Biochemistry is one of the important basic subjects in medical college. It is hard for students to master because of its complicated theories and abstract contents. It has been found that carrying out case-teaching method in biochemistry teaching is good for students to arouse study interest and enhance the abilities of autonomic learning, question-analyzing and question-solving as well as consolidate theory knowledge. It is worth generalizing as a new teaching method for biochemistry in medical college.

AIM: To investigate the effect of puerarin on diabetic myocardial damage and to explore its possible mechanisms in rats. METHODS: The male Sprague-Dawley rats were randomly divided into normal control group, diabetic group, high dose puerarin (160 mg/kg), middle dose puerarin (120 mg/kg), low dose puerarin (80 mg/kg) treatment groups and aminoguanidine (100 mg/kg) treatment group. Corresponding drugs were intraperitoneally injected once a day. The animals in normal control group and diabetic group were given equal propylene glycol. 12 weeks later, the rats were sacrificed and their cardiac muscles were collected. Myocardial structure was observed under transmission electron microscope (TEM). The blood glucose concentration and the activities of superoxide dismutase (SOD), Ca~(2+)-ATPase, Na~+-K~+-ATPase and the content of malondialdehyde (MDA) in myocardial homogenate were measured biochemically. In addition, the mRNA expressions of peroxisome proliferator activated receptor γ (PPAR-γ), glucose transporter-4 (GLUT-4) and aldose reductase (AR) in myocardial tissues were determined by reverse transcription polymerase chain reaction (RT-PCR). RESULTS: It is observed that the myofibrils were diminished, broken or fused, some lipid droplets deposited in the cytoplasm of cardiocytes and part of cristae of mitochondria were broken or disappeared under TEM in diabetic group. The activities of SOD, Ca~(2+)-ATPase, Na~+-K~+-ATPase as well as the mRNA expressions of PPAR-γ and GLUT-4 decreased significantly (all P<0.01). The blood glucose concentration and the MDA level and the AR mRNA expression increased obviously (all P<0.01) in diabetic group as compared to those in normal control group. How-ever, in puerarin treatment groups, the above changes were reversed, a significant differences of those were found as compared to those in diabetic group (P<0.05 or P<0.01, respectively). The pathological change of cardiac muscles was relieved. It showed that myofibrils were well-arranged and only few lipid droplets deposited in the cytoplasm of cardiocytes and most mitochondria had clear and regular cristae under TEM in puerarin treatment groups. CONCLUSION: Puerarin exerts preventive and remedial effects on the diabetic myocardium, which may be related to up-regulating the mRNA expressions of PPAR-γ and GLUT-4, promoting glucose uptake and relieving oxidative stress damage.

ObjectiveTo observe the protective effects of extract gingko biloba (EGb) on the myocardium mitochondria of diabetic rats.Methods40 Sprague-Dauley rats were divided randomly into the normal control group, diabetic group and EGb treatment group. The morphologic changes of myocardium mitochondria were studied by electron microscope, and the activities of succinate dehydrogenase (SDH), superoxide dismutase (SOD), nitric oxide synthase (NOS) and content of nitric oxide (NO), malondialdehyde (MDA) in the myocardium mitochondria were assayed by spectophotometer respectively.ResultsThe expansion of mitochondria, shorten of mitochondrial crest were observed under transmission electron microscope in diabetic rats. The activities of SOD and SDH decreased, but that of NOS and the content of NO increased in the diabetic group compared with control group. In EGb treatment group, the morphological change was slight, the activities of SOD and SDH were increased as well as NOS and the content of NO, MDA decreased compared with the diabetic group.ConclusionEGb can protect myocardium mitochondria of experimentally diabetic rats from lesion of free radical and excessive NO, and enhance the activity of SDH, protect myocardium of diabetic rat consequently.

AIM: To study effect of extract of ginkgo biloba(EGb) on the lipid metabolism and the function of macrophages from diabetic rats.METHODS: Sprague-Dauley rats were divided into four groups: normal control group,high-fat group,diabetic group and EGb treatment group.At the end of experiment,the rats were sacrificed,the blood glucose,blood insulin and serum lipid were measured.The activity of superoxide dismutase(SOD),content of malondialdehyde(MDA),nitric oxide(NO) in alveolar macrophages(AM) and peritoneal macrophages(PM) were assayed.In addition,peroxisome proliferator activated receptor ?(PPAR?),CD36 mRNA expression in AM was measured by RT-PCR.RESULTS: The concentration of the blood glucose,blood insulin and total cholesterol(TC),total triglycerides(TG),low-density lipoprotein-cholesterol(LDL-C) in blood increased significantly in type 2 diabetic group.The supplement of EGb decreased blood glucose,blood insulin and TC,TG,LDL-C levels.The activity of SOD decreased,while the content of NO,MDA increased in the diabetic macrophages,the activity of SOD became increased,but the content of NO and MDA decreased in EGb-treated group.The mRNA expression level of CD36 and PPAR? in alveolar macrophages from diabetic group increased,while expression level of CD36 and PPAR? mRNA in EGb treated rats continued to rise.CONCLUSIONS: EGb corrected insulin resistance and ameliorated disturbance of lipid metabolism caused by type2 diabetes in rats.Adjustment of PPAR? and CD36 mRNA expression of as well as reduction of lipid peroxidation and NO level may be involved in this process.

AIM: To investigate the protective effect of Ginkgo biloba extract (GBE) on diabetic testis and explore its possible mechanism. METHODS: Testicular structure of streptozotocin-induced diabetic rats was observed under light microscopy (LM) and transmission electron microscopy (TEM). Content of malondialdehyde (MDA), NO_2~-/NO_3~- and activity of superoxide dismutase (SOD), nitric oxide synthase (NOS) were determined in testicular homogenate. RESULTS: In diabetic rats, it was manifestated as deformation of seminiferous tubule, atrophy and shedding of germinal epithelium under LM, while expansion of smooth endoplasmic reticulum, formation of fatty vacuoles and decrease of lysosome obviously in the cytoplasm of sertoli cell under TEM, the injury of testicular tissue was improved by GBE. Compared with diabetic rats, activity of SOD increased while activity of tNOS and iNOS, content of MDA and NO_2~-/NO_3~- decreased in GBE-treated rats. CONCLUSION: GBE could effectively prevent the development of diabetic testis and the effect may be partly achieved by resisting lipid peroxidation,restraining the activity of testicular tissue iNOS and reducing the pathological alterations of NO. [

AIM: To investigate the effects of extract of Ginkgo biloba (EGb) on diaphragm from diabetic rats. METHODS: Sprague-Dauley rats were divided into three groups: normal control, diabetic group and EGb treatment group. The morphologic changes of diaphragm tissues were studied by light and electron microscopy, the activities of succinate dehydrogenase (SDH), superoxide dismutase (SOD), nitric oxide synthase (NOS) and contents of malondialdehyde (MDA), nitric oxide (NO_2~-/NO_3~-) in the diaphragm mitochondria were assayed by spectophotometer, respectively. RESULTS: The activities of SOD, SDH decreased in diabetic diaphragm mitochondria, but the activitiy of NOS, the contents of NO_2~-/NO_3~-, MDA increased compared with control group. The activities of SOD, SDH were increased as well as NOS were decreased and the contents of NO_2~-/NO_3~-, MDA decreased in EGb treatment group compared with the diabetic group. CONCLUSION: EGb may protects the diaphragm mitochondria of diabetic rats by enhancing the function of respiratory chain, anti-oxidation and decreasing NO level. [

AIM:To investigate the protective effect of puerarin on testis in diabetic rats.METHODS:The male Sprague-Dawley rats were randomly divided into normal control group,diabetic group,high dose puerarin(160 mg/kg),middle dose puerarin(120 mg/kg),low dose puerarin(80 mg/kg)treatment groups and aminoguanidine(100 mg/kg)treatment group.Corresponding drugs were intraperitoneal injected once a day.The animals in normal control group and diabetic group were given equal propylene glycol.12 weeks later,the rats were sacrificed and their testes were collected.Testicular structure was observed under transmission electronic microscope(TEM).The contents of nitric oxide(NO),malondialdehyde(MDA)and the activity of nitric oxide synthase(NOS),inducible nitric oxide synthase(iNOS),superoxide dismutase(SOD),Ca2+-ATPase and Na+-K+-ATPase in testis homogenate were detected biochemically.The levels of endothelin-1(ET-1)and calcitonin gene-related peptide(CGRP)were also measured by radioimmunoassay.In addition,the mRNA expressions of eNOS,iNOS,CGRP,ET-1 and AR in testis tissues were determined by reverse transcription polymerase chain reaction(RT-PCR).RESULTS:The pathologic changes such as cytoplasmic inclusion of sertoli cell and obvious vacuoles between sertoli cells and basal membrane of the contorted seminiferous tubules were observed under TEM in diabetic group.The contents of NO and CGRP,the activities of SOD,Ca2+-ATPase,Na+-K+-ATPase as well as the mRNA expressions of eNOS and CGRP decreased significantly(P