Transcription of the transfer genes traY and traM of the antibiotic resistance plasmid R100-1 is linked

Three separate traY deletion mutants of R100-1 were prepared by allele replacement. These mutants retained the ability to transfer at a level 100 times greater than R100 and 1/50 that of the parental R100-1. The mutants were complemented to normal R100-1 transfer levels by pDSP06, a multicopy traY clone. Comparison of transcripts initiated at the traY promoter, P(Y), by primer extension experiments showed that there was no detectable P(Y) activity in R100 and that the level of P(Y) activity in the traY deletion mutants was lower than that in R100-1. Similar measurements performed on RNA from a set of previously described traM deletion mutants showed that those traM deletion mutants that produced more traM and finM (M) transcripts than the parental R100-1 also produced more traY transcripts than R100-1 and that those traM mutants that produced fewer M transcripts than R100-1 also produced fewer traY transcripts than R100-1. We conclude that in R100, TraY regulates P(Y) activity and that transcripts originating in traM affect P(Y) activity.

Acclimation response of spring wheat in a free-air CO(2) enrichment (FACE) atmosphere with variable soil nitrogen regimes. 1. Leaf position and phenology determine acclimation response

We have examined the photosynthetic acclimation of wheat leaves grown at an elevated CO(2) concentration, and ample and limiting N supplies, within a field experiment using free-air CO(2) enrichment (FACE). To understand how leaf age and developmental stage affected any acclimation response, measurements were made on a vertical profile of leaves every week from tillering until maturity. The response of assimilation (A) to internal CO(2) concentration (C(i)) was used to estimate the in vivo carboxylation capacity (Vc(max)) and maximum rate of ribulose-1,5-bisphosphate limited photosynthesis (A (sat)). The total activity of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), and leaf content of Rubisco and the Light Harvesting Chlorophyll a/b protein associated with Photosystem II (LHC II), were determined. Elevated CO(2) did not alter Vc(max) in the flag leaf at either low or high N. In the older shaded leaves lower in the canopy, acclimatory decline in Vc(max) and A (sat) was observed, and was found to correlate with reduced Rubisco activity and content. The dependency of acclimation on N supply was different at each developmental stage. With adequate N supply, acclimation to elevated CO(2) was also accompanied by an increased LHC II/Rubisco ratio. At low N supply, contents of Rubisco and LHC II were reduced in all leaves, although an increased LHC II/Rubisco ratio under elevated CO(2) was still observed. These results underscore the importance of leaf position, leaf age and crop developmental stage in understanding the acclimation of photosynthesis to elevated CO(2) and nutrient stress.

Appetitive behavior, compulsivity, and neurochemistry in Prader-Willi syndrome

Advances in genetic research have led to an increased understanding of genotype-phenotype relationships. Excessive eating and weight gain characteristic of Prader-Willi syndrome (PWS) have been the understandable focus of much of the research. The intense preoccupation with food, lack of satiation, and incessant food seeking are among the most striking features of PWS. It has become increasingly clear that the behavioral phenotype of PWS also includes symptoms similar to obsessive compulsive disorder, which in all probability interact with the incessant hunger and lack of satiation to engender the intense preoccupation and food seeking behavior that is characteristic of this disorder. Several lines of evidence suggest that genetic material on chromosome 15 may alter synthesis, release, metabolism, binding, intrinsic activity, or reuptake of specific neurotransmitters, or alter the receptor numbers and/or distribution involved in modulating feeding. Among the likely candidates are GABAnergic, serotonergic, and neuropeptidergic mechanisms. This review summarizes what is known about the appetitive behavior and compulsivity in PWS and discusses the possible mechanisms underlying these behaviors. MRDD Research Reviews 2000;6:125-130.

Description of the postcloacal glands of Plethodon cinereus, the red-backed salamander, during bouts of scent marking

Plethodon cinereus, the red-backed salamander, is a small territorial vertebrate that defends refugia located on the forest floor. As a component of territorial defense, these animals use scent marks to advertise their refugia. Behavioral evidence indicates that scent marks are produced by the postcloacal glands located on the ventral surface of the tail just posterior to the cloaca. We placed animals on unmarked substrates and recorded changes in serous acini from the postcloacal and shoulder region over a 48-h period. Within the first hour there was an increase in the number of acini filled with secretory product in the postcloacal region. At 12 h the number of full acini decreased and the number of empty acini increased. By 24 h the number of empty acini had decreased and the number of renewing acini containing secretory cells producing product had increased. By 48 h the ratio of full to empty to renewing acini was similar to those observed at the start of the study. In the shoulder region, no significant changes in the ratio of full to empty to renewing acini were observed. Observations of the serous acini within the postcloacal region and the shoulder region indicate that the mode of secretory production is holocrine. These findings are additional evidence that the postcloacal glands are the site of scent mark production.

The Westdoc Internet Questionnaire--a survey of the use of "on-line" resources by West Lothian general practitioners

OBJECTIVE

To investigate the extent to which a representative sample of Scottish GPs used on-line resources for medical applications and their attitudes to various aspects of the technology at a time just prior to the introduction of the Scottish Office Computers offering Internet access to the majority of Scottish practices.

DESIGN

Questionnaire survey.

SETTING

"Out of hours" GP emergency service cooperative.

SUBJECTS

All the (106) GP principals in practice in the Scottish District of West Lothian in June 1997. Locums and Registrars were excluded.

RESULTS

There was an 87% response rate. Nineteen (21%) respondents used the Internet once a month or more, 12(13%) used it to communicate with colleagues by e-mail and 4(4%) with patients. Only 8% found it useful for medical purposes though more than half thought it would be a significant part of practice in five years time. Younger GPs were more likely to use the Internet. Many users expressed concern about reliability of the information and the ease with which it could be applied.

CONCLUSION

By identifying a mismatch between levels of Internet use and the perceived potential of this new technology this study points to the need for training initiatives. It also forms a benchmark against which the uptake of Internet technology by GPs can be measured in years to come.

Influence of age on outcome after percutaneous transluminal coronary angioplasty

This study estimates the influence of age on outcomes (mainly survival) of 21,516 patients who underwent percutaneous transluminal coronary angioplasty (PTCA) between 1980 and 1996. We prospectively analyzed the patients in 5 age groups: <50, 50 to 59, 60 to 69, 70 to 79, and > or =80 years old. During the in-hospital period after PTCA, mortality increased from 0.28% in patients aged <50 to 3.45% in patients aged > or =80; Q-wave myocardial infarction was not significantly associated with age, and the 2 older groups were referred less often to coronary artery bypass graft surgery. During follow-up, lasting up to 10 years, the hazard of death was significantly influenced by age; Q-wave myocardial infarction was influenced by age, although the magnitude of the effect was relatively small and of questionable clinical significance; and coronary artery bypass graft surgery was performed less often in the 2 older age groups. Additional PTCA was similarly performed among the age groups. Age, diabetes mellitus, systemic hypertension, heart failure class, angioplasty in graft vessel, number of coronary vessels narrowed, and previous myocardial infarction were predictors of death over the 10-year follow-up. Age was the most important correlate of death after PTCA, with a 65% increase in the hazard of death for each 10-year increase in age. Age has an independent effect on early and late survival after PTCA.

Development and validation of a measurement system for assessment of energy expenditure and physical activity in Prader-Willi syndrome

OBJECTIVE

The morbid obesity associated with Prader-Willi syndrome (PWS) may result from either excessive energy intake or reduced energy expenditure (EE). In this report, we describe the development and validation of an Activity-Energy Measurement System (AEMS) to measure EE and physical activity components in an environment approximating free-living conditions.

RESEARCH METHODS AND PROCEDURES

The AEMS consists of a live-in, whole-room indirect calorimeter equipped with a novel force platform floor system to enable simultaneous measurements of EE, physical activity, and work efficiency during spontaneous activities and standardized exercises. Free-living physical activity and estimated free-living EE are measured using portable triaxial accelerometers individually calibrated in each subject during their stay in the AEMS.

RESULTS

Representative data from two PWS patients and two matched control (CTR) subjects displayed EE during their inactive lifestyles.

DISCUSSION

This combination of methods will allow the quantification of daily EE and its components, the amount and energy cost of physical activity, and the relationships between body composition and EE, in order to determine their roles in the development and maintenance of the morbid obesity in PWS.

Self-injurious behavior and Prader-Willi syndrome: behavioral forms and body locations

With few exceptions (e.g., Lesch-Nyhan syndrome), the specific nature of self-injury in relation to identified genetic syndromes associated with mental retardation is poorly understood. In the present study we surveyed the families of 62 persons with Prader-Willi syndrome to determine the prevalence, topographies, and specific body locations of self-injurious behavior. Self-injury was reported for 81% of the participants. Skin-picking was the most prevalent form, with the front of the legs and head being disproportionately targeted as preferred self-injury body sites. Individuals with the 15q11-q13 deletion injured significantly more body sites than did individuals with maternal disomy 15. Results are discussed in relation to previous self-injury body site findings and implications for the relevance of syndrome-specific behavioral phenotypes.

Managing year 2000 (Y2K) compliance in the medical practice

It is the responsibility of every medical practice to examine the year 2000 compliance of all medical devices, facilities, and computer systems that it uses, and whether external business partners are also taking appropriate steps in this area. You need a plan, and you need to start right now.

Predictive ability of social cognitive theory in exercise research: an integrated literature review

The mechanisms that underlie successful initiation and adherence to physical activity regimens are not well understood. Few theoretical models have used consistent explanatory variables that are theory-driven and many findings that use extant models are equivocal. Social Cognitive Theory (SCT) as presented by Bandura (1986, 1997) appears to have strong promise as a guide to understanding physical activity behaviors and developing clinically relevant interventions to promote the initiation and maintenance of physical activity. This critical systematic review of research using SCT was completed to determine the predictive ability of model constructs in explaining physical activity behavior and in identifying key intervention components found to enhance physical activity initiation and maintenance. Following review for quality and adequacy, published research during the years 1990-1998 contained 27 studies that examined the relationship between the construct of SCT, self-efficacy, and physical activity. All of the descriptive studies found a statistically significant relationship between self-efficacy and exercise behavior. Intervention studies demonstrated that participation in an exercise program promoted self-efficacy, and that programs designed to increase outcome expectations and self-efficacy significantly increased exercise behavior. Due to the centrality of self-efficacy in many of the social psychological theories that help explain the attitude-intention-behavior triad, a strong need remains to design interventions to maximize its usefulness. Clear, generalizable, systematic and theoretically comprehensive, randomized, controlled studies are needed to understand the usefulness of the construct.

Hepatic transcatheter arterial chemoembolization alternating with systemic protracted continuous infusion 5-fluorouracil for gastrointestinal malignancies metastatic to liver: a phase II trial of the Puget Sound Oncology Consortium (PSOC 1104)

We assessed a regimen of alternating regional and systemic therapy in patients with gastrointestinal malignancies with liver-dominant metastases for feasibility, toxicity, response rate, response duration, patterns of progression, and progression-free and overall survival. Regional therapy comprised selective hepatic transcatheter arterial chemoembolization (TACE) using a suspension of cisplatin and particulate polyvinyl alcohol. This procedure was delivered between cycles of protracted continuous infusion 5-fluorouracil (PCI-5FU) as systemic chemotherapy. Patient eligibility criteria included: (a) having histologically documented adenocarcinoma arising from a gastrointestinal primary site with unresectable liver metastases bidimensionally measurable on computerized tomography scan; (b) age greater than 18 years; and (c) performance status 0-2 (Zubrod). PCI-5FU (250 mg/m2/day) was administered i.v. for 28 days, followed by the first TACE (TACE 1) delivered to the hepatic artery supplying the lobe with the greatest tumor burden. Restaging was performed before TACE 2 and TACE 3, which followed at monthly intervals. PCI-5FU for 21 days was sandwiched between each of the TACE treatments. After the final TACE, maintenance PCI-5FU was given for 28 days of each 35-day cycle until toxicity or progression. Between December 23, 1991, and January 19, 1995, 32 patients were registered in this trial, of whom 27 were eligible; 20 completed one or more treatment cycles and were evaluable for radiographic response. Patients with colorectal liver metastases predominated (74%). Twelve (44%) of 27 patients had failed one or more prior treatment regimens. There were no treatment-related deaths, and hematological and hepatic toxicities were generally manageable and reversible. Two patients, however, developed hepatic abscesses requiring drainage, and one patient developed an infarcted gallbladder, which necessitated cholecystectomy. There were no patients with complete responses; there were 8 (40%) with partial responses, 4 (20%) with minor responses, 2 (10%) with stable disease, and 6 (30%) who progressed on the treatment. The median duration of response for partial responders was 4.2 months (127 days; range, 56-245 days). The median reduction in carcinoembryonic antigen for responders was 87.5%. Two patients underwent subsequent resection of residual metastases; one of them is still alive at 58.4 months follow-up. The predominant site of disease progression was the liver; 25% of the patients progressed in extrahepatic sites. The median overall survival for the whole group is 14.3 months (95% confidence interval, 7.2-16.2). Actuarial overall survival for the whole group at 1 year and 2 years is 57 and 19%, respectively. Alternating systemic PCI-5FU and regional TACE (cisplatin/polyvinyl alcohol) is an active and feasible regimen with manageable toxicities in patients with metastatic gastrointestinal malignancies with liver-dominant disease and merits further investigation. The complications seen were in line with those reported at other specialized centers.

Architectural acoustics in residences for adults with mental retardation and its relation to perceived homelikeness

Previous investigators examined how architectural features of residences for adults with mental retardation contributed to the visual appearance of homelikeness. Acoustical characteristics of 18 residences for people with mental retardation were examined here. As part of a concurrent study, college undergraduates rated photographs of rooms in each house for their apparent homelikeness. Reverberation times in living and dining rooms were negatively correlated with mean homelikeness ratings. The less homelike rooms had reverberation times that may interfere with speech perception for some people and that were comparable with those found in larger public rooms (e.g., lecture halls). The larger reverberation times in these rooms were the result of insufficient sound absorption by these rooms' furnishings.

Sustained ventricular arrhythmias in patients receiving thrombolytic therapy: incidence and outcomes. The GUSTO Investigators

BACKGROUND

Sustained ventricular tachycardia (VT) and fibrillation (VF) occur in up to 20% of patients with acute myocardial infarction (MI) and have been associated with a poor prognosis. The relationships among the type of arrhythmia (VT versus VF or both), time of VT/VF occurrence, use of thrombolytic agents, and eventual outcome are unclear.

METHODS AND RESULTS

In the GUSTO-I study, we examined variables associated with the occurrence of VT/VF and its impact on mortality. Of the 40 895 patients with ventricular arrhythmia data, 4188 (10.2%) had sustained VT, VF, or both. Older age, systemic hypertension, previous MI, Killip class, anterior infarct, and depressed ejection fraction were associated with a higher risk of sustained VT and VF (P<0.001). In-hospital and 30-day mortality rates were higher among patients with sustained VT/VF than among patients without sustained ventricular arrhythmias (P<0.001). Both early (<2 days) and late (>2 days) occurrences of sustained VT and VF were associated with a higher risk of later mortality (P<0. 001). In addition, patients with both VT and VF had worse outcomes than those with either VT or VF alone (P<0.001). Among patients who survived hospitalization, no significant difference was found in 30-day mortality between the VT/VF and no VT/VF groups. However, after 1 year, the mortality rate was significantly higher in the VT alone and VT/VF groups (P<0.0001).

CONCLUSIONS

Despite the use of thrombolytic therapy, both early and late occurrences of sustained VT or VF continue to have a negative impact on patient outcome; patients with both VT and VF had the worst outcome; and among patients who survived hospitalization, the 1-year mortality rate was significantly higher in those who experienced VT alone or VT and VF.

The latent variable structure of the Compulsive Behaviour Checklist in people with Prader-Willi syndrome

The presence and severity of compulsive behaviours may be evaluated via the Compulsive Behaviour Checklist (CBC) and this instrument has been successfully employed in people with intellectual disability. However, the applicability of the overall CBC scoring system, which entails tallying the number of behavioural categories represented (i.e. five) as well as the number of individual behaviours endorsed (i.e. 25), is not known in the population with Prader-Willi syndrome (PWS). The present investigation examined the latent variable structure of the CBC in people with PWS in order to identify possible population-specific scoring and interpretation considerations. The 25 behaviour-specific items of the CBC were analysed for 75 people with PWS (44 females and 31 males) aged between 4 and 41 years (mean +/- SD = 11.4+/-9.4) via factor analysis with principal component extraction and equamax rotation. The most suitable solution was determined on the basis of multiple empirical criteria: (1) the scree test; (2) eigenvalues >1.00; (3) salient loadings >0.30; (4) the clarity of item assignment to a single latent dimension; (5) the internal consistency of the latent dimension(s) (coefficient alpha > or = 0.70); and (6) item-total correlations between 0.20 and 0.79. In addition, solutions were examined with respect to psychological theory and previous research. A 'general factor' (i.e. single latent dimension) solution which adhered to all a priori criteria was indicated. Twenty-four out of 25 items achieved salient loadings ranging from 0.46 to 0.80 on the general factor. The single item which failed to achieve salience, 'deviant grooming-skin picking', exhibited both substantial unique variance (0.997) and moderate reliability (r = 0.59, P<0.001). The internal consistency of the general factor was strong (alpha = 0.93) and all salient items were suitably correlated with the unit-weighted total score (r(item-total) = 0.41-0.77). The traditional CBC scoring system, which includes tallying the number of categories represented, would not be relevant in this PWS sample. In addition, the recommended tallying of the number of individual behaviours endorsed does not reflect the empirically indicated notion of compulsive behaviour in this special population. These findings indicate that the 24 salient items should be scored as a unit-weighted composite and that the score on the substantially unique item (skin picking) should be considered a separate measure when evaluating compulsive behaviours via the CBC in people with PWS.

Acute respiratory distress syndrome. Patient position and motion strategies

A review of the literature since 1974 indicates that, although there is no consensus as to the mechanism, positioning strategies in patients with ARDS improve PaO2 and may diminish lung parenchymal damage. The effect of these maneuvers on patient outcomes is uncertain. There is no uniform algorithm for the application of these techniques; however, there is sufficient evidence cited in the referenced articles to support the use and early application of the techniques to improve oxygenation.

Streptococcal emm types associated with T-agglutination types and the use of conserved emm gene restriction fragment patterns for subtyping group A streptococci

The T-agglutination types were determined for a diverse collection of 1531 group A streptococci for which the 5' M protein gene (emm) sequences had been analysed. The majority of the T-agglutination types correlated with previously seen M/emm/T-type associations; however, several new associations were found. Analysis of a subset of this collection -- which included 1157 clinical isolates with multiply encountered emm types -- found that emm amplicon restriction profiles of isolates sharing identical T types and opacity factor phenotypes are useful for detecting groups of isolates with identical emm genes. Many emm genes of known 5' sequence display a highly conserved restriction pattern amongst clinical isolates widely separated both geographically and temporally.

Trilateral retinoblastoma: insights into histogenesis and management

Trilateral retinoblastoma (TRb) is a syndrome involving midline intracranial malignancies in children with the heritable form of retinoblastoma. All cases of TRb reported from 1971 to 1997 were reviewed. The histopathologic findings, clinical features, treatment modalities, and survival rates from 80 cases were evaluated. Histopathologic findings from intracranial malignancies demonstrated primitive neuroectodermal tumors in 61.5% of cases. Various degrees of neuronal or photoreceptor differentiation were seen in the other 38.5% of cases. Autopsy, histopathologic, and radiologic examinations did not show a more definitive site of origin of these intracranial tumors, although "pinealoblastoma" was often the diagnosis reported. These findings, together with analysis of the histopathologic similarities among human primitive neuroectodermal tumors, pinealoblastoma, retinoblastoma, and ependymoblastoma, suggest that TRb more likely arises from a germinal layer of predisposed primitive subependymal neuroblasts that are not necessarily destined for pineal or photoreceptor differentiation. Trilateral tumors have also been found in transgenic mice expressing the simian virus 40 T-antigen. Transgenic murine intracranial tumors are primitive neuroectodermal tumors arising from the subependymal layer. Transgenic mice with the murine interphotoreceptor cell binding protein promoter and simian virus 40 T-antigen also develop pineal tumors. Trilateral retinoblastoma is usually fatal, with an average survival time of 11.2 months. Therapies include radiation, systemic chemotherapy, intrathecal chemotherapy, and surgical resection/craniotomy in combination with radiation and/or chemotherapy. Survival may be prolonged with combination chemotherapy (24.6 months) and if neuroradiologic screening identifies TRb before symptoms are present (23.5 months). Recent success with platinum-based chemoreduction of intraocular retinoblastoma may indicate a similar role for platinum-based chemotherapy in the treatment of TRb. Routine central nervous system imaging should be considered in the management of TRb.

Variation in human plasma cholinesterase activity during low-dose cocaine administration

BACKGROUND

Cocaine is metabolized by a number of enzymes, the activity of one of which, plasma cholinesterase has been associated with dinical manifestations of toxicity. Patients with life-threatening complications of cocaine intoxication have lower plasma cholinesterase activity than less toxic controls. In addition, relatively healthy cocaine users have lower plasma cholinesterase activity than noncocaine using controls. Thus, low plasma cholinesterase activity could be a contributing factor to cocaine toxicity, a consequence of cocaine use, or a confounding variable. The following study was designed to further assess the relationship between cocaine use and plasma cholinesterase activity.

METHODS

We studied fluctuations in plasma cholinesterase activity in nine subjects enrolled in an inpatient study of the behavioral pharmacology of smoked cocaine. Subjects used at least 2 g of cocaine weekly for at least 1 year prior to enrollment. The subjects were admitted to the research unit where they remained drug-free for 2 days. They then received smoked cocaine for 4 days (up to 405 mg over 5 hours daily) and were then drug-free again for 2 days. Plasma cholinesterase activity was measured at 9 AM and 4 PM each day.

RESULTS

Baseline plasma cholinesterase ranged from 265 to 930 U/L (normal > 450 U/L). The mean plasma cholinesterase increased 112+/-100 U/L from day 1 to day 8 (p = 0.025). There was no daily change in plasma cholinesterase levels from 9 AM to 4 PM (15+/-165 U/L, p > 0.6), and there was no difference in the daily change between high- and low-dose cocaine days (-3+/-137 U/L vs 28+/-165 U/L, p = 0.52).

CONCLUSION

These preliminary data suggest that plasma cholinesterase levels do not change over a 7-hour period as a result of cocaine administration, but may increase during a period of inpatient study. Such an increase could potentially influence the pharmacokinetics or effects of cocaine studied in an inpatient setting and may give insight into the etiology of the observed low-plasma cholinesterase activity in cocaine users.