Characterization of Virus- and Endotoxin-induced Interferons Obtained from the Serum and Urine of Rabbits

Interferons induced in the rabbit by Newcastle disease virus or by endotoxin have been further characterized as to their physicochemical stability and molecular size by Sephadex G-100 gel filtration. Endotoxin-induced interferon obtained from serum was more labile than virus-induced interferon. Both endotoxin and virus induced interferons obtained from serum contained two peaks: a minor high molecular weight (>100,000) peak and a major lower molecular weight peak. The molecular weight of the major peak induced by endotoxin was 54,000, and that induced by Newcastle disease virus was 46,000. The gel filtration pattern of interferon recovered from the urine of animals inoculated with virus reflected faithfully the pattern found in serum except that there was proportionately less of the high molecular weight peak. However, the urine interferon from endotoxin-inoculated animals contained only one broad peak with a molecular weight of 35,000. This was not the peak fraction present in the serum of such animals. It is postulated that this may represent the basic unit of endotoxin-induced interferon, and that the serum components are either polymers or conjugates of this basic unit.     

Role of interferon-like viral inhibitor in endotoxin-induced corneal resistance to Newcastle disease virus

Oh, J. O. (University of British Columbia, Vancouver, B.C., Canada), and E. J. Gill. Role of interferon-like viral inhibitor in endotoxin-induced corneal resistance to Newcastle disease virus. J. Bacteriol. 91:251-256. 1966.-A state of marked resistance to the toxic corneal effects of Newcastle disease virus (NDV) was observed in rabbit eyes after intravenous injection of 10 or 100 mug of typhoid endotoxin. By use of tissue cultures of rabbit corneal endothelial cells for assay, high titers of an interferon-like viral inhibitor were detected in serum and in ocular aqueous humor of these animals. The pretreatment of eyes with aqueous humor or serum containing the inhibitor markedly suppressed the production of corneal toxicity by NDV. The intravenous injection of 1 mug of the endotoxin had a negligible effect on the corneal reaction, and little or no inhibitor was found in either serum or aqueous humor. Normal aqueous humor or serum contained no inhibitor and had no suppressive effect on the NDV-induced reactions. The results indicated that the inhibitor played an important role in the induction of corneal resistance to NDV in vivo. The inhibitor in aqueous humor of endotoxin-injected rabbits was found to be derived from blood after an increase in the permeability of "blood-aqueous barrier" of iris due to the endotoxin. Therefore, intravenously administered typhoid endotoxin induced corneal resistance to NDV in rabbits through its dual action on host: (i) release of an interferon-like viral inhibitor into the blood stream and (ii) disruption of the blood-aqueous barrier of the iris, thus allowing the passage of the viral inhibitor from blood into the anterior chamber, where it modified the corneal endothelial cells to render them resistant to NDV.     

The Mode of Production of Endotoxin-Induced Interferon in Rabbit Tissue Cells

In vitro production of endotoxin-induced interferon in rabbit tissue cell cultures could be enhanced by pretreatment with interferon. The enhancible state developed from the first hr of incubation at 37 C and a maximal priming effect was attained at 6 hr of incubation. Yields of interferon from unprimed cultures were usually 20–200 units/ml. In contrast, the primed cultures constantly yielded 1,000–2,500 units/ml of interferon. The pretreatment with interferon seemed to cause an earlier appearance of detectable interferon and the primed cells became more sensitive to endotoxin. It turned out that 10–30 units/ml of rabbit interferon were enough to develop the maximal priming. Even when cells were pretreated with higher doses of rabbit interferon such as 1.0 × 10⁴–1.0 × 10⁵ units/ml, the same level of priming effect was always observed without diminution. Various types of homologous (rabbit) and heterologous (human and mouse) interferon preparations showed similar dose-dependent enhancement of interferon production in proportion to the antiviral titers of these preparations as tested with RK-13 cells of rabbit origin.     

Dynamics of endotoxin fever in the rabbit

To analyze the dynamic properties of body temperature and effector mechanisms during endotoxin fever, both experimental and mathematical procedures were applied. Experiments were carried out on rabbits in a climatic chamber at various ambient temperatures. Salmonella typhosa endotoxin (0.1 microgram/kg) was injected into an ear vein. A biphasic core temperature increase evoked by different effector mechanisms depending on ambient temperature was observed. A mathematical model based on experimental results with nonfebrile rabbits predicts the effector behavior at all ambient temperatures. From a comparison of experimental results with the model prediction, it is concluded that the increase of core temperature during fever is essentially caused by a dynamic shift of the controller characteristics. The effect of the pyrogen may be simulated by a resultant fever-controlling signal that is biphasic but increases more steeply than does core temperature. The analysis suggests that the three possible fever-driving effectors, metabolism, ear blood flow, and respiratory evaporative heat loss, should be controlled by the same resultant signal, although the time courses of the effectors and of core temperature vary distinctly at different air temperatures. The model uses an additive controller structure.     

不同基础体温的家兔对热原检查结果的影响

对实验中使用的普通级家兔基础体温进行统计,观察不同基础体温家兔注射血液制品后的升温情况。按照中华人民共和国药典(2005)年版三部的热原检查规定进行测定,将实验家兔基础体温38.0℃~39.6℃分为3组:38.0℃~38.5℃为1组;38.6℃~39.0℃为2组;39.1℃~39.6℃为3组。注射制品后,家兔升温≥0.4℃记为升温家兔,统计升温≥0.4℃的家兔升温百分率并对其进行统计学处理。经卡方检验,升温家兔≥0.4℃的百分率1组与2组、1组与3组有显著性差异(p<0.05);2组与3组无显著性差异(p>0.05)。家兔对热原的敏感性随基础体温的高低而有明显的差异,基础体温偏低的家兔对热原更敏感,其升温幅度大于基础体温偏高的家兔。     

Interferon-Inducing Activity of Acidic Polysaccharides

Readily available polysaccharides, amylopectin, amylose, dextrin, and yeast mannan, were chemically phosphorylated using polyphosphoric acid in the presence of a tertiary amine, and the resultant phosphates were examined for their interferon-inducing activity in rabbits employing an assay system consisting of a primary culture of rabbit kidney cells and vesicular stomatitis virus. All the phosphates were shown to be active as interferon inducer, and, especially, the activity of those containing more than 2% phosphorus were quite strong. Interferons evoked by the above phosphates resembled those induced by bacterial endotoxin, e.g., the viral inhibiting activity was susceptible to heat treatment, low pH and tryptic digestion. Since all the parent polysaccharides showed no interferon-inducing activity, it is reasonable to assume that the active center of these inducers might reside or be due to the anionic phosphate groups.     

Comparison of the effector mechanisms during endotoxin fever in the adult rabbit.

In unanaesthetized adult rabbits an intravenous dose of E. coli endotoxin evoked a febrile rise in colonic temperature at ambient temperatures of 9 to 31 degrees C. The rise in colonic temperature and oxygen consumption did not depend on the ambient temperature, while, among the heat loss effectors, in warmer environments only the depression of respiratory heat loss and in cooler environments only ear skin vasoconstriction contributed to the febrile rise in colonic temperature. In moderately warm environments the endotoxin first induced a maximum inhibition of respiratory frequency and this was followed by vasoconstriction. Later, a transient rise in oxygen consumption occurred. During defervescence the timing of the effectors was reversed. The results showed that a febrile response is not necessarily characterized by simultaneous changes in the thermoregulatory effector mechanisms.     

Nutritional state and endotoxin fever of newborn rabbits.

At thermoneutral environments 6-10 day-old well-fed rabbits responded to 20 microgram/kg I.V. E. coli endotoxin with biphasic fever: temperature peaks at 60 and 120-150, and a transient fall between 60 and 90 min after endotoxin injection. In rabbits starved for 24 hours, and in runt rabbits body temperature did not rise, but a decline started 60 min after endotoxin administration, corresponding to the transient fall observed in well-fed animals and continuing until about the 100-120th min; thereafter body temperature tended to stabilize at the low level.     

Effect of ambient temperature on the productive and carcass traits of growing rabbits divergently selected for body fat content

Rabbits are particularly sensitive to heat stress which can affect productive performance, with rabbit breed/line possibly playing a role on the response to this condition. The study aimed at evaluating the effect of different ambient temperatures on the live performance and carcass traits of growing rabbits divergently selected for total body fat content. The two genetic lines (Lean and Fat) were selected based on the total body fat content estimated by computer tomography during five generations. From birth to slaughter (13 weeks of age), the rabbits were housed in two rooms where the temperature was controlled with air conditioners: in the control room the average ambient temperature was 20 °C and in the high temperature room it was 28 °C. After weaning (35 d), 60 Lean and 60 Fat rabbits/room were housed by two in wire-mesh cages and fed ad libitum with commercial pellets. The BW and feed intake (FI) were measured at 5, 7, 9, 11 and 13 weeks of age to calculate the daily weight gain (DWG) and feed conversion ratio (FCR). Mortality was recorded daily. At the end of the experiment, rabbits were slaughtered and carcass traits were measured. Mortality was independent of temperature and line. The temperature significantly influenced the FI, DWG, BW and the fat deposits: they were lower at higher ambient temperature. The effect of temperature differed according to the rabbits' total body fat content. At control temperature, the FI (165 vs 155 g/day; P < 0.05) and FCR (4.67 vs 4.31; P < 0.05) were higher in Fat rabbits, which also had more perirenal (36.2 vs 23.1 g; P < 0.05) and scapular fat (10.8 vs 7.1 g; P < 0.05). At high temperature, no differences in fat depots (14.5 vs 9.8 g; 5.3 vs 3.5 g) were found between the two lines. It can be concluded that temperature × genetic line interaction had an important role in productive and carcass traits, as the effect of temperature differs between Lean and Fat rabbits.     

Nocturnal loss of body reserves reveals high survival risk for subordinate great tits wintering at extremely low ambient temperatures

Winter acclimatization in birds is a complex of several strategies based on metabolic adjustment accompanied by long-term management of resources such as fattening. However, wintering birds often maintain fat reserves below their physiological capacity, suggesting a cost involved with excessive levels of reserves. We studied body reserves of roosting great tits in relation to their dominance status under two contrasting temperature regimes to see whether individuals are capable of optimizing their survival strategies under extreme environmental conditions. We predicted less pronounced loss of body mass and body condition and lower rates of overnight mortality in dominant great tits at both mild and extremely low ambient temperatures, when ambient temperature dropped down to ?43 °C. The results showed that dominant great tits consistently maintained lower reserve levels than subordinates regardless of ambient temperature. However, dominants responded to the rising risk of starvation under low temperatures by increasing their body reserves, whereas subdominant birds decreased reserve levels in harsh conditions. Yet, their losses of body mass and body reserves were always lower than in subordinate birds. None of the dominant great tits were found dead, while five young females and one adult female were found dead in nest boxes during cold spells when ambient temperatures dropped down to ?43 °C. The dead great tits lost up to 23.83 % of their evening body mass during cold nights while surviving individuals lost on average 12.78 % of their evening body mass. Our results show that fattening strategies of great tits reflect an adaptive role of winter fattening which is sensitive to changes in ambient temperatures and differs among individuals of different social ranks.     

Endotoxin fever in the rat.

In rats intravenous injections of E. coli endotoxin at thermoneutral or slightly warmer environmental temperatures resulted in biphasic febrile response: two rises of temperature being separated by a transient fall. At an ambient temperature of 20 degrees C the change in body temperature still had a biphasic pattern, however, the fall was the dominant change. Each part of the response was the result of a coordinated reaction which involved heat production mechanisms (including interscapular and periaortic brown fat thermogenesis) and heat loss effectors (tail vasomotor changes) separately or in combination. Beside ambient temperature, the initial body temperature at the start of endotoxin action exerted an important role in determining which of the effector functions would be involved in the response.     

Effect of exogenous interferon on the transplantation reactions of mice]

The authors studied the influence of the serum obtained at various periods after the administration of interferon inductors (New castle disease virus, amino ethylisothiouronium, E. coli endotoxin) on the rate of rejection of the skin or cell transplant of mice C3H and CBA, and also CC57Br. The allogenous skin transplant perished more rapidly; there was also an acceleration of elimination of allogenous lymphoid cells, suppression of colony formation by the cells of allogenous bone marrow in the spleen of the irradiated recipient in administration of the serum obtained at the period of maximal content of interferon induced by the Newcastle disease virus and by amino ethylisothiouronium. The cytotoxic activity of lymphocytes of mice CC57Br against the allogenous target cells rose in the presence of these sera. The serum containing interferon induced with E. coli endotoxin failed to influence the rate of the allotransplant rejection and did not increase the cytotoxic activity of lymphocytes.     

Temperature regulation in the unrestrained rabbit during exposure to 600 MHz radiofrequency radiation

Six male New Zealand white rabbits were individually exposed to 600 MHz radiofrequency (RF) radiation for 90 min in a waveguide exposure system at an ambient temperature (Ta) of 20 or 30 degrees C. Immediately after exposure, the rabbit was removed from the exposure chamber and its colonic and ear skin temperatures were quickly measured. The whole-body specific absorption rate (SAR) required to increase colonic and ear skin temperature was determined. At a Ta of 20 degrees C the threshold SAR for elevating colonic and ear skin temperature was 0.64 and 0.26 W/kg, respectively. At a Ta of 30 degrees C the threshold SARs were slightly less than at 20 degrees C, with values of 0.26 W/kg for elevating colonic temperature and 0.19 W/kg for elevating ear skin temperature. The relationship between heat load and elevation in deep body temperature shown in this study at 600 MHz is similar to past studies which employed much higher frequencies of RF radiation (2450-2884 MHz). On the other hand, comparison of these data with studies on exercise-induced heat production and thermoregulation in the rabbit suggest that the relationship between heat gain and elevation in body temperature in exercise and from exposure to RF radiation may differ considerably. When combined with other studies, it was shown that the logarithm of the SAR required for a 1.0 degree C elevation in deep body temperature of the rabbit, rat, hamster, and mouse was inversely related to the logarithm of body mass. The results of this study are consistent with the conclusion that body mass strongly influences thermoregulatory sensitivity of the aforementioned laboratory mammals during exposure to RF radiation.     

Disaggregation of brain polysomes after LSD in vivo

LSD-induced hyperthermia is implicated in the brain-specific disaggregation of polysomes which is induced following intravenous administration of the drug to rabbits. Both LSD-induced hyperthermia and brain polysome disaggregation were found to increase in parallel under conditions which accentuated the effect of the drug on brain protein synthesis. Pretreatment with neurotransmitter receptor blockers or placing the animal at an ambient temperature of 4°C after LSD administration prevented both hyperthermia and brain polysome disaggregation. The administration of apomorphine, which causes hyperthermia in rabbits also caused disaggregation of brain polysomes. Direct elevation of the body temperature to levels similar to that found after LSD was achieved by placing animals at an ambient temperature of 37°C. Under these conditions a brain-specific disaggregation of polysomes resulted which was not due to RNAase activation. After either LSD or direct heating, the brain polysome shift was associated with a relocalization of polyadenylated mRNA from polysomes to monosomes as determined by [³H]polyuridylate hybridization. Since polysome disaggregation was found only in brain, it appears that the brain may be more sensitive to elevations in body temperature compared to other organs.     

Microwave radiation (2450 MHz) alters the endotoxin-induced hypothermic response of rats

The parenteral administration of bacterial endotoxin to rats causes a hypothermia that is maximal after approximately 90 minutes. When endotoxin-injected rats were held in a controlled environment at 22°C and 50% relative humidity and exposed for 90 minutes to microwaves (2450 MHz, CW) at 1 mW/cm², significant increases were observed in body temperature compared with endotoxintreated, sham-irradiated rats. The magnitude of the response was related to power density (10 mW/cm² > 5 mW/cm² > 1 mW/cm²). Saline-injected rats exposed for 90 minutes at 5 mW/cm² (specific absorption rate approximately 1.0 mW/g) showed no significant increase in body temperature compared with saline-injected, sham-irradiated rats. The hypothermia induced by endotoxin in rats was also found to be affected by ambient temperature alone. Increases in ambient temperature above 22°C in the absence of microwaves caused a concomitant increase in body temperature. This study reveals that subtle microwave heating is detectable in endotoxin-treated rats that have an impaired thermoregulatory capability. These results indicate that the interpretation of microwave-induced biological effects observed in animals at comparable rates and levels of energy absorption should include a consideration of the thermogenic potential of microwaves.     

Quantitative aspects of inhibition of virus replication by interferon in chick embryo cell cultures

Hallum, J. V. (University of Pittsburgh, Pittsburgh, Pa.), and J. S. Youngner. Quantitative aspects of inhibition of virus replication by interferon in chick embryo cell cultures. J. Bacteriol. 92:1047-1050. 1966.-The effect of interferon on single cycles of replication of vesicular stomatitis virus and Mahoney poliovirus ribonucleic acid was studied in chick embryo cell cultures. The results showed that the titer of a given interferon preparation was independent of the input multiplicity of the challenge virus. In addition, the increase in virus yield with increasing virus challenge was a function of the number of infected cells, each of which yielded progeny at a level determined by the concentration of interferon to which the cells were exposed. These findings are not compatible with the concept that increases in the size of the virus challenge reverse or overcome protection of cells by interferon.     

Endotoxin and prostaglandin fever of newborn guinea pigs at different ambient temperatures.

At an ambient temperature (Ta) of 30 degrees C, injection of 0.2 micrograms E. coli endotoxin into the lateral cerebral ventricle (icv) of three-day-old or younger guinea pigs was followed by a biphasic febrile rise in body temperature (Tc) and oxygen consumption (VO2), interrupted by a transient fall. At Ta 20 degrees C the change in Tc and VO2 was still biphasic, the first rise was similar as that seen at Ta 30 degrees C, but the subsequent fall was more pronounced. Thus, Tc became lower than before endotoxin and remained below the pre-injection level during and after the second rise. Injection of 10 ng PGE1 icv caused sustained monophasic hyperthermia at both Ta-s. Icv injection of 0.9% NaCl did not affect Tc and VO2 at either Ta. Accordingly, prostaglandins might contribute to, but cannot account for, the whole febrile response to endotoxin.     

Carcass and meat quality traits of rabbits under heat stress

Rabbits are very sensitive to heat stress because they have difficulty eliminating excess body heat. The objective of the current study was to evaluate the effects of heat stress on slaughter weight, dressing percentage and carcass and meat quality traits of rabbits from two genetic groups. Ninety-six weaned rabbits were used: half were from the Botucatu genetic group and half were crossbreds between New Zealand White sires and Botucatu does. They were assigned to a completely randomized design in a 2 × 3 factorial arrangement (two genetic groups and three ambient temperatures: 18°C, 25°C and 30°C) and kept under controlled conditions in three environmental chambers from 5 to 10 weeks of age. Slaughter took place at 10 weeks, on 2 consecutive days. Meat quality measurements were made in the longissimus muscle. Actual average ambient temperature and relative humidity in the three chambers were 18.4°C and 63.9%, 24.4°C and 80.2% and 29.6°C and 75.9%, respectively. Purebred rabbits were heavier at slaughter and had heavier commercial and reference carcasses than crossbreds at 30°C; however, no differences between genetic groups for these traits were found at lower temperatures. No genetic group × ambient temperature interaction was detected for any other carcass or meat quality traits. The percentages of distal parts of legs, skin and carcass forepart were higher in crossbred rabbits, indicating a lower degree of maturity at slaughter in this group. The percentage of thoracic viscera was higher in the purebreds. Lightness of the longissimus muscle was higher in the purebreds, whereas redness was higher in the crossbreds. Slaughter, commercial and reference carcass weights and the percentages of thoracic viscera, liver and kidneys were negatively related with ambient temperature. Commercial and reference carcass yields, and the percentage of distal parts of legs, on the other hand, had a positive linear relationship with ambient temperature. Meat redness and yellowness diminished as ambient temperature increased, whereas cooking loss was linearly elevated with ambient temperature. Meat color traits revealed paler meat in the purebreds, but no differences in instrumental texture properties and water-holding capacity between genetic groups. Purebred rabbits were less susceptible to heat stress than the crossbreds. Heat stress resulted in lower slaughter and carcass weights and proportional reductions of organ weights, which contributed to a higher carcass yield. Moreover, it exerted a small, but negative, effect on meat quality traits.     

Metabolism of rabbit plasma-derived factor VII in relation to prothrombin in rabbits

In the human circulation, factor VII is present in relatively low plasma concentration (0.01 microM) and has been reported to have a short half-life (t(1/2); 6 h). In contrast, prothrombin is present in a relatively high plasma concentration (2 microM) and has a relatively long catabolic half-life (t(1/2) = approximately 2-3 days). This report examines the metabolic characteristics of purified rabbit plasma factor VII and prothrombin, radiolabeled with (125)I and (131)I, respectively, in healthy young rabbits. From the plasma clearance curves of protein-bound radioactivities, fractional catabolic rates and compartmental distributions were calculated using a three-compartment model. Turnover of factor VII within the intravascular space (2.95 days) exceeded that of prothrombin (1.9 days). However, the whole body fractional catabolic rate of factor VII (0.34 days(-1); catabolic t(1/2) = 2.04 days) was significantly slower than that of prothrombin (0.53 days(-1); t(1/2) = 1.31 days). Furthermore, the fractional distributions of factor VII in the intravascular (0.14) and extravascular compartments (0.76) differed from those of prothrombin (0.29 and 0.53). Absolute quantities of factor VII and prothrombin catabolized by a 3-kg rabbit amounted to 0.18 and 24.0 mg/day, respectively (molar ratio of prothrombin to factor VII = 100). The molar ratio of catabolism was compared with the release rates of factor VII and prothrombin from rabbit livers perfused ex vivo. After correction for uptake of factor VII and prothrombin by the liver, the molar ratio of released prothrombin to factor VII in the perfusate was approximately 293:1 over a 0.25- to 3-h interval. These results indicate that, compared with prothrombin, factor VII in the healthy rabbit circulates as a relatively long-lived protein. This behavior does not reflect that reported for factor VII in the human circulation.     

Evaluation of Culture Media for the Isolation of Salmonellae from Feces

Serial passage of the 64-2389 strain of type 3 parainfluenza virus in cercopithecus monkey kidney tissue cultures at low temperatures resulted in the selection of a variant which had a higher efficiency of plaque formation at 25 C than the parent line grown at 37 C. The cold variant, unlike the parent strain, plaqued readily at 25 C, and at 37 C it produced significantly larger plaques. Virus titers of the cold variant in hamster lungs were significantly lower and this was probably caused by the stimulation of interferon by the cold variant during the early phase of the infection. The cold variant, like the virus grown at 37 C, also induced the synthesis of interferon late in the infection. Hamsters responded to the intranasal inoculation of each virus line by the development of hemagglutinating-inhibiting antibodies in the sera.