A nuclear mutant of Chlamydomonas that exhibits increased sensitivity to UV irradiation, reduced recombination of nuclear genes, and altered transmission of chloroplast genes

Meiotic progeny of Chlamydomonas reinhardtii normally receive chloroplast genomes only from the mt+ parent. However, exceptional zygotes, which transmit the chloroplast genomes of both parents or, more rarely, only those of the mt- parent, arise at a low frequency. Mutations at the mt(+)-linked mat-3 locus were found previously to elevate the transmission of chloroplast genomes from the mt- parent, resulting in a much higher than normal frequency of exceptional zygotes. In this paper we demonstrate that an ultraviolet-sensitive nuclear mutation mapping at the uvsE1 locus, which is unlinked to mating type, also promotes chloroplast genome transmission from the mt- parent. This mutant, which was previously shown to reduce recombination of nuclear genes in meiosis, acts synergistically with the mat-3-3 mutation to produce an extremely high frequency of exceptional zygotes. Through the use of restriction fragment length polymorphisms existing in the chloroplast genomes of C. reinhardtii and the interfertile strain C. smithii, we show that chloroplast DNA fragments from the mt- parent normally begin to disappear shortly after zygote formation. However, this process appears to be blocked totally in the absence of wild-type uvsE1 and mat-3 gene products. Our findings are consistent with the hypothesis that both gene products contribute to the mechanism responsible for uniparental inheritance of the chloroplast genome from the mt+ parent.     

Contractile activity of neonatal heart cells in culture derived from offspring of exercised pregnant rats

Summary 5-day-old neonatal offspring of exercised or non-exercised pregnant Sprague Dawley rats were used to prepare primary cultures of beating myocardial cells. The cells from the exercise group exhibited a slower beating rate for both single and aggregate cells; a larger cell size; an increased percentage of contracting cells; a greater capacity to form confluent monolayers, and a greater viability. It was concluded that exercise during the period of pregnancy produced morphological alterations in the myocardium of the progeny.     

Macrophage proteases and rheumatic diseases: Regulation of plasminogen activator by thymus-derived lymphocytes

Macrophages in culture secrete a variety of products including neutral protease activities such as plasminogen activator(s) (P.A.), collagenase and elastase. These products are not made by unstimulated macrophages, but only after induction by inflammatory stimuli, phagocytosis and lymphokines. Phagocytosis induces the prompt release of high levels of P.A. by endotoxin-primed macrophages and prolonged secretion follows uptake of non-degradable particles. Stimulation of lymphocytes results in the release of a supernatant product which enhances P.A. secretion by unstimulated mouse macrophages up to 5-fold. The production of the P.A. inducer (P.A.I.) is immunologically specific and is found in allogeneic mixed leukocyte culture (MLC) reactions, but not in syngeneic controls. The P.A. is also induced in activated macrophages from animals infected with BCG orT. cruzi and challenged with specific antigen. Production of the P.A.I. in MLC reactions depends on the presence of thymus-derived (T) lymphocytes and is closely correlated with the appearance of macrophage migration inhibition factor (MIF).The induction of macrophage P.A. and other proteases provides an important pathway for activating macrophages in delayed hypersensitivity reactions and could contribute significantly to tissue destruction in chronic inflammatory diseases in joints.     

Detection of binding antibodies to native and recombinant human immunodeficiency virus type 1 envelope glycoproteins following recombinant gp160 immunization measured by flow cytometry and enzyme immunoassays. The AIDS Vaccine Clinical Trials Network.

The ability of antibody induced by vaccination with recombinant gp160 (rgp160) to bind to native and recombinant human immunodeficiency virus type 1 (HIV-1) envelope glycoproteins was measured. Thirty-three HIV-1-seronegative healthy adult volunteers were injected four times with 40 or 80 micrograms of an HIV-1LAV envelope glycoprotein candidate vaccine per dose. The vaccine consisted of rgp160 produced in insect tissue culture cells infected with a recombinant baculovirus which contains the gp160 gene from the HIV-1LAV strain. By using a flow cytometric indirect immunofluorescence assay (FIFA) to detect vaccine-induced antibody to native envelope glycoprotein expressed by target cells infected with HIV-1IIIB, sera from 9 of the 33 vaccinees were positive. These included sera from eight vaccinees which stained HIV-1IIIB-infected cells and sera from two vaccinees which stained target cells infected with HIV-1MN, a heterologous virus strain. None of the sera stained cells infected with the HIV-1RF strain. Envelope glycoprotein-binding antibody was more frequently detectable in an enzyme-linked immunosorbent assay (ELISA) by using rgp160 compared with that which was detectable in the FIFA with uninfected target cells which were pulsed with rgp160 antigen. Positive correlations were observed between the rgp160 FIFA and a whole-virus-lysate enzyme immunoassay, between the rgp160 FIFA and the rgp160 ELISA, and between the rgp160 ELISA and the whole-virus-lysate enzyme immunoassay. The ability of sera from some volunteers who received rgp160 vaccine to bind to HIV-1-infected cells suggests that further studies with this vaccine should be done.     

Synthetic peptides from a conserved region of gp120 induce broadly reactive anti-HIV responses.

In our efforts to identify products that might be used for active immunotherapy in human immunodeficiency virus (HIV) infection, we have studied synthetic peptides derived from the CD4 attachment site of gp120. Two peptides have emerged with particularly interesting properties. The first (B138) is linear and spans the envelope residues 421-438; the second (1005/45) encompasses amino acids 418-445 and is cyclized by way of a disulphide bond joining its terminal cysteines. Both species have been shown to inhibit syncytial formation in a conventional bioassay, B138 being the most efficient. Both peptides elicit high titres of anti-peptide antibodies in immunized mice, rabbits and goats, with titres exceeding 1:10(5) in many cases. A substantial portion of this response is directed against gp120 as determined by enzyme-linked immunosorbent assay (ELISA). Analysis by flow cytometry has demonstrated that the antisera are broadly reactive with multiple diverse strains of HIV. The anti-gp120 activity of the anti-peptide antiserum was further confirmed by radioimmuno-precipitation (RIP) assays. Furthermore, RIP analysis and inhibition experiments in a GD4-gp120 binding assay have revealed that anti-peptide sera contain antibodies directed against the CD4 attachment site on gp120 and interfere with this receptor-ligand interaction.     

Human macrophages acquire a hyporesponsive state of tumor necrosis factor alpha production in response to successive Mycobacterium avium serovar 4 stimulation.

Human macrophages (M phi) from most donors respond to inoculation with Mycobacterium avium serovar 4 (M. avium) by tumor necrosis factor alpha (TNF-alpha) production, which is of critical importance for proper defense against microorganisms. An initial infection of M phi with M. avium results in an incapacity to accumulate TNF-alpha mRNA after reinfection with M. avium, indicating adaptation to a hyporesponsive state by preexposure of the cells to M. avium. Adaptation to stimulation with M. avium is abrogated by the cyclooxygenase inhibitor indomethacin. In the presence of prostaglandin E2, indomethacin-exposed, M. avium-treated M phi remain unresponsive to a subsequent M. avium stimulus to increase steady-state TNF-alpha mRNA, suggesting that prostaglandin E2 is instrumental for the adaptation to an M. avium challenge. TNF-alpha mRNA accumulation induced by a second M. avium stimulus in the presence of indomethacin is blocked by the protein tyrosine kinase inhibitor herbimycin. In contrast, the initial M phi response to M. avium is inhibited by staurosporin, an inhibitor of phospholipid Ca(2+)-dependent protein kinases, indicating that the initial and the successive TNF-alpha responses to M. avium are dependent on different mechanisms.     

Effect of repeated high dose prophylaxis with amoxycillin on the resident oral flora of adult volunteers

Healthy adult volunteers received either single or repeated 3-g doses of amoxycillin by mouth at weekly intervals on three occasions. The salivary flora of each volunteer was monitored before, during and up to 11 weeks after the final dose of antibiotic. Viable counts of anaerobic bacteria, streptococci and streptococci resistant to amoxycillin 2 mg/L and 40 mg/L were determined in samples of saliva. All 20 volunteers harboured low numbers of streptococci resistant to amoxycillin 2 mg/L (mean count = 6.57 X 10(3) cfu/ml of saliva) before administration of the antibiotic; much lower carriage rates (45%) were observed for bacteria resistant to amoxycillin 40 mg/L (mean count = 116 cfu/ml of saliva). Each dose of amoxycillin had a rapid but transient effect on the numbers of salivary bacteria. A placebo lacking the antibiotic had no effect. A single 3-g dose of amoxycillin had little or no effect on the numbers of resistant streptococci and, therefore, it was concluded that in patients at risk of infective endocarditis a second prophylactic dose would not be invalidated. The numbers of resistant streptococci increased significantly after the second and third doses of amoxycillin, and persisted for 4-7 weeks. Consequently, in at-risk patients requiring repeated dental procedures liable to produce bacteraemia, either alternative antibiotic regimens should be used each time or intervals of at least 4 weeks should be left between treatment sessions.     

An Analytic Model of Subminiature Auditory Sensation System for Sound Source Localization

It is reported that some types of insects have a remarkable ability to detect the direction of an incident sound even though its acoustic sensory organs are in very close proximity each other. Maybe the ears are jointed by a cuticular structure with which the separated motions can be coupled mechanically and thus be magnified. In this paper, a detailed model is setup to describe the principle of this type of localization using a mechanical coupled structure. The transfer functions and the responses of the model in terms of time and frequency are analyzed to describe the mechanism of its ability of directional hearing. This analytical model provides a method to design the experimental model for the predetermined incident sound pressure, and the analysis of this model shows that this structure have the ability to determine the direction of the incident stimulus.     

Oligonucleotide mapping of picornavirus RNAs by two-dimensional electrophoresis.

Considerable differences have been found in two-dimensional polyacrylamide gel electrophoresis fingerprints of complete ribonuclease T₁ digestion products of the RNAs of representative members of the entero-, cardio-, and foot-and-mouth disease virus subgroups of the picornavirus family. Individual members of the different subgroups, serotypes of a virus, and even subtypes within a serotype can be distinguished by the use of this technique. The method has also facilitated the identification of homopolymeric regions within the different picornavirus genomes, and the presence of a poly(C) tract in the cardio- and foot-and-mouth disease virus subgroups has been confirmed. A poly(A)-rich tract of approx 40–100 nucleotides has been detected in all the picornaviruses studied. Oligonucleotide fragments possibly specific to the enterovirus subgroup were also detected and partially characterised.