Capillary transport of macromolecules: pores and other endothelial pathways

Can a pore or pore-equivalent model account for transport of macromolecules across microvascular endothelium, or are alternate nonpore pathways necessary? Pores may be defined as aqueous channels of any shape or configuration, including those through a fiber matrix. Such pathways exhibit selective restriction to passage of macromolecules depending on their size, shape, and electrical charge. At least two pore pathways (small and large), differing in both sieve-element spacing and in hydraulic conductivity by an order of magnitude, are required to account for observed size selectivity for plasma proteins of similar shapes and charges. For the two organs examined critically in this review (cat ileum and dog paw), transport of macromolecules through small and large pore pathways is predominately convective. Total transport through small and large pores (alternatively, narrow and wide slits or fine and coarse fiber matrices) is insufficient to account for observed transport rates at low-to-moderate levels of volume flow. Either the estimated pore sizes and hydraulic conductivities derived from measurements of high volume-flow sieving are incorrect or other nonconvective transport pathways contribute substantially to macromolecular transport at low (normal) volume flow.     

Teixeiria lusitanica, a new fossil flower from the Early Cretaceous of Portugal with affinities to Ranunculales

A charcoalified fossil flower bud of a new genus and species (Teixeiria lusitanica) is described from the Early Cretaceous of Portugal. The flower is actinomorphic and unisexually male. At the base of the bud there are several bracts of different sizes, which are followed by sepal-like and petal-like tepals. Bracts and perianth organs seem to be arranged spirally and to exhibit transitions between different organ categories. The androecium has numerous stamens in two sizes, but with unclear arrangement. Pollen is small and tricolpate with a perforate tectum and a densely columellate infratectal layer. No carpels or remains of carpels could be observed on the floral axis. Teixeiria lusitanica shows most affinities to members of Ranunculales. There are also some similarities with Berberidopsis (Berberidopsidaceae, Berberidopsidales) and members of the Saxifragales (Hamamelidaceae and Daphniphyllaceae).     

Analysis of 6-mercaptopurine in human plasma with a high-performance liquid chromatographic method including post-column derivatization and fluorimetric detection

A relatively simple assay with improved reliability and sensitivity for measuring levels of 6-mercaptopurine in human plasma is presented. After extraction of the compound and the added internal standard with phenyl mercury acetate, samples were separated by ion-pair reversed-phase high-performance liquid chromatography. On-line the analytes were oxidized to fluorescent products and detected in a flow-fluorimeter. The within-day coefficient of variation was 3.8% at a concentration of 25 ng/ml. The lower detection limit was 2 ng/ml when 1.0 ml of plasma was used. Mercaptopurine concentration versus time curves of two subjects after a single oral dose of azathioprine are shown.     

Genetic diversity of durum wheat as determined by AFLP in fluorescence

The DNA of fifteen Italian cultivars of durum wheat (Triticum turgidum L. ssp. durum) were analyzed by in fluorescence amplified fragment length polymorphism (fAFLP) in order to obtain the characteristic fingerprintings of genotypes and assess their genetic relatedness. Among 64 combinations of fluorescence labelled primers, three different combinations were chosen as producing a total of 6630 AFLP fragments, 2277 (34.3 %) of them being polymorphic. By using this fAFLP methodology a DNA fingerprinting of each durum wheat cultivar was generated for genotype identification. Analysis of the genetic relationships show the low variability among durum wheat cultivars.     

Antibody-targeted photolysis: in vitro immunological, photophysical, and cytotoxic properties of monoclonal antibody-dextran-Sn(IV) chlorin e6 immunoconjugates.

A set of anti-melanoma immunoconjugates were prepared which contained chlorin e6: antibody molar ratios of 18.9:1, 11.2:1, 6.8:1, and 1.7:1. All immunoconjugates retained antigen binding activity regardless of the chromophore:antibody substitution ratio that was attained. In contrast, the ground-state absorption spectra of the immunoconjugates showed features which appeared to be dependent on the chromophore:antibody molar ratio. In addition, the quantum yield of singlet oxygen generated by the conjugated chromophores was observed to be significantly less than that observed with the unbound dye. Time-resolved absorbance spectroscopy of the chromophore excited triplet state indicated that the loss of singlet oxygen quantum yield resulted from diminished chromophore triplet yield. Analysis of data obtained from in vitro photolysis of target melanoma cells, in combination with that obtained from the immunochemical and photochemical studies, indicates that the observed immunoconjugate phototoxicity can be reasonably quantitatively represented by (1) the ability of the immunoconjugate to bind SK-MEL-2 cell surface antigen, (2) the amount of chromophore localized at the target cells by immunoconjugate binding, (3) the delivered dose of light at 634 nm, and (4) the singlet oxygen quantum yield of the antibody-bound photosensitizer. Though these data argue strongly for photolysis by the cumulative dosage of singlet oxygen at the cell membrane, nonetheless, the concurrent photoinduced release of other cytotoxic agents should not be ruled out.     

Different effects of serotonin antagonists on 3H-mianserin and 3H-ketanserin recognition sites

In minces prepared from the frontal cortex of rats treated with ketanserin (10 mg/kg i.p.) or mianserin (5 mg/kg i.p.) twice daily for 21 days, the Vmax of the adenylate cyclase stimulated by NE (100 microM) is attenuated, suggesting that ketanserin and mianserin share with a number of antidepressants the ability to attenuate the adenylate cyclase stimulation by NE. Ketanserin, given with the above mentioned dose schedule for 7 consecutive days, reduced the Bmax of 5HT2 recognition sites but failed to change either the Bmax or the apparent Kd of H-mianserin binding. A significant decrease in the Bmax of 5HT2 binding sites is elicited also by a single injection of mianserin (1). This drug also down-regulates its own binding when given twice daily for 3 weeks. From this and other information (2,3), it is concluded that ketanserin and mianserin bind to distinct recognition sites. The possibility that 5HT2 and mianserin recognition sites are functionally related and that serotonergic synapses are modulated by multiple chemical signals might be considered.