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PubMed2003

Ga+ primary ion ToF-SIMS fragment pattern of metals and inorganic compounds.

The appearance regularity of the Ga+ primary ion ToF-SIMS fragment pattern of metals and inorganic compounds is discussed. For inorganic compounds formulated like M-A, where the valence of the cation M is +n, that of the anion A is -p; also, the chemical composition of the ToF-SIMS fragment is MxAy, the rule nx > or = (py + 1) is satisfied for positive ion fragments and nx < or = (py + 1) for negative ones. For example, for an oxide fragment of chemical composition MxOy (valence of M is +n), the chemical composition of the fragment appears obeying the rule nx > or = (2y + 1) for positive ions and nx < or = (2y + 1) for negative ones, respectively. The regularity of ToF-SIMS fragment patterns of sulfides, nitrates, sulfates etc. is discussed. Further, when the Ga+ primary ion ToF-SIMS fragment patterns of metals are observed, it can be inferred that the overlapped particle emission occurs from metal surfaces through alloying and/or clustering of Ga with metal on surfaces.

Journal Article↗
PubMed1987

Fragmentation and flow of grazed coastal Bermudagrass through the digestive tract of cattle.

Samples of forage fragments were obtained from the upper (RUS) and lower (RLS) strata of the reticulorumen and feces (F) of four Brahman X Jersey steers grazing Coastal bermudagrass (CB) of two maturities with dry matter digestibilities (DMD) of 54.8 and 64.3%. Forage fragments were separated by particle size and evaluated histochemically for tissue type and fragmentation pattern. Fragmentation pattern was similar to that previously observed due to ingestive mastication. There was longitudinal separation of vascular bundles (VB) and severing at VB ends. Microscopically, similar size fragments from RUS were indistinguishable from those of RLS. The major difference between RUS and RLS was the distribution of different size particles. Larger particles were associated with the RUS in cattle consuming immature and mature CB. More large particles were associated with mature compared with the immature CB in the RUS and RLS. The distribution of different size particles in the F was similar for both maturities, suggesting that similar particle size reduction was required regardless of maturity. Smaller particles in the rumen and F appeared to contain more lignin (determined histochemically) and were composed of indigestible fragments of cuticle and lignified vascular tissue. Cattle grazing mature CB had higher ruminal fills (2.40 vs 2.02 kg dry matter/100 kg body weight), reduced rates of passage and lower voluntary intake (2.50 vs 3.14 kg DM/100 kg body weight). Lower intake of mature CB may have resulted from a reduced rate of particle size reduction. Similarities in fragmentation patterns due to ingestive and ruminative mastication were interpreted to indicate that mastication was responsible for most of the particle size reduction of CB and that mastication facilitated digestion of potentially digestible tissues.

Animal Feed↗
PubMed2005

Identification of the immunogenic domains in HBsAg preS1 region using overlapping preS1 fragment fusion proteins.

AIM: The incorporation of hepatitis B virus (HBV) preS1 region into epitope-based vaccines against HBV has been accepted widely, but the incorporate site and size of preS1 sequence is controversial. Therefore our purpose was to further investigate its immunogenic domains for the epitope-based hepatitis B vaccine design. METHODS: Eight GST fusion proteins containing overlapping preS1 fragments in preS1 (21-119) region were expressed in E.coli. Using these purified fusion proteins, the immunogenic domains in preS1 region were identified in detail in mice and humans by Western blot analysis and ELISA. RESULTS: The results in mice showed that the immu-nogenic domains mainly existed in preS1 (21-59) and preS1 (95-109). Similarly, these fragments had strong immunogenicity in humans; whereas the other parts except for preS1 (60-70) also had some immunogenicity. More importantly, a major immunogenic domain, preS1 (34-59), which has much stronger immunogenicity, was identified. Additionally, the antibodies against some preS1 fragments, especially preS1 (34-59), were speculated to be virus-neutralizing. CONCLUSION: Eight GST fusion proteins containing overlapping preS1 fragments were prepared successfully. They were used for the study on the immunogenic dom-ains in preS1 (21-119) region. The preS1 (34-59) fragments were the major immunogenic domains in the preS1 region, and the antibodies against these fragments were speculated to be virus-neutralizing. Therefore, the incorporation of preS1 (34-59) fragments into epitope-based HBV vaccines may be efficient for enhancement of immune response. Additionally, the results also imply that there are more complex immune responses to preS1 region and more abundant immunogenic domains in humans.

Animals↗
PubMed2005

Human scFv antibody fragments specific for hepatocellular carcinoma selected from a phage display library.

AIM: To identify the scFv antibody fragments specific for hepatocellular carcinoma by biopanning from a large human naive scFv phage display library. METHODS: A large human naive scFv phage library was used to search for the specific targets by biopanning with the hepatocellular carcinoma cell line HepG2 for the positive-selecting and the normal liver cell line L02 for the counter-selecting. After three rounds of biopanning, individual scFv phages binding selectively to HepG2 cells were picked out. PCR was carried out for identification of the clones containing scFv gene sequence. The specific scFv phages were selected by ELISA and flow cytometry. DNA sequences of positive clones were analyzed by using Applied Biosystem Automated DNA sequencers 3 730. The expression proteins of the specific scFv antibody fragments in E.coli HB2151 were purified by the affinity chromatography and detected by SDS-PAGE, Western blot and ELISA. The biological effect of the soluble antibody fragments on the HepG2 cells was investigated by observing the cell proliferation. RESULTS: Two different positive clones were obtained and the functional variable sequences were identified. Their DNA sequences of the scFv antibody fragments were submitted to GenBank (accession nos: AY686498 and AY686499). The soluble scFv antibody fragments were successfully expressed in E.coli HB2151. The relative molecular mass of the expression products was about 36 ku, according to its predicted M(r) value. The two soluble scFv antibody fragments also had specific binding activity and obvious growth inhibition properties to HepG2 cells. CONCLUSION: The phage library biopanning permits identification of specific antibody fragments for hepatocellular carcinoma and affords experiment evidence for its immunotherapy study.

Carcinoma, Hepatocellular↗
PubMed1999

Induction and rejoining of large DNA fragments after ion irradiation.

Radiation-induced DNA double-strand breaks (DSBs) were analyzed by separating large DNA fragments by pulsed-field gel electrophoresis. Human U-343MG glioma and K562 erythroleukemia cells were irradiated with 60Co gamma rays or nitrogen ions with high linear energy transfer (125 keV/microm). By comparing the fraction of DNA released into the gel below different size thresholds, corresponding to megabase-pair-sized DNA fragments, the relative effectiveness of the nitrogen ions was found to be dependent on both dose and the threshold size used in the evaluation. This dose dependence was most evident for the smallest threshold (6 Mbp) and was due to a linear dose response for release of the fragments for the ions compared to the curvilinear response for the gamma rays. The two curves intersected, and the relative yield of fragments (nitrogen ions/gamma rays) decreased from more than 3 below 1.5 Gy to 0.8 at 30 Gy. For the larger sizes (6-10.5 Mbp), the relative yield was constant at around 0.7. Thus the ion-induced fragments were shifted to smaller sizes compared to the 60Co gamma rays, and the data for nitrogen ions could not be fitted to random fragment distributions at doses < or =20 Gy. From these results, we conclude that a substantial fraction of the DSBs induced by heavy ions were nonrandomly distributed, correlated with DSBs within a region of < or =2 Mbp. After a dose of 20 Gy, the rejoining curves for ion-induced DSBs were different for each fragment size, resulting in different levels of unrejoined breaks after 6 h.

DNA↗
PubMed2000

[Subcloning and sequencing of DNA fragment related to salt tolerance in Sinorhizobium fredii RT19].

A 23 kb DNA fragment related to salt tolerance was obtained from the gene library of S. fredii strain RT19. In this study, BamH I was selected to digest 23 kb DNA fragment into different length of DNA fragments. The resulting fragments were ligated with plasmid pML122, then the recombinant plasmids were transformed to competent cells of E. coli S17-1 on selective medium and three transformants TR were obtained. Two-parental mating experiments were carried out with these transformants as donor and salt sensitive S. fredii strain RC3-3 as recipient, and the transconjugant BR2 was selected on FY plates containing gentamycin and 0.4 mol/L NaCl. Thus, a 4.4 kb DNA fragment related to salt tolerance was obtained. Based on its physical map, six restriction fragments were subcloned into plasmid pUC18 for DNA sequencing. Subsequently, sequencing and analysis of 4.4 kb DNA fragment showed that fixO, fixN genes and three ORFs were obtained.

Amino Acid Sequence↗
PubMed2002

[An ambiguous pedigree of facioscapulohumeral muscular dystrophy which showed double EcoRI/BlnI resistant short fragments].

We report a facioscapulohumeral muscular dystrophy (FSHD) pedigree having double short (25 kb and 33 kb) BlnI resistant (4 q-like) fragments. Two of three male siblings developed shoulder-girdle weakness and minimum facial involvement from their adolescence. Although the rest (third) brother had non-progressive hemi-palsy in face and upper-extremity and strabismus caused by birth trauma, he had no clinical symptoms of FSHD. Mother presented mild shoulder weakness after cholecystectomy at the age of 50 years, but with no facial involvement and normal serum creatine kinase (CK) level (45 IU/L). On the contrary, father had high CK level (450 IU/L) despite no neurological abnormalities. After EcoRI/BlnI double digestion, two short fragments were detected in the two affected siblings. Then, all family members were examined to determine pathognomonic fragment. Consequently, mother (25 kb and 90 kb) and the third non-affected brother (25 kb and 51 kb) had two 4 q-like fragments, however, three 4 q-like fragments were detected in father (33 kb, 51 kb and 130 kb), proband (25 kb, 33 kb and 130 kb) and affected brother (25 kb, 33 kb and 51 kb). These findings revealed that the 4 q-like 33 kb fragment actually located on 10q26 through inter-chromosomal exchange. Thus the 25 kb fragment inherited from mother was determined as co-segregating with the disease. To ensure genetic diagnosis for FSHD, investigation of family members is surely required.

Adult↗
PubMed1992

Cell-mediated cleavage of Pseudomonas exotoxin between Arg279 and Gly280 generates the enzymatically active fragment which translocates to the cytosol.

Pseudomonas exotoxin (PE) is a three-domain toxin which is cleaved by a cellular protease within cells and then reduced to generate two prominent fragments (Ogata, M., Chaudhary, V. K., Pastan, I., and FitzGerald, D. J. (1990) J. Biol. Chem. 265, 20678-20685). The N-terminal fragment is 28 kDa in size and contains the binding domain. The 37-kDa C-terminal fragment, which translocates to the cytosol, contains the translocation domain and the ADP-ribosylation domain. Cleavage followed by reduction is essential for toxicity since mutant forms of the toxin that cannot be cleaved by cells are nontoxic. Previous results with these mutants suggest that cleavage occurred in an arginine-rich (arginine residues are at positions 274, 276, and 279) disulfide loop near the beginning of the translocation domain, but the exact site of cleavage was not determined. Since very few molecules of the 37-kDa fragment are generated within cells it was not possible to determine the site of cleavage by performing a conventional N-terminal sequence analysis of the 37-kDa fragment. Two experimental approaches were used to overcome this limitation. First, existing amino acids near the cleavage sites were replaced with methionine residues; this was followed by the addition of [35S]methionine-labeled versions of these toxins to cells. The pattern of radioactive toxin fragments recovered from the cells indicated that the toxin was cleaved either just before or just after Arg279. Second, [3H]leucine-labeled toxin was produced and added to the cells. Sequential Edman degradations were performed on the small amount of radioactive 37-kDa fragment that could be recovered from toxin-treated cells. A peak of radioactivity in the fifth fraction indicated that leucine was the 5th amino acid on the C-terminal side of the cleavage site. This result confirmed that cleavage was between Arg279 and Gly280.

ADP Ribose Transferases↗
PubMedDate not supplied

[The fragmentation of representational space in schizophrenia].

Existent neurocognitive models of schizophrenia converge towards a core of impairments involving working memory, context processing, action planning, controlled and intentional processing. However, the emergence of this core remains itself difficult to explain and more specific hypotheses do not explain the heterogeneity of schizophrenia. To overcome these limits, we propose a new paradigm based on representational theory from cognitive science. Some recent developments of this theory enable us to describe a subjective universe as a representational space which is displayed from memory. We outline a conceptual framework to construct such a representational space from analogical -representations that can be activated in working memory and are connected to a network of symbolic structures. These connections are notably made through an analytic process of the analogical fragments, which involves the attentional focus. This framework allows us to define rigorously some defense processes in response to traumatic tensions that are expressed on the representational space. The fragmentation of representational space is a consequence of a defensive denial based on an impairment of the analytic process. The fragmentation forms some parasitic areas in memory which are excluded from the main part of the representational space and disturb information processing. The key clinical concepts of paranoid syndromes can be defined in this conceptual framework: mental automatism, delusional intuition, acute destructuration, psychotic dissociation, and autistic withdrawal. We show that these syndromes imply each other, which in return increases the fragmentation of the representational space. Some new concepts emerge naturally in this framework, such as the concept of "suture" which is defined as a link between a parasitic area and the main representational space. Schizophrenia appears as a borderline case of fragmentation of the representational space. This conceptual framework is compatible with numerous etiological factors. Multiple clinical forms can be differentiated in accordance with the persistence of parasitic areas, the degree of fragmentation, and the formation of sutures. We use this approach to account for an empirical study concerning the analysis of analogical representations in schizophrenia. We used the Parallel Visual Information Processing Test (PVIPT) which assesses the analysis of interfering visual information. Subjects were asked to connect several small geometric figures printed on a transparency. The transparency was displayed above four photographs which were the interfering material. Then, subjects completed three tasks concerning the photographs: a recognition task, a recall task, and an affective qualification task. Using a case-by-case study, this test allows us to access the defense processes of the subjects, which is not possible with the usual methods in cognitive psychopathology. Twelve clinically-stable schizophrenic subjects participated in the study which also included a self-assessment of alexithymia by the Toronto Alexithymia Scale. We obtained 2 main results: (a) creation of items in recall or false recognition by 8 subjects, and (b) lack of the usual -negative correlations between the alexithymia score and the recall, recognition and affective qualification scores in the PVIPT. These 2 results contrast with what has been previously observed for alexithymia using the same methodology. The result (a) confirms an interfering activation in schizophrenic memory, which can be interpreted in our framework as indicative of parasitic areas. The creation of items suggests the formation of sutures between the semantic content of photographs and some delusional fragments. The result (b) suggests that the apparent alexithymia in schizophrenia is a defense against interfering activation in parasitic areas. We underline the interest of individual protocols to exhibit the dynamic interplay between an interfering activity in memory and a defensive flattening of affects.

Affective Symptoms↗
PubMed2004

Asymmetric interference effects in fragment completion: the consequences of recognition failures and successes.

We examined the extent to which implicit and explicit memory performance is susceptible to the effects of proactive and retroactive interference produced by orthographic similarity. Participants studied target and nontarget words that were orthographically similar or dissimilar. At test, they were given fragments of the target words intermixed with fragments of nonstudied words. Participants' initial task was to determine whether each fragment was a studied word. If they recognized it, they were to complete the fragment with the studied word; if not, they were to complete the fragment with the first word that came to mind. Completion rates including both recognized and nonrecognized target fragments provided evidence of proactive but not retroactive interference. The implicit processing engaged by the nonrecognized target fragments was found to be the primary source of the proactive interference effect.

Achievement↗
PubMed2005

[Fragmentation process of wetland landscape in watersheds of Sanjiang Plain, China].

The Sanjiang Plain is the largest fresh water wetland distribution area in China and the center of waterfowls breeding and habitat area in Asia, but over the past 50 years, more than 73% of its wetland had lost because of agricultural development, and as a result, the wetland biodiversity declines dramatically, and the remnant wetlands are in a very fragment state. Based on historical maps, remote sensing data and GIS techniques, this paper selected two watersheds to analyze their wetland landscape fragmentation process during 1950-2000. It was indicated that land reclamation resulted in a decrease of 98% wetland corridors in Qixing River, 90% in Naoli River, 87% in the middle reach of Bielahong River, and 94% in the lower reach of Bielahong River; The amount of isolated wetlands in watershed increased dramatically; The maximum patch areas of wetland decreased by 92.6% in Naoli River watershed and 74.6% in Bielahong River watershed, and the mean wetland patch area in the two watersheds decreased by 99%. Before 1983, the wetland landscape was in an extensive area distribution state (the index of patch density was < 0.1), but after 1983, it fragmented dramatically, with the index of patch density larger than 1.5. The shape fragmentation indices of wetland decreased from 1950 to 2000, indicating a very big change in wetland patch shapes in the watersheds. The area fragmentation indices of wetland also increased from 1950 to 2000, especially after 1983, showing that the wetlands were in a serious fragmentation state. The wetland landscape fragmentation changed from a landmass and island model to a satellite model, and finally to a completely isolated model, which indicated the great changes in spatial structure of wetland in the Sanjiang Plain.

Agriculture↗
PubMed1992

Characterization of the gamma chain platelet binding site on fibrinogen fragment D.

Glycoprotein (GP) IIb/IIIa on adenosine diphosphate (ADP)-activated human platelets interacts with specific sites on the fibrinogen molecule leading to aggregation. We characterized the platelet-binding site on the gamma chains of fibrinogen using plasmic fragments D gamma A and D gamma'. Fragment D gamma A, which contains the carboxy terminal gamma A400-411 platelet-binding sequence (HHLGGAKQAGDV), was 70-fold more active than the synthetic gamma A400-411 peptide in inhibiting ADP-induced platelet aggregation. Fragment D gamma A inhibited fibrinogen binding and also bound directly to ADP-activated platelets. The Kd values determined for fibrinogen and fragment D gamma A binding were 0.55 mumol/L and 1.2 mumol/L, respectively. In contrast, fragment D gamma', which differs from fragment D gamma A with respect to its gamma chain sequence from position 408 to the COOH-terminus at position 427, did not inhibit platelet aggregation or fibrinogen binding, and did not bind directly to the platelet surface. Denaturation of fragment D gamma A with guanidine-HCl caused a loss of inhibitory activity in platelet aggregation assays. These data indicate that the native conformation of the gamma chain platelet-binding site on fibrinogen is important for optimal binding to GPIIb/IIIa.

Adenosine Diphosphate↗
PubMed2005

Fibronectin fragments in human seminal plasma.

The study has revealed the presence of fibronectin (FN) fragments and a lack of intact FN in 72 seminal plasma samples. The FN fragmentation was examined by immunoblotting with a monoclonal antibody specific to the central cellular FN domain and was confirmed with a monoclonal antibody directed to the C-terminal domain of FN. Nine FN fragments between 60 and 200 kDa and five fragments of 60-150 kDa were identified in seminal plasma samples of normozoospermic and of terato-, oligoterato-, and oligoasthenoterato-spermic groups, respectively. The relative amounts of the 60, 90 and 100 kDa FN fragments were 2-3 times higher in seminal plasmas with abnormal semen characteristics than in the normozoospermic group. The results suggest that seminal plasma FN fragments may contribute to fertilization and the analysis of FN fragmentation may have a diagnostic value in andrological investigations.

Electrophoresis, Polyacrylamide Gel↗
PubMed1991

Biological effectiveness of high-energy protons: target fragmentation.

High-energy protons traversing tissue produce local sources of high-linear-energy-transfer (LET) ions through nuclear fragmentation. We examine the contribution of these target fragments to the biological effectiveness of high-energy protons using the cellular track model. The effects of secondary ions are treated in terms of the production collision density using energy-dependent parameters from a high-energy fragmentation model. Calculations for mammalian cell cultures show that at high dose, at which intertrack effects become important, protons deliver damage similar to that produced by gamma rays, and with fragmentation the relative biological effectiveness (RBE) of protons increases moderately from unity. At low dose, where sublethal damage is unimportant, the contribution from target fragments dominates, causing the proton effectiveness to be very different from that of gamma rays with a strongly fluence-dependent RBE. At high energies, the nuclear fragmentation cross sections become independent of energy. This leads to a plateau in the proton single-particle-action cross section, below 1 keV/micron, since the target fragments dominate.

Cell Survival↗
PubMed1992

Coordinated leading- and lagging-strand synthesis at the Escherichia coli DNA replication fork. I. Multiple effectors act to modulate Okazaki fragment size.

The coordinated action of many enzymatic activities is required at the DNA replication fork to ensure the error-free, efficient, and simultaneous synthesis of the leading and lagging strands of DNA. In order to define the essential protein-protein interactions and model the regulatory pathways that control Okazaki fragment synthesis, we have reconstituted the replication fork of Escherichia coli in vitro in a rolling circle-type DNA replication system. In this system, in the presence of the single-stranded DNA binding protein, the helicase/primase function on the lagging-strand template is provided by the primosome, and the synthesis of DNA strands is catalyzed by the DNA polymerase III holoenzyme. These reconstituted replication forks synthesize equivalent amounts of leading- and lagging-strand DNA, move at rates comparable to those measured in vivo (600-800 nucleotides/s at 30 degrees C), and can synthesize leading strands in the range of 150-500 kilobases in length. Using this system, we have studied the cycle of Okazaki fragment synthesis at the replication fork. This cycle is likely to have several well defined decision points, steps in the cycle where incorrect execution by the enzymatic machinery will result in an alteration in the product of the reaction, i.e. in the size of the Okazaki fragments. Since identification of these decision points should aid in the determination of which of the enzymes acting at the replication fork control the cycle, we have endeavored to identify those reaction parameters that, when varied, alter the size of the Okazaki fragments synthesized. Here we demonstrate that some enzymes, such as the DnaB helicase, remain associated continuously with the fork while others, such as the primase, must be recruited from solution each time synthesis of an Okazaki fragment is initiated. We also show that variation of the concentration of the ribonucleoside triphosphates and the deoxyribonucleoside triphosphates affects Okazaki fragment size, that the control mechanisms acting at the fork to control Okazaki fragment size are not fixed at the time the fork is assembled but can be varied during the lifetime of the fork, and that alteration in the rate of the leading-strand DNA polymerase cannot account for the effect of the deoxyribonucleoside triphosphates.

Base Sequence↗
PubMed1992

Coordinated leading- and lagging-strand synthesis at the Escherichia coli DNA replication fork. V. Primase action regulates the cycle of Okazaki fragment synthesis.

Replication forks formed during rolling-circle DNA synthesis supported by a tailed form II DNA substrate in the presence of the primosome, the single-stranded DNA binding protein, and the DNA polymerase III holoenzyme (Pol III HE) that had been reconstituted from the purified subunits, beta, tau, and the gamma.delta complex, at limiting (with respect to nucleotide incorporation) concentrations of the Pol III core (alpha, epsilon, and theta) produced aberrantly small Okazaki fragments, while the synthesis of the leading strand was unperturbed. These small Okazaki fragments were not arrayed in tandem along the lagging-strand DNA template, but were separated by large gaps. Similarly structured synthetic products were not manufactured by replication forks reconstituted with higher, saturating concentrations of the Pol III core. Replication forks producing these small fragments could respond, by modulating the size of the Okazaki fragments produced, to variations in the concentration of NTPs or the primase, conditions that affect the frequency of priming on the lagging strand, but not to variation in the concentration of dNTPs, conditions that affect the frequency of utilization of the primers. Significantly longer Okazaki fragments (greater than 7 kilobases) could be produced in the presence of a limiting amount of Pol III core at low concentrations of the primase. These observations indicated that the production of small Okazaki fragments was not a result of a debilitated lagging-strand Pol III core, but rather a function of the time available for nascent strand synthesis during the cycle of events that are required for the manufacture of an Okazaki fragment and that it was the association of primase with the replication fork that keyed this cycle.

DNA↗
PubMed1991

Mouse targets undergo double-strand DNA fragmentation when exposed to syngeneic or xenogeneic LAK cells whereas human targets undergo single-strand breaks.

A number of recent studies have shown that mouse target cells (TC) of hematopoietic origin, when exposed to cytotoxic lymphocytes, undergo double-stranded DNA fragmentation. The cause and relevance of the fragmentation remain controversial. In this study we generated a number of mouse (M-LAK) and human LAK (H-LAK) cells and exposed them to a variety of mouse and human TC. YAC and SP/2, 2 mouse TC underwent rapid and extensive fragmentation when lysed by either human or mouse LAK whereas K562 and Daudi, 2 human TC, under the same conditions did not. All 4 TC, however, were killed quite efficiently. Next we labeled TC with 125I-deoxyuridine, exposed them to LAK cells for up to 18 h and loaded the LAK:TC mixtures over an alkaline linear sucrose gradient. After lysing the cells with a lysis buffer containing Triton X-100 we showed that K562 that had been in contact with LAK cells for more than 1 h exhibited single-strand nicks. However, whereas double-strand fragmentation preceded chromium release (lytic activity), the appearance of single-strand nicks did not. Finally, protein synthesis was not required for either type of fragmentation. In summary, we have demonstrated that: (1) the ability to undergo DNA fragmentation is a property of the TC rather than the effector cells that mediated their death, and (2) K562 and Daudi, 2 human TC, undergo single-strand nicks when lysed by LAK cells whereas SP/2 and YAC, 2 mouse TC undergo double-strand fragmentation when exposed to the same syngeneic or xenogeneic effector cells.

Animals↗
PubMed1991

A shared kappa reciprocal fragment and a high frequency of secondary Jk5 rearrangements among influenza hemagglutinin specific B cell hybridomas.

Ig kappa-chain gene rearrangement results in the displacement or loss of the DNA immediately 5' of Jk. This retained DNA is found on a different size fragment than in the germline (a reciprocal fragment), and contains the reciprocal joint of rearranged Vk and Jk genes, the back-to-back fusion of the heptamer/nonamer recombination signals. B cells of independent origin rarely have reciprocal fragments of the same size. However, we report that 9 of 15 B cell hybridomas of independent origin have reciprocal fragments of the same size (8-kb BamHI fragments) unrelated to their productive rearrangements. An 8-kb reciprocal fragment has also occurred on about 25% of the kappa alleles of normal splenic B cells. We find that the reciprocal fragments in two of these hybridomas contain the reciprocal joints of Jk1 genes and different Vk8 genes. In addition, we find that at least 8 of the 12 Jk4 or Jk5 expressing hybridomas have undergone double recombinations on their productive kappa alleles. The implications of these findings on the high frequency of 8-kb reciprocal rearrangements and on Vk rearrangement are discussed.

Amino Acid Sequence↗

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