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.     

家兔化学裸露心肌标本制备及其张力-pCa关系

家兔右室乳头肌在含3mM EDTA、5mM Na_2ATP、10mM Tris、140 mM KCl的溶液中浸浴150min,其Ca~(2+)通透性显著增高。Ca~(2+)浓度为10~(-7)M时,便可产生张力,10~(-4.6)M时,张力达到最大。相对张力-pCa(Ca~(2+)浓度的负对数)关系近似一S形曲线,产生50％最大张力的Ca~(2+)(pCa_(50))约为10~(-6.6)M。同法制备的大鼠乳头肌Ca~(2+)通透性未见增高。     

Post-capillary venules in the “milky spots” of the greater omentum are the major site of plasma protein and leukocyte extravasation in rodent models of peritonitis

Intraperitoneal injection of inflammatory agents in the mouse and rat causes plasma protein and leukocyte extravasation into the peritoneal cavity. Following an intraperitoneal injection of zymosan A, the milky spots of the omentum were the only abdominal sites detected where intravenously administered Monastral Blue labeled interendothelial cell gaps responsible for plasma extravasation. In addition, when colored microspheres were intraventricularly administered to quantify blood flow, the omentum was the only abdominal organ which showed an increase in blood flow during zymosan A peritonitis. A combination of light and electron microscopy, plus measurement of myeloperoxidase activity (a marker of neutrophil accumulation) demonstrated that the omental milky spots are the major route through which leukocytes migrate into the peritoneal cavity. Identical structures in the pleura likewise are the sites of protein leakage into the pleural cavity. In contrast, selective sites of protein and cellular extravasation could not be detected in the synovial lining of the inflamed knee joint.     

Influence of preformed α-helix and α-helix induction on the activity of cationic antimicrobial peptides

One prominent class of cationic antibacterial peptides comprises the α-helical class, which is unstructured in free solution but folds into an amphipathic α-helix upon insertion into the membranes of target cells. To investigate the importance of α-helicity and its induction on interaction with membranes, a series of peptides was constructed based on a hybrid of moth cecropin (amino acids 1-8) and bee melittin (amino acids 1-18) peptides. The new peptides were predicted to have a high tendency to form α-helices or to have preformed α-helices by virtue of construction of a lactam bridge between glutamate and lysine side-chains at positions i and i+ 4 at various locations along the primary sequence. In two examples where the use of lactam bridge constraints induced and stabilized α-helical structure in benign (aqueous buffer) and/or hydrophobic medium, there was a decrease in antibacterial activity relative to the linear counterparts. Thus the preformation of α-helix in solution was not necessarily beneficial to antimicrobial activity. In the one case where the lactam bridge did result in increased antibacterial activity (lower minimal inhibitory concentration values) it did not increase α-helical content in benign or hydrophobic medium. Broadly speaking, good activity of the peptides against Pseudomonas aeruginosa correlated best (r²= 0.88) with a helican parameter which was calculated as the induction of α-helix in α membrane-mimicking environment divided by the α-helix formation under benign conditions. Interestingly, the activity of the lactam bridge peptide constructs correlated in part with alterations in bacterial outer or cytoplasmic membrane permeability.     

Analysis of Intestinal Perfusion Data for Highly Permeable Drugs Using a Numerical Aqueous Resistance—Nonlinear Regression Method

Purpose. To develop, validate and apply a method for analyzing the intestinal perfusion data of highly permeable compounds using the Numerical Aqueous Resistance (NAR) theory and nonlinear regression (NAR-NLR) and to compare the results with the well-established Modified Boundary Layer (MBL) Analysis. Methods. The NAR-NLR method was validated and the results were compared to the MBL analysis results using previously reported cephradine jejunal perfusion data. Using the Single Pass Intestinal Perfusion (SPIP) method, the concentration dependence of intestinal permeability was investigated for formycin B, proline, and thymidine, three compounds reported to be absorbed by carrier-mediated transport processes. The MBL and NAR-NLR analyses were then applied to the three sets of SPIP data. Results. The results demonstrate that the intrinsic MBL transport parameters were highly variable and, in one case, the analyses failed to give a statistically significant Michaelis constant. The MBL mean dimensionless wall permeabilities (P*_w) were greater than the NAR-NLR P*_w and were also highly variable. In all cases, the NAR-NLR variability was significantly lower than the MBL variability. The extreme variability in the MBL-calculated P*_w is due to the sensitivity of P*_w when the fraction of unabsorbed drug (C_m/C_o) is low or, alternatively, when P*_w approached the aqueous permeability, P*_aq. Conclusions. The NAR-NLR method facilitates the analysis of intestinal perfusion data for highly permeable compounds such as those absorbed by carrier-mediated processes at concentrations below their K_m. The method also allows for the use of a wider range of flow conditions than the MBL analysis resulting in more reliable and less variable estimates of intestinal transport parameters as well as intestinal wall permeabilities.     

Lateral percutaneous spinothalamic tractotomy

Summary The main elements of the perrcutaneous spinothalamic tractotomy technique by the lateral approach are presented and the results obtained in 163 consecutive patients are communicated. We emphasize the importance of its early use in cases of intractable pain avoiding drug addiction. The simplicity of the method permits a less strict selection of the patients compared with the classic open cordotomy.     

Preventing percutaneous absorption of industrial chemicals: the "skin" denotation

Percutaneous absorption has received comparatively little attention in occupational health, although this route of entry has repeatedly caused occupation-related intoxications. In practice, the evaluation of skin penetration rates is far from simple. Much evidence has been obtained from studies of chemicals used for cosmetics and topical therapeutics, but the information available on compounds encountered in occupational health is limited. The data obtained from experimental studies have confirmed that the concentration, type of vehicle, skin area, skin condition, and extent of occlusion are important factors in determining the degree of percutaneous absorption, but no general model has been developed. Also, too little is known about the basic chemical properties governing the rate of penetration. Thus, prediction is difficult and bound to be rather inaccurate. Current preventive practice follows the procedure used by ACGIH and is mainly based on a "skin" denotation in official listings of chemicals to which exposure limits have been allocated. The number of substances and groups of chemicals which have received skin denotation in 17 selected countries varies between 24 and 179 and a total of 275 are listed as a skin hazard in one or more countries; ACGIH lists 143. Thus, the denotation practice varies. As an unfortunate result of these discrepancies and the dichotomy of skin denotation, the absence of skin denotation may erroneously indicate that efforts to protect the skin are unnecessary. Thus, an evaluation of skin penetration potentials should be incorporated in occupational health practice as a supplement to the official denotations.     

经皮射频消融与手术切除治疗直径≤ 3 cm原发性小肝癌的疗效分析

目的 分析经皮射频消融（PRFA）与手术切除治疗直径≤3 cm原发性小肝癌的疗效。方法 选取2015年1月—2017年6月兰州市第二人民医院收治的原发性小肝癌患者78例。将36例接受PRFA治疗的患者作为观察组,另外42例行手术切除的患者作为对照组。采用全自动生化分析仪检测血清谷草转氨酶（AST）、谷丙转氨酶（ALT）、总胆红素（TBIL）水平,电化学发光全自动免疫分析仪检测血清甲胎蛋白（AFP）水平。结果 观察组手术时间、术中出血量、住院时间均少于对照组（P <0.05）;观察组治疗前后AST、ALT、TBIL、AFP的差值均高于对照组组（P <0.05）。两组术后并发症比较,差异无统计学意义（P>0.05）;两组治疗后1、2、3、5年的生存率和复发率比较,差异均无统计学意义（P>0.05）。结论 与手术切除比较,PRFA治疗直径≤3 cm原发性小肝癌可缩短手术时间,减少术中出血量,促进肝功能恢复,但两者术后并发症发生率、生存率和复发率接近。