Evaluation of conductive cooling of lactating dairy cows under controlled environmental conditions.

Cooling systems used to reduce heat stress in dairy operations require high energy, water usage, or both. Steady increases in electricity costs and reduction of water availability and an increase in water usage regulations require evaluation of passive cooling systems to cool cows and reduce use of water and electricity. A study was conducted to evaluate the use of heat exchangers buried 25 cm below the surface as components in a conductive system for cooling cows. Six cows were housed in environmentally controlled rooms with tie-stall beds, which were equipped with a heat exchanger and filled with 25 cm of either sand or dried manure. Beds were connected to supply and return lines and individually controlled. Two beds (one per each kind of bedding material) constituted a control group (water off), and the other 4 (2 sand and 2 dried manure) used water at 7°C passing through the heat exchangers (water on). The experiment was divided in 2 periods of 40 d, and each period involved 3 repetitions of 3 different climates (hot and dry, thermo neutral, and hot and humid). Each cow was randomly assigned to a different treatment after each repetition was over. Sand bedding remained cooler than dried manure bedding in all environments and at all levels of cooling (water on or off). Bed temperatures were lower and heat flux higher during the bed treatment with sand and water on. We also detected a reduction in core body temperatures, respiration rates, rectal temperatures, and skin temperatures of those cows during the sand and water on treatment. Feed intake and milk yield numerically increased during the bed treatment with sand and water on for all climates. No major changes were observed in the lying time of cows or the composition of the milk produced. We conclude that use of heat exchangers is a viable adjunct to systems that employ fans, misters, and evaporative cooling methods to mitigate effects of heat stress on dairy cows. Sand was superior to dried manure as a bedding material in combination with heat exchangers.

The brain and child development: time for some critical thinking.

There is widespread interest in the claim that new breakthroughs in neuroscience have radical implications for early child care policy. Yet despite parents', educators', and policy makers' enthusiasm, there are good reasons to be skeptical. The neuroscience cited in the policy arguments is not new, depending primarily on three well-established neurobiological findings: rapid postnatal synapse formation, critical periods in development, and the effects of enriched rearing on brain connectivity in rats. Furthermore, this neuroscience is often oversimplified and misinterpreted. While child care advocates are enthusiastic about potential applications of brain science, for the most part neuroscientists are more cautious and skeptical. After reviewing the evidence and the arguments, the author suggests that in the interest of good science and sound policy, more of us might adopt a skeptical stance.

Ketone bodies maintain normal cardiac function and myocardial high energy phosphates during insulin-induced hypoglycemia in vivo.

It has been suggested that myocardial utilization of ketone bodies might cause deterioration of cardiac function. Therefore, the influence of ketonemia (mean: 1.3 and 3.3 mM) in the presence of hypoglycemia (mean: 33 mg/dl) on cardiac function, substrate utilization and myocardial high energy phosphate levels was studied in 10 mongrel dogs. Hypoglycemia alone led to a significant increase of mean aortic pressure, total peripheral resistance and myocardial oxygen consumption, but other hemodynamic parameters and regional myocardial function were not changed. Additional infusion of 3-hydroxybutyrate did not affect hemodynamic variables significantly. During both metabolic interventions in vivo phosphorus-31 nuclear magnetic resonance (NMR) spectroscopy showed stable levels of myocardial Pi, PCr, ATP, as well as PCr/Pi (3.2-3.4) and PCr/ATP (3.0-3.2) ratios. Biochemical measurements revealed that ketonemia led to significant alterations in arterial concentrations and arterio-coronary venous differences of selected citric acid cycle intermediates, thus confirming previous reports which suggested a blockade of the 2-oxoglutarate-dehydrogenase reaction induced by ketone body oxidation. However, despite this blockade, the energy supply to the heart was not impaired as shown by normal NMR spectroscopy and cardiac performance. It is speculated that the blockade might be due to an enhanced NADH/NAD ratio.

Methodological rigor and citation frequency in patient compliance literature.

An exhaustive bibliography which assesses the methodological rigor of the patient compliance literature, and citation data from the Science Citation Index (SCI) are combined to determine if methodologically rigorous papers are used with greater frequency than substandard articles by compliance investigators. There are low, but statistically significant, correlations between methodological rigor and citation indicators for 138 patient compliance papers published in SCI source journals during 1975 and 1976. The correlation is not strong enough to warrant use of citation measures as indicators of rigor on a paper-by-paper basis. The data do suggest that citation measures might be developed as crude indicators of methodological rigor. There is no evidence that randomized trials are cited more frequently than studies that employ other experimental designs.

Selective medical libraries and library networks for developing countries.

The growth and rising cost of bibliographic materials require that attempts to make all medical libraries comprehensive and self-contained be replaced by the provision of selective collections devoted to the most used and useful materials, particularly in developing countries with limited resources. Journals constitute the most important and expensive component of a biomedical collection. While use data are important, a method is presented to guide selection in the absence of this information. The method identifies 35 nucleus journals and uses citation analysis to generate a list of 92 journals, partitioned into 31 medical specialty classes. Local expert consensus can guide selection of important local or regional literature not in the international archives. Careful selection results in efficient collections. Access to less used materials can be provided to individual libraries through resource sharing networks with affiliations to major comprehensive international libraries.

Liberal arts and the premedical curriculum.

Twenty-five leading physicians, medical educators, and humanists convened and affirmed the contributions of a liberal arts education to the study and practice of medicine. Participants agreed that overemphasizing technical expertise does have deleterious effects on premedical and medical education, which might be alleviated by encouraging a more broadly based undergraduate and medical curriculum. Admissions statistics show that approximately 50% of all applicants of medical school are admitted to some school and that there is no apparent bias against nonscience majors in the admissions process. Increased student awareness of these statistics should relieve anxieties and intense competitive pressures. A publication based on the conference recommendations will be made available to deans, advisors, and career counselors.