Structural and functional characterization of mutants of the bovine leukemia virus transactivator protein p34

Mutants of the bovine leukemia virus (BLV) transactivator protein (tat, tax, p34, the XLOR gene product) were constructed by site-directed deletions, in-phase linker insertions, or fragment replacements (swapping) among BLV variants. The mutant constructs were transfected into cos cells and transiently expressed. Western blot analysis using a mixture of monoclonal antibodies to wild-type p34 revealed the presence of mutated XLOR gene products in all the mutants tested. The transactivating activity of 11 tax mutants containing site-directed deletions and in-phase linker insertions was completely abolished. Only the swapping mutant tested, a hybrid between two BLV variants, transactivated LTR-directed gene expression at wild-type levels. These data illustrate the narrow range of structural variations that allow full activity of the BLV tax product and suggest that the present molecular structure of the transactivator protein results from heavy evolutionary constraints.

Subclasses of antibodies to hepatitis B core antigen in chronic HBV infection: changes during treatment with alpha interferons and predictors of response

Response to interferon therapy in chronic hepatitis B virus (HBV) carriers is preceded by the appearance of IgM class anti-HBc (antibody to hepatitis B core antigen). The temporal relationship and magnitude of the IgM anti-HBc response is variable suggesting that the antibody is not directly involved in hepatocyte lysis, but is merely a marker of a changed state of immunity to the nucleocapsid proteins, induced by interferon. IgG 1, 2, 3, and 4 class anti-HBc did not change during therapy, but IgG 3 anti-HBc was significantly lower in responders than non-responders. IgG anti-HBc of all subclasses was absent in two Chinese HBV carriers. Lower than normal titres of anti-HBc (p less than 0.001) were detected in human immunodeficiency virus antibody positive (anti-HIV) HBV carriers. These data indicate the presence of altered immunity to the nucleocapsid antigens in these two types of chronic HBV carrier that are known to respond poorly to antiviral therapy.

Biological activity of hydroxylated chloroethylnitrosoureas

1-Nitroso-1-(2-hydroxyethyl)-3-(2-chloroethyl)urea (Compound I) and 1-nitroso-1-(2-hydroxypropyl)-3-(2-chloroethyl)urea (Compound II) display significantly reduced antitumor activity compared to the corresponding isomeric derivatives 1-nitroso-1-(2-chloroethyl)-3-(2-hydroxyethyl) urea (Compound III) and 1-nitroso-1-(2-chloroethyl)-3-(2-hydroxypropyl) urea (Compound IV). Their low therapeutic activity is paralleled by low toxicity while mutagenicity and carcinogenicity are high. A comparative investigation of the genotoxicity of Compounds I and III using primary cultures of fetal hamster lung cells revealed an about 14-fold higher rate of DNA single-strand breaks following exposure (100 microM, 1 h) to Compound I as compared to Compound III. The rate of DNA interstrand cross-links, on the other hand, was 11-fold higher following Compound III as compared to Compound I. The results underline that the therapeutic activity of chloroethylnitrosoureas is mainly attributable to their cross-linking potential while induction of DNA single-strand breaks plays a decisive role for mutagenicity and carcinogenicity but appears not to be relevant for antineoplastic effectiveness.

Long-term effects of progestin and RU 486 on prolactin production and synthesis in human endometrial stromal cells

Previous studies have shown that the production of prolactin (PRL) is increased in human endometrial stromal cells cultured with medroxyprogesterone acetate (MPA) for 3-5 days. In the present study, we have investigated the effect of prolonged treatment of progestin and anti-progestin, RU 486, on the production and synthesis of PRL. Stromal cells were isolated from human endometrium obtained from non-pregnant women and cultured for 20-30 days in medium RPMI 1640 with 2% fetal calf serum or supplemented with MPA, RU 486, alone or in sequence. The PRL content in medium was measured by radioimmunoassay. The production rate was estimated from the PRL content in medium accumulated in 24 h. The PRL production rate was progressively increased in stromal cells continuously treated with MPA for 30 days (greater than 100-fold over the control value, i.e. 0-0.01 microgram/0.1 mg cell DNA/day). RU 486 alone had no effect on the production of PRL. However, the production of PRL was increased by MPA in stromal cells pretreated with RU 486 indicating that the effect of RU 486 is reversible. When stromal cells were treated with MPA and RU 486 sequentially, RU 486 stimulated the PRL production (approximately 2-fold over the MPA-treated cells) for 2-3 days and then reduced to basal levels over a 5-day period. The stimulatory and inhibitory effects of RU 486 on PRL production in stromal cells pretreated with progestin was also observed in the rate of synthesis of PRL estimated by incubating the stromal cells with [35S]methionine and immuno-isolating the [35S]PRL with anti-PRL.(ABSTRACT TRUNCATED AT 250 WORDS)

More monensin-sensitive, ammonia-producing bacteria from the rumen

Two monensin-sensitive bacteria which utilized carbohydrates poorly and grew rapidly on amino acids were isolated from the bovine rumen. The short rods (strain SR) fermented arginine, serine, lysine, glutamine, and threonine rapidly (greater than 158 nmol/mg of protein per h) and grew faster on casein digest containing short peptides than on free amino acids ().34 versus 0.29 h(-1)). Gelatin hydrolysate, an amino acid source containing an abundance of long peptides, was unable to support growth or ammonia production, but there was a large increase in ammonia production if strain SR was cocultured with peptidase-producing ruminal bacteria (Bacteroides ruminicola or Streptococcus bovis). Cocultures showed no synergism with short peptides. Strain SR washed out of continuous culture ().1 h(-1)) at pH 5.9. The irregularly shaped organisms (strain F) deaminated glutamine, histidine, glutamate, and serine rapidly (greater than 137 nmol/mg of protein per min) and grew faster on free amino acids than on short peptides ().43 versus 0.21 h(-1)). When strain F was provided with casein or gelatin hydrolysate and cocultured with peptidase-producing bacteria, there was a more than additive increase in ammonia production. Strain F grew in continuous culture (0.1 h(-1)) when the pH was as low as 5.3. The irregularly shaped cells and short rods were present at less than 10(9)/ml in vivo, but they ahd very high specific activities of ammonia production (greater than 310 nmol of ammonia/mg of protein per min) and could play an important role in ruminal amino acid fermentation.

Some electrical properties of the endothelium-dependent hyperpolarization recorded from rat arterial smooth muscle cells

1. Electrical responses produced by acetylcholine (ACh) and histamine were recorded from smooth muscle cells of the intralobular small pulmonary artery (SPA), main pulmonary artery (MPA) and thoracic aorta of rats. 2. In MPA and SPA, ACh and histamine produced a transient hyperpolarization of the membrane, and the potential decayed exponentially with a time constant of 2-3 min. In aorta, ACh produced a sustained and histamine produced a transient hyperpolarization. 3. The ACh- and histamine-induced hyperpolarizations were blocked by atropine and mepyramine, respectively, or by removing the endothelial cells. 4. The amplitude of the hyperpolarization was increased in low [K+]o solutions and decreased in high [K+]o solutions. The ionic conductance of the membrane was increased during the hyperpolarization, suggesting an involvement of the increased potassium conductance. 5. A reproducible amplitude of hyperpolarization was generated when ACh or histamine was applied at intervals of over 10 or 30 min, respectively. 6. In aorta, after the transient hyperpolarization had ceased during continued application of histamine, ACh again produced a hyperpolarization, i.e. the transient nature of the hyperpolarization was not due to desensitization of the receptor upon which the hyperpolarizing substance acted, assuming histamine and ACh release the same hyperpolarizing substance. 7. ACh and histamine relaxed the tissues from SPA, MPA and aorta during the noradrenaline (NA)- or high [K+]o solution-induced contraction, in a concentration-dependent manner, only when the endothelial cells were intact. Both ACh and histamine were potent relaxants in MPA and aorta, but showed weak relaxing actions in SPA. 8. In aorta, ACh and histamine produced a sustained relaxation for up to 10 min, and Methylene Blue diminished and altered it to a transient relaxation (for histamine) or an initial large, followed by a small sustained (for ACh), relaxation. 9. In the presence of NA and NA plus Methylene Blue, ACh and histamine also produced a hyperpolarization similar to that seen in the control. 10. It is concluded that in arteries of the rat, ACh and histamine release a hyperpolarizing substance from the endothelial cells. This substance may be different from the endothelium-derived relaxing factor (EDRF), and is released mainly transiently. The hyperpolarization is generated by an increase in potassium conductance of the membrane, and this has some contribution to the endothelium-dependent relaxation.

Impedance cardiography-dipyridamole test in detecting coronary artery disease

Thallium-201 dipyridamole test (Tl-201DT) has high sensitivity and specificity in the assessment of coronary disease (CAD), but is not always available. We proposed impedance cardiography DT (IDT)instead. To determine the characteristic changes of impedance cardiogram (ICG) in patients with typical angina and to compare with those in normal subjects, 37 subjects undergoing IDT were divided into 3 groups: typical angina (15), suspected chest pain (11) and normals (11). Dipyridamole (DP) was infused intravenously for over 10 minutes at a total dose of 0.75 mg/kg. Simultaneous recording of ECG, PCG, and ICG were repeated immediately 2 minutes and 4 minutes after infusion of DP, and immediately and 5 minutes after intravenous infusion of aminophylline. Eleven parameters, HR, SPRP, QZ/ZA2, HI, SV, CO, A wave, A/C, O wave, O/C, A + O/C were observed. Only in O/C and A + O/C there were changes of significant differences (P less than 0.01) between groups. Specificity was 100% (0/11 positive) in normals. Sensitivity was 80% (12/15 positive) in the angina group, but only 46.7% (7/15) with ECG. The characteristic changes in CAD patients during IDT were angina induced by DP, abnormal O wave on ICG and change from deep A wave to abnormal O wave. No serious complication occurred after IDT. Our results indicate that IDT is a simple, practical and valuable method for detecting CAD.

Acetylcholine releases endothelium-derived hyperpolarizing factor and EDRF from rat blood vessels

1. The effects of haemoglobin and methylene blue on the acetylcholine (ACh)-induced electrical and mechanical responses of smooth muscle cells were investigated in rat aorta and rat main pulmonary artery. 2. When the endothelium was intact, ACh induced a transient hyperpolarization and sustained relaxation of tissues precontracted with noradrenaline. Both hyperpolarization and relaxation were absent in preparations without endothelium. 3. Haemoglobin and methylene blue inhibited the ACh-induced relaxation, but not the transient hyperpolarization. 4. In aorta with an intact endothelium, ACh produced an increase in both the rate of 86Rb efflux and tissue cyclic GMP levels. The changes in ion flux were unaffected by either haemoglobin or methylene blue in concentrations which almost abolished the increase in cyclic GMP concentrations. 5. In arteries with an intact endothelium, indomethacin had no effect on the ACh-induced electrical and mechanical responses or on the increase in 86Rb efflux and tissue cyclic GMP levels. 6. It is concluded that in the rat aorta and rat main pulmonary artery, ACh releases two different substances, an endothelium-derived relaxing factor (EDRF) and a hyperpolarizing factor (EDHF), from the endothelial cells. Neither substance appears to be derived from a pathway dependent on cyclo-oxygenase. EDHF seems to play a minor role in the relaxation of noradrenaline-induced contractions.

Even transcriptionally competent proviruses are silent in bovine leukemia virus-induced sheep tumor cells

To investigate the role of proviral integration and expression in cellular transformation induced by bovine leukemia virus (BLV), three BLV-induced tumors harboring a single proviral copy were selected upon restriction and hybridization analysis. Tumors 344 and 395 were shown to contain a full-size proviral copy, whereas in tumor 1345 the provirus appeared to be heavily deleted. RNA gel blot hybridization with an antisense RNA probe showed no transcription of the viral sequences in the fresh tumors or in sheep tumor cells growing in vitro. The proviruses were cloned and transfected in mammalian cell lines. Transient-expression experiments revealed that the complete proviruses were still able to express the trans-activating protein (Tat) as well as structural proteins, demonstrating that the nonexpression of a provirus in a tumor cell does not necessarily imply a structural alteration of the viral information. In contrast, sequence analysis of the provirus with a large deletion and transient-expression assays proved that this truncated provirus, isolated from a tumor, was unable to code for viral proteins. These data indicate that expression of viral genes, including tat, is not required for the maintenance of the transformed state.

The Magnon Pairing Mechanism of Superconductivity in Cuprate Ceramics

The magnon pairing mechanism is derived to explain the high-temperature superconductivity of both the La2-xSrxCu(1)O(4) and Y(1)Ba(2)Cu(3)O(7) systems. Critical features include (i) a one- or two-dimensional lattice of linear Cu-O-Cu bonds that contribute to large antiferromagnetic (superexchange) coupling of the Cu(II)(d(9)) orbitals; (ii) holes in the oxygen ppi bands [rather than Cu(III)(d(8))] leading to high mobility hole conduction; and (iii) strong ferromagnetic coupling between oxygen ppi holes and adjacent Cu(II)(d(9)) electrons. The ferromagnetic coupling of the conduction electrons with copper d spins induces the attractive interaction responsible for the superconductivity, leading to triplet-coupled pairs called "tripgems." The disordered Heisenberg lattice of antiferromagnetically coupled copper d spins serves a role analogous to the phonons in a conventional system. This leads to a maximum transition temperature of about 200 K. For La(1.85)Sr(0.15)Cu(1)O(4), the energy gap is in excellent agreement with experiment. For Y(1)Ba(2)Cu(3)O(7), we find that both the CuO sheets and the CuO chains can contribute to the supercurrent.

Expression in bacteria of beta-galactosidase fusion proteins carrying antigenic determinants of the two X gene products of bovine leukemia virus

A cDNA corresponding to the bovine leukemia virus post-envelope region (X gene) was subcloned into the lambda gt11 expression vector. Two large protein fragments corresponding respectively to the long and short open reading frames of the X region were expressed as beta-galactosidase fusion proteins. These products were specifically recognized by sera from bovine leukemia virus-infected cattle.

The bovine leukemia virus p34 is a transactivator protein

Recombinant Moloney murine retroviruses containing the BLV post-envelope long open reading frame were constructed and transfected into the psi 2 packaging cell line. They were shown to encode and to express a 34-kd protein able to transactivate the BLV long terminal repeat-directed gene expression in the respective transfected cells. These data demonstrate that the BLV X-LOR gene encodes a p34 transactivator product. Furthermore, the different cell lines produced infectious recombinant retroviruses capable of transferring X-LOR genes into recipient cells. The availability of the BLV transactivator protein should allow us to understand the role of the transactivator protein in BLV-induced leukemogenesis.

Effect of hydrophobicity of utilization of peptides by ruminal bacteria in vitro

When mixed ruminal bacteria were incubated with a pancreatic casein hydrolysate and free amino acids of a similar composition, rates of ammonia production were much greater for peptides than for amino acids. The pancreatic digest of casein was then fractionated with 90% isopropyl alcohol. Hydrophobic peptides which dissolved in alcohol contained an abundance of phenolic and aliphatic amino acids, while the hydrophilic peptides which were precipitated by alcohol contained a large proportion of the highly charged amino acids. The Km values of the mixed ruminal bacteria for each fraction were similar (0.88 versus 0.98 g/liter), but the Vmax of the hydrophilic peptides was more than twice that of the hydrophobic peptides (18 versus 39 mg of NH3 per g of bacterial protein per h). Pure cultures of ruminal bacteria had a similar preference for hydrophilic peptides and likewise utilized peptides at a faster rate than free amino acids. Since peptide degradation rates differed greatly, hydrophobicity is likely to influence the composition of amino acids passing unfermented to the lower gut of ruminant animals.

A procedure for measuring peptides in rumen fluid and evidence that peptide uptake can be a rate-limiting step in ruminal protein degradation

A relatively simple and sensitive procedure was developed to measure the concentration of peptides in rumen fluid. Feed particles and microorganisms were removed by centrifugation, and the supernatant was treated with perchloric acid (5% final concentration). Perchloric acid precipitated macromolecules that included protein, RNA, and DNA. Perchlorate was subsequently removed by precipitation with an excess of potassium carbonate. Ammonia was removed by boiling the alkaline sample. Supernatant samples were then analyzed for ninhydrin reactive material before and after HCl hydrolysis. Because ninhydrin reaction was 3 to 7.5 times greater after HCl hydrolysis, peptides rather than amino acids were the primary source of nonprotein, nonammonia nitrogen. Rumen fluid from a cow fed timothy hay and concentrate supplement (16% crude protein) contained more than 1200 mg peptides/L (192 mg N/L), 1 h after feeding, and this value declined the prefeeding value of 400 mg/L (64 mg N/L) by 8 h after feeding. Comparison of ninhydrin reactivity with and without HCl hydrolysis indicated that peptides present before feeding contained more peptide bonds than the peptides soon after feeding. High pressure liquid chromatography revealed a variety of peaks soon after feeding and fewer dominant peaks 8 h later. The data suggest that peptide uptake into rumen microorganisms can be a rate-limiting step in ruminal protein degradation.

Concentration and estimated flow of peptides from the rumen of dairy cattle: effects of protein quantity, protein solubility, and feeding frequency

Experiments were conducted to ascertain the effect of dietary protein (type and amount) and feeding frequency on peptide concentration and flow from the rumen of lactating Holstein cows. When rations supplemented with soybean meal were fed 12 times/d and CP was 14.5, 17.1, or 20.6%, the estimated flow of N from the rumen was 22, 33, and 34 g/d, respectively. When the soybean meal was autoclaved to decrease protein solubility (14.4, 16.9, and 19.3% CP the flow of peptide N was 19, 26, and 31 g/d, respectively. In both of these experiments rumen volume and dilution rate remained relatively constant throughout the day, and flow was proportional to concentration. If the cows were fed rations containing 17.8% CP once a day, the peptide concentration and dilution rate were highest 2 h after feeding and declined significantly thereafter. Replacement of half the soybean protein with either extruded soybean meal or fish meal decreased the flow of peptide N from the rumen (19 versus 14 and 15 g/d, respectively). Because the total flow of soluble protein and ammonia as well as peptides was less if cows were fed once a day than 12 times per day, increased feeding frequency appeared to increase ruminal proteolysis.

Simultaneous visualization of vascular permeability change and leukocyte egress in the central nervous system during autoimmune encephalomyelitis

An unresolved issue in the study of demyelinating disease is whether blood-brain barrier damage is dependent upon the migration of inflammatory cells into the central nervous system (CNS). In a study of experimental autoimmune encephalomyelitis (EAE) in rabbits, a freeze-dried, paraffin-embedded tissue technique was exploited to enable (1) the immobilization of intravenously injected sodium fluorescein tracer, as an index of vascular permeability; and (2) an effective labeling by monoclonal antibodies of both T-lymphocytes and mononuclear phagocytes in "unfixed" neural tissue. Using these newly combined methods, evidence was found that increased vascular permeability in the CNS during EAE occurs concomitantly with, and not prior to, infiltration by mononuclear phagocytes.

Radiographic and histologic analyses of stress fracture in rabbit tibias

Sequential changes in remodeling of the internal structure of the tibia caused by controlled, excessive jumping and running were studied in 20 rabbits. Vascular changes and circulatory disturbances within the cortical bone occurred before osteoclastic resorption. Degeneration and necrosis of osteocytes due to circulatory disturbances also occurred. Periosteal new bone formation, found at and after 12 days of the experiment, was a compensatory reaction to support the tibia weakened by accelerated osteoclastic resorption. Small cracks appeared at the cement line and developed through the neighboring cement line of the haversian systems. At 21 days, incomplete fracture of the tibial cortex was found in two rabbits. Complete fracture through one side of the cortex was seen in one animal at the 50th day of the experiment. In this study, however, most of the tibias did not have visible fracture lines after a period of stressful exercise. This result suggests that most tibias adapt to changes in stress requirements through proper internal remodeling so that a complete fracture does not occur.

A critique of MSHA procedures for determination of permissible respirable coal mine dust containing free silica

The literature in selected technical subject areas related to the Mine Safety and Health Administration's (MSHA) respirable mine dust control policy was critically reviewed. Specific topics included: (1) the technical aspects of respirable dust sampling, (2) the development of a sampling strategy and (3) currently used analytical techniques for free silica content of respirable coal mine dust. The 2.0 Lpm MSHA respirable dust sampling flow rate does not conform with published results which indicate that to simulate existing pulmonary particle deposition models, the sampling flow rate should range from 1.4 to 1.7 Lpm. MSHA's sampling strategy focuses on controlling respirable coal mine dust with both area and personal samples of workers in selected occupations or activities. Many uncertainties are encountered as area samples are used to estimate personal exposures. Although all of the analytical methods for crystalline free silica are sufficiently sensitive to be able to detect and quantitate free silica at environmentally significant concentrations, they are all plagued with similar difficulties. Analytical standards representing the various forms of silica are not available. Available analytical methods do not differentiate among polymorphs of silica. Recommendations are presented to resolve identified problem areas.

The role of the human caudate nucleus in acupuncture analgesia

The role of the caudate nucleus in acupuncture analgesia was studied in 17 patients receiving caudate stimulation through chronic implanted electrodes to relieve intractable pain caused by late malignancy. Electrical stimulation of the head of the caudate nucleus provided relief from intractable pain in all 17 patients. The pain and pain tolerance threshold were elevated, the alteration in skin galvanic activity, respiratory movement and fingertip plethysmography elicited by a given painful stimulus were depressed. The analgesia required a period of induction and persisted for some time after cessation of stimulation; it showed no obvious segmental topography. These characteristics are similar to those observed in acupuncture analgesia. The effect of caudate stimulation was similar to that of electric needling in depressing the late component of the somatosensory evoked potentials (SEPs) recorded over the scalp and from the centrum medianum of the thalamus. Evoked potentials could be recorded from the caudate nucleus when an acupuncture point was electrically stimulated. The evoked potential record was a complex wave of positive and negative components, the peak latencies of main components being 100-180 msec for positive wave and 148-332 msec for negative wave components. The present study supports the supposition that the caudate nucleus may play a role in acupuncture analgesia. The possibility that the effect of caudate stimulation is brought on by inhibiting the activity of the medial thalamus is discussed.