Dry/wet cycling reduces spore germination and viability in six peatland bryophytes

Dry/wet cycling driven by water level fluctuation in wetlands may strongly influence the destiny of seeds. However, how dry/wet cycling affects spore survival and germinability in peatland bryophytes is poorly understood. Six peatland bryophytes, three hummock- and three hollow-dwelling Sphagnum species, were chosen as study species. We tested the effects of dry (60% air RH)/wet (waterlogging) cycle frequency (once per 12, 8 or 4 days for low, medium or high, respectively) and ratio (3:1, 1:1 or 1:3 dry:wet time per cycle) on spore germinability, viability, dormancy percentage and protonema development. Dry/wet cycling significantly reduced spore germination percentage and viability and slowed protonema development in all Sphagnum species, being more pronounced with higher dry/wet cycling frequencies. The hummock species S. capillifolium and S. fuscum had higher spore germination percentage after the continuous dry treatment, while the hollow species S. angustifolium, S. squarrosum and S. subsecundum showed the opposite response, compared to the continuously wet treatment. Except for S. squarrosum, spore viability was higher after the dry than after the wet treatment. Spore viability and dormancy percentage were higher after a dry/wet ratio of 1:3 than after ratios of 3:1 and 1:1. Our study shows that both germinability and viability of bryophyte spores are reduced by dry/wet cycling (especially when frequent) in peatlands. This emphasizes the need to ensure constant water levels and low frequencies of water level fluctuation, which are relevant in connection with wetland restoration, to promote Sphagnum spore survival and establishment in peatlands after disturbances.

A minimally invasive model of myocardial infarction made by video-assisted thoracoscopic surgery

The general myocardial infarction model was made by ligating the left anterior descending coronary artery through traditional large opening thoracotomy, although there were many drawbacks such as severe injuries and pain in this method. The present study tried to find a new method to establish a minimally invasive canine model of myocardial infarction that was less injurious and more accurate. Twelve mongrel dogs were used in this study. After three 10-mm-long incisions were made on the left thoracic wall, pericardium was cut, left anterior descending coronary artery was found and titanium nips were clamped through video-assisted thoracoscopy. Two or three titanium nips were used until ECG showed a definite ST-segment elevation more than 0.1 mV, then the thoracic wall was sutured. The survival time of the dogs was 4 weeks. During this period, a series of thoracoscopy were performed. White blood count, biochemical analysis of oxidatively modified proteins, creatine kinase and cardiac Troponin I were examined at the baseline and in the 1st and 6th hour, and 1st, 4th, 7th, 14th and 28th day after surgery. The dogs were then killed and the ratio of fibrosis area to whole left ventricular area was measured and calculated to assess the extent of fibrosis. The sections from different parts of the heart were stained with Masson trichrome stain to assess degree of fibrosis. In the model group we observed that ST-segment of ECG elevated more than 0.1 mV instantly when titanium nips were clamped and the elevation could last for 28 days after surgery. Significant difference between the model and control group was discerned in white blood count, the levels of oxidatively modified proteins, creatine kinase, cardiac Troponin I and the ratio of fibrosis area to whole left ventricular area. Masson trichrome staining showed a large amount of collagen deposition in the fibrosis area. All these results demonstrated that a new canine model of myocardial infarction could be established with a minimally invasive procedure through video-assisted thoracoscopy. This minimally invasive pharmacological animal model was perhaps a more promising animal model for some newly rising science fields such as the study of Metabonomics.

Subacute bloodstream blockade effect by supercontraction of spider silk

The present experiment was designed to test the subacute bloodstream blockade effect of supercontraction of spider silk on the femoral artery of rats. Observation on ligated femoral artery lasted 10 days. Blood flow, systolic/diastolic blood pressure, and oxidatively modified proteins in serum were measured before and after ligation. Meanwhile, histological manifestations of femoral artery at different times were observed by HE stain. We found that blood flow and systolic/diastolic blood pressure of femoral artery showed a descending tendency. Biochemical assay showed that oxidatively modified proteins significantly increased in the first 3 days and reached peak on the third day. Histological examination demonstrated that there was a progressive procedure from partial to complete occlusion of lumen of blood vessel and there was possibility of recanalization at last in the occlusive vessel. Our study indicated that ligation by spider silk might be applied to models of subacute ischemic disease such as subacute femoral artery ischemia, subacute or chronic ischemic cardiocerebrovascular disease, etc.