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Biomedical subjects

K Peters

Publications and source records attributed to K Peters.

At least 217 records · Page 12Linked to original sources
PubMed1991

Nickel concentrations in fingernails as a measure of occupational exposure to nickel.

The nickel concentration in fingernails from 2 groups of people occupationally exposed to nickel was determined. In one group, comprising 83 persons moderately exposed to nickel, the mean +/- standard deviation (SD) was 29.2 micrograms/g +/- 56.7 micrograms/g and the median 13.8 micrograms/g (range 0.926-396 micrograms/g). In the other group, comprising 51 persons heavily exposed to nickel, the mean +/- SD was 123 micrograms/g +/- 289 micrograms/g and the median 29.9 micrograms/g (range 1.95-1770 micrograms/g). Both levels were significantly different from the normal nickel concentration in nails (p less than 0.001). The difference between the 2 levels was also significant (p less than 0.001). No correlation between the nickel concentration in fingernails and the duration of exposure could be demonstrated. It was concluded that the higher the nickel level in the fingernails, the greater is the possibility that the person is occupationally exposed to nickel. Nail analysis is suggested as a measure of occupational exposure to nickel.

Adolescent↗
PubMed1991

A conventional compression bandage lacks effect on subcutaneous blood flow when walking and during passive dependence in chronic venous insufficiency.

Blood flow in subcutaneous tissue of the lower leg decreased by 45% on changing from recumbency to the sitting position in patients suffering from chronic venous insufficiency. When walking, blood flow increased significantly to values near those measured during resting recumbency. A conventional elastic compression bandage (Weromedium) had no effect on these parameters, indicating that therapeutic gain through compression is not mediated by an improvement in subcutaneous blood flow.

Adipose Tissue↗
PubMed1991

Reference values for the nickel concentration in human finger nails.

A reference value for the nickel concentration in finger nails from people who are not occupationally exposed to nickel was determined on the basis of nail samples from 95 healthy individuals. The mean +/- standard deviation was 1.19 +/- 1.61 mg/kg and the median was 0.49 mg/kg (range 0.042-7.50 mg/kg). The 95% confidence interval of the population mean was 0.51-1.26 mg/kg and the 95% confidence interval of the population median was 0.39-0.74 mg/kg. The random sample consisted of 59 women and 36 men. No significant difference between the nickel levels in finger nails from men and women could be demonstrated. The age of the subjects varied from 16 to 66 years. There was no correlation between age and nickel concentration in finger nails.

Adolescent↗
PubMed1991

L-651,582 inhibition of intracellular parasitic protozoal growth correlates with host-cell directed effects.

L-651,582 (5-amino-[4-(4-chlorobenzoyl)-3,5-dichlorobenzyl]-1,2,3-triazole-4- carboxamide), which is active in vivo against coccidiosis caused by the intracellular parasitic protozoan Eimeria tenella, is also effective against this organism in tissue culture in Maden Darby bovine kidney (MDBK) host cells. L-651,582 inhibited 45Ca++ uptake, as well as [3H]hypoxanthine incorporation into soluble nucleotide pools, in MDBK cells at concentrations similar to those required for antiparasitic activity (IC50 = 0.3 microgram/ml). However, the drug did not inhibit the [3H] hypoxanthine incorporation into the nucleotide pools of the intracellular E. tenella under the same conditions. The antiparasitic activity of several L-651,582 analogs paralleled their ability to inhibit [3H]hypoxanthine incorporation in MDBK cells. L-651,582 similarly inhibited the growth of the intracellular parasitic protozoan Toxoplasma gondii in vitro with either HeLa cells or Normal Human Fibroblasts as host cells. The IC50 for inhibition of T. gondii growth in normal human fibroblasts was similar to that for [3H]hypoxanthine incorporation inhibition. In HeLa cells, however, 40-fold higher levels were required for the inhibition of [3H]hypoxanthine incorporation than were required to inhibit parasite growth, showing that antiparasitic activity was not a consequence of the alteration in host nucleotide metabolism. This was also consistent with the observation that the effect of L-651,582 against E. tenella in MDBK cells was not reversed by the addition of nutrients involved in nucleotide biosynthesis. This study suggests that L-651,582 has antiparasitic activity which correlates with host cell effects and which may be a result of blocking Ca++ entry in the host cells, but is not the result of an alteration of host nucleotide biosynthesis.

Adenosine Triphosphate↗
PubMed1990

[The problem of selective determination of PSP toxins in mussels].

Levels of paralytic shellfish poisoning (PSP) toxins in shellfish are routinely determined by mouse bioassay. In order to improve the qualitative and quantitative determination of PSP toxins, chromatographic techniques with fluorescence detection have been developed. These HPLC methods and the HPLC/MS coupling were used to determine a second PSP toxin which was found, in addition to saxitoxin, in canned Spanish mussels. These canned mussels were rejected in 1986 by the German food control because PSP concentrations were too high. It has been shown that these samples contained mainly dc-saxitoxin.

Animals↗
PubMed1990

Peptide diazomethyl ketones are inhibitors of subtilisin-type serine proteases.

Peptide diazomethyl ketones, well known as specific cysteine protease inhibitors are also potent inhibitors of the microbial serine proteases thermitase (EC 3.4.21.14) and subtilisin Carlsberg (EC 3.4.21.14). The affinity of the enzymes towards the synthetic inhibitors Z-Ala(n)-PheCHN2 (n = 0, 1, 2) depends on the chain length and is in the same range as for the corresponding chloromethyl ketones. Both kinds of inhibitors react irreversibly in a 1:1 ratio with the enzymes and covalently bind to the active site histidine of both subtilisin Carlsberg and thermitase despite the fact that thermitase contains an active-site cysteinyl residue. The mechanism of the inhibition reaction is discussed.

Amino Acid Sequence↗
PubMed1990

[Affinity chromatography of proteases using peptide methyl ketones as ligands].

Peptide methyl ketones acting as reversible inhibitors of serine and cysteine proteases were introduced as a new type of ligands in the affinity chromatography. Subtilisins and related serine proteases with an inhibition constant to the soluble inhibitor Z-Ala2-PheCH3 of less or equal than 3 x 10(-5) M are nearly completely adsorbed by the affinity gel Sepharose 4B-epsilon-aminocaproic acid-Ala2-PheCH3. The well-known cysteine protease papain binds also to this gel. The elution of the enzymes could be performed by means of iso-propanol. Thermitase purified with this method is, regarding to its quality, comparable with enzyme preparations using isoelectric focusing and adsorption at porous glass bodies, respectively.

1-Propanol↗
PubMed1989

[Prevention of cigarette smoking in school. A prospective controlled study].

752 schoolchildren, mean age 12.7 years, were asked by multiple-choice questionnaire about their smoking experience. After this, eight educational lessons were given in seven of the schools ("intervention schools") to reinforce non-smoking. In six control schools no activities were performed. After 2.3 years, 579 schoolchildren (301 males and 278 females, mean age 15.0 years) again filled in a similar questionnaire. In the control schools 12.4% of children had begun to smoke, (greater than 1 cigarette per month), but only 7.4% in the intervention group (P less than 0.06). Daily cigarette smoking had been taken up by 8.4% in the control schools, but by only 4% in the intervention schools (P less than 0.04). 9.9% of children in the control schools and 3.8% in the intervention schools had smoked during the 24 hours before the questionnaire was filled in (P less than 0.004). The data indicate that an eight-hour course of instruction with reinforcement of non-smoking can lastingly influence smoking behaviour of juveniles.

Adolescent↗
PubMed1989

Subcutaneous blood flow in early male pattern baldness.

The subcutaneous blood flow (SBF) was measured by the 133Xe washout method in the scalp of 14 patients with early male pattern baldness. Control experiments were performed in 14 normal haired men matched for age. The SBF in the scalp of the normal individuals was about 10 times higher than previously reported SBF values in other anatomical regions. In patients with early male pattern baldness, SBF was 2.6 times lower than the values found in the normal individuals (13.7 +/- 9.6 vs 35.7 +/- 10.5 ml/100 g/min-1). This difference was statistically significant (p much less than 0.001). A reduced nutritive blood flow to the hair follicles might be a significant event in the pathogenesis of early male pattern baldness.

Alopecia↗
PubMed1989

Isolation and mapping of DNA probes within the linkage group I gene cluster of Caenorhabditis elegans.

We have isolated probes for DNA polymorphisms across the linkage group I gene cluster in Caenorhabditis elegans, using Tc1-linkage selection. The probes detect strain polymorphism between the wild-type strains of var. Bristol and var. Bergerac. As a result of mapping the sites hP4, hP5, hP6, hP7, hP9, and sPl, more than 1000 kilobases (kb) of cloned cosmid DNA has been positioned on the genetic map. We found there is more DNA per map unit in the center of the gene cluster than expected on the basis of the genomic average. Furthermore, the amount is not constant across the entire region but reaches a peak in the hP9 unc-13 interval. To find the coding regions, we examined DNA cross-homology between two species, Caenorhabditis elegans and Caenorhabditis briggsae. Approximately one-third of the DNA in the hP5 hP9 interval was examined for coding regions and 21 sequences were identified within 318 kb of DNA.

Animals↗
PubMed1988

Comparative characterization of the substrate-binding subsites in subtilisins DY and Carlsberg by fluorescence and kinetic studies.

Peptide chloromethanes with the general formula dansyl-(Ala)n-Phe-CH2Cl where n = 0, 1, 2, 3 and dansyl fluoride were used to investigate the substrate-binding sites A and B in subtilisins DY and Carlsberg. Kinetic evidence for the introduction of the dansyl group at the subsites S2, S3, S4 and S5 were obtained. Fluorescence experiments showed that the micro-environment of these subsites is quite apolar. However, some differences in their accessibility to external reagents can be revealed in fluorescence quenching experiments. Efficient singlet-singlet radiationless energy transfer from the single Trp 113 to the dansyl group selectively bound at the respective subsites was observed and intramolecular distances between the chromophores were determined. The values calculated for the pairs Trp 113 plus Dns at S2, Trp 113 plus Dns at S4 and Trp 113 plus Dns at S5 are practically identical (1.7-2.0 nm) for the two enzymes. Conclusions on the shape of the substrate-binding sites in subtilisins DY and Carlsberg are drawn. The mutual spatial orientation of the donor (Trp 113) and acceptor (Dns at Sn) dipoles is also elucidated.

Binding Sites↗