Cold tolerance and diapause within and across trophic levels: Endoparasitic wasps and their fly host have similar phenotypes

Low temperatures associated with winter can limit the survival of organisms, especially ectotherms whose body temperature is similar to their environment. However, there is a gap in understanding how overwintering may vary among groups of species that interact closely, such as multiple parasitoid species that attack the same host insect. Here, we investigate cold tolerance and diapause phenotypes in three endoparasitoid wasps of the apple maggot fly Rhagoletis pomonella (Diptera: Tephritidae): Utetes canaliculatus, Diachasma alloeum, and Diachasmimorpha mellea (Hymenoptera: Braconidae). Using a combination of respirometry and eclosion tracking, we found that all three wasp species exhibited the same three diapause duration phenotypes as the fly host. Weak (short duration) diapause was rare, with <5 % of all three wasp species prematurely terminating diapause at 21 °C. Most D.mellea (93 %) entered a more intense (longer duration) diapause that did not terminate within 100 d at this warm temperature. The majority of U.canaliculatus (92 %) and D. alloeum (72 %) averted diapause (non-diapause) at 21 °C. There was limited interspecific variation in acute cold tolerance among the three wasp species: wasps and flies had similarly high survival (>87 %) following exposure to extreme low temperatures (-20 °C) as long as their body fluids did not freeze. The three wasp species also displayed little interspecific variation in survival following prolonged exposure to mild chilling of 8 or more weeks at 4 °C. Our study thus documents a remarkable conservation of cold tolerance and diapause phenotypes within and across trophic levels.

359 Incidental Fatty Liver Disease; Are We Adhering to Guidelines?

Aim

Hepatic steatosis is an increasingly prevalent condition, with estimates of up to 30% amongst western populations. Fatty liver is a common incidental finding on abdominal imaging. Current British Society of Gastroenterology guidelines suggest the use of scoring systems, such as FIB-4 or NFS, to stratify these patients into risk categories for the development of non-alcoholic steatohepatitis, and subsequent liver failure or hepatocellular carcinoma. We carried out an audit of our own practice, to see if these guidelines were being followed.

Method

We interrogated the national imaging management system to identify all scans performed in Wexford general hospital from 16th April to 16th October 2020 which identified “hepatic steatosis” or “fatty liver”. Data extracted included: patient demographics, imaging modality & finding. We correlated this data with the patient’s LFTs to calculate their FIB-4/NFS score and investigated whether suitable patients had been referred to gastroenterology.

Results

Of the 145 patients identified as having hepatic steatosis on imaging, 65 (44.8%) had ALT derangement, 42 (29%) had ALP derangement, 81 (56%) had GGT derangement and 23 (16%) had an elevated total bilirubin. Only 26 (17.9%) of these patients had evidence of subsequent liver serology studies, and only 11 (7.6%) had been referred to gastroenterology. None of the patient cohort had either a FIB-4 or NFS score calculated.

Conclusions

There is clear evidence that guidelines are not being followed in the management of patients who are incidentally found to have hepatic steatosis.

Condom negotiation self-efficacy and preparatory behaviors among Mozambican women at sexual risk

Background

Preparatory behaviors (intention to use and buy/get condoms) are extremely important for sexual protection among African women, because the intentions to use and get condoms are the best predictors of effective condom use in some African contexts. However, these preventive behaviors are not as successful as desired, because they are often associated with negative meanings in the context of the sexual relationship. This study aims to identify whether condom negotiation self-efficacy is associated with sexual preparatory behaviors among Mozambican women at risk for HIV/AIDS infection.

Methods

Women (173), patients at a public Hospital and at risk for HIV infection, completed measures of sociodemographic and marital characteristics, condom negotiation self-efficacy, and sexual preparatory behaviors.

Results

Socio-demographic variables (age and education) explained 16.1% of variance (ΔF(2, 170)=16.30, p &lt;.001), and marital variables, “marital status” and “talking about AIDS with partner” explained 22.3% of additional variance (ΔF(2, 168)=30.36, p &lt;.001) in preparatory behaviors. The final model with condom negotiation self-efficacy explained 11.7% of additional variance (ΔF(1, 167)= 39.14, p &lt;.001), this being the most important correlate in the model (β = .48). We observed that higher condom negotiation self-efficacy is associated with higher levels of preparatory behaviors. The overall model explained 48.6% of variance in sexual preparatory behaviors.

Conclusions

These results seem to support an exploratory predictive model of sexual preparatory behaviors that can inform interventions directed at behavioral change among Mozambican women at sexual risk.

Key messages

Women who were younger, had a higher level of education, were single, and talked about AIDS, had higher levels of preparatory behaviors. Women who had a higher level of condom negotiation self-efficacy, had higher levels of preparatory behaviors.

Barriers against safer sex as predictors of condom negotiation self-efficacy among Mozambican Women

Background

Negotiation self-efficacy is one of the main predictors of effective condom use. Therefore, it is essential to identify the factors that influence condom use negotiation self-efficacy in vulnerable women. The aim of this paper is to examine whether socio-demographic and marital factors, and perceived barriers against safer sex are associated with condom use negotiation self-efficacy among Mozambican women at sexual risk.

Methods

173 women, patients at a Mozambican public Hospital and at risk for HIV infection, completed measures of sociodemographic and marital characteristics, perceived barriers against safer sex, and condom use negotiation self-efficacy. Measures included the Mozambican version of the “Women's Health Study Questionnaire”, which presented good psychometric properties in this sample.

Results

Demographic variables (age and education) explained 20% of the variance (ΔF(2, 170)=20.92, p&lt;.001) in condom use negotiation self-efficacy, and the marital variables, “marital status” and “talking about AIDS with partner”, explained 30% of the variance in the outcome (ΔF(2, 168)=50.06, p&lt;.001). Barriers against safer sex explained 6.5% of unique variance in condom use negotiation self-efficacy (ΔF(1, 167)= 24.68, p&lt;.001). The overall model explained 55% of the variance in condom use negotiation self-efficacy.

Conclusions

These results support an exploratory predictive model of condom use negotiation self-efficacy that can inform interventions directed at behavioral change among Mozambican women at sexual risk.

Key messages

Women who were younger, had a higher level of education, were single, and talked about AIDS, had higher levels of condom use negotiation self-efficacy. Women who had lower levels of perceived barriers, had higher levels of condom use negotiation self-efficacy.

Quantifying imperfect camera-trap detection probabilities: implications for density modelling

Abstract ContextData obtained from camera traps are increasingly used to inform various population-level models. Although acknowledged, imperfect detection probabilities within camera-trap detection zones are rarely taken into account when modelling animal densities. AimsWe aimed to identify parameters influencing camera-trap detection probabilities, and quantify their relative impacts, as well as explore the downstream implications of imperfect detection probabilities on population-density modelling. MethodsWe modelled the relationships between the detection probabilities of a standard camera-trap model (n=35) on a remotely operated animal-shaped soft toy and a series of parameters likely to influence it. These included the distance of animals from camera traps, animal speed, camera-trap deployment height, ambient temperature (as a proxy for background surface temperatures) and animal surface temperature. We then used this detection-probability model to quantify the likely influence of imperfect detection rates on subsequent population-level models, being, in this case, estimates from random encounter density models on a known density simulation. Key resultsDetection probabilities mostly varied predictably in relation to measured parameters, and decreased with an increasing distance from the camera traps and speeds of movement, as well as heights of camera-trap deployments. Increased differences between ambient temperature and animal surface temperature were associated with increased detection probabilities. Importantly, our results showed substantial inter-camera (of the same model) variability in detection probabilities. Resulting model outputs suggested consistent and systematic underestimation of true population densities when not taking imperfect detection probabilities into account. ConclusionsImperfect, and individually variable, detection probabilities inside the detection zones of camera traps can compromise resulting population-density estimates. ImplicationsWe propose a simple calibration approach for individual camera traps before field deployment and encourage researchers to actively estimate individual camera-trap detection performance for inclusion in subsequent modelling approaches.

Pre- and post-surgical factors that predict the provision of rescue analgesia following hysterectomy

BACKGROUND

To better manage post-surgical pain, standardized analgesic protocols allow for rescue analgesia (RA). This study seeks to determine which pre- and post-surgical clinical and patient-related factors, in addition to post-surgical pain, may influence health care professional decisions on RA administration.

METHODS

A consecutive sample of 185 women, submitted to hysterectomy for benign disorders, was assessed 24 h before (time 1; T1) and 48 h after (time 2; T2) surgery. At T1, baseline demographic, clinical and psychological predictors were assessed and at T2, post-surgical pain, anxiety and RA administration were recorded.

RESULTS

After controlling for post-surgical acute pain intensity, logistic regression results revealed several pre-surgical (T1) and surgical factors associated with post-surgical RA: having other previous pain states [odds ratio (OR), 4.551; 95% confidence interval (CI), 1.642-12.611, p = 0.004], being anaesthetized with only general or loco-regional anaesthesia (OR, 5.349; 95% CI, 1.976-14.483, p = 0.001) and pre-surgical fear of immediate consequences of surgery (OR, 1.306; 95% CI, 1.031-1.655, p = 0.027). Concerning post-surgical variables, higher pain intensity (OR, 1.591; 95% CI, 1.353-1.871, p < 0.001) and post-surgical anxiety (OR, 1.245; 95% CI, 1.084-1.430, p = 0.002) were significantly associated with RA provision.

CONCLUSIONS

Health care decision making to administer RA might be influenced not only by post-surgical pain intensity but also by pre-surgical and surgical clinical factors, such as previous pain and type of anaesthesia. Patient-related psychological characteristics, such as pre-surgical fear and post-surgical anxiety, may also play a role in decision making on RA provision. Implications for practice are discussed.

Acute superior mesenteric artery embolism: reperfusion with AngioJet hydrodynamic suction thrombectomy and pharmacologic thrombolysis with the EKOS catheter

Acute mesenteric ischemia is commonly treated by surgical exploration and open thrombectomy. Very few reports describe using newer, minimally invasive methods which utilize catheter-based mechanical and pharmacological thrombolysis. Herein, we report a case of acute superior mesenteric embolism successfully treated with AngioJet hydrodynamic mechanical thrombectomy and EKOS catheter pharmacological thrombolysis. A 76-year-old man with new onset atrial fibrillation presented with abdominal pain of 48 hours duration. Subsequent contrast computed tomography scan of the abdomen revealed a filling defect in the superior mesenteric artery (SMA), suggestive of an acute embolus, which was confirmed by SMA angiogram. The AngioJet aspiration device was used for hydrodynamic suction thrombectomy. The repeat angiogram demonstrated only a partial restoration of blood flow, and thus the EKOS tissue plasminogen activator catheter was left in the SMA for continuous thrombolysis. The patient underwent continuous thrombolysis for two days, with two subsequent sessions of angiography. Thereafter, the patient improved symptomatically and serum lactate was normalized. In conclusion, the AngioJet suction thrombectomy and pharmaco-mechanical thrombolysis using the EKOS catheter is associated with minimal morbidity and can be rapidly performed. It may be used as an alternative to open surgical thrombectomy in selected cases of acute SMA embolism.

Nurses' attitudes to a medical emergency team service in a teaching hospital

BACKGROUND

Cultural barriers including allegiance to traditional models of ward care and fear of criticism may restrict use of a medical emergency team (MET) service, particularly by nursing staff. A 1-year preparation and education programme was undertaken before implementing the MET at the Austin Hospital, Melbourne, Australia. During the 4 years after introduction of the MET, the programme has continued to inform staff of the benefits of the MET and to overcome barriers restricting its use.

OBJECTIVE

To assess whether nurses value the MET service and to determine whether barriers to calling the MET exist in a 400-bed teaching hospital.

METHODS

Immediately before hand-over of ward nursing, we conducted a modified personal interview, using a 17-item Likert agreement scale questionnaire.

RESULTS

We created a sample of 351 ward nurses and obtained a 100% response rate. This represents 50.9% of the 689 ward nurses employed at the hospital. Most nurses felt that the MET prevented cardiac arrests (91%) and helped manage unwell patients (97%). Few nurses suggested that they restricted MET calls because they feared criticism of their patient care (2%) or criticism that the patient was not sufficiently unwell to need a MET call (10%). 19% of the respondents indicated that MET calls are required because medical management by the doctors has been inadequate; many ascribed this to junior doctors and a lack of knowledge and experience. Despite hospital MET protocol, 72% of nurses suggested that they would call the covering doctor before the MET for a sick ward patient. However, 81% indicated that they would activate the MET if they were unable to contact the covering doctor. In line with hospital MET protocol, 56% suggested that they would make a MET call for a patient they were worried about even if the patient's vital signs were normal. Further, 62% indicated that they would call the MET for a patient who fulfilled MET physiological criteria but did not look unwell.

CONCLUSIONS

Nurses in the Austin Hospital value the MET service and appreciate its potential benefits. The major barrier to calling the MET appears to be allegiance to the traditional approach of initially calling parent medical unit doctors, rather than fear of criticism for calling the MET service. A further barrier seems to be underestimation of the clinical significance of the physiological perturbations associated with the presence of MET call criteria.

Cell adhesion regulates gene expression at translational checkpoints in human myeloid leukocytes

Engagement of adhesion molecules on monocytes and other myeloid leukocytes, which are effector cells of the innate immune system, not only tethers the leukocytes in place but also transmits outside-in signals that induce functional changes and alter gene expression. We found that a subset of mRNAs that are induced or amplified by adhesion of human monocytes to P-selectin via its surface ligand, P-selectin glycoprotein 1, have characteristics that suggest specialized translational control. One of these codes for urokinase plasminogen activator receptor (UPAR), a critical surface protease receptor and regulator of cell adhesion and migration. Although UPAR transcripts are induced by adhesion, rapid synthesis of the protein uses constitutive mRNA without a requirement for new transcription and is regulated by mammalian target of rapamycin, demonstrating new biologic roles for the signal-dependent translation pathway controlled by this intracellular kinase. The synthesis of UPAR in monocytic cells is also regulated by eukaryotic translation initiation factor 4E, a second key translational checkpoint, and phosphorylation of eukaryotic translation initiation factor 4E is induced by adhesion of monocytes to P-selectin. Translationally controlled display of UPAR by monocytes confers recognition of the matrix protein, vitronectin. Adhesion-dependent signaling from the plasma membrane to translational checkpoints represents a previously unrecognized mechanism for regulating surface phenotype that may be particularly important for myeloid leukocytes and other cells that are specialized for rapid inflammatory and vascular responses.

Intact soil-core microcosms compared with multi-site field releases for pre-release testing of microbes in diverse soils and climates

Intact soil-core microcosms were used to compare persistence of Pseudomonas chlororaphis 3732RN-L11 in fallow soil and on wheat roots with field releases at diverse sites. Parallel field and microcosm releases at four sites in 1996 were repeated with addition of one site in 1997. Microcosms were obtained fresh and maintained at 60% soil water holding capacity in a growth chamber at 70% relative humidity, a 12-hour photoperiod, and constant temperature. Persistence of 3732RN-L11 was measured at each site in field plots and microcosms at 7-21 day intervals, and in duplicate microcosms sampled at an independent laboratory. Linear regression slopes of field plot and microcosm persistence were compared for each site, and between identical microcosms sampled at different sites, using log10 transformed plate counts. Microcosm persistence closely matched field plots for wheat roots, but persistence in fallow soil differed significantly in several instances where persistence in field plots was lower than in microcosms. Analysis of weather variations at each site indicated that rainfall events of 30-40 mm caused decreased persistence in fallow soil. Cooler temperatures enhanced persistence in field plots at later time points. Inter-laboratory comparison of regression slopes showed good agreement for data generated at different sites, though in two instances, longer sampling periods at one site caused significant differences between the sites. Soil characteristics were compared and it was found that fertility, namely the carbon to nitrogen ratio, and the presence of expanding clays, were related to persistence. These microcosm protocols produced reliable data at low cost, and were useable for pre-release risk analyses for microorganisms.

Analysis of oxidized glycerophosphocholine lipids using electrospray ionization mass spectrometry and microderivatization techniques

Oxidized low-density lipoprotein (LDL) is thought to play an important role in atherogenesis and cardiovascular disease in humans. Oxidized LDL is a complex mixture of many oxidized species, including numerous oxidized glycerophospholipids. Electrospray ionization and tandem mass spectrometry as well as microchemical derivatization of high-performance liquid chromatographically purified fractions derived from oxidized LDL were investigated as means to determine the structure of individual components present in oxidized LDL. One major oxidized phosphocholine lipid had an [M + H](+) ion at m/z 650. Derivatization to the trimethylsilyl ether and methoxime caused shifts in mass which, along with negative ion collision-induced dissociation mass spectra, were consistent with the presence of three species, 1-palmitoyl-2-(9-oxononanoyl)glycerophosphocholine and two isomeric 1-octadecanoyl-2-(hydroxyheptenoyl)glycerophosphocholines. These species were chemically synthesized. Trimethylsilylation of free hydroxyl groups increased the mass of the phospholipid acyl chains containing hydroxyl groups by 72 u. Conversion of carbonyl groups to the methoxylamine derivative increased the mass by 29 u. Ozonolysis of those products which contained double bonds proved to be a facile technique to determine the position and number of double bonds present. The use of these techniques was illustrated in the structural characterization of one major component (m/z 650, positive ions) in oxidized LDL as 1-octadecanoyl-2-(7-hydroxyhepta-5-enoyl)glycerophosphocholi ne. A possible mechanism for the formation of this unique chain-shortened glycerophospholipid is proposed.

Immunocompetence in the long sleep and short sleep mouse lines: baseline versus primed responses

Two lines of mice which were selectively bred for high (Long Sleep; LS) and low (Short Sleep; SS) reactivities to a sedative dose of ethanol, are also differentiated by agents that act at the GABAA-receptor complex. Since this supramolecular complex may also modulate immune function, measures of immunity have been examined in these lines. In the present study the immune responsiveness before and after an allogeneic priming stimulus was investigated. Lower mitogen-induced T-cell proliferation, mixed leukocyte reaction, and cytotoxic T lymphocyte activity were found in unprimed LS compared to unprimed SS mice. In contrast, the LS line exhibited a marked augmentation of these responses after priming, while the SS mice appeared unresponsive to this challenge. Addition of splenocytes or cell-free splenic cultures from primed mice to cultures from unprimed mice suggested that differences in priming-induced cell-to-cell interactions, rather than the release of a soluble helper factor(s) into the medium, are responsible for the marked augmentation of the secondary response in LS, compared to SS mice. Fewer T-helper and T-suppressor/cytotoxic cells were found in LS compared to SS mice, and this was unaffected by priming. These results extend previous findings demonstrating a higher natural killer cell activity and rate of tumor rejection in LS mice and suggest that these lines may be useful in studying the regulatory role of the GABAA complex in immune function.

Clinical use of androgenic steroids at a major medical center: who prescribes androgens and how well do they do it?

To assess prescribing practices for androgens at Wilford Hall USAF Medical Center, the authors analyzed prescriptions for all patients receiving therapy during a 12-month period (n = 201) and reviewed the available outpatient records not maintained elsewhere (n = 105). The most commonly prescribed androgens were testosterone enanthate (144/201; 56.7%), and danazol (52/201; 25.9%). Review of the available outpatient medical records of 73 male patients using testosterone enanthate showed a mean age of 59.5 years, mean frequency of injection of 20 days, mean duration of therapy of 3.5 years, and mean dose of 226 mg. Therapy was initiated by a urologist (34/73; 46.6%), an endocrinologist (33/73; 45.2%), or an internist (6.73; 8.2%). Indications for therapy based on pretreatment laboratory and historical data included hypergonadotropic hypogonadism (24/73; 32.9%), hypogonadotropic hypogonadism (23/73; 31.5%), unspecified hypogonadism (7/73; 9.6%), and empiric treatment of elderly men with erectile dysfunction without evidence of hypogonadism (9/73; 26%). Pretreatment prostate examinations as well as measurement of serum testosterone (66/73; 90.4%) and serum gonadotropins (52/73; 71.2%) were often not performed. The authors conclude that records of patients treated with androgens show: 1) Doses are appropriate; 2) Empiric treatment of erectile dysfunction in elderly men is common despite the associated risks; 3) Laboratory and physical evaluation before treatment is often incomplete; 4) There was no evidence of androgenic substance abuse in patients studied.

Stimulus (instructional) fading during extinction of self-injurious escape behavior

Three individuals with developmental disabilities were exposed to a series of assessment conditions to identify the source of reinforcement for their self-injurious behavior. In each case, self-injury occurred most often in instructional (demand) situations containing a brief time-out from the task contingent on self-injury, indicating that the behavior was an escape response (i.e., maintained by negative reinforcement). Treatment was implemented in a multiple baseline across subjects design and consisted of extinction (prevention of escape) plus instructional fading (initial elimination of instructions followed by their gradual reintroduction). Results showed that the combined treatment produced immediate and large reductions in self-injury that were maintained as the frequency of instructions was increased across sessions to match the original baseline rate of presentation. Results of a component analysis conducted with 1 subject suggested that stimulus fading accelerated the behavior-reducing effects of extinction.

Ethanol inhibits mitogen-induced calcium mobilization in mouse splenocytes

Ethanol inhibited the mitogen-induced initial increase in cytoplasmic free-calcium [Ca2+]i in mouse splenocytes. This effect was concentration-dependent, reversible, and observed at pharmacologically relevant concentrations (24-166mM). Other short-chain alcohols such as propanol, butanol, and pentanol also inhibited this mitogen-induced increase in [Ca2+]i. The potencies of these alcohols to produce this effect were highly correlated (r = 0.98, p less than 0.001) with their membrane/buffer partition coefficients. Analysis of mouse splenocyte subpopulations demonstrated that this effect was manifest in both B and T lymphocytes. Within T lymphocyte subpopulations, both CD4+ and CD8+ T cells were affected. These results suggest that the inhibition of [Ca2+]i increase may be an early event mediating ethanol-induced immunosuppression and that this may be a predisposing factor to infection and malignancies associated with alcoholism.

Effects of various music conditions on multiple dimensions of behavior of emotionally disturbed adolescents

The effects of music on the behaviors of 5 to 8 emotionally disturbed adolescents were investigated. Six behavioral categories of aggressive motor, aggressive verbal, disruptive motor, disruptive verbal, nondisruptive/off task, and on task, were monitored in class daily for 40 min. for 12 wk. to assess whether three conditions of "sedative," "stimulating," and "no music" influenced the frequency of these behaviors. Analysis indicated no significant differences in frequencies of any of the six behavior categories among music conditions.

Inhibition of calcium mobilization is an early event in opiate-induced immunosuppression

Morphine administered as a subcutaneous implant inhibits the initial increase in cytoplasmic free-calcium [Ca2+]i induced by mitogens in mouse splenocytes. This effect was not reproduced by incubation of splenocytes with morphine (10(-8)-10(-4) M). Analysis of splenocyte subpopulations demonstrates that this effect was manifest in both B and T cells. However, within T cell subpopulations, CD4+ but not CD8+ cells were affected. Adrenalectomy abolished this effect of morphine in CD4+ T but not CD4-, CD8- spleen cells (most likely Thy 1.2- B cells). Moreover, simultaneous administration of the opiate antagonist naltrexone blocked the effect of morphine in CD4-, CD8- spleen cells, but not in CD4+ T cells. These data indicate that the effects of morphine on mitogen-stimulated increase in [Ca2+]i may be mediated through distinct glucocorticoid-dependent and -independent mechanisms. The morphine-induced inhibition of an increase in [Ca2+]i in immune cells reported here may be an early event mediating opiate-induced immunosuppression.

t-[35S]butylbicyclophosphorothionate binding under equilibrium and nonequilibrium conditions: differential effects of barbiturates and gamma-aminobutyric acid in the long-sleep and short-sleep selected mouse lines

Significant differences were demonstrated between the long-sleep (LS) and short-sleep (SS) selected mouse lines in the abilities of barbiturates and gamma-aminobutyric acid (GABA) to inhibit t-[35S]butylbicyclophosphorothionate [( 35S]TBPS) binding to well-washed cerebral cortical membranes. Thus, using phenobarbital to initiate the dissociation of [35S]TBPS, the extent of inhibition was significantly greater in LS mice (but not SS mice) than would be predicted using equilibrium conditions. Pentobarbital had the opposite effect, causing [35S]TBPS to dissociate to a greater extent in SS than LS membranes. [35S]TBPS binding was dissociated from LS and SS membranes by GABA to a greater and lesser extent, respectively, than would be predicted from equilibrium studies. Because no line differences in the potencies of these drugs to inhibit [35S]TBPS binding were found using equilibrium conditions, these results indicate that the association rates of barbiturates and GABA may be different between these lines. These findings are consistent with neurochemical studies indicating differences in the benzodiazepine/GABA receptor-chloride channel complex in these selected lines and may explain their differential sensitivities to certain agents acting through this supramolecular complex.

Morphine-induced thymic hypoplasia is glucocorticoid-dependent

Mice administered morphine as a s.c. pellet implant exhibit a marked and sustained thymic hypoplasia as well as suppression of T lymphocyte functions. In the present study, the effects of morphine on thymocyte differentiation were characterized. Morphine produced a significant decrease in both the number and proportion of CD4+/CD8+ double positive (DP) cells. The percentage of the CD4+/CD8-, CD4-/CD8+, and CD4-/CD8- double negative subsets in these mice was proportionally increased. Morphine also increased the proportion of cells expressing either the epsilon-chain of the CD3 complex or the IL-2R. The initial reduction in the proportion of DP thymocytes appeared fully recovered by 10 days post-implantation, although the number of DP thymocytes gradually returned to normal over a 3-wk period. Morphine administration resulted in a marked increase in serum corticosterone levels, and a single injection of dexamethasone mimicked the effects of morphine on thymus differentiation. Furthermore, adrenalectomy abolished the morphine-induced decrease in CD4+/CD8+ thymocytes relative to a sham-operated group. The present findings are consistent with the hypothesis that morphine-induced thymic hypoplasia may be mediated by an increase in the circulating levels of corticosterone.

Stress modulates calcium mobilization in immune cells

Both acute and chronic restraint stress modulated mitogen-induced increases in cytoplasmic free-calcium concentrations ([Ca2+]i) in mouse spleen cells. Dual-color analysis of lymphocyte subpopulations demonstrated that acute (2 hour) restraint stress suppressed mitogen-stimulated increases in [Ca2+]i in CD4+ T cells, but enhanced [Ca2+]i in CD8+ T cells. Chronic restraint stress (2 hours daily for up to 21 days) resulted in a significant suppression of mitogen-stimulated increases in [Ca2+]i in CD4+ T cells at 3 and 7 days, but not at 21 days. CD8+ T cells were unaffected by chronic stress. Chronic stress (for 7 days) had a modest suppressive effect on mitogen-induced Ca2+ responses in B cells. Within T lymphocyte subpopulations, both acute and chronic stress predominantly affected CD4+ T cells, which may induce a functional reversal of the CD4/CD8 ratios in vivo. Such a reversal could result in suppression of a variety of immune responses such as lymphocyte proliferation and antigen-specific antibody production. These findings indicate that the inhibitory effects of stress on calcium mobilization in lymphocytes may be an early event mediating stress-induced immunosuppression.

Morphine-induced thymic hypoplasia is glucocorticoid-dependent

Mice administered morphine as a s.c. pellet implant exhibit a marked and sustained thymic hypoplasia as well as suppression of T lymphocyte functions. In the present study, the effects of morphine on thymocyte differentiation were characterized. Morphine produced a significant decrease in both the number and proportion of CD4+/CD8+ double positive (DP) cells. The percentage of the CD4+/CD8-, CD4-/CD8+, and CD4-/CD8- double negative subsets in these mice was proportionally increased. Morphine also increased the proportion of cells expressing either the epsilon-chain of the CD3 complex or the IL-2R. The initial reduction in the proportion of DP thymocytes appeared fully recovered by 10 days post-implantation, although the number of DP thymocytes gradually returned to normal over a 3-wk period. Morphine administration resulted in a marked increase in serum corticosterone levels, and a single injection of dexamethasone mimicked the effects of morphine on thymus differentiation. Furthermore, adrenalectomy abolished the morphine-induced decrease in CD4+/CD8+ thymocytes relative to a sham-operated group. The present findings are consistent with the hypothesis that morphine-induced thymic hypoplasia may be mediated by an increase in the circulating levels of corticosterone.