True potato seed research and development in Vietnam

Quality tuber planting material is unavailable in the Red River Delta (RRD). The use of True Potato Seed (TPS) was considered as an alternative planting material. During the 1985–86 and 1986–87 seasons, 21 and 40 kilos of open pollinated TPS, respectively, were collected in the southern highlands and distributed to over 40 cooperative groups of farmers in the RRD. Fifty-two hectares (1985-86) and 120 hectares (1986-87) of potatoes were produced from transplants in the two years of on-farm production. Approximately 50% of the farmers were successful in both years. Lack of experience and too wet or too dry growing conditions caused most of the failures. Yields from transplants ranged from 5 to 13 t/ha with 150 to 300 seedling tubers/m². Seedling tubers can be stored for eight months with low storage losses and when replanted give substantially higher yields than those obtained from locally grown, degenerated seed tubers.     

Thermal challenge of the Indian shrimp Penaeus indicus

This study investigated short‐term effects of increasing water temperature from 27 to 41°C on survival and feed consumption of Penaeus indicus at three different ages: PL₂₅ (postlarvae 25 days old), PL₅₀ and PL₉₀. For each age group, water temperature was maintained at 27°C in the control, but increased to 32, 35, 38 and 41°C at a rate of 1°C every eight hours. The temperature was then kept stable until the end of the 7‐day experiment. Results showed that increasing water temperature affected both survival and feed consumption of the experimental shrimps (p < .01). Survival was highest at 32 and 35°C ranging from 93.8% to 100%, but significantly reduced to 40.0%–81.6% at 38°C. No shrimp survived the 41°C treatment. PL₂₅ were more tolerant to 38–41°C than PL₅₀ and PL₉₀ in terms of survival. Increasing water temperature had no effects on feed consumption of PL₂₅ (p > .05). For PL₅₀ and PL_90, feed consumption significantly increased at 38 and 41°C (p < .01) and was similar within the range of 27–35°C. This study suggests that P. indicus in tropical areas can tolerate water temperatures of at least 35°C and should be considered for farming during the summer time.     

Experimental challenge studies in Vietnamese catfish,Pangasianodon hypophthalmus (Sauvage), exposed to Edwardsiella ictaluri and Aeromonas hydrophila

The two main diseases in the pangasius catfish industry are bacillary necrosis of Pangasianodon (BNP) and motile aeromonas septicaemia (MAS), where the aetiological agents have been identified as Edwardsiella ictaluri and Aeromonas hydrophila, respectively. In this study, apparently healthy Pangasianodon hypophthalmus were exposed to E. ictaluri, A. hydrophila or both bacterial species by intraperitoneal injection or immersion. There were 20 fish per treatment group, and the bacterial isolates used for the study were recovered from natural infections of BNP or MAS in farmed Vietnamese P. hypophthalmus. The results of the experimental infections mimicked the natural disease outbreaks reported from these pathogens in P. hypophthalmus. Furthermore, it was clearly demonstrated that E. ictaluri was only recovered from the fish exposed to the bacterium and not recovered from the animals receiving A. hydrophila.     

Antihypertensive effects of Lactobacillus-fermented milk orally administered to spontaneously hypertensive rats

Products fermented with lactic acid bacteria may show antihypertensive effects via substances such as angiotensin I-converting enzyme inhibitor (ACEI) and γ-aminobutyric acid (GABA). It was previously found that milk fermented with Lactobacillus paracasei subsp. paracasei NTU 101 (101FM) or Lactobacillus plantarum NTU 102 (102FM) has ACEI and GABA activities. This study aimed to investigate the antihypertensive effects of 101FM and 102FM orally administered to spontaneously hypertensive rats (SHRs). Eight hours after a single oral administration or after 8 weeks of weekly (chronic) administration, 101FM and 102FM significantly decreased systolic and diastolic blood pressures in the SHRs. Microscopic examination of aortic tissue demonstrated that 101FM and 102FM reduced the disorganization of the media layer. These findings suggest that orally administered 101FM and 102FM have antihypertensive effects, possibly via ACEI and GABA activity, in SHRs. Therefore, 101FM and 102FM may be useful ingredients in physiologically functional foods to prevent hypertension.     

Neuroprotective effects of resveratrol on cerebral ischemia-induced neuron loss mediated by free radical scavenging and cerebral blood flow elevation

Resveratrol is a natural phytoestrogen and possesses many biological functions such as anti-inflammatory activity and protection against atherosclerosis and myocardial infraction. The present study was carried out to elucidate the neuroprotective effect and possible mechanism of resveratrol on cerebral ischemia-induced hippocampus neuron loss. Sixty adult male rats underwent general anesthesia (urethane, 1.4 g/kg, i.p.) and were divided into three groups: sham operation, ischemia treatment, and ischemia combined with resveratrol administration (20 mg/kg, i.v.). The carotid artery was bilaterally ligated to induce cerebral ischemia. Microdialysis and high-performance liquid chromatography were used to analyze dihydroxybenzoic acid (DHBA) that reflected the hippocampal hydroxyl radical level. Hippocampal nitric oxide was assayed among different groups. During cerebral ischemia, the hydroxyl radical levels were elevated in rats and animals displayed severe neuronal loss. A single dose of resveratrol significantly increased the nitric oxide level and decreased the hydroxyl radical level. The reduction of cerebral blood flow and neuronal loss were also attenuated by resveratrol treatment. The results demonstrated that a single infusion of resveratrol could elicit neuroprotective effects on cerebral ischemia-induced neuron damage through free radical scavenging and cerebral blood elevation due to NO release.