A preputial odor imprinted on female mice

Female mice (Mus musculus) which were reared by a preputialectomized female and exposed to an intact male from 14 to 18 days of age preferred the odor of an intact male over that of a preputialectomized male when tested at 15 weeks of age. However, those females which were exposed to an intact male from 28 to 32 days of age preferred the odor of a preputialectomized male over that of an intact male, and those females which were exposed to an intact male from 0 to 4 days of age showed no reliable preferences. Females which were reared by an intact female and exposed a preputialectomized male for 4 days tended to reverse preferences. Females which were exposed to a preputialectomized male from 14 to 18 days of age preferred the odor of a preputialectomized male. However, females which were exposed to a preputialectomized male from 28 to 32 days of age preferred the odor of an intact male, as did females which were exposed to a preputialectomized male from 0 to 4 days.     

An algebraic analysis of the two state Markov model on tripod trees

Methods of phylogenetic inference use more and more complex models to generate trees from data. However, even simple models and their implications are not fully understood. Here, we investigate the two-state Markov model on a tripod tree, inferring conditions under which a given set of observations gives rise to such a model. This type of investigation has been undertaken before by several scientists from different fields of research. In contrast to other work we fully analyse the model, presenting conditions under which one can infer a model from the observation or at least get support for the tree-shaped interdependence of the leaves considered. We also present all conditions under which the results can be extended from tripod trees to quartet trees, a step necessary to reconstruct at least a topology. Apart from finding conditions under which such an extension works we discuss example cases for which such an extension does not work.     

A cell-free assay for the insertion of a viral glycoprotein into the plasma membrane

A cell-free assay has been developed for the delivery of influenza virus neuraminidase to the plasma membrane. Two types of postnuclear supernatant, which acted as donor and acceptor of the enzyme, were prepared from baby hamster kidney cells. Donor preparations were obtained from cells infected with influenza virus and containing neuraminidase en route to the plasma membrane. Acceptor preparations were obtained from cells containing, bound to their plasma membranes, Semliki Forest virus with envelope glycoproteins bearing [3H]N-acetylneuraminic acid. Fusion between vesicles from these two preparations permits access of the enzyme to its substrate, which results in the release of free [3H]N-acetylneuraminic acid. This release was detected through the transfer of radioactivity from a trichloroacetic acid-insoluble to a trichloroacetic acid-soluble fraction. An ATP-dependent component of release was found, which appears to be a consequence of vesicle fusion. This component was enhanced when the donor was prepared from cells in which the enzyme had been concentrated in a compartment between the Golgi complex and the plasma membrane, which indicates that a specific exocytic fusion event has been reconstituted. The extent of fusion is greatly reduced by pre-treatment of donor and acceptor preparations with trypsin, which points to the involvement of proteins in the fusion reaction.     

A novel microtubule-associated protein from mammalian nerve shows ATP- sensitive binding to microtubules

We report the isolation of a protein from mammalian nerve which shows ATP-sensitive binding to microtubules and ATPase activity. This protein, which we have designated HMW4, was prepared from bovine spinal nerve roots by microtubule affinity and ATP-induced release, and was further purified by sucrose density gradient centrifugation. It is a high molecular weight protein with a denatured Mr of 315,000, a Stokes radius of 90 A, and a sedimentation value of approximately 19S. It can be resolved electrophoretically from the well-characterized bovine brain microtubule-associated proteins (MAPs) and also appears to be distinct from MAP 1C. HMW4 has a vanadate-sensitive and azide-insensitive ATPase activity which averages 20 nmol Pi/min per mg protein and is different from dynein and myosin ATPases. HMW4 prepared on sucrose gradients exhibits binding to MAP-free microtubules in the absence of ATP which is reduced by ATP addition. Assayed by darkfield microscopy, HMW4 causes bundling of MAP-free microtubules which is reversed by ATP addition.     

A single affinity column step method for the purification of ricin toxin from castor beans (Ricinus communis)

A rapid method for purifying ricin toxin from castor beans is presented which uses a single affinity column step to obtain pure toxin from a crude extract of castor beans. A galactosyl-Sepharose affinity matrix was used to bind ricin toxin and its associated agglutinin, which both bind specifically to galactose, from a crude extract. The selective elution of ricin toxin and agglutinin was then achieved by eluting the affinity column with a galactose gradient, which sequentially elutes the two proteins due to a difference in binding avidity to the matrix.     

Molecular analysis of transferable tetracycline resistance plasmids from Clostridium perfringens.

Conjugative tetracycline resistance plasmids from 15 Clostridium perfringens isolates from piggeries were analyzed by restriction endonuclease digestion and agarose gel electrophoresis. Seven isolates from one farm were found to carry a 47-kilobase pair (kb) plasmid, pJIR5, which had EcoRI, XbaI, and ClaI profiles that were identical to those of a previously characterized plasmid, pCW3. An isolate from a second farm was found to carry a plasmid, pJIR6, which also was indistinguishable from pCW3. Five additional isolates from a third farm carried a 67-kb plasmid, pJIR2, which had at least 29 kb of DNA in common with pCW3. Finally, two isolates from a fourth farm were found to carry a 50-kb plasmid pJIR4, which appeared to consist of an entire pCW3 molecule with a 3-kb insertion. Comparative restriction maps of pCW3, pJIR2, and pJIR4 that identified the regions of homology among these plasmids were constructed. We suggest that many conjugative tetracycline resistance plasmids in C. perfringens may contain a pCW3-like core.     

Trends in phytoremediation of radionuclides

Phytoremediation, a novel plant-based remediation technology, is applied to a variety of radionuclide-contaminated sites all over the world. Phytoremediation is defined as the use of green plants to remove pollutants from the environment or to render them harmless. Current status of several subsets of phytoremediation of radionuclides is discussed: (a) phytoextraction, in which high biomass radionuclide-accumulating plants and appropriate soil amendments are used to transport and concentrate radionuclides from the soil into the above-ground shoots, which are harvested with conventional agricultural methods, (b) rhizofiltration, in which plant roots are used to precipitate and concentrate radionuclides from polluted effluents, (c) phytovolatilization, in which plants extract volatile radionuclides from soil and volatilize them from the foliage and (d) phytostabilization, in which plants stabilize radionuclides in soils, thus rendering them harmless. It is shown that phytoremediation is a fast developing field and the phytoremediation of radionuclides might soon become an integral part of the environment management and risk reduction process.     

Additional non-avian theropod and bird remains from the early Late Cretaceous (Santonian) of Hungary and a review of the European abelisauroid record

Hitherto unpublished remains of non-avian and avian theropods from the Late Cretaceous (Formation Csehbánya, Santonian) Iharkút locality (western Hungary) are described. Non-avian theropod remains include an abelisaurid femur, which confirms the presence of this theropod family at Iharkút, and a metacarpal and a tibiotarsus from a paravian which may belong to Pneumatoraptor fodori, previously described from Iharkút. Birds are represented by two femora which clearly belong to enantiornithines, possibly to Bauxitornis, previously described from Iharkút. The abelisauroid record from the Cretaceous of Europe is reviewed.     

Rotavirus antibodies in hanuman langurs (Presbytis entellus)

Serum samples from wild Hanuman langurs (Presbytis entellus) from Mysore State, India, were compared to samples from a laboratory colony from Davis, Calif., for antibodies to rotavirus, which is an important cause of gastroenteritis in mammals. Animals from the laboratory colony had a higher frequency and higher levels of antibody than wild animals. It is likely that wild populations of langurs have a much lower incidence of rotaviral infection than laboratory populations, which are exposed to both crowded conditions and rotaviruses from other species.     

Genotypes Suppressing Meiotic Drive of a B Chromosome in the Mealybug, PSEUDOCOCCUS OBSCURUS

The rate of transmission (k) of a supernumerary B chromosome in male mealybugs is shown to depend strongly on the chromosome set of maternal origin. When both parents came from an isofemale line in which the frequency of the B chromosome increased rapidly and stabilized at a mean of more than 4.0 B chromosomes per individual, k was 0.92 and 0.95 in two series of crosses. However, when the female parent came from one of two isofemale lines in which the frequency of the B chromosome decreased from 2.0 to 0 in a few generations, k ranged from 0.53 to 0.78. The high ks, which represent a strong meiotic drive, are apparently responsible for the observed increase in the frequency of the B chromosome in several lines from a mean of about 0.5 to more than 4.0 in about 20 generations. The rapid loss of the B chromosome in other lines is attributed to genetic factors which caused the reduction in the rate of transmission of the B chromosome.     

Experiments on resting site selection by the typical and melanic forms of the moth, Allophyes oxyacanthae (Caradrinidae)

Six families of the cryptic moth, Allophyes oxyucanthae , four of which contained both the typical and melanic forms of this polymorphic species, were tested for evidence of resting site selection in a large box lined with oak bark of three reflectances. Moths from different families were tested separately. Typicals from all four families tended to show a preference for the background which most closely matched their reflectance and on which they were most cryptic. Melanic moths from different families showed different resting site selection behaviour; those from two families preferring dark bark, on which melanics were most cryptic, while those from other families did not. The significance of these results in relation to previous suggestions about the control of resting site selection is discussed     

Evidence that the Bacteroides thetaiotaomicron chondroitin lyase II gene is adjacent to the chondro-4-sulfatase gene and may be part of the same operon.

The chondroitin lyase II gene from Bacteroides thetaiotaomicron has previously been cloned in Escherichia coli on a 7.8-kilobase (kb) fragment (pA818). In E. coli, the chondroitin lyase II gene appeared to be expressed from a promoter that was about 0.5 kb from the beginning of the gene. However, when a subcloned 5-kb fragment from pA818 which contained the chondroitin lyase II gene and the promoter from which the gene is expressed in E. coli was introduced into B. thetaiotaomicron on a multicopy plasmid (pEG800), the chondroitin lyase specific activity of B. thetaiotaomicron was not altered. Further evidence that the promoter that is recognized in E. coli may not be the promoter from which the chondroitin lyase II gene is transcribed in B. thetaiotaomicron was obtained by making an insertion in the B. thetaiotaomicron chromosome at a point which is 1 kb upstream from the chondroitin lyase II gene. This insertion stopped synthesis of the chondroitin lyase II gene product, as would be predicted if the gene was part of an operon and was transcribed in B. thetaiotaomicron from a promoter that was at least 1 kb upstream from the chondroitin lyase II gene. A region of pA818 which was adjacent to the chondroitin lyase II gene and which included the region used to make the insertional mutation was found to code for chondro-4-sulfatase, an enzyme that breaks down one of the products of the chondroitin lyase reaction. The upstream insertion mutant of B. thetaiotaomicron which stopped synthesis of chondroitin lyase II had no detectable chondro-4-sulfatase activity. This mutant was still able to grow on chondroitin sulfate, although the rate of growth was slower than that of the wild type.     

Evolution of protein complexity: The blue copper-containing oxidases and related proteins

Summary The blue copper proteins and their relatives have been compared by sequence alignments, by comparison of three-dimensional structures, and by construction of phylogenetic trees. The group contains proteins varying in size from 100 residues to over 2,300 residues in a single chain, containing from zero to nine copper atoms, and with a broad variation in function ranging from electron carrier proteins and oxidases to the blood coagulation factors V and VIII. Difference matrices show the sequence difference to be over 90% for many pairs in the group, yet alignment scores and other evidence suggest that they all evolved from a common ancestor. We have attempted to delineate how this evolution took place and in particular to define the mechanisms by which these proteins acquired an ever-increasing complexity in structure and function. We find evidence for six such mechanisms in this group of proteins: domain enlargement, in which a single domain increases in size from about 100 residues up to 210; domain duplication, which allows for a size increase from about 170 to about 1,000 residues; segment elongation, in which a small segment undergoes multiple successive duplications that can increase the chain size 50-fold; domain recruitment, in which a domain coded elsewhere in the genome is added on to the peptide chain; subunit formation, to form multisubunit proteins; and glycosylation, which in some cases doubles the size of the protein molecule. Size increase allows for the evolution of new catalytic properties, in particular the oxidase function, and for the formation of coagulation factors with multiple interaction sites and regulatory properties. The blood coagulation system is examined as an example in which a system of interacting proteins evolved by successive duplications of larger parts of the genome. The evolution of size, functionality, and diversity is compared with the general question of increase in size and complexity in biology.     

Repair replication of DNA in the intact animal following treatment with dimethylnitrosamine and with methyl methanesulphonate, studied by fractionation of nuclei in a zonal centrifuge.

To relate repair of lesions in DNA with carcinogenesis, it is necessary to study repair in the intact animal under conditions which will and will not induce cancer. The methods used to study the replications stage of repair in isolated cells are not suitable for use in the intact animal. A method is presented which depends on the fact that during cell replication the nuclei enlarge, and may be separated from nuclei of non-replicating cells by rate zonal centrifugation on a sucrose gradient in a zonal rotor. Thus incorporation of [3H]thymidine as a result of de novo synthesis of DNA in replicating nuclei can be separated from incorporation due to repair synthesis in non-replicating nuclei. Treatment of animals with dimethylnitrosamine or with methyl methanesulphonate produced a "repair-type" profile, which contrasted with that given by liver nuclei from untreated animals, or from animals in which DNA synthesis had been reduced by treatment with cycloheximide, a compound which is not known to cause direct damage to DNA. Evidence is presented which suggests that the method is a rapid sensitive test for the occurrence of repair replication of some kind in the liver of the intact animal.     

Assisted assignment of ligands corresponding to unknown electron density

A semi-automated computational procedure to assist in the identification of bound ligands from unknown electron density has been developed. The atomic surface surrounding the density blob is compared to a library of three-dimensional ligand binding surfaces extracted from the Protein Data Bank (PDB). Ligands corresponding to surfaces which share physicochemical texture and geometric shape similarities are considered for assignment. The method is benchmarked against a set of well represented ligands from the PDB, in which we show that we can identify the correct ligand based on the corresponding binding surface. Finally, we apply the method during model building and refinement stages from structural genomics targets in which unknown density blobs were discovered. A semi-automated computational method is described which aims to assist crystallographers with assigning the identity of a ligand corresponding to unknown electron density. Using shape and physicochemical similarity assessments between the protein surface surrounding the density and a database of known ligand binding surfaces, a plausible list of candidate ligands are identified for consideration. The method is validated against highly observed ligands from the Protein Data Bank and results are shown from its use in a high-throughput structural genomics pipeline.     

The inactivation of tet genes on a plasmid by the duplication of one inverted repeat of a transposon-like structure which itself mediates tetracycline resistance

Derivatives of a naturally occurring IncFII tetracycline resistance plasmid (pUB889) which are unable to confer resistance to tetracycline, and which were isolated from both partners of a married couple, have been examined. The tet genes are part of a transposon-like structure which is closely related to, but distinct from, Tn10. The lesions in the two plasmids examined are identical and involve the insertion of a nucleotide sequence of 0.9 × 10⁶ within the region encoding tetracycline resistance, expression of which is lost as a consequence. The extra DNA is homologous with the nucleotide sequence, a pair of which form the inverted repeats of the Tn10-like structure. We conclude that this nucleotide sequence comprises an IS element. The epidemiological implications arising from the origin of these plasmids are discussed.     

Form,function and evolution of the mouthparts of blood-feeding Arthropoda

This review compares the mouthparts and their modes of operation in blood-feeding Arthropoda which have medical relevance to humans. All possess piercing blood-sucking proboscides which exhibit thin stylet-shaped structures to puncture the host's skin. The tips of the piercing structures are serrated to provide anchorage. Usually, the piercing organs are enveloped by a soft sheath-like part which is not inserted. The piercing process includes either back and forth movements of the piercing structures, or sideways cutting motions, or the apex of the proboscis bears teeth-like structures which execute drilling movements. Most piercing-proboscides have a food-canal which is separate from a salivary canal. The food-canal is functionally connected to a suction pump in the head that transports blood into the alimentary tract. The salivary canal conducts saliva to the tip of the proboscis, from where it is discharged into the host. Piercing blood-sucking proboscides evolved either from (1) generalized biting-chewing mouthparts, (2) from piercing mouthparts of predators, or plant sap or seed feeders, (3) from lapping or sponging mouthparts. Representatives of one taxon of Acari liquefy skin tissue by enzymatic action. During feeding, many blood-feeding arthropods inadvertently transmit pathogens, which mostly are transported through the discharged saliva into the host.     

Quantitative flow dichroism. I. Correction for disorientation in a solution of rods

Flow dichroism suffers from two ambiguities which have prevented it from being a useful analytical technique. One is imperfect particle orientation, and the other is the unknown importance of form dichroism. This paper presents a method for calculating from experimental data the dichroism which would be observed from a solution in which all rods were aligned parallel to one another. The procedure utilizes anisotropic light scattering as an independent measure of particle orientation and requires only that the solute particles may be approximated by thin rods.     

Assembly of SV40 chromatin in a cell-free system from Xenopus eggs.

A cell-free system is described which assembles chromatin from purified DNA in 1 hr under physiological incubation conditions. It consists of a 145,000 x g (maximum) supernatant fraction from eggs of Xenopus laevis. It converts SV40 DNA to a nucleoprotein which co-sediments with naturally occurring SV40 chromatin and which can be cleaved by micrococcal nuclease to a highly ordered pattern of DNA fragments resembling those from digestion of liver chromatin. It inserts superhelical turns into relaxed, covalently closed DNA. The assembly process is not cooperative. Under limiting conditions, each DNA molecule becomes partially assembled. Assembly does not require replication of the DNA or protein synthesis, but occurs from a stored histone pool of at least 40 ng per egg. Under conditions of DNA excess, assembly becomes dependent upon the amount of exogenous histones added to the incubation. Apart from histones and a nicking-closing activity, chromatin assembly requires an additonal thermolabile factor which is present in the egg supernatant.