[Mechanism of noise induced hidden hearing loss based on proteomics]

Objective: To explore the mechanism of noise-induced hidden hearing loss by proteomics. Methods: In October 2022, 64 SPF male C57BL/6J mice were divided into control group and noise exposure group with 32 mice in each group according to random sampling method. The noise exposure group was exposed to 100 dB sound pressure level, 2000-16000 Hz broadband noise for 2 h, and the mouse hidden hearing loss model was established. Auditory brainstem response (ABR) was used to test the change of hearing threshold of mice on the 7th day after noise exposure, the damage of basal membrane hair cells was observed by immunofluorescence, and the differentially expressed proteins in the inner ear of mice in each group were identified and analyzed by 4D-Label-free quantitative proteomics, and verified by Western blotting. The results were statistically analyzed by ANOVA and t test. Results: On the 7th day after noise exposure, there was no significant difference in hearing threshold between the control group and the noise exposure group at click and 8000 Hz acoustic stimulation (P>0.05) . The hearing threshold in the noise exposure group was significantly higher than that in the control group under 16000 Hz acoustic stimulation (P<0.05) . Confocal immunofluorescence showed that the basal membrane hair cells of cochlear tissue in noise exposure group were arranged neatly, but the relative expression of C-terminal binding protein 2 antibody of presynaptic membrane in middle gyrus and basal gyrus was significantly lower than that in control group (P<0.05) . GO enrichment analysis showed that the functions of differentially expressed proteins were mainly concentrated in membrane potential regulation, ligand-gated channel activity, and ligand-gated ion channel activity. KEGG pathway enrichment analysis showed that differentially expressed proteins were significantly enriched in phosphatidylinositol 3 kinase-protein kinase B (PI3K-Akt) signaling pathway, NOD-like receptor signaling pathway, calcium signaling pathway, etc. Western blotting showed that the expression of inositol 1, 4, 5-trisphosphate receptor 3 (Itpr3) was increased and the expression of solute carrier family 38 member 2 (Slc38a2) was decreased in the noise exposure group (P<0.05) . Conclusion: Through proteomic analysis, screening and verification of the differential expression proteins Itpr3 and Slc38a2 in the constructed mouse noise-induced hidden hearing loss model, the glutaminergic synaptic related pathways represented by Itpr3 and Slc38a2 may be involved in the occurrence of hidden hearing loss.

Research progress on ecological adaptation and prevention of Parengyodontium album on the surface of cultural relics

Cultural relics as the crystallization of human history are non-renewable and irreplaceable resources. Microorganisms are widely colonized on ancient wall paintings, stone cultural relics, and other types of cultural heritages to cause harm. The dominant disease fungus, Parengyodontium album, is extensively distributed and can seriously threaten the long-term preservation of precious cultural heritage due to surviving in various cultural relics and extreme environments. The classification and nomenclature of P. album have undergone several changes, so its impact on cultural relic received little attention. Here, we summarized the brief histories of its classification and development, distribution range, and cultural heritage preference of P. album. We further analyzed the physiological, biochemical, and ecological characteristics and potential biological degradation mechanism. We proposed that P. album could be used as an indicative species of microbial hazardous effects on cultural heritage. We discussed the prevention and control countermeasures of such typical mural microorganisms and pointed out key research directions in this field.

Seasonal Variation of Hypolithic Microbiomes in the Gobi Desert : Seasonal Variation of Hypolithic Microbiomes in the Gobi Desert

Understanding how microbial communities adapt to environmental stresses is critical for interpreting ecological patterns and microbial diversity. In the case of the Gobi Desert, little is known on the environmental factors that explain hypolithic colonization under quartz stones. By analyzing nine hypolithic communities across an arid gradient and the effects of the season of the year in the Hexi Corridor of this desert, we found a significant decrease in hypolithic colonization rates (from 47.24 to 15.73%) with the increasing drought gradient and found two distinct communities in Hot and Cold samples, which survived or proliferated after a hot or a cold period. While Cold communities showed a greater species diversity and a predominance of Cyanobacteria, Hot communities showed a predominance of members of the Proteobacteria and the Firmicutes. In comparison, Cold communities also possessed stronger functions in the photosynthesis and carbon metabolism. Based on the findings of this study, we proposed that the hypolithic communities of the Hexi Corridor of the Gobi Desert might follow a seasonal developmental cycle in which temperature play an important role. Thus after a critical thermal threshold is crossed, heterotrophic microorganisms predominate in the hot period, while Cyanobacteria predominate in the cold period.

[Research progress on the bioweathering and controlling of stone cultural relics]

The bioweathering of stone cultural relics is a ubiquitous problem. Weathering prevention is an escalating challenge under the increasing global climate and environmental changes. Here, the mechanisms of lichen-microorganism mediated weathering of stone materials and their relationships with climatic and environmental factors were reviewed. The biological protection of lichens and the evaluation of the efficacy of biocides in lichen-control were discussed. The potential research directions in this field were proposed. Research on lichen-rock interfaces suggested that biological weathe-ring could be mainly attributed to physical and chemical weathering which represented by mycelium penetration and calcium oxalate formation. Bioweathering of outdoor stone cultural relics is closely related with the whole ecosystem encompassing factors, such as stone matrix, surrounding environment, and climate factors. Lichens have both biological weathering and protection effects on stone heritage. For the restoration of bioweathered stone cultural relics, environmental conditions for pre-servation of stone cultural relics should be improved step by step. The related industry regulations and national standards for evaluating biological weathering and control efficiency should be established to promote the efficient development of scientific protection.

[Developmental characteristics of various types of hand bones of Poland's syndrome]

OBJECTIVE

To explore development status in different types of the hand bone and its developmental characteristics with Poland syndrome.

METHODS

There were 32 cases with Poland's syndrome who accepted bilateral hand X-ray examination in Department of Hand Surgery, Beijing Jishuitan Hospital from February 2013 to August 2014.There were 24 male and 8 female patients aged from 1.0 to 15.0 years with median age of 2.4 years. Right hand deformity was 23 cases and left hand deformity was 9 cases. According to Tanner-Whitehouse skeletal age scoring system, 20 bones (radius and ulna, 7 carpal bones, 11 metacarpal and phalangeal bones) selected from the affected and contralateral limb respectively, were evaluated. Besides, hand deformity of the cases was classified into 5 types based on relevant literature. Each bone was given an individual age using the references of Greulich-Pyle chart. The average of all individual ages was taken as gross bone age, the average of individual ages of radius and ulna was taken as bone age of long bones, the average of individual ages of carpal bone was taken as bone age of carpal bones, and the average of individual age of metacarpal and phalangeal bones was taken as bone age of short bones.The delay of bone age was evaluated by correlation test, while the curve of cubic equation was used for analyzing the variance of skeletal development with age.

RESULTS

The delay of long bone age of patients with Poland's syndrome in this study were 0-1.9 years ((0.5±0.5) years), 0-2.2 years ((0.7±0.5)years) for carpal bone, 0.5-2.0 years((0.6±0.4) years)for short bone and 0.1-1.7 years((0.6±0.4)years) for gross bone.Twelve cases in type Ⅱ hand deformity, 15 cases in type Ⅲ and 5 cases in type Ⅳ. The delay of bone ages, including long bone age, carpal bone age, short bone age and gross bone age, was not related with gender and side(all P>0.05), but related with degree of deformity(F=3.663-12.971, P=0.000-0.038).

CONCLUSION

Compared with normal upper limb, the bone age in the affected limb in Poland's syndrome is delayed and it is correlated with gender, age and the extent of hand deformity and negative with side.

A randomized phase II study of the MEK1/MEK2 inhibitor trametinib (GSK1120212) compared with docetaxel in KRAS-mutant advanced non-small-cell lung cancer (NSCLC)†

BACKGROUND

KRAS mutations are detected in 25% of non-small-cell lung cancer (NSCLC) and no targeted therapies are approved for this subset population. Trametinib, a selective allosteric inhibitor of MEK1/MEK2, demonstrated preclinical and clinical activity in KRAS-mutant NSCLC. We report a phase II trial comparing trametinib with docetaxel in patients with advanced KRAS-mutant NSCLC.

PATIENTS AND METHODS

Eligible patients with histologically confirmed KRAS-mutant NSCLC previously treated with one prior platinum-based chemotherapy were randomly assigned in a ratio of 2 : 1 to trametinib (2 mg orally once daily) or docetaxel (75 mg/m(2) i.v. every 3 weeks). Crossover to the other arm after disease progression was allowed. Primary end point was progression-free survival (PFS). The study was prematurely terminated after the interim analysis of 92 PFS events, which showed the comparison of trametinib versus docetaxel for PFS crossed the futility boundary.

RESULTS

One hundred and twenty-nine patients with KRAS-mutant NSCLC were randomized; of which, 86 patients received trametinib and 43 received docetaxel. Median PFS was 12 weeks in the trametinib arm and 11 weeks in the docetaxel arm (hazard ratio [HR] 1.14; 95% CI 0.75-1.75; P = 0.5197). Median overall survival, while the data are immature, was 8 months in the trametinib arm and was not reached in the docetaxel arm (HR 0.97; 95% CI 0.52-1.83; P = 0.934). There were 10 (12%) partial responses (PRs) in the trametinib arm and 5 (12%) PRs in the docetaxel arm (P = 1.0000). The most frequent adverse events (AEs) in ≥20% of trametinib patients were rash, diarrhea, nausea, vomiting, and fatigue. The most frequent grade 3 treatment-related AEs in the trametinib arm were hypertension, rash, diarrhea, and asthenia.

CONCLUSION

Trametinib showed similar PFS and a response rate as docetaxel in patients with previously treated KRAS-mutant-positive NSCLC.

CLINICALTRIALSGOV REGISTRATION NUMBER

NCT01362296.

Functional and symptom impact of trametinib versus chemotherapy in BRAF V600E advanced or metastatic melanoma: quality-of-life analyses of the METRIC study

BACKGROUND

In a randomized phase III study, trametinib prolonged progression-free survival and improved overall survival versus chemotherapy in patients with BRAF V600 mutation-positive melanoma.

PATIENTS AND METHODS

Patients' quality of life (QOL) was assessed at baseline and follow-up visits using the European Organisation for Research and Treatment of Cancer Core QOL questionnaire.

RESULTS

In the primary efficacy population (BRAF V600E+, no brain metastases) from baseline to weeks 6 and 12, patients' global health status scores worsened by 4-5 points with chemotherapy but improved by 2-3 points with trametinib. Rapid and substantive reductions in QOL functionality (e.g. role functioning, 8-11 points at weeks 6 and 12) and symptom exacerbation (e.g. fatigue, 4-8 points; nausea and vomiting, 5 points, both at weeks 6 and 12) were observed in chemotherapy-treated patients. In contrast, trametinib-treated patients reported small improvements or slight worsening from baseline at week 12, depending on the functional dimension and symptom. The mean symptom-scale scores for chemotherapy-treated patients increased from baseline (symptoms worsened) for seven of eight symptoms at week 6 (except insomnia) and six of eight symptoms at week 12 (except dyspnea and insomnia). In contrast, at weeks 6 and 12, the mean symptom-scale scores for trametinib decreased from baseline (symptoms improved) for pain (11-12 points), insomnia (10-12 points), and appetite loss (1-5 points), whereas those for diarrhea worsened (15-16 points). Mixed-model repeated-measures analyses showed significant (P < 0.05) and/or clinically meaningful improvements (small to moderate) from baseline in favor of trametinib for global health; physical, role, and social functioning; fatigue; pain; insomnia; nausea and vomiting; constipation; dyspnea; and appetite at weeks 6 and/or 12. QOL results for the intent-to-treat population were consistent.

CONCLUSIONS

This first QOL assessment for a MEK inhibitor in metastatic melanoma demonstrated that trametinib was associated with less functional impairment, smaller declines in health status, and less exacerbation of symptoms versus chemotherapy.

Noncompetitive inhibition of the glycine receptor-mediated current by melatonin in cultured neurons

The effect of melatonin on the glycine receptor-mediated response was studied in cultured chick spinal cord neurons using the whole-cell voltage-clamp recording technique. Melatonin rapidly and reversibly inhibited the glycine-induced current in a dose-dependent fashion, with an EC(50) of 934 microM and a maximal inhibition of 100%. Furthermore, melatonin noncompetitively inhibited the glycine response by an agonist-independent mechanism that was distinct from that of an open-channel blocker.

Non-competitive inhibition of 5-HT3 receptor-mediated currents by progesterone in rat nodose ganglion neurons

The effect of progesterone on the serotonin type 3 (5-HT3) receptor-mediated response was studied in acutely dissociated rat nodose ganglion neurons by using the whole-cell voltage-clamp technique. Progesterone rapidly and reversibly inhibited 5-HT-induced currents in a dose-dependent manner, with an EC50 of 31 microM and a maximal inhibition of 75%. Neither the 5-HT response nor inhibition of the 5-HT response by extracellularly applied progesterone was significantly affected by inclusion of a saturating concentration of progesterone in the electrode buffer, arguing that progesterone acted at the extracellular surface of the membrane. Progesterone also inhibited the 5-HT response non-competitively by a voltage- and agonist-independent mechanism that was distinct from that of open-channel blockers.

The tumor suppressor p53 can reduce stable transfection in the presence of irradiation

The tumor suppressor p53 is believed to play an essential role in maintaining genome stability. Although it is currently unknown how p53 is involved in this important biological safeguard, several previous publications indicate that p53 can help to maintain genome integrity through the recombination-mediated DNA repair process. The integration of linearized plasmid DNA into the host chromosome utilizes the same repair process, and the frequency can be measured by clonogenic assays in which cells that were stably transfected by plasmid integration can be scored by their colony-forming abilities. To gain insight into whether p53 has a direct role in plasmid integration into the host chromosome, we determined the frequency of stable transfection with CHO cells expressing either wild-type or mutant p53 in the presence and absence of irradiation. We found that low-dose irradiation ( approximately 50 to 100 cGy) increased stable transfection frequencies in CHO cells regardless of their p53 status. However, the increase of transfection frequency was significantly lower in CHO cells expressing wild-type p53. Our data thus suggest that wild-type p53 can suppress plasmid DNA integration into the host genome. This p53 function may play a direct and significant role in maintaining genome stability.

Melatonin potentiates the GABA(A) receptor-mediated current in cultured chick spinal cord neurons

The effect of melatonin on the gamma-aminobutyric acidA (GABA(A)) receptor-mediated response was studied in cultured chick spinal cord neurons using the whole-cell voltage-clamp recording technique. Melatonin rapidly and reversibly potentiated the GABA-induced current in a dose-dependent fashion, with an EC50 of 766 microM and a maximal potentiation of 148%. Potentiation of the GABA response by melatonin was mediated by increasing the potency of GABA rather than the efficacy. Prolonged exposure to a saturating concentration of the disulfide-reducing agent dithiothreitol did not attentuate the effect of melatonin on the GABA response, indicating that melatonin does not act through the redox site. Furthermore, our results demonstrate that melatonin and 5alpha-pregnan-3alpha-ol-20-one (a positive steroid modulator of the GABA(A) receptor) act through different sites.

Pregnenolone sulfate exacerbates NMDA-induced death of hippocampal neurons

Excessive stimulation of the N-methyl-d-aspartate (NMDA)-type glutamate receptor has been implicated in the neuronal death resulting from focal hypoxia-ischemia. Certain neurosteroids, steroids synthesized de novo in the central nervous system (CNS), have been shown to modulate the action of neurotransmitters at their cellular receptors. Pregnenolone sulfate (PS) is an abundant neurosteroid that enhances the current evoked by NMDA. Using the Ca2+-sensitive fluorescent dye, Fluo-3, AM, and a trypan blue exclusion assay, we evaluated the ability of PS to modulate NMDA-induced changes in intracellular free calcium concentration ([Ca2+]i) and neuronal death in primary cultures of rat hippocampal neurons. The results demonstrate that PS potentiates NMDA-induced increases in [Ca2+]i by 150%. Further, PS exacerbates the MK-801-sensitive neuronal death produced by acute (PS EC50=37 microM) or chronic NMDA exposure, reducing the EC50 of NMDA from 13 to 4 microM under chronic exposure conditions, whereas pregnenolone is ineffective. Our results show that PS, or related sulfated neurosteroids, may play a role in the onset of excitotoxic neuronal death in vivo.

Mechanism underlying potentiation by progesterone of the kainate-induced current in cultured neurons

The effect of the neurosteroid progesterone on the kainate receptor-mediated response was studied in cultured chick spinal cord neurons using the whole-cell voltage-clamp recording technique. Progesterone rapidly and reversibly potentiates the kainate-induced current in a dose-dependent manner, with an EC50 of 35 microM and a maximal potentiation of 30%. Potentiation of the kainate response by extracellularly applied progesterone is not significantly affected by inclusion of a saturating concentration of progesterone in the electrode buffer, indicating that progesterone acts at the extracellular surface of the membrane. Furthermore, progesterone enhances the kainate maximal response with little effect on the kainate EC50.

Distinct sites for inverse modulation of N-methyl-D-aspartate receptors by sulfated steroids

Steroid sulfation occurs in nervous tissue and endogenous sulfated steroids can act as positive or negative modulators of N-methyl-D-aspartate (NMDA) receptor function. In the current study, structure-activity relationships for sulfated steroids were examined in voltage-clamped chick spinal cord and rat hippocampal neurons in culture and in Xenopus laevis oocytes expressing NR1(100) and NR2A subunits. The ability of pregnenolone sulfate (a positive modulator) and epipregnanolone sulfate (a negative modulator) to compete with each another, as well as with other known classes of NMDA receptor modulators, was examined. The results show that steroid positive and negative modulators act at specific, extracellularly directed sites that are distinct from one another and from the spermine, redox, glycine, Mg2+, MK-801, and arachidonic acid sites. Sulfated steroids are effective as modulators of ongoing glutamate-mediated synaptic transmission, which is consistent with their possible role as endogenous neuromodulators in the CNS.

Competitive inhibition of the glycine-induced current by pregnenolone sulfate in cultured chick spinal cord neurons

The effect of the neurosteroid pregnenolone sulfate (PS) on the glycine receptor-mediated response was studied in cultured chick spinal cord neurons using the whole-cell voltage-clamp recording technique. PS rapidly and reversibly inhibits the glycine-induced current in a dose-dependent manner, with an EC50 of 3.7 microM and a maximal inhibition of 100%. The fact that antagonism of the glycine response by PS is neither voltage- nor agonist-dependent indicates that PS does not act as an open-channel blocker. Furthermore, inhibition by PS of the glycine-induced current appears to be of a competitive type since the drug induces a parallel, rightward shift of the glycine dose-response curve.

Mechanism underlying the effect of pregnenolone sulfate on the kainate-induced current in cultured chick spinal cord neurons

The effect of the neurosteroid pregnenolone sulfate on the kainate receptor-mediated response was studied in cultured chick spinal cord neurons using the whole-cell voltage-clamp recording technique. Pregnenolone sulfate rapidly and reversibly inhibits the kainate-induced current in a dose-dependent manner, with an EC50 of 67 microM and maximal inhibition of 38%. Inhibition by pregnenolone sulfate of the kainate response is not attenuated by increasing concentrations of kainate, suggesting that the blocking action of pregnenolone sulfate is non-competitive. Antagonism of the kainate response by pregnenolone sulfate is neither agonist- nor voltage-dependent, indicating that pregnenolone sulfate does not act as an open-channel blocker. Furthermore, our results demonstrate that pregnenolone sulfate and 1-(4-aminophenyl)-4-methyl-7,8-methylenedioxy-5H-2,3-benzodiazepine (GYKI 52466; a potent non-competitive kainate antagonist) do not act through a common site.

3 alpha-Hydroxy-5 beta-pregnan-20-one sulfate: a negative modulator of the NMDA-induced current in cultured neurons

We have shown previously that the neurosteroid pregnenolone sulfate acts as a positive allosteric modulator at the N-methyl-D-aspartate (NMDA) receptor while inhibiting the kainate, the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA), the glycine, and the gamma-aminobutyric acid (GABA) responses of chick spinal cord neurons. Here, we report that 3 alpha-hydroxy-5 beta-pregnan-20-one sulfate (5 beta 3 alpha S), a sulfated form of naturally occurring 5 beta 3 alpha, inhibits both the NMDA and the non-NMDA receptor-mediated responses as measured by whole cell voltage clamp recordings. 100 microM 5 beta 3 alpha S rapidly and reversibly inhibits the response to 30 microM NMDA by 66%, 50 microM kainate by 37%, and 25 microM AMPA by 29%. Application of 50 microM nonsulfated 5 beta 3 alpha does not produce any significant effect on the NMDA response, demonstrating that the sulfate moiety is important for the effect of 5 beta 3 alpha S on the NMDA response. The effect of 5 beta 3 alpha S on the NMDA response is concentration dependent, with an EC50 of 62 microM. 5 beta 3 alpha S reduces the maximum NMDA response with little effect on the NMDA EC50, indicating that antagonism of the NMDA response by 5 beta 3 alpha S is noncompetitive. The fact that 5 beta 3 alpha S inhibition of the NMDA response is neither agonist nor voltage dependent demonstrates that 5 beta 3 alpha S does not act as an open channel blocker. Furthermore, inhibition of the NMDA response by 5 beta 3 alpha S is not reduced by the addition of a maximal concentration (10 microM) of glycine, indicating that 5 beta 3 alpha S does not act via the glycine recognition site. The inhibitory action of 5 beta 3 alpha S on the NMDA and non-NMDA receptors may provide a basis for inhibiting glutamate receptor-induced seizures and excitotoxic cell death.

Dual activation of GABAA and glycine receptors by beta-alanine: inverse modulation by progesterone and 5 alpha-pregnan-3 alpha-ol-20-one

The differential sensitivity of the glycine and GABAA receptors to modulation by progesterone and 5 alpha-pregnan-3 alpha-ol-20-one (5 alpha 3 alpha) was used to determine whether beta-alanine acts through its own receptor, or through the glycine and/or GABAA receptor(s). The response to beta-alanine resembles the glycine response as it is inhibited by strychnine (a competitive glycine antagonist) or progesterone (a negative modulator of the glycine response). Significantly, the response to beta-alanine also resembles the GABA response in that it is inhibited by 2-(carboxy-3'-propyl)-3-amino-6-paramethoxy-phenylpyridazinium+ ++ bromide (SR-95531; a competitive GABA antagonist) and potentiated by 5 alpha 3 alpha (a positive modulator of the GABA response). The efficacy of beta-alanine at the GABAA receptor is comparable to that of GABA. Similarly, the efficacy of beta-alanine at the glycine receptor is comparable to that of glycine. The greater potency of beta-alanine at the glycine receptor indicates that, if beta-alanine is a neurotransmitter, its effects are more likely to be mediated by glycine receptors than by GABAA receptors. However, activation of the GABAA receptor by beta-alanine may become important in the presence of steroid modulators such as progesterone or 5 alpha 3 alpha.

An early outward transient K+ current that depends on a preceding Na+ current and is enhanced by insulin

A whole-cell early transient outward current occurs in rat myoballs if and only if there is an immediately preceding current of large amplitude through the voltage-gated, tetrodotoxin-inhibitable Na+ channel. This early outward transient is a K+ current, designated IK(Na+). Under the conditions in which IK(Na+) appears, simultaneous measurement of voltage and current, under voltage clamp, demonstrates that there is transient voltage escape to depolarized levels, peaking at about the time of peak inward Na+ current and resembling an action potential. IK(Na+) was never seen in the absence of this breach of the voltage clamp, suggesting that IK(Na+) might be an artefact due to transient depolarization from the clamp. However, when the voltage escape was mimicked by voltage commands under conditions in which the Na+ channel was not activated, there was no IK(Na). Insulin increased or produced IK(Na+) even though insulin had no effect on INa or on the delayed rectifier K+ current or on the escape from voltage clamp. It is concluded that there is a population of rat myoballs in which there is an early outward K+ current that requires an immediately preceding current through the voltage-gated, tetrodotoxin-inhibitable Na+ channel and is enhanced by insulin.

Transgenic turf-type tall fescue (Festuca amndinacea Schreb.) plants regenerated from protoplasts

To improve turfgrasses using genetic engineering, we have developed a transformation system in turf-type tall fescue, one of the most important turfgrass species. Embryogenic cell cultures were established after callus induction from embryos of mature seed. The agarose-bead method with nurse cells was used to culture protoplasts and plants were regenerated from protoplasts of tall fescue cultured cells. To develop transgenic tall fescue plants, the hygromycin resistance gene and the β-glucuronidase gene were introduced into the tall fescue protoplasts by electroporation. A high concentration (200 mg/l) of hygromycin was required to select transformed cells because of the high level of endogenous resistance to the antibiotic in tall fescue. Most of the transformed cells exhibited GUS activity and several plants were regenerated from these cells. The presence of introduced genes was confirmed by Southern blot hybridization of PCR amplified DNA from transgenic plants.

Pregnenolone sulfate: a positive allosteric modulator at the N-methyl-D-aspartate receptor

The N-methyl-D-aspartate (NMDA) receptor is believed to play a major role in learning and in excitotoxic neuronal damage associated with stroke and epilepsy. Pregnenolone sulfate, a neurosteroid, specifically enhances NMDA-gated currents in spinal cord neurons, while inhibiting receptors for the inhibitory amino acids glycine and gamma-aminobutyric acid, as well as non-NMDA glutamate receptors. This observation is consistent with the hypothesis that neurosteroids such as pregnenolone sulfate are involved in regulating the balance between excitation and inhibition in the central nervous system.

Venom constituents of Notechis scutatus scutatus (Australian tiger snake) from differing geographic regions

Column chromatography and polyacrylamide gel electrophoresis of Notechis scutatus scutatus venom showed that the venoms from different geographical locations had variations in their constituents. The venom collected from South Australia region contained both notexin and notechis II-5. The relative quantity of notechis II-5 was about three times that of notexin. On the other hand, the venom from Victoria region contained large amounts of notexin, but lacked notechis II-5. Instead, an unknown nontoxic protein, designated as notechis II-5b, exhibiting weak phospholipase A2 activity appeared in the position of notechis II-5 elution. This protein had an N-terminal sequence of N-L-I-Q-L-S-N-M-I-K-C-A-I-P-G-S-Q-P-L-F, sharing 45% homology with notexin and notechis II-5 and 60% homology with notechis II-1. The antibodies raised against Trp-modified notexin inhibited the enzymatic activities of notexin and notechis II-5 by 88 and 68%, respectively. However, the affinity of notexin for the antibodies was nine-fold greater than that of notechis II-5. This result is contrary to the previous finding (Mollier et al., FEBS Lett. 250, 479-482, 1989) in which notexin and notechis II-5 had similar binding affinities for antibodies raised against native notexin. This observation suggests that the antibodies prepared in this study could differentiate between isoforms of notexin.

Inverse modulation of gamma-aminobutyric acid- and glycine-induced currents by progesterone

The ability of certain synthetic and endogenous steroids to modulate neuronal responses to gamma-aminobutyric acid (GABA) is well documented, but little is known of the effect of steroids on glycine responses. We show here that in voltage-clamped neurons progesterone (10-100 microM) itself enhances GABA-induced chloride currents but, surprisingly, antagonizes those induced by glycine. Some, but not all, progesterone metabolites also display these effects. The effects of progesterone on GABA and glycine responses are dose dependent, with EC50 values of 26 and 16 microM and maxima of +156 and -60%, respectively. Progesterone and its reduced metabolite 5 alpha-pregnan-3 alpha-ol-20-one potentiate GABA responses by acting through a common site. The site through which progesterone acts to inhibit glycine responses is distinct from the strychnine and glycine binding sites. These results not only provide an important distinction between chloride-mediated GABA and glycine responses but also suggest that endogenous progesterone or its metabolites may differentially modulate the inhibitory actions of these two neurotransmitters.

Calcium currents in rat myoballs and their inhibition by insulin

Two Ca2+ currents were found in myoballs prepared from primary culture of hindlimb muscles from rat embryos. One whole cell current, not described previously, was early, fast, and transient. It depended on the presence of Na+ in the bathing solution and was blocked by tetrodotoxin. Despite this behavior suggesting that it might be via a Na+ channel, its reversal potential exceeded 80 mV compared to 46 mV for the Na+ equilibrium potential. It was increased by increased Ca2+ concentration in the bathing solution and eliminated by Co2+ and by diltiazem. The other Ca2+ current resembled the slow inward Ca2+ current ICa(si), described in other cell types. Insulin decreased both Ca2+ currents; even at 64 pM insulin reduced ICa(si). When outward K+ currents were prevented, the myoball action potential was altered greatly, owing to the unopposed effect of ICa(si). Its duration was on the order of seconds. Insulin, in a concentration-dependent manner, beginning at 60 pM, reduced the duration of this action potential more effectively than nimodipine. This is the most sensitive response to insulin observed in skeletal muscle.

Insulin depolarization of skeletal muscle in absence of external Na+

Three mechanisms have been proposed by which insulin might increase the electrical potential difference across the cell membrane of some of its main target cells: stimulation of an electrogenic pump; increased permeability to K+ (PK); and decreased ratio of permeability to Na+ (PNa) compared to PK, with an absolute decrease in permeability to both ions. Our laboratory has reported that insulin-induced hyperpolarization (IIH) of rat skeletal muscle is not due to stimulation of a ouabain-inhibitable pump and that insulin decreases 42K efflux, apparently eliminating the first two candidate mechanisms. If the remaining hypothesis is correct, when Na+ is removed from the bathing solution, insulin should depolarize, not hyperpolarize. It did. With Tris or N-methyl-D-glucamine substituted for Na+, insulin depolarized by approximately 3 mV. Ouabain had no effect. PNa decreased by greater than 90%; PK was reduced by less than 40%. The main component of the immediate mechanism of IIH is the near elimination of PNa. Furthermore, when a poorly permeable cation was substituted for Na+, muscles hyperpolarized in the absence of insulin. This gave us an opportunity to test the hypothesis that hyperpolarization is a link in the insulin-transduction chain. Consistent with this hypothesis, rat muscles hyperpolarized in this manner in the absence of insulin took up more glucose than paired controls in normal Na+ solution.

Localization of mitochondria in plant cells by vital staining with rhodamine 123

The positively-charged fluorescent dye rhodamine 123 (r-123) specifically stains mitochondria in living plant protoplasts, suspensionculture cells, and root hairs. This dye functions as a vital stain and permits visualization of the localization, distribution and movement of the mitochondria. Dehydration of root hairs caused mitochondria to aggregate into clumps. Mitochondria were either homogenous or heterogeneous and were frequently seen to accumulate in the perinuclear regions of suspension-culture cells but not in those of protoplasts or root-hair cells. Dinitrophenol and high concentrations of ethyleneglycol-bis(β-aminoethyl ether)-N,N,N',N'-tetraacetic acid and KCl immediately eliminated fluorescence in r-123-stained mitochondria whereas ionomycin enhanced it. Treatment of seedlings with r-123 resulted in differential brightness of fluorescence in different tissues. Meristematic tissues, such as root and shoot tips, exhibited the brightest fluorescence. The cytotoxicity of r-123 in both germinating seedlings and suspension-culture cells was low. The specificity, sensitivity and low toxicity of r-123 should make it a useful tool in experiments designed to examine agents and conditions which affect the location, the physiological status or the viability of mitochondria.

Changes in protein and amino acid content during anther development in fertile and cytoplasmic male sterile Petunia

Development of anthers in cytoplasmic male sterile (CMS) Petunia diverges from the normal sequence of events early in meiosis. Quantitative and qualitative changes in morphology, proteins and free amino acid contents correlate with this divergence. In anthers of the fertile line (5719), total protein content increases, and SDS-PAGE protein patterns change as the anthers mature. Enhanced levels of three polypeptides with molecular weights of 64,000, 63,000 and 45,000 daltons characterize premeiosis in fertile anthers. Protein levels and patterns from anthers of the CMS line (5707) show little alteration during anther development. Protein synthesis seems to be at least partially blocked in the CMS microspore. The 63,000 and 45,000 dalton proteins are not present, and the absence of any unique protein(s) in the CMS line argues against a virus as the causal agent of CMS in Petunia. Analysis of free amino acids from anthers of the fertile line shows levels of proline and pipecolic acid 2-3 and 10-20 fold higher, respectively, than in the CMS line. The amino acids incorporated into proteins show no such differences; analysis of protein hydrolysates shows similar levels of each amino acid in both fertile and CMS lines at every developmental stage examined.

Proteolytic activity in anther extracts of fertile and cytoplasmic male sterile petunia

Proteolytic activity is compared in anther extracts from Petunia parodii fertile and cytoplasmic male sterile lines. It is characterized relative to developmental stage of the anthers, effect of variable incubation times, pH of isolation buffers, and degradation of marker proteins. In fertile anthers, proteolytic activity increases at the end of microsporogenesis and peaks early in microgametogenesis. Degradation is most severe in extracts of fertile anthers and in high molecular weight proteins and reaches its maximum within 20 minutes. Degradation of marker proteins is greatest at pH 5.6 to 8.0 in fertile anther extracts and is eliminated under strong acid conditions (pH 2.8 to 4.0) in both fertile and cytoplasmic male sterile anther extracts. Marker proteins degrade more severely in extracts of fertile anthers; however, the order of substrate sensitivity-myosin > phosphorylase b > bovine serum albumin and ovalbumin > beta-galactosidase-is the same in extracts from fertile and cytoplasmic male sterile anthers.

Insulin stimulation of an electrogenic pump at high extracellular potassium concentration

There is no agreement about the immediate mechanism by which insulin hyperpolarizes skeletal muscle, adipocytes, and myocardium. Of three candidates, one has been eliminated; the hyperpolarization is not secondary to an increase in intracellular [K]. There are reports that insulin hyperpolarizes by increasing relative permeability to K compared with that to Na ions, and other reports that insulin stimulates an ouabain-sensitive electrogenic Na-K exchange pump. Our evidence has been interpreted to support the former and deny the latter, when rat skeletal muscle is bathed at normal [K]. Crucial evidence for the latter has not been reported: insulin hyperpolarizes to a potential more negative than the K equilibrium potential. We now report that when rat caudofemoralis muscle is incubated with insulin at normal extracellular [K], then depolarized by increasing extracellular [K] to 38.4 mM, by equimolar substitution of KCl for NaCl, there is hyperpolarization compared with potentials of muscles treated similarly with respect to [K] but without insulin. Under these circumstances, the membrane potential in the presence of insulin is more negative than the new K equilibrium potential, and, in contrast to our previous experience with muscles bathed only in normal [K], the hyperpolarization in high [K] is reduced or eliminated by ouabain.

Insulin action on membrane potential and glucose uptake: effects of high potassium

These experiments were designed to test the hypothesis that insulin-induced hyperpolarization is a link in the chain of events leading to stimulation of glucose transport. External potassium concentration, [K+]o, was increased by equimolar substitution of KCl for NaCl, a method known to cause cell swelling, and by substitution of [K+]o for [Na+]o with maintenance of constant [K+]o X [Cl-]o product, a method that does not cause cell swelling. When there was constant KCl product, even at 76.8 meq [K+]o insulin continued to hyperpolarize, although by only approximately 44% as much as in normal [K+]o, and insulin-stimulated 2-deoxyglucose uptake was only approximately 60% of that at normal [K+]o. With equimolar substitution of KCl for NaCl: electrical potential difference across cell membranes of surface fibers of rat caudofemoralis muscle decreased with logarithm [K+]o, in the presence or absence of insulin. Insulin-induced hyperpolarization decreased as [K+]o increased and disappeared at 36 mM [K+]o. The amount of insulin bound to its receptors in 1 h was not affected by [K+]o over the range studied. Insulin effects on membrane potential and on 2-deoxyglucose uptake, as both were altered by [K+]o, correlated well. As the probe moved in depth through the first six fibers there was stepwise decrease in depolarization in high [K+]o in the absence of insulin. Insulin hyperpolarized the deepest of these fibers, even when it did not hyperpolarize the outermost. The decrease in insulin-induced hyperpolarization as [K+]o increases is consistent with the hypothesis that insulin hyperpolarizes by decreasing the ratio PNa/PK.

Extraction of proteins for sodium dodecyl sulfate-polyacrylamide gel electrophoresis from protease-rich plant tissues

A method of extracting proteins for sodium dodecyl sulfate-polyacrylamide gel electrophoresis from plant tissues with high protease activity was described. It resolved protein bands in high-molecular-weight regions of the gel and replaced commonly used procedures which showed severe degradation of proteins, even in the presence of protease inhibitors.

Selective stimulation of the synthesis of an 80,000-dalton protein by calcium ionophores

Brief exposure of cultured chicken pectoralis muscle cells to ionomycin or A23187 selectively increases the rate of incorporation of [35S]methionine into an 80,000-dalton protein was also observed upon cell-free translation of poly(A)-enriched RNA isolated from ionomycin-treated, as compared with control, cultures. These observations suggest that ionomycin selectively increases the cellular concentration of mRNA, which codes for the 80,000-dalton protein. The effect is probably mediated through an increase in cytoplasmic [Ca2+] caused by the ionophore. A similar effect of ionomycin was observed in cultured fibroblasts, HeLa cells, mouse LSP cells, and monkey kidney CV1 cells.

The effect of Ca2+ ionophores upon the synthesis of proteins in cultured skeletal muscle

The influence of the Ca2+ ionophores, ionomycin and A23187 upon the incorporation of [35S]methionine into proteins of cultured chicken pectoralis muscle was studied during differentiation of myoblasts into multinucleated myotubes. Fusion was reversibly arrested by growing cells in low-calcium media from the time of plating. Exposure of normal and fusion blocked cultures to 10-6-10-5 M ionomycin or A23187 for 2-6 h on the second to fourth day of growth, resulted in a selective increase in the incorporation of [35S]methionine into two proteins of about 100 000 and 80 000 dalton. When 10-5 M ionomycin or A23187 were added to older cultures, all large myotubes contracted and detached from the plate. Only the adhering myoblasts and small myotubes incorporated [35s[methionine into the muscle proteins and showed increased incorporation of label into 100 000 and 80 000 proteins. After ionophore pulse, the adhering cells retained the ability to differentiate and accumulate myosin. The effect of Ca2+ ionophores upon the rate of protein synthesis is presumably related to increased influx of extracellular Ca2+ with a rise in the Ca2+ concentration of the cytoplasm. We conclude that Ca2+ sensitive mechanisms may regulate the synthesis of a select group of muscle proteins.

Inhibition of ribonucleic acid accumulation in mouse L cells infected with vesicular stomatitis virus requires viral ribonucleic acid transcription

The accumulation of ribonucleic acid (RNA) in mouse L-929 cells infected with temperature-sensitive mutants of vesicular stomatitis virus or ultraviolet- (UV-) irradiated virus was studied. At the permissive temperature (30 degrees C infection by all mutants resulted in an inhibition of cellular RNA accumulation. At the nonpermissive temperature (40 degrees C) mutants G114 (I) and G22 (II) failed to inhibit RNA accumulation, but mutants G11 (I), O52 (II), G31 (III), G33 (III), G41 (IV), W10 (IV), O45 (V), and O110 (V) were still active in this respect. In most cases the accumulation of 28S and 18S mature rRNA was inhibited to a greater extent than the synthesis of the 45S rRNA precursor. UV irradiation of wild type virus considerably reduced its capacity to inhibit cellular RNA synthesis. The target size for inactivation of this capacity of the virus was approximately 17% of the viral genome or that corresponding to the N gene. These results indicate that the virion proteins themselves are incapable of inhibiting cellular RNA synthesis and that transcription of approximately 17% of the genome is required. Expression of RNA synthesis inhibition also requires some function of virion NS protein in addition to its transcriptase activity.

Inhibition of synthesis of ribosomal proteins and of ribosome assembly after infection of L cells with vesicular stomatitis virus

The effect of infection of mouse L cells by vesicular stomatitis virus on the synthesis of ribosomal proteins was investigated using two-dimensional polyacrylamide gel electrophoresis to analyze the ribosomal proteins. It was found that the synthesis of nearly all of the cytoplasmic ribosomal proteins examined was inhibited by infection and mostly to the same extent. Analysis of the ribosomal proteins extracted from intact ribosomes indicated that infection also reduces the incorporation of all the ribosomal proteins tested into assembled ribosomes. The inhibition of ribosome assembly was greater than the inhibition of synthesis of ribosomal proteins, suggesting that some other factor was also limiting the assembly of ribosomes. As shown in this report, infection also inhibits ribosomal RNA production. Thus, the decreased assembly of ribosomes in infected cells probably results from the inhibition of synthesis of both ribosomal proteins and ribosomal RNA.