Use ofLeucaena leucocephala (Lam. de Wit) leaves as a nitrogen source for crop production

Field and pot trials were conducted to determine optimum management practices for usingLeucaena leucocephala (Lam. de Wit) leaves as a N source for crop production. Field trials with maize showed no benefit from split application of leucaena leaves or from application of fresh as opposed to dried material. Field trials also failed to show any difference between incorporation as opposed to surface application of leucaena leaves. This may be attributed to the low nitrogen response observed. Pot trials however, showed that soil incorporation of leucaena leaves was more effective than surface application in increasing plant dry weight.Leucaena leaves were not as effective as inorganic N in increasing maize grain yield (field trials) or dry matter production (pot trial). Unlike inorganic N, leucaena leaves had a significant residual effect on the succeeding maize crop. In decomposition studies, buried leucaena leaves decomposed more quickly than surface-applied leaves, and fresh leaves decomposed more rapidly than dried leaves.     

Boundary layer drug delivery using a helical catheter

BACKGROUND: A catheter-based approach for local endovascular drug delivery has been developed. The catheter is deployed percutaneously, while the end of the catheter is in the form of a helix that is placed just proximal to the vascular site to be treated. The helices are in contact with the vessel wall. A number of small holes is drilled in the coils of the catheter through which drug is infused, so that the infused drug remains within the blood fluid 'boundary layer' adjacent to the vessel wall. This approach is expected to be highly efficient for administration of antithrombotic and antiproliferative agents that target processes leading to vascular occlusion, heart attacks, and strokes. METHODS: The helical catheter was qualitatively evaluated using optical dye density measurements of Evans blue dye infused using an in vitro steady flow system under a physiologic range of conditions. To further demonstrate the efficiency of the technique, its capacity to inhibit thrombosis was evaluated in a baboon thrombosis model. The catheter was inserted into a femoral arteriovenous shunt (blood flow rate = 100 ml/min) and placed proximal to a segment of highly thrombogenic Dacron vascular graft (4.0 mm i.d.). Integrelin (an inhibitor of platelet glycoprotein IIb/IIIa; doses: 0.25-1.0 microg/min) and hirudin (an antithrombin; doses: 10-100 microg/min) were used to inhibit thrombus formation. RESULTS: Experimental flow visualization studies demonstrated that high concentrations of the infused Evans blue dye were retained near the vessel wall. In the animal experiments, platelet deposition on the Dacron graft surface was reduced by 82-97% (Integrelin) and 68-92% (hirudin) over 1-2 h of blood exposure. The local antithrombotic effects produced were found to be 200-fold and 30-fold more efficient than systemic administration of the same agents. CONCLUSIONS: Local drug infusion using the helical catheter approach can achieve high drug concentration levels at target sites, may avoid systemic effects, and can reduce cost of therapy by reducing total drug requirements.     

Effect of percutaneous endoscopic gastrostomy on gastric emptying in clinically normal cats

OBJECTIVE: To assess the effect of percutaneous endoscopic gastrostomy (PEG) tube placement on gastric emptying in clinically normal cats. ANIMALS: 8 healthy adult 3- to 5-year-old cats. PROCEDURE: Cats were accommodated to the diet for 2 weeks prior to scintigraphy. Caloric needs were divided into 3 feedings/d. Food was withheld for 24 hours after tube placement, then was fed as a third of the caloric needs on day 1, two-thirds on day 2, and full caloric requirements thereafter. Gastric emptying was measured via nuclear scintigraphy. Labeled meals contained 111 MBq (3 mCi) of 99mTc-labeled disofenin. Sixty-second ventral scintigraphic images were acquired immediately, every 20 minutes for the first hour, then every 30 minutes for 4 hours after feeding. Each cat was evaluated 3 times prior to PEG tube placement. Cats were anesthetized, and 16-F mushroom-tipped Pezzar gastrostomy tubes were placed, using a video endoscope. Scintigraphy was repeated on days 1, 4, 7, 11, 14, and 21 after PEG tube placement. RESULTS: Gastric emptying was faster with a PEG tube in place. Percentage of retained gastric activity was significantly lower after PEG for 150, 180, 210, and 240 minutes versus time before PEG tube placement. CONCLUSION: Placement of a PEG tube does not delay gastric emptying in clinically normal cats. CLINICAL RELEVANCE: Gastric retention of food, vomiting, and aspiration pneumonia after PEG tube placement may not be related to delayed gastric emptying.     

Summary of the II International Symposium on Cytomegalovirus

Human cytomegalovirus (HCMV) is a highly species-specific DNA virus belonging to the Betaherpesvirinae subfamily of the herpesviridae family. Like other herpesviruses, primary infection with HCMV is followed by persistence of the virus in a latent form. The sites of latency are still largely undefined, but they probably include bone marrow progenitor cells and peripheral blood monocytes. From these sites, the virus can reactivate, resulting in renewed shedding of the virus, or, in immunocompromized persons, development of disease. Humans are the only reservoir of HCMV and transmission occurs by person-to-person contact. Infection with HCMV is common. In most developed countries, HCMV seroprevalence steadily increases after infancy and 10-20% of children are infected before puberty. In adults, the prevalence of antibodies ranges from 40 to 100%. Although HCMV has a world-wide distribution, infection with HCMV is more common in the developing countries and in areas of low socioeconomic conditions, which is predominantly related to the closeness of contacts within these populations. Except for a mononucleosis-like illness in some persons, infection with HCMV rarely causes disease in immunocompetent individuals. However, HCMV can cause severe morbidity and mortality in congenitally infected newborns and immunocompromized patients, most notably transplant-recipients and HIV-infected persons. This article provides a review of the information presented at the Second International Symposium on Cytomegalovirus organized and convened by The Macrae Group (New York City, NY) in Acapulco, Mexico on 24-28 April 1998. During this symposium, the state-of-the-art knowledge on diagnosis, treatment and prophylaxis of HCMV infections were discussed, and, based on this information, attempts to highlight the future directions in basic and clinical research areas that need to be stimulated to facilitate advancement in prevention and treatment of CMV disease.     

Analysis of solid renal dysplasia by flow cytometry: malignant potential?

The iron-chelating agent desferrioxamine now finds extensive use in the treatment and diagnosis of aluminum-related diseases in renal patients. We review the chemistry and pharmacokinetics of desferrioxamine in chelation therapy for patients on hemodialysis.     

Localization of allatostatin-immunoreactive material in the central nervous system, stomatogastric nervous system, and gut of the cockroach Blattella germanica

Immunoreactivity against peptides of the allatostatin family having a typical YXFGL-NH2 C-terminus has been localized in different areas of the central nervous system, stomatogastric nervous system and gut of the cockroach Blattella germanica. In the protocerebrum, the most characteristic immunoreactive perikarya are situated in the lateral and median neurosecretory cell groups. Immunoreactive median neurosecretory cells send their axons around the circumesophageal connectives to form arborizations in the anterior neuropil of the tritocerebrum. A group of cells in the lateral aspect of the tritocerebrum project to the antennal lobes in the deutocerebrum, where immunoreactive arborizations can be seen in the periphery of individual glomeruli. Nerve terminals were shown in the corpora allata. These terminals come from perikarya situated in the lateral neurosecretory cells in the pars lateralis and in the subesophageal ganglion. Immunoreactive axons from median neurosecretory cells and from cells positioned in the anteriormost part of the tritocerebrum enter together in the stomatogastric nervous system and innervate foregut and midgut, especially the crop and the valve between the crop and the midgut. The hindgut is innervated by neurons whose perikarya are located in the last abdominal ganglion. Besides immunoreactivity in neurons, allatostatin-immunoreactive material is present in endocrine cells distributed within the whole midgut epithelium. Possible functions for these peptides according to their localization are discussed.     

Histology of rat small bowel transplants: cyclosporine A ameliorates features of rejection including apoptosis and ganglion cell reduction

The spectrum of photoaging in human skin shows a recognizable progression from subtle to profound, reflecting the various anatomic and structural changes that appear with aging skin. Qualification and quantification of these changes on both the macroscopic and microscopic levels enable the physician to select and evaluate appropriate therapeutic approaches to the problem of chronic solar damage. Comparative studies remain to be done that will further refine our abilities to match the right solutions to the recognized problems.     

Leucine transport in Xenopus laevis oocytes: functional and morphological analysis of different defolliculation procedures

L-leucine uptake in stage V Xenopus laevis oocytes was affected by the specific methods used to remove the follicle cells. In the presence of 100 mM NaCl, L-leucine uptake was reduced by 67.5% +/- 5.7 when defolliculation was performed enzymatically by collagenase treatment, whereas the reduction was 30.5% +/- 6.4 after mechanical defolliculation. The Na(+)-dependent uptake of 0.1 mM L-leucine was 18.6 +/- 4.6 pmol oocyte-1 40 min-1 in folliculated oocytes and 5.6 +/- 1.9 in collagenase defolliculated oocytes (means +/- SE). L-leucine uptake was not affected by the removal of the follicular layer if defolliculation occurred after the transport period; radiolabeled L-leucine is therefore not taken up into a compartment that is removed by the defolliculation process. The different L-leucine uptake rates observed in folliculated and defolliculated oocytes were not due to non-specific L-leucine binding to membranes. L-leucine kinetics showed that the L-leucine Vmax and Km values were lower in oocytes deprived of the follicular layer than in control oocytes enveloped in intact follicular layers. The Vmax and Km values of Na(+)-dependent L-leucine transport, calculated from data obtained the day after defolliculation by collagenase treatment, were: 16 +/- 1.5 pmol oocyte-1 40 min-1 and 57 +/- 21 mumol (mean +/- SD). The Na(+)-activation curve of 0.1 mM L-leucine was hyperbolic in folliculated oocytes and sigmoidal in defolliculated oocytes. The morphological analysis performed in parallel with the transport experiments showed that after defolliculation, the fibers forming the vitelline membrane tended to be arranged in a more regular orthogonal array, and the number of oocyte microvilli was reduced after collagenase treatment. Mechanical defolliculation did not appreciably affect the oocyte microvilli, however this procedure did not completely remove all follicle cells. The damage to collagenase treated oocytes was reversible, and the functional and structural features of most oocytes improved upon subsequent in vitro incubation. The recovery process seemed to involve protein synthesis in view of the increased value of L-leucine Vmax, and microscopic observation showing recovery of the microvillar apparatus.     

Stress and strain in staphylococcal nuclease

Protein molecules generally adopt a tertiary structure in which all backbone and side chain conformations are arranged in local energy minima; however, in several well-refined protein structures examples of locally strained geometries, such as cis peptide bonds, have been observed. Staphylococcal nuclease A contains a single cis peptide bond between residues Lys 116 and Pro 117 within a type VIa beta-turn. Alternative native folded forms of nuclease A have been detected by NMR spectroscopy and attributed to a mixture of cis and trans isomers at the Lys 116-Pro 117 peptide bond. Analyses of nuclease variants K116G and K116A by NMR spectroscopy and X-ray crystallography are reported herein. The structure of K116A is indistinguishable from that of nuclease A, including a cis 116-117 peptide bond (92% populated in solution). The overall fold of K116G is also indistinguishable from nuclease A except in the region of the substitution (residues 112-117), which contains a predominantly trans Gly 116-Pro 117 peptide bond (80% populated in solution). Both Lys and Ala would be prohibited from adopting the backbone conformation of Gly 116 due to steric clashes between the beta-carbon and the surrounding residues. One explanation for these results is that the position of the ends of the residue 112-117 loop only allow trans conformations where the local backbone interactions associated with the phi and psi torsion angles are strained. When the 116-117 peptide bond is cis, less strained backbone conformations are available. Thus the relaxation of the backbone strain intrinsic to the trans conformation compensates for the energetically unfavorable cis X-Pro peptide bond. With the removal of the side chain from residue 116 (K116G), the backbone strain of the trans conformation is reduced to the point that the conformation associated with the cis peptide bond is no longer favorable.