Cerebrovascular and cardiorespiratory responses to conditions of local ischaemia and systemic hypoxaemia

Conditions of local ischaemia and systemic hypoxemia trigger necessary cardiorespiratory and cerebrovascular responses to ensure nutrients and oxygen (O2) are delivered to vital organs such as the brain and the heart. The aim of this thesis is to determine cardiorespiratory and cerebrovascular responses to conditions of local ischaemia and systemic hypoxemia. Four experimental studies investigated cardiorespiratory and cerebrovascular responses during diving (simulated by facial cooling), the ventilatory response during hypoxia and the interaction between hypoxia and metaboreflex during exercise. The first experimental study aimed to uncouple the effects of trigeminal nerve stimulation on cerebral blood flow (CBF), from other modifiers associated with the diving response, such as apnoea and changes in arterial carbon dioxide tension. It was observed that the CBF responses to diving are attributable to factors related with breath-hold and not facial cooling (i.e., trigeminal nerve stimulation). The second experimental study determined whether moderate acute systemic hypoxia increases cerebral perfusion via the hypoxic ventilatory response, independently of changes in arterial oxygenation. Increases in cerebral perfusion during hypoxia were observed to be mainly influenced by reduced arterial oxygen saturation (SpO2) and not the hypoxic ventilatory response. The final experimental studies investigated the influence of hypoxia on cardiorespiratory and cerebrovascular responses to metaboreflex activation. Normobaric poikilocapnic hypoxia (FiO2=13.5%) failed to augment the cardiorespiratory and cerebrovascular responses to metaboreflex activation. However, a more robust normobaric isocapnic hypoxia (FiO2=10.5%) caused augmented heart rate (HR) and minute ventilation (VE) to metaboreflex activation. Collectively, these studies reinforce the notion that conditions of local ischaemia and systemic hypoxaemia evoke a highly integrated cardiorespiratory and cerebrovascular response

A comparison of the gene expression profiles of non-alcoholic fatty liver disease between animal models of a high-fat diet and methionine-choline-deficient diet

Non-alcoholic fatty liver disease (NAFLD) embraces several forms of liver disorders involving fat disposition in hepatocytes ranging from simple steatosis to the severe stage, namely, non-alcoholic steatohepatitis (NASH). Recently, several experimental in vivo animal models for NAFLD/NASH have been established. However, no reproducible experimental animal model displays the full spectrum of pathophysiological, histological, molecular, and clinical features associated with human NAFLD/NASH progression. Although methionine-choline-deficient (MCD) diet and high-fat diet (HFD) models can mimic histological and metabolic abnormalities of human disease, respectively, the molecular signaling pathways are extremely important for understanding the pathogenesis of the disease. This review aimed to assess the differences in gene expression patterns and NAFLD/NASH progression pathways among the most common dietary animal models, i.e., HFD- and MCD diet-fed animals. Studies showed that the HFD and MCD diet could induce either up- or downregulation of the expression of genes and proteins that are involved in lipid metabolism, inflammation, oxidative stress, and fibrogenesis pathways. Interestingly, the MCD diet model could spontaneously develop liver fibrosis within two to four weeks and has significant effects on the expression of genes that encode proteins and enzymes involved in the liver fibrogenesis pathway. However, such effects in the HFD model were found to occur after 24 weeks with insulin resistance but appear to cause less severe fibrosis. In conclusion, assessing the abnormal gene expression patterns caused by different diet types provides valuable information regarding the molecular mechanisms of NAFLD/NASH and predicts the clinical progression of the disease. However, expression profiling studies concerning genetic variants involved in the development and progression of NAFLD/NASH should be conducted

The middle cerebral artery blood velocity response to acute normobaric hypoxia occurs independently of changes in ventilation in humans

Hypoxia induces ventilatory, cardiovascular and cerebrovascular adjustments to defend against reductions in systemic oxygen delivery. We aimed to determine whether the ventilatory response to moderate acute hypoxia increases cerebral perfusion independently of changes in arterial oxygenation. Eleven young healthy individuals were exposed to four 15 minute experimental conditions; 1) normoxia [partial pressure of end‐tidal oxygen; PETO2 = 100 mmHg], 2) hypoxia [PETO2 = 50 mmHg], 3) normoxia with breathing volitionally matched to levels observed during hypoxia [hyperpnoea; PETO2 = 100 mmHg], and 4) hypoxia [PETO2 = 50 mmHg] respiratory frequency and tidal volume were volitionally matched to levels observed during normoxia (i.e., restricted breathing [RB]). Isocapnia was maintained in all conditions. Middle cerebral artery mean blood flow velocity (MCA Vmean) assessed by transcranial Doppler ultrasound), was increased during hypoxia (58 ± 12 cm s–1, P = 0.04) and hypoxia + RB (61 ± 14 cm s–1, P0.05). These findings suggest that the hypoxic ventilatory response does not increase cerebral perfusion, indexed using MCA Vmean, during moderate isocapnic acute hypoxia beyond that elicited by reduced oxygen saturation

Frequencies of HBV, HCV, HIV, and Syphilis Markers Among Blood Donors: A Hospital-Based Study in Hodeidah, Yemen

Purpose: This study aimed to determine the frequency rates of human immunodeficiency virus (HIV), hepatitis B virus (HBV), hepatitis C virus (HCV), and syphilis among blood donors. Methods: Physically fit persons aged 18 – 48 years who came for blood donation at the blood bank unit of the military hospital in Hodeidah, Yemen (MHH) from November 2008 to October 2010 were screened using standard diagnostic (SD) reagents. Based on the results, donors with clinical anemia and with history of jaundice were excluded. Results: A total of 1,483 male donors (96 % semi-voluntary and 4 % replacement donors) with a mean age of 24.3 years were enrolled in this study. The frequencies of HBV, HCV, HIV and syphilis in the samples were 2.35, 0.79, 0.14, and 0.34 %, respectively. Compared with the first year, the decrease in HBV and HCV positive cases and the increase in HIV and syphilis positive cases in the second year were not statistically significant (p = 0.91, p = 0.74, p = 0.72, and p = 0.92, respectively). Conclusion: While the frequency rate of transfusion-transmitted infections (TTIs) is low, it remains a major problem in blood transfusion. Proper protocol should be applied in selecting and screening donors to safeguard the health of people receiving blood transfusions

Prevalence and Association of Transfusion Transmitted Infections with ABO and Rh Blood Groups among Blood Donors at the National Blood Bank, Amman, Jordan

Background and objectives: Blood screening is considered a compulsory procedure in health care services to reduce the occurrence of transfusion transmitted infections (TTIs). This study estimated the distribution rates of ABO and Rh blood group systems, prevalence rates of TTIs among blood donors and their association with the ABO blood group and Rh system. Materials and Methods: A retrospective study was conducted at the national blood bank, Amman, Jordan for a period of 6 years (from January 2013 to December 2018). For TTIs analysis, about 5 mL blood sample was collected from each volunteer. A total of 365,029 persons (346,048 (94.8%) males and 18,981 (5.2%) females) donated their blood at the national blood bank, Amman, Jordan from January 2013 to December 2018. Results: The results revealed that O and A were the most prevalent blood groups (37.44% and 36.82%, respectively), followed by B (18.62%) and AB (7.12%). The distribution of Rh + ve and Rh − ve among blood donors showed that Rh + ve donors were more prevalent (88.73%) compared with Rh − ve (11.27%). HBsAg was the most prevalent viral infection (0.38%) followed by HCV (0.13%), syphilis (0.02%), HIV (0.006%) and the male donors were highly infected when compared with female donors. The association between ABO/Rh blood groups and TTIs infections was nonsignificant. Conclusions: In conclusion, low frequency rates of TTIs among blood donors were detected in the current study, but improvements are still continuously required. Low percentages of female donors need to be managed via conducting health cultural education programs