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Biomedical subjects

D M Robertson

Publications and source records attributed to D M Robertson.

At least 325 records · Page 18Linked to original sources
PubMed1978

Biological and immunological characterization of human luteinizing hormone: IV. Biological and immunological profile of two international reference preparations after electrofocusing.

The first IRP of Human Pituitary Gonadotrophins (FSH/LH) for bioassay (69/104) and the 1st IRP of Human Pituitary Luteinizing Hormone (LH) for immunoassay (68/40) were fractionated by an electrofocusing technique in a sucrose density gradient and the profile of biological and immunological activities was determined. The partially purified LH preparation (69/104) gave a broad pattern of biolgical and immunological activities which extended from pH 4 to 10. The biological : immunological (B/I) ratio of the various fractions (using the 68/40 preparation as standard) ranged from 0.04 to 1.05. The low B/I ratios indicate the presence of high levels of immunologically active, biologically inactive material in this preparation. In contrast to the behaviour of the 69/104 preparation, the major proportion (88%) of the biological activity recovered after electrofocusing of the highly purified LH preparation (68/40) was found within the pH range 7--9, with B/I ratios (again using as standard the 68/40 preparation) ranging from 0.4 to 1.5. Multiple dose parallel line design radioimmunoassays revealed a lack of parallelism between the 69/104 and 68/40 International Reference Preparations. This was attributed to the presence of acidic material in the former preparation, which is practically absent from the latter. The biological LH profiles of both the 69/104 and 68/40 preparations differed from those previously reported for aqueous extracts of pituitaries. It is concluded that the dissimilarity in the electrofocusing profiles of the biological and immunological activities of the 69/104 preparation renders this preparation unsuitable as a reference preparation for the quantitation of biologically active LH by radioimmunoassay methods. Using the same criteria, the 68/40 preparation would appear to be a more suitable standard.

Animals↗
PubMed1978

Studies on a human chorionic gonadotrophin-like material present in non-pregnant subjects.

The presence of an hCG-like material in urinary and pituitary extracts and plasma obtained from non-pregnant subjects was investigated. Two assay methods were used to detect this material following fractionation of pituitary and urinary extracts by gel filtration (Ultrogel AcA 54) and/or isoelectrofocusing: a) a radioimmunoassay employing an antiserum raised against a specific sequence of the carboxy terminal region (residues 115--145) of the beta-subunit of hCG, and b) an in vitro bioassay method which measures both hLH and hCG activities. The fractionation procedures employed provide a satisfactory separation of highly purified hCG and hLH preparations. In the pituitary and urinary extracts hCG beta-peptide-like immunoactive (PIA) material was found consistently, which co-eluted with iodinated hCG following gel filtration and possessed pI values similar to those of hCG when subjected to isoelectrofocusing. The PIA material also exhibited in vitro biological activity similar to that shown by hLH and hCG. Detectable levels of immunoactive material were also found in plasma; however, the plasma levels of this PIA material were not influenced by classical endocrine measures such as the stimulation or inhibition of gonadotrophin secretion. The low levels of this material in plasma precluded its further characterization by gel filtration or electrofocusing. Whereas the present data and those reported by other investigators seem to suggest the presence of some hCG-like material in urinary and pituitary extracts and possibly in plasma of non-pregnant subjects, it is emphasized that the available evidence is not sufficiently conclusive to exclude other interpretations as to the nature of this material.

Biological Assay↗
PubMed1978

Influence of the purity of the iodinated tracer on the specificity of the radioimmunoassay of human luteinizing hormone.

Human luteinizing hormone (HLH) iodinated with 125I by the use of a lactoperoxidase method, was fractionated by either cellulose adsorption, gel filtration or by the combination of these methods. The products of iodination were characterized by their in vitro biological LH activity and by their binding profiles with antisera to HLH, HLHalpha and HLHbeta subunits. Several radioactive components were obtained after gel filtration with or without an initial cellulose adsorption step. One of these fractions was identified as biologically active HLH and another as the HLHalpha subunit. Radioimmunoassay studies were conducted with different iodinated fractions as tracers, using three well defined and widely available antisera to HLH. The standard used was the HLH International Reference Preparation for immunoassay (68/40). Cross-reactivity was examined with several purified pituitary preparations, such as HFSH, HTSH, HLHalpha and HLHbeta subunit. A significantly higher cross-reactivity with HLHalpha, HFSH and HTSH was obtained with the [125I]HLHalpha fraction as tracer than with biologically active [125I]HLH. Furthermore, in the radioimmunoassay of HLH preparations of varying purity, significantly higher estimates of immunological activity were obtained with the [125I]HLHalpha tracer than with the biologically active [125I]HLH. It is concluded that the presence of [125I]HLHalpha in the [125I]HLH tracer can result in serious overestimates of the immunological activity in the measurement of LH. Therefore [125I]HLHalpha should be separated from [125I]HLH prior to radioimmunoassay. Many of the fractionation methods commonly used (cellulose adsorption and short column gel filtration systems) are inadequate for this purpose. However, an adequate separation can be achieved by the use of high resolution gel filtration systems.

Biological Assay↗
PubMed1978

Delayed absorption of subretinal fluid after scleral buckling procedures: the significance of subretinal precipitates.

A delay in absorption of subretinal fluid after surgical repair for rhegmatogenous retinal detachment beyond 6 weeks was recognized in 39 of 575 consecutive cases undergoing scleral buckling procedures. The most common preoperative condition that was identified in these eyes was large clumps of cells on the undersurface of the detached retina. These cream-colored aggregates appeared similar to mutton-fat keratic precipitates and are referred to as subretinal precipitates. Most likely caused by aggregates of macrophages, they were present in 12 percent of the overall series of cases; subretinal precipitates also were recognized and documented before operation in nearly half of the eyes with delayed fluid absorption, a relationship that is highly significant in statistical analysis (P less than 0.001). On recognizing them before operation, the clinician can expect that approximately a fourth of the eyes will have fluid persisting beyond 6 weeks from the time of surgical repair until complete absorption. A second relatively common condition associated with delayed absorption of fluid that could be recognized in advance of surgical treatment was a long-standing peripheral (usually inferior) retinal detachment, which typically spared the macula, was associated with demarcation lines, and was caused by round atrophic holes with or without lattice degeneration. The presence of demarcation lines (reflecting relatively long-standing retinal detachment) was also positively correlated with delayed fluid absorption (P less than 0.02). Other conditions associated with delayed absorption of fluid included detachments of long-standing duration by history (especially when associated with previous unsuccessful efforts to repair the retina), vitreoretinal traction, and conditions whereby the choriocapillaris-retinal pigment epithelial complex and been significantly disturbed. Such conditions included hemorrhage into the subretinal space as a complication of surgical relase of subretinal fluid, previous retinal surgery, and possibly heavy treatment with cryopexy, especially when associated with exudative detachment. An analysis of subretinal fluide from 39 eyes showed a positive relationship between protein concentration and duration of the detachment but no relationship to a variety of other factors, including the presence of subretinal precipitates. Commonly identified cellular structures in the subretinal space consisted of pigmentladen macrophages. When studied by electron microscopy, some of these were thought to have originated from the retinal pigment epithelium.

Absorption↗
PubMed1977

Hereditary vitelliform macular degeneration: variable fundus findings within a single pedigree.

A pedigree of 141 persons with hereditary vitelliform macular degeneration was studied. Of the 80 patients examined, 20 were affected. Fundus photographs of selected lesions in this pedigree demonstrated the broad spectrum of phenotypic expression of this hereditary disorder. This entity has an extremely variable expression even among affected members of the same family.

Adolescent↗
PubMed1977

The ocular manifestations of Behçet's disease.

Of 32 patients with Behçet's disease, 21 had uveitis. The uveitis was seldom the initial manifestation of systemic disease, but once established, it tended to become chronic and bilateral, involving the anterior and posterior segments. Hypopyon was a relatively uncommon occurrence in this series. All patients with uveal inflammation had obvious cellular reactions within the vitreous body. Other posterior segment manifestations of the disease included localized retinal edema, macular edema, disc edema, retinal pigmentary changes, and accumulation of exudative material in the deep retina. One patient developed a necrotizing retinitis with deep retinal exudation and subsequent retinal detachment. Occlusions of retinal vessels were common. Neuro-ophthalmologic manifestations of Behçet's disease included cranial nerve palsies, a homonymous hemianopic field defect, and papillitis.

Adolescent↗
PubMed1977

Pigmented preretinal membranes.

Continuous growth and an increase in pigmentation of a preretinal membrane occurred in a 46-year-old woman after a scleral buckling procedure for rhegmatogenous retinal detachment. Ten additional patients had pigmented preretinal membranes in eyes treated for rhegmatogenous retinal detachment. Although we made no attempts to determine the incidence of pigmented preretinal membrane formation in eyes with retinal detachments, these 11 cases, in a consecutive series of 500 eyes treated for rhegmatogenous retinal detachment, indicated that the development of pigmented preretinal membranes is not uncommon. Our clinical observations supported recent experimental findings implicating retinal pigment epithelial cells as a cause of preretinal membrane formation.

Female↗
PubMed1977

Biological and immunological characterization of human luteinizing hormone: I. Biological profile in pituitary and plasma samples after electrofocusing.

Pituitary and plasma pools from postmenopausal women and plasma pools from women at midcycle were fractionated by electrofocusing in sucrose density gradients. The biological LH activity was determined in each of the electrofocusing fractions by the use of an in vitro bioassay method. A heterogeneous profile of LH activity was found in both pituitary and plasma samples with a large proportion present within the pH range 6.5-10. In a total of 11 electrofocusing runs 7 main regions of high LH activity were found within this range with mean pI values (+/- SD) of 6.75 +/- 0.08 (n = 6), 7.33 +/- 0.08 (11), 7.80 +/- 0.09 (11), 8.23 +/- 0.10 (11), 8.81 +/- 0.04 (7), 9.17 +/- 0.05 (6) and 9.55 (2). A significantly higher proportion of LH activity was found in the midcycle plasma samples (36%) in the pH regions with mean pI values of 8.81, 9.17 and 9.55 than in postmenopausal plasma (7%) and pituitary extracts (5%). This indicates that the profile of biologically active LH in women in the fertile age is different from that present in postmenopausal women. By detailed fractionation based on narrow pH range studies and the refocusing of specific peak fractions it was shown that each of the regions studied consisted of several peaks of LH activity indicating the presence of a large number of molecular species exhibiting varying degrees of LH activity. The relative proportions of these species showed considerable differences between sources but also between samples from the same source.

Animals↗
PubMed1977

Biological and immunological characterization of human luteinizing hormone: II. A comparison of the immunological and biological activities of pituitary extracts after electrofocusing using different standard preparations.

The profile of immunologically active human luteinizing hormone (hLH) was determined in aqueous pituitary extracts after electrofocusing using two radioimmunoassay systems and the estimates for each fraction were compared to those obtained by an in vitro bioassay method. Similar biological and immunological profiles were obtained in the pH 7.0-9.0 region, where most of the biological activity was present. Biological to immunological (B/I) ratios ranging from 0.6 to 1.7 (mean ratio 1.01; n = 21) were found in the major biologically active fractions of this pH region when a highly purified human pituitary LH preparation (68/40) was used as standard in both types of assays. The close proximity of these ratios to unity indicates a similar composition of biological and immunological activities in all these fractions in relation to that of the highly purified standard. However, marked discrepancies were observed in the pH region 3.0-7.0 where the B/I ratios ranged from 0.1 to 0.9, indicating the presence of immunological activity associated with relatively little biological activity. When impure human LH preparations of pituitary (69/104) and urinary (hMG 2nd IRP) origin were used as standards for the bioassay and radioimmunoassay of the hLH present in the major fractions of the pH region 7.0-9.0, significantly higher B/I ratios were obtained than with the use of the highly purified standard (68/40). These elevated B/I ratios are attributed to the presence in the impure standard preparations of immunological activity, which is associated with little or no biological activity. These observations may provide an explanation for the differences in B/I ratios which were reported for hLH in plasma, using different standard preparations.

Biological Assay↗
PubMed1977

Biologically active luteinizing hormone (LH) in plasma: II. Comparison with immunologically active LH levels throughout the human menstrual cycle.

The levels of biologically active luteinizing hormone were determined by an in vitro bioassay method in plasma samples collected daily over a complete menstrual cycle from 12 menstruating women. These cycles were normal according to a number of criteria, including daily plasma levels of oestradiol, 17-hydroxyprogesterone and progesterone. Immunoreactive LH was estimated in the same 12 cycles by a radio-immunoassay (RIA) procedure (HCG-RIA) using an HCG antiserum and iodinated HCG. The 2nd IRP of HMG was selected as standard although significant deviations from parallelism were found with 7 out of the 12 plasma pools studied. The use of the 1st IRP of human pituitary gonadotrophins (FSH and LH (ICSH)) for bioassay (herafter HPG-1st IRP) as standard in this system resulted invariably in invalid assays, due to lack of parallelism. Immunoreactive LH was also measured in 8 of the 12 cycles by a RIA procedure (HLA-RIA) using a human LH antiserum and iodinated human LH of pituitary origin. Results are expressed in terms of the HPG-1st IRP. The plasma levels of biologically and immunologically active LH were qualitatively similar throughout the menstrual cycle. However, the LH levels measured by the bioassay invariably exceeded those estimated by the RIA procedures. The biological to immunological (B/I) ratio over the entire menstrual cycle (312 comparisons) was 5.5 with 95% confidence limits at 5.2 and 5.8 when the HCG-RIA system was employed. Using the HLH-RIA system (208 comparisons), the corresponding ratio was 6.4 (6.0:6.9). When regression lines were calculated using the bioassay results as the independent variable and the RIA results as the dependent variable, the 95% confidence limits of the regression lines did not include the origin. Furthermore,, in keeping with the high B/I ratios, the slopes of the two regression lines and their conficence limits differed markedly from unity. It is concluded that although qualitatively similar profiles were observed between the biological and immunological activities throughtout the menstrual cycle, two aspects require further attention. Firstly, the elevated B/I ratios together with the behaviour of the dose-effect lines obtained with different standards in the various RIA systems suggest that presently available reference standard preparations of pituitary and/or urinary origin are not suitable for the assay of LH in human plasms. Secondly, from the regression analyses of the biological and immunological activities it is infered that the RIA methods detect immunological activity which is not associated with biological activity. If so, the validity of these RIA procedures for specifically measuring low levels of biologically active LH in plasma may be in question.

Adult↗
PubMed1977

Cerebral cortical changes in acute experimental hypertension: An ultrastructural study.

Multiple focal cortical areas of increased vascular permeability to tracer substances occur in experimental hypertensive encephalopathy. In this study, rats with angiotensin-induced acute hypertension were used to determine whether increased permeability was associated with focal cerebral edema and if so, the tissue component involved. In addition, the mechanism of increased permeability and the types of vessels involved were investigated using horseradish peroxidase as a tracer. Quantitative morphometric studies 8 minutes after the onset of hypertension demonstrated significant perivascular glial swelling around arterioles, venules, and capillaries; the swelling was confirmed to the permeable areas and absent in the nonpermeable areas of the same animals. Ninety seconds after the onset of hypertension, horseradish peroxidase reaction product was present in focal superficial segments of the walls of penetrating arterioles but rarely in venular and capillary walls. At this time period endothelial cells showed prominent pinocytotic uptake of tracer. Eight minutes after the onset of hypertension, reaction product was again found in arteriolar walls and had extravasated into the surrounding extracellular space of the neuropil as well. Extravasation also occurred through capillary and venular walls but was less frequent. At this time interval endothelial pinocytotic activity was still prominent. There was no mechanical damage of vessel walls in the form of endothelial discontinuities or disruption of interendothelial spaces. Tracer was not found in interendothelial jundtions in continuity from lumen to base. The principle mechanism of increased permeability was enhanced pinocytosis, which occurred rapidly, being demonstrable 90 seconds after the onset of hypertension; it was observed principally in permeable arteriolar segments.

Acute Disease↗
PubMed1977

Analysis of misdiagnosed retinoblastoma in a series of 726 enucleated eyes.

Of 726 eyes consecutively enucleated at the Mayo Clinic from 1954 through 1974, 41 contained retinoblastoma. In no instance was unsuspected retinoblastoma identified, nor could retinoblastoma be confirmed pathologically in an additional eight eyes in which retinoblastoma was considered in the differential diagnosis. In each of our eight misdiagnosed cases, the eyes were already blind and were cosmetically defective. The frequency of clinical misdiagnosis of retinoblastoma is high in part because it must be considered in every case of leukokoria. Although every effort was made to arrive at an accurate clinical diagnosis, the clinical misdiagnosis of retinoblastoma in a blind eye is of far less serious consequence than the clinical misdiagnosis of a tumor in a seeing eye.

Child, Preschool↗
PubMed1976

Cycloleucine uptake in the brainstem of thiamine-deficient rats.

Immature female rats were subjected to acute dietary deficiency of thiamine. An autoradiographic method was used in the semi-quantitative determination of concentration of 1-aminocyclopentane-1-carboxylic acid-carboxylic-14C (cycloleucine) in brainstem regions after intravenous administration of tracer quantities. The time course of tissue concentrations was followed and compared with that of normal and isocaloric control animals. Our data indicate that thiamine deficiency of sufficient magnitude to induce brainstem lesions has an effect on the transport of cycloleucine. The initial 2 min values in the nuclear areas are appreciably reduced whereas the 6 min values are significantly elevated as compared with controls; no change was demonstrated in the white matter of the inferior cerebellar peduncle. The effect on transport appears to be more on the mechanism of efflux than of influx in terms of blood brain barrier function.

Amino Acids↗
PubMed1976

Retinal lesions in tuberous sclerosis.

Retinal lesions in 116 patients with tuberous sclerosis included three types: the relatively flat, semitransparent, non-calcified tumors; the more commonly described nodular, calcified tumors; and a third lesion that possessed features of the other two. Other less definite pigmented and plaque-like lesions also were seen. The evolution of a relatively flat, noncalcified lesion into an elevated nodular, apparently calcified lesion during an interval of two decades was photographically recorded.

Eye Neoplasms↗