Molecular identification of two novel Munc-18 isoforms expressed in non-neuronal tissues

Munc-18, also known as n-Sec1 or rbSec1, is a syntaxin-binding protein thought to play a role in regulating synaptic vesicle exocytosis. Although a gene family of syntaxins has been identified, only a limited subset bind to Munc-18. This implicates the existence of other mammalian Munc-18 homologues that may be involved in a range of vesicle transport reactions. The purpose of the present study was to identify other members of the Munc-18 family by cDNA cloning. Three distinct Munc-18 isoforms, Munc-18a, previously identified in neuronal tissue, and two novel isoforms, Munc-18b and Munc-18c, were isolated from a 3T3-L1 adipocyte cDNA library by screening with a rat brain Munc-18 DNA probe. Munc-18a is identical to Munc-18 and by Northern analysis is expressed predominantly in brain and to a lesser extent in testis and 3T3-L1 cells. Munc-18b is 62% identical to Munc-18 at the amino acid level and is expressed in testis, intestine, kidney, rat adipose tissue, and 3T3-L1 cells. Munc-18c is 51% identical to Munc-18 and is ubiquitously expressed. It is likely, based on these findings, that unique Munc-18/syntaxin interactions may play an important role in generating a combinatorial mechanism for the regulation of vesicle transport in mammalian cells.

Incidence of complications after carotid sinus massage in older patients with syncope

OBJECTIVE

To review the incidence of neurological complications occurring after carotid sinus massage performed for diagnostic purposes.

DESIGN

Case review and comparison with previously published work.

SETTING

Syncope Clinic, Royal Victoria Infirmary, Newcastle-upon-Tyne, and Chelsea and Westminster Hospital, London.

PARTICIPANTS

Patients undergoing investigation of dizziness, syncope, or unexplained falls.

METHODS

Carotid sinus massage performed for 5 seconds in both supine and erect postures, both before and after atropine. Contraindications to carotid sinus massage were the presence of carotid bruits, recent myocardial or cerebral ischemia, or previous ventricular tachyarrhythmias.

RESULTS

Two cases of neurological complications were reported from a total of 500 patients (2000 massage episodes) investigated in one center, giving an incidence of 0.1%. Combining this data with another center performing investigations in a similar fashion, seven neurological complications arose from a total of 5000 massage episodes, an incidence of 0.14%. Reported complications were pyramidal signs in five cases and visual field defects in two. Pyramidal weakness persisted in one case with a pre-existing stroke on the same side, and a visual field loss was permanent in one.

CONCLUSIONS

Neurological complications following carotid sinus massage for diagnosis of the carotid sinus syndrome are uncommon and usually transient. Contraindications to carotid sinus massage should be respected and the standardized technique used.

Determination of inorganic arsenic and its organic metabolites in urine by flow-injection hydride generation atomic absorption spectrometry

A method has been developed for the determination of inorganic arsenic [As(III) and As(V)] and its organic metabolites (monomethylarsenic and dimethylarsenic) in urine by flow-injection hydride generation atomic absorption spectrometry. The nontoxic seafood-derived arsenobetaine and arsenocholine species were first separated by a solid-phase extraction procedure. The remaining sample was digested with a mixture of nitric and sulfuric acids and potassium dichromate, followed by attack with hydrogen peroxide. The resulting As(V) was reduced to As(III) with potassium iodide in hydrochloric acid before injection into the flow-injection manifold. The percentage analytical recoveries (mean +/- 95% confidence interval) of various arsenic species added to a urine specimen at 250 micrograms/L were 108 +/- 2, 112 +/- 11, 104 +/- 7, and 95 +/- 5 for As(III), As(V), monomethylarsenic, and dimethylarsenic, respectively. For the determination of arsenic in Standard Reference Material 2670 (toxic metals in human urine), results agreed with the certified value (480 +/- 100 micrograms/L). Analyses of samples for the Centre de Toxicologie du Quebec, containing seafood-derived species, demonstrated the viability of the separation procedure. Detection limits were between 0.1 and 0.2 microgram/L in the solution injected into the manifold, and precision at 10 micrograms/L was between 2% and 3% (CV). These preliminary results show that the method might be applicable to determinations of arsenic in a range of clinical urine specimens.

Determination of inorganic arsenic and its organic metabolites in urine by flow-injection hydride generation atomic absorption spectrometry

A method has been developed for the determination of inorganic arsenic [As(III) and As(V)] and its organic metabolites (monomethylarsenic and dimethylarsenic) in urine by flow-injection hydride generation atomic absorption spectrometry. The nontoxic seafood-derived arsenobetaine and arsenocholine species were first separated by a solid-phase extraction procedure. The remaining sample was digested with a mixture of nitric and sulfuric acids and potassium dichromate, followed by attack with hydrogen peroxide. The resulting As(V) was reduced to As(III) with potassium iodide in hydrochloric acid before injection into the flow-injection manifold. The percentage analytical recoveries (mean +/- 95% confidence interval) of various arsenic species added to a urine specimen at 250 micrograms/L were 108 +/- 2, 112 +/- 11, 104 +/- 7, and 95 +/- 5 for As(III), As(V), monomethylarsenic, and dimethylarsenic, respectively. For the determination of arsenic in Standard Reference Material 2670 (toxic metals in human urine), results agreed with the certified value (480 +/- 100 micrograms/L). Analyses of samples for the Centre de Toxicologie du Quebec, containing seafood-derived species, demonstrated the viability of the separation procedure. Detection limits were between 0.1 and 0.2 microgram/L in the solution injected into the manifold, and precision at 10 micrograms/L was between 2% and 3% (CV). These preliminary results show that the method might be applicable to determinations of arsenic in a range of clinical urine specimens.

Benefits of fludrocortisone in the treatment of symptomatic vasodepressor carotid sinus syndrome

OBJECTIVE

To assess treatment with fludrocortisone in vasodepressor carotid sinus syndrome.

PATIENTS AND METHODS

Eleven patients, mean (SD) age 83 (5) years, with daily dizzy episodes and a median of five (range two to 20) syncopal episodes over a median of one year were studied. All had vasodepressor carotid sinus syndrome (> 50 mm Hg fall in systolic blood pressure during carotid sinus massage independent of bradycardia). Carotid sinus massage was carried out while the patient was supine and upright (tilt table) before and after 600 micrograms intravenous atropine. Phasic heart rate and blood pressure recordings were monitored throughout. The study was repeated after 100 micrograms of fludrocortisone daily by mouth for two weeks. Patients continued to take fludrocortisone for a six month follow up period.

RESULTS

Baseline systolic blood pressure was (mean (SD)) 169 (31) mm Hg and the RR interval was 770 (150) ms. After carotid sinus massage, systolic blood pressure fell to 113 (27) mm Hg (p < 0.01) and RR was 1060 (210) ms (NS). The vasodepressor response was 56 (12) mm Hg. Baseline systolic blood pressure after two weeks of fludrocortisone treatment was 171 (37) mm Hg (NS); but the fall in systolic blood pressure during carotid sinus massage was significantly reduced (32 (14) mm Hg; p < 0.01). At six months follow up, two patients complained of intermittent dizziness and no patients had syncope.

CONCLUSION

Fludrocortisone effectively reduces the vasodepressor response and relieves the symptoms of vasodepressor carotid sinus syndrome.

Outcome of an integrated approach to the investigation of dizziness, falls and syncope in elderly patients referred to a 'syncope' clinic

Sixty-five consecutive elderly patients (mean age 78 years) referred to a 'syncope' clinic over a six-month period were prospectively studied. Initial evaluation included ambulatory electrocardiography, carotid sinus massage before and after atropine and prolonged head-up tilt. Diagnostic criteria for causes of syncope were assigned at the beginning of the study. Overall, a diagnosis was attributed to symptoms in 92% of patients; overlap was present in a quarter. Diagnoses were cardioinhibitory carotid sinus syndrome (CSS; 5%), vasodepressor CSS (26%), mixed CSS (14%), orthostatic hypotension (32%), vasodepressor vasovagal syncope (11%), cardiac arrhythmia (21%), epilepsy (9%), cerebrovascular disease (6%) and others (12.5%). Sixty per cent of patients with vasodepressor CSS also had orthostatic hypotension or vasodepressor vasovagal syncope suggesting a common aetiology. Using an integrated approach incorporating head-up tilt and carotid sinus massage in a selected group of elderly patients referred to a 'syncope' clinic, the diagnostic yield was high.

Fibrinogen Ledyard (A alpha Arg16----Cys): biochemical and physiologic characterization

Fibrinogen Ledyard was discovered in a 10-year-old boy with a mild bleeding history. His father had the same defect and a bleeding history after surgery. Both patients were heterozygous. The plasma fibrinogen concentration was normal immunologically (335 mg/dL) and very low functionally (52 mg/dL). Purified fibrinogen Ledyard had a prolonged polymerization, which was somewhat corrected by addition of Ca2+ ions. High performance liquid chromatography (HPLC) analyses of the fibrinopeptides released by thrombin showed 1 mol of fibrinopeptide A (FPA) and 2 mol of fibrinopeptide B (FPB) released per mole of fibrinogen Ledyard. Steady-state kinetic parameters were evaluated for release of FPA by thrombin. When the concentration of fibrinogen Ledyard was corrected to 50% of total protein, because only 50% of fibrinogen Ledyard can release FPA, the kinetic constants were similar to those of control fibrinogen (Km = 7.5 mumol/L for A alpha chain, kcat = 54 s-1). This finding indicates that the cleavage site of the A alpha chain in these abnormal molecules may not interact with the catalytic site of thrombin. The three chains of fibrinogen Ledyard were isolated on reverse-phase C4-HPLC. The sequence of the amino terminus of A alpha chain showed that Arg in position 16 was replaced by Cys in the abnormal molecules. Approximately half of fibrinogen Ledyard (52%) was clotted by reptilase, suggesting that fibrinogen Ledyard may consist of 50% normal homodimers (A alpha Arg16 . A alpha Arg16) and 50% abnormal homodimers (A alpha Cys16 . A alpha Cys16). Abnormal molecules could form disulfide bond between the A alpha Cys16 residues. Thus, the abnormal molecules have a different structure that does not bind to thrombin. Probably the abnormality of polymerization of fibrinogen Ledyard results from the interaction of the abnormal molecules with normal fibrin monomers, so that the growth of fibrin protofibrils is inhibited. This abnormal fibrinogen supports adenosine diphosphate-induced platelet aggregation in a normal manner.

Development and evaluation of the revised Alcohol Evaluation Instrument

This study reports on the development of a revised version of the Alcohol Evaluation Instrument (ALCEVAL-R). Items in the four major areas of the ALCEVAL-R were factor analyzed separately and relationships among factors were examined. Results suggest that the ALCEVAL-R measures clinically meaningful aspects of the alcoholic patient's occupational and social status, and reveals important dimensions of alcohol consumption and of the personal and social consequences of alcohol abuse.

Elective splenopexy for wandering spleen

The diagnosis of wandering spleen is usually made at the time of operation owing to symptoms caused by torsion of the spleen. Splenectomy has been performed in almost all of the reported cases. A 6-year-old girl presented with intermittent abdominal pain and a mobile abdominal mass. The diagnosis of wandering spleen was confirmed by computerized tomography. Elective splenopexy was performed by securing the spleen in an extraperitoneal pocket.