Plasmodium falciparum: carbohydrates as receptor sites of invasion

Monosaccharides, disaccharides, and trisaccharides were tested as inhibitors of the in vitro growth of Plasmodium falciparum (strain FCB). While certain monosaccharides (N-acetyl-D-glucosamine, D-mannose, and 3-O-methyl-D-glucose) proved to exhibit a toxic or reversibly retarding effect on the intraerythrocytic development of the parasite, the corresponding alpha- or beta-methylglycosides did not. Several methylglycosides, synthetic di- and tri-saccharides, and artificial blood group antigens were further tested for inhibitory effects on invasion of host red blood cells in vitro. The synthetic disaccharides beta DGlcNAc(1----4) alpha DManOMe and beta DGlcNAc(1----4) DGlcNAc (chitobiose) were good inhibitors of invasion at 10 mM concentration, whereas beta DGal(1----4)beta DGlcNAcOMe was negligibly inhibitory. The inhibition rate of N-acetyl-D-glucosamine, beta-glycosidically linked to bovine serum albumin (BSA) by an alipathic spacer, -(CH2)8CO-, was not enhanced, compared to the corresponding hapten, beta DGlcNAcO(CH2)8COOCH3. The inhibition rates of blood group A- and B-trisaccharide haptens, which were inhibitors of invasion, were also not significantly enhanced when coupled to BSA by way of the corresponding amide spacer, -(CH2)2NHCO(CH2)7CO-. A remarkable enhancement of the inhibition rate was, however, observed when beta DGal(1----3) alpha DGalNAcO(CH2)2NHCO(CH2)7COOCH3 (T-hapten) was coupled to BSA. A clear-cut decrease in the inhibition rates of different beta-glycosides of N-acetyl-D-glucosamine, beta DGlcNAcOR, was observed, depending on the nature of the aglycon R(p-nitrophenyl greater than -(CH2)8COOCH3 greater than -(CH2)2NHCO(CH2)2COOCH3 greater than -CH3). Also, p-nitrophenyl-alpha-D-glucopyranoside was a much better inhibitor of invasion than the corresponding methyl glycoside, alpha DGlcOMe, which was not inhibitory. The properties of the aglycon spacer, used for the covalent attachment of the carbohydrate to the carrier protein, may thus be crucial for the outcome of the inhibition rate.     

Hybrid recombinant human leukocyte interferon inhibits differentiation in murine B-16 melanoma cells

We have investigated the effects of recombinant human leukocyte interferons (IFN-alpha A and IFN-alpha D) and various hybrid recombinant human leukocyte interferons on differentiation in B-16 mouse melanoma cells. Inhibition of both spontaneous and melanocyte hormone stimulated differentiation was observed with one hybrid construct, IFN-alpha A/D (Bgl) consisting of amino acids 1 to 62 from IFN-alpha A and amino acids 64 to 166 from IFN-alpha D. In contrast, the parental human interferons, IFN-alpha A and IFN-alpha D, when used alone or in combination, as well as other hybrid human leukocyte interferons, did not cause significant inhibition of melanogenesis in B-16 mouse cells. The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) also inhibited B-16 differentiation and the combination of TPA with IFN-alpha A/D (Bgl) or mouse L-cell interferon was synergistic in delaying melanogenesis. These studies indicate that the IFN-alpha A/D (Bgl) hybrid that exhibits antiviral activity on mouse cells can also inhibit differentiation of murine cells.     

X-ray Crystallographic Study of an HIV-1 Fusion Inhibitor with the gp41 S138A Substitution

The S138A substitution of fusion inhibitory peptides derived from the C-terminal heptad repeat (C-HR) of the human immunodeficiency virus type 1 (HIV-1) gp41 leads to enhanced binding affinity to the N-terminal heptad repeat (N-HR). As such, these peptides exhibit highly potent anti-HIV-1 activity. X-ray crystallographic analysis was performed to understand the effect of the substitution on binding affinity. The comparison of the native and S138A crystal structures indicated that the increase in the hydrophobicity of the S138A substitution may aid the stabilization of the N-HR/C-HR complex through additional hydrophobic contacts. Free-energy calculations suggest that the difference between the desolvation free energies of the C-HR-derived peptides with and without the S138A mutation dominates the observed difference in anti-HIV-1 activity.     

Cytokine-induced stable neuronal differentiation of human bone marrow mesenchymal stem cells in a serum/feeder cell-free condition

The characteristics and multilineage differentiation potential of bone marrow mesenchymal stem cells (BM MSC) remain controversial. This study aimed to characterize human BM MSC isolated by plastic adherent or antibody selection and their neuronal differentiation potential using growth factors or chemical inducing agents. MSC were found to express low levels of neuronal markers: neurofilament-M, beta tubulin III, and neuron specific enolase. Under a serum- and feeder cell-free condition, basic fibroblast growth factor, epidermal growth factor, and platelet-derived growth factor induced neuronal morphology in MSC. In addition to the above markers, these cells expressed neurotransmitters or associated proteins: gamma-aminobutyric acid, tyrosine hydroxylase and serotonin. These changes were maintained for up to 3 months in all bone marrow specimens (N = 6). In contrast, butylated hydroxyanisole and dimethylsulfoxide were unable to induce sustained neuronal differentiation. Our results show that MSC isolated by two different procedures produced identical lineage differentiation with defined growth factors in a serum- and feeder cell-free condition.     

Identification of the PXW sequence as a structural gatekeeper of the headpiece C-terminal subdomain fold

The HeadPiece (HP) domain, present in several F-actin-binding multi-domain proteins, features a well-conserved, solvent-exposed PXWK motif in its C-terminal subdomain. The latter is an autonomously folding subunit comprised of three alpha-helices organised around a hydrophobic core, with the sequence motif preceding the last helix. We report the contributions of each conserved residue in the PXWK motif to human villin HP function and structure, as well as the structural implications of the naturally occurring Pro to Ala mutation in dematin HP. NMR shift perturbation mapping reveals that substitution of each residue by Ala induces only minor, local perturbations in the full villin HP structure. CD spectroscopic thermal analysis, however, shows that the Pro and Trp residues in the PXWK motif afford stabilising interactions. This indicates that, in addition to the residues in the hydrophobic core, the Trp-Pro stacking within the motif contributes to HP stability. This is reinforced by our data on isolated C-terminal HP subdomains where the Pro is also essential for structure formation, since the villin, but not the dematin, C-terminal subdomain is structured. Proper folding can be induced in the dematin C-terminal subdomain by exchanging the Ala for Pro. Conversely, the reverse substitution in the villin C-terminal subdomain leads to loss of structure. Thus, we demonstrate a crucial role for this proline residue in structural stability and folding potential of HP (sub)domains consistent with Pro-Trp stacking as a more general determinant of protein stability.     

分子人类学与现代人的起源*

1953年Watson & Crick 对于DNA双螺旋结构模型的提出及对其遗传机理的解释,标志着现代分子生物学的诞生。其后短短50年的时间里,分子生物学在各个学科之间广泛渗透,相互促进,不断深入和发展。在以研究人类的起源和进化为首要任务的人类学领域,由于现代分子生物学理论和方法的应用,诞生了分子人类学这一全新的结合型分支学科,为人类学的发展提供了科学可信的研究方法和具发展前景的研究方向。系统地介绍了分子人类学的发展历史、研究方法及原理;另外,结合分子人类学在古人类学研究中的应用,讨论了关于现代人起源的“非洲起源说”和“多地区连续演化说”。Abstract: Since Watson & Crick put forward the double-helix model of DNA structure and hereditary mechanism in 1953, it is generally accepted that this event marks the birth of modern molecular biology. This new field of biology has experienced a flourishing development in the past 50 years. On one hand, the development of molecular biology has been deeply influencing many relative fields; on the other hand, its own proceeding pace has been accelerated by the reaction from the other fields. Anthropology is one of the fields most deeply impacted by the theory and method of molecular biology. Most importantly, molecular anthropology was born as a result of combination of molecular biology, anthropology as well as paleoanthropology. This new branch provides reliable method and vital direction for paleoanthropology. This paper systematically reviews the history, principle and method of molecular anthropology. Two hypotheses on the origin of modern human, which include “out-of-African theory” and “theory of multiregional evolution” are also discussed for the purpose of showing how molecular anthropology is applied in paleoanthropology.     

Regional isolation in the Balkan region: an analysis of craniofacial variation

Biological variation is investigated among contemporary Croatians, Bosnians, American whites, and other multitemporal Balkan populations (World War II Croatians, Macedonians, and Greeks) via multivariate statistics and distance measures of the craniofacial complex. This study demonstrates that there is considerable variation among groups of European ancestry. Bosnians and Croatians who are thought to be relatively homogenous and historically to originate from the same Slav ancestry show local variations. While environmental plasticity has been used to explain cranial changes among human groups, it does not adequately explain the variation observed between Bosnians and Croatians. It is an oversimplification to exclusively attribute the vast range of variability observed among local as well as geographic populations to environmental adaptations.     

Hormonal induction of spermiation,courting behavior and spawning in the southern bell frog,Litoria raniformis

We trialled the efficacy of various exogenous hormones to induce spermiation, courtship behavior, and spawning in the “endangered” southern bell frog, Litoria raniformis. Intralymphatic administration of Lucrin^®, a synthetic nonapeptide luteinizing hormone releasing hormone (LHRH), was used successfully to induce courting behaviors and ejaculation of spermatozoa in males. Various hormones, including Lucrin^®, another synthetic LHRH analog ([des‐Gly¹⁰, D‐Ala⁶]‐LHRH), human chorionic gonadotropin, progesterone, and a dopamine receptor antagonist failed to promote oviposition and spawning in females. This and earlier studies indicate that in the efficacy of hormonal induction in amphibians varies between taxa, hormones, and genders. The lack of response in females may limit the use of reproduction technology in the southern bell frog and closely related species of Australian bell frogs. Zoo Biol 29:774–782, 2010. © 2010 Wiley‐Liss, Inc.     

Relationship between antibody productivity by activated human lymph node lymphocytes from lung cancer patients and lymphocyte subsets

Regional lymph node lymphocytes from five patients with primary lung cancer were analyzed for subset composition, and exposed in vitro to the polyclonal human B cell mitogen Staphylococcus aureus Cowan I (SACI) or the murine B cell mitogen lipopolysaccharide (LPS) and then fused with mouse myeloma cells for investigation at the clonal level of their antibody (Ab) production and its statistical relation to the original subset composition. No correlation was found between the proportion of CD19+, CD23+, or CD3+ cells in the lymphocyte sample prior to its exposure to either SACI or LPS, and the Ab production efficiency, defined as the ratio of the number of Ab producing wells to the total number of proliferating wells. For lymphocytes exposed to LPS, however, a strong correlation (r = 0.931, p = 0.02) was observed between the Ab production efficiency and the ratio of CD8+ to CD3+ cells (CD8/CD3) in the original sample at least within the ranges studied (CD8/CD3 = 0.216–0.288). For those exposed to SACI, no correlation was found between the Ab production efficiency and the CD8/CD3 ratio (r = 0.881, p = 0.12) or the proportion of CD8+ cells (r = 0.808, p = 0.19) in the original sample. These results suggest that the repertoire of B cells responsive to LPS is different at least in part from the repertoire responsive to SACI and that the ratio CD8/CD3 could serve as a practical predictor for Ab production by human lymphocytes stimulated with LPS. This revised version was published online in July 2006 with corrections to the Cover Date.     

Loss of viability during freeze–thaw of intact and adherent human embryonic stem cells with conventional slow-cooling protocols is predominantly due to␣apoptosis rather than cellular necrosis

Summary A major challenge in the widespread application of human embryonic stem (hES) cells in clinical therapy and basic scientific research is the development of efficient cryopreservation protocols. Conventional slow-cooling protocols utilizing standard cryoprotectant concentrations i.e. 10% (v/v) DMSO, yield extremely low survival rates of <5% as reported by previous studies. This study characterized cell death within frozen–thawed hES colonies that were cryopreserved under standard conditions. Surprisingly, our results showed that immediately after post-thaw washing, the overwhelming majority of hES cells were viable (≈98%), as assessed by the trypan blue exclusion test. However, when the freshly-thawed hES colonies were incubated within a 37 °C incubator, there was observed to be a gradual reduction in cell viability over time. The kinetics of cell death was drastically slowed-down by keeping the freshly-thawed hES colonies at 4 °C, with >90% of cells remaining viable after 90 min of incubation at 4 °C. This effect was reversible upon re-exposing the cells to physiological temperature. The vast majority of low temperature-exposed hES colonies gradually underwent cell death upon incubation for a further 90 min at 37 °C. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end-labeling (TUNEL) assay confirmed apoptosis-induced nuclear DNA fragmentation in frozen–thawed hES cells after incubation at 37 °C for 90 min. Expression of active caspase-3 enzyme, which is another prominent marker of apoptosis, was confirmed by immunocytochemical staining, while transmission electron microscopy showed typical ultrastructural features of apoptosis such as chromatin condensation and margination to the nuclear membrane. Hence, our results demonstrated that apoptosis instead of cellular necrosis, is the major mechanism of the loss of viability of cryopreserved hES cells during freeze–thawing with conventional slow-cooling protocols.