Bridging imaging users to imaging analysis - A community survey

The 'Bridging Imaging Users to Imaging Analysis' survey was conducted in 2022 by the Center for Open Bioimage Analysis (COBA), BioImaging North America (BINA) and the Royal Microscopical Society Data Analysis in Imaging Section (RMS DAIM) to understand the needs of the imaging community. Through multichoice and open-ended questions, the survey inquired about demographics, image analysis experiences, future needs and suggestions on the role of tool developers and users. Participants of the survey were from diverse roles and domains of the life and physical sciences. To our knowledge, this is the first attempt to survey cross-community to bridge knowledge gaps between physical and life sciences imaging. Survey results indicate that respondents' overarching needs are documentation, detailed tutorials on the usage of image analysis tools, user-friendly intuitive software, and better solutions for segmentation, ideally in a format tailored to their specific use cases. The tool creators suggested the users familiarise themselves with the fundamentals of image analysis, provide constant feedback and report the issues faced during image analysis while the users would like more documentation and an emphasis on tool friendliness. Regardless of the computational experience, there is a strong preference for 'written tutorials' to acquire knowledge on image analysis. We also observed that the interest in having 'office hours' to get an expert opinion on their image analysis methods has increased over the years. The results also showed less-than-expected usage of online discussion forums in the imaging community for solving image analysis problems. Surprisingly, we also observed a decreased interest among the survey respondents in deep/machine learning despite the increasing adoption of artificial intelligence in biology. In addition, the community suggests the need for a common repository for the available image analysis tools and their applications. The opinions and suggestions of the community, released here in full, will help the image analysis tool creation and education communities to design and deliver the resources accordingly.

Bridging Imaging Users to Imaging Analysis - A community survey

The "Bridging Imaging Users to Imaging Analysis" survey was conducted in 2022 by the Center for Open Bioimage Analysis (COBA), Bioimaging North America (BINA), and the Royal Microscopical Society Data Analysis in Imaging Section (RMS DAIM) to understand the needs of the imaging community. Through multi-choice and open-ended questions, the survey inquired about demographics, image analysis experiences, future needs, and suggestions on the role of tool developers and users. Participants of the survey were from diverse roles and domains of the life and physical sciences. To our knowledge, this is the first attempt to survey cross-community to bridge knowledge gaps between physical and life sciences imaging. Survey results indicate that respondents' overarching needs are documentation, detailed tutorials on the usage of image analysis tools, user-friendly intuitive software, and better solutions for segmentation, ideally in a format tailored to their specific use cases. The tool creators suggested the users familiarize themselves with the fundamentals of image analysis, provide constant feedback, and report the issues faced during image analysis while the users would like more documentation and an emphasis on tool friendliness. Regardless of the computational experience, there is a strong preference for 'written tutorials' to acquire knowledge on image analysis. We also observed that the interest in having 'office hours' to get an expert opinion on their image analysis methods has increased over the years. In addition, the community suggests the need for a common repository for the available image analysis tools and their applications. The opinions and suggestions of the community, released here in full, will help the image analysis tool creation and education communities to design and deliver the resources accordingly.

Ultrasound for the Objective Measurement of Breast Lymphedema

OBJECTIVES

Breast lymphedema has supplanted upper extremity lymphedema as a common and debilitating sequela of breast cancer treatment, but has no objective measurement. We assessed the utility of ultrasound-measured difference in dermal thickness between affected and unaffected breasts as a measure of breast lymphedema. We associated this measure with patient characteristics, treatment parameters, and patient-reported impact on quality of life.

METHODS

We enrolled 30 invasive breast carcinoma patients treated with breast-conserving surgery, sentinel lymph node biopsy, and radiotherapy, and 10 control patients evaluated for benign breast conditions without prior breast surgery or radiotherapy. Patient and treatment variables were ascertained from medical records and radiotherapy instruments. Impacts on quality of life were measured with a modified Disability of the Arm, Shoulder, and Hand questionnaire. We characterized breast lymphedema by calculating the difference in ultrasound-measured dermal thickness between affected and unaffected breasts. Associations with patient characteristics, treatment, and quality of life were quantified with log-binomial regression models.

RESULTS

Breast lymphedema was defined as a dermal thickness difference of >0.3 mm. Nineteen patients in the invasive group (63%) had breast lymphedema by this definition. We observed positive associations between ultrasound-defined breast lymphedema and surgical factors (size of primary tumor, number of lymph nodes removed), radiotherapy factors (breast volume irradiated, receipt of radiation boost), and patient-reported outcomes (sleep quality and overall confidence).

CONCLUSIONS

Difference in dermal thickness is an easy and inexpensive measurement for quantifying breast lymphedema, and correlates with treatment parameters and patient-reported impacts on quality of life.

Impact of and Response to Cyberattacks in Radiation Oncology

Cyberattacks on health care facilities are increasing and significantly affecting health care delivery throughout the world. The recent cyberattack on our hospital-based radiation facility exposed vulnerabilities of radiation oncology systems and highlighted the dependence of radiation treatment on integrated and complex radiation planning, delivery and verification systems. After the cyberattack on our health care facility, radiation oncology staff reconstructed patient information, schedules, and radiation plans from existing paper records and physicians developed a system to triage patients requiring immediate transfer of radiation treatment to nearby facilities. Medical physics and hospital information technology collaborated to restore services without access to the system backup or network connectivity. Ultimately, radiation treatments resumed incrementally as systems were restored and rebuilt. The experiences and lessons learned from this response were reviewed. The successes and shortcomings were incorporated into recommendations to provide guidance to other radiation facilities in preparation for a possible cyberattack. Our response and recommendations are intended to serve as a starting point to assist other facilities in cybersecurity preparedness planning. Because there is no one-size-fits-all response, each department should determine its specific vulnerabilities, risks, and available resources to create an individualized plan.

Neuronal Graphs: A Graph Theory Primer for Microscopic, Functional Networks of Neurons Recorded by Calcium Imaging

Connected networks are a fundamental structure of neurobiology. Understanding these networks will help us elucidate the neural mechanisms of computation. Mathematically speaking these networks are "graphs"-structures containing objects that are connected. In neuroscience, the objects could be regions of the brain, e.g., fMRI data, or be individual neurons, e.g., calcium imaging with fluorescence microscopy. The formal study of graphs, graph theory, can provide neuroscientists with a large bank of algorithms for exploring networks. Graph theory has already been applied in a variety of ways to fMRI data but, more recently, has begun to be applied at the scales of neurons, e.g., from functional calcium imaging. In this primer we explain the basics of graph theory and relate them to features of microscopic functional networks of neurons from calcium imaging-neuronal graphs. We explore recent examples of graph theory applied to calcium imaging and we highlight some areas where researchers new to the field could go awry.

The multiscale top-hat tensor enables specific enhancement of curvilinear structures in 2D and 3D images

Quantification and modelling of curvilinear structures in 2D and 3D images is a common challenge in a wide range of biomedical applications. Image enhancement is a crucial pre-processing step for curvilinear structure quantification. Many of the existing state-of-the-art enhancement approaches still suffer from contrast variations and noise. In this paper, we propose to address such problems via the use of a multiscale image processing approach, called Multiscale Top-Hat Tensor (MTHT). MTHT produces a better quality enhancement of curvilinear structures in low contrast and noisy images compared with other approaches in a range of 2D and 3D biomedical images. The proposed approach combines multiscale morphological filtering with a local tensor representation of curvilinear structure. The MTHT approach is validated on 2D and 3D synthetic and real images, and is also compared to the state-of-the-art curvilinear structure enhancement approaches. The obtained results demonstrate that the proposed approach provides high-quality curvilinear structure enhancement, allowing high accuracy segmentation and quantification in a wide range of 2D and 3D image datasets.

Active Surveillance for Medically Inoperable Stage IA Lung Cancer in the Elderly

Objectives

Treatment for stage IA lung cancer may be too aggressive an approach in elderly patients with competing co-morbidities. We report outcomes for those electing active surveillance (AS) and investigate factors that may predict indolent disease.

Materials and methods

Retrospective review was performed for 12 consecutive patients, ≥70 years old, with medically inoperable stage IA, T1N0M0 lung cancer and significant co-morbidities, who chose AS with radiation therapy (RT) reserved for clear disease progression. Collected data included Charlson-Deyo Comorbidity Index (CDCI) grades, histology, and tumor size changes. Volume doubling time (VDT) calculations used a modified Schwartz equation.

Results

Fifteen nodules underwent AS in 12 patients; three patients had more than one nodule. Median age of all patients was 78 (range, 71–85). All patients’ CDCI grades were ≥1, 7 were ≥2. Eleven of 12 patients were deemed to be at high-risk for falls. Twelve nodules in 12 patients were biopsied; adenocarcinoma the prevailing common (47%) histology. The median, one, two and three year patient freedom-from-RT values were 21.4 months (95% CI: 11.6-not reached), 81%, 43%, and 29%, respectively. Median VDT of treated vs. untreated nodules was 189 days (range, 62-infinite) vs. 1153 days (range, 504-infinite), respectively. No patient progressed regionally or distantly, and there have been no cancer-related deaths. Due to cardiovascular events, two patients died and one remains on hospice. Median duration of AS for those still continuing computed tomography (CT) surveillance is 35.1 months.

Conclusion

Selected elderly patients with stage IA lung cancer and significant co-morbidities may undergo AS without detriment in outcome. Prospective AS studies are warranted.

Extracting 3D Parametric Curves from 2D Images of Helical Objects

Helical objects occur in medicine, biology, cosmetics, nanotechnology, and engineering. Extracting a 3D parametric curve from a 2D image of a helical object has many practical applications, in particular being able to extract metrics such as tortuosity, frequency, and pitch. We present a method that is able to straighten the image object and derive a robust 3D helical curve from peaks in the object boundary. The algorithm has a small number of stable parameters that require little tuning, and the curve is validated against both synthetic and real-world data. The results show that the extracted 3D curve comes within close Hausdorff distance to the ground truth, and has near identical tortuosity for helical objects with a circular profile. Parameter insensitivity and robustness against high levels of image noise are demonstrated thoroughly and quantitatively.

Protective effect of Allium sativum (garlic) aqueous extract against lead-induced oxidative stress in the rat brain, liver, and kidney

The present investigation was undertaken to evaluate the ameliorative activity of Allium sativum against lead-induced oxidative stress in the brain, liver, and kidney of male rats. Four groups of male Wistar strain rats (100-120 g) were taken: group 1 received 1000 mg/L sodium acetate and group 2 was given 1000 mg/L lead acetate through drinking water for 2 weeks. Group 3 and 4 were treated with 250 mg/kg body weight/day of A. sativum and 500 mg/kg body weight/day of A. sativum, respectively, by oral intubation for a period of 2 weeks along with lead acetate. The rats were sacrificed after treatment and the brain, liver, and kidney were isolated on ice. In the brain, four important regions namely the hippocampus, cerebellum, cerebral cortex, and brain stem were separated and used for the present investigation. Blood was also drawn by cardiac puncture and preserved in heparinized vials at 4 °C for estimation of delta-aminolevulinic acid dehydratase (ALAD) activity. The results showed a significant (p < 0.05) increase in reactive oxygen species (ROS), lipid peroxidation products (LPP), total protein carbonyl content (TPCC), and lead in the selected brain regions, liver, and kidney of lead-exposed group compared with their respective controls. Blood delta-ALAD activity showed a significant (p < 0.05) decrease in the lead-exposed rats. However, the concomitant administration of A. sativum resulted in tissue-specific recovery of oxidative stress parameters namely ROS, LPP, and TPCC. A. sativum treatment also restored the blood delta-ALAD activity back to control. Overall, our results indicate that A. sativum administration could be an effective antioxidant treatment strategy for lead-induced oxidative insult.

Blobs and curves: object-based colocalisation for plant cells

Blobs and curves occur everywhere in plant bioimaging: from signals of fluorescence-labelled proteins, through cytoskeletal structures, nuclei staining and cell extensions such as root hairs. Here we look at the problem of colocalisation of blobs with blobs (protein-protein colocalisation) and blobs with curves (organelle-cytoskeleton colocalisation). This article demonstrates a clear quantitative alternative to pixel-based colocalisation methods and, using object-based methods, can quantify not only the level of colocalisation but also the distance between objects. Included in this report are computational algorithms, biological experiments and guidance for those looking to increase their use of computationally-based and quantified analysis of bioimages.

Erectile function recovery in patients after non-nerve sparing radical prostatectomy

Few studies have looked at erectile function recovery (EFR) rates in men undergoing non-nerve sparing resection during radical prostatectomy (RP). Existing studies show great variation in EFR rates owing to multiple factors that minimize their utility in counselling RP patients. We investigated the EFR rate and its predictors in unilateral cavernous nerve resection and bilateral cavernous nerve resection patients 24 months after RP. We conducted a population-based, prospective cohort study of 966 patients who underwent RP at a tertiary cancer centre from 2008 to 2012. Cavernous nerve condition was evaluated on a 4-point nerve sparing score and assigned to one of three groups: bilateral sparing, unilateral resection (UNR) and bilateral nerve resection (BNR). EF was assessed pre-RP and 24-30 months post-op using a validated 5-point patient-reported scale (1 = fully rigid; 5 = no tumescence). EFR was defined as a post-op EF grade of 1-2. Statistical analysis included descriptive statistics, anova, chi-square, Fisher's exact test and logistic regression. Mean baseline EF was 1.84 ± 1.3 and 2.74 ± 1.5 for UNR and BNR patients respectively. Thirty-three percent of UNR patients and 13% of BNR patients exhibited EFR. Age, baseline EF were predictors of EFR. Multivariable analysis showed baseline EF was a significant predictor of EFR at 24 months for UNR. For BNR patients, pre-RP EF was the only factor predictive of EFR. Patients undergoing nerve resection still have a significant chance of achieving true EFR, with UNR surgery patients showing more potential for improvement than patients undergoing BNR surgery. Age and baseline EFR characterize recovery prospects in these two groups. Physicians should thus measure and account for baseline EF in addition to age and the degree of nerve resection when advising patients about expectations for successful EF following RP.

Plant-determined variation in the cardenolide content, thin-layer chromatography profiles, and emetic potency of monarch butterflies,Danaus plexippus L. Reared on milkweed plants in California: 2.Asclepias speciosa

The pattern of variation in gross cardenolide concentration of 111Asclepias speciosa plants collected in six different areas of California is a positively skewed distribution which ranges from 19 to 344 μg of cardenolide per 0.1 g dry weight with a mean of 90 μg per 0.1 g. Butterflies reared individually on these plants in their native habitats ranged from 41 to 547 μg of cardenolide per 0.1 g dry weight with a mean of 179 μg. Total cardenolide per butterfly ranged from 54 to 1279 μg with a mean of 319 μg. Differences in concentrations and total cardenolide contents in the butterflies from the six geographic areas appeared minor, and there were no differences between the males and the females, although the males did weigh significantly more than females. The uptake of cardenolide by the butterflies was found to be a logarithmic function of the plant concentration. This results in regulation: larvae which feed on low-concentration plants produce butterflies with increased cardenolide concentrations relative to those of the plants, and those which feed on high-concentration plants produce butterflies with decreased concentrations. No evidence was adduced that high concentrations of cardenolides in the plants affected the fitness of the butterflies. The mean emetic potencies of the powdered plant and butterfly material were 5.62 and 5.25 blue jay emetic dose fifty units per milligram of cardenolide and the number of ED50 units per butterfly ranged from 0.28 to 6.7 with a mean of 1.67. Monarchs reared onA. speciosa, on average, are only about one tenth as emetic as those reared onA. eriocarpa. UnlikeA. eriocarpa which is limited to California,A. speciosa ranges from California to the Great Plains and is replaced eastwards byA. syriaca L. These two latter milkweed species appear to have a similar array of chemically identical cardenolides, and therefore both must produce butterflies of relatively low emetic potency to birds, with important ecological implications. About 80% of the lower emetic potency of monarchs reared on A. speciosa compared to those reared onA. eriocarpa appears attributable to the higher polarity of the cardenolides inA. speciosa. Thin-layer Chromatographie separation of the cardenolides in two different solvent systems showed that there are 23 cardenolides in theA. speciosa plants of which 20 are stored by the butterflies. There were no differences in the cardenolide spot patterns due either to geographic origin or the sex of the butterflies. As when reared onA. eriocarpa, the butterflies did not store the plant cardenolides withR f values greater than digitoxigenin. However, metabolic transformation of the cardenolides by the larvae appeared minor in comparison to when they were reared onA. eriocarpa. AlthoughA. eriocarpa andA. speciosa contain similar numbers of cardenolides and both contain desglucosyrioside, the cardenolides ofA. speciosa overall are more polar. ThusA. speciosa has no or only small amounts of the nonpolar labriformin and labriformidin, whereas both occur in high concentrations inA. eriocarpa. A. speciosa plants and butterflies also contain uzarigen, syriogenin, and possibly other polar cardenolides withR f values lower than digitoxin. The cardenolide concentration in the leaves is not only considerably less than inA. eriocarpa, but the latex has little to immeasurable cardenolide, whereas that ofA. eriocarpa has very high concentrations of several cardenolides. Quantitative analysis ofR f values of the cardenolide spots, their intensities, and their probabilities of occurrence in the chloroform-methanol-formamide TLC system produced a cardenolide fingerprint pattern very different from that previously established for monarchs reared onA. eriocarpa. This dispels recently published skepticism about the predictibility of chemical fingerprints based upon ingested secondary plant chemicals.

Comparison of the effects of phosphate-coated and sandblasted acid-etched titanium implants on osseointegration: a microcomputed tomographic examination in the canine model

PURPOSE

This study tested the effects of phosphate treatment of titanium on bone volume fraction (BV/TV) at 30 to 60 Μm from the implant surface using microcomputed tomography to analyze the mineralized tissue.

MATERIALS AND METHODS

Electrolytically phosphated (50/100 volts [T1/T2]) or nonphosphated 3.3- X 8-mm titanium implants (C) with sandblasted acid-etched surfaces were placed in 40 mandibular sites in five foxhounds 6 weeks after the extraction of the premolars. After 4 weeks, the animals were sacrificed, and BV/TV was analyzed using microcomputed tomography.

RESULTS

The mean BV/TV (± standard deviation) of the control implants was 31.4% ± 15.3% (range, 10.9% to 55.3%). For the T1 implants, a mean BV/TV of 38.4% ± 10.7% (range, 21.6% to 57.3%) was seen, and for T2 implants, the mean BV/TV was 40.3% ± 15.1% (range, 16.5% to 61.1%). Mean BV/TV values for the groups were not significantly different. For all groups (C, T1, and T2), there were no significant differences in BV/TV at the most coronal slices. For all groups, there was a positive slope showing more bone apposition as the slices moved from coronal to apical. The T2 group showed significantly increased mineralized tissue moving from the coronal to the apical section of the implant, compared to the control and T1 implants.

CONCLUSION

Access to better blood supply and bone cells from the marrow spaces in the apical regions may lead to a better trabecular bone response. Increased mineralized tissue apposition may allow for accelerated loading and more predictable implant placement in sites with poor quality bone or patients with compromised bone healing.

Effect of phosphate treatment of Acid-etched implants on mineral apposition rates near implants in a dog model

PURPOSE

This study evaluated the effects of phosphate coating of acid-etched titanium on the mineral apposition rate (MAR) and new bone-to-implant contact (BIC) in a canine model.

MATERIALS AND METHODS

Titanium implants (2.2 3 4 mm) with acid-etched surfaces that were electrolytically phosphated or not were placed in 48 mandibular sites in six foxhounds. Tetracycline and calcein dyes were administered 1 week after implant placement and 1 week before sacrifice. At 12 weeks after implant placement, the animals were sacrificed. MAR and BIC were evaluated using fluorescence microscopy. Light microscopic and histologic evaluations were performed on undecalcified sections.

RESULTS

Microscopic evaluation showed the presence of healthy osteoblasts lining bone surfaces near implants. Similar BIC was observed in phosphated and nonphosphated titanium implant sites. MAR was significantly higher around the nonphosphated titanium implant surfaces than around the phosphated titanium samples. No significant differences were found between dogs or implant sites.

CONCLUSION

Acid-etched implants showed significantly higher MARs compared to acid-etched, phosphate-coated implants. Int J Maxillofac Implants 2010;25:278-286.

Unresectable carcinoma of the paranasal sinuses: outcomes and toxicities

PURPOSE

To evaluate long-term outcomes and toxicity in patients with unresectable paranasal sinus carcinoma treated with radiotherapy, with or without chemotherapy.

METHODS AND MATERIALS

Between January 1990 and December 2006, 39 patients with unresectable Stage IVB paranasal sinus carcinoma were treated definitively with chemotherapy plus radiotherapy (n = 35, 90%) or with radiotherapy alone (n = 4, 10%). Patients were treated with three-dimensional conformal radiotherapy (n = 18, 46%), intensity-modulated radiotherapy (n = 12, 31%), or conventional radiotherapy (n = 9, 23%) to a median treatment dose of 70 Gy. Most patients received concurrent platinum-based chemotherapy (n = 32, 82%) and/or concomitant boost radiotherapy (n = 29, 74%).

RESULTS

With a median follow-up of 90 months, the 5-year local progression-free survival, regional progression-free survival, distant metastasis-free survival, disease-free survival, and overall survival were 21%, 61%, 51%, 14%, and 15%, respectively. Patients primarily experienced local relapse (n = 25, 64%), mostly within the irradiated field (n = 22). Nine patients developed neck relapses; however none of the 4 patients receiving elective neck irradiation had a nodal relapse. In 13 patients acute Grade 3 mucositis developed. Severe late toxicities occurred in 2 patients with radionecrosis and 1 patient with unilateral blindness 7 years after intensity-modulated radiation therapy (77 Gy to the optic nerve). The only significant factor for improved local progression-free survival and overall survival was a biologically equivalent dose of radiation >/=65 Gy.

CONCLUSIONS

Treatment outcomes for unresectable paranasal sinus carcinoma are poor, and combined-modality treatment is needed that is both more effective and associated with less morbidity. The addition of elective neck irradiation may improve regional control.

Effects of phosphated titanium and enamel matrix derivatives on osteoblast behavior in vitro

PURPOSE

The purpose of this study was to evaluate the effects of phosphated titanium and enamel matrix derivatives (EMD) on osteoblast function.

MATERIALS AND METHODS

Primary rat osteoblasts were cultured on disks of either phosphated or nonphosphated titanium. In half of the samples 180 microg of EMD was immediately added. The medium was changed every 2 days for 28 days and then analyzed using transforming growth factor-beta1 (TGF-beta1) and interleukin-1beta (IL-1beta) enzyme-linked immunosorbent assays (ELISAs). Scanning electron microscopy and light microscopy were used to evaluate nodule formation and mineralization.

RESULTS

Microscopic evaluation revealed no differences in osteoblast attachment between the 4 groups. Osteoblast nodule formation was observed in all groups. In the absence of mineralizing media, nodules on the nonphosphated titanium samples showed no evidence of mineralization. All nodules on the phosphated titanium had evidence of mineralization. ELISA revealed no significant differences in IL-1beta production between any of the groups. The EMD-treated osteoblasts produced significantly more TGF-beta1 than non-EMD-treated cells for up to 8 days, and osteoblasts on phosphated titanium produced significantly more TGF-beta1 at 8 days.

DISCUSSION AND CONCLUSION

Osteoblast attachment appeared unaffected by surface treatment. EMD initiated early TGF-beta1 production, but production decreased to control levels within 10 days. Phosphated titanium increased TGF-beta1 production at 8 days and induced nodule mineralization even in the absence of mineralizing medium.

Managing nutrients across regions of the United States

Nutrient balance in the ecosystem involves profitability of the agricultural enterprise and commitments to resource management to maintain quality of air, water, and land resources. Phosphorus and N are the two nutrients of major concern, and they behave differently in soils. Most P adheres strongly to soil particles and moves laterally with the soil during erosion processes, but with high concentrations more P remains in soluble forms and moves in the water fraction. Most N is soluble and moves laterally or downward with soil water. Soil scientists and agronomists have researched soil processes, plant nutrition, cropping systems, and water quality issues mainly on a field and farm level, but now the movement is to management and regulation of nonpoint problems on a watershed basis as proposed in the Clean Water Action Plan. The plan recognizes the vast diversity of soil parent materials and climates among geographic areas, even among and within watersheds, that determine crop adaptation and cropping systems, the role of states in regulatory processes, and the need for local citizens to have operational involvement. This process insures that nutrient management guidelines will be more site-specific and solutions can be focused on the direct problem. Directed efforts will be needed to educate local citizens, landowners, and caretakers of agricultural enterprises, and regulatory agencies. Several factors, including economic and social incentives for implementation must be considered along with the technologies available. The solutions are multidisciplinary, will require long-term research to accommodate climate variation, and should be associated with a strong commitment to education. Public funding will be needed to support the effort.

Involvement of substance P and central opioid receptors in morphine modulation of the CHS response

Morphine administration prior to challenge with the antigen 2,4-dinitro-fluorobenzene increases the contact hypersensitivity (CHS) response in rats. The present study extended these findings by showing that central, but not systemic, administration of N-methylnaltrexone antagonized the morphine-induced enhancement of the CHS response. The importance of the neuroimmune mediator substance P was shown via the attenuation of the morphine-induced enhancement following both systemic and topical administration of the NK-1 antagonist WIN51,708. Taken together, the findings of the present study provide new data showing that central opioid receptors and peripheral substance P are involved in the morphine-induced enhancement of the CHS response.

Morphine modulation of the contact hypersensitivity response: characterization of immunological changes

Previous investigations in our laboratory showed that systemic morphine administration 1 h prior to elicitation of the in vivo contact hypersensitivity (CHS) response produced a robust increase in inflammation at the site of antigen reexposure. The present study extended those findings by characterizing the effect of morphine on immunological processes important in the development of the CHS response. To induce contact hypersensitivity, the antigen 2,4-dinitrofluorobenzene was applied to the pinnae of previously sensitized rats. Morphine administration produced an increase in inducible nitric oxide synthase mRNA and the proinflammatory cytokine interleukin-6, at the site of antigen reexposure. In contrast, morphine did not alter expression of the anti-inflammatory cytokine interleukin-10. Morphine also produced an increase in the proliferation of lymphocytes from the peripheral (i.e., cervical) lymph nodes when assessed 72 h following challenge. These studies show that the morphine-induced increase in the in vivo CHS response involves immunologically specific alterations.

Depression, hopelessness, and desire for hastened death in terminally ill patients with cancer

CONTEXT

Understanding why some terminally ill patients desire a hastened death has become an important issue in palliative care and the debate regarding legalization of assisted suicide.

OBJECTIVES

To assess the prevalence of desire for hastened death among terminally ill cancer patients and to identify factors corresponding to desire for hastened death. Design Prospective survey conducted in a 200-bed palliative care hospital in New York, NY.

PATIENTS

Ninety-two terminally ill cancer patients (60% female; 70% white; mean age, 65.9 years) admitted between June 1998 and January 1999 for end-of-life care who passed a cognitive screening test and provided sufficient data to permit analysis.

MAIN OUTCOME MEASURE

Scores on the Schedule of Attitudes Toward Hastened Death (SAHD), a self-report measure assessing desire for hastened death among individuals with life-threatening medical illness.

RESULTS

Sixteen patients (17%) were classified as having a high desire for hastened death based on the SAHD and 15 (16%) of 89 patients met criteria for a current major depressive episode. Desire for hastened death was significantly associated with a clinical diagnosis of depression (P=.001) as well as with measures of depressive symptom severity (P<.001) and hopelessness (P<.001). In multivariate analyses, depression (P=.003) and hopelessness (P<.001) provided independent and unique contributions to the prediction of desire for hastened death, while social support (P=.05) and physical functioning (P=.02) added significant but smaller contributions.

CONCLUSIONS

Desire for hastened death among terminally ill cancer patients is not uncommon. Depression and hopelessness are the strongest predictors of desire for hastened death in this population and provide independent and unique contributions. Interventions addressing depression, hopelessness, and social support appear to be important aspects of adequate palliative care, particularly as it relates to desire for hastened death.

Naltrexone administration attenuates surgery-induced immune alterations in rats

Surgery is a commonly performed procedure which produces substantial alterations in immune function in both humans and animals. To better understand the mechanism of surgery-induced immunomodulation, the present study investigated the effect of the opioid antagonist naltrexone on surgery-induced immune alterations in rats. Based on previous investigations in our laboratory, rats underwent a 6-cm laparotomy with no internal manipulation and immunological assessments were completed 24 h following the surgical procedure. Naltrexone was administered at the time of surgery and every 4 h thereafter until immune assessment. Results showed that naltrexone attenuated the surgery-induced decrease in natural killer cell cytotoxicity, B-cell proliferation, T-cell proliferation, and production of the cytokine IFN-gamma. These results are among the first to show that pharmacological antagonism of opioid receptors can prevent deleterious immune changes in the postoperative state, suggesting a detrimental role of the endogenous opioids in surgical procedures.

pH dependence of formation of a partially unfolded state of a Lys 73 --> His variant of iso-1-cytochrome c: implications for the alkaline conformational transition of cytochrome c

The alkaline conformational transition of a lysine 73 --> histidine variant of iso-1-cytochrome c has been studied. The transition has been monitored at 695 nm, a band sensitive to the presence of the heme-methionine 80 bond, at the heme Soret band which is sensitive to the nature of the heme ligand, and by NMR methods. The guanidine hydrochloride dependence of the alkaline conformational transition has also been monitored. The histidine 73 protein has an unusual biphasic alkaline conformational transition at both 695 nm and the heme Soret band, consistent with a three-state process. The conformational transition is fully reversible. An equilibrium model has been developed to account for this behavior. With this model, it has been possible to obtain the acid constant for the trigger group, pK(H), of the low-pH phase from the equilibrium data. A pK(H) value of 6.6 +/- 0.1 in H(2)O was obtained, consistent with a histidine acting as the trigger group. The NMR data for the low-pH phase of the alkaline conformational transition are consistent with an imidazole ligand replacing Met 80. For the high-pH phase of the biphasic alkaline transition, the NMR data are consistent with lysine 79 being the heme ligand. Guanidine hydrochloride m values of 1.67 +/- 0.08 and 1.1 +/- 0.2 kcal mol(-1) M(-1) were obtained for the low- and high-pH phases of the biphasic alkaline transition of the histidine 73 protein, respectively, consistent with a greater structural disruption for the low-pH phase of the transition.

Cloning and functional analysis of sucrose:sucrose 1-fructosyltransferase from tall fescue

Enzymes of grasses involved in fructan synthesis are of interest since they play a major role in assimilate partitioning and allocation, for instance in the leaf growth zone. Several fructosyltransferases from tall fescue (Festuca arundinacea) have previously been purified (Lüscher and Nelson, 1995). It is surprising that all of these enzyme preparations appeared to act both as sucrose (Suc):Suc 1-fructosyl transferases (1-SST) and as fructan:fructan 6(G)-fructosyl transferases. Here we report the cloning of a cDNA corresponding to the predominant protein in one of the fructosyl transferase preparations, its transient expression in tobacco protoplasts, and its functional analysis in the methylotrophic yeast, Pichia pastoris. When the cDNA was transiently expressed in tobacco protoplasts, the corresponding enzyme preparations produced 1-kestose from Suc, showing that the cDNA encodes a 1-SST. When the cDNA was expressed in P. pastoris, the recombinant protein had all the properties of known 1-SSTs, namely 1-kestose production, moderate nystose production, lack of 6-kestose production, and fructan exohydrolase activity with 1-kestose as the substrate. The physical properties were similar to those of the previously purified enzyme, except for its apparent lack of fructan:fructan 6(G)-fructosyl transferase activity. The expression pattern of the corresponding mRNA was studied in different zones of the growing leaves, and it was shown that transcript levels matched the 1-SST activity and fructan content.

Endomorphin-1 induces antinociception without immunomodulatory effects in the rat

RATIONALE

Although there is evidence that central opioid receptors are involved in immunomodulation, it has been only recently that an endogenous agonist, designated endomorphin-1, possessing high selectivity and affinity for the mu opioid receptor has been identified.

OBJECTIVE

The present study assesses the immunomodulatory effects of endomorphin- in the rat and provides further evaluation of the antinociceptive effects of endomorphin-1.

METHODS

Rats were surgically implanted with cannulae directed at the lateral cerebral ventricle. Animals received vehicle or endomorphin-1 at doses of 31.63 or 56.23 microg (ICV) and were tested for antinociception in two different assays, the warm water tail withdrawal procedure and the hotplate assay. Additional studies assessed the effect of naltrexone on the antinociception produced by endomorphin-1 in both antinociceptive assessments. Assessments of immune status following endomorphin-1 treatment included measurements of splenic natural killer cell activity, production of interferon-y, and lymphocyte proliferative responses to mitogenic stimulation by Con-A, LPS, and the microbial superantigen, TSST-1.

RESULTS

Endomorphin-1 induced significant and naltrexone reversible antinociception 30 and 60 min following drug administration, as measured by the hotplate assay and warm water tail withdrawal procedure. In marked contrast, endomorphin-1 did not produce immunomodulatory effects up to 120 min following ICV administration.

CONCLUSIONS

Endomorphin-1 produces antinociception but does not induce immunomodulatory effects in the rat. These findings suggest that it is possible to develop therapeutic strategies for separating antinociception and immunomodulatory properties through the mu opioid receptor.

Involvement of central mu- but not delta- or kappa-opioid receptors in immunomodulation

Studies completed in both humans and animals have shown that opioids have significant effects on the immune system via pharmacological interactions with the opioid receptor. However, the type of opioid receptor at which morphine binding produces changes in immune status has not been well characterized. To determine the type of opioid receptor involved in opioid-induced immune alterations, the present study assessed the effects of agonists selective for the mu-, delta-, and kappa-opioid receptors. The site of action (i.e., peripheral vs central) at which opioids produce immune changes was investigated by injecting the agonists directly into the left lateral ventricle of the brain. Specifically, Lewis rats received an intracerebroventricular administration of [d-Ala(2),N-Me-Phe(4), Gly-ol(5)]enkephalin (DAMGO), a mu-receptor selective agonist, [D-Pen(2,5)]enkephalin (DPDPE), a delta-opioid receptor agonist, or U69,593, a kappa-receptor agonist. Immune assessments completed 1 h following drug administration showed that the mu-receptor selective agonist DAMGO produced a dose-dependent decrease in natural killer cell activity and T-lymphocyte proliferation to the mitogen concanavalin A (Con A); no immunological changes were found following DPDPE or U69,593 treatment. Calculation of the number of white blood cells per sample showed no differences between rats treated with saline and rats treated with any of the selective agonists. Administration of the opioid antagonist N-methylnaltrexone prior to DAMGO treatment attenuated the DAMGO-induced changes in immune status. Results from the present study indicate that the immunomodulatory effects of opioids can be attributed to interactions with the mu-opioid receptor.

The schedule of attitudes toward hastened death: Measuring desire for death in terminally ill cancer patients

BACKGROUND

The authors examined the reliability and validity of the Schedule of Attitudes toward Hastened Death (SAHD), a self-report measure of desire for death previously validated in a population of individuals with the acquired immunodeficiency syndrome (AIDS), among terminally ill patients with cancer.

METHODS

The authors interviewed 92 terminally ill cancer patients, all with a life expectancy of < 6 months, after admission to a palliative care hospital. Patients were administered the SAHD, a clinician-rated measure of desire for death (the Desire for Death Rating Scale [DDRS]), and several measures of physical and psychosocial well-being.

RESULTS

The average number of SAHD items endorsed was 4. 76 (standard deviation, 4.3); 15 patients (16.3%) endorsed > or = 10 items, indicating a high desire for death. Internal consistency was strong (coefficient alpha = 0.88, median item-total correlation = 0. 49), as were indices of convergent validity. Total SAHD scores were correlated significantly (correlation coefficient [r] = 0.67) with the DDRS, and somewhat less so with measures of depression (r = 0. 49) and hopelessness (r = 0.55). Lower, but substantial, correlations were observed between the SAHD and measures of spiritual well-being (r = -0.42), quality of life (r = -0.36), physical symptoms (r = 0.38), and symptom distress (r = 0.38). No significant correlation was observed between SAHD scores and social support (r = -0.06) or pain intensity (r = 0.16); however, pain-related functional interference and overall physical functioning were correlated significantly with SAHD scores (r = 0.31 and r = -0.23, respectively).

CONCLUSIONS

The SAHD appears to be a reliable and valid measure of desire for death among terminally ill cancer patients. Coupled with previous research in patients with AIDS, these results support the utility of the SAHD for research addressing interest in hastened death in patients with a life-threatening medical illness.

Phenotypic and functional assessments of immune status in the rat spleen following acute heroin treatment

Heroin use is associated with an increased incidence of several types of infections, including HIV. Yet few studies have assessed whether heroin produces pharmacological alterations of immune status that might contribute to the increased rate of infections amongst heroin users. The present study investigated whether a single administration of heroin to rats produces dose-dependent alterations in functional measures of immune status and in the distribution of leukocyte subsets in the spleen. The results showed that heroin produces a dose-dependent, naltrexone-reversible suppression of the concanavalin A-stimulated proliferation of T cells, lipopolysaccharide-stimulated proliferation of B cells, production of interferon-gamma and cytotoxicity of natural killer (NK) cells in the spleen. Heroin's suppressive effect on NK cell activity results in part from a heroin-induced decrease in the relative number of NKR-P1A(hi) CD3- NK cells in the spleen. Heroin also decreases the percent of a splenic granulocyte subset, the CD11b/c+ HIS48(hi) cells, whose function currently is unknown. In contrast, heroin does not alter relative numbers of CD4+ CD3+ T cells, CD8+ CD3+ T cells, CD45+ B cells, NKR-P1A(lo) CD3+ T cells, CD11b/c+ ED1+ (or CD11b/c+ HIS48-) monocytes/macrophages or CD11b/c+ ED1- (or CD11b/c+ HIS48+) total granulocytes in the spleen. Collectively, these findings demonstrate that heroin produces pharmacological effects on functional and phenotypic measures of immune status.

Topics of conflict between parents and young adolescents

ISSUES AND PURPOSE

Parents often examine and question interactions with their young teen and may ask the advice of healthcare professionals. Topics, frequency, and intensity of conflicts between young adolescents and parents were therefore examined.

DESIGN AND METHODS

A descriptive survey using the 44-item Issues Checklist (Robin, 1975) with 163 parent and young adolescent (ages 11-14) dyads.

RESULTS

Parents and teens were congruent about their reports of the topics, frequency, and intensity of conflict. Discussion of the topics generally was not angry. Mothers reported the greatest quantity of issues. Potentially sensitive topics such as substance use, dating, and sex were rarely approached by either parent or young adolescent. Sociodemographic characteristics did not distinguish or were not associated with IC scores.

PRACTICE IMPLICATIONS

Conflict is a common component of the parent-young adolescent relationship. Families with children entering adolescence can expect conflict about issues that recur but usually are not that "hot". Anticipating topics may put conflict in perspective. Nurses help families resolve conflicts associated with day-to-day conflicts as a first step toward opening up larger, potentially sensitive topics.

Enhancement of the contact hypersensitivity reaction by acute morphine administration at the elicitation phase

The present study investigated the effects of morphine on the irritant contact sensitivity (ICS) and contact hypersensitivity (CHS) reaction. ICS was induced by croton oil application on the pinnae of naïve rats. Morphine injected prior to croton oil application did not affect the ICS response when assessed by measurements of pinnae thickness. CHS was induced by applying the antigen 2,4-dinitro-1-fluorobenzene (DNFB) to the pinnae of rats sensitized to DNFB. Rats received an injection of morphine prior to either initial antigen exposure (sensitization) or antigen reexposure (challenge). Morphine prior to challenge, but not sensitization, resulted in a pronounced enhancement of the CHS response as measured by pinna thickness. Quantitative PCR also showed increased IFN-gamma mRNA levels in the inflamed tissue of morphine-treated rats. Naltrexone blocked the morphine-induced enhancement of the CHS response. The differential effects of morphine suggest that opioids have a more pronounced effect on in vivo immune responses that involve immunological memory.

Severity, time, and beta-adrenergic receptor involvement in surgery-induced immune alterations

Although investigations of surgical stress in animals have reported immune alterations, surprisingly little is known about the variables or mechanisms contributing to the effect. Thus, we completed a series of experiments investigating the immune-altering effects of surgery severity, time of maximal immune alterations, and recovery, as well as the involvement of beta-adrenergic receptors in surgery-induced immune alterations in Lewis rats. Immune alterations included natural killer (NK) cell cytotoxicity as well as B- and T-cell proliferation. Results showed increased immune suppression with larger incisions (6 cm > 3 cm > anesthesia > saline). In addition, maximal immune alterations induced by surgery occurred after 24 h; anesthesia effects predominated at the earlier time points. Recovery of immune status varied depending on the immunological measure of interest. Although NK cell cytotoxicity returned to control values within 2 days, B-cell proliferation remained suppressed for at least 8 days, and T-cell proliferation did not begin to recover until 4-8 days following the surgical procedure. To assess the mechanisms involved in surgery-induced immune alterations, follow-up assessments evaluated the effect of nadolol, a beta-adrenergic receptor antagonist, on surgery-induced immune alterations. Results show that nadolol blocks the surgery-induced reduction in B- and T-cell proliferation but has no effect on the suppression of NK cell cytotoxicity. These results indicate the need to consider surgical severity and postoperative time of immune assessment when investigating the immune-altering effects of surgery. Importantly, activation of beta-adrenergic receptors appears to play a modulatory role in surgery-induced immune alterations.

A dose-response study of chronic cocaine on maternal behavior in rats

To determine if there was a dose-response relationship with regard to cocaine treatment and maternal behavior exhibited by lactating rats at doses that had not been previously investigated, we examined the effects of three doses of chronic cocaine administration throughout gestation on both onset and established maternal behavior. Dams were injected (SC) with 6.3, 13, or 25 mg/kg cocaine HCl or an equivalent volume of saline throughout gestation; maternal behavior was tested on postpartum days 1 and 3. At the doses employed, cocaine disrupted the onset of only one pup-directed component of maternal behavior significantly in a dose-response manner, although there were several statistically nonsignificant dose-dependent trends of behavioral disruptions. No pup-directed behaviors were disrupted during testing for established maternal behavior. These results indicate that gestational cocaine treatment at doses of 25 mg/kg and less have only minimal effects on the onset and no effect on the maintenance of maternal behavior using our paradigm. The relationship of the present findings to previous work is discussed.

Gender differences in factor structure of the Self-Administered Alcoholism Screening Test

Recent studies have revealed differences between men and women alcoholics in symptoms, consequences, and help-seeking behavior related to alcohol usage. Based on these findings, it was hypothesized that gender differences also would appear on alcohol screening instruments. The Self-Administered Alcoholism Screening Test (Colligan, Davis, & Morse, 1988: SAAST: Swenson & Morse, 1975) of 1,920 men and 1,775 women was subjected to a within-gender, principle-components, factor analysis with a varimax rotation. Gender differences at the component level were revealed. Men endorsed the "help-seeking for alcohol-related problems" component while women endorsed the "help-seeking for emotional problems" component. In addition, men expressed concern about receiving a psychiatric label while women expressed concern about receiving a drinker label. The results suggest that different items need to be used in screening women for alcohol-related problems.

Characterization and use of a recombinant retroviral system for the analysis of drug resistant HIV

A recombinant retroviral system was used for the analysis of early HIV breakthrough infection in the presence of antiviral drugs. The use of replication-defective HIV allowed a quantitative analysis of a single cycle of infection. This report characterizes this recombinant HIV system and demonstrates it's validity in comparison to standard assays. It is demonstrated that the protease inhibitor XM323 inhibits both early and late events in the HIV life-cycle, while dextran sulphate inhibits only early events. In addition, it is shown that this system can be used for detecting and quantitating drug resistant HIV. Thus, the use of this system may provide both novel information about the stage of the viral life-cycle inhibited and a preliminary assessment of the mechanism(s) responsible for breakthrough infection in the presence of antiretroviral drugs.

Dose-dependent effects of multiple acute cocaine injections on maternal behavior and aggression in Sprague-Dawley rats

Rat dams, which had no prior drug treatment, were either nontreated controls or were injected subcutaneously 4 times during a 10-day period with a single dose of 30, 15 or 7.5 mg/kg of cocaine hydrochloride HCl, or normal saline. Injections were given immediately postpartum following delivery of their final pup (PPD 1), and again on postpartum day 3 (PPD 3), postpartum day 6 (PPD 6) and postpartum day 10 (PPD 10). Dams were observed 30 min following injections for maternal behavior (MB) towards 8 surrogate male pups on PPD 1 and PPD 3 and for aggression towards a male or female intruder in the presence of their litter on PPD 6 and PPD 10. Compared to saline and untreated controls, cocaine-treated dams exhibited more disruptions in MB on both PPD 1 and PPD 3 and were less aggressive towards an intruder, regardless of intruder sex, on PPD 6 and PPD 10. In most cases MB was altered in a dose-dependent manner with the higher doses of cocaine resulting in a greater disruption of behavior.

Comparison of the time course of morphine's analgesic and immunologic effects

Morphine, an opioid analgesic commonly prescribed and abused, produces immune-altering effects. Whether morphine's antinociceptive and immunologic effects occur concurrently is unknown. Therefore, we investigated the time course of morphine's immunologic and antinociceptive effects. Rats were given a 15-mg/kg morphine injection (subcutaneously), and experimental assessments were taken at 30 min, 1 h, 2 h, 6 h, 12 h, and 24 h after treatment. Immune measures included natural killer (NK) cell activity, proliferation of splenic T and B lymphocytes, and cytokine production. Antinociception was assessed by using the tail withdrawal assay. Results show that morphine's immunomodulatory effects on NK cell activity begin within 30 min, continue for at least 12 h, and return to control values by 24 h. In contrast, proliferation of splenic T and B cells and interferon-gamma production are not altered within 30 min; maximal suppression occurs at 1 h, and recovery begins within 2 h. In all immune measures, therefore, maximal suppression is present at the 1-h time point, and recovery is complete within 24 h. Morphine induces antinociception 30 min to 2 h after drug administration; recovery is complete within 6 h. These results suggest the possibility that different mechanisms modulate morphine's immunologic and analgesic effects.

IMPLICATIONS

Acute morphine treatment in rats produces immune alterations and antinociception. Although there are slight differences in morphine's maximal immunological and antinociceptive effects, morphine suppresses immune status at time points concordant with its antinociceptive effects. These effects should be considered when administering morphine to patients whose systems are immunocompromised.

Daily fluoxetine administration impairs avoidance learning in the rat without altering sensory thresholds

1. Male rats given daily intraperitoneal injections of fluoxetine (10 mg/kg) were slower to escape foot shock by jumping a low barrier. 2. When switched to a shuttle task requiring two crosses to terminate shock, the FLU-treated animals failed to learn in 55 trials. 3. A second experiment found FLU-treated animals could learn a one-way avoidance response, but were significantly slower to learn than control animals. 4. FLU-treated animals were no different than controls on tests of sensory thresholds for foot shock or heat. 5. Tests of motor behaviors revealed no differences in latency to traverse a narrow beam to reach a goal box, however FLU-treated animals were less active in an open field. 6. Several hypotheses can account for these data, the most promising being that a central motivational system (fear) is less active in FLU-treated animals.

Epidemiology, preventive services, and illnesses of international travelers

Medical preparation of travelers to overseas locations is an important part of military medical care. We reviewed pre-travel records of patients attending the travel clinic at the National Naval Medical Center (NNMC) and used a post-travel questionnaire to determine the most frequent medical problems associated with international travel. Among 1,416 individuals who received pre-travel care at NNMC, there were 760 (54%) males and 656 (46%) females, the median patient age was 48 years, the most common reason for travel was pleasure, and the median duration of travel was 21 days. The most common destinations were Asia (27%), Africa (15%), Europe (13%), Central America/Caribbean (12%), and South America (11%). The median number of immunizations prescribed was three. Malaria chemoprophylaxis was prescribed to 45%. The average cost of vaccines and medications to medically prepare a traveler was $67. Among 271 (82%) who returned the post-travel questionnaire, the most common illnesses reported were diarrhea (23%) and upper respiratory infections (19%); medical treatment was sought by 9%. Properly informed, military physicians can provide a valuable service at a reasonable cost to reduce the risk of travel-acquired medical problems and illnesses.

Sanctuary growth of human immunodeficiency virus in the presence of 3'-azido-3'-deoxythymidine

Human immunodeficiency virus (HIV) resistance to the nonnucleoside reverse transcriptase inhibitors emerges very rapidly under selection in culture and in patients. In contrast, zidovudine (3'-azido-3'-deoxythymidine [AZT])-resistant HIV generally emerges in patients only after more-prolonged therapy. Although HIV can be cultured from many patients shortly after the initiation of AZT treatment, characterization of the virus that is cultured generally indicates that it is sensitive to AZT. To initiate an evaluation of the mechanisms contributing to early HIV breakthrough in the presence of AZT and other nucleoside analogs, we have utilized replication-defective HIV encoding reporter genes. These recombinant HIV allow a quantitative analysis of a single cycle of infection. Results with these defective HIV indicate that early infection in the presence of AZT often results from the infection of a cell which is refractory to the antiretroviral effects of AZT. Characterization of a cell line derived from one such cell has demonstrated decreased accumulation of AZT triphosphate, increased phosphorylation of thymidine to thymidine triphosphate, and increased levels of thymidine kinase activity. In addition, AZT inhibition of replication-competent HIV infection is also significantly impaired in this cell line. Attempts to detect and characterize the mechanisms responsible for early viral infection after initiation of AZT therapy may result in the development of new strategies for prolonged suppression of viral infection prior to the emergence of drug-resistant virus.

Epidermal cell division and the coordination of leaf and tiller development

Initiation and development of grass leaves and tillers are often described individually with little attention to possible interrelationships among organs. In order to better understand these interrelationships, this research examined epidermal cell division during developmental transitions at the apical meristem of tall fescue (Festuca arundinacea Schreb.). Ten seedlings were harvested each day for a 9-d period, and lengths of main shoot leaves and primary tillers were measured. In addition, numbers and lengths of epidermal cells were determined for 0.5 mm segments along the basal 3 mm of each leaf and tiller. Primordia development and onset of rapid leaf elongation were characterized by an increase in the number of cells per epidermal file with mean cell length remaining near 20 microm per cell. After the leaf had lengthened to 1-1.5 mm, cells near the leaf tip ceased dividing and increased in length, at which time leaf elongation rate increased rapidly. Ligule formation, marking the boundary between blade and sheath cells, occurred prior to leaf tip emergence above the whorl of older sheaths, while the earliest differentiation between blade and sheath cells probably began when leaves were < 1 mm long. Major transitions in leaf and tiller development appeared to be synchronized among at least three adjacent nodes. At the oldest node, cessation of cell division in the leaf sheath was accompanied by initiation of cell division and elongation in the associated tiller bud. At the next younger node the ligule was being initiated, while at the youngest node cell division commenced in the leaf primordium, as elongation of a new leaf blade began. This synchronization of events suggests a key role for the cell division process in regulating leaf and tiller development.