Adiponectin profile at baseline is correlated to progression and severity of multiple sclerosis.

BACKGROUND AND PURPOSE: Adiponectin is a cytokine linking energy metabolism and immune system. After being assembled, adiponectin circulates as oligomers of different molecular weight, i.e. low, medium and high (HMW) molecular weight. These have the most potent biological effects. Multiple sclerosis (MS) is an autoimmune disease of the human central nervous system. The aim of this study was to characterize the expression levels of both total adiponectin and its oligomerization state in the serum from 99 patients with MS at baseline (i.e. not influenced by therapies). We also investigated the potential relationships between adiponectin and disease progression and severity. METHODS: Adiponectin was quantified and visualized by enzyme-linked immunosorbent assay, western blotting and fast protein liquid chromatography. During the follow-up (3.6 ± 2.20 years), the patients were evaluated using total annualized relapse rate and Expanded Disability Status Scale score. RESULTS: Total adiponectin is statistically higher in patients with MS compared with matched controls (12.18 vs. 10.02 µg/mL, P = 0.001). Interestingly, the adiponectin oligomerization state is altered in MS, with an increase of HMW oligomers. In addition, patients with MS with higher levels of adiponectin at baseline have significantly higher risk of progression and severity (Multiple Sclerosis Severity Score, 3.84 vs. 2.44, P = 0.001). No statistical difference in adiponectin expression was found between active and inactive patients with MS and among the different forms of disease. CONCLUSIONS: This study demonstrated that adiponectin and its HMW oligomers are greatly involved in MS autoimmune disorder representing a potential biomarker to predict worse MS prognosis and severity. Further studies are required to clarify the molecular mechanisms underlying the properties of adiponectin and HMW oligomers in MS.

The role of heavy metals and polychlorinated biphenyls (PCBs) in the oncogenesis of head and neck tumors and thyroid diseases: a pilot study.

Previous literature has highlighted the mechanisms of molecular toxicity induced by substances such as arsenic, cadmium, chromium, nickel, lead, barium and PCBs. The research was carried out on 20 volunteers, all the patients gave their consent to the research: the aim of the study was to evaluate the presence of metals and PCBs in these different matrices (blood and hair), correlating the biochemical data to pathological conditions present, and also to the area in which patients resided. Various quantitative determinations were carried out on samples of blood and hair for 14 heavy metals and on blood samples for 12 PCBs. For the 11 patients the results indicated that blood levels for half of the 14 displayed heavy metals measured considerably higher compared to the reference values, whilst the levels measured in hair evidenced some positive values significantly higher than the maximum reference. Of the 12 PCBs assayed in blood some showed higher positive values compared to the maximum tabular reference (although there is no clear reference quantified in the WHO-2005 report). In the 9 healthy patients heavy metals in the blood were within the expected target range, with those showing positive results (≤ 3 out of 14 heavy metals for each patient) having values only slightly higher than the reference maximum. The levels of 14 heavy metals measured in hair were below thresholds, and levels for the 12 PCBs measured in blood showed negativity or positivity with values close to the minimum benchmarks. The analyses carried out on biological matrices have uncovered important and significant differences between healthy and unhealthy subjects, both qualitative and quantitative differences with respect to heavy metals and PCBs. All patients with head and neck cancer enlisted for the study had heavy metal and PCB blood levels at least twice the maximum reference level. The levels of heavy metals in hair were at least double the maximum reference. In contrast, all healthy volunteers enrolled showed no significant levels for either metals or PCBs.

The natural history of gastro-esophageal reflux disease: a comprehensive review.

Gastroesophageal reflux disease (GERD) is a common disorder of the upper gastrointestinal tract which is typically characterized by heartburn and acid regurgitation. These symptoms are widespread in the community and range from 2.5% to more than 25%. Economic analyses showed an increase in direct and indirect costs related to the diagnosis, treatment and surveillance of GERD and its complications. The aim of this review is to provide current information regarding the natural history of GERD, taking into account the evolution of its definition and the worldwide gradual change of its epidemiology. Present knowledge shows that there are two main forms of GERD, that is erosive reflux disease (ERD) and non-erosive reflux disease (NERD) and the latter comprises the majority of patients (up to 70%). The major complication of GERD is the development of Barrett esophagus, which is considered as a pre-cancerous lesion. Although data from medical literature on the natural history of this disease are limited and mainly retrospective, they seem to indicate that both NERD and mild esophagitis tend to remain as such with time and the progression from NERD to ERD, from mild to severe ERD and from ERD to Barrett's esophagus may occur in a small proportion of patients, ranging from 0 to 30%, 10 to 22% and 1 to 13% of cases, respectively. It is necessary to stress that these data are strongly influenced by the use of powerful antisecretory drugs (PPIs). Further studies are needed to better elucidate this matter and overcome the present limitations represented by the lack of large prospective longitudinal investigations, absence of homogeneous definitions of the various forms of GERD, influence of different treatments, clear exclusion of patients with functional disorders of the esophagus.

Fluctuations and the rate-limiting step of peptide-induced membrane leakage.

Peptide-induced vesicle leakage is a common experimental test for the membrane-perturbing activity of antimicrobial peptides. The leakage kinetics is usually very slow, requiring minutes to hours for complete release of vesicle contents, and exhibits a biphasic behavior. We report here that, in the case of the peptaibol trichogin GA IV, all processes involved in peptide-membrane interaction, such as peptide-membrane association, peptide aggregation, and peptide translocation, take place on a timescale much shorter than the leakage kinetics. On the basis of these findings, we propose a stochastic model in which the leakage kinetics is determined by the discrete nature of a vesicle suspension: peptides are continuously exchanging among vesicles, producing significant fluctuations over time in the number of peptide molecules bound to each vesicle, and in the formation of pores. According to this model, the fast initial leakage is caused by vesicles that contain at least one pore after the peptides are randomly distributed among the liposomes, whereas the slower release is associated with the time needed to occasionally reach in an intact vesicle the critical number of bound peptides necessary for pore formation. Fluctuations due to peptide exchange among vesicles therefore represent the rate-limiting step of such a slow mechanism.

The proteasome as a druggable target with multiple therapeutic potentialities: Cutting and non-cutting edges.

Ubiquitin Proteasome System (UPS) is an adaptable and finely tuned system that sustains proteostasis network under a large variety of physiopathological conditions. Its dysregulation is often associated with the onset and progression of human diseases; hence, UPS modulation has emerged as a promising new avenue for the development of treatments of several relevant pathologies, such as cancer and neurodegeneration. The clinical interest in proteasome inhibition has considerably increased after the FDA approval in 2003 of bortezomib for relapsed/refractory multiple myeloma, which is now used in the front-line setting. Thereafter, two other proteasome inhibitors (carfilzomib and ixazomib), designed to overcome resistance to bortezomib, have been approved for treatment-experienced patients, and a variety of novel inhibitors are currently under preclinical and clinical investigation not only for haematological malignancies but also for solid tumours. However, since UPS collapse leads to toxic misfolded proteins accumulation, proteasome is attracting even more interest as a target for the care of neurodegenerative diseases, which are sustained by UPS impairment. Thus, conceptually, proteasome activation represents an innovative and largely unexplored target for drug development. According to a multidisciplinary approach, spanning from chemistry, biochemistry, molecular biology to pharmacology, this review will summarize the most recent available literature regarding different aspects of proteasome biology, focusing on structure, function and regulation of proteasome in physiological and pathological processes, mostly cancer and neurodegenerative diseases, connecting biochemical features and clinical studies of proteasome targeting drugs.

Skeletal myogenic progenitors originating from embryonic dorsal aorta coexpress endothelial and myogenic markers and contribute to postnatal muscle growth and regeneration.

Skeletal muscle in vertebrates is derived from somites, epithelial structures of the paraxial mesoderm, yet many unrelated reports describe the occasional appearance of myogenic cells from tissues of nonsomite origin, suggesting either transdifferentiation or the persistence of a multipotent progenitor. Here, we show that clonable skeletal myogenic cells are present in the embryonic dorsal aorta of mouse embryos. This finding is based on a detailed clonal analysis of different tissue anlagen at various developmental stages. In vitro, these myogenic cells show the same morphology as satellite cells derived from adult skeletal muscle, and express a number of myogenic and endothelial markers. Surprisingly, the latter are also expressed by adult satellite cells. Furthermore, it is possible to clone myogenic cells from limbs of mutant c-Met-/- embryos, which lack appendicular muscles, but have a normal vascular system. Upon transplantation, aorta-derived myogenic cells participate in postnatal muscle growth and regeneration, and fuse with resident satellite cells.The potential of the vascular system to generate skeletal muscle cells may explain observations of nonsomite skeletal myogenesis and raises the possibility that a subset of satellite cells may derive from the vascular system.

Muscle regeneration by bone marrow-derived myogenic progenitors.

Growth and repair of skeletal muscle are normally mediated by the satellite cells that surround muscle fibers. In regenerating muscle, however, the number of myogenic precursors exceeds that of resident satellite cells, implying migration or recruitment of undifferentiated progenitors from other sources. Transplantation of genetically marked bone marrow into immunodeficient mice revealed that marrow-derived cells migrate into areas of induced muscle degeneration, undergo myogenic differentiation, and participate in the regeneration of the damaged fibers. Genetically modified, marrow-derived myogenic progenitors could potentially be used to target therapeutic genes to muscle tissue, providing an alternative strategy for treatment of muscular dystrophies.

Long-term results of laparoscopic adrenalectomy for primary aldosteronism.

BACKGROUND: The management of primary aldosteronism is currently achieved by both medical and surgical treatment. Laparoscopy has in recent years unquestionably become the gold standard in adrenal surgery for benign lesions. This study aims to evaluate our clinical results among patients who underwent laparoscopic adrenalectomy (LA) for primary aldosteronism. METHODS: From January 1994 to January 2006, amid LA series, 59 primary aldosteronism patients were treated in our institution. Patients were 33 males and 26 females with mean age 49.3 yr (19-78). The mean body mass index was 25.9 kg/m2 (20.5-33.3). The mean size of lesion was 2.9 cm (1-5.5). Clinical symptoms were as follows: hypertension and symptomatic/asymptomatic hypokalemia (54), hypokalemia (5). RESULTS: Thirty-five left and 24 right LA were performed. On the left side, 22 procedures were carried out by anterior approach, 9 by anterior submesocolic route, and 4 by means of flank approach. All right procedures were completed by the anterior supine approach. The mean operative time was 103.5 min for left and 92.8 min for right adrenalectomy. There was one major complication, a colonic post-operative fistula, regarding a left adrenalectomy case. The mean post-operative hospital stay was 3 days (1-9). The cure rate of hypertension and hypokalemia was similar to the current literature results. CONCLUSIONS: LA is a safe and effective option in the treatment of primary aldosteronism. Appropriate selection of patients, larger adrenal masses and duration of symptoms are determining factors in the success rate of hypertension management.

Ubiquitin binds the amyloid ß peptide and interferes with its clearance pathways.

Several lines of evidence point to a compromised proteostasis associated with a reduction of the Ubiquitin Proteasome System (UPS) activity in patients affected by Alzheimer's Disease (AD) and suggest that the amyloid ß peptide (Aß) is an important player in the game. Inspired also by many reports, underlining the presence of ubiquitin (Ub) in the amyloid plaques of AD brains, here we set out to test whether Ub may bind the Aß peptide and have any effect on its clearance pathways. By using an integrated array of MALDI-TOF/UPLC-HRMS, fluorescence, NMR, SPR, Microscale Thermophoresis (MST) and molecular dynamics studies, we consistently demonstrated that Aß40 binds Ub with a 1 : 1 stoichiometry and K d in the high micromolar range. In particular, we show that the N-terminal domain of the Aß peptide (through residues D1, E3 and R5) interacts with the C-terminal tail of Ub (involving residues K63 and E64), inducing the central region of Aß (14HQKLVFFAEDVGSNK28) to adopt a mixed α-helix/ß-turn structure. ELISA assays, carried out in neuroblastoma cell lysates, suggest that Aß competitively binds Ub also in the presence of the entire pool of cytosolic Ub binding proteins. Ub-bound Aß has a lower tendency to aggregate into amyloid-like fibrils and is more slowly degraded by the Insulin Degrading Enzyme (IDE). Finally, we observe that the water soluble fragment Aß1-16 significantly inhibits Ub chain growth reactions. These results evidence how the non-covalent interaction between Aß peptides and Ub may have relevant effects on the regulation of the upstream events of the UPS and pave the way to future in vivo studies addressing the role played by Aß peptide in the malfunction of proteome maintenance occurring in AD.

Increased release and activity of matrix metalloproteinase-9 in patients with mandibuloacral dysplasia type A, a rare premature ageing syndrome.

Mandibuloacral dysplasia type A (MADA; OMIM 248370), a rare disorder caused by mutation in the LMNA gene, is characterized by post-natal growth retardation, craniofacial and skeletal anomalies (mandibular and clavicular hypoplasia, acroosteolysis, delayed closure of cranial sutures, low bone mass and joint contractures), cutaneous changes and partial lipodystrophy. Little is known about the molecular mechanisms by which LMNA mutations produce bone alterations. An altered bone extracellular matrix (ECM) remodelling could play a pivotal role in this disorder and influence part of the typical bone phenotype observed in patients. Therefore, we have focused our investigation on matrix metalloproteinases (MMPs), which are degradative enzymes involved in ECM degradation and ECM remodelling, thus likely contributing to the altered bone mineral density and bone metabolism values seen in five MADA patients. We evaluated the serum levels of several MMPs involved in bone development, remodelling and homeostasis, such as MMP-9, -2, -3, -8 and -13, and found that only the 82 kDa active enzyme forms of MMP-9 are significantly higher in MADA sera compared with healthy controls (n = 16). The serum level of MMP-3 was instead lower in all patients. No significant differences were observed between controls and MADA patients for the serum levels of MMP-2, -8 and -13 and of tissue inhibitor of metalloproteinase 2, a natural inhibitor of MMP-9. Similarly, normal serum levels of tumour necrosis factor alpha (TNF-alpha), interleukin (IL)-6 and IL-1beta were detected. These data suggest a possible involvement of MMP-9 in MADA disease, underlying the potential use in diagnosis and therapy.

The learning curve in laparoscopic adrenalectomy.

BACKGROUND: Laparoscopic adrenalectomy (LA) is the procedure of choice for surgical management of most adrenal tumors. LA learning curve (LC) varies among surgeons and may be influenced by factors depending on surgeon, patient, and lesion peculiarities. The aim of this study was to evaluate the LC by multi-dimensional analysis. METHODS: Between August 1994 and August 2005, 241 LA were performed in our department. Data were prospectively collected. The pre-operative variables evaluated were patient-related (age, gender, body mass index, co-morbidities) and disease-related (histology, size, and side of lesion). Level of experience of surgical team and surgical approach (anterior, flank, submesocolic routes) were evaluated as well. Flank approached and bilateral procedures were excluded, while submesocolic LA, were collected separately. Operating time (OpT), conversion rate (CR), intra-operative and post-operative complications were evaluated. Patient, surgeon, and procedure-related factors involved in LC were investigated by a multi-factorial logistic regression analysis. RESULTS: Body mass index, side, size, histology, technology improvement, and experience of surgical team, evaluated through the progressive series of surgical procedures, were independent predictors of CR and OpT. The CR for right adrenalectomy was 3% (3 cases) compared to 4.2% for left side (6 cases). The submesocolic approach significantly influenced OpT, but not CR. Mean OpT for right and left LA was 83 and 109 min, respectively. Based on surgical experience increase, the OpT and CR flattened their curves, roughly at 30 and 40 procedures for right and left LA, respectively. Post-operative complications did not change considerably throughout the series. Readmission rate within 30 days was negligible. CONCLUSIONS: Manifold factors may affect LC and outcome in LA. Their knowledge may support teaching activities as well as reducing conversion and complication rates.

Skeletal myogenic potential of human and mouse neural stem cells.

Distinct cell lineages established early in development are usually maintained throughout adulthood. Thus, adult stem cells have been thought to generate differentiated cells specific to the tissue in which they reside. This view has been challenged; for example, neural stem cells can generate cells that normally originate from a different germ layer. Here we show that acutely isolated and clonally derived neural stem cells from mice and humans could produce skeletal myotubes in vitro and in vivo, the latter following transplantation into adult animals. Myogenic conversion in vitro required direct exposure to myoblasts, and was blocked if neural cells were clustered. Thus, a community effect between neural cells may override such myogenic induction. We conclude that neural stem cells, which generate neurons, glia and blood cells, can also produce skeletal muscle cells, and can undergo various patterns of differentiation depending on exposure to appropriate epigenetic signals in mature tissues.

Electrothermal bipolar energy-based device in laparoscopic right colectomy: our experience.

AIM: Aim of the present study was to evaluate effectiveness of bipolar electrothermal energy in laparoscopic right colectomy, both for vascular pedicle ligature and dissecting manoeuvres. METHODS: Eighty-nine consecutive unselected patients underwent laparoscopic right colectomy between 2003 and 2006. All procedures were performed or supervised by the same surgical team (two staff of surgeons). Forty-four laparoscopic right colectomy were carried out with ultrasonic coagulating shears (UCS), (group 1) and forty-five by means of electrothermal bipolar atlas (EBA), (group 2). Intraoperative bleeding and postoperative blood loss, operating time, complication and hospital stay have been investigated within two groups. RESULTS: No mortality and no major intraoperative were reported in both series. A conversion to open surgery occurred in one case in both groups. A duodenal perforation occurred in UCS group as major postoperative complication. Comparing 1 and 2 series statistically significant differences were found concerning mean operating time (122.7 vs 98.4) and blood loss (220 vs 115 mL), with a P value <0.05. CONCLUSIONS: Both UCS and EBA devices were safe and effective in performing laparoscopic right colectomy. However, EBA did allow a statistically significant shorter operative time and bleeding/blood loss, tracing back its effectiveness in vessel sealing and dissection.

High efficiency myogenic conversion of human fibroblasts by adenoviral vector-mediated MyoD gene transfer. An alternative strategy for ex vivo gene therapy of primary myopathies.

Ex vivo gene therapy of primary myopathies, based on autologous transplantation of genetically modified myogenic cells, is seriously limited by the number of primary myogenic cells that can be isolated, expanded, transduced, and reimplanted into the patient's muscles. We explored the possibility of using the MyoD gene to induce myogenic conversion of nonmuscle, primary cells in a quantitatively relevant fashion. Primary human and murine fibroblasts from skin, muscle, or bone marrow were infected by an E1-deleted adenoviral vector carrying a retroviral long terminal repeat-promoted MyoD cDNA. Expression of MyoD caused irreversible withdrawal from the cell cycle and myogenic differentiation in the majority (from 60 to 90%) of cultured fibroblasts, as defined by activation of muscle-specific genes, fusion into contractile myotubes, and appearance of ultrastructurally normal sarcomagenesis in culture. 24 h after adenoviral exposure, MyoD-converted cultures were injected into regenerating muscle of immunodeficient (severe combined immunodeficiency/beige) mice, where they gave rise to beta-galactosidase positive, centrally nucleated fibers expressing human myosin heavy chains. Fibers originating from converted fibroblasts were indistinguishable from those obtained by injection of control cultures of lacZ-transduced satellite cells. MyoD-converted murine fibroblasts participated to muscle regeneration also in immunocompetent, syngeneic mice. Although antibodies from these mice bound to adenoviral infected cells in vitro, no inflammatory infiltrate was present in the graft site throughout the 3-wk study period. These data support the feasibility of an alternative approach to gene therapy of primary myopathies, based on implantation of large numbers of genetically modified primary fibroblasts massively converted to myogenesis by adenoviral delivery of MyoD ex vivo.

Interaction of inositol hexakisphosphate with liganded ferrous human hemoglobin. Direct evidence for two functionally operative binding sites.

Inositol hexakisphosphate (InsP6) binding to the oxygenated, carbonylated and nitrosylated derivatives of ferrous human hemoglobin (HbO2, HbCO and HbNO, respectively) has been measured at pH 7.0 (0.1 M Bis-Tris buffer, 0.1 M NaCl) and 20 degrees C. The observations indicate the presence of two InsP6 binding sites per tetramer in all the heme liganded hemoglobin derivatives, with different affinities for the polyphosphate. For each binding site, InsP6 interacts with similar affinity constants to HbO2, HbCO and HbNO. Such a finding indicates that different heme ligands do not alter significantly the stereochemistry of the polyphosphate binding cleft. This behaviour seems to indicate that, even though different heme ligands are likely to affect the tertiary conformation of the subunit in a different fashion, the perturbation does not seem to be transmitted to the quaternary arrangement of the whole macromolecule, and, thus, to the InsP6 binding site.

Oxidation reaction of Scapharca inaequivalvis hemoglobins with nitrite.

The oxidation reaction with nitrite of the dimeric and tetrameric hemoglobins from the mollusc Scapharca inaequivalvis has been studied kinetically and at equilibrium. In line with previous findings obtained with ferricyanide as oxidant, in both proteins the stable oxidation product is a hemichrome, although the nitrite-methemoglobin complex is formed in significant amount when excess nitrite is employed. The reaction kinetics are characterized by a lag period followed by an autocatalytic phase, as in the case of human hemoglobin. However, with respect to human hemoglobin, in the two molluscan proteins the lag phase is prolonged significantly due to the instability of their met-form, an obligatory intermediate for the onset of autocatalysis. All the data obtained in spectrophotometric, EPR and sedimentation velocity experiments under a variety of experimental conditions conform to the reaction mechanism proposed for human hemoglobin (Spagnuolo et al., Biochim. Biophys. Acta 911 (1987) 59-63) provided hemichrome formation and nitrite binding are taken into account.

Redox properties of components I and IV of trout hemoglobins: kinetic and potentiometric studies.

Redox properties of component I and IV from trout hemoglobin (Salmo irideus) have been studied kinetically and at equilibrium. In the case of component I of trout hemoglobin, the mid-point potential (Eh) is pH independent below the acid-alkaline transition (pKa approximately equal to 8.6) and decreases at higher pH, following the deprotonation of the water molecule. Similarly to human hemoglobin, the mid-point potential of component IV of trout hemoglobin is pH-dependent, but the redox Bohr effect is extended to more acid pH. Moreover, the cooperativity of the redox equilibrium process is higher than in human hemoglobin. These features parallel the oxygen-binding properties of the same hemoglobin components from trout hemolysate. Differently from human hemoglobin, the oxidation kinetics of the two hemoglobins from trout by potassium ferricyanide show markedly biphasic progress curves with pH-independent second-order rate constants. This behavior suggests a different energy barrier for the interaction with ferricyanide in the two types of subunit of both Hb components from trout.

Root effect of Panulirus interruptus hemocyanin.

Panulirus interruptus hemocyanin exhibits a progressive decrease in oxygen affinity and a parallel loss of cooperativity with decrease in pH, resulting in an apparent loss of the oxygen-binding capacity of the protein. For a characterization of this system, oxygen-binding curves have been determined over the complete range of oxygen saturation, applying a special technique which involves high-pressure spectrophotometry. Although the oxygen-binding behavior as a function of pH is complex and cannot be described within the frame of a simple two-state Monod-Wyman-Changeux model, the observed Root effect is clearly related to a progressive stabilization of a low oxygen affinity state of the protein and functional heterogeneity is not apparent.

Oxidation reaction of human oxyhemoglobin with nitrite: a reexamination.

The oxidation reaction of human oxyhemoglobin with nitrite is complex and is characterized by a lag period followed by an autocatalytic phase. On the basis of contradictory experimental results, in order to describe the time-course of the reaction, two different mechanisms have been proposed, involving either hydrogen peroxide or the superoxide anion as reaction intermediates. This paper reports a careful reinvestigation of this reaction carried out as a function of reagent concentration, buffer composition, presence of enzymatic scavengers of oxygen radicals or of other compounds which may affect the intermediate steps of the reaction. The results obtained show that: hydrogen peroxide can be definitely identified as the reaction intermediate, in agreement with the mechanism proposed by Kosaka et al. (Biochim. Biophys. Acta 702 (1982) 237-241); the reaction time-course depends in a different way on the concentrations of hemoglobin and nitrite, a finding that cannot be explained on the basis of this mechanism. A more complex reaction scheme is proposed, that provides a satisfactory description in quantitative terms for all the available experimental data.

Binding of the bovine basic pancreatic trypsin inhibitor (Kunitz) to human alpha-, beta- and gamma-thrombin; a kinetic and thermodynamic study.

Kinetic and thermodynamic parameters for the binding of the bovine basic pancreatic trypsin inhibitor (BPTI, Kunitz inhibitor) to human alpha-, beta- and gamma-thrombin have been determined, between 5 and 45 degrees C, at pH 7.5. BPTI-binding properties to human thrombins have been analyzed in parallel with those of serine (pro)enzymes acting on cationic and non-cationic substrates, with particular reference to the bovine beta-trypsin/BPTI system. The observed binding behaviour of BPTI to human alpha-, beta- and gamma-thrombin has been related to the inferred stereochemistry of the enzyme/inhibitor contact region(s).