Clinical predictors of donor antibody titre and correlation with recipient antibody response in a COVID-19 convalescent plasma clinical trial

BACKGROUND

Convalescent plasma therapy for COVID-19 relies on transfer of anti-viral antibody from donors to recipients via plasma transfusion. The relationship between clinical characteristics and antibody response to COVID-19 is not well defined. We investigated predictors of convalescent antibody production and quantified recipient antibody response in a convalescent plasma therapy clinical trial.

METHODS

Multivariable analysis of clinical and serological parameters in 103 confirmed COVID-19 convalescent plasma donors 28 days or more following symptom resolution was performed. Mixed-effects regression models with piecewise linear trends were used to characterize serial antibody responses in 10 convalescent plasma recipients with severe COVID-19.

RESULTS

Donor antibody titres ranged from 0 to 1 : 3892 (anti-receptor binding domain (RBD)) and 0 to 1 : 3289 (anti-spike). Higher anti-RBD and anti-spike titres were associated with increased age, hospitalization for COVID-19, fever and absence of myalgia (all P < 0.05). Fatigue was significantly associated with anti-RBD (P = 0.03). In pairwise comparison amongst ABO blood types, AB donors had higher anti-RBD and anti-spike than O donors (P < 0.05). No toxicity was associated with plasma transfusion. Non-ECMO recipient anti-RBD antibody titre increased on average 31% per day during the first three days post-transfusion (P = 0.01) and anti-spike antibody titre by 40.3% (P = 0.02).

CONCLUSION

Advanced age, fever, absence of myalgia, fatigue, blood type and hospitalization were associated with higher convalescent antibody titre to COVID-19. Despite variability in donor titre, 80% of convalescent plasma recipients showed significant increase in antibody levels post-transfusion. A more complete understanding of the dose-response effect of plasma transfusion amongst COVID-19-infected patients is needed.

Impact of patient decision aids on appropriate and timely access to hip or knee arthroplasty for osteoarthritis: a randomized controlled trial

OBJECTIVE

To evaluate the effectiveness of patient decision aids (PtDA) compared to usual education on appropriate and timely access to total joint arthroplasty in patients with osteoarthritis.

METHOD

A randomized controlled trial (RCT) with patients undergoing orthopedic screening. Control and intervention arms received usual education; intervention arm also received a PtDA and a surgeon preference report. Wait times (primary outcome) were described using stratified Kaplan-Meier survival curves with patients censored at the time of death or loss to follow-up, and multivariable Cox proportional hazards regression. Secondary outcomes were compared using stratified Cochran-Mantel-Haenszel chi-squared tests.

RESULTS

343 patients were randomized to intervention (n = 174) or control (n = 169). The typical patient was 66 years old, retired, living with someone, and 51% had high school education or less. The intervention was associated with a trend towards reduction in wait time (hazard ratio (HR) 1.25, 95% confidence interval (CI) 0.99-1.60, P = 0.0653). Median wait times were 3 weeks shorter in intervention than in control at the community site with no difference at the academic site. Good decision quality was reached by 56.1% intervention and 44.5% control (Relative risk (RR) 1.25; 95% CI 1.00-1.56, P = 0.050). Surgery rates were 73.2% intervention and 80.5% controls (RR 0.91: 95% CI 0.81-1.03) with 12 intervention (7.3%) and eight control participants (4.9%) returning to have surgery within 2 years (P = 0.791).

CONCLUSION

Compared to controls, decision aid recipients had shorter wait times at one site, fewer surgeries, and were more likely to reach good decision quality, but overall effect was not statistically significant.

TRIALS REGISTRATION

The full trial protocol is available at ClinicalTrials.Gov (NCT00911638).

Volumetric and Diffusion Properties of Water/Surfactant/n-Propanol/4-Allylanisole Micellar Systems

Sol-gel encaged [(C8H17)3NCH3][RhCl4] catalyses the double bond isomerization in the flavoring agent 4-allylanisole in aqueous microemulsions. In order to provide optimal composition of the reaction medium water/n-propanol/surfactant/4-allylanisole micellar systems were formulated. The surfactants were sodium dodecyl sulfate, cetyltrimethylammonium bromide, sucrose monolaurate, and polyethylene glycol (7) glyceryl cocoate. The ratio (w/w) of n-propanol/surfactant equals 2/1. The extent of the microemulsions region as function of temperature was determined. The micellar systems were characterized by the volumetric parameters, density, excess volume, ultrasonic velocity and isentropic compressibility. The micellar densities increase with the increase in the water volume fraction. Ultrasonic velocities increase with the increase in water volume fraction up to 0.8 then decrease. Ultrasonic velocities increase with temperature for water volume fractions below 0.8 and decrease for water volume fractions above 0.8. Quantitative analysis of the volumetric parameters enabled the characterization of structural transition along the micellar phase. The particle hydrodynamic diameter of the oil-in-water systems was determined as function of temperature. The particle hydrodynamic diameter decreases in the case of the ionic surfactants while in the case of nonionic surfactants it increases.

A trial of inpatient indication based prescribing during computerized order entry with medications commonly used off-label

BACKGROUND

Requiring indications for inpatient medication orders may improve the quality of prescribing and allow for easier placement of diagnoses on the problem list. Indications for inpatient medication orders are also required by some regulators.

OBJECTIVE

This study assessed a clinical decision support (CDS) system designed to obtain indications and document problems during inpatient computerized physician order entry (CPOE) of medications frequently used off-label.

METHODS

A convenience sample of three medications frequently used off-label were selected: the PPI lansoprazole; intravenous immune globulin, and recombinant Factor VIIa. Alerts triggered when a medication was ordered without an FDA approved indication in the problem list. The alerts prompted clinicians to enter either a labeled or off-label indication for the order. Chart review was used as the gold standard to assess the accuracy of clinician entered information.

RESULTS

The PPI intervention generated 873 alerts during 60 days of operation; IVIG 55 alerts during alerts during 93 days; Factor VIIa 25 alerts during 175 days. Agreement between indications entered and chart review was 63% for PPI, 49% for IVIG, and 29% for Factor VIIa. The alerts for PPI, IVIG and Factor VIIa alerts produced accurate diagnoses for the problem list 9%, 16% and 24% respectively. Rates of off-label use measured by chart review were 87% for PPI, and 100% for IVIG and factor VIIa, which were higher than if measured using the ordering clinicians' indications.

CONCLUSION

This trial of indication-based prescribing using CDS and CPOE produced less than optimal accuracy of the indication data as well as a low yield of accurate problems placed on the problem list. These results demonstrate the challenge inherent in obtaining accurate indication information during prescribing and should raise concerns over potential mandates for indication based prescribing and motivate further study of appropriate mechanisms to obtain indications during CPOE.

Additive and suppressive response summation with a chain schedule

Rats responded in a two-segment (variable-interval variable-interval) chain schedule. In one experiment, three subjects had either clicker, light, or clicker plus light as terminal-segment stimuli. All three responded at the highest rate when clicker plus light were present, thus showing additive summation. For three other subjects, initial-segment stimuli were either clicker, light, or clicker plus light. Two subjects responded at the lowest rate when clicker plus light were present, thus showing suppressive summation. In a second experiment, three subjects had either clicker, light, or neither clicker nor light as terminal-segment stimuli. None of these subjects showed reliable additive summation. Three other subjects had clicker, light, or neither as the initial-segment stimulus, and all three showed suppressive summation. Additive and suppressive summation both can be demonstrated with chain schedules, but stimulus parameters may be major variables in producing the effect.

Bar press and bar release as avoidance responses

Two experiments were performed in which rats had to avoid shock by both pressing and releasing a bar within specified intervals. When the release-shock interval was held constant and the press-shock interval was increased, response rate decreased and bar holding increased. When the press-shock interval was held constant and the release-shock interval was increased, both response rate and bar holding decreased.

Perception of African American men of their likelihood of a cancer diagnosis at the time of prostate biopsy

6503

Background: Men are supposed to have an “informed discussion” before undergoing PCa screening. African Americans (AA) are diagnosed at later stages of prostate cancer (PCa) than their white counterparts. We studied racial differences in self-prediction compared with actual likelihood of positive biopsy. Method: Face-to-face surveys with patients (n = 172), referred after screening positive for possible PCa, were conducted in urology clinics at the time of biopsy. The surveys include socio-demographics, general anxiety (Hospital Anxiety and Depression Scale), disease-specific anxiety (Memorial Anxiety Scale for Prostate Cancer), and self-estimated likelihood of a positive biopsy. Medical records were reviewed for biopsy results. Results: Average age was 63±7.9, AA comprised 39% of the sample, and 56% had at least a college degree. The overall rate of positive biopsy was 55%, with AA being much more likely to have a positive biopsy (70% vs. 44%; p< 0.05). Despite being referred for biopsy for concern about PCa, 37% of the men indicated that they had a 0% likelihood of having prostate cancer (i.e. that it was impossible), and AA were more likely than whites to say this (58% vs. 24%; p < 0.01). In a logistic regression with important covariates, patients’ ratings of their likelihood of PCa diagnosis were not predictive of a positive biopsy, while older age, higher PSA score, and lower self-rated health were. Generalized anxiety was not correlated with estimated likelihood of having PCa, but cancer-specific anxiety was correlated (p = 0.02). Neither was correlated with likelihood of having PCa. Conclusion: AA are more likely to have PCa at biopsy than whites. Both groups dramatically underestimate their statistical likelihood of having PCa at the time of biopsy. More concerning, AA estimates are lower, yet their likelihood is higher.

No significant financial relationships to disclose.

Impact of interpreter services on delivery of health care to limited-English-proficient patients

OBJECTIVE

To determine whether professional interpreter services increase the delivery of health care to limited-English-proficient patients.

DESIGN

Two-year retrospective cohort study during which professional interpreter services for Portuguese and Spanish-speaking patients were instituted between years one and two. Preventive and clinical service information was extracted from computerized medical records.

SETTING

A large HMO in New England.

PARTICIPANTS

A total of 4,380 adults continuously enrolled in a staff model health maintenance organization for the two years of the study, who either used the comprehensive interpreter services (interpreter service group [ISG]; N = 327) or were randomly selected into a 10% comparison group of all other eligible adults (comparison group [CG]; N = 4,053).

MEASUREMENTS AND MAIN RESULTS

The measures were change in receipt of clinical services and preventive service use. Clinical service use and receipt of preventive services increased in both groups from year one to year two. Clinical service use increased significantly in the ISG compared to the CG for office visits (1.80 vs. 0.70; P <.01), prescriptions written (1.76 vs 0.53; P <.01), and prescriptions filled (2.33 vs. 0.86; P<.01). Rectal examinations increased significantly more in the ISG compared to the CG (0.26 vs. 0.02; P =.05) and disparities in rates of fecal occult blood testing, rectal exams, and flu immunization between Portuguese and Spanish-speaking patients and a comparison group were significantly reduced after the implementation of professional interpreter services.

CONCLUSION

Professional interpreter services can increase delivery of health care to limited-English-speaking patients.

Hospitalists and the doctor-patient relationship

Hospitalists--physicians whose practice focuses on the care of hospitalized general medicine patients--are increasingly common in the United States, often displacing primary care physicians from this role. While advocates of hospitalists point to evidence of cost reduction and perhaps improved short-run outcomes, critics question whether costs or long-run outcomes are improved and whether there may be insidious effects on the doctor-patient relationship. I define a framework for addressing these questions, assess the available evidence, and identify a research agenda to better understand the implications of the hospitalist movement for the doctor-patient relationship. Using a framework that emphasizes general and patient-specific knowledge as crucial to a successful doctor-patient relationship, I argue that the success of the hospitalist model will depend on its ability to continue to develop its areas of technical expertise while ensuring care that is both continuous and appropriate to the needs and values of individual patients.

Addressing uncertainty in medical cost-effectiveness analysis implications of expected utility maximization for methods to perform sensitivity analysis and the use of cost-effectiveness analysis to set priorities for medical research

This paper examines the objectives for performing sensitivity analysis in medical cost-effectiveness analysis and the implications of expected utility maximization for methods to perform such analyses. The analysis suggests specific approaches for optimal decision making under uncertainty and specifying such decisions for subgroups based on the ratio of expected costs to expected benefits, and for valuing research using value of information calculations. Though ideal value of information calculations may be difficult, certain approaches with less stringent data requirements may bound the value of information. These approaches suggest methods by which the vast cost-effectiveness literature may help inform priorities for medical research.

Patterns of prostate cancer treatment by clinical stage and age

OBJECTIVES

This study analyzed prostate cancer treatment rates by age and clinical stage and contrasted these with rates by most accurate stage.

METHODS

We determined surgery and radiation rates by most accurate and clinical stage by using 1996 Surveillance, Epidemiology, and End Results data.

RESULTS

Treatment rates by clinical stage vs best stage differ significantly. For example, surgery rates for stages B, C, and D are 37%, 78%, and 13% by most accurate stage but 33%, 6%, and 1% by clinical stage. Treatment patterns by clinical stage vary substantially by age.

CONCLUSIONS

Treatment patterns should be described by clinical stage rather than most accurate stage, and they vary by age.

Effect of future costs on cost-effectiveness of medical interventions among young adults: the example of intensive therapy for type 1 diabetes mellitus

OBJECTIVES

Recent research based on a lifetime utility maximization model has suggested that cost-effectiveness analyses should account for all future costs, including medical costs for related and unrelated illnesses and nonmedical costs. This work has also shown that analyses that omit future costs are biased to favor interventions among the elderly that extend life over interventions that improve quality of life. However, the effect of including future costs on the cost-effectiveness of interventions among the young has not been studied. This article examines the effect of including future costs on the cost-effectiveness of intensive therapy for type 1 diabetes mellitus among young adults.

METHODS

By modifying a cost-effectiveness model based on the Diabetes Control and Complications Trial to include future costs, the effect of including future costs on the cost-effectiveness of intensive therapy for type 1 diabetes mellitus among young adults was examined. Future costs added to the model included future costs for medical expenditures for illnesses unrelated to diabetes and future nonmedical expenditures net of earnings.

RESULTS

Intensive therapy among young adults led to approximately equal increases in the expected number of years lived before age 65, when people generally produce more than they consume, and after age 65, when the opposite tends to hold. Because the discounted value of savings due to lower mortality before age 65 exceeded the discounted value of later increases in costs due to lower mortality after age 65, accounting for future costs decreased the cost-effectiveness ratio from $22,576 to $9,626 per quality-adjusted life-year.

CONCLUSIONS

The inclusion of future costs can significantly improve the cost-effectiveness of interventions that decrease mortality among young adults. The common practice of excluding future costs may bias cost-effectiveness analyses against such interventions.

How patients with diabetes perceive their risk for major complications

CONTEXT

To educate patients with diabetes about their illness and to motivate these patients to pursue intensive treatment, physicians often inform them about their risk for serious complications. However, little is known about patient perceptions of these risks.

OBJECTIVE

To compare patient perceptions of risk for major complications of diabetes with actual risk for these complications.

DESIGN

Structured interviews were done to obtain the patient's estimate of their risk for complications. To generate estimates of actual risk for each patient, we used a simulation model based on the Diabetes Control and Complications Trial (DCCT).

SETTING

Four university-affiliated diabetes clinics in the midwestern United States.

PATIENTS

139 patients with type 1 diabetes mellitus.

MAIN OUTCOME MEASURES

Probability of blindness, end-stage renal disease (ESRD), and lower-leg amputation over 20 years.

RESULTS

Participants were young (mean age, 30 years) and reported having had diabetes for an average of 15 years. Seventy-nine percent reported their current diabetic therapy to be "intensive." Ninety-eight percent had completed high school, and 51% were college graduates. The patients' estimates of their risks far exceeded the DCCT estimates for all three complications. The mean patient estimate of the risk for blindness was 31.6% (DCCT estimate, 17.0%), of the risk for ESRD was 33.7% (DCCT estimate, 8.7%), and of the risk for amputation was 25.1% (DCCT estimate, 1.9%). Similarly, patients overestimated the benefit of intensive therapy. They estimated, on average, that intensive therapy would result in a 17.0% absolute risk reduction for blindness (DCCT estimate, 12.2%), an 18.1% risk reduction for ESRD (DCCT estimate, 7.0%), and a 14.2% risk reduction for amputation (DCCT estimate, 1.2%).

CONCLUSION

Patients with diabetes overestimated their risk for major complications and the benefits of intensive treatment.

Inconsistencies in the "societal perspective" on costs of the Panel on Cost-Effectiveness in Health and Medicine

A key recommendation of the recent Panel on Cost-Effectiveness in Health and Medicine was that cost-effectiveness analyses be carried out from a societal perspective. The authors show that two of the Panel's recommendations concerning costs are not consistent with a societal perspective, and how to correct those inconsistencies. In its recommendations concerning costs resulting from morbidity, the Panel advises excluding lost income from costs in the belief that individuals take income changes into account when they respond to the quality-of-life questions that are used to calculate quality-adjusted life years (QALYs). It is shown that even if individuals do consider income changes in responding to these quality-of-life questions, this recommendation would seriously underestimate production losses due to morbidity, since individuals do not bear a major part of lost production. In its recommendations concerning costs resulting from mortality, the Panel does not require that health care costs for "unrelated" illness and non-health care consumption and production during added life years be included in the Reference Case. It is shown that omitting these costs will seriously distort comparisons of programs at different ages and favor programs that extend life over those that improve quality of life. This can be corrected by including total consumption minus production in added life-years among costs.

Perspective and the measurement of costs and benefits for cost-effectiveness analysis in schizophrenia

A valid and compelling cost-effectiveness analysis of psychopharmacologic treatment of schizophrenia requires the application of analytically rigorous methods. All cost-effectiveness analyses must consider the issue of perspective as the well as the appropriate measurement of benefits and costs. Many of these issues are particularly difficult to address in the case of schizophrenia. Since costs may be borne by a wide range of parties, the choice of perspective is of critical importance. The fact that treatments for schizophrenia can extend life and the complexities raised by taking a broad perspective on the benefits and costs of treating schizophrenia can create challenges in the measurement of both benefits and costs. The measurement of benefits through quality-adjusted life years is also crucial in demonstrating the cost-effectiveness of treatments for schizophrenia, but is challenging because of the difficulty of measuring quality of life in schizophrenic patients. Attention to these important methodological issues is essential if cost-effectiveness analyses are to be useful in shepherding scarce resources to worthwhile treatments for patients with schizophrenia.

Incorporating future costs in medical cost-effectiveness analysis: implications for the cost-effectiveness of the treatment of hypertension

It has been shown that the difference between consumption and production during life years gained should be included as a cost in cost-effectiveness analysis. In this study the authors estimate the impact of including these future costs on the cost-effectiveness of the treatment of hypertension in Sweden. The cost per quality-adjusted life year (QALY) gained changes little among young men and women due to the addition of future costs, but increases by about $14,000 for middle-aged men and women and about $27,000 for older men and women. When future costs are not included, the cost per QALY gained is generally lowest among older men and women, but when future costs are included, the cost per QALY gained is generally lowest among middle-aged men and women. The authors conclude that the total resource consequences of changes in mortality should be routinely considered in cost-effectiveness analyses.

Accounting for future costs in medical cost-effectiveness analysis

Most medical cost-effectiveness analyses include future costs only for related illnesses, but this approach is controversial. This paper demonstrates that cost-effectiveness analysis is consistent with lifetime utility maximization only if it includes all future medical and non-medical expenditures. Estimates of the magnitude of these future costs suggest that they may substantially alter both the absolute and relative cost-effectiveness of medical interventions, particularly when an intervention increases length of life more than quality of life. In older populations, current methods overstate the cost-effectiveness of interventions which extend life compared to interventions which improve the quality of life.

Profile of exercising women

Responses to a questionnaire by 497 women on their exercise, nutrition, and health habits were studied. Analysis showed respondents were well educated and represented a wide age range. The majority exercised at least 3 times a week for at least half an hour per session. Slightly more than half had been engaging in exercise for more than 5 years, with about 1 in 4 beginning for health goals and 1 in 4 motivated by weight control. Health was ranked in the top three most important reasons for continuing to exercise by more than half the women, but so were weight control, pleasure, and tension reduction. Lack of time limited regularity.

Ambiguous stimuli and delayed matching to sample

Four pigeons learned a delayed matching task in which the sample and choice stimuli were line orientations. After performance had reached a high level of accuracy the procedure was altered so that only one of the line choice stimuli was presented on each trial and a uniform white field was presented on the other key. In the first experiment the position of the white key alternated between left and right in successive sessions. Three of the four subjects suffered no loss in accuracy when the white key was on one side but responded only slightly better than chance when it was on the other. A second experiment showed that this position effect was not eliminated by keeping the white key in the same position for a number of sessions and, for three of the four subjects, was not affected by changing the color from white to red.

Hemorrhoids: associated pathologic conditions in a family practice population

BACKGROUND

Hemorrhoidal disease is an affliction that in referral populations coexists with other significant anorectal diseases. Published texts recommend aggressive procedures to diagnose associated pathologic conditions and as an aid for planning the extirpation of these diseases. Procrastination in management is said to be characteristic of both patient and primary care physician. The purpose of this study was to ascertain whether patients with hemorrhoids in the general population are truly at high risk for significant anorectal disease.

METHODS

Charts of 173 patients with hemorrhoids from a nonselected population were reviewed for treatment management, associated anorectal disease, and sequelae.

RESULTS

A small subpopulation of persons aged more than 55 years was identified who may be at higher risk for colon polyps. Anoscopy, barium enema, fecal occult blood testing, and complete blood counts had very low yields. These findings differ significantly from data collected on highly selected populations that suggest hemorrhoids rarely exist alone.

CONCLUSIONS

It appears that family physicians have not been cavalier in their attitudes toward and management of this common ailment. Clinical investigation of hemorrhoids should be initiated based on clinical impression from evaluating symptoms and signs combined with age-specific screening recommendations.

SEQUENTIAL EFFECTS OF INTERVAL DURATION ON FIXED-INTERVAL PERFORMANCE

The bar pressing of rats was reinforced on a multiple fixed-interval schedule. The schedule intervals were 1 and 5 min long, and the sequence was such that intervals of either duration were equally likely to be followed by intervals of the same or of the other duration. Rates were higher during 1-min and after 5-min intervals. Best fit equations for cumulative responses during the 5-min intervals produced very similar exponents regardless of preceding duration. It was concluded that preceding duration may have affected the subjects' performances through direct effects on temporal discrimination.

Genetic basis for species vulnerability in the cheetah

A population genetic survey of over 200 structural loci previously revealed that the South African cheetah (Acinonyx jubatus jubatus) has an extreme paucity of genetic variability, probably as a consequence of a severe population bottleneck in its recent past. The genetic monomorphism of the species is here extended to the major histocompatibility complex, since 14 reciprocal skin grafts between unrelated cheetahs were accepted. The apparent consequences of such genetic uniformity to the species include (i) great difficulty in captive breeding, (ii) a high degree of juvenile mortality in captivity and in the wild, and (iii) a high frequency of spermatozoal abnormalities in ejaculates. The species vulnerability of the cheetah was demonstrated by an epizootic of coronavirus-associated feline infectious peritonitis in an Oregon breeding colony in 1983. Exposure and spread of the coronavirus, which has a very low morbidity in domestic cats (approximately 1 percent), has decimated a heretofore productive and healthy captive population. The extreme genetic monomorphism, especially at the major histocompatibility complex, and the apparent hypersensitivity of the cheetah to a viral pathogen may be related, and provide a biological basis for understanding the adaptive significance of abundant genetic variation in outbred mammalian species.

Pituitary and gonadal response to LH releasing hormone administration in the female and male cheetah

Luteinizing hormone releasing hormone (LHRH, 50 micrograms) or saline was administered (i.m.) to adult female and male cheetahs under anaesthesia to evaluate pituitary and gonadal response. Serum LH levels did not fluctuate over a 120-min sampling period in saline-treated animals. Serum LH concentrations were raised (P less than 0.05) in both female and male cheetahs after LHRH injection, the temporal response being similar to previously reported results in unanaesthetized, domestic carnivores. The magnitude of the LHRH-induced LH response was sex-dependent. Over a 120-min post-injection period both saline control and LHRH-induced LH levels were about twofold greater in males than females. Although LHRH had no acute influence on ovarian oestradiol-17 beta production in the female, serum testosterone levels were raised (P less than 0.05) in male cheetahs by 60 min after treatment. This study (1) provides introductory endocrine information on the cheetah, an endangered species, and (2) indicates that exogenous LHRH is effective in acutely altering pituitary (female) and pituitary/gonadal (male) function in an anaesthetized, non-domestic felid.

Adrenal-testicular-pituitary relationships in the cheetah subjected to anesthesia/electroejaculation

The influence of electroejaculation on the acute response in serum cortisol, testosterone and luteinizing hormone (LH) was studied in the South African cheetah . Males were either anesthetized with CT-1341 and 1) serially bled only (controls, n = 7) or 2) serially bled during and following a regimented protocol of rectal probe electroejaculation (n = 14). In the control cheetahs , mean cortisol concentrations declined over time (P less than 0.05) and neither testosterone nor LH varied over the 145-min sampling interval. Serum cortisol rose immediately in electroejaculated cheetahs , peaked at the end of electroejaculation in 13 of 14 males and then declined during the next 90 min. Temporal profiles and serum levels of testosterone and LH were similar in the electroejaculated and control groups (P greater than 0.05). Within individual cheetahs , serum levels of LH and testosterone were highly correlated (r = 0.77, P less than 0.01). Awake (n = 2) and CT-1341 anesthetized (n = 2) cheetahs also were bled and then challenged with an i.m. injection of 25 IU adrenocorticotropic hormone (ACTH, Cortrosyn). Serial blood samples were collected during the next 2 h and assayed. Cortisol concentrations prior to ACTH administration were greater in awake than in anesthetized males. In all animals, cortisol rose immediately and peaked within 30-60 min of injection. Whereas all 4 ACTH-treated cheetahs produced cortisol titers in excess of 200 ng/ml, only 4 of 14 electroejaculated males produced cortisol levels comparable to this concentration range. Neither testosterone nor LH profiles were affected by ACTH-induced elevations in cortisol.(ABSTRACT TRUNCATED AT 250 WORDS)

Unique seminal quality in the South African cheetah and a comparative evaluation in the domestic cat

Analysis of 40 semen samples collected by electroejaculation from 18 cheetahs revealed no major differences in seminal traits among Transvaal, South West (Namibia) or hybrid (Transvaal X South West) males. However, mean spermatozoal concentration (14.5 X 10(6) spermatozoa/ml of ejaculate) and percent motility (54.0%) were less in cheetahs than in domestic cats (147.0 X 10(6) spermatozoa/ml of ejaculate, 77.0% motility) subjected to the same electroejaculation regimen. On the average, cheetah ejaculates contained 71.0% morphologically abnormal spermatozoa compared to 29.1% aberrant spermatozoal forms in the domestic cat. These results indicate that seminal characteristics in the cheetah are markedly inferior compared to the domestic cat, particularly with respect to the incidence of pleiomorphic spermatozoa. Because a recent parallel study demonstrates that the cheetah lacks genetic variation, it appears likely that spermatozoal abnormalities are a genetic consequence of genomic homozygosity characteristic of this endangered species.

Conditional discrimination with ambiguous stimuli

Five pigeons learned a two-key conditional discrimination. When background color on both keys was red, pecks on the key with a horizontal line produced food. When the color was green, pecks on the key with a vertical line produced food. During part of the experiment, color was presented on only one of the keys. It was found that accuracy was higher when color was combined with the line stimulus correlated with nonreinforcement. In another part of the experiment, color was presented on both keys but a line was present only on one. Accuracy was higher when the line accompanied the nonreinforced option than when the line accompanied the reinforced option. Superior performance when the combined stimuli were displayed on the nonfood key may be explained by the association of different components of the compound stimuli with reinforcement or as the result of rules pigeons follow in solving conditional discriminations.

Drug-induced thrombocytopenia is associated with increased binding of IgG to platelets both in vivo and in vitro

Thrombocytopenia is a common serious adverse effect of drug treatment. A variety of in vitro diagnostic techniques to confirm the diagnosis are available, but the majority lack sufficient sensitivity to detect all cases of drug-induced thrombocytopenia. We studied 19 patients with suspected drug-induced thrombocytopenia and demonstrated that platelet-associated IgG (PAIgG) was elevated in all at the time of thrombocytopenia, and PAIgG returned to normal levels as the thrombocytopenia resolved. In the majority of patients, the platelet count rapidly returned to normal after the drug was discontinued; however, in six patients, the thrombocytopenia persisted well beyond the period of time that the offending drug would be expected to be cleared from the blood. In 13 patients, serum obtained after recovery was used to identify the drug responsible for the thrombocytopenia in an in vitro assay. In all cases, the addition of the drug historically associated with the thrombocytopenic episode was associated with an increased binding of IgG to control platelets. For uncertain reasons, the concentration of drug required to increase the in vitro binding of IgG to test platelets was often more than the concentration usually achieved in vivo. Wider application of these techniques may provide better understanding of the clinical characteristics and mechanisms responsible for drug-induce thrombocytopenia.

Conditioned suppression and conditioned enhancement with the same positive UCS: an effect of CS duration

Previous experiments have shown that positively reinforced operant responding is suppressed during a conditioned stimulus terminated with an electric shock (conditioned suppression). In the present experiment, the conditioned stimulus was terminated with a positive unconditioned stimulus, and it was found that the duration of the conditioned stimulus was a key factor in determining whether response suppression or response enhancement was observed during the stimulus. The lever-pressing responses of rats were maintained by a variable-interval schedule of food reinforcement. While the rats were pressing the lever, a light was occasionally turned on, its offset coincident with a brief period of access to a sucrose solution. In consecutive blocks of sessions, the light duration was 40 sec, 12 sec, or 120 sec. Results showed that the rate of lever pressing was substantially suppressed during the 12-sec stimulus, slightly suppressed during the 40-sec stimulus, and enhanced during the 120-sec stimulus.

Sequential amatching in the squirrel monkey

Three squirrel monkeys were trained to perform a sequential matching problem by use of a fading technique. One of three differently colored standard stimuli was presented on the left key when S responded on that key. A response on the right key then resulted in presentation of a comparison stimulus on the right. Each additional response on the right key changed the color of the comparison stimulus. When the standard and comparison stimuli matched, a response on the left key was reinforced; a response on the left key when the colors did not match resulted in a time out. Exp. 2 showed that all three Ss could learn to match standard and comparison stimuli of different colors (e.g., a red standard and blue comparison stimulus.) The colors of the standard stimuli in this experiment were all different from any of the comparison colors.

Subject control of reinforcement density on an interval schedule

Rats were trained on schedules in which the rate of responding in one inter-reinforcement time (ISRT) determined the minimum duration of the following ISRT. The durations of the four ISRTs which were used were related in a simple arithmetic ratio; T, 2T, 3T, and 4T sec. For one group high rates in the current ISRT shortened the following ISRT from the basic value of 4T sec. A high response rate lengthened the next ISRT from the basic value of T sec. in the other group. Ss in each group were able to approximate the response rate which would result in maximum reinforcement density.