Hx Content Research Articles

Changes in growth and chemical defences upon defoliation in maize

The effect of defoliation on growth and on levels and allocation patterns of hydroxamic acids (Hx) in maize seedlings was evaluated 6 days after treatment. No significant differences were found between defoliated and nondefoliated plants for the Hx concentration, relative Hx content and Hx-aglucone to Hx-glucoside ratio in shoots, roots and root exudates, with the exception of Hx concentration in shoots, which decreased upon defoliation. However, growth of defoliated seedlings was considerably higher than that of nondefoliated ones. These results indicate that maize responds to defoliation by allocating its resources mainly to growth rather than to defence. Since previous work described the opposite strategy in rye, responses to defoliation in both species are discussed in relation to current theories of plant defence.

ELECTRON BEAM IRRADIATION, OXYGEN, AND TEMPERATURE EFFECTS ON NUCLEOTIDE DEGRADATION IN STORED AQUACULTURE HYBRID STRIPED BASS FILLETS1

ABSTRACTSkinless fillets from commercially‐grown aquaculture hybrid striped bass (Morone saxatilis x M. chrysops) were electron beam‐irradiated in the presence of air or vacuum‐packaged and stored at 4C and ‐20C for 14 days. A mean low dose level of 2.0 or 3.0 kGy (± 0.5 kGy) and high dose level of 20 kGy (± 4 kGy) were used for irradiated samples. Hypoxanthine (Hx) concentrations, Ki‐ values {[(1NO + Hx)/(IMP + INO + Hx)] × 100}, and H‐values {[(Hx)/(IMP + INO + Hx)] × 100} indicated that irradiation did not influence the rate of nucleotide degradation compared with nonirradiated controls at either refrigerated or frozen temperatures. Vacuum packaging or freezing of stored samples resulted in lower H‐values and Hx contents compared with nonirradiated controls regardless of irradiation treatment.

Evaluation of Hydroperoxide Content and Nucleotide-Based Indicators in Assessing Freshness of Stored Aquaculture and Wild-Captured Striped Bass Fillets

Descriptive sensory-analysis data from frozen and thawed refrigerated wild-captured striped bass (Morone saxatilis) and commercially-grown aquaculture hybrid striped bass (M. saxatilis x M. chrysops) fillets were compared to nucleotide concentrations and hydroperoxide contents at selected time intervals. Results indicated that Ki-values and hydroperoxide contents were not adequate indicators of freshness for either wild-captured or aquaculture fish. However, when H-values were less than 40%, inosine to hypoxanthine ratios (INO:Hx) greater than 2, or Hx contents less than 3 µmoles/g, sensory attributes of refrigerated striped bass and hybrid striped bass were not significantly different from their frozen cantrols. These latter indicators showed that aquaculture fish maintained freshness up to 10 d of refrigerated storage and wildcaptured fish up to 5 d of storage.

Changes in the hydroxamic acid content of maize leaves with time and after artificial damage; implications for insect attack

SummaryThe dynamics of hydroxamic acids (Hx) in maize plants were examined, along with the effects on this process of artificial leaf damage. The concentration of Hx in maize (cv. LGH) leaves declined rapidly with age, although young emerging tissue did have relatively high levels. The decline was not entirely due to a growth dilution effect, as the total Hx content in leaves also decreased with age. This effect was less pronounced in isolated leaves. The plant hormone abscisic acid (ABA) accelerated the decline in Hx in isolated maize leaves, while indole acetic acid (IAA) had no apparent effect. Artificial leaf damage on growing plants produced a significant increase in the concentration of Hx relative to undamaged controls. The difference was greatest (about 18%) two days after damage, but seemed to be largely due to a slower rate of decline relative to controls. Isolated maize leaves generally showed a much higher level of increase (20 ‐ 40%). The results are generally consistent with the theory that Hx functions as a defence against insect attack.

Gastric mucosal hexosamine contents in patients with renal diseases.

Since gastric mucosal lesions are frequently encountered in patients with renal disease, we measured the gastric mucosal hexosamine (Hx) content in 51 patients with renal disease. Endoscopic examination revealed that nearly half of the patients had erosive gastritis, and that duodenal ulcers (Dus) were more common than gastric ulcers (Gus). The gastroduodenal lesions were increased in patients with advanced renal dysfunction. The relationship between Hx content and various indicators of renal function, including creatinine clearance (Ccr), serum creatinine (cr), blood urea nitrogen (BUN), and 24-h urine protein excretion, were also evaluated. The Hx content decreased in the early stage of renal dysfunction. However, it returned to normal to near normal levels in advanced renal disease and patients who underwent hemodialysis. Since the Hx content was decreased in the early stage of renal dysfunction, careful follow-up appears to be necessary in patients with renal disease.

クルマエビの生化学的死後変化と鮮度の判定

The changes in content of ATP related compounds, polyamines, volatile basic nitrogen (VBN), and lactic acid were investigated in the kuruma prawn muscle during storage at 5°C, 0°C, and -1°C in relation to freshness During storage at low temperatures, ATP decreased rapidly, while AMP and IMP accumulated. Although the levels of inosine (HxR) and hypoxanthine (Hx) were low at the acceptable stage, Hx increased remarkably as decomposition progressed. The increase in K values was considerably slow and reached around 20% at the stage of initial decomposition. As for polyamines, putrescine (Put) was absent at the acceptable stage, detected in a small amount at the stage of initial decom-position, and then increased markedly at the stage of advanced decomposition. VBN increased linearly with storage time and reached 20 to 26mg/100g at the stage of initial decomposition. Lactic acid increased to the level of about 50mg/100g during storage at low temperatures and decreased as the decomposition progressed. K value, VBN, and lactic acid contents appeared to be useful as potential indices for the freshness of kuruma prawn. Furthermore, Put and Hx con-tents seemed to be useful as decomposition indices for kuruma prawn.

Hexose Monophosphate Accumulation and Related Metabolic Changes in Unfrozen and Thawed Adductor Muscle of the Sea Scallop (Placopecten magellanicus)

The hexose monophosphates (glucose-6-phosphate (G6P), fructose-6-phosphate, and glucose-1-phosphate) accumulate postmortem in scallop adductor muscle (meats) during chill storage, increasing from only traces at death to levels totalling about 10 μmole/g after 8–10 days. In both unfrozen and thawed meats, G6P accounted consistently for 80–85% of the total hexose monophosphate, over a wide range of actual concentrations. Quick freezing at any time postmortem did not affect the concentrations of hexose monophosphates or related metabolic constituents. Thawing of the prerigor-frozen muscle, however, either slowly or rapidly, resulted in considerable G6P formation, and accelerated markedly the subsequent rate and extent of G6P production. The exceptionally high levels (− 20 μmole/g) reached in the thawed meats after 1–2 days at 5 C are implicated in the development of burned flavors, odors, and discolorations (i.e. Maillard browning reactions) observed in these thawed meats when cooked. While thawing of the prerigor-frozen muscle led to some hypoxanthine (Hx) and octopine formation, the subsequent rate of Hx accumulation at 5 C was three times faster in the thawed meats than in unfrozen meats. In meats frozen postrigor, thawing resulted in negligible change in concentrations of the metabolites; subsequent patterns of change during storage differed little from those in unfrozen muscle, although Hx accumulation was more rapid. Hx content showed potential as an index of quality in thawed scallop muscle.

Principal Acid-Soluble Nucleotides in Adductor Muscle of the Scallop Placopecten magellanicus and Their Degradation during Postmortem Storage in Ice

In scallop adductor muscle stored at 0 C, postmortem degradation of adenosine triphosphate (ATP), the predominant nucleotide at death, primarily follows the route ATP → adenosine diphosphate (ADP) → adenosine monophosphate (AMP) → adenosine → inosine → hypoxanthine (Hx). In one lot of scallops, however, inosine monophosphate (IMP) was present as an intermediate along with AMP. Hence, an alternate pathway, similar to that in fish muscle, whereby AMP is degraded to inosine and Hx via IMP rather than adenosine, may exist under certain (undefined) conditions. ATP dephosphorylation was much slower than in fish muscle; however, a rapid turnover of the intermediates in the degradative sequence, indicating relatively high activities of the enzymes catalyzing these reactions, resulted in the formation of appreciable amounts of Hx (3–4 μmole/g) within the edible storage period. In preliminary tests, taste scores correlated well with Hx contents, suggesting that measurement of Hx content may be a useful index of quality in scallop meats.Column chromatographic analyses showed that adenine nucleotides and their degradation products accounted for about 90% of the total acid-soluble purines and pyrimidines in scallop adductor muscle, with nicotinamide adenine dinucleotide and uridine diphosphate glucose as the principal minor nucleotide constituents. The muscle also contained considerable amounts of homarine (2–3 μmole/g). Glycolysis showed no relation to nucleotide degradation, both processes demonstrating a relatively slow postmortem catabolic rate in scallop muscle.