Functionally diverging molecular quasi-species evolve by crossing two enzymes

Molecular evolution is frequently portrayed by structural relationships, but delineation of separate functional species is more elusive. We have generated enzyme variants by stochastic recombinations of DNA encoding two homologous detoxication enzymes, human glutathione transferases M1-1 and M2-2, and explored their catalytic versatilities. Sampled mutants were screened for activities with eight alternative substrates, and the activity fingerprints were subjected to principal component analysis. This phenotype characterization clearly identified at least three distributions of substrate selectivity, where one was orthogonal to those of the parent-like distributions. This approach to evolutionary data mining serves to identify emerging molecular quasi-species and indicates potential trajectories available for further protein evolution.     

Hearing loss in migrant agricultural workers

BACKGROUND: Farmers have high rates of hearing loss, yet little is known about the hearing status of migrant agricultural workers. We performed a cross-sectional survey to assess the prevalence and impact of hearing loss in this population. METHODS: One hundred fifty migrant and seasonal agricultural workers were surveyed at a series of health fairs held at migrant camps. A bilingual questionnaire included items related to hearing loss risk factors and subjective hearing difficulties. Pure tone audiometry and tympanometry were performed in a mobile testing van. RESULTS: More than half the subjects had some degree of hearing loss at audiometric frequencies between 500 and 6,000 Hz, especially in the higher frequencies. Hispanic males in the sample had significantly greater prevalence of high-frequency hearing loss compared to adults in the national Hispanic Health and Nutrition Examination Survey (HHANES). More than 35% of respondents complained of subjective difficulty hearing or understanding speech, yet no workers reported use of hearing aids. Even after adjusting for measured hearing loss, Hispanic farm workers were more likely than their English- speaking counterparts to complain of difficulty hearing or understanding speech, suggesting that language barriers could worsen the impact of hearing loss. Risk factors for hearing loss included age and abnormal tympanometry. Occupational exposures to noise from tractors and other machinery as well as pesticides were frequently reported, while use of hearing protection was rare. CONCLUSION: Hearing loss is a significant and under-recognized problem in the migrant worker population. Further preventive and treatment efforts are warranted.     

High calcium activates the EGF receptor potentially through the calcium-sensing receptor in Leydig cancer cells

Epidermal growth factor (EGF) plays an important role in the physiology and pathophysiology of the Leydig cell. In H-500 rat Leydig cancer cells, a model for humoral hypercalcemia of malignancy (HHM), we previously showed that the calcium-sensing receptor (CaR) stimulates PTHrP release and proliferation, both involving multiple mitogen-activated protein kinases. An emerging concept of signaling by G-protein coupled receptors (GPCR) is that it occurs via transactivation of receptor tyrosine kinases. Therefore, we investigated whether stimulation with calcium activates the EGFR in H-500 Leydig cancer cells. We show that treatment of H-500 cells with Ca(2+) results in EGFR phosphorylation. The CaR-induced activation of ERK1/2, induction of PTHrP release and stimulation of cellular proliferation in H-500 cells are likewise mediated, in large part, through the EGFR. In conclusion, the calcium activates the EGFR, possibly through the CaR, to regulate downstream signaling events and important biological functions in a model of HHM.     

Extreme gastric dilation caused by chronic lead poisoning： A case report

Lead is a toxic metal that affects many organ systems and functions in humans. In the majority of adults, chronic lead poisoning comes from exposures to work places and can occur in numerous work settings, such as manufacturing, lead smelting and refinement, or due to use of batteries, pigments, solder, ammunitions, paint, car radiators, cable and wires, certain cosmetics. In some countries, lead is added to petrol. We present a rare case of gastric dilation caused by long-term petrol ingestion. A 16-year-old young man was admitted to our hospital due to a 6-mo history of exhaustion, dizziness, nausea, abdominal cramps and constipation. X-ray examination revealed dilated stomach descending into the pelvis and small bowel distension. After a long clinical observation, we found that the reason for the chronic lead poisoning of the patient was due to a 3-year history of petrol ingestion. The patient spontaneously recovered and stomach returned to its normal position and size. Lead poisoning should be taken into consideration in all unexplained cases of gastric dilation.     

Citalopram overdose: Late presentation of torsades de pointes (TdP) with cardiac arrest

Introduction

Citalopram overdose may produce bradycardia, QT prolongation, and torsades de pointes (TdP). A cardiotoxic metabolite may be responsible for the delayed onset of cardiotoxicity. Although some authorities recommend a minimum of 24 hours of observation following citalopram overdose, a recent analysis suggested that dysrhythmias rarely occur beyond 13 hours post-ingestion. We present a case of citalopram overdose with a substantially delayed onset of cardiac toxicity.

Case Report

A 36-year-old woman complained of shakiness, numbness in the arms, and palpitations that began approximately 32 hours after ingesting 50 (20-mg) tablets of citalopram. Her initial vital signs were: blood pressure, 84/44 mmHg; pulse, 102–150/minute; respirations, 17/min; temperature, 99.3° F (37.3° C). Her initial ECG showed sinus rhythm with a prolonged corrected QT interval (572 msec) with paroxysmal, self-limited runs of wide-complex tachycardia that appeared multifocal in nature. Approximately 20 minutes after presentation, she experienced self-terminating TdP, with transient hypotension and loss of consciousness. Her serum citalopram concentration (33 hours post-ingestion) was 477 ng/mL (therapeutic: 40–110 ng/mL); desmethylcitalopram concentration was 123.2 ng/mL (therapeutic: 14–40 ng/mL). She was treated with magnesium and lidocaine, and her corrected QT interval remained abnormal for 24 hours after presentation.

Discussion

Citalopram overdose can produce life-threatening cardiac toxicity with a clinical onset that may be delayed beyond a routine observation period of 6 hours. Once the QT interval is prolonged, it seems prudent to prolong the observation period.     

Robust GLP‐1 secretion by basic L‐amino acids does not require the GPRC6A receptor

The G protein‐coupled receptor GPRC6A (GPCR, Class C, group 6, subtype A) has been proposed to be a sensor for basic L‐amino acids that are hypothesized to translate ingestive behaviour to endocrine information. However, the contribution of the GPRC6A receptor to L‐amino acid‐induced glucagon‐like peptide 1 (GLP‐1) secretion is unclear. Therefore, to discover whether the GPRC6A receptor is indispensible for amino acid‐induced secretion of GLP‐1, we treated, with oral gavage, GPRC6A knock‐out (KO) and wild‐type (WT) littermate mice with GPRC6A ligands (L‐arginine and L‐ornithine) and assessed GLP‐1 levels in circulation. We found that oral administration of both L‐arginine and L‐ornithine significantly increased total plasma GLP‐1 levels to a similar level in GPRC6A KO and WT mice 15 minutes after gavage (both amino acids) and accumulated up to 60 minutes after gavage (L‐arginine). Conversely, GLP‐1 secretion at the 30‐ and 60‐minute time points in the KO mice was attenuated and did not reach statistical significance. In summary, these data confirm that L‐arginine is a potent GLP‐1 secretagogue and show that the main effect occurs independently of GPRC6A. In addition, this is the first study to show that also L‐ornithine powerfully elicits GLP‐1 release in vivo.     

High calcium activates the EGF receptor potentially through the calcium-sensing receptor in Leydig cancer cells

Epidermal growth factor (EGF) plays an important role in the physiology and pathophysiology of the Leydig cell. In H-500 rat Leydig cancer cells, a model for humoral hypercalcemia of malignancy (HHM), we previously showed that the calcium-sensing receptor (CaR) stimulates PTHrP release and proliferation, both involving multiple mitogen-activated protein kinases. An emerging concept of signaling by G-protein coupled receptors (GPCR) is that it occurs via transactivation of receptor tyrosine kinases. Therefore, we investigated whether stimulation with calcium activates the EGFR in H-500 Leydig cancer cells. We show that treatment of H-500 cells with Ca²⁺ results in EGFR phosphorylation. The CaR-induced activation of ERK1/2, induction of PTHrP release and stimulation of cellular proliferation in H-500 cells are likewise mediated, in large part, through the EGFR. In conclusion, the calcium activates the EGFR, possibly through the CaR, to regulate downstream signaling events and important biological functions in a model of HHM.