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Biomedical subjects

D M Robertson

Publications and source records attributed to D M Robertson.

At least 307 records · Page 17Linked to original sources
PubMed1979

Influence of the purity of the iodinated tracer on the specificity of the radioimmunoassay of human follicle-stimulating hormone.

The objective of this study was to establish whether [125I]hFSH subunits are formed during iodination of hFsh by a mild (lactoperoxidase) technique, and if so which fractionation procedure provides the best separation of [125I]hFSH from its subunits. In addition, the effect of the 125I subunits on the specificity of the hFSH radioimmunoassay technique was examined. The products of iodination of hFSH were fractionated by a number of techniques consisting of low and high resolution gel filtration procedures and adsorption on either cellulose of Concanavalin A coupled to Sepharose. The efficacy of the adsorption methods was assessed by a subsequent high resolution gel filtration procedure (Ultrogel AcA 54). Radioreceptor and radioimmunoassay methods were used to monitor the profiles of hFSH, hFSH alpha and hFSH beta subunits and to assess the recoveries of radioreceptor-active hFSH obtained by the different procedures. Iodination of a highly purified hFSH preparation invariably resulted in the formation of both [125I]hFSH subunits. The proportion of radioactivity associated with the 125I subunit peak to that of the [125I]hFSH peak was 10% when the iodination products after low resolution gel filtration were fractionated by a high resolution gel filtration procedure. The corresponding amount of subunits obtained by adsorption on cellulose and Concanavalin A was 71% and 6%, respectively. Thus in comparison with low resolution gel filtration there was a partial separation of [125I]hFSH from [125I]hFSH subunits on Concanavalin A while no separation was effected on cellulose. In fact, the results suggest that 125I subunits were formed during fractionation on cellulose. The recoveries of hFSH activity following fractionation on cellulose and Concanavalin A were significantly lower (27% and 65%) than those obtained by either low or high resolution gel filtration techniques. A marked reduction ;n the specificity of the RIA of hFSH was found when [125I]hFSH subunits rather than [125I]hFSH were used as tracer in the assay. It is concluded that the presence of 125I subunits in [125I]hFSH preparations used as tracer in the RIA of hFSH can diminish the specificity of the assay. The routine employment of a high resolution gel filtration procedure which provides a complete separation of 125I subunits from the intact hormone, is suitable for the elimination of this source of assay invalidity while the other fractionation procedures tested (cellulose adsorption or Concanavalin A) are not.

Adsorption↗
PubMed1979

Effect of storage on the bioactivity of two international reference preparations of human pituitary luteinizing hormone in vitro.

There was no loss of biological activity in vitro when the 1st International Reference Preparation (IRP) for human pituitary gonadotrophins [FSH and LH/interstitial cell stimulating hormone (ICSH) for bioassay] code no. 69/104 and the 1st IRP for human pituitary LH/ICSH [for immunoassay] code no. 68/40 were stored for 1 year at -70 degrees C in a buffered 0.8% saline solution containing 1% bovine plasma albumin (BPA). However, storage of the 69/104 preparation at -20 degrees C in either 0.1 or 1% BPA, or at -70 degrees C in the presence of 0.1% BPA showed a small but significant decrease (approximately 10%) in activity over the same period. It is, therefore, advantageous to store these reference preparations at -70 degrees C in the presence of 1% BPA.

Drug Storage↗
PubMed1979

Subependymal giant-cell astrocytoma. Case report with ultrastructural study.

A 13-year-old boy presented with an obstructive left lateral intraventricular mass. Pathological examination revealed a subependymal giant-cell astrocytoma. Further clinical investigation confirmed the diagnosis of tuberous sclerosis. Ultrastructural examination confirmed previously reported features of this tumor. Tumor cells containing large dense granulated bodies and dense-core vesicles, not previously described in this tumor, were identified.

Adolescent↗
PubMed1979

Biologically active luteinizing hormone (LH) in plasma. III. Validation of the in vitro bioassay when applied to male plasma and the possible role of steroidal precursors.

An in vitro bioassay method for measuring LH activity was applied to male plasma. This method is based on the specific testosterone response to LH activity by interstitial cells from mouse testes. In contrast to assays conducted on female plasma, non-parallel response lines were obtained between serial dilutions of untreated male plasma and the International Reference Preparation for Human Pituitary Gonadotrophins FSH and LH/ICSH) for bioassay (code no. 69/104). In an attempt to eliminate this source of error, which would invalidate the assays, plasma was subjected to either ether extraction or charcoal adsorption prior to assay. While ether extraction was ineffective, charcoal treatment eliminated the source of non-parallelism. Evidence is presented indicating that the inclusion of a charcoal pre-treatment step provides an assay method for LH which fulfils the recognized criteria of reliability when applied to male plasma. An investigation of the likely causes of non-parallelism was undertaken by incubating mouse interstitial cells with various steroids and steroid sulphates at concentrations likely to be present in plasma. While most of the presumed precursors of testosterone were converted to testosterone, steroid sulphates (dehydroepiandrosterone sulphate and pregnenolone sulphate) at high concentrations as present in male plasma were the most active compounds in forming testosterone. However, the amount of testosterone produced from these precursors under controlled conditions was insufficient to account entirely for the deviation from parallelism observed with male plasma. Hence, the non-parallelism observed with untreated plasma samples cannot be entirely explained by the presence of steroidal testosterone precursors in male plasma.

Adsorption↗
PubMed1979

Peripheral neuropathy in the diabetic mutant mouse. An ultrastructural study.

Structural changes in peripheral nerves were studied sequentially in mutant diabetic mice. Axonal changes were found in both myelinated and unmyelinated fibers, the outstanding early change being the development of honeycombed Schwann cell-axon networks followed by axonal atrophy in both myelinated and unmyelinated fibers. In the late stages of the diabetic syndrome, this axonopathy was accompanied by secondary corrugated myelin breakdown. The changes, indicative of a primary axonal degeneration, are comparable to findings in human diabetic neuropathy for which this seems a suitable experimental model.

Animals↗
PubMed1979

Biologically active luteinizing hormone (LH) in plasma. V. A re-analysis of the differences in the ratio of biological to immunological LH activities during the menstrual cycle.

The relationship between the biological and immunological activities of human luteinizing hormone (hLH) in plasma collected from female subjects was examined. The biological activity was measured by an in vitro bioassay and the immunological activity by an hLH radioimmunoassay (RIA), using improved reagents, such as the 1st IRP for human pituitary LH for immunoassay (code No. 68/40) as standard, a subunit-free biologically active iodinated hLH preparation as tracer and an anti-hLH serum of relatively high specificity. Similar profiles of biological (B) and immunological (I) activity were obtained in the plasma samples collected daily throughout 40 menstrual cycles (5 cycles from each of 8 subjects). However, the B/I ratios were significantly lower during the period of LH surge (P less than 0.001) than throughout the remainder of the cycle. The within- and between-assay variation in B/I ratios was investigated by the simultaneous assay of biological and immunological activities in plasma pools obtained by combining equal aliquots of plasma from each daily sample of the menstrual cycle from each of 5 cycles of each of 4 subjects. The analysis of these 20 pools revealed highly significant individual differences in B/I ratios, ranging from 0.81 to 1.33. The coefficient of variation was 20% between-subjects and 5% within-subjects. There was no seasonal variation in B/I ratios. That the individual differences in plasma B/I ratios were not attributable to the procedure of pooling was ascertained by the simultaneous assay of both activities in parellel in daily plasma samples and in the pools formed from these samples from three complete cycles. Thus the analysis of the differences in B/I ratios obtained throughout the menstrua- cycle revealed three major sources of variation. The first occurs in the form of generally elevated (higher than unity) B/I ratios, the second consists of a significant drop in B/I ratios during the midcycle LH surge, and the third source is represented by the significant between-subject differences. It is concluded that the first source is attributable to the relatively higher levels of "impurity" (i.e. biologically inactive, immunologically active material) in the standard preparation compared to those present in plasma of biologically inactive, immunologically active material of unknown composition and origin. If so, the latter source limits the quantitative significance of the RIA procedures employed. It is suggested that these three sources of variation account for most of the differences in B/I ratios for plasma lLH reported in the literature.

Adult↗
PubMed1978

The perineurial and blood-nerve barriers in experimental diabetes.

The permeabilities of the blood-nerve barrier and the perineurial barrier were investigated in alloxan and streptozotocin diabetic rats and in the mutant diabetic mouse [C57BL/Ks(db/db)]. In the mouse model both fluorescence and electron microscopic techniques were employed using Evans blue albumin (EBA) and horseradish peroxidase (HRP), respectively, as exogeneous tracers. In the rat models only HRP was used. Tracers were applied locally around the sciatic nerve in order to investigate the perineurial barrier, and systemically to detect changes in the blood nerve barrier. None of the models was found to show increased permeability across either of the barriers.

Animals↗
PubMed1978

Induction of a tumor with greatly increased metastatic growth potential by injection of cells from a low-metastatic H-2 heterozygous tumor cell line into an H-2 incompatible parental strain.

An H-2 heterozygous sarcoma, MDAY, originally induced with methylcholanthrene in an (A X DBA/2)F1 ((H-2a X H-2d) hybrid host was selected for growth in the H-2d homoxygous parental DBA/2 strain by serial intraperitoneal transplantation of ascites tumor cells. An apparent variant, designated MDAY-D2, was obtained which showed the expected loss of the private and public H-2Kk haplotype antigens normally associated with the A strain parent and the original MDAY tumor. Comparison of the original and variant lines revealed a wide variety of a cell surface antigen and receptor differences. Both tumors were found to be highly anaplastic and histologically unclasssifiable. Examination of the two tumor lines growing in vivo revealed a remarkable difference in their metastatic growth potential. The original MDAY line showed little propensity to spread to any organ site, with the occasional exception of liver, after subcutaneous inoculation of (A X DBA/2)F1 mice. In striking contrast, there was a rapid and massive spread of MDAY-D2 to liver, spleen, lungs and kidneys within 12-16 days: liver and spleen could be totally replaced by tumor within 2-3 weeks. These characteristics were observed in both (A X DBA/2)F1 and DBA/2 mice. The tendency to metastasize, as well as loss of the H-2Kk haplotype, appeared stable and irreversible. Although the precise origin of MDAY-D2 is not clear, its metastasizing properties are unique, making it a useful and desirable model to study the biology of metastasis.

Animals↗
PubMed1978

Peripheral neuropathy in mutant diabetic mouse [C57BL/Ks (db/db)].

A new animal model for the study of diabetic neuropathy is presented. The homozygote (db/db) of the mouse strain C57BL/Ks shows severe diabetes with longstanding hyperglycemia. Electrophysiological studies showed severely decreased motor nerve conduction velocity. Morphometric examination of sensory and motor nerves at different levels revealed absence of large myelinated fibers, with morphological features indicative of axonal atrophy.

Animals↗
PubMed1978

Involvement of peripheral nerve and muscle in Fabry's disease. Histologic, ultrastructural, and morphometric studies.

Light microscopic and ultrastructural studies of biopsy specimens from the sural nerve and the gastrocnemius muscle in a patient with Fabry's disease showed accumulation of lipids in endothelial and perithelial cells of the vessel walls. In addition, the peripheral nerve exhibited deposition of lipids in the perineurial cells, occasionally in unmyelinated and myelinated axons, and infrequently in Schwann cell cytoplasm. In the muscle biopsy specimen, stored lipid was found in the sarcoplasm. Quantitative histologic studies showed loss of large unmyelinated and thin myelinated nerve fibers. Excruciating pain and loss of sweating, characteristic of this disorder, may result from loss of these fiber categories. The peripheral neuropathy is probably secondary to perikaryal deposition of lipid as described previously in the literature.

Adolescent↗
PubMed1978

Cavernous hemangioma of the retina.

Cavernous hemangioma of the retina is recognized as a distinct clinical entity. Although neurocutaneous findings are sometimes associated with these retinal tumors, in most of the cases reported to date, systemic features have not been described. This report describes two patients with cavernous hemangioma of the retina. One had neurologic symptoms and signs that were highly suggestive of a hemangioma of the brain stem, and the other had major congenital cardiovascular anomalies. During a five-year interval, the second patient had spontaneous incomplete sclerosis of the retinal hemangioma.

Adult↗
PubMed1978

Cytoplasmic filaments in intracerebral cortical vessels.

Actin filaments measuring 5 nm in diameter are present in the endothelium of systemic vessels and presumably have a contractile function that may be related to vascular permeability. Little attention has been directed to the presence of similar cytoplasmic filaments in the endothelium of cerebral vessels. This study was undertaken to determine whether filaments are present in the endothelial cells of intracerebral cortical vessels of rats and humans. Ultrastructural studies revealed two populations of endothelial cytoplasmic filaments 5 nm and 10 nm in diameter, respectively. The 5-nm filaments were abundant in the endothelium of penetrating cortical arterioles, being grouped near the cytoplasmic margins in proximity to cell junctions and along the abluminal side of the endothelial cells. The filaments were scant in capillaries and venules.

Animals↗
PubMed1978

Acute macular neuroretinopathy.

A 17-year-old boy had minor visual impairment, paracentral scotomata, and parafoveal retinal lesions following a presumed viral infection. Contact lens biomicroscopy demonstrated the retinal defects to be located at the level of the deep sensory retina. Fluorescein angiography revealed subtle areas of hypofluorescence which corresponded to the visible disturbances of the sensory retina. Follow-up examination three months later revealed persistent complaints of paracentral scotomata and persistent, but less recognizable retinal lesions. We believe the primary site of involvement to be the deep sensory retina.

Acute Disease↗