HT Treatment Research Articles

Photosynthetic characteristics in leaves of ‘Valencia’ orange ( Citrus sinensis (L.) Osbeck) grown under high and low temperature regimes

The photosynthetic activities of leaves of 1-year-old ‘Valencia’ orange ( Citrus sinensis (L.) Osbeck) were determined after trees were maintained for 30 consecutive days in controlled growth chambers under high temperature (HT, 32.2°C day/21.1°C night) and low temperature (LT, 15.6°C day/4.4°C night). Leaf CO 2 exchange rates ( CER), stomatal conductance ( C s), transpiration ( E), chlorophyll (Chl), soluble protein, and proline of the LT treatment were 48, 55, 26, 78, 113 and 265%, respectively, of the HT treatment. The water potentials (ψ) of leaves from HT treatment were about 0.5 MPa more negative than those from LT leaves. Activities of ribulose-1,5-bisphosphate carboxylase (RuBPCase) and phosphoenolpyruvate carboxylase (PEPCase) of the HT treatment, expressed on a leaf fresh weight basis, were 91 and 49%, respectively, of the LT treatment. PEPCase of both temperature treatments, however, showed no differences in affinities for HCO 3 − and PEP, having a Km (HCO 3 −) of 0.61 mM and a Km (PEP) of 0.15 mM. The ratio of RuBPCase/PEPCase was 6.6 for the HT treatment, compared to 3.5 for the LT treatment. When the 30-day HT-treated trees were transferred to the LT chamber, CER, C s and ψ, determined 24 hr after transfer, were comparable to values of 30-day LT-treated trees; the RuBPCase activity decreased about 18% and PEPCase activity increased about 31% after 96 hr in the LT chamber. These relative changes decreased the RuBPCase/PEPCase ratio from 6.6 to 3.7. Switching trees from the 30-day LT treatment to the HT chamber resulted in increases in CER, C s and E and decreases in ψ; the RuBPCase activity decreased about 10%, but PEPCase activity was relatively unaffected after 96 hr following the transfer to the HT chamber. The LT-induced changes in the ratio of carboxylase activities would indicate that some alteration in the photosynthetic carbon metabolism might occur in ‘Valencia’ orange leaf tissues subjected to cold acclimation conditions.

The use of heat-treated Factor VIII-concentrates in von Willebrand's disease.

In vitro investigations have demonstrated a high F VIII:Rcof potency and a high F VIII:Rcof/F VIII R:Ag ratio of two heat-treated F VIII concentrates. We therefore studied the in vivo effectiveness of these preparations (F VIII HSR, Behringwerke Marburg and F VIII HTR, Travenol) in five patients with von Willebrand's disease (vWd). In the steady state in vivo recoveries of F VIII:Rcof ranged from 73-153% after transfusion of F VIII HSR and from 11.5-17% after F VIII HTR respectively. The gain of F VIII-complex after F VIII HS was comparable to cryopecipitate (KryobulinR SP, Immuno AG Wien). All three products shortened the bleeding-time. Three of our five patients underwent surgery (Billroth I, papillotomy, laparatomy, open heart surgery) under F VIII HS cover without bleeding complications. The dose applied ranged from 20 to 40 U/kg at 8 or 12 h intervals for a period of approx. 14 days. Serum-transaminase elevations were observed in two of four patients after F VIII HT treatment. Although the risk of hepatitis of heat-treated F VIII concentrates remains to be determined, these products proved to be effective in vWd. The major advantages of these preparations are stability, rapid solubility, a low content of contaminating proteins, and a rapid, general availability.

Effect of post-mortem time and temperature on bovine intramuscular collagen

A section of longissimus muscle was excised from six steers within 1 h post mortem. Half of the muscle section from each animal was held at 37°C (HT) and the other half was maintained at 1°C (C). Samples were collected from each muscle section in each treatment at 12 and 24 h to study the effect of conditioning temperature and incubation time on collagen properties by comparing the per cent soluble collagen and the relative distribution of collagen components. More of each collagen component ( α 1, α 2, β 11 and β 12) was present on SDS gels of samples incubated for 24 h versus 12 h. Although the collagen solubility did not increase to a great extent in the HT conditioned samples when compared with C samples, the HT treatment increased the effect of post-mortem ageing (i.e. more collagen molecules were solubilised and entered the gel during electrophoresis). Each collagen component, expressed as a percentage of total collagen, remained relatively constant when comparing different temperatures or post-mortem times. This indicates that the increase in collagen components being absorbed on the gels of 24 h post-mortem samples is mainly caused by an increase in the release of total collagen from the connective tissue matrix and not by the specific release of any one component. It was also found that some breakage of collagen crosslinks occurred during high temperature conditioning. No change in type III collagen of intramuscular connective tissue was found in this study.

HIGH TEMPERATURE EFFECTS ON LYSOSOMAL ENZYME DISTRIBUTION AND FRAGMENTATION OF BOVINE MUSCLE

ABSTRACTBovine muscle samples were fractionated and assayed to assess the effects of high postmortem temperatures on lysosomal enzymes and muscle fragmentation values. Samples of the longissimus dorsi muscle were excised from both sides of six animals. One muscle was held at 37°C (HT) and the other was maintained at 2°C as control (C). The pH of the muscles was determined at 1, 4, and 12 hr postmortem. After 12 hr the muscles were homogenized and centrifuged to separate sedimen‐table and unsedimentable fractions which were assayed for β‐glucuronidase and cathepsin C activities. A fragmentation value was also determined for each sample. The pH of the HT samples dropped more rapidly and was significantly lower at both 4 and 12 hr. No detectable difference in total β‐glucuronidase activity was observed between HT and C samples but the distribution was markedly altered as shown by significant differences in the percent of total activity that was unsedimentable (HT > C, P < 0.025) and specific activities of the sedimen‐table (HT > C, P < 0.025) and unsedimentable (HT > C, P < 0.025) fractions. For cathepsin C there was a significant drop in total enzyme activity (HT > C, P < 0.005) resulting from an apparent degradation of the unsedimentable enzyme which had been released by the HT treatment. The fragmentation values were significantly different showing that the HT samples had probably undergone limited proteolysis resulting in a reduction of muscle fragment size after homogenization. These results add support for the role of lysosomal enzymes in postmortem tenderization.