Cell-specific Dyt1 ∆GAG knock-in to basal ganglia and cerebellum reveal differential effects on motor behavior and sensorimotor network function.

Dystonia is a neurological movement disorder characterized by repetitive, unintentional movements and disabling postures that result from sustained or intermittent muscle contractions. The basal ganglia and cerebellum have received substantial focus in studying DYT1 dystonia. It remains unclear how cell-specific ∆GAG mutation of torsinA within specific cells of the basal ganglia or cerebellum affects motor performance, somatosensory network connectivity, and microstructure. In order to achieve this goal, we generated two genetically modified mouse models: in model 1 we performed Dyt1 ∆GAG conditional knock-in (KI) in neurons that express dopamine-2 receptors (D2-KI), and in model 2 we performed Dyt1 ∆GAG conditional KI in Purkinje cells of the cerebellum (Pcp2-KI). In both of these models, we used functional magnetic resonance imaging (fMRI) to assess sensory-evoked brain activation and resting-state functional connectivity, and diffusion MRI to assess brain microstructure. We found that D2-KI mutant mice had motor deficits, abnormal sensory-evoked brain activation in the somatosensory cortex, as well as increased functional connectivity of the anterior medulla with cortex. In contrast, we found that Pcp2-KI mice had improved motor performance, reduced sensory-evoked brain activation in the striatum and midbrain, as well as reduced functional connectivity of the striatum with the anterior medulla. These findings suggest that (1) D2 cell-specific Dyt1 ∆GAG mediated torsinA dysfunction in the basal ganglia results in detrimental effects on the sensorimotor network and motor output, and (2) Purkinje cell-specific Dyt1 ∆GAG mediated torsinA dysfunction in the cerebellum results in compensatory changes in the sensorimotor network that protect against dystonia-like motor deficits.

Specific cerebellar regions are related to force amplitude and rate of force development.

The human cerebellum has been implicated in the control of a wide variety of motor control parameters, such as force amplitude, movement extent, and movement velocity. These parameters often covary in both movement and isometric force production tasks, so it is difficult to resolve whether specific regions of the cerebellum relate to specific parameters. In order to address this issue, the current study used two experiments and SUIT normalization to determine whether BOLD activation in the cerebellum scales with the amplitude or rate of change of isometric force production or both. In the first experiment, subjects produced isometric pinch-grip force over a range of force amplitudes without any constraints on the rate of force development. In the second experiment, subjects varied the rate of force production, but the target force amplitude remained constant. The data demonstrate that BOLD activation in separate sub-areas of cerebellar regions lobule VI and Crus I/II scales with both force amplitude and force rate. In addition, BOLD activation in cerebellar lobule V and vermis VI was specific to force amplitude, whereas BOLD activation in lobule VIIb was specific to force rate. Overall, cerebellar activity related to force amplitude was located superior and medial, whereas activity related to force rate was inferior and lateral. These findings suggest that specific circuitry in the cerebellum may be dedicated to specific motor control parameters such as force amplitude and force rate.

Comparison of three methods of sampling for endometrial cytology in the mare. Preliminary study.

OBJECTIVE: This prospective study aims to compare three different sampling techniques for the collection of endometrial cytological specimens in the mare: the guarded culture swab, the uterine cytobrush and the low volume uterine flush. MATERIAL AND METHODS: The study population consisted of six healthy Standardbred mares in dioestrus. In each mare an acute endometritis was induced by performing a low- volume uterine flush 6days after ovulation using a sterile isotonic solution (lactated Ringer's solution or ViGro™ Complete Flush Solution). Two days after initiating inflammation, samples were collected from each mare using the three compared techniques: the double guarded cotton swab, the uterine cytobrush and the low volume uterine flush. The cytological evaluation of the samples was based on following criteria: the quality and cellularity of the samples and the number of neutrophils recovered. RESULTS: The uterine cytobrush yielded slides of significantly (p=0.02) better quality than the low volume uterine flush. There was no significant difference between the cytobrush and the double guarded swab technique for the quality. There was no difference between techniques in the number of endometrial cells (p=0.55) and neutrophils recovered (p=0.28). CONCLUSION AND CLINICAL RELEVANCE: Endometrial cytology is a practical method for the diagnosis of acute endometrial inflammation in the mare. Since no difference in the number of neutrophils was found between the three techniques, the choice of the sampling method should be based on other factors such as practicability, costs and disadvantages of each technique.

Cell-specific effects of Dyt1 knock-out on sensory processing, network-level connectivity, and motor deficits.

DYT1 dystonia is a debilitating movement disorder characterized by repetitive, unintentional movements and postures. The disorder has been linked to mutation of the TOR1A/DYT1 gene encoding torsinA. Convergent evidence from studies in humans and animal models suggest that striatal medium spiny neurons and cholinergic neurons are important in DYT1 dystonia. What is not known is how torsinA dysfunction in these specific cell types contributes to the pathophysiology of DYT1 dystonia. In this study we sought to determine whether torsinA dysfunction in cholinergic neurons alone is sufficient to generate the sensorimotor dysfunction and brain changes associated with dystonia, or if torsinA dysfunction in a broader subset of cell types is needed. We generated two genetically modified mouse models, one with selective Dyt1 knock-out from dopamine-2 receptor expressing neurons (D2KO) and one where only cholinergic neurons are impacted (Ch2KO). We assessed motor deficits and performed in vivo 11.1 T functional MRI to assess sensory-evoked brain activation and connectivity, along with diffusion MRI to assess brain microstructure. We found that D2KO mice showed greater impairment than Ch2KO mice, including reduced sensory-evoked brain activity in key regions of the sensorimotor network, and altered functional connectivity of the striatum that correlated with motor deficits. These findings suggest that (1) the added impact of torsinA dysfunction in medium spiny and dopaminergic neurons of the basal ganglia generate more profound deficits than the dysfunction of cholinergic neurons alone, and (2) that sensory network impairments are linked to motor deficits in DYT1 dystonia.

Effects of ventral intermediate nucleus deep brain stimulation across multiple effectors in essential tremor.

OBJECTIVE: Essential tremor (ET) prominently affects the upper-limbs during voluntary movements, but can also affect the lower-limbs, head, and chin. Although deep brain stimulation (DBS) of the ventral intermediate nucleus (VIM) of thalamus improves both clinical ratings and quantitative measures of tremor, no study has quantified effects of DBS on tremor across multiple body parts. Our objective was to quantify therapeutic effects of DBS across multiple body parts in ET. METHODS: We performed quantitative assessment of tremor in ET patients who had DBS for at least one year. We assessed tremor on and off VIM-stimulation using triaxial accelerometers on the upper-limbs, lower-limbs, head and chin during seated and standing tasks. RESULTS: VIM-DBS significantly reduced tremor, but there was no statistical difference in degree of tremor reduction across the measured effectors. Compared to healthy controls, ET patients treated with DBS showed significantly greater tremor power (4-8 Hz) across all effectors during seated and standing tasks. CONCLUSIONS: VIM-DBS reduced tremor in ET patients. There was no significant difference in the degree of tremor reduction across the measured effectors. SIGNIFICANCE: This study provides new quantitative evidence that VIM-DBS is effective at reducing tremor across multiple parts of the body.

Effect of age, ethnicity, sex, cognitive status and APOE genotype on amyloid load and the threshold for amyloid positivity.

The threshold for amyloid positivity by visual assessment on PET has been validated by comparison to amyloid load measured histopathologically and biochemically at post mortem. As such, it is now feasible to use qualitative visual assessment of amyloid positivity as an in-vivo gold standard to determine those factors which can modify the quantitative threshold for amyloid positivity. We calculated quantitative amyloid load, measured as Standardized Uptake Value Ratios (SUVRs) using [18-F]florbetaben PET scans, for 159 Hispanic and non-Hispanic participants, who had been classified clinically as Cognitively Normal (CN), Mild Cognitive Impairment (MCI) or Dementia (DEM). PET scans were visually rated as amyloid positive (A+) or negative (A-), and these judgments were used as the gold standard with which to determine (using ROC analyses) the SUVR threshold for amyloid positivity considering factors such as age, ethnicity (Hispanic versus non-Hispanic), gender, cognitive status, and apolipoprotein E ε4 carrier status. Visually rated scans were A+ for 11% of CN, 39.0% of MCI and 70% of DEM participants. The optimal SUVR threshold for A+ among all participants was 1.42 (sensitivity = 94%; specificity = 92.5%), but this quantitative threshold was higher among E4 carriers (SUVR = 1.52) than non-carriers (SUVR = 1.31). While mean SUVRs did not differ between Hispanic and non-Hispanic participants;, a statistically significant interaction term indicated that the effect of E4 carrier status on amyloid load was greater among non-Hispanics than Hispanics. Visual assessment, as the gold standard for A+, facilitates determination of the effects of various factors on quantitative thresholds for amyloid positivity. A continuous relationship was found between amyloid load and global cognitive scores, suggesting that any calculated threshold for the whole group, or a subgroup, is artefactual and that the lowest calculated threshold may be optimal for the purposes of early diagnosis and intervention.

Effects of focal hand dystonia on visually guided and internally guided force control.

BACKGROUND: A fundamental feature underlying many movement disorders is increased variability in the motor response. Despite abnormalities of grip force control in people with dystonia, it is not clear whether dystonia is also associated with increased variability in force output and whether force variability in dystonia is affected by the presence or absence of visual feedback. OBJECTIVE: To examine force variability in 16 patients with writer's cramp and 16 matched controls. METHODS: The variability of force output at the wrist under conditions of both vision and no vision was examined. The underlying frequency structure of the force signal was also compared across groups. Participants produced isometric wrist flexion to targets at 25% and 50% of their maximum voluntary contraction strength under conditions of both vision and no vision. RESULTS: Similar levels of force variability were observed in patients with dystonia and controls at the lower force levels, but patients with dystonia were less variable in their force output than controls at the higher force level. This reduction in variability in people with dystonia at 50% maximum voluntary contraction was not affected by vision. Although a similar dominant frequency in force output was observed in people with dystonia and controls, a reduced variability in the group with dystonia at the higher force level was due to reduced power in the 0-4-Hz frequency bin. CONCLUSIONS: The first evidence of a movement disorder with reduced variability is provided. The findings are compatible with a model of dystonia, which includes reduced cortical activation in response to sensory input from the periphery and reduced flexibility in motor output.

Impact of staff education on pressure sore development in elderly hospitalized patients.

To test the hypothesis that an educational program alone without the introduction of new technology could result in both higher quality care and cost savings, the incidence of development of pressure sores among patients over the age of 65 years was concurrently reviewed before and after an education program developed and disseminated by a skin care team composed of physicians and nurses. Before the education program, 18 (14.6%) of 123 patients with no pressure sores developed pressure sores during their hospital admission. After the education program, only six (5.4%) of 105 patients who entered the hospital with intact skin developed a pressure sore during their hospital stay. The data show that an educational program was effective in decreasing by 63% the development of pressure sores in an elderly hospitalized population. Furthermore, a cost savings of $74,372 in the use of special care beds was realized.

Visual control of isometric force in Parkinson's disease.

The current article reports an investigation of the influence of visual feedback on force production in Parkinson's disease (PD) that required subjects to maintain a constant amount of isometric force with their index finger and thumb with and without visual feedback. Eight PD and eight matched control subjects produced force at 5, 25 and 50% of their maximal voluntary contraction for 20 s. In conditions of full vision, the force trajectory and force target were viewed on the computer monitor. In the no visual feedback condition, visual feedback of the force trajectory vanished after the initial 8 s of the trial. The results showed that under the vision condition PD subjects produced levels of maximal and submaximal force that were similar to controls. Approximately 1.5-2.5 s following the removal of visual feedback, the force level in both subject groups decreased to steady-state levels. There was no difference in the time between visual feedback removal and the beginning of force decay in PD. There was a larger amount and faster rate of force decay after visual feedback removal in PD subjects compared to the controls. It is proposed that the increased force decay in PD does not result from sensory reflex deficits but from higher order sensory-motor memory processes.

The dynamics of resting and postural tremor in Parkinson's disease.

OBJECTIVE: The study examines the time and frequency structure of Parkinson's disease tremor in patients that exhibit no clinical signs of tremor. METHODS: Eight mild to moderate Parkinson's disease and 8 matched control subjects maintained their limb in a constant position (30 s) under a postural finger, postural hand and resting tremor condition. Finger acceleration from the middle phalange, electromyographic (EMG) activity from extensor digitorum communis and flexor digitorum superficialis (FDS) were recorded. RESULTS: The data confirmed that there were no differences in the amount of limb motion and the modal frequency was around 9 Hz for each subject group. The time-dependent organization of tremor was more regular (lower approximate entropy [ApEn]) in Parkinson's disease. Both time and frequency analyses between the acceleration and extensor EMG signals demonstrate a reduction in the 20-25 Hz tremor component and an increase in the 8-12 Hz region of tremor. CONCLUSIONS: The results are discussed in relation to the proposal that increased regularity results from an increase in motor unit synchronization at 8-12 Hz and a reduction in the amplitude of the 20-25 Hz tremor component. The time and frequency structure of tremor may be useful in assessing individuals with Parkinson's disease.

Amplitude changes in the 8-12, 20-25, and 40 Hz oscillations in finger tremor.

OBJECTIVE: The study examined the amplitude and frequency modulation of the 8-12, 20-25, and 40 Hz frequencies of tremor to determine the degree to which increments of load affect the amplitude of these neural rhythms. METHODS: Finger acceleration from the middle phalange and electromyographic (EMG) activity of the extensor digitorum communis (EDC) muscle were recorded on 10 normal adult subjects. Two experiments are reported that manipulated loads ranging from 0 to 40 and 0 to 200 g that were attached to the distal portion of the outstretched middle phalange. RESULTS: There were 8-12, 20-25, and 40 Hz oscillations in the EMG recording but only the 8-12 and 20-25 Hz rhythms were present in the tremor and tremor-EMG coherence. Adding load to the finger reliably decreased the 20-25 Hz band of acceleration, reduced the relative power within the 20-25 Hz EMG band, increased the relative power of the 40 Hz band, but had no effect on the relative power within the 8-12 Hz EMG frequency band. The tremor-EMG coherence in the 8-12 and 40 Hz regions was independent of load, but was markedly reduced with load in the 20-25 Hz band. CONCLUSIONS: The 8-12, 20-25, and 40 Hz neural rhythms of physiological tremor have a stable frequency consistent with central oscillations. There is an increase in the relative power of the 40 Hz EMG band with force, but only the amplitude of the 20-25 Hz band is modulated by mechanical-reflex feedback.

Regularity of force tremor in Parkinson's disease.

OBJECTIVES: The study examines the time-dependent structure of force tremor to investigate two hypotheses: (1), the regularity of tremor can help in discriminating normal aging from that of Parkinson's disease (PD); and (2), there is increased tremor regularity with increases in the severity of PD. METHODS: Eight young (21-29 years), eight elderly (68-80 years), and eight PD (68-80 years) subjects produced constant grip force at 5, 25 and 50% of their maximal voluntary contraction by squeezing two load cells with their index finger and thumb under a vision and no vision condition. Spectral analysis and approximate entropy (ApEn) were used, respectively, to analyze the frequency and time-dependent structure of tremor. RESULTS: The analyses showed that there were no differences in the amplitude and modal frequency of force tremor between groups. The ApEn was significantly lower in the PD group compared with the controls. For the PD group, the linear relations between the total scores taken from the Unified Parkinson's Disease Rating Scale-motor section and the dependent variables were r(2)=0.71 (P<0.01) for ApEn, r(2)=0.20 (P>0.05) for the modal frequency, and r(2)=0.23 (P>0.05) for the standard deviation. Surrogate analyses revealed that the time-dependent structure of tremor provided additional information beyond that of amplitude and modal frequency analyses. CONCLUSIONS: These findings indicate that tremor analyses should not be limited to just the frequency and amplitude of the oscillation, and that the time-dependent structure of tremor is useful in differentiating tremor in healthy people from those with PD. The hypothesis that more regular tremor in PD is due to a loss of multiple neuronal oscillators contributing to the tremor output is discussed.

EMG remains fractionated in Parkinson's disease, despite practice-related improvements in performance.

OBJECTIVE: We studied the ability of patients with Parkinson's disease to improve their performance in a motor task requiring both speed and accuracy in the execution of elbow flexion movements. Our goal was to investigate the changes in electromyographic activity associated with the changes in movement performance. METHODS: Eleven patients on anti-Parkinsonian medication were tested. The patients were selected for being bradykinetic, having little or no resting tremor or dyskinesias, and being in stages II or III of the Hoehn and Yahr rating scale. RESULTS: The untrained patients displayed multiple bursts of agonist activity, characteristic of Parkinsonian EMG recordings. All patients improved their performance by increasing peak velocity while maintaining movement accuracy within strict boundaries. With practice, the patients' performance changed in a manner similar to that which has been previously observed for performance curves in neurologically normal subjects. As movement duration decreased (i.e. peak velocity increased), we observed a slight decrease in the number of agonist bursts and an increase in the average burst duration. However, the patients continued to generate a fractionated, multi-burst agonist pattern. CONCLUSIONS: We conclude that Parkinsonian patients benefit from practice by improving their performance but remain fundamentally impaired in the generation of muscle activation patterns. This study has shown that the generation of fractionated, multiple short bursts of EMG activity that is characteristic of movements made by Parkinsonian patients is not normalized by practice.

Dimensional change in motor learning.

Bernstein (The Co-ordination and Regulation of Movements, Pergamon, London, 1967) outlined a theoretical framework for the degrees of freedom problem in motor control that included a 3-stage approach to the reorganization of the peripheral biomechanical degrees of freedom in motor learning and development. We propose that Bernstein's conception of change through the stages of learning is too narrow in its consideration of the degrees of freedom problem and the actual pathways of change evident in motor learning. It is shown that change in both the organization of the mechanical degrees of freedom and the dimension of the attractor dynamic organizing motor output can either increase or decrease, according to the confluence of constraints imposed on action. The central issue determining directional change in dimension is whether the dimensionality of the task relevant intrinsic dynamic needs to be increased or decreased to realize new task demands.

Control of in vitro prostaglandin F2 alpha and E2 synthesis by caruncular and allantochorionic tissues from cows that calved normally and those with retained fetal membranes.

High concentrations of PGF2 alpha and PGE2 are produced by the uterus during the early postpartum period in cows and may play an important role in both placental separation and uterine involution. In the present study, we have examined the hormonal and intracellular control mechanisms involved in PGF2 alpha and PGE2 secretion by caruncular and allantochorionic tissue in vitro. Tissue explants, obtained about 6 hr postpartum from cows that delivered normally (NFM, n = 10) or cows with retained fetal membranes (RFM, n = 4), were incubated for 6 hr and PGF2 alpha and PGE2 concentrations in the medium were determined by radioimmunoassay. Addition of oxytocin (100 microU/ml), platelet activating factor (PAF, 100 ng/ml) and epidermal growth factor (EGF, 100 ng/ml) had no effect on secretion of PGF2 alpha from the caruncle, but oxytocin and PAF did stimulate PGE2. There was no difference between groups of cows. All three substances stimulated PGF2 alpha from the allantochorion of NFM, but not RFM, cows and stimulated PGE2 secretion from the allantochorion of both groups of cows. Incubation of the tissues with cholera toxin (100 ng/ml), dibutyryl cyclic adenosine 3',5'-monophosphate (dibutyryl cAMP, 1 mM), calcium ionophore A23187 (5 microM) or phorbol ester 12-myristate-13 acetate (PMA, 100 nM) showed that PGF2 alpha secretion is essentially via the calcium-protein kinase C effector pathway. However, calcium-protein kinase C and cAMP second messenger systems appear to be involved in the secretion of PGE2. Prostaglandin secretion was sensitive to cycloheximide in both caruncular and allantochorionic tissues, suggesting that protein synthesis may be involved. In conclusion, these data show that in vitro PGF2 alpha secretion can be modulated by the agonists used only in allantochorion and is essentially via the calcium-protein kinase C effector pathway. PGE2 secretion can be modified in both caruncular and allantochorion tissues and involves both inositol triphosphate-diacylglycerol and cAMP second messenger systems.

Steroid synthesis by equine conceptuses between days 7 and 14 and endometrial steroid metabolism.

The objective of this study was to determine if changes in steroid synthesis occurred in the horse blastocyst about the time of maternal recognition of pregnancy. Embryos collected between days 7.5 and 14.5 were incubated for 8 hr in vitro in HAM's F10 containing radiolabelled pregnenolone. The steroid metabolites in the incubation medium were separated by reverse phase HPLC and the major peaks expressed as a percentage of total metabolites. It was found that there were no major changes in the profile of metabolites throughout the period of study, although there was increased conversion as the conceptuses developed. It was found that the major metabolite produced was 17 alpha-hydroxyprogesterone and not estradiol as expected. A second experiment was conducted to determine if 17 alpha-hydroxyprogesterone was metabolized by endometrial tissue. Endometrial biopsies from anestrous mares and from pregnant and nonpregnant mares at day 11 were incubated with radiolabelled 17 alpha-hydroxyprogesterone, progesterone or pregnenolone. The 17 alpha-hydroxyprogesterone, but not progesterone nor pregnenolone, was converted to a more polar metabolite in all groups. Production of this metabolite was significant greater in the anestrous mares. This metabolite has not been unidentified conclusively. Thus, results of this study show that 17 alpha-hydroxyprogesterone is the major steroid synthesized by the equine blastocyst and that this steroid is further metabolized to an unidentified steroid by the endometrium. These steroids could play a role in conceptus development or maternal recognition of pregnancy.

Effect of bacterial cell wall and lipopolysaccharide on arachidonic acid metabolism by caruncular and allantochorionic tissues from cows that calved normally and those that retained fetal membranes.

Immunoactive eicosanoids may have a role in both placental separation and uterine involution in cattle. In the present study, we examined the effects of bacterial cell wall preparation and endotoxins on in vitro prostaglandin synthesis and arachidonic acid (AA) metabolism by caruncular and allantochorionic tissues. Placentomes were obtained about 6 h post partum from cows that delivered normally (n = 10) or those with retained fetal membranes (n = 4); the tissue explants were incubated for 6 h in the presence of labeled or nonlabeled AA. Prostaglandin F(2alpha) (PGF(2alpha)) and E(2) (PGE(2)) were measured by radioimmunoassay, and labeled AA metabolites were separated by reverse phase-high pressure-liquid chromatography. There was no effect of bacterial cell wall preparations or endotoxins on in vitro caruncular PGF(2alpha) secretion. However, bacterial products increased caruncular PGE(2) secretion in both cows that delivered normally and those with retained fetal membranes. For normal delivery cows caruncular tissue, bacterial product also increased leukotriene B(4) (LTB(4)) and decreased both thromboxane B(2) (TXB(2)) and hydroxy-eicosatetranoic acids (HETE) in vitro secretion. For the allantochorion, bacterial products increased in vitro PGF(2alpha) secretion only in cows that delivered normally and increased PGE(2) secretion essentially in cows with retained fetal membranes. In general, 6 keto PGF(1alpha) was the main metabolite secreted by both allantochorionic and carucular tissues. However, in cows with retained fetal membranes, PGE(2) became the most important metabolite secreted by allantochorion, especially in the presence of endotoxin. In conclusion, these results suggest that bacteria found in the early postpartum uterus or their endotoxin affect primarily caruncular and allantochorionic PGE(2) synthesis.

Determination of gestational age in sheep and goats using transrectal ultrasonographic measurement of placentomes.

Three experiments were conducted to determine gestational age in the ewe and doe by measuring placentomes with a B-mode ultrasonograph and a 5 MHz transducer. Transrectal measurements were obtained by placing the female over a bale of hay. In Experiment 1, ewes (n = 12) and does (n = 15) were examined by transrectal ultrasonography every week from breeding to parturition to determine the growth pattern of placentomes during pregnancy. In Experiment 2, placentomes from 132 ewes and 169 does were measured between 30 and 90 d of gestation. A linear regression relationship between fetal age in days and placentome size in mm was calculated and adjusted for does (gestational age = 28.74 + 1.80PL + e, r(2) = 70.34) and for ewes (age = 47.98 + 0.62PL + e, r(2) = 15.59). In Experiment 3, the placentomes of 63 does were measured to validate this relationship by using linear regression. Gestational age was determined correctly in 66% of the does, with a range of +/- 7 d and in 96% with a margin of +/- 14 d. In conclusion, transrectal ultrasonography allowed for the measurement of placentome size, which increased rapidly during the first 70 to 90 d of gestation in ewes and does. In ewes, however, there was a poor correlation of placentome size with gestational age, while in goats, measurement of placentomes could be used along with pregnancy diagnosis by transrectal ultrasonography as an indication of gestation age.

Estrus induction with prostaglandin F2alpha, cloprostenol or fenprostalene during the normal estrous cycle, superovulation and after embryo collection.

Holstein heifers used as embryo donors were treated with three luteolytic agents (PGF2alpha, cloprostenol, fenprostalene) during the normal estrous cycle, superovulation or after embryo collection to determine the interval from treatment to estrus. A similar return-to-estrus interval was observed for each luteolytic agent among the three groups of heifers. Nevertheless, after embryo collection, fenprostalene had a tendency to induce the longest delays (p = 0.08). This tendency is supported by a higher proportion of delayed luteolysis and more heifers showing estrus later than 11 d post treatment. Also, during normal estrous cycles, 5/10 and 0/8 fenprostalene- and cloprostenol-treated heifers, respectively, showed progesterone concentrations higher than 1 ng/mL 48 h after treatment. Regardless of the luteolytic agent used, estrus was induced earlier (P < 0.005) during superovulation than when heifers were treated between Days 9 to 16 of the normal estrous cycle or after embryo collection. However, the return-to-estrus interval was similar between heifers treated during superovulation and those treated between Days 6 to 8 of the normal estrous cycle. After embryo collection, intervals before the return to estrus increased with the number of Corpora lutea (CL) palpated except in the nonresponding group (0 to 1 CL), which returned to estrus later than the low responding group (2 to 4 CL).

Seasonality and variability of the interestrous interval in the bitch.

Records from two breeding colonies (A and B) located near each other were analyzed for this experiment. Colony A consisted of 19 bitches (8 Maltese, 5 Yorkshire, 3 Lhasa Apso, and 3 Bouvier des Flandres), while Colony B consisted of 48 Beagle bitches. A total of 126 interestrous intervals (141 estrous cycles) from Colony A were reviewed to quantitate the variability of the interestrous interval. Analysis of variance showed that the degree of variation of the estrous cycle length within bitches (65%) was about twice the degree of variation of means of the estrous cycle length among bitches (35%). It was found that the estrous cycle length is extremely variable, and it cannot be used to predict the next estrus in a single bitch, although some bitches were very consistent. The seasonal and monthly distribution of estrous cycles throughout the year was also analyzed from bitches kept in Colonies A and B for a total of 210 estrous cycles. The data were collected over a four-year period. A seasonal pattern was observed when the cumulative distributions over years were analyzed. A higher frequency of estrous cycles was observed during winter and summer. This seasonality pattern was not observed when individual years were analyzed separately. However, the overall probability that an estrus would occur at any month of the year was the same for each month (1/12) when cumulative distribution over years were analyzed.