Ecological countermeasures to prevent pathogen spillover and subsequent pandemics

Substantial global attention is focused on how to reduce the risk of future pandemics. Reducing this risk requires investment in prevention, preparedness, and response. Although preparedness and response have received significant focus, prevention, especially the prevention of zoonotic spillover, remains largely absent from global conversations. This oversight is due in part to the lack of a clear definition of prevention and lack of guidance on how to achieve it. To address this gap, we elucidate the mechanisms linking environmental change and zoonotic spillover using spillover of viruses from bats as a case study. We identify ecological interventions that can disrupt these spillover mechanisms and propose policy frameworks for their implementation. Recognizing that pandemics originate in ecological systems, we advocate for integrating ecological approaches alongside biomedical approaches in a comprehensive and balanced pandemic prevention strategy.

A simple method for the simultaneous measurement of sodium and chloride fluxes across transporting epithelia

A simple technique for the separation of 22Na and 36Cl radioactivity in the same solution is described. Two samples were taken from a solution containing both 22Na and 36Cl. One sample was precipitated with AgNO3 and the other was untreated. Samples were assayed for radioactivity by liquid scintillation spectrophotometry. Precipitation with AgNO3 removed 100% of the 36Cl activity from solution while having no effect on the 22Na radioactivity. Thus precipitated samples contained only 22Na radioactivity. Subtraction of the radioactivity in the supernatants of precipitated samples (i.e. 22Na) from the total radioactivity of untreated samples (i.e. 22Na and 36Cl) yielded the level of 36Cl activity in these samples.

Chloride transport in glands of frog skin

The effects of beta-adrenergic stimulation on the bidirectional fluxes of Na+ and Cl- across the frog skin glands were determined. Isoproterenol elicited net serosal-to-mucosal fluxes of both Na+ (JNanet) and Cl- (JClnet) equal to 0.19 +/- 0.05 (SE) and 0.57 +/- 0.05 mueq X cm-2 X h-1, respectively. The residual current (JClnet - JNanet) of 0.38 +/- 0.05 mueq X cm-2 X h-1 closely approximates the isoproterenol-induced short-circuit current of 0.30 +/- 0.04 mueq X cm-2 X h-1. Furosemide added to the serosal side prior to isoproterenol inhibited the isoproterenol-induced net fluxes of both Na+ and Cl-. The addition of dibutyryl cAMP and 3-isobutyl-1-methylxanthine to the serosal side mimicked the action of isoproterenol by stimulating glandular short-circuit current. We conclude that an active Cl(-)-transport mechanism resides in the frog skin glands and is 1) stimulated by a beta-adrenergic agonist (its action is mimicked by cAMP) and 2) inhibited by the loop diuretic furosemide.

Effects of extracellular calcium removal and anoxia on isolated rat myocytes

Calcium-tolerant myocytes were isolated from adult rat ventricles by successive perfusion and incubation with buffer containing collagenase and hyaluronidase. Greater than 70% of the cells excluded trypan blue, maintained normal morphology, and contracted in response to an externally applied electric field. We have characterized metabolic defects present in isolated calcium-tolerance myocytes when exposed to low concentrations of extracellular calcium under aerobic and anaerobic conditions. In control cells exposed to 1.25 mM Ca2+, the following metabolic parameters were measured (in mumol/g protein): adenosine triphosphate (ATP) 28.8 +/- 3.3, creatine phosphate (CrP) 49.1 +/- 7.5, intracellular Na+ 37.7 +/- 8.1, intracellular K+ 352.9 +/- 49.3, cellular Ca2+ 12.3 +/- 1.8, as well as rate of protein synthesis 0.34 +/- 0.03 mumol . g protein-1 . h-1. In aerobic cells incubated in medium without added Ca2+, the corresponding values (in mumol/g protein) were ATP 27.9 +/- 4.4, CrP 25.3 +/- 4.3, intracellular Na+ 130.9 +/- 23.1, intracellular K+ 217.2 +/- 32.0, cellular Ca2+ 3.9 +/- 1.0, and rate of protein synthesis 0.09 +/- 0.02 mumol . g protein-1 . h-1. These data indicated major metabolic aberrations in myocytes exposed to medium low in Ca2+ (less than 10 microM). Metabolic depression was most severe in cells incubated in the absence of both Ca2+ and O2. It is postulated that Ca2+ removal resulted in an increase in Na+ and K+ permeability, causing a net gain of intracellular Na+ and loss of intracellular K+. These ionic shifts might stimulate the activity of membrane-associated Na+-K+-ATPase, accounting for lower levels of CrP.

Isoproterenol-induced current changes in glands of frog skin

In this study we report on isoproterenol-induced changes in short-circuit current (SCC) that are located in the glands of the frog skin. Following complete inhibition of the SCC with amiloride (10(-4) M), the addition of isoproterenol (9.0 X 10(-7) M) to the serosal side of the skin elicits a significant increase in SCC from 0.6 +/- 0.1 to 3.9 +/- 0.5 microA/cm2 (p less than 0.001). The conductance is doubled, and both effects are blocked completely with the beta-blocking agent propranolol. In the split-skin preparation, in which no glands are present, there is no current response to isoproterenol following amiloride. This indicates that the amiloride-insensitive isoproterenol-stimulated SCC resides in the glands. In the intact skin, removal of sodium (choline replacement) from the serosal (but not the mucosal) medium abolishes this current change. The postisoproterenol current change in amiloride-inhibited skins is also dependent on the presence of chloride in the serosal bath. Preincubation of the amiloride-inhibited skin with ouabain (10(-4) M) for 10 min prior to the addition of isoproterenol reduces the isoproterenol response by 50%. These results indicate that there is a sodium- and chloride-dependent ouabain-sensitive secretory mechanism in the skin glands of the frog that is responsible for the development of the isoproterenol-stimulated SCC observed in the presence of amiloride.

The isolation of single cells from the avian salt gland

Collagenase, hyaluronidase, and trypsin were used to isolate single cells from the avian salt gland. Three cell types were distinquishable in the resultant cell suspension: peripheral, intermediate, and principal cells. The fine structure of these cells is described and related to the morphology of the intact gland.

Localization of K+-stimulated p-NPPase in the lachrymal 'salt' gland of Malaclemys, using cytochemical and autoradiographical techniques

Using two independent techniques, histochemistry and autoradiography, an enzyme (E.C. 3.6.1.3.) has been localized on basolateral cell membranes of salt secreting cells in the lachrymal gland of Malaclemys. This enzyme is ouabain sensitive. In addition an L-tetramisole sensitive alkaline phosphatase is found in the same sites, and an ethacrynic acid sensitive K+-stimulated p-NPPase is found on the apical membrane. The significance of these results with regard to the location of the pump responsible for net transepithelial sodium transport is discussed.