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Biomedical subjects

J Aitken

Publications and source records attributed to J Aitken.

17 recordsLinked to original sources
PubMed1992

Relative expression of aromatase cytochrome P450 in human fetal tissues as determined by competitive polymerase chain reaction amplification.

The aromatase enzyme complex is responsible for the conversion of C19 steroids to estrogens. Aromatase activities ranging from moderate to very low have been measured in human fetal tissues. The inability to demonstrate aromatase cytochrome P450 (P450AROM) messenger RNA (mRNA) in several fetal tissues by northern blotting has been attributed to low levels of specific message. In order to identify and compare P450AROM mRNA levels in fetal tissues, we developed a specific competitive polymerase chain reaction amplification technique. This reaction uses coamplification of a rat P450AROM complementary RNA to normalize differences in amplification efficiencies. Using this technique, P450AROM mRNA was identified in all fetal tissues studied including; liver, lung, brain, skin, intestine, kidney, spleen, and heart. Fetal liver contained far more P450AROM mRNA per total RNA than any other tissues studied. Fetal brain and intestine also tended to have slightly higher levels than other tissues.

Aromatase↗
PubMed1992

Determination of aromatase cytochrome P450 messenger ribonucleic acid in human breast tissue by competitive polymerase chain reaction amplification.

Local production of estrogen in breast tissue may influence the growth of breast cancers. Peripheral conversion of C19 steroids to estrogens is catalyzed by the aromatase enzyme complex which is comprised of a specific form of cytochrome P450, aromatase cytochrome P450 (P450AROM) and the flavoprotein, NADPH-cytochrome P450 reductase. To evaluate P450AROM mRNA levels in breast tissue, a specific competitive polymerase chain reaction amplification procedure was devised. In this method, a rat P450AROM complementary RNA is coamplified as an internal standard in order to compare amplification reactions. The amplification products are recognized by hybridization with 32P-labeled oligonucleotides specific for each species. Densitometry is used to quantitate autoradiographs. Initial studies using RNA from whole breast tissue obtained from reduction mammoplasty revealed linearity of the relationship between the densitometer signal from the human amplification product and total RNA concentration. Breast tissue was then separated into a floating adipocyte fraction and a pelleted fraction containing the other cellular elements by collagenase digestion and centrifugation. Comparison of specific content of aromatase amplification product per unit weight of RNA extracted from adipocytes and pelleted cells revealed considerably higher levels in the RNA from the nonadipocyte fraction. Immunocytochemical characterization of this fraction revealed the presence of several cell types including macrophages, ductal epithelial cells, and endothelial cells, but primary cells of stromal origin.

Animals↗
PubMed1990

The aromatase enzyme: from cloning to cancer.

Estrogen production by adipose tissue has been implicated in the etiology of such human cancers as endometrial and breast cancer. Estrogen production by adipose cells is subject to complex multifactorial regulation by a number of growth factors and cytokines, including those produced by breast cancer cells. In order to understand the mechanisms responsible for aromatase regulation, the structural gene encoding aromatase cytochrome P-450 (P-450AROM) was isolated from human genomic DNA. The gene spans at least 70 kb and is comprised of 10 exons, the first of which is untranslated. DNA sequence analysis indicates that the gene has a putative TATA (ATAAAA) sequence at -23 bp and putative CAAT binding sequences beginning at -41, -67, and -83 bp, that constitute a promoter region responsible for expression in placenta. However, this promoter does not appear to be responsible for expression in adipose, which may therefore be under the control of another, tissue-specific, promoter. Use of Polymerase Chain Reaction (PCR) technology has allowed for determination of expression of P-450AROM in samples of breast adipose. Preliminary results indicate that expression is highest in the upper lateral region, similar to the site of most frequent localization of tumors.

Adipose Tissue↗
PubMed1986

Campylobacter-like organisms in gastric biopsies: a Christchurch study.

Following a 20 patient pilot investigation for Campylobacter pyloridis in selected gastric biopsy specimens, 56 consecutive patients subjected to routine gastroscopies were further examined. 14/56 had positive gram stains for spiral gram negative bacilli in gastric biopsy imprints and 4/14 had positive culture for this organism. All 14 positive specimens showed histological gastritis of varying degrees (grade 3 inflammation). The methodology, significance and implications of these findings are discussed in this first New Zealand report of C pyloridis in the stomach.

Adult↗
PubMed1986

A comparison of fixed regimens for obtaining human cleaving oocytes for research purposes.

A fixed schedule for ovarian stimulation and follicular aspiration, previously used in our department for research purposes, was modified in an attempt to increase the recovery and cleavage rates of the oocytes. Three different clomiphene regimens were used to stimulate the ovaries of normal volunteer women requesting laparoscopic sterilization (50 mg and 150 mg daily for 5 days, and 50 mg daily for 10 days). Oocytes were recovered from 83% of the aspirated follicles, i.e. 1.6 oocytes/patient: 65% of the oocytes cleaved after in-vitro fertilization and, on average, 1.0 cleaving egg was obtained per patient. There were no differences in the recovery and cleavage rates between the three clomiphene regimens. It is concluded that a sufficient number of cleaving embryos for research purposes can be generated with the present fixed regimen, which offers little inconvenience to the volunteers as the day of egg recovery can be predicted some time in advance.

Adult↗
PubMed1985

Meiosis-inducing substances in human preovulatory follicular fluid related to time of follicle aspiration and to the potential of the oocyte to fertilize and cleave in vitro.

Meiosis-inducing substance (MIS) and steroid and gonadotropic hormones were investigated in 41 preovulatory follicular fluids (FFs) aspirated at either 0, 12, or 36 hours after human chorionic gonadotropin (hCG) administration in 25 women with clomiphene citrate-stimulated cycles. Twenty-one oocytes were recovered from these FFs and subjected to in vitro fertilization. MIS activity was present in 25 (61%) of the FFs. The frequency of MIS-active FFs increased from 11% (1 of 9) at 0 hours and 40% (2 of 5) at 12 hours to 81% (22 of 27) at 36 hours after hCG administration (P less than 0.001). The concentration of hormones in MIS-active FFs was not significantly different from that of MIS-inactive FFs. Twelve (86%) of 14 oocytes that fertilized and cleaved in vitro were recovered from MIS-active FFs. By contrast, all seven oocytes that remained unfertilized in vitro were recovered from MIS-inactive FFs. These findings support the notion that resumption of meiosis in the preovulatory oocyte is triggered by MIS in FF and suggest that follicular MIS production may be one of the factors that determines the success of in vitro fertilization and early embryonic development.

Androstenedione↗