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Alessandro Finzi,1 Simone Ottoboni,1 Mauro Cellini,1 Beniamino Corcioni,2 Caterina Gaudiano,2 Luigi Fontana1 1Ophthalmology Unit, Department of Experimental, Diagnostic and Specialty Medicine, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, Italy; 2Department of Radiology, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Bologna, ItalyCorrespondence: Alessandro Finzi, Ophthalmology Unit, Department of Experimental, Diagnostic and Specialty Medicine, IRCCS Azienda Ospedaliero-Universitaria di Bologna, Via Pelagio Palagi 9, Bologna, 40138, Italy, Tel +39 051 2142831, Email finzialessandro@gmail.comPurpose: Age-related macular degeneration (AMD) presents a multifaceted etiopathogenesis involving ischemic, inflammatory, and genetic components. This study investigates the correlation between ocular hemodynamics, scleral rigidity (SR), and plasma endothelin-1 (ET1) levels in treatment-naive patients with asymmetrical AMD.Patients and Methods: This study included 20 treatment-naive patients (12 females and 8 males) with an average age of 76.4 ± 3.7 years, who presented with AMD with neovascular membrane formation (nAMD) in one eye, and intermediate grade 2 AMD (iAMD) in the other eye. The control group consisted of 20 healthy subjects (13 females and 7 males) with a mean age of 74.7 ± 3.9 years. All patients and healthy controls underwent color Doppler imaging (i) of the ophthalmic artery (OA), short posterior ciliary arteries (SPCAs), and central retinal artery (CRA); Plasma ET-1 levels were measured for all patients and healthy subjects. Corneal biomechanics were assessed using an Ocular Response Analyzer and two indices were obtained: corneal hysteresis (CH) and corneal resistance factor (CRF).Results: Results showed reduced blood flow velocities and increased resistance indices in AMD eyes, particularly affecting the short posterior ciliary arteries. According to mechanical theory, ARMD eyes exhibited elevated scleral rigidity and corneal resistance factor compared to controls, with a notable rise in SR in neovascular AMD (nAMD) eyes. As per the chronic subacute inflammation theory, plasma ET-1 levels were significantly higher in AMD patients, correlating with abnormal SPCAs blood flow and increased resistance indices.Conclusion: Findings suggest a multifactorial etiology of AMD involving an increase of ET-1 plasma levels with biomechanic damages of corneal and scleral tissue in nAMD.Keywords: AMD, endothelin-1, corneal biomechanics, scleral rigidity, hemodynamics

Introduction: This study examined the efficacy of a therapy based on a combination of Platelet Rich Plasma and hydroxyapatite nanoparticles in a severe clinical case involving a young Rottweiler with a complex spiral fracture of the tibia., Method: Following a worsening of the lesion after traditional surgical intervention, the subject was treated with the combined therapy. X-rays were taken at the following stages: immediately post-surgery, four weeks post-surgery, and 10 days post-treatment. Fracture gap and callus density measurements were obtained using ImageJ analysis, allowing for a detailed quantitative assessment of bone regeneration over time., Results: Post-operative radiographs indicated a clinical worsening of the fracture, revealing an increased fracture gap due to bone loss. However, significant improvements were observed ten days following the treatment, with a marked reduction in fracture gaps and increased callus density. These results demonstrated a notable acceleration in bone healing and callus formation compared to typical recovery times for similar lesions., Conclusion: The method showed potential for enhancing osteogenic regeneration, facilitating faster healing of serious orthopedic injuries compared to traditional methods., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Barbaro, Marconi, Innocenzi, Altigeri, Zepparoni, Monteleone, Alimonti, Marcoccia, Ghisellini, Rando, Ottoboni, Rau, Eggenhöffner and Scicluna.)

This study aims to report the efficacy of a combined intrastromal injection in optimizing the outcome of severe mycotic keratitis. Herein, we report a case series of 20 consecutive patients with positive fungal cultures not responding to topical antifungal treatment. Patients received cycles of intrastromal injections of voriconazole (50 µg/0.1 mL) and amphotericin B (2.5 µg/0.1 mL); all patients continued their topical antifungal therapy. The organisms isolated were Fusarium ( n = 5), Aspergillus ( n = 4), Candida ( n = 4), Rhodotorula ( n = 2), Penicillium ( n = 2), Alternaria ( n = 1), Bipolaris ( n = 1), and Curvularia ( n = 1). The size of the infiltrate varied from 6.5 to 1.5 mm. At presentation, the best corrected visual acuity (BCVA, namely, the best visual acuity achieved with glasses, if needed) was less than 20/400 in all patients, improving to better than 20/400 in eleven patients. Seven patients required surgical intervention; four of them underwent penetrating keratoplasty (PK) à chaud one month after the first intrastromal injection. Patients who underwent surgery achieved a BCVA of 20/40 or better. Combined intrastromal injections before therapeutic penetrating keratoplasty (TPK) effectively reduced ulcer size and graft diameter, preventing infection recurrence. Our results highlight the efficacy of combined intrastromal injections in optimizing outcomes for severe mycotic keratitis undergoing TPK.

A digital design tool that can transfer material property information between unit operations to predict the product attributes in integrated purification processes has been developed to facilitate end-to-end integrated pharmaceutical manufacturing. This work aims to combine filtration and washing operations frequently using active pharmaceutical ingredient (API) isolation. This is achieved by coupling predicted and experimental data produced during the upstream crystallization process. To reduce impurities in the isolated cake, a mechanistic model-based workflow was used to optimize an integrated filtration and washing process model. The Carman-Kozeny filtration model has been combined with a custom washing model that incorporates diffusion and axial dispersion mechanisms. The developed model and approach were applied to two systems, namely, mefenamic acid and paracetamol, which are representative compounds, and various crystallization and wash solvents and related impurities were used. The custom washing model provides a detailed evolution of species concentration during washing, simulating the washing curve with the three stages of the wash curve: constant rate, intermediate stage, and diffusion stage. A model validation approach was used to estimate cake properties (e.g., specific cake resistance, cake volume, cake composition after washing, and washing curve). A global systems analysis was conducted by using the calibrated model to explore the design space and aid in the setup of the optimization decision variables. Qualitative optimization was performed in order to reduce the concentration of impurities in the final cake after washing. The findings of this work were translated into a final model to simulate the optimal isolation conditions., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

To facilitate integrated end-to-end pharmaceutical manufacturing using digital design, a model capable of transferring material property information between operations to predict product attributes in integrated purification processes has been developed. The focus of the work reported here combines filtration and washing operations used in active pharmaceutical ingredient (API) purification and isolation to predict isolation performance without the need of extensive experimental work. A fixed Carman-Kozeny filtration model is integrated with several washing mechanisms (displacement, dilution, and axial dispersion). Two limiting cases are considered: case 1 where there is no change in the solid phase during isolation (no particle dissolution and/or growth), and case 2 where the liquid and solid phases are equilibrated over the course of isolation. In reality, all actual manufacturing conditions would be bracketed by these two limiting cases, so consideration of these two scenarios provides rigorous theoretical bounds for assessing isolation performance. This modeling approach aims to facilitate the selection of most appropriate models suitable for different isolation scenarios, without the requirement to use overly complex models for straightforward isolation processes. Mefenamic acid and paracetamol were selected as representative model compounds to assess a range of isolation scenarios. In each case, the objective of the models was to identify the purity of the product reached with a fixed wash ratio and minimize the changes to the crystalline particle attributes that occur during the isolation process. This was undertaken with the aim of identifying suitable criteria for the selection of appropriate filtration and washing models corresponding to relevant processing conditions, and ultimately developing guidelines for the digital design of filtration and washing processes., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Washing is a key step in pharmaceutical isolation to remove unwanted crystallization solvents and dissolved impurities (mother liquor) from the active pharmaceutical ingredient (API) filter cake to ensure the purity of the product whilst maximizing yield. It is therefore essential to avoid both product dissolution and impurity precipitation during washing, especially precipitation of impurities caused by the wash solvent acting as an antisolvent, affecting purity and causing agglomerate formation. This work investigates the wash solvent flow through a saturated filter cake to optimize washing by displacement, taking account of diffusional mechanisms and manipulating the wash contact time. Constant rate filtration/washing is employed in this study using readily available laboratory equipment. One advantage of using constant rate filtration in this work is that it allows for the collection of separate aliquots during all stages of filtration, washing, and deliquoring of the API cake. This enables a wash profile to be obtained, as well as providing an overall picture on the mass of API lost during isolation and so can assist in optimizing the washing strategy. Particle size analysis of damp cake obtained straight after washing is also performed using laser diffraction. This allowed for agglomerate formation caused during washing to be distinguished from agglomeration that would be caused by subsequent drying of the wet filter cake. This work aims at improving pharmaceutical product quality, increasing sustainability, and reducing manufacturing cost., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

A predictive tool was developed to aid process design and to rationally select optimal solvents for isolation of active pharmaceutical ingredients. The objective was to minimize the experimental work required to design a purification process by (i) starting from a rationally selected crystallization solvent based on maximizing yield and minimizing solvent consumption (with the constraint of maintaining a suspension density which allows crystal suspension); (ii) for the crystallization solvent identified from step 1, a list of potential isolation solvents (selected based on a series of constraints) is ranked, based on thermodynamic consideration of yield and predicted purity using a mass balance model; and (iii) the most promising of the predicted combinations is verified experimentally, and the process conditions are adjusted to maximize impurity removal and maximize yield, taking into account mass transport and kinetic considerations. Here, we present a solvent selection workflow based on logical solvent ranking supported by solubility predictions, coupled with digital tools to transfer material property information between operations to predict the optimal purification strategy. This approach addresses isolation, preserving the particle attributes generated during crystallization, taking account of the risks of product precipitation and particle dissolution during washing, and the selection of solvents, which are favorable for drying., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Washing is a key step in pharmaceutical isolation to remove the unwanted crystallization solvent (mother liquor) from the active pharmaceutical ingredient (API) filter cake. This study looks at strategies for optimal wash solvent selection, which minimizes the dissolution of API product crystals while preventing the precipitation of product or impurities. Selection of wash solvents to avoid both these phenomena can be challenging but is essential to maintain the yield, purity, and particle characteristics throughout the isolation process. An anti-solvent screening methodology has been developed to quantitatively evaluate the propensity for precipitation of APIs and their impurities of synthesis during washing. This is illustrated using paracetamol (PCM) and two typical impurities of synthesis during the washing process. The solubility of PCM in different binary wash solutions was measured to provide a basis for wash solvent selection. A map of wash solution composition boundaries for precipitation for the systems investigated was developed to depict where anti-solvent phenomena will take place. For some crystallization and wash solvent combinations investigated, as much as 90% of the dissolved PCM and over 10% of impurities present in the PCM saturated mother liquor were found to precipitate out. Such levels of uncontrolled crystallization during washing in a pharmaceutical isolation process can have a drastic effect on the final product purity. Precipitation of both the product and impurities from the mother liquor can be avoided by using a solvent in which the API has a solubility similar to that in the mother liquor; for example, the use of acetonitrile as a wash solvent does not result in precipitation of either the PCM API or its impurities. However, the high solubility of PCM in acetonitrile would result in noticeable dissolution of API during washing and would lead to agglomeration during the subsequent drying step. Contrarily, the use of n -heptane as a wash solvent for a PCM crystal slurry resulted in the highest amount of precipitation among the solvent pairs evaluated. This can be mitigated by designing a multi-stage washing strategy where wash solutions of differing wash solvent concentrations are used to minimize step changes in solubility when the mother liquor and the wash solvent come into contact., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

Context: Many people claim winter sea bathing gives them energy and health. According to the psychoneuroendocrinoimmunology (PNEI) paradigm, the stress response elicited by cold water immersion could indeed induce several beneficial psychophysical alterations., Objective: To determine the effects of winter sea bathing on psychological wellbeing, stress and immune markers., Design: A cross-sectional study., Participants: 228 people, between 19 and 88 years, including 107 winter sea bathers and 121 controls., Main Outcome Measures: A battery of questionnaires was administered to assess sociodemographic characteristics, self-perception of mental and physical heath, the number, duration and intensity of Upper Respiratory Tract Infections (URTIs) in the last year, and Big Five personality traits. 17 winter sea bathers and 15 controls (mean age 67 years) were further examined to evaluate physiological health, underwent one ear-nose-throat (ENT) examination, and provided saliva samples for measurements of biological markers (cortisol, sIgA, IL-1β, IL-6)., Results: Winter sea bathing was associated with lower levels of self-reported stress and higher wellbeing. The ENT examinations did not reveal signs of URTIs in winter sea bathers, who exhibited significantly higher levels of salivary sIgA compared to controls. Neither salivary IL-1β nor cortisol levels were significantly different between the two groups., Conclusions: Winter sea bathers (even the elderly) had a perception of higher wellbeing and reported better health: thus, they appeared to take advantage of potential distress (cold water exposure) to improve their health., (Copyright © 2020. Published by Elsevier Inc.)

Developing a continuous isolation process to produce a pure, dry, free-flowing active pharmaceutical ingredient (API) is the final barrier to the implementation of continuous end-to-end pharmaceutical manufacturing. Recent work has led to the development of continuous filtration and washing prototypes for pharmaceutical process development and small-scale manufacture. Here, we address the challenge of static drying of a solvent-wet crystalline API in a fixed bed to facilitate the design of a continuous filter dryer for pharmaceutical development, without excessive particle breakage or the formation of interparticle bridges leading to lump formation. We demonstrate the feasibility of drying small batches on a time scale suitable for continuous manufacturing, complemented by the development of a drying model that provides a design tool for process development. We also evaluate the impact of alternative washing and drying approaches on particle agglomeration. We conclude that our approach yields effective technology, with a performance that is amenable to predictive modeling., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)

A key challenge during the transition from laboratory/small batch to continuous manufacturing is the development of a process strategy that can easily be adopted for a larger batch/continuous process. Industrial practice is to develop the isolation strategy for a new drug/process in batch using the design of experiment (DoE) approach to determine the best isolation conditions and then transfer the isolation parameters selected to a large batch equipment/continuous isolation process. This stage requires a series of extra investigations to evaluate the effect of different equipment geometry or even the adaptation of the parameters selected to a different isolation mechanism (e.g., from dead end to cross flow filtration) with a consequent increase of R&D cost and time along with an increase in material consumption. The CFD25 is an isolation device used in the first instance to develop an isolation strategy in batch (optimization mode) using a screening DoE approach and to then verify the transferability of the strategy to a semicontinuous process (production mode). A d-optimal screening DoE was used to determine the effect of varying the input slurry. Properties such as solid loading, particle size distribution, and crystallization solvent were investigated to determine their impact on the filtration and washing performance and the characteristics of the dry isolated product. A series of crystallization (ethanol, isopropanol, and 3-methylbutan-1-ol) and wash solvents ( n -heptane, isopropyl acetate and n -dodcane) were used for the process. To mimic a real isolation process, paracetamol-related impurities, acetanilide and metacetamol, were dissolved in the mother liquor. The selected batch isolation strategy was used for the semicontinuous isolation run. Throughput and filtration parameters, such as cake resistance and flow rate, cake residual liquid content and composition, cake purity, particle-particle aggregation, and extent and strength of agglomerates, were measured to evaluate the consistency of the isolated product produced during a continuous experiment and compared with the isolated product properties obtained during the batch process development. Overall, the CFD25 is a versatile tool which allows both new chemical entity process development in batch and the production of the active pharmaceutical ingredient in semicontinuous mode using the same process parameters without changing equipment. The isolated product properties gained during the semicontinuous run are overall comparable between samples. The residual solvent content and composition differs between some samples due to filter plate blockage. In general, the mean properties obtained during semicontinuous running are comparable with the product properties simulated using the DoE., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

The lack of a commercial laboratory, pilot and small manufacturing scale dead end continuous filtration and drying unit it is a significant gap in the development of continuous pharmaceutical manufacturing processes for new active pharmaceutical ingredients (APIs). To move small-scale pharmaceutical isolation forward from traditional batch Nutsche filtration to continuous processing a continuous filter dryer prototype unit (CFD20) was developed in collaboration with Alconbury Weston Ltd. The performance of the prototype was evaluated by comparison with manual best practice exemplified using a modified Biotage VacMaster unit to gather data and process understanding for API filtration and washing. The ultimate objective was to link the chemical and physical attributes of an API slurry with equipment and processing parameters to improve API isolation processes. Filtration performance was characterized by assessing filtrate flow rate by application of Darcy's law, the impact on product crystal size distribution and product purity were investigated using classical analytical methods. The overall performance of the 2 units was similar, showing that the prototype CFD20 can match best manual lab practice for filtration and washing while allowing continuous processing and real-time data logging. This result is encouraging and the data gathered provides further insight to inform the development of CFD20., (Copyright © 2019 American Pharmacists Association®. All rights reserved.)

Vascular endothelial leukocyte adhesion molecules, such as E-selectin, are acutely upregulated in myocardial ischemia/reperfusion and are thus "ischemic memory" biomarkers for recent cardiac ischemia. We sought to develop an ultrasound molecular imaging agent composed of microbubbles (MBs) targeted to E-selectin to enable the differential diagnosis of myocardial ischemia in patients presenting with chest pain of unclear etiology. Biodegradable polymer MBs were prepared bearing a peptide with specific human E-selectin affinity (MB ESEL ). Control MBs had scrambled peptide (MB CTL ) or nonspecific IgG (MB IgG ). MB ESEL adhesion to activated rat endothelial cells (ECs) was confirmed in vitro in a flow system and in vivo with intravital microscopy of rat cremaster microcirculation. Ultrasound molecular imaging of recent myocardial ischemia was performed in rats 4 hours after transient (15 minutes) coronary occlusion. MB ESEL adhesion was higher to inflamed versus normal ECs in vitro; there was no difference in MB CTL or MB IgG adhesion to inflamed versus normal ECs. There was greater adhesion of MB ESEL to inflamed versus noninflamed microcirculation and minimal adhesion of MB CTL or MB IgG under any condition. Ultrasound imaging after injection of MB SEL demonstrated persistent contrast enhancement of the previously ischemic region. Videointensity in postischemic myocardium after MB ESEL was higher than that in the nonischemic bed (11.6 ± 2.7 dB vs 3.6 ± 0.8 dB, p < .02) and higher than that after MB CTL (4.0 ± 1.0 dB, p < .03) or MB IgG (1.7 ± 0.1 dB, p < .03). MBs targeted to E-selectin via a short synthetic peptide with human E-selectin binding affinity enables echocardiographic detection of recent ischemia, setting the stage for clinical myocardial ischemic memory imaging to identify acute coronary syndromes.

Background: Antibodies to stratified epithelia characterize chronic ulcerative stomatitis, an entity that very closely resembles erosive lichen planus both clinically and histologically. These antibodies are directed against a 70-kd antigen., Objective: Our aim was to verify whether antibodies to stratified epithelia are present in patients with common lichen planus., Patients and Methods: One hundred thirty-eight patients with various forms of lichen planus were studied. Indirect immunofluorescence was performed on both monkey esophagus and HEp2-2000 cells. Immunoblotting was done with cultured keratinocytes used as the source antigen., Results: Nineteen patients had antibodies to stratified epithelia (in 9 directed against an antigen of 70 kd). Forty-eight patients had circulating antibodies detected by indirect immunofluorescence on both monkey esophagus and HEp2-2000 cells (in 7 directed against an antigen of 70 kd). Indirect immunofluorescence was positive only on HEp2-2000 cells in 21 patients. Indirect immunofluorescence was negative in 50 patients on both HEp2-2000 cells and monkey esophagus. None of the last 71 patients had antibodies directed to an antigen of 70 kd., Limitations: This is a serological study; results from direct immunofluorescence studies would be interesting., Conclusion: Antibodies to stratified epithelia directed to an antigen of 70 kd are not exclusive to chronic ulcerative stomatitis, but are also present in some patients with lichen planus.

We have developed novel adhesion molecule-targeted double-shelled microspheres which encapsulate nitrogen. We report in vitro targeting studies utilizing these microspheres conjugated to target-specific antibodies directed towards ICAM-1 and VCAM-1. In static adherence experiments, the adherence patterns of microspheres conjugated to three different monoclonal antibodies (two targeted to ICAM-1 and one to VCAM-1) to their target surfaces were very different. Maximum microsphere adherence at the lowest target and/or ligand densities was observed with the VCAM-1 system. Differences in target-specific adherence were also observed between anti-ICAM-1 and anti-VCAM-1 microsphere conjugates in flow adherence studies. Equilibrium binding studies of the target proteins in solution to the microsphere-bound ligands showed that the affinity constants of two microsphere-bound monoclonal antibodies for their target proteins are similar. Thus, ligand-target affinity is not the only determinant of microsphere adherence to the target surface in our systems. Shear stress was found to have an effect on the mean diameter of adhered microspheres; a decrease in the mean diameter with increasing shear was observed. The magnitude of this effect was dependent on both microsphere-bound ligand and target surface densities, with a more pronounced change at lower densities. Adhered microspheres were readily detectable using ultrasound at the lowest tested surface density of 40 mm(-2)., (Copyright 2006 John Wiley & Sons, Ltd.)

The aim of this study was to compare the efficacy and the safety of a short oral ribosomal immunotherapy (Immucytal) in the prevention of chronic otitis media in children. Seventy-two patients were enrolled in this study, 41 males and 31 females, aged between 6 and 14 years, with an history of recurrent otitis media. Patients were randomised to receive Immucytal (group A) or placebo (group B) according to the following protocol: one tablet daily in the morning 8 days per month for three consecutive months. Immucytal and placebo were identical in shape and size, in order to maintain double-blind conditions. The efficacy parameters were (evaluated before, at the end and 6 months after the beginning of the therapy): clinical score; changes in immunological parameters; patient's parents assessment of symptoms on a scale from 0 (much worse) to 4 (much improved) and hearing tests. Patients of group A, had an improvement of clinical items measured, serum concentrations of immunoglobulins, subjective patient's parents assessment of symptoms and hearing tests. For all evaluations, a significant difference between treatment groups was found. Using this dosage and posology (shorter than others) the beneficial effects of Immucytal were maintained until the end of the 6-month study period.

Background: Recurrent acute pharyngotonsillitis remains a common illness in children and young adults and can lead to serious complications if not treated. cefpodoxime proxetil is a second-generation oral cephalosporin, which shows potent antibacterial activity against both Gram-positive and Gram-negative bacteria and high stability in the presence of beta-lactamases., Objective: We aimed to evaluate the efficacy of second-generation cephalosporins in the prophylaxis of recurrent pharyngotonsillitis in children., Methods: A total of 180 children aged between 4 and 14 years with recurrent pharyngotonsillitis were randomized to receive either cefpodoxime proxetil (100 mg twice a day, 6 days a month for 6 months) or placebo (at the same dosage)., Results and Conclusions: Our results show that treatment with cefpodoxime proxetil may be effective in reducing symptoms of recurrent pharyngotonsillitis and preventing recurrences without causing side effects or developing bacterial resistance.

DSPAalpha1 is a recombinant form of the vampire bat plasminogen activator which we have produced in mammalian cell culture. During the development of a recovery process for DSPAalpha1 we observed an unexpected binding interaction between this protein and several types of gel filtration chromatography resins. Under typical operating conditions using neutral pH buffers, we found that DSPA flows through the sizing resin and is fractionated, as expected, according to its molecular size. However, DSPA applied under certain acidic conditions (

In vitro metabolic studies have established that rat liver cytochromes P-450IIB1 and P-450IA1 but not rabbit liver cytochrome P-450IIB4 catalyze the oxidation of the Parkinsonian inducing neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to the corresponding dihydropyridinium (MPDP+) and pyridinium (MPP+) species. Kinetic experiments with the most effective isozyme, cytochrome P-450IA1, indicate that the reaction proceeds at a moderate velocity [Vmax = 20.1 nmol/(min.nmol of P-450IA1)] and high Km (0.87 mM). Furthermore, kinetic deuterium isotope effect measurements provided DV and D(V/K) values of 2.99 and 1.04, respectively. A comparison with the corresponding values for the monoamine oxidase B (MAO-B) catalyzed reaction (4.37 and 9.35, respectively) suggests that either these enzymes catalyze the ring alpha-carbon oxidation of MPTP by different pathways or that the initial one-electron transfer to generate an aminium radical intermediate previously proposed for both enzyme systems is reversible in the case of MAO-B and irreversible in the case of cytochrome P-450IA1.