Cooperative binding of Agrobacterium tumefaciens VirE2 protein to single-stranded DNA

The VirE2 protein of Agrobacterium tumefaciens Ti plasmid pTiA6 is a single-stranded-DNA-binding protein. Density gradient centrifugation studies showed that it exists as a tetramer in solution. Monomeric VirE2 active in DNA binding could also be obtained by using a different protein isolation procedure. VirE2 was found to be thermolabile; brief incubation at 37 degrees C abolished its DNA-binding activity. It was insensitive to the sulfhydryl-specific reagent N-ethylmaleimide. Removal of the carboxy-terminal 37 residues of the 533-residue VirE2 polypeptide led to complete loss of DNA-binding activity; however, chimeric fusion proteins containing up to 125 residues of the VirE2 C terminus were inactive in DNA binding. In nuclease protection studies, VirE2 protected single-stranded DNA against degradation by DNase I. Analysis of the DNA-VirE2 complex by electron microscopy demonstrated that VirE2 coats a single-stranded DNA molecule and that the binding of VirE2 to its substrate is cooperative.

Unusual presentation: testicular seminoma

A case of seminoma is described in a patient with HIV infection. The tumor presented atypically with no lymphocytic infiltrates within the stroma. HIV infection has been reported to be associated with an increased incidence of Kaposi's sarcoma, non-Hodgkin's lymphomas, oropharyngeal carcinoma and pancreatic carcinoma.

Biochemical and pharmacological evidence for central cholinergic regulation of shock-induced aggression in rats

Acetylcholinesterase (AChE) activity was estimated in brain and heart homogenates and plasma of 'aggressive' and 'nonaggressive' rats. Brain homogenates of 'nonaggressive' rats hydrolyzed significantly more substrate when compared to the 'aggressive' rats. Such differences were not seen in the heart homogenates or plasma of these two groups of rats. Acute DFP (0.1, 0.3 and 1.0 mg/kg) attenuated shock-induced aggression (SIA) 2 hr after treatment but facilitated SIA 24 hr and 48 hr after drug administration. Long-term DFP (0.3 mg/kg x 10 days), on the other hand, induced a significant enhancement in the SIA score, whereas atropine (1.0 and 5.0 mg/kg) produced a dose-related attenuation of the same. Pretreatment of rats with atropine (5 mg/kg) antagonized the long-term DFP-induced facilitation of SIA. These results are discussed in the light of an inhibitory central cholinergic mechanism in the regulation of SIA.

Effect of beta-adrenoceptor antagonists and some related drugs on maximal electroshock seizures in mice

(+/-) Propranolol (1-50 mg/kg), (+) propranolol (50 mg/kg) and pindolol (10-50 mg/kg) exhibited significant protective effects against MES (maximum electroshock seizures), whereas, timolol (1 mg/kg), the propranolol analog, UM-272 (1 and 10 mg/kg), and the beta-agonist, terbutaline (1 and 10 mg/kg) were ineffective. Cholinergic agents, physostigmine (0.01-1.0 mg/kg), and atropine (1 and 10 mg/kg), the serotonin antagonist, cyproheptadine (0.05 mg/kg), and the prostaglandin synthesis inhibitor, indomethacin (10 mg/kg), were also without effect on the MES extensor phase. Further, pretreatment of mice with terbutaline, atropine, cyproheptadine or indomethacin did not influence the anti-MES effect of propranolol to any significant extent. The results indicate that the observed anticonvulsant effects of beta-adrenoceptor antagonists are unrelated to noradrenergic or other central neurotransmitter systems and that a non-specific mechanism, probably a membrane stabilizing effect is involved.

Assessment of cardiac function in patients with the acquired immunodeficiency syndrome

We have assessed right and left ventricular function by multigated radionuclide ventriculography in 12 consecutive patients with acquired immunodeficiency syndrome (AIDS) grouped according to the CDC classification system for HIV infection. Results were correlated with clinical, electrocardiographic and echocardiographic findings. Clinical examination and chest x-ray films showed no evidence of acute cardiac or pulmonary pathology. Five patients had evidence of ventricular dysfunction by radionuclide ventriculography along with significant ECG abnormalities. Three patients had abnormal ECG findings with normal ejection fractions. Echocardiography showed no evidence of significant valvulopathy or pericardial disease except for one patient with fibrinous strands associated with the pericardium. Decreased ejection fractions did not correlate with disease classification, risk group or survival. This study suggests that a major percentage of AIDS patients have some evidence of cardiac abnormalities. We conclude that abnormal ECG findings in an AIDS patient should alert the clinician to possible underlying ventricular dysfunction.

Heterogeneity in chromosome damage and repair rates after bleomycin in ataxia telangiectasia cells

Cells derived from patients with ataxia telangiectasia (AT) are known to be exceptionally sensitive to ionizing radiation and chemotherapeutic agents such as bleomycin (BLM), neocarzinostatin, and etoposide. This increased sensitivity is manifested by high chromosome aberration frequencies after treatment. In order to probe the underlying basis for this phenomenon, the technique of premature chromosome condensation was used to determine whether the increased chromosome damage observed after bleomycin treatment is due to increased initial chromosome damage or to a decreased capability of these cells to repair chromosome damage. Five AT cell lines were brought to quiescence and treated with BLM, and initial chromosome damage and repair rates were determined in the G1 prematurely condensed chromosomes. AT cells exhibited increased aberration frequencies compared to normal human fibroblasts immediately after BLM treatment. The five AT cell lines were heterogeneous in the fast component of chromosome break repair, varying from a nearly normal fast repair component in one cell line to a nearly defunct fast repair component in two other AT cell lines. Thus, while the AT cell lines were heterogeneous in the basis for their chromosome breakage sensitivity, all AT cell lines tested showed increased residual chromosome damage after BLM treatment while still in the quiescent phase.

Modulation of humoral immune responses by endogenous opioids

The effects of opioid agonists and antagonists were investigated on humoral immune mechanisms in mice and rats. Opioid agonists like morphine, Leu-enkephalin, and Met-enkephalin, enhanced antigen-induced histamine release from mixed peritoneal cells of rats in vitro; this enhancement was effectively antagonized by naloxone, an opioid antagonist. Naloxone, per se, decreased anaphylactic mortality in doses of 10 mg/kg, while it increased mortality in a dose of 1 mg/kg. Reduced IgE antibody titer, measured by passive cutaneous anaphylaxis, decreased hemagglutination titer to sheep red blood cells, blocked histamine release from mixed peritoneal cells of rats in vitro induced by antigen, but had no significant effect when histamine release was induced by compound 48/80. Thus, it appears that endogenous opioids are involved in humoral immune responses.

Chromosomal alterations in cell lines derived from mouse rhabdomyosarcomas induced by crystalline nickel sulfide

Prior studies have shown a preferential decondensation (or fragmentation) of the heterochromatic long arm of the X chromosome of Chinese hamster ovary cells when treated with carcinogenic crystalline NiS particles (crNiS). In this report, we show that the heterochromatic regions of mouse chromosomes are also more frequently involved in aberrations than euchromatic regions, although the heterochromatin in mouse cells is restricted to centromeric regions. We also present the karyotypic analyses of four cell lines derived from tumors induced by leg muscle injections of crystalline nickel sulfide which have been analyzed to determine whether heterochromatic chromosomal regions are preferentially altered in the transformed genotypes. Common to all cell lines was the presence of minichromosomes, which are acrocentric chromosomes smaller than chromosome 19, normally the smallest chromosome of the mouse karyotype. The minichromosomes were present in a majority of cells of each line although the morphology of this extra chromosome varied significantly among the cell lines. C-banding revealed the presence of centromeric DNA and thus these minichromosomes may be the result of chromosome breaks at or near the centromere. In three of the four lines a marker chromosome could be identified as a rearrangement between two chromosomes. In the fourth cell line a rearranged chromosome was present in only 15% of the cells and was not studied in detail. One of the three major marker chromosomes resulted from a centromeric fusion of chromosome 4 while another appeared to be an interchange involving the centromere of chromosome 2 and possibly the telomeric region of chromosome 17.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the localization of chromosome damage induced by calcium chromate and nickel compounds

Chromosomal aberrations were studied in Chinese hamster ovary cells and in C3H10T1/2 cells following treatment with NiCl2, crystalline NiS, and CaCrO4. All three compounds caused an increase in chromosomal aberrations in a concentration- and time-dependent fashion. The chromosomal aberrations induced by NiCl2 and crystalline NiS occurred predominantly in heterochromatic regions of the chromosomes. Additionally, treatment of cells with crystalline NiS and to a smaller extent long-term treatment with NiCl2 caused a preferential effect on the condensation state of the heterochromatic long arm of the X-chromosome in hamster cells. In contrast, treatment of cells with CaCrO4 did not induce aberrations preferentially in heterochromatin. These results are interesting because nickel(II), which is thought to be the ultimate carcinogen of nickel compounds, binds poorly to DNA, is weakly mutagenic, but induces chromosome damage, probably because of its interaction with nuclear proteins in heterochromatin. Chromate binds to DNA, is mutagenic, and interacts with chromatin randomly.

Involvement of brain transmitters in the modulation of shock-induced aggression in rats by propranolol and related drugs

(+/-)Propranolol (1, 3, 10 and 30 mg/kg) exhibited a differential effect on footshock aggression (FSA) in rats. Lower doses (1 and 3 mg/kg) of the drug facilitated FSA, whereas an inhibitory effect was observed with higher doses (10 and 30 mg/kg) of the same. (+)Propranolol (30 mg/kg) and UM-272 (1 and 10 mg/kg) as well as physostigmine (0.1 and 0.5 mg/kg) all produced inhibition of FSA. Similar FSA inhibitory effects were also observed with salbutamol (1 and 5 mg/kg). Pretreatment with atropine and not methylatropine attenuated the anti-aggressive effect of (+/-)propranolol (10 mg/kg) without appreciably altering the facilitatory effect (1 mg/kg) of the drug on FSA. In addition, at the anti-aggressive doses, (+/-)propranolol (10 mg/kg) and UM-272 (10 mg/kg), significantly inhibited brain cholinesterase enzyme activity when compared to saline controls. (+/-)Propranolol (10 mg/kg) also inhibited significantly the aggression induced by reserpine-apomorphine treatment. It is inferred that a central cholinergic and dopaminergic mechanism is involved in the anti-aggressive effect of (+/-)propranolol, whereas the low dose induced facilitation of affective aggression could be attributed to central beta-adrenoceptor blockade.

Nonstereoselective aspects of propranolol pharmacodynamics

Twenty years after its discovery, the beta-adrenergic blocking agent propranolol continues to interest pharmacologists and clinicians. Its therapeutic profile has extended to areas beyond the purview of the cardiovascular system, and its ocular and central nervous system effects have been well documented. In addition, it still remains a very good pharmacological tool to map out the adrenergic beta-receptors in the body, and stereoisomers of propranolol and other beta-blockers serve as valuable agents to distinguish between the effects related to beta-adrenoceptors and those which are not. The primary purpose of this review is to summarize the evidence indicating that beta-adrenergic blocking agents lack stereoselectivity in some of their effects, including several of considerable therapeutic importance. Because many pharmacological actions of propranolol followed a nonsteroselective pattern, the involvement of beta-adrenoceptors in them was questioned and this led to the search for alternate mechanisms to explain these effects. Studies with propranolol and some related drugs indicated the involvement of a cholinergic mechanism in their antiarrhythmic, ocular hypotensive and some central effects. Also, a presynaptic inhibitory effect at the skeletal neuromuscular junction has been suggested to explain the benefical effect of propranolol and other beta-blockers in tremor. Biochemical studies with these drugs revealed their inhibitory action on the cholinesterase enzyme in blood and other tissues like myocardium and brain. It is thus hypothesized that modulation of cholinergic neurotransmission by propranolol could explain some of its nonstereoselective actions and open new vistas in propranolol pharmacodynamics.

Tissue cholinesterase inhibition by propranolol and related drugs

The effect of (+/-)-propranolol and some related drugs have been investigated on the cholinesterase (ChE) enzyme activity of heart and brain tissues of the rat. Brain homogenates hydrolysed more methacholine than benzoylcholine and the reverse was true for the heart tissue. In-vitro, (+/-)-, (+)- and (-)-propranolol, as well as its quaternary analogue, UM-272, all significantly inhibited heart and brain ChE. Timolol and sotalol, however, were less potent. In-vivo, (+/-)-propranolol (30 mumol kg-1) significantly inhibited brain ChE activity in rats when compared with saline controls. It is inferred that propranolol inhibits brain and heart ChE enzyme in a non-stereoselective manner and that this cholinomimetic action could be involved in the mediation of some of its therapeutic effects.

Incidence and localization of sister chromatid exchanges induced by nickel and chromium compounds

Carcinogenic nickel compounds enhanced the incidence of sister chromatid exchanges (SCEs) in a concentration-dependent fashion in intact Chinese hamster ovary cells. There was a preferential induction of these exchanges in the heterochromatic regions of the chromosomes. CaCrO4 also caused a dose-dependent induction of SCEs. However, in contrast to NiCl2, the exchanges induced by CaCrO4 were not localized in any particular chromosomal region. The total incidence of exchanges was higher with CaCrO4 than with NiCl2. CaCrO4, crystalline NiS and NiCl2 enhanced the incidence of SCEs at concentrations below the threshold of DNA damage as detected by the technique of alkaline elution. Additionally, following treatment time intervals of 24-48 h, there was an increase in SCEs at concentrations of NiCl2 or CaCrO4 that produced little disruption of cell cycle progression. These results are consistent with the hypothesis that potently carcinogenic nickel compounds which are not very mutagenic exert selective effects on genetically inactive heterochromatin, while potently mutagenic and carcinogenic chromate do not appear to produce a similar predominance of SCEs in heterochromatic regions.

Pathway of nickel uptake influences its interaction with heterochromatic DNA

Exposure of intact Chinese hamster ovary cells to water-soluble NiCl2 and to particulate crystalline NiS induced a concentration-dependent incidence of chromosomal aberrations which included gaps, breaks, and exchanges. Exposure of cells to crystalline NiS particles caused a high incidence of chromatid exchanges and dicentrics and produced what appears to be an effect on the condensation state of the heterochromatic long arm of the X chromosome. Treatment of cells with NiCl2 did not cause any significant effect on the long arm of the X chromosome, and there was a much lower incidence of the dicentric type of chromosomal aberrations compared to NiS. To examine whether the fragmentation/decondensation of the long arm of the X chromosome produced by crystalline NiS particles was due to a phagocytic pathway of uptake of NiS particles, cells were treated with NiCl2-albumin complexes that had been encapsulated in liposomes. Although treatment of cells with NiCl2-albumin complexes yielded higher intracellular nickel levels than were obtained by treatment of cells with NiCl2, at comparable intracellular levels fragmentation/decondensation of the heterochromatic long arm of the X chromosome was observed when nickel (II) was delivered by way of a liposome but not when cells were treated with unencapsulated NiCl2. Ionic nickel alone irrespective of its delivery mechanism exhibited some preference for heterochromatin, since there was a higher incidence of aberrations observed in the heterochromatic centromeric region of chromosomes. These observations suggest that the pathway of delivery of Ni2+ from NiS particles may be responsible for a preferential interaction of this metal with heterochromatin leading to an effect on the condensation state/fragmentation of the heterochromatic long arm of the X chromosome.

Antagonistic effect of magnesium chloride on the nickel chloride-induced inhibition of DNA replication in Chinese hamster ovary cells

The degree of inhibition of semiconservative DNA replication induced by nickel chloride (NiCl2) was analyzed by radiolabeled-thymidine incorporation alone or with cesium chloride (CsCl) density gradient centrifugation. The onset and duration of this Ni2+-induced inhibition was time- and concentration-dependent, but the degree of inhibition was not. A maximal reduction in the rate of DNA synthesis was observed within the first hour of treatment with 2.5 mM NiCl2, which was the highest noncytotoxic concentration utilized. After six hours, 500 microM and 1 mM as well as 2.5 mM NiCl2 all produced the same 50% to 60% reduction in [3H]-thymidine incorporation into DNA. The inhibitory effect of nickel ions on DNA synthesis was reversible. The rate of DNA synthesis following a 500 microM or 1 mM NiCl2 treatment began to increase after washout of nickel, but a six-hour exposure of cells to 2.5 mM NiCl2 produced a sustained 50% to 60% suppression of DNA synthetic activity for at least 36 hours. At all concentrations of NiCl2 used in this study, some inhibition of DNA synthesis persisted for at least 48 hours, but by 72 hours after treatment, the rate of [3H]-thymidine incorporation was actually 10% above the control. Examination of autoradiographic slides of cells treated with 2.5 mM NiCl2 for six hours demonstrated a 60% reduction of silver grains, but there was no preferential reduction in the quantity of grains in the nucleolus or any other region. Cesium chloride density gradient analysis of the replication of nucleolar DNA in cells treated with 2.5 mM nickel supported the autoradiographic findings. The inhibitory effect of NiCl2 on DNA replication was prevented by the addition of magnesium chloride (MgCl2) to cells maintained in a simple salts/glucose medium (SGM). This effect did not appear to be due to an antagonism of the cellular uptake of nickel by Mg2+, since the maximally effective dose of Mg2+ reduced 63Ni2+ uptake by no more than 25% while the inhibition of replication was completely reversed.

Autonomic regulation involved in the ocular hypotensive action of beta-adrenergic blocking agents

The effects of racemic propranolol and some related drugs on the intraocular pressure (IOP) were studied after topical application in rabbits. These drugs produced a significant reduction in IOP with the following order of potency: (-)-propranolol greater than timolol greater than (+/-)-propranolol greater than sotalol greater than (+)-propranolol greater than pranolium. Pretreatment of rabbit eyes with atropine significantly antagonized the ocular hypotensive action of (+/-)-propranolol, timolol and pranolium. Both (+/-)-propranolol and timolol produced a significant increase in pupil diameter in the presence of a submydriatic dose of atropine. The activities of monoamine oxidase and carbonic anhydrase were unaffected by (+/-)-propranolol, timolol and pranolium in-vitro. It is concluded from the results that both cholinergic and adrenergic mechanisms may be involved in the ocular hypotensive effects of the drugs.

Effects of chloroquine on the serum complement system

Chloroquine, a well-known anti-malarial and anti-inflammatory agent, was studied with respect to its effect on the serum complement system. The drug exhibited significant in vitro anti-complementary activity only at a very high non-therapeutic dose of 48 mg/ml. Chloroquine-induced in vitro complement consumption was observed to take place even in the absence of Ca2+ and Mg2+ ions. The drug also haemolyses rabbit erythrocytes in the presence of Mg2+-EGTA and immunoelectrophoretic studies of fresh human serum and chloroquine incubation mixture against specific anti-C3 and anti-factor B antisera have demonstrated that it cleaves both C3 and factor B. In another experiment, chloroquine failed to exert inhibitory effects on complement utilisation by immune complexes. Studies of the serum complement profile of Plasmodium falciparum-infected malaria patients receiving chloroquine therapy indicated that, in contrast to the situation in vitro, the serum C3 level is invariably decreased. Marginal reductions in the levels of C4, factor B and properdin were also found in some of these patients, while administration of chloroquine to normal human individuals failed to produce any significant change in their serum complement profile. It is, therefore, probable that malarial parasites and not chloroquine are responsible for complement activation in patients suffering from malaria.

Induction of chromosomal damage in Chinese hamster ovary cells by soluble and particulate nickel compounds: preferential fragmentation of the heterochromatic long arm of the X-chromosome by carcinogenic crystalline NiS particles

Treatment of intact Chinese hamster ovary cells with crystalline NiS and NiCl2 resulted in the induction of chromosomal aberrations which included gaps, breaks, and exchanges. The incidence of these aberrations increased in a time- and concentration-dependent fashion. NiCl2 was more potent in inducing chromosomal aberrations in cells that were maintained with a salts/glucose medium during metal treatment than when cells were treated in culture growth medium. Chromosomal aberrations induced by NiCl2 occurred randomly among the autosomal arms; however, the heterochromatic centromeric regions of the chromosomes were preferentially damaged. In addition to inducing the same type of aberrations found with NiCl2, crystalline NiS particles also caused the selective fragmentation of the heterochromatic long arms of the X-chromosomes. This fragmentation was attributed to the difference in the mechanism of delivery of nickel ions from phagocytized crystalline NiS particles which aggregate around the nuclear membrane and release large amounts of nickel ions from a dissolving phagocytized particle. Previous studies have demonstrated that treatment of intact cells with crystalline NiS particles produces a considerably higher level of nickel in the nucleus compared with similar exposure to water-soluble NiCl2. Since heterochromatin is known to form the inside lining of the interface nucleus, nickel ions, as they are solubilized from a phagocytized particle and enter the nucleus, are likely to encounter heterochromatin before they interact with euchromatin. In contrast, nickel ions derived from NiCl2 do not preferentially accumulate in the cell, and those ions that enter the cell are taken up by a nonphagocytic mechanism. It is proposed that when cells are treated with high levels of NiCl2 in an attempt to achieve the cellular levels of nickel produced by NiS phagocytosis, this overloading results in cytotoxic responses rather than the preferential fragmentation of heterochromatin observed with particles. Since liposome-mediated delivery of NiCl2 also results in fragmentation of the long arm of the X-chromosome, the selective breakage of heterochromatin by NiS particles may be due solely to the mechanism of Ni2+ delivery in cells.

Anterior thigh pain or tenderness. A diagnostically useful manifestation of bacteremia

In four patients with putative infectious process, anterior, bilateral proximal thigh pain and tenderness unaccompanied by generalized myalgias developed. This unusual manifestation, observed in these and other patients, was associated with demonstrable bacteremia. Aside from tenderness, no local abnormalities were found and the pain and tenderness disappeared after appropriate therapy. Creatine kinase levels, measured in three of the four patients, were elevated in only one. This manifestation is useful clinically as it strongly suggests bacteremia; attention to this finding can be lifesaving.

Characterization of G-banded chromosomes of the Indian muntjac and progression of banding patterns through different stages of condensation

Muntjac prophase and metaphase chromosomes were G-banded following methotrexate-mediated synchronization of peripheral lymphocytes. Bands and subbands were characterized from prophase through metaphase, and the progression of band patterns from late prophase to mid-metaphase was analyzed. Extended prophase chromosomes exhibited more bands and subbands, a number of which became fused with each other, giving rise to fewer and thicker bands in the condensed metaphase chromosomes. It appeared that the dark bands condensed relatively more than the light bands. Precise delineation of the bands and subbands on extended prophase chromosomes and the usage of a proposed banding pattern nomenclature should aid in better detection and localization of induced chromosomal rearrangements with this extremely useful experimental material.

Induction of chromosome damage by Neurospora endonuclease in repair-inhibited quiescent normal human fibroblasts

The purpose of these experiments was to determine the role of double-strand breaks in chromosome aberration formations. Quiescent normal human fibroblasts were treated with 3 microM nitrogen mustard and then allowed to repair their DNA damage for 24 h prior to cell fusion and induction of premature chromosome condensation. The extent of chromosome damage was determined in the G1 prematurely condensed chromosomes (G1 PCC). The presence of cytosine arabinoside and hydroxyurea during the repair period in order to accumulate single-strand DNA breaks resulted in an increase in the chromosome-break frequency. Treatment of these repair-inhibited cells with single-strand-specific neurospora endonuclease during fusion to change single-strand lesions into double-strand breaks resulted in a doubling of the aberration frequency. These results support the notion that double-strand breaks are important in chromosome-aberration formation.

Role of vagus in the antagonism of ouabain induced arrhythmias in dogs by beta-adrenoceptor antagonists and related drugs

The effects of propranolol and related drugs were investigated on ouabain-induced ventricular tachycardia (VT) in dogs with intact and ablated vagi. Propranolol and UM-272 completely antagonized the ouabain VT in dogs with intact vagi, whereas timolol was ineffective. Bilateral vagotomy completely abolished the effect of UM-272 and reduced the effect of propranolol. Diphenylhydantoin, however, reversed ouabain VT in dogs with both intact and ablated vagi. It is inferred that the vagus plays a significant role in the arrhythmolytic effect of propranolol and UM-272.

Effect of drugs influencing synthesis of prostaglandins on haloperidol-induced catalepsy in rats

Rats pretreated with prostaglandin synthesis stimulators, phenoxymethyl penicillin (2, 4 and 8 mg/kg, ip) and levamisole (2.5, 5 and 10 mg/kg, ip) showed a dose related potentiation of catalepsy after subthreshold doses of haloperidol (0.1 mg/kg, ip). Pretreatment with prostaglandin synthesis inhibitors paracetamol and indomethacin exhibited significant inhibition of catalepsy at lower doses (2.5, 6, 10 and 15 mg/kg, ip). However, this antagonism was paradoxically less at higher dose levels (20 and 30 mg/kg, ip). The data suggest neuromodulatory contribution of prostaglandins in neuroleptic-induced catalepsy.

Effect of chloroquine and some other antimalarials on the immune mechanism in experimental animals

The effects of chloroquine and some other antimalarials on the immune responses in experimental animals have been examined. Chloroquine and quinine caused significant decrease of serum anti-SRBC haemagglutination titre. Chloroquine lowered the serum IgM level and also reduced plaque-forming cells in the spleen of mice. The delayed-type hypersensitivity responses to SRBC and the passive cutaneous anaphylaxis were also diminished in rats treated with chloroquine. Thus, the immunosuppressant activity of chloroquine may explain its efficacy in various types of immune disorders.

Kinetics and extent of repair of bleomycin-induced chromosome damage in quiescent normal human fibroblasts and human mononuclear blood cells

The kinetics of chromosome damage repair after bleomycin treatment was studied in quiescent mononuclear human blood cells and human fibroblasts using the technique of premature chromosome condensation. Quiescent cells were treated with bleomycin for 30 min, washed free of drug, and fused with mitotic HeLa cells after various repair times. The amount of chromosome damage remaining was assayed in the G1 prematurely condensed chromosomes. The chromosome repair kinetics profile exhibited fast- and slow-repair components. The fast chromosome repair component was apparent within 2 hr after bleomycin treatment, with a significant amount of repair having occurred within 30 min. The absolute rate of chromosome repair then significantly slowed beyond 2 hr after treatment. The rate of chromosome repair was slightly dependent on dose with a higher rate observed at a higher dose. Interestingly, while quiescent fibroblasts were more sensitive to bleomycin than were mononuclear blood cells, both cell populations exhibited similar repair kinetics. These results suggest the following: (a) quiescent human fibroblasts and mononuclear blood cells show similar chromosome repair kinetics after bleomycin treatment; (b) there exist both fast- and slow-repair components after bleomycin treatment; and (c) the rate of chromosome repair is dependent on the degree of initial damage.