Meiotically induced rec7 and rec8 genes of Schizosaccharomyces pombe

The Schizosaccharomyces pombe rec7 and rec8 genes, which are required for meiotic intragenic recombination but not for mitotic recombination, have been cloned and their DNA sequences determined. Genetic and physical analyses demonstrated that the cloned fragments contained the rec genes rather than rec mutation suppressors. A 1.6-kb DNA fragment contained a functional rec7 gene, and a 2.1-kb fragment contained a functional rec8 gene. The nucleotide sequences of these fragments revealed open reading frames predicting 249 amino acids for the rec7 gene product and 393 amino acids for the rec8 gene product. Northern hybridization analysis showed that both rec gene mRNAs were detectable only at 2-3 hr after induction of meiosis. The absence of these mRNAs in mitosis and their disappearance at 4 hr and later in meiosis suggest that the rec7 and rec8 gene products may be involved primarily in the early steps of meiotic recombination in S. pombe.

Absence of hepatitis B virus precore mutants in patients with chronic hepatitis B responding to interferon-alpha

Precore defective HBV mutants may gradually prevail because of immune selection and explain spontaneous seroconversion from HBeAg to anti-HBe in HBV carriers. We have analyzed whether the presence of precore HBV mutants is a determinant of responsiveness to interferon-alpha therapy. Fifteen carriers (nine responders and six nonresponders) who were treated with interferon-alpha were examined. Serum samples were collected before and after therapy. After extraction of DNA, the precore region was amplified by the polymerase chain reaction, and the product was identified by gel electrophoresis and ethidium bromide staining and then Southern blotting and molecular hybridization. The amplified products in all patients were asymmetrically amplified by a modified polymerase chain reaction, and the precore region was directly sequenced. All patients were HBV DNA positive initially. Circulating HBeAg-negative mutants were not identified before treatment in either responders or nonresponders. All nine responders were negative for HBV DNA in serum by dot blot during or after treatment, but seven remained positive by polymerase chain amplification and Southern-blot hybridization. All of the nonresponders remained positive for HBV DNA by dot blot. A silent mutation involving the substitution of an A for G at position 1888 was found in seven carriers; however, no HBeAg-negative mutants were detected in the follow-up of either responders or nonresponders to interferon-alpha.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental investigation of Bessel beam characteristics

We report on an experimental characterization of Bessel beams with finite apertures. We show that real Bessel beams can be generated with intensity profiles that closely resemble the ideal J(0)(2) transverseintensity distribution of Bessel beams. We also show interferometrically that these beams have planar phase fronts with pi-phase shifts from one Bessel ring to the next. We report tolerance conditions for Bessel beam generation and give an example of this generation that uses an unstable resonator as the light source.

A novel regulatory protein that affects the functions of caldesmon and myosin light chain kinase

A caldesmon (CaD)-binding protein of about 65 kDa (by SDS-PAGE) was purified from smooth muscle of chicken gizzard. The 65-kDa protein prevented the inhibitory effect of CaD on the ATP-dependent interaction between actin and myosin. Unlike the case with calmodulin (CaM), Ca2+ was not required for this effect. As reported in the preceding communication, myosin light chain kinase (MLCK), another well characterized protein that binds CaM, has CaD-like activity that modulates the interaction by binding to actin. The 65-kDa protein was also effective in relieving the modulation, while leaving unaffected the kinase activity that phosphorylates the light chain of smooth muscle myosin.

A novel regulatory effect of myosin light chain kinase from smooth muscle on the ATP-dependent interaction between actin and myosin

The actin-binding activity of myosin light chain kinase (MLCK) from smooth muscle was studied with special reference to the ATP-dependent interaction between actin and myosin. MLCK in the presence of calmodulin endowed sensitivity to Ca2+ on the movement of actin filaments on phosphorylated myosin from smooth muscle that was fixed on a coverslip. This regulatory effect was not attributable to the kinase activity of MLCK but could be explained by its actin-binding activity. The importance of the actin-binding activity was further substantiated by results of an experiment with Nitellopsis actin-cables in which MLCK regulated the interaction under conditions where MLCK was exclusively associated with the actin-cables.

The priming of cytotoxic T-cell precursors is strictly helper T cell-dependent

Allogeneic chimaeras that utilize C.B-17 SCID mice (H-2d) as recipients of MHC mismatched bone marrow from C57B1/6 (H-2b) or SJL/J (H-2s) mice have been used to provide experimental evidence demonstrating the necessity for a direct interaction between an effector T helper and the cytotoxic T-cell precursor in order to generate cytotoxic effector T cells specific for the minor histocompatibility (H) antigens of DBA/2 (H-2d) mice. No effect of helpers specific for antigen-processed or not-presented on antigen-presenting cells could be observed. Allo-chimaeras that contain T cells bearing H-2s, and which are restricted to H-2d, make a cytotoxic T-cell response to minor H antigens which is H-2d restricted if, and only if, cloned anti-H-2s effector T helpers are present during the in vivo priming step. Cloned anti-H-2d effector helpers, which are without effect in the allo-chimaeras, do provide a strong helper activity when tested in normal H-2d mice. These findings cannot be reconciled with a strict single recognitive model of restrictive antigen recognition, but they are consistent with a dual recognitive model, which incorporates many of the features of the single recognitive model.

Protein disulfide isomerase activity is released by activated platelets

The release of protein disulfide isomerase by activated platelets was hypothesized on the basis of reported intermolecular and intramolecular thiol-disulfide exchange and disulfide reduction involving released thrombospondin in the supernatant solution of activated platelets (Danishefsky, Alexander, Detwiler: Biochemistry, 23:4984, 1984; Speziale, Detwiler: J Biol Chem, 265:17859, 1990; Speziale, Detwiler: Arch Biochem Biophys 286:546, 1991). Protein disulfide isomerase activity, measured by catalysis of the renaturation of ribonuclease inactivated by randomization of disulfide bonds, was detected in the supernatant solution after platelet activation. The activity was inhibited by peptides known to inhibit protein disulfide isomerase; the peptides also inhibited formation of disulfide-linked thrombospondin-thrombin complexes. The reaction catalyzed by the supernatant solution showed a pH dependence distinct from that of the uncatalyzed reaction. The activity was excluded by a 50-Kd dialysis membrane, and it was eluted in the void volume of a gel-filtration column, indicating that it was associated with a macromolecule. The activity was not removed by centrifugation at 100,000 g for 150 minutes indicating that it was not associated with membrane microvesicles. Possible functions for the release of protein disulfide isomerase by activated platelets are discussed.

Effects of antioxidants on oxygen toxicity in vivo and lipid peroxidation in vitro

Convulsions and pulmonary damage result when animals are exposed to hyperbaric oxygen at pressures above about 300 kPa. Several hydroxyl radical scavengers (namely dimethylsulphoxide, dimethylthiourea and mannitol), the iron chelator desferrioxamine and the lipid antioxidant butylated hydroxytoluene were tested for possible protection against such hyperbaric oxygen toxicity. Dimethylthiourea and dimethylsulphoxide prolonged the latency to the first convulsion, but, surprisingly, dimethylthiourea very significantly increased pulmonary damage at both pressures used (515 and 585 kPa). Desferrioxamine also slightly increased lung damage at 585 kPa. Other antioxidants did not alter neurotoxicity or pulmonary toxicity induced by hyperbaric oxygen at 515 or 585 kPa. The antioxidants were also tested for their ability to inhibit lipid peroxidation (TBARS formation) in vitro. Desferrioxamine (5 and 50 microM), and butylated hydroxytoluene (0.1 mM and 1 mM) greatly inhibited TBARS formation in brain and lung homogenates incubated at 37 degrees. None of the hydroxyl radical scavengers affected TBARS levels in homogenates. There was no correlation between in vitro inhibition of lipid peroxidation and in vivo protection against oxygen toxicity.

[Experience of focal debridement in the treatment of tuberculosis of lumbar spine]

Experiences of 882 cases with tuberculosis of lumbar spine treated by focal debridement during 1956-1986 all patients survived the operation and 661 patients were cured in our department were reported. The relationship between chemotherapy and focal debridement was discussed. The selection of the appropriate time for this operation and important points to which attention should be paid during operation were described in detail.

Deoxycoformycin and oxypurinol: protection against focal ischemic brain injury in the rat

We have previously demonstrated that oxypurinol (40 mg/kg i.p.), a xanthine oxidase inhibitor, can reduce focal ischemic brain injury in the rat when applied pre-ischemically. By using a model of occlusion of the middle cerebral artery (MCA) in tandem with occlusion of the ipsilateral carotid artery, the present study further demonstrates that delayed (60 min) administration of oxypurinol also exhibits a protective action on ischemic damage in the stroked rat brain. Oxypurinol significantly reduced the ischemic cerebral infarct zone by preventing the development of brain damage primarily in areas distant to the central lesion core. A corresponding amelioration of brain swelling and attenuation of neurological deficits were evident. Similar protection against focal ischemic brain damage was evident when the adenosine deaminase inhibitor, deoxycoformycin (500 micrograms/kg), was administered prior to the onset of ischemia. However, with delayed (60 min) administration deoxycoformycin had no protective effect. These findings support the hypothesis that manipulation of adenosine catabolism can be an effective therapeutic approach to the prevention or treatment of brain injuries, such as those occurring during ischemic stroke or cardiac arrest.

Inducible transformation of cells from transgenic mice expressing SV40 under lac operon control

If it were possible to clone in vitro cells of any type, at any stage of differentiation, from an extensively characterized animal such as the mouse, many areas of cell biology would benefit. Indeed, it would be even more helpful if these cells could subsequently be restored to their normal in vivo phenotype whenever required. Here, we describe a step on the pathway to such an idealized "clonable" mouse. In principle, it seeks to link a "universal" transforming agent to a regulatory system that is relatively simple, yet quite foreign to the mouse. A plasmid containing the bacterial lac operator/promoter region linked to the SV40 large T antigen and a vector containing the lac repressor that can be expressed in mammalian cells were coinjected into fertilized mouse oocytes utilizing the standard techniques for generating transgenic mice. Two progeny were obtained that express large T antigen in the presence, but not the absence, of the nonmetabolizable lac inducer, isopropyl-beta-thio-D-galactoside. This report characterizes fibroblast cell lines established from these transgenics that are readily transformed in vitro with isopropyl-beta-thio-D-galactoside. A significant proportion of the cells are restored to their "normal" (nontransformed phenotype) when isopropyl-beta-thio-D-galactoside is removed.

Two New Glycosides from the Roots of Cynanchum versicolor

Two new glycosides named cynanversicoside-A and -B, together with glaucogenin-C as the aglycone, were isolated from the Chinese crude drug "Pai-Wei", CYNANCHUM VERSICOLOR Bunge (Asclepiadaceae). Their structures were determined on the basis of spectral and chemical evidence as glaucogenin-C 3- O-beta- D-cymaropyranosyl-(1-->4)-alpha- L-diginopyranosyl-(1-->4)-beta- D-thevetopyranoside and glaucogenin-C 3- O-beta- D-glucopyranosyl-(1-->4)-beta- D-cymaropyranosyl-(1-->4)-alpha- L-diginopyranosyl-(1-->4)-beta- D-thevetopyranoside.

Limunectin. A phosphocholine-binding protein from Limulus amebocytes with adhesion-promoting properties

A protein that binds to and precipitates with pneumococcal C-polysaccharide and a phosphocholine (PC) derivative of bovine serum albumin has been affinity purified from Limulus amebocytes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis reveals that the isolated protein consists of a single polypeptide chain of approximately 50 kDa. It is an intracellular protein localized in the secretory granules of amebocytes according to immunogold staining. Although it shares the PC-binding property with C-reactive protein isolated from Limulus and other animal species, it differs from C-reactive protein in that the latter binds to PC only in the presence of Ca2+, whereas the newly isolated protein binds to PC in a Ca(2+)-independent manner. In this respect, the newly isolated PC-binding protein resembles the antibodies to PC of mouse myelomas. The gene coding for this protein has been isolated. The gene sequence predicts a protein of 54 kDa with an unusual structural feature: it consists almost entirely of 10 contiguous segments, 45 amino acids in length, with extensive homology. Some limited sequence homologies were found between the 54-kDa protein and segments of vitronectin, gelatinase, and collagenase. It binds to bacterial cells, fixed amebocytes, and a number of extracellular matrix molecules. Due to its structural and some functional similarities to other adhesion molecules, the Limulus 54-kDa protein was named "Limunectin."

Muscarinic receptor agonist-mediated modulation of neuronal activity in rat cerebral cortex

Multiple cortical neuronal responses were elicited by the iontophoretic application of muscarinic receptor agonists and antagonists in the rat cerebral sensorimotor cortex in vivo. (1) The muscarinic receptor agonist, oxotremorine-M induced a biphasic effect on spontaneous firing. This was evident as an early brief increase in the firing rate over the spontaneous discharge followed by secondary inhibition of spontaneous activity. The excitation could be blocked by the muscarinic receptor non-selective antagonist atropine and by both the M1 receptor antagonist pirenzepine and the M2 receptor antagonists gallamine or methoctramine. Oxotremorine-M inhibition of spontaneous activity was not affected by the M1 receptor antagonist pirenzepine, while evaluation of its sensitivity to gallamine and methoctramine was not possible since these two M2 receptor antagonists also depressed spontaneous activity, unlike pirenzepine. Of the other two muscarinic receptor agonists, oxotremorine had inconsistent and weak excitatory effects whilst McN-A-343 had only weak excitatory or inhibitory effects on spontaneous activity. (2) Oxotremorine-M, oxotremorine and McN-A-343 had a depressant action on neuronal discharges evoked by glutamate or acetylcholine. A depressant effect of oxotremorine-M was also demonstrated on the early excitation evoked by subsequent applications of oxotremorine-M itself. Of the three muscarinic receptor agonists tested, oxotremorine-M was the most potent in evoking a long-term depression of evoked discharges, lasting from several minutes (greater than 5 min) to as long as 40 min. Oxotremorine-M-induced depression of evoked responses was most sensitive to the M2 receptor antagonists, whereas oxotremorine-induced depression was more sensitive to the M1 receptor antagonist pirenzepine.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscarinic agonist oxotremorine-M-induced long-term depression in rat cerebral cortex

A long-lasting depression (LTD) of neuronal-evoked responses was induced in a dose-dependent fashion in neurons of rat sensorimotor cortex by a brief application of the muscarinic agonist oxotremorine-M. The depression was characterized as being of rapid onset (within 30 seconds), long duration (up to 40 minutes), and was evident for both glutamate- and acetylcholine-evoked discharges. Antagonism could be achieved by application of the nonspecific muscarinic antagonist atropine, and with the M2 antagonists gallamine or methoctramine. The M1 antagonist pirenzepine displayed only a weak effect. LTD could also be induced by the muscarinic agonists, oxotremorine and McN-A-343, but their potencies were lower than that of oxotremorine-M. Oxotremorine-M may be a useful tool for studies of long-term changes in synaptic efficacy.

Muscarinic agonist-mediated induction of long-term potentiation in rat cerebral cortex

A long-lasting potentiation (usually following an initial short depression) of neuronal evoked responses was induced in neurons of rat sensorimotor cortex after a single application of the muscarinic agonists, oxotremorine, McN-A-343, or oxotremorine-M. The potentiation was characterized as being of slow onset (several minutes), progressive development, long-lasting (for as long as two hours), and was evident for both glutamate- and acetylcholine-evoked neuronal discharges. Potentiation was manifested as an increase in the frequency and duration of the evoked neuronal discharges, in a dose-dependent fashion. Blockade could be achieved if a muscarinic antagonist (atropine, pirenzepine or gallamine) was applied prior to, but not after, development of the long-lasting potentiation. These results suggest that certain muscarinic agonists may be useful in reducing the memory deficits of patients with Alzheimer's disease.

Oxypurinol reduces focal ischemic brain injury in the rat

When measured within 2 days of a unilateral occlusion of the middle cerebral artery (MCA) combined with tandem occlusion of the ipsilateral common carotid artery in rats, contralateral neurological deficits were detectable, with brain swelling and a consistent degree of neocortical infarction in the ipsilateral hemisphere. Oxypurinol (40 mg/kg i.p. administered 0.5 h prior to, and 24 h after, the onset of focal ischemia) significantly reduced the development of the ischemic infarct (P less than 0.001); attenuated tissue swelling (P less than 0.01) and ameliorated the neurological deficits (P less than 0.05). These findings suggest that this compound may be useful for the prevention or treatment of ischemic brain injuries, such as those occurring during stroke.

In vitro selection of a cell line for resistance to lysis by tumor necrosis factor-alpha selects for reduced tumorigenicity

Experimentally, TNF-alpha can mediate the hemorrhagic necrosis of certain tumors. Furthermore, evidence indicates that natural cytotoxic (NC) activity, a cell-mediated cytolytic activity that utilizes TNF-alpha in the lysis of target cells, is involved in preventing the outgrowth of certain NC/TNF-alpha-sensitive tumor cells. These observations raise the issue of whether soluble TNF-alpha normally serves as a tumor surveillance mechanism preventing the outgrowth of some tumors. To address this issue, we have used TNF-alpha to select TNF-alpha-resistant variants from the NC/TNF-alpha-sensitive mouse fibroblast cell line 10ME. Previously, we have demonstrated that 10ME is tumorigenic in immune-deficient mice but fails to form tumors in normal mice. Moreover, selection of NC-resistant variants from 10ME selects for both TNF-alpha resistance and tumorigenicity in normal mice. As cells that have been selected for NC resistance form tumors in normal mice, whereas the NC-sensitive parental cell line does not, it seems that escape from NC activity is sufficient to significantly increase the tumorigenic potential of the cell line. We show that the selection with TNF-alpha, although associated with NC resistance, does not increase the tumorigenic potential of 10ME cells but reduces it. Thus, NC activity appears to function as a mechanism to prevent tumor formation, and escape from NC activity allows for tumor formation; TNF-alpha does not have similar activity. Moreover, this suggests that NC activity is not equivalent to soluble TNF-alpha activity, but utilizes TNF-alpha more efficiently than soluble TNF-alpha, or NC activity involves both TNF-alpha and other effector mechanisms.

In vitro selection of a cell line for resistance to lysis by tumor necrosis factor-alpha selects for reduced tumorigenicity

Experimentally, TNF-alpha can mediate the hemorrhagic necrosis of certain tumors. Furthermore, evidence indicates that natural cytotoxic (NC) activity, a cell-mediated cytolytic activity that utilizes TNF-alpha in the lysis of target cells, is involved in preventing the outgrowth of certain NC/TNF-alpha-sensitive tumor cells. These observations raise the issue of whether soluble TNF-alpha normally serves as a tumor surveillance mechanism preventing the outgrowth of some tumors. To address this issue, we have used TNF-alpha to select TNF-alpha-resistant variants from the NC/TNF-alpha-sensitive mouse fibroblast cell line 10ME. Previously, we have demonstrated that 10ME is tumorigenic in immune-deficient mice but fails to form tumors in normal mice. Moreover, selection of NC-resistant variants from 10ME selects for both TNF-alpha resistance and tumorigenicity in normal mice. As cells that have been selected for NC resistance form tumors in normal mice, whereas the NC-sensitive parental cell line does not, it seems that escape from NC activity is sufficient to significantly increase the tumorigenic potential of the cell line. We show that the selection with TNF-alpha, although associated with NC resistance, does not increase the tumorigenic potential of 10ME cells but reduces it. Thus, NC activity appears to function as a mechanism to prevent tumor formation, and escape from NC activity allows for tumor formation; TNF-alpha does not have similar activity. Moreover, this suggests that NC activity is not equivalent to soluble TNF-alpha activity, but utilizes TNF-alpha more efficiently than soluble TNF-alpha, or NC activity involves both TNF-alpha and other effector mechanisms.

[Activity of 5 alpha-reductase in human hyperplastic prostates]

To Study the relationship between the activity of 5 alpha-reductase and benign hyperplastic prostate (BPH), we have measured the T and dihydrotestosterone (DHT) contents and the specific activity of this enzyme in mechanically separated stroma and epithelium and in both the nucleus and cytoplasm from 20 cases of BPH and 7 cases of normal human prostate. The results were as follows: (1) The content of DHT in the BPH group was about 3 times higher than that in the N group. (2) The Michaelis constant (Km) of 5 alpha-reductase in both the stroma and epithelium was similar. (3) The specific activity of the enzyme in the stroma was higher than that in the epithelium, and in the BPH group, increased activity was found in the tissue or stroma but not in the epithelium. The activity was predominant in the nucleus. So our experiment supports that the elevation of the activity of 5 alpha-reductase may be related to the pathogenesis of human BPH.