SEARCH · Search PubMed

Results for “Fragmentation”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31Linked to original sources

PubMed1995

Effect of medical management and residual fragments on recurrent stone formation following shock wave lithotripsy.

Minimal emphasis has been placed on the clinical sequelae of residual stone fragments following shock wave lithotripsy. Moreover, there are no studies investigating the role of medical therapy on the course of stone disease in patients with residual fragments. In this retrospective, nonrandomized review, we evaluated 80 patients who had undergone shock wave lithotripsy at various institutions in Texas and were referred to our mineral metabolism clinic for metabolic evaluation and medical management of the stone disease. Of the patients 31 were determined to be stone-free following lithotripsy, while 49 had residual stone fragments. All patients were contacted an average of 43.2 months (range 9 to 79) following shock wave lithotripsy and the radiographs were reviewed. Patients were placed into 4 groups after shock wave lithotripsy: stone-free or residual fragments on or off medical therapy. In the stone-free group (19 patients), medical treatment produced a significant decrease in stone formation from a median of 0.67 to 0.0 stones per patient per year (p < 0.001). In 36 patients with residual fragments stone formation before shock wave lithotripsy was higher than in the stone-free group but there was also a significant decrease in the stone formation rate from a median of 2.47 to 0.00 stones per patient per year while on medical therapy (p < 0.001). Of the 12 stone-free patients who did not remain on medical therapy there was a slight decrease in the stone formation rate from a mean of 0.83 to 0.40 stones per patient per year, although this decrease was not significant (p = 0.07). In 13 patients with residual fragments not on medical treatment there was only a minimal decrease in the stone formation rate from a median of 1.33 to 0.77 stones per patient per year (p = 0.06). We also assessed the significance of so-called clinically insignificant residual fragments (smaller than 5 mm.) following shock wave lithotripsy in 26 of the 36 patients with residual fragments. More than half of the 26 patients with clinically insignificant fragments in the group that did not continue on medical therapy demonstrated significant stone growth during followup, suggesting that these fragments were not insignificant. Moreover, only 16% of the patients with fragments smaller than 5 mm. demonstrated an increase in fragment size while on medical therapy, again suggesting that appropriate medical treatment can decrease the risk of recurrent stone formation or growth (p < 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed2004

Exponential and power-law mass distributions in brittle fragmentation.

Generic arguments, a minimal numerical model, and fragmentation experiments with gypsum disk are used to investigate the fragment-size distribution that results from dynamic brittle fragmentation. Fragmentation is initiated by random nucleation of cracks due to material inhomogeneities, and its dynamics are pictured as a process of propagating cracks that are unstable against side-branch formation. The initial cracks and side branches both merge mutually to form fragments. The side branches have a finite penetration depth as a result of inherent damping. Generic arguments imply that close to the minimum strain (or impact energy) required for fragmentation, the number of fragments of size s scales as s(-(2D-1)/D) f(1) (- (2/lambda)(D) s)+ f(2) (- s(-1 )(0 ) (lambda+ s(1/D) )(D) ), where D is the Euclidean dimension of the space, lambda is the penetration depth, and f(1) and f(2) can be approximated by exponential functions. Simulation results and experiments can both be described by this theoretical fragment-size distribution. The typical largest fragment size s(0) was found to diverge at the minimum strain required for fragmentation as it is inversely related to the density of initially formed cracks. Our results also indicate that scaling of s(0) close to this divergence depends on, e.g., loading conditions, and thus is not universal. At the same time, the density of fragment surface vanishes as L-1, L being the linear dimension of the brittle solid. The results obtained provide an explanation as to why the fragment-size distributions found in nature can have two components, an exponential as well as a power-law component, with varying relative weights.

Journal Article↗

PubMed2005

Estimation of genetic parameters for the prevalence of osseous fragments in limb joints of Hanoverian Warmblood horses.

Genetic parameters were estimated for the prevalence of osseous fragments in distal (DIJ) and proximal interphalangeal (PIJ), fetlock (FJ) and hock joints (HJ) of Hanoverian Warmblood horses by using residual maximum likelihood (REML) with linear animal models. The analyses were based on the results of 10 standardized radiographs of all four limbs of 3725 young riding horses selected for sale at auction. Transformation factors onto the underlying liability scale were verified by a simulation study. The heritability estimates of osseous fragments on the liability scale were in the range of h2 = 0.19-0.60. Further analyses of osseous fragments in FJ and HJ were performed separately in males and females. In both sexes, the heritabilities of osseous fragments in HJ were higher (h2 = 0.41 in males, h2 = 0.25 in females) than those of osseous fragments in FJ (h2 = 0.21 in males, h2 = 0.23 in females). Osseous fragments in the phalangeal joints (DIJ, PIJ, FJ) were genetically correlated moderately positive (r(g) = 0.19-0.41). The genetic correlations between osseous fragments in the phalangeal joints and in HJ were negative (r(g) = -0.27 to -0.67). Particularly, this applied to osseous fragments in FJ in both sexes, to those in front FJ in males and to osseous fragments in front and hind FJ of females (up to r(g) = -1). The heritability of height at withers was estimated at h2 = 0.27-0.28. Genetic correlations between height at withers and osseous fragments in equine limb joints were mostly moderately positive (up to r(g) = 0.75). We conclude from our results that osseous fragments in phalangeal and hock joints are genetically different traits but sex-specific expression of osseous fragments was unlikely.

Animals↗

PubMed2000

I-CeuI fragment analysis of the Shigella species: evidence for large-scale chromosome rearrangement in S. dysenteriae and S. flexneri.

I-CeuI fragments of four Shigella species were analyzed to investigate their taxonomic distance from Escherichia coli and to collect substantiated evidence of their genetic relatedness because their ribosomal RNA sequences and similarity values of their chromosomal DNA/DNA hybridization had proved their taxonomic identity. I-CeuI digestion of genomic DNAs yielded seven fragments in every species, indicating that all the Shigella species contained seven sets of ribosome RNA operons. To determine the fragment identities, seven genes were selected from each I-CeuI fragment of E. coli strain K-12 and used as hybridization probes. Among the four Shigella species, S. boydii and S. sonnei showed hybridization patterns similar to those observed for E. coli strains; each gene probe hybridized to the I-CeuI fragments with sizes similar to that of the corresponding E. coli fragment. In contrast, S. dysenteriae and S. flexneri showed distinct patterns; rcsF and rbsR genes that located on different I-CeuI fragments in E. coli, fragments D and E, were found to co-locate on a fragment. Further analysis using an additional three genes that located on fragment D in K-12 revealed that some chromosome rearrangements involving the fragments corresponding to fragments D and E of K-12 took place in S. dysenteriae and S. flexneri.

Blotting, Southern↗

PubMed2006

Factors affecting calcium oxalate dihydrate fragmented calculi regrowth.

BACKGROUND: The use of extracorporeal shock wave lithotripsy (ESWL) to treat calcium oxalate dihydrate (COD) renal calculi gives excellent fragmentation results. However, the retention of post-ESWL fragments within the kidney remains an important health problem. This study examined the effect of various urinary conditions and crystallization inhibitors on the regrowth of spontaneously-passed post-ESWL COD calculi fragments. METHODS: Post-ESWL COD calculi fragments were incubated in chambers containing synthetic urine varying in pH and calcium concentration: pH = 5.5 normocalciuria (3.75 mM), pH = 5.5 hypercalciuria (6.25 mM), pH = 6.5 normocalciuria (3.75 mM) or pH = 6.5 hypercalciuria (6.25 mM). Fragment growth was evaluated by measuring increases in weight. Fragment growth was standardized by calculating the relative mass increase. RESULTS: Calcium oxalate monohydrate (COM) crystals formed on COD renal calculi fragments under all conditions. Under pH = 5.5 normocalciuria conditions, only COM crystals formed (growth rate = 0.22 +/- 0.04 microg/mg x h). Under pH = 5.5 hypercalciuria and under pH = 6.5 normocalciuria conditions, COM crystals and a small number of new COD crystals formed (growth rate = 0.32 +/- 0.03 microg/mg x h and 0.35 +/- 0.05 microg/mg x h, respectively). Under pH = 6.5 hypercalciuria conditions, large amounts of COD, COM, hydroxyapatite and brushite crystals formed (growth rate = 3.87 +/- 0. 34 microg/mg x h). A study of three crystallization inhibitors demonstrated that phytate completely inhibited fragment growth (2.27 microM at pH = 5.5 and 4.55 microM at pH = 6.5, both under hypercalciuria conditions), while 69.0 microM pyrophosphate caused an 87% reduction in mass under pH = 6.5 hypercalciuria conditions. In contrast, 5.29 mM citrate did not inhibit fragment mass increase under pH = 6.5 hypercalciuria conditions. CONCLUSION: The growth rate of COD calculi fragments under pH = 6.5 hypercalciuria conditions was approximately ten times that observed under the other three conditions. This observation suggests COD calculi residual fragments in the kidneys together with hypercalciuria and high urinary pH values may be a risk factor for stone growth. The study also showed the effectiveness of specific crystallization inhibitors in slowing calculi fragment growth.

Calcium↗

PubMed1994

Glycosaminoglycans prevent induction of fragmentation of porcine oocytes stimulated by dibutyryl cyclic adenosine 3',5'-monophosphate in culture.

The in vitro effects of derivatives of cyclic adenosine 3',5'-monophosphate (cAMP) and glycosaminoglycans (GAGs) on the spontaneous induction of fragmentation of cultured porcine oocytes were examined. Oocytes cultured for 72 h or longer undergo spontaneous fragmentation, and the percent of fragmented oocytes increased thereafter. The fragmented oocytes consisted of several "blastomeres" showing uneven distribution of DNA among the "blastomeres". Cytoplasmic bodies were also identified on the surface of fragmented oocytes and in the space among fragmented "blastomeres". Dibutyryl cyclic adenosine 3',5'-monophosphate (dbcAMP) at concentrations exceeding 50 microM markedly increased the induction of fragmentation. 8-bromoadenosine 3',5'-cyclic monophosphate, butyrate, cAMP and GAGs isolated from porcine follicular fluid (pFF) did not stimulate the induction of fragmentation. pFF-GAGs added to the suspending medium at concentrations of 10 micrograms/ml or greater prevented the occurrence of dbcAMP-stimulated fragmentation of isolated porcine oocytes in a dose-dependent manner. Preparations of hyaluronic acid and chondroitin sulfate from a commercial source prevented the occurrence of fragmentation stimulated by dbcAMP. The present findings suggest that cAMP may involve the induction of fragmentation of porcine oocytes and GAGs prevent the activation of cAMP-dependent fragmentation.

Animals↗

PubMed2006

Complex responses within a desert bee guild (Hymenoptera: Apiformes) to urban habitat fragmentation.

Urbanization within the Tucson Basin of Arizona during the past 50+ years has fragmented the original desert scrub into patches of different sizes and ages. These remnant patches and the surrounding desert are dominated by Larrea tridentata (creosote bush), a long-lived shrub whose flowers are visited by > 120 native bee species across its range. Twenty-one of these bee species restrict their pollen foraging to L. tridentata. To evaluate the response of this bee fauna to fragmentation, we compared species incidence and abundance patterns for the bee guild visiting L. tridentata at 59 habitat fragments of known size (0.002-5 ha) and age (up to 70 years), and in adjacent desert. The 62 bee species caught during this study responded to fragmentation heterogeneously and not in direct relation to their abundance or incidence in undisturbed desert. Few species found outside the city were entirely absent from urban fragments. Species of ground-nesting L. tridentata specialists were underrepresented in smaller fragments and less abundant in the smaller and older fragments. In contrast, cavity-nesting bees (including one L. tridentata specialist) were overrepresented in the habitat fragments, probably due to enhanced nesting opportunities available in the urban matrix. Small-bodied bee species were no more likely than larger bodied species to be absent from the smaller fragments. The introduced European honey bee, Apis mellifera, was a minor faunal element at > 90% of the fragments and exerted little if any influence on the response of native bee species to fragmentation. Overall, bee response to urban habitat fragmentation was best predicted by ecological traits associated with nesting and dietary breadth. Had species been treated as individual units in the analyses, or pooled together into one analysis, these response patterns may not have been apparent. Pollination interactions with this floral host are probably not adversely affected in this system because of its longevity and ability to attract diverse pollinators but will demand careful further study to understand.

Animals↗

PubMed2001

The effect of surgically implanted bullet fragments on the spinal cord in a rabbit model.

BACKGROUND: Whether or not to remove bullets or bullet fragments from the spinal column of a neurologically intact patient has been a subject of continual debate. The controversy is due in part to a lack of information about the long-term effects of bullet fragments on spinal cord tissue. Although many studies have demonstrated the toxic effects of metal fragments on brain tissue, to our knowledge no one has evaluated the effects of the metals contained in commercially available bullets on spinal cord tissue. METHODS: Copper, aluminum, and lead fragments from three commercially available bullet cartridges were implanted in intradural and extradural locations in seventeen New Zealand White rabbits. At an average of 9.8 months, the metal content of specimens of blood, cerebrospinal fluid, and liver were determined. The spinal cords were harvested and examined histologically. RESULTS: There was a significant increase in the copper level of blood from the rabbits with an implanted copper fragment compared with that of the control animals (p = 0.007). Concentrations of copper and lead were not elevated, compared with the control values, in the serum or liver. Histological examination of the spinal cords revealed major destruction of both the axons and the myelin of the dorsal column adjacent to the intradural copper fragments. Intradural fragments of lead caused similar destruction of myelin and axons in the dorsal column, but to a lesser degree. Minimal spinal cord or meningeal histological changes were noted around the aluminum intradural fragments, and no pathological changes were found near any fragments placed in an extradural location. CONCLUSIONS: The results of this study show that certain metals contained in commercially available bullets can cause varying degrees of neural destruction independent of the initial mechanical injury caused by implantation. Of the three metals tested, copper fragments consistently caused a substantial localized area of neural injury within the spinal cord. CLINICAL RELEVANCE: In our study, copper fragments caused local neural toxicity involving as much as 10% of the spinal cord area, suggesting that there may be a scientific basis for removal of copper fragments lodged in the spinal cord, even in the absence of a neurological deficit.

Aluminum↗

PubMed2005

Effects of size of ingestively masticated fragments of plant tissues on kinetics of digestion of NDF.

Ingestively masticated fragments were collected and sized via sieving. Different sizes of esophageal masticate and ruminal digesta fragments, and ground fragments of larger masticated pieces were incubated in vitro, and undigested NDF remaining at intervals of up to 168 h of incubation was determined. The ruminal age-dependent time delay (tau) for onset of digestion of NDF was positively correlated (P < 0.004) with the mean sieve aperture estimated to retain 50% of the fragments between successive sieve apertures (MRA). Degradation rate of potentially degradable NDF (PDF) and level of indigestible NDF were not related (P > 0.10) to MRA of masticated and ground fragments. Estimates of tau were positively related to MRA, with slopes of bermudagrass < corn silage < ruminal fragments of corn silage. It was concluded that fragment size-, and consequently, ruminal age-dependent onset of PDF degradation of a mixture of different fragment sizes results in an age-dependent rate of degradation of the more rapidly degrading of two subentities of PDF. Models are proposed that assume a tau before onset of simultaneous degradation of PDF from two pools characterized as having gamma-modeled age-dependency and age-constant rates. The ruminal age-dependent pool seems to be associated with the faster-degrading pool, and its rate parameter increases with range in MRA in the population of fragments. Conceptually, the ruminal age-dependent rate parameter for PDF degradation seems to represent a composite of several effects: 1) effects of the size-dependent tau; 2) range in MRA of the population of ingestively masticated fragments; and 3) subentities of PDF that degrade via more rapid age-dependent rates compared with subentities of PDF that degrade via age-constant rates. The estimated fractional rates of ruminative comminution of ingestively masticated fragments (0.060 to 0.075/h) were of a magnitude similar to the mean fractional rates of PDF digestion (0.030 to 0.085/h), which implies that ruminative comminution may be first-limiting to fractional rate of PDF digestion. The in vivo roles of ingestive and ruminative mastication of fragments on PDF degradation must be considered in any kinetic system for estimating PDF digestion in the rumen. These results and others in the literature suggest that the rate of surface area exposure rather than intrinsic chemical attributes of PDF may be first-limiting to degradation rate of PDF in vivo.

Animal Nutritional Physiological Phenomena↗

PubMed2003

Fragmented forest in tropical landscape--the case of the state of Selangor, Malaysia.

This paper presents the pattern and changes of fragmented forest in relation with changes of total forest cover in the state of Selangor in three decades. In this study, inventoried forest cover maps of Selangor in 1971/1972, 1981/1982 and 1991/1992 produced by the Forestry Department of Peninsular Malaysia were digitized to examine the changes in area and number of fragmented forest. Results showed that in 1971/1972, 16 fragmented forests were identified in Selangor. All fragmented forests were identified as dipterocarp forest. A decade later the number of fragmented forests increased by approximately 44% (23). Of the 23 fragmented forests, two were peat swamp forests whereas the remaining were dipterocarp forests. In 1991/1992 the number of fragmented forests (12) was reduced by 47.8%. Two of the fragmented forests were identified as peat swamp forest, seven dipterocarp forest and the other three was mixed of dipterocarp forests and plantation forests. Fragmentation of both dipterocarp and peat swamp forests occurred profoundly during the period between 1971/1972 and 1981/1982, which consequently increased the number of fragmented forests compared with before the period of 1971/1972 where fragmentation happened only at dipterocarp forests. However, many fragmented forests vanished between the 1981/1982 and 1991/1992 periods.

Conservation of Natural Resources↗

PubMed1976

Localization of ionophore activity in a 20,000-dalton fragment of the adenosine triphosphatase of Sarcoplasmic reticulum.

The (Ca2+ + Mg2+)-dependent ATPase of sarcoplasmic reticulum has been shown to ast as a Ca2+-dependent and selective ionophore in artificial lipid bilayers. Four fragments of 55,000, 45,000, 30,000, and 20,000 daltons have been purified from tryptic digests of the enzyme and it has been shown that the 55,000- and 45,000-dalton fragments are obtained from a single cleavage of the 100,000-dalton ATPase, while the 30,000- and 20,000-dalton fragments are obtained subsequently by a cleavage of the 55,000-dalton fragment. The 55,000- and 20,000-dalton fragments have ionophore activity inhibited by ruthenium red and by mercuric chloride but not by methylmercuric chloride, an inhibitor of the hydrolytic site of the enzyme. Under standard conditions the 45,000-dalton fragment was not active as an ionophore, while the 30,000-dalton fragment acted as a nonselective ionophore. The 55,000- and 30,000-dalton fragments have been shown to contain the site of phosphorylation and of N-ethyl [2-3H]-maleimide binding indicative of the hydrolytic site in the enzyme, and this site is absent from the 20,000-dalton fragment. Therefore, the ionophoric and hydrolytic sites are localized in separate regions of the ATPase molecule and they have now been physically separated. The 20,000-dalton fragment was degraded with cyanogen bromide and fragments were separated by molecular sieving. Ionophore activity was found in fragments of molecular mass less than 2,000 daltons.

Adenosine Triphosphatases↗

PubMed1992

Binding of fibrin fragments to one-chain and two-chain tissue-type plasminogen activator.

To explore whether fibrin fragments have binding affinity for the tissue-type plasminogen activator (t-PA) molecule, the interactions were studied of (DD)E complex and fragments DD, E1, and E3 with one-chain and two-chain t-PA. For this purpose, a solid-phase binding assay was developed using microtiter plates with nitrocellulose filters. It was found that (DD)E complex and fragments DD and E3 retained the t-PA binding function of the parent fibrin molecule, thus demonstrating that t-PA binds to both the D and E domains of fibrin. Unexpectedly, fragment E1 did not bind t-PA. Fibrin fragments had different binding properties for one-chain and two-chain t-PA. (DD)E complex had the highest and fragment E3 the lowest affinity for one-chain t-PA, both binding curves being consistent with one class of binding sites. However, binding of the fragments with two-chain t-PA was distinguished by more than one class of binding sites, with fragment E3 having the highest affinity for this form of the activator. epsilon-Aminocaproic acid, even at 50 mmol/L concentration, had only minimal effect on binding of (DD)E complex or fragment DD to either one-chain or two-chain t-PA. The potentiating effect of fibrin fragments on plasminogen activation by t-PA was measured by a chromogenic substrate assay. Fragment DD was the most effective stimulator of plasminogen activation by t-PA. In conclusion, (DD)E complex and fragment DD retained most of the regulatory functions of fibrin, which included t-PA binding and t-PA-mediated acceleration of plasminogen activation to plasmin.

Aminocaproic Acid↗

PubMed1985

Adhesion of axolemmal fragments to Schwann cells: a signal- and target-specific process closely linked to axolemmal induction of Schwann cell mitosis.

Radioiodinated rat CNS axolemmal fragments adhered to cultured rat Schwann cells by a time-, temperature-, and concentration-dependent process independent of extracellular ionized calcium. Adhesion showed target and signal specificity; axolemmal fragments adhered to endoneurial or dermal fibroblasts to a much lesser extent than to Schwann cells, and plasma membrane fragments from skeletal muscle, erythrocytes, or PNS myelin adhered to Schwann cells to a lesser extent than did axolemmal fragments. Brief trypsinization removed 94 to 97% of bound radioactivity from Schwann cells previously incubated with 125I-axolemmal fragments for up to 24 hr, indicating that adhesion was largely a surface phenomenon rather than the result of rapid internalization of axolemmal fragments by the Schwann cells. When adhesion was compared to the axolemmal mitogenic response of Schwann cells, the concentration of axolemmal fragments yielding half-maximal adhesion was the same as the concentration producing half-maximal stimulation of Schwann cell mitosis. Trypsin digestion, homogenization, or heating of axolemmal fragments before application to cultured Schwann cells diminished adhesion and axolemmal fragment-induced stimulation of Schwann cell mitosis in a parallel fashion. Whereas adhesion of axolemmal fragments to the surfaces of the cultured Schwann cells reached completion within 4 hr in this assay system, induction of Schwann cell mitosis by the fragments required contact with Schwann cells for a minimum of 6 to 8 hr and reached a maximum when the axolemmal fragments had adhered to the Schwann cells for 24 hr or more.

Animals↗

PubMed1999

Effect of various short-term storage methods on viability of cancellous bone fragments.

OBJECTIVE: To determine effects of various storage methods on ex vivo viability of cancellous bone fragments. SAMPLE POPULATION: Cancellous bone fragments obtained from 4 New Zealand White rabbits. PROCEDURE: Cancellous bone fragments were stored for 3 hours on ice in 1 of 5 preservation solutions or in 0.9% NaCl. Fragments were then reperfused (37 C) in oxygenated physiologic buffer solution for 1 hour. Cellular viability in fragments was assessed by ethidium monoazide labeling and fluorescence microscopy. RESULTS: Viability in fresh cancellous bone ranged from 85 to 100% (mean+/-SEM, 88+/-7%). Storage of fragments significantly reduced viability. Viability in bone fragments stored at 22 C in blood-soaked sponges or 0.9% NaCl solution was 63.8+/-3 and 65.2+/-7%, respectively. Use of cold 0.9% NaCI solution reduced viability to 53.6+/-3%. Viability was significantly better for fragments stored in cold phosphate-buffered sucrose (70.4+/-2%) and EuroCollins (71.4+/-3%) solutions. After warm reperfusion, viability was best for fragments stored in cold phosphate-buffered sucrose (70.2+/-4%), EuroCollins (72.6+/-3%), or UW lactobionate solutions (69.6+/-3%), compared with those stored in cold 0.9% NaCl (47.6+/-3%) or hypertonic citrate (53.0+/-3%) solutions or blood-soaked sponges (57.2+/-3%). CONCLUSIONS: Hypothermic storage in solutions designed to prevent temperature-dependent cell injury were best for maintaining cancellous bone fragment viability. CLINICAL RELEVANCE: Hypothermia may be advantageous for use in storing cancellous bone fragments during procedures that dictate a prolonged period between harvest and placement of graft fragments.

Affinity Labels↗

PubMed1979

Isolation of enzymatically derived fragments of porcine IgG and an examination of their reactivity against staphylococcal protein A.

Papain digestion of porcine IgG in the absence of cysteine resulted in a rather poor yield of fragments (less than 5 per cent). In the presence of cysteine, 70 to 80 per cent of the IgG was degradated in 4 h. Fragments with molecular weight of about 100,000 and 50,000 were separated by gel filtration. The minor fraction (mol. wt. 100,000) most probably consisted of F(c)2 fragments. Fab/c fragments with both Fc and Fab determinants, and also probably some F(ab)2-like fragments. The F(c)2 fragments appeared to be a dimer of Fc stabilized by disulphide bonds. The second main fraction (mol. wt. 50,000) contained Fc and Fab fragments. Mild reduction of the Fc fragments resulted in Fc subfragments of different sizes, thus indicating that papain cleavages had occurred on different spots in the Fc chain. Non-reduced Fc fragments therefore seem to consist of several Fc subfragments stabilized by disulphide bonds. The protein A reactivity of the isolated Fc fragments were rather low compared to the reactivity of intact IgG, respectively 5--15 and 90 per cent. In addition, protein A reactive Fab fragments were isolated from normal porcine IgG.

Animals↗

PubMed2004

Single-cell gel electrophoresis assay monitors precise kinetics of DNA fragmentation induced during programmed cell death.

BACKGROUND: Single-cell gel electrophoresis, or the comet assay, a technique widely used for DNA damage analysis, has been used recently for detecting DNA fragmentation in cells undergoing apoptosis. However, the number of variants of this assay used thus far primarily detected the late stages of DNA fragmentation. Therefore, monitoring the progression of DNA fragmentation, which could greatly improve the analysis of cell death induction and progression at the single-cell level, has not been possible with this assay. METHODS: In the present study, a modification of the original neutral comet assay developed by Ostling and Johanson (Biochem Biophys Res Commun 123:291-298, 1984) was used to detect various stages of DNA fragmentation. This assay involves cell lysis with anionic detergents at nearly neutral pH (9.5) and does not include high salt concentration, unlike most other published methods. BMG-1 human glioma cells were induced to undergo programmed cell death by treating with a large dose (100 microM) of etoposide, and comets were prepared after different durations (1-24 h) of treatment. RESULTS: In contrast to results of previously published studies, comets with different shapes reflecting progressive stages of DNA fragmentation were observed. Of these, six distinct shapes were identified and divided into three different categories based on the extent of fragmentation. Type A comets had a large head separated by a narrow "neck" region from an oval bulging tail that indicated initiation of fragmentation. Type B and C comets had a constantly diminishing head associated with a corresponding expansion of the tail and reflected intermediate and late stages of fragmentation, respectively. Type A and B comets appeared at a high frequency during early time points (1-6 h), whereas type C comets that indicated late stages of fragmentation were observed only after extended treatment (24 h). As a result, an elaborate kinetics of the progression of DNA fragmentation could be obtained. CONCLUSION: The present single-cell gel electrophoresis assay offers a significant improvement in monitoring the kinetics of DNA fragmentation induced during programmed cell death. Coupled with its simplicity and the ability to detect responses of small cell subpopulations, this method can be used for a reliable and sensitive analysis of the progression of cell death in different cell types and treatment conditions.

Animals↗

PubMed1999

Conformations of peptide fragments from the FK506 binding protein: comparison with the native and urea-unfolded states.

The helix-forming tendency of seven peptide fragments corresponding with the entire sequence of the FK506 binding protein (FKBP) has been investigated in aqueous buffer and in 2,2,2-trifluoroethanol (TFE) using CD and NMR spectroscopy. All fragments exhibited random coil conformations in aqueous buffer, whereas the amount of helix induced in the peptide fragments by TFE varied. The fragment with the highest degree of helicity in TFE corresponded with the single (alpha-helix in native FKBP. Fragments corresponding with beta-strands 2 and 3 also exhibited strong propensity towards helix formation. In contrast, the fragment corresponding with beta-strand 1 did not form helix in TFE. The inherent helix-forming tendencies are interpreted in light of the native structure to suggest possible folding nucleation sites. Conformational sampling in each peptide fragment was also compared with that observed in urea-denatured FKBP. With the exception of the fragment corresponding with beta-strand 2, the formation of helical structures in the peptide fragments in TFE was correlated with the observation of turn and/or helix conformers in urea-unfolded FKBP. Surprisingly, peptide fragments in aqueous solution were less structured than the corresponding regions in urea-denatured FKBP. The conformational differences between the peptide fragments and unfolded FKBP were not due to the urea buffer or to differences in their rotational correlation times. We conclude that local amino acid interactions are not generally sufficient to account for the formation of non-random conformations in unfolded FKBP. Formation of non-random structures in unfolded FKBP may require stabilization of incipient turn or helical conformations through transient contact with non-local non-polar residues.

Amino Acid Sequence↗

PubMed1992

Tumour localization and pharmacokinetics of iodine-125 human monoclonal IgM antibody (COU-1) and its monomeric and half-monomeric fragments analysed in nude mice grafted with human tumour.

Human monoclonal IgM antibodies reactive with cancer-associated antigens may not have the optimal imaging capability due to their large size. Fragmentation of human IgM is less than straight-forward due to the loss of immunoreactivity. From the human monoclonal IgM antibody COU-1 we have prepared monomeric and half-monomeric fragments, which retain the ability to bind to colon cancer cells in vitro. The pharmacokinetics and tumour localization were evaluated in nude mice bearing human colon adenocarcinoma and human melanoma grafts. Faster clearance from the circulation was seen for the smaller half-monomeric fragment with a half-life (rapid phase/slow phase) of 2 h/16 h compared with the intact antibody, 4 h/25 h, and the monomeric fragment, 3 h/27 h. Intact COU-1 as well as the fragments accumulated in the colon tumour graft. Higher amounts of radioactivity were found in the colon tumour as compared to normal organs for intact COU-1 at days 4 and 6, for the monomeric fragment at day 4, and for the half-monomeric fragment at day 2 after injection. This investigation demonstrates the favourable biodistribution of the half monomeric COU-1 fragment. The fast clearance of this fragment resulted in a tumour-to-muscle ratio as high as 22 on day 2 after injection. Also, only this fragment gave a positive tumour-to-blood ratio. Normal IgM and its fragments were used as controls. Radioimmunoscintigraphy demonstrated the colon tumour discriminatory properties of each of the three iodine-labelled antibody preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗