-77913.

Pantethine and the amino phosphorothioate, WR-77913, protected lenses against increased light scattering and opacification during cataract formation in five animal models: (1) radiation, (2) selenite, (3) galactose, (4) streptozotocin and (5) Royal College of Surgeons. In the radiation or selenite models, each test reagent was administered 15 to 30 min prior to initiation of cataract by a single injection of Na2SeO3 or a single exposure to 15 Gy (gray) gamma radiation. In the galactose, streptozotocin and Royal College of Surgeons models where the cataractogenic insult was continuous, repeated administrations of pantethine and WR-77913 were necessary. The results suggested that protein aggregation and lens opacification associated with a variety of physiological and biochemical mechanisms can be delayed or inhibited using a systemic administration of pantethine or WR-77913.

Amifostine↗
PubMed1995

Phase I trial of 2B1, a bispecific monoclonal antibody targeting c-erbB-2 and Fc gamma RIII.

2B1 is a bispecific murine monoclonal antibody (BsMAb) with specificity for the c-erbB-2 and Fc gamma RIII extracellular domains. This BsMAb promotes the targeted lysis of malignant cells overexpressing the c-erbB-2 gene product of the HER2/neu proto-oncogene by human natural killer cells and mononuclear phagocytes expressing the Fc gamma RIII A isoform. In a Phase I clinical trial of 2B1, 15 patients with c-erbB-2-overexpressing tumors were treated with 1 h i.v. infusions of 2B1 on days 1, 4, 5, 6, 7, and 8 of a single course of treatment. Three patients were treated with daily doses of 1.0 mg/m2, while six patients each were treated with 2.5 mg/m2 and 5.0 mg/m2, respectively. The principal non-dose-limiting transient toxicities were fevers, rigors, nausea, vomiting, and leukopenia. Thrombocytopenia was dose limiting at the 5.0 mg/m2 dose level in two patients who had received extensive prior myelosuppressive chemotherapy. Murine antibody was detectable in serum following 2B1 administration, and its bispecific binding properties were retained. The pharmacokinetics of this murine antibody were variable and best described by nonlinear kinetics with an average t 1/2 of 20 h. Murine antibody bound extensively to all neutrophils and to a proportion of monocytes and lymphocytes. The initial 2B1 treatment induced more than 100-fold increases in circulating levels of tumor necrosis factor-alpha, interleukin 6, and interleukin 8 and lesser rises in granulocyte-monocyte colony-stimulating factor and IFN-gamma. Brisk human anti-mouse antibody responses were induced in 14 of 15 patients. Several minor clinical responses were observed, with reductions in the thickness of chest wall disease in one patient with disseminated breast cancer. Resolution of pleural effusions and ascites, respectively, were noted in two patients with metastatic colon cancer, and one of two liver metastases resolved in a patient with metastatic colon cancer. Treatment with 2B1 BsMAb has potent immunological consequences. The maximum tolerated dose and Phase II daily dose for patients with extensive prior myelosuppressive chemotherapy was 2.5 mg/m2. Continued dose escalation is required to identify the maximally tolerated dose for patients who have been less heavily pretreated.

Adult↗
PubMed1995

Quantitative analysis of the lens cell microstructure in selenite cataract using a two-dimensional Fourier analysis.

Using two-dimensional (2-D) Fourier methods, we analysed the cellular microstructure of three rat lenses: normal transparent, selenite-induced cataractous and selenite-treated plus a phase separation inhibitor (PSI) to prevent cataract. 2-D Fourier analysis of electron micrographs of the lens cells quantified the dimensions of the spatial fluctuations in electron density of the lens cell microstructure. The 2-D Fourier spectra of the transparent normal and PSI-treated lens cells were remarkably similar while those of the opaque selenite-treated lens cells were dramatically different. In the opaque cells the contributions of large Fourier components (larger than half the wavelength of light) in the 2-D Fourier spectra were much greater than in the transparent cells. The results of the 2-D Fourier analysis of electron micrographs are consistent with the theory of transparency of the eye.

Amifostine↗
PubMed1995

Clinical development of 2B1, a bispecific murine monoclonal antibody targeting c-erbB-2 and Fc gamma RIII.

Bispecific monoclonal antibodies (BsmAb) can be used to specifically target tumor cells for cytotoxicity mediated by defined effector cells. One such BsmAb, 2B1, targets the extracellular domains of both the c-erbB-2 protein product of the HER-2/neu oncogene and Fc gamma RIII (CD16), the Fc gamma receptor expressed by human natural killer cells, neutrophils, and differentiated mononuclear phagocytes. 2B1 promotes the conjugation of cells expressing these target antigens. It efficiently promotes the specific lysis of tumor cells expressing c-erbB-2 by human NK cells and macrophages over a broad concentration range. 2B1 selectively targets c-erbB-2-positive human tumor xenografts growing in immunodeficient SCID mice. Treatment of such mice with 2B1 plus interleukin 2 (IL-2) inhibits the growth of early, established human tumor xenografts overexpressing c-erbB-2. A phase I clinical trial of 2B1 has been initiated to determine the toxicity profile and maximum tolerated dose (MTD) of this BsmAb and to examine the biodistribution of the antibody and the biologic effects of treatment. Preliminary results of this trial indicate that the dose-limiting toxicity for patients with extensive prior bone marrow-toxic therapy is thrombocytopenia for as yet undetermined reasons. Toxicities of fevers, rigors, and associated constitutional symptoms are explained, in part, by treatment-induced systemic expression of cytokines, such as tumor necrosis factor-alpha. Circulating, functional BsmAb is easily detectible in treatment patients' sera and exhibits complex elimination patterns. HAMA and anti-idiotypic treatment-induced antibodies are induced by 2B1 treatment. Some preliminary indications of clinical activity have been observed. BsmAb therapy targeting tumor antigens and Fc gamma RIII has potent immunologic effects. Future studies will include the development of more relevant animal models for BsmAb therapy targeting human Fc gamma RIII. The ongoing phase I trial will be completed to identify the MTD for patients without extensive prior bone marrow-toxic chemotherapy and radiation. A phase II clinical trial of 2B1 therapy in women with metastatic breast cancer is planned, as is a phase I trial incorporating treatment with both 2B1 and IL-2.

Animals↗
PubMed1995

Inhibition of lens opacification during the early stages of cataract formation.

PURPOSE: To characterize the time period during cataract formation in which administration of pantethine inhibits lens cell opacification in the selenite model for cataract. METHODS: Pantethine was administered to neonatal rat pups at selected time points from -0.5 to 17 hours with respect to injection of selenite at time = 0. The injection dose of pantethine was 820 mg/kg (1.5 mmol/kg) diluted in water at 410 mg/ml concentration. The injection dose of selenite was 3.28 mg/kg (19 mumol/kg) diluted in saline at 1.8 mg/ml concentration. Opacification was observed using a slit lamp microscope at selected time points over a 14-day period. Cataracts were staged using a classification of opacity from 0 (normal) to 6 (mature). RESULTS: The effect of pantethine was characterized by three different time periods: administration -0.5 to 6 hours with respect to selenite injection provided highly significant protection, P < 0.001; administration 8 hours after selenite provided significant protection, P < 0.005; administration 10 to 17 hours after selenite was not protective. CONCLUSIONS: The metabolite pantethine inhibited lens opacification during cataract formation in the selenite model. Even when pantethine was injected several hours after the administration of selenite, opacification was inhibited. Advanced stages of opacification were unresponsive to the administration of pantethine. The inhibitory effect of pantethine was statistically significant when administered during the earliest stage of opacification in the selenite model for cataract.

Animals↗
PubMed1995

Two-dimensional fourier analysis of electron micrographs of human skin for quantification of the collagen fiber organization in the dermis.

Two-dimensional (2-D) Fourier analysis was used to quantify the structural organization of collagen fibers in the dermis of the human skin. The 2-D Fourier spectra of electron micrographs of collagen fibers contained large amplitude Fourier components (1 fundamental and 3 harmonic peaks), representing the predominant structural parameter of the fibers, the center-to-center spacing of collagen fibrils. The average center-to-center spacing of the collagen fibrils was found from the position of the peaks. For a normal fiber of reticular dermis, this spacing was 116 nm. The fibril diameter appeared to modulate the peak heights.

Collagen↗
PubMed1994

Quantitative analysis of the microstructure of the human cornea and sclera using 2-D Fourier methods.

A two-dimensional (2-D) Fourier analysis was used to characterize the microstructure of the human cornea and sclera. The average centre-to-centre spacing of collagen fibrils was found to be 59 nm for the cornea and 285 nm for the sclera. These results agreed with those obtained by direct measurement using the electron micrographs, and those reported in the literature. The spatial order in the microstructure of the cornea was much greater when compared with that of the sclera. The results of the 2-D Fourier analysis were consistent with the theory of transparency of the eye. The 2-D Fourier analysis will be useful in quantitative characterization and analysis of the complex microstructure of biological cells and tissues in normal development and abnormal pathogenesis.

Cornea↗
PubMed1993

Phase separation inhibitors and lens transparency.

A phase separation inhibitor, WR77913 [S-3(amino-2-hydroxypropyl) phosphorothioate], was tested for its effects on lens opacification in the radiation (RAD), selenite (SEL), galactose (GAL), streptozotocin (STZ), and Royal College of Surgeons (RCS) models for cataract. A single i.p. injection of WR77913, approximately 15 min before induction of cataract formation by RAD, SEL, STZ delayed or inhibited opacification. Repeated administration was necessary to delay or inhibit opacification in the GAL or RCS models for cataracts. The results suggest that phase separation inhibitors such as WR77913 have the potential to delay or inhibit lens opacification resulting from a variety of physiological or biochemical mechanisms.

Amifostine↗
PubMed1992

Phase-separation inhibitors and prevention of selenite cataract.

The variation of the phase-separation temperature (Tc) was studied in lenses during formation of cataracts induced by a subcutaneous injection of sodium selenite. In normal control animals, the Tc decreased monotonically with increasing age. Approximately 2 days after administration of the selenite the Tc decreased sharply to a minimum, and then at day 4 the Tc increased dramatically toward body temperature. Mature irreversible cataracts formed approximately 6 days after injection of the selenite. Intraperitoneal administration of WR-77913, a phase-separation inhibitor, prevented the abnormal variation of Tc in vivo. When injected into control animals without selenite, WR-77913 produced no abnormal variation in Tc. The results confirm that Tc is a sensitive measure of early changes in the lens and that opacification associated with abnormal variation in Tc can be prevented in vivo by using a phase-separation inhibitor.

Amifostine↗