Systematics within Gyps vultures: a clade at risk

Background  

Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis.     

The adult fast isozyme of myosin is present in a nerve-muscle tissue culture system

Abstract. Organotypic nerve-muscle cultures were prepared from foetal mouse spinal cord and adult mouse muscle fibres. In this system, the adult fibres degenerate and new myotubes form. The regenerated muscle fibres become innervated, develop cross-striations, and survive for several months. We have investigated the isozymes of myosin present in these muscle fibres using histochemistry and immunocytochemistry with antibodies to rat embryonic, neonatal, and adult fast myosins. We demonstrate that some of the regenerated fibres contain adult fast but not embryonic or neonatal myosin. This is the first demonstration of the production of adult myosin heavy chain in tissue culture. This system therefore offers the possibility for further study of the development of adult myosin isoforms in vitro.     

Heat shock-induced changes in the structural stability of proteinaceous karyoskeletal elements in vitro and morphological effects in situ

Karyoskeletal protein fractions prepared from Drosophila melanogaster embryos contain morphologically identifiable remnants of nuclear pore complexes and peripheral lamina as well as what appears to be an internal nuclear "matrix" (Fisher, P. A., M. Berrios, and G. Blobel, 1982, J. Cell Biol., 92: 674-686). Structural stability of these proteinaceous assemblies is dependent on thermal incubation in vitro (37 degrees C, 15 min) before subfractionation of nuclei. In the absence of such incubation, greater than 90% of the total karyoskeletal protein including major polypeptide components of internal "matrix," pore complexes, and the peripheral lamina, is solubilized by 1 M NaCl. In vivo heat shock induces karyoskeletal stabilization resembling that resulting from thermal incubation in vitro. Immunocytochemical studies have been used to establish the effects of heat shock on the organization and distribution of major karyoskeletal marker proteins in situ. Taken together, these results are consistent with the notion that in vivo, regulation of karyoskeletal plasticity (and perhaps form) may be a functionally significant component of the Drosophila heat shock response. They also have broad practical implications for studies pertaining to the structure and function of karyoskeletal protein (nuclear "matrix") fractions isolated from higher eukaryotic cells.     

Natural killer cells can enhance the proliferative responses of B lymphocytes

In addition to lytic activity against malignant and virally transformed target cells, recent evidence has suggested that natural killer (NK) cells can modulate immune activities such as the suppression of B cell responses through noncytotoxic means. Using human B cells and highly purified autologous NK cells, we have demonstrated that NK cells can substantially augment the proliferative responses of B cells stimulated with the surface immunoglobulin crosslinking agents anti-IgM or Staphylococcus aureus Cowan strain I (SAC). This "enhancer" activity of NK cells was quite potent and was observed at an NK:B cell ratio as low as 0.05. Peak blastogenic responses of B cells cocultured with NK cells in the presence of B cell activators were observed at 2-3 days, similar to the responses of B cells in the absence of NK cells. Using the inhibitor of DNA synthesis mitomycin C, we determined that B cells and not NK cells were proliferating in cocultures of these lymphocytes stimulated with SAC. Activated B cells neither prevented the lysis of the isotope-labeled NK-sensitive target cell line K562 nor formed conjugates with NK cells, suggesting that cell contact was not a prerequisite for the effect. These studies have further expanded the functional repertoire of NK cells to include enhancer as well as suppressor and lytic activities.     

Neonatal and adult myosin heavy chain isoforms in a nerve-muscle culture system

When adult mouse muscle fibers are co-cultured with embryonic mouse spinal cord, the muscle regenerates to form myotubes that develop cross-striations and contractions. We have investigated the myosin heavy chain (MHC) isoforms present in these cultures using polyclonal antibodies to the neonatal, adult fast, and slow MHC isoforms of rat (all of which were shown to react specifically with the analogous mouse isoforms) in an immunocytochemical assay. The adult fast MHC was absent in newly formed myotubes but was found at later times, although it was absent when the myotubes myotubes were cultured without spinal cord tissue. When nerve-induced muscle contractions were blocked by the continuous presence of alpha-bungarotoxin, there was no decrease in the proportion of fibers that contained adult fast MHC. Neonatal and slow MHC were found at all times in culture, even in the absence of the spinal cord, and so their expression was not thought to be nerve-dependent. Thus, in this culture system, the expression of adult fast MHC required the presence of the spinal cord, but was probably not dependent upon nerve-induced contractile activity in the muscle fibers.     

Mechanisms underlying the asynchronous replacement of myosin light chain isoforms during stimulation-induced fibre-type transformation of skeletal muscle

During the fibre-type transformation induced by chronic electrical stimulation of rabbit fast-twitch muscle, replacement of the fast forms of the two classes of myosin light chain by their slow isoforms occurs asynchronously. Studies of total cellular myosin light chains and of the slow-to-fast transition now justify the conclusion that the asynchrony is due to switching between the expression of fast and slow genes for the two light chain classes at sequential stages of the transformation process.     

INTRACORPOREAL HEAT DISSIPATION FROM A RADIOISOTOPE-POWERED ARTIFICIAL HEART

The feasibility of radioisotope-fueled circulatory support systems depends on the ability of the body to dissipate the reject heat from the power source driving the blood pump as well as to tolerate chronic intracorporeal radiation. Our studies have focused on the use of the circulating blood as a heat sink. Initial in vivo heat transfer studies utilized straight tube heat exchangers (electrically and radioisotope energized) to replace a segment of the descending aorta. More recent studies have used a left ventricular assist pump as a blood-cooled heat exchanger. This approach minimizes trauma, does not increase the area of prosthetic interface with the blood, and minimizes system volume. Heat rejected from the thermal engine (vapor or gas cycle) is transported from the nuclear power source in the abdomen to the pump in the thoracic cavity via hydraulic lines. Adjacent tissue is protected from the fuel capsule temperature (900 to 1200 degrees F) by vacuum foil insulation and polyurethane foam. The in vivo thermal management problems have been studied using a simulated thermal system (STS) which approximates the heat rejection and thermal transport mechanisms of the nuclear circulatory support systems under development by NHLI. Electric heaters simulate the reject heat from the thermal engines. These studies have been essential in establishing the location, suspension, surgical procedures, and postoperative care for implanting prototype nuclear heart assist systems in calves. The pump has a thermal impedance of 0.12 degrees C/watt. Analysis of the STS data in terms of an electrical analog model implies a heat transfer coefficient of 4.7 x 10(-3) watt/cm(2) degrees C in the abdomen compared to a value of 14.9 x 10(-3) watt/cm(2) degrees C from the heat exchanger plenum into the diaphragm.     

Effects of beta-adrenergic receptor activation, cholera toxin and forskolin on human natural killer cell function.

Membranes from highly purified natural killer (NK) cells were ADP-ribosylated by treatment with cholera toxin (CTX). CTX resulted in a single band of specific 32P incorporation at Mr 43,600. CTX treatment of intact NK cells caused a 9-fold increase in cyclic AMP (cAMP) concentrations. Pretreatment of NK cells with CTX diminished their ability to lyse K562 tumour cells by up to 79%. Forskolin treatment elevated NK cell cAMP levels 8-fold and decreased lysis of K562 cells by up to 45%. Adrenaline and isoprenaline (isoproterenol) both inhibited lysis of K562 cells by approx. 35% and elevated cAMP by at least 2.5-fold, and their inhibition of lysis was reversed by propranolol. These data suggest that the stimulatory guanine-nucleotide-binding protein GS coupled to beta-adrenergic receptors is involved in transducing signals which inhibit NK cell lysis of tumour cells. CTX and forskolin also diminish the ability of NK cells to bind K562 cells (binding is necessary for lysis). This suggests that the NK-cell receptor(s) for the tumour cell may be altered as a consequence of cAMP-mediated events or by activation of GS.