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Biomedical subjects

F W George

Publications and source records attributed to F W George.

At least 73 records · Page 4Linked to original sources
PubMed1980

pathogenesis of the henny feathering trait in the Sebright bantam chicken. Increased conversion of androgen to estrogen in skin.

In female chickens of all breeds development of female feathering pattern is mediated by estrogens, whereas normal males and castrated chickens of both sexes develop male feathering. Male chickens carrying the henny feathering trait (such as the Sebright bantam and golden Campine) develop a female feathering pattern but otherwise virilize normally. To examine the possibility that the henny feathering trait is the result of increased conversion of androgen to estrogen in skin, estrogen formation from [1,2,6,7-3H]testosterone was measured in tissue slices from control breeds and chickens with the henny feathering trait. Rates of estrogen formation were undetectable or low in all control tissues other than ovary, whereas rates were high in skin and skin appendages and detectable in many tissues from Sebright and Campine birds. The increased rate of estrogen formation in skin was demonstrable in Sebright chicks and in all areas of skin biopsied in the mature bird. Furthermore, plasma levels of 17 beta-estradiol were higher in Sebright and Campine than in control male cocks. Thus, increased formation of estrogen from androgen in the peripheral tissues probably explains the henny feathering trait.

Androgens↗
PubMed1980

Mammography at reduced doses: present performance and future possibilities.

Reduced dose mammography is assessed with the aid of very recent work. It is concluded that there are technical and clinical reasons for believing that the reduced dose systems and their interpreters should perform more effectively than their predecessors. Review of known technologic achievements suggests a possible 6 to 7 reduction factor from present screen-film mammography dose levels without sacrificing image quality. Reasonable estimates of representative doses presently achieved by both xeroradiography and screen-film systems are given. The screen-film value is about 3 times higher than some previous estimates for these systems.

Adult↗
PubMed1980

Description of an afterloading 192Ir interstitial-intracavitary technique in the treatment of carcinoma of the vagina.

This is a preliminary report of an afterloading 192Ir interstitial-intracavitary technique used in the treatment of carcinoma of the vagina. Thirteen cases of carcinoma of the vagina, stages I through III, were treated at the Southern California Cancer Center and University of Southern California Radiation Medicine Unit between November 1976 and February 1978. The Syed-Neblett perineal template is described in detail, as are the precise clinical application techniques. The hallmarks of the method are: 1) ease of use by the physician, 2) homogeneous radiation dose distribution, and 3) differential radiation dose delivery capabilities. The technique is believed to be an improvement over previous modalities of therapy reported in the literature.

Adult↗
PubMed1979

Uterine cervical cancer: treatment with megavoltage radiation results and afterloading intracavitary techniques.

Results were evaluated for 651 consecutive patients with invasive cancer of the intact uterine cervix. From 1963 through 1967 319 patients were treated primarily with the older Los Angeles County Hospital system of orthovoltage radiation and intracavitary radium therapy. Thereafter, 1968--1974, 332 patients were treated primarily with a newer modified M. D. Anderson Tumor Institute system of megavoltage radiation and afterloading intracavitary radium therapy. Age distribution and histology were similar for both groups, but clinical stage was slightly more advanced for patients treated earlier. Crude and net 5 year survival rates were 36% and 49% for the early group and 54% and 67% for the later group. Net 5 year survival rates for the earlier group by stage were: stage I, 74%; II, 62%; III, 23%; and IV, 6%. Survival rates for the later group were: I, 81%; II 76%; III, 50%; and IV, 15%. We believe this improvement can be attributed to more effective intracavitary radium therapy for handling local cancer and to delivery of cancericidal doses of radiation to regional nodes with the megavoltage radiation apparatus, as well as to the greater cooperative efforts put forth in the management of County Hospital patients.

Adenocarcinoma↗
PubMed1978

Estrogen formation in the early rabbit embryo.

Androgen formation (3beta-hydroxysteroid dehydrogenase activity) was detectable in the rabbit blastocyst on day 5 of gestation (before implantation); estrogen formation was first detectable on day 7. The capacity to form estrogen on the day of implantation suggests that estrogen formation in the blastocyst may play a role in the implantation process.

3-Hydroxysteroid Dehydrogenases↗
PubMed1978

Primary treatment of carcinoma of the lower rectum and anal canal by a combination of external irradiation and interstitial implant.

Ten patients with carcinoma of the anorectum were treated with a combination of external irradiation and after-loading interstitial 192Ir implant, which seems to be effective in controlling relatively small cancers of the anorectum and providing effective palliation of extensive lesions. Five of the 10 patients remain free of tumor after a minimum follow-up of 15 months. Four of the 10 were treated with one interstitial implant and 4,000--5,000 rads of external irradiation and 6 were treated with the same amount of irradiation and two implants. When two implants were used, complications were minimal.

Adenocarcinoma↗
PubMed1978

Aromatase activity in the developing rabbit brain.

The formation of 17beta-[3H]estradiol from [1,2,6,7-3H]testosterone was assessed in placenta and central nervous system tissues from rabbit embryos that varied in age from 13-28 days of gestation. In the fetal brain, significant rates of aromatase activity were limited exclusively to the forebrain, and the highest rates of activity (approximately 0.5 pmol/h/mg protein) were found in the diencephalon both male and female embryos between days 19 and 25 of gestation. These rates of aromatase activity are second only to the fetal ovary when expressed per mg protein; moreover, forebrain is the only tissue in the male embryo capable of synthesizing significant amounts of estrogens in vitro. When projected to the whole organ, the capacity of the diencephalon for aromatization exceeds the capacity of the fetal ovary approximately 9-fold. Placental aromatase activity was high (2.1 pmol/h/mg protein) on day 13 but fell to a level approximately 20-fold lower by day 19 of gestation. These findings indicate the potential importance of the forebrain as a source of estrogens during embryogenesis.

Androstenedione↗
PubMed1978

Conversion of androgen to estrogen by the human fetal ovary.

The conversion of radiolabeled androgen to estrone and 17 beta-estradiol was assessed in tissues of human embryos that varied from phenotypically indifferent stages (1-3 cm crownrump length) to midgestation (15. 1-20 cm crownrump length). Significant rates of estrogen synthesis were demonstrated only in ovaries, liver, and brain. Estrogen synthesis was undetectable in gonads from 1-3 cm fetuses, but by the 3.1-5-cm stage it had reached an average rate of 1.9 pmol . h-1 . mg protein -1 in ovaries and remained at this level of activity through the latest stages examined. Estrogen formation was undetectable in testes at all stages examined, but the time of appearance of the capacity to form estrogens in the fetal ovary is similar to the onset of the capacity of the fetal testis to synthesize testosterone. The capacity of the fetal ovary to form estrogen develops before histological differentiation of the tissue.

Androgens↗
PubMed1977

Persistent carcinoma of the oropharynx and oral cavity re-treated by after-loading interstitial 192Ir implant.

After-loading implantation techniques apparently offer an effective alternative in the management of persistent (or recurrent) oropharynx and oral cavity carcinoma postirradiation. A total of 29 patients with such lesions was treated from February 1974, to July 1975, in the LAC/USC Radiation Medicine Section, using after-loading 192Ir implantation techniques. These patients all had extensive persistent cancer after "full tolerance" irradiation (with or without previous surgery) and were referred for palliation or for possible salvage. Additional doses administered ranged from 5000 to 7000 rads in three to five days. Eighteen of the 29 patients (63%) have had complete local control for 18 to 36 months. These patients have maintained a relatively satisfactory palliative status. Ten of the 29 are dead. Follow-up periods are short, but early indications are that problem patients with persistent cancer after "full tolerance irradiation" can be salvaged, or at least satisfactorily palliated, with after-loading interstitial implant techniques. Clinical details, sites of involvement, implantation techniques, dosimetry methodology, reactions and complications will be described.

Adult↗
PubMed1977

Estrogen formation by the ovary of the rabbit embryo.

The conversion of [1,2,6,7-3H]- testosterone to radioactive estradiol was assessed in tissue slices of 18 different tissues from rabbit embryos that varied in age from 16 to 29 days gestation. Significant rates of estradiol synthesis were demonstrated only in ovaries [4.2 +/- 0.7 (mean +/- SEM) pmol/h/mg) protein], placenta (0.7 +/- 0.2 pmol/h/mg protein) and brain (0.3 +/- 0.1 pmol/h/mg protein). Estradiol formation was undetectable in day 16 gonads of both sexes and in tests at all ages examined, but by day 18 it was demonstrable in ovaries and rose rapidly to reach a level of 6 pmol/h/mg protein by day 19. The time of appearance of the enzymatic capacity to convert testosterone to estradiol in the ovary is similar to the onset of the enzymatic capacity to form testosterone by the fetal testis, suggesting that the acquisition of the enzymatic activies that allow specific endocrine function by these two tissues may be regulated by the same or similar factors during embryonic development.

Androstenedione↗
PubMed1977

Afterloading interstitial implant in the treatment of oral cavity and oropharyngeal cancers.

(1) In all, 70 patients with carcinoma of the oral cavity and oropharynx have been treated utilizing one or more of several interstitial iridium-192 afterloading techniques. (2) After an 18-month minimum follow-up period, local control is still maintained in 9 of 10 patients with T1 and T2 lesions (UICC), in 17 of 22 patients with T3 lesions, and in 21 of 38 patients reirradiated for recurrent disease. The complication rate of 29% in the reirradiated patients, though high, is considered acceptable in these essentially hopeless cases. (3) This preliminary report is made to stimulate interest in the role of interstitial iridium-192 afterloading techniques. We feel they deserve evaluation in a controlled study of other head and neck cancer management techniques (including external irradiation, surgical resection and adjunctive chemotherapy).

Follow-Up Studies↗