Foliar absorption — penetration of the cuticular membrane and nutrient uptake by isolated leaf cells

Summary Foliar absorption consists of penetration of a cuticular membrane and uptake by living cells within the leaf. A detailed analysis of nutrient absorption by these two systems has revealed that ionic penetration of the cuticular membrane is by diffusion, and that the coupling between active transport and metabolism is at the cellular level. Urea penetrates the cuticular membrane and is absorbed by leaf cells much more rapidly than are nutrient ions. Furthermore, urea facilitates penetration and absorption of other materials simultaneously applied. Penetration of nutrient ions through cuticular membranes has been localized by microautoradiography as occurring around stomatal pores and along periclinal cell walls. Chelation of metals such as iron, manganese and zinc reduces the rate of foliar absorption, but increases the translocation of the absorbed nutrient. At the cellular level the nutrient ion is absorbed and the ligand is excluded.

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Zusammenfassung Blattabsorption erfolgt durch Eindringen in Kutikularschichten der Membran und durch Aufnahme durch die lebenden Zellen innerhalb des Blattes. Eine detaillierte Analyse der N?hrstoffabsorption nach diesen beiden Systemen zeigte, da? die Ionen-Aufnahme über die Kutikularmembran durch Diffusion und da? die Koppelung des aktiven Transports mit dem Stoffwechsel im Zellbereich erfolgt. Harnstoff dringt durch die Kutikularmembran ein und wird viel schneller als N?hrstoff-Ionen durch die Blattzellen absorbiert. Weiterhin erleichtert Harnstoff das Eindringen und die Absorption anderer, gleichzeitig applizierter Substanzen. Die Fixierung der Eindringungsstelle von N?hrstoff-Ionen in Kutikularmembrane wurde durch Mikroautoradiographie ermittelt. Das Eindringen erfolgt um die Stomata-?ffnungen und entlang der periklinalen Zellw?nde. Metallgelate von Eisen, Mangan und Zink mindern die Zellabsorption, vermehren aber die Translokation der absorbierten N?hrstoffe. Im Bereich der Zellen werden N?hrstoff-Ionen absorbiert, aber Verbindungen ausgeschlossen.

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Résumé L'absorption foliaire consiste en une pénétration à travers la membrane cuticulaire, et l'assimilation par les cellules vivantes à l'intérieur de la feuille. Une analyse détaillée de l'absorption des éléments nutritifs par ces deux systèmes a révélé que la pénétration des ions à travers la membrane cuticulaire se fait par diffusion, et que le couplage entre le transport actif et le métabolisme se fait au niveau cellulaire. L'urée pénètre à travers la membrane cuticulaire et est absorbée par les cellules de la feuille beaucoup plus rapidement que ne le sont les ions nutritifs. D'autre part l'urée facilite la pénétration et l'absorption d'autres substances appliquées simultanément. La pénétration des ions nutritifs à travers la membrane cuticulaire a été localisée par microautoradiographie comme se faisant autour des pores stomatiques, et le long des parois des cellules périclinales. La chélation de métaux tels que fer, manganèse, zinc, réduit la vitesse d'absorption foliaire mais augmente la vitesse de transport de l'ion nutritif absorbé. Au niveau de la cellule, l'ion nutritif est absorbé, et le complexant est exclu.

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Report No. COO-888-51 in cooperation with the Division of Biology and Medicine of the United States Atomic Energy Commission, Contract AT (11-1)-888. Journal Article No. 3692 of the Michigan Agricultural Experiment Station.     

Characterization of Mannheimia (Pasteurella) haemolytica leukotoxin interaction with bovine alveolar macrophage beta2 integrins

Mannheimia (Pasteurella) haemolytica, the etiologic agent of bovine pneumonic mannheimiosis, produces an exotoxic leukotoxin. The leukotoxin (LktA) is a member of the RTX (repeats in toxin) family of bacterial cytolysins and is distinguished from other toxins by its unique target cell specificity to ruminant leukocytes occurring through binding to a specific receptor. We have demonstrated previously that the beta2 integrin LFA-1 is a receptor for LktA in bovine leukocytes and is involved in leukotoxin-induced biological effects. However the subunits within LFA-1 involved in binding to LktA, and post-binding signaling leading to cellular activation have not been well characterized. The purpose of our study was to pinpoint these precise subunits on bovine alveolar macrophages and to characterize their interaction with LktA. The results in this study indicate that although LktA can efficiently bind to the CD18 subunit of both LFA-1 and Mac-1, post-binding signaling events including elevation of intracellular calcium and CD18 tail phosphorylation are only observed through LFA-1. Furthermore, LktA also binds to the CD11a subunit of LFA-1. LktA binding to CD11a could be inhibited by a small molecule inhibitor of the I(inserted)-domain, the major ligand binding interface on CD11a. I-domain inhibition significantly blunts LktA-induced intracellular calcium elevation and tyrosine phosphorylation of the CD18 tail. Based on our results we suggest that LFA-1 serves as the functional leukotoxin receptor on bovine alveolar macrophages.     

An Efficient Micropropagation Protocol for High-Frequency Plantlet Regeneration from Liquid Culture of Nodal Tissues in a Medicinal Plant,Turnera ulmifolia L.

A highly efficient, stable, and cost-effective micropropagation protocol for the conservation of a medicinal plant Turnera ulmifolia L. was established from nodal tissues via multiple axillary shoot proliferation on using Murashige and Skoog’s (MS) liquid nutrient medium. To begin with, nodal explants were placed on agar gelled medium amended with 2.0 mg L^?1 6-benzylaminopurine (BAP) and 0.1 mg L^?1 indole-3 acetic acid (IAA) for shoot induction. Subsequently, elongation of regenerated shoots could be possible on liquid MS medium supplemented with 0.5 mg L^?1 BAP and Kin (kinetin) each along with 0.1 mg L^?1 IAA where high frequency of regeneration in terms of number of shoots (47.2 shoots/explant) was achieved. Furthermore, long and healthy shoots (4?5 cm in length) were rooted on agar gelled half-strength of MS medium supplemented with 2.0 mg L^?1 indole-3 butyric acid (IBA). Finally, in vitro regenerated plantlets were gradually acclimatized in the greenhouse and transferred to the field successfully.     

Soil chemical and microbiological properties in hay production systems: residual effects of contrasting N fertilization of swine lagoon effluent versus ammonium nitrate

This study characterized soil chemical and microbiological properties in hay production systems that received from 0 to 600 kg plant-available N (PAN) ha⁻¹ year⁻¹ from either swine lagoon effluent (SLE) or ammonium nitrate (AN) from 1999 to 2001. The forage systems contained plots planted with bermudagrass (Cynodon dactylon L.) or endophyte-free tall fescue (Festuca arundinaceae Schreb.). In March 2004, the plots were sampled for measurements of a suite of soil chemical and microbiological properties. Nitrogen fertilization rates were significantly correlated with soil pH and K₂SO₄-extractable soil C but not with total soil C, soil C/N ratio, electrical conductivity, or Mehlich-3-extractable nutrients. Soil supplied with SLE had significantly lower Mehlich-3-extractable nutrients than the soil supplied with AN. Two indicators of soil N-supplying capacity (potentially mineralizable N and amino sugar N) varied with plant species and the type of N fertilizer. However, they generally peaked at an application rate of 200 or 400 kg PAN ha⁻¹ year⁻¹. Soil microbial biomass C also peaked at an application rate of 200 or 400 kg PAN ha⁻¹ year⁻¹. Nitrification potential was significantly higher in soil supplied with AN than in the unfertilized control but was similar between SLE-fertilized and unfertilized soils. Our results indicated that an application rate as high as 600 kg PAN ha⁻¹ year⁻¹ did not benefit soil microbial biomass, microbial activity, and N transformation processes in these forage systems.     

Shackling of broilers: Effects on stress responses and breast meat quality

1. Experiments were conducted to study the welfare and meat quality effects of shackling. In experiment 1, broilers with or without leg problems were shackled (S) for 4 min on a moving line and blood sampled; or handled (H), returned to the crate and sampled after 4 min; or sampled immediately after removal from the crate (control, C).

2. Plasma corticosterone (CORT) concentrations, as measured by radioimmunoassay, were highest in S and lowest in C, while the H group was intermediate. Leg problems had no effect on CORT.

3. In experiment 2, tonic immobility (TI) was induced in broilers after 2 min inverted handling to determine fear responses. One week later, the birds were fasted, transported and then shackled on a moving shackle line for 0, 1, 3 or 4 min, then unshackled and blood sampled. Wing flapping during shackling was also quantified.

4. Shackling time did not influence CORT concentrations. There was a negative correlation (r= ? 0.714) between CORT and wing flapping duration in the 1 min shackling treatment. There was no relationship between TI and wing flapping or CORT.

5. In experiment 3, broilers were exposed to two food withdrawal (FW) times (food withdrawn overnight or during crating only) and held for 4 h prior to processing, shackled (0, 2 or 4 min shackling time, ST), and then killed by exsanguination. Blood samples were collected during the neck‐cut. Pectoralis superficialis and Supracoracoideus samples were either collected after 15 min and individually quick frozen (IQF) in liquid nitrogen or collected at 4 h post mortem from carcases chilled on slush ice (COI).

6. CORT increased significantly with increased ST. There was a FW × ST interaction effect on the initial pH of fillets. ST influenced the b*, chroma and Hue values of the COI fillets. FW influenced the L* and Hue values of both IQF and COI fillets as well as the a* value of the COI fillets.

7. In summary, CORT increased with shackling time when birds were held after transport. FW and ST also influenced the colour of fillets, although it is not clear whether these changes are perceptible to the consumer. The duration of wing flapping during shackling did not appear to be related to fearfulness, although it was influenced by properties of the shackle line. We suggest that there be a maximum time lapse between shackling and stunning or killing of 2 min to minimise stress and meat quality changes.     

Use of continuous renal replacement therapy for treatment of dogs and cats with acute or acute-on-chronic renal failure: 33 cases (2002–2006)

Objective: To describe the indications, clinical features, outcomes and complications associated with use of continuous renal replacement therapy (CRRT) in 17 client-owned dogs and 16 client-owned cats with acute or acute-on-chronic renal failure refractory to aggressive medical management.
Series summary: Twenty-nine percent of dogs and 44% of cats had evidence of pre-existing chronic kidney disease (CKD). Median duration of CRRT was 16.3 hours (range 0.3–83.0 hours) in dogs and 11.5 hours (range 1.0–35.5 hours) in cats. Median canine blood urea nitrogen (BUN) improved from 41.0 mmol/L (115.0 mg/dL) to 11.8 mmol/L (33.0 mg/dL) and creatinine from 636.5 mmol/L (7.2 mg/dL) to 274 mmol/L (3.1 mg/dL). Median feline BUN improved from 46.4 mmol/L (130 mg/dL) to 13.9 mmol/L (39.0 mg/dL) and creatinine from 1069.6 mmol/L (12.1 mg/dL) to 291.7 mmol/L (3.3 mg/dL). Metabolic acidosis resolved in 80% of affected dogs and 71% of affected cats. Hyperkalemia resolved in 100% of affected dogs and 88% of affected cats. Complications noted with CRRT included iatrogenic hypokalemia, iatrogenic metabolic alkalosis, clinical hypocalcemia, total hypercalcemia, filter clotting, anemia, hypothermia, and neurologic complications. Forty-one percent of dogs and 44% of cats survived to discharge. No dogs and only 1 cat developed newly diagnosed CKD.
New or unique information provided: CRRT can be a viable option for the management of acute or acute-on-chronic renal failure in dogs and cats that are refractory to aggressive medical management. The frequency of complications associated with CRRT in this study warrants further experience with this modality before its widespread use can be recommended.     

Characteristics and outcomes in surgical management of severe acute pancreatitis: 37 dogs (2001–2007)

Objective – Describe clinical characteristics and outcomes associated with canine patients undergoing surgical intervention for treatment of acute pancreatitis.
Design – Retrospective outcome study from 2001 to 2007.
Animals – Thirty-seven dogs.
Interventions – None.
Measurements and Main Results – The following data were collected for dogs who underwent surgical intervention in the course of treatment for severe acute pancreatitis: preoperative clinicopathologic and physical data, ultrasonographic findings, surgical procedure detail, histopathologic findings, and transfusion requirements. The survival rate was 80.8% in dogs with extrahepatic biliary obstruction, 64.3% in dogs undergoing necrosectomy, and 40.6% with pancreatic abscess. Overall survival was 63.6%. Surgical complications included intraoperative and postoperative hemorrhage in 12 dogs, postoperative development of diabetes mellitus in 3 dogs, exocrine pancreatic insufficiency in 1 dog, and bacterial peritonitis in 2 dogs.
Conclusion – Surgical intervention and aggressive postoperative care may be pursued in select dogs with severe acute pancreatitis. In dogs with extrahepatic biliary obstruction secondary to acute pancreatitis, surgical intervention may be associated with a good prognosis whereas dogs with pancreatic abscess formation may have a more guarded prognosis.     

传染性支气管炎的新动态

1传染支气管炎病毒的变异 1.1 变异特性 传染性支气管炎病毒(IBV)很重要的特性是会发生变异,它是一种不断进化的病毒.病毒表面的s蛋白很重要,与病毒的中和反应、HI活性、免疫性及血清定型相关.S蛋白由S1和S2蛋白组成,S1蛋白基因的改变是病毒不断进化的原因.     

Evaluation of chitosan and alginate immobilized Methylobacterium oryzae CBMB20 on tomato plant growth

Methylobacterium oryzae CBMB20, a promising plant growth promoting bacteria (PGPB) and a biocontrol agent, was immobilized in different formulations such as wet chitosan, dry chitosan, wet alginate and dry alginate and were tested for tomato plant growth promotion. Chitosan solution (1.5%) with pH 5.5–6.0 and 90 min contact time was found optimal for immobilization. The chitosan formulations showed better entrapment efficiency and good degradability resistance apart from slow release of cells under prolonged incubation. Survivability of bacteria (80%) was observed in wet chitosan formulation even after 90 days of storage at 4°C. The spermosphere survival of bacteria was high in both dry and wet chitosan formulations applied soils even after 21 days under greenhouse conditions. While the alginate formulation degraded fully, partial degradation of chitosan formulation was observed even after 30 days, indicating its ability to support the survival of M. oryzae CBMB20 in soil. Plants inoculated with wet chitosan formulation registered 1.3 fold increase in the shoot and root length and dry weight compared to other treatments. Hence, chitosan formulation supporting better plant growth compared to alginate will be a better carrier for taking bacteria to the plant rhizosphere and thereby promote plant growth.