TheRhizobium-legume symbiosis Two methods to discriminate between nodules and other root-derived structures

Summary Two methods have been developed in order to discriminate between lateral roots, nodules and root-derived structures which exhibit both root and nodule histological features and which can develop on legumes inoculated with certainRhizobium mutants. The first method, known as the clearing method, allows the observation by light microscopy of cleared undissected root-structures. The second, known as the slicing method, is a complementary technique which provides a greater degree of structural information concerning such structures. The two methods have proved invaluable in defining unequivocally the nature of the interaction between a rhizobial strain and a legume host.     

A ten-month study of endogenous testosterone levels and behaviour in outdoor-living female rhesus monkeys (Macaca mulatta)

Endogenous testosterone levels were measured in association with sexual, aggressive, and social/affiliative behaviors in 11 outdoor-housed female rhesus monkeys over a ten-month period. Several behaviors (sex directed toward the male, sex received from the male, aggression directed toward the male, submission directed toward the male, submission directed toward the female, and groom another female) were significantly (p<0.05) positively correlated with testosterone in from one to five females. No trends were strong enough across all females to suggest that any of these correlations have species-wide significance. Factor analysis revealed clearcut clusters of behaviors, but elevations in testosterone were not strongly associated with any of these clusters. It is concluded that endogenous testosterone levels have little measurable effect on overt behavior in female rhesus monkeys.     

DNA polymorphism in Allium cepa cytoplasms and its implications concerning the origin of onions

Summary Mitochondrial and chloroplast DNA was isolated from fertile and cytoplasmic male sterile cultivars of cultivated onions. Restriction fragment length polymorphism led to the distinction between cytoplasms S and M. Mitochondrial DNA patterns from S cytoplasms appeared dentical and characterized mostly male sterile lines. An open-pollinated variety was found to bear this cytoplasm and thought to be the origin of S types. Mitochondrial DNA patterns from M cytoplasms were subdivided into four types, M₁ and M₂ corresponding to normal N cytoplasm, M₃ and M₄ probably corresponding to T cytoplasms. S and M cytoplasms were also distinguished by chloroplast DNA restriction patterns. Our results confirm previous genetic distinction between S, N and T cytoplasms.     

Tomato resistance to Alternaria stem canker: localization in host genotypes and functional expression compared to non-host resistance

Summary The Alternaria stem canker resistance locus (Asc-locus), involved in resistance to the fungal pathogen Alternaria alternata f. sp. lycopersici and in insensitivity to host-specific toxins (AAL-toxins) produced by the pathogen, was genetically mapped on the tomato genome. Susceptibility and resistance were assayed by testing a segregating F₂ population for sensitivity to AAL-toxins in leaf bioassays. Linkage was observed to phenotypic markers solanifolium and sunny, both on chromosome 3. For the Asc-locus, a distance of 18 centiMorgan to solanifolium was calculated, corresponding to position 93 on chromosome 3. This map position of the resistance locus turned out to be the same in three different resistant tomato accessions, one Dutch and two American, that are at least 40 years apart. AAL-toxin sensitivity in susceptible and resistant tomato genotypes was compared with AAL-toxin sensitivity in a non-host Nicotiana tabacum during different levels of plant cell development. In susceptible and resistant tomato genotypes, inhibitory effects were demonstrated at all levels, except for leaves of resistant genotypes. However, during pollen and root development, inhibitory effects on susceptible genotypes were larger than on resistant genotypes. In the non-host Nicotiana tabacum, hardly any effects of AAL-toxins were demonstrated. Apparently, a cellular target site is present in tomato, but not in Nicotiana tabacum. It was concluded that three levels of AAL-toxin sensitivity exist: (1) a susceptible host sensitivity, (2) a resistant host sensitivity, (3) a non-host sensitivity, and that the resistance mechanism operating in tomato is different from that operating in Nicotiana tabacum.     

Observations on the lungworm, Pneumostrongylus calcaratus, in impala (Aepyceros melampus) from Swaziland

The lungworm, Pneumostrongylus calcaratus, was found in 85% (164 of 193) of impala (Aepyceros melampus) collected in Mlawula Nature Reserve in Swaziland. Infection was confirmed at 4.5 mo of age, and the prevalence increased to 100% at 11 mo, with a prevalence of 98% in animals greater than 1 yr of age. Pneumostrongylus calcaratus was usually found in firm, tangrey nodules along the lobar borders of the lungs, although an extensive granulomatous pneumonia with miliary caseous abscesses and calcified nodules was observed in some older animals. In the primary infection in lambs, adult parasites, larvae and eggs were observed in the alveoli and bronchioles within the nodule. There was peribronchial and perivascular mononuclear cuffing, with infiltration of mononuclear cells in the alveolar septum in the vicinity of worms. In lesions in older animals, there was local consolidation with macrophages and giant cells, and foci of parenchymal necrosis associated with degenerating eosinophils, which appeared to lead to the formation of eosinophilic granulomas. Resolving lesions caused interstitial fibrosis, with mineralized nodules. Pneumostrongylosis does not appear to pose a significant threat to the health of impala in Swaziland.     

A division inhibitor and a topological specificity factor coded for by the minicell locus determine proper placement of the division septum in E. coli

The E. coli minicell locus (minB) was shown to code for three gene products (MinC, MinD, and MinE) whose coordinate action is required for proper placement of the division spetum. Studies of the phenotypic effects of expression of the three genes, alone and in all possible combinations, indicated the following: cell poles contain potential division sites that will support additional septation events unless specifically inactivated; the minC and minD gene products act in concert to form a nonspecific inhibitor of septation that is capable of blocking cell division at all potential division sites; and the minE gene codes for a topological specificity factor that, in wild-type cells, prevents the division inhibitor from acting at internal division sites while permitting it to block septation at polar sites.     

Effects of GnRH on superovulated cattle

Gonadotropin releasing hormone (GnRH) was given to 109 cows and heifers during the course of 224 superovulations. Follicle stimulating hormone (FSH) was administered twice daily (5 or 6 mg) for 3.5 to 4 days beginning on any of Days 9 to 14 of the estrous cycle; prostaglandin (45 mg PGF(2)alpha or 750 ug cloprostenol) was given in a split dose on the fourth day. Donor cows and heifers were placed into four groups according to previous superovulation treatments, which consisted of one to three treatments or of no previous treatment. Every other cow or heifer within each of the four subgroups was treated with GnRH (200 mug i.m.) at standing estrus. Only donors that exhibited estrus within 32 to 72 h after the first prostaglandin treatment were used in the study. Animals were inseminated artificially 12 and 24 h after standing estrus was first observed. No differences were noted in the number of ovulations, total ova or transferable embryos recovered from the GnRH or control groups; however, two interactions were detected. Cows given GnRH had fewer palpable corpora lutea than control cows (P < 0.05), but this difference was not seen in heifers. The second interaction was that GnRH seemed to depress ovulation rate in donors not previously superovulated, but this effect was not observed with subsequent superovulations. Cows yielded more total ova than heifers (P < 0.01). There was no difference in return to estrus between GnRH and control groups after a second prostaglandin treatment at the time of embryo recovery. Most donors within each group resumed cycling between 5 and 12 d after embryo recovery.     

The association of H-2Ld with human beta-2 microglobulin induces localized conformational changes in the alpha-1 and- 2 superdomain

We have analyzed changes in the antigenicity of major histocompatibility complex class I molecules resulting from the association of human beta-2 micro-globulin (B2m) with the mouse class I heavy chain. In particular, the H-2L^d molecule exhibited enhanced crossreactivity for the 34-1-2 monoclonal antibody. In order to assess the nature of this structural alteration induced by human B2m, we utilized H-2 class I hybrid molecules in the mapping of the 34-1-2 determinant to the helical region of the alpha-1 domain. H-2L^d class I hybrid molecules were then used to establish the importance of the alpha-2 and- 3 domains in the observed increase of 34-1-2 cross-reactivity following exchange with human B2m. The H-2L^d hybrids suggest that alterations in interdomain contact are responsible for enhanced 34-1-2 cross-reactivity on the H-2L^d molecule. It is likely that this alteration arises through changes in class I conformation at regions of the molecule distant from points of contact between B2m and the class I molecule. This suggests that perturbations induced by association of human B2m with H-2L^d can affect the conformation of the alpha-1 and- 2 superdomain. That class I antigenic determinants are altered by the association of human B2m with mouse class I further suggests that the class I molecule is structurally flexible and may reflect the ability of the class I molecule to bind and present a vast array of disparate peptides to the T-cell receptor.     

Analysis of the HLA-A10-crossreacting group of antigens by one-dimensional isoelectric focusing

The antigens belonging to the HLA-A10 group, HLA-A25, -A26, -Aw34, and -Aw66, have been characterized serologically during the International Histocompatibility Workshops. However, it remains difficult to discriminate between the HLA-A26 antigen on the one hand and the HLA-Aw34 and -Aw66 antigens on the other on the basis of serology. In this paper, we compare the serologically defined antigens with the data obtained by one-dimensional isoelectric focusing. The results indicate that the serologically well-defined HLA-A25 antigen cannot be discriminated from the HLA-A26 antigen by one-dimensional isoelectric focusing. In contrast, this technique can indeed be used to discriminate between HLA-A26, -Aw34 and -Aw66 antigens. In addition, the biochemical analysis suggests further heterogeneity of the HLA-Aw34 antigen. This antigen can be subdivided into three variants.