BACKBONE TORSIONAL POTENTIAL FUNCTIONS FOR ROTATIONS ABOUT N-Cα AND Cα-C BONDS IN DIPEPTIDE MODEL SYSTEMS IN RELATION TO NUCLEAR MAGNETIC RESONANCE AND INFRA RED SPECTRAL DATA*

A comparative study of the conventional three-fold torsional potential functions (referred to as “Old V”), the potential function having zero φ barrier and a twofold ψ-barrier, proposed from this laboratory (“Int V”), and those developed recently in this laboratory from the study of dipeptide conformations in protein crystal structures (“New V”) has been carried out by comparing theoretically calculated and experimentally observed NH-C^αH coupling constants from n.m.r. studies and the relative occupancy of hydrogen-bonded conformations from i.r. studies of dipeptide model systems. It is observed that no fully satisfactory agreement with both n.m.r. and i.r. data is possible in any one of the three functions. For the hydrogen bond-disrupting solvent DMSO, (NH-C^αH) coupling constant values were predicted equally well in all three. However, only for New V are values of the constants A (= 8.62), B (= -2.33), C (= 1.51) as obtained by the least-squares method in the expression J(θ) = A cos²θ+ B cos θ+ C sin²θ such that J-values in excess of 10Hz, observed experimentally in some cases, are permissible. However, the same potential function yields unsatisfactory agreement in the case of hydrogen bond-promoting solvent CCl₄. This was interpreted to be because the potential function concerned was obtained from data in solid state where solvent interaction is absent. In view of the lack of satisfactory agreement with the solution data for all three potential functions, it was concluded that solvent effects other than the promotion of intramolecular hydrogen bonding, which were ignored in the present study, must be taken into account for better prediction of experimental data from theoretical potential functions.     

Chronic oral arsenic intoxication as a possible aetiological factor in idiopathic portal hypertension (non-cirrhotic portal fibrosis) in India.

Estimates were made of the arsenic concentration in liver specimens from nine patients having idiopathic portal hypertension (IP), and in four livers these were found to be significantly higher than those in patients with cirrhosis and in control subjects. The splenovenogram revealed extensive portosystemic collateral circulation. Corrected sinusoidal pressure and blood flow studies showed higher levels in four patients than in normal subjects. Microscopic examination of liver tissues revealed periportal fibrosis. The higher hepatic arsenic levels that were found were due to the inadvertent drinking of water contaminated with arsenic, adulterated opium, and indigenous medicines. A history of opium intake was not forthcoming but two patients had drunk water contaminated with arsenic and two others had taken bhasams (Ayurvedic medicines prepared by repeated oxidation of ores). Though the aetiology of idiopathic portal hypertension is not known, it is possible that arsenic intake may be one of the factors.     

Y chromosome microdeletions in azoospermic patients with Klinefelter＇s syndrome

Aim： To study the occurrence of Y chromosome microdeletions in azoospermic patients with Klinefelter＇s syndrome （KFS）. Methods： Blood and semen samples were collected from azoospermic patients with KFS （n = 14） and a control group of men of proven fertility （n = 13）. Semen analysis was done according to World Health Organization （WHO） guidelines. Blood samples were processed for karyotyping, fluorescent in situ hybridization （FISH） and measurement of plasma follicle stimulating hormone （FSH） by radioimmunoassay. To determine Y chromosome microdeletions, polymerase chain reaction （PCR） of 16 sequence tagged sites （STS） and three genes （DFFRY, XKRY and RBM1 Y） was performed on isolated genomic DNA. Testicular fine needle aspiration cytology （FNAC） was done in selected cases. Results： Y chromosome microdeletions spanning the azoospermia factor （AZF）a and AZFb loci were found in four of the 14 azoospermic patients with KFS. Karyotype and FISH analysis revealed that, of the four cases showing Y chromosome microdeletion, three cases had a 47,XXY/46,XY chromosomal pattern and one case had a 46,XY/47,XXY/48,XXXY/48,XXYY chromosomal pattern. The testicular FNAC of one sample with Y chromosome microdeletion revealed Sertoli cell-only type of morphology. However, no Y chromosome microdeletions were observed in any of the 13 fertile men. All patients with KFS had elevated plasma FSH levels. Conclusion： Patients with KFS may harbor Y chromosome microdeletions and screening for these should be a part of their diagnostic work-up, particularly in those considering assisted reproductive techniques. （Asian JAndrol 2006 Jan; 8： 81-88）     

Fluid resuscitation in major burns

BACKGROUND: The Parkland formula is established as the "gold standard" for initial fluid resuscitation for major burns. The purpose of this study was to review our fluid resuscitation practice for major burns to determine whether anecdotal observations of significant variations from the Parkland formula were wide spread and whether any difference could be used as a basis for a revision of fluid resuscitation in major burns. METHODS: A retrospective review of 127 presentations to The Alfred Burns Unit with total body surface area (TBSA) affected > or =15% was conducted. A retrospective review of the resuscitation data from these patients was compared with the Parkland formula as well as other studies. RESULTS: A total of 49 patients with complete data on fluid administration and uncomplicated burns were included in the analysis. Significantly larger volumes of fluid (5.58 mL/kg per %TBSA) were given to these patients in the first 24 h than predicted by the Parkland formula. Mean arterial pressure, pulse rate and urine output were at satisfactory levels. Clinically evident complications from fluid administration were minimal. Mortality was similar to that in other centres. CONCLUSION: Fluid resuscitation volumes significantly higher than those predicted by the Parkland formula were given, without adverse consequences. This retrospective review supports a prospective, multicentre, randomized, controlled study comparing this study with the Parkland formula, resulting in a better guide to initial fluid resuscitation in major burns.     

Shape imposed by secondary structure of a polypeptide affects its free diffusion through liquid-filled pores

The purpose of the present study was to investigate the effect of secondary structure of three model polypeptides on their apparent permeability (P(app)) across a synthetic, microporous membrane. Poly-L-lysine (PL), poly-L-glutamate (PGlu), and poly-L-lysine-L-phenylalanine (1:1) (PLP) were selected because a solution environment in which their predominant secondary structure is random coil (RC), alpha-helix, and beta-sheet, respectively, is easily achieved. The conformation of each polypeptide was verified by circular dichroism (CD). Diffusion studies were conducted under sink conditions at 25 degrees C across a microporous polyester membrane using a donor concentration of 0.02 mM for each model polypeptide. NMR was utilized to obtain a second estimation of the diffusion coefficient for each polypeptide. The equivalent hydrodynamic radii (R(e)) of the three model polypeptides were calculated using the values of the diffusion coefficient obtained by both NMR and the classic in vitro diffusion studies. The viscosity of each polypeptide solution was also determined to investigate the effect of viscosity on the aqueous diffusion coefficient. Statistical analysis demonstrated a significant (P < 0.05) difference in both P(app) and the aqueous diffusion coefficient (D(aq)), as well as the calculated R(e) values, between all three model polypeptides and there was no significant (P > 0.05) difference in the viscosity of the polypeptide solutions. Values of D(aq) and R(e) calculated from the diffusion studies were in relatively close agreement to those obtained using NMR. The logarithm of P(app) was highly correlated (r = -0.961) with the values of R(e) calculated from NMR (R(e (NMR))) rather than the mw of the polypeptides (r = 0.681). Values of the Perrin or shape factor which deviate substantially from unity are suggestive of a non-spherical or ellipsoid shape and were 1.22 +/- 0.20, 1.55 +/- 0.11, and 2.38 +/- 0.20 for PGlu, PL, and PLP, respectively. In conclusion, the observed difference in the membrane transport/diffusion of the three model polypeptides is suggested to be due to the shape associated with the secondary structure of each macromolecule, rather than the polypeptide's mw or the viscosity of the dilute polypeptide solution.