Influence of volume expansion on capillary transport in the gut of Pichindé virus infected strain 13 guinea pigs.

Hydropenic strain 13 guinea pigs (GP13) injected with Pichindé virus show marked jejunal capillary disruption determined by a reduction in protein reflection coefficient (sigma) [Katz and Starr, 1990]. These studies examined whether this is reversed by a 2% Ringer's expansion, and whether anorexia may contribute to reduced sigma. GP13 were either infected or given a 60% expected ad lib diet, and were studied while under a 2% Ringer's expansion. The results showed 1) infected GP13 separated into groups with either a persistently low sigma (volume unresponsive) or a normal sigma (volume responsive), but no obvious feature of the animals could predict responsiveness; 2) caloric restriction had minimal to no effect on sigma; and 3) both responsive and unresponsive GP had increased heart, lung, and kidney weights. Volume expansion may have salutary effects in some infected GP13, and this is probably due to pressure mediated effects on the capillary wall. The findings support the possibility that conservative management of hemorrhagic fevers may directly ameliorate capillary leak.

Pichinde virus infection in strain 13 guniea pigs reduces intestinal protein reflection coefficient with compensation.

Pichinde virus inoculation into strain 13 guinea pigs is a model with features reputed to be similar to hemorrhagic fever in humans. Although the infection is lethal by day 13-19, guinea pigs of approximately 600 g do not show edema or effusions. This raises the questions of whether capillary damage is present in such infected animals and, if it is, why edema is absent. The effects of Pichinide virus on protein transport across jejunal capillaries were examined in 38 normal and 7 infected strain 13 guinea pigs 12 days after inoculation. The latter lost 20.3% body weight but maintained normal blood pressure, serum protein concentration, and jejunal lymph flow. However, their protein solvent drag reflection coefficient (sigma) was reduced to .52 +/- .03 (mean +/- SE) from .73 +/- .02 (2P less than .001), while permeability-surface area product was not changed. In the absence of gross edema or effusions, Pichinde virus-infected guinea pigs demonstrated a leaky gut capillary wall to protein compatible with an increase in pore size or large pore number less than sufficient to change permeability-surface area product. Compensatory mechanisms that prevent edema at this stage are efficient and may include reduced capillary pressure or some degree of capillary flow stasis.

Dynamics of water and protein transport through and around the canine medial iliac lymph nodes.

Although isolated popliteal node perfusion studies have shown intranodal exchange of water between blood and lymph, questions remain about the significance of such studies. Do some nodes exchange protein with blood, and are there shunt pathways around nodes which tend to buffer intranodal exchange of water? Finally, what is the magnitude of difference in using postnodal lymph to compute tissue capillary membrane parameters of reflection coefficient, sigma, and permeability-surface area product, PS? Seventeen conditioned dogs were randomly divided into matched experimental (N = 8) and sham (N = 9) groups in which lumbar trunk lymph was measured for flow (JV) and lymph/plasma protein concentration ratios (R) before and after ligation or sham ligation of the medial iliac lymph node (MILN). Ligation reduced (JV) from 25.89 +/- 4.21 SEM microliter . min-1 . kg-1 to 20.45 +/- 1.84 (P less than .008), decreased R from .66 +/- .04 to .55 +/- .02 (P less than .0000), increased sigma from .42 +/- .04 to .55 +/- .04 (P less than .004), and did not change PS which was 11.45 +/- 2.13 before and 14.43 +/- 4.19 after ligation. No similar changes occurred in the sham group. Of four hypotheses tested, the data were compatible only with post ligation flow equal to the sum of tissue lymph production and efferent flow from upstream nodes. Protein moved from blood into the nodal lymph nearly with the ease of water. Reflection coefficient was 23% higher at the afferent level than in the post nodal lymph, but PS was unaffected by the MILN. Differences in using post nodal sigma and PS to compute tissue fluid levels of protein are about 10% at these flow, and shunt flow is as high as 79% of lumbar trunk flow. Conclusions based upon sigma and PS differences across the node must be tempered because of the possibility of the trend toward lymph-blood equilibration of afferent lymph if it passed through several upstream nodes.