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Macrocyclic peptides show promise in targeting high-value therapeutically relevant binding sites due to their high affinity and specificity. However, their clinical application is often hindered by low membrane permeability, which limits their effectiveness against intracellular targets. Previous studies focused on peptide conformations in various solvents, leaving a gap in understanding their interactions with and translocation through lipid bilayers. Addressing this, our study explores the membrane interactions of stapled peptides, a subclass of macrocyclic peptides, using solid-state nuclear magnetic resonance (ssNMR) spectroscopy and molecular dynamics (MD) simulations. We conducted ssNMR measurements on ATSP-7041M, a prototypical stapled peptide, to understand its interaction with lipid membranes, leading to an MD-informed model for peptide membrane permeation. Our findings reveal that ATSP-7041M adopts a stable α-helical structure upon membrane binding, facilitated by a cation-π interaction between its phenylalanine side chain and the lipid headgroup. This interaction makes the membrane-bound state energetically favorable, facilitating membrane affinity and insertion. The bound peptide displayed asymmetric insertion depths, with the C-terminus penetrating deeper (approximately 9 Å) than the N-terminus (approximately 4.3 Å) relative to the lipid headgroups. Contrary to expectations, peptide dynamics was not hindered by membrane binding and exhibited rapid motions similar to cell-penetrating peptides. These dynamic interactions and peptide-lipid affinity appear to be crucial for membrane permeation. MD simulations indicated a thermodynamically stable transmembrane conformation of ATSP-7041M, reducing the energy barrier for translocation. Our study offers an in silico view of ATSP-7041M's translocation from the extracellular to the intracellular region, highlighting the significance of peptide-lipid interactions and dynamics in enabling peptide transit through membranes.

The structural investigation of amorphous pharmaceuticals is of paramount importance in comprehending their physicochemical stability. However, it has remained a relatively underexplored realm primarily due to the limited availability of high-resolution analytical tools. In this study, we utilized the combined power of X-ray pair distribution functions (PDFs) and solid-state nuclear magnetic resonance (ssNMR) techniques to probe the molecular packing of amorphous posaconazole and its amorphous solid dispersion at the molecular level. Leveraging synchrotron X-ray PDF data and employing the empirical potential structure refinement (EPSR) methodology, we unraveled the existence of a rigid conformation and discerned short-range intermolecular C-F contacts within amorphous posaconazole. Encouragingly, our ssNMR 19 F- 13 C distance measurements offered corroborative evidence supporting these findings. Furthermore, employing principal component analysis on the X-ray PDF and ssNMR data sets enabled us to gain invaluable insights into the chemical nature of the intermolecular interactions governing the drug-polymer interplay. These outcomes not only furnish crucial structural insights facilitating the comprehension of the underlying mechanisms governing the physicochemical stability but also underscore the efficacy of synergistically harnessing X-ray PDF and ssNMR techniques, complemented by robust modeling strategies, to achieve a high-resolution exploration of amorphous structures.

Small molecule developability challenges have been well documented over the last two decades. One of these critical developability parameters is aqueous solubility. In general, more soluble compounds have improved oral absorption. While enabling formulation technologies exist to improve bioperformance for low solubility compounds, these are often more complex, expensive, and challenging to scale up. Therefore, to avoid these development issues, medicinal chemists need tools to rapidly profile and improve the physicochemical properties of molecules during discovery. Dose number (Do) is a simple metric to predict whether a compound will be reasonably absorbed based on solubility at an expected clinical dose and represents a valuable parameter to the medicinal chemist defining a clinical candidate. The goal of this mini-Perspective is to present the background of the Do equation and how it can be effectively used to rapidly predict oral absorption potential for molecules in the discovery space.

The process of bringing a drug to market involves innumerable decisions to refine a concept into a final product. The final product goes through extensive research and development to meet the target product profile and to obtain a product that is manufacturable at scale. Historically, this process often feels inflexible and linear, as ideas and development paths are eliminated early on to allow focus on the workstream with the highest probability of success. Carrying multiple options early in development is both time-consuming and resource-intensive. Similarly, changing development pathways after significant investment carries a high "penalty of change" (PoC), which makes pivoting to a new concept late in development inhibitory. Can drug product (DP) development be made more flexible? The authors believe that combining a nonlinear DP development approach, leveraging state-of-the art data sciences, and using emerging process and measurement technologies will offer enhanced flexibility and should become the new normal. Through the use of iterative DP evaluation, "smart" clinical studies, artificial intelligence, novel characterization techniques, automation, and data collection/modeling/interpretation, it should be possible to significantly reduce the PoC during development. In this Perspective, a review of ideas/techniques along with supporting technologies that can be applied at each stage of DP development is shared. It is further discussed how these contribute to an improved and flexible DP development through the acceleration of the iterative build-measure-learn cycle in laboratories and clinical trials.

Protein therapeutics carry inherent limitations of membrane impermeability and structural instability, despite their predominant role in the modern pharmaceutical market. Effective formulations are needed to overcome physiological and physicochemical barriers, respectively, for improving bioavailability and stability. Knowledge of membrane affinity, cellular internalization, encapsulation, and release of drug-loaded carrier vehicles uncover the structural basis for designing and optimizing biopharmaceuticals with enhanced delivery efficiency and therapeutic efficacy. Understanding stabilizing and destabilizing interactions between protein drugs and formulation excipients provide fundamental mechanisms for ensuring the stability and quality of biological products. This article reviews the molecular studies of biologics using solution and solid-state NMR spectroscopy on structural attributes pivotal to drug delivery and stability. In-depth investigation of the structure-function relationship of drug delivery systems based on cell-penetrating peptides, lipid nanoparticles and polymeric colloidal, and biophysical and biochemical stability of peptide, protein, monoclonal antibody, and vaccine, as the integrative efforts on drug product design, will be elaborated., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Despite the wide utilization of amorphous solid dispersions (ASDs) for formulating poorly water-soluble drugs, fundamental understanding of the structural basis behind their stability and dissolution behavior is limited. This is largely due to the lack of high-resolution structural tools for investigating multicomponent and amorphous systems in the solid state. In this study, we present what is likely the first publication quantifying the molecular interaction between the drug and polymer in ASDs at an angstrom level by utilizing 19 F magic angle spinning (MAS) nuclear magnetic resonance (NMR) techniques. A variant of the 19 F- 13 C rotational-echo and double-resonance (REDOR) technique was developed to quantify interatomic distances by implementing a supercycled symmetry-based recoupling schedule and synchronized simultaneous detection. We successfully deployed the technique to identify "head-to-head" and "head-to-tail" packing of crystalline posaconazole (POSA). To probe molecular interactions between POSA and hypromellose acetate succinate (HPMCAS) in the dispersion, as a major goal of this study, two-dimensional (2D) 1 H- 19 F correlation experiments were performed. The approach facilitated observation of intermolecular hydrogen-to-fluorine contacts between the hydroxyl group of the polymer and the difluorophenyl group of the drug substance. Atomic distance measurement, utilizing the developed 19 F- 13 C REDOR technique, revealed the close proximity of 13 C OH - 19 F at 4.3 Å. Numerical modeling analysis suggested a possible hydrogen bonding interaction between the polymer O-H group as an acceptor and POSA fluorine (O-H···F) or difluorophenyl ring (O-H···Ph) as a donor. These 19 F MAS NMR techniques, including 2D 19 F- 1 H heteronuclear correlation and 19 F- 13 C atomic distance measurement, may shed light on the nature (i.e., type and strength) of drug-polymer interactions in ASDs and offer a new high-resolution analytical protocol for probing the microstructure of amorphous pharmaceutical materials.

Crystalline and amorphous materials usually possess distinct physicochemical properties due to major variations in long-range and local molecular packings. Enhanced fundamental knowledge of the molecular details of crystalline-to-amorphous interconversions is necessary to correlate the intermolecular structure to material properties and functions. While crystal structures can be readily obtained by X-ray crystallography, the microstructure of amorphous materials has rarely been explored due to a lack of high-resolution techniques capable of probing local molecular structures. Moreover, there is increasing interest in understanding the molecular nature of amorphous solids in pharmaceutical sciences due to the widespread utilization of amorphous active pharmaceutical ingredients (APIs) in pharmaceutical development for solubility and bioavailability enhancement. In this study, we explore multidimensional 13 C and 19 F magic angle spinning (MAS) NMR spectroscopy to study the molecular packing of amorphous posaconazole (POSA) in conjunction with the crystalline counterpart. Utilizing methods integrating homonuclear and heteronuclear 1 H, 13 C, and 19 F correlation spectroscopy and atomic 19 F-to- 13 C distance measurements, we identified the major differences in molecular packing between crystalline and amorphous POSA. The intermolecular "head-to-head" interaction along the molecule's major axis, as well as the "head-to-tail" molecular packing perpendicular to the major axis in POSA crystals, was recapitulated by MAS NMR. Furthermore, critical intermolecular distances in the crystal lattice were determined. Most importantly, the head-to-tail contact of two neighboring molecules was found to be preserved in amorphous POSA, suggesting localized molecular order, whereas crucial interactions for head-to-head packing are absent in the amorphous form resulting in long-range disorder. Our study, likely one of the first documented examples, provides molecular-level structural details to understand the molecular mechanism of crystalline-to-amorphous conversion of fluorine-containing drug substances occurring in drug processing and development and establish a high-resolution experimental protocol for investigating amorphous materials.

Understanding the relationship between the structure and the physicochemical attributes of crystalline pharmaceuticals requires high-resolution molecular details. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy is an indispensable tool for analyzing molecular structures, but often experiences challenges of low spectral resolution and sensitivity, particularly in the characterization of unlabeled pharmaceutical materials. Besides, the relatively long spin-lattice relaxation times in pharmaceutical crystals result in time-consuming data collections. In this study, we utilize ultrafast magic angle spinning (UF-MAS) of the sample at 60 and 110 kHz to enable proton and fluorine spectroscopies for probing the structural details of crystalline posaconazole. Paramagnetic relaxation enhancement (PRE), obtained by doping Cu(ii) ions into the crystalline lattice and coating on particle surface, is implemented to shorten the spin-lattice relaxation time for speeding up the ssNMR acquisition. Our results demonstrate a remarkably improved 1 H and 19 F resolution and sensitivity, which enables multi-dimensional 1 H- 1 H and heteronuclear 1 H- 19 F correlations. In combination with density functional theory (DFT) calculations of chemical shifts, molecular details of posaconazole are established in terms of 1 H and 19 F networks for identifying "head-to-tail" and "head-to-head" intermolecular packings, with presumably critical contacts that stabilize the crystalline structure. The PRE and UF-MAS techniques enable the high-resolution structure characterization of fluorinated drug molecules in pharmaceutical formulations at natural abundance.

This article describes how the increased use of energy-efficient solid-state light sources (e.g., light-emitting diode [LED]-based illumination) in hospitals, pharmacies, and at home can help alleviate concerns of photodegradation for pharmaceuticals. LED light sources, unlike fluorescent ones, do not have spurious spectral contributions <400 nm. Because photostability is primarily evaluated in the International Council of Harmonization Q1B tests with older fluorescent bulb standards (International Organization for Standardization 10977), the amount of photodegradation observed can over-predict what happens in reality, as products are increasingly being stored and used in environments fitted with LED bulbs. Because photodegradation is premised on light absorption by a compound of interest (or a photosensitizer), one can use the overlap between the spectral distribution of a light source and the absorption spectra of a given compound to estimate if photodegradation is a possibility. Based on the absorption spectra of a sample of 150 pharmaceutical compounds in development, only 15% would meet the required overlap to be a candidate to undergo direct photodegradation in the presence of LED lights, against a baseline of 55% of compounds that would, when considering regular fluorescent lights. Biological drug products such as peptides and monoclonal antibodies are also expected to benefit from the use of more efficient solid-state lighting., (Copyright © 2019 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

Advances in technologies related to the design and manufacture of therapeutic peptides have enabled researchers to overcome the biological and technological challenges that have limited their application in the past. As a result, peptides of increasing complexity have become progressively important against a variety of disease targets. Developing peptide drug products brings with it unique scientific challenges consistent with the unique physicochemical properties of peptide molecules. The identification of the proper characterization tools is required in order to develop peptide formulations with the appropriate stability, manufacturability, and bioperformance characteristics. This knowledge supports the build of critical quality attributes and, ultimately, regulatory specifications. The purpose of this review article is to provide an overview of the techniques that are employed for analytical characterization of peptide drug products. The techniques covered are highlighted in the context of peptide drug product understanding and include chemical and biophysical approaches. Emphasis is placed on summarizing the recent literature experience in the field. Finally, the authors provide regulatory perspective on these characterization approaches and discuss some potential areas for further research in the field., (Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

The ICH Q1B guidance and additional clarifying manuscripts provide the essential information needed to conduct photostability testing for pharmaceutical drug products in the context of manufacturing, packaging, and storage. As the previous 2 papers in this series highlight for drug products administered by injection (part 1) and drug products administered via topical application (part 2), there remains a paucity of guidance and methodological approaches to conducting photostability testing to ensure effective product administration. Part 3 in the series is presented here to provide a similar approach and commentary for photostability testing for oral drug products. The approach taken, as was done previously, is to examine "worst case" photoexposure scenarios in combination with ICH-defined light sources to derive a set of practical experimental approaches to support the safe and effective administration of photosensitive oral drug products., (Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

Although essential guidance to cover the photostability testing of pharmaceuticals for manufacturing and storage is well-established, there continues to be a significant gap in guidance regarding testing to support the effective administration of photosensitive drug products. Continuing from Part 1, (Baertschi SW, Clapham D, Foti C, Jansen PJ, Kristensen S, Reed RA, Templeton AC, Tønnesen HH. 2013. J Pharm Sci 102:3888-3899) where the focus was drug products administered by injection, this commentary proposes guidance for testing topical drug products in order to support administration. As with the previous commentary, the approach taken is to examine "worst case" photoexposure scenarios in comparison with ICH testing conditions to provide practical guidance for the safe and effective administration of photosensitive topical drug products., (© 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.)

Telcagepant potassium salt (MK-0974) is an oral calcitonin gene-related peptide receptor inhibitor investigated for the treatment of acute migraine. Under gastric pH conditions, the salt rapidly gels, then converts to an insoluble neutral form that creates an impervious shell on the tablet surface, resulting in a slow and variable release dissolution rate and poor bioavailability. Early attempts to develop a solid dosage form, including solid dispersion and nanosuspension formulations, resulted in low exposures in preclinical studies. Thus, a liquid-filled soft gelatin capsule (SGC) formulation (oblong 20) was used for clinical studies. However, a solid dosage form was desirable for commercialization. The slow dissolution of the tablet formulations was overcome by using a basifying agent, arginine, and inclusion of a nonionic surfactant, poloxamer 407. The combination of arginine and poloxamer in the formulation created a local transient basic microenvironment that promoted the dissolution of the salt and prevented rapid precipitation of the neutral form on the tablet surface to form the gel layer. The tablet formulation achieved fast absorption and comparable exposure to the SGC formulation. The final optimized 280 mg tablet formulation was successfully demonstrated to be bioequivalent to the 300 mg SGC formulation., (© 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.)

Basic guidance on the photostability testing of pharmaceuticals, designed to cover manufacturing and storage over shelf life, has long been established within ICH Q1(ICH,B(10) , but the guideline does not cover the photostability of drugs during or after administration (i.e., under conditions of use). To date, there has been a paucity of guidance covering the additional testing that would be of value during the clinical preparation and use of products. This commentary suggests a systematic approach, based on realistic "worst case" photoexposure scenarios and the existing ICH Option 1 and 2 light sources, to provide valuable data to pharmaceutical manufacturers and compounding pharmacists for the safe and effective use of photosensitive injection products., (© 2013 Wiley Periodicals, Inc. and the American Pharmacists Association.)

Drug discovery lead optimization teams face many diverse challenges in the search for drug development candidates. This includes understanding the toxicology profile of a candidate, and some strategies call for in vivo preclinical safety studies to be moved increasingly earlier in the discovery phase to increase the likelihood of success in development. One of the final hurdles in these pursuits is achieving adequate exposure to support safety margins for human clinical trials. In this article, we describe several strategies on early toxicology studies along with various enabling formulation methods that can be employed to achieve optimal oral absorption. These two elements of research together can significantly increase the speed preclinical drug candidates can move through development, and the overall probability of success in identifying viable new drugs., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

The past decade has yielded a significant body of literature discussing approaches for development and discovery collaboration in the pharmaceutical industry. As a result, collaborations between discovery groups and development scientists have increased considerably. The productivity of pharma companies to deliver new drugs to the market, however, has not increased and development costs continue to rise. Inability to predict clinical and toxicological response underlies the high attrition rate of leads at every step of drug development. A partial solution to this high attrition rate could be provided by better preclinical pharmacokinetics measurements that inform PD response based on key pathways that drive disease progression and therapeutic response. A critical link between these key pharmacology, pharmacokinetics and toxicology studies is the formulation. The challenges in pre-clinical formulation development include limited availability of compounds, rapid turn-around requirements and the frequent un-optimized physical properties of the lead compounds. Despite these challenges, this paper illustrates some successes resulting from close collaboration between formulation scientists and discovery teams. This close collaboration has resulted in development of formulations that meet biopharmaceutical needs from early stage preclinical in vivo model development through toxicity testing and development risk assessment of pre-clinical drug candidates., (Published by Elsevier B.V.)

While the physical properties of pharmaceutical excipients have been well characterized, impurities that may influence the chemical stability of formulated drug product have not been well studied. In this work, the hydroperoxide (HPO) impurity levels of common pharmaceutical excipients are measured and presented for both soluble and insoluble excipients. Povidone, polysorbate 80 (PS80), polyethylene glycol (PEG) 400, and hydroxypropyl cellulose (HPC) were found to contain substantial concentrations of HPOs with significant lot-to-lot and manufacturer-to-manufacturer variation. Much lower HPO levels were found in the common fillers, like microcrystalline cellulose and lactose, and in high molecular weight PEG, medium chain glyceride (MCG), and poloxamer. The findings are discussed within the context of HPO-mediated oxidation and formulating drug substance sensitive to oxidation. Of the four excipients with substantial HPO levels, povidone, PEG 400, and HPC contain a mixture of hydrogen peroxide and organic HPOs while PS80 contains predominantly organic HPOs. The implications of these findings are discussed with respect to the known manufacturing processes and chemistry of HPO reactivity and degradation kinetics. Defining critical HPO limits for excipients should be driven by the chemistry of a specific drug substance or product and can only be defined within this context., ((c) 2006 Wiley-Liss, Inc. and the American Pharmacists Association.)

Polysorbate 80 is used in the pharmaceutical industry as an additive to enhance the solubility of non-polar compounds in formulation design and during dissolution analysis. In this paper we present the spectroscopic and chromatographic characteristics for a series of commercially available sources of this non-ionic surfactant. The large UV/vis absorbance and broad chromatographic elution of Polysorbate 80 often makes it difficult to accurately quantitate pharmaceutically active compounds in solutions where the surfactant is present. Boundary conditions have been established where analytical interferences can be avoided in spectrophotometric analysis by choice of analysis wavelength and solution concentrations. Chromatographic method development is also presented enabling the removal of Polysorbate interference in instances where spectroscopic interference is too great.

The rapid, accurate determination of headspace oxygen and moisture in various pharmaceutical packages is important for both product packaging development and the implementation of new packaging technologies. Current headspace oxygen measurement techniques suffer from serious drawbacks in terms of potential sampling contamination, lengthy analysis times, and large required analysis volumes. In addition, relatively few techniques currently exist for the convenient determination of headspace moisture in packaging systems. Efforts herein focused on the development and application of a new method for the rapid and simultaneous determination of headspace oxygen and moisture in pharmaceutical packages using micro-gas chromatography (muGC). Studies showed that both headspace oxygen and moisture could be simultaneously quantified in <90 s on sample volumes of 50-100 microL by employing muGC with dual chromatographic analysis modules. Sampling issues common to manual syringe-based injections were also alleviated in the current studies by use of the built-in diaphragm pump sampling interface of the portable muGC system. The performance of the analytical approach was evaluated and shown to exhibit excellent linearity, accuracy, and precision for both analytes. High sensitivity for headspace oxygen was demonstrated, allowing for levels of oxygen as low as 0.03% to be accurately quantified. The subject method was applied to measure the headspace oxygen and moisture in pharmaceutical blister packaging and glass vials.

A phenyl ether-based drug substance exhibits photochemical degradation in citrate buffers with both ultraviolet (300-450 nm range) and visible light (380-700 nm range) exposure, even though the drug molecule itself is non-light absorbing at wavelengths > 300 nm. The major contributors to the observed photosensitivity are the citrate buffer, parts per billion (ppb) levels of iron, oxygen, and light exposure level. Although a primary phenol photodegradate is generated, there are at least eight other species formed as well. The molecular weights and abundance of these species suggest that the product distribution is generated by the reaction of hydroxyl radicals with the drug substance. The generation of the primary photodegradate is linearly proportional to the light exposure amount for a fixed concentration of iron present in the formulation. Conversely, the amount of photodegradation is also nearly linear with iron concentration (through 200 ppb levels) for a fixed amount of light exposure. The proposed mechanism for the photochemical generation of hydroxyl radicals has precedence in the literature for similar combinations of iron, oxygen, carboxylate buffers, and light. Since the buffer salt and oxygen molecular equivalents in the product are significantly higher than the ppb levels of iron employed and more difficult to remove, the control of the extent of photodegradation largely rests on the control of trace levels of iron in the formulated product and control of light exposure. Exposure of drug solutions to a series of transition metals clearly indicates that iron is the key transition metal involved in the observed photochemistry. At manufacture, the primary source of iron is the raw materials (water, drug or excipients) used in the formulation. The level of iron for product stored in glass increases with sample age and can be attributed to iron leaching from borosilicate glass vials. Consideration of adequate light control during the manufacturing and packaging processes will be discussed and can only be defined as a function of the amount of iron present at the time of manufacture in the formulation. The generality of this chemistry to other drug candidates and in the presence of other common buffers will also be discussed.

5-Hydroxymethylfurfural (5-HMF) is the major thermal decomposition product formed in aqueous dextrose solutions during sterilization and upon storage. Current compendial tests employ a spectrophotometric assay for 5-HMF and a separate assay based on optical rotation for dextrose. Efforts herein focused on identification of approaches to simultaneously quantify both 5-HMF and dextrose in aqueous solutions. Initial studies employed anion exchange chromatography with pulsed amperometric detection (PAD). These studies showed that the low anion exchange column loading capacity and concentration mismatch of dextrose and 5-HMF in typical commercial solutions makes simultaneous quantitation impractical at a single sample concentration. However, mixed modes of detection for each analyte using refractive index (RI) detection for dextrose and UV detection for 5-HMF proved viable for simultaneous quantitation. The performance of both approaches was evaluated and extremely high sensitivity for 5-HMF demonstrated (30-50 ppb). The formation of 5-HMF upon the forced thermal decomposition of dextrose was monitored and compared with results from the USP spectrophotometric assay.

A novel application of near-infrared (near-IR) spectroscopy for the on-line determination of nanoparticle size of a drug compound in a high solids dispersion is described. The on-line spectroscopic technique provides real-time data for process monitoring and control and overcomes the limitations that are encountered using laboratory-based instrumentation for nanoparticle size determination. Near-IR spectroscopy is capable of providing an accuracy of 2.4 nm near the endpoint of particle production, where the volume-weighted D90 particle size is determined to be 200-220 nm. The accuracy is adequate for endpoint control, which minimizes excess processing and provides control over the particle size throughout nanoparticle production.

The purpose of the present study is to apply and contrast several analytical techniques to understand the change in moisture content of 20 mm diameter bromobutyl rubber stoppers as a function of typical stopper processing conditions. Three separate methods were examined and Karl-Fischer titration and techniques based on capacitance measurements at a thin-film sensor were found to provide comparable results. Stopper moisture levels were examined in stoppers: (i) as received from the manufacturer, (ii) following steam sterilization, (iii) as a function of various drying cycles, and (iv) during simulated hold conditions prior to use. Finally, the transfer of moisture from stopper to an actual product is examined on storage and general agreement observed between stopper drying conditions and cake moisture levels.

The infrequent occurrence of benign epithelial cysts of the pancreas is the reason why little is known regarding their clinical relevance and surgical management. We report the case of a 38-year-old woman with a benign epithelial cyst that was resected by the rarely performed central pancreatectomy. The presentation, evaluation, and differences between this and other cystic lesions of the pancreas are discussed. The benefits of central pancreatectomy for this benign lesion are reviewed.

In this report, we evaluate the present state of the rapidly emerging field of monolayer-protected cluster (MPC) molecules with regard to their synthesis and monolayer functionalization, their core and monolayer structure, their composition, and their properties. Finally, we canvass some of the important remaining research opportunities involving MPCs.

This report describes how the electrochemical double-layer capacitances of nanometer-sized alkanethiolate monolayer-protected Au clusters (MPCs) dissolved in electrolyte solution depend on the alkanethiolate chain length (C4 to C16). The double-layer capacitances of individual MPCs (C(CLU)) are sufficiently small (sub-attoFarad, aF) that their metal core potentials change by >0.1 V increments for single electron transfers at the electrode/solution interface. Thus, the current peaks observed are termed "quantized double layer charging peaks", and their spacing on the potential axis varies with C(CLU). Differential pulse voltammetric measurements of C(CLU) in solutions of core-size-fractionated (i.e., monodisperse) MPCs are compared to a simple theoretical model, which considers the capacitance as governed by the thickness of a dielectric material (the monolayer, whose chain length is varied) between concentric spheres of conductors (the Au core and the electrolyte solution). The experimental results fit the simple model remarkably well. The prominent differential pulse voltammetric charging peaks additionally establish this method, along with high-resolution transmission electron microscopy and laser ionization-desorption mass spectrometry, as a tool for evaluating the degree of monodispersity of MPC preparations. We additionally report on a new tactic for the preparation of monodisperse MPCs with hexanethiolate monolayers.

To explore the efficacy of ultraviolet B-irradiated donor-specific leukocyte transfusions (UV-DSLT) with short-term cyclosporine to control intestinal allograft rejection, 75 adult Lewis (RT1l) rats underwent total small-intestinal transplantation from Brown-Norway (RT1n) donors. Recipients were randomly divided into ten treatment and control groups utilizing various combinations of donor-specific and third-party (Wistar-Furth, RT1u) leukocyte transfusions (TPLT), with or without transfusion UVB irradiation, and either alone or in combination with short-term cyclosporine administration (5 mg/kg intramuscularly on days -7, 0, 1, and 2 relative to transplantation). Leukocytes (10(8) cells) separated from a spleen cell suspension were infused on day -7. Certain transfused leukocytes were treated with 12,000 joules/m2 of UVB irradiation. Groups were monitored for mean survival time (MST) and cause of death. UV-DSLT alone (MST = 19.8 +/- 4.6) or in combination with cyclosporine (UV-DSLT+CsA, MST = 53.1 +/- 22.5) significantly (P less than 0.003-0.0002, Mantel-Cox) prolonged recipient survival when compared with appropriate controls (i.e., no treatment, MST = 11.2 +/- 3.4; CsA, MST = 17.2 +/- 9.0; UV-TPLT, MST = 12.4 +/- 4.0; and UV-TPLT+CsA, MST = 25.1 +/- 9.7) No significant increase in graft-versus-host disease occurred in any group, with 85% (64/75) of the recipients dying of acute rejection. Conversely, the UV-DSLT+CsA group had a significant increase (9/11; chi-square, P less than 0.0001) in chronic rejection. Because UV-DSLT+CsA improved survival as compared with third-party controls, a limited donor-specific unresponsiveness may have been induced. Furthermore, this treatment produces a consistent, chronic rejection rodent intestinal allograft model.

A case of a hemangiopericytoma of the nasal cavity in a 79-year-old woman is presented. Ultrastructural examination confirmed the pericytic origin of the tumor. Most of the reported hemangiopericytomas of the sinonasal tract are histologically low-grade and their biologic course is in concert with their appearance.

The distribution of neural crest cells is briefly reviewed. The behaviour of neural crest derivatives in Africans is different from that seen in Caucasians, both in terms of physiology and pathology. The most obvious variation is in the depth of pigmentation of the skin, but most diseases of neural crest derived tissues show differences between Black and White subjects. The reason for these differences are not readily apparent but appear to be of genetic rather than environmental origin.

A case of Crohn's disease occurring in a Kenyan African is described. Review of literature disclosed 14 acceptable cases occurring in African subjects. The symptoms, anatomical distribution, signs, and pathology in black patients in Africa and America are similar to that described in whites. The disease is probably underdiagnosed in Africa because of difficulties in distinguishing schistosomiasis and tuberculosis of the bowel.

Five hundred and sixty-nine patients with breast cancer presenting for treatment at a community hospital were studied. The results showed no significant change in tumor size at presentation or reported patient delay over a 12-year span. This was in spite of considerable national discussion and increasing public concern about this disease during this period. We compared this patient group with a group of 27 cancer patients with training in health professional fields: seven of these 27 women reported delays of more than six months between discovery of a mass and reporting to a physician. Their masses were somewhat larger than those of women not medically trained (3.82 versus 3.47 cm). These results suggest a need for re-evaluation of the impact of medical education on an individual's reaction to personal health care.

A 23-year-old white man presented with a thyroid mass 12 years after receiving high-dose radiotherapy for a T2 and N1 lymphoepithelioma of the nasopharynx. Following subtotal thyroidectomy, a histopathologic examination revealed liposarcoma of the thyroid gland. The relationship between sarcomas and irradiation is described and Cahan and colleagues' criteria for radiation-induced sarcomas are reviewed. To our knowledge, we are presenting the first such case of a radiation-induced sarcoma of the thyroid gland.

Two cases of angiomyolipoma of the kidney in middleaged Black women are described. This may be a more common cause of a renal mass than a carcinoma; it is important to distinguish between the two because of differences in management.

Autopsies were performed on 47 patients who died of Burkitt lymphoma in Uganda between 1967 and 1971. The patients were separated into four groups based on the duration of survival from the time of diagnosis. Twenty patients survived less than three weeks; all had massive tumors. Six patients died between 10 and 16 weeks after diagnosis, usually from side effects of drug therapy. Of 16 patients who died between 24 and 52 weeks after diagnosis, 13 showed involvement of the central nervous system. Five patients died one year or more after diagnosis; two had a late relapse following a disease-free interval of one and four years, respectively; the other three had survived with clinically apparent tumor that was not responsive to therapy. In recent years, there has been a steady reduction in the proportion of patients showing residual systemic involvement at autopsy. This reduction is balanced by an increase in the proportion of patients with lesions of the central nervous system.

We studied and followed up 112 African patients with Kaposi's sarcoma for at least 3 years or until death to determine what features of the disease at presentation most accurately predicted the prognosis. The clinical pattern of disease at presentation was most important. All patients with generalized disease died of their disease; the only deaths among those with nodular disease were due to intercurrent illness. The 3-year survuval rate among patients with locally aggressive lesions with 64%. We could obtain greater refinement of prognosis by noting the response to a dinitrochlorobenzene challenge, the presence of nodal involvement, and the histologic pattern of the tumor. The age and sex of the patient influenced the pattern of disease likely to be found, but the prognosis for a given clinical pattern was the same in both sexes and at different ages.