Evaluation of subcutaneous chambers as an alternative to conventional methods of antibody production in chickens.

We compared antibody levels among serum, egg yolk extract, and granuloma fluid in chickens immunized with bovine serum albumin (BSA). One group of hens was immunized by intramuscular and subcutaneous injection of bovine serum albumin in complete Freund's adjuvant, followed by two subsequent booster injections in incomplete Freund's adjuvant. Two other groups were surgically implanted with plastic, perforated wiffle balls (subcutaneous chambers). After a 30-day recovery period, one of the groups with subcutaneous chambers was immunized with BSA in sterile water with two subsequent boosts. The other group was injected with only sterile water. Serum samples, eggs, and granuloma fluid were collected biweekly and analyzed to determine specific IgG, total IgG, and total protein. The subcutaneous chambers were well tolerated. Quantitative ELISAs of serum, egg yolk extract, and granuloma fluid specimens disclosed that specific antibody levels were present in all specimens by 2 weeks after primary immunization. During the course of the experiment, specific antibody levels of serum and egg yolk specimens were significantly higher than those of granuloma fluid (P less than 0.05). However, an additional injection of antigen into the subcutaneous chambers resulted in specific antibody levels in granuloma fluid specimens that were comparable to those of serum and egg yolk extract. Use of subcutaneous chambers in chickens may be a viable alternative to routine antibody production methods.

Growth and functional assessment of pulmonary valves in pigs after replacement of sinuses of Valsalva.

Neopulmonary artery stenosis may occur after the arterial switching procedure to correct transposition of the great arteries. One technique to reduce this complication is to use a single rectangular piece of autogenous pericardium to reconstruct two adjacent sinuses of Valsalva and maintain pulmonary artery size. The long-term effect of this technique on pulmonary artery and valve growth and function is unknown. To assess this technique, Yorkshire-cross pigs (n = 5) weighing 29 +/- 1.7 kg (mean +/- SEM) were anesthetized, and during cardiopulmonary bypass, the pulmonary artery was transected distal to the pulmonary valve. Pulmonary artery diameter and commissure distances were measured. Two adjacent pulmonary artery sinuses of Valsalva were completely excised from the anulus to 4 mm distal to the commissures, leaving 2 mm of pulmonary artery tissue attached to the skeletonized commissure and on each side of the one remaining intact sinus of Valsalva. A single rectangular patch of fresh autologous pericardium was sutured to the anulus and remnant of the pulmonary artery along the commissure and edges of the one intact sinus of Valsalva. Pericardium composed two thirds of the circumference of the proximal pulmonary artery; this was anastomosed to the distal pulmonary artery. Weight gain occurred at a rate of 0.6 kg/day (median). The animals underwent right heart catheterization and cineangiography. They were killed 157.2 +/- 12.9 days post-operatively. The reconstructed pulmonary artery grew from 17.6 +/- 0.8 mm to 30.8 +/- 1.5 mm (p < 0.01), and the commissure distances grew from 17.0 +/- 1 mm to 27.2 +/- 1.6 mm (p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Tumorigenic potential of a myc-containing strain of feline leukemia virus in vivo in domestic cats.

The oncogenic capacity of a myc-containing strain of feline leukemia virus (FeLV), termed LC-FeLV, has been examined after inoculation of the virus into neonatal kittens. Like other myc-containing strains of FeLV, LC-FeLV may induce with relatively short latency, but does not necessarily induce, thymic lymphosarcoma in viremic animals. Naturally occurring and experimentally induced tumors are T-cell lymphomas which contain clonally integrated LC-FeLV proviral DNA and which cannot readily be cultivated in vitro in the presence or absence of exogenously supplied interleukin-2. Acquisition of myc by FeLV decreases the period of latency before the appearance of tumors but does not expand the spectrum of tumors induced by FeLV alone.

Regional blood flow during continuous low-dose endotoxin infusion.

Escherichia coli endotoxin (ET) was administered to adult rats by continuous IV infusion from a subcutaneously implanted osmotic pump (Alzet). Cardiac output and regional blood flow were determined by the radiolabeled microsphere method after 6 and 30 hr of ET or saline infusion. Cardiac output (CO) of ET rats was not different from time-matched controls, whereas arterial pressure was 13% lower after 30 hr of infusion. After both 6 and 30 hr of ET, pancreatic blood flow and percentage of cardiac output were lower than in controls. Estimated portal venous flow was decreased at each time point, and an increased hepatic arterial flow (significant after 30 hr) resulted in an unchanged total hepatic blood flow. Blood flow to most other tissues, including epididymal fat, muscle, kidneys, adrenals, and gastrointestinal tract, was similar between treatments. Maintenance of blood flow to metabolically important tissues indicates that the previously reported alterations in in vitro cellular metabolism are not due to tissue hypoperfusion. Earlier observations of in vitro myocardial dysfunction, coexistent with the significant impairment in pancreatic flow, raise the possibility that release of a myocardial depressant factor occurs not only in profound shock but also under less severe conditions of sepsis and endotoxemia.

Lipolytic patterns in isolated adipocytes of continuously endotoxemic rats.

Lipolytic patterns were studied in adipocytes isolated from rats after 6 and 30 hr of continuous Escherichia coli endotoxin (ET) or saline infusion via a subcutaneously implanted osmotic pump. By 6 hr, ET cells responded to norepinephrine (NE) stimulation with significantly greater increase above basal rates of glycerol and free fatty acid (FFA) release than did control adipocytes. By 30 hr of continuous infusion, basal glycerol release was enhanced; the in vitro lipolytic response evoked by NE was significantly reduced in ET cells compared to rates on the previous day, and NE-stimulated lipolysis in ET cells was significantly below that of controls. At the same time, the in vitro antilipolytic effect of insulin was attenuated. We conclude that 1) an initial metabolic response can be observed within a few hours of a continuous, low dose ET infusion, 2) the biphasic nature of the sequential changes in lipolysis is likely to reflect alterations in the hormonal environment in vivo, and 3) these features are consonant with some aspects of the metabolic profile of septic patients.

Time course of changes in gluconeogenesis from various precursors in chronically endotoxemic rats.

Rates of gluconeogenesis (GNG) from lactate and triosephosphate precursors were measured in hepatocytes isolated from rats that have received endotoxin or physiological saline by continuous infusion from an implanted pump. Six hours after the onset of infusion (day 2 postsurgery) GNG from lactate was significantly elevated in hepatocytes of endotoxemic (ET) animals. By 24 hours later, the gluconeogenic rate was depressed, compared to cells of NaCl-infused controls. However, providing ET cells with lactate at concentrations found in the in vivo milieu resulted in glucose production at rates not different from those of control cells incubated at their respective in vivo (lower) substrate levels. On day 2 postsurgery, ET rats were hyperglycemic and hyperlactacidemic; on day 3 the elevated blood lactate concentration was maintained, but the plasma glucose values were not different from those of NaCl controls. The glucagon-induced increment in glucose synthesis was depressed in cells of ET rats both on day 2 and day 3 postsurgery, although the total amount of glucose released was significantly less only on day 3. The pattern of norepinephrine stimulation was similar to that of glucagon, except for the increase above the basal rate of GNG on day 3 being the same for control and ET cells. GNG was also assessed from oxidized substrates (fructose (F) and dihydroxyacetone (DHA] and reduced substrates (sorbitol and glycerol) entering the pathway at the triosephosphate level. On day 2 both cell populations produced glucose from each of the four precursors at comparable basal rates.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional hypoxic pulmonary vasoconstriction in dogs with asymptomatic dirofilariasis.

The pulmonary hemodynamic response to unilateral alveolar hypoxia was investigated in pentobarbital-anesthetized dogs with mild heartworm (HW) disease and in dogs free of HW (HWF). Left lung nitrogen ventilation in HWF dogs resulted in a decrease in the fraction of the cardiac output (QT) perfusing the left lung (QL) from 0.37 +/- 0.03 (SEM) to 0.20 +/- 0.02 (P less than 0.01). In contrast, dogs with mild HW disease did not develop a significant decrease in QL/QT which decreased from 0.38 +/- 0.02 to 0.33 +/- 0.02. This attenuated pulmonary vascular response to regional alveolar hypoxia in dogs with HW disease was associated with a normal pulmonary arterial pressure (14.8 +/- 1.5 mm of Hg) that was not different from that seen in HWF dogs (15.8 +/- 1.7 mm of Hg). These results indicate that mild HW disease interferes with the ability of hypoxic pulmonary vasoconstriction to redistribute pulmonary blood flow away from hypoxic regions of the lung.

Myocardial dysfunction in a nonlethal, nonshock model of chronic endotoxemia.

Escherichia coli endotoxin (ET) was administered to adult rats by continuous IV infusion from a subcutaneously implanted osmotic pump (Alzet). Myocardial function was assessed after 6 and 30 hr of ET infusion and compared with control rats which received a saline infusion and were fasted to match the anorexia of ET rats. Cardiac output (CO) and coronary blood flow, measured by the radiolabeled microsphere method, and mean arterial blood pressure, heart rate, total peripheral resistance, and stroke volume, were determined in vivo. Treatment differences were limited to a 13% lower arterial pressure in ET rats after 30 hr of infusion. Myocardial function was evaluated in vitro in similarly treated rats with the isolated perfused working heart preparation; preload was altered by raising the left atrial filling pressure (LAFP) from 10 to 30 cm water. After both 6 and 30 hr of infusion, hearts from ET rats exhibited a significantly lower peak systolic pressure (PSP), CO, and coronary flow in response to increasing LAFP, and a greater oxygen consumption per unit of myocardial work (CO X PSP). Reduced in vitro work performance of hearts from endotoxemic rats was demonstrated early in the course of chronic endotoxemia and in the absence of in vivo evidence of cardiac dysfunction. Myocardial dysfunction, masked in vivo by compensatory mechanisms used to maintain adequate cardiovascular function, may be an important feature in the pathogenesis of both experimental endotoxemia and clinical gram-negative sepsis.

Continuous infusion of endotoxin from an osmotic pump in the conscious, unrestrained rat: a unique model of chronic endotoxemia.

Endotoxin (ET) was administered to conscious, unrestrained rats by continuous intravenous infusion from an Alzet osmotic pump. Delivery of ET was delayed 42 h after surgery by inserting a 100-cm coil of PE-60 tubing between pump and jugular vein. Rats were anorectic following onset of ET delivery; therefore control rats were either fed ad libitum or food-deprived (FD) to match the voluntary consumption of ET rats. Blood was collected from carotid catheters and oxygen consumption determined daily. Body weight, colon temperature, and plasma glucose were similar in ET and FD rats, but ET rats exhibited a transient hyperlactacidemia, progressive leukocytosis, and fall in hematocrit which was not seen in FD rats. Food deprivation resulted in a marked drop in plasma insulin which was not seen in ET rats, despite similar food intake and plasma glucose concentration. Oxygen consumption of ET rats was significantly greater than both fed and FD animals on days 1 and 2 of ET infusion, while mean arterial pressure and heart rate were similar to controls. A unique model of endotoxemia is presented which is characterized by a transient hypermetabolic state, and changes in plasma lactate and insulin levels, white cell count, and hematocrit, which cannot be attributed to food deprivation. The results suggest that ET may be important in the pathogenesis of hypermetabolic sepsis.

Effects of excessive iodide administered in the dry period on thyroid function and health of dairy cows and their calves in the periparturient period.

Experiments were conducted in three successive years in which iodide (I) doses of 1.25, 2.5, 5.0 and 7.5 mg/kg body weight were given to 47 dairy cows during the dry period, compared with 16 control cows on basal diets of 1 ppm I. Effects on cows dosed at 1.25 and 2.5 mg I/kg (50 and 100 ppm dry feed) were not different from controls in terms of vitality of calves, changes in plasma thyroxine (T4), plasma triiodothyronine (T3), thyroxine secretion rate and 10-mo milk yields of the lactation after treatment. Cows dosed with 5 and 7.5 mg I/kg (200 and 300 ppm dry feed) averaged 272.8 d gestation, which was significantly shorter than 279.5 d for all cows on lesser I intakes. Abnormal calves at birth were 25% from the two highest I dosages vs 8% from controls plus the two lowest I dosages. Average plasma T4 and T3 decreased on the day of calving by about 30%, while plasma total I increased about 20%. Changes were greatest in cows fed high I dosages for the longest period prepartum. Plasma I and T3 of calves at birth were about three times the concentrations in their dam's plasma and plasma T4 of neonatal calves was four to five times greater than their dams. Highest dosages of I for dams tended to depress plasma T4 and T3 in neonatal calves.

Effects of excessive intakes of iodine upon growth and thyroid function of growing Holstein heifers.

Thirty Holstein heifer calves averaging 120 days of age and 102 kg of body weight were allocated to one control and four treatment groups of six each. Iodine, as ethylenediamine dihydriodide, was mixed 1:9 with dextrose and administered once daily atop feed at .625, 1.25, 2.5, or 5.0 mg iodine per kilogram body weight. Calves were housed individually in unheated, well-ventilated barns and fed complete mixed feeds containing less than 1 ppm iodine. Feed intakes were recorded daily and body weights weekly. Jugular venous blood was collected from iodine treated calves at 0, 4, 8, and 12 wk of the experiment and analyzed for iodine, thyroxine, and triiodothyronine of plasma. Feed intake per unit body weight and per unit gain were not significantly different between treated and control calves. However, daily feed intake and average daily gain decreased slightly at the highest iodine intake. Thyroxine and triiodothyronine were not different among treatments. Thyroxine declined in all calves from 0 to 12 wk. Thyroxine of calves fed 5.0 mg of iodine per kilogram body weight decreased more than of calves fed less iodine. Iodine intake as high as 5.0 mg/kg body weight was tolerated without morbidity, although a minor effect on performance and thyroid activity was indicated.

Hydroxyproline in serum as a homeostatic index for calcium in cattle.

Hydroxyproline, calcium, magnesium, phosphorus, and alkaline phosphatase values were determined in serum over 24 h in Holstein cows. The cows represented two age groups and three percents of diet calcium. Hydroxyproline followed a cyclic pattern dipping at 0800 and 1600 h after milking at 0500 and 1530 h. Phosphorus showed a 24 h rhythm peaking at 1600 h. No other time effects were demonstrated. Hydroxyproline and alkaline phosphatase were both lower in the older cows, indicating a decreased calcium mobilization from bone with age. There was a correlation coefficient of only .20 between serum calcium and hydroxyproline. The calcium concentration in serum was maintained within a narrow range presumably as a result of homeostatic mechanisms involving bone resorption, i.e. the release of calcium and hydroxyproline may indicate the degree of homeostasis required to maintain serum calcium.