Canine hypoadrenocorticism: Insights into the Addisonian crisis

Objective

Primary objectives of this study were to determine presenting complaints, physical examination, clinicopathologic findings, and hospitalization time of dogs with spontaneous hypoadrenocorticism presenting with critical disease; and to compare those end points to dogs with a more stable presentation. Secondary objectives were to evaluate the shock index and to identify precipitating stressors.

Animals

Eighty-four dogs at the Western College of Veterinary Medicine between 1998 and 2018 were included.

Procedure

Data were retrieved from the medical records.

Results

Collapse and depression were more common among critically ill dogs. Hyperlactatemia was rare despite a diagnosis of hypovolemic shock, and a shock index was ineffective in this patient subset. Isosthenuria, total hypocalcemia, and more severe acidosis were more common (P < 0.05) in critical dogs. Owner separation was the most common precipitating stressor.

Conclusion and clinical relevance

We concluded that the critical Addisonian dog has unique characteristics that may aid in early disease identification.

Surveillance of Babesia odocoilei in wild and farmed cervid populations of Saskatchewan, Canada

OBJECTIVE

To investigate whether Babesia odocoilei could be detected from farmed and wild cervid diagnostic submissions prior to its first reported occurrence in Saskatchewan.

PROCEDURE

Polymerase chain reaction (PCR) for B. odocoilei was used to survey 85 fresh-frozen samples and 112 formalin-fixed, paraffin-embedded samples from Saskatchewan cervids submitted for necropsy between 2000 and 2014.

RESULTS

The PCR was positive for B. odocoilei in 1/84 white-tailed deer, 1/41 moose, 0/37 mule deer, and 1/35 elk. The positive elk was from a farmed herd, but the remaining 2 positive samples were from wild cervids. The positive moose sample was the earliest confirmed infection, dating back to 2008. Therefore, 1.5% of the study population tested positive over the 14-year period.

CONCLUSION

There were low numbers of cervids infected with B. odocoilei in the study population.

CLINICAL RELEVANCE

Babesiosis should be included as a differential diagnosis for disease in susceptible cervids when clinical signs are compatible; however, a lack of suggestive clinical signs or necropsy findings does not preclude infection. Thus, monitoring prevalence of the disease within Saskatchewan (and Canada) will likely require targeted surveillance.

Species-specific PCR assay for the detection of Babesia odocoilei

We developed a PCR assay for the detection of Babesia odocoilei based on the 18S rRNA gene. Multiple specimens of B. odocoilei were examined, and the assay consistently produced a small specific PCR product of 306 bp. The PCR assay was also challenged with DNA from 13 other Babesia species and 2 Theileria species, originating from 10 different host species; however, nonspecific DNA amplification and multiple banding patterns were observed, and the amplicon banding patterns varied between different isolates of the same species. Sensitivity was determined to be 6.4 pg of DNA, and an estimated 0.0001% parasitism. This assay can be utilized for species-specific differential detection of B. odocoilei.

Marginal zone lymphoma in a dog

A 13-year-old spayed female American Cocker Spaniel was presented for evaluation of a cough and weight loss. Physical exam revealed generalized lymphadenopathy. The patient was diagnosed with marginal zone lymphoma (MZL) on histopathology of an extirpated lymph node. This report demonstrates an unusual case of a pleomorphic neoplastic population documented on cytologic evaluation that had moncytoid features and peripheral blood involvement; a previously undocumented IgG1 monoclonal gammopathy was also an interesting feature of this canine MZL. The patient did not undergo chemotherapy for lymphoma and was euthanized over 4 years after the initial presentation.

1151 Is Timing Of Light Exposure Different In Women With Chronic Migraine?

Introduction

Light avoidance is a common coping behavior of individuals with migraine headaches. It is not known whether timing of light exposure is different in individuals with chronic migraine (CM) compared to those without migraine and how this may relate to headache frequency and severity. We tested this by examining timing of the brightest and darkest light and headaches in women with chronic migraines and healthy controls.

Methods

Sixteen women with CM (mean age = 33.07) and 18 female healthy controls (HC; mean age = 32.22) completed daily ratings of headache severity (0-10, severity &gt; 2 classified as headache) concurrent with light exposure measured by wrist actigraphy for approximately one month (M=28.00 days, range=21-36). Start time of each day’s 10-hour periods of maximum light (M10) and 5-hour periods of lowest light (L5) were calculated and averaged for each participant. T-tests and Cohen’s d effect sizes were used to compare groups. Pearson correlation coefficients were calculated to examine associations between M10/L5 timing and headache frequency and severity.

Results

M10 was earlier in the CM group compared to the HC group (07:42±00:47 vs. 08:50±00:58, t(32)=3.69, p=0.0008, d=1.08). The CM group exhibited non-significant trend towards earlier L5 compared to the HC group (12:26±00:48 vs. 01:07±01:03, t(32)=1.89, p=0.0723, d=0.62). Among individuals with CM, later M10 timing was associated with more severe average daily headache (r=0.60, p=0.0136) and more frequent headaches (r=0.55, p=0.0257). Later L5 timing was significantly associated with more severe average daily headache (r=0.66, p=0.0052) and showed a non-significant trend toward association with more frequent headaches (r=0.47, p=0.0686).

Conclusion

Timing of the greatest light exposure period was earlier in CM compared to HC. Within the CM group, those who had earlier light and dark periods reported lower headache severity and fewer days with headaches. These findings suggest the possibility of a role for the circadian system in chronic migraine.

Support

This study was supported by grant R21NS081088 from the National Institutes of Health.

The association between serial point-of-care test results and hospitalization time in canine parvovirus infection (2003-2015)

The objectives of this study were to describe serial point-of-care test results in dogs infected with canine parvovirus (CPV), highlight clinicopathologic abnormalities at various timepoints, and investigate their association with the duration of hospitalization. Two-hundred and four dogs positive for CPV at the Western College of Veterinary Medicine between 2003 and 2015 were included. Data were recorded pertaining to emergency panel and venous blood gas tests at presentation, and every 12 hours thereafter (+/- 4 hours) for the first 72 hours of hospitalization. Common persistent abnormalities included hypoproteinemia, acidosis, hyponatremia, hypochloremia, hyperkalemia, and hyperbicarbonatemia. Ionized hypocalcemia was associated with a longer duration of hospitalization and mild hyperkalemia was associated with a shorter duration of hospitalization (P < 0.05). This study suggests that the use of point-of-care tests for in-hospital monitoring may provide insight into CPV case complexity and predict total hospitalization times.

Use of slide scrape lysates for polymerase chain reaction confirmation of disseminated Mycobacterium avium infection in a cat

Disseminated mycobacteriosis in a 3-year-old domestic medium-haired cat was diagnosed on lymph node cytology. Slide scrape lysates from the cytology submission were used to confirm Mycobacterium avium by polymerase chain reaction (PCR) and sequencing and proved a simple technique that could be a valuable tool in veterinary diagnostics and research.

Does antimicrobial therapy improve outcomes in horses with severe equine asthma and a positive tracheal wash bacterial culture?

The objective of this study was to observe the outcomes of adding an antimicrobial treatment to a conventional treatment regime in horses with severe equine asthma in a clinical setting. Eleven client-owned horses with a history consistent with severe equine asthma, increased respiratory effort and nostril flaring, ≥ 20% neutrophils on bronchoalveolar lavage (BAL), and a positive tracheal wash (TW) bacterial culture were treated with environmental management, corticosteroids, and bronchodilators. Six horses were also treated with an antimicrobial (principal group), while the other 5 were administered saline as a placebo (control group). Treatment with antimicrobials significantly improved the post-treatment clinical score of the principal group compared with the pre-treatment score, whereas no significant difference occurred in the control group. The principal group also had significantly less neutrophil myeloperoxidase (MPO) activity post-treatment than pre-treatment, with a median difference of -0.39 units/[protein] in the principal group and a median difference of -0.21 units/[protein] in the controls. There was no difference in MPO activity pre- versus post-treatment in the control group. No differences were noted in the intra-group comparisons of pre- versus post-treatment BAL neutrophil counts, mucus scores, and concentrations of interleukin-8 (IL-8) or tumor necrosis factor-alpha (TNF-α) in bronchoalveolar lavage fluid (BALF) in either group. There were no differences found in the inter-group comparisons of the principal versus controls for each of the pre- and post-treatment time periods for BAL neutrophil count, mucus score, clinical scores, MPO activity, and IL-8 or TNF-α concentrations. The role of airway bacteria in horses with severe equine asthma requires further investigation as antimicrobial therapy improved post-treatment clinical scores and decreased MPO activity in the group of horses studied, but did not affect other measures of airway inflammation.

Characterizing Sleep in Adolescents and Adults with Autism Spectrum Disorders

We studied 28 adolescents/young adults with autism spectrum disorders (ASD) and 13 age/sex matched individuals of typical development (TD). Structured sleep histories, validated questionnaires, actigraphy (4 weeks), and salivary cortisol and melatonin (4 days each) were collected. Compared to those with TD, adolescents/young adults with ASD had longer sleep latencies and more difficulty going to bed and falling asleep. Morning cortisol, evening cortisol, and the morning-evening difference in cortisol did not differ by diagnosis (ASD vs. TD). Dim light melatonin onsets (DLMOs) averaged across participants were not different for the ASD and TD participants. Average participant scores indicated aspects of poor sleep hygiene in both groups. Insomnia in ASD is multifactorial and not solely related to physiological factors.

Fine-needle aspiration in the diagnosis of equine skin disease and the epidemiology of equine skin cytology submissions in a western Canadian diagnostic laboratory

Fine-needle aspiration (FNA) is commonly used to diagnose skin disease in companion animals, but its use in horses appears to be infrequent. Equine veterinarians in western Canada were surveyed to determine their opinions about FNA and 15 years of diagnostic submissions were used to compare the perceived to actual value of FNA in the diagnosis of skin disease in horses. Practitioners viewed FNA as quick, easy, economical, and minimally invasive. However, most veterinarians rarely chose to use FNA due to a perception that sample quality and diagnostic yield were poor and there was a narrow range of diseases the technique could diagnose. Analysis of the FNA cytology samples from a veterinary diagnostic laboratory showed a wide variety of equine skin disease conditions, but the frequency of non-diagnostic results was significantly higher in equine submissions compared to those from dogs and cats.

Identification of microfilaria in a mammary mass aspirate from a female dog

A filarial nematode larva (microfilaria) was found in an aspirate of a mammary mass from a dog imported to Saskatchewan from Myanmar. This was an unusual location for a microfilaria and numerous filarial nematodes infecting dogs in Asia had to be considered. This report describes the laboratory diagnosis of canine heartworm disease in this dog.

Comparison between available serologic tests for detecting antibodies against Anaplasma phagocytophilum and Borrelia burgdorferi in horses in Canada

To investigate the agreement between available serologic tests for the detection of antibodies against Anaplasma phagocytophilum and Borrelia burgdorferi, 50 serum samples from horses of unknown clinical status and at low risk for infection were tested. In addition to a point-of-care enzyme-linked immunosorbent assay (pocELISA), the evaluated tests included 2 indirect fluorescent antibody tests (IFATs) for antibodies against A. phagocytophilum and an IFAT, an ELISA confirmed with Western blot, and the Lyme multiplex assay for antibodies against B. burgdorferi. For each pair-wise comparison between serologic tests, the difference in the proportion of seropositive results as well as kappa and the prevalence-adjusted, bias-adjusted kappa were calculated. The proportion of seropositive results differed significantly in each pairwise comparison of tests for detection of antibodies against A. phagocytophilum, and between the pocELISA and IFAT as well as between the pocELISA and Lyme multiplex assay for detection of antibodies against B. burgdorferi. Agreement based on kappa varied from poor to fair while agreement was improved when evaluating prevalence-adjusted, bias-adjusted kappa. Lack of agreement may be explained by differences in methodology between the evaluated tests, cross-reactivity or false-positive and false-negative tests. In addition to the limitations of serologic test interpretation in the absence of clinical disease, this data suggest that screening of horses for exposure to tick-borne diseases in nonendemic areas may not be warranted.

Seroprevalence of equine granulocytic anaplasmosis and lyme borreliosis in Canada as determined by a point-of-care enzyme-linked immunosorbent assay (ELISA)

Equine granulocytic anaplasmosis (EGA) and Lyme borreliosis (LB) are an emerging concern in Canada. We estimated the seroprevalence of EGA and equine LB by testing 376 convenience serum samples from 3 provinces using a point-of-care SNAP(®) 4Dx(®) ELISA (IDEXX Laboratories, Westbrook, Maine, USA), and investigated the agreement between the point-of-care ELISA and laboratory-based serologic tests. The estimated seroprevalence for EGA was 0.53% overall (0.49% in Saskatchewan, 0.71% in Manitoba), while the estimated seroprevalence for LB was 1.6% overall (0.49% in Saskatchewan, 2.86% in Manitoba). There was limited agreement between the point-of-care ELISA and an indirect fluorescent antibody test for EGA (kappa 0.1, PABAK 0.47) and an ELISA/Western blot combination for LB (kappa 0.23, PABAK 0.71). While the SNAP(®) 4Dx(®) ELISA yielded expected seroprevalence estimates, further evaluation of serologic tests for the purposes of disease exposure recognition may be needed.

Passive surveillance for ticks on horses in Saskatchewan

Passive surveillance of ticks on horses in Saskatchewan revealed that the horses were parasitized by 3 species, Dermacentor albipictus, D. andersoni, and D. variabilis. The nymphs and adults of D. albipictus occurred on horses earlier in the year than did adults of the 2 other species.

Use of the polymerase chain reaction assay for the detection of Babesia odocoilei 18S ribosomal RNA in formalin-fixed tissues

The effect of fixation and storage conditions on the performance of polymerase chain reaction (PCR) assays for Babesia odocoilei were examined using 3 different primer sets targeting the eukaryotic 18S ribosomal RNA gene, with variably sized products of 1,723 base pairs (bp), 483 bp, and 306 bp. All primer sets performed well on fresh-frozen tissue, and storage for 1 year at −20°C did not affect PCR performance. Formalin fixation markedly affected the amplicon length that could be amplified. However, DNA was successfully amplified after storage in formalin for 2 months using the primer set with a 483-bp product, and up to 6 months using the primer set with a 306-bp product. The latter primer set successfully differentiated B. odocoilei and Babesia microti DNA; however, further evaluation is required to confirm its specificity. Treatment of tissues with formic acid, at concentrations typically used to denature prions, degraded the DNA and made it unsuitable for PCR testing.

Prevalence and geographic distribution of canine and feline blastomycosis in the Canadian prairies

This retrospective study reports patient signalment, method of diagnosis and geographic distribution, and examines trends in prevalence and seasonal distribution of blastomycosis cases submitted to a veterinary diagnostic laboratory in Saskatchewan over a 21-year period. Of the 143 cases that originated from Saskatchewan and Manitoba 137 were from canine and 6 from feline patients. Signalment was similar to that previously reported. All cases originated in southern Saskatchewan and Manitoba, primarily from Regina, Moose Jaw, Swift Current, and Winnipeg. Case numbers showed a significant increase in the period 2001 to 2010 compared to 1990 to 2000. Seasonally, there was an increasing trend in the number of diagnoses from February to November. There was no correlation between average seasonal temperature or average seasonal total precipitation and the number of cases of blastomycosis. The persistence of blastomycosis in southern Saskatchewan indicates that Blastomyces dermatitidis is now endemic in this region.

Babesia odocoilei infection in a Saskatchewan elk (Cervus elaphus canadensis) herd

An 8-year-old female elk (Cervus elaphus canadensis) cow, presented for chronic severe weight loss and unthriftiness, was diagnosed with Babesia odocoilei infection based on blood smear evaluation, polymerase chain reaction (PCR), and DNA sequence analysis. Subsequently, velvet antler from a male that died acutely on the same farm was also PCR positive for Babesia spp. Both animals originated from a game ranch of Saskatchewan-bred and -raised animals with no known history of tick exposure, but with a history of numerous sudden deaths of unknown etiology. The presence of B. odocoilei in Canada might be a result of a recent introduction that could have deleterious effects on local wild ungulates or may represent discovery of a previously unrecognized endemic disease in local wildlife.

Utility of nuclear morphometry in the cytologic evaluation of canine cutaneous soft tissue sarcomas

Cytopathologists lack reliable criteria to distinguish neoplastic from reactive spindle cells; however, with computer-based nuclear morphometry, it is now possible to more objectively and precisely quantify differences between selected populations of cells. Forty-four cutaneous soft tissue sarcomas and 5 cases of reactive spindle cell proliferations in the dog were morphometrically analyzed with regard to median and standard deviation (SD) of nuclear area, diameter (max, min, mean), radius (max, min), perimeter, and roundness. Overall, nuclei from reactive spindle cells were larger, with greater variation in nuclear size and shape. Significant differences ( P < 0.05) were found for several nuclear parameters, including the median and SD of maximum diameter and radius, as well as the SD of roundness. No significant differences were found in nuclear parameters between soft tissue sarcomas divided by histologic grade, mitotic index, or tumor necrosis score. Analysis of the sources of variation indicated near-perfect intraobserver and substantial interobserver agreement. The largest source of variation was due to selection of different measurement fields, reflecting the inherent biological variation in nuclear size within the tumor cell population. The results indicate that nuclear morphometry on cytologic preparations is a reproducible method that may be able to differentiate cutaneous soft tissue sarcomas from reactive mesenchymal lesions in the dog. Further studies, including a larger number of cases, are warranted to assess repeatability of results.

Cytokeratin and vimentin co-expression in 21 canine primary pulmonary epithelial neoplasms

Co-expression of cytokeratin and vimentin has been traditionally associated with a few select tumors. However, this phenomenon is being recognized in a wider range of tumors. Twenty-one canine primary pulmonary epithelial neoplasms were evaluated for the co-expression of cytokeratin and vimentin. The histologic pattern and grade, and an immunohistochemical grade for cytokeratin and vimentin staining, were determined for each neoplasm. Adenocarcinomas predominated, and histologically, most tumors were grade II. All of the neoplasms stained positive for cytokeratin, while only 8 (38%) stained positive for both vimentin and cytokeratin. Papillary adenocarcinomas were consistently vimentin negative. The anaplastic histologic pattern had significantly more vimentin staining than the other histologic patterns. There was no significant difference in histologic grade or grading criteria between those tumors that stained with vimentin and those that did not. The present study established that cytokeratin and vimentin co-expression occurs in canine primary pulmonary epithelial tumors at a similar frequency to human pulmonary neoplasms. Further investigation will be needed to characterize the significance of this finding, particularly with respect to prognosis.

Use of a questionnaire to predict von Willebrand disease status and characterize hemorrhagic signs in a population of dogs and evaluation of a diagnostic profile to predict risk of bleeding

The objective of this study was to use a questionnaire 1) for characterization of hemorrhagic signs; 2) to assess its value as a predictor of von Willebrand Disease (vWD) status; and 3) for evaluation of the vWD diagnostic profile [platelet function analysis using the PFA-100, Collagen binding assay (vWF:CBA), and vWF antigen ELISA (vWF:Ag)], partial thromboplastin time (PTT) and Factor VIII activity (FVIII) as predictors of hemorrhagic risk. von Willebrand factor (vWF) concentration and function was assessed for each of the 165 canine participants using the vWD diagnostic profile. Hemorrhagic signs for each dog were obtained using a standardized questionnaire. Questionnaires were scored according to a previously prepared scoring key. Of the 165 dogs in the study, 43.6% had a low vWF concentration, with only 48.6% of dogs in this group having reports of hemorrhagic signs. Oral bleeding was the most commonly reported sign. The questionnaire had a sensitivity of 48.6% and a specificity of 78.5% for the prediction of vWD status. Using the Spearman correlation coefficient, a statistical association was found between the questionnaire and the vWD diagnostic profile components. However, this could not be translated into an ability to predict hemorrhage. The questionnaire allowed characterization of hemorrhagic signs in a large population of dogs over a range of vWF:Ag concentrations, and demonstrated that the vWD diagnostic profile was unsuccessful in the prediction of hemorrhagic risk. Although the sensitivity was insufficient for a screening tool, the questionnaire did have some discriminatory power in the prediction of vWD status.

Evaluation of laboratory methods to improve characterization of dogs with von Willebrand disease

The objective of the study was to investigate the value of additional tests [platelet count, partial thromboplastin time (PTT), platelet function analysis using the PFA-100, Collagen binding assay (vWF:CBA), and Factor VIII activity], for use in conjunction with the von Willebrand factor antigen enzyme-linked immunosorbent assay (ELISA), as part of a newly developed diagnostic profile for improved characterization of patients with von Willebrand disease (vWD). The study population included 183 clinically healthy canines ranging in vWF:Ag concentration from 1% to 125%. The Asserachrom vWF:Ag ELISA assay was used as an external control for the determination of vWD status. Degree of association between the additional tests and vWF concentration was evaluated, and associations between the additional tests were also assessed, including their ability to distinguish dogs with vWD from those without vWD. In addition, a reference interval was determined for the PFA-100 platelet function analyzer. Strong associations were found between the PFA-100, vWF:CBA, and Asserachrom vWF:Ag assay, and a significant association was found between the PFA-100 and vWF:CBA. An association was detected between Factor VIII activity and the Asserachrom vWF:Ag assay, the vWF:CBA and the PFA-100; however, a corresponding pattern was not visually apparent in the raw data, making the association clinically irrelevant. The association between the platelet count and the PTT with the other additional tests was negligible. Based on our results, the vWF:CBA and PFA-100 would be valuable assets, in conjunction with a vWF:Ag assay, in a canine vWD diagnostic profile to further characterize patients with this disease.

The impact of a week of simulated night work on sleep, circadian phase, and performance

AIMS

To investigate factors that may contribute to performance adaptation during permanent night work.

METHODS

Fifteen healthy subjects participated in an adaptation and baseline night sleep, directly followed by seven simulated eight-hour night shifts (2300 to 0700 hours). At the end of each shift they were taken outside and exposed to natural light for 20 minutes. They then slept from approximately 0800 hours until they naturally awoke.

RESULTS

There was a significant increase in mean performance on a visual psychomotor vigilance task across the week. Daytime sleep quality and quantity were not negatively affected. Total sleep time (TST) for each of the daytime sleeps was reduced, resulting in an average cumulative sleep debt of 3.53 hours prior to the final night shift. TST for each of the daytime sleep periods did not significantly differ from the baseline night, nor did TST significantly vary across the week. There was a significant decrease in wake time after sleep onset and sleep onset latency across the week; sleep efficiency showed a trend towards greater efficiency across the consecutive daytime sleeps. Hours of wakefulness prior to each simulated night shift significantly varied across the week. The melatonin profile significantly shifted across the week.

CONCLUSIONS

Results suggest that under optimal conditions, the sleep debt that accumulates during consecutive night shifts is relatively small and does not exacerbate decrements in night-time performance resulting from other factors. When sleep loss is minimised, adaptation of performance during consecutive night shifts can occur in conjunction with circadian adaptation.

Performance, sleep and circadian phase during a week of simulated night work

The current study investigated changes in night-time performance, daytime sleep, and circadian phase during a week of simulated shift work. Fifteen young subjects participated in an adaptation and baseline night sleep, directly followed by seven night shifts. Subjects slept from approximately 0800 hr until they naturally awoke. Polysomnographic data was collected for each sleep period. Saliva samples were collected at half hourly intervals, from 2000 hr to bedtime. Each night, performance was tested at hourly intervals. Analysis indicated that there was a significant increase in mean performance across the week. In general, sleep was not negatively affected. Rather, sleep quality appeared to improve across the week. However, total sleep time (TST) for each day sleep was slightly reduced from baseline, resulting in a small cumulative sleep debt of 3.53 (SD = 5.62) hours. Finally, the melatonin profile shifted across the week, resulting in a mean phase delay of 5.5 hours. These findings indicate that when sleep loss is minimized and a circadian phase shift occurs, adaptation of performance can occur during several consecutive night shifts.

Daytime cardiac autonomic activity during one week of continuous night shift

Shift workers encounter an increased risk of cardiovascular disease compared to their day working counterparts. To explore this phenomenon, the effects of one week of simulated night shift on cardiac sympathetic (SNS) and parasympathetic (PNS) activity were assessed. Ten (5m; 5f) healthy subjects aged 18-29 years attended an adaptation and baseline night before commencing one week of night shift (2300-0700 h). Sleep was recorded using a standard polysomnogram and circadian phase was tracked using salivary melatonin data. During sleep, heart rate (HR), cardiac PNS activity (RMSSD) and cardiac SNS activity (pre-ejection period) were recorded. Night shift did not influence seep quality, but reduced sleep duration by a mean of 52 +/- 29 min. One week of night shift evoked a small chronic sleep debt of 5 h 14 +/- 56 min and a cumulative circadian phase delay of 5 h +/- 14 min. Night shift had no significant effect on mean HR, but mean cardiac SNS activity during sleep was consistently higher and mean cardiac PNS activity during sleep declined gradually across the week. These results suggest that shiftwork has direct and unfavourable effects on cardiac autonomic activity and that this might be one mechanism via which shiftwork increases the risk of cardiovascular disease. It is postulated that sleep loss could be one mediator of the association between shiftwork and cardiovascular health.

The effects of day-time exogenous melatonin administration on cardiac autonomic activity

Melatonin has a functional role in the nocturnal regulation of sleep and thermoregulation. In addition to its action on peripheral receptors, melatonin may act by altering autonomic activity. To determine the effect of melatonin on cardiac autonomic activity, 5 mg of melatonin or placebo was orally administered to 12 young subjects at 14:00 hr, in a repeated measures design. Melatonin decreased sleep onset latency to Stage 2 sleep by 4.92+/-1.81 min (measured by Multiple Sleep Latency Tests), rectal temperature by 0.19+/-0.05 degrees C, and increased foot temperature by 0.74+/-0.45 degrees C (all P<0.05). Melatonin decreased heart rate by 3.66+/-1.68 beats/min (P<0.05) and pre-ejection period (measure of cardiac sympathetic activity) by 16.48+/-4.28 ms (P<0.05), but had no effect on respiratory sinus arrhythmia (measure of cardiac parasympathetic activity) (P>0.05). As the decrease in pre-ejection period is likely to have resulted from a decrease in blood pressure, these results do not confirm an effect of melatonin on cardiac sympathetic activity. However, the results do clearly indicate that melatonin is unlikely to drive the previously observed presleep increase in cardiac parasympathetic activity.

Effects of bright light and melatonin on sleep propensity, temperature, and cardiac activity at night

Melatonin increases sleepiness, decreases core temperature, and increases peripheral temperature in humans. Melatonin may produce these effects by activating peripheral receptors or altering autonomic activity. The latter hypothesis was investigated in 16 supine subjects. Three conditions were created by using bright light and exogenous melatonin: normal endogenous, suppressed, and pharmacological melatonin levels. Data during wakefulness from 1.5 h before to 2.5 h after each subject's estimated melatonin onset (wake time + 14 h) were analyzed. Respiratory sinus arrhythmia (cardiac parasympathetic activity) and preejection period (cardiac sympathetic activity) did not vary among conditions. Pharmacological melatonin levels significantly decreased systolic blood pressure [5.75 +/- 1.65 (SE) mmHg] but did not significantly change heart rate. Suppressed melatonin significantly increased rectal temperature (0.27 +/- 0.06 degrees C), decreased foot temperature (1.98 +/- 0.70 degrees C), and increased sleep onset latency (5.53 +/- 1.87 min). Thus melatonin does not significantly alter cardiac autonomic activity and instead may bind to peripheral receptors in the vasculature and heart. Furthermore, increases in cardiac parasympathetic activity before normal nighttime sleep cannot be attributed to the concomitant increase in endogenous melatonin.

The relationship between slow-wave activity, body temperature, and cardiac activity during nighttime sleep

STUDY OBJECTIVES

Recent work indicates that cardiac sympathetic activity is not influenced by the circadian system and instead decreases after sleep onset. However, little is known about the pattern of change in cardiac sympathetic activity during NREM/REM sleep cycles and whether this is associated with alterations in slow-wave activity (SWA). To address these questions, we examined SWA, cardiac sympathetic activity, heart rate and rectal and foot temperatures during the first three NREM/REM sleep cycles and during transitions between NREM and REM sleep.

DESIGN

Subjects were required to maintain a constant sleep-wake cycle for at least a week and have at least one adaptation night, before their night of recording.

SETTING

Individual temperature controlled bedrooms.

PARTICIPANTS

10 young healthy males and females.

INTERVENTIONS

NA.

MEASUREMENTS AND RESULTS

All variables showed the greatest change in the first NREM cycle. Specifically, SWA, sympathetic activity, heart rate and foot temperature increased while rectal temperature decreased. After the initial increase, cardiac sympathetic activity decreased across the sleep phase, in association with a decrease in heart rate. Cardiac sympathetic activity did not significantly alter across NREM-REM cycles.

CONCLUSIONS

The results suggest that increases in heart rate and cardiac sympathetic activity early in the sleep period are, in part, a compensatory reaction to the concomitant thermoregulatory changes observed. These results also indicate that the effect of time asleep on cardiac sympathetic activity may be greater than the influence of sleep cycles. These results are discussed with reference to the recuperative value of naps.

Attenuation of sleep propensity, core hypothermia, and peripheral heat loss after temazepam tolerance

If changes in thermoregulation mediate sleepiness induced by sedative/hypnotics, then a reduction in the soporific efficacy (tolerance) of these agents may be accompanied by a concomitant reduction in their thermoregulatory effects. We compared the thermoregulatory and soporific effects of acute temazepam (30 mg at 1400) in 11 young male subjects before and immediately after 7 consecutive days of temazepam (30 mg). Subjects lay supine (0800-2030), while foot (T(ft)) and rectal (T(c)) temperatures were recorded. Sleep onset latency (SOL) was measured hourly using 20-min multiple sleep latency tests. Relative to placebo, temazepam significantly reduced both T(c) and SOL (-0.31 degrees C and 14.1 min) while increasing T(ft) (3.39 degrees C). A significant tolerance developed after the week of temazepam, with a mean reduction in soporific efficacy of 4.0 +/- 0.8 min. This was accompanied by a concomitant attenuation in both T(c) (-0.16 degrees C) and T(ft) (1.44 degrees C). Furthermore, SOL was temporally related to T(ft) and the maximum rate of decline in T(c) before and after tolerance. Together, these results indicate that the thermoregulatory system may be functionally involved in the regulation of sleepiness.

Serotonin-2 receptors and human sleep: effect of a selective antagonist on EEG power spectra

To investigate the effect on the sleep EEG, a 1-mg oral dose of SR 46349B, a novel 5-HT2 antagonist, was administered three hours before bedtime. The drug enhanced slow wave sleep (SWS) and reduced stage 2 without affecting subjective sleep quality. In nonREM sleep (NREMS) EEG slow-wave activity (SWA; power within 0.75-4.5 Hz) was increased and spindle frequency activity (SFA; power within 12.25-15 Hz) was decreased. The relative NREMS power spectrum showed a bimodal pattern with the main peak at 1.5 Hz and a secondary peak at 6 Hz. A regional analysis based on bipolar derivations along the antero-posterior axis revealed significant 'treatment' x 'derivation' interactions within the 9-16 Hz range. In enhancing SWA and attenuating SFA, the 5-HT2 receptor antagonist mimicked the effect of sleep deprivation, whereas the pattern of the NREMS spectrum differed.

Cardiac autonomic nervous system activity during presleep wakefulness and stage 2 NREM sleep

Previous research has found that cardiac parasympathetic nervous system (PNS) activity increases and cardiac sympathetic nervous system (SNS) activity decreases during night-time sleep. This study aimed to examine in greater detail the time course of these changes in cardiac autonomic nervous system (ANS) activity. In the week prior to the experimental night, nine subjects maintained a constant sleep-wake schedule and experienced an adaptation night. Each subject's experimental night consisted of 2 h of presleep wakefulness, followed by a night of sleep, commencing at each subject's normal sleep onset time. One hundred and twenty beat blocks of presleep wakefulness and stable Stage 2 non-rapid eye movement (NREM) sleep across the night were selected. SNS activity was assessed using pre-ejection period, the amplitude of the T-wave in the ECG and the 0.1 Hz peak from the spectral analysis of the ECG. PNS activity was assessed using respiratory sinus arrhythmia (spectral analysis). Heart rate and respiratory rate were also measured. The results indicated a progressive decrease in SNS activity throughout sleep and a rise in PNS activity during the first half of the normal sleep period. The changes in PNS activity were similar, while the changes in SNS activity were altered, compared with a previous study in which stage of sleep was not controlled. This indicates a likely sleep stage influence on SNS activity, but not on cardiac PNS activity. These results are consistent with the concept of a primarily circadian, but not sleep, influence on PNS activity, and primarily a sleep, but not circadian, influence on SNS activity.

Cardiac activity during sleep onset

Alterations in a number of measures of cardiac activity were examined during sleep onset in 6 participants over 3 experimental nights. Each sleep onset was divided into four consecutive phases: wakefulness, mixed alpha and theta activity, stage 2 NREM sleep with arousals, and stable stage 2 sleep. The variables measured were heart rate (HR), respiratory sinus arrhythmia (RSA), pre-ejection period (PEP) and T-wave amplitude (TWA). Respiration rate (RR) was also measured. HR and RR were lower in stable Stage 2 sleep compared with wakefulness, whereas PEP, TWA and RSA did not change significantly. During the second and third phases of sleep onset, HR decreased at each transition into sleep and increased following each spontaneous arousal. This increase resolved rapidly, with a return to sleep levels by 12 beats after the arousal. HR changes are discussed with reference to RSA, PEP, TWA and the concept of a waking reflex.

Sleep and circadian influences on cardiac autonomic nervous system activity

To assess the separate contributions of the sleep and circadian systems to changes in cardiac autonomic nervous system (ANS) activity, 12 supine subjects participated in two 26-h constant routines, which were counterbalanced and separated by 1 wk. One routine did not permit sleep, whereas the second allowed the subjects to sleep during their normal sleep phase. Parasympathetic nervous system activity was assessed with respiratory sinus arrhythmia as measured from the spectral analysis of cardiac beat-to-beat intervals. Sympathetic nervous system activity was primarily assessed with the preejection period as estimated from impedance cardiography, although the 0.1-Hz peak from the spectral analysis of cardiac beat-to-beat intervals, the amplitude of the T wave in the electrocardiogram, and heart rate were also measured. Respiratory sinus arrhythymia showed a 24-h rhythm independent of sleep, whereas preejection period only showed a 24-h rhythm if sleep occurred. Thus the findings indicate that parasympathetic nervous system activity is mostly influenced by the circadian system, whereas sympathetic nervous system activity is mostly influenced by the sleep system.

Cardiac parasympathetic nervous system activity does not increase in anticipation of sleep

Parasympathetic Nervous System (PNS) activity increases while Sympathetic Nervous System (SNS) activity remains relatively stable from wakefulness to NREM sleep. However, it is not clear whether these changes are specifically associated with NREM sleep, or whether they anticipate sleep onset. The latter may occur if ANS activity was influenced by the circadian system. This issue was investigated by conducting spectral analysis of heart beat-to-beat intervals (Periodogram method), collected from 20 healthy male and female subjects at three different times across 24 h; in the morning, just prior to normal sleep onset time, and in slow-wave sleep (SWS). Subjects were supine in all conditions and awake in the first two conditions. The high- and low-frequency peaks, reflecting PNS and SNS activity, respectively, were expressed as proportions of the total power. PNS activity decreased significantly from the morning (0.22) to the presleep period (0.19), before it increased to its maximum during SWS (0.33). In contrast, SNS activity was similar in each of the three conditions (0.07, 0.06, and 0.05 for morning, presleep and SWS, respectively). Thus there do not appear to be changes in PNS activity in anticipation of sleep, as would be predicted on the basis of a circadian influence on the PNS. Instead the increased PNS activity appears to be sleep dependent.

A field worker's guide to a nutritional status survey

This guide has been prepared specifically for the medical worker in a developing country who has little experience for survey methodology and few outside sources on which to draw. All, or only portions of the guide, may be used as local needs dictate. It provides an outline of necessary preparations, sampling, field organization, measuring techniques and recording form. To aid the statistical treatment and presentation of the data, a sample recording form is given together with coding instructions and output table layout.