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Biomedical subjects

S Barton

Publications and source records attributed to S Barton.

At least 73 records · Page 4Linked to original sources
PubMed1995

Dehydroepiandrosterone reduces progressive dermal ischemia caused by thermal injury.

Progressive ischemia and necrosis of the skin following thermal injury are reduced by postburn administration of the steroid hormone dehydroepiandrosterone (DHEA). Thermally injured animals were provided with a subcutaneous injection of DHEA, or a related species of steroid hormone, at various times after burning. During the 96 hr following administration of the scald burn, tissue necrosis was closely monitored. Subcutaneous administration of DHEA at approximately 1 mg/kg/day achieved optimal protection against the development of progressive dermal ischemia. DHEA, 17 alpha-hydroxy-pregnenelone, 16 alpha-bromo-DHEA, and androstenediol each demonstrated, a similar level of protection. Other forms of steroids, including DHEA sulfate, androstenedione, 17 beta-estradiol, or dihydrotestosterone, exhibited no protective effect under the conditions tested. Additionally, intervention therapy with DHEA could be initiated up to 4 hr, but not 6 hr, after burn without a marked reduction in therapeutic benefit. Examination of the microvasculature of thermally injured dorsal skin suggested that postburn intervention with DHEA, either directly or indirectly, maintained a normal architecture in most of the dermal capillaries and venules within burn-exposed tissue. These findings suggest that systemic intervention therapy of burn patients with DHEA or a similar acting steroid hormone may be useful in preventing the progressive tissue destruction caused by progressive ischemia.

17-alpha-Hydroxypregnenolone↗
PubMed1994

Tandemly repeated transgenes of the human minisatellite MS32 (D1S8), with novel mouse gamma satellite integration.

The human hypervariable minisatellite MS32 has a well characterised internal repeat unit array and high mutation rates have been observed at this locus. Analysis of MS32 mutants has shown that male germline mutations are polarised to one end of the array and frequently involve complex gene conversion-like events, suggesting that tandem repeat instability may be modulated by cis-acting sequences flanking the locus. In order to investigate the processes affecting MS32 mutation rate and mechanism, we have created transgenic mice harbouring an MS32 allele. Here we describe the organisation of eight transgenic insertions. Analysis of these transgenic loci by MVR-PCR and structural analysis of the junctions between mouse flanking DNA and the transgenic loci has shed light on mechanisms of integration and rearrangement of the tandem repeated transgenes. Sequence analysis of the mouse DNA flanking these transgenes has shown that 5 of the 8 insertions have integrated into mouse gamma satellite repeated sequence. This suggests a non-random integration of the MS32 transgene construct into the mouse genome.

Alleles↗
PubMed1994

The non-viability of uniparental mouse conceptuses correlates with the loss of the products of imprinted genes.

Diploid parthenogenetic or androgenetic mouse conceptuses produce characteristic and opposite mutant phenotypes and are non-viable, presumably due to different contributions from the maternal and paternal genomes. This is likely to be the result of the preferential expression of only one parent's copy of certain genes in the offspring. So far, four such endogenous imprinted genes are known: the paternal alleles of Igf2 and Snrpn and the maternal alleles of Igf2r and H19 are active, while their opposite parental alleles are inactive. Here we demonstrate that the expression patterns of the Igf2 and Igf2r genes in androgenetic and parthenogenetic conceptuses correlate with which parental alleles normally express them, implying that the imprint can be maintained in the absence of the other parent's genome for these genes. This also indicates that both types of uniparental conceptuses are lacking developmentally important gene products. We did find, however, that the H19 gene was highly expressed not only in the parthenogenetic conceptus, but also in giant trophoblasts and secondary giant cells in the androgenetic placenta, in spite of the imprinting of the H19 gene in normal mouse extra embryonic tissues. We discuss these observations with respect to the non-viability of uniparental conceptuses and the reciprocal imprinting patterns of the Igf2 and H19 genes.

Animals↗
PubMed1994

Chaos, self-organization, and psychology.

A variety of investigators in recent years have proposed models of psychological systems based on the concepts of chaos, nonlinear dynamics, and self-organization. Unfortunately, psychologists in general have little understanding of these important ideas. These terms are defined, and their relationships are discussed. The value of applying these concepts to psychological systems is demonstrated by exploring their utility in areas ranging from neuroscience to clinical psychology. Some of the difficulties in using nonlinear concepts and methodologies in empirical investigations are also discussed.

Animals↗
PubMed1993

cDNA cloning and characterisation of novel ripening-related mRNAs with altered patterns of accumulation in the ripening inhibitor (rin) tomato ripening mutant.

A cDNA library produced from mRNA isolated from the pericarp of wild-type tomato fruit (Lycopersicon esculentum Mill. cv Ailsa Craig) at the first visible sign of fruit ripening was differentially screened to identify clones whose homologous mRNAs were present at reduced levels in fruit of the tomato ripening mutant, ripening inhibitor,rin. Five clones were isolated (pERT 1, 10, 13, 14, 15). Accumulation of mRNA homologous to each of these clones increased during the ripening of wild-type fruit and showed reduced accumulation in ripening rin fruit. The levels of three of them (homologous to ERT 1, 13 and 14) were increased by ethylene treatment of the mutant fruit. A further clone, ERT 16 was identified for a mRNA present at a high level in both normal and mutant fruit at early stages of ripening. Database searches revealed no significant homology to the DNA sequence of ERT 14 and 15; however, DNA and derived amino acid sequence of ERT 1 both contain regions of homology with several reported UDP-glucosyl and glucuronosyl transferases (UDPGT) and with a conserved UDPGT motif. A derived amino acid sequence from the ERT 10 cDNA contains a perfect match to a consensus sequence present in a number of dehydrogenases. The ERT 13 DNA sequence has homology with an mRNA present during potato tuberisation. The presence of these mRNAs in tomato fruit is unreported and their role in ripening is unknown. The ERT 16 DNA sequence has homology with a ripening/stress-related cDNA isolated from tomato fruit pericarp.

Amino Acid Sequence↗
PubMed1993

[Genetic composition of Chilean population: the Pehuenches from Trapa-Trapa].

This study describes the genetic composition of Pehuenche indians from Trapa-Trapa. The admixture analysis revealed that this group has conserved most of its pre-Columbian gene pool and therefore, is representative of the indians that lived in Southern Chile before the Spanish conquest. A relatively high frequency of a esterase D variant seems to indicate that this is a Chilean aboriginal population marker. The Chilean Pehuenches are genetically similar to their Argentinean relatives, which is not surprising since this last group crossed the Andes Mountains in historic times.

Blood Group Antigens↗
PubMed1992

Stereological studies of desmosomes in ichthyosis vulgaris.

Standardized stereological methods were performed on biopsies from three subjects with normal skin and from three patients with autosomal dominant and three with autosomal recessive sex-linked ichthyosis to determine the relative numbers and dimensions of desmosomes. The results showed an increase in the persistence of desmosomes in the stratum corneum in both ichthyotic groups. This suggests a pathogenetic role for desmosomes in the abnormal desquamation of the two types of ichthyosis vulgaris.

Adolescent↗
PubMed1992

[Genetic evidence corroborates Negme's hypothesis about the greater mildness of American trypanosomiasis in Chile].

Chagas disease is present in northern and central Chile. Not more than 25% of infected individuals have had a pathologic condition presumably due to Trypanosoma cruzi. The majority of individuals with chronic infectious Chagas disease in Chile are asymptomatic in contrast to what has been observed in other South American countries. Historic and paleopathologic evidences suggest that this particular behavior could be explained by a genetic adaptation of Chilean aborigines to T cruzi. Associations between ethnic admixture, presence of Chagas disease, associated cardiac pathology and 4 blood groups (ABO, MNSs, Rh and Duffy) were investigated among inhabitants of San Pedro de Atacama in northern Chile. Cardiac pathology was determined by positive serologic reactions in individuals with abnormal electrocardiographic findings. Individuals with negative serologic results had a significantly greater aboriginal admixture (88%) compared to those with positive serology (66%). This findings supports the hypothesis of genetic adaptation explaining mildness of Chagas disease in Chile.

Adaptation, Physiological↗
PubMed1991

Human antibody production in transgenic mice: expression from 100 kb of the human IgH locus.

In order to study the requirements for a human antibody repertoire to be engineered in transgenic animals, we have created mouse strains that express human immunoglobulin genes from 100 kb of cosmid DNA. Undisrupted integration of the human DNA in the mouse germ line, encoding germ-line V,D,J and the Cmu constant region, was achieved, and proved sufficient for the production of human IgM in the mouse serum. Co-integration of one cosmid (containing the VH6 gene and a 36-kb region of the J-proximal D cluster) with a second cosmid (containing VH26, a further 38-kb of the D cluster, JH and Cmu) results in V-D-J rearrangements in the transgenic mice, similar to those seen in human DNA, were found only in spleen but not in thymus. Random hybridomas made from these transgenic mice show heterogeneous rearrangements of the human transgenes. Sequences of V-D-J units derived from transgene rearrangements reveal extensive N-region and apparent D segment diversity. These results show that utilisation of human Ig genomic segments does occur in transgenic mice, paving the way for the derivation of a mouse strain that makes authentic human antibodies from inserted heavy and light chain gene loci.

Animals↗
PubMed1991

Transverse cerebellar diameter: a useful predictor of gestational age for fetuses with asymmetric growth retardation.

There have been conflicting reports regarding the ability of cerebellar diameter to satisfactorily predict the gestational age of growth-retarded fetuses. Gestational age prediction intervals were derived from 270 normal fetuses between 14 and 40 weeks' gestation for biparietal diameter, head circumference, abdominal circumference, femur length, and transverse cerebellar diameter. We evaluated the ability of these parameters to predict gestational age for 19 small-for-gestational-age fetuses. The cerebellar diameter regression model led to the smallest differences between observed and predicted gestational age for all growth-retarded fetuses. Transverse cerebellar diameter satisfactorily predicted gestational age for all six fetuses with asymmetric intrauterine growth retardation and was associated with the least amount of underestimation bias when compared with other ultrasonographic parameters. However, transverse cerebellar diameter appeared to be no better than biparietal diameter, head circumference, or femur length for accurately predicting gestational age of fetuses with symmetric intrauterine growth retardation (n = 13) despite the finding that cerebellar growth was also relatively spared under these circumstances. We conclude that transverse cerebellar diameter can be used to reliably approximate gestational age in fetuses with asymmetric intrauterine growth retardation. However, caution is warranted when using it to predict the gestational age of fetuses affected by symmetric intrauterine growth retardation.

Anthropometry↗