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Biomedical subjects

P Oliver

Publications and source records attributed to P Oliver.

At least 55 records · Page 3Linked to original sources
PubMed1993

Expression of the recA gene in recombination-deficient (rec-) strains of Escherichia coli.

Basal and induced levels of recA expression in wild-type and isogenic derivatives of Escherichia coli carrying various rec mutations were measured using a low-copy number recApo-lacZ fusion, pKLC3.2. Basal recA expression in wild-type and isogenic derivatives containing single rec- mutations, as well as in the recBCsbcA strain and isogenic recA, recF and recJ derivatives, ranged from 1000 to 3900 units. In the recBCsbcBC strain and isogenic recL and recN derivatives basal recA expressions were 3- to 5-fold higher than that of wild-type cells and were inducible by mitomycin C. Except for the recA and lexA3(lnd-) mutants, recA expression was induced by mitomycin C in wild-type cells and its isogenic recB, recD, recF, recG, recJ, recL, recN, recO and ruv derivatives. RecF was required for induction of recA expression by mitomycin C, but not by naladixic acid in the recBCsbcA and recBCsbcBC genetic backgrounds. In wild-type cells, induction of recA expression by naladixic acid required the recBC, but not the recD function of the RecBCD enzyme. This requirement is suppressed by either an additional sbcA or sbcC mutation, but not by an sbcB mutation.

Cloning, Molecular↗
PubMed1993

Radiopharmacological studies of 99mTc-CPI: experience with isolated rat atrial tissue.

Extraction, washout and chemical integrity of technetium(I) hexakis (2-carbomethoxy-2-isocyano propane), (99mTc-CPI) were evaluated in isolated contractile rat atrial tissue. 99mTc-CPI accumulated linearly over time at 32 degrees C with uptakes that were both concentration dependent and temperature sensitive. Uptake rates also increased with contractile strength, indicating a dependence of retention on metabolic status of the tissue. Retention indices showed that percent washout of 99mTc-CPI was much slower than control studies with 99mTcO4. HPLC analysis of retained radioactive products in atrial tissue showed most of the activity present as the 99mTc-CPI complex (75%). These observations in isolated rat atrial tissue help explain the interspecies differences in biodistribution of 99mTc-CPI and support the membrane potential dependent model for uptake and retention of technetium isonitrile complexes.

Animals↗
PubMed1993

Saccadic eye movements as a measure of the effect of low vision rehabilitation on reading rate.

We assessed saccadic eye movements and reading capabilities in individuals with macular disease by a masked clinical study to determine whether changes in saccadic frequency were correlated to changes in reading rates or number of errors for a reading task. We used a measure of eye movement characteristics in the form of a saccadic frequency score (SFS). Twelve subjects with macular disease were tested before and after an intense 6-week inpatient vision rehabilitation program. The mean age was 70.9 years (63 to 77 years). Mean visual acuity was 10/100 (10/40 to 10/200). Mean reading rates at entry and discharge were 8.5 words/min and 20.9 words/min, respectively (p = 0.02). SFS improved from 2.709 to 2.022 (p = 0.07). Reading errors improved from 5.60 to 4.00 (p = 0.03). Reading rates and SFS's were highly inversely correlated both pre- and post-treatment (Pearson r = -0.892 and -0.896, respectively). SFS and the number of reading errors were highly correlated with both pre- and post-treatment as well (Pearson r = 0.782 and 0.601, respectively). Interestingly the data appeared to cluster into two groups, one showing improvement and the other showing none. Cluster analysis revealed a strong association among reading rate, saccade scores, and reading errors. Membership in the two clusters is consistent pre- and post-rehabilitation in all but one case. Clustering is most evident for reading rate and reading errors and less so for saccade scores.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Intramolecular homologous recombination of linearized plasmids in Escherichia coli K12.

The efficacy of linear DNA as a substrate for general homologous recombination was demonstrated using BamHI-linearized pKLC8.5, a plasmid that carries internal direct repeats flanking the unique BamHI site. An analogous plasmid, pKLC2.31, was used in a parallel and comparative study of intramolecular homologous recombination in circular DNA substrates. When the rec+ wild-type strain, AB1157, and its isogenic rec- derivatives were transformed with linear pKLC8.5 DNA, intramolecular homologous recombination was independent of recA, recB, recN, recO and exonuclease III (xth-1) functions. Although the recBCsbcA and recBCsbcBC cells were both very recombination proficient, only linear but not circular DNA was used as substrate for intramolecular homologous recombination in the recBCsbcA cells. In both the recBCsbcA and recBCsbcBC genetic backgrounds, the recombination frequencies for linearized pKLC8.5 DNA were 100%. A notable difference between the two strains was that none of the recBCsbcA transformants obtained with circular pKLC8.5 DNA were Tcs recombinants, whereas 11% of the corresponding recBCsbcBC transformants were Tcs recombinants. The sbcB mutation was responsible for the recombination proficiency of the recBCsbcBC cells. Unlike the case in recBCsbcA cells, intramolecular homologous recombination of linear DNA in the recBCsbcBC cells was dependent on recA and recF as well as recN and recO gene functions, but was independent of recJ and recL gene functions.

DNA, Bacterial↗
PubMed1990

Nuclear freedom and students' sense of efficacy about prevention of nuclear war.

Questionnaire and interview responses of young New Zealanders, living in a nuclear-free zone, reveal general concerns about nuclear war but relatively little personal, subjective worry. Their sense of citizen and national efficacy is stronger than that reported by youngsters in other countries, but is not reflected in feelings of self-efficacy. Responses are compared to those reported in North American and European research, and the importance of adult role models in facilitating children's belief in the efficacy of antinuclear activities is highlighted.

Adolescent↗
PubMed1989

Localization of epidermal growth factor precursor in tooth and lung during embryonic mouse development.

The murine epidermal growth factor (EGF) precursor is a 1217 amino acid protein which contains mature EGF (amino acid residues 977-1029) as well as eight EGF-like repeats. Although the highest levels of EGF are found in the adult male mouse submandibular gland, the results of in situ hybridization studies and mRNA analyses suggest that EGF precursor mRNA is synthesized in several adult mouse tissues including the lung and the incisor. To determine if EGF precursor gene expression is intrinsic to the developmental program for either embryonic tooth or lung organogenesis, sense and antisense oligodeoxyribonucleotide probes corresponding to amino acids 1070-1081 of the precursor were used to localize cellular sites of synthesis of EGF precursor mRNA by in situ hybridization. Antibodies directed against amino acid residues 348-691 of the precursor were used in immunodetection techniques to identify either EGF precursor protein or processed derivatives. In contrast to earlier reports indicating that embryonic mouse tissues do not synthesize EGF precursor mRNA, we found that EGF precursor mRNA is present in clusters of ectoderm-, mesoderm-, and ectomesenchyme-derived cells associated with embryonic teeth and lung organs. Moreover, epitopes common to the EGF precursor were immunolocalized in both the epithelial and mesenchymal tissues of embryonic mouse tooth and lung organs. These results suggest that the EGF precursor and/or motifs contained within the precursor molecule, including mature EGF, may play an instructive or permissive role in epithelial-mesenchymal interactions pursuant to organogenesis.

Aging↗
PubMed1989

Lamellar body formation precedes pulmonary surfactant apoprotein expression during embryonic mouse lung development in vivo and in vitro.

The purpose of this investigation was to determine whether lamellar inclusion body (LB) formation and surfactant apoprotein (SP-35) production are directly coordinated by temporal and positional information during development. In the present study we report a comparison between embryonic B10.A mouse lung morphogenesis and cytodifferentiation in vivo with that observed during organ culture in serumless medium. Precursor LB were first detected at embryonic day 12 (E12d), and progressively larger numbers and forms were produced during subsequent differentiation of respiratory alveolar duct epithelium. SP-35 was first detected during the canalicular period (E16.5d). Lung cultures (E12d) showed pseudoglandular and canalicular periods of morphogenesis, and both ciliated epithelial and type II cell differentiation. Nonciliated cells produced increasing numbers of lamellar inclusion bodies throughout the culture period. SP-35 was detected at 9 days in vitro (d.i.v.). These observations indicate (i) precursor LB formation precedes SP-35 expression and is not dependent on apoprotein synthesis; (ii) E12d lung development in vitro using serumless medium proceeds at a rate equivalent to 0.5 days in vivo through 11 d.i.v.; and (iii) morphogenesis and differentiation occur in the absence of exogenous hormones and growth factors. The cell-cell interactions that play a role in morphogenesis and cell differentiation appear to be intrinsic to the developmental program for embryonic lung development and are likely to be mediated by autocrine and/or paracrine factors.

Apoproteins↗
PubMed1988

Factors influencing the expression of dental extracellular matrix biomineralization.

The forming tooth organ provides a number of opportunities to investigate the cellular and molecular biology of cell-mediated extracellular matrix (ECM) biomineralization. Regulatory processes associated with tooth formation are being investigated by identifying when and where cell adhesion molecules (CAMs), substrate adhesion molecules (SAMs), dentine phosphoprotein and enamel gene products are expressed during sequential developmental stages. In vitro organotypic culture studies in serumless, chemically-defined medium, have shown that instructive and permissive signalling are required for both morphogenesis and cytodifferentiation. Intrinsic developmental instructions (autocrine and paracrine factors) act independently of long-range hormonal or exogenous growth factors and mediate morphogenesis from the initiation of the dental lamina to the crown stages of tooth development. This review summarizes the results of studies using experimental embryology, recombinant DNA technology and immunocytology to elucidate mechanisms responsive to instructive epithelial-mesenchymal interactions associated with ameloblast differentiation, odontoblast differentiation, and dentine and enamel ECM biomineralization.

Animals↗
PubMed1988

Molecular determinants of cranial neural crest-derived odontogenic ectomesenchyme during dentinogenesis.

Positional information on tooth morphogenesis is investigated by the identification of when and where phenotypic markers are expressed during odontogenesis. This temporal and positional information is correlated with the instructive and permissive signaling required for both dentinogenesis and amelogenesis. Of particular interest is the establishment of a map for the cranial neural crest-derived dental papilla ectomesenchyme and the odontoblast cell lineages. The expression of ectomesenchyme-derived cytotactin, dentin phosphoprotein, and epithelial-derived enamel proteins was studied in mice using embryonic, fetal, and postnatal mandibular first molar tooth organ development. This review summarizes the observations in the context of instructive epithelial-mesenchymal interactions and suggests that amelogenesis imperfecta and dentinogenesis imperfecta may in part be explained by alterations in these differentiation markers. Recombinant DNA methods should facilitate future investigations of these inherited dental disorders.

Animals↗
PubMed1987

Effects of retinal dopamine depletion on the rabbit electroretinogram.

This study evaluated the effects of intravitreal injections of 300 micrograms of 6-hydroxydopamine (6-OHDA) on electroretinogram (ERG) amplitudes and implicit response times of adult pigmented rabbits. One eye was injected intravitreally with 300 micrograms 6-OHDA and 600 micrograms ascorbic acid in a 0.3 ml 0.9% NaCl solution; the fellow eye received a similar solution containing only 600 micrograms ascorbic acid. Following this treatment ERG recordings were performed at 1, 4, and 7 days. After the last recordings, animals were sacrificed and retinas were isolated for biochemical analyses. Significant and progressive reductions in retinal concentrations of dopamine (DA) and its main metabolites homovanillic acid (HVA), and dihydroxyphenylacetic acid (DOPAC) were found in treated retinas. Concentrations of norepinephrine (NE), serotonin (5HT), and 5 hydroxyindoleacetic acid (5-HIAA) were not affected, thus demonstrating the specific neurotoxic action of 6-OHDA on retinal dopaminergic neurons. Concurrently, significant increases in ERG a- and b-wave amplitudes as well as in implicit response times were observed. These electrophysiological changes were progressive reaching a maximum 7 days after intravitreal injections. Changes in b-wave amplitudes and response times were more pronounced at low intensities of stimulation. These results clearly show that, in rabbits, selective decreases in retinal DA concentrations result in pronounced ERG changes, which offer additional evidence supporting a role for this transmitter in lateral inhibition in the retina.

Animals↗
PubMed1987

The human Mr 90,000 heat shock protein and the Escherichia coli Lon protein share an antigenic determinant.

1. A monoclonal antibody (TG7A) reacts with a Mr 90,000 mammalian protein, accumulating during virus infection and heat shock. 2. This protein is encoded by a member of the Mr 90,000 heat shock gene family present in a range of organisms form yeast to man. 3. The antibody also recognises a Mr 94,000 protein in E. coli which similarly accumulates in virus infection and heat shock. 4. This protein has been identified as the Lon protease of E. coli. 5. The shared epitope and similar stress inducibility of the two proteins suggests that a functional and/or evolutionary relationship exists between them.

ATP-Dependent Proteases↗
PubMed1984

Isolation and characterization of spontaneous srl-recA deletion mutants in Escherichia coli K-12.

A method was developed for the isolation of spontaneous mutants of Escherichia coli K-12 with deletions extending from the srl operon to the adjacent recA gene. The srl-recA deletion mutants were extremely sensitive to dNA-damaging agents; unable to support growth of the feckless red gam mutant lambda bio11; and recombination-deficient in transduction and in conjugation. They therefore resembled recA point mutants such as recA13. The existence of these recA deletion mutants shows that the recA gene is not essential for viability.

Bacteriological Techniques↗
PubMed1984

Ultrastructural studies of attachment site formation in aortic smooth muscle cells cultured on collagen-hydroxyethylmethacrylate hydrogels.

Hydroxyethylmethacrylate (HEMA) hydrogels have a peculiar crater-like topography which renders them ideal for studying cell-to-substrate contact formation. The hydrogel is quite suitable for such studies since it is transparent, which allows for light microscopic observations, it is not toxic, and it will support cell growth only when an additional protein component such as collagen is integrated into its surface. Cultured rabbit aortic smooth muscle cells (SMC) were grown on collagen-HEMA hydrogels, and the ultrastructure of developing cell attachment sites was studied. By 3 hr after cell seeding, both the rounded and the spreading SMC appeared anchored to the hydrogel via extracellular connective tissue-like material. The fully formed attachment site present at 5-8 days was characterized by large bundles of intracellular myofilaments inserting onto areas of increased electron density along the plasmalemmal membrane; large amounts of extracellular connective tissue-like material also appeared attached to the areas of increased electron density. Fully formed cell substratum attachment sites were not observed when either elastin-HEMA hydrogels or hydrogels polymerized in the absence of protein were employed.

Actin Cytoskeleton↗
PubMed1984

Treatment of hereditary hemorrhagic telangiectasia by Nd-YAG laser photocoagulation.

Hereditary hemorrhagic telangiectasia (Rendu-Osler-Weber disease) is an inherited abnormality of the vasculature characterized by abnormal subepidermal vessels. Frequent, sometimes severe, epistaxis often requiring blood transfusions is present in most patients. Septal dermatoplasty and estrogen have proved to be the most successful therapies. However, the frequency of failure in treatment has stimulated a search for an alternative therapy. The Nd-YAG laser was used at low-power settings (20-25 W) to treat 6 patients with hereditary hemorrhagic telangiectasia, all of whom had been treated previously using other modalities. Laser photocoagulation diminished the frequency and severity of hemorrhage in 5 of 6 patients without complications (6 to 9 month follow-up period). The Nd-YAG laser may be used repeatedly when new accessible lesions arise, and it appears to be a useful therapeutic option for this disease that is difficult to treat.

Adult↗
PubMed1983

Ultrastructural effects of Clostridium difficile toxin B on smooth muscle cells and fibroblasts.

The mechanism by which Clostridium difficile toxin B causes cells in culture to round was investigated. Cultured human lung fibroblasts and rabbit aortic smooth muscle cells were treated with partially purified or purified toxin B and monitored by light and transmission electron microscopy (TEM). Both preparations caused progressive cell rounding which correlated with disorganization of actin-containing myofilament bundles. Thin myofilaments became fragmented and finally disappeared (after 24 h) and dense bodies became more prominent, while all other organelles appeared unaffected.

Animals↗