RESUMEN

Forces play a key role in a wide range of biological phenomena from single-protein conformational dynamics to transcription and cell division, to name a few. The majority of existing microbiological force application methods can be divided into two categories: those that can apply relatively high forces through the use of a physical connection to a probe and those that apply smaller forces with a detached probe. Existing magnetic manipulators utilizing high fields and high field gradients have been able to reduce this gap in maximum applicable force, but the size of such devices has limited their use in applications where high force and high-numerical-aperture (NA) microscopy must be combined. We have developed a magnetic manipulation system that is capable of applying forces in excess of 700 pN on a 1 mum paramagnetic particle and 13 nN on a 4.5 mum paramagnetic particle, forces over the full 4pi sr, and a bandwidth in excess of 3 kHz while remaining compatible with a commercially available high-NA microscope objective. Our system design separates the pole tips from the flux coils so that the magnetic-field geometry at the sample is determined by removable thin-foil pole plates, allowing easy change from experiment to experiment. In addition, we have combined the magnetic manipulator with a feedback-enhanced, high-resolution (2.4 nm), high-bandwidth (10 kHz), long-range (100 mum xyz range) laser tracking system. We demonstrate the usefulness of this system in a study of the role of forces in higher-order chromosome structure and function.

RESUMEN

Breast cancer is the most prevalent tumor in American woman. Multiple factors, including age, diet, genetics, environment, geographic location, parity, as well as race, influence the development of this heterogeneous disease. As the process of oncogenesis involves the disruption of diverse cellular pathways including cell cycle, growth, survival, and apoptosis, the high throughput technique of microarray analyses provides a powerful insight into multiple cellular processes. These techniques have identified particular expression patterns that can classify tumors into new groups and aid in the prediction of the natural history of the disease and the therapeutic response. This wealth of information may also form the basis for the development of new types of targeted therapies. Studies to identify the earliest molecular events in oncogenesis and progressive changes in the human disease have been difficult to perform within the same patient. The use of transgenic mouse mammary cancer models provides an opportunity to decipher molecular changes that occur at progressive stages of tumor development. This paper reviews microarray technology, and the insights gained from published breast cancer microarray analyses, and considers the contribution of microarray studies in identifying mouse cancer models that may be appropriate for answering particular experimental questions.

Asunto(s)

RESUMEN

Breast cancer is a leading cause of cancer morbidity and mortality. Given that the majority of human breast cancers appear to be due to non-genetic factors, identifying agents and mechanisms of prevention is key to lowering the incidence of cancer. Genetically engineered mouse models of mammary cancer have been important in elucidating molecular pathways and signaling events associated with the initiation, promotion, and the progression of cancer. Since several transgenic mammary models of human breast cancer progress through well-defined cancer stages, they are useful pre-clinical systems to test the efficacy of chemopreventive and chemotherapeutic agents. This review outlines several oncogenic pathways through which mammary cancer can be induced in transgenic models and describes several types of preventive and therapeutic agents that have been tested in transgenic models of mammary cancer. The effectiveness of farnesyl inhibitors, aromatase inhibitors, differentiating agents, polyamine inhibitors, anti-angiogenic inhibitors, and immunotherapeutic compounds including vaccines have been evaluated in reducing mammary cancer and tumor progression in transgenic models.

Asunto(s)

RESUMEN

The male accessory sex organs and epididymis regress following androgen depletion, although the onset of apoptosis varies temporally depending upon the tissue type. Transforming growth factor-beta1 (TGF-beta1) is an androgen-repressed gene and believed to be an apoptotic agent in the regressing rat ventral prostate (VP). Hence, in order to investigate the status of TGF-beta isoforms following castration in androgen-dependent tissues other than VP, this study was undertaken. Northern blot analysis using total RNA from these tissues of intact animals showed higher levels of TGF-beta1 expression as compared with VP, indicating a function other than that of an apoptotic agent for this isoform. Following orchiectomy, TGF-beta1 was induced in all organs studied and the levels were highest at day 3 following castration in seminal vesicle (SV) and the epididymis and decreased by day 5 despite the absence of androgens. This observation implies that TGF-beta1 might not be a truly androgen-repressed gene in these tissues. TGF-beta2 was up-regulated in VP, SV, caput and corpus epididymis but was undetectable in the dorsolateral prostate and cauda epididymis. On the other hand, TGF-beta3 expression was refractory to the androgen status in corpus epididymis and SV but was up-regulated in the remaining tissues. The castration-induced induction of mRNAs was attenuated after exogenous androgen administration. Most importantly, all the isoforms differed significantly in the time and magnitude of induction following castration, suggesting that a single hormone, testosterone, modulates the expression of TGF-betas in an isoform- and tissue-specific manner.

Asunto(s)

RESUMEN

We studied the expression and distribution of transforming growth factor-beta (TGF-beta) isoforms in the rat male accessory sex glands and the epididymis. Our data demonstrate the expression of both TGF-beta1 and -beta3 isoforms in ventral prostate (VP), seminal vesicle (SV), coagulating gland (CG), and epididymis (E) by Northern blot analysis. In addition, there was differential expression of TGF-beta3 in the three regions of epididymis, the corpus region being the highest. Immunostaining data showed intense staining for latent TGF-beta1 in all the male accessory glands. In contrast, no staining using antibodies specific for active TGF-beta1 was observed. No expression of TGF-beta2 was evident either by immunohistochemistry or Northern blot analysis. The presence of mature TGF-beta3 protein was observed in the secretory epithelium of VP, CG, and corpus E. There was no detectable staining of TGF-beta3 in the seminal vesicle and caput and cauda regions of epididymis. These data suggest possible differential regulation of TGF-beta isoform expression in the male reproductive system and predict unique roles for individual TGF-beta isoforms in sperm maturation and maintenance.

Asunto(s)

RESUMEN

Transforming Growth Factors-beta (TGF-betas) have been described in many vertebrate species of amphibians, aves and mammals. In this report we demonstrate the presence of TGF-beta2 in pisces. TGF-beta2 has been cloned from a fish, Cyprinus carpio, by RT-PCR using degenerate oligonucleotide primers. Sequence analysis of the amplified product and alignment of the deduced amino acid sequence with the human TGF-beta2 amino acid sequence revealed 81% and 93% identity in the precursor and the mature regions, respectively. The northern blot analysis of fish heart RNA shows a major messenger RNA species of about 8.0 kb and two messages of very low abundance of about 5.0 kb and 4.0 kb. The identification of TGF-beta2 isoform in Pisces and it's high degree of homology with the mammalian isoform suggests that among all TGF-beta isoforms, TGF-beta2 is the most conserved during evolution.

Asunto(s)