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Biomedical subjects

D M Robertson

Publications and source records attributed to D M Robertson.

At least 145 records · Page 8Linked to original sources
PubMed1991

Circulating half-lives of follicle-stimulating hormone and luteinizing hormone in pituitary extracts and isoform fractions of ovariectomized and intact ewes.

Previous studies have shown that the circulating half-life (t 1/2) of serum FSH in ewes after hypophysectomy (HPX) increased 10-fold after ovariectomy (OVEX). The basis for this difference was examined in this study by determining the circulating half-life of serum FSH and LH in HPX ewes after administration of pituitary extracts and gonadotropin isoform fractions. High-speed supernatants of pituitaries from gonadal-intact and OVEX ewes were fractionated by electrofocusing in sucrose gradients and based on the pI distribution of FSH and LH divided into four pools, pH 4.3-4.8, 4.8-5.55, 5.8-6.7, and 6.7-10. These extracts were administered by iv bolus injection to HPX gonadal-intact ewes and blood samples collected between 15-1000 min later. The clearance pattern for both serum FSH and LH was heterogenous, indicative of a major rapid and a minor slow dissociating component. A significant (P less than 0.05) difference in circulating half-lives (rapid component) was observed between pituitary extracts from intact and OVEX ewes for FSH (t 1/2 = 32.8 +/- 8.6 min vs. 89.9 +/- 32.3 min) but not LH (31.3 +/- 9.2 min vs. 39.3 +/- 6.1 min, respectively), whereas no significant difference was observed between the corresponding FSH or LH isoform preparations. To establish if the difference in circulating half-lives obtained after HPX and bolus iv injection was due to mode of delivery, an extract of pituitaries from OVEX ewes was infused for 12 h into HPX sheep and the t 1/2 values determined after cessation of treatment and compared to those after a bolus injection. The clearance of both FSH and LH from plasma after infusion was significantly prolonged than after a bolus injection. It is concluded that the difference in circulating half-lives of FSH between pituitary extracts from intact and OVEX ewes after bolus administration is due to a difference in pituitary FSH composition. However, the prolonged clearance with infusion compared to bolus administration suggests that extrapituitary factors are also responsible.

Animals↗
PubMed1991

The effect of follicle-stimulating hormone-suppressing protein or follistatin on luteinizing bovine granulosa cells in vitro and its antagonistic effect on the action of activin.

The time- and dose-dependent effects of bovine FSH-suppressing protein (FSP)/follistatin and human recombinant activin A (hr-Act) on oxytocin (OT) and progesterone (P) production, markers of luteinization, were studied in mature and immature bovine granulosa cells (GC), using three forms of FSP (31, 35, and 39 kDa) and a FSP pool consisting of 35, 39, and 45 kDa forms. FSP alone had no detectable effect on OT and P production when added to cultures of fully differentiated bovine GC. On the other hand, all FSP forms (10-100 ng/ml) enhanced and prolonged OT and P production of immature GC induced by bovine LH (10 ng/ml). Overall, 35 kDa FSP was more effective than the other forms tested. Hr-Act alone had a dose-dependent inhibitory effect on OT and P production on LH-stimulated immature GC. All four forms of FSP (30 or 100 ng/ml) added to cultures treated with hr-Act, reversed the inhibitory effect of hr-Act, with a significant increase (25%) above control levels using the 35 and 39 kDa FSP forms. In conclusion, FSP enhanced and prolonged the luteinization process, as indicated by OT and P production induced in immature GC by bovine LH, and was able to antagonize the inhibitory effect of hr-Act in this system. These studies suggest a physiological role for activin and FSP, as modulators of folliculogenesis and luteinization in the ovary. We propose that activin and FSP act in an autocrine fashion on GC in the ovarian follicle to regulate folliculogenesis and luteinization.

Activins↗
PubMed1991

Inhibin concentrations throughout the menstrual cycles of normal, infertile, and older women compared with those during spontaneous conception cycles.

Plasma immunoreactive inhibin levels have been measured in a series of normal conception cycles (group I; n = 7), and the data compared to inhibin concentrations in normal menstrual cycles (group II; n = 8), in women with luteal phase defects (group III; n = 7), and in women in the perimenopausal period (group IV; n = 6). Daily plasma levels of LH, FSH, progesterone, estradiol, and inhibin were determined in each subject, and daily mean profiles for each hormone in each subject group were calculated and expressed as geometric means with 68% confidence limits. During the follicular and early luteal phases, inhibin concentrations in the normal nonpregnant group (group II) were significantly higher than those in the conception cycles of group I, but after implantation in the conception cycles, inhibin concentrations increased to levels in excess of those seen at any time in nonconception cycles (716-1352 U/L; P less than 0.02). The postimplantation rise in inhibin did not initially appear to follow the same pattern as progesterone. While progesterone concentrations rose within 24 h of the first detectable increase in hCG, inhibin levels did not increase until 3 days later, although after this point concentrations increased serially and in parallel with progesterone. LH and FSH concentrations were markedly suppressed after implantation. Follicular and early luteal inhibin concentrations in cycles with luteal phase defects were also higher than those in conception cycles, although this difference was only significant in the midfollicular phase. Follicular phase inhibin concentrations in cycles from older women (group IV) were lower than those in groups II and III, but were not distinguishable from those in the conception cycles. Estradiol concentrations in the same subjects were significantly lower during the early follicular phase, while follicular and luteal FSH concentrations were significantly higher than those during conception cycles. Finally, examination of the relationship between inhibin, FSH, and estradiol around menstruation in the older women revealed a far closer temporal association between FSH and estradiol than between FSH and inhibin. In conclusion, inhibin concentrations rise and fall throughout the human menstrual cycle in a manner that is similar to but at specific times significantly different from that of either of the ovarian steroids estradiol and progesterone. It is considered to be a peptide of granulosa cell origin and may be an indicator of the size of the follicular pool during the early stage of the cycle. However, although there is some degree of inverse correlation between profiles of inhibin and profiles of FSH, this relationship is not particularly clear.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1991

Serum FSH-suppressing activity of human recombinant inhibin A in male and female rats.

After a single i.v. injection of purified human recombinant inhibin A (hr-inhibin) or bovine follicular fluid (bFF) to 3-day castrated 35-day-old male rats, serum FSH concentrations fell (P less than 0.05) between 4 and 8 h, returning to control concentrations by 16-24 h. Administration of graded doses of hr-inhibin (0.625-10 micrograms/100 g body wt) and bFF (31.3-250 microliters/100 g body wt) resulted in a parallel dose-related suppression of serum FSH with a maximum suppression 50% of controls. Similar experiments in 2-day ovariectomized 85-day-old female rats also showed a dose-related suppression with a maximum suppression approximately 30% of controls. Serum LH concentrations remained unchanged in all studies with male or female rats. The biological activity of hr-inhibin in vivo was determined for male and female rats in terms of a standard bFF preparation defined by an in-vitro bioassay based on the suppression of FSH content in rat pituitary cells in culture. In males hr-inhibin exhibited a biopotency of 407 (159:1050; fiducial limits) U/micrograms protein and in females the biopotency was 358 (226:565) U/micrograms protein. These potencies are lower than that measured in the in-vitro bioassay (1120 (1040:1210) U/micrograms protein) and differences between in-vivo and in-vitro systems were attributed to the use of bFF rather than a purified human inhibin preparation as standard. These results indicate that hr-inhibin behaves similarly in vivo to bFF. Furthermore, based on the large working range and relatively good precision, the female rat system provides a good basis for an inhibin in-vivo bioassay method.

Animals↗
PubMed1990

Presumed small choroidal melanomas with serous macular detachments with and without surface laser photocoagulation treatment.

We reviewed the records of 22 patients (22 eyes) who had presumed small choroidal melanomas associated with a serous macular detachment. In 13 eyes, the tumor surface was treated with laser photocoagulation to reattach the retina and improve vision. After photocoagulation, the retina reattached in 11 eyes (85%), and the visual acuity improved in eight eyes (62%), returning to 20/25 or better in six eyes (46%). Twelve of the tumors (92%) that received surface photocoagulation grew after treatment. Seven of these tumors (54%) developed a collar-button configuration and showed evidence of basal expansion. Of the nine tumors that did not receive surface photocoagulation, seven (78%) eventually grew, but none developed a collar-button configuration. Surface photocoagulation applied to a growing melanoma appears to increase the likelihood of tumor extension through Bruch's membrane in a collar-button configuration. The impact of such growth on tumor metastasis is unknown.

Adult↗
PubMed1990

The effect of bovine activin and follicle-stimulating hormone (FSH) suppressing protein/follistatin on FSH-induced differentiation of rat granulosa cells in vitro.

The time- and dose-dependent effects of bovine activin A and bovine follicle stimulating hormone (FSH) suppressing protein (FSP) or follistatin on basal and FSH-induced steroidogenesis and inhibin production were studied in granulosa cells from immature, diethylstilbestrol (DES)-treated rats. In the presence of rat FSH (20 ng/ml) which stimulates aromatase activity and the production of progesterone and inhibin, activin (0.3-100 ng/ml) augmented all three parameters, whereas FSP (0.3-100 ng/ml) enhanced progesterone production and attenuated the other two parameters. In the absence of FSH, the basal parameters were unaffected by treatment with either activin or FSP alone, except for a statistically significant increase in basal inhibin in the presence of activin alone (P less than 0.05, at doses of 30 and 100 ng/ml). Neither activin nor FSP influenced the timing of the maxima of FSH-induced activities over 5 days. These findings suggest that activin and FSP, both present in follicular fluid, may play an important role in the local regulation of granulosa cell differentiation.

Activins↗
PubMed1990

Fatal streptokinase-induced intracerebral haemorrhage in cerebral amyloid angiopathy.

A fatal intracerebral haemorrhage (ICH) associated with streptokinase (SK) treatment of an acute myocardial infarction is described. Autopsy examination showed a lobar ICH and severe cerebral amyloid angiopathy (CAA). The close temporal relationship between SK administration and intracranial haemorrhage, the absence of pretreatment risk factors for ICH, and the presence of CAA suggests that these are related phenomena. Accordingly: 1. There may be a synergistic relationship between CAA and intracranial haemorrhage induced by fibrinolytic agents; 2. Thrombolytic agents may induce more frequent than expected intracranial haemorrhage in conditions associated with a high incidence of CAA, notably old age and Alzheimer's disease; 3. A regional defect in haemostasis other than vessel fragility may contribute to the intracranial haemorrhagic predisposition of CAA; 4. Autopsy examination of cases of ICH is an essential part of the audit of clinical trials of fibrinolytic agents.

Amyloidosis↗
PubMed1990

Intragonadal regulation of immune system functions.

Immune responses within the mammalian gonads, and in particular the testis, are deficient in spite of adequate lymphatic drainage and the presence of lymphocytes and MHC II+ macrophages. There is considerable evidence from in vivo and in vitro studies that this 'suppression' of the immune system may be due, at least in part, to localized inhibition or regulation of normal lymphocyte and/or macrophage functions within the gonads. In the testis, both steroidal and non-steroidal products of the Leydig cells, including androgens, endorphins, and inhibin-related proteins, have been implicated in mediating this activity. In turn, a number of immune cell cytokines affect steroidogenic cell function in vitro. The studies described in this paper indicated that [3H]-thymidine incorporation by adult rat thymocytes in vitro was inhibited by conditioned medium collected from short-term incubations of Percoll-purified adult rat Leydig cells, but stimulated by testicular interstitial fluid and by conditioned medium collected from short-term incubations of adult rat seminiferous tubules. The factors responsible for these effects on thymocyte function appeared to be of large molecular weight, as they were retained by ultrafiltration membranes with exclusion limits of 10,000 or 30,000 daltons. It is hypothesized that an 'immunosuppressive' mechanism, principally mediated by non-steroidal factors secreted by the steroidogenic cells of the gonadal interstitial tissue, exists within the gonads in order to prevent activation of the immune system by germ cell antigens and growth factors associated with germ cell proliferation and differentiation. This mechanism probably acts in parallel with normal antigen-specific tolerance mechanisms operating at the gonadal level. As immune responses to germ cells are believed to be a significant causative factor in infertility, particularly in men, this represents an important area for further study.

Animals↗
PubMed1990

Identification of inhibin and inhibin-related proteins in human follicular fluid.

Inhibin-related proteins were identified in human follicular fluid following fractionation by gel permeation chromatography under neutral and acidic conditions, reversed-phase high performance liquid chromatography (HPLC) and preparative polyacrylamide gel electrophoresis. A number of molecular mass forms of inhibin (30-36 and 59-66 kDa) based on their in vitro biological and immunological activities were identified, of which 59-66 kDa inhibin was the predominant form. Bioactive fractions devoid of inhibin immunoactivity were also identified with molecular masses of 46 and 55 kDa. Based on their retention positions on reversed-phase HPLC and their lack of inhibin immunoactivity, these proteins are likely to be follicle stimulating hormone (FSH) suppressing proteins/follistatins previously identified in bovine and porcine follicular fluids. In addition, an immunoactive inhibin fraction devoid of bioactivity was identified in large amounts in the 50-70 kDa region of the gel permeation chromatogram at neutral pH. This material, based on previous findings with the fractionation of bovine follicular fluid, is likely to be the alpha-inhibin subunit precursor protein. No FSH stimulating activity (activin) was identified in any of the chromatograms, suggesting that the levels of activin in human follicular fluid are low. In conclusion, inhibins of molecular mass 30, 36, 59 and 66 kDa have been identified in human follicular fluid. Proteins with inhibin bioactivity devoid of immunoactivity and vice versa have also been detected and these proteins are probably FSH suppressing protein and an alpha-inhibin subunit precursor protein. Activin could not be identified.

Chemical Fractionation↗
PubMed1990

Neovascularization of the disc in pars planitis.

Neovascularization of the disc (NVD) was present in 9 of 163 patients with pars planitis. In all cases, NVD was unilateral and observed in eyes with recent exacerbation of the inflammatory process. To reduce intraocular inflammation, all nine eyes were treated with varying combinations of topical, periocular, and systemic corticosteroids. In addition to corticosteroids, one eye received Argon laser photocoagulation, two eyes underwent peripheral cryotherapy, and one eye was treated with both Argon laser photocoagulation and peripheral cryotherapy. With decrease or disappearance of intraocular inflammation, NVD resolved in all cases without recurrence during follow-up study, which ranged from 6 to 189 (mean, 81) months. Rhegmatogenous retinal detachments developed in two eyes treated with peripheral cryotherapy. Both detachments were successfully repaired with surgery. Control of intraocular inflammation appears to be the key factor for regression of NVD in pars planitis. If NVD does not regress or vitreous hemorrhage occur, photocoagulation and peripheral cryotherapy may be beneficial.

Adolescent↗
PubMed1990

Magnetic resonance imaging of juxtapapillary plaques in cadaver eyes.

Adequate treatment of juxtapapillary melanomas with episcleral plaque brachytherapy using lower energy radiation sources may be difficult because of uncertainties regarding the relationship of the plaque to the optic nerve and tumour base. We obtained magnetic resonance images of a dummy plaque placed in a juxtapapillary location in cadaver specimens. Although it is possible to place a plaque in close association with the optic nerve sheath, a tissue barrier exists which may prevent actual contact between the plaque and nerve. Posterior tilting of the plaque may also occur. Because of these uncertainties regarding plaque placement, juxtapapillary melanomas should be considered a distinct subgroup when evaluating the efficacy of radioactive plaque brachytherapy in the treatment of choroidal melanoma.

Brachytherapy↗
PubMed1990

Inhibin concentrations in ovarian and jugular venous plasma and the relationship of inhibin with follicle-stimulating hormone and luteinizing hormone during the ovine estrous cycle.

A heterologous RIA for ovine inhibin was developed which was sufficiently sensitive and specific to describe the peripheral concentrations of immunoreactive inhibin (iINH) during the estrous cycle of the ewe and to examine the effects of cautery of ovarian follicles on concentrations of iINH in ovarian and jugular venous plasma. Parallel logit-log dose-response lines were observed among ovine follicular fluid, ewe plasma, and pure native ovine (31 kDa) and bovine (31 kDa) inhibin. iINH could not be detected in ovariectomized ewe plasma, and there was no apparent cross-reactivity with a variety of structurally related and unrelated hormones and peptides, except a monomeric form of the alpha-subunit of INH, iINH in follicular fluid was 10(4)-fold higher than that in ovarian venous plasma, which was 3-fold higher than that in peripheral plasma. Cautery of the follicles resulted in a 35% reduction in iINH and an 81% reduction in estrogen concentrations in the ovarian vein within 10 min. During the estrous cycle, iINH and FSH were inversely related in samples taken over 30 h in the luteal phase (r = -0.69; P less than 0.001) and in the pre- and postovulatory phases (r = -0.45; P less than 0.001). iINH and LH were not related in the luteal phase, but were weakly positively correlated in the follicular phase (r = 0.31; P less than 0.01). iINH and estrogen concentrations in the follicular phase were also weakly correlated (r = 0.30; P less than 0.001). Furthermore, iINH concentrations rose in the follicular phase and decreased within 3-6 h of the preovulatory surges of LH and FSH, reaching a nadir around the time of the second rise in FSH 24-48 h later. It is concluded that 1) large antral follicles are a major source of peripheral iINH during the ovine estrous cycle; 2) iINH levels increase in the follicular phase with the growth of the dominant follicle and may be inhibited by the preovulatory surge of gonadotropin; 3) the fall in inhibin after the LH surge may be responsible for the second rise in FSH; and 4) the inverse relationship between FSH and iINH is consistent with the hypothesis that inhibin is involved in the feedback regulation of FSH.

Animals↗
PubMed1990

Physicochemical and biological characterization of recombinant human inhibin A.

Recombinant human inhibin A was isolated from recombinant mammalian cell line culture media. Two forms of inhibin were identified with Mr of 34 and 31 Kd composed of subunits (alpha, beta) of 24 and 15 Kd and 21 and 15 Kd respectively. Both forms are bioactive in an inhibin in vitro bioassay and immunoactive with potencies comparable to or higher than purified bovine inhibin. Amino acid analyses and NH2-terminal sequences of each of the subunits are consistent with those predicted from their cDNA structures. The inhibin alpha- but not beta-subunit is glycosylated based on its binding to the lectins concanavalin A and wheat germ lectin. The difference in molecular weight of 31 and 34 Kd inhibin is attributed to variation in glycosylation of the alpha-subunit. The 31+34 Kd inhibin is heterogeneous on isoelectric focusing gels consisting of four isoforms in the pH range 6.2-7.6. Inhibition also exhibits in vivo biological activity by suppressing serum FSH but not LH in castrate male rats. These physicochemical and biological characteristics of recombinant human inhibin are similar to those described for native inhibin isolated from a variety of other species.

Amino Acid Sequence↗
PubMed1990

Quantitative cytological studies of spermatogenesis in intact and hypophysectomized rats: identification of androgen-dependent stages.

A stereological study of the numbers of germ cells in various stages of spermatogenesis was undertaken in testosterone-treated intact and hypophysectomized (HPX) rats. Adult Sprague-Dawley rats were given testosterone by Silastic implants, which either inhibited (3-cm length) or partially maintained (10 cm) spermatogenesis over a 13-week period. The numbers of nuclei of the various germ cell categories (spermatogonia, spermatocytes, and round spermatids) in the testes were estimated by profile counting and measurement of nuclear diameter. The numbers of elongated spermatids were determined separately in testicular homogenates. Testis weight, seminiferous tubule volume, and tubule diameter were significantly decreased in intact rats with 3- and 10-cm testosterone implants and in HPX rats, although they were partially maintained in groups with 10-cm implants compared to those in groups with 3-cm implants (P less than 0.05). The effect of 3-cm testosterone implants in the intact group was to suppress the number of spermatogonia to 57%, reduce the conversion of spermatogonia to spermatocytes to 85%, and reduce the conversion of round to elongated spermatids to 19% of the control value. This latter effect was largely overcome with 10-cm testosterone implants. In HPX rats, only 10-cm implants were effective in maintaining the conversion of round spermatids to elongated spermatids. However, testosterone alone was less effective in maintaining the conversion of spermatocytes to round spermatids, suggesting that a pituitary factor, probably FSH, was involved. It is concluded that testosterone has a major effect on the conversion of round to elongated spermatids. The conversion of spermatogonia to spermatocytes and the conversion of spermatocytes to round spermatids depend on the synergistic action of both FSH and testosterone. However, the effect of FSH is greatest on the conversion of spermatocytes to spermatids, i.e. meiosis.

Animals↗
PubMed1990

The quantification of steroidogenesis-stimulating activity in testicular interstitial fluid by an in vitro bioassay employing adult rat Leydig cells.

An in vitro bioassay for steroidogenesis-stimulating activity (SSA) in charcoal-extracted rat testicular interstitial fluid (IF) was developed. The bioassay was based upon stimulation of testosterone production by Percoll gradient-purified adult rat Leydig cells during a 20 h incubation in the presence of a maximally stimulating dose of human CG (hCG). The hCG-stimulated conditions were employed to avoid assay interference by endogenous LH in the sample preparations. The standard preparation (a pool of IF from normal adult rats) stimulated testosterone production 3- to 4-fold above that obtained with a maximal dose of either hCG or LH alone, and a linear log dose-testosterone response was observed over the range from 150% to 300% of hCG-stimulated testosterone production. The bioassay had a mean index of precision (lambda) of 0.13 (n = 10 assays), a between assay variation of 10.7-11.7%, and a useful working range from 4.9-28 microliters IF including at least three serial half-dilutions. Parallelism with the IF standard was obtained with IF collected from aged (greater than 15 months old) rats, adult rats made bilaterally cryptorchid for either 4 weeks or 12 months, or injected 6 h previously with 100 IU hCG, and with ovine testicular lymph. Testicular SSA was not affected by coincubation with rat LH antiserum and was not attributable to prevention of oxygen-mediated enzyme damage during the incubation period. Although charcoal-extracted rat serum log dose-response relationships were nonparallel with the standard, serum displayed an apparent relative bioactivity of approximately 20% that of normal IF based on ED50 comparisons. The activity of testicular IF was not affected by coincubation with serum. Untreated and charcoal-extracted rat albumin, at an assay concentration equivalent to that present in normal rat serum or IF, caused only a minor stimulation of testosterone production. Charcoal-extracted bovine albumin, ovalbumin, epidermal growth factor, insulin-like growth factor-1, bovine 31 kDa inhibin, and transforming growth factor-beta were inactive. Activity was nondetectable in rat thoracic duct lymph or high speed supernatants of adult rat testicular extracts. Testicular SSA and serum from normal rats displayed slightly different time-courses of action, with SSA active during both acute (1.0 h) and longer term (2.0-20 h) incubations, while serum stimulated testosterone production only in the longer term incubations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗