The break point of the curve of blood lactate vs exercise load has been called anaerobic threshold (AT) and is considered to be an important indicator of endurance exercise capacity in human subjects. There are few studies of AT determination in animals. We describe a protocol for AT determination by the "lactate minimum test" in rats during swimming exercise. The test is based on the premise that during an incremental exercise test, and after a bout of maximal exercise, blood lactate decreases to a minimum and then increases again. This minimum value indicates the intensity of the AT. Adult male (90 days) Wistar rats adapted to swimming for 2 weeks were used. The initial state of lactic acidosis was obtained by making the animals jump into the water and swim while carrying a load equivalent to 50% of body weight for 6 min (30-s exercise interrupted by a 30-s rest). After a 9-min rest, blood was collected and the incremental swimming test was started. The test consisted of swimming while supporting loads of 4.5, 5.0, 5.5, 6.0 and 7.0% of body weight. Each exercise load lasted 5 min and was followed by a 30-s rest during which blood samples were taken. The blood lactate minimum was determined from a zerogradient tangent to a spline function fitting the blood lactate vs workload curve. AT was estimated to be 4.95 ± 0.10% of body weight while interpolated blood lactate was 7.17 ± 0.16 mmol/l. These results suggest the application of AT determination in animal studies concerning metabolism during exercise.

BACKGROUND There is recently a concern regarding the reinfection and reactivation of previously reCoVered coronavirus disease 2019 (CoVID-19) patients. AIM To summarize the recent findings and reports of CoVID-19 reinfection in patients previously reCoVered from the disease. METHODS This study was a systematic review of current evidence conducted in August 2020. The authors studied the probable reinfection risk of novel coronavirus (CoVID-19). We performed a systematic search using the keywords in online databases. The investigation adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist to ensure the reliability and validity of this study and results. RESULTS We reviewed 31 studies. Eight studies described reCoVered patients with reinfection. Only one study reported reinfected patients who died. In 26 studies, there was no information about the status of the patients. Several studies indicated that reinfection is not probable and that post-infection immunity is at least temporary and short. CONCLUSION Based on our review, we concluded that a positive polymerase chain reaction retest could be due to several reasons and should not always be considered as reinfection or reactivation of the disease. Most relevant studies in positive retest patients have shown relative and probably temporary immunity after the reCoVery of the disease.

Background and Aims: Older people have higher rates of comorbidities and may experience more severe inflammatory responses; therefore, are at higher risk of death. Herein, we aimed to systematically review the mortality in coronavirus disease 2019 (COVID-19) patients and its predictors in this age group.Methods: We searched PubMed, Web of Science, and Science Direct using relevant keywords. Retrieved records underwent a two-step screening process consisting of title/abstract and full-text screenings to identify the eligible studies.Results: Summarizing findings of 35 studies demonstrated that older patients have higher mortality rates compared to the younger population. A review of articles revealed that increasing age, body mass index, a male gender, dementia, impairment or dependency in daily activities, presence of consolidations on chest X-ray, hypoxemic respiratory failure, and lower oxygen saturation at admission were risk factors for death. High D-dimer levels, 25-hydroxy vitamin D serum deficiencies, high C-reactive protein (≥5 mg/L) levels plus any other abnormalities of lymphocyte,

Introduction: Patients with COVID-19 may present different viral loads levels. However, the relationship between viral load and disease severity in COVID-19 is still unknown. Therefore, this study aimed to systematically review the association between SARS-CoV-2 viral load and COVID-19 severity. Methods: The relevant studies using the keywords of "COVID-19" and "viral load" were searched in the databases of PubMed, Scopus, Google Scholar, and Web of Science. A two-step title/abstract screening process was carried out and the eligible studies were included in the study. Results: Thirty-four studies were included from the initial 1015 records. The vast majority of studies have utilized real-time reverse transcriptionpolymerase chain reaction of the nasopharyngeal/respiratory swabs to report

Introduction While COVID-19 pandemic continues to spread worldwide, researchers have linked patterns of traits to poor disease outcomes. Risk factors for COVID-19 include asthma, elderly age, being pregnant, having any underlying diseases such as cardiovascular disease, diabetes, obesity, and experiencing lifelong systemic racism. Recently, connections to certain genes have also been found, although the susceptibility has not yet been established. We aimed to investigate the available evidence for the genetic susceptibility to COVID-19. Methods This study was a systematic review of current evidence to investigate the genetic susceptibility of COVID-19. By systematic search and utilizing the keywords in the online databases including Scopus, PubMed, Web of Science, and Science Direct, we retrieved all the related papers and reports published in English from December 2019 to September 2020. Results According to the findings, COVID-19 uses the angiotensin-converting enzyme 2 (ACE2) receptor for cell entry. Previous studies have shown that people with ACE2 polymorphism who have type 2 transmembrane serine proteases (TMPRSS2) are at high risk of SARS-CoV-2 infection. Also, two studies have shown that males are more likely to become infected with SARS-CoV-2 than females. Besides, research has also shown that patients possessing HLA-B*15:03 genotype may become immune to the infection. Conclusion Combing through the genome, several genes related to immune system’s response were related to the severity and susceptibility to the COVID-19. In conclusion, a correlation was found between the ACE2 levels and the susceptibility to SARS-CoV-2 infection.