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Biomedical subjects

D L Evans

Publications and source records attributed to D L Evans.

At least 55 records · Page 3Linked to original sources
PubMed2000

Nonradiometric detection of cytotoxicity of teleost nonspecific cytotoxic cells.

The development of a sensitive, rapid and reliable nonradiometric cytotoxicity assay would significantly facilitate studies of teleost nonspecific cytotoxic cells. Such an assay would not require handling and disposal of radionuclides and it would not depend on secondary enzyme or colorimetric determinations. The requirements for this assay would consist of a one-step binding protocol which could detect early target cell membrane lesions and at very low effector:target cell ratios. In this chapter, we have developed a flow cytometry based cytotoxicity assay utilizing the uptake of propidium iodide (PI) into cells containing damaged (i.e. permeabilized) cell membranes. The basis of detection of cellular damage depended on flow discrimination of targets from effector cells by establishing 'scatter' gates from these mixtures. Teleost (catfish) anterior kidney NCC were mixed with human transformed targets (IM-9 and HL-60 cells) at effector:target cell ratios of 1, 5 and 10 and PI uptake was determined at 3 and 14 hours post-incubation. Percent specific uptake (PSU) was calculated by determining total binding capacity (TBC) (i.e. uptake of PI by cold acetone permeabilized target cells) and spontaneous binding capacity (SBC) (i.e. PI uptake by target cells incubated in media w/o effectors). This was represented by the formula PSU = [T - SBC/TBC - SBC] x 100 where T is the PI uptake of targets following addition of effector cells. Using this technique, NCC initiated target cell permeabilization as early as 30 minutes co-incubation (25:1 E:T ratio) and damaged membranes were detected in mixtures containing as few as 1:1 effector:target cell ratios. At 5:1 E:T ratios, greater than 50 PSU was determined following 14 hours co-incubation. Using these criteria, a new and sensitive cytotoxicity assay has been developed to determine NCC activity.

Animals↗
PubMed2000

High versus low basal cortisol secretion in asymptomatic, medication-free HIV-infected men: differential effects of severe life stress on parameters of immune status.

The authors hypothesized that HIV-infected men with high basal cortisol secretion would exhibit greater stress-related reductions in the ratio of Th1/Th2 cell-derived cytokines and numbers of CD8+ T and NK lymphocytes than low basal cortisol secretors. A semistructured interview was used to assess life stress during the preceding 6 months of 94 HIV-infected men classified as high and low cortisol secretors (n = 47/group). Increased levels of severe life stress were highly correlated with lower numbers of CD8+ T cells, CD16+ and CD56+ NK cells, CD57+ cells, and higher DHEA-S concentrations in the high cortisol group. Conversely, no significant correlations were found in the low cortisol group. No correlations were found between stress and CD4+ T helper/inducer cell counts, cytokine production, or testosterone levels in either participating group. These data suggest that severe stress in combination with high glucocorticoid activity may modify select parameters of immune status in HIV-infected men.

Adaptation, Psychological↗
PubMed2000

Clinical abnormalities detected in post-race examinations of poorly performing Standardbreds.

OBJECTIVE: To describe the clinical abnormalities found on post-race examination of poorly performing Standardbreds. METHOD: The results of 541 post-race veterinary examinations on Standardbreds were analysed. The horses were selected for examination by the stipendiary stewards on the basis of poor performance from a population of approximately 20,000 runners which competed at Harold Park Paceway, Sydney. RESULTS: Clinical abnormalities were detected on post-race examination in 264 of the 541 poorly performing horses. Some horses displayed more than one abnormality. Twenty three individual abnormalities were reported. Seventy three horses had suffered interference-type injuries (cross firing, scalping, over reaching) during the race. Lameness was the second most commonly found abnormality (n = 60), with 73% of these lamenesses being in a forelimb. Twenty nine horses had sacroiliac pain (representing 10.6% of the abnormalities detected). Poor recovery, exercise induced pulmonary haemorrhage, respiratory infection or nasal discharge, gluteal pain, unilateral nasal haemorrhage and mouth injuries complete the list of the ten most common findings. CONCLUSION: Interference-type injuries, lameness and sacroiliac pain were the most common abnormalities found on post-race examination of Standardbreds, which performed poorly.

Animals↗
PubMed2000

Treadmill exercise training blunts suppression of splenic natural killer cell cytolysis after footshock.

This study extended to treadmill exercise training our prior report (Dishman RK, Warren JM, Youngstedt SD, Yoo H, Bunnell BN, Mougey EH, Meyerhoff JL, Jaso-Friedmann L, and Evans DL. J Appl Physiol 78: 1547-1554, 1995) that activity wheel running abolished the suppression of footshock-induced natural killer (NK) cell cytolysis. Twenty-four male Fischer 344 rats were assigned to one of three groups (n = 8, all groups): 1) a home-cage control group, 2) a sedentary treatment group, or 3) a treadmill-running group (0 degrees incline, 25 m/min, 35 min/day, 6 days/wk). After 6 wk, the treadmill and sedentary groups received 2 days of footshock. Splenic NK cytotoxicity was determined by standard 4-h (51)Cr release assay. Percentages of lymphocytes were determined by flow cytometry. Plasma levels of ACTH, corticosterone, and prolactin concentration were measured by radioimmunoassay. After footshock, percentage of lysis relative to home-cage controls was 40% and 80% for sedentary and treadmill-trained animals, respectively (P < 0.05). Our results indicate that the protective effect of chronic exercise on innate cellular immunity in the Fischer 344 male rat is not restricted to activity wheel running, nor is it explained by elevations in basal NK activity, increased percentages of splenic NK and cytotoxic T cells, or increased plasma levels of ACTH, corticosterone, and prolactin.

Adrenocorticotropic Hormone↗
PubMed2000

Impact of stressful life events, depression, social support, coping, and cortisol on progression to AIDS.

OBJECTIVE: This study examined prospectively the effects of stressful events, depressive symptoms, social support, coping methods, and cortisol levels on progression of HIV-1 infection. METHOD: Eighty-two homosexual men with HIV type-1 infection without AIDS or symptoms at baseline were studied every 6 months for up to 7. 5 years. Men were recruited from rural and urban areas in North Carolina, and none was using antiretroviral medications at entry. Disease progression was defined as CD4(+) lymphocyte count <200/microl or the presence of an AIDS indicator condition. RESULTS: Cox regression models with time-dependent covariates were used adjusting for race, baseline CD4(+) count and viral load, and cumulative average antiretroviral medications. Faster progression to AIDS was associated with higher cumulative average stressful life events, coping by means of denial, and higher serum cortisol as well as with lower cumulative average satisfaction with social support. Other background (e.g., age, education) and health habit variables (e.g., tobacco use, risky sexual behavior) did not significantly predict disease progression. The risk of AIDS was approximately doubled for every 1.5-unit decrease in cumulative average support satisfaction and for every cumulative average increase of one severe stressor, one unit of denial, and 5 mg/dl of cortisol. CONCLUSIONS: Further research is needed to determine if treatments based on these findings might alter the clinical course of HIV-1 infection.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Bipolar disorder: diagnostic challenges and treatment considerations.

A review of the criteria for the diagnosis of bipolar disorder identifies a number of complicating factors that historically have interfered with the accurate and precise diagnosis of patients. Patients with different subtypes of the disorder sometimes present with different symptoms, and the careful diagnostician must be aware of them. These include comorbidity of bipolar disorder and attention-deficit/hyperactivity disorder, comorbidity of bipolar disorder and substance abuse, and mania secondary to prescription drugs or physical illness, particularly in the elderly. As a result of these factors and others. bipolar disorder is significantly underdiagnosed. Accurate and precise diagnosis has a direct impact on the choice of treatment and will be easier for those clinicians who are aware of the several subtypes of mania and depression and are familiar with the relevant Expert Consensus Guidelines for treatment.

Acute Disease↗
PubMed2000

Wrestling mats: are they a source of ringworm infections?

OBJECTIVE: To determine if the fungal molds (dermatophytes) responsible for causing ringworm could be isolated from a section of wrestling mat during the 1998-1999 season. DESIGN AND SETTING: A 2-part study was conducted. The first phase involved a culture evaluation of material taken from wrestling mats at 8 local high schools. The second phase was a bench laboratory study to determine if the fungus and molds could be grown from a wrestling mat in an optimal setting. SUBJECTS: We obtained material from areas of the practice mats of 8 high school wrestling teams at monthly intervals during the wrestling season. A 0.61-m (2-ft)x 0.31-m (1-ft) area of mat from 1 of the schools was used for the laboratory phase of the study. MEASUREMENTS: We cultured samples taken from each school's wrestling mats for growth of dermatophytes and used a questionnaire to determine the mat-washing habits and policies of each school. Also, wrestlers from the 8 schools were screened weekly by the designated team physician and certified athletic trainer. Any suspicious lesions were cultured for fungi. RESULTS: No dermatophytes were grown from the swab specimens taken at the 8 schools, and no dermatophytes were isolated from a section of mat evaluated in optimal laboratory conditions. CONCLUSIONS: It is unlikely that wrestling mats are a source of ringworm infections in wrestlers.

Journal Article↗
PubMed1999

Apoptotic effect of outer-membrane proteins from Campylobacter jejuni on chicken lymphocytes.

Campylobacter jejuni is a significant cause of food-borne diseases in humans. The bacterium is considered a commensal organism in chickens, and it can heavily colonize chickens without causing inflammation. Poultry may be the major reservoir for the human infection in developed countries. Here we show that an outer-membrane protein extract prepared from the bacteria caused apoptosis of chicken lymphocytes detected in vitro with the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling assay that preferentially labels individual apoptotic cells. Blood- and spleen-lymphocytes from different-aged chickens displayed a significantly greater percentage of apoptotic cells after culture with the outer-membrane proteins from C. jejuni than controls treated with phosphate-buffered saline, chicken ovalbumin, or outer-membrane proteins prepared from E. coli strain BL21. The C. jejuni extract also produced apoptosis of chicken lymphoblastoid tumor cell lines. Apoptosis was blocked by pretreating the extract with proteinase K or antiserum against outer-membrane proteins. The results suggest that C. jejuni may be capable of achieving immune avoidance in chickens by causing apoptosis of lymphocytes.

Age Factors↗
PubMed1999

Plasma cortisol and beta-endorphin concentrations in trained and over-trained standardbred racehorses.

The effects of training and over-training on plasma cortisol and beta-endorphin (betaEP) concentrations at rest and after standardised exercise tests and the cortisol responses to adrenocorticotropin (ACTH) administration were investigated in standardbred horses. Twelve horses were divided randomly into control and over-trained (OT) groups after 17 weeks slow- and moderate-intensity treadmill training. The standardised treadmill exercise test consisted of 2 min at velocities corresponding to 30, 50, 70 and 100% of maximum O2 consumption. Over-training, defined as a significant decrease in body weight and treadmill run-time-to-fatigue in an incremental velocity test, occurred in the OT group after 32 weeks of training exercise. Peak cortisol concentrations after exercise decreased significantly in the OT group from 320+/-15.6 at week 8 to 245+/-17.0 nmol l(-1) at week 32, and mean cortisol concentrations over a 120-min period after exercise decreased from 258+/-11.7 to 192+/-16.6 nmol l(-1) (P<0.05). Mean and total cortisol and betaEP concentrations in resting horses were not significantly different after over-training. Peak cortisol concentrations after adrenocorticotropin (ACTH) administration were not significantly different in the over-trained group. Dysfunction of the hypothalamo-pituitary-adrenocortical axis occurs in over-trained horses, but this adaptation is not associated with a change in the adrenocortical responsiveness to ACTH.

Adrenal Glands↗
PubMed1999

An antigen receptor (NCCRP-1) on nonspecific cytotoxic cells is a phosphoprotein associated with the JAK-STAT activation pathway.

The antigen receptor (nonspecific cytotoxic cell receptor protein-1/NCCRP-1) on nonspecific cytotoxic cells (NCC) is a 32-kDa predicted Type III membrane protein. The N-terminal cytoplasmic portion of this receptor contains full length and truncated BOX-1 motifs. These motifs are also found on cytokine, erythropoietin and growth hormone receptors and provide docking sites for JAK kinases. In the present study, we investigated a relationship between NCCRP-1 and JAK2 kinase binding. A possible association with further downstream STAT activation was suggested. NCCRP-1 was phosphorylated on C-terminal domain serine residues. To examine the possibility that NCCRP-1 was associated with JAK kinase(s), NCC were purified and lysates were probed by Westen blotting (WB) for the presence of JAK2 kinase. Unlike their mammalian counterparts, NCC JAK2 kinase existed as a 90-95-kDa primary and a 35-40-kDa secondary breakdown product. Both mol wt. forms were significantly smaller than those reported for human JAK kinases. To determine if NCCRP-1 was physically associated with JAK2 kinase, chemical cross-linking experiments were conducted. NCC membrane preparations were treated with the chemical cross-linker DSS, solubilised and immunoprecipitated with anti-NCCRP-1 (e.g., 32 kDa) mab 5C6. WB analysis using anti-JAK2 mab and mab 5C6 demonstrated that the immunoprecipitate contained both the 32-kDa NCCRP-1 and 85-90-kDa JAK2 kinase. To examine further the possibility that STAT proteins may be associated with NCC/NCCRP-1 activation, NCC lysates were probed (WB) with various anti-STAT mabs. The strongest signal was produced by a 100-kDa STAT-6 protein. Lysates were negative for STAT-1, STAT-3 and STAT-5. These data indicate that the N-terminus of NCCRP-1 may initiate cytokine gene transcription by the JAK-STAT signalling pathway.

Animals↗
PubMed1999

Sonographic observations of the peripheral vasculature of the equine thoracic limb.

Investigations of the equine peripheral vascular system have been constrained by the lack of a non-invasive method of examining the arteries and veins of the limbs of the conscious horse. Precise correlations were established between the gross anatomical features of the peripheral vessels and their B-mode sonographic appearance in each thoracic limb of 35 horses. A sonographic imaging protocol was established. Additional Doppler sonographic recordings defined the arterial waveforms and demonstrated that blood flow to the foot could be evaluated in the lateral proper digital artery, distal to the level of the coronary band. Valves (with 2-4 cusps) were identified in the lumina of the medial and lateral palmar common digital veins and those of the medial and lateral palmar proper digital veins. Spontaneous echo contrast, a smoke-like haze of echoic blood, was seen in the lateral and medial palmar common digital veins, the distal deep palmar venous arch and communicating branches, and the palmar proper digital veins, and occasionally seen in the distal deep palmar arterial arch and distal proper palmar digital arteries. The value of duplex sonography (B-mode and Doppler) for anatomical and physiological studies of the peripheral vasculature of the horse was clearly established. Such data could be applied to the investigation of diseases affecting the peripheral circulation.

Animals↗
PubMed1999

Blood gas changes during incremental and sprint exercise.

We investigated and compared arterial blood gas and ventilatory changes during rapid acceleration sprint and during incremental treadmill exercise. Seven clinically normal racehorses completed standardised incremental exercise tests and rapid acceleration tests at speeds calculated to elicit 115% VO2max. Arterial oxygen tension decreased (P < 0.001) between 15 s (mean +/- s.d. 103.8 +/- 14.3 mmHg) and 30 s (85.0 +/- 7.7 mmHg) after the onset of rapid acceleration exercise, but did not change significantly during the remainder of the sprint. This was accompanied by an increase in PaCO2 of 5.9 mmHg (P < 0.05). Despite reductions in SaO2 during exercise, CaO2 did not change due to increases in haemoglobin concentration. Heart rate increased rapidly (P < 0.001) during the first 15 s of exercise and thereafter remained constant. The mean maximum speed during the incremental test (11.4 +/- 0.5 m/s) was not significantly different to the speed calculated to elicit 115% VO2max during the sprint test (12.2 +/- 0.8 m/s). The mean peak HR and Hb during the sprint test were significantly less than during the incremental test. However, there were no significant differences in the maximum or minimum values achieved for other variables. We conclude that rapid acceleration exercise is accompanied by rapid changes in blood gas variables, reaching steady state within 45 s. Blood gas responses during the simpler incremental test describe maximal changes during high-intensity sprint exercise.

Animals↗
PubMed1999

Effects of low- and moderate-intensity training on metabolic responses to exercise in thoroughbreds.

This experiment was undertaken to determine whether there were differences in cardiorespiratory, haematological and muscular responses in horses trained at either low or moderate intensities. Ten Thoroughbred horses previously rested in paddocks for 4 months were trained 5 days/week for 9 weeks. Horses were allocated randomly into fast or slow groups and exercised the same distance each day. Training distances were 1600 m in Weeks 0 and 1 up to 4000 m in Week 9. The fast group were trained at an intensity inducing a post training blood lactate of 4-8 mmol/l. This intensity was determined for each horse each week. The slow group trained at half the speed of the fast group (blood lactate < 2 mmol/l). Horses performed a standardised exercise test prior to (Week 0) and on Weeks 1, 2, 3, 4, 7 and 9 of training. HR, VO2, VCO2 and blood lactate concentration were recorded during the last 15 s of each step. Blood samples were collected at the end of each test for determination of red cell and plasma volume. Muscle biopsies were collected from the middle gluteal muscle before training and after 4 and 9 weeks training. Training intensity had few effects on the majority of variables measured and results for both groups are combined unless otherwise stated. Bodyweight was unaffected by training. Economy of locomotion decreased from 12.0 +/- 0.4 ml/kg bwt/m prior to training to 13.8 +/- 0.6 ml/kg bwt/m at the end of training in the fast group. Run time to fatigue was not affected by training intensity. VO2max increased from 120.3 +/- 4.8 to 144.7 +/- 3.5 ml/kg bwt/min with a significant correlation between run time and VO2max. Peak HR was 221.4 +/- 2.5 beats/min prior to training and 226.5 +/- 1.7 beats/min after the first 4 weeks of training. V200 and VLa4 increased in response to training. Similarly, VLa4 increased from 7.0 +/- 0.5 to 9.2 +/- 0.2 m/s with VLa4 correlated to VO2max. Plasma volume decreased from 29.1 +/- 1.7 to 25.8 +/- 0.9 l during the last 3 weeks of training. Blood volume, red cell volume and/or red cell volume/kg were unaffected by intensity or duration of training. The activity of CS in muscle increased in the first 5 weeks of training whereas HAD activity was not affected by intensity or duration of training.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1999

Maximal exercise transiently disrupts hormonal secretory patterns in standardbred geldings.

Basal concentrations of cortisol (CORT), beta-endorphin (beta EP), growth hormone (GH) and testosterone (T) and their disruption during 32 h of recovery after treadmill exercise were investigated in 4 geldings. Blood samples were collected from resting horses every 20 min between 0600-1000 and 1500-1900 h, and hourly between 1000-1500 h on 3 consecutive days. Treadmill exercise tests comprising 2 min intervals at 30, 50, and 70% VO2max then to fatigue at 100% VO2max were conducted between 1020-1130 h on Day 2. Blood was collected before, during and 15, 30, 60 and 90 min after exercise. Mean (Cav), peak (Cmax) and total (i.e. integrated) (Ctot) concentrations were calculated for CORT, beta EP and GH during the 20 min sampling sessions, and for CORT, beta EP, GH and T between 1000-1300 h on Days 1-3 (incorporating the samples during exercise on Day 2) and 1300-1900 h on Days 1-3. Cav, Cmax and Ctot for CORT, beta EP, GH and T were greater during exercise and recovery than in the same period on Day 1. Cav and Ctot values for plasma T during the 1300-1900 h period were significantly elevated on Day 2 and compared to Day 1 (P < 0.05), but there were no differences between Days 1 and 3 values for these variables. We concluded that plasma T concentration increases in response to maximal exercise in geldings, as does plasma CORT, beta EP and GH. Furthermore, maximal exercise disrupts basal plasma concentrations of CORT, beta EP and GH for up to 24 h and T for 26-32 h post exercise in geldings, therefore reflecting the minimum recovery periods required before evaluating normal, resting levels of these hormones in horses undergoing training.

Animals↗
PubMed1999

Haematological and biochemical responses to training and overtraining.

We sought a physiological marker of overtraining in horses, using commonly practised field and laboratory tests to allow early prediction and treatment of the syndrome. Thirteen Standardbred horses were trained as follows: phase 1 (endurance, 7 weeks), phase 2 (high intensity, 9 weeks) and phase 3 (overload, 18 weeks). In phase 3 the horses were divided into 2 groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies and durations than the C group. Overtraining occurred after 31 weeks and was defined as a significant decrease in treadmill run time to fatigue (RT) in response to a standardised exercise test (SET). Variables measured included: feed intake, bodyweight (BWT), resting haematology and plasma biochemistry and treadmill SETs to measure RT. The OLT group had a decrease in BWT after week 28 (P < 0.05) without a reduction in feed intake and a reduction in RT during the SET after 31 weeks. Signs persisted after 2 weeks of a reduced training load confirming overtraining. Haematology and biochemistry failed to detect any markers of overtraining. Although no physiological markers of overtraining were identified, empirical observations revealed that the behaviour of horses in the OLT group was different from those in the C group during the period of overtraining. This study reflects that a model of overtraining has been developed based on measurement of a reduction in performance; however, there were no consistent changes in haematology or serum biochemical values in association with the decrement in performance capacity.

Animals↗