Mechanism of l-cysteine-induced fibrous structural changes of soybean protein at different high-moisture extrusion zones

In this study, the fibrous structure formation mechanism of soybean protein during high moisture extrusion processing was investigated using a dead-stop operation, and based on the interaction between soybean protein concentrate (SPC) and L-cysteine (CYS). The thermal properties, SDS-PAGE and particle size distribution of the samples from different extrusion zones were investigated. It was revealed that the addition of a moderate amount of CYS (0.1 %) promoted the fibrous structure formation in the SPC extrudates and optimised the textural properties of the SPC extrudates. In the extruder barrel, addition of CYS (0.1 %) promoted protein depolymerisation and unfolding in the mixing and cooking zones, and facilitated protein aggregation in the die and cooling zones. Protein solubility and raman spectroscopy revealed that disulfide bonds were principally responsible for fibrous structure formation; favoured when the intermolecular disulfide bonds (t-g-t mode) was increased. Finally, the transformation of protein conformation was revealed by secondary structure and surface hydrophobicity, which confirmed that the effect of CYS on protein conformation mainly occurred in the cooling zone. This study provides a theoretical basis for the application of CYS to regulate the fibrous structure of meat analogues.

Cytomegalovirus Infection and Alzheimer's Disease: A Meta-Analysis

BACKGROUND

Evidence on the association of cytomegalovirus (CMV) infection with Alzheimer's disease (AD) is scarce and the results are inconsistent.

OBJECTIVE

To investigate the association of CMV infection with the risk of AD.

METHODS

Observational studies on the relationship between CMV infection and AD were identified from PubMed, Embase, Web of Science, and the Cochrane Library until September 30, 2022. The quality of included studies was assessed using the Newcastle-Ottawa Scale. Random-effect meta-analysis was performed using a generic inverse-variance method, followed by sensitivity analyses and subgroup analyses based on study designs, regions, adjustments, and population types.

RESULTS

Our search yielded 870 articles, of which 200 were duplicates and 663 did not meet the inclusion criteria, and finally yielded seven studies with 6,772 participants. No strong evidence was observed in the summary analysis for the association of CMV infection and risk of AD (odds ratio [OR] = 1.33; 95% confidence interval [CI]: 0.88, 2.03, I2 =69.9%). However, subgroup analysis showed that an increased risk of AD was detected in East Asians (OR = 2.39; 95% CI: 1.63, 3.50, I2 = 0.00%), cohort studies (OR = 1.99; 95% CI: 1.35, 2.94, I2 = 28.20%), and studies with confounder adjustment (OR = 2.05; 95% CI: 1.52, 2.77, I2 = 0.00%).

CONCLUSIONS

This meta-analysis provides evidence to support the heterogeneity of the associations between CMV infection and AD. Future studies with larger sample sizes and multi-ethnic populations are necessary.

Use of soybean oil to modulate the gel properties of soybean protein isolation-wheat gluten composite with or without CaCl2

BACKGROUND

Plant protein is widely used in the study of animal protein substitutes and healthy sustainable products. The gel properties are crucial for the production of plant protein foods. Therefore, the present study investigated the use of soybean oil to modulate the gel properties of soybean protein isolation-wheat gluten composite with or without CaCl2 .

RESULTS

Oil droplets filled protein network pores under the addition of soybean oil (1-2%). This resulted in an enhanced gel hardness and water holding capacity. Further addition of soybean oil (3-4%), oil droplets and some protein-oil compounds increased the distance between the protein molecule chain. The results of Fourier transform infrared spectroscopy and intermolecular interaction also showed that the disulfide bond and β-sheet ratio decreased in the gel system, which damaged the overall structure of the gel network. Compared with the addition of 0 m CaCl2 , salt ion reduced the electrostatic repulsion between proteins, and local protein cross-linking was more intense at 0.005 m CaCl2 concentration. In the present study, structural properties and rheological analysis showed that the overall strength of the gel was weakened after the addition of CaCl2 .

CONCLUSION

The presence of appropriate amount of soybean oil can fill the gel pores and improve the texture properties and network structure of soy protein isolate-wheat gluten (SPI-WG) composite gel. Excessive soybean oil may hinder protein-protein interaction and adversely affect protein gel. In addition, the presence or absence of CaCl2 significantly affected the gelling properties of SPI-WG composite protein gels. © 2023 Society of Chemical Industry.

Impact of Insoluble Dietary Fiber and CaCl2 on Structural Properties of Soybean Protein Isolate-Wheat Gluten Composite Gel

The effect and mechanism of soybean insoluble dietary fiber (SIDF) (0~4%) and CaCl₂ (0~0.005 M) on the properties of soybean protein isolate (SPI)-wheat gluten (WG) composite gel were studied. It was revealed that the addition of insoluble dietary fiber (1~2%) increased the strength and water-holding capacity (WHC) of the composite gel (p < 0.05) and enhanced the gel network structure compared with the control. WHC and LF-NMR showed that the water-binding ability of the gel system with only 2% SIDF was the strongest. The addition of excessive SIDF increased the distance between protein molecules, impeded the cross-linking of protein, and formed a three-dimensional network with low gel strength. The infrared spectrum and intermolecular force indicated that the interaction between SIDF and SPI were mainly physical, and the hydrophobic interaction and disulfide bond were the main forces in the gel system. The addition of CaCl₂ can increase the critical content of gel texture destruction caused by SIDF, and the gel strength attained its peak at 3% SIDF, indicating that appropriate CaCl₂ improved gel structure weakening caused by excessive SIDF. This study provides insights in enhancing the production of multi-component composite gel systems.

Effect of polysaccharides on the rheological behaviour of soy-wheat protein aggregation and conformational changes during high-moisture extrusion

BACKGROUND

Due to the extrusion black box effect, polysaccharides determine the formation of meat-like fibrous structures by modulating the flow behaviour and structural changes of plant proteins under high-moisture extrusion conditions. However, there is limited knowledge on the mechanism of resolution. This study simulated the rheological properties of soy protein-wheat protein under 57% moisture conditions with addition of 4% sodium alginate (SA), 2% xanthan gum (XG), and 2% maltodextrin (MD). The effect of these polysaccharides on the aggregation behaviour and conformation of raw protein during high-moisture extrusion was investigated.

RESULTS

It was revealed that the three polysaccharides were effective in increasing the interaction between proteins and between proteins and water. Among them, 4% SA elicited a significantly stronger storage modulus (gelation behaviour) compared to the control. Analysis of different zones of extrudates by protein electrophoresis, particle size, and turbidity showed that SA-4% was able to form more high molecular protein aggregates (> 245 kDa) and promoted crosslinking of low molecular subunits (< 48 kDa), resulting in moderately sized protein aggregated particles. Fluorescence and ultraviolet spectra showed the transformation of protein tertiary structures in different extrusion zones, confirming that the key extrusion zone for protein conformational transformation by polysaccharides is the die-cooling zone. Furthermore, stretching of polypeptide chains and accelerated protein rearrangement facilitated the formation of more fibrillar structures.

CONCLUSION

Theoretical support for polysaccharide modulation of plant protein quality in high moisture extruded products is provided by this study. © 2023 Society of Chemical Industry.

The decreased circular RNA hsa_circ_0072309 promotes cell apoptosis of ischemic stroke by sponging miR-100

OBJECTIVE

To investigate the expression of circ_0072309 in patients with ischemic stroke (IS) and in LIFR humanized mice with middle cerebral artery occlusion (MCAO). Further, we explored the underlying mechanism of circ-0072309 in IS.

MATERIALS AND METHODS

The content of circ-0072309 in serum of patients with IS (n = 70) was measured by qRT-PCR, and the ROC curve was analyzed. LIFR humanized mice were used to measure the content of circ-0072309 in ischemic hemisphere by qRT-PCR and the protein expression of cleaved-caspase-3, cleaved-caspase-8 were detected by Western blot. After that, the expression of miR-100 in serum of patients with IS and in ischemic hemisphere of MCAO mice were detected, and then, we analyzed the correlation between the expression of circ-0072309 and miR-100. The binding sites between circ-0072309 and miR-100 were predicted by online database. We detected whether cric-0072309 bind to miR-100 by Dual-Luciferase report in bEnd2. In addition, bEnd2 was treated with oxygen-glucose deprivation (OGD) to simulate injury of cerebral vascular after cerebral ischemia. After treated with miR-100 mimic or miR-100-inhibitor, we detected the cell survival and rate of cell apoptosis, and the content of cleaved-caspase-3 and caspase-8 protein. The target mRNA of miR-100 was predicted by bioinformatics analysis and analyzed by Dual-Luciferase. After treating bEnd2 with circ-0072309 and miR-100 mimic, we analyzed the cell survival and apoptosis to identify the potential regulatory mechanism.

RESULTS

The results of qRT-PCR showed that the expression of circ-0072309 was significantly decreased while the content of miR-100 was significantly increased in the serum of IS patients and in the ischemic hemisphere of MCAO mice. There was a negative correlation between the expression of circ-0072309 and miR-100. The results of Dual-Luciferase showed that circ-0072309 could directly bind to miR-100. After treating bEnd2 with OGD, miR-100-mimic caused a decrease rate of cell survival and an increased rate of apoptosis. Dual-Luciferase showed that miR-100 regulated cell survival and apoptosis by directly binding to mTOR. By comparing treated bEnd2 with circ-0072309, co-transfected bEnd2 with circ-0072309 and miR-100 reduced cell survival and increased apoptosis.

CONCLUSIONS

According to these results, this study revealed that the circ_0072309-miR-100-mTOR regulatory axis could alleviate IS, and it may be a potential target for the treatment of IS.

[Analysis of outcomes and learning curve of endoscopic transsphenoidal surgeries for 124 patients with pituitary adenomas]

OBJECTIVE

To investigate the outcomes of the Endoscopic transsphenoidal surgery for patients with pituitary adenomas, analyze the learning curve and provide reference for future surgeries.

METHODS

Retrospective analysis was carried out on 124 patients by endoscopic transsphenoidal surgery with a single neurosurgeon over a period spanning from January 2010 to January 2014 at Peking Union Medical College Hospital.The changes of endocrine and tumor imaging before and after surgery were analysed. Operative time and complication rates of one surgeon in the early period of learning curve were compared with that in later period.

RESULTS

There were significant differences in Gross total resection (GTR) rate of pituitary adenomas with different sizes and different Knosp classifications (P<0.01, P<0.01). GTR rate of huge adenomas was significantly lower than that of macroadenoma and adenomas (P<0.05). GTR rate of Knosp 4 grade adenoma was significantly lower than that of Knosp 0-3 level (P<0.05). No significant difference in GTR among all types of functional pituitary adenomas and hormone levels after surgery was observed (P>0.05). In addition, no significant difference (P>0.05) in complications among different sizes, Knosp grade and type of pituitary adenomas was observed.GTR of Knosp 4 adenoma in later period of the learning curve was significantly higher than that in early period (P<0.05). Meanwhile the operative time was significantly lower than early period (P<0.05).

CONCLUSIONS

Endoscopic transsphenoidal pituitary adenoma resection has the advantages of wider surgical field, higher GTR rate, less trauma, fewer complications and better life quality of patients.Through standardized learning, the GTR rate of the invasive pituitary adenomas can be improved.

Analysis of bromocriptine treatment in pregnant pituitary prolactinoma patients

OBJECTIVE

To investigate the therapeutic effects and duration of bromocriptine treatment during pregnancy in patients with pituitary prolactinoma.

MATERIALS AND METHODS

A retrospective analysis of the clinical data of 230 female pituitary prolactinoma patients at the Beijing Union Medical College Hospital neurosurgery clinic from January 2001 to May 2014 was conducted. When confirmed pregnant, patients in the control group immediately stopped taking bromocriptine, but patients in the treatment group continued to take the same dose of bromocriptine.

RESULTS

The embryos stop rate in the control group was 16.7%, significantly higher than the rate in the natural population (p < 0.05), while the rate in the treatment group (0.9%) not statistically different from that of the natural population (p > 0.05). There was no significant difference in the embryonic malformation rate between the two study groups compared to the normal pregnancy group (p > 0.05).

CONCLUSION

Pregnant pituitary prolactinoma patients should not stop bromocriptine treatment, but should instead continue with the same dose for four months. For patients with macroadenoma, bromocriptine should be taken during the entire pregnancy. Blood prolactin, progesterone, human chorionic gonadotropin (hCG), and visual dysfunction should be monitored every two weeks during treatment. Patients should be treated with progesterone and hCG if the blood levels become too low. If regular monitoring shows that prolactin has increased too fast and/or visual dysfunction worsened, the dose of bromocriptine should be in- creased. The authors have found that bromocriptine treatment during pregnancy significantly reduces the embryo stop rate without in- creasing the embryo deformity rate; therefore, bromocriptine treatment is safe and necessary during pregnancy of pituitary prolactinoma patients.

[The surgery of thyrotropin-secreting pituitary adenomas and the significance of thyroid stimulating hormone level in follow-up]

Objective: To explore the clinical characteristics of thyrotropin-secreting pituitary adenomas and the effect of the transsphenoidal approach of procedure with/without drug treatment for thyrotropin-secreting pituitary adenomas, and to investigate the correlation between the prognosis of thyrotropin-secreting pituitary adenomas and the postoperative level of thyroid stimulating hormone (TSH). Methods: A total of 45 patients with thyrotropin-secreting pituitary adenoma who hospitalized in Peking Union Medical College Hospital from 2000 to 2015 were enrolled in the study.We collected the clinical features, hormone levels, imaging findings, treatment and follow-up data of these patients. Results: The average age of the patients was 40.26 years old and the average disease duration was 5.83 years.Among them, 8 cases were microadenomas and 37 cases were macroadenoma.Thirty patients were treated with somatostatin analogues before surgery.TSH level was significantly decreased after operation (P=0.012). All of them had done the pituitary surgery, including 44 transsphenoidal surgery and 1 subfrontal surgery that had recurrence one year after the transsphenoidal surgery.The TSH level of 34 cases went back to normal on the third day after surgery.The remission rates on three months and one year after surgery in patients with TSH level<0.1 mIU/L on postoperative day (POD) 3 were significantly higher than those in patients with TSH level>0.1 mIU/L on POD3.As well as the remission rates on three months and one year after surgery in patients with TSH level normal on postoperative one month were significantly higher than those in patients with TSH level abnormal on postoperative one month. Conclusions: TSH level of postoperative one month could be used to predict prognosis and monitor recurrence.

[The value and comparison of plasma adrenocorticotropic hormone and urinary free cortisol in predicting long-term outcome after operation of Cushing's disease]

Objective: To study and the value of morning plasma adrenocorticotropic hormone (ACTH) and urinary free cortisol (24 h UFC) within 3 days after operation in patients with Cushing's disease in predicting the long-term outcome. Methods: The clinical data of 140 patients with Cushing's disease who were treated in Department of Neurosurgery of PUMCH from 2012 to 2014 were analyzed retrospectively.The univariate analysis, multivariate Logistic analysis, ROC curve analysis and other statistical methods were used to study the predicting value of morning plasma ACTH and 24 h UFC in 3 days post operation. Results: Univariate analysis showed that in the two groups of the early remission and no remission, there was significant statistical difference between the preoperative ACTH, preoperative 24 h UFC, postoperative ACTH and postoperative 24 h UFC (P<0.05, <0.01, <0.01). Logistic analysis showed that ACTH and 24 h UFC after operation of two groups had significant difference (P<0.01, <0.05). ROC curve analysis showed that postoperative cutoff values of ACTH and 24 h UFC were 4.11 pmol/L (18.7 pg/ml) and 281.42 nmol (102 μg)/24 h. ROC analysis was performed to evaluate the predicting performance of postoperative ACTH, resulting in an area under the curve (AUC) of 0.917 (95%CI: 0.858-0.957, P<0.01). In comparison, 24 h UFC had an AUC of 0.814 (95%CI: 0.739-0.875, P<0.01). The predicting value of ACTH is significantly better than that of 24 h UFC (P=0.005). Conclusion: Early morning 24 h UFC and ACTH within 3 days after operation both showed considerable accuracy in predicting the long-term outcome of Cushing's disease, and the significance of ACTH was even greater than that of 24 h UFC.

[Use early morning serum cortisollevel to evaluate the effect of Cushing's disease after transsphenoidal surgery]

OBJECTIVE

To predict the therapeutic effect of Cushing's disease after transsphenoidal surgery by using morning serum cortisol level.

METHODS

The clinical data of 275 cases that had transsphenoidal surgery in Peking Union Medical College Hospital from 2010 to 2014 were analyzed retrospectively.Early morning serum cortisol level less than 140 nmol/L 3 days postoperation was usedto predict endocrinological remission. And long-term efficacy was evaluated by follow-up.

RESULTS

Of the 275 patients, there were 49 males and 226 females; average age was 36.5 years old.Remission wasconfirmed in 201 cases, the remission rate was 73.1%, and 8 cases recurrent duringfollow-up.There were 17 macroadenomas, theremission rate was 47.1%; 258 microadenomas and MRI negative adenomas, the remission rate was 74.8%.And 43 recurrent cases had reoperations; the remission rate was 46.5%.

CONCLUSION

Early morningserum cortisol 3 days post operation can evaluate the effectof transsphenoidal surgery, but even if the level of cortisol is less than 140 nmol/L, there is still tumor recurrence.Patients should be follow-up for a lifetime.

Mechanical comparison between lengthened and short sacroiliac screws in sacral fracture fixation: a finite element analysis

OBJECTIVE

To compare the stability of lengthened sacroiliac screw and standard sacroiliac screw for the treatment of unilateral vertical sacral fractures; to provide reference for clinical applications.

METHODS

A finite element model of Tile type C pelvic ring injury (unilateral Denis type II fracture of the sacrum) was produced. The unilateral sacral fractures were fixed with lengthened sacroiliac screw and sacroiliac screw in six different types of models respectively. The translation and angle displacement of the superior surface of the sacrum (in standing position on both feet) were measured and compared.

RESULTS

The stability of one lengthened sacroiliac screw fixation in S1 or S2 segment is superior to that of one sacroiliac screw fixation in the same sacral segment. The stability of one lengthened sacroiliac screw fixation in S1 and S2 segments respectively is superior to that of one sacroiliac screw fixation in S1 and S2 segments respectively. The stability of one lengthened sacroiliac screw fixation in S1 and S2 segments respectively is superior to that of one lengthened sacroiliac screw fixation in S1 or S2 segment. The stability of one sacroiliac screw fixation in S1 and S2 segments respectively is markedly superior to that of one sacroiliac screw fixation in S1 or S2 segment. The vertical and rotational stability of lengthened sacroiliac screw fixation and sacroiliac screw fixation in S2 is superior to that of S1.

CONCLUSION

In a finite element model of type C pelvic ring disruption, S1 and S2 lengthened sacroiliac screws should be utilized for the fixation as regularly as possible and the most stable fixation is the combination of the lengthened sacroiliac screws of S1 and S2 segments. Even if lengthened sacroiliac screws cannot be systematically used due to specific conditions, one sacroiliac screw fixation in S1 and S2 segments respectively is recommended. No matter which kind of sacroiliac screw is used, if only one screw can be implanted, the fixation in S2 segment is more recommended than that in S1.

LEVEL OF EVIDENCE

Experimental study Level III.

Molecular cloning and characterization of the mouse and human TUSP gene, a novel member of the tubby superfamily

We report here the cloning and characterization of a novel gene belonging to the tubby superfamily proteins (TUSP) in mouse and human. The mouse Tusp cDNA is 9120 bp in length and encodes a deduced protein of 1547 amino acids, while the human TUSP gene is 11,127 bp and encodes a deduced protein of 1544 amino acids. The human and mouse genes are 87% identical for their nucleotide sequences and 85% identical for their amino acid sequences. The protein sequences of these genes are 40-48% identical to other tubby family proteins at the C-terminal conserved 'tubby domain'. In addition, the TUSP proteins contain a tubby signature motif (FXGRVTQ), two bipartite nuclear localization signals (NLSs) at the C-terminal, two proline-rich regions, one WD40 repeat region and one suppressor of cytokines signaling domain. Transfection assay with green fluorescent protein-tagged TUSP expression constructs showed that the complete TUSP protein and the N-terminal portion of TUSP are localized in the cytoplasm but the C-terminal portion with the two NLSs produced distinct dots or spots localized in the cytoplasm. Northern blotting analysis showed that the major transcript with the complete coding sequence is expressed mainly in the brain, skeletal muscle, testis and kidney. Radiation hybrid mapping localized the mouse gene to chromosome 17q13 and the human TUSP gene to chromosome 6q25-q26 near the type 1 diabetes gene IDDM5. However, association analysis in diabetic families with a polymorphic microsatellite marker did not show any evidence for association between TUSP and type 1 diabetes. The precise biological function of the tubby superfamily genes is still unknown; the highly conserved tubby domain in different species, however, suggests that these proteins must have fundamental biological functions in a wide range of multi-cellular organisms.

Molecular cloning and characterization of a novel mammalian endo-apyrase (LALP1)

Here we describe the cloning, localization, and characterization of a novel mammalian endo-apyrase (LALP1) in human and mouse. The predicted human LALP1 gene encodes a 604-amino acid protein, whereas the mouse Lalp1 gene encodes a 606-amino acid protein. The human and mouse genes have 88% amino acid sequence identity. These genes share considerable homologies with hLALP70, a recently discovered mammalian lysosomal endo-apyrase. The human LALP1 gene resides on chromosome 10q23-q24 and contains 12 exons and 11 introns covering a genomic region of approximately 46 kilobase pairs. The subcellular localization and enzymatic activity of LALP1 indicated that LALP1 is indeed an endo-apyrase with substrate preference for nucleoside triphosphates UTP, GTP, and CTP.

Structure of neurolysin reveals a deep channel that limits substrate access

The zinc metallopeptidase neurolysin is shown by x-ray crystallography to have large structural elements erected over the active site region that allow substrate access only through a deep narrow channel. This architecture accounts for specialization of this neuropeptidase to small bioactive peptide substrates without bulky secondary and tertiary structures. In addition, modeling studies indicate that the length of a substrate N-terminal to the site of hydrolysis is restricted to approximately 10 residues by the limited size of the active site cavity. Some structural elements of neurolysin, including a five-stranded beta-sheet and the two active site helices, are conserved with other metallopeptidases. The connecting loop regions of these elements, however, are much extended in neurolysin, and they, together with other open coil elements, line the active site cavity. These potentially flexible elements may account for the ability of the enzyme to cleave a variety of sequences.

Crystallization and preliminary analysis of neurolysin

Neuropeptidases inactivate or modify the activity of peptide neurotransmitters and neurohormones. The neuropeptidase neurolysin acts only on short peptides and accepts a variety of cleavage-site sequences. Structures of the enzyme and enzyme-substrate complexes will help to determine the mechanisms of substrate selectivity used by this enzyme. Crystals of recombinant neurolysin have been grown in the orthorhombic space group P2(1)2(1)2, with unit-cell parameters a = 157.8, b = 88.0, c = 58.4 A. Data have been collected to 2.3 A at 110 K with observed diffraction to 1.8 A. Circular dichroism measurements suggest that the enzyme is primarily alpha-helical, with little beta-strand secondary structure. Sequence-based secondary-structure prediction supports this conclusion.

Physical and biological properties of compound membranes incorporating a copolymer with a phosphorylcholine head group

A copolymer (PMB) having a polar head group 2-methacryloyloxyethyl phosphorylcholine (MPC) copolymerized with n-butyl methacrylate (BMA) may provide a haemocompatible surface for implantable devices. Pure PMB membranes and compound membranes composed of PMB coated onto polyurethane (PU + PMB) and poly(vinyl chloride) (PVC + PMB) have been prepared. Fundamental studies on these membranes included the analysis of molecular distribution and orientation, the characterization of surface physical properties and the examination of blood membrane interactions. The experimental techniques used were Fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Significant differences between PU + PMB and PVC + PMB membranes were found. Compound PVC + PMB and pure PMB membranes exhibited favourable surface properties for haemocompatibility and also showed low adhesion of blood components, whereas PU + PMB displayed the contrary. This leads to the hypothesis that the underlying material has a major influence on the surface properties of compound membranes.

[Hemorheologic change after strong blood flow disturbance caused by gunshot and its influence on the prognosis of the wounded animals]

Three types of experimental models were used in this study: 1. Both thighs of dogs were wounded by 5.56 mm bullet. 2. Femoral artery and vein were tied at the time of wounding. 3. Shock caused by simply bleeding the dogs' femoral arteries. We observed the characteristics of change hemorheology and analyzed its effects on the wounded dogs. The results showed that strong blood flow disturbances always brought about hemorheologic changes such as rapidly increased blood viscosity and red cell's aggregation index and the simultaneous phenomenon of blood concentration. These may be related to extensive endothelium injury and destruction of a number of blood cells caused by disturbance wave. The above change may give rise to abnormality of microcirculation and disturbance of matter transmission; in that sense, it may provide the physiopathologic basis for the occurrence and development of the complication.

[Chemical constituents of Strychnos nitida G. Don]

Six compounds were isolated from the root and stem of Strychnos nitida for the first time. On the basis of chemical properties and spectral data, the compounds were identified as beta-sitosterol, strychnine, brucine, cantieyine, lignoceric acid and palmitic acid.

Heterologous expression and characterization of recombinant Lactococcus lactis neutral endopeptidase (neprilysin)

A neutral endopeptidase (NEP) from Lactococcus lactis has recently been cloned and shown to contain high sequence homology with the human neutral endopeptidase, endopeptidase 24.11 (I. Mierau et al., J. Bacteriol. 175, 2087-2096, 1993). The gene for the neutral endopeptidase from L. lactis was cloned into the pQE expression vector, resulting in the fusion of a hexahistidine at the N-terminus. The recombinant enzyme was expressed to high levels in Escherichia coli (approximately 10 mg/liter of culture) and purified to homogeneity in a two-step procedure. A number of peptides were studied as substrates for the enzyme. The enzyme cleaves the following peptides at the Gly3-Phe4 bond: enkephalins, dynorphins A-6, A-8, A-9, A-10, A-13, and A-17, and alpha-neo-endorphin. In addition the enzyme hydrolyzes bradykinin, substance P, beta-endorphin, ACTH, and VIP. Although the cleavage patterns observed are similar to that seen with mammalian neutral endopeptidase, the lactococcal enzyme more efficiently cleaves larger peptide substrates. As observed with the mammalian neutral endopeptidase, the lactococcal enzyme exhibits higher kcat/K(m) values for the enkephalins than for their corresponding amides, indicating the functionality of an active-site arginine. Inactivation of the lactococcal endopeptidase by diethyl pyrocarbonate and protection afforded by the substrate dynorphin A-6 indicate the functionality of a positionally conserved active-site histidine. This was confirmed by demonstrating that conversion of this histidine, histidine 587, to glutamine generated inactive enzyme. Similarly, conversion of the putative zinc ligand glutamate 535 to glutamine led to inactive enzyme. These studies indicate a conservation of critical catalytic residues between the two enzymes and suggest that the lactococcal endopeptidase is a better model than thermolysin for the mammalian enzyme.

Activation of rat choline acetyltransferase by limited proteolysis

In the past, purification of choline acetyltransferase (ChAT, EC 2.3.1.6.), the enzyme responsible for the biosynthesis of the neurotransmitter acetylcholine, has yielded fragmented species of the enzyme. The nature and possible function of these forms of ChAT are not well understood. Using a bacterial expression system, recombinant rat ChAT in its active form has been purified to homogeneity. The purified enzyme was found to be activated to >25-fold when assayed at low ionic strength and >5-fold when assayed at high ionic strength by limited proteolysis with either trypsin or chymotrypsin, but not with proteinase K. The activated ChAT shows an increased Km for both substrates, diminished sensitivity to salt activation and a pH optimum that is shifted approximately 1 pH unit. On a denaturing SDS-polyacrylamide gel, the activated ChAT is composed of three to four polypeptides; however, it migrates as an intact 68-k-Da protein species on gel filtration. In order to delineate the site of cleavage by proteolysis, the newly generated fragments have been subjected to N-terminal sequencing. By comparing cleavage sites between trypsin and chymotrypsin, the putative activation sites were identified.

Borrelia burgdorferi DNA in biological samples from patients with sarcoidosis using the polymerase chain reaction technique

Polymerase chain reaction (PCR) was used to detect the presence of Borrelia burgdoferi DNA in biological samples from patients with sarcoidosis. The target DNA sequence was of chromosomal origin. The amplified DNA sequence was analyzed by agarose gel electrophoresis, PAGE with silver staining, and the identity of amplified DNA was confirmed by restriction enzyme cleavage and DNA-DNA hybridization with a 32P-labelled probe. The assay was sensitive to fewer than two copies of B. burgdorferi genome, even in the presence of a 10(4)-fold excess of human eukaryotic DNA, and was also specific to different B. burgdorferi strains tested. Sera serologically positive to B. burgdorferi (n = 26), bronchoalveolar lavage fluid and supernatant of BALF (n = 26) and peripheral blood (n = 9) from sarcoidosis patients were tested. The positive rate was low (4/26, 2/26, and 0/9, respectively). It was considered that DNA from B. burgdorferi may be identified in a minority of patients with sarcoidosis, and it may play a pathogenetic role in such cases. More studies need to be done before advancing the hypothesis of an etiologic role of B. burgdorferi in sarcoidosis.

Expression, purification, and characterization of recombinant Drosophila choline acetyltransferase

A cDNA for Drosophila choline acetyltransferase (EC 2.3.1.6; ChAT) was fused with a polyhistidine sequence and expressed in Escherichia coli. The recombinant enzyme was purified to a specific activity of 500 mumol/min/mg of protein using metal affinity chromatography and ion exchange chromatography. Kinetic properties of the recombinant enzyme did not differ significantly from those previously determined. Circular dichroism (CD) spectra revealed that the secondary structure of the enzyme is largely alpha-helical. Intrinsic fluorescence spectra of the enzyme indicate that its tryptophan residues are buried. Neither CD nor fluorescence spectra changed significantly in the presence of substrates. The cysteine content of the recombinant Drosophila ChAT was determined to be 16 in the absence and 22 in the presence of 6 M guanidine hydrochloride. Finally, crystallization of recombinant Drosophila ChAT was achieved.