链脲佐菌素致胰岛NO自由基损伤模型的建立和应用

以链脲佐菌素Streptozotocin（简称STZ）为糖尿病的诱因,以NO自由基含量为响应指标,建立了体外小鼠胰岛水平糖尿病药物筛选模型。当STZ作用浓度在0～50mmol/L内变化时,培养液中被检测到的NO大部分是来源于STZ溶于水后释放出的,而很小一部分是由胰岛培养物自身释放的,后者稳定在30～35mmol/L之间。另一方面,NO含量与胰岛素分泌量的剂量关系表明NO的增加伴随着胰岛素分泌量的下降,这标志着NO对胰岛功能的氧化性损伤,从而验证了NO作为该模型响应参量的可靠性。最终确定STZ致胰岛NO自由基损伤模型中STZ的作用浓度为5.0mmol/L,此时NO含量和胰岛素分泌量分别为STZ未加入前的10.81倍和0.43倍。最后应用该模型,快捷地考察了不同铬含量的魔芋葡甘露寡糖铬络合物（简称KOSCr）清除NO自由基的能力。     

New arylpiperazine derivatives with high affinity for alpha1A,D2 and 5-HT2A receptors

A series of novel long-chain arylpiperazines bearing a coumarin fragment was synthesized and the compounds were evaluated for their affinity at alpha(1), D(2 )and 5-HT(2A) receptors. Most of the new compounds showed high affinity for the three types of receptors alpha(1A), D(2) and 5-HT(2A) which depends, fundamentally, on the substitution of the N(4) of the piperazine ring. From the series emerged compound 6, which had an haloperidol-like profile at D(2) and 5HT(2A) receptors (pK(i) values of 7.93 and 6.76 respectively). The higher alpha(1A) receptor affinity (pA(2)=9.07) of this compound could contribute to a more atypical antipsychotic profile than the haloperidol.     

Evaluation in rabbits of different anti-SHIV vaccine strategies based on DNA/fowlpox priming and virus-like particle boosting

Two different prime-boost immunization protocols were tested in rabbits and their immune response was evaluated and compared with the final aim of defining a vaccine strategy that might be able to protect non-human primates from infection with the pathogenic simian/human immunodeficiency virus, SHIV(89.6P). The two regimens were based on three priming immunizations with either an expression plasmid plus a fowlpox (FP) recombinant vector or with two FP recombinant vectors, each one expressing either the SIV(mac239) gag/pol or the HIV-1env(89.6P) genes. In both protocols, priming immunizations were followed by two boosts with SHIV-mimicking virus-like particles (VLP). A complete SHIV-specific response was observed in all animals. Interestingly, the DNA vaccine was three to 10 times more efficient than the FP recombinant in inducing an anti-gag humoral response. Real-time PCR confirmed the memory effect on T-cell subsets secreting interleukin-4 and interferon-gamma, as a consequence of stimulation of both arms of the immune system. Although both protocols were almost equally effective in eliciting homologous neutralizing antibodies and highlighted the efficacy of VLP administration for boosting, protocol A seemed to be more effective in promoting a balanced T-cell memory immune response and appears more promising for vaccine purposes.     

15N and 1H NMR evidence for multiple conformations of the complex of dihydrofolate reductase with its substrate, folate

The binding of folate to Lactobacillus casei dihydrofolate reductase in the presence and absence of NADP+ has been studied by 15N NMR, using [5-15N]folate. In the presence of NADP+, three separate signals were observed for the single 15N atom, in agreement with our earlier evidence from 1H and 13C NMR for multiple conformations of this complex [(1982) Biochemistry 21, 5831-5838]. The 15N spectra of the binary enzyme-folate complex provide evidence for the first time that this complex also exists in at least two conformational states. This is confirmed by the observation of two separate resonances for the 7-proton of bound folate, located by two-dimensional exchange spectroscopy.     

Malic enzyme from archaebacterium Sulfolobus solfataricus. Purification, structure, and kinetic properties

An NADP-preferring malic enzyme ((S)-malate:NADP oxidoreductase (oxalacetate-decarboxylating) EC 1.1.1.40) with a specific activity of 36.6 units per mg of protein at 60 degrees C and an isoelectric point of 5.1 was purified to homogeneity from the thermoacidophilic archaebacterium Sulfolobus solfataricus, strain MT-4. The purification procedure employed ion exchange chromatography, ammonium sulfate fractionation, affinity chromatography, and gel filtration. Molecular weight determinations demonstrated that the enzyme was a dimer of Mr 105,000 +/- 2,000 with apparently identical Mr 49,000 +/- 1,500 subunits. Amino acid composition of S. solfataricus enzyme was determined and found to be significantly higher in tryptophan content than the malic enzyme from Escherichia coli. In addition to the NAD(P)-dependent oxidative decarboxylation of L-malate, S. solfataricus malic enzyme was able to catalyze the decarboxylation of oxalacetate. The enzyme absolutely required divalent metal cations and it displayed maximal activity at 85 degrees C and pH 8.0 with a turnover number of 376 s-1. The enzyme showed classical saturation kinetics and no sigmoidicity was detected at different pH values and temperatures. At 60 degrees C and in the presence of 0.1 mM MnCl2, the Michaelis constants for malate, NADP, and NAD were 18, 3, and 250 microM, respectively. The S. solfataricus malic enzyme was shown to be very thermostable.     

The coiled-coil domain of Escherichia coli FtsLB is a structurally detuned element critical for modulating its activation in bacterial cell division

The FtsLB complex is a key regulator of bacterial cell division, existing in either an off state or an on state, which supports the activation of septal peptidoglycan synthesis. In Escherichia coli, residues known to be critical for this activation are located in a region near the C-terminal end of the periplasmic coiled-coil domain of FtsLB, raising questions about the precise role of this conserved domain in the activation mechanism. Here, we investigate an unusual cluster of polar amino acids found within the core of the FtsLB coiled coil. We hypothesized that these amino acids likely reduce the structural stability of the domain and thus may be important for governing conformational changes. We found that mutating these positions to hydrophobic residues increased the thermal stability of FtsLB but caused cell division defects, suggesting that the coiled-coil domain is a “detuned” structural element. In addition, we identified suppressor mutations within the polar cluster, indicating that the precise identity of the polar amino acids is important for fine-tuning the structural balance between the off and on states. We propose a revised structural model of the tetrameric FtsLB (named the “Y-model”) in which the periplasmic domain splits into a pair of coiled-coil branches. In this configuration, the hydrophilic terminal moieties of the polar amino acids remain more favorably exposed to water than in the original four-helix bundle model (“I-model”). We propose that a shift in this architecture, dependent on its marginal stability, is involved in activating the FtsLB complex and triggering septal cell wall reconstruction.     

Schwannomas of the peroneal nerves: Clinical and functional results of surgical treatment

Objectives:Peroneal nerves Schwannomas are rare benign tumors. Literature is still poor of studies about clinical and functional outcomes after surgical treatment. We evaluated the pre-operative presentation of the disease and assessed clinical and functional outcomes after surgery.Methods:We collected all the cases of peroneal nerves’ neurinoma treated surgically between June 2016 and June 2020. We analyzed each patients’ personal data and carried out accurate clinical examinations before and after surgery. MRI was performed both pre-operatively and post-operatively.Results:We reported 9 cases of peroneal nerves schwannomas: five arising from the common peroneal nerve and four arising from the deep or superficial branches alone. Their mean size was 22.6 mm. Each patient showed sensation deficits before surgery; pre-operative MRC score was 4.2. Pre-Operative MSTS and LEFS scores were 23.6 and 64.4. Surgery was successful in each case. No local recurrence nor major complication occurred. Tumor size was significantly associated with both diagnostic delay and development of pre-operative deficits. Surgery was proven to be globally successful: post-operative evaluations highlighted a marked reduction of neurological signs and overall functional limitations.Conclusions:Surgical treatment at early stages of the disease represents a reliable and relatively safe therapeutic option.