Cluster analysis as a method for evaluation of genetic similarity in specific host — parasite interaction (Lactuca sativa — Bremia lactucae)

Summary In gene-for-gene systems, specificity of hostparasite interactions is most often estimated qualitatively using the symbols +, –, (i.e. susceptibility and/or resistance). In large sets (interaction patterns) it becomes impossible to analyze numerous data by mere comparison. This is overcome by application of cluster analysis. In our experiments the methods in question were used to estimate the data obtained in a study on interactions between more than 220 Lactuca sativa cultivars and 12 Bremia lactucae physiological races (isolates) of Czechoslovak origin. The matrix of similarity coefficients was analyzed by hierarchical clustering. Similarity and/or dissimilarity of host R-genotypes was graphically expressed using the method of two principal components. The results obtained are related to genetic constitution of race specific resistance of the host and the possibility of predicting effective resistance sources.     

Patch-clamp study of isolated taste receptor cells of the frog

Summary Taste discs were dissected from the tongue ofR. ridibunda and their cells dissociated by a collagenase/low Ca/mechanical agitation protocol. The resulting cell suspension contained globular epithelial cells and, in smaller number, taste receptor cells. These were identified by staining properties and by their preserved apical process, the tip of which often remained attached to an epithelial (associated) cell. When the patch pipette contained 110mm KCl and the cells were superfused with NaCl Ringer's during whole-cell recording, the mean zero-current potential of 22 taste receptor cells was –65.2 mV and the slope resistance 150 to 750 M. Pulse-depolarization from a holding voltage of –80 mV activated a transient TTX-blockable inward Na current. Activation became noticeable at –25 mV and was half-maximal at –8 mV. Steady-state inactivation was half-maximal at –67 mV and complete at –50 mV. Peak Na current averaged –0.5 nA/cell. The Ca-ionophore A23187 shifted the activation and inactivation curve to more negative voltages. Similar shifts occurred when the pipette Ca was raised. External Ni (5mm) shifted the activation curve towards positive voltages by 10 mV. Pulse depolarization also activated outward K currents. Activation was slower than that of Na current and inactivation slower still. External TEA (7.5mm) and 4-aminopyridine (1mm) did not block, but 5mm Ba blocked the K currents. K-tail currents were seen on termination of depolarizing voltage pulses. A23187 shifted theI _K(V)-curve to more negative voltages. Action potentials were recorded when passing pulses of depolarizing outward current. Of the frog gustatory stimulants, 10mm Ca caused a reversible 5-to 10-mV depolarization in the current-clamp mode. Quinine (0.1mm, bitter) produced a reversible depolarization accompanied by a full block of Na current and, with slower time-course, a partial block of K currents. Cyclic AMP (5mm in the external solution or 0.5 m in the pipette) caused reversible depolarization (to –40 to –20 mV) due to partial blockage of K currents, but only if ATP was added to the pipette solution. Similar responses were elicited by stimulating the adenylate cyclase with forskolin. Blockage of cAMP-phosphodiesterase enhanced the response to cAMP. These results suggest that cAMP may be one of the cytosolic messengers in taste receptor cells. Replacement of ATP by AMP-PNP in the pipette abolished the depolarizing response to cAMP. Inclusion of ATP--S in the pipette caused slow depolarization to –40 to –20 mV, due to partial blockage of K currents. Subsequently, cAMP was without effect. The remaining K currents were blockable by Ba. These results suggest that cAMP initiates phosphorylation of one set of K channels to a nonconducting conformation.     

Multiple forms of male-specific simple repetitive sequences in the genusMus

Summary Previous reports indicate that in laboratory strains of mice, males are distinct from females in possession of repetitive DNA, notably devoid of Eco RI and Hae III sites and rich in the simple tetranucleotides GATA/GACA. We report here that such sequences originated in an ancestor common to laboratory mice,Mus hortulanus, M. spretus, and possibly alsoM. cookii. Interestingly, other male-specific satellite sequences were detected inM. caroli, M. cookii, M. saxicola, andM. minutoides. This novel satellite is also likely to be composed of simple repetitious sequences, but does not contain GATA and GACA. Thus, the Y chromosome appears to contain a disproportionately large amount of simple repetitious DNA. An attractive explanation for these results is that long tandem arrays of simple repeated sequences are generated at high frequency throughout the genome and that they are retained for a longer time on the Y chromosome due to the absence of homologous pairing at meiosis.     

墨红鲜花香气(头香)成分分析

利用 XAD-4憎水性吸附树脂采集墨红头香,以毛细管气相色谱双柱保留指数和 GC/MS/DS 联用方法鉴定头香的化学成份。共分离鉴定或初步鉴定了45种组份,其中含量较大的有乙酸芳樟酯(14.98%),柠檬烯(12.07%),甲基苯甲醚(9.88%),香茅醇(4.82%),乙酸巳酯(3.98%),β-石竹烯(4.55%),芳樟醇(3.18%),正巳醇(3.17%)等.     

Behavioral changes of a juvenile gorilla after a transfer to a more naturalistic environment

Play behavior and stress-associated behavior of a captive juvenile gorilla were observed before and after his transfer to a larger and more natural environment. The gorilla was observed for 4 months after the transfer and at 1 and 4 years after the transfer. Throughout his first month in the new environment play decreased dramatically. Although play subsequently increased again 2 months and 1 year after the transfer, it never reached the levels of play in the old environment. Four years after the move his play had decreased again to the low level of his first month in the new environment. Two of his stress-associated behaviors, coprophagy and regurgitation/reingestion, decreased after the transfer. Self-clasping behavior increased initially in the new environment and remained at high levels 1 year after the move. Four years after the move his self-clasping behavior was significantly less than at 1 year after the move; however, it continued to be significantly greater than in the old environment. These findings suggest that larger and more natural environments do not necessarily result in more play activity or a reduction in all stress-associated behavior.     

Fertile heteroallelic combinations of mutant alleles of the otu locus of Drosophila melanogaster

Summary This paper describes the ovarian pathologies observed when 108 different heteroallelic combinations were made involving 17 independent mutations at the ovarian tumor (otu) locus. Most of the mutant phenotypes can be explained as graded responses by individual germ cells to different levels of functionally active otu gene product (OGP) synthesized by the mutant cells themselves. The lowest and highest levels of OGP appear to be produced by otu ¹⁰ and otu ¹⁴, respectively. In most heteroallelic ovaries the alleles have additive effects, and hybrid germ cells reach a developmental stage more advanced than the weaker homozygote but less advanced than the stronger homozygote. However, examples of both positive and negative complementation also have been found, and these suggest that the products encoded by different mutant alleles can combine to form dimers or multimers which may be superior or inferior to the homodimers. In flies homozygous for otu ¹¹ most ovarioles contain tumors, but some germ cells are able to develop further than those in otu ¹⁴ homozygotes. This suggests that, while otu ¹¹ produces intermediate levels of OGP, it also produces a second product (which otu ¹⁴ cannot make) that is utilized at the period in oogenesis when development in cells homozygous for otu ¹⁴ is blocked. When otu ¹¹ is combined with any one of eight specific alleles, it allows oocyte/nurse cell syncytia to differentiate that can complete development and undergo embryogenesis, if fertilized. The endopolyploid nurse cells of these hybrids have giant polytene chromosomes, and the presence of GPCs in functionally active, germ-line derived cells provides an interesting new system for experimental study. Analysis of the characteristic ovarian pathologies produced by flies of different genotypes leads to the conclusion that the products of the otu ⁺ gene are utilized during at least six different periods in Drosophila oogenesis.     

Selection of Lactobacillus acidophilus strains for use in “acidophilus products”

Recent studies by DNA-DNA hybridization revealed that strains now designated as L. acidophilus, can be divided into several groups and only one group should be classified as L. acidophilus. We studied several phenotypic characteristics in representative strains from the six DNA-homology groups of L. acidophilus. No group specific pattern was observed among the strains for fermentation of eight carbohydrates, growth at 15 and 45°C, resistance to 0.2% oxgall, lysis by lysozyme or sensitivity to 17 antibiotics. However, some differences among groups were observed in -galactosidase (-gal) activity and surface layer (s-layer) protein. Strains in B1 do not have a s-layer or -gal while B2 strains also lack a s-layer but do possess -gal. All strains in groups A1, A2, A3 and A4, capable of growing in lactose, have -gal activity and also have a s-layer composed of protein subunits of different molecular weights (MW). Strains in A1 homology group have a s-layer with 46 Kd protein subunits while strains in other A groups have s-layer protein subunits that varied in MW within each group. On the basis of these two traits several isolates of unknown homology groups have been tentatively placed in A1, B1 or B2 groups. L. acidophilus from A1 group showed strain variation in -gal specific activity and rate of acid production and growth. For use in dietary adjuncts, L. acidophilus strains should be selected for these three and other desirable traits. They should be maintained and grown in media containing lactose.     

A gene (Bmn) controllingβ-mannosidase activity in the mouse is located in the distal part of chromosome 3

A gene (Bmn) with a major effect on -mannosidase activity in kidney and liver of the house mouse was revealed by assay with the synthetic substratep-nitrophenyl--d-mannoside. Activity is low in DBA/2J and CSB mice and high in C57BL/6J mice. By the use of the BXD series of recombinant inbred strains and by crosses between C57BL and CSB, it was possible to map the gene to the distal part of chromosome 3 by demonstration of linkage to a gene for cadmium resistance,cdm, as well as to theAdh-3 locus.This work was supported by Swedish Natural Science Research Council Project B-BU 2992-108.     

Abnormal subcellular distribution of β-glucuronidase in mice with a genetic alteration in enzyme structure

Liver -glucuronidase is structurally altered in inbred strain PAC so that a peptide subunit with a more basic isoelectric point, GUS-SN, is produced. This allele of -glucuronidase was transferred to strain C57BL/6J by 12 backcross matings to form the congenic line B6 · PAC-Gus ⁿ. Liver -glucuronidase activity was halved in males of the congenic strain compared to normal males. The lowered activity was specifically accounted for by a decrease in the lysosomal component. There was no alteration in the concentration of microsomal activity. This alteration in the subcellular distribution of -glucuronidase in Gus ⁿ/Gus ⁿ mice was confirmed by two independent gel electrophoretic systems which separate microsomal and lysosomal components. -Glucuronidase activity was likewise approximately halved in mutant spleen, lung, and brain, organs which contain exclusively or predominantly lysosomal -glucuronidase. The loss of liver lysosomal -glucuronidase activity was shown by immunotitration to be due to a decrease in the number of -glucuronidase molecules in lysosomes of the congenic strain. The Gus ⁿ structural alteration likely causes the lowered lysosomal -glucuronidase activity since the two traits remain in congenic animals. Heterozygous Gus ⁿ/Gus ^b animals had intermediate levels of liver -glucuronidase. Also, the effect was specific, in that three other lysosomal enzymes were not reproducibly lower in Gus ⁿ/Gus ⁿ mice. Gus ⁿ is, therefore, an unusual example of a mutation which causes a change in the subcellular distribution of a two-site enzyme.This work was supported by National Institutes of Health Grants GM-33559 and GM-33160 and National Science Foundation Grant PCM-8215808.     

Structure and function relationship of staphylocoagulase

The bacterial protein staphylocoagulase binds stoichiometrically to human prothrombin, resulting in a coagulant complex, staphylothrombin. The enzymatic properties of staphylothrombin differ from those of -thrombin in their substrate specificities toward natural and synthetic substrates, in addition to their interaction with protease inhibitors. In order to obtain information about the region of staphylocoagulase that interacts with human prothrombin, staphylocoagulase was cleaved by -chymotrypsin. Limited -chymotryptic cleavage of staphylocoagulase yielded three large fragments, of 43, 30, and 20 kD. The 43-kD fragment exhibited a high affinity for human prothrombin (K_d=1.7 nM), which is comparable to the affinity observed using intact staphylocoagulase (K_d=0.46 nM). A complex of the 43-kD fragment and prothrombin possessed both clotting and amidase activity essentially identical to that observed in a complex of intact staphylocoagulase and prothrombin. The 30-kD fragment exhibited weaker affinity for prothrombin (K_d=120 nM.) While clotting activity was not observed with a complex of this fragment and prothrombin, it nonetheless possessed a weak amidase activity. The 20-kD fragment was found only to bind to prothrombin. The NH₂-terminal sequence analyses of these fragments revealed that the 43-kD fragment constitutes the NH₂-terminal portion of staphylocoagulase, and contains the 30-kD and 20-kD fragments. It is therefore concluded that the functional region of staphylocoagulase for binding and activation of prothrombin is localized in the NH₂-terminal region of the intact protein. The 43-kD fragment contained 324 amino acids with a molecular weight of 38,098. The 43-kD fragment had an unusual amino acid composition based on a sequence in which the sum of Asp (28 residues), Asn (22), Glu (35), Gln (9), and Lys (52) residues accounted for more than 45% of the total. A comparison of the amino acid sequence of the 43-kD fragment with that of streptokinase did not reveal any obvious sequence homology. There was also no sequence homology with that of trypsin, -chymotrypsin, and elastase.This article was presented during the proceedings of the International Conference on Macromolecular Structure and Function, held at the National Defence Medical College, Tokorozawa, Japan, December 1985.