The characterization and localization of the glutamate receptor subunit GluR1 in the rat brain.

The cloning of cDNAs that encode functional glutamate receptors makes it possible to produce antibodies that can be used as high-affinity probes for the localization and characterization of these receptors in the mammalian brain. We have made antibodies to different regions of the first cloned member of this family, GluR1, using bacterially overproduced antigen. On Western blots, these antisera detect glycoprotein(s) of 105 kDa present in crude membranes of the hippocampus and cerebellum. The 105-kDa band is associated with postsynaptic densities, and it is observed in cultured cells upon transfection with the GluR1 cDNA. Although glutamate receptors are thought to be the most prevalent excitatory ligand-gated ion channel in the mammalian brain, immunohistochemistry reveals that the receptors recognized by these antisera are localized predominantly in neurons of the cerebellum and some structures of the limbic system, including the hippocampus, the central nucleus of the amygdala, and portions of the septum. This pattern of expression is, in general, consistent with the distribution of GluR1 mRNA as determined by in situ hybridization histochemistry. Our results suggest that glutamate excitatory circuits recognized by these antisera are predominantly found in regions of the limbic system that are reciprocally interconnected.     

The spectral signature method for the analysis of PET brain images

We introduce the concept of the metabolic centroid spectrum as the feature space to characterize the distribution of metabolic activity in three-dimensional brains. The method computes the metabolic centroid of a brain subvolume for each increment of metabolic activity occurring in the whole brain. The result is the metabolic spectral signature, a continuous three-dimensional curve whose shape reflects the distribution of metabolic rates in the brain. The method's sensitivity to metabolic distribution asymmetries is greatly increased over that of the metabolic centroid method, while retaining its advantages; it is almost invariant to head size, head positioning, photon scatter, and the positron emission tomography (PET) camera's full width at half-maximum. It does not require magnetic resonance, computed tomography, or x-ray images. To test the method we analyzed the metabolic PET images of 40 normal subjects and 20 schizophrenics. The results show a unification of several metabolic characteristics of schizophrenic brains, such as laterality, hypofrontality, cortical/subcortical abnormalities, and overall brain hypometabolism, which were identified by different laboratories in separate studies using differing methodologies. Here they are presented by a single automatic objective method.     

Ganglioside or sialic acid attenuates ethanol-induced decrements in locomotion, nose-poke exploration, and anxiety, but not body temperature.

1. This laboratory has previously reported that pretreatment with ganglioside, or even with its constituent, sialic acid (SA), can attenuate certain intoxicating effects of ethanol. It was important to see if these findings could be replicated, particularly by using other measures of ethanol effects. Herein we report that pretreatment with either gangliosides or SA attenuated ethanol-induced decrements in locomotion, nose-poke exploration, and anxiety, but not body temperature. 2. An ethanol dose of 4 gm/kg caused a temperature drop of about 3 degrees C, which was unaffected by any pretreatment. The onset to sleep, however, was delayed an average of 18 or 36 secs in mice pretreated with ganglioside or SA, respectively. Ethanol-only (4 gm/kg) depressed mean cumulative locomotor activity to 31% of normal, whereas the depression was 83% of normal with beef brain ganglioside pretreatment. At 2 gm/kg ethanol alone decreased nose poking in a hole-board test to 29% of normal, but the depression was only 55-63% of normal with SA or ganglioside pretreatment. In a staircase climbing anxiety test, this dose of ethanol had no effect by itself, but both ganglioside and SA pre-treatment increased climbing by 22%. Ethanol did depress rearing to only 11% of normal, whereas rearing was 51 and 99% of normal with SA and ganglioside pretreatment, respectively. In a dark-preference test, ethanol-only caused mice to spend 64% of the time in the light, compared to 31% for controls. Time in the light was only 39 and 46% with ganglioside and SA pretreatment, respectively. 3. Blood levels of ethanol were not significantly affected by pretreatment. 4. When given alone, gangliosides significantly stimulated locomotion and staircase climbing. SA significantly decreased rearing in the staircase test. Both gangliosides and SA tended to increase nose poking, number of crossings in the dark-preference test, and time in a lighted compartment. Thus, it is possible that some of the attenuation of intoxication is attributable to non-specific stimulant properties of gangliosides and SA.     

Peripheral neuropathy associated with hypereosinophilia.

Three patients with hypereosinophilia showed different forms of peripheral neuropathy: severe polyneuropathy of prevalently sensory type (case 1), mild sensory neuropathy (case 2), acute mononeuropathy of the median nerve with subclinical polyneuropathy (case 3). Hypereosinophilia was probably idiopathic, however the presence of atypical findings suggested transition to vasculitides or collagen disease. Sural nerve biopsy in cases 1 and 2 showed features of axonopathy in both, although of different severity, reflecting the variability of clinical involvement and, probably, heterogeneous pathogenic mechanisms. Peripheral nerve involvement associated with hypereosinophilia may be related to neurotoxicity of eosinophils, or to vascular damage.     

Platelet 5-hydroxytryptamine increases with platelet age in dogs.

Thrombocytopenia was induced in mongrel dogs by two mechanisms: immunologically, by intravenous injection of heterologous antiplatelet antibody, and non-immunologically, by circulating the blood through glass beads in anesthetized animals. The platelet content of 5-HT was monitored before and during the recovery of the blood platelet counts. This period is associated with the normalization of the mean platelet survival time and with a progressive increase in the mean age of the circulating platelet population. A continuous increment in platelet 5-HT closely followed the increase in platelet counts in both models of thrombocytopenia, and a strong correlation was found between the platelet age and 5-HT content. These findings support the concept that platelets accumulate 5-HT during their physiological aging process, contradicting the notion that a negative balance in 5-HT content results at the end of their physiological lifespan in circulation. These results are not in conflict with the concept that circulating platelets release and re-uptake 5-HT.     

Differences in the abilities of human tau isoforms to promote microtubule assembly.

Three isoforms of human tau protein were compared for their abilities to induce microtubule assembly. The three isoforms, tau 3 (tau containing three microtubule-binding domains), tau 4 (tau containing four microtubule-binding domains) and tau 4L (tau containing four microtubule binding domains plus a 58-amino-acid insert near the N-terminus) were expressed in E. coli and purified using ammonium sulfate precipitation, ion exchange, and size exclusion chromatography. All three isoforms induced microtubule assembly at micromolar concentrations and showed similar critical concentrations for assembly of 0.4-0.45 microM. However, tau 4 induced microtubule formation at a rate five- to tenfold faster than either tau 3 or tau 4L. The rate of microtubule elongation seen with tau 4 was twofold greater than with tau 3 or tau 4L, suggesting that the faster rate of microtubule assembly seen with tau 4 was due, at least in part, to faster elongation. Tau 4 induced a greater number of microtubules to form at steady state than did tau 3 or tau 4L. The microtubules generated with each tau isoform had similar steady-state length distributions and were equally susceptible to cold-induced disassembly. These results indicate that the additional microtubule-binding domain in tau 4 enhances microtubule assembly, while the 58-amino-acid insert negates the stimulatory effect of the fourth microtubule-binding domain.     

Isolation of a rat S100 alpha cDNA and distribution of its mRNA in rat tissues.

In order to clarify the reported discrepancies in S100 alpha protein and mRNA distribution in rat tissues, a rat S100 alpha cDNA has been isolated and this species homologous probe along with a rat S100 beta cDNA probe has been used to examine S100 mRNA expression in rat tissues. Although the rat S100 alpha cDNA was missing approximately 30 nucleotides of coding sequence, only 4 conservative changes in amino acid sequence were observed when the deduced amino acid sequence was compared to the bovine S100 alpha amino acid sequence. Thus, S100 alpha proteins, like S100 beta proteins, are highly conserved among species. All nineteen of the tissues examined (including cerebrum and cerebellum) contained S100 alpha mRNA. In addition, S100 beta mRNA was detected in thirteen of the nineteen tissues examined. These results are in agreement with previous protein distribution studies and further demonstrate that S100 proteins are not brain-specific and are expressed in a large number of tissues. Although S100 alpha and S100 beta mRNAs were detected in rat tissues which had previously been reported to contain S100 alpha and S100 beta protein, a direct correlation between the protein and mRNA levels were not observed, suggesting that different mechanisms regulate S100 expression in various tissues. S100 alpha exhibited a single similar size mRNA species (0.5 Kb) in all tissues examined, as did S100 beta (1.5 Kb), suggesting that the individual S100 proteins are expressed as single mRNA and protein products in rat tissues.     

Physiological responses of typical versus heavy weight triathletes to treadmill and bicycle exercise.

A physiological comparison of the responses of typical weight (less than 90 kg) versus heavy weight (greater than 90 kg) male triathletes to maximal treadmill and maximal bicycle exercise was performed to better understand the effects of weight on endurance performance. The heavy triathlete group (90.9 +/- 3.2 kg, mean +/- SD) had significantly (p less than .01) greater percent body fat (11.9 +/- 3.6 vs 7.4 +/- 1.8%) while having significantly (p +/- .01) lower VO2max values expressed in ml.kg-1.min-1 on both the treadmill (55.6 +/- 4.1 vs 69.9 +/- 5.5) and bicycle ergometer (51.9 +/- 3.9 vs 60.5 +/- 6.2) than the typical triathlete group (66.6 +/- 5.9 kg). Analysis of covariance using body fat as the covariate resulted in persistent significant (p less than .02) VO2max (ml.kg-1.min-1) differences between the groups. Statistically significant (p less than .05) differences in running economy existed between the groups (33.7 +/- 2.7 vs 37.1 +/- 1.5 ml.kg-1.min-1; typical vs heavy). The heavy triathletes also had a significantly (p less than .01) shorter treadmill performance time (9.6 +/- 2.3 vs 13.2 +/- 1.7 min) and significantly (p less than .01) lower power per weight ratio on the bicycle ergometer (5.37 +/- 0.48 vs 6.47 +/- 0.59 watts/kg). These findings indicate that the heavy triathlete is at a physiological disadvantage when competing in endurance events and supports the inclusion of a weight category in these events. The reported triathlon results support these physiological findings.     

Temporomandibular joint eminence augmentation by down-fracture and inter-positional cartilage graft. A new surgical technique.

A new surgical technique for the treatment of recurrent temporomandibular joint subluxation or dislocation is described. Following a horizontal osteotomy and down-fracture of the articular eminence an inter-positional bovine cartilage xenograft is inserted in order to augment the vertical height of the eminence. The procedure combines simplicity with minimal post-operative morbidity. The increase in eminence height is both predictable and stable.     

Cochlear ablation in deafness mutant mice: 2-deoxyglucose analysis suggests no spontaneous activity of cochlear origin

Deafness mutant mice show no stimulus-related cochlear potentials as well as abnormal electrically-evoked responses recorded from the inferior colliculus. Abnormal spontaneous activity in the auditory periphery could result in abnormal development and/or maintenance of the central auditory pathways. We therefore assessed spontaneous activity of cochlear origin in the central nuclei of the mutants by ablating one cochlea and subsequently using the 2-deoxyglucose (2DG) technique to study metabolic activity. Any asymmetries in labeling in a given nucleus should be due to spontaneous activity in the cochlear nerve on the unoperated side. In control animals (+/dn mice undergoing unilateral cochlea ablation), statistically significant decreased 2DG labeling was observed in the ipsilateral PVCN and AVCN, and contralateral MNTB and IC; all receive primary excitatory input from the ablated ear. No significant differences in labeling between right and left sides were observed in any of the nuclei studied in the mutant animals. These findings suggest that there is no spontaneous activity of cochlear origin in these mutants, even though many cochlear nerve fibers and spiral ganglion cells survive.