Alterations in expression of gluconeogenic genes during heat stress and exogenous bovine somatotropin administration.

Study objectives were to evaluate hepatic gluconeogenic enzyme gene expression in recombinant bovine somatotropin (rbST)-treated lactating dairy cattle during heat stress (HS) or in thermal-neutral, pair-fed (PF) animals. Twenty-two multiparous (99 d in milk, 656 kg of BW) Holstein cows were subjected to 3 consecutive experimental periods (7 d each): (1) thermal neutral, (2) HS or PF, and (3) HS or PF with rbST (Posilac, administered on d 1 of period 3). Liver biopsies were obtained on the final day of each period. Heat stress conditions progressively decreased dry matter intake for the first 5 to 6 d during period 2 before stabilizing (a decrease of 6.15 kg; 30%) on d 6 and 7, and feed intake remained stable and not different from period 2 during period 3. Cytosolic phosphoenolpyruvate carboxykinase mRNA abundance increased during PF, but was unaffected by HS or bST. Pyruvate carboxylase gene expression increased during HS and PF, and administering bST decreased pyruvate carboxylase mRNA abundance during both HS and PF. Insulin-like growth factor-I gene expression increased following bST administration during HS and PF, confirming hepatic bST responsiveness. Exposure to HS leads to a change in hepatic gluconeogenic enzyme profile that appears to be dependent on plane of nutrition.

Magnetic resonance imaging of metastatic disease to the brain with gadobenate dimeglumine.

Seventy-four patients with one to eight proven intraaxial brain metastases received a total cumulative dose of 0.2 mmol/kg bodyweight gadobenate dimeglumine, administered as sequential injections of 0.05, 0.05 and 0.1 m mol/kg over a 20-min period. MR imaging was performed before the first administration (T2- and T1-weighted sequences) and after each injection of contrast agent (T1-weighted sequences only). Quantitative assessment of images revealed significant (P <0.01) dose-related increases in lesion-to-brain (L/B) ratio and percent enhancement of lesion signal intensity. Qualitative assessment by two independent, blinded assessors revealed additional lesions in 22%, 25% and 38% (assessor 1) and 29%, 32% and 34% (assessor 2) of patients after each cumulative dose when compared with combined T1- and T2-weighted pre-contrast images. Significantly more lesions (P < 0.01) were noted by both assessors after the first injection and by one assessor after each subsequent injection. For patients with just one lesion observed on unenhanced T1- and T2-weighted images, additional lesions were noted in 12%, 16% and 28% of patients by assessor 1 following each dose and in 24%, 27% and 30% of patients by assessor 2. Contemporaneously, diagnostic confidence was increased and lesion conspicuity improved over unenhanced MRI. For patients with one lesion observed after an initial dose of 0.05 mmol/kg, additional lesions were noted by assessors 1 and 2 in 9.1% and 11.8% of patients, respectively, after a cumulative dose of 0.1 mmol/kg and in a further 9.1% and 5.9% of patients, respectively, after a cumulative dose of 0.2 mmol/kg. No safety concerns were apparent.

Gadobenate dimeglumine-enhanced magnetic resonance imaging of intracranial metastases: effect of dose on lesion detection and delineation.

Seventy-four patients with one to eight proven intraaxial metastatic lesions to the brain received a total gadobenate dimeglumine dose of 0.3 mmol/kg of body weight, administered as three sequential bolus injections of 0.1 mmol/kg, at 10-minute intervals over a 20-minute period. Quantitative and qualitative assessments of efficacy were performed after each injection and a full evaluation of safety was conducted. Cumulative dosing produced significant (P < 0.01) dose-related increases in lesion-to-brain (L/B) ratio and lesion signal intensity (SI) enhancement. Two independent, blinded assessors noted additional lesions, compared to unenhanced images in 31% and 33%, 49% and 42%, and 50% and 48% of patients after each cumulative dose, respectively. Significantly more lesions were noted after the first injection, compared to unenhanced images (P = 0.002 and P < 0.001; assessors 1 and 2, respectively), and after a second injection, compared to the first (P < 0.001 and P = 0.039; assessors 1 and 2, respectively). Neither assessor noted significantly more lesions after the third injection. For patients with just one lesion observed on unenhanced T1- and T2-weighted images, additional lesions were noted by assessors 1 and 2 for 27% and 26%, 48% and 35%, and 42% and 41% of patients, respectively, following each injection. Contemporaneously, diagnostic confidence was increased and lesion conspicuity improved over unenhanced magnetic resonance imaging (MRI). For patients with one lesion observed after 0.1 mmol/kg of gadobenate dimeglumine, additional lesions were noted for 24% and 17% of patients (assessors 1 and 2, respectively) following a second 0.1 mmol/kg injection. Only assessor 2 noted additional lesions following the third 0.1 mmol/kg injection. The findings of on-site investigators concurred with those of the two off-site assessors. No safety concerns were apparent.

Gadobenate dimeglumine and cerebral glucose metabolism. Continuous monitoring of striatal lactate levels in freely moving rats.

PURPOSE: Brain contrast-enhanced MR imaging reflects the leakage of contrast material into the brain tissue due to blood-brain barrier (BBB) disruption. The contact between brain tissue and contrast material requires a high level of neurotolerability of the contrast agent (CA). In the present study, we investigated the neurotolerability of the paramagnetic CA gadobenate dimeglumine, locally applied into the corpus striatum of freely moving rats, by evaluating its potential effects on cerebral glucose metabolism based on lactate levels. MATERIAL AND METHODS: Lactate levels were monitored using a microdialysis technique coupled with an enzyme reaction. A microdialysis probe for extracellular fluid sampling, together with a stainless steel cannula for CA administration, were inserted into the right corpus striatum of rats. Lactate levels were monitored for 2 h after gadobenate dimeglumine administration at 120 nmol/rat, at fixed volume of 1.2 microl. The same volume of artificial cerebrospinal fluid (aCSF) was administered to control rats. RESULTS: Gadobenate dimeglumine did not induce any significant changes in the lactate striatal levels over the 30-min period after administration. Small, but significant, reductions in lactate concentration were found from the 45-min control point after gadobenate dimeglumine administration. Lactate response showed the same pattern in rats given aCSF. CONCLUSION: Gadobenate dimeglumine, intracerebrally administered, did not affect cerebral glucose metabolism in rats as it showed the same behaviour as aCSF on cerebral glucose utilization. The gradual attenuation in the endogenous lactate release observed 45 min after test compound administration is possibly due to a slight reduction in the probe recovery. The present findings confirm the neurotolerability of gadobenate dimeglumine previously shown in behavioural and electrophysiological studies.

MultiHance in the assessment of intracranial tumors: results of phase II clinical studies.

PURPOSE: To assess preliminarily the efficacy of 0.1 and 0.2 mmol/kg doses of MultiHance for contrast-enhanced magnetic resonance imaging of brain tumors. METHODS: Patients were imaged pre-dose using proton density (PD), T2-weighted and T1-weighted spin-echo sequences, and post-dose by repetition of the T1-weighted sequences at 0-15, 15-30, 30-45 and 45-60 min after the completion of MultiHance administration. Qualitative efficacy assessments of the image sets were performed by two blinded neuroradiologists in terms of the level of diagnostic information, the type of additional information provided by post-contrast images, the best post-contrast image set in terms of diagnostic information, the radiological utility of MultiHance, and the detectability of brain metastases. Extensive safety and tolerability controls were performed at 3 and 24 h post-contrast. RESULTS: Additional diagnostic information was available on MultiHance-enhanced images as compared to pre-contrast images for 58.678.9% of patients administered 0.1 mmol/kg MultiHance and 66.1-74.6% of patients administered 0.2 mmol/kg MultiHance. Generally, the early (0 to 30 min) post-contrast image sets were preferred, with a clear superiority at the 15-30 min post-dose time point. In a subgroup of 21 patients with brain metastases, a higher number of lesions was detected in 55.6-66.7% of the cases with 0.1 mmol/kg MultiHance and in 58.3% of the cases with 0.2 mmol/kg MultiHance. Overall, the usefulness of MultiHance was judged as good to excellent in 91.4% of the patients at both dose levels. A total of 12 of 120 patients (10%) reported 15 transient, self-resolving adverse events of mild-to-moderate intensity. No difference between doses was observed in the incidence of adverse events and no laboratory, ECG or vital signs abnormalities were reported. CONCLUSION: MultiHance is a safe and effective contrast agent for magnetic resonance assessment of brain tumors when administered intravenously at doses up to 0.2 mmol/kg.

General pharmacology in experimental animals of gadobenate dimeglumine (MultiHance), a new magnetic resonance imaging contrast agent.

OBJECTIVES: To assess in animals the pharmacological tolerability for intravascular gadobenate dimeglumine. RESULTS: Cardiovascular effects: In healthy animals no relevant effects were observed apart from slight and transient increases in cardiac output and decreases in systemic vascular resistance. In pigs with myocardial ischemia: doses up to 3.0 mmol/kg caused dose-dependent decreases in heart rate, systemic vascular resistance and mean arterial blood pressure along with transient increases in cardiac output. In vitro: Myocardial contractility was slightly depressed after direct exposure to a 30 mM solution. Respiratory effects in healthy pigs: no effects after 1.0 mmol/kg i.v. Effects on the central nervous system: In healthy animals: gadobenate dimeglumine, 1.0 mmol/kg i.v, did not penetrate nor impair the blood-brain barrier in rats and did not affect behavior, motor coordination or EEG. In pathological models: even in the presence of an osmotically disrupted blood-brain barrier, brain penetration of gadobenate was poor and no signs of epileptogenic potential were evident. Effects on blood: No hemolytic potential was observed. Plasma coagulation was slightly affected in vitro but not in vivo. Effects on kidney and liver function: Transient increases in diuresis, without effects on blood and urine enzymes were observed at doses of 1.25 and 2.5 mmol/kg. CONCLUSIONS: The clinical use of gadobenate dimeglumine as an intravascular magnetic resonance imaging contrast agent is strongly supported by the good tolerability of the product in healthy and pathological animal models.

Neurotolerability of gadobenate dimeglumine. Evaluation of brain dopamine concentration in freely moving rats by microdialysis.

RATIONALE AND OBJECTIVES: Magnetic resonance imaging with contrast agents (CAs) is a procedure currently used for the diagnosis of neurologic pathologies. These pathologies are often characterized by blood-brain barrier disruptions, which determines a direct contact between CA and brain tissue. For this reason, an accurate assessment of neurotolerability is useful for the development of new CAs. The present study was designed to evaluate the neurotolerability of a new CA for MRI, gadobenate dimeglumine, employing a neurochemical method. The effect of gadobenate dimeglumine on the striatal levels of neurotransmitters was determined. In particular, the brain concentrations of dopamine and dopamine metabolites, 3,4-dihydroxyphenylacetic and homovanillic acid, were measured using microdialysis, after the direct application of gadobenate dimeglumine into the rat corpus striatum. Gadopentetate dimeglumine and gadoteridol were employed as reference compounds. METHODS: A microdialysis probe for brain extracellular fluid sampling and a stainless-steel cannula for CA application were chronically inserted into the right corpus striatum of rats. All CAs were administered at a dose of 5.4 nmol/rat. Dopamine and metabolite concentrations were analyzed using high-performance liquid chromatography. RESULTS: Gadobenate dimeglumine did not induce any significant changes in the extracellular levels of dopamine or dopamine metabolites up to 2 hours after administration. Gadoteridol produced similar results. Gadopentetate dimeglumine caused a moderate but not significant increase in dopamine levels throughout the duration of the experiments. CONCLUSIONS: Gadobenate dimeglumine directly administered into the corpus striatum of freely moving rats did not affect the dopaminergic system. This result demonstrates the safety of gadobenate dimeglumine under the experimental conditions used, thus confirming previous behavioral and electrophysiologic findings.

Neurotolerability of gadobenate dimeglumine in a rat model of focal brain ischemia: EEG evaluation.

RATIONALE AND OBJECTIVES: The neurologic pathologies for which contrast-enhanced MRI is indicated are often accompanied by a disruption of the blood-brain barrier (BBB), which allows the contrast agent to come into contact with the nervous tissue. Thus, assessment of the neurologic safety for a new contrast agent is of crucial importance. The objective of this study was to assess the neurotolerability of the new MRI contrast agent gadobenate dimeglumine using EEG in the presence of focal lesions of the BBB. METHODS: Lesions of the BBB were obtained inducing a photochemical ischemia in rats. Gadobenate dimeglumine was intravenously administered at 4.0 mmol/kg. An EEG was recorded during sleep/awake behavior and was analyzed for pathologic tracing and for changes in spectral content in terms of total power and frequency index. The presence of the BBB lesions was verified using high-performance liquid chromatography measurement of the gadobenate ion content in the brain. RESULTS: Gadobenate dimeglumine did not have any epileptogenic effect in ischemic rats. However, it caused a transitory shift of the EEG power spectrum toward the 0.5 to 9 Hz frequency bands of the lesioned hemisphere during quiet wake. In the lesioned cortex, higher levels of gadobenate ion were found until 3 hours after administration. CONCLUSIONS: In experimental conditions of focal brain ischemia associated with BBB lesions, gadobenate dimeglumine was well tolerated up to doses even 10 times higher than the maximum clinical dose (0.3 mmol/kg) intended for brain imaging procedures.

An experimental study on the neurotolerability of gadobenate dimeglumine in a rat model of focal brain ischemia.

RATIONALE AND OBJECTIVES: The neurologic safety of the new magnetic resonance imaging contrast agent gadobenate dimeglumine has been assessed in rats suffering from localized blood-brain barrier damage. METHODS: The adopted experimental model was the photochemically induced brain ischemia in the rat. Flash-evoked visual potentials were recorded simultaneously from the damaged area and from the corresponding contralateral position in conscious rats before and after the administration of the contrast medium. RESULTS: The intravenous administration of 0.9 mmol/kg of gadobenate dimeglumine did not induce any significant changes in the visual responses recorded from the ischemic side compared with the intact side. Rats treated with saline or with the reference compounds gadopentetate dimeglumine (Magnevist) and gadoteridol (ProHance) gave comparable results. CONCLUSIONS: The results are in favor of the use of gadobenate dimeglumine in patients suffering from a localized damage to blood-brain barrier.

Brain penetration of intrathecal iomeprol in dogs.

PURPOSE: Iomeprol, a new nonionic iodinated compound for intravascular use, is being evaluated as a myelographic contrast agent because of its low neurotoxicity. This study aimed to assess the degree of brain penetration of iomeprol after intrathecal administration. MATERIAL AND METHODS: Brain penetration in dogs was investigated by CT and compared with that of iopamidol, iohexol, and ioversol, currently used as myelographic contrast media (CM). Nervous tissue density was determined in different brain structures by recording Hounsfield values. RESULTS: The experiments revealed that CM diffused from the cisternae into the parenchyma, reaching a maximum at 5-24 h after injection. The density of the examined brain regions was still higher than the preinjection levels 24 h later. No differences in brain penetration were observed among the CM investigated. CONCLUSION: The study has shown that iomeprol penetrates into the brain to the same extent as the most widely used myelographic CM.

Conditioned taste aversion in rats following intrathecal administration of contrast media.

PURPOSE: The occurrence of side-effects such as visceral malaise after intrathecal administration of the non-ionic radiography contrast media iomeprol, iopamidol, and iotrolan was assessed in rats by the conditioned tasted aversion procedure. METHODS: Reduced preference towards a saccharose solution compared with normal water following intraventricular administration of a contrast medium was used as a measure of the aversive response. RESULTS: At a dose of 100 mg I/kg none of the tested contrast media induced aversion. At 200 and 300 mg I/kg, both iopamidol and iomeprol induced significant aversive responses with respect to control, although the response of the iomeprol group appeared milder than that of the iopamidol group at a dose of 200 mg I/kg. Iotrolan could be tested only at the lowest dose since the high doses caused excessive mortality. CONCLUSION: Intrathecally administered iomeprol appeared to be well tolerated in rats at doses higher than those suggested for clinical use.

Preclinical safety assessment of iomeprol for injection as contrast medium for myelography.

A series of pharmaco-toxicological investigations were carried out in animals in order to assess the neurotolerance of iomeprol, a new nonionic iodinated contrast medium. After intrathecal administration iomeprol was completely eliminated from the cerebrospinal fluid, rapidly cleared from the plasma and excreted unchanged through the kidneys. When administrated intrathecally, iomeprol did not significantly alter the behavioural functions or the physiological activities of the brain. Unlike other contrast media, iomeprol was devoid of any epileptogenic activity. The acute neurotoxicity of iomeprol was comparable with that of iopamidol, but less than that of iohexol, iotrolan and iodixanol. Iomeprol was well tolerated in both rats and dogs following weekly intrathecal administrations for four weeks of doses up to three times higher than those foreseen for clinical use. High neurotolerance in animals and favourable physico-chemical characteristics make iomeprol particularly suitable as a contrast medium for both myelography and cerebral ventriculography.

Influence of the cerebellar posterior vermis on the acquisition of the classically conditioned bradycardic response in the rabbit.

The magnitude of classically conditioned bradycardia was studied in rabbits in which various cerebellar regions (lobule IX or the posterior vermis or the hemispheres) had been removed surgically. Lesions were shown histologically to be restricted to the cortex and the underlying white matter without any damage to the deep cerebellar nuclei. In the conditioning procedure, tones were employed as conditioned stimuli (CS) and ear shocks as unconditioned stimuli (US). Cerebellar lesions did not affect the characteristics of the bradycardic orienting response, baseline heart rate or the unconditioned tachycardic response to US. The conditioned bradycardia was significantly reduced in magnitude with respect to controls in rabbits submitted to removal of posterior vermis, while it was unaffected in lobule IX and hemispheric lesioned rabbits. The temporal pattern of development and habituation of the bradycardiac response through the conditioning session, as well as its topography, did not differ from controls in any of the lesioned rabbits. After the first conditioning session, some control rabbits were submitted to removal of the posterior vermis and then conditioned again, following an identical procedure. Their pre- and post-lesion conditioned responses did not exhibit any appreciable differences and were similar to the responses exhibited by a group of unoperated controls which were submitted to a reconditioning session. It is concluded that in the rabbit the cerebellar posterior vermis is involved in the initial acquisition of the classically conditioned bradycardia, but it is not the site of its memory trace.

Efferent connections of lobule IX of the posterior cerebellar cortex in the rabbit--some functional considerations.

The Purkinje cell projection from the cardiovascular region of sublobule b of the uvula (medial area of zone A) has been investigated using anterograde tracing methods in the rabbit. The importance of the integrity of the identified pathways in mediating the cardiovascular responses from the uvula has been studied in subsequent lesioning experiments. Wheat germ agglutinin-conjugated horseradish peroxidase or tritiated amino acids were microinjected into sublobule IXb. This resulted in anterogradely labelled Purkinje cell axons in both the inferior and superior cerebellar peduncle. In agreement with previous studies in rabbit we also found labelled fibres at the level of the fastigial nucleus and vestibular complex. However, the labelled fibres we observed in the parabrachial nucleus have not been reported in previous studies except in the prosimian primate. Projections from IXb showed terminal-like patterns of label in the ventromedial region of the caudal fastigial nucleus, the dorsal areas of the superior and inferior vestibular nuclei and in the medial and lateral divisions of the parabrachial nucleus. Labelled fibres were also seen coursing in the lateral vestibular nucleus. Lesioning experiments have revealed that the integrity of the superior cerebellar peduncle is essential for the expression of the cardiovascular responses (bradycardia and depressor response) elicited from the uvula in the anaesthetized rabbit. In contrast, the pattern of cardiovascular response evoked in a decerebrate rabbit (tachycardia and pressor response) was abolished when the inferior cerebellar peduncle was lesioned.

The influence of lobule IX of the cerebellar posterior vermis on the baroreceptor reflex in the decerebrate rabbit.

Stimulation of lobule IX (the uvula) of the cerebellar posterior vermis, either electrically or chemically, has been shown to evoke marked cardiovascular effects in both rabbit and cat. Recent experiments suggest that this stimulation can also reduce the responsiveness of neurons in the nucleus tractus solitarii to baroreceptor inputs. The aim of the present study was thus to determine whether the uvula exerts an influence on the baroreceptor reflex. In order to evoke a reflex bradycardia in decerebrate rabbits, blood pressure was increased by inflating a Swan-Ganz catheter positioned in the descending aorta, and in some rabbits the aortic nerve was also stimulated electrically. In most rabbits, following uvula removal, significantly larger reflex falls in heart rate were observed. In a second group of rabbits, a lesion of cerebellar lobules VI-VIII had no effect on reflex bradycardia. It is concluded that the uvula tonically depresses the cardioinhibitory component of the baroreceptor reflex in the rabbit. The possible functional implications of these results are discussed.

An electrophysiological and anatomical study of afferents reaching the cerebellar uvula in the rabbit.

Stimulation of a medial region of the cerebellar uvula cortex produces sympathetically mediated cardiovascular effects in the decerebrate rabbit. In the present study the afferents to this cerebellar area have been determined using electrophysiological and neuroanatomical methods. Field potentials of prevalent mossy origin evoked by single-shock stimulation of different peripheral nerves have been recorded from sublobules IXa and IXb. No response to vagus and aortic nerves stimulation has been found. A modulation of Purkinje cell discharge following natural vestibular stimulation has been found. A modulation of Purkinje cell discharge following natural vestibular stimulation has been recorded from sublobules IXb and IXc. The retrograde transport of horseradish peroxidase from the uvula cortex has revealed a widespread afferent input to this cerebellar region arising from brain stem reticular and sensory nuclei. On the basis of the results obtained, together with the results of experiments performed in conscious rabbits, contained in the following paper (Bradley, Ghelarducci, La Noce & Spyer, 1990), it is suggested that the uvula participates in co-ordination of the visceral and somatic components of the alerting reaction in the rabbit.

Autonomic and somatic responses evoked by stimulation of the cerebellar uvula in the conscious rabbit.

The present study has investigated the effects of electrical stimulation of the cerebellar posterior cortex in the conscious rabbit. Stimulation of lobule IX (the uvula) elicited an increase in mean arterial blood pressure and heart rate, accompanied by EEG desynchronization, pupillary dilatation and a specific motor reaction, consisting of pricking of the ears, neck stiffening and running movements. Stimulation of lobule VIII was ineffective in evoking equivalent responses. The administration of barbiturates reversed the cardiovascular response to uvula stimulation, producing a fall in mean arterial pressure. The characteristics of the pattern of responses obtained, together with the anatomical and electrophysical observations provided in the preceding paper (Bradley, Ghelarducci, La Noce, Paton, Spyer & Withington-Wray, 1990), suggest a possible involvement of uvula cortex in the expression of the alerting reaction in the rabbit.

Dark-rearing modifies serotonin and 5-hydroxyindoleacetic acid contents in specific regions of rabbit brain.

The contents of serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in specific brain regions of rabbits dark-reared from birth until 3 months of age are higher than those of controls. After light exposure, 5-HT and 5-HIAA levels become similar to normal values. In adult rabbits kept in darkness for 3 months, 5-HT and 5-HIAA contents increase only in the superior colliculi. These results are discussed in relation to the early development of the vestibulo-ocular reflex.

Development of vertical vestibulo-ocular reflex characteristics in intact and flocculectomized rabbits visually deprived from birth.

The vertical vestibulo-ocular reflex (VOR) was recorded in dark-reared rabbits 3 months of age submitted in the dark to lateral sinusoidal oscillations of different frequencies and fixed amplitude. While the phase of the response was perfectly adequate to ensure head movements compensation, the gain values recorded showed a clear reduction with respect to the values obtained in a normally raised control group of the same age. After exposure to light, the visually deprived animals showed a complete and rapid recovery of normal VOR gain values. Another group of animals was flocculectomized prior to light exposure. The bilateral ablation of flocculus and paraflocculus did not affect the VOR characteristics of the deprived animals. After exposure to light, in the flocculectomized animals, no recovery of the VOR gain values was observed. The present results confirm that visual experience in early life is necessary for a correct development of the VOR. If visual deprivation is limited to the first few months of life, the impairment of the reflex characteristics is completely reversible. Finally our data suggest that in the rabbit, the flocculus controls the early life development of the VOR.