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51.
Priv.-Doz. Dr. Brita von Gaudecker Ulrich Pfingsten Hans-Konrad Müller-Hermelink 《Cell and tissue research》1984,238(1):135-143
Summary In the present study attention was focussed on several lymphoid subpopulations and specific stationary cells of the human tonsilla palatina. They were labeled at the light- and electron-microscopic levels by means of monoclonal antibodies to cell surface antigens. Cells resembling interdigitating cells (IDC-like cells) within the crypt epithelium and the interdigitating cells in the parafollicular T-cell region express the HLA-DR antigen. This fact suggests a relationship between these two populations of cells. Both cell types were frequently found in close contact to T-helper cells labeled with Anti-Leu 3a. This fact is discussed as a confirmation of earlier suggestions that the tonsillar crypt epithelium serves as T-cell region. Cytotoxic/ suppressor-T cells (OKT 8
+) and Leu 7-positive cells do not appear to contact interdigitating cells. Anti-Leu 7 is a monoclonal antibody, that defines a differentiation antigen shown to be selectively expressed on human natural killer cells (NK-cells). With the use of the immuno-electron-microscopic labeling method it was possible to analyze the ultrastructure of this lymphoid subpopulation. Two morphologically distinguishable subtypes of Leu 7-positive cells populate different microenvironments: The Leu 7-positive large-granular lymphocyte was predominantly found in the crypt epithelium, while numerous Leu 7-positive cells located in the germinal centers had the appearance of small lymphocytes. This finding is discussed in favour of distinct phenotypes representing different stages in a differentiation pathway of the maturing NK-cell: Small Leu 7-positive lymphocytes in the germinal centers are supposed to be functionally inactive precursors, and only the Leu 7-positive large granulated lymphocytes in the crypt epithelium may represent differentiated active NK-cells. This interpretation is in agreement with the observation that the tonsilla palatina, in spite of containing numerous Leu 7-positive cells, shows only low NK-activity against tumor cells.Glossary of Abbreviations used in this Paper DAB
diamino-benzidine
- DMSO
dimethyl sulfoxide
- HLA
human leucocyte antigen
- HLA-DR
human leucocyte antigen, D-region related
- Ia-antigen
immune-associated antigen of the MHC
- IDC
interdigitating cell
- IDC-like cell
cell that resembles an interdigitating cell
- LGL
large granular lymphocyte
- MHC
major histocompatibility gene complex
- NK-cell
natural killer cell
- PBS
phosphate-buffered saline 相似文献
52.
In this study, we are interested in the problem of estimating the parameters in a nonlinear regression model when the error terms are correlated. Throughout this work, we restrict ourselves to the special case when the error terms follow a pth order stationary autoregressive model (AR(p)). Following the idea of LAWTON and SYLVESTRE (1971) and GALLANT and GOEBEL (1976), a parameter-elimination method is proposed, which has the advantages that it is not sensitive to the initial values and convergence of the procedure may be more stable because of the reduced dimension of the problem. The parameter-elimination method is compared with the methods by GALLANT and GOEBEL (1976) and GLASBEY (1980) by Monte Carlo Simulation, and the results of applying the first two methods to the real data obtained from the Environmental Protection Administration of the Executive Yuan of the Republic of China are presented. 相似文献
53.
《Chirality》2017,29(7):340-347
Acrylamide (AM) was copolymerized with ethylene glycol dimethacrylate (EGDMA) in the presence of (R )‐1,1′‐binaphthalene‐2‐naphthol (BINOL) as the template molecules on the surface of silica gel by a free radical polymerization to produce a chiral stationary phase based on the surface molecularly imprinted polymer (SMIP‐CSP). The SMIP‐CSP showed a much better separation factor (α = 4.28) than the CSP based on the molecularly imprinted polymer (MIP‐CSP) without coating on the silica gel (α = 1.96) during the chiral separation of BINOL enantiomers by high‐performance liquid chromatography. The influence of the pretreatment temperature and the content of the template molecule ((R )‐BINOL) of the SMIP‐CSP, and the mobile phase composition on the separation of the racemic BINOL were systematically investigated. 相似文献
54.
55.
Vassili V. Velkov 《Journal of biosciences》1999,24(4):529-559
This review is focused on the physiological and evolutionary strategies of the processes occurring during the entry of microbial
cells into stationary phase and the subsequent period of stasis. The molecular mechanisms adapting microorganisms from exponential
growth to a static state involve activation and complex regulation of the stationary factor Sigma-S, which directs RNA polymerase
to the specific promoters. As a result the static cells acquire general resistance (simultaneous tolerances) to different
environmental stresses. In parallel with the physiological adaptation to stasis, diverse genetical processes are aimed towards
resuming the growth of the static cells. Different types of mutagenesis occur: (i) in cells entering stasis and (ii) in static
cells (adaptive mutagenesis). Cessation of growth induces the transient hypermutator state resulting in the accumulation of
random mutations in the subpopulation of the static cells. If by chance, one or a few of such mutations lead to resumption
of division, the growing cell will return to a normal mechanism of spontaneous mutagenesis.
Another mechanism for generating genetical variability in stressed cells involves transposons and conjugative plasmids. Stresses
can stimulate the excision of some transposons, which, in turn, can generate chromosomal mutations and activate intracellular
mechanisms of mutagenesis. Under stress some conjugative plasmids activate genes encoding antirestriction proteins that repress
restriction-modification systems of the recipient cells. Moreover, under stress special cellular mechanisms decrease (alleviate)
the activity of restriction-modification systems which, in turn, enhance the probability of gene transfer into the stressed
cells.
Under stress, the efficiency of inter-species genetical barriers also decreases. This, stimulates inter-species gene transfer
and may lead to a burst of incipient speciation in the population of non-growing cells. After resumption of growth the genetical
barriers leading to isolation will be restored.
In general, the cessation of growth “switches on”, and resumption of growth “switches off”, a set of special processes that
are responsible for generating bursts of genetical variability in populations of microorganisms.
This article is dedicated to the memory of Nikolai V Timofeev-Ressovsky (1900–1981). 相似文献
56.
Murat Acemoglu Ernst Küsters Jürgen Baumann Ivan Hernandez Ching Pong Mak 《Chirality》1998,10(4):294-306
Various cellulose-2,3-bis-arylcarbamate-6-O-arylesters and cellulose-2,3-bis-arylester-6-O-arylcarbamates, designed to test the possible combined effects of the known tris-arylcarbamate and tris-arylester classes, were synthesized with high regioselectivity at O-C(6), and their use as CSP s in liquid chromatography for enantiomeric separations was investigated. The separations obtained with the synthesized CSP s were compared to the separations achieved on a self-packed reference column, consisting of cellulose-tris-(3,5-dimethylphenyl-carbamate) as CSP standard. Among the synthesized, regioselectively substituted cellulose derivatives, 2,3-bis-O-(3,5-dimethylphenylcarbamate)-6-O-benzoate-cellulose and 2,3-bis-O-(benzoate)-6-O-(3,5-dichlorophenylcarbamate)-cellulose gave the best CSP s for the separation of the test racemates. CSP s from regioselectively substituted cellulose derivatives seem to exhibit higher selectivities than cellulose-tris-(3,5-dimethylphenylcarbamate) for certain classes of racemic compounds. Chirality 10:294–306, 1998. © 1998 Wiley-Liss, Inc. 相似文献
57.
Zdzisaw Chilmonczyk Hanna Ksyciska Jacek Cybulski Mariusz Rydzewski Andrzej Le 《Chirality》1998,10(9):821-830
Direct separation of several α-hydroxy acid racemic mixtures was performed by the aid of ligand exchange chromatography using L-hydroxyproline chemically bound to silica stationary phase and aqueous solutions of copper (II) sulphate as a mobile phase. The elution order of the D- and L-enantiomers of α-hydroxy acids is interpreted in terms of a modified Davankov's rule. Several aspects of the Davankov's model of selectand-Cu(II)-selector ternary complexes are discussed based on the theoretical calculations within the quantum mechanical semiempirical and density functional theories. Chirality 10:821–830, 1998. © 1998 Wiley-Liss, Inc. 相似文献
58.
Cellulose triphenylcarbamate derivatives have been used as stationary phases for resolution of the enantiomers of the β-blockers propranolol and bupranolol by TLC. The derivatives examined were: cellulose trisphenylacarbamate (1), cellulose tris(2,3-dichlorophenyl carbamate) (2), cellulose tris(2,4-dichlorophenyl carbamate) (3), cellulose tris(2,6-dichlorophenyl carbamate) (4), cellulose tris (2,3-dimethylphenyl carbamate) (5), cellulose tris(3,4-dichlorophenyl carbamate) (6), cellulose tris(3,5-dichlorophenyl carbamate) (7), and cellulose tris(3,5-dimethylphenyl carbamate) (8). A variety of mobile phases were used to achieve useful separations and the effects of solvent polarity are also discussed. The best resolution of rac-propranolol was obtained on CSP 8 (RfR = 0.26, RfS = 0.06, α = 4.33) in mobile phase hexane:propan-2-ol (80:20 v/v). The best resolution of rac-bupranolol was obtained on CSP 5 (RfR = 0.29, RfS = 0.09, α = 3.22) in mobile phase hexane:propan-2-ol (80:20 v/v). These results demonstrated the potential of cellulose triphenylcarbamates as chiral stationary phases in TLC and indicate that this is potentially a useful method for the direct, simple, and rapid (within 30 min) resolution of racemates in the analytical control of enantiomeric purity. Physical aspects such as problems in cracking of the CSP, adhesion to plate, and interference of spot detection due to triphenylcarbamate chromphores are also discussed, along with the method employed to overcome them. Chirality 9:139–144, 1997. © 1997 Wiley-Liss, Inc. 相似文献
59.
Four 4-halogen-substituted phenylcarbamate derivatives of amylose were prepared and their chiral recognition abilities as chiral stationary phases (CSPs) for high-performance liquid chromatography (HPLC) were evaluated and compared with those of the corresponding cellulose derivatives. The amylose derivatives with fluoro, chloro, bromo, or iodo group at the four-position on the phenyl group were found to show higher chiral resolving ability than the corresponding cellulose derivatives. Among four amylose derivatives 4-fluoro- and 4-chlorophenylcarbamates showed an excellent chiral recognition ability. Especially, amylose tris(4-chlorophenylcarbamate) resolved (±)-1,2,2,2-tetraphenylethanol with a very high α value (α = 8.29). In order to obtain useful information concerning the chiral recognition mechanism of this resolution, we also performed enantioseparation of a variety of analogous racemic alcohols, and found that both the hydroxy and bulky triphenylmethyl groups of the racemate are essential for the effective chiral recognition. Chirality 9:63–68, 1997. © 1997 Wiley-Liss, Inc. 相似文献
60.
Carlos Cativiela María D. Díaz‐de‐Villegas Ana I. Jimnez Pilar Lpez Michel Marraud Laureano Oliveros 《Chirality》1999,11(7):583-590
Bonded polysaccharide‐derived chiral stationary phases were found to be useful for the preparation of the four stereoisomers of the cyclopropane analogue of phenylalanine (c3Phe) as well as for the direct determination of the enantiomeric purity of c3Phe derivatives by HPLC. Three chiral stationary phases, consisting of cellulose and amylose derivatives chemically bonded on allylsilica gel, were tested. The mixed 10‐undecenoate/3,5‐dimethylphenylcarbamate of cellulose, 10‐undecenoate/3,5‐dimethylphenylcarbamate of amylose and 10‐undecenoate/p‐methylbenzoate of cellulose were the starting polysaccharide derivatives for CSP‐1, CSP‐2, and CSP‐3, respectively. Using mixtures of n‐hexane/chloroform/2‐propanol as mobile phase on a semi‐preparative column (150 mm × 20 mm ID) containing CSP‐2, we separated about 1.7 g of racemic cis‐methyl 1‐tert‐butoxycarbonylamino‐2‐phenylcyclopropanecarboxylate (cis‐ 6 ) and 1.2 g of racemic trans‐methyl‐1‐tert‐butoxycarbonylamino‐2‐phenylcycloprop‐anecarboxylate (trans‐ 6 ) by successive injections. Chirality 11:583–590, 1999. © 1999 Wiley‐Liss, Inc. 相似文献