Evidence for 5-HT2 involvement in the mechanism of action of hallucinogenic agents

The affinities (Ki values) of twenty two psycho-active agents, including LSD, 5-OMe DMT and a series of phenalkylamine derivatives, for cortical 5-HT1 and 5-HT2 binding sites were compared with two measures of behavioral activity. It was found that a significant correlation (r = 0.938) exists between the 5-HT2 binding affinities of these agents and their ED50 values as determined in tests of stimulus generalization using 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) as the training drug. Furthermore, for fifteen of these agents where human data were available, a significant correlation (r = 0.924) also exists between 5-HT2 binding affinities and their human hallucinogenic potencies. The results of this study suggest that the mechanism of action of these agents involves 5-HT2-related events.     

Biotin interference in immunoassays based on biotin-strept(avidin) chemistry: An emerging threat

Biotinylated antibodies/antigens are currently used in many immunoassay formats in clinical settings for diversified analytes and biomarkers to offer high detection selectivity and sensitivity. Biotin cannot be synthesized by mammals and must be taken as an essential supplement. Normal intake of biotin from various foods and milk causes no effect on the streptavidin/biotin-based immunoassays. However, overconsumption of biotin (daily doses 100–300 mg) poses a significant problem for immunoassays using the biotin-strept(avidin) pair. Biotin interferences are noted in immunoassays of thyroid markers, drugs, hormones, cancer markers, the biomarker for cardiac function (β–human chorionic gonadotropin), etc. The biotin level required for serious interference in test results varies significantly from test to test and cannot easily be predicted. Immunoassay manufacturers with technologies based on strept(avidin)-biotin binding must investigate the interference from biotin (up to at least 1200 ng/mL or 4.9 μM of biotin) in various formats. There is no concrete solution to circumvent the biotin interference encountered in blood samples, short of biotin removal. Considering the short half-life of biotin in the human body, patients must stop taking biotin supplements for >48 h before the test. However, this scenario is not considered for patients in emergency situations or those with biotinidase deficiency, mitochondrial metabolic disorders or multiple sclerosis. Apparently, a rapid analytical procedure for biotin is urgently needed to quantify for its interference in immunoassays using strep(avidin)-biotin chemistry. To date, there is no quick and reliable procedure for the detection of biotin at below nanomolar levels in blood and biological samples.Traditional lab-based techniques including HPLC/MS-MS cannot process an enormous number of public samples. Biosensors with high detection sensitivity, miniaturization, low cost, and multiplexing have the potential to address this issue.     

Ecogeographic isolation: a reproductive barrier between species and between cytotypes in Houstonia (Rubiaceae)

‘Ecogeographic isolation’ describes the combined role of ecology and geography as a reproductive barrier, and an important component in speciation. Evidence increasingly shows that this form of isolation is important for maintaining the genetic integrity of populations and species. Further, ecogeographic isolation can be a reproductive barrier between polyploid individuals and their diploid progenitors. New ecoinformatic methods, which includes niche modeling and associated statistical assessments of these models with spatially explicit environmental data, allow us to test if ecogeographic isolation is a contributing isolating barrier between species and between cytotypes within a species. We tested the hypothesis that ecogeographic isolation contributes to isolation of species and cytotypes within species of the plant genus Houstonia. We found that species in this group occupied significantly different niches, which suggests ecogeographic isolation is a contributing reproductive barrier. We also found that diploid and tetraploid forms of H. longifolia show some level of ecogeographic isolation, but H. purpurea diploids and tetraploids did not. Our results suggest that ecogeographic isolation plays a role in reproductive isolation between Houstonia species and between cytotypes of H. longifolia.     

The non-specificity of dog serum albumin and the N-terminal model peptide glycylglycyl-L-tyrosine N-methylamide for nickel is due to the lack of histidine in the third position.

Equilibrium dialysis of dog serum albumin (DSA) against Ni(II) in 0.1 M-N-ethylmorpholine/HCl, pH 7.53, demonstrates the absence of a specific Ni(II)-binding site in DSA. To evaluate at the molecular level the influence of the genetic substitution of L-tyrosine for L-histidine at the N-terminal of DSA, a simple model tripeptide of the N-terminal residues, glycylglycyl-L-tyrosine N-methylamide, was synthesized and its Ni(II)-binding properties studied. A comparison of the visible absorption characteristics of Ni(II)-DSA with those of Ni(II)-glycylglycyl-L-tyrosine N-methylamide reveals a similar change from octahedral to planar co-ordination as the pH is increased. Both systems exhibit a low Ni(II)-binding affinity at physiological pH, with DSA binding a greater percentage of Ni(II) owing to the availability of at least two binding sites of similar affinities. The complex equilibria between Ni(II) and glycylglycyl-L-tyrosine N-methylamide were studied by analytical potentiometry (0.15 M-NaCl, 25 degrees C). Four major complex species, MHA, MH-1A2, MH-2A2 and MH-3A [where M and A represent Ni(II) ion and anionic peptide respectively], were detected, MHA being the single species at physiological pH. There is no evidence for the involvement of the phenolic hydroxy group in the octahedral MHA complex, or within the plane of co-ordination in the high-pH species. The results provide direct evidence that the low Ni(II)-binding affinity of DSA is due to the genetic substitution of tyrosine for histidine at the N-terminal region of the protein.     

The effect of chirality on serotonin receptor affinity.

α-Methylation of phenethylamines or tryptamine appears to have very little effect on serotonin (5-HT) receptor affinity when racemates are examined. Examination of resolved materials, using an isolated rat stomach fundus preparation, reveals that the R-isomers of DOM and MDA and the S-isomer of α-methlytryptamine possess a higher 5-HT receptor affinity than do their enantiomers. While S(+)-DOB possesses a lower affinity than its racemate, R(-)-DOB produces an appreciable agonistic response which interferes with the measurement of p_A2 values.     

In situ Raman spectroscopy for simultaneous monitoring of multiple process parameters in mammalian cell culture bioreactors

In this study, the application of Raman spectroscopy to the simultaneous quantitative determination of glucose, glutamine, lactate, ammonia, glutamate, total cell density (TCD), and viable cell density (VCD) in a CHO fed‐batch process was demonstrated in situ in 3 L and 15 L bioreactors. Spectral preprocessing and partial least squares (PLS) regression were used to correlate spectral data with off‐line reference data. Separate PLS calibration models were developed for each analyte at the 3 L laboratory bioreactor scale before assessing its transferability to the same bioprocess conducted at the 15 L pilot scale. PLS calibration models were successfully developed for all analytes bar VCD and transferred to the 15 L scale. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012