Biomedical subjects

D M Robertson

Publications and source records attributed to D M Robertson.

At least 217 records · Page 12Linked to original sources

PubMed1986

The human placenta: a novel source of inhibin.

Human placental extracts contain inhibin bioactivity and immunoactivity giving dose response curves parallel to a human follicular fluid inhibin standard. Inhibin bioactivity in vitro was neutralised by preincubation of extracts with antisera raised to pure bovine inhibin. Umbilical cord blood from term infants contained immunoactivity. Human placental inhibin differs from human ovarian inhibin in terms of its biological: immunological ratio.

Animals↗

PubMed1986

Serous detachments of the macula associated with presumed small choroidal melanomas.

Eight cases of presumed small choroidal melanomas, associated with subretinal fluid in the macula, were studied to determine the eventual outcome of these tumors and the value of photocoagulation in eliminating subretinal fluid. Photocoagulation resulted in resolution of subretinal fluid involving the macula in six cases for a mean duration of 12 months. Six cases showed tumor growth over a mean interval of 24 months. Two cases were eventually managed with enucleation and two with I125 brachytherapy. The occurrence of subretinal fluid involving the macula in cases of small choroidal melanomas implies a high chance of subsequent tumor growth. Photocoagulation may be useful in eliminating subretinal fluid and improving vision during this observation period.

Adult↗

PubMed1986

Plasma inhibin levels during gonadotropin-induced ovarian hyperstimulation for IVF: a new index of follicular function?

Human plasma inhibin was measured by radioimmunoassay in 26 women undergoing ovarian hyperstimulation for in-vitro fertilisation. Plasma inhibin rose in parallel with oestradiol during gonadotropin therapy (r = 0.79, p less than 0.001). Peak plasma inhibin levels correlated with follicle number as determined by ultrasonography (p less than 0.001) and with the number of oocytes recovered at laparoscopy (p less than 0.05). The increase in production of human ovarian inhibin by exogenous follicle stimulating hormone (FSH) is thus consistent with its proposed role in FSH regulation. Human plasma inhibin may be useful as a circulating protein marker of granulosa-cell function and may have therapeutic implications in human ovulation-induction programmes.

Chorionic Gonadotropin↗

PubMed1986

Photic retinopathy from the operating room microscope.

Photic retinopathy was produced in two patients after a 60-minute exposure to light from an operating room microscope (Zeiss OpMi 6). The first patient had a blind eye with clear (phakic) media and a normal-appearing retina. A 60-minute exposure produced an oval gray lesion in the posterior pole at the level of the pigment epithelium. With an ultraviolet-400 filter added for a second exposure, a second lesion was produced. The second patient received a 60-minute exposure (without an ultraviolet filter) 72 hours before enucleation for a malignant melanoma. This produced photic retinopathy that resulted in a slight decrease in central visual acuity and a dense paracentral scotoma. This conclusively establishes a cause-and-effect relationship between exposure to the light from an operating room microscope and a retinal lesion in the human eye.

Adult↗

PubMed1986

Prognostic factors in choroidal and ciliary body melanomas with extrascleral extension.

In a retrospective study, 50 (8.2%) of 610 patients with malignant melanoma of the ciliary body or choroid had extrascleral extension. Of 46 patients for whom follow-up data were available, 24 (52%) survived five years, 20 (42%) survived ten years, and 17 (37%) survived 15 years. Factors that seemed to affect survival significantly included intraocular tumor size and extraocular tumor size and location. Our observations did not support the role of primary exenteration. Five patients (11%) with extrascleral extension had orbital recurrences and all died within 31 months of surgery regardless of treatment.

Adult↗

PubMed1986

Metastasis from untreated uveal melanomas.

From 1969 to 1985, 224 cases of choroidal or ciliary body malignant melanoma had metastatic evaluations at the Mayo Clinic, Rochester, Minn. Five cases (2.2%) were found to have evidence of metastasis during the pretreatment evaluation. In each case, metastatic melanoma was verified histologically. Prior to enucleation or radiation treatment, we recommend a general medical evaluation, liver enzyme studies, and chest roentgenogram. Computed tomography (CT) of the liver should be performed if liver involvement is suggested by either the general medical evaluation or liver enzyme studies. Although CT of the liver in the initial surveillance of patients with choroidal or ciliary body melanoma is routinely performed at our institution, CT is not likely to produce a high yield of detectable disease in the presence of normal liver enzyme levels.

Humans↗

PubMed1986

Acute stages of batrachotoxin-induced neuropathy: a morphologic study of a sodium-channel toxin.

The acute effects of batrachotoxin, a steroidal neurotoxin which opens the membrane sodium channel, were observed morphologically at various time points up to 3 h after injection into rat peroneal nerve. Three changes were found. First, there was massive swelling of the axon at the node of Ranvier accompanied by retraction of paranodal myelin. Second, a similar swelling of unmyelinated axons was seen. Third, extracellular fluid accumulated along the internode in the adaxonal space, the intraperiod line of myelin and, rarely, the external mesaxon, with concomitant shrinkage of the axon. The first two changes might be explained on the basis of massive shift of sodium through the batrachotoxin-modified sodium channel into the axon and subsequent osmotic shift of fluid. The reason for the third change is not clear but probably also has a ionic basis.

Animals↗

PubMed1986

The effects of inhibin purified from bovine follicular fluid in several in vitro pituitary cell culture systems.

The effects of inhibin purified from bovine follicular fluid (bFF) and a charcoal-treated bFF preparation were investigated in several inhibin in vitro systems based on the use of pituitary cells in culture. FSH, LH, TSH and PRL were determined in the medium and cell extracts before and after a 4 h LHRH stimulation test. Both pure inhibin and bFF preparations markedly inhibited the basal release, cell content and LHRH-stimulated release of FSH in a parallel dose-dependent manner with minor or negligible effects on LH, TSH and PRL. Using parallel line bioassay statistics the inhibin activities of the purified inhibin preparations in the various in vitro systems were calculated with the charcoal-treated bFF as standard. Significantly higher inhibin values were obtained using the basal release procedure than with the cell content or LHRH-stimulated release procedures. This difference was influenced by the length of time the inhibin preparations were in culture. The highly purified preparations showed no signs of cytotoxicity in culture as assessed by a 51Cr release test. It is concluded that purified bFF inhibin is specific in suppressing pituitary FSH and not LH, TSH or PRL. The observation that purified bFF inhibin is more active in the basal release procedure is attributed to a loss of activity of the bFF standard in this system in contrast to that observed in either the cell content or LHRH-stimulated release procedure.

Animals↗

PubMed1986

Degradation of luteinizing hormone-releasing hormone (LHRH) and an LHRH agonist by the rat testis.

Degradation of LHRH and [D-Ser(tBu)6,des-Gly-NH10(2)]LHRH ethylamide (LHRH-A), during incubation with high-speed supernatants of rat testes, as assessed by reversed-phase (RP)-HPLC fractionation of the iodinated peptides and by radioimmunoassays for LHRH or LHRH-A, was principally due to a neutral 43 000 Da peptidase with apparent Km values at 25 degrees C of 0.15 microM for LHRH and 1.19 microM for LHRH-A. The peptidase was inhibited by sulphydryl reagents, TLCK, 1,10-phenanthroline, EDTA, bacitracin, other LHRH analogues, oxytocin, [Lys8]vasopressin and somatostatin. It was predomantly located in seminiferous tubule supernatants (98% of recovered activity), with much lower levels in interstitial fluid (2%), interstitial tissue or testicular particulate fractions (less than 0.8%). Extracts of cultured immature Sertoli cells produced LHRH- and LHRH-A-degradation profiles, as assessed by RP-HPLC, that were identical to those produced by testicular supernatants. Similar levels of peptidase activity/mg protein were observed in immature and adult rat testes. These studies indicate that the principal LHRH-peptidase in the rat testis is produced by cells of the seminiferous epithelium, chiefly the Sertoli cell, and may play an important role in regulating the activity of LHRH and other peptide hormones in the testis.

Animals↗

PubMed1986

The radioimmunoassay of bovine and human follicular fluid and serum inhibin.

A radioimmunoassay for inhibin in bovine and human follicular fluid (bFF, hFF) and serum from both species was developed based on an antiserum raised in a rabbit to purified bovine 58 kDa inhibin. Following immunization, parallel changes in plasma FSH and inhibin antibody titre were observed suggesting inhibin neutralization in vivo. The antiserum neutralized bFF, hFF and purified 31 kDa and 58 kDa inhibin activity in an in vitro bioassay system. Purified 58 kDa and 31 kDa inhibin were iodinated using a chloramine-T procedure and the 125I-inhibin purified by elution from Matrex Red A, with the iodinated molecules showing similar physicochemical properties to non-iodinated inhibin. Both tracers were stable in bFF but only 125I-31 kDa inhibin was stable in serum. A second antibody RIA system using either tracer yielded a parallel displacement between purified 31 kDa and 58 kDa inhibin. The cross-reaction in the RIA of inhibin from different species when expressed in terms of their bioactivity was bFF 100%, hFF 30%, ovine FF less than 1% and rat ovarian extract non-detectable. Rat LH and FSH, ovine LH and FSH, hCG, bovine TSH, LHRH, ovalbumin and bovine serum albumin showed less than 0.5% cross-reactivity using either tracer. Similar profiles of both bio- and immunoactive inhibin were observed at each stage of the inhibin purification procedure. The in vitro biological to immunological ratios for a number of purified 31 kDa and 58 kDa inhibin preparations using both tracers in the RIA, ranged from 0.30 to 0.43. The RIA was modified for serum by using 125I-31 kDa inhibin as tracer and an elevated temperature (30 degrees C) to minimize non-specific effects. No detectable activity was determined in steer or human post-menopausal serum whilst bull and human female serum showed parallel dose-response curves to their respective follicular fluid standards with circulating levels of 0.9 and 1.1 ng/ml respectively.

Animals↗

PubMed1986

Isolation of a 31 kDa form of inhibin from bovine follicular fluid.

The introduction of a pH 4.75 precipitation step to a previously described purification procedure from bovine follicular fluid (bFF) resulted in the isolation of a 31 kDa form of inhibin, in addition to 58 kDa inhibin. The procedure was monitored by an in vitro bioassay based on the suppression of the FSH cell content by pituitary cells in culture. The 31 kDa form was purified 5550-fold with approximately 5% recovery. On SDS-polyacrylamide gel electrophoresis a single band was detected with a molecular weight of 31 000 +/- 1500 (mean +/- SD) which upon reduction gave 2 subunits of 20 200 +/- 300 and 14 800 +/- 600. The biological activity expressed on mg protein basis was similar for both 31 kDa and 58 kDa inhibin although on a molar basis the 58 kDa inhibin was 2-3 times higher. A high degree of cross-reaction was observed between both forms in a radioimmunoassay of bovine inhibin using an antiserum raised against the larger form with either iodinated 31 kDa or 58 kDa inhibin as tracer. Based on the subunit composition of the 31 kDa and 58 kDa inhibin, their similar cross-reaction in a radioimmunoassay system and the apparent generation of the 31 kDa inhibin following a pH precipitation step, it is concluded that 31 kDa inhibin is a smaller form of the 58 kDa inhibin resulting from a shortening of the 43 kDa subunit to a 20 kDa subunit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Argon laser photocoagulation treatment in central serous chorioretinopathy.

Central serous chorioretinopathy, a sporadic self-limited disease of young adults, is associated with loss of central vision, image distortion, and imparied dark adaptation. The diagnosis is verified with fluorescein angiography, which demonstrates and expanding point of fluorescein dye leakage under a serous detachment of the sensory retina. Treatment should ordinarily be delayed four or more months but may be considered if there is evidence of microarchitectural changes in the macular retina, if the best corrected visual acuity declines to 20/40 or less, or if there have been multiple recurrences. Argon laser photocoagulation should be directed to the leakage site, using spot sizes of 200 mu in diameter, exposure times of 0.2 seconds, and low-power intensities.

Adult↗

PubMed1986

Pharmacological modification of bradykinin induced breakdown of the blood-brain barrier.

Internal carotid artery infusion of bradykinin caused extensive breakdown of the blood-brain barrier to protein as demonstrated by the extravasation of the marker, horseradish peroxidase, into vessel walls and the adjacent parenchyma. Pretreatment of the animals with indomethacin, trifluoperazine, or imidazole significantly reduced the quantity of abnormally permeable vessels as determined by light microscopy. By electron microscopy, it was determined that bradykinin caused an intense increase in the number of pinocytotic vesicles in the permeable segments, but no change in the interendothelial junctions. After imidazole pretreatment, although the extent of the permeability change was markedly reduced, the intensity of pinocytotic activity in the involved areas was not altered.

Animals↗

PubMed1986

Cloning and sequence analysis of cDNA species coding for the two subunits of inhibin from bovine follicular fluid.

The primary amino acid structures of the 43-kDa (A) and 15-kDa (B) subunits of the 58-kDa form of the hormone inhibin have been elucidated by cloning and analysis of cDNA species derived from bovine granulosa cell mRNA. The A subunit (Mr = 32,298) is a protein of 300 amino acids with two potential N-glycosylation sites and two potential proteolytic processing sites and has a pre-pro region of 60 amino acids. The mature B subunit (Mr = 12,977) is a protein of 116 amino acids synthesized from a separate mRNA. These data establish that a 31-kDa form of inhibin also isolated from bovine follicular fluid, with subunits of 20 kDa (Ac) and 15 kDa (B), is derived from the 58-kDa form by proteolytic processing of the A subunit.

Amino Acid Sequence↗

PubMed1986

Measurement of inhibin and an index of inhibin production by rat testes during postnatal development.

Our previous studies have shown that inhibin activity in rat testes can be measured using an in vitro inhibin bioassay. In animals that have undergone unilateral efferent duct ligation (EDL), the difference in inhibin content between the ligated and nonligated testis can be used as an index of the rate of inhibin production in vivo. In the present study we examined postnatal changes in inhibin content in the testes, and the production rates of inhibin and seminiferous tubule fluid in groups of neonatal, immature, and adult rats from 1 to 80 days old. We detected inhibin activity in testes of 1-day-old rats; the activity level rose linearly to Day 8, subsequently increasing markedly from Day 30 until it reached a plateau at Day 45. Increments in the content of inhibin and weight of the testis after unilateral EDL, interpreted to represent production of inhibin and seminiferous tubule fluid, commenced at Day 20 and increased rapidly between Days 30 and 50, decreasing thereafter to Day 80. The increase in content and production of inhibin was directly correlated to the rise in serum follicle-stimulating hormone (FSH) and testosterone, suggesting that these two hormones are important in controlling inhibin secretion. In addition, the changes in serum FSH from the high, postnatal levels to those typical of adults were inversely correlated to the content and production rate inhibin in the testes and concentrations of testosterone in the serum. These data support the hypothesis that inhibin is specifically involved in the feedback control of pituitary FSH secretion during postnatal development, although a role for testosterone or a synergistic interaction between the two hormones cannot be excluded.

Aging↗

PubMed1986

Effects of testosterone on testicular inhibin and fluid production in intact and hypophysectomized adult rats.

Rats were given s.c. implants of high (HT) or low (LT) doses of testosterone and 10 days later hypophysectomy or sham-operation was performed. The rats were killed after 50 days. Unilateral efferent duct ligation was performed 16 h before death to measure seminiferous tubule fluid production and the increment in testicular inhibin values (inhibin production). Inhibin levels in testis cytosols were measured by a pituitary cell culture bioassay. The LT implants maintained serum testosterone at control values and decreased testicular weight whereas HT implants raised serum testosterone 3-fold and maintained testicular weight at 75-85% of pretreatment levels. In intact rats, LT implants caused no change in testicular inhibin content but decreased inhibin production; no significant changes occurred with HT implants. After hypophysectomy both values were significantly suppressed and could not be maintained by HT or LT implants. However, the HT implants partly restored inhibin production despite their inability to influence testicular inhibin content. In contrast, tubule fluid production depended mainly on intratesticular testosterone levels and occurred normally in intact or hypophysectomized rats with HT but not LT implants. These results indicate that inhibin and seminiferous tubule fluid production, both functions of the Sertoli cell, are under different hormonal control. The maintenance of inhibin production by the testis requires the support of pituitary hormones, presumably FSH, while seminiferous tubule fluid production requires testosterone, presumably through LH stimulation of Leydig cells. These findings are consistent with the hypothesis that inhibin is produced in response to trophic stimulation by FSH.

Animals↗

PubMed1986

Resistant ovary syndrome and premature ovarian failure in young women with galactosaemia.

Three young women with galactosaemia presented with amenorrhoea and elevated plasma levels of FSH and LH. Two of these women are sisters and ovarian biopsy confirmed premature ovarian failure in one and resistant ovary syndrome in the other. The history and ovarian histology suggested that the sister with ovarian failure may have progressed through a stage of 'follicle resistance' prior to follicular atresia. All subjects had specific bioassays for LH which were grossly elevated, and higher than the levels recorded by immunoassay.

Adult↗

PubMed1985

Iris melanomas.

Most iris tumors behave benignly, reflecting their small size and the high proportion of nevi and spindle A melanomas. Of 1,043 reported iris melanomas, 31 metastasized (3%). Metastasis from a spindle A melanoma is not known to occur despite documented growth and local recurrence after excision. If known spindle A melanomas are excluded from all reported spindle cell tumors of the iris, the rate of metastasis for spindle cell tumors is 2.6%. Mixed-cell melanomas have a metastasis rate of 10.5% and epithelioid melanomas a rate of 6.9%. The interval between the histologic diagnosis and death from metastases ranged from three months to 12 years, with an average of 6.5 years. Five- and ten-year mortality rates for different cell types cannot be ascertained. Iris angiography may be useful in defining the limits of tumor involvement but is of uncertain value in differentiating benignancy from malignancy. Of the 31 cases with metastases, 21 included information on the type of surgical procedure used to obtain the histologic diagnosis. In 13 of the 21 cases (62%), the tumors were initially involved with either incomplete excision or inadvertent transection before enucleation.

Adolescent↗