[Sacrococcygeal chordoma simulating pilonidal cyst]. / Cordoma sacro-coccigeo simulante una cisti pilonidale.

Chordoma is a rare neoplasm arising in the cerebrospinal axis from nothochordal remnants. The commonest location is in the sacrococcygeal area, then in the sphenooccipital region and less frequently in other parts of the vertebral column. Chordoma has been found in all age groups, but the greatest incidence was found between the fifth and the seventh decades: there is a male predominance. Signs and symptoms of chordoma are related to tumor location and are often present for a long period of time because of the slow growth of the neoplasia. Sacrococcygeal chordomas may produce lower back pain, bladder or anorectal dysfunction or mass. Three histologic subtypes are currently considered: conventional, chondroid and dedifferentiated chordoma. Comparing with conventional chordoma, chondroid chordoma shows a better prognosis while dedifferentiated chordoma has a worse prognosis. However the malignant potential of chordoma is most likely due to incomplete surgical excision because of the multifocality of the neoplastic growth. For that reason, local recurrence is common and accounts in large part for the mortality for this tumor. The best treatment consists of a wide surgical excision coupled with adjuvant radiation therapy. We report a case of sacrococcygeal chordoma arised in a 48 year-old-man; the clinical features of the tumor showed a close resemblance with a pilonidal cyst. When the diagnosis of conventional chordoma was done the patient were treated by surgery and by intraoperative radiotherapy followed by external radiotherapy. This peculiar therapy was adopted in the attempt to reduce the risk of local recurrence. Six months after this treatment the patient was well and no signs of local recurrence was found by the magnetic resonance imaging.

Intrinsic pKas of ionizable residues in proteins: an explicit solvent calculation for lysozyme.

Molecular dynamics simulations of triclinic hen egg white lysozyme in aqueous solution were performed to calculate the intrinsic pKas of 14 ionizable residues. An all-atom model was used for both solvent and solute, and a single 180 ps simulation in conjunction with a Gaussian fluctuation analysis method was used. An advantage of the Gaussian fluctuation method is that it only requires a single simulation of the system in a reference state to calculate all the pKas in the protein, in contrast to multiple simulations for the free energy perturbation method. pKint shifts with respect to reference titratable residues were evaluated and compared to results obtained using a finite difference Poisson-Boltzmann (FDPB) method with a continuum solvent model; overall agreement with the direction of the shifts was generally observed, though the magnitude of the shifts was typically larger with the explicit solvent model. The contribution of the first solvation shell to the total charging free energies of the titratable groups was explicitly evaluated and found to be significant. Dielectric shielding between pairs of titratable groups was examined and found to be smaller than expected. The effect of the approximations used to treat the long-range interactions on the pKint shifts is discussed.

Molecular mechanics and electrostatic effects.

Continuum solvent models predict a quadratic charge dependence (linear response) of the free energy of a system of charged solutes. The relation between this prediction and the structure of the solvation shell around the solutes is discussed. Studies of the derivative of the free energy with respect to the charges for different reference states are shown to be a convenient way of testing the linear response assumption without resorting to the standard free energy perturbation method. We illustrate this with a system of two oppositely charged ions in aqueous solution, where nonlinearities are observed before the full charging process is completed. Since molecular mechanics (MM) simulations preserve the full nonlinearity of the problem, they are well suited to the investigation of the conditions under which linear response accurately reflects the behavior of the system. The error when using linear response theory to calculate the free energies of charging is estimated to be as large as 10-20%.

Circadian rhythms of melatonin, cortisol and prolactin in patients with obsessive-compulsive disorder.

Plasma melatonin, cortisol and prolactin (PRL) levels were measured over a 24-h period in 13 drug-free patients with obsessive-compulsive disorder and in matched healthy subjects. The circadian profiles of melatonin and PRL were altered in patients; the circadian rhythm of cortisol was preserved, although at a higher level compared with normal controls. These changes were significantly related to the severity of the obsessive-compulsive symptoms. Further studies need to clarify the state- or trait-dependent character of these abnormalities.

[Obstructive jaundice caused by solitary nonparasitic cyst of the liver]. / Ittero ostruttivo da cisti solitaria non parassitaria del fegato.

The Authors describe a rare case of obstructive jaundice secondary to solitary nonparasitic cyst of the liver. The anatomopathology, embriological and clinical aspects are analyzed with emphasis on the importance of the instrumental investigation in differential diagnosis of malignancy. Finally they describe the indications to various surgical and non surgical treatment.