Cyclopeptides from Stellaria yunnanensis

In a previous paper, we reported the structural elucidation of stellarin A, a new cyclic heptapeptide, from the fresh roots of Stellarina yunnanensis Franch. Further chemical study on this plant led to the isolation of another two new cyclopeptides named stellarin B and C. Their structures were established to be cyclo(Gly-Ser-HOIle-Phe-Phe-Ala) and cyclo(Gly-Ser-HOIle-Phe-Phe-Ser), respectively, by spectral methods.

Factor analysis for extraction of blood time-activity curves in dynamic FDG-PET studies

Arterial sampling in dynamic PET studies can be eliminated by using left ventricular or aortic time-activity curves (TAC) obtained from user drawn regions of interest (ROIs) after appropriate spillover correction. In this study, we evaluated the feasibility of extracting the "pure" arterial TAC from dynamic PET images using factor analysis of dynamic structures (FADS).

METHODS

Computer simulations were used to study the performance of the FADS algorithm with positivity constraints. Ten canine 13N-ammonia and two human FDG-PET dynamic studies were used to extract the blood TACs from FADS. Plasma samples and compartmental model fittings were used to validate the accuracy of the FADS-generated blood factors.

RESULTS

We found that FADS with positivity constraints was sufficient to extract the blood factor from the composite dynamic images. The "pure" blood-pool TACs that matched well with the arterialized well counter measurements were generated from FADS in the canine and human studies.

CONCLUSION

FADS has the potential to accurately extract "pure" blood TAC from dynamic PET images, allowing reliable quantitation of biological information from PET studies without blood sampling, ROI drawing or spillover correction.

Leigh syndrome presenting with dystonia: report of one case

A 22-month-old female presented with developmental delay and dystonia. The T2 weighted image of the brain MRI showed bilateral symmetrical high signal lesions over the putamen. An increased serum lactate pyruvate ratio (29.25) and a positive oral glucose lactate stimulation test were noted. Electron microscopic examination showed abnormal mitochondrial aggregation with band cristae in the subsarcolemmal area. These findings were indicative of clinical Leigh's syndrome. However, unusually the mt DNA analysis showed a point mutation at the nucleotide position 8344.

A floral transmitting tissue-specific glycoprotein attracts pollen tubes and stimulates their growth

Pollen tubes elongate directionally in the extracellular matrix of pistil tissues to transport the male gametes from the apically located stigma to the basally located ovary for fertilization. The molecular mechanisms underlying directional pollen tube growth in the pistil are poorly understood. We have purified a glycoprotein, TTS, from tobacco stylar transmitting tissue, which supports pollen tube growth between the stigma and the ovary. TTS proteins belong to the arabinogalactan protein family, and they polymerize readily in vitro in a head-to-tail fashion into oligomeric forms. TTS proteins stimulate pollen tube growth in vitro and attract pollen tubes grown in a semi-in vivo culture system. In vivo, the pollen tube growth rate is reduced in transgenic plants that have significantly reduced levels of TTS proteins as a result of either antisense suppression or sense cosuppression. These results identify TTS protein as a pistil component that positively contributes to pollen tube growth.

A pollen tube growth stimulatory glycoprotein is deglycosylated by pollen tubes and displays a glycosylation gradient in the flower

In plant sexual reproduction, pollen tubes elongate from the stigma, through the stylar transmitting tissue, to the ovary of the pistil to deliver the male gametes for fertilization. TTS protein is a tobacco transmitting tissue glycoprotein shown to attract pollen tubes and promote their growth. Here, we show TTS proteins adhere to the pollen tube surface and tips, suggesting that they may serve as adhesive substrates for pollen tube growth. TTS proteins are also incorporated into pollen tube walls and are deglycosylated by pollen tubes, suggesting that they may provide nutrients to this process. Within the transmitting tissue, TTS proteins display a gradient of increasing glycosylation from the stigmatic end to the ovarian end of the style, coincident with the direction of pollen tube growth. These results together suggest that the TTS protein-bound sugar gradient may contribute to guiding pollen tubes from the stigma to the ovary.

New triterpenoid saponins, asterbatanoside D and E, from Aster batangensis

Two new triterpenoid saponins named asterbatanoside D and E have been isolated from Aster batangensis and their structures elucidated as 3-O-beta- D-glucopyranosyl-bayogenin-28-O-beta-D-glucopyranosyl-(1-->6)-beta -D- glucopyranoside and 3-O-6'-acetyl-beta-D-glucopyranosyl-bayogenin-28-O-beta-D- glucopyranosyl-(1-->6)-beta-D-glucopyranoside by means of MS, 1D and 2D NMR techniques (COSY, TOCSY, ROESY, HMQC, and HMBC), and chemical reactions.

Lipopolysaccharide-induced E-selectin expression requires continuous presence of LPS and is inhibited by bactericidal/permeability-increasing protein

Endothelial cells stimulated by LPS express E-selectin, which plays an important role in mediating neutrophil adhesion during inflammation. E-selectin is induced within 1-2 h, peaks at 4-6 h, and gradually returns to basal level by 24 h. rBPI21, a recombinant N-terminal fragment of human bactericidal/permeability-increasing protein (BPI), inhibited LPS-induced E-selectin expression when added at the same time as, and up to 6 h after, LPS. Delayed administration of rBPI21 also affected LPS-mediated activation of the nuclear factor, NF-kappa B. Two to 4 h following LPS addition to endothelial cells, when NF-kappa B was already activated, addition of rBPI21 resulted in marked reduction of NF-kappa B detectable at 4 or 6 h. These results indicate that endothelial activation requires continuous presence of LPS, and rBPI21 acts to reverse LPS-mediated endothelial activation by interrupting the on-going LPS signal.

A modeling method to improve quantitation of fluorodeoxyglucose uptake in heterogeneous tumor tissue

The standard approach for evaluating FDG-PET kinetic studies is based upon an assumption that tissue within a representative region of interest (ROI) is relatively homogeneous in terms of FDG kinetics. In neoplasms and other disease states, tissue within an ROI may be grossly heterogeneous, due to adjacent infarcted tissue and other causes. We have developed a method employing two ROIs (one over the tumor and another over a "reference region") to deal with this level of heterogeneity.

METHODS

The method is based on the regular FDG model but consists of six variable parameters (6P model) which uses the kinetics in the reference region to account for the normal tissue within the tumor ROI, so that the kinetic data only associated with the tumor can be estimated. Monte Carlo simulations and human PET FDG studies were used to analyze the performance of the 6P model.

RESULTS

The narrower 95% confidence intervals of parameter estimates, which centered at the true tumor rate constants, and the smaller correlation matrix of the 6P model showed the better performance of the 6P model compared to the standard "homogeneous" four-parameter FDG model. Computer simulations further showed that the 6P model can accurately estimate the microparameters (rate constants: K1* (ml/min/g), k2* (min-1), k3* (min-1), k4* (min-1)) and the macroparameter (K (ml/min/g)) of tumor cells regardless of the percent weight of tumor cells in the lesions.

CONCLUSIONS

The new method can produce more reliable and accurate estimates of tumor glucose metabolic rates with dynamic PET FDG studies.

Characterization of the increased cytotoxicity of gelonin anti-T cell immunoconjugates compared with ricin A chain immunoconjugates

Ribosomal inactivating proteins such as gelonin (Gel) and ricin A chain (RTA) conjugated to MoAbs bind to specific target cells, and upon internalization inhibit protein synthesis, ultimately resulting in cell death. We report here that Gel anti-T cell MoAb conjugates are more cytotoxic than RTA conjugates when tested against human peripheral blood mononuclear cells (PBMC). This increased cytotoxicity is observed whether Gel is conjugated to the anti-T cell MoAb or to an anti-mouse immunoglobulin Fab' fragment which then binds to the murine anti-human T cell MoAb. Gel conjugates are not only effective at lower concentrations, but also produce a greater extent of inhibition of cellular proliferation. Moreover, a 10 min exposure to a Gel conjugate is as effective as a 90 h exposure to an RTA conjugate. When part of anti-T cell F(ab')2 or Fab' conjugates, Gel affects the early steps in cellular intoxication more than RTA; Gel conjugates bind more avidly and accelerate the modulation of antigen. In contrast, when part of whole IgG conjugates, Gel does not affect the binding to or modulation of surface antigen compared with RTA, while it does increase conjugate cytotoxicity. These observations suggest that Gel may be delivered more efficiently into the cytosol than RTA. A divergent intracellular pathway for Gel is also supported by the inability of chemical potentiators, which strongly enhance RTA potency, to affect Gel potency. These properties of Gel might also be advantageous for immunoconjugates made with other MoAbs or receptor-binding molecules.

Effect of age and streptozocin concentration on the induction by streptozocin of hyperglycaemia in fasting rats

The effect of age and streptozocin concentration on the induction by streptozocin of hyperglycaemia in fasting rats is investigated. The data show that there is a dose dependent effect of streptozocin on the hyperglycaemia induced by streptozocin, and 60 mg/kg streptozocin is significantly more effective than 20 or 40 mg/kg streptozocin in inducing hyperglycaemia. Moreover, the hyperglycaemia induced by 60 mg/kg streptozocin is greater in 8 week old rats than in 4 or 6 week old rats, suggesting an influence of age on streptozocin-induced hyperglycaemia.

A tobacco gene family for flower cell wall proteins with a proline-rich domain and a cysteine-rich domain

Flowering is known to be associated with the induction of many cell wall proteins. We report here five members of a tobacco gene family (CELP, Cys-rich extensin-like protein) whose mRNAs are found predominantly in flowers and encode extensin-like Pro-rich proteins. CELP mRNAs accumulate most abundantly in vascular and epidermal tissues of floral organs. In the pistil, CELP mRNAs also accumulate in a thin layer of cells between the transmitting tissue and the cortex of the style and in a surface layer of cells of the placenta in the ovary. This unique accumulation pattern of CELP mRNAs in the pistil suggests a possible role in pollination and fertilization processes. CELP genes encode a class of plant extracellular matrix proteins that have several distinct structural features: a Pro-rich extensin-like domain with Xaa-Pro3-7 motifs and Xaa-Pro doublets, a Cys-rich region, and a highly charged C terminus. The extensin-like domains in these proteins differ significantly in their length and these differences appear to be results of both long and short deletions within the coding regions of their genes. Furthermore, the number of charged amino acid residues in the C-terminal region varies among the CELPs. These structural differences may contribute to functional versatility in the CELPs. On the other hand, the Cys-rich domain is highly conserved among CELPs and the positions of the Cys residues are conserved, suggesting that this region may have a common functional role. The presence of a Pro-rich domain and a Cys-rich domain in these CELPs is reminiscent of a class of hydroxyproline-rich glycoproteins, solanaceous lectins, that are believed to be important in cell-cell recognition. The structure of these CELPs indicates that they may be multifunctional and that their genes may have arisen from recombinational events.

Effective use of pictures as extra stimulus prompts

Past research on learning single words in the presence of pictures has suggested that the pictures can function as a blocking element which inhibits the development of an association between the written word and its spoken response. The purpose of this study was to investigate whether the extra stimulus pictorial prompts can be arranged in a different manner which does not inhibit the learning of the words. Three presentation techniques were investigated using samples (N = 12) of kindergarten children: matching, matching with the fading of the pictorial stimulus prompts, and feedback cueing. The results showed that, in general, the best learning occurred in the absence of the pictorial prompts, that is, when the words were presented alone. In the case of the feedback cueing condition, however, this technique neutralised the blocking effect of the pictures and the performance was as good as the word-alone condition.

Characterization of cDNAs for stylar transmitting tissue-specific proline-rich proteins in tobacco

The pistil of flowers is a specialized organ which contains the female gametophytes and provides the structures necessary for pollination and fertilization. Pollen deposited on the stigmatic surface of a compatible plant germinates a pollen tube which penetrates the stigmatic papillae and grows intercellularly through the style towards the ovules in the ovary. Pollen tube growth is largely restricted to the transmitting tissue in the style. Therefore the stylar transmitting tissue is extremely important for the migration of the pollen cell towards the ovary. We have isolated two related cDNAs, transmitting tissue-specific (TTS)-1 and TTS-2, derived from two proline-rich protein (PRP)-encoding mRNAs that accumulate specifically in the transmitting tissue of tobacco. The deduced PRP sequences share similarities with proline-rich cell wall glycoproteins found in a variety of plants. TTS-1 and TTS-2 mRNAs are induced in very young floral buds, accumulate most abundantly during the later stages of flower development when style elongation is the most rapid, and remain at relatively high levels at anthesis. These mRNAs become undetectable in maturing green fruits. In situ hybridization shows that TTS-1 and TTS-2 mRNA accumulation is restricted to the transmitting tissue of the style. The possible roles that these transmitting tissue-specific PRPs may play in maintaining the structural integrity of the style or in the function of this organ is discussed.

Characterization of cDNAs for stylar transmitting tissue-specific proline-rich proteins in tobacco

The pistil of flowers is a specialized organ which contains the female gametophytes and provides the structures necessary for pollination and fertilization. Pollen deposited on the stigmatic surface of a compatible plant germinates a pollen tube which penetrates the stigmatic papillae and grows intercellularly through the style towards the ovules in the ovary. Pollen tube growth is largely restricted to the transmitting tissue in the style. Therefore the stylar transmitting tissue is extremely important for the migration of the pollen cell towards the ovary. We have isolated two related cDNAs, transmitting tissue-specific (TTS)-1 and TTS-2, derived from two proline-rich protein (PRP)-encoding mRNAs that accumulate specifically in the transmitting tissue of tobacco. The deduced PRP sequences share similarities with proline-rich cell wall glycoproteins found in a variety of plants. TTS-1 and TTS-2 mRNAs are induced in very young floral buds, accumulate most abundantly during the later stages of flower development when style elongation is the most rapid, and remain at relatively high levels at anthesis. These mRNAs become undetectable in maturing green fruits. In situ hybridization shows that TTS-1 and TTS-2 mRNA accumulation is restricted to the transmitting tissue of the style. The possible roles that these transmitting tissue-specific PRPs may play in maintaining the structural integrity of the style or in the function of this organ is discussed.

A flower-specific cDNA encoding a novel thionin in tobacco

We isolated a flower-specific cDNA, FST (flower-specific thionin), which encodes a novel thionin from tobacco. Thionins are basic and cysteine (Cys)-rich, low molecular weight proteins found in many plants. They are believed to play a role in plant defense against pathogens. The central domain of the FST protein shares homology with three gamma-thionins. Like other thionin precursors, the FST protein has an N-terminal domain characteristic of a signal peptide and an acidic C-terminal domain. FST mRNA accumulates specifically in developing flowers and its level drops as flowers mature. Transcripts are present in petals, stamens and pistil but are not detectable in sepals. In situ hybridization revealed that FST mRNA is most abundant in the epidermal cells along the adaxial surface of petals, and in the surface cell layers of the carpel and anther walls. If the FST protein indeed has a protective role in flowers, this pattern of spatial distribution of FST mRNA would appear to maximize this effect on the two internal reproductive whorls. A possible biological role for FST is discussed.

Prognostic significance of DNA flow cytometry in non-Hodgkin's lymphoma

A series of cases of non-Hodgkin's lymphoma (NHL) were studied by morphology and flow cytometry. The DNA analysis was performed by applying a trypsin digestion method to archival paraffin-embedded samples. DNA aneuploid tumors constituted 47.4% of the total cases, and the frequency in the intermediate and the high malignant grade groups (51.9%, 76.8%) were significantly higher than that of the low grade group (17.6%; P less than 0.05). The S phase fraction (SPF) increased significantly with a high histological malignant grade (P less than 0.005). The mean SPF values of the low, intermediate and high grade lymphomas were 6.5 (0.6-18.8)%, 13.5 (3.2-37.3)% and 23.4 (4.4-41.4)%, respectively. Differences in ploidy status were not associated with survival rate. The survival rate of the cases with high SPF value in all cases of our series and low grade group of NHLs tended to become lower (P = 0.1 and 0.08, respectively). These results suggest that the flow cytometric analysis of DNA content should be a useful means for prediction of prognosis in non-Hodgkin's lymphoma.

Cytotoxicity against human peripheral blood mononuclear cells and T cell lines mediated by anti-T cell immunotoxins in the absence of added potentiator

Several in vitro assays have indicated that anti-T cell immunotoxins (IT), composed of monoclonal antibodies (MoAbs) conjugated to ricin A chain (RTA), are maximally effective against T cells only in the presence of potentiators. It was thought that such IT might not be sufficiently cytotoxic to deplete T cells in vivo upon administration to patients. Therefore, we have re-evaluated the in vitro assays and report herein that even with a short exposure time (2 h), the two anti-T cell IT, H65-RTA (anti-CD5 MoAb coupled to RTA) and 4MRTA (anti-CD7 MoAb coupled to RTA30), were specifically cytotoxic for peripheral blood mononuclear cells (PBMC) in the absence of potentiators. Moreover, as has been reported for IT when tested against T cell lines, prolonging the exposure time of the IT with PBMC from 2 h to as long as 90 h, without added potentiators, enhanced their cytotoxicity from 2- to 40-fold. In contrast, most T cell lines were more sensitive to IT in the presence of potentiator, and IT cytotoxicity was much less enhanced by prolonging the exposure time. Thus, T cell lines may not serve as accurate models to determine the efficacy of IT against PBMC in vitro or in vivo. We conclude that IT-induced cytotoxicity of PBMC can be demonstrated in vitro at pharmacologically achievable concentrations in the absence of added potentiators.

Chemical and physiochemical comparison of advanced atherosclerotic lesions of similar size and cholesterol content in cholesterol-fed New Zealand White and Watanabe Heritable Hyperlipidemic rabbits

Watanabe Heritable Hyperlipidemic (WHHL) and cholesterol-fed New Zealand White (CH-FED NZW) rabbits were sacrificed at 15 months of age or after 16 weeks of cholesterol feeding, respectively. During the experimental period, the arterial walls of both the CH-FED NZW and WHHL rabbits were exposed to similar amounts of cholesterol and the lesions which developed at the aortic arch had similar intimal thicknesses, total lipid and cholesterol content. However, the lesions of the WHHL rabbits morphologically resembled human plaques, and contained lipid in the form of smectic liquid crystalline droplets and cholesterol monohydrate crystals. The CH-FED NZW rabbits had lesions which were fatty streak-like, containing liquid crystalline cholesteryl ester droplets but few crystals. The aortic arch intimas of the CH-FED NZW rabbits contained significantly more cholesteryl ester, and less unesterified cholesterol and triglyceride, than those of the WHHL rabbits. The intimal compositions of the two rabbit models did not overlap. Analysis of the compositions predicted precipitation of cholesterol monohydrate crystals in the WHHL but not the CH-FED NZW. The physical state of the deposited cholesterol esters was similar in both with about half being in smectic liquid crystalline form at body temperature. Since the size and total lipid content of the lesions of the CH-FED NZW and WHHL rabbits were similar, we suggest that the greater time of exposure to hypercholesterolemia was important in the formation of cholesterol monohydrate crystal-containing plaques in the aortic arch of the WHHL rabbits.

Monoclonal antibody-mediated protection and neutralization of motility in experimental Proteus mirabilis infection

A panel of monoclonal antibodies with specificity for a wound isolate of Proteus mirabilis was established. Of nine antibodies studied in detail, three were broadly reactive with various Proteus isolates, while six reacted in a serotype-specific fashion with the strain used for immunization. Five of the six serotype-specific antibodies were reactive with lipopolysaccharide. The sixth serotype-specific antibody, 4-F (immunoglobulin G1 [IgG1]), was potently protective in a burn wound sepsis model and recognized a protein antigen. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot (immunoblot) analysis were used to determine that 4-F was reactive with flagellar protein. Approximately 1.3 micrograms of the antibody was sufficient to provide protection against 8 50% lethal doses of wound isolate, and approximately 26 micrograms provided full protection against challenge with 333 50% lethal doses. In vitro test results indicated that 4-F inhibited the motility of the wound isolate, and in vivo testing showed that it inhibited dissemination of the inoculum from the burn site to the liver and spleen. Whereas the antibody was highly effective in preventing the death of mice subsequent to challenge at a burn site, no protection was seen following an intraperitoneal challenge. These results may therefore indicate that the protection observed in the burn model is solely a reflection of the capacity of 4-F to neutralize bacterial motility.

Mode of inhibition of brain Na+,K+-ATPase by agelasidines and agelasines from a sea sponge

The Na+,K+-ATPase from brain or kidney and sarcoplasmic reticulum (SR) Ca2+-ATPase were inhibited potently by agelasidine C (Agd-C) and agelasine B (Ags-B), the bioactive principles of sea sponge, while Agd-C and Ags-B exerted less potent inhibition of heart Na+,K+-ATPase. The ionized moiety in Agd-C and the long nonpolar side chains in Ags-B play important roles in their inhibitory action. The inhibition of Na+,K+-ATPase by Agd-C or Ags-B was virtually reversed by diluting with the inhibitor-free solution. Kinetic analysis of the inhibitory effects of Agd-C and Ags-B indicates that the inhibition of pig brain Na+,K+-ATPase is parabolic and noncompetitive with respect to ATP. This may indicate that the inhibition of Na+,K+-ATPase results from the binding of two molecules of Agd-C or Ags-B to one enzyme. The sigmoidal behavior (n = 1.3-1.4) in the K+ activation curve for Na+,K+-ATPase was strikingly intensified (n = 2.1) by Agd-C, whereas it was almost eliminated (n = 1.1) by Ags-B. These results suggest that the cooperative interaction between K+-binding sites on the enzyme was dramatically altered.

Bending and flexibility of kinetoplast DNA

We have evaluated the extent of bending at an anomalous locus in DNA restriction fragments from the kinetoplast body of Leishmania tarentolae using transient electric dichroism to measure the rate of rotational diffusion of DNA fragments in solution. We compare the rate of rotational diffusion of two fragments identical in sequence except for circular permutation, which places the bend near the center in one case and near one end of the molecule in the other. Hydrodynamic theory was used to conclude that the observed 20% difference in rotational relaxation times is a consequence of an overall average bending angle of 84 +/- 6 degrees between the end segments of the fragment that contains the bending locus near its center. If it is assumed that bending results from structural dislocations at the junctions between oligo(dA).oligo(dT) tracts and adjacent segments of B DNA, a bend angle of 9 +/- 0.5 degrees at each junction is required to explain the observations. The extent of bending is little affected by ionic conditions and is weakly dependent on temperature. Comparison of one of the anomalous fragments with an electrophoretically normal control fragment leads to the conclusion that they differ measurably in apparent stiffness, consistent with a significantly increased persistence length or contour length in the kinetoplast fragments.

DNA bending at adenine . thymine tracts

Intrinsic bending of DNA molecules results from local structural polymorphism in regions of homopolymeric dA . dT which are at least 4 base pairs long; the A . T tracts must be repeated in phase with the helix screw. Bending, in the direction of base-pair tilt rather than roll, occurs at the junctions between the A . T tract and adjacent B-DNA, with a larger angle at the 3' than at the 5' end of the A tract.

The locus of sequence-directed and protein-induced DNA bending

The bending locus of trypanosome kinetoplast DNA, identified by gel electrophoresis, has tracts of a simple repeat sequence (CA5-6 T) symmetrically distributed about it, with a repeat interval of 10 base pairs. The analogous bending induced when catabolite gene activating protein binds to its recognition sequence near the promoter of the Escherichia coli lac operon is centred on a site about 5-7 base pairs away from the centre of the protein binding site.

A retrospective survey on side effects of praziquantel among 25,693 cases of schistosomiasis japonica

A retrospective survey involving 25,693 persons was carried out in four provinces and the city of Shanghai, China between December 1981 until May 1982 to document relatively serious side effects of praziquantel used in a mass treatment programme for schistosomiasis japonica. Only 122 or 0.47% of those participating in the study had experienced relatively serious side reactions to the drug. Most had only one kind of side effects but two or more were recorded in a few patients. Neuropsychiatric reactions were seen in 39 persons (0.15%,) cardiovascular reactions in 37 (0.14%), hepatic changes in four (0.02%), dermatological reactions in 18 (0.07%) and delayed reactions resulting in fatigue and inability to work in 29 (0.11%). Praziquantel remains the drug of choice for the treatment of oriental schistosomiasis, it is highly effective and although side effects are minimal, caution should be taken in the treatment of chronic disease with heart failure, ascites, poor hepatic compensation and renal failure.

CAP binding to B and Z forms of DNA

We have examined the interaction between the cyclic AMP receptor protein (CAP) and a small DNA fragment containing its specific recognition sequence by circular dichroism spectroscopy. The binding of CAP to this fragment induces a B to "C-like" change in the CD spectrum, which is different from that observed for non-specific binding. A one-to-one (CAP dimer to DNA) binding stoichiometry was deduced from spectroscopic titration data, as was a non-specific binding site size of 17 bp/dimer. In addition, we have compared the non-specific binding affinity of CAP for the B and Z forms of synthetic DNA copolymers. A slight preference for the B form was found. These results do not support the recent specific suggestion that CAP binds to a left-handed form of DNA (1), but indicate more generally that an optically detectable conformational change takes place in DNA on binding CAP.

Stability of carbohydrate-modified vesicles in vivo: comparative effects of ceramide and cholesterol glycoconjugates

The stability and tissue distribution of lipid vesicles modified at the surface by the incorporation of either a galactosyl ceramide (GalCer) or a galactosyl cholesterol (GalChol) glycoconjugate have been studied in mice by measuring the release of vesicle-entrapped 111In. Although the tissue distributions of both vesicle types were similar, the GalCer-containing vesicles were markedly less stable than those prepared with GalChol, whether administered orally or by intraperitoneal injection. Physical characterization of the vesicles in vitro suggests that the increased disruption rate for GalCer vesicles in vivo is related to structural instabilities induced by the cerebroside, which can then result in either an increased rate of vesicle uptake by tissues or a greater susceptibility to lysis. These studies demonstrate the importance of the nonpolar anchoring groups in determining the fate of surface-modified vesicles in vivo.

Solution structural studies of the A and Z forms of DNA

We report transient electric dichroism studies of short double-helical DNA and poly[d(G-C)] fragments in alcohol/water mixtures. The limiting reduced dichroism and the rotational correlation time changed abruptly in the alcohol concentration range expected for the DNA B-to-A and poly[d(G-C)] B-to-Z transitions. The Z form of poly[d(G-C)] was also induced by mitomycin C crosslinking in aqueous solution. The rotational correlation times observed for A- and Z-DNA were approximately consistent with dimensions determined by crystallographic and fiber diffraction analysis: the estimated rise per base pair was 2.8 A for A-DNA and 3.7 A for Z-DNA in solution. In addition, the observed limiting reduced dichroism values for A- and Z-DNA were close to the theoretical limit of -1.5, requiring a structure in which the base transition moments are effectively perpendicular to the double-helix axis. This is the result expected for any DNA double helix having dyad symmetry in which the base pairs are flat and the base transition moments lie predominantly in the short axis of the base pair and therefore close to a helix dyad axis. Only B-DNA deviates from this rule, strongly reinforcing our earlier conclusion that the base pairs in B-DNA are not flat but are propeller twisted, either statically or as a dynamic average.

Kin preference in infant Macaca nemestrina

The ability to recoginize conspecifics is a prerequisite for many types of social behaviour, including, for example, parent-offspring relation, mate selection and recognition, territorial defence and dominance coalitions. This ability is of special importance to Hamilton's kin selection hypothesis, which predicts that an individual's behaviour towards a conspecific will depend on the degree of genetic relatedness between them. Although recognition depends on previous experience between individuals in some species, this does not precluded the possibility that recognition could occur in its absence. For example, juveniles who disperse before nonlittermate siblings are born or adult males who do not participate in rearing their young might benefit from recognition abilities that are independent of prior association between the individuals. Here we show that young pigtail macaques prefer to interact with a related over an unrelated monkey in a laboratory test. Because subjects were separated from their dams at birth and reared apart from all other relatives, results suggest that kin recognition can occur in the absence of prior association with relatives.

Unfolding of nucleosomes by ethidium binding

We report spectroscopic, hydrodynamic, and biochemical studies on the complex of ethidium bromide with 140 base pair nucleosomal core particles. Fluorescence titration indicates a greater intrinsic affinity of ethidium for nucleosomes than for DNA, and fluorescence depolarization measurements imply increased immobilization of ethidium bound to nucleosomes, but with more extensive dye-dye energy transfer compared to DNA-bound dye. Ethidium intercalated into DNA in nucleosomes has a limiting reduced linear dichroism of -0.45 at 320 nm and -0.25 at 530 nm. Both the energy transfer and dichroism results are consistent with clustering of the nucleosome-bound dye molecules. Electric dichroism measurements and ultracentrifugation studies reveal that structural distortion of the nucleosome accompanies ethidium binding, occurring in the range of r (ethidium residues per base pair) values from 0.02 to 0.06. The distortion transition is characterized by an increase in the negative limiting reduced dichroism from 0.29 to 0.45 at 265 nm, an increase in the field-induced viscosity-limited rotational orientation time from 0.8 to 3 mus, and a decrease in sedimentation coefficient from 10.5 to 8.2 S. The complex was modeled hydrodynamically as a cylinder of 335-A length and 67-A diameter, containing 1.4 superhelical turns of DNA. Dimethylsuberimidate cross-linked nucleosomes, or native nucleosomes in the presence of Mg2+, bind ethidium weakly and are not distorted. The periodicity of cutting sites produced by DNase II digestion of nucleosomes remains constant as ethidium is added, but the bandwidth increases. A thermodynamic model is proposed to interpret the binding isotherm, based on enhancement of drug binding affinity due to release of superhelical stress in the nucleosome-ethidium complex.