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PubMed1986

The pH dependence of proton-deuterium exchange, hydrogen production and uptake catalyzed by hydrogenases from sulfate-reducing bacteria.

Different patterns have been found in the pH dependence of hydrogenase activity with enzymes purified from different species of Desulfovibrio. With the cytoplasmic hydrogenase from Desulfovibrio baculatus strain 9974, the pH optima in H2 production and uptake were respectively 4.0 and 7.5 with a higher activity in production than in uptake. The highest D2-H+ exchange activity was found also at pH 4.0 but the optima differed for the HD and the H2 components. Both similarly rose when the pH decreased from 9.0 to 4.5, but the rate of H2 evolution slowed whereas the HD evolution continued rising till pH values around 3.0 were reached. The H2 to HD ratio at pH above 4.5 was higher than one. With the periplasmic hydrogenase from Desulfovibrio vulgaris Hildenborough, the highest exchange activity was near pH 5.5, the same value as in hydrogen production. The periplasmic hydrogenase from Desulfovibrio gigas had in contrast the same pH optimum in the exchange (7.5-8.0) as in the H2 uptake. The ratio of H2 to HD was below one for both enzymes. These different patterns may be related to functional and structural differences in the three hydrogenases so far studied, particularly in the composition of their catalytic centers.

Cytoplasm↗
PubMed1996

Codon reassignment in Candida species: an evolutionary conundrum.

A number of Candida species translate the standard leucine CUG codon as serine rather than as leucine. Such codon reassignment in nuclear-encoded mRNAs is unusual and raises a number of important questions about the origin of the genetic code and its continuing evolution. In particular we must establish how a codon can come to be reassigned without extinction of the species and what, if any, selective pressure drives such potentially catastrophic changes. Recent studies on the structure and identity of the novel CUG-decoding tRNA(Ser) from several different Candida species have begun to shed light on possible evolutionary mechanisms which could have facilitated such changes to the genetic code. These findings are reviewed here and a possible molecular mechanism proposed for how the standard leucine CUG codon could have become reassigned as a serine codon.

Base Sequence↗
PubMedDate not supplied

Medicaid managed care and the emergency department: the first one hundred days.

Spurred by concerns over increasing costs and variable quality, public and private third-party payors are moving their subscribers into managed care plans. A central feature of many of these plans is coordination of patient care through a primary care provider (PCP). In exchange for easy access to the PCP, patients are expected to limit their use of emergency services for episodic, primary, and urgent care problems. The State of Connecticut has begun a transition from a fee-for-service Medicaid plan into a managed care product. Because many Medicaid patients had freely used emergency services under the fee-for-service arrangement, urban teaching hospital emergency departments rapidly became a focus of efforts to control cost and change care-seeking behavior. The Hartford Hospital Emergency Department (ED) began screening, education, and referral of managed Medicaid patients in the fall of 1995 and recorded experiences with patients, administrators, and health care providers involved in the implementation of the managed care program. The first 3 mo following plan implementation were chaotic and frustrating for all parties, with many difficulties due to an unprepared infrastructure. Changes in ED operations and maturation of the payor and health care provider network eventually resulted in a reasonably smooth system accompanied by reductions in ED visit volumes of at least 15%. Continual evolution of role and goals will be necessary if EDs are to maintain an active presence in a health care system dominated by managed care plans.

Aid to Families with Dependent Children↗
PubMed1992

A randomized controlled trial of early surgery in Duchenne muscular dystrophy.

We performed a randomized controlled trial of early surgical treatment of contractures in 20 boys with Duchenne muscular dystrophy, age 4-6 yr. Surgery consisted of release of hip flexors, removal of iliotibial bands, and lengthening of tendo Achilles bilaterally. All patients were monitored for at least 12 months post-randomization, and assessed quantitatively for muscle strength and function. Surgery corrected the deformities, but had no beneficial effect on strength or function. Indeed, data in the second year showed more rapid deterioration of function in some of the operated boys. There appeared to be continued evolution of pathology following surgery, as assessed by sequential muscle ultrasound and muscle biopsy. We cannot recommend this type of surgery as a routine treatment.

Biopsy↗
PubMed1993

[Characteristics and mechanisms of action of leukocyte depletion filters].

Since their creation, leukocyte depletion filters, used to prepare leukocyte-poor red cell or platelet concentrates, have been continuously evoluting: their volume has been reduced and their composition has been modified, polyester fibers have replaced cotton wool or cellulose acetate. In the same way, their capacity to remove leukocytes has increased. The mechanisms of cell separation are still unclear. Through published studies, different factors seem to be implicated, such as wetable surface of the filter, surface tension or charge density of fibers. It was also observed that removal of lymphocytes from red cell concentrates is rather based on trapping in the fiber network, and that removal of granulocytes, monocytes and platelets is partly due to activation and subsequent adhesion to the fibers. There have been few studies of the mechanism of leukocytes depletion from platelets concentrates.

Adsorption↗
PubMed1995

Orthoses and prostheses.

Orthoses and prostheses include a wide range of devices and strategies for correcting and alleviating dysfunction and disability. Features in these areas of technology include continuing evolution of new devices, further development of well-established approaches, a need for critical assessment, requirements for support from technical and health care workers, and the need to identify funding to achieve efficient programs.

Persons with Disabilities↗
PubMed1994

Geminate recombination of diatomic ligands CO, O2, and NO with myoglobin.

The kinetics of geminate recombination of horse heart myoglobin with the diatomic ligands carbon monoxide, dioxygen, and nitric oxide have been reexamined. The new measurements are distinguished from previous studies by (1) consideration of the complete time range longer than 1 ps, (2) inclusion of the effect of temperature changes near ambient, (3) attention to the relation between recombination kinetics and the yield of dissociated partners on the millisecond time scale, and (4) use of singular value decomposition in the analysis. These picosecond results, together with earlier nanosecond data, for O2 prove that models incorporating one, two, or even three discrete intermediates are not sufficient to account for all features of geminate recombination kinetics. Instead, a continuous evolution of the geminate pair distribution is preferred.

Animals↗
PubMed1994

Laparoscopically implantable nerve-stimulating electrode (LINSE): application to the cavernous nerve in acute and chronic canine models.

Using a new laparoscopic procedure, we investigated stimulation of the cavernous nerves to achieve erection in a canine model. The technique was developed during acute experiments in four dogs, following which, chronic studies (4- to 6-weeks survival after surgery) were undertaken in three dogs. A monopolar cuff electrode was inserted laparoscopically by a transperitoneal approach and placed around the cavernous nerve. The leads were brought out to the subcutaneous space, where they were attached to stimulation receivers that could be activated by an external radiofrequency transmitter. An intracavernous pressure elevation indicative of successful stimulation was obtained acutely in five of eight cavernous nerves in the four acute-study dogs and in four of six nerves in the three chronic-study dogs. The implanted equipment associated with four of six cavernous nerves failed mechanically in the chronic-study animals, such that only two receiver-electrode sites were intact at the time of sacrifice 4 to 6 weeks later. Transmitter-driven stimulation of one of these two sets produced an intracavernous pressure rise above 100 cm H2O. We present this technique as part of the continuing evolution of laparoscopy as both a research and a clinical tool. The present use of the laparoscopically implantable nerve-stimulating electrode is a new animal research tool and a potential first step in the human application of the technology.

Animals↗
PubMed1996

Laparoscopic common bile duct exploration: a review.

The use of laparoscopic methods to explore the common bile duct is now well-established, although they continue to undergo continuous evolution and improvement. In experienced hands laparoscopic management of choledocholithiasis may be undertaken with morbidity and mortality at least as good as that of open surgery. The use of diagnostic endoscopic retrograde cholangiopancreatography (ERCP) with or without sphincterotomy before or after laparoscopic intervention must be evaluated. The degree of acceptance that laparoscopic techniques for common bile duct exploration (CBDE) will achieve within the surgical community remains to be determined, but will likely increase as more practicing surgeons familiarize themselves with them.

Cholangiography↗
PubMed1993

Prevalence of the type I and type II DHFR genes in trimethoprim-resistant urinary isolates of Escherichia coli from Greece.

Trimethoprim resistance in 64 Escherichia coli urinary isolates from five hospitals in Greece was studied. Of the 40 isolates exhibiting transferable high-level resistance (MIC > 1024 mg/L), 21 hybridized with a specific probe for dihydrofolate reductase (DHFR) I, 13 with a probe for DHFR II, and one with a probe for DHFR V. Eleven isolates hybridized with a probe for transposon Tn7. Among the 17 isolates with non-transferable high-level resistance, seven hybridized with the probe for DHFR I, three with the probe for DHFR II, and eight were Tn7-positive. None of the seven isolates with low-level resistance (MIC 4-1024 mg/L) reacted with the probes used. Of the 28 isolates positive for DHFR I, 12 (43%) failed to hybridize with the Tn7 probe. Conversely, three isolates hybridized with the Tn7 probe, but not with the probe for DHFR I. Colony hybridization experiments showed that all but three transconjugants reacted similarly to their respective parent strains. The plasmids coding for trimethoprim-resistant DHFRs were found to differ on the basis of restriction enzyme analysis. These findings suggest that trimethoprim resistance among E. coli urinary isolates in Greece is mediated predominantly by heterogeneous transferable plasmids encoding either DHFR I or DHFR II. The dissociation between DHFR I and Tn7, together with the high incidence of trimethoprim-resistant isolates which did not hybridize with the probes for the common DHFR I or II types, indicates the continued evolution of trimethoprim resistance determinants.

Bacteriuria↗
PubMed1987

Combined therapy as an alternative to exenteration for locally advanced vulvovaginal cancer. II. Results, complications, and dosimetric and surgical considerations.

We have introduced a therapeutic alternative to exenteration for locally advanced vulvovaginal cancer using surgery for the vulvar (external genital) phase of this disease presentation, combined with radiotherapy for the internal genital phase (with adequate overlap of fields to protect surgical margins). The rationale is that this approach treats the cancer and its dual regional spread patterns, while at the same time preserving the bladder and/or rectum, and should be associated with less morbidity and mortality than exenterative surgery. This report updates our experience with a total of 48 treated cases (37 primary cases and 11 cases of recurrent disease). Of the 37 primary cases, 20 were FIGO stage III, 4 were FIGO stage IV, and 3 other cases represented "field" cancers involving vulva and/or cervix and/or vagina. Utilizing a Life Table analysis, the 5-year survival for the primary cases was 75.6%. Published FIGO survival for stage III is 32% and for stage IV 10.5%. Life Table analysis projects a 62.6% survival for recurrent cases and an overall 72% 5-year survival for all 48 cases treated. With 48 patients treated, 48 bladders and 48 rectums were at risk for surgical removal had exenteration been employed. One patient had a total pelvic exenteration for local failure, and one had a posterior exenteration for local failure. One bladder and one rectum were lost to permanent diversion because of radiation injury. Thus, 5 of these major viscera were lost of the 96 total, and 91 (94.8%) were retained. Radiation therapy and surgical details have been reviewed relevant to local control and local failure and complications. The continuing evolution of treatment modifications of all modalities will be discussed. The apparent advantages of this combined therapeutic approach over exenterative surgery include high probability of bladder and/or rectal preservation, low primary mortality, low treatment morbidity, and very good results in cancer control.

Brachytherapy↗
PubMed1981

Medical technology and academic medicine: the doctor-producers' dilemma.

Diagnostic technologies differ from therapeutic technologies in several ways. Use of a diagnostic technologies is increasing faster than overall medical care. New diagnostic technologies tend to be additive and often have multiple uses. In evaluating their benefits, one should assess marginal, not absolute, utilities and measure clinical as well as financial costs. Although the use of therapeutic technologies is more circumscribed, these technologies tend to be in continuous evolution, especially when new. Comparative evaluations of therapeutic technologies are expensive and time-consuming. Pro-technology reimbursement biases may be the most important of the many factors promoting technology use. Academic medical centers, which have become increasingly clinically specialized, must now compete with their own graduates for specialty patients. At the same time they are urged to respond to contradictory national health policies that favor production of more generalists under a pro-specialty reimbursement system. Suggestions for more appropriate technology use should cover multiple approaches, including the changing of current financial incentives and the use of technology assessment to improve quality of care and education.

Academic Medical Centers↗
PubMed1988

Red cell size heterogeneity during ontogeny.

To determine the manner in which erythrocyte changes occur during ontogeny, several red cell parameters were analyzed in fetuses, newborn infants, children, and adults. Although mean cell volume (MCV) and hemoglobin F (HbF) levels decreased as expected during in utero development, the coefficient of variation of red cell size (%CV), or red cell distribution width (RDW), increased from fetuses to newborn infants. In normal adults, the %CV was 15 (RDW was 13). The %CV in fetuses at 18-24 weeks gestation was 18, and it was 21 at term birth. High values for %CV or RDW indicate significant anisocytosis. Erythropoiesis at the time of birth is not a steady-state condition. Erythrocytes of a wide variety of sizes are present, with the appearance of new small cells on a background of older, larger red cells. This increased anisocytosis suggests that these new erythrocytes do not appear to be due to a smooth, continuous evolution of red cell size, but rather to discrete, perhaps clonal, changes.

Adolescent↗
PubMed1996

Adhesive and migratory behaviors of nevus cells differ from those of epidermal melanocytes and are not linked to the histological type of nevus.

It has been postulated that acquired nevi undergo life span continuous evolution from junctional, presumably in radial expanding phase at the dermal epidermal junction, to compound and then to dermal nested nevi. In an attempt to correlate the morphology of nevi with biological data, we have investigated whether migratory and adhesive phenotypes of nevus cells could account for histological patterns and possible spatiotemporal changes in nevi. Nevus cells were cultured from compound and dermal nevi and compared to normal epidermal cultured melanocytes from children and adults. AR nevus cells showed similar in vitro adhesive and migratory indexes on laminin-1, laminin-5/nicein, fibronectin, or collagen IV substrates, suggesting that these intrinsic characteristics do not account for the tendency to dermal nesting and/or to radial growth along the dermal-epidermal junction. The cells from epidermal and dermal parts of compound nevi migrated similarly across a reconstituted basement membrane. The results show that intrinsic adhesive and migratory behaviors of nevus cells were not associated with a histological type of nevus. Interestingly, differences in migratory phenotype and intercellular adhesion capacities between nevus cells and normal melanocytes indicated that they could represent different melanocytic cell subpopulations. Finally, melanocytes from adults and children expressed similar levels of the same integrins as all nevus cells but showed differences in function of both alpha3 and alpha6 integrin subunits and in migratory/adhesive behaviors, which may suggest different states of melanocyte maturation.

Adult↗
PubMed1989

The therapeutic community: exploring the boundaries.

The past 20 years have demonstrated the effectiveness of therapeutic community (TC) treatment for drug abuse as it evolved in the United States. We now better understand the influence that psychodynamic features of TC treatment have on character disorder. Best perceived as a setting designed--as society is not--to encourage and support social learning, the TC has succeeded in modifying its programs and adapting self-help methods to serve drug abusers of all kinds and abusers of all drugs. Continued evolution of the TC depends upon development of its already-demonstrated capacity to affect disordered behaviour other than drug abuse. The growth of disordered populations in the United States and increasingly in Great Britain gives urgency to such future employment. Therapeutic communities and TC-like programs for non-drug abusers already exist. But widespread use depends upon strengthening the theoretical underpinnings of TC treatment and establishing closer working relationships between TC's and mainstream medical, mental health and social service institutions.

Humans↗
PubMed1993

Delayed success following radiofrequency catheter ablation.

Two patients who underwent attempted radiofrequency catheter ablation of an atrioventricular accessory pathway experienced delayed abolition of pathway conduction. During the procedures there was transient block in the accessory pathway following multiple ablation attempts at closely spaced sites. Both patients showed evidence of preexcitation at the conclusion of the ablation session but neither showed evidence of accessory pathway conduction during a second electrophysiological study. These observations demonstrate that in patients in whom transient block of the accessory pathway is produced, continued evolution of radiofrequency energy lesions may result in the eventual success of an initially unsuccessful ablation session.

Adenosine↗
PubMed1978

Behavioral marriage therapy. III. The contents of Gurman et al. may be hazardous to our health.

This paper was written as a reply to a critique of behavioral marital therapy (BMT) by Gurman, Kniskern, and Knudson (6, 7). The reply is divided into four sections. First, the paper addresses the critics' comments on the conceptual model put forth by BMT, correcting and clarifying various misconceptions, and restating some of the basic ideological principles in the behavioral model. Second, the paper discusses behavioral change techniques and technology, along with extratechnological treatment considerations. Again, misrepresentations of BMT are corrected. Third, an analysis of the literature investigating the therapeutic efficacy of BMT is reviewed, and the conclusion is reached that BMT is demonstrably effective, at least for a substantial number of mildly to moderately distressed couples. Criticisms are made of the analysis of the same literature conducted by Gurman et al. We conclude that, contrary to the spirit of the paper by Gurman et al., BMT is a viable framework for conceptualizing and treating relationship problems and that the commitment of its adherents to experimental investigation promises continued evolution, refinement, and improvement.

Behavior Therapy↗