Hypothetical chloroplast reading frame 51 encodes a photosystem I assembly factor in cyanobacteria.

Hypothetical chloroplast open reading frames (ycfs) are putative genes in the plastid genomes of photosynthetic eukaryotes. Many ycfs are also conserved in the genomes of cyanobacteria, the presumptive ancestors of present-day chloroplasts. The functions of many ycfs are still unknown. Here, we generated knock-out mutants for ycf51 (sll1702) in the cyanobacterium Synechocystis sp. PCC 6803. The mutants showed reduced photoautotrophic growth due to impaired electron transport between photosystem II (PSII) and PSI. This phenotype results from greatly reduced PSI content in the ycf51 mutant. The ycf51 disruption had little effect on the transcription of genes encoding photosynthetic complex components and the stabilization of the PSI complex. In vitro and in vivo analyses demonstrated that Ycf51 cooperates with PSI assembly factor Ycf3 to mediate PSI assembly. Furthermore, Ycf51 interacts with the PSI subunit PsaC. Together with its specific localization in the thylakoid membrane and the stromal exposure of its hydrophilic region, our data suggest that Ycf51 is involved in PSI complex assembly. Ycf51 is conserved in all sequenced cyanobacteria, including the earliest branching cyanobacteria of the Gloeobacter genus, and is also present in the plastid genomes of glaucophytes. However, Ycf51 has been lost from other photosynthetic eukaryotic lineages. Thus, Ycf51 is a PSI assembly factor that has been functionally replaced during the evolution of oxygenic photosynthetic eukaryotes.

Safety and Clinical Activity of SHR7390 Monotherapy or Combined With Camrelizumab for Advanced Solid Tumor: Results From Two Phase I Trials.

BACKGROUND: SHR7390 is a novel, selective MEK1/2 inhibitor. Here, we report results from two phase I trials conducted to evaluate the tolerability, safety and antitumor activity of SHR7390 monotherapy for advanced solid tumors and SHR7390 plus camrelizumab for treatment-refractory advanced or metastatic colorectal cancer (CRC). PATIENTS AND METHODS: Patients received SHR7390 alone or combined with fixed-dose camrelizumab (200 mg every 2 weeks) in an accelerated titration scheme to determine the maximum tolerated dose (MTD). A recommended dose for expansion was determined based on the safety and tolerability of the dose-escalation stage. The primary endpoints were dose limiting toxicity (DLT) and MTD. RESULTS: In the SHR7390 monotherapy trial, 16 patients were enrolled. DLTs were reported in the 1.0 mg cohort, and the MTD was 0.75 mg. Grade ≥3 treatment-related adverse events (TRAEs) were recorded in 4 patients (25.0%). No patients achieved objective response. In the SHR7390 combination trial, 22 patients with CRC were enrolled. One DLT was reported in the 0.5 mg cohort and the MTD was not reached. Grade ≥3 TRAEs were observed in 8 patients (36.4%), with the most common being rash (n=4). One grade 5 TRAE (increased intracranial pressure) occurred. Five patients (22.7%) achieved partial response, including one of 3 patients with MSS/MSI-L and BRAF mutant tumors, one of 15 patients with MSS/MSI-L and BRAF wild type tumors, and all 3 patients with MSI-H tumors. CONCLUSIONS: SHR7390 0.5 mg plus camrelizumab showed a manageable safety profile. Preliminary clinical activity was reported regardless of MSI and BRAF status.

Aberrant Wnt/ß-catenin signaling and elevated expression of stem cell proteins are associated with osteosarcoma side population cells of high tumorigenicity.

According to the cancer stem cell theory, the presence of a small sub­population of cancer cells, termed cancer stem cells (CSCs), have a significant implication on cancer treatment and are responsible for tumor recurrence. Previous studies have reported that alterations in the Wnt/ß­catenin signaling are crucial in the maintenance of CSCs. In the present study, the characteristic features and activation of Wnt/ß­catenin signaling in CSCs from osteosarcoma, an aggressive human bone tumor, were investigated. In total, ~2.1% of the cancer stem­like side population (SP) cells were identified in the osteosarcoma samples. The results of subsequent western blot and reverse transcription­quantitative polymerase chain reaction analyses revealed that the protein levels of ß­catenin and cyclin D1 were markedly upregulated in the fluorescence­activated cell sorted osteosarcoma SP cells. In addition, the elevated expression levels of stem cell proteins, including CD133, nestin Oct­4, Sox­2 and Nanog were significantly higher in the SP cells, which contributed to self­renewal and enhanced the proliferation rate of the SP cells. Furthermore, the SP cells were found to be highly invasive and able to form tumors in vivo. Taken together, these data suggested that the identification of novel anticancer drugs, which suppress the Wnt/ß­catenin signaling and its downstream pathway may assist in eradicating osteosarcoma stem cells.

[Effects of amygdala kindled seizures on memory retention of passive-avoidance test in rats].

OBJECTIVE: To investigate the effects of amygdala kindled seizures on memory retention of passive-avoidance test in rats. METHODS: Chronic kindled seizures were achieved by daily application of electric stimulations on amygdala until the occurrence of 3 consecutive convulsive seizures. Then a passive-avoidance test was performed to measure memory retention ability in rats; another group of rats received an electric stimulation on amygdala 5 min before the training trail to observe the effects of acute seizure attack on memory retention ability. RESULT: In the training trail and the 1st day of the test trail, there was no difference in the latency to enter dark compartment between chronic kindled seizure group and its corresponding control group. However, the latency significantly increased at the 5 th day of test trail. In addition, the latency of acute seizure attack group rats significantly decreased at the 1 st day and 5 th day of test trail. CONCLUSION: Chronic amygdala kindled seizures increase memory retention of passive-avoidance test in rats, and acute seizure attack impairs this action.

Low-frequency stimulation of the tuberomammillary nucleus facilitates electrical amygdaloid-kindling acquisition in Sprague-Dawley rats.

Histamine plays a suppressive role in seizure. The tuberomammillary nucleus (TM) is the only locus of histaminergic neurons in the brain. To determine whether deep brain stimulation (DBS) of the TM provides protection against seizures, we tested the effects of low-frequency stimulation (LFS, 1 Hz), high frequency stimulation (HFS, 100 Hz), and electrolytic lesions of the TM on seizures generated by amygdaloid kindling, pentylenetetrazol (PTZ) and maximal electroshock (MES) in rats. LFS of TM accelerated the progression of behavioral seizure stage and increased the mean afterdischarge duration (ADD) during acquisition of amygdaloid-kindling seizures, but had no considerable anticonvulsive effect in fully kindled animals. It augmented the MES-induced seizures as well, but had no appreciable effects on PTZ-kindled seizures. In addition, both HFS and bilateral lesions of the TM exacerbated the progression of amygdaloid-kindling seizures. These results suggest that specific negative sites for DBS exist in the brain, such as the TM. This study indicates that it is crucial to choose a suitable target for DBS in the clinical treatment of epilepsy.

[Involvement of endogenous histamine in modulatory effect of morphine on seizure susceptibility in mice].

OBJECTIVE: To investigate the modulatory effects of morphine on the susceptibility to pentylenetetrazole-induced seizures, and the involvement of endogenous histamine in this process. METHODS: Both the wild-type (WT) mice and histidine decarboxylase (a key enzyme for histamine biosynthesis) deficient (HDC-KO) mice were subcutaneously injected with different doses of morphine, and 1 hour later the pentylenetetrazole solution (1.5 %) was infused into the tail vein at a constant rate of 0.3 ml/min. The minimal dose of pentylenetetrazole (mg/kg) needed to induce myoclonic jerks and clonus convulsion was recorded as the thresholds of seizures. RESULT: In WT mice, morphine dose-dependently decreased the thresholds of both myoclonic jerks and clonus convulsion. In HDC-KO mice, morphine at 10 mg/kg only significantly decreased the threshold of myoclonic jerks from (38.6 +/-2.9)mg/kg to (32.5 +/-0.7)mg/kg, but had no significant effect on the threshold of clonus convulsion [from (51.8 +/-2.1)mg/kg to (47.6 +/-1.2)mg/kg]. In addition, the value of decreased myoclonic jerks (15.8 +/-1.4)% and clonus convulsion (8.3 +/-0.9)% thresholds were much lower in HDC-KO mice than in WT mice [(26.1 +/-2.5)% and (20.8 +/-2.4)%, respectively]. CONCLUSION: Morphine can decrease the thresholds of pentylenetetrazole in induction of seizure, and the endogenous histamine may be involved in this process.

Lesion of the tuberomammillary nucleus E2-region attenuates postictal seizure protection in rats.

Postictal seizure protection (PSP) is an endogenous anticonvulsant phenomenon that follows an epileptic seizure and inhibits the induction of further seizures. The tuberomammillary nucleus (TM), located in the posterior hypothalamus, consists of five subregions and is the sole source of histaminergic neurons in the brain. To determine whether the TM is involved in PSP in rats, we tested the effects of bilateral electrolytic lesions of the TM E2-region on seizures induced by intermittent maximal electroshock (MES). The TM E2-region lesions significantly attenuated PSP during the intermittent MES procedure. Furthermore, intracerebroventricular injection of alpha-fluoromethylhistidine (100 microg), a selective and irreversible histidine decarboxylase inhibitor, mimicked the attenuation of PSP induced by the lesion of TM E2-region. In addition, neurochemical experiments revealed that the TM E2-region lesions markedly decreased basal histamine levels in the cortex, hippocampus, brainstem and hypothalamus, but had no significant effect on basal glutamate and GABA levels. Moreover, intermittent MES induced a persistent decrease of brain histamine levels in both sham-operated and lesioned rats. These results indicate that through its intrinsic histaminergic system, the TM may exert powerful inhibitory function during the intermittent MES procedure and actively participate in the mechanisms of PSP.

Carnosine, a precursor of histidine, ameliorates pentylenetetrazole-induced kindled seizures in rat.

Carnosine (beta-alanyl-l-histidine) has been characterized as a putative neurotransmitter. However, so far, understanding of the role of carnosine in the brain is very limited. The objective of this study was to examine the effects of carnosine on the development of pentylenetetrazol (PTZ) kindling seizures and protection against the PTZ kindled seizures in rats. Chemical kindling was elicited by repeated intraperitoneal injection of PTZ (35 mg/kg) once every 48 h until the occurrence of Stage 4-5 seizures, and the seizure activity of kindling was recorded for 30 min. In an acute PTZ challenge study, 60 mg/kg PTZ was used to induce kindled seizure. Injection of carnosine (200, 500 mg/kg, i.p.) significantly decreased seizure stage, and prolonged the latencies for myoclonic jerks, in a dose- and time-dependent manner. In the seizure development process, 500 mg/kg carnosine also significantly delayed the onset of PTZ kindled seizures. In addition, carnosine significantly reversed decreased histamine levels induced by PTZ kindled seizure in the hippocampus. These results indicate that carnosine can protect against PTZ-induced seizures in both the development of kindling and the challenge process in rats. The results suggest that carnosine might be an endogenous anticonvulsant factor in the brain and can be used as a new antiepileptic drug in future.

Histidine enhances carbamazepine action against seizures and improves spatial memory deficits induced by chronic transauricular kindling in rats.

AIM: To investigate whether histidine can enhance the anticonvulsant efficacy of carbamazepine (CBZ) and simultaneously improve the spatial memory impairment induced by transauricular kindled seizures in Sprague-Dawley rats. METHODS: Chronic transauricular kindling was induced by repeated application of initially subconvulsive electrical stimulation through ear-clip electrodes once every 24 h until the occurrence of 3 consecutive clonic-tonic seizures. An 8-arm radial maze (4 arms baited) was used to measure spatial memory, and histamine and gamma-amino-butyric acid levels were measured by high performance liquid chromatography (HPLC). RESULTS: Chronic transauricular kindling produced a significant impairment of spatial memory and a marked decrease in histamine content in the hypothalamus, the brainstem, and the hippocampus. Injection of histidine (1000 mg/kg or 1500 mg/kg, ip) significantly inhibited transauricular kindled seizures. Injection of histidine at lower doses (200 mg/kg or 500 mg/kg, ip) had no appreciable anticonvulsant effect when administered alone, whereas it significantly potentiated the protective effects of CBZ against kindled seizures. CBZ had no ameliorative effect on memory deficit, but, in contrast, histidine (200 mg/kg or 500 mg/kg, ip) alone or co-administered with CBZ significantly ameliorated the memory deficits induced by the seizures. CONCLUSION: Chronic transauricular kindling is a very useful animal model for evaluating memory deficits associated with epilepsy, and histidine has both a potentiate effect on the anticonvulsant efficacy of CBZ and an ameliorative effect on the spatial memory deficits induced in this model. Histidine at a specific dosage range might serve as a beneficial adjuvant for the clinical treatment of epilepsy, especially when accompanied by impaired spatial memory.

Influence of low dietary histamine on seizure development of chemical kindling induced by pentylenetetrazol in rats.

AIM: To determine the role of dietary low histamine on the seizure development of pentylenetetrazol (PTZ)-induced kindling in rats. METHODS: After 14 d of feeding on a low histamine diet (LH, containing 0.145 mumol/g of histamine), the rats were chemically kindled by repeated intraperitoneal injection of a subconvulsant dose of PTZ (35 mg/kg) once every 48 h, and seizure activity of kindling was recorded for 30 min. Histamine in brain samples was analyzed using a high performance liquid chromatography system with a fluorescence spectrofluorometer. RESULTS: The LH diet induced an increase in seizure response (seizure susceptibility) to the first trial of PTZ, and resulted in facilitation of subsequent PTZ kindling process (seizure development). The histamine levels in the cortex, hippocampus, and hypothalamus of LH-treated rats decreased significantly and these changes correlated well with seizure behavior (r = 0.875, 0.651, and 0.796, respectively). In addition, chronic kindled seizures resulted in a significant increase of the histamine content in the cortex and hypothalamus in the LH-fed groups. CONCLUSION: These findings indicate that the histamine in daily food could influence the brain histaminergic function, and play an important role in regulating seizure susceptibility.