352 THE IMPACT OF ETHNICITY ON ACUTE STROKE ADMISSIONS IN AN IRISH HOSPITAL

Background

Recent studies have demonstrated the variability of aetiology, clinical presentation and overall mortality between different ethnic groups presenting with acute stroke. The non-native Irish population accounts for almost 13% of the total population and is predicted to grow over the next decade. Recording and analysis of acute stroke patients based on their ethnicity and population demographics is an important step in planning for the future of stroke care in Ireland. In this study, we aimed to evaluate key differences between the Irish and non-Irish population presenting with acute stroke to an Irish hospital.

Methods

We reviewed our hospital stroke registry over a 12-month period (January-December 2021). Key parameters including country of birth, ethnicity, other patient demographics, clinical presentation, aetiology and subtype of stroke, stroke management and clinical outcomes.

Results

Of the 245 acute strokes admitted to our hospital in 2021, non-ethically Irish patients made up 12.2% (n = 30). The average age of non-ethnically Irish stroke presentations was younger than Irish stroke presentations (59 versus 71 years). Haemorrhagic strokes were more common in the non-Irish population (13.3% in non-Irish cohort vs 9.8% in Irish cohort). Median time of symptom onset to presentation to hospital was 3 hours and 58 minutes in the Irish patients and 6 hours and 10 minutes in the non-Irish patients. The overall length of stay in hospital post stroke was similar between the two population groups at an average of 19 days duration.

Conclusion

This study identifies disparities in acute stroke presentation between the Irish and non-Irish population presenting to an Irish hospital. This study demonstrated the importance of further research on a national scale to record the variability of strokes in different ethnic groups in order to adequately plan primary and secondary stroke care and provide targeted public health campaigns to remain inclusive to Ireland’s growing and increasingly diverse population.

150 ESTABLISHING A PFO PATHWAY FOR ACUTE STROKE PATIENTS WITH A POSITIVE BUBBLE STUDY

Background

A bubble study is performed routinely on patients under the age of 65 years of age with a confirmed diagnosis of either acute ischaemic stroke or TIA in order to assist with the presence of a Patent Foramen Ovale(PFO)/Atrial Septal Defect(ASD) as an aetiology for the stroke event. Historically, a referral letter would be written to a hospital who specialises in cardiac structural surgeries, requesting a review of a patient with a positive bubble study and acute stroke. Closure would typically exceed 9 months.

Methods

The Stroke RANP led out on the project as she performs all bubble studies in stroke survivors. A designated Cardiologist, who also works in a hospital where PFO closures takes place, is notified by the RANP or team about a positive bubble study and the images are reviewed. It is then decided if the patients requires a TOE or not. A 2-page PFO referral form was created which contains all relevant information.

Results

Stroke RANP performed 92 bubble studies between January 2021 and May 2022. There were 18 positive studies (20% positivity rate): 7 positive studies from January to August 2021 (pre-pathway) and 11 positive studies from September 2021 to May 2022 (post-pathway). 72% (5/7) of patients had a TOE performed following a positive bubble study result pre-pathway, whereas only 1 TOE was performed out of 11 cases (9%) post-pathway. The time from positive bubble study to closure time reduced from 9months on average to 3 months.

Conclusion

There was a 63% reduction in the number of TOEs being performed for patients with a positive bubble study with the introduction of this PFO pathway. Additionally, there was a 6-month reduction time from the positive bubble study result to closure. This pathway has improved patient outcomes for this young group of stroke survivors and assists with the reduction of further stroke events in the future.

1030 EXPERIENCES OF EARLY SUPPORTED DISCHARGE SERVICES FOLLOWING A STROKE: A QUALITATIVE EVIDENCE SYNTHESIS

Background

Early supported discharge (ESD) facilitates people with a stroke to be discharged from the hospital environment earlier than conventional care to continue their rehabilitation within the home with a multi-disciplinary team. Known benefits of ESD from Randomised Controlled Trials conducted include reducing the length of a hospital stay, long term dependency, and cost savings. There is limited qualitative evidence available on ESD. This systematic review and qualitative synthesis explored the experiences of those involved in ESD including people with stroke, family members, caregivers as well as healthcare professionals.

Method

A literature search was completed in 11 databases which generated 3,425 articles. Qualitative or mixed

Method

studies that included qualitative data on the experiences of people with stroke, family members, caregivers and healthcare professionals of an ESD service were included. The Critical Appraisal Skills Programme checklist was used to appraise the methodological quality of the papers. The findings were synthesised using the three step process for thematic synthesis.

Results

A total of fourteen studies were included with the methodological quality of the studies deemed good overall. Four key themes emerged: 1) ESD is experienced by people with stroke as a goal-focused and supportive process leading to positive outcomes, 2) ESD eases the transition from the hospital to the home environment but the transition from ESD to social and community services is often problematic, 3) Organisational, logistical and inter-professional factors are critical to the success of ESD and 4) The home environment enhances rehabilitation.

Conclusion

The findings of this qualitative evidence synthesis highlight the importance of the home environment in the rehabilitation process post stroke. Key practice implications point to the need for increased attention to periods where care transitions occur from ESD to community services.

24 EXPERIENCES OF EARLY SUPPORTED DISCHARGE SERVICES FOLLOWING A STROKE: A QUALITATIVE EVIDENCE SYNTHESIS

Background

Early supported discharge (ESD) facilitates people with a stroke to be discharged from the hospital environment earlier than conventional care to continue their rehabilitation within the home with a multi-disciplinary team. From Randomised Controlled Trials, benefits of ESD include reducing long term dependency, the length of hospital stay and cost savings. This systematic review and qualitative synthesis explores the experiences of those involved in ESD including people with stroke, family members, caregivers as well as the healthcare professionals.

Methods

A literature search was completed in 11 databases which generated 3,425 articles. Qualitative or mixed methods studies that included qualitative data on the experiences of people with stroke, family members, caregivers and healthcare professionals of an ESD service were included. Methodological quality was appraised using the Critical Appraisal Skills Programme checklist. Findings were synthesised using thematic synthesis.

Results

A total of fourteen studies were identified. The methodological quality of the studies was good overall. Four key themes emerged: 1) ESD is experienced by people with stroke as a goal-focused and supportive process leading to positive outcomes, 2) ESD eases the transition from the hospital to the home environment but the transition from ESD to social and community services is often problematic, 3) Organisational, logistical and inter-professional factors are critical to the success of ESD and 4) The home environment enhances rehabilitation.

Conclusion

Our findings highlight the importance of home in the rehabilitation process post stroke. Key practice implications point to the need for increased attention to periods where care transitions occur.

Inflammatory cytokines, high-sensitivity C-reactive protein, and risk of one-year vascular events, death, and poor functional outcome after stroke and transient ischemic attack

Background

Inflammation driven by pro-inflammatory cytokines is a new therapeutic target in coronary disease. Few data exist on the association of key upstream cytokines and post-stroke recurrence. In a prospective cohort study, we investigated the association between pivotal cytokines, high-sensitivity C-reactive protein (hsCRP) and one-year outcomes.

Methods

BIO-STROKETIA is a multi-center prospective cohort study of non-severe ischemic stroke (modified Rankin score ≤ 3) and transient ischemic attack. Controls were patients with transient symptoms attending transient ischemic attack clinics with non-ischemic final diagnosis. Exclusion criteria were severe stroke, infection, and other pro-inflammatory disease; hsCRP and cytokines (interleukin (IL) 6, IL-1β, IL-8, IL-10, IL-12, interferon-γ (IFN-γ), tumor-necrosis factor-α (TNF-α)) were measured. The primary outcome was one-year recurrent stroke/coronary events (fatal and non-fatal).

Results

In this study, 680 patients (439 stroke, 241 transient ischemic attack) and 68 controls were included. IL-6, IL-1β, IL-8, IFN-γ, TNF-α, and hsCRP were higher in stroke/transient ischemic attack cases (p ≤ 0.01 for all). On multivariable Cox regression, IL-6, IL-8, and hsCRP independently predicted one-year recurrent vascular events (adjusted hazard ratios (aHR) per-quartile increase IL-6 1.31, confidence interval (CI) 1.02–1.68, p = 0.03; IL-8 1.47, CI 1.15–1.89, p = 0.002; hsCRP 1.28, CI 1.01–1.62, p = 0.04). IL-6 (aHR 1.98, CI 1.26–3.14, p = 0.003) and hsCRP (aHR 1.81, CI 1.20–2.74, p = 0.005) independently predicted one-year fatality. IL-6 and hsCRP (adjusted odds ratio per-unit increase 1.02, CI 1.01–1.04) predicted poor functional outcome, with a trend for IL-1β (p = 0.054).

Conclusion

Baseline inflammatory cytokines independently predicted late recurrence, supporting a rationale for randomized trials of anti-inflammatory agents for prevention after stroke and suggesting that targeted therapy to high-risk patients with high baseline inflammation may be beneficial.

The influence of acute exercise on bone biomarkers: protocol for a systematic review with meta-analysis

BACKGROUND

Bone is a plastic tissue that is responsive to its physical environment. As a result, exercise interventions represent a potential means to influence the bone. However, little is currently known about how various exercise and participant characteristics interact to influence bone metabolism. Acute, controlled, interventions provide an in vivo model through which the acute bone response to exercise can be investigated, typically by monitoring circulating bone biomarkers. Currently, substantial heterogeneity in factors such as study design, quality, exercise, and participant characteristics render it difficult to synthesize and evaluate the available evidence. Using a systematic review and meta-analytic approach, the aim of this investigation is to quantify the effect of an acute exercise bout on circulating bone biomarkers as well as examine the potential factors that may moderate this response, e.g., variation in participant, exercise, and sampling characteristics.

METHODS

This protocol was designed in accordance with the PRISMA-P guidelines. Seven databases (MEDLINE, Embase, Sport Discus, Cochrane CENTRAL, PEDro, LILACS, and Ibec) will be systematically searched and supplemented by a secondary screening of the reference lists of all included articles. The PICOS (Population, Intervention, Comparator, Outcomes and Study Design) approach was used to guide the determination of the eligibility criteria. Participants of any age, sex, training, or health status will be considered for inclusion. We will select studies that have measured the bone biomarker response before and after an acute exercise session. All biomarkers considered to represent the bone metabolism will be considered for inclusion, and sensitivity analyses will be conducted using reference biomarkers for the measurement of bone resorption and formation (namely β-CTX-1 and P1NP). Multi-level, meta-regression models within a Bayesian framework will be used to explore the main effect of acute exercise on bone biomarkers as well as potential moderating factors. The risk of bias for each individual study will be evaluated using a modified version of the Downs and Black checklist while certainty in resultant outcomes will be assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

DISCUSSION

A better understanding of the bone metabolic response to an acute bout of exercise has the potential to advance our understanding of the mechanisms through which this stimulus impacts bone metabolism, including factors that may moderate this response. Additionally, we will identify current gaps in the evidence base and provide recommendations to inform future research.

SYSTEMATIC REVIEW REGISTRATION

This protocol was prospectively registered in the Open Science Framework Registry ( https://osf.io/6f8dz ).

Changing Trends in Life Expectancy in Intellectual Disability over Time

Decreased life expectancy (LE) has historically been found among people with intellectual disability (ID) compared to the general population. Several recent studies have looked into ageing and cause of death in ID. Results of many of these studies suggest that, although LE in ID remains lower than the general population, it has increased across many Western societies in recent decades. Increases in LE in the general and ID populations appear to follow similar trends. Some major causes of mortality in ID are similar to the general population, and therefore may be amenable to similar preventative healthcare interventions. In this article, we have outlined possible reasons for improved LE in ID, and potential areas that may require further intervention. However, more detailed studies on mortality in ID may provide more accurate insight into areas requiring intervention in ID populations.

Plasma Cell-Free DNA Next-Generation Sequencing to Diagnose and Monitor Infections in Allogeneic Hematopoietic Stem Cell Transplant Patients

Allogeneic hematopoietic stem cell transplant patients are at risk for common and atypical infections. Superior diagnostics can decrease infection-related morbidity and mortality. A novel plasma cell-free DNA next-generation sequencing test detected an uncommon presentation of Chlamydia trachomatis and recurrent and metastatic complications of Staphylococcus aureus bacteremia before standard microbiology.

A Comparative Study of Hummingbirds and Chickens Provides Mechanistic Insight on the Histidine Containing Dipeptide Role in Skeletal Muscle Metabolism

Histidine containing dipeptides (HCDs) have numerous ergogenic and therapeutic properties, but their primary role in skeletal muscle remains unclear. Potential functions include pH regulation, protection against reactive oxygen/nitrogen species, or Ca²⁺ regulation. In recognition of the challenge of isolating physiological processes in-vivo, we employed a comparative physiology approach to investigate the primary mechanism of HCD action in skeletal muscle. We selected two avian species (i.e., hummingbirds and chickens), who represented the extremes of the physiological processes in which HCDs are likely to function. Our findings indicate that HCDs are non-essential to the development of highly oxidative and contractile muscle, given their very low content in hummingbird skeletal tissue. In contrast, their abundance in the glycolytic chicken muscle, indicate that they are important in anaerobic bioenergetics as pH regulators. This evidence provides new insights on the HCD role in skeletal muscle, which could inform widespread interventions, from health to elite performance.

Per-protocol investigation of a best practice exercise referral scheme

OBJECTIVES

To investigate the effects of an exercise referral scheme (ERS) aligned to the UK best practice guidelines on a range of outcomes including those associated with key health concerns of the Scottish population.

STUDY DESIGN

A longitudinal design with data collection at three time points (baseline, midway and post) during a 12-week ERS intervention was employed.

METHODS

Health-related physical fitness was assessed through measurement of resting heart rate, blood pressure, FEV1:FEV6 (ratio of forced expiratory volume over one [FEV1] and six [FEV6] seconds), body mass and peak oxygen uptake (VO₂ peak), whilst functional capacity was assessed through the five times sit to stand test. Psychosocial well-being and quality of life were measured using the World Health Organization Quality of Life questionnaire (WHOQOL-BREF) and the Profile of Mood State questionnaires. Growth curve analyses were used to model each outcome variable across the three time periods.

RESULTS

A range of effects were obtained with significant linear improvements in physical performance tests (P < 0.001) and psychosocial assessments (P ≤ 0.002). Additionally, significant quadratic effects of time were obtained for body composition variables and physical activity levels (P < 0.001) with the greatest improvements obtained between baseline and midway assessments.

CONCLUSIONS

An ERS aligned to the UK best practice guidelines can positively influence a range of health outcomes including those associated with lung function and cardiovascular fitness which are prevalent medical conditions in Scotland. In addition, results indicate that ERS can positively affect outcomes related to functional capacity as well as mental well-being and perceptions of health. The findings of the study identify the need for further investigation including consideration of the initial health status of referred clients.

Nitrate-rich beetroot juice selectively lowers ambulatory pressures and LDL cholesterol in uncontrolled but not controlled hypertension: a pilot study

BACKGROUND

Dietary nitrate has been shown to increase nitrate/nitrite levels in multiple populations, with potential blood pressure lowering effects. However, there are few reports among hypertensives.

AIMS

We aimed to assess the effect of daily nitrate in subjects with controlled hypertension vs. uncontrolled hypertension.

METHODS

On day 0, hypertensives wore an ambulatory BP monitor (ABPM) for 24 h and fasting blood was taken. Subjects then consumed concentrated beetroot juice (12.9 mmol nitrate) for 14 consecutive days. On day 14 subjects consumed their last nitrate dose after fasting blood was drawn and again had an ABPM for 24 h.

RESULTS

According to baseline ABPM, 11 subjects had controlled BP while 8 had uncontrolled BP. There were similar, significant increases in serum nitrate/nitrite in both groups. We observed little change in BP variables among controlled hypertensives. However, there were reductions in BP variables in uncontrolled hypertensives where decreases in nighttime DBP (-6 ± 4.8 mmHg), arterial stiffness (-0.08 ± 0.03 ambulatory arterial stiffness index) and LDL (-0.36 ± 0.42 mmol/L) reached significance (p = 003, 0.05 and 0.046, respectively).

CONCLUSIONS

Our results support the existing data suggesting an anti-hypertensive effect of nitrate-containing beetroot juice, but only among those with uncontrolled hypertension.

Nutritional considerations during prolonged exposure to a confined, hyperbaric, hyperoxic environment: recommendations for saturation divers

Saturation diving is an occupation that involves prolonged exposure to a confined, hyperoxic, hyperbaric environment. The unique and extreme environment is thought to result in disruption to physiological and metabolic homeostasis, which may impact human health and performance. Appropriate nutritional intake has the potential to alleviate and/or support many of these physiological and metabolic concerns, whilst enhancing health and performance in saturation divers. Therefore, the purpose of this review is to identify the physiological and practical challenges of saturation diving and consequently provide evidence-based nutritional recommendations for saturation divers to promote health and performance within this challenging environment. Saturation diving has a high-energy demand, with an energy intake of between 44 and 52 kcal/kg body mass per day recommended, dependent on intensity and duration of underwater activity. The macronutrient composition of dietary intake is in accordance with the current Institute of Medicine guidelines at 45-65 % and 20-35 % of total energy intake for carbohydrate and fat intake, respectively. A minimum daily protein intake of 1.3 g/kg body mass is recommended to facilitate body composition maintenance. Macronutrient intake between individuals should, however, be dictated by personal preference to support the attainment of an energy balance. A varied diet high in fruit and vegetables is highly recommended for the provision of sufficient micronutrients to support physiological processes, such as vitamin B12 and folate intake to facilitate red blood cell production. Antioxidants, such as vitamin C and E, are also recommended to reduce oxidised molecules, e.g. free radicals, whilst selenium and zinc intake may be beneficial to reinforce endogenous antioxidant reserves. In addition, tailored hydration and carbohydrate fueling strategies for underwater work are also advised.

Falls and fractures 2 years after acute stroke: the North Dublin Population Stroke Study

BACKGROUND

Stroke patients are at increased risk of falls and fractures. The aim of this study was to determine the rate, predictors and consequences of falls within 2 years after stroke in a prospective population-based study in North Dublin, Ireland.

DESIGN

Prospective population-based cohort study.

SUBJECTS

567 adults aged >18 years from the North Dublin Population Stroke Study.

METHODS

Participants were enrolled from an Irish urban population of 294,592 individuals, according to recommended criteria. Patients were followed for 2 years. Outcome measures included death, modified Rankin Scale (mRS), fall and fracture rate.

RESULTS

At 2 years, 23.5% (124/522) had fallen at least once since their stroke, 14.2% (74/522) had 2 or more falls and 5.4% (28/522) had a fracture. Of 332 survivors at 2 years, 107 (32.2%) had fallen, of whom 60.7% (65/107) had 2 or more falls and 23.4% (25/107) had fractured. In a multivariable model controlling for age and gender, independent risk factors for falling within the first 2 years of stroke included use of alpha-blocker medications for treatment of hypertension (P = 0.02). When mobility measured at Day 90 was included in the model, patients who were mobility impaired (mRS 2-3) were at the highest risk of falling within 2 years of stroke [odds ratio (OR) 2.30, P = 0.003] and those functionally dependent (mRS 4-5) displayed intermediate risk (OR 2.02, P = 0.03) when compared with independently mobile patients.

CONCLUSION

Greater attention to falls risk, fall prevention strategies and bone health in the stroke population are required.

Stroke recurrence within the time window recommended for carotid endarterectomy

OBJECTIVE

In the North Dublin Population Stroke Study, we investigated the risk of recurrent stroke within the 14-day time window recommended for endarterectomy.

METHODS

In a population-based prospective cohort study, all ischemic stroke patients were identified over 1 year and categorized into those with (CS-positive) and without (CS-negative) ipsilateral carotid stenosis (CS) (≥50% lumen narrowing). Nonprocedural stroke recurrence was determined at 72 hours and 7 and 14 days.

RESULTS

Of 365 ischemic stroke patients with carotid imaging, 51 were excluded due to posterior circulation or nonlateralizing stroke, ipsilateral carotid occlusion, or intracranial stenosis, leaving 314 included for analysis (36 CS-positive and 278 CS-negative). Recurrent stroke occurred in 5.6% (2/36) CS-positive and 0.4% (1/278) CS-negative patients by 72 hours of symptom onset (p =0.003), 5.6% (2/36) CS-positive and 0.7% (2/278) CS-negative patients (p =0.01) by 7 days, and in 8.3% (3/36) CS-positive and 1.8% (5/278) CS-negative patients by 14 days (p =0.02). On multivariable Cox regression analysis, CS was the only independent predictor of recurrence at 72 hours (adjusted hazard ratio [HR] 36.1, 95% confidence interval [CI] 1.6-837.5, p =0.03), and 7 days (HR 9.1, 1.1-79.2, p =0.05), with a trend at 14 days (HR 4.6, 0.9-22.8, p =0.06).

CONCLUSIONS

Although only a minority of patients with symptomatic CS had a recurrent stroke within 14 days, early recurrent stroke risk was high, particularly within the first 72 hours. Earlier carotid revascularization or improved acute medical treatment may reduce recurrence in this high-risk group.

Interaction between the intermediary electron acceptor (pheophytin) and a possible plastoquinone-iron complex in photosystem II reaction centers

Photoreduction of the intermediary electron acceptor, pheophytin (Pheo), in photosystem II reaction centers of spinach chloroplasts or subchloroplast particles (TSF-II and TSF-IIa) at 220 K and redox potential E(h) = -450 mV produces an EPR doublet centered at g = 2.00 with a splitting of 52 G at 7 K in addition to a narrow signal attributed to Pheo([unk]) (g = 2.0033, DeltaH approximately 13 G). The doublet is eliminated after extraction of lyophilized TSF-II with hexane containing 0.13-0.16% methanol but is restored by reconstitution with plastoquinone A (alone or with beta-carotene) although not with vitamin K(1). TSF-II and TSF-IIa are found to contain approximately 2 nonheme Fe atoms per reaction center. Incubation with 0.55 M LiClO(4) plus 2.5 mM o-phenanthroline (but not with 0.55 M LiClO(4) alone) decreases this value to approximately 0.6 and completely eliminates the EPR doublet, but photoreduction of Pheo is not significantly affected. Partial restoration of the doublet (about 25%) was achieved by subsequent incubation with 0.2 mM Fe(2+), but not with either Mn(2+) or Mg(2+). The Fe removal results in the development of a photoinduced EPR signal (g = 2.0044 +/- 0.0003, DeltaH = 9.2 +/- 0.5 G) at E(h) = 50 mV, which is not observed after extraction with 0.16% methanol in hexane. It is ascribed to plastosemiquinone no longer coupled to Fe in photosystem II reaction centers. The results show that a complex of plastoquinone and Fe can act as the stable "primary" electron acceptor in photosystem II reaction centers and that the interaction of its singly reduced form with the reduced intermediary acceptor, Pheo([unk]), is responsible for the EPR doublet.

Spectral and kinetic evidence for two early electron acceptors in photosystem I

Triton-fractionated photosystem-I particles poised at -625 mV, where the two bound iron-sulfur proteins are reduced, have been studied by optical and electron paramagnetic resonance spectroscopies from 293 to 5 K. At 5-9 K, these particles exhibit two decay components with lifetimes of 1.3 and 130 msec in the laser pulse-induced absorption and electron paramagnetic resonance signal changes. Spectral properties of the 130-msec decay component reflect the charge separation between P-700 and some iron-sulfur center having a broad optical absorbance in the 400- to 550-nm region and a previously reported electron paramagnetic resonance signal with g = 1.78, 1.88, and 2.08. Spectral properties of the 1-msec decay component indicate photoinduced charge separation between P-700 and a chlorophyll a dimer having absorption bands at 420, 450, and 700 nm. It is assumed that these two acceptors participate in the electron transfer from P-700(*) to the bound iron-sulfur proteins.

Determinants of white-coat hypertension

BACKGROUND

The prevalence of white-coat hypertension (WCH) is considerable in patients referred with elevated office blood pressure. Failure to recognise this phenomenon can lead to the inappropriate use of antihypertensive medications. We undertook this study to determine the profile of patients with WCH.

METHODS

Baseline clinic and daytime ambulatory blood pressures were available from 5716 patients referred over a 22-year period. Individuals were considered to have WCH if they had an elevated clinic blood pressure measurement greater than 140/90 mmHg and normal daytime mean ambulatory blood pressure. Mean age was 53.6 years and 53.2% were female.

RESULTS

The overall prevalence of white-coat hypertension was 15.4%. A higher prevalence was seen amongst older adults, females, and non-smokers.

CONCLUSION

Multivariate logistic regression analysis confirmed these characteristics as independent predictors of WCH.

Rapid reductive dechlorination of atrazine by zero-valent iron under acidic conditions

The dechlorination of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) via reaction with metallic iron under low-oxygen conditions was studied using reaction mixture pH values of 2.0, 3.0, and 3.8. The pH control was achieved through addition of sulfuric acid throughout the duration of the reaction. The lower the pH of the reaction mixture, the faster the degradation of atrazine. The surface area of the sulfuric acid-treated iron particles was 0.31 (+/- 0.01) m2 g-1 and the surface area normalized initial pseudo-first order rate constants (kSA, where rate = kSA x (surface area/l) x [Atrazine]) at pH values of 2.0, 3.0, and 3.8 were equal to, respectively, 3.0 (+/- 0.4) x 10(-3) min-1 m-2 l, 5 (+/- 3) x 10(-4) min-1 m-2 l, and 1 (+/- 1) x 10(-4) min-1 m-2 l. The observed products of the degradation reaction were dechlorinated atrazine (2-ethylamino-4-isopropylamino-1,3,5-triazine) and possibly hydroxyatrazine (2-ethylamino-4-isopropylamino-6-hydroxy-s-triazine). Triazine ring protonation may account, at least in part, for the observed effect of pH on atrazine dechlorination via metallic iron.

Methylator resistance mediated by mismatch repair deficiency in a glioblastoma multiforme xenograft

A methylator-resistant human glioblastoma multiforme xenograft, D-245 MG (PR), in athymic nude mice was established by serially treating the parent xenograft D-245 MG with procarbazine. D-245 MG xenografts were sensitive to procarbazine, temozolomide, N-methyl-N-nitrosourea, 1,3-bis(2-chloroethyl)-1-nitrosourea, 9-aminocamptothecin, topotecan, CPT-11, cyclophosphamide, and busulfan. D-245 MG (PR) xenografts were resistant to procarbazine, temozolomide, N-methyl-N-nitrosourea, and busulfan, but they were sensitive to the other agents. Both D-245 MG and D-245 MG (PR) xenografts displayed no O6-alkylguanine-DNA alkyltransferase activity, and their levels of glutathione and glutathione-S-transferase were similar. D-245 MG xenografts expressed the human mismatch repair proteins hMSH2 and hMLH1, whereas D-245 MG (PR) expressed hMLH1 but not hMSH2.

Absence of correlation between chemo- and radioresistance in a range of human tumour cell lines

The correlation between cellular resistance to radiation and to chemotherapeutic drugs has been investigated in a number of solid tumour cell lines, and preliminary results indicate no direct relationship. The acquisition of a multidrug resistance (MDR) profile by adriamycin-selected variants of a human squamous lung carcinoma, an ovarian carcinoma, a cervical carcinoma and by a colchicine-selected variant of a Chinese hamster ovarian carcinoma resulted in alterations to their radiosensitivity. However, the degree of change in the radiosensitivity of the MDR cell lines could not be predicted from their level of resistance to adriamycin. Clonal populations derived from DLKP-A, an adriamycin-selected MDR variant of the human lung carcinoma cell line DLKP, exhibited individual radiosensitivity profiles, which did not correlate with their chemoresistance. Exposure of DLKP to consecutive increasing doses of radiation did not confer cross-resistance to chemotherapeutic drugs.

Sideways dislocation of the temporomandibular joint meniscus: the edge sign

Seventy temporomandibular joint arthrograms of 49 patients with symptoms of internal joint derangement were reviewed. Twenty-three of these arthrograms (33%) were abnormal but atypical for anteriorly dislocated meniscus. The lower temporomandibular joint space had a well-defined edge located inferiorly, which was attributed to pressure from a sideways-dislocated meniscus. We called this appearance the "edge sign." Seven patients with radiologically apparent sideways dislocation were operated on. The meniscus was dislocated laterally in six and medially in one. The incidence of irreducibility and perforation was higher in sideways-dislocated than in anteriorly dislocated menisci.

Regional metabolism of experimental brain tumors

Experimental brain tumors were produced in rats by stereotactical implantation of various neoplastic cell lines (RG 2, RG1 2.2, G 13/11, F 98, RN 6, B 104, and E 367). Using autoradiographic, bioluminescence, and fluoroscopic methods, the following regional hemodynamic and metabolic parameters were measured on intact brain sections: blood flow, glucose utilization, pH, and the tissue content of ATP, glucose, and lactate. Tumors exhibited a considerable diversity of regional blood flow and metabolic activity which did not correlate with the implanted cell line, location, or growth pattern. In solid regions of tumors the most consistent finding was a higher glucose utilization rate, a higher lactate, and a higher pH than in the surrounding brain tissue. Tumor ATP was slightly higher and glucose slightly lower than in the brain. In large spherical tumors a declining gradient of blood flow, glucose, and ATP from the periphery to the central parts was frequently observed, the decline being more pronounced for glucose than for ATP. In regions with high ATP tissue pH was usually higher than in the brain, but it decreased in areas in which ATP was depleted. The results obtained indicate that tumors are able to control tissue pH despite increased glycolysis and lactate production, as long as the energy state is not impaired. The mechanisms of pH regulation, therefore, have to be considered for establishing therapeutic procedures which intend to lower tumor pH for induction of tissue necrosis.

The value of histopathological examination of surgically removed blood clot in determining the etiology of spontaneous intracerebral hemorrhage

The surgical specimens from all evacuated spontaneous intracerebral and intracerebellar hemorrhages at the Toronto General Hospital from 1976 to 1981 were reviewed. Cases resulting from trauma or from pre-operatively diagnosed aneurysms or arteriovenous malformations were excluded, leaving 84 cases in which the etiology was unknown. Seventy-five of the cases were intracerebral hemorrhages, while 6 were intracerebellar and 3 were intraventricular. Brain tissue was received with the blood clot in 54 cases (64%). From this tissue, an anatomic diagnosis was made in 37 cases; and in 14, the specific etiology of the hemorrhage could be determined. The specific etiologic diagnoses were tumor (7), amyloid angiopathy (6) and abscess (1). In 4 other cases, vasculopathy associated with hypertension was suggested as a possible etiologic diagnosis. The high incidence of a specific etiologic diagnosis made from specimens in which tissue was included (25%) suggests that biopsy of adjacent brain tissue or preservation of tissue fragments identified at the time of surgery is of diagnostic value.

Microsurgical anatomy of spinal subarachnoid space

The anatomy of the spinal subarachnoid space is reviewed with special reference to the work of Key and Retzius, the authors' own cadaver dissections, and experience from operative cases. It appears that despite some variations in the spinal arachnoid anatomy, there are many consistent features that can serve to guide the operating neurosurgeon.

[Functions of pheophytin, plastoquinone, iron and carotenoids in plant photosystem 2 reaction centers]

Photoreduction of the intermediary electron acceptor, pheophytin (Ph), in photosystem-2 (PS-2) reaction centers of spinach chloroplasts or subchloroplast particles (TSF-II and TSF-IIa) at 220 K and Eh approximately -450 mV produces a narrow ESR signal of Ph. (g = 2.0033; delta H approximately 13 G) and a "doublet" centered at g = 2.00 with a splitting of 52 G at 7 K. The doublet (but not the narrow signal) is eliminated after extraction of lyophylized TSF-II with hexane, containing 0.1-0.2% methanol, or after extraction of Fe with LiClO4 and o-phenantroline, and the signal is restored by reconstitution with plastoquinone-A (PQ) or Fe++, respectively. The Fe removal results also in the development of a photoinduced ESR signal of PQ. (g approximately 2.0044; delta H approximately 9.2 G). The conclusion is made that the primary electron acceptor, Q, is in fact a complex PQ-Fe++ and that the exchange interaction of Ph. with PQ. -Fe++ is responsible for the ESR doublet. Photoreduction of Ph in TSF-IIa is accompanied by the 3-fold decrease in the formation of carotenoid triplet state (measured by the characteristic flash-induced absorbance changes) which is suggested to be a result of charge recombination in the pair [P680+ .PH.].

Energy transfer from phycobiliproteins to photosystem I in vegetative cells and heterocysts of Anabaena variabilis

The presence of phycobilins in heterocysts of Anabaena variabilis is established on the basis of absorption and fluorescence spectroscopy. At 77 K heterocysts exhibit fluorescence emission bands at 645 and 661 nm indicative of phycocyanin and allophycocyanin, respectively. Both allophycocyanin levels and fluorescence emission at 695 nm were low in heterocysts relative to whole filaments. In situ fluorescence microscopy confirmed the presence of phycobilins in individual heterocysts, but the pigment levels varied considerably among cells. Heterocysts exhibited Photosystem I activity, as evidenced by photooxidation of P-700, but no Photosystem II activity. The quantum efficiency of phycobilins in sensitizing P-700 photooxidation was 50-70% that of chlorophyll a. Phycoibins were also effective in promoting light-dependent reduction of acetylene to ethylene. The results are discussed in terms of the role of the heterocyst in nitrogen fixation and of the significance of energy transfer from phycobilins to Photosystem I in heterocysts.