Standard electrical quantity (a), chronaxie (?), rheobase (Rh), "b" in Weiss' formula and intensity threshold of duration being 40 ?s and 300 ?s (T_(?) and T_(200)) were measured on peroneus nerves in rabbits. The results show that "a" is an actual index for measuring the excitability of various groups of fibers. The larger fibers, the higher excitability and the smaller "a" values. "b" does not indicate excitability. "?" , "Rh" , "T_(40)" and "T_(200)" are not actual indexes for measuring excitability because they are influenced by "b" in Weiss' formula.

Objective To study the effects of pulsed electromagnetic field (PEMF) in promoting tibia and fibula fracture healing in rats. Methods Thirty rats were divided randomly into two groups after establishing the animal model of artificial tibia and fibula fracture: a PEMF treated group and a control group. Radiographs were taken immediately postoperatively and once a week thereafter until being sacrificed after week 5. The blood was sampled to measure the activity of alkaline phosphatase (ALP) and the concentration of bone gamma-carboxyglutamic-acid-con-taining proteins (BGP), calcium and phosphate in serum once a week, respectively. Histological sections were taken at weeks 3 and 5 to observe the pathological change of bony callus. Results PEMF of 15 Hz and 1.0 mT could sig-nificantly increase the amount of bony callus, significantly increase the amount of bony callus, promote the disappea-ring of fracture lines and the appearance of endochondral ossification and mature bone trabecula. The amount of colla-gen in bony callus raised and the process of callus moulding accelerated in PEMF treated group. In addition, the ac-tivity of ALP(P<0.04) and the concentration of BGP(P<0.05) in serum increased. Conclusions The PEMF of 15 Hz and 1.0 mT can obviously promote fracture healing of tibia and fibula in rats.

According to the constructivism approach, instructors have to adapt to the role of fa-cilitators but not teachers. Whereas a teacher gives a didactic lecture that covers the subject matter , a fa-cilitator helps the learner to get to his or her own understanding of the content. In the former scenario the learner plays a passive role and in the latter scenario the learner plays an active role in the learning pro-cess. Under the guidance of this theory, a multi-dimension teaching model based on classroom teaching, network platform and innovate experiments has been established in the course of basis of clinical labora-tory. It has been found that this model is conducive to raising students' interests in learning and to culti-vating student's comprehensive quality.

OBJECTIVETo study whether previously intravenous injection of anisodamine can prevent endotoxemia of heat stroke of rats.

METHODSExperimental animals were randomly divided into two groups, their average artery pressure, heart rate, survival time, survival rate and rectal temperature were measured at an environmental temperature of 38 degrees C-40 degrees C and 50%-60% retative humidity. Blood samples for endotoxins analyses were taken both before and after heat-stress.

RESULTSDuring heat stress, the animals of rectal temperature of the experimental and control groups continuously increased and two hours later, separately to (42.7 +/- 0.6) degree C and (43.1 +/- 0.5) degree C, without statistic difference(P > 0.05), and to (44.6 +/- 0.4) degree C and (44.2 +/- 0.3) degree C prior to death, with statistic difference(P < 0.05). Before the experiment, the contents of endotoxins of portal vein blood were (45.7 +/- 5.2) pg/ml and (42.6 +/- 5.4) pg/ml, and that of systemic blood was (14.8 +/- 4.5) pg/ml and (13.9 +/- 7.2) pg/ml, without statistic difference(P > 0.05). Two hours later, the contents of portal vein blood separately increased to (122.2 +/- 16.7) pg/ml and (49.7 +/- 10.2) pg/ml, obviously higher than that before heat-stress(P < 0.01). And there were clear statistic difference between the two groups(P < 0.01). The changing tendency of the heart rhythm is almost the same in two groups, that is, first rose and then fell. But it is without statistic difference before and two hours later(P > 0.05): before heat-stress, the average artery pressures were (13.3 +/- 0.6) kPa and (13.6 +/- 0.5) kPa, without statistic difference(P > 0.05), and two hours later, were (9.6 +/- 0.5) kPa and (8.6 +/- 0.6) kPa, with obvious statistic difference(P < 0.01). The survival time of the animals were (166.5 +/- 16.9) min and (144.5 +/- 18.2) min with obvious statistic difference(P < 0.01), the survival rate of heat stressed rats in the experimental group were obviously higher than control group(P < 0.01 or P < 0.05).

CONCLUSIONSAnisodamine can prevent endotoxemia in rats suffering heat stroke.

Animals ; Blood Pressure ; Body Temperature ; Endotoxemia ; prevention & control ; Endotoxins ; blood ; Heat Stress Disorders ; drug therapy ; mortality ; physiopathology ; Hot Temperature ; Rats ; Solanaceous Alkaloids ; therapeutic use ; Survival Rate

The aim of this study was to detect the relationship between age and biomechanical properties in porcine common bile duct (CBD). The CBDs of 50 Hubei white pigs aged 3-12 months were obtained. The experiment of pressure-diameter was conducted on the biomechanical experiment stand for soft tissues, and then the elastic modulus and compliance were calculated. The materials were transversely extracted, refrigerated, and sliced up before HE staining. The diameter and wall thickness of the CBD were measured by a computer image analysis system. The results showed that there was statistically significant difference in regard to the compliance of the porcine CBDs of different months (F = 59.69, P = 0.00). The compliance of the porcine CBD increased gradually with monthly age. However, after the pigs being aged 10 months, the compliance decreased gradually with monthly age. The compliance of the CBD of pigs aged 7-10 months was not significantly different (P > 0.05), but the compliance of the CBDs of pigs' aged 3-6 months and 11-12 months was significantly lower than that of pigs aged 7-10 months (P < 0.01). The changes in elastic modulus of porcine CBD with age were opposed to the changes in compliance. The results of the present study suggests that the in biomechanical properties of pigs' CBDs change with their ages, and the CBDs of pigs aged 7-10 months have good compliance. Thus, for the pig-to-human liver xenotransplantation, the livers of pigs aged 7-10 months, being chosen as donators, may be more conducive to matching.
Age Factors ; Aging ; physiology ; Animals ; Biomechanical Phenomena ; Biophysical Phenomena ; Common Bile Duct ; anatomy & histology ; physiology ; Compliance ; physiology ; Elastic Modulus ; physiology ; Swine ; Transplantation, Heterologous

This paper was designed to investigate the effect of laminar shear stress on matrix metalloproteinase -9 (MMP-9) expression in rat bone marrow-derived mesenchymal stem cells (MSCs), and the possible signal transduction mechanism involved. Rat bone marrow MSCs were isolated and cultured, then, exposed to laminar shear stress at indicated strengths such as low (5dyne/cm2), medium (15 dyne/cm2) and high (30 dyne/cm2) via parallel plate flow chamber. RT-PCR was used to analyze the expression of MMP-9. The signaling inhibitors such as Wortmannin (PI3K specific inhabitor), SB202190 (p38MAPK specific inhabitor), and PD98059 (ERK1/2 specific inhabitor) were used to investigate the possible mechanical signal transduction pathway. The results showed: (1) The expression of MMP-9 was weak in static state, however, MMP-9 expression increased when MSCs were exposed to 15 dyne/cm2 shear stress for 2 hours, and MMP-9 expression increased with the extension of stimulating time, and it reached the peak at 24 h; (2) MSCs were stimulated by shear stress for 2 hours at different strengths (5 dyne/cm2, 15 dyne/cm2, 30 dyne/cm2), and under all these conditions, the expression of MMP-9 increased, and reached the peak at 15 dyne/cm2; (3) After MSCs were pretreated by three kinds of signal pathway inhibitors, the expression of MMP-9 did not change obviously in Wortmannin group and PD98059 group, but it was significantly inhibited in SB202190 group. This study demonstrated that shear stress could induce the expression of MMP-9 in rat bone marrow-derived mesenchymal stem cells; the amount of MMP-9 expression was closely related to stimulating time and the strengths of shear stress; and p38MAPK signal pathway played a critical role during the process.
Animals ; Bone Marrow Cells ; cytology ; metabolism ; Cells, Cultured ; Matrix Metalloproteinase 9 ; genetics ; metabolism ; Mesenchymal Stromal Cells ; cytology ; metabolism ; Rats ; Signal Transduction ; Stress, Mechanical