Electron transport through one-dimensional lateral surface superlattices in magnetic fields.
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Journal Article↗
Biomedical subjects
H Xu
Publications and source records attributed to H Xu.
A preliminary study of skin electrical injury with computerized image analysis.
This paper reports the application of computerized image analysis to a quantitative study of skin electrical injury in order to provide an objective and quantitative standard for identifying the electrical mark. The differences between antemortem and postmortem electrical injuries were also studied. In normal and electrically-injured human skin, the long/short axes ratio of nuclei were measured. The mean of epithelial basal cells was 1.4344 and 5.9325, respectively, the mean of hair follicle cells was 1.6193 and 4.5988, respectively, and the mean of capillary endothelial cells was 4.0229 and 4.3593, respectively. In rat specimens, the long/short axes ratio of nuclei of normal skin, at 15 and 5 min ante-mortem and at 5 min postmortem injury, the mean epithelial basal cells was 1.4124, 4.5417, 5.2282 and 5.0447, respectively. The mean of hair follicle cells was 1.4140, 4.4863, 4.1146 and 4.4522, respectively, while the mean of capillary endothelial cells was 2.8398, 3.7514, 3.6159 and 3.6977, respectively. The results indicate that the differences between electrical injuries and normal skin with respect to the ratios of long/short axes of the epithelial basal cell nuclei and hair follicle cell nuclei are of remarkable significance. On the other hand, no significant difference could be found between antemortem and postmortem injuries, nor between electrical injury and normal skin, concerning the long/short axes ratios of capillary endothelial cell nuclei. This result provides a preliminary objective standard for the changes of electrical skin injury.
Animals↗
cDNA selection and other approaches in positional cloning.
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Animals↗
A search for genes from the dark band regions of human chromosome 21.
As part of an effort to isolate genes from the entire long arm of human chromosome 21, we performed cDNA selection with 15 YACs from the regions of the pericentromeric heterochromatin and the two Giemsa dark bands of this chromosome using cDNA libraries from six different tissues. Nine of these YACs mapped to the Giemsa dark band, 21q21. The 9 YACs cover approximately 6 Mb of DNA, representing 15% of 21q and a significant portion of the 12-15 Mb estimated to be within this band. Several lines of evidence from analysis of the selected cDNA libraries suggest that this region of 21q has very few single-copy transcribed sequences. An EcoRI library was constructed with DNA from 1 of the 9 YACs. Grail analysis of the sequences of both ends of 24 YAC-specific clones from this EcoRI library revealed no potential exons. In contrast to these results, the selected cDNA libraries of a control YAC from the human MHC region in 6p21.3 as well as those from most of the other 21q YACs consisted largely of YAC-specific single-copy cDNA clones. Given the success of the cDNA selection method for finding a large number of genes in YACs from other chromosomal regions, these results suggest that the 6 Mb of DNA in the dark band 21q21 contains few single-copy sequences expressed in this tissue set. In contrast, selected cDNA libraries from the pericentromeric region, the telomeric border of the dark band 21q21, and the dark band 21q22.2 yielded more than 30 new ESTs.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Probes for narcotic receptor-mediated phenomena. 20. Alteration of opioid receptor subtype selectivity of the 5-(3-hydroxyphenyl)morphans by application of the message-address concept: preparation of delta-opioid receptor ligands.
Derivatives of racemic and optically active 5-(3-hydroxyphenyl)-2-methylmorphan (5-(3-hydroxyphenyl)-2-methyl-2-azabicyclo[3.3.1]nonane, 1) were synthesized containing additional aromatic moieties, as an application of the message-address concept targeted at producing delta-opioid receptor selective ligands. In vitro radioreceptor binding studies in rat brain revealed that both of the parent enantiomers, (-)- and (+)-1, had a high affinity for the mu-opioid receptor (21 nM), a slight affinity for kappa 1-opioid receptors (approximately 800-900 nM), and less than 1000 nM affinity for the delta-opioid receptor (mu/delta IC50 ratio of < 0.02 for both). A derivative of (-)-1 containing an indole moiety fused at the C6-C7 position of the phenylmorphan nucleus, (-)-11, displayed a > 180-fold increase in affinity for the delta-opioid receptor with an IC50 value of 6 nM. The parent compound (-)-1 had only 26% agonist activity at 30 microM in the mouse vas deferens (delta) bioassay, whereas compound (-)-11 had an IC50 of 393 nM in this preparation, indicating the importance of the indole moiety in imparting delta-opioid agonist activity to the phenylmorphan (-)-11. A structure-activity relationship (SAR) study of N-alkyl derivatives of the racemic nor 11 indicated similarities between the interaction of various derivatives with the mu- and delta- but not the kappa 1-opioid receptor. As studies on the molecular basis of the interaction of opioid ligands with their respective receptors continue to gain momentum, the SAR data described herein for the synthetic phenylmorphans will prove useful for further studies.
Animals↗
Enantiomers of diastereomeric cis-N-[1-(2-hydroxy-2-phenylethyl)- 3-methyl-4-piperidyl]-N-phenylpropanamides: synthesis, X-ray analysis, and biological activities.
(+/-)-cis-N-[1-(2-Hydroxy-2-phenylethyl)-3-methyl-4-piperidyl]-N- phenylpropanamide (1) is a mixture of four stereoisomers [(2S,3R,4S)-1a, (2R,3R,4S)-1b, (2R,3S,4R)-1c, and (2S,3S,4R)-1d], which together constitute two diastereoisomeric pairs of optical isomers. These four stereoisomers were prepared from optically active intermediates of known absolute configuration by procedures which had no effect on the configurations of the piperidine 3- and 4-carbons. The configuration of the phenylethyl 2-carbon in the final products was determined by X-ray analysis of (2S,3S,4R)-1d. A 1H NMR comparison of the final products to ohmefentanyl established that the racemic pair previously known as ohmefentanyl was a mixture of (2S,3R,4S)-1a and (2R,3S,4R)-1c. The individual activities of 1a, 1b, 1c, and 1d were evaluated in a variety of binding and pharmacological assays. The binding data revealed that isomers 1b and 1c had the highest affinity and selectivity for the mu site labeled with [3H]DAMGO. In contrast, the four isomers displaced [3H]etorphine in the order 1a approximately 1b > 1c approximately 1d. Evaluation of the four isomers on the mouse vas deferens (MVD) preparation revealed a potency order of 1a > 1b > 1c > 1d with concentrations of 1a and 1b in the femtomolar range causing inhibition. Experiments using the antagonists naltrexone (mu), ICI 174864 (delta), and norbinaltorphimine (kappa) demonstrated that the effects of 1a were mediated largely by the mu receptor while both delta and kappa agonist effects contributed to the actions of 1b and 1c. Isomer 1d acted as a weak mu antagonist in the MVD preparation. The same potency order was observed in a mouse analgesic assay and a rhesus monkey single dose suppression study. From the latter study the potency of 1a was estimated to be 20,000-50,000 times that of morphine, making this isomer one of the most potent opiates known. In the rhesus monkey study, isomer 1d failed to substitute for morphine and seemed to exacerbate withdrawal at doses of 0.6, 3.0, and 6.0 mg/kg. On the basis of the mouse data, isomer 1a was 21,000 times more potent than 1d, whereas isomers 1b and 1c were similar in their opiate activity in vivo. Using the optical isomers of cis-3-methylfentanyl as reference compounds, we analyzed the effects on the pharmacological activities of introducing a phenylethyl 2-hydroxyl group into the molecule.(ABSTRACT TRUNCATED AT 400 WORDS)
Analgesics↗
Newborn baboon serum lacks natural anti-pig xenoantibody.
Discordant xenotransplantation represents an attractive alternative to allotransplantation in light of the shortage of donor organs currently available for cardiac allotransplantation. Unfortunately, discordant xenotransplantation is still limited by hyper-acute rejection, a process thought to be mediated by natural anti-xenodonor antibody. Based on data that cytotoxic natural xenoantibodies are IgM in nature, we postulated that natural xenoantibodies may be absent from newborn serum. Baboon sera were collected from infant baboons. Pooled adult baboon sera were used as controls. A whole cell ELISA was performed to determine the binding of xenoantibodies to pig aortic endothelial cells and pig lymphocytes. The cytotoxicity of both adult and newborn baboon sera to pig aortic endothelial cells was measured by a MTT (3-(4,5-dimethyl-thiazoyl-2-y) 2,5 diphenyl-tetrazolium bromide) assay. Newborn baboon sera demonstrated very low levels of binding of natural IgM xenoantibodies to pig endothelial cells and lymphocytes, whereas natural IgM xenoantibodies from adult baboon sera bound significantly to both pig aortic endothelial cells and lymphocytes. IgG natural antibodies in both adult and newborn sera bound to pig endothelial cells and pig lymphocytes. The MTT assay demonstrated high levels of cytotoxicity to pig endothelial cells from adult baboon sera and very low levels of cytotoxicity from newborn baboon sera. In this study, newborn baboon sera were demonstrated to be free of natural IgM xenoantibodies to pig endothelial cells and lymphocytes. Although natural anti-pig IgG antibodies were present in newborn sera, newborn baboon sera lack cytotoxicity to pig target cells. These findings suggest that IgM is the more important xenoantibody and that hyperacute rejection of discordant cardiac xenografts may be avoidable in the newborn.
Aging↗
IL-12 induces growth of the IL-4-dependent CT4S line and has a synergistic effect on IL-4-induced CT4S proliferation.
In the course of studies designed to explore the effect of interleukin 12 (IL-12) on the development of experimental autoimmune uveoretinitis (EAU), we observed that supernatants from IL-12-treated cultures of ocular antigen-specific lymphocytes induced proliferation of the interleukin 4 (IL-4)-dependent CT4S line. This result was surprising, as these supernatants were not expected to contain high levels of IL-4. We therefore explored the possibility that IL-12 itself, that remained in the supernatants, could induce proliferation of CT4S cells. In this series of experiments we demonstrate that CT4S cells proliferate to recombinant as well as to naturally produced IL-12, and that IL-4 and IL-12 synergize in supporting proliferation of CT4S cells. The proliferation induced by IL-12, as well as the synergistic effect with IL-4, can be reversed by neutralizing anti-IL-12 antibodies. Proliferation of CT4S can be abrogated completely by a combination of antibodies against IL-4 and IL-12. Our data have important implications for the use of CT4S as a specific bioassay for IL-4, since both IL-4 and IL-12 may be found together in at least some culture supernatants. Furthermore, our results suggest that the CT4S line (or a derivative selected from it) could be used as a bioassay for detection of IL-12 in combination with the specific antibodies.
Animals↗
Erratum: C60-induced reconstruction of the Ge(111) surface
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Journal Article↗
Bcp1, a gene required for male fertility in Arabidopsis.
Male fertility in flowering plants is dependent on production of viable pollen grains within the anther. Genes expressed exclusively in the anther are likely to include those that control male fertility. On the basis of their tissue specificity, such genes have been isolated, yet in none of them has this function been demonstrated. Here we report that one such gene, Bcp1, is active in both diploid tapetum and haploid microspores and is required for pollen fertility. Perturbation of this gene in either tapetum or microspores prevents production of fertile pollen in transgenic Arabidopsis plants. When tapetum expression of this gene is perturbed, mature anthers contain dead shriveled pollen. On the other hand, when microspore expression is perturbed, anthers show 1:1 segregation of viable/aborted pollen. These findings identify a class of sporophytic/gametophytic genes controlling male fertility and, hence, reproduction in flowering plants.
Amino Acid Sequence↗
Absence of hyperacute rejection in pig-to-primate orthotopic pulmonary xenografts.
The shortage of organ donors for transplantation is more pronounced for the lung than for any other solid organ. To address this problem, we evaluated the feasibility of pulmonary xenotransplantation. Preliminary investigations demonstrated that orthotopically placed pig lungs in cynomologous monkey recipients could be engrafted up to 9 hr after reperfusion without evidence of hyperacute rejection. In this study, the rejection reaction of pig lungs transplanted orthotopically into baboons (n = 6) was further investigated by ELISA and immunohistochemistry. Four baboon recipients were killed at 24 hr and 2 recipients were killed at 72 hr after transplantation. Pulmonary arterial flow measurements demonstrated flow to the grafts, and systemic arterial and xenograft pulmonary venous blood gas analysis suggested function of the donor lungs during the course of engraftment. Serum levels of baboon anti-pig endothelial cell xenoantibody were normal and decreased minimally over time. Immunohistochemical staining of biopsies demonstrated trace IgG and IgM along graft endothelium 2 hr after reperfusion. At 8 hr, biopsy samples showed no immunoglobulin bound to endothelial cells. Staining for complement was negative. Fibrin and platelets were detected along xenograft endothelium. Despite these findings, the lung xenografts appeared injured and clinically rejected. During the first 8 hr after reperfusion, the grafts were hyperemic and subsequently became focally ecchymotic. Chest x-rays showed progressive pulmonary congestion. These findings suggest that the lung may be relatively resistant to antibody-mediated hyperacute rejection and efforts are being directed toward identifying the mechanism of the observed xenograft lung injury.
Animals↗
Absence of hyperacute rejection in newborn pig-to-baboon cardiac xenografts.
The shortage of organs for transplantation is especially severe for the critically ill newborn infant, for whom donors of the appropriate size are particularly scarce. One way to overcome this problem is to use animals in lieu of humans as organ donors. The major limitation to using animals for this purpose is the susceptibility of animal organs to hyperacute rejection, a violent rejection reaction thought to be mediated by antidonor antibody and complement. To evaluate the potential application of xenotransplantation to newborns, we tested neonatal humans and neonatal baboons and found that neither population expressed significant levels of xenoreactive anti-pig antibodies. We transplanted heterotopically hearts from newborn pigs into unmanipulated newborn baboons (n = 4). There was no evidence of hyperacute rejection in any of the grafts; the animals were killed with functioning grafts at 15, 81, 82, and 82 hr. This outcome contrasts with that of newborn pig-to-mature baboon and mature pig-to-mature baboon cardiac xenografts, which were rejected within 1 hr of transplantation. The histology of pig graft biopsies from the newborn recipients was normal. Immunohistochemistry revealed only traces of IgM, C3, C4, and the membrane attack complex along graft endothelium. Fibrin deposition along endothelial surfaces was observed early after transplantation and became more extensive with time; in the absence of endothelial bound antibody or complement, this change may represent preservation injury. This study suggests that due to low levels of natural antibody, the newborn infant may permit prolonged xenograft survival.
Animals↗
Synthesis, properties, and pharmacokinetic studies of N2-phenylguanine derivatives as inhibitors of herpes simplex virus thymidine kinases.
Two series of selective inhibitors of herpes simplex virus types 1 and 2 (HSV1,2) thymidine kinases (TK) have been developed as potential treatment of recurrent virus infections. Among compounds related to the potent base analog N2-[m-(trifluoromethyl)phenyl]guanine (mCF3-PG), none was a more potent inhibitor than mCF3PG itself. Compounds related to the nucleoside N2-phenyl-2'-deoxyguanosine (PhdG), but with alkyl, hydroxyalkyl, and related substituents at the 9-position in place of the glycosyl group of PhdG, retained significant but variable inhibitory potencies against the HSV TKs. The most potent inhibitor of HSV1 TK among 9-substituted derivatives, 9-(4-hydroxybutyl)-N2-phenylguanine (HBPG), was a competitive inhibitor with respect to the substrate thymidine but was not itself a substrate for the enzyme. Water solubilities and 1-octanol:water partition coefficients for the 9-substituted N2-phenylguanines were linearly but oppositely related to the sum of hydrophobic fragmental constants (sigma f) of the 9-substituents. Four of the inhibitors were given as solutions to mice by iv and ip routes, and the time course of their plasma concentrations was determined by HPLC analysis of the parent compounds. HBPG was completely absorbed by the ip route, and the plasma concentration could be prolonged by use of suspension formulations. HBPG is a candidate for animal trials of the ability of TK inhibitors to prevent recurrent herpes virus infections.
Antiviral Agents↗
6 beta-[125iodo]-3, 14-dihydroxy-17-methyl-4, 5 alpha-epoxymorphinan ([125I]IOXY-AGO): a potent and selective radioligand for opioid mu receptors.
The recent cloning and expression of an opioid mu receptor has opened up new opportunities for research in opioid pharmacology. The relatively low level of transient receptor expression in COS cells emphasizes the need for radioligands with high specific activity and low nonspecific binding with which to label receptors. In addition, recent data indicating that agonists and antagonists bind to different domains on the same receptor protein indicate the utility of having both agonist and antagonist radioligands available for the study of opioid receptor mechanisms. Previous studies characterized the binding of the opioid antagonist 6 beta-[125iodo]-3,14-dihydroxy-17-cyclopropylmethyl-4,5 alpha-epoxymorphinan ([125I]IOXY) and showed that this naltrexone analog labels mu and kappa 2 receptors in rat and guinea pig brain with high affinity and low nonspecific binding. In the present study, we synthesized the agonist congener of IOXY, 6 beta-iodo-3,14-dihydroxy-17-methyl-4,5 alpha-epoxymorphinan. We named this novel agent IOXY-AGO for IOXY-agonist. Competition binding studies showed that IOXY-AGO has high affinity for mu receptors (Ki = 0.28 nM) and lower affinity for delta (Ki = 18.7 nM) and kappa 1 (Ki = 33.9 nM), kappa 2a (Ki = 38.4 nM) and kappa 2b (Ki = 58.2 nM) binding sites. IOXY-AGO was radioiodinated to a specific activity of 2,200 Ci/mmol. [125I]IOXY-AGO binding was rapid, readily reversible, and characterized by low nonspecific binding.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Ligand selectivity of cloned human and rat opioid mu receptors.
Opiate receptors play major roles in analgesic and euphoric effects of opiate drugs. Recent cloning of cDNAs encoding the rodent and human mu receptor revealed high homology between the predicted receptors but also some sequence differences. To determine if these sequence differences produced significant changes in ligand-selectivity profiles, we assessed these profiles in expressing COS and CHO cell lines using the agonist ligand [125I]IOXY-AGO (6 beta-[125Iodo]-3,14-dihydroxy-17-methyl-4,5 alpha- epoxymorphinan). This ligand's high specific activity (2,200 Ci/mmol) and high affinity for mu opioid receptors generated high signal-to-noise ratio binding. The resulting ligand-selectivity profiles of the human and rat mu receptors reveal modest differences in affinities for morphine and naloxone in COS cells but not CHO cells. Ligand-selectivity profiles of the rat and human mu receptors were otherwise similar. Interesting differences between these data and data previously obtained with the peptide agonist [3H]DAMGO suggest that the peptide and alkaloid agonists may label different domains of the mu receptor.
Analgesics↗
p32, a platelet autoantigen recognized by an SLE-derived autoantibody that inhibits platelet aggregation.
We have previously described an SLE-derived human hybridoma autoantibody, 9604, which binds to activated but not to resting platelets, inhibits platelet aggregation, and immunoprecipitates a surface-labelled poly-peptide of 32,000 molecular weight (MW) (p32). In the present study, using a murine monoclonal anti-p32 antibody (8E8), we show that p32 is responsible for the binding of 9604 to activated platelets. First, 8E8 bound to the surface of activated but not resting platelets, as detected by flow cytometry, showing saturation with 1900 antibody molecules bound/platelet and a Kd of 72 nM. Second, complete inhibition of the binding of 9604 to ADP-activated platelets by 8E8 and inhibition of the reactivity of 8E8 with p32 by 9604 demonstrated that 8E8 and 9604 recognize the same 32,000 MW platelet polypeptide. Isolation of platelet proteins, using an 8E8-affinity column, showed high MW bands corresponding to multimers of p32 under non-reducing conditions, and isolated p32 tended to self-associate even under reducing conditions. High performance liquid chromatography (HPLC) demonstrated that the native p32-containing protein has an approximate MW of 450,000. A comparison of the functional properties of murine monoclonal 8E8 and human monoclonal 9604 revealed that both antibodies are cytotoxic to platelets in 51Cr-release assays. In contrast, 8E8, unlike 9604, did not affect platelet aggregation, suggesting that different epitopes may be recognized by the two antibodies. These findings demonstrate that p32 is a subunit of an activation marker that is expressed on the surface of activated platelets and recognized by an SLE-derived anti-platelet autoantibody. Our data also indicate that murine monoclonal antibodies produced against platelet autoantigens may not mimic the functional activities of spontaneously occurring autoantibodies, probably due to the recognition of different epitopes.
Animals↗
Dendritic cells differentiated from human monocytes through a combination of IL-4, GM-CSF and IFN-gamma exhibit phenotype and function of blood dendritic cells.
Our previous studies demonstrated that monocytes, when cultured under certain conditions, are able to differentiate into DC-like cells (MoDC) presenting a high accessory activity and low phagocytic function. In the present study, we demonstrate that under the effect of a triple combination of IL-4, IFN-gamma and GM-CSF human blood monocytes are able to differentiate into the cells expressing an identical phenotype and functional features of blood dendritic cells. MoDC stimulated T cell proliferation 20-30 times higher than untreated monocytes, similar to blood DC. They expressed abundant HLA-DR molecules, but only trace amounts of the monocyte/macrophage markers CD16 (FcR III), CD32 (FcR II), and CD14. Phagocytosis of Ig- and complement-opsonized bacteria was reduced by 93%.
Cell Differentiation↗
A cDNA clone encoding an IgE-binding protein from Brassica anther has significant sequence similarity to Ca(2+)-binding proteins.
Thirteen cDNA clones encoding IgE-binding proteins were isolated from expression libraries of anthers of Brassica rapa L. and B. napus L. using serum IgE from a patient who was specifically allergic to Brassica pollen. These clones were divided into two groups, I and II, based on the sequence similarity. All the group I cDNAs predicted the same protein of 79 amino acids, while the group II predicted a protein of 83 amino acids with microheterogeneity. Both of the deduced amino acid sequences contained two regions with sequence similarity to Ca(2+)-binding sites of Ca(2+)-binding proteins such as calmodulin. However flanking sequences were distinct from that of calmodulin or other Ca(2+)-binding proteins. RNA-gel blot analysis showed the genes of group I and II were preferentially expressed in anthers at the later developmental stage and in mature pollen. The recombinant proteins produced in Escherichia coli was recognized in immunoblot analysis by the IgE of a Brassica pollen allergic patient, but not by the Ige of a non-allergic patient. The cDNA clones reported here, therefore, represent pollen allergens of Brassica species.
Amino Acid Sequence↗