Mitochondrial DNA in anucleate human blood cells

Homogeneous populations of human blood platelets or erythrocytes were lysed in alkaline EDTA, bound to nitrocellulose and hybridized to a radioactive mtDNA probe. By comparison to standards of known mtDNA concentration, we determined that platelets contained 4 mtDNA molecules per cell. Rhodamine 123 staining revealed an average of 4 mitochondria per platelet indicating that each mitochondrion contains a single mtDNA molecule. No detectable mtDNA was found in erythrocyte lysates. Using the same procedure, we found that in nucleated cells, mitochondria contained multiple mtDNAs per mitochondrion.     

Parameters that specify the timing of cytokinesis.

One model for the timing of cytokinesis is based on findings that p34(cdc2) can phosphorylate myosin regulatory light chain (LC20) on inhibitory sites (serines 1 and 2) in vitro (Satterwhite, L.L., M.H. Lohka, K.L. Wilson, T.Y. Scherson, L.J. Cisek, J.L. Corden, and T.D. Pollard. 1992. J. Cell Biol. 118:595-605), and this inhibition is proposed to delay cytokinesis until p34(cdc2) activity falls at anaphase. We have characterized previously several kinase activities associated with the isolated cortical cytoskeleton of dividing sea urchin embryos (Walker, G.R., C.B. Shuster, and D.R. Burgess. 1997. J. Cell Sci. 110:1373-1386). Among these kinases and substrates is p34(cdc2) and LC20. In comparison with whole cell activity, cortical H1 kinase activity is delayed, with maximum levels in cortices prepared from late anaphase/telophase embryos. To determine whether cortical-associated p34(cdc2) influences cortical myosin II activity during cytokinesis, we labeled eggs in vivo with [(32)P]orthophosphate, prepared cortices, and mapped LC20 phosphorylation through the first cell division. We found no evidence of serine 1,2 phosphorylation at any time during mitosis on LC20 from cortically associated myosin. Instead, we observed a sharp rise in serine 19 phosphorylation during anaphase and telophase, consistent with an activating phosphorylation by myosin light chain kinase. However, serine 1,2 phosphorylation was detected on light chains from detergent-soluble myosin II. Furthermore, cells arrested in mitosis by microinjection of nondegradable cyclin B could be induced to form cleavage furrows if the spindle poles were physically placed in close proximity to the cortex. These results suggest that factors independent of myosin II inactivation, such as the delivery of the cleavage stimulus to the cortex, determine the timing of cytokinesis.     

Opiate receptors in mice: genetic differences.

The concentration of opiate receptors in the brains of mice was determined by means of a naloxone-binding assay. The strains of mice used in these experiments were C57BL/6By, BALB/cBy, their reciprocal F₁ hybrids, and 7 recombinant-inbred strains derived by inbreeding from the F₂ generation. These strains could be divided into 3 groups on the basis of the number of opiate receptors: high (CXBH); low (CXBK); and intermediate (all the other strains). The difference in stereospecific binding of naloxone reflects a difference in the total number of receptor sites rather than in the affinity for the drug. The recombinantinbred strains also differ in their analgesic response to morphine, as previously determined by the tail-flick assay. The differences in the number of opiate receptors are not enough to account for the genetic difference in analgesic responsiveness. Both these parameters appear to be under different genetic control, and at least 2 genetic determinants may be involved in regulating the level of opiate receptors.     

Phosphorylating-dephosphorylating enzymes of avian oviductal secretions

Avian oviductal fluids contain phosphorylating-dephosphorylating enzymes that might function in sperm-oocyte interactions. Phosphorprotein phosphatase and protein kinase have been purified 20-fold and 40-fold, respectively. The latter easily aggregates and is highly labile. Other properties are comparable to those of holoenzymes.     

Developmental Basis of Phallus Reduction during Bird Evolution

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The role of fish-poultry integration on fish growth performance,yields and economic benefits among smallholder farmers in sub-Saharan Africa,Tanzania

Aquaculture practices from sub-Saharan Africa are characterised by low production, owing to improper technology. Production can be increased through integrating fish farming with other existing on-farm activities, particularly livestock husbandry. We assessed the role of fish-poultry integration on all male Nile tilapia, Oreochromis niloticus growth performance, yields and economic benefits among smallholder farmers in sub-Saharan Africa, Tanzania. The study also compared phytoplankton species composition, abundance and biomass between the fish-poultry integration and non-integrated system. After 180 days of the experiment, all male O. niloticus cultured under fish-poultry integration exhibited significantly higher growth rates than those in the non-integrated system (p < 0.05). Gross fish yield (GFY), net fish yield (NFY) and net annual yields (NAY) obtained from fish-poultry integration were significantly higher than those from non-integrated system (p < 0.05). Partial enterprise budget analysis revealed that fish-poultry integration was more profitable than the non-integrated system. Moreover, fish-poultry integrated system produced significantly higher phytoplankton abundance and biomass than those from the non-integrated system. Results demonstrate that rural smallholder farmers can achieve higher growth rate, farm net yields and income by integrating all male O. niloticus with other on-farm activities than practising a stand-alone fish culture system.     

The role of the plastic surgeon in the management of surgical infection.

At our Medical Center, our reconstructive service has actively sought referrals of acute and chronic infections by declaring an interest in undertaking the integrated management and reconstruction of these cases. The practices of the two senior surgeons were reviewed for three academic years (1992 to 1995). Cases of surgical infection were analyzed as to site, ablative procedures, and reconstructive procedures. In total, 139 patients with 147 infections were identified. Sites of infection included head and neck (9.5 percent), trunk and pelvis (39.5 percent), upper extremity (22 percent), and lower extremity (29 percent). One-hundred thirty-one ablative procedures were done on this group, as were 126 reconstructive procedures, including 17 fasciocutaneous flaps, 26 pedicled muscle flaps, and 28 microsurgical flaps. With a mean follow-up of 14 months, 92 percent of these patients had resolution of infection. The 8 percent failure group included recurrences, amputation, and death. This series demonstrates that a plastic surgery service can attract a diverse population of surgical infections and manage them successfully with ablation and a wide variety of reconstructive procedures. The coordination of ablation and reconstruction may be optimally performed by the plastic surgeon.