Precision displacement measurement by active laser heterodyne interferometry

We demonstrate an active laser heterodyne interferometer which can automatically compensate environmental disturbances and is capable of precision displacement measurement. Two Zeeman He-Ne lasers were employed. Laser II was used as the light source to stabilize the interferometer by using a piezomirror in a feedback loop. The hetereodyne signal of the two lasers was used to directly calibrate mirror displacement, with the wavelength of laser I tuned to compensate change in the interference signal due to displacement only. Separation of the contributions to the interference signal from displacement and external disturbances was accomplished by using polarization optics. This interferometer was used to measure the hysteresis of a piezoelectric transducer (PZT) over a dynamic range of 0.5 microm with a resolution of +/-0.8 nm.

Effects of deoxycholate on the transepithelial transport of sucrose and horseradish peroxidase in filter-grown Madin-Darby canine kidney (MDCK) cells

Madin-Darby canine kidney (MDCK) epithelial cells grown on microporous polycarbonate filters were used as a model system to investigate the mechanisms of enhancement by deoxycholate in the transepithelial transport of horseradish peroxidase (HRP) and 14C-sucrose. Deoxycholate at 0.025% had no effect on the transepithelial electrical resistance (TEER); a fivefold enhancement on the transepithelial transport of HRP, but not on that of 14C-sucrose, was observed. Deoxycholate at 0.05% induced a reversible decrease of TEER; a 2- and 50-fold enhancement on the transepithelial transport of 14C-sucrose and HRP, respectively, was observed. At 0.1%, deoxycholate induced an irreversible decrease in TEER and the epithelial barrier in the cell monolayer was completely eliminated. A 3.3-fold increase in cellular uptake in HRP, but not in 14C-sucrose, was also observed in the presence of 0.025% deoxycholate. The increase in cellular uptake was abolished when HRP was conjugated to polylysine. These results suggest that deoxycholate can increase the transepithelial transport by at least two different mechanisms, i.e., a transcellular pathway, possibly due to the enhancement of cellular uptake of selective molecules, and a nonselective paracellular pathway, due to the loosening of tight junctions by deoxycholate at higher concentrations.

Protease-like sequence in hepatitis B virus core antigen is not involved in the cleavage processes of core protein in Escherichia coli

A DNA fragment, coding for hepatitis core antigen (HBcAg), was amplified by polymerase chain reaction and inserted into a lambda PL promoter-derived expression vector. The recombinant plasmid was transformed into Escherichia coli and proteins produced after heat induction were analyzed. In addition to the 21 kDa HBcAg protein, several smaller related polypeptides, particularly one of 17 kDa in size, were also detected with rabbit anti-HBcAg antiserum. Whether the protease-like sequence of core protein involved in the self-cleavage process to form the 17 kDa polypeptide was investigated by a deletion experiment. Our results with a mutant in which 7 amino acids of the conserved protease-like region in the core protein have been deleted suggest that the cleavage does not depend on the presence of these protease-like sequence. In addition, the core protein synthesized from in vitro translation reaction was not cleaved. Core particles from E. coli lysate were purified by sucrose and cesium chloride density gradient centrifugations and subsequently treated with 0.2% of SDS and 0.2% of beta-mecaptoethanol. Immunoblotting analysis, however, did not reveal any conversion of the 21 kDa protein to smaller ones. In conclusion, our results suggest that the protease-like domain at the N-terminus of the core protein does not contain intrinsic autocleavage activity, nor could the HBcAg be converted to smaller antigens by detergent treatment.

Caffeine-sensitive calcium stores in bovine adrenal chromaffin cells

Caffeine was used to study the intracellular Ca2+ pools of bovine chromaffin cells. Its effects on cytosolic Ca2+ concentration ([Ca2+]i) were examined using fura-2. Caffeine caused a transient increase in [Ca2+]i in the presence or absence of extracellular Ca2+. In the former case, the caffeine-induced [Ca2+]i increase was higher and stayed above the basal value for several minutes. In the latter case, the [Ca2+]i rise was lower and fell to the basal level within 1 min. These results suggest that caffeine increases [Ca2+]i by causing both Ca2+ influx and Ca2+ release from intracellular pools. In the absence of extracellular Ca2+, ionomycin but not caffeine caused a further increase in [Ca2+]i in cells that had been treated with caffeine. Apparently there are at least two intracellular Ca2+ pools, only one of which is sensitive to caffeine. The caffeine-induced [Ca2+]i rise became smaller when the cells were pretreated with the inositol trisphosphate-generating agonists, methacholine and bradykinin. In addition, methacholine was unable to initiate a [Ca2+]i transient after the cells had been treated with caffeine. The results indicate that the caffeine-sensitive Ca2+ pools overlap with the inositol trisphosphate-sensitive pool and that the size of the latter pool is smaller than that of the former. The caffeine-sensitive Ca2+ pools were refilled after high K+ treatment, which suggests that the caffeine-sensitive Ca2+ pools may be important in buffering the cytosolic Ca2+. The effect of caffeine on [Ca2+]i is not due to inhibition of phosphodiesterase. Our results support a Ca2+ entry model in which depletion of intracellular Ca2+ pools controls the rate of Ca2+ entry across the plasma membrane.

New crystalline forms of neuraminidase of type B human influenza virus

New crystalline forms of tetrameric neuraminidase heads from two strains (B/Lee/40 and B/mem/89) of type B human influenza virus were obtained and the crystals diffracted using X-rays to 2.5 A resolution without lattice disorder. The new B/Lee/40 crystalline form is tetragonal, space group P42(1)2, with unit cell dimensions a = 123.8 A, c = 71.8 A. The B/mem/89 crystalline form is also tetragonal, space group I422, with unit cell dimensions a = 122.9 A, c = 164.4 A. There is one neuraminidase monomer per asymmetric unit in both forms.

Triclosan: a safety profile

Triclosan (2, 4, 4'-trichloro-2'-hydroxydiphenyl ether), an antimicrobial agent, has been used extensively for 20 years in consumer products, principally in deodorants, soaps and other dermatological preparations. Recently, the use of triclosan has been extended to oral health care products such as dentifrices. This paper reviews safety information, both pre-clinical and clinical studies, from the literature, data submitted to the Antimicrobial I OTC Review Panel and unpublished work from the Pharmacology and Toxicology Department of the Colgate-Palmolive Company. The data spans acute, subacute, subchronic and chronic toxicity; mutagenicity, carcinogenicity, reproduction/teratology and pharmacokinetics. Results of these studies show that triclosan is well tolerated by a variety of species including man. In clinical studies with triclosan in solutions and dentifrices, a steady state was reached by day 7 with blood levels in the parts per billion (ppb) range and urine as the main route of excretion. Based on these studies, triclosan can be considered safe for use in dentifrice and mouthrinse products.

Human hepatitis delta virus RNA subfragments contain an autocleavage activity

Hepatitis delta virus (HDV) contains a single-stranded circular RNA genome of 1.7 kilobases. In this report we demonstrate that subfragments of HDV RNA can undergo autocatalytic cleavage. This cleavage requires at least 500 microM of Mg2+ or Ca2+, is not affected by varying the pH from 5.0 to 9.1, and occurs with RNA fragments as small as 133 nucleotides. The larger RNA fragments containing additional HDV sequences have a lower efficiency of cleavage. Deletion analysis at both ends of RNA subfragments suggested that the catalytic ability of HDV RNA resides in a stretch of no more than 117 nucleotides around the cleavage site. The cleavage occurs at the phosphodiester bond between nucleotides 688 and 689 on the HDV genomic map, generating a 5' fragment with a terminal uridyl 2',3'-cyclic monophosphate residue and a 3' fragment with a guanosyl residue with a 5'-hydroxyl group. The smallest autocleaving RNA does not contain the "hammerhead" sequence required for the autocleavage of other known self-cleaving RNA. The cleavage of HDV RNA occurs at a much faster rate, even at a very low Mg2+ concentration, than that of other "ribozymes." Thus, HDV RNA represents a distinct class of ribozyme.

Chromosomal analysis of recurrent laryngeal papillomas

Recurrent laryngeal papillomas are tumors believed to be induced by human papillomaviruses. Severity of this disease varies due to the unpredictability of clinical remissions and recurrences. However, the severity of the disease does not affect the classification of these tumors as benign, and the rate of spontaneous conversion of recurrent laryngeal papillomas to carcinomas is very low. Laryngeal papillomas from six patients were evaluated cytogenetically after short-term culture. All six specimens were chromosomally normal, consistent with their classification as benign tumors with a low rate of malignant conversion. The presence of human papillomaviruses has no detectable effect on the chromosomes of these tumors.

The three-dimensional structure of trichosanthin molecule

A model completed recently of two trichosanthin molecules in an asymmetric unit belonging to the monoclinic system is reported. It can be seen that the molecular structure consists of two domains, one large and one small, and that there are some features in the secondary structure. The dissimilarity between two molecules as well as their interactions in an independent unit correlated in a non-symmetric way has been described, moreover, the binding sites of the heavyatom position in the derivatives are also discussed.

Surfactants: a survey of short-term genotoxicity testing

The available results for tests on over 200 surfactants in nine short-term genotoxicity assay systems were reviewed. These tests included the Salmonella/microsome mutation assay, bacterial DNA repair tests, mitotic recombination in Saccharomyces cerevisiae, the mouse lymphoma cell-mutation assay, unscheduled DNA synthesis and sister chromatid exchange assays in mammalian cells, mammalian chromosome damage tests in vitro and in vivo, the dominant lethal test in rodents, and mammalian cell-transformation tests. The collected data cover all four major classes of surfactants: anionic, cationic, nonionic and amphoteric. The results of these genotoxicity tests were overwhelmingly negative. Although there were occasional positive results in bacterial or cell-transformation systems, the testing performed to date indicates that surfactants have negligible potential to cause genetic damage. The available data also indicate that none of the assays were incompatible with testing surfactants for genotoxicity.

Pulmonary absorption of amino acids in the rat: evidence of carrier transport

To investigate the absorption of nonmetabolized amino acids from the rat lung, 0.1 ml of Krebs-Ringer phosphate solution containing either 14C-labeled 1-aminocyclopentanecarboxylic acid (cycloleucine) or alpha-aminoisobutyric acid (AIB) was administered to anesthetized animals by way of a catheter introduced through a tight-fitting tracheal cannula. After various times, lungs were removed and assayed for the amount of amino acid that remained. Cycloleucine appeared to be absorbed by a combination of at least two processes: saturable carrier-type transport and a nonsaturable process. The saturable process was inhibited to varying degrees by a number of L- and D-amino acids but not by D-ornithine, betaine, 3-O-methyl-D-glucose, phenol red, disodium cromoglycate, or tetraethylammonium. The nonsaturable process appeared to be too rapid to be accounted for by diffusion alone, thus suggesting interaction with a second carrier system of high capacity. Although AIB was a weak inhibitor of cycloleucine transport, it appeared to be absorbed solely by a nonsaturable process at a rate consistent with diffusion through aqueous membrane channels.

Fine structure of meiotic prophase chromosomes and modified synaptonemal complexes in diploid and triploid Rhoeo spathacea

The synaptonemal complex (SC) in the diploid Rhoeo consists of 2 amorphous lateral elements, each about 46.0 nm thick, and one amorphous central element about 30.0 nm thick. The central region is about 115.0 nm wide. SC in the triploid have essentially the same dimensions as those of the diploid; both lateral (46.0 nm) and central (30.0 nm) elements are amorphous, and the central region is about 117.5 nm wide. The coil, observed in both diploid and triploid, is a modified short segment of SC with several twists at the end of a synapsed bivalent that is attached to the nuclear membrane. Serial sections in a diploid cell reveal that a coil extends inwards about 3.5 micron from the nuclear membrane and makes a complete turn at a distance of every 0.5 micron. There is a correlation between the modified ends of SC and terminal chiasmata in Rhoeo. The coils might have a positive role in the process of crossing over, or alternatively might be involved in ring formation by holding chromosome ends together while chiasmata are not involved. SC are present in chromocentres of both diploid and triploid. Chromocentres in diploid and triploid are indistinguishable, and appear to be formed from the aggregation of pericentromeric heterochromatin as a result of translocations which occured close to the centromeres. 3-dimensional hypothetical pachytene configuration of the diploid is presented.

New method for detecting and quantitating pharmacokinetic drug-drug interactions applied to ethanol-propranolol

A novel method for detecting and quantitating pharmacokinetic drug-drug interactions is described. The method involves perturbation of an existing steady-state whole blood (or plasma) concentration of one drug by the other drug. The method would allow differentiation of "pharmacokinetic" drug interactions from "pharmacologic" interactions. It is shown that a bolus intravenous injection of propranolol reduced a steady-state arterial blood concentration of ethyl alcohol by 26% in the cat.