Genomic Selection Improves Heat Tolerance in Dairy Cattle

Dairy products are a key source of valuable proteins and fats for many millions of people worldwide. Dairy cattle are highly susceptible to heat-stress induced decline in milk production, and as the frequency and duration of heat-stress events increases, the long term security of nutrition from dairy products is threatened. Identification of dairy cattle more tolerant of heat stress conditions would be an important progression towards breeding better adapted dairy herds to future climates. Breeding for heat tolerance could be accelerated with genomic selection, using genome wide DNA markers that predict tolerance to heat stress. Here we demonstrate the value of genomic predictions for heat tolerance in cohorts of Holstein cows predicted to be heat tolerant and heat susceptible using controlled-climate chambers simulating a moderate heatwave event. Not only was the heat challenge stimulated decline in milk production less in cows genomically predicted to be heat-tolerant, physiological indicators such as rectal and intra-vaginal temperatures had reduced increases over the 4 day heat challenge. This demonstrates that genomic selection for heat tolerance in dairy cattle is a step towards securing a valuable source of nutrition and improving animal welfare facing a future with predicted increases in heat stress events.

Wide Complex Tachycardia - Ventricular Tachycardia or Not Ventricular Tachycardia, That Remains the Question

Arriving at the correct diagnosis in cases of wide complex tachycardia remains problematic for many clinicians. In this paper, we review the historical development of criteria used to differentiate among the major diagnostic possibilities and compare the strengths and weaknesses of various differentiating algorithms.

Cervical vagal nerve stimulation activates the stellate ganglion in ambulatory dogs

Background and Objectives

Recent studies showed that, in addition to parasympathetic nerves, cervical vagal nerves contained significant sympathetic nerves. We hypothesized that cervical vagal nerve stimulation (VNS) may capture the sympathetic nerves within the vagal nerve and activate the stellate ganglion.

Materials and Methods

We recorded left stellate ganglion nerve activity (SGNA), left thoracic vagal nerve activity (VNA), and subcutaneous electrocardiogram in seven dogs during left cervical VNS with 30 seconds on-time and 30 seconds off time. We then compared the SGNA between VNS on and off times.

Results

Cervical VNS at moderate (0.75 mA) output induced large SGNA, elevated heart rate (HR), and reduced HR variability, suggesting sympathetic activation. Further increase of the VNS output to >1.5 mA increased SGNA but did not significantly increase the HR, suggesting simultaneous sympathetic and parasympathetic activation. The differences of integrated SGNA and integrated VNA between VNS on and off times (ΔSGNA) increased progressively from 5.2 mV-s {95% confidence interval (CI): 1.25-9.06, p=0.018, n=7} at 1.0 mA to 13.7 mV-s (CI: 5.97-21.43, p=0.005, n=7) at 1.5 mA. The difference in HR (ΔHR, bpm) between on and off times was 5.8 bpm (CI: 0.28-11.29, p=0.042, n=7) at 1.0 mA and 5.3 bpm (CI 1.92 to 12.61, p=0.122, n=7) at 1.5 mA.

Conclusion

Intermittent cervical VNS may selectively capture the sympathetic components of the vagal nerve and excite the stellate ganglion at moderate output. Increasing the output may result in simultaneously sympathetic and parasympathetic capture.

Causes and management of drug-induced long QT syndrome

Long QT syndrome (LQTS) is characterized by inherited or acquired prolonged QT interval on the surface electrocardiogram. This can lead to torsade de pointes ventricular tachycardia (TdP VT) and ventricular fibrillation. In the acquired form of the disease, medications from several classes can cause TdP VT or potentiate the electrocardiographic findings. These include class IA and III antiarrhythmics, antibiotics (macrolides and quinolones), antidepressants (tricyclics and selective serotonin reuptake inhibitors), antipsychotics (haloperidol and phenothiazines), and antiemetics (ondansetron and prochlorperazine). We present four cases of drug-induced LQTS resulting in life-threatening cardiac arrhythmias. Antiarrhythmic medications were the cause in two cases, and the other two cases involved noncardiac medications. All four patients had at least one risk factor for LQTS in addition to the offending drug, including female gender, hypokalemia, hypomagnesemia, and bradycardia. In one patient, amiodarone was administered for treatment of VT, although the correct diagnosis was actually TdP VT. In patients with polymorphic VT or ventricular fibrillation without a significant history of cardiovascular disease, drug-induced LQTS should be high in the differential diagnosis. Prompt diagnosis is key, as amiodarone, while often used to suppress VT, is potentially harmful in the setting of LQTS and TdP VT.

Gender differences in the presentation, treatment, and short-term mortality of acute chest pain

The Halifax County MONICA database was used to estimate the gender bias in presentation, prehospital and in-hospital treatment, and 28-d mortality of patients suffering an episode of acute chest pain. The study population consisted of all county residents aged 25-74, admitted between 1984 and 1990 to a CCU, or suffering a myocardial infarction anywhere in a hospital. The mean age for men was 58.5 (n = 6561), for women 61.5 (n = 3176). Women of all age groups were more likely to have a history of diabetes or hypertension, and below age 55 had a higher prevalence of peripheral vascular disease. Typical symptoms for infarction were present in 30.8% of women and 38.1% of men (p < 0.0001). More women were taking beta-blockers, Ca-antagonists, digitalis, diuretics, and nitrates (p < 0.001), and more men were on antiarrhythmics. A gender difference was observed for coronary arteriography (24% in men, 18% in women) and for the exercise stress test (23% in men, 18% in women). In hospital, men had more episodes of severe arrhythmias (OR = 1.52). Except for aspirin and antiarrhythmics, the difference in hospital medication and 28-d mortality (9.6% in women vs. 7.8% in men) could be explained by the existing clinical conditions.

Deviance estimates of sample size for equivalence tests in vaccine trials

This paper proposes a sample size procedure for both equivalence and conventional tests for the comparison of two binomial proportions, based on the signed square root of the deviance. When the comparison is based on the odds ratio, I describe an alternate 'close' conditional exact method that gives results that support those given by the deviance method. I summarize the advantages of the deviance-based method and also show that in general equivalence situations the sample size estimate depends upon the measure of comparison selected, odds ratio, risk ratio or risk difference.

A case-control study of unexplained antepartum stillbirths

OBJECTIVE

To ascertain factors that will identify women who are at increased risk of unexplained antepartum stillbirth.

DESIGN

Matched case-control study. The cases and controls were initially analysed as a whole group and again after dichotomizing into those of low birthweight (< 2500 g) and those of normal birthweight (> or = 2500 g).

SETTING

Western Australia 1980-1983.

SUBJECTS

Unexplained antepartum stillbirths of > or = 1000 g birthweight (cases) and liveborn infants individually matched for year of birth, plurality, sex and birthweight of infant and race of mother (controls).

RESULTS

The case pregnancies had more polyhydramnios (OR 10.83, 95% CI 2.41-48.69) and cord problems (OR 6.57 95% CI 1.36-31.75) than the controls but, paradoxically, other obstetric and medical complications were less common in the cases. The association with polyhydramnios persisted when the analysis was confined to those with low birthweight. With normal birthweight fetal distress was more frequent in the cases (OR 3.65 95% CI 1.36-9.80) but there were few other differences.

CONCLUSIONS

The clinical and diagnostic systems currently in use are unable to identify many fetuses at risk of death. Decreases in the rate of unexplained antepartum stillbirths await the discovery of new preventable causes, or of innovations in clinical or laboratory aspects of obstetric care.

Randomized controlled trial of antenatal social support to prevent preterm birth

OBJECTIVE

To test the effect of a programme of additional antenatal social support on the occurrence of preterm birth (a birth from 20 to 36 weeks gestation) in women at risk of preterm birth.

DESIGN

A prospective randomized controlled trial. The design was one of randomization before consent for a new treatment.

SETTING

Three public hospital antenatal clinics in Perth and the offices of 87 obstetricians and general practitioners in Western Australia.

SUBJECTS

1970 pregnant women with poor obstetric histories entered the trial; 983 of these were randomly allocated to the programme group and 987 to the control group.

INTERVENTIONS

Normal antenatal care was provided for both groups. In addition, members of the programme group were offered an intervention aimed at providing expressive (emotional) social support, consisting of antenatal home visits and telephone calls by midwives. Of the women allocated to the programme group, 24 refused consent and 69 were not traced before completion of their pregnancies, the remaining 890 women (90.5%) agreed to enter the programme, and each received at least one intervention.

MAIN OUTCOME MEASURES

Gestational age at completion of the pregnancy. A pregnancy ending before 20 weeks was labelled a miscarriage.

RESULTS

There were 126/981 (12.8%) preterm births in the programme group and 147/986 (14.9%) in the control group. The outcome data for two women in the programme group and one in the control group could not be found. The unadjusted odds ratio for preterm birth in the programme was 0.84 (95% CI 0.65-1.09). The observed relative reduction in preterm births associated with the programme was 13.8% (95% CI -8.2% to +31.5%) and the trial had a 60% power to exclude a true relative reduction of 25%.

CONCLUSIONS

The results of this trial and those of other controlled clinical trials provide little evidence for the effectiveness of social support interventions in the prevention of preterm birth in women with poor obstetric histories.

The standard error of Cohen's Kappa

This paper gives a standard error for Cohen's Kappa, conditional on the margins of the observed r x r table. An explicit formula is given for the 2 x 2 table, and a procedure for the more general situation. A parsimonious log-linear model is suggested for the general case and an approximate confidence interval for kappa is based on that model. Numerical illustrations are given comparing the standard results with exact conditional results and those of the present paper. The conclusions are, first, that the standard error of kappa under the null hypothesis (that kappa is zero) should not be used except when the null is plausible; secondly, that the usual formula for the standard error appears appropriate except in the unusual circumstance of kappa taking large negative values; and, thirdly, in small samples the distribution of the estimate of kappa appears very non-symmetric, and it is preferable to base confidence intervals on transformations of kappa. A PC program with source code implementing the suggested procedures is available from the author.

Mathematical analysis of multisolute renal flow in a single nephron model of the kidney

A single nephron model, which includes the Bowman's space, Cortical interstitium, and Pelvis as well-stirred baths, is investigated. A boundary value problem, which allows for pelvic reflux, is established for the fluid-multisolute flow in the nephron. The implicit function theorem is used to establish the existence and uniqueness of a solution of the boundary value problem for the case of small permeability coefficients and transport rates.

The effects of propranolol, phentolamine, and atropine on canine coronary vascular gradients

The objective of this study was to measure pressure gradients in the coronary circulation following the administration of three receptor-blocking drugs, propranolol, phentolamine, and atropine when administered singly and in sequence. As well, we examined the responses of these gradients to eight interventions: left stellate ganglion or left vagosympathetic trunk stimulation, administration of isoproterenol, acetylcholine, noradrenaline, adenosine, phenylephrine, or adrenaline. Using a multiple linear regression model we examined the actions and interactions of the receptor-blocking agents on hemodynamic variables and vascular gradients. Propranolol reduced heart rate as expected and blocked the responses to isoproterenol administration. As well, it abolished the epicardial coronary artery diastolic gradient. The gradient was restored when propranolol was the second receptor blocker administered but was abolished when it was the third. Phentolamine induced vasodilation with a decrease in coronary small vessel gradients. This effect persisted without regard to the sequence of administration. When it was the second or third agent it decreased the microcirculation and small vein gradients, an action it did not manifest when given singly. Atropine singly did not alter pressures or gradients; but as the second agent it altered the transmural, outflow tract, epicardial diastolic, and microcirculation and small vein diastolic gradients; and as the third agent the changes were in the transmural, epicardial systolic and diastolic, and small artery systolic and diastolic gradients. The pattern of responses was not predictable and that indicates that unique changes occur in the responses of the coronary circulation when multiple receptor-blocking agents are employed. Adrenergic control tends to dominate in the coronary arterial circulation, and muscarinic control in the coronary microcirculation and veins with considerable overlap.

Existence and uniqueness of solutions in general multisolute renal flow problems

This paper considers systems of differential equations that describe flows in renal networks. The flow geometry is of the type that occurs in modelling the renal medulla. The unknowns in the system include the flow rate, the hydrostatic pressure, and the concentrations of the various solutes. Existence and uniqueness of solutions of the appropriate boundary value problems are established, in the case of small permeability coefficients and transport rates, or large diffusion coefficients and small resistance to flow constants.

Coronary circulatory pressure gradients

The pressure gradients of the canine coronary circulation were measured in 37 dogs during control and following eight interventions: left stellate ganglion or left vagosympathetic trunk stimulation, as well as isoproterenol, acetylcholine, noradrenaline, adenosine, phenylephrine, or adrenaline infusions. During control, pressure gradients in the epicardial coronary arteries (measured from the aorta to coronary artery branch) were 15.2 +/- 1 mmHg (1 mmHg (1 mmHg = 133.32 Pa) during systole and 10.6 +/- 1.5 mmHg during diastole. Adrenaline increased this systolic gradient, while acetylcholine and phenylephrine decreased it. In contrast, the pressure gradients in the small coronary arteries (from the branch of an epicardial artery to the pressure in an obstructed coronary artery) were 56 +/- 1.3 mmHg during systole and 63.7 +/- 1.3 mmHg during diastole. These gradients were increased by phenylephrine during both systole and diastole, noradrenaline and adrenaline during diastole and decreased by isoproterenol (systolic), left vagosympathetic trunk stimulation (diastolic), acetylcholine (systolic and diastolic), and adenosine (diastolic). The microcirculation and small vein gradients during control were 16.4 +/- 1.2 mmHg during systole and 8.5 +/- 0.8 mmHg during diastole. Decreases in this gradient were produced by isoproterenol, acetylcholine, and adenosine during systole and adenosine during diastole. These observations are consistent with the concept that the coronary circulation has considerable regulatory capacity in all of its component parts. Specifically, epicardial arteries appear to function as both conduits and as resistance vessels, small arteries as major resistance vessels, and the microcirculation and small veins as both capacitors and resistors.

Prevalence of major mental retardation and associated disabilities in the Canadian Maritime Provinces

A cross-sectional survey of the prevalence of major mental retardation in 7- to 10-year-olds in the three Canadian Maritime provinces was carried out in 1980. Case ascertainment from multiple sources was considered to be virtually complete and resulted in a study group of 307 children, for whom 72% of the parents consented to personal data collection. The overall regional prevalence of major mental retardation was 3.65/1,000. Variation in county prevalence rate (based on parental residence at the time of birth) was associated, by regression analysis, with maternal age, areas of greater population concentrations, and number of physicians per capita. These associations were still present when children with Down syndrome were excluded from the analysis. Speech and behavior disorders and epilepsy were the major associated disabilities.

Causal origins of major mental handicap in the Canadian Maritime provinces

From a retrospective epidemiological survey, the prevalence of major mental handicap among seven- to 10-year-old children in the Maritime region of Canada in 1980 was estimated to be 36.5 per 10,000 children. Based on information obtained for 221 of the 307 children ascertained by the survey, prenatal origins dominated (58 per cent), followed by perinatal (10 per cent) and postnatal (4 per cent). No specific cause could be determined for 27 per cent of the children, but 41 per cent of this group had epilepsy and/or cerebral palsy in addition to major mental handicap. Significant differences were found in the causal spectrum between the Maritime region of Canada and regions studied in other developed countries. The results of this survey have implications for planning prevention programs, and for epidemiological surveillance and monitoring of adverse reproductive outcomes.

Associations of body mass index and waist:hip ratio with hypertension

Canada Fitness Survey data for people aged 20 to 69 years were analysed by means of linear discriminant analysis to determine the effect of age, weight relative to height (body mass index) and weight distribution (waist:hip ratio) on hypertension (defined as diastolic blood pressure of 90 mm Hg or more) for both sexes separately. All three variables had independent effects on hypertension, but partial correlation coefficients indicated that the contribution of waist:hip ratio was secondary to that of body mass index. The association of measurements of body fat (five skinfold measurements) with hypertension was also examined; overall these measurements gave no advantage over the more simply measured body mass index. The results confirm the importance of assessing the predominant location of body fat and the body mass index when examining excess weight in relation to disease.

Association of cytomegalovirus and herpes simplex virus infections of the cervix in four clinic populations

The rates of isolation of cervical cytomegalovirus (CMV) and herpes simplex virus (HSV) were compared for populations of four different clinics attended by a total of 1,755 women. The prevalence of CMV infection could be predicted by the prevalence of HSV infection, with CMV being 2.5 times as prevalent as HSV in each population. The overall infection rates for CMV and HSV were 4.1% and 1.7%, respectively. The 252 women attending the Sexually Transmitted Disease Clinic had significantly higher rates of CMV and HSV infection (12.5% and 5.6%, respectively) than populations attending the other clinics. A strong relationship between marital status and CMV infection was observed. The estimated relative risk for single compared to married women was 2.9. These data verify the importance of the sexual route of transmission in the epidemiology of cervical infection with CMV.

Spontaneous intracerebral haemorrhage: an analysis of factors affecting prognosis

A retrospective study of 100 patients with spontaneous intracerebral haemorrhage was carried out, to identify clinical factors which have a predictive value for outcome. Numerical equivalents for the admission level of consciousness (the Glasgow Coma Scale), ventricular rupture, partial pressure of oxygen in the blood, the electrocardiogram, clot location, and clot size were combined into equations predicting outcome. The best single parameter for prediction was the Glasgow Coma Scale.

Prevalence of Ascaris lumbricoides infection in a small Nova Scotian community

A survey of Ascaris lumbricoides prevalence was conducted during 1976 and 1977 in a rural community of Nova Scotia. Of 431 individuals tested, 121 (28.1%) were infected. All those infected were under 20 years of age. There was no difference in the rate of infection between households with pigsties and those without. A significantly higher prevalence rate was found in homes where feces were disposed of in the yard and water was obtained from a dug well. In a concurrent random survey taken in the Halifax metropolitan area, none of the 276 individuals tested was infected.

A proportional hazards analysis of the clinical characteristics of infertile couples

Evaluated were methods of ordering the many possible predictors of infertility outcome. The clinical characteristics of infertile couples were studied with respect to the occurrence of pregnancy during follow-up, by means of the methods of survival analysis. Among 1,297 couples who were infertile for 12 months or more, the cumulative pregnancy rate at 36 months with 95% confidence limits was 49% +/- 4%. The proportional hazards analysis identified three independent predictors of the occurrence of pregnancy from the couple's history (with P values in brackets): a history of pregnancy in the partnership (0.0001); shorter duration of infertility (0.0001); and shorter length of marriage (0.005). The predictors arising from the diagnostic process (with P values in brackets) were: fewer infertility diagnoses (0.0001); a favorable primary clinical diagnosis (0.001); and the presence of any tubal disease, regardless of the primary clinical diagnosis (0.001). The analysis selected an economical set of significant predictor variables and demonstrated that a longer period of contraception was associated with a lower pregnancy rate among infertile couples. Also, three simple questions from the history were nearly equivalent to the entire diagnostic process as predictors of the outcome.

Prevalence of antibodies to hepatitis A virus in Nova Scotia children

Blood samples from 304 children aged 6 months to 16 years were tested by radioimmunoassay for antibodies to hepatitis A virus (anti-HAV). Of several factors examined for a possible association with the prevalence of anti-HAV--age, sex, race, geographic location and presence of malignant disease--only age showed a positive correlation with the prevalence of these antibodies.

Physical training in diabetic rats: effect on glucose tolerance and serum lipids

The effect of 10 wk of treadmill training on glucose tolerance, serum lipids, tissue lipoprotein lipase (LPL) activities, and triglyceride secretion rates (TGSR) were studied in normal and diabetic rats. Training had little effect on the glucose tolerance of the normal rats but ameliorated the deterioration of glucose intolerance seen in the sedentary diabetic rats. Trained diabetic and normal rats had lower serum triglycerides than their sedentary counterparts [diabetic 34 +/- 5 vs. 61 +/- 4 (means +/- SE); normal 34 +/- 3 vs. 50 +/- 3 mg/dl]. This hypotriglyceridemic effect was associated with a reduction in the TGSR in the trained rats (diabetics 0.34 +/- 0.05 vs. 0.51 +/- 0.02; normal 0.48 +/- 0.05 vs. 0.53 +/- 0.04 mg/min). There were no differences in the tissue LPL activities (soleus, gastrocnemius, epididymal fat, and heart) between the trained and sedentary rats in both groups. Training also did not affect the serum cholesterol and the high-density lipoprotein cholesterol levels in both groups of rats.

Cancer of the cervix and the smoking husband

Information was gathered on 22 patients with in situ and 11 patients with invasive carcinoma of the cervix as part of a 20-year follow up study. Patients were compared with 29 controls who had had hysterectomies for non-cancer reasons. A significant relationship was found between the amount of cigarets smoked by the husband and the occurrence of cancer of the cervix in the wife. When compared with other risk factors, data showed a smoking husband to be the most significant indicator of whether or not a woman developed cancer of the cervix.

Cytomegalovirus in the semen

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Flexibility and musculoskeletal symptomatology in female gymnasts and age-matched controls

Sixty competitive female gymnasts and 35 age-matched nonathletic controls were interviewed for musculoskeletal symptoms and examined for flexibility. A significantly greater number of gymnasts (P less than 0.01) had musculoskeletal symptoms in the wrist, low back, hip, shin, and foot regions than did the controls. The average number of symptomatic regions per subject was significantly greater (P less than 0.001) in gymnasts (6.17) than in controls (2.25). Gymnasts had greater shoulder flexion and horizontal abduction, lumber flexion, hip extension, and toe-touching abilities (P less than 0.001). Controls surpassed gymnasts only in the extent of elbow supination (P less than 0.001). There were no significant differences in lumbar, knee or elbow extension. No statistically significant correlations in flexibility between different body regions were identifiable in gymnasts or controls. The gymnasts with low back discomfort and greater toe-touching ability than those without symptoms. No other consistent and significant relationships between symptomatology and flexibility in a region were found.

Stability of plasma low density lipoprotein with abnormal glycolipid composition from patients with Fabry's disease

Fabry's disease is a glycosphingolipid storage disease associated with premature generalized arteriosclerosis. Plasma low density lipoprotein (d 1.019--1.055 g/ml; LDL) was isolated from 4 healthy male volunteers (LDL-N) and from 4 patients with Fabry's disease (LDL-F), in whom plasma globotriaosylceramide (GbOse3) levels were 2--4 times above normal. LDL-N was labeled with 131I and LDL-F with 125I by the iodine monochloride method; both were then injected together intravenously into 4 mongreal dogs. The rates at which they were metabolized were determined by measuring plasma radioiodine levels daily for 7--8 days. No significant difference (Fisher's F-test) was observed between LDL-N and LDL-F in terms of the size of the intravascular compartments (LDL-N, 86.3 +/- 4.2%;; LDL-F, 94.2 +/- 7.7%), biological half-lives (LDL-N, 24.1 +/- 4.2 h; LDL-F, 23.5 +/- 3.7 h), or fractional catabolic rates (LDL-N, 0.849 +/- 0.066; LDL-F, 0.796 +/- 0.070). The results indicate that significant abnormalities of the neutral glycosphingolipid composition of LDL, such as occur in Fabry's disease, do not affect the metabolism of the lipoprotein apoprotein in dogs. The arteriosclerosis in patients with the disease is probably due to damage to vessel walls occurring as a result of defective GbOse3 metabolism and accumulation of glycosphingolipid in the tissue, rather than to abnormal LDL metabolism.