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Biomedical subjects

J Stein

Publications and source records attributed to J Stein.

At least 451 records · Page 25Linked to original sources
PubMed1980

Mutagenesis of ultraviolet-irradiated lambda phage by host cell irradiation: induction of Weigle mutagenesis is not an all-or-none process.

Ultraviolet mutagenesis of lambda phage to clear plaque formers is the same in the total phage population and in subpopulations of phage which have also mutated to gam- or at an amber codon. This is true for phage assayed in host cells in which Weigle mutagenesis has been either partially induced by low levels of ultraviolet irradiation, or fully induced by higher levels. If induction of Weigle mutagenesis were all-or-none, clear plaque formers in phage subpopulations selected for another mutation elsewhere would come mainly from induced cells; then the clear plaque mutation rate would always be that for fully induced host cells. Therefore, induction requires more than one lesion in host cell DNA. Although thymine starvation of cells induces synthesis of recA protein, it does not induce Weigle mutagenesis; in fact starvation inhibits induction of this process on subsequent ultraviolet irradiation of the cells.

Bacteriophage lambda↗
PubMed1980

Identification of the Low Molecular Weight Copper Protein from Copper-intoxicated Mung Bean Plants.

Mung bean plants (Wilczek) accumulate increasingly greater amounts of buffer-extractable copper in both their shoots and roots when grown in liquid medium containing greater than 2 micrograms per milliliter copper (31.4 micromolar) as cupric sulfate. This increase in soluble copper is accompanied by an increase in the relative amount of low molecular weight (7,000 to 20,000) macromolecular-bound copper and a decrease in the relative amount of high molecular weight (greater than 20,000) copper. The major low molecular weight copper protein has been isolated from copper-intoxicated mung bean plants by a combination of ammonium sulfate fractionation, gel filtration, and ion exchange chromatography. It was identified as mung bean plastocyanin on the basis of its molecular weight, optical behavior, and amino acid composition. No evidence was found for a low molecular weight copper-binding protein corresponding to mammalian thionein or chelatin.

Journal Article↗
PubMed1980

Visual pontocerebellar projections in the cat.

1. Projections of pontine visual cells onto the cat cerebellar cortex were studied by antidromic activation and by the retrograde transport of horseradish peroxidase (HRP). 2. Cells in the medial pontine visual area, which receive visual cortex projections, were activated antidromically principally from the contralateral cerebellar hemisphere. Cells in the dorsolateral pontine visual area, which receive an input from the superior colliculus, were activated principally from the vermis and ipsilateral hemisphere. There is some overlap in the projections of these two different populations of pontine cells, which probably occurs by way of bifurcated axons. 3. The HRP technique confirmed that there is a major difference in the pattern of projections from these two pontine visual regions. Many cells in the rostral-medial portion of the pontine nuclei, which receive their input from visual cortex, were labeled following HRP injections in the contralateral cerebellar hemisphere. Far fewer of these cells were labeled following vermal injection. Cells in the dorsolateral pontine nucleus, which receive visual input from the superior colliculus, were labeled following an HRP injection in the vermis or the ipsilateral hemisphere. Cells in the region of pontine nuclei that receive input from the ventral lateral geniculate nucleus were also labeled after a vermian injection. 4. If the vermis is related to the control of whole-body movements and the hemisphere to control of ipsilateral limbs, these results suggest that the corticopontocerebellar and the tectopontocerebellar pathways may be involved in different classes of visually guided movement.

Animals↗
PubMed1980

[Dermatoglyphic findings in children with mucoviscidosis and their parents].

Dermatoglyphics were investigated in 37 children with cystic fibrosis (17 boys, 20 girls, 4 pairs of them sibs) between two months and 17 years of age and in 30 of their parents. For the pattern distribution there were no differences between the patients or their parents respectively and the general population except for a higher tendency of reduction (O and X) of the main line C. Concerning the ridge structure in the children, all variations from normal ridges over enlarged sweat gland pores to complete ridge dissociation were found. For the degree of these structural changes and the jontophorese values a correlation coefficient r=+0.39 (p <0.05) resulted. While the frequency of ridge dissociation on the hypothenar is 56.8 % in the children with cystic fibrosis, the parents have a frequency of 23.4%. This value is lying between that of their children and the general population (13.4%).

Adolescent↗
PubMed1980

[Early and late complications of endocardial pacemaker wires (author's transl)].

Comparison of early and late complications of 769 endocardial pacemaker wires implanted in the period between 1969 and 1973 with 861 wires implanted between 1974 and 1978 revealed a decline of the complication rate from 17% to 7.6%. The dislocation rate could be lowered from 6.2% to 1.6%. Other early complications (exist and entrance block) were not effected (3.5% as compared with 3.2%). Late complications declined from 6.2% to 2.9%. Of these the number of intravascular wire breakages constitutes a high proportion. The main reason for this improvement is the use of a flexible Flange-tip lead. A variation of testing the positional stability of the wire is described.--The indications for pacemaker implantation shifted from 3rd degree AV-Block to the diagnoses "pathological bradycardia" and "hypersensitive carotis sinus". The comparatively low complication rate permits the application of new types of wires only in a few selected patients until a sufficient number of cases and an adequate follow-up period have been reached for clinical evaluation of these wires.

Aged↗
PubMed1979

Sensitivity differences displayed by Drosophila melanogaster larvae of different ages to the toxic effects of growth on media containing aflatoxin B1.

Using Drosophila melanogaster, the relative sensitivities of various larval stages to the toxic effects of growth on media supplemented with either 0.44 or 0.88 ppm aflatoxin B1 (AFB1) were determined. Two strains of fruit flies were tested: strain A-11 which is relatively resistant to AFB1 induced toxicity, and strain A-9 which is quite sensitive. Eggs, mid-first, mid-second and early-, mid- and late-third instar larvae were transferred onto AFB1 media and allowed to complete larval and pupal development and eclose as adults. At the 0.44 ppm concentration, strain A-11 showed no effect, while only first instar larvae of strain A-9 showed significant mortality rates for first instar larvae, but the A-9 larvae die at higher rates than the A-11 larvae. In addition, second and third instar larvae of strain A-9 show significant mortality rates when grown at 0.88 ppm AFB1, while these stages are not affected in strain A-11.

Aflatoxins↗
PubMed1979

Reassessment of histone gene expression during cell cycle in human cells by using homologous H4 histone cDNA.

The representation of H4 histone mRNA sequences in RNAs isolated from G1 and S phase HeLa cells was assessed by use of a homologous H4 histone cDNA. S phase cells were obtained by double thymidine block, and G1 cells were obtained by double thymidine block or mitotic selective detachment. Nuclear and cytoplasmic RNAs from S phase cells hybridized with H4 histone cDNA as did nuclear and cytoplasmic RNAs from G1 cells synchronized by double thymidine block. In contrast, significant levels of hybridization were not observed between H4 histone cDNA and nuclear, polysomal, or postpolysomal cytoplasmic RNAs of G1 cells synchronized by mitotic selective detachment. Double thymidine block yields a G1 cell population containing 20-25% S phase cells whereas the G1 population obtained by mitotic detachment contains less than 0.1% S phase cells. The ability of H4 histone cDNA to hybridize with the RNAs from G1 cells obtained after release from double thymidine block can therefore be explained by the presence of S phase cells in such a G1 population--an artifact of the synchronization procedure. We interpret these results to be consistent with the presence of H4 histone mRNA sequences during the S but not G1 phase of the cell cycle in continuously dividing HeLa S3 cells.

Cell Cycle↗
PubMed1979

Specificity of DNA-associated nuclear antigens in HeLa cells and distribution during the cell cycle.

Chromosomal nonhistone protein:DNA complexes prepared from synchronized HeLa cells were used to immunize white rabbits. The antisera reacted specifically in complement fixation tests with chromatins isolated from HeLa cells and not with those from a number of other human and animal tissues. Specificity to this cell type was also demonstrated by immunocytochemical reaction. Both immunochemical tests revealed that the specific antigens are continuously present throughout the cell cycle. The immunological activity was dependent upon chromosomal nonhistone protein(s) being bound to DNA. Our findings are consistent with these chromatin antigens being stable nuclear components [complexes of chromosomal non-histone protein(s) with DNA] characteristic of cellular differentiation.

Antigens↗
PubMed1977

Mutagenesis of lambda phage: 5-bromouracil and hydroxylamine.

Mutagenesis by 5-bromouracil of lambda phage to clear plaque formers does not depend on the recA function of the host E. coli cell or on the red function of the phage. Pretreatment of the host cells with ultraviolet light does not affect bromouracil mutagenesis of the adsorbed phage. Mutagenesis by hydroxlamine to clear plaque formers takes place at a high level in recA- host cells, and is not changed by preirradiation of of rec+ (wild type) hosts with ultraviolet light. Thus, bromouracil and hydroxylamine appear to mutate lambda phage by a process which differs from that responsible for ultraviolet mutagenesis. Two characteristics of bromouracil mutagenesis--the nonlinear dependence of the number of mutants on bromouracil incorporation, and a high frequency of heterozygotes--fit in with Rydberg's (1977) picture of bromouracil mutagenesis as a consequence of base mispairing, with mismatch repair removing the mutations at low incorporation of the analog.

Bromouracil↗