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Biomedical subjects

A Kremer

Publications and source records attributed to A Kremer.

At least 37 records · Page 2Linked to original sources
PubMed2001

Sugar-based tertiary amino gemini surfactants with a vesicle-to-micelle transition in the endosomal pH range mediate efficient transfection in vitro.

Novel reduced sugar gemini amphiphiles linked through their tertiary amino head groups via alkyl spacers of 4 or 6 carbons, and with varying (unsaturated) alkyl tail lengths of 12--18, have been synthesized and tested for transfection in vitro in an adherent Chinese hamster ovary cell line (CHO-K1). Transfection efficiencies peaked at 2.7 times that of the commercial standard Lipofectamine Plus/2000 for pure solutions of the compound bearing unsaturated (oleyl) alkyl tails. For those compounds bearing saturated alkyl tails, transfection efficiency peaked at a tail length of 16, at a level similar to Lipofectamine Plus/2000. All of the amphiphiles formed bilayer vesicles at physiological pH. Some of the amino groups at the surface were protonated, and vesicles therefore bore a positive charge. Increased protonation with reduced pH resulted in greatly increased monomer solubility and a morphology change from vesicle to micelle at characteristic pH values, dependent on the tail length. For the compounds promoting high transfection efficiency, this characteristic pH was within the range found in the endosomal compartment (7.4--4.0). Formation of mixed micelles between gemini surfactant and membrane phospholipids at reduced pH may therefore provide a method of endosome rupture and subsequent escape of entrapped DNA, thus discarding the need for extra fusogenic or endosomolytic agents. The positive charge on the vesicles at physiological pH drives the colloidal association with DNA. Small angle X-ray scattering measurements indicate that lamellar aggregates are formed, which have a d spacing of 48--54 A. Preliminary differential scanning calorimetric measurements suggest that reduction of pH causes a disordering of the hydrocarbon region of the DNA-surfactant complex.

Animals↗
PubMed2001

[Economic assessment of iron deficiency. Replacement of ferritin and serum iron by other parameters].

Economic assessment of iron deficiency. Replacement of serum iron and ferritin by other parameters. Serum iron and ferritin are still widely used parameters for the assessment of iron deficiency, in spite of their poor diagnostic performance. Compared to the combined use of ferritin, zinc protoporphyrin and soluble transferrin receptors an increase of the percentage of hypochromic erythrocytes (PEH) was found to be highly sensitive and specific for iron deficiency. We suggest to use it in a two phase strategy. Normal PEH excludes iron deficiency. Increased PEH may be confirmed by zinc protoporphyrin and/or soluble transferrin receptors.

Anemia, Hypochromic↗
PubMed2000

Cloning and characterization of human histone deacetylase 8.

To date, seven different human histone deacetylases (HDACs) have been identified, which fall into two distinct classes. We have isolated and characterized a cDNA encoding a novel human HDAC, which we name HDAC8. HDAC8 shows a high degree of sequence similarity to HDAC1 and HDAC2 and thus belongs to the class I of HDACs. HDAC8 is expressed in a variety of tissues. Human cells overexpressing HDAC8 localize the protein in sub-nuclear compartments whereas HDAC1 shows an even nuclear distribution. In addition, the HDAC8 gene is localized on the X chromosome at position q13, which is close to the XIST gene and chromosomal breakpoints associated with preleukemia.

Amino Acid Sequence↗
PubMed2000

Pharmacokinetics of levamisole in cancer patients treated with 5-fluorouracil.

PURPOSE: To investigate the pharmacokinetics of levamisole and a metabolite, p-hydroxylevamisole in patients with colorectal cancer treated with 5-fluorouracil (5-FU). METHODS: Following an intravenous bolus dose of 5-FU, 20 patients with colorectal cancer received oral doses of 50 mg levamisole every 8 h for 3 days. Immediately after the last dose, blood and urine samples were collected over at least an 8-h period. Samples were assayed for levamisole and p-hydroxylevamisole by GC/MS. The levamisole plasma and urine data were subjected to pharmacokinetic analysis using NONMEM software. RESULTS: Substantial interpatient variability was observed in the levamisole plasma concentration-time curves. Patients with cardiovascular or gastrointestinal complications demonstrated altered absorption of levamisole. Pharmacokinetic parameter values for levamisole were similar to those obtained previously in healthy subjects and other cancer patients. CONCLUSIONS: There is no evidence that the pharmacokinetics of levamisole are altered by 5-FU administered immediately prior to levamisole administration. The relationship between the substantial intersubject variability in levamisole plasma concentration-time curves and clinical outcome following 5-FU/levamisole adjuvant chemotherapy should be examined.

Adjuvants, Immunologic↗
PubMed2000

A phase II pilot study of KW-2189 in patients with advanced renal cell carcinoma.

BACKGROUND: KW-2189 is a semi-synthetic, water-soluble analog of duocarmycin B2, a new class of potent antitumor antibiotics produced by streptomyces, with improved in vitro antitumor potency. PATIENTS AND METHODS: Forty patients with pathologically confirmed metastatic renal cell carcinoma were treated in this multicenter, open-label phase II trial. All patients received 0.4 mg/m2 KW-2189 as an i.v. infusion for Cycle I. Cycles were repeated every 5 to 6 weeks with escalations to 0.5 mg/m2 in the absence of significant toxicity or disease progression. RESULTS: No patient had an objective response. The most common drug-related toxicity was hematological-delayed neutropenia and thrombocytopenia, with recovery by week 6. Non-hematologic toxicity consisted of mild to moderate fatigue, nausea and vomiting, and anorexia that was generally manageable. CONCLUSIONS: KW-2189 in this dose and schedule has a predictable safety profile of reversible myelosuppression. No activity in metastatic renal cell carcinoma was demonstrated.

Antibiotics, Antineoplastic↗
PubMed2000

Comparison of microsatellites and amplified fragment length polymorphism markers for parentage analysis.

This study compares the properties of dominant markers, such as amplified fragment length polymorphisms (AFLPs), with those of codominant multiallelic markers, such as microsatellites, in reconstructing parentage. These two types of markers were used to search for both parents of an individual without prior knowledge of their relationships, by calculating likelihood ratios based on genotypic data, including mistyping. Experimental data on 89 oak trees genotyped for six microsatellite markers and 159 polymorphic AFLP loci were used as a starting point for simulations and tests. Both sets of markers produced high exclusion probabilities, and among dominant markers those with dominant allele frequencies in the range 0.1-0.4 were more informative. Such codominant and dominant markers can be used to construct powerful statistical tests to decide whether a genotyped individual (or two individuals) can be considered as the true parent (or parent pair). Gene flow from outside the study stand (GFO), inferred from parentage analysis with microsatellites, overestimated the true GFO, whereas with AFLPs it was underestimated. As expected, dominant markers are less efficient than codominant markers for achieving this, but can still be used with good confidence, especially when loci are deliberately selected according to their allele frequencies.

DNA, Plant↗
PubMed2000

Spatial and temporal distribution of chloroplast DNA polymorphism in a tropical tree species.

The level and the spatial organization of chloroplast DNA polymorphism were investigated in Dicorynia guianensis Hamshoff (Caesalpiniaceae) at different spatial and temporal scales. D. guianensis is a canopy tree of the rain forest that is distributed throughout the Guiana plateau in small aggregates. Twelve different haplotypes were identified using restriction analysis of polymerase chain reaction (PCR) amplified fragments of the chloroplast genome. When populations from different areas of French Guiana were compared, a clear geographical pattern of haplotype frequencies was identified along the Atlantic coast. This pattern is most likely the result of the restriction-expansion dynamics of the tropical forest during the Quaternary. At the local level, D. guianensis was characterized by a high level of within population diversity. Maintenance of within population diversity results from the dynamics of the aggregates; stochastic demography associated with the turnover of aggregates generates genetic differentiation among them. At the stand level, a strong spatial aggregation of haplotypes persisted from the adult to the seedling cohort indicating limited seed flow. There was also a strong difference in levels of diversity between the cohorts which suggested that recruitment over several years is needed in order to maintain genetic diversity during regeneration.

DNA, Chloroplast↗
PubMed1999

Prognostic significance of extent of disease in bone in patients with androgen-independent prostate cancer.

PURPOSE: To evaluate the prognostic significance of a bone scan index (BSI) based on the weighted proportion of tumor involvement in individual bones, in relation to other factors and to survival in patients with androgen-independent prostate cancer. PATIENTS AND METHODS: Baseline radionuclide bone scans were reviewed in 191 assessable patients with androgen-independent disease who were enrolled onto an open, randomized trial of liarozole versus prednisone. The extent of skeletal involvement was assessed by scoring each scan using the BSI and independently according to the number of metastatic lesions. The relationship of the scored bone involvement to other known prognostic factors was explored in single- and multiple-variable analyses. RESULTS: In single-variable analyses, the pretreatment factors found to be associated with survival were age (P = .0446), performance status (P = .0005), baseline prostate-specific antigen (P = .0001), hemoglobin (P = .0001), alkaline phosphatase (P = .0002), AST (P = .0021), lactate dehydrogenase (P = .0001), and treatment (P = .0098). The extent of osseous disease was significant using both the BSI (P = .0001) and the number of lesions present (P = .0001). In multiple-variable proportional hazards analyses, only BSI, age, hemoglobin, lactate dehydrogenase, and treatment arm were associated with survival. When the patient population was divided into three equal groups, with BSI values of < 1.4%, 1.4% to 5.1%, and > 5.1%, median survivals of 18.3, 15.5, and 8.1 months, respectively, were observed (P = .0079). CONCLUSION: The BSI quantifies the extent of skeletal involvement by tumor. It allows the identification of patients with distinct prognoses for stratification in clinical trials. Further study is needed to assess the utility of serial BSI determinations in monitoring treatment effects. The BSI may be particularly useful in the evaluation of agents for which prostate-specific antigen changes do not reflect clinical outcomes accurately.

Aged↗
PubMed1998

Water-deficit-responsive proteins in maritime pine.

Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) was used to identify drought-responsive proteins during progressive water deprivation of two-year old maritime pine seedlings. Stress was applied by withholding water during vegetative growth. Needles were sampled before, during and after the stress. Out of about 1000 spots that were quantified by computer analysis, 38 responded during stress. Some proteins were accumulated while others were suppressed. One to three internal microsequences were obtained for 11 proteins, 10 of which were identified on the basis of sequence homologies. These proteins are quite diverse and are involved in photosynthesis, cell elongation, antioxidant metabolism and lignification.

Amino Acid Sequence↗
PubMed1998

The early baculovirus he65 promoter: On the mechanism of transcriptional activation by IE1.

We have initiated studies on the mechanism of early transcriptional activation of the early he65 promoter during infection with Autographa californica multicapsid nuclear polyhedrosis virus. This analysis is based on a comparison of the sequences required for he65 promoter activation with those sequences that support specific protein binding. The he65 promoter is located immediately downstream of the homologous region (hr) 4a. The sequences of hr4a are characterized by two imperfect palindromes of 24 bp. The results of transient expression assays indicate promoter activation in the presence of both the proximal palindrome and the known viral trans-regulator IE1. The results of mobility shift assays and DNaseI footprinting analyses reveal differences in specific protein binding at and close to the proximal palindrome depending on whether the nuclear protein extracts are prepared from uninfected or infected cells. The analysis of the protein binding complex at the proximal inverted repeat with extracts from infected cells suggests the involvement of both IE1 and IE0 as oligomers. The minimal protein binding sequences include the left half-site of the 24 bp repeat with 9 additional bp of the flanking sequences. The right half-site of the repeat also directs binding although with lower affinity as confirmed by phenanthroline-copper footprinting assays. Both half-sites of the repeat are thus essential for he65 promoter activation, suggesting that IE1 acts via cooperative binding. We conclude that the proximal inverted repeat is able to interact with both IE1 and IE0 although IE1 is sufficient for activation at least in transient expression assays.

Animals↗
PubMed1997

Chloroplast DNA footprints of postglacial recolonization by oaks.

Recolonization of Europe by forest tree species after the last glaciation is well documented in the fossil pollen record. This spread may have been achieved at low densities by rare events of long-distance dispersal, rather than by a compact wave of advance, generating a patchy genetic structure through founder effects. In long-lived oak species, this structure could still be discernible by using maternally transmitted genetic markers. To test this hypothesis, a fine-scale study of chloroplast DNA (cpDNA) variability of two sympatric oak species was carried out in western France. The distributions of six cpDNA length variants were analyzed at 188 localities over a 200 x 300 km area. A cpDNA map was obtained by applying geostatistics methods to the complete data set. Patches of several hundred square kilometers exist which are virtually fixed for a single haplotype for both oak species. This local systematic interspecific sharing of the maternal genome strongly suggests that long-distance seed dispersal events followed by interspecific exchanges were involved at the time of colonization, about 10,000 years ago.

Journal Article↗
PubMed1997

A simple and inexpensive screening test for low protein levels in urine.

Nigrosin binds to proteins yielding a dark blue complex. This reaction is used for detecting low protein concentrations in urine by applying spots of urine to cellulose acetate strips which are coloured by nigrosin. The intensity of coloured spots remaining after washing of the strips indicates protein concentration. With a cut-off at 50 mg protein/l, the test offers an excellent possibility for first line screening for microalbuminuria at lowest cost.

Albuminuria↗
PubMed1997

Identification and characterization of (GA/CT)n-microsatellite loci from Quercus petraea.

In this study a size selected genomic library from Quercus petraea was screened for (GA/CT)n-microsatellite sequences. The resulting loci were analysed by PCR for their usefulness as molecular markers in Q. petraea and Q. robur. 17 out of 52 tested primer pairs resulted in the amplification of a polymorphic single-locus pattern. The number of alleles found per locus varied from 6 to 16. Combining the genetic variation observed for the characterized loci provides a unique genotype for all the individuals tested. Using intraspecific controlled crosses of Q. robur trees Mendelian inheritance could be shown for five loci.

Base Sequence↗
PubMed1997

Multilocus and multitrait measures of differentiation for gene markers and phenotypic traits.

Multilocus measures of differentiation taking into account gametic disequilibrium are developed. Even if coupling and repulsion heterozygotes cannot be separated at the multilocus level, a method is given to calculate a composite measure of differentiation (CFst) at the zygotic level, which accounts for allelic associations combining both gametic and nongametic effects. Mean and maximum differentiations may be relevant when multilocus measures are computed. Maximum differentiation is the highest eigenvalue of the Fst matrix, whereas mean differentiation corresponds to the mean value of all eigenvalues of the Fst matrix. Gametic disequilibrium has a stronger effect on maximum differentiation than on mean differentiation and takes into account the anisotropy that may exist between within- and between-population components of disequilibria. Multilocus mean and maximum differentiation are calculated for a set of 81 Quercus petraea (sessile oak) populations assessed with eight allozyme loci and two phenotypic traits (bud burst and height growth). The results indicate that maximum differentiation increases as more loci (traits) are considered whereas mean differentiation remains constant or decreases. Phenotypic traits exhibit higher population differentiation than allozymes. The applications and uses of mean and maximum differentiations are further discussed.

Analysis of Variance↗
PubMed1997

Baculovirus transactivator IE1 is functional in mammalian cells.

IE1 of Autographa californica multicapsid nuclear polyhedrosis virus acts as a transactivator of several viral promoters in insect cells. Transient expression assays indicate that IE1 is involved in the activation of the early promoter he65 in both insect TN-368 and mammalian BHK-21 cell lines. IE1 activation of the he65 promoter was compared with IE1 activation of the early 39K promoter. In contrast to the he65 promoter, the 39K promoter was not inducible by IE1 in BHK-21 cells.

Animals↗
PubMed1995

Screening for oligoalbuminuria by means of Micral-Test II. A new immunological test strip.

A new dip-and-read test strip for systematic detection of oligoalbuminuria was assessed. The test is based on a competition for gold-labelled anti-albumin antibodies between specimen albumin and albumin molecules immobilised in the test strip. The final detection area is coloured by excess free antibodies. The colour reaction is compared to a colour scale reflecting 0, 20, 50 and 100 mg/l albumin. Method comparison with an immuno-turbidimetric quantitative technique was performed on 747 unselected specimens. The correlation coefficient was 0.938, the Spearman rank coefficient 0.863. In spite of considerable overlap of the results attributed to the 4 colour blocks, the test was found to be perfectly useful as a 2-class-test, as there were practically no false negative tests and as all the specimens yielding reactions stronger than the 20 mg/l colour block were found to contain 20 mg/l albumin or more by the reference method. The colour block 20 mg/l represents the inevitable grey zone, results in this range being found to be normal and increased above this pathological cut-off by the reference method. Follow-up by quantitative albumin dosage in timed morning urine for all specimens found positive by the dipstick confirms the existence of oligoalbuminuria, eliminating the cases of orthostatic albuminuria, of oligoalbuminuria simulated by low diuresis and the false positives due to oversensitivity of the test strip. The test strip is easy to handle. The reaction time is short and the colour reaction is stable and easy to read. Systematic use of this test in routine urine chemistry is suggested.

Albuminuria↗
PubMed1993

Maturation of maritime pine (Pinus pinaster Ait.) seedlings after exposure to a period of continuous light.

Nine half-sib families of maritime pine (Pinus pinaster Ait.) of known adult performance were grown in continuous light at either 25 degrees C or 25/20 degrees C for 18 weeks. They were then exposed to a dormancy induction period followed by a dormancy release period and then grown for a further 9 weeks in a 16-h photoperiod at a day/night temperature of 25/20 degrees C. Seedlings exhibited great diversity in morphology at the end of the first growth period. The number of morphogenetic cycles varied between one and three and the form of the apical meristem ranged from a typical rosette to an adult-like bud. The type of seedling obtained at the end of the first growth period strongly influenced later growth, independently of the temperature regime. Maturity was proportional to the number of morphogenetic cycles achieved during the first growth period and was characterized by short growth duration, small primary needles and a high degree of fixed growth. The state of the apical meristem that underwent the dormancy period had less influence on the rate of maturation than the number of morphogenetic cycles. The time course of maturation was endogenously controlled and varied among traits. Conspicuous morphological differences were not associated with changes in the relationship between growth components at the phenotypic level. However, there seemed to be a shift in the genetic correlations between growth components after first budset.

Journal Article↗