Orientation in a desert lizard (Uma notata): time-compensated compass movement and polarotaxis

Summary The diurnal escape response of fringetoed lizards (Uma notata) startled by predators demonstrates clear directional orientation not likely to depend on local landmarks in the shifting sands of their desert environment. Evidence that celestial orientation is involved in this behavior has been sought in the present experiments by testing the effects of (1) phase shifting the animal's internal clock by 6 h and (2) by training the lizards to seek shelter while exposed to natural polarization patterns. In the first case, 90° shifts in escape direction were demonstrated in outdoor tests, as expected if a time-compensated sun or sky polarized light compass is involved. In the second instance, significant bimodale-vector dependent orientation was found under an overhead polarizing light filter but this was only evident when the response data were transposed to match the zenithe-vector rotation dependent on the sun's apparent movement through the sky. This extends to reptiles the capacity to utilize overheade-vector directions as a time-compensated sky compass. The sensory site of this discrimination and the relative roles of sun and sky polarization in nature remain to be discovered.     

Mapping of brain activity in mesencephalic and diencephalic structures of toads during presentation of visual key stimuli: a computer assisted analysis of (14C)2DG autoradiographs

Summary The (¹⁴C)2DG autoradiographic technique has been employed to quantitatively map glucose utilization in the mesencephalon, the diencephalon and the cerebellum, of toads in response to configurational moving visual stimuli: (i) a 0.4 cm × 2.8 cm worm-like stripe (W) which elicited prey catching responses, (ii) a 8.4 cm × 8.4 cm square (S) that released predator avoidance responses, and (iii) a 2.8 cm × 0.4 cm antiworm-like stripe (A) which elicited no motor activity.For various brain nuclei different relationships were obtained: The optic tectum showed statistical significant higher 2DG uptake during worm-stimulation (¯X _W) than during antiworm stimulation (¯X _A), i.e.¯X _W>¯X _A. The latter visual pattern led to a 2DG utilization that was statistically significant stronger than during stimulation with a square (¯X _S), i.e.¯X _A>¯X _S. Thus, in comparison between right and left hemisphere as well as between brains the following ratios were obtained:Optic tectum:¯X _W>¯X _A>¯X _S; nucleus isthmi:¯X _W>¯X _A-¯X _s; posterodorsal lateral thalamic nucleus:¯X _S>¯X _A>¯X _W; posteroventral lateral thalamic nucleus:¯X _S>¯X _A¯X _W; posterior thalamic nucleus:¯X _W>¯X _A¯X _S; anteripr division of the lateral thalamic nucleus:¯X _W>¯X _A¯X _S; anterior thalamic nucleus:¯X _A>¯X _S>¯X _W; nucleus of Bellonci and dorsal division of the ventrolateral thalamic nucleus:¯X _W¯X _A¯X _S; cerebellum:¯X _S¯X _W>¯X _A.Abbreviations A anterior thalamic nucleus - Cb cerebellum - Hyp hypothalamus - Ist nucleus isthmi - cl. Ist contralateral Ist - La lateral thalamic nucleus, anterior division - Lpd lateral thalamic nucleus, posterodorsal division - Lpv lateral thalamic nucleus, posteroventral division - MP medial pallium - NB/VLd nucleus of Bellonci and ventrolateral thalamic nucleus, dorsal division - P posterior thalamic nucleus - PO preoptic area - Sna snapping evoking area=ventrolateral tectum - Str striatum - Tec tectum opticum     

Structural features are as important as sequence homologies inDrosophila heat shock gene upstream regions

Summary Pelham has shown that theDrosophila hsp 70 gene is not transcribed under heat shock conditions unless a given upstream region is present. Davidson et al. have recently compiled a list of sequences homologous to this region in otherDrosophila heat shock genes. They proposed that a set of unlinked genes, such as the heat shock genes, could be coordinately induced through an interaction in cis with a common regulatory molecule. That this interaction involves structural elements is suggested by the fact that these upstream regions share inverted repeats as well as areas of Z-DNA potential. Furthermore, using the Calladine-Dickerson rules for local helical parameters, we show that these regions share structural homology. This is significant because the presence of regions homologous to a derived consensus sequence does not necessarily imply structural similarity. Therefore, we suggest that these structural features are at least as important as the sequence homologies in enabling the heat shock response.     

Allelic variation at the frizzled locus of Drosophila

The epidermis of Drosophila has a tissue polarity that is manifested by a parallel array of polarized structures (primarily hairs and bristles). The production of normal tissue polarity requires the function of the frizzled (fz) locus. We have isolated a large number of alleles at this locus and have phenotypically characterized more than 25 of them. We have found extensive allelic variation that a previous study failed to detect. Most of the alleles fall into a hypomorphic to amorphic series. Two alleles, however, have unusual properties. These alleles, which in general are moderately strong alleles, fail to produce a rough eye phenotype that is characteristic of all the other moderate or strong fz alleles. Thus, these two alleles are tissue specific in effect. Furthermore, these two alleles also have a neomorphic or antimorphic effect on hair polarity in one region of the wing.     

Qa alloantigen expression on functional T lymphocytes from spleen and thymus

The cell-surface expression of the class I alloantigen Qa-2 was analyzed on resting and activated spleen and thymus cells using cytotoxic elimination and immunofluorescence and flow cytometry. Spleen cells activated by mitogens or alloantigen were homogeneously positive for cell surface Qa-2, but activated splenic T cells expressed only about one-third as much Qa-2 per cell as did nonstimulated T cells. These data correlated with the ability to perform cytotoxic elimination with Qa-2-specific monoclonal antibodies (mAbs) in that cytotoxic T lymphocyte (CTL) activity was completely abrogated by pretreatment of spleen cells prior to in vitro culture but was only partially eliminated by treatment of CTL effectors. Qa-2-positive cells constituted only a small subpopulation of fresh normal thymocytes, but were enriched (>40% positive) among cortisone-resistant thymocytes (CRT). These Qa-2-positive CRT contained mature thymocytes as defined by Ly phenotype Ly-2^–, Ly-1^hi. When normal thymocytes were treated with Qa-2-specific mAb and complement prior to in vitro sensitization for generation of allogeneic CTL, CTL activity was completely abrogated despite the fact that the fraction of cells eliminated were undetectable as assessed by cell recovery. CTL effectors from alloantigen-stimulated thymocytes were also susceptible to cytotoxic elimination with Qa-2-specific mAb. These data suggest that the Qa-2 molecule may serve not only as a marker on resting and activated peripheral T cells, but also as a unique marker for functionally mature T cells in the thymus.     

The acquired immune deficiency syndrome and epidemic of infection with human immunodeficiency virus: costs of care and prevention in an inner London district.

The epidemic of the acquired immune deficiency syndrome (AIDS) and infection with human immunodeficiency virus (HIV) necessitates early planning of services and allocation of resources. The use of hospital resources by patients with AIDS and the planned additional costs of clinical and preventive services for the epidemic of infection with HIV were calculated for an inner London health district that has treated 18% of the cases in the United Kingdom. Patients with AIDS required on average 50 days of inpatient hospital care each at an estimated current average lifetime cost of pounds 6800. These costs, however, underestimated the additional capital and revenue costs of planned new preventive and treatment services, estimated as being pounds 388,000 revenue and pounds 472,000 capital for 1986-7. It is important to invest now in preventive services throughout the United Kingdom to reduce the future social and financial costs of AIDS.     

DNA-dependent in vitro synthesis of enzymes of the galactose operon of Escherichia coli

Summary Two active enzymes of the galactose operon of Escherichia coli, uridyl transferase and galactokinase have been synthesized with high yields in a DNA dependent system for protein synthesis. The unspecific blank values amount to less than two percent of the rate obtained under optimal conditions and permit the accurate determination of even a small fraction of the maximum synthesis rate. Therefore this system provides a sensitive assay for the biological activity of DNA that contains the intact galactose operon of Escherichia coli.The synthesis of these galactose enzymes is to a high extent dependent on the presence of cyclic adenosine-3:5-monophosphate.D-fucose, known as an inducer of the galactose operon in vivo, stimulates the synthesis of galactokinase, indicating that the repressor of the galactose operon in active under these conditions. This stimulation is not observed, if the bacterial extract is prepared from a strain defective for the galactose repressor or if the DNA carries an operator constitutive mutation in the galactose operon. Therefore the stimulation by D-fucose is true derepression.     

Properties of Mutants in Galactose Taxis and Transport

beta-Methylgalactoside (mgl) permease mutants of Escherichia coli, which are defective in three genes, mglA, mglB, and mglC, were assayed for galactose taxis and galactose transport. The mglB product is the galactose-binding protein. Previous evidence, supported by our new findings, shows that the galactose-binding protein is the recognition component for galactose taxis as well as for galactose transport. Most mutants defective in mglB showed strong effects on both chemotaxis and transport; however, a couple showed effects chiefly on one process or the other, thus allowing a separation of chemotaxis and transport. The mglA and mglC products have not yet been identified, but they must be components of the galactose transport machinery since mutants defective in mglA or mglC, or both, showed strongly reduced transport. Although some of these mutants showed little chemotaxis, most gave close to wild-type chemotactic responses. Thus, transport is not required for galactose taxis. The bacteria detect changes in the fraction of binding protein associated with galactose, not changes in the rate of transport.     

Change in Properties of Physarum polycephalum Amoebae During Extended Culture

During two years of passage, several myxamoebal strains of Physarum polycephalum changed with regard to their properties in crosses and plaque morphology. These changes have been correlated with increased nuclear deoxyribonucleic acid content.