HYLAS: program for generating H curves (abstract three-dimensional representations of long DNA sequences)

The computer program HYLAS generates from a standard DNA lettersequence a three-dimensional space curve (H curve) which embodiesthe entire information content of the original nucleotide sequence.The program can display H curves either as two-dimensional (frontand side view) projections or as stereo-pair images. The curvescan be marked at specific nucleotide locations, annotated, rotatedfor observation from any viewing angle, and manipulated forconvenient side-by-side comparisons. Unlike the cumbersome lettersequences, H curves can be drastically condensed in size withoutlosing their ability to reflect the global nucleotide-distributionpattern of the entire DNA sequence. Often, biologically importantloci can be visually identified on the H curves. HYLAS is writtenin FORTRAN with separate mainframe (IBM- VM/CMS) and microcomputer(MS-DOS) versions. It uses the Tektronix-TCS library of graphicsubroutines. Received on October 24, 1988; accepted on July 15, 1989     

Effects of selective cholecystokinin antagonists L364,718 and L365,260 on food intake in rats

The selective type A and B cholecystokinin (CCK) receptor antagonists L364,718 and L365,260 were used to identify the receptor subtype that mediates the satiety effect of endogenous CCK. Male rats (n = 12–13/group), fed ground rat chow ad lib, received L364,718 (0, 1, 10, 100, or 1000 μg/kg IP) or L365,260 (0, 0.1, 1, 10, 100, 1000, or 10,000 μg/kg IP) 2 h after lights off, and food intake was measured 1.5, 3.5, and 5.5 h later. L364,718 significantly stimulated 1.5-h food intake by more than 40% at 10 μg/kg and higher doses; cumulative intake at 3.5 and 5.5 h remained elevated by about 20% at 1000 and 100 μg/kg of L364,718, respectively. In contrast, L365,260 had no significant stimulatory effect on feeding at any dose. The potency of L365,260 for antagonizing gastrin-stimulated gastric acid secretion was examined in unanesthetized rats. Male rats (n = 14), prepared with gastric and jugular vein cannulas, received doubling doses of gastrin (G-17I) (0.16–5 nmol/kg/h IV), each dose for 30 min, and gastric juice was collected for each 30-min period. G-17I stimulated gastric acid output dose dependently; the minimal effective dose was 0.16 nmol/kg/h, while maximal output (5-fold above basal) occurred at 5 nmol/kg/h. L365,260 (0, 1, 10, 100, 1000, or 10,000 μg/kg IV), administered 30 min before continuous infusion of G-17I (1.25 or 5 nmol/kg/h), significantly inhibited acid output only at 10,000 μg/kg; cumulative 60-min output was decreased by 60%. These results suggest that CCK acts at CCK-A receptors to produce satiety during the dark period in ad lib-feeding rats.     

Effect of F-2 and T-2 fusariotoxins on experimental Cryptosporidium baileyi infection in chickens

The course of Cryptosporidium baileyi infection in chickens fed with different doses of fusariotoxins was compared with that of control groups. F-2 toxin levels of 0.187–1.5 mg kg⁻¹ and T-2 toxin levels of 0.187–6.0 mg kg⁻¹ were investigated. The experimental amimals were orally infected with 6 × 10⁵ C. baileyi oocysts at 1 week of age. Total daily oocyst output was monitored by a quantitative method. Acquired immunity was tested at the age of 4 weeks, by ELISA and by a challenge infection with an equal number of oocysts, upon recovery from the primary infection. The results show that in chickens kept on the lower doses of F-2 and T-2 toxins, the parasite infection ran a similar course to that in the control groups, and the animals became resistant to re-infection. However, when higher doses (2.0–6.0 mg kg⁻¹) of T-2 toxin were used, a depression of weight gain was observed with some other physiological parameters (PCV, weight of bursa, weight of thymus, skin thickness in PHA-P skin test) also indicating toxic effect and, simultaneously, the oocyst output decreased significantly and the patent period was slightly prolonged. Although certain modifications of the immune response could be revealed, the chickens became resistant to re-infection. Only early (1 week of age) parasite infection and 6 mg kg⁻¹ T-2 toxin in the feed significantly depressed body weight gain and immunity.     

Effect of somatostatin and its fragments on turning behaviour induced by unilateral substantia nigra lesion in the rat

The effect of somatostatin and its two tetrapeptide fragments was investigated on turning activity induced by unilateral substantia nigra lesion in rats. Somatostatin in a dose of 0.6 nM had no action on the turning behavior, while a dose of 6 nM increased slightly while a dose of 12 nM significantly the contralateral turning. Cys-Lys-Asn-Phe and Phe-Trp-Lys-Thr had no action in low or high doses on the turning activity of the animals. The results suggest that somatostatin has a direct postsynaptic dopamine receptor stimulating effect. It seems that for dopamine receptor stimulating action the complete somatostatin molecule is needed.     

Photosensitizers and antioxidants: a way to new drugs?

Photodynamic therapy (PDT) is a relatively new modality of treatment of diseases involving uncontrolled cell proliferation. It is based on the production of reactive species upon illumination of a photosensitizer in the presence of oxygen. Antioxidants are primarily reducing agents prone to scavenge reactive species in one way or another. Their presence in photodynamic reactions usually reduces the efficacy of PDT. Some antioxidants like ascorbic acid, alpha-tocopherol or butyl-4-hydroxyanisole, however, when added to cells at adequate concentrations may enhance the photodamaging activity of PDT. The presence of transition metals and precise timing of antioxidant administration may also be important factors in increasing the efficacy of PDT. Antioxidant carrier sensitizers have been designed, synthesised and tested for their antibacterial PDT activity. The promising results raise the question whether the introduction of antioxidant moieties into sensitizer molecules would lead to the synthesis of highly effective new drugs.     

Kaposi's sarcoma-associated herpesvirus forms a multimolecular complex of integrins (alphaVbeta5, alphaVbeta3, and alpha3beta1) and CD98-xCT during infection of human dermal microvascular endothelial cells, and CD98-xCT is essential for the postentry stage of infection

Kaposi's sarcoma-associated herpesvirus (KSHV) interacts with cell surface heparan sulfate (HS) and α3β1 integrin during the early stages of infection of human dermal microvascular endothelial cells (HMVEC-d) and human foreskin fibroblasts (HFF), and these interactions are followed by virus entry overlapping with the induction of preexisting host cell signal pathways. KSHV also utilizes the amino acid transporter protein xCT for infection of adherent cells, and the xCT molecule is part of the cell surface heterodimeric membrane glycoprotein CD98 (4F2 antigen) complex known to interact with α3β1 and αVβ3 integrins. KSHV gB mediates adhesion of HMVEC-d, CV-1, and HT-1080 cells and HFF via its RGD sequence. Anti-αV and -β1 integrin antibodies inhibited the cell adhesion mediated by KSHV-gB. Variable levels of neutralization of HMVEC-d and HFF infection were observed with antibodies against αVβ3 and αVβ5 integrins. Similarly, variable levels of inhibition of virus entry into adherent HMVEC-d, 293 and Vero cells, and HFF was observed by preincubating virus with soluble α3β1, αVβ3, and αVβ5 integrins, and cumulative inhibition was observed with a combination of integrins. We were unable to infect HT1080 cells. Virus binding and DNA internalization studies suggest that αVβ3 and αVβ5 integrins also play roles in KSHV entry. We observed time-dependent temporal KSHV interactions with HMVEC-d integrins and CD98/xCT with three different patterns of association and dissociation. Integrin αVβ5 interaction with CD98/xCT predominantly occurred by 1 min postinfection (p.i.) and dissociated at 10 min p.i., whereas α3β1-CD98/xCT interaction was maximal at 10 min p.i. and dissociated at 30 min p.i., and αVβ3-CD98/xCT interaction was maximal at 10 min p.i. and remained at the observed 30 min p.i. Fluorescence microscopy also showed a similar time-dependent interaction of αVβ5-CD98. Confocal-microscopy studies confirmed the association of CD98/xCT with α3β1 and KSHV. Preincubation of KSHV with soluble heparin and α3β1 significantly inhibited this association, suggesting that the first contact with HS and integrin is an essential element in subsequent CD98-xCT interactions. Anti-CD98 and xCT antibodies did not block virus binding and entry and nuclear delivery of viral DNA; however, viral-gene expression was significantly inhibited, suggesting that CD98-xCT play roles in the post-entry stage of infection, possibly in mediating signal cascades essential for viral-gene expression. Together, these studies suggest that KSHV interacts with functionally related integrins (αVβ3, α3β1, and αVβ5) and CD98/xCT molecules in a temporal fashion to form a multimolecular complex during the early stages of endothelial cell infection, probably mediating multiple roles in entry, signal transduction, and viral-gene expression.