Effects of pyrolytic and petrogenic polycyclic aromatic hydrocarbons on swimming and metabolic performance of zebrafish contaminated by ingestion

Depending on their origins, polycyclic aromatic hydrocarbons (PAH) are characterized by different chemical properties. Petrogenic PAH (e.g. from fossil fuels) and pyrolytic PAH (e.g. those produced by incineration processes) are therefore expected to affect organisms differently. The impact of trophic exposure to these PAH was investigated on swimming and metabolic performance of zebrafish Danio rerio. Two-month-old juveniles and six-month-old adults were individually challenged following a swimming step protocol. While pyrolytic exposure did not affect fish whatever the duration of exposure, it appeared that petrogenic PAH impaired adults' performance. Indeed, the active metabolic rate in petrogenic PAH-contaminated adults was significantly reduced by 35%, and critical swimming speed by 26.5%. This was associated with cardiac abnormalities, which are expected to contribute to the reduction of oxygen transport, particularly during intensive effort. These results may be due to the different composition and toxicity of PAH mixtures.

Impact of bladder volume on radiation dose to the rectum in the definitive treatment of prostate cancer

BACKGROUND AND OBJECTIVE

Our group created and routinely reviewed a dedicated prostate intensity-modulated radiation therapy (IMRT) delivery program. Previously, a retrospective review of our experience demonstrated that a larger bladder volume reduced radiation dose to the rectum. We conducted an observational study to confirm this relationship.

METHODS

Men receiving definitive radiation for prostate cancer were eligible for the study. Eligible patients received 2 computed axial tomography (CT) scans on the day of their planning CT scan: 1 with a full bladder and 1 with an empty bladder. On each CT data set, the prostate, rectum, bladder, penile bulb, and femoral heads were contoured. 2 IMRT plans were completed on each dataset: 1 by a medical dosimetrist and 1 by a medical physicist. The study plans targeted the prostate to 79.2 Gray (Gy) while respecting predefined dose tolerances to the other contoured structures. Rectal doses were compared on empty and full bladder CT data sets.

RESULTS

From June 29, 2010 to December 14, 2011, 17 full bladder data sets and 15 empty bladder data sets were available for analysis. Median change in bladder volume was 63 ml. Full vs empty bladder set-up was associated with a statistically significant reduction in the mean rectal dose of 25.41 Gy vs 27.6 Gy (𝑃 = .031).

LIMITATIONS

Small sample size and small variations in bladder volumes.

CONCLUSIONS

A greater bladder volume resulted in a reduced mean dose to the rectum irrespective of planning method.

Trophic contamination by pyrolytic polycyclic aromatic hydrocarbons does not affect aerobic metabolic scope in zebrafish Danio rerio

The effect of trophic exposure to pyrolitic polycyclic aromatic hydrocarbons (PAH) on aerobic metabolism of zebrafish Danio rerio was investigated. There were no significant differences in standard metabolic rate (SMR), active metabolic rate (AMR) or aerobic metabolic scope (AS) at any sublethal concentration of PAH in the diet of adult or juvenile fish. This suggests that under these experimental conditions, exposure to PAH in food did not influence aerobic metabolism of this species.

The role of the kidney in hypertension

The role of the kidney in hypertension is reviewed in terms of sodium and water homeostasis, of the secretion of renin inappropriate to the state of sodium and water balance and of other renal humoral factors which might be implicated in the hypertensive process. Fundamental to the long-term maintenance of hypertension is an alteration in the relationship between renal perfusion pressure and the excretion of sodium and water. This alteration may be brought about as a result of renal structural damage, sympathetically mediated renal vasoconstriction or the action of renal or extrarenal hormones which modulate sodium and water excretion. When renin is secreted in excess of the prevailing level of sodium and water balance, the generated angiotensin contributes to the hypertension directly through peripheral and renal vasoconstriction. The level of blood pressure in two hypertensive patients with chronic renal failure was found to be highly correlated with the level of plasma renin activity as this was lowered by the administration of a beta-blocking drug. In rats deprived of sodium, renal artery constriction and contralateral nephrectomy was followed by hypertension without any elevation of plasma angiotensin and with a minimal expansion of plasma volume unaccompanied by expansion of extracellular fluid volume. The possible role of this small volume change and of other possible factors in producing hypertension is discussed. Studies in the nephrectomised rat confirmed eariler reports that renal medullayr auto-explants inhibited renoprival hypertension, but neither the identity nor mode of action of the medullary hypotensive factor were further clarified.