Biomedical subjects

J J Ford

Publications and source records attributed to J J Ford.

At least 91 records · Page 5Linked to original sources

PubMed1987

Influences of pre- and postnatal testosterone treatment on defeminization of sexual receptivity in pigs.

Sexual receptivity was evaluated in female and male pigs that had experienced varying periods of exposure to testosterone pre- and postnatally. For prenatal exposure, pregnant sows were treated with testosterone propionate (TP) from Day 29-35 or Day 39-45 of gestation at a dosage that caused virilization of the external genitalia of their female offspring. Eighty-three percent of the females that received TP prenatally had regular estrous cycles, but reached puberty later than control females. Only 26% of the females that received TP both pre- and postnatally (4-6 mo of age) were observed in estrus by 10 mo of age. After ovariectomy and acute treatment with estradiol benzoate (EB), the proportion of females that showed the immobilization response (receptivity) was similar for all groups of females independent of pre- or postnatal TP treatment. Females treated prenatally from Day 39-45 showed the immobilization response for fewer days after treatment with a high dosage of EB than did controls. On the basis of these observations, we conclude that receptivity in female pigs is not affected greatly by testosterone treatment at the stages of development that were investigated. Males castrated at birth and treated with a single injection of EB after 9.5 mo showed the immobilization response. In contrast, few males castrated at 8 mo or castrated at birth and treated with TP from 3 to 6 mo showed the immobilization response after EB treatment. These observations provide direct evidence for a postnatal component of testosterone-dependent defeminization of receptivity in male pigs.

Age Factors↗

PubMed1987

Effects of MR imaging on murine natural killer cell cytotoxicity.

To determine the effect of MR imaging on the immune system, 21 male C57BL/6 X DBA/2 F1 mice were exposed to MR imaging at a field strength of 0.15 T for 2 hr. Another nine mice (controls) were sham exposed for the same amount of time. Mice were sacrificed and their spleens removed 24, 72, and 144 hr after the exposure (MR or sham). Spleen cell suspensions were passed over nylon wool columns and then used as effector cells in a short-term natural killer cell cytotoxicity assay with 51Cr-labeled YAC-1 cells as target cells. The results showed no evidence of decreased cytotoxicity due to exposure to MR. On the contrary, at all three times after exposure and for all target-to-effector cell ratios, mean cytotoxicity was greater for MR-exposed groups than for sham-exposed groups. The results show that MR exposure has no adverse effect on the immune system, as evidenced by natural killer cell activity.

Animals↗

PubMed1987

Prenatal androgen exposure and growth and secretion of growth hormone and prolactin in ewes postweaning.

Growth and secretion of growth hormone (GH) and prolactin (PRL) in ewe lambs exposed to androgen during fetal development were investigated. Testosterone cypionate was administered to the pregnant dams from approximately Days 28 to 84 of gestation. Ewe lambs from dams that received androgen exhibited masculinized external genitalia and some masculine behavioral characteristics. Intact androgenized ewe lambs grew faster (P less than 0.05) and were more efficient in conversion of food to body gain (P less than 0.05) than ewe lambs born to untreated dams over the period from 70 to 224 days of age. One-half of the ewe lambs in each group was ovariectomized at 58 days of age. Ovariectomy had no effect on subsequent growth or efficiency of growth in the control ewe lambs. However, ovariectomy of androgenized ewe lambs abolished the observed stimulated rate of growth and decreased the improvement in efficiency of food conversion. Blood samples were collected from the lambs at 85 and 136 days of age at 15-min intervals for 8 hr to determine parameters of GH and PRL secretion. Prenatal androgen exposure had no effect on any parameter of GH or PRL secretion. These data indicate that prenatal androgen exposure altered differentiation of growth potential in ewe lambs, but the growth response was not mediated through dramatic changes in secretion of adenohypophysial somatotropic hormones, GH and PRL.

Animals↗

PubMed1986

Proton NMR spectroscopy of glucose consumption by cultured lens epithelial cells.

Proton NMR spectroscopy was performed on media collected from cultured lens epithelial cells of the rabbit eye incubated with Krebs-Ringer's solution containing 5.5mM 13C-glucose (labeled at the C-1 position). Comparing proton resonance intensities of the lactate-methyl group of the C-3 carbon (both 12C and 13C) enabled us to quantify the hexose monophosphate shunt (HMPS) activity. Our results showed that the epithelial cells remained stable in both lactate production and HMPS activity for at least 8 hours. In addition, although tBHP (1mM) resulted in an increase of glucose flow through the HMPS, the rate of lactate production was not affected. In contrast, KCN (2mM) caused a 72% increase of lactate production and a slight (6%) decrease of glucose consumption through the HMPS.

Animals↗

PubMed1986

Changes in Leydig cell ultrastructure and function during pubertal development in the boar.

Changes in the ultrastructure of Leydig cells during pubertal development in the boar (40 to 250 days of age) were assessed using quantitative morphometric procedures, and the results were compared to the in vitro steroid-producing capacity and gonadotropin sensitivity of testicular tissue obtained from the same boars. Volume of individual Leydig cells declined through 100 days of age, increased rapidly to a peak at 130-160 days (i.e., puberty), and then declined to intermediate levels by 220-250 days of age. The pattern of change in the number of intracellular organelles per Leydig cell was very similar to the change that occurred in Leydig cell volume. Changes in the total intracellular volume occupied by each type of organelle were highly correlated with changes in Leydig cell volume (r = 0.40-0.99, p less than 0.01), and this was particularly true for the nucleus (r = 0.63), mitochondria (r = 0.88), smooth endoplasmic reticulum (SER; r = 0.97), and total cytoplasm (r = 0.99) of the boar Leydig cell. In vitro production of testosterone and estradiol, expressed per Leydig cell, also peaked at 130-160 days, and was highly correlated to average Leydig cell volume, volume of SER, and number and total volume of mitochondria (r = 0.63-0.84; p less than 0.01). Observations in the present study indicated that onset of puberty in boars coincides with a dramatic increase in average Leydig cell size and SER volume per Leydig cell, accompanied by an increase in number of other intracellular organelles, including mitochondria, lysosomes, and lipid droplets, and a peak in the steroid-producing capacity per Leydig cell. A decline in Leydig cell size, intracellular organelles, and sensitivity to gonadotropin stimulation occurred postpubertally.

Aging↗

PubMed1986

Inhibin-like activity in ovarian venous serum after unilateral ovariectomy in prepubertal gilts.

To examine a role for inhibin in compensatory ovarian hypertrophy after unilateral ovariectomy (ULO) of prepubertal gilts, changes in inhibin activity in ovarian venous blood were estimated by bioassay. Three groups of 130-day-old gilts were unilaterally ovariectomized after collecting blood from an ipsilateral ovarian vein (Day O); blood samples were obtained from the remaining ovary on Day 2, 4, or 8. Coetaneous gilts underwent sham ovariectomy on Day 0, and venous blood was collected from both ovaries on Day 2, 4, or 8. An assay for inhibin activity, which measured inhibition of secretion of follicle-stimulating hormone (rFSH) by rat pituitary cells in culture, was validated for serum samples. Presumptive inhibin activity was always greater in ovarian venous serum than in peripheral serum samples. In the ULO groups, inhibin activity (in terms of a house reference preparation) in ovarian venous serum was 55 +/- 13 micrograms/ml (means +/- SE, n = 13) on Day 0, 251 +/- 79 (n = 5) on Day 2, 275 +/- 111 (n = 4) on Day 4, and 68 +/- 14 micrograms/ml (n = 4) on Day 8. The five-fold increases on Days 2 and 4 were significant (p less than 0.05). In contrast, no significant differences in inhibin activity were detected between ovarian venous serum (within gilts) or between Days 2, 4, and 8: 82 +/- 29, 73 +/- 30, and 99 +/- 48 micrograms/ml (n=4/day) in control groups. These results demonstrate that, in prepubertal gilts, the remaining ovary's response to ULO includes a major increase in release of inhibin-like activity.

Age Factors↗

PubMed1986

Myocardial infarct size quantification by MR imaging early after coronary artery occlusion in dogs.

The feasibility of using magnetic resonance (MR) imaging to estimate myocardial infarct size was explored in an in vitro model using only the inherent differences in contrast between infarcted and noninfarcted myocardium. Eight dogs underwent coronary occlusion; their hearts were removed 6 hours later. Estimates of T2 for normal and infarcted myocardium were derived from MR images. Infarct size was quantified anatomically using triphenyltetrazolium-chloride (TTC) staining and compared with MR estimates. The T2 values derived from the images clearly discriminated between infarcted (126 +/- 22 msec) and normal myocardium (88 +/- 10 msec, P less than .05), providing images with good contrast between normal and infarcted myocardium. Comparable differences in T2 values were also noted from spectrometric determinations. Estimates of infarct size by MR imaging compared well with TTC estimates (r = 0.98) over a wide range of infarct sizes from 3% to 29% of the left ventricular mass. These results suggest the potential for in vivo quantification of infarct size based on the inherent contrast difference between infarcted and normal myocardium.

Animals↗

PubMed1986

Ovarian compensatory hypertrophy following unilateral ovariectomy in the suckled sow.

The effects of unilateral ovariectomy on ovarian compensatory hypertrophy (OCH), endocrine profiles and the pituitary response to gonadotropin releasing hormone (GnRH) were studied in 46 multiparous suckled sows. On d 20 of lactation (d 0 of experiment), sows were subjected to sham ovariectomy (Sham; n = 23) or unilateral ovariectomy (ULO; n = 23). On d 1 (n = 16), 2 (n = 15) or 8 (n = 15) following initial surgery the remaining ovaries in both Sham and ULO sows were removed. Immediately following removal of the remaining ovaries, GnRH (10 micrograms) was administered to each sow. Peripheral blood samples were taken every 10 min for 80 min beginning 20 min prior to GnRH administration. No difference in ovarian weight was observed between ULO and Sham sows until d 8, when ovarian weight was greater (P less than .05) for the remaining ovary from ULO sows (3.96 +/- .21 vs 5.91 +/- .39 g). Ovarian follicular fluid weights from ULO sows were greater (P less than .05) than Sham sows on both d 2 and 8. On d 1, plasma concentrations of follicle stimulating hormone (FSH) were greater (P less than .05) in ULO sows than in Sham sows (2.9 +/- .2 vs 2.1 +/- .1 ng/ml). Plasma FSH concentrations, however, did not differ between Sham and ULO sows on either d 2 or 8. Ovarian venous concentrations of estradiol-17 beta were also greater (P less than .05) in ULO sows compared with Sham sows on d 2 but not d 8.

Animals↗

PubMed1986

Growth hormone and prolactin secretion after hypothalamic deafferentation in pigs.

Control of growth hormone (GH) and prolactin (PRL) secretion was investigated in ovariectomized, prepuberal Yorkshire gilts by comparing the effects of anterior (AHD), complete (CHD), and posterior (PHD) hypothalamic deafferentation with sham-operated controls (SOC). Blood samples were collected sequentially via an indwelling jugular catheter at 20-min intervals during surgery and recovery from anesthesia (Day 0) and Days 1 and 2 after cranial surgery. Mean serum concentrations of GH after AHD, CHD, and PHD were reduced (P less than 0.01) when compared with SOC gilts. Furthermore, episodic GH release evident in SOC animals was obliterated after hypothalamic deafferentation. PRL concentrations in peripheral serum of hypothalamic deafferentated gilts remained similar (P greater than 0.05) to those of SOC animals. These results indicate that anterior and posterior hypothalamic neural pathways play a minor role in the control of PRL secretion in the pig in as much as PRL levels remained unchanged after hypothalamic deafferentation. These findings may be interpreted to suggest that the hypothalamus by itself seems able to maintain tonic inhibition of PRL release. In contrast, the maintenance of episodic GH secretion depends upon its neural connections traversing the anterior and posterior aspects of the hypothalamus in the pig.

Animals↗

PubMed1985

Phase alterations of spin echoes by motion along magnetic field gradients.

Using a Taylor series expansion of the phase shift of a moving isochromatic spin group in the presence of a magnetic field gradient, the refocusing effects of the Carr-Purcell-Meiboom-Gill pulse sequence on stationary nuclei and those with constant, rectilinear velocity are readily demonstrated. Continuing the analysis to higher orders of motion reveals that nuclei with a constant, rectilinear acceleration have a phase shift at the spin echoes which increases linearly with echo number. Constant, rectilinear jerk (the time rate of change of acceleration) leads to an increase in phase shift from echo to echo which is quadratic in nature with an overlying reduction of the odd-numbered echoes by a constant amount. Motion parameters may be measured by parameter identification techniques. These principles may be applied to phase-sensitive NMR imaging.

Magnetic Resonance Spectroscopy↗

PubMed1985

Improvements in the clinical utility of calculated T2 images of the human brain.

Magnetic Resonance Imaging (MRI) affords a considerable improvement in image contrast over other methods by virtue of the intrinsic NMR parameters spin density, T1, and T2. However, the clinical utility of routine quantification of these parameters is currently unknown. Calculated T2 images might afford additional disease specific information provided the calculation algorithm generates accurate T2 values. In this study, calculated T2 images of a MnCl2 phantom (spanning a T2 range of interest of 45.7 ms to 346.6 ms at 6 MHz) were generated utilizing a variety of calculation algorithms based upon a data set of 32 sequential spin-echo (SE) images. In general, when utilizing only the earliest sequential SE after the 90 degree pulse for the T2 calculation, the greater the number of SE used in the calculation algorithm, regardless of how they were averaged, the more accurate and less noisy was the calculated image. When only limited numbers of SE were used in the calculation algorithm, accuracy and noise varied with the choice of TE suggesting that there may be optimal timings for TE for a particular T2 range of interest. Forty-two calculated T2 head images of normal subjects, based upon data sets of 16 sequential SE, were evaluated for the T2 values of normal brain. These were compared to T2 images calculated via 7 different algorithms based upon 16 SE data sets from two patients with CNS pathology. An optimal algorithm was identified in which 16 SE Carr-Purcell-Meiboom-Gill (CPMG) were averaged into two images for the T2 calculation. With this algorithm, calculated images could be generated efficiently which were accurate and relatively noise free. The availability of such images maximized whatever disease specificity, and thus clinical utility, T2 information affords.

Brain↗

PubMed1985

Effect of follicular fluid treatment on follicle-stimulating hormone, luteinizing hormone and compensatory ovarian hypertrophy in prepuberal gilts.

Prepuberal 130-day-old gilts were treated with 10 ml of charcoal-stripped porcine serum (PS), whole porcine follicular fluid (WpFF) or charcoal-stripped pFF (CpFF) twice daily beginning the day before and continuing 8 days after unilateral ovariectomy (ULO). Follicle-stimulating hormone (FSH) declined for the first 14 h after ULO in WpFF and CpFF gilts and then by 24 h returned to values observed at or before ULO, whereas FSH was increased nearly twofold at 14 h in PS gilts. At 8 days after ULO the remaining ovaries from PS-treated gilts were heavier than ovaries from follicular fluid-treated gilts. In a second experiment, ovariectomized 130-day-old gilts were assigned to either a group infused with PS, a group infused with 5 ml CpFF, or a group infused with 10 ml Cpff at 18 and 2 h before a gonadotropin-releasing hormone (GnRH) challenge. Porcine follicular fluid had no effect on luteinizing hormone (LH) response to GnRH, depressed the FSH response to a 10-micrograms challenge of GnRH, but had no effect on FSH response to a 50-micrograms challenge of GnRH. In a third study, gilts were subjected to sham ovariectomy (Sham) or ULO at 130 days of age. GnRH (10 micrograms) was given on Days 1, 2 or 8 after surgery. The response to GnRH in ULO versus Sham gilts did not differ for FSH or LH on any day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Metabolic clearance and production rates of oestradiol and progesterone during pubertal and postpubertal development in gilts.

The crossbred gilts studied were aged 80 days (prepubertal), 180 days (prepubertal or postpubertal) and 260 days (postpubertal or pregnant). Estimates of metabolic clearance rate (MCR) of oestradiol and progesterone were consistently less (21 and 27%) in plasma than in blood, and these differences were not influenced by age of gilt. The MCR (1/day per kg body weight) for oestradiol and progesterone in plasma was greater (P less than 0.05) for 80-day-old prepubertal gilts than for older gilts. The MCR values of oestradiol and progesterone were similar in 180-day-old and 260-day-old gilts independent of reproductive state. Production rate (PR) of oestradiol and progesterone increased with age (80-180 days), and age and reproductive state differences were much more pronounced for PR of progesterone than of oestradiol. These results support the hypothesis that a reduction in the MCR and an increase in PR of oestradiol and progesterone in the gilt are associated with the process of pubertal development, and changes in gonadal steroid concentrations appear not to alter the MCR of oestradiol and progesterone.

Age Factors↗

PubMed1985

Cortisol response of gilts in tether stalls.

Several experiments were conducted to evaluate serum cortisol concentrations and the circadian rhythm of this hormone in gilts tethered in stalls. Control animals were penned individually. In the initial experiment, 18 nongravid gilts were placed in tether stalls after being in either tether stalls or individual pens for 2 wk. No significant differences were found in serum cortisol concentrations. In a second experiment, 16 ovariectomized gilts were placed in tether stalls or individual pens for up to 5 wk. Estrus was induced during wk 3 and 4. During the first day in tether stalls, serum cortisol concentrations increased (P less than .05) and the circadian rhythm of cortisol was disrupted for 4 d. During estrus, the circadian rhythm of cortisol was interrupted for several days in the gilts, regardless of housing. After 4 wk, morning concentrations of cortisol were higher for gilts in tether stalls. The results indicate that: 1) the initial response to tethering varies according to previous penning and handling experience, 2) although the circadian rhythm of cortisol was either altered or disrupted during estrus, such disruptions were not influenced by type of penning and 3) tether stalls may chronically increase cortisol concentrations in gilts.

Animals↗

PubMed1985

Reevaluation of the role of progesterone in stimulating sexual receptivity in estrogen-treated gilts.

Three studies were conducted to examine the role of progesterone in stimulating sexual receptivity in estrogen-treated, ovariectomized gilts. Progesterone was administered either before, simultaneously with, or 48 h after estrogen. In each study, gilts were treated with either a suboptimal or an optimal dosage of estradiol benzoate (EB). Progesterone treatment (600 micrograms/kg BW-1 X injection-1) on alternate days for a total of four injections produced serum concentrations of progesterone that were maximal at 9.4 ng/ml and remained greater than 1 ng/ml for 15 d. Estradiol benzoate was administered 22 d after the first of these progesterone injections. When progesterone was administered concurrently with or 48 h after EB, the dosage was 100 micrograms/kg BW and produced a maximal serum progesterone concentration of 1.8 ng/ml 4 h after treatment. Gilts were placed in an evaluation pen with a boar for 5 min on d 3 and 4 after EB treatment. Traits of interest were total number of mounts by the boar, mounts before the gilt showed the immobilization response, proportion of gilts that showed the immobilization response, and latency from entry of the gilt into the evaluation pen until the immobilization response. In none of the three studies did progesterone improve any of the traits of interest. In each study the immobilization response was observed in a higher proportion of gilts treated with the optimal than in those treated with the suboptimal dosage of EB. Latency from entry of gilts into the evaluation pen until the immobilization response was less on d 4 than on d 3 after EB in all studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Interval to first postweaning estrus and causes for leaving the breeding herd in Large White, Landrace, Yorkshire and Chester White females after three parities.

Three hundred and five Large White (LW, 93), Landrace (L, 92), Yorkshire (Y, 69) and Chester White (CW, 51) gilts produced at the Roman L. Hruska U.S. Meat Animal Research Center over 3 yr with 15 to 41 gilts per breed group per year were housed in total confinement and mated to farrow at 1 yr of age. After 28 to 30 d lactation, piglets were weaned and all females were observed for estrus daily for 30 d. During the year that each gilt initially farrowed, she was mated to produce a second and third litter if she returned to estrus within 30 d after piglet removal. Interval from weaning (d 0) to estrus and reason for leaving the breeding herd were recorded for each animal. Interval from weaning to estrus was influenced by breed (P less than .01), parity (P less than .01) and interaction between breed and parity (P less than .01). Intervals from weaning to estrus, in first parity females which exhibited estrus, were 7.8, 6.6, 9.3 and 14.0 d for the LW, L, Y and CW breeds. Intervals for all females after the second litter were 6.8, 4.9, 8.0 and 9.1 d, and after the third litter 6.4, 5.2, 8.3 and 10.1 d for the LW, L, Y and CW breeds. Breed, parity and year (P less than .01) affected the number of females not exhibiting estrus. Percentages of females not exhibiting estrus were 6.5, 18.7, 37.7 and 23.5 for the LW, L, Y and CW breeds and 16.1, 2.3 and 2.0 for sows after the first, second and third parities.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1985

Maturation of ovarian follicles in the prepubertal gilt.

The processes of follicle development and puberty are closely related, and both are associated with maturation of the hypothalamic-pituitary-ovarian axis. Prenatal development of the ovary is independent of gonadotrophic stimulation. Beyond 60 days of age (postnatally), tertiary follicles develop and gonadotrophins begin to influence ovarian follicular development. Negative feedback regulation of pituitary gonadotrophins by ovarian secretions develops between 60 and 100 days of age. In the prepubertal gilt, no consistent changes in peripheral FSH, oestrogen or progesterone concentrations have been identified which are associated with recruitment of the first set of preovulatory follicles. Whether LH secretion increases before this recruitment remains equivocal. Few details are available on how gonadotrophic hormones stimulate ovarian function in the prepubertal gilt. On the basis of a follicular maturation model that has been described for the rat, the actions of FSH, LH and oestrogens on follicular cell receptors and the regulation of aromatase activity seem paramount. Aromatization of androgens to oestrogens has been proposed as a central regulator for follicular maturation. In the prepubertal gilt, a selective increase in peripheral FSH concentration occurs on Day 1 after unilateral ovariectomy, followed by significant increases in ovarian venous concentrations of oestradiol and inhibin on Days 2 and 4 and compensatory growth as measured by follicular fluid volume on Days 2, 4 and 8. Administration of pig follicular fluid to the prepubertal gilt during and after unilateral ovariectomy suppresses compensatory ovarian hypertrophy by mechanisms yet to be determined. In pigs a number of intraovarian factors have been identified, but there is little information on how these factors regulate follicular recruitment and growth. The factor(s) that prevents ovarian follicles in the prepubertal gilt from progressing to ovulation after acquiring the ability to ovulate in response to exogenous gonadotrophins remains unknown.

Animals↗

PubMed1984

Nuclear magnetic resonance diagnosis of an anaplastic astrocytoma.

A patient presented with an 8-month history of a progressive left homonymous visual field deficit, left hemiparesis, and a left thalamocortical sensory deficit that was not detectable by repeated conventional neurodiagnostic evaluations. Proton nuclear magnetic resonance (NMR) imaging revealed a right parietal lesion characterized by a prolonged T2 (spin-spin relaxation time). At surgery, the mass proved to be an anaplastic astrocytoma. NMR appears to be more sensitive than x-ray computerized tomography scanning in some patients with malignant gliomas and offers the clinician an additional probe with which to evaluate these patients.

Astrocytoma↗