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Biomedical subjects

D M Robertson

Publications and source records attributed to D M Robertson.

At least 19 recordsLinked to original sources
PubMed1992

Massive epithelium-lined inclusion cysts after scleral buckling.

Two patients with massive epithelium-lined inclusion cysts of the orbit became symptomatic five and 16 years after scleral buckling. Each patient described diplopia and displacement of the previously treated eye. An orbitotomy in the first patient disclosed a loculated epithelium-lined inclusion cyst that extended posteriorly from the insertion of the inferior rectus muscle nearly to the apex of the orbit. In the second patient, a loculated epithelium-lined inclusion cyst extended into the superior nasal portion of the orbit from its origin near the insertions of the superior and medial recti muscles. We speculated that epithelial cells of the conjunctiva were shed at the time of scleral buckling and became lodged in the exposed sulcus created by the surgical retraction of Tenon's capsule. Here they proliferated and formed the large epithelium-lined cysts. In each patient, removal of the cyst was followed by a decrease in diplopia as the displaced globe returned toward its normal position.

Aged↗
PubMed1992

Scleritis as an initial manifestation of choroidal malignant melanoma.

PURPOSE: The purpose of this article is to present the unusual circumstances in which malignant melanoma of the choroid can masquerade as scleritis, thus confounding its diagnosis. METHODS: Three cases of plaque-like malignant melanomas of the choroid are reported that, on initial examination, had features of scleritis. The events leading to their eventual correct diagnosis also are presented. RESULTS: In each case, there was ocular pain, blurred vision, anterior chamber and/or vitreous cavity cellular reaction, and an exudative retinal detachment associated with an ill-defined, relatively flat variably pigmented choroidal mass. In all three cases, the inflammatory component responded promptly to corticosteroid treatment and was accompanied by visual improvement. In two eyes, shrinkage of the choroidal mass accompanied the corticosteroid treatment, lending support to a working diagnosis of scleritis. By demonstrating expansion of the choroidal masses, examination of sequential fundus photographs influenced the decision to enucleate the eyes for presumed malignant choroidal melanoma. CONCLUSION: Clinicians should be alert to the circumstances in which malignant melanomas of the choroid can masquerade as scleritis. Careful evaluation by ophthalmoscopy, ultrasonography, fundus photography, and subsequent sequential examination is necessary to arrive at the correct diagnosis.

Adult↗
PubMed1992

The physiology of testicular inhibin and related proteins.

The roles of inhibin and related proteins in the male remain unclear, although it is becoming increasingly evident that they play a part in FSH regulation and testicular function, including spermatogenesis. The difficulties associated with these questions have been the limited availability of inhibin and related proteins for in vivo studies, the absence of specific assay methods, and the unclear relationship of inhibin and testosterone in the regulation of FSH secretion. With the availability of human recombinant preparations and the current development of new assays, it is anticipated that many of these questions will be resolved.

Animals↗
PubMed1992

Inhibin and inhibin alpha-chain precursors are produced by immature rat Sertoli cells in culture.

Stimulation of Sertoli cells from immature rats with dibutyryl cyclic (dbc) AMP resulted in a decrease in the ratio of inhibin biological (B):immunological (I) activities in vitro. To establish the basis for this decrease, culture medium from Sertoli cells stimulated with dbcAMP was fractionated by dye-affinity chromatography, reverse-phase HPLC, and preparative PAGE. Two peaks of inhibin activity were identified: a predominantly bioactive 29-kDa peak I material (B:I ratio = 5.0) and a bio-inactive, immunoactive 27-kDa peak II material (B:I ratio = 0.1). Evidence of a subunit structure was established by iodination and immunopurification using an inhibin alpha-subunit antiserum. On reduction, peak I (29-kDa) material showed bands of 19 kDa and 14 kDa, whereas peak II (27-kDa) material showed a single 20-kDa band. On the basis of HPLC retention position, molecular mass, evidence of subunit structures and their molecular masses, and inhibin in vitro bio- and immunoactivities, peak I and II materials were most likely inhibin and the alpha-subunit precursor protein pro-alpha C. Western blotting of Sertoli cell culture medium using antiserum directed against the NH2 terminal region (alpha N) of the alpha-subunit precursor also indicated the presence of 24-kDa alpha N. It is concluded that after dbcAMP stimulation, Sertoli cells produce 29-kDa inhibin and the alpha-subunit precursor proteins pro-alpha C and alpha N. The production of the alpha-subunit precursor in addition to inhibin provides an explanation for the decrease in the inhibin B:I ratio following dbcAMP stimulation of Sertoli cells in culture.

Animals↗
PubMed1992

Inhibin/activin beta-subunit monomer: isolation and characterization.

Using an activin RIA that showed limited cross-reaction with inhibin, activin immunoactivity was monitored throughout the isolation of activin from bovine follicular fluid and side-fractions during the isolation of human recombinant inhibin. Two peaks of activin immunoactivity were identified in both materials and isolated to homogeneity by dye affinity chromatography, hydrophobic interaction and gel permeation chromatography, and reverse phase HPLC. The purified proteins in all four peaks had terminal amino acid sequences identical to those of the inhibin/activin beta-subunit. The molecular masses determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under nonreducing (and reducing) conditions were 25 and 15 and 15 and 15 kilodaltons (kDa) for each pair of proteins from both sources. Based on these criteria, the bovine and human recombinant 25-kDa proteins correspond to the inhibin/activin beta A-subunit dimer (activin-A), while the 15-kDa proteins correspond to the inhibin/activin beta A-subunit monomer. The activity of the monomer was 17% of the activity of the dimer in the activin RIA. Based on this level of cross-reaction and the proportion of monomer to dimer immunoactivity found after reverse phase HPLC of bovine follicular fluid, it is estimated that the levels of monomer in bovine follicular fluid are 25-60% those of the dimer. The biological activities of the human recombinant activin monomer and dimer were investigated in two different cell culture systems. In a rat pituitary cell system the activity of the activin monomer was 19% of the activity of the dimer in stimulating FSH release, while in rat thymocyte cultures the activity of the monomer was 45% the activity of the dimer in suppressing lectin-stimulated [3H]thymidine uptake. It is concluded that the beta A-subunit monomer is found in bovine follicular fluid at a level 25-60% that of the beta A-subunit dimer (activin-A). The monomer displays in vitro responses similar to those of the dimer, although the monomer is less active (18-45%) than the dimer. It is unclear if dimerization of the monomer is a necessary prerequisite for biological activity.

Activins↗
PubMed1992

Isolation and physicochemical characterization of human follicle-stimulating hormone isoforms.

Twenty hFSH isoforms were isolated from human pituitary extracts, 15 of which were highly pure. The mild purification procedure, which used a FSH RRA to monitor FSH activity, involved an initial fractionation of pituitary extracts by gel filtration and isoelectric focusing. Six pI regions (mean pI values, 3.63, 3.88, 4.07, 4.23, 4.84, and 5.13) of human (h) FSH were obtained and further fractionated on ion exchange and gel filtration HPLC. Recoveries of FSH radioreceptor activity at each stage were greater than 80%. Fifteen isoform preparations were judged as near homogeneous by HPLC-gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, exhibiting elution and migration behaviors consistent with the known mol wt of intact hFSH and its subunits. The remaining 5 isoform preparations contained a higher mol wt component that is probably hFSH related, as this component was detected after iodination, immunoprecipitation with hFSH antiserum, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Similar amino acid compositions were obtained for the 20 hFSH isoforms, except for evidence of some oxidative degradation of serine, threonine, and tyrosine and decreased levels of glutamic acid, possibly due to carboxy-terminal heterogeneity of the beta-subunit. An average amino acid composition value for all isoforms was comparable to that of 2 other highly purified hFSH preparations. Using the First International Standard for pituitary hFSH (83/575) as standard, radioreceptor activities were obtained ranging from 7,800-56,300 IU/mg protein. It is concluded that a mild purification procedure for the isolation of hFSH isoforms has been developed which gives high recoveries and has enabled the isolation of 15 isoforms in high purity suitable for further physicochemical and biological characterization.

Aged↗
PubMed1992

Effects of activin and follicle-stimulating hormone (FSH)-suppressing protein/follistatin on FSH receptors and differentiation of cultured rat granulosa cells.

The aim of this study was to investigate the actions of both activin and FSH-suppressing protein (FSP)/follistatin either alone or in combination on FSH receptor number and on the responsiveness of granulosa cells to FSH and LH. Granulosa cells were harvested from diethylstilbestrol-treated immature Sprague-Dawley rats and cultured 48 h in serum-free medium with or without treatment. Activin treatment alone (3-100 ng/ml) resulted in a 4-fold increase in FSH receptor number with no change in binding affinity. This effect of activin was inhibited 31% by FSP (100 ng/ml) treatment which alone had no effect on FSH receptor number. Treatment with activin (100 ng/ml) prevented FSH-induced down-regulation of FSH receptor number, whereas at lower concentrations (3-30 ng/ml) activin enhanced down-regulation of FSH receptor number by 20% (P less than 0.05). In contrast, FSP alone prevented FSH-induced down-regulation by increasing FSH receptor number up to 40-50%. Pretreatment of granulosa cells with activin, but not FSP, for 24 h increased the responsiveness of cells to FSH (20 ng/ml) and LH (40 ng/ml) shown by increases in aromatase activity, progesterone, and immunoreactive inhibin production over and above control in a manner which depended upon activin doses. We conclude that 1) activin enhancement of FSH action on rat granulosa cells may be mediated in part via regulation of FSH receptor number, and 2) the effects of FSP on granulosa cells are likely to be due to its activin binding properties.

Activins↗
PubMed1992

Characterization of inhibin and related proteins in bovine fetal testicular and ovarian extracts: evidence for the presence of inhibin subunit products and FSH-suppressing protein.

Bovine fetal gonads have been shown previously to contain inhibin bio- and immunoactivity although the ratio of these activities was markedly lower in testicular compared with ovarian extracts throughout gestation. The basis for this difference is examined in this study. Fetal testicular and ovarian high-speed supernatant preparations from bovine fetuses aged 180 to 270 days of gestation were sequentially fractionated by dye affinity chromatography, gel permeation chromatography, reversed phase high-performance liquid chromatography and preparative polyacrylamide gel electrophoresis and monitored by inhibin radioimmunoassay and in-vitro bioassay. Three immunoactive fractions were identified in testicular extracts with molecular masses of 30 kDa (Peak I), 43 kDa (Peak IIa) and 29 kDa (Peak IIb). Peak I material only was bioactive. On the basis of these characteristics, Peak I is probably 31 kDa inhibin as previously described, and Peaks IIa and IIb are probably different inhibin alpha subunit precursor fragments. In ovarian extracts, two bio- and immunoactive fractions were identified with molecular masses of 30 kDa (Peak I) and 29 kDa (Peak II). On the basis of size, and biological and immunological activities, the ovarian extract Peak I material is probably bovine 31 kDa inhibin, while the Peak II material is probably a novel inhibin-like protein. FSH-suppressing protein (or follistatin) bio- and immunoactivities were also identified in both testicular and ovarian extracts. It is concluded that the low ratio of inhibin biological/immunological activity in testicular extracts is attributed to the presence of high concentrations of immunoactive alpha subunit precursor fragments which are low to non-detectable in ovarian extracts. These results support our previous hypothesis that, in contrast to the ovary, the inhibin alpha subunit is produced in excess in the fetal testis.

Animals↗
PubMed1992

Sclerochoroidal calcification.

We studied 19 patients with sclerochoroidal calcification. The findings were bilateral in 16 patients and unilateral in the remaining three patients. The lesions, which were usually multifocal, had two characteristic appearances, plaque-like and tumorlike. Eleven patients had relatively flat, irregularly shaped, plaque-like, yellow-white lesions located between the arcades and the equator. Eight patients had more elevated tumorlike lesions, ranging up to 6 mm in height. All showed patterns on echography consistent with calcification. The calcification was often documented in both the choroid and sclera; sometimes it appeared only in the choroid, but never only in the sclera. Calcium metabolism appeared to be normal in all but two of the nine patients in whom it was investigated. Idiopathic sclerochoroidal calcification has a characteristic echographic and ophthalmoscopic appearance and may be more common than has been realized.

Aged↗
PubMed1991

Pathologic findings of photic retinopathy in the human eye.

The macular retina of a patient whose eye was scheduled for enucleation because of progressive growth of a malignant melanoma that had invaded the iris and filtration angle was exposed to unfiltered light from the operating-room microscope for 60 minutes. Photic maculopathy was documented with fundus photography and fluorescein angiography 67 hours after light exposure. Seventy-two hours after light exposure, the eye was enucleated, fixed in Trumpe's solution, and studied with light microscopy and electron microscopy. Findings included localized necrosis of the retinal pigment epithelium; loss of the apical villi, plasma membranes, and cytoplasmic organelles; extrusion of pigment granules; and extensive disruption of the outer lamellae of the photoreceptors. The inner segments of the photoreceptors were edematous and contained swollen mitochondria. Near the margins of the photic retinopathy, thinned retinal pigment epithelial cells appeared to have migrated under injured retinal pigment epithelial cells, suggesting early attempts at repair. Additional findings included Müller-cell swelling.

Eye↗
PubMed1991

Elevation of follicular phase inhibin and luteinizing hormone levels in mothers of dizygotic twins suggests nonovarian control of human multiple ovulation.

OBJECTIVE: To determine whether multiple ovulation in mothers of spontaneous dizygotic (DZ) twins is because of higher hypothalamic stimulation or is in response to lower serum levels of ovarian inhibin. DESIGN: Serum hormone levels were measured at five times throughout the cycle in a sample of eight mothers of DZ twins and paired controls. On day 12, ovarian ultrasonography was performed. SETTING: Blood samples were collected in participants' homes except on day 12 when they were collected at the ultrasonography clinic. PATIENTS, PARTICIPANTS: Human volunteers who had at least one set of spontaneous DZ twins were paired with controls matched for age and parity. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Serum inhibin, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) levels on approximate cycle days 1,2,8,12, and 21. RESULTS: Serum inhibin levels were elevated throughout the cycle (significantly on day 1) in mothers of DZ twins. Also elevated were early follicular FSH levels, LH levels throughout the follicular phase (significantly on days 1,2, and 8), and early to midfollicular E2 (significantly on day 8) in DZ mothers, indicative overall of greater follicular activity. CONCLUSION: It is concluded (1) that the primary cause of multiple ovulation in humans is not a decrease in inhibin secretion from the ovary; (2) the increased secretion of FSH and LH may be caused by elevated secretion of, or sensitivity to gonadotropin-releasing hormone; and (3) the elevated inhibin and E2 levels are a response to increased gonadotropin release.

Female↗
PubMed1991

Steroidogenesis-stimulating activity in the gonads: comparison of rat testicular fluid with bovine and human ovarian follicular fluids.

The steroidogenesis-stimulating activities of ovarian follicular fluid from bovine (bFF) and human (hFF) sources, were compared with those of adult rat testicular fluid (rTF) using an in vitro bioassay system based on stimulation of testosterone production by purified adult rat Leydig cells during a 20-h incubation. Rat TF and bFF were charcoal-treated to remove steroids prior to assay, and the major active fraction of hFF was collected after gel-permeation chromatography. All three fluid samples stimulated both basal and maximal hCG-stimulated testosterone production, although the resulting log dose-response lines of bFF and the hFF extracts were not parallel with those of rTF. Both rTF and bFF were active over a similar dose range (5.2-150 microliters and 9.7-150 microliters, respectively) and both had a more than additive interaction with hCG on testosterone production. The stimulatory activity of the hFF extract was considerably greater than that of either rTF or bFF in the absence of hCG, but hFF extract had only an additive effect with hCG in stimulating testosterone production. Moreover, unlike rTF activity, which was inhibited by co-incubation with the protein synthesis inhibitor, cycloheximide, the activity of the hFF extract was not affected by cycloheximide. The factors responsible for activity in all three fluids were of a large molecular size (greater than 30 kDa), as determined by ultrafiltration or gel-permeation chromatography. However, in contrast to both rTF and bFF, hFF extract activity was removed by charcoal extraction. Human FF extract was inactivated by heat (100 degrees C, 30 min), whereas rTF activity was partially (70%) heat-labile and bFF was not affected by heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ophthalmic manifestations of tuberous sclerosis.

The ophthalmic manifestations of tuberous sclerosis include a variety of nonretinal ophthalmic findings which, other than adenoma sebaceum of the lids, are uncommon. Approximately half the patients with tuberous sclerosis have retinal or optic nerve hamartomas; in half of these patients the hamartomas occur bilaterally. Three basic morphologic types of retinal hamartomas are recognized: the most common type is a subtle, relatively flat, smooth-surfaced, salmon-colored, semitransparent, and circular or oval-shaped lesion located in the superficial retina, most commonly near or at the posterior pole. The second type is an easily recognized opaque, white, elevated, multinodular calcified lesion that is frequently described as resembling a mulberry. A third type of lesion contains features of the other two, being calcified and nodular centrally, whereas its perimeter is semitranslucent, smooth, and salmon-colored. The hamartomas may be richly vascularized. They generally do not grow, but over decades some of the lesions may become calcified. Visual loss from retinal and optic nerve hamartomas rarely occurs. Because growth and change of the fundus lesions are rare, treatment is not indicated. Retinoblastoma of the optic nerve and retina is the most important lesion that must be differentiated from the hamartomas seen with tuberous sclerosis.

Blindness↗
PubMed1991

The radioimmunoassay of follicle-stimulating hormone (FSH)-suppressing protein (FSP): stimulation of bovine granulosa cell FSP secretion by FSH.

A RIA for bovine (b) FSH-suppressing protein (FSP) was developed using an antiserum raised in a rabbit to purified 39-kDa bFSP, iodinated 35-kDa FSP as tracer, and purified 35-kDa bFSP as standard. Purified 35-kDa FSP was iodinated using the iodogen procedure, and the iodinated FSP was purified by dye affinity chromatography. After a logit log-dose transformation of the dose-response curves, parallel displacement lines were observed between 31-, 35-, and 39-kDa FSP, bovine follicular fluid, bovine granulosa cell culture medium, and medium from bovine granulosa cells stimulated with bFSH. The specificity of the assay was investigated by comparing the immunoassay levels of FSP with in vitro bioassay levels based on the ability of FSP/inhibin to suppress FSH in rat anterior pituitary cell cultures in fractions obtained throughout the purification procedure of FSP from bovine follicular fluid. This demonstrated that 1) the FSP immunoactivity was associated with in vitro bioactivity in all fractions of the purification procedure; 2) a number of inhibin-related and other proteins showed low (less than 0.5%) or nondetectable cross-reactivity in the RIA; and 3) the in vitro biological to immunological ratios for 31-, 35-, and 39-kDa FSP were similar, indicating that the RIA detects all forms of purified bFSP. The secretion of FSP by bovine granulosa cells in culture was investigated in the presence and absence of bFSH and bLH, respectively. FSP production was proportional to granulosa cell number and decreased from highest levels at 24 h to lowest levels at 96 h of culture. The addition of either bFSH or 8-bromo-cAMP to the culture medium stimulated FSP production by a factor of 2-3 at 48 and 72 h of culture, while the addition of bLH had no effect on FSP production. Theca interna tissue cultured under the same conditions did not produce FSP. In contrast to FSP, stimulation of bovine granulosa cells with bFSH or bLH had no effect on inhibin production during the 96 h of culture, while the addition of bFSH and bLH caused a stimulation of progesterone production at 48 and 72 h of culture. It is concluded that 1) the RIA described here is specific for all mol wt forms of bFSP; 2) FSP was secreted by bovine granulosa cells and not thecal cells in vitro; and 3) FSP secretion by bovine granulosa cells in vitro is regulated by bFSH and not bLH.

Animals↗