Biomedical subjects

D M Robertson

Publications and source records attributed to D M Robertson.

At least 343 records · Page 19Linked to original sources

PubMed1976

Preliminary observations of bone ingrowth into porous materials.

A preliminary investigation has been performed (a) to determine the kinetics of bone ingrowth into porous materials and to determine if this ingrowth could be catalyzed by the presence of a foreign substrate; and (b) to measure the bonding capability of bone with a porous-surfaced metallic implant. Tests on porous-surfaced implants corroborate the work of other investigators in showing that bony tissue will grow into a porous substance that has pores large enough to support tissue nourishment. The shear strength of the bone-implant interface appears to increase with pore size and time of healing. Furthermore, it may be possible to catalyze this tissue ingrowth by the introduction into the fracture site of a foreign substance; in this experiment, glass beads 200-290mu in diameter were used.

Animals↗

PubMed1976

Safety glasses as protection against shotgun pellets.

I designed this experiment to determine if spectacle lenses would protect against a No. 6 shot fired from a 12-gauge shotgun over progressively longer testing distances, and compared plastics, heat-tempered glass, and chemical-tempered glass lenses of standard and industrial thicknesses. The likelihood of a spectacle lens being hit by a well-centered shot pattern at 40, 50, and 60 yards was approximately 66%, 25%, and 20%, respectively. Virtually all lenses were destroyed at a testing distance of 30 yards. At 40 yards, standard-thickness plastic and heat-tempered lenses were destroyed but the chemical-tempered lenses offered some protection. At 40 yards, all types of industrial-thickness lenses provided protection but the most protection was provided by the chemical-tempered lenses. At 50 yards, chemical-tempered lenses offered more protection than either plastic or heat-tempered lenses. Throughout the experiment, plastic lenses performed no better than heat-tempered lenses.

Eye Injuries↗

PubMed1976

Radioactive phosphorus uptake testing of choroidal lesions. A report of two false-negative tests.

Two false-negative results from 32P testing for histologically verified malignant melanomas of the choroid are reported. In the first case, a haemorrhagic choroidal detachment caused an increase in probe; additionally, the tumour was necrotic. Both factors are likely to have contributed to the false-negative result. A satisfactory explanation for the false-negative result in the second case was not determined, although it may have accurately reflected a period of minimal tumour activity, inasmuch as repeat 32P testing was strongly positive eight months later, when unequivocal evidence of tumour growth was present. An alternative explanation is that the orally administered 32P was incompletely absorbed. Since 32P testing is frequently accompanied by significant manipulation both in the manoeuvre associated with tumour localization and in that associated with the actual radioactive counting, it would seem desirable to perform indicated enucleation immediately after completion of the 32P testing. While the properly performed 32P test remains a valuable diagnostic test for helping to establish the presence or absence of malignancies of the posterior globe, it is important to guard against the tendency to underestimate careful clinical evaluation.

Aged↗

PubMed1976

Biologically active luteinizing hormone (LH) in plasma. 1. Validation of the in vitro bioassay when applied to plasma of women.

A recently described in vitro bioassay method for the measurement of biologically active LH (Van Damme et al. 1974) has been applied to the plasma of normally menstruating and post-menopausal women. The specificity of the procedure was established according to the following evidence: 1. Parallelism was observed between dose response curves obtained with serial dilution of a standard LH preparation (HMG 2nd IRP) and plasma pools collected during the follicular phase, at the LH-peak, during the luteal phase and after menopause. 2. There was no evidence for the presence of any synergistic or antagonistic factor in the various plasma specimens. The assay design used to establish this consisted of assaying the standard and plasma pool separately and then together as a mixture followed by an assessment of the difference (if any) in the potencies obtained. Strict additivity should yield a relative potency of 1.0. Plasma pools which were obtained every 2-3 days throughout the menstrual cycle were assayed using this design against the standard (HMG 2nd IRP) and against a mid-cycle plasma pool obtained at the time of the LH-peak. The latter was also assayed against partially purified plasma fractions obtained from a post-menopausal plasma pool after gel filtration and isoelectric focusing. With the exception of 3 assays, in which the estimates of relative potency were 0.91, 0.94 and 0.95, respectively, in 19 assays of additivity, the fiducial limits always included unity. 3. Non-detectable LH levels were found in the plasma or serum of either hypophysectomized or hypopituitary hypogonadal men or women treated with oestrogen/progestogen combined pills. 4. The presence of calf of human serum in the assay medium is an essential requirement for a valid comparison of standard and unknown preparations. In their absence, non-parallel dose response curves between plasma and stardard were obtained. The other established criteria of reliability (sensitivity and precision) were also examined. The method is sufficiently sensitive (3.5-8.0 mIU/ml plasma; HMG (2ng IRP) as standard) for the measurement of LH throughout the cycle. The mean index of precision (gamma) in 230 multiple assays was 0.040. It is concluded that the modified bioassay yields valid and reliable estimates of LH when applied to human plasma obtained throughout the menstrual cycle and after menopause.

Biological Assay↗

PubMed1975

Optochiasmatic arachnoiditis in multiple sclerosis.

A patient had visual field loss and optochiasmatic arachnoiditis and subsequently developed other evidence of multiple sclerosis. The possibility is raised that many of the "idiopathic" cases of optochiasmatic arachnoiditis may have a similar origin. Special emphasis is placed on the functional role of the fibrosis in the pathogenesis of optochiasmatic arachnoiditis.

Arachnoiditis↗

PubMed1975

Adult cytomegalovirus inclusion retino-uveitis.

A 27-year-old male renal transplant recipient acquired cytomegalovirus (CMV) infection of both eyes. This was characterized early by a distinctive necrotic retinitis with discrete advancing edges. A large exudative retinal detachment and hypopyon developed in one eye, and cultures from the anterior chamber aspirate grew CMV. Cytomegalovirus was also isolated from the urine and throat; after serial negative base-line titers, CMV antibody titer became positive. At autopsy CMV was isolated from lung, esophagus, and kidney tissue. Light and electron microscopic studies demonstrated extensive necrosis and disruption of the sensory retina and retinal pigment epithelium with exudative retinal detachments. The diseased retinal cells contained a multiplicity of viral particles in various stages of maturity. Cytomegalic inclusion-bearing cells were demonstrated in the choroid of the more severely affected eye.

Adult↗

PubMed1975

Ring scotomata in fundus flavimaculatus.

Ring scotomata were associated with fundus flavimaculatus in six patients. The demonstration of ring scotomata in patients with fundus flavimaculatus helps to explain persistent visual complaints that may exist in the presence of normal central visual acuity. In many instances, ring scotomata cannot be predicted on the basis of the ophthalmoscopic findings. The presence of ring scotomata appears to be an ominous finding, even when associated with normal central visual acuity, for in three of our patients it preceded loss of central vision by 1 1/2 to four years.

Adult↗

PubMed1975

Anterior segment ischemia after segmental episcleral buckling and cryopexy.

A 63-year-old man with a one-quadrant retinal detachment developed anterior segment ischemia after an operation that included the use of cryopexy, release of subretinal fluid, and segmental episcleral buckling without detachment of the extraocular muscles. A compromised cardiovascular condition of long duration and an episode of transient hypotension immediately preceding operation were factors in the pathogenesis of the ischemia. Although the anterior segment changes were moderately severe, recovery of vision ultimately was excellent.

Cardiovascular Diseases↗

PubMed1975

Oestradiol receptor levels in the human fallopian tube during the menstrual cycle.

The levels of cytoplasmic high-affinity oestradiol receptor sites were determined in the isthmus, isthmus-ampulla, ampulla and fimbria of human Fallopian tubes obtained from 23 women during the proliferative and secretory phase of the menstrual cycle and after menopause. Each segment was homogenized in 0.25 M sucrose and fractionated by differential centrifugation into an 800 g X 15 min nuclear pellet and a 100,000 g X 1 h cytoplasmic supernatant and pellet. The nuclear and cytoplasmic pellets were extracted with 0.01 M Tris/HCl pH 8.0 containing 0.25 M sucrose, 1 mM EDTA and 0.1 M KCl. The receptor levels were determined in the 100,000 g X 1 h supernatant (free receptors) and in the KCl extracts (bound receptors). Values are expressed per mug DNA. The concentration of receptors (total, free and bound) was significantly greater in the ampulla than in the isthmus in both phases of the menstrual cycle (P less than 0.001). The concentration of free receptors in the isthmus, isthmus-ampulla and ampulla obtained in the proliferative phase was not significantly different from that of the secretory phase. In the fimbria a significantly higher concentration (P less than 0.01) was observed in the proliferative phase. The bound receptors were significantly higher in all regions in the proliferative phase than in the secretory phase (P less than 0.01). As a consequence the concentration of total receptors was significantly greater along the tube in the proliferative phase (P less than 0.01). The levels of oestradiol in the nuclear pellet of each segment as measured by radioimmunoassay were significantly greater in the isthmic region (P less than 0.01) than in other regions of the tube. The inverse relationship between the concentration of oestradiol receptor sites and the nuclear levels of oestradiol along the Fallopian tube is discussed.

Adult↗

PubMed1975

Microscope densitometer system for point measurement of autoradiograms.

A photometric system for measuring optical densities generated by tissue autoradiograms has been adapted to an ordinary light microscope. The optics of the microscope are used to direct the light transmitted through the autoradiogram to ocular-mounted photoconductive cells coupled to a bridge amplifier. Readout is on a digital panel meter. The integrated area analyzed varies between 33.16 to 0.02 0.02 mm2 depending on the objective magnification. The system is linear over a range of optical densities from 0.5 to 0.05.

Animals↗

PubMed1975

Glucose uptake in the brainstem of thiamine-deficient rats.

Acute dietary deficiency of thiamine was produced in immature female rats. Uptake of glucose by brainstem nuclei was determined by autoradiographic examination of tissue concentrations of 14-C-3-O-methyl-d-glucose following a test dose, and compared with levels in normal and isocaloric control animals. The experiment showed that glucose uptake was depressed in the lesions of thiamine deficiency as compared with the controls, that the depression occurred with the occurrence of morphologic evidence of tissue edema, and that the depression was temporally independent of the breakdown of the blood-brain barrier to protein which is found in the late, necrotic lesions.

Animals↗

PubMed1975

Congenital displacement of temporal cortex into the central spinal canal.

This is a report of the first recorded observation of displacement of temporal cortex into the central spinal canal in an infant with Arnold Chiari malformation, platybasia, aqueductal atresia, hydrocephalus and meningomyelocele. The combination of an absent right cerebellar hemisphere and malformed fourth ventricular roof provided the anatomical background for this unique event.

Arnold-Chiari Malformation↗

PubMed1975