Hepatic protein kinase C: translocation stimulated by prolactin and partial hepatectomy

Prolactin stimulates a hepatotrophic response similar to that caused by phorbol esters or partial hepatectomy in rats. Since phorbol esters, which activate protein kinase C, mimic prolactin action in liver, the relationship between prolactin administration and subsequent hepatic protein kinase C translocation was assessed. Prolactin administration rapidly stimulated a 4-fold elevation of membrane protein kinase C activity. The effect of prolactin on hepatic protein kinase C was specific for lactogenic hormones but could be duplicated by phorbol esters. Further, an increase in serum prolactin was demonstrated subsequent to partial hepatectomy and preceding hepatic protein kinase C translocation. Therefore, translocation of hepatic protein kinase C appears important for hepatic proliferation in response to prolactin administration and to partial hepatectomy.     

Impact of six lignocellulosic biochars on C and N dynamics of two contrasting soils

Both soil and biochar properties are known to influence greenhouse gas emissions from biochar‐amended soils, but poor understanding of underlying mechanisms challenges prediction and modeling. Here, we examine the effect of six lignocellulosic biochars produced from the pyrolysis of corn stover and wood feedstocks on CO₂ and N₂O emissions from soils collected from two bioenergy cropping systems. Effects of biochar on total accumulated CO₂‐C emissions were minimal (<0.45 mg C g^?1 soil; <10% of biochar C), consistent with mineralization and hydrolysis of small labile organic and inorganic C fractions in the studied biochars. Comparisons of soil CO₂ emissions with emissions from microbially inoculated quartz–biochar mixtures (‘quartz controls’) provide evidence of soil and biochar‐specific negative priming. Five of six biochar amendments suppressed N₂O emissions from at least one soil, and the magnitude of N₂O emissions suppression varied with respect to both biochar and soil types. Biochar amendments consistently decreased final soil NO₃^? concentrations, while contrasting effects on pH, NH₄⁺, and DOC highlighted the potential for formation of anaerobic microsites in biochar‐amended soils and consequential shifts in the soil redox environment. Thus, results implicated both reduced substrate availability and redox shifts as potential factors contributing to N₂O emission suppression. More research is needed to confirm these mechanisms, but overall our results suggest that soil biochar amendments commonly reduce N₂O emissions and have little effect on CO₂ emissions beyond the mineralization and/or hydrolysis of labile biochar C fractions. Considering the large C credit for the biochar C, we conclude that biochar amendments can reduce greenhouse gas emissions and enhance the climate change mitigation potential of bioenergy cropping systems.     

Interior-Point Methods for Estimating Seasonal Parameters in Discrete-Time Infectious Disease Models

Infectious diseases remain a significant health concern around the world. Mathematical modeling of these diseases can help us understand their dynamics and develop more effective control strategies. In this work, we show the capabilities of interior-point methods and nonlinear programming (NLP) formulations to efficiently estimate parameters in multiple discrete-time disease models using measles case count data from three cities. These models include multiplicative measurement noise and incorporate seasonality into multiple model parameters. Our results show that nearly identical patterns are estimated even when assuming seasonality in different model parameters, and that these patterns show strong correlation to school term holidays across very different social settings and holiday schedules. We show that interior-point methods provide a fast and flexible approach to parameterizing models that can be an alternative to more computationally intensive methods.     

Taking a big bite: Working together to better understand the evolution of feeding in primates

The study of adaptation requires the integration of an array of different types of data. A single individual can find such integration daunting, if not impossible. In an effort to clarify the role of diet in the evolution of the primate craniofacial and dental apparatus, we assembled a team of researchers that have various types and degrees of expertise. This interaction has provided a range of insights for all contributors, and this has helped to refine questions, clarify the possibilities and limitations that laboratory and field settings offer, and further explore the ways in which laboratory and field data can be suitably integrated. A complete and accurate picture of dietary adaptation cannot be gained in isolation. Collaboration provides the bridge to a more holistic view of primate biology and evolution.     

Prolactin-stimulated mitogenesis in the Nb2 rat lymphoma cell: lack of protoporphyrin IX effects

Pharmacological characterization of the Nb2 cell peripheral-type benzodiazepine receptor (PBR) was determined using selected 1,4-benzodiazepines, PK 11195, and protoporphyrin IX (PPIX) to compete for specific [3H] Ro5-4864 binding. These data suggest that PPIX possesses an affinity for the Nb2 cell PBR (Ki = 142 nM). We have previously reported that the peripheral benzodiazepine ligands, Ro5-4864 and PK 11195, modulate prolactin-stimulated mitogenesis in the Nb2 cell(1). In contrast, PPIX, a putative endogenous ligand for the PBR had no effect on prolactin-stimulated mitogenesis in the Nb2 cell over the concentration range from 10(-15) M to 10(-6) M. Taken together these data show that PPIX has an affinity for the Nb2 cell PBR but does not modulate prolactin-stimulated mitogenesis at concentrations which should bind to the Nb2 cell PBR.     

<Emphasis Type="Italic">Spiroplasma</Emphasis> dominates the microbiome of khapra beetle: comparison with a congener,effects of life stage and temperature

Khapra beetle, Trogoderma granarium (Coleoptera: Dermestidae), is among the world’s most invasive and destructive pests of stored agricultural products. Its pest status is enhanced by the ability of the larvae to undergo diapause, which increases their tolerance to adverse conditions including insecticides and extreme temperatures. The ability of insects to tolerate extreme conditions can be influenced by their associated bacterial community (the microbiome). Understanding this relationship may lead to improved methods of pest control, but the microbiome of T. granarium is unknown. Here we use next-generation sequencing to address three main questions: 1) How similar are the microbiomes of the closely-related species T. granarium and T. variabile? 2) How does the microbiome change across life stage and physiological state? 3) How is the microbiome of adult T. granarium affected by extreme temperatures? Our results show that the core microbiomes of T. granarium and T. variabile are similar in composition. However, adults of former species have a microbiome dominated by Spiroplasma bacteria (99% of amplified sequences), whereas Spiroplasma in the latter species is almost absent (< 2%). The microbiome of T. granarium differs across life stage (feeding vs non-feeding life stages); its presence in eggs confirms the vertical transmission of Spiroplasma. High temperatures significantly reduced the relative abundance of Spiroplasma, but an effect of low temperatures on the microbiome of T. granarium was not detected. Given its dominance in a key pest species, further study of the interaction between Spiroplasma and its T. granarium host is warranted.     

Loss of Gap Junction Plaques and Inhibition of Intercellular Communication in Ilimaquinone-treated BICR-M1Rk and NRK Cells

To examine the mechanism(s) and pathways of gap junction formation and removal a novel and reversible inhibitor of protein secretion, ilimaquinone (IQ), was employed. IQ has been reported to cause the vesiculation of Golgi membranes, block protein transport at the cis-Golgi and depolymerize cytoplasmic microtubules. Connexin43 (Cx43) immunolabeling and dye microinjection experiments revealed that gap junction plaques were lost and intercellular communication was inhibited following IQ treatment for 1 hr in BICR-M1R_k rat mammary tumor cells and for 2 hr in normal rat kidney (NRK) cells. Gap junction plaques and intercellular communication recovered within 2 hr when IQ was removed. IQ, however, did not affect the distribution of zonula occludens-1, a protein associated with tight junctions. Western blot analysis revealed that the IQ-induced loss of gap junction plaques was accompanied by a limited reduction in the highly phosphorylated form of Cx43, previously shown to be correlated with gap junction plaques. The presence of IQ inhibited the formation of new gap junction plaques in BICR-M1R_k cells under conditions where preexisting gap junctions were downregulated by brefeldin A treatment. Treatment of BICR-M1R_k and NRK cells with other microtubule depolymerization agents did not inhibit plaque formation or promote rapid gap junction removal. These findings suggest that IQ disrupts intercellular communication by inhibiting the events that are involved in plaque formation and/or retention at the cell surface independent of its effects on microtubules. Our results also suggest that additional factors other than phosphorylation are necessary for Cx43 assembly into gap junction plaques. Received: 16 January 1996/Revised: 20 September 1996