Hydrazine and amphetamine binding to amine oxidases: old drugs with new prospects

Tranylcypromine (TCP), an amphetamine, is a reversible inhibitor of copper-containing amine oxidases. We have solved the structure of the complex of TCP with the amine oxidase from E. coli (ECAO) and shown that only the (+)-enantiomer of TCP binds. Kinetic studies on 2-phenylethylamine and TCP binding to wild-type ECAO and mutational variants fully support the model in which binding of the protonated amine is the first step in the catalytic cycle. Hydrazines are irreversible inhibitors of copper-containing amine oxidases. Binding of hydrazines leads to an adduct ("Adduct 1") with a chromophore at 430 nm which converts at higher pH to another adduct ("Adduct 2") with a chromophore at 520 nm. We have determined the structures of Adduct 1 and 2 for 2-hydrazinopyridine reacted with ECAO. It has been found that Adduct 1 corresponds to the hydrazone and azo tautomers whilst Adduct 2 corresponds to the azo tautomer coordinated to the active site copper. The implications of these results in developing more specific drugs are discussed.

A transcription factor involved in skeletal muscle gene expression is deleted in patients with Williams syndrome

Williams-Beuren syndrome (WS) is a developmental disorder caused by a hemizygous microdeletion of approximately 1.4MB at chromosomal location 7q11.23. The transcription map of the WS critical region is not yet complete. We have isolated and characterised a 3.4 kb gene, GTF3, which occupies about 140 kb of the deleted region. Northern blot analysis showed that the gene is expressed in skeletal muscle and heart, and RT-PCR analysis showed expression in a range of adult tissues with stronger expression in foetal tissues. Part of the conceptual GTF3 protein sequence is almost identical to a recently reported slow muscle-fibre enhancer binding protein MusTRD1, and shows significant homology to the 90 amino-acid putative helix-loop-helix repeat (HLH) domains of the transcription factor TFII-I (encoded for by the gene GTF2I). These genes may be members of a new family of transcription factors containing this HLH-like repeated motif. Both GTF3 and GTF2I map within the WS deleted region, with GTF2I being positioned distal to GTF3. GTF3 is deleted in patients with classic WS, but not in patients we have studied with partial deletions of the WS critical region who have only supravalvular aortic stenosis. A feature of WS is abnormal muscle fatiguability, and we suggest that haploinsufficiency of the GTF3 gene may be the cause of this.

An elastin gene mutation producing abnormal tropoelastin and abnormal elastic fibres in a patient with autosomal dominant cutis laxa

Elastin is the protein responsible for the characteristic elastic properties of many tissues including the skin, lungs and large blood vessels. Loss-of-function mutations in the elastin gene are known to cause the heart defect supravalvular aortic stenosis (SVAS). We and others have identified deletions, nonsense mutations and splice site mutations in SVAS patients that abolish the function of one elastin gene. We have now identified an elastin mutation in a patient with a completely different phenotype, the rare autosomal dominant condition cutis laxa. A frameshift mutation in exon 32 of the elastin gene is predicted to replace 37 amino acids at the C-terminus of elastin by a novel sequence of 62 amino acids. mRNA and immunoprecipitation studies show that the mutant allele is expressed. Electron microscopy of skin sections shows abnormal branching and fragmentation in the amorphous elastin component, and immunocytochemistry shows reduced elastin deposition in the elastic fibres and fewer microfibrils in the dermis. These findings suggest that the mutant tropoelastin protein is synthesized, secreted and incorporated into the elastic matrix, where it alters the architecture of elastic fibres. Interference with cross-linking would reduce elastic recoil in affected tissues and explain the cutis laxa phenotype.

Of balloon axilloscopy and avoidance of iatrogenic injury to the long thoracic nerve

BACKGROUND

Laparoscopic removal of axillary lymph nodes is possible and affords an excellent view of all structures, allowing preservation of vessels and nerves. The technique uses pediatric trocars and a lifting device to maintain the newly created axillary space.

OBJECTIVE

To prove that a newly developed technique of balloon axilloscopy can be performed using only one 10-mm and two 5-mm standard trocars and constant carbon dioxide flow to preserve the axillary space and that preservation of all nerves and vessels is possible with this approach.

DESIGN

Prospective study on 4 fresh-frozen human cadavers and 7 live porcine models.

SETTING

A hospital department of minimal surgery access and a university department of anatomy.

RESULTS

The balloon dissection consistently revealed and preserved the nerves and vessels, and exposure and dissection of the first rib could similarly be accomplished. An alternative route to the apex of the axilla has been developed--between the pectoralis minor and pectoralis major muscles--after their careful separation. The axillary content of surgical interest (lymph nodes) is easily separated from the other anatomical elements and is simply dissected under complete visualization and preservation of all vital axillary structures.

CONCLUSIONS

Balloon axilloscopy was easy to perform, provided the surgeon with constant visualization of vital anatomical structures, and allowed easy separation and dissection of the axillary lymph nodes and the first rib. As a technical aid prior to a conventional axillary dissection, or as part of a pure endoscopic procedure in the axilla, balloon axilloscopy is 100% reliable in identifying the long thoracic nerve and moving it out of the way, separating the lymph nodes from it and from the intercostobrachial nerve and axillary vein and artery, rendering the whole dissection process safer for both the surgeon and the patient.

Structure and mechanism of galactose oxidase. The free radical site

Crystallographic and spectroscopic studies on galactose oxidase have shown that the active site involves a free radical on tyrosine 272, one of the ligands coordinated to the Cu2+ cofactor. A novel thioether bond between tyrosine 272 and cysteine 228, and a stacking tryptophan 290, over this bond, are features of the crystal structure. The present study describes the development of a high level heterologous expression system for galactose oxidase and the construction of mutational variants at these key active site residues. The expressed wild-type enzyme and mutational variants (W290H and C228G) have been characterized by x-ray crystallography, visible spectroscopy, and catalytic activity measurements. A further variant protein, Y272F, could not be purified. The data establish that the thioether bond and stacking tryptophan are essential for activity and further support a role for tryptophan 290 as a component of the free radical site.

The effects of the electroejaculation procedure on sperm motility

Electroejaculation is becoming more available for obtaining semen from spinal cord injured men wishing to father children. This study was undertaken to determine what effect the electroejaculation procedure itself had on sperm motility. Factors which were found to impact on sperm motility were osmolarity, electric current and aqueous jelly lubricant used for bladder catheterisation. pH did not affect sperm motility.

Inhibition of hypertonic saline-induced bronchoconstriction by terfenadine and flurbiprofen. Evidence for the predominant role of histamine

We investigated the possible inhibitory effects of terfenadine, a histamine H1-receptor antagonist, and flurbiprofen, a cyclooxygenase inhibitor, on the bronchoconstrictor effect of inhaled 3.6% hypertonic saline in a randomized, double-blind study. Nine mildly asthmatic subjects with a history of exercise-induced asthma took part. This was conducted, first as a dose-response study and, second, as a time-course study. In the dose-response study, the provocative dose of saline-laden air causing a 25% fall in FEV1 was calculated (PD25). Terfenadine (180 mg) and the combination of terfenadine (180 mg) plus flurbiprofen (100 mg) both protected significantly against hypertonic saline challenge, achieving increases in PD25 values by factors of 7.24 and 6.30, respectively. Flurbiprofen (100 mg) also displaced the dose-response to the right, increasing the PD25 by a factor of 1.92, but this protection was significantly less than that afforded by terfenadine. In the time-course studies, a single inhalation of hypertonic saline previously shown to cause at least a 25% fall in FEV1 was administered, and FEV1, was followed for 30 min. Preadministration of terfenadine reduced the mean area under the curve of percentage fall in FEV1-time response by 68.5%, with similar results obtained with the combination of terfenadine and flurbiprofen. We conclude that the bronchoconstriction in asthma provoked by inhaled hypertonic saline is mediated predominantly through the hyperosmolar release of histamine from airway mast cells, with a minor contribution being made by prostanoids.

Neuropsychiatric assessment of a spinal cord injury patient with sudden recovery

Reported here is the case of a 23-year-old man who, presenting as a spinal cord injury patient with paraplegic and bilateral sensory impairments in the legs, made a rather dramatic recovery after receiving a trivial jolt while moving about in his wheelchair. In addition to clinical findings, both hypnotic and somatosensory evoked potential test results were used to help determine whether there was or was not actual spinal cord injury and whether there was or was not a psychologic overlay involving either malingering or a conversion disorder. In this case, evidence pointed to malingering in the presence of a minor spinal cord injury documented by somatosensory evoked potential patterns.

Neurological prognosis after traumatic quadriplegia. Three-year experience of California Regional Spinal Cord Injury Care System

Between January, 1974, and December, 1976, 123 patients with traumatic quadriplegia were admitted to the California Regional Spinal Cord Injury Care System. The spinal cord injury resulted from gunshot wounds in five, from a stab wound in one, from neck injuries with no bone damage seen on x-ray studies in 10, and from fracture dislocations of the cervical spine in 107. One-year following-up information was available on 114 patients. Neurological impairment using the Frankel classification system was compared at 72 hours postinjury to the 1-year follow-up examination. Fifty of 62 patients with complete injury at 72 hours were unchanged at 1 year. Five of these 62 patients had developed motor useful function in the legs or became ambulatory by 1 year, but all had sustained serious head injuries at the time of their trauma making initial neurological assessment unreliable. Ten percent of all cases had combined head injury impairing consciousness. Among 103 cognitively intact patients, none with complete injury at 72 hours were walking at 1 year. Of patients with sensory incomplete functions at 72 hours postinjury, 47% were walking at 1 year; 87% of patients with motor incomplete function at 72 hours postinjury were walking at 1 year. Spinal surgery during the first 4 weeks postinjury did not improve neurological recovery. A method of analyzing neurological and functional outcomes of spinal cork injury is presented in order to more accurately evaluate the results of future treatment protocols for acute spinal injury.