Language dysfunction after stroke and damage to white matter tracts evaluated using diffusion tensor imaging.

BACKGROUND AND PURPOSE: Knowledge of the anatomic basis of aphasia after stroke has both theoretic and clinical implications by informing models of cortical connectivity and providing data for diagnosis and prognosis. In this study we use diffusion tensor imaging to address the relationship between damage to specific white matter tracts and linguistic deficits after left hemisphere stroke. MATERIALS AND METHODS: Twenty patients aged 38-77 years with a history of stroke in the left hemisphere underwent diffusion tensor imaging, structural MR imaging, and language testing. All of the patients were premorbidly right handed and underwent imaging and language testing at least 1 month after stroke. RESULTS: Lower fractional anisotropy (FA) values in the superior longitudinal and arcuate fasciculi of the left hemisphere, an indication of greater damage to these tracts, were correlated with decreased ability to repeat spoken language. Comprehension deficits after stroke were associated with lower FA values in the arcuate fasciculus of the left hemisphere. The findings for repetition were independent of MR imaging ratings of the degree of damage to cortical areas of the left hemisphere involved in language function. There were no findings for homotopic tracts in the right hemisphere. CONCLUSION: This study provides support for a specific role for damage to the superior longitudinal and arcuate fasciculi in the left hemisphere in patients with deficits in repetition of speech in aphasia after stroke.

The effects of noradrenergic activation of the nucleus tractus solitarius on memory and in potentiating norepinephrine release in the amygdala.

Although it is known that norepinephrine (NE) modulates memory by acting on limbic areas, few studies describe how structures supplying NE to the limbic system, such as the nucleus tractus solitarius (NTS) contribute to this process. The present study examined the effects on memory of activating the NE pathway between the NTS and the amygdala (AMYG). Rats received buffer or the beta-noradrenergic agonist clenbuterol (CLN; 10, 50, or 100 ng/0.5 microl) into the NTS after footshock training in a Y-maze discrimination task. Infusion of 100 ng CLN significantly improved memory when retention was tested in the absence or presence of cues associated with the footshock. Experiment 2 used in vivo microdialysis to determine whether the mnemonic effects of CLN are mediated by influencing NE output in the AMYG. Subjects were given an intra-NTS infusion of CLN or phosphate buffered saline, footshock (0.8 mA, 1 s), and injected with epinephrine (EPI; 0.3 mg/kg ip) or saline. CLN or EPI injection produced a significant increase in NE sampled from the AMYG. These findings indicate that activation of NTS neurons that project to and release NE in the AMYG modulates memory storage processing.

Enhanced release of norepinephrine in rat hippocampus during spontaneous alternation tests.

Recent evidence suggests that release of acetylcholine (ACh) in the hippocampus is associated with performance on a spontaneous alternation task and with enhancement of that performance by systemic and central injections of glucose. The present study extended these findings by examining norepinephrine (NE) release in the hippocampus using in vivo microdialysis while rats were tested for spontaneous alternation performance with and without prior injections (ip) of glucose. Microdialysis samples were collected every 12 min and assayed for NE content by HPLC-ECD. Like ACh, NE release in hippocampus increased during spontaneous alternation testing. As in past experiments, administration of glucose (250 mg/kg) significantly enhanced alternation scores. However, glucose did not influence NE release either during behavioral testing or at rest. These findings contrast with prior evidence showing that glucose augments testing-related increases in ACh release. The findings suggest that norepinephrine is released within the hippocampus while rats are engaged in alternation performance. However, increased release of norepinephrine apparently does not contribute to the enhancement of alternation scores produced by glucose.

Effect of prenatal stress on plasma corticosterone and catecholamines in response to footshock in rats.

The effect of prenatal stress was investigated on the sympathoadrenal response to novelty and footshock by measuring the time course of the changes in circulating corticosterone (COR) catecholamines and their metabolites. Pregnant rats were subjected to noise and light stress, three times weekly on an unpredictable basis throughout gestation. When the male offspring of stressed rats (PS) and those of unstressed mothers (C) were 4.5-5 months of age, they were prepared with indwelling catheters in the tail artery 24 h before the experiment. Resting levels of plasma COR, noradrenaline (NA), adrenaline (AD), dihydroxyphenylglycol (DHPG), dihydroxyphenylacetic acid (DOPAC), and dihydroxyphenylalanine (DOPA) were measured. Further blood samples were taken within 3 min of their transfer to the shock box, 1-2, 5, 15, and 45 min after footshock. Plasma COR was significantly higher in PS than in C rats at rest, but those of adrenaline, NA, and their metabolites did not differ in the two groups. Transfer of the rats to the shock box increased plasma COR, NA, adrenaline, and dihydroxyphenylglycol in both groups, and dihydroxyphenylalanine and dihydroxyphenylacetic acid only in PS rats. All the catechols increased further 2-3 min after footshock, except dihydroxyphenylalanine in PS rats. Plasma NA and dihydroxyphenylglycol levels were significantly higher in PS than in C rats immediately after footshock, indicating a greater activation of the sympathetic nervous system in PS rats. The findings demonstrate for the first time that prenatal stress can induce long term changes in the sensitivity of the sympathoadrenal system to stress.

Gender differences in sympathoadrenal activity in rats at rest and in response to footshock stress.

A comparison was made of the dynamics of sympathoadrenal activity in 11 age-matched male and female rats, under basal conditions and after exposure to footshock. Rats were prepared with indwelling catheters in the tail artery 24 h before the experiment. Measurements were made of plasma corticosterone (COR), norepinephrine (NE), epinephrine (EPI), dihydroxyphenylalanine (DOPA), dihydroxyphenylglycol (DHPG) and dihydroxyphenylacetic acid (DOPAC) under resting conditions, after transfer to the shock box (novelty) and at various times after footshock. Under basal conditions, males have significantly higher blood pressure and plasma DHPG/NE ratios but lower plasma levels of COR, NE and DOPAC than females. Three min after exposure to the shock chamber (novelty stress) there were significant increases in COR, EPI, NE and DHPG in both sexes, while DOPA increased only in females and DOPAC remained unchanged in both sexes. Footshock produced a further increase in EPI, NE and DOPAC within 2 min, which lasted about 15 min. There were significant sex differences in the extent and duration of the response of COR, EPI and DHPG. The data show that the female sympathoadrenal system is more reactive than that of the male to the stresses of a novel environment and footshock. The smaller DHPG/NE ratios in females at rest and after stress suggest that neuronal uptake of NE is lower in females than in males. The finding that stress produces larger increments of plasma DOPA and DOPAC in female rats indicates that tyrosine hydroxylase in the sympathetic nerve terminals and adrenal medulla may also be higher than in males.

Activity-dependent regulation of dopamine content in the olfactory bulbs of naris-occluded rats.

Several lines of evidence strongly suggest that reduced olfactory nerve activity results in decreased bulb dopamine content. In the present study, high performance liquid chromatography with electrochemical detection was used to assess catecholamine levels in bulbs from postnatal day 60 rats that had undergone either unilateral naris cautery or a sham surgery on day 30. Thirty days of odor deprivation dramatically reduced dopamine and dihydroxyphenylacetic acid levels in functionally-deprived bulbs (ipsilateral to occluded nares) as compared to contralateral controls, while norepinephrine and dihydroxyphenylglycol levels were unchanged. The loss of dopamine was more severe in medial as compared to lateral aspects of experimental bulbs, while the loss of dihydroxyphenylacetic acid was similar on the two sides. To test directly the hypothesis that afferent activity regulates dopamine and dihydroxyphenylacetic acid content, 1 h of high frequency tetanic nerve stimulation was provided to the rostral-medial olfactory nerve layer in deprived olfactory bulbs, and catecholamine levels were assessed from 6 to 192 h later. Partial and temporary recovery of dopamine was observed in medial aspects of the bulb when rats were examined 96 h later, while consistent recovery of dihydroxyphenylacetic acid content was not apparent. These data corroborate evidence that olfactory nerve activity is a potent regulator of bulb dopamine and indicate that continued afferent input is necessary to maintain dopamine levels.

Norepinephrine release in the amygdala after systemic injection of epinephrine or escapable footshock: contribution of the nucleus of the solitary tract.

Several findings based largely on lesions and drug manipulations within the amygdala suggest that norepinephrine (NE) systems in the amygdala contribute to enhancement of memory processes by epinephrine (EPI). However, no studies to date have directly measured changes in the release of NE in the amygdala after EPI injection. In Experiment 1, in vivo microdialysis was used to assess amygdala NE release after systemic injection of saline, EPI (0.1 or 0.3 mg/kg), and administration of an escapable footshock (0.8 mA, 1 s). Both doses of EPI produced a significant elevation in NE release that persisted for up to 60 min. In Experiment 2, the local anesthetic lidocaine (2%) was infused (0.5 microl) into the nucleus of the solitary tract (NTS) immediately before injection of 0.3 mg/kg EPI. The EPI-induced elevation in amygdala NE release observed in Experiment I was attenuated by inactivation of the NTS. These findings indicate that systemic injection of EPI increases release of NE in the amygdala and suggest that the effects are mediated in part by activation of brainstem neurons in the NTS that project to the amygdala.

Somatosensory afferent inputs release 5-HT and NA from the spinal cord.

Endogenous serotonin (5-HT) and noradrenaline (NA) release by somatosensory afferent inputs was investigated at the level of the spinal cord using in vivo microdialysis technique combined with high performance liquid chromatography and electrochemical detection (HPLC-ECD). Selective stimulation of large myelinated A beta afferent fibers significantly increased 5-HT release to 151.1 +/- 10.1% of the control, but did not affect NA release. However, selective stimulation of small myelinated A delta fibers released NA rather than 5-HT. The NA level enhanced to 128.8 +/- 6.4% of the control after A delta fibers were stimulated with the intensity of 6 times threshold. Stimulation of unmyelinated C fibers unavoidably excited the A beta and A delta afferent fibers, causing both 5-HT and NA release from the spinal cord. The results suggest that both innocuous and noxious information may activate serotonergic descending pathways. The noradrenergic descending pathways are only triggered by noxious inputs transmitted by small afferent fibers.

Construction of a stable expression vector carrying sop genes [ZJ1].

Mini-F, the fifth fragment of F plasmid from EcoRI digestion, is known to carry an efficient partitioning function. Two pBR322 plasmid derivatives, pDMC32 and pDMC311, have been constructed from this fragment. The plasmid pDMC32 carries all the relative genes for plasmid stability, ccd, repD, and sop genes (sopA, sopB, and sopC), along with oriS and oriV, while pDMC311 carries only sop genes (sopA, sopB, and sopC). The plasmid maintenance proportions for pDMC32 and pDMC311 in E. coli were 93% and 100%, respectively, after 100 generations continuous cultivation of cells harboring the derivatives, MI32 (pDMC32) and MI311 (pDMC311), in a phosphate-limited basal medium. As a control, the maintenance proportion of plasmid pBR322 dropped down to a low of 10% at generation 55 of continuous cultivation of E. coli MIR322 (pBR322) in the same medium. In order to make a stable expression vector that carries only sop genes, plasmid pDMC40 was constructed by adding a trp promoter from pDR720 to pBR322. The stable expression vector pDMC48 was then derived from pDMC40 by inserting sop genes into it from pDMC311. The maintenance proportion of plasmid pDMC48 in E. coli was still 100% after 100 generations of continuous cultivation of cells harboring the plasmid in phosphate-limited basal medium.

Activation of descending noradrenergic system by peripheral nerve stimulation.

Noradrenaline (NA) release in the rat lumbar spinal cord (L3-4) in response to variable intensity, selective stimulation of large (A-beta), small myelinated (A-delta), and unmyelinated (C) afferent fibers was examined by in vivo microdialysis with high performance liquid chromatography and electrochemical detection. Application of 100 mM K+ solution via the dialysis probe increased NA in the dialysate. Thoracic segment transection rostral to the probe depressed the NA level. Transcutaneous stimulation of peripheral nerves had the following effects: 1) High intensity stimulation of afferent A-delta or C fibers increased spinal NA release, which was decreased by thoracic spinal cord transection. 2) Stimulation of afferent A-beta or A-delta fibers at low intensity did not affect the NA level. 3) High intensity stimulation of afferent A-beta fibers depressed NA release in half of the trials. Results indicate that many NA-containing nerve terminals that innervate the lumbar spinal cord originate from supraspinal structures. Somatic neural inputs from afferent C fibers and high-threshold A-delta, but not A-beta nor low-threshold A-delta fibers, activate the descending NA system and release the NA in the spinal cord. The descending NA system may participate in antinociception.

Peripheral nerve stimulation increases serotonin and dopamine metabolites in rat spinal cord.

Extracellular serotonin (5-HT), dopamine (DA), and their metabolites, 5-hydroxyindoleacetic acid (5-HIAA), 3,4-dihydroxyphenylacetic acid (DOPAC), and homovanillic acid (HVA), were assessed in the rat lumbar spinal cord (L3-4) by in vivo microdialysis with high performance liquid chromatography and electrochemical detection (HPLC-ECD). Under urethane-chloralose anesthesia, basal levels of 5-HT and DA in the dialysates were approximately 1.0-1.2 pg/22 microliters sample, 5-HIAA, DOPAC, and HVA were constant at 322.6 +/- 14.9, 8.6 +/- 0.7, and 10.4 +/- 0.4 pg/22 microliters sample (mean +/- SE), respectively. Local application of 100 mM KCl via the dialysis probe increased the 5-HT and DA. Peripheral nerve stimulation that selectively excited the large (A-beta) or small (A-delta) myelinated fibres increased the metabolites. Excitation of the A-beta fibers increased the levels of 5-HIAA to 138%, DOPAC to 155%, and HVA to 143% of the controls. Stimulation of the A-delta fibers increased 5-HIAA to 121%, DOPAC to 120%, and HVA to 124% of the controls. The results suggest that non-nociceptive peripheral nerve stimulation may activate the descending 5-HT and DA systems in the spinal cord.

Determination of nucleotide sequence of Corynebacterium plasmid pXZ10145.

With ABI370A Autosequencer, the total nucleotide sequence of plasmid pXZ10145 from Corynebacterium glutamicum 1014-6T has been determined using the dideoxy chain termination method. The plasmid contain 4887 base pairs (bp). Computer-aided-analysis of the sequence showed the location and number of restriction enzyme cutting sites and revealed eight open reading frames (ORF) on the plasmid. The two sites on the plasmid pXZ10145, where deletion occurred to result in plasmid pNAT65 were confirmed. At these two sites a seven-base pairs sequence "ATCTAGC" was found.

[Screening of strain producing extracellular penicillin acylase].

Ninety-eight strains having extracellular penicillin acylase activity were derived from soil samples by colour-developing method. 10 strains of them possess higher activity of penicillin acylase. All of those are found to be Bacillus megaterium. The optimum condition of enzyme production was investigated with the strain No. 46 which is from No. 247 by single colony isolation. The productivity of penicillin acylase in the optimum condition have been enhanced 2.5 times more than that in the screening condition. The mutant strain, Bacillus megaterium UL-81, which penicillin acylase activity reached the level of 723u/100ml of broth was obtained from No. 46 by treatment with physical and chemical factors. The penicillin acylase activity of UL-81 can reach 820u/100 ml in 500L fermentor. The mutant strain differed from parent strain in the morphology of colony, the size of cells, the effect of concentration and the addition time of phenylacetic acid on the production of penicillin acylase.

Characterization of the natural deletion mutant of plasmid pXZ10145 in Corynebacterium glutamicum and construction of a recombinant plasmid.

Plasmid pNAT65, carrying the chloramphenicol resistance marker, was chosen from a number of natural deletion mutants of pXZ10145 when pXZ10145 DNA, originally isolated from Corynebacterium glutamicum 1014-6T, was used to transform the protoplast of Corynebacterium crenatum T6-13. The size of pNAT65 was 2.4 kb, determined by electrophoresis on 0.7% agarose gel. The physical map of plasmid pNAT65 was determined. One recombinant plasmid, pNAR67, was constructed with the DNA fragments of pNAT65 and pBR322 digested respectively with EcoRI. This plasmid was capable of replication in E. coli, expressing ampicillin and tetracycline resistance; but with lower chloramphenicol, the resistance was only about 2 micrograms/ml.