A study of neuropsychiatric manifestations in COVID-19 infection in inpatients and its long-term outcomes in Malaysia

INTRODUCTION

This study aimed to determine the prevalence and association between the severity of COVID-19 and short and long-term neuropsychiatric symptoms, as well as the risk factors for the development of these symptoms.

MATERIALS AND METHODS

A prospective observational study was conducted between 1st October 2021 till September 2022 in the state of Johor, Malaysia. 300 patients with confirmed SARS-CoV-2 infection were randomly selected and followed up for six months. Data were analysed by using Chi-square test, Fisher's Exact test, Paired t test and Multiple logistic regression.

RESULTS

The prevalence of short-term neuropsychiatric symptoms was 78%, with anosmia being the most prevalent symptom. Long-term symptoms were found in 22.75% of patients, with headache being the most prevalent (p= 0.001). COVID-19 Stage 2 and 3 infections were associated with a higher risk of short-term neuropsychiatric symptoms, OR for Stage 2 infection was 5.18 (95% CI: 1.48-16.97; p=0.009) and for Stage 3 infection was 4.52 (95% CI: 1.76-11.59; p=0.002). Complete vaccination was a significant predictor of longterm symptoms with adjusted OR 3.65 (95% CI 1.22-10.91; p=0.021).

CONCLUSION

This study demonstrated that neuropsychiatric symptoms were common among COVID-19 patients in Johor, Malaysia and the risk of these symptoms was associated with the severity of the infection. Additionally, complete vaccination does not completely protect against long-term neuropsychiatric deficits. This is crucial for continuous monitoring and addressing neuropsychiatric symptoms in COVID-19 survivors.

New Zealand and Australian MRI technologists' (radiographers) MRI safety knowledge and confidence levels

INTRODUCTION

The MRI technologist (radiographer) is at the frontline of MRI safety decision-making and has the primary responsibility to provide high quality, efficient and safe patient care in the MRI environment. As MRI technology advances and new safety issues emerge, this study aimed to provide a snapshot of the preparedness of MRI technologists in New Zealand (NZ) and Australia to practise confidently and safely.

METHOD

An online questionnaire, administered via Qualtrics and covering a range of MRI safety topics, was distributed in 2018 via the New Zealand MR Users Group, the MRI Australia-NZ Group Facebook, and relevant professional bodies.

RESULTS

A total of 312 MRI technologists attempted the questionnaire, with 246 surveys being fully completed. Of these, 61% (n = 149) were in Australia, 36% (n = 89) in NZ, and 3% (n = 8) from other countries. Findings indicated that current MRI education is preparing MRI technologists in NZ and Australia to practise safely. However, while these technologists are confident in their MRI safety decision-making, accuracy levels within some groups need addressing.

CONCLUSION

To develop a consistent level of safe practice, it is proposed that a minimum level of MRI-specific education is defined and mandated to practise. Continuing professional development focussing on MRI safety must be encouraged and, if audited as part of registration, could also be mandated. Implementation of a supporting regulatory framework similar to NZ is recommended for other countries.

IMPLICATIONS FOR PRACTICE

All MRI technologists are responsible for the safety of their patients and staff. Employers must support and ensure MRI-specific education has been completed. Ongoing engagement in MRI safety events provided by MRI safety experts, professional bodies and/or universities is essential to remain up-to-date.

Methods and reference data for middle ear transfer functions

Human temporal bone specimens are used in experiments measuring the sound transfer of the middle ear, which is the standard method used in the development of active and passive middle ear implants. Statistical analyses of these experiments usually require that the TB samples are representative of the population of non-pathological middle ears. Specifically, this means that the specimens must be mechanically well-characterized. We present an in-depth statistical analysis of 478 data sets of middle ear transfer functions (METFs) from different laboratories. The data sets are preprocessed and various contributions to the variance of the data are evaluated. We then derive a statistical range as a reference against which individual METF measurements may be validated. The range is calculated as the two-sided 95% tolerance interval at audiological frequencies. In addition, the mean and 95% confidence interval of the mean are given as references for assessing the validity of a sample group. Finally, we provide a suggested procedure for measuring METFs using the methods described herein.

Knock-down of PSAT1 Enhances Sensitivity of NSCLC Cells to Glutamine-limiting Conditions

BACKGROUND/AIM

Phosphoserine aminotransferase 1 (PSAT1) is an enzyme implicated in serine biosynthesis, and its overexpression has been linked to cancer cell proliferation. Therefore, targeting PSAT1 is considered to be an anticancer strategy.

MATERIALS AND METHODS

The viability of non-small cell lung cancer (NSCLC) cells was measured by MTT assay. Protein and mRNA expression were determined by western blot and reverse transcription polymerase chain reaction, respectively.

RESULTS

Glutamine-limiting conditions were generated through glutamine deprivation or CB-839 treatment, which induced PSAT1 expression in NSCLC cells. PSAT1 expression induced by glutamine-limiting conditions was regulated by activating transcription factor 4. Knock-down of PSAT1 enhanced the sensitivity of NSCLC cells to glutamine-limiting conditions. Interestingly, ionizing radiation induced PSAT1 expression, and knocking down PSAT1 increased cell sensitivity to ionizing radiation.

CONCLUSION

Inhibiting PSAT1 might aid in the treatment of lung cancer, and PSAT1 may be a therapeutic target for lung cancer.

Comprehensive Analysis of in Vivo Phosphoproteome of Mouse Liver Microsomes

Protein phosphorylation at serine, threonine, and tyrosine residues are some of the most widespread reversible post-translational modifications. Microsomes are vesicle-like bodies, not ordinarily present within living cells, which form from pieces of the endoplasmic reticulum (ER), plasma membrane, mitochondria, or Golgi apparatus of broken eukaryotic cells. Here we investigated the total phosphoproteome of mouse liver microsomes (MLMs) using TiO2 enrichment of phosphopeptides coupled to on-line 2D-LC-MS/MS. In total, 699 phosphorylation sites in 527 proteins were identified in MLMs. When compared with the current phosphoSitePlus database, 155 novel phosphoproteins were identified in MLM. The distributions of phosphosites were 89.4, 8.0, and 2.6% for phosphoserine, phosphotheronine, and phosphotyrosine, respectively. By Motif-X analysis, eight Ser motifs and one Thr motif were found, and five acidic, two basophilic-, and two proline-directed motifs were assigned. The potential functions of phosphoproteins in MLM were assigned by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. In GO annotation, phosphorylated microsomal proteins were involved in mRNA processing, mRNA metabolic processes, and RNA splicing. In the KEGG pathway analysis, phosphorylated microsomal proteins were highly enriched in ribosome protein processing in ER and ribosomes and in RNA transport. Furthermore, we determined that 52 and 23 phosphoproteins were potential substrates of cAMP-dependent protein kinase A and casein kinase II, respectively, many of which are 40S/60S ribosomal proteins. Overall, our results provide an overview of features of protein phosphorylation in MLMs that should be a valuable resource for the future understanding of protein synthesis or translation involving phosphorylation.

In-plane motions of the stapes in human ears

The piston-like (translation normal to the footplate) and rocking-like (rotation along the long and short axes of the footplate) are generally accepted as motion components of the human stapes. It has been of issue whether in-plane motions, i.e., transversal movements of the footplate in the oval window, are comparable to these motion components. In order to quantify the in-plane motions the motion at nine points on the medial footplate was measured in five temporal bones with the cochlea drained using a three-dimensional (3D) laser Doppler vibrometer. It was found that the stapes shows in-plane movements up to 19.1 ± 8.7% of the piston-like motion. By considering possible methodological errors, i.e., the effects of the applied reflective glass beads and of alignment of the 3D laser Doppler system, such value was reduced to be about 7.4 ± 3.1%. Further, the in-plane motions became minimal (≈ 4.2 ± 1.4% of the piston-like motion) in another plane, which was anatomically within the footplate. That plane was shifted to the lateral direction by 118 μm, which was near the middle of the footplate, and rotated by 4.7° with respect to the medial footplate plane.

Immunohistochemical expression of matrix metalloproteinases in the granulomatous rosacea compared with the non-granulomatous rosacea

BACKGROUND

There is a granulomatous variant which is recognized in the rosacea spectrum. However, the pathogenesis of granuloma formation in rosacea has not been clearly demonstrated. Matrix metalloproteinases (MMPs) are required for recruitment of inflammatory cells and for tissue remodelling, making way for the development of well-organized granuloma.

OBJECTIVE

The aim of this study was to investigate the expression of transforming growth factor (TGF)-β, TGF-β type II receptor (TβRII), Tumour necrosis factor (TNF)-α, MMP-1, 2 and 9 in the granulomatous rosacea (GR) compared with the non-granulomatous rosacea (NGR) and test the hypothesis that the changes of these profiles in GR would be related with chronic ultraviolet radiation (UVR)-exposure.

METHODS

Facial skin samples were obtained from 20 patients with GR and NGR (control group). The sections were stained using haematoxylin and eosin, Verhoeff's elastic stain, and antibodies to TGF-β, TβRII, TNF-α, MMP-1, -2 and -9.

RESULTS

The amount of elastotic material was significantly increased in the dermis of GR lesions. Expression of TGF-β was significantly decreased in the epidermis of GR lesions compared with NGR lesions. In addition, the expression of MMP-9 was significantly increased in the dermis of GR lesions compared with NGR lesions, especially at the centre of the granuloma on a semi-quantitative analysis. MMP-2 expression was also increased in GR lesions, although the difference between the two groups was not statistically significant.

CONCLUSIONS

The results of this study suggest that the increased expression of MMPs in the dermis may participate in granuloma formation of GR in association with UVR.

Altered expression of costimulatory molecules in Behçet's disease according to clinical activity

BACKGROUND

The reduced expression of molecules limiting excessive immune responses has been considered a pathogenic mechanism associated with autoimmune diseases.

OBJECTIVES

To understand the implications of costimulatory molecules in Behçet's disease (BD), the expression of CTLA-4 and PD-1 on T-cell subsets and of their ligands CD80, CD86 and PD-L1 on antigen-presenting cells (APCs) was investigated.

METHODS

Peripheral blood mononuclear cells (PBMC) from 11 patients with active BD, eight patients with inactive BD, eight patients with recurrent aphthous ulcers and 10 healthy volunteers as healthy controls (HC) were stimulated with phorbol myristate acetate and ionomycin. The expression of costimulatory molecules was then analysed by flow cytometry. Soluble CTLA-4 (sCTLA-4) concentrations were determined by enzyme-linked immunosorbent assay and the transcript level of PD-L1 was measured by real-time polymerase chain reaction. The PD-L1 expression in skin lesions of patients with BD was evaluated by immunohistochemistry.

RESULTS

Compared with the HC group, reduced expression of CTLA-4 in CD4+ T cells after stimulation was observed in the active BD group, with no difference in the production of sCTLA-4. CD86 expression, in the resting APCs, was reduced in the active BD group compared with the HC group. PD-L1 expression in the APCs was decreased in the active BD group with or without stimulation of cells. Concordantly, the mRNA levels of PD-L1 in PBMC, and PD-L1 expression in the cutaneous lesions, were low in the active BD group.

CONCLUSIONS

The results of this study suggest that altered expression of PD-L1, CTLA-4 and CD86 may be involved in the pathogenesis of BD.

Comparison of the clinical efficacy of NBUVB and NBUVB with benzoyl peroxide/clindamycin in progressive macular hypomelanosis

BACKGROUND

Progressive macular hypomelanosis (PMH) is a skin disorder characterized by multiple hypopigmented patches symmetrically distributed on the trunk. Several treatment modalities have been attempted; however, a standard treatment modality has not been agreed to.

OBJECTIVES

The aim of this study was to compare the effectiveness of antimicrobial therapy combined with narrow band ultraviolet B (NBUVB) with NBUVB monotherapy.

METHODS

A randomized left-right comparison study was conducted in a total of 10 patients. Patients received NBUVB therapy with daily application of antimicrobial gel on one side of the trunk (comb-NBUVB) and without it (mono-NBUVB) for 8 weeks. The clinical efficacy was determined by objective measurements using a colour analyser and subjective assessment by evaluating pictures taken with a digital camera at baseline, at the time of treatment cessation and 6 months after treatment.

RESULTS

Significant repigmentation was observed in all 10 patients during the 8 weeks of treatment. The mean difference in L values between lesional and non-lesional skin was reduced in the comb-NBUVB area (from 4.52 ± 1.65 to 0.94 ± 0.65), and in the mono-NBUVB area, (from 4.34 ± 1.39 to 1.18 ± 0.94). There was no significant difference between treated sites at both of the evaluation points in time. At 6 months after treatment, 7 of 10 patients completed the clinical trial, and some degree of clinical improvement remained in four of seven patients; recurrence occurred in the other patients.

CONCLUSIONS

Although recurrence occurred in some patients, NBUVB treatment appears to be a safe and useful modality for the treatment of PMH.

Microelectrode recording: lead point in STN-DBS surgery

BACKGROUND

Microelectrode recording is an integral part of many surgical procedures for movement disorders. We evaluate the Lead point compared to the NeuroTrek system. We used NeuroTrek in 18 Parkinsonian patients, Lead point-4 in 12 patients, during STN-DBS surgery. We compared MR-Stir image with Microelectrode recording.

METHOD

The MicroGuide system with its integrated screen display provides the user with all the information needed during the surgery on its screen. Microelectrode recordings showed characteristic neuronal discharges on a long trajectory (5-6 mm), intraoperative stimulation induces dramatic improvement of Parkinsonian motor symptoms.

FINDINGS

Microrecording data of the Leadpoint showed high background activity, and firing rate of 14-50 Hz. The discharge pattern is typically chaotic, with frequent irregular bursts and pauses.

DISCUSSION

The microelectrode recording of the neuroTrek and Lead point-4 showed unique results of the typical STN spike. The DBS effect is maximized associated by MER mapping.

Molecular basis and characteristics of KATP channel in human corporal smooth muscle cells

Relaxation of the corpus cavernosum smooth muscle is an absolute prerequisite for penile erection. Potassium channels play a role in the physiologic regulation of corporal smooth muscle tone. In spite of the physiological importance of K(ATP) channel in the modulation of corporal smooth muscle tone, there is a shortage of information available about the K(ATP) channel subtype(s) present in the corporal smooth muscle. The purpose of this study was to investigate the subunit type of K(ATP) channel, that is, the combinations of the Kir subunit and the SUR subunit in the human corporal smooth muscle and determine whether the electrophysiological kinetics and pharmacological properties of K(ATP) channels meet the subunit characteristics of the ion channel. We used cultured human corporal smooth muscle cells. To determine the presence of Kir and SURs subunits, RT-PCR was performed using Kir6.1, Kir6.2, SUR1, SUR2A, and SUR2B gene-specific primers. For electrophysiological recordings, the whole-cell, inside-out, and cell-attached configurations of the patch-clamp technique were used. We observed transcripts for Kir6.1, Kir6.2, and SUR2B in mRNA isolated from smooth muscle cells of cultured human corpus carvernosum. We recorded the unitary K(ATP) channel under the condition of intracellular and extracellular 140 mM [K(+)], and the slope conductance of the channel was 42.0+/-2.6 pS which is an intermediate conductance between that of either Kir6.1 or Kir6.2. The pinacidil (10 microM) increased the magnitude of the outward K(+) current (214.6+/-89.2%, n=12, < or = 0.05), which was blocked by the subsequent addition of the specific K(ATP) channel subtype selective blocker, glibenclamide (10 microM). The SIN-1(200 microM) induced increases in whole-cell outward K(+) currents (126.0+/-1.4%, n=4). The increased currents by SIN-1 were inhibited by glibenclamide (10 microM). We are the first to show that K(ATP) channel in human corporal smooth muscle is composed of Kir6.1-Kir6.2 construct expressed with SUR2B by RT-PCR. These findings, taken together with the electrophysiological results, suggest that K(ATP) channel in corporal smooth muscle cells is composed of heteromultimers of Kir6.1 and Kir6.2 with the ratio of 3 : 1 or 4 : 0 and SUR2B.

Capsaicin inhibits the voltage-operated calcium channels intracellularly in the antral circular myocytes of guinea-pig stomach

Studies of the effect of capsaicin (CAP) on the smooth muscle contractions have shown both contraction and relaxation in various preparations. The direct effect of CAP on gastric smooth muscle itself has not yet been reported, though CAP was reported to relax the isolated guinea-pig stomach by releasing nitric oxide from the CAP-sensitive sensory neurons. Here we showed an evidence that CAP evokes a prolonged relaxation of gastric antral circular smooth muscle (CAP-induced relaxation) by blocking the voltage-operated Ca2+ channels (VOCC) from inside of the cell. CAP suppressed dose-dependently the spontaneous contractions of guinea-pig gastric circular muscle strip under the condition without neural influence (IC50 = 5.8 microM). The inhibitory effects of CAP both on the high K+ contracture induced by 50 mM K+ Tyrode solution and on the slow waves recorded using a conventional intracellular microelectrode technique were similar to those of Ca2+ channel antagonists, indicating that Ca2+ influx through the VOCC is decreased by CAP. Ca2+ channel current (I(Ba)) decreased in a concentration-dependent manner on superfusing the physiological salt solution containing various concentrations of CAP. The steady-state activation and inactivation curves of I(Ba) were not affected by the treatment with CAP. The experiment using a synthetic water-soluble analog of CAP, DA-5018 x HCl, suggested that the acting site of CAP is present in the intracellular side. Spontaneous transient outward K+ currents (STOCs) recorded at a holding potential of 0 mV were also inhibited by CAP and verapamil, Ca channel blocker. Taken together, these results indicate that CAP-induced relaxation is associated with the direct inhibitory action on the VOCC from inside of the cell.

The properties of carbachol-activated nonselective cation channels at the single channel level in guinea pig gastric myocytes

We investigated the properties of carbachol (CCh)-activated nonselective cation channels (NSC(CCh)) at the single channel level in the gastric myocytes of guinea pigs using a magnified whole-cell mode or an outside-out mode. The channel activity (NPo) recorded in a magnified whole-cell mode increased with depolarization (from -120 to -20 mV) and had the half activation potential of -81 mV under the symmetrical 140 mM Cs+ condition. The single channel conductance depended upon the extracellular monovalent cations with the order of Cs+ (35 pS) > Na+ (25 pS) > Li+ (21 pS). The channel activities markedly diminished or disappeared when external Cs+ was replaced with Na+ or N-methyl-D-glucamate (NMDG+). With Cs+ and Na+ as external cations, the channel showed a monotonic increase in NPo with the increased mole fraction of Cs+ over Na+, and it had an intermediate conductance value in solution containing 67% Cs+ with 33% Na+. These data suggested that the extracellular monovalent cations regulate the whole-cell current of NSC(CCh) by modulating both the open state probability and the unitary conductance, and there is one binding site for the extracellular cations within the pore.

Protein kinase C suppresses spontaneous, transient, outwards K+ currents through modulation of the Na/Ca exchanger in guinea-pig gastric myocytes

The effect of protein kinase C (PKC) on the Ca2+-activated K+ current (IK,Ca) in guinea-pig gastric myocytes was studied using the whole-cell voltage-clamp technique. At a holding potential of 0 mV, IK,Ca, recorded as spontaneous, transient, outwards currents (STOCs), was markedly inhibited, both in mean amplitude (54 +/- 5%) and frequency (60 +/- 8%) by 1 microM phorbol 12, 13 dibutyrate (PDBu, n = 6). These effects were antagonized by pretreatment with 10 nM bisindolylmaleimide I (n = 5), a selective inhibitor of PKC. The possibility that the inhibition of STOCs was due to direct channel inhibition by PKC was addressed using inside-out or open-cell-attached patch-clamp techniques, the latter established using beta-escin. PDBu did not alter the conductance or open probability of the KCa channel in any mode, suggesting that PKC does not inhibit the KCa channel directly. To study the involvement of the Na/Ca exchanger in the inhibition of STOCs by PDBu, its operation was prevented by replacing Na+ in the internal solution by tris(hydroxymethyl)aminomethane (TRIS) and external Na+ by equimolar K+ and Ca2+-activated inwards K+ currents recorded at a holding potential of 0 mV. Neither the mean amplitude (96 +/- 8%) nor the frequency of these currents was inhibited significantly by 1 microM PDBu (n = 5). Like PDBu, 5 microM 2-(2-[4-(4-nitrobenzyloxy)phenyl]ethyl) isothiourea methanesulphonate (KB-R7943), a selective inhibitor of the reverse mode Na/Ca exchanger, also inhibited the mean amplitude (45 +/- 6%) and frequency (26 +/- 2%) of STOCs at the holding potential of 0 mV (n=6). The results suggest that the suppression of STOCs by PKC is mediated by inhibition of the Na/Ca exchanger.

Background nonselective cationic current and the resting membrane potential in rabbit aorta endothelial cells

The ion channel conductances that regulate the membrane potential was investigated by using a perforated patch-clamp technique in rabbit aorta endothelial cells (RAECs). The whole-cell current/voltage (I-V) relation showed a slight outward rectification under physiological ionic conditions. The resting membrane potential was -23.3 +/- 1.1 mV (mean +/- SEM, n = 19). The slope conductances at the potentials of -80 and 50 mV were 31.0 +/- 4.0 and 62.8 +/- 7.1 pS pF(-1), respectively (n = 15). Changes in the extracellular and intracellular Cl(-) concentrations did not affect the reversal potential on I-V curves. The background nonselective cationic (NSC) current was isolated after the K(+) current was suppressed. The relative permeabilities calculated from the changes in reversal potentials using the constant-field theory were P(K):P(Cs):P(Na):P(Li) = 1:0.87:0.40:0.27 and P(Cs):P(Ca) = 1:0.21. Increases in the external Ca(2+) decreased the background NSC current in a dose-dependent manner. The concentration for half block by Ca(2+) was 1.1 +/- 0.3 mM (n = 7). Through the continuous recording of the membrane potential in a current-clamp mode, it was found that the background NSC conductance is the major determinant of resting membrane potential. Taken together, it could be concluded that the background NSC channels function as the major determinant for the resting membrane potential and can be responsible for the background Ca(2+) entry pathway in freshly isolated RAECs.

A case of very large cyst formation with Gamma Knife radiosurgery for an arteriovenous malformation

A 17-year-old male patient underwent Gamma Knife radiosurgery (GKRS) for a left parietal arteriovenous malformation (AVM), which presented with hemorrhage. The 15.0 cm3 nidus was covered with the 50% isodose. The maximum dose was 50 Gy and the margin dose was 25 Gy. Eleven months later he developed a right hemiparesis and MRI showed a large cyst. Cerebral angiography showed partial obliteration of the AVM nidus. Stereotactic removal of cyst fluid (about 70 cm3) was performed, and an Ommaya reservoir was inserted. Cyst formation after GKRS for cerebral arteriovenous malformation is a is side effect of radiosurgery about which we need to learn more.

Gamma Knife radiosurgery for functioning pituitary microadenoma

Transsphenoidal microsurgery remains the treatment of choice for pituitary microadenomas One hundred and six patients were treated with Gamma Knife radiosurgery (GKRS) for pituitary adenomas, and of these, 23 patients (1 male, 22 female) had microadenomas. Twenty-two of these patients were followed up and endocrinological tests were available for 15 of these 22. Thirteen of these 15 had prolactinomas, while the remaining 2 had acromegaly. The follow-up period was from 3 to 26 months (median 12 months). The mean age was 33.6 years (range 21 to 60 years). The mean maximum tumor dose was 35.7 Gy and the mean margin dose was 22 Gy. Serum prolactin (PRL) was normalized in three patients, decreased in eight and unchanged in two. The growth hormone (GH) secretion in the acromegalic patients has remained unchanged through the follow-up period. Thus, GKRS is a valuable adjuvant to transsphenoidal microsurgery for patients with pituitary microadenomas.

Intracranial aneurysms in Korea

We have 32 university hospitals and 18 general hospitals for neurosurgical training in Korea. Recently I have analyzed intracranial aneurysm cases which had an operation in 28 university hospitals and nine general hospitals. I have reported 2863 aneurysm operation cases. The location of aneurysm consisted of 865 aneurysms (30.2%) in the anterior communicating artery, 724 aneurysms (25.3%) in the internal carotid artery, 687 aneurysms (24.0%) in the middle cerebral artery, 129 aneurysms (4.5%) in the anterior cerebral artery, 152 aneurysms (5.3%) in the posterior circulation, and 306 (10.7%) multiple aneurysms. The overall approximation of the operation rate of aneurysm is approximately 6.6 cases per 100,000 population in 1996 in Korea.

Suppression of the carbachol-activated nonselective cationic current by antibody against alpha subunit of Go protein in guinea-pig gastric myocytes

In this study, we investigated which subtype of GTP-binding protein (G protein) is related to muscarinic activation of nonselective cation (NSC) channels in gastric smooth muscle. Inward cationic current was activated by the application of 50 microM carbachol (ICCh) at a holding potential of -60 mV with the same CsCl-rich solution in both pipette and bath. The same cationic current as ICCh was slowly activated by the dialysis of guanosine 5'-O-(3-thiotriphosphate) (GTP[gamma-S]) through the pipette. Since it is known that pertussis toxin pretreatment can block ICCh, antibodies (Abs) against Galpha,i (anti-Galpha,i) or Galpha,o (anti-Galpha,o) were tested. Activation of ICCh was blocked by the addition of anti-Galpha,o. However, anti-Galpha,i Abs had no significant effect on ICCh. The expression of Galpha,o in guinea-pig gastric smooth muscle was confirmed by Western immunoblot analysis. These results suggest that Go-type protein may mediate signals from the muscarinic receptor to NSC channel in guinea-pig gastric myocytes.

Protein kinase C mediates the desensitization of CCh-activated nonselective cationic current in guinea-pig gastric myocytes

The possibility of the protein kinase C (PKC) pathway being a mechanism underlying the desensitization of carbachol- (CCh-)activated nonselective cationic current (ICCh) was investigated in a study of guinea-pig gastric myocytes. Using the conventional whole-cell patch-clamp technique with symmetrical CsCl-rich solution in pipette and bath, ICCh was induced by bath application of 50 microM CCh. With 0.5 mM EGTA [ethyleneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] in the pipette solution (0.5 mM [EGTA]i), ICCh decayed spontaneously (desensitization of ICCh) to around 20% within 10 min. Desensitization of ICCh was significantly attenuated with 2 mM [EGTA]i. At a concentration of 20 microM OAG (1-oleoyl-2-acetyl-sn-glycerol), a PKC activator, inhibited ICCh at 0.5 mM [EGTA]i but far less at 2 mM [EGTA]i (18% and 81% of control, respectively). The same cationic current induced by intracellular guanosine-5'-O-(3-thiotriphosphate) (GTP[gamma-S]) was not inhibited by OAG with 0.5 mM [EGTA]i. The pretreatment of gastric myocytes with PKC inhibitors, either 1 microM chelerythrine or 1 microM peptide inhibitor, attenuated the desensitization of ICCh. [Ca2+]i was also measured by single cell microfluorometry using fura-2. Under CCh stimulation with 2 mM [EGTA]i, [Ca2+]i did not increase above 100 nM while it increased to around 260 nM with 0.5 mM [EGTA]i. These results suggest that the desensitization of ICCh is partly due to the Ca2+-dependent PKC pathway in guinea-pig gastric myocytes.

Separation of recombinant human growth hormone from Escherichia coli cell pellet extract by capillary zone electrophoresis

Free zone capillary electrophoresis (FZCE) was used to resolve recombinant human growth hormone (rhGH) and its variants from very crude mixtures of Escherichia coli (E. coli) cell paste extract. The methodology employs a phosphate deactivated fused-silica capillary and a 250 mM phosphate (pH 6.8), 1% (v/v) propylene glycol buffer with a high field strength of 600 V/cm. Resolution of rhGH and its variants from very crude mixtures did not change after 80 injections for the PSC capillaries. Bare silica and PVA coated capillaries had a more limited lifetime when injected with the same crude mixtures (10 to 30 injections). This FZC method provides a very powerful tool for assessing rhGH modification during the fermentation and isolation of rhGH that is not possible with other current analytical techniques.