Augmentation of adipofascial flaps using the long-term local delivery of insulin and insulin-like growth factor-1

The adipofascial flaps currently described in the literature frequently lack the volume requirements for reconstructive goals. In this study, the authors examined the use of long-term local delivery of insulin and insulin-like growth factor-1 (IGF-1) using polylactic-coglycolic acid/polyethylene glycol (PLGA/PEG) microspheres to augment inguinal adipofascial flaps based on the inferior epigastric vessels in the rat. Two flap models, the island flap and the limited dissection flap, were used to demonstrate simultaneous treatment and pretreatment modalities, respectively. Experimental groups received 12.5 mg of insulin microspheres (carrying 1 IU of insulin) plus 12.5 mg of IGF-1 microspheres (carrying 2.5 microg of IGF-1). A group undergoing the operation only (no treatment with microspheres) and a group treated with blank microspheres (no growth factor) served as external controls for the surgical procedure and the drug delivery device, respectively. In all groups (n = 5 animals in each), the contralateral flap served as an internal control. Upon harvest on postoperative day 28, the insulin and IGF-1-treated flaps in both models weighed statistically more than the internal control flaps and the two external control flaps. Likewise, on gross inspection, the adipogenic growth factor-treated flaps had greater volumes than the internal control flap groups and both of the external control flap groups (operation only and blank microspheres). Other intergroup comparisons suggested the absence of a systemic insulin and IGF-1 effect on adiposity. A histomorphometric analysis suggested (1) that insulin and IGF-1 treatment does not alter flap cell composition and (2) that flap augmentation is secondary to the stimulation of cell proliferation and adipocytic differentiation rather than the hypertrophy of mature adipocytes. Further evidence in favor of cell proliferation and differentiation was the discovery of nonanatomic, ectopic fat islands on the pedicle sheath of the treated flaps and the lack of variation in cell size distribution among groups. The authors concluded that the long-term local delivery of insulin and IGF-1 with PLGA/PEG microspheres is an effective method of adipofascial flap augmentation; this method increases the number of mature adipocytes rather than increasing the size of preexisting cells.     

Surfactant transport over airway liquid lining of nonuniform depth

Numerous effects (e.g., airway wall buckling, gravity, airway curvature, capillary instabilities) give rise to nonuniformities in the depth of the liquid lining of peripheral lung airways. The effects of such thickness variations on the unsteady spreading of a surfactant monolayer along an airway are explored theoretically here. Flow-induced film deformations are shown to have only a modest influence on spreading rates, motivating the use of a simplified model in which the liquid-lining depth is prescribed and the monolayer concentration satisfies a spatially inhomogeneous nonlinear diffusion equation. Two generic situations are considered: spreading along a continuous annular liquid lining of nonuniform depth, and spreading along a rivulet that wets the airway wall with zero contact angle. In both cases, transverse averaging at large times yields a one-dimensional approximation of axial spreading that is valid for the majority of the monolayer. However, a localized monolayer remains persistently two dimensional in a region at its leading edge having axial length scales comparable to the length scale of transverse depth variation. It is also shown how the transverse spreading of a monolayer may be arrested as it approaches a static contact line at the edge of a rivulet. Implications for Surfactant Replacement Therapy are discussed.     

The effects of weight asymmetry and resource distribution on aggression in groups of unacquainted pigs

The relationship between weight asymmetry and aggression when mixing groups of unacquainted pigs in two different environments was investigated. Ten groups of 4 female (LandracexYorkshire), unacquainted pigs with a weight asymmetry of 3.1+/-0.2 kg (mean weight: 16.6+/-0.6 kg) between each pig, and another 10 groups with a weight asymmetry of 1.2+/-0.1 kg (mean weight: 14.1+/-0.1 kg), were mixed at the age of 7 weeks. Ten of the groups (five of each) were mixed in an experimental pen with a heterogeneous distribution of straw. The pen consisted of two main compartments with straw in one of them, and a passage area with concrete floor in between. The other 10 groups were mixed in the same pen, but with a homogenous distribution of straw (straw spread all over the pen).The results showed that fighting duration was significantly shorter in groups with large weight asymmetry than in groups with small weight asymmetry irrespective of the environment. The number of bites delivered during the fights in the heterogeneous environment was lower in groups with large weight asymmetry than in groups with small weight asymmetry. In the homogenous environment, however, there was no significant difference between groups with large and small weight asymmetries regarding the number of bites. The combination of a limited straw area and a small weight asymmetry resulted in the greatest number of bites. In groups with large weight asymmetry, the largest pig won around 50% of the fights, and 25% of the variation in the percentage of fights won was explained by the weight asymmetry.In groups with small weight asymmetry, less than 10% of the variation in the percentage of fights won could be explained by weight asymmetry. The two largest pigs delivered significantly more bites and spent significantly more time fighting than the smallest pig. The second largest pig received significantly more bites and body lesions than the smallest pig in the groups. Fights between the two largest pigs had a significantly longer duration than when other pigs were involved. The results were discussed in relation to sequential assessment theory and resource defence theory.     

Functional Similarity between Archaeal and Bacterial CorA Magnesium Transporters

The constitutively expressed CorA Mg²⁺ transporter is the major Mg²⁺ influx system of Salmonella typhimurium and Escherichia coli. Genomic sequence data indicated the presence of a homolog in the archaeal organism Methanococcus jannaschii. The putative M. jannaschii CorA was expressed in an Mg²⁺-transport-deficient strain of S. typhimurium to determine its functional characteristics. The archaeal CorA homolog is a functional Mg²⁺ uptake system when expressed in S. typhimurium and has properties which are highly similar to those of the normal CorA transporter of S. typhimurium despite having a low level of sequence identity with the protein and being expressed in a lipid membrane of quite different composition than normal. This implies that the overall function of the proteins is the same and further suggests that their structures are very similar.     

Reconstitution of an Active Magnesium Chelatase Enzyme Complex from the bchI, -D, and -H Gene Products of the Green Sulfur Bacterium Chlorobium vibrioforme Expressed in Escherichia coli

Magnesium-protoporphyrin chelatase, the first enzyme unique to the (bacterio)chlorophyll-specific branch of the porphyrin biosynthetic pathway, catalyzes the insertion of Mg²⁺ into protoporphyrin IX. Three genes, designated bchI, -D, and -H, from the strictly anaerobic and obligately phototrophic green sulfur bacterium Chlorobium vibrioforme show a significant level of homology to the magnesium chelatase-encoding genes bchI, -D, and -H and chlI, -D, and -H of Rhodobacter sphaeroides and Synechocystis strain PCC6803, respectively. These three genes were expressed in Escherichia coli; the subsequent purification of overproduced BchI and -H proteins on an Ni²⁺-agarose affinity column and denaturation of insoluble BchD protein in 6 M urea were required for reconstitution of Mg-chelatase activity in vitro. This work therefore establishes that the magnesium chelatase of C. vibrioforme is similar to the magnesium chelatases of the distantly related bacteria R. sphaeroides and Synechocystis strain PCC6803 with respect to number of subunits and ATP requirement. In addition, reconstitution of an active heterologous magnesium chelatase enzyme complex was obtained by combining the C. vibrioforme BchI and -D proteins and the Synechocystis strain PCC6803 ChlH protein. Furthermore, two versions, with respect to the N-terminal start of the bchI gene product, were expressed in E. coli, yielding ca. 38- and ca. 42-kDa versions of the BchI protein, both of which proved to be active. Western blot analysis of these proteins indicated that two forms of BchI, corresponding to the 38- and the 42-kDa expressed proteins, are also present in C. vibrioforme.     

Thy-1 Is a Component Common to Multiple Populations of Synaptic Vesicles

Thy-1, a glycosylphosphatidylinositol-linked integral membrane protein of the immunoglobulin superfamily, is a component of both large dense-core and small clear vesicles in PC12 cells. A majority of this protein, formerly recognized only on the plasma membrane of neurons, is localized to regulated secretory vesicles. Thy-1 is also present in synaptic vesicles in rat central nervous system. Experiments on permeabilized PC12 cells demonstrate that antibodies against Thy-1 inhibit the regulated release of neurotransmitter; this inhibition appears to be independent of any effect on the Ca²⁺ channel. These findings suggest Thy-1 is an integral component of many types of regulated secretory vesicles, and plays an important role in the regulated vesicular release of neurotransmitter at the synapse.     

Patch Clamp on the Luminal Membrane of Exocrine Gland Acini from Frog Skin (Rana esculenta) Reveals the Presence of Cystic Fibrosis Transmembrane Conductance Regulator–like Cl? Channels Activated by Cyclic AMP

Chloride channels in the luminal membrane of exocrine gland acini from frog skin (Rana esculenta) constituted a single homogeneous population. In cell-attached patches, channels activated upon exposure to isoproterenol, forskolin, or dibutyryl-cAMP and isobutyl-1-methyl-xanthine rectified in the outward direction with a conductance of 10.0 ± 0.4 pS for outgoing currents. Channels in stimulated cells reversed at 0 mV applied potential, whereas channels in unstimulated cells reversed at depolarized potentials (28.1 ± 6.7 mV), indicating that Cl⁻ was above electrochemical equilibrium in unstimulated, but not in stimulated, cells. In excised inside-out patches with 25 mM Cl⁻ on the inside, activity of small (8-pS) linear Cl⁻-selective channels was dependent upon bath ATP (1.5 mM) and increased upon exposure to cAMP-dependent protein kinase. The channels displayed a single substate, located just below 2/3 of the full channel amplitude. Halide selectivity was identified as P_Br > P_I > P_Cl from the Goldman equation; however, the conductance sequence when either halide was permeating the channel was G_Cl > G_Br >> G_I. In inside-out patches, the channels were blocked reversibly by 5-nitro-2-(3-phenylpropylamino)benzoic acid, glibenclamide, and diphenylamine-2-carboxylic acid, whereas 4,4-diisothiocyanatostilbene-2,2-disulfonic acid blocked channel activity completely and irreversibly. Single-channel kinetics revealed one open state (mean lifetime = 158 ± 72 ms) and two closed states (lifetimes: 12 ± 4 and 224 ± 31 ms, respectively). Power density spectra had a double-Lorentzian form with corner frequencies 0.85 ± 0.11 and 27.9 ± 2.9 Hz, respectively. These channels are considered homologous to the cystic fibrosis transmembrane conductance regulator Cl⁻ channel, which has been localized to the submucosal skin glands in Xenopus by immunohistochemistry (Engelhardt, J.F., S.S. Smith, E. Allen, J.R. Yankaskas, D.C. Dawson, and J.M. Wilson. 1994. Am. J. Physiol. 267: C491–C500) and, when stimulated by cAMP-dependent phosphorylation, are suggested to function in chloride secretion.     

Flax (Linum usitatissimum L.) depends on arbuscular mycorrhizal fungi for growth and P uptake at intermediate but not high soil P levels in the field

The contribution of indigenous arbuscular mycorrhizal fungi (AMF) to growth and phosphorus (P) uptake by oilseed flax (Linum usitatissimum L.) was examined in two field experiments covering soil P levels from 20–86 mg kg-1 NaHCO3-extractable P. The fumigant dazomet was applied to the soil in half of the plots to obtain control plants with reduced mycorrhiza formation. An extensive AMF colonization of up to 48% of the root length was established in untreated soil of both experiments, although P fertilization reduced colonization to 28–39% at the latest harvests. Fumigation markedly decreased or totally prevented AMF colonization throughout the experiments. Root growth responded to fumigation by increased total and specific root length. Shoot P uptake was decreased by fumigation at soil P levels lower than ca. 50 mg kg-1 whereas shoot growth was reduced by fumigation at soil P levels lower than ca. 40 mg kg-1. The effects of fumigation were ascribed to the suppression of mycorrhiza formation. The effect of the AMF increased with decreasing soil P levels. Phosphorus inflow through roots (based on shoot P uptake) was reduced more strongly by fumigation than total P uptake. The P inflow through fungal tissue in roots was estimated to 4 × 10-14 mol P cm-1 s-1. We conclude that AMF are essential to flax growth at soil P levels below ca. 40 mg P kg-1, which is representative of the conditions under which most flax is grown.