Neurological effects of acute uranium exposure with and without stress

Circulating uranium rapidly enters the brain and may cause adverse effects on the nervous system that are potentially modulated by stress. In this study, the neurological effects of a single intramuscular injection of 0, 0.1, 0.3, or 1 mg uranium/kg (as uranyl acetate, UA) in rats were examined in the presence and absence of stress. Treatment with UA produced time and dose-dependent increases in serum and regional brain uranium levels. While serum levels returned to control levels by day 30, brain levels remained elevated. Application of stress did not affect the distribution or retention of uranium. Exposure to 1 mg U/kg significantly decreased ambulatory activity, weight gain, forelimb grip strength and transiently impaired working memory. Effects on grip strength and memory were prevented by application of stress prior to uranium exposure. Striatal dopamine content was reduced by 30% 3 days after treatment with 1mg/kg (59+/-6 nmol/mg tissue versus 41+/-5 nmol/mg tissue), but levels returned to control 7 days after uranium exposure. The effect on dopamine was ameliorated by prior application of stress. Exposure to UA did not alter 3,4 dihydroxyphenylacetic acid (DOPAC) levels or numbers of D2 receptors in the striatum. No effect of uranium or stress was observed on levels of GABA, serotonin, norepinephrine, or glutathione (GSH) in the striatum, hippocampus, cerebellum, or cortex. These results indicate that single intramuscular exposures to uranium produce sustained elevation of brain uranium levels and at doses above 0.3 mg/kg can have adverse neurological effects. Application of stress prior to uranium administration modulates neurological effects, but the mechanism is not due to effects on uranium distribution. Uranium exposure also produced renal toxicity which must be considered to accurately assess the effects of uranium on neurological function.

Intestinal carriage of Campylobacter jejuni and Campylobacter coli among cattle from south-western Norway and comparative genotyping of bovine and human isolates by amplified-fragment length polymorphism

In a survey conducted in 1999-2001, the carriage of thermotolerant Campylobacters in cattle was investigated, and the genetic diversity of C. jejuni within one herd was examined and compared with human isolates. C. jejuni, C. coli and other thermotolerant Campylobacter spp. were isolated from intestinal contents from 26%, 3% and 2% of 804 cattle, respectively. The carriage rate was higher in calves (46%) than in adults (29%). Twenty-nine C. jejuni isolates from one herd and 31 human isolates from the study area were genotyped with amplified-fragment length polymorphism (AFLP). Eighty-three % of the bovine isolates fell into three distinct clusters with 95-100% similarity, persistent in the herd for 5-10 months. Among human isolates, 58% showed >90% similarity with bovine isolates. The results show that cattle are a significant and stable reservoir for C. jejuni in the study area. Transmission between individuals within the herd may be sufficient to maintain a steady C. jejuni population independent of environmental influx. The results of this study have provided new information on C. jejuni and C. coli transmission, and also on the carriage in cattle, genotypes stability and similarity between bovine and human isolates.

Molecular and clinical characteristics of respiratory syncytial virus infections in hospitalized children

The objective of this study was to determine the importance of respiratory syncytial virus (RSV) for hospitalization in the north east of Germany and to obtain molecular epidemiological data of the circulating strains. Using a rapid and sensitive reverse transcriptase-PCR, it was found that a quarter of pediatric respiratory disease admissions were due to RSV. Infections caused by RSV in hospitalized patients were determined over the whole year. Both RSV groups A and B were identified with a predominance of RSV A (86%) over the entire period. The analysis of the deduced amino acid sequences by direct sequencing showed that very similar RSV strains are circulating in the community.

Central mineralocorticoid receptor blockade improves volume regulation and reduces sympathetic drive in heart failure

The mineralocorticoid (MC) receptor antagonist spironolactone (SL) improves morbidity and mortality in patients with congestive heart failure (CHF). We tested the hypothesis that the central nervous system actions of SL contribute to its beneficial effects. SL (100 ng/h for 28 days) or ethanol vehicle (VEH) was administered intracerebroventricularly or intraperitoneally to rats with CHF induced by coronary artery ligation (CL) and to SHAM-operated controls. The intracerebroventricular SL treatment prevented the increase in sodium appetite and the decreases in sodium and water excretion observed within a week of CL in VEH-treated CHF rats. Intraperitoneal SL also improved volume regulation in the CHF rats, but only after 3 wk of treatment. Four weeks of SL treatment, either intracerebroventricularly or intraperitoneally, ameliorated both the increase in sympathetic drive and the impaired baroreflex function observed in VEH-treated CHF rats. These findings suggest that activation of MC receptors in the central nervous system plays a critical role in the altered volume regulation and augmented sympathetic drive that characterize clinical heart failure.

Clinical significance of the preoperative plasma carcinoembryonic antigen (CEA) level in patients with carcinoma of the large bowel

Preoperative levels of perchloric acid extractable plasma CEA were measured in 911 patients with complaints of the digestive system. A final diagnosis of benign disease was made for 579 patients; 332 patients were found to have cancer. Data for the preoperative CEA values were examined for clinical significance as an aide to diagnosis, preoperative disease staging, and prognosis. The results of our analysis support the conclusions of many investigators that the CEA assay is not a clinically useful diagnostic test, but it shows limited value in preoperative staging and a somewhat stronger correlation with prognosis.

The homeodomain-containing gene Xdbx inhibits neuronal differentiation in the developing embryo

The development of the vertebrate nervous system depends upon striking a balance between differentiating neurons and neural progenitors in the early embryo. Our findings suggest that the homeodomain-containing gene Xdbx regulates this balance by maintaining neural progenitor populations within specific regions of the neuroectoderm. In posterior regions of the Xenopus embryo, Xdbx is expressed in a bilaterally symmetric stripe that lies at the middle of the mediolateral axis of the neural plate. This stripe of Xdbx expression overlaps the expression domain of the proneural basic/helix-loop-helix-containing gene, Xash3, and is juxtaposed to the expression domains of Xenopus Neurogenin related 1 and N-tubulin, markers of early neurogenesis in the embryo. Xdbx overexpression inhibits neuronal differentiation in the embryo and when co-injected with Xash3, Xdbx inhibits the ability of Xash3 to induce ectopic neurogenesis. One role of Xdbx during normal development may therefore be to restrict spatially neuronal differentiation within the neural plate, possibly by altering the neuronal differentiation function of Xash3.

Cardiac hypertrophy is not a required compensatory response to short-term pressure overload

BACKGROUND

Cardiac hypertrophy is considered a necessary compensatory response to sustained elevations of left ventricular (LV) wall stress.

METHODS AND RESULTS

To test this, we inhibited calcineurin with cyclosporine (CsA) in the setting of surgically induced pressure overload in mice and examined in vivo parameters of ventricular volume and function using echocardiography. Normalized heart mass increased 45% by 5 weeks after thoracic aortic banding (TAB; heart weight/body weight, 8.3+/-0.9 mg/g [mean+/-SEM] versus 5. 7+/-0.1 mg/g unbanded, P<0.05). Similar increases were documented in the cell-surface area of isolated LV myocytes. In mice subjected to TAB+CsA treatment, we observed complete inhibition of hypertrophy (heart weight/body weight, 5.2+/-0.3 mg/g at 5 weeks) and myocyte surface area (endocardial and epicardial fractions). The mice tolerated abolition of hypertrophy with no signs of cardiovascular compromise, and 5-week mortality was not different from that of banded mice injected with vehicle (TAB+Veh). Despite abolition of hypertrophy by CsA (LV mass by echo, 83+/-5 mg versus 83+/-2 mg unbanded), chamber size (end-diastolic volume, 33+/-6 microL versus 37+/-1 microL unbanded), and systolic ejection performance (ejection fraction, 97+/-2% versus 97+/-1% unbanded) were normal. LV mass differed significantly in TAB+Veh animals (103+/-5 mg, P<0.05), but chamber volume (end-diastolic volume, 44+/-6 microL), ejection fraction (92+/-2%), and transstenotic pressure gradients (70+/-14 mm Hg in TAB+Veh versus 77+/-11 mm Hg in TAB+CsA) were not different.

CONCLUSIONS

In this experimental setting, calcineurin blockade with CsA prevented LV hypertrophy due to pressure overload. TAB mice treated with CsA maintain normal LV size and systolic function.

Electrophysiological characterization of CGP68730A a N-methyl-D-aspartate antagonist acting at the strychnine-insensitive glycine site

1. Electrophysiological experiments were performed in vitro and in vivo. Voltage clamp recordings were done in Xenopus oocytes. Extracellular recordings were done in vitro in the neocortical slice and in the CA1 region of the hippocampal slice and in vivo in the CA1 region of the hippocampus of the anaesthetized rat. 2. In oocytes expressing either the human NMDAR1A/2A or 1A/2B subunit combinations, CGP68730A [sodium (-)-9-bromo-2,3,6,7-tetrahydro-5,6-dioxo-5H-pyrazino[1,2,3-de]-1,4-benzo thiazine-3-acetic acid] antagonized L-glutamate / glycine induced currents with calculated IC50s of 20.5 and 81.6 nM, respectively. 3. In vitro, CGP68730A was tested on NMDA induced depolarizations in the neocortical slice preparation and on epileptiform activity in hippocampal slices bathed in Mg2+-free-medium, which is known to be NMDA mediated. In both in vitro models CGP68730A exhibited antagonistic effects on the NMDA receptor mediated responses. 4. In vivo CGP68730A was tested on NMDA induced excitations in the CA1 region. CGP68730A abolished NMDA induced excitations when applied microiontophoretically. However, only weak effects on NMDA induced excitation were observed after systemic administration at 100 mg/kg i.v.. These results indicate that CGP68730A has poor central nervous system bioavailability. 5. In oocytes, an increase in the glycine concentration from the EC80 to the EC95.99 shifted the inhibition curves for CGP68730A to the right. Furthermore, in neocortical slices and in anaesthetized rats CGP68730A inhibited NMDA mediated depolarizations, and this effect could be reversed by the addition of the glycine mimetic D-serine. This indicates that these effects of CGP68730A are mediated by an action on the strychnine-insensitive glycine site. 6. Selectivity tests in oocytes and in the neocortical slice preparation, using NMDA, kainate and AMPA showed that CGP68730A was selective in antagonizing NMDA receptor mediated responses. In oocytes, the compound was about 1000 times less potent on the rat GluR3 and the human GluR6 receptors than on the human NMDAR1A/2A subunit combination. In the neocortical slice preparationCGP68730A had no effects on AMPA or kainate induced depolarizations at concentrations of 3 and 10 microM. At 30 microM CGP68730A reduced the effects of each of the three agonists tested. 7. Thus, CGP68730A seems to be a selective antagonist at the strychnine-insensitive glycine coagonist site of the NMDA receptor. However, the compound showed no obvious central NMDA antagonistic effects following intravenous application.

Age-related deterioration of motion perception and detection

PURPOSE

The purpose of this study was to evaluate the effect of aging on motion detection and perception.

METHODS

Forty-six subjects, ages 19-92 years, were asked to view a motion stimulus. Infrared oculography was used to objectively evaluate motion detection by documenting the presence of optokinetic nystagmus as the subjects viewed the stimulus. Subjective responses to motion perception were recorded using a computer joystick.

RESULTS

Optokinetic nystagmus was clearly detectable in all 46 subjects. Motion detection and perception thresholds showed age-related deterioration. No relationship was found to gender or age-gender interaction.

CONCLUSION

The results indicate motion detection and perception thresholds deteriorate with age. This may reflect a susceptibility to age-related degeneration in specific cortical areas responsible for motion perception as well as neurodegeneration in the retinogeniculate pathway.

XATH-1, a vertebrate homolog of Drosophila atonal, induces a neuronal differentiation within ectodermal progenitors

XATH-1, a basic/helix-loop-helix transcription factor and a homolog of Drosophila atonal and mammalian MATH-1, is expressed specifically in the dorsal hindbrain during Xenopus neural development. In order to investigate the role of XATH-1 in the neuronal differentiation process, we have examined the effects of XATH-1 overexpression during Xenopus development. XATH-1 induces the expression of neuronal differentiation markers, such as N-tubulin, within the neural plate as well as within nonneural ectodermal progenitor populations, resulting in the appearance of process-bearing neurons within the epidermis. The related basic/helix-loop-helix genes neurogenin-related-1 and neuroD are not induced in response to XATH-1 overexpression within the embryo, suggesting that XATH-1 may activate an alternate pathway of neuronal differentiation. In further contrast to neurogenin-related-1 and neuroD, high-level expression of general neural markers expressed earlier in development, such as N-CAM, is not induced by XATH-1 overexpression. Competent ectodermal progenitors therefore respond to ectopic XATH-1 expression by initiating a distinct program of neuronal differentiation.

Differential prenyl pyrophosphate binding to mammalian protein geranylgeranyltransferase-I and protein farnesyltransferase and its consequence on the specificity of protein prenylation

Protein geranylgeranyltransferase-I (PGGT-I) and protein farnesyltransferase (PFT) attach geranylgeranyl and farnesyl groups, respectively, to the C termini of eukaryotic cell proteins. In vitro, PGGT-I and PFT can transfer both geranylgeranyl and farnesyl groups from geranylgeranyl pyrophosphate (GGPP) and farnesyl pyrophosphate (FPP) to their protein or peptide prenyl acceptor substrates. In the present study it is shown that PGGT-I binds GGPP 330-fold tighter than FPP and that PFT binds FPP 15-fold tighter than GGPP. Therefore, in vivo, where both GGPP and FPP compete for the binding to prenyltransferases, PGGT-I and PFT will likely be bound predominantly to GGPP and FPP, respectively. Previous studies have shown that K-Ras4B and the Ras-related GTPase TC21 are substrates for both PGGT-I and PFT in vitro. It is shown that TC21 can compete with the C-terminal peptide of the gamma subunit of heterotrimeric G proteins and with the C-terminal peptide of lamin B for geranylgeranylation by PGGT-I and for farnesylation by PFT, respectively. K-Ras4B competes in both cases but is almost exclusively farnesylated by PFT in the presence of the lamin B peptide competitor. Rapid and single turnover kinetic studies indicate that the rate constant for the PGGT-I-catalyzed geranylgeranyl transfer step of the reaction cycle is 14-fold larger than the steady-state turnover number, which indicates that the rate of the overall reaction is limited by a step subsequent to prenyl transfer such as release of products from the enzyme. PGGT-I-catalyzed farnesylation is 37-fold slower than geranylgeranylation and is limited by the farnesyl transfer step. These results together with earlier studies provide a paradigm for the substrate specificity of PGGT-I and PFT and provide information that is critical for the design of prenyltransferase inhibitors as anti-cancer agents.

Genes involved in cerebellar cell specification and differentiation

The conservation of transcriptional regulatory mechanisms across species, combined with the restricted expression of these molecules in time and space within the embryo, has offered new insights into CNS cell specification. Studies examining transcriptional control in the generation of specific cell classes within the cerebellar cortex have been particularly elucidative.

Comparison of visual function in fellow eyes after bilateral nonarteritic anterior ischemic optic neuropathy

PURPOSE

Although previous studies have examined the risk of bilaterality of nonarteritic ischemic optic neuropathy (NAION), none have compared extensively the extent of visual loss between fellow eyes. The authors examined cases of bilateral NAION to determine the extent of vision loss in the second eye compared with that in the first eye.

METHODS

Thirty-one cases of bilateral NAION were reviewed. Variables included age, gender, and the presence of comorbid disease. Visual function was assessed by Snellen visual acuity, color vision, and pattern and mean deviation of the visual fields.

RESULTS

No correlation was detected between the extent or pattern of visual loss in fellow eyes. No significant difference in visual function existed between first and second eyes for the patients overall. Patients who retained better visual function in the second eye were significantly older than those who retained better visual function in the first eye (visual acuity, P = 0.0005; color vision, P = 0.07; mean deviation, P = 0.02). In patients older than 50 years of age (25 of 31 cases), the second eye had significantly better visual acuity (P = 0.04) and less Humphrey visual field mean deviation (P = 0.04) than the first eye.

CONCLUSION

Visual function in the second eye correlated poorly with that of the first eye. Older patients with bilateral NAION retained better visual function in the second eye than in the first eye. For younger patients, the extent of visual loss in the second eye could not be predicted based on the visual loss in the first eye.

Effect of celiac ganglionectomy on tachykinin innervation, receptor distribution and intestinal responses in the rat

Substance P (SP) is an important neurotransmitter in the control of intestinal motility and is found in both the enteric and sympathetic nervous systems. This study examined the effect of celiac ganglionectomy on (1) mechanical properties of the circular muscles of the duodenum, ileum and proximal colon, (2) circular muscle responses to SP and neurokinin A. (3) distribution of substance P-like immunoreactive nerves, and (4) the distribution of neurokinin 1 and neurokinin 2 receptors. Celiac ganglionectomy resulted in an effective sympathectomy as evidenced by a marked decrease in norepinephrine content and tyrosine hydroxylase staining in the duodenum, ileum and proximal colon. The in vitro length/tension characteristics of the circular muscle of the duodenum, ileum and colon were unchanged after ganglionectomy. In all regions of the gut studied, substance P and neurokinin A caused dose-dependent contractions that were unaltered by celiac ganglionectomy. Immunohistochemistry revealed moderate substance P-like immunoreactive fibers in the myenteric plexus, submucosal plexus and circular muscle of the ileum, while in the colon, substance P-like immunoreactivity was intense in the myenteric plexus, and moderate in the circular muscle. In vitro autoradiography showed minimal binding of SP (NK1 receptor) or neurokinin A (NK2 receptor) in the ileum and significantly greater binding in the circular muscle layer of the colon. Celiac ganglionectomy did not affect substance P-like immunoreactivity, or NK1 or NK2 receptor binding. A greater contractile response to neurokinins was seen in the colon than in the duodenum or ileum, which paralleled the receptor density. The studies demonstrate that surgical celiac ganglionectomy, unlike chemical sympathectomy, does not affect the substance P innervation, receptor density or physiological responses of the intestine. The greater contractile response of the colon than the ileum parallels the greater receptor density rather than the peptide content as determined by immunhistochemistry.

Diverticular bleeding and the pigmented protuberance (sentinel clot): clinical implications, histopathological correlation, and results of endoscopic intervention

Over a 3-yr period, we performed colonoscopy on five patients (mean age 71 yr) in whom a specific diverticulum that contained a pigmented protuberance (PiP) was unequivocally identified as the cause for hemorrhage. Four of these individuals had endoscopic bipolar cauterization of the PiP, and two patients had surgery.

AIM

To (1) determine the clinical significance of an intradiverticular PiP, (2) correlate endoscopic features of a PiP with histopathological findings and, (3) assess results of endoscopic treatment for affected patients with lower GI bleeding.

METHODS

Medical charts were reviewed to garner data and assess outcome for patients. The bleeding diverticulum in one surgical case was detected in the resected specimen, and histological examination was performed.

RESULTS

The mean number of transfusions, bleeding days, and lowest hemoglobin concentration before definitive treatment was 4.8, 3.4, and 8.4 gm%, respectively. All patients rebled before treatment. In all instances, the PiP projected through the neck of the diverticulum, which was actively bleeding in two patients. Endoscopic bipolar cautery directed at the PiP achieved permanent hemostasis in three of four subjects (75%) (morbidity 0%). Endoscopic therapy failed in one subject, and a hemicolectomy was performed. Histological evaluation of the resected specimen showed erosion of a medium sized artery into the diverticulum. The PiP represented a sentinel clot (not a visible vessel) adherent to a breach in the vessel wall. A patient who had surgery instead of endoscopic therapy had a prolonged, complicated postoperative course.

CONCLUSIONS

(1) The presence of an intradiverticular PiP may identify a subset of patients at risk for severe recurrent diverticular bleeding. (2) Histopathological analysis showed the PiP to be a sentinel clot rather than a visible vessel. (3) In patients with severe recurrent diverticular bleeding, endoscopic treatment of the vessel beneath this lesion may be a viable alternative to surgery.

Two-year outcome of social skills training and group psychotherapy for outpatients with schizophrenia

OBJECTIVE

The authors evaluated the effectiveness of behaviorally oriented social skills training and supportive group therapy for improving the social adjustment of schizophrenic patients living in the community and for protecting them against psychotic relapse.

METHOD

Eighty male outpatients with schizophrenia were stabilized with a low dose of fluphenazine decanoate (5 to 10 mg every 14 days), which was supplemented with oral fluphenazine (5 mg twice daily) or a placebo when they first met criteria for a prodromal period. (Half of the patients did so at some time during the study.) Patients were randomly assigned to receive either social skills training or supportive group therapy twice weekly for 6 months and then weekly for the next 18 months. Rates of psychotic exacerbation were monitored, as were scores on the Social Adjustment Scale II.

RESULTS

There were significant main effects favoring social skills training over supportive group therapy on two of the six Social Adjustment Scale II cluster totals examined (personal well-being and total) and significant interactions between psychosocial treatment and drug treatment for three items (external family, social and leisure activities, and total). In each case, these interactions indicated that the advantage of social skills training over supportive group therapy was greatest when it was combined with active drug supplementation. Social skills training did not significantly decrease the risk of psychotic exacerbation in the full group, but an advantage was observed (post hoc) among patients who received placebo supplementation.

CONCLUSIONS

These findings suggest that social skills training resulted in greater improvement in certain measures of social adjustment than supportive group therapy. The greatest improvement in social outcomes occurred when social skills training was combined with a pharmacological strategy of active drug supplementation at the time prodromal worsening of psychotic symptoms was first observed. However, these improvements were modest in absolute terms and confined to certain subgroups of patients.

Involvement of the alpha subunit of farnesyl-protein transferase in substrate recognition

Using photoaffinity labeling, we have identified a region in mammalian farnesyl-protein transferase (FPTase) involved in substrate recognition. The photolabel used (Compound 1) is a peptide containing the photoactive amino acid p-benzoylphenylalanine (Bpa). Upon exposure to UV light. Compound 1 inhibits FPTase activity in a time- and concentration-dependent manner. Photoinhibition of FPTase activity by Compound 1 is prevented by adding H-Ras to the reaction mixture, indicating that labeling is targeted to the enzyme active site. We used peptide mapping by HPLC, Edman sequencing, and matrix-assisted time-of-flight (MALDI-TOF) mass spectrometry to identify the site of interaction with radiolabeled Compound 1. These experiments indicate that a specific region of the alpha subunit of the enzyme, Asp110-Arg112, is involved in substrate binding and suggest that Glu111 is likely to be the residue covalently modified by the photoaffinity label. Sequence alignments between yeast and mammalian FPTases reveal that Glu111 is conserved. The implications of this finding are discussed in light of previous mutagenesis studies on FPTase.