Computational studies on biphenyl derivatives. Analysis of the conformational mobility,molecular electrostatic potential,and dipole moment of chlorinated biphenyl: searching for the rationalization of the selective toxicity of polychlorinated biphenyls (PCBs)

With the objective to understand how the pattern and degree of chlorination influence on the properties of the title molecules, a computational study on biphenyl and all the chlorinated biphenyls (from 1 to 10 chlorine atoms, 209 congeners) has been undertaken. The study includes conformational searches (and further refinement by molecular dynamics simulations) and the ab initio calculation of the molecular electrostatic potential (MEP) and the dipole moments for all the congeners. The most significant property is the MEP, finding a good correlation between the MEPs and the substitution pattern on chlorinated biphenyls. The most toxic congeners possess highly positive values of electrostatic potential on the aromatic rings and highly negative values of electrostatic potential on the chlorine atoms. Additionally, we have found that the toxic congeners possess conformations with low dipole moments, a fact that may be linked to the ready accumulation on the adipose tissue. The results on the geometry and electrostatic properties of chlorinated biphenyls can be useful to rationalize their selective toxicities.     

Cytodiagnosis of yolk sac tumor

To analyze cytomorphologic features of yolk sac tumors of childhood. Four cases of pediatric yolk sac tumor (YST), diagnosed by Fine needle aspiration cytology were reviewed (1998–2002). Age of patients ranged from 11/2 to 5 years. Three cases presented clinically with an intra-abdominal mass while one case presented with a testicular mass. Fine needle aspirates had been obtained directly as well as under radiologic (USG/CT) guidance. Smears were stained with H & E and Papanicolaou stain. In all cases values of serum α-Fetoprotein and ΒhCG were available preoperatively. Histopathologic diagnosis was correlated with cytologie findings in all the cases. Cytologie examination showed richly cellular smears with a combination of morphological patterns. Characteristically, tumor cells were arranged in papillary groups, tight cell clusters and formed acinar structures. Cells showed enlarged, moderately pleomorphic, hyperchromatic nuclei and moderate amount of cytoplasm, some of which displayed cytoplasmic vacuolation, displacing the nuclei eccentrically. Preoperatively, serum α-fetoprotein level was raised in all cases. Histopathology confirmed the cytologie diagnosis. Yolk sac tumor is common among the germ cell tumors of pediatric age group which presents a spectrum of cytomorphologic features having important differences with other germ cell neoplasm,e.g. embryonal carcinoma. Clinicoradiologic features and tumor markers are additionally helpful for an accurate cytologie diagnosis.     

Chronic cocaine pretreatment facilitates Pavlovian sexual conditioning in male Japanese quail

Repeated drug exposure that results in behavioral sensitization has been shown to enhance sex-seeking behaviors in rats as well as facilitate Pavlovian excitatory and inhibitory conditioning. In the present experiment, male Japanese quail were given repeated presentations of cocaine (10 mg/kg, i.p.) that resulted in increased locomotor activity relative to saline. After a 10-day withdrawal period, subjects received sexual conditioning trials that consisted of presentation of an object conditioned stimulus (CS) followed by sexual reinforcement. Results showed that birds that previously received chronic cocaine demonstrated more conditioned approach behavior to the CS object, a shorter latency to copulate with a female, and made more cloacal contacts (copulatory behavior) during sexual reinforcement than saline-treated birds. The findings suggest that chronic cocaine later facilitates Pavlovian conditioning in a sexual behavior paradigm. This may be the result of cocaine facilitating learning via the dopaminergic system. The findings are discussed in the context of the incentive sensitization theory and possible neuronal mechanisms.     

The clinical application of posterior resin-bonded cast metal restorations

There has been much interest in the development of adhesive dentistry over recent years. Greater understanding of materials and bonding methods have improved the clinical predictability of restorations. Resin-bonded cast metal restorations can now provide a genuine alternative to conventional fixed restorations for both premolar and molar teeth. This paper illustrates the clinical application of such restorations.     

The relation between the clinical subtypes of delirium and the urinary level of 6-SMT

Delirium is a common syndrome among hospitalized elderly patients. In humans, sleep and circadian rhythms are disturbed during delirium, and both are influenced by the hormone melatonin. This prompted us to investigate the relationship of the clinical subtypes of delirium: 1). hyperactive, 2). hypoactive, and 3). mixed, with melatonin, as reflected by a patient's urinary metabolite 6-SMT. Results support our hypothesis that urinary 6-SMT during delirium was higher in hypoactive and lower in hyperactive patients. Because this is the first time a biochemical parameter related to the clinical subtypes of delirium has been reported, further research on the link between melatonin and delirium is necessary.     

The prognostic importance of c-myc oncogene expression in head and neck melanoma

Melanomas of the head and neck have a poorer prognosis than melanomas arising at other cutaneous sites. To study the biology of this disease, the expression of the c-myc oncogene was studied in tumors from 97 patients with head and neck melanoma using the technique of flow cytometry. Survival analysis revealed that stratification of patients according to oncogene expression provided a prognostic marker with shorter overall survival in tumors with high nuclear c-myc oncoprotein positivity (log-rank test, chi2 = 8.77, p < 0.005). Multifactorial analysis using Cox's proportional hazards model revealed nuclear c-myc oncoprotein to be an independent prognostic marker (log-rank test, chi2 = 8.82, p = 0.005). These results support the authors' previous studies of the prognostic value of c-myc expression in melanoma and suggest that estimation of c-myc oncoprotein may be of clinical importance in identifying high-risk patients.