Return to Activity After Concussion: A Qualitative Study to Explore Expert OT Perspectives on Concussion Rehabilitation

Date Presented 03/31/2022

A qualitative descriptive study using focus groups of 13 expert OTs across settings is the first to describe the OT intervention process of rehabilitation for adults with persistent symptoms from concussion. A logic model was created to communicate the evaluation and intervention process using content analysis, deductive strategy, open coding, and unconstrained matrix to help people return to their everyday life roles and highest capacity.

Primary Author and Speaker: Mary Ann B. Roelke

Contributing Authors: Vanessa Jewell, Mary Radomski

Associations between a sense of connection and existential and psychosocial outcomes in gynecologic and breast cancer survivors

BACKGROUND

A cancer diagnosis may lead to existential despair but potentially also to perceived inner growth. This growth may be fostered through meaningful connections with others. We sought to describe existential and related psychosocial outcomes and their association with a sense of connection with others in individuals with gynecological and breast cancers.

METHODS

We used cross-sectional data from two ongoing cohort studies of gynecologic (N = 236) and breast (N = 62) cancer survivors at the University of Minnesota. We summarized self-reported post-traumatic growth (PTG), sense of meaning, peace, spirituality, hopelessness, loneliness, and three exploratory measures of sense of connections with others, and used multivariate linear regression models to describe the associations between them.

RESULTS

Hope, sense of meaning, peace, and spirituality were generally high among participants, but PTG and loneliness scores varied more. Sense of connection with others was consistently associated with greater PTG and decreased loneliness with medium effect sizes: for example having positive interactions with most/all versus nobody on one's medical team, PTG (coefficient 10.49, 95% CI: 4.10, 16.87, Cohen's D 0.44); loneliness (coefficient - 0.85, 95% CI: - 1.36, - 0.34, Cohen's D 0.43). Those who knew someone in a similar life situation felt a strong sense of connection with such a person; however, 28% of participants had not met anyone in a similar situation.

CONCLUSIONS

There may be untapped opportunities to nurture beneficial existential outcomes in cancer survivors. Potential interventions include connecting survivors with one another and creating opportunities for more authentic patient-provider relationships, for example, within palliative care.

Cognitive Dysfunction: Feasibility of a Brief Intervention to Help Breast Cancer Survivors

BACKGROUND

Many cancer survivors experience cancer-related cognitive dysfunction (CRCD), which is believed to be the result of multiple contributing biologic, situational, and personal factors. Efficacious, clinically implementable interventions addressing the multifactorial nature of CRCD are needed.

OBJECTIVES

This study evaluated the feasibility of an intervention to help breast cancer survivors mitigate the effects of modifiable factors that contribute to CRCD and improve cognitive functioning.

METHODS

A single-group pre-/post-test design was used. Treatment fidelity was tracked to evaluate implementability; attendance rates, experience surveys, and homework engagement were used to characterize acceptability. Pre- and post-test cognitive functioning, stress, fatigue, and mood were measured to evaluate preliminary efficacy.

FINDINGS

The intervention was implementable and acceptable to participants. Participants made statistically significant improvements.

Front Desk Duty Multitasking Test After Mild Stroke: Preliminary Reliability and Validity

Background.

Performance-based multitasking assessments may be more sensitive than cognitive screens to detect executive dysfunction after a mild stroke.

Purpose.

This cross-sectional study examined inter-rater reliability and preliminary convergent and discriminant validity of the Front Desk Duty Test (FDDT).

Method.

Adults with mild stroke ( n = 35) and community controls ( n = 33) were administered the FDDT and other measures of executive functions.

Findings.

Inter-rater reliability of the FDDT subscores were high (ICC 0.971–0.999). There were weak but statistically significant correlations between participants’ scores on some of the executive function tests and some FDDT subscores. Participants with mild stroke and community controls had statistically significant different FDDT scores (performance accuracy p = .006; performance time, p = .033), with rank order FDDT score patterns across community controls, participants with mild stroke who passed the executive function screen, and participants with mild stroke who failed the executive function screen.

Implications.

Preliminary validation results suggest that the FDDT warrants further study.

Front Desk Duty (FDD): Validation of a Novel Multitasking Performance-Based Test on Adults With Mild Stroke

Date Presented 04/07/19

We conducted a validation study on a performance-based assessment of EF called Front Desk Duty in mild stroke patients. Preliminary findings suggest that FDD can be scored reliably and distinguishes between groups of healthy adults and those with mild stroke who fail an EF screen. This study expands the repertoire of available multitasking assessments, which will contribute to better identification of people with mild stroke who could benefit from OT intervention.

Primary Author and Speaker: Ginger Carroll

Additional Authors and Speakers: Romina Takimoto

Contributing Authors: Mary Radomski, Jerry Halsten, Shayne Hopkins, Kristen Johnson, Kristina Kath, Rob Kreiger, Amy Meyers, Stacey Rabusch

Strain concentration in beams under cyclic plastic straining

Cyclic plastic-straining tests with controlled deflections have been conducted on beams subject to uniform bending, three-point bending, and a cosine distribution of bending moment; the second and third beams represent cases of strain concentration. Three different materials were used, namely mild steel, stainless steel, and aluminium.

The strain-concentration tests show stainless steel and aluminium to be more resistant to deflection cycling than mild steel. A similar difference is not found in the uniform bending tests to anything like the same extent. Stainless steel shows a more pronounced strain-hardening characteristic in the cyclic stress-strain curve than does mild steel and it is concluded that this produces a more favourable strain distribution along the length of the beam, so that the maximum strain is less and the endurance is correspondingly greater.

For materials which show settled cyclic stress-strain relations, reasonable predictions may be made of life in deflection cycling of beams under strain-concentration conditions if the strains are calculated from the cyciic relations and the corresponding endurance is obtained from uniform bending tests. If, for design purposes, the strains determining the life are calculated from monotonic stress-strain relations, the design will be safe, provided the material does not soften with cyclic straining.

Some theoretical considerations relating to strain concentration in elastic-plastic bending of beams

Theoretical derivations are presented for the relations between maximum deflection and the corresponding maximum strain for some simple beams subject to elastic-plastic bending. Both elastic-perfectly plastic and arbitrary stress-strain relations are considered. Where possible, explicit analytical solutions are given, but where this is not possible numerical solutions are obtained by means of computer programmes.

The calculations show that in elastic-perfectly plastic material short plastic zones may develop and cause large strains in the beam even though the deflection corresponding to first yield is not greatly exceeded. On the other hand, strain hardening elongates the plastic zones, so producing a more favourable strain distribution along the length of the beam than would exist without it. The more pronounced the strain-hardening characteristic, i.e. the greater the rate of increase of stress with strain, the less concentrated will be the strains.

The mode of loading is important in that the higher the rate of change of bending moment, in the region of ihe maximum bending moment, the more concentrated will be the local strains.

A local pathway for increased testosterone supply from the testis to the epididymis, vas deferens and accessory genital glands of the rat

Radiolabeled testosterone (3H-T) was infused into the testes or left and right mesofuniculus (106 dpm) or injected into a testes (2 x 10(6) dpm). The 3H-T concentration was estimated 15 or 10 min after 3H-T infusion or injection, respectively, in the tissue samples collected from the prostate, seminal vesicles, caput and cauda epididymides, vasa deferentia and the mesofuniculi. The abdominal aorta and posterior vena cava were cannulated, and the posterior part of the body perfused with blood (at blood pressure 70-140 or 260-300 mm Hg in abdominal aorta) was used to study 3H-T transfer from the testes to venous blood and other male genital organs. The concentration of 3H-T found in the accessory genital glands, epididymes and vasa deferentia was affected by blood pressure in the abdominal aorta. The reduced blood pressure and partial blocking of blood supply to the genital organs (after ligation of both testicular arteries or the terminal part of the abdominal aorta) increased the concentration of 3H-T in accessory genital glands, vasa deferentia and epididymes. The removal of the mesofuniculi and vasa deferentia with their mesoducti reduced 3H-T concentration in the prostate, seminal vesicles and cauda epididymides. Both arterial trunks, testicular arteries and common iliac arteries, were shown to be connected by anastomoses in target organs so effectively, that supplying the male genital organs with blood by only one of them assures the transfer of testosterone from the testes to the epididymes, vasa deferentia, mesofuniculi as well as prostate and seminal vesicles. It was concluded that lymphatic vessels of the mesofunicules and of the spermatic cords as well as venous and arterial vasculature of the mesofunicules create a recently unknown pathway for the increase of testosterone supply from the testes to the epididymes, vasa deferentia and accessory genital glands of rats.

Therapeutic effect of phenantroline in two rat models of inflammatory bowel disease

BACKGROUND

Phenantroline is a zinc-chelator that inhibits biological activities of matrix metalloproteinases (MMPs). Over-expression of MMPs can accelerate tissue destruction and disrupt subsequent tissue repair. The effects of phenantroline in two rat models of inflammatory bowel disease (IBD) are evaluated: transmural colitis induced by trinitrobenzensulphonic acid (TNBS) and distal colitis caused by dextran sulphate sodium (DSS).

METHODS

Transmural colitis was induced by TNBS in two groups of 15 rats each, and distal colitis was induced by DSS in two other groups of 15 rats each. Phenantroline was administered by oral gavage at 20 mg kg(-1) day(-1) to the test groups, whereas matched control groups received oral vehicle. On the last day of dosing, rats were subjected to intracolonic dialysis under anaesthesia for assessment of luminal eicosanoid release (PGE2, TXB2 and LTB4) and euthanized. Colons were removed and lesions were blindly scored according to macroscopic and histological scales. Myeloperoxidase (MPO) activity was measured in homogenates of colonic tissue.

RESULTS

In the TNBS model, phenantroline treatment significantly reduced colonic strictures; in the DSS model, phenantroline significantly decreased scores of epithelial injury. In both models, the levels of PGE2, TXB2 and LTB4 and tissue MPO were not significantly altered.

CONCLUSIONS

Although phenantroline did not modify the activity of inflammatory mediators, this compound substantially reduced intestinal injury associated with tissue remodelling.

Melatonin and zopiclone as pharmacologic aids to facilitate crew rest

PURPOSE

In response to mission imperatives, transport aircrews must often sleep at inappropriate circadian times resulting in inadequate sleep. This study was undertaken to determine whether either melatonin or zopiclone could facilitate early circadian sleep, and to assess whether either of these medications would result in a psychomotor performance decrement which would preclude their use in aircrew.

METHOD

Thirteen subjects from DCIEM completed a double-blind cross-over protocol. All subjects were assessed for psychomotor performance during 3 drug conditions (placebo, 10 mg melatonin, and 7.5 mg zopiclone), which were separated by one week. Each of these conditions involved 2 nights of sleep, back-to-back, with the first night being a normal circadian control sleep (23:00 h bedtime, arising at 06:45 h), and the second night being an early circadian drug sleep (drugs at 16:45 h, 17:00 h bedtime, arising at 23:45 h). All subjects were tested for psychomotor performance, on both nights of each of the 3 drug conditions, pre- and post-sleep. Further, during the early circadian drug night, all subjects were tested every hour after arising at 23:45 h (24:00 h until 07:00 h. At the beginning of each psychomotor test session, subjects were asked for their subjective levels of sleepiness and fatigue.

RESULTS

Relative to placebo (339.5 min) the subjects slept more on melatonin (370.2 min, p < 0.01), and zopiclone (373.3 min, p < 0.01). Performance in serial reaction time (SRT) task (p < 0.001), logical reasoning task (LRT) (p < 0.001), serial subtraction task (SST) (p < 0.02), and Multitask (MT) (p < 0.03) were impaired for all 3 drug conditions immediately on awakening, compared with pre-sleep performance, as a result of a sleep-inertia effect. With respect to the subjective data, sleep inertia effects were evident for sleepiness (p < 0.001), mental fatigue (p < 0.002), and physical fatigue (p < 0.05). For SRT, LRT, and SST, performance recovered to pre-sleep levels within 1.25 h of awakening, and for MT recovery occurred 2.25 h after awakening. There were no differences in performance or subjective measures between placebo, melatonin and zopiclone.

CONCLUSIONS

Both zopiclone and melatonin improved sleep relative to placebo. After sleep inertia, performance recovered to pre-sleep levels for all tasks and was sustained at that level throughout the balance of the testing period. There was no impact of melatonin or zopiclone on performance measures compared with placebo.

Differential expression of matrix metalloproteinases and the tissue inhibitor in human milk

There are differences in the temporal expression of MMP-2 and TIMP-4 in human milk from Day 1 to 30 postpartum in healthy mothers of term pregnancies: (i) MMP-2 activity peaked at Day 1 (colostrum) then exponentially decreased afterwards; and (ii) The expression of TIMP-4 was maximal at Day 7 and persisted thereafter. From our preliminary findings, the differential expression of MMP and the tissue inhibitor in human milk may be related to the protective action of human milk.

The terminal portion of the T wave: a new electrocardiographic marker of risk of ventricular arrhythmias

Experimental studies have shown that transmural dispersion of repolarization (DoR), defined as the difference in action potential duration between mid-myocardial M-cells, epicardial, and endocardial cells is reflected in the duration of the terminal portion of the T wave (TpTe) on the surface ECG. Since DoR is an important factor associated with the propensity for reentrant arrhythmias, this study examined if TpTe may serve as a marker of risk of ventricular arrhythmias. Data from 18 patients with coronary artery disease and inducible sustained ventricular tachycardia (VT group) were compared with those of 16 survivors of myocardial infarction without inducible VT (control group). TpTe was automatically measured in each beat of 24-hour ECG recordings, and programmed ventricular stimulation was performed in the antiarrhythmic drug-free state. TpTe was expressed as the absolute interval in milliseconds, and relative to the duration of QTe (TpTe/QTe x 100%). TpTe duration was 74 +/- 14 ms in the VT group versus 63 +/- 16 ms in the control group (P < 0.004). The TpTe interval expressed as a percent of the QT interval was 21 +/- 4% in the VT group versus 17 +/- 3% in the control group (P = 0.02). In patients with coronary artery disease. TpTe was longer in patients with, versus without, inducible VT. The results of this study support the hypothesis that TpTe reflects transmural dispersion of repolarization.

Nitric oxide-dependent and independent effects on human platelets treated with peroxynitrite

OBJECTIVE

Peroxynitrite (ONOO-) is an oxidant formed from the rapid reaction of superoxide and nitric oxide (NO) at sites of inflammation. The literature reports conflicting data on the effects of ONOO- in biological systems, with both NO- and oxidant-dependent effects having been demonstrated. The aim of this study was to investigate these distinct mechanisms through examining molecular aspects of the effects of ONOO- on human platelets, a system in which we have previously shown that ONOO- has both pro- and anti-aggregatory effects.

METHODS

Platelet function was assessed by measuring platelet P-selectin expression flow cytometrically, intraplatelet Ca2+ concentrations, and by light aggregometry. A colorimetric method was used to measure extracellular platelet membrane thiols. The contribution of NO and cGMP to the pharmacological effects of ONOO- was investigated using an inhibitor of the soluble guanylate cyclase (sGC), 1H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ), and the NO scavenger oxy-haemoglobin.

RESULTS

Peroxynitrite (50-400 microM) caused a concentration-dependent increase in the number of platelets expressing P-selectin, an increase in intraplatelet Ca2+ concentrations and a decrease in platelet membrane thiols. Peroxynitrite-induced P-selectin expression was augmented by ODQ. In contrast, when P-selectin expression was elicited by collagen, ONOO- acted as an inhibitor of this process, an effect that was further enhanced by the addition of 1% plasma, ODQ or oxy-haemoglobin abolished this inhibitory effect. Finally, low concentrations (50-100 microM) of ONOO- inhibited collagen-induced platelet aggregation, an effect that was reversed by oxy-haemoglobin.

CONCLUSIONS

Peroxynitrite exerts dual effects on platelets, which are either activating or inhibitory due to the conversion of ONOO- to NO or NO donors. Peroxynitrite-induced platelet activation seems to be due to thiol oxidation and an increase in intracellular Ca2+. It is important to note that inhibitory, NO-dependent effects occur at lower concentrations than the activating effects. These data are then consistent with the conflicting literature, showing both damaging and cytoprotective effects of ONOO- in biological systems. We hypothesize that the conversion of ONOO- to NO is the critical factor determining the outcome of ONOO- exposure in vivo.

Direct measurement of nitric oxide in human beings

Nitric oxide is a short-lived radical involved in various biological processes. We have used an electrochemical microsensor to detect nitric oxide signals in blood vessels of healthy volunteers. The sensor was inserted into a hand vein, and the vessel was stimulated with acetylcholine or bradykinin. Dose-dependent signals were detected and were attenuated by an inhibitor of nitric oxide synthase. The results provide further evidence that endothelium-derived relaxing factor is nitric oxide and demonstrate a method for monitoring the L-arginine/nitric-oxide pathway in human beings.

Systemic effects of S-nitroso-glutathione in the human following intravenous infusion

Nitric oxide (NO) is a potent vasodilator and inhibitor of platelet aggregation. At present the clinical use of NO donors as inhibitors of platelet activation is limited by their concomitant hypotensive effect. The new NO donor S-nitroso-glutathione (GSNO) has a significant antiplatelet effect at doses that cause only a small decrease in blood pressure in rats. We have examined the antiplatelet and vasodilator properties of this nitrosothiol following systemic intravenous infusion in the human. GSNO was administered intravenously to 10 normal females of reproductive age noting changes in blood pressure, pulse and reported side effects. Ex vivo platelet aggregation to ADP was then performed in a platelet-ionized calcium lumiaggregometer on blood samples taken both before and after the infusions. Side effects such as headache or palpitations occurred only in two subjects at the highest infusion rate of 250 micrograms min-1. Blood pressure and pulse did not vary significantly during the study. Ex vivo platelet aggregation in response to ADP was significantly reduced by the infusion. These results suggest that GSNO is a more potent inhibitor of platelet activation than it is a vasodilator and therefore potentially represents a more clinically useful NO donor than has so far been available where an anti-thrombotic effect is required.

Megakaryocytes from patients with coronary atherosclerosis express the inducible nitric oxide synthase

Endothelial and platelet generation of nitric oxide (NO) plays an important role in the regulation of hemostasis. Alterations in NO biosynthesis are described in atherosclerosis. We have investigated the NO pathway in megakaryocytes and platelets from patients with atherosclerosis and age-matched control subjects. Megakaryocytes and platelets were isolated from patients with severe coronary atherosclerosis (n = 19) and normal coronary arteries (n = 9) as demonstrated by selective angiography. Constitutive (Ca(2+)-dependent) and inducible (Ca(2+)-independent) NO synthase (cNOS and iNOS, respectively) activities were measured by using the citrulline assay and by immunostaining techniques using an anti-peptide antibody to iNOS. Megakaryocytes from patients with atherosclerosis expressed significantly greater amounts of iNOS (1.28 +/- 0.46 pmol citrulline.mg-1.min-1) than cNOS (0.29 +/- 0.40 pmol.mg-1.min-1). In contrast, megakaryocytes from patients with normal coronary arteries expressed significantly more cNOS (1.48 +/- 0.23 pmol.mg-1.min-1) than iNOS (0.49 +/- 0.40 pmol.mg-1.min-1). Platelets isolated from both groups showed no significant difference in cNOS expression, and no iNOS was seen in either group. Immunostaining confirmed the presence of the iNOS in megakaryocytes. These results suggest there is a link between the expression of iNOS in the megakaryocyte and atherosclerosis.

Glucocorticoids inhibit the induction of nitric oxide synthase in macrophages

The effect of glucocorticoids on the production of NO2- and NO by the macrophage cell line J774 was investigated. Stimulation of the cells with lipopolysaccharide (LPS) resulted in a time-dependent accumulation of NO2- in the medium, reaching a plateau after 48h. Concomitant incubation of the cells for 24h with dexamethasone (0.001-1.0 microM) or hydrocortisone (0.01-10.0 microM) caused a concentration-dependent inhibition of NO2- formation. The cytosol of J774 cells stimulated with LPS and IFN-gamma produced a time-dependent increase in the release of NO. This was blocked in a concentration-dependent manner by dexamethasone and hydrocortisone, but not progesterone, administered concomitantly with the immunological stimulus. None of these compounds had any effect on the release of NO once the enzyme had been induced. The inhibitory effect of hydrocortisone on NO formation was blocked by cortexolone. These data suggest that part of the anti-inflammatory and immunosuppressive actions of glucocorticoids is due to their inhibition of the induction of the NO synthase.

Increased activity of circulating polymorphonuclear leukocytes in acute myocardial infarction

Acute myocardial infarction results in an increased sensitivity of circulating polymorphonuclear leukocytes to ex vivo aggregation. This increase was prevented by pretreatment of leukocytes with BW755, but not with aspirin, suggesting that the activation of blood leukocytes in infarction is due to a stimulation of cellular lipoxygenase.

Moderate exercise and hemodilution during sleep deprivation

The effect of 52 h of sleep deprivation (SD) upon blood constituents was studied in 12 young women aged 21.5 +/- 0.4 years. Subjects were individually isolated without time cues, performing a sequence of cognitive tasks. Significant decreases in hematocrit (p less than 0.002) and red cell count (p less than 0.04) developed, mainly over the first 28 h of SD, reaching a subsequent plateau or partial recovery. The calculated plasma volume also increased by 10.7 +/- 3.1% at 52 h, with recovery to a 6.9 +/- 3.2% increase the following day. About 1 L of water was retained over the first 30 h of SD, with a subsequent partial elimination of this excess. Plasma albumin and total protein concentrations were largely sustained in the face of the plasma expansion. The plasma pH showed a progressive fall from a baseline value of 7.381 +/- 0.014 to 7.332 +/- 0.006 at 52 h, while plasma bicarbonate decreased from a baseline figure of 31.2 +/- 0.7 to 26-27 mM/L (p less than 0.05). After 8 weeks, all subjects repeated the experiment, with the introduction of 30 min of exercise in the 40th h of wakefulness. Hematocrit and plasma volume changes were similar to those of the first experiment up to the time of exercise, but hematocrit decreased and plasma volume increased after the exercise bout, rather than reaching a plateau. Plasma pH increased with exercise, but returned to the previous low level at 52 h. Any arousing effect of the exercise bout was transient. The plasma expansion reflects metabolic and/or respiratory acidosis, plus possible effects of a prolonged period without recumbency.

Maximal aerobic exercise following prolonged sleep deprivation

The effect of 60 h without sleep upon maximal oxygen intake was examined in 12 young women, using a cycle ergometer protocol. The arousal of the subjects was maintained by requiring the performance of a sequence of cognitive tasks throughout the experimental period. Well-defined oxygen intake plateaus were obtained both before and after sleep deprivation, and no change of maximal oxygen intake was observed immediately following sleep deprivation. The endurance time for exhausting exercise also remained unchanged, as did such markers of aerobic performance as peak exercise ventilation, peak heart rate, peak respiratory gas exchange ratio, and peak blood lactate. However, as in an earlier study of sleep deprivation with male subjects (in which a decrease of treadmill maximal oxygen intake was observed), the formula of Dill and Costill (4) indicated the development of a substantial (11.6%) increase of estimated plasma volume percentage with corresponding decreases in hematocrit and red cell count. Possible factors sustaining maximal oxygen intake under the conditions of the present experiment include (1) maintained arousal of the subjects with no decrease in peak exercise ventilation or the related respiratory work and (2) use of a cycle ergometer rather than a treadmill test with possible concurrent differences in the impact of hematocrit levels and plasma volume expansion upon peak cardiac output and thus oxygen delivery to the working muscles.

Effects of cold stress and exercise on fat loss in females

A Latin Square design has been used to test the responses of 24 relatively fit young women to 200 minute bouts of exercise performed over 5 day trials under each of three different ambient conditions: 15 degrees C (warm-warm; (WW)); -20 degrees C while inhaling, from a facemask, air heated to 18 degrees C (cold-warm; (CW)); and -20 degrees C (cold-cold; (CC)). In both of the cold environments, special clothing and boots were provided (insulation 0.47 degree C X watt-1 X m-2 and 0.62 degree C X watt-1 X m-2; (4 and 3 CLO units)). All three trials led to a small (0.6-0.7 degree C) rise of rectal temperature, but in the two cold environments mean body temperatures fell by over 1.0 degree C. A large increase of serum ketones occurred under all conditions, and the exercise respiratory quotient suggested some increase of fat utilization, WW (0.85) through CW (0.84) to CC (0.83). A fat loss of about 0.5 kg over the five days was confirmed by hydrostatic weighing and measurement of skinfold thicknesses. This was much less than the change previously observed in men, and moreover, it seemed to be independent of ambient conditions. Possible reasons why cold did not increase fat loss in these women include: a lower relative intensity of exercise; a greater stability of fat stores in women; avoidance of caffeine; a possible translocation of subcutaneous fat to deep fat depots; and a greater desire to "lose weight" irrespective of environmental conditions.

Salicylates and 12-lipoxygenase activity in human washed platelets

In vitro salicylates /aspirin, salicylic acid, salicylamide and gentisic acid/ inhibited formation of 12-lipoxygenase products in intact human washed platelets which were stimulated with thrombin or arachidonic acid. Salicylates did not affect 12-lipoxygenase activity in platelet lysates. Ex vivo aspirin or salicylamide at a dose of 1 g given orally to healthy volunteers potentiated formation of 12-lipoxygenase products in washed platelets. It is concluded that the effect of salicylates on 12-lipoxygenase pathway is independent from their influence on cyclooxygenase activity in platelets and aspirin cannot be considered as a selective inhibitor of platelet cyclooxygenase.

Stimulatory cholinergic effect on the release of antiaggregatory activity into the circulation of cat and man and its modification by beta-adrenergic antagonists

The release of PGI2-like activity into the circulation in response to cholinergic agonists and modification of this response by beta-adrenergic antagonists was investigated in anaesthetized cats and healthy humans. Antiaggregatory activity in the arterial blood was continuously assayed by measuring platelet aggregation on blood superfused collagen strip. In some of the human experiments, after the administration of the drugs, the conversion of [14C]-arachidonate to [14C]-prostaglandins in the pulmonary vascular bed was studied. Cholinergic agonists stimulated the release of PGI2-like activity into the circulation, which effect was potentiated in cats by beta-adrenergic antagonists. In humans the latter agents did not stimulate the conversion of [14C]-arachidonate to prostaglandins in the pulmonary circulation and, moreover, inhibited the stimulatory cholinergic effect. The results suggest that an interplay between cholinergic and beta-adrenergic mediators may be involved, although in a different way in cats and in humans, in the release of PGI2-like activity into the systemic circulation.

The biological role of thromboxane A2 in the process of hemostasis and thrombosis; pharmacology and perspectives of therapeutical use of thromboxane synthetase inhibitors and receptor PGH2/TXA2 antagonists

The biological role of thromboxane A2 in the process of hemostasis and thrombosis; pharmacology and perspectives of the therapeutical use of thromboxane synthetase inhibitors and receptor PGH2/TXA2 antagonists. Acta physiol. pol., 1985, 36 (3): 153-164. The biology of thromboxane A2 and pharmacology of drugs that selectively inhibit generation and action of this eicosanoid are reviewed. Author's opinion on therapeutical perspectives for thromboxane synthetase inhibitors and receptor PGH2/TXA2 antagonists is also presented.

Inhibition of human platelet aggregation by vitamin K

The effect of several vitamin K (Vit K) analogues on the aggregation of human platelets was examined. The analogues were potent inhibitors of aggregation induced by ADP, thrombin, collagen and arachidonate but were less active against aggregation induced by the calcium ionophore A23187. Vit K3 also prevented platelet membrane phosphatide breakdown induced by collagen. These effects were not due to a direct inhibition of enzymes involved in the liberation of arachidonate or its subsequent transformation. The analogues exerted no effects on enzymes regulating intraplatelet cAMP. However, these effects could be overcome by increasing extracellular Ca++ levels, indicating a possible interaction with Ca++ regulation in platelets.

Prostacyclin prolongs viability of washed human platelets

The functional viability of stored human platelets, washed in the presence and absence of prostacyclin, was examined over a 96 h period. Platelet counts, aggregation responses and cyclic AMP levels were monitored as well as the spontaneous generation of thromboxane B2 and the liberation of labelled oleate from cellular phosphatides. In suspensions prepared without prostacyclin in the medium, platelet counts declined rapidly as did the sensitivity to aggregating agents. In addition, substantial amounts of thromboxane B2 were generated during preparation and storage and oleate liberation occurred at a rapid rate. In contrast, in prostacyclin-washed platelets, aggregation was maintained throughout the study period and there was little generation of thromboxane B2. Moreover, only a gradual decrease in platelet count and a slow increase in the rate of oleate liberation was observed when compared with controls. However, cyclic AMP levels rapidly declined when platelets were resuspended in prostacyclin-free medium.

The use of prostacyclin in the separation from plasma and washing of human platelets

A new method for the separation from plasma and washing of human platelets is described. The use of prostacyclin (PGI2) throughout the procedure prevents the activation of platelets. The method allows a 60-70% yield of platelets from PRP. The platelet sensitivity to ADP, collagen, adrenaline, arachidonic acid and thrombin is the same as in PRP. The platelet suspension is stable for long periods and the reactivity to aggregating agents remains unchanged for periods greater than 48 h when platelets are stored at 4 degrees C.

Conversion of exogenous arachidonic acid to prostaglandins in the pulmonary circulation in vivo. A human and animal study

The capacity of human lungs to synthetize prostaglandins (PGs) from exogenous arachidonic acid (AA) was investigated in healthy male volunteers. 14C-labelled AA was infused at a constant rate into the right atrium under simultaneous sampling of blood from the ascending aorta. The arterial content of 14C-AA metabolites was extracted, separated with thin-layer chromatography and quantified using fractionated liquid scintillation spectrometry. Conversion of exogenous AA to prostacyclin (PGI2) was also studied in the lungs of anaesthetized cats. In these experiments different doses of unlabelled AA were administered intravenously. Simultaneously PGI2-activity in the arterial blood was assayed using a technique for continuous measurement of platelet aggregation on blood superfused collagen strip. Radiochromatograms of the human arterial plasma revealed no clearly defined peaks corresponding to any of the unlabelled standards of PGD2, PGE2, 6-keto-PGF1 alpha, PGF2 alpha or TxB2. The 14C-activity in the chromatograms materialized only in one (apart from AA) prominent peak in parallel to 13,14-dihydro-15-keto-PGE2. Neither in cats did significant amounts of PGI2 appear in the arterial blood after administration of AA in moderate doses. Only very high AA doses caused a slight increase in arterial PGI2-activity. The results demonstrate that human lungs do not convert exogenous AA to PGs under physiological conditions. In cats the reluctance of the lungs to utilize exogenous precursor can only be overcome with high, non-physiological AA doses. The data may suggest the existence of special regulatory mechanisms which control release of PGs from the lungs and promote utilization of endogenous precursor.

Human sleep and adrenal individual reactions to exercise

Six fit men, aged 20, participated in the 16 day experiment. After a 5 day control period, the subjects marched on 6 consecutive days (from 09:00 h to 17:00 h) for 34 km/day at a speed of 6 km/h, with a backpack adjusted to complete a 35% of individual VO2 max energy expenditure. Control conditions were resumed for a 5 day recovery period. Sleep records were taken every night from 22:00 h to 06:00 h. Urinary 17-hydroxycorticosteroids (17-OHCS) were analysed from a 09:00 h to 17:00 h sample and from overnight urines. Two groups of subjects were defined by their responses to exercise. Four subjects exhibited an increase in stage 3 during the last third of the exercise nights (mean: 163.8 +/- 7.3% of control values) without any change in their adrenal response. Two subjects had no change or a slight decrease in stage 3 but showed increased 09:00--17:00 h 17-OHCS urine excretion (mean: 147 +/- 13% of control values). Sleep latencies were decreased in both groups. However, the 2 subjects of the second group exhibited increased restlessness as measured by the levels of wakefulness, stage 1 and EMG activity. In all subjects, paradoxical sleep was not altered, along with an unchanged all-night excretion of 17-OHCS. It is suggested that differences in adrenal responses to exercise may be responsible for differences in sleep quality. This could explain the discrepancies encountered in the literature about sleep variations after physical exercise.