Dissociation of the receptor for immunoglobulin E in mild detergents

We previously showed that, in the absence of phospholipids, exposure of the tetrameric receptor for immunoglobulin E to mild detergents dissociates the intact beta chain and two gamma chains from the alpha chains. Having developed a practical method for assaying the dissociation, we have now explored a variety of different detergents, detergent concentrations, temperatures, times, salts, pHs, and other factors that influence the detergent-induced dissociation. Our findings should be useful for optimizing the stability of the receptor and for future studies on recombination of the subunits. The data suggest the following: (1) The critical perturbant is micellar detergent. (2) Unlike solubilization of membranes, where a molar ratio of micellar detergent:lipid of 2 is adequate, dissociation of the receptor is incomplete even at molar ratios of micellar detergent:receptor of greater than 10(5) and may be limited by a reversible component. (3) Detergents that are best for solubilizing membranes are also best for dissociating the receptors. (4) The latter observation and other data implicate bound lipid as stabilizing the receptor. Our findings may be applicable to the study of interactions between membrane proteins in general.     

Interaction of guanosine cyclic 3',5'-phosphate dependent protein kinase with lin-benzoadenine nucleotides

Using the activated cGMP-dependent protein kinase in the presence of the phosphorylatable peptide [[Ala34]histone H2B-(29-35)], we found that lin-benzoadenosine 5'-diphosphate (lin-benzo-ADP) was a competitive inhibitor of the enzyme with respect to ATP with a Ki (22 microM) similar to the Kd (20 microM) determined by fluorescence polarization titrations. The Kd for lin-benzo-ADP determined in the absence of the phosphorylatable peptide, however, was only 12 microM. ADP bound with lower affinity (Ki = 169 microM; Kd = 114 microM). With [Ala34]histone H2B-(29-35) as phosphoryl acceptor, the Km for lin-benzo-ATP was 29 microM, and that for ATP was 32 microM. The Vmax with lin-benzo-ATP, however, was only 0.06% of that with ATP as substrate [0.00623 +/- 0.00035 vs. 11.1 +/- 0.17 mumol (min.mg)-1]. Binding of lin-benzo-ADP to the kinase was dependent upon a divalent cation. Fluorescence polarization revealed that Mg2+, Mn2+, Co2+, Ni2+, Ca2+, Sr2+, and Ba2+ supported nucleotide binding to the enzyme; Ca2+, Sr2+, and Ba2+, however, did not support any measurable phosphotransferase activity. The rank order of metal ion effectiveness in mediating phosphotransferase activity was Mg2+ greater than Ni2+ greater than Co2+ greater than Mn2+. Although these results were similar to those observed with the cAMP-dependent protein kinase [Hartl, F. T., Roskoski, R., Jr., Rosendahl, M. S., & Leonard, N. J. (1983) Biochemistry 22, 2347], major differences in the Vmax with lin-benzo-ATP as substrate and the effect of peptide substrates on nucleotide (both lin-benzo-ADP and ADP) binding were observed.     

Foraging-efficiency-predation-risk trade-off in the grey squirrel

Many animals must often respond to environmental patterns that simulatneously influence both foraging efficiency and predation risk. We noted that grey squirrels (Sciurus carolinensis) sometimes immediately consume food items in areas of relatively great exposure to predators, and at other times carry food items to the safety of a tree prior to consumption. We outlined a hypothesis that the squirrels were somehow trading-off energy intake rate against predation risk. A simple model shows that maximal energetic efficiency is associated with immediate consumption, whereas (under the field conditions studied) carrying items to the safety of trees provides for minimal exposure to predation. Our analysis of the model predicts that the tendency to carry a food item should decrease with distance of food from cover (travel time) and increase with item size (handling time). To test our predictions, we presented free-roaming grey squirrels with patches containing a fixed number of identical food items. We estimated the proportion of items carried to trees before consumption for 12 different combinations of distance to the nearest tree and item size. The results support our hypothesis and indicate that a simple behavioural criterion based solely on foraging rate or time exposed to predators is insufficient to explain the variation in the data.     

An information-theory analysis of task specialization among worker honey bees performing hive duties

Worker honey bees (Apis mellifera) performing field duties are known to possess individual task specializations. However, little evidence has been forthcoming about individual specializations among the younger pre-foraging worker bees performing hive duties. This paper reports results obtained from behavioural observations of worker bees in seven hives. An information-theory analysis of these data reveals that the divergence from independence (D₂) of worker bee identity and behavioural pattern performed has a low value in all of the experimental hives. Young worker bees performing hive duties therefore do not possess detectable individual specializations. Environmental and life-history considerations that may account for this difference in behaviour between field and hive worker bees are discussed.     

Arthrin: a new actin-like protein in insect flight muscle

There are one or more proteins of 50,000 to 60,000 Mr in the thin filaments of insect flight muscle. A protein of 55,000 Mr has been isolated from insect fibrillar flight muscle and called arthrin. Despite its higher molecular weight, arthrin is in many ways like actin. The amino acid composition of arthrin was similar to that of actin. There were similarities in the peptides produced by digesting the denatured proteins and mild digestion of polymerized proteins cleaved similar-sized fragments from arthrin and actin. Polymerized arthrin activated the Mg2+ ATPase of myosin to the same extent as actin and the ATPase was regulated by rabbit or Lethocerus troponin and tropomyosin. Arthrin did not itself act as troponin-T. Electron microscopy of negatively stained specimens showed that arthrin and actin filaments were similar in structure and that arthrin could be decorated by rabbit subfragment-1 to form normal-looking arrowheads. Arthrin formed paracrystals at an optimum concentration of MgCl2 (25 mM) that was somewhat lower than the optimum for actin paracrystals. Optical diffraction showed that the structure of the paracrystals was similar to those formed from actin. The mass of arthrin and actin filaments relative to phage fd was measured by scanning transmission electron microscopy; the relative mass of arthrin and actin was 1.33, in agreement with molecular weight estimations. Therefore arthrin has the properties of a heavy form of actin. The proportion of actin, arthrin and troponin-T in Lethocerus myofibrils was six moles of actin to one mole of arthrin and one mole of troponin-T. The function of arthrin is not known.     

Spatial variation in larval concentrations as a cause of spatial variation in settlement for the barnacle,Balanus glandula

Summary Settlement rates of the high intertidal barnacle, Balanus glandula, were monitored at three sites in the rocky intertidal zone in Central California simultaneously with measurements of larval concentrations in the adjacent water column. In both 1983 and 1984, settlement rates onto vacant substrate differed among the sites by nearly two orders of magnitude. For all sampling dates, this spatial variation in settlement mirrored the spatial distribution of Balanus glandula cyprid concentration in the water column. A perfect rank correlation was found between cyprid concentrations near a site and subsequent settlement. A noteworthy observation was that the sites switched rank in their settlement rates from 1983 to 1984. This change in settlement rankings matched a switch in rankings for cyprid concentrations.Settlement itself appears to be an important cause of the spatial pattern of cyprid concentrations. Comparing the rates of settlement to estimates of the number of cyprids available at a site suggests that settlement causes a large drain on the cyprid population as a water mass passes over successive sites. No consistent spatial patterns were found in the distribution of other major plankton groups (calanoid copepods) that are similar in size to Balanus cyprids but do not settle.The large differences in settlement rates among these sites were previously shown to be a leading cause of large differences in the structure of benthic barnacle populations. The close correspondence shown here between these large differences in settlement and differences in larval concentrations suggests that nearshore oceanic processes affecting larval arrival contribute to the control of benthic community structure.     

Genetic Variation for the Sex Ratio in NASONIA VITRIPENNIS

We detected genetic variation for the sex ratio in the parasitoid wasp Nasonia vitripennis by analysis of inbred lines and with an artificial selection experiment. Sex ratios differed significantly among five independently isolated lines. Furthermore, sex ratio in broods produced by single females in single hosts shifted from 80-90% female to 50-55% female in 13 to 15 generations in each of two replicate selection lines. The final sex ratios of both selection lines were significantly lower than any of the inbred line sex ratios. Backcrosses revealed that the selection response was due to nuclear genes acting through the female parent. In light of known facultative sex ratio behavior and major genes affecting sex ratio in Nasonia, our results suggest that population and individual sex ratios in this species are molded by processes at both genetic and behavioral levels.     

Photochemical reactions in interstellar grains photolysis of co,NH3, and H2O

A simulation of the organic layer accreted onto interstellar dust particles was prepared by slow deposition of a CO:NH₃:H₂O gas mixture on an Al block at 10K, with concomitant irradiation with vacuum UV. The residues were analyzed by GC-MS, HPLC, and near IR; a reaction pathway leading from NH₃ to complex alcohol, fatty acid, and amide products in 27 stages is postulated. The astronomical relevance and significance of the observations are discussed.     

Canadian survey of thyroid cancer

We report the results of a multicentre retrospective chart review of 2214 patients with thyroid cancer registered at 13 radiotherapy centres between 1958 and 1978. The data analysed included sex, age at the time of diagnosis, pathological diagnosis, extent of disease before treatment, types of treatment and their complications, and the rates of recurrence and survival up to 24 years after diagnosis. Although papillary cancers were most common, anaplastic and miscellaneous tumours were more frequent than expected, which reflects the type of patients referred by endocrinologists and surgeons to radiotherapy centres. There were marked differences in patterns of referral to the centres. Some patients with papillary and follicular thyroid cancers died of these cancers up to 20 years after diagnosis. The clinical manifestations, treatment and outcome of the rarer types of thyroid malignant tumours were of particular interest. The influence of age at the time of diagnosis on survival rates for patients with papillary or follicular thyroid cancer was highly significant, indicating much more aggressive behaviour of these cancers in older patients, particularly those beyond the age of 60 years. A more detailed analysis of tumour subtypes should provide new information on their natural history and lead to better management.     

Eye movements and the enhancement of edges

A mathematical examination of retinal photochemistry leads to a hypothesis for Mach band phenomena based on eye movements. This retinal model suggests why minimally distinct borders fade under eye fixation and agrees qualitatively with subjective measures of border contrast as a function of overall field luminance.Deceased