Effects of repeated administration of baclofen on transient lower esophageal sphincter relaxation in the dog

The metabotropic gamma-aminobutyric acid (GABA) receptor (GABA(B) receptor) agonist baclofen inhibits transient lower esophageal sphincter relaxation in dogs, ferrets, and humans. Since transient lower esophageal sphincter relaxations are the major cause of gastroesophageal reflux, GABA(B) receptor agonists may have a therapeutic value in the treatment of gastroesophageal reflux disease. However, repeated stimulation of the GABA(B) receptor may induce receptor desensitization which, depending on the magnitude, would limit the therapeutic effect. The aim of the present study was to follow the effects of baclofen on transient lower esophageal sphincter relaxation in the dog after repeated administration. The effect of 7 micromol/kg baclofen b.i.d. (given intragastrically) on transient lower esophageal sphincter relaxation and related parameters was determined in four dogs. Transient lower esophageal sphincter relaxations stimulated by infusion of liquid nutrient and insufflation of air were quantified after placebo and then after the 1st, 13th, and 27th dose. Baclofen reduced the number of transient lower esophageal sphincter relaxations without affecting their duration, and the latency to the first transient lower esophageal sphincter relaxation was prolonged. Basal sphincter pressure was unaffected by baclofen, and the number of reflux episodes and esophageal acid exposure decreased. There was a statistically insignificant numerical decrease (approximately 30%) in the effect of baclofen on transient lower esophageal sphincter relaxation after the seventh dose but this was not further accentuated after the 27th dose. The effect on latency was also reduced with repeated dosing, but again, the effects after the 1st, 13th, and 27th doses were not statistically significant. The attenuation of acid exposure and reflux episodes was unaltered after repeated dosing. Three of the dogs greatly reduced their food intake within the first 2-3 days but this side effect was resolved subsequently. It is concluded that repeated dosing of baclofen leads to mild tolerance development in terms of the effects on transient lower esophageal sphincter relaxation, but that the tolerance is much less pronounced than that previously reported in other animal models.

Comparison of two different anesthesia regimens in patients undergoing aortocoronary bypass grafting surgery: sufentanil-midazolam versus remifentanil-propofol

OBJECTIVE

To compare intraoperative hemodynamics and depth of anesthesia using sufentanil-midazolam (SM) versus remifentanil-propofol (RP) anesthesia.

DESIGN

Prospective, randomized study.

SETTING

Clinical investigation in an urban, university-affiliated hospital.

PARTICIPANTS

Forty patients undergoing elective first-time coronary artery bypass graft surgery.

INTERVENTIONS

Twenty patients were anesthetized using SM and 20 patients using RP.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic monitoring included a 5-lead electrocardiogram, a radial artery catheter, and a pulmonary artery catheter. Depth of anesthesia was assessed using bispectral index (BIS). Data were obtained after induction of anesthesia (T1), after sternotomy (T2), after pericardiotomy (T3), 5 minutes after cardiopulmonary bypass (CPB) (T4), after closure of thorax (T5), and at the end of surgery (T6). The 2 groups were comparable with regard to demographic and perioperative data. There were no significant differences of any hemodynamic parameter at any time between the 2 groups. In both groups, systemic vascular resistance increased at T2 and decreased at T4 from baseline value (p < 0.05). Cardiac index increased at T4 in both groups from baseline value (p < 0.05); 55% of the patients of both groups needed low-dose dobutamine after CPB. During CPB, 40% of the RP patients needed norepinephrine versus 35% of the SM patients. BIS was lower in the RP than in the SM group at T2 and T3 (p < 0.05). BIS values indicating intraoperative awareness were not noted.

CONCLUSION

Both anesthesia regimens provided stable hemodynamics and adequate anesthesia in patients undergoing coronary artery bypass graft surgery.

Expression of CD44 during early development of the chick embryo

CD44, the major cell-surface receptor for hyaluronate, is expressed on many cell types to mediate different functions including cell activation, homing and adhesion. The early pattern of CD44 expression was determined in the avian embryo by using a specific monoclonal antibody in whole-mount and tissue sections. CD44 was first expressed on cephalic neural fold cells and later on by subpopulations of pre-and migratory cranial neural crest cells. Trunk neural crest cells did not express CD44. At the 18-20 somite stage, CD44 expressing cells were also localized in the caudal region of the embryo, in the mesoderm of the remaining primitive streak and in the caudal ectoderm and above the secondary neural tube during the process of cavitation. In addition, some hemopoietic cells present in the blood stream were also CD44 positive.

Diagnostic value of urinary alanine aminopeptidase and N-acetyl-beta-D-glucosaminidase in comparison to alpha 1-microglobulin as a marker in evaluating tubular dysfunction in glomerulonephritis patients

To estimate the diagnostic value of tubular parameters, the urinary alanine aminopeptidase (AAP), N-acetyl-beta-D-glucosaminidase (NAG) and the alpha(1)-microglobulin (a1M) of 150 patients with histologically proven glomerulonephritis (GN) were determined. In addition, the reabsorption rate of the proximal tubule and the fractional excretion of sodium, the free water clearance and the renal function were assessed by inulin and p-aminohippurate (PAH) clearance. Compared to healthy controls, urinary AAP, NAG and a1M were found significantly elevated in GN patients. Morphological tubular changes were confirmed by significant differences in urinary laboratory parameters. In patients with tubular atrophy, the diagnostic sensitivity and specificity were calculated as follows: AAP (0.94/0.35), NAG (0.75/0.59) and a1M (0.73/0.52). In patients showing tubular protein droplets, the values were 0.90/0.17 for AAP, 0.78/0.76 for NAG and 0.84/0.74 for a1M and in patients with interstitial fibrosis, the values were AAP (0.95/0.35), NAG (0.75/0. 46) and a1M (68/0.38). Urinary AAP, NAG and a1M reflect histologically proven tubulus alteration in GN, although in most cases, the renal function is still intact. AAP indicates very early tubular impairment and, in some cases, AAP is elevated although NAG and a1M are still within normal ranges. We suggest that the enzyme activities are useful in the diagnostics of early stages of the disease.

Volume therapy with a new hydroxyethyl starch solution in cardiac surgical patients before cardiopulmonary bypass

OBJECTIVE

To compare the hemodynamic efficacy of a new hydroxyethyl starch (HES) preparation (130/0.4) with an HES 200/0.5 solution.

DESIGN

Prospective, randomized, double-blind, phase II study.

SETTING

An urban, university-affiliated hospital.

PARTICIPANTS

Twenty patients undergoing elective first-time cardiac surgery.

INTERVENTIONS

After induction of anesthesia and before the start of surgery, a new HES 130/0.4 (molecular weight, 130,000 d; degree of substitution, 0.4) (n = 10) or HES 200/0.5 (molecular weight, 200,000 d; degree of substitution, 0.5) (n = 10) was infused (10 mL/kg) within 30 minutes when pulmonary capillary wedge pressure was less than 10 mmHg.

MEASUREMENTS AND MAIN RESULTS

Extensive hemodynamic monitoring was performed 30 and 60 minutes after the end of infusion. Then surgery was started. Standard laboratory parameters were measured before surgery and on the 1st postoperative day. A similar amount of HES was given in both groups (HES 130, 795+/-75 mL; HES 200, 820+/-90 mL). Filling pressures (central venous pressure, pulmonary capillary wedge pressure) and cardiac index increased similarly in both groups and remained significantly elevated 60 minutes after the end of infusion. All other hemodynamic parameters were similar between the two volume groups. Renal (creatinine) and hepatic function (aspartate aminotransferase, alanine aminotransferase) and hemostasis (platelet count, activated partial thromboplastin time, blood loss) were without group differences until the morning of the 1st postoperative day.

CONCLUSIONS

The new 6% HES 130/0.4 was as effective as a 6% HES 200/0.5 preparation in regard to hemodynamic efficacy. No negative side effects on organ function were seen. The 6% HES 130/0.4 solution may become an alternative strategy for volume therapy in cardiac surgery.

Pneumoperitoneum secondary to endoscopic harvest of saphenous vein graft

Endoscopic harvest of saphenous vein graft for coronary artery bypass grafting decreases leg wound complications compared with traditional longitudinal incision. A case of pneumoperitoneum secondary to endoscopic harvest of saphenous vein using insufflation of carbon dioxide is reported. Hypercarbia, increased peak airway pressure, but no significant changes of hemodynamics, or myocardial ischemia were noted. The management of this rare complication is described.

A method for the chemical generation of N-terminal peptide sequence tags for rapid protein identification

We describe a method for generating multiple small sequences from the N terminal of peptides in unseparated protein digests by stepwise thioacetylation and acid cleavage. The mass differences between a series of N-terminally degraded peptides give short sequences of defined length. Such short "sequence tags" together with the mass of the parent peptide can be used to identify the protein in a database. The sequence ladders are generated without the use of chain terminators or sample aliquoting and the degradation reagents are water soluble so that the chemistry can be carried out on peptides immobilized on C-18 reversed-phase supports without any peptide loss due to washing with organic solvents as occurs in Edman type sequencing. The entire procedure can be automated, and we describe a prototype device for the parallel analysis of multiple samples. We demonstrate the effectiveness of this chemical tagging method in a comparison with Edman sequencing, peptide mass fingerprinting, and MS/MS analysis of crude protein fractions obtained from an HPLC separation of the Escherichia coli ribosome complex which consists of 57 proteins. We show that chemical tagging is a viable first-pass high-throughput identification method to be used prior to an in depth MS/MS analysis.

Immunocytochemical distribution of the GABA(B) receptor splice variants GABA(B) R1a and R1b in the rat CNS and dorsal root ganglia

The anatomical distribution of the GABA(B) receptor (GBR) splice variants GBR1a and 1b in the CNS has not previously been studied. In the present study, distribution of the splice variants was mapped using immunohistochemistry. Polyclonal antibodies against splice variant unique epitopes were raised in rabbits. Affinity purified antibodies were used according to routine immunohistochemical procedures in sections from the rat CNS or dorsal root ganglia (DRG). The staining intensity was high in the cerebral cortex but lower in basal ganglia and the hippocampus. In the cerebellum, there was a marked difference in the distribution of GBR1a- and 1b-like immunoreactivity (LI). GBR1a-LI was preferentially localised in the granule cell layer whilst GBR1b-LI was mostly found in Purkinje cells and in the molecular layer. Cell bodies of the deep cerebellar nuclei stained for the GBR1a antibody while terminals surrounding the cell bodies were strongly labelled with the GBR1b antibody. A similar pre- vs postsynaptic pattern was seen in several nuclei ventral or caudal to the cerebellum (e.g. the cochlear nucleus, the facial nucleus, the spinal cord) but not in regions rostral to the cerebellum. In the spinal cord, strong labelling for both antibodies was seen in the dorsal horn. The GBR1b but not the GBR1a antibody stained tanycytes in the epithelium of the 3rd ventricle and in the central canal at the brain stem level. DRG neurons were positive for both the GBR1a and 1b antibody, but the former stained the cells much more intensely. Satellite cells were labelled with the GBR1b antibody. The most important aspect of these findings is that in some nuclei, GBR1b may mediate inhibition of transmitter release while in the same regions, GBR1a may mediate postsynaptic inhibition. Further, the observations support previous findings that GBR1b is the predominant splice variant in Purkinje cells.

Control of transient lower esophageal sphincter relaxations and reflux by the GABA(B) agonist baclofen in normal subjects

BACKGROUND & AIMS

Transient lower esophageal sphincter (LES) relaxations are the major mechanism of gastroesophageal reflux in normal subjects and in most patients with reflux disease. gamma-Aminobutyric acid (GABA) is an important inhibitory neurotransmitter within the central nervous system which is present in regions of the brainstem that are believed to mediate transient LES relaxations. The aim of this study was to investigate the effect of a GABA(B) agonist baclofen on postprandial gastroesophageal reflux and transient LES relaxations.

METHODS

In 20 healthy volunteers, esophageal motility and pH were measured, with the subjects in the sitting position, for 3 hours after a 3000-kJ mixed nutrient meal. On separate days at least 1 week apart, 40 mg oral baclofen or placebo was given 90 minutes before the meal.

RESULTS

Baclofen significantly reduced the rate of reflux episodes by more than 60% from 1.0 (0.3-2.7) to 0.3 (0-1.0) per hour (median [interquartile range]). Baclofen also reduced the rate of transient LES relaxations from 5.7 (4.9-7.8) to 2.2 (1.3-3.8) per hour and increased basal LES pressure from 8.7 +/- 1.4 to 10.8 +/- 0.8 mm Hg.

CONCLUSIONS

In normal human subjects, the GABA(B) agonist baclofen significantly inhibits gastroesophageal reflux by inhibition of transient LES relaxations. These findings suggest that GABA(B) agonists may be useful as therapeutic agents for the management of reflux in patients with gastroesophageal reflux disease.

Activation of the GABA(B) receptor inhibits transient lower esophageal sphincter relaxations in dogs

BACKGROUND & AIMS

Transient lower esophageal sphincter relaxation (TLESR) appears to be the most frequent motor event responsible for gastroesophageal reflux. Because TLESRs are considered to be triggered by activation of gastric mechanoreceptors, and because the gamma-aminobutyric acid type B (GABA(B))-receptor agonist baclofen is known to inhibit transmitter release from mechanosensitive afferents, the effects of baclofen on TLESRs in the dog were assessed.

METHODS

A total of 183 recordings of the pharyngeal, esophageal, lower esophageal sphincter, and gastric pressures as well as measurement of esophageal pH were performed in 15 awake dogs. Racemic baclofen, its enantiomers, and the GABA(B)-receptor antagonist CGP36742 were administered before stimulation of TLESRs by a liquid meal and air insufflation. The pharmacodynamics of baclofen were compared with its pharmacokinetics.

RESULTS

Baclofen dose-dependently inhibited TLESRs, with a 50% effective dose (ED(50)) of 1.0 micromol/kg after intravenous administration. The maximal inhibition amounted to approximately 80%. Intragastric baclofen was almost equally effective (ED(50), 1.8 micromol/kg), compatible with the complete oral availability of the drug (100%). The inhibitory effect of baclofen resided in the pharmacologically active R enantiomer, and CGP36742 reduced some of the effects of baclofen.

CONCLUSIONS

Baclofen is a potent and efficacious inhibitor of TLESRs and reflux in the dog. Activation of the GABA(B) receptor may be a new approach to the treatment of reflux disease.

Simultaneous myocardial revascularization and aortic valve replacement: stentless versus stented bioprostheses

Implantation of stentless aortic valve prostheses is more time-consuming than implantation of conventional stented bioprostheses. Simultaneous myocardial revascularization can result in a considerably prolonged operation time. We reviewed our patients with regard to surgical aspects in the specific patient cohorts. From April 1996 to April 1999, 303 patients were operated for aortic valve disease with or without concomitant coronary artery revascularization. Mean age was 75 years, ranging between 36 and 90 years. Using the Medtronic Freestyle valve, the following techniques of implantation were used: subcoronary technique, 163 patients, 61.5%; root inclusion technique, 7 patients, 3.5%; total root replacement, 30 patients, 15%. Total hospital mortality rate was 5.6%, reflecting age and concomitant disease of these patients. For isolated aortic valve replacement, the mortality rate was 4.7% and 6.7% for combined procedures. Coronary artery patients who are not suitable for stentless valve implantation owing to extensive aortic root calcification have a higher perioperative mortality rate. Compared with the isolated valve replacement and despite more extensive surgery and prolonged operative time, simultaneous myocardial revascularization in patients with stentless prostheses implantation can be performed without an increased risk.

Inhibition of transient LES relaxations and reflux in ferrets by GABA receptor agonists

Transient lower esophageal sphincter (LES) relaxation is the major mechanism of gastroesophageal reflux. This study uses an established ferret model to evaluate GABA(B) receptor agonists' ability to reduce triggering of transient LES relaxations. One hundred sixty manometric/pH studies were performed on 18 conscious ferrets. In untreated animals, intragastric infusion of 25 ml glucose (pH 3.5) led to 2.0 +/- 0.6 reflux episodes over the first 30 min. Twenty-nine of forty-seven reflux episodes occurred during transient LES relaxation, and 18 occurred after downward drifts (<1 mmHg/s) in basal LES pressure. The GABA(B) receptor agonists baclofen (7 micromol/kg ip), CGP-44532, and SKF-97541 (both ED(50) <0.3 micromol/kg) reduced reflux episodes and transient LES relaxations. The putative peripherally selective GABA(B) receptor agonist 3-aminopropylphosphinic acid (80-240 micromol/kg) was ineffective, as was the GABA(A) receptor agonist muscimol (5 micromol/kg). Baclofen's inhibition of transient LES relaxations and reflux was unaffected by low-affinity GABA(B) receptor antagonists CGP-35348 and CGP-36742 at 100 micromol/kg but was reversed by higher-affinity CGP-54626 and CGP-62349 (0.7 micromol/kg) or by CGP-36742 at 200 micromol/kg. Therefore, GABA(B) receptor inhibition of reflux shows complex pharmacology. Our and other data indicate the therapeutic potential for these drugs.

GFP-labelling of 26S proteasomes in living yeast: insight into proteasomal functions at the nuclear envelope/rough ER

26S proteasomes are multisubunit protease complexes that play the central role in the ubiquitin-dependent protein degradation pathway. The proteolytically active core is formed by the 20S proteasome. Regulatory subunits, principally the 19S cap complex, confer the specificity towards ubiquitinated substrates and an ATP-dependence on proteolysis. Green fluorescence protein (GFP)-tagged versions of either an alpha-subunit of the 20S core or an ATPase subunit of the 19S cap complex were functionally incorporated into the protease complex, thus allowing to monitor the subcellular distribution of 26S proteasomes in living yeast. Our localization studies suggest that proteasomal proteolysis mainly occurs at the nuclear envelope (NE)/rough ER. Implications of proteasomal functions at the NE/rough ER are discussed in the context of published work on ER degradation and with regard to possible targeting mechanisms.

Influence of different intragastric stimuli on triggering of transient lower oesophageal sphincter relaxation in the dog

Gastro-oesophageal reflux in the dog is mainly caused by transient lower oesophageal sphincter relaxation (TLOSR), the major stimulus for which is distension of the stomach. The possibility that liquid and/or acid sensors in the proximal stomach reduce the incidence and/or shorten the duration of TLOSR was addressed in the present study. Manometric recordings of the pharynx, oesophagus, lower oesophageal sphincter and stomach were made in awake dogs equipped with an oesophagostomy. TLOSRs were induced by insufflation of air or infusion of liquid nutrients with varying pH. Intragastric distension with air provoked TLOSRs with a significantly shorter duration than those seen after distension with liquid (4.3 +/- 0.5 vs 9.6 +/- 0.3 sec; P < 0.05). There were fewer TLOSRs at high intragastric pH (pH 5.0: 3.1 +/- 0.5/90 min) than at low pH (pH 1.5: 5.5 +/- 0.9/90 min, P < 0.05). Successfully propagated peristalsis following a TLOSR was more common after stimulation with liquid than with air. It can be concluded that there are H(+)-sensing mechanisms in the stomach which stimulate triggering of TLOSR. In addition, the reduced duration of TLOSR during air insufflation shows that the physical state of the distending stimulus can affect the patterning of TLOSR.

Total intravenous anesthesia with remifentanil and propofol for implantation of cardioverter-defibrillators in patients with severely reduced left ventricular function

OBJECTIVE

To determine the cardiocirculatory effects of total intravenous anesthesia (TIVA) using remifentanil and propofol in high-risk cardiac surgical patients.

DESIGN

Prospective study of 20 patients undergoing first-time implantation of a cardioverter-defibrillator (ICD).

SETTING

Major, community, university-affiliated hospital.

PARTICIPANTS AND INTERVENTIONS

In 20 patients with severely reduced left ventricular function (left ventricular ejection fraction <30%) undergoing first-time implantation of an ICD, TIVA using remifentanil and propofol was performed.

MEASUREMENTS AND MAIN RESULTS

Extensive hemodynamic monitoring using a pulmonary artery catheter was performed: (T1) before induction of anesthesia, (T2) after intubation, (T3) after skin incision, (T4) after first defibrillation, and (T5) 10 minutes after extubation. Propofol, 3.0 +/- 0.6 mg/kg/h (range, 1.9 to 4.4 mg/kg/h), and remifentanil, 0.30 +/- 0.05 microg/kg/min (range, 0.21 to 0.40 microg/kg/min), were used. Total costs added up to US $44.60 per patient. Patients could be extubated within 12.5 +/- 4.2 minutes after stopping anesthesia. There were significant decreases in heart rate (HR; from 77 +/- 12 to 57 +/- 10 beats/min [T3]), mean arterial blood pressure (MAP; from 98 +/- 14 to 70 +/- 12 mmHg [T2]), and systemic vascular resistance (from 1,551 +/- 309 to 1,233 +/- 274 dyne x s x cm(-5) [T2]). Cardiac index (CI) slightly decreased only at T3 (from 2.46 +/- 0.42 to 1.92 +/- 0.29 L/min/m2; p = 0.04). The decrease in MAP could easily be treated by volume infusion in most patients (17 patients). Sixty-five percent of the patients needed dobutamine to increase CI to greater than 2.0 L/min/m2 (mean dose, 2.2 +/- 1.8 microg/kg/min). Dobutamine could be stopped before extubation in all patients. No patient needed sustained inotropic or ventilatory support and intensive care therapy could be avoided.

CONCLUSION

TIVA using remifentanil and propofol in patients with severely reduced left ventricular function is safe, well-controllable, and allows early extubation after implantation of an ICD. Because patients without complications did not need a postoperative intensive care stay, costs may be considerably reduced.

Dynamic cardiomyoplasty in patients with end-stage heart failure: anaesthetic considerations

Dynamic cardiomyoplasty is used increasingly for patients with chronic heart failure, with approximately 500 cases having been performed. The latissimus dorsi muscle is prepared maintaining its vascular supply and the muscle flap is wrapped around the heart and connected to a cardiomyostimulator. The muscle is later stimulated synchronously with ventricular systole to augment the heart. Our experience of 22 patients with chronic heart failure (NYHA III-IV) undergoing dynamic cardiomyoplasty is described from the anaesthetist's point of view. Two patients are reported as case reports. The challenge is to manage patients with severely impaired left ventricular function, who do not obtain immediate benefit from the operation. Our experience supports the importance of early use of inotropic agents.

Pain management in cardiac surgery patients: comparison between standard therapy and patient-controlled analgesia regimen

OBJECTIVE

To compare standard nurse-based pain therapy with a patient-controlled analgesia (PCA) regimen.

DESIGN

Prospective, randomized study.

SETTING

Single-institutional, clinical investigation in an urban, university-affiliated hospital.

PARTICIPANTS

Sixty patients undergoing elective first-time cardiac surgery were included.

INTERVENTIONS

In 30 patients, a standard analgesic regimen was used, and in 30 patients, a PCA regimen was used. The perioperative and postoperative management was similar for all patients.

MEASUREMENTS AND MAIN RESULTS

Degree of sedation, satisfaction, and pain (by visual analog scale [VAS]) was assessed within the first 3 postoperative days. Vital capacity (VC) and forced expiratory volume in 1 second (FEV1) were measured using a portable spirometry system. Cortisol and troponin T (TnT) plasma levels were also measured. The expectation of pain was similar in both groups, and the postoperative pain score was significantly lower in the PCA than in the standard group throughout the study period. Significantly more piritramid was used in the PCA (total, 75.6 +/- 33.4 mg) than in the standard group (total, 20.1 +/- 31.9 mg). VC and FEV1 were significantly lower in the standard group compared with the PCA patients. Cortisol and TnT plasma levels were similar in both groups. Frequency of side effects were similar for both groups.

CONCLUSION

Because of the beneficial effects with regard to degree of pain and satisfaction, pain management using PCA systems can be recommended for cardiac surgery patients. It appears to be superior to standard nurse-based pain therapy.

Subcellular distribution of proteasomes implicates a major location of protein degradation in the nuclear envelope-ER network in yeast

26S proteasomes are the key enzyme complexes responsible for selective turnover of short-lived and misfolded proteins. Based on the assumption that they are dispersed over the nucleoplasm and cytoplasm in all eukaryotic cells, we wanted to determine the subcellular distribution of 26S proteasomes in living yeast cells. For this purpose, we generated yeast strains that express functional green fluorescent protein (GFP) fusions of proteasomal subunits. An alpha subunit of the proteolytically active 20S core complex of the 26S proteasome, Pre6/YOL038w, as well as an ATPase-type subunit of the regulatory 19S cap complex, Cim5/YOL145w, were tagged with GFP. Both chimeras were shown to be incorporated completely into active 26S proteasomes. Microscopic analysis revealed that GFP-labelled 20S as well as 19S subunits are accumulated mainly in the nuclear envelope (NE)-endoplasmic reticulum (ER) network in yeast. These findings were supported by the co-localization and co-enrichment of 26S proteasomes with NE-ER marker proteins. A major location of proteasomal peptide cleavage activity was visualized in the NE-ER network, indicating that proteasomal degradation takes place mainly in this subcellular compartment in yeast.

Enhancement of XPG mRNA expression by human interferon-beta in Cockayne syndrome cells

Using PCR-differential display, we have searched for genes expressed specially in human interferon (HuIFn)-beta-treated Cockayne syndrome (CS) fibroblast cells. Eighteen expressed genes induced by HuIFN-beta were identified, the sequences of seven of which were highly homologous to previously cloned sequences. The cDNAs of six of these seven clones were similar to expression tagged sequences from unknown genes in databases and the remaining one was identical to the cDNA of the xeroderma pigmentosum XPG gene. These results, together with our previous finding of increased resistance to ultraviolet (UV) cell-killing of CS cells pretreated with HuIFN-beta prior to UV irradiation suggest that XPG might be one of the genes possibly involved in the HuIFN-beta-induced UV-resistance.

Eye movements evoked by proprioceptive stimulation along the body axis in humans

Proprioceptive input arising from torsional body movements elicits small reflexive eye movements. The functional relevance of these eye movements is still unknown so far. We evaluated their slow components as a function of stimulus frequency and velocity. The horizontal eye movements of seven adult subjects were recorded using an infrared device, while horizontal rotations were applied at three segmental levels of the body [i.e., between head and shoulders (neck stimulus), shoulders and pelvis (trunk stimulus), and pelvis and feet (leg stimulus)]. The following results were obtained: (1) Sinusoidal leg stimulation evoked an eye response with the slow component in the direction of the movement of the feet, while the response to trunk and neck stimulation was oriented in the opposite direction (i.e., in that of the head). (2) In contrast, the gain behavior of all three responses was similar, with very low gain at mid- to high frequencies (tested up to 0.4 Hz) but increasing gain at low frequencies (down to 0.0125 Hz). We show that this gain behavior is mainly due to a gain nonlinearity for low angular velocities. (3) The responses were compatible with linear summation when an interaction series was tested in which the leg stimulus was combined with a vestibular stimulus. (4) There was good correspondence of the median gain curves when eye responses were compared with psychophysical responses (perceived body rotation in space; additionally recorded in the interaction series). However, correlation of gain values on a single-trial basis was poor. (5) During transient neck stimulation (smoothed position ramp), the neck response noticeably consisted of two components -- an initial head-directed eye shift (phasic component) followed by a shift in the opposite direction (compensatory tonic component). Both leg and neck responses can be described by one simple, dynamic model. In the model the proprioceptive input is fed into the gaze network via two pathways which differ in their dynamics and directional sign. The model simulates either leg or neck responses by selecting an appropriate weight for the gain of one of the pathways (phasic component). The interaction results can also be simulated when a vestibular path is added. This model has similarities to one we recently proposed for human self-motion perception and postural control. A major difference, though, is that the proprioceptive input to the gaze-stabilizing network is weak (restricted to low velocities), unlike that used for perception and postural control. We hold that the former undergoes involution during ontogenesis, as subjects depend on the functionally more appropriate vestibulo-ocular reflex. Yet, the weak proprioceptive eye responses that remain may have some functional relevance. Their tonic component tends to stabilize the eyes by slowly shifting them toward the primary head position relative to the body support. This applies solely to the earth-horizontal plane in which the vestibular signal has no static sensitivity.