Infection with cytotoxic T-lymphocyte escape mutants results in increased mortality and growth retardation in mice infected with a neurotropic coronavirus

C57BL/6 mice infected with mouse hepatitis virus strain JHM (MHV-JHM) develop a chronic demyelinating encephalomyelitis several weeks after inoculation. Previously, we showed that mutations in the immunodominant CD8 T-cell epitope (S-510-518) could be detected in nearly all samples of RNA and virus isolated from these mice. These mutations abrogated recognition by T cells harvested from the central nervous systems of infected mice in direct ex vivo cytotoxicity assays. These results suggested that cytotoxic T-lymphocyte (CTL) escape mutants contributed to virus amplification and the development of clinical disease in mice infected with wild-type virus. In the present study, the importance of these mutations was further evaluated by infecting naive mice with MHV-JHM variants isolated from infected mice and in which epitope S-510-518 was mutated. Compared to mice infected with wild-type virus, variant virus-infected animals showed higher mortality and morbidity manifested by decreased weight gain and neurological signs. Although a delay in the kinetics of virus clearance has been demonstrated in previous studies of CTL escape mutants, this is the first illustration of significant changes in clinical disease resulting from infection with viruses able to evade the CD8 T-cell immune response.

Intracellular calcium distribution in apoptosis of HL-60 cells induced by harringtonine: intranuclear accumulation and regionalization

Harringtonine (HT), an anticancer drug with high chemotherapeutic efficiency to human chronic granulocytic/myelomonocytic leukemia, has been reported to rapidly induce apoptosis in HL-60 cells in a wide scope/range of dosage by investigators from our lab and others. In the present studies, by using video enhancement contrast (VEC) microscopy, we dynamically analyzed changes in intracellular calcium distribution in a single HL-60 cell over the period from the initiation of apoptosis to the obvious appearance of chromatin condensation. The results from this paper demonstrated the striking distinction of intracellular calcium distribution at different time points after treatment with HT. Before treatment in normal HL-60 cells the highest [Ca2+]i accumulation was observed in the peri-nuclear area and the lowest was observed in the nucleus; after treatment with 1 microg/ml HT for 30 min intracellular calcium diffused all over the cell compartments, while intranuclear calcium increased comparatively and significantly. The phenomenon of intranuclear calcium accumulation was further confirmed by using laser scanning confocal microscopy (LSCM). In addition, co-localization of the highest calcium region with condensed chromatin in apoptotic HL-60 cells was also observed by LSCM. Our results suggest that two sequential alterations of intracellular calcium distribution occurred in apoptotic HL-60 cells induced by HT, i.e. (a) accumulation of calcium in the nucleus and (b) regionalization in a specific nuclear region.

Antigen specificity of CD4 T cell response in the central nervous system of mice infected with mouse hepatitis virus

Previously, we showed that the transmembrane (M) and surface (S) glycoproteins were recognized by splenic CD4 T lymphocytes harvested from mice infected intraperitoneally with mouse hepatitis virus, strain JHM (MHV-JHM), whereas only the S protein was recognized by splenocytes derived from mice with MHV-induced chronic demyelination. From these results, it could not be determined which proteins were recognized by T cells localized in the infected central nervous system (CNS). Herein, we show that CD4 T cells responding to both the M and S proteins can be detected in the CNS of mice with either acute encephalitis or the chronic demyelinating disease. As part of these analyses, two CD4 T cell epitope regions encompassing residues 328-347 and 358-377 within the S protein were identified. Both epitopes, as well as a previously identified M-specific epitope, were recognized by the CNS-derived lymphocytes. Finally, viral RNA harvested from mice with chronic demyelination was analyzed for mutations in the S specific CD4 T cell epitopes since changes resulting in escape from CD8 T cell surveillance were previously identified in these samples. A mutation in epitope region S(328-347) (ala to thr at position 337) was detected in a minority of samples but this change did not abrogate recognition of the epitope and therefore was unlikely to contribute to virus persistence. In conclusion, these studies identify epitopes recognized by MHV-specific CD4 T cells in the infected CNS and show that these cells are preferentially located at the site of infection in mice with clinical disease.

Microstimulation of auditory nerve for estimating cochlear place of single fibers in a deaf ear

Multielectrode cochlear prostheses seek to approximate the cochlea's normal frequency-place mapping through spatial segregation of stimulus currents. Various electrode configurations have been employed to achieve such segregation. Direct measurements of stimulation regions among single auditory nerve (AN) fibers has been possible only when normal hearing is preserved, such that each fiber's cochlear place can be inferred from its tuning curve. This precludes measurements in deafened ears, or ears compromised by implantation of the electrodes. Data presented here demonstrate that the cochlear place of an AN fiber can be estimated without acoustic sensitivity, using electrical microstimulation through a recording pipette in the AN bundle. The procedure exploits cochleotopic projection to isofrequency laminae within the contralateral inferior colliculus (IC). Microstimulation excites a small group of fibers neighboring the recorded fiber, generating centrally propagated volleys along a narrow frequency-specific pathway. Evoked potential recordings at varying depths are made to identify the ICC lamina where the response to AN microstimulation is greatest. Preliminary data are also presented for an alternative method of identifying the lamina using a frequency domain measure of binaural interactions within the IC.

Cytotoxic T-cell-resistant variants arise at early times after infection in C57BL/6 but not in SCID mice infected with a neurotropic coronavirus

Under certain conditions, C57BL/6 mice persistently infected with mouse hepatitis virus strain JHM (MHV-JHM) develop clinical disease and histological evidence of demyelination several weeks after inoculation with virus. In a previous report, we showed that mutations in the RNA encoding an immunodominant CD8 T-cell epitope within the surface glycoprotein (epitope S-510-518) were present in all persistently infected animals and that these mutations abrogated recognition by virus-specific cytotoxic T cells (CTLs) in direct ex vivo cytotoxicity assays. To obtain further evidence that these mutations were necessary for the development of clinical disease, the temporal course of their appearance was determined. Mutations in the epitope were identified by 10 to 12 days after inoculation, and in some mice, virus containing mutated epitope was the dominant species detected by 15 days. In addition, most mice that remain asymptomatic at 80 days after inoculation, a time after which clinical disease almost never develops, were infected with only wild-type virus. Finally, analysis of virus isolated from mice with severe combined immunodeficiency (SCID) revealed the presence only of wild-type epitope S-510-518. These results, by showing that mutations are not selected in SCID mice and occur at early times after inoculation in C57BL/6 mice, support the view that they result from immune pressure and contribute to virus persistence and demyelination in mice infected persistently with MHV-JHM.

Changes in activity of cytosolic phospholipase A2 in human amnion at parturition

OBJECTIVE

The purpose of this study was to determine whether increased cytosolic phospholipase A2 activity mediated arachidonic acid mobilization for prostaglandin synthesis in amnion at parturition.

STUDY DESIGN

Amnion was collected immediately after delivery from four groups of patients: preterm (<37 weeks) with no labor or labor and term (>37 weeks) with no labor or labor and stored at -70 degrees C. Tissues were homogenized and centrifuged for 1 hour at 100,000 g, and cytosol was assayed for cytosolic phospholipase A2 activity with use of carbon 14-labeled 1-stearoyl-2 arachidonyl phosphatidylcholine plus 10 micromol/L unlabeled substrate and 5 mmol/L calcium in 10 mmol/L N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid, pH 7.4. Incubations were performed in duplicate +/- 10 micromol/L arachidonyl trifluoromethyl ketone, a specific inhibitor of cytosolic phospholipase A2 activity, at 30 degrees C for 45 minutes.

RESULTS

Total cytosolic phospholipase A2 activity (in picomoles of arachidonic acid per minute per milligram of protein) calculated as the difference between the activity in the presence and absence of arachidonyl trifluoromethyl ketone was (mean +/- SE) as follows: preterm no labor (n = 7) 8.94 +/- 3.08, preterm with labor (n = 6) 6.79 +/- 2.31, term no labor (n = 7) 14.85 +/- 1.66, and term with labor (n = 5) 5.51 +/- 1.52. Enzyme activity increased with gestational age and was highest in the term no labor group. A significant decrease in cytosolic phospholipase A2 activity occurred with labor (p < 0.05). The greatest decrease in activity was in the term group (p < 0.05).

CONCLUSION

Total cellular cytosolic phospholipase A2 activity in amnion is highest in anticipation of labor but during labor total activity is depleted, resulting in the low activity measured after delivery of the placenta. The substrate specificity and changes in amnion total cytosolic phospholipase A2 activity with labor strongly suggests a role in mediation of arachidonic acid mobilization and prostaglandin synthesis at labor.

Superior laryngeal nerve stimulation in the cat: effect on oropharyngeal swallowing, oesophageal motility and lower oesophageal sphincter activity

Superior laryngeal nerve (SLN) stimulation can activate the brainstem swallowing mechanism to produce a complete swallowing sequence consisting of oropharyngeal, oesophageal and lower oesophageal sphincter (LOS) components. However, little is known of the effect of SLN stimulation (peripheral-sensory input from the pharynx) on the characteristics of oesophageal motor activity, especially in the smooth muscle portion. The present study examined the effect of varying stimulus train length and frequency on each of the three components of the reflex. Acute studies were performed in urethane anaesthetized cats. Oesophageal motility was monitored using conventional manometric techniques, and oropharyngeal swallowing by the mylohyoid electromyogram. SLN stimulus train length (1-10 sec) and frequency (5-30 Hz) were varied independently. Increased train length or frequency resulted in (1) an increase in oropharyngeal swallowing and incidence of the complete swallowing response, (2) an increase in latency to onset of the oesophageal peristaltic wave, (3) reduction of the amplitude of the evoked peristaltic contraction in the smooth muscle portion, without altering its velocity, (4) increased LOS relaxation, and increased LOS after-contraction. The LOS contraction was abolished by atropine (100 micrograms kg-1). Therefore, increased SLN stimulation not only results in excitation of the central swallowing program and the oropharyngeal stage of swallowing, but has major effects on the oesophageal and LOS stages of swallowing. Afferent SLN stimuli can impact on the control mechanisms for each stage, to inhibit or excite the stages in different ways.

An Investigation of the Safety of Midazolam Use in Hospital

OBJECTIVE

To investigate whether an association exists between midazolam use and serious cardiorespiratory events or death.

DESIGN

Retrospective analysis of data in an inpatient record linkage database, collected between March 1986 and October 1987 from 14 hospitals in the United States.

PATIENTS

A cohort of 19,112 patients who received injectable midazolam or diazepam on the same day that a medical procedure was performed.

MAIN OUTCOME MEASURES

An attempt was made to identify suspected serious cardiorespiratory adverse events and deaths that occurred within 24 h of study-drug administration. Death rates within 24 h following study-drug administration were compared between patients who received injectable midazolam and those who received injectable diazepam.

RESULTS

Validation analysis of the information in the computerized record linkage database indicated that serious cardiac and respiratory adverse events that occurred within 24 h of study-drug administration could not be reliably identified. Therefore, a comparison of the serious cardiorespiratory adverse event rates following administration of midazolam versus diazepam could not be made. Death rates within 24 h of study-drug administration could be evaluated. For the cohort as a whole, the death rate was significantly lower among patients who received midazolam than among those who received diazepam (0.76% versus 1.93%, p<0.01). This difference remained statistically significant, after adjusting for age, sex, comorbidity diagnosis, concomitant drug use, type of medical procedure, and hospital size and teaching capability.

CONCLUSIONS

The results suggest that there is no increased risk of death associated with midazolam administration when compared to diazepam administration for endoscopic, conscious sedative, and general anesthetic procedures in hospitals.

[Transfer and expression of rh-SCF gene in human hematopoietic stem/progenitor cells]

OBJECTIVE

To explore the transfer and expression of recombinant human stem cell factor (rh-SCF) gene in human hematopoietic stem/progenitor cell.

METHODS

pLXSN-SCF, a recombinant retrovirus vector of soluble human SCF gene, was constructed by recombinant gene technique. The recombinant plasmid was introduced into virus packaging cells psi2 and PA317 by lipofectin-mediated DNA transfection, and PA317/SCF, the recombinant virus producing cell, was obtained by G418 screening [the virus potency was (2.4-8.5) x 10(5) CFU/ml]. Then, human hematopoietic stem/progenitor cells were transfected with PA317/SCF. The transfer and expression of human SCF gene were assayed by PCR, APAAP immunohistochemical staining and chemoluminance-direct ELISA.

RESULTS AND CONCLUSION

retrovirus-mediated rh-SCF gene was successfully transferred and expressed in human hematopoietic stem/progenitor cells.

Effects of nitric oxide synthase blockade on esophageal peristalsis and the lower esophageal sphincter in the cat

The present study explores the role of nitric oxide (NO) in control of esophageal peristalsis and lower esophageal sphincter (LES) function in the cat. Studies were performed on 20 ketamine-anesthetized cats with manometric recording at the LES, 0, 2, 4, and 6 cm above the LES (smooth muscle section), and 12 and (or) 14 cm above the LES (striated muscle section). L-Ng-Nitro-arginine (L-NNA, 10(-6)-10(-4) mol/kg) was given intravenously, and the effects on swallow-induced esophageal peristalsis were assessed. (i) L-NNA increased the velocity of swallow-induced peristalsis in the smooth muscle esophagus; the effect was dose dependent, more prominent distally, and completely reversed by L-arginine (10(-3) mol/kg). (ii) L-NNA decreased the amplitude of peristaltic contraction in the very distal esophagus; the decrease also was dose dependent but not returned to normal by L-arginine. (iii) L-NNA inhibited LES relaxation (reversed by L-arginine) and decreased the LES "after-contraction" amplitude (unaffected by L-arginine). (iv) L-NNA was associated with the appearance of repetitive contractions. Basal LES tone was unaffected by L-NNA. In conclusion, NO is an important mediator for the timing of peristalsis in the distal smooth muscle esophagus and for LES relaxation in the cat, a species whose contraction amplitude is largely determined by cholinergic excitation. The role of NO in controlling esophageal body and LES contraction amplitude, and in preventing repetitive contractions, requires further study.

Induction of both cytosolic phospholipase A2 and prostaglandin H synthase-2 by interleukin-1 beta in WISH cells in inhibited by dexamethasone

In previous studies we have shown that IL-1 beta induced both PGE2 release and total cellular cPLA2 activity and cPLA2 protein synthesis in human amnion-derived WISH cells. In this study, the effect of IL-1 beta on cPLA2 and PGHS-2 mRNA expression was investigated. Using RT-PCR, we found that IL-1 beta (0.1 ng/ml) coordinately induced both cPLA2 and PGHS-2 mRNA expression within 2 hours. The synthetic glucocorticoid dexamethasone (10(-10)-10(-6)M) inhibited IL-1 beta-induced cPLA2 and PGHS-2 mRNA expression activity and protein synthesis and PGE2 release in a concentration dependent manner. In the absence of IL-1 beta, dexamethasone alone (10(-6)M) inhibited basal cPLA2 activity, mRNA expression and protein synthesis. In addition, cycloheximide (5 micrograms/ml) apparently superinduced, but actinomycin D (2 micrograms/ml) inhibited IL-1 beta-induced cPLA2 and PGHS-2 mRNA expression suggesting that both are immediate early genes and a transcriptional mechanism is involved in the induction of both cPLA2 and PGHS-2 mRNA by IL-1 beta.

Cloning of the human erythropoietin exons and their expression in COS-7 cells

Human erythropoietin exons (hEPO-E) were isolated from a Chinese fetal liver DNA library by using the PCR method with gene recombination. One nucleotide mutation was found in exon 3 leading to the Leu in position 62 being changed to Ser. The hEPO-E coding for the full-length mature protein was inserted into different clone sites of PSV-2-dhfr to create different transferring plasmids (pSV2-dhfr/F1, pSV2/F2, pSV2-dhfr/F3, pSV2-dhfr/F4, pSV2-dhfr/G1, and pSV2-dhfr/G3) which were transfected into COS-7 cells. Results obtained from the comparative experiments indicate that biological activity of hEPO was found in all culture supernatants and its expression level was higher than that of its genome.

Acoustic enhancement of electrically evoked otoacoustic emissions reflects basilar membrane tuning: a model

A simple model for the acoustic enhancement of electrically evoked otoacoustic emissions (EEOEs) is presented in this paper. The model is based on the assumption that the enhancement is a result of the local interaction between the electrical current spreading in the scala media and the basilar membrane (BM) response to acoustic input. The analytical, steady-state response of the 1-dimensional linear cable to sinusoidal current injection is derived and is used to predict the current spreading in the cochlea. Acoustic enhancement at an emission generator is modeled as a magnitude change that is a sigmoid function of the local BM motion. The model results are in good agreement with the experimental findings and support our interpretation that the acoustic enhancement of EEOEs reflects BM tuning.

Electrical slow wave activity of the cat stomach: its frequency gradient and the effect of indomethacin

The present study was performed to establish the intrinsic frequency of the slow waves in different regions of the cat stomach, to define the propagation velocity of the slow wave along the stomach, and to determine whether endogenous prostaglandins can affect the slow wave frequency. In 20 cats, electrical activity was recorded from the anterior wall of the intact stomach in vivo and in vitro, and in vitro after cutting the stomach into 16 pieces to isolate each pair of electrodes. In vivo, slow waves (4.1 +/- 0.5 cpm) were seen only from mid corpus to pylorus, the apparent propagation velocity decreasing towards the antrum. In vitro: (a) after cutting, the slow wave frequency increased, to a maximum in 1 h (12 +/- 1.8 cpm; range 10.2-17.3), with the highest frequency always in the mid or orad corpus, usually on the greater curvature (GC), (b) with indomethacin (10(-5) M) the increase in slow wave frequency was prevented or reversed, and there was a frequency gradient with the highest frequency (4.4 +/- 1.2 cpm) uniformly located in the most proximal active site on the GC, and (c) slow waves on the GC were more stable, regular and continuous than on the lesser curvature (LC), the difference being most evident in the corpus. The results suggest that the cat stomach behaves as a system of electrically coupled oscillators of different frequencies. The dominant oscillator of highest frequency is situated in the proximal corpus of the GC, with the remainder of the distal stomach entrained at this frequency. All gastric slow wave oscillators can be driven to higher frequencies by endogenous prostaglandins. The decreasing velocity of slow wave propagation distally suggests that oscillator properties and/or coupling among oscillators differs in the cat.

Interleukin-1 beta induces the synthesis and activity of cytosolic phospholipase A2 and the release of prostaglandin E2 in human amnion-derived WISH cells

The objective of this study was to examine the expression and activity of cytosolic phospholipase A2 (cPLA2) in relation to prostaglandin E2 (PGE2) synthesis in human amnion-derived WISH cells in response to stimulation by interleukin-1 beta (IL-1 beta). cPLA2 activity was characterized by sensitivity to heat and acid treatment, stability to dithiothreitol, and inhibition by the specific inhibitor, arachidonyl trifluoromethyl ketone (AACOCF3). Treatment of WISH cells with IL-1 beta (0.01-1 ng/mL) for up to 24 h resulted in a significant increase in PGE2 release in a concentration- and time-dependent manner accompanied by increases both in total cellular cPLA2 activity and in cPLA2 protein levels detected by Western blot analysis. The parallel increase in total cellular cPLA2 activity and cPLA2 protein level indicates that IL-1 beta may induce the synthesis of cPLA2. Incubation of the cells with 10 microM AACOCF3 for 24 h significantly inhibited IL-1 beta-induced PGE2 production strongly suggesting that cPLA2 mediates IL-1 beta-induced PGE2 formation. In unstimulated cells, there is appreciable total cellular cPLA2 activity and protein, but these cells produce low amounts of PGE2 until stimulated by IL-1 beta, suggesting that cPLA2 translocation from cytosol to the membrane is necessary for its bioactivity. In contrast to IL-1 beta, treatment with phorbol ester (12-O-tetradecanoyl phorbol-13-acetate, TPA, 10(-10)-10(-6)M) for 24 h significantly inhibited total cellular cPLA2 activity in a concentration-dependent manner. The amount of total cellular cPLA2 protein seen on Western blot remained unchanged following TPA treatment. These data suggest that in WISH cells, IL-1 beta induces both translocation to the membrane and de novo synthesis of cPLA2 protein to sustain prostaglandin (PG) synthesis. In contrast, TPA may only cause cPLA2 translocation but no increase in cPLA2 protein synthesis, resulting in limited PG synthesis. Our results provide a mechanism for the effect of IL-1 beta on prostaglandin synthesis in human amnion cells and provide support for a role of cPLA2 in the mechanism initiating human parturition.

Electrically evoked basilar membrane motion

Electrically induced outer hair cell (OHC) motility, demonstrated by a number of investigators in isolated OHC preparations, has been considered to be a key mechanism in the active process which brings about the excellent sensitivity and frequency selectivity of the mammalian cochlea. In this study, electrical-to-mechanical transduction in the gerbil cochlea was demonstrated in vivo by direct measurement of basilar membrane motion evoked by sinusoidal electrical current injected into the scala media. The characteristic frequency (CF) of the measurement place was approximately 40 kHz as determined by the basilar membrane (BM) responses to acoustic stimulation. The results showed that basilar membrane motion could be evoked by electrical current of frequencies from below 10 Hz to exceeding 40 kHz. The magnitude and phase of the BM velocity response to constant current stimulation, from 100 Hz to 10,000 Hz, were similar to the acoustically driven BM velocity for constant umbo velocity. For frequencies in this range, the BM motion evoked by a current of 50 microA was comparable to the BM motion evoked by a 60 dB SPL acoustic stimulus. The phase of the electrically evoked BM motion indicates that positive current injected into the scala media caused the BM to move toward scala vestibuli for frequencies between 100 and 10 kHz. This result is consistent with the hypothesis that the electrically evoked BM motion is due to electrically evoked OHC length changes.

Identification of a CD4+ T cell epitope within the M protein of a neurotropic coronavirus

A significant CD4+ T cell response against the transmembrane (M) protein can be detected in the spleens of C57Bl/6 mice infected intraperitoneally with a sublethal injection of the neurotropic JHM strain of mouse hepatitis virus (MHV-JHM), but not in those of mice with the chronic demyelinating encephalomyelitis caused by this virus. With the ultimate goal of determining the role of the M-specific response in the pathogenesis of MHV-JHM-induced neurological diseases, CD4+ T cell epitopes within the M protein were identified using vaccinia virus recombinants expressing truncated forms of the protein and peptides spanning most of the M protein in cell proliferation assays. Peptides covering residues 128-147 contain at least one CD4+ T cell epitope for MHV-JHM. Within this region is a sequence (residues 135-143) which matches the recently described MHC class II I-Ab binding motif. Delineation of this epitope should facilitate analysis of the role of the M-specific CD4+ T cell response in the development of acute and chronic neurological infections caused by MHV-JHM.

The relationships between erythroblast denucleation and the nuclear matrix--intermediate filaments

We present a novel approach for making cybrids. By introducing neo gene expression plasmids into rabbit reticulocytes, fusing the gene transferred reticulocytes with K562 cells and selecting in G418 selection medium, a cybrid strain K-RRneo was established. Whole mount TEM study demonstrated that after cybridization, there was a reorganization of the intermediate filaments which showed a tendency to differentiate towards reticulocytes. SDS-PAGE and western blot analysis verified the above observation, in which the vimentin blot pattern of the cybrids was similar to that of reticulocytes, but totally different from that of K562 cells. Using this model, we reaffirmed the hypothesis that the erythroid differentiation factor (EDF) might be responsible for erythroid differentiation as well as the initiation of denucleation.

Antispermatogenic effect of Tripterygium wilfordii and tripchlorolide (T4) on rat gametogenesis and spermatozoa

The multiglycosides of Tripterygium wilfordii (TII), a ready-made Chinese herbal medicine used for the treatment of rheumatoid arthritis, have been shown to cause oligospermia in patients. In the present study, the antifertility effects of TII and tripchlorolide (T4, isolated from TII) were observed in male rats. In rats fed with TII at a dose of 10 mg.kg.d for 7 weeks, the seminiferous tubules were essentially not influenced. However, most of the sperm heads along the surface of the tubular lumen were transformed from the normal sickle-shaped to round shaped, suggesting a possible mutagenic action. There was minimal testicular change but prominent epididymal spermatozoa damage in all rats treated with T4 (0.05 mg.kg.d) for 7 weeks. The epididymal spermatozoa showed various structural abnormalities, including disrupted connecting pieces and cracked midpieces, and more than 80% of the spermatozoa were decapitated. No significant changes were seen in the main visceral organs. The data suggest that T4 may have good prospects as a male contraceptive.

[A practical method of whole mount TEM sample preparation and the study of nuclear matrix-intermediate filament scaffolds in K562 cells]

We applied culture plates with bored holes covered with FORMVAR and coated with carbon, to replace the gold grids used in conventional whole mount TEM study. Human erythroleukemia cell line K562 cells plated on the plate surface were extracted using a modified protocol to study scaffolds of nuclear matrix (NM) and intermediate filament (IF). The NM of the K562 cells was found to be composed of interweaving filaments of different diameters, while the cytoplasmic IF were mainly distributed in a radialized pattern. Compared with other techniques of whole mount TEM sample preparations, this one is much more practical and economical, yielding clear NM-IF structures with few artifacts. Study of NM-IF scaffolds in K562 cells might provide a basis for further elucidation of the involvement of NM-IF in the denucleation of mammalian erythroblasts.

Effects of electrical biasing on electrically-evoked otoacoustic emissions

Electrically-evoked otoacoustic emissions were produced using a 10 microA, 750 Hz AC current plus a biasing DC current in the range of +/- 10 microA. Concurrently, a 1643 Hz tonal stimulation was delivered to the eardrum. At low sound levels, negative DC current increased the emission while positive DC current reduced the emission. Such findings are reasonably explained by a negative-feedback model of cochlear function. At high sound levels, negative DC current reduces the emission, while positive current has little effect. These data can be accounted for by voltage-dependent length changes shown to occur in isolated outer hair cells, with the additional requirement that voltage-dependent K+ channels in outer hair cells reduce the effectiveness of positive DC current in changing membrane potential.

[Experimental gene transfer study using anucleated reticulocytes as target cells]

We report here a novel approach to introduce reporter beta-galactosidase genes into anucleated rabbit reticulocytes. The results indicate that the beta-galactosidase gene was expressed to certain degree in the cytoplasm of the reticulocytes. Our study has provided a useful model system for gene expression studies in anucleated eukaryotic cells.

Acoustic enhancement of electrically-evoked otoacoustic emissions reflects basilar membrane tuning: experiment results

Acoustic enhancement of the electrically-evoked otoacoustic emissions (EEOEs) was investigated by systematically varying acoustic frequency and intensity. The results demonstrated that simultaneous acoustic stimulation at frequencies around the characteristic frequency of the electrical current injection place was most effective in enhancing low-frequency EEOEs. Moreover, it was demonstrated that the enhancement was tuned and graded. The enhancement threshold tuning curves (defined as sound pressure level needed to achieve 1 dB of enhancement) resembled basilar membrane tuning at high sound pressure levels. The data suggest that the emissions were generated from a cochlear region near the electrode place, and the magnitude of the enhancement depends on the magnitude of the basilar membrane response to the acoustic stimulus.

Responses to salinity of grapevine plants with split root systems

Grape yield, shoot and root vigour and water use by grapevine plants with split root systems were investigated. Some plants had both root parts continuously irrigated either with fresh or with saline water. Some plants got a dual treatment; one portion got fresh water and the other saline water. The irrigation water of a third group was changed during the experiment from fresh to saline water or vice versa. Fruit yield and root and shoot viability were positively correlated with the actual water use. Water ascent along the stem of the grapevines was found to be sectorial. Most of the water was supplied by the freshwater roots. Only small quantities of water were supplied by salt-affected roots to their respective twigs. Changes in the water quality of the root medium induced a dual effect: (a) a fast response, caused by the direct change in the ambient w⁷ ater potential; and (b) a long-term response that developed over several weeks. The latter response was induced by the development of new roots, or by death of others, upon a change in the quality of the irrigation water. The commonly used grapevine plants of the Arava valley are negatively affected by NaCl already at concentrations below 100 mM. Under such conditions, shoot growth and fruit yield were seriously inhibited, even when one part only of the root system was exposed to saline water.