A three hours study of the response of plasma corticosterone and of three liver enzymes in rats subjected to stress in the late afternoon or during the morning hours.

In adult male rats kept under controlled illumination (lights on from 6 a.m.--6 p.m.) the existence of higher afternoon values of plasma corticosterone ("B") is reconfirmed. Moreover, plasma "B" increases induced by 400 revolutions in Noble-Collip drums or immobilization for 2.5 h were found substantially less pronounced if stressor application took place at 4 p.m. rather than 8 a.m. so that essentially no difference between morning and afternoon poststress peaks was observed. Also the response to 0.05 mg ACTH i.p. was smaller in the afternoon experiments. Additionally three liver enzymes the activity of which is increased by corticosterone released under conditions of stress were also studied. Higher afternoon activity of liver tyrosine aminotransferase (TAT) and tryptophan pyrrolase (TP) was observed in spite of fasting from 8 a.m. imposed to the animals taking part in the afternoon experiments. The activity of phosphoenolpyruvate carboxykinase (PEPCK) was also increased in the afternoon probably because of the food deprivation. Immobilization-induced increase in the activity of all three enzymes showed a similar blunting as plasma "B" response, so that no differences between morning and afternoon were found in peak poststress values. In conclusion, the low plasma "B" response of rats at a time when the animals begin the active part of their day seems to have important metabolic implications.     

Changes in the size of the long tubular bones and body weight of rats exercised at different times of the day

The observations were performed in autumn in 100 rats at the age of 1 month. The animals were trained in a horizontal treadmill with the speed 40 m/min, beginning with 3 min/day and gradually increasing the time up to 30 min. The control animals were not trained, the test animals were trained either once a day (at 7 a. m., 3 p. m., 11 p. m.), or three times a day and the total loading was equal to a single loading. The animals were weighed daily. Elongation of the bones, increase in their mass and in the body mass were different at training during different time of the day and the effect was not similar in different bones. Certain sexual differences of the training effect were revealed.     

Exaltation phenomenon during the teaching of an instrumental defense reflex to animals of various ages

Dogs of 1.5 and 7 months and rats of 15, 20, 30, 45, 60, 80, and 100 days of age were given acquisition training in an escape task. The previous observations suggested that difficulties in defensive conditioning typically found in young animals were connected with their generalized perception of Igarning conditions. To facilitate the discrimination of the environmental factors a conditioned signal was not applied and the home cage was used as a "safe" compartment. The intertrial intervals were increased up to 2 hours for dogs and 24 hours for rats. Under such conditions an acquisition of escape reaction was most rapid in animals of early age. The period of effective learning (exaltation) in rats began from 20 and lasted to 60 days of age, the maximal efficiency being observed at 20 days. Pups of 1.5 months had learned more quickly than those of 7 months of age. Variations of learning efficiency in ontogeny of rats were positively correlated with changes of correct escape reaction search activity. Phenomenon of learning exaltation in ontogeny was supposed to be connected with the high level of activity of perception and association cerebral mechanisms being the result of immaturity of inhibitory structures.     

Acquisition and extinction of conditioned suppression of a graft-vs-host response in the rat

Injection of rats with cyclophosphamide (CY) after their consumption of a novel saccharin-flavored drinking solution results in a conditioned aversion to saccharin and a conditioned suppression of immune responses. In this study, female Lewis X Brown Norwegian F1 rats were conditioned by pairing saccharin with 50 mg/kg CY. Seven weeks later (day 0), a graft-vs-host response (GvHR) was induced in these animals by injecting splenic leukocytes from Lewis donors into a rear footpad. At this time, some conditioned animals were reexposed to saccharin, the conditioned stimulus. During the 7-wk interval between conditioning and immunization, subgroups of conditioned rats were given 0, 4, 9, or 18 extinction trials (saccharin followed by saline injections). Animals receiving 4, 9, or 18 extinction trials showed a greater preference for saccharin on day 0 than did animals receiving no extinction trials, but these groups did not differ among themselves; all conditioned groups showed a lower preference for saccharin than placebo-treated animals. There was a clear effect of number of extinction trials on the GvHR. Animals receiving 9 or 18 extinction trials did not differ from controls, whereas animals receiving 0 or 4 trials had a milder GvHR than did conditioned rats that were not reexposed to saccharin at the time of immunization. These results confirm a previous report of conditioned suppression of a GvHR, demonstrate that conditioned immunopharmacologic responses are subject to experimental extinction, and indicate that conditioned immunosuppression can be dissociated from conditioned taste aversion.     

Relationship between the proliferation waves of the hepatocytes after hepatectomy and the waves of diurnal rhythm of mitotic activity. 1. Dependence of the form of the mitotic wave and the time of attaining its maximal degree on the time of operation]

The diurnal rhythm of mitotic activity (MA) of intact animal hepatocytes and the proliferative wave of hepatocytes after partial hepatactomy at time t0 are thought to appear as a result of formation of an initial proliferative wave, Pk-wave, within the G0-phase at constant moments of the day--time tk+1=tk+TMA(TMA=24hrs/K, k=1, or 2, . . ., or K) under the influence of the regulating system of the organism. Cells of the Pk-wave pass during a short time deltat (deltat less than TMA) from the G0-phase into the transformation phase, and then into the G1-phase. The 1st stimulated proliferative wave is formed at time tk, if tk--TMA less than t0 less than or equal to tk; its intensity depends most likely on the intensity of the corresponding Pk-wave of the intact liver. It was noted that time t0 of partial hepatectomy was necessary to coordinate with tk, but not with the time of the maximal mitotic activity, and that it was necessary to hepatectomize all animals within the interval from time tk--TMA to time tk. The model was shown to compare well with data by Post et al. (1963), Barbason (1970), and Van Cantfort and Barbason (1972) for hepatocytes of Wistar rats with TMA=8hrs, and tk (k=1,2,3) within intervals (2 a.m.; 4 a.m), (10 p.m.; noon), and (6 p.m. 8 p.m.). The maximal rate of liver generation was observed for all the hepactomized animals with the time of operation being between 8 p. m. and 2 a.m.     

Effect of dopamine enriched ganglion xenografts from the immature CNS of Helix aspersa L. snail on the learning time during acquisition of an operant food-procuring reflex in WAG/RIJ rats

Xenografts from the ganglia of a newborn terrestrial snail Helix aspersa L. were implanted into the right parietal area of the brain cortex of WAG/Rij rats with absence epilepsy. Rats with implanted xenografts were trained for reaching a food ball from a tube (reaching test). It was shown that the mean duration of each leaning stage and total time necessary for acquisition of the instrumental conditioning (till the learning criterion) were shorter in animals with xenografts than in control groups of animals.     

多巴胺D2受体拮抗剂、激动剂对SD大鼠条件化位置偏好的影响

通过慢性吗啡处理方式建立起SD大鼠吗啡依赖的条件化位置偏好(CPP)模型,用行为学手段研究多巴胺(DA)D2受体拮抗剂及激动剂对SD大鼠CPP的影响,探讨眶额叶DAD2受体在阿片精神依赖中的作用。通过腹腔注射吗啡同环境因素相结合,建立大鼠吗啡依赖的CPP模型;采用局部脑内微量注射法向额叶注射DAD2受体拮抗剂或激动剂或盐水(对照组),以得到SD大鼠在戒断期间的CPP的时间数据。CPP显示DAD2受体拮抗剂组与对照组相比,从戒断第2天起,前者表现出更明显的CPP增加现象,差异显著(P<0·05)。而DAD2受体激动剂组与对照组相比无显著差异(P>0·05)。采用腹腔小剂量注射吗啡,成功地建立了吗啡依赖SD大鼠的CPP模型;眶额叶微量注射DAD2受体拮抗剂增加了CPP时间,提示眶额叶多巴胺系统在吗啡依赖的过程中有着较为重要的作用;也提示了对于已经成瘾的动物,损伤其眶额叶,会使药物渴求增强。因而提示对于药物依赖患者进行手术干预治疗要极其慎重。     

Water exercise prevents femur density loss associated with ovariectomy in the retired breeder rat

The effect of non-weight-bearing exercise on skeletal bone remains controversial. The objective of this pilot study was to examine the effects of water exercise training on femur density and serum alkaline phosphatase activity in ovariectomized and sham-operated (ovaries left intact) retired breeder rats. Exercised animals swam at progressively increasing duration from 5 minutes to 75 min.d(-1), 5 d.wk(-1), for a 6-week conditioning period. Exercised rats had greater (p < 0.02) soleus muscle citrate synthase activity than sedentary rats, confirming an aerobic training effect. Femur density (g.cm(-3)) was greater (p < 0.0007) for exercised rats than sedentary rats but lower (p < 0.01) for ovariectomized rats compared to sham rats. Serum alkaline phosphatase activity tended (p < 0.06) to be greater for exercised rats compared to sedentary rats. These results indicate that dynamic water-flotation exercise prevents the femur bone loss associated with ovariectomy in rats. We conclude that this form of exercise could be beneficial in maintaining bone density in hormone-deficient postmenopausal women, especially the elderly who may not be able to perform weight-bearing activities.     

Effect of morphine withdrawal on food and water intake, urine output and electrolyte excretion in the rat: participation of the renin-aldosterone-system in renal excretory changes

Male Wistar rats received two i.p. injections of morphine-HCl, 2.5 mg/kg at 8.00 a.m. and 2.00 p.m. on the 1st day: the dose was doubled every other day to reach a total daily dose of 40 mg/kg on the 4th day. This schedule was maintained for 12 days. On day 16 the animals received the last injection of morphine, 20 mg/kg. One hour later (9.00 a.m.) six rats were decapitated and PRA, PAC and ACTH were measured by radioimmunoassay. Groups of six rats were killed at 9.00 a.m. on the 1st, 2nd, 5th and the 8th day after morphine withdrawal. Control data for PRA, PAC and ACTH were obtained from eighteen saline-injected rats. Nine out of morphine-treated animals were kept in metabolism cages to investigate simultaneously food and water intake. and renal excretion. Morphine withdrawal after chronic morphine treatment in the rat resulted in antidiuresis and a reduction of electrolyte excretion which were not due to a reduction in water and food intake. The simultaneous increase of PRA and PAC associated with decreased electrolyte excretion indicates that, in addition to antidiuretic hormone, also the renin-aldosterone-system probably play a relevant role in the renal excretory changes after morphine withdrawal.     

Light/dark cycle-dependent metabolic changes in adipose tissue of pinealectomized rats.

We investigated the effects of pinealectomy on adipose tissue metabolism at different times of day. Adult male Wistar rats were divided into two groups: pinealectomized and control (sham-operated). Eight weeks after surgery, the animals were killed at three different times (at 8.00 a.m., at 4.00 p.m. and 11.00 p.m.). We collected blood samples for glucose, insulin, corticosterone, and leptin determinations, and periepididymal adipocytes for in vitro insulin-stimulated glucose uptake, oxidation, and incorporation into lipids. Pinealectomy caused insulin resistance as measured by 2-deoxyglucose uptake (a fall of approximately 40 % in the maximally insulin-stimulated rates) accompanied by hypercorticosteronemia at the three time points investigated without changes in plasma insulin an or leptin levels. Furthermore, pinealectomy increased the insulin-induced glucose incorporation into lipids (77 %) at 4.00 p.m. and insulin-induced glucose oxidation in the morning and in the afternoon, while higher rates were observed in the evening and in the morning in control rats. In conclusion, cell responsiveness to insulin was differentially affected by pineal ablation and time of day, and persistent insulin resistance was obtained in pinealectomized rats. We hypothesize that pinealectomy exposes the animal to an inadequate match between energy requirements and fuel mobilization.     

Chronologic and quantitative modalities of luteinization and ovulation in the female rat exposed to FSH action at the beginning of 4-day cycles]

Female Wistar rats were injected with two successive doses of 150 mug FSH on dioestrus I (5 p. m.) and dioestrus II (9 a.m.) of 4-day cycles. Superovulation and formation of an increased number of corpora lutea with included oocytes occurred in these animals. Meprobamate or pentobarbitone injections at 11.30 a.m. et 1.30 p.m. respectively completely blocked ovulation and luteinization phenomena in FSH-treated females. Ovulation normally occurred in FSH-treated females injected with meprobamate at 5.30 p.m. It was concluded that no modification of timing of the 'critical period' resulted from FSH treatment.     

Differential Behavioral and Endocrinological Effects of Corticotropin-Releasing Hormone (CRH) in the Syracuse High- and Low-Avoidance Rats

The Syracuse high- and low-avoidance rats, which have been selectively bred for good (SHA/Bru) or poor (SLA/Bru) avoidance learning in a two-way shuttle box, differ in emotionality. This experiment investigated the effect of corticotropin-releasing hormone (CRH), administered centrally (0, 0.1, 0.5, and 1.0 μg), on conditioned suppression and on the hypothalamic–pituitary–adrenocortical system. Three groups of animals were used: SHA/Bru rats conditioned at 0.21 or 0.43 mA and SLA/Bru rats conditioned at 0.21 mA. The results confirm those of previous studies which found that SLA/Bru rats show greater conditioned suppression than the SHA/Bru rats at the low shock intensity and that at 0.43 mA, the SHA/Bru animals acquire a level of conditioning comparable to that of the SLA/Bru animals at 0.21 mA. The results show that the nonlinear behavioral effect of CRH is independent of strain and produces comparable effects in animals of both strains, but only when level of conditioning is equated. Adrenal and plasma concentrations of corticosterone increased in all three groups of animals as a direct linear function of dose of CRH. Both greater levels of conditioning and larger amounts of CRH increase the synthesis of corticosterone more in SHA/Bru animals than in the SLA/Bru animals. Thus, genetic variation, which differentiates the behavioral and endocrinological characteristics of these animals, shows that these effects of CRH can be independent of each other and suggests that some minimal level of conditioned fear is necessary for CRH to exert its anxiogenic effect.     

Late effects of cyclophosphamide and total body irradiation as a conditioning regimen for bone marrow transplantation in rats (a preliminary report)

The longterm survival and occurrence of neoplastic and nonneoplastic lesions following total body irradiation (TBI), 8.5 Gy, with or without additional cyclophosphamide (Cy; 100 mg kg-1 i.p.) treatment as a conditioning regimen for bone marrow transplantation (BMT) were studied in male BN/BiRij rats. The two groups of rats that were treated with Cy (Cy and Cy + TBI) that survived beyond 100 days after treatment, had a severely decreased median (post treatment) survival time (Cy + TBI: 14.5 months and Cy: 14.1 months). Survival time in the TBI group was moderately decreased (18.5 months) as compared with the untreated controls (27.2 months). All treatment modalities were carcinogenic according to the raw data. After Cy-treatment a high incidence of, frequently multiple, malignant nerve-sheath tumours (Cy: 66 per cent, Cy + TBI: 31 per cent, controls: 2 per cent) was observed. TBI induced an increased occurrence of a great variety of tumours, especially mesenchymal tumours. This effect was more pronounced in animals receiving TBI alone as compared to animals receiving the combined treatment of Cy + TBI; an effect that most likely resulted from the longer median survival after TBI. The multi-target effect of TBI was also reflected in the occurrence of nonneoplastic effects in a variety of tissues, including high incidences of biliary cysts in the liver and severe testicular atrophy. The most important Cy-induced nonneoplastic lesion was incisor dysplasia, which resulted in feeding problems that could only be partly overcome by administering powdered food. Early mortality in the Cy-treated groups was associated with emaciation and generalized organ atrophy. A more definitive estimate of the late effects of supralethal chemoradiotherapy as part of a treatment of malignant disease has to await the results of various conditioning regimens for BMT in rats employing the acute BN myelocytic leukaemia (BNML) as a rat model for human acute myelocytic leukaemia (AML).     

Prior exposure to a single stress session facilitates subsequent contextual fear conditioning in rats. Evidence for a role of corticosterone

Previous studies showed that exposure of rats to chronic restraint stress for 21 days enhances subsequent contextual fear conditioning. Since recent evidence suggest that this effect is not dependent on stress-induced neurodegenerative processes, but to elevated training-elicited glucocorticoid release in chronically stressed animals, we aimed to explore here whether a single exposure to restraint stress, which is not expected to induce neuronal damage, would also affect contextual fear conditioning. We also questioned whether post-training corticosterone levels might be associated with any potential effect of stress on fear conditioning. Adult male Wistar rats were exposed to acute restraint stress for 2 h and, two days later, trained in the contextual fear conditioning task, under training conditions involving either moderate (0.4 mA shock) or high (1 mA shock) stress levels. The results showed that acute stress enhanced conditioned freezing at both training conditions, although data from the 1 mA shock intensity experiment only approached significance. Stressed animals were shown to display higher post-training corticosterone levels. Furthermore, the facilitating effect of prior stress was not evident when animals were trained in the hippocampal-independent auditory-cued conditioning task. Therefore, these findings support the idea that stress experiences preceding exposure to new types of stressors facilitate the development of contextual fear conditioning. They also indicate that not only repeated, but also a single exposure to aversive stimulation is sufficient to facilitate context-dependent fear conditioning, and suggest that increased glucocorticoid release at training might be implicated in the mechanisms mediating the memory facilitating effects induced by prior stress experiences.     

Studies on the role of zinc in parturition in the rat.

1. Pregnant rats were fed either low (less than 1 p.p.m.) Zn or control (40 p.p.m. Zn) diets from day 10 of gestation. They were killed at intervals during the last 96 h preceding the normal time for onset of parturition, and differences in plasma progesterone, oestradiol-17 beta and ovarian 20 alpha-hydroxysteroid dehydrogenase were assessed. 2. Gestation was prolonged in Zn-deficient rats. 3. Although the preparturient decline in plasma progesterone began at the same time in all groups, at term, plasma progesterone concentration in Zn-deficient rats remained significantly higher than in normal females. 4. Induction of ovarian 20 alpha-hydroxysteroid dehydrogenase activity was delayed by about 8 h by Zn deficiency. This delay was not observed if prostaglandin F2 alpha was injected previously. 5. The results suggest a Zn-dependent step(s) in uterine synthesis and/or release of prostanoids.     

Pavlovian conditioning of lung anaphylactic response in rats

The present experiment was undertaken to verify if it is possible to impose Pavlovian conditioning on a lung anaphylactic response (LAR) in rats. Two experiments were done. In the 1st, egg albumin (OVA) aerosol inhalation, which induces signs and symptoms of LAR in OVA- sensitized rats, was paired with an audiovisual cue (conditional stimulus, CS). After reexposure to the CS, the signs and symptoms of LAR were quantitatively measured using a scoring system specially developed for this evaluation; the levels of stress response and anxiety were also quantified. Results showed that the rats reexposed to CS only, displayed LAR scores not significantly different from those reexposed to both CS and the antigen; animals of these groups showed significantly higher LAR scores than rats that received no OVA aerosol challenge. High levels of stress and anxiety were observed 30-40 min after the challenge with OVA aerosol. In the 2nd experiment, rats sensitized with OVA and submitted or not to Pavlovian conditioning were observed in the open-field and in the plus maze apparatus in the absence of OVA aerosol but in the presence of the CS; after behavioral observations the animals were sacrificed for serum corticosterone level determination. Both behavioral and biochemical data showed high levels of stress and anxiety in rats for which the antigen was previously paired with the CS; these changes were not observed in animals which received the antigen 24 h after the presentation of the CS (unpaired) or in those exposed to PBS aerosol (the OVA vehicle) only. The present data show not only that LAR can be submitted to Pavlovian conditioning, but also and importantly, that high levels of stress and anxiety are related to the course of LAR.     

Effects of long-chain fatty alcohol on peripheral nerve conduction and bladder function in diabetic rats

Diabetic cystopathy as manifested by an enlarged bladder is mainly caused by peripheral neuropathy. Long-chain fatty alcohol, which has been isolated from the Far-Eastern traditional medicinal plant, Hygrophilia erecta, Hochr., has been found to possess some neurotrophic activities on the central neuron. Cyclohexenonic long-chain fatty alcohol (FA) used in this study were synthesized in order to improve the efficiency of the molecules. The effects of this compound on peripheral nerves, however, have not yet been studied. To get more information, we evaluated the effects of this compound on peripheral nerves in streptozotocin-induced diabetic rats in terms of nerve conduction velocity and bladder function. Three experiments were performed 8 weeks after the administration of streptozotocin to 8-week-old rats: (i) motor sciatic nerve conduction (MNCV), (ii) monitoring micturition behavior in the metabolic cage, and (iii) cystometrogram under urethane anesthesia (CMG). Half of the diabetic rats were treated with FA (8 mg/kg/day, i.p.). The difference in MNCV between control rats (49.0 +/- 2.2 m/s) and untreated diabetic rats (42.4 +/- 0.5 m/s) after 8 weeks reached significance (p = 0.0183). FA-administrated diabetic rats showed an improved MNCV (45.8 +/- 1.2 m/s). We also identified a significant improvement of bladder function in these animals. The diabetic rats had a much higher maximal micturition volume per 24 hours (4.9 +/- 0.4 ml) than control animals (1.5 +/- 0.1 ml). However, the diabetic rats treated with FA had a maximal micturition volume of only 3.7 +/- 0.3 ml. Likewise, the diabetic rats had a CMG bladder capacity of 0.90 +/- 0.14 ml while the diabetic rats treated with FA had a capacity of 0.54 +/- 0.07 ml. These results indicate that cyclohexenonic long-chain fatty alcohol has a beneficial effect on peripheral neuropathy and cystopathy in streptozotocin-induced diabetic rats.     

Effect of immunization with neurospecific proteins and tubulin on learning in the rat

The paper deals with the effect of anticerebral antibodies on rats learning in T-shaped maze with food reinforcement. The rats of August line were immunized by neurospecific proteins 10-40-4 from the human and rat's brain, 14-3-2 and cerebral tubuline. Rats immunized by bovine serum albumine (BSA) served as a control of the influence of antibodies to noncerebral protein. Rats injected with Freund adjuvant and saline, served as control of Freund adjuvant action. At the time of antibodies formation (from the 7-th day after the last injection) the rats were trained in a T-shaped maze during 4 days. The acquisition of conditioned reactions was inhibited in rats immunized with neurospecific proteins 10-40-4 from the rats brain, 14-3-2 and cerebral tubuline. Antibodies to neurospecific protein 10-40-4 from the rats brain produced the greatest effect on the process of learning. They elicited a significant decrease of conditioning and an increase of the number of errors. Antibodies to the neurospecific protein 10-40-4 from the human brain and to the BSA, i.e. to proteins which are not present in the nervous tissue of the rats, did not affect the learning. The obtained results indirectly confirm the permeability for the antibodies of the blood-brain barrier in immunized animals.     

Adaptations of the antioxidant system in erythrocytes of trained adult rats: impact of intermittent hypobaric-hypoxia at two altitudes

We have investigated the effects of daily exposure to intermittent hypobaric-hypoxia to two simulated altitudes (5700 m and 6300 m) in adult male rats that had been regularly swim trained in normoxia at sea level prior to exposures. Superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) along with the oxidative stress (OS) indices, malondialdehyde (MDA) and protein carbonyl content were measured in erythrocytes and their membranes. Hemoglobin increased in the trained animals exposed to 5700 m and in untrained rats exposed to 6300 m. Osmotic fragility in terms of hemolysis increased in altitude exposed animals. SOD increased in those exposed to 6300 m, while CAT increased in trained rats exposed to 5700 m and to 6300 m unlike in untrained rats where CAT increased only at 6300 m. GSH-Px showed varying degrees of elevation in all animals exposed to both altitudes. Erythrocyte membranes showed significant elevations in malondialdehyde (MDA) at 6300 m, while elevated protein carbonyls were noticeable at both altitudes in whole cells and membranes. These results suggest a positively associated elevation in protein oxidation with altitude in trained rats. At 5700 m, animals were less stressed, unlike at 6300 m, as seen from the magnitude of elevations in the OS indices and from the responses of the antioxidant enzymes.     

Effects of a 4-week youth baseball conditioning program on throwing velocity

Effects of a 4-week youth baseball conditioning program on throwing velocity. This study examined the effects of a 4-week youth baseball conditioning program on maximum throwing velocity. Thirty-four youth baseball players (11-15 years of age) were randomly and equally divided into control and training groups. The training group performed 3 sessions (each 75 minutes) weekly for 4 weeks, which comprised a sport specific warm-up, resistance training with elastic tubing, a throwing program, and stretching. Throwing velocity was assessed initially and at the end of the 4-week conditioning program for both control and training groups. The level of significance used was p < 0.05. After the 4-week conditioning program, throwing velocity increased significantly (from 25.1 ± 2.8 to 26.1 ± 2.8 m·s) in the training group but did not significantly increase in the control group (from 24.2 ± 3.6 to 24.0 ± 3.9 m·s). These results demonstrate that the short-term 4-week baseball conditioning program was effective in increasing throwing velocity in youth baseball players. Increased throwing velocity may be helpful for pitchers (less time for hitters to swing) and position players (decreased time for a runner to advance to the next base).