A cholinergic receptor site on murine lymphocytes with novel binding characteristics

To further analyze functionally important cholinergic receptors on lymphocytes, we studied the binding of the muscarinic antagonist Quinuclidinyl benzilate (QNB) to murine splenic lymphocytes. Studies of displacement of [³H]QNB by unlabelled QNB on lymphocytes revealed at least two binding sites. Scatchard analysis of equilibrium binding isotherms also distinguished two sites with apparent Kds of 480 nM and 16 μM. There was greater specific QNB binding to B cell-enriched lymphocyte fractions than to T cell fractions. Lymphocyte binding demonstrated temperature-dependent dissociability, and specific binding occurred on isolated lymphocyte membranes as well. Both muscarinic and nicotinic ligands competed for QNB binding to lymphocytes with low and nearly equal affinity. Therefore, QNB binding sites on lymphocytes appear to be of low affinity and of mixed muscarinic and nicotinic character.     

Barbiturate Mortality as an Index of Barbiturate Use,Canada, 1950-1963

Changes in Canadian rates of mortality from barbiturates are examined, and their relation to barbiturate use in the general population is discussed. While the number of deaths attributed to barbiturates quadrupled, from 63 in 1950 to 232 in 1963, there has been a concomitant decrease in the number of deaths from inhalation of utility gas.Combined rates for deaths from utility gas and barbiturates declined steadily for most age groups between 1950-52, 1955-57, and 1959-63. It is possible that the increased mortality from barbiturates represents a change in fashion in regard to method of suicide. Changed mortality from barbiturates is not a valid measure of the extent to which consumption of barbiturates has increased in the Canadian population.     

T cell recognition of HIV synthetic peptides in a natural infection

Because T cell responses are critical for defense against viral infections, a series of synthetic peptides derived from the predicted sequence for HIV-1 proteins gp41, pg120, gag, and viral polymerase were used to test the T cell proliferative response of HIV-1 seropositive individuals. Of HIV-1-infected donors from various clinical categories 90% (27/30) had sensitized cells that proliferated in response to at least one of 21 HIV peptides tested. Cells from HIV seronegative controls did not proliferate (0/9) in response to these HIV peptides. Individuals with fewer clinical manifestations of HIV-1 disease responded to a greater number of peptides (average for asymptomatic seropositives = 8.1 peptides; AIDS patients averaged 2.0). The number of peptides recognized also correlated with absolute number of CD4+ cells, but not with delayed cutaneous hypersensitivity to a (non-HIV) battery of Ag. However, clinical stage at no time correlated with the response to any particular peptide. Response patterns differed considerably among individuals, and some peptides stimulated proliferation in many (48%) HIV-infected donors (peptides gp41-2 and pol-3), whereas another peptide elicited no T cell response in any donor tested (peptide gp120-8). We have also begun to investigate the basis for individual heterogeneity of T lymphocyte proliferative responses of HIV-infected donors to the 21 HIV synthetic peptides. Peptide structure and HLA class II determinants both influenced patterns of lymphocyte responses. Reactivity correlated with peptide size, the presence of alpha and beta secondary structure and lack of reverse turn potential. Hydropathy and charge had no predictive value. Peptides derived from HIV sequences that vary highly among strains tended to be recognized less frequently. HIV-infected lymphocyte donors were HLA typed to examine the influence of the MHC on T lymphocyte proliferation. Analysis of the frequencies of individuals reacting to specific peptides, when compared to the allele frequencies in the population at large, indicated association of some responses to DR alleles. More DR association was observed with peptides that showed "moderate" reactivity than with those that were "highly" reactive. We suggest that highly reactive peptides are capable of forming a structure closer to an "ideal" T cell epitope that can associate with many DR alleles. In contrast, "moderately" reactive determinants have less favorable structures for interaction, are more limited in their ability to interact and therefore show more restriction to specific class II alleles.     

Motion behavior of nauplii and early copepodid stages of marine planktonic copepods

The goal of this study was to quantify periods of activity andvelocities of late naupliar and early copepodid stages of planktoniccopepods occurring regularly on the southeastern continentalshelf of the USA. We obtained quantitative information on eightspecies, including adult females of Oithona plumifera. All studieswere conducted at food concentrations near or above satiationlevels. Activities ranged from 0.85% (adult females of O.plumifera)to 100% of time (nauplii and copepodids of various calanoidspecies). Motion velocities (excluding escape motion) coveredmore than one order of magnitude: from 0.39 mm s^–1 fornauplii of Temora stylifera to 5.24 mm s^–1 for naupliiof Oncaea mediterranea. Ranges of activities of species rangefrom occasional for early juveniles to adult females of O.plumiferato 100% for the same range of T.stylifera, the latter creatinga feeding current from N III onwards, the former not at all.Of notable interest is Centropages velificatus which moves intermittentlyas a late nauplius, continuously as an early copepodid and intermittentlyas an adult. All observed calanoid late nauplii and copepodidsmove in three dimensions, excluding copepodids of the shelfbreak/oceanicParacalanus aculeatus. The results indicate not only significantdifferences in motion behavior between cyclopoids and calanoids,but also between calanoid species. Yet, some calanoid speciesshow little ontogenetic changes at all.     

Learning from rejection: the evolutionary biology of single-locus incompatibility

The self-incompatibility (S-) locus of flowering plants is among the most polymorphic known. PCR methods can now be used to estimate both the number of alleles in natural populations and their sequence diversity. The number of alleles provides an estimate of recent effective population size, thus the S-locus provides a tool for examining how species characteristics affect population size. Sequence relationships among alleles provide another estimate of population size extending millions of years into the past. Relationships between S-alleles and related genes provide a means of dating the age of origin of incompatibility systems and determining which, if any, angiosperm families share incompatibility by homology.     

Direct comparison of bromodeoxyuridine and Ki-67 labelling indices in human tumours

Direct comparison of bromodeoxyuridine (BrdUrd) and Ki-67 labelling indices was achieved by selecting similar areas from serial sections of human tumours. Fifteen patients were selected who had been administered BrdUrd in vivo and both proliferation markers were assessed by immunohistochemistry. The data show a good correlation between both BrdUrd LI and MIB-1 LI and T_pot (calculated using the flow cytometry derived duration of S phase) and MIB-1 LI. The contribution of BrdUrd LI to growth fraction varied as a function of proliferation characteristics. In tumours with a high LI, the number of DNA synthesizing cells represented half the growth fraction, whilst in tumours with lower LI's (<10%) the ratio of DNA precursor labelled cells as a function of growth fraction fell to between 10% and 20%. T_pot showed a linear correlation with MIB-1/BrdUrd ratio with a slope approaching unity. It was apparent that both intra- and interpatient variation in proliferation index was greater for BrdUrd labelling than for MIB-1 expression.