Artificial bone of porous tricalcium phosphate ceramics and its preliminary clinical application

Summary The authors have prepared the artificial bone of porous tricalcium phosphate ceramics according to an appropriate formula and manufacturing technology. Physical and chemical testing shows that it possesses several distinguishing features: the communicating pores and macro/micropores; mean pore size, 380 μm (from 240 μm to 510 μm); porosity, 46.4 %; and compressive strength, 97.4 kg/cm². It consists of CaO (49.09 %) and P₂O₅ (48.84 %). The testing of its biocompatibility shows that it is devoid of systemic or local toxicity, and free of irritation or foreign body response in tissues, and it does not result in hemolysis or mutation. The new bone readily grows into its pores with direct contact to the implanted material. 11 cases of bone defects were treated with this artificial bone with satisfactory results.     

Neutrophilic defensins penetrate the blood-brain barrier

Defensins are small, cationic, cyclic peptides that are abundantly stored in granules of neutrophils. Defensins non-specifically interact with membranes by forming weakly ion-selective pores. Here we demonstrate immunolocalization of defensin-secreting cells in human brain. Defensins, secreted by activated granulocytes, apparently are not prevented by the blood-brain barrier (BBB) from diffusing across cerebral endothelium to penetrate the neuropil for a considerable distance from the granulocyte. This is in contrast to other neutrophil proteins like the granuleassociated enzyme elastase or the cytosolic protein MRP-14, which are strictly localized to the cytoplasm or granules of neutrophils. Thus, defensins, known chemokinetic and chemotactic molecules, display a unique distribution at BBB sites. © 1995 Wiley-Liss, Inc.     

Computer-Assisted Design of an Implantable, Intrathoracic Artificial Lung

Abstract: A semiempirical mathematical model of convective oxygen transport is used to design a new, low pressure loss, implantable artificial lung that could be used as a bridge to lung transplantation in patients with advanced respiratory failure. The mass transfer and flow friction relations pertinent to the design of a cross–flow hollow fiber membrane lung are described. The artificial lung is designed to transfer over 200 ml/min of oxygen at blood flow rates up to 5 L/min. A compact design and a blood-side pressure loss of <15 mm Hg allows the device to be implanted in the left chest without the need for a prosthetic blood pump. Surgical implantation of the artificial lung would require the creation of inflow and outflow anastomoses. Oxygen would be supplied via an external source. Blood properties, operating conditions, and empirically determined mass transfer and flow properties are all specified and input into a computer program that numerically solves the design equations. Computer–generated values for the device frontal area, blood path length, and fiber surface area are thereby obtained. The use of this computer–assisted design minimizes the need for extensive trial–and–error testing of prototype devices. Results from in vitro tests of a prototype implantable lung indicate that the mathematical model we describe is an accurate and useful tool in the design of hollow fiber artificial lungs.     

Cytochemical characteristics of neurons in the trigeminal mesencephalic nucleus of hatchling chicks

The goal of the present study was to identify cytochemical markers characteristic of muscle afferents in hatchling chicks. To this end, we stained neurons in the trigeminal mesencephalic nucleus with a variety of markers that label subsets of neurons in avian dorsal root ganglia. We found that trigeminal mesencephalic neurons are surprisingly heterogeneous in their cytochemical make-up, expressing, to varying degrees, substance P, cholecystokinin, carbonic anhydrase, calbindin D-28k, parvalbumin, and S-100β. Calbindin D28k and S-100β appeared to be expressed equally in medial and lateral divisions of the trigeminal mesencephalic nucleus. In contrast, substance P- and cholecystokinin-immunoreactive neurons were more abundant in the medial division, whereas carbonic anhydrase activity and parvalbumin immunoreactivity were stronger in the lateral division. We were unable to detect met-enkephalin, neuropeptide Y, calcitonin gene-related peptide, vasoactive intestinal peptide, somatostatin, γ-aminobutyric acid, or tyrosine hydroxylase in the trigeminal mesencephalic nucleus. Moreover, these neurons did not appear to bind the lectin Dolichos biflorus agglutinin. The heterogeneity of expression of markers among trigeminal mesencephalic nucleus neurons, especially between neurons in the medial and lateral divisions, suggests that these neurons are functionally diverse.     

Transhemation of bovine and human hemoglobin polymers in a simulated circulatory system

All-Union Hematology Research Center, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR A. I. Vorob'ev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 11, pp. 500–501, November, 1991.     

人工肾的最新进展及临床应用

本介绍了人工肾的发展史、临床应用、选购和发展趋势。指出:随着高新技术和透析原理的发展，目前已从血液透析演变为血液净化，拓宽了其临床应用范围。采用组织工程、基因、细胞技术研制的生物人工肾，可望生产出易携带或可移植的生物人工肾，可完全替代肾功能，减少肾衰竭病人的死亡率，成为代肾发展史上的又一个里程碑。     

Synthesis of cyclic tryptathionine peptides

The helicity of the tryptathionine moiety of the phallotoxins has been recognized by comparison with cyclic tryptathionine tripeptides. In order to investigate the influence of the configuration of the component amino acids on the conformation of the cyclic peptides, six analogue thioether tripeptides containing L- and D-alanine and L- and D-cysteine, respectively, have been synthesized. The CD spectra of the peptides are very similar to each other, showing mirror images of the CD of phalloidin and, therefore, negative helicity. The spectra of the D-cysteine containing compounds differ from the L-cysteine containing compounds by their weakly positive ellipticity values around 270 nm. The cyclization reaction of Boc-Hpi-D-Ala-D-Cys(STrt)OCH₃, along with the cyclic tripeptide, afforded a cyclic hexapeptide by dimerization. The CD spectrum of the dimer is very similar to that of phalloidin, thus pointing to a positive helicity of its two tryptathionine moieties. The dimeric thioether peptide forms a rather strong complex with Cu²⁺ ions.     

Regional distribution of cholecystokinin receptors in primate cerebral cortex determined by in vitro receptor autoradiography

Cholecystokinin (CCK) is a putative peptide neurotransmitter present in high concentration in the cerebral cortex. By using techniques of in vitro receptor autoradiography, CCK binding sites in primate cortex were labeled with 125I-Bolton-Hunter-labeled CCK-33 (the 33-amino-acid C-terminal peptide) and 3H-CCK-8 (the C-terminal octapeptide). Biochemical studies performed on homogenized and slide-mounted tissue sections showed that the two ligands labeled a high-affinity, apparently single, saturable site. Autoradiography revealed that binding sites labeled by both ligands were anatomically indistinguishable and were distributed in two basic patterns. A faint and diffuse label characterized portions of medial prefrontal cortex, premotor and motor cortices, the superior parietal lobule, and the temporal pole. In other cortical areas the pattern of binding was layer-specific; i.e., binding sites were concentrated within particular cortical layers and were superimposed upon the background of diffuse label. Layer-specific label was found in the prefrontal cortex, anterior and posterior cingulate gyrus, somatosensory cortex, inferior parietal lobule, retrosplenial cortex, insula, temporal lobe cortices, and in the primary visual and adjacent visual association cortices. The areal and laminar localization of layer-specific CCK binding sites consistently coincided with the cortical projections of thalamic nuclei. In prefrontal cortex, CCK binding sites were present in layers III and IV, precisely paralleling the terminal fields of thalamocortical projections from the mediodorsal and medial pulvinar nucleus of the thalamus. In somatosensory cortex, the pattern of CCK binding in layer IV coincided with thalamic inputs arising from the ventrobasal complex, while in the posterior cingulate gyrus, insular cortex, and retrosplenial cortex, layer IV and lower III binding mirrored the laminar distribution of cortical afferents of the medial pulvinar. CCK binding in layers IVa, IVc alpha, IVc beta, and VI of primary visual cortex corresponded to the terminal field disposition of lateral geniculate neurons, whereas in adjacent visual association cortex, binding in layers III, IV, and VI faithfully followed the cortical distribution of projections from the inferior and lateral divisions of the pulvinar nucleus of the thalamus. We interpret the diffusely labeled binding sites in primate cortex as being associated with the intrinsic system of CCK-containing interneurons that are distributed throughout all layers and areas of the cortex. The stratified binding sites, however, appear to be associated with specific extrinsic peptidergic projections.(ABSTRACT TRUNCATED AT 400 WORDS)     

Conformations of neurotensin in solution and in membrane environments studied by 2-D NMR spectroscopy

Two-dimensional HOHAHA and ROESY nuclear magnetic resonance techniques are used to obtain complete proton resonance assignments and to perform a conformational investigation of the neuropeptide neurotensin (pGlu-Leu-Tyr-Glu-Asn-Lys-Pro-Arg-Arg-Pro-Tyr-Ile-Leu) in aqueous solution, methanol, and membrane-mimetic [deuterated sodium dodecylsulfate (SDS)] environments. Results suggest the absence of discernible elements of secondary structure in water and methanol. ROESY spectra confirm that Lys-Pro and Arg-Pro peptide bonds are all-trans, but that a significant population of cis Arg-Pro bonds arises in aqueous solution, which increases in the environment of SDS micelles. The conformational ensemble of the peptide is observed to narrow as it becomes bound through its cationic mid-region to SDS micelles, with the accompanying advent of local extended structure. The overall results indicate the inherent conformational flexibility of neurotensin, and emphasize the environmental dependence of conformation in peptides of medium length.     

舍蝇抗菌肽的提取及其对肿瘤细胞生长的抑制作用

目的：研究含蝇抗菌肽的提取对肿瘤细胞生长的抑制作用；方法：对舍蝇幼虫采用针刺损伤及金黄色葡萄球菌感染诱导方法，并通过研磨、加热、阳离子交换柱层析及Sephadex G—50葡聚糖凝胶柱层析等步骤提取抗菌肽；结果：经SDS—PAGE电泳分离到2条带，分子量分别为4kD，9．6kD；结论：提取的舍蝇抗菌肽能有效地抑制人胃癌细胞MGC80—3和BGC—823，人乳腺癌细胞MCF—7及人肺癌细胞SPC—A—1的体外增殖，并且呈浓度依赖关系。