Attenuation of inflammation and cellular stress‐related pathways maintains insulin sensitivity in obese type I interleukin‐1 receptor knockout mice on a high‐fat diet

The development of insulin resistance in the obese is associated with chronic, low‐grade inflammation. We aimed to identify novel links between obesity, insulin resistance and the inflammatory response by comparing C57BL/6 with type I interleukin‐1 receptor knockout (IL‐1RI^?/?) mice, which are protected against diet‐induced insulin resistance. Mice were fed a high‐fat diet for 16 wk. Insulin sensitivity was measured and proteomic analysis was performed on adipose, hepatic and skeletal muscle tissues. Despite an equal weight gain, IL‐1RI^?/? mice had lower plasma glucose, insulin and triacylglycerol concentrations, compared with controls, following dietary treatment. The higher insulin sensitivity in IL‐1RI^?/? mice was associated with down‐regulation of antioxidant proteins and proteasomes in adipose tissue and hepatic soluble epoxide hydrolase, consistent with a compromised inflammatory response as well as increased glycolysis and decreased fatty acid β‐oxidation in their muscle. Their lower hepatic triacylglycerol concentrations may reflect decreased flux of free fatty acids to the liver, decreased hepatic fatty acid‐binding protein expression and decreased lipogenesis. Correlation analysis revealed down‐regulation of classical biomarkers of ER stress in their adipose tissue, suggesting that disruption of the IL‐1RI‐mediated inflammatory response may attenuate cellular stress, which was associated with significant protection from diet‐induced insulin resistance, independent of obesity.     

Does the Small White Butterfly (Pieris rapae L.) Aggregate Eggs on Plants with Greater Gas Exchange Activity?

Few studies have investigated insect egg-laying preferences in relation to photosynthesis or transpiration of their host plants. It has been suggested that intravarietal preferences of the small white butterfly (Pieris rapae L.: Pieridae) include larger plants with characteristically higher transpiration rates. Interestingly this species, like many other Lepidoptera, may detect biogenic CO₂ gradients associated with photosynthesis. We studied egg-laying preferences in working farm environments examining relationships among host choice, plant gas exchange activity, and plant size. Females discriminated between plants in monocultures on the basis of height. A balance of pre- and post–alighting preferences resulted in plants of medium size receiving eggs. Post–alighting preferences led to plants, but not alighted leaves, with higher rates of photosynthesis supporting eggs. These findings do not support a mechanistic basis for the use of gas exchange activity during host selection but, for the first time, indicate the greater physiological activity of crop plants that ultimately received the eggs of a pest insect.     

Neutrophil Responses to Sterile Implant Materials

In vivo implantation of sterile materials and devices results in a foreign body immune response leading to fibrosis of implanted material. Neutrophils, one of the first immune cells to be recruited to implantation sites, have been suggested to contribute to the establishment of the inflammatory microenvironment that initiates the fibrotic response. However, the precise numbers and roles of neutrophils in response to implanted devices remains unclear. Using a mouse model of peritoneal microcapsule implantation, we show 30–500 fold increased neutrophil presence in the peritoneal exudates in response to implants. We demonstrate that these neutrophils secrete increased amounts of a variety of inflammatory cytokines and chemokines. Further, we observe that they participate in the foreign body response through the formation of neutrophil extracellular traps (NETs) on implant surfaces. Our results provide new insight into neutrophil function during a foreign body response to peritoneal implants which has implications for the development of biologically compatible medical devices.     

Studies on the mechanism of activation of mitotic histone H1 kinase

A chromatin-associated histone H1 kinase has been detected in synchronized Novikoff hepatoma cells. Enzyme specific activity increased 4 to 6-fold from late G-2 to mid-metaphase, then decayed exponentially ($\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, 28.5 min) to the interphase level. Extracts of the mitotic kinase retained the ability to decay $\text{in}\text{vitro}$ at 37°C but not at 0°C ($\text{T}{}_{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$, 24 min), under conditions in which interphase activity was stable. Sedimentation rates in sucrose density gradients of interphase and mitotic enzymes (before and after decay) were identical. Purification did not alter the rate of enzyme decay. However, high ionic strength prevented decay of crude but not purified preparations of mitotic enzyme. The results are discussed in terms of an allosteric mechanism for reversible activation of enzyme activity.     

Palmitoylation of the human prostacyclin receptor. Functional implications of palmitoylation and isoprenylation

We have previously established that isoprenylation of the prostacyclin receptor (IP) is required for its efficient G protein coupling and effector signaling (Hayes, J. S., Lawler, O. A., Walsh, M. T., and Kinsella, B. T. (1999) J. Biol. Chem. 274, 23707-23718). In the present study, we sought to investigate whether the IP may actually be subject to palmitoylation in addition to isoprenylation and to establish the functional significance thereof. The human (h) IP was efficiently palmitoylated at Cys(308) and Cys(311), proximal to transmembrane domain 7 within its carboxyl-terminal (C)-tail domain, whereas Cys(309) was not palmitoylated. The isoprenylation-defective hIP(SSLC) underwent palmitoylation but did not efficiently couple to G(s) or G(q), confirming that isoprenylation is required for G protein coupling. Deletion of C-tail sequences distal to Val(307) generated hIP(Delta307) that was neither palmitoylated nor isoprenylated and did not efficiently couple to G(s) or to G(q), whereas hIP(Delta312) was palmitoylated and ably coupled to both effector systems. Conversion of Cys(308), Cys(309), Cys(311), Cys(308,309), or Cys(309,311) to corresponding Ser residues, while leaving the isoprenylation CAAX motif intact, did not affect hIP coupling to G(s) signaling, whereas mutation of Cys(308,311) and Cys(308,309,311) abolished signaling, indicating that palmitoylation of either Cys(308) or Cys(311) is sufficient to maintain functional G(s) coupling. Although mutation of Cys(309) and Cys(311) did not affect hIP-mediated G(q) coupling, mutation of Cys(308) abolished signaling, indicating a specific requirement for palmitoylation of Cys(308) for G(q) coupling. Consistent with this, neither hIP(C308S,C309S), hIP(C308S,C311S), nor hIP(C308S,C309S,C311S) coupled to G(q). Taken together, these data confirm that the hIP is isoprenylated and palmitoylated, and collectively these modifications modulate its G protein coupling and effector signaling. We propose that through lipid modification followed by membrane insertion, the C-tail domain of the IP may contain a double loop structure anchored by the dynamically regulated palmitoyl groups proximal to transmembrane domain 7 and by a distal farnesyl isoprenoid permanently attached to its carboxyl terminus.     

Effects of metaldehyde and methiocarb on feeding preferences and survival of a slug predator (Pterostichus melanarius (F.): Carabidae,Pterostichini)

The potential for reducing slug populations in crops through predation by generalist carabid beetles is well documented. However, few studies have considered interactions between biological and chemical control agents of slugs. Laboratory assays supported previous findings that the consumption of metaldehyde by slugs (Deroceras reticulatum) leads to increased duration of feeding bouts by carabid beetles (such as Pterostichini) on sub‐lethally affected individuals. However, a similar effect was not found for Pterostichus melanarius exposed to slugs fed on the other widely applied pelleted molluscicide formulation (methiocarb). Examination of beetle survival after consumption of slugs containing molluscicides demonstrated the strong biocidal properties of methiocarb, whereas metaldehyde consumption (ingested through slug predation) did not differ from control slugs killed by freezing. Beetle avoidance of slugs containing a more toxic molluscicide compound and the interaction between slug mucus production and beetle attack rates are discussed.     

Membranes of Rhodopseudomonas sphaeroides. IV. Assembly of chromatophores in low-aeration cell suspensions.

Chromatophore membrane formation was induced in low-aeration suspensions of Rhodopseudomonas sphaeroides and highly purified chromatophore preparations were isolated at various intervals between 4 and 18 h. The levels of several functional components associated with the isolated strucures were investigated. B-875, the light-harvesting bacteriochlorophyll complex associated with the reaction center, was preferentially inserted into the chromatophore membrane during the early stages of induction, and thereafter its levels reached a steady state; b- and c-type cytochromes were also maintained at essentially constant levels. In contrast, the levels of B-850, the accessory light-harvesting bacteriochlorophyll, together with its associated protein, continued to increase throughout the induction process. Increases in the levels of the major carotenoid component followed a similar course. These findings are consistent with a stepwise assembly mechanism for associated bacteriochlorophyll and protein components and suggest that separate regulatory mechanisms control the levels of functionally essential and accessory components within the membrane.     

Disposable Soma Theory and the Evolution of Maternal Effects on Ageing

Maternal effects are ubiquitous in nature and affect a wide range of offspring phenotypes. Recent research suggests that maternal effects also contribute to ageing, but the theoretical basis for these observations is poorly understood. Here we develop a simple model to derive expectations for (i) if maternal effects on ageing evolve; (ii) the strength of maternal effects on ageing relative to direct environmental effects; and (iii) the predicted relationships between environmental quality, maternal age and offspring lifespan. Our model is based on the disposable soma theory of ageing, and the key assumption is thus that mothers trade off their own somatic maintenance against investment in offspring. This trade-off affects the biological age of offspring at birth in terms of accumulated damage, as indicated by biomarkers such as oxidative stress or telomere length. We find that the optimal allocation between investment in maternal somatic investment and investment in offspring results in old mothers and mothers with low resource availability producing offspring with reduced life span. Furthermore, the effects are interactive, such that the strongest maternal age effects on offspring lifespan are found under low resource availability. These findings are broadly consistent with results from laboratory studies investigating the onset and rate of ageing and field studies examining maternal effects on ageing in the wild.     

Extracellular polysaccharide-degrading proteome of Butyrivibrio proteoclasticus

Plant polysaccharide-degrading rumen microbes are fundamental to the health and productivity of ruminant animals. Butyrivibrio proteoclasticus B316(T) is a gram-positive, butyrate-producing anaerobic bacterium with a key role in hemicellulose degradation in the rumen. Gel-based proteomics was used to examine the growth-phase-dependent abundance patterns of secreted proteins recovered from cells grown in vitro with xylan or xylose provided as the sole supplementary carbon source. Five polysaccharidases and two carbohydrate-binding proteins (CBPs) were among 30 identified secreted proteins. The endo-1,4-β-xylanase Xyn10B was 17.5-fold more abundant in the culture medium of xylan-grown cells, which suggests it plays an important role in hemicellulose degradation. The secretion of three nonxylanolytic enzymes and two CBPs implies they augment hemicellulose degradation by hydrolysis or disruption of associated structural polysaccharides. Sixteen ATP-binding cassette (ABC) transporter substrate-binding proteins were identified, several of which had altered relative abundance levels between growth conditions, which suggests they are important for oligosaccharide uptake. This study demonstrates that B. proteoclasticus modulates the secretion of hemicellulose-degrading enzymes and ATP-dependent sugar uptake systems in response to growth substrate and supports the notion that this organism makes an important contribution to polysaccharide degradation in the rumen.