Perceptions towards online learning among medical students during the COVID-19 pandemic.

Social distancing has been essential during the COVID-19 pandemic to slow the spread of the disease. Online learning ensures students can participate in learning activities while also maintaining a physical distance from other students. Although online learning was used to prevent the spread of COVID-19, the development of online learning has also been promoted. Here, we sought to explore the perceptions and responses of students to online learning during the pandemic using a cross-sectional study. Electronic questionnaire was used for data collection. Statistical analyses were performed for 1614 valid questionnaires and P < 0.05 was considered statistically significant. Overall, COVID-19 had more effect on female students, such as fear of COVID-19 (2.4 times higher than the number of male students) and length of time spent learning (H = 42.449, P < 0.05). However, the higher the students' grades were, the less the impact of COVID-19. For the style of lessons, all students would prefer shorter lessons (P < 0.05). Female and fifth-grade students were more prefer combined online and face-to-face learning, and male and freshmen students were more likely to prefer face-to-face learning after the pandemic. More than 50% of students thought the main advantage of online learning was convenience, with low efficiency being a disadvantage. The main factors negatively influencing online learning were eyestrain, poor network connections, and poor learning environments at home. In conclusion, synchronous online and face-to-face learning may become more common in future curricula, however the efficiency of online learning and the female students more attentions.

[Effect of whisker trimming on behavior and barrel cortex of rat].

OBJECTIVE: To investigate the change of behavior, as well as the plasticity of somatosensory cortex after whisker trimming. METHODS: SD rats were divided into 4 groups. Group A is the normal control group; group B: bilateral vibrissotomy on the second postnatal day; group C: unilateral right vibrissotomy on the second postnatal day; group D: right unilateral whisker trimmed during 1-5 days after birth, and leave untreated after the 5th postnatal day. Their body weight, length of the left D2 whiskers was measured on the 30th postnatal day. At the same time, the changes of their behavior (including the slit-detection test, the home exploring behavior and thigmotaxis test) were also recorded on the 30th postnatal day. Cytochrome oxydase histochemistry (CO reaction)was applied to study the development and arrangement of barrel cortex. RESULTS: In the slit-detection test, control rats could find and get into the right slit very quickly. The rats in group B could get into the slit only if their noses touched the slit. The rats in group C couldn't identify the slit by right face, but if they turned their body and touched the slit with the left whiskers, they could get into the slit very quickly. The behavior of rats in group D was similar to that in group C. The time spent for finding out the right slit of the rats in group A, B, C was obviously longer than that of group A (P < 0.01, P < 0.05, P < 0.01). In the exploring behavior and thigmotaxis test, the time for left thigmotaxis, right thigmotaxis and total thigmotaxis of rats in group B was longer than that of control animals. The time for right thigmotaxis of group C was significantly shorter than that of group A (P < 0.05). Both the weight of the rats and the length of left D2 whiskers of rats in all the four groups had no significant difference. CO reaction showed that the barrels became smaller, the septum was not clear, the arrangement of the barrels was not tidy in the mice whose right whiskers were trimmed from 2-30 days after birth. CONCLUSION: Deafferentation doesn't change the body weight and length of the whiskers left. But the stimulation of whiskers is important for rodent especially in thigmotaxis and exploring behavior. Deafferentation can also induce the plastic change of barrel cortex.

[The protective effect of melatonin on auditory cortex toxicity induced by cis-platinum].

AIM: To investigate the toxic response in auditory cortex of guinea pigs caused by cis-platinum (DDP), and the protective role of melatonin in this effect. METHODS: Cis-platinum and melatonin were injected peritoneally. LDH, MDA, NO in the auditory cortex were detected by spectrophotometeR. RESULTS: The body weight of the guinea pigs was diminished by peritoneal injection of Cis-platinum for 7 days (P < 0.01). Peritoneal injection of Cis-platinum induced the increased leakage of LDH (P < 0.05 vs injection of normal saline). This effect was reduced by injection of MT (P < 0.05). The content of MDA in the auditory cortex was also increased because of injection of Cis-platinumv for 7 days (P < 0.01) and MT reduced this effect (P < 0.05). The change of NO in the auditory cortex was not statistically significant after injection of Cis-platinum or Cis-platinum with MT. CONCLUSION: Peritoneal injection of Cis-platinum could destroy neurons in the auditory cortex. This effect could be reduced by melatonin by an anti-free radials mechanism.

Mechanisms underlying biochanin A-induced relaxation of the aorta differ between normotensive and hypertensive rats.

1. The aim of the present study was to investigate the mechanism underlying biochanin A-induced relaxation of the aorta in spontaneously hypertensive rats (SHR). 2. The tension in isolated ring preparations of thoracic aortas from normotensive (Wistar-Kyoto (WKY) rats) and SHR at 5 and 10 weeks of age was measured isometrically. 3. Biochanin A (10(-7) to 10(-4) mol/L) induced a concentration-dependent relaxation in aortic rings from both strains at the age of 5 and 10 weeks and the relaxation was greater in rings from 10-week-old SHR compared with age-matched WKY rats. The vasorelaxation induced by biochanin A was significantly reduced by denudation of the endothelium in aortic rings from SHR, but not WKY rats. Treatment with either indomethacin, a cyclo-oxygenase inhibitor, or N(omega)-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, had little effect on the relaxation induced by biochanin A in aortic rings from either strain. Glibenclamide, a selective inhibitor of ATP-sensitive potassium channels, significantly attenuated the relaxation induced by biochanin A in aortic rings from both strains, although the extent of reduction was greater in WKY rats than SHR. Conversely, treatment with 4-aminopyridine, a selective inhibitor of voltage-dependent potassium channels, or tetraethylammonium, an inhibitor of calcium-activated potassium channels, significantly reduced the vasorelaxation induced by biochanin A in rings from SHR but not WKY rats. 4. The greater vasorelaxation produced by biochanin A in aortic rings from 10-week-old SHR is endothelium dependent. Different mechanisms underlie the relaxant effects of biochanin A in aorta from SHR and WKY rats. The mechanisms of biochanin A-induced vasorelaxation in thoracic aortas from both normotensive and hypertensive rats involve ATP-sensitive potassium channels and, in addition, in rings from the hypertensive strain at 10 weeks of age, an endothelium-derived activation of smooth muscle cell potassium channels contributes to the vasorelaxation observed.

Losartan attenuates bleomycin-induced pulmonary fibrosis in rats.

BACKGROUND: In addition to regulating blood pressure and body fluid homeostasis, the renin-angiotensin system is also involved in lung fibrogenesis. OBJECTIVE: To study the effect of losartan, an angiotensin II antagonist, on bleomycin-induced pulmonary fibrosis in rats and its possible mechanism. METHODS: Pulmonary fibrosis was induced in SD rats by intratracheal instillation of bleomycin (5 mg x kg(-1)). Subsequently, the rats received daily losartan (3, 9 and 27 mg x kg(-1)) or prednisone (20 mg x kg(-1)) orally. Six rats in each group were sacrificed 14 and 21 days after intratracheal instillation. Hydroxyproline, superoxide dismutase (SOD), and malondialdehyde (MDA) levels in lung tissues were determined by spectroscopy. The levels of TGF-beta1 in serum were measured by ELISA. Histological changes in the lungs were evaluated by hematoxylin-eosin stain, and scored. RESULTS: Rat body weight evidently decreased while the indices of lung and hydroxyproline contents in lung tissue were significantly increased 14 and 21 days after intratracheal bleomycin instillation. Inflammatory cell infiltration and fibrotic scores were more prominent in the model group compared to the sham group. Losartan (3, 9 and 27 mg.kg(-1), i.g.) apparently attenuated the degree of pulmonary fibrosis. Further study showed that losartan significantly increased SOD levels while it decreased MDA contents in lung homogenates. Serum TGF-beta1 levels of pulmonary fibrosis rats were also decreased by losartan. CONCLUSIONS: Losartan had an inhibitory effect on bleomycin-induced pulmonary fibrosis, and its effect may be associated with its anti-free radicals and the reduction in TGF-beta1.

[Endothelium-independent vasorelaxation of plant-derived estrogen biochanin A and its mechanism in rat aortic rings].

AIM: To investigate the mechanisms of vasodilatation of plant-derived estrogen biochanin A. METHODS: Isolated aortic ring preparations from Sprague-Dawley rats were suspended in individual organ baths. The tension was measured isometrically. RESULTS: Biochanin A at the range of 10(-9)-10(-4) mol/L provoked concentration-dependent and endothelium-independent relaxation of the rings constricted by phenylephrine (10(-5) mol/L). Biochanin A caused concentration-dependent relaxation of denuded rings precontracted with KCl (6 x 10(-2) mol/L). Glibenclamide (3 x 10(-6) mol/L), a selective inhibitor of ATP-sensitive potassium channels, and tetraethylammonium (5 x 10(-3) mol/L), a Ca2+ -activated K+ channel inhibitor, significantly attenuated the relaxation induced by biochanin A. The vasoconstriction induced by phenylephrine was decreased by biochanin A in Ca2+ -free medium. CONCLUSION: The endothelium-independent relaxation of thoracic aorta induced by biochanin A might be mediated by ATP-sensitive K+ channels, Ca2+ -activated K+ channels and intracellular Ca2+ release from sarcoplasmic reticulum.

Endothelium-independent Vasorelaxant Effect of the Phyto-oestrogen Biochanin A on Rat Thoracic Aorta.

Epidemiological data suggest that the incidence of cardiovascular disease is reduced in people who have a high intake of phytoestrogens. The plant-derived estrogen biochanin A is known to cause vasodilation, but its mechanisms of action remain unclear. This study was undertaken to investigate the effects and mechanisms of biochanin A on rat thoracic aorta. Isolated aortic rings were suspended in individual organ baths and isometric tension was measured. Biochanin A induced significant relaxation in rings with or without endothelium. Contractile responses induced by phenylephrine (PE), KCl and CaCl2were antagonized by 10-7~10-4mol/L biochanin A. The transient contraction elicited by PE was significantly attenuated by 10-5mol/L biochanin A in Ca2+-free medium. The relaxant effect of biochanin A was significantly inhibited by pretreatment with the K+channel antagonists tetraethylammonium and glibenclamide in endothelium-denuded aorta. We conclude that biochanin A induces an endothelium-independent relaxation in rat aortic rings. The underlying mechanism may involve the blockage of Ca2+entry through both voltage-dependent and receptor-operated Ca2+channels, the inhibition of intracellular Ca2+release, and the activation of large-conductance Ca2+-activated K+channels and ATP-sensitive K+channels.

Montelukast, a cysteinyl leukotriene receptor-1 antagonist, dose- and time-dependently protects against focal cerebral ischemia in mice.

Our previous studies showed that cysteinyl leukotriene receptor-1 (CysLT1) antagonist pranlukast has a neuroprotective effect on cerebral ischemia in rats and mice. However, whether the neuroprotective effect of pranlukast is its special action or a common action of CysLT1 receptor antagonists remains to be clarified. This study was performed to determine whether montelukast, another CysLT1 receptor antagonist, has the neuroprotective effect on focal cerebral ischemia in mice, and to observe its dose- and time-dependent properties. Permanent focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO). Montelukast was injected intraperitoneally either as multiple doses (once a day for 3 days and 30 min before MCAO) or as a single dose (at 30 min before, 30 min after, or 1 h after MCAO), respectively, and pranlukast and edaravone were used as controls. The neurological deficits, infarct volumes, brain edema, neuron density, and Evans blue extravasation in the brain were determined 24 h after MCAO. Pretreatments with multiple doses or a single dose of montelukast (0.1 and 1.0 mg/kg) before MCAO significantly attenuated all the ischemic insults. Post-treatment with a single dose of montelukast (0.1 and 1.0 mg/kg) at 30 min after MCAO also significantly decreased brain edema and infarct volume, but not neurological deficits. However, post-treatment with a single dose of montelukast at 1 h after MCAO had no significant effect. Pranlukast showed the same effects as montelukast, but edaravone attenuated the ischemic insults only with multiple doses before MCAO. Thus, montelukast has a dose- and time-dependent neuroprotective effect on permanent focal cerebral ischemia in mice, with an effective dose range of 0.1-1.0 mg/kg and a therapeutic window of 30 min. These findings further support the therapeutic potential of CysLT1 receptor antagonists in the treatment of cerebral ischemia at earlier phases.

[Mechanisms of the effect of brain histamine on chronic epilepsy induced by pentylenetetrazole].

OBJECTIVE: To investigate the mechanisms of histamine on chronic epilepsy induced by pentylenetetrazole (PTZ). METHODS: To induce chemical kindling, a subconvulsive dose (35mg/kg) of PTZ was ip injected every 48 h in rats. Behavior changes were observed for 30 min after every injection of PTZ. RESULT: Ip injection of histidine or icv injection of clobenpropit inhibited the development of kindling induced by PTZ, presenting prolonged latency for myoclonic jerks and clonic generalized seizures and depressed seizure stages in a dose-dependent manner. H(3)receptor agonist, immepip, and histidine decarboxylase, alpha-fluoromethylhistidine reversed the ameliorating effect of clobenpropit on seizure development in a dose-dependent manner. CONCLUSION: Brain histamine plays an important role in protection against myoclonic jerks and clonic generalized clonic seizures and its action may be via H(3)receptor.

Neuroprotective effect of ONO-1078, a leukotriene receptor antagonist, on focal cerebral ischemia in rats.

AIM: To determine whether ONO-1078 (pranlukast), a potent leukotriene receptor antagonist, has neuroprotective effect on focal cerebral ischemia in the rat. METHODS: Focal cerebral ischemia was induced by 30 min of middle cerebral artery (MCA) occlusion and followed by 24 h reperfusion. ONO-1078 (0.003-1.0 mg/kg) or vehicle (saline 1 mL/kg) was ip injected 30 min before MCA occlusion and 2 h after reperfusion. The neurological score, infarct volume, neuron density (in cortex, hippocampus, and striatum), brain edema, and albumin exudation around the vessels were determined 24 h after reperfusion. RESULTS: ONO-1078 slightly improved the neurological deficiency, and dramatically decreased infarct volume and neuron loss which showed a bell shaped dose response effect with highest effect at doses of 0.01-0.3 mg/kg. Enlargement of the ischemic hemisphere and albumin exudation were inhibited at doses of 0.01-1.0 mg/kg. CONCLUSION: ONO-1078 has the protective effect on focal cerebral ischemia in rats, which is partially attributed to the inhibition of brain edema. This may represent a novel approach to the treatment of acute cerebral ischemia with cysteinyl leukotriene receptor antagonists.