Body composition and amino acid concentrations of select birds and mammals consumed by cats in northern and central California

The diet of the feral domestic cat consists of primarily birds and small mammals, but the nutritional composition is relatively unknown. Because of the increasing popularity of natural diets for cats and other wild captive carnivores, the purpose of this study was to describe the body composition and AA concentrations of select birds and small mammals in northern and central California: wild-caught mice (n = 7), Norway rats (n = 2), roof rats (n = 2), voles (n = 4), moles (n = 2), gophers (n = 3), and birds (n = 4). Body water, crude fat (CFa), CP, ash, and AA composition for each specimen were determined. Results are reported as mean ± SD. All results are reported on a DM basis except body water (as-is basis) and AA (g/16 g N). Combined, carcasses had this mean composition: 67.35 ± 3.19% water, 11.72 ± 6.17% CFa, 62.19 ± 7.28% CP, and 14.83 ± 2.66% ash. Concentrations of Arg, Tau, Cys, and Met were 5.63 ± 0.46, 0.92 ± 0.33, 1.91 ± 0.89, and 1.82 ± 0.19 g/16 g N, respectively. Using NRC physiologic fuel values for CP, CFa, and carbohydrate by difference, the combined average energy content of the carcasses was 3,929 kcal/kg DM, but the fiber content was not determined. With the exception of mice and rats, little historical data exist regarding the body and AA composition of many of the species analyzed in this study. Wild-caught mice and rats were composed of less fat but more ash compared with previously reported data in their purpose-bred counterparts. The CP content of mice in this study was similar to previous reports in purpose-bred mice. The CP content of rats was similar or slightly greater compared with historical findings in purpose-bred rats. The N content of rats and AA concentrations on a per-N basis for both rats and mice were similar to previously published data on purpose-bred rodents. The discrepancies in nutrient composition, especially fat concentration, indicate that using purpose-bred animals to represent the diet of the feral domestic cat may not be valid in many instances. When consumed to meet energy needs, the nutrient content of the species reported in the present study exceed the NRC (2006) recommended allowances (RA) for total fat, CP, and essential AA for felines at all life stages.

Self-sustaining status epilepticus: a condition maintained by potentiation of glutamate receptors and by plastic changes in substance P and other peptide neuromodulators

We describe a model of self-sustaining status epilepticus (SSSE) induced by stimulation of the perforant path in free-running rats. In this model, seizures can be transiently suppressed by intrahippocampal injection of a blocker of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid/ kainate synapses but return in the absence of further stimulation when the drug ceases to act. However, seizures are irreversibly abolished by blockers of N-methyl-D-aspartate receptors given locally or systemically. SSSE is enhanced by substance P and its agonists and blocked by its antagonists. SSSE induces novel expression of substance P-like immunoreactivity in hippocampal principal cells. These changes and those in other limbic peptides may contribute to the maintenance of SSSE and to the modulation of hippocampal excitability during epileptic seizures. NMDA

Felbamate in experimental model of status epilepticus

PURPOSE

To examine the putative seizure-protective properties of felbamate in an animal model of self-sustaining status epilepticus (SSSE).

METHODS

SSSE was induced by 30-min stimulation of the perforant path (PPS) through permanently implanted electrodes in free-running male adult Wistar rats. Felbamate (FBM; 50, 100, and 200 mg/kg), dizepam (DZP; 10 mg/kg), or phenytoin (PHT; 50 mg/kg) were injected i.v. 10 min after SSSE induction. Electrographic manifestations of SSSE and the severity of SSSE-induced neuronal injury were analyzed.

RESULTS

Felbamate injected during the early stages of SSSE (10 min after the end of PPS), shortened the duration of seizures in a dose-dependent manner. Total time spent in seizures after FBM and 290 +/- 251 min (50 mg/kg), 15.3 +/- 9 min (100 mg/kg), and 7 +/- 1 min (200 mg/kg), whereas control animals spent 410 +/- 133 min seizing. This effect of FBM was stronger than that of DZP (10 mg/kg, 95 +/- 22 min) and comparable to that of PHT (50 mg/kg, 6.3 +/- 2.5 min). In the applied doses, FBM (200 mg/kg) was more effective than PHT (50 mg/kg) or DZP (10 mg/kg) in shortening seizure duration and decreasing spike frequency, when administered on the pleateau of SSSE (injection 40 min after the end of PPS). Anticonvulsant action of FBM was confirmed by milder neuronal injury compared with control animals.

CONCLUSIONS

Felbamate, a clinically available AED with a moderate affinity for the glycine site of the NMDA receptor, displayed a potent seizure-protective effect in an animal model of SSSE. These results suggest that FBM might be useful when standard AEDs fail in the treatment of refractory cases of SE.

Reverse transport of glutamate during depolarization in immature hippocampal slices

We studied the source of extracellular glutamate released by hippocampal slices obtained from P14 or adult rats, during 50 mM K+ depolarization by using two potent inhibitors of Na+-dependent glutamate transport: l-trans-pyrrolidine-2,4-dicarboxylate (PDC), which is a relatively non-selective inhibitor of various glutamate transporter subtypes and dihydrokainic acid (DHK), a specific inhibitor of the glial transporter, GLT-1. Most depolarization-induced glutamate release was Ca2+-dependent in adults, while in P14 slices most glutamate release was Ca2+-independent. PDC decreased depolarization-induced glutamate release in P14 slices but not in adults. DHK increased glutamate release in adults but not in P14 slices. These data suggest that most depolarization-induced glutamate release in immature hippocampal slices is due to reversal of transport through a PDC-sensitive Na+-dependent glutamate transporter, presumably acting on presynaptic or cytoplasmic neuronal pools, and is not due to exocytosis from vesicular pools.

Time-dependent decrease in the effectiveness of antiepileptic drugs during the course of self-sustaining status epilepticus

An animal model of self-sustaining status epilepticus (SSSE) induced in rats by brief intermittent perforant path stimulation (PPS) was examined with regard to the effects of two conventional antiepileptic drugs, diazepam and phenytoin. Thirty or sixty minutes PPS induced SSSE characterized by continuous behavioral and electrographic seizures lasting for hours. Both diazepam (10 mg/kg i. v.) and phenytoin (50 mg/kg i.v.) prevented the establishment of SSSE when administered 10 min prior to PPS. The injection of diazepam to seizing animals, 10 min after the end of 30 min PPS, was significantly less effective than pretreatment in attenuating SSSE. Administration of diazepam after 60 min PPS was characterized by a further decrease of its efficacy. Phenytoin was effective in aborting SSSE when injected 10 min after 30 min PPS. However, its efficacy was vastly decreased if injected 40 min after 30 min PPS, or 10 min after 60 min PPS. It is concluded that antiepileptic drugs, while highly effective in blocking the induction of SSSE, failed to affect its maintenance. SSSE induced by PPS is an advantageous animal model of refractory status epilepticus, which may be used in preclinical studies of novel antiepileptic drugs.

The effect of sampling error and measurement error and its correlation on the estimation of multi-locus fixed-bin VNTR RFLP genotype probabilities

Bootstrapping was used to examine the effect of sampling error and measurement error and its correlation on fixed-bin genotype probabilities. Bootstrap confidence intervals (Cls) were made relative to the point estimate using the log of the inverse of the probabilities. From databases of 200-250 genotypes, sampling error alone yielded median relative 95% CIs of from one order of magnitude out of five for one locus to one out of ten for four loci. Measurement error of the test genotype fragments increased the latter to about one order of magnitude out of eight. Database measurement error and its correlation had only a slight effect on multi-locus probability uncertainty. Together, these uncertainties are several orders of magnitude greater than error due to population substructuring of a race by its major component ethnic groups.

Nitric oxide mediates the increase in local cerebral blood flow during focal seizures

The role of nitric oxide (NO) in the increase in local cerebral blood flow (LCBF) elicited by focal cortical epileptic seizures was investigated in anesthetized adult rats. Seizures were induced by topical bicuculline methiodide applied through two cranial windows drilled over homotopic sites of the frontal cortex, and LCBF was measured by quantitative autoradiography by using 4-iodo[N-methyl-14C]antipyrine. Superfusion of an inhibitor of NO synthase, N omega-nitro-L-arginine (NA; 1 mM), for 45 min abolished the increase of LCBF induced by topical bicuculline methiodide (10 mM) [164 +/- 18 ml/100 g per min in the artificial cerebrospinal fluid (aCSF)-superfused side and 104 +/- 12 ml/100 g per ml in the NA-superfused side; P < 0.005]. This effect was reversed by coapplication of an excess of L-arginine substrate (10 mM) (218 +/- 22 ml/100 g per min in the aCSF-superfused side and 183 +/- 31 ml/100 g per min in the NA + L-Arg-superfused side) but not by 10 mM D-arginine, a stereoisomer with poor affinity for NO synthase (193 +/- 17 ml/100 g per min in the aCSF-superfused side and 139 +/- 21 ml/100 g per min in the NA + D-Arg-superfused side; P < 0.005). Superfusion of the guanylyl cyclase inhibitor methylene blue attenuated the LCBF increase elicited by topical bicuculline methiodide by 25% +/- 16% (P < 0.05). The present findings suggest that NO is the mediator of the vasodilation in response to focal epileptic seizures.

Nitric oxide participates in excitotoxic mechanisms induced by chemical hypoxia

Changes in the activity of the NMDA receptor-gated ionic channels induced by potassium cyanide were studied in rat hippocampal slices utilizing a [3H]MK-801 binding technique. A 30-min exposure of slices to potassium cyanide (KCN) increased MK-801 binding by 252%. Co-application of N omega-nitro-L-arginine (NNLA), a competitive antagonist of nitric oxide (NO) synthase, reduced this increase by 72%. This inhibition by NNLA was completely reversed by an excess of L-arginine, a substrate for NO synthase, suggesting that the KCN-induced increase in MK-801 binding is mediated by NO synthase activity. KCN had no effect on MK-801 binding in synaptic membranes. In Ca(2+)-containing medium, KCN increased the release of glutamate, aspartate and glycine by 4- to 5-fold, and this was blocked by application of NNLA. NNLA inhibition was reversed by an excess of L-arginine, indicating that KCN-stimulated release of these amino acids is mediated by NO synthase activity. In Ca(2+)-free medium, a KCN-induced increase in MK-801 binding and in excitatory amino acid release was also observed, however, this increase was not influenced by NO-related agents, suggesting that these changes were not mediated by NO synthase activation. NNLA given after the end of exposure to KCN did not reverse the increase in MK-801 binding. These findings suggest that NO is involved in the initial activation of NMDA receptor-gated ionic channels and in the enhanced amino acid transmitter release induced by KCN, but that KCN can also induce some of these effects by a Ca(2+)- and NO-independent mechanism.

Does muscular dystrophy affect metabolic rate? A study in mdx mice

In this study metabolic consequences of muscular dystrophy were investigated using the mdx mouse model. Measurements were performed on C57BL/10SNJ (control) and dystrophic (mdx) mice of ages 4-6 weeks (young) and 1 year (adult), i.e. at times when muscle degeneration and regeneration are known to be high (young) and low (adult). Whole body metabolic rate (MR) was measured indirectly under usual living conditions by recording O2 consumption and CO2 production over 24 h. Physical activity of mice was measured simultaneously. Oxygen consumption of soleus (SOL) and extensor digitorum longus (EDL) muscles of control and mdx mice was recorded in vitro, using polarographic O2 electrodes. MR in young mdx was significantly decreased compared to young control, but no differences were found in adults. Also, food consumption and physical activity of mdx were decreased significantly compared to control in young but not in adult mice. There was no difference in resting oxygen consumption of muscles from young mdx and control mice, but oxygen consumption of EDL from adult mdx was less than control. Results suggest that muscular dystrophy results in decreased rate of energy metabolism mainly as a consequence of decreased physical activity. The extensive muscular degeneration and regeneration characteristic of muscular dystrophy therefore do not appear to lead to an increase in whole body metabolism.

Taurine in toad brain and blood under different conditions of osmolality: an immunohistochemical study

The concentrations of taurine in blood and brain regions of the toad Bufo boreas have been measured. Most of these values are considerably lower than those found in mammals. Using an antibody prepared against conjugated taurine, the distribution of taurine in three brain regions of the toad has been visualized. The possible osmoregulatory functions of taurine have been investigated by making toads hyper- or hypo-osmotic in vivo. Induction of hypoosmolality is accompanied by a massive taurine tide in blood plasma, but has no immediate effects upon the taurine concentrations in the brain areas studied. However, histochemical visualization indicates a marked redistribution of taurine between cellular components and extracellular space of brain tissues. This may indicate that taurine has an osmoregulatory function in brain tissue under hypo-osmotic conditions. Hyperosmolality results in no elevation of the taurine concentration in blood plasma of toads, but rather in a very gradual decline of total plasma taurine content over a prolonged time period. Histochemical studies reveal little change in frontal cortex after 1 hour but deeper staining of many neurons in optic lobe accompanied by greater staining in the extracellular fluid. By 3 hours there is a depletion of taurine from all compartments of cerebral cortex tissues. No evidence of any prolonged direct osmoregulatory role for taurine is indicated under hyperosmotic conditions. A possible indirect osmoregulatory function of taurine is discussed.

GABA metabolism in the substantia nigra, cortex, and hippocampus during status epilepticus

The metabolism of GABA and other amino acids was studied in the substantia nigra, the hippocampus and the parietal cortex of rats following microinjections of GAMMA-vinyl-GABA during status epilepticus induced by lithium and pilocarpine. GABA metabolism showed striking regional variations. In controls, both GABA concentration and rate of GABA synthesis were highest in the substantia nigra and lowest in cortex, as expected. In substantia nigra, status epilepticus resulted in a 2 1/2 fold decline in the rate of GABA synthesis and in a 307% increase in the turnover time of the GABA pool. In hippocampus, the rate of GABA synthesis was not altered significantly, but the turnover time of the GABA pool was 284% of controls, and the size of that pool increased to 208% of controls. By contrast, in cortex, where seizure activity is limited in this model, the rate of GABA synthesis increased to 230% of controls while pool size and turnover time did not change. Aspartate concentration decreased in all three brain regions. These data suggest that the observed reduction of the rate of GABA synthesis in substantia nigra could play a key role in seizure spread in this model of status epilepticus.

Alterations of GABA metabolism and seizure susceptibility in the substantia nigra of the kindled rat acclimating to changes in osmotic state

Seizure susceptibility and GABA metabolism were altered in the substantia nigra [SN] of adult male Sprague Dawley rats when these animals were acclimating to an altered plasma osmolality. Changes in GABA metabolism were measured in vivo in SN of the freely moving rat. Suitable precautions were taken to avoid any post-mortem flux of glutamate to GABA and to correct for the underestimation of GABA build up in SN due to the finite diffusion rate of gamma-vinyl GABA [GVG] after stereotaxic injection of small amounts into one side of the brain. Control experiments provided evidence that changes in osmolality, within a normal physiological range, did not affect significantly gamma-aminobutyric acid transaminase [GABA-T]. Also kindling via the medial septum [MS], in the absence of electrical stimulation did not alter GABA metabolism in SN, thus providing a stable baseline for studies of osmotic effects. Hyperosmolality was associated with a rise in seizure thresholds, with a marked reduction of the rate of GABA synthesis in SN, and with a substantial increase in turnover time of the GABA pool. Hypoosmolality, of a degree known to be associated with mild cerebral edema and swelling localized to astrocytes, markedly reduced seizure threshold, and reduced GABA pool size in SN, but did not alter the rate of GABA synthesis significantly. These results demonstrate by new and independent means the relationship between GABA metabolism in the SN and seizure susceptibility in vivo.

Changes of amino acid gradients in brain tissues induced by microwave irradiation and other means

Focused microwave irradiation to the head (FMI) has been used extensively by neurochemists for rapid inactivation of enzymatic activity in brain tissues and the preservation, for in vitro analysis, of in vivo substrate concentrations. Periodically the suitability of this technique for regional studies has been questioned. Evidence has now been obtained, on the basis of altered concentration gradients for GABA and taurine from the Substantia Nigra (SN) to an Adjacent Dorsal Area (ADJ), that FMI not only inactivates enzymes, but also facilitates rapid diffusion of small molecules from areas of high concentrations to adjacent areas of lower concentration. To a lesser extent, the implantation of plastic injection cannulas also decreased these concentration gradients. These results offer clear evidence that FMI is ill suited and unreliable for studies designed to map and compare the "in vivo" regional concentrations of diffusible organic molecules (such as amino acids) in brain tissues. Any invasive technique that compromises membrane barriers is likely to produce smaller similar effects.

Abnormal feeding behavior of western toads (Bufo boreas) kept in a hyperosmotic environment. I. A quantitative behavioral analysis as related to cerebral amino acid concentrations

Discriminant analysis of eleven behavioral variables associated with feeding permitted the assignment of hyperosmotically-acclimating (HOA) toads (Bufo boreas) to six different behavioral states. These behavioral states could be correlated with specific alterations in the level of select amino acids in three regions of the toad's central nervous system. By considering only those amino acids that showed equivalent levels in corresponding brain regions of normally-behaving, freshwater-acclimating (FWA) and HOA toads, it was possible to focus upon just nine amino acids as possible modulators of feeding behavior. Four of these amino acids were markedly elevated in two or more abnormal behavioral states: gamma-aminobutyric acid (GABA) in all three brain areas; glutamate in the cerebral hemispheres; aspartate in the cerebral hemispheres and olfactory bulbs; and phenylalanine in the olfactory bulbs and optic lobes. Other possible behavior modulators identified were: lysine and threonine in the cerebral hemispheres; carnosine in the olfactory bulbs; and valine and alanine in the optic lobes.

High proline levels in the brains of mice as related to specific learning deficits

Hyperprolinemic PRO/Re mice have been studied as potential models for hyperprolinemia in man. In addition to high proline levels, some heretofore unreported amino acid abnormalities in the brains of PRO/Re mice are described. The T-maze and shuttlebox learning abilities of PRO/Re mice were compared with those of CD-1 mice having normal proline levels. PRO/Re mice had a significant deficit for T-maze learning, but a significantly greater aptitude for shuttlebox learning when compared to CD-1 mice. By studying the F3 progency of the PRO/Re X CD-1 cross, these strain-specific differences in learning ability for different tasks were shown to be unrelated to the differences in brain proline levels. F3 mice could be subdivided into two distinct groups: those with high proline (HP+) and low proline (HP-) titers. Other amino acids in brain tissues were essentially identical in both groups. A comparison of learning abilities of these HP+ mice with their HP- littermates showed no meaningful differences. However, the slightly slower rate at which HP+ mice acquired shuttlebox learning was sufficiently consistent over the 8 day training period so that it became significant. These results do not support the hypothesis that high levels of proline in brain tissues and blood are necessarily accompanied by impaired learning and memory, but are in agreement with those studies of hyperprolinemia in man that suggest no consistent learning deficits in hyperprolinemic subjects. The results seem to validate the suitability of the PRO/Re mouse as a model for hyperprolinemia in man. The data suggest also that the altered amino acid pattern in brains of PRO/Re mice has multiple etiologies.(ABSTRACT TRUNCATED AT 250 WORDS)

Proline in the cerebrospinal fluid of normal subjects and Alzheimer's-disease patients, as determined with a new double-labeling assay technique

Past studies have implicated proline involvement in the function of memory and learning. A new micromethod has been developed that is suitable for measuring proline accurately in as little as 0.1 ml of CSF. In normal human CSF, the average proline level was found to be consistently about 1.3 microM. In the CSF of patients with Alzheimer's disease and mixed dementias, the levels of proline showed no statistically significant difference from proline levels in the CSF of normal controls. Furthermore, the proline levels in the CSF of the Alzheimer's disease patients did not reflect, consistently, the cognitive deficits or the symptomatic severity of the disease. Proline levels in CSF showed no statistically significant change with the age of individuals tested.