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H Keller

Publications and source records attributed to H Keller.

At least 127 records · Page 7Linked to original sources
PubMed1995

[50 years of clinical chemistry, first hand experience].

Approximately since 1945, progress in the field of photometric analysis also found its way into the laboratories of clinical chemistry. These techniques almost completely replaced the then prevailing gravimetric and titrimetric methods. At the same epoch, many of the biochemical reagents which up to then had to be prepared by the clinical laboratories themselves with great expenditure of work became commercially available. The increasing number of analytical orders could only be mastered thanks to the newly developed analyzers. Novel microliter techniques made it possible to diminish drastically the volumes of samples and reagents necessary. The radioimmunoassay opened up new analytical dimensions, the limits of detection and of quantification were expanded downwards to the picomol range. Soon afterwards, enzymes and/or fluorochromes were used as markers in immunoassays. The development of monoclonal antibodies constituted further important progress in this field. The latest revolutionary invention is doubtlessly the polymerase chain reaction (PCR), and related techniques. These methods are bound to bring about fundamental change not only in clinical chemistry but in the medical laboratory diagnostics in general.

Antibodies, Monoclonal↗
PubMed1995

Effects of cytochalasin D on shape and fluid pinocytosis in human neutrophils as related to cytoskeletal changes (actin, alpha-actinin and microtubules).

We report that cytochalasin D (CD) is not a reliable tool to inhibit all forms of cell motility and actin polymerization in neutrophil granulocytes. In addition to the well-established effects of CD such as altered localization of F-actin, inhibition of surface ruffling, fluid pinocytosis and actin polymerization in agonist-stimulated cells, we find that in human neutrophils CD can 1) induce another type of continuous shape changes (10(-6) M and 10(-5) M CD), 2) stimulate fluid pinocytosis (10(-5) M CD), 3) increase actin polymerization (10(-5) to 10(-4) M CD) and alter the localization of F-actin and alpha-actinin (10(-6) to 10(-4) M CD). At 10(-5) M CD F-actin and alpha-actinin are preferentially located in different areas of the cell. At 10(-4) M CD actin and alpha-actinin may colocalize at the membrane but not in cytoplasmic foci. Thus, stimulation of shape changes, pinocytosis, actin polymerization and differential reorganization of the cytoskeleton occur at CD concentrations which are widely used to inhibit cell motility. The results show that CD is not a reliable tool to inhibit all movements of cells and actin polymerization in general. Shape changes, but not fluid pinocytosis and the relative redistribution of F-actin and alpha-actinin induced by 10(-5) M cytochalasin D are suppressed by 10(-5) colchicine. This indicates that also microtubules can play a role in determining neutrophil shape and movements.

Actinin↗
PubMed1995

[Radiologic follow-up examination of podotrochlosis].

X-rays of 205 horses having navicular disease and having been reexamined up to six times are evaluated. For this, the x-rays of each foreleg are evaluated in the dorsopalmar (Oxspring) and lateromedial view. Additionally to changes of the navicular bone, changes of the distal part of the toe are also assessed. Differences can be found in the radiographic process in view of the limitation of vascular foramina and cyst-like lesions. Vascular foramina with sclerotic rim grow less frequent than poorly defined ones and therefore allow for easier prognostication. Cyst-like lesions with sclerotic rim often stay unchanged or decrease separately, whereas poorly defined areas of rarefication show a stronger tendency to expand into the surrounding spongiosa. Changes of vascular and bone structure occur already within a few months, whereas most of the margination changes are already formed in the early stages of disease and proceed slowly. Finally the effects of the therapy are being examined for the radiographic course of disease. Following a neurectomy, a more intensive development of the changes can be observed. The rate of only minimally altered navicular bones as well as the often simultaneous occurrence of changes in the joints of the toe do not allow for a diagnosis only on the basis of radiographic findings. The often slow development of the pathological radiographic changes requires intervals of examination of at least one year and shows that prognostic statements can only be made with caution even after follow-up examinations.

Animals↗
PubMed1994

Analysis of the post-translational processing of alpha-MSH in the pituitaries of the chondrostean fishes, Acipenser transmontanus and Polyodon spathula.

Multiple forms of alpha-MSH were isolated from the pituitaries of the white sturgeon, Acipenser transmontanus, and the paddlefish, Polyodon spathula, following fractionation of the pituitary extracts by reversed-phase HPLC. In both species, immunoreactive forms which eluted with the same retention times as synthetic mammalian ACTH(1-13)NH2, monoacetylated alpha-MSH, and diacetylated alpha-MSH were detected. In the pituitary of the sturgeon, N-acetylated forms of alpha-MSH represented 91% of the total alpha-MSH isolated. However, in the pituitary of the paddlefish, N-acetylated forms of alpha-MSH accounted for only 45% of the total alpha-MSH isolated. The presence of N-acetylated forms of alpha-MSH in the pituitaries of representatives of the two extant genera of chondrostean fish coupled with the observation that N-acetylated forms of alpha-MSH are present in the pituitaries of cladistian and neopterygian fishes indicates that the alpha-MSH specific N-acetylation mechanism evolved prior to the radiation of the Actinopterygii. A conspicuous feature of the chondrostean alpha-MSH N-acetylation reaction was the low levels of diacetylated alpha-MSH produced relative to the levels of monoacetylated alpha-MSH. Similar observations have been made for the cladistian fish, Calamoichthys calabaricus, and the cartilaginous fish, Hydrolagus colliei. However, in holostean fishes, lungfishes, and tetrapods, the diacetylated form of alpha-MSH is the major end product produced in the intermediate pituitary. The phylogenetic implications of these observations will be discussed.

Acetylation↗
PubMed1994

Incidence, diagnosis, and treatment of ureteric stenosis in 1298 renal transplant patients.

Of 1130 patients who had undergone a total of 1298 kidney transplantations, 40 developed a stenosis of the ureter (3.1%). In all of the transplants, the anastomosis between the ureter and the urinary bladder was established as extravesical ureteroneocystostomy. Up until 1984, in cases where an obstruction in the urinary tract was suspected, the diagnosis was made by an i.v. pyelogram or by nuclear scans of the transplant. Thereafter, in 28 patients, in cases of sonographically suspected stenosis of the ureter, the diagnosis was established by means of a simplified Whitaker test. Nearly one-half of the stenoses of the ureter developed within the first 3 months after transplantation. In five patients (12.5%) the stenosis developed significantly later, 3-10 years after kidney transplantation. Seventy percent of the stenoses were localized in the distal third of the ureter. About 75% of the surgically explored stenoses could be corrected by resection and reimplantation of the ureter. During the post-operative follow-up, restenosis occurred in three patients. At present, 62% of all patients whose ureteric stenoses were corrected have well-functioning kidney transplants.

Adolescent↗
PubMed1994

Detection of N-acetylated forms of alpha-MSH and beta-endorphin in the intermediate pituitary of the holostean fishes, Lepisosteus spatula, Lepisosteus osseus, and Amia calva.

Acid extracts of the intermediate pituitaries of the gars, L. spatula and L. osseus, were fractionated by Sephadex G-50 column chromatography and analyzed by radioimmunoassay. This procedure revealed that immunoreactive forms of N-acetylated beta-endorphin- and alpha-MSH-sized material were present in equimolar amounts and represented the major end products of the POMC biosynthetic pathway in these species. Cation-exchange chromatography indicated that multiple N-acetylated forms of beta-endorphin were present in the intermediate pituitaries of the two species of gar, and that these forms differed in their net positive charge and in their apparent molecular weight. Reversed-phase HPLC analysis of the alpha-MSH-related material indicated that up to 90% of the total MSH in the pituitary of the gar was N-acetylated. Furthermore, the predominant form of alpha-MSH in both species of gar was N,O-diacetyl-ACTH(1-13)-NH2. Nearly identical results were obtained following the analysis of alpha-MSH-related peptides in the intermediate pituitary of the bowfin, A. calva. The pattern of posttranslational processing of POMC observed in the intermediate pituitaries of holostean fishes is very similar to the processing events observed in lungfishes, turtles, and mammals; hence, the processing of POMC has been remarkably conserved during vertebrate evolution.

Acetylation↗
PubMed1994

FTZ-F1-related orphan receptors in Xenopus laevis: transcriptional regulators differentially expressed during early embryogenesis.

Orphan receptors of the FTZ-F1-related group of nuclear receptors (xFF1r) were identified in Xenopus laevis by isolation of cDNAs from a neurula stage library. Two cDNAs were found, which encode full length, highly related receptor proteins, xFF1rA and B, whose closet relative known so far is the murine LRH-1 orphan receptor. xFF1rA protein expressed by a recombinant vaccinia virus system specifically binds to FTZ-F1 response elements (FRE; PyCAAGGPyCPu). In cotransfection studies, xFF1rA constitutively activates transcription, in a manner dependent on the number of FREs. The amounts of at least four mRNAs encoding full-length receptors greatly increase between gastrula and early tailbud stages and decrease at later stages. At early tailbud stages, xFTZ-F1-related antigens are found in all nuclei of the embryo.

Amino Acid Sequence↗
PubMed1994

Sensitivity and specificity of cocaine metabolite screening in view of the analytical performance of a fluorescence polarisation immunoassay.

Immunoassays for drug screening are called 'qualitative' or 'semiquantitative' by the manufacturers of these tests and they urgently recommend the user to verify each result exceeding the recommended cut-off value by a confirmation test. For therapeutic drug monitoring assays or for the determination of tumour markers or hormones, similar recommendations are not given, although the same analytical technologies are used for these assays. A scientific validation of the commonly used cut-off values recommended by the official bodies (e.g. NIDA, DoD) is unfortunately not described in the accessible scientific literature. A solution to this problem was sought by evaluating the analytical characteristics of the assay and determining the diagnostic validity of the test using an immunoassay for the cocaine metabolite as an example. Hundred urine samples from people suspected of cocaine abuse and 50 urine samples from patients unlikely to have consumed cocaine were analysed in triplicate with a commercially available fluorescence polarisation immunoassay. From this data we assessed the analytical variance of the assay using the computer program of Sadler & Smith (Clin. Chem. 36 (1990), 1346-1350). Using the functions provided, we calculated the limit of detection (LD) and the lower limit of quantification (LLQ) as well as the so-called power of definition (PD) using a recently published method (Gautschi et al., this journal 31 (1993), 433-440). This procedure is mathematically well defined, uses no artificial standards or calibrators and is in compliance with IFCC recommendations. A clearly defined assessment of the diagnostic performance of an assay is of utmost importance for the discussion of adequate decision levels.(ABSTRACT TRUNCATED AT 250 WORDS)

Cocaine↗
PubMed1994

Recombinant hemoglobin A produced in transgenic swine: structural equivalence with human hemoglobin A.

Recombinant human hemoglobin A produced by coexpressing human alpha and beta globin genes in swine, and purified from the lysate of transgenic swine has been subjected to detailed protein chemical analysis. These structural studies involving laser desorption mass spectrometry, separation of globin chains by RPHPLC, amino terminal sequence analysis of the isolated globin chains, the tryptic peptide mapping of the purified globin chains and the amino acid composition analysis of the purified tryptic peptides of globin chains have established the primary structural equivalence of the globin chains of the transgenic swine derived hemoglobin A with that of human hemoglobin A. These results demonstrate that the transgenic swine system correctly translates the human alpha and beta globin m-RNA; carries out the correct cotranslational processing of globin chains, and does not introduce any unwanted post translational modifications into the mature chains. Thus, the transgenic swine expression system is an excellent approach for the production of HbA for developing an effective hemoglobin based oxygen carrier.

Amino Acid Sequence↗
PubMed1994

Variance function as basis for assessment of test performance: methodological studies with two assays of prostate-specific antigen.

We evaluated the usefulness of a recently described procedure to assess the analytical performance of an assay. To demonstrate the advantages of this approach, we compared the performance of two analytical systems for determining prostate-specific antigen (PSA). Triplicate measurements of PSA with the IMx (Abbott) and the ACS 180 (Ciba Corning) were used to calculate the variance function. This function was the basis for the derivation of the critical limit (LC), the limit of detection (LD), the power of definition (PD), and the lower limit of the quantification interval. The standard deviation of the blank was extrapolated by means of the variance function. LC was calculated as the concentration at which the normal distribution of the blank intersects an adjacent normal distribution (with a defined overlap, e.g., 5%). The mean of the adjacent normal distribution represents the LD. The PD is a new mathematical approach to describe the analytical sensitivity of an assay in different ranges of the quantification interval. The procedure is statistically well defined and allows one to obtain the data on the test performance directly from patients' samples, without artificial zero controls. Therefore, use of the variance function could be a general model for the assessment of the analytical performance of an assay.

Chemistry, Clinical↗
PubMed1994

Vitamin status of a healthy French population: dietary intakes and biochemical markers.

The vitamin status of a representative population sample in a French district in the Paris area was assessed using a biochemical and dietary approach. Complete data were obtained for 1039 subjects 6 to 97 years old. Dietary intakes of most vitamins increased up to adolescence and then remained stable or decreased slightly in adult life. Total vitamin intakes were higher in men than in women (except for ascorbic acid), but the vitamin density of the diet was higher in females. Most subjects presented dietary intakes below the French recommended allowances for vitamin B1, B6, C, A and E. A variation in biochemical parameters according to age and sex was observed only for serum concentration of retinol, beta-carotene, vitamin E and C. Multiple regression analysis showed that dietary vitamin intakes were related to the biological status for vitamin B2, B6, C, folates, beta-carotene and vitamin E. Tobacco smoking, alcohol consumption and oral contraceptive were significantly correlated with biological status for several vitamins. While biochemical evidence of severe vitamin deficiency was not observed, a sizeable minority of the French population is not lavishly supplied with some vitamins, and this situation deserves investigation to see if any deleterious effects are associated with it.

Adolescent↗
PubMed1994

[Isolated fracture of the lesser tuberosity of the humerus: case reports and review of the literature].

Only 17 cases of isolated avulsion fracture of the lesser tuberosity have been reported in the literature since Hartigan's report in 1895. Whereas in children, conservative treatment is almost successful, in adults operative restoration is the method of choice in order to obtain full painless range of motion with normal strength of muscle control. Surgical excision of the fragment of lesser tuberosity after failed conservative treatment may relieve the patient's symptoms. Three own cases and a review of the literature are discussed.

Adult↗
PubMed1993

Peroxisome proliferator-activated receptors and lipid metabolism.

PPARs are nuclear hormone receptors which, like the retinoid, thyroid hormone, vitamin D, and steroid hormone receptors, are ligand-activated transcription factors mediating the hormonal control of gene expression. Two lines of evidence indicate that PPARs have an important function in fatty acid metabolism. First, PPARs are activated by hypolipidemic drugs and physiological concentrations of fatty acids, and second, PPARs control the peroxisomal beta-oxidation pathway of fatty acids through transcriptional induction of the gene encoding the acyl-CoA oxidase (ACO), which is the rate-limiting enzyme of the pathway. Furthermore, the PPAR signaling pathway appears to converge with the 9-cis retinoic acid receptor (RXR) signaling pathway in the regulation of the ACO gene because heterodimerization between PPAR and RXR is essential for in vitro binding to the PPRE and because the strongest stimulation of this gene is observed when both receptors are exposed simultaneously to their activators. Thus, it appears that PPARs are involved in the 9-cis retinoic acid signaling pathway and that they play a pivotal role in the hormonal control of lipid metabolism.

Acyl-CoA Oxidase↗
PubMed1993

Fatty acids and retinoids control lipid metabolism through activation of peroxisome proliferator-activated receptor-retinoid X receptor heterodimers.

The nuclear hormone receptors called PPARs (peroxisome proliferator-activated receptors alpha, beta, and gamma) regulate the peroxisomal beta-oxidation of fatty acids by induction of the acyl-CoA oxidase gene that encodes the rate-limiting enzyme of the pathway. Gel retardation and cotransfection assays revealed that PPAR alpha heterodimerizes with retinoid X receptor beta (RXR beta; RXR is the receptor for 9-cis-retinoic acid) and that the two receptors cooperate for the activation of the acyl-CoA oxidase gene promoter. The strongest stimulation of this promoter was obtained when both receptors were exposed simultaneously to their cognate activators. Furthermore, we show that natural fatty acids, and especially polyunsaturated fatty acids, activate PPARs as potently as does the hypolipidemic drug Wy 14,643, the most effective activator known so far. Moreover, we discovered that the synthetic arachidonic acid analogue 5,8,11,14-eicosatetraynoic acid is 100 times more effective than Wy 14,643 in the activation of PPAR alpha. In conclusion, our data demonstrate a convergence of the PPAR and RXR signaling pathways in the regulation of the peroxisomal beta-oxidation of fatty acids by fatty acids and retinoids.

Animals↗