Biomedical subjects

J A Barber

Publications and source records attributed to J A Barber.

29 records · Page 2Linked to original sources

PubMed1996

Regulation of insulin-like growth factor I biosynthesis in porcine granulosa cells.

In the present studies we examined the regulation of insulin-like growth factor I (IGF-I) expression in porcine granulosa cells in vitro. Using Northern analysis and ribonuclease protection assays with exon-specific probes, we identified the IGF-I messenger RNA (mRNA) transcripts present in these cells under basal and hormone-stimulated conditions. We also assessed changes in secreted IGF-I using Western blots and correlated the change in protein secretion after hormone treatment with changes in mRNA levels. By analogy to the human IGF-I gene and its transcription, two major transcripts of approximately 1 and 7.5 kilobases, seen in freshly isolated granulosa cells and follicle wall and in single passaged granulosa (MDGp1) cells, most likely correspond to IGF-IA. Minor transcripts of 3-4 kilobases, which appeared after FSH or forskolin treatments or in control cells after long exposure of the autoradiographs, were attributed to incompletely processed RNA precursors. Ribonuclease protection assay analysis using probes to detect alternative use of exon 5 or exon 6 indicated that most, if not all, of the transcripts contained only exon 6 sequence (IGF-IA). Both class 1 and class 2 transcripts were identified using exon 1- and exon 2-specific probes, respectively. GH increased steady state levels of IGF-I mRNA 3-fold, FSH increased it approximately 10-fold, and forskolin maximally increased it 12- to 15-fold. Estradiol had no effect alone or in combination with the other treatments. All treatments that increased IGF-I mRNA coordinately increased both class 1 and class 2 transcripts, with the increase in class 1 greater than that in class 2. Multiple forms of IGF-I protein were seen under basal conditions and after hormone treatment. These were identified based on mRNA analysis and biochemical methods as both glycosylated and nonglycosylated IGF-IA prohormone, incompletely processed forms of prohormone, and the mature peptide. Changes in the levels of total protein were similar to the changes in mRNA (GH, 3-fold; FSH and forskolin, 10- to 20-fold). All forms of the protein changed coordinately, suggesting that these hormones had no major effect on the intracellular processing mechanism. IGF-binding protein-3 was able to bind to all IGF-I forms. These data conclusively demonstrate FSH and GH induction of ovarian IGF-I. The porcine granulosa cell culture system used in these studies should be an excellent system for studying the hormonal regulation of IGF-I expression.

Animals↗

PubMed1995

Rat brain glucose and energy metabolites: effect of +Gz (head-to-foot inertial load) exposure in a small animal centrifuge.

A unique small animal centrifuge with on-line physiological monitoring and brain tissue collection (in < 1 s) capability was used to investigate the effect of increasing +Gz levels, exposure duration, number of exposures, and time course of metabolic changes in the rat brain. To determine the +Gz tolerance, rats were exposed to +7.5 to 25 Gz (30 s each) and EEG was monitored. G-induced loss of consciousness (G-LOC) defined as isoelectric EEG (I-EEG) occurred only at +22.5 and 25 Gz within 14.5 +/- 3 s. To study the effect of increasing +Gz levels on metabolism, rats were exposed to either 0.5 (control) or +7.5 to 25 Gz (30 s each), and brains were collected 1 min postcentrifugation by freeze fixation. A significant increase in lactate (> or = +7.5 Gz) and a decrease in glucose, creatine phosphate (Cr-P), and ATP levels were observed at +15 Gz and higher. The effect of exposure duration was investigated by exposing the rats to +22.5 Gz for 15-60 s. Brain lactate levels increased six-fold while glucose decreased (75%) following the 60-s exposure. The level of Cr-P and ATP decreased significantly after the 15- and 30-s exposures with no further changes at longer +Gz exposures. For time course studies, brains were collected both during (5-35 s) and after (1-15 min) a +25 Gz exposure. A significant decrease in Cr-P occurred within 5 s, but changes in glucose, ATP, and lactate required 15 s. All metabolites returned to control levels within 3 min, except lactate and adenosine, which required 15 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Recovery from severe dysspermatogenesis in a bull: A case report.

An 18-month-old Holstein bull with a history of producing ejaculates of freezable quality was presented with marked oligozoospermia, teratozoospermia and akinozoospermia. Ejaculates also contained many spheroids and medusa forms. The severe dysspermatogenesis was associated with Haemophilus somnus infection based upon positive semen cultures and serology. The bull was treated systemically with the antibiotic, ceftiofur, for 15 days. Approximately 3 months after initial presentation, the bull was again producing semen of freezable quality. The case presented provides one example in which severe dysspermatogenesis resolved to the point of apparently normal spermatogenesis.

Journal Article↗

PubMed1994

Porcine ovarian granulosa cells secrete insulin-like growth factor-binding proteins-4 and -5 and express their messenger ribonucleic acids: regulation by follicle-stimulating hormone and insulin-like growth factor-1.

Using ligand blotting, Western immunoblotting, and Northern analysis, we have characterized the insulin-like growth factor (IGF)-binding proteins (IGFBPs) produced by cultures of porcine granulosa cells. Ligand blot analysis of conditioned medium from untreated cultures of moderately differentiated granulosa cells (MDGCs; from 4-6-mm follicles) revealed mainly IGF-binding activity associated with IGFBP-2 (34 kDa) and IGFBP-3 (40/44-kDa doublet), which have previously been identified and characterized. In addition, these cultures secreted 30- and 22-kDa forms under some circumstances. The identification and regulation of these IGFBPs of lower molecular mass were the focus of the current studies. Treatment of these MDGCs with IGF-I dramatically stimulated the production (to a detectable level) of a 30-kDa IGFBP that was identified by immunoblotting with antiserum to IGFBP-5 but not antisera to IGFBP-1, -2, -3, -4, or -6. Production of IGFBP-5 was attenuated by concurrent treatment with FSH. IGFBP-5 mRNA in these cultures was correspondingly stimulated by IGF-I but unaffected by FSH. FSH increased the level of a minor 22-kDa IGFBP. Messenger RNAs for IGFBP-1, -4, and -6 were also examined but only IGFBP-4 mRNA was detectable, suggesting that the 22-kDa band was IGFBP-4. These results were compared to those in cultures of immature granulosa cells from 1-3-mm follicles, in which 22- and 30-kDa IGFBPs were readily detectable. An antiserum to IGFBP-4 precipitated the 22- and 30-kDa bands whereas deglycosylation shifted the 30-kDa IGFBP to 22 kDa, suggesting that both these bands represent glycosylation variants of IGFBP-4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Steroidogenic cytochrome P450 enzyme messenger ribonucleic acids and follicular fluid steroids in individual follicles during preovulatory maturation in the pig.

Changes in follicular concentrations of steroidogenic cytochrome P450 enzyme mRNAs were determined during preovulatory maturation. RNA was isolated from 59 individual follicles dissected from 18 pigs during altrenogest-synchronized preovulatory follicular maturation: at Day 1 (pre-follicular phase), Day 3 (early follicular phase), Day 5 (mid-follicular phase), and Day 7 (late follicular phase, 24-36 h after the onset of the LH surge). Follicular fluid was aspirated for steroid RIA. RNA was also isolated from pooled granulosa cells, theca tissue, and luteal tissue. RNA was analyzed by Northern and slot-blot procedures using cDNA probes to human aromatase cytochrome P450 (P450arom), porcine 17 alpha-hydroxylase cytochrome P450 (P450(17) alpha), and porcine cholesterol side-chain cleavage cytochrome P450 (P450scc). P450arom mRNA was expressed in both granulosa and theca interna cells but was not detectable in luteal tissue from Day 13 of the estrous cycle. Follicular P450arom mRNA concentration tended to increase between Days 1 and 5 and decreased (p < or = 0.05) by 92% between Days 5 and 7. Follicular fluid estradiol-17 beta concentration increased 17-fold between Days 1 and 5 and then decreased (p < or = 0.05) by 96% between Days 5 and 7. P450(17) alpha mRNA was present in theca interna but was not detected in granulosa cells or luteal tissue. Follicular P450(17) alpha mRNA concentrations did not differ significantly among days, but the content per follicle increased (p < 0.05) between Days 1 and 5 and decreased (p < 0.05) between Days 5 and 7.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Multiple +Gz exposures cause brain edema in rats.

The most serious effect of high sustained +Gz (head-to-foot inertial load) known to occur in pilots of high performance aircraft is +Gz-induced loss of consciousness (G-LOC), which may result in pilot incapacitation and subsequent loss of life. G-LOC is believed to occur due to a critical reduction in cerebral blood flow (CBF). Recently, using a small animal centrifuge (SAC), we showed that +Gz exposure causes global cerebral ischemia in a rodent animal model. Since ischemia, depending upon the severity and duration, has been associated with increased brain water content or edema, the present study was undertaken. Rats were exposed to six exposures of either +25 Gz (30 s each) or +10 Gz (2 min each) in the SAC at +20 Gz.s-1 G onset rate. The appearance of G-LOC was monitored by the flattening of the electroencephalography (EEG) brain wave recording. G-LOC was observed at 101 +/- 46 and 19.2 +/- 5 s during +10 and +25 Gz exposures, respectively. The brains from these animals were removed 15 min to 24 h after the +Gz exposure and analyzed for edema formation (increase in the percentage of tissue water), metabolites, and cerebral blood volume (CBV). A significant decrease in glucose and an increase in lactate concentration were observed during +Gz exposure. Edema formation was observed 15 min after six exposures of either +10 or +25 Gz. A slight but significant decrease in CBV was also observed in rats exposed to six +10 Gz exposures. Edema formation was transient and resolved within 24 h. We concluded that multiple exposures of either +25 Gz, short duration or +10 Gz, long duration, that resulted in G-LOC, can cause cytotoxic brain edema which probably results from tissue hyperosmolality due to metabolic changes and accumulation of lactate during ischemia.

Acceleration↗

PubMed1994

Effect of pyridostigmine bromide on acceleration tolerance and performance.

Pyridostigmine Bromide (PB) is used as a pre-exposure antidote for the prevention of potentially lethal effects of certain chemical warfare nerve agents by reversibly inhibiting acetylcholinesterase (AChE). This study was designed to determine whether PB has any deleterious effects on acceleration tolerance (+Gz) or performance. Double-blind placebo trials were conducted to evaluate the effects of PB (90 mg) per day on +Gz tolerances and performance. Three types of exposures were used: 1) gradual onset rate (GOR) exposures of 0.1 G/s; 2) a series of rapid onset rate (ROR) exposures of 6.0 G/s; and 3) a simulated aerial combat maneuver (SACM) of 4.5 to 9.0 +Gz. Performance tasks included the Unified Tri-Service Cognitive Performance Assessment Battery (UTC-PAB). The subjects were not able to correlate their symptoms with PB, placebo, or the acceleration exposure itself. Plasma PB individual levels ranged between 6 and 31 ng/ml and AChE levels of inhibition had a range of 12 to 45%. There were no significant effects on +Gz tolerance or performance related to PB. Based on the results of this study, PB does not significantly alter +Gz tolerance or performance. Therefore, we do not expect aircrew taking prophylactic doses of PB to be adversely affected during aerial combat operations.

Acceleration↗

PubMed1993

Expression of the mRNAs for the insulin-like growth factors and their binding proteins during development of porcine ovarian follicles.

We examined the expression of the mRNAs for the insulin-like growth factors (IGFs) and two of their binding proteins (BPs), IGFBP-2 and IGFBP-3, in individual follicles of the porcine ovary. Follicular development was synchronized with a progestin (altrenogest). Individual follicles were isolated on days 1, 3, 5 and 7 after progestin withdrawal. No IGFBP-3 mRNA was detected. While IGF-II mRNA was easily detected, the levels of expression did not change. IGF-I and IGFBP-2 mRNAs increased and decreased, respectively, with follicle development until day 7 when IGF-I expression declined. Regression analysis of IGF-I and IGFBP-2 mRNA expression was performed to assess the relative strength of correlations with day, diameter and steroid concentrations as covariates. IGFBP-2 mRNA was correlated with both day and diameter (r = -.713 and -.705, respectively, n = 24) and neither estrogen (E2) nor progesterone (P4) contributed to the fit. While IGF-I mRNA expression was correlated to both day (r = .483) and diameter (r = .587), the strongest predictor was E2 concentration (r = .694, n = 27). In conclusion, the expression of IGF-I and IGFBP-2 mRNAs in the ovarian follicle are discordantly regulated during follicular growth and maturation. The observed changes in these parameters should result in increased bioavailable IGF-I. This supports a pivotal autocrine/paracrine role for these factors during follicle growth and development.

Animals↗

PubMed1992

Gonadotropin and cAMP modulation of IGE binding protein production in ovarian granulosa cells.

Porcine granulosa cells (GC) produce insulin-like growth factor (IGF) binding protein (BP)-3 and IGFBP-2 in culture. A gonadotropin, follicle-stimulating hormone (FSH), dramatically inhibited GC production of these IGFBPs in control cultures and in cultures stimulated by insulin plus epidermal growth factor (EGF) or IGF-I plus EGF. Stimulators of adenylate cyclase (forskolin, cholera toxin) and a derivative of adenosine 3',5'-cyclic monophosphate (cAMP), 8-bromoadenosine 3',5'-cyclic monophosphate, inhibited IGFBP synthesis in a manner similar to FSH. In contrast, the antagonist of cAMP action, (R)-p-adenosine 3',5'-cyclic phosphorothioate [(R)-p-cAMPS], significantly stimulated production of IGFBP-3 and IGFBP-2 compared with controls. This stimulatory effect of (R)-p-cAMPS was counteracted by cotreatment with FSH in a dose-dependent manner. Finally, treatment of GC cultures with FSH plus 3-isobutyl-1-methylxanthine resulted in a significant reduction in cellular content of mRNA coding for IGFBP-3 with no change in IGFBP-2 mRNA. In summary, agents that elevate intracellular cAMP were found to mimic the effects of FSH on IGFBP production.

Animals↗

PubMed1980

Clotting predisposition in carcinoma of the prostate.

To delineate factors that might increase the risk of thromboembolic events in patients on estrogen therapy for prostatic carcinoma a study was undertaken of various coagulation parameters. A correlation was demonstrated between advanced stages of prostatic carcinoma and depression of the serum antithrombin III activity. The addition of estrogen therapy resulted in further depression. Since low levels of serum antithrombin III activity have been associated with thrombosis this observation may have clinical relevance.

Aged↗

PubMed1977

The effects of operative stress on the coagulation profile.

There is a tendency toward hypercoagulability in the postoperative period. This is manifested by changes in a number of coagulation parameters, and if not offset by some protective mechanism, thrombosis may occur. This protection appears to be mediated more through the fibrinolytic mechanism than through the action of antithrombin 3 (AT-3) because AT-3 activity diminishes in the early postoperative period. The introduction of variables such as invasion of the vascular system, intraoperative heparin administration, administration of whole blood, and insertion of a Dacron prosthesis does not appreciably affect the response of the coagulation profile to operative stress.

Abdomen↗