西瓜新品种小绿皇的选育及其特征特性

小绿皇系湖南省西瓜甜瓜研究所以多代自交06HS214为母本,以06S213为父本配制的高瓜氨酸含量的小果型功能性西瓜新品种。该品种早熟,全生育期88 d,果实发育期30 d,果实高圆形、绿皮布深绿条带,单瓜重2.1 kg左右,瓜肉鲜黄,中心可溶性固形物含量12.1%,极易坐果,抗性强。适宜大棚高效种植。     

A quantitative study on arginine catabolism by mixed ruminal bacteria,protozoa and their mixture in vitro

The catabolism of arginine (Arg) by mixed rumen bacteria (B), mixed rumen protozoa (P), and their mixture (BP) was quantitatively investigated in an in vitro system in order to confirm the metabolic pathway of Arg and provide basic information for enzymatic and molecular studies as well as an understanding of the quantitative distribution of metabolites. Rumen microbial suspensions (B, P, and BP) collected from fistulated goats were anaerobically incubated with or without 1 mmol/L Arg at 39°C for 12 h. Arg and other related compounds such as citrulline (Cit), ornithine (Orn), proline (Pro) and 5‐aminovaleric acid (5AV) in both supernatant and hydrolyzates of B, P, and BP suspensions were analyzed by HPLC. The metabolic pathways of Arg in mixed rumen bacteria and mixed rumen protozoa were considered to be as follows: rumen bacteria, Arg → Cit → Orn → Pro → 5AV → VFAs + NH₃; rumen protozoa, Arg → Cit → Orn → Pro → 5AV. The disappearance of Arg (1 mmol/L) was approximately 52.9 and 88.2% in B, 33.9 and 55.6% in P, and 52.8 and 85.2% in BP during 6 and 12 h incubations, respectively. When expressed in units of ‘per gram (g) of microbial nitrogen (MN)’, the net degradation rate of Arg in BP (50.3 µmol/g MN/h) was approximately 46% lower than that of B during a 12 h incubation period. The presence of protozoa tended to inhibit the production of Orn from Cit and the production of 5AV from Pro which were thought to be rate‐limiting steps of Arg metabolism in rumen microorganisms. As a result, protozoa appeared to have a saving effect on Arg metabolism, that is, protozoa protected Arg from wasteful exhaustion in the rumen.     

不同倍性小型西瓜果实中番茄红素、瓜氨酸含量比较分析

采用分光光度法测定比较分析9组纯合二倍体及其人工诱变的同源四倍体小型西瓜的番茄红素、瓜氨酸含量。结果表明：与对应的二倍体小型西瓜相比,同源四倍体小型西瓜番茄红素、瓜氨酸含量均随着倍性的增加而增加,其中番茄红素增幅最高的为PI4,增幅达28.27%;瓜氨酸含量增幅最高的为PI8,增幅达19.12%。番茄红素含量依次为大红瓤＞红瓤＞粉红瓤＞黄瓤,与其瓤色有关。瓜氨酸含量依次为黄瓤＞大红瓤＝红瓤＞粉红瓤,大红瓤与红瓤之间差异不显著,其它各个材料之间均达显著水平。     

黄瓤无籽西瓜新品种‘金兰无籽’

‘金兰无籽’是以‘950002LY’四倍体西瓜为母本,‘CL’二倍体西瓜为父本杂交育成的中小果型三倍体西瓜新品种。早中熟,果实发育期33 d。植株生长势、分枝能力中等,易坐瓜。果实圆球形,绿色果皮上显墨绿色齿条,外形美观,单果质量2.4 ~ 3.0 kg。果肉柠檬黄色,中心糖12%,瓜氨酸2.8 mg · g-1,质细而酥脆,风味好,白秕子小、少,品质优。果皮厚0.8 cm。抗病耐湿,耐储运,全国各地均可栽培。     

不同倍性小型西瓜果实中番茄红素、瓜氨酸含量比较分析

采用分光光度法测定比较分析9组纯合二倍体及其人工诱变的同源四倍体小型西瓜的番茄红素、瓜氨酸含量。结果表明:与对应的二倍体小型西瓜相比,同源四倍体小型西瓜番茄红素、瓜氨酸含量均随着倍性的增加而增加,其中番茄红素增幅最高的为PI4,增幅达28.27%;瓜氨酸含量增幅最高的为PI8,增幅达19.12%。番茄红素含量依次为大红瓤>红瓤>粉红瓤>黄瓤,与其瓤色有关。瓜氨酸含量依次为黄瓤>大红瓤=红瓤>粉红瓤,大红瓤与红瓤之间差异不显著,其它各个材料之间均达显著水平。     

Synthesis of citrulline from ornithine by the small intestinal mucosa of cattle

Three segments of cattle small intestine (duodenum, upper jejuno‐ileum and lower jejuno‐ileum) were examined in an in vitro system for activity of ornithine carbamoyltransferase (OCT; EC 2.1.3.3) which is involved in the synthesis of citrulline (Cit) from ornithine (Orn). The mucosa of the three segments of small intestine was collected from Japanese black cattle, homogenized and then centrifuged. The supernatant fraction was used as the crude OCT enzyme solution. The OCT activity was assayed by the production of Cit from Orn determined directly by HPLC. The optimal pH and temperature for OCT activities in the duodenum, upper jejuno‐ileum and lower jejuno‐ileum of cattle small intestine were 7.47 and 39°C. Little difference was observed between the three segments. The OCT activity in cattle kidney was also examined for comparison, and almost no activity was found. The OCT activities in crude enzyme solutions of the three segments of small intestine were stable for up to one month of storage at ?20°C in Tris HCl buffer solution. Finally, the role of the small intestine in supplying Cit as a precursor for arginine synthesis in cattle kidney was discussed.     

A quantitative study on arginine synthesis from argininosuccinic acid and citrulline by crude enzymes of cattle kidney

In vitro experiments were conducted to examine the synthesis of arginine (Arg) from argininosuccinic acid (ASA) and citrulline (Cit) by crude enzymes of cattle kidney cortex. Kidney samples, collected from Japanese black cattle, were homogenized in KCl solution (ice‐cold), and centrifuged at 27 000 × g for 20 min at 4°C, and the supernatant fluid was used as a crude enzyme solution. The enzyme solution was incubated at 39°C in Tris HCl buffer with 15 mmol/L ASA or with 10 mmol/L Cit in the presence of 10 mmol/L aspartic acid (Asp), 10 mmol/L ATP and 5 mmol/L MgCl₂ to examine the activities of two enzymes, argininosuccinate lyase and argininosuccinate synthetase, which work at the terminal steps of Arg biosynthesis. The production of Arg from ASA, or ASA and Arg from Cit by argininosuccinate lyase and argininosuccinate synthetase activities, respectively, were determined directly by the HPLC method. The optimum pH for argininosuccinate lyase activity was 7.85. Unfortunately, the optimum pH for argininosuccinate synthetase activity could not be determined because no inhibitor of argininosuccinate lyase was used in the Cit incubation, so the ASA produced from Cit spontaneously converted to Arg during incubation with Cit. The maximum production of ASA from Cit was found at pH 6.45 under these conditions. We observed the optimum pH for the synthesis of Arg from Cit at 7.7. The production of Arg from ASA or Cit was quantitatively determined as 14.4 or 8.83 µmol/g kidney tissue/h, respectively, at the optimal pH values. This suggests that the daily production of Arg from ASA or Cit by the kidney might be sufficient to cover the daily requirement of Arg in cattle.     

Effects of L‐citrulline supplementation on heat stress physiology,lactation performance and subsequent reproductive performance of sows in summer

Lactating sows are susceptible to heat stress (HS). Part of the thermoregulatory response to HS is to increase peripheral blood flow, which is mediated in part by the vasodilator, nitric oxide (NO). Therefore, the aim of this experiment was to determine the effect of supplementation of L‐citrulline, a NO precursor, on symptoms of HS, lactation performance and subsequent reproductive performance of sows in summer. A total of 221 summer farrowing mixed parity sows were fed either a control diet or supplemented with 1% L‐citrulline upon entry to the farrowing house (6 ± 1.8 days for mean ± standard deviation [SD] before farrowing) until weaning (26 ± 1.5 days). The average daily minimum and maximum temperature in the farrowing house was 21.0 ± 1.88 and 29.2 ± 3.82°C (mean ± SD). Rectal temperature, respiration rate, and plasma and urinary nitrite and nitrate (NOx) of sows were measured on the 19th day post‐farrowing. Supplemental L‐citrulline in the diet did not affect the number of piglets born alive, feed intake of sows, body weight or backfat thickness of sows at weaning, or litter weight gain. L‐citrulline tended to reduce piglet pre‐weaning mortality rate from 18.6% to 15.6% (p = 0.058). L‐citrulline reduced the respiration rate of sows compared to the control diet at 17:00 hr (Time × Diet, p < 0.001); however, rectal temperature was not affected. L‐citrulline tended to increase urinary NOx concentrations (127 vs. 224 µM, p = 0.057) but not plasma NOx concentrations. L‐citrulline did not affect farrowing rate or number of piglets born alive in the subsequent parity. In conclusion, L‐citrulline supplementation reduced respiration rate of lactating sows and reduced piglet pre‐weaning mortality rate in summer. Whether the effects were due to a NO‐dependent mechanism requires further validation.     

Plasma citrulline and arginine kinetics in juvenile channel catfish, Ictalurus punctatus, given oral gabaculine

Experiments with young mammals have indicated that renal arginine synthesis is a major endogenous source of this amino acid. The kidney readily synthesizes arginine from intestinally derived citrulline, which is produced from glutamate, the so-called intestinal-renal axis. The present experiment was conducted to ascertain whether or not citrulline and arginine are synthesized in channel catfish via this pathway by administering gabaculine, an effective inhibitor of ornithine aminotransferase, and then monitoring circulating levels of arginine, citrulline, glutamate and ornithine. A conditioning diet was fed to apparent satiation to triplicate groups of channel catfish initially averaging 150 g/fish. After 2 weeks of acclimation, fish were lightly anesthetized with MS-222 and were intubated with a gelatin capsule containing gabaculine (3 mg/kg body weight) in one dose. Then, 24 and 48 h after gabaculine treatment, blood plasma was obtained and analyzed for amino acids via HPLC. Oral gabaculine administration significantly (p < 0.05) decreased plasma concentrations of citrulline (–41.8%) and arginine (–8.9%). It also increased (p < 0.05) plasma glutamine (+17.5%) and ornithine (+256.6%). A reasonable explanation for the increase in plasma glutamine and the decrease in citrulline and arginine is offered by the inhibition of glutamine degradation and a decrease in synthesis of citrulline caused by gabaculine. Results of this experiment suggest that endogenous synthesis of citrulline occurs in channel catfish, most likely at the small intestine, and it may serve as a de novo source of arginine. Therefore, the physiological needs of fish tissues and organs for arginine appear to be met via both dietary arginine and the endogenous synthesis of this amino acid.     

Biosynthesis of arginine from citrulline and related compounds by mixed ruminal bacteria, protozoa and their mixture in vitro

Biosynthesis of arginine (Arg) from citrulline (Cit), ornithine (Orn), proline (Pro), and 5-aminovaleric acid (5AV) by mixed rumen bacteria (B), protozoa (P), and their mixture (BP) was quantitatively investigated in an in vitro system from the standpoint of protein nutrition in ruminants. Rumen microorganisms, collected from ruminally fistulated goats, were anaerobically incubated with or without 1 mmol/L each of substrates at 39°C for 12 h. Arginine and other related compounds, produced in both supernatants and acid-hydrolyzates of microorganisms in B, P, and BP suspensions, were analyzed by high-performance liquid chromatography. Arginine production from Cit in BP, when expressed with a unit of 'μmol/g microbial nitrogen', was approximately 70% and 94% higher than that in B and P, respectively, in a 12-h incubation period. In the case of Orn, the values were approximately 30% and 75%. Both rumen bacteria and protozoa could produce Cit and Orn from Pro, so it is assumed that they can produce Arg from Pro. Rumen protozoa were unable to degrade 5AV and it was the final product in the metabolism of Cit, Orn and Pro in P suspension. A trace amount of Orn and Pro produced from 5AV in B and BP suspensions indicated that the reversible reaction of 5AV formation was performed only by rumen bacteria. This is the first quantitative report on Arg biosynthesis from its precursors by rumen microorganisms.