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Biomedical subjects

A Simons

Publications and source records attributed to A Simons.

At least 37 records · Page 2Linked to original sources
PubMed1997

Isolation of osteosarcoma-associated amplified DNA sequences using representational difference analysis.

Comparative genomic hybridization analysis of a primary osteosarcoma and its metastasis revealed two regions of DNA amplification, one at 17p11.2-12 and one at 19q12-13. Subsequent representational difference analysis of the primary tumor resulted in the isolation of two distinct tumor-amplified DNA fragments originating from chromosome 19. A YAC clone corresponding to one of the two isolated DNA fragments was used for fluorescence in situ hybridization on normal human lymphocyte metaphases and tumor-derived nuclei. This resulted in the localization of this YAC to 19q12-13.1 and confirmed the amplification status of the isolated fragment in the tumors. The availability of such RDA-isolated sequences may be instrumental in the search for genes relevant for tumor development.

Adolescent↗
PubMed1995

The use of a particulate, microporous, calcified copolymer as a ridge maintenance device in dogs.

HTR polymer Synthetic Bone was found to be an osteoconductive, biocompatible, reliable nonresorbable matrix ridge maintenance material (Ridge Preservation). When used as socket implants immediately after the extraction of teeth over a one-year period in 16 beagle dogs, HTR was observed clinically and radiographically and compared with controls (unimplanted, sutured) extraction sites. As the control areas resorbed, the stability and effectiveness of the synthetic bone material in the operative sites became more clearly delineated. Quantitative analyses could not be made using radiographic techniques, but radiographs supported by subjective clinical observations as well as study casts taken of the height and width of the implanted areas, showed greater ridge retention compared with controls. Histological sections demonstrated dense laminar bone gradually forming into and around the HTR particulate material.

Alveolar Bone Loss↗
PubMed1994

Clinical characteristics associated with interpersonal depression: symptoms, course and treatment response.

A range of theories, including environmental, personality and cognitive theories, have suggested that loss may be a particularly critical form of stress in the etiology and expression of depression. The current study examines whether interpersonal depression predicted a unique clinical presentation and course in subjects with major depression. Subjects who became depressed following a severe interpersonal event were contrasted with two control groups: patients without antecedent stressors and patients with major non-interpersonal stressors. The hypothesized interpersonal subgroup was differentiated from the control groups only in the speed of treatment response. Proposals for future research are discussed.

Adult↗
PubMed1994

Does wild-type p53 play a role in normal cell differentiation?

Inactivation of the p53 tumor suppressor gene plays a major role in malignant transformation. The central question in this issue is concerned with the understanding of the function of p53 in normal cells and its deregulation in cancer cells. Several in vitro and in vivo experimental models have indicated that induction of cells to undergo differentiation involve up-regulation in the expression of the p53. In the case of B cell differentiation, p53 was found to be involved in several steps of the differentiation pathway. The conclusion that p53 plays a role in normal development and differentiation in vivo is substantiated by the observation that p53 is expressed during embryonic development and is detected at low levels in a number of organs of adult mice. Accentuated levels of p53 in testes of adult mice, suggests that p53 plays a role in the meiotic process of spermatogenesis. B cell differentiation and spermatogenesis are biological pathways which normally involve DNA reshuffling and rearrangements. In accordance with the notion that p53 is associated with DNA repair it is tempting to speculate that at least in these physiological pathways p53 functions as a master gene that controls genome integrity.

Animals↗
PubMed1993

Cloning, nucleotide sequence, and regulatory analysis of the Lactococcus lactis dnaJ gene.

The dnaJ gene of Lactococcus lactis was isolated from a genomic library of L. lactis NIZO R5 and cloned into pUC19. Nucleotide sequencing revealed an open reading frame of 1,137 bp in length, encoding a protein of 379 amino acids. The deduced amino acid sequence showed homology to the DnaJ proteins of Escherichia coli, Mycobacterium tuberculosis, Bacillus subtilis, and Clostridium acetobutylicum. The level of the dnaJ monocistronic mRNA increased approximately threefold after heat shock. The transcription initiation site of the dnaJ gene was determined and appeared to be preceded by a typical gram-positive vegetative promoter sequence (TTGCCA-17 bp-TAAAAT). Upstream of the promoter region, an inverted repeat is located that is identical to those detected upstream of heat shock genes of other gram-positive organisms. A transcriptional fusion between the dnaJ expression signals and a usp45-amyS secretion cassette caused a significant increase in alpha-amylase activity after heat shock induction. Deletion mutagenesis showed that the inverted repeat is involved in heat shock regulation of the dnaJ gene. The conservation of this palindromic sequence in gram-positive heat shock genes suggests a common regulatory pathway distinct from the system used in gram-negative bacteria.

Amino Acid Sequence↗
PubMed1993

Clinical trials with a polycrystalline alumina dental implant.

The Tübingen polycrystalline alumina implant utilizes bony apposition as the method of stabilization. Its cylindrical configuration allows the implant site to be prepared by use of ultra-low-speed drills. This study focused on the use of the implant as a single-tooth, free-standing device. Thirty patients were selected. Devices were followed for five years. The implants were placed in one of two applications: immediate extraction site or healed edentulous ridge. A simple purse-string suture technique was used for closure. Periodic observations were recorded. Of the 30 planned implants, all have been completed to date. Twenty-five of the 30 have been considered successful. Twenty-three of the 25 successes were from the immediate extraction group. Only 2 of 5 were successful in the healed ridge group. Due to the structural requirements of the Tübingen implant, its size makes it usable only in wider-than-average edentulous ridges. The success rate was 83.3%, and for those devices placed in immediate extraction sites, a success rate of 92% was recorded.

Adolescent↗
PubMed1991

Evaluation of computer generated neonatal discharge summaries.

Computer generated and dictated discharge summaries were compared for all 133 babies admitted for intensive and special care during a six month period. Whereas 130/133 (98%) had a computer generated summary, only 94/133 (71%) had a dictated summary. In addition, computerised summaries were completed at discharge, but there was a delay up to 26 weeks for dictated summaries. Dictated summaries had more items of basic data missing but were more readable. A main diagnosis was missing in only 5/95 (5%) of dictated and 1/130 (1%) computerised summaries. Of the computer generated summaries, 114/133 (86%) were suitable to give to parents. Satisfactory discharge summaries for babies requiring intensive or special care can be generated with an on line computer system.

Communication↗
PubMed1991

Persistently low natural killer cell activity, age, and environmental stress as predictors of infectious morbidity.

In recent studies of 'low natural killer (NK) cell syndrome', low NK activity was measured in individuals who were symptomatic, and therefore a causal relationship between low NK activity and infectious or other disease manifestations could not be concluded. However, preliminary work by members of our collaborative team (S.L. and R.H.) provided some indications for chronic low NK activity preceding and predicting subsequent infectious morbidity. This present study was designed to address this causal question in a larger sample, using a longitudinal design. Subjects were 106 healthy normal volunteers from the community. They were examined medically and psychosocially at baseline, and were then followed over a 6-month interval, with serial monthly assessments over the study period. The results supported our hypothesis that individuals who were currently healthy, but who exhibited a pattern of natural immunity characterized by persistently low NK cytotoxicity would be at risk for development of infectious sequelae over a 6-month follow-up period. The results also showed that younger age and the perception of more severe 'hassles' or stressors also predicted more infectious morbidity during the 6-month study period. Chronological age appeared to have both a direct, as well as indirect (via NK activity) association with illness outcome. Contrary to our expectation, the report of environmental stressors was directly associated with illness outcome, but not indirectly associated with outcome via natural immunity.

Adolescent↗
PubMed1989

The role of IL-4 in the generation of B lymphocytes in the bone marrow.

It has been indicated that IL-4 supports the maturation of pre-B cells to B lymphocytes. The present study was designed to investigate the mechanism by which IL-4 influences this maturational process. In order to determine whether IL-4 acts directly on pre-B cells, we sorted out B220+, sIg- cells from bone marrow of young adult (C3H X C57BL/6)F1 mice. These purified populations of pre-B cells (greater than 95%) were incubated with and without 4 to 200 U/ml of rIL-4, and the generation of new B lymphocytes in these cultures was followed for several days. We found that the frequency of newly generated B lymphocytes (%sIg+) was similar in control and in IL-4-containing cultures. However, the total number of B lymphocytes was significantly higher in IL-4-containing cultures. This high number of B lymphocytes was a result of an increased survival of cells in IL-4-containing cultures. The effect was IL-4 specific because anti-IL-4 antibodies completely prevented this phenomenon. We thus conclude that IL-4 does not induce the maturation of pre-B cells but may be important in the process of B lymphocytes generation by providing a signal for survival of these cells.

Animals↗
PubMed1989

Persistently low natural killer cell activity in normal adults: immunological, hormonal and mood correlates.

This current study is concerned with the identification of the incidence of persistently low natural killer (NK) cell activity in an essentially healthy population of young adults, and the characterization of the psychological profile associated with this pattern of NK activity. Eighty-eight individuals, between the ages of 18 and 44 years, were accrued to this project. Subjects were tested serially, at baseline induction into the study, and at 2 and 4 weeks follow-up. Baseline assessment included a complete physical examination and laboratory work-up in order to exclude anyone ill at the time of enrollment, and to have complete physical status information on all subjects at the time of accrual. NK activity, urinary catecholamine levels and psychological status were also assessed at baseline, and at the specified follow-up intervals. Individuals with low NK activity were operationally defined as those having NK function either below the group mean, or below the group lowest quartile, at baseline and at two follow-up assessments. Results showed that in both univariate analyses, as well as in logistic regression models, age and the perception of environmental stressors or 'hassles' predicted persistently low NK activity. Younger subjects, who perceived environmental events to which they were exposed as more serious in nature, were more likely to exhibit a persistently low NK profile over time than older individuals who perceived daily events as less important to them.

Adult↗
PubMed1984

Possible ideal lac operator: Escherichia coli lac operator-like sequences from eukaryotic genomes lack the central G X C pair.

Five DNA fragments have been cloned from yeast, chicken, and mouse DNA that titrate lac repressor in an Escherichia coli lac+ I+Z+ wild-type strain when on a multi-copy plasmid. The five repressor-binding sequences have been identified by DNA sequence determinations and DNase cleavage-inhibition patterns. They share the 14-base-pair symmetrical consensus sequence 5' T-G-T-G-A-G-C:G-C-T-C-A-C-A 3' (the colon represents the center of symmetry), which is an inverted repeat of 7 base pairs of the left half of the E. coli lac operator. A similar perfect palindromic DNA fragment--an 11-base-pair inverted repeat of the left half of the lac operator--was synthesized. The cloned synthetic DNA 5' G-A-A-T-T-G-T-G-A-G-C:G-C-T-C-A-C-A-A-T-T-C 3' binds lac repressor 8-fold more tightly than does wild-type E. coli lac operator DNA.

Animals↗