Behavior of Lambs in Rest Pens During Long-Distance Transport

The aim of this study was to determine how one group of lambs utilized 2 consecutive rest periods in novel environments with access to food and water that occurred during 22 hr of motor transport. The 18.5 ± 0.6 kg lambs (n = 15) were transported for 8 hr and then unloaded for a 6-hr rest period. After 6 hr, the lambs were reloaded for another 8 hr of transport followed by a 24-hr rest period. Reloading for a second 8 hr of transport followed the initial rest period. The percentage of lambs engaged in drinking, eating, lying, playing, or “other” was determined at 15-min intervals. During the 6-hr rest period, peak lying behavior occurred during the 2nd and 6th hr of the period. During the first 6 hr of the 24-hr rest period, the percentage of lambs lying increased while the percentage of lambs eating decreased. In addition, the percentage of lambs lying during the first 6 hr of the 24-hr rest period was greater than during the 6-hr rest period. Lying down had a greater priority than eating during the second (24-hr) rest period.     

The internal synchronization of five circadian functions of the rabbit

Five different physiological functions of the rabbit (hard faeces and urine excretion, food and water intake and locomotor activity) were registered during LD 12:12 and during continuous light conditions (LL).

(1) In LD 12:12 a strong synchronization of the five parameters existed. The minima of all functions consistently occurred during the hours of light. The nocturnal percentage of overall 24-hr events was increased significantly in 'hard faeces excretion' (66±8 (S.D.) %), 'water intake' (64±15 (S.D.) %) and 'urine excretion' (58±10 (S.D.) %). The nocturnal percentage of locomotor activity was significantly increased during the dark-hours in 9 out of 14 animals. In the other five individuals prominent peaks were present even during the photoperiod. On the average of all 14 animals 5S±13 (S.D.) % of the 24 hr events of locomotor activity occurred during the night. Despite a trough during the cessation of hard faeces excretion the events of food intake were not elevated significantly during the dark hours.

(2) During LL the synchronization of the five functions within each animal persisted during the complete 90-day LL period. A free-running circadian rhythm with-: = 24.8±0.5 (S.D.) hr was present in the four rabbits kept in LL conditions within 5-16 days after the withdrawal of the zeitgeber.

(3) In addition to the circadian period the power spectrum analysis of data obtained during LD 12:12 revealed significant ultradian periods of an average period length of 11,6 hr (hard faeces and urine excretion), 8 hr (food and water intake, locomotor activity) and 4 hr (food intake, locomotor activity). During the free-run ultradian periods of 8 and 3.2-4.2 hr were significant in almost all parameters.

(4) During LL the level of locomotor activity was reduced for 13±16 (S.D.) %, the events of food intake were increased for 17±12 (S.D.) %.

(5) The reinserted LD 12:12 zeitgeber re-entrained the circadian rhythms within 25-45 days.

(6) These results provided evidence of a predominant nocturnality of the rabbits under investigation.     

Effects of age on fasting-induced changes in insulin, glucose, urea nitrogen, and free fatty acids in sera of sheep

The hypothesis that prepubertal ewe lambs are metabolically different from postpubertal ewes was tested. Ovariectomized ewes (4 years of age; n = 4) and lambs (6 months of age; n = 4) were fasted for 72 hr. Serum concentrations of insulin, glucose, urea nitrogen, and free fatty acids (FFA) were measured in blood samples taken at 6-hr intervals between 30 hr before and 72 hr after feed removal. Serum concentrations of urea nitrogen and glucose were not different (P greater than 0.20) between age groups before fasting. Serum concentrations of insulin in ewes increased toward the end of the prefast period whereas those in lambs did not (age x time, P less than 0.01). Serum concentrations of FFA in ewes tended to be lower (P less than 0.07) than those in lambs prior to fasting. During fasting, concentrations of insulin decreased (P less than 0.02) over time in ewes and lambs and did so in a similar manner (age x time, P greater than 0.70). Urea nitrogen increased (P less than 0.0001) in both fasted ewes and fasted lambs in a comparable manner (age x time, P greater than 0.20). Concentrations of glucose during fasting were not significantly affected (P greater than 0.90) by age. There was a tendency (P = 0.08) for concentrations of glucose to change over time but the pattern did not appear to be related to fasting. During fasting, concentrations of FFA tended to be higher (P less than 0.07) in lambs than in ewes and increased (P less than 0.0001) in both groups in a similar fashion (age x time, P greater than 0.10). The findings herein suggest that turnover of FFA in lambs may be slightly greater than that in ewes during the fed and fasted states.     

Effects of constant darkness and constant light on circadian organization and reproductive responses in the ram

The relationship between circadian rhythms in the blood plasma concentrations of melatonin and rhythms in locomotor activity was studied in adult male sheep (Soay rams) exposed to 16-week periods of short days (8 hr of light and 16 hr of darkness; LD 8:16) or long days (LD 16:8) followed by 16-week periods of constant darkness (dim red light; DD) or constant light (LL). Under both LD 8:16 and LD 16:8, there was a clearly defined 24-hr rhythm in plasma concentrations of melatonin, with high levels throughout the dark phase. Periodogram analysis revealed a 24-hr rhythm in locomotor activity under LD 8:16 and LD 16:8. The main bouts of activity occurred during the light phase. A change from LD 8:16 to LD 16:8 resulted in a decrease in the duration of elevated melatonin secretion (melatonin peak) and an increase in the duration of activity corresponding to the changes in the ratio of light to darkness. In all rams, a significant circadian rhythm of activity persisted over the first 2 weeks following transfer from an entraining photoperiod to DD, with a mean period of 23.77 hr. However, the activity rhythms subsequently became disorganized, as did the 24-hr melatonin rhythms. The introduction of a 1-hr light pulse every 24 hr (LD 1:23) for 2 weeks after 8 weeks under DD reinduced a rhythm in both melatonin secretion and activity: the end of the 1-hr light period acted as the dusk signal, producing a normal temporal association of the two rhythms. Under LL, the 24-hr melatonin rhythms were disrupted, though several rams still showed periods of elevated melatonin secretion. Significant activity rhythms were either absent or a weak component occurred with a period of 24 hr. The introduction of a 1-hr dark period every 24 hr for 2 weeks after 8 weeks under LL (LD 23:1) failed to induce or entrain rhythms in either of the parameters. The occurrence of 24-hr activity rhythm in some rams under LL may indicate nonphotoperiodic entrainment signals in our experimental facility. Reproductive responses to the changes in photoperiod were also monitored. After pretreatment with LD 8:16, the rams were sexually active; exposure to LD 16:8, DD, or LL resulted in a decline in all measures of reproductive function. The decline was slower under DD than LD 16:8 or LL.(ABSTRACT TRUNCATED AT 400 WORDS)     

Administration-time-dependency of the pharmacokinetic behavior and therapeutic effect of a once-a-day theophylline in asthmatic children

Using a double-blind, placebo-control, crossover study design, 8 asthmatic children (8-15 years) were evaluated for temporal patterns in airways function throughout separate study periods when treatment was placebo or Theo-24 once-daily on separate occasions at 0600, 1500 or 2100 hr. During 39-hr in-hospital observations, pulmonary function and serum theophylline concentrations (STC) were assessed every 3 hr under all treatments. The pharmacokinetics of Theo-24 varied greatly depending on the dosing time. For the afternoon and evening dosings, the Cmax, Tmax, AUC, % swing, % fluctuation, % AUC fluctuation, % nocturnal excess and Cav(2-6 hr) were all statistically significantly greater than for the morning dosing. Compared with the placebo regimen, dosing patients with Theo-24 at 1500 hr disrupted circadian patterns of airways function, especially airways patency, while dosing at 2100 hr, reduced the amplitude and shifted the acrophase of several spirometric measures to a slightly earlier time. Theo-24 treatment irrespective of dosing time resulted in comparable enhancement of the group 24-hr mean, minimum and maximum values of airways patency with reference to placebo baselines. Theo-24 dosing at 1500 or 2100 hr, however, resulted in the best effect on the airways as assessed by the 24-hr mean FEV 1.0 level in 7 of the 8 asthmatic children. When the drug was given at 1500 hr, the time of lowest FEV 1.0 was shifted from the nighttime hours in 5 of 8 patients. These findings suggest that clinicians need to individualize the theophylline dosing schedule of patients to best control the symptoms of asthma.     

Rapid photoperiodic responses in Japanese quail: is daylength measurement based upon a circadian system?

Experimental photoperiods, presented either once only or repeatedly, were used to assess the oscillatory and hourglass properties of the photoperiodic clock in Japanese quail. Gonadectomized quail on 8-hr daylengths respond to a single skeleton photoperiod consisting of two 8-hr light pulses separated by 2 hr of darkness (i.e., LDLD 8:2:8:6) with a marked increase in secretion rate of luteinizing hormone (LH). This response suggests that the second light pulse interacts with a "photoinducible phase" (phi i) lying some 10-16 hr from "dawn" (start of the first light pulse). If, however, groups of quail maintained on 8-hr daylengths are transferred to continuous darkness (DD), and the position of the phi i is sought by a single 8-hr light pulse applied at various times on the first or third day of DD, then an increase in circulating LH is, at best, barely detectable. It would appear that a strongly responsive phi i does not recur rhythmically in DD. Instead, the light pulse apparently acts primarily as a "dawn" signal that triggers a single cycle of photoinducibility, since a second 8-hr light pulse, placed to begin 2 hr after the end of the first, induces a large increase in plasma LH. Similar results are obtained if any single 8-hr light pulse presented to animals held in darkness is preceded, 10 hr earlier, by a short "dawn" light signal. Such dawn signals can be effective when very short; a pulse of only 30 sec can cause a subsequent phi i. The dawn pulse is effective at any circadian phase and leads to a single cycle in photoinducibility. In contrast, a much longer light pulse (perhaps not less than 4 hr) is needed to interact with phi i if significant gonadotropin secretion is to be stimulated. In confirmation of the findings described above, we found that Nanda-Hammer lighting schedules have remarkably little effect in stimulating gonadotropin secretion in gonadectomized quail. There is, for example, a very marked difference between the effectiveness of "resonating" schedules such as LD 6:6, which stimulates a high LH secretion rate since each "inductive" light pulse is preceded by an appropriate "dawn" signal, and a theoretically effective schedule such as LD 6:30, which induces a very small response by comparison. Such schedules (even theoretically noninductive ones) can, however, be made very highly inductive if alternate light pulses are preceded by an appropriately positioned 15-min light pulse to act as "dawn."     

Growth Characteristics of Kilham Rat Virus and Its Effect on Cellular Macromolecular Synthesis

Kilham rat virus (KRV) is adsorbed into the rat nephroma cell within 1 hr after infection. There follows a latent period of about 12 hr during which less than 1% of the input infectious virus can be accounted for. New infectious virions can be detected at about 12 hr and the maximal yield of virus is attained by 23 hr after infection. The increase in final virus yield is about 200-fold over that found in the latent period. During this 23-hr period of virus growth, the rate of protein synthesis remains 75 to 100% of that in the uninfected cell. Ribonucleic acid (RNA) synthesis during this period is maintained at 100 to 150% of that found in the control cells. The addition of the inhibitor of deoxyribonucleic acid (DNA) synthesis, 5-fluoro-deoxyuridine (FUDR), up to 8 hr after infection completely suppresses virus production. After 8 hr, viral DNA production has started and FUDR inhibition progressively decreases until by 23 hr the addition of the inhibitor no longer causes a reduced virus yield. Viral DNA synthesis once initiated is required for the remainder of the 23-hr virus cycle. Viral DNA synthesis probably begins about 4 hr before the production of infectious virions. In the KRV-infected cells, DNA synthesis decreased sharply for 6 to 7 hr after infection in comparison to the uninfected cell. At 7 to 8 hr after infection, DNA synthesis in the infected cell increased and was maintained at a higher level than in the control cells for the rest of the virus growth period.     

Relationship of diaphragmatic contractility to diaphragmatic blood flow in newborn lambs

We determined the relationship of diaphragmatic contraction rate to diaphragmatic blood flow (Qdi), metabolism, and contractility in nine open-chested mechanically ventilated newborn lambs. The diaphragm was paced for 15 min at slow (20/min) and fast (100/min) contraction rates each followed by a 30-min rest period. There was a mild reduction in transdiaphragmatic pressure (Pdi) during the slow contraction period accompanied by a shift to the right of the curve relating stimulation frequency (10-100 Hz) to Pdi. Pdi returned to control at the start of the fast contraction period, but then fell by 30% within 2 min with continued fast contraction rates. The frequency-Pdi curve was significantly shifted to the right. Qdi, O2 transport, and O2 consumption increased during slow contraction and to an even greater extent during fast contraction. Fractional O2 extraction reached an apparent maximum during slow contraction. Lactate efflux from the right phrenic vein during slow contraction remained unchanged from control. During fast contraction lactate efflux rose proportionately more than did O2 consumption. We conclude that the energy demands at fast rates of diaphragmatic contraction in newborn lambs cannot be met by aerobic metabolism alone despite increasing O2 transport to the diaphragm.     

Atypical 24-hour rhythms of serotonin N-acetyltransferase activity in the rat pineal gland

Previous long-term studies have shown that in the pineal gland of rats melatonin synthesis is subject to infradian rhythms with periods between 4 and 7 days. Since in these studies melatonin-related parameters were measured at one timepoint of a 24-hr cycle only, the aim of the present investigation was to extend these experiments by more frequent sampling, to characterize the infradian rhythmicity in more detail. Male Sprague-Dawley rats kept under a light schedule of LD 12:12 (lights on at 0700) were killed at 6-hr intervals on 8 consecutive days. After decapitation the pineal gland was rapidly dissected out, followed by measurements of one of the melatonin-forming enzymes, serotonin N-acetyltransferase (NAT) activity. It was found that pineal NAT activity exhibited the well known day/night rhythm, i.e. low activity during daytime and strikingly enhanced activity at night, during the first 4 days of the experiment. On the fifth night (from Saturday to Sunday) an unusually high NAT peak occurred at 2400 hr, followed by two atypical 24-hr cycles. In the first cycle the midnight and 0600 hr values were equal and in the second cycle the 0600 hr value was significantly higher than the midnight value. To investigate whether the unusually high NAT peak was a single event or not, four additional short-term experiments were carried out at 2400 hr on 4 consecutive weekends, from Friday to Monday. In each of the four 4-day experiments a distinctly higher peak of NAT activity was found on Saturday, but with time the peaks became less prominent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased urinary polyamine excretion during liver regeneration

Tumor growth is a process associated with both cell proliferation and cell death. The increase in polyamine excretion observed in cancer patients may be partly due to leakage of polyamines from proliferating cells, which all contain an elevated polyamine level. However, the increased polyamine excretion may also be due to a release of polyamines from dead or damaged cells. To determine if actively proliferating cells release polyamines, the urinary polyamine excretion was measured during a proliferative event associated with minimal cell necrosis. Rats subjected to partial hepatectomy were used as an experimental model. Their 24-hr urines were collected during 6 consecutive days following the operation. Rat liver regeneration is characterized by a proliferation wave with a maximum 24 hr after the operation. The 24-hr urinary putrescine excretion reached a maximum 2 days after the operation and then decreased. The 24-hr urinary spermidine excretion increased during the second day following operation and remained essentially unchanged during the rest of the experimental period. Although there is an apparent correlation between elevated urinary polyamine excretion and the proliferative activity, concurrent permeability changes and necrotic events may contribute to the increase in polyamine excretion.     

Reorganization and stabilization of acetylcholine receptor aggregates on rat myotubes

Aggregation of acetylcholine receptors (AChRs) is an important early feature of the postsynaptic development of the vertebrae neuromuscular junction. At later stages of differentiation, aggregates are remodeled and stabilized. Aggregation of AChRs can be induced on rat myotubes in culture within 4 hr by treatment with embryonic pig brain extract (EBX). In this study, further sequential changes in the distribution of AChRs were followed by video-intensified fluorescence microscopy. These studies have revealed that groups of AChR aggregates that have formed after 4 hr in EBX are reorganized during the exposure to EBX for 20 additional hr to form a smaller number of larger, oval-shaped aggregates. We have named these two types of aggregates "4-hr aggregates" and "24-hr aggregates". This reorganization occurs by the expansion and merging of individual aggregates within a group, and by the incorporation of newly inserted AChRs. The 24-hr aggregates are an average of 15 times greater in area than 4-hr aggregates, and contain regions with an apparent AChR site density (fluorescence intensity) that is more than twice that of 4-hr aggregates. Electron microscopy of mapped 24-hr aggregates revealed that folded plasma membrane is associated with these regions, probably accounting for the elevated fluorescence. The 24-hr aggregates are more stable than 4-hr aggregates, as determined by their significantly slower disassembly after removal of EBX, elevation of temperature (38 degrees C), reduction of extracellular calcium levels (0.1 mM), or the addition of sodium azide (7 mM). This was determined by following disassembly both statistically (using fixed cultures) and by direct observations of living myotubes. These findings were confirmed by measuring the sequential changes in relative AChR site density over time in individual living myotubes. Thus, 24-hr aggregates form by the reorganization of 4-hr aggregates; exhibit a more regular, compact shape; and are more stable than 4-hr aggregates. These changes in AChR organization and aggregate stability resemble the changes occurring after the initial formation of junctional AChR aggregates during embryonic development, demonstrating additional similarities between this model system and the developing neuromuscular junction.     

Effects of duration, concentration, and timing of ionomycin and 6-dimethylaminopurine (6-DMAP) treatment on activation of goat oocytes

The protocol of ionomycin followed by 6-dimethylaminopurine (6-DMAP) is commonly used for activation of oocytes and reconstituted embryos. Since numerous abnormalities and impaired development were observed when oocytes were activated with 6-DMAP, this protocol needs optimization. Effects of concentration and treatment duration of both drugs on activation and development of goat oocytes were examined in this study. The best oocyte activation (87-95%), assessed by pronuclear formation, was obtained when oocytes matured in vitro for 27 hr were treated with 0.625-20 microM ionomycin for 1 min before 6-hr incubation in 2 mM 6-DMAP. Progressional reduction of time for 6-DMAP-exposure showed that the duration of 6-DMAP treatment can be reduced to 1 hr from the second up to the fourth hour after ionomycin, to produce activation rates greater than 85%. Activation rates of oocytes in vitro matured for 27, 30, and 33 hr were higher (P < 0.05) than that of oocytes matured for 24 hr when treated with ionomycin plus 1-hr (the third hour) 6-DMAP, but a 4-hr incubation in 6-DMAP enhanced activation of the 24-hr oocytes. Goat activated oocytes began pronuclear formation at 3 hr and completed it by 5-hr post ionomycin. An extended incubation in 6-DMAP (a) impaired the development of goat parthenotes, (b) quickened both the release from metaphase arrest and the pronuclear formation, and (c) inhibited the chromosome movement at anaphase II (A-II) and telophase II (T-II), leading to the formation of one pronucleus without extrusion of PB2. In conclusion, duration, concentration, and timing of ionomycin and 6-DMAP treatment had marked effects on goat oocyte activation, and to obtain better activation and development, goat oocytes matured in vitro for 27 hr should be activated by 1 min exposure to 2.5 microM ionomycin followed by 2 mM 6-DMAP treatment for the third hour.     

Circadian rhythm of serotonin binding in rat brain--II. Influence of sleep deprivation and imipramine

Sleep deprivation (SD) modified the circadian rhythm of specific high affinity serotonin (5-HT) binding to rat brain membranes. In control rats a 24-hr rhythm was evident with a trough at 1000-1200 and a nadir at 0000. During the last 26 hr of a 49 hr SD period, trough and peak values were delayed by 4-6 hr. The 24-hr mean binding was significantly (P less than 0.001) different from that of controls. If sleep deprivation was followed by recovery sleep (RS), the normal rhythm of 5-HT binding was obtained already within 1 hr after SD. The effects of SD and RS were ascertained by plasma ACTH and corticosterone assay. No significant change in the hormone rhythms were observed through the mean plasma level of ACTH and corticosterone were enhanced to about 180 and 150%, respectively. Chronic treatment with the antidepressant imipramine resulted in a decrease of the 24-hr mean 5-HT binding by about 50% and a 2-hr delay of peak and trough values. Imipramine treatment decreased the peak value of 5-HT concentration at 1000 to about 65% and appears to abolish the rhythm of 5-HT concentration.     

A new protocol for studying the early events during liver regeneration

Hepatic amino acid transport and ornithine decarboxylase (ODC) activity were measured as early events during liver regeneration in rats adapted to a meal-feeding protocol in which food was presented during the first 2 hr of a daily 12-hr dark period. Surgeries were performed during the early hours of the light period, and food was withheld on the day following surgery to control the effect of feeding on the parameters measured. Initial experiments indicated that rats maintained on this schedule were capable of surviving partial hepatectomy. The survival rate was greater and the fat pads larger among 56-day-old than among 42-day-old rats; this indicated that animals with greater metabolic reserves were better suited for these experiments. The hepatic α-aminoisobutyric acid (α-AIB) distribution ratio and ODC activity increased above control values by 2 hr following partial hepatectomy. The α-AIB distribution ratio peaked at 10 hr after surgery and remained above control values for an additional 16 hr. In contrast, ODC activity peaked by 4 hr after surgery, followed by two smaller peaks at 10 and 20 hr. In sham-hepatectomized rats both the α-AIB distribution ratio and the ODC activity increased above control values by 3 hr after surgery, but fell to control values by 15 hr. These findings show that increases in amino acid transport and ODC activity following partial hepatectomy occur independently of feeding. The identical time course for the initiation of both of these events suggests that they result from a common effector.     

Origin of esterified cholesterol transported in the very low density lipoproteins of human plasma

In two subjects the specific activity of esterified cholesterol in plasma lipoprotein subfractions was measured for up to 9 hr after an intravenous injection of [(3)H]mevalonic acid. It was found to be consistently higher in larger (S(f) > 100) than in smaller (S(f) 20-100) very low density lipoproteins (VLDL). Four subjects were given an intravenous injection of heparin so that the VLDL could be studied as its concentration fell and subsequently rose again. During the first hour the relative reduction was greatest for triglyceride, intermediate for free cholesterol, and least for esterified cholesterol. Between 1 and 7 hr postheparin, the VLDL pool was restored, but the pattern of increase of individual lipids was not parallel. The triglyceride increment was much greater during the 1-4-hr period than during the 4-7-hr period; in three of the subjects the free cholesterol increment was also greater during the earlier period. The increase in esterified cholesterol, however, was consistently greater during the 4-7-hr period. In six other subjects the specific activity of VLDL esterified cholesterol was related to that of its possible plasma precursors in samples collected at 1-hr intervals for 8 hr after the injection of [(3)H]mevalonic acid. Free cholesterol emerged as the most likely immediate precursor with the possibility of a hepatic as well as an intraplasma origin. The results did not support a major in vivo transfer of esterified cholesterol from high density lipoproteins to VLDL.     

Reduced space in outdoor feedlot impacts beef cattle welfare

There is a trend to reduce the space allowance per animal in cattle feedlot, despite its potential negative impact on animal welfare. Aiming to evaluate the effects of space allowance per animal in outdoor feedlots on beef cattle welfare, a total of 1350 Nellore bulls (450 pure and 900 crossbred) were confined for 12 weeks using three space allowances: 6 (SA6), 12 (SA12) and 24 (SA24) m²/animal (n = 450 per treatment). Bulls were housed in three pens per treatment (n = 150 per pen). The first 6 weeks in the feedlot were defined as ‘dry’ and the last as ‘rainy’ period, according to the accumulated precipitation. Animal-based (body cleanliness, health indicators and maintenance behaviour) and environmental-based indicators (mud depth and air dust concentration) were assessed weekly during the feedlot period. Most of the health indicators (nasal and ocular discharge, hoof and locomotion alterations, diarrhoea, bloated rumen and breathing difficulty) were assessed in a subset of 15 animals randomly selected from each pen. Coughs and sneezes were counted in each pen. Maintenance behaviours (number of animals lying and attending the feed bunk) were recorded with scan sampling and instantaneous recording at 20-min intervals. Postmortem assessments were carried out in all animals by recording the frequencies of macroscopic signs of bronchitis, pulmonary emphysema, nephritis and urinary cyst and by measuring the weight and cortical and medullar areas of adrenal glands (n = 30 per pen). Compared with SA12 and SA24, SA6 showed a greater number of sneezes per minute during the dry period and a greater percentage of animals with locomotion alterations during the rainy period. Coughing, diarrhoea and nasal discharge affected a larger number of animals in the SA6 relative to the other two groups. During the rainy period, there was a lower percentage of animals with nasal and ocular discharge, and a greater percentage of animals with abnormal hoof and lying. A lower percentage of animals in SA6 and SA12 (but not SA24) attended the feed bunk during the rainy relative to the dry period. A mud depth score of 0 (no mud) was most frequent in SA24 pens, followed by SA12 and then SA6. Adrenal gland weight and cortical area were lower in SA24 animals compared with those in SA6 and SA12. The results show that decreasing the space allowance for beef cattle in outdoor feedlots degrades the feedlot environment and impoverishes animal welfare.     

Hemodynamic Changes During Long Meditation

Changes in heart rate (HR) and blood pressure (BP) in advanced male meditators during 1 hr of meditation were compared with matched control participants resting for 1 hr. Also, changes in HR and BP during 3-hr meditation were analyzed. HR was recorded continuously during meditation (n = 38) and the control rest (n = 21). BP was measured before and after the meditation (n = 44) and the rest (n = 30). During the first hour, HR declined more in the meditators than the controls (p < .01). Within participant variability of HR was significantly lower during meditation than rest (p < .05). In the second hour of meditation, HR declined further (p = .01). BP was unaffected by either meditation or rest. In conclusion, meditation reduced the level of HR and within participant variability of HR more than rest. HR continued to decline during the second hour of meditation.     

Effects of Endurance Exercise on Nocturnal Hormone Concentrations in Males

A preliminary study was conducted to evaluate the change in nocturnal concentrations of testosterone, luteinizing hormone, growth hormone, prolactin, thyroxine, and Cortisol following a control day (no exercise) and on a day in which exercise was performed. Exercise consisted of 90 min of cycling at 70% of each subject's maximal oxygen uptake. The exercise occurred from 1630 to 1800 hr on the exercise day while a comparable period of rest took place on the control day. Hormonal concentrations were evaluated at 2-hr intervals for a 12-hr period each night (2000-0800 hr). The subjects slept from 2255 (± 20 min [x ± S.E.M.]) until 0715 (± 15) during each night. All hormone responses were plotted and integrated for the 12-hr period. Analysis indicated that a significant augmentation of the prolactin and thyroxine responses occurred, while concurrently an attenuation of the growth hormone and Cortisol responses were observed. Contrastingly, no significant effects were found for the testosterone and luteinizing hormones responses. The physiological significance of these findings remained to be determined, but the results do suggest that further research is warranted in the area.     

Daily changes in concentrations of prolactin in serum of prepubertal bulls exposed to short- or long-day photoperiods

Early temporal changes in concentrations of prolactin (PRL) in serum after a sudden change in photoperiod and daily responsiveness to PRL-releasing and inhibiting factors were investigated in prepubertal Holstein bull calves exposed to different photoperiods. In calves switched from 8-hr light: 16-hr dark to 16-hr light:8-hr dark, there was no observable change in the daily pattern of serum concentrations of PRL after 1, 2, or 4 days. On the other hand, in animals switched from 16-hr light:8-hr dark to 8-hr light:16-hr dark, there was a consistent increase in serum PRL from 33.4 ng/ml on Day 0 to maximum values of 57.3, 62.7, and 78.9 ng/ml between 14 and 18 hr after onset of light on Days 1, 2, and 4, respectively. Thus, absence of light allowed expression of a daily rhythm in serum concentrations of PRL that persisted for at least 4 days after the photoperiod switch. There were no differences in L-dopa inhibition of PRL release in animals exposed to 16-hr light:8-hr dark at 3 or 15 hr after onset of light. However, thyrotropin-releasing hormone-induced release of PRL was greater 3 hr after onset of light (11 hr after onset of dark) compared with release at 9, 15, and 21 hr after onset of light in animals exposed to 16-hr light:8-hr dark, but not in bulls exposed to 8-hr light:16-hr dark. The results provide evidence that the cue for the putative photosensitive period of PRL secretion in cattle may be more closely associated with onset of dark, not onset of light.     

Changes in the sensitivity of lipogenesis in rat hepatocytes to hormones and precursors over the diurnal cycle and during longer-term starvation of donor animals

In rat hepatocytes freshly isolated from donor rats at different times of the day, the rates of lipogenesis (de novo fatty acid synthesis) varied with a diurnal periodicity. The maximal rate occurred approximately 5 hr after the end of the normal 8-hr feeding period and at this time was four- to fivefold higher than the minimum rate which occurred midway through the feeding period. A similar diurnal pattern of change persisted even when the supply of lipogenic substrate, present in the medium as pyruvate, was not limiting. Although insulin stimulated the basal rates of lipogenesis to different relative extents in hepatocytes isolated at different times of the day, in absolute terms the hormone had little effect on the overall pattern of change during the diurnal cycle. The presence of pyruvate protected lipogenesis against inhibition by glucagon. The degree of protection varied over the diurnal cycle. During the early stages of starvation (up to 24 hr) there was a continuous decline in the rate of hepatocyte lipogenesis, irrespective of whether insulin and/or lipogenic substrate (pyruvate) were available or not. After this time the decline in the rate of lipogenesis was much less rapid. Seventeen hr after removal of food from donor rats, a point was reached beyond which pyruvate was incapable of supporting the maximum basal rate of lipogenesis which occurred during the normal diurnal cycle of fed rats. After this time lipogenesis in the presence of pyruvate was inhibited by glucagon to a much greater relative extent than that observed during feeding. The results suggest that variations in the rate of lipogenesis over the diurnal cycle and during the first 24 hr of starvation could not be accounted for entirely by fluctuations in substrate availability. In contrast, changes which occurred subsequent to this (up to 43 hr of starvation) could be eliminated when lipogenic substrate was made more abundant. Longer periods of starvation were marked by a relative increase in the ability of glucagon to prevent the substrate-induced stimulation of lipogenesis.