Beta-blockers and mechanical dyssynchrony in heart failure assessed by radionuclide ventriculography

BACKGROUND

Radionuclide ventriculography (RNVG) can be used to quantify mechanical dyssynchrony and may be a valuable adjunct in the assessment of heart failure with reduced ejection fraction (HFrEF). The study aims to investigate the effect of beta-blockers on mechanical dyssynchrony using novel RNVG phase parameters.

METHODS

A retrospective study was carried out in a group of 98 patients with HFrEF. LVEF and dyssynchrony were assessed pre and post beta-blockade. Dyssynchrony was assessed using synchrony, entropy, phase standard deviation, approximate entropy, and sample entropy from planar RNVG phase images. Subgroups split by ischemic etiology were also investigated.

RESULTS

An improvement in dyssynchrony and LVEF was measured six months post beta-blockade for both ischemic and non-ischemic groups.

CONCLUSIONS

A significant improvement in dyssynchrony and LVEF was measured post beta-blockade using novel measures of dyssynchrony.

Radionuclide ventriculography phase analysis for risk stratification of patients undergoing cardiotoxic cancer therapy

BACKGROUND

Accurate diagnostic tools to identify patients at risk of cancer therapy-related cardiac dysfunction (CTRCD) are critical. For patients undergoing cardiotoxic cancer therapy, ejection fraction assessment using radionuclide ventriculography (RNVG) is commonly used for serial assessment of left ventricular (LV) function.

METHODS

In this retrospective study, approximate entropy (ApEn), synchrony, entropy, and standard deviation from the phase histogram (phase SD) were investigated as potential early markers of LV dysfunction to predict CTRCD. These phase parameters were calculated from the baseline RNVG phase image for 177 breast cancer patients before commencing cardiotoxic therapy.

RESULTS

Of the 177 patients, 11 had a decline in left ventricular ejection fraction (LVEF) of over 10% to an LVEF below 50% after treatment had commenced. This patient group had a significantly higher ApEn at baseline to those who maintained a normal LVEF throughout treatment. Of the parameters investigated, ApEn was superior for predicting the risk of CTRCD. Combining ApEn with the baseline LVEF further improved the discrimination between the groups.

CONCLUSIONS

The results suggest that RNVG phase analysis using approximate entropy may aid in the detection of sub-clinical LV contraction abnormalities, not detectable by baseline LVEF measurement, predicting a subsequent decline in LVEF.

Indoor PM2.5, VOCs and asthma outcomes: A systematic review in adults and their home environments

INTRODUCTION

As the amount of time people spend indoors increases globally, exposure to indoor air pollutants has become an important public health concern. Asthma is a complex disease caused and/or exacerbated by increased exposure to diverse chemical, physical and biological exposures from multiple indoor and outdoor sources. This review aims to investigate the relationship between increased indoor PM and VOC concentrations (i.e. objectively measured) and the risk of adult asthma in higher-income countries.

METHODS

Eleven databases were systematically searched on the February 1, 2019 and again on the February 2, 2020. Articles were limited to those published since 1990. Reference lists were independently screened by three reviewers and authors were contacted to identify relevant articles. Backwards and forward citation chasing was used to identify further studies. Data were extracted from included studies meeting our eligibility criteria by three reviewers and assessed for quality using the Newcastle-Ottawa scale designed for case-control and cohort studies.

RESULTS

Twelve studies were included in a narrative synthesis. We found insufficient evidence to determine the effect of PM2.5 on asthma in the indoor home environment. However, there was strong evidence to suggest that VOCs, especially aromatic compounds, and aliphatic compounds, were associated with increased asthma symptoms.

DISCUSSION & CONCLUSION

Although no single exposure appears to be responsible for the development of asthma or its associated symptoms, the use of everyday products may be associated with increased asthma symptoms. To prevent poor health outcomes among the general population, health professionals and industry must make a concerted effort to better inform the general population of the importance of appropriate use of and storage of chemicals within the home as well as better health messaging on product labelling.

A preliminary evaluation of dexamethasone palmitate emulsion: a novel intravitreal sustained delivery of corticosteroid for treatment of macular edema

PURPOSE

Dexamethasone palmitate (DXP) is a lipophilic prodrug of dexamethasone (DXM), a potent corticosteroid used to treat a variety of ophthalmic diseases. The aim of the study was to characterize the sustained release capacity (in rabbit), efficacy (in rat and rabbit), and safety (in rabbit, cat, and minipig) of intravitreal (IVT) DXP emulsions in preclinical models.

METHODS

Oil-in-water emulsions of DXP were administered by IVT injections in rats, rabbits, cats, or minipigs. Efficacy was assessed in rabbits by the inhibition of VEGF-induced vascular leakage and in rats by inhibition of laser-induced choroidal neovascularization. Concentrations of DXP and DXM in aqueous humor, vitreous, retina, choroid, and blood were determined to characterize the ocular and systemic pharmacokinetic (PK) profile. Complete ophthalmic examinations (indirect ophthalmoscopy, slit-lamp biomacroscopy, electroretinography, tonometry) were performed to assess the ocular safety of IVT DXP doses up to 2,600 μg in minipig, followed by histopathologic examinations. A validated feline model of DXM-induced elevated intraocular pressure (IOP) was used to assess the ocular hypertensive impact (i.e., the safety) of an IVT injection of DXP emulsion.

RESULTS

Rat and rabbit efficacy data demonstrated that IVT injections of DXP emulsions were effective. Rabbit PK data demonstrated that following a single 1,280 μg IVT injection resulted in sustained DXM levels in the retina and choroid (1,179.6 and 577.7 ng/g with a half-life of 189 and 103 days, respectively) sufficient to inhibit VEGF-induced vascular hyper-permeability for up to 9 months. No adverse ocular findings were observed in the rabbit at the 1,280 μg DXP dose. Plasma levels of DXP and DXM were close to the lower limit of quantification (0.5 ng/mL). In minipigs, no systemic effects were observed at a dose up to 2,600 μg DXP. In steroid responsive cats, IVT DXP emulsions increased IOP to a lesser extent than triamcinolone acetonide with a more rapid return to basal levels and no evidence of cataract formation.

CONCLUSIONS

IVT injections of DXP emulsions were well tolerated and shown to be efficacious for the sustained release of the drug, with the potential to control vascular leakage up to 9 months following a single IVT injection. These data suggest that IVT injections of DXP emulsions could be a safe and effective alternative IVT drug delivery vehicle for corticosteroid to treat back of the eye diseases complicated by macular edema.

The effect of hydrogen peroxide on sarco/endoplasmic and plasma membrane calcium ATPase gene expression in cultured human lens epithelial cells

The loss of calcium homeostasis in the lens of the eye appears to be a factor contributing to lens opacity. In the human lens, calcium homeostasis depends on the Ca²⁺-ATPase pumps found only in the epithelium. A plasma membrane calcium pump, PMCA2 is upregulated in human cataractous lenses. To determine if oxidation caused the plasma membrane Ca²⁺-ATPases (PMCA) or sarcoplasmic/endoplasmic Ca²⁺-ATPases (SERCA) to become upregulated, we cultured a human lens epithelial cell line, in the presence of hydrogen peroxide. We observed an increase in PMCA1, PMCA2 SERCA2b and SERCA3 mRNA levels and protein expression with increasing hydrogen peroxide concentrations and treatment times. Hydrogen peroxide caused a rise in the intracellular calcium which could be an initiating factor in the concerted upregulation of PMCA1 and SERCA3. Our data support the idea that oxidative stress could contribute to a selective rise in PMCA/SERCA expression in human cataractous lenses.

Plasma membrane Ca-ATPase isoform expression in human cataractous lenses compared to age-matched clear lenses

The plasma membrane calcium ATPase (PMCA) pump is the major mechanism by which calcium is removed from the lens. The aim of this study was to determine if mRNA and proteins levels of PMCA isoforms changed with age or lens opacity. mRNA was quantified using a quantitative real-time reverse transcription polymerase chain reaction assay (RT-PCR). PMCA protein levels were quantified using Western blot analysis. No PMCA mRNA or proteins were detected in human lens fiber cells. The mRNA and protein levels of PMCA1, 3 and 4 in the epithelium of cataractous lenses were similar to those of epithelium from age-matched clear lenses and were also the same in younger lenses. PMCA2 mRNA and protein levels were 1.6-2.5 times higher, respectively, in cataractous lenses compared to age-matched clear lenses. Elevated PMCA2 expression in cataractous lenses might be a compensatory mechanism to overcome higher intracellular calcium levels in cataract.

Modulation of ocular inflammatory responses by EP1 receptors in mice

The purpose of the study was to investigate the role of EP1 receptors in intraocular inflammation and to determine possible interplay between EP1, EP2 and EP4 receptors. The eyes of separate groups of EP1 receptor knockout and wild type mice were: 1) treated topically with prostaglandin E2 (PGE2) or the EP2 receptor selective agonist, butaprost; 2) given intravitreal injection of LPS; or 3) paracentesis performed. Another group of knockout mice were pretreated topically with an EP4 receptor selective antagonist prior to paracentesis or LPS treatment. Results demonstrated a significant increase (50% or more) in the protein levels of aqueous humor of the EP1 knockout mice in response to PGE2, paracentesis or LPS. The leukocyte infiltration in the aqueous humor of the knockout mice was 47% higher when compared with that in the wild type controls in response to LPS injection. No significant change was observed in the protein levels in response to butaprost. Pretreating the knockout mice with an EP4 receptor antagonist prior to paracentesis and LPS treatment substantially reduced the aqueous humor protein levels. Also, the leukocyte count in the aqueous humor of the knockout mice in response to LPS was reduced 4 fold after pretreatment with EP4 receptor antagonist when compared with the findings in knockout mice receiving LPS only. We concluded that EP1 receptor has no modulatory effect on EP2 receptors but there is definitely cross-talk between EP1 and EP4 receptors.

Ocular inflammatory responses in the EP2 and EP4 receptor knockout mice

PURPOSE

To examine the role of EP2 and EP4 receptors in murine ocular inflammation.

METHODS

Prostaglandin EP2 and EP4 receptor knockout and wild-type mice were treated topically with prostaglandin E2, SDF-1, and RANTES and lipopolysaccharide by intravitreal injection. Paracentesis was performed by puncturing the cornea. The increase in the level of aqueous humor protein and the number of leukocytes were measured and the vascular leakage of protein was visualized using fluorescein angiography.

RESULTS

In the EP2 receptor knockout mice, there was significant inhibition of the disruption of the blood-aqueous barrier caused by lipopolysaccharides, paracentesis, prostaglandin E2, SDF-1, and RANTES. Reductions in the disruption in the blood-aqueous barrier and leukocyte infiltration after lipopolysaccharide injection and paracentesis were significant, but there was no increase in the aqueous humor protein level after prostaglandin E2 treatment in EP4 receptor knockout mice.

CONCLUSIONS

The results of the present experiments suggest that EP2 and EP4 receptors partly mediate the disruption of the blood-aqueous barrier and leukocyte infiltration induced by prostaglandin E2, SDF-1, RANTES, and lipopolysaccharides.

Ocular inflammatory responses in the EP2 and EP4 receptor knockout mice

PURPOSE

To examine the role of EP2 and EP4 receptors in murine ocular inflammation.

METHODS

Prostaglandin EP2 and EP4 receptor knockout and wild-type mice were treated topically with prostaglandin E2, SDF-1, and RANTES and lipopolysaccharide by intravitreal injection. Paracentesis was performed by puncturing the cornea. The increase in the level of aqueous humor protein and the number of leukocytes were measured and the vascular leakage of protein was visualized using fluorescein angiography.

RESULTS

In the EP2 receptor knockout mice, there was significant inhibition of the disruption of the blood-aqueous barrier caused by lipopolysaccharides, paracentesis, prostaglandin E2, SDF-1, and RANTES. Reductions in the disruption in the blood-aqueous barrier and leukocyte infiltration after lipopolysaccharide injection and paracentesis were significant, but there was no increase in the aqueous humor protein level after prostaglandin E2 treatment in EP4 receptor knockout mice.

CONCLUSIONS

The results of the present experiments suggest that EP2 and EP4 receptors partly mediate the disruption of the blood-aqueous barrier and leukocyte infiltration induced by prostaglandin E2, SDF-1, RANTES, and lipopolysaccharides.

Regulation of sarco/endoplasmic and plasma membrane calcium ATPase gene expression by calcium in cultured human lens epithelial cells

Since Ca(2+)-ATPase is a major determinant of calcium homeostasis in the lens, we examined the expression of Ca(2+)-ATPase by calcium. An immortalized human lens epithelial cell line, HLE B-3, was treated with thapsigargin to inhibit sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) releasing calcium from intracellular stores. Isoforms of the plasma membrane Ca(2+)-ATPase (PMCA) and SERCA were quantified by Western blot and quantitative real time reverse transcription polymerase chain reaction. We showed that both PMCA1 and SERCA3 isoform protein and mRNA are upregulated two- to three-fold in thapsigargin-treated HLE B-3 cells in a time and dose-dependent manner. Thapsigargin did not change the protein or mRNA levels of PMCA2, 3, 4 or SERCA2b. Considering the harmful effects of increased intracellular calcium levels, the upregulation of both SERCA and PMCA pumps suggests it is a compensatory mechanism to restore the calcium concentration to the physiological resting level.

The influence of membrane lipid structure on plasma membrane Ca2+ -ATPase activity

Lipid composition and Ca(2+)-ATPase activity both change with age and disease in many tissues. We explored relationships between lipid composition/structure and plasma membrane Ca(2+)-ATPase (PMCA) activity. PMCA was purified from human erythrocytes and was reconstituted into liposomes prepared from human ocular lens membrane lipids and synthetic lipids. Lens lipids were used in this study as a model for naturally ordered lipids, but the influence of lens lipids on PMCA function is especially relevant to the lens since calcium homeostasis is vital to lens clarity. Compared to fiber cell lipids, epithelial lipids exhibited an ordered to disordered phase transition temperature that was 12 degrees C lower. Reconstitution of PMCA into lipids was essential for maximal activity. PMCA activity was two to three times higher when the surrounding phosphatidylcholine molecules contained acyl chains that were ordered (stiff) compared to disordered (fluid) acyl chains. In a completely ordered lipid hydrocarbon chain environment, PMCA associates more strongly with the acidic lipid phosphatidylserine in comparison to phosphatidylcholine. PMCA associates much more strongly with phosphatidylcholine containing disordered hydrocarbon chains than ordered hydrocarbon chains. PMCA activity is influenced by membrane lipid composition and structure. The naturally high degree of lipid order in plasma membranes such as those found in the human lens may serve to support PMCA activity. The absence of PMCA activity in the cortical region of human lenses is apparently not due to a different lipid environment. Changes in lipid composition such as those observed with age or disease could potentially influence PMCA function.

Plasma membrane Ca2+-ATPase expression in the human lens

The focus of the study was to characterize plasma membrane calcium-ATPase pump (PMCA) isoform expression in the human lens and cultured lens epithelial cells as a basis for future studies of calcium homeostasis in the lens. Proteins and mRNA expression were analysed using Western Immunoblotting and reverse transcription polymerase chain reaction (RT-PCR), respectively. Clear human lenses from the Kentucky Lions Eye Bank and an immortalized human lens epithelial cell line (HLE B-3) were used. RT-PCR products of PMCA1, PMCA2, and PMCA4 primers were detected at 429, 557, and 849bp, respectively. All these products were identified as PMCA isoforms by sequence analysis. Protein bands at approximately 130, 115, and 135kDa were detected by Western blot analysis for PMCA1, PMCA2 and PMCA4, respectively. PMCA3 was not detected at protein or mRNA level in any human lens sample or cell culture, but was detected in the rat brain cortex used as a control. Several bands with lower molecular weights, especially for PMCA2, were detected in the epithelial samples and probably represent break down products of PMCA2. No PMCA proteins or breakdown products were detected in the nuclear or cortical fractions from human lenses. PMCA1, 2, and 4 proteins and mRNAs are expressed in human lens epithelium and cultured epithelial cells; PMCA3 is not. PMCA was not detected at all in the lens fibre cells. The calcium pump must be selectively processed, independent of other membrane proteins such as the Na-K-ATPase pumps, because the distribution of the Na-K-ATPase pump is asymmetrical in the epithelium and present throughout the lens whereas the calcium pumps are not. The findings of this study provide a basis for further studies to examine the role and modulation of PMCA isoforms in calcium homeostasis and in the development of cataract.

Prostaglandin E2 receptor subtypes, EP1, EP2, EP3 and EP4 in human and mouse ocular tissues--a comparative immunohistochemical study

The purpose of the present study was to compare the localization of prostaglandin E(2) receptor subtypes in normal human and mouse ocular tissues. Paraffin embedded sections of normal human and mouse (129 Sv/Ev) eyes were treated with EP(1), EP(2), EP(3) and EP(4) specific antibodies and subsequently incubated with Alexa Fluor secondary antibody (Ex/Em=555/571) to detect the presence of EP receptor proteins. Fluorescence of the localized antibodies was visualized in a Carl Zeiss Microscope (Axiovert 200) and photographed using Carl Zeiss Axiocam camera. In mice EP(1) and EP(3) receptor subtypes were only moderately expressed, EP(3) receptor expression being almost negligible. In human cornea and iris ciliary body, EP(1) and EP(3) receptors were prominently expressed. EP(4) receptor was expressed moderately in human and mouse ocular tissues. EP(2) receptor was the most prominently and abundantly expressed receptor in both human and mouse ocular tissues. It is concluded that the pattern of the distribution of EP receptor subtypes in the ocular tissues are similar in human and mouse. Thus, 129 Sv/Ev strains of mice would make an appropriate animal model for studying the ocular pathophysiological roles of prostaglandin receptor agonists.

ATPases and lens ion balance

In the lens, different cells appear to be specialized such that some have a high capacity for energy-dependent ion transport while others do not. This short review describes the distribution of functional Na,K-ATPase activity and Ca-ATPase activity in the lens. Movement of ions in the extracellular space between lens fibers, a topic studied by David Maurice 25 years ago, is discussed together with cell-to-cell movement of ions which is facilitated by extensive coupling in the lens cell mass. The expression of different Na,K-ATPase and Ca-ATPase isoforms in lens epithelium and fiber cells is considered along with mechanisms that potentially regulate the activity of these transport proteins.

Independent predictors of morbidity and mortality in blunt colon trauma

We sought to determine the impact of (1) grade of the colon injury, (2) the formation of an ostomy, and (3) associated injuries on outcomes such as morbidity and mortality after blunt colon injuries. We retrospectively reviewed 16,814 cases of blunt abdominal trauma. Patients with colonic injuries were selected and charts reviewed for demographic, clinical, and outcomes data. Injuries were grouped by the Colon Injury Scale (grades I-V). Independent risk factors of morbidity included spine and lung injuries, as well as increased age. A higher grade of colon injury trended toward a significant association with intra-abdominal complications. Independent risk factors of mortality included liver, heart, and lung injuries, as well as intracerebral blood and female gender. The grade of colon injury, the formation of an ostomy, and management of the colon trauma did not independently predict increased intra-abdominal complications, morbidity, or mortality. These results indicate that patients afflicted with blunt colon trauma experience a high rate of morbidity and mortality from associated injuries and or increased age. Treatment regimens directed at these factors will be most helpful in reducing the high morbidity and mortality after blunt colon trauma. Factors such as ostomy formation and management strategy are not associated with increased morbidity or mortality after blunt colon trauma.

Regional distribution of Na,K-ATPase activity in porcine lens epithelium

PURPOSE

It has been established that Na,K-ATPase activity is higher in lens epithelium than fibers. However, others have suggested the Na,K-ATPase enzyme may be inactive or absent in the central 10% of the epithelium. Studies were conducted to measure and compare Na,K-ATPase specific activity and to examine Na,K-ATPase protein expression in the anterior and equatorial regions of porcine lens epithelium.

METHODS

Na,K-ATPase activity was determined by measuring the ouabain-sensitive rate of adenosine triphosphate (ATP) hydrolysis. Western blot analysis was used to detect Na,K-ATPase catalytic subunit (alpha) and glycoprotein subunit (beta) protein as well as beta-actin which was used as a loading control.

RESULTS

Na,K-ATPase specific activity was more than two times higher in the equatorial epithelium than the anterior 50% of the epithelium. However, the abundance of Na,K-ATPase alpha1 isoform protein was similar in the two regions. Neither the alpha2 nor alpha3 Na,K-ATPase isoform could be detected in the anterior or equatorial epithelium, but Na,K-ATPase beta1 protein was detected in both regions. In contrast to the observed regional difference in Na,K-ATPase activity, the activity of a different P-type ATPase, plasma membrane Ca-ATPase (PMCA), was not significantly different in the anterior and central epithelium. Western blot analysis indicated the presence of two PMCA isoforms, PMCA2, and PMCA4.

CONCLUSIONS

Na,K-ATPase activity is significantly higher at the equatorial region of the epithelium compared with the anterior, even though the level of Na,K-ATPase protein is similar in the two regions. It is possible that nonuniform distribution of functional Na,K-ATPase activity contributes to the driving force for circulating solute movement through the lens fiber mass.

AL-2512, a novel corticosteroid: preclinical assessment of anti-inflammatory and ocular hypertensive effects

The anti-inflammatory efficacy and ocular hypertensive effect of AL-2512 were characterized in rodent and feline models of ocular inflammation. Neutrophil influx into ocular tissue following topical ocular administration of test drugs was evaluated in models of endotoxin-induced uveitis. In rats, the anti-inflammatory efficacy of AL-2512 was compared with that of 0.1% dexamethasone. Test drug or vehicle was administered topically before subplantar injection of endotoxin. Neutrophil influx was assessed at 24 hours. Feline eyes, injected intravitreally with endotoxin, were treated topically with 0.1% AL-2512, 1.0% prednisolone acetate or vehicle at various timepoints before and after endotoxin injection. At 12 hours, protein concentration and leukocyte count in aqueous humor were determined. In the feline intraocular pressure (IOP) model, after baseline IOP values were established, AL-2512, dexamethasone, or vehicle was administered topically to both eyes of cats. IOP was measured daily before and during treatment. Topical ocular administration of AL-2512 inhibited endotoxin-induced leukocyte influx in rodent and feline models of uveitis. In rats, AL-2512 significantly inhibited neutrophil influx by 89%, compared with 93% by dexamethasone. In feline eyes, AL-2512 significantly (p < 0.05) inhibited leukocyte infiltration of aqueous humor by 59%, compared to 37% inhibition by prednisolone acetate. Intraocular pressure in cats treated for 32 days with AL-2512 or dexamethasone increased 6% and 18%, respectively. The ocular anti-inflammatory effect of AL-2512 was equivalent to dexamethasone and superior to prednisolone acetate in rat and feline models of ocular inflammation, respectively. This steroid provides anti-inflammatory efficacy equivalent to dexamethasone with a reduced risk of inducing ocular hypertension.

Regulation of sarco/endoplasmic Ca2+ -ATPase expression by calcium in human lens cells

Maintenance of cellular calcium levels is critical to cell function. Loss of calcium homeostasis might be a contributing factor to the development of cataract in the lens. In lens epithelium, calcium is involved in cell signaling and its precise regulation is vital. In this study, we investigated the regulation of sarco/endoplasmic reticulum Ca(2+)-ATPase2b (SERCA2b) and SERCA3 isoform expression in cultured epithelial B-3 cells from human lenses. Both mRNA and membrane proteins samples were collected for semi quantitative RT-PCR using GAPDH as a control. Western blot analyses were performed on membrane samples.Thapsigargin, a SERCA isoform inhibitor which causes increased cytosolic levels elicited dose-and time-dependent up-regulation of SERCA3 at both mRNA and protein levels; SERCA2b expression was unaffected. Both EGTA and actinomycin partially inhibited the thapsigargin-induced SERCA3 up-regulation. These results indicate that the up-regulation of SERCA3 by thapsigargin is dependent on a calcium-mediated pathway that is likely to occur at the transcription level.

Blood-aqueous barrier in prostaglandin EP2 receptor knockout mice

The role of prostaglandin EP(2) receptors in the disruption of the blood-aqueous barrier was examined using EP(2) receptor-deficient mice. Eyes were topically treated with EP receptor agonists or subjected to paracentesis. Fluorescein angiography was performed after topical treatment with 2.0 icrog butaprost. The results show that EP receptor agonists, PGE( 2) and the EP(2) receptor-selective agonist butaprost, increased aqueous humor protein in EP(2) +/+ wild-type mice to 18.0 mg/ml and 12.0 mg/ml, respectively, from the control value of 2.7 mg/ml. The increase in aqueous humor protein concentration in response to these EP receptor agonists was reduced significantly in EP(2) receptor-deficient mice. Fluorescein leakage into the anterior chamber, two minutes after its injection, was significantly greater in butaprost-treated wild-type mice than in butaprost-treated knockout mice. Protein concentration, 15 min after paracentesis, increased from 2.2 mg/ml to 25.0 mg/ml in the aqueous humor of the eyes of wild-type mice, while the increase in knockout mice was 10.6 mg/ml. These results suggest that EP( 2) and EP(4) receptors mediate the disruption of the blood-aqueous barrier induced by EP receptor agonists and paracentesis.

Studies on receptor binding and signal transduction pathways of unoprostone isopropyl

We examined the binding characteristics of unoprostone isopropyl and its metabolite, M1 (M1), in bovine corpus luteum membranes, mobilization of intracellular calcium in human ciliary muscle cells and cyclic AMP generation in rabbit iris-ciliary body. The ligand binding assay of 3H-unoprostone isopropyl and M1 did not demonstrate any specific binding of these compounds in the bovine corpus luteum membranes. However, there was a high specific binding of prostaglandin F2alpha. Competitive ligand binding studies showed that neither the docosanoid, unoprostone isopropyl, nor M1 binds to prostaglandin receptor sites. In human ciliary muscle cells that express EP1, EP2 and FP receptors, unoprostone isopropyl did not increase the mobilization of intracellular calcium nor was it able to generate cyclic AMP at low concentrations in rabbit iris-ciliary body. Similar observations were made with M1 on the above signal transduction pathways. From these results, it is concluded that unoprostone isopropyl and M1 do not bind to prostaglandin (PG) receptor sites in the bovine corpus luteum membranes and do not have affinity for PG receptors linked to intracellular calcium and cyclic AMP second messenger systems.

Anaylsis of birefringence during wound healing and remodeling following alkali burns in rabbit cornea

The use of synthetic inhibitors of metalloproteinases (SIMP) or medroxyprogesterone (MP) can prevent or significantly delay the ulceration of alkali-injured corneas by influencing collagen degradation. We have examined the remodeling of rabbit corneal stroma following alkali injury and have assessed the effect of SIMP and MP treatment. Following a defined alkali injury to the rabbit cornea, animals were divided into three subgroups, one group treated with topical beta-mercaptomethyl tripeptide (SIMP), one treated by subconjunctival injection of MP and one treated with a control solution. The corneal tissue was taken at 3 days, 1, 2, 3, 4, 9 and 26 weeks after alkali injury and prepared for light microscopy and transmission electron microscopy (TEM). A quantitative measurement of birefringence, in terms of the optical path difference (OPD), was made using a modified polarized microscopy technique based on the analysis of interference colours. The results showed that SIMP effectively prevented deep corneal ulceration. MP could delay the ulceration and the corneas treated with MP appeared to have better transparency than the other groups. There was a significant difference of the OPD between the anterior (5.8 +/-0.3 nm) and posterior (7.8 +/-0.4 nm) stroma of the normal cornea (P<0.001). The OPD values from the central corneas from alkali-injured eyes were generally lower than normal during the first 4 weeks and then gradually recovered to the normal level or above, except for the posterior stroma of the MP-treated eyes. We found that the OPD changes were very dependent on the presence of corneal lesions. The stroma near corneal ulceration, scar tissue, calcified stroma and the retro-corneal collagen layer showed a significant reduction of birefringence (lower OPD values). These OPD values remained much lower than normal up to the end of the experiment. TEM showed disrupted corneal stroma in all three groups, with thinner scar tissue in the MP group. The fibril diameters did not change significantly 3 days and 1 week after the alkali burns (27.1+/-2.3 nm in the control group, 27.3+/-2.2 nm in the SIMP group and 27.7+/-2.1 nm in the MP group) and there were no differences compared with 29.7+/-1.7 nm of the normal cornea (P>0.05). After 2 weeks of tissue remodeling, the fibril diameters in alkali-injured corneas showed a large variation (the range was between 11.5 and 80 nm) with a bimodal distribution, especially in the control group. The technique presented here for birefringence evaluation can provide an alternative way to monitor wound healing and tissue remodeling, both visually and quantitatively.

Nitrergic and cholinergic vagal pathways involved in the regulation of canine proximal gastric tone: an in vivo study

To better understand the relationship between cholinergic and nitrergic (NO) innervation in the regulation of proximal gastric (fundic) tone in vivo, the effects of nitric oxide synthase blockade on fundic tone were studied in conscious dogs using vagal cooling and an electronic barostat. Vagal cooling, atropine (0.05 mg kg-1 i. v. bolus) and hexamethonium (1 mg kg-1 i.v. bolus) all markedly decreased fundic tone as reflected by increased intragastric volume, indicating a significant contribution of vagal and enteric cholinergic pathways to the maintenance of canine fundic tone. Administration of L-NNA (10 mg kg-1 i.v. bolus) increased fundic tone and the effects of L-NNA were completely prevented by prior vagal cooling or atropine administration, but not by pretreatment with hexamethonium. The relaxation effects of neurally derived NO appear primarily related to inhibition of ongoing vagal cholinergic activity. The data are consistent with the primary site of action of nitrergic mechanisms on gastric fundic tone in conscious dogs being at a presynaptic site on vagal cholinergic efferent nerves.

Determinants of occurrence and volume of transpyloric flow during gastric emptying of liquids in dogs: importance of vagal input

The precise factors and their relative contributions that lead to individual flow pulses across the pylorus during liquid gastric emptying remain unclear. Our objective was to determine the factors leading to individual flow pulses, their relative contributions and the role of the vagus nerve in their modulation. Proximal gastric tone had a strong positive correlation with the volume of the corresponding transpyloric flow pulse whereas pyloric tone had an inverse correlation. Antral contractions were associated with the presence but not the volume of the pulse. Acute vagal blockade retarded emptying via loss of proximal gastric tone and increased outflow resistance and loss of propagating antral pressure waves. In conclusion, the major determinants of the volume of pulsatile transpyloric flow are proximal gastric and pyloric tone. The vagus nerve plays a key role in regulating both proximal gastric and pyloric tone as well as moderating propagating antral contractions.

Plasma membrane calcium ATPase gene expression in bovine lens epithelium

Plasma membrane calcium adenosine triphosphatase (Ca(2+)-ATPase) is an energy-dependent protein responsible for transporting cytosolic calcium across the plasma membrane. Multiple plasma membrane Ca(2+)-ATPase isoforms are expressed from four genes (PMCA1-4) and alternative mRNA splicing. We have studied PMCA gene expression in bovine lens epithelium tissues by reverse transcription-polymerase chain reaction, Southern blot, and Northern blot hybridization. All four PMCA genes are expressed in the lens epithelium, the PMCA3 transcript being the most abundant. The transcripts for PMCA1, PMCA2, and PMCA4 exist in decreasing order of abundance. There is no evidence for the expression of any novel PMCA genes in bovine lens epithelium.

Mice lacking the vascular endothelial growth factor-B gene (Vegfb) have smaller hearts, dysfunctional coronary vasculature, and impaired recovery from cardiac ischemia

Vascular endothelial growth factor-B (VEGF-B) is closely related to VEGF-A, an effector of blood vessel growth during development and disease and a strong candidate for angiogenic therapies. To further study the in vivo function of VEGF-B, we have generated Vegfb knockout mice (Vegfb(-/-)). Unlike Vegfa knockout mice, which die during embryogenesis, Vegfb(-/-) mice are healthy and fertile. Despite appearing overtly normal, Vegfb(-/-) hearts are reduced in size and display vascular dysfunction after coronary occlusion and impaired recovery from experimentally induced myocardial ischemia. These findings reveal a role for VEGF-B in the development or function of coronary vasculature and suggest potential clinical use in therapeutic angiogenesis.

Expression of sarco/endoplasmic reticular Ca(2+)-ATPase in human lens epithelial cells and cultured human lens epithelial B-3 cells

PURPOSE

Sarco/Endoplasmic Reticulum Ca(2+ )-ATPase (SER-CAs) isoforms, SERCA2b (100Kd) and SERCA3 (97Kd), are co-expressed in some non-muscle tissues. Both types of SERCAs play important roles in Ca(2+) regulation in non-muscle tissues such as brain and platelets. We tested whether these two SERCAs are present in human lens epithelial cells, human lens epithelial B-3 cells (HLE B-3 cells) and rat lens epithelial cells providing a basis for further studies the role of SERCAs in cataract formation.

METHODS

Lens epithelial cells from rat lens, human lens and cultured human lens epithelial B-3 cell line (HLE B-3) were used to extract mRNA and membrane proteins. Reverse transcription polymerase chain reaction (RT-PCR) was employed to detect SERCA3 and SERCA2b mRNA using SERCA2b and SERCA3 primers. Western blotting was used to detect SERCA3 and SERCA2b proteins using anti-SERCA2b and 3 antibodies.

RESULTS

A 270 bp fragment was amplified with SERCA2b primers and a 186 bp fragment amplified with SERCA3 primer in human lens epithelial cells, human lens epithelial B-3 cells and rat lens epithelial cells. Both fragments are the expected SERCA2b and SERCA3 products. The sequences of these two fragments in human lens epithelial cells are 100% and 98% homologous to the published partial SERCA2b and SERCA3 mRNA sequence, respectively. The amino acid sequences translated from both PCR products are 100% homologous to the published SERCA2b and SERCA3 sequences in GeneBank. Western blotting confirmed that the expected 100 KDa and a 97 KDa proteins are recognized by anti-SERCA2b and anti-SERCA3 antibodies.

CONCLUSION

Sarco/Endoplasmic Reticulum Ca(2+)-ATPase (SERCAs) isoforms 2b and 3 mRNAs are expressed in human lens epithelial cells, the cultured human lens epithelial B-3 cell line (HLE B-3) and rat lens epithelial cells. SERCA2b and SERCA3 may play an important role in the regulation of calcium homeostasis in lens epithelial cells.

Responses of intraocular pressure and the pupil of feline eyes to prostaglandin EP1 and FP receptor agonists

PURPOSE

Previous studies suggested that FP receptors do not mediate the relaxation of the ciliary muscle and reduction of intraocular pressure in cats by prostaglandin (PG) F2alpha. The present study was undertaken to determine whether the reduction of intraocular pressure in cats induced by PGF2alpha is mediated by FP or other prostaglandin receptors.

METHODS

One eye of each cat was treated topically with prostaglandin F2alpha, fluprostenol (FP receptor agonist), or 17-phenyl trinor PGE2 (EP1 receptor agonist) in a dose range of 12.5 to 50 microg. The effects of SC19220 and SC51089 (EP1 receptor antagonists), BWA868c, and SQ29548 (DP and TP receptor antagonists, respectively) on the intraocular response to PGF2alpha were also examined. At intervals up to 6 hours after treatment, intraocular pressure was measured with a pneumotonometer, and pupil diameters were measured with a millimeter ruler.

RESULTS

In the dose ranges used, PGF2alpha and 17-phenyl trinor PGE2 decreased intraocular pressure and pupil diameter. The greatest reduction of intraocular pressure by 50.0 microg PGF2alpha was 5.0+/-1.4 mm Hg, whereas that by 50 microg 17-phenyl trinor PGE2 was 6.2+/-1.5 mm Hg. The isopropyl ester of PGF 2alpha at a dose of 1.25 microg reduced intraocular pressure by 3.75+/-0.25 mm Hg at 2 hours. At doses up to 100 microg, fluprostenol did not decrease intraocular pressure but did reduce pupil diameter. SC19220, a weak but selective EP1 receptor antagonist, inhibited the intraocular pressure response to both PGF2alpha and 17-phenyl trinor PGE2. The more potent EP1 receptor antagonist SC51089 had a greater inhibitory effect than SC19220 on the intraocular pressure response to PGF2alpha. Both of these antagonists had a small but non-dose dependent and statistically insignificant effect on the pupil response to PGF2alpha. These observations suggest that in cats, intraocular pressure and pupil responses to PGF2alpha, are mediated by EP1 and FP receptors, respectively. However, SC19220 significantly and dose-dependently inhibited the pupil response to 17-phenyl trinor PGE2alpha suggesting that EP1 receptors mediate pupil response to this agonist. DP and TP receptor antagonists at doses 5- to 20-fold greater than the IC50 values had no effect on the ocular hypotensive response to PGF2alpha. The concurrent administration of 12.5 microg of each of PGF2alpha and 17-phenyl trinor PGE2 did not produce an additive effect on intraocular pressure, indicating that in cats PGF2alpha and 17-phenyl trinor PGE2 act on the same receptor type.

CONCLUSIONS

These results suggest that a significant proportion of the ocular hypotensive action of PGF2alpha in cats is mediated by EP1 but not by FP receptor. Evidence was also provided to show that 17-phenyl trinor PGE2 is an ocular hypotensive agent in cats.

Basal cell carcinoma of the perianal region: 20-year experience

INTRODUCTION

Although basal cell carcinoma remains the most common cutaneous malignancy, its occurrence in the perianal region is very rare. Earlier reports have suggested that basal cell carcinoma in this region may be more aggressive than basal cell carcinoma in other regions of the body.

METHODS

A chart review of patients with perianal basal cell carcinoma who presented consecutively during a 20-year period (ending December 1996) was performed. Patients included were those with a histologically proven diagnosis of basal cell carcinoma in the perianal region.

RESULTS

Twenty-one cases were identified (15 male) with a mean age at diagnosis of 67 (range, 43-81) years. Follow-up data were available on 19 patients with a mean follow-up time of 72 (range, 2-214) months. Seventeen patients were treated by local excision, one by electrocautery, and one by Moh's surgery. No patients developed a local recurrence. Seven patients (33 percent) had multiple basal cell carcinomas at other anatomic sites. Four patients died of other causes during the follow-up period.

CONCLUSIONS

Perianal basal cell carcinoma is a rare tumor. Given the significant association with multiple lesions at other sites, a diagnosis of perianal basal cell carcinoma should prompt an examination of all cutaneous surfaces. It does not seem to be more aggressive in this region than in other areas. Local excision seems to provide adequate control.

Ca(2+)-ATPase activity and lens lipid composition in reconstituted systems

Lens lipid composition and lipid hydrocarbon chain structure change with age, region and cataract. Since the lens Ca(2+)-ATPase pump is important to the maintenance of calcium homeostasis and lens clarity, muscle sarcoplasmic reticulum Ca(2+)-ATPase was reconstituted with bovine lens lipids and dihydrosphingomyelin, the rare and major phospholipid of the human lens. Ca(2+)-ATPase activity was found to be about 5 times lower when the pump was reconstituted into dihydrosphingomyelin or lens lipids compared to native sarcoplasmic reticulum lipids. The addition of cholesterol to levels ranging from 13-53 mole%, had no affect on reconstituted Ca(2+)-ATPase activity. Ca(2+)-ATPase activity correlated with the degree of hydrocarbon chain saturation. The greater levels of saturation are a consequence of the high sphingolipid content in the reconstituted systems. These data support the hypothesis that changes in lens lipid composition or structure could affect Ca(2+)-ATPase activity in human lenses. Because the mechanisms governing Ca(2+)-ATPase activity in vivo are much more complex than in these simple reconstituted systems, this study represents an initial step in the elucidation of the relationships of endogenous membrane lipid composition-structure and function.

Effect of oxidation on Ca2+ -ATPase activity and membrane lipids in lens epithelial microsomes

Membrane oxidation may contribute to cataractogenesis. In our pursuit to understand the etiology of cataracts, we assessed the effect of membrane oxidation products on the activity of the lens epithelium calcium pump. Microsome preparations from bovine lens epithelium were oxidized to varying degrees with a ferrous and ferric ascorbate system to generate hydrogen peroxide and superoxide. Ca2+ -ATPase activity was measured using a colorometric assay. Lipid oxidation was quantified by infrared spectroscopy. Ca2+ -ATPase activity decreased as a function of ascorbate concentration between 0 and 200 microM. The level of Ca2+ -ATPase inhibition was correlated to both the level of lipid oxidation and the degree of lipid hydrocarbon chain order. At 25 degrees C when lipids are more ordered, the Ca2+ -ATPase activity was similar to that observed in the oxidized system measured at 37 degrees C. Glutathione, mercaptoethanol, and iodoacetate were able to reverse the oxidative inhibition of the calcium pump, suggesting that the ascorbate/iron oxidant directly oxidized the protein sulfhydryl moieties. To further probe the mechanism of Ca2+ ATPase inhibition, hydrogen peroxide was used to oxidize muscle sarcoplasmic reticulum Ca2+ -ATPase reconstituted in its native lipid vesicles, egg phosphatidylcholine, and dihydrosphingomyelin, with saturated hydrocarbon chains. In these systems, oxidation inhibited the Ca2+ -ATPase pump by 60-80%. There was no statistical difference between the level of oxidative inhibition and the percentage of dihydrosphingomyelin. Because dihydrosphingomyelin cannot be oxidized, whereas egg phosphatidylcholine (PC) can, and because the percentage of inhibition was the same for reconstituted systems using either lipid, the mechanism of inhibition is likely not via a secondary process involving oxidation-induced lipid structural changes or products of lipid oxidation.

Pharmacological validation of a feline model of steroid-induced ocular hypertension

OBJECTIVE

To validate pharmacologically the feline model of steroid-induced ocular hypertension.

METHODS

Serial studies were conducted in domesticated adult female cats trained to accept topical ocular drug administration and pneumotonometry. To establish intraocular pressure (IOP) values for each study, measurements were performed at the same time of day for 6 consecutive days. Beginning on day 7, cats received either steroid or vehicle administered topically to both eyes three times a day for approximately 28 days. The IOP measurements were performed daily.

RESULTS

After 5 to 7 days of treatment with 0.1% dexamethasone or 1.0% prednisolone acetate, IOP began to increase, reaching peak values within 2 weeks. These values were sustained throughout dosing but declined rapidly to baseline upon cessation of treatment. Maximum IOPs for the dexamethasone- and prednisolone-treated groups averaged 4.5 +/- 0.3 mm Hg (n = 12) greater than the mean IOP value obtained in vehicle-treated cats. Cats treated with 0.25% fluorometholone, 1.0% loteprednol etabonate, and 1.0% rimexolone exhibited increases of 0.6, 1.2, and 1.7 mm Hg, respectively. These values were significantly lower than those observed following treatment with dexamethasone or prednisolone.

CONCLUSIONS

The ocular hypertensive effects of selected anti-inflammatory topical ocular steroids in this model are consistent with clinical findings.

CLINICAL RELEVANCE

This feline model is a useful tool for assessing the potential IOP liability of novel anti-inflammatory steroids.

Bovine iris-sphincter muscle lacks FP receptor binding sites

PURPOSE

To determine the affinity, density, and specificity of the binding sites of tritium-labeled prostaglandin F2alpha in membrane preparations of bovine iris-sphincter muscle and corpus luteum.

METHODS

Membrane preparations were incubated with 0.312-40.0 nM 3H-prostaglandin F2alpha in saturation experiments, or 8 nM 3H-prostaglandin F2alpha in competition studies, in the presence or absence of varying concentrations of unlabeled prostaglandin F2alpha or other prostaglandin receptor agonists. The affinity (Kd) and the density of the binding sites (Bmax) of 3H-prostaglandin F2alpha in the bovine iris-sphincter muscle were determined by Scatchard analysis. Reverse transcription polymerase chain reaction was performed with bovine iris-sphincter muscle and corpus luteum total RNA and the PCR products were hybridized with specific 32P-labeled probe for further confirmation of FP receptor expression.

RESULTS

Specific binding sites of 3H-prostaglandin F2alpha in the membranes of bovine iris-sphincter muscle are saturable with an affinity of 9.5 nM and a density of 596 fmoles/mg of protein. Prostaglandin E2, 17-phenyl trinor prostaglandin E2, and GR63799 (EP, EP1, and EP3 receptor agonists, respectively) inhibited 3H-prostaglandin F2alpha binding with an IC50 of 0.0048 microM, 0.0038 microM, and 0.044 microM, respectively. Fluprostenol, a specific FP receptor agonist did not inhibit 3H-prostaglandin F2alpha binding. In contrast, prostaglandin F2alpha and fluprostenol effectively inhibited 3H-prostaglandin F2alpha binding in the bovine corpus luteum with an IC50 of 0.031 microM and 0.037 microM, respectively.

CONCLUSIONS

Our results demonstrate that in the bovine iris-sphincter muscle, FP receptors are not expressed and 3H-prostaglandin F2alpha binds to EP1 and EP3 receptor sites. RT-PCR results demonstrated that FP receptor mRNA, which is present in bovine corpus luteum, is probably absent in iris-sphincter muscle.

"She looked at me crazy": escalation of conflict through telegraphed emotion

This exploratory study investigated a feature of adolescent social interaction that can quickly initiate or escalate conflict: telegraphed emotion (a specific emotion conveyed through a subset of its expressive components or through a brief, extreme display of the complete expression; Shields & Maybury, manuscript in preparation). In the form of "the look," telegraphed emotion conveys intensely felt, yet controlled, affect. Using focus groups, teenage females were asked to define the look and to discuss its use, such as who employs it, when it is used, and the consequence of using the look. They reported that the look has different meanings depending on whether it is directed at a friend or a nonfriend, and whether it is used by females or males. With friends, the purpose is to communicate anger, sadness, or disgust; with nonfriends, it indicates disgust or anger, but within a framework of asserting power or status. The look often results in escalation of conflict, especially a verbal or physical fight. These findings are discussed, and the implications for investigating and preventing adolescent interpersonal conflict are explored.

Membrane lipid alpha-crystallin interaction and membrane Ca2+ -ATPase activities

PURPOSE

To determine the effect of alpha-crystallin binding on lens membrane lipid characteristics and the stability of Ca2+ -ATPase activity when challenged with H2O2 or elevated temperatures.

METHODS

Alpha-Crystallin binding to muscle sarcoplasmic reticulum membranes was quantified using a centrifugation protocol. Alpha-Crystallin binding to lens epithelial lipids was measured by a fluorescence energy transfer technique. Lipid phase transition temperature and lipid order was measured using fluorescence spectroscopy. Ca2+ -ATPase activity was measured using classical biochemical assays.

RESULTS

The main phase transition temperatures of multilamellar vesicles composed of sphingomyelin or lipids extracted from bovine lens were 40 degrees C and 20 degrees C, respectively. In the presence of saturating amounts of alpha-crystallin, the phase transition temperature and lipid order of both sphingomyelin and lens lipid membranes remained almost the same as that without alpha-crystallin. The interaction of alpha-crystallin and lipid is likely to be restricted to the membrane surface. The binding of alpha-crystallin did not influence the oxidative or thermal inactivation of the Ca2+ -ATPase pump.

CONCLUSION

Alpha-Crystallin-lens membrane binding does not protect the Ca2+ -ATPase pump from thermal derangement or oxidation by H2O2.

Expression of prostaglandin receptors EP4 and FP in human lens epithelial cells

PURPOSE

To examine the expression of prostaglandin (PG) receptors EP2, EP4, and FP in a human lens epithelial cell line (HLE-B3) at molecular and pharmacologic levels.

METHODS

Reverse transcription-polymerase chain reactions (RT-PCR) were performed with total RNA preparations from HLE-B3 cells using sense and antisense primers for each of the three prostaglandin receptors. The PCR products were hybridized with specific 32P-labeled probes and, for further confirmation, digested with appropriate restriction enzymes. At the pharmacologic level, the expression of EP4 receptors was determined by measuring intracellular cyclic adenosine monophosphate (cAMP) formation in response to PGE2 (EP1, EP2, EP3, and EP4 agonist) and the EP4 receptor-selective antagonist AH23848. The expression of FP receptors in HLE-B3 cells was explored by measuring intracellular [Ca2+]i mobilization.

RESULTS

RT-PCR generated DNA products of predicted sizes corresponding to the EP2, EP4, and FP receptors. Hybridization of the PCR products with specific 32P-labeled probes and restriction digestion of the PCR products further confirmed that they were generated from the respective EP2, EP4, and FP mRNAs. The EP receptor agonist PGE2 significantly increased the cAMP level in HLE-B3 cells. The formation of cAMP by PGE2 was concentration-dependently inhibited by the EP4 receptor-selective antagonist AH23848. Stimulation of HLE-B3 cells by the FP receptor agonist fluprostenol increased [Ca2+]i in a time-dependent manner.

CONCLUSIONS

The results of the molecular biologic and pharmacologic experiments showed conclusively the presence of EP4 and FP receptor messenger RNAs and proteins, respectively, in HLE-B3 cells.

Bisulfite genomic sequencing-derived methylation profile of the xist gene throughout early mouse development

Differential epigenetic modification by methylation of CpG dinucleotides is a candidate mechanism that may identify the alleles of imprinted genes and result in monoallelic expression of either the maternal or the paternal allele. Determination of the allelic methylation status of imprinted genes in the gametes and during early development is constrained by the limiting quantities of genomic DNA available from these early developmental stages. To circumvent this problem we have used bisulfite genomic sequencing to determine the allelic methylation status of the minimal promoter and a 1-kb region within the Xist gene during preimplantation development. We find that the parental Xist alleles are not differentially methylated in these regions. Our findings are discussed in the context of previous conflicting data obtained using methylation-sensitive restriction enzyme digestion followed by PCR amplification to assay for methylation.

Acute effect of ethanol on lens cation homeostasis

This study examined the effect of ethanol on the calcium homeostasis of the bovine lens. After acute exposure of the whole lens to physiologically related ethanol concentration, the calcium content of the lens cortex increased from 0.345 +/- 0.075 to 0.476 +/- 0.047 micromol/g (p < 0.05). In contrast, other cation levels such as sodium, potassium, and magnesium did not change. In the study of the lens calcium transport, ethanol caused an increase in the calcium permeability of the lens lipid membrane by about 12% at 30 mM ethanol. Ethanol did not alter the calcium pump activity at ethanol concentration up to 400 mM. Above 600 mM ethanol, the calcium pump was almost completely inhibited. It has been suggested that moderate to heavy alcohol consumption is a risk factor for cataracts. This study indicates that acute ethanol exposure can cause a loss in the lens calcium homeostasis, which maybe one of the cellular mechanisms to contribute to the cataract development in the alcoholic individual.

Acute calcification in alkali-injured rabbit cornea treated with synthetic inhibitor of metalloproteinases (SIMP)

PURPOSE

The aim of this study was to evaluate the ultrastructure of acute calcification observed in alkali-injured rabbit corneas treated with synthetic inhibitor of metalloproteinases (SIMP).

METHODS

A 12-mm alkali burn was made on the right corneas of 16 rabbits. Eight eyes were treated with topical phosphate-buffered SIMP, and eight control eyes were given the buffer only. Six corneas (five in the SIMP group and one in the control group) developed chalky white opacification in the central area of the cornea within 6-30 days. The corneas were excised for the following examinations: (a) light microscopy, (b) energy-dispersive x-ray analysis, (c) electron microscopy, and (d) high-angle x-ray diffraction.

RESULTS

The results confirmed that there was stromal calcification in these corneas, as shown by positive van Kossa staining, needle-shaped calcium crystal aggregates, and increased calcium in the opaque areas of the corneas. Proteoglycans in the corneal stroma of both the SIMP group and the control group significantly decreased after alkali burns. Very few proteoglycan filaments could be identified in the calcified areas of the stroma. X-ray diffraction reflections with a Bragg spacing of 3.44 +/- 0.04 A were observed from all the calcified corneas treated with SIMP. The intermolecular spacings of collagen fibrils in the calcified stroma (1.24 +/- 0.34 nm) were significantly lower than those in the noncalcified stroma (1.64 +/- 0.04 nm) and the control corneas (1.64 +/- 0.02 nm). The results indicate that the collagen molecules within the fibrils of the calcified stroma are packed more closely than normal.

CONCLUSION

The comparison of the x-ray diffraction patterns from the calcified corneas and chicken bone suggests that the calcium deposits in these corneas are in a form similar to those found in bone. The higher rate and more extensive calcification in the SIMP-treated corneas may result from the inhibitory action of SIMP on debris processing, but the mechanism is unknown.

Effects of GLP-1 on gastric emptying, antropyloric motility, and transpyloric flow in response to a nonnutrient liquid

Glucagon-like polypeptide 1 (GLP-1) may be a major enterogastrone, slowing gastric emptying when released by intestinal nutrients. In six conscious dogs, we studied the effects of GLP-1, on antropyloric motility, gastric emptying, and transpyloric flow after instillation of 500 ml of saline into the stomach. The meal was given and recordings were started 15 min after intravenous bolus and infusion of either saline or three different doses of GLP-1. Intravenous GLP-1 produced a dose-related retardation of gastric emptying associated with a decrease in the number and volume of flow pulses in comparison to saline. This change in transpyloric flow was associated with an inhibition of antropyloric pressure waves, a stimulation of isolated pyloric pressure waves, and an increase in basal pyloric tone induced by intravenous GLP-1 infusion. Our findings show that GLP-1 has a potent dose-dependent inhibitory effect on transpyloric flow and gastric emptying. This effect is temporally associated with inhibition of antral "pumping" and stimulation of pyloric "braking" mechanisms.

Role of nitric oxide mechanisms in control of pyloric motility and transpyloric flow of liquids in conscious dogs

The role of nitric oxide (NO) mechanisms in control of pyloric function and transpyloric flow were investigated in six conscious dogs. Antropyloroduodenal motility, transpyloric flow, and gastric emptying were measured 15 min after intravenous injection of 100 ml of either saline, L-arginine (50 mg/kg), L-NNA (5 mg/kg), or L-arginine (50 mg/kg) followed by L-NNA (5 mg/kg). Infusion of L-NNA was associated with retardation of gastric emptying (65 +/- 6%) in the first 30 min, in comparison to the saline (90 +/- 3%) or L-arginine (90 +/- 2%). This effect was prevented by infusion of L-arginine prior to L-NNA, after which 89 +/- 3% of the liquid emptied in 30 min. There was a significant reduction (P < 0.05) in the number and volume of flow pulses, and an increase in pyloric tone (P < 0.05) after L-NNA in comparison to the other three test conditions. There were no differences, however, in the number of antropyloric or isolated pyloric pressure waves under the four conditions. Our findings suggest that NO mechanisms influence gastric emptying and transpyloric flow of nonnutrient liquids by altering the pyloric tone, thus increasing resistance to flow.

Generation second messengers by prostanoids in the iris-sphincter and ciliary muscles of cows, cats and humans

We have examined the generation of second messengers after stimulation of feline, bovine, human iris-sphincter and ciliary muscles by selected prostaglandins (PGs). The tissues, labeled or unlabeled with 3H-myo-inositol, were stimulated by a range of concentrations of 16,16-dimethyl PGE2, 11-deoxy PGE1, 17-phenyl trinor PGE2 and PGF2alpha. In both tissues of all three species, 16,16-dimethyl PGE2 and 11-deoxy PGE1 stimulated the formation of cyclic AMP. Butaprost, an EP2 receptor agonist, which was tested only in feline ciliary muscle, generated cyclic AMP. In the feline iris-sphincter and in bovine and feline ciliary muscles, 17-phenyl trinor PGE2, an EP1 receptor agonist, significantly increased inositol phosphate turnover. The FP receptor agonist, PGF2alpha stimulated inositol phosphate turnover in the bovine, feline, and human iris-sphincter muscles and in human ciliary muscles. Feline and bovine ciliary muscles did not respond to PGF2alpha. These results suggest that EP1 receptors are present in feline iris-sphincter muscle and in bovine and feline ciliary muscles. The EP2 receptors exist in both tissue. These results also suggest the presence FP receptors in bovine, feline, and human iris-sphincter and in human ciliary muscles. Bovine and feline ciliary muscles do not appear to express FP receptors.

Detection of EP2, EP4, and FP receptors in human ciliary epithelial and ciliary muscle cells

We have examined the expression of three prostaglandin (PG) receptors, EP2, EP4, and FP, in a nonpigmented ciliary epithelial cell line (ODMCl-2) and in human ciliary muscle (HCM) cells. Total RNA preparations from either ODMCl-2 or HCM cells were subjected to reverse transcription-polymerase chain reaction (RT-PCR) with sense and antisense primers for each of the three PG receptors. The RT-PCR generated DNA products of predicted sizes corresponding to the EP2, EP4, and FP receptors in both ODMCl-2 and HCM cells. PCR products corresponding to each receptor were hybridized with specific 32P-labeled probes and, for further confirmation, digested with appropriate restriction enzymes. Pharmacological studies with the EP2 receptor-selective agonist butaprost resulted in a significant increase in the cyclic AMP level in ODMCl-2 cells. The stimulation of cyclic AMP in ODMCl-2 cells by PGE2 and 11-deoxy PGE1, the respective EP1/EP2/EP3/EP4 and EP2/EP3/EP4 receptor agonists, was concentration-dependently inhibited by the EP4 receptor-selective antagonist AH23848. These results conclusively demonstrate the presence of both mRNA and protein for EP2, EP4, and FP receptors in ODMCl-2 and HCM cells.

Calcium ATPase activity and membrane structure in clear and cataractous human lenses

PURPOSE

Maintenance of calcium homeostasis is imperative for the clarity of the lens. Ca(2+)-ATPase is essential for the removal of cytosolic calcium, either across the plasma membrane or through intracellular organelles such as the endoplasmic reticulum. In this study, membranes prepared from clear lens epithelium were compared to membranes prepared from cataractous lens epithelium.

METHODS

Human lens membranes were prepared by a protocol utilizing homogenization and centrifugation. Ca(2+)-ATPase activity was measured biochemically using Gamma-32P labeled ATP. Lipid order was measured using infrared and Raman spectroscopy.

RESULTS

Ca(2+)-ATPase activity was similar in membranes prepared from cataractous lenses that were classified as nuclear subcapsular, nuclear and brunescent cataracts. Ca(2+)-ATPase activity was approximately 50% less in membranes prepared from cataractous lenses in comparison to clear lenses. Because clear lenses from Indian donors was unavailable, clear human lenses were used as a qualitative control for the measurement for Ca(2+)-ATPase activity. Lipid order was measured in lens fibers from cataractous and clear lenses from the United States donors. Lipid order increased from 55% in the hydrocarbon chains from clear lens fibers to 84% in cataractous lens fibers.

CONCLUSIONS

These findings support the hypothesis that membranes are deranged in cataractous tissue, which should lead to altered levels of calcium.

Effect of hybrid peptides of cecropin A and melittin in an experimental model of bacterial keratitis

Synthetic peptides, ranging from 12 to 18 residues, containing partial sequences from natural cecropin A and melittin were tested for activity in an experimental pseudomonas keratitis model in rabbits. In separate experiments, two Pseudomonas aeruginosa strains: (a) a clinical isolated strain, and (b) an American Type Culture Collection (ATCC) strain, were inoculated into the stroma of one cornea of each rabbit. Peptides were topically applied at 0.1% in phosphate-buffered saline (PBS) and compared with PBS alone and 0.3% gentamicin eye drops. Clinical evaluation, based on the McDonald-Shadduck scale, was performed during a > 48-h period after the bacterial inoculation. The peptide-treated animals showed significantly lower (p < 0.05) inflammatory signs and lower anterior-segment bacterial damage compared with PBS-treated animals, after the first 6 h. The antiinflammatory/antimicrobial activity was non significantly differnt (p > 0.05) from that in animals treated with gentamicin. We conclude that peptides keeping the sequence KWKLFKK from cecropin A and at least the sequence VLKVL from melittin show promise as novel agents in topical ocular therapy of bacterial keratitis.

Calcium permeability in large unilamellar vesicles prepared from bovine lens cortical lipids

The loss of calcium homeostasis in the lens is thought to play an important role in cataract formation. Although both lens Ca(2+)-ATPase and membrane lipid permeability are essential to calcium homeostasis, membrane permeability has been studied less extensively. In the present study, the calcium permeability of large unilamellar vesicles (LUVs) prepared from bovine lens cortical lipids has been characterized. When a calcium gradient had been established by the addition of CaCl2 to the external medium, calcium influx through the membrane was monitored by calcium concentration sensitive changes in Fura-2 fluorescence as a function of time. The calcium permeability coefficient, P, was 4.46 x 10(-13) cm s-1 at 37 degrees C. This value was about 4 fold higher than that for LUVs prepared from egg phosphatidylcholine and many times higher than that for LUVs prepared from sphingomyelin. These results provide a basis for future studies of factors that influence the permeability of lens cell membranes to calcium.

Comparative studies on prostanoid receptors in human non-pigmented ciliary epithelial and mouse fibroblast cell lines

To examine the expression of functional prostanoid receptors in the human non-pigmented ciliary epithelial (ODMC1-2) and mouse fibroblast cell lines (NIH 3T3) we have measured the generation of the second messengers, cyclic AMP, inositol phosphates and the mobilization of intracellular calcium ([Ca2+]i) following stimulation by prostaglandin receptor agonists. The amount of cyclic AMP generated was measured by a protein binding method. Radiolabeled inositol phosphates were separated using ion exchange columns and quantified by counting the radioactivity. For intracellular calcium measurements, Fura 2-AM loaded cells were stimulated by PG receptor agonists and the calcium activated fluorescence was measured in a spectrofluorometer. In the ODMC1-2 cell line, the formation of cyclic AMP was stimulated by prostaglandin E2, butaprost and 11-deoxy-prostaglandin E1. The stimulation of cyclic AMP production by prostaglandin E2 was partially inhibited by the EP4 receptor antagonist AH23848. Prostaglandin E2 and 11-deoxy-prostaglandin E1 stimulated the formation of cyclic AMP in NIH 3T3 cells. In ODMC1-2 cells, total inositol phosphate turnover was not increased by 17-phenyl-trinor-prostaglandin F2 alpha, 17-phenyl-trinor-prostaglandin E2 or 11-deoxy-prostaglandin E1. In contrast, all these agonists, with the exception of 11-deoxy-prostaglandin E1, significantly increased total inositol phosphates in NIH 3T3 cells. In the NIH 3T3 cell line, only prostaglandin F2 alpha and 17-phenyl-trinor-prostaglandin F2 alpha increased [Ca2+]i in a dose-dependent manner; in ODMC1-2 cells, neither these agonists nor 17-phenyl-trinor-prostaglandin E2 increased [Ca2+]i. The present studies suggest that in ODMC1-2 cells, EP2 and EP4 receptors but neither EP1 nor FP receptors are expressed; these studies also imply, NIH 3T3 cells express EP2 and FP receptors, while EP1 receptors appear to be absent in this cell line.

Lipid-protein interactions in human and bovine lens membranes by Fourier transform Raman and infrared spectroscopies

In other systems, proteins have been shown to alter the molecular structures of lipids in the cell membrane bilayer. We wished to determine if proteins altered the structure of lens lipids. The structure of lipid hydrocarbon chains in urea purified human lens membrane vesicles containing intrinsic, hydrophobically bound proteins was compared to the structure of lipids in vesicles without protein. Fourier transform Raman spectroscopy was used to characterize lipid and protein structure. To study lipid interactions with extrinsic, surface bound proteins, the lipid structure was compared in bovine lipid vesicles with and without alpha-crystallin bound to the surface of the membrane. Lipid structure was studied using Fourier transform infrared spectroscopy. No change in lipid structure was detected even at protein/lipid weight ratios of two to one. Human lens intrinsic proteins contained a high amount of a helical structure (60%), but did not alter hydrocarbon chain interactions.