Reversible Self-Assembly of Backbone-Thermoresponsive Long Chain Hyperbranched Poly(N-Isopropyl Acrylamide)

In this paper, we mainly described the reversible self-assembly of a backbone-thermoresponsive, long-chain, hyperbranched poly(N-isopropyl acrylamide) (LCHBPNIPAM) in aqueous solution. Here, we revealed a reversible self-assembly behavior of LCHBPNIPAM aqueous solution derived from temperature. By controlling the temperature of LCHBPNIPAM aqueous solution, we tune the morphology of the LCHBPNIPAM self-assemblies. When the solution temperature increased from the room temperature to the lower critical solution temperature of PNIPAM segments, LCHBPNIPAM self-assembled from multi-compartment vesicles into solid micelles. The morphology of LCHBPNIPAM self-assemblies changed from solid micelles to multi-compartment vesicles again when the temperature decreased back to the room temperature. The size presented, at first, an increase, and then a decrease, tendency in the heating-cooling process. The above thermally-triggered self-assembly behavior of LCHBPNIPAM aqueous solution was investigated by dynamic/static light scattering, transmission electron microscopy, atomic force microscopy, fluorescence spectroscopy, ¹H nuclear magnetic resonance in D₂O, and attenuated total reflectance Fourier transform infrared spectroscopy. These results indicated that LCHBPNIPAM aqueous solution presents a reversible self-assembly process. The controlled release behaviors of doxorubicin from the vesicles and micelles formed by LCHBPNIPAM further proved the feasibility of these self-assemblies as the stimulus-responsive drug delivery system.

Needlescopic, laparoscopic, and open appendectomy: a comparative study

SUMMARY

The benefits of laparoscopic appendectomy appear to be controversial. Since 1994, several abdominal procedures have been completed by using the needlescopic technique, but there appear to be no prospective studies to demonstrate the perceived benefits of needlescopic appendectomy. The authors compared open, laparoscopic, and needlescopic appendectomy in a randomized fashion with regard to duration of surgery, length of hospitalization, analgesic dosage, and surgery-associated complications. From March to July 1998, 75 patients admitted at the emergency station of the authors' hospital with a final diagnosis of acute appendicitis without tumor formation were randomized to receive one of the three treatment categories: open (OA), laparoscopic (LA), and needlescopic (nLA) appendectomy. Laparoscopic and needlescopic appendectomy were performed by using a three-port technique, although the size of the trocar used varied. There were 26 patients in the OA group, 23 in the LA group, and 26 in the nLA group. The mean operation durations for the OA, LA, and nLA groups were 55.4 +/- 28.0 minutes, 69.1 +/- 48.8 minutes, and 62.3 +/- 26.3 minutes, respectively, and these were not significantly different from one another. The mean number of the analgesic doses (Pethidine 1 mg/kg) required was 1.3 +/- 1.2 mg/kg, 0.5 +/- 0.8 mg/kg, and 0.2 +/- 0.6 mg/kg, respectively. Significant differences were noted when comparing the OA with the LA or nLA groups (OA vs. LA, P = 0.02; OA vs. nLA, P = 0.0002; LA vs. nLA, P = 0.06). The mean oral intake durations were 32.2 +/- 16.9 hours, 21.0 +/- 14.6 hours, and 20.8 +/- 16.4 hours, respectively, after surgery for the OA, LA, and nLA groups, and the between-group differences were statistically significant for the OA versus LA group ( P = 0.004) and for the OA versus nLA group ( P = 0.003). The mean durations of hospitalization for the OA, LA, and nLA groups were 3.6 +/-1.8 days, 2.8 +/- 1.4 days, and 2.4 +/- 0.9 days, and difference was detected between the OA and the nLA groups ( P = 0.02). The OA group rendered a greater wound-complication rate and ileus than did the other two groups, but the differences were not detected between the three categories ( P = 0.065, 0.6935). The result of the current study confirmed that the nLA procedure is a feasible and safe one. The nLA procedure provided substantial advantages over the OA procedure in the contexts of diminished postoperative pain and shorter hospital stay without significant increases in postoperative complication rate or surgical time.

Laparoscopic versus open vertical banded gastroplasty for the treatment of morbid obesity

Vertical banded gastroplasty (VBG) is an effective treatment for morbid obesity. Recent advancement in laparoscopic surgery has made laparoscopic VBG possible. The authors compared retrospectively the outcomes of laparoscopic VBG versus open VBG in patients with morbid obesity. From June 1998 to April 1999, 100 patients (18 men, 82 women; average age, 32.6 years) underwent laparoscopic VBG, and 40 patients (7 men, 33 women; average age, 28.8 years) underwent conventional open VBG. The two groups were similar regarding sex, age, and body mass index distribution. Mean surgical time, blood loss estimate, duration of postoperative recovery, analgesic usage, complications, and weight reduction were compared among the two groups. Laparoscopic VBG was successful in 99 (99%) of the 100 patients. Mean surgical time was longer in duration for the laparoscopic VBG group than it was for the open VBG group (173 vs. 101 minutes, P < 0.01). The laparoscopic VBG group had earlier flatus passage (1.9 vs. 2.6 days; P < 0.01), less usage of analgesics (meperidine 50 mg/unit; 0.9 vs. 2.3 units; P < 0.01), and a shorter postoperative hospital stay (3.7 vs. 6.0 days; P < 0.01). Estimated blood loss, surgical complication rate, and weight reduction were similar among the two groups. Although laparoscopic VBG required a longer surgical time and was technically more demanding, it resulted in shorter recovery time, less analgesic use, and less severe physical discomfort. The authors' findings show that the two methods were approached safely equally.

Duration of action and tissue distribution of zinc protoporphyrin in neonatal rats

Zinc protoporphyrin IX (ZnPP) has been shown to inhibit heme oxygenase (HO) activity effectively in vivo and has potential in the treatment of neonatal jaundice. Because this is a transitional or temporary condition lasting only several days, an effective chemopreventive agent with a relatively short duration of action would be desirable for the treatment of severe neonatal jaundice. To determine the effective duration of action of ZnPP, we administered either 40 nmol/g of body weight ZnPP or 5 microL/g body weight diluent intraperitoneally to neonatal rats 24-36 h after birth. Between 0 and 21 d after ZnPP dosing, the duration of action was investigated through measurements of serum bilirubin and hepatic and splenic HO inhibition, which were correlated to measurements of ZnPP distribution. Significant (p < 0.05) hepatic HO inhibition, ranging from 27 to 51%, was observed in the liver between 1 and 4 d after dosing, concurrent with a 23-28% reduction in serum bilirubin levels, and was associated with ZnPP tissue concentrations of 27-38 nmol/g. Splenic HO was not inhibited measurably by the much lower concentrations of ZnPP found in the spleen (2.8-20.1 nmol/g) between 0 and 21 d after dosing. Furthermore, HO isoform 1 (HO-1) induction was apparently not a confounding factor in the duration of action of ZnPP, because the modest increases in HO-1 protein levels were not sustained longer than 24 h after ZnPP administration. Our findings demonstrated that the duration of action of ZnPP in neonatal rats is less than 1 wk. The reduction in serum bilirubin levels, the short duration of action and minimal confounding effects suggest that ZnPP may be an effective chemopreventive agent for the treatment of severe neonatal jaundice.