Search PubMed⌕ Search

Biomedical subjects

J D Kirby

Publications and source records attributed to J D Kirby.

At least 19 recordsLinked to original sources
PubMed1999

Electrocardiographic and genetic evaluation of giant jungle fowl, broilers, and their reciprocal crosses following unilateral bronchus occlusion.

Electrocardiography is useful as a noninvasive technique for detecting right ventricular hypertrophy in birds developing pulmonary hypertension (PH) and pulmonary hypertension syndrome (PHS, ascites). The objective of this study was to identify every aspect of the Lead II ECG wave form (amplitude or duration) that can be correlated with right ventricular hypertrophy [increased right:total ventricular weight ratios (RV:TV)] indicative of PH across a broad genetic background. Sham operations were conducted, or PH was induced by occluding one extrapulmonary primary bronchus in 14-d-old chicks produced from matings of broilers (B x B), Giant Jungle Fowl (J x J), and their reciprocal crosses (B x J and J x B). Standard three-lead electrocardiograms (ECG) were recorded on Days 28 and 42, and final necropsies were conducted to evaluate the incidence of ascites, confirm sex, and obtain ventricular weights for calculating RV:TV. Ascites did not develop in the J x J, and one each of the B x J and J x B chicks developed ascites; consequently, only data from birds that did not develop ascites were compared. Heart rate was recorded, and the following amplitudes and durations were measured or calculated for three consecutive wave cycles of the Lead II ECG: base of R to the peak of R (RbR), peak of R to base of S (RS), base of S to peak of R' (SR'), S, peak of R' to base of R' (R'R'b), and base of S to peak of T (ST). Differences between the ECG of sham and bronchus clamp groups were more prominent in B x B and B x J than in J x B, and bronchus occlusion did not affect the ECG, growth, or RV:TV ratios of J x J. In contrast, sex influences were more prominent in J x J and J x B than in B x J and B x B. These observations suggest a paternal pattern of inheritance for Lead II ECG wave forms, with crosses sired by broilers (B x B, B x J) exhibiting susceptibility to PH and few ECG differences related to sex, whereas crosses sired by Giant Jungle Fowl U x J, J x B) exhibited resistance to PH and numerous ECG differences related to sex.

Animals↗
PubMed1999

Electrocardiographic evaluation of broilers following unilateral occlusion of an extrapulmonary primary bronchus.

This study was conducted to provide a comprehensive evaluation of both the amplitudes and durations of the Lead II electrocardiogram (ECG) in nonascitic and ascitic broilers. At 14 d of age, male and female broiler chicks were sham-operated (SHAM, n = 27), or pulmonary hypertension was initiated by occluding one extrapulmonary primary bronchus (BRONCHUS CLAMP, n = 57). Lead II ECG and BW were recorded on Days 28 (ECG1) and 42 (ECG2), necropsies were conducted on all birds dying after Day 28, and final necropsies were conducted on Day 49. Data collected at necropsy included the presence (ASCITIC) or absence (NONASCITIC) of ascites, sex, and ventricular weights for calculating the right:total ventricular weight ratio (RV:TV), which serves as a reliable index of pulmonary hypertension. In each bird, three consecutive ECG1 and ECG2 wave cycles were quantified for both amplitude and duration of the following wave segments: Rb-R, R-S, S-R', R'-R'b, and S-T. The S wave amplitude was calculated by subtracting R-S from Rb-R and heart rate (HR) was measured from the peak of one T wave to the peak of the next. In the majority of comparisons, ASCITIC and BRONCHUS CLAMP broilers had larger S, R'-R'b, and S-T amplitudes, longer R-S, R'-R'b, and S-T durations, and a slower HR than NONASCITIC and SHAM broilers, regardless of sex. The differences in ECG wave forms and durations between ASCITIC and NONASCITIC broilers were greater on Day 42 (ECG2) than on Day 28 (ECG1), but when both ECG were used to develop a regression equation to estimate RV:TV, the R2 was 0.79. The most important Lead II ECG parameters associated with the development of ascites were an increasingly negative S wave amplitude and greater amplitudes and durations for R'-R'b and S-T as well as a decrease in the HR.

Airway Obstruction↗
PubMed1998

Effects of 6-N-propyl-2-thiouracil on growth, hormonal profiles, carcass and reproductive traits of boars.

Neonatal 6-N-propyl-2-thiouracil (PTU)-induced hypothyroidism reduces body weight but increases testicular size in adult male rodents. The objective of this study was to determine the effect of prepubertal PTU treatment on boars. For Experiment I, boars (n = 28) were randomly allotted to eight pens. Each pen received one of four PTU doses (0, 0.01, 0.03 and 0.1% in a basal diet) between 28 and 56 days of age (DOA). Due to a lack of difference among three PTU treatments, PTU-treated boars were pooled. Boars treated with PTU had lower (P < 0.05) ADG during treatment, lighter (P < 0.05) BW after 56 DOA and less (P < 0.05) developed epididymides at 154 DOA. For Experiment II, boars (n = 19) were randomly allotted to six pens. Each pen received one of three PTU treatments orally as: control (carrier), PTU-I (0.002% BW of PTU daily between 7 and 70 DOA), or PTU-II (0.002% BW of PTU daily between 28 and 91 DOA). During treatment, PTU-treated boars had lower (P < 0.05) serum T4 levels, rectal temperature, feed intake and ADG. Boars treated with PTU had lower (P < 0.05) BW between 63 and 154 DOA but higher (P < 0.05) gain/feed between 105 and 133 DOA. Boars treated with PTU had less (P < 0.05) developed epididymides and sperm count per gram testis at 238 DOA. These results suggest that prepubertal PTU-induced hypothyroidism had significant effects on growth, hormonal profiles, and reproductive traits of boars; however, it does not appear to be an effective method for increasing testis size and sperm production of commercial boars.

Aging↗
PubMed1998

Evaluation of the duration of sperm fertilizing ability in five lines of commercial broiler breeder and Delaware cross males.

The ability to characterize the reproductive potential of male fowl can be affected by a number of factors, including age, type, insemination scheme, and number of sperm inseminated. Fertility is a complex interaction of traits involving two individuals of differing genetic composition: In modern broiler breeders, selected predominantly for growth and carcass characteristics, fertility problems may be exacerbated. In order to evaluate the male components of fertility, an experiment investigating the effects of male line on both average fertility and the duration of fertility was completed. Male chicks from five commercial broiler breeder male lines or sired by subfertile Delaware cross roosters were reared to adulthood. Between 30 and 60 wk of age, semen was collected from five males per line, extended and used to inseminate each of 10 to 12 hens from four broiler breeder female lines or Single Comb White Leghorn hens with 80 x 10(6) live sperm. Following a single insemination eggs were collected for 21 d and fertility determined by visual inspection following 4 d incubation. The percentages of live sperm and overall fertility data for the replicate trials were analyzed, following transformation, with a linear model and daily fertility data were analyzed by iterative least squares regression. Whereas there were large differences in fertility among individual males (durations from 3.4 to 14.5 d) within a line, there were no significant male line or replicate effects on overall fertility or the duration of fertility. However, there was a significant (P < 0.05) line-dependent reduction in the percentage of live sperm in broiler breeder males, with the subfertile Delaware cross males being intermediate. There were no significant female line or replicate effects on the duration of fertility; however, there were significant female line effects on overall fertility at both 7 and 21 d. These data suggest that although individual males varied widely, there were no male line effects on the duration of fertility in the lines of broiler breeders evaluated when analyzed by iterative least squares. Furthermore, these data suggest that although females may have significant affects on overall fertility, the duration of fertility appears to be a predominantly male characteristic. Therefore, iterative least squares regression may be a useful tool for identifying males with superior sperm fertilizing ability.

Animals↗
PubMed1997

Evaluation of logistic versus linear regression models for predicting pulmonary hypertension syndrome (ascites) using cold exposure or pulmonary artery clamp models in broilers.

Syndromes such as ascites (pulmonary hypertension syndrome) present difficulties both in the interpretation of associated physiological observations and in their analyses. The ability to predict which physiological variables have the greatest influence on survival or, more importantly, which individuals are most susceptible or resistant to ascites would be very useful selection tools. When addressed in this manner, ascites data become binary data sets (healthy or affected). Binary data can be problematic in that they do not meet all of the assumptions necessary for more traditional analyses such as ANOVA and linear regression. Binary data are discrete and do not have normally distributed errors, which violates a fundamental assumption of linear models. The predictive abilities of linear and logistic regression were evaluated in two replicated experiments using two methods to induce ascites, cold exposure (COLD) and surgical clamping of one pulmonary artery (PAC). The logistic and linear predictive models were derived using the same data and variables. The first data set from PAC and COLD were used to develop the predictive models and the replicate data sets of PAC and COLD were used as "test data sets" for the prediction of ascites. The linear models developed were complex, using four or five variables and requiring up to seven different measurements. On average, the linear models predicted ascites correctly 87.6% of the time. The logistic models were simple (single variable) models that predicted ascites correctly 92.0% of the time. The variables used in the logistic models were derivations of the ratio of right ventricular weight to total ventricular weight, either corrected for age or the body weight of the bird. Although linear regression predicted the incidence of ascites almost as well as logistic regression did, logistic regression is the more appropriate test statistic to use.

Analysis of Variance↗
PubMed1997

Neonatal hypothyroidism alters the pattern of prostatic growth and differentiation, as well as plasminogen activator and metalloprotease expression, in the rat.

The purpose of this study was to examine whether changes in growth, ductal histology, and expression of plasminogen activator (PA) and matrix metalloproteases are associated with the increased prostatic weight and DNA content seen in adult rats that were treated neonatally with the goitrogen 6-propyl-2-thiouracil (PTU). Ventral prostatic weights were initially reduced in PTU-treated rats but were increased 40% over those of controls by Day 180; this increase in prostatic weight was also accompanied by increases in the number of prostatic ductal tips. In controls, prostatic PA and gelatinase A activities decreased after completion of morphogenesis at 21-28 days of age. In contrast to controls, PA and gelatinase A activities were maintained through puberty (42 days) in PTU-treated rats but declined by 90 days. The elevated PA activity in both prostatic lobes at 42 days of age in PTU-treated rats was inhibited by amiloride, indicating that it is the urokinase form of PA. These data show that the increased prostatic weight and DNA content in adult rats following neonatal PTU treatment results from a delayed but extended period of growth and the formation of new ductal elements. There is a temporal overexpression of urokinase and gelatinase A associated with the increased ductal branching, indicating as well an extended period of morphogenesis that results in their eventual increased adult size. The prostatic enlargement in PTU-treated rats may serve as a useful model to study regulation of both normal and abnormal prostatic growth and morphogenesis.

Amiloride↗
PubMed1997

Determination of testis temperature rhythms and effects of constant light on testicular function in the domestic fowl (Gallus domesticus).

There is a wide range of opinions regarding the operating temperature of the testis in the domestic fowl. We used physiological monitoring techniques to investigate testis and body temperature over daily periods and under various light regimes to elucidate body temperature gradients in the fowl. We confirm that the operating temperature of the adult fowl's testes is equivalent to core body temperature (40-41 degrees C). Long-term continuous temperature monitoring showed that there was no difference between the temperature of the testis, liver, and peritoneum during a 24-h period either in a normal light:dark cycle or under constant light conditions. However, there was a slight decrease in all temperatures at subjective night in each case, a decrease that does not appear to be sufficient to influence spermatogenesis. Birds maintained under constant light throughout two cycles of the seminiferous epithelium (28 days) still exhibited normal testis function and structure, even when "nightly" testis temperature decrease was the lowest. Thus, by undergoing spermatogenesis at an elevated temperature, the domestic fowl system is unique among the homeothermic animal systems studied to date.

Animals↗
PubMed1997

Neonatal hypothyroidism permanently alters follicle-stimulating hormone and luteinizing hormone production in the male rat.

Transient neonatal hypothyroidism, induced with the goitrogen 6-n-propyl-2-thiouracil (PTU), results in dramatic increases in both testis size and sperm production in the adult rat. The observed increases in testis size and function occur in the presence of normal circulating testosterone levels. However, circulating gonadotropin levels are chronically reduced by 30-50% at all times in treated males. To better understand the permanent reduction in serum gonadotropin levels following transient neonatal hypothyroidism, we conducted a series of experiments to evaluate pituitary and hypothalamic function in the adult male PTU-treated rat. PTU treatment led to a significant reduction in GnRH-stimulated LH production. Castration resulted in 3.9- to 8.5-fold increases in circulating gonadotropin levels in both treated and control males; however, the absolute increases were significantly reduced in treated males. In contrast to circulating levels, pituitary gonadotropin contents did not increase in treated males after castration. PTU treatment did not lead to a reduction in the density of either luteotropes or folliculotropes, and both cell types increased in size and density after castration. The relative concentrations of both gonadotropin beta-subunit messenger RNAs increased more slowly in treated males than in controls after castration. Thus, although treated rats have the intrinsic ability to produce normal circulating levels of LH and FSH, gonadal feedback and an overall reduction in gonadotrope synthetic ability combine to produce the chronically reduced circulating levels of these hormones.

Animals↗
PubMed1997

Treatment of severe Raynaud's syndrome by injection of autologous blood pretreated by heating, ozonation and exposure to ultraviolet light (H-O-U) therapy.

OBJECTIVE: To determine the effect of re-injection of small samples of autologous blood, pretreated with heat, ozone and ultraviolet light (H-O-U therapy) in patients with severe Raynaud's syndrome. EXPERIMENTAL DESIGN: Open trial in 4 patients. SETTING: Temperature/humidity controlled vascular laboratory. PATIENTS: Severe Raynaud's syndrome of more than 5 years duration and defined as more than 5 attacks daily or 10 attacks in one week, at least half of which were painful and lasting for more than 30 minutes. Three patients were refractory to infusions of Iloprost. INTERVENTIONS: Patients were treated daily or on alternate days for a two to three weeks period by re-injection of citrated autologous blood pre-treated with heat, ozone and ultraviolet light (H-O-U therapy). MEASURES: Clinical observations; mean equilibrated hand temperature (infrared thermography); distributive and microcirculatory blood-flow (venous occlusion strain-gauge plethysmography, infrared photoplethysmography, laser Doppler flowmetry) iontophoresis of acetylcholine and sodium nitroprusside; estimations: serum levels of 6-keto-PGF1alpha and serum levels of anti-hsp65 antibody. RESULTS: Reduction or abolition of Raynaud's attacks for at least three months after treatment. Mean equilibrated hand temperature increased but did not normalise. Blood flow parameters improved but did not reach statistical significance. Iontophoresis of acetylcholine showed an increase in laser Doppler flowmetry which was statistically significant. Serum levels of 6-keto-PGF1alpha, fell significantly in three patients. Serum levels of anti-hsp65 antibody fell in the one patient which was followed sequentially. CONCLUSIONS: H-O-U therapy may prove useful in patients with severe Raynaud's syndrome.

6-Ketoprostaglandin F1 alpha↗
PubMed1996

Effects of transient prepubertal 6-N-propyl-2-thiouracil treatment on testis development and function in the domestic fowl.

It has been well established that thyroid hormones play an important role in regulating the onset of puberty and reproductive function in birds. In mammals it has been shown that transient hypothyroidism induced with the reversible goitrogen 6-N-propyl-2-thiouracil (PTU) can result in tremendous increases in testis size and sperm production and that the timing of hypothyroidism must correspond to the period of Sertoli cell proliferation. As the period of Sertoli cell proliferation is not precisely known in the fowl, an experiment was conducted to determine whether chicken testes have a similar window of sensitivity to PTU treatment. Broiler breeder male chicks (Peterson) were placed in floor pens at one day of age and reared according to the breeder's management guide for the entire 28-wk duration (controls) or up to the point of dietary treatment with PTU (0.1% w:w) for 6 wk that began at 2-wk intervals (2-8, 4-10, 6-12, 8-14, and 10-16 wk of age); after treatment, birds were returned to feed restriction and photostimulated at 20 wk of age. Birds were bled and killed, and testes were collected at 4-wk intervals. At 28 wk, one testis was fixed for histological examination and one was immediately placed in liquid N2 for sperm counts. Treatment with PTU from 6 to 12 wk of age resulted in a 96% increase in mean testis weight at 28 wk of age (treated 39.3 +/- 4.1 g per testis vs. control 20.0 +/- 1.6 g per testis). These testes exhibited normal morphology and increased relative sperm production. Treatment with PTU from either 8 to 14 or 10 to 16 wk of age resulted in approximately a 35% increase in testis mass at 28 wk of age relative to the control value (27.2 +/- 2.0 g and 27.7 +/- 3.6 g vs. 20.0 +/- 1.6 g per testis, respectively). However, both of these groups clearly demonstrated precocious puberty and abnormal spermatogenesis. These results suggest that appropriately timed PTU treatment may result in permanent increases in testis size and sperm production in the domestic fowl.

Animals↗
PubMed1996

Analysis of poultry fertility data. 3. Analysis of the duration of fertility in naturally mating Japanese quail.

The purpose of the present study was to test the appropriateness of iterative least squares regression for the evaluation of fertility data in naturally mating quail. In each of four trials, 20 male and 200 female randombred Japanese quail were housed in stacked breeder cages. Paired females were exposed to their assigned male for a single 48-h period. Eggs were collected for 2 wk following removal of the male, incubated, and fertility determined by visual inspection at egg breakout. In Trials 1 and 3, sexually experienced males were placed with experienced and inexperienced females, respectively. In Trials 2 and 4, inexperienced males were placed with experienced and inexperienced females, respectively. Duration of fertility, by male, was analyzed by iterative least squares, using the model y(x) = gamma/(1 + e beta(tau - x)). Overall fertility was analyzed with a log odds model following transformation to logits. Iterative least squares provided estimates of fertility duration of 3.75 to 9.18 d, with significant (P < 0.05) differences in the duration of fertility observed between individual males as well as between the trials. Differences (P < 0.05) in overall fertility (17.7 to 58.3%) were also observed, with inexperienced males paired with experienced females exhibiting the lowest overall means. Taken together, these results suggest that iterative least squares may be used to evaluate fertility in naturally mating populations and that reproductive experience can have a profound effect on the interpretation of fertility in naturally mating quail.

Animals↗
PubMed1996

A new method for rapid determination of sperm concentration in turkey semen.

The routine determination of sperm concentration not only provides a measure of semen quality but also supplies a means of delivering precise sperm numbers in modern artificial insemination (AI) programs. Methods for estimating sperm numbers in laboratory settings (e.g., hemacytometer) are not practical for use in breeding facilities. A microprocessor-controlled semen analyzer (Densimeter, Model 534-B-Mod1, Animal Reproductive Systems) is commercially available for evaluating stallion semen. We calibrated and modified the semen analyzer to determine sperm concentration in turkey semen and to provide information on the required dilution for a constant AI dose. To calibrate the semen analyzer for turkeys, six samples of pooled semen (10 toms per sample) were collected by abdominal massage. A dilution curve of undiluted and 1:0.5, 1:1, 1:1.5, 1:2, 1:3, 1:5, and 1:10 diluted semen was established using Beltsville Poultry Semen Extender. Sperm concentration in diluted samples was determined by hemacytometer counts. The hemacytometer counts were used to develop an equation for estimating sperm concentration from the semen analyzer's absorbance readings and the equation programmed into the instrument. The newly developed program on the semen analyzer was subsequently validated by comparing instrument values for sperm concentrations with concurrent hemacytometer counts, which compared well to concentrations determined by a previously calibrated photoelectric colorimeter (Klett). Correlation coefficients between the semen analyzer and hemacytometer counts and the Klett and hemacytometer counts were r = 0.996 and r = 0.992, respectively (P < 0.001). The semen analyzer method was accurate and precise and could be beneficial to commercial turkey AI programs because it is easy to use, requires limited technological skills, and provides results for determining sperm concentration and AI dose in approximately 1 min.

Animals↗
PubMed1995

Oral iloprost as a treatment for Raynaud's syndrome: a double blind multicentre placebo controlled study.

OBJECTIVE: To compare the efficacy, tolerance and safety of 50-150 micrograms orally administered iloprost given twice a day versus placebo in patients with Raynaud's syndrome. METHODS: The study was multicentre (n = 3), double blind and placebo controlled. Sixty three patients who had eight or more vasospastic attacks per week were enrolled. After a one week run-in period, all patients received either iloprost or placebo treatment to a maximum tolerated dose of 150 micrograms twice a day for 10 days. Diary cards assessed the duration and severity of the vasospastic attacks. Side effects were monitored by direct questioning. A global assessment of treatment efficacy was made by the patient at the end of treatment and two weeks later. RESULTS: Patient opinion tended to favour iloprost at the end of the 10 day treatment phase (p = 0.09) and this was significant at day 24 (the follow up visit) (p = 0.011). Although the duration and severity of attacks tended to decrease in the iloprost treated group, these results tended not to reach statistical significance (for severity p = 0.06 at end of treatment, p = 0.09 on day 24). CONCLUSION: Iloprost administered intravenously has been shown to be of benefit in the treatment of the Raynaud's syndrome associated with systemic sclerosis, but this route of administration is inconvenient. This study evaluated the use of iloprost administered orally to patients with Raynaud's syndrome. Patient documented improvement was significantly improved by iloprost. Diary card analysis showed a trend in favour of iloprost, but these results did not reach statistical significance.

Administration, Oral↗
PubMed1994

Expression of heat shock factor 2 in mouse testis: potential role as a regulator of heat-shock protein gene expression during spermatogenesis.

We have examined the expression and function of heat shock transcription factor 2 (HSF2) in spermatogenic cells of mouse testis. The results of in situ RNA hybridization analysis, RNA filter hybridization, and reverse transcription-polymerase chain reaction (RT-PCR) analysis indicate that HSF2 mRNA expression in testis is subject to developmental and cell type-dependent, as well as stage-dependent, regulation. Localized expression of HSF2 mRNA in testis first appears between Day 14 and Day 21 of postnatal development. In adult testis, HSF2 mRNA is found at highest levels in spermatocytes and round spermatids. Immunocytochemical staining and gel mobility shift analysis demonstrate that HSF2 protein is localized to the nuclei of spermatocytes and round spermatids and that this transcription factor exists in testis in a constitutively active DNA-binding state. We further demonstrate that the constitutive HSF2 DNA-binding activity present in testis is able to interact with promoter sequences of the hsp70.2 gene, a testis-specific member of the hsp70 gene family. Taken together, our results show that the expression and functional properties of HSF2 are regulated in spermatogenic cell types of the mouse testis, supporting a role for this transcription factor as a regulator of hsp gene expression during spermatogenesis.

Animals↗
PubMed1994

Hodgkin's disease presenting with digital ischaemia.

A 52-year-old man with primary Raynaud's disease developed increasingly severe Raynaud's phenomenon with digital ischaemia in all limbs, and gangrene in two digits of the left hand. He was subsequently found to have Hodgkin's disease. Cervical sympathectomy led to initial improvement in acute ischaemia, and chemotherapy was followed by further improvement in the general severity of Raynaud's phenomenon together with remission of the lymphoma.

Fingers↗
PubMed1994

Analysis of subfertility associated with homozygosity of the rose comb allele in the male domestic fowl.

Sperm metabolism and duration of fertility were compared between roosters homozygous (RR) and heterozygous (Rr) for the rose comb allele. In the absence or presence of Ca+2, a motility agonist, the metabolic rate of spermatozoa from RR males was 76 to 77% of that of spermatozoa from Rr males. In the presence of caffeine, the metabolic rate of spermatozoa from RR males was increased significantly (P < .05) to 86% of that of spermatozoa from Rr males. Although intramagnal insemination of ejaculated spermatozoa reduced the disparity in duration of fertility between RR and Rr males, the duration of fertility of RR males was still less than that of Rr males. No difference in duration of fertility was observed following intramagnal insemination of testicular spermatozoa. Subfertility associated with RR males seems to stem from an aberrant activation or regulation of spermatozoal metabolism and not a reduction in absolute metabolic capacity per se.

Alleles↗
PubMed1993

A cholinergic antagonist, mecamylamine, blocks light-induced fos immunoreactivity in specific regions of the hamster suprachiasmatic nucleus.

Recent studies have shown that light-induced phase shifts of the circadian rhythm of locomotor activity are associated with c-fos expression in the suprachiasmatic nucleus (SCN) of rodents. In order to explore further the importance of c-fos expression for the phase-shifting effects of light, we examined the effects of mecamylamine on light-induced Fos-like immunoreactivity (Fos-lir) in the SCN. Mecamylamine was chosen because it is a cholinergic antagonist that blocks the phase-shifting effects of light on the circadian activity rhythm in the golden hamster. Golden hamsters were entrained for at least 14 days to a 14 h light: 10 h dark photoperiod. Animals were then placed in constant darkness (DD) and during exposure to DD were subjected to one or more of the following treatments: (1) vehicle alone; (2) mecamylamine alone (450 micrograms, i.c.v.) at circadian time (CT) 19; (3) vehicle plus a light pulse at CT 19; (4) mecamylamine 10 min prior to the light pulse at CT 19. Mecamylamine blocked the phase-shifting effects of light on the circadian rhythm of locomotor activity when compared to vehicle-treated animals (P < 0.001). A light pulse at CT 19 induced Fos-lir in the SCN within 1 h, whereas treatment with vehicle or mecamylamine had no noticeable effect on Fos-lir in the SCN. Mecamylamine pretreatment dramatically reduced light-induced Fos-lir in the SCN by 75%. The most striking observation was the clear inhibition of Fos-lir by mecamylamine in the dorsomedial region of the SCN while there was little inhibition of Fos-lir in the most ventral portions of the SCN.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗