Supply and demand: sink regulation of sugar accumulation in sugarcane.

Sugarcane (Saccharum spp. hybrids) accumulates sucrose to high concentrations and, as a result, has been the focus of extensive research into the biochemistry and physiology of sucrose accumulation. Despite this, the relationship between source leaf photosynthetic activity and sucrose accumulation in the culm sink is not well understood. The observations that photosynthetic activity declines during culm maturation in commercial cultivars and that high-sucrose-accumulating noble ancestral genotypes (Saccharum officinarum L.) photosynthesize at rates two-thirds of those of low-sucrose ancestors (Saccharum spontaneum L.) indicate that source-sink communication may play a pivotal role in determining sucrose yield. Although maturation of the culm results in a decreased demand for sucrose, recent evidence from partial leaf shading, defoliation, and transgenic studies indicates that sugarcane cultivars are capable of further increases in sugar content. Furthermore, sugarcane leaves appear to retain the capacity to increase the supply of assimilate to culm tissues under conditions of increased assimilate demand. The relationship between source and sink tissues in sugarcane should be viewed within a supply-demand paradigm; an often neglected conceptual approach in the study of this crop. Uncoupling of the signalling pathways that mediate negative feedback between source and sink tissues may result in improved leaf assimilation rates and, consequently, lead to increased sugarcane sucrose yields.

Changes in photosynthetic rates and gene expression of leaves during a source-sink perturbation in sugarcane.

BACKGROUND AND AIMS: In crops other than sugarcane there is good evidence that the size and activity of carbon sinks influence source activity via sugar-related regulation of the enzymes of photosynthesis, an effect that is partly mediated through coarse regulation of gene expression. METHODS: In the current study, leaf shading treatments were used to perturb the source-sink balance in 12-month-old Saccharum spp. hybrid 'N19' (N19) by restricting source activity to a single mature leaf. Changes in leaf photosynthetic gas exchange variables and leaf and culm sugar concentrations were subsequently measured over a 14 d period. In addition, the changes in leaf gene response to the source-sink perturbation were measured by reverse northern hybridization analysis of an array of 128 expressed sequence tags (ESTs) related to photosynthetic and carbohydrate metabolism. KEY RESULTS: Sucrose concentrations in immature culm tissue declined significantly over the duration of the shading treatment, while a 57 and 88% increase in the assimilation rate (A) and electron transport rate (ETR), respectively, was observed in the source leaf. Several genes (27) in the leaf displayed a >2-fold change in expression level, including the upregulation of several genes associated with C(4) photosynthesis, mitochondrial metabolism and sugar transport. Changes in gene expression levels of several genes, including Rubisco (EC 4.1.1.39) and hexokinase (HXK; EC 2.7.1.1), correlated with changes in photosynthesis and tissue sugar concentrations that occurred subsequent to the source-sink perturbation. CONCLUSIONS: These results are consistent with the notion that sink demand may limit source activity through a kinase-mediated sugar signalling mechanism that correlates to a decrease in source hexose concentrations, which, in turn, correlate with increased expression of genes involved in photosynthesis and metabolite transport. The signal feedback system reporting sink sufficiency and regulating source activity may be a potentially valuable target for future genetic manipulation to increase sugarcane sucrose yield.

Sink strength regulates photosynthesis in sugarcane.

The relationship in sugarcane (Saccharum spp.) between photosynthetic source tissue and sink material was examined through manipulation of the sink:source ratio of field-grown Saccharum spp. hybrid cv. N19 (N19). To enhance sink strength, all leaves, except for the third fully expanded leaf, were enclosed in 90% shade cloth for varying periods of time. Variations in sucrose, glucose and fructose concentrations were measured and the effects of shading on the leaf gas exchange and fluorescence characteristics recorded. Changes in carbon partitioning caused by shading were examined based on the uptake and translocation of fixed 14CO2. Following a decline in sucrose concentrations in young internodal tissue and shaded leaves, significant increases in the CO2-saturated photosynthetic rate (Jmax), carboxylation efficiency (CE) and electron transport rate were observed in unshaded leaves after 8 d of shading treatment. It was concluded that up-regulation of source-leaf photosynthetic capacity is correlated with a decrease in assimilate availability to acropetal culm sink tissue. Furthermore, a significant relationship was revealed between source hexose concentration and photosynthetic activity.

Lower limb salvage to allow planned trans-tibial amputation.

Early, primary amputations are still necessary for certain patients sustaining high impact lower limb trauma. For cases with extensive proximal tibial bone loss a turn-up bone flap technique has been described to achieve a below-knee stump suitable for a prosthesis. However, in certain circumstances, for example if posterior soft tissues are injured, this type of reconstruction is not possible. This case report demonstrates that converting a severe open proximal tibial fracture to a successful below-knee amputation is also possible with acute limb shortening, flap cover and planned subsequent trans-tibial amputation.

Video microsurgery: early experience with an alternative operating magnification system.

Since Nylen first used an operating microscope in 1921, its basic design has remained fundamentally unchanged. Microsurgical procedures are still performed while viewing the subject through binocular eyepieces. This article examines the potential to perform microsurgery using video technology, operating with a television monitor. The development of the videomicroscope is discussed together with its early trials. The results show the potential to perform simple microsurgical procedures while viewing the procedure in a two-dimensional format. The advantages and disadvantages of such a system are discussed, together with future implications.

The origin and mode of fibroblast migration and proliferation in granulation tissue.

The factors which regulate the properties of granulation tissue remain uncertain. The key cells in granulation tissue are fibroblasts and their role was investigated in rat skin excisional wounds. Full thickness wounds in 28 Hooded Lister rats were made and traced. On days 1 to 7, animals in groups of 4 received colchicine 1 mg/kg subcutaneously, 4 h before being killed. Wound sections were stained to locate and count mitotic cells. All wounds healed with a normal coefficient of contraction. The fibroblasts' mitotic indices (% of mitotic cells) were calculated. Dermis: 0.1% vs. 2.9% (control vs. test P < 0.001, paired t-test); fascia; 0.07% vs. 5.6% (control vs. test P < 0.001); granulation tissue: 9.7%. Granulation tissue fibroblasts come mainly from the adjacent fascia although the dermis may have an initial role. Once they are in the wound replication is extremely rapid. This study highlights for the first time the rapidity of fibroblastic migration and proliferation in excisional wounds, and suggests that future therapeutic interventions to control granulation tissue should consider these kinetics.

Serum creatine kinase and creatine kinase MB isoenzyme responses of post-infarction patients after a graded exercise test.

The response of total creatine kinase (CK) and the creatine kinase isoenzyme (CK MB) was studied in 22 male post-infarction patients (three to six months after myocardial infarction) after a functional graded exercise test, before entering a rehabilitation programme. Eleven subjects (group A) completed the test without developing significant electrocardiographic abnormalities. Eleven subjects (group B) showed changes that necessitated premature termination of the test. No significant differences were observed before the functional graded exercise test between the groups in serum concentration of CK, CK MB, and the percentage of CK MB to CK (MB/ CK%). The two groups were significantly different (p less than 0.01) 24 hours after the graded exercise test in CK MB and MB/CK%, but not in CK. In group B, CK and CK MB rose significantly after the graded exercise test (p less than 0.05) as did MB/CK% (p less than 0.01). In group A only CK showed a significant rise (p less than 0.05). It is probable that increases in CK MB after exercise arise from myocardial tissue efflux, reflecting reversible ischaemia. It is concluded from this study that CK MB appears to be a specific indicator of myocardial ischaemia and could, therefore, be of significant assistance in the clinical and functional assessment of the post-infarction patient.

Serum creatine kinase and isoenzyme responses of veteran class fell runners.

The exercise response of creatine kinase (CK) and creatine kinase MB (CK-MB) was studied in 11 veteran class male fell runners (aged greater than 40 years) following (1) a laboratory functional diagnostic test (GXT) to maximum oxygen uptake (VO2max), (2) a competitive fell race (8 km distance and 419 m total height gain) at approx. 80% VO2max. Subjects rested for 72 h pre- and 24 h post-GXT test, resuming normal training for 8 days before resting again 72 h pre- and 24 h post-fell race. Blood samples were obtained during normal training, pre- and 24 h post-GXT test, and pre-, 24 and 48 h post-fell race. Two distinct exercise profiles emerged. Post-GXT test CK-MB rose significantly (mean 2.0 U x 1(-1), p less than 0.05) with the mean values of per cent CK-MB to CK (MB/CK%) rising to 4.4% (p less than 0.01). Total CK remained stable at 50 U x 1(-1). Post-fell race CK-MB rose significantly (mean 2.4 U x 1(-1), p less than 0.01) with the mean MB/CK% rising to 3.1% (p less than 0.05) and total CK to 81.6 U x 1(-1) (p less than 0.01). Two subjects who exhibited ECG abnormalities during and post-GXT test, were observed to have the highest MB/CK% post-test (8.2 and 5.6% respectively) and the highest CK-MB (2.3 and 3.7 U x 1(-1). An inverse relationship was observed between MB/CK% and time to complete the fell race. It is probably that the increase in serum isoenzyme CK-MB following exercise arises from myocardial tissue efflux, reflecting reversible ischaemia. CK-MB appears to be a very specific indicator of myocardial stress during exercise.

Testicular pathology of Merino rams.

The scrotal contents of 2,281 Merino rams of wide age range examined at 3 abattoirs in Perth, Western Australia, showed a 40% prevalence of rams with 1 or more gross lesions. The percentage prevalence of gross lesions found on autopsy were: adhesions 21, testicular atrophy/hypoplasia 14, testicular calcification 13, congenital cyst of the epididymis 6, cryptorchidism 4, chronic epididymitis/scrotal abscesses 2, varicocoele 2, testicular aplasia less than 1, seminoma less than 1. The prevalence of lesions increased with age of rams. Testicular atrophy was often present when varicocoele, chronic epididymitis and scrotal abscess affected that side of the scrotal sac. Corynebacterium spp was the most frequent isolate from chronic epididymitis. Actinobacillus seminis was isolated once and Brucella ovis was not isolated. About 20% of the rams showed lesions compatible with a diagnosis of reproductive unsoundness. A large proportion of lesions were revealed only after removal of the scrotum and most of these did not appear to affect normal spermatogenesis except for an estimated 9% of rams, which showed mild atrophy/hypoplasia. Samples of these testes showed mild to moderate changes in spermatogenesis on histopathology. It was postulated that the latter group of rams might represent those ill-defined clinical cases which show equivocal results on appraisal of semen samples despite the presence of palpably normal testes.

Patient tolerance of long-term diuretic/potassium supplement therapy.

Forty patients with congestive heart failure or hypertensive heart disease were given long-term maintenance treatment with a combined bumetanide/slow-release potassium supplement preparation ('Burinex K'). Stabilised doses ranged from 0.5 mg to 2 mg bumetanide with from 7.7 mmol to 30.8 mmol potassium. Patients took doses either at 9 a.m. or at 5 p.m. daily during a series of alternate 2 to 4-weekly treatment periods. Analysis of patient preference for morning or evening diuresis showed that the majority (72.5%), including all 18 patients who went out to work, preferred the evening regimen. Bumetanide proved to be a highly effective diuretic, irrespective of time of administration. Evening diuresis was associated with a statistically significant increase in the 24-hour excretion of sodium. Serial laboratory analyses showed no clinically significant changes in serum potassium or other parameters examined an in contrast to other diuretics bumetanide produced no significant hyperuricaemic effects.