Safety and efficacy of SGLT2 inhibitors in diabetic and non-diabetic heart failure patients, a meta-analysis of randomized controlled trials

Background

Heart failure (HF) is the most common cardiovascular causes of hospitalization in people over 60 years affecting about 64.3 million people worldwide. Few studies have investigated sodium glucose like transporter-2 inhibitors (SGLT-2I) role in diabetic and non-diabetic patients with HF.

Objective

We conducted our meta-analysis to further investigate SGLT-2I role in diabetic and non-diabetic HF patients.

Methods

PubMed, Scopus, web of science, and Embase were searched. All clinical trials that compared the effect of SGLT2 inhibitors versus placebo on heart failure patients were included. Dichotomous data were extracted, pooled as risk ratio (RR) with 95% confidence interval, and analyzed via RevMan version 5.3 for windows using Mantel Haenszel (M-H) method.

Results

Twelve randomized clinical trials were included for analysis with a total number of 69024 patients. SGLT2I significantly lowered the risk of hospitalization for heart failure (HHF) in diabetic (RR=0.68, 95% CI 0.63–0.74) and non-diabetic patients (RR=0.75, 95% CI 0.62–0.89). Also, it significantly lowered mortality risk in both diabetic (RR=0.87, 95% CI 0.77–0.99) and non-diabetic patients (RR=0.93, 95% CI 0.70–1.23). Further analyses for serious adverse events were conducted, and SGLT-2I showed a significant lower risk in diabetic (RR=0.94, 95% CI 0.90–0.98) and non-diabetic patients (RR=0.72, 95% CI 0.38–1.39), yet with no observed difference over placebo in the risk of stroke.

Conclusion

SGLT2 inhibitors showed a favorable effect in lowering cardiovascular mortality, HHF, and stroke in diabetic patients with heart failure. In non-diabetic patients, they significantly reduce HHF, yet with no difference on cardiovascular mortality and stroke. Therefore, more trials are needed to establish their effect in non-diabetic patients.

Funding Acknowledgement

Type of funding sources: None.

Quantitative Evaluation of 4 Computer Keyboards: Wrist Posture and Typing Performance

The present study focuses on an ergonomic evaluation of 4 computer keyboards, based on a quantitative analysis of wrist posture and typing performance and on subjective analyses of operator comfort during typing. The objectives of this study are (1) to quantify differences in the wrist posture and in typing performance when the four different keyboards are used, and (2) to analyze the subjective preferences of the subjects for alternative keyboards compared to the standard flat keyboard.

The association between community-level economic hardship and childhood obesity prevalence in Los Angeles

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

Neighbourhood social, economic and environmental factors are associated with childhood obesity. Childhood obesity disproportionately impacts those living in low-income neighbourhoods.

WHAT THIS STUDY ADDS

Childhood obesity prevalence is strongly associated with community-level social and economic conditions as measured using a composite Economic Hardship Index. Childhood obesity prevalence among communities in the highest hardship quartile was more than double the prevalence among communities in the lowest hardship quartile (26.9 vs. 12.5%). The relationship between economic hardship and obesity differs by race/ethnicity.

OBJECTIVE

The association between community-level economic hardship and childhood obesity prevalence was examined in Los Angeles County, one of the largest and most racially and ethnically diverse regions in the United States.

METHODS

Data from the 2008-2009 California Department of Education's Physical Fitness Testing Program were analyzed to assess obesity prevalence among 5th, 7th and 9th grade students attending public schools (n = 298,485). Community-level socioeconomic conditions were compared using a census-tract-based Economic Hardship (EH) index. Mixed-effects modelling was used to examine the association between obesity prevalence and gender, grade, race/ethnicity and EH.

RESULTS

Higher community-level EH was associated with higher childhood obesity prevalence (P < 0.001). The obesity prevalence among communities in the highest EH quartile (26.9%) was more than double the obesity prevalence among communities in the lowest EH quartile (12.5%). The slope of the association between EH and childhood obesity differed by racial/ethnic group. The slope was higher for non-Hispanic White students, Hispanics, and non-Hispanic Asians, and lower for non-Hispanic Black students. Racial/ethnic disparities were observed across the socioeconomic spectrum.

CONCLUSIONS

Findings suggest that efforts to improve community socioeconomic conditions could reduce childhood obesity prevalence. Prevention efforts should target communities with high economic hardship and also focus on providing culturally relevant interventions that address disparities in obesity prevalence across communities.

An integrated approach for identification of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) pollutant sources based on human blood contents

BACKGROUND, AIM, AND SCOPE

This study developed an integrated approach to identify pollutant sources of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) of workers based on their blood contents.

MATERIALS AND METHODS

We first measured blood PCDD/F contents of sinter plant workers and residents living near the plant. By comparing those blood indicatory PCDD/Fs found for residents with those for sinter plant workers, exposure-related blood indicatory PCDD/Fs were identified for each selected worker. We then measured PCDD/F concentrations of four different sinter plant workplaces and three different ambient environments of the background. By comparing those airborne indicatory PCDD/Fs found for ambient environments with those for sinter plant workplaces, exposure-related airborne indicatory PCDD/Fs for each workplace were obtained. Finally, by matching exposure-related blood indicatory PCDD/Fs with exposure-related airborne indicatory PCDD/Fs, all suspected pollutant sources were identified for each selected worker.

RESULTS

Poor Pearson correlations were found between workers' blood contents and their corresponding PCDD/F exposures. Significant differences were found in the top three blood indicatory PCDD/Fs among the selected workers. By matching exposure-related blood indicatory PCDD/Fs with exposure-related airborne indicatory PCDD/Fs, two to three suspected pollutant sources were identified for each selected worker.

DISCUSSION

The poor Pearson correlation found between workers' airborne PCDD/Fs exposures and their blood contents was because workers' blood PCDD/Fs contents were contributed not only by workers' occupational exposures, but also by other exposure sources and exposure routes. The difference in blood indicatory PCDD/Fs among the selected workers were obviously due to the intrinsic differences in their time/activity patterns in the involved workplaces. While workers used a dust respirator to perform their jobs, gas phase exposure-related airborne indicatory PCDD/Fs played an important role on identifying suspected pollutant sources. But if a dust respirator was not used, the gas + particle phase exposure-related airborne indicatory PCDD/Fs would become the key factor for identifying suspected pollutant sources.

CONCLUSIONS

The developed integrated approach could identify all suspected pollutant sources effectively for selected workers based on their blood contents. The identified pollutant sources were theoretically plausible since they could be verified by examining workers' time/activity patterns, their status in using dust respirators, and the concentrations of PCDD/Fs found in the selected workplace atmospheres.

RECOMMENDATIONS AND PERSPECTIVES

The developed technique can be used to identify possible pollutant sources not only for workers but also for many other exposure groups associated with various emission sources and exposure routes in the future.

A novel tongue implant for tongue advancement for obstructive sleep apnea: feasibility, safety and histology in a canine model

Obstructive sleep apnea (OSA) is a sleep related breathing disorder caused by partial or complete collapse of the upper airway during sleep. The disease is linked with important cardiovascular and cerebrovascular morbidity and mortality. Tongue base collapse is a major cause of upper airway occlusion in OSA and present surgical procedures to prevent this are invasive and inefficient. A novel implantable system to stabilize the tongue was evaluated in a canine model for feasibility, safety and histology. Successful implantation of the Advance System was performed in 21 canines and follow-up evaluations were performed at 30, 60, 90, 120 and 150 days. No technical or clinical adverse events were seen during the procedure. Minor clinical adverse events at some of the follow-up evaluations were treated successfully. Histologic evaluation of the implant was performed at different time points during follow-up and showed good biocompatibility, stability and osteointegration. The outcome of this study resulted in an implant for adjustable tongue advancement in humans with OSA.

Expression of calpain small subunit 2 in mammalian tissues

PURPOSE

The purpose of the current experiments was to more closely define the distribution and the function of calpain small subunit 2 (css2). Css2 is a newly discovered regulatory protein for the calcium activated proteases, mu- and m-calpains.

METHODS

Tissues from rat, monkey, and man of various ages were used to determine expression patterns of css2 by relative quantitative RT-PCR using 18S rRNA as an endogenous standard. Recombinant css2 and the 80 kDa catalytic subunit of m-calpain (80 kDa/css2) were co-expressed in Escherichia coli. Casein zymography was used to measure the enzymatic activity of 80 kDa/css2 proteins. Lens alpha-crystallin and beta B1-crystallin were used as substrates to determine proteolysis by 80 kDa/css2. Computer-based homology modeling was used to predict interactions between the traditional small subunit (css1) or css2 with the 80 kDa catalytic subunit.

RESULTS

Css2 appears to be a functional equivalent of css1 in vitro in that the calcium-dependent proteolytic activity of 80 kDa/css2 was similar to recombinant m-calpain (80 kDa/css1). In rat and human lens, css2 transcripts increased with age, whereas css1 transcripts decreased with age. Human beta B1-crystallin and rat alpha A-crystallin were cleaved similarly by 80 kDa/css2 and 80 kDa/css1. Interestingly, alpha A-insert crystallin was not hydrolyzed when css2 was substituted for css1 in the calpain dimer, suggesting that css2 may perform different functions from css1 in terms of proteolysis of lens crystallins during maturational growth of the lens. Css2 may also assist in the proper folding of the 80 kDa subunit and regulate protease activity in the absence of calcium.

CONCLUSIONS

The wide distribution of css2 transcripts in rat and monkey suggested that css2 is a second, widely distributed (rather than tissue-specific) calpain small subunit, in addition to the long-recognized css1. Further studies at the protein level will indicate if css2 has unique functions apart from css1.

Particle size distributions and health-related exposures of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) of sinter plant workers

This study measured particle size distributions of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in two workplace atmospheres of the sintering grate and rough roll shredder in a sintering plant, and to assess their workers' health-related exposures. We found that the PCDD/F concentration of the sintering grate (site A=14.47 pg m(-3)) was lower than that of the rough roll shredder (site B=17.20 pg m(-3)). Particle size distributions of PCDD/Fs were in the form of the unimodal with the mass median aerodynamic diameter (MMAD) of 4.74 microm and 5.23 microm, and geometric standard deviation (sigma(g)) of 3.15 and 2.15 for the site A and B, respectively. The above results suggest that the workplace of the site A had a less fraction of coarse particles than that of the site B. The estimated PCDD/F concentrations of the inhalable fraction (11.0 pg m(-3)) and thoracic fraction (8.89 pg m(-3)) of the site A were lower than those of the site B (12.4 and 9.39 pg m(-3), respectively). But to the contrary the estimated respirable fraction of the site A (5.05 pg m(-3)) was slightly higher than that of the site B (4.93 pg m(-3)). Our results clearly indicate the importance to conduct particle size segregating samplings for assessing human PCDD/F exposures.

Exposure and health-risk assessment of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) for sinter plant workers

This study was set out to assess polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) exposures and health-risk impact posed on sinter plant workers. One sinter plant located in southern Taiwan was selected and their workers were divided into four exposure groups based on their work tasks, including raw material charging workers, sintering grate workers, shredding workers, and others. Results show that their mean total PCDD/F and the corresponding total I-TEQ exposure levels shared the same trend as: shredding workers>others>sintering grate workers>raw material charging workers. For all selected exposure groups, their PCDD/F exposures were dominated by the particle phase contents. Congener profiles of the gaseous+particle phase PCDD/Fs were found with more fractions of high chlorinated congeners than low chlorinated congeners. The lifetime average daily doses (LADDs) and their resultant excess cancer risks (ECRs) found for sinter plant workers were higher than those residents living at the residential area and rural area, but were lower than those living at the nearby of the selected sinter plant, urban area, industrial area. Considering ECRs of the sinter plant workers were still higher than 10(-6) suggesting the need for adopting proper control measurements for reducing workers' PCDD/F exposures, particularly for those sinter zone workers.

Characterization of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the atmosphere of different workplaces of a sinter plant

This study investigated concentrations, contents and congener profiles of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the workplaces of a sintering plant. Air samples were collected from the charging zone, the sintering zones of the sintering grate and the rough roll shredder, and the control room. The charging zone was found to have a higher total suspended particulate (TSP) but lower PCDD/F concentrations (=4969 microg nm(-3) and 7.61 pg nm(-3), respectively) than the sintering zone (=1422-1448 microg nm(-3) and 19.16-23.17 pg nm(-3), respectively). The TSP and PCDD/F concentrations were lowest in the control room (=98 microg nm(-3) and 1.75 pg nm(-3), respectively). However, the above concentrations were within the range of a typical urban-industrial area. Quite similar PCDD/F contents were found in particles in the sintering zones and control room (=11.72-14.30 and 15.85 ng g(-1), respectively) suggesting that the sintering zone and the control room are very similar. In both charging and sintering zones, 2,3,4,7,8-PeCDF contributed 40-60% to the total I-TEQ in both the gas phase and particle phase. However, in control room, both congeners 2,3,4,7,8-PeCDF and 2,3,7,8-TCDD were the main contributors; the later contributed 30% of the total I-TEQ in gas phase. In control room, the contribution of 2,3,7,8-TCDD to the total PCDD/F concentration in the gas phase greatly exceeded that in particle phase (=5.5% and 0.8%, respectively). Therefore, solutions must be sought to avoid the transfer of not only the particle-phase but also the gas-phase PCDD/Fs from the sintering zone to the control room in the future.

Total toxicity equivalents emissions of SF6, CHF3, and CCl2F2 decomposed in a RF plasma environment

Sulfur hexafluorine compound (SF6), trifluoromethane (CHF3) and diclorodifluoromethane (CCl2F2) are extensively used in the semiconductor industry. They are global warming gases. Most studies have addressed the effective decomposition of fluorine compounds, rather than the toxicity of decomposed by-products. Hence, the concepts of toxicity equivalents (TEQs) were applied in this work. The results indicated that HF and SiF4 were the two greatest contributors of TEQ to the SF6/H2/Ar plasma system, while F2 and SiF4 were the two greatest contributors to the SF6/O2/Ar system. Additionally, SiF4 and HF were the two greatest contributors of TEQ to both the CHF3/H2/Ar and CHF3/O2/Ar plasma systems. HF and HCl were the two greatest contributors of TEQ to the CCl2F2/H2/Ar plasma system, and Cl2 and COCl2 were the two greatest contributors to the CCl2F2/O2/Ar system. HCl and HF can be recovered using wet scrubbing, which reduces the toxicity of these emission gases. Consequently, the hydrogen-based plasma system was a better alternative for treating gases that contained SF6, CHF3 and CCl2F2 from the TEQs point of view.

Dry deposition of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in ambient air

The PCDD/Fs in the ambient air associated with concentration and dry deposition flux of four seasons were characterized in rural area. The mean PCDD/F concentrations were 0.342, 0.221, 0.675, 0.741 pg m(-3) and the mean I-TEQ values were 0.027, 0.016, 0.024, 0.063 pg m(-3) in spring, summer, fall and winter, respectively. Ambient air in winter was higher by a factor of 3.4 and 3.9 for PCDD/F concentration and I-TEQ, respectively, than in summer. The study area is located in a Tropical region. Hence, domestic heating is not found in this area and is not responsible for the elevated winter concentration in comparison to other studies. A smooth plate with a sharp leading edge that is pointed into the wind by a wind vane was used for measuring dry deposition flux of PCDD/Fs. Atmospheric dry deposition fluxes of total PCDD/Fs were 140, 116, 137, and 207 pg m(-2)day(-1) in spring, summer, fall, and winter, respectively, and averaged approximately 150 pg m(-2)day(-1). The total dry deposition flux was found to decrease as the temperature increased. Calculated dry deposition velocities of total PCDD/Fs were 0.45, 0.52, 0.32 and 0.39 cm s(-1) in spring, summer, fall, and winter, respectively, and averaged 0.42 cm s(-1).

Biochemical properties of lens-specific calpain Lp85

Lens-specific Lp82 and ubiquitous m-calpain are neutral, calcium-activated, cysteine proteases. Both calpains are activated during rodent lens maturation and cataract formation. Lp85 calpain (Lens protein with MW=85 kDa) is a slightly larger splice variant of Lp82. Lp85 contains a 28 amino acid insert peptide (IS3) in calcium binding domain IV. Theoretically, the insert could alter the properties of Lp85 and influence proteolytic activity. The purpose of the present experiment was to compare the biochemical properties of Lp85 to Lp82 and m-calpain. Recombinant Lp85 and Lp82 were separately expressed using the baculovirus system and partially purified using Co2+ affinity and DEAE chromatographies. Calcium activation, pH dependency, and susceptibility to calpain inhibitors were assessed in a protease assay using BODIPY fluorescence-labeled casein substrate. Hydrolysis of lens proteins was assessed by SDS-PAGE and immunoblotting. Cleavage site analysis was performed by mass spectroscopy and Edman sequencing. Computer-based homology modeling was used to predict the influence of the IS3 region on the 3-dimensional structure of Lp85. Compared to m-calpain, Lp85 showed a lower calcium-activation requirement (K(50%act)=20 microM), marked insensitivity to, and cleavage of, the endogenous tissue inhibitor of calpains-calpastatin, and different preferred cleavage sites on alphaA-crystallin (five amino acid C-terminal truncation) and on aquaporin 0 (G239 and N246). Although the IS3 insert was predicted to form a loop protruding from the calcium binding region of Lp85, the biochemical properties of Lp85 studied were nearly identical to those of Lp82. Lp85 and Lp82 did not catalyze hydrolysis of each other, but both hydrolyzed m-calpain. Lp85 seems to be the enzymatic equivalent of Lp82. Both calpains could become active at lower cellular calcium levels than m-calpain. Lp85/Lp82 may have different functions than m-calpain since they cleave substrates at different sites. Lp85/Lp82 may regulate m-calpain activity by catalyzing the hydrolysis of calpastatin. The function of the IS3 insert on Lp85 remains unknown but is speculated to control subcellular distribution.

Decomposition of benzene in the RF plasma environment. Part II. Formation of polycyclic aromatic hydrocarbons

This study investigated the characteristics of polycyclic aromatic hydrocarbons (PAHs) formed during the decomposition of benzene (C(6)H(6)) in radio-frequency (RF) plasma environments. The identification and quantification were accomplished by using a GC/MS for PAHs and an on-line Fourier transform infrared (FT-IR) spectrometer for the reactants and gaseous products. The analytical results show that PAHs were formed in both C(6)H(6)/Ar and C(6)H(6)/H(2)/Ar systems. In terms of individual PAHs, naphthalene (C(10)H(8)) was the predominant species found among the 21 PAHs under all operational conditions, phenanthrene and chrysene are the next. High-ring PAHs did not form easily in the C(6)H(6)/Ar and C(6)H(6)/H(2)/Ar system, especially at high input power and high C(6)H(6) feed concentration (C(C(6)H(6))) for the former system. Yields of PAHs with different ring numbers decreased with increasing ring number. At low input power, increasing C(C(6)H(6)) would promote yields of PAHs, while adding hydrogen as the auxiliary gas suppressed PAHs formation. Higher input power or addition of oxygen not only effectively suppresses PAHs formation but also completely destroys C(6)H(6). Owing to the absence of the principal intermediate species, phenol (C(6)H(5)OH), from the gas products of C(6)H(6)/O(2)/Ar system, H-abstraction-C(2)H(2)-addition (HACA) pathway is proposed as the primary mechanism for PAHs formation in the present study. Gas phase distribution of total-PAHs accounts for 20-95.3% at 2% of C(C(6)H(6)) among C(6)H(6)/Ar, C(6)H(6)/H(2)/Ar and C(6)H(6)/O(2)/Ar systems. This study suggests that gas-phase PAHs should not be ignored, particularly in C(6)H(6)/Ar systems under high input power and high C(C(6)H(6)) , or in C(6)H(6)/O(2)/Ar systems.

Decomposition of benzene in the RF plasma environment. Part I. Formation of gaseous products and carbon depositions

This study employed radio-frequency (RF) plasma for decomposing benzene (C6H6) gas, and examined both gaseous products and solid depositions after reaction. The reactants and products were analyzed mainly by using both an on-line Fourier transform infrared (FT-IR) spectrometer and a gas chromatography. The analyses for solid deposition included electron spectroscopy for chemical analysis (ESCA), element analysis and heat value analysis. The C2H2, C2H4, C2H6, CH4, CO2 and CO were detected and discussed. The analytical results demonstrate that in the C6H6/Ar plasma, C2H2 is the sole gaseous product being detected. The fraction of total carbon input converted into C2H2 YC2H2 increased with increasing C6H6 feed concentration, but decreased with increasing input power. In the C6H6/H2/Ar system, besides C2H2, CH4, C2H4 and C2H6 were also detected, and their yields increased with increasing H2/C6H6 ratio. The above results indicated that the addition of H2 (auxiliary gas) achieves the benefit of creating hydrogen-rich species like CH4, C2H4 and C2H6. In the C6H6/O2/Ar system, C6H6 could be totally oxidized into CO2, CO and H2O, and no measurable phenol was found. Analyses of solid depositions revealed that the carbon depositions were similar to those of Anthracite. The carbon deposition has a heat value of 7000 kcal/kg. Additionally, the possible reaction pathways were also built up and discussed.

Emissions of polycyclic aromatic hydrocarbons from batch hot mix asphalt plants

This study was set out to assess the characteristics of polycyclic aromatic hydrocarbon (PAH) emissions from batch hot mix asphalt (HMA) plants and PAH removal efficiencies associated with their installed air pollution control devices. Field samplings were conducted on six randomly selected batch HMA plants. For each selected plant, stack flue gas samples were collected from both stacks of the batch mixer (n = 5) and the preheating boiler (n = 5), respectively. PAH samples were also collected from the field to assess PAHs that were directly emitted from the discharging chute (n = 3). To assess PAH removal efficiencies of the installed air pollution control devices, PAH contents in both cyclone fly ash (n=3) and bag filter fly ash (n = 3) were analyzed. Results show that the total PAH concentration (mean; RSD) in the stack flue gas of the batch mixer (354 microg/Nm3; 78.5%) was higher than that emitted from the discharging chute (107 microg/Nm3; 70.1%) and that in the stack flue gas of the preheating boiler (83.7 microg/Nm3; 77.6%). But the total BaPeq concentration of that emitted from the discharging chute (0.950 microg/Nm3; 84.4%) was higher than contained in the stack flue gas of the batch mixer (0.629 microg/Nm3; 86.8%) and the stack flue gas of the preheating boiler (= 0.112 microg/Nm3; 80.3%). The mean total PAH emission factor for all selected batch mix plants (= 139 mg/ton x product) was much higher than that reported by U.S. EPA for the drum mix asphalt plant (range = 11.8-79.0 mg/ton x product). We found the overall removal efficiency of the installed air pollution control devices (i.e., cyclone + bag filter) on total PAHs and total BaPeq were 22.1% and 93.7%, respectively. This implies that the installed air pollution control devices, although they have a very limited effect on the removal of total PAHs, do significantly reduce the carcinogenic potencies associated with PAH emissions from batch HMA plants.

Decomposition of SF6 in an RF plasma environment

Sulfur hexafluoride (SFd)-contained gas is a common pollutant emitted during the etching process used in the semiconductor industry. This study demonstrated the application of radio-frequency (RF) plasma in the decomposition of SF6. The decomposition fraction of SF6 [etaSF6 (C(in)-C(out))/C(in) x 100%] and the mole fraction profile of the products were investigated as functions of input power and feed O2/SF6 ratio in an SiO2 reactor. The species detected in both SF6/Ar and SF6/O2/ Ar RF plasmas were SiF4, SO2, Fe2, SO2F2, SOF2, SOF4, S2F10, S2OF10, S2O2F10, and SF4. The results revealed that at 40 W, etaSF6 exceeded 99%, and the reaction products were almost all converted into stable compounds such as SiF4, SO2, and F2 with or without the addition of oxygen. Sulfur oxyfluorides such as SO2F2, SOF2, SOF4, S2OF10, and S2O2F10 were produced only below 40 W. The results of this work can be used to design a plasma/chemical system for online use in a series of a manufacturing process to treat SF6-containing exhaust gases.

Stereotype susceptibility in children: effects of identity activation on quantitative performance

A growing body of research indicates that the activation of negative stereotypes can impede cognitive performance in adults, whereas positive stereotypes can facilitate cognitive performance. In two studies, we examined the effects of positive and negative stereotypes on the cognitive performance of children in three age groups: lower elementary school, upper elementary school, and middle school. Very young children in the lower elementary grades (kindergarten-grade 2) and older children in the middle school grades (grades 6-8) showed shifts in performance associated with the activation of positive and negative stereotypes; these shifts were consistent with patterns previously reported for adults. The subtle activation of negative stereotypes significantly impeded performance, whereas the subtle activation of positive stereotypes significantly facilitated performance. Markedly different effects were found for children in the upper elementary grades (grades 3-5). These results suggest that the development of stereotype susceptibility is a critical domain for understanding the connection between stereotypes and individual behavior

Stereotype susceptibility in children: effects of identity activation on quantitative performance

A growing body of research indicates that the activation of negative stereotypes can impede cognitive performance in adults, whereas positive stereotypes can facilitate cognitive performance. In two studies, we examined the effects of positive and negative stereotypes on the cognitive performance of children in three age groups: lower elementary school, upper elementary school, and middle school. Very young children in the lower elementary grades (kindergarten-grade 2) and older children in the middle school grades (grades 6-8) showed shifts in performance associated with the activation of positive and negative stereotypes; these shifts were consistent with patterns previously reported for adults. The subtle activation of negative stereotypes significantly impeded performance, whereas the subtle activation of positive stereotypes significantly facilitated performance. Markedly different effects were found for children in the upper elementary grades (grades 3-5). These results suggest that the development of stereotype susceptibility is a critical domain for understanding the connection between stereotypes and individual behavior

Proteolysis by m-calpain enhances in vitro light scattering by crystallins from human and bovine lenses

PURPOSE

To determine if proteolysis by the calcium-activated protease m-calpain (EC 34.22.17) enhances in vitro light scattering in crystallins from human and bovine lenses.

METHODS

Total soluble proteins from bovine, human, and rodent lenses, betaH crystallin, or recombinant betaB1 polypeptide were pre-incubated in the presence or absence of activated m-calpain. Heat-induced light scattering was assayed by measuring changes in optical density at 405 nm. Proteolysis and cleavage sites were detected by SDS-PAGE, two dimensional electrophoresis, and N-terminal Edman sequencing.

RESULTS

The in vitro cleavage sites produced by m-calpain on the N-termini of human betaB1, betaA3, and betaB2-crystallins were similar to some of those on bovine and rat crystallins. Proteolysis of alpha- and beta-crystallins was associated with enhanced, heat-induced light scattering by human and bovine lens proteins.

CONCLUSIONS

Proteolysis may be a contributing factor in the insolubilization of crystallins occurring during normal maturation of lens or during cataract formation in such species as man and cows.

Characterization and expression of calpain 10. A novel ubiquitous calpain with nuclear localization

Calpains are calcium-dependent intracellular nonlysosomal proteases that are believed to hydrolyze specific substrates important in calcium-regulated signaling pathways. Recently, an atypical member of the calpain family, calpain 10, was described, and genetic variation in this gene was associated with an increased risk of type II diabetes mellitus in humans. In the present report, a polyclonal antibody directed against rat calpain 10 was developed. This antibody was used to monitor the expression of calpain 10 protein in tissues from rats, mice, and humans. Calpain 10 protein was found to be present in all tissues examined by Western blotting including the lens, retina, brain, heart, and skeletal muscle. Although some calpain 10 was detectable in the water-soluble protein fraction of these tissues, it was preferentially found in the water-insoluble fraction. In the lens, immunohistochemistry revealed that calpain 10 was predominately located in the cytoplasm of epithelial and newly differentiating lens fibers at the transition zone. However, calpain 10 was found to be associated with the plasma membrane of differentiated lens fiber cells and the sarcolemma of skeletal muscle. In the lens epithelium-derived cell line, alphaTN4-1, the calpain 10 protein was found in a punctate distribution in the cell nucleus as well as the cytoplasm. After the elevation of intracellular calcium levels with ionomycin, calpain 10 protein levels in the nucleus of alphaTN4-1 cells increased markedly, whereas those in the cytoplasm decreased. In the lens, the elevation of intracellular calcium levels after selenite administration resulted in increased levels of calpain 10 RNA within 1 day and a loss of calpain 10 protein from the lens nucleus coincident with the onset of selenite cataract. In conclusion, calpain 10 seems to be a ubiquitous calpain, the expression level and subcellular distribution of which are dynamically influenced by calcium.

Decomposition of ethylene oxide in the RF plasma environment

A radio frequency (RF) plasma system was used to decompose the ethylene oxide (EO) contained gas in the EO/Ar, and EO/O2/Ar system, respectively. The reactants and final products were analyzed by using FTIR (Fourier transform infrared spectroscopy). The effects of plasma operational parameters, including input power wattage (W), total gas flow rate (Q), feeding concentration (C) of EO and operational pressure for EO decomposition were evaluated. Due to the importance of the high-energy electrons in the RF plasma system, the EO decomposition fraction in plasma reaction increased with decreasing operational pressure, while that of thermal reaction, reported by previous investigations, increased with increasing operational pressure. However, owing to the electrophilic characteristic of oxygen atoms in the EO molecule causing the effect of electron attachment, in conditions of higher EO feeding concentration, the pressure dependence became the same for both plasma- and thermal-reaction. The EO oxidation reaction has also been investigated, the result shows that EO almost completely oxidized at 600-692 K gas temperature. The main products for the EO/Ar system are CO, CH4, C2H6, C2H4, and C2H2, and those for the EO/O2/Ar system are CO2 and H2O.

Influence of specific regions in Lp82 calpain on protein stability, activity, and localization within lens

PURPOSE

To determine the influence of specific regions within Lp82 calpain on protein stability, enzymatic activity, and localization within lens and to test the influence of an Lp82 knockout mouse on normal maturational proteolysis in lens.

METHODS

DNA constructs for Lp82 and Lp82-related proteins were subcloned into the pcDNA 3.1 vector. The constructs contained a substitution of the novel sequence (NS) region from p94 for the AX1 N-terminal region of Lp82 and insertions of the p94 IS1 and IS2 regions into Lp82. Transient expression of these Lp82-related proteins was performed in COS-7 mammalian cells. Immunoblotting and casein zymography were used to measure protein stability and enzymatic activity of the expressed proteins. Homologous recombination was used to knock out p94 gene expression and p94 splice variants such as Lp82 and Lp85 in the lenses of 10-day-old mice. Confocal microscopy revealed the immunohistochemical localization Lp82 and Lp85 within lens.

RESULTS

Insertion of IS1 into Lp82 resulted in a lack of stable protein and loss of enzymatic activity. In contrast, substitution of the NS region for AX1 and insertion of IS2 into Lp82 had no effect on the stability of the Lp82-related proteins. p94 knockout mice at 10 days of age exhibited a total absence of Lp82 activity in the lens but normal activity for the separate mu- and m-calpain gene products. Calcium-induced in vitro proteolysis was retarded in these Lp82/p94 knockout lenses. Lp82 and Lp85 immunostaining was intense throughout the cytoplasm of the cortical and nuclear fibers of newborn mouse lenses with little staining in the epithelium. In contrast, immunostaining for the ubiquitous m-calpain was highest in the epithelium and bow region, with much lower levels in the nucleus. The naturally occurring IS3 insert in Lp85 also promoted the association of Lp85 with the perinuclear region of the nucleated lens fibers.

CONCLUSIONS

The lack of the IS1 region in Lp82 accounts for the stability and abundance of enzymatically active Lp82 protein in rodent lenses. Conversely, the presence of the IS1 region is responsible for the lability of p94 and Rt88 calpains in muscle and retina, respectively. The insert in Lp85 may promote membrane association. A consequence of the specific loss of Lp82 in the lens may be to retard normal maturational proteolysis.

Social dominance orientation and group context in implicit group prejudice

We tested the joint influence of individual difference and situational factors on implicit group prejudice. Participants in Experiments 1 and 2 were briefly shown in-group or out-group pronouns prior to evaluating good or bad trait adjectives. Under standard conditions (Experiment 1), there was no difference between participants with high and low social dominance orientation (SDO), but when the intergroup context was made more salient (Experiment 2), high-SDO participants alone showed implicit group prejudice. Implications for the malleability and consensuality of implicit prejudice are discussed.

Attitudes of clinical faculty about career progress, career success and recognition, and commitment to academic medicine. Results of a survey

OBJECTIVE

To assess attitudes about career progress, resources for career development, and commitment to academic medicine in physician faculty at an academic medical center who spend more than 50% of their time in clinical care.

DESIGN

Faculty survey.

SETTING

Academic medical center and associated Veterans Affairs medical center.

RESULTS

A total of 310 physician faculty responded to the survey. Half of the faculty reported spending 50% or less of their time in clinical care (mean, 31% of time) (group 1) and half reported spending more than 50% of their time in clinical care (mean, 72% of time) (group 2). Group 2 faculty had one third of the time for scholarly activities, reported slower career progress, and were less likely to be at the rank of professor (40% and 16% for groups 1 and 2, respectively; P<.001) or to be tenured (52% and 26%, respectively; P<.001) despite similar age and years on faculty. Group 2 faculty were 50% more likely to report that tenure and promotion criteria were not reviewed at their annual progress report (P =.003) and that they did not understand the criteria (P<.001). Group 2 faculty valued excellence in patient care over scholarship and national visibility. Group 2 faculty reported greater dissatisfaction with academic medicine and less commitment to a career in academic medicine.

CONCLUSIONS

Physician faculty who spend more than 50% of their time in clinical care have less time, mentoring, and resources needed for development of an academic career. These obstacles plus differences in their attitudes about career success and recognition contribute to significant differences in promotion. These factors are associated with greater dissatisfaction with academic medicine and lower commitment to academic careers.

Contribution of calpain Lp82-induced proteolysis to experimental cataractogenesis in mice

PURPOSE

The purpose of the present experiments was to provide a biochemical mechanism for the involvement of lens-specific calpain Lp82 in experimental cataractogenesis in mice.

METHODS

Nuclear cataracts were produced by culturing lenses from 4-week-old mice and rats in calcium ionophore A23187 or by injection of buthionine sulfoximine (BSO) into 7-day-old mice. Casein zymography, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblot analysis, calcium determinations, in vitro precipitation, and cleavage site analysis by mass spectrometry were performed on lens samples.

RESULTS

Amino acid sequences for Lp82 were found to be highly conserved in lenses from mouse to cow, and expressed Lp82 proteolytic activity was high in the mouse and rat. Lenses from mice were more susceptible to A23187-induced cataract and BSO cataracts than rats. Both types of cataracts showed rapid elevation of calcium, activation of Lp82 and m-calpain, and proteolysis of crystallins. Lp82 caused in vitro precipitation of crystallins; and in contrast to m-calpain, Lp82 truncated only the first five amino acids from the C-terminus of alphaA-crystallin.

CONCLUSIONS

Under pathologic conditions of massive elevation of lens calcium found in young rodent lenses, overactivation of Lp82 and m-calpain leads to rapid truncation of crystallins at both common and unique cleavage sites, precipitation of truncated crystallins, and cataract.

Obstacles to promotion? Values of women faculty about career success and recognition. Committee on the Status of Women and Minorities, Virginia Commonwealth University, Medical College of Virginia Campus

PURPOSE

To assess attitudes of female faculty about career progress, resources for career development, and values related to academic success and recognition.

METHOD

In 1997, the authors surveyed all faculty at Virginia Commonwealth University School of Medicine and its associated Veterans Affairs Medical Center.

RESULTS

Of 918 faculty, 567 (62%) responded to the survey; 33% of the respondents were women. Compared with men, women faculty were less likely to be tenured or at the level of professor, spent more time in clinical activities, had less time for scholarly activity, and reported slower career progress. Women were more likely to report that promotion and tenure criteria had not been reviewed with them. Significant differences were found between female physicians and non-physician faculty; female physicians reported the least time for scholarly activities and poorest understanding of promotion and tenure criteria. When the authors asked faculty how they valued certain indicators of career success, women were less likely to value leadership than were men. Female physicians were less likely to value scholarship and national recognition as indicators of their career success.

CONCLUSION

This survey found important differences in career progress of male and female faculty, with women reporting less time for career development. In addition, there were differences in values related to career success and recognition, which were most pronounced for female physicians. These differences may have an important impact on promotion for women in general and particularly for female physicians.

Lp85 calpain is an enzymatically active rodent-specific isozyme of lens Lp82

PURPOSES

To clone and sequence the cDNA for Lp85 calpain from young rat lens, and to test for Lp85 protein expression and proteolytic activity.

METHODS

RT-PCR and molecular cloning were performed on total RNA from 12 day-old rats. Lp85 protein expression was visualized by immunoblotting using a specific antibody developed to the unique peptide sequence in Lp85. Proteolytic activity was assessed by casein zymography. Transient expression of Lp85 and previously characterized lens-specific calpain Lp82 were separately performed in mammalian COS-7 cells.

RESULTS

The 2410-bp cDNA for rat lens Lp85 encoded a protein of 737 amino acid residues with a calculated molecular weight of 85.0 kDa and a predicted pI of 5.67. The amino acid sequence of Lp85 was identical to Lp82 except for an insert region of 28 amino acids in domain IV of the calcium-binding region. mRNA and protein for Lp85 were present only in rat and mouse lenses and not in other tissues or species. Lp85 protein concentrations were highest in the nuclear region, most concentrated in the insoluble fraction, disappeared with lens maturation, and Lp85 exhibited migration similar to Lp82 on native PAGE gels. Lp85 was enzymatically active when expressed in COS-7 cells.

CONCLUSIONS

Lp85 is a newly classified, lens- and rodent-specific, enzymatically active, member of the AX1 (alternative exon 1) subclass of calpains. In conjunction with Lp82 and m-calpain in lens, Lp85 may be responsible for proteolysis during normal lens development and maturation or during cataract formation in young rodents.

Decreased sensitivity of lens-specific calpain Lp82 to calpastatin inhibitor

The purpose of the present investigation was to test three calpain inhibitors (recombinant calpastatin domain I, E64, and SJA6017) against Lp82 calpain in rat lenses. Lp82 is a lens-specific isoenzyme from the calpain super family of calcium-activated, cysteine proteases (EC 34.22.17). Lp82 and m-calpain proteolytic activities and protein levels were measured by casein zymography and immunoblotting. Activity of endogenous Lp82 against vimentin was also tested by in vitro incubation of rat lens soluble and insoluble fractions with calcium. Most of the Lp82 activity could be inhibited by irreversible inhibitor E64 and reversible inhibitor SJA6017. However, a major finding of the present investigation was that Lp82 in the soluble and insoluble fractions of the lens was less sensitive to inhibition by recombinant domain I from the endogenous tissue inhibitor of ubiquitous calpains, calpastatin, than m-calpain. By using recombinant calpastatin to inhibit endogenous lens m-calpain, we were able to demonstrate the first example of a substrate for Lp82, vimentin. These data suggest that Lp82-induced proteolysis in rodent lenses may occur even in the presence of calpastatin.

Lp82 is the dominant form of calpain in young mouse lens

The purpose of this study was to characterize Lp82 calpain in normal mouse. Lp82 is a lens-specific, calcium-activated isozyme from the calpain super family of cysteine proteases (EC 34.22.17). RT-PCR and molecular cloning were performed on total RNA from 12 day-old mice. Lp82 and m-calpain protein levels and proteolytic activities in lenses were measured by casein zymography, immunoblotting, and ELISA after partial purification by DEAE-HPLC. The 2334-bp cDNA encoding for mouse Lp82 contained a single large open reading frame encoding a protein of 709 amino acid residues with a calculated molecular weight of 82.2 kDa and a predicted pI of 5.8. The amino acid sequence of mouse lens Lp82 was 99% homologous to rat lens Lp82. As in rat, mouse lens Lp82 showed a unique N -terminus and deletion of the IS1 and IS2 regions. In contrast to rat, Lp82 was the dominant calpain in young mouse lens. Lp82 was lens-specific, and the lens nucleus contained the highest specific activity of Lp82 and very little m-calpain. Endogenous Lp82 in lens soluble proteins was activated by addition of calcium and caused limited proteolysis of crystallins even in the presence of large amounts of recombinant domain I from the natural calpain inhibitor calpastatin. Loss of Lp82 protein accompanied aging of mouse lens. Lp82 may be responsible for a major portion of crystallin proteolysis occurring during normal lens development and maturation, or during cataract formation in young mice.

Dynamic complexes of beta2-adrenergic receptors with protein kinases and phosphatases and the role of gravin

Signals mediated by G-protein-linked receptors display agonist-induced attenuation and recovery involving both protein kinases and phosphatases. The role of protein kinases and phosphatases in agonist-induced attenuation and recovery of beta-adrenergic receptors was explored by two complementary approaches, antisense RNA suppression and co-immunoprecipitation of target elements. Protein phosphatases 2A and 2B are associated with the unstimulated receptor, the latter displaying a transient decrease followed by a 2-fold increase in the levels of association at 30 min following challenge with agonist. Protein kinase A displays a robust, agonist-induced association with beta-adrenergic receptors over the same period. Suppression of phosphatases 2A and 2B with antisense RNA or inhibition of their activity with calyculin A and FK506, respectively, blocks resensitization following agonist removal. Recycling of receptors to the plasma membrane following agonist-promoted sequestration is severely impaired by loss of either phosphatase 2B or protein kinase C. In addition, loss of protein kinase C diminishes association of phosphatase 2B with beta-adrenergic receptors. Overlay assays performed with the RII subunit of protein kinase A and co-immunoprecipitations reveal proteins of the A kinase-anchoring proteins (AKAP) family, including AKAP250 also known as gravin, associated with the beta-adrenergic receptor. Suppression of gravin expression disrupts recovery from agonist-induced desensitization, confirming the role of gravin in organization of G-protein-linked signaling complexes. The Ht31 peptide, which blocks AKAP protein-protein interactions, blocks association of beta-adrenergic receptors with protein kinase A. These data are the first to reveal dynamic complexes of beta-adrenergic receptors with protein kinases and phosphatases acting via an anchoring protein, gravin.

Lp82 calpain during rat lens maturation and cataract formation

PURPOSE

To measure changes in levels of Lp82 during maturation and selenite cataract formation in rat lens. Lp82 is a lens-specific, calcium-activated isozyme from the calpain family of cysteine proteases (EC 34.22.17).

METHODS

Competitive RT-PCR was used to assess Lp82 and m-calpain mRNA concentrations. Immunoblotting and ELISA after DEAE chromatography measured Lp82 and m-calpain protein levels. Casein zymography assessed proteolytic activities in regions and whole lenses from maturing rats.

RESULTS

Levels of Lp82 mRNA, protein, and caseinolytic activity decreased more rapidly during maturation of rat lens than for m-calpain. Unexpectedly, the water-insoluble fraction of rat lens contained enzymatically active Lp82. Selenite injection also caused major loss of Lp82 protein during cataract formation.

CONCLUSIONS

Lp82 is a proteolytic enzyme likely functioning in early lens development and maturation. The rapid loss of Lp82 activity during lens maturation is probably caused by three factors: autodegradation associated with the proteolysis of soluble and insoluble proteins occurring in the rat lens nucleus, association of Lp82 with the lens insoluble fraction, and loss of Lp82 mRNA. Lp82 may function early in lens maturation along with m-calpain, which then is predominant in the latter stages of maturation. Proteolysis in selenite cataract is partially caused by over-activation of Lp82.

Serum and insulin induce a Grb2-dependent shift in agonist affinity of beta-adrenergic receptors

Beta-adrenergic receptors transduce catecholamine binding to activation of adenylylcyclase, a response counter-regulated by insulin. Insulin stimulates tyrosine phosphorylation of Tyr 350/354, which abolishes the catecholamine response. Phosphorylation of Try 350/354 creates a Src homology 2 (SH2) domain on the beta2-adrenergic receptor and the binding of adaptor protein Grb2 to this SH2 domain of the beta-adrenergic receptor takes place in an insulin-dependent manner. In membranes from serum-deprived S49 mouse lymphoma cells, GTPgammaS yields the well-known agonist-specific shift in agonist affinity for beta2-adrenergic receptors. The agonist-specific shift is observed in cell membranes either in the absence or in the presence of exogenously added purified Grb2. In membranes for serum-fed cells, in contrast, the addition of Grb2 induces an agonist-specific shift in receptor affinity that mimics addition of GTPgammaS to the membranes. The ability of the Grb2 to induce an agonist-specific shift in the membranes from serum-fed cells was abolished equally effectively either by competition with phosphopeptide harbouring the (p)YVNV motif or by disruption of the SH2 domain of added Grb2. Challenging Chinese hamster ovary cells with insulin (100 nM) for 30 min enabled Grb2 to induce an agonist-specific shift in agonist affinity for beta2-adrenergic receptors, suggestive of uncoupling of the receptors from G proteins. The insulin-dependent Grb2 effect on receptor-G-protein coupling was sensitive to competition by the pYVNY phosphopeptide and to disruption of the SH2 domain of Grb2. These data provide a biochemical link between the ability of insulin to counter-regulate catecholamine stimulation of cyclic AMP accumulation and the phosphorylation of the beta-adrenergic receptor, consequent biding of the adaptor molecule Grb2 and disruption of receptor-G-protein coupling.

Protein for Lp82 calpain is expressed and enzymatically active in young rat lens

mRNA for a newly discovered isoform of calpain, termed Lp82, was recently discovered in young rat lens. The purpose of the present experiments was to test for expression of Lp82 protein. Casein zymography after incubation with calcium was used to detect Lp82 proteolytic activity in regions of lenses from young rats. Lp82 protein was detected by immunoblotting or by ELISA after DEAE-5PW chromatography using a polyclonal antibody generated to a peptide sequence in Lp82. Northern blot analysis assessed expression of Lp82 mRNA. Four results demonstrated expression of Lp82 protein; (1) immunoblot reactivity at the predicted molecular mass of 82 kDa, (2) a unique band of calcium-activated lysis in casein zymograms, (3) partial purification and retention of activity from a single Lp82 peak on DEAE-5PW chromatography, and (4) positive immunoblotting and Northern blot analysis only in lens and not in other rat tissues. These results showed that Lp82 protein is lens-preferred, relatively abundant in young rats (especially nucleus), and enzymatically active. Proteolysis of crystallins in the nucleus of young rat lens during normal maturation and cataract formation, formerly attributed solely to m-calpain, may in fact be due to concerted action of both lens Lp82 and ubiquitous m-calpain.

Age-related changes in human lens crystallins identified by two-dimensional electrophoresis and mass spectrometry

The purpose of this study was to identify the major protein components in adult human lenses and to analyse the specific age-related changes in these proteins using two-dimensional electrophoresis, Edman sequencing, and in conjunction with the data in the accompanying manuscript, mass spectrometry. The majority of changes in the two-dimensional electrophoretic pattern of lens proteins occurred prior to 17 years of age, and included a decrease in proteins migrating to the original positions of beta B1, beta B3, beta A3, gamma C and gamma D, and the appearance of many new species with apparent molecular weights on two-dimensional electrophoretic gels similar to beta B2 and gamma S, but having more acidic pIs. These proteins were identified as deamidated forms of beta B1 and beta A3/A1 missing portions of their N-terminal extensions. With the exception of alpha B, deamidation was detected in all crystallin species. These data indicated that a major fraction of the water-soluble protein of the adult human lens is composed of truncated beta B1 and beta A3/A1 crystallins, and that nearly all human crystallins, including the, beta-crystallins, are susceptible to deamidation. The results also provided the most detailed map to date of the identities of protein species on two-dimensional electrophoresis gels of adult human lenses.

Cleavage of beta crystallins during maturation of bovine lens

PURPOSE

(1) Identify major crystallin proteins in fetal and adult bovine lens, (2) examine the N-termini of beta-crystallins for truncation, and (3) determine if the protease m-calpain (EC 3.4.22.17) is responsible for the cleavage of bovine beta-crystallins during maturation.

METHODS

Crystallins from fetal and adult bovine lenses were analyzed by one and two-dimensional electrophoresis and Edman sequencing of separated proteins and their tryptic fragments. Identical techniques were used to analyze crystallins following their incubation with purified m-calpain.

RESULTS

The identities of the major crystallins and several additional crystallin species missing portions of their N-terminal extensions were identified in the fetal bovine lens. Besides the previously identified form of betaB1 missing 15 residues from its N-terminus, forms of betaA3 >missing 11 and 22 residues were identified. With aging, the betaA3 (-22) species became a major protein in the adult bovine lens, and minor forms of betaB2 and betaB3 missing 8 and 22 residues from their N-termini, respectively, appeared. Purified m-calpain cleaved within the N-terminal extensions of bovine beta-crystallins and removed: 12 or 15 residues from betaB1; 8 residues from betaB2; 5 or 10 residues from betaB3; and 11 or 17 residues from betaA3.

CONCLUSIONS

Based on the cleavage sites in vitro, m-calpain may be partially responsible for cleavage of bovine betaB1, betaB2, and betaA3 during lens maturation. However, the preference of m-calpain to remove 12 residues from betaB1, and 11 and 17 residues from betaA3, suggested that the betaB1 (-15) and betaA3 (-22) species found in vivo were produced by a different protease. This unidentified protease may have a preference for the asparagine-proline-X-proline sequence found in the N-terminal extensions of betaB1 and betaA3.

Changes in calpain II mRNA in young rat lens during maturation and cataract formation

The purpose of these experiments was to describe the expression of mRNA for calpain II proteolytic enzyme (EC 3.4.22.17) during normal maturation of rat lens and in cataract formation. Quantitative RT-PCR indicated that the concentration of mRNA for calpain II in whole lens was 3-24 times higher than in age-matched rat liver, kidney, lung and brain, and it was at least five times higher than in young human lens. mRNA levels for calpain II were highest in the outer regions of young rat lens at 5 x 10(6) copies microgram-1 total RNA. Early-stage experimental cataract caused increased calpain II mRNA, while mature nuclear cataract showed a 64% loss. In contrast, mRNA levels for GAPDH, beta-actin, and lens-specific structural protein beta A4 remained constant during experimental cataract formation. Unlike the lower and constant levels in rat liver, kidney and lung; calpain II mRNA levels in whole rat lens decreased with age. These data help explain the high enzymatic activity of calpain II in young rat lens, susceptibility of young rat lens to a variety of cataracts showing increased calcium and calpain-induced proteolysis, and low calpain enzyme activity in human lens. Since the up-regulation of calpain II mRNA was more dynamic than either the amounts of calpain II enzyme or proteolysis of crystallins in cortex, resulting proteolytic activity against the bulk of lens proteins seems to be regulated by post-translational factors, such as increased calcium. The precise role of the up-regulation of calpain II mRNA is unknown, but we hypothesize that it may be associated with the initial cataractogenic response in the epithelial cells or peripheral cortical fibers.

Sequence analysis of betaA3, betaB3, and betaA4 crystallins completes the identification of the major proteins in young human lens

A combination of Edman sequence analysis and mass spectrometry identified the major proteins of the young human lens as alphaA, alphaB, betaA1, betaA3, betaA4, betaB1, betaB2, betaB3, gammaS, gammaC, and gammaD-crystallins and mapped their positions on two-dimensional electrophoretic gels. The primary structures of human betaA1, betaA3, betaA4, and betaB3-crystallin subunits were predicted by determining cDNA sequences. Mass spectrometric analyses of each intact protein as well as the peptides from trypsin-digested proteins confirmed the predicted amino acid sequences and detected a partially degraded form of betaA3/A1 missing either 22 or 4 amino acid residues from its N-terminal extension. These studies were a prerequisite for future studies to determine how human lens proteins are altered during aging and cataract formation.

Protein kinase C deficiency blocks recovery from agonist-induced desensitization

Protein phosphorylation is central to agonist-induced attenuation of the function of G-protein-linked receptors. Stable expression of RNA antisense to specific protein kinase mRNAs permitted analysis of loss-of-function mutants of A431 human epidermoid carcinoma cells, lacking protein kinase A, protein kinase C, or beta-adrenergic receptor kinase. Deficiency of protein kinase C, but not the others, amplified rather than attenuated agonist-induced desensitization. In wild-type cells, the t1/2 for recovery from desensitization was approximately 25 min following removal of agonist. In the protein kinase C-deficient cells, no resensitization was observed even 60 min after agonist removal. Like protein kinase C-deficiency, inhibition of protein kinase C with bisindolylmaleimide or calphostin C blocked resensitization. Resensitization was suppressed by FK506, an inhibitor of protein phosphatase 2B, mimicking protein kinase C-deficiency, but in a non-additive manner. The data reveal protein kinase C and protein phosphatase 2B to be critical elements of resensitization.

Crystallins from rat lens are especially susceptible to calpain-induced light scattering compared to other species

PURPOSE

To compare the susceptibility of crystallins from various animal species to formation of light scattering elements after proteolysis by calpain II enzyme (EC 3.4.22.17).

METHODS

Lens, total soluble proteins from: 12-day and 4-week old rat, fetal and adult bovine, 16-day embryonic and 10-week chicken, and young human cortex and nucleus were proteolyzed by either endogenous lens calpain or addition of purified calpain II for 24 h followed by incubation for up to 11 days. Absorbance of light at 405 nm estimated light scattering by crystallins; SDS-PAGE and 2D-electrophoresis assessed proteolysis on the crystallins.

RESULTS

Most rapid light scattering occurred with total soluble proteins from young rat lens, either after adding purified calpain or by activating endogenous lens calpain with calcium. (Only rat lens showed activation of endogenous calpain II.) beta-crystallin polypeptides from rat, bovine, human, and to a more limited extent, chick lens were partially proteolyzed by addition of purified calpain II. In spite of this proteolysis, total soluble proteins from chicken, bovine, and human lenses showed no obvious light scattering by action of calpain. Crystallins from older rat lens showed approximately 50% of the light scattering displayed by crystallins from younger rats after 3 days, but only when purified calpain was added.

CONCLUSIONS

Our results indicate an unusually high susceptibility of crystallin polypeptides from young rat lens to formation of light scattering elements after limited proteolysis. Thus, young rat lens provides a unique opportunity to investigate how properties of crystallins influence the development of light scattering found in cataract.