A unique Hawaiian Schiedea (caryophyllaceae: Alsinoideae) with only five fertile stamens.

The floral organogenesis and subsequent ontogenies of the Hawaiian endemic species Schiedea pubescens from Maui, Moloka'i, and Lana'i, and the Wai'anae Mountains, O'ahu, populations previously considered to be varietally distinct, were examined using the scanning electron microscope (SEM). The O'ahu population consistently produced only five fertile stamens, those of the inner whorl. The five stamens of the alternisepalous or outer whorl abort prior to microsporogenesis and fail to elongate. Additional vegetative differences between the two taxa, combined with the floral morphology characters, merit the description of the O'ahu population as a new species, S. pentandra, described herein.

Crystal structure of adenylosuccinate synthetase from Escherichia coli. Evidence for convergent evolution of GTP-binding domains.

The structure of the P2(1) crystal form of adenylosuccinate synthetase from Escherichia coli has been determined to a resolution of 2.8 A. The refined model for the enzyme gives an R factor of 0.20 and a root-mean-square deviation from expected bond lengths and angles of 0.016 A and 2.27 degrees, respectively. The dominant structural element of each monomer of the homodimer is a central beta-sheet of 10 strands. The first nine strands of the sheet are mutually parallel with right-handed crossover connections between the strands. The 10th strand is antiparallel with respect to the first nine strands. In addition, the enzyme has two antiparallel beta-sheets, comprised of two strands and three strands each, 11 alpha-helices and two short 3/10-helices. The overall fold of the polypeptide chain has not been observed heretofore in any other protein structure. Residues tentatively assigned to the active site of the enzyme on the basis of chemical modification and directed mutation cluster in two separate regions. Gly12, Gly15, Gly17, Lys18, Ile19, and Lys331 lie at one end of a crevice that measures 12 A by 30 A by 12 A deep. Lys140 and Arg147 are not part of this crevice, but instead lie at the interface between monomers of the dimer. Lys140 makes a salt link with Asp231 of a monomer related by molecular symmetry and Arg147 binds to the carbonyl of the same Asp231. Superposition of the p21 ras protein (Pai, E. F., Kabsch, W., Krengel, U., Holmes, K., John, J., and Wittinghofer, A. (1989) Nature 341, 209-214) onto the synthetase reveals significant correspondences between side chains of the two proteins. Residues which interact with GTP in the p21ras protein have structurally equivalent residues in the synthetase. The GTP molecule, when transformed to the coordinate frame of the synthetase, falls into the crevice defined by studies in directed mutation. We suggest that the similarities in the GTP-binding domains of the synthetase and the p21ras protein are an example of convergent evolution of two distinct families of GTP-binding proteins.

Refined structure for the complex of 1-deoxynojirimycin with glucoamylase from Aspergillus awamori var. X100 to 2.4-A resolution.

The three-dimensional structure of the complex of 1-deoxynojirimycin with glucoamylase II-(471) from Aspergillus awamori var. X100 has been determined to 2.4-A resolution. The model includes residues corresponding to residues 1-471 of glucoamylase I from Aspergillus niger, two molecules of bound 1-deoxynojirimycin and 605 sites for water molecules. The crystallographic R factor from refinement is 0.119, and the root-mean-squared deviation in bond distances is 0.012 A. The inhibitor complex confirms the location of the active site in the packing void of the alpha/alpha-barrel as proposed by Aleshin et al. [Aleshin, A., Golubev, A., Firsov, L., & Honzatko, R. B. (1992) J. Biol. Chem. 267, 19291-19298]. One inhibitor molecule is associated with strong electron density and represents the principal site of interaction of 1-deoxynojirimycin with the enzyme. The other 1-deoxynojirimycin molecule is associated with weak electron density and therefore, probably represents a binding site of low affinity. Interactions of 1-deoxynojirimycin with the enzyme at its principal site involve Arg 45, Asp 55, Arg 305, and carbonyl 177. In addition, a water molecule (water 500) hydrogen bonds to Glu 400 and the 6-hydroxyl of 1-deoxynojirimycin and is at an approximate distance of 3.3 A from the "anomeric" carbon of the inhibitor. The structural arrangement of functional groups near the inhibitor molecule suggests that Glu 179 is a catalytic acid, Glu 400 a catalytic base, and water 500 the attacking nucleophile in the hydrolysis of maltooligosaccharides. The relevance of the X-ray work to proposed mechanisms of enzymatic hydrolysis of oligosaccharides is discussed.

The Romano-Ward syndrome: a case presenting as near drowning with a clinical review.

Patients with the Romano-Ward syndrome, a form of congenital long Q-T syndrome (LQTS), present with syncopal episodes and are at risk for sudden death. Patients with LQTS may be misdiagnosed if the physician is unaware of this entity. The risk of sudden death makes recognition important so that appropriate therapy can be initiated. A case is discussed in which the patient presented following a near-drowning episode. Family history revealed a familial "seizure disorder." After analysis of the patient's and father's ECGs, the diagnosis of Romano-Ward syndrome was made. A review of the literature was done, concentrating on presentation, pathophysiology, electrocardiographic findings, etiology, diagnosis, prognosis, and treatment of congenital LQTS. This paper is presented to emphasize the importance of physician awareness of LQTS because of the risk of sudden death. Proper diagnosis can lead to treatment that is effective in reducing mortality by more than 90%.

Accessing community development research methodologies.

This paper is a perspective on the strengths and weaknesses of community development research offered to health promoters by a community development insider. The author provides her rationale for the opinion that no research paradigm other than the qualitative one satisfies the naturalistic context of either community development or health promotion, including inquiry into concepts such as community health, community wellbeing, community competence and community self-reliance. Attention is drawn to key aspects of the community development process with relevance to health promoters which are largely undertheorized, including clarity about the central issue of the nature of the interaction among learning, action and change. Finally, the paper specifies three implications of the naturalistic paradigm for either research or practice. These include academic prejudice against qualitative research from some quarters, the limitations of all research paradigms for some questions, and essential uncertainties of naturalistic inquiry.

Chronic mountain sickness in Tibet.

A clinical syndrome identical to the chronic mountain sickness of the Andes occurs commonly in Lhasa, Tibet. It affects, almost exclusively, the immigrant Han population and develops after an average of 15 years' residence at high altitude. The early symptoms are attributable to polycythaemia--headache, dizziness, loss of memory and fatigue being prominent. In the later stages of the disease, dyspnoea and peripheral oedema develop. Haemodynamic investigations show pulmonary hypertension with a normal cardiac output and dilatation of the right ventricle in the long-established case. Respiratory gas studies provide evidence of alveolar underventilation and ventilation: perfusion inhomogeneity. Both clinical and investigatory data suggest that the earlier stages of the disease are dominated by polycythaemia, while cardiopulmonary involvement increases with the duration of the disease. The disease is rare in women and uncommon in Tibetans. Cigarette smoking appears to be a contributory factor.

Compensation for resistance in series with excitable membranes.

Extracellular resistance in series (Rs) with excitable membranes can give rise to significant voltage errors that distort the current records in voltage-clamped membranes. Electrical methods for measurement of and compensation for such resistances are described and evaluated. Measurement of Rs by the conventional voltage jump in response to a current step is accurate but the measurement of sine-wave admittance under voltage-clamp conditions is better, having about a fivefold improvement in resolution (+/- 0.1 omega cm2) over the conventional method. Conventional feedback of the membrane current signal to correct the Rs error signal leads to instability of the voltage clamp when approximately two-thirds of the error is corrected. We describe an active electronic bridge circuit that subtracts membrane capacitance from the total membrane current and allows full, yet stable, compensation for the voltage error due to ionic currents. Furthermore, this method provides not only fast and accurate control of the membrane potential in response to a command step, but also fast recovery following an abrupt change in the membrane conductance. Marked changes in the kinetics and amplitude of ionic currents resulting from full compensation for Rs are shown for several typical potential patterns.

Pulmonary effects of furosemide in preterm infants with lung disease.

Twenty preterm infants recovering from respiratory distress syndrome at 1 week of age were randomized in this study either to a control or a treatment group. Those treated received a single daily dose of furosemide (1 mg/kg) intravenously. Pulmonary compliance was observed to improve significantly at two hours in the treated group, as compared with that in the controls. The calculated alveolar-arterial oxygen gradient was noted to decrease two hours after furosemide and to remain decreased over the four-day period in the treated group. This improvement in lung function was not secondary to diuresis in the infants treated with furosemide. We conclude that furosemide may have a direct pulmonary effect and improve lung function acutely as well as with chronic administration.