Activation of K-p21ras and N-p21ras, but not H-p21ras, is necessary for mitogen-induced human airway smooth-muscle proliferation

Ras proteins (H-, K-, and N-p21ras) play critical roles in the control of normal and neoplastic cell growth. To date, however, little is known about the role of p21ras in regulating mitogen-induced smooth muscle and, specifically, human airway smooth-muscle (HASM) cell growth. We postulate that p21ras is a critical signaling event regulating mitogen-induced HASM cell proliferation. Growth-arrested, confluent HASM cells were treated for 1 h with 10 ng/ml epidermal growth factor (EGF), 1 U/ml thrombin, or 5 microM bradykinin, then cell lysates were immunoprecipitated using anti-p21ras antibody. Immunoblot analysis using a pan p21ras antibody, which recognizes H-, K-, and N-p21ras, found no significant difference in p21ras expression in HASM after stimulation with either agent, as compared with control. In parallel experiments, we characterized that HASM cells express K- and N-p21ras, but not H-p21ras. Further, there was no difference between the levels of each p21ras isoform after stimulation with any of the agonists. The time course of p21ras activation, however, was markedly different among agonists. EGF rapidly activated p21ras within 30 s and was sustained for up to 30 min. Although thrombin also induced a rapid rise in p21ras activity after 2.5 min, the activation was transient. In contrast, bradykinin, which is nonmitogenic for HASM cells, did not activate p21ras. Using single-cell microinjection, the role of p21ras activation in modulating mitogen-induced HASM DNA synthesis was determined by 5-bromo-2'-deoxyuridine (BrdU) incorporation and anti-BrdU immunofluorescent staining. Thrombin- and EGF-induced DNA synthesis in cells microinjected with Y13-259, a neutralizing p21ras antibody, was significantly inhibited as compared with those microinjected with isotype-matched rat immunoglobulin G(1) or a vehicle control. These data suggest that activation of p21ras appears to be necessary for EGF and thrombin-induced HASM cell proliferation and that activation of K- and N-p21ras, but not H-p21ras, mediates smooth-muscle cell growth.     

Spinal intradural tumours: Part I--Extramedullary

Sixty-six patients had surgery for an intramedullary nerve sheath tumour under the care of one surgical team in a 16-year period. Surgery concentrated on radical intra- and extradural excision combined if necessary with vertebral column reconstruction. Ninety procedures were used in 35 males and 30 females with an age range 12-81 years. Forty-five per cent were located in the cervical, 26% in the thoracic and 29% in the lumbosacral region. Eighteen patients had NF1 and two patients NF2. Sixty-five per cent were schwannomas, 27% were mixed histology and 6% malignant. In terms of functional outcome, 37 patients improved by one or more Frankel grades, three deteriorated by one Frankel grade and no one who presented with symptoms alone deteriorated. There were no operative deaths; no instrumentation failures and five patients developed a CSF leak.     

Facilitation of spontaneous defibrillation by moxonidine during regional ischaemia in an isolated working rabbit heart model

Moxonidine has been shown to be antiarrhythmic during ischaemia in vivo. This study aimed to investigate its electrophysiological effects in isolated working rabbit hearts in vitro. Monophasic action potential duration, effective refractory period and conduction delay were measured at three ventricular sites. The hearts were treated before and during ischaemia and reperfusion with vehicle, moxonidine (0.01, 0.1 and 1 microM) or labetalol (1 microM). In all groups, ventricular fibrillation was always induced during ischaemia. Only 0.1 microM moxonidine decreased the incidence of sustained ventricular fibrillation from 86 to 17%, although it did not affect any electrophysiological parameters measured. Similarly, labetolol, an adrenoceptor blocker, facilitated spontaneous defibrillation without any electrophysiological effects. In conclusion, moxonidine directly facilitates spontaneous defibrillation of ventricular fibrillation during ischaemia. Since the same effect is observed with labetalol, it is possible that the defibrillatory action of moxonidine is related to its peripheral antiadrenergic activity, although other mechanisms cannot be excluded.     

Evaluation of phosphoramidon and three synthetic phosphonates for inhibition of botulinum neurotoxin B catalytic activity

Three putative metalloprotease inhibitors were synthesized and tested for their ability to inhibit the catalytic activity of botulinum neurotoxin B light chain (BoNT/B LC). The compounds were designed to emulate the naturally occurring metalloprotease inhibitor phosphoramidon, which has been reported to be a weak antagonist of BoNT/B action. All three analogs contained the dipeptide Phe-Glu in place of Leu-Trp of phosphoramidon and possessed a phenyl, ethyl or methyl group in place of the rhamnose sugar of the parent compound. The inhibitors were evaluated in a cell-free assay based on the detection of a fluorescent product following cleavage of a 50-mer synaptobrevin peptide ([Pya(88)] S 39-88) by BoNT/B LC. This peptide corresponds to the hydrophilic core of synaptobrevin-2 and contains a fluorescent analog L-pyrenylalanine (Pya) in place of Tyr(88). Cleavage of [Pya(88)] S 39-88 by BoNT/B LC gives rise to fragments of 38 and 12 amino acid residues. Quantification of BoNT/B-mediated substrate cleavage was achieved by separating the 12-mer fragment (FETSAAKLKRK-Pya) that contains the C-terminal fluorophore and measuring fluorescence at 377 nm. The results indicate that the phenyl-substituted synthetic compound ICD 2821 was slightly more active than phosphoramidon, but analogs with methyl or ethyl substitutions were relatively inactive. These findings suggest that phosphonate monoesters may be useful for providing insights into the structural requirement of BoNT/B protease inhibitors.     

The role of pancreatic venous sampling in the localization of occult insulinomas

The palpation and enucleation of occult insulinomas (less than 15 mm) can be a difficult surgical problem even with good arteriographic localization. In the authors' limited experience, confirmation of arteriographic findings by pancreatic venous sampling provided little additional localizing information. However, if arteriography is negative or equivocal, venous sampling can indicate the segment of pancreas to be "blindly" resected if the adenoma is not palpable. Venous sampling may be misleading in polyendocrine syndromes because of the frequency of multiple adenomas and variable hormone production.     

Scoliosis prevalence: a call for a statement of terms

Recently published prevalence studies of scoliosis reveal a disconcerting variability, largely due to the use of different diagnostic "cutting points", which are frequently unstated. A statistical analysis of the prevalence of moderate and severe scoliotic curves shows that the distribution of scoliotic curves conforms best to a log normal distribution. Using this analysis, and using 10 degrees as the "cutting point" for the diagnosis, the adolescent scoliosis population consists of approximately 25 per 1,000.