A comparison of patients’ heart rate variability and blood flow variability during surgery based on the Hilbert–Huang Transform

Previous studies have indicated that heart rate variability (HRV) is considered to be one of the effective parameters for assessing autonomous nervous system activity. Therefore, HRV can be used to detect the state of patients during surgery, even for estimating depth of anaesthesia (DOA). However, the heartbeat can be affected by anaesthesia drugs, breathing rate and electric influence during surgery, which can result in inaccurate information about the patient. To contend with this problem, blood flow variability (BFV) is proposed in this paper as an indicator to monitor the patient's status when HRV is not appropriate. In our experiments, thirty patients undergoing ear, nose, and throat (ENT) surgery with different anaesthetics are used to compare the efficiency and validity between the fast Fourier transform (FFT) and the Hilbert–Huang transform (HHT). Of another thirty patients, twenty patients accepted ENT surgery, of which ten have received Atropine, while the others have not. The other ten patients who have accepted abdominal surgery with an electric knife were compared with the previously mentioned ten patients who did not receive an Atropine injection for ENT surgery. As a result, the FFT that is applied in this study was replaced with the HHT for analysing the data in a particular frequency range of sympathetic and parasympathetic divisions, because of the lesser response of the results that were analysed by FFT for intubation. Also, BFV is proven to be a useful indicator for assisting doctors to assess the state of the patients instead of HRV during the operation in comparison with HRV under drugs (i.e., Atropine and Glycopyrrolate) and diathermy effects (i.e., high frequency interference from electric knife).     

The adrenocortical function of alloxan-induced diabetic rats

The purpose of this study is to investigate the adrenocortical function of alloxan-induced diabetic rats. Male rats of Wistar strain, weighing 200-250 gm were used. The results indicated that the adrenocortical response to stress and exogenous corticotropin (ACTH1-24) is decreased during the early diabetic stages (up to 6 days). Evidence from in vivo and in vitro studies shows that the depression is caused by the toxicity of alloxan on the adrenal cortex cells and not by the sudden rise of blood glucose levels. Streptozotocin (another diabetogen) has the same effect as alloxan on adrenal cortex cells.     

Nanotribological characterization of tooth enamel rod affected by surface treatment

Tooth enamel is a hybrid organic–inorganic bionanocomposite comprised predominantly of enamel rods. Understanding the effects of anti-caries treatment on the biomechanical properties of these rods is essential in developing effective caries prevention strategies. Calcium fluoride-like deposits play an important role in caries prevention and their nanotribological properties have a direct effect upon their long-term effectiveness. Accordingly, this study utilizes a variety of techniques, namely nanoindentation, nanoscratch tests, nanowear tests and atomic force microscopy (AFM), to characterize the mechanical and tribological properties of single enamel rods before and after topical fluoride application. The results show that the CaF₂-like deposits formed on the enamel surface following fluoride application increase the coefficient of friction of the enamel rods, but decrease their critical load and nanohardness. As a result, the nanowear depth of the treated enamel surface is around six times higher than that of the native enamel surface under an applied load of 300 μN. Following the removal of the surface deposits, however, the modulus of elasticity and wear depth of the underlying enamel surface are found to be similar to those of the original enamel surface. However, a notable increase in the surface roughness is observed.     

HRP-labeled masticatory neurons in the rat trigeminal mesencephalic nucleus: a light and electron microscopic study

The neurons innervating the muscles of mastication were labeled retrogradely with horseradish peroxidase (HRP) which was injected into each muscle of mastication of the rats. The TMB-HRP labeled neurons were for light microscopic and DAB-HRP labeled neurons for electron microscopic study. Many HRP-labeled mesencephalic neurons were observed in the trigeminal mesencephalic nucleus (TMEN) after HRP injection in jaw-closing muscles (JCM). On the other hand, no labeled neurons were found following the application of HRP to the lateral pterygoid and the anterior belly of the digastric muscles, with the exception of a very few from the mylohyoid muscle. The latter three muscles were jaw-opening muscles (JOM). The mesencephalic neurons of each JCM in the TMEN were rather randomly distributed, although they were concentrated more in the caudal region of this nucleus. These neurons were typically unipolar, with spherical to oval perikarya. Each neuron had a single process which coursed caudolaterally to join the mesencephalic tract of the trigeminal nerve. Ultrastructurally, mesencephalic masticatory neurons had a rather regular nucleus locating either centrally or eccentrically in the perikaryon, which is rather plump. The cytoplasm was endowed with very well developed Golgi apparatus and rough endoplasmic reticulum. Neurofilaments, varying in number, intermingled mostly with the Golgi apparatus in the cytoplasm. Somatic spines were frequently observed; however, synapses abutting upon the soma were few. Macula adherens-like structures were occassionally encountered in the contact zone between two cells.     

Solvent selection and optimization of α‐chymotrypsin‐catalyzed synthesis of N‐Ac‐Phe‐Tyr‐NH2 using mixture design and response surface methodology

A peptide, N‐Ac‐Phe‐Tyr‐NH₂, with angiotensin I‐converting enzyme (ACE) inhibitor activity was synthesized by an α‐chymotrypsin‐catalyzed condensation reaction of N‐acetyl phenylalanine ethyl ester (N‐Ac‐Phe‐OEt) and tyrosinamide (Tyr‐NH₂). Three kinds of solvents: a Tris–HCl buffer (80 mM, pH 9.0), dimethylsulfoxide (DMSO), and acetonitrile were employed in this study. The optimum reaction solvent component was determined by simplex centroid mixture design. The synthesis efficiency was enhanced in an organic‐aqueous solvent (Tris‐HCl buffer: DMSO: acetonitrile = 2:1:1) in which 73.55% of the yield of N‐Ac‐Phe‐Tyr‐NH₂ could be achieved. Furthermore, the effect of reaction parameters on the yield was evaluated by response surface methodology (RSM) using a central composite rotatable design (CCRD). Based on a ridge max analysis, the optimum condition for this peptide synthesis included a reaction time of 7.4 min, a reaction temperature of 28.1°C, an enzyme activity of 98.9 U, and a substrate molar ratio (Phe:Tyr) of 1:2.8. The predicted and the actual (experimental) yields were 87.6 and 85.5%, respectively. The experimental design and RSM performed well in the optimization of synthesis of N‐Ac‐Phe‐Tyr‐NH₂, so it is expected to be an effective method for obtaining a good yield of enzymatic peptide. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012     

Interactions of alpha-chymotrypsin and Carlsberg subtilisin with methyl N alpha-acetyl-2-(alkylthio)-L-tryptophanoates

Methyl N alpha-acetyl-2-(alkylthio)-L-tryptophanoates bearing different alkylthio groups were synthesized and employed as substrates for alpha-chymotrypsin and Carlsberg subtilisin in an attempt to investigate the properties of the hydrophobic pocket or cleft (S1 subsite) of the enzymes which accommodates the side-chain of the P1 amino acid residue of the substrates. The derivatives with ethylthio, 2-hydroxyethylthio, 2,3-dihydroxypropylthio, 2-aminoethylthio, carboxymethylthio, 2-carboxyethylthio, 1,2-dicarboxyethylthio, and 2-amino-2-carboxyethylthio (cysteinyl-S) groups were hydrolyzed by alpha-chymotrypsin but with kcat/Km values 4.6 to 15 times smaller than that of methyl N alpha-acetyl-L-tryptophanoate, due mainly to larger Km values. The glutathionyl derivative was only weakly bound to the enzyme. Analyses of the kinetic parameters suggested that the S1 pocket of alpha-chymotrypsin is rather more spacious than has been supposed and is able to interact flexibly with substrates so as to orient the scissile bond to the catalytic residues. On the other hand, none of the derivatives were hydrolyzed by Carlsberg subtilisin but they all inhibited the enzyme with Ki values which are generally smaller than the Km values for N alpha-acetyl-L-aromatic (modified aromatic) amino acid methyl esters. The S1 cleft of Carlsberg subtilisin interacts rather strongly with the derivatives but lacks the flexibility necessary for catalysis.