Family Functioning and Community Resilience During the COVID-19 Lockdown Period in Turkey

The COVID-19 outbreak has left families with many adverse effects that can disrupt functioning. The aim of this study was to evaluate the associations between family functioning and community resilience during the COVID-19 lockdown. An online survey was conducted with community-dwelling adult people (n= 411) based on quantitative descriptive-correlational research. According to the results, families show dysfunctional trends during the COVID-19 outbreak (%56), especially in affective involvement, problem-solving, and behavior control categories. Community resilience was positively associated with family functioning. Also, income dissatisfaction, use of social services, and social trust were determined as predictors of family functioning in the COVID-19 lockdown. Further research and social work practices in public health to address the family system as a whole should be evaluated and interventions aiming at community resilience should be designed to increase families' functioning during the pandemics.

Workplace Age Discrimination and Affecting Factors in Turkey: A Validation Study

Objective: This study was undertaken to adapt Workplace Age Discrimination Scale (WADS) to Turkish. Methods: The sample of the study was composed of 465 volunteered women and men (18+ years) who had an active working life. Corrected item total correlation and Cronbach's alpha internal consistency coefficient were calculated for reliability of WADS. High order confirmatory factor analysis was performed to test the theoretical suitability and construct validity for Turkish context. Results: In this study, WADS has one factor construction. Cronbach's Alpha Reliability Coefficient was found as 0.904 for WADS. Predictors of workplace age discrimination in Turkish population were determined as age, hierarchical structure, job satisfaction, and income satisfaction Conclusion: These results showed that the Turkish version of WADS may be used as a valid and reliable tool in determining workplace age discrimination and in other relevant research. Exploring the validity and reliability of the scale should be repeated in groups who have different socio-demographics and health situations.

The impact of catheter ablation for patients with asymptomatic atrial fibrillation: subanalysis of kansai plus atrial fibrillation (kpaf) registry

Background

Catheter ablation (CA) of atrial fibrillation (AF) for symptomatic patients improves the quality of life and prognosis of patients with heart failure. However, the impact of CA for asymptomatic patients is still controversial.

Purpose

We aimed to investigate the clinical outcomes of CA of AF for asymptomatic patients compared to those for symptomatic patients.

Methods

A total of 5,013 patients from the Kansai Plus Atrial Fibrillation (KPAF) Registry who underwent CA were screened. The patients were divided into three groups by type of AF; paroxysmal (PAF), persistent (PEAF) and long standing (LSAF) and the patients in each type of AF were divided into two groups: asymptomatic and symptomatic. The primary endpoint was recurrent supraventricular tachyarrhythmias lasting for more than 30 seconds during follow-up 4 years after CA. The secondary endpoint was a composite of cardiovascular, cerebral, and gastrointestinal events during follow-up 4 years after CA. The incidence of complications related to CA between asymptomatic and symptomatic patients was also evaluated. Kaplan–Meier analysis was employed to estimate the primary and secondary endpoints. The statistical differences in primary and secondary endpoints between asymptomatic and symptomatic patients were evaluated using a log–rank test. The impact of symptom due to AF on the primary and secondary endpoint was evaluated using a Cox hazard analysis. The difference in incidence of complications between asymptomatic and symptomatic patients was evaluated using a chi–square test.

Results

In this study population, PAF was the most frequent at 64.4%, followed by PEAF (22.7%) and LSAF (13.0%). There were some significant differences in the baseline characteristics between asymptomatic and symptomatic patients in each type of AF. The proportion of male was significantly higher in asymptomatic patients than symptomatic patients in PAF (81.2% versus 67.2%, p<0.001) and PEAF (86.4% versus 74.3%, p<0.001). Left atrial diameter was larger in asymptomatic patients than symptomatic patients only in PAF (40±6mm versus 38±6mm, p<0.001). In all types of AF, there was no significant difference in primary endpoint between asymptomatic and symptomatic patients as follows: 37.5% versus 40.6% (p=0.6) in PAF, 45.2% versus 55.1% (p=0.09) in PEAF and 59.3% versus 63.6% (p=1.0) in LSAF. There was also no significant difference in secondary endpoint between asymptomatic and symptomatic patients: 7.1% versus 6.8% (p=0.7) in PAF, 5.4% versus 8.7% (p=0.3) in PEAF and 4.4% versus 5.1% (p=0.5) in LSAF. In a Cox hazard analysis, the symptom did not affect both of the primary and secondary endpoints in each type of AF. In regard to the incidence of complications related to CA, there was no significant difference between asymptomatic and symptomatic patients in each type of AF.

Conclusion

CA of AF for asymptomatic patients can be safe and can lead to equivalent outcomes as well as symptomatic patients.

Funding Acknowledgement

Type of funding source: None

The Relationship between Anxiety Levels and Perceived Social Support during the Pandemic of COVID-19 in Turkey

The uncertainty which is threatening and stressful prevents a person's perception of control and leads to maladaptive psychological reactions such as anxiety. We aimed to define the relationship between the state/trait anxiety levels and perceived social support in the COVID-19 pandemic as a global crisis and stressor. Our main hypothesis was that perceived social support would negatively affect the levels of anxiety. A cross-sectional community-based study was carried out using the relational screening model. The data were collected between March 20 and April 15, 2020, by using an online survey (N = 630). Anxiety levels of individuals, particularly the state anxiety were high during the pandemic. Also, perceived social support and state/trait anxiety levels were analyzed for various variable categories. Anxiety levels decreased significantly when perceived social support increased. Perceived social support as a determinant of state and trait anxiety should be the focus of social work practices in this period.

The prevalence and associated risk factors of elder abuse among older people applied to the family health center in the rural district of Turkey

In this study, face-to-face interviews were conducted with older people who applied to the family health center (N = 152) in the traditional rural district of Turkey. Although the prevalence rate was 23%, the mean value of "Characteristics of the elder that make him or her vulnerable to abuse" subscale (X̄ = .37) was highest among other subscales. The mean values for "Characteristics of potentially abusive situations" (X̄ = .06) and "Overt violation of personal rights and direct abuse" (X̄ = .05) were quite low. The majority of the elder abuse prevalence was composed of participants who were vulnerable to elder abuse. The rural area makes older individuals vulnerable to abuse. Also, risk factors associated with elder abuse in rural areas were interaction with family (p = .000), interaction with neighbors/friends (p = .001), chronic diseases (p = .002), psychiatric diseases (p = .007), gender and marital status (p = .008), and additional income (p = .028), respectively. The only predictor of elder abuse in rural areas was family interaction. There was a significant negative relationship between rural elder abuse and family interaction (T= -4.239, p < .001).

P642What is the most important residual risk after achievement of appropriate low-density lipoprotein cholesterol lowering therapy in secondary prevention of Japanese patients?

Background

In secondary prevention of coronary artery disease, target value of low-density lipoprotein cholesterol (LDL-C) <100mg/dL with using statins is recommended as standard therapy in Japanese guideline. However, impact of residual risks after achievement of standard LDL-C lowering therapy was not fully examined. Furthermore, there is little information whether more strict management of LDL-C lowering is effective to prevent long-term cardiovascular events than standard management.

Purpose

The purpose of this study was to evaluate the relationship between residual risks after achievement of standard LDL-C lowering therapy and long-term coronary events in secondary prevention of Japanese patients.

Methods

From January 2007 to August 2018, 333 patients with previous percutaneous coronary intervention underwent late coronary angiography to examine recurrence of cardiac ischemia beyond the early phase of restenosis. We defined appropriate LDL-C lowering therapy as achieved LDL-C <100mg/dL with using statins. Patients whose achieved LDL-C was <100mg/dL with using statins were classified as Appropriate-group (n=139), and patients who were not using statins or whose achieved LDL-C was ≥100mg/dL were classified as Inappropriate-group (n=194). Endpoints of the study were recurrence of cardiac ischemia as acute coronary syndrome (recurrence-ACS) and any late coronary revascularization.

Results

During average 7.1 years follow-up, 195 patients (59%) underwent any late coronary revascularization. In 91 of those patients, clinical presentation of recurrence-ACS was observed. Kaplan-Meier curve analysis revealed that the incidence of recurrence-ACS and any late coronary revascularization were significantly lower in Appropriate-group than in Inappropriate-group (p=0.017 and p<0.001, respectively). In Appropriate-group, recurrence-ACS was significantly lower in patients with achieved LDL-C <70mg/dL than in those with LDL-C 70 to <100mg/dL (p=0.042), however, any late revascularization was not different between the two groups. On the other hand, in Inappropriate-group, recurrence-ACS was significantly lower in patients with using statins than in those without using statins (p=0.038), and any late revascularization was less frequent in patients with achieved LDL-C <100mg/dL than in those with LDL-C ≥100mg/dL (p=0.035). Moreover, multivariate analysis identified that only LDL-C was an independent predictor of recurrence-ACS in Appropriate-group (HR: 1.047, p=0.006), in contrast, LDL-C (HR: 1.008, p=0.020), using statins (HR: 0.555, p=0.034) and triglyceride (HR: 1.003, p=0.038) were independent predictors of recurrence-ACS in Inappropriate-group.

Conclusions

LDL-C was the most important residual risk of recurrence-ACS even after recommended standard therapy has been achieved. More strict management of LDL-C targeting to <70mg/dL should be considered in secondary prevention of Japanese patients.

Large energy storage efficiency of the dielectric layer of graphene nanocapacitors

Electric capacitors are commonly used in electronic circuits for the short-term storage of small amounts of energy. It is desirable however to use capacitors to store much larger energy amounts to replace rechargeable batteries. Unfortunately existing capacitors cannot store sufficient energy to be able to replace common electrochemical energy storage systems. Here we examine the energy storage capabilities of graphene nanocapacitors, which are tri-layer devices involving an Al film, Al₂O₃ dielectric layer, and a single layer of carbon atoms, i.e., graphene. This is a purely electronic capacitor and therefore it can function in a wide temperature interval. The capacitor shows a high dielectric breakdown electric field strength, of the order of 1000 kV mm^-1 (i.e., 1 GV m^-1), which is much larger than the table value of the Al₂O₃ dielectric strength. The corresponding energy density is 10-100 times larger than the energy density of a common electrolytic capacitor. Moreover, we discover that the amount of charge stored in the dielectric layer can be equal or can even exceed the amount of charge stored on the capacitor plates. The dielectric discharge current follows a power-law time dependence. We suggest a model to explain this behavior.

Concurrent chaperone and protease activities of ClpAP and the requirement for the N-terminal ClpA ATP binding site for chaperone activity

ClpA, a member of the Clp/Hsp100 family of ATPases, is both an ATP-dependent molecular chaperone and the regulatory component of ClpAP protease. We demonstrate that chaperone and protease activities occur concurrently in ClpAP complexes during a single round of RepA binding to ClpAP and ATP-dependent release. This result was substantiated with a ClpA mutant, ClpA(K220V), carrying an amino acid substitution in the N-terminal ATP binding site. ClpA(K220V) is unable to activate RepA, but the presence of ClpP or chemically inactivated ClpP restores its ability to activate RepA. The presence of ClpP simultaneously facilitates degradation of RepA. ClpP must remain bound to ClpA(K220V) for these effects, indicating that both chaperone and proteolytic activities of the mutant complex occur concurrently. ClpA(K220V) itself is able to form stable complexes with RepA in the presence of a poorly hydrolyzed ATP analog, adenosine 5'-O-(thiotriphosphate), and to release RepA upon exchange of adenosine 5'-O-(thiotriphosphate) with ATP. However, the released RepA is inactive in DNA binding, indicating that the N-terminal ATP binding site is essential for the chaperone activity of ClpA. Taken together, these results suggest that substrates bound to the complex of the proteolytic and ATPase components can be partitioned between release/reactivation and translocation/degradation.

The essential Gcd10p-Gcd14p nuclear complex is required for 1-methyladenosine modification and maturation of initiator methionyl-tRNA

Gcd10p and Gcd14p are essential proteins required for the initiation of protein synthesis and translational repression of GCN4 mRNA. The phenotypes of gcd10 mutants were suppressed by high-copy-number IMT genes, encoding initiator methionyl tRNA (tRNAiMet), or LHP1, encoding the yeast homolog of the human La autoantigen. The gcd10-504 mutation led to a reduction in steady-state levels of mature tRNAiMet, attributable to increased turnover rather than decreased synthesis of pre-tRNAiMet. Remarkably, the lethality of a GCD10 deletion was suppressed by high-copy-number IMT4, indicating that its role in expression of mature tRNAiMet is the essential function of Gcd10p. A gcd14-2 mutant also showed reduced amounts of mature tRNAiMet, but in addition, displayed a defect in pre-tRNAiMet processing. Gcd10p and Gcd14p were found to be subunits of a protein complex with prominent nuclear localization, suggesting a direct role in tRNAiMet maturation. The chromatographic behavior of elongator and initiator tRNAMet on a RPC-5 column indicated that both species are altered structurally in gcd10Delta cells, and analysis of base modifications revealed that 1-methyladenosine (m1A) is undetectable in gcd10Delta tRNA. Interestingly, gcd10 and gcd14 mutations had no effect on processing or accumulation of elongator tRNAMet, which also contains m1A at position 58, suggesting a unique requirement for this base modification in initiator maturation.

A site in the dinucleotide-fold domain contributes to the accuracy of tRNA selection by Escherichia coli methionyl-tRNA synthetase

Interactions of specific amino acid residues of the carboxyl-terminal domain of MetRS with the CAU anticodon of tRNAMet assure accurate and efficient aminoacylation. The substitution of one such residue, Trp461 by Phe, impairs the binding of cognate tRNA, but enhances the binding of noncognate tRNAs, particularly those containing G at the wobble position. However, the enhanced binding of noncognate tRNAs is not accompanied by the increased aminoacylation of these tRNAs. A genetic screening procedure was designed to isolate methionyl-tRNA synthetase mutants which were able to aminoacylate a GGU (threonine) anticodon derivative of tRNAfMet. One such mutant, obtained from W461F MetRS, had an Ile29 to Thr substitution in helix A located in the amino-terminal dinucleotide-fold domain that forms the site for amino acid activation. Analysis of the catalytic properties of the I29T/W461F enzyme indicates that the mutation in helix A of the dinucleotide-fold domain affects kcat for aminoacylation of tRNAs having a GGU threonine anticodon. Interactions with cognate tRNAfMet (CAU), as well as with methionine and ATP were not affected by the Ile29 to Thr substitution. We conclude that the I29T substitution leads to a slight adjustment of the alignment of the CCA stem of noncognate tRNAs (GGU) in the catalytic domain of the enzyme, reflected in the increase in kcat, which also allows mischarging in vivo. A function of Ile29 is therefore to minimize the mischarging of tRNAThr (GGU) by methionyl-tRNA synthetase. The methods described here provide useful tools for examining the mechanisms of tRNA selection by aminoacyl-tRNA synthetases.

The role of the ClpA chaperone in proteolysis by ClpAP

ClpA, a member of the Clp/Hsp100 family of ATPases, is a molecular chaperone and, in combination with a proteolytic component ClpP, participates in ATP-dependent proteolysis. We investigated the role of ClpA in protein degradation by ClpAP by dissociating the reaction into several discrete steps. In the assembly step, ClpA-ClpP-substrate complexes assemble either by ClpA-substrate complexes interacting with ClpP or by ClpA-ClpP complexes interacting with substrate; ClpP in the absence of ClpA is unable to bind substrates. Assembly requires ATP binding but not hydrolysis. We discovered that ClpA translocates substrates from their binding sites on ClpA to ClpP. The translocation step specifically requires ATP; nonhydrolyzable ATP analogs are ineffective. Only proteins that are degraded by ClpAP are translocated. Characterization of the degradation step showed that substrates can be degraded in a single round of ClpA-ClpP-substrate binding followed by ATP hydrolysis. The products generated are indistinguishable from steady-state products. Taken together, our results suggest that ClpA, through its interaction with both the substrate and ClpP, acts as a gatekeeper, actively translocating specific substrates into the proteolytic chamber of ClpP where degradation occurs. As multicomponent ATP-dependent proteases are widespread in nature and share structural similarities, these findings may provide a general mechanism for regulation of substrate import into the proteolytic chamber.

Mechanism of protein remodeling by ClpA chaperone

ClpA, a newly discovered ATP-dependent molecular chaperone, remodels bacteriophage P1 RepA dimers into monomers, thereby activating the latent specific DNA binding activity of RepA. We investigated the mechanism of the chaperone activity of ClpA by dissociating the reaction into several steps and determining the role of nucleotide in each step. In the presence of ATP or a nonhydrolyzable ATP analog, the initial step is the self-assembly of ClpA and its association with inactive RepA dimers. ClpA-RepA complexes form rapidly and at 0 degrees C but are relatively unstable. The next step is the conversion of unstable ClpA-RepA complexes into stable complexes in a time- and temperature-dependent reaction. The transition to stable ClpA-RepA complexes requires binding of ATP, but not ATP hydrolysis, because nonhydrolyzable ATP analogs satisfy the nucleotide requirement. The stable complexes contain approximately 1 mol of RepA dimer per mol of ClpA hexamer and are committed to activating RepA. In the last step of the reaction, active RepA is released upon exchange of ATP with the nonhydrolyzable ATP analog and ATP hydrolysis. Importantly, we discovered that one cycle of RepA binding to ClpA followed by ATP-dependent release is sufficient to convert inactive RepA to its active form.

Effects of vasodilators guanethidine, nicardipine, nitroglycerin, and prostaglandin E1 on primary afferent nociceptors in humans

Although vasodilator agents have been used to alleviate the pain of complex regional pain syndromes, the precise mechanism of pain relief is not well known. In this study the effects of various kinds of vasodilators on primary afferent nociceptors were investigated by measuring the thermal pain threshold. Evaluated in the study were the effects of guanethidine (2 mg/mL), nicardipine (0.2 mg/mL). Nitroglycerin (0.3 mg/mL), and prostaglandin E1 (1 microgram/mL) on the cutaneous pain threshold and blood flow at 7-day intervals in six healthy volunteers. Each aliquot of 0.5 mL of the test vasodilator or lidocaine (10 mg/mL) and saline (control) were intradermally injected at three sites each on both forearms. The pricking-pain threshold and skin tissue blood flow were determined using a radiant heat-stimulating system and a laser-Doppler tissue-blood flowmeter, respectively. The pain threshold increased with lidocaine, guanethidine, and nicardipine; remained unchanged with Nitroglycerin; but decreased with prostaglandin E1. In contrast, the skin tissue blood flow increased by four to nine times with all vasodilators. These results indicate that the effect of vasodilators on primary afferent nociceptors is not related to the vasodilating effect and may not involve a common mechanism of action for pain relief in complex regional pain syndromes.

Differences in desensitization between human beta 1- and beta 2-adrenergic receptors stably expressed in transfected hamster cells

It is well-established that agonist-mediated desensitization of the beta 2-adrenergic receptor (beta 2AR) involves its phosphorylation by protein kinase A (PKA) and the beta AR kinase (beta ARK). The phosphorylated receptor is less efficient at mediating agonist stimulation of adenylyl cyclase activity. The result is an increase in the concentration of agonist required for half-maximal stimulation (EC50) and a reduction in maximal stimulation (Vmax). As less is known about desentization of the human beta 1 AR, we compared the desensitization pattern of human beta 1 AR and beta 2AR stably expressed in two different hamster cell lines: Chinese hamster ovary (CHO), and Chinese hamster fibroblast (CHW). Following agonist treatment, all of the cell lines exhibited an increase in EC50, and a reduction in Vmax was observed in CHO-beta 2 but not beta 1 cells. CHW-beta 1 cells were resistant to acute agonist-mediated reduction in Vmax compared to CHW-beta 2 cells. More prolonged agonist exposure produced a modest reduction in Vmax and this effect was more noticeable when the CHW cells expressed lower levels of beta 1AR. To explore the role of protein kinases in these effects, digitonin-permeabilized CHW cells were loaded either with heparin (a beta ARK inhibitor) or a peptide inhibitor of PKA and exposed to agonist. In both beta 2AR- and beta 1AR-expressing cells, heparin inhibited the reduction in Vmax and the PKA inhibitor blocked the increase in EC50. Finally, exposing CHW cells expressing either subtype to a permeable cyclic AMP derivative caused an increase in EC50 similar to that observed in agonist-treated cells, but without any reduction in maximal activity. Our data suggest that whereas PKA-mediated desensitization is not subtype-specific, human beta 1AR is more resistant to beta ARK-mediated desensitization compared to the human beta 2AR.

Analysis of acceptor stem base pairing on tRNA(Trp) aminoacylation and function in vivo

The role of acceptor stem base pairs in determining the identity of Escherichia coli tRNA(Trp) was examined by complementation of an E. coli strain containing a temperature-sensitive tRNA(Trp) gene (trpTts) and by monitoring aminoacylation levels in vivo. All derivatives of tRNA(Trp) containing substitutions at the first 3 base pairs in the acceptor stem complemented the trpTts mutation at the nonpermissive temperature (42 degrees C). However, three acceptor stem derivatives (tRNA(Trp)/C1.G72, tRNA(Trp)/C2.G71, and tRNA(Trp)/A3.U70) required overexpression for growth at 42 degrees C. Northern analysis of these derivatives following acid/urea gel electrophoresis showed no defects in tRNA aminoacylation at the nonpermissive temperature. Instead, these tRNAs appear to be defective in translation. This was suggested by the weak opal suppressor activities of the corresponding tRNA(UCATrp) derivatives. These results demonstrate that the three terminal acceptor stem base pairs do not contribute to the identity of tRNA(Trp). Substitution of the C1.A72 base pair in a methionine initiator tRNA containing the tryptophan anticodon and discriminator base (tRNA(CCAfMet)/G73) with A1.U72, the base pair found in tRNA(Trp), or G1.C72 resulted in the conversion of these tRNAs into tryptophan-inserting elongator tRNAs in vivo. However, changes to U1.A72 or C1.G72 in tRNA(CCAfMet)/G73 resulted in misaminoacylation and/or defects in translation. Our data indicate that the A1.U72 base pair is a context-dependent, negative identity element of tRNA(Trp).

Alterations in pain threshold and psychomotor response associated with subanaesthetic concentrations of inhalation anaesthetics in humans

We studied the effects of six inhalation anaesthetics at subanaesthetic concentrations of 0.2 MAC on pain threshold and psychomotor function in six healthy volunteers. When compared with 100% oxygen inhalation, nitrous oxide and methyoxyflurane significantly increased pain threshold as measured by a radiant heat algometer, and prolonged the response time to auditory stimuli. In contrast, halothane, enflurane, isoflurane and sevoflurane produced prolongation of the response time to auditory stimuli but did not influence pain perception. The pain threshold with nitrous oxide remained significantly increased 30 min after its discontinuation, while the response time returned to the preinhalation value. We conclude that nitrous oxide and methoxyflurane possess both analgesic and hypnotic actions but halothane, enflurane, isoflurane and sevoflurane do not have an analgesic action at subanaesthetic concentrations, and the analgesic action of nitrous oxide persists after its elimination.

Prolongation of canine epidural anesthesia by liposome encapsulation of lidocaine

The purpose of our study was to produce a long-acting lidocaine by using a liposome that would entrap the drug. Egg yolk phosphatidylcholine and cholesterol were used as liposome materials. After epidural administration, the pharmacodynamics and pharmacokinetics of liposomal and free lidocaine were studied in 20 dogs. Two percent liposomal or free lidocaine (3.0 mL) was injected into the lumbar epidural space. Nerve blocking effects were estimated by measuring somatosensory evoked potentials. Recovery time from the epidural block in the liposomal lidocaine group (170 +/- 49.5 min) was approximately three times longer than that in the free lidocaine group (61 +/- 18.1 min). The areas under the drug concentration-time curves (AUC0-infinity) and time to maximal concentration (Tmax) in the liposomal lidocaine group were significantly larger than those in the free lidocaine group. These results suggest that the prolongation of epidural blockade by liposomal lidocaine is caused by a slow release of the drug from liposomes. The present study suggests that liposomal lidocaine can be used as a long-acting local anesthetic.

Conversion of a methionine initiator tRNA into a tryptophan-inserting elongator tRNA in vivo

The role of the anticodon and discriminator base in aminoacylation of tRNAs with tryptophan has been explored using a recently developed in vivo assay based on initiation of protein synthesis by mischarged mutants of the Escherichia coli initiator tRNA. Substitution of the methionine anticodon CAU with the tryptophan anticodon CCA caused tRNA(fMet) to be aminoacylated with both methionine and tryptophan in vivo, as determined by analysis of the amino acids inserted by the mutant tRNA at the translational start site of a reporter protein containing a tryptophan initiation codon. Conversion of the discriminator base of tRNA(CCA)fMet from A73 to G73, the base present in tRNA(Trp), eliminated the in vivo methionine acceptor activity of the tRNA and resulted in complete charging with tryptophan. Single base changes in the anticodon of tRNA(CCA)fMet containing G73 from CCA to UCA, GCA, CAA, and CCG (changes underlined) essentially abolished tryptophan insertion, showing that all three anticodon bases specify the tryptophan identity of the tRNA. The important role of G73 in tryptophan identity was confirmed using mutants of an opal suppressor derivative of tRNA(Trp). Substitution of G73 with A73, C73, or U73 resulted in a large loss of the ability of the tRNA to suppress an opal stop codon in a reporter protein. Base pair substitutions at the first three positions of the acceptor stem of the suppressor tRNA caused 2-12-fold reductions in the efficiency of suppression without loss of specificity for aminoacylation of the tRNA with tryptophan.(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of bacterial collagenase on regeneration of severed rat sciatic nerves

Regeneration of peripheral nerve fibers is impeded by the formation of scar tissue at the site of injury. The possible beneficial effect of collagenase on nerve regeneration was studied using clinical, neurophysiological (evoked potentials) and histological (nerve fiber counts) methods. The sciatic nerves of rats were transected and the severed ends abutted and sewn together. In one series, the area about the lesion was covered with fibrin adhesive and infused with either isotonic saline (controls) or collagenase (treatment group). In the other series, the severed ends of the nerve were inserted into a silicone tube and separated by a collagen plug, which was infused with either saline or collagenase. Compared to the controls, the treated animals showed a significant improvement of clinical and neurophysiological parameters. After 3 months of observation, the collagen content of the transection site was reduced, and in the silicone series, the total number of myelinated axons 5 mm distal to the site of transection was increased, while the fiber diameter distribution was unchanged.

Genomic organization, nucleotide sequence, and cellular distribution of a Shaw-related potassium channel gene, Kv3.3, and mapping of Kv3.3 and Kv3.4 to human chromosomes 19 and 1

Genomic and cDNA clones encoding a novel Shaw-related potassium channel gene have been isolated from mice and humans. The mouse-Kv3.3 gene encodes a protein of 679 amino acids. Unlike the vertebrate Shaker-related genes that have intronless coding regions, mouse Kv3.3 is encoded by at least two exons separated by 3 kb of intervening sequence. The amino-terminal 212 amino acids are encoded by a single exon, and the hydrophobic core of the protein beginning at the S1 transmembrane segment is contained in a separate exon. Multiple Kv3.3-hybridizing transcripts are visible in the mouse brain, liver, thymus, and heart. Using probes derived from a human genomic clone containing the 3' exon of human Kv3.3 (KCNC3), we have localized the gene to human chromosome 19. The related gene, human Kv3.4 (KCNC4), was localized to human chromosome 1.

K+ current diversity is produced by an extended gene family conserved in Drosophila and mouse

The Drosophila Shaker gene on the X chromosome has three sister genes, Shal, Shab, and Shaw, which map to the second and third chromosomes. This extended gene family encodes voltage-gated potassium channels with widely varying kinetics (rate of macroscopic current activation and inactivation) and voltage sensitivity of steady-state inactivation. The differences in the currents of the various gene products are greater than the differences produced by alternative splicing of the Shaker gene. In Drosophila, the transient (A current) subtype of the potassium channel (Shaker and Shal) and the delayed-rectifier subtype (Shab and Shaw) are encoded by homologous genes, and there is more than one gene for each subtype of channel. Homologs of Shaker, Shal, Shab, and Shaw are present in mammals; each Drosophila potassium-channel gene may be represented as a multigene subfamily in mammals.