Physical standards for scuba divers

Scuba diving has become a popular aquatic sport during the past 2 decades, and family physicians are frequently involved in examining scuba divers and in the decision making that allows them to pursue their training or careers in this sport. The purpose of this article is to review the physiology and gas laws that are involved in diving and to provide guidelines for assessing each diving candidate. The clinical manifestations of decompression sickness are discussed as well as the medical problems that could cause severe morbidity or mortality if diving is attempted.     

Interleukin-15 is not required for the induction or maintenance of orally induced peripheral tolerance

Orally induced tolerance is a physiologically relevant form of peripheral tolerance, which is believed to be important for the prevention of pathological immune responses in the gut. Of several mechanisms proposed to mediate oral tolerance, one that has received much attention recently is the concept of regulatory CD4+ T cells. As recent studies have suggested that interleukin (IL)-15 may be important for the differentiation and maintenance of regulatory CD4+ T cells, we have examined the role of IL-15 in oral tolerance, using a soluble form of the IL-15 receptor (sIL-15R) which blocks the biological effects of IL-15 in vivo. Oral tolerance induced by feeding mice ovalbumin (OVA) in a low-dose regimen believed to induce regulatory T cell activity was not affected by the administration of sIL-15R during either the induction or maintenance phase of tolerance. Thus, oral tolerance does not involve an IL-15-dependent mechanism.     

Residing in a food desert is associated with an increased risk of readmission following esophagectomy for cancer

BackgroundNutritional status is related to treatment outcomes for esophageal cancer. Residing in a food desert (FD) has been associated with worse outcomes in breast and colon cancer. We assessed the association of residing in a FD on 30-day outcomes of esophageal cancer patients who received tri-modality therapy.MethodsA retrospective review of patients who underwent esophagectomy (1/2015 to 7/2020, in New Hampshire, USA) was performed. Patients were excluded if they did not undergo neo-adjuvant treatment, required treatment outside of standard Chemoradiotherapy for Oesophageal Cancer Followed by Surgery Study (CROSS) protocol, or lacked both pre and post neo-adjuvant treatment computed tomography (CT) scans for review. Demographics, nutrition parameters, treatment characteristics, 30-day complications and 90-day mortality were reviewed. FD status was defined by the United States Department of Agriculture (USDA) Food Access Research Atlas and cross-referenced with patients’ home zip code. Readmission was defined as readmission to any hospital for any reason within 30-day of discharge. Univariable analysis was conducted using Student’s t-test or Wilcoxon rank-sum for continuous variables, and Fisher’s exact test for categorical variables. Multivariable logistic regression was then used to model readmission status on FD status adjusted for measures statistically associated with readmission status at the P<0.10 in univariable analyses.ResultsSeventy-eight patients were included in the analysis. Overall pre-treatment prevalence of sarcopenia was 11.5% (9/78) and did not vary by FD status. Univariable analysis, demonstrated few significant differences between those who were readmitted and those who were not. On unadjusted analysis, patients who lived in a FD were 5 times more likely to be readmitted [5.16; 95% confidence interval (CI): 1.70–15.67] compared to those who did not. Residing in a FD remained a significant risk factor for readmission after adjustment for operative time, discharge to a rehabilitation facility and development of a grade III/IV complication [adjusted odds ratio (OR): 6.38; 95% CI: 1.45–28.08].ConclusionsOur data suggest that residing in a FD is a prognostic factor for readmission after tri-modality therapy for esophageal cancer. Clinicians need to be aware that previously established nutritional markers may not completely capture nutritional status and living in a FD may significantly increase the risk of readmission in these patients.     

Sodium pancratistatin 3,4-o-cyclic phosphate, a water-soluble synthetic derivative of pancratistatin, is highly effective in a human colon tumor model

Sodium pancratistatin 3,4- O-cyclic phosphate ( 2) is a novel water-soluble synthetic derivative of pancratistatin ( 1), a natural alkaloid constituent of Amaryllidaceae plants, that exhibits good cytostatic and antineoplastic activity but is highly insoluble. Unlike most other natural alkaloids it does not act by binding to tubulin, and its mechanism of action has yet to be fully elucidated. Here the efficacy of 2 in a human colon adenocarcinoma model, DLD-1, and some understanding of its mode of action are investigated. Agreeing with previous studies, low cytotoxicity in vitro was seen for 2 with IC 50's of 253 and 19.7 microM for 1 and 96 h exposures, respectively. However in vivo the compound caused statistically significant tumor growth delays ( p < 0.01) at its maximum tolerated dose, and significant vascular shutdown and tumor necrosis were observed. Like 1, the compound appeared to have an unconventional mechanism of action with no effect on microtubule structure, yet causing a G 2/M block, while it was seen to disrupt mitochondrial function. The mechanism of action of 1 and 2 appears to be similar. Thus compound 2, being considerably more soluble than 1, has good potential as an anticancer agent, and further investigation is warranted.     

The vasa vasorum and angioplasty

Interruption of flow in the vasa vasorum may lead to medial necrosis and aneurysm formation. The purpose of this study was to determine whether angioplasty produces significant alterations in the morphology or blood flow of the vasa vasorum of the dilated artery. The morphology of the canine vasa vasorum was studied before and after angioplasty; in a separate experiment vessel wall blood flow (VWBF) in canine carotid arteries was measured after angioplasty to determine whether physiologic regulation of the blood flow was disrupted by arterial dilation. No morphologic changes could be demonstrated in the vasa vasorum of the dilated artery; however, VWBF was increased by 1194 +/- 215% (mean +/- standard error, p less than 0.01) between 90 and 120 minutes after angioplasty. VWBF in the adjacent nondilated arterial segment was also increased (720 +/- 177% between 10-30 minutes, p less than 0.01) but returned toward normal after 60 minutes. Adenosine caused a "paradoxical" decrease in VWBF (p less than 0.05) of the dilated arterial segment while causing increased VWBF (p less than 0.05) in the thoracic aorta. Angioplasty appears to produce persistent hyperemia in the dilated arterial wall. A paradoxical response to adenosine suggests that vasa vasorum in the dilated arterial segment are maximally vasodilated. This may be due to mechanical disruption of vasomotor tone or to release of vasoactive substances.