Bcl-xL dependency coincides with the onset of neurogenesis in the developing mammalian spinal cord.

The bcl-2 family of survival and death promoting proteins play a key role in regulating cell numbers during nervous system development. Bcl-xL, an anti-apoptotic bcl-2 family member is highly expressed in the developing nervous system. However; the early embryonic lethality of the bcl-x germline null mouse precluded an investigation into its role in nervous system development. To identify the role of bcl-x in spinal cord neurogenesis, we generated a central nervous system-specific bcl-x conditional knockout (BKO) mouse. Apoptotic cell death in the BKO embryo was initially detected at embryonic day 11 (E11) in the ventrolateral aspect of the spinal cord corresponding to the location of motor neurons. Apoptosis reached its peak at E13 having spread across the ventral and into the dorsal spinal cord. By E18, the wave of apoptosis had passed and only a few apoptotic cells were observed. The duration and direction of spread of apoptosis across the spinal cord is consistent with the spatial and temporal sequence of neuronal differentiation. Motor neurons, the first neurons to become post mitotic in the spinal cord, were also the first apoptotic cells. As neurogenesis spread across the spinal cord, later born neuronal populations such as Lim2+ interneurons were also affected. The onset of apoptosis occurred in cells that had exited the cell cycle within the previous 24h and initiated neural differentiation as demonstrated by BrdU birthdating and ßIII tubulin immunohistochemistry. This data demonstrates that spinal cord neurons become Bcl-xL dependent at an early post mitotic stage in developmental neurogenesis.

Prostate-specific antigen testing for prostate cancer screening: A national survey of Canadian primary care physicians' opinions and practices.

INTRODUCTION: In 2014, the Canadian Task Force on Preventive Health Care (CTFPHC) recommended against routine prostate cancer screening with the prostate-specific antigen (PSA) blood test. We surveyed Canadian primary care physicians (PCPs) to understand their opinions and attitudes towards prostate cancer screening in 2016. METHODS: Twenty PCPs piloted the survey to assess its accessibility. We distributed a flyer to 19 633 PCPs as an insert in a large mailed package inviting them to attend a national meeting, and later promoted the survey at the meeting. Multinomial logistic regression models examined factors associated with agreement of key guideline statements and the overall benefit of PSA screening. RESULTS: A total of 1254 PCPs responded (rate of 6.4%); 54.7% of physicians aware of the CTFPHC recommendations report screening less often as a result. Overall, 55.6% of PCPs feel that the risks of PSA screening outweigh the benefits. On multivariable analysis, physicians who did not read the guidelines, did not have an academic appointment, or were in practice for over 20 years were significantly more likely to disagree with the statement that men 55-69 years old should not be screened for prostate cancer with PSA. CONCLUSIONS: Our national survey found that the prostate cancer screening practices of Canadian PCPs varies widely across physician demographic groups, with almost equal numbers for or against. This has significant ethical, medical, and legal implications. The poor response rate to highly incentivized survey request may suggest a reluctance or general apathy towards this subject because of the Task Force recommendations. Future efforts should provide physicians with objective guidance around PSA screening, incorporating input from all stakeholders, including PCPs, urologists, and patients.