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Biomedical subjects

L K Gordon

Publications and source records attributed to L K Gordon.

At least 37 records · Page 2Linked to original sources
PubMed1986

Studies on the combined administration of Haemophilus influenzae type B--diphtheria toxoid conjugate vaccine (PRP-D) and DTP.

The safety and immunogenicity of an Haemophilus influenzae type b capsular polysaccharide-diphtheria toxoid vaccine (PRP-D) has been evaluated when administered alone or simultaneously with other vaccines in over 1,400 2-24 month old subjects. In the first infant study, groups of subjects received either the PRP-D, PRP or placebo vaccine at 3, 5 and 7 months, one month after DPT immunization at 2, 4 and 6 months of age. In a subsequent study infants received either the PRP-D or PRP vaccine simultaneously with DPT. Safety of the PRP-D vaccine was indistinguishable from that of the PRP and placebo vaccines. In both studies, greater than 90% of the PRP-D recipients developed protective levels of antibody (greater than 0.15 microgram/ml) and the majority developed greater than 1.0 microgram/ml of anti-PRP. Following a booster dose of PRP-D at 14-18 months, simultaneously with either MMR, DPT or polio vaccine, all children in these studies developed greater than 1.0 micrograms/ml of antibody. Several other administration schedules have been evaluated in separate clinical studies. Acceptability of a combined DPT/PRP-D vaccine is currently being evaluated in experimental studies.

Antibodies, Bacterial↗
PubMed1985

Antibody levels achieved in infants by course of Haemophilus influenzae type B polysaccharide/diphtheria toxoid conjugate vaccine.

A Haemophilus influenzae type b (Hib) capsular polysaccharide (polyribosylribitol phosphate, PRP)/diphtheria toxoid (D) conjugate vaccine was given to 71 infants. The level of anti-PRP antibody believed to predict long-term protection, 1.0 microgram/ml, was reached in 50% of the infants who were vaccinated at 3, 5, and 7 months, and in 57% of the infants who received PRP-D at 7 and 9 months of age. A lower level of antibody, 0.15 micrograms/ml, which has been associated with protection at the time of assay, was reached in 92% and 87% of the two groups. Thus, the seroresponse was dependent upon both the frequency of immunisation and age of the infant. Comparison of these results with previous experience with PRP immunisation in Finland showed that PRP-D induced substantial antibody rises at an earlier age than did PRP.

Age Factors↗
PubMed1985

Inhibition of lectin-induced lymphocyte activation by 2-cyclohexene-1-one: analysis of DNA synthesis in individual cells by BUdR quenching of Hoechst 33258.

A novel technique utilizing the quenching of fluorescence Hoechst 32258 by bromodeoxyuridine (BUdR) was used to investigate the effect of depressed glutathione (GSH) on the activation of human peripheral blood lymphocytes by phytohemagglutinin (PHA) or concanavalin A (con A). This technique allows the quantification of DNA synthesis in individual cells. Lymphocytes were purified by Ficoll-Hypaque density gradient centrifugation and treated with 5 X 10(-5) M to 1 X 10(-6) M 2-cyclohexene-1-one (2-CHX-1), a reagent which specifically depletes intracellular GSH, and/or interferes with GSH-protein interactions, and 25 micrograms/ml BUdR in the presence or absence of PHA or con A. At 72 h lymphocyte smears were stained with Hoechst 33258 and examined using a computer controlled microscope photometer. When DNA synthesis was assayed using BUdR quenching two populations of lymphocytes were noted; a population which incorporated little or no BUdR (unactivated) and a population which incorporated BUdR sufficient to quench 33258 fluorescence by approximately 35%. Cells treated with graded doses of 2-CHX-1 which reduced glutathione levels by 10-90%, showed a progressive loss of cells from the activated population and the appearance of these cells in the inactivated population. Statistical analysis of the frequency histograms demonstrated that there were no cells which incorporated an intermediate amount of BUdR. This data demonstrates that depressed intracellular GSH or inhibition of GSH-protein interactions inhibits an early step in the biochemical sequence of events leading to DNA synthesis but does not inhibit the DNA synthetic process per se.

Benzimidazoles↗
PubMed1985

Safety and immunogenicity of Haemophilus influenzae type b-polysaccharide diphtheria toxoid conjugate vaccine in infants 9 to 15 months of age.

Sixty 9- to 15-month-old infants were randomly assigned to receive two doses, 1 month apart, of a Haemophilus influenzae type b capsular polysaccharide-diphtheria toxoid conjugate vaccine (PRP-D) or PRP vaccine, each containing 20 micrograms PRP. There were no significant local or systemic reactions. After one dose of PRP-D, 93% of the subjects attained levels of greater than or equal to 0.15 microgram/ml and 59% achieved greater than or equal to 1 microgram/ml antibody protein. These percentages rose to 100% and 86%, respectively, after the second dose, at which time the geometric mean titer of anti-PRP antibody was 4.8 micrograms/ml. IgG anti-PRP levels were 4.3 times higher than IgM. The proportion of IgG to IgM antibody induced by PRP-D increased with age. After two doses, 33% of the PRP recipients responded with a level of greater than or equal to 0.15 microgram/ml and only 19% responded to a level of greater than or equal to 1.0 microgram/ml. One year later, all of the PRP-D recipients tested still had greater than or equal to 0.15 microgram/ml and more than half had greater than or equal to 1.0 microgram/ml antibody protein.

Antibodies, Bacterial↗
PubMed1984

Safety and immunogenicity of Haemophilus influenzae type B polysaccharide-diphtheria toxoid conjugate vaccine in adults.

Sixty-one adults received either Haemophilus influenzae type b capsular polyribosephosphate (PRP) vaccine or H. influenzae type b polysaccharide-diphtheria toxoid conjugate (PRP-D) vaccine in two doses, one month apart. Both vaccines were well tolerated with no fever or systemic reactions. There were no significant local reactions. Mild local tenderness was reported by about half of the subjects in both groups. There was no observed effect of the vaccines on hematologic parameters, including reticulocyte and platelet counts, evaluated before immunization, one month after the first dose, and seven to 10 days after the second dose. A single dose of PRP-D induced levels of IgG antibody to PRP three times that observed with PRP alone one month after the first inoculation.

Adult↗
PubMed1982

New approaches to DNA damage and repair: the ultraviolet light example.

DNA fragments of defined sequence are used as probes to study DNA damage and repair. The case of ultraviolet light is presented and includes the following: (a) Description of the distribution of cyclobutane pyrimidine dimers within defined DNA sequences. Considerations of the effect of neighboring base composition, dose rate, and double- or single-stranded property of the DNA are discussed. (b) Dissection of the anatomy of the incision event and subsequent repair steps. A three-step incision model for repair of cyclobutane dimers by the Micrococcus luteus repair enzymes will be presented. The steps are (1) recognition of the lesion and N-glycosylase scission, (2) cleavage of the phosphodiester bond 3' to the newly created apyrimidinic site, and (3) scission of the apyrimidinic sugar on the 5' side. (c) Use of human alphoid sequences as indicators of DNA damage in intact human cells. (d) Biological significance of a novel ultraviolet light-induced photoproduct. This photoproduct occurs at pyrimidine-cytosine sequences and may have a significant biological role.

Base Sequence↗
PubMed1981

Use of exonuclease III to determine the site of stable lesions in defined sequences of DNA: the cyclobutane pyrimidine dimer and cis and trans dichlorodiammine platinum II examples.

A method to detect chemically stable lesions in DNA has been developed using Exonuclease III, a double strand specific nuclease, to digest 5'-end labeled DNA. The products, when analyzed on high resolution DNA sequencing gels, reveal the sites of DNA modification. Cyclobutane pyrimidine dimers induced by UV irradiation can be localized by comparison of the fragments produced by Exonuclease III digestion with fragments obtained after digestion of the DNA with UV specific endonuclease. The experiments demonstrate the Exonuclease III stops one base away from the cyclobutane pyrimidine dimers. Similar experiments with cis- and trans-dichlorodiammine-platinum (II) showed that modification of DNA by these agents also impede Exonuclease III digestion. In general the same stop sites were found for cis-and trans-platinum adducts. They occur at sites of guanine bases. Additional stop sites were found for cis-platinum at sites of adjacent guanine bases. These results are in agreement with the model that cis-platinum forms intrastrand guanine-guanine dimers, whereas trans-platinum does not.

Base Sequence↗
PubMed1981

Early steps of excision repair of cyclobutane pyrimidine dimers by the Micrococcus luteus endonuclease. A three-step incision model.

The early steps of excision repair of cyclobutane pyrimidine dimers are investigated. It is demonstrated that the apurinic/apyrimidinic endonuclease associated with the Micrococcus luteus uv-specific endonuclease cleaves the phosphodiester bond on the 3' side of the deoxyribose leaving a 3' hydroxy terminus and a 5' phosphoryl terminus. This nick is not a substrate for T4 polynucleotide ligase. The 3' base-free deoxyribose terminus is not a substrate for either the polymerase or the 3' to 5' exonuclease activities of Escherichia coli DNA polymerase I. However, the 3' terminus of the nick is converted to a substrate for DNA polymerization by the action of a 5' apurinic/apyrimidinic endonuclease. A three-step model for the incision step of excision repair of cyclobutane pyrimidine dimers is presented.

Alkaline Phosphatase↗
PubMed1981

A reliable method for repetitively bleeding rabbits from the central artery of the ear.

A method is presented for repeatedly bleeding rabbits from the central ear artery. The use of hypodermic needle with the hub removed provides a smooth flow of blood and avoids the problem of clot formation in the hub. Blood can be obtained aseptically and free of hemolysis with little risk to the animal. Volumes of 35 ml can be obtained from an initial bleed, increasing to 100 ml from subsequent bleeds. Advantages of the method include reliability, minimal trauma to the animal, and little contamination of the sample.

Animals↗
PubMed1981

Distribution of UV light-induced damage in a defined sequence of human DNA: detection of alkaline-sensitive lesions at pyrimidine nucleoside-cytidine sequences.

The distribution of UV light-induced damage to the highly reiterated alpha sequence of human DNA was investigated. The results show that the distribution of UV light-induced cyclobutane dimers within a defined sequence is similar whether the DNA is exposed to UV light as part of the chromosome of intact cells or as naked DNA. However, the cellular environment shields the nuclear DNA, resulting in about 50% decrease in apparent dose. A new type of UV photodamage was detected. Treatment of UV light-irradiated DNA with hot alkali results in strand breaks at positions of cytidine located 3' to pyrimidine nucleosides. The chemical nature and biological significance of the pyrimidine nucleoside-cytidine lesion is discussed.

Base Sequence↗
PubMed1981

A microfluorometric assay for the measurement of de novo DNA synthesis in individual cells.

A microfluorometric assay has been developed for the quantitation of de novo DNA synthesis. The assay reliably detects newly synthesized DNA in individual cells and provides a relative measure of the proportion of new DNA in each cell. When combined with microscopic techniques for cell identification, selected subpopulations can be examined in samples containing a complex mixture of interacting cell types. The assay employs the quenching of Hoechst-33258 fluorescence by bromodeoxyuridine incorporated into newly synthesized DNA. The ability of BUdR to quench H-33258 fluorescence is lost after a brief exposure of ultraviolet fluorescence excitation. Therefore, quenched and unquenched fluorescence intensity measurements from the same cell can be compared. Increases in fluorescence intensity occur only in cells that have synthesized DNA after the addition of BUdR. In addition the change in fluorescence intensity is proportional to the degree of BUdR substitution within the range of the assay and provides a relative measure of DNA synthesis.

Bisbenzimidazole↗
PubMed1980

Comparison of the cleavage of pyrimidine dimers by the bacteriophage T4 and Micrococcus luteus UV-specific endonucleases.

A comparison was made of the activity of the UV-specific endonucleases of bacteriophage T4 (T4 endonuclease V) and of Micrococcus luteus on ultravilet light-irradiated DNA substrates of defined sequence. The two enzymes cleave DNA at the site of pyrimidine dimers with the same frequency. The products of the cleavage reaction are the same, suggesting that the scission of DNA by T4 endonuclease V occurs via the combined actin of a pyrimidine dimer specific DNA glycosylase and an apyrimidinic-apurinic (AP) endonuclease as was recently shown for the M. luteus enzyme. The pyrimidine dimer DNA-glycosylase activity of both enzymes is more active on double-stranded DNA than it is on single-stranded DNA.

Base Sequence↗
PubMed1980

Cleavage of pyrimidine dimers in specific DNA sequences by a pyrimidine dimer DNA-glycosylase of M. luteus.

Pyrimidine dimer formation in response to UV radiation is governed by the thymine content of the potential dimer and the two flanking nucleotides. An enzymatic activity can be purified from Micrococcus luteus that cleaves the N-glycosyl bond between the 5' pyrimidine of a dimer and the corresponding sugar without rupture of a phosphodiester bond. We propose that strand scission at a dimer site by the M. luteus enzyme requires two activities, a pyrimidine dimer DNA-glycosylase and an apyrimidinic/apurinic endonuclease.

Apurinic Acid↗
PubMed1980

Cyclic AMP concentrations in human peripheral blood lymphocytes. Changes in association with cell purification.

In studies over a several year period of cAMP in human peripheral blood lymphocytes, a wide range of concentrations has been from low values (1 to 5 pmole/10(7) cells) to high values (80 to 160). Evaluation of this variation indicated that between cell separation and completion of the experiment, there eas a progressive decrease in lymphocyte cAMP as determined by RIA or immunocytochemistry. After a 2 hr incubation at 37 degrees C, a new steady state was reached at 5% to 30% of the initial concentration. This phenomenon was unique to lymphocytes and not preventable by manipulation of the incubation conditions. The cause of the cAMP reduction was shown to be decreasing AC activity. These data suggested the possibility that AC was activated during cell isolation. However, the phenomenon was present in cells not exposed to dextran or Ficoll-Hypaque, and simulation of conditions employed during purification did not result in increased cAMP. Consequently, high-lymphocyte cAMP concentrations may be the normal levels in vivo.

Adenylyl Cyclases↗
PubMed1980

The activation of blast transformation and DNA synthesis in human peripheral blood lymphocytes by wheat germ agglutinin.

Wheat germ agglutinin (WGA) has been shown to induce blast transformation and DNA synthesis in a minor subpopulation of human peripherl blood T lymphocytes (PBL). These cells enter DNA synthesis between 24 and 48 hr after stimulation, and demonstrate maximal blast transformation after 48 hr. In cultures of Ficoll/Hypaque purified PBL, the activation appears to be aborted 48 to 72 hr after WGA stimulation. After that time DNA synthesis is arrested and activated cells are rapidly lost from culture. The addition of N-acetyl glucosamine to cultures within 2 hr after WGA stimulation results in an increase in the proportion of cells activated and in the amount of DNA synthesized per cell. These experiments suggest that the abortive response may be due to the presentation of superimposed positive and negative signals.

Acetylglucosamine↗
PubMed1978

Demonstration of Thy-1 antigen on pluripotent hemopoietic stem cells in the rat.

Three approaches were used to demonstrate the presence of Thy-1 antigen on the surface of pluripotent hemopoietic stem cells in the rat. In the first, stem cells from fetal liver, neonatal spleen, and adult bone marrow were prevented from forming hemopoietic colonies in the spleens of irradiated recipients spleen (colony-forming unit assay) by incubation with antibodies to Thy-1 antigen. Highly specific rabbit heteroantiserum to purified rat brain Thy-1 antigen and mouse alloantisera to Thy-1.1-positive thymocytes were equally effective. This inhibition was neutralized by purified Thy-1 antigen. In a second series of experiments, Thy-1-positive and Thy-1-negative populations of nucleated bone marrow cells were separated by the FACS. All of the hemopoietic stem cell activity was recovered in the Thy-1-positive population. The stem cells were among the most strongly positive for Thy-1 antigen, being in the upper 25th percentile for relative fluorescence intensity. The relationships of Thy-1 antigen to the rat bone marrow lymphocyte antigen (BMLA) was shown in a third series of experiments. Rabbit anti-BMLA serum, which is raised against a null population of lymphocyte-like bone marrow cells, has been shown to have anti-stem cell activity. Here we demonstrate by double immunofluorescence, cocapping, and differential absorption studies that Thy-1 and BMLA are parts of the same molecule.

Animals↗
PubMed1978

Distribution of identity of Thy-1-bearing cells during ontogeny in rat hemopoietic and lymphoid tissues.

The distribution and identity of Thy-1+ cells during ontogeny in the rat were examined by immunofluorescent and histologic techniques, and the relative amount of Thy-1 antigen on different cell types was assessed by quantitative absorption. Thy-1+ cells were subsequently studied by dual immunofluorescence for the simultaneous expression of either T or B lymphocyte markers. The results indicate that the Thy-1 antigen is present on hemopoietic precursors and on at least some of their lymphoid (both T and B) and nonlymphoid descendants. In addition, six serologically distinct subpopulations of lymphoid cells were identified, and their position in T and B cell maturational pathways is discussed.

Animals↗