A test for photorefractoriness in high-producing stocks of laying pullets

1. Pullets of 2 high-producing commercial stocks (both brown-egg layers) were exposed to 5 different lighting patterns between 18 and 72 weeks to test the hypothesis that photoperiods used in commercial lighting programmes early in the laying year may be unnecessarily long and, by accelerating the development of photorefractoriness, may contribute to the decline in egg production observed after the initial peak. Two rooms of 288 pullets were allocated to each treatment. 2. The rate of lay observed with a Step-Up treatment which gave increases in photoperiod from 8L:16D at 18 weeks to 15L:9D at 27 weeks of age was not significantly different from that of treatments which held the birds on 11L:13D during peak egg production but gave increments up to 15L:9D later in the laying year. 3. A control group maintained on 11L:13D from 20 to 72 weeks laid 295 eggs per bird housed and a further group held on 8L:16D from 0 to 72 weeks laid 284 eggs per bird. These yields were lower than the Step-Up treatment (299 eggs) but show the potential of modern hybrid stocks to lay prolifically even without light stimulation. 4. It is concluded that the stocks tested in this experiment showed no advantage when given lighting programmes in the first laying year which were designed to minimise the adverse effects of photorefractoriness.     

Dual origins of Finns revealed by Y chromosome haplotype variation

The objective of this study was to determine effects of photoperiod and age on the circulating concentrations of LH, testosterone (T), thyroxine (T4), and semen production in male turkeys. Male turkeys from 10 or 12 wk of age were maintained under either a long-day (LD) photoperiod of 16L:8D up to 35 wk (LL), or a short-day (SD) photoperiod of 6L:18D to 29 wk and then an LD photoperiod of 16L:8D up to 35 wk of age (SL). Plasma concentrations of both LH and T increased by 17 or 18 wk of age under both photoperiods, but higher levels were attained in the LL group prior to 29 wk of age. Both LH and T levels increased significantly within days in the SL group after the group was switched to LD at 29 wk of age. Higher levels of T4 were present in the LL group prior to sexual maturation. No differences were observed in T4 concentration between lighting treatments after sexual maturation. The LL group first produced semen at 20-22 wk of age, which was about 1 wk earlier than first semen production in the SL group. A significantly larger volume of semen was produced in the LL group at most ages. No further increase in semen production was observed in the first 6 wk after the SL group was switched to the LD photoperiod at 29 wk of age. Pulsatile patterns of LH and T were characterized by serial blood sampling at 13, 23, and 35 wk of age under both the LL and SL photoperiods. The baseline levels of both LH and T in male turkeys were influenced by age and photoperiod. However, pulse characteristics (numbers, duration, and amplitude) of LH did not change with age or lighting treatment, while pulse characteristics of T did change with age. We conclude that exposing male turkeys to an LD photoperiod from 10 or 12 wk of age advanced the age of sexual maturation and induced earlier increased concentrations of LH and T.     

Lessons learned from the DIASTAT vascular access graft

In male Syrian hamsters, short days induce regression of the reproductive system, but eventually spontaneous recrudescence occurs ensuing from refractoriness to the inhibitory photoperiod. Although the photoperiod of 12 L:12 D (12 h light:12 h dark) may act like a short day by inducing the testicular cycle outlined above, it may fail to evoke the increase of circulating concentrations of prolactin that accompanies testicular recrudescence. This photoperiod may fail to induce photorefractoriness, as indicated by the prolonged low concentrations of prolactin in the blood. Herein, hamsters were exposed to either 8 L:16 D or 12 L:12 D from weaning and by 28 weeks exposure to either photoperiod, the hamsters had large testes following recrudescence from a photoperiod induced-regression). Transfer to 8 L:16 D from 12 L:12 D at 28 weeks resulted in a second testicular regression and recrudescence. In a second experiment, the testes of hamsters moved to 8 L:16 D from 12 L:12 D after 29 weeks exposure to the latter photoperiod similarly regressed and then regrew. Serum concentrations of prolactin decreased in these males after transfer to the shorter daylength but also decreased in hamsters kept under 12 L:12 D both groups were usually below those of hamsters moved to 14 L:10 D. These results show that exposure for 28 or 29 weeks to 12 L:12 D was insufficient to induce photorefractoriness, despite the recrudescence of the testes following involution.     

The effect of accidental pre-lighting of turkey hens on subsequent reproduction

The length of the light day was accidentally increased from nine hours to continuous light on one group of thirty-week old hens for an unknown period of not more than eleven days. Egg production, after attaining a level of twenty-five percent, ceased five weeks later as the result of restricting the length of the light day to four hours and two series of feed and water deprivations. One month later hens from the pre-lighted and control groups were brought into egg production. Pre-lighting depressed later egg production more in medium-bodied hens than in large-bodied hens. The major effect of pre-lighting was to reduce the length of a laying period included 9 weeks later with no significant effects on intensity of lay, number of broody periods or average length of the broody period. It was concluded that the egg production would not be greatly reduced by pre-lighting under the above conditions if the length of the laying period were shortened from 180 days to a normal 140-day period.     

Fosinoprilate prolongs the action potential: reduction of iK and enhancement of the L-type calcium current in guinea pig ventricular myocytes

Changes in the gross and cellular morphology of the nucleus preopticus medianus (POMn) were measured in response to changes in photoperiod in adult male Japanese quail (Coturnix japonica). POMn volume and the soma size of a dorsolateral population of neurons within POMn decreased when birds were moved from long day housing conditions (16L,8D) to short day housing conditions (8L,16D), and then increased again when birds were moved back to long day conditions, presumably as a function of the changes in circulating testosterone that accompanied changing daylengths. Male Japanese quail exhibit sexual behavior only when housed under long day housing conditions that approximate the photoperiod of the spring/summer breeding season, and do not exhibit sexual behavior when housed under short day conditions characteristic of fall/winter. Because POMn is known to be critically involved in the expression of male copulatory behavior, these morphological changes in the adult brain likely represent key functional events associated with the seasonal regulation of sexual behavior in male Japanese quail.     

Effects of wavelength and intensity of light in initiation of body fattening and gonadal growth in a migratory bunting under complete and skeleton photoperiods

A series of experiments investigated the effects of wavelength and intensity of light in initiation of body fattening (gain in body weight) and gonadal growth in migratory blackheaded bunting under complete and skeleton photoperiods. Using fluorescent light at an intensity approximately 700 lx, the first experiment compared the inductiveness of a complete (13 h continuous light coupled with 11 h darkness; 13L:11D) and a skeleton (two light pulses of 6 and 1 h at 6 h apart; 6L:6D:1L:11D) photoperiod. Observations at the beginning and after 3, 8, 10, and 13 weeks of the treatment indicated that both photoperiods were fully inductive but that birds under 13L photoperiod fattened and lost body weight significantly earlier than birds under skeleton photoperiod. In the second experiment, bunting were subjected to 13L:11D (L = 100 lx; D = 0 lx) of white, green (528 nm), and red (654 nm) light for a period of 5 weeks. Birds gained weight and testes grew in all groups except for an inconsistent fattening response in the white light group. The third experiment tested if the inductive effects of 1-h light pulse in a skeleton photoperiod were intensity dependent. Groups of bunting were exposed to 6L:6D:1L:11D (intensity of 1-h white light pulse = 2, 10, 50, or 100 lux) and examined at the beginning and after 3 and 8 weeks of the treatment. Photoinduction occurred at a slower rate and only at 50- and 100-lx intensities. The fourth experiment was similar to the third in design but it employed 1-h light pulse of two different wavelengths (green = 528 nm, and red = 654 nm) at 50- and 100-lx intensities. Birds fattened and testes grew only under red light. The last experiment varied the wavelength and intensity of the first (6 h) light pulse of the skeleton photoperiod (6L:6D:1L:11D): 6-h entraining light pulse of white, green (528 nm), or red (654 nm) colour at 10- or 50-lx intensity was used with 1-h inducing light pulse of white light at approximately 700-lx intensity. Testes grew in all groups but significant fattening occurred only in birds entrained to 50-lx light intensity. These results indicate i) the dissociation of body weight and gonadal responses, in the sense that the timing of photostimulation and/or magnitude of photoperiod-induced body weight and testicular responses differed under various photoperiodic manipulations, and ii) the circadian processes involved in photoperiod-induced responses have differential spectral and intensity sensitivity.     

Effects of photoperiod on reproduction and the gonadotropin-releasing hormone-immunoreactive neuron system in the postpubertal male Djungarian hamster

The present study tested the hypothesis that photoperiodic control of reproductive function in the postpubertal Djungarian hamster is associated with changes in the number, morphology, or distribution of GnRH-immunoreactive cell bodies in the brain. To initiate or arrest sexual maturation, males were reared in long (LD, 16L:8D) or short (SD, 10L:14D) days from birth. In two other groups that were chronologically past the normal onset of puberty, males were transferred at 30 days of age from LD to SD or from SD to LD to arrest or initiate reproductive function, respectively. At 40, 60, or 90 days of age, 4-6 hamsters in each of the four photoperiod treatment groups were killed by intracardiac perfusion. Testes weights were significantly increased in males exposed to long days (LD and SD-to-LD groups) compared to those treated with short days (SD and LD-to-SD groups). Serum FSH concentrations at 40 days of age were also increased in the two groups of males in long days compared to those in both groups in short days (p < 0.05, ANOVA); LH concentrations were unaffected by photoperiod treatments. Brain sections (60 microns) from the corpus callosum decussation to the suprachiasmatic nucleus in the anterior hypothalamus were processed for GnRH immunocytochemistry. In brain regions that contained the majority of GnRH neurons, i.e., the medial preoptic area and diagonal band of Broca, the numbers of GnRH-immunoreactive cell bodies were the same among the four treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inheritance of body weight and rate of gain in Japanese quail

The effects of hatch date, location and sex on the body weight and rate of gain in Coturnix coturnix japonica were examined. 2. The data conformed to a mixed and adjustments were made for the fixed effects sex, hatch date and location. Adjustment improved the precision of the estimates by reducing the error variances significantly. 3. Rearing equal numbers of birds from each family at different locations made the interactions negligible. 4. Weight gain was greater if illumination intensity up to 35 d was less. 5. Females were not heavier on the 1st day but were heavier on the 14th and 35th days than males. 6. Variance components and genetic parameters were estimated.     

Exposure to constant photoperiod alters serum prolactin concentrations and behavioral response to estradiol in the ovariectomized goat

The effects of constant photoperiod on serum prolactin concentrations and sexual behavior of ovariectomized goats was investigated. Fourteen ovariectomized goats were divided into groups of seven goats each and placed in photoperiod-controlled rooms with either 8L:16D or 16L:8D. All goats received six estradiol (E2) treatments in a Latin square design. Following each treatment six 1-h observation periods were conducted. Blood was collected before E2 treatment and at each observation period for prolactin quantification. During the observation periods measures of attractivity, proceptivity, and receptivity were recorded. Goats exposed to 8L:16D displayed sexual behavior in response to doses of E2 lower than those required by goats exposed to 16L:8D. Prolactin concentrations were higher in goats exposed to 16L:8D than in those exposed to 8L:16D. It was concluded that photoperiod affects prolactin concentrations and behavioral sensitivity to E2 in goats. The effect of continued exposure to constant photoperiod on these variables was then investigated. The goats were held in constant photoperiod for 211 d and behavior tests as described for Exp. 1 were repeated. Scores for attractivity, proceptivity, and receptivity did not differ between the two groups after 211 d of exposure to constant photoperiod. Prolactin concentrations did not differ in this study between the two groups. It was concluded that after chronic exposure to 8L:16D ovariectomized goats become refractory to the stimulatory effects of short photoperiod.     

Olfactory bulbectomy induces reproductive recrudescence in golden hamsters on short photoperiod

Olfactory bulbectomy results in a marked increase in gonadotropin secretion and prevents the reproductive regression associated with short photoperiod when the olfactory bulbectomy is done before exposure to the inhibitory photoperiod. The present study tested whether olfactory bulbectomy would offset the influence of short photoperiod if done after the reproductive system had regressed. Adult golden hamsters Mesocricetus auratus were divided into four groups: early sham (surgery at week-4); early olfactory bulbectomy (surgery at week-4); late sham (surgery at week 14) and late olfactory bulbectomy (surgery at week 14). At t = 0, all golden hamsters were placed in a short photoperiod (L:D 10:14). Early olfactory bulbectomy prevented testicular regression; the late olfactory bulbectomy group recrudesced much earlier than the sham groups. These results indicate that the tonic inhibitory influence of the olfactory bulbs is required for initiation of short photoperiod induced testicular regression and is also essential for the maintenance of the regressed state.     

One year of exercise training does not alter resting left ventricular systolic or diastolic function

This study tested the effects of light schedules on performance and yields of broiler chickens. In Experiment 1, light treatments during Days 1 to 49 of age were: 1) 23 h light (L):1 h dark (D); 2) 16L:8D;3) 16L: 3D:1L:4D; and 4) 16L:2D:1L:2D:1L:2D. In Experiment 2, Light Treatments 1 and 2 were the same as Treatments 1 and 4, respectively, in Experiment 1; 3) 23L:1D Days 1 to 7, 16L:8D Days 8 to 14, the light period was increased by 2 h/wk during Days 15 to 35, and 23L:1D Days 36 to 42; and 4) 23L:1D Days 1 to 7, 16L:8D Days 8 to 14, 16L:3D: 2L:3D Days 15 to 21, 16L:2D:4L:2D Days 22 to 28, 16L: 1D:6L:1D Days 29 to 35, and 23L:1D thereafter. In Experiment 1, BW was greater in Treatment 4 than Treatment 2 at 22 (708 vs 642 g) and 49 d (2,948 vs 2,797 g), percentage leg problems was lower in Treatments 2 to 4 (9, 10 and 6%, respectively) than in Treatment 1 (20%), and percentage Grade A was greater in Treatment 4 than Treatment 2 (60 vs 46%) at 49 d. In Experiment 2, BW was greater in Treatment 1 (692 g) than Treatments 3 (617 g) and 4 (620 g) at 21 d, and the incidence of tibial dyschondroplasia was lower in Treatment 2 (3.1%) than Treatment 3 (15.3%) at 42 d. There were no differences for mortality among treatments in either experiment.     

Effect of constant and of changing photoperiods on age at first egg and related traits in pullets

1. The effects of constant photoperiods and of single (5 h) changes in photoperiod applied at 12 or 17 weeks of age upon age at first egg (AFE) were studied using ISA Brown and Shaver 288 pullets. 2. Birds reared from 2 d of age until after maturity on constant 10 h photoperiods matured 8 d earlier than birds reared on constant 8 h and 5 d earlier than the average for 13 or 18 h photoperiods. 3. A single increment in photoperiod from 8 to 13 h advanced AFE by 23 d (compared to 8 h constant day controls) when applied at 84 d, but by only 6 d when given at 119 d. An increase in photoperiod from 13 to 18 h advanced AFE by only 4 d, averaged across breeds and age at increase. A reduction in photoperiod from 13 to 8 h delayed AFE by 22 d when given at 84 d and by 16 d at 119 d. A similar 5 h reduction in photoperiod, but from 18 to 13 h, retarded maturity by 11 d in ISA Brown pullets, but only when given at 84 d, and delayed AFE in Shaver 288 by 12 d, but only when given at 119 d. This interaction may be partly explained by the different physiological stages reached by the two breeds when the photoperiod was changed. 4. Under constant daylengths cumulative food intake before first egg was positively correlated with photoperiod, but the early AFE for birds on 10 h photoperiods resulted in this group having the lowest cumulative food intake to first egg. 5. A 5 h increase in photoperiod at 84 d significantly reduced the food consumed to first egg, but had no effect when given at 119 d. A 5 h decrease in photoperiod generally increased the food consumed to first egg, but the effect was only significant when the daylength was reduced from 13 to 8 h at 119 d. Food intake to first egg in birds subjected to a change in photoperiod was highly correlated with AFE. 6. The data confirm that sexual development in growing pullets responds more to changes in photoperiod than to the absolute daylength, that changes made at different daylengths are not equivalent and that sensitivity changes with age.     

Diurnal variation and effects of feeding on blood glucose in the giant tiger prawn, Penaeus monodon

Previous studies on crustacea have demonstrated significant diurnal rhythms in blood glucose. However, glucose concentration in the blood of food-deprived Penaeus monodon, held in indoor or outdoor tanks, did not exhibit a diurnal rhythm under photoperiods of 8 h light and 16 h darkness (8L: 16D) or under a 13.5L: 9.5D photoperiod, with simulated or natural full moon conditions. Prawns held on photoperiods of constant light, 20L : 4D, 16L : 8D, 12L : 12D, 8L : 16D, 4L : 20D, or continuous darkness did not have significantly different mean blood glucose levels. Mean blood glucose levels varied between 0.77 and 1.39 mmol/L, depending on conditions. Pronounced and significant increases in blood glucose levels occurred within 20 min of feeding, with peak levels after 100 min. The rise in blood glucose level observed after feeding was independent of the eyestalks, and hence putative crustacean hyperglycaemic hormone, and was not from endogenous carbohydrate stores. Under appropriately controlled conditions, blood glucose concentrations can be used as an index of nutritional status in penaeid prawns.     

Functional maturation of neuroendocrine gonadal axis is altered by specific phase relations of circadian neurotransmitter activity in Japanese quail

The present study was designed to ascertain the effects of temporal relationship of circadian neural oscillations on puberty attainment and reproductive growth of Japanese Quail, Coturnix coturnix japonica. Serotonin and dopamine precursors (5-hydroxytryptophan, 5-HTP and L-dihydroxyphenylalanine, L-DOPA; 5 mg/100 g body weight) were injected daily, 8 and 12 h apart in two groups of one-day old chicks, while controls received two daily injections of normal saline. Weekly/biweekly observations (body weight, cloacal gland size, testicular volume and activity, ovarian follicular diameter and rate of egg production) were made until 9 weeks of age, when the experiment was terminated. Results indicate that 8 h relationship completely suppressed gonadal growth even under long photoperiod (LD 16:8), while a 12 h relationship induced precocious sexual maturity and increased the rate of reproduction (spermatogenesis and egg production). It is concluded that circadian phase relationship of serotonergic and dopaminergic activity may not only determine the onset of reproduction in this poultry species, but may also alter the rate of reproduction possibly by affecting photoperiodic mechanism of reproductive regulation.     

Role of lipids in the transmission of the infective stage (L3) of Strongylus vulgaris (Nematoda: Strongylida)

Infective larvae (L3) of Strongylus vulgaris have limited energy stores for host finding and for infection. For transmission to occur, the larvae must have sufficient energy to (a) migrate onto grass, where they are ingested by their equine host (host finding), and (b) penetrate into the host gut. This study is designed to test the hypothesis that L3 larvae of S. vulgaris partition their energy stores between locomotory activity (used in host finding) and infection activity (penetration). Chronic locomotory activity was stimulated by incubating S. vulgaris L3 larvae at a constant temperature (38 C). After 8 days of treatment, locomotory activity ceased (exhaustion). Exhausted L3 larvae had significantly decreased total lipid when compared to controls (P < 0.05), but there was no decrease in levels of protein of carbohydrate. Lipids of S. vulgaris L3 larvae are comprised of 9 fatty acids, some of which are depleted in exhausted worms (14:0, 14:1, 16:0, 16:1, 18:1, 18:2), whereas others (18:0, 20:4, 24:0) remain unchanged. These data suggest that specific fatty acids provide the energy source for locomotory activity in S. vulgaris. Exhausted L3 larvae were also less able to penetrate host cecal tissue in in vitro penetration assays when compared to controls (P < 0.05), suggesting that the depletion of individual fatty acids during locomotory activity also reduced infectivity. These data do not support the hypothesis that S. vulgaris L3 larvae partition their energy stores between host-finding and infection activities. A comparison of lipid storage profiles in the L3 larvae of 4 nematode species with similar transmission strategies (S. vulgaris, Strongylus edentatus, Strongylus equinus, and Haemonchus contortus) revealed similarities in the fatty acid composition of these species. These data suggest a relationship between transmission patterns and energy storage strategies in the L3 larvae of nematode parasites of vertebrates.     

Systematic review and meta-analysis of early postnatal dexamethasone for prevention of chronic lung disease

AIM: To review systematically the evidence to determine whether dexamethasone treatment of very low birthweight infants begun within 14 days of age prevents chronic lung disease (CLD) without clinically significant side effects. METHODS: Randomised controlled trials of dexamethasone started within this time frame were identified through a search of electronic databases, proceedings of scientific meetings, and personal files. Meta-analyses using event rate ratio (ERR), event rate difference (ERD), and if significant, numbers needed to treat (NNT) for benefits and numbers needed to harm (NNH) for adverse effects were calculated. Weighted mean difference were used for continuous variables. Three prespecified subgroup analyses were performed for; (i) dexamethasone begun within 36 hours (hours) of birth; (ii) dexamethasone initiated between 7-14 days of age; or (iii) if surfactant treatment was used. RESULTS: Ten studies were included in the review; six where dexamethasone was initiated within 36 hours of age, four studies for dexamethasone started between 7 and 14 days and six studies using surfactant. Mortality ERR and NNT with 95% confidence intervals for dexamethasone initiated at 7-14 days of age were 0.35 (0.16, 0.74) and 8 (4, 30). ERRs and NNTs for CLD at 28 days and 36 weeks of postmenstrual age were 0.71 (0.61, 0.84), 8 (5, 17), and 0.57 (0.44, 0.76), 10 (6, 23) in the overall analyses. When dexamethasone was started at 7 to 14 days of age ERR and NNT for CLD at 36 weeks were 0.63 (0.47, 0.85) and 3 (2, 9). Clinically significant side effects included increased risk of hypertension, hyperglycaemia, and increased time to regain birthweight. CONCLUSIONS: These meta-analyses show a significant reduction in risk of CLD at 28 days and 36 weeks of postmenstrual age. In the subgroup where dexamethasone was started between 7 and 14 days of age mortality was significantly reduced. Caution is warranted in the routine use of dexamethasone because of lack of data on long term neurodevelopmental outcomes.     

Neuromuscular contacts of expanded motor units in rat soleus muscles are rescued by leupeptin

In the soleus muscle of the rat following section of the L5 ventral ramus (partial denervation) the remaining motor axons increase their territory by sprouting. Nerve sprouts are first seen two to three days after the operation, their number peaks at 10-14 days and subsequently remains at this level. The time course of the initial sprouting in partially denervated muscles is not altered by paralysing the muscles with alpha-bungarotoxin, and the initial extent of the sprouting is, if anything, greater in the paralysed muscles. However, unlike in controls, this level of sprouting is not maintained and neuromuscular contacts are lost when muscles recover from the paralysis. The loss of these contacts can be prevented by treatment of these partially denervated paralysed muscles with leupeptin, an inhibitor of calcium-activated neutral protease. Interestingly, more contacts are rescued when leupeptin is applied 10 days after alpha-bungarotoxin treatment, when sprouting has reached high levels, than at three days, when sprouting has just begun. The neuromuscular connections rescued by leupeptin are functional. Maximum tetanic tension produced by untreated soleus muscles two to five months after partial denervation is 66 +/- 9% of contralateral control muscles, but only 39 +/- 8% when the muscles were paralysed with alpha-bungarotoxin for 12-14 days after partial denervation. However, when partially denervated paralysed muscles were treated with leupeptin three and 10 days after alpha-bungarotoxin treatment their tension output is 74 +/- 3% and 81 +/- 8%, respectively. After partial denervation alone, motor units are twice their normal size. Short-term paralysis with alpha-bungarotoxin prevents this increase in motor unit territory. However, the application of leupeptin to the paralysed muscles rescues neuromuscular contacts, allowing motor unit size to remain expanded, at around 2-2.5-fold. Thus, following recovery from temporary paralysis with alpha-bungarotoxin, there is a sudden withdrawal of neuromuscular contacts and these can be rescued by treatment with leupeptin.     

The role of epidemiology in cancer prevention

1. ISA Brown and Shaver 288 pullets were changed from 8 h to 8, 10, 13 or 16 h photoperiods at 42, 63, 84, 105, 126 or 142 d of age. 2. Age at first egg (AFE) was curvilinearly affected by the size and timing of the change in photoperiod. AFE was advanced most by a photoperiod change from 8 to 13 h made at 63 or 84 d. ISA birds were generally more responsive than Shaver to the photoperiod changes. 3. Longer photoperiods significantly increased survivors' egg production, but decreased liveability to 504 d. so that eggs per hen housed were unaffected. Retarding AFE by 10 d reduced survivors' egg numbers by 7.0, but increased mean egg weight by 1.26 g. Egg output by Shaver birds was unaffected by AFE, but that of ISA was curvilinearly affected, with an apogee at an AFE of 135 d. In both breeds, egg weight and egg output were greater following an early or late, rather than a mid-term photostimulation. 4. Photoperiod significantly increased mean daily food intake during lay by 1.26 g/h. A 10 d retardation in AFE resulted in a reduction in food intake of 1 g/d. Efficiency of food conversion deteriorated according to the square of the photoperiod, and changed curvilinearly according to age at photostimulation. Food conversion efficiency improved by 0.05 g/g for each 10 d delay in AFE. 5. Shell quality was unaffected by AFE, but deteriorated with increasing photoperiod and was curvilinearly affected by age at photostimulation with the smallest shell weights associated with photostimulation at 63 d. The incidence of double-yolked (DY) egg production increased with photoperiod and decreased with delayed photostimulation. There was an exponential regression of DY eggs on AFE. 6. Body weight at first egg increased by 75 g/d delay in AFE, but body weight at 504 d of age was unaffected by AFE, photoperiod or age at photostimulation. Body weight gain during lay increased by 15 g/h increase in photoperiod, decreased by 6 g per 10 d delay in photostimulation and by 40 g per 10 d delay in AFE. Fat content at 504 d increased by about 10 g/kg and by 23 g/bird for each 10 d delay in AFE. 7. Mortality in lay increased by 0.8%/h increase in photoperiod, but was unaffected by either age at photostimulation or AFE.     

Kinetics of humoral response in children with acute lymphoblastic leukemia immunized with influenza vaccine in 1993 in Poland

Songbirds exhibit seasonal changes in the volumes of song control nuclei. Birds on long, spring-like days have larger nuclei than do birds on short, winter-like days. The mechanisms mediating volumetric changes have not been determined unequivocally, but testosterone (T) is probably involved. This study examined whether testicular factors are uniquely responsible for seasonal changes in the song system, or whether photoperiod has testis-independent effects. Male American tree sparrows were exposed to one of three photoperiodic conditions: (1) Photosensitive birds were retained on short days (8L:16D). Plasma T is rarely detected in such birds. (2) Photosensitive birds were moved from short days to long days (20L:4D) and photostimulated for three weeks. Photostimulation elevates circulating T in photosensitive birds. (3) Photorefractory birds were held at least four months on 20L:4D. Such birds seldom have detectable levels of T, even though they are on long days. In each condition, there were both intact and castrated birds. Castration typically removes circulating T in tree sparrows. The volumes of the high vocal center (HVC), nucleus robustus archistriatalis (RA), and area X were measured. Song nuclei were largest in intact photostimulated birds. Other long-day birds (i.e. castrated photostimulated, and intact and castrated photorefractory groups) had larger song nuclei than did short-day intact or castrated photosensitive birds and did not differ from each other. These data indicate that photoperiod has both testis-dependent and -independent effects on the volumes of song control nuclei.     

Short photoperiod accelerates preoptic and ventral telencephalic salmon GnRH synthesis and precocious maturation in underyearling male masu salmon

The temporal relationship between testicular maturation and salmon gonadotropin-releasing hormone (sGnRH) mRNA expression was investigated in underyearling precocious male masu salmon, Oncorhynchus masou. Testicular maturation could be experimentally manipulated by changing the length of the light-dark photoperiod; maturation was accelerated in the short photoperiod group (8L-16D) and delayed in the long photoperiod group (16-8D). sGnRH mRNA and total silver grains in these loci in individual fish, increased with advancing testicular maturation. They were maximal in the short photoperiod group in August and in the long photoperiod group in September, when spermiation occurred. In contrast, marked changes in sGnRH synthetic activity in relation to testicular maturation were not observed in the terminal nerve ganglion or in the olfactory bulbs. sGnRH neurons in the preoptic area and the ventral telencephalon are clearly influenced by photoperiod and are involved in the control of gonadal maturation probably via gonadotropin secretion.