Root morphology and physiological of their relationship with nitrogen uptake in wheat (Triticum aestivum L.)

Nitrogen (N) application is believed to improve photosynthesis in flag leaf ultimately increase final yield. The main results at 20-30 days after anthesis, the activities of superoxide dismutase (SOD) and peroxidase (POD) and soluble protein in flag leaves of N150 were found to be the most effective. Increased root weight density, root length density and root volume density at flowering stage, up to 10.6 %, 15.0 %, respectively. The root weight density, root length density and root bulk density at flowering and mature stages were the highest at the N180. Delaying the senescence physiology of post flowering leaves in the middle, and late stage, photosynthesis of leaves in the middle and late stage, improving the light energy interception of wheat, and then improving the light energy utilization efficiency. The stomatal conductance of flag leaves 15-30 days after anthesis, the maximum potential photochemical efficiency 20-30 days after anthesis, and the photochemical quenching of flag leaves 25-30 days after anthesis, and improved the light energy utilization efficiency by 9.6%-11.1 %. Yunhan-20410 the gene expressions of TaTZF1, TaNCY1, TaNCY3 and TaAKaGall in wheat flag leaves were significantly up-regulated YH-20410 gene expressions of N application treatment were significantly up-regulated compared with no N application treatment. The goal of high yield high efficiency, and high quality can be achieved by YH-20410 and combined to N180 kg ha-1. The senescence physiology and gene expression of post flowering leaves in the middle and late stage, prolonging the photosynthesis of leaves in the middle and late stage, improving the light energy interception of canopy, and then improving the light energy utilization efficiency.

Effects of social capital and technology cognition on farmers' adoption of soil and water conservation tillage technology in the Loess Plateau of China

From the aspect of regional differences, this paper investigated the impact of social capital and technology cognition on the adoption of soil and water conservation tillage technology in the Loess Plateau in China. We find social networks and social trust had significant impact on the adoption of contour tillage technology by farmers in Shanxi and Shaanxi. Social participation had a significant impact in Shaanxi, whereas social prestige had a significant impact in Gansu, and social norms had a significant impact on the adoption of contour tillage technology in the three provinces. Technology cognition played an intermediary role in the effects of social networks, social trust, and social norms on technology adoption in Shaanxi and Shanxi, and on the impact of social norms on technology adoption in Gansu. Considering social networks, the frequency of communication between farmers and villagers had the greatest impact on technology adoption in Shanxi and Shaanxi, while farmers' trust in villagers had the greatest impact on technology adoption in these two provinces. The participation in collective activities in the village had the greatest impact on technology adoption in Shaanxi. Furthermore as for social prestige there was little difference in the degree of impact of observation variables on technology adoption by farmers in Gansu. Finally, regarding social norms, the attitudes and behaviors adopted by relative's friends, and villagers in the village had the greatest impact.

Genome-wide identification, phylogeny and expression analysis of the R2R3-MYB gene family in quinoa (Chenopodium quinoa) under abiotic stress

The MYB transcription factor (TF) are among the largest gene families of plants being responsible for several biological processes. The R2R3-MYB gene family are integral player regulating plant primary and secondary metabolism, growth and development, and responses to hormones and stresses. The phylogenetic analysis combined with gene structure analysis and motif determination resulted in division of R2R3-MYB gene family into 27 subgroups. Evidence generated from synteny analyses indicated that CqR2R3-MYBs gene family is featured by tandem and segmental duplication events. On the basis of RNA-Seq data, the expression patterns of different tissues under salt treatment were investigated resulting CqR2R3-MYB genes high expression both in roots and stem of quinoa (Chenopodium quinoa ) plants. More than half of CqR2R3-MYB genes showed expression under salt stress. Based on this result, CqR2R3-MYB s may regulate quinoa plant growth development and resistance to abiotic stresses. These findings provided comprehensive insights on role of CqR2R3-MYBs gene family members in quinoa and candidate MYB gene family members can be further studies on their role for abiotic stress tolerance in crop plants.

Nitrogen fertilization and precipitation affected Wheat (Triticum aestivum L.) in dryland the Loess Plateau of South Shanxi, China

Wheat (Triticum aestivum L.) is a staple crop worldwide, and its yield has improved since the green revolution, which was attributed to chemical nitrogen (N) fertilizer application. An experiment was conducted to set seven nitrogen application levels of N0, N90, N120, N150, N180, N210 and N240 kg ha^-1 before sowing. The results showed that grain yield under the nitrogen rate of N210 kg ha^-1 was significantly increase the water intake during jointing to anthesis, Soil water storage of dryland wheat in fallow period was higher than water consumption in jointing stage and the leaf area index at anthesis, the tiller percentage rate, the jointing-anthesis, and nitrogen accumulation were closely related to yield and its components. Nitrogen fertiliser rate N150 kg ha^-1 significantly increased dry matter buildup from jointing to flowering in dryland wheat compared to N fertiliser rate N210 kg ha^-1. The rise of nitrogen application rate, there were no significant variance in nitrogen accumulation of Stem + leaf sheath and cob + glume at maturity, respectively. N fertiliser rate N210 kg ha^-1 compared to N180 kg ha^-1 significantly reduced grain gliadin content in dryland wheat, respectively. Wheat crops under N210 kg ha^-1 could achieve both high NUE and grain yield simultaneously with only moderate N fertilizer in South Shanxi, China.

Long-Term Nutrient Cycle in Improved Grain Yield of Dryland Winter Wheat (Triticum aestivum L.) under Hydrological Process of Plant Ecosystem Distribution in the Loess Plateau of China

Precipitation is the major cause of crop yield variation in rainfed agriculture production in the Loess Plateau. As over fertilization is economically and environmentally undesirable, and crop yield and the resulting returns for N input are uncertain when rainfall variability is high, optimizing N management according to precipitation during fallow season is vital for efficient crop water use and high yield in dryland rainfed farming systems. Results show that the nitrogen treatment rate of 180 treatment significantly increased the tiller percentage rate, and the leaf area index at anthesis, the jointing anthesis, anthesis maturity dry matter, and nitrogen accumulation was closely related to yield. N150 treatment compared to N180 treatment significantly increased the percentage of ear-bearing tiller by 7%, dry substance accretion from jointing to anthesis by 9%, and yield by 17% and 15%, respectively. Our study has important implications for the assessment of the effects of fallow precipitation, as well as for the sustainable development of dryland agriculture in the Loess Plateau. Our results indicate that adjusting N fertilizer inputs based on summer rainfall variation could enhance wheat yield in rainfed farming systems.

Deep ploughing in the summer fallow season and optimizing nitrogen rate can increase yield, water, and nitrogen efficiencies of rain-fed winter wheat in the Loess Plateau region of China

Background

About 60% of the annual precipitation in the Loess Plateau occurs during the summer fallow season, and does not align with the wheat growing season. In addition, the nitrogen use efficiency is low in this area because nutrient availability is affected by drought. As a result, rainwater storage during the summer fallow season is very important to increasing nitrogen use efficiency, and to the stable production of dryland wheat in the Loess Plateau.

Methods

A 3-year field experiment in the eastern part of the Loess Plateau was conducted with two tillage methods (no tillage (NT) and deep ploughing (DP)) and five N rates (0, 120, 150, 180, and 210 kg N ha^-1) to study the effect of tillage on soil water utilization, plant nitrogen utilization, and wheat yield.

Result

Compared to NT, DP showed a larger increase in soil water storage (SWS_f) and precipitation storage efficiency (PSE_f) during the two dry summer fallow seasons than in the normal summer fallow season. DP substantially increased the pre-anthesis soil water consumption (SWC_pre) and N translocation. The average yield under DP was 12.46% and 14.92-18.29% higher than under NT in the normal and dry seasons, respectively. A 1 mm increase in SWC_pre could increase grain yield by 25.28 kg ha^-1, water use efficiency (WUE) by 0.069 kg ha^-1 mm^-1, and nitrogen utilization efficiency (NU_tE) by 0.029 kg kg^-1. DP could reduce the N rate by 11.49-53.34% in the normal seasons and 40.97-65.07% in the dry seasons compared to the same highest point of yield, WUE, and NU_tE under NT.

Conclusion

Deep ploughing in the summer fallow season, paired with optimized N application, could help increase wheat yield and nitrogen efficiency in dryland.

Wide space sowing achieved high productivity and effective nitrogen use of irrigated wheat in South Shanxi, China

Wheat (Triticum aestivum L.) is a staple crop worldwide, and its yield has improved since the green revolution, which was attributed to chemical nitrogen (N) fertilizer application. However, regular N application decreases N use efficiency (NUE, the ratio of grain dry matter yield to N supply from soil and fertilizer). Various practices have been implemented to maintain high crop yield and improve NUE. Nowadays, the enhanced sowing method, i.e., wide space sowing (WS), has improved the productivity of wheat crops. However, how the sowing method and N application rate affect N use and yield productivity has not been fully elucidated. Field experiments with treatments using two sowing methods (WS, and drill sowing, DS) and four N application rates (0, 180, 240, and 300 kg ha^-1, represented as N0, N180, N240, and N300, respectively) were conducted from 2017 to 2019. The results showed that grain yield under WS was 13.57-16.38% higher than that under DS. The yield advantage under WS was attributed to an increased ear number. Both the higher stem and productive stem percentage accounted for the increased ear number under WS. Higher total N quantity and larger leaf area index at anthesis under WS contributed to higher dry matter production, resulting in higher grain yield. Higher dry matter production was due to pre-anthesis dry weight and post-anthesis dry weight. The wheat crop under WS had a 12.44-15.00% higher NUE than that under DS. The increased NUE under WS was attributed to higher N uptake efficiency (the ratio of total N quantity at maturity to N supply from soil and fertilizer), which was the result of greater total N quantity. The higher total N quantity under WS was due to both higher pre-anthesis N uptake and post-anthesis N uptake. Remarkably, compared to DS with 240 kg N ha^-1, WS with 180 kg N ha^-1 had almost equal grain yield, dry matter, and total N quantity. Therefore, wheat crops under WS could achieve both high NUE and grain yield simultaneously with only moderate N fertilizer in South Shanxi, China.

Chlorophyll fluorescence and grain filling characteristic of wheat (Triticum aestivum L.) in response to nitrogen application level

BACKGROUND

This study aims to understand the influence of chlorophyll fluorescence parameters on yield of winter wheat in some areas of China. Nitrogen (N) application is believed to improve photosynthesis in flag leaf ultimately increase final yield.

METHODS AND RESULTS

To understand the response of chlorophyll fluorescence parameters of wheat, flag leaf and the effect of N fertilization was carried out at booting stage under greenhouse during year 2018-2019 using winter wheat cultivar "Yunhan-20410' 'Yunhan-618". The results showed that the maximum chlorophyll content of flag leaves occurred at booting stage. Under, Yunhan-20410 condition, maximum photochemical quantum efficiency (FV/Fm), potential activity (ΦPSII), potential activity of PSII (FV/FO), and photochemical quenching coefficient (qp) showed "high-low" variation, and the maximum values were observed between May 4 and May 12. However, Yunhan-20410 showed FV/Fm, FV/FO, and qp showed "low-high-low" curve at booting stage. Compared to Yunhan-618, Yunhan-20410 at booting stage significantly decreased FV/Fm, FV/FO, qp, and ΦPSII (P<0.05), and non-photochemical quenching (NPQ) significantly increased (P<0.05).

CONCLUSION

The outcome of present investigation suggest that chlorophyll fluorescence parameters could be valuable insight to understand yield stability under stress condition. Moreover, the investigated parameters could be useful criteria for selection of genotypes under varying nitrogen application levels.

Effects of fallow tillage on winter wheat yield and predictions under different precipitation types

In northern China, precipitation that is primarily concentrated during the fallow period is insufficient for the growth stage, creates a moisture shortage, and leads to low, unstable yields. Yield prediction in the early growth stages significantly informs field management decisions for winter wheat (Triticum aestivum L.). A 10-year field experiment carried out in the Loess Plateau area tested how three tillage practices (deep ploughing (DP), subsoiling (SS), and no tillage (NT)) influenced cultivation and yield across different fallow periods. The experiment used the random forest (RF) algorithm to construct a prediction model of yields and yield components. Our results revealed that tillage during the fallow period was more effective than NT in improving yield in dryland wheat. Under drought condition, DP during the fallow period achieved a higher yield than SS, especially in drought years; DP was 16% higher than SS. RF was deemed fit for yield prediction across different precipitation years. An RF model was developed using meteorological factors for fixed variables and soil water storage after tillage during a fallow period for a control variable. Small error values existed in the prediction yield, spike number, and grains number per spike. Additionally, the relative error of crop yield under fallow tillage (5.24%) was smaller than that of NT (6.49%). The prediction error of relative meteorological yield was minimum and optimal, indicating that the model is suitable to explain the influence of meteorological factors on yield.

Mechanisms and Adaptation Strategies to Improve Heat Tolerance in Rice. A Review

The incidence of short episodes of high temperature in the most productive rice growing region is a severe threat for sustainable rice production. Screening for heat tolerance and breeding to increase the heat tolerance of rice is major objective in the situation of recent climate change. Replacing sensitive genotypes with heat tolerant cultivars, modification in sowing time, and use of growth regulators are some of the adaptive strategies for the mitigation of yield reduction by climate change. Different strategies could be adopted to enhance the thermos-tolerance of rice by (1) the modification of agronomic practices i.e., adjusting sowing time or selecting early morning flowering cultivars; (2) induction of acclimation by using growth regulators and fertilizers; (3) selecting the genetically heat resistant cultivars by breeding; and, (4) developing genetic modification. Understanding the differences among the genotypes could be exploited for the identification of traits that are responsible for thermo-tolerance for breeding purpose. The selection of cultivars that flowers in early morning before the increase of temperature, and having larger anthers with long basal pore, higher basal dehiscence, and pollen viability could induce higher thermo-tolerance. Furthermore, the high expression of heat shock proteins could impart thermo-tolerance by protecting structural proteins and enzymes. Thus, these traits could be considered for breeding programs to develop resistant cultivars under a changing climate.

P04.16 TP53 mutations in codon 273 is predictive of overall survival in astrocytoma patients

BACKGROUND

Tumour Protein 53 (TP53) is a tumour suppressor gene that is mutated in at least 50% of human malignancies. The prevalence of TP53 mutation is much higher in astrocytomas with reports of up to 75% TP53 mutant cases. Rare cases of TP53 mutation also exist in oligodendroglial tumours (10–13%). P53 pathway is therefore an important factor in low-grade glioma tumorigenesis. Although the prognostic impact of TP53 mutations has been studied previously, no concrete concordance were reached between the studies. In this study, we investigated the prognostic effects of TP53 mutation in astrocytoma and oligodendroglioma.

MATERIAL AND METHODS

A cohort of 65 matched primary and recurrent fresh frozen tumours were sequenced to identify hotspot exons of TP53 mutation. Exons 1 to 10 were sequenced and pathogenic mutations were mostly predominant between Exons 4 and 8. The cohort was further expanded with 78 low grade glioma fresh frozen tissues and hotspot exons were sequenced. Selecting only the primary tumour from 65 matched tumours, a total of 50 Astrocytoma cases and 51 oligodendroglioma cases were analysed for prognostic effects of TP53. Only pathogenic TP53 mutations confirmed through COSMIC and NCBI databases were included in the over survival and progression-free survival analysis.

RESULTS

62% (31/50) of astrocytomas and 16% (8/51) of oligodendrogliomas harboured pathogenic TP53 mutations. Pathogenic hotspot mutations in codon 273 (c.817 C>T and c.818 G>A) was prevalent in astrocytoma with 58% (18/31) of tumours with these mutations. TP53 mutation status was maintained between primary and recurrent tumours in 93% of cases. In astrocytoma, overall survival of TP53 mutant patients was longer compared to TP53 wild-type patients (p<0.01) but was not significant after adjusting for age, gender, grade and IDH1 mutation status. In contrast, astrocytoma patients with specific TP53 mutation in codon 273 showed significantly better survival compared to other TP53 mutant and TP53 wild-type patients combined (p<0.01) in our multivariate analysis. Time to first recurrence (progression-free survival) of TP53 mutant patients was significantly longer than TP53 wild-type patients (p<0.01) after adjustments were made, while TP53 mutation in codon 273 was not prognostic for progression-free survival. In oligodendroglioma patients, TP53 mutations did not significantly affect overall survival and progression-free survival.

CONCLUSION

In agreement with others, TP53 mutation is more prevalent in Astrocytoma and mutations in codon 273 are significantly associated with longer survival.

Efficacy of Isoniazid Prophylaxis in Renal Allograft Recipients

The efficacy of isoniazid (INH) prophylaxis in renal allograft recipients who are on long-term immunosuppression in a region highly prevalent for tuberculosis (TB) was studied. INH (300 mg/d in patients weighing more than 35 kg and 5 mg/kg/d in patients with <35 kg body weight) together with Pyridoxine 50 mg/d for 1 year was started in randomly assigned renal allograft recipients. Occurrence of clinical tuberculosis during the initial 2 years posttransplantation was observed in the risk group and patients at no risk. Risks were defined as acute rejection episodes and exposure to antirejection therapy, past history of TB completely or incompletely treated, radiological evidence of past tuberculosis, history of tuberculosis in close contacts. Among 480 patients registered in the study, INH prophylaxis was given to 219 randomly assigned renal allograft recipients. Results were compared among patients developing TB during the initial 2 years posttransplantation in both the groups. Risk factors were analyzed for comparison in both groups. No significant difference was observed in terms of past history of TB, TB in close contacts, episodes of acute rejection during the initial 3 months, and comorbidities such as cytomegalovirus infection, hepatitis C virus infection, and posttransplant diabetes. One patient from the INH group and 10 patients from the non-INH group developed TB during the initial 2 years posttransplantation (P < .0001). None of patients required discontinuation of INH. INH was observed to be safe and effective as a chemoprophylactic agent in renal allograft recipients.

Outcome of Pregnancy in Renal Allograft Recipients: SIUT Experience

The course of pregnancy and its outcome was studied in renal allograft recipients. Between November 1985 and November 2005, a total of 1481 renal transplants were carried out at the Sindh Institute of Urology and Transplantation (SIUT); among them were 348 females, with 73 potential females for pregnancy. All patients received cyclosporine and prednisolone, with 82% also receiving azathioprine and 4 patients mycophenolate mofetil as a third immunosuppressant drug. We evaluated incidence of hypertension, diabetes, pre-eclampsia, urinary tract infection (UTI), rejection during pregnancy and during 3 months' postdelivery as well as outcomes of pregnancy. Among 73 potential candidates, 31 had 47 pregnancies, after an average of 31 months (8-86 months). Of 31 subjects, 21 subjects were hypertensive on one or two drugs prior to conception. A rise in blood pressure during pregnancy was noticed in 7 patients. Albuminuria from trace to 3+ appeared in 13 patients and glycosuria in one other. Blood sugar levels remained within normal range in all subjects. UTIs occurred during pregnancy in 7 patients. Among 47 pregnancies, 9 had abortions (7 spontaneous, 2 therapeutic) and 6 had preterm deliveries. The others were full-term deliveries: 12 via a lower segment caesarean section and 20 were normal vaginal deliveries. Average birth weight was 4.8 lbs. At an average follow-up of 38 months the serum creatinine values ranged from 0.94 to 2.3 mg %. One patient developed acute irreversible graft dysfunction soon after delivery. Our study demonstrated that pregnancy did not reduce renal graft survival, but newborns are at greater risk of premature birth and low birth weight.

Air quality in Malaysia: impacts, management issues and future challenges

OBJECTIVE

Observations have been made on the long-term trends of major air pollutants in Malaysia including nitrogen dioxide, carbon monoxide, the ozone and total suspended particulate matter (particularly PM10), and sulfur dioxide, emitted from industrial and urban areas from early 1970s until late 1998.

METHODOLOGY

The data show that the status of atmospheric environment in Malaysia, in particular in highly industrialized areas such as Klang Valley, was determined both by local and transboundary emissions and could be described as haze and non-haze periods.

RESULTS

During the non-haze periods, vehicular emissions accounted for more than 70% of the total emissions in the urban areas and have demonstrated two peaks in the diurnal variations of the aforementioned air pollutants, except ozone. The morning 'rush-hour' peak was mainly due to vehicle emissions, while the late evening peak was mainly attributed to meteorological conditions, particularly atmospheric stability and wind speed. Total suspended particulate matter was the main pollutant with its concentrations at few sites often exceeding the Recommended Malaysia Air Quality Guidelines. The levels of other pollutants were generally within the guidelines. Since 1980, six major haze episodes were officially reported in Malaysia: April 1983, August 1990, June 1991, October 1991, August to October 1994, and July to October 1997. The 1997 haze episode was the worst ever experienced by the country. Short-term observations using continuous monitoring systems during the haze episodes during these periods clearly showed that suspended particulate matter (PM10) was the main cause of haze and was transboundary in nature. Large forest fires in parts of Sumatra and Kalimantan during the haze period, clearly evident in satellite images, were identified as the probable key sources of the widespread heavy haze that extended across Southeast Asia from Indonesia to Singapore, Malaysia and Brunei. The results of several studies have also provided strong evidence that biomass burning is the dominating source of particulate matter. The severity and extent of 1997's haze pollution was unprecedented, affecting some 300 million people across the region. The amount of economic costs suffered by Southeast Asian countries during this environmental disaster was enormous and is yet to be fully determined. Among the important sectors severely affected were air and land transport, shipping, construction, tourism and agro-based industries. The economic cost of the haze-related damage to Malaysia presented in this study include short-term health costs, production losses, tourism-related losses and the cost of avertive action. Although the cost reported here is likely to be underestimated, they are nevertheless significant (roughly RM1 billion).

CONCLUSIONS

The general air quality of Malaysia since 1970 has deteriorated. Studies have shown that should no effective countermeasures be introduced, the emissions of sulfur dioxide, nitrogen oxides, particulate matter, hydrocarbons and carbon monoxide in the year 2005 would increase by 1.4, 2.12, 1.47 and 2.27 times, respectively, from the 1992 levels.

Effect of exposure to dust on lung function of cement factory workers

Exposure to Portland cement dust has long been associated with the prevalence of respiratory symptoms and varying degrees of airway obstruction in man. Apart from respiratory diseases, it was also found to be the cause of lung and laryngeal cancer, gastrointestinal tumours and also dermatitis. This study was done to investigate the effect of dust exposure on ventilatory lung function of Portland cement factory workers in Rawang, Selangor. Spirometry tests of 62 male workers (exposed to total dust concentration of 10,180 micrograms/m3 and PM10 of 8049 micrograms/m3) and 70 subjects from UPM (exposed to mean total dust of 192 micrograms/m3 and PM10 of 177 micrograms/m3--controls) revealed significant differences in spirometry values between the groups. The workers showed i) significantly lower FEV1% and FEF25-75%, and higher FMFT, ii) reduced FEV1% with increasing level of dust exposure and iii) higher prevalence of respiratory symptoms. Therefore, we suggest that exposure to dust in the cement factory leads to higher incidence of respiratory symptoms and impaired lung function.

Pharmacological characterisation of the antihyperglycaemic properties of Tinospora crispa extract

The efficacy of Tinospora crispa (Menispermaceae) extract for the treatment of diabetes has previously been verified in animal models. In order to substantiate the antidiabetic effect, we characterised the antihyperglycaemic properties by studying its effect on intestinal glucose absorption and glucose uptake into adipocytes. We also performed experiments to characterise in more detail the mechanism of T. crispa-evoked insulin release by challenging it with insulin secretory antagonists viz. adrenaline, somatostatin, verapamil and nifedipine. In addition, we also performed experiments to determine the effect of the extract on cAMP content. The results clearly showed that the antihyperglycaemic effect is not due to interference with intestinal glucose uptake or uptake of the sugar into the peripheral cells. Rather, the antihyperglycaemic effect of T. crispa is probably due to stimulation of insulin release via modulation of beta-cell Ca2+ concentration. That the insulinotropic effect of T. crispa is physiological suggests that the extract contains compounds which could be purified for use in the treatment of type II diabetes.

The hypoglycaemic and insulinotropic activity of Tinospora crispa: studies with human and rat islets and HIT-T15 B cells

In Malaysia, Tinospora crispa extract is taken orally by Type 2 (non-insulin-dependent) diabetic patients to treat hyperglycaemia. We have evaluated the claimed hypoglycaemic property by adding aqueous extract to the drinking water of normal and alloxan-diabetic rats. After one week, fasting blood glucose levels were significantly (p less than 0.01) lower and serum insulin levels were significantly (p less than 0.01) higher in treated diabetic animals (10.4 +/- 1.0 mmol/l and 12.8 +/- 1.1 muU/ml respectively) compared to untreated diabetic controls (17.4 +/- 1.7 mmol/l and 8.0 +/- 0.7 muU/ml respectively). The insulinotropic action of T. crispa was further investigated in vitro using isolated human or rat islets of Langerhans and HIT-T15 cells. In static incubations with rat islets and HIT-T15 B cells, the extract induced a dosage dependent stimulation and potentiation of basal and glucose-stimulated insulin secretion respectively. This insulinotropic effect was also evident in perifused human and rat islets and HIT-T5 B-cells. The observations that (i) in all three models insulin secretory rates rapidly returned to basal levels on removal of the extract and (ii) in rat islets, a second challenge with T. crispa induced an additional, stimulated response, are all consistent with physiological release of insulin by B cells. Moreover, the rate of HIT-T15 glucose utilisation was not affected by incubation with T. crispa, suggesting that the cells were viable throughout. These are the first studies to provide biochemical evidence which substantiates the traditional claims for an oral hypoglycaemic effect of Tinospora crispa, and which also show that the hypoglycaemic effect is associated with increased insulin secretion.