The effect of inflammation on rat liver beta-galactosidase and beta-N-acetylglucosaminidase.

Reduced activities of β-galactosidase and β-N-acetylglucosaminidase were found in rat livers following experimentally induced inflammation. The greatest reduction in glycosidase activities were found 24 h after inflammation. The lysosomal fraction accounted for the bulk of both glycosidase activities in experimental and control rats. Kinetic experiments showed that inflammation did not affect K_m values, but did result in a significant reduction in V_max values. One suggestion to explain the results is that inflammation causes a reduction in biosynthesis or activation of the two glycosidases in rat liver.     

Daphnia population growth but not moulting is a substantial phosphorus drain for phytoplankton

SUMMARY 1. Negative effects of zooplankton on the availability of phosphorus (P) for phytoplankton as a result of the retention of nutrients in zooplankton biomass and the sedimentation of exoskeletal remains after moulting, have been recently proposed. 2. In a mesocosm study, the relative importance of these mechanisms was tested for the freshwater cladoceran Daphnia hyalina×galeata. A total of 13 mesocosm bags was suspended in a mesotrophic German lake during summer 2000 and fertilised with inorganic P in order to obtain a total nitrogen to total P ratio closer to the Redfield ratio. D. hyalina×galeata was then added at a logarithmically scaled density gradient of up to 40 ind. L^?1. Zooplankton densities, dissolved inorganic, particulate organic (seston <100 μm), as well as total nutrient concentrations were monitored. Additionally, nutrient concentrations of sediment water removed from the bottom of the mesocosm bags via a manual pump were determined. 3. Seston carbon (C), seston P and total P were significantly negatively correlated with Daphnia densities. The amount of particulate P (～5–6 μg P L^?1) sequestered from the seston compartment by Daphnia corresponded roughly to the increase of zooplankton biomass (population growth). Soluble reactive phosphorous (SRP) was at all times high (～25–35 μg P L^?1) and possibly unavailable to phytoplankton as a result of P adsorption to calcite during a calcite precipitation event (whiting). P concentrations determined in sediment water were generally <60 μg P m^?2 and thus never exceeded 1% of the total amount of P bound in particulate matter of the overlying water column. 4. Seston C : P ratios followed a polynomial second‐order function: At Daphnia densities <40 ind. L^?1 a positive linear relationship was evident, which is explained by the stronger reduction of P compared with C in seston, and transfer of seston P to zooplankton. Highest seston C : P ratios of ～300 : 1 were observed at Daphnia densities of ～30–50 ind. L^?1, which is in agreement with proposed threshold values limiting Daphnia reproductive growth. At Daphnia densities >40–50 ind. L^?1 C : P ratios were decreased because of the strong reduction of seston C at close to constantly low seston P‐values of ～3–4 μg P L^?1. 5. At least for Daphnia, it may be concluded that – unlike population growth – the sedimentation of faecal pellets and carapaces after moulting seem negligible processes in pelagic phosphorus dynamics.     

Effects of N-acetylglucosamine and platelet inhibitors on the synergistic interaction of platelets and aggregating agents in the presence of wheat germ agglutinin

Low concentrations of wheat germ agglutinin (4 micrograms/ml) have been shown to act synergistically to induce platelet aggregation with epinephrine, collagen, arachidonate and ionophore A23187. Aggregation ceased on the addition of the haptenic sugar N-acetylglucosamine at any time following the onset of aggregation with these agonists and a small degree of disaggregation was observed during the reversible first wave with the biphasic aggregating agents epinephrine and ADP. Cyclooxygenase inhibitors such as indomethacin and aspirin blocked the second wave of aggregation with the biphasic aggregating agents epinephrine and ADP but a synergistic response continued to be shown with the first wave in the presence of these inhibitors. Release of [14C]serotonin and the mobilization of [3H]arachidonate by epinephrine and collagen were markedly stimulated in the presence of wheat germ agglutinin but there was no increase of either radiolabel in the case of ADP. Platelet shape change, but not aggregation, occurred with low levels of wheat germ agglutinin and the synergistic response with ADP, collagen or ionophore A23187 occurred without further shape change. Wheat germ agglutinin did not affect the basal or stimulated levels of cyclic AMP. The membrane fluidity of platelets was not affected by the lectin or by thrombin as shown by the lack of change in fluorescence polarization with diphenylhexatriene. It is suggested that the binding of wheat germ agglutinin to the platelet surface induces platelet activation by mechanisms similar to those of other agonists and that it may affect the distribution of membrane-bound Ca2+ by a reversible perturbation of the platelet membrane.     

MHC variation reflects the bottleneck histories of New Zealand passerines

Most empirical evidence suggests that balancing selection does not counter the effects of genetic drift in shaping postbottleneck major histocompatibility complex (MHC) genetic diversity when population declines are severe or prolonged. However, few studies have been able to include data from historical specimens, or to compare populations/species with different bottleneck histories. In this study, we examined MHC class II B and microsatellite diversity in four New Zealand passerine (songbird) species that experienced moderate to very severe declines. We compared diversity from historical samples (collected c. 1884–1938) to present‐day populations. Using a Bayesian framework, we found that the change in genetic diversity from historical to contemporary samples was affected by three main factors: (i) whether the data were based on MHC or microsatellite markers, (ii) species (as a surrogate for bottleneck severity) and (iii) whether the comparison between historical and contemporary samples was made using historical samples originating from the mainland, or using historical samples originating from islands. The greatest losses in genetic diversity occurred for the most severely bottlenecked species, particularly between historical mainland and contemporary samples. Additionally, where loss of diversity occurred, the change was greater for MHC genes compared to microsatellite loci.     

Development of cell surface saccharides on embryonic pancreatic cells

Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life.     

Liver transplantation in 100 children: Cambridge and King's College Hospital series.

To review the results of the Addenbrooke''s and King''s College Hospital children''s liver transplantation programme.Retrospective analysis of the first 100 children to receive liver grafts at Addenbrooke''s Hospital, Cambridge, from December 1983 to March 1990.Addenbrooke''s Hospital, Cambridge, and King''s College Hospital, London.153 children assessed for liver transplantation, of whom 22 died before a donor became available and 31 were considered unsuitable. 100 children received grafts, of whom 27 had second grafts.One year actuarial patient survival was 71%, with 57% one year graft survival. In the last two years survival rates had improved considerably, with 86% of patients and 63% of grafts surviving for at least one year. Sixty five children were alive 12 to 86 months after transplantation; 63 were well and leading normal active lives and 56 had entirely normal liver function. Children''s growth and development were essentially normal, with many showing remarkable catch up growth.Liver transplantation offers children with terminal liver disease a high chance of a return to full quality life and normal development. Improved surgical and medical care have progressively improved survival. The timing of transplantation is critical but has been constrained particularly by the availability of donors and resources.     

Phylogenetic relations between microbats, megabats and primates (Mammalia: Chiroptera and Primates)

We examine the paraphylectic hypothesis of bat origins, both in the light of previous discussions, and in the light of new evidence from our analyses of neurological traits and wing morphology. Megabats share with primates a variety of complex details in the organization of neural pathways that have not been found in any other mammalian group, particularly not in microbats. The features previously used to link microbats and megabats have been examined and found to be questionable bases for support of a monophyletic origin. In particular, morphological analyses of the musculoskeletal adaptations associated with the flight apparatus are consistent with two separate origins of the mammalian wing. Taken together, these analyses suggest that megabats evolved from an early branch of the primate lineage. This branch was comprised of moderate-sized, phytophagous gliders, of which the other living descendants are the dermopterans. Microbats, in contrast, probably evolved much earlier from small, agile insectivores whose forelimbs had long metacarpals in relation to their phalanges.     

Development of secretagogue response in rat pancreatic acinar cells

Two to 3 days prior to birth, acinar cells of the rat pancreas acquire morphologic and biochemical characteristics of the adult gland. To determine if differentiation of the secretory apparatus coincides temporally with the capacity of the cell to respond to secretory stimuli, lobules of embryonic, neonatal, and adult rat pancreas were compared for their ability to respond to secretagogues presumed to act directly via hormone receptors [caerulein and carbamylcholine (carbachol)] or indirectly (cyclic nucleotide analogs and the Ca²⁺ ionophore A23187). Of all agents tested, only dibutyryl cAMP elicited discharge of secretory proteins at day 20 in utero and preceded hormone stimulation by 1 day. A23187 elicited discharge by Day 21 in utero; its action was near adult levels in contrast to hormonal stimuli whose effect was maximal only at birth. All secretagogues required Ca²⁺ and energy to induce discharge. Pulse-chase autoradiography of lobules from Day 20 embryonic glands indicated that the acinar cells were capable of transporting [³H]leucine-labeled proteins to zymogen granules at rates roughly equivalent to those in adult glands. SDS gel electrophoretograms confirmed that the bulk of ¹⁴C-amino acid incorporation into proteins at a given age was primarily into exportable proteins. The results indicate that acinar cells synthesize and package secretory proteins into zymogen granules about 2 days before they are capable of responding to hormonal stimuli and to intracellular effectors.     

Nucleotide binding by membrane components of bacterial periplasmic binding protein-dependent transport systems.

Bacterial periplasmic binding protein-dependent transport systems require the function of a specific substrate-binding protein, located in the periplasm, and several membrane-bound components. We present evidence for a nucleotide-binding site on one of the membrane components from each of three independent transport systems, the hisP, malK and oppD proteins of the histidine, maltose and oligopeptide permeases, respectively. The amino acid sequence of the oppD protein has been determined and this protein is shown to share extensive homology with the hisP and malK proteins. Three lines of evidence lead us to propose the existence of a nucleotide-binding site on each of these proteins. A consensus nucleotide-binding sequence can be identified in the same relative position in each of the three proteins. The oppD protein binds to a Cibacron Blue affinity column and can be eluted by ATP but not by CTP or NADH. The oppD protein is labelled specifically by the nucleotide affinity analogue 5'-p-fluorosulphonylbenzoyladenosine. The identification of a nucleotide-binding site provides strong evidence that transport by periplasmic binding protein-dependent systems is energized directly by the hydrolysis of ATP or a closely related nucleotide. The hisP, malK and oppD proteins are thus responsible for energy-coupling to their respective transport systems.