Search PubMed⌕ Search

Biomedical subjects

B Lambert

Publications and source records attributed to B Lambert.

At least 217 records · Page 12Linked to original sources
PubMed1977

Ultrastructural immunoenzymatic study of alpha-fetoprotein-producing cells in the human fetal liver.

Cells producing alpha-fetoprotein in human fetal liver have been studied with specific horseradish peroxidase labeled immunoglobulins. Under light microscopy, the alpha-fetoprotein is strictly localized in the cytoplasm of certain hepatocytes, distributed randomly in the hepatic lobule. Ultrastructural examination of thesame cells shows that the alpha-fetoprotein is present within the cytoplasm. Ultrastructural differences are described in hepatocytes according to whether or not the cell is producing alpha-fetoprotein at the time of sampling. These observations lead to the hypothesis that alpha-fetoprotein may correspond to a particular functional state of the hepatocyte in human fetal liver.

Cytoplasm↗
PubMed1977

The binding of 8-methoxypsoralen to nuclear DNA of UVA irradiated human fibroblasts in vitro.

Human fibroblasts were exposed to tritium-labelled 8-methoxypsoralen (8-MOP) and longwave ultraviolet (UVA) light in vitro. The proportions of photochemically bound 8-MOP in the nucleus and cytoplasm were studied by autoradiography. The results show that UVA-irradiation of the cells in the presence of 8-MOP gives rise to a significant dose-dependent binding of 8-MOP in the cell nucleus.

Animals↗
PubMed1976

Relationship between prostaglandin biosynthesis and the effect of insulin on hormone-stimulated lipolysis in rat adipose tissue.

Lipolysis in rat fat pads was studied by determination of free fatty acid and glycerol production in various experimental conditions (in the absence or presence of glucose, adrenalin and insulin). These results were compared to the accumulation of endogenous prostaglandins E2 and F2alpha during lipolysis. In the absence of glucose the prostaglandin production followed the adrenalin-induced fluctuations in released free fatty acids both in the presence or absence of insulin. In the presence of glucose and insulin, a drop in prostaglandin accumulation was observed whereas free fatty acids production was strongly stimulated. These results suggest that either free fatty acid composition is modified, influencing the activity of prostaglandin synthetase, or that there exists a specific mechanism controlling prostaglandin synthesis.

Adipose Tissue↗
PubMed1976

Ultraviolet-induced dna repair synthesis in lymphocytes from patients with actinic keratosis.

Actinic keratosis is an epidermal cancer in situ. Extensive exposure to sunlight is considered as a contributing factor to the etiology of this tumor. Ultraviolet (UV) light of solar radiation induces structural damage in DNA, which may give rise to mutations and transformed cells if the damage is not repaired. Repair of UV-induced DNA lesions is an essential property of human cells. The conditions so far reported to have defective DNA repair are all associated with an increased incidence of malignancy. Do patients with actinic keratosis also exhibit a reduced capacity to repair UV-induced DNA lesions? DNA repair synthesis in peripheral leukocytes was studied in 10 patients with actinic keratosis and 10 healthy subjects of corresponding age. After irradiation with various doses of UV light the leukocytes were incubated for 2 hr with [3H]thymidine in the presence of hydroxyurea. A dose-response relationship for the UV-induced DNA repair synthesis was established for each individual. The average repair capacity in the patients with actinic keratosis was about 30% below that of the controls. The difference is statistically significant (p less than 0.02). Reduced DNA repair synthesis may therefore be an important factor in the etiology of actinic keratosis.

Aged↗
PubMed1976

DNA repair and frequency of x-ray and u.v.-light induced chromosome aberrations in leukocytes from patients with Down's syndrome.

DNA-repair and the frequency of chromosome aberration after u.v. and X-ray irradiation was studied on leukocytes from patients with Down's syndrome. The u.v.-induced DNA-repair synthesis was followed by the incorporation of [3H]thymidine in the presence of hydroxyurea. Similar dose-response curves were established for Down's syndrome leukocytes and controls. The cells from patients with Down's syndrome incorporated 70-75% of the activity of control cells at the various doses (32-196 erg/mm.2). This difference was significant for the two highest u.v.-doses (P less than 0-01). The yield of dicentric chromosomes after X-ray exposure (150 rad.) was 35% higher in Down's syndrome leukocytes than in the control cells (P less than 0-001). Combined u.v. and X-ray irradiation caused a twofold increase in the frequency of dicentric chromosomes in control cells, while the increase was only 27% in Down's syndrome leukocytes. This synergistic effect of u.v. and X-ray irradiation on the yield of dicentric chromosomes suggests that healing of X-ray and u.v.-induced DNA lesions may partly utilize the same repair enzymes. The results also indicate that DNA repair mechanisms are impaired in leukocytes from patients with Down's syndrome, which may contribute to the increased incidence of leukemia and the susceptibility to X-ray irradiation in this disorder.

Adult↗
PubMed1975

The location of repeated DNA sequences in the chromosomes of Chironomus tentans.

Polytene chromosomes of Chironomus tentans were hybridized in situ with in vivo labelled nuclear and chromosomal RNA. Nuclear RNA formed hybrids preferentially in five distinct regions considered to contain clustered, repeated DNA sequences. These are the two nucleolar organizer regions, Balbiani ring 1 and 2, and the 5 S RNA genes in region 2A of chromosome II, which together comprised almost 70% of the total number of grains over the complement. The remaining grains were diffusely distributed over the chromosomes. There was a significant difference in the distribution of grains when RNA from different chromosomes was used for hybridization. Chromosome I RNA hybridized preferentially with chromosome I, and chromosome II+III RNA preferentially with chromosome II+III. Some regions within the chromosomes hybridized significantly more chromosomal RNA than other regions. A considerable cross-hybridization of RNA from one particular type of chromosome with the other chromosomes was also found. It is concluded that repeated DNA sequences which hybridize with heterogeneous chromosomal RNA in C. tentans are widely dispersed in the genome. Some of these sequences have a delimited localization, others are dispersed, and some sequences which are transcribed in one particular chromosome are present also in the other chromosomes.

Amino Acid Sequence↗
PubMed1975

The chromosomal distribution of balbiani ring dna in chironomus tentans.

RNA from Balbiani ring 2 (BR 2) of Chironomus tentans salivary gland cells was hybridized to polytene chromosomes of rectum cells, in which the Balbiani ring is not expressed. The distribution of the RNA:DNA hybrids was studied by autoradiography, using ultrathin emulsion to increase the resolution. The grains were estimated to cover 3-5 polytene chromosome bands, which indicates that information expressed by transcription in BR 2 may be present in several adjoining chromomeres. From a comparison of grain numbers over BR 2 of salivary gland chromosomes and over the BR 2 region of rectum chromosomes, it appears unlikely that selective amplification of BR DNA in the salivary glands could explain the efficient hybridization seen in this tissue. The conclusion is advanced that BR 2 DNA contains nucleotide sequences which are extensively repeated within 3-5 transcription units.

Animals↗
PubMed1975

Homology of Balbiani ring DNA in two closely related Chironomus species.

Cytogenetic analysis indicates that Balbiani Ring 2 (BR 2) in the two sibling species Chironomus tentans and Chironomus pallidivittatus arises from identifically banded segments in the salivary gland polytene chromosomes, although chromosomal rearrangements have occurred. In situ hybridization of BR 2 RNA to the polytene chromosomes of each individual species, as well as their F1 hybrids, reveals that the repetitious BR 2 DNA in the two species has, within the limits of the technique, retained identity of nucleotide sequences and degree of repetition. The DNA of the naturally expressed BR 1 and BR 3 in both species and that ot the galactose induced BR 6 in C. pallidivittatus did not hybridize with BR 2 RNA, indicating that these BR's are different from BR 2 with regard to sequence content.

Animals↗
PubMed1975

Localization of 5 S RNA genes in Chirnomus tentans.

The genes for 5 S RNA in Chironomus tentans have been located to region 2A of chromosome II by cytological hybridization. RNA from individual chromosomes, nuclear sap and nucleoli of salivary gland cells hybridized with the identified 5 S RNA genes in region 2A of chromosome II. The results suggest a common origin of 5 S RNA in these different nuclear compartments.

Animals↗
PubMed1975

Treatment of psoriasis with oral psoralens and longwave ultraviolet light. Therapeutic results and cytogenetic hazards.

The purpose of the present investigation was to study the usefulness of oral treatment of psoriasis with psoralens and longwave ultraviolet light and the possible cytogenetic hazards of this therapy. 8-methoxypsoralen (8-MOP) in doses between 15 and 60 mg orally followed 2 hours later by UVA irradiation of one side of the body gave a healing of the irradiated side in 24 of 40 cases and an improvment in another 11 cases while only one case healed on the side of body that was not irradiated. The most common undesired side effect was pruritus on the irradiated side of the body. The cytogenetic study showed that 8-MOP and UVA treatment of lymphocytes in vitro gives rise to chromosomal aberrations. In a combined in vivo-in vitro study where the lymphocytes had been isolated from a patient 2 hours after intake of 60-80 mg 8-MOP and then irradiated with therapeutic UVA doses, a significant increase in chromosomal aberrations was found. When chromosome analyses were made on the patients whilst the 8-MOP treatment was temporarily withdrawn and when the lymphocytes were not irradiated in vitro, no increased frequency of chromosomal abberations was found on comparison with a group of psoriatic patients receiving dithranol therapy.

Administration, Oral↗