Utility of cranial MRI in non-traumatic headache patients with prior negative head CT within 1 month

AIM

To investigate the importance of additional cranial magnetic resonance imaging (cMRI) in non-traumatic headache patients with a prior negative head computed tomography (CT) examination within 1 month.

MATERIALS AND METHODS

This retrospective study analysed 162 adult patients with non-traumatic headache who underwent cMRI within 1 month of a negative initial head CT at the emergency department (ED). The diagnostic yield and false-referral rate were analysed according to the revisit duration (early [≤1 week] versus late [>1-4 weeks] revisits), patient care settings (ED versus outpatient clinics [OPC]), and clinical variables. Subsequent patient management change (PMC), such as admission and treatment (AT) or outpatient clinic treatment (OT), were also investigated.

RESULTS

The overall diagnostic yield of cMRI was 17.3% (28/162) and the false-referral rate was 1.2% (2/162). The diagnostic yield of cMRI was significantly different according to the patient care settings (ED, 24.7% [21/85] versus OPC, 9.1% [7/77]; p=0.02). The diagnostic yield was highest in the ED-early-revisit group (25.4% [18/71]), 45% (9/20) in those with systemic signs, and 46.7% (14/30) in those with symptom change. Among patients with positive cMRI findings, 90% (27/30) received AT and 3.3% (1/30) received OT. Among OPC-revisit-negative cMRI patients, PMC occurred in 0% (0/50).

CONCLUSION

The diagnostic yield of cMRI was relatively high for headache patients who revisited the ED earlier, especially in those with systemic signs or symptom change. Most positive cMRI cases experienced PMC. Negative cMRI in OPC-revisit patients might help clarify the benign nature of a condition.

Review on fate, transport, toxicity and health risk of nanoparticles in natural ecosystems: Emerging challenges in the modern age and solutions toward a sustainable environment

In today's era, nanoparticles (NPs) have become an integral part of human life, finding extensive applications in various fields of science, pharmacy, medicine, industry, electronics, and communication. The increasing popularity of NP usage worldwide is a testament to their tremendous potential. However, the widespread deployment of NPs unavoidably leads to their release into the environmental matrices, resulting in persistence in ecosystems and bioaccumulation in organisms. Understanding the environmental behavior of NPs poses a significant challenge due to their nanoscale size. Given the current environmental releases of NPs, known negative consequences, and the limited knowledge available for risk management, comprehending the toxicity of NPs in ecosystems is both awaiting and crucial. The present review aims to unravel the potential environmental influences of nano-scaled materials, and provides in-depth inferences of the current knowledge and understanding in this field. The review comprehensively summarizes the sources, fate, transport, toxicity, health risks, and remediation solutions associated with NP pollution in aquatic and soil ecosystems. Furthermore, it addresses the knowledge gaps and outlines further investigation priorities for the sustainable control of NP pollution in these environments. By gaining a holistic understanding of these aspects, we can work toward ensuring the responsible and sustainable use of NPs in today's fast-growing world.

Estimating ammonium changes in pilot and full-scale constructed wetlands using kinetic model, linear regression, and machine learning

Constructed wetlands (CWs) are a widely utilized nature-based wastewater treatment method for various effluents. However, their application has been more focused on pilot and full-scale CWs with substantial surface areas and extended operation times, which hold greater relevance in practical scenarios. This study used kinetics, linear regression (LR), and machine learning (ML) models to estimate effluent ammonium in pilot and full-scale CWs. From screening 1476 papers, 24 pilot and full-scale CW studies were selected to extract data containing 15 features and 975 data points. Nine models were fit to this data, revealing that linear models were less effective in capturing CW effluent compared to nonlinear ML algorithms. For training data, the Monod kinetic model predicted the poorest performance with an RMSE of 41.84 mg/L and R2 of 0.34, followed by simple LR (RMSE 24.29 mg/L and R2 0.77) and multiple LR (RMSE 22.63 mg/L and R2 0.80). In contrast, Cubist and Random Forest achieved high performances, with an average RMSE of 12.01 ± 5.38 and an average R2 of 0.93 ± 0.07 for Cubist, and an average RMSE of 15.94 ± 10.69 and an average R2 of 0.91 ± 0.08 for RF. The trained Random Forest performed the best for new data, with an R2 of 0.93 and RMSE of 13.48 mg/L. This ML-based model is a valuable tool for efficiently estimating effluent ammonium concentration in pilot and full-scale CWs, thereby facilitating the design of systems.

Occurrence, fate, and potential risk of pharmaceutical pollutants in agriculture: Challenges and environmentally friendly solutions

In recent years, pharmaceutical active compounds (PhACs) have attained global prevalence. The behavior of PhACs in agricultural soils is complex and depends on several factors, such as the nature of the compounds and their physicochemical characteristics, which affect their fate and potential threats to human health, ecosystems, and the environment. The detection of residual pharmaceutical content is possible in both agricultural soils and environmental matrices. PhACs are commonly found in agricultural soil, with concentrations varying significantly, ranging from as low as 0.048 ng g-1 to as high as 1420.76 mg kg-1. The distribution and persistence of PhACs in agriculture can lead to the leaching of these toxic pollutants into surface water, groundwater, and vegetables/plants, resulting in human health risks and environmental pollution. Biological degradation or bioremediation plays a critical role in environmental protection and efficiently eliminates contamination by hydrolytic and/or photochemical reactions. Membrane bioreactors (MBRs) have been investigated as the most recent approach for the treatment of emerging persistent micropollutants, including PhACs, from wastewater sources. MBR- based technologies have proven to be effective in eliminating pharmaceutical compounds, achieving removal rates of up to 100%. This remarkable outcome is primarily facilitated by the processes of biodegradation and metabolization. In addition, phytoremediation (i.e., constructed wetlands), microalgae-based technologies, and composting can be highly efficient in remediating PhACs in the environment. The exploration of key mechanisms involved in pharmaceutical degradation has revealed a range of approaches, such as phytoextraction, phytostabilization, phytoaccumulation, enhanced rhizosphere biodegradation, and phytovolatilization. The well-known advanced/tertiary removal of sustainable sorption by biochar, activated carbon, chitosan, etc. has high potential and yields excellent quality effluents. Adsorbents developed from agricultural by-products have been recognized to eliminate pharmaceutical compounds and are cost-effective and eco-friendly. However, to reduce the potentially harmful impacts of PhACs, it is necessary to focus on advanced technologies combined with tertiary processes that have low cost, high efficiency, and are energy-saving to remove these emerging pollutants for sustainable development.

Facile preparation of porphyrin@g-C3N4/Ag nanocomposite for improved photocatalytic degradation of organic dyes in aqueous solution

In the quest of improving the photocatalytic efficiency of photocatalysts, the combination of two and more semiconductors recently has garnered significant attention among scientists in the field. The doping of conductive metals is also an effective pathway to improve photocatalytic performance by avoiding electron/hole pair recombination and enhancing photon energy absorption. This work presented a design and fabrication of porphyrin@g-C₃N₄/Ag nanocomposite using acid-base neutralization-induced self-assembly approach from monomeric porphyrin and g-C₃N₄/Ag material. g-C₃N₄/Ag material was synthesized by a green reductant of Cleistocalyx operculatus leaf extract. Electron scanning microscopy (SEM), X-ray diffraction (XRD), FT-IR spectroscopy, and UV-vis spectrometer were utilized to analyse the properties of the prepared materials. The prepared porphyrin@g-C₃N₄/Ag nanocomposite showed well integration of porphyrin nanostructures on the g-C₃N₄/Ag's surface, in which porphyrin nanofiber was of the diameter in nanoscales and the length of several micrometers, and Ag NPs had an average particle size of less than 20 nm. The photocatalytic behavior of the resultant nanocomposite was tested for the degradation of Rhodamine B dye, which exhibited a remarkable RhB photodegrading percentage. The possible mechanism for photocatalysis of the porphyrin@g-C₃N₄/Ag nanocomposite toward Rhodamine B dye was also proposed and discussed.

Kinetic study on methylene blue removal from aqueous solution using UV/chlorine process and its combination with other advanced oxidation processes

This study investigated the kinetic degradation of methylene blue (MB) by a UV/chlorine process and its combination with other advanced oxidation processes. The ∙OH and reactive chlorine species (RCS: Cl∙, ClO∙, etc.) were the primary reactive species, which accounted for 56.7% and 37.6% of MB degradation at pH 7, respectively. The second-order rate constant of Cl∙ towards MB was calculated to be 2.8 × 10⁹ M^-1 s^-1. When the pH increased from 3 to 7, k_MB by ∙OH increased from 0.15 to 0.21 min^-1 before being reduced to 0.11 min^-1 at pH 11. k_MB by RCS continuously reduced from 0.16 to 0.13 min^-1 when the pH was increased to 11. Humic acid (HA), Br^-, and Cl^- inhibited the degradation with k_MB in the order: k_MB (in HA) < k_MB (in Br^-) < k_MB (in Cl^-). HCO₃^- increased k_MB from 0.37 to 0.48 min^-1. The experimental and modeling methods fit well, indicating the effectiveness of using Kintecus® in predicting concentrations of free radicals in complex water matrices. TOC removal was achieved at 60% after 30 min in a control process and it was strongly inhibited by the presence of HA, with 22% removal achieved at 5 mg_c L^-1 HA. UV/chlorine/electrochemical oxidation (UV/chlorine/EO) significantly improves k_MB from 0.37 to 0.94 min^-1 at a high current (240 mA), while UV/chlorine/H₂O₂ decreased k_MB at a low concentration of 0.01 mM H₂O₂ (k_MB decreased by 6.1%). The results indicate that the energy cost for UV irradiation was the main cost in MB treatment in both UV/chlorine and UV/persulfate (UV/PS) processes, accounting for 91% and 84%, respectively.

Can electrocoagulation technology be integrated with wastewater treatment systems to improve treatment efficiency?

Considerable amounts of domestic and industrial wastewater that should be treated before reuse are discharged into the environment annually. Electrocoagulation is an electrochemical technology in which electrical current is conducted through electrodes, it is mainly used to remove several types of wastewater pollutants, such as dyes, toxic materials, oil content, chemical oxygen demand, and salinity, individually or in combination with other processes. Electrocoagulation technology used in hybrid systems along with other technologies for wastewater treatment are reviewed in this work, and the articles reviewed herein were published from 2018 to 2021. Electrocoagulation is widely employed in integrated systems with other electrochemical technologies or conventional methods for effective removal of different pollutants with less cost and sometimes over shorter durations of operation. It has also been observed that the hybrid effects besides increasing the removal efficiency can overcome the disadvantages of using electrocoagulation alone, such as less sludge formation, high cost of operation and increased life of the used electrodes, and stable flux of water with longer periods of operation. More than 20 types of other technologies have been combined efficiently with electrocoagulation.

Green synthesis of a photocatalyst Ag/TiO2 nanocomposite using Cleistocalyx operculatus leaf extract for degradation of organic dyes

Green synthesis has emerged as a sustainable approach for the fabrication of nanomaterials in the last few decades. Leaf extracts have been considered low-cost and highly efficient reactants for the synthesis of nanoparticles. In this study, an aqueous extract of Cleistocalyx operculatus leaves was employed as a reductant to synthesize Ag/TiO₂ nanocomposites. The morphology, structure, and interface interaction of the Ag/TiO₂ nanocomposites were investigated by (i) X-ray diffraction (XRD) to determine the crystallinity, (ii) scanning electron microscopy (SEM) to determine the morphologies, (iii) energy dispersive X-ray spectroscopy (EDX) to determine the elemental composition and distribution, and (iv) diffuse reflectance spectroscopy (DRS) to understand the optical properties. The results showed that Ag nanoparticles (AgNPs) with particle sizes of 20-40 nm homogeneously covered the surface of the TiO₂ nanoparticles. The green-synthesized Ag/TiO₂ nanocomposite also exhibited an excellent photodegradation ability for Rhodamine B with a removal percentage up to 91.4% after 180 min of photocatalytic reaction.

Novel pure α-, β-, and mixed-phase α/β-Bi2O3 photocatalysts for enhanced organic dye degradation under both visible light and solar irradiation

Combining the pure α- and β-phases of bismuth oxide enhances its photocatalytic activity under both visible and solar irradiation. α-Bi₂O₃, β-Bi₂O_3, and α/β-Bi₂O₃ were synthesized by a solvothermal calcination method. The structural, optical, and morphological properties of the as-synthesized catalysts were analyzed using XRD, UV-DRS, XPS, SEM, TEM, and PL. The bandgaps of α/β-Bi₂O₃, α-Bi₂O₃, and β-Bi₂O₃ were calculated to be 2.59, 2.73, and 2.34 eV, respectively. The photocatalytic activities of the catalysts under visible and solar irradiation were examined by the degradation of carcinogenic reactive blue 198 and reactive black 5 dyes. The kinetic plots of the degradation reactions followed pseudo-first-order kinetics. α/β-Bi₂O₃ exhibited higher photocatalytic activity (∼99%) than α-Bi₂O₃ and β-Bi₂O₃ under visible and solar irradiation. The TOC and COD results confirmed the maximum degradation ability of α/β-Bi₂O₃, and the decolorization percentage remained above 90%, even after five cycles under visible irradiation. The photocatalytic dye degradation mechanism employed by α/β-Bi₂O₃ was proposed based on active species trapping experiments.

Generation patterns and consumer behavior of single-use plastic towards plastic-free university campuses

This study was conducted to estimate the generation of single-use plastics (SUPs) and elucidate consumer behavior towards a plastic-free university. The results show that the consumption rate of plastic bottles was the highest at 1.39 g per student per day (g.s^-1.d^-1), followed by plastic cups (0.20 g s^-1.d^-1), and plastic bags (0.14 g s^-1.d^-1). Approximately 94.41% of students were highly aware of the negative impacts of SUPs. More than four-fifths of the students (82.32%) assumed that they were responsible for the SUP pollution issue, whereas 59.52% considered SUP reduction (or lack thereof) by individuals, governments, and producers/businesses be important factors. Approximately 19.03% of the students supported implementing a high fine, one-tenth agreed for a total ban on SUPs, while nearly one-fifth believed reducing SUP consumption was unnecessary. Strategies for plastic-free universities was initiated by establishing the goal of "plastic-free university" and implementing integrated actions including a ban (plastic cups and bags) awareness-raising, and suitable alternatives.

Biological treatment of saline domestic wastewater by using a down-flow hanging sponge reactor

In this study, the effect of salinity on the removal of organic matter and nitrogen concentrations in bioreactor was investigated using a hybrid bench scale down-flow hanging sponge (DHS) system for 145 days of operation. The reactor had three identical sections that were filled to 30% volume with Bio-Bact to serve as attached media. The DHS reactor was fed with domestic wastewater that was mixed with increasing concentration of sodium chloride from 0.5 to 3.0% stepwise. The influent and effluent concentrations of BOD₅, COD_Cr, NH₄⁺-N, and TN were analyzed to evaluate the performance of the DHS reactor during the operational period. Results indicate that when salinity was increased from 0.5 to 3.0%, the removal efficiency gradually decreased from 80.3% to 61.5% for COD_Cr, 76.4%-65.0% for BOD₅, 64.1%-48.4% for NH₄⁺-N, and 50%-36% for TN. Besides, the changes in biofilm characteristics with increasing salinity were observed during the operational period. The results indicate that salinity has a significant influence on the removal of organic matters and nitrogen transformation in the biofilm of the bioreactor. Even so, the DHS reactor revealed a good potential for treating saline wastewater.

Sustainable carbonaceous biochar adsorbents derived from agro-wastes and invasive plants for cation dye adsorption from water

This study investigated methyl orange (MO) dye adsorption using three biochars produced from agro-waste and invasive plants; the latter consisted of wattle bark (BA), mimosa (BM), and coffee husks (BC). BC had the lowest specific surface area (2.62 m²/g) compared to BA (393.15 m²/g) and BM (285.53 m²/g). The adsorption efficiency of MO was stable at pH 2-7 (95%-96%), whilst it had reduced stability at pH 7-12. Between 0 and 30 min, MO adsorption efficiency was >82%, and at 120 min, representative adsorption equilibrium had occurred. The maximum adsorption capacity of the biochars was 12.3 mg/g. The underlying adsorption mechanisms of the three biochars were governed by electrostatic adsorption and pore diffusion. There was an abundance of active sites for adsorption in BA and BM, while chemical adsorption appeared to be more vital for BC, as it contained more functional groups on its surface. The highest MO adsorption efficiency occurred with BM. BC was not recommended for MO removal, as it was observed to stain the water when a dose exceeding 5.0 g/L was utilized.

Two-step system consisting of novel vertical flow and free water surface constructed wetland for effective sewage treatment and reuse

This study developed a unique system by combining the novel vertical flow (NVF) using expanded clay (ExC) and free flow surface constructed wetland (FWS) for dormitory sewage purification and reuse. The NVF tank consisted of filter layers of ExC, sandy soil, sand, and gravel. The FWS consisted of sandy soil substrate and was installed after the NVF. Colocasia esculenta and Dracaena sanderiana was planted in NVF and FWS, respectively. The treatment system was operated and tested for more than 21 weeks by increasing the hydraulic loading rate (HLR) from 0.02 m/d to 0.12 m/d. The results demonstrated that effluents in the system changed proportionally to the HLRs, except for nitrate nitrogen. Furthermore, the maximum removal efficiencies for TSS, BOD5, NH4-N, and Tcol were 76 ± 13%, 74 ± 11%, 90 ± 3%, and 59 ± 18% (0.37 ± 0.19 log10MPN/100 mL), respectively. At HLRs of 0.04-0.06 m/d, the treatment system satisfied the limits of agriculture irrigation.

Scalable Fabrication of Modified Graphene Nanoplatelets as an Effective Additive for Engine Lubricant Oil

The use of nano-additives is widely recognized as a cheap and effective pathway to improve the performance of lubrication by minimizing the energy loss from friction and wear, especially in diesel engines. In this work, a simple and scalable protocol was proposed to fabricate a graphene additive to improve the engine lubricant oil. Graphene nanoplates (GNPs) were obtained by a one-step chemical exfoliation of natural graphite and were successfully modified with a surfactant and an organic compound to obtain a modified GNP additive, that can be facilely dispersed in lubricant oil. The GNPs and modified GNP additive were characterized using scanning electron microscopy, X-ray diffraction, atomic force microscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The prepared GNPs had wrinkled and crumpled structures with a diameter of 10–30 µm and a thickness of less than 15 nm. After modification, the GNP surfaces were uniformly covered with the organic compound. The addition of the modified GNP additive to the engine lubricant oil significantly enhanced the friction and antiwear performance. The highest reduction of 35% was determined for the wear scar diameter with a GNP additive concentration of approximately 0.05%. The mechanism for lubrication enhancement by graphene additives was also briefly discussed.

MRI to differentiate benign from malignant soft-tissue tumours of the extremities: a simplified systematic imaging approach using depth, size and heterogeneity of signal intensity

OBJECTIVE

Differentiating between malignant and benign lesions on the basis of MR images depends on the experience of the radiologist. For non-experts, we aimed to develop a simplified systematic MRI approach that uses depth, size and heterogeneity on T(2) weighted MR images (T(2)WI) to differentiate between malignant and benign lesions, and evaluated its diagnostic accuracy.

METHODS

MR images of 266 patients with histologically proven soft-tissue tumours of the extremities (102 malignant, 164 benign) were analysed according to depth (superficial or deep), size (<50, ≥50 mm) and signal intensity (homogeneous or heterogeneous) on T(2)WI, to determine the ability of each to predict benign and malignant tumours. These three parameters were categorised into systematic combinations of different orders of application, and each combination was assessed for its ability to differentiate between benign and malignant lesions.

RESULTS

Univariate analysis showed that depth, size and heterogeneity on T(2)WI differed significantly between benign and malignant masses (p<0.0001 each). Multiple logistic regression analysis, however, showed that depth was not helpful in distinguishing benign from malignant lesions. The systematic combination of signal intensity, size and depth, in that order, was superior to other combinations, resulting in higher diagnostic values for malignancy, with a sensitivity of 64%, a specificity of 85%, a positive predictive value of 32%, a negative predictive value of 59% and an accuracy of 77%.

CONCLUSION

A simplified systematic imaging approach, in the order signal intensity, size and depth, would be a reference to distinguish between benign and malignant soft-tissue tumours for non-experts.

Factors predictive of perforation during endoscopic submucosal dissection for the treatment of colorectal tumors

BACKGROUND AND AIM

Although perforation of the colon is known as one of the main complications of endoscopic submucosal dissection (ESD) for colorectal tumor management, factors predictive of perforation have not been fully evaluated. This study aimed to determine the factors associated with perforation during colorectal ESD.

METHODS

Patients with colorectal tumors undergoing ESD were enrolled and their records were reviewed retrospectively. Age, sex, co-morbidity, medication history, procedure time, resection method, tumor size, location, gross morphology, the presence of fibrosis, and histologic findings were included as possible risk factors. In the cases where perforation had occurred, factors associated with the duration of hospitalization were analyzed.

RESULTS

One hundred eight lesions in 108 patients were eligible for inclusion in the study (68 patients were male; mean patient age was 63.01 ± 10.71 years). Mean tumor size was 27.59 ± 10.10 mm (range: 8 - 53 mm). Laterally spreading tumor was the most common type (75 %), followed by the protruding type (25 %). Procedure time was 61.95 ± 41.90 minutes (range: 5 - 198 minutes). Complete en bloc resection was achieved for 85 lesions (78.7 %). Perforation occurred in 22 patients (20.4 %). Multivariate analysis confirmed that tumor size [odds ratio (OR): 1.084; 95 % confidence interval (CI): 1.015 - 1.158; P = 0.017] and the presence of fibrosis (OR: 4.551; 95 %CI: 1.092 - 18.960; P = 0.037) were independent risk factors for perforation. All cases of perforation were managed with nonsurgical treatment. Younger age and abdominal pain appeared to be related to prolonged hospitalization.

CONCLUSION

Tumor size and fibrosis are important factors related to complications during colorectal ESD. Younger age and development of abdominal pain can predict the hospital course in patients with perforation after ESD.

Gain-clamped Raman fiber oscillator

Gain band expansion of a Raman amplifier based on a Raman fiber oscillator (RFO) was tested with two Raman lasers, which yielded a broad gain spectrum of about 40 nm. However, they also introduced gain-clamping behavior in the short-wavelength range and abnormal excessive gain in long-wavelength channels, which were undesirable for practical application. The proper mechanism of the behavior was analyzed and experimentally demonstrated to apply to a gain-clamped (GC) amplifier based on a RFO. Appropriate configuration of the GC-RFO for wide gain bandwidth was proposed and characterized.

Participation of protein kinase C beta in osteoclast differentiation and function

Protein kinase C (PKC) proteins have been shown to be involved in diverse cellular responses of various cell types. In experiments to identify genes regulated during osteoclast differentiation by a cDNA microarray approach, we found that the gene expression of PKC-betaII was upregulated in differentiated cells. Reverse transcription-polymerase chain reaction and Western blotting analyses also showed an increase in PKC-betaI as well as PKC-betaII during osteoclast formation in mouse bone marrow cell cultures in the presence of macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor-kappaB ligand (RANKL). Use of an antisense oligonucleotide to PKC-betaII resulted in a reduction in the RANKL-driven osteoclastogenesis. Pharmacological intervention with PKC-beta activity by the specific inhibitor CG53353 suppressed cellular differentiation and fusion processes during osteoclastogenesis and inhibited bone-resorbing function of mature osteoclasts. PKC-beta inhibition abolished the ERK and MEK activation by macrophage-colony stimulating factor and RANKL in osteoclast precursor cells whereas the cytokine-induced NF-kappaB activation was not hampered by the PKC-beta inhibition. Our findings indicate that PKC-beta has a role in regulation of osteoclast formation and function potentially by participating in the ERK signaling pathway of M-CSF and RANKL.

Waste load allocation for water quality management of a heavily polluted river using linear programming

A waste load allocation model using linear programming has been developed for economic water quality management. A modified Qual2e model was used for water quality calculations and transfer coefficients were derived from the calculated water quality. This allocation model was applied to the heavily polluted Gyungan River, located in South Korea. For water quality management of the river, two scenarios were proposed. Scenario 1 proposed to minimise the total waste load reduction in the river basin. Scenario 2 proposed to minimise waste load reduction considering regional equity. Waste loads, which have to be reduced at each sub-basin and WWTP, were determined to meet the water quality goal of the river. Application results of the allocation model indicate that advanced treatment is required for most of the existing WWTPs in the river basin and construction of new WWTPs and capacity expansion of existing plants are necessary. Distribution characteristics of pollution sources and pollutant loads in the river basin was analysed using Arc/View GIS.

Tumor necrosis factor-alpha supports the survival of osteoclasts through the activation of Akt and ERK

Differentiated osteoclasts have a short life span. We tested various cytokines and growth factors for the effects on the survival of purified mature osteoclasts. In the absence of any added factors, osteoclasts exhibited the survival rate of less than 25% after a 24-h incubation. Among the tested factors, tumor necrosis factor-alpha (TNF-alpha) was found to increase the survival rate to approximately 80%. The TNF-alpha-enhanced survival of osteoclasts appeared to be associated with reduction in apoptosis and suppression of caspase activation. The antiapoptotic signaling pathways involved in the TNF-alpha-induced osteoclast survival were investigated. TNF-alpha treatment increased the phosphorylation of Akt in osteoclasts, which was suppressed by a phosphatidylinositol 3-kinase inhibitor LY294002 and an Src family kinase-selective inhibitor PP1. These inhibitors also attenuated the TNF-alpha stimulation of osteoclast survival. In addition an increase in the phosphorylation of ERK was observed upon TNF-alpha stimulation. PD98059, a specific inhibitor of the ERK-activating kinase MEK-1, abolished the TNF-alpha-induced ERK phosphorylation and osteoclast survival, and in these responses the involvement of Grb2 and ceramide was observed. These results suggest that TNF-alpha promotes the survival of osteoclasts by engaging the phosphatidylinositol 3-kinase Akt and MEK/ERK signaling pathways.

Selective involvement of reactive oxygen intermediates in platelet-activating factor-mediated activation of NF-kappaB

Although it has been suggested that some biological activities of platelet-activating factor (PAF) are mediated by, at least in part, reactive oxygen intermediates (ROI), the precise mechanisms underlying the interaction between the two remains to be elucidated. Antioxidants, such as alpha-tocopherol acid succinate, N-acetyl-L-Cysteine, pyrrolidinedithiocarbamate failed to inhibit PAF-induced immediate systemic reactions such as lethality, symptoms of disseminated intravascular coagulation, and histological changes such as pulmonary edema and hemorrhage in renal medullae 10 min following PAF injection. In contrast. antioxidants significantly inhibited both the in vivo and in vitro PAF-induced NF-kappaB activation and NF-kappaB-dependent TNF-alpha expression. The effects of the antioxidants were due to their inhibition of PAF-induced degradation of IkappaBalpha, a protein responsible for keeping NF-kappaB in an inactive form. A protein tyrosine kinase and N-tosyl-L-phenylalanine chloromethyl ketone sensitive serine protease were involved in both PAF- and H2O2-induced NF-kappaB activation. Collectively, these data indicate that the PAF-induced NF-kappaB activation is selectively mediated through the generation of ROI.

Temporal appearance of the presynaptic cytomatrix protein bassoon during synaptogenesis

Bassoon is a 420-kDa presynaptic cytomatrix protein potentially involved in the structural organization of neurotransmitter release sites. In this study, we have investigated a possible role for Bassoon in synaptogenesis and in defining synaptic vesicle recycling sites. We find that it is expressed at early stages of neuronal differentiation in which it is selectively sorted into axons. As synaptogenesis begins, Bassoon clusters appear along dendritic profiles simultaneously with synaptotagmin I, sites of synaptic vesicle recycling, and the acquisition of functional excitatory and inhibitory synapses. A role for Bassoon in the assembly of excitatory and inhibitory synapses is supported by the colocalization of Bassoon clusters with clusters of GKAP and AMPA receptors as well as GABA(A) receptors. These data indicate that the recruitment of Bassoon is an early step in the formation of synaptic junctions.

Resveratrol inhibits cyclooxygenase-2 transcription in human mammary epithelial cells

A large body of evidence suggests that inhibiting cyclooxygenase-2 (COX-2), the inducible form of COX, will be an important strategy for preventing cancer. In this study, we investigated whether resveratrol, a chemopreventive agent found in grapes, could suppress phorbol ester (PMA)-mediated induction of COX-2 in human mammary and oral epithelial cells. Treatment of cells with PMA induced COX-2 mRNA, COX-2 protein, and prostaglandin synthesis. These effects were inhibited by resveratrol. Nuclear runoffs revealed increased rates of COX-2 transcription after treatment with PMA, an effect that was inhibited by resveratrol. Resveratrol inhibited PMA-mediated activation of protein kinase C and the induction of COX-2 promoter activity by c-Jun. Phorbol ester-mediated induction of AP-1 activity was blocked by resveratrol. These data are likely to be important for understanding the anticancer and anti-inflammatory properties of resveratrol.

Piccolo, a presynaptic zinc finger protein structurally related to bassoon

Piccolo is a novel component of the presynaptic cytoskeletal matrix (PCM) assembled at the active zone of neurotransmitter release. Analysis of its primary structure reveals that Piccolo is a multidomain zinc finger protein structurally related to Bassoon, another PCM protein. Both proteins were found to be shared components of glutamatergic and GABAergic CNS synapses but not of the cholinergic neuromuscular junction. The Piccolo zinc fingers were found to interact with the dual prenylated rab3A and VAMP2/Synaptobrevin II receptor PRA1. We show that PRA1 is a synaptic vesicle-associated protein that is colocalized with Piccolo in nerve terminals of hippocampal primary neurons. These data suggest that Piccolo plays a role in the trafficking of synaptic vesicles (SVs) at the active zone.

Inhibition of cyclooxygenase-2 gene expression by p53

Oncogenes enhance the expression of cyclooxygenase (Cox)-2, but interactions between tumor suppressor genes and Cox-2 have not been studied. In the present work, we have compared the levels of Cox-2 and the production of prostaglandin E2 in mouse embryo fibroblasts that do not express any p53 ((10)1) versus the same cell line ((10. 1)Val5) engineered to overexpress wild-type (wt) p53 at 32 degrees C or mutant p53 at 39 degrees C. Cells expressing wt p53 showed about a 10-fold decrease in synthesis of prostaglandin E2 compared with those expressing mutant p53. Levels of Cox-2 protein and mRNA were markedly suppressed by wt p53 but not by mutant p53. Nuclear run-offs revealed decreased rates of Cox-2 transcription in cells expressing wt p53. The activity of the Cox-2 promoter was reduced by 85% in cells expressing wt p53 but was reduced only by 30% in cells expressing mutant p53 compared with cells null for p53. The effect of p53 on the suppression of Cox-2 promoter activity was localized to the first 40 base pairs 5' from the transcription start site. Electrophoretic mobility shift assay revealed that p53 competed with TATA-binding protein for binding to mouse Cox-2 or human Cox-2 promoter extending from -50 to +52 base pairs. The results of this study suggest that interactions between p53 and Cox-2 could be important for understanding why levels of Cox-2 are undetectable in normal cells and increased in many tumors.

Transcriptional activation of cyclooxygenase-2 in Wnt-1-transformed mouse mammary epithelial cells

Wnt-1 acts as a mammary oncogene when ectopically expressed in the mouse mammary gland. APC is a tumor suppressor gene, mutations in which cause intestinal tumorigenesis in humans and rodents. Both Wnt-1 expression and APC mutation activate a common signaling pathway involving transcriptional activation mediated by beta-catenin/Tcf complexes, but few targets relevant to carcinogenesis have yet been identified. Expression of the inducible prostaglandin synthase cyclooxygenase-2 appears critical for intestinal tumorigenesis resulting from APC mutation, suggesting that cyclooxygenase-2 might be a transcriptional target for beta-catenin/Tcf complexes. Here, we have investigated the effect of Wnt-1 on cyclooxygenase-2 expression. Wnt-1 expression in the mouse mammary epithelial cell lines RAC311 and C57MG induces stabilization of cytosolic beta-catenin and morphological transformation. Expression of Wnt-1 in these cells caused transcriptional up-regulation of the cyclooxygenase-2 gene, resulting in increased levels of cyclooxygenase-2 mRNA and protein. Prostaglandin E2 production was increased as a consequence of the elevated cyclooxygenase-2 activity and could be decreased by treatment with a selective cyclooxygenase-2 inhibitor. Cyclooxygenase-2 thus appears to be a common downstream target for APC mutation and Wnt-1 expression. In view of the critical role of cyclooxygenase-2 in intestinal tumorigenesis, cyclooxygenase-2 up-regulation in response to Wnt signaling may contribute to Wnt-induced mammary carcinogenesis.

Noninvasive evaluation of coronary artery bypass graft patency using three-dimensional angiography obtained with contrast-enhanced electron beam CT

OBJECTIVE

The purpose of this study was to determine the accuracy of three-dimensional coronary angiography obtained with electron beam CT in the assessment of the patency of coronary artery bypass grafts.

SUBJECTS AND METHODS

Twenty-five patients who had undergone coronary artery bypass graft surgery were included. All patients underwent electron beam CT and conventional coronary angiography for the evaluation of the status of their bypass grafts. Three-dimensional reconstructions of the heart and bypass grafts were compared with selective angiographic images of the bypass grafts.

RESULTS

Fifty-seven saphenous vein grafts and 22 left internal mammary artery grafts were evaluated for occlusion or patency. Sensitivity and specificity of electron beam CT in revealing left internal mammary artery patency were 80% and 82.4%, respectively. Sensitivity and specificity of electron beam CT in revealing saphenous vein graft patency were 91.7% and 91.1%, respectively. Sensitivity and specificity of electron beam CT for evaluating saphenous vein grafts according to coronary area were as follows: saphenous vein grafts to left anterior descending artery, 100% and 100%, respectively; to diagonal branch, 100% and 100%; to left circumflex artery, 100% and 88.9%; and to right coronary artery, 75% and 85.7%.

CONCLUSION

Three-dimensional coronary angiography obtained with electron beam CT is a promising, useful, and relatively accurate diagnostic imaging technique for the evaluation of graft patency in patients who have undergone coronary artery bypass graft surgery.

Growth and development of Gymnophalloides seoi in immunocompetent and immunosuppressed C3H/HeN mice

The growth and development of Gymnophalloides seoi were studied in C3H/HeN mice and effects of immunosuppression of the host on the worm development were observed. Two hundred metacercariae of G. seoi were orally administered to each mouse, and worms were recovered on days 1, 3, 5, 7, 14 and 21 post-infection (PI). The worm recovery rate was significantly higher in immunosuppressed (ImSP) mice than in immunocompetent (ImCT) mice except on days 1 and 3 PI. The worms attained sexual maturity by day 3 PI with eggs in the uterus, and worm dimensions and the number of uterine eggs continuously increased until day 14 PI in ImSP mice. Worms recovered from ImSP mice were significantly larger in size than those from ImCT mice on days 1 and 3 PI, and the number of uterine eggs was significantly larger in ImSP mice on days 5 and 7 PI. Genital organs such as the ovary, testes, and vitellaria, that were already developed in the metacercarial stage, grew a little in size until day 14 PI. The results show that the C3H/HeN mouse is, though not excellent, a suitable laboratory host for G. seoi.

Ceramide regulates the transcription of cyclooxygenase-2. Evidence for involvement of extracellular signal-regulated kinase/c-Jun N-terminal kinase and p38 mitogen-activated protein kinase pathways

The ceramide signaling pathway is activated by the sphingomyelinase (SMase)-mediated hydrolysis of cell membrane sphingomyelin to ceramide. We determined whether ceramide, a lipid second messenger, induced cyclooxygenase-2 (COX-2) in human mammary epithelial cells. Treatment of cells with neutral SMase or C2- or C6-ceramide enhanced prostaglandin E2 synthesis and increased levels of COX-2 protein and mRNA. Nuclear runoff assays revealed increased rates of COX-2 transcription after treatment with SMase and C2- and C6-ceramide. Transient transfections utilizing COX-2 promoter deletion constructs and COX-2 promoter constructs in which specific enhancer elements were mutagenized indicated that the effects of ceramide were mediated via a cAMP response element. The induction of COX-2 by ceramide was inhibited by calphostin C, an inhibitor of protein kinase C. Induction of COX-2 promoter activity by SMase was blocked by overexpressing kinase-deficient Raf-1. Triggering of the ceramide pathway also led to increases in extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 mitogen-activated protein kinase (MAPK) activities; pharmacological inhibitors of MAPK kinase (MEK) and p38 MAPK blocked the induction of COX-2 by SMase. Overexpressing ERK1, JNK, or p38 led to severalfold increases in COX-2 promoter activity. By comparison, overexpression of dominant negatives for ERK1/2, JNK, or p38 blocked the activation of COX-2 promoter activity by SMase. A dominant negative for c-Jun inhibited the activation of COX-2 promoter activity by ceramide. Thus, in response to ceramide, increased MAPK signaling activates c-Jun, which, in turn, induces COX-2 gene expression via the cAMP response element in the COX-2 promoter.

Effect of U-995, a potent shark cartilage-derived angiogenesis inhibitor, on anti-angiogenesis and anti-tumor activities

BACKGROUND

A potent angiogenesis inhibitor, U-995, has been purified from the cartilage of the blue shark (Prionace glauca). U-995 is composed of two single peptides with molecular mass of 10 and 14 kDa, respectively.

MATERIALS AND METHODS

U-995 was designed to study human umbilical vein endothelial cell (HUVEC) migration and proliferation in vitro and angiogenesis induced by TNF alpha in chicken chorioallantoic membrane (CAM). Furthermore, we determined the ability of U-995 to inhibiting tumor cell growth and metastasis.

RESULTS

U-995 (15 and 30 micrograms/ml) markedly inhibited HUVEC migration and, at 15-50 micrograms/ml produced a dose-dependent decline in [3H]-thymidine incorporation. 30 and 50 micrograms/ml of U-995, when added to TNF alpha-induced angiogenesis caused discontinuous and disrupted blood vessels. Moreover, U-995 (30 micrograms/ml) markedly prevented collagenase-induced collagenolysis. In addition, when 200 micrograms U-995 was injected i.p. into mice it suppressed sarcoma-180 cell growth and B16-F10 mouse melanoma cell metastasis in vivo.

CONCLUSIONS

These results suggest that the anti-angiogenic effects of U-995 may be be due to interference with the proliferation and migration of HUVECs as well as inhibition of collagenolysis, thereby leading to inhibition of both angiogenesis and tumor cell growth.

Resveratrol inhibits cyclooxygenase-2 transcription and activity in phorbol ester-treated human mammary epithelial cells

We determined whether resveratrol, a phenolic antioxidant found in grapes and other food products, inhibited phorbol ester (PMA)-mediated induction of COX-2 in human mammary and oral epithelial cells. Treatment of cells with PMA induces COX-2 and causes a marked increase in the production of prostaglandin E2. These effects were inhibited by resveratrol. Resveratrol suppressed PMA-mediated increases in COX-2 mRNA and protein. Nuclear run-offs revealed increased rates of COX-2 transcription after treatment with PMA, an effect that was inhibited by resveratrol. PMA caused about a 6-fold increase in COX-2 promoter activity, which was suppressed by resveratrol. Transient transfections utilizing COX-2 promoter deletion constructs and COX-2 promoter constructs, in which specific enhancer elements were mutagenized, indicated that the effects of PMA and resveratrol were mediated via a cyclic AMP response element. Resveratrol inhibited PMA-mediated activation of protein kinase C. Overexpressing protein kinase C-alpha, ERK1, and c-Jun led to 4.7-, 5.1-, and 4-fold increases in COX-2 promoter activity, respectively. These effects also were inhibited by resveratrol. Resveratrol blocked PMA-dependent activation of AP-1-mediated gene expression. In addition to the above effects on gene expression, we found that resveratrol also directly inhibited the activity of COX-2. These data are likely to be important for understanding the anti-cancer and anti-inflammatory properties of resveratrol.

Subcellular targeting and cytoskeletal attachment of SAP97 to the epithelial lateral membrane

The synapse-associated protein SAP97 is a member of a novel family of cortical cytoskeletal proteins involved in the localization of ion channels at such membrane specializations as synaptic junctions. These multidomain proteins have binding sites for protein 4.1, GKAPs/SAPAPs, voltage- and ligand-gated ion channels and cell-adhesion molecules containing C-terminal T/SXV motifs. In this study, we evaluated the contribution of individual domains in SAP97 to its selective recruitment and attachment to the cortical cytoskeleton in epithelial cells. We find that the PDZ, SH3 and GK domains, as well as the I3 insert in SAP97, are not essential for subcellular targeting, though both PDZ1-2 domains and the I3 insert affect the efficiency of localization. Instead, we show that the first 65 amino acid residues in SAP97, which are absent from SAP90/PSD-95 and SAP102, direct the selective subcellular localization and can mediate at least one point of attachment of SAP97 to the cytoskeleton assembled at sites of cell-cell contact. Our data demonstrate that it is the sequences unique to SAP97 that direct its subcellular targeting to the epithelial lateral membrane.

Interaction of the N-methyl-D-aspartate receptor complex with a novel synapse-associated protein, SAP102

Ionotropic glutamate receptors are known to cluster at high concentration on the postsynaptic membrane of excitatory synapses, but the mechanism by which this occurs is poorly understood. Studies on the neuromuscular junction and central inhibitory synapses suggest that clustering of neurotransmitter receptors requires its interaction with a cytoplasmic protein. Recently, in vitro studies have shown that members of the N-methyl--aspartate (NMDA) class of glutamate receptors interact with a synapse-associated protein, SAP90 (PSD-95). However, evidence for the in vivo interaction of NMDA receptors with SAPs is still lacking. In the present study, we demonstrate the specific interaction between SAP102, a novel synapse-associated protein, and the NMDA receptor complex from the rat cortical synaptic plasma membranes using co-immunoprecipitation techniques. No association was observed between SAP102 and GluR1, a member of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate class of glutamate receptors. To identify the domain on the NMDA receptor responsible for this interaction, we constructed hexahistidine fusion proteins from different regions of the NR1a and NR2 subunits of the NMDA receptor. Immunoblot overlay experiments showed that while the C-terminal domain of the NR2 subunit displayed strong binding, the NR1a intracellular C-terminal tail did not interact with SAP102. The site of interaction was more precisely located to the last 20 amino acids of the NR2 subunit as indicated by the interaction of the synthetic peptide with SAP102. In summary, we demonstrate here for the first time an in vivo interaction between the native NMDA receptor complex and a synapse-associated protein. These results suggest that SAP102 may play an important role in NMDA receptor clustering and immobilization at excitatory synapses.

SAP102, a novel postsynaptic protein that interacts with NMDA receptor complexes in vivo

Synapse-associated proteins (SAPs) are constituents of the pre- and postsynaptic submembraneous cytomatrix. Here, we present SAP102, a novel 102kDa SAP detected in dendritic shafts and spines of asymmetric type 1 synapses. SAP102 is enriched in preparations of synaptic junctions, where it biochemically behaves as a component of the cortical cytoskeleton. Antibodies directed against NMDA receptors coimmunoprecipitate SAP102 from rat brain synaptosomes. Recombinant proteins containing the carboxy-terminal tail of NMDA receptor subunit NR2B interact with SAP102 from rat brain homogenates. All three PDZ domains in SAP102 bind the cytoplasmic tail of NR2B in vitro. These data represent direct evidence that in vivo SAP102 is involved in linking NMDA receptors to the submembraneous cytomatrix associated with postsynaptic densities at excitatory synapses.

MAP2a, an alternatively spliced variant of microtubule-associated protein 2

MAP2, a dendritically localized microtubule-associated protein (MAP), consists of a pair of high molecular mass (280 kDa) polypeptides, MAP2a and MAP2b, and several low molecular mass (70 kDa) proteins called MAP2c. Although MAP2b and MAP2c have been shown to arise via alternative splicing. It was not clear whether MAP2a is also created by alternative splicing or by posttranslational modification. Using epitope peptide mapping, we have demonstrated that an element specific to MAP2a is situated at its N-terminal end. A cDNA clone from an adult rat brain library was found to contain an additional 246 nucleotides situated at the 5' end of the 9-kb MAP2 mRNA. Antibodies generated against the encoded protein sequence recognize specifically MAP2a in rat brain homogenates. Moreover, although MAP2a, like MAP2b, is found in dendrites and cell bodies, its temporal appearance and cell type-specific distribution in rat brain differs from MAP2b.

Molecular characterization of dendritically localized transcripts encoding MAP2

Transcripts encoding high molecular weight (Hwt) isoforms of microtubule-associated protein 2 (MAP2) have been localized in the dendritic compartment of neurons. In contrast, nearly all other neuronal messages, including transcripts encoding low molecular weight (Lwt) MAP2 isoforms, are restricted to cell somas. The mechanisms underlying the dendritic localization of Hwt-MAP2 transcripts are not known. In non-neuronal systems, mRNAs, are localized via signal sequences situated in their 3' untranslated regions (3' UTRs). In this study, we have localized the putative dendritic targeting element (DTE) in Hwt-MAP2 mRNAs by comparing the nucleotide sequences of the somatically localized 6 kb Lwt-MAP2 transcripts with the dendritcally localized 9 kb messages. Our analysis shows that both 6 kb and 9 kb transcripts have identical 3' - and 5'- UTRs, precluding the possibility that the DTE lies in these regions. Within the coding region a single segment that is unique to 9 kb Hwt MAP2 transcripts was identified. These findings suggest that the DTE lies within the 4 kb RNA segment that encodes the projection domain of Hwt-MAP2.

Differential modulation of astrocyte cytokine gene expression by TGF-beta

In this study, we demonstrate that TGF-beta inhibits TNF-alpha expression, and induces/enhances IL-6 expression by primary rat astrocytes. Treatment of astrocytes with TGF-beta alone had no effect on TNF-alpha mRNA or protein expression; however, TGF-beta suppressed induction of TNF-alpha expression by three different stimuli (IFN-gamma/LPS, IFN-gamma/IL-1 beta, TNF-alpha) at both the protein and mRNA level. The extent of TGF-beta-mediated inhibition was greatest when astrocytes were pretreated with TGF-beta for 6 to 24 h, then exposed to the inducing stimuli. Inhibition of TNF-alpha mRNA steady-state levels by TGF-beta was a result of inhibition of TNF-alpha gene transcription, rather than degradation of the TNF-alpha message. In contrast, TGF-beta alone induced expression of IL-6 by astrocytes and synergized with two other cytokines, IL-1 beta and TNF-alpha, for enhanced IL-6 expression. TGF-beta-induced/enhanced IL-6 expression was mediated by transcriptional activation of the IL-6 gene. These results indicate that TGF-beta is an important regulator of cytokine production by astrocytes under inflammatory conditions in the brain.

Differential modulation of astrocyte cytokine gene expression by TGF-beta

In this study, we demonstrate that TGF-beta inhibits TNF-alpha expression, and induces/enhances IL-6 expression by primary rat astrocytes. Treatment of astrocytes with TGF-beta alone had no effect on TNF-alpha mRNA or protein expression; however, TGF-beta suppressed induction of TNF-alpha expression by three different stimuli (IFN-gamma/LPS, IFN-gamma/IL-1 beta, TNF-alpha) at both the protein and mRNA level. The extent of TGF-beta-mediated inhibition was greatest when astrocytes were pretreated with TGF-beta for 6 to 24 h, then exposed to the inducing stimuli. Inhibition of TNF-alpha mRNA steady-state levels by TGF-beta was a result of inhibition of TNF-alpha gene transcription, rather than degradation of the TNF-alpha message. In contrast, TGF-beta alone induced expression of IL-6 by astrocytes and synergized with two other cytokines, IL-1 beta and TNF-alpha, for enhanced IL-6 expression. TGF-beta-induced/enhanced IL-6 expression was mediated by transcriptional activation of the IL-6 gene. These results indicate that TGF-beta is an important regulator of cytokine production by astrocytes under inflammatory conditions in the brain.

Metal affinity engineering of proinsulin carrying genetically attached (His)10-X-Met affinity tail and removal of the tag by cyanogen bromide

An E. coli expression clone coding for human proinsulin, which was fused to NH2-terminal beta-galactosidase, was engineered for the separation from host proteins by introducing peptide devices, and for the sequential removal of the fused polypeptide by cyanogen bromide in front of the NH2 terminal residue (methionine) of the human proinsulin gene. Short synthetic genes encoding oligopeptide residues including (Glu)n, (His)n, (Trp)n, and (Ser)n (n = 10 or 11), which have certain characteristic physical properties such as metal-affinity, polarity, hydrophobicity, and hydrophilicity, respectively, were inserted at the junction region of the gene fusion. Interestingly, it was found that among the oligopeptides, the oligohistidine residue as an affinity-tag has greatly facilitated the procedures for FPI purification, particularly in the manner of selective metal-affinity precipitation. The chelating peptide covering the NH2-terminal beta-galactosidase portion could then be removed simply after purification to generate a protein with the natural amino acid sequence of proinsulin by cyanogen bromide.

Protease Ti from Escherichia coli requires ATP hydrolysis for protein breakdown but not for hydrolysis of small peptides

Protease Ti, a new ATP-dependent protease in Escherichia coli, degrades proteins and ATP in a linked process, but these two hydrolytic functions are catalyzed by distinct components of the enzyme. To clarify the enzyme's specificity and the role of ATP, a variety of fluorogenic peptides were tested as possible substrates for protease Ti or its two components. Protease Ti rapidly hydrolyzed N-succinyl(Suc)-Leu-Tyr-amidomethylcoumarin (AMC) (Km = 1.3 mM) which is not degraded by protease La, the other ATP-dependent protease in E. coli. Protease Ti also hydrolyzed, but slowly, Suc-Ala-Ala-Phe-AMC and Suc-Leu-Leu-Val-Tyr-AMC. However, it showed little or no activity against basic or other hydrophobic peptides, including ones degraded rapidly by protease La. Component P, which contains the serine-active site, by itself rapidly degrades the same peptides as the intact enzyme. Addition of component A, which contains the ATP-hydrolyzing site and is necessary for protein degradation, had little or no effect on peptide hydrolysis. N-Ethylmaleimide, which inactivates the ATPase, did not inhibit peptide hydrolysis. In addition, this peptide did not stimulate the ATPase activity of component A (unlike protein substrates). Thus, although the serine-active site on component P is unable to degrade proteins, it is fully functional against small peptides in the absence of ATP. At high concentrations, Suc-Leu-Tyr-AMC caused a complete inhibition of casein breakdown, and diisopropylfluorophosphate blocked similarly the hydrolysis of both protein and peptide substrates. Thus, both substrates seem to be hydrolyzed at the same active site on component P, and ATP hydrolysis by component A either unmasks or enlarges this proteolytic site such that large proteins can gain access to it.