Anti-predator defences of a web-building spider, Holocnemus pluchei (Araneae, Pholcidae)

Anti-predator defence behaviour of Holocnemus pluchei (Araneae, Pholcidae) was studied in the laboratory and the field. Bouncing, in which this web-building spider moves its body rapidly up and down while keeping its legs on the silk, was the most frequent response to disturbance. Less often, H. pluchei left the web when disturbed. Experiments were carried out to determine the types of stimuli that elicited bouncing and leaving the web: tactile stimulation (striking the spider with a brush) and air movement (blowing on the spider) elicited bouncing and leaving the web, but there was no evidence that chemical stimuli from potential predators were important. Tactile stimulation elicited stronger responses than air movement. There were no evident differences in how H. pluchei responded to tactile stimulation in the laboratory and the field.     

Structurally defined synthetic cancer vaccines: analysis of structure, glycosylation and recognition of cancer associated mucin, MUC-1 derived peptides

Translation of an immune response into therapy is probably the toughest task in designing vaccines for cancer due to the heterogeneity of the cell surface antigens which display tremendous variations in glycoforms. Consequently, a small segment (antigen) of the cancer-associated mucin, in spite of generating antigen-specific immune responses, may be limited in therapeutic value. It is important that the synthetic segment resembles the native cancer-associated mucin in both structure and conformation. Synthetic cancer associated mucin derived 16 amino acid peptide GVTSAPDTRAPAPGSTA and its partially glycosylated forms have demonstrated specific binding to two monoclonal antibodies, B27.29 and BCP8, raised against the native cancer associated mucin, MUC-1 and a MUC-1 derived synthetic peptide, respectively. In spite of the structural similarities at the core peptide level of both glycosylated and unglycosylated peptides, it appears that partial glycosylation does not inhibit and even slightly enhances binding to the MAb B27.29 indicating that the glycosylated synthetic peptide more closely resembles the native mucin epitope recognized by MAb B27.29. From molecular dynamic simulations using NMR derived distance constraints, both glycosylated and unglycosylated peptides have shown a type I turn involving the same amino acids in both glycosylated and unglycosylated peptides. The GalNAc attached to the threonine (T³) and serine (S⁴) in the 16 amino acid sequence has not imposed any conformational changes to the peptide backbone nor has offered severe steric resistance to the binding of either antibody to the glycopeptides as indicated by hapten inhibition studies. Nevertheless, all peptides have displayed glycosylation dependent specificities in binding to these antibodies, i.e. the glycosylated peptides demonstrated relative higher affinities to the native mucin antibody B27.29 while the unglycosylated peptide is more specific to the MAb BCP8. Immune responses generated by these synthetic glycopeptides are highly specific in recognizing the native cancer associated mucin.     

Incidence of acute symptomatic toxoplasma retinochoroiditis in south London according to country of birth.

OBJECTIVE--To determine the incidence of acute symptomatic toxoplasma retinochoroiditis presenting to ophthalmologists for patients born in Britain and elsewhere. DESIGN--Population based, cross sectional study. SETTING--11 districts in south Greater London. SUBJECTS--All patients presenting to NHS ophthalmologists with symptoms due to acute toxoplasma retinochoroiditis in 1992-3. MAIN OUTCOME MEASURE--Intraocular inflammation in association with a retinochoroidal scar, active adjoining retinitis, and IgG serum antibodies to toxoplasma. RESULTS--The estimated incidence of acute symptomatic retinochoroiditis for all people born in Britain was 0.4/100,000/year. If a mean of two symptomatic episodes per lifetime is assumed, 100 people born in Britain may be affected each year, about a fifth of the estimated 500-600 congenitally infected people born each year. CONCLUSIONS--A substantial proportion of people with acute symptomatic toxoplasma retinochoroiditis were born outside the country, and the number born in Britain was smaller than the number previously estimated to develop retinochoroidal lesions due to congenital toxoplasmosis. These findings suggest that prenatal screening for toxoplasmosis in Britain may be of limited benefit.     

Inhibition of lipid peroxidation in muscle homogenates by phospholipase A2 inhibitors

Chlorpromazine, mepacrine, tetracaine, dibucaine, chloroquine, and procaine have been shown to inhibit the iron- and ascorbate-induced lipid peroxidation of skeletal-muscle hornogenates in vitro. These compounds are known to be inhibitors of phospholipase activity, but they were also found to be effective in blocking free-radical-mediated damage to lipids in denatured homogenates, to linoleate suspensions, and to glutamic acid solutions where phospholipase activity was not a relevant factor. The inhibitory action did not appear to be related to any iron-binding activity of the compounds.     

Long-term superfusion of rat pituitary cells: interaction of 17 beta-estradiol with pulses of gonadotropin-releasing hormone on luteinizing hormone release

In a series of four experiments, the temporal development of acute inhibitory and delayed stimulatory effects of 17 beta-estradiol (E) on luteinizing hormone (LH) release by superfused rat anterior pituitary cells pulsed with gonadotropin-releasing hormone (GnRH) was studied. Dispersed anterior pituitary cells from ovariectomized rats were cultured on Bio-Beads for 3 days and then placed in columns and superfused for up to 24 hr. During superfusion, the cells were exposed to GnRH pulses (3 X 10(-9) M, one 6-min pulse/hr). Cells treated with E (3 X 10(-10) M) either before (only 24 hr prior to superfusion) or before and during superfusion released significantly (P less than 0.05) more LH in response to the first few pulses of GnRH than cells treated with diluent. In contrast, cells treated with E only during superfusion initially released less GnRH-induced LH than cells treated with diluent. In a subsequent experiment, the inhibitory effect of E reached a maximum by 1.5 hr (P less than 0.01), and then gradually disappeared after 4.5 hr. Cells superfused simultaneously with E and fixed "low"-dose GnRH (5 X 10(-10) M) pulses did not exhibit enhanced LH responses with time to that dose of GnRH. However, E-superfused cells responded more than diluent-superfused cells to subsequent stimulation with a higher-dose GnRH pulse. Superfusion of cells with E for 16.5 hr in the absence of GnRH pulses also did not increase release of LH to low-dose (5 X 10(-10) M) pulses of GnRH, yet did cause a transitory increase to subsequent high-dose (10(-8) M) GnRH pulses. In conclusion, these results demonstrate the direct biphasic inhibitory then stimulatory effects of E on GnRH-induced LH release by superfused rat anterior pituitary cells. Expression of the stimulatory effect of E is related to the dose of GnRH.     

CO2 elimination as a function of frequency and tidal volume in rabbits during HFO

CO2 elimination (VCO2) was monitored during high-frequency oscillation (HFO) over a frequency (f) range of 2-30 Hz in anesthetized and paralyzed rabbits to determine whether effective gas exchange could be achieved in this species, to determine the f and tidal volume (VT) dependence of gas exchange in this species, and to compare these results with those from dog and human studies. We were able to produce VCO2 levels during HFO that exceeded normal steady-state levels of CO2 production with VT's less than the total dead space volume. VCO2 was related to f in a curvilinear fashion, whereas in some rabbits VCO2 became independent of f at higher frequencies. This curvilinear relationship between f and VCO2 is similar to data from humans but contrasts with the linear relationship found in dogs. Evidence is presented indicating frequency-dependent behavior of gas exchange is correlated with a frequency-dependent decrease in respiratory system resistance. We propose that the frequency-dependent mechanical properties of the rabbit lung may also account for the species differences in HFO gas exchange.     

Photosynthetic electron transport in guard cells of diverse species

Guard cells of plants representing 18 species were assayed qualitatively for potential to conduct photosynthetic linear electron transport. These plants included C₃ pteridophytes, C₃ and C₄ monocots, and C₃, C₄, and Crassulacean acid metabolism dicots. By use of a microfluorospectrophotometer, guard cell samples in epidermal peels were isolated optically. Chlorophyll fluorescence was monitored from the onset of excitation light. For guard cells of all these species, fluorescence intensity increased during illumination. When samples were preincubated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea, diuron, however, there was a more rapid increase in fluorescence. These results indicate that all tested guard cells conduct photosynthetic electron transport through the reaction center of photosystem II.