Studies on the biochemical basis of the nutritional quality of tsetse fly diets

Batches of freeze-dried pig and cow blood, whose nutritional value to G. p. palpalis ranged from low to near optimum, were analysed for amino acid, triglyceride and cholesterol content. The results of the chemical analyses were compared with the nutritional quality parameters observed when each batch of blood was fed to G. p. palpalis in an attempt to establish a chemical basis for the nutritional quality of diets for Glossina. In general, those pig or cow blood diets that had a higher nutritional quality also had a significantly higher amino acid content than the suboptimal diets. There were significant differences between the triglyceride and cholesterol content of pig and cow blood, with pig blood having more triglyceride, but less cholesterol than bovine blood. There was no apparent correlation between the triglyceride and cholesterol content and the nutritional quality of blood.     

Interaction of hydrophobic bis (D-mannose) derivatives with adipocyte and erythrocyte sugar transport systems

The inhibition of sugar uptake by a series of hydrophobic bis(D-mannose) derivatives has been measured in rat adipocytes. When the D-mannose moieties of the bis compounds are separated by a hexane bridge the transport inhibition constant (Ki) is greater than for a decane-bridged molecule. This is probably due to the increased hydrophobicity of the bridge of the decane-bridged compound. The enhancement in affinity due to the second sugar in the bis(D-mannose) derivatives is probably only 2-fold, since half reduction of the bis(D-mannosyloxy)hexane increases Ki approx. 2-3-fold. N'-DNP-1,3-bis(D-mannos-4'-yloxy)propyl-2-amine has very high affinity in insulin-treated cells. The affinity is approx. 1000-fold higher than for D-mannose. This enhancement is probably due to the hydrophobicity of the DNP group. The distance from the sugar to the hydrophobic group is important because an increase in Ki occurs if an aminocaproyl spacer is introduced between the DNP group and 1,3-bis(D-mannos-4'-yloxy)propyl-2-amine. Aminocaproyl and glycyl spacers also increase the Ki for NAP derivatives of 1,3-bis(D-mannos-4'-yloxy)propyl-2-amine. Each of the hydrophobic bis(D-mannose) derivatives has a lower Ki in insulin-treated cells. This may be due to an insulin responsive hydrophobic interaction between the hydrophobic portion of the sugar and a hydrophobic domain in the transport system. The inhibition constants for the hydrophobic bis(D-mannose) compounds have also been measured in human erythrocytes.     

Survival in sinoatrial disorder (sick-sinus syndrome).

A total of 381 patients with established (156) or potential (225) sinoatrial dysfunction were included in a 10-year prospective survey to determine the course of the disease and the benefits of pacing. With the exclusion of nine patients who were lost to follow-up, 61 were fitted with pacemakers. The overall survival of patients with established and potential dysfunction was similar and apparently indistinguishable from that of the normal population. Pacemaker implantation had little discernible effect on mortality though it reduced some incapacitating symptoms. These findings suggest that sinoatrial dysfunction is a relatively benign condition. Hence pacing should probably not be adopted as a routing measure but be reserved for patients with troublesome symptoms.     

Structural and functional characterization of second-coordination sphere mutants of soybean lipoxygenase-1.

Lipoxygenases are an important class of non-heme iron enzymes that catalyze the hydroperoxidation of unsaturated fatty acids. The details of the enzymatic mechanism of lipoxygenases are still not well understood. This study utilizes a combination of kinetic and structural probes to relate the lipoxygenase mechanism of action with structural modifications of the iron's second coordination sphere. The second coordination sphere consists of Gln(495) and Gln(697), which form a hydrogen bond network between the substrate cavity and the first coordination sphere (Asn(694)). In this investigation, we compared the kinetic and structural properties of four mutants (Q495E, Q495A, Q697N, and Q697E) with those of wild-type soybean lipoxygenase-1 and determined that changes in the second coordination sphere affected the enzymatic activity by hydrogen bond rearrangement and substrate positioning through interaction with Gln(495). The nature of the C-H bond cleavage event remained unchanged, which demonstrates that the mutations have not affected the mechanism of hydrogen atom tunneling. The unusual and dramatic inverse solvent isotope effect (SIE) observed for the Q697E mutant indicated that an Fe(III)-OH(-) is the active site base. A new transition state model for hydrogen atom abstraction is proposed.     

A high-throughput mass spectrometric assay for discovery of human lipoxygenase inhibitors and allosteric effectors

Lipoxygenases (LOXs) regulate inflammation through the production of a variety of molecules whose specific downstream effects are not entirely understood due to the complexity of the inflammation pathway. The generation of these biomolecules can potentially be inhibited and/or allosterically regulated by small synthetic molecules. The current work describes the first mass spectrometric high-throughput method for identifying small molecule LOX inhibitors and LOX allosteric effectors that change the substrate preference of human lipoxygenase enzymes. Using a volatile buffer and an acid-labile detergent, enzymatic products can be directly detected using high-performance liquid chromatography–mass spectrometry (HPLC–MS) without the need for organic extraction. The method also reduces the required enzyme concentration compared with traditional ultraviolet (UV) absorbance methods by approximately 30-fold, allowing accurate binding affinity measurements for inhibitors with nanomolar affinity. The procedure was validated using known LOX inhibitors and the allosteric effector 13(S)-hydroxy-9Z,11E-octadecadienoic acid (13-HODE).     

ULTRASTRUCTURE OF GLANDULAR OVARIAN TRICHOMES OF CYPRIPEDIUM CALCEOLUS AND C. REGINAE (ORCHIDACEAE)

Trichomes on the orchid ovary are a possible site of synthesis and secretion of the floral scent. Scanning electron microscopy of these trichomes shows a bulbous cell on a two-celled stalk. Thin sections of the tip cell revealed the morphology of an active, secretory cell with unusual coated vesicles in the extra-cellular deposition. Abundant smooth endoplasmic reticulum (ER) aggregated beneath the plasma membrane in the apical region of the cell and the limited dictyosomes in the cell suggest direct secretion by ER. Numerous lipid droplets are present in the apical area. Plastids, found only in the basal region of this cell, are more round in profile than typical chloroplasts and contain only a few unstacked thylakoids and a limited membranous reticulum. In addition to the normal plastid envelope, a double layer of membrane (probably ER) is tightly appressed to each dense, starch-free plastid. Highly specialized morphology and subcellular localization of organelles suggest the secretory nature of these trichomes.     

Does phospholipase C stimulate thymide kinase activity of rat liver extracts prepared after partial hepatectomy.

Our purpose was to determine whether phospholipase C stimulated thymidine kinase activity of regenerating rat liver. We determined effects of phospholipase C upon TMP formation by rat liver extracts prepared at 0, 12, 24, 36 and 48 hr following partial hepatectomy. Data were obtained which supported these conclusions: (a) Commercial preparations of phospholipase C contained nucleoside phosphotransferase activity; (b) phospholipase C exerted no appreciable stimulatory influence upon thymidine kinase activity of regenerating rat liver; and (c), apparent stimulation of thymidine kinase was associated with linked activities of two enzymes, viz., liver extract-ATPase activity and nucleoside phosphotransferase activity.     

Using Social Network Methods to Test for Assortment of Prosociality among Korean High School Students

Assortative interaction among altruistic individuals is a necessary condition for the evolution of cooperation. The requirement for assortment holds regardless of whether a meta-population is subdivided into distinct and isolated subgroups or has ephemeral boundaries with a high migration rate. The assumption, however, is rarely tested directly. In this paper, we develop a method to test for assortment of prosociality in network-structured data. The method is applied to a friendship network collected from 238 Korean students attending the same high school. A mixing matrix was used to explore the presence of assortative friendship among more prosocial individuals. An exponential random graph model of network structure that accounts for additional observed relational propensities (higher-than-expected number of people nominating no friends) and sampling constraints (upper bound on friendship nominations) found that individual prosociality predicted friendship propensity, and that individuals with higher prosocial scores had a higher probability of befriending other more prosocial individuals. The results reveal that a considerable level of assortment of prosociality characterizes this population.     

Synthesis and storage of a neurohormone in insect brains in vitro

The build-up of neurosecretory material in the median neurosecretory cells and fibre tracts of cultured cockroach brains was demonstrated by staining and bioassay. Examination of the cultured brains by electron microscopy showed active production of neurosecretory granules after 3 days in vitro. The close correlation of the results obtained by these different methods of assay leaves little doubt that a neurohormone is being synthesized and stored.