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Biomedical subjects

J L Matthews

Publications and source records attributed to J L Matthews.

14 recordsLinked to original sources
PubMed1992

An exonuclease requiring an intact helical stem for specificity produces the 3' end of Acanthamoeba castellanii 5 S RNA.

A nuclear extract from Acanthamoeba castellanii which contains all of the components necessary for specific transcription of a 5 S RNA gene was separated into fractions required for specific transcription initiation and an additional fraction needed in the reconstituted system to produce the 3' end characteristic of mature 5 S RNA. The latter fraction contained a novel processing activity characterized by an exonuclease specific for highly structured RNAs, including 5 S RNA. An intact helical stem formed between the 5' and 3' ends of the 5 S RNA precursor determines the 3' nucleotide. In addition, the presence of ATP is required for specific processing. However, the possibility has not been ruled out that ATP inhibits a nonspecific ribonuclease in the extract since processing proceeds into the helical stem in its absence.

Acanthamoeba↗
PubMed1992

Thermal effects in tissues from combined simultaneous coaxial CO2 and Nd:YAG laser beams.

This study examines the depth of thermal coagulation and charring in swine liver, kidney cortex, tongue (inferior surface), skeletal muscle, inflated lung, and skin resulting from in vivo incision with simultaneous coaxial CO2 and Nd:YAG (1.064 microM) laser beams. At values of 20 w and 40 w, respectively, and at values of 30 w and 60 w, respectively, of combined CO2 and Nd:YAG laser radiation, coagulation depths determined histologically in liver were significantly greater (P less than 0.01) than in the other tissues and were significantly less in inflated lung (P less than 0.05) than in other tissues for the larger laser power settings employed. Coagulation depths achieved at 10 w and 20 w, respectively, and at 20 w and 40 w, respectively, of CO2 and Nd:YAG laser power were comparable to those obtained by other workers in liver and other relatively vascular tissues using a contact Nd:YAG laser tip. Charring depths obtained at power settings of 30 w (CO2) and 60 w (Nd:YAG) were greater in liver (P less than 0.001) than in all other tissues examined. Hemostasis during incision was achieved only for values of the ratio of CO2 to Nd:YAG laser power in the range 2-3 in the more vascular tissues, liver and kidney cortex, whereas hemostasis was achieved also in the lesser vascular tissues at higher values. These results strongly suggest the usefulness of combined simultaneous CO2 and Nd:YAG laser beams in surgery of the more vascular organs and tissues.

Animals↗
PubMed1992

Inactivation of viruses with photoactive compounds.

The transmission of human immunodeficiency virus (HIV-1) and other enveloped virus by blood transfusion is a major concern. Photosensitive dyes such as hematoporphyrin derivative (HPD), dihematoporphyrin ether (DHE), benzoporphyrin derivatives (BPD), extended ring porphyrins, sapphyrins and texaphyrins, and various cyanines were used with viral cultures to test the feasibility of using those light-excitable dyes to kill virus. A photodynamic flow cell was used to irradiate viral suspensions or viral infected cells in culture media or in whole blood. Herpes virus (HSV-1) was used to screen compounds. Effective compounds were subsequently tested for their ability to kill HIV-1, CMV, and SIV in culture medium and in blood and proved to effectively kill free virus and infected cells at significant viremias. Irradiation was achieved with a filtered xenon light source and/or tunable dye laser. Concentrations of dyes at 10 times viral kill dose were irradiated in blood which was tested for damage to erythrocytes (RBC), platelets, and blood proteins. No damage to RBC, complement factors, and immunoglobulins was evident immediately after photodynamic treatment. Platelet condition is minimally modified with time. Photodynamic treatment of blood appears to be a feasible means of eradicating virus and some protozoans from blood.

Blood↗
PubMed1992

Preactivated merocyanine 540 inactivates HIV-1 and SIV: potential therapeutic and blood banking applications.

A novel photodynamic procedure employing "preactivated" merocyanine 540 (P-MC 540) was assessed for its effectiveness in inactivating human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV). Merocyanine 540 was preactivated by exposure to laser light at 514 nm prior to addition to viruses or infected cells. Treatment of cell-free HIV-1 and SIV with P-MC 540 significantly reduced their ability to infect and kill MT-4 cells in vitro. Preactivated MC 540 treatment of in vitro HIV-1-infected human peripheral blood mononuclear cells also decreased viral infection as assessed by a reduction in the amounts of HIV-1 p24 antigen produced and in the number of HIV-1 antigen-positive cells. Indirect immunofluorescence assays of target cell binding showed that treatment of cell-free HIV-1 and SIV with P-MC 540 interfered with their ability to bind to CD4+ target cells. Immunoprecipitation with a monoclonal anti-CD4 antibody of P-MC 540-treated and radiolabeled HIV-1 incubated with soluble recombinant CD4 (srCD4) resulted in coprecipitation of HIV-1 viral p17 and p24 core antigens with the envelope gp120/CD4 complex, suggesting cross-linking of viral components. However, no significant decrease in the binding of treated HIV-1 to srCD4 was observed. Because of the antitumor and antiviral properties of P-MC 540, this photopreactivation procedure may represent a promising therapeutic means for controlling systemic malignancies and viral infections, and for eliminating viral contaminants in biological fluids. Unlike conventional phototherapy, this procedure does not require the delivery of light energy at the target sites following binding of the photosensitizing compounds.

Antiviral Agents↗
PubMed1991

Preliminary studies of photoinactivation of human immunodeficiency virus in blood.

The transmission of human immunodeficiency virus (HIV) by blood or blood components is a major concern in blood banking. A photodynamic flow cell system was designed to inactivate cell-free HIV mixed with blood from a healthy donor. Blood containing 4 x 10(3) infectious units of HIV was treated with 10 and 20 micrograms per mL of commercially available dihematoporphyrin ether (DHE) per mL. Aliquots of this mixture were then held in the dark or irradiated in a flow cell illuminated at a light energy density of 5 J per cm2 provided by a xenon light source equipped with a 630 +/- 5 nm band-pass interference filter; the aliquots were subsequently placed in A.301 cells. All infected cultures were assessed for reverse transcriptase (RT) activity for 17 days. RT activity for either concentration of dye was significantly reduced in irradiated samples as compared to that in samples held in the dark. Blood samples from volunteers also were assessed for the effects of the inactivation process on red cells at concentrations of DHE up to 200 micrograms per mL. No effects were observed on red cell 2,3 DPG or ATP, whole blood potassium concentrations, red cell osmotic fragility, or blood cell antigens.

Antiviral Agents↗
PubMed1978

Calcium localization in normal rachitic, and D3-treated chicken epiphyseal chondrocytes utilizing potassium pyroantimonate-osmium tetroxide.

Normal, rachitic, and vitamin D3-replete chicken growth plates were studied utilizing the potassium pyroantimonate-osmium tetroxide procedure. A marked membrane and mitochondrial calcium was revealed in all specimens in the maturing and early hypertrophic zones which disappeared as heavy matrix mineralization began. The most significant difference shown in the specimens was in the marked intracellular lipid content of chondrocytes in all zones of the rachitic and D3-replete growth plates. There was negligible lipid present in normal specimens. It is suggested that as most of the mechanisms postulated as necessary for calcification are present in rachitic chicks, perhaps the increased intracellular lipid pool results from the formation of abnormal lipids for insertion into the plasma membrane and thus prevents normal calcium transport. Chains of intracellular vesicles were also visualized in maturing and hypertrophic chondrocytes. These were more often seen in rachitic growth plates and in increased numbers in the early D3-replete specimens. The etiology is unknown at the present time.

Animals↗
PubMed1977

The effect of cytochalasin B on the endosteal lining cells of mammalian bone. A scanning electron microscopic study.

The lining osteoblasts of the rat tibial endosteum were treated for various times (between 1 and 60 min) and increasing doses (3.87-38.7 microgram/ml) with the macrolide fungal metabolite cytochalasin B (CB). Dimethylsulfoxide (DMSO) served as the vehicle for CB and was administered to control tissues. An in vitro incubation system and scanning electron microscopy (SEM) were used to evaluate the effects of CB. The drug initiated cell rounding (contraction), nuclear protrusion, bleb formation, and the subsequent clustering of blebs and microvilli into aggregates. All CB-induced aberrations of the surface structure were readily reversible when tissues were washed with CB-free media. DMSO had no significant effect on cell surface morphology. The reversible structural changes brought about by CB are explained in terms of alterations of the subplasmalemmal cortical microfilament system of osteoblasts. The potential use of CB in evaluating the bone cell cytoskeleton and its relationship to the physiology of the cellular functional membrane (endosteum) of bone is discussed.

Animals↗
PubMedDate not supplied

Preactivation: a new concept for generation of photoproducts for potential therapeutic applications.

Controlled exposure of photoactive compounds to light prior to their use in biological targets results in the formation of heretofore unknown photoproducts. This process of photoproduct generation, termed preactivation, renders the photoactive compound capable of systemic use without further dependence on light. We have demonstrated that preactivated Merocyanine and preactivated Photofrin-II possess significant antitumor and antiviral activity against certain tumor cells and viruses, while under identical conditions normal cells and tissues are minimally affected. Thus, the preactivation procedure may represent a promising therapeutic modality for controlling systemic malignancies and viral infections.

Animals↗