discordia mutations specifically misorient asymmetric cell divisions during development of the maize leaf epidermis

In plant cells, cytokinesis depends on a cytoskeletal structure called a phragmoplast, which directs the formation of a new cell wall between daughter nuclei after mitosis. The orientation of cell division depends on guidance of the phragmoplast during cytokinesis to a cortical site marked throughout prophase by another cytoskeletal structure called a preprophase band. Asymmetrically dividing cells become polarized and form asymmetric preprophase bands prior to mitosis; phragmoplasts are subsequently guided to these asymmetric cortical sites to form daughter cells of different shapes and/or sizes. Here we describe two new recessive mutations, discordia1 (dcd1) and discordia2 (dcd2), which disrupt the spatial regulation of cytokinesis during asymmetric cell divisions. Both mutations disrupt four classes of asymmetric cell divisions during the development of the maize leaf epidermis, without affecting the symmetric divisions through which most epidermal cells arise. The effects of dcd mutations on asymmetric cell division can be mimicked by cytochalasin D treatment, and divisions affected by dcd1 are hypersensitive to the effects of cytochalasin D. Analysis of actin and microtubule organization in these mutants showed no effect of either mutation on cell polarity, or on formation and localization of preprophase bands and spindles. In mutant cells, phragmoplasts in asymmetrically dividing cells are structurally normal and are initiated in the correct location, but often fail to move to the position formerly occupied by the preprophase band. We propose that dcd mutations disrupt an actin-dependent process necessary for the guidance of phragmoplasts during cytokinesis in asymmetrically dividing cells.

Investigation of hypersensitivity to fractionated low-dose radiation exposure

PURPOSE

Hypersensitivity to cell killing of exponentially growing cells exposed to X-rays and gamma rays has been reported for doses below about 0.5 Gy. The reported results have been interpreted to suggest that a dose of 0.5 Gy or less is not sufficient to trigger an inducible repair mechanism. The purpose of this study was to examine this suggested hypersensitivity after multiple low doses (0.3 Gy) of gamma rays where a) the effect would be expected to be significantly magnified, and b) the effect might be of clinical relevance.

METHODS AND MATERIALS

C3H 10T1/2 mouse embryo cells were grown to confluence in culture vessels. While in plateau phase of growth, cells were exposed to 6 Gy of gamma rays, delivered in either 6 Gy, 3 Gy, 2 Gy, 1 Gy, or 0.3 Gy well-separated fractions. Corresponding experiments were performed with V-79 and C3H 10T1/2 cells in exponential growth. Cells were replated at low density and assayed for clonogenicity.

RESULTS

The results of this study were not inconsistent with some hypersensitivity at low doses, in that 20 fractions each of 0.3 Gy produced a slightly lower (though nonsignificant) surviving fraction compared with the same dose given in 2-Gy fractions. However, the results of the 20 x 0.3 Gy exposures also agreed well with the standard linear-quadratic (LQ) model predictions based on high dose per fraction (1-6 Gy) data. In addition, effects of cellular redistribution were seen which were explained quantitatively with an extended version of the LQ model.

CONCLUSIONS

These experiments were specifically designed to magnify and probe possible clinical implications of proposed "low-dose hypersensitivity" effects, in which significant deviations at low doses from the LQ model have been suggested. In fact, the results at low doses per fraction were consistent with LQ predictions based on higher dose per fraction data. This finding is in agreement with the well-documented utility of the LQ approach in estimating isoeffect doses for alternative fractionation schemes, and for brachytherapy.

Conventional external-beam radiation therapy alone or with androgen ablation for clinical stage III (T3, NX/N0, M0) adenocarcinoma of the prostate

PURPOSE

To evaluate the outcome of clinical Stage III (T3, N0/NX, M0) prostate cancer treated by conventional radiation alone or with adjuvant androgen ablation.

METHODS AND MATERIALS

Three hundred forty-four men with T3, N0/NX, M0 adenocarcinoma of the prostate who received conventional radiation alone (260) or with androgen ablation (84) were analyzed for relapse or rising prostate-specific antigen (PSA), using univariate and multivariate techniques.

RESULTS

With a median follow-up of 68 months, the 260 men treated with radiation alone had a 10-year actuarial rate of relapse or rising PSA of 76%. Pretreatment PSA level (< or = 10 ng/ml vs. > 10 < or = 20 ng/ml vs. > 20 ng/ml) and radiation dose (< 68 Gy vs. > or = 68 Gy) were the only independently significant determinants of biochemical failure; Gleason score (2-7 vs. 8-10) was an additional determinant of metastatic relapse. Patients treated to doses < 68 Gy experienced 6-year failure rates exceeding 50% regardless of PSA level. Patients with PSA < or = 10 ng/ml and receiving 68-70 Gy had a 6-year failure of 24%, but those with PSA > 10 ng/ml had relapse rates exceeding 50% even at doses of 70 Gy. At a median follow-up of 44 months, the 84 patients treated with radiation and androgen ablation had a 6-year biochemical failure rate of 22%. The only significant determinant of outcome in this group was pretreatment PSA; patients with PSA < or = 80 ng/ml had a 6-year failure rate of only 12% compared to a failure rate of 53% for those with PSA > 80 ng/ml. The outcome for those treated with combined modalities was significantly better than for those treated with radiation alone in all PSA strata.

CONCLUSION

Conventional radiation alone has little curative potential for Stage III disease. Doses < 68 Gy are particularly ineffective. Patients with PSA < or = 10 ng/ml may be candidates for conventional radiation to a dose of 70 Gy. Other patients are probably best served by combined radiation-androgen ablation or high-dose conformal radiation.

The utility of an in-hospital observation period after discontinuing intravenous antibiotics

PURPOSE

To determine whether observing patients overnight in the hospital after intravenous antibiotics have been discontinued is a useful way to identify important clinical events.

SUBJECTS AND METHODS

We performed a retrospective chart review of patients admitted during a 6-month period to a tertiary care teaching hospital with a primary diagnosis of either pneumonia, urinary tract infection, or cellulitis who were treated with intravenous antibiotics. Charts were abstracted for patient characteristics, including comorbid illnesses and laboratory values, as well as for evidence of recurrent infection or other adverse events.

RESULTS

Of the 374 patients in the study, 63 (17%) were discharged on the day intravenous antibiotics were discontinued. These patients were 10 years younger (P = 0.0009) and had fewer comorbid illnesses (P = 0.02) than those who were observed in the hospital. Recurrent infection was noted in 3 (1%; 95% confidence interval 0.2% to 3%) of the 308 patients who were observed. A mild adverse antibiotic reaction was also noted in three observed patients. The readmission rate to the same institution for recurrent infection was 3% for patients with an observation period and 2% for patients without an observation period (P = 0.70).

CONCLUSIONS

Observing patients overnight in the hospital after discontinuing intravenous antibiotics is a common clinical practice. There was an extremely low incidence of adverse events during the observation period, and the events that did occur would have been discovered in an outpatient setting. In-hospital observation after discontinuing intravenous antibiotics is unnecessary for most patients with pneumonia, urinary tract infection, or cellulitis and greatly increases health-care costs.

The Tangled1 gene is required for spatial control of cytoskeletal arrays associated with cell division during maize leaf development

The cytoskeleton plays a major role in the spatial regulation of plant cell division and morphogenesis. Arrays of microtubules and actin filaments present in the cell cortex during prophase mark sites to which phragmoplasts and associated cell plates are guided during cytokinesis. During interphase, cortical microtubules are believed to influence the orientation of cell expansion by guiding the pattern in which cell wall material is laid down. Little is known about the mechanisms that regulate these cytoskeleton-dependent processes critical for plant development. Previous work showed that the Tangled1 (Tan1) gene of maize is required for spatial regulation of cytokinesis during maize leaf development but not for leaf morphogenesis. Here, we examine the cytoskeletal arrays associated with cell division and morphogenesis during the development of tan1 and wild-type leaves. Our analysis leads to the conclusion that Tan1 is required both for the positioning of cytoskeletal arrays that establish planes of cell division during prophase and for spatial guidance of expanding phragmoplasts toward preestablished cortical division sites during cytokinesis. Observations on the organization of interphase cortical microtubules suggest that regional influences may play a role in coordinating cell expansion patterns among groups of cells during leaf morphogenesis.

Measuring outcomes and costs for major depression

This article addresses briefly the measurement of multidimensional outcomes and costs for major depression. We emphasize the importance of measuring outcomes in a variety of domains, including the broader issues of improvement or decline in functioning and impairment based on domains known to be affected by major depression. We emphasize the importance of measuring the economic costs of illness, both the direct total health care costs and indirect costs. Direct costs include mental health treatment costs and all other health care costs. Indirect costs include such varied factors as lost wages for the depressed individual and caregiver burden. We demonstrate the usefulness and importance of using these measures with several examples from our own research.

Perspectives on switching oral acyclovir from prescription to over-the-counter status: report of a consensus panel

The proposed switching of oral acyclovir from prescription to over-the-counter (OTC) status for the 5-day episodic treatment of genital herpes was considered by a consensus panel. It was concluded that self-diagnosis/misdiagnosis, misuse, and adverse drug effects were potential problems with the OTC use of acyclovir. While acyclovir reduces asymptomatic shedding of herpes simplex virus type 2, the reduction in transmission of virus potentially resulting from increased acyclovir use was felt to be of unknown extent but likely to be of benefit overall. The availability of acyclovir would likely be improved. There were differences in opinion as to whether widespread availability of acyclovir (prescription or OTC) may speed the development of viral resistance. However, all panel members felt that granting OTC status may set an undesirable precedent for the switch from prescription to OTC use of other systemically administered antiinfective agents. The effect of this precedent, in terms of accelerating development of multidrug-resistant bacteria, was a major concern of all panel members. The consensus was that the switch of acyclovir to OTC status could not be supported.

Implementing a statewide outcomes management system for consumers of public mental health services

The authors describe the development and implementation of an outcomes management system designed to measure outcomes and processes of care for public mental health consumers in Arkansas. The public-academic project was implemented in 1995 and is based on the Shewhart-Deming model of continuous quality improvement. All 15 community mental health centers (CMHCs) in the state participate in the project, which prospectively measures longitudinal outcomes of care for the tracer conditions of major depression and schizophrenia. Multiperspective measurement tools are used to measure patients' psychiatric status and general health status at periodic intervals; information is gathered on functioning, symptoms, severity of illness, social factors, demographic characteristics, and quality of life. A problem encountered during implementation was the relatively low rate of referral of patients with the tracer conditions for monitoring. Voluntary rather than mandatory participation in the outcomes management system by the CMHCs as well as clinicians' misperceptions about the system's purpose and concerns about confidentiality may have partly accounted for the low rate.

Asymmetric cell division and cell fate in plants

A variety of approaches has recently been employed to investigate how sister cells adopt distinct fates following asymmetric divisions during plant development. Surgical and drug studies have been used to analyze asymmetric divisions during both early embryogenesis in brown algae and pollen development in tobacco. Genetic screens have been used to identify genes in Arabidopsis thaliana that are required for specific asymmetric cell divisions during pollen and root development. These studies indicate that cell polarity and division orientation are closely tied to the process of cell fate specification, and suggest that differential inheritance of determinants and positional information may both be involved in the specification of cell fates following asymmetric cell division.

Neonatal effects and serum cortisol levels after multiple courses of maternal corticosteroids

OBJECTIVE

To determine the effects of multiple courses of maternal betamethasone for fetal lung maturation on neonatal serum cortisol levels and clinical Cushing syndrome.

METHODS

Seventy-nine mother-infant pairs delivered between 24 and 36 weeks' gestation were enrolled in the study. They were grouped according to the number of courses of betamethasone received between 24 and 34 weeks' gestation for fetal lung maturation: those receiving no courses, one course, and two or more courses. Physical examinations were performed and serum glucose, electrolyte, and cortisol levels were measured on days 1 and 3 of life.

RESULTS

For those receiving multiple courses of betamethasone (n = 43), the mean (+/- standard error of the mean [SEM]) number of courses was 5.3 +/- 0.4, with a mean (+/-SEM) total dose of 125.0 +/- 10.7 mg. No neonates had findings suggestive of Cushing syndrome. Day 1 cortisol levels (pooled mean +/- SEM) were 12.6 +/- 2.4, 5.3 +/- 3.2, and 4.4 +/- 1.8 microg/dL in those receiving no courses, one course, and two or more courses, respectively (P = .03; no courses versus two or more courses, P = .03), but the differences were not significant when corrected for multiple variables. Differences among day 3 cortisol levels (pooled mean +/- SEM) were not significant: 8.3 +/- 1.6, 5.8 +/- 1.4, and 5.8 +/- 0.9 microg/dL in those receiving no courses, one course, and two or more courses, respectively. None of the neonates in the group receiving no courses of betamethasone had day 1 cortisol levels lower than normal, whereas 22% and 11% of the neonates receiving one and two or more courses, respectively, had day 1 levels lower than normal. On day 3, 15% of those receiving one course and 10% of those receiving two or more courses had serum cortisol levels lower than normal, whereas none of those who received no courses had a low cortisol level. Multivariate regression analysis could show no association between the number of courses or total dose of betamethasone and the day 1 or day 3 cortisol values. The day 1 cortisol level (log10) was most associated with the severity of respiratory distress syndrome (RDS) and day 3 cortisol level (log10) with race and severity of RDS. Only in neonates with absent or mild RDS did number of courses correlate with day 3 cortisol levels (log10), but this was a positive correlation.

CONCLUSION

Serum cortisol levels either were independent of the number of courses or total dose of corticosteroids given or, in a subpopulation, were associated with increasing levels with increasing doses, suggesting that there is no suppressive effect with repeated dosing.

Loss-of-function mutations in the maize homeobox gene, knotted1, are defective in shoot meristem maintenance

The product of the maize homeobox gene, knotted1 (kn1), localizes to the nuclei of cells in shoot meristems, but is absent from portions of the meristem where leaf primordia or floral organs initiate. Recessive mutant alleles of kn1 were obtained by screening for loss of the dominant leaf phenotype in maize. Mutant kn1 alleles carrying nonsense, splicing and frame shift mutations cause severe inflorescence and floral defects. Mutant tassels produce fewer branches and spikelets. Ears are often absent, and when present, are small with few spikelets. In addition, extra carpels form in female florets and ovule tissue proliferates abnormally. Less frequently, extra leaves form in the axils of vegetative leaves. These mutations reveal a role for kn1 in meristem maintenance, particularly as it affects branching and lateral organ formation.

Antigenic characterization of a turkey coronavirus identified in poult enteritis- and mortality syndrome-affected turkeys

A turkey coronavirus (TCV [NC95]) was characterized by antigenic comparison with other avian and mammalian coronaviruses using immunofluorescence (FA) and immunoperoxidase (IP) procedures. Based on FA and IP procedures, TCV (NC95) was determined to be antigenically indistinguishable from turkey enteric (bluecomb) coronavirus (TECV). In addition, TCV (NC95) and TECV were found to be closely related to infectious bronchitis virus (IBV); a one-way antigenic relationship was demonstrated. Polyclonal antibodies specific for TECV and IBV reacted strongly against TCV (NC95), as determined by FA procedures. Monoclonal antibodies (MAbs) specific for IBV matrix protein (MAb 919) reacted strongly against TCV (NC95) and TECV as determined by FA and IP procedures; an IBV peplomer protein-specific MAb (MAb 94) did not recognize the two viruses. These studies suggest an identification of TCV (NC95) as a strain of TECV, and provide evidence of a close antigenic relationship between these viruses and IBV.

Internal medicine residents' assessment of the subspecialty fellowship application process

PURPOSE

The application process for fellowships in internal medicine subspecialties begins approximately 18 to 24 months before the start of training, requiring residents to decide on a career by the beginning of their second year of residency. The authors surveyed the internal medicine residents at Mount Sinai Hospital to assess their attitudes toward the fellowship application process.

METHOD

A survey instrument was designed and given to all 121 residents in 1994-95. The instrument surveyed the residents' career plans and the timing of their decisions, inquired about the effect on their residency of applying for a fellowship, and asked the residents to assess and comment on the timing of the fellowship application process.

RESULTS

In all, 80% (97) of the residents responded. Nearly two-thirds intended to apply for fellowship training; however, 17% of the first-year residents had changed their minds about their fellowship plans, and 50% of the second- and third-year residents had changed career plans. Whereas 79% of the first-year residents intended to apply "on time" during their second year, only 29% of the second-year residents intended to do so; 25% of the third-year residents planned to delay entry into a fellowship. Nearly two-thirds of the first- and second-year residents felt uncomfortable making an informed fellowship decision in their second year. In all, 60% of the residents felt they had to do research in order to get a competitive fellowship, and 68% said they had to change their assigned residency schedule to "get credentials" for fellowship applications. The consensus of nearly all the residents was that the timing of fellowship applications was much too early and should be moved to the middle of the third year.

CONCLUSION

As the current system of applying for medical fellowships is generally experienced negatively by residents, the authors recommend that the process be moved to the middle of the third year and that medical schools, residency programs, and fellowship training programs reconsider the entire fellowship application process.

Utilization of echocardiography by internists and cardiologists: a comparative study

OBJECTIVE

To compare the utilization of echocardiography as a diagnostic tool by internists and cardiologists.

DESIGN

Retrospective study.

SETTING

Tertiary care university hospital.

METHODS

Indications and clinical utility of echocardiographic studies ordered by cardiologists (group A, n = 301) and internists (group B, n = 297) were compared by chart review. The two groups of patients were analyzed to determine if the studies detected new cardiac pathology and/or altered patient management.

RESULTS

The proportion of studies with abnormal results were similar in both groups (19% versus 14%, P > 0.05). The results of echocardiography, however, led to a change in management more often when the study was ordered by cardiologists (16% versus 10%, P < 0.05). A significantly greater proportion of studies were ordered for evaluation of valvular function by internists (44% versus 33%, P < 0.05). Echocardiography detected valvular abnormalities in a similar proportion of cases in groups A and B (14% versus 10%, P > 0.05). However, diagnostic yield was very poor when the study was performed in patients with suspected mitral valve prolapse in both groups. Cardiologists utilized echocardiography more often for evaluation of left ventricular function (35% versus 18%, P < 0.01) and in the setting of atherosclerotic heart disease for detecting wall motion abnormalities (14% versus 5%, P < 0.01).

CONCLUSION

Diagnostic yield of echocardiography is similar when ordered by internists and cardiologists. With the information obtained, management is altered in a slightly greater proportion of cases involving a cardiologist. This may be due to utilization of echocardiography more often for estimating left ventricular function and for detecting wall motion abnormalities by cardiologists.

Combining medical and mechanical methods of cervical ripening. Does it increase the likelihood of successful induction of labor?

OBJECTIVE

To determine if combining two commonly used methods or cervical ripening (intracervical prostaglandin E2 [Pge2] gel and Foley balloon catheter) would result in a higher number of successful inductions and fewer cesarean sections when compared to PGE2 gel alone.

STUDY DESIGN

Seventy-eight patients with unfavorable cervixes eligible for induction of labor were prospectively randomized to receive either one dose (0.5 mg) of PGE2 gel followed by insertion of a 24-French Foley catheter (group 1, 41 patients) or two doses of 0.5 mg of intracervical gel (group 2, 37 patients). Outcome parameters included change in Bishop score, number of failed inductions, rate of cesarean section, rate of uterine hyperstimulation and postpartum infection.

RESULTS

Patients in group 1 had a significant increase in posttreatment Bishop scores (7.26 +/- 2.0 SD vs. 4.82 +/- 1.8 P = .0001) and fewer failed inductions (0 vs. 6, P = .009) when compared to patients in group 2. Abdominal delivery rates, uterine hyperstimulation and infections complications were not different between the two groups.

CONCLUSION

The combination of the Foley balloon and prostaglandin gel significantly improved the Bishop score and led to fewer failed inductions, although it did not increase the vaginal delivery rate.

Insulin resistance and development of diabetes mellitus associated with megestrol acetate therapy

We describe a case of diabetes mellitus induced by megestrol acetate in a patient with the acquired immunodeficiency syndrome. Metabolic studies including an arginine infusion test excluded an insulinopenic state and suggested insulin resistance as the underlying mechanism for hyperglycaemia. Withdrawal of megestrol acetate resulted in rapid correction of all metabolic abnormalities and eliminated the need for exogenous insulin therapy.

The tangled-1 mutation alters cell division orientations throughout maize leaf development without altering leaf shape

It is often assumed that in plants, where the relative positions of cells are fixed by cell walls, division orientations are critical for the generation of organ shapes. However, an alternative perspective is that the generation of shape may be controlled at a regional level independently from the initial orientations of new cell walls. In support of this latter view, we describe here a recessive mutation of maize, tangled-1 (tan-1), that causes cells to divide in abnormal orientations throughout leaf development without altering overall leaf shape. In normal plants, leaf cells divide either transversely or longitudinally relative to the mother cell axis; transverse division are associated with leaf elongation and longitudinal divisions with leaf widening. In tan-l mutant leaves, cells in all tissue layers at a wide range of developmental stages divide transversely at normal frequencies, but longitudinal divisions are largely substituted by a variety of aberrantly oriented divisions in which the new cell wall is crooked or curved. Mutant leaves grow more slowly than normal, but their overall shapes are normal at all stages of their growth. These observations demonstrate that the generation of maize leaf shape does not depend on the precise spatial control of cell division, and support the general view that mechanisms independent from the control of cell division orientations are involved in the generation of shape during plant development.