Mortality and age differences in marriage.

Data from the 1971 census population were used to evaluate the effects of age differences of married partners on mortality rates. Different age groups were isolated to highlight the association between mortality and age of spouse for specific ages of married men and women. Men married to much younger or to older women exhibited a higher mortality rate than men married to women who were only a few years younger than themselves. A similar trend was observed among women married to much younger or much older men compared with those whose spouses were a few years older or of similar ages as themselves. Trends for other age groups (women aged 60-69 years, men below 40, and women below 30) did not exhibit a clear pattern. Although statistical biases within age groups may in part account for the differences in the findings, the trend which emerged from the analysis suggests that lower morbidity is associated with the most common age combinations (husbands same age or slightly older than wives). Other factors could also account for the differences (e.g., selection of healthy partners in 1st marriages, differences in lifestyles between married and single).     

Insect grazing on Eucalyptus in response to variation in leaf tannins and nitrogen

Summary Many species of Eucalyptus, one of the dominant genera in Australian forests and woodlands, contain high levels of tannins and other phenols and are also heavily damaged by grazing insects. These phenols do not appear to affect insect attack because a wide range of concentrations of condensed tannins and other phenols in leaves of 13 Eucalyptus sp. influenced neither feeding rates of Paropsis atomaria larvae, nor their nitrogen use efficiencies. We discuss reasons why tannins may not appreciably reduce the availability of nitrogen (N) to these insects. Performance was directly related to leaf N concentration, and growth rates, N gains, and N use efficiencies all increased as leaf N content increased, although absolute feeding rates remained constant. These relationships differ from those found in insects feeding on other plants, and we suggest that the low N contents common in Eucalyptus leaves may be responsble. We propose that the extensive damage observed in many eucalypts is in part related to the high feeding rates maintained by individual larvae.To whom offprint requests shouid be sent     

Preliminary observations on different reproduction strategies in the bullhead (Cottus gobio L.) in northern and southern England

The size distribution and numbers of oocytes were examined in samples of ovaries from two sites and in fish in tanks whose past spawning activities were known. In an upland stream in northern England Cottus gobio would seem to be an annual spawner, maturing a single batch of eggs each year. In a more productive stream in southern England, where the reproductive life is short, fish mature and lay a succession of batches of eggs during a long spawning season. The physiological and ecological implications of these characteristics are discussed.     

Phytanyl-glycerol ethers and squalenes in the archaebacteriumMethanobacterium thermoautotrophicum

Summary The lipids of a thermophilic chemolithotroph,Metbanobacterium thermoautotropbicum, have been analyzed by chromatographic techniques and identified by infrared spectrometry and combined gas chromatography-mass spectrometry. Of the total chloroform soluble lipids 79% and 21% are polar and non-polar lipids, respectively. The major components of the polar lipids are dialkyl ethers of glycerol or its derivatives. The nature of the glycerol ether alkyl groups was found to be that of the saturated tetraisoprenoid hydrocarbon phytane. The non-polar lipids of the chloroform soluble fraction consist principally of three series of C₂₀, C₂₅ and C₃₀ acyclic isoprenoid hydrocarbons, the major components being squalene and a continuous range of hydrosqualene derivatives, from dihydrosqualene up to and including decahydrosqualene. These data establish thatM. tbermoautotropbicum contains predominantly non-sapo-nifiable lipids as doHalobacterium, Halococcus, Sulfolobus andTbermoplasma. In particular, the composition of the chloroform soluble lipids ofM. tbermoautotropbicum is quite similar to that ofHalobacterium cutirubrum. The results strongly support the recent proposal, based on 16S rRNA sequence homologies, that the extreme halophiles and methanogens share a common ancestor. In addition, it is pointed out that the occurrence of phytane and related polyisoprenoid compounds in ancient sediments can no longer be considered unequivocally as indicative of past photosynthetic activity. Finally, speculations are made concerning the possible role of and evolutionary significance of the presence of squalene and hydrosqualenes in these organisms. To our knowledge this is the first report of squalene and hydrosqualenes in a strictly anaerobic microorganism.To either of whom reprint requests should be sent.     

Adenosine metabolism: Modification by S-adenosylhomocysteine and 5′-methylthioadenosine

To elucidate potential toxic properties of S-adenosylhomocysteine and 5′-methylthioadenosine, we have examined the inhibitory properties of these compounds upon enzymes involved with adenosine metabolism. S-Adenosylhomocysteine, but not S-adenosylmethionine, was a noncompetitive inhibitor of adenosine kinase with K_i values ranging from 100 to 400 μm. Methylthioadenosine competitively inhibited adenosine kinase with variable adenosine below 1 μm with a K_i of 120 μm, increased adenosine kinase activity when the adenosine concentration exceeded 2 μm, and did not appear to be a substrate for adenosine kinase. Methylthioadenosine inactivated S-adenosylhomocysteine hydrolase from erythrocytes, B-lymphoblasts, and T-lymphoblasts with K_i values ranging from 65 to 117 μm and “k₂” from 0.30 to 0.55 min^?1. Adenosine deaminase was not inhibited by 5′-methylthioadenosine up to 1000 μm. To clarify how 5′-methylthioadenosine might accumulate, 5′-methylthioadenosine phosphorylase was evaluated. This enzyme was not blocked by up to 500 μm adenosine, deoxyadenosine, S-adenosylhomocysteine, or S-adenosylmethionine and was not decreased in erythrocytes from patients with adenosine deaminase deficiency, purine nucleoside phosphorylase deficiency, or hypogammaglobulinemia. These observations suggest that the inhibitory properties of 5′-methylthioadenosine upon adenosine kinase and S-adenosylhomocysteine hydrolase may contribute to the toxicity of the exogenously added compound. The toxicity resulting from S-adenosylhomocysteine accumulation intracellularly may be related to adenosine kinase inhibition in addition to disruption of transmethylation reactions.     

Parallel measurements of bound calcium and force in glycerinated rabbit psoas muscle fibers

A simple double-isotope procedure has been developed for making simultaneous measurements of bound Ca²⁺ and relative force in glycerinated rabbit psoas bundles containing two fibers. With this preparation it is possible to study Ca²⁺-troponin interactions coincident with MgATP-induced force development. Over the free [Ca²⁺] range 6 · 10^?8–1.2 · 10^?5 M the bound Ca²⁺ varied from 0.25 to 1.65 μmol/g protein. The free [Ca²⁺] at half-maximal Ca²⁺ saturation was 2 · 10^?7 M while that a half-maximal force was 5 · 10^?7 M. Half-maximal Ca²⁺ saturation was associated with 20% maximal force. The force-[Ca²⁺] saturation curve showed a steep rise in slope at greater than half saturation. The observed relationship was consistent with a model in which multiple occupancy of troponin Ca²⁺-binding sites is essential for initiation of cross-bridge cycling.     

The effects of actinomycin on the structure of dAn.dTn and (dA-dT)n regions surrounding its GC binding site. A footprinting study.

The effect of actinomycin on the structure of DNA fragments containing the sequences (AT)5GC(AT)5, (TA)5GC(TA)5, A9GCT9, and T9GCA9, cloned into the SmaI site of pUC19, has been studied by footprinting analysis using a variety of probes known to be sensitive to DNA structure. In each case clear footprints are found around the central GC sites. DNase I cleavage of fragments containing alternating AT shows much greater cutting at ApT than TpA; in the presence of actinomycin, although this preference is retained, there is a large increase in the cutting efficiency at the closest TpA steps. DNase I cleavage in homopolymeric regions of A and T, which is normally very poor, is greatly enhanced by drug binding. With T9GCA9 the enhancements are propagated in both directions, whereas changes are only found to the 5'-side of the GC site in A9GCT9. The results are confirmed by similar experiments with micrococcal nuclease and DNase II. Small increases in sensitivity to diethylpyrocarbonate are found at adenines proximal to GC. Experiments performed at 4 degrees C suggest that conformational changes are a necessary consequence of drug binding.     

Phylogeny of Helicobacter felis sp. nov., Helicobacter mustelae, and related bacteria.

Strain CS1T (T = type strain) is a gram-negative, microaerophilic, urease-positive, spiral-shaped bacterium that was isolated from the gastric mucosa of a cat. Additional strains which possessed biochemical and ultrastructural characteristics similar to those of strain CS1T were isolated from the gastric mucosa of cats and dogs. The guanine-plus-cytosine content of the DNA of strain CS1T was 42.5 mol%. The 16S rRNA sequences of strain CS1T, strain DS3 (a spiral-shaped isolate from a dog), and Helicobacter mustelae were determined by direct RNA sequencing, using a modified Sanger method. These sequences were compared with the 16S rRNA sequences of Helicobacter pylori, "Flexispira rappini," Wolinella succinogenes, and 11 species of campylobacters. A dendrogram was constructed based upon sequence similarities. Strains CS1T and DS3 were very closely related (level of similarity, 99.3%). Two major phylogenetic groups were formed; one group consisted of strains CS1T and DS3, H. mustelae, H. pylori, "F. rappini," and W. succinogenes, and the other group contained the true campylobacters. The average level of similarity between members of these two groups was 84.9%. Within the first group, strains CS1T and DS3, H. pylori, and H. mustelae formed a cluster of organisms with an interspecies similarity level of 94.5%. The phylogenetic positions of W. succinogenes and "F. rappini" were just outside this cluster. On the basis of the results of this study, we believe that strains CS1T (= ATCC 49179T) and DS3 represent a new species of the genus Helicobacter, for which we propose the name Helicobacter felis.     

2.9 A resolution structure of an anti-dinitrophenyl-spin-label monoclonal antibody Fab fragment with bound hapten

The crystal structure of the Fab fragment of the murine monoclonal anti-dinitrophenyl-spin-label antibody AN02 complexed with its hapten has been solved at 2.9 A resolution using a novel molecular replacement method. Prior to translation searches, a large number of the most likely rotation function solutions were subjected to a rigid body refinement against the linear correlation coefficient between intensities of observed and calculated structure factors. First, the overall orientation of the search model and then the orientations and positions of the four Fab domains (VH, VL, CH1 and CL) were refined. This procedure clearly identified the correct orientation of the search model. The refined search model was then subjected to translation searches which unambiguously determined the enantiomer and position in the unit cell of the crystal. The successful search model was refined 2.5 A crystal structure of the Fab fragment of HyHel-5 from which non-matching residues in the variable domains had been removed. HyHel-5 is a murine monoclonal antibody whose heavy and light chains are of the same subclass (gamma 1, kappa, respectively) as AN02. After molecular replacement the structure of the AN02 Fab has been refined using simulated annealing in combination with model building and conjugate gradient refinement to a current crystallographic R-factor of 19.5% for 12,129 unique reflections between 8.0 and 2.9 A. The root-mean-square (r.m.s.) deviation from ideal bond lengths is 0.014 A, and the r.m.s. deviation from ideal bond angles is 3.1 degrees. The electron density reveals the hapten sitting in a pocket formed by the loops of the complementarity determining region. The dinitrophenyl ring of the hapten is sandwiched between the indole rings of Trp96 of the heavy-chain and Trp91 of the light-chain. The positioning of the hapten and general features of the combining site are in good agreement with the results of earlier nuclear magnetic resonance experiments.