An efficient ligation reaction promoted by a Varkud Satellite ribozyme with extended 5'- and 3'-termini.

The Neurospora Varkud Satellite (VS) RNA is capable of promoting a reversible self-cleavage reaction important for its replication pathway. In vivo the VS RNA performs a cis-cleavage reaction to generate monomeric length transcripts that are subsequently ligated to produce circular VS RNA. The predominant form of VS RNA observed in vivo is the closed circular form, though minimal VS ribozyme self-cleavage constructs lack detectable ligation activity. MFOLD analysis of the entire VS RNA sequence revealed an extended region 5' and 3' of the minimal self-cleaving region that could anneal to form a complementary helix, which we have termed helix 7. In full-length VS RNA, this helix appears to span over 40 bp of sequence and brings the 5'- and 3'-ends of the RNA into proximity for the ligation reaction. Here we report a variant of the VS ribozyme with an extended 5'- and 3'-terminus capable of forming a truncated helix 7 that promotes the ligation reaction in vitro. Through mutation and selection of this RNA we have identified a ribozyme containing two point mutations in the truncated helix 7 that ligates with >70% efficiency. These results show that an additional helical element absent in current VS ribozyme constructs is likely to be important for the ligation activity of VS RNA.

Intraoperative use of automated external defibrillator.

We report on the anesthetic management of a patient with peripartum cardiomyopathy and frequent episodes of ventricular tachycardia, who underwent surgery for tracheal stenosis. Prior to this surgery, the patient had been implanted with an automatic implantable cardioverter-defibrillator (AICD), placed abdominally. In the operating room, the AICD was deactivated, and an automated external defibrillator (AED) was placed. Intraoperatively, the AED identified and treated the patient's ventricular tachycardia. Advantages of the AED in this hospital setting included rapid response to the cardiomyopathy, safe, hands-free operation, and minimal disruption of the surgical procedure. Safety concerns when using the AED are also detailed.

Homosexuality and the military.

OBJECTIVE: Homosexuality has remained a focus of military concern despite society's increasing acceptance of homosexual men and women and evidence that homosexuals have served and currently serve in the U.S. armed forces. President Clinton has stated a determination to end discrimination against homosexuals in the military and reverse the exclusionary policy on homosexuals serving in the armed forces. The authors review the history of the policy of the U.S. military to exclude homosexuals from serving in the armed forces. METHOD: The data for this study were drawn from military archives and court cases that have shaped U.S. policy excluding homosexuals from serving in the armed forces. The three main arguments are addressed: 1) homosexuality is a mental disorder rendering a person unstable, 2) homosexual service members are a source of poor morale for military units, and 3) homosexual service members are poor security risks. RESULTS: Considerable evidence demonstrates that homosexuals in the military pose no documented threat to national security and show no evidence of poor work performance. CONCLUSIONS: Although issues of morale and fraternization in the military remain challenges, no evidence in this review supports the exclusion of homosexuals from service in the U.S. armed forces.

Fragmentation into small vesicles of dioleoylphosphatidylcholine bilayers during freezing and thawing.

Multilayered liposomes of some phosphatidylcholines progressively fragment into small vesicles when the electrolyte solution in which they are suspended is subjected to successive cycles of freezing and thawing. The fragmentation process, routinely monitored by absorbance measurements and verified by electron microscopy and dynamic light scattering, involves bilayer breakage and resealing. After 10 cycles of freezing and thawing in 0.1 M electrolyte solution, the result is a population of vesicles smaller than 200 nm diameter. Sucrose, a common cryoprotectant, completely inhibits fragmentation. Fragmentation is absolutely dependent upon the presence of an electrolyte. Those electrolytes most effective in promoting liposome fragmentation have large freezing point depressions and corresponding high solubilities at the freezing point. This, coupled with the observation that saturating concentrations of electrolyte are less effective than 0.1 M solutions indicates that an essential stage in the fragmentation process is osmotic extraction of water from the vesicles, i.e., ice formation in the external phase leads to a progressive increase in the electrolyte concentration of the residual external solution, which, in turn, dehydrates the vesicle. In addition, for maximal fragmentation, the minimum temperature must be at least as low as the solute eutectic temperature. Particular physical properties of the bilayer are also important, for dioleoyl and diphytanoyl derivatives are much more susceptible to fragmentation than are other phosphatidylcholines, and inclusion of 50 mol% cholesterol in dioleoylphosphatidylcholine completely inhibits membrane breakup. This system provides insight into mechanisms of freezing damage to membranes and may also offer a very simple and rapid assay for biological cryoprotectants.

Clinical features of young adult Hispanic psychiatric in-patients: the so-called "Puerto Rican syndrome".

Among 118 young Hispanic (101 Puerto Rican) psychiatric inpatients, somatic complaints, violence, suicidal tendency, hallucinations, sudden onset of symptoms, and dissociative behavior each occurred in 46% or more of patients. There was no difference in clinical presentation between island Puerto Rican patients and Puerto Rican patients raised on the mainland. There was no relationship between these behaviors and any specific psychiatric disorder. Although there is a suggestion that more of these behaviors may occur among Puerto Rican Hispanics, further study with larger control groups is needed.

Cytopathology of neoplasms of the central nervous system in specimens obtained by the Cavitron Ultrasonic Surgical Aspirator.

The Cavitron Ultrasonic Surgical Aspirator (CUSA) is a dissecting system that removes tissue by vibration, irrigation and suction; fluid and particulate matter from tumors are aspirated and subsquently deposited in a canister. The CUSA permits the neurosurgeon to remove large tumors by debulking them quickly and effectively, without traction or manipulation and with minimal transmission of movement to adjacent normal tissues. The cytomorphologic appearances of 22 central nervous system tumors in CUSA samples were evaluated and compared with the findings in biopsy or resection specimens. Papanicolaou-stained and Diff-Quik-stained Cytospin preparations were prepared from the saline irrigation fluid along with a cell block in every case. Three specimens (13.6%) were insufficient for interpretation. Of the materials from seven astrocytic neoplasms examined, two were insufficient for diagnosis. The other insufficient case was tissue obtained from an ependymoma. All 11 meningiomas had diagnostic material in the slides and cell blocks. In general, the cytologic smears and cell block preparations were best preserved in meningiomas and schwannomas. Varying degrees of degeneration were noted in the glial neoplasms. Since tissue obtained from the CUSA may represent the bulk of the specimen, the examination of cytologic smears and especially cell blocks from the tissue that "went down the sucker" and were previously discarded may be quite useful.

Suicide in the U.S. Army: epidemiological and periodic aspects.

An overview of suicide in the U.S. Army is presented in two sections: (1) the epidemiology of U.S. Army suicides, based on biennium reports, and (2) the temporal aspects of those suicides compared with the data for the United States as a whole. A brief historical review documents some of the changes in contemporary military suicide rates compared to those of the past century. The cycles in the number of suicides by day of the week, day of the month, and the month of the year for the U.S. Army are computed and contrasted with those reported for the U.S. resident population.

The surgical exposure of penetrating injuries to the carotid artery at the skull base.

Injuries of the internal carotid artery at the skull base present complex technical problems for the surgeon. Exposure is difficult, distal control of the vessel for shunting or repair is frequently impossible, and thus ligation of the ICA is often necessary as definitive treatment. Three cases involving penetrating injury to the carotid artery at the skull base are presented. The issue of primary repair vs. ligation for carotid injuries is briefly addressed, and the various methods of surgical exposure of the distal extracranial ICA are reviewed.

Lipomyelomeningocele: prenatal diagnosis and management.

Spina bifida is one of the many congenital malformations possibly detectable in utero with ultrasound. Prenatal diagnosis can be useful in planning prompt, appropriate neonatal care of the infant. Lipomyelomeningocele (lipomyeloschisis) is a common subtype of spinal dysraphism. Prognosis for the infant with this skin-covered lesion is very good if appropriate care is provided early. Neonatal resection of these congenital lipomatous tumors is necessary to prevent tethering of the spinal cord that might lead to irreversible neurologic damage if not released. The prenatal ultrasonic appearance of lipomyelomeningocele is illustrated and the clinical presentation, implications, and neonatal neurosurgical care are reviewed.