Characterization of a subset of bovine T lymphocytes that express BoT4 by monoclonal antibodies and function: similarity to lymphocytes defined by human T4 and murine L3T4

We report the identification of a subset of bovine T cells by two monoclonal antibodies (mAb), IL-A11 and IL-A12, and some functional analyses of these cells. Both mAb precipitate two polypeptides, called BoT4, with apparent molecular mass of 52 and 55 kilodaltons. The epitopes recognized by these two mAb are different, however. BoT4 is found on approximately 70% of thymocytes and 30% of peripheral blood mononuclear cells (PBM), is not expressed by monocytes or B cells, and is found on cells in the T-dependent areas of lymph nodes. BoT4+ lymphocytes purified by a fluorescence-activated cell sorter proliferate in response to mitogenic and alloantigenic stimulation without addition of exogenous growth factors, whereas BoT4- lymphocytes do not. Monoclonal antibodies IL-A11 and IL-A12 have no effect on mitogen- (PHA and Con A) or alloantigen-induced proliferation of PBM. Monoclonal antibody IL-A12 has no inhibitory effect on the cytolytic activity of bulk populations of alloreactive T lymphocytes, and most of the cytolytic activity generated in mixed leukocyte culture is ascribable to the BoT4- population. Using cloned alloantigen-specific lymphocytes, we found that the ability of BoT4+ clones to proliferate to alloantigenic stimuli without exogenous growth factors is a characteristic of some clones, as is susceptibility to inhibition of proliferation by mAb IL-A12. These results implicate the BoT4 molecule in antigen recognition but indicate that the requirement for BoT4 is variable among clones. Our findings, together with those in the companion paper, which provides evidence that BoT4+ lymphocytes are class II restricted, indicate that BoT4+ lymphocytes are the bovine equivalent of Leu3/T4+ lymphocytes of humans and analogous lymphocytes of other species.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

The hemoglobin concentration ofChironomus cf.Plumosus l. (Diptera: Chironomidae) larvae from two lentic habitats

Hemoglobin concentrations ofChironomus cf.plumosus larvae were measured in two different habitats of the same pond. Larger larvae have higher hemoglobin concentrations than small larvae. There is strong indication that the animals of poorly oxygenated deep water, have higher hemoglobin concentrations than the animals from the well-oxygenated littoral zone.     

Intraspecific diversity in the fungal speciesChaunopycnis alba: Implications for microbial screening programs

Intraspecific variation among 84 isolates of the anamorphic fungusChaunopycnis alba from 26 different geographical locations was analyzed by investigating optimal growth temperatures, differences in the production of secondary metabolites and presence or absence of the cyclosporin synthetase gene. The genetic diversity was assessed using random amplified polymorphic DNA (RAPD). Analysis of these data showed high genetic, metabolic and physiological diversity within this species. Isolates from the Antarctic represented the most homogeneous group withinC. alba and together with isolates from the Arctic these polar strains differed from alpine, temperate and tropical strains by low optimal growth temperatures and by low production of secondary metabolites. Isolates from tropical climes were characterized by high optimal growth temperatures and by the production of comparatively diverse metabolite spectra. Most of the isolates that were similar in the combination of their physiological and metabolic characters were also genetically related. Isolates from different geographical origins did not show many similarities, with the exception of the cyclosporin A-producing isolates, and large diversity could be observed even within a single habitat. This leads us to the suggestion that for pharmaceutical screening programs samples should be collected from a diversity of different geographical and climatic locations. For the selection of strains for screening the RAPD assay seems to be the most powerful tool. It reflected the highest intraspecific diversity and the results corresponded well with the other characteristics.     

The Meckel syndrome. Pathological and cytogenetic observations in eight cases

Summary Eight new cases of Meckel syndrome, two of them occurring in the same family, are presented. Occipital encephalocele of varying extent, multicystic renal dysplasia not associated with urinary tract obstruction, and postaxial hexadactyly comprise the three basic features of this lethal syndrome with autosomal recessive inheritance. From our observations it appears that congenital hepatic fibrosis, abnormal external genitalia in male infants and a malformed tongue with lipomatous excrescences are also frequently occurring anomalies with important diagnostic value.The statement that the majority of cases of Meckel syndrome can be detected prenatally is further supported by two cases in the present series. The incidence of this syndrome may be much higher than previously thought.     

Perinatal mortality and XY/XX mosaicism

Summary An XX/XY mosaicism was detected in two phenotypically male newborns with perinatal death. The importance of chromosome studies at the paediatric necropsy and the significance of the present findings are discussed.     

A covalently bound photoisomerizable agonist. Comparison with reversibly bound agonists at electrophorus electroplaques

After disulphide bonds are reduced with dithiothreitol, trans-3- (α-bromomethyl)-3’-[α- (trimethylammonium)methyl]azobenzene (trans-QBr) alkylates a sulfhydryl group on receptors. The membrane conductance induced by this “tethered agonist” shares many properties with that induced by reversible agonists. Equilibrium conductance increases as the membrane potential is made more negative; the voltage sensitivity resembles that seen with 50 [mu]M carbachol. Voltage- jump relaxations follow an exponential time-course; the rate constants are about twice as large as those seen with 50 μM carbachol and have the same voltage and temperature sensitivity. With reversible agonists, the rate of channel opening increases with the frequency of agonist-receptor collisions: with tethered trans-Qbr, this rate depends only on intramolecular events. In comparison to the conductance induced by reversible agonists, the QBr-induced conductance is at least 10-fold less sensitive to competitive blockade by tubocurarine and roughly as sensitive to “open-channel blockade” bu QX-222. Light-flash experiments with tethered QBr resemble those with the reversible photoisomerizable agonist, 3,3’,bis-[α-(trimethylammonium)methyl]azobenzene (Bis-Q): the conductance is increased by cis {arrow} trans photoisomerizations and decreased by trans {arrow} cis photoisomerizations. As with Bis-Q, ligh-flash relaxations have the same rate constant as voltage-jump relaxations. Receptors with tethered trans isomer. By comparing the agonist-induced conductance with the cis/tans ratio, we conclude that each channel’s activation is determined by the configuration of a single tethered QBr molecule. The QBr-induced conductance shows slow decreases (time constant, several hundred milliseconds), which can be partially reversed by flashes. The similarities suggest that the same rate-limiting step governs the opening and closing of channels for both reversible and tethered agonists. Therefore, this step is probably not the initial encounter between agonist and receptor molecules.     

A new lethal syndrome with cloudy corneae,diaphragmatic defects and distal limb deformities

Summary Two female sibs are reported with a possibly new lethal malformation pattern, the major anomalies of which are: coarse face with small eyes and cloudy corneae, cleft soft palate, hypoplasia and absence of lobulation of both lungs, diaphragmatic defects, digitalisation of thumbs and distal limb deformities.