The development of anoxia following occlusion

Following arteriolar occlusion, tissue oxygen concentration decreases and anoxic tissue eventually develops. Although anoxia first appears in the region most distal to the capillary at the venous end, it eventually spreads throughout the entire region of supply. In this paper the changing oxygen concentration, from the time of occlusion until the tissue is entirely anoxic, is examined mathematically. The equations governing oxygen transport to tissue are solved by iterating a nonlinear integral equation. This solution is valid until anoxia first appears. After anoxia develops it is necessary to solve a moving boundary problem. This is done using the method of matched asymptotic expansions, and accurate solutions are obtained for a wide range of physiological conditions.     

Purification and autophosphorylation of insulin receptors from rat skeletal muscle

Insulin receptors of rat skeletal muscle were purified by first extracting a plasma membrane-enriched pellet obtained from a muscle homogenate with Triton X-100, followed by WGA-Sepharose and insulin-Sepharose affinity chromatography. Routinely, 4-5 micrograms of purified receptor were obtained from 15 g of tissue. The purified receptors are composed of two major polypeptides with molecular weights of 130,000 and 95,000, respectively. The binding of [125I]insulin by the purified receptors was analyzed by a Scatchard plot. There are at least two binding components. The high-affinity component, with an apparent association constant (Ka) of 2.0 X 10(9) M-1, comprises 10% of the total insulin binding sites; while the low-affinity component, with a Ka value of 1.4 X 10(8) M-1, represents 90% of the binding sites. Assuming the insulin receptor to have a molecular weight of 300,000, the receptor binds 1.7 mol of insulin per mol at saturation. Insulin is capable of stimulating the autophosphorylation of the beta-subunit of the muscle insulin receptor (Mr 95,000) by 5-10-fold. The stoichiometry of this phosphorylation reaction was determined as 0.8 phosphate per insulin binding site after a 10 min incubation with 100 nM insulin. In a previous report, I showed that the insulin stimulation of glucose transport in diaphragms from neonatal rats was small, even although the diaphragms had normal levels of insulin receptors and glucose transporters (Wang, C. (1985). Proc. Natl. Acad. Sci. USA 82, 3621-3625). To determine whether or not receptor autophosphorylation might be related to this insensitivity to insulin, the level of receptor phosphorylation was quantitated in diaphragms from rats at different stages of development. Autophosphorylation remains unchanged from birth to 21 days of age, suggesting that the lower insulin-stimulated glucose uptake by diaphragms at early stages of postnatal development as compared to that by diaphragms of older rats, is not due to a difference in receptor kinase.     

Rapid high-performance liquid chromatographic determination of serum gabapentin

Gabapentin (GBP) is a new antiepileptic drug approved for clinical treatment of partial seizures in the USA. Serum GBP concentrations in 283 patients were studied using high-performance liquid chromatography with fluorescence detection. The standard curves were linear over a range of 60 ng to 15 μg/ml. The coefficient of variations were 3.4 to 8.8% and 1.4 to 9.8% for intra- and inter-assay studies, respectively. The lower limit of quantitation was 10 ng/ml. Of the 283 patients studied, 72.5% had GBP levels between 2 and 10 μg/ml, 14.8% were below 2 μg/ml and 12.7% above 10 μg/ml. The mean±S.E. of GBP in 283 patients was 5.38±0.23 μg/ml. Peak concentrations of more than 15 μg/ml and trough levels as low as 0.1 μg/ml were not uncommon. The method described was rapid, simple, highly sensitive and reproducible. Other antiepileptic drugs and endogenous compounds did not interfere with the assay.     

Computational and Experimental Investigation of the Antimicrobial Peptide Cecropin XJ and its Ligands as the Impact Factors of Antibacterial Activity

Cecropin XJ, as a heat stable antimicrobial peptide (AMP), displayed broad bacteriostatic activities, effectively inhibited proliferation of cancer cells and induced cell apoptosis in vitro. However, it exhibited little hemolytic activity and very low cytotoxicity to erythrocytes and normal cells. Although exerts multiple remarkable bioactivities, the refined molecular conformation of native Cecropin XJ remains unsolved. The aim of the present study is to comprehensively investigate the physicochemical characteristics and structure-function relationship of this antimicrobial peptide by using a series of bioinformatics and experimental approaches. In this study, we revealed that the mature Cecropin XJ consists of 41 amino acids, containing two α-helical structures from Lys⁷ to Lys²⁵ and from Ala²⁹ to Ile³⁹. The phylogenetic tree indicated that Cecropin XJ belongs to the Class I AMPs of cecropin family. Hydrophobic analysis showed Cecropin XJ is a typical amphiphilic molecule. The surface of Cecropin XJ was found to have a much wide range of electrostatic potential from ?83.243 to +83.243. The amphipathicity and surface potential of Cecropin XJ partially supported the AMP pore-forming hypothesis. Scanning electron microscopy experimentally confirmed the damages of Cecropin XJ to microbial membrane. Four predicted docking sites respectively for magnesium ion (Mg²⁺), adenosine diphosphate (ADP), bacteriopheophytin (BPH), and guanosine triphosphate (GTP) were found on the surface of Cecropin XJ. Thereinto, Mg²⁺ was experimentally proved to suppress the antibacterial activity of Cecropin XJ; both GTP and ADP enhanced the bactericidal activities to varying degrees. The present study provides a foundation for further investigation of molecular evolution, structural modification, and functional mechanisms of Cecropin XJ.     

Measurement of 7-dehydrocholesterol and cholesterol in hair can be used in the diagnosis of Smith-Lemli-Opitz syndrome

7-dehydrocholesterol (7-DHC) and cholesterol (CHOL) are biomarkers of Smith-Lemli-Opitz Syndrome (SLOS), a congenital autosomal recessive disorder characterized by elevated 7-DHC level in patients. Hair samples have been shown to have great diagnostic and research value, which has long been neglected in the SLOS field. In this study, we sought to investigate the feasibility of using hair for SLOS diagnosis. In the presence of antioxidants (2,6-ditert-butyl-4-methylphenol and triphenylphosphine), hair samples were completely pulverized and extracted by micro-pulverized extraction in alkaline solution or in n-hexane. After microwave-assisted derivatization with N,O-Bis(trimethylsilyl)trifluoroacetamide, the analytes were measured by GC-MS. We found that the limits of determination for 7-DHC and CHOL were 10 ng/mg and 8 ng/mg, respectively. In addition, good linearity was obtained in the range of 50–4000 ng/mg and 30–6000 ng/mg for 7-DHC and CHOL, respectively, which fully meets the requirement for SLOS diagnosis and related research. Finally, by applying the proposed method to real hair samples collected from 14 healthy infants and two suspected SLOS patients, we confirmed the feasibility of hair analysis as a diagnostic tool for SLOS. In conclusion, we present an optimized and validated analytical method for the simultaneous determination of two SLOS biomarkers using human hair.     

Repeated pre-training sleep restriction in adolescent rats impaired spatial performance

Sleep and Biological Rhythms - Chronic sleep deprivation (SD) is an overwhelming problem in young students. Firstly, we investigated whether different levels of pre-training SD had effects on...