Random perturbation: a potential aid in treatment of children with cerebral palsy.

BACKGROUND AND PURPOSE: The motor behaviour of children with cerebral palsy (CP) can be viewed in terms of a stable mode with very little flexibility that prevents adaptation to tasks. We hypothesized that the use of random perturbations (RP) would weaken excessive stability, introduce flexibility and enhance the effects of physical treatment. The objective was to evaluate the contribution of RP to gross motor function and mechanical efficiency (MEg) during intensive physiotherapy in children with CP. METHODS: A convenience sample of 20 children with CP (mean age 8.2, range: 5.9-12.9 yrs) were matched by age and GMFCS level, and randomly assigned to structured intensive treatment (SIT) or to SIT + RP groups. Groups received one month of daily treatment. RP was applied by engine-induced random passive cycling for upper and lower limbs for up to 10 min in a 90-min treatment session. Gross Motor Function Measure (GMFM)-66 and gross mechanical efficiency (MEg) during stair climbing (MEg) were measured before and after treatment. RESULTS: GMFM-66 scores increased by about 1.0 in both groups. However, external work and MEg increased significantly more in SIT + RP than SIT. The increase in MEg in SIT + RP was independent of the level of motor function at baseline. CONCLUSION: The addition of RP in treatment of children with CP may have weakened previously established stereotypical motor patterns and introduced flexibility, thereby improving mechanical efficiency of a complex motor task. RP may enhance the effects of intensive treatment.

Method of analysing the performance of self-paced and engine induced cycling in children with cerebral palsy.

PURPOSE: To develop a method of quantifying the features of cycling in children with CP by comparing them to typically developed children, and to demonstrate the applications of this tool for evaluating treatment effects in children with CP. METHODS: Twenty-seven typically developed children and 51 with CP, classified by their gross motor function levels, were studied. Angular velocities were measured during self-paced active cycling and during passive cycling imposed by an electrically powered stationary cycle. Angular velocities were compared with the gross motor function levels, Modified Ashworth Scale and the Adductor Tone Rating. RESULTS: Significant differences between children with CP and those typically developed demonstrated in passive mode that the cycling task is sensitive to differences in resistance offered by the subjects. Active and passive cycling velocities differ significantly between groups classified by their functional levels (p < 0.01). Children with CP in the mild group showed no differences from typically developed children. The correlations between passive cycling and clinical tests were significant and higher at higher speeds (r = 0.62). Correlations with anthropometric measurements for the typically developed group associated the cycling task with growth and development, and for children with CP with motor control adjustments and impairments. CONCLUSIONS: Measuring of these two cycling modes could be applicable in assessing lower extremity function in children with CP and changes following interventions.

Involvement of PGE2 and TNF-alpha in LPS-tolerance in rat glial primary cultures.

The effect of repeated exposure of primary newborn rat brain glial cultures to the endotoxin lipopolysaccharide (LPS), a component of Escherichia coli membrane, on PGE(2) and TNF-alpha production was examined. PGE(2) production by cell cultures exposed to LPS at a dose of 5 microg/ml, 4 and 24 h after initial exposure did not differ from PGE(2) production by the same cultures 4 and 24 h after the first exposure to the same dose of LPS. TNF-alpha production was significantly lower with the second exposure as compared with the production by the same culture, exposed to the same dose of LPS, examined 4 and 24 h after the first exposure. We concluded that endotoxin tolerance in our culture model is associated with reduced secretion of TNF-alpha, caused by the initial exposure to LPS, while PGE(2) production remained unchanged.

Vagotomy attenuates the effect of lipopolysaccharide on body temperature of rats in a dose-dependent manner.

There is a growing body of evidence suggesting that vagal afferents play a major role in peripheral-neural communication. This study was undertaken to determine whether a dose-dependent effect of lipopolysaccharide (LPS) on vagotomy-induced febrile unresponsiveness exists, and to examine the effect of vagotomy on LPS-induced increase in hypothalamic prostaglandin E2 (HT PGE2) production. Vagotomized and sham-operated rats were subjected to two experimental protocols. In the first, vagotomized and sham-operated rats were injected intraperitoneally with different doses of LPS (200, 500 and 1000 microg/kg) in order to examine the dose-dependent effect of LPS on the biphasic febrile response of the rats. In the second protocol, vagotomized and sham-operated rats were injected intraperitoneally with LPS (500 microg/kg). Two hours post injection, body temperature was measured, the rats were decapitated and blood was collected. Simultaneously, the rats' hypothalami were excised and incubated for 1 h in a Krebs-Henseleit buffer. Next, HT PGE2 was determined by radioimmunoassay. Vagotomy-induced gastric enlargement was then measured to examine the correlation between the magnitude of the enlargement and that of the vagotomy-related febrile unresponsiveness. It was found that vagotomized-induced febrile unresponsiveness is a dose-dependent effect. Subdiaphragmatic resection of the vagus prevented the biphasic febrile response caused by the lowest dose (200 microg/kg) of LPS, whereas the highest dose of LPS (1000 microg/kg) caused a similar biphasic febrile response in both vagotomized and sham-operated rats. Indeed, vagotomy attenuates LPS-induced increase in HT PGE2, and blocks the hypothermic phase of the febrile response. On the other hand, no correlation between gastric enlargement and febrile unresponsiveness was found. The results of the present study may cast further light on the crucial role of the vagus nerve as a peripheral-neural pathway in the mediation of the febrile response.

Time-dependent effect of LPS on PGE2 and TNF-alpha production by rat glial brain culture: influence of COX and cytokine inhibitors.

This study was undertaken to investigate the effect of lipopolysaccharide (LPS) stimulation on the time course of prostaglandin E2 (PGE2) and tumor necrosis factor alpha (TNF-alpha) production by rat glial brain culture. A concentration of 10 microg/ml LPS from Escherichia coli was used as stimulation treatment. The effect of pentoxifylline (PXF), nimesulide (NIM), indomethacin (INDO) and dexamethasone (DEX) on the regulation of PGE2 and TNF-alpha production was tested. Stimulation of rat glial cells with LPS resulted in different time-dependent production patterns of PGE2 and TNF-alpha The time course of TNF-alpha elevation was short, reaching its peak at 6 h post LPS and decreasing to undetectable levels after 24 h. On the other hand, the time course of PGE2 elevation was longer, starting at 6 h post LPS treatment and increasing 100-fold compared with basal levels, 24 h post LPS exposure. The COX inhibitors (NIM and INDO) and DEX were found to inhibit the LPS-induced elevation in PGE2 production, while PXF lacked such an inhibitory effect. Furthermore, NIM, DEX and PXF were found to reduce the LPS-induced elevation in TNF-alpha levels, while INDO caused a greater elevation in TNF-alpha levels. These results may cast further light on the LPS-induced production of PGE2 and TNF-alpha by rat glial cell cultures and the relation between the two systems.

Effect of different ambient temperature and lipopolysaccharide administration on the circadian rhythm of rectal temperature and hypothalamic PGE2 production in aged male rats.

Old and young male rats (22 and 7 months respectively) were exposed to ambient temperatures of 4, 22, 27 and 35 degrees C. The rats' rectal temperatures (RTs) were measured periodically, after exposure to the varying temperatures at different hours during the day. The mean circadian value of RTs in the aged rats was different from that of the young rats. Whereas exposure to low temperatures caused a decrease of 2.0 degrees C in the RTs of the old rats, exposure to heat (35 degrees C) caused an increase of 1 degree C in their RTs. An injection of 200 micrograms (intraperitoneally) of E. coli lipopolysaccharide caused them to experience a long period of hypothermia. Elevation in the RTs after the hypothermic period ended was significantly lower in the old rats. However no significant differences in hypothalamic PGE2 production were to be found between the old and young groups 24 h after pyrogen administration.

Delayed febrile response in old rats is not associated with an inability of hypothalamus to produce prostaglandin E2.

E. coli lipopolysaccharide (100 micrograms per rat, i.p.) induced a twofold increase in hypothalamic prostaglandin E2 (PGE2) production both in young adult (8 months) and old (28-30 months) male Wistar rats. It seems that the ability of the hypothalamus to produce PGE2 in response to bacterial endotoxin is not affected with aging, and hence delayed febrile response observed in old rats is not related to hypothalamic PGE2 production.

Brain eicosanoids and LPS fever: species and age differences.

The results of the present study, summarized in Table 2, demonstrate that different species and strains of rodents (rats and mice) and birds (chickens) exhibit rather specific fever response. Systemic administration of LPS caused monophasic elevation in Tb of chickens, biphasic changes in Tb of rats (initial drop followed by an increase in Tb), whereas mice failed to develop hyperthermia and responded by a decreased Tb. The LPS-induced alterations in hypothalamic prostanoid synthesis were also rather species-specific and differ markedly even between the two strains of mice. We failed to find a common direct correlation between LPS-induced changes in Tb and hypothalamic prostanoid production in rodents (rats and mice). This observation is supported by our recent study on age-related changes in fever response in rats, where we found that hypothalami of LPS-treated old and young adult rats produced similar amounts of PGE2 and PGI2, in spite of more pronounced and prolonged hypothermia, and a delayed elevation in Tb of old rats, as compared with young (Fraifeld et al., 1995b). Moreover, the hypothalamus of febrile chickens did not display any detectable activation of PGE2 production, suggesting that PGE2 is not a common central mediator of fever in homeotherms (Fraifeld et al., 1995a). Apparently, the actual body temperature not always reflects the functional state of central thermostat, and increased PGE2 production in hypothalamus would not directly, at least in rodents, lead to body temperature elevation. Furthermore, peripheral effects, including PG-mediated ones, of pyrogens can interfere and even overcome their centrally-mediated effects (Morimoto et al., 1991; Burysek et al., 1993). Previously, we have shown that no additional elevation in hypothalamic PGE2 production occurs in response to doses of LPS over 10 micrograms in rats and 25 micrograms in mice, while the increased doses led to further changes in Tb response (Kaplanski et al., 1993). Morimoto et al. (1991) have considered that PGE2 acts centrally to cause fever and peripherally to cause hypothermia, and, hence, these opposing actions, both being induced by LPS, may act together to determine the final thermoregulatory response. Other possibilities could be related to counterbalance of endogenous antipyretics (Kluger, 1991; Kozak et al., 1995), that may occur not only at the level of thermoregulatory center but also outside the CNS (Klir et al., 1995), and to the existence of PG-independent mechanisms of LPS fever. The latter have been shown for IL-8 (Rothwell et al., 1990; Zampronio et al., 1994) and MIP-1 (Davatelis et al., 1989; Minano et al., 1990; Hayashi et al., 1995; Lopez-Valpuesta and Myers, 1995), which are, apparently, mediated via CRF (Strijbos et al., 1992; Zampronio et al., 1994), and INF-alpha, mediated via the opioid receptor mechanisms (Hori et al., 1991, 1992). However, it has been shown recently that in different species the same pyrogenic cytokines (IL-8) may induced fever via different, PG-independent (in rats; Zampronio et al., 1994) or PG-dependent (in rabbits; Zampronio et al., 1995) mechanisms. It should be noted that fever response is not always accompanied by an elevation in Tb. The final effect of pyrogens on body temperature depends upon the balance between heat production and heat loss, which in turn is highly dependent upon body size and ambient temperature, especially in small animals. Perhaps, the hypothermic response observed in our mice and rats at 22 degrees C may be in part attributed to ambient temperature, which was below a thermoneutral zone. The reduced febrile response is considered, at least in part, to contribute to an increased mortality and prolonged recovery from infections (Kluger, 1986). From this point, it is difficult to suggest whether the hypothermia observed in our mice and rats could be of somewhat adaptive significance. It has been shown that at the ambient temperature of 30 degrees C, Swiss Webster mice can re

Nimesulide prevents lipopolysaccharide-induced elevation in plasma tumor necrosis factor-alpha in rats.

The present study was undertaken to test the hypothesis of possible inhibitory effect of nimesulide (4-nitro-2-phenoxymethane-sulfoxide) on plasma TNF-alpha level. Male Sprague-Dawley rats were injected intraperitoneally (i.p.) with E. coli lipopolysaccharide (LPS; 1 mg/kg), which resulted in a dramatic increase in plasma TNF-alpha level peaked 60 min post injection (3890+/-280 pg/ml, compared to undetectable values in the control group). Nimesulide (30 mg/kg) injected i.p. 60 min prior to LPS, prevented LPS-induced elevation in plasma TNF-alpha. Nimesulide alone did not alter circulating levels of TNF-alpha. It appears that the anti-inflammatory properties of nimesulide may in part be attributed to its inhibitory effect on TNF-alpha production.

A reduction of tumor necrosis factor-alpha in paw exudate of lipopolysaccharide treated rats by nimesulide.

TNF-alpha is considered to play a pivotal role in many inflammatory and illness states. In our previous study we found that nimesulide, a COX-2 selective inhibitor, prevents the lipopolysaccharide-induced elevation in plasma TNF-alpha in rats. The present study was undertaken to elucidate the effect of nimesulide on TNF-alpha levels in the paw exudate of rats pretreated with lipopolysaccharide (LPS). Rats were injected (subplantar) with LPS (100 microg/paw) in the right hind, which resulted in a prominent increase in paw exudate TNF-alpha levels, peaked at one hour post injection. In rats pretreated with nimesulide (30 mg/kg, i.p.), the elevation in TNF-alpha in the paw exudate was significantly reduced, as compared to the LPS treated group. These results further stress the multiple antiinflammatory effects of nimesulide.

Cardiac glycoside toxicity in small laboratory animals.

Cardiac glycosides are frequently administered to laboratory animals for research purposes. The effects achieved depend not only upon the particular glycoside and dose administered, but also upon an entire array of variables from the species of animal to the temperature of the animal housing facility. We review a number of these factors and their influence upon the effects achieved by the administration of cardiac glycosides to laboratory animals.

Is hypothalamic prostaglandin E2 involved in avian fever?

In chickens, the effect of Escherichia coli lipopolysaccharide (LPS) on body temperature and ex vivo hypothalamic prostaglandin E2 (PGE2) production was examined to test the possible involvement of PGE2 in mechanisms of avian fever. PGE2 is reported to be the major central mediator of fever in mammals; it has not been examined in birds. An intraperitoneal injection of LPS caused an elevation of body temperature but not an elevation of hypothalamic PGE2 production. It seems that: (a) hypothalamic PGE2 is not involved in the development of the febrile response in birds; (b) central mechanisms of avian fever differ from those in mammals.

Tolerance to lipopolysaccharide is not related to the ability of the hypothalamus to produce prostaglandin E2.

The effects of repeated administration of Escherichia coli lipopolysaccharide (LPS) on body temperature and hypothalamic prostaglandin E2 (PGE2) production was examined in male Sprague-Dawley rats to elucidate whether the development of endotoxin tolerance is related to the ability of the hypothalamus to produce PGE2. Initial injection of LPS resulted in hyperthermia, preceded by short-termed hypothermia, while no changes in body temperature were observed after the second injection (administered 48 h later). In contrast, LPS induced elevation in hypothalamic PGE2 production after both the first and second injections of the pyrogen. This led us to conclude that endotoxin tolerance is independent of the hypothalamic production of PGE2 in response to repeated administration of LPS.

Gonadotoxicity and kinetics of dibromochloropropane in male rats.

Adult male rats were injected with [3H]dibromochloropropane dissolved in dimethylsulfoxide containing about 10 X 10(6) dpm. Blood from the tail and 24-h urine samples were collected up to 2 days post-injection. Tissue samples were further taken from the kidneys, liver, spleen, adrenals, epididymis, seminal vesicles and testes 7 h and 7 days post-injection. The results demonstrate that there is no preference in labelling of the testes compared with other organs, and the kidney and liver may have an important role in the elimination of DBCP.

Inhibition of cyclooxygenase 2 by nimesulide decreases prostaglandin E2 formation but does not alter brain edema or clinical recovery after closed head injury in rats.

Recently, the enzyme cyclooxygenase (COX) has been recognized to exist as constitutive (COX-1) and inducible isoforms (COX-2). In previous studies, drugs that were inhibitors of both COX-1 and COX-2 failed to decrease brain edema formation or improve Neurological Severity Score (NSS) after closed head trauma (CHT), although some did decrease prostaglandin-E2 (PGE2) formation. The present study examined whether or not a specific inhibitor of COX-2 (nimesulide) exerts a beneficial effect after CHT in rats. Halothane-anesthetized rats (n = 8 in each group) were randomly assigned to one of four groups: surgery, no CHT, no drug (group 1); surgery, no CHT, nimesulide 30 mg/kg intraperitoneally (IP) (group 2); surgery, CHT, no drug (group 3); and surgery, CHT, nimesulide 30 mg/kg IP (group 4). NSS was determined at 1 and 24 h, and brain tissue PGE2 concentration and water content were determined after killing at 24 h. Treatment with nimesulide did not improve NSS (NSS at 24 h = 11+/-6 [median +/- range] in group 3 and 12+/-4 in group 4) or edema formation (brain water content at 24 h = 84.3+/-1.8% [mean +/- SD] in group 3 and 83.8+/-1.9% in group 4). However, nimesulide did decrease cortical and hypothalamic PGE2 formation by 41% and 47%, respectively during the first hour of incubation after brain tissue sampling. The authors conclude that although nimesulide does reduce tissue PGE2 formation, it does not exert a beneficial effect on brain tissue edema or functional activity after CHT in rats.

Effects of closed head trauma and lipopolysaccharide on body temperature, brain tissue water content, and PGE2 production in rats.

Closed head trauma (CHT) increases brain tissue prostaglandin E2 (PGE2) concentration, and that increase is associated with cerebral edema formation and worsening of the neurologic severity score (NSS). Injection of the bacterial endotoxin lipopolysacharride (LPS) increases cerebral and hypothalamic PGE2, and the hypothalamic increase is associated with increased body temperature. The present study determined (a) whether LPS-induced increase of PGE2 causes brain edema or worsens NSS and (b) whether CHT increases hypothalamic PGE2 and thereby increases body temperature. Halothane-anesthetized rats were divided into four groups: group 1 = surgery with no CHT and no LPS (n = 8); group 2 = surgery with LPS and no CHT (n = 8); group 3 = surgery with CHT and no LPS (n = 8); and group 4 = surgery with CHT plus LPS (n = 8). NSS was determined at 1 and 24 h after injury, and brain tissue PGE2 and edema were determined when animals were killed 24 h after injury. As compared with group 1, LPS alone, but not CHT or CHT plus LPS, increased rectal temperature. CHT and CHT plus LPS, but not LPS alone increased brain water content and worsened NSS. LPS, CHT, and CHT plus LPS all increased hypothalamic and cerebral PGE2 production. We conclude that although LPS and CHT increased PGE2 levels, LPS alone did not affect neurologic status or brain edema, CHT did not increase rectal temperature, and addition of LPS to CHT did not aggravate the sequelae of CHT.

Comparison of digoxin-induced cardiac toxicity in resistant and sensitive species.

We have examined the species-specific arrhythmogenic effects of digoxin in the rat (resistant species) and in the guinea-pig (sensitive species). 26 adult rats and 23 adult guinea-pigs were anaesthetized with pentobarbitone and injected subcutaneously with varying doses of digoxin. Electrocardiograms were monitored continuously for 4 1/2 h following digoxin administration. The arrhythmogenic dose (AD50) and lethal dose 50 under anaesthesia (LD50) were determined using the method of Litchfield & Wilcoxin. AD50 in rats was 13.0 +/- 1.0 mg kg-1 (mean +/- s.d.) compared with 0.60 +/- 0.04 (P less than 0.01) in the guinea-pig and LD50 was 30.0 +/- 1.9 mg kg-1 in the rat compared with 0.60 +/- 0.04 (P less than 0.01) in the guinea-pig. The onset of arrhythmias was not dose-dependent in the rat but was clearly so in the guinea-pig; for example 102 +/- 15 min (mean +/- s.e.m.) following 0.5 mg kg-1, and 43 +/- 2 min following 1 mg kg-1. In the rat the onset of arrhythmias was 54.0 +/- 11.5 min. Supraventricular arrhythmias (paroxysmal atrial tachycardia) appeared in 73% of rats compared with only 18% of guinea-pigs whereas ventricular arrhythmias (ventricular tachycardia), multiple premature ventricular contractions and or multifocal PVC's occurred in 100% of guinea-pigs compared with only 32% of rats. All guinea-pigs that developed arrhythmias died whereas several rats recovered from supraventricular tachycardias. In conclusion, the guinea-pig is much more sensitive to digoxin toxicity than the rat, develops arrhythmias at much lower doses and these arrhythmias are much more likely to be ventricular in origin and cause fatality.

Disposition of hexobarbitone and antipyrine in DOCA-hypertensive rats.

The disposition of antipyrine and hexobarbitone, and their effects on drug metabolizing hepatic enzymes have been investigated in DOCA-hypertensive rats. Antipyrine pharmacokinetic parameters were the same in hypertensive and control animals. Hexobarbitone sleeping time was longer in hypertensive rats compared with controls, while the activity of hepatic hexobarbitone hydroxylase was the same in both groups. Hepatic aminopyrine-N-demethylase activity was elevated in hypertensive rats while aniline hydroxylase and aryl hydrocarbon hydroxylase were lower. Glucuronyl transferase was the same in both groups. The sensitivity of the central nervous system of hypertensive rats to hexobarbitone was not altered, as determined by hexobarbitone concentration in blood and in brain. The total hepatic blood flow (arterial and portal) was significantly increased. Thus it is suggested that the difference in the disposition of the two drugs is probably not due to drug metabolizing enzyme activity. It is likely that the increase in total hepatic blood flow and rapid saturation of hepatic hexobarbitone metabolizing enzymes have significant roles in the slower metabolism and increased activity of hexobarbitone in hypertensive rats as compared with control rats.

Dietary restriction modifies fever response in aging rats.

Intermittent (every-other-day) feeding initiated at 19 months of age and continued for 12 weeks, led to a moderate decrease in body weight of aging rats, enhanced survival and modified diurnal changes in body temperature and fever response to bacterial endotoxin (E. coli lipopolysaccharide, LPS). Diet-restricted animals which survived LPS administration, displayed reduced febrile response, i.e. (i) a moderate hypothermia in an early phase, and (ii) a delayed onset of body temperature elevation, as compared with their ad libitum-fed controls. However, peak body temperature values were similar in both groups. The rats of both groups which did not develop hyperthermia in response to LPS, died within 24 h of LPS administration. In control, but not in diet-restricted rats, variations in body weight during the 12 weeks prior LPS administration may be predictable in regard to their survival after LPS treatment. It seems that the resistance to bacterial endotoxin in aging rats is associated with their ability to develop hyperthermia.

Age-related digoxin-verapamil interactions in the adult rat.

We have previously described a method for inducing atrial ectopic tachycardia (AET) in the anesthetized adult rat using digoxin, 30 mg/kg s.c. In this study, we used this model to study digoxin-verapamil interactions in young and older male rats and have found age-related differences in their responses to digoxin alone and to digoxin-verapamil interactions as well. Overall, 90% of the animals of both groups combined that developed AET, developed a ventricular proarrhythmic response to verapamil. Thus, this model might broaden the pre-clinical evaluation of anti-arrhythmic agents and predict which drugs are most likely to have a proarrhythmic effect.