Is milk fat globule size correlated with milk fat content in Ruminants?

In milk, fat exists in the form of milk fat globules (MFGs). The average size (average fat globules of different particle sizes) is the most common parameter when describing MFG size. There are different views on whether there is a correlation between MFG size and milk fat content. Is the MFG size correlated with milk fat content in ruminants? To address this question, we conducted two experiments. In experiment Ⅰ, dairy cows (n = 40) and dairy goats (n = 30) were each divided into a normal group and a low-fat group according to the milk fat content. In experiment Ⅱ, dairy cows (n = 16) and dairy goats (n = 12) were each divided into a normal group and a conjugated linoleic acid (CLA)-induced low-fat group. The normal groups were fed a basal diet, and the CLA-induced low-fat groups were fed the basal diet + 300 g/d CLA (cows) or the basal diet + 90 g/d CLA (goats). In both experiments, we determined the correlation between MFG size and milk composition and MFG distribution. The results showed that in the normal and low-fat groups of cows and goats, MFG size was not correlated with milk fat, protein, or lactose content or fat-to-protein ratio. Additionally, there was no difference in the distribution of large, medium, and small MFGs (P > 0.05). However, in the CLA-induced low-fat groups, we found a correlation between MFG size and milk fat content and fat-to-protein ratio (R2 > 0.3). Moreover, there was a significant change in the size distribution of MFGs. Therefore, in natural milk, MFG size was not correlated with milk fat content. Following CLA supplementation, MFG size was correlated with milk fat content. Our findings revealed that CLA and not milk fat affects MFG distribution and size.

Constructing N-Containing Poly(p-Phenylene) (PPP) Films Through A Cathodic-Dehalogenation Polymerization Method

Developing the films of N-containing unsubstituted poly(p-phenylene) (PPP) films for diverse applications is significant and highly desirable because the replacement of sp2 C atoms with sp2 N atoms will bring novel properties to the as-prepared polymers. In this research, an electrochemical-dehalogenation polymerization strategy is employed to construct two N-containing PPP films under constant potentials, where 2,5-diiodopyridine (DIPy) and 2,5-dibromopyrazine (DBPz) are used as starting agents. The corresponding polymers are named CityU-23 (for polypyridine) and CityU-24 (for polypyrazine). Moreover, it is found that both polymers can form films in situ on different conductive substrates (i.e., silicon, gold, ITO, and nickel), satisfying potential device fabrication. Furthermore, the as-obtained thin films of CityU-23 and CityU-24 exhibit good performance of alkaline hydrogen evolution reaction with the overpotential of 212.8 and 180.7 mV and the Tafel slope of 157.0 and 122.4 mV dec-1, respectively.

Constructing Chiral Covalent-Organic Frameworks for Circularly Polarized Light Detection

The use of chiral covalent organic frameworks (COFs) as active elements in photodetectors to directly identify circularly polarized light (CPL) can meet the requirement of integration and miniaturization of the as-fabricated devices. Herein, the design and synthesis of two isoreticular chiral two-dimensional (2D) COFs (CityU-7 and CityU-8) by introducing photosensitive porphyrin-based amines (5,10,15,20-tetrakis(4-aminophenyl)porphyrin) to enhance the optical absorption and chiral aldehyde linkage (2,5-bis((S/R))-2-methylbutoxy)terephthalaldehyde) to engender chirality for direct CPL detection  are  reported. Their crystalline structures  were  confirmed by powder X-ray diffraction, Fourier-transform infrared spectroscopy, and low-dose transition electron microscopy. Employing both chiral COFs as the active layers in photodetectors, left-handed circularly (LHC) and right-handed circularly (RHC) polarized light at 405 nm can be well distinguishable with short response time, high responsivity, and satisfying detectivity. The study provides the first example on the design and synthesis of chiral COFs for direct detection of CPL.

A Metal-Free Helical Covalent Inorganic Polymer: Preparation, Crystal Structure and Optical Properties

Helical morphologies are widely observed in nature, however, it is very challenging to prepare artificial helical polymers. Especially, precisely understanding the structure information of artificial metal-free helical covalent inorganic polymers via single-crystal X-ray diffraction (SCXRD) analysis is rarely explored. Here, we successfully prepare a novel metal-free helical covalent inorganic polymer ({[Te(C6 H5 )2 ] [PO3 (OH)]}n , named CityU-10) by introducing angular anions (HOPO3 2- ) into traditional tellurium-oxygen chains. The dynamic reversibility of the reaction is realized through the introduction of organic tellurium precursor and the slow hydrolysis of polyphosphoric acid. High-quality and large-size single crystals of CityU-10 have been successfully characterized via SCXRD, where the same-handed helical inorganic polymer chains form a pseudo-two-dimensional layer via multiple hydrogen-bonding interactions. The left-handed layers and right-handed layers alternatively stack together through weak hydrogen bonds to form a three-dimensional supramolecular structure. The single crystals of CityU-10 are found to display promising optical properties with a large birefringence. Our results would offer new guidelines for designing and preparing new crystalline covalent polymers through tellurium-based chemistry.

Thermally Induced Persistent Covalent-Organic Frameworks Radicals

Persistent covalent-organic framework (COF) radicals hold important applications in magnetics and spintronics; however, their facile synthesis remains a daunting challenge. Here, three p-phenylenediacetonitrile-based COFs (named CityU-4, CityU-5, and CityU-6) were synthesized. Upon heat treatment (250 °C for CityU-4 and CityU-5 or 220 °C for CityU-6), these frameworks were brought into their persistent radical forms (no obvious changes after at least one year), together with several observable factors, including color changes, red-shifted absorption, the appearance of electron spin resonance (ESR) signals, and detectable magnetic susceptibility. The theoretical simulation suggests that after heat treatment, lower total energy and nonzero spin density are two main factors to guarantee persistent COFs radicals and polarized spin distributions. This work provides an efficient method for the preparation of persistent COF radicals with promising potentials.

Construction of Crystalline Nitrone-Linked Covalent Organic Frameworks Via Kröhnke Oxidation

Developing diverse synthetic routes to prepare various crystalline covalent organic frameworks (COFs) and enrich the family of COFs is very important and highly desirable. In this research, we demonstrate that Kröhnke oxidation (originally developed to prepare carbonyl compounds) can be employed as an efficient method to construct two crystalline nitrone-linked COFs (CityU-1 and CityU-2) through the ingenious design of the polynitroso-containing precursors as well as the exquisite control of the polymerization conditions. The formation and structure of nitrone-based linkage units have been confirmed through a mode reaction. The as-obtained crystalline COFs have been characterized by Fourier transform infrared and X-ray photoelectron spectroscopy, powder X-ray diffraction patterns, and scanning electron microscopy. Notably, CityU-1 exhibits a BET specific surface area of 497.9 m²g^-1 with an I₂ capture capacity of 3.0 g g^-1 at 75 °C. Our research would provide more chances to prepare various crystalline COFs for diverse applications.

Design and synthesis of a NAD(P)H:quinone oxidoreductase 1-activatable photosensitiser for controlled photodynamic therapy

The utilisation of enzymes as stimuli can activate theranostic agents in a highly specific manner. We report herein a far-red-absorbing boron dipyrromethene-based photosensitiser that is responsive towards the cancer-associated human NAD(P)H:quinone oxidoreductase 1, enabling the controlled restoration of photodynamic activity for selective elimination of cancer cells.

Evaluation of Lipid Droplet Size and Fusion in Bovine Hepatic Cells

Lipid droplets (LDs) are organelles that play an important role in lipid metabolism and neutral lipid storage in cells. They are associated with a variety of metabolic diseases, such as obesity, fatty liver disease, and diabetes. In hepatic cells, the sizes and numbers of LDs are signs of fatty liver disease. Moreover, the oxidative stress reaction, cell autophagy, and apoptosis are often accompanied by changes in the sizes and numbers of LDs. As a result, the dimensions and quantity of LDs are the basis of the current research regarding the mechanism of LD biogenesis. Here, in fatty acid-induced bovine hepatic cells, we describe how to use oil red O to stain LDs and to investigate the sizes and numbers of LDs. The size distribution of LDs is statistically analyzed. The process of small LDs fusing into large LDs is also observed by a live cell imaging system. The current work provides a way to directly observe the size change trend of LDs under different physiological conditions.

Polynitrosoarene Radical as an Efficient Cathode Material for Lithium-Ion Batteries

Organic radical batteries (ORBs) with radical-branched polymers as cathode materials represent a valuable alternative to meet the continuously increasing demand on energy storage. However, the low theoretical capacities of current radical-contained compounds strongly hamper their practical applications. To address this issue, a chemically robust polynitrosoarene (tris(4-nitrosophenyl)amine) with a pronounced radical property is rationally designed as an efficient cathode for ORBs. Its unique multi-nitroso structure displays remarkably reversible charge/discharge capability and a superior capacity up to 300 mA h g-1 (93% theoretical capacity) after 100 cycles at 100 mA g-1 within a broad potential window of 1.3-4.3 V (vs Li+/Li). Moreover, the ultra-long cycle life is also achieved at 1000 mA g-1 with 85% preservation of the capacity after 1000 cycles, making it the best-reported organic radical cathode material for lithium-ion batteries.

A Nitro-Rich Small-Molecule-Based Organic Cathode Material for Effective Rechargeable Lithium Batteries

Organic cathode materials have attracted extensive research interest for rechargeable lithium-ion batteries (LIBs) because of their diverse structures and tunable properties. However, the preparation of organic cathode materials with high capacities, long cycling life, and high energy densities still remains a big challenge. To address these issues, we designed and synthesized a novel multinitro-decorated organic small molecule, N⁴,N^4''-bis(2,4-dinitrophenyl)-5'-(4-((2,4-dinitrophenyl)amino)phenyl)-[1,1':3',1''-terphenyl]-4,4''-diamine (TAPB-6NO₂), where the unique electronic character of nitro group should enable TAPB-6NO₂ to be a promising cathode candidate for LIBs. We found that the introduction of multiple nitro groups could efficiently reduce the solubility of TAPB-6NO₂ in organic electrolytes, resulting in a high specific capacity of around 180 mAh g^-1 and stable cycling with a capacity retention of 91% after 1100 cycles at 1000 mA g^-1. This work suggests that attaching multiple nitro groups on a small molecule is an effective approach to construct high-performance organic cathode materials for stable and sustainable rechargeable LIBs.

Design strategies for improving the crystallinity of covalent organic frameworks and conjugated polymers: a review

Highly crystalline covalent organic frameworks (COFs) or conjugated polymers (CPs) are very important and highly desirable because these materials would display better performance in diverse devices and provide more structure-property related information. However, how to achieve highly crystalline or single-crystal COFs and CPs is very challenging. Recently, many research studies have demonstrated the possibility of enhancing the crystallinity of COFs and CPs. Thus, it is timely to offer an overview of the important progress in improving the crystallinity of COFs and CPs from the viewpoint of design strategies. These strategies include polycondensation reaction optimization, improving the planarity, fluorine substitution, side chain engineering, and so on. Furthermore, the challenges and perspectives are also discussed to promote the realization of highly crystalline or single-crystal COFs and CPs.

A soluble iron(II)-phthalocyanine-catalyzed intramolecular C(sp3)-H amination with alkyl azides

Herein, we describe a soluble iron(II)-phthalocyanine, [Fe^II(^tBu₄Pc)(py)₂] (Pc = phthalocyaninato(2-)), as an effective catalyst in intramolecular C(sp³)-H bond amination, with alkyl azides as the nitrogen source, to afford the amination products in moderate to excellent yields with a broad substrate scope.

Sucralose enhances the susceptibility to dextran sulfate sodium (DSS) induced colitis in mice with changes in gut microbiota

Sucralose is one of the most widely used artificial sweeteners, free of nutrients and calories. Its approval and uses correlate with many of the worldwide epidemiological changes in inflammatory bowel disease (IBD). Multiple animal studies by us and others showed that sucralose exacerbated ileitis in SAMP1/YitFc mice and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. In this study, we further investigated the effect of sucralose on dextran sulfate sodium (DSS)-induced colitis in mice and the associated mechanisms. Male C57BL/6 mice received 1.5 mg ml^-1 sucralose in drinking water for 6 weeks. Then, 2.5% DSS was added to drinking water for 7 days to induce ulcerative colitis (UC). The results showed that, compared with the DSS group, administration of sucralose exacerbated the severity of colitis as indicated by the further decrease in body weight, increase in disease activity index (DAI) and the expression of pro-inflammatory cytokines, as well as the activation of the TLR5-MyD88-NF-κB signaling pathway, and the disturbances of intestinal barrier function, along with changes in the intestinal microbiota. Our findings indicate that sucralose may increase the susceptibility to DSS-induced colitis through causing dysbiosis of intestinal microbiota and damage to the intestinal barrier.

HIF-1α Mediates Osteoclast-Induced Mandibular Condyle Growth via AMPK Signaling

During the mandibular condylar growth, the absorption of calcified cartilage matrix induced by osteoclasts is crucial for the continuous endochondral osteogenesis. Meanwhile, recent studies showed that subchondral bone resided within the low-oxygen microenvironment, and our previous study revealed that hypoxia-inducible transcription factor 1α (HIF-1α) promoted osteoclastogenesis under hypoxia. However, whether HIF-1α regulates the function of osteoclasts in the mandibular condyle cartilage remains elusive. Our study indicated that severe deformity of the mandibular condyle was displayed in 10-wk-old osteoclast-specific HIF-1α conditional knockout (CKO) mice, accompanied by shortened length of condylar process and disorganized fibrocartilage. In 1-, 2-, and 4-wk-old CKO mice, the size of the hypertrophic layer and chondrocytic layer was significantly thickened. In the chondrocytic layer, chondrocytes were atrophied, showing a form of apoptosis in 4-wk-old CKO mice. Furthermore, an increase in the thickness of the fibrous and proliferating layer was observed in 10-wk-old CKO mice, as well as a significant decrease in that of the chondrocytic and hypertrophic chondrocyte layers. Interestingly, the articular surface of the condylar process abnormally presented a horizontal concave shape, and a disk-like acellular connective tissue appeared. In addition, genetic ablation of HIF-1α blunted cartilage matrix loss by subchondral osteoclast deficiency, resulting in a high subchondral bone mass phenotype, accompanied with a decreased number of blood vessels, alkaline phosphatase staining, and vascular endothelial growth factor (VEGF) expression. Mechanistically, the number of osteoclasts in the center of the condyle in CKO mice was significantly reduced by attenuated expression of adenosine 5′-monophosphate-activated protein kinase (AMPK) signaling. These findings reveal a novel influence of HIF-1α function in osteoclasts on maintenance of osteoclast-induced resorption of calcified cartilage matrix via AMPK signaling, as well as subchondral bone formation through VEGF-dependent angiogenesis in bone marrow.

[The clinical significance of PRL-3,VEGF expression in sinonasalsquamous cell carcinoma]

Objective:To analyze the clinical significance of phosphatase of regenerating liver-3(PRL-3) and vascular endothelial growth factor(VEGF)expression in sinonasal squamous cell carcinomas.Method:We use immunohistochemical analysis and RT-PCR to detecte the expression of PRL-3 and VEGF protein in 62 cases of sinonasal squamous carcinoma tissues(SNSCC),30 cases of nasal polyps(NP),and 25 cases of normal nasal mucosa(NM).Result:①The expression of PRL-3 and VEGF in sinonasal squamous cell carcinoma tissues were statistically higher than in nasal polyps and normal nasal mucosa tissues (P<0.05).②The expression of PRL-3 and VEGF were not correlated with patient's age or gender(P>0.05).But the High expression of PRL-3 and VEGF in SNSCC was significantly related with advanced,lower tumor differentiation and lymph node metastasis(P<0.05).③The expression of PRL-3 and VEGF was positively correlated in sinonasal squamous cell carcinomas.Conclusion:The expression of PRL-3 and VEGF in SNSCC may involve in the regulation of tumor growth and differentiation.The expressing intensity may reflect the proliferation activity of sinonasal squamous cell carcinoma cell.PRL-3 and VEGF may promote the tumor metastasis in a synergistic manner.

Male requires a higher median target effect-site concentration of propofol for I-gel placement when combined with dexmedetomidine

OBJECTIVE

The supraglottic airway device (SAD) can be used for airway management of spontaneous breathing patients, and propofol is commonly applied for the SAD placement. This study was designed to assess the effect of gender on median target effect-site concentration (Ce₅₀) of propofol for I-gel placement when combined with dexmedetomidine.

MATERIAL AND METHOD

19 males and 18 females, aged 18 to 59 and undergoing elective surgery, were enrolled. After intravenous infusion of dexmedetomidine 1.0μg/kg over 10min followed by continuous infusion of 0.4μg/kg/h, target-controlled infusion of propofol under Marsh model was started and the initial Ce of propofol was set at 4.79μg/mL and 4.35μg/mL in the male and female patients, respectively. The I-gel was inserted when the Ce of propofol reached the pre-set concentration and bispectral index value was less than 60. The Ce of propofol required for I-gel placement was determined by the Dixon up-and-down method.

RESULTS

The Ce₅₀ (95% confidence interval) of propofol required for I-gel placement were 4.082μg/mL (3.798-4.332μg/mL) and 3.509μg/mL (3.266-3.749μg/mL) in male and female patients, respectively, with a significantly higher Ce₅₀ in males.

CONCLUSION

When combined with dexmedetomidine, males require a higher Ce₅₀ of propofol for I-gel placement compared to females.

Xanthotoxin prevents bone loss in ovariectomized mice through the inhibition of RANKL-induced osteoclastogenesis

Xanthotoxin (XAT) is extracted from the seeds of Ammi majus. Here, we reported that XAT has an inhibitory effect on osteoclastogenesis in vitro through the suppression of both receptor activator of nuclear factor-κB ligand (RANKL)-induced ROS generation and Ca(2+) oscillations. In vivo studies showed that XAT treatment decreases the osteoclast number, prevents bone loss, and restores bone strength in ovariectomized mice.

INTRODUCTION

Excessive osteoclast formation and the resultant increase in bone resorption activity are key pathogenic factors of osteoporosis. In the present study, we have investigated the effects of XAT, a natural furanocoumarin, on the RANKL-mediated osteoclastogenesis in vitro and on ovariectomy-mediated bone loss in vivo.

METHODS

Cytotoxicity of XAT was evaluated using bone marrow macrophages (BMMs). Osteoclast differentiation, formation, and fusion were assessed using the tartrate-resistant acid phosphatase (TRAP) stain, the actin cytoskeleton and focal adhesion (FAK) stain, and the fusion assay, respectively. Osteoclastic bone resorption was evaluated using the pit formation assay. Reactive oxygen species (ROS) generation and removal were evaluated using dichlorodihydrofluorescein diacetate (DCFH-DA). Ca(2+) oscillations and their downstream signaling targets were then detected. The ovariectomized (OVX) mouse model was adopted for our in vivo studies.

RESULTS

In vitro assays revealed that XAT inhibited the differentiation, formation, fusion, and bone resorption activity of osteoclasts. The inhibitory effect of XAT on osteoclastogenesis was associated with decreased intracellular ROS generation. XAT treatment also suppressed RANKL-induced Ca(2+) oscillations and the activation of the resultant downstream calcium-CaMKK/PYK2 signaling. Through these two mechanisms, XAT downregulated the key osteoclastogenic factors nuclear factor of activated T cells c1 (NFATc1) and c-FOS. Our in vivo studies showed that XAT treatment decreases the osteoclast number, prevents bone loss, rescues bone microarchitecture, and restores bone strength in OVX mice.

CONCLUSION

Our findings indicate that XAT is protective against ovariectomy-mediated bone loss through the inhibition of RANKL-mediated osteoclastogenesis. Therefore, XAT may be considered to be a new therapeutic candidate for treating osteoporosis.

Dihydroartemisinin attenuates lipopolysaccharide-induced osteoclastogenesis and bone loss via the mitochondria-dependent apoptosis pathway

Dihydroartemisinin (DHA) is a widely used antimalarial drug isolated from the plant Artemisia annua. Recent studies suggested that DHA has antitumor effects utilizing its reactive oxygen species (ROS) yielding mechanism. Here, we reported that DHA is inhibitory on lipopolysaccharide (LPS)-induced osteoclast (OC) differentiation, fusion and bone-resorption activity in vitro. Intracellular ROS detection revealed that DHA could remarkably increase ROS accumulation during LPS-induced osteoclastogenesis. Moreover, cell apoptosis was also increased by DHA treatment. We found that DHA-activated caspase-3 increased Bax/Bcl-2 ratio during LPS-induced osteoclastogenesis. Meanwhile, the translocation of apoptotic inducing factor (AIF) and the release of cytochrome c from the mitochondria into the cytosol were observed, indicating that ROS-mediated mitochondrial dysfunction is crucial in DHA-induced apoptosis during LPS-induced osteoclastogenesis. In vivo study showed that DHA treatment decreased OC number, prevents bone loss, rescues bone microarchitecture and restores bone strength in LPS-induced bone-loss mouse model. Together, our findings indicate that DHA is protective against LPS-induced bone loss through apoptosis induction of osteoclasts via ROS accumulation and the mitochondria-dependent apoptosis pathway. Therefore, DHA may be considered as a new therapeutic candidate for treating inflammatory bone loss.

An additive-multiplicative rates model for recurrent event data with informative terminal event

In this article, we propose an additive-multiplicative rates model for recurrent event data in the presence of a terminal event such as death. The association between recurrent and terminal events is nonparametric. For inference on the model parameters, estimating equation approaches are developed, and the asymptotic properties of the resulting estimators are established. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a bladder cancer study is provided.

Effect of additives on the release of a model protein from PLGA microspheres

The purpose of this study was to investigate the effect of 2 additives, poly(ethylene glycol) (PEG) 1000 and 1,2,3-tridecanoyl glycerol (tricaprin), on the physico-chemical characteristics and in vitro release of a model protein, bovine serum albumin (BSA), form poly(D,L-lactic-co-glycolic acid) (PLGA) microspheres. BSA-loaded microspheres were prepared by the double emulsion solvent evaporation method. Additives were incorporated into microspheres to modify the release of protein. The addition of PEG 1000 and tricaprin changed the surface characteristics of microspheres from smooth and nonporous to porous and dimpled, respectively. The in vitro release profiles showed that the additives significantly (P < 0.05) increased the early-stage release of BSA from microspheres.

Mercurial sensitivity of aquaporin 1 endofacial loop B residues

The water channel protein aquaporin-1 (AQP1) has two asparagine-proline-alanine (NPA) repeats on loops B and E. From recent structural information, these loops are on opposite sides of the membrane and meet to form a pore. We replaced the mercury-sensitive residue cysteine 189 in AQP1 by serine to obtain a mercury-insensitive template (C189S). Subsequently, we substituted three consecutive cysteines for residues 71-73 near the first NPA repeat (76-78) in intracellular loop B, and investigated whether they were accessible to extracellular mercurials. AQP1 and its mutants were expressed in Xenopus laevis oocytes, and the osmotic permeability (P(f)) of the oocytes was determined. C189S had wild-type P(f) but was not sensitive to HgCl(2). Expression of all three C189S cysteine mutants resulted in increased P(f), and all three mutants regained mercurial sensitivity. These results, especially the inhibitions by the large mercurial p-chloromercunbenzene-sulfonic acid (pCMBS) ( approximately 6A wide), suggest that residues 71-73 at the pore are accessible to extracellular mercurials. A 30-ps molecular dynamics simulation (at 300 K) starting with crystallographic coordinates of AQP1 showed that the width of the pore bottleneck (between Connolly surfaces) can vary (w(avg) = 3.9 A, sigma = 0.75; hydrated AQP1). Thus, although the pore width would be > or = 6 A only for 0.0026 of the time, this might suffice for pCMBS to reach residues 71-73. Alternative explanations such as passage of pCMBS across the AQP1 tetramer center or other unspecified transmembrane pathways cannot be excluded.

[The protective effect of ligustrazine on optic nerve axons in rabbit eyes with continuous elevated IOP]

OBJECTIVE

To investigate the effects of ligustrazine on optic nerve axons in rabbit eyes with continuous elevated intraocular pressure (IOP).

METHOD

Thirty-six NZ rabbits with continuous elevated IOP induced by injection of alpha-chymotrypsin into anterior chamber were divided into two groups by randomization: treatment and control group. Ten mg/kg ligustrazine injected into the treatment group every day for 3 weeks began on the 7(th) day after IOP elevated continuously. The changes of conjunctival microcirculation and optic nerve axonal ultrastructure were observed at different time points.

RESULTS

The destruction of conjunctival microcirculation and axonal ultrastructure was milder in treatment group than that in the control group. In addition, the total number of axons and the percentage of axons in optic nerve area were higher, whereas the axonal diameter was smaller in the treatment group.

CONCLUSION

It is suggested that ligustrazine protect optic nerve axons from more damage induced by elevated IOP through improving ocular microcirculation.

[Cultured bovine corneal epithelial cells express functional water channel]

OBJECTIVE

To investigate the water permeability (P(f)) of the cultured bovine corneal epithelial cells (CBCEC) and whether aquaporins (AQPs) were present.

METHODS

Laser light-scattering system was used to determine the volume change of CBCEC from isotonic status rapidly transferred to hypotonic one, and the P(f) value was calculated. Messenger RNA obtained from CBCEC was injected into Xenopus laevis oocytes. After four days, the P(f) was determined by monitoring volume changes of oocytes upon hypoosmotic challenge (180 mOsm/L changed to 15 mOsm/L).

RESULTS

CBCEC challenged with 10% hypoosmotic solution at 37 degrees C swelled rapidly; the cellular P(f) was 72 microm/s. In the oocytes injected with mRNA from CBCEC, the P(f) increased to 76 microm/s. This increase was inhibited (by 89%) by 0.3 mmol/L HgCl(2).

CONCLUSION

Our results suggest that CBCEC express a typical mercurial-sensitive functional water channel in good numbers, judging from the comparatively high P(f) we measured. These begin to reopen the question of the presence and extent of an epithelial role in control of corneal hydration.

Profilin promotes barbed-end actin filament assembly without lowering the critical concentration

The mechanism of profilin-promoted actin polymerization has been systematically reinvestigated. Rates of barbed-end elongation onto Spectrin.4.1. Actin seeds were measured by right angle light scattering to avoid confounding effects of pyrenyl-actin, and KINSIM was used to analyze elongation progress curves. Without thymosin-beta4, both actin and Profilin. Actin (P.A) are competent in barbed-end polymerization, and kinetic simulations yielded the same bimolecular rate constant ( approximately 10 x 10(6) M(-1) s(-1)) for actin monomer or Profilin. Actin. When measured in the absence of profilin, actin assembly curves over a 0.7-4 microM thymosin-beta4 concentration range fit a simple monomer sequestering model (1 microM K(D) for Thymosin-beta4. Actin). The corresponding constant for thymosin-beta4.pyrenyl-Actin, however, was significantly higher ( approximately 9-10 microM), suggesting that the fluorophore markedly weakens binding to thymosin-beta4. With solutions of actin (2 microM) and thymosin-beta4 (2 or 4 microM), the barbed-end assembly rate rose with increasing profilin concentration (0.7-2 microM). Actin assembly in presence of thymosin-beta4 and profilin fit a simple thermodynamic energy cycle, thereby disproving an earlier claim (D. Pantaloni and M.-F. Carlier (1993) Cell 75, 1007-1014) that profilin promotes nonequilibrium filament assembly by accelerating hydrolysis of filament-bound ATP. Our findings indicate that profilin serves as a polymerization catalyst that captures actin monomers from Thymosin-beta4. Actin and ushers actin as a Profilin. Actin complex onto growing barbed filament ends.

Transport of fluid by lens epithelium

We report for the first time that cultured lens epithelial cell layers and rabbit lenses in vitro transport fluid. Layers of the alphaTN4 mouse cell line and bovine cell cultures were grown to confluence on permeable membrane inserts. Fluid movement across cultured layers and excised rabbit lenses was determined by volume clamp (37 degrees C). Cultured layers transported fluid from their basal to their apical sides against a pressure head of 3 cmH2O. Rates were (in microliter. h-1. cm-2) 3.3 +/- 0.3 for alphaTN4 cells (n = 27) and 4.7 +/- 1.0 for bovine layers (n = 6). Quinidine, a blocker of K+ channels, and p-chloromercuribenzenesulfonate and HgCl2, inhibitors of aquaporins, inhibited fluid transport. Rabbit lenses transported fluid from their anterior to their posterior sides against a 2.5-cmH2O pressure head at 10.3 +/- 0.62 microliter. h-1. lens-1 (n = 5) and along the same pressure head at 12.5 +/- 1.1 microliter. h-1. lens-1 (n = 6). We calculate that this flow could wash the lens extracellular space by convection about once every 2 h and therefore might contribute to lens homeostasis and transparency.

Cultured bovine corneal epithelial cells express a functional aquaporin water channel

PURPOSE

Given recent physiological and in situ hybridization evidence for the presence of a water channel in corneal epithelium, this study was conducted to investigate its expression and characteristics using cultured bovine corneal epithelial cells (CBCEPCs).

METHODS

CBCEPCs were grown in DMEM containing 2 ng/ml fibroblast growth factor and 6% fetal bovine serum. To determine their osmotic permeability (Pf), cells were passaged onto rectangular glass coverslips, and anisotonically induced volume changes were monitored by light scattering. To investigate expression, poly(A+) RNA from CBCEPCs was injected into Xenopus laevis oocytes, and the Pf of the oocytes was determined.

RESULTS

For CBCEPCs challenged with a 10% hypotonic solution at 37 degrees C, the kinetic constant of volume change was k=0.52+/-0.04 seconds(-1), and the calculated Pf 72+/-6 microm/sec (n=16). The Pf of oocytes injected with water was 14+/-1.8 microm/sec (n=4); injection with poly(A+) RNA from CBCEPCs increased Pf to 77+/-6 microm/sec (n=6). This increase in Pf was inhibited by 72% (reduced to 22+/-1 microm/sec) by 0.3 mM HgCl2 and was inhibited by 56% to 58% by coinjection with aquaporin (AQP)5 antisense oligonucleotide.

CONCLUSIONS

The comparatively high Pf determined for CBCEPCs, the presence of mRNA encoding water channels, and sensitivity to mercurial agents are typical of the expression of functional water channels. The predominant message is for AQP5, although the evidence was consistent with the presence of additional water channels. These findings bring renewed support for the notion that the epithelium can contribute to corneal hydration homeostasis.

Effects of ciprofloxacin, streptomycin, and gentamicin on rabbit corneal transendothelial electrical potential difference

PURPOSE

A previous report suggested that high concentrations of ciprofloxacin in the anterior chamber may cause dose-dependent acute corneal decompensation. Therefore we evaluated the effect of varying concentrations of ciprofloxacin in the anterior chamber on the corneal endothelium and compared these effects with those of gentamicin and streptomycin.

METHODS

We assessed endothelial transport function by determining transendothelial electrical potential differences (TEPDs) of rabbit corneas. Our control solution was bicarbonate-buffered balanced saline with glucose (BSG), to which we added ciprofloxacin (50, 100, 125, and 150 microg/ml), gentamicin (1,000 and 2,000 microg/ml), and streptomycin (196, 437, and 696 microg/ml).

RESULTS

At high concentrations exceeding minimal inhibitory concentrations against 90% of common ocular isolates (MIC90), accelerated decay of TEPDs was seen with all three antibiotics. Adverse effects on TEPDs were noted at concentrations corresponding to >50 times MICs with ciprofloxacin and 40 x MICs with gentamicin, but only 2 times MICs with streptomycin.

CONCLUSION

Our study shows that concentrations of ciprofloxacin, gentamicin, and streptomycin below or equal to their MIC90 levels do not adversely affect endothelial transport function in a rabbit model.

Sodium, potassium, two chloride cotransport in corneal endothelium: characterization and possible role in volume regulation and fluid transport

PURPOSE

To search for membrane transporter proteins that could contribute to volume regulation and fluid transport by corneal endothelium. As an initial step, the authors have focused on Na+-K+-2Cl- cotransporters.

METHODS

Bovine corneal endothelial cells were cultured to confluence. 86Rubidium was used as a tracer for K+ uptake determinations; uptake values were normalized per milligram of cell protein.

RESULTS

Three components of K+ uptake were characterized: ouabain (1 mM) sensitive, bumetanide (0.1 mM) sensitive, and ouabain-bumetanide insensitive. Both the ouabain-sensitive and bumetanide-sensitive components increased in the presence of 26.2 mM HCO3-; 0.5 mM 4,4'-diisothiocyanato-stilbene-2,2'-disulfonic acid abolished this increase. The bumetanide-sensitive component was completely inhibited in the absence of Na+ or Cl-. This component was increased 33% by a 33% hypertonic solution and was decreased 38% by a 33% hypotonic solution. The protein kinase C activator phorbol 12-myristate 13-acetate decreased the activity of the cotransporter, whereas forskolin, in the presence of isobutylmethylxanthine, decreased it. Calyculin A (100 nM), an inhibitor of phosphatases 1 and 2a, produced a large (97%) activation of this component.

CONCLUSIONS

These results provided for the first time conclusive evidence for the presence of a Na+-K+-2Cl- cotransporter in corneal endothelium and of its possible involvement in volume-regulatory processes in these cells. Given the uptake values reported here, such cotransporter could contribute significantly to electrolyte transport and hence to fluid transport across this preparation.

Vinculin proteolysis unmasks an ActA homolog for actin-based Shigella motility

To generate the forces needed for motility, the plasma membranes of nonmuscle cells adopt an activated state that dynamically reorganizes the actin cytoskeleton. By usurping components from focal contacts and the actin cytoskeleton, the intracellular pathogens Shigella flexneri and Listeria monocytogenes use molecular mimicry to create their own actin-based motors. We raised an antibody (designated FS-1) against the FEFPPPPTDE sequence of Listeria ActA, and this antibody: (a) localized at the trailing end of motile intracellular Shigella, (b) inhibited intracellular locomotion upon microinjection of Shigella-infected cells, and (c) cross-reacted with the proteolytically derived 90-kD human vinculin head fragment that contains the Vinc-1 oligoproline sequence, PDFPPPPPDL. Antibody FS-1 reacted only weakly with full-length vinculin, suggesting that the Vinc-1 sequence in full-length vinculin may be masked by its tail region and that this sequence is unmasked by proteolysis. Immunofluoresence staining with a monoclonal antibody against the head region of vinculin (Vin 11-5) localized to the back of motile bacteria (an identical staining pattern observed with the anti-ActA FS-1 antibody), indicating that motile bacteria attract a form of vinculin containing an unmasked Vinc-1 oligoproline sequence. Microinjection of submicromolar concentrations of a synthetic Vinc-1 peptide arrested Shigella intracellular motility, underscoring the functional importance of this sequence. Western blots revealed that Shigella infection induces vinculin proteolysis in PtK2 cells and generates p90 head fragment over the same 1-3 h time frame when intracellular bacteria move within the host cell cytoplasm. We also discovered that microinjected p90, but not full-length vinculin, accelerates rates of pathogen motility by a factor of 3 +/- 0.4 in Shigella-infected PtK2 cells. These experiments suggest that vinculin p90 is a rate-limiting component in actin-based Shigella motility, and that supplementing cells with p90 stimulates rocket tail growth. Earlier findings demonstrated that vinculin p90 binds to IcsA (Suzuki, T.A., S. Saga, and C. Sasakawa. 1996. J. Biol. Chem. 271:21878-21885) and to vasodilator-stimulated phosphoprotein (VASP) (Brindle, N.P.J., M. R. Hold, J.E. Davies, C.J. Price, and D.R. Critchley. 1996. Biochem. J. 318:753-757). We now offer a working model in which proteolysis unmasks vinculin's ActA-like oligoproline sequence. Unmasking of this site serves as a molecular switch that initiates assembly of an actin-based motility complex containing VASP and profilin.

[The toxicity of gentamicin on corneal cells in culture]

OBJECTIVE

To determine the safe local concentration of gentamicin.

METHODS

The authors studied the toxicity of gentamicin (no preservative) on 3 types of human corneal cell in culture with different concentrations.

RESULTS

There was no toxic effect on the corneal epithelium, stroma and endothelium with gentamicin 1 mg. per milliliter in 48 h. in vitro, while the concentration was up to 2 mg. or 4 mg. per milliliter, all types of corneal cells appeared cytopathic effect (CPE), the toxicity of gentamicin to the corneal cells is in direct proportion to its concentration and time term of incubation, and the toxicity was the greatest on endothelium, slightest on stroma:

CONCLUSION

It is suggested that the safe dosage of local concentration of gentamicin be 1 mg. per milliliter in human eyes.

Macular holes: migratory gaps and vitreous as obstacles to glial closure

PURPOSE

Retinal glia may play an important role in the closure of macular holes. This in vitro study examines whether and how the specific pathoanatomy, including foveal eversion and foveal vitreous, may interfere with glial closure of macular holes.

METHODS

Culture dishes used to grow glial cells were modified by the placement of slopes, vertical steps, and gaps to mimic the in vivo migratory surface in and surrounding macular holes. In separate experiments, defects were made in a rodent glial monolayer. These defects were exposed to hyaluronic acid (HA) and to rabbit (RV) and bovine (BV) vitreous gel. The migratory behavior and completeness of closure of defects were compared to controls.

RESULTS

As expected, glial cells migrated further and in greater numbers on a smooth surface. Slopes and steps were moderate obstacles to migration; gaps in the surface were absolute obstacles. HA modified the pattern of adhesion of cells at the bottom of defects. Defects in the glial monolayer were repaired in 5-7 days. Compared to these controls, repair was inhibited by 11% (n.s.), 28% (P = 0.02), and 58% (P = 0.004) after direct exposure of defects to HA, RV and BV, respectively.

CONCLUSION

The elevated and everted margins of macular holes represent slope, step, and gap-like obstacles to the migration of glial cells and hence to the healing of defects. The defect allows extension of extracellular matrix into it and the subretinal space. Our results indicate that gaps in the migratory surface caused and aggravated by eversion and the presence of vitreous present obstacles to glial migration and closure of macular holes.

Profilin interacts with the Gly-Pro-Pro-Pro-Pro-Pro sequences of vasodilator-stimulated phosphoprotein (VASP): implications for actin-based Listeria motility

Intracellular actin-based motility of Listeria monocytogenes requires protein-protein interactions involving two different proline-rich sequences: first, the tightly bound bacterial surface protein ActA uses its multiple oligoproline registers [consensus sequence = FE(D)FPPPPTD(E)E(D)] to tether vasodilator-stimulated phosphoprotein (VASP) to the bacterial surface; and second, VASP then deploys its own multiple GPPPPP (or GP5) registers to localize the actin-regulatory protein profilin to promote actin polymerization. We now report that fluorescence titration showed that GP5GP5GP5 peptide binds to profilin (KD of 84 microM), and the peptide weakly inhibits exchange of actin-bound nucleotide in the absence or presence of profilin. Microinjection of synthetic GPPPPP triplet into Listeria-infected PtK2 cells promptly arrested motility at an intracellular concentration of 10 microM. This inhibition was completely neutralized when equimolar concentrations of profilin and GP5GP5GP5 were simultaneously microinjected. Fluorescence studies with [His-133-Ser]-profilin, a site-directed mutant previously shown to be defective in binding poly-l-proline [Bjorkegren, C., Rozycki, M., Schutt, C. E., Lindberg, U., & Karlsson, R. (1993) FEBS Lett. 333, 123-126], exhibits little or no evidence of saturable GP5GP5GP5 binding. When an equimolar concentration of this [His-133-Ser]-profilin mutant was co-injected with GP5GP5GP5, the peptide's inhibitory action remained completely unaffected, indicating that GP5GP5GP5 binding to wild-type profilin represents a key step in actin-based pathogen motility. We also present a model that shows how the focal binding of VASP with its GPPPPP registers can greatly increase the local concentration of profilin and/or profilin-actin-ATP complex at the bacteria/rocket-tail interface.

Platelet activating factor inhibits fluid transport by corneal endothelium

PURPOSE

Given reports of corneal edema after endothelial exposure to platelet activating factor (PAF), the authors have investigated whether PAF can affect the function of corneal endothelium in vitro.

METHODS

The endothelial side of deepithelialized rabbit corneas was perfused with BSS+ and test agents: PAF, its inactive receptor ligand analog Lyso-PAF, and its antagonist BN52021. Stromal thickness was determined by specular microscopy. Translayer-specific electrical resistance (rho) was measured in cultured bovine corneal endothelial cells grown on permeable substrates at 36.5 degrees C.

RESULTS

Control corneas perfused with BSS+ or with BSS+ containing Lyso-PAF swelled at a very slow rate (6.2 +/- 0.1, and 7.9 +/- 0.2 microns/hour, respectively). Corneas exposed to PAF swelled appreciably faster and at rates that were a saturable function of PAF (K(m), 2.1 microM); maximal rates of swelling were < 20 microns/hour, indicating no appreciable damage to intercellular junctions. BN52021 prevented PAF-induced swelling (Ki, 1.1 microM). PAF led also to a decrease in rho (from 42.8 +/- 1.4 to 24.5 +/- 0.6 omega cm2 in 1 hour; 46.8 +/- 1.5 to 38.3 +/- 1.4 omega cm2 in control layers; and 43.0 +/- 1.2 to 30.8 +/- 1.6 omega cm2 in layers exposed to PAF+BN52021). Such rho changes are consistent with swelling of intercellular spaces.

CONCLUSIONS

Results suggest that PAF inhibits transendothelial fluid transport on binding to an endothelial cell receptor for it; continuous stimulation of a PAF-induced signaling cascade may lead to such inhibition. From these and other results, fluid transport might result from cascades activating sequentially basolateral and apical transporters or channels.