Reviewing research priorities in weed ecology, evolution and management: a horizon scan

Weedy plants pose a major threat to food security, biodiversity, ecosystem services and consequently to human health and wellbeing. However, many currently used weed management approaches are increasingly unsustainable. To address this knowledge and practice gap, in June 2014, 35 weed and invasion ecologists, weed scientists, evolutionary biologists and social scientists convened a workshop to explore current and future perspectives and approaches in weed ecology and management. A horizon scanning exercise ranked a list of 124 pre-submitted questions to identify a priority list of 30 questions. These questions are discussed under seven themed headings that represent areas for renewed and emerging focus for the disciplines of weed research and practice. The themed areas considered the need for transdisciplinarity, increased adoption of integrated weed management and agroecological approaches, better understanding of weed evolution, climate change, weed invasiveness and finally, disciplinary challenges for weed science. Almost all the challenges identified rested on the need for continued efforts to diversify and integrate agroecological, socio-economic and technological approaches in weed management. These challenges are not newly conceived, though their continued prominence as research priorities highlights an ongoing intransigence that must be addressed through a more system-oriented and transdisciplinary research agenda that seeks an embedded integration of public and private research approaches. This horizon scanning exercise thus set out the building blocks needed for future weed management research and practice; however, the challenge ahead is to identify effective ways in which sufficient research and implementation efforts can be directed towards these needs.

Glucagon-like peptide-2 inhibits antral emptying in man, but is not as potent as glucagon-like peptide-1

BACKGROUND

GLP-1 (glucagon-like peptide-1) and GLP-2 (glucagon-like peptide-2) are released in equimolar amounts in response to meal ingestion. GLP-1 inhibits gastric emptying and reduces postprandial gastric and exocrine pancreatic secretion and may play a physiological regulatory role in controlling appetite and energy intake in humans. The role of GLP-2 is more uncertain. Based on the results of animal studies, it has been suggested that GLP-2 may induce intestinal epithelial growth and inhibit gastric motility. The aim of this study was to determine to what extent GLP-2 alone or together with GLP-1 inhibits gastric emptying and the sensation of hunger in man.

METHODS

Eight healthy volunteers were tested in a double-blind, placebo-controlled fashion. Antral emptying of a liquid meal and hunger ratings were determined using ultrasound technology and visual analogue scales scoring during infusions of saline, GLP-2 (0.5, and 1.0 pmol kg body wt(-1) min(-1)), GLP-1 (0.5 pmol kg body wt(-1) min(-1)) or GLP-1 and GLP-2 (0.5 pmol kg body wt(-1) min(-1)).

RESULTS

The GLP-2 infusions resulted in a dose-dependent increase in antral emptying time (35%; ns and 75%; P = 0.049) compared to saline, but GLP-2 was less potent than GLP-1, which increased the antral emptying time by 192% (P < 0.001). Addition of GLP-2 to the GLP-1 infusion did not alter the antral emptying time compared with GLP-1 alone. The GLP-1 infusion decreased the sensation of hunger compared with saline (P = 0.023), whereas the two GLP-2 infusions had no significant effect. Addition of GLP-2 to the GLP-1 infusion did not decrease the sensation of hunger further.

CONCLUSIONS

Both GLP-1 and GLP-2 inhibit antral emptying in man, but GLP-1 is more potent.

Computed tomography for staging of oesophageal cancer

BACKGROUND AND AIMS

Computed tomography (CT) is still widely used in the staging of patients with carcinoma of the oesophagus. The aim of the study was to evaluate the diagnostic accuracy of CT in a series of patients with carcinoma of the oesophagus or the cardia. Results were compared with findings at surgery or autopsy.

MATERIAL AND METHODS

47 consecutive patients of whom 30 underwent operation while 17 patients were not candidates for surgery due to advanced disease.

RESULTS

Demonstration of tumour invasion on CT in 30 patients who underwent operation had an accuracy of 63%, a nosographic sensitivity of 10% and a specificity of 90%. Diagnosis of metastases to abdominal lymph nodes had an accuracy of 57%, and a nosographic sensitivity and specificity of respectively 37% and 90%. The assessment of tumour invasion and metastases to lymph nodes in patients not candidates for surgery was expectedly more accurate (100 and 67%, respectively, in nine autopsies).

CONCLUSION

CT may provide valuable information in pretherapeutic staging of oesophageal cancer by identifying patients with advanced disease, who are not candidates for surgery. In patients without signs of dissemination on CT additional information may be obtained from endoscopic ultrasonography and laparoscopy.

Long-acting growth hormones produced by conjugation with polyethylene glycol

Derivatives of human growth hormone (hGH) of increasing size were produced by reaction with the N-hydroxysuccinimide ester of polyethylene glycol-5000 (PEG5000), a 5-kDa reagent that selectively conjugates to primary amines. By adjusting the reaction conditions and purification procedure, it was possible to isolate hGH derivatives containing up to seven PEG moieties that altered the Stokes radius and thereby the effective molecular masses of the unmodified hormone from 22 to 300 kDa. Fortunately, the most reactive amines were ones that did not lie in either of the two sites important for receptor binding. Nonetheless, increasing the level of PEG modification linearly reduced the affinity of hGH for its receptor and increased the EC50 in a cell-based assay up to 1500-fold. Most of the reduction in affinity was the result of slowing the association rate for the receptor. The clearance rate of hGH in rats was inversely proportional to effective molecular weight and closely fit a filtration model. We have tested the potency of these analogs by injecting them daily or every 6 days into hypophysectomized rats and determining the effects on body and organ growth. The efficacy of these analogs was optimal for hGH conjugated with 5 eq of PEG5000, and the potency was increased by about 10-fold compared with unmodified hGH. Such PEG-hGH derivatives show promise as long-acting alternatives to daily injections of hGH. More generally these studies show that improving hormone clearance properties, even at the expense of reducing receptor binding affinity, can lead to dramatic increases in hormone efficacy.

Growth responses to patterned GH delivery

We have investigated the effects of different patterns of administration of recombinant human growth hormone (rhGH) on weight gain, organ growth, serum GH binding protein (GHBP) and insulin-like growth factor-l (IGF-1) levels in a series of studies using hypophysectomized (Hx) or GH-deficient dwarf (dw/dw) rats. Animals were given rhGH either by subcutaneous (s.c.) injections (1 or 2 per day) or s.c. infusions and rhlGF-1 (2 mg/kg/day) by s.c. infusion. In Hx rats, all rhGH regimes increased body weight, tibial epiphyseal plate width, and organ weights in a dose-related manner. Dwarf rats showed a smaller growth response to rhGH than Hx rats, whereas rhGH induced greater elevations in serum GHBP in drarf rats. Growth responses depended on the pattern of rhGH administration (twice daily injections > continuous infusions > daily injections). The shape of the body growth curves also differed; rhGH injections increased weight gain linearly, whereas infusions gave an initial rapid weight gain which slowed with time (a curvilinear response). For both regimens, tibial epiphyseal plate width increased linearly with rhGH dose but infusions were 5-fold more potent than daily injections. Spleen and thymus weights were markedly increased by rhGH and were also affected by the pattern of GH exposure. At 5 mg rhGH/kg/day, thymus weights were 390±35 mg for injectionsvs. 613 ± 34 mg for infusions (P<0.001) compared with 248 ± 16 mg in vehicle-treated Hx controls. Infusions of rhlGF-1 also stimulated specific organ growth but caused less weight gain. RhlGF-1 additively increased the weight gain caused by rhGH injections but not by rhGH infusions. Circulating IGF-1 and GHBP levels were increased in a dose-dependent manner by rhGH infusion, whereas daily injections were ineffective. Thus, differential organ growth could be related to the higher serum IGF-1 concentrations induced by continuous rhGH administration. These studies show that whole body growth is best maintained by intermittent rhGH exposure, whereas, paradoxically, differential organ growth is most pronounced with continuous rhGH administration.

Recovery from acute ischaemic renal failure is accelerated by des-(1-3)-insulin-like growth factor-1

1. Acute renal failure carries a high risk of morbidity and mortality, so there is a need for agents that minimize renal injury after an insult and that hasten repair. Insulin-like growth factor-1 is mitogenic for renal tubular cells; in normal kidneys it has haemodynamic effects and it is potently anabolic. We tested the theory that insulin-like growth factor-1 may be of use in the treatment of acute renal failure by administering recombinant des-(1-3)-insulin-like growth factor-1, a truncated form of insulin-like growth factor-1, which occurs naturally. Ischaemic renal failure was induced in normal rats by occluding both renal pedicles for 60 min. Then des-(1-3)-insulin-like growth factor-1 (0.8 mg day-1 kg-1) or vehicle was given by subcutaneous minipump for 7 days. The rats were weighed and bled daily and in one experiment were housed in metabolic cages and urine was collected. 2. Des-(1-3)-insulin-like growth factor-1 caused a lower and earlier peak in both serum creatinine and blood urea-nitrogen levels, and a more rapid and complete return toward basal values than in untreated animals. Also des-(1-3)-insulin-like growth factor-1 significantly increased creatinine clearance and reduced fractional excretion of filtered sodium. Besides these beneficial effects on kidney function, des-(1-3)-insulin-like growth factor-1 was anabolic as treated rats gained weight while control rats lost weight. The mortality in control rats was 28% compared with 6% in treated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo administration of insulin-like growth factor-I stimulates primary B lymphopoiesis and enhances lymphocyte recovery after bone marrow transplantation

Recombinant human insulin-like growth factor-I (IGF-I) (100 micrograms/day) was infused by osmotic minipumps into mice to evaluate its effects on bone marrow B lymphopoiesis. IGF-I treatment resulted in a significant increase in the total number of bone marrow B lineage cells by 2 wk post-treatment in both normal, adult mice and animals that had been lethally irradiated and reconstituted with syngeneic bone marrow. Effects were still apparent at wk 3, even though pumps delivered IGF-I for only 14 days. In addition, the results confirm previous observations that IGF-I treatment results in an increase in numbers of splenic B cells and suggest that this is in part the result of stimulation of B cell proliferation in that organ.

In vivo administration of insulin-like growth factor-I stimulates primary B lymphopoiesis and enhances lymphocyte recovery after bone marrow transplantation

Recombinant human insulin-like growth factor-I (IGF-I) (100 micrograms/day) was infused by osmotic minipumps into mice to evaluate its effects on bone marrow B lymphopoiesis. IGF-I treatment resulted in a significant increase in the total number of bone marrow B lineage cells by 2 wk post-treatment in both normal, adult mice and animals that had been lethally irradiated and reconstituted with syngeneic bone marrow. Effects were still apparent at wk 3, even though pumps delivered IGF-I for only 14 days. In addition, the results confirm previous observations that IGF-I treatment results in an increase in numbers of splenic B cells and suggest that this is in part the result of stimulation of B cell proliferation in that organ.

Recombinant human insulin-like growth factor binding protein-3 (rhIGFBP-3): effects on the glycemic and growth promoting activities of rhIGF-1 in the rat

The effects of IGFBPs on IGF-1 bioactivity in vivo remain largely unknown. We have tested the ability of rhIGFBP-3, made in 293 cells or CHO cells, to affect the glycemic and anabolic activities of co-administered rhIGF-1. For glycemic studies female dw/dw rats were anesthetized, a jugular catheter inserted, basal blood samples taken and i.v. injections given of rhIGF-1 (0.25 mg/kg), rhIGFBP-3 (0.50 mg/kg), or rhIGF-1 plus rhIGFBP-3 (0.25 plus 0.50 mg/kg, respectively). The blood glucose (20 min later, as a percent of initial, mean +/- SD) reached its nadir for rhIGF-1 alone (58 +/- 5%) but was not changed by rhIGFBP-3 alone (99 +/- 4%) or rhIGF-1 plus rhIGFBP-3 (93 +/- 5%). In growth studies, young female hypophysectomized rats (90-105 g) were injected s.c. twice daily for 3-4 days, or infused s.c. for 7 days, with excipient, rhIGF-1 or rhIGF-1 plus rhIGFBP-3 at doses similar to those used in the hypoglycemia studies. Weight gain induced by rhIGF-1 was either unchanged, or enhanced, when the rhIGF-1 was delivered with rhIGFBP-3. The hypoglycemic activity of IGF-1 was greatly reduced if IGF-1 was administered bound to 293-cell rhIGFBP-3 but anabolic activity was unchanged or enhanced.