Pulmonary arterial disease in cats seropositive for Dirofilaria immitis but lacking adult heartworms in the heart and lungs

OBJECTIVE

To determine the prevalence and severity of pulmonary arterial lesions in cats seropositive for heartworms (Dirofilaria immitis) but lacking adult heartworms in the heart and lungs during necropsy.

ANIMALS

630 adult cats from an animal control shelter in Florida.

PROCEDURE

Cats were tested for adult heartworms in the heart and pulmonary arteries and antibody against heartworms in the serum. Histologic examination was conducted on the right caudal lung lobe of 24 heartworm- and antibody-positive cats; 24 heartworm-negative and antibody-positive cats; and 24 heartworm-, antibody-, and antigen-negative cats. Wall areas of 10 small to medium-sized pulmonary arteries of each cat were measured and expressed as a proportion of total cross-sectional area.

RESULTS

Heartworm infection or seropositive status was significantly and strongly associated with seventy of medial hypertrophy of pulmonary arterial walls. Heartworm- and antibody-positive cats and heartworm-negative and antibody-positive cats had a significant increase in wall thickness, compared with wall thickness for heartworm- and antibody-negative cats. Heartworm- and antibody-positive cats had the most severe hypertrophy. The proportion with occlusive medial hypertrophy was significantly higher in heartworm- and antibody-positive cats (19/24 [79%]) and heartworm-negative and antibody-positive cats (12/24 [50%]), compared with heartworm- and antibody-negative cats (3/24 [13%]).

CONCLUSIONS AND CLINICAL RELEVANCE

Cats with serologic evidence of exposure to heartworms, including those without adult heartworms in the lungs and heart, have a greater prevalence of pulmonary arterial lesions than heartworm-negative cats without serologic evidence of exposure. Additional studies are needed to define the pathogenesis, specificity, and clinical importance of these lesions.

Nutritional management and the multisystem organ failure/systemic inflammatory response syndrome in critically ill preterm neonates

Current information and concepts regarding unique features and practical aspects of metabolism and the nutritional management of critically ill, very low birthweight neonates are reviewed in this article. The use of "gut priming" (early hypocaloric minimal enteral feeding) and parenteral nutrition and their application to the treatment of specific disease states is discussed. The concepts of critical oxygen delivery and multiorgan failure and their impact on nutritional management in adults show striking similarities to metabolic observations of progressively deteriorating, sick neonates.

Feeding practices for infants weighing less than 1500 G at birth and the pathogenesis of necrotizing enterocolitis

This article examines clinical issues regarding gut maturation, gut colonizatiion, gut luminal starvation, a germ-free gut, and the role of enteral intake in the pathogenesis of necrotizing enterocolitis (NEC) in very low birth weight neonates and micropremies. NEC is identified as the final common pathway for a variety of etiologic mechanisms, only one of which is consistent with the enteral-based theory of NEC. The technique of minimal enteral intake ("gut priming") is discussed as a strategy to maintain the normal ontological processes of the developing gut ex utero. A combination of enteral plus parenteral intake is described to achieve nutritional goals.

The role of cortical Na,K-ATPase in distal nephron potassium secretion by the immature canine kidney

Amiloride-sensitive potassium secretion in response to acute potassium loading is lower in the newborn than in the adult. Potassium secretion is a function of late distal tubule and cortical collecting tubule Na,K-ATPase activity. Na,K-ATPase activity in vivo is determined by enzyme abundance and catalytic turnover. Chronic potassium supplementation increases potassium secretory capacity in the adult by increasing enzyme abundance in the late distal and cortical collecting tubules. We hypothesized that the lower potassium secretory capacity of the newborn was the result of lower late distal and cortical collecting tubule Na,K-ATPase activity and could be similarly enhanced. To test this hypothesis, newborn dogs were supplemented with 6 mmol KCl.d-1.kg-1 for 1 wk; age-matched litter mate controls were not (n = 8 pairs). Potassium supplementation resulted in a mean increase in Vmax Na,K-ATPase activity in vitro (proportional to pump abundance) of 70 +/- 42%. Mean Na,K-ATPase activities +/- SEM were 279 +/- 58 versus 198 +/- 44 nmol inorganic P. h-1.microgram DNA-1, p = 0.05. However, amiloride-sensitive potassium secretion after an acute potassium load of 20 mumol.min-1.kg-1 over 150 min was not enhanced (9.6 +/- 1.8 versus 8.9 +/- 0.8 mumol.min-1.kg-1, potassium-supplemented versus control animals). We conclude that lower enzyme abundance is not primarily responsible for the newborn's lower potassium secretory capacity. We speculate that the factor that limits secretion in the newborn during acute potassium loading does so by restricting catalytic turnover of the enzyme in vivo.

Chronic potassium supplementation of newborn dogs increases cortical Na,K-ATPase but not urinary potassium excretion

The distal nephron of the newborn dog cannot secrete an acute potassium load as efficiently as can that of the adult dog. Distal nephron potassium secretion is dependent upon basolateral Na,K-ATPase activity. Because Na,K-ATPase activity is lower in the immature than the mature distal nephron, it was hypothesized that lower Na,K-ATPase activity may be responsible for the lower potassium secretory capacity of the immature nephron. In the adult, chronic high dietary potassium intake increases renal tubular potassium secretory capacity by increasing Na/K pump abundance in distal nephron segments responsible for potassium secretion. Therefore, in order to test the above hypothesis, renal cortical and outer medullary Na,K-ATPase activity under Vmax conditions (a measure of pump abundance) and urinary potassium excretion during acute potassium loading were determined in 7 age-matched, litter mate pairs (chronically potassium supplemented versus control) newborn dogs. The potassium supplemented member of each pair received 6 mmol.day-1.kg-1 of KCl as a 150 mM solution for 7-21 days after birth and the control member received an equal volume of water for the same period of time. This protocol resulted in a doubling of renal cortical Vmax Na,K-ATPase activity in the potassium supplemented animals (from 369 +/- 186 to 718 +/- 286 nmol Pi liberated.h-1.micrograms DNA-1, P = 0.025). There was no significant change in outer medullary enzyme activity. Contrary to the above hypothesis, this increase in cortical enzyme activity was not associated with increased potassium excretion at baseline or during acute potassium loading.(ABSTRACT TRUNCATED AT 250 WORDS)

Interruption of response ofDendroctonus brevicomis to attractive pheromone by release of pheromone at several rates and spacings

The number of western pine beetles,Dendroctonus brevicomis, trapped at the center of three 90 × 90-m plots was reduced during a 16-hr period after surrounding an attractive source ofexo-brevicomin, frontalin, and myrcene with 16, 48, or 168 sources of the same attractant. Compounds were released from the center of the plot at 1 mg/16 hr/compound, and from the surrounding sources at 4-280 mg/16 hr/compound. About half of these amounts was released between 1530 hr and 1930 hr, the period of peak beetle flight. No treatment differences were apparent in reduction of catch within the range of release rates and spacings tested. When compounds were released continuously from 168 stations for 17 days, catch at the center of a plot was generally lower than catch before or after this period, but fluctuated daily. More beetles were caught on traps hung on ponderosa pines within a plot and the number of these traps catching beetles was greater when compounds were released from all stations than from only the center station. Beetles caught on traps were attracted into the plots from the surrounding forest, but appeared to be dispersed within the plot when compounds were released from many stations.D. brevicomis attacked at least 91 trees in the plots, of which 25 were killed during two summers.

Western pine beetle: specificity among enantiomers of male and female components of an attractant pheromone

The flight response of both sexes of Dendroctonus brevicomis to the mixture of myrcene, racemic frontalin, and (1R,5S,7R)-(+)-exo-brevicomin and to the mixture of myrcene, (1S,5R)-(-)-frontalin and racemic exo-brevicomin was significantly greater than the response to the same mixtures in which the antipodes were substituted. The flight response to these two mixtures was also greater than the response to the ternary mixture of myrcene, racemic frontalin, and racemic exo-brevicomin (MFE). The walking response of both sexes to the mixture of myrcene, racemic frontalin, and (+)-exo-brevicomin was not different from the response to MFE. Substitution of the antipode lowered the response when compared to that of MFE. When evaporated with ponderosa pine turpentine, (-)-frontalin was active in the field while its antipode was not.

Response of Ips confusus to synthetic sex pheromones in nature

The first flight response of bark beetles to synthetic sex pheromones under natural conditions is reported. Two insect species predaceous on this bark beetle also responded. The synthetic compounds delivered in an airstream from a substrate of Carbowax 20M on Chromosorb A appear to elicit the same response as the natural attractant from male-infested bolts of ponderosa pine elicits.

Brevicomin: principal sex attractant in the frass of the female western pine beetle

The principal component of the sex attractant produced by the female western pine beetle (Dendrotonus brevicomis) is exo-7-ethyl-5-methyl-6,8-dioxabicyclo[3.2.1]octane; the trivial name brevicomin is suggested.