Structural and biological investigation of chitosan/hyaluronic acid with silanized-hydroxypropyl methylcellulose as an injectable reinforced interpenetrating network hydrogel for cartilage tissue engineering

Cartilage damage continues to pose a threat to humans, but no treatment is currently available to fully restore cartilage function. In this study, a new class of composite hydrogels derived from water-soluble chitosan (CS)/hyaluronic acid (HA) and silanized-hydroxypropyl methylcellulose (Si-HPMC) (CS/HA/Si-HPMC) has been synthesized and tested as injectable hydrogels for cartilage tissue engineering when combined without the addition of a chemical crosslinking agent. Mechanical studies of CS/HA and CS/HA/Si-HPMC hydrogels showed that as Si-HPMC content increased, swelling rate and rheological properties were higher, compressive strength decreased and degradation was faster. Our results demonstrate that the CS and HA-based hydrogel scaffolds, especially the ones with 3.0% (w/v) Si-HPMC and 2.5/4.0% (w/v) CS/HA, have suitable physical performance and bioactive properties, thus provide a potential opportunity to be used for cartilage tissue engineering. In vitro studies of CS/HA and CS/HA/Si-HPMC hydrogels encapsulated in chondrocytes have shown that the proper amount of Si-HPMC increases the proliferation and deposition of the cartilage extracellular matrix. The regeneration rate of the CS/HA/Si-HPMC (3%) hydrogel reached about 79.5% at 21 days for long retention periods, indicating relatively good in vivo bone regeneration. These CS/HA/Si-HPMC hydrogels are promising candidates for tissue compatibility injectable scaffolds. The data provide proof of the principle that the resulting hydrogel has an excellent ability to repair joint cartilage using a tissue-engineered approach.

RESEARCH HIGHLIGHTS

• An injectable hydrogel based on CS/HA/Si-HPMC composites was developed.
• The CS/HA/Si-HPMC hydrogel displays the tunable rheological with mechanical properties.
• The CS/HA/Si-HPMC hydrogel is highly porous with high swelling and degradation ratio.
• Increasing concentration of Si-HPMC promote an organized network in CS/HA/Si-HPMC hydrogels.
• Injectable CS/HA/Si-HPMC hydrogels have a high potential for cartilage tissue engineering.

     

Alterations in membrane-bound and cytoplasmic K-ras protein levels in mouse lung induced by treatment with lovastatin,cholestyramine, or niacin: effects are highly mouse strain dependent

Agents that either increase (cholestyramine, CS) or decrease (lovastatin, Lov) de novo peripheral cholesterol synthesis may increase (CS) or decrease (Lov) ras protein membrane localization by altering protein prenylation, and potentially have pro- or anti-carcinogenic effects. Male A/J, Swiss, and C57/BL6 mice were treated with 2 or 4% CS, 1% dietary niacin, or 25mg/kg of Lov three times per week (Lov-3X) or five times per week (Lov-5X). After 3 weeks, serum cholesterol and triglycerides were determined enzymatically. Membrane and cytoplasmic K-ras proteins in lung were determined by immunoprecipitation followed by western blotting with a K-ras specific antibody. Results confirmed the hypothesis only in isolated instances. A/J mice had a significant 30% increase in cytoplasmic K-ras and a 40% decrease in membrane K-ras from Lov treatment, as predicted. C57/BL6 mice had a significant 77% increase in membrane K-ras, as expected from CS feeding. At variance with the hypothesis, Swiss mice had increased levels (3-28%) of membrane K-ras with all treatments (including Lov), and C57/BL6 mice treated with Lov had a 58-78% increase in cytoplasmic K-ras without any reduction in the levels of membrane K-ras. Niacin, predicted to have no effect on ras membrane localization, decreased cytoplasmic K-ras in A/J mice, increased both membrane and cytoplasmic K-ras in Swiss mice, and had no effect in C57/BL6 mice. Results may have differed from those predicted because of strain-dependent differences in response to the cholesterol-lowering agents. A difference in response among the mouse strains suggests that individual genetic differences may alter the effect of hypocholesterolemic agents on K-ras membrane localization, and potentially the risk of ras-dependent cancer.     

高强度聚焦超声治疗8例剖宫产术后腹壁子宫内膜异位症临床初步报告

目的探讨高强度聚焦超声(HIFU)在治疗剖宫产术后腹壁子宫内膜异位症中的临床应用价值。方法利用HIFU单独或联合药物治疗8例剖宫产术后腹壁子宫内膜异位症患者。结果5例患者临床症状消失,2例患者临床症状缓解,1例患者临床症状无缓解后行手术治疗,无皮肤灼伤、大出血、疼痛等并发症出现,有效率87.5%。结论HIFU治疗剖宫产术后腹壁子宫内膜异位症,具有初步的临床应用价值。     

Clinical and Experimental Aspects of Olmesartan Medoxomil,a New Angiotensin II Receptor Antagonist

Olmesartan medoxomil is a new orally active angiotensin II (Ang II) type 1 receptor antagonist. It is a prodrug and is rapidly de‐esterified during absorption to form olmesartan, the active metabolite. Olmesartan is a potent, competitive and selective Ang II type 1 receptor antagonist. Olmesartan is not metabolized by the cytochrome P‐450 and has a dual route of elimination, by kidneys and liver. In patients with essential hypertension olmesartan medoxomil administered once daily at doses of 10–80 mg dose‐dependently reduced diastolic blood pressure (DBP). Troughto‐peak ratios for both DBP and systolic blood pressure (SBP) were above 50%. At the recommended once‐daily starting doses, olmesartan medoxomil (20 mg) was more effective than losartan (50 mg), valsartan (80 mg) or irbesartan (150 mg) in reducing cuff DBP in patients with essential hypertension. The results of cuff SBP and mean 24‐h DBP and SBP were similar to those of cuff DBP measurement. In mild‐to‐moderate hypertensive patients the recommended starting dose of olmesartan medoxomil was as effective as that of amlodipine besylate (5 mg/day) in reducing both cuff and 24‐h blood pressure. In lowering DBP olmesartan medoxomil, at 10–20 mg/day, was as effective as atenolol at 50–100 mg/day. In mild‐to‐moderate hypertensive patients, olmesartan medoxomil, at 5–20 mg once daily, was more effective than captopril at 12.5–50 mg twice daily. At 20–40 mg once daily olmesartan medoxomil was as effective as felodipine, at 5–10 mg once daily. Olmesartan medoxomil has minimal adverse effects with no clinically important drug interactions. Animal studies have shown that olmesartan medoxomil provides a wide range of organ protection. Olmesartan medoxomil ameliorated atherosclerosis in hyperlipidemic animals and ameliorated cardiac remodeling and improved survival in rats with myocardial infarction. Olmesartan medoxomil has renoprotective effects in a remnant kidney model and type 2 diabetes models. Future investigation should reveal whether these beneficial effects of olmesartan medoxomil are applicable to human diseases.     

An investigation on the nature of continuous avoidance deficits: differential response to chlordiazepoxide treatment

Four groups of 18 rats each were given 12 30-min sessions of lever press avoidance training with long and equal response-shock (R-S) and shock-shock (S-S) intervals (30 sec) and a high shock intensity (2 mA for 2 sec), but with different stimulus conditions. A 2×2 design was used, with (A) light on versus light off as CS in the last 10 sec of R-S, and (B) different versus equal stimulus conditions in R-S and S-S (respectively CS on versus CS off in S-S). Each group was then subdivided into two subgroups receiving either placebo or chlordiazepoxide for 12 additional sessions, starting 23 days after the last pretraining session (20 mg/kg s.c. 30 min before testing for the first 6 sessions and 40 mg/kg for the remaining 6 sessions). Finally, all animals were given 3 additional series of 6 or 5 sessions each without treatment, starting respectively 2, 30 and 58 days after the last drug or placebo session. The data confirmed that continuous avoidance tasks with long and equal R-S and S-S intervals and strong punishment are difficult to learn. The use of light off as CS and the use of CS off in S-S led to a further retardation of avoidance learning. All untreated groups, except the one with light on as CS and CS on in S-S, still received an average of about 70% of the scheduled shocks after a total of 41 sessions (20.5 hr of training). A clear-cut drug facilitation was obtained in the schedule with light off as CS and Cs on in S-S, while slight or even opposite effects were obtained in the other schedules. Furthermore, the very low asymptotic performance in the untreated group with light off as CS and CS on in S-S permitted the demonstration of a significant carry-over effect in this schedule, i.e., a much higher performance in previously treated, than in previously untreated animals during the posttreatment period. The above results were compared with those of limited tests carried out with amphetamine and scopolamine after the completion of the main experiment, showing a wider range of facilitating effects with the latter drugs, than with chlordiazepoxide. These results may be taken as evidence that chlordiazepoxide lacks general stimulant and/or response-disinhibiting properties. Therefore, the drug allows the emission of available responses suppressed by punishment, but not of responses not learned due to the lack of appropriate feedbacks in the early phases of training.     

Combination of acute preoperative plateletpheresis, cell salvage, and aprotinin minimizes blood loss and requirement during cardiac surgery

Acute preoperative plateletpheresis (APP), cell salvage (CS) technique, and the use of aprotinin have been individually reported to be effective in reducing blood loss and blood component transfusion while improving hematological profiles in patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). In this prospective randomized clinical study, the efficacy of these combined approaches on reducing blood loss and transfusion requirements was evaluated. Seventy patients undergoing primary coronary artery bypass grafting (CABG) were randomly divided into four groups: a control group (group I, n = 10) did not receive any of the previously mentioned approaches. An APP and CS group (group II, n = 20) experienced APP in which preoperative platelet-rich plasma was collected and reinfused after reversal of heparin, along with the cell salvage technique throughout surgery. The third group (group III, n = 22) received aprotinin in which 5,000,000 KIU Trasylol was applied during surgery, and a combination group (group IV, n = 18) was treated with all three approaches, i.e., APP, CS, and aprotinin. Compared with group I (896+/-278 mL), the postoperative total blood loss was significantly reduced in groups II, III, and IV (468+/-136, 388+/-122, 202+/-81 mL, respectively, p < 0.05). The requirements of packed red blood cells in the three approached groups (153+/-63, 105+/-178, 0+/-0 mL, respectively) also were reduced when compared with group I (343+/-118 mL, p < 0.05). In group I, six patients (6/10) received fresh-frozen plasma and three patients (3/10) received platelet transfusion, whereas no patients in the other three groups required fresh-frozen plasma and platelet. In conclusion, both plateletpheresis concomitant with cell salvage and aprotinin contribute to the improvement of postoperative hemostasis, and the combination of these two approaches could minimize postoperative blood loss and requirement.     

Normal development and post-traumatic plasticity of corticospinal neurons in rats

Corticospinal (CS) neurons projecting to the spinal cord in the adult rat, identified by retrograde axonal transport of horseradish peroxidase (HRP), formed a caudal band in areas 3, 4, and 6 and a rostral band in area 10, separated by a gap. In the infant the gap was filled with CS neurons. The problem: What happened to the transient infant neurons as the mantle expanded, and would they persist if other CS neurons were destroyed in infancy? Identification of CS neurons by HRP and measurements of the growth of the mantle and cortical areas 3, 4, and 6 showed that CS neurons were scattered widely in the cortex as well as in the gap and future bands at 2 to 10 days. By about 2 weeks, CS neurons labeled from the cervical cord were limited to the “adult” bands. The greatest mantle expansion postnatally was in the occipital and bregma regions, including the anterior, but not the posterior, part of area 3, 4, and 6. Thus, expansion of the mantle, growth of areas 3, 4, and 6, and axonal growth of transient and permanent CS neurons did not parallel each other closely. When one or both caudal band regions were ablated at 5, 7, or 10 days, the gap CS neurons persisted bilaterally to adult life. No necrosis of layer V neurons was observed between 10 days and 2 weeks. It was assumed that the gap neurons and other extraneous CS neurons generated exploratory axons which normally disappeared, but when caudal band neurons were destroyed the transient axons attempted to fill the pathway.     

Modulation of auditory cortex unit activity during the performance of a conditioned response

Single-unit activity in primary auditory cortex was studied in unanesthetized, paralyzed cats during the performance of a classical conditioning task. The conditioned stimulus was a 0.5-s white noise (WN) burst paired with tail shock delivered 4.5 s later. Cats habituated to WN without shock served as controls. Overlayed on these tasks was a continuous background of 1/s, behaviorally irrelevant, 100-ms duration tone bursts set to the best frequency and optimal intensity for the particular unit being studied. Spontaneous activity and tone responses following WN were compared with the respective activity preceding WN. The spontaneous or evoked activity of 75% of the cells recorded in the trained animals changed significantly after WN, whereas the activity of 28% of the cells recorded in habituated animals changed. Augmentation and suppression of both spontaneous and evoked activity were found. These results have implications for the encoding of acoustic stimuli in terms of the modulation of lemniscal sensory system activity.