Biomedical subjects

K May

Publications and source records attributed to K May.

At least 37 records · Page 2Linked to original sources

PubMed1998

Expression of two consecutive genes of a secondary metabolic pathway in transgenic tobacco: molecular diversity influences levels of expression and product accumulation.

We have created a population of transgenic tobacco plants carrying cDNAs encoding two consecutive enzymes from early stages in monoterpenoid alkaloid biosynthesis in Catharanthus roseus. The cDNAs, encoding tryptophan decarboxylase (tdc) and strictosidine synthase (str1) together with a selectable marker gene, were introduced on a single transforming plasmid into tobacco leaves by particle bombardment. Analysis of 150 independent transgenic plants at the DNA and RNA levels demonstrated a range of integration events and steady-state transcript levels for the tdc and str1 transgenes. Southern blot analysis indicated that the tdc and str1 transgenes were integrated at least once in all 150 transformants giving a 100% co-integration frequency of the two unselected genes carried on the same plasmid. A comparison of Southern and northern data suggested that in 26% of the plants, both tdc and str1 transgenes were silenced, 41% demonstrated a preferential silencing of either the tdc or the str1 transgene, with the remaining 33% of the plants expressing both transgenes. We observed no clear correlation between the number of integration events of a specific transgene and the levels of accumulated transcript. Twenty plants representing the range of molecular diversity in the transgenic population were selected for further analysis. Seeds were collected from self-fertilised transformants and germinated on medium containing kanamycin. Seedlings were harvested after 7 weeks and TDC and STR1 enzymatic assays were carried out. We observed a 24- and 110-fold variation in levels of TDC and STR1 activities, respectively. Our data correlate molecular diversity with biochemistry and accumulation of end-product and provide a detailed molecular and biochemical characterization of transgenic plants transformed with a single plasmid carrying two genes of secondary metabolism.

Alkaloids↗

PubMed1998

The effects of restorative material and location on the detection of simulated recurrent caries. A comparison of dental film, direct digital radiography and tuned aperture computed tomography.

OBJECTIVES: To explore the effects of restorative material and lesion location on the detection of recurrent caries using intra-oral film, direct digital radiography and unprocessed and iteratively restored tuned aperture computed tomography (TACT) images. METHODS: An in vitro model with simulated lesions in half the surfaces studied was used. Lesions of varying sizes were created at either the intersection of the facial or lingual wall and the gingival floor or on the gingival floor midway between the facial and lingual walls in the proximal boxes of 24 molar teeth with MOD inlay preparations that had been restored with amalgam, radiopaque composite or radiolucent composite. RESULTS: Sensitivity and specificity values based on restoration were: amalgam: 59 and 87%; radiopaque composite: 68 and 78%; radiolucent composite: 36 and 93%; based on lesion location, mid-cervical floor region: 51 and 97%; point angle region: 44 and 90%; based on imaging modality, film: 40 and 85%; digital: 44 and 76%; unprocessed TACT slices: 50 and 87%, iteratively restored TACT images: 83 and 96%. Iteratively restored TACT images had the best intra- and inter-reader agreement. CONCLUSIONS: The use of restorative materials with a density approximating that of enamel is more effective for the detection of recurrent caries. Lesions located at the buccal point angle or mid-gingival floor are more easily detected than at the lingual point angle region. The sensitivity and specificity of TACT and iteratively restored TACT images were superior to those of film and direct digital images.

Analysis of Variance↗

PubMed1998

Regulation of ciliary beat frequency by both PKA and PKG in bovine airway epithelial cells.

Ciliary beating is required for the maintenance of lung mucociliary transport. We investigated the role of cyclic nucleotide-dependent protein kinases in stimulating ciliary beat frequency (CBF) in bovine bronchial epithelial cells (BBECs). cAMP-dependent protein kinase (PKA) activity and cGMP-dependent protein kinase (PKG) activity were distinguished after DEAE-Sephacel chromatography of BBEC extracts. cAMP levels and PKA activity are increased in BBECs stimulated with 0.01-1 mM isoproterenol, with a corresponding increase in CBF. cGMP levels and PKG activity are increased in BBECs stimulated with 0.1-10 microM sodium nitroprusside, with a corresponding increase in CBF. Direct protein kinase-activating analogs of cAMP and cGMP (dibutyryl cAMP and 8-bromo-cGMP, respectively) also activate their specific kinases and stimulate CBF. Preincubation of BBECs with inhibitors of PKA or PKG [KT-5720 or Rp-8-(p-chlorophenylthio)-guanosine 3',5'-cyclic monophosphothioate] results in the inhibition of specific kinase activity as well as in the inhibition of CBF. These studies suggest that the activation of either PKA or PKG can lead to the stimulation of CBF in bovine airway epithelium.

Animals↗

PubMed1998

Tuned aperture computed tomography and detection of recurrent caries.

This study compared the diagnostic efficacy of four imaging modalities for the detection of artificially induced recurrent caries: intraoral film, direct digital bitewing images, tuned apertuce computed tomography (TACT) slices and iteratively restored TACT images using an in vitro model. Twenty-four posterior teeth were prepared for MOD inlay restorations. These were then restored with different restorative materials (amalgam, Herculite and Durafill). Lesions were simulated in half the number of surfaces studied. These lesions were created either at the intersection of the facial or lingual walls and the gingival floor or on the gingival floor midway between the facial and lingual walls in the proximal boxes of the MOD restorations. Analysis of observations from 8 observers using ROC curve reveal the superior diagnostic efficacy with TACT iteratively restored images (Az for TACT iteratively restored images = 0.9171, TACT slices = 0.7052, Film = 0.6608, direct digital images = 0.5979). ANOVA revealed significance with respect to the imaging modality used (p < 0.0001). The results suggest that TACT images hold promise as a more effective imaging modality than film or direct digital systems for detection of recurrent caries.

Analysis of Variance↗

PubMed1997

Mussels and algae as bioindicators for long-term tendencies of element pollution in marine ecosystems.

Results of more than ten years of experience in the determination of metals in mussels and algae collected in the North Sea and the Baltic Sea are presented. The various elements determined here are Hg, As, Se, Cd, Pb, Cu, Na, K, S, P, Zn, Mn, Fe, Sr, Ca, Ba, Mg, Tl, Ni, Co using techniques such as cold vapor AAS, INAA, hydride generation AAS, electrothermal AAS, ICP-AES, IDMS and stripping voltammetry. The results indicate the occurrence of three groups of elements with respect to long-term tendencies of their concentrations. In the first group, the concentrations in both mussels and algae varied in the same manner; in the second group no change was observed in either matrix while in the third group, the concentrations of elements changed in an opposite manner.

Animals↗

PubMed1997

The effect of pentoxifylline on spontaneous and experimental metastasis of the mouse Neuro2a neuroblastoma.

Pentoxifylline (PTX) has been reported to have both direct and indirect anti-tumor effects in experimental tumor models. We studied the effect of PTX on (1) the proliferation of Neuro2a mouse neuroblastoma cells in vitro and in vivo, (2) spontaneous and experimental metastasis, (3) tumor cell membrane fluidity and (4) adhesion to a fibronectin-coated surface. PTX significantly reduced the proliferation of Neuro2a cells in vitro as determined by DNA measurement (P < 0.01) and total cell count (P < 0.02). In vivo, PTX reduced the growth of subcutaneously transplanted primary tumors in syngeneic A/J mice (P < 0.01; n = 15). All seven animals (100%) receiving intravenous tumor cells developed extensive liver metastasis. In contrast, only 1/11 (9%) of animals pre-treated with oral PTX and injected with PTX-treated cells developed liver metastases. Of five mice receiving PTX-treated cells without oral pretreatment of PTX, two out of five (40%) developed liver metastases. There was a slight, but not significant (P = 0.08) increase in both experimental and spontaneous lung metastases formation in PTX-treated animals. However, tumor nodule formation on the lung surface was inefficient. PTX also increased membrane fluidity of the Neuro2a cells and significantly decreased tumor cell adhesion to fibronectin-coated microtiter wells (P < 0.01). We conclude that PTX has a cytostatic effect on the Neuro2a mouse neuroblastoma and exerts an anti-tumor effect on liver metastases following intravenous administration of neuroblastoma cells. Whether these results are directly related to the changes in membrane properties caused by pentoxifylline remains to be established.

Animals↗

PubMed1996

The importance of platelets in the expression of monocyte tissue factor antigen measured by a new whole blood flow cytometric assay.

Previous methods for the determination of monocyte tissue factor (TF) have been technically complex, difficult to standardize, prone to spuriously elevated results and difficult to implement in a clinical laboratory environment. We report the development of a two-color whole blood cytometric technique that overcomes many of these disadvantages. The assay uses small volumes of citrated blood (1.0 ml), can be performed in under one hour (if endotoxin stimulation is not performed), is reproducible (CV = 5%) and uses methodology commonly available in clinical laboratories. Baseline (mean +/- SD) expression of monocyte TF in normal subjects was very low (1.1 +/- 0.95%, Mean Fluorescence [Mean FL] 0.20 +/- 0.01) making relatively small increases easy to detect. Monocyte TF expression following endotoxin (LPS) stimulation for 1 h was 34.6 +/- 11.2% (Mean FL 0.32 +/- 0.04). LPS-stimulated activity varied between subjects (21-68%) but was remarkably consistent for individual subjects (CV = 5.4%). Stimulated monocyte TF expression was directly proportional to the platelet count and was reduced by platelet protective anticoagulants and by ingestion of aspirin. Non LPS-stimulated monocyte TF was markedly increased, in a dose-dependent manner, by adding collagen to whole blood. This was apparently associated with platelet-monocyte binding and could be abolished by anti-P-Selectin. We conclude that the whole blood flow cytometric assay of monocyte TF may be a valuable tool for clinical use and a useful model system for evaluating the humoral and cellular factors governing monocyte TF expression in a natural environment.

Adult↗

PubMed1996

[Deaths from asthma, bronchitis and pulmonary heart disease in Warsaw in the years 1993-1994].

By the regular checking the death certificates in the municipal offices in 7 districts of Warsaw, the morality rate from asthma has been established as 2.98/100.000, from chronic bronchitis as 8.71/100.000 and from pulmonary heart disease as 6.27/100.000. During one year of this survey only 15 deaths (4.7%) from these diseases were below age of 50.67% of patients died in hospitals and 22 (7%) died suddenly (at home). In general, deaths reported as the results of COLD were only 1.59% of the total number of deaths in Warsaw (21.530). 6.9% of all death certificates were without clinical diagnosis (Number 798 of ICD)-described as "natural death", "death before doctor's arrival" or "noncriminal death". Authors discuss the problem of over- and under-diagnosis of asthma as the cause of death, the historical background of asthma mortality and also put the question of the righteousness of regard the pulmonary heart disease as the primary cause of death.

Aged↗

PubMed1994

Low density lipoprotein receptors in rat adipose cells: subcellular localization and regulation by insulin.

The distribution of LDL receptors within subcellular compartments of isolated rat adipose cells and the effects of insulin on their expression have been assessed. By immunoblotting with specific anti-rat LDL receptor antibodies, LDL receptors were 2.3- and 4.5-fold enriched in endoplasmic reticulum-rich high-density microsomes (HDM) and Golgi complex-rich low-density microsomes (LDM), respectively, compared to plasma membranes (PM). This distribution was similar in cultured cells in which total receptors were increased 2.5-fold compared to freshly isolated cells. After correction for enzyme recoveries, LDL receptors were distributed approximately 4% in HDM, approximately 73% in LDM, and approximately 23% in PM. Insulin decreased total LDL receptors in adipose cells approximately 44%, with a 48% and 49% decrease in HDM and LDM, respectively, without any changes in PM. In contrast, insulin caused an increase of glucose transporters in PM while also decreasing glucose transporters in LDM. When adipose cells were depleted of potassium to inhibit receptor-mediated endocytosis, insulin again caused a decrease of LDL receptors in LDM but now increased LDL receptors in PM. Insulin increased the rate of LDL receptor synthesis approximately 24%, but decreased their half life approximately 40%. Thus, in isolated adipose cells the majority of LDL receptors appear to be located in an intracellular compartment that co-sediments with the Golgi complex rather than located in the PM. The LDL receptors localized in intracellular compartments seem to be functionally regulated as insulin acutely diminishes the number of receptors by apparently accelerating their rate of degradation through, as yet, incompletely determined mechanisms.

Adipose Tissue↗

PubMed1993

Destabilizing effects of replacing a surface lysine of cytochrome c with aromatic amino acids: implications for the denatured state.

A series of mutations at the highly solvent-exposed lysine 73 of iso-1-cytochrome c have been prepared by site-directed mutagenesis. These mutations were designed to probe denatured-state effects on the unfolding equilibrium of this protein. The hydrophilic amino acid Lys was replaced with the hydrophobic amino acids Met, Tyr, Phe, and Trp. The idea was to induce stabilizing hydrophobic interactions in the unfolded state, while having little effect on the folded-state energy due to the high solvent exposure of this site. Fourier transform infrared spectral analyses indicate that none of these mutations significantly affect the native fold of the protein. The stability of each protein to guanidine hydrochloride denaturation was monitored at 25 degrees C by circular dichroism spectroscopy. All four hydrophobic mutants decreased the value of delta Go uH2O, the free energy of unfolding of the protein in the absence of denaturant, by 1.0-1.5 kcal/mol. The delta Go uH2O values for these proteins correlate linearly (correlation coefficient of 0.98) with the hydrophobicity of the amino acid at position 73 of the sequence. These data are consistent with the idea that the position-73 mutants are more buried in the denatured state than in the native state, suggestive of a compact denatured state where such interactions would be possible.

Base Sequence↗

PubMed1993

Y chromosome mosaicism in the gonads, but not in the blood, of a girl with the Turner phenotype and virilized external genitalia.

We describe a girl with virilized external genitalia and phenotypic features of Turner syndrome whose blood karyotype is 45,X. The presence of dysgenetic testicular tissue was confirmed by pathology. Using PCR and primers for the distal long arm, centromere and short arm of the Y chromosome, Y chromosome material was detected in her gonads but not in blood.

Base Sequence↗

PubMed1992

Preparation of the renal function and imaging agent 99mTc-MAG3 starting from S-unprotected mercaptoacetyltriglycine.

A new approach that obviates inconvenient heating of the labelling solution when preparing the renal function and imaging agent 99mTc-MAG3 is described. The labelling procedure involves reduction of 99mTc-generator eluate with stannous chloride in alkaline solution in the presence of S-unprotected mercaptoacetyltriglycine (MAG3) and the co-ligand sodium tartrate, followed by neutralization with a phosphate buffer solution. After optimization of the kit preparation the radiochemical purity of the radiopharmaceutical amounts to greater than 98%. During the labelling process intermediate Tc-species occur.

Oligopeptides↗

PubMed1991

Home tests to monitor fertility.

Industry has been intimately involved in the development of products used in the monitoring of fertility at home. The perspective of industry and the development of such tests including their rationale are presented. The methods taken by industry to utilize current technology in the development of reliable, rapid, one-step tests for urinary human chorionic gonadotropin and luteinizing hormone and the subsequent expansion into other areas are covered.

Antibodies, Monoclonal↗

PubMed1991

Evaluation of effectiveness and tolerability of isosorbide mononitrate during a three-year period in patients with angina pectoris.

The antianginal effect and tolerability of isosorbide mononitrate (ISMN), 20 mg 2-3 times daily, orally were investigated in an open study in 28 patients, suffering from coronary heart disease and stable angina pectoris. Ergometric exercise tests were carried out before treatment and 2 h after drug intake, every 3 months during the first year and at 6-month intervals during the following 2 years. At the conclusion of the 3-year study the reduction of ST-segment depression, which had amounted to 58% after 1 year, could be improved to 78% (p less than 0.01). The frequency of angina was markedly reduced during the treatment with ISMN. While 14 of the patients had more than 3 episodes per day prior to the study, 16 patients were symptom-free at the end of the three years' therapy, and none of the patients had more than 1 or 2 attacks per day. The consumption of sublingual nitroglycerin diminished by 94% after one year and by 98% after 3 years of therapy (p less than 0.01). Headache was the only adverse effect observed in some of the patients (at the initiation of the treatment only). In conclusion this study demonstrated (1) the good tolerability of ISMN, at the doses used, and (2) the fact that the antianginal efficacy may be enhanced during the course of the therapy.

Adult↗

PubMed1990

The primary structure of a halorhodopsin from Natronobacterium pharaonis. Structural, functional and evolutionary implications for bacterial rhodopsins and halorhodopsins.

We cloned and sequenced the gene coding for the polypeptide of a halorhodopsin in Natronobacterium pharaonis (named here pharaonis halorhodopsin). Peptide sequencing of cyanogen bromide fragments, and immunoreactions of the protein and synthetic peptides derived from the COOH-terminal gene sequence, confirmed that the open reading frame is the structural gene for the pharaonis halorhodopsin polypeptide. The flanking DNA sequences, as well as those for other bacterial rhodopsins, were compared to previously proposed archaebacterial consensus sequences. In pairwise comparisons of the open reading frame with DNA sequences for bacterio-opsin and halo-opsin from Halobacterium halobium, silent divergences (mutations/nucleotide at codon positions which do not result in amino acid changes) were calculated. These indicate very considerable evolutionary distance between each pair of genes. In spite of this, the three protein sequences show extensive similarities, indicating strong selective pressures. Conserved and conservatively replaced amino acid residues in all three proteins identify general features essential for ion-motive bacterial rhodopsins, responsible for overall structure and chromophore properties. Comparison of the bacteriorhodopsin sequence with those of the two halorhodopsins, on the other hand, identifies features involved in their specific (proton and chloride ion) transport functions.

Amino Acid Sequence↗

PubMed1990

Analysis of non-disjunction in sex chromosome tetrasomy and pentasomy.

X-linked DNA markers were used to determine the parental origin of the additional sex chromosomes in eight individuals with sex chromosome tetrasomy or pentasomy. In all cases studied, one parent contributed a single sex chromosome while the other parent contributed three or four sex chromosomes. Thus, it seems likely that most, if not all, sex chromosome tetrasomy and pentasomy is attributable to successive non-disjunctional events involving the same parent.

Female↗

PubMed1990

Isolation, identification, and characterization of a palladium complex in the catalytic deprotection of a protected peptide.

The final catalytic deprotection in the large scale synthesis of thymopentin (Arg-Lys-Asp-Val-Tyr) produced an impurity which had not previously been observed. Isolation by preparative HPLC and spectroscopic characterization led to a postulated structure of the impurity as the 1:1 thymopentin-palladium complex. A complex corresponding to the proposed structure was independently synthesized and shown to have identical chromatographic and spectroscopic properties with the isolated material. Proton and carbon (13) NMR were used to determine the coordination sites of the peptide with palladium. The susceptibility of the complex to hydrogenation indicated a possible source for its formation.

Catalysis↗

PubMed1990

The parental origin of the missing or additional chromosome in 45,X and 47,XXX females.

We used X-linked DNA polymorphisms to study the parental origin of the missing or additional X chromosome in conceptuses with 45,X or 47,XXX chromosome constitutions. Fifty-three (80.3%) of 66 cases of sex chromosome monosomy had a maternal X, demonstrating that paternal sex chromosome loss is the most common error leading to this condition. In contrast, 29 (93.5%) of 31 47,XXX cases resulted from maternal nondisjunction. In studies of parental age, we detected no obvious parental age effect for sex chromosome monosomy. For the 47,XXXs, there was an apparent association between increasing maternal age and errors at maternal meiosis I, but not maternal meiosis II. In other analyses, we detected no obvious effect of parental origin on the phenotype of either 45,X or 47,XXX conceptuses, at least as measured by comparing the ratio of paternal:maternal errors among different ascertainment categories.

Aneuploidy↗