Gonadotropin-releasing hormone (GnRH) cells arise from cranial neural crest and adenohypophyseal regions of the neural plate in the zebrafish, Danio rerio.

The olfactory placodes generate the primary sensory neurons of the olfactory sensory system. Additionally, the olfactory placodes have been proposed to generate a class of neuroendocrine cells containing gonadotropin-releasing hormone (GnRH). GnRH is a multifunctional decapeptide essential for the development of secondary sex characteristics in vertebrates as well as a neuromodulator within the central nervous system. Here, we show that endocrine and neuromodulatory GnRH cells arise from two separate, nonolfactory regions in the developing neural plate. Specifically, the neuromodulatory GnRH cells of the terminal nerve arise from the cranial neural crest, and the endocrine GnRH cells of the hypothalamus arise from the adenohypophyseal region of the developing anterior neural plate. Our findings are consistent with cell types generated by the adenohypophysis, a source of endocrine tissue in vertebrate animals, and by neural crest, a source of cells contributing to the cranial nerves. The adenohypophysis arises from a region of the anterior neural plate flanked by the olfactory placode fields at early stages of development, and premigratory cranial neural crest lies adjacent to the caudal edge of the olfactory placode domain [Development 127 (2000), 3645]. Thus, the GnRH cells arise from tissue closely associated with the developing olfactory placode, and their different developmental origins reflect their different functional roles in the adult animal.

Preservation of augmented breasts in patients with breast cancer.

It is not uncommon for a patient who has previously undergone breast augmentation to be diagnosed with breast cancer. The options available to such a patient are a modified radical mastectomy and breast conservation treatment. If the patient chooses breast conservation treatment, the concerns that need to be addressed are whether the breast prosthesis should be removed before irradiation and whether the presence of the prosthesis would impair local control of the tumor or cosmetic results. This article presents the feasibility of breast conservation treatment without impairing the augmentation. Five patients underwent lumpectomy, perioperative placement of interstitial catheters in the tumor bed for immediate postoperative boost brachytherapy, and external beam irradiation to the entire breast. Results of follow-up examinations for a median of 60 months revealed successful local control and satisfactory cosmetic results. No long-term effects of radiation therapy on the breast prostheses have been observed. Thus, it seems feasible to conserve the breast and the augmentation with limited surgical resection and radiation therapy, including an immediate interstitial boost.

Dosimetric analysis in brachytherapy of carcinoma of the cervix.

Brachytherapy plays an essential role in the definitive radiation treatment of cervical carcinoma. The dosimetry of intracavitary irradiation is complex in that the optimum doses that can be delivered are dictated not only by the volume and extent of tumor but also by the close vicinity of dose-limiting structures, such as the small and large intestines, rectum, and bladder. To facilitate understanding of the relationships between the various dosimetric parameters involved, a retrospective analysis of 50 randomly chosen intracavitary insertions with Cesium-137 in 41 patients performed at our institution between 1975 and 1985 was carried out. All 50 cases utilized Fletcher-Suit-Delcos applicators and only the insertions using three sources in the tandem and one in each of the ovoids were included in this analysis. Using the AP and lateral radiographs and the lymphatic trapezoid, the reference points were obtained and transferred digitally to the treatment planning computer, and computerized dosimetry performed. In addition to the specified reference points, points were added and modified to obtain more complete information. The doses at the specified points were normalized to the average dose at AT, a reference point 2 cm superior to external os and 2 cm lateral to the tandem, and expressed as a percentage. It was noted that the average dose at the closest bladder point was 103 +/- 41% of the dose at AT, the maximum rectal dose 77 +/- 29% of the dose at AT and the maximum small bowel dose 65 +/- 16% of that at AT. The analysis of percent contribution of various sources to different reference points revealed that the dose to point AT was equally contributed to by all sources; bladder and rectal doses were mainly contributed to by the lowermost uterine and ovoid sources. Our analysis may provide a model for optimizing brachytherapy in cervical carcinoma.

A unique nasopharynx brachytherapy technique.

To deliver a curative dose of radiation therapy to the nasopharynx using either external beam radiotherapy or conventional brachytherapy, it is often necessary to expose a large volume of normal tissue. Tolerance of normal tissue also limits the dose of radiation given for salvage therapy in failed nasopharyngeal carcinoma. A unique brachytherapy technique with associated treatment planning is presented as an alternative method of treatment. This technique combines a single linear cesium-137 source inserted in the nasopharynx via a modified cuffed endotracheal tube, in conjunction with a plaque of iridium-192 ribbons applied in the form of a modified upper denture appliance. This method allows additional treatment to the primary area while neither exposing more normal tissue than necessary nor exceeding tolerance doses to surrounding structures.