Design and synthesis of diaminopyrrolidinone inhibitors of human osteoclast cathepsin K

The structure-based design and synthesis of lactam-constrained azapeptide inhibitors of human cathepsin K are described. Enhanced stability to proteolytic cleavage over acyclic analogues is discussed.

Atypical glandular cells of undetermined significance on cervical smears. A study with cytohistologic correlation

OBJECTIVE

The incidence of endocervical adenocarcinoma has increased steadily over the past two decades. Since the Bethesda System was introduced, the diagnosis of atypical glandular cells of undetermined significance (AGUS) has also risen and now accounts for 0.46-1.83% of all cervical (Pap) smears. The purpose of this study was to evaluate the significance of a diagnosis of AGUS using cytohistologic correlation.

STUDY DESIGN

A retrospective review of archival material from 1993 through 1996 identified 64 patients who had smears diagnosed as AGUS and had a subsequent surgical biopsy. The smears were reviewed and cytologic features analyzed and correlated with the histologic diagnosis.

RESULTS

On biopsy, 3 (5%) of the 64 cases showed endocervical adenocarcinoma in situ (AIS) (1 case with invasive adenocarcinoma also), 14 (22%) had a benign glandular lesion (endocervical polyp, tubal metaplasia, microglandular hyperplasia, reactive changes), 35 (54%) had squamous intraepithelial lesion (SIL) (15 diagnosed on the original smear), and 12 (19%) had no abnormality. Among the cytologic criteria evaluated, feathering (P = .01), palisading (P < .001) and chromatin clearing (P = .002) were shown to have a significant association with the histopathologic diagnosis of AIS/adenocarcinoma. These features were also useful in distinguishing AIS/adenocarcinoma from SIL and benign glandular changes from AIS/adenocarcinoma but not benign/reactive glandular changes from SIL.

CONCLUSION

A diagnosis of AGUS correlated with a clinically significant lesion in the majority of cases. Squamous dysplasia (SIL) was the most common lesion identified. The presence of feathering, nuclear palisading and chromatin clearing increased the likelihood of a histologic diagnosis of AIS/adenocarcinoma.

Structure-based design of non-peptide, carbohydrazide-based cathepsin K inhibitors

Using binding models which were based on the X-ray crystal structure of an amino acid-based active site-spanning inhibitor complexed with cathepsin K, Cbz-leucine mimics have been developed, leading ultimately to the design of a potent cathepsin K inhibitor free of amino acid components. These mimics, which consist of alpha-substituted biphenylacetyl groups in place of Cbz-leucine moieties, effectively mimic all aspects of the Cbz-leucine moieties which are important for inhibitor binding. The predicted directions of binding for the inhibitors were confirmed by mass spectral analysis of their complexes with cathepsin K, which gave results consistent with acylation of the enzyme and loss of the acylhydrazine portion of the inhibitor which binds on the S' side of the active site. The binding models were found to be very predictive of relative inhibitor potency as well as direction of inhibitor binding. These results strengthen the validity of a strategy involving iterative cycles of structure-based design and inhibitor synthesis and evaluation for the discovery of non-peptide inhibitors.

Potent dipeptidylketone inhibitors of the cysteine protease cathepsin K

Cathepsin K (EC 3.4.22.38) is a cysteine protease of the papain superfamily which is selectively expressed within the osteoclast. Several lines of evidence have pointed to the fact that this protease may play an important role in the degradation of the bone matrix. Potent and selective inhibitors of cathepsin K could be important therapeutic agents for the control of excessive bone resorption. Recently a series of peptide aldehydes have been shown to be potent inhibitors of cathepsin K. In an effort to design more selective and metabolically stable inhibitors of cathepsin K, a series of electronically attenuated alkoxymethylketones and thiomethylketones inhibitors have been synthesized. The X-ray co-crystal structure of one of these analogues in complex with cathepsin K shows the inhibitor binding in the primed side of the enzyme active site with a covalent interaction between the active site cysteine 25 and the carbonyl carbon of the inhibitor.

Use of papain as a model for the structure-based design of cathepsin K inhibitors: crystal structures of two papain-inhibitor complexes demonstrate binding to S'-subsites

Papain has been used as a surrogate enzyme in a drug design effort to obtain potent and selective inhibitors of cathepsin K, a new member of the papain superfamily of cysteine proteases that is selectively and highly expressed in osteoclasts and is implicated in bone resorption. Here we report the crystal structures of two papain-inhibitor complexes and the rational design of novel cathepsin K inhibitors. Unlike previously known crystal structures of papain-inhibitor complexes, our papain structures show ligand binding extending deep within the S'-subsites. The two inhibitor complexes, carbobenzyloxyleucinyl-leucinyl-leucinal and carbobenzyloxy-L-leucinyl-L-leucinyl methoxymethyl ketone, were refined to 2.2- and 2.5-A resolution with R-factors of 0.190 and 0. 217, respectively. The S'-subsite interactions with the inhibitors are dominated by an aromatic-aromatic stacking and an oxygen-aromatic ring edge interaction. The knowledge of S'-subsite interactions led to a design strategy for an inhibitor spanning both subsites and yielded a novel, symmetric inhibitor selective for cathepsin K. Simultaneous exploitation of both S- and S'-sites provides a general strategy for the design of cysteine protease inhibitors having high specificity to their target enzymes.

Structure-based design of cathepsin K inhibitors containing a benzyloxy-substituted benzoyl peptidomimetic

Peptidomimetic cathepsin K inhibitors have been designed using binding models which were based on the X-ray crystal structure of an amino acid-based, active site-spanning inhibitor complexed with cathepsin K. These inhibitors, which contain a benzyloxybenzoyl group in place of a Cbz-leucine moiety, maintained good inhibitory potency relative to the amino acid-based inhibitor, and the binding models were found to be very predictive of relative inhibitor potency. The binding mode of one of the inhibitors was confirmed by X-ray crystallography, and the crystallographically determined structure is in close qualitative agreement with the initial binding model. These results strengthen the validity of a strategy involving iterative cycles of structure-based design, inhibitor synthesis and evaluation, and crystallographic structure determination for the discovery of peptidomimetic inhibitors.

Spatial sampling

Sampling in a spatial setting is typically done for the purpose of estimating or predicting a population quantity such as the total of a variable in a study region, to predict a new value at an unobserved site, or to find regions of high values for further study. Spatial covariance and conditional variance patterns have led to the use of designs such as systematic and stratified arrangements to increase precision and cluster or multistage sampling to increase cost effectiveness. In addition, adaptive procedures can be used to take advantage of patterns not discovered prior to the survey. An adaptive sampling design is one in which the procedure for selecting sites or units to include in the sample can depend on values of the variable of interest observed during the survey. For example, in a survey of an unevenly distributed insect species, neighbouring sites may be added to the sample whenever high abundance of the insects is encountered. Examples of adaptive designs include adaptive cluster sampling and adaptive allocation. Issues of design optimality or effectiveness and choice of inference methods with different types of designs will be discussed.

Introduction to wavelet-based compression of medical images

Medical image compression can significantly enhance the performance of picture archiving and communication systems and may be considered an enabling technology for telemedicine. The wavelet transform is a powerful mathematical tool with many unique qualities that are useful for image compression and processing applications. Although wavelet concepts can be traced back to 1910, the mathematics of wavelets have only recently been formalized. By exploiting spatial and spectral information redundancy in images, wavelet-based methods offer significantly better results for compressing medical images than do compression algorithms based on Fourier methods, such as the discrete cosine transform used by the Joint Photographic Experts Group. Furthermore, wavelet-based compression does not suffer from blocking artifacts, and the restored image quality is generally superior at higher compression rates.

Design of potent and selective human cathepsin K inhibitors that span the active site

Potent and selective active-site-spanning inhibitors have been designed for cathepsin K, a cysteine protease unique to osteoclasts. They act by mechanisms that involve tight binding intermediates, potentially on a hydrolytic pathway. X-ray crystallographic, MS, NMR spectroscopic, and kinetic studies of the mechanisms of inhibition indicate that different intermediates or transition states are being represented that are dependent on the conditions of measurement and the specific groups flanking the carbonyl in the inhibitor. The species observed crystallographically are most consistent with tetrahedral intermediates that may be close approximations of those that occur during substrate hydrolysis. Initial kinetic studies suggest the possibility of irreversible and reversible active-site modification. Representative inhibitors have demonstrated antiresorptive activity both in vitro and in vivo and therefore are promising leads for therapeutic agents for the treatment of osteoporosis. Expansion of these inhibitor concepts can be envisioned for the many other cysteine proteases implicated for therapeutic intervention.

Cytologic diagnosis of Ki-1 lymphoma in pleural and peritoneal effusions: a case report

This is a report of a case of Ki-1-positive large-cell anaplastic lymphoma in an 87-year-old man diagnosed on pleural and peritoneal fluids by cytomorphologic and immunohistochemical examination. Papanicolaou-stained smears revealed many single, large neoplastic cells containing one or two nuclei with occasional multinucleated cells having a wreath-like nuclear arrangement. The tumor cells expressed Ki-1 antigen and epithelial membrane antigen. This is the first known report of Ki-1 lymphoma diagnosed initially on cytologic examination of pleural and peritoneal fluids.

Identification of a loop outside the active site cavity of the human immunodeficiency virus proteases which confers inhibitor specificity

We have investigated the inhibitor specificity for the proteases of the human immunodeficiency viruses, types 1 and 2. Using a series of related inhibitors, the P1' side chain was confirmed to play a significant role in determining both the absolute and relative affinity for the enzymes. To further define the residues in the enzymes responsible for the difference in affinity, chimeric proteins were constructed in which domains of the respective proteases were exchanged at the genetic level. The results of these studies demonstrated that inhibitor affinity is conferred by a combination of the active site residues (32, 47, and 82) along with a loop comprised of residues 31 and 33-37, which lies outside of the active site cavity. These results are discussed in terms of existing structural data.

Adaptive sampling in behavioral surveys

Studies of populations such as drug users encounter difficulties because the members of the populations are rare, hidden, or hard to reach. Conventionally designed large-scale surveys detect relatively few members of the populations so that estimates of population characteristics have high uncertainty. Ethnographic studies, on the other hand, reach suitable numbers of individuals only through the use of link-tracing, chain referral, or snowball sampling procedures that often leave the investigators unable to make inferences from their sample to the hidden population as a whole. In adaptive sampling, the procedure for selecting people or other units to be in the sample depends on variables of interest observed during the survey, so the design adapts to the population as encountered. For example, when self-reported drug use is found among members of the sample, sampling effort may be increased in nearby areas. Types of adaptive sampling designs include ordinary sequential sampling, adaptive allocation in stratified sampling, adaptive cluster sampling, and optimal model-based designs. Graph sampling refers to situations with nodes (for example, people) connected by edges (such as social links or geographic proximity). An initial sample of nodes or edges is selected and edges are subsequently followed to bring other nodes into the sample. Graph sampling designs include network sampling, snowball sampling, link-tracing, chain referral, and adaptive cluster sampling. A graph sampling design is adaptive if the decision to include linked nodes depends on variables of interest observed on nodes already in the sample. Adjustment methods for nonsampling errors such as imperfect detection of drug users in the sample apply to adaptive as well as conventional designs.

Proteolytic activity of human osteoclast cathepsin K. Expression, purification, activation, and substrate identification

Human cathepsin K is a recently identified protein with high primary sequence homology to members of the papain cysteine protease superfamily including cathepsins S, L, and B and is selectively expressed in osteoclasts (Drake, F.H., Dodds, R., James I., Connor J., Debouck, C., Richardson, S., Lee, E., Rieman, D., Barthlow, R., Hastings, G., and Gowen, M. (1996) J. Biol., Chem. 271, 12511-12516). To characterize its catalytic properties, cathepsin K has been expressed in baculovirus-infected SF21 cells and the soluble recombinant protein isolated from growth media was purified. Purified protein includes an inhibitory pro-leader sequence common to this family of protease. Conditions for enzyme activation upon removal of the pro-sequence have been identified. Fluorogenic peptides have been identified as substrates for mature cathepsin K. In addition, two protein components of bone matrix, collagen and osteonectin, have been shown to be substrates of the activated protease. Cathepsin K is inhibited by E-64 and leupeptin, but not for by pepstatin, EDTA, phenylmethylsulfonyl fluoride, or phenanthroline, consistent with its classification within the cysteine protease class. Leupeptin has been characterized as a slow binding inhibitor of cathepsin K (kobs/[I] = 273,000 m(-1).s(-1)). Cathepsin K may represent the elusive protease implicated in degradation of protein matrix during bone resorption and represents a novel molecular target in treatment of disease states associated with excessive bone loss such as osteoporosis.

Design and evaluation of small peptides mapping the exposed surface of IL-8

In an effort to determine which regions of IL-8 are involved in interactions with its receptors, eight peptides were designed to correspond to distinct exposed regions of the IL-8 monomer, using the proton NMR-derived structure of the dimer as a basis. The peptides were evaluated singularly, and as equimolar mixtures of two to six peptides, in an IL-8 receptor binding assay and found to have no binding interaction with either alpha or beta IL-8 receptor as single peptides or mixtures of two peptides. In contrast, one of these peptides having the sequence AVLPRSAKEL, which corresponds to the N-terminal 10 amino acid residues of the 77 amino acid form of IL-8, exhibited potent chemotactic activity in human neutrophils. These results indicate that there is no contiguous ligand that can be designed based on the NMR and X-ray determined structure of IL-8 and that there may be multiple receptors responsible for neutrophil activation and chemotaxis.

Rational design, synthesis, and crystallographic analysis of a hydroxyethylene-based HIV-1 protease inhibitor containing a heterocyclic P1'--P2' amide bond isostere

The rational design and synthesis of a highly potent inhibitor of HIV-1 protease have been accomplished. The inhibitor, SB 206343, is based on a model derived from the structure of the MVT-101/HIV-1 protease complex and contains a 4(5)-acylimidazole ring as an isosteric replacement for the P1'--P2' amide bond. It is a competitive inhibitor with an apparent inhibition constant of 0.6 nM at pH 6.0. The three-dimensional structure of SB 206343 bound in the active site of HIV-1 protease has been determined at 2.3 A resolution by X-ray diffraction techniques and refined to a crystallographic discrepancy factor, R (= sigma parallel Fo magnitude of/Fc parallel/sigma magnitude of), of 0.194. The inhibitor is held in the enzyme by a set of hydrophobic and polar interactions. N-3 of the imidazole ring participates in a novel hydrogen-bonding interaction with the bound water molecule, demonstrating the effectiveness of the imidazole ring as an isosteric replacement for the P1'--P2' amide bond in hydroxyethylene-based HIV-1 protease inhibitors. Also present are hydrogen-bonding interactions between N-1 of the imidazole ring and the carbonyl of Gly-127 as well as between the imidazole acyl carbonyl oxygen and the amide nitrogen of Asp-129, exemplifying the peptidomimetic nature of the 4(5)-acylimidazole isostere. All of these interactions are in qualitative agreement with those predicted by the model.

Detectability in conventional and adaptive sampling

In this paper a simple but very general method is given for estimating a population total with any sampling design when objects in sampled units are observed with imperfect detectability--a problem characteristic of many surveys of natural and human populations. In the most general case, the method consists of dividing the value of the variable of interest associated with each detected object by the detection probability for that object and then proceeding to use the estimation method that would ordinarily be used under the design if there were no detectability problems. Examples illustrating the method include simple random sampling, conventional unequal probability sampling, and adaptive cluster sampling.

Paranuclear blue inclusions: an aid in the cytopathologic diagnosis of primary and metastatic pulmonary small-cell carcinoma

Accurate diagnosis of small-cell carcinoma of the lung (SCLC) is clinically important because of the therapeutic implications. SCLC must be distinguished from non-small-cell carcinoma (NSCLC) and lymphoma. Paranuclear blue inclusions (PBIs) were recently described as a feature of metastatic SCLC on air-dried Wright-stained bone marrow aspirate smears. To determine the utility of PBIs in distinguishing SCLC from NSCLC and lymphoma, we evaluated air-dried Diff-Quik-stained smears from 103 fine-needle aspiration (FNA) specimens and 14 touch imprint specimens. PBIs were identified in 24 (89%) of 27 cases of SCLC, in 6 (9%) of 64 non-small-cell carcinomas (P < 0.00001), and in two (8%) of the 26 lymphoma cases (P < 0.00001). No PBIs were seen on any of the alcohol-fixed Papanicolaou or hematoxylin-eosin (H&E) stained smears examined. In conclusion, PBIs appear to be a feature of SCLC on air-dried cytologic material stained with Romanowsky type stains. In the presence of cytologic features of SCLC, the identification of PBIs provides a useful diagnostic feature for differentiating between SCLC and NSCLC carcinomas, and between SCLC and lymphomas in FNA specimens and touch imprints from surgical specimens.

Radiation-induced changes in the breast: a potential diagnostic pitfall on fine-needle aspiration

The authors report a case of fine-needle aspiration (FNA) of a breast mass in a 36-year-old woman with previous history of lumpectomy and therapeutic radiation for breast carcinoma. The changes seen were interpreted as recurrent carcinoma, while subsequent biopsy showed only radiation changes. Radiation-induced changes in breast tissue are a potential diagnostic pitfall. The characteristic cytopathologic changes and their differential diagnosis are discussed.

Cytologic diagnosis of a chordoma without physaliforous cells

Fine-needle aspiration cytology of a presacral chordoma without the classic physaliforous cells is reported. The potential for the misdiagnosis of these lesions when these cells are absent is discussed. The pertinent literature related to this case is reviewed.

Refracture of the patella

Mildly displaced fractures of the patella, with an intact extensor mechanism, are widely treated in a plaster cylinder. This may lead to disuse osteoporosis of the patella and a subsequent refracture, which may be at a different site. A suggested method of splintage is to use a removable back splint for a period of 1-2 weeks.

Cerebral function before and after extra-intracranial carotid bypass

Thirty-eight patients had their cerebral function measured before and after extra-intracranial carotid bypass surgery using the Halstead-Reitan neuropsychology test battery. Two composite indices of cerebral function for each patient showed them to be impaired before operation. There was no improvement in the composite measures after operation to match that previously demonstrated after carotid endarterectomy. This may reflect the greater pre-operative cerebral impairment of the extra-intracranial group.

Prognosis in infantile idiopathic scoliosis

A review was performed of 86 cases of infantile idiopathic scoliosis treated between 1962 and 1979. The single primary curves were classified as resolving, stable, progressive with a low rib--vertebra angle difference (RVAD) and progressive with a high RVAD. Two single primary curves subsequently developed a second curve and 17 were double when first diagnosed. Prognosis was difficult to establish before the age of five years. Only 18 per cent of curves showing progression beyond 50 degrees reached that point before the age of four. Conversely, if a scoliosis of 50 degrees or more was present before the age of four it always progressed. A more favourable outcome was indicated by male sex, a left-sided curve, a low initial curve measurement, an RVAD of less than 20 degrees in the initial radiograph, and the onset of scoliosis in the first year of life.

Gender-deviant boys compared with normal and clinical control boys

The physical movement and social characteristics of effeminate behavior-problem, referred boys (N = 13) were compared with those of normal boys (N = 25) and boys (N = 12) referred for nongender problems. Parent reports, observer ratings, and videotapes were collected in a series of structured tasks. As expected, mothers described gender-problem sons as much more feminine than the other two groups in interests, activities, and mannerisms. Gender-problem sons were also seen as relatively inactive and introverted. Further, they were nonsignificantly lower than the clinical control boys in perceived behavior problems, but both groups had marginally more problems than the normal boys. Gender-problem and clinical control boys both showed more body constriction than normal boys in ratings of a videotaped interview. They also both showed less ideal ball-throw form than normal boys on a set of variables scored with slow-motion video. However, in a set of behaviors directly rated in the various tasks, the gender-problem boys gave a uniquely general impression of uncoordination. The groups did not differ on seven additional variables.

Anterior cruciate ligament repair for rotatory instability: the Lindemann dynamic muscle-transfer procedure

The Lindemann operation, originally performed in 1950 as a reconstructive procedure for the anterior cruciate ligament, was performed in the knees of eight patients suffering from rotatory instability. Although the instability persisted, as shown by roentgenographic and clinical examination, treatment with the tendon transfer appears to have provided dynamic stabilization. Seven of the eight patients so treated were subjectively improved, and they returned to sports or activities which they had not been able to perform prior to surgery.

Recognition of verbal labels of pictured objects and events by 17- to 30-month-old infants

A technique for efficiently presenting a large number of vocabulary items was developed for the testing of vocabulary comprehension in children younger than two years. The technique, incorporating slides of real objects, had the advantages of maintaining the child's attention, motivating task continuation, and overcoming the extraneous contextual cues of test materials. The subjects were 106 children aged 17 to 30 months from a wide range of social status groups, and from both English and Spanish language families. Results indicated significant stability over time as well as a significant relationship to maternal report. Analysis of errors suggested that comprehension develops similarly to production, in that simple nouns were the easiest items, verbs were more difficult, and modifiers and locatives were the most difficult. There were no significant main effects of sex or social status. However, specific environmental variables such as parental attitudes and playmate patterns were significantly correlated with test performance. More flexible family control systems and more interaction with peers were both associated with better vocabulary comprehension in first born children.

EEG sleep changes as predictors in depression

The authors conducted a study of 18 depressed patients to see whether EEG sleep measurements might provide a predictive tool for response to antidepressant medication. They found that although the sedative characteristics of amitriptyline did not differentiate good responders from poor responders until the third week of drug treatment, the good responders showed significant increases in REM latency, decreases in REM sleep time, decreases in REM sleep percent, and decreases in REM activity after only 2 nights of drug treatment.

Gender labels and early sex role development

A series of tests was designed for 24-, 30-, and 36-month-old children to measure their ability to apply various gender labels to the appropriate sexes, their capacity to place themselves in their own gender category, and their usage of labels to guide preference behavior. Also, the child's awareness of sex role stereotyping and the relationship of the above measures to parental SES and sex role attitudes were examined. In general, unlike the younger children, the oldest children consistently applied gender labels properly, were certain of their own gender, used same-sex gender labels to guide behavior, and were aware of sex role stereotyping. There was no relation between these measures and demographic variables.