Comparison of organ uptake and disappearance half-time of human epidermal growth factor and insulin

Epidermal growth factor (EGF), which was originally identified in salivary glands and saliva, has been also found in the kidney and urine, suggesting that the kidney may be an alternate source of this peptide. Liver was considered as the major site of the degradation of EGF but the involvement of other organs has been little studied. Therefore, we carried out comparative studies on the organ uptake and the disappearance half-time of EGF and insulin (having similar molecular size) in the same model of anesthetized dog with arterial (from aorta) and venous (from mesenteric, portal, hepatic, renal, femoral and jugular veins) blood sampling from various organs. Basal plasma level of EGF (1.32 +/- 0.33 pmol/l) and insulin (62.1 +/- 13.8 pmol/l) in the aorta was not significantly different from that recorded at various sampling sites. During i.v. infusion of EGF at 41.6 and 166.6 pmol/kg/h, the respective arterial EGF concentrations averaged 103 +/- 21 and 240 +/- 49 pmol/kg/h and the percent reduction in plasma EGF after passage through the head, leg, intestines and liver was about 30-50% and that after passage through the kidney was about 95%. During insulin (6.9 pmol/kg/h) infusion, the arterial hormone level averaged 227 +/- 21 pmol/l and this level was significantly reduced (by 23-42%) after passage through the head, leg, intestine, liver and kidney but no significant difference was found between various venous sampling sites. EGF and insulin appearing in the urine during EGF or insulin infusion accounted for about 40 and 7% of the difference between the entering and leaving renal masses of the peptide. Mean disappearance half time on stopping of EGF and insulin infusion was, respectively, 2.32 +/- 0.58 and 6.88 +/- 1.25 min. We conclude that unlike insulin, which is removed to similar extent by various organs including the kidney and the liver, EGF is taken up mainly by kidney and EGF present in urine originates mainly from renal clearance of peptide.     

Review: Hydrogels for cell immobilization

Hydrogels are being investigated for mammalian cell immobilization. Their material properties can be engineered for biocompatibility, selective permeability, mechanical and chemical stability, and other requirements as specified by the application including uniform cell distribution and a given membrane thickness or mechanical strength. These aqueous gels are attractive for analytical and tissue engineering applications and can be used with immobilization in therapies for various diseases as well as to generate bioartificial organs. Recent advances have broadened the use of hydrogel cell immobilization in biomedical fields. To provide an overview of available technology, this review surveys the current developments in immobilization of mammalian cells in hydrogels. Discussions cover hydrogel requirements for use in adhesion, matrix entrapment, and microencapsulation, the respective processing methods, as well as current applications. (c) 1996 John Wiley & Sons, Inc.     

Mini-review: Islet transplantation to create a bioartificial pancreas

Donor scarcity precludes the use of pancreatic transplantation to treat type I diabetes. Xenogeneic islet transplantation offers the possibility of overcoming this problem; however, it entails the use of immunoisolation devices to prevent immune rejection of the transplanted islets. These devices consist of a semipermeable membrane, which surrounds the islets and isolates them from the host's immune system, while allowing the passage of insulin and essential nutrients, including glucose. Problems associated with proposed device designs include diffusion limitations, biocompatibility, device retrieval in the event of failure, and mechanical integrity. Microencapsulation appears to be the most promising system of immunoisolation, however, the design of a device suitable for human clinical use remains a challenge. (c) 1994 John Wiley & Sons, Inc.     

Shell variation in sympatric freshwater Lymnaea peregra and L. ovata (Gastropoda: Lymnaeidae)

Snails of the genus Lymnaea are morphologically variable and their taxonomy is unclear. In particular, the forms peregra and ovata , distinguished by shell shape, are often considered variants of the same species, L. peregra. We studied a rare situation in a Swiss mountain lake where both forms are sympatric. First, we found that the forms shows complete separation for a number of allozymes. Second, we examined the response of the two snail forms to infection by the trematode Diplostomum phoxini . For the ovata form, there was a transitory, 10% increase in the growth of infected snails compared to uninfected controls. The peregra form showed no gigantism and had higher parasite-induced mortality. Third, we assessed differences between the forms in reproduction under different environmental conditions. Density negatively influenced egg production to the same degree in both forms. However, decreasing water levels, characteristic of part of the lake studied, led to a 30% decrease in egg production for the ovata form, but only a 10% decrease for the peregra form. These differences are discussed in relation to the microdistributions of the snails in the lake and we conclude that the two forms are almost certainly separate species.     

Variability in host plant resistance of Sorghum to Striga Hermonthica infestation in West Africa

Fourteen elite sorghum lines were evaluated for their resistance to Striga hermonthica at three locations in Nigeria and Mali. Results showed that many of the lines especially MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64 (Keninkédié) and the check SRN 39 remained resistant to Striga in all locations with low emerged Striga counts, while SAMSORG 14 had the highest Striga infestation in all locations. Considerable variation in reaction to Striga infestation was observed on Séguètana, 97-SB-F5DT-63 (Wasa), 97-SB-F5DT-65, CMDT 38, CMDT 39 and CMDT 45 which were susceptible to Striga at Samaru, Nigeria but were resistant to Striga at both locations in Mali. Based on low Striga resistance and high grain yield, lines MALISOR 84-1, SAMSORG 41, 97-SB-F5DT-64, 97-SB-F5DT-65, CMDT 39 and SAMSORT 14 have been nominated for wider evaluation across more West African countries.     

An optimized method for the chemiluminescent detection of alkaline phosphatase levels during osteodifferentiation by bone morphogenetic protein 2

Differentiation of osteoprogenitor cells into osteoblasts is a pivotal step during the normal development and repair of bone. Upregulation of endogenous cellular alkaline phosphatase activity (AP) is a commonly used intracellular marker for the assessment of osteoprogenitor cell differentiation into the osteoblastic phenotype. Current methods for assaying AP involve colorimetric detection of the enzyme's activity using the synthetic substrate p-nitrophenol phosphate. In this paper, we explored an alternative method of detecting AP using the chemiluminescent substrate disodium 3-(4-methoxyspiro[1,2-dioxetane-3,2'-(5'-chloro)tricyclo[3.3.1.1(3,7)]decan]-4-yl) phenyl phosphate (CSPD) for enhanced AP sensitivity and a more simplified assay. Using calf intestinal alkaline phosphatase as a standardizing enzyme, we determined that the chemiluminescent detection system was four orders of magnitude more sensitive than the standard colorimetric method of detection. Moreover, the chemiluminescent assay was faster and markedly simpler to perform. To maximize the utility of this assay system, two osteoprogenitor cell lines were compared for their ability to generate alkaline phosphatases in vitro when exposed to recombinant human bone morphogenetic protein (rhBMP-2). The W20-17 cell line was substantially more sensitive to rhBMP-2 than the C3H10T1/2 cell line, where each cell line produced detectable increases in AP after exposure to rhBMP-2 levels of 5 and 25 ng/ml, respectively. The experimental design for AP responsiveness to rhBMP-2 was further optimized for chemiluminescent detection with the W20-17 cell line by comparing the effects of reporter cell seeding density and the day of assay. In summary, the data presented in this paper demonstrate a faster, simpler, and more sensitive chemiluminescent method to monitor changes in AP levels during osteodifferentiation.     

Synthesis of in situ cross-linkable macroporous biodegradable poly(propylene fumarate-co-ethylene glycol) hydrogels

This study describes a synthesis method of biodegradable macroporous hydrogels suitable as in situ cross-linkable biomaterials. Macroporous hydrogels were based on poly(propylene fumarate-co-ethylene glycol) and prepared via coupled free radical and pore formation reactions. Cross-linking was initiated by a pair of redox initiators, ammonium persulfate and L-ascorbic acid. Pores were formed by the reaction between L-ascorbic acid and sodium bicarbonate, a basic component, which evolved carbon dioxide. Sol fraction of the hydrogels was varied from 0.06 +/- 0.01 to 0.64 +/- 0.01. A stereological approach was used to analyze the morphological properties of the macroporous hydrogels by relating the morphological properties of thin sections to the original three-dimensional macroporous hydrogel. Prepared macroporous hydrogels had porosities between 0.43 +/- 0.08 and 0.84 +/- 0.02 and surface area densities between 55 +/- 3 and 108 +/- 7 cm(-1). Sodium bicarbonate concentration had the greatest effect on both the porosity and surface area density. The effect of copolymer formulation on the porosity and surface area density was insignificant. From thin sections of the macroporous hydrogels, the profile size distributions were determined as an estimate of the pore size distribution. Two formulations synthesized with varying L-ascorbic acid concentration of 0.05 and 0.1 M had median profile sizes of 50-100 and 150-200 microm, respectively. This novel synthesis method allows for the in situ cross-linking of biodegradable macroporous hydrogels with morpholological properties suitable for consideration as an injectable tissue engineering scaffold.     

Two common nonsynonymous paraoxonase 1 (<Emphasis Type="Italic">PON1</Emphasis>) gene polymorphisms and brain astrocytoma and meningioma

Background  

Human serum paraoxonase 1 (PON1) plays a major role in the metabolism of several organophosphorus compounds. The enzyme is encoded by the polymorphic gene PON1, located on chromosome 7q21.3. Aiming to identify genetic variations related to the risk of developing brain tumors, we investigated the putative association between common nonsynonymous PON1 polymorphisms and the risk of developing astrocytoma and meningioma.     

Synthesis and in vitro hydroxyapatite binding of peptides conjugated to calcium-binding moieties

To confer bone-binding properties to proteins and other biological agents that lack specific targeting capacity, model peptide-based molecules were synthesized containing poly(aspartic acid), poly(glutamic acid), or a bisphosphonate (pamidronate). These motifs have well-documented affinities to hydroxyapatite, a property desirable for the targeting of molecules to bone for drug delivery and tissue engineering applications. Model peptides of increasing molecular mass (5-33 amino acids) were directly conjugated to eight aspartic acids (Asp8), eight glutamic acids (Glu8), or pamidronate, purified by high-performance liquid chromatography, and characterized by matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy. The modified peptides were incubated with hydroxyapatite in phosphate-buffered saline at physiological conditions over 24 h. This study revealed a significant amount (>90%) of conjugated peptides adsorbed to the hydroxyapatite as compared to unmodified peptides (<5%). It was found that while there were significant differences between the different hydroxyapatite-binding and control groups for all time points, the size of the peptide had no statistical effect on peptide-hydroxyapatite binding. These results demonstrate that bisphosphonate and oligopeptide conjugates hold great promise for the development of new bioactive molecules for bone-specific applications.     

Long-term effects of graduated compression stockings on cardiorespiratory performance

The use of graduated compression stockings (GCS) in sport has been increasing in the last years due to their potential positive effects for athletes. However, there is little evidence to support whether these types of garments actually improve cardiorespiratory performance. The aim of this study was to examine the cardiorespiratory responses of GCS during running after three weeks of regular use. Twenty recreational runners performed three tests on different days: test 1) – a 5-min maximal effort run in order to determine the participants’ maximal aerobic speed; and tests 2) and 3) – a fatigue running test of 30 minutes at 80% of their maximal aerobic speed with either GCS or PLACEBO stockings at random. Cardiorespiratory parameters (minute ventilation, heart rate, relative oxygen consumption, relative carbon dioxide production, ventilatory equivalents for oxygen and carbon dioxide, and oxygen pulse) were measured. Before each test in the laboratory, the participants trained with the randomly assigned stockings (GCS or PLACEBO) for three weeks. No significant differences between GCS and PLACEBO were found in any of the cardiorespiratory parameters. In conclusion, the present study provides evidence that running with GCS for three weeks does not influence cardiorespiratory parameters in recreational runners.