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Biomedical subjects

J R Day

Publications and source records attributed to J R Day.

50 records · Page 3Linked to original sources
PubMed1990

Effects of estradiol and progesterone on early embryonic development in aging rats.

Regularly cyclic, middle-aged female rats exhibit a decreased incidence of fertility, and those females that are fertile produce small litters. These decreases in fertility and litter size are associated with reduced numbers of normal blastocysts formed and implanted, suggesting that pre- and/or peri-implantation failures may be the causes for these aging-related reproductive declines. The present study examined the relationships and influence of circulating estradiol (E2) and progesterone (P) levels on early embryonic development and implantation in middle-aged rats. Serial blood samples obtained from cannulated, middle-aged pregnant rats revealed minor decreases in plasma P and increases in E2 levels during Days 2-4 of pregnancy, compared to young pregnant rats, resulting in significantly (p less than 0.001) decreased plasma P/E2 ratios. These alterations in endogenous hormone secretion in middle-aged pregnant rats were associated with fewer normal blastocysts on Day 5 of pregnancy and reduced numbers of normally implanting embryos. Correlation analysis further revealed a significant (p less than 0.05) inverse relationship between mean circulating E2 levels and numbers of normal conceptuses on Day 12 of gestation. Moreover, s.c. administration of P implants (in Silastic) to middle-aged pregnant rats increased serum P levels by about 34-40 ng/ml, and significantly (p less than 0.05) reduced the incidence of abnormal embryos before implantation. In contrast, treatment with E2 minipumps produced a sustained rise in serum E2 (by about 7-15 pg/ml) and resulted in the complete absence of embryos in the reproductive tracts by Day 5 of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1990

Castration enhances expression of glial fibrillary acidic protein and sulfated glycoprotein-2 in the intact and lesion-altered hippocampus of the adult male rat.

This study concerns effects of the testes on two macromolecules in the rat hippocampus that were previously not known to be responsive to this endocrine axis. Castration for 3 weeks elevated the expression of glial fibrillary acidic protein (GFAP) and sulfated glycoprotein-2 (SGP-2) in male rat hippocampus, as shown by Northern blots and immunocytochemistry. SGP-2 mRNA was colocalized with GFAP, implying increased prevalence in astrocytes after castration. During hippocampal responses to deafferentation by entorhinal cortex lesions that damage the perforant path and induce synaptic reorganization, both mRNA and protein for SGP-2 and GFAP increase. Moreover, prior castration had an additive effect with entorhinal cortex lesions in the increase in GFAP and SGP-2 mRNA. These data suggest that testicular hormones regulate hippocampal astrocyte activity in intact adult rats as well as during synaptic reorganization in response to deafferenting lesions.

Animals↗
PubMed1989

Mammary gland development and alpha-lactalbumin production in hypophysectomized, pregnant mice.

Swiss Webster mice were hypophysectomized on Day 10 of pregnancy and the effect of the ablation on mammary gland development was estimated by measuring the total weight and the DNA, RNA, and alpha-lactalbumin contents and concentrations of the mammary gland on Days 14 and 18 of gestation. Although a significant increase in mammary gland weight occurred in the hypophysectomized animals between Days 10 and 18 of pregnancy, the mammary gland weight of the hypophysectomized mice was significantly reduced when compared with intact and sham-operated mice on both Days 14 and 18 of pregnancy. The total RNA content of the mammary gland was also reduced in the hypophysectomized mice, although it increased significantly from Day 10 to Day 18. The alpha-lactalbumin content of the mammary gland increased only slightly between Days 10 and 14 of gestation in the intact and sham-operated mice, but a large increase was found on Day 18 in both groups. There was, on the other hand, no increment in the alpha-lactalbumin content of the mammary gland in the hypophysectomized mice either on Day 14 or 18 of gestation. The DNA content of the mammary gland was not affected by hypophysectomy when estimated on Days 14 and 18 of pregnancy. The effects of hypophysectomy on the concentrations of mouse placental lactogen II (mPL-II), progesterone, corticosterone, and thyroxine in the maternal serum were also assessed. The concentration of mPL-II was significantly elevated in the hypophysectomized mice, whereas the circulating concentrations of both corticosterone and thyroxine were greatly reduced. The serum progesterone concentration was not significantly altered by hypophysectomy. (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

An abnormal pattern of embryonic development during early pregnancy in aging rats.

There is recent evidence that a decline in fertility and litter size precedes the cessation of regular estrous cyclicity in middle-aged female rats. This decline in litter size is related to a decrease in the number of normal blastocysts that are present on Day 5 of gestation, immediately prior to implantation. Thus, the pattern of embryonic development during the first 5 days of pregnancy may be altered in middle-aged rats, resulting in fewer implanting embryos and smaller litter sizes. The present study examined the ovulation rates, fertilization rates, and the patterns of embryonic development in regularly cyclic, young and middle-aged females during the first 5 days of pregnancy. Examination of the numbers of ovulated ova revealed that the ovulation rate was significantly reduced in 12- to 14-mo-old females (13 mo; 9.0 +/- 1.0/rat), but not in 9- to 11-mo-old females (10 mo; 12.2 +/- 0.8/rat), as compared to that in young animals (12.8 +/- 1.0/rat). However, there was no decrease in fertilization rate in either the 10-mo or 13-mo group. While the total numbers of embryos present on Days 2-5 were similar among all 3 groups, embryos from 10-mo females displayed a delayed pattern of development and an increased incidence of morphological abnormalities. These changes in embryo development were even more pronounced in the 13-mo group. By Day 5 of pregnancy there was a significant reduction in normal blastocysts in 10-mo (7.3 +/- 1.2/rat) and 13-mo (6.0 +/- 1.6/rat) rats, as compared to young females (10.6 +/- 0.9/rat).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1989

Professional shopping of physician services: an extension of the simulated patient technique.

Health care researchers have recently begun to use professional shopping to evaluate physician services. The results of two studies conducted by The Cleveland Clinic Foundation indicate that: (1) such studies are easily conducted; (2) physicians are comfortable with the use of professional shopping to obtain patient feedback; (3) the technique is a valuable research tool for improving medical services from a patient's perspective; and (4) there is potential value in using professional shopping as a quality assurance technique.

Consumer Behavior↗
PubMed1988

Male stimulation of luteinizing hormone surge, progesterone secretion and ovulation in spontaneously persistent-estrous, aging rats.

In aging, persistently estrous (PE) female rats, there are no estrous cycles or cyclic increases in luteinizing hormone (LH) secretion, but the sexual receptivity to the male is consistently maintained. We recently reported that caging and mating with fertile males elicits an LH surge followed by ovulation in aging PE rats. The present study examined the relationship between the LH surge, the increase in progesterone (P) secretion and ovulation in PE females exposed to males, and assessed whether intromission was essential for the male-induced pre-ovulatory LH surge. PE rats were implanted with intra-atrial cannulae. Six to eight days later, these females were individually caged with a fertile male and repeatedly sampled (once every 30 or 60 min) between 1400 and 1900 h for assays of plasma LH and P. Sexual behavior of the female was recorded and correlated with the changes in plasma LH and P values. Similar experiments were also performed on cannulated PE rats with their vaginal orifice blocked with adhesive tape during the caging and sampling session. In both experiments, over 90% of the PE females displayed a high degree of lordosis response to mounting by the male, and over 60% of those sexually receptive PE females exhibited an LH surge followed by ovulation. The male-induced preovulatory LH surge occurred in PE females without actual intromission. Caging with fertile males also elicited a marked increase in plasma P concentrations in PE rats and in PE females prevented from experiencing intromission.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1986

Group-specific component (vitamin D binding protein) prevents the interaction between G-actin and profilin.

Profilin purified from human platelets formed a 1:1 molar ratio complex with rabbit skeletal muscle G-actin but was displaced by purified serum Gc (vitamin D binding protein) in a dose-dependent fashion as assessed by chromatography and ultrafiltration. This suggested that Gc and profilin competed for the same binding area on G-actin, with Gc-G-actin complexes being more stable than profilin-G-actin complexes in vitro. The binding domain for Gc on G-actin was localized to a 16,000-Da C-terminal fragment of G-actin generated by Staphylococcus aureus V8 protease, as judged by comigration on two-dimensional electrophoresis and also by overlaying electrophoresis gels with 125I-Gc. Previous studies have reported that residues 374 and 375 of G-actin are essential for binding of profilin. In this study, experiments involving tryptic removal of Cys-374 labeled with the fluorescent probe N-(iodoacetyl)-N'-(5-sulfo-1-naphthyl)-ethylenediamine showed that these C-terminal amino acids were not necessary for interaction with Gc.

Actins↗
PubMed1986

Gc (vitamin D-binding protein) binds the 33.5 K tryptic fragment of actin.

Limited proteolysis of G-actin was performed with trypsin and chymotrypsin to compare the binding sites for Gc and DNase. DNase I bound to the N-terminal area corresponding to the major cleavage site on G-actin (residues 62-68) and inhibited proteolysis, but did not bind the 33.5K C-terminal fragment (G-actin33.5) generated. In contrast, Gc did not exert any inhibitory effect upon proteolysis of the intact native G-actin42.0 molecule, although its presence protected G-actin33.5 from further proteolysis. This was shown by gel filtration to be due to the formation of complexes between Gc and G-actin33.5.

Actins↗
PubMed1986

The effect of hypophysectomy on serum placental lactogen and progesterone in the mouse.

Hypophysectomy of pregnant mice on days 10, 12, and 16 of gestation resulted in a large and rapid (12-24 h postoperatively) increase in serum placental lactogen (mPL) concentrations, as measured by homologous RIA. Serum progesterone (P4) concentrations decreased compared to those in intact and sham-operated controls. Significantly, the increase in serum mPL in mice hypophysectomized on days 10 and 12 preceded any decrease in serum P4 concentrations by at least 24 h, suggesting that two indirectly related mechanisms may be involved in the control of the serum concentrations of these hormones. The weight of the uterus, including the feto-placental units, placental weight, and placental content of mPL did not differ between intact, sham-operated, and hypophysectomized groups. The gestational profiles of serum GH and PRL concentrations were similar in the sham-operated and intact controls. Although serum P4 concentrations decreased after hypophysectomy on days 10 and 12 of gestation, the maintenance of the pregnancy was not affected; thus, the reduced concentrations of serum P4 (approximately 50% of control by day 16) were adequate to allow the pregnancy to continue. Hypophysectomy on day 16 of gestation resulted in spontaneous abortion 48 h postoperatively in all but one animal. We conclude that the absence of some pituitary factor(s) results in a rapid increase in serum mPL, while a concomitant, albeit gradual, decrease in serum P4 begins 48 h postoperatively. Therefore, when the pituitary no longer contributes to the luteotropic complex of the midpregnant mouse, an increase in serum mPL alone cannot maintain serum P4 concentrations at control values.

Animals↗
PubMedDate not supplied

GFAP mRNA increases with age in rat and human brain.

Glial fibrillary acidic protein (GFAP) mRNA was examined by RNA blot hybridization in three age groups of two cohorts of male F-344 rats and in 47 human postmortem brain samples. GFAP mRNA increased in the hippocampus and striatum of 24 versus 6- to 7-month-old rats. Another astrocytic molecular marker, glutamine synthetase mRNA, did not change with age in rat brain. Rat GFAP mRNA prevalence was inversely correlated with serum testosterone but not correlated with serum corticosterone. In human hippocampus, frontal and temporal cortex, GFAP mRNA also increased in older (60-79 years) compared with middle-aged (25-59 years) individuals. In contrast, mitochondrial cytochrome oxidase subunit 1 mRNA did not change between age groups in any region. By combining the three regions for further analysis, GFAP mRNA increased with age irregardless of gender, alcoholism in the middle-aged group, or whether brains were classified as normal or neuropathologic (excluding Alzheimer's disease pathology). These data indicate that increased GFAP protein or GFAP-immunoreactive astrocytes in rats and humans may result from transcriptional or post-transcriptional regulation and extend the number to three species (including mouse) showing an increase in GFAP mRNA with age. Factors that are known to regulate GFAP mRNA expression in young brains are considered as possible causes of age-related increases.

Adult↗
PubMedDate not supplied

Life-long dietary restriction attenuates age-related increases in hippocampal glial fibrillary acidic protein mRNA.

The expression of astrocyte-specific glial fibrillary acidic protein increases after experimental lesions and is elevated throughout the brain in aged rodents and primates. Clusterin (ApoJ) expression increases in astrocytes and microglia after lesions, but changes during aging have not been reported. Dietary restriction (DR) delays the onset and progression of many age-related physiological deficits in rodents. This study showed that the age-related increase in glial fibrillary acidic protein mRNA in the hippocampus was attenuated in 24-month-old male Fischer 344 rats subjected to a 50% DR beginning at 6 weeks of age. ApoJ mRNA expression in astrocytes was unchanged by DR. These results demonstrate that DR can delay neurodegeneration in aged rats as assessed by a marker of reactive astrogliosis.

Aging↗
PubMedDate not supplied

Osteopontin gene expression in the Holstein bull reproductive tract.

The objective of this study was to localize gene expression of osteopontin in the Holstein bull reproductive tract using Northern blot analysis and in situ hybridization. For Northern blot analysis, a digoxigenin-labeled osteopontin complementary deoxyribonucleic acid (cDNA) was used to probe blots containing total ribonucleic acid (RNA) isolated from the testis, epididymis, vas deferens, ampulla, seminal vesicle, prostate, and bulbourethral glands. The digoxigenin-labeled cDNA for the bovine homologue of osteopontin was hybridized to a single band at approximately 1.6 kb to RNA samples from the ampulla and seminal vesicle. For in situ hybridization studies, antisense and sense riboprobes were synthesized and used to hybridize cryosections that had been obtained from bull reproductive tissues. In situ hybridization of the bull testis detected osteopontin messenger RNA in the developing germ cells. Osteopontin gene expression was detected only in seminiferous tubules that contained elongated spermatids, which suggests that expression varies with the stage of the seminiferous epithelium. Within the epididymis, silver grains were distributed over the sperm that were located within the lumen of the caput, corpus, and cauda epididymis. Osteopontin expression was primarily observed in the epithelial cells of the ampulla. Antisense riboprobes also hybridized to sperm that were located within the lumen of the ampulla, confirming the presence of osteopontin transcripts in the haploid male gamete.

Animals↗