Rhythm scrambling: good, bad or indifferent?

The scrambling of rhythms, i.e. their mixing-up or throwing into disorder, on a variety of schedules of lighting and feeding, left the average overall life span of several groups of mice unaffected. One particularly scrambled schedule prolonged 10th-decile survival time. The phase-shifting of rhythms, in a mammalian simulation of shift-work schedules, need not be harmful and can be indifferent or even beneficial. Such findings have important implications for health, performance and safety in human shift-work by both sexes and for the choice of other schedules, such as those for drug treatments or exercise.

Strategic planning with family physicians: a case study

Family physicians at Sunnybrook Medical Centre were engaged in a strategic planning process to develop a practice philosophy, mission statement, short-term goals, and plan for future programming. Numerous issues were identified in relation to the need for planning, the successful involvement of family physicians in the planning process, and the traditional relationship between physicians and managers which, in the past, has inhibited productive collaboration. Strategies were developed to overcome potential obstacles in these areas, and suggestions are outlined for administrators wishing to involve physicians more fully in the planning process.

Increased intrinsic pumping of intestinal lymphatics following hemorrhage in anesthetized sheep

The return of fluid and protein to the bloodstream by the lymphatic circulation may play an important role in reconstituting intravascular volume following hemorrhage. In this study, we have defined the lymph-flow changes that occur in cannulated mesenteric lymphatics following a 25% blood loss in anesthetized sheep and investigated the effects of hemorrhage on the intrinsic contractile activity (lymph pumping) of these vessels in vivo using a new model system. The removal of 25% of the calculated blood volume resulted in increases in lymph flow over a 6-hour period, with peak changes to 3.5 times the prebleed levels. Systemic arterial pressures dropped to roughly 50% of control values immediately following the bleed and returned to control in 3 hours. To directly assess the effects of hemorrhage on lymphatic pumping, a segment of intestinal lymphatic was isolated from all lymph input and supplied with fluid from a reservoir. While there was no net pressure driving fluid through the duct, a transmural distending pressure was applied to the vessel, which stimulated resting lymphatic contractions and fluid pumping. A 25% blood loss resulted in increased activity of the lymph pump; up to 6 times more fluid was propelled through this "isolated" vessel in vivo than in similar preparations in sheep that were not bled (p less than 0.01). Measurements of fluid pulse pressures in this preparation indicated increased pumping frequency and/or force after hemorrhage compared with prebleed levels. We conclude that lymphatic contractile activity is stimulated after a blood loss independent of changes in lymph formation and speculate that this mechanism may play an important role in the reexpansion of the vascular space.

Meal-timing, circadian rhythms and life span of mice

The possibility that circadian rhythm alteration may contribute to the life-prolonging effect of food restriction was investigated in female CD2F1 mice housed in a room with a 12-h span of fluorescent lighting daily. A control group was allowed to feed ad libitum throughout life while three other groups began lifelong restriction to about 75% of ad libitum intake when 6 wk old. The daily schedule of food accessibility differed among these three groups: a single meal during early darkness; a single meal during early light; six smaller meals at about 2-h intervals during darkness. Food restriction as such clearly prolonged life, but there were no statistically significant differences in overall mean life span or in 10th-decile life span among the three restricted groups. Telemetered body temperature data confirmed marked differences in the effects of these different restricted feeding schedules on circadian rhythms. The effect of food restriction on survival is probably not due to altered relations among circadian rhythmic variables. Possible contributing factors suggested by the results are a lower body temperature, a reduced overall metabolic rate and an increased circadian amplitude.

Referrals and investigation patterns in a family physician group: questions for teaching cost containment

Analysis of laboratory use and referrals within a family practice teaching group showed large differences in physicians' behavior. There were three- to four-fold differences between physicians, both for the number and the costs of laboratory use and X-ray services. There were equally large variations in the types of referrals (to medical, dermatologic, obstetric and gynecologic, surgical, ophthalmological and psychological services). There was no consistent pattern for any physician: that is, if a physician used laboratory investigations often, that physician might seldom use X-ray services or might refer fewer patients to specialists. These results have major implications for teachers and for teaching cost containment.

Schedule-shifts, circadian rhythms and lifespan of freely-feeding and meal-fed mice

Mice feeding ad lib were subjected to weekly 12-hr shifts of the daily light-dark (LD) schedule beginning at either 7, 20 or 52 weeks of age and continuing until death. Other mice were meal-fed and, from 7 weeks of age until death, experienced weekly 12-hr shifts of the LD schedule alone (with mealtime fixed) or of both the LD schedule and mealtime. Telemetered core temperature data indicated marked differences in response to the different shift conditions and suggested, in the case of meal-fed animals, involvement of a food-anticipatory rhythm. Shifting of the LD schedule had no statistically significant effect on the mean survival time of mice feeding ad lib, regardless of when shifting began. While meal-feeding in itself prolonged life, the added imposition of schedule-shifting had no statistically significant effect on mean survival time, regardless of whether the meal schedule reinforced or opposed shifts of the LD schedule. In the latter case, tenth-decile survival time may have been increased.

Relative costs of specialist services in a family practice population

The frequency and cost of referrals to specialists in March 1984 for 8980 rostered patients attending a family practice clinic located in a teaching hospital were analysed. The patients made 1891 visits to specialists. In all age groups and for all specialties female patients were more likely to be seen. The total direct provider costs were higher for female patients than for male patients. However, costs per patient seen were higher for male patients, except for psychiatry and medicine. Visits to surgeons had the highest total cost, while visits to psychiatrists had the highest cost per patient seen. Of the direct provider costs 61% was for specialist services. The family physician, in the "gatekeeper" role, has an opportunity to control some of the costs of the health care system by ensuring that the best and most efficient use is made of the referral network.

Demyelinating encephalopathy in Lyme disease

A 38-year-old man from southeastern Connecticut developed a diffuse encephalopathy with partial complex seizures, followed weeks later by arthritis, cryoglobulinemia, and increased serum IgM. CT showed confluent low-density lesions in the deep cerebral white matter consistent with demyelination. Neither the encephalopathy nor the CT abnormalities improved. Lyme disease was diagnosed serologically 4 years later.

Behavioral and physiological effects of ethanol in high-risk and control children: a pilot study

Blood and breath acetaldehyde levels were measured following ethanol ingestion (0.5 ml/kg) in 11 boys familially at risk for alcoholism and 11 age-matched controls. No significant differences were found between groups for acetaldehyde, objective, or subjective measures of intoxication. Previous reports of acetaldehyde as a marker of risk for alcoholism were not confirmed. Baseline behavioral state predicted response to alcohol. Children tended to have a subjective response in a direction opposite from the baseline mood state.

Construction of rhythm-specified reference intervals and regions, with emphasis on 'hybrid' data, illustrated for plasma cortisol

Time-specified reference intervals, so-called chronodesms for the interpretation of single samples, have heretofore been proposed for longitudinal data, consisting of repeated samples from a single individual, and for transverse data: single time-specified samples from many individuals. Herein the problem of dealing with hybrid data, namely time series of data collected on a group of subjects, is considered for a derivation of reference intervals that take into account both inter- and intra-individual variability. The formulae are applied to cortisol data (72 samples from each of 10 healthy young adult North American women) with interpretation from both Bayesian and frequentist viewpoints. The provision of reference limits for both single samples and paired rhythm characteristics offers the opportunity of introducing an overdue time-specification and time-structure evaluation into microscopic chronobiology and through it into medical, veterinarian and other practice.

Circadian murine ouabain chronotolerance revisited

Data published earlier on a possible circadian variation in murine susceptibility to intravenously-administered ouabain and analyzed by conventional biometric methods, were reanalyzed by cosinor procedures. A statistically significant circadian rhythm could thus be demonstrated, contradicting the earlier conclusion that there was no circadian rhythm in susceptibility to ouabain when injected intravenously. Results from this reanalysis agreed with those from previous investigations in which ouabain was injected intraperitoneally or subcutaneously. Thus, a circadian rhythm characterizes murine susceptibility to ouabain given via 3 different routes.

Glycine and benzoate conjugation and glycine acyltransferase activity in the developing and adult rat: possible relationships to nonketotic hyperglycinemia

We report investigations of benzoate and glycine metabolism and glycine acyltransferase activity in rats. These studies provide insights related to the therapy and pathophysiology of human nonketotic hyperglycinemia. Liver acyltransferase activity increased sharply postnatally from low levels at birth, but transferase activity was absent in the brain. The enzyme level was unchanged in either organ after administration of 2,3,7,8-tetrachlordibenzodioxin, phenobarbital, benzoate or a high glycine diet. Brain and liver glycine levels remained unaltered during acute or chronic benzoate-induced reductions in plasma glycine levels. Plasma and brain glycine contents were measured in rats at different ages following a single injection of 3 mg glycine/g body weight; after injection, glycine levels in the brain were comparable in severely symptomatic neonatal rats and older asymptomatic rats, suggesting a similar glycine influx but a selective susceptibility of the newborn brain to toxicity from acute hyperglycinemia. When a 3.4% glycine diet was ingested for up to 30 days ad libitum, levels of plasma glycine rose about 4- to 5-fold from those achieved on a diet containing one tenth as much glycine, but brain and liver glycine concentrations increased only 2-fold or less in the chronically hyperglycinemic animals.

Rhythm-adjusted age effects in a concomitant study of twelve hormones in blood plasma of women

The concentrations of luteinizing hormone, prolactin, estrone, estradiol, 17-hydroxyprogestrone, cortisol, aldosterone, dehydroepiandrosterone, thyrotropic hormone, triiodothyronine, thyroxin and insulin were determined in blood plasma obtained from women aged 15 to 59 years. Blood was sampled at intervals of 20 to 100 min throughout 24-hour spans in each of the four seasons and (in the case of cycling women) in four different stages of the menstrual cycle. With such sampling allowing for rhythmic and other fluctuations over a broad time scale it was possible to demonstrate statistically significant effects of age on hormones associated with the menstrual cycle (luteinizing hormone, prolactin, estrone, estradiol and 17-hydroxyprogesterone) and on dehydroepiandrosterone, but not on the remainder. The amplitude of circadian rhythms in several of the hormones also varied with age, thus affirming the value of sampling throughout this particular rhythm.

Cryoanalgesia for post-thoracotomy pain

Intercostal block by a freezing technique was compared with blockade by local anaesthetics or no blockade as a method of treating post-thoracotomy pain. The 15 patients who received cryotherapy had significantly less postoperative pain than the 9 patients whose nerves were blocked by local anaesthetics or who did not receive any nerve block. The interruption of nerve function produced by cryotherapy was temporary (not more than 30 days), and there were no adverse sequelae.

Attempts at use of strychnine sulfate in the treatment of nonketotic hyperglycinemia

In two cases of nonketotic hyperglycinemia treated from early ages with strychnine sulphate, the patients demonstrated persistent severe psychomotor retardation and seizures. Strychnine therapy improved tone and feeding, but did not seem to alter fundamentally the course of the disease in either patient.

Strain-difference in circadian murine chronotolerance to the antidepressant drug nomifensine

The anti-depressant drug nomifensine (8-amino-1,2,3,4-tetrahydro-methyl-4-phenylisoquinoline) was administered at several dose levels to mice of 2 inbred strains at one of 6 circadian times 4h apart under conditions standardized for light-dark synchronized rhythmometry. A circadian rhythm in tolerance to nomifensine reflected by differences in mortality was demonstrated for both C57 and DBA mice. An interstrain difference in tolerance was also observed.