L-serine deaminating enzymes in Escherichia coli crude extracts

(a) The measured L-serine deaminating activity of a crude bacterial extract may originate from L-serine deaminase, from biosynthetic L-threonine deaminase, or from degradative L-serine deaminase. Nevertheless, the contribution of the individual enzymes can be determined.(b) About a half of the L-serine deaminating activity of wild type E. coli bacteria, grown in synthetic minimal medium, originates from L-serine deaminase and about half from biosynthetic L-threonine deaminase.(c) Ninety percent of L-serine deaminating activity of wild type E. coli bacteria, grown in yeast extract-tryptone medium, originates from L-serine deaminase, and the remainging ten percent from the degradative L-threonine deaminase.(d) Conditions have been established in which threonine deaminases are eliminated and the activity of L-serine deaminase alone could be measured, even in crude extracts.     

L-serine deaminase of Escherichia coli

The native l-serine deaminase (l-serine hydrolyase, deaminating, EC 4.2.1.13) of Escherichia coli K-12, which seems to be a very labile protein, is rather stable in concentrated solution. Dilution rapidly inactivates it, but in the presence of a saturating concentration of l-serine the molecule is protected from inactivation. It is a very specific enzyme; l-serine is the sole substrate with a K(m) value of 6.60 x 10(-3)m. d-Serine and l-cysteine are competitive inhibitors. Substrate saturation curves of the native enzyme show sigmoid shape, whereas the enzyme liberated from the bacteria in the presence of l-serine exhibits normal Michaelis-Menten kinetics.     

Enantioselective determination of isradipine in human serum using chiral stationary phase liquid chromatography and gas chromatography with nitrogen selective detection

rac-Isradipine is a dihydropyridine type calcium antagonist. Its calcium entry blocking effect is due primarily to the (+)-(S)-enantiomer. This study describes a sensitive enantioselective method for the determination of isradipine in human serum. Following alkaline extraction into hexane, the enantiomers of isradipine are separated quantitatively by high-performance liquid chromatography on a Chiralcel OJ column at 39°C. The collected fractions were evaporated and assayed using capillary gas chromatography on a HP 50+ column with nitrogen selective detection. Using 2.0 ml of serum, 0.7 nmol/1 (0.26 ng/ml) of each enantiomer could be determined with acceptable precision. The method has successfully been used to measure (+)-(S)- and (−)-(R)-isradipine concentrations in samples from volunteers after intravenous and oral administration of isradipine. Chirality 10:808–812, 1998. © 1998 Wiley-Liss, Inc.     

Chemical Diversity and Antimicrobial Activity of Volatile Compounds from Zanthoxylum zanthoxyloides Lam. according to Compound Classes,Plant Organs and Senegalese Sample Locations

The chemical diversity of Zanthoxylum zanthoxyloides growing wild in Senegal was studied according to volatile compound classes, plant organs and sample locations. The composition of fruit essential oil was investigated using an original targeted approach based on the combination of gas chromatography (GC) and liquid chromatography (LC) both coupled with mass spectrometry (MS). The volatile composition of Z. zanthoxyloides fruits exhibited relative high amounts of hydrocarbon monoterpenes (24.3 – 55.8%) and non‐terpenic oxygenated compounds (34.5 – 63.1%). The main components were (E)‐β‐ocimene (12.1 – 39%), octyl acetate (11.6 – 21.8%) and decanol (9.7 – 15.4%). The GC and GC/MS profiling of fruit essential oils showed a chemical variability according to geographical locations of plant material. The LC/MS/MS analysis of fruit oils allowed the detection of seven coumarins in trace content. The chemical composition of fruit essential oils was compared with volatile fractions of leaves and barks (root and trunk) from the same plant station. Hexadecanoic acid, germacrene D and decanal were identified as the major constituents of leaves whereas the barks (root and trunk) were dominated by pellitorine (85.8% and 57%, respectively), an atypic linear compound with amide group. The fruit essential oil exhibited interesting antimicrobial activities against Staphylococcus aureus and Candida albicans, particularly the alcohol fraction of the oil.     

Electroconvulsive therapy for manic state with mixed and psychotic features in a teenager with bipolar disorder and comorbid episodic obsessive–compulsive disorder: a case report

Background

Comorbidity of bipolar disorder and obsessive–compulsive disorder is common in adolescence. Obsessive–compulsive disorder symptoms may be episodic and secondary to alterations in mood, and display specific features. Management of pediatric bipolar disorder-obsessive–compulsive disorder is challenging, as pharmacotherapy of obsessive–compulsive disorder may induce or exacerbate manic episodes and there is limited evidence of treatment efficacy. Electroconvulsive therapy is sparsely used in children and adolescents, but is documented to be a safe and efficacious intervention in adults with bipolar disorder. In view of the severity of symptoms in juvenile mania, studies on treatment strategies are warranted. We report a case of an adolescent with bipolar disorder-obsessive–compulsive disorder who was successfully treated with electroconvulsive therapy during an episode of severe mania.

Case presentation

A 16-year-old girl of Middle East origin first presented to us with depressed mood, irritability, and increased obsessive–compulsive disorder symptoms, which were initially interpreted in the context of acute stress secondary to migration. She had been diagnosed with bipolar disorder and obsessive–compulsive disorder in her previous home country, but had difficulties in accounting for earlier psychiatric history. During hospitalization her mood switched to a manic state with mixed and psychotic features, at times showing aggression toward others. Interruption in her lithium treatment for a short period and possibly the introduction of an atypical antipsychotic could in part have been triggering factors. After 8 weeks of in-patient care and psychotropic drug trials, electroconvulsive therapy was initiated and administered every second or third day for 4 weeks, with marked positive response. No apparent side effects were reported.

Conclusions

This case demonstrates the need for a detailed medical history, taking special note of periodicity and character of obsessive–compulsive disorder symptoms, in adolescents with mood disorders. When treating culturally diverse patients, extra consideration should be taken. Special concerns in the pharmacological treatment to avoid the patient’s condition from worsening must be addressed, including giving priority to mood stabilization before obsessive–compulsive disorder symptoms. There are potential benefits in considering electroconvulsive therapy in young patients with severe mania where first-line treatment options have failed.