Investigation of a naphthalene pitch by high-resolution solid-state dynamic nuclear polarization

The possibility of applying the dynamic nuclear polarization (DNP) technique to a study of char is explored with a naphthalene-derived pitch. It is shown that a 13C DNP enhancement factor of about 10(2) is obtained when the polarization is directly transferred from the unpaired electrons to the 13C nuclei. An undistorted spectrum with an enhancement factor of 8 is obtained by the DNP cross-polarization magic-angle spinning nuclear magnetic resonance (DNP-CP-MAS NMR) method. With such a high increase in S/N, it is possible to measure the 13C polarization time (Tp) and the spin-lattice relaxation time (T1) of the system in a reasonable experimental time. The resultant values are Tp = 19 s and T1 = 38 s, respectively. Based on the DNP enhancement as a function of the microwave frequency, it is found that the predominant DNP mechanism in the pitch is the solid-state effect.

Developmental state and the circadian clock interact to influence the timing of eclosion in Drosophila melanogaster

In Drosophila melanogaster, the emergence of adults from their pupal cases (eclosion) is gated by the circadian clock such that it occurs during a window of approximately 8-10 h starting 1-2 h before lights-on in 12-h light:12-h dark cycles (LD). This gate is shifted several hours earlier by the clock mutant per(s), indicating that the clock controls the phase of eclosion under these conditions. Both the day and the time of eclosion are determined by the interplay between developmental state and the circadian clock. At a certain phase of the circadian cycle, the circadian clock, either directly or through some circadian clock-controlled mechanism, measures development state, and those pharate adults that have reached a certain developmental state by this phase eclose during the first available gate, while those that have not wait until a subsequent gate. Using wing pigmentation as a late developmental state marker, an early boundary for when the circadian clock assesses developmental state occurs roughly at the time when lights go out during LD cycles. This event is shifted several hours earlier in per(s), showing that it is under circadian control. A fly's developmental state at the time of developmental assessment also influences when eclosion will occur (during the gate) in that flies whose wings have become pigmented early (12-24 h before assessment) will eclose earlier in the gate than those whose wings become pigmented late (0-12 h before assessment). These data suggest that the circadian clock (or some clock-controlled mechanism) measures developmental state (wing pigmentation) in wild-type flies between lights-off and expression of the first clock-regulated marker approximately 4-5 h before eclosion and that the developmental state of the fly determines both which gate is chosen for eclosion and when eclosion occurs during that gate.

Analysis of the specificity of bacterial immunoglobulin A (IgA) proteases by a comparative study of ape serum IgAs as substrates

Immunoglobulin A (IgA) proteases are bacterial enzymes with substrate specificity for human serum and secretory IgAs. To further define the basis of this specificity, we examined the ability of IgA proteases of Clostridium ramosum, Streptococcus pneumoniae (EC 3.4.24.13), Neisseria meningitidis (EC 3.4.21.72), and Haemophilus influenzae (EC 3.4.21.72) to cleave serum IgAs of gorillas, chimpanzees, and orangutans. All enzymes cleaved the IgAs of the three apes despite differences in ape IgA1 hinge sequence relative to the human prototype. To directly compare the ape and human hinge cleavage sites, the sites were identified in eight ape IgA digests. This analysis confirmed that ape proteins were all cleaved in the IgA hinge region, in all but one case after proline residues. The exception, C. ramosum protease, cleaved gorilla and chimpanzee IgAs at peptide bonds having no proline, but the scissile bonds were in the same hinge location as the Pro-221-Val-222 cleaved in human IgA1. These data indicate that proline is not an invariant substrate requirement for all IgA proteases and that the location of the scissile bond, in addition to its composition, is a critical determinant of cleavage specificity.

Lack of interference between IgA-binding proteins and IgA proteases of human pathogenic bacteria

Some human bacterial pathogens produce specific immunoglobulin A1 (IgA1) proteases that cleave the heavy chain of human IgA1, generating intact Fab and Fc fragments. Other pathogenic bacterial species express surface proteins which bind to the Fc part of human IgA in a non-immune manner. To analyse whether IgA-binding proteins affect the activity of IgA1 proteases, the ability of seven different IgA1 proteases to hydrolyse IgA1 in the presence of either of two different bacterial IgA-binding proteins was tested. Data obtained in two different types of experiment suggest that IgA1 bound to IgA-binding proteins still functions as a substrate for IgA1 proteases. As Fc fragments produced by cleaving IgA1 with IgA1 proteases still bind to IgA-binding proteins, we conclude that these two types of bacterial protein act independently of each other.

[Observation on activity of carbonic anhydrase in the vestibule of guinea pigs]

The localization of carbonic anhydrase (CA) activity in the inner ear vestibule of guinea pigs were studied by histochemistry and cytochemistry. We found that numerous enzymatic reaction products were localized in the sterecocilia, cuticles of hair cells, no reaction product was seen in their cell bodies; revealed reaction products in the cell membrane, microvilli, lateral infolding and basolateral infolding of the supporting cell, dark cell, transitional cell and wall cell. It is suggeated that the CA is a membrane-associated CA and the membrane-associated CA plays an important role in the homeistasis of the vestibule and otolithic metabolism.

Damage to rat spermatozoal DNA after chronic cyclophosphamide exposure

Treatment of male rats with low dosages of cyclophosphamide causes a dramatic increase in early embryo death among their progeny without significantly affecting the general health of the male. It is hypothesized that cyclophosphamide exerts its effects by targeting specific components of spermatozoal nuclei. The purpose of the present studies was to investigate the effects of chronic cyclophosphamide treatment on spermatozoal DNA. Two approaches were pursued. The first was to determine total DNA damage by using the alkaline elution method. The second was to study spermatozoal DNA template function by using an in vitro DNA synthesis system. Adult male rats were treated with saline or cyclophosphamide (6.1 mg/kg/day) daily for 1 or 6 wk. Cauda epididymal spermatozoa were collected and subjected to alkaline elution using DNA-DNA dot hybridization to quantify the fractionated DNA. One week of treatment with cyclophosphamide caused DNA single strand breaks that could be detected only in the presence of proteinase K in the lysis solution; no DNA cross-links were observed in the animals that received 1-wk drug treatment. In contrast, 6 wk of treatment with cyclophosphamide induced a significant increase in both DNA single strand breaks and cross-links in spermatozoal nuclei; the cross-links were attributable primarily to DNA-DNA linkages. The availability of spermatozoal DNA for template function was not affected by 1 wk of treatment with cyclophosphamide but was markedly affected after 6 wk of treatment with this drug. It is proposed that during chromatin transition processes the male genome may be in an open dynamic state with many exposed sites that are vulnerable to alkylating agents. Since there is no DNA repair during spermiogenesis, damage to the genome by alkylation at this stage may be cumulative, resulting in the production of dysfunctional germ cells.

[Cryosurgical resection of pulmonary metastases (experience of twenty years)]

Cryosurgical resection of pulmonary metastases was performed in 112 patients from 1973 to 1993. The cumulative 1, 3, 5, 10 year survival rate was 80.37%, 41.81%, 28.01% and 17.28%. One patient died of respiratory failure after operation. Thirty-day mortality rate was 0.89%. The disease-free interval (DFI) between the control of primary tumor and appearance of metastases was significantly correlated with post-thoracotomy survival. The multiple factor analysis also demonstrated that DFI was the most important prognostic factor for patients after cryosurgical resection of pulmonary metastatic lesions. The overall 5 year survival rate of patients treated with cryosurgery in our report was higher than that of those treated by local resection of pulmonary metastases reported by other authors. Our results indicated that cryosurgical resection of pulmonary metastases was effective and safe, the survival time of most patients could be prolonged and some patients could be cured.

[Influence of PGE2 on the oxidative modification of LDL and the scavenger receptor activities of macrophages]

The influence of oxidized LDL (OX-LDL) on scavenger receptor of macrophages and the protective effects of PGE2 and selenium was studied by means of BA-ELISA technique, immunohistochemical methods and oil red O histochemistry. The results indicated that the scavenger receptor activities of macrophages in two treated groups were much lower than that of OX-LDL group. Oil red O staining showed that the macrophages in OX-LDL group were full of fatty drops and became foam cells while little lipid could be found in the treated groups. Immunohistochemical study revealed that the entry of OX-LDL into the macrophages was by way of scavenger receptors. The results confirmed that both PGE2 and selenium had marked antioxidizing effects and that PGE2 was slightly more effective than selenium.

Temporal and spatial expression of an adult cuticle protein gene from Drosophila suggests that its protein product may impart some specialized cuticle function

An adult cuticle protein gene (Dacp-1) from Drosophila melanogaster has been isolated and characterized. This gene was classified as an adult cuticle protein gene because it maintains the conserved structure of other cuticle protein genes, the sequence of its conceptual translation product contains a repeated motif that is found almost exclusively in a subset of adult cuticle proteins from Locust migratoria, and the gene is expressed in the epidermis underlying the head and thoracic cuticle. The bulk of Dacp-1 expression starts approximately 72 hr after pupariation, peaks approximately 12 hr after eclosion, and decreases thereafter to undetectable levels by 3 days after eclosion. The stage specificity and spatial restriction of Dacp-1 expression as well as the physical properties of its conceptual translation product suggest that it may be involved in some specialized function such as thickening of the adult cuticle.

Experimental study on antiatherosclerotic treatment by PGE2 combined with vitamin E and estradiol

The effects of single dose of PGE2 combined with vitamin E and with estradiol on experimental atherosclerosis were studied by means of morphological, ultrastructural, autoradiographic and several functional techniques. The results showed that two combined treatment groups had more coordinative inhibition on aortic and coronary atherosclerotic lesions, as well as on platelet aggregation, smooth muscle cell proliferation and lipid peroxidation than that of single dose of PGE2. It was revealed that the coordinative mechanism might be closely related to the synergistic inhibitory function of above-mentioned drugs on endothelial permeability, platelet aggregation, smooth muscle cell proliferation and lipid peroxidation.

DNA topoisomerase II isozymes involved in anticancer drug action and resistance

DNA topoisomerase II is a major protein of the nuclear matrix. The enzyme appears to have a central role in both DNA organization and replication. The importance of nuclear matrix topoisomerase II alpha as a target for certain anticancer agents was evaluated in CEM human leukemia cells. Studies were done to determine the extent to which the alpha (170 kDa) and beta (180 kDa) isozymes of topoisomerase II form covalent enzyme-DNA complexes in whole cells and in the nuclear matrix and nonmatrix fractions of CEM cells that are either sensitive or resistant to topoisomerase II-active anticancer agents. Topoisomerase II alpha was detected in both the high salt-soluble (nonmatrix) and matrix fractions of nuclei from parental CEM cells. Most of the matrix topoisomerase II alpha was tightly bound to DNA in cells incubated with VM-26. In contrast, topoisomerase II beta was detected only in the high salt-soluble (nonmatrix) fraction of the nucleus. The subnuclear distribution of the alpha and beta topoisomerase II isozymes in CEM/VM-1 cells resistant to topoisomerase-active drugs was similar to that in drug-sensitive CEM cells. However, the amount and activity of topoisomerase II alpha in nuclear matrices of CEM/VM-1 cells were decreased 3- to 6-fold relative to that of CEM cells. The differences observed in the subnuclear distribution and DNA binding pattern of the topoisomerase II isozymes support the hypotheses that each isozyme has a distinct cellular function. Furthermore, these results provide evidence that topoisomerase II alpha is the nuclear matrix target for VM-26, and that depletion of the nuclear matrix isozyme contributes to cellular resistance to this anticancer agent.

Effects of chronic low-dose cyclophosphamide exposure on the nuclei of rat spermatozoa

Previous studies from our laboratory have shown that chronic exposure of the father to low doses of cyclophosphamide results in a significant increase in early embryonic death with little effect on the male reproductive system in rats. Such effects on progeny outcome are hypothesized to be mediated by an action of the drug on the nucleus of spermatozoa. The purpose of the present studies was to investigate the effects of cyclophosphamide treatment for 1 or 6 wk on the pattern of decondensation of sperm nuclei and on the sulfhydryl content of sperm nuclear proteins. Adult male rats were treated with cyclophosphamide (6.1 mg/kg/day) daily for 1 or 6 wk. Cauda epididymal spermatozoa were collected, demembranated, and then incubated with dithiothreitol (DTT) and proteinase K. The in vitro decondensation pattern of the nuclei of spermatozoa was divided into two phases: nuclear swelling and nuclear elongation. Spermatozoa from animals treated for 1 wk with cyclophosphamide showed the same decondensation pattern as those treated with vehicle (saline) alone. However, spermatozoa from animals treated for 6 wk with cyclophosphamide showed normal initial nuclear swelling but had a markedly affected nuclear elongation pattern. The changes with time in the decondensation pattern of these spermatozoa were quantitated by morphometric analysis of the head region of the spermatozoa. The nuclear area, curvature, and length of spermatozoa obtained from chronically drug-treated males were all significantly smaller than for those obtained from controls, while cell diameter was not affected.(ABSTRACT TRUNCATED AT 250 WORDS)

Study of natural diamonds by dynamic nuclear polarization-enhanced 13C nuclear magnetic resonance spectroscopy

The results of a study of two types of natural-diamond crystals by dynamic nuclear polarization (DNP)-enhanced high-resolution solid-state 13C nuclear magnetic resonance (NMR) are reported. The home-built DNP magic-angle spinning (MAS) 13C NMR spectrometer operates at 54 GHz for electrons and 20.2 MHz for carbons. The power of the microwave source was about 30 W and the highest DNP enhancement factor came near to 10(3). It was shown that in the MAS spectra the 13C NMR linewidths of the Ib-type diamond were broader than those of IaB3-type diamond. From the hyperfine structure of the DNP enhancement as a function of frequency, four kinds of nitrogen-centred and one kind of carbon-centred free radicals could be identified in the Ib-type diamond. The hyperfine structures of the DNP enhancement curve that originated from the anisotropic hyperfine interaction between electron and nuclei could be partially averaged out by MAS. The 13C polarization time of DNP was rather long, i.e. 1500 s, and the spin-lattice relaxation time (without microwave irradiation) was about 300 s, which was somewhat shorter than anticipated. Discussions on these experimental results have been made in this report.

Subcellular distribution of the alpha and beta topoisomerase II-DNA complexes stabilized by VM-26

Studies were done to determine (a) the subcellular distribution of the alpha (170 kDa) and beta (180 kDa) isozymes of topoisomerase II, and (b) the extent to which each isozyme forms complexes with DNA in tumor cells incubated with and without VM-26. Western blotting revealed that topoisomerase II beta was highly unstable during cell fractionation. However, preincubation of human CEM leukemia cells with 5-100 microM VM-26 for 30 min protected the beta isozyme from degradation by progressively increasing the amount of this isoform bound to DNA. The amount of topoisomerase II beta detected in nuclei of CEM cells incubated for 30 min with 25 microM VM-26 was 7-fold greater than in nuclei from untreated control cells. VM-26 also had a protective effect on topoisomerase II beta in HL-60 leukemia and WiDR colon carcinoma cells. In contrast, the intercalating agents mitoxantrone and m-AMSA did not protect topoisomerase II beta from degradation during cell fractionation. The stabilization of topoisomerase II beta by VM-26 allowed subsequent studies of the subcellular distribution of the topoisomerase II isozymes. Both isozymes were detected in the nonmatrix (high salt-soluble) fraction of nuclei from CEM cells, but only topoisomerase II alpha was present in the nuclear matrix. VM-26 stabilized binding of the alpha and beta topoisomerase II isoenzymes to nonmatrix DNA and topoisomerase II alpha to matrix DNA. The differences observed in the subnuclear distribution and DNA binding pattern of the topoisomerase II isozymes support the hypotheses that each isozyme has a distinct cellular function, and that both the alpha and beta isozymes are potential targets for VM-26 in intact cells. In addition, the results demonstrated that pretreatment of various cell lines with VM-26 is a useful way to stabilize topoisomerase II beta during cell fractionation.