PubMed · 11288559
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S J Schweon. 2001. Learning about ginkgo.. https://doi.org/10.1097/00152193-200131030-00034
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The chi-chi of Ginkgo biloba L. are cylindrical woody structures that grow downwards from the branches and trunks of old trees, eventually entering the soil where they give rise to adventitious shoots and roots. Examination of segments of young chi-chi taken from a mature ginkgo tree revealed an internal woody portion with irregular growth rings of tracheid-containing secondary xylem covered by a vascular cambium and bark. The cambium was composed of both fusiform cells and parenchymatous ray cells. Near the tip of the chi-chi, these two types of cambial cells had orientations ranging between axial, radial and circumferential with respect to the cylindrical form of the chi-chi. The xylem rays and tracheids that derived from the cambium showed correspondingly variable orientations. Towards the base of the chi-chi, the fusiform cells and young tracheids were aligned parallel to the axis, indicating that the orientation of the cambial cells in basal regions of the chi-chi gradually became normalised as the tip of the chi-chi extended forwards. Nevertheless, in such basal sites, tracheids near the centre of the chi-chi showed variable orientations in accordance with their mode of formation during the early stages of chi-chi development. The initiation of a chi-chi is proposed to derive from a localised hyperactivity of vascular cambial-cell production in the supporting stem. The chi-chi elongates by tip growth, but it does so in a manner different from organ growth driven by an apical meristem. It is suggested that the chi-chi of Ginkgo is an "evolutionary experiment" that makes use of the vascular cambium, not only for its widening growth but also for its elongation.
BACKGROUND: Ginkgo biloba extract is widely used in the treatment of acute ischaemic stroke in China. We aimed to assess the evidence from randomised controlled trials and quasi-randomised controlled trials on the use of Ginkgo biloba extract in acute ischaemic stroke. OBJECTIVES: The primary objective was to determine whether Ginkgo biloba extract improves functional outcome without causing undue harm in patients with acute ischaemic stroke. Secondary objectives were to assess the effect of Ginkgo biloba extract on neurological impairment and quality of life. SEARCH STRATEGY: We searched the Cochrane Stroke Group Trials Register (last searched October 2004), the Trials Register of the Cochrane Complementary Medicine Field (last searched October 2004) and the Chinese Stroke Trials Register (last searched June 2004). In addition, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library Issue 3, 2004), MEDLINE (1966 to August 2004), EMBASE (1980 to June 2004), AMED (1985 to May 2002) and the China Biological Medicine Database (CBM-disc, 1979 to August 2004). We searched relevant clinical trials and research registers and contacted pharmaceutical companies and researchers in an effort to identify further published and unpublished studies. SELECTION CRITERIA: Randomised controlled trials or quasi-randomised controlled clinical trials comparing Ginkgo biloba extract with placebo or open control (no placebo) in patients with acute ischaemic stroke. DATA COLLECTION AND ANALYSIS: Two reviewers independently selected trials for inclusion, assessed trial quality and extracted the data. MAIN RESULTS: Fourteen trials were identified, of which 10 trials (792 patients) were included. Four trials are awaiting assessment. In the 10 included trials follow up was performed at 14 to 35 days after stroke. In all studies neurological outcome was assessed but none of them reported on disability (activities of daily living function) or quality of life. Only three trials reported adverse events. In nine trials, all of them assessed to be of inferior quality, significant improvement in neurological deficit at the end of the treatment was used as the outcome measure. When analysing these trials together, Ginkgo biloba extract was associated with a significant increase in the number of improved patients (Peto odds ratio (OR) 2.66; 95% confidence interval (CI) 1.79 to 3.94). One placebo-controlled trial, assessed to be of good quality, reported neurological outcome as a continuous variable. It failed to show an improvement of neurological deficit at the end of treatment (weighted mean difference (fixed) 0.81; 95% CI -8.9 to 10.52). No deaths or major adverse events were reported during the follow-up period. AUTHORS' CONCLUSIONS: There was no convincing evidence from trials of sufficient methodological quality to support the routine use of Ginkgo biloba extract to promote recovery after stroke. High-quality and large-scale randomised controlled trials are needed to test its efficacy.
The investigation into the effects of Ginkgo biloba extracts on tinnitus has suffered from a dearth of effective animal models as well as systematic clinical trials employing double-blind and placebo-controlled designs. Some clinical trials have yielded positive results, however, these studies are few and have been limited either by design flaws, the small size of the significant effects, or else the results have not been published in peer-reviewed journals and therefore the quality of the research is not assured. By contrast, the two most systematic clinical trials, both double-blind and placebo controlled, and published in respected peer-reviewed journals, have yielded negative results and suggest that Ginkgo biloba extracts are of little more use in the treatment of tinnitus than a placebo. Treatments for tinnitus that do not have therapeutic efficacy not only waste money but can potentially prevent patients from seeking therapy that is efficacious. Furthermore, the unsupervised use of Ginkgo biloba extracts with other medications could lead to adverse side effects which are unnecessary and not justified in terms of therapeutic benefit.