A Correlation Between the Permeability Characteristics of a Series of Peptides Using an in Vitro Cell Culture Model (Caco-2) and Those Using an in Situ Perfused Rat Ileum Model of the Intestinal Mucosa

In an attempt to establish an in vitro/in situ correlation of intestinal permeability data, the permeability coefficients (P _app) for a series of model peptides, which were determined using an in situ perfused rat ileum model, were compared to the permeability coefficients (P _mono) determined using an in vitro cell culture model (Caco-2). The model peptides, which were all blocked on the N-terminal (acetyl, Ac) and the C-terminal (amide, NH2) ends, consisted of D-phenylalanine (F) residues (e.g., AcFNH₂, AcFFNH₂, AcFFFNH₂). To alter the degree of hydrogen bonding potential, the nitrogens of the amide bonds were sequentially methylated [e.g., AcFF(Me)FNH₂, AcF(Me)F(Me)FNH₂, Ac(Me)F(Me)F(Me)FNH₂, Ac-(Me)F(Me)F(Me)FNH(Me)]. These peptides were shown not to be metabolized in the in situ perfused rat ileum system. The results of the transport experiments showed that there were poor correlations between the apparent permeability coefficients (P _app) determined in an in situ perfused rat ileum model and the octanol–water partition coefficients (r = 0.60) or the hydrogen bonding numbers (r = 0.63) of these peptides. However, good correlations were observed between the in situ P _app values for these peptides and their partition coefficients in heptane–ethylene glycol (r = 0.96) and the differences in their partition coefficients between octanol–water and isooctane–water (r = 0.86). These results suggest that lipophilicity may not be the major factor in determining the intestinal permeability of these peptides and that hydrogen bonding potential may be a major contributing factor. A good correlation (r = 0.94) was also observed between the P _app values determined for these peptides in the in situ perfused ileum model and those P _mono values determined in the in vitro cell culture model (Caco-2) (Conradi et al., Pharm. Res. 8:1453–1460, 1991). These results suggest that the permeability values determined in the Caco-2 cell culture model may be a good predictor of the intestinal permeability of peptides.     

Synthesis and conformational analysis of a coumarinic acid‐based cyclic prodrug of an opioid peptide with modified sensitivity to esterase‐catalyzed bioconversion

Abstract: The coumarinic acid‐based cyclic DADLE (H‐Tyr‐D ‐Ala‐Gly‐Phe‐D ‐Leu‐OH) prodrug 1a exhibited more favorable physicochemical properties than did DADLE for permeation across the intestinal mucosa. However, prodrug 1a , whose bioconversion to DADLE was slow, was subject to extensive biliary clearance when administered to rats in vivo. To increase the rate of esterase‐catalyzed bioconversion of prodrug 1a , thus decreasing its biliary clearance, the oxymethyl‐modified prodrug 1 , in which an aldehyde equivalent is inserted between the phenolic group of the promoiety and the carboxylic acid group of the peptide, was synthesized from benzofuran‐2‐carboxylic acid 16 via a nine‐step procedure. Briefly, phenacyl‐protected 3‐(2‐hydroxyphenyl)‐propynoic acid 17 was coupled with Boc‐d ‐Leu‐OCH₂I 5 to give the intermediate 18 , which was further elaborated and conjugated with tetrapeptide 4 to give linear precursor 2 . Precursor 2 was then deprotected and cyclized to obtain compound 1 using a high dilution technique. In an attempt to investigate the effect of the physicochemical properties and the conformation of prodrug 1 on its permeation characteristics, we calculated its physicochemical parameters and determined its solution conformation using spectroscopic techniques (CD and NMR) and molecular dynamics simulations. Prodrug 1 showed a cLogP value and a molecular size similar to that of prodrug 1a . The deconvoluted CD spectra indicated that prodrug 1 has more random component (71%) than prodrug 1a (42%). 2D‐NMR studies of prodrug 1 showed no signals for amide–amide hydrogen interactions and few ROE cross‐peaks in ROESY spectra. Using distance restraints constructed from ROESY spectra, molecular dynamics simulations of prodrug 1 generated five conformation families. One family satisfied most of the distance restraints and all of the dihedral angles measured by NMR coupling constants. In summary, prodrug 1 showed favorable physicochemical properties for permeation of the intestinal mucosa. Prodrug 1 adopted a more random conformation in solution than prodrug 1a . These differences in solution conformation could affect the permeation of the prodrugs across the intestinal mucosa by passive diffusion and/or their ability to interact with efflux transporter(s) that would limit their transcellular permeation.     

Resection of parietal lobe gliomas： incidence and evolution of neurological deficits in 28 consecutive patients correlated to the location and morphological characteristics of the tumor

OBJECT： The goal of this study is to report the incidence and clinical evolution of neurological deficits in patients who underwent resection of gliomas confined to the parietal lobe. METHODS： Patient demographics, findings of serial neurological examinations, tumor location and neuroimaging characteristics, extent of resection, and surgical outcomes were tabulated by reviewing inpatient and office records, as well as all pre- and postoperative magnetic resonance （MR） images obtained in 28 consecutive patients who underwent resection of a glial neoplasm found on imaging studies to be confined to the parietal lobe. Neurological deficits were correlated with hemispheric dominance, location of the lesion within the superior or inferior parietal lobules, subcortical extension, and involvement of the postcentral gyms. The tumors were located in the dominant hemisphere in 18 patients （64%）; had a mean diameter of 39 mm （range 14-69 mm）; were isolated to the superior parietal lobule in six patients （21%） and to the inferior parietal lobule in eight patients （29%）; and involved both lobules in 14 patients （50%）. Gross-total resection, documented by MR imaging, was achieved in 24 patients （86%）. Postoperatively, nine patients （32%） experienced new neurological deficits, whereas seven （25%） had an improvement in their preoperative deficit. A correlation was noted between larger tumors and the presence of neurological deficits both before and after resection. Postoperatively higher-level （association） parietal deficits were noted only in patients with tumors involving both the superior and inferior parietal lobules in the dominant hemisphere. At the 3-month follow-up examination, five of nine new postoperative deficits had resolved. CONCLUSIONS： Neurological deterioration and improvement occur after resection of parietal lobe gliomas. Parietal lobe association deficits, specifically the components of Gerstmann syndrome, are mostly associated with large tumors that involve both the superior and inferior parietal lobules of the dominant hemisphere. New hemineglect or sensory extinction was not noted in any patient following resection of lesions located in the nondominant hemisphere. Nevertheless, primary parietal lobe deficits （for example, a visual field loss or cortical sensory syndrome） occurred in patients regardless of hemispheric dominance.     

Use of CO2 to move structures as an aid to percutaneous procedures

By injecting small amounts of CO2 through a needle, one can move bowel or bladder from the intended path of instruments during interventional procedures. The technique worked well in six of seven cases in the pelvis and retroperitoneum; it was not effective in the mediastinum or midabdomen (n = 6).     

Successful renal transplantation in a family with a novel mutation in COL4A3 gene and autosomal recessive Alport syndrome

Alport syndrome (AS) is an inherited disorder of basement membranes caused by mutations affecting specific proteins of the type IV collagen family, presenting with nephropathy and extrarenal manifestations such as sensorineural deafness and ocular anomalies. Ten percentage to 15% of the patients with AS have autosomal recessive (ARAS) due to mutation in either COL4A3 or COL4A4 gene. We report a novel mutation in the COL4A3 gene in an Indian family with ARAS. The above‐mentioned genetic anomaly was a missense variation in exon 26 of the COL4A3 gene (chr2:228137797G>A; c.1891G>A) that resulted in the amino acid substitution of Arginine for Glycine at codon 631 (p.Gly631Arg) that was present in the heterozygous state in the asymptomatic parents and homozygous state in the male offspring who presented with early‐onset end‐stage renal disease, lenticonus and hearing loss. The patient (male offspring) underwent successful renal transplantation with his mother as a donor.